Patent Publication Number: US-2022216478-A1

Title: Active material, method of manufacturing the same, electrode, and secondary battery

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of PCT application no. PCT/JP2020/034059 filed on Sep. 9, 2020, which claims priority to Japanese patent application no. JP2019-174299 filed on Sep. 25, 2019, the entire contents of which are being incorporated by reference. 
    
    
     BACKGROUND 
     The present technology relates to an active material including silicon and oxygen as constituent elements, a method of manufacturing the active material, an electrode including the active material, and a secondary battery including the active material. 
     Various electronic apparatuses such as mobile phones have been widely used. Such widespread use has promoted the development of a secondary battery that is smaller in size and lighter in weight and allows for a higher energy density, as a power source. The secondary battery includes electrodes, i.e., a positive electrode and a negative electrode, and an electrolytic solution. The electrodes include an active material contributing to an electrode reaction. A configuration of the secondary battery influences a battery characteristic. Accordingly, the configuration of the secondary battery has been considered in various ways. 
     For example, silicon dioxide is heated to generate a silicon oxide gas, following which the silicon oxide gas is condensed into silicon oxide (SiO x ) powder. To improve a cyclability characteristic or other characteristics of a secondary battery including silicon oxide as a negative electrode active material, different elements are added to the silicon oxide. To obtain the negative electrode active material for high-capacity applications, a pyroxene silicic acid compound and a reduced product of tin oxide (SnO x ) acquired as a result of heat reduction using a reducing gas are used. 
     SUMMARY 
     The present disclosure relates to an active material including silicon and oxygen as constituent elements, a method of manufacturing the active material, an electrode including the active material, and a secondary battery including the active material. 
     Although consideration has been given in various ways to improve a battery characteristic of the secondary battery, the battery characteristic of the secondary battery still remains insufficient. Accordingly, there is still room for improvement in terms of the battery characteristic of the secondary battery. 
     The technology of the present disclosure has been made in view of such an issue, and thus to provide, for example, an active material, a method of manufacturing the active material, an electrode, and a secondary battery that are each able to achieve a superior battery characteristic according to an embodiment. 
     An active material according to an embodiment of the technology includes silicon (Si), oxygen (O), a first element, a second element, and a third element as constituent elements. The first element includes boron (B), phosphorus (P), or both. The second element includes at least one of an alkali metal element, a transition element, or a typical element. The typical element excludes silicon, oxygen, boron, phosphorus, an alkali metal element, and an alkaline earth metal element. The third element includes an alkaline earth metal element. The content of silicon with respect to all the constituent elements excluding oxygen and carbon (C) is 60 at % or greater and 98 at % or less. The content of the first element with respect to all the constituent elements excluding oxygen and carbon is 1 at % or greater and 25 at % or less. The content of the second element with respect to all the constituent elements excluding oxygen and carbon is 1 at % or greater and 34 at % or less. The content of the third element with respect to all the constituent elements excluding oxygen and carbon is 0 at % or greater and 6 at % or less. A first peak is detected in an XPS spectrum of Si2p relating to the active material. The XPS spectrum of Si2p is measured using X-ray photoelectron spectroscopy (XPS) and defined by a horizontal axis indicating a binding energy (eV) and a vertical axis indicating a spectrum intensity. The first peak includes an apex within a range of the binding energy of 102 eV or greater and 105 eV or less, and a shoulder on a smaller binding energy side of the apex. A second peak is detected in a Raman spectrum relating to the active material. The Raman spectrum is measured using Raman spectroscopy and defined by a horizontal axis indicating a Raman shift (cm −1 ) and a vertical axis indicating a spectrum intensity. The second peak includes an apex within a range of the Raman shift of 435 cm −1  or greater and 465 cm −1  or less. 
     A method of manufacturing an active material according to an embodiment of the technology includes: preparing silicate glass including, as constituent elements, silicon (Si), oxygen (O), a first element including boron (B), phosphorus (P), or both, a second element including at least one of an alkali metal element, a transition element, or a typical element excluding silicon, oxygen, boron, phosphorus, an alkali metal element, and an alkaline earth metal element, and a third element including an alkaline earth metal element; mixing the silicate glass with a carbon source to thereby obtain a mixture of the silicate glass and the carbon source; and heating the mixture to thereby manufacture an active material including silicon, oxygen, the first element, the second element, and the third element as constituent elements. In the active material, the content of silicon with respect to all the constituent elements excluding oxygen and carbon (C) is 60 at % or greater and 98 at % or less. The content of the first element with respect to all the constituent elements excluding oxygen and carbon is 1 at % or greater and 25 at % or less. The content of the second element with respect to all the constituent elements excluding oxygen and carbon is 1 at % or greater and 34 at % or less. The content of the third element with respect to all the constituent elements excluding oxygen and carbon is 0 at % or greater and 6 at % or less. 
     An electrode according to an embodiment of the technology includes an active material. The active material has a configuration similar to the configuration of the active material according to the embodiment of the technology described above. 
     A secondary battery according to an embodiment of the technology includes a positive electrode, a negative electrode, and an electrolytic solution. The negative electrode includes a negative electrode active material. The negative electrode active material has a configuration similar to the configuration of the active material according to an embodiment of the technology. 
     According to the active material, the electrode, or the secondary battery of the embodiment of the technology, the active material, i.e., the negative electrode active material, includes silicon, oxygen, the first element, the second element, and the third element as constituent elements, and the content of each of the constituent elements satisfies the condition described above. Further, the first peak described above is detected in the XPS spectrum of Si2p relating to the active material measured using X-ray photoelectron spectroscopy, and the second peak described above is detected in the Raman spectrum relating to the active material measured using Raman spectroscopy. Accordingly, it is possible to obtain a superior battery characteristic. 
     According to the method of manufacturing the active material of an embodiment of the technology, the silicate glass including silicon, oxygen, the first element, the second element, and the third element as constituent elements is mixed with the carbon source, following which the mixture of the silicate glass and the carbon source is heated to thereby manufacture the active material. The content of each of the constituent elements in the active material satisfies the condition described above. Accordingly, it is possible to obtain an active material achieving a superior battery characteristic. 
     Note that effects of the technology are not necessarily limited to the effects described above and may include any of a series of suitable effects including described below in relation to the technology according to an embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a sectional view of a configuration of an active material according to an embodiment of the technology. 
         FIG. 2  is an example of a result of analysis (an XPS spectrum of Si2p) of the active material using XPS. 
         FIG. 3  is an example of a result of analysis (a Raman spectrum) of the active material using Raman spectroscopy. 
         FIG. 4  is a flowchart for describing a method of manufacturing the active material according to an embodiment of the technology. 
         FIG. 5  is a perspective view of configurations of an electrode and a secondary battery of a laminated-film type according to an embodiment of the technology. 
         FIG. 6  is a sectional view of a configuration of a wound electrode body illustrated in  FIG. 5 . 
         FIG. 7  is a plan view of respective configurations of a positive electrode and a negative electrode illustrated in  FIG. 6 . 
         FIG. 8  is a sectional view of configurations of another electrode and another secondary battery of a cylindrical type according to one embodiment of the technology. 
         FIG. 9  is a perspective view of a configuration of a secondary battery of another laminated-film type according to Modification 2. 
         FIG. 10  is a sectional view of a configuration of a stacked electrode body illustrated in  FIG. 9 . 
         FIG. 11  is a block diagram illustrating a configuration of an application example of the secondary battery, which is a battery pack including a single battery. 
         FIG. 12  is a block diagram illustrating a configuration of an application example of the secondary battery, which is a battery pack including an assembled battery. 
         FIG. 13  is a block diagram illustrating a configuration of an application example of the secondary battery, which is an electric vehicle. 
         FIG. 14  is a sectional view of a configuration of a secondary battery of a coin type for testing. 
     
    
    
     DETAILED DESCRIPTION 
     One or more embodiments of the technology of the present disclosure are described below in detail with reference to the drawings. 
     First, a description is given of an active material according to an embodiment of the technology. Note that a manufacturing method of an active material according to an embodiment of the technology is a manufacturing method of the active material described herein, and is therefore descried below together. 
     The active material is a material contributing to an electrode reaction. More specifically, the active material is a material into which an electrode reactant is insertable and from which an electrode reactant is extractable. The active material is used as an electrode material of a device that is operable using the electrode reaction. In this case, the electrode reactant is inserted into the active material or extracted from the active material in an ionic state. Note that the active material may be used as an electrode material for a positive electrode (a positive electrode active material) or an electrode material for a negative electrode (a negative electrode active material). 
     Applications of the active material are not limited to particular applications as long as they are devices that are operable using an electrode reaction. Specifically, examples of the applications of the active material include a battery and a capacitor. Note that the battery may be a primary battery or a secondary battery. 
     The electrode reactant is not limited to a particular kind and may be a light metal such as an alkali metal, an alkaline earth metal, or aluminum. Examples of the alkali metal include lithium, sodium, and potassium, and examples of the alkaline earth metal include beryllium, magnesium, and calcium. 
     First, a description is given of a configuration of the active material.  FIG. 1  illustrates a sectional configuration of an active material  100 , which is an example of the active material. 
     As illustrated in  FIG. 1 , the active material  100  includes a center part  101  and a covering part  102 . Note that the center part  101  has a spherical three-dimensional shape in  FIG. 1  for simple illustration; however, the three-dimensional shape of the center part  101  is not limited to a particular shape. 
     The center part  101  is a main part of the active material  100  into which the electrode reactant is inserted and from which the electrode reactant is extracted. The center part  1101  includes carbon-reduced silicate glass. Unlike ordinary silicate glass (hereinafter simply referred to as “silicate glass”), the carbon-reduced silicate glass is formed by a carbon reduction treatment on silicate glass using a carbon source as a reducing agent, as to be described later. Note that only one kind of the carbon-reduced silicate glass may be included, or two or more kinds of the carbon-reduced silicate glass may be included. 
     In the carbon-reduced silicate glass formed by the carbon reduction treatment, a reduction reaction of the silicate glass which is a raw material is facilitated due to the use of the carbon source as the reducing agent. This allows the silicate glass to be so reduced (activated) that the electrode reactant is sufficiently inserted and extracted from the silicate glass. That is, the silicate glass is hardly reduced by an ordinary reduction treatment in which a reducing gas is used as a reducing agent, whereas the silicate glass is sufficiently reduced in a special reduction treatment, i.e., the carbon reduction treatment, in which the carbon source is used as a reducing agent. Thus, the carbon-reduced silicate glass has a physical property different from the physical property of silicate glass. Details of the physical property of the carbon-reduced silicate glass will be described later. 
     Specifically, the carbon-reduced silicate glass includes silicon, oxygen, a first element, a second element, and a third element, as constituent elements. 
     The content of each constituent element with respect to all the constituent elements excluding oxygen and carbon in the carbon-reduced silicate glass is set within a predetermined range. In a case where the total content of all the constituent elements excluding oxygen and carbon is assumed to be 100 at %, the content of each constituent element represents the atomic percent of the content of the constituent element. Note that the content (atomic percent) of each constituent element is measured by analyzing the carbon-reduced silicate glass using scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX) spectrometry. 
     (Silicon) 
     Silicon is a primary constituent element of the carbon-reduced silicate glass. The content of silicon with respect to all the constituent elements excluding oxygen and carbon is from 60 at % to 98 at % both inclusive. 
     Oxygen is another primary constituent element of the carbon-reduced silicate glass that forms an oxide with silicon. Thus, the carbon-reduced silicate glass includes SiO x  (where x satisfies 0≤x≤2) as a primary component. The SiO x  is supposed to include nano silicon (Si) dispersed in amorphous silicon dioxide (SiO 2 ). Alternatively, the SiO x  is supposed to include, in the glass component, silicon into which electrode reactant is sufficiently insertable and from which electrode reactant is sufficiently extractable. 
     The first element includes one or more network-forming elements. More specifically, the first element includes boron, phosphorus, or both. A reason for this is that silicate glass including the first element in addition to silicon and oxygen as constituent elements is easily and sufficiently reduced in the carbon reduction treatment. This facilitates easy and stable formation of the carbon-reduced silicate glass in the carbon reduction treatment. 
     The term “network-forming element” is a generic term for a series of elements capable of forming a network-forming body (network-forming oxide). The first element may thus include, for example, germanium (Ge) in addition to boron and phosphorus described above. 
     The content of the first element with respect to all the constituent elements excluding oxygen and carbon is from 1 at % to 25 at % both inclusive. A reason for this is that the silicate glass is easily and sufficiently reduced in the carbon reduction treatment. 
     Note that, in a case where the first element includes two or more elements, the content of the first element is the sum of the contents of these elements. Likewise, in a case where the second or third element includes two or more elements, the content of the second or third element to be described later is the sum of the contents of these constituent elements. 
     The second element includes one or more of an alkali metal element, a transition element, and a typical element. A reason for this is that, unlike the third element to be described later, the second element hardly affects the reducibility of the silicate glass in the carbon reduction treatment even if included in the silicate glass as a constituent element. Accordingly, the silicate glass is sufficiently reduced in the carbon reduction treatment even if the second element is included in the silicate glass as a constituent element. 
     The term “alkali metal element” is a generic term for a series of elements belonging to the Group 1 in the long period periodic table. Specifically, examples of the alkali metal element include lithium (Li), sodium (Na), and potassium (K). 
     The term “transition element” is a generic term for a series of elements belonging to any of Groups 3 to 11 in the long period periodic table. Specifically, examples of the transition element include scandium (Sc), titanium (Ti), zirconium (Zr), and cerium (Ce). However, the transition element is not limited to a particular kind as long as the transition element belongs to any of Groups 3 to 11 in the long period periodic table. Thus, the examples of the transition element may further include elements including, without limitation, lanthanum (La), hafnium (Hf), tantalum (Ta), and tungsten (W) other than the series of elements such as scandium described above. 
     The term “typical element” is a generic term for a series of elements belonging to any of Groups 1, 2, and 12 to 18 in the long period periodic table. However, silicon, oxygen, boron, phosphorus, an alkali metal element, and an alkaline earth metal element are excluded from the typical element described here. Thus, examples of the typical element described here include aluminum (Al), sulfur (S), chlorine (Cl), zinc (Zn), and bismuth (Bi). However, the typical element is not limited to a particular kind as long as the typical element belongs to any of Groups 1, 2, and 12 to 18 in the long period periodic table. Thus, the examples of the typical element may further include elements including, without limitation, antimony (Sb) other than the series of elements such as aluminum described above. 
     The content of the second element with respect to all the constituent elements excluding oxygen and carbon is from 1 at % to 34 at % both inclusive. A reason for this is that the silicate glass is easily and sufficiently reduced in the carbon reduction treatment even if the second element is included in the silicate glass as a constituent element. 
     The third element is an optional constituent element of the carbon-reduced silicate glass. The carbon-reduced silicate glass may thus include the third element as a constituent element or may not include the third element as a constituent element. 
     The third element includes one or more alkaline earth metal elements. The term “alkaline earth metal element” is a generic term for a series of elements belonging to Group 2 in the long period periodic table. Specifically, examples of the third element include magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). 
     Note that the content of the third element with respect to all the constituent elements excluding oxygen and carbon is from 0 at % to 6 at % both inclusive. 
     The reason why the lower limit of the content of the third element is 0 at % is that the carbon-reduced silicate glass may not include the third element as a constituent element since the third element is an optional constituent element of the carbon-reduced silicate glass, as described above. 
     The reason why the upper limit of the content of the third element is 6 at % is that the content of the third element should be within a range that does not affect the reducibility of the silicate glass in the carbon reduction treatment since the third element affects the reducibility of the silicate glass in the carbon reduction process, as described above. 
     Specifically, in a case where the content of the third element is greater than 6 at %, the silicate glass is hardly reduced in the carbon reduction treatment because the amount of the third element present in the silicate glass is excessively large. As a result, substantially no carbon-reduced silicate glass is manufactured. In contrast, in a case where the content of the third element is 6 at % or less, the silicate glass is easily reduced in the carbon reduction treatment because the amount of the third element present in the silicate glass is appropriately decreased. As a result, the carbon-reduced silicate glass is substantially manufactured. 
     The covering part  102  covers a portion or all of a surface of the center part  101 . Note that, in a case where the covering part  102  covers a portion of the surface of the center part  101 , a plurality of locations separated from each other on the surface of the center part  101  may be covered with the covering parts  102 . 
     The covering part  102  includes carbon as a constituent element to have an electrically conductive property. A reason for this is that the electrically conductive property of the active material  100  as a whole enhances in a case where the surface of the center part  101  is covered with the covering part  102  having an electrically conductive property, as compared with a case where the surface of the center part  101  is not covered with the covering part  102 . A material included in the covering part  102  is not limited to a particular material as long as carbon is included therein as a constituent element. 
     Specifically, the covering part  102  is formed as a coating film covering the surface of the center part  101  as a result of thermal decomposition of a carbon source (a mixture of silicate glass and a reducing agent) when the carbon source is heated in a manufacturing process of the active material (carbon reduction treatment) as to be described later. In this case, the covering part  102  may include the carbon source as it is, may include a decomposition product of the carbon source (organic substance decomposition carbon), or may include both of them. 
     The thickness of the covering part  102  is not limited to a particular thickness. A reason for this is that the electrically conductive property of the active material  100  as a whole enhances in a case where the covering part  102  is present even in a slight amount on the surface of the center part  101 , as compared with a case where the covering part  102  is not present at all on the surface of the center part  101 . 
     Next, a description is given of physical properties of the active material  100 . In the following, two physical properties are described in order that are specified on the basis of the results of analyses of the active material  100  using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. 
       FIG. 2  illustrates an example of a result of the analysis (an XPS spectrum of Si2p) of the active material  100  using XPS for describing a first physical property. The XPS spectrum is defined by a horizontal axis representing the binding energy (eV), and a vertical axis representing the spectrum intensity. Note that the result of the analysis using XPS described here is an analysis result obtained after argon (Ar) ion sputtering for a sputtering time of 1000 seconds. 
       FIG. 2  also illustrates an XPS spectrum of the silicate glass indicated with a dashed line in addition to the XPS spectrum of the carbon-reduced silicate glass indicated with a solid line. That is, the carbon-reduced silicate glass of which XPS spectrum is detected as indicated with the solid line is obtainable by conducting the carbon reduction treatment on the silicate glass of which XPS spectrum is detected as indicated with the dashed line. Note that shading is applied to the range of the binding energy from 102 eV to 105 eV both inclusive. 
     As illustrated in  FIG. 2 , the carbon-reduced silicate glass has a physical property different from the physical property of the silicate glass in terms of the result of analysis using XPS or the shape of the XPS spectrum. 
     Specifically, a peak XA (first peak) is detected in the solid-line XPS spectrum relating to the carbon-reduced silicate glass. The peak XA has an apex XAT within the range of the binding energy from 102 eV to 105 eV both inclusive, and a shoulder XAS on a smaller binding energy side of the apex XAT (i.e., on the right side in  FIG. 2 ). The shoulder XAS is a shoulder-like portion protruding toward the low binding energy side from a portion of the middle of the peak XA having the apex XAT. That is, the shoulder XAS is a stepped portion. 
     In contrast, a peak XB is detected in the dashed-line XPS spectrum relating to the silicate glass. The peak XB has an apex XBT within the range of the binding energy from 102 eV to 105 eV both inclusive, but does not have a shoulder corresponding to the shoulder XAS on a smaller binding energy side of the apex XBT. 
     The following tendencies are derived from these results of the analysis of the active material  100  using XPS or the shapes of XPS spectra. Regarding the carbon-reduced silicate glass, the peak XA having the apex XAT and the shoulder XAS is detected because silicate glass, which is the raw material of the carbon-reduced silicate glass, has been sufficiently reduced by the carbon reduction treatment. In contrast, regarding the silicate glass, the peak XB having only the apex XBT is detected because the silicate glass has not been subjected to the carbon reduction treatment yet. 
     Accordingly, it is possible to identify which of the carbon-reduced silicate glass or the silicate glass the analyte is on the basis of the results of analysis using XPS. The carbon-reduced silicate glass manufactured by the carbon reduction treatment therefore differs in physical property from the silicate glass in that the above-described condition is satisfied in terms of XPS. 
     Likewise, it is possible to identify the center part  101  of the active material  100  by the above-described identification method. That is, the center part  101  includes the carbon-reduced silicate glass in a case where the peak XA is detected by the analysis of the center part  101  using XPS, whereas the center part  101  includes the silicate glass in a case where the peak XB is detected. 
     Note that the silicate glass is hardly reduced by the ordinary reduction treatment, as described above. Accordingly, even if the ordinary reduction treatment is performed using the silicate glass, the silicate glass is hardly reduced and expected to exhibit the peak XB rather than the peak XA. 
     Here, the peak XA relating to the carbon-reduced silicate glass has the shoulder XAS, whereas the peak XB relating to the silicate glass has no shoulder, as described above. Accordingly, it is also possible to identify which of the carbon-reduced silicate glass or the silicate glass the analyte is by the following methods. 
     First, the width of the middle of the peak XA in a height direction is larger than the width of the middle of the peak XB in the height direction. The half-width of the peak XA is therefore larger than the half-width of the peak XB. More specifically, the half-width of the peak XA is 4.0 eV or greater. Although the half-width of the peak XA is 4.0 eV or greater, the half-width of the peak XB is not 4.0 eV or greater. Accordingly, it is also possible to identify which of the reduced silicate glass or the silicate glass the analyte is by measuring the half-width instead of examining the presence or absence of the shoulder XAS. That is, it is possible to identify the kind of the analyte by measuring the half width even in a case where it is difficult to determine the presence or absence of the shoulder XAS because the shoulder XAS is small. 
     Second, the area of the middle of the peak XA is larger than the area of the middle of the peak XB. Accordingly, in a case where each of the peaks XA and XB is decomposed into five Si-attributed peaks (a Si 0  peak, a Si 1+  peak, a Si 2+  peak, a Si 3+  peak, and a Si 4+  peak), the area ratio S2/S1 of the peak XA is larger than the area ratio S2/S1 of the peak XB. More specifically, the area ratio S2/S1 of the peak XA is 0.85 or greater. 
     Here, the area S1 is the area of the Si 4+  peak, while the area S2 is the sum of the area of the Si 0  peak, the area of the Si 1+  peak, the area of the Si 2+  peak, and the area of the Si 4+  peak. Each of the areas S1 and S2 may be calculated using an analysis (arithmetic) function of an XPS device. 
     Although the area ratio S2/S1 of the peak XA is 0.85 or greater, the area ratio S2/S1 of the peak XB is not 0.85 or greater. Accordingly, it is also possible to identify which of the reduced silicate glass or the silicate glass the analyte is by measuring the area ratio S2/S1 instead of examining the presence or absence of the shoulder XAS. That is, it is possible to identify the kind of the analyte by measuring the half width even in a case where it is difficult to determine the presence or absence of the shoulder XAS because the shoulder XAS is small, as described above. 
       FIG. 3  illustrates an example of a result of the analysis (a Raman spectrum) of the active material  100  using Raman spectroscopy for describing a second physical property. The Raman spectrum is defined by a horizontal axis representing the Raman shift (cm −1 ) and a vertical axis representing the spectrum intensity. 
       FIG. 3  also illustrates a Raman spectrum of the silicate glass indicated with a dashed line in addition to the Raman spectrum of the carbon-reduced silicate glass indicated with a solid line. That is, the carbon-reduced silicate glass of which Raman spectrum is detected as indicated with the solid line is obtainable by conducting the carbon reduction treatment on the silicate glass of which Raman spectrum is detected as indicated with the dashed line. Note that shading is applied to the range of the Raman shift from 435 cm −1  to 465 cm −1  both inclusive. 
     As illustrated in  FIG. 3 , the carbon-reduced silicate glass has a physical property different from the physical property of the silicate glass in terms of the result of analysis using Raman spectroscopy or the shape of the Raman spectrum. 
     Specifically, a peak RA (second peak) is detected in the solid-line Raman spectrum relating to the carbon-reduced silicate glass. The peak RA has an apex RAT within the range of the Raman shift from 435 cm −1  to of 465 cm −1  both inclusive. 
     In contrast, a peak RB is detected in the dashed-line Raman spectrum relating to the silicate glass. The peak RB has an apex RBT outside the range of the binding energy from 435 cm −1  to 465 cm −1  both inclusive rather than within the range. Specifically, the peak RB has the apex RBT within the range of the binding energy from 470 cm −1  to 490 cm −1  both inclusive. Note that, just for reference, a peak having an apex within the range of the binding energy from 510 cm −1  to 525 cm −1  both inclusive is detected in the Raman spectrum relating to a single substance of silicon having crystallinity. 
     The following tendencies are derived from these results of the analysis of the active material  100  using Raman spectroscopy or the shape of Raman spectrum. Regarding the carbon-reduced silicate glass, the peak RA having the apex RAT within the range from 435 cm −1  to 465 cm −1  both inclusive is detected because silicate glass, which is the raw material of the carbon-reduced silicate glass, has been sufficiently reduced by the carbon reduction treatment. In contrast, regarding the silicate glass, the peak RB having the apex RBT outside the above-described range is detected because the silicate glass has not been subjected to the carbon reduction treatment yet. The carbon-reduced silicate glass manufactured by the carbon reduction treatment therefore differs in physical property from the silicate glass in that the above-described condition is satisfied in terms of Raman spectroscopy. 
     Likewise, it is possible to identify the center part  101  of the active material  100  by the above-described identification method. That is, the center part  101  includes the carbon-reduced silicate glass in a case where the peak RA is detected by the analysis of the center part  101  using Raman spectroscopy, whereas the center part  101  includes the silicate glass in a case where the peak RB is detected. 
     Note that the silicate glass is hardly reduced by the ordinary reduction treatment, as described above. Accordingly, even if the ordinary reduction treatment is performed using the silicate glass, the silicate glass is hardly reduced and expected to exhibit the peak RB rather than the peak RA. 
     These results indicate that, in the case of the carbon-reduced silicate glass, the peak XA is detected in the XPS spectrum of Si2p measured using XPS, and the peak RA is detected in the Raman spectrum measured using Raman spectroscopy. Thus, the active material  100  includes the carbon-reduced silicate glass in a case where both of the peaks XA and RA described above are detected by analyzing the active material  100  (the center part  101 ) using both XPS and Raman spectroscopy. 
     In contrast, the active material  100  does not include the carbon-reduced silicate glass in a case where the peak XA, the peak RA, or both are not detected by analyzing the active material  100  using both XPS and Raman spectroscopy. 
     The reduced silicate glass included in the active material  100  (the center part  101 ) satisfies the two physical property conditions relating to XPS and Raman spectroscopy described above because the crystallinity of a glass material including the above-described SiO x  as a primary component is optimized due to the reduction reaction of the reduced silicate glass which proceeds more easily than that of silicate glass. This makes it easy for the electrode reactants to be sufficiently and stably inserted into or extracted from the active material  100 , and also continuously makes it easy for the electrode reactant to be inserted into or extracted from the active material  100  even if the electrode reaction is repeated. 
     Next, a description is given of a method of manufacturing the active material  100 .  FIG. 4  is a flowchart for describing the method of manufacturing the active material  100 . Step numbers in parentheses described below correspond to step numbers illustrated in  FIG. 4 . 
     In a case of manufacturing the active material  100 , first, powder of silicate glass is prepared as a raw material (Step S 1 ). In this case, previously synthesized silicate glass may be acquired by a method such as purchase, or silicate glass may be synthesized by a user. 
     The silicate glass does not satisfy the two physical property conditions relating to XPS and Raman spectroscopy described above because the silicate glass has not been subjected to the carbon reduction treatment yet. Except this point, the silicate glass has a configuration substantially similar to that of the carbon-reduced silicate glass. That is, the silicate glass includes silicon, oxygen, the first element, the second element, and the third element as constituent elements. Details of each of the first element, the second element, and the third element are as described above. 
     Note that, in a case of synthesizing the silicate glass, silicon dioxide (SiO 2 ) is mixed with respective sources of the first element, the second element, and the third element, following which the mixture is heated. Conditions including, without limitation, a heating temperature and a heating time may be set to any values. 
     These sources are compounds including respective constituent elements. The compounds are not limited to particular kinds. Specifically, the compounds are, for example, oxides of the respective constituent elements. That is, examples of the source of the first element include boron trioxide (B 2 O 5 ) and phosphorus pentoxide (P 2 O 5 ). Examples of the source of the second element include sodium oxide (Na 2 O), potassium oxide (K 2 O), scandium oxide (ScO), titanium oxide (TiO 2 ), zirconium oxide (Zr 2 O), cerium oxide (CeO), hafnium oxide (HfO 2 ), tantalum oxide (Ta 2 O 5 ), tungsten oxide (WO 3 ), aluminum oxide (Al 2 O 3 ), phosphorus pentasulfide (P 2 S 5 ), lithium sulfide (Li 2 S), magnesium sulfide (MgS), silicon tetrachloride (SiCl 4 ), zinc oxide (ZnO 2 ), bismuth oxide (BiO), and antimony oxide (Sb 2 O 3 ). Examples of the source of the third element include magnesium oxide (MgO), calcium oxide (CaO), strontium oxide (SrO), and barium oxide (BaO). 
     The silicon dioxide and the respective sources of the first element, the second element, and the third element are thereby mixed with each other to form a solid solution. A glass body is thereby formed which includes silicon, oxygen, the first element, the second element, and the third element as constituent elements. As a result, the silicate glass is synthesized. 
     After preparing the silicate glass, the silicate glass is mixed with a carbon source to obtain a mixture (Step S 2 ). The term “carbon source” is a generic term for a material usable as a source of carbon. Specifically, the carbon source includes, without limitation, one or more of carbon materials and carbonizable organic substances. In other words, only a carbon material may be used, only a carbonizable organic substance may be used, or both of them may be used as the carbon source. Examples of the carbon material include non-fibrous carbon and fibrous carbon. Examples of the non-fibrous carbon include carbon black, and examples of the fibrous carbon include carbon nanotubes and carbon nanofibers. Examples of the carbonizable organic substance include saccharides and polymer compounds. Examples of the saccharide include sucrose, maltose, and cellulose. Examples of the polymer compounds include polyimide, polyvinylidene difluoride, polymethyl methacrylate, polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylic acid. A reason why such a material is used as the carbon source is that the silicate glass is sufficiently reduced in the carbon reduction treatment. Another reason is that the covering part  102  having a sufficient electrically conductive property is easily and stably formed by using the carbon source, as to be described later. 
     In this case, the mixture may be stirred using a stirring device. Conditions including, without limitation, a stirring speed and a stirring time may be set to any values. 
     Alternatively, a mixture in a paste state may be obtained by adding materials including, without limitation, a binder and a solvent to the mixture. In this case, it is preferable to stir the mixture using the stirring device described above. The binder is not limited to a particular kind, and may be one or more polymer compounds including, without limitation, polyvinylidene difluoride, polyimide, and polymethyl methacrylate. The solvent is not limited to a particular kind, and may be one or more of organic solvents including, without limitation, N-methyl-2-pyrrolidone. Note that a binder solution in which a binder is previously dissolved in a solvent may be used. 
     Lastly, the mixture is heated (Step S 3 ). In this case, one or more of heating devices including, without limitation, an oven may be used. Conditions including, without limitation, a heating temperature and a heating time may be set to any values. Specifically, the heating temperature is from 700° C. to 1400° C. both inclusive, and the heating time is from one hour to twenty hours both inclusive. 
     In a case where a mixture including a binder is used, the mixture may be heated in two stages. Specifically, first, the mixture is subjected to first heating to dry the mixture. Although the condition of the first heating is not limited to a particular condition, the heating temperature is from 40° C. to 500° C. both inclusive, and the heating time is from 10 minutes to three hours both inclusive. Thereafter, the dried mixture is pulverized. Lastly, the pulverized mixture is subjected to second heating. Although the condition of the second heating is not limited to a particular condition, the heating temperature is from 700° C. to 1200° C. both inclusive, and the heating time is from one hour to twenty hours both inclusive. 
     The silicate glass is thereby subjected to the carbon reduction treatment, and the silicate glass is sufficiently reduced using the carbon source as a reducing agent. In other words, the crystalline state of SiO x  is so optimized that the electrode reactant is allowed to be sufficiently inserted and extracted. Accordingly, carbon-reduced silicate glass is synthesized that includes SiO x  as a primary component. As a result, the center part  101  is formed that includes the carbon-reduced silicate glass. 
     In addition, carbon (organic substance decomposition carbon) adheres to the surface of the center part  101  in the carbon reduction treatment due to thermal decomposition of the carbon source used as the reducing agent, as described above. As a result, the covering part  102  including carbon as a constituent element is formed in such a manner as to cover the surface of the center part  101 . 
     The active material  100  including the center part  101  and the covering part  102  is thereby manufactured (Step S 4 ). In a case of synthesizing the active material (the center part  101  including the carbon-reduced silicate glass), the composition or another factor of the silicate glass used as a raw material is so adjusted that the content of each constituent element with respect to all the constituent elements excluding oxygen, lithium, and carbon satisfies the condition described above. Specifically, the adjustment is so performed that the content of silicon is from 60 at % to 98 at % both inclusive, the content of the first element is from 1 at % to 25 at % both inclusive, the content of the second element is from 1 at % to 34 at % both inclusive, and the content of the third element is from 0 at % to 6 at % both inclusive in the carbon-reduced silicate glass. 
     In the active material  100  (the center part  101 ) including the carbon-reduced silicate glass manufactured by the carbon reduction treatment, the physical property of the silicate glass has changed due to the carbon reduction process. The two physical property conditions relating to XPS and Raman spectroscopy described above are thus satisfied. 
     According to the active material  100  and the method manufacturing the active material  100  described above, the following action and effects are obtained. 
     The active material  100  includes silicon, oxygen, the first element, the second element, and the third element as constituent elements, and the content of each constituent element with respect to all the constituent elements excluding oxygen and carbon satisfies the condition described above. In addition, the peak XA (the apex XAT and the shoulder XAS) is detected as the result of analysis of the active material  100  measured by XPS (the XPS spectrum of Si2p), and the peak RA (the apex RAT) is detected as the result of analysis of the active material  100  measured by Raman spectroscopy (the Raman spectrum). 
     In this case, unlike the case where the two physical property conditions relating to XPS and Raman spectroscopy are not satisfied, the reduction reaction of the silicate glass sufficiently proceeds, as described above. Accordingly, the crystallinity of the glass material including SiO x  as a primary component is optimized. This makes it easy for the electrode reactant to be sufficiently and stably inserted into or extracted from the active material  100 , and also continuously makes it easy for the electrode reactant to be inserted into or extracted from the active material  100  even if the electrode reaction is repeated. It is therefore possible to obtain a superior battery characteristic in a secondary battery including the active material  100 . 
     In particular, the half width of the peak XA may be 4.0 eV or greater. In this case, the center part  101  includes the carbon-reduced silicate compound satisfying the two physical property conditions relating to XPS and Raman spectroscopy. Thus, it is possible to obtain a superior battery characteristic as described above. Further, the area ratio S2/S1 may be 0.85 or greater in a case where the peak XA is decomposed into the five Si-attributed peaks (the Si 0  peak, the Si 1+  peak, the Si 2+  peak, the Si 3+  peak, and the Si 4+  peak). In this case, it is also possible to obtain a superior battery characteristic for a similar reason. 
     Further, the active material  100  may include the center part  101  and the covering part  102 . This allows the surface of the center part  101  including the carbon-reduced silicate glass to be covered with the covering part  102  having an electrically conductive property. This improves the electrically conductive property of the active material  100  as a whole. It is therefore possible to obtain a higher effect. 
     According to the method of manufacturing the active material  100 , the silicate glass including silicon, oxygen, the first element, the second element, and the third element as constituent elements is mixed with the carbon source, following which the mixture of the silicate glass and the carbon source is heated. Accordingly, the active material  100  is synthesized that includes the carbon-reduced silicate compound in which the content of each constituent element satisfies the condition described above and which satisfies the two physical property conditions relating to XPS and Raman spectroscopy. It is therefore possible to obtain the active material  100  that achieves a superior battery characteristic. 
     Moreover, to manufacture the active material  100  including SiO x  as a primary component, only simple and inexpensive treatments including, without limitation, a mixing treatment and a heating treatment are needed. This eliminates the need to perform a complicated and expensive treatment such as codeposition of two vapor deposition sources (SiO 2  and Si). It is therefore possible to manufacture the active material  100  easily and stably at low costs. 
     In particular, the carbon source may include the material such as a carbon material. This allows the silicate glass to be sufficiently reduced in the carbon reduction treatment, and allows the covering part  102  having a sufficient electrically conductive property to be formed easily and stably. It is therefore possible to obtain a higher effect. 
     Next, a description is given of a secondary battery according to an embodiment of the technology, which is one application example of the active material described above. Note that an electrode according to an embodiment of the technology is a part (one constituent element) of the secondary battery, and is thus described below together. 
     A description is given below of a case where the active material  100  is used as a negative electrode active material, and is therefore used for a negative electrode. 
     The secondary battery described here is a secondary battery that obtains a battery capacity by utilizing insertion and extraction of the electrode reactant. The secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution. 
     In the secondary battery, in order to prevent precipitation of the electrode reactant on a surface of the negative electrode in the middle of charging, a charge capacity of the negative electrode is greater than a discharge capacity of the positive electrode. In other words, an electrochemical capacity per unit area of the negative electrode is set to be greater than an electrochemical capacity per unit area of the positive electrode. 
     In the following, a description is given of an example case where the electrode reactant is lithium. A secondary battery utilizing insertion and extraction of lithium as the electrode reactant is a so-called lithium-ion secondary battery. 
     First, a secondary battery of a laminated-film type is described. The secondary battery of the laminated-film type includes a film  20  having softness or flexibility as an outer package member for containing a battery device. 
       FIG. 5  is a perspective view of a configuration of the secondary battery of the laminated-film type.  FIG. 6  illustrates a sectional configuration of a wound electrode body  10  illustrated in  FIG. 5 .  FIG. 7  illustrates a plan configuration of each of a positive electrode  11  and a negative electrode  12  illustrated in  FIG. 6 . 
     Note that  FIG. 5  illustrates a state in which the wound electrode body  10  and the film  20  are separated away from each other.  FIG. 6  illustrates only a portion of the wound electrode body  10 .  FIG. 7  illustrates a state in which the positive electrode  11  and the negative electrode  12  are separated away from each other. 
     As illustrated in  FIG. 5 , the secondary battery has the film  20  having a pouch-shape in which a wound-type battery device (the wound electrode body  10 ) is contained. A positive electrode lead  14  and a negative electrode lead  15  are coupled to the wound electrode body  10 . 
     The film  20  is a single film member foldable in a direction of an arrow R (a dash-dot-dash line) illustrated in  FIG. 5 . The film  20  has a depression  20 U. The depression  20 U is a so-called deeply-drawn portion designed to contain the wound electrode body  10 . 
     Specifically, the film  20  is a laminated film including three layers: a fusion-bonding layer, a metal layer, and a surface protective layer that are laminated in this order from an inner side. In a state where the film  20  is folded, outer edges of the fusion-bonding layer are fusion-bonded to each other. The fusion-bonding layer includes a polymer compound such as polypropylene. The metal layer includes a metal material such as aluminum. The surface protective layer includes a polymer compound such as nylon. Note that the number of layers laminated into the film  20  is not limited to three. The film  20  may include one layer, two layers, or four or more layers. 
     A sealing film  21  is interposed between the film  20  and the positive electrode lead  14 , and a sealing film  22  is interposed between the film  20  and the negative electrode lead  15 . The sealing films  21  and  22  are members for preventing outside air from entering. The sealing films  21  and  22  include, without limitation, one or more polyolefin resins having adherence to the positive electrode lead  14  and the negative electrode lead  15 , respectively. Examples of the polyolefin resin include polyethylene, polypropylene, modified polyethylene, and modified polypropylene. Note that the sealing film  21 , the sealing film  22 , or both may be omitted. 
     As illustrated in  FIGS. 5 and 6 , the wound electrode body  10  includes the positive electrode  11 , the negative electrode  12 , a separator  13 , and an electrolytic solution. The electrolytic solution is a liquid electrolyte. The wound electrode body  10  has a structure in which the positive electrode  11  and the negative electrode  12  are stacked on each other with the separator  13  interposed therebetween, and the stack of the positive electrode  11 , the negative electrode  12 , and the separator  13  is wound. 
     The positive electrode  11 , the negative electrode  12 , and the separator  13  are each impregnated with the electrolytic solution. 
     As illustrated in  FIG. 6 , the positive electrode  11  includes a positive electrode current collector  11 A, and two positive electrode active material layers  11 B provided on respective sides of the positive electrode current collector  11 A. However, the positive electrode active material layer  11 B may be provided on only one side of the positive electrode current collector  11 A. 
     The positive electrode current collector  11 A includes one or more of electrically conductive materials including, without limitation, aluminum, nickel, and stainless steel. 
     The positive electrode active material layer  11 B includes one or more of positive electrode active materials into which lithium is inserted and from which lithium is extracted. The positive electrode active material layer  11 B may further include a material such as a positive electrode binder or a positive electrode conductor. 
     The positive electrode active material is not limited to a particular kind, and is a lithium-containing compound such as a lithium-containing transition metal compound. The lithium-containing transition metal compound includes lithium and one or more of transition metal elements, and may further include one or more of other elements. The other elements may be any elements other than a transition metal element, and are not limited to particular kinds. In particular, the other elements are preferably those belonging to Groups 2 to 15 in the long period periodic table. Note that the lithium-containing transition metal compound may be an oxide, or may be, for example, one of a phosphoric acid compound, a silicic acid compound, and a boric acid compound. 
     Specific examples of the oxide include LiNiO 2 , LiCoO 2 , LiCo 0.98 Al 0.01 Mg 0.33 O 2 , LiNi 0.5 Co 0.2 Mn 0.302 , LiNi 0.8 Co 0.15 Al 0.05 O 2 , LiNi 0.33 Co 0.33 Mn 0.33 O 2 , Li 1.2 Mn 0.52 Co 0.175 Ni 0.1 O 2 , Li 1.15 (Mn 0.65 Ni 0.22 Co 0.13 )O 2 , and LiMn 2 O 4 . Specific examples of the phosphoric acid compound include LiFePO 4 , LiMnPO 4 , LiFe 0.5 Mn 0.5 PO 4 , and LiFe 0.3 Mn 0.7 PO 4 . 
     The positive electrode binder includes one or more of materials including, without limitation, a synthetic rubber and a polymer compound. Examples of the synthetic rubber include a styrene-butadiene-based rubber, a fluorine-based rubber, and ethylene propylene diene. Examples of the polymer compound include polyvinylidene difluoride, polyimide, and carboxymethyl cellulose. 
     The positive electrode conductor includes one or more of electrically conductive materials including, without limitation, a carbon material. Examples of the carbon material include graphite, carbon black, acetylene black, and Ketjen black. The positive electrode conductor may be a material such as a metal material or an electrically conductive polymer as long as the material has an electrically conductive property. 
     The positive electrode active material layer  11 B is provided on a portion of the positive electrode current collector  11 A on both sides of the positive electrode current collector  11 A. Accordingly, a portion of the positive electrode current collector  11 A on which the positive electrode active material layer  11 B is not provided is exposed without being covered with the positive electrode active material layer  11 B. 
     Specifically, the positive electrode current collector  11 A extends in a longitudinal direction (X-axis direction) as illustrated in  FIG. 7 , and includes a covered portion  11 AX and paired uncovered portions  11 AY. The covered portion  11 AX is a portion which are located at the middle portion of the positive electrode current collector  11 A in the longitudinal direction and on which the positive electrode active material layer  11 B is formed. The paired uncovered portions  11 AY are portions which are located at respective ends of the positive electrode current collector  11 A in the longitudinal direction and on which the positive electrode active material layer  11 B is not formed. Accordingly, the covered portion  11 AX is covered with the positive electrode active material layer  11 B, whereas the paired uncovered portions  11 AY are exposed without being covered with the positive electrode active material layer  11 B. In  FIG. 7 , the positive electrode active material layer  11 B is slightly shaded. 
     As illustrated in  FIG. 6 , the negative electrode  12  includes a negative electrode current collector  12 A, and two negative electrode active material layers  12 B provided on respective sides of the negative electrode current collector  12 A. However, the negative electrode active material layer  12 B may be provided only on one side of the negative electrode current collector  12 A. 
     The negative electrode current collector  12 A includes one or more of electrically conductive materials including, without limitation, copper, aluminum, nickel, and stainless steel. 
     The negative electrode active material layer  12 B includes one or more of negative electrode active materials into which lithium is inserted and from which lithium is extracted. The negative electrode active material layer  12 B may further include a material such as a negative electrode binder or a negative electrode conductor. Details of each of the negative electrode binder and the negative electrode conductor are similar to details of each of the positive electrode binder and the positive electrode conductor described above. 
     The negative electrode active material has a configuration similar to that of the active material  100  described above. However, the negative electrode active material may further include one or more other materials. Examples of the other materials include a carbon material and a metal-based material. Examples of the carbon material include graphitizable carbon, non-graphitizable carbon, and graphite. The metal-based material is a metal element or a metalloid element that is able to form an alloy with lithium. More specifically, the metal-based material is, for example, silicon or tin. The metal-based material may be a simple substance, an alloy, a compound, or a mixture of two or more thereof. The carbon-reduced silicate glass described above is excluded from the examples of the metal-based material described here. 
     Specific examples of the metal-based material include SiB 4 , SiB 6 , Mg 2 Si, Ni 2 Si, TiSi 2 , MoSi 2 , CoSi 2 , NiSi 2 , CaSi 2 , CrSi 2 , Cu 5 Si, FeSi 2 , MnSi 2 , NbSi 2 , TaSi 2 , VSi 2 , WSi 2 , ZnSi 2 , SiC, Si 3 N 4 , Si 2 N 2 O, SiO v  (0&lt;v≤2 or 0.2&lt;v&lt;1.4), LiSiO, SnO w  (0&lt;w≤2), SnSiO 3 , LiSnO, and Mg 2 Sn. 
     A method of forming the negative electrode active material layer  12 B is not limited to a particular method, and includes one or more of methods including, without limitation, a coating method, a vapor-phase method, a liquid-phase method, a thermal spraying method, and a firing (sintering) method. 
     The negative electrode active material layer  12 B is provided on the entire negative electrode current collector  12 A on both sides of the negative electrode current collector  12 A. Accordingly, the negative electrode current collector  12 A is entirely covered with the negative electrode active material layer  12 B without being exposed. 
     Specifically, as illustrated in  FIG. 7 , the negative electrode current collector  12 A extends in the longitudinal direction (X-axis direction), and the negative electrode active material layer  12 B includes paired non-opposed portions  12 BZ. The paired non-opposed portions  12 BZ are opposed to the paired uncovered portions  11 AY. That is, the paired non-opposed portions  12 BZ are not opposed to the positive electrode active material layer  11 B and thus do not contribute to charging and discharging reactions. In  FIG. 7 , the negative electrode active material layer  12 B is darkly shaded. 
     The negative electrode active material layer  12 B is entirely provided on each of both sides of the negative electrode current collector  12 A, whereas the positive electrode active material layer  11 B is provided on only a portion (the covered portion  11 AX) of each of both sides of the positive electrode current collector  11 A, in order to prevent lithium extracted from the positive electrode active material layer  11 B at the time of charging from precipitating on the surface of the negative electrode  12 . 
     In a case of examining whether the two physical property conditions relating to XPS and Raman spectroscopy described above are satisfied ex post facto, i.e., after the completion of the secondary battery or during use of the secondary battery, it is preferable to use the non-opposed portions  12 BZ as the negative electrode active material layer  12 B for collecting the negative electrode active material for analysis. A reason for this is that the non-opposed portions  12 BZ hardly contribute to the charging and discharging reactions, and the state (e.g., the composition and the physical property) of the negative electrode active material (carbon-reduced silicate glass) is thus easily maintained as the state at the time of forming the negative electrode  12  without being influenced by the charging and discharging reactions. Accordingly, it is possible to examine whether the two physical property conditions are satisfied in a highly stable and reproducible manner even in a case where the secondary battery has been used. 
     As illustrated in  FIG. 6 , the separator  13  is interposed between the positive electrode  11  and the negative electrode  12 . The separator  13  is an insulating porous film that allows lithium to pass therethrough while preventing contact (short circuiting) between the positive electrode  11  and the negative electrode  12 . The separator  13  may be a single-layer film including one porous film, or may be a multi-layer film including two or more porous films that are stacked on each other. The porous film includes one or more of polymer compounds including, without limitation, polytetrafluoroethylene, polypropylene, and polyethylene. 
     The electrolytic solution includes a solvent and an electrolyte salt. Only one solvent may be used, or two or more solvents may be used. In addition, only one electrolyte salt may be used, or two or more electrolyte salts may be used. 
     The solvent includes a non-aqueous solvent (an organic solvent), and the electrolytic solution including the non-aqueous solvent is a so-called non-aqueous electrolytic solution. 
     Examples of the non-aqueous solvent include esters and ethers. More specifically, examples of the non-aqueous solvent include a carbonic-acid-ester-based compound, a carboxylic-ester-based compound, and a lactone-based compound. 
     Examples of the carbonic-acid-ester-based compound include a cyclic carbonic acid ester and a chain carbonic acid ester. Examples of the cyclic carbonic acid ester include ethylene carbonate and propylene carbonate. Examples of the chain carbonic acid ester include dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. Examples of the carboxylic-ester-based compound include ethyl acetate, ethyl propionate, and ethyl trimethylacetate. Examples of the lactone-based compound include γ-butyrolactone and γ-valerolactone. Examples of the ethers other than the lactone-based compounds described above include 1,2-dimethoxyethane, tetrahydrofuran, 1,3-dioxolane, and 1,4-dioxane. 
     Examples of the non-aqueous solvent further include an unsaturated cyclic carbonic acid ester, a halogenated carbonic acid ester, a sulfonic acid ester, a phosphoric acid ester, an acid anhydride, a nitrile compound, and an isocyanate compound. A reason for this is that chemical stability of the electrolytic solution improves. 
     Specific examples of the unsaturated cyclic carbonic acid ester include vinylene carbonate, vinylethylene carbonate, and methylene ethylene carbonate. Examples of the halogenated carbonic acid ester include fluoroethylene carbonate and difluoroethylene carbonate. Examples of the sulfonic acid ester include 1,3-propane sultone. Examples of the phosphoric acid ester include trimethyl phosphate. Examples of the acid anhydride include a cyclic carboxylic acid anhydride, a cyclic disulfonic acid anhydride, and a cyclic carboxylic acid sulfonic acid anhydride. Examples of the cyclic carboxylic acid anhydride include succinic anhydride, glutaric anhydride, and maleic anhydride. Examples of the cyclic disulfonic acid anhydride include ethane disulfonic anhydride and propane disulfonic anhydride. Examples of the cyclic carboxylic acid sulfonic acid anhydride include sulfobenzoic anhydride, sulfopropionic anhydride, and sulfobutyric anhydride. Examples of the nitrile compound include acetonitrile and succinonitrile. Examples of the isocyanate compound include hexamethylene diisocyanate. 
     The electrolyte salt includes one or more of light metal salts including, without limitation, a lithium salt. Examples of the lithium salt include lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), lithium bis(fluorosulfonyl)imide (LiN(FSO 2 ) 2 ), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF 3 SO 2 ) 2 ), lithium tris(trifluoromethanesulfonyl)methide (LiC(CF 3 SO 2 ) 3 ), and lithium bis(oxalato)borate (LiB(C 2 O 4 ) 2 ). The content of the electrolyte salt is not limited to a particular content; however, the content is from 0.3 mol/kg to 3.0 mol/kg both inclusive with respect to the solvent. A reason for this is that high ion conductivity is obtainable. 
     The positive electrode lead  14  is coupled to the positive electrode  11  (the positive electrode current collector  11 A), and the negative electrode lead  15  is coupled to the negative electrode  12  (the negative electrode current collector  12 A). The positive electrode lead  14  and the negative electrode lead  15  are each extracted from inside the film  20  to outside in a similar direction. The positive electrode lead  14  includes one or more of electrically conductive materials including, without limitation, aluminum, and the negative electrode lead  15  includes one or more of electrically conductive materials including, without limitation, copper, nickel, and stainless steel. The positive electrode lead  14  and the negative electrode lead  15  each have a shape such as a thin plate shape or a meshed shape. 
     The secondary battery operates as follows. Upon charging the secondary battery, lithium is extracted from the positive electrode  11 , and the extracted lithium is inserted into the negative electrode  12  via the electrolytic solution. In contrast, upon discharging the secondary battery, lithium is extracted from the negative electrode  12 , and the extracted lithium is inserted into the positive electrode  11  via the electrolytic solution. Upon charging and discharging the secondary battery, lithium is inserted and extracted in an ionic state. 
     In a case of manufacturing the secondary battery, the positive electrode  11  and the negative electrode  12  are fabricated and the electrolytic solution is prepared, following which the secondary battery is assembled according to a procedure described below. 
     First, the positive electrode active material is mixed with, on an as-needed basis, a material such as the positive electrode binder or the positive electrode conductor to thereby obtain a positive electrode mixture. Thereafter, the positive electrode mixture is put into a solvent such as an organic solvent to thereby prepare a positive electrode mixture slurry in a paste state. Lastly, the positive electrode mixture slurry is applied on each of both sides of the positive electrode current collector  11 A to thereby form the positive electrode active material layer  11 B. Thereafter, the positive electrode active material layer  11 B may be compression-molded using a roll pressing machine. In this case, the positive electrode active material layer  11 B may be heated. The positive electrode active material layer  11 B may be compression-molded multiple times. The positive electrode active material layer  11 B is thus formed on each of both sides of the positive electrode current collector  11 A. As a result, the positive electrode  11  is fabricated. 
     The negative electrode active material layer  12 B is formed on each of both sides of the negative electrode current collector  12 A by a procedure similar to the fabrication procedure of the positive electrode  11  described above. Specifically, the negative electrode active material is mixed with, on an as-needed basis, a material such as the negative electrode binder or the negative electrode conductor to thereby obtain a negative electrode mixture. Thereafter, the negative electrode mixture is put into a solvent such as an organic solvent to thereby prepare a negative electrode mixture slurry in a paste state. Thereafter, the negative electrode mixture slurry is applied on each of both sides of the negative electrode current collector  12 A to thereby form the negative electrode active material layer  12 B. Thereafter, the negative electrode active material layer  12 B may be compression-molded. The negative electrode active material layer  12 B is thus formed on each of both sides of the negative electrode current collector  12 A. As a result, the negative electrode  12  is fabricated. 
     The electrolyte salt is put into the solvent such as an organic solvent. This allows the electrolyte salt to be dispersed or dissolved into the solvent. As a result, the electrolytic solution is prepared. 
     First, the positive electrode lead  14  is coupled to the positive electrode  11  (the positive electrode current collector  11 A) by a method such as a welding method, and the negative electrode lead  15  is coupled to the negative electrode  12  (the negative electrode current collector  12 A) by a method such as a welding method. Thereafter, the positive electrode  11  and the negative electrode  12  are stacked on each other with the separator  13  interposed therebetween, following which the stack of the positive electrode  11 , the negative electrode  12 , and the separator  13  is wound to thereby fabricate a wound body. Thereafter, the wound body is contained inside the depression  20 U and the film  20  is folded, following which outer edges of two sides of the film  20  (the fusion-bonding layer) are bonded to each other by a method such as a thermal fusion bonding method. Thus, the wound body is placed into the film  20  having the pouch shape. Lastly, the electrolytic solution is injected into the film  20  having the pouch shape, following which the outer edges of the remaining one side of the film  20  (the fusion-bonding layer) are bonded with each other using a method such as a thermal fusion bonding method. In this case, the sealing film  21  is disposed between the film  20  and the positive electrode lead  14 , and the sealing film  22  is disposed between the film  20  and the negative electrode lead  15 . The wound body is thereby impregnated with the electrolytic solution. Thus, the wound electrode body  10  is fabricated. Accordingly, the wound electrode body  10  is sealed in the film  20  having the pouch shape. As a result, the secondary battery of the laminated-film type is completed. 
     According to the secondary battery of the laminated-film type, the negative electrode active material included in the negative electrode  12  has a configuration similar to that of the active material  100 . This makes it easy for lithium to be sufficiently and stably inserted into or extracted from the negative electrode active material, and also continuously makes it easy for lithium to be inserted into or extracted from the negative electrode active material even if the charging and discharging reactions are repeated, for a reason similar to that described above in relation to the active material  100 . It is therefore possible to obtain a superior battery characteristic. 
     Other action and effects of the secondary battery of the laminated-film type and the manufacturing method thereof are similar to the other action and effects of the active material  100  and the manufacturing method thereof. 
     Next, a description is given of the secondary battery of a cylindrical type including a battery can  41  with stiffness as an outer package member for containing a battery device inside. 
       FIG. 8  illustrates a sectional configuration of the secondary battery of the cylindrical type. In the following description, reference will be made as necessary to the components of the secondary battery of the laminated-film type, which have been already described above, and  FIG. 6 . 
     As illustrated in  FIG. 8 , the secondary battery includes a pair of insulating plates  42  and  43  and a battery device of a wound type (a wound electrode body  30 ) that are provided inside the battery can  41  having a cylindrical shape. A positive electrode lead  34  and a negative electrode lead  35  are coupled to the wound electrode body  30 . 
     The battery can  41  has a hollow structure with a closed end and an open end, and includes one or more of metal materials including, without limitation, iron, aluminum, and an alloy thereof. The battery can  41  has a surface that may be plated with, for example, a metal material such as nickel. The insulating plates  42  and  43  are disposed in such a manner as to sandwich the wound electrode body  30  therebetween, and extend in a direction intersecting a wound peripheral surface of the wound electrode body  30 . 
     A battery cover  44 , a safety valve mechanism  45 , and a positive temperature coefficient device (PTC device)  46  are crimped at the open end of the battery can  41  by means of a gasket  47  having an insulating property, thereby sealing the open end of the battery can  41 . The battery cover  44  includes a material similar to a material included in the battery can  41 . The safety valve mechanism  45  and the PTC device  46  are each disposed on an inner side of the battery cover  44 . The safety valve mechanism  45  is electrically coupled to the battery cover  44  via the PTC device  46 . When an internal pressure of the battery can  41  reaches a certain level or higher as a result of causes including, without limitation, internal short circuiting and heating from outside, a disk plate  45 A inverts, thereby cutting off the electrical coupling between the battery cover  44  and the wound electrode body  30 . The PTC device  46  involves an increase in resistance in accordance with a rise in temperature, in order to prevent abnormal heat generation resulting from a large current. The gasket  47  may have a surface on which a material such as asphalt is applied, for example. 
     The wound electrode body  30  includes a positive electrode  31 , a negative electrode  32 , a separator  33 , and an electrolytic solution. The wound electrode body  30  has a structure in which the positive electrode  31  and the negative electrode  32  are stacked on each other with the separator  33  interposed therebetween, and the stack of the positive electrode  31 , the negative electrode  32 , and the separator  33  is wound. The positive electrode  31 , the negative electrode  32 , and the separator  33  are each impregnated with the electrolytic solution. The positive electrode lead  34  is coupled to the positive electrode  31  (a positive electrode current collector  31 A), and the negative electrode lead  35  is coupled to the negative electrode  32  (a negative electrode current collector  32 A). 
     A center pin  36  is disposed in a space provided at the winding center of the wound electrode body  30 . Note, however, that the center pin  36  may be omitted. The positive electrode lead  34  includes one or more of electrically conductive materials including, without limitation, aluminum. The positive electrode lead  34  is electrically coupled to the battery cover  44  via the safety valve mechanism  45 . The negative electrode lead  35  includes one or more of electrically conductive materials including, without limitation, copper, nickel, and stainless steel (SUS). The negative electrode lead  35  is electrically coupled to the battery can  41 . The positive electrode lead  34  and the negative electrode lead  35  each have a shape such as a thin plate shape or a meshed shape. 
     As illustrated in  FIG. 6 , the positive electrode  31  includes the positive electrode current collector  31 A and a positive electrode active material layer  31 B, and the negative electrode  32  includes the negative electrode current collector  32 A and a negative electrode active material layer  32 B. The positive electrode current collector  31 A, the positive electrode active material layer  31 B, the negative electrode current collector  32 A, and the negative electrode active material layer  32 B have configurations similar to the configurations of the positive electrode current collector  11 A, the positive electrode active material layer  11 B, the negative electrode current collector  12 A, and the negative electrode active material layer  12 B, respectively. The separator  33  has a configuration similar to the configuration of the separator  13 . 
     The secondary battery operates as follows. Upon charging the secondary battery, lithium is extracted from the positive electrode  31 , and the extracted lithium is inserted into the negative electrode  32  via the electrolytic solution. In contrast, upon discharging the secondary battery, lithium is extracted from the negative electrode  32 , and the extracted lithium is inserted into the positive electrode  31  via the electrolytic solution. Upon charging and discharging the secondary battery, lithium is inserted and extracted in an ionic state. 
     In a case of manufacturing the secondary battery, the positive electrode  31  and the negative electrode  32  are fabricated, following which the secondary battery is assembled according to a procedure described below. Note that the description of the procedure for preparing the electrolytic solution, which has been already given above, is omitted here. 
     The positive electrode  31  is fabricated through a procedure similar to the procedure for fabricating the positive electrode  11 , and the negative electrode  32  is fabricated through a procedure similar to the procedure for fabricating the negative electrode  12 . That is, in a case of fabricating the positive electrode  31 , the positive electrode active material layer  31 B is formed on each of both sides of the positive electrode current collector  31 A. In a case of fabricating the negative electrode  32 , the negative electrode active material layer  32 B is formed on each of both sides of the negative electrode current collector  32 A. 
     First, the positive electrode lead  34  is coupled to the positive electrode  31  (the positive electrode current collector  31 A) by a method such as a welding method, and the negative electrode lead  35  is coupled to the negative electrode  32  (the negative electrode current collector  32 A) by a method such as welding method. Thereafter, the positive electrode  31  and the negative electrode  32  are stacked on each other with the separator  33  interposed therebetween, following which the stack of the positive electrode  31 , the negative electrode  32 , and the separator  33  is wound to thereby fabricate a wound body. Thereafter, the center pin  36  is disposed in the space provided at the winding center of the wound body. 
     Thereafter, the wound body is interposed between the pair of insulating plates  42  and  43 , and the wound body in that state is contained in the battery can  41  together with the insulating plates  42  and  43 . In this case, the positive electrode lead  34  is coupled to the safety valve mechanism  45  by a method such as a welding method, and the negative electrode lead  35  is coupled to the battery can  41  by a method such as a welding method. Thereafter, the electrolytic solution is injected into the battery can  41  to thereby impregnate each of the positive electrode  31 , the negative electrode  32 , and the separator  33  with the electrolytic solution. As a result, the wound electrode body  30  is fabricated. 
     Lastly, the open end of the battery can  41  is crimped by means of the gasket  47  to thereby attach the battery cover  44 , the safety valve mechanism  45 , and the PTC device  46  to the open end of the battery can  41 . Thus, the wound electrode body  30  is sealed in the battery can  41 . As a result, the secondary battery of the cylindrical type is completed. 
     According to the secondary battery of the cylindrical type, the negative electrode active material included in the negative electrode  32  has a configuration similar to that of the active material  100 . This makes it possible for the secondary battery of the cylindrical type to provide a superior battery characteristic for a reason similar to that described above in relation to the secondary battery of the laminated-film type. 
     Other action and effects of the secondary battery of the cylindrical type are similar to the other action and effects of the secondary battery of the laminated-film type. 
     Next, a description is given of modifications of the active material and the secondary battery described above. The configuration of each of the active material and the secondary battery may be changed as appropriate as described below. However, any two or more of the modifications described in sequence below may be combined to each other. 
     [Modification 1] 
     The active material  100  illustrated in  FIG. 1  includes the center part  101  and the covering part  102 . However, the active material  100  may include only the center part  101  and may not include the covering part  102 . In this case, the covering part  102  may be removed after the active material  100  including the center part  101  and the covering part  102  is manufactured. Similar effects are obtainable also in this case as the electrode reactant is insertable into and extractable from the active material  100  (the center part  101 ). 
     However, to improve the electrically conductive property of the active material  100  as a whole, the active material  100  preferably includes both the center part  101  and the covering part  102  as described above. 
     [Modification 2] 
     The battery device of the wound type (the wound electrode body  10 ) is used in  FIGS. 5 and 6 . However, a battery device of a stacked type (a stacked electrode body  50 ) may be used instead of the wound electrode body  10 , as illustrated in  FIG. 9  corresponding to  FIG. 5 , and  FIG. 10  corresponding to  FIG. 6 . 
     The secondary battery of the laminated-film type illustrated in  FIGS. 9 and 10  has a configuration similar to that of the secondary battery of the laminated-film type illustrated in  FIGS. 5 and 6  except that the stacked electrode body  50  (the positive electrode  51 , the negative electrode  52 , and the separator  53 ), the positive electrode lead  54 , and the negative electrode lead  55  are included instead of the wound electrode body  10  (the positive electrode  11 , the negative electrode  12 , and the separator  13 ), the positive electrode lead  14 , and the negative electrode lead  15 . 
     The positive electrode  51 , the negative electrode  52 , the separator  53 , the positive electrode lead  54 , and the negative electrode lead  55  have configurations similar to the configurations of the positive electrode  11 , the negative electrode  12 , the separator  13 , the positive electrode lead  14 , and the negative electrode lead  15 , respectively, except the following points. 
     In the stacked electrode body  50 , the positive electrode  51  and the negative electrode  52  are alternately stacked on each other with the separator  53  interposed therebetween. The number of the positive electrodes  51 , the negative electrodes  52 , and the separators  53  to be stacked are not limited to a particular number. Here, the multiple positive electrodes  51  and the multiple negative electrodes  52  are alternately stacked on each other with the multiple separators  53  interposed therebetween. The positive electrodes  51 , the negative electrodes  52 , and the separators  53  are each impregnated with the electrolytic solution having the configuration described above. The positive electrode  51  includes a positive electrode current collector  51 A and a positive electrode active material layer  51 B. The negative electrode  52  includes a negative electrode current collector  52 A and a negative electrode active material layer  52 B. 
     As illustrated in  FIGS. 9 and 10 , the positive electrode current collector  51 A includes a projecting part  51 AT on which the positive electrode active material layer  51 B is not formed, and the negative electrode current collector  52 A includes a projecting part  52 AT on which the negative electrode active material layer  52 B is not formed. The projecting part  52 AT is disposed at a position not overlapping the projecting part  51 AT. Two or more projecting parts  51 AT are joined to each other to form a single joint part  51 Z having a lead shape. The two or more projecting parts  52 AT are joined to each other to form a single joint part  52 Z having a lead shape. The positive electrode lead  54  is coupled to the joint part  51 Z, and the negative electrode lead  55  is coupled to the joint part  52 Z. 
     A manufacturing method of the secondary battery of the laminated-film type illustrated in  FIGS. 9 and 10  is similar to the manufacturing method of the secondary battery of the laminated-film type illustrated in  FIGS. 5 and 6  except that the stacked electrode body  50  (the positive electrode lead  54  and the negative electrode lead  55 ) is fabricated instead of the wound electrode body  10  (the positive electrode lead  14  and the negative electrode lead  15 ). 
     In a case of fabricating the stacked electrode body  50 , first, the positive electrode  51  including the positive electrode active material layer  51 B formed on each of both sides of the positive electrode current collector  51 A (except the projecting part  51 AT) and the negative electrode  52  including the negative electrode active material layer  52 B formed on each of both sides of the negative electrode current collector  52 A (except the projecting part  52 AT) are fabricated, following which the multiple positive electrodes  51  and the multiple negative electrodes  52  are alternately stacked on each other with the plurality of separators  53  interposed therebetween to thereby form a stacked body. Thereafter, the two or more projecting parts  51 AT are joined to each other by a method such as a welding method to form the joint part  51 Z, and the two or more projecting parts  52 AT are joined to each other by a method such as a welding method to form the joint part  52 Z. Thereafter, the positive electrode lead  54  is coupled to the projecting part  51 AT by a method such as a welding method, and the negative electrode lead  55  is coupled to the projecting part  52 AT by a method such as a welding method. Lastly, the electrolytic solution is injected into the film  20  having the pouch shape in which the stacked body is contained, following which the film  20  is sealed. Thus, the stacked body is impregnated with the electrolytic solution. As a result, the stacked electrode body  50  is fabricated. 
     In a case where the stacked electrode body  50  is used, it is also possible to obtain effects similar to the effects obtained in a case where the wound electrode body  10  is used. Although not specifically illustrated here, the battery device of the stacked type (the stacked electrode body  50 ) may be applied to the secondary battery of the cylindrical type illustrated in  FIGS. 6 and 8 . 
     [Modification 3] 
     The number of the positive electrode leads  54  and the number of the negative electrode leads  55  in the secondary battery of the laminated-film type illustrated in  FIGS. 9 and 10  are each not limited to a particular number. That is, the number of the positive electrode leads  54  is not limited to one and may be two or greater. The number of the negative electrode lead  55  is not limited to one and may be two or greater. Similar effects are obtainable also in the case where the number of the positive electrode leads  54  and the number of the negative electrode leads  55  are changed. Although not specifically illustrated here, the number of the positive electrode leads  34  and the number of the negative electrode leads  35  may be changed in the secondary battery of the cylindrical type illustrated in  FIGS. 6 and 8 . 
     [Modification 4] 
     The separator  13  which is a porous film is used in the secondary battery of the laminated-film type illustrated in  FIGS. 5 and 6 . However, although not specifically illustrated here, a separator of a stacked type which includes a polymer compound layer may be used instead of the separator  13  which is the porous film. 
     Specifically, the separator of the stacked type includes a base layer which is the porous film described above, and a polymer compound layer provided on one or both sides of the base layer. A reason for this is that adherence of the separator to each of the positive electrode  11  and the negative electrode  12  is improved, which helps to prevent occurrence of a positional displacement of the wound electrode body  10 . This helps to prevent swelling of the secondary battery, for example, even when the decomposition reaction of the electrolytic solution occurs. The polymer compound layer includes a polymer compound such as polyvinylidene difluoride. A reason for this is that polyvinylidene difluoride has a high physical strength and is electrochemically stable. 
     The base layer, the polymer compound layer, or both may include one or more of a plurality of kinds of particles including, without limitation, inorganic particles and resin particles. A reason for this is that materials, for example, the particles dissipate heat when the secondary battery generates heat, thereby improving the thermal resistance and safety of the secondary battery. The inorganic particles are not limited to a particular kind. Examples of the inorganic particles include particles of aluminum oxide (alumina), aluminum nitride, boehmite, silicon oxide (silica), titanium oxide (titania), magnesium oxide (magnesia), and zirconium oxide (zirconia). 
     In a case of fabricating the separator of the stacked type, a precursor solution including, without limitation, a polymer compound and an organic solvent is prepared, following which the precursor solution is applied on one or both sides of the base layer. 
     Similar effects are obtainable also in the case where the separator of the stacked type is used, as lithium is movable between the positive electrode  11  and the negative electrode  12 . Note that the separator of the stacked type may be applied to the secondary battery of the cylindrical type illustrated in  FIGS. 5 and 6 . 
     [Modification 5] 
     In the secondary battery of the laminated-film type illustrated in  FIGS. 5 and 6 , the electrolytic solution, which is a liquid electrolyte, is used. However, although not specifically illustrated here, an electrolyte layer which is a gel electrolyte may be used instead of the electrolytic solution. 
     In the wound electrode body  10  including the electrolyte layer, the positive electrode  11  and the negative electrode  12  are stacked on each other with the separator  13  and the electrolyte layer interposed therebetween, following which the stack of the positive electrode  11 , the negative electrode  12 , the separator  13 , and the electrolyte layer is wound. The electrolyte layer is interposed between the positive electrode  11  and the separator  13 , and between the negative electrode  12  and the separator  13 . 
     Specifically, the electrolyte layer includes a polymer compound together with the electrolytic solution. The electrolytic solution is held by the polymer compound in the electrolyte layer. The configuration of the electrolytic solution is as described above. The polymer compound includes, for example, polyvinylidene difluoride. In a case of forming the electrolyte layer, a precursor solution that includes materials including, without limitation, the electrolytic solution, the polymer compound, and an organic solvent is prepared, following which the precursor solution is applied on each of both sides of the positive electrode  11  and each of both sides of the negative electrode  12 . 
     Similar effects are obtainable also in the case where the electrolyte layer is used, as lithium is movable between the positive electrode  11  and the negative electrode  12  via the electrolyte layer. Note that the electrolyte layer may be applied to the secondary battery of the cylindrical type illustrated in  FIGS. 6 and 8 . 
     Next, a description is given of applications (application examples) of the above-described secondary battery. 
     The applications of the secondary battery are not particularly limited as long as they are, for example, machines, equipment, instruments, apparatuses, or systems (an assembly of a plurality of pieces of equipment, for example) in which the secondary battery is usable mainly as a driving power source, an electric power storage source for electric power accumulation, or any other source. The secondary battery used as a power source may serve as a main power source or an auxiliary power source. The main power source is preferentially used regardless of the presence of any other power source. The auxiliary power source may be used in place of the main power source, or may be switched from the main power source on an as-needed basis. In a case where the secondary battery is used as the auxiliary power source, the kind of the main power source is not limited to the secondary battery. 
     Specific examples of the applications of the secondary battery include: electronic equipment including portable electronic equipment; portable life appliances; apparatuses for data storage; electric power tools; battery packs to be mounted as detachable power sources on, for example, laptop personal computers; medical electronic equipment; electric vehicles; and electric power storage systems. Examples of the electronic equipment include video cameras, digital still cameras, mobile phones, laptop personal computers, cordless phones, headphone stereos, portable radios, portable televisions, and portable information terminals. Examples of the portable life appliances include electric shavers. Examples of the apparatuses for data storage include backup power sources and memory cards. Examples of the electric power tools include electric drills and electric saws. Examples of the medical electronic equipment include pacemakers and hearing aids. Examples of the electric vehicles include electric automobiles including hybrid automobiles. Examples of the electric power storage systems include home battery systems for accumulation of electric power for a situation such as emergency. Note that the secondary battery may have a battery structure of the above-described laminated-film type, a cylindrical type, or any other type. Further, multiple secondary batteries may be used, for example, as a battery pack or a battery module. 
     In particular, the battery pack and the battery module are each effectively applied to relatively large-sized equipment, etc., including an electric vehicle, an electric power storage system, and an electric power tool. The battery pack, as will be described later, may include a single battery, or may include an assembled battery. The electric vehicle is a vehicle that operates (travels) using the secondary battery as a driving power source, and may be an automobile that is additionally provided with a driving source other than the secondary battery as described above, such as a hybrid automobile. The electric power storage system is a system that uses the secondary battery as an electric power storage source. An electric power storage system for home use accumulates electric power in the secondary battery which is an electric power storage source, and the accumulated electric power may thus be utilized for using, for example, home appliances. 
     Some application examples of the secondary battery will now be described in detail. The configurations of the application examples described below are merely examples, and are appropriately modifiable. The secondary battery used in the following application examples is not limited to a particular type, and may be the laminated-film type or the cylindrical type. 
       FIG. 11  illustrates a block configuration of a battery pack including a single battery. The battery pack described here is a simple battery pack (a so-called soft pack) including one secondary battery, and is to be mounted on, for example, electronic equipment typified by a smartphone. 
     As illustrated in  FIG. 11 , the battery pack includes an electric power source  61  and a circuit board  62 . The circuit board  62  is coupled to the electric power source  61 , and includes a positive electrode terminal  63 , a negative electrode terminal  64 , and a temperature detection terminal (a so-called T terminal)  65 . 
     The electric power source  61  includes one secondary battery. The secondary battery has a positive electrode lead coupled to the positive electrode terminal  63  and a negative electrode lead coupled to the negative electrode terminal  64 . The electric power source  61  is couplable to outside via the positive electrode terminal  63  and the negative electrode terminal  64 , and is thus chargeable and dischargeable via the positive electrode terminal  63  and the negative electrode terminal  64 . The circuit board  62  includes a controller  66 , a switch  67 , a PTC device  68 , and a temperature detector  69 . However, the PTC device  68  may be omitted. 
     The controller  66  includes, for example, a central processing unit (CPU) and a memory, and controls an overall operation of the battery pack. The controller  66  detects and controls a use state of the electric power source  61  on an as-needed basis. 
     If a battery voltage of the electric power source  61  (the secondary battery) reaches an overcharge detection voltage or an overdischarge detection voltage, the controller  66  turns off the switch  67 . This prevents a charging current from flowing into a current path of the electric power source  61 . In addition, if a large current flows upon charging or discharging, the controller  66  turns off the switch  67  to block the charging current. The overcharge detection voltage and the overdischarge detection voltage are not particularly limited. For example, the overcharge detection voltage is 4.2 V±0.05 V and the overdischarge detection voltage is 2.4 V±0.1 V. 
     The switch  67  includes, for example, a charge control switch, a discharge control switch, a charging diode, and a discharging diode. The switch  67  performs switching between coupling and decoupling between the electric power source  61  and external equipment in accordance with an instruction from the controller  66 . The switch  67  includes, for example, a metal-oxide-semiconductor field-effect transistor (MOSFET) including a metal-oxide semiconductor. The charging and discharging currents are detected on the basis of an ON-resistance of the switch  67 . 
     The temperature detector  69  includes a temperature detection device such as a thermistor. The temperature detector  69  measures a temperature of the electric power source  61  using the temperature detection terminal  65 , and outputs a result of the temperature measurement to the controller  66 . The result of the temperature measurement to be obtained by the temperature detector  69  is used, for example, in a case where the controller  66  performs charge/discharge control upon abnormal heat generation or in a case where the controller  66  performs a correction process upon calculating a remaining capacity. 
       FIG. 12  illustrates a block configuration of a battery pack including an assembled battery. In the following description, reference will be made as necessary to the components of the battery pack including the single battery ( FIG. 11 ). 
     As illustrated in  FIG. 12 , the battery pack includes a positive electrode terminal  81  and a negative electrode terminal  82 . Specifically, the battery pack includes, inside a housing  70 , the following components: a controller  71 , an electric power source  72 , a switch  73 , a current measurement unit  74 , a temperature detector  75 , a voltage detector  76 , a switch controller  77 , a memory  78 , a temperature detection device  79 , and a current detection resistor  80 . 
     The electric power source  72  includes an assembled battery in which two or more secondary batteries are coupled to each other, and a type of the coupling of the two or more secondary batteries is not particularly limited. Accordingly, the coupling scheme may be in series, in parallel, or of a mixed type of both. For example, the electric power source  72  includes six secondary batteries coupled to each other in two parallel and three series. 
     Configurations of the controller  71 , the switch  73 , the temperature detector  75 , and the temperature detection device  79  are similar to those of the controller  66 , the switch  67 , and the temperature detector  69  (the temperature detection device). The current measurement unit  74  measures a current using the current detection resistor  80 , and outputs a result of the measurement of the current to the controller  71 . The voltage detector  76  measures a battery voltage of the electric power source  72  (the secondary battery) and provides the controller  71  with a result of the measurement of the voltage that has been subjected to analog-to-digital conversion. 
     The switch controller  77  controls an operation of the switch  73  in response to signals supplied by the current measurement unit  74  and the voltage detector  76 . If a battery voltage reaches an overcharge detection voltage or an overdischarge detection voltage, the switch controller  77  turns off the switch  73  (the charge control switch). This prevents a charging current from flowing into a current path of the electric power source  72 . This enables the electric power source  72  to perform only discharging through the discharging diode, or only charging through the charging diode. In addition, if a large current flows upon charging or discharging, the switch controller  77  blocks the charging current or the discharging current. 
     The switch controller  77  may be omitted and the controller  71  may thus also serve as the switch controller  77 . The overcharge detection voltage and the overdischarge detection voltage are not particularly limited, and are similar to those described above in relation to the battery pack including the single battery. 
     The memory  78  includes, for example, an electrically erasable programmable read-only memory (EEPROM) which is a non-volatile memory, and the memory  78  stores, for example, a numeric value calculated by the controller  71  and data (e.g., an initial internal resistance, a full charge capacity, and a remaining capacity) of the secondary battery measured in the manufacturing process. 
     The positive electrode terminal  81  and the negative electrode terminal  82  are terminals coupled to, for example, external equipment that operates using the battery pack, such as a laptop personal computer, or external equipment that is used to charge the battery pack, such as a charger. The electric power source  72  (the secondary battery) is chargeable and dischargeable through the positive electrode terminal  81  and the negative electrode terminal  82 . 
       FIG. 13  illustrates a block configuration of a hybrid automobile which is an example of the electric vehicle. As illustrated in  FIG. 13 , the electric vehicle includes, inside a housing  83 , the following components: a controller  84 , an engine  85 , an electric power source  86 , a motor  87 , a differential  88 , an electric generator  89 , a transmission  90 , a clutch  91 , inverters  92  and  93 , and sensors  94 . The electric vehicle also includes a front wheel drive shaft  95 , a pair of front wheels  96 , a rear wheel drive shaft  97 , and a pair of rear wheels  98 . The front wheel drive shaft  95  and the pair of front wheels  96  are coupled to the differential  88  and the transmission  90 . 
     The electric vehicle is configured to travel by using one of the engine  85  and the motor  87  as a driving source. The engine  85  is a major power source, such as a gasoline engine. In a case where the engine  85  is used as a power source, a driving force (a rotational force) of the engine  85  is transmitted to the front wheels  96  and the rear wheels  98  via the differential  88 , the transmission  90 , and the clutch  91 , which are driving parts. Note that the rotational force of the engine  85  is transmitted to the electric generator  89 , and the electric generator  89  thus generates alternating-current power by utilizing the rotational force. In addition, the alternating-current power is converted into direct-current power via the inverter  93 , and the direct-current power is thus accumulated in the electric power source  86 . In contrast, in a case where the motor  87  which is a converter is used as a power source, electric power (direct-current power) supplied from the electric power source  86  is converted into alternating-current power via the inverter  92 . Thus, the motor  87  is driven by utilizing the alternating-current power. A driving force (a rotational force) converted from the electric power by the motor  87  is transmitted to the front wheels  96  and the rear wheels  98  via the differential  88 , the transmission  90 , and the clutch  91 , which are the driving parts. 
     When the electric vehicle is decelerated by means of a brake mechanism, a resistance force at the time of the deceleration is transmitted as a rotational force to the motor  87 . Thus, the motor  87  may generate alternating-current power by utilizing the rotational force. The alternating-current power is converted into direct-current power via the inverter  92 , and direct-current regenerative power is accumulated in the electric power source  86 . 
     The controller  84  includes, for example, a CPU, and controls an overall operation of the electric vehicle. The electric power source  86  includes one or more secondary batteries and is coupled to an external electric power source. In this case, the electric power source  86  may be supplied with electric power from the external electric power source and thereby accumulate the electric power. The sensors  94  are used to control the number of revolutions of the engine  85  and to control an angle of a throttle valve (a throttle angle). The sensors  94  include one or more of sensors including, without limitation, a speed sensor, an acceleration sensor, and an engine speed sensor. 
     The case where the electric vehicle is a hybrid automobile has been described as an example; however, the electric vehicle may be a vehicle that operates using only the electric power source  86  and the motor  87  and not using the engine  85 , such as an electric automobile. 
     Although not specifically illustrated here, other application examples are also conceivable as application examples of the secondary battery. 
     Specifically, the secondary battery is applicable to an electric power storage system. The electric power storage system includes, inside a building such as a residential house or a commercial building, the following components: a controller, an electric power source including one or more secondary batteries, a smart meter, and a power hub. 
     The electric power source is coupled to electric equipment such as a refrigerator installed inside the building, and is couplable to an electric vehicle such as a hybrid automobile stopped outside the building. Further, the electric power source is coupled, via the power hub, to a home power generator such as a solar power generator installed at the building, and is also coupled, via the smart meter and the power hub, to a centralized power system of an external power station such as a thermal power station. 
     Alternatively, the secondary battery is applicable to an electric power tool such as an electric drill or an electric saw. The electric power tool includes, inside a housing to which a movable part such as a drilling part or a saw blade part is attached, the following components: a controller, and an electric power source including one or more secondary batteries. 
     EXAMPLES 
     A description is given of Examples of the technology of the present disclosure according to an embodiment. 
     Experiment Examples 1 to 16 
       FIG. 14  illustrates a sectional configuration of a secondary battery of a coin type for testing. In the following, a negative electrode active material was manufactured, following which the secondary battery of the coin type was fabricated using the negative electrode active material. Thereafter, a battery characteristic of the secondary battery was evaluated. 
     As illustrated in  FIG. 14 , the secondary battery of the coin type includes a test electrode  111  inside an outer package cup  114 , and includes a counter electrode  113  inside an outer package can  112 . The test electrode  111  and the counter electrode  113  are stacked on each other with the separator  115  interposed therebetween, and the outer package can  112  and the outer package cup  114  are crimped to each other by means of a gasket  116 . The test electrode  111 , the counter electrode  113 , and the separator  115  are each impregnated with an electrolytic solution. 
     [Manufacture of Negative Electrode Active Material] 
     First, silicate glass was prepared as a raw material. The kinds of constituent elements (excluding oxygen and carbon) and the content (at %) of each of the constituent elements in carbon-reduced silicate glass synthesized with the silicate glass are as listed in Tables 1 and 2. 
     As described above, the content of each of the constituent elements is measured by analyzing the carbon-reduced silicate glass using SEM-EDX. In the analysis using the SEM-EDX, detection sensitivity to lithium is markedly low, and therefore the content of lithium is small enough to hardly affect the content of the second element. Thus, the content of lithium is not listed in Tables 1 and 2. 
     
       
         
           
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 Constituent element/Content (at %) 
               
            
           
           
               
               
               
            
               
                   
                 First 
                   
               
            
           
           
               
               
               
               
               
            
               
                 Experiment 
                   
                 element 
                 Second element 
                 Third element 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 example 
                 Si 
                 B 
                 P 
                 Na 
                 K 
                 Sc 
                 Ti 
                 Zr 
                 Ce 
                 Al 
                 S 
                 Cl 
                 Zn 
                 Bi 
                 Mg 
                 Ca 
                 Sr 
                 Ba 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 1 
                 98 
                 — 
                 1 
                 1 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 2 
                 72 
                 15 
                 — 
                 1 
                 4 
                 — 
                 — 
                 — 
                 — 
                 7 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 1 
               
               
                 3 
                 55 
                 10 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 3 
                 — 
                 20 
                 — 
                 12  
                 — 
               
               
                 4 
                 80 
                 15 
                 — 
                 — 
                 3 
                 — 
                 — 
                 — 
                 — 
                 2 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 5 
                 60 
                 — 
                 — 
                 1 
                 — 
                 1 
                 1 
                 — 
                 — 
                 5 
                 — 
                 — 
                 1 
                 — 
                  2 
                 4 
                 10  
                 15  
               
               
                 6 
                 60 
                 5 
                 1 
                 3 
                 — 
                 — 
                 — 
                 — 
                 — 
                 3 
                 — 
                 — 
                 3 
                 — 
                 — 
                 — 
                 — 
                 25  
               
               
                 7 
                 60 
                 5 
                 1 
                 1 
                 3 
                 — 
                 — 
                 — 
                 — 
                 20  
                 — 
                 — 
                 10  
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 8 
                 65 
                 10 
                 — 
                 1 
                 — 
                 — 
                 — 
                 — 
                 — 
                 1 
                 — 
                 — 
                 — 
                 — 
                 10 
                 7 
                 2 
                 4 
               
               
                 9 
                 70 
                 25 
                 — 
                 1 
                 2 
                 — 
                 — 
                 1 
                 — 
                 1 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 10 
                 15 
                 20 
                 1 
                 2 
                 — 
                 — 
                 4 
                 6 
                 1 
                 5 
                 — 
                 — 
                 — 
                 45 
                 — 
                 — 
                 1 
                 — 
               
               
                 11 
                 37 
                 — 
                 1 
                 10  
                 22  
                 — 
                 30  
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 12 
                 32 
                 — 
                 2 
                 25  
                 13  
                 — 
                 16  
                 — 
                 — 
                 2 
                 — 
                 — 
                 1 
                 — 
                 — 
                 7 
                 2 
                 — 
               
               
                 13 
                 75 
                 2 
                 — 
                 6 
                 5 
                 — 
                 — 
                 — 
                 — 
                 4 
                 1 
                 1 
                 — 
                 — 
                 — 
                 — 
                 — 
                 6 
               
               
                 16 
                 100 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 2 
               
             
            
               
                   
                   
               
               
                   
                 Raman 
                   
                 Capacity 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 Constituent element/Content (at %) 
                 XPS spectrum (Si2p) 
                 spectrum 
                 Charge 
                 Discharge 
                 retention 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Experiment 
                   
                 First 
                 Second 
                 Third 
                 Apex 
                   
                 Half-width 
                   
                 Apex 
                 capacity 
                 capacity 
                 rate 
               
               
                 example 
                 Si 
                 element 
                 element 
                 element 
                 (eV) 
                 Shoulder 
                 (eV) 
                 S2/S1 
                 (cm −1 ) 
                 (mAh/g) 
                 (mAh/g) 
                 (%) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 1 
                 98 
                 1 
                 1 
                 — 
                 103.2 
                 Observed 
                 4.0 
                 0.97 
                 457 
                 1020 
                 500 
                 81 
               
               
                 2 
                 72 
                 15 
                 12 
                 1 
                 103.1 
                 Observed 
                 4.7 
                 0.94 
                 457 
                 1219 
                 620 
                 90 
               
               
                 3 
                 55 
                 10 
                 3 
                 32 
                 102.5 
                 Not 
                 2.9 
                 1.82 
                 449 
                 272 
                 130 
                 87 
               
               
                   
                   
                   
                   
                   
                   
                 observed 
               
               
                 4 
                 80 
                 15 
                 5 
                 — 
                 103.8 
                 Observed 
                 4.3 
                 0.85 
                 462 
                 1271 
                 640 
                 91 
               
               
                 5 
                 60 
                 — 
                 9 
                 31 
                 102.3 
                 Not 
                 2.6 
                 1.72 
                 451 
                 242 
                 106 
                 83 
               
               
                   
                   
                   
                   
                   
                   
                 observed 
               
               
                 6 
                 60 
                 6 
                 9 
                 25 
                 102.4 
                 Not 
                 2.9 
                 1.52 
                 450 
                 224 
                 103 
                 86 
               
               
                   
                   
                   
                   
                   
                   
                 observed 
               
               
                 7 
                 60 
                 6 
                 34 
                 — 
                 103.2 
                 Observed 
                 4.3 
                 0.97 
                 455 
                 1016 
                 486 
                 95 
               
               
                 8 
                 65 
                 10 
                 2 
                 23 
                 103.3 
                 Not 
                 2.7 
                 0.71 
                 450 
                 281 
                 82 
                 78 
               
               
                   
                   
                   
                   
                   
                   
                 observed 
               
               
                 9 
                 70 
                 25 
                 5 
                 — 
                 103.5 
                 Observed 
                 4.8 
                 0.88 
                 450 
                 1280 
                 644 
                 91 
               
               
                 10 
                 15 
                 21 
                 63 
                 1 
                 101.3 
                 Not 
                 3.8 
                 1.69 
                 442 
                 418 
                 201 
                 21 
               
               
                   
                   
                   
                   
                   
                   
                 observed 
               
               
                 11 
                 37 
                 1 
                 62 
                 — 
                 102.9 
                 Not 
                 2.5 
                 0.32 
                 449 
                 875 
                 421 
                 61 
               
               
                   
                   
                   
                   
                   
                   
                 observed 
               
               
                 12 
                 32 
                 2 
                 57 
                 9 
                 103.0 
                 Not 
                 4.3 
                 0.46 
                 445 
                 482 
                 238 
                 84 
               
               
                   
                   
                   
                   
                   
                   
                 observed 
               
               
                 13 
                 75 
                 2 
                 17 
                 6 
                 102.9 
                 Observed 
                 5.2 
                 1.55 
                 454 
                 1173 
                 792 
                 93 
               
               
                 14 
                 72 
                 15 
                 12 
                 1 
                 103.2 
                 Observed 
                 4.6 
                 0.95 
                 458 
                 1262 
                 610 
                 89 
               
               
                 15 
                 72 
                 15 
                 12 
                 1 
                 103.1 
                 Observed 
                 4.7 
                 0.94 
                 457 
                 1240 
                 600 
                 91 
               
               
                 16 
                 100 
                 — 
                 — 
                 — 
                 103.0 
                 Observed 
                 5.1 
                 1.61 
                 475 
                 2240 
                 1648 
                 72 
               
               
                   
               
               
                 * Carbon source: Carbon black (Experiment examples 1 to 13), Polyimide (Experiment example 14), Sucrose (Experiment example 15) 
               
            
           
         
       
     
     Thereafter, the silicate glass was mixed with a carbon source (carbon black, which is a carbon material) to thereby obtain a mixture. In this case, used as the carbon sources were carbon black (Experiment examples 1 to 13), which is a carbon material, and polyimide (Experiment example 14) and sucrose (Experiment example 15), which are carbonizable organic substances. In addition, the mixing ratio (weight ratio) of the silicate glass to the carbon source was 5:1. 
     Thereafter, a slurry was prepared by adding a binder solution (N-methyl-2-pyrrolidone solution of polyimide, solid content=18.6%) to the mixture and stirring the mixture at a (rotation speed of 2000 rpm for a stirring time of 3 minutes using a stirring device (rotating and revolving mixer, Awatori Rentaro, manufactured by THINKY Corporation). In this case, the amount of the binder solution added to the mixture was 10 weight percent (solid content ratio). 
     Thereafter, the slurry was dried in an oven at a temperature of 80° C. to obtain a dried product, following which the dried product was pulverized into pulverized flakes. 
     Thereafter, the pulverized flakes were put into an alumina boat, following which the pulverized flakes were heated at a heating temperature of 950° C. for a heating time of 10 hours in an argon atmosphere in a vacuum gas displacement furnace. In this case, the silicate glass was reduced in the presence of the carbon source (carbon reduction treatment) to synthesize the carbon-reduced silicate glass. As a result, a center part including the carbon-reduced silicate glass was formed. Further, a substance such as a decomposition product of the carbon source (organic substance decomposition carbon) was deposited on the surface of the center part, forming a covering part. Thus, a negative electrode active material in a flake state was obtained which included the center part and the covering part. 
     Lastly, the negative electrode active material in the flake state was pulverized in a mortar into the negative electrode active material in a powder state, following which the negative electrode active material in the powder state was sieved using a mesh (53 μm). 
     When the state of the negative electrode active material was observed using a scanning electron microscope (SEM), the negative electrode active material remained in the powder state without being melted, even though the pulverized frames were heated at a temperature (=950° C.) higher than the glass transition temperature (=about 700° C.) of the silicate glass in the carbon reduction treatment. The reason for this is considered to be that the center part including the carbon-reduced silicate glass was covered with the covering part. 
     When the negative electrode active material was analyzed using X-ray diffraction analysis (XRD), a broad halo pattern was detected within the range of 20 from 20° to 25° both inclusive, despite the carbon reduction treatment of the silicate glass. Accordingly, it was confirmed that the negative electrode active material (carbon-reduced silicate glass) had not been crystallized. 
     When the negative electrode active material was analyzed using Raman spectroscopy, distinct G and D bands were detected in the Raman spectrum. Accordingly, it was confirmed that the center part was covered with the covering part including carbon as a constituent element. 
     The results of analysis of the negative electrode active material using XPS are as listed in Table 2. In this case, the position of the apex XAT (binding energy: eV), the presence or absence of the shoulder XAS, the half-width of the peak XA (eV), and the area ratio S2/S1 were examined on the basis of the result of analysis of the negative electrode active material (XPS spectra of Si2p illustrated in  FIG. 2 ) in accordance with the procedure described above. 
     The results of analysis of the negative electrode active material using Raman spectroscopy are as listed in Table 2. In this case, the position of the apex RAT (Raman shift: cm −1 ) was examined on the basis of the result of analysis of the negative electrode active material (Raman spectra illustrated in  FIG. 3 ) in accordance with the procedure described above. 
     The test electrode  111  was fabricated and an electrolytic solution was prepared, following which the secondary battery of the coin type was assembled in accordance with the following procedure. 
     Here, a negative electrode was fabricated as the test electrode  111 . First, the negative electrode active material described above, a negative electrode binder precursor (polyamic acid solution (polyimide precursor), U-varnish-A, manufactured by Ube Industries, Ltd.), and a negative electrode conductor (carbon powder KS6 manufactured by TIMCAL Co., Ltd., and acetylene black, Denca black (registered trademark) manufactured by Denka Co., Ltd.) were mixed to thereby obtain a negative electrode mixture. In this case, the mixing ratio (mass ratio) among the negative electrode active material, the negative electrode binder precursor, and two kinds of negative electrode conductors was 7:0.5:1:0.25. Thereafter, the negative electrode mixture was put into an organic solvent (N-methyl-2-pyrrolidone), following which the organic solvent was stirred to thereby prepare a negative electrode mixture slurry in a paste state. 
     Thereafter, the negative electrode mixture slurry was applied to one side of a negative electrode current collector (copper foil, thickness=15 μm) using a coating apparatus, following which the negative electrode mixture slurry was heated and dried (heating temperature=425° C.) in a vacuum sintering furnace. A negative electrode binder (polyimide) was thereby synthesized, forming a negative electrode active material layer including the negative electrode active material, the negative electrode binder, and the negative electrode conductor. Lastly, the negative electrode current collector on which the negative electrode active material layer had been formed was punched into a disk shape (outer diameter=15 mm), and the punched negative electrode active material layer was compression-molded using a roll pressing machine. As a result, the test electrode  111  which is the negative electrode was fabricated. 
     Note that, a test electrode  111  for comparison was prepared (Experiment example 16) by a similar procedure except that another negative electrode active material (silicon monoxide (SiO)) was used instead of the negative electrode active material described above. 
     As the counter electrode  113 , a lithium metal plate was used. In this case, lithium metal foil was punched into a disk shape (outer diameter=15 mm). 
     An electrolyte salt (lithium hexafluoride phosphate) was added to a solvent (ethylene carbonate, fluoroethylene carbonate, and dimethyl carbonate), following which the solvent was stirred. In this case, the mixing ratio (mass ratio) of the solvent among ethylene carbonate, fluoroethylene carbonate, and dimethyl carbonate was 40:10:50. The content of the electrolyte salt was 1 mol/kg with respect to the solvent. 
     First, the test electrode  111  was housed inside the outer package cup  114 , and the counter electrode  113  was housed inside the outer package can  112 . Thereafter, the test electrode  111  housed inside the outer package cup  114  and the counter electrode  113  housed inside the outer package can  112  were stacked on each other with the separator  115  (microporous polyethylene film, thickness=5 μm), impregnated with the electrolytic solution, interposed therebetween. Thus, the test electrode  111  and the counter electrode  113  were each impregnated with a portion of the electrolytic solution contained in the separator  115 . Lastly, the outer package can  112  and the outer package cup  114  were crimped to each other by means of the gasket  116  in a state where the test electrode  111  and the counter electrode  113  were stacked on each other with the separator  115  interposed therebetween. Accordingly, the test electrode  111 , the counter electrode  113 , the separator  115 , and the electrolytic solution were sealed by the outer package can  112  and the outer package cup  114 . As a result, the secondary battery of the coin type was completed. 
     Evaluation of a battery characteristic (a charging characteristic, a discharging characteristic, and a cyclability characteristic) of the secondary batteries revealed the results listed in Table 2. 
     In a case of examining the battery characteristic, first, the secondary battery was charged and discharged for one cycle in an ambient temperature environment (temperature=23° C.) to stabilize a state of the secondary battery. Thereafter, the secondary battery was charged in the same environment, and a second-cycle charge capacity (mAh) was measured. A charge capacity per unit weight (mAh/g) was thereby calculated on the basis of the weight (g) of the negative electrode active material in order to evaluate the charge characteristic. 
     Thereafter, the secondary battery in a charged state was discharged in the same environment, and a second-cycle discharge capacity (mAh) was measured. A discharge capacity per unit weight (mAh/g) was thereby calculated on the basis of the weight (g) of the negative electrode active material in order to evaluate the discharge characteristic. 
     Thereafter, the secondary battery was repeatedly charged and discharged in the same environment until the total number of cycles of charging and discharging reached 100 cycles, and a 100th-cycle discharge capacity (mAh) was measured. Lastly, to evaluate the cyclability characteristic, a capacity retention rate was calculated as follows: capacity retention rate (%)=(100th-cycle discharge capacity (mAh)/second-cycle discharge capacity (mAh))×100. 
     Upon charging, the secondary battery was charged with a constant current of 0.1 C until the voltage reached 4.20 V, following which the secondary battery was charged with a constant voltage of 4.20 V until the current reached 0.05 C. Upon discharging, the secondary battery was discharged with a constant current of 0.1 C until the voltage reached 2.50 V. “0.1 C” refers to a value of a current that causes a battery capacity (theoretical capacity) to be completely discharged in 10 hours, and “0.05 C” refers to a value of a current that causes the battery capacity described above to be completely discharged in 20 hours. 
     As apparent from Tables 1 and 2, the battery characteristic of the secondary battery greatly varied depending on the composition and the physical property of the negative electrode active material. 
     Specifically, in a case where the composition of the negative electrode active material satisfied the following constitutional conditions and where the results of analysis of the negative electrode active material using XPS and Raman spectroscopy (the XPS spectrum of Si2p and the Raman spectrum) satisfied the following physical property conditions (e.g., Experiment example 1), a high capacity retention rate was obtained while a high charge capacity and a high discharge capacity were secured regardless of the kind of the carbon source, as compared with a case where the constitutional conditions and the physical property conditions were not satisfied (e.g., Experiment example 3). 
     The constitutional conditions regarding the composition of the negative electrode active material are as follows: The negative electrode active material includes silicon, oxygen, the first element, the second element, and the third element as constituent elements. The content of silicon with respect to all of the constituent elements excluding oxygen and carbon is 60 at % or greater and 98 at % or less. The content of the first element with respect to all of the constituent elements excluding oxygen and carbon is 1 at % or greater and 25 at % or less. The content of the second element with respect to all of the constituent elements excluding oxygen and carbon is 1 at % or greater and 34 at % or less. The content of the third element with respect to all of the constituent elements excluding oxygen and carbon is 0 at % or greater and 6 at % or less. 
     The physical property conditions regarding the results of analysis of the negative electrode active material are as follows: In the XPS spectrum (Si2p) measured using XPS, the peak XA is detected which has the apex XAT (at a position within a range of the binding energy from 102 eV to 105 eV both inclusive) and the shoulder XAS illustrated in  FIG. 2 . In addition, in the Raman spectrum measured using Raman spectroscopy, the peak RA is detected which has the apex RAT (at a position within a range of the Raman shift from 435 cm −1  to 465 cm −1  both inclusive) illustrated in  FIG. 3 . 
     In particular, in a case where the above-described constitutional conditions regarding the composition of the negative electrode active material were satisfied and where the above-described physical property conditions regarding the results of analysis of the negative electrode active material were satisfied, a high capacity retention rate was obtained together with a sufficient charge capacity and a sufficient discharge capacity if the half-width was 4.0 eV or greater or the area ratio S2/S1 was 0.85 or greater. 
     In the case where the above-described constitutional conditions regarding the composition of the negative electrode active material were satisfied and where the above-described physical property conditions regarding the results of analysis of the negative electrode active material were satisfied, substantially similar performance was obtained, as compared with a case where an existing other negative electrode active material (SiO) was used (Experiment example 16). 
     Specifically, in a case where the negative electrode active material satisfying the constitutional conditions and the physical property conditions described above was used, each of the charge capacity and the discharge capacity was decreased, as compared with the case where the other negative electrode active material was used. However, each of the charge capacity and the discharge capacity was sufficiently high within an acceptable range. 
     Moreover, in the case where the negative electrode active material satisfying the constitutional conditions and the physical property conditions described above was used, the capacity retention rate was greatly increased, as compared with the case where the other negative electrode active material was used. 
     Accordingly, in the case where the negative electrode active material satisfying the constitutional conditions and the physical property conditions described above was used, the capacity retention rate was markedly improved while each of the charge capacity and the discharge capacity was secured, as compared with the case where the other negative electrode active material was used. 
     As in the results listed in Tables 1 and 2, in the case where the above-described constitutional conditions regarding the composition of the negative electrode active material were satisfied and where the above-described physical property conditions regarding the results of analysis of the negative electrode active material were satisfied, a superior cyclability characteristic was obtained together with a superior charge characteristic and a superior discharge characteristic. Accordingly, a superior battery characteristic was obtained in the secondary battery. 
     Although the technology has been described above with reference to the embodiments and Examples, configurations of the technology are not limited to those described with reference to the embodiments and Examples above, and are therefore modifiable in a variety of ways. 
     Specifically, although the description has been given of the case where the liquid electrolyte (electrolytic solution) and the gel electrolyte (electrolyte layer) are used, the electrolyte is not limited to a particular kind. Alternatively, an electrolyte in a solid state (solid electrolyte) may be used. 
     Moreover, although the description has been given of the case where the structure of the secondary battery is of the laminated-film type, the cylindrical type, or the coin type, the structure is not limited to a particular structure. Alternatively, the secondary battery may have other structures including, without limitation, those of a prismatic type and a button type. 
     Moreover, although the description has been given of the case where the structure of the battery device is of the wound type or the stacked type, the structure of the battery device is not limited to a particular structure. Alternatively, the battery device may have other structures including, without limitation, those of a zigzag folded type in which the electrodes (the positive electrode and the negative electrode) are folded in a zigzag manner. 
     Further, although the description has been given of the case where the electrode reactant is lithium, the electrode reactant is not limited to a particular element. Specifically, the electrode reactant may be another alkali metal such as sodium or potassium, or may be an alkaline earth metal such as beryllium, magnesium, or calcium, as described above. Alternatively, the electrode reactant may be another light metal such as aluminum. 
     Note that the effects described herein are mere examples, and effects of the technology are therefore not limited to those described herein. Accordingly, the technology may achieve any other suitable effect according to an embodiment. 
     It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.