JP5713206B2 - Non-aqueous secondary battery - Google Patents

Description

  The present invention relates to a non-aqueous secondary battery.

  In the present specification, the “secondary battery” generally refers to a battery that can be repeatedly charged, and includes so-called storage batteries such as lithium secondary batteries (typically lithium ion secondary batteries) and nickel metal hydride batteries. In the present specification, the “active material” refers to reversibly occlusion and release (typically insertion and removal) of a chemical species that serves as a charge carrier in a secondary battery (for example, lithium ions in a lithium ion secondary battery). A possible substance. Further, among secondary batteries, a secondary battery in which a non-aqueous electrolyte (for example, a non-aqueous electrolyte) is used as an electrolyte is appropriately referred to as a “non-aqueous secondary battery”.

  For example, Japanese Patent Application Laid-Open No. 2008-47402 exemplifies a secondary battery in which a sheet-like positive electrode and a negative electrode face each other with a polymer support layer holding a non-aqueous electrolyte and a separator interposed therebetween. Here, the positive electrode has a structure in which a positive electrode current collector is covered with a positive electrode active material layer. The positive electrode active material layer includes a positive electrode active material and a binder polymer. The negative electrode has a structure in which a negative electrode current collector is coated with a negative electrode active material layer. The negative electrode active material layer includes a negative electrode active material and a binder polymer. Specific examples of the binder polymer include polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HEP), (PVdF-HEP-CTFE), styrene-butadiene copolymer ( SBR).

  The polymer support layer is a layer having ionic conductivity and capable of holding a non-aqueous electrolyte, and is made of a matrix polymer. Examples of the matrix polymer used in the polymer support layer include acrylonitrile-based polymers, aromatic polyamides, acrylonitrile / butadiene copolymers and the like having a copolymerization amount of acrylonitrile of 50% or more.

  The solvent swelling ratio of the matrix polymer constituting the polymer support layer (polymer support) is the solvent swelling ratio of the binder polymer contained in one or both of the positive electrode mixture layer and the negative electrode mixture layer. It has been proposed to select a larger material. According to such a configuration, it is described that it is possible to provide a secondary battery that eliminates leakage of the electrolytic solution and has excellent current load characteristics and improved charge / discharge cycle characteristics.

  Japanese Patent Application Laid-Open No. 2002-50405 proposes a polymer electrolyte battery using a blend of two kinds of polymers having different swelling ratios with an electrolytic solution as a polymer contained in a mixture layer of a positive electrode and a negative electrode. In this case, only a polymer with a high swelling rate is gelled, and the other polymer with a low swelling rate maintains the polymer network. Thus, it is described that a polymer electrolyte battery excellent in safety can be realized in which the battery characteristics are not deteriorated even when charge and discharge are repeated and there is no free electrolyte in the battery.

JP 2008-47402 A JP 2002-50405 A

  By the way, as a typical form of an electrode body of a non-aqueous secondary battery, a positive electrode and a negative electrode are overlapped with a strip-shaped positive electrode, a strip-shaped negative electrode, and a strip-shaped separator, with a separator interposed therebetween. A structure provided with a wound electrode body wound around is known. In such a structure, for example, it can be employed in a lithium ion secondary battery.

  In addition, a power source used for a drive mechanism of a hybrid vehicle or an electric vehicle requires a high output during acceleration and generates a large discharge. In addition, during braking, rapid charging is performed in order to efficiently store regenerative energy. For this reason, depending on the running pattern, large discharge and rapid charging are repeated. Such repeated large discharge and rapid charge are particularly likely to occur in automobile applications in various applications of secondary batteries.

  When the present inventor uses a non-aqueous secondary battery equipped with a wound electrode body for an application in which rapid charging and rapid discharging are repeated, battery characteristics such as increased resistance and decreased input / output characteristics are used depending on use. We found that it is easy to deteriorate. In automotive applications, it is desirable that battery characteristics such as increased resistance and decreased input / output characteristics be maintained at a high level even when rapid charging and rapid discharging are repeated.

  Here, a non-aqueous secondary battery according to an embodiment of the present invention includes a wound electrode body, a battery case containing the wound electrode body, and a non-aqueous electrolyte injected into the battery case. ing. Here, the wound electrode body includes a positive electrode current collector, a positive electrode active material layer held by the positive electrode current collector, a negative electrode current collector, a negative electrode active material layer held by the negative electrode current collector, and a positive electrode A separator interposed between the active material layer and the negative electrode active material layer.

  Each of the positive electrode current collector and the negative electrode current collector is a band-shaped member, and is aligned in the longitudinal direction so that the positive electrode active material layer and the negative electrode active material layer face each other with a separator interposed therebetween. Has been placed. The positive electrode current collector and the negative electrode current collector are accommodated in a battery case in a state of being wound around a positive electrode current collector or a winding axis set in the width direction of the negative electrode current collector. In this non-aqueous secondary battery, in the direction of the winding axis of the wound electrode body, the edge on both sides of at least one of the positive electrode active material layer and the negative electrode active material layer is an intermediate except the edge. The degree of swelling with respect to the non-aqueous electrolyte is higher than that of the part.

  According to this non-aqueous secondary battery, the non-aqueous electrolyte is maintained in the intermediate portion in the winding axis direction even in applications where rapid charging and rapid discharging are repeated. For this reason, it is possible to suppress deterioration of battery characteristics such as resistance increase and input / output characteristic deterioration.

  In this case, the active material layer of at least one of the positive electrode active material layer and the negative electrode active material layer has a material having a higher degree of swelling with respect to the non-aqueous electrolyte at the edge in the winding axis direction than in the intermediate portion. It may be included. Moreover, the center part may contain more material with a low swelling degree with respect to a non-aqueous electrolyte than an edge part.

  In addition, at least one of the positive electrode active material layer and the negative electrode active material layer includes a binder, and the binder included in the edge in the winding axis direction excludes the edge. The degree of swelling with respect to the non-aqueous electrolyte may be higher than that of the binder contained in the intermediate portion in the winding axis direction. In this case, for example, the binder contained in the edge portion in the winding axis direction and the binder contained in the intermediate portion may be evaluated for an average degree of swelling of the binder contained in each portion.

  As a specific example, when the negative electrode active material layer includes SBR, the SBR included in the edge of the negative electrode active material layer is more resistant to the non-aqueous electrolyte than the SBR included in the intermediate portion. The degree of swelling should be high. In addition, the edge portion may be defined, for example, in an area of 10% from the edges on both sides of the active material layer in the direction of the winding axis.

FIG. 1 is a diagram illustrating an example of the structure of a lithium ion secondary battery. FIG. 2 is a view showing a wound electrode body of a lithium ion secondary battery. 3 is a cross-sectional view showing a III-III cross section in FIG. 2. FIG. 4 is a cross-sectional view showing the structure of the positive electrode mixture layer. FIG. 5 is a cross-sectional view showing the structure of the negative electrode mixture layer. FIG. 6 is a side view showing a welding location between an uncoated portion of the wound electrode body and the electrode terminal. FIG. 7 is a diagram schematically illustrating a state of the lithium ion secondary battery during charging. FIG. 8 is a diagram schematically showing a state of the lithium ion secondary battery during discharge. FIG. 9 is a schematic view showing a wound electrode body according to an embodiment of the present invention. FIG. 10 is a schematic view showing a laminated structure of wound electrode bodies according to an embodiment of the present invention. FIG. 11 is a view showing a wound electrode body according to an embodiment of the present invention. 12 is a cross-sectional view taken along the line XII-XII in FIG. FIG. 13 is a diagram illustrating an example of a coating process of the negative electrode active material layer. FIG. 14 is a diagram illustrating a typical example of a Cole-Cole plot (Nyquist plot) in the AC impedance measurement method. FIG. 15 shows the results of measuring the reaction resistance before and after the charge / discharge cycle for Sample A and Sample B. FIG. 16 evaluates the rate of increase in reaction resistance before and after the charge / discharge cycle for sample A and sample B. FIG. 17 shows the measurement result of the molar concentration (mol / L) of LiPF _{6 in} the width direction of the negative electrode active material layer of the evaluation cell before the charge / discharge cycle. FIG. 18 shows the measurement result of the molar concentration (mol / L) of LiPF _{6 in} the width direction of the negative electrode active material layer after the charge / discharge cycle for sample A. FIG. 19 shows the measurement result of the molar concentration (mol / L) of LiPF _{6 in} the width direction of the negative electrode active material layer after the charge / discharge cycle for sample B. FIG. 20 is a diagram illustrating a vehicle equipped with a lithium ion secondary battery.

  Hereinafter, a non-aqueous secondary battery according to an embodiment of the present invention will be described with reference to the drawings. Here, a structural example of a non-aqueous secondary battery will be described first, and then a non-aqueous secondary battery (lithium ion secondary battery) according to an embodiment of the present invention will be described in detail. In addition, the same code | symbol is attached | subjected suitably to the member and site | part which show | play the same effect | action. Each drawing is schematically drawn and does not necessarily reflect the real thing. Each drawing shows an example only and does not limit the present invention unless otherwise specified. Here, one structural example of a non-aqueous secondary battery and a non-aqueous secondary battery (lithium ion secondary battery) according to an embodiment of the present invention will be described as appropriate based on common drawings. Yes.

≪Lithium ion secondary battery 100≫
FIG. 1 shows a lithium ion secondary battery 100. As shown in FIG. 1, the lithium ion secondary battery 100 includes a wound electrode body 200 and a battery case 300. FIG. 2 is a view showing the wound electrode body 200. FIG. 3 shows a III-III cross section in FIG.

  As shown in FIG. 2, the wound electrode body 200 includes a positive electrode sheet 220, a negative electrode sheet 240, and separators 262 and 264. The positive electrode sheet 220, the negative electrode sheet 240, and the separators 262 and 264 are respectively strip-shaped sheet materials.

≪Positive electrode sheet 220≫
The positive electrode sheet 220 includes a strip-shaped positive electrode current collector 221 and a positive electrode active material layer 223. For the positive electrode current collector 221, a metal foil suitable for the positive electrode can be suitably used. For the positive electrode current collector 221, for example, a strip-shaped aluminum foil having a predetermined width and a thickness of approximately 15 μm can be used. An uncoated portion 222 is set along the edge on one side in the width direction of the positive electrode current collector 221. In the illustrated example, the positive electrode active material layer 223 is held on both surfaces of the positive electrode current collector 221 except for the uncoated portion 222 set on the positive electrode current collector 221 as shown in FIG. The positive electrode active material layer 223 contains a positive electrode active material. The positive electrode active material layer 223 is formed by applying a positive electrode mixture containing a positive electrode active material to the positive electrode current collector 221.

<< Positive Electrode Active Material Layer 223 and Positive Electrode Active Material Particles 610 >>
Here, FIG. 4 is a cross-sectional view of the positive electrode sheet 220. In FIG. 4, the positive electrode active material particles 610, the conductive material 620, and the binder 630 in the positive electrode active material layer 223 are schematically illustrated so that the structure of the positive electrode active material layer 223 becomes clear. As shown in FIG. 4, the positive electrode active material layer 223 includes positive electrode active material particles 610, a conductive material 620, and a binder 630.

As the positive electrode active material particles 610, a material that can be used as a positive electrode active material of a lithium ion secondary battery can be used. Examples of the positive electrode active material particles 610 include LiNiCoMnO ₂ (lithium nickel cobalt manganese composite oxide), LiNiO ₂ (lithium nickelate), LiCoO ₂ (lithium cobaltate), LiMn ₂ O ₄ (lithium manganate), LiFePO _And lithium transition metal oxides such as ₄ (lithium iron phosphate). Here, LiMn ₂ O ₄ has, for example, a spinel structure. LiNiO ₂ or LiCoO ₂ has a layered rock salt structure. LiFePO ₄ has, for example, an olivine structure. LiFePO ₄ having an olivine structure includes, for example, nanometer order particles. Moreover, LiFePO _{4 having} an olivine structure can be further covered with a carbon film.

≪Conductive material 620≫
Examples of the conductive material 620 include carbon materials such as carbon powder and carbon fiber. As the conductive material 620, one kind selected from such conductive materials may be used alone, or two or more kinds may be used in combination. As the carbon powder, various carbon blacks (for example, acetylene black, oil furnace black, graphitized carbon black, carbon black, graphite, ketjen black), graphite powder, and the like can be used.

≪Binder 630≫
Further, the binder 630 binds the positive electrode active material particles 610 and the conductive material 620 included in the positive electrode active material layer 223, or binds these particles and the positive electrode current collector 221. As the binder 630, a polymer that can be dissolved or dispersed in a solvent to be used can be used. For example, in a positive electrode mixture composition using an aqueous solvent, a cellulose polymer (carboxymethylcellulose (CMC), hydroxypropylmethylcellulose (HPMC), etc.), a fluorine resin (eg, polyvinyl alcohol (PVA), polytetrafluoroethylene, etc.) (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP, etc.), rubbers (vinyl acetate copolymer, styrene butadiene copolymer (SBR), acrylic acid-modified SBR resin (SBR latex), etc.) A water-soluble or water-dispersible polymer such as can be preferably used. In the positive electrode mixture composition using a non-aqueous solvent, a polymer (polyvinylidene fluoride (PVDF), polyvinylidene chloride (PVDC), polyacrylonitrile (PAN), etc.) can be preferably employed.

≪Thickener, solvent≫
The positive electrode active material layer 223 is prepared, for example, by preparing a positive electrode mixture in which the above-described positive electrode active material particles 610 and the conductive material 620 are mixed in a paste (slurry) with a solvent, applied to the positive electrode current collector 221, and dried. And is formed by rolling. At this time, as the solvent for the positive electrode mixture, either an aqueous solvent or a non-aqueous solvent can be used. A suitable example of the non-aqueous solvent is N-methyl-2-pyrrolidone (NMP). The polymer material exemplified as the binder 630 may be used for the purpose of exhibiting a function as a thickener or other additive of the positive electrode mixture in addition to the function as a binder.

  The mass ratio of the positive electrode active material in the total positive electrode mixture is preferably about 50 wt% or more (typically 50 to 95 wt%), and usually about 70 to 95 wt% (for example, 75 to 90 wt%). It is more preferable. Moreover, the ratio of the electrically conductive material to the whole positive electrode mixture can be, for example, about 2 to 20 wt%, and is usually preferably about 2 to 15 wt%. In the composition using the binder, the ratio of the binder to the whole positive electrode mixture can be, for example, about 1 to 10 wt%, and usually about 2 to 5 wt% is preferable.

<< Negative Electrode Sheet 240 >>
As illustrated in FIG. 2, the negative electrode sheet 240 includes a strip-shaped negative electrode current collector 241 and a negative electrode active material layer 243. For the negative electrode current collector 241, a metal foil suitable for the negative electrode can be suitably used. The negative electrode current collector 241 is made of a strip-shaped copper foil having a predetermined width and a thickness of about 10 μm. On one side in the width direction of the negative electrode current collector 241, an uncoated part 242 is set along the edge. The negative electrode active material layer 243 is formed on both surfaces of the negative electrode current collector 241 except for the uncoated portion 242 set on the negative electrode current collector 241. The negative electrode active material layer 243 is held by the negative electrode current collector 241 and contains at least a negative electrode active material. In the negative electrode active material layer 243, a negative electrode mixture containing a negative electrode active material is applied to the negative electrode current collector 241.

<< Negative Electrode Active Material Layer 243 >>
FIG. 5 is a cross-sectional view of the negative electrode sheet 240 of the lithium ion secondary battery 100. As shown in FIG. 5, the negative electrode active material layer 243 includes negative electrode active material particles 710, a thickener (not shown), a binder 730, and the like. In FIG. 5, the negative electrode active material particles 710 and the binder 730 in the negative electrode active material layer 243 are schematically illustrated so that the structure of the negative electrode active material layer 243 becomes clear.

<< Negative Electrode Active Material Particles 710 >>
As the negative electrode active material particles 710, one or two or more materials conventionally used for lithium ion secondary batteries can be used as the negative electrode active material without any particular limitation. For example, a particulate carbon material (carbon particles) including a graphite structure (layered structure) at least in part. More specifically, the negative electrode active material is, for example, natural graphite, natural graphite coated with an amorphous carbon material, graphite (graphite), non-graphitizable carbon (hard carbon), graphitizable carbon ( Soft carbon) or a carbon material combining these may be used. Here, the negative electrode active material particles 710 are illustrated using so-called scaly graphite, but the negative electrode active material particles 710 are not limited to the illustrated example.

≪Thickener, solvent≫
The negative electrode active material layer 243 is prepared, for example, by preparing a negative electrode mixture in which the negative electrode active material particles 710 and the binder 730 described above are mixed in a paste (slurry) with a solvent, and applied to the negative electrode current collector 241 and dried. It is formed by rolling. At this time, any of an aqueous solvent and a non-aqueous solvent can be used as the solvent for the negative electrode mixture. A suitable example of the non-aqueous solvent is N-methyl-2-pyrrolidone (NMP). For the binder 730, the polymer material exemplified as the binder 630 of the positive electrode active material layer 223 (see FIG. 4) can be used. Further, the polymer material exemplified as the binder 630 of the positive electrode active material layer 223 may be used for the purpose of exhibiting a function as a thickener or other additive of the positive electrode mixture in addition to the function as a binder. possible.

<< Separators 262, 264 >>
The separators 262 and 264 are members that separate the positive electrode sheet 220 and the negative electrode sheet 240 as shown in FIG. 1 or FIG. In this example, the separators 262 and 264 are made of a strip-shaped sheet material having a predetermined width and having a plurality of minute holes. As the separators 262 and 264, for example, a single layer structure separator or a multilayer structure separator made of a porous polyolefin resin can be used. In this example, as shown in FIGS. 2 and 3, the width b1 of the negative electrode active material layer 243 is slightly wider than the width a1 of the positive electrode active material layer 223. Furthermore, the widths c1 and c2 of the separators 262 and 264 are slightly wider than the width b1 of the negative electrode active material layer 243 (c1, c2>b1> a1).

  In the example shown in FIGS. 1 and 2, the separators 262 and 264 are made of sheet-like members. The separators 262 and 264 may be members that insulate the positive electrode active material layer 223 and the negative electrode active material layer 243 and allow the electrolyte to move. Therefore, it is not limited to a sheet-like member. The separators 262 and 264 may be formed of a layer of insulating particles formed on the surface of the positive electrode active material layer 223 or the negative electrode active material layer 243, for example, instead of the sheet-like member. Here, as the particles having insulating properties, inorganic fillers having insulating properties (for example, fillers such as metal oxides and metal hydroxides) or resin particles having insulating properties (for example, particles such as polyethylene and polypropylene). ).

  In this wound electrode body 200, as shown in FIG. 2 and FIG. 3, the positive electrode sheet 220 and the negative electrode sheet 240 have a positive electrode active material layer 223 and a negative electrode active material layer 243 with separators 262 and 264 interposed therebetween. Are stacked so that they face each other. More specifically, in the wound electrode body 200, the positive electrode sheet 220, the negative electrode sheet 240, and the separators 262 and 264 are stacked in the order of the positive electrode sheet 220, the separator 262, the negative electrode sheet 240, and the separator 264.

  At this time, the positive electrode active material layer 223 and the negative electrode active material layer 243 are opposed to each other with the separators 262 and 264 interposed therebetween. Then, on one side of the portion where the positive electrode active material layer 223 and the negative electrode active material layer 243 face each other, a portion of the positive electrode current collector 221 where the positive electrode active material layer 223 is not formed (uncoated portion 222) protrudes. Yes. A portion of the negative electrode current collector 241 where the negative electrode active material layer 243 is not formed (uncoated portion 242) protrudes on the side opposite to the side where the uncoated portion 222 protrudes. Further, the positive electrode sheet 220, the negative electrode sheet 240, and the separators 262 and 264 are wound along the winding axis WL set in the width direction of the positive electrode sheet 220 in a state where they are overlapped in this way.

≪Battery case 300≫
In this example, as shown in FIG. 1, the battery case 300 is a so-called square battery case, and includes a container body 320 and a lid 340. The container main body 320 has a bottomed rectangular tube shape and is a flat box-shaped container having one side surface (upper surface) opened. The lid 340 is a member that is attached to the opening (opening on the upper surface) of the container body 320 and closes the opening.

  In a vehicle-mounted secondary battery, it is desired to improve the weight energy efficiency (battery capacity per unit weight) in order to improve the fuel efficiency of the vehicle. In this embodiment, the container main body 320 and the lid body 340 constituting the battery case 300 are made of a lightweight metal such as aluminum or an aluminum alloy. Thereby, weight energy efficiency can be improved.

  The battery case 300 has a flat rectangular internal space as a space for accommodating the wound electrode body 200. Further, as shown in FIG. 1, the flat internal space of the battery case 300 is slightly wider than the wound electrode body 200. In this embodiment, the battery case 300 includes a bottomed rectangular tubular container body 320 and a lid 340 that closes the opening of the container body 320. Electrode terminals 420 and 440 are attached to the lid 340 of the battery case 300. The electrode terminals 420 and 440 pass through the battery case 300 (lid 340) and come out of the battery case 300. The lid 340 is provided with a liquid injection hole 350 and a safety valve 360.

  As shown in FIG. 2, the wound electrode body 200 is flatly pushed and bent in one direction orthogonal to the winding axis WL. In the example shown in FIG. 2, the uncoated part 222 of the positive electrode current collector 221 and the uncoated part 242 of the negative electrode current collector 241 are spirally exposed on both sides of the separators 262 and 264, respectively. As shown in FIG. 6, in this embodiment, the intermediate portions 224 and 244 of the uncoated portions 222 and 242 are gathered together and welded to the tip portions 420 a and 440 a of the electrode terminals 420 and 440. At this time, for example, ultrasonic welding is used for welding the electrode terminal 420 and the positive electrode current collector 221 due to the difference in materials. Further, for example, resistance welding is used for welding the electrode terminal 440 and the negative electrode current collector 241. Here, FIG. 6 is a side view showing a welded portion between the intermediate portion 224 (244) of the uncoated portion 222 (242) of the wound electrode body 200 and the electrode terminal 420 (440), and VI in FIG. It is -VI sectional drawing.

  The wound electrode body 200 is attached to the electrode terminals 420 and 440 fixed to the lid body 340 in a state where the wound electrode body 200 is pressed and bent flat. The wound electrode body 200 is accommodated in a flat internal space of the container body 320 as shown in FIG. The container body 320 is closed by the lid 340 after the wound electrode body 200 is accommodated. The joint 322 (see FIG. 1) between the lid 340 and the container main body 320 is welded and sealed, for example, by laser welding. Thus, in this example, the wound electrode body 200 is positioned in the battery case 300 by the electrode terminals 420 and 440 fixed to the lid 340 (battery case 300).

≪Electrolytic solution≫
Thereafter, an electrolytic solution is injected into the battery case 300 from a liquid injection hole 350 provided in the lid 340. As the electrolytic solution, a so-called non-aqueous electrolytic solution (non-aqueous electrolyte) that does not use water as a solvent is used. In this example, an electrolytic solution in which LiPF ₆ is contained at a concentration of about 1 mol / liter in a mixed solvent of ethylene carbonate and diethyl carbonate (for example, a mixed solvent having a volume ratio of about 1: 1) is used. Yes. Thereafter, a metal sealing cap 352 is attached (for example, welded) to the liquid injection hole 350 to seal the battery case 300. The electrolytic solution is not limited to the electrolytic solution exemplified here. For example, non-aqueous electrolytes conventionally used for lithium ion secondary batteries can be used as appropriate.

≪Hole≫
Here, the positive electrode active material layer 223 has minute gaps 225 that should also be referred to as cavities, for example, between the positive electrode active material particles 610 and the conductive material 620 (see FIG. 4). An electrolytic solution (not shown) can penetrate into the minute gaps of the positive electrode active material layer 223. In addition, the negative electrode active material layer 243 has minute gaps 245 that should also be referred to as cavities, for example, between the negative electrode active material particles 710 (see FIG. 5). Here, the gaps 225 and 245 (cavities) are appropriately referred to as “holes”. As shown in FIG. 2, the wound electrode body 200 has uncoated portions 222 and 242 spirally wound on both sides along the winding axis WL. On both sides 252 and 254 along the winding axis WL, the electrolytic solution can permeate from the gaps between the uncoated portions 222 and 242. For this reason, in the lithium ion secondary battery 100, the electrolytic solution is immersed in the positive electrode active material layer 223 and the negative electrode active material layer 243.

≪Gas escape route≫
In this example, the flat internal space of the battery case 300 is slightly wider than the wound electrode body 200 deformed flat. On both sides of the wound electrode body 200, gaps 310 and 312 are provided between the wound electrode body 200 and the battery case 300. The gaps 310 and 312 serve as a gas escape path. For example, when the temperature of the lithium ion secondary battery 100 becomes abnormally high, for example, when overcharge occurs, the electrolyte may be decomposed and gas may be generated abnormally. In this embodiment, the abnormally generated gas moves toward the safety valve 360 through the gaps 310 and 312 between the wound electrode body 200 and the battery case 300 on both sides of the wound electrode body 200, and from the safety valve 360 to the battery case 300. Exhausted outside.

  In the lithium ion secondary battery 100, the positive electrode current collector 221 and the negative electrode current collector 241 are electrically connected to an external device through electrode terminals 420 and 440 that penetrate the battery case 300. Hereinafter, the operation of the lithium ion secondary battery 100 during charging and discharging will be described.

≪Operation when charging≫
FIG. 7 schematically shows the state of the lithium ion secondary battery 100 during charging. At the time of charging, as shown in FIG. 7, the electrode terminals 420 and 440 (see FIG. 1) of the lithium ion secondary battery 100 are connected to the charger 290. Due to the action of the charger 290, lithium ions (Li) are released from the positive electrode active material in the positive electrode active material layer 223 to the electrolytic solution 280 during charging. In addition, charges are released from the positive electrode active material layer 223. The discharged electric charge is sent to the positive electrode current collector 221 through a conductive material (not shown), and further sent to the negative electrode sheet 240 through the charger 290. In the negative electrode sheet 240, electric charges are stored, and lithium ions (Li) in the electrolytic solution 280 are absorbed and stored in the negative electrode active material in the negative electrode active material layer 243.

<< Operation during discharge >>
FIG. 8 schematically shows a state of the lithium ion secondary battery 100 during discharging. At the time of discharging, as shown in FIG. 8, charges are sent from the negative electrode sheet 240 to the positive electrode sheet 220, and lithium ions stored in the negative electrode active material layer 243 are released to the electrolyte solution 280. In the positive electrode, lithium ions in the electrolytic solution 280 are taken into the positive electrode active material in the positive electrode active material layer 223.

  Thus, in charging / discharging of the lithium ion secondary battery 100, lithium ions travel between the positive electrode active material layer 223 and the negative electrode active material layer 243 through the electrolytic solution 280. At the time of charging, electric charge is sent from the positive electrode active material to the positive electrode current collector 221 through the conductive material. On the other hand, at the time of discharging, the charge is returned from the positive electrode current collector 221 to the positive electrode active material through the conductive material.

  During charging, the smoother the movement of lithium ions and the movement of electrons, the more efficient and rapid charging is considered possible. At the time of discharging, it is considered that the smoother the movement of lithium ions and the movement of electrons, the lower the resistance of the battery, the amount of discharge, and the output of the battery.

≪Other battery types≫
The above shows an example of a lithium ion secondary battery. The lithium ion secondary battery is not limited to the above form. Similarly, an electrode sheet in which an electrode mixture is applied to a metal foil is used in various other battery forms. For example, as another battery type, a cylindrical battery or a laminate battery is known. A cylindrical battery is a battery in which a wound electrode body is accommodated in a cylindrical battery case. A laminate type battery is a battery in which a positive electrode sheet and a negative electrode sheet are stacked with a separator interposed therebetween.

  Hereinafter, a non-aqueous secondary battery according to an embodiment of the present invention will be described using the lithium ion secondary battery 100 as an example. Here, the non-aqueous secondary battery according to an embodiment of the present invention will be described with reference to the above-described diagram of the lithium ion secondary battery 100 as appropriate. In addition, here, members or parts that exhibit the same action will be described using the same reference numerals as appropriate, without being particularly distinguished from the lithium ion secondary battery 100 described above.

≪Deterioration of battery characteristics in high-rate continuous charge / discharge application≫
By the way, this inventor used the non-aqueous secondary battery 100 provided with the wound electrode body 200 as shown in FIG. 1 for an application (high-rate continuous charge / discharge application) in which rapid charging and rapid discharging are repeated. In some cases, it has been found that battery characteristics such as resistance increase and output decrease tend to deteriorate. About this tendency, this inventor thinks that the electrolyte (electrolytic solution) contained in the inside of the wound electrode body 200 decreases.

  That is, in the lithium ion secondary battery 100 (non-aqueous secondary battery) provided with the wound electrode body 200 as shown in FIG. 1, the positive electrode active material layer 223 releases lithium ions during charging, and the negative electrode active material layer 243 absorbs lithium ions. At this time, the positive electrode active material layer 223 contracts and the negative electrode active material layer 243 expands depending on the degree of charge. Further, during discharge, the positive electrode active material layer 223 absorbs lithium ions, and the negative electrode active material layer 243 releases lithium ions. At this time, the positive electrode active material layer 223 expands and the negative electrode active material layer 243 contracts depending on the degree of discharge.

  In applications where rapid charging and rapid discharging are repeated, the positive electrode active material layer 223 and the negative electrode active material layer 243 are repeatedly expanded and contracted. In such an application, the rate of expansion and contraction is greater and the degree of expansion and contraction is greater than when slow charging and discharging are repeated. For this reason, the wound electrode body 200 may behave as if it is a pump, and the non-aqueous electrolyte may be pushed out from the inside of the wound electrode body 200. When the non-aqueous electrolyte is pushed out from the inside of the wound electrode body 200, the lithium ions required for charging and discharging are insufficient inside the wound electrode body 200. As a result, battery characteristics such as an increase in resistance and a decrease in input / output characteristics of the secondary battery are deteriorated. The present inventor considers one of the causes of the deterioration of battery characteristics such as an increase in resistance and a decrease in input / output characteristics of the secondary battery. The present inventor has conceived a novel structure that maintains the input / output characteristics of the secondary battery at a high level based on such estimation.

<< Lithium-ion secondary battery 100 according to an embodiment of the present invention >>
As shown in FIG. 1, the lithium ion secondary battery 100 includes a wound electrode body 200, a battery case 300 that accommodates the wound electrode body 200, and a non-aqueous electrolyte injected into the battery case 300. ing. In addition, as shown in FIG. 2, the positive electrode current collector 221 and the negative electrode current collector 241 are band-shaped members, which are aligned in the longitudinal direction, and the positive electrode active material layer 223, the negative electrode active material layer 243, Are disposed so as to face each other with the separators 262 and 264 interposed therebetween. In the wound electrode body 200, the positive electrode current collector 221 and the negative electrode current collector 241 were wound around the winding axis WL set in the width direction of the positive electrode current collector 221 or the negative electrode current collector 241. The battery case 300 is housed in a state.

  FIG. 9 is a schematic diagram showing a wound electrode body 200 according to an embodiment of the present invention. FIG. 10 is a conceptual diagram showing a laminated structure of the wound electrode body 200. In one embodiment of the present invention, as shown in FIGS. 9 and 10, at least one of the positive electrode active material layer 223 and the negative electrode active material layer 243 in the direction of the winding axis WL of the wound electrode body 200. The edge portions E1 and E2 on both sides of the layer have a higher degree of swelling with respect to the non-aqueous electrolyte than the intermediate portion C in the direction of the winding axis WL excluding the edge portions E1 and E2.

  FIG. 11 is an embodiment of the present invention, and illustrates a wound electrode body 200 in which the edge portions E1a and E2a of the negative electrode active material layer 243 have a higher degree of swelling with respect to the non-aqueous electrolyte than the intermediate portion Ca. ing. 12 is a cross-sectional view taken along the line XII-XII in FIG. 11 and shows a laminated structure of the wound electrode body 200 shown in FIG.

  In this case, the edge portions E1a and E2a of the active material layer of the negative electrode active material layer 243 have a higher degree of swelling with respect to the non-aqueous electrolyte than the intermediate portion Ca. For this reason, the edge parts E1a and E2a of the negative electrode active material layer 243 are thicker than the intermediate part Ca in the state where the battery case 300 is accommodated and the nonaqueous electrolyte is injected into the battery case 300. Therefore, as schematically illustrated in FIG. 10, the positive electrode active material layer 223 and the negative electrode active material layer 243 are formed at the edges E1 and E2 on both sides of the wound electrode body 200 in the direction of the winding axis WL. In addition, the separators 262 and 264 come into close contact with each other. For this reason, the non-aqueous electrolyte that has soaked into the intermediate portion C of the wound electrode body 200 is not easily pushed out of the wound electrode body 200.

  Further, the edges E1a and E2a (see FIG. 11) of the negative electrode active material layer 243 are thickened. For this reason, in the intermediate part C of the wound electrode body 200, the contact pressure of the positive electrode active material layer 223, the negative electrode active material layer 243, and the separators 262 and 264 is reduced. Further, in the intermediate portion C of the wound electrode body 200, the positive electrode active material layer 223, the negative electrode active material layer 243, and the separators 262 and 264 come into contact more gently than the edges E1 and E2. For this reason, even when expansion / contraction occurs in the wound electrode body 200 due to repeated charge / discharge at a high input / output rate, the action of pushing out the non-aqueous electrolyte from the intermediate portion C of the wound electrode body 200 can be suppressed to a small level. obtain. Thus, the non-aqueous electrolyte is likely to stay in the intermediate part C of the wound electrode body 200.

  That is, in one embodiment of the present invention, the non-aqueous electrolyte is likely to stay in the intermediate part C of the wound electrode body 200, so that shortage of lithium ions is prevented in the intermediate part C of the wound electrode body 200. Since lithium ions are not insufficient in the intermediate portion C of the wound electrode body 200, lithium ions are smoothly absorbed and released in the positive electrode active material layer 223 and the negative electrode active material layer 243. Therefore, it is possible to suppress deterioration of battery characteristics such as resistance increase and input / output decrease.

  In this embodiment, as shown in FIG. 11 and FIG. 12, the degree of swelling of the negative electrode active material layer 243 with respect to the nonaqueous electrolyte at the edges E1a and E2a on both sides in the direction of the winding axis WL is determined. The degree of swelling of the intermediate portion Ca in the direction of the winding axis WL of the layer 243 with respect to the nonaqueous electrolytic solution is set higher. Further, the present invention is not limited thereto, and in the direction of the winding axis WL of the wound electrode body 200, the edges on both sides of at least one of the positive electrode active material layer 223 and the negative electrode active material layer 243 are the edges. The degree of swelling with respect to the non-aqueous electrolyte solution is preferably higher than that of the intermediate portion in the direction of the winding axis WL excluding the portion. Therefore, in the direction of the winding axis WL of the wound electrode body 200, the degree of swelling with respect to the non-aqueous electrolyte at the both sides of the positive electrode active material layer 223 is higher than the degree of swelling with respect to the non-aqueous electrolyte in the middle part. Also good. In both the positive electrode active material layer 223 and the negative electrode active material layer 243, the edge in the direction of the winding axis WL may have a higher degree of swelling with respect to the non-aqueous electrolyte than the intermediate portion.

≪Measurement of swelling degree of active material layer≫
Here, the swelling degree of the active material layer can be measured from the weight of the active material layer before and after being immersed in the non-aqueous electrolyte. For example, a predetermined part is cut out from the electrode sheet with a predetermined size. The weight of the cut electrode sheet is measured. The weight of the current collector is subtracted from the weight of the cut electrode sheet. Here, the weight of the current collector can be obtained from the thickness of the current collector, the cut area, and the specific gravity of the current collector material. By subtracting the weight of the current collector from the weight of the cut electrode sheet, the weight of the active material layer before immersion can be measured.

The cut-out electrode sheet is taken out after being immersed in a non-aqueous electrolyte at a predetermined temperature for a sufficient time, and the weight of the electrode sheet after immersion is measured. The degree of swelling of the active material layer is obtained by subtracting the weight of the current collector from the weight of the electrode sheet after immersion, and obtaining the weight of the active material layer after immersion. The degree of swelling of the active material layer is evaluated by a value obtained by dividing the weight of the active material layer after immersion by the weight of the active material layer before immersion.
Swelling degree of active material layer = {(weight of active material layer after immersion) / (weight of active material layer before immersion)} × 100% = {(weight of electrode sheet after immersion−weight of current collector) / (Weight of electrode sheet before immersion−weight of current collector)} × 100%;

  In this embodiment, as shown in FIG. 11, the edge portions E1a and E2a on both sides along the winding axis WL of the negative electrode active material layer 243 have a degree of swelling with respect to the non-aqueous electrolyte and the wrinkles of the negative electrode active material layer 243. It is higher than the intermediate portion Ca in the direction of the rotation axis WL. In this embodiment, SBR having a high degree of swelling with respect to the non-aqueous electrolyte is used as the binder of the negative electrode active material layer 243 at the edges E1a and E2a. On the other hand, in the intermediate part Ca, SBR having a lower degree of swelling than the edge parts E1a and E2a with respect to the non-aqueous electrolyte was used. Here, SBR is used in the same weight ratio for the intermediate part Ca and the edge parts E1a and E2a.

≪SBR swelling degree≫
Here, the degree of swelling of SBR with respect to the non-aqueous electrolyte is such that the SBR emulsion is dried to form a film having a predetermined thickness (for example, about 100 μm). This film is cut into a predetermined size (for example, a 3 cm × 3 cm square). With the film sufficiently dried, the weight of SBR (the weight of SBR before immersion) is measured. Next, it is immersed for 24 hours in a non-aqueous electrolyte kept warm at 80 ° C. The weight of SBR taken out from the non-aqueous electrolyte (the weight of SBR after immersion) is measured. The swelling degree of SBR is determined by the following formula based on the value obtained by dividing the weight of SBR after immersion by the weight of SBR before immersion.
SBR swelling degree (%) = (weight of SBR after immersion) / (weight of SBR before immersion) × 100;

  Further, as the SBR having a high degree of swelling with respect to the non-aqueous electrolyte, SBR having a small difference in SP value from the non-aqueous electrolyte may be used. Further, as the SBR having a low degree of swelling with respect to the non-aqueous electrolyte, SBR having a large difference in SP value (solubility parameter) from the non-aqueous electrolyte may be used.

<< SP value >>
Here, the SP value is also referred to as “dissolution parameter”. The SP value (solubility parameter) is obtained by regarding the intermolecular force as the SP value (solubility parameter) when the force acting between the solvent and the solute is assumed to be only the intermolecular force. Here, assuming only the force for aggregating the liquid and the intermolecular force, the aggregation energy ΔE has a relationship of evaporation enthalpy and ΔH = ΔE + PΔV. Here, the solubility parameter δ is defined by the following equation based on the molar evaporation heat ΔH and the molar volume V. Based on the solubility parameter δ, the SP value of the non-aqueous electrolyte and the SP value of the SBR may be calculated. Here, P is atmospheric pressure, R is a gas constant, and here R = 8.31 L / mol · K, and T is temperature.

  In the embodiment shown in FIGS. 11 and 12, SBRs with different degrees of swelling with respect to the non-aqueous electrolyte are selectively used as binders at the edge portions E1a and E2a on both sides of the negative electrode active material layer 243 and the intermediate portion Ca. Using. That is, a plurality of SBRs having different degrees of swelling with respect to the non-aqueous electrolyte are prepared (for example, two types of SBRs having different degrees of swelling (SP values) with respect to the non-aqueous electrolyte are prepared). As a mixture to be applied to the edge portions E1a and E2a on both sides of the negative electrode active material layer 243, SBR having a high degree of swelling with respect to the non-aqueous electrolyte is selected. For the mixture to be applied to the intermediate portion Ca, SBR having a low degree of swelling with respect to the nonaqueous electrolytic solution is selected. Then, a mixture for the edge portions E1a and E2a and a mixture for the intermediate portion Ca are prepared, and the mixture is separately applied to the edge portions E1a and E2a on both sides of the negative electrode active material layer 243 and the intermediate portion Ca.

  As a result, the edge portions E1a and E2a of the negative electrode active material layer 243 have SBR having a high degree of swelling with respect to the non-aqueous electrolyte (SBR having a small SP value difference with respect to the non-aqueous electrolyte) in the winding axis WL direction. More than the intermediate portion Ca. Further, in the intermediate portion Ca of the negative electrode active material layer 243, SBR having a low degree of swelling with respect to the non-aqueous electrolyte (SBR having a large SP value difference with respect to the non-aqueous electrolyte) is an edge in the winding axis WL direction. More than E1a and E2a. As a result, the negative electrode active material layer 243 in which the edge portions E1a and E2a on both sides in the direction of the winding axis WL have a higher degree of swelling with respect to the non-aqueous electrolyte than the intermediate portion Ca in the direction of the winding axis WL is obtained. Here, the expansion of the edge portions E1a and E2a of the negative electrode active material layer 243 is such that the thickness increases by about 2% compared to the intermediate portion Ca. FIG. 12 shows a state before the wound electrode body 200 is immersed, and the explicit illustration of the expansion of the edges E1a and E2a of the negative electrode active material layer 243 is omitted here.

<< Method for Forming Negative Electrode Active Material Layer 243 >>
FIG. 13 illustrates a configuration example of the coating apparatus. Here, a state in which the negative electrode mixture is applied by the die 60 while the negative electrode current collector 241 is supported by the back roll 46 in the coating apparatus is illustrated. Here, the coating of the mixture of the edges E1a and E2a and the intermediate portion Ca has, for example, a horizontally long discharge port 62 in which the intermediate portion 62a and both side portions 62b1 and 62b2 are partitioned as shown in FIG. A coating apparatus including a die 60 and a plurality of mixture supply channels 41, 42, and 43 that can supply different mixtures to the plurality of discharge ports 62 a, 62 b 1, and 62 b 2 respectively partitioned may be used. In this case, by applying the mixture to be applied to the intermediate portion Ca from the intermediate portion 62a of the die 60 and applying the mixture to be applied to the edge portions E1a and E2a from the both side portions 62b1 and 62b2, the edge portion The mixture of E1a and E2a and the intermediate portion Ca may be applied separately.

  As another method, the mixture to be applied to the intermediate portion Ca is applied to the entire surface of the region where the negative electrode active material layer 243 is applied, dried, and then applied to the regions corresponding to the edges E1a and E2a. Remove the mixture. The removal may be performed, for example, by masking a mixture applied to the intermediate portion Ca and scraping off the mixture applied to the region corresponding to the edge portions E1a and E2a from the negative electrode current collector 241. Thereafter, a mixture to be applied to the edges E1a and E2a may be applied to the edges E1a and E2a.

≪Evaluation test≫
As a non-aqueous secondary battery evaluation test, the swelling degree of the active material layer with respect to the non-aqueous electrolyte at both edges in the direction of the winding axis WL is higher than the swelling degree with respect to the non-aqueous electrolyte in the middle part. An evaluation cell was prepared and its effect was verified. Here, for the evaluation cell, the reaction resistance before and after a predetermined charge / discharge cycle was measured, the resistance increase rate was evaluated, and the salt concentration in the wound electrode body was evaluated.

≪Evaluation cell≫
Here, samples A and B having different negative electrode active material layer structures were prepared as evaluation cells. Hereinafter, sample A will be described, and further sample B will be described in order.

≪Evaluation cell positive electrode≫
In forming the positive electrode active material layer in the positive electrode, a positive electrode mixture was prepared. Here, the positive electrode mixture includes a ternary lithium transition metal oxide (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) as a positive electrode active material, acetylene black (AB) as a conductive material, and polyfluoride as a binder. Vinylidene chloride (PVDF) was used. The mass ratio of the positive electrode active material, the conductive material, and the binder was positive electrode active material: conductive material: binder = 91: 6: 3. A positive electrode mixture was prepared by mixing these positive electrode active material, conductive material, and binder with ion-exchanged water. Next, the positive electrode mixture was applied in order on one side of the positive electrode current collector and dried to prepare a positive electrode (positive electrode sheet) in which a positive electrode active material layer was applied on both sides of the positive electrode current collector.

The amount of the positive electrode mixture applied to the positive electrode current collector is approximately equal on both surfaces of the positive electrode current collector, and the positive electrode current collector per unit area of the positive electrode current collector after the positive electrode mixture is dried. The positive electrode active material layer was set to 30 mg / cm ² on both sides. Here, an aluminum foil (thickness: 15 μm) was used as the positive electrode current collector. After drying, the positive electrode sheet was about 150 μm thick by rolling with a roller press. The positive electrode sheet was shared by the cells for evaluation. The positive electrode current collector and the positive electrode active material layer both had a width of 54 mm.

≪Negative electrode of evaluation cell≫
In forming the negative electrode active material layer in the negative electrode, a negative electrode mixture was prepared. Here, as the negative electrode mixture, scaly natural graphite was used as the negative electrode active material, and carboxymethyl cellulose (CMC) and a binder were used as the thickener. As the binder, styrene-butadiene rubber (SBR), which is a rubber-based binder, was used. The mass ratio of the negative electrode active material, the thickener (CMC), and the binder (SBR) was negative electrode active material: CMC: SBR = 98: 1: 1. A negative electrode mixture was prepared by mixing these negative electrode active materials, CMC, and SBR with ion-exchanged water.

Next, the negative electrode mixture was applied in order on one side of the negative electrode current collector and dried to prepare a negative electrode (negative electrode sheet) in which the negative electrode active material layers were coated on both sides of the negative electrode current collector. The amount of the negative electrode mixture applied to the negative electrode current collector is approximately equal on both surfaces of the negative electrode current collector, and after the negative electrode mixture is dried, the negative electrode current collector per unit area of the negative electrode current collector The negative electrode active material layer was set to 15 mg / cm ² on both sides. Here, a copper foil (thickness: 10 μm) was used as the negative electrode current collector. After drying, the thickness of the negative electrode sheet was about 100 μm by rolling with a roller press. The widths of the negative electrode current collector and the negative electrode active material layer were both 56 mm.

  Here, a negative electrode sheet with a uniform degree of swelling of the negative electrode active material layer with respect to the non-aqueous electrolyte solution, and a negative electrode sheet with a different degree of swelling with respect to the non-aqueous electrolyte solution at the edge portion and the intermediate portion of the negative electrode active material layer. Prepared. Each negative electrode sheet will be described in detail in the description of each sample of the evaluation cell.

≪Evaluator cell separator≫
As the separator, a separator made of a porous sheet having a three-layer structure (PP / PE / PP) of polypropylene (PP) and polyethylene (PE) was used.

≪Assembly of evaluation cell≫
A test 18650 type cell (lithium ion battery) was constructed using the negative electrode prepared above, the positive electrode, and the separator. Here, a cylindrical wound electrode body was manufactured by laminating and winding a positive electrode sheet and a negative electrode sheet with a separator interposed. Then, the wound electrode body was housed in a cylindrical battery case, and a nonaqueous electrolyte was injected and sealed to construct an evaluation cell. Here, as the non-aqueous electrolyte, ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are in a predetermined volume ratio (EC: DMC: EMC = 3: 4: 3). Then, an electrolyte solution in which 1 mol / L LiPF ₆ as a lithium salt was dissolved in a mixed solvent was used. The SP value of such a non-aqueous electrolyte is about 9.

≪Sample A≫
For sample A, a negative electrode sheet having a uniform degree of swelling of the negative electrode active material layer with respect to the non-aqueous electrolyte was used. The negative electrode sheet having a uniform degree of swelling of the negative electrode active material layer with respect to the non-aqueous electrolyte does not separate the negative electrode mixture between the edge and the intermediate part of the negative electrode active material layer, and The degree of swelling was made uniform. Here, as the binder, a negative electrode mixture is produced using SBR (SP value: 12) having a degree of swelling of about 150% with respect to the non-aqueous electrolyte, and the negative electrode mixture is formed in a region where the negative electrode active material layer is formed. Coated.

≪Sample B≫
For sample B, a negative electrode sheet provided with a negative electrode active material layer having a higher degree of swelling with respect to the non-aqueous electrolyte at the edge than at the intermediate part was used. Here, as a binding material, SBR (a) (SP value: about 9) having a degree of swelling of about 300% with respect to the nonaqueous electrolytic solution and SBR (b) (with a degree of swelling of about 150% with respect to the nonaqueous electrolytic solution). SP value: about 12) was used. Then, a negative electrode mixture (Ga) using SBR (a) having a high degree of swelling and a negative electrode mixture (Gb) using SBR (a) having a low degree of swelling were prepared. Here, the negative electrode mixture (Ga) and the negative electrode mixture (Gb) were produced under the same conditions except that the SBR as the binder was different. Here, the negative electrode mixture (Ga) using SBR (a) having a high degree of swelling is applied to the edges on both sides in the width direction in the region where the negative electrode active material layer is formed, and the intermediate portion excluding the edges The negative electrode mixture (Gb) using SBR (a) having a low degree of swelling was applied. Thus, the negative electrode mixture was applied separately at the edge and the intermediate part of the negative electrode active material layer, and a negative electrode sheet having a higher degree of swelling at the edge of the negative electrode active material layer than that of the intermediate part was obtained.

  Sample A and sample B have the same configuration except for the negative electrode sheet. Here, for Sample B, the edge of the negative electrode active material layer is a region approximately 10% from the edges on both sides of the negative electrode active material layer in the direction of the winding axis, and from the edges on both sides of the negative electrode active material layer, respectively. The negative electrode mixture was applied separately in an area of approximately 10%. In this way, the edge portion having a high degree of swelling with respect to the non-aqueous electrolyte is formed in the region of about 10% from both edges of the negative electrode active material layer in the direction of the winding axis. The effect of preventing the electrolytic solution from being pushed out can be sufficiently obtained.

≪Rules of the edge≫
In other words, in the sample B described above, in the width direction of the negative electrode active material layer, a region that is approximately 20% of the width from the center of the negative electrode active material layer to the edge of the negative electrode active material layer is used as the edge. Note that the definition of the edge is not limited to this. The region of the edge that increases the degree of swelling with respect to the non-aqueous electrolyte may be set so that the effect of preventing the non-aqueous electrolyte from being pushed out from the intermediate portion is sufficiently obtained. For example, in a form in which the negative electrode active material layer is stacked so as to cover the positive electrode active material layer, it is desirable to set the edge of the negative electrode active material layer having a high degree of swelling so as to sufficiently overlap the positive electrode active material layer. In this case, the edge of the negative electrode active material layer having a high degree of swelling may be approximately 5% of the edge from both edges of the negative electrode active material layer, 15% of the edge, or 20 % Region. Further, in a form using a positive electrode sheet in which the degree of swelling of the edge of the positive electrode active material layer is higher than that of the intermediate part, the edge of the positive electrode active material layer is similarly formed on both sides of the positive electrode active material layer in the direction of the winding axis. You may prescribe | regulate as a predetermined area | region from the edge, respectively. In this case, from the edges on both sides of the positive electrode active material layer, for example, the region may be approximately 5%, may be 10%, may be 15%, or may be 20%. Good.

≪Evaluation test≫
Here, after preparing a plurality of evaluation cells for each sample and performing a predetermined conditioning, for each sample, a reaction resistance after a predetermined charge / discharge cycle determined in advance, and a resistance increase rate in a low temperature environment, The salt concentration (the molar concentration of LiPF ₆ (mol / ml)) in the negative electrode sheet was measured.

<< conditioning >>
Here, conditioning is performed by the following procedures 1 and 2.
Procedure 1: After reaching 4.1 V with a constant current charge of 1 C, pause for 5 minutes.
Procedure 2: After Procedure 1, charge for 1.5 hours by constant voltage charging and rest for 5 minutes.
In such conditioning, a required reaction occurs due to initial charging, and gas is generated. Moreover, a required film formation is formed on the negative electrode active material layer or the like.

≪Measurement of rated capacity≫
After the conditioning, the rated capacity is measured for the evaluation cell. The rated capacity is measured by the following procedures 1 to 3. Here, in order to make the influence of temperature constant, the rated capacity is measured in a temperature environment of 25 ° C.
Procedure 1: After reaching 3.0V by constant current discharge of 1C, discharge by constant voltage discharge for 2 hours, and then rest for 10 seconds.
Procedure 2: After reaching 4.1 V by constant current charging at 1 C, charge for 2.5 hours by constant voltage charging, and then rest for 10 seconds.
Procedure 3: After reaching 3.0 V by constant current discharge of 0.5 C, discharge at constant voltage discharge for 2 hours, and then stop for 10 seconds.
Here, the discharge capacity (CCCV discharge capacity) in the discharge from the constant current discharge to the constant voltage discharge in the procedure 3 is defined as “rated capacity”.

≪SOC adjustment≫
The SOC adjustment is performed by the following procedures 1 and 2. Here, the SOC adjustment may be performed after the conditioning process and the measurement of the rated capacity. Here, in order to make the influence of temperature constant, SOC adjustment is performed in a temperature environment of 25 ° C.
Procedure 1: Charging at a constant current of 3V to 1C to obtain a charged state (SOC 60%) of about 60% of the rated capacity.
Procedure 2: After procedure 1, charge at constant voltage for 2.5 hours.
Thereby, the cell for evaluation can be adjusted to a predetermined charge state. In addition, although the case where SOC is adjusted to 60% is described here, it can be adjusted to any charged state by changing the charged state in procedure 1. For example, when adjusting to SOC 40%, in the procedure 1, the evaluation cell may be set to a charged state (SOC 40%) of 40% of the rated capacity.

≪Reaction resistance≫
Here, the reaction resistance is adjusted to a predetermined SOC (a predetermined charged state with a rated capacity) after performing a predetermined conditioning for each evaluation cell. And alternating current impedance measurement was implemented within the thermostat adjusted to the predetermined temperature atmosphere. Here, in a temperature environment of −30 ° C., complex impedance measurement is performed in a frequency range of 10 ⁻³ Hz to 10 ⁵ Hz based on an evaluation cell adjusted to SOC 40% (a charged state of approximately 40% of the rated capacity). Was done.

FIG. 14 is a diagram illustrating a typical example of a Cole-Cole plot (Nyquist plot) in the AC impedance measurement method. As shown in FIG. 14, the DC resistance (R _sol ) and the reaction resistance (R _ct ) can be calculated based on the Cole-Cole plot obtained by equivalent circuit fitting in the AC impedance measurement method. Here, as shown in FIG. 14, the contact (R _sol ) with the X axis of the Nyquist plot was defined as “DC resistance”. Further, the reaction resistance _{(R ct)} is the inflection point of the Nyquist plots _(R sol ₊ R _ct) based, it can be obtained by the following equation.
_Rct = ( _Rsol + _Rct ) _-Rsol

Such measurement and calculation of direct current resistance (R _sol ) and reaction resistance (R _ct ) can be performed using a commercially available apparatus programmed in advance. As such an apparatus, for example, Frequency Response Analyzer (FRA) manufactured by Toyo Technica Co., Ltd., model number: solartron 1255B is used, and a potentio / galvanostat type 1287A (manufactured by Solartron, UK) may be used in combination.

≪Charge / discharge cycle≫
Here, the evaluation cell is first adjusted to SOC 60%. Then, one cycle of the charge / discharge cycle is constituted by a discharge of 10 seconds with a constant current of 30 C and a charge of 1 minute (60 seconds) with a constant current of 5 C in a temperature environment of 25 ° C. Moreover, it is made to rest for 10 minutes between this discharge and charge, respectively. Here, the charge / discharge cycle is performed for 30000 cycles while adjusting the evaluation cell to 60% SOC every 500 cycles. That is, this charge / discharge cycle is a charge / discharge cycle with a discharge rate of 30 C, which is extremely high.

  And reaction resistance was measured before and after this charging / discharging cycle. FIG. 15 shows the results of measuring the reaction resistance before the charge / discharge cycle and the reaction resistance after the charge / discharge cycle for the evaluation cells of sample A and sample B, respectively. Here, the evaluation cell of Sample A includes a negative electrode sheet having a uniform degree of swelling of the negative electrode active material layer with respect to the non-aqueous electrolyte. The evaluation cell of sample B includes a negative electrode sheet in which the degree of swelling of the edge of the negative electrode active material layer is higher than that of the intermediate part.

  The reaction resistance before the charge / discharge cycle is about the same between sample A and sample B. However, the reaction resistance is significantly higher in Sample A after the charge / discharge cycle. Thus, in sample A in which the degree of swelling of the negative electrode active material layer with respect to the non-aqueous electrolyte is uniform, the reaction resistance tends to increase greatly after the charge / discharge cycle at the high rate as described above. On the other hand, in sample B in which the degree of swelling of the edge of the negative electrode active material layer is higher than that in the middle part, the reaction resistance after the charge / discharge cycle at the high rate is slightly higher than that before the charge / discharge cycle. Not as high as As described above, in Sample B, the rate of increase in reaction resistance after the charge / discharge cycle can be suppressed to be considerably lower than that in Sample A.

≪Resistance increase rate (Increase rate of reaction resistance after charge / discharge cycle (%)) ≫
FIG. 16 shows the results of measuring the initial reaction resistance V1 before the charge / discharge cycle and the reaction resistance V2 after the charge / discharge cycle for Sample A and Sample B, and evaluating the rate of increase of the reaction resistance. Here, the increasing rate V of the reaction resistance is a ratio (V2 / V1) between the post-cycle resistance V2 and the initial resistance V1.
V = (V2 / V1);

  In Sample B in which the degree of swelling at the edge of the negative electrode active material layer is higher than that in the middle part, the rate of increase in reaction resistance after the charge / discharge cycle is suppressed to a value less than about 1.3. On the other hand, in sample A in which the degree of swelling of the negative electrode active material layer with respect to the non-aqueous electrolyte is uniform, the rate of increase in reaction resistance after the charge / discharge cycle is higher than 2.0. Thus, compared with the case where the swelling degree with respect to the non-aqueous electrolyte of a negative electrode active material layer is uniform (sample A), when the swelling degree of the edge part of a negative electrode active material layer is made higher than an intermediate part (sample B) ), The increase in the reaction resistance after the charge / discharge cycle can be suppressed to a considerably low level.

  The present inventor has found that when the degree of swelling of the edge of the negative electrode active material layer is made higher than that of the intermediate part (sample B), the increase in reaction resistance after the charge / discharge cycle can be suppressed to a considerably low level. Regarding such an event, the present inventor made the edge of the negative electrode active material layer absorb the non-aqueous electrolyte in the battery case by making the swelling degree of the edge of the negative electrode active material layer higher than the intermediate portion. A little thicker than the middle part. For this reason, the negative electrode active material layer, the separator, and the positive electrode active material layer are in close contact with each other at the edge in the winding axis WL direction of the wound electrode body. On the other hand, in the intermediate part in the winding axis WL direction of the wound electrode body, the contact between the negative electrode active material layer, the separator, and the positive electrode active material layer becomes gentle.

For this reason, even if it is used in a charge / discharge cycle at a high rate as described above and the wound electrode body is repeatedly expanded and contracted, it is immersed in the intermediate portion of the wound electrode body in the direction of the winding axis WL. The non-aqueous electrolyte contained therein tends to stay in the intermediate portion. In addition, an event that the non-aqueous electrolyte is reduced in the intermediate portion of the wound electrode body hardly occurs, and the increase in reaction resistance after the charge / discharge cycle can be suppressed to a very low level. The present inventor thus presumes an event in which the increase in reaction resistance after the charge / discharge cycle can be suppressed to a very low level for sample B. Such inference can be verified by the distribution of the molar concentration of LiPF ₆ in the negative electrode active material layer in the winding axis WL direction of the wound electrode body for Sample A and Sample B before and after the above-described charge / discharge cycle.

<< Molar concentration distribution of LiPF ₆ >>
The distribution of the molar concentration of LiPF ₆ may be examined by the following procedure.
1. Remove the wound electrode body from the evaluation cell.
2. Separate the negative electrode sheet from the wound electrode body.
3. The negative electrode sheet is cut at a predetermined width in the longitudinal direction for each of a plurality of regions in the direction of the winding axis WL.
4). Next, the molar concentration of LiPF _{6 and} the molar concentration of EC of the non-aqueous electrolyte are measured for each cut piece of the cut negative electrode sheet.
5. From the molar concentration of LiPF _{6 in} each cut piece and the molar concentration of the EC component of the non-aqueous electrolyte, the distribution of the non-aqueous electrolyte in the wound electrode body of the evaluation cell and the molar concentration of LiPF ₆ can be known.

<< Measurement of molar concentration of LiPF ₆ >>
The molar concentration of LiPF _{6 and} the molar concentration of EC can be measured by, for example, NMR measurement (NMR: Nuclear Magnetic Resonance). Here, we want to examine the distribution of the molar concentration of LiPF ₆ along the direction of the winding axis WL of the negative electrode sheet. For this reason, as described above, for each of a plurality of regions in the direction of the winding axis WL, a cut piece obtained by cutting the negative electrode sheet with a predetermined width in the longitudinal direction is measured by NMR to measure the molar concentration of LiPF _{6 and} the molar concentration of EC. To do.

≪NMR measurement≫
The NMR measurement is performed by the following procedure, for example.
1. The cut pieces are immersed in the extract for 12 hours in a dry box at room temperature (about 25 ° C.).
2. The cut pieces are immersed from the extract for 12 hours. Then, a predetermined amount of the extract is collected with a Pasteur pipette.
3. The collected extract is filtered through a filter.
4). The filtrate is subjected to NMR measurement.

  Here, the cut piece is a cut piece obtained by cutting a portion of the negative electrode sheet coated with the negative electrode active material layer into, for example, a rectangle of 1 cm in the width direction (direction of the winding axis WL) of the negative electrode sheet and 5 cm in the longitudinal direction. It is. Moreover, the extraction liquid which immerses a cut piece used the liquid mixture which mixed 100 microliters of 1 mol / L DFA (difluoroanisole) as an internal standard liquid in d-THF (tetrahydrofuran) 1.5mL. In addition, as an internal standard solution, it is good to employ | adopt the component which can measure F and H simultaneously. As the filter, a filter having a pore size of about 0.2 μm may be used.

Here, since the molar concentration of LiPF6 can be calculated | required with a following formula, it is good to measure the molar amount of LiPF6 and the volume of electrolyte solution.
Molar concentration of LiPF6 (mol / L) = LiPF6 (mol) / volume of electrolyte (L);

Here, in the above NMR measurement, 19F-NMR measurement and 1H-NMR measurement are performed. As for the molar amount of LiPF ₆ , the relative molar amount of PF ₆ with respect to DFA may be calculated by 19F-NMR measurement. Moreover, the molar amount of EC is good to calculate the relative molar amount of EC with respect to DFA by 1H-NMR measurement. From the molar amount of EC, the volume of the non-aqueous electrolyte can be converted from the solvent composition ratio (EC: DMC: EMC) of the non-aqueous electrolyte. Here, DMC and EMC are volatile substances, and the relative molar amount of EC with respect to DFA is calculated by 1H-NMR measurement. The molar amount of LiPF _{6 and} the volume of the non-aqueous electrolyte obtained here are relative amounts with respect to DFA. From the molar amount of LiPF _{6 and} the volume of the non-aqueous electrolyte, LiPF ₆ contained in the cut piece is obtained. Can be calculated.

The molar concentration of LiPF ₆ is calculated for each cut piece cut out for each of a plurality of regions in the width direction of the negative electrode active material layer (direction of the winding axis WL). Thereby, the molar concentration distribution of LiPF _{6 in} the width direction of the negative electrode active material layer is obtained. Moreover, it is good to perform this measurement about the evaluation cell before a charging / discharging cycle and the evaluation cell after a charging / discharging cycle about each sample, respectively.

FIG. 17 shows the measurement result of the molar concentration (mol / L) of LiPF _{6 in} the width direction of the negative electrode active material layer of the evaluation cell before the charge / discharge cycle. As shown in FIG. 17, LiPF ₆ is distributed approximately uniformly in the width direction in the negative electrode active material layer of the evaluation cell before the charge / discharge cycle. Such distribution is not significantly different between sample A in which the degree of swelling of the negative electrode active material layer with respect to the non-aqueous electrolyte is uniform and sample B in which the degree of swelling of the edge of the negative electrode active material layer is higher than that in the intermediate part.

FIG. 18 shows the measurement result of the molar concentration (mol / L) of LiPF _{6 in} the width direction of the negative electrode active material layer after the charge / discharge cycle for sample A having a uniform degree of swelling of the negative electrode active material layer with respect to the non-aqueous electrolyte. Is shown by a black plot. In FIG. 18, white plots show the measurement results of the molar concentration (mol / L) of LiPF ₆ before the charge / discharge cycle. In Sample A, as shown in FIG. 18, after the charge / discharge cycle, the molar concentration of LiPF ₆ is maintained at substantially the same level as that before the charge / discharge cycle at the edge of the negative electrode active material layer of the evaluation cell. However, in the intermediate portion of the negative electrode active material layer, the concentration of LiPF ₆ is reduced to about half before the charge / discharge cycle.

FIG. 19 shows the measurement result of the molar concentration (mol / L) of LiPF _{6 in} the width direction of the negative electrode active material layer after the charge / discharge cycle for Sample B in which the degree of swelling of the edge of the negative electrode active material layer is higher than that of the intermediate portion. Is shown by a black plot. In FIG. 19, the white plots show the measurement results of the molar concentration (mol / L) of LiPF ₆ before the charge / discharge cycle. In sample B, as shown in FIG. 19, after the charge / discharge cycle, the negative electrode active material layer of the evaluation cell has a slight increase / decrease, but the molar concentration of LiPF ₆ is approximately uniform in the width direction. It is maintained at about the same level as before.

  As described above, in the evaluation cell in which the swelling degree of the edge of the negative electrode active material layer is higher than that of the intermediate part, the non-aqueous electrolyte is sufficiently contained in the intermediate part of the non-aqueous electrolyte after the charge / discharge cycle at the high rate. It remains (Figure 19). For this reason, as shown in FIGS. 15 and 16, it is possible to suppress deterioration of battery characteristics such as an increase in resistance and a decrease in input / output characteristics of the secondary battery, and a high level of input / output characteristics of the secondary battery. Can be maintained.

  As described above, the non-aqueous secondary battery includes the positive electrode active material layer 223 (see FIG. 1) and the negative electrode active material layer 243 (see FIG. 1) in the direction of the winding axis WL of the wound electrode body 200, as shown in FIG. The edge portions E1 and E2 on both sides of at least one active material layer in FIG. 1) preferably have a higher degree of swelling with respect to the nonaqueous electrolyte solution than the intermediate portion C excluding the edge portions E1 and E2.

  As a result, after the charge / discharge cycle at a high rate, the non-aqueous electrolyte can be sufficiently retained also in the intermediate portion of the non-aqueous electrolyte. Further, deterioration of battery characteristics such as an increase in resistance of the secondary battery and a decrease in input / output characteristics can be suppressed, and the input / output characteristics of the secondary battery can be maintained at a high level.

  In this case, in the above-described embodiment, as shown in FIGS. 11 and 12, the SBR that is the binder component of the negative electrode active material layer 243 is applied to the edges E1a and E2a of the negative electrode active material layer 243 by nonaqueous electrolysis. SBR having a high degree of swelling with respect to the liquid was employed. Thereby, the edge parts E1a and E2a of the negative electrode active material layer 243 are expanded in the cell, and the effect of retaining the non-aqueous electrolyte in the intermediate part of the wound electrode body 200 is obtained. In this case, for the edge portions E1a and E2a of the negative electrode active material layer 243, SBR having a high degree of swelling may be adopted as the binder component, so that the other performance of the secondary battery is hardly reduced.

  On the other hand, even if the edge portions E1a and E2a of the negative electrode active material layer 243 are formed thicker in advance than the intermediate portion Ca without changing the degree of swelling of the edge portions E1a and E2a of the negative electrode active material layer 243, similarly. In addition, an action of retaining the non-aqueous electrolyte in the middle portion of the non-aqueous electrolyte may be obtained. However, in that case, since the edges E1a and E2a of the negative electrode active material layer 243 are formed thicker than the intermediate part Ca in advance, only the edges E1a and E2a of the negative electrode active material layer 243 are thickly coated. A special pressing process is required. When changing the swelling degree of the edge portions E1a and E2a of the negative electrode active material layer 243, it is not necessary to change the pressing step and the non-aqueous secondary battery can be easily manufactured. In addition, when the mixture is thickly applied only to the edges E1a and E2a of the negative electrode active material layer 243, the irreversible capacity increases, and thus the output at low SOC may deteriorate.

  In addition, for example, the edges E1a and E2a of the negative electrode active material layer 243 may include other materials having a high degree of swelling with respect to the nonaqueous electrolytic solution. That is, the negative electrode mixture applied to the edges E1a and E2a includes another material having a high degree of swelling with respect to the non-aqueous electrolyte, and the negative electrode mixture is applied to the edges E1a and E2a. A negative electrode active material layer 243 is formed. Even in this case, the swelling degree with respect to the non-aqueous electrolyte can be increased for the edges E1a and E2a of the negative electrode active material layer 243. Thereby, the edge parts E1a and E2a of the negative electrode active material layer 243 are thicker than the intermediate part Ca, and an effect of retaining the nonaqueous electrolytic solution in the intermediate part of the nonaqueous electrolytic solution is obtained.

  Such a configuration replaces the SBR that is the binder component of the negative electrode active material layer 243 with respect to the edges E1a and E2a of the negative electrode active material layer 243 by adopting SBR that has a higher degree of swelling than the non-aqueous electrolyte. Or in combination. In addition, the edge portions E1a and E2a of the negative electrode active material layer 243 are exemplified by increasing the degree of swelling with respect to the non-aqueous electrolyte. For example, the degree of swelling of the edge portion of the positive electrode active material layer 223 may be higher than that of the nonaqueous electrolytic solution. In this case, for the edge of the positive electrode active material layer 223, a material having a high degree of swelling with respect to the non-aqueous electrolyte may be selected for the binder component or the thickener component, or the positive electrode active material layer 223 may be selected. The other edge portion may include another material having a high degree of swelling with respect to the non-aqueous electrolyte.

  Further, as described above, at least one of the positive electrode active material layer 223 and the negative electrode active material layer 243 (see FIG. 1) has the edge portions E1 and E2 in the winding axis WL direction (see FIG. 9). In addition, it is preferable that a material having a high degree of swelling with respect to the non-aqueous electrolyte is contained more than the intermediate portion. That is, it is only necessary that the edge portions E1 and E2 have a higher degree of swelling with respect to the non-aqueous electrolyte in at least one of the positive electrode active material layer 223 and the negative electrode active material layer 243 (see FIG. 1). In this case, in the active material layer in which the edge portions E1 and E2 have a high degree of swelling with respect to the non-aqueous electrolyte, the edges E1 and E2 have more material with a high degree of swelling with respect to the non-aqueous electrolyte than in the intermediate portion. It may be included. In addition, a material having a low degree of swelling with respect to the non-aqueous electrolyte may be included in the central portion in the winding axis WL direction more than the edge portion. Thereby, the active material layer whose edge parts E1 and E2 have a high degree of swelling with respect to the non-aqueous electrolyte can be realized.

  For example, as in the above-described embodiment, when the binding material included in the edge portions E1 and E2 in the winding axis WL direction has a higher degree of swelling with respect to the non-aqueous electrolyte than the binding material included in the intermediate portion. Good. In the case of preparing with the degree of swelling of the binder, the production is easy as described above.

  In the above-described embodiment, as shown in FIG. 11, by selectively adopting the SBR of the negative electrode active material layer 243 as a binder, the swelling degree of the edges E1a and E2a of the negative electrode active material layer 243 can be increased. The degree of swelling of the part Ca was adjusted. SBR is added in an emulsion state, and it is easy to adjust the SP value according to the non-aqueous electrolyte. Here, as a material having a high degree of swelling with respect to the non-aqueous electrolyte, it is sufficient that the difference in SP value from the non-aqueous electrolyte is small. Further, as a material having a low degree of swelling with respect to the non-aqueous electrolyte, it is sufficient that the difference in SP value from the non-aqueous electrolyte is large. For example, as a material having a high degree of swelling with respect to the non-aqueous electrolyte, the difference in SP value from the non-aqueous electrolyte is within ± 1.5, more preferably within ± 1.0, and even more preferably within ± 0.5. Good. As a material having a low degree of swelling with respect to the non-aqueous electrolyte, the difference in SP value from the non-aqueous electrolyte is ± 2.0 or more, more preferably ± 2.5 or more, and even more preferably ± 3.0 or more. .

  The non-aqueous secondary battery according to one embodiment of the present invention has been described above, but the present invention is not limited to any of the above-described embodiments, and various modifications can be made.

  The non-aqueous secondary battery disclosed here can provide a lithium-ion secondary battery that can maintain a low resistance after a charge / discharge cycle, for example, and exhibits high performance in a low-temperature environment. Therefore, as shown in FIG. 20, the lithium ion secondary battery 100 is particularly suitable as a vehicle driving battery 1000 that requires low resistance and high capacity in various temperature environments. Here, the vehicle driving battery 1000 may be in the form of an assembled battery formed by connecting a plurality of the lithium ion secondary batteries 100 in series. The vehicle 1 provided with such a vehicle driving battery as a power source typically includes an automobile, particularly an automobile provided with an electric motor such as a hybrid automobile (including a plug-in hybrid car) and an electric automobile.

100 Lithium ion secondary battery (non-aqueous secondary battery)
200 Winding electrode body 220 Positive electrode sheet 221 Positive electrode current collector 222 Uncoated part 223 Positive electrode active material layer 240 Negative electrode sheet 241 Negative electrode current collector 242 Uncoated part 243 Negative electrode active material layer 262, 264 Separator 280 Electrolytic solution 290 Charging 300 Battery case 340 Lid 350 Injection hole 352 Sealing cap 360 Safety valve 420 Electrode terminal (positive electrode terminal)
440 Electrode terminal (negative electrode terminal)
610 Positive electrode active material particles 620 Conductive material 630 Binder 710 Negative electrode active material particles 730 Binder 1000 Vehicle drive battery C Winding electrode body intermediate portion Ca Negative electrode active material layer intermediate portion E1, E2 Winding electrode body edge E1a, E2a Edge WL of negative electrode active material layer Winding shaft

Claims (7)

A wound electrode body;
A battery case containing the wound electrode body;
A non-aqueous electrolyte injected into the battery case,
The wound electrode body is:
A positive electrode current collector;
A positive electrode active material layer held by the positive electrode current collector;
A negative electrode current collector;
A negative electrode active material layer held by the negative electrode current collector;
A separator interposed between the positive electrode active material layer and the negative electrode active material layer,
The positive electrode current collector and the negative electrode current collector are:
Each is a band-shaped member,
The longitudinal direction is aligned, and the positive electrode active material layer and the negative electrode active material layer are arranged to face each other with the separator interposed therebetween,
In a state of being wound around a winding axis set in the width direction of the positive electrode current collector or the negative electrode current collector, the battery case is accommodated in the battery case,
At least one of the positive electrode active material layer and the negative electrode active material layer includes a binder, and the binder contained at both edges in the winding axis direction is A non-aqueous secondary battery having a higher degree of swelling with respect to the non-aqueous electrolyte than a binder contained in an intermediate portion in the winding axis direction excluding edges on both sides . The negative electrode active material layer includes SBR,
2. The non-aqueous secondary battery according to claim 1, wherein the SBR included in the edge portion has a higher degree of swelling with respect to the non-aqueous electrolyte than the SBR included in the intermediate portion . A wound electrode body;
A battery case containing the wound electrode body;
A non-aqueous electrolyte injected into the battery case;
With
The wound electrode body is:
A positive electrode current collector;
A positive electrode active material layer held by the positive electrode current collector;
A negative electrode current collector;
A negative electrode active material layer held by the negative electrode current collector;
A separator interposed between the positive electrode active material layer and the negative electrode active material layer;
With
The positive electrode current collector and the negative electrode current collector are:
Each is a band-shaped member,
The longitudinal direction is aligned, and the positive electrode active material layer and the negative electrode active material layer are arranged to face each other with the separator interposed therebetween,
In a state of being wound around a winding axis set in the width direction of the positive electrode current collector or the negative electrode current collector, the battery case is accommodated in the battery case,
The negative electrode active material layer includes SBR,
In the direction of the winding axis of the wound electrode body, the SBR included in the edge portions on both sides of the negative electrode active material layer has a higher degree of swelling with respect to the non-aqueous electrolyte than the SBR included in the intermediate portion. Non-aqueous secondary battery. The non-aqueous system according to any one of claims 1 to 3 , wherein the edge portion is defined by a region of 10% from each edge of the active material layer in the direction of the winding axis. Secondary battery. The nonaqueous secondary battery according to any one of claims 1 to 4 , wherein the nonaqueous secondary battery is configured as a lithium ion secondary battery. An assembled battery in which a plurality of the nonaqueous secondary batteries according to any one of claims 1 to 5 are combined. A non-aqueous secondary battery according to any one of claims 1 to 5 , or a vehicle driving battery comprising the assembled battery according to claim 6 .

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