Patent Publication Number: US-2007111103-A1

Title: Current collector, anode, and battery

Description:
CROSS REFERENCES TO RELATED APPLICATIONS  
      The present invention contains subject matter related to Japanese Patent Application JP 2005-328545 filed in the Japanese Patent Office on Nov. 14, 2005, the entire contents of which being incorporated herein by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a current collector containing copper (Cu) as an element, an anode using the current collector, and a battery using the current collector.  
      2. Description of the Related Art  
      In recent years, as mobile devices have been sophisticated and multi-functionalized, a higher capacity of secondary batteries as a power source for these mobile devices has been demanded. As a secondary battery to meet such a demand, there is a lithium ion secondary battery. However, since graphite is used for the anode in the lithium ion secondary battery in practical use currently, the battery capacity thereof is in a saturated state and thus it is difficult to attain a vastly high capacity thereof. Therefore, it is considered to use silicon or the like for the anode. Recently, forming an active material layer on a current collector by vapor-phase deposition method or the like has been reported. Silicon or the like is largely expanded and shrunk due to charge and discharge, and thus there has been a disadvantage that the cycle characteristics are lowered due to pulverization. However, when using the vapor-phase deposition method or the like, such pulverization can be prevented, and the current collector and the active material layer can be integrated. In the result, electron conductivity in the anode becomes extremely favorable, and high performance both in the capacity and the cycle life is expected.  
      However, even in the anode in which the current collector and the active material layer are integrated, there has been a disadvantage as follows. That is, when charge and discharge are repeated, stress is applied between the current collector and the active material layer by intense expansion and shrinkage of the active material layer, leading to separation or the like of the active material layer and deformation of the current collector, and thus the cycle characteristics are lowered. Therefore, it has been reported that a tensile strength of the current collector is set to a given value or more, or that elongation of the current collector is set to a given value or more (for example, refer to International Publication No. WO01/029912 and Japanese Unexamined Patent Application Publication No. 2005-135856).  
     SUMMARY OF THE INVENTION  
      However, expansion and shrinkage of an active material due to cycles are generated microscopically. Therefore, there is low correlation between macroscopic physical characteristics of a current collector such as a tensile strength and elongation percentage and cycle characteristics. In the result, there has been a disadvantage that even when such macroscopic physical characteristics are controlled, the characteristics are not improved sufficiently.  
      In view of the foregoing, in the invention, it is desirable to provide a current collector capable of relaxing stress, of preventing deformation, and thereby improving characteristics, an anode using the current collector, and a battery using the current collector.  
      According to an embodiment of the invention, there is provided a current collector containing copper as an element, wherein where a peak area resulting from (220) crystal face of copper obtained by X-ray diffraction is I 220 , and a peak area resulting from (200) crystal face of copper obtained by X-ray diffraction is I 200 , ratio I 220 /I 200  as a ratio of the peak area I 220  to the peak area I 200  is 2.5 or less at least in part.  
      According to an embodiment of the invention, there is provided an anode provided with an active material layer on a current collector, wherein the current collector contains copper as an element, and where a peak area resulting from (220) crystal face of copper obtained by X-ray diffraction is I 220 , and a peak area resulting from (200) crystal face of copper obtained by X-ray diffraction is I 200 , ratio I 220 /I 200  as a ratio of the peak area I 220  to the peak area I 200  is 2.5 or less at least in part.  
      According to an embodiment of the invention, there is provided a battery including a cathode, an anode, and an electrolyte, wherein the anode has a current collector and an active material layer, the current collector contains copper as an element, and where a peak area resulting from (220) crystal face of copper obtained by X-ray diffraction is I 220 , and a peak area resulting from (200) crystal face of copper obtained by X-ray diffraction is I 200 , ratio I 220 /I 200  as a ratio of the peak area I 220  to the peak area I 200  is 2.5 or less at least in part.  
      According to the current collector of the embodiment of the invention, the ratio I 220 /I 200  as a ratio of the peak area I 220  to the peak area I 200  is 2.5 or less at least in part. Therefore, stress due to expansion and shrinkage can be relaxed, and deformation can be prevented. Therefore, according to the anode and the battery of the embodiments of the invention, separation or the like can be prevented, and battery characteristics such as a capacity and cycle characteristics can be improved.  
      Other and further objects, features and advantages of the invention will appear more fully from the following description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a cross section showing a structure of an anode according to an embodiment of the invention;  
       FIG. 2  is a cross section showing a structure of a secondary battery using the anode shown in  FIG. 1 ;  
       FIG. 3  is an exploded perspective view showing another structure of a secondary battery using the anode shown in  FIG. 1 ; and  
       FIG. 4  is a cross section showing a structure taken along line I-I of the secondary battery shown in  FIG. 3 .  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      An embodiment of the invention will be hereinafter described in detail with reference to the drawings.  
       FIG. 1  shows a structure of an anode  10  according to an embodiment of the invention. For example, the anode  10  has a current collector  11  and an active material layer  12  provided on the current collector  11 . The active material layer  12  may be provided on one face of the current collector  11 , or the both faces thereof.  
      The current collector  11  is made of a material containing copper as an element. Copper has high conductivity and high stability. The current collector  11  may be made of simple substance of copper or an alloy of copper. The current collector  11  may be made of a single layer or a plurality of layers. It is enough that the current collector  11  is made of a material containing copper as an element in part.  
      Where a peak area resulting from (220) crystal face of copper obtained by X-ray diffraction is I 220 , and a peak area resulting from (200) crystal face of copper obtained by X-ray diffraction is I 200 , the current collector  11  has ratio I 220 /I 200  as a ratio of the peak area I 220  to the peak area I 200  is 2.5 or less at least in part. Thereby, even when the active material layer  12  is largely expanded and shrunk due to charge and discharge, the stress can be relaxed, and the current collector  11  can be prevented from being deformed. The ratio I 220 /I 200  is preferably from 0.03 to 2.5 at least in part, since thereby higher effects can be obtained. The ratio I 220 /I 200  can be controlled by adjusting forming conditions of the current collector  11 , or by providing heat treatment after forming the current collector  11 .  
      The surface roughness of the current collector  11  on which the active material layer  12  is provided is, based on ten point height of roughness profile Rz described in JIS B0601, preferably 1 μm or more, more preferably 9 μm or less, and much more preferably in the range from 1.3 μm to 3.5 μm. Thereby, contact characteristics with the active material layer  12  can be improved. The surface roughness of the current collector  11  may be adjusted by roughening the surface by lapping, for example. Otherwise, the surface roughness of the current collector  11  may be adjusted by forming granular protrusions by plating, vapor deposition or the like. Providing the protrusions on the surface is preferable, since thereby higher effects can be obtained. While the protrusions are preferably made of a material containing copper as an element, the protrusions may be made of other material.  
      The active material layer  12  contains, for example, an active material containing an element capable of forming an alloy with lithium (Li). The element capable of forming an alloy with lithium may be contained in the form of a simple substance, an alloy, or a compound. Specially, the active material layer  12  preferably contains an active material containing silicon (Si) as an element. Silicon has a high ability to insert and extract lithium, and can provide a high energy density. In this specification, alloys include an alloy of one or more metal elements and one or more metalloid elements, in addition to an alloy containing two or more metal elements.  
      The active material layer  12  is, at least in part, preferably formed by, for example, one or more methods selected from the group consisting of vapor-phase deposition method, spraying method, and firing method, or may be formed by a combination of two or more methods thereof. Thereby, deformation due to expansion and shrinkage of the active material layer  12  due to charge and discharge can be prevented. In addition, the current collector  11  and the active material layer  12  can be integrated, and electron conductivity in the active material layer  12  can be improved. “Firing method” means a method in which a layer formed from a mixture of powder containing an active material and a binder is heat-treated under the non-oxidizing atmosphere and thereby a denser layer with a higher volume density than the layer before heat treatment is formed.  
      The active material layer  12  may be formed by coating, more specifically, may be a layer containing an active material and if necessary, a binder such as polyvinylidene fluoride. However, as described above, the layer formed by vapor-phase deposition method, spraying method, or firing method at least in part is more preferable.  
      The active material layer  12  is preferably alloyed with the current collector  11  in at least part of the interface with the current collector  11 . Specifically, in the interface, the element of the current collector  11  is preferably diffused in the active material layer  12 , or the element of the active material layer  12  is preferably diffused in the current collector  11 , or the both elements thereof are preferably diffused in each other. Thereby, the contact characteristics can be more improved. In this application, the foregoing diffusion of elements is regarded as one form of alloying.  
      The anode  10  can be formed as follows, for example.  
      For example, when the current collector  11  is formed by plating, the crystallinity is controlled by adjusting a plating current density, plating bath temperatures, plating bath additives or the like so that the ratio I 220 /I 200  falls within a given range. Further, the crystallinity may be controlled by providing heat treatment after forming the current collector  11 . When the current collector  11  is formed by rolling, for example, crystallinity of an ingot as a raw material is adjusted or heat treatment is performed, so that the ratio I 220 /I 200  falls within a given range. If necessary, after the current collector  11  is formed, the surface thereof is roughed. Such roughening may be provided before or after heat treatment.  
      Next, the active material layer  12  is formed on the current collector  11  by vapor-phase deposition method, spraying method, firing method, coating or the like. The active material layer  12  may be formed by combination of two or more methods thereof. As vapor-phase deposition method, for example, physical deposition method or chemical deposition method can be cited. Specifically, vacuum vapor deposition method, sputtering method, ion plating method, laser ablation method, CVD (Chemical Vapor Deposition) method or the like can be cited. In some cases, the active material layer  12  and the current collector  11  are alloyed concurrently when the active material layer  12  is formed. However, it is possible that after the active material layer  12  is formed, heat treatment is performed under the vacuum atmosphere or under the non-oxidizing atmosphere to alloy the active material layer  12  and the current collector  11 . Thereby, the anode  10  shown in  FIG. 1  is obtained.  
      The anode  10  is used for the secondary battery as follows, for example.  
       FIG. 2  shows a structure of the secondary battery. The secondary battery is a so-called coin-type secondary battery in which the anode  10  contained in a package cup  21  and a cathode  23  contained in a package can  22  are layered with a separator  24  in between.  
      Peripheral edges of the package cup  21  and the package can  22  are hermetically sealed by being caulked with an insulating gasket  25 . The package cup  21  and the package can  22  are respectively made of a metal such as stainless and aluminum.  
      The cathode  23  has, for example, a current collector  23 A and an active material layer  23 B provided on the current collector  23 A. Arrangement is made so that the active material layer  23 B side is opposed to the active material layer  12 . The current collector  23 A is made of, for example, aluminum, nickel, or stainless.  
      The active material layer  23 B contains, for example, as a cathode active material, one or more cathode materials capable of inserting and extracting lithium. The active material layer  23 B may contain an electrical conductor such as a carbon material and a binder such as polyvinylidene fluoride according to needs. As a cathode material capable of inserting and extracting lithium, for example, a lithium-containing metal complex oxide expressed by a general formula, Li x MIO 2  is preferable, since thereby a high voltage can be generated and a high density can be obtained, and thus a higher capacity of the secondary battery can be obtained. MI represents one or more transition metals, and is, for example, preferably at least one of cobalt and nickel. x varies according to charge and discharge states of the battery, and is generally in the range of 0.05≦x≦1.10. As a specific example of such a lithium-containing metal complex oxide, LiCoO 2 , LiNiO 2  or the like can be cited.  
      The cathode  23  can be formed as follows, for example. A mixture is prepared by mixing a cathode active material, an electrical conductor, and a binder. The mixture is dispersed in a disperse medium such as N-methyl-2-pyrrolidone to form mixture slurry. The current collector  23 A made of a metal foil is coated with the mixture slurry, which is dried and compression-molded to form the active material layer  23 B.  
      The separator  24  separates the anode  10  from the cathode  23 , prevents current short circuit due to contact of the both electrodes, and lets through lithium ions. The separator  24  is made of, for example, polyethylene or polypropylene.  
      An electrolytic solution which is a liquid electrolyte is impregnated in the separator  24 . The electrolytic solution contains, for example, a solvent and an electrolyte salt dissolved in the solvent. The electrolytic solution may contain an additive according to needs. As a solvent, for example, a nonaqueous solvent such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate can be cited. One of the foregoing solvents may be used singly, or two or more thereof may be used by mixing.  
      As an electrolyte salt, for example, a lithium salt such as LiPF 6 , LiCF 3 SO 3 , and LiClO 4  can be cited. One of the electrolyte salts may be used singly, or two or more thereof may be used by mixing.  
      The secondary battery can be manufactured by, for example, layering the anode  10 , the separator  24  impregnated with an electrolytic solution, and the cathode  23 , inserting the resultant lamination between the package cup  21  and the package can  22 , and caulking the package cup  21  and the package can  22 .  
      In the secondary battery, when charged, for example, lithium ions are extracted from the cathode  23  and inserted in the anode  10  through the electrolytic solution. When discharged, for example, lithium ions are extracted from the anode  10  and inserted in the cathode  23  through the electrolytic solution. In this embodiment, the current collector  11  with the ratio I 220 /I 200  of 2.5 or less at least in part is used for the anode  10 . Therefore, even when the active material layer  12  is expanded and shrunk due to charge and discharge, the stress can be relaxed, the current collector  11  can be prevented from being deformed, and separation or the like of the active material layer  12  can be prevented.  
      The anode  10  according to this embodiment may be used for the following secondary battery.  
       FIG. 3  shows a structure of the secondary battery. In the secondary battery, a spirally wound electrode body  30  on which leads  31  and  32  are attached is contained inside a film package member  41 . Thereby, a small, light, and thin secondary battery can be obtained.  
      The leads  31  and  32  are respectively directed from inside to outside of the package member  41  and derived in the same direction, for example. The leads  31  and  32  are respectively made of, for example, a metal material such as aluminum, copper, nickel, and stainless, and are in a state of a thin plate or mesh, respectively.  
      The package member  41  is made of a rectangular aluminum laminated film in which, for example, a nylon film, an aluminum foil, and a polyethylene film are bonded together in this order. The package member  41  is, for example, arranged so that the polyethylene film side and the spirally wound electrode body  30  are opposed to each other, and the respective outer edges are contacted to each other by fusion bonding or an adhesive. Adhesive films  42  to protect from entering of outside air are inserted between the package member  41  and the leads  31  and  32 . The adhesive film  42  is made of a material having contact characteristics to the leads  31  and  32 , for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, and modified polypropylene.  
      The package member  41  may be made of a laminated film having other structure, a polymer film such as polypropylene, or a metal film, instead of the foregoing aluminum laminated film.  
       FIG. 4  shows a cross sectional structure taken along line I-I of the spirally wound electrode body  30  shown in  FIG. 3 . In the spirally wound electrode body  30 , the anode  10  and a cathode  33  are layered and spirally wound with a separator  34  and an electrolyte layer  35  in between. The outermost periphery thereof is protected by a protective tape  36 .  
      The anode  10  has a structure in which the active material layer  12  is provided on the both faces of the current collector  11 . The cathode  33  also has a structure in which an active material layer  33 B is provided on the both faces of a current collector  33 A. Arrangement is made so that the active material layer  33 B is opposed to the active material layer  12 . The structures of the current collector  33 A, the active material layer  33 B, and the separator  34  are similar to those of the current collector  23 A, the active material layer  23 B, and the separator  24  respectively described above.  
      The electrolyte layer  35  is made of a so-called gelatinous electrolyte in which an electrolytic solution is held in a holding body composed of a polymer. The gelatinous electrolyte is preferable, since a high ion conductivity can be thereby obtained, and leakage of the battery can be thereby prevented. The composition of the electrolytic solution is similar to that of the coin-type secondary battery shown in  FIG. 2 . As a polymer material, for example, polyvinylidene fluoride can be cited.  
      The secondary battery can be manufactured, for example, as follows.  
      First, the electrolyte layer  35  in which an electrolytic solution is held in a holding body is formed on the anode  10  and the cathode  33 , respectively. Then, the leads  31  and  32  are attached thereto. Next, the anode  10  and the cathode  33  formed with the electrolyte layer  35  are layered and spirally wound with the separator  34  in between. The protective tape  36  is adhered to the outermost periphery thereof to form the spirally wound electrode body  30 . Subsequently, for example, the spirally wound electrode body  30  is sandwiched between the package members  41 , and outer edges of the package members  41  are contacted by thermal fusion bonding or the like to enclose the spirally wound electrode body  30 . Then, the adhesive films  42  are inserted between the leads  31  and  32  and the package member  41 . Thereby, the secondary battery shown in  FIG. 3  and  FIG. 4  is completed.  
      Otherwise, the secondary battery may be manufactured as follows. First, the leads  31  and  32  are respectively attached to the anode  10  and the cathode  33 . After that, the anode  10  and the cathode  33  are layered and spirally wound with the separator  34  in between. The protective tape  36  is adhered to the outermost periphery thereof, and a spirally wound body as a precursor of the spirally wound electrode body  30  is formed. Next, the spirally wound body is sandwiched between the package members  41 , and the outermost peripheries except for one side are thermally fusion-bonded to obtain a pouched state. After that, an electrolytic composition containing an electrolytic solution, a monomer as a raw material for a polymer, a polymerization initiator, and if necessary other material such as a polymerization inhibitor is injected into the package member  41 . Subsequently, the opening of the package member  41  is thermally fusion-bonded and hermetically sealed in the vacuum atmosphere. Then, the resultant is heated to polymerize the monomer to obtain a polymer. Thereby, the gelatinous electrolyte layer  35  is formed. In the result, the secondary battery shown in  FIG. 3  and  FIG. 4  is completed.  
      The actions of the secondary battery are similar to that of the coin-type secondary battery shown in  FIG. 2 .  
      As above, according to this embodiment, the current collector  11  which contains copper as an element with the ratio I 220 /I 200  of 2.5 or less at least in part is used. Therefore, even when the active material layer  12  is largely expanded and shrunk due to charge and discharge, the stress can be relaxed, the current collector  11  can be prevented from being deformed, and the active material layer  12  can be prevented from being separated. In the result, the battery characteristics such as a capacity and cycle characteristics can be improved.  
     EXAMPLES  
      Further, specific examples of the invention will be hereinafter described in detail with reference to the drawings.  
     Examples 1 to 17  
      The secondary batteries shown in  FIGS. 3 and 4  were fabricated.  
      First, the current collector  11  made of a copper foil was prepared. Then, in Examples 1 to 17, the ratio I 220 /I 200  of the current collector  11  was changed by using manufacturing methods different from each other. For the current collector  11  of Examples 1 to 17, X-ray diffraction measurement was performed to examine the ratio I 220 /I 200 . As a measurement apparatus, an X-ray apparatus of Rigaku Corporation was used. The X-ray tube was CuKa, the tube voltage was 40 kV, the tube current was 40 mA, the scanning method was θ-2θ method, and the measurement range was 20 deg-80 deg. Based on the obtained X-ray diffraction pattern, the ratio I 220 /I 200  was obtained from the peak area I 220  resulting from the (220) crystal face of copper observed in the vicinity of 74.1 deg and the peak area I 200  resulting from the (200) crystal face of copper observed in the vicinity of 50.4 deg. The obtained results are shown in Table 1.  
      Next, the active material layer  12  containing silicon being about 5 μm thick was formed on the current collector  11  by sputtering method to form the anode  10 . Further, the active material layer  12  was formed by coating the current collector  11  of Examples 1 to 17 with silicon powder with an average particle diameter of 2 μm and pressing the resultant, and thereby the anode  10  was formed. For the formed respective anodes  10 , X-ray diffraction measurement was performed to examine the ratio I 220 /I 200 . The almost same results as those before forming the active material layer  12  were obtained.  
      Further, lithium cobaltate (LiCoO 2 ) powder with an average particle diameter of 5 μm as a cathode active material, carbon black as an electrical conductor, and polyvinylidene fluoride as a binder were mixed. A resultant mixture was put in N-methyl-2-pyrrolidone as a disperse medium to obtain slurry. Next, the current collector  33 A made of an aluminum foil being 15 μm thick was coated with the slurry, which was dried and pressed to form the active material layer  33 B.  
      Subsequently, 37.5 wt % of ethylene carbonate, 37.5 wt % of propylene carbonate, 10 wt % of vinylene carbonate, and 15 wt % of LiPF 6  were mixed to prepare an electrolytic solution. The both faces of the anode  10  and the cathode  33  were respectively coated with a mixture obtained by mixing the electrolytic solution and polyvinylidene fluoride as a block copolymer with weight average molecular weight of 0.6 million to form the electrolyte layer  35 . After that, the leads  31  and  32  were attached, the anode  10  and the cathode  33  were layered and spirally wound with the separator  34  in between, and the resultant body was enclosed in the package member  41  made of an aluminum laminated film. Thereby, the secondary batteries of Examples 1 to 17 were obtained.  
      As Comparative examples 1 to 5 relative to Examples 1 to 17, secondary batteries were fabricated in the same manner as in Examples 1 to 17, except that current collectors with the ratio I 220 /I 200  different from those of Examples 1 to 17 were used. For the current collectors of Comparative examples 1 to 5, the ratio I 220 /I 200  was examined in the same manner as in Examples 1 to 17. The results are shown in Table 2.  
      For the fabricated secondary batteries of Examples 1 to 17 and Comparative examples 1 to 5, charge and discharge test was performed at 25 deg C., and the capacity retention ratio at the 50th cycle to the second cycle was obtained. Then, charge was performed until the battery voltage reached 4.2 V at a constant current density of 1 mA/cm 2 , and then performed until the current density reached 0.05 mA/cm 2  at a constant voltage of 4.2 V. Discharge was performed until the battery voltage reached 2.5 V at a constant current density of 1 mA/cm 2 . Charge was performed so that a utility ratio of the capacity of the anode  10  became 90% to prevent metal lithium from being precipitated on the anode  10 . The capacity retention ratio was calculated as a ratio of the discharge capacity at the 50th cycle to the discharge capacity at the second cycle, that is, as (the discharge capacity at the 50th cycle/the discharge capacity at the second cycle)×100. The results are shown in Table 1.  
      Further, for the secondary batteries of Examples 1 to 17, the secondary batteries were disassembled and the anodes  10  were taken out after repeating charge and discharge 50 cycles. X-ray diffraction measurement was performed and the ratio I 220 /I 200  was examined. The almost same results as the values shown in Table 1 were obtained  
                       TABLE 1                                      Capacity retention ratio (%)                                 Current   Active material   Active material           collector   layer formed   layer formed           I 220 /I 200     by sputtering   by coating                                         Example 1   2.423   76   76       Example 2   2.246   78   76       Example 3   1.629   81   77       Example 4   1.548   82   77       Example 5   0.99   83   75       Example 6   0.785   84   77       Example 7   0.757   86   78       Example 8   0.431   87   80       Example 9   0.411   86   79       Example 10   0.361   89   80       Example 11   0.335   89   81       Example 12   0.208   90   80       Example 13   0.194   88   80       Example 14   0.155   91   80       Example 15   0.035   82   78       Example 16   0.023   73   75       Example 17   0.011   74   75       Comparative example 1   7.147   50   73       Comparative example 2   6.554   44   72       Comparative example 3   3.323   29   71       Comparative example 4   3.174   55   69       Comparative example 5   2.782   68   72                  
 
      As shown in Table 1, according to Examples 1 to 17 in which the current collector  11  with the ratio I 220 /I 200  of 2.5 or less was used, the capacity retention ratio could be improved compared to Comparative examples 1 to 5 in which the current collector with the ratio I 220 /I 200  larger than 2.5 was used. Further, the improvement degree was larger in the case that the active material layer  12  was formed by sputtering method than in the case that the active material layer  12  was formed by coating.  
      Further, some secondary batteries were taken out from the secondary batteries of Examples and Comparative examples, and a relation between the elongation percentage/the tensile strength of the current collector  11  and the capacity retention ratio was examined. The results are shown in Table 2. In Table 2, the upper frame shows elongation percentages in descending order, and the lower frame shows tensile strengths in descending order.  
                                   TABLE 2                                   Elongation       Current   Capacity           percentage   Tensile strength   collector   retention (%)           (%)   (N/mm 2 )   I 220 /I 200     (sputtering)                                                        Comparative   15   352   2.782   68       example 5       Example 11   12.5   258   0.335   89       Comparative   12.3   392   6.554   44       example 2       Example 9   9.2   354   0.411   86       Example 12   7   333   0.28   90       Comparative   6   320   3.174   55       example 4       Example 17   2   440   0.011   72       Example 16   1.5   260   0.023   73       Example 17   2   440   0.011   72       Comparative   12.3   392   6.554   44       example 2       Example 9   9.2   354   0.411   86       Comparative   15   352   2.782   68       example 5       Example 12   7   333   0.28   90       Comparative   6   320   3.174   55       example 4       Example 16   1.5   260   0.023   73       Example 11   12.5   258   0.335   89                  
 
      As shown in Table 2, no relation was found between the elongation percentage/the tensile strength and the capacity retention ratio. For example, Comparative example 5 and Example 9 have the tensile strength almost similar to each other. However, though Comparative example 5 has the elongation percentage of 15%, which is higher than that of Example 9, Example 9 with smaller elongation percentage shows a higher capacity retention ratio. Further, Comparative example 2 and Example 11 have the elongation percentage almost similar to each other. However, though Comparative example 2 has the tensile strength of 392 N/mm 2 , which is higher than that of Example 11, Example 11 with a smaller tensile strength shows a higher capacity retention ratio.  
      That is, it was found that when the current collector  11  containing copper as an element and having the ratio I 220 /I 200  of 2.5 or less at least in part was used, stress could be relaxed, and the battery characteristics such as a capacity and cycle characteristics could be improved. Further, it was found that at least part of the active material layer  12  was formed by vapor-phase deposition method such as sputtering, higher effects could be obtained.  
      The invention has been described with reference to the embodiment and the examples. However, the invention is not limited to the foregoing embodiment and the foregoing examples, and various modifications may be made. For example, in the foregoing embodiment and the foregoing examples, descriptions have been given of the case using the electrolytic solution as a liquid electrolyte or the gelatinous electrolyte. However, other electrolyte may be used. As other electrolyte, a solid electrolyte having ion conductivity, a mixture of a solid electrolyte and an electrolytic solution, or a mixture of a solid electrolyte and a gelatinous electrolyte can be cited.  
      As a solid electrolyte, for example, a polymer solid electrolyte in which an electrolyte salt is dispersed in a polymer having ion conductivity, or an inorganic solid electrolyte formed of ion conductive glass, ionic crystal or the like can be used. As a polymer of the polymer solid electrolyte, for example, an ether polymer such as polyethylene oxide and a cross-linked body containing polyethylene oxide, an ester polymer such as poly methacrylate, or an acrylate polymer can be used singly, by mixing, or by copolymerization. As an inorganic solid electrolyte, a substance containing lithium nitride, lithium phosphate or the like can be used.  
      Further, in the foregoing embodiment and the foregoing examples, descriptions have been given of the coin type secondary battery and the spirally wound laminated type secondary battery. However, the invention can be similarly applied to a secondary battery having other shape such as a cylinder type secondary battery, a square type secondary battery, a button type secondary battery, a thin secondary battery, a large secondary battery, and a laminated type secondary battery. Further, the invention can be applied to primary batteries in addition to the secondary batteries.  
      It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alternations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.