Patent Publication Number: US-2023132785-A1

Title: Secondary battery

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of PCT patent application no. PCT/JP2021/032812, filed on Sep. 7, 2021, which claims priority to Japanese patent application no. JP2020-156446, filed on Sep. 17, 2020, the entire contents of which are herein incorporated by reference. 
    
    
     BACKGROUND 
     The present technology relates to a secondary battery. 
     Various kinds of electronic equipment, including mobile phones, have been widely used. Such widespread use has promoted development of a secondary battery as a power source that is smaller in size and lighter in weight and allows for a higher energy density. The secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution. A configuration of the secondary battery has been considered in various ways. 
     Specifically, in order to reduce internal resistance, a predetermined amount of a film derived from a sulfonic acid compound is provided on a surface of a positive electrode active material, and a predetermined amount of a mix film derived from a sulfonic acid compound and vinylene carbonate is provided on a surface of a negative electrode active material. 
     Similarly, in order to reduce internal resistance, a predetermined amount of a film derived from a lithium salt having a sulfonic acid skeleton is provided on a surface of a positive electrode active material, and a predetermined amount of a film derived from vinylene carbonate is provided on a surface of a negative electrode active material. 
     In order to reduce an amount of gas generation during high-temperature storage, a first film derived from a disulfonic acid dilithium salt is provided on a surface of a positive electrode active material, and a predetermined amount of a second film derived from a disulfonic acid dilithium salt and vinylene carbonate is provided on a surface of a negative electrode active material. 
     In order to suppress an increase in resistance caused by long-term storage, a film including a predetermined amount of sulfur element is provided on a surface of a positive electrode active material. 
     In order to improve a cyclability characteristic and a storage characteristic, an electrolytic solution includes a cyclic sulfone compound having a structure of —S(═O) 2 —O—S(═O) 2 —. 
     SUMMARY 
     The present technology relates to a secondary battery. 
     Although consideration has been given in various ways to improve performance of a secondary battery, an electric resistance characteristic and a cyclability characteristic of the secondary battery are not sufficient yet. Accordingly, there is still room for further improvement in terms thereof. 
     It is therefore desirable to provide a secondary battery that is able to achieve a superior electric resistance characteristic and a superior cyclability characteristic. 
     A secondary battery according to an embodiment includes a positive electrode, a negative electrode, a negative electrode wiring line, and an electrolytic solution. The negative electrode wiring line is coupled to the negative electrode. The negative electrode includes a negative electrode active material layer and a film. The film covers a surface of the negative electrode active material layer. The film includes sulfur as a constituent element. The electrolytic solution includes a chain carboxylic acid ester. Where the film is divided, in a direction away from the negative electrode wiring line, into thirds including a first film part, a second film part, and a third film part: a content of sulfur in the first film part, the third film part, or each of the first film part and the third film part is greater than or equal to 11 μmol/m 2  and less than or equal to 22 μmol/m 2 ; a content of sulfur in the second film part is greater than or equal to 7 μmol/m 2  and less than or equal to 13 μmol/m 2 ; and a ratio of the content of sulfur in the first film part, the third film part, or each of the first film part and the third film part to the content of sulfur in the second film part is greater than or equal to 1.2 and less than or equal to 2.1. 
     According to the secondary battery of an embodiment, the film of the negative electrode includes sulfur as a constituent element, and the electrolytic solution includes the chain carboxylic acid ester. Further, the film (including the first film part, the second film part, and the third film part) satisfies the above-described conditions regarding: the content of sulfur in the first film part, the third film part, or each of the first film part and the third film part; the content of sulfur in the second film part; and the ratio of the content of sulfur in the first film part, the third film part, or each of the first film part and the third film part to the content of sulfur in the second film part. Accordingly, it is possible to achieve a superior electric resistance characteristic and a superior cyclability characteristic. 
     Note that effects of the present technology are not necessarily limited to those described herein and may include any of a series of suitable. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG.  1    is a perspective view of a configuration of a secondary battery according to an embodiment. 
         FIG.  2    is a sectional view of a configuration of a battery device illustrated in  FIG.  1   . 
         FIG.  3    is a plan view of a configuration of a negative electrode illustrated in  FIG.  2   . 
         FIG.  4    is a perspective view for describing a process of manufacturing (a stabilization treatment to be performed on) the secondary battery according to an embodiment. 
         FIG.  5    is a perspective view of a configuration of a secondary battery according to an embodiment. 
         FIG.  6    is a sectional view of a configuration of a battery device illustrated in  FIG.  5   . 
         FIG.  7    is a plan view of a configuration of a negative electrode illustrated in  FIG.  6   . 
         FIG.  8    is a perspective view for describing a process of manufacturing (a stabilization treatment to be performed on) the secondary battery according to an embodiment. 
         FIG.  9    is a block diagram illustrating a configuration of an application example of the secondary battery. 
     
    
    
     DETAILED DESCRIPTION 
     One or more embodiments of the present technology are described below in further detail including with reference to the drawings. 
     A description is given first of a secondary battery according to an embodiment. 
     The secondary battery to be described here is a secondary battery that obtains a battery capacity using insertion and extraction of an electrode reactant, and includes a positive electrode, a negative electrode, and an electrolytic solution which is a liquid electrolyte. In the secondary battery, to prevent precipitation of the electrode reactant on a surface of the negative electrode during 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. 
     Although not particularly limited in kind, the electrode reactant is specifically a light metal such as an alkali metal or an alkaline earth metal. Examples of the alkali metal include lithium, sodium, and potassium. Examples of the alkaline earth metal include beryllium, magnesium, and calcium. 
     Examples are given below of a case where the electrode reactant is lithium. A secondary battery that obtains a battery capacity using insertion and extraction of lithium is a so-called lithium-ion secondary battery. In the lithium-ion secondary battery, lithium is inserted and extracted in an ionic state. 
       FIG.  1    illustrates a perspective configuration of the secondary battery.  FIG.  2    illustrates a sectional configuration of a battery device  20  illustrated in  FIG.  1   .  FIG.  3    illustrates a planar configuration of a negative electrode  22  illustrated in  FIG.  2   . 
     Note that  FIG.  1    illustrates a state in which an outer package film  10  and the battery device  20  are separated away from each other, and a section of the battery device  20  along an XZ plane is indicated by a dashed line.  FIG.  2    illustrates only a portion of the battery device  20 .  FIG.  3    illustrates a state in which a negative electrode lead  32  is coupled to the negative electrode  22 . 
     As illustrated in  FIGS.  1  to  3   , the secondary battery includes the outer package film  10 , the battery device  20 , a positive electrode lead  31 , the negative electrode lead  32 , and sealing films  41  and  42 . The secondary battery described here is a secondary battery of a laminated-film type in which the outer package film  10  having flexibility or softness is used. 
     As illustrated in  FIG.  1   , the outer package film  10  is a flexible outer package member that contains the battery device  20 . The outer package film  10  has a pouch-shaped structure in which the battery device  20  is sealed in a state of being contained inside the outer package film  10 . The outer package film  10  thus contains a positive electrode  21 , the negative electrode  22 , and an electrolytic solution that are to be described later. 
     Here, the outer package film  10  is a single film-shaped member and is foldable toward a folding direction F. The outer package film  10  has a depression part  10 U to place the battery device  20  therein. The depression part  10 U is a so-called deep drawn part. 
     Specifically, the outer package film  10  is a three-layered laminated film including a fusion-bonding layer, a metal layer, and a surface protective layer that are stacked in this order from an inner side. In a state in which the outer package film  10  is folded, outer edge parts of the fusion-bonding layer opposed to each other 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 outer package film  10  is not particularly limited in configuration or the number of layers, and may be single-layered or two-layered, or may include four or more layers. Further, in a case where the outer package film  10  is a multilayered laminated film, a material included in each layer may be selected as desired. 
     The sealing film  41  is interposed between the outer package film  10  and the positive electrode lead  31 . The sealing film  42  is interposed between the outer package film  10  and the negative electrode lead  32 . Note that the sealing film  41 , the sealing film  42 , or both may be omitted. 
     The sealing film  41  is a sealing member that prevents entry, for example, of outside air into the outer package film  10 . The sealing film  41  includes a polymer compound such as a polyolefin that has adherence to the positive electrode lead  31 . Examples of the polyolefin include polypropylene. 
     A configuration of the sealing film  42  is similar to that of the sealing film  41  except that the sealing film  42  is a sealing member that has adherence to the negative electrode lead  32 . That is, the sealing film  42  includes a polymer compound such as a polyolefin that has adherence to the negative electrode lead  32 . 
     As illustrated in  FIGS.  1  to  3   , the battery device  20  is a power generation device that includes the positive electrode  21 , the negative electrode  22 , a separator  23 , and the electrolytic solution (not illustrated). The battery device  20  is contained inside the outer package film  10 . 
     Here, the battery device  20  is a so-called wound electrode body. That is, in the battery device  20 , the positive electrode  21  and the negative electrode  22  are stacked on each other with the separator  23  interposed therebetween, and the positive electrode  21 , the negative electrode  22 , and the separator  23  are wound about a winding axis P. The winding axis P is a virtual axis extending in a Y-axis direction. Thus, the positive electrode  21  and the negative electrode  22  are opposed to each other with the separator  23  interposed therebetween, and are wound. 
     A three-dimensional shape of the battery device  20  is not particularly limited. Here, the battery device  20  has an elongated shape. Accordingly, a section of the battery device  20  intersecting the winding axis P, that is, a section of the battery device  20  along the XZ plane, has an elongated shape defined by a major axis J 1  and a minor axis J 2 . The major axis J 1  is a virtual axis that extends in an X-axis direction and has a larger length than the minor axis J 2 . The minor axis J 2  is a virtual axis that extends in a Z-axis direction intersecting the X-axis direction and has a smaller length than the major axis J 1 . Here, the battery device  20  has an elongated cylindrical three-dimensional shape. Thus, the section of the battery device  20  has an elongated, generally elliptical shape. 
     The positive electrode  21  includes, as illustrated in  FIG.  2   , a positive electrode current collector  21 A and a positive electrode active material layer  21 B. 
     The positive electrode current collector  21 A has two opposed surfaces on which the respective positive electrode active material layers  21 B are to be provided, and supports the positive electrode active material layers  21 B. The positive electrode current collector  21 A includes an electrically conductive material such as a metal material. Examples of the metal material include aluminum. 
     Here, the positive electrode active material layer  21 B is provided on each of the two opposed surfaces of the positive electrode current collector  21 A. The positive electrode active material layer  21 B includes one or more of positive electrode active materials into which lithium is insertable and from which lithium is extractable. Note that the positive electrode active material layer  21 B may be provided only on one of the two opposed surfaces of the positive electrode current collector  21 A. Further, the positive electrode active material layer  21 B may further include one or more of other materials including, without limitation, a positive electrode binder and a positive electrode conductor. A method of forming the positive electrode active material layer  21 B is not particularly limited, and specifically includes one or more of methods including, without limitation, a coating method. 
     The positive electrode active material is not particularly limited in kind, and specific examples thereof include a lithium-containing compound. The lithium-containing compound is a compound including lithium and one or more transition metal elements as constituent elements. The lithium-containing compound may further include one or more other elements as a constituent element or constituent elements. The one or more other elements are not particularly limited in kind as long as the one or more other elements are each an element other than lithium and the transition metal elements. Specifically, the one or more other elements are any one or more of elements belonging to groups 2 to 15 in the long period periodic table of elements. The lithium-containing compound is not particularly limited in kind, and specific examples thereof include an oxide, 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 0.01 O 2 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 , 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 electrically conductive material may be a metal material or a polymer compound, for example. 
     The negative electrode  22  includes, as illustrated in  FIG.  2   , a negative electrode current collector  22 A, a negative electrode active material layer  22 B, and a film  22 C. 
     The negative electrode current collector  22 A has two opposed surfaces on which the respective negative electrode active material layers  22 B are to be disposed, and supports the negative electrode active material layers  22 B. The negative electrode current collector  22 A includes an electrically conductive material such as a metal material. Examples of the metal material include copper. 
     Here, the negative electrode active material layer  22 B is provided on each of the two opposed surfaces of the negative electrode current collector  22 A. The negative electrode active material layer  22 B includes one or more of negative electrode active materials into which lithium is insertable and from which lithium is extractable. Note that the negative electrode active material layer  22 B may be provided only on one of the two opposed surfaces of the negative electrode current collector  22 A. Further, the negative electrode active material layer  22 B may further include one or more of materials including, without limitation, a negative electrode binder and a negative electrode conductor. A method of forming the negative electrode active material layer  22 B is not particularly limited, and specifically 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 is not particularly limited in kind, and specifically includes a carbon material, a metal-based material, or both, for example. A reason for this is that a high energy density is obtainable. Specific examples of the carbon material include graphitizable carbon, non-graphitizable carbon, and graphite (natural graphite and artificial graphite). The term “metal-based material” is a generic term for a material that includes, as a constituent element or constituent elements, one or more elements among metal elements and metalloid elements that are each able to form an alloy with lithium. Examples of such metal elements and metalloid elements include silicon, tin, or both. The metal-based material may be a simple substance, an alloy, a compound, a mixture of two or more thereof, or a material including two or more phases thereof. Specific examples of the metal-based material include TiSi 2  and SiO x  (0&lt;x≤2 or 0.2&lt;x&lt;1.4). 
     Details of the negative electrode binder are similar to those of the positive electrode binder. Details of the negative electrode conductor are similar to those of the positive electrode conductor. 
     The film  22 C covers a surface of the negative electrode active material layer  22 B. In this case, the film  22 C may cover the entire surface of the negative electrode active material layer  22 B, or may cover only a portion of the surface of the negative electrode active material layer  22 B. Note that, in the latter case, multiple films  22 C may cover the surface of the negative electrode active material layer  22 B at respective locations separate from each other.  FIG.  2    illustrates a case where the film  22 C covers the entire surface of the negative electrode active material layer  22 B. 
     As will be described later, the film  22 C is formed on the surface of each of the negative electrode active material layers  22 B through a stabilization treatment (a first charge and discharge treatment) on the secondary battery after being assembled in a process of manufacturing the secondary battery, and includes sulfur as a constituent element. 
     Here, as will be described later, the electrolytic solution includes a sulfur-containing compound. The sulfur-containing compound in the electrolytic solution decomposes and reacts upon the stabilization treatment, and the film  22 C therefore includes, as a constituent element, sulfur derived from the sulfur-containing compound. The term “sulfur-containing compound” is a generic term for a compound including sulfur as a constituent element, and is a substance to be a source of sulfur. Details of the sulfur-containing compound will be described later. 
     In the secondary battery, predetermined physical property conditions are satisfied regarding the film  22 C, in order to improve each of an electric resistance characteristic and a cyclability characteristic. Details of the physical property of the film  22 C will be described later. 
     The separator  23  is an insulating porous film interposed between the positive electrode  21  and the negative electrode  22  as illustrated in  FIG.  2   , and allows lithium ions to pass therethrough while preventing contact (a short circuit) between the positive electrode  21  and the negative electrode  22 . The separator  23  includes a polymer compound such as polyethylene. 
     The positive electrode  21 , the negative electrode  22 , and the separator  23  are each impregnated with the electrolytic solution. The electrolytic solution includes a solvent and an electrolyte salt. 
     The solvent includes one or more of chain carboxylic acid esters each of which is a non-aqueous solvent (an organic solvent). A reason for this is that the chain carboxylic acid ester has low viscosity and an ionic conductivity (a lithium-ion conductive property) of the electrolytic solution thus improves. As a result, a charge and discharge characteristic at a high rate (a large charging current and a large discharging current) is improved, and a battery capacity is thus prevented from decreasing easily even if the secondary battery is charged and discharged at a high rate. An electrolytic solution including a non-aqueous solvent (a chain carboxylic acid ester) is a so-called non-aqueous electrolytic solution. 
     The chain carboxylic acid ester is not particularly limited in kind, and specific examples thereof include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, and ethyl isobutyrate. A reason for this is that the ionic conductivity of the electrolytic solution sufficiently improves. A content of the chain carboxylic acid ester in the solvent is not particularly limited, and is specifically greater than or equal to 30 vol %. A reason for this is that the ionic conductivity of the electrolytic solution further improves. 
     In particular, the chain carboxylic acid ester preferably includes ethyl acetate, propyl acetate, ethyl propionate, and propyl propionate. A reason for this is that the ionic conductivity of the electrolytic solution further improves. 
     The solvent may further include one or more of other non-aqueous solvents. The other non-aqueous solvent is not particularly limited in kind, and specific examples thereof include a carbonic-acid-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 lactone-based compound include a lactone. 
     Note that the solvent may include one or more of the sulfur-containing compounds. A reason for this is that it becomes easier to form, on the surface of the negative electrode active material layer  22 B, the film  22 C that includes sulfur as a constituent element due to the decomposition and the reaction of the sulfur-containing compound upon the stabilization treatment of the secondary battery. Further, even if a portion of the film  22 C is decomposed upon charging and discharging, it becomes easier to additionally form the film  22 C due to decomposition and a reaction of the sulfur-containing compound at a subsequent cycle of charging and discharging. 
     As described above, the sulfur-containing compound is a substance to be a source of sulfur, that is, a compound including sulfur as a constituent element. The sulfur-containing compound may be a cyclic compound or a chain compound. Further, the sulfur-containing compound may include a carbon-carbon double bond, a carbon-carbon triple bond, or both. The carbon-carbon double bond and the carbon-carbon triple bond are each an unsaturated carbon bond. 
     The sulfur-containing compound is not particularly limited in kind, and specific examples thereof include a cyclic sulfonic acid ester, a chain sulfonic acid ester, a cyclic disulfonic acid anhydride, and a cyclic sulfonic acid carboxylic acid anhydride. A reason for this is that it becomes sufficiently easier to form the film  22 C on the surface of the negative electrode active material layer  22 B. A content of the sulfur-containing compound in the electrolytic solution is not particularly limited, and may thus be set as desired. 
     Specific examples of the cyclic sulfonic acid ester include propane sultone (1,3-propane sultone), propene sultone (1-propene 1,3-sultone), 4-methyl-1,3,2-dioxathiolane 2,2-dioxide, and 1,3,2-dioxathiolane 2,2-dioxide. 
     Specific examples of the chain sulfonic acid ester include propargyl methanesulfonate, propargyl ethanesulfonate, and 2-propynyl benzenesulfonate. 
     Examples of the cyclic disulfonic acid anhydride include an ethane disulfonic acid anhydride and a propane disulfonic acid anhydride. 
     Specific examples of the cyclic sulfonic acid carboxylic acid anhydride include a sulfobenzoic acid anhydride, a sulfopropionic acid anhydride, and a sulfobutyric acid anhydride. 
     The electrolyte salt includes one or more of light metal salts including, without limitation, a lithium salt. A content of the electrolyte salt in the electrolytic solution is not particularly limited, and may thus be set as desired. 
     [Positive Electrode Lead and Negative Electrode Lead] 
     As illustrated in  FIG.  1   , the positive electrode lead  31  is a positive electrode wiring line coupled to the battery device  20  (the positive electrode  21 ), and is led from an inside to an outside of the outer package film  10 . The positive electrode lead  31  includes an electrically conductive material such as aluminum. The positive electrode lead  31  has a shape such as a thin plate shape or a meshed shape. 
     As illustrated in  FIGS.  1  and  3   , the negative electrode lead  32  is a negative electrode wiring line coupled to the battery device  20  (the negative electrode  22 ). Details of a state of coupling between the negative electrode  22  and the negative electrode lead  32  will be described later. Here, the negative electrode lead  32  is led from the inside to the outside of the outer package film  10  toward a direction similar to that in which the positive electrode lead  31  is led out. The negative electrode lead  32  includes an electrically conductive material such as copper. Details of a shape of the negative electrode lead  32  are similar to those of the shape of the positive electrode lead  31 . 
     In the secondary battery, as described above, the predetermined physical property conditions are satisfied regarding the film  22 C that includes sulfur as a constituent element, in order to improve each of the electric resistance characteristic and the cyclability characteristic. In the following, the state of coupling between the negative electrode  22  and the negative electrode lead  32  will be described first, following which the physical property conditions of the film  22 C will be described. In those cases, where appropriate, reference is made to  FIGS.  2  and  3    which have already been described. 
     As illustrated in  FIG.  2   , the negative electrode  22  includes the negative electrode current collector  22 A, the negative electrode active material layer  22 B, and the film  22 C. 
     In this case, as illustrated in  FIG.  3   , the negative electrode current collector  22 A has a band shape extending in a length direction (the X-axis direction). Here, the negative electrode active material layer  22 B is provided on the entire surface of the negative electrode current collector  22 A, and the film  22 C covers the entire surface of the negative electrode active material layer  22 B. In  FIG.  3   , the film  22 C is shaded. 
     Here, the negative electrode lead  32  is provided separately from the negative electrode  22  (the negative electrode current collector  22 A). The negative electrode lead  32  extends in a width direction (the Y-axis direction) intersecting the length direction, and a portion of the negative electrode lead  32  is coupled to the negative electrode  22 , in order to make an area coupled to the negative electrode  22  sufficiently small within an allowable range. Accordingly, one end part of the negative electrode lead  32  overlaps with one end part of the negative electrode  22  in the width direction, and is thus coupled to the one end part of the negative electrode  22 . Note that another end part of the negative electrode lead  32  does not overlap with the one end part of the negative electrode  22 , and protrudes outward relative to the negative electrode  22  (the negative electrode active material layer  22 B). 
     In a region in which the negative electrode  22  and the negative electrode lead  32  overlap with each other, neither the negative electrode active material layer  22 B nor the film  22 C is provided on the surface of the negative electrode current collector  22 A. The negative electrode current collector  22 A in the region is thus exposed. In this manner, the negative electrode lead  32  is coupled to the negative electrode current collector  22 A. 
     In the battery device  20  which is the wound electrode body, a position where the negative electrode lead  32  is coupled to the negative electrode  22  is not particularly limited. In other words, in a case where the negative electrode  22  is wound, the negative electrode lead  32  may be coupled to the negative electrode  22  on an outer side of winding, may be coupled to the negative electrode  22  on an inner side of the winding, or may be coupled to the negative electrode  22  in the middle between the outer side of the winding and the inner side of the winding. In  FIG.  3   , the right side represents the outer side of the winding and the left side represents the inner side of the winding. Accordingly,  FIG.  3    illustrates a case where the negative electrode lead  32  is coupled to the negative electrode  22  on the inner side of the winding. 
     On the basis of the position of the negative electrode lead  32  coupled to the negative electrode  22 , the film  22 C is divided into thirds in a direction away from the negative electrode lead  32  (i.e., a direction D along the width direction). The film  22 C is thus divided into a film part  22 C 1  which is a first film part, a film part  22 C 2  which is a second film part, and a film part  22 C 3  which is a third film part. In this case, all of the following three physical property conditions are satisfied. 
     (Physical Property Condition 1) 
     A content X (μmol/m 2 ) of sulfur in the film part  22 C 1 , the film part  22 C 3 , or each of the film parts  22 C 1  and  22 C 3  is within a range from 11 μmol/m 2  to 22 μmol/m 2  both inclusive. Out of the film parts  22 C 1  to  22 C 3 , the film part  22 C 1  and the film part  22 C 3  are opposite end parts in the width direction. 
     In other words, the physical property condition 1 may be as follows: the content X of sulfur in the film part  22 C 1  is within the range from 11 μmol/m 2  to 22 μmol/m 2  both inclusive; the content X of sulfur in the film part  22 C 3  is within the range from 11 μmol/m 2  to 22 μmol/m 2  both inclusive; or the content X of sulfur in each of the film parts  22 C 1  and  22 C 3  is within the range from 11 μmol/m 2  to 22 μmol/m 2  both inclusive. 
     The content X is adjustable to a desired value by changing conditions including, without limitation, a heating temperature, a heating time, and an aging time after heating when a portion (the film part  22 C 1 , the film part  22 C 3 , or each of the film parts  22 C 1  and  22 C 3 ) of the battery device  20  is heated upon the stabilization treatment of the assembled secondary battery, as will be described later. Further, the content X is also adjustable to a desired value by changing the content of the sulfur-containing compound in the electrolytic solution. 
     (Physical Property Condition 2) 
     A content Y (μmol/m 2 ) of sulfur in the film part  22 C 2  is within a range from 7 μmol/m 2  to 13 μmol/m 2  both inclusive. Out of the film parts  22 C 1  to  22 C 3 , the film part  22 C 2  is a middle part in the width direction. 
     The content Y is adjustable to a desired value by changing the content of the sulfur-containing compound in the electrolytic solution. Further, similarly to the case of adjusting the content X, the content Y is also adjustable to a desired value by heating a portion (the film part  22 C 2 ) of the battery device  20  upon the stabilization treatment of the secondary battery. 
     (Physical Property Condition 3) 
     A content ratio Z that is a ratio of the content X to the content Y is within a range from 1.2 to 2.1 both inclusive. The content ratio Z is calculated on the basis of the following calculation expression: content ratio Z=content X/content Y. 
     All of the physical property conditions 1 to 3 are satisfied. Therefore, in the negative electrode  22  including the film  22 C, an amount of the film  22 C provided in the opposite end parts (the film parts  22 C 1  and  22 C 3 ) in the width direction, i.e., the content X, is larger than an amount of the film  22 C provided in the middle part (the film part  22 C 2 ) in the width direction, i.e., the content Y. In this case, the content ratio Z is made appropriate to be within the range from 1.2 to 2.1 both inclusive. 
     A reason why all of the physical property conditions 1 to 3 are satisfied is that, as will be described later, in a case where the electrolytic solution includes the chain carboxylic acid ester, distribution of the amount of the film  22 C provided in the negative electrode  22  is made appropriate. This suppresses an increase in electric resistance and improves the lithium-ion conductive property in the negative electrode  22 . Thus, the suppression of the increase in the electric resistance and the improvement in the ion conductivity are both achieved. Details of the reason described here will be described later. 
     The film  22 C is analyzed by inductively coupled plasma (ICP) optical emission spectroscopy, and the contents X and Y are thereby each calculated on the basis of a result of the analysis. The content ratio Z is measured on the basis of respective results of the calculations regarding the contents X and Y. 
     A specific procedure of calculating each of the contents X and Y and the content ratio Z is as described below. 
     First, the secondary battery is discharged until a voltage reaches 3 V. A current at the time of the discharge is not particularly limited and may thus be set as desired. Thereafter, the secondary battery after the discharge is disassembled to thereby collect the negative electrode  22 . Thereafter, the negative electrode  22  is washed with a washing solvent. Although not particularly limited in kind, the washing solvent is specifically an organic solvent such as dimethyl carbonate. Thereafter, the negative electrode  22  is punched into a disk shape (having a diameter of 19 mm) to thereby obtain a sample for analysis. 
     Thereafter, the sample (the film  22 C) is analyzed by means of an ICP optical emission spectrometer. In this case, the film part  22 C 1 , the film part  22 C 3 , or both are analyzed to thereby measure the content (μg) of sulfur included in the film part  22 C 1 , the film part  22 C 3 , or each of the film parts  22 C 1  and  22 C 3 . As the ICP optical emission spectrometer, for example, SPS  3500 , a sequential-type ICP optical emission spectrometer available from Hitachi High-Tech Science Corporation (formerly: SII Nanotechnology Inc.) is usable. Thereafter, the content X (μmol/m 2 ) is calculated on the basis of the content (a value obtained by converting μg into μmol) of the sulfur described above and an area (m 2 ) of the sample. 
     Thereafter, the content Y (μmol/m 2 ) is calculated by a similar procedure except that the film part  22 C 2  is analyzed instead of the film part  22 C 1 , the film part  22 C 3 , or both. 
     Lastly, the content ratio Z (=content X/content Y) is calculated on the basis of the contents X and Y. In this manner, the contents X and Y and the content ratio Z are each calculated on the basis of the analysis result on the film  22 C obtained by ICP optical emission spectroscopy. 
     Upon charging the secondary battery, in the battery device  20 , lithium is extracted from the positive electrode  21 , and the extracted lithium is inserted into the negative electrode  22  via the electrolytic solution. Upon discharging the secondary battery, in the battery device  20 , lithium is extracted from the negative electrode  22 , and the extracted lithium is inserted into the positive electrode  21  via the electrolytic solution. Upon charging and discharging, lithium is inserted and extracted in an ionic state. 
     The secondary battery is manufactured according to a procedure to be described below. In this case, as will be described later, the secondary battery is assembled using the positive electrode  21 , a negative electrode precursor, and the electrolytic solution, following which the stabilization treatment is performed on the assembled secondary battery. 
       FIG.  4    illustrates a perspective configuration corresponding to  FIG.  1    for describing the process of manufacturing (the stabilization treatment to be performed on) the secondary battery.  FIG.  4    omits illustration of the outer package film  10  and the sealing films  41  and  42  for easy understanding of a heating region of the wound body  20 Z. 
     The positive electrode active material is mixed with materials including, without limitation, the positive electrode binder and the positive electrode conductor on an as-needed basis to thereby obtain a positive electrode mixture. Thereafter, the positive electrode mixture is put into the solvent to thereby prepare a paste positive electrode mixture slurry. The solvent may be an aqueous solvent, or may be a non-aqueous solvent (an organic solvent). Thereafter, the positive electrode mixture slurry is applied on the two opposed surfaces of the positive electrode current collector  21 A to thereby form the positive electrode active material layers  21 B. Thereafter, the positive electrode active material layers  21 B may be compression-molded by means of, for example, a roll pressing machine. In this case, the positive electrode active material layers  21 B may be heated. The positive electrode active material layers  21 B may be compression-molded multiple times. In this manner, the positive electrode active material layers  21 B are formed on the respective two opposed surfaces of the positive electrode current collector  21 A. Thus, the positive electrode  21  is fabricated. 
     The negative electrode active material layers  22 B are formed on the respective two opposed surfaces of the negative electrode current collector  22 A by a procedure similar to the fabrication procedure of the positive electrode  21  described above. Specifically, the negative electrode active material is mixed with materials including, without limitation, the negative electrode binder and the negative electrode conductor on an as-needed basis to thereby obtain a negative electrode mixture. Thereafter, the negative electrode mixture is put into the solvent to thereby prepare a paste negative electrode mixture slurry. Details of the solvent are as described above. Thereafter, the negative electrode mixture slurry is applied on the two opposed surfaces of the negative electrode current collector  22 A to thereby form the negative electrode active material layers  22 B. Thereafter, the negative electrode active material layers  22 B may be compression-molded. In this manner, the negative electrode active material layers  22 B are formed on the respective two opposed surfaces of the negative electrode current collector  22 A. Thus, the negative electrode precursor (not illustrated) is fabricated. 
     Lastly, as will be described later, the secondary battery is assembled using the negative electrode precursor, following which the stabilization treatment is performed on the assembled secondary battery. As a result, the film  22 C including sulfur as a constituent element is formed on the surface of each of the negative electrode active material layers  22 B. In this manner, the negative electrode active material layers  22 B and the films  22 C are formed on the respective two opposed surfaces of the negative electrode current collector  22 A. Thus, the negative electrode  22  is fabricated. 
     The electrolyte salt is put into the solvent, following which the sulfur-containing compound is added to the solvent. The solvent is not particularly limited in kind, and specific examples thereof include a non-aqueous solvent (an organic solvent). The electrolyte salt and the sulfur-containing compound are thereby each dispersed or dissolved in the solvent. As a result, the electrolytic solution is prepared. 
     First, the positive electrode lead  31  is coupled to the positive electrode precursor (the positive electrode current collector  21 A) by a method such as a welding method, and the negative electrode lead  32  is coupled to the negative electrode precursor (the negative electrode current collector  22 A) by a method such as a welding method. 
     Thereafter, the positive electrode  21  and the negative electrode precursor are stacked on each other with the separator  23  interposed therebetween, following which the stack of the positive electrode  21 , the negative electrode precursor, and the separator  23  is wound to thereby fabricate a wound body  20 Z, as illustrated in  FIG.  4   . The wound body  20 Z has a configuration similar to that of the battery device  20  except that the wound body  20 Z includes the negative electrode precursor instead of the negative electrode  22 , and that the positive electrode  21 , the negative electrode precursor, and the separator  23  are each not impregnated with the electrolytic solution. Thereafter, the wound body  20 Z is pressed by means of, for example, a pressing machine to thereby shape the wound body  20 Z into an elongated shape. 
     Thereafter, the wound body  20 Z is placed inside the depression part  10 U, following which the outer package film  10  (the fusion-bonding layer/the metal layer/the surface protective layer) is folded to thereby cause portions of the outer package film  10  to be opposed to each other. Thereafter, outer edge parts of two sides of the outer package film  10  (the fusion-bonding layer) opposed to each other are fusion-bonded to each other by a method such as a thermal-fusion-bonding method to thereby contain the wound body  20 Z in the outer package film  10  having the pouch shape. 
     Lastly, the electrolytic solution is injected into the outer package film  10  having the pouch shape, following which the outer edge parts of the remaining one side of the outer package film  10  (the fusion-bonding layer) are fusion-bonded to each other by a method such as a thermal-fusion-bonding method. In this case, the sealing film  41  is interposed between the outer package film  10  and the positive electrode lead  31 , and the sealing film  42  is interposed between the outer package film  10  and the negative electrode lead  32 . The wound body  20 Z is thereby impregnated with the electrolytic solution. In this manner, the wound body  20 Z is sealed in the outer package film  10  having the pouch shape. As a result, the secondary battery is assembled. 
     The assembled secondary battery is charged and discharged. Conditions including, for example, an environment temperature, the number of times of charging and discharging (the number of cycles), and charging and discharging conditions may be set as desired. As a result, the sulfur-containing compound in the electrolytic solution decomposes and reacts, and the film  22 C including sulfur as a constituent element is formed on the surface of each of the negative electrode active material layers  22 B. In this manner, the negative electrode active material layers  22 B and the films  22 C are formed on the respective two opposed surfaces of the negative electrode current collector  22 A. Thus, the negative electrode  22  is fabricated. As a result, the battery device  20  is fabricated. 
     In this case, a portion of the wound body  20 Z is heated by a heating device such as a heater. Specifically, as illustrated in  FIGS.  3  and  4   , the wound body  20 Z includes a wound part  201  corresponding to the film part  22 C 1 , a wound part  202  corresponding to the film part  22 C 2 , and a wound part  203  corresponding to the film part  22 C 3 . The wound part  201 , the wound part  203 , or both of the wound body  20 Z are heated. Heating conditions are not particularly limited. Specifically, a heating temperature is from 60° C. to 80° C. both inclusive and a heating time is from 1 hour to 24 hours both inclusive. 
     The heating treatment increases the amount of the film  22 C formed in the wound part  201 , the wound part  203 , or each of the wound parts  201  and  203 . In contrast, the amount of the film  22 C formed in the wound part  202  where the heating treatment is not performed does not increase. In this case, changing the above-described heating conditions makes it possible to control each of the contents X and Y, which also makes it possible to control the content ratio Z. 
     This brings the assembled secondary battery into an electrochemically stable state. Thus, the secondary battery including the outer package film  10 , that is, the secondary battery of the laminated-film type, is completed. 
     After the stabilization treatment of the secondary battery is completed, the secondary battery may be aged. Aging conditions are not particularly limited. Specifically, an aging temperature is from 60° C. to 80° C. both inclusive, and an aging time is from 6 hours to 48 hours both inclusive. Changing the aging conditions also makes it possible to control each of the contents X and Y, which therefore makes it possible to control the content ratio Z. 
     Further, after the stabilization treatment of the secondary battery is completed, that is, after the negative electrode  22  is fabricated (after the film  22 C is formed on the surface of each of the negative electrode active material layers  22 B), the sulfur-containing compound used for forming the film  22 C may or may not remain in the electrolytic solution. 
     According to the secondary battery, the film  22 C of the negative electrode  22  includes sulfur as a constituent element, and the electrolytic solution includes the chain carboxylic acid ester. Further, the film  22 C (including the film parts  22 C 1  to  22 C 3 ) satisfies all of the physical property conditions 1 to 3 (the content X is within the range from 11 μmol/m 2  to 22 μmol/m 2  both inclusive, the content Y is within the range from 7 μmol/m 2  to 13 μmol/m 2  both inclusive, and the content ratio Z is within the range from 1.2 to 2.1 both inclusive). Accordingly, it is possible to achieve a superior electric resistance characteristic and a superior cyclability characteristic for reasons to be described below. 
     In more detail, the electrolytic solution includes the chain carboxylic acid ester that is a low-viscosity solvent, and this improves the lithium-ion conductive property of the electrolytic solution. As a result, it becomes easier for the lithium ions to be inserted into and extracted from the negative electrode  22  upon charging and discharging. This improves the cyclability characteristic, and in particular, it is possible to achieve a superior cyclability characteristic even if the secondary battery is charged and discharged at a high rate. 
     However, the chain carboxylic acid ester that is the low-viscosity solvent is highly volatile. Thus, the chain carboxylic acid ester in the electrolytic solution easily volatilizes during long-term use (during long-term storage) of the secondary battery. This tendency of the chain carboxylic acid ester to volatilize is particularly apparent in the opposite end parts (the film parts  22 C 1  and  22 C 3 ) that are easily exposed to outside air as compared with in the middle part (the film part  22 C 2 ) that is less easily exposed to the outside air in the negative electrode  22 . In other words, an amount of volatilization of the chain carboxylic acid ester in each of the film parts  22 C 1  and  22 C 3  is greater than an amount of volatilization of the chain carboxylic acid ester in the film part  22 C 2 . 
     Volatilization of the chain carboxylic acid ester in each of the film parts  22 C 1  and  22 C 3  increases viscosity of the electrolytic solution. As a result, the lithium-ion conductive property in the electrolytic solution lowers, which easily causes precipitation of a lithium metal on the surface of the negative electrode  22 . 
     Here, in a case where the film  22 C including sulfur as a constituent element is provided on the surface of the negative electrode active material layer  22 B, the surface of the negative electrode  22  is protected with use of the film  22 C. This suppresses the precipitation of the lithium metal on the surface of the negative electrode  22 . However, if the film  22 C is provided on the surface of the negative electrode active material layer  22 B, the precipitation of the lithium metal is suppressed, but the secondary battery (the negative electrode  22 ) is increased in internal resistance, which lowers the cyclability characteristic after all. In particular, the cyclability characteristic markedly lowers if the secondary battery is charged and discharged at a high rate. 
     Based upon the foregoing, in a case where the electrolytic solution includes the chain carboxylic acid ester but no film  22 C is provided on the surface of the negative electrode active material layer  22 B, the following trade-off relationship is exhibited. The electric resistance characteristic improves due to the absence of the film  22 C, but the cyclability characteristic lowers due to the fact that the precipitation of the lithium metal occurs easily. In other words, improvement in one characteristic causes degradation in the other characteristic. 
     Further, in a case where the film  22 C is provided on the surface of the negative electrode active material layer  22 B but the electrolytic solution does not include the chain carboxylic acid ester, the following trade-off relationship is exhibited. The cyclability characteristic improves due to the fact that the precipitation of the lithium metal is prevented from occurring easily, but the electric resistance characteristic lowers due to the presence of the film  22 C. 
     In contrast, in a case where the electrolytic solution includes the chain carboxylic acid ester and where the film  22 C is provided on the surface of the negative electrode active material layer  22 B, if all of the physical property conditions 1 to 3 are satisfied, the distribution of the amount of the provided film  22 C is made appropriate, as described above. In other words, the amount of the film  22 C provided in the film part  22 C 1 , the film part  22 C 3 , or each of the film parts  22 C 1  and  22 C 3  is appropriately larger than the amount of the film  22 C provided in the film part  22 C 2 . 
     In this case, in the film part  22 C 1 , the film part  22 C 3 , or both, the precipitation of the lithium metal is prevented from occurring easily due to the presence of the film parts  22 C 1  and  22 C 3 , and this improves the cyclability characteristic. Moreover, in the film part  22 C 2 , the electric resistance is prevented from increasing easily even if the film part  22 C 2  is present, and this improves the electric resistance characteristic. 
     Based upon the foregoing, in a case where all of the physical property conditions 1 to 3 are satisfied, the above-described trade-off relationship is overcome. Thus, an increase in the electric resistance is suppressed and the cyclability characteristic is improved. In this case, needless to say, a similar tendency is obtained even if the secondary battery is charged and discharged at a high rate. Accordingly, it is possible to achieve a superior electric resistance characteristic and a superior cyclability characteristic. 
     In particular, the chain carboxylic acid ester may include, for example, ethyl acetate. This sufficiently improves the ionic conductivity of the electrolytic solution. Accordingly, it is possible to achieve higher effects. 
     Further, the electrolytic solution may include the sulfur-containing compound. This makes it easier to form the film  22 C including sulfur as a constituent element on the surface of the negative electrode active material layer  22 B. Accordingly, it is possible to achieve higher effects. In this case, the electrolytic solution may include the sulfur-containing compound also after the stabilization treatment of the secondary battery (i.e., after the formation of the film  22 C). This makes it easier to additionally form the film  22 C upon charging and discharging after the stabilization treatment. Accordingly, it is possible to achieve further higher effects. Further, the sulfur-containing compound may include, for example, the cyclic sulfonic acid ester. This makes it easier to form the film  22 C on the surface of the negative electrode active material layer  22 B. Accordingly, it is possible to achieve further higher effects. 
     Further, the secondary battery may include a lithium-ion secondary battery. This makes it possible to obtain a sufficient battery capacity stably through the use of insertion and extraction of lithium. Accordingly, it is possible to achieve higher effects. 
     The configuration of the secondary battery is appropriately modifiable as described below according to an embodiment. Note that any two or more of the following series of modifications may be combined with each other. 
     In  FIGS.  1  to  3   , the secondary battery includes the battery device  20  which is the wound electrode body. However, as illustrated in  FIGS.  5  to  7    respectively corresponding to  FIGS.  1  to  3   , the secondary battery may include a battery device  50  which is a stacked electrode body instead of the battery device  20  which is the wound electrode body. 
     A secondary battery of a laminated-film type illustrated in  FIGS.  5  to  7    has a configuration similar to that of the secondary battery of the laminated-film type illustrated in  FIGS.  1  to  3   , except that the secondary battery of the laminated-film type illustrated in  FIGS.  5  to  7    includes the battery device  50  (a positive electrode  51 , a negative electrode  52 , and a separator  53 ), a positive electrode lead  61 , and a negative electrode lead  62 , instead of the battery device  20  (the positive electrode  21 , the negative electrode  22 , and the separator  23 ), the positive electrode lead  31 , and the negative electrode lead  32 . 
     Respective configurations of the positive electrode  51 , the negative electrode  52 , and the separator  53  are similar to the respective configurations of the positive electrode  21 , the negative electrode  22 , and the separator  23  except for those described below. 
     In the battery device  50 , the positive electrode  51  and the negative electrode  52  are alternately stacked on each other with the separator  53  interposed therebetween. The respective numbers of the positive electrodes  51 , the negative electrodes  52 , and the separators  53  to be stacked are not particularly limited. The positive electrode  51  includes a positive electrode current collector  51 A and a positive electrode active material layer  51 B respectively corresponding to the positive electrode current collector  21 A and the positive electrode active material layer  21 B. The negative electrode  52  includes a negative electrode current collector  52 A, a negative electrode active material layer  52 B, and a film  52 C respectively corresponding to the negative electrode current collector  22 A, the negative electrode active material layer  22 B, and the film  22 C. A configuration of the electrolytic solution is as described above. 
     Note that, as illustrated in  FIGS.  5  and  7   , the positive electrode current collector  51 A and the negative electrode current collector  52 A are each a sheet having a rectangular shape. The positive electrode current collector  51 A includes a protruding part  51 AT in which no positive electrode active material layer  51 B is provided. The negative electrode current collector  52 A includes a protruding part  52 AT in which no negative electrode active material layer  52 B is provided. The protruding part  52 AT is disposed at a position which does not overlap with the protruding part  51 AT. Multiple protruding parts  51 AT are joined to each other to thereby form the positive electrode lead  61  which is a single positive electrode wiring line having a lead shape. Multiple protruding parts  52 AT are joined to each other to thereby form the negative electrode lead  62  which is a single negative electrode wiring line having a lead shape. In other words, the positive electrode lead  61  coupled to the positive electrode  51  is integrated with the positive electrode current collector  51 A, and the negative electrode lead  62  coupled to the negative electrode  52  is integrated with the negative electrode current collector  52 A. 
     In the battery device  50  also, all of the physical property conditions 1 to 3 are satisfied as with the battery device  20  described above. Specifically, on the basis of a position of the negative electrode lead  62  coupled to the negative electrode  52 , the film  52 C is divided into thirds (film parts  52 C 1  to  52 C 3 ) in the direction D away from the negative electrode lead  62 . In this case, the content X of sulfur in the film part  52 C 1 , the film part  52 C 3 , or each of the film parts  52 C 1  and  52 C 3  is within the range from 11 μmol/m 2  to 22 μmol/m 2  both inclusive (the physical property condition 1). The content Y of sulfur in the film part  52 C 2  is within the range from 7 μmol/m 2  to 13 μmol/m 2  both inclusive (the physical property condition 2). The content ratio Z that is the ratio of the content X to the content Y is within the range from 1.2 to 2.1 both inclusive (the physical property condition 3). 
     A method of manufacturing the secondary battery of the laminated-film type illustrated in  FIGS.  5  to  7    is similar to the method of manufacturing the secondary battery of the laminated-film type illustrated in  FIGS.  1  to  4   , except that, as illustrated in  FIG.  8    corresponding to  FIG.  4   , a stacked body  50 Z is fabricated instead of the wound body  20 Z, and the stabilization treatment is performed on the secondary battery which is assembled using the stacked body  50 Z. 
     In a case of fabricating the battery device  50 , first, the positive electrode  51  is fabricated in which the positive electrode active material layer  51 B is provided on each of two opposed surfaces (excluding the protruding part  51 AT) of the positive electrode current collector  51 A, and the negative electrode  52  is fabricated in which the negative electrode active material layer  52 B is provided on each of two opposed surfaces (excluding the protruding part  52 AT) of the negative electrode current collector  52 A. Thereafter, the positive electrode  51  and the negative electrode  52  are alternately stacked on each other with the separator  53  interposed therebetween, to thereby form the stacked body  50 Z, as illustrated in  FIG.  8   . Thereafter, the protruding parts  51 AT are joined to each other by a method such as a welding method to thereby form the positive electrode lead  61 , and the protruding parts  52 AT are joined to each other by a method such as a welding method to thereby form the negative electrode lead  62 . 
     In the stabilization treatment of the assembled secondary battery, a portion of the stacked body  50 Z is heated by a heating device such as a heater. Specifically, as illustrated in  FIG.  8   , the stacked body  50 Z includes a stacked part  501  corresponding to the film part  52 C 1 , a stacked part  502  corresponding to the film part  52 C 2 , and a stacked part  503  corresponding to the film part  52 C 3 . The stacked part  501 , the stacked part  503 , or both of the stacked body  50 Z are heated. The film  52 C including sulfur as a constituent element is thereby formed on the surface of each of the negative electrode active material layers  52 B. Thus, the negative electrode  52  is fabricated, and the battery device  50  is fabricated. In this case, changing the above-described heating conditions makes it possible to control each of the contents X and Y, which also makes it possible to control the content ratio Z. 
     In the case where the battery device  50  which is the stacked electrode body is used also, all of the physical property conditions 1 to 3 are satisfied. It is therefore possible to achieve effects similar to those in the case where the battery device  20  which is the wound electrode body is used. In other words, it is possible to achieve a superior electric resistance characteristic and a superior cyclability characteristic. 
     The separator  23  which is a porous film is used. However, although not specifically illustrated here, a separator of a stacked type including a polymer compound layer may be used instead of the separator  23  which is the porous film. 
     Specifically, the separator of the stacked type includes a porous film having two opposed surfaces, and the polymer compound layer disposed on one of or each of the two opposed surfaces of the porous film. A reason for this is that adherence of the separator to each of the positive electrode  21  and the negative electrode  22  improves to suppress the occurrence of misalignment (irregular winding of each of the positive electrode  21 , the negative electrode  22 , and the separator) of the battery device  20 . This helps to prevent the secondary battery from easily swelling even if, for example, 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 the polymer compound such as polyvinylidene difluoride has superior physical strength and is electrochemically stable. 
     Note that the porous film, the polymer compound layer, or both may each include one or more kinds of insulating particles. A reason for this is that the insulating particles dissipate heat upon heat generation by the secondary battery, thus improving safety or heat resistance of the secondary battery. Examples of the insulating particles include inorganic particles and resin particles. Specific examples of the inorganic particles include particles of: aluminum oxide, aluminum nitride, boehmite, silicon oxide, titanium oxide, magnesium oxide, and zirconium oxide. Specific examples of the resin particles include particles of acrylic resin and particles of styrene resin. 
     In a case of fabricating the separator of the stacked type, a precursor solution including, without limitation, the polymer compound and an organic solvent is prepared, following which the precursor solution is applied on one of or each of the two opposed surfaces of the porous film. In this case, insulating particles may be added to the precursor solution on an as-needed basis. 
     In the case where the separator of the stacked type is used also, lithium ions are movable between the positive electrode  21  and the negative electrode  22 , and similar effects are therefore obtainable. 
     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 battery device  20  including the electrolyte layer, the positive electrode  21  and the negative electrode  22  are stacked on each other with the separator  23  and the electrolyte layer interposed therebetween, following which the stack of the positive electrode  21 , the negative electrode  22 , the separator  23 , and the electrolyte layer is wound. The electrolyte layer is interposed between the positive electrode  21  and the separator  23 , and between the negative electrode  22  and the separator  23 . 
     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. A reason for this is that liquid leakage is prevented. 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 including, for example, the electrolytic solution, the polymer compound, and an organic solvent is prepared, following which the precursor solution is applied on one side or both sides of the positive electrode  21  and on one side or both sides of the negative electrode  22 . 
     In a case where the electrolyte layer is used also, lithium ions are movable between the positive electrode  21  and the negative electrode  22  via the electrolyte layer, and similar effects are therefore obtainable. 
     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. The secondary battery used as a power source serves as a main power source or an auxiliary power source of, for example, electronic equipment and an electric vehicle. The main power source is preferentially used regardless of the presence of any other power source. The auxiliary power source is used in place of the main power source, or is switched from the main power source. 
     Specific examples of the applications of the secondary battery include: electronic equipment; apparatuses for data storage; electric power tools; battery packs to be mounted on, for example, electronic equipment; 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, headphone stereos, portable radios, and portable information terminals. 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 or industrial battery systems for accumulation of electric power for a situation such as emergency. The above-described applications may each use one secondary battery, or may each use multiple secondary batteries. 
     The battery packs may each include a single battery, or may each 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 a hybrid automobile that is additionally provided with a driving source other than the secondary battery. In an electric power storage system for home use, electric power accumulated in the secondary battery which is an electric power storage source may be utilized for using, for example, home appliances. 
     An application example of the secondary battery will now be described in detail. The configuration of the application example described below is merely an example, and is appropriately modifiable. 
       FIG.  9    illustrates a block configuration of a battery pack. The battery pack described here is a 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.  9   , the battery pack includes an electric power source  71  and a circuit board  72 . The circuit board  72  is coupled to the electric power source  71 , and includes a positive electrode terminal  73 , a negative electrode terminal  74 , and a temperature detection terminal  75 . 
     The electric power source  71  includes one secondary battery. The secondary battery has a positive electrode lead coupled to the positive electrode terminal  73  and a negative electrode lead coupled to the negative electrode terminal  74 . The electric power source  71  is couplable to outside via the positive electrode terminal  73  and the negative electrode terminal  74 , and is thus chargeable and dischargeable. The circuit board  72  includes a controller  76 , a switch  77 , a thermosensitive resistive device (a positive temperature coefficient (PTC) device)  78 , and a temperature detector  79 . However, the PTC device  78  may be omitted. 
     The controller  76  includes, for example, a central processing unit (CPU) and a memory, and controls an overall operation of the battery pack. The controller  76  detects and controls a use state of the electric power source  71  on an as-needed basis. 
     If a voltage of the electric power source  71  (the secondary battery) reaches an overcharge detection voltage or an overdischarge detection voltage, the controller  76  turns off the switch  77 . This prevents a charging current from flowing into a current path of the electric power source  71 . 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  77  includes, for example, a charge control switch, a discharge control switch, a charging diode, and a discharging diode. The switch  77  performs switching between coupling and decoupling between the electric power source  71  and external equipment in accordance with an instruction from the controller  76 . The switch  77  includes, for example, a metal-oxide-semiconductor field-effect transistor (MOSFET). The charging and discharging currents are detected on the basis of an ON-resistance of the switch  77 . 
     The temperature detector  79  includes a temperature detection device such as a thermistor. The temperature detector  79  measures a temperature of the electric power source  71  using the temperature detection terminal  75 , and outputs a result of the temperature measurement to the controller  76 . The result of the temperature measurement to be obtained by the temperature detector  79  is used, for example, in a case where the controller  76  performs charge/discharge control upon abnormal heat generation or in a case where the controller  76  performs a correction process upon calculating a remaining capacity. 
     EXAMPLES 
     A description is given of Examples of the present technology below according to an embodiment. 
     Examples 1 to 13 to Comparative Examples 1 to 9 
     Secondary batteries were manufactured, following which the secondary batteries were each evaluated for a battery characteristic as described below. 
     [Manufacturing of Secondary Battery] 
     The secondary batteries (lithium-ion secondary batteries) of the laminated-film type illustrated in  FIGS.  1  to  4    were manufactured in accordance with the following procedure. 
     (Fabrication of Positive Electrode) 
     First, 95 parts by mass of the positive electrode active material, 4 parts by mass of the positive electrode binder (polyvinylidene difluoride), and 1 part by mass of the positive electrode conductor (graphite) were mixed with each other to thereby obtain a positive electrode mixture. Thereafter, the positive electrode mixture was put into an organic solvent (N-methyl-2-pyrrolidone), following which the organic solvent was stirred to thereby prepare a paste positive electrode mixture slurry. Thereafter, the positive electrode mixture slurry was applied on the two opposed surfaces of the positive electrode current collector  21 A (a band-shaped aluminum foil having a thickness of 15 μm) by means of a coating apparatus, following which the applied positive electrode mixture slurry was dried to thereby form the positive electrode active material layers  21 B. Lastly, the positive electrode active material layers  21 B were compression-molded by means of a roll pressing machine. In this manner, the positive electrode active material layers  21 B were formed on the respective two opposed surfaces of the positive electrode current collector  21 A. Thus, the positive electrode  21  was fabricated. 
     (Fabrication of Negative Electrode) 
     First, 90 parts by mass of the negative electrode active material (graphite) and 10 parts by mass of the negative electrode binder (polyvinylidene difluoride) were mixed with each other to thereby obtain a negative electrode mixture. 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 paste negative electrode mixture slurry. Thereafter, the negative electrode mixture slurry was applied on the two opposed surfaces of the negative electrode current collector  22 A (a band-shaped copper foil having a thickness of 15 μm) by means of a coating apparatus, following which the applied negative electrode mixture slurry was dried to thereby form the negative electrode active material layers  22 B. Thereafter, the negative electrode active material layers  22 B were compression-molded by means of a roll pressing machine. In this manner, the negative electrode active material layers  22 B were formed on the respective two opposed surfaces of the negative electrode current collector  22 A. Thus, the negative electrode precursor was fabricated. Lastly, as will be described later, the secondary battery was assembled using the negative electrode precursor, following which the stabilization treatment (a first charge and discharge treatment) was performed on the assembled secondary battery. In this manner, the film  22 C including sulfur as a constituent element was formed on the surface of each of the negative electrode active material layers  22 B. Thus, the negative electrode  22  was fabricated. 
     (Preparation of Electrolytic Solution) 
     The electrolyte salt (lithium hexafluorophosphate (LiPF 6 )) was put into the solvent, following which the solvent was stirred. Used as the solvent were ethylene carbonate and propylene carbonate which are each the cyclic carbonic acid ester, and propyl propionate (PP) which is the chain carboxylic acid ester. In this case, a mixture ratio (a volume ratio) of the solvent between ethylene carbonate, propylene carbonate, and chain carboxylic acid ester was set to 10:20:70, and a content of the electrolyte salt was set to 1 mol/kg with respect to the solvent. 
     Thereafter, the sulfur-containing compound (propane sultone (PS) which is the cyclic sulfonic acid ester) was added to the solvent including the electrolyte salt, following which the solvent was stirred. In this case, a content of the sulfur-containing compound in the electrolytic solution was set to 1 wt %. Thus, the electrolytic solution including the sulfur-containing compound was prepared. 
     (Assembly of Secondary Battery) 
     First, the positive electrode lead  31  (a band-shaped aluminum foil) was welded to the positive electrode  21  (the positive electrode current collector  21 A), and the negative electrode lead  32  (a band-shaped copper foil) was welded to the negative electrode precursor (the negative electrode current collector  22 A). 
     Thereafter, the positive electrode  21  and the negative electrode precursor were stacked on each other with the separator  23  (a fine-porous polyethylene film having a thickness of 25 μm) interposed therebetween, following which the stack of the positive electrode  21 , the negative electrode precursor, and the separator  23  was wound to thereby fabricate the wound body  20 Z. Thereafter, the wound body  20 Z was pressed by means of a pressing machine, and was thereby shaped into an elongated shape. 
     Thereafter, the outer package film  10  was folded in such a manner as to sandwich the wound body  20 Z contained inside the depression part  10 U, following which the outer edge parts of two sides of the outer package film  10  were thermal-fusion-bonded to each other to thereby allow the wound body  20 Z to be contained inside the outer package film  10  having the pouch shape. As the outer package film  10 , an aluminum laminated film was used in which a fusion-bonding layer (a polypropylene film having a thickness of 30 μm), a metal layer (an aluminum foil having a thickness of 40 μm), and a surface protective layer (a nylon film having a thickness of 25 μm) were stacked in this order from an inner side. In this case, the outer edge parts of the two sides of the fusion-bonding layer that were opposed to each other were thermal-fusion-bonded to each other. 
     Lastly, the electrolytic solution was injected into the outer package film  10  having the pouch shape and thereafter, the outer edge parts of the remaining one side of the outer package film  10  (the fusion-bonding layer) were thermal-fusion-bonded to each other in a reduced-pressure environment. In this case, the sealing film  41  (a polypropylene film having a thickness of 5 μm) was interposed between the outer package film  10  and the positive electrode lead  31 , and the sealing film  42  (a polypropylene film having a thickness of 5 μm) was interposed between the outer package film  10  and the negative electrode lead  32 . In this manner, the wound body  20 Z was impregnated with the electrolytic solution, and the wound body  20 Z was sealed in the outer package film  10  having the pouch shape. The secondary battery was thus assembled. 
     (Stabilization of Secondary Battery) 
     The assembled secondary battery was charged and discharged for one cycle in an ambient temperature environment (at a temperature of 25° C.). Upon charging, the secondary battery was charged with a constant current of 0.1 C until a voltage reached 4.45 V, and was thereafter charged with a constant voltage of 4.45 V until a current reached 0.005 C. Upon the discharging, the secondary battery was discharged with a constant current of 0.1 C until the voltage reached 3.0 V. Note that 0.1 C is a value of a current that causes a battery capacity (a theoretical capacity) to be completely discharged in 10 hours, and 0.005 C is a value of a current that causes the battery capacity to be completely discharged in 200 hours. 
     In this case, portions (the wound parts  201  and  203 ) of the wound body  20 Z were heated by a heater. In the heating treatment, a heating temperature was varied within a range from 60° C. to 80° C. both inclusive, and a heating time was varied within a range from 1 hour to 24 hours both inclusive. 
     In this manner, as described above, the film  22 C was formed on the surface of each of the negative electrode active material layers  22 B in the negative electrode precursor, and the negative electrode  22  was thus fabricated. As a result, the battery device  20  was fabricated and the state of the secondary battery was electrochemically stabilized. The secondary battery of the laminated-film type was thus completed. 
     After the secondary battery was completed, the secondary battery was disassembled to thereby collect the negative electrode  22 . Thereafter, the negative electrode  22  (the film  22 C) was analyzed by ICP optical emission spectroscopy to thereby calculate each of the contents X and Y (μmol/m 2 ) and the content ratio Z, which revealed the results presented in Tables 1 to 3. 
     In the process of manufacturing the secondary battery, each of the contents X and Y and the content ratio Z was adjusted by varying the heating conditions (the heating temperature and the heating time) upon the stabilization treatment. 
     Evaluation of the secondary batteries for their battery characteristics (the electric resistance characteristic and the cyclability characteristic) revealed the results presented in Tables 1 to 3. Here, the evaluation of the cyclability characteristic included evaluation of two kinds of cyclability characteristics. 
     In a case of examining the electric resistance characteristic, first, the secondary battery was charged in an ambient temperature environment (at a temperature of 23° C.), following which the electric resistance (a pre-storage electric resistance) of the secondary battery was measured. Charging conditions were similar to those in the case of performing the stabilization treatment on the secondary battery described above. Thereafter, the secondary battery in the charged state was stored (for a storing time of 1 month) in a high-temperature environment (at a temperature of 60° C.), following which the electric resistance (a post-storage electric resistance) of the secondary battery was measured. Lastly, a resistance variation rate (%) which is an index for evaluating the electric resistance characteristic was calculated on the basis of the following calculation expression: resistance variation rate=(post-storage electric resistance/pre-storage electric resistance)×100. 
     In a case of examining the cyclability characteristic of a first kind, first, the secondary battery was charged and discharged in an ambient temperature environment (at a temperature of 23° C.) to thereby measure a discharge capacity (a first-cycle discharge capacity). Thereafter, the secondary battery was left to stand (for a leaving time of 1 month) in the same environment. Thereafter, the secondary battery was repeatedly charged and discharged in the same environment until the number of cycles (the number of times of charging and discharging) reached 100 to thereby measure the discharge capacity (a 100th-cycle discharge capacity). Lastly, a capacity retention rate 1(%) which is an index for evaluating the cyclability characteristic was calculated on the basis of the following calculation expression: capacity retention rate 1=(100th-cycle discharge capacity/first-cycle discharge capacity)×100. Charging and discharging conditions were similar to the charging conditions in the case of performing the stabilization treatment on the secondary battery described above, except that the current at the time of charging and the current at the time of discharging were each changed to 3 C. Note that 3 C is a value of a current that causes the battery capacity to be completely discharged in 10/3 hours. 
     In a case of examining the cyclability characteristic of a second kind, a capacity retention rate 2(%) which is another index for evaluating the cyclability characteristic was calculated by a procedure similar to that of the case of examining the cyclability characteristic of the first kind, except that the leaving time of the secondary battery was changed to 12 months. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 Electrolytic solution 
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Chain carboxylic 
                 Sulfur-containing 
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 acid ester 
                 compound 
                 Film 
                 Resistance 
                 Capacity 
                 Capacity 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                 Content 
                   
                 Content 
                 Content X 
                 Content Y 
                 Content 
                 variation 
                 retention 
                 retention 
               
               
                   
                 Kind 
                 (vol %) 
                 Kind 
                 (wt %) 
                 (μmol/m 2 ) 
                 (μmol/m 2 ) 
                 ratio Z 
                 rate (%) 
                 rate 1 (%) 
                 rate 2 (%) 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Comparative 
                 PP 
                 70 
                 PS 
                 1 
                 15.0 
                 15.0 
                 1.0 
                 305 
                 94 
                 78 
               
               
                 example 1 
               
               
                 Comparative 
                 PP 
                 70 
                 PS 
                 1 
                 10.0 
                 10.0 
                 1.0 
                 197 
                 90 
                 60 
               
               
                 example 2 
               
               
                 Comparative 
                 PP 
                 70 
                 PS 
                 1 
                 12.5 
                 12.5 
                 1.0 
                 240 
                 90 
                 68 
               
               
                 example 3 
               
               
                 Comparative 
                 PP 
                 70 
                 PS 
                 1 
                 15.0 
                 13.6 
                 1.1 
                 288 
                 94 
                 78 
               
               
                 example 4 
               
               
                 Example 1 
                 PP 
                 70 
                 PS 
                 1 
                 15.0 
                 12.5 
                 1.2 
                 260 
                 94 
                 82 
               
               
                 Example 2 
                 PP 
                 70 
                 PS 
                 1 
                 15.0 
                 10.7 
                 1.4 
                 222 
                 94 
                 88 
               
               
                 Example 3 
                 PP 
                 70 
                 PS 
                 1 
                 15.0 
                 9.4 
                 1.6 
                 201 
                 95 
                 90 
               
               
                 Example 4 
                 PP 
                 70 
                 PS 
                 1 
                 15.0 
                 7.9 
                 1.9 
                 188 
                 93 
                 82 
               
               
                 Example 5 
                 PP 
                 70 
                 PS 
                 1 
                 15.0 
                 7.1 
                 2.1 
                 179 
                 91 
                 71 
               
               
                 Comparative 
                 PP 
                 70 
                 PS 
                 1 
                 15.0 
                 6.8 
                 2.2 
                 175 
                 90 
                 59 
               
               
                 example 5 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 2 
               
             
            
               
                   
                   
               
               
                   
                 Electrolytic solution 
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Chain carboxylic 
                 Sulfur-containing 
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 acid ester 
                 compound 
                 Film 
                 Resistance 
                 Capacity 
                 Capacity 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                 Content 
                   
                 Content 
                 Content X 
                 Content Y 
                 Content 
                 variation 
                 retention 
                 retention 
               
               
                   
                 Kind 
                 (vol %) 
                 Kind 
                 (wt %) 
                 (μmol/m 2 ) 
                 (μmol/m 2 ) 
                 ratio Z 
                 rate (%) 
                 rate 1 (%) 
                 rate 2 (%) 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Comparative 
                 PP 
                 70 
                 PS 
                 1 
                 10.0 
                 6.3 
                 1.6 
                 171 
                 93 
                 66 
               
               
                 example 6 
               
               
                 Example 6 
                 PP 
                 70 
                 PS 
                 1 
                 11.0 
                 6.9 
                 1.6 
                 177 
                 93 
                 73 
               
               
                 Example 7 
                 PP 
                 70 
                 PS 
                 1 
                 13.0 
                 8.1 
                 1.6 
                 190 
                 95 
                 87 
               
               
                 Example 3 
                 PP 
                 70 
                 PS 
                 1 
                 15.0 
                 9.4 
                 1.6 
                 201 
                 95 
                 90 
               
               
                 Example 8 
                 PP 
                 70 
                 PS 
                 1 
                 18.0 
                 11.3 
                 1.6 
                 218 
                 96 
                 87 
               
               
                 Example 9 
                 PP 
                 70 
                 PS 
                 1 
                 22.0 
                 13.8 
                 1.6 
                 262 
                 97 
                 82 
               
               
                 Comparative 
                 PP 
                 70 
                 PS 
                 1 
                 23.0 
                 14.4 
                 1.6 
                 312 
                 96 
                 80 
               
               
                 example 7 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 3 
               
             
            
               
                   
                   
               
               
                   
                 Electrolytic solution 
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Chain carboxylic 
                 Sulfur-containing 
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 acid ester 
                 compound 
                 Film 
                 Resistance 
                 Capacity 
                 Capacity 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                 Content 
                   
                 Content 
                 Content X 
                 Content Y 
                 Content 
                 variation 
                 retention 
                 retention 
               
               
                   
                 Kind 
                 (vol %) 
                 Kind 
                 (wt %) 
                 (μmol/m 2 ) 
                 (μmol/m 2 ) 
                 ratio Z 
                 rate (%) 
                 rate 1 (%) 
                 rate 2 (%) 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Comparative 
                 PP 
                 70 
                 PS 
                 1 
                 9.6 
                 6.0 
                 1.6 
                 170 
                 93 
                 62 
               
               
                 example 8 
               
               
                 Example 10 
                 PP 
                 70 
                 PS 
                 1 
                 11.2 
                 7.0 
                 1.6 
                 175 
                 93 
                 75 
               
               
                 Example 11 
                 PP 
                 70 
                 PS 
                 1 
                 12.5 
                 8.0 
                 1.6 
                 183 
                 93 
                 80 
               
               
                 Example 3 
                 PP 
                 70 
                 PS 
                 1 
                 15.0 
                 9.4 
                 1.6 
                 201 
                 95 
                 90 
               
               
                 Example 12 
                 PP 
                 70 
                 PS 
                 1 
                 17.6 
                 11.0 
                 1.6 
                 225 
                 95 
                 85 
               
               
                 Example 13 
                 PP 
                 70 
                 PS 
                 1 
                 20.8 
                 13.0 
                 1.6 
                 254 
                 96 
                 81 
               
               
                 Comparative 
                 PP 
                 70 
                 PS 
                 1 
                 21.0 
                 14.0 
                 1.5 
                 289 
                 96 
                 77 
               
               
                 example 9 
               
               
                   
               
            
           
         
       
     
     As indicated in Tables 1 to 3, the resistance variation rate and the capacity retention rates 1 and 2 of the secondary battery in which the electrolytic solution (the solvent) included the chain carboxylic acid ester each varied greatly depending on the contents X and Y and the content ratio Z of the film  22 C. 
     Specifically, in a case where not all of the physical property conditions 1 to 3 (the content X was within the range from 11 μmol/m 2  to 22 μmol/m 2  both inclusive, the content Y was within the range from 7 μmol/m 2  to 13 μmol/m 2  both inclusive, and the content ratio Z was within the range from 1.2 to 2.1 both inclusive) were satisfied (Comparative examples 1 to 9), a trade-off relationship was exhibited in which improvement of any of the resistance variation rate and the capacity retention rates 1 and 2 caused degradation of the others. Thus, not all of the resistance variation rate and the capacity retention rates 1 and 2 were improved. 
     In contrast, in a case where all of the physical property conditions 1 to 3 were satisfied (Examples 1 to 13), the above-described trade-off relationship was overcome, which allowed for improvement in all of the resistance variation rate and the capacity retention rates 1 and 2. 
     In particular, in the case where all of the physical property conditions 1 to 3 were satisfied, the following tendencies were observed. First, the use of propyl propionate as the chain carboxylic acid ester allowed for sufficient improvement in all of the resistance variation rate and the capacity retention rates 1 and 2. Second, the use of the cyclic sulfonic acid ester as the sulfur-containing compound allowed for sufficient improvement in all of the resistance variation rate and the capacity retention rates 1 and 2. 
     Examples 14 to 17 
     The secondary batteries were fabricated by a similar procedure except that the sulfur-containing compound was changed in kind, and were thereafter evaluated for their battery characteristics. Newly used as the sulfur-containing compound were propene sultone (PRS) which is the cyclic sulfonic acid ester, propargyl methanesulfonate (PMS) which is the chain sulfonic acid ester, the propane disulfonic acid anhydride (PSAH) which is the cyclic disulfonic acid anhydride, and the sulfopropionic acid anhydride (SPAH) which is the cyclic sulfonic acid carboxylic acid anhydride. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 4 
               
             
            
               
                   
                   
               
               
                   
                 Electrolytic solution 
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Chain carboxylic 
                 Sulfur-containing 
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 acid ester 
                 compound 
                 Film 
                 Resistance 
                 Capacity 
                 Capacity 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                 Content 
                   
                 Content 
                 Content X 
                 Content Y 
                 Content 
                 variation 
                 retention 
                 retention 
               
               
                   
                 Kind 
                 (vol %) 
                 Kind 
                 (wt %) 
                 (μmol/m 2 ) 
                 (μmol/m 2 ) 
                 ratio Z 
                 rate (%) 
                 rate 1 (%) 
                 rate 2 (%) 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Example 3 
                 PP 
                 70 
                 PS 
                 1 
                 15.0 
                 9.4 
                 1.6 
                 201 
                 95 
                 90 
               
               
                 Example 14 
                 PP 
                 70 
                 PRS 
                 1 
                 15.0 
                 9.4 
                 1.6 
                 208 
                 94 
                 86 
               
               
                 Example 15 
                 PP 
                 70 
                 PMS 
                 1 
                 15.0 
                 9.4 
                 1.6 
                 208 
                 93 
                 88 
               
               
                 Example 16 
                 PP 
                 70 
                 PSAH 
                 1 
                 15.0 
                 9.4 
                 1.6 
                 204 
                 93 
                 87 
               
               
                 Example 17 
                 PP 
                 70 
                 SPAH 
                 1 
                 15.0 
                 9.4 
                 1.6 
                 206 
                 94 
                 85 
               
               
                   
               
            
           
         
       
     
     As indicated in Table 4, results similar to those indicated in Tables 1 to 3 were obtained even if the sulfur-containing compound was changed in kind. In other words, if all of the physical property conditions 1 to 3 were satisfied, it was possible to improve all of the resistance variation rate and the capacity retention rates 1 and 2. 
     Based upon the results presented in Tables 1 to 4, all of the resistance variation rate and the capacity retention rates 1 and 2 improved if: the film  22 C of the negative electrode  22  included sulfur as a constituent element; the electrolytic solution included the chain carboxylic acid ester; and all of the physical property conditions 1 to 3 were satisfied. The secondary battery therefore achieved a superior electric resistance characteristic and a superior cyclability characteristic. 
     Although the present technology has been described above with reference to one or embodiments including Examples, the configuration of the present technology is not limited thereto, and is therefore modifiable in a variety of suitable ways. 
     Specifically, the description has been given of the case where the secondary battery has a battery structure of the laminated-film type. However, the battery structure of the secondary battery is not particularly limited, and may thus be, for example, a cylindrical type, a prismatic type, a coin type, or a button type. 
     Further, the description has been given of the case where the battery device has a device structure of a wound type and the case where the battery device has a device structure of a stacked type. However, the device structure of the battery device is not particularly limited, and may thus be, for example, a zigzag folded type in which 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 particularly limited. 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. In addition, the electrode reactant may be another light metal such as aluminum. 
     The effects described herein are mere examples, and effects of the present technology are therefore not limited thereto and may achieve any other suitable effect. 
     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.