Non-aqueous electrolyte secondary battery

Abstract

To provide a non-aqueous electrolyte secondary battery preferably suppressed in high-rate deterioration.SOLUTION: In an embodiment of a non-aqueous electrolyte secondary battery disclosed here, a length S of a negative electrode active material layer 24a in a direction where a winding shaft WL of winding electrode bodies 20a, 20b, and 20c is extended is 200 mm or more, a liquid penetration speed of a non-aqueous electrolyte 13 in the negative electrode active material layer 24a is 0.02 μL / s to 0.05 μL / s. In the direction where the winding shaft WL is extended, a distance B between an end part of a positive electrode active material layer 22a and an end part of the negative electrode active material layer 24a is larger than 0 mm and is 5 mm or less. In a full charging state, a ratio of the non-aqueous electrolyte 13 with respect to gaps in the positive electrode active material layer 22a and the negative electrode active material layer 24a in the winding electrode bodies 20a, 20b, and 20c is 130% or less.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present disclosure relates to a non-aqueous electrolyte secondary battery.

Background Art

[0002] For example, Patent Document 1 below discloses a large non-aqueous electrolyte secondary battery including a wound electrode body having a large length in the winding axis direction.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, according to the study of the present inventor, it has been found that there is still room for improvement, particularly in the non-aqueous electrolyte secondary battery as described above, from the viewpoint of suppressing high-rate deterioration because the movement path of the non-aqueous electrolyte is long.

[0005] The present disclosure has been made in view of such circumstances, and its main object is to provide a non-aqueous electrolyte secondary battery in which high-rate deterioration is preferably suppressed.

Means for Solving the Problems

[0006] To achieve such an object, the present disclosure provides a non-aqueous electrolyte secondary battery including a wound electrode body in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound with a strip-shaped separator interposed therebetween, a non-aqueous electrolyte, and a battery case that houses the wound electrode body and the non-aqueous electrolyte. The positive electrode includes a positive electrode active material layer, the negative electrode includes a negative electrode active material layer, the length of the negative electrode active material layer in the direction in which the winding axis of the wound electrode body extends is 200 mm or more, the liquid penetration rate of the non-aqueous electrolyte in the negative electrode active material layer is 0.02 μL / s to 0.05 μL / s, in the direction in which the winding axis extends, the distance between the end of the positive electrode active material layer and the end of the negative electrode active material layer is greater than 0 mm and 5 mm or less, and in a fully charged state, the ratio of the volume of the non-aqueous electrolyte to the volume of the voids of the positive electrode active material layer and the negative electrode active material layer in the wound electrode body is 130% or less. Although details will be described later, according to the non-aqueous electrolyte secondary battery having such a configuration, high-rate deterioration can be preferably suppressed.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Best Mode for Carrying Out the Invention

[0008] Hereinafter, some embodiments of the technology disclosed herein will be described with reference to the drawings. In the following drawings, members and parts having the same function are denoted by the same reference numerals for description. Also, the dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect the actual dimensional relationships. In addition, matters other than those specifically mentioned in this specification and matters necessary for the implementation of the technology disclosed herein (for example, the general configuration and manufacturing process of a battery that does not characterize the present invention) can be grasped as design matters of those skilled in the art based on the prior art in the relevant field. The technology disclosed herein can be implemented based on the content disclosed in this specification and the common general knowledge in the relevant field. In this specification, the notation "A to B" indicating a range means "A or more and B or less". Also, it shall include the meanings of "exceeding A" and "less than B".

[0009] In the present technology, the term "secondary battery" refers to general rechargeable energy storage devices, including so-called storage batteries such as lithium secondary batteries and lithium polymer batteries, as well as energy storage elements such as electric double layer capacitors. The term "non-aqueous electrolyte secondary battery" refers to a secondary battery that realizes charge and discharge using a non-aqueous electrolyte as a charge carrier, and the electrolyte may be either a gel electrolyte or a non-aqueous electrolyte. As a configuration that can enjoy the benefits of the present technology, for example, it may be a non-aqueous electrolyte solution that is liquid at room temperature (e.g., 25°C) and in which a supporting salt (electrolyte salt) serving as a charge carrier is dissolved in a non-aqueous solvent. Examples of such non-aqueous electrolyte secondary batteries include lithium-ion secondary batteries and sodium-ion secondary batteries. The term "active material" refers to a substance that can reversibly occlude and release a chemical species serving as a charge carrier in a secondary battery. In the present technology, "SOC" means the state of charge, and in the range of the operating voltage that can be reversibly charged and discharged, the state of charge is indicated with the charge state at which the upper limit voltage is obtained being 100% and the charge state at which the lower limit voltage is obtained being 0%. Hereinafter, the present technology will be described by taking the case where the non-aqueous electrolyte secondary battery (or non-aqueous electrolyte solution secondary battery) is a lithium-ion secondary battery as an example.

[0010] <Configuration of the battery> FIG. 1 is a perspective view of a non-aqueous electrolyte secondary battery (hereinafter, also simply referred to as "battery 100") according to the present embodiment. FIG. 2 is a schematic longitudinal sectional view taken along line II-II of FIG. 1. FIG. 3 is a schematic longitudinal sectional view taken along line III-III of FIG. 1. FIG. 4 is a schematic cross-sectional view taken along line IV-IV of FIG. 1. In the following description, the reference signs L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, upper, and lower, respectively, and the reference signs X, Y, and Z in the drawings represent the short side direction, the long side direction orthogonal to the short side direction, and the vertical direction of the battery 100, respectively. However, these are merely directions for convenience of explanation and do not limit the installation form of the battery 100 in any way.

[0011] As shown in FIG. 2, the battery 100 includes a case 10 (battery case) and an electrode body group 20. In addition to the case 10 and the electrode body group 20, the battery 100 according to the present embodiment further includes a positive electrode terminal 30, a positive electrode external conductive member 32, a negative electrode terminal 40, a negative electrode external conductive member 42, an external insulating member 92, a positive electrode current collector 50, a negative electrode current collector 60, a positive electrode internal insulating member 70, and a negative electrode internal insulating member 80. The sealing plate 14 has the positive electrode terminal 30 and the negative electrode terminal 40. Although not shown, the battery 100 according to the present embodiment further includes a non-aqueous electrolyte 13. The battery 100 is a lithium-ion secondary battery here. The battery 100 is a rectangular secondary battery.

[0012] The case 10 is a housing that houses the electrode body group 20. Here, the case 10 has a flat and bottomed rectangular parallelepiped shape (rectangular). The case 10 has a hexahedral rectangular outer shape. The case 10 may be flat as in the present embodiment, or may not be flat (for example, it may have a cubic shape or the like). The material of the case 10 may be the same as that conventionally used, and there is no particular limitation. The case 10 is preferably made of a metal having a predetermined strength. Examples of the metal material constituting the case 10 include aluminum, aluminum alloy, iron, iron alloy, and the like.

[0013] The case 10 includes a case body 12, a sealing plate 14, and a gas discharge valve 17. The case body 12 is a flat rectangular container with one surface being an opening 12h. Specifically, as shown in FIG. 1, the case body 12 includes an opening 12h, a substantially rectangular bottom wall 12a, a pair of second side walls 12c extending upward U from the short sides of the bottom wall 12a and facing each other, and a pair of first side walls 12b extending upward U from the long sides of the bottom wall 12a and facing each other. The area of the first side wall 12b is larger than the area of the second side wall 12c. The opening 12h is formed on the upper surface of the case body 12 surrounded by the pair of first side walls 12b and the pair of second side walls 12c. The sealing plate 14 is attached to the case body 12 so as to close the opening 12h of the case body 12. The sealing plate 14 is a plate material substantially rectangular in plan view. The sealing plate 14 faces the bottom wall 12a of the case body 12. The case 10 is formed by joining (for example, welding) the sealing plate 14 to the periphery of the opening 12h of the case body 12. The joining of the sealing plate 14 can be performed by welding such as laser welding. Specifically, each of the pair of second side walls 12c is joined to the short side of the sealing plate 14, and each of the pair of first side walls 12b is joined to the long side of the sealing plate 14.

[0014] As shown in FIGS. 1 and 2, the gas discharge valve 17 is formed in the sealing plate 14. The gas discharge valve 17 is configured to open when the pressure inside the case 10 reaches a predetermined value or more and discharge the gas inside the case 10. The gas discharge valve 17 in the present embodiment is a substantially circular recess in plan view that is recessed from the outer surface of the sealing plate 14 toward the electrode body group 20 side. A thin portion thinner than the thickness of the sealing plate 14 is formed on the bottom surface of such a gas discharge valve 17. This gas discharge valve 17 breaks the thin portion when the internal pressure of the case reaches a predetermined value or more. Thereby, the gas inside the case 10 can be discharged to the outside, and the increased internal pressure of the case can be reduced.

[0015] In addition to the gas discharge valve 17, the sealing plate 14 is provided with a liquid injection hole 15 and two terminal insertion holes 18 and 19. The liquid injection hole 15 communicates with the internal space of the case body 12 and is an opening provided for injecting a non-aqueous electrolyte in the manufacturing process of the battery 100. The liquid injection hole 15 is sealed by a sealing member 15a. As such a sealing member 15a, for example, a blind rivet is suitable. Thereby, the sealing member 15a can be firmly fixed inside the case 10. Further, the terminal insertion holes 18 and 19 are respectively formed at both ends in the long side direction Y of the sealing plate 14. The terminal insertion holes 18 and 19 penetrate the sealing plate 14 in the vertical direction Z. As shown in FIG. 2, the positive electrode terminal 30 is inserted into the terminal insertion hole 18 on one side (left side) in the long side direction Y. Also, the negative electrode terminal 40 is inserted into the terminal insertion hole 19 on the other side (right side) in the long side direction Y.

[0016] FIG. 5 is a perspective view schematically showing the electrode body group 20 attached to the sealing plate 14. FIG. 6 is a perspective view schematically showing the wound electrode body 20a to which the second positive current collector 52 and the second negative current collector 62 are attached. In the present embodiment, a plurality (here, three) of wound electrode bodies 20a, 20b, and 20c are accommodated inside the case 10. Note that the number of electrode bodies accommodated inside one case 10 is not particularly limited, and may be one or two or more (plural). As shown in FIG. 5, the positive current collector 50 is disposed on one side (left side in FIG. 5) in the long side direction Y of each electrode body, and the negative current collector 60 is disposed on the other side (right side in FIG. 5) in the long side direction Y. And each of the wound electrode bodies 20a, 20b, and 20c is connected in parallel. However, the wound electrode bodies 20a, 20b, and 20c may be connected in series. The electrode body group 20 is accommodated inside the case body 12 of the case 10 in a state covered with an electrode body holder 29 (see FIG. 3) made of a resin sheet here.

[0017] FIG. 7 is a perspective view schematically showing the wound electrode body 20a. Hereinafter, the wound electrode body 20a will be described in detail as an example, but the electrode bodies 20b and 20c may have the same configuration.

[0018] As shown in FIG. 7, the wound electrode body 20a has a positive electrode 22, a negative electrode 24, and a separator 26. The wound electrode body 20a is a wound electrode body in which the strip-shaped positive electrode 22 and the strip-shaped negative electrode 24 are laminated via two strip-shaped separators 26 and wound around a winding axis WL. The wound electrode body 20a (20b, 20c) is preferably arranged such that the winding axis WL is parallel to the bottom wall 12a of the battery case 10.

[0019] The wound electrode body 20a has a flat shape. In other embodiments, the wound electrode body may be cylindrical or the like, but it is preferably flat as in this embodiment. The wound electrode body 20a is arranged inside the case body 12 in a direction such that the winding axis WL is substantially parallel to the long side direction Y. Specifically, as shown in FIG. 3, the wound electrode body 20a has a pair of curved portions (R portions) 20r facing the bottom wall 12a and the sealing plate 14 of the case body 12, and a flat portion 20f connecting the pair of curved portions 20r and facing the second side wall 12c of the case body 12. The flat portion 20f extends along the second side wall 12c.

[0020] As shown in FIG. 7, the positive electrode 22 has a positive electrode current collector 22c, and a positive electrode active material layer 22a and a positive electrode protective layer 22p fixed on at least one surface of the positive electrode current collector 22c. However, the positive electrode protective layer 22p is not essential and can be omitted in other embodiments. The positive electrode current collector 22c is strip-shaped. The positive electrode current collector 22c is made of a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. Here, the positive electrode current collector 22c is a metal foil, specifically an aluminum foil.

[0021] At one end (the left end in FIG. 7) in the long side direction Y of the positive electrode current collector 22c, a plurality of positive electrode tabs 22t are provided. The plurality of positive electrode tabs 22t are provided at intervals (intermittently) along the longitudinal direction of the strip-shaped positive electrode 22. The plurality of positive electrode tabs 22t protrude outside the separator 26 toward one side in the axial direction of the winding axis WL (the left side in FIG. 7). Note that the positive electrode tabs 22t may be provided on the other side in the axial direction of the winding axis WL (the right side in FIG. 7), or may be provided on each of both sides in the axial direction of the winding axis WL. The positive electrode tab 22t is a part of the positive electrode current collector 22c and is made of a metal foil (aluminum foil). However, the positive electrode tab 22t may be a member different from the positive electrode current collector 22c. In at least a part of the positive electrode tab 22t, a region where the positive electrode current collector 22c is exposed is formed without forming the positive electrode active material layer 22a and the positive electrode protective layer 22p.

[0022] As shown in FIG. 4, the plurality of positive electrode tabs 22t are laminated at one end in the axial direction of the winding axis WL (the left end in FIG. 4) to form a positive electrode tab group 23. Each of the plurality of positive electrode tabs 22t is bent so that the outer ends are aligned. Thereby, the battery 100 can be downsized by improving the compatibility with the case 10. As shown in FIG. 2, the positive electrode tab group 23 is electrically connected to the positive electrode terminal 30 via the positive electrode current collecting portion 50. Specifically, the positive electrode tab group 23 and the second positive electrode current collecting portion 52 are connected at a connection portion J (see FIG. 4). The second positive electrode current collecting portion 52 is electrically connected to the positive electrode terminal 30 via the first positive electrode current collecting portion 51. Note that the sizes of the plurality of positive electrode tabs 22t (the length along the long side direction Y and the width orthogonal to the long side direction Y, see FIG. 7) can be appropriately adjusted depending on, for example, the formation position and the like in consideration of the state of being connected to the positive electrode current collecting portion 50. Here, the sizes of the plurality of positive electrode tabs 22t are different from each other so that the outer ends are aligned when bent.

[0023] As shown in FIG. 7, the positive electrode active material layer 22a is provided in a strip shape along the longitudinal direction of the strip-shaped positive electrode current collector 22c. The positive electrode active material layer 22a contains a positive electrode active material (for example, a lithium transition metal composite oxide such as lithium nickel cobalt manganese composite oxide) that can reversibly occlude and release charge carriers. When the total solid content of the positive electrode active material layer 22a is 100% by mass, the positive electrode active material may generally occupy 80% by mass or more, typically 90% by mass or more, for example 95% by mass or more. The positive electrode active material layer 22a may contain optional components other than the positive electrode active material, such as a conductive material, a binder, and various additive components. As the conductive material, for example, a carbon material such as acetylene black (AB) can be used. As the binder, for example, polyvinylidene fluoride (PVdF) or the like can be used.

[0024] As shown in FIG. 7, the positive electrode protective layer 22p is provided at the boundary between the positive electrode current collector 22c and the positive electrode active material layer 22a in the long side direction Y. Here, the positive electrode protective layer 22p is provided at one end in the axial direction of the winding axis WL of the positive electrode current collector 22c (the left end in FIG. 7). However, the positive electrode protective layer 22p may be provided at both ends in the axial direction. The positive electrode protective layer 22p is provided in a strip shape along the positive electrode active material layer 22a. The positive electrode protective layer 22p contains an inorganic filler (for example, alumina). When the total solid content of the positive electrode protective layer 22p is 100% by mass, the inorganic filler may generally occupy 50% by mass or more, typically 70% by mass or more, for example 80% by mass or more. The positive electrode protective layer 22p may contain optional components other than the inorganic filler, such as a conductive material, a binder, and various additive components. The conductive material and the binder may be the same as those exemplified as being contained in the positive electrode active material layer 22a.

[0025] As shown in FIG. 7, the negative electrode 24 has a negative electrode current collector 24c and a negative electrode active material layer 24a fixed on at least one surface of the negative electrode current collector 24c. The negative electrode current collector 24c is strip-shaped. The negative electrode current collector 24c is made of a conductive metal such as copper, a copper alloy, nickel, or stainless steel. Here, the negative electrode current collector 24c is a metal foil, specifically a copper foil.

[0026] At one end in the axial direction of the winding axis WL of the negative electrode current collector 24c (the right end in FIG. 7), a plurality of negative electrode tabs 24t are provided. The plurality of negative electrode tabs 24t are provided at intervals (intermittently) along the longitudinal direction of the strip-shaped negative electrode 24. Each of the plurality of negative electrode tabs 24t protrudes outward from the separator 26 toward one side in the axial direction (the right side in FIG. 7). However, the negative electrode tab 24t may be provided at the other end in the axial direction (the left end in FIG. 7), or may be provided at each of both ends in the axial direction. The negative electrode tab 24t is a part of the negative electrode current collector 24c and is made of a metal foil (copper foil). However, the negative electrode tab 24t may be a member different from the negative electrode current collector 24c. At least a part of the negative electrode tab 24t is provided with a region where the negative electrode current collector 24c is exposed without the formation of the negative electrode active material layer 24a.

[0027] As shown in FIG. 4, the plurality of negative electrode tabs 24t are laminated at one end in the axial direction (the right end in FIG. 4) to form a negative electrode tab group 25. The negative electrode tab group 25 is preferably provided at a position symmetric to the positive electrode tab group 23 in the axial direction. And each of the plurality of negative electrode tabs 24t is bent so that the outer ends thereof are aligned. Thereby, the compatibility with the case 10 can be improved and the battery 100 can be miniaturized. As shown in FIG. 2, the negative electrode tab group 25 is electrically connected to the negative electrode terminal 40 via the negative electrode current collecting portion 60. Specifically, the negative electrode tab group 25 and the second negative electrode current collecting portion 62 are connected at the connection portion J (see FIG. 4). And the second negative electrode current collecting portion 62 is electrically connected to the negative electrode terminal 40 via the first negative electrode current collecting portion 61. Similar to the plurality of positive electrode tabs 22t, here, the sizes of the plurality of negative electrode tabs 24t are different from each other so that the outer ends are aligned when bent.

[0028] As shown in FIG. 7, the negative electrode active material layer 24a is provided in a strip shape along the longitudinal direction of the strip-shaped negative electrode current collector 24c. The negative electrode active material layer 24a contains a negative electrode active material (for example, a carbon material or a silicon-based material) that can reversibly occlude and release charge carriers. Here, examples of such a carbon material include graphite, hard carbon, soft carbon, amorphous carbon, combinations thereof, and the like. Examples of such a silicon-based material include silicon, silicon oxide (silica), combinations thereof, and the like. The silicon-based material may contain, for example, other metal elements (for example, alkaline earth metals) and their oxides. When the total solid content of the negative electrode active material layer 24a is 100% by mass, the negative electrode active material may generally occupy 80% by mass or more, typically 90% by mass or more, for example 95% by mass or more. The negative electrode active material layer 24a may contain optional components other than the negative electrode active material, such as a binder, a dispersant, and various additive components. As the binder, for example, rubbers such as styrene-butadiene rubber (SBR) can be used. As the dispersant, for example, celluloses such as carboxymethyl cellulose (CMC) can be used. Also, the electrode density of the negative electrode active material layer 24a is, for example, 0.8 g / cm 3 or more, and the liquid penetration rate of the non-aqueous electrolyte is slow. From the viewpoint of being preferable as an object to which the technology disclosed herein is applied, it is preferably 1.0 g / cm 3 or more, and more preferably 1.3 g / cm 3 or more. Also, the upper limit of the electrode density of the negative electrode active material layer 24a is, for example, 3.0 g / cm 3 or less, and may be 2.0 g / cm 3 or less.

[0029] As shown in FIG. 7, the separator 26 is a member that insulates the positive electrode active material layer 22a of the positive electrode 22 and the negative electrode active material layer 24a of the negative electrode 24. As the separator 26, for example, a porous sheet made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP) is suitable. The separator 26 may have a base material portion made of a porous sheet made of resin and a heat resistance layer (HRL) provided on at least one surface of the base material portion and containing an inorganic filler. As the inorganic filler, for example, alumina, boehmite, aluminum hydroxide, titania, etc. can be used.

[0030] The non-aqueous electrolyte (non-aqueous electrolyte solution) may be the same as the conventional one and is not particularly limited. The non-aqueous electrolyte typically contains a non-aqueous solvent and a supporting salt (electrolyte salt). As the non-aqueous solvent, various organic solvents such as carbonates, ethers, esters, nitriles, sulfones, lactones, etc. used in the electrolytes of general lithium-ion secondary batteries can be used without particular limitation. Specific examples include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), monofluoroethylene carbonate (MFEC), difluoroethylene carbonate (DFEC), monofluoromethyl difluoromethyl carbonate (F-DMC), trifluorodimethyl carbonate (TFDMC), etc. Such non-aqueous solvents can be used alone or in appropriate combinations of two or more.

[0031] As the supporting salt, for example, lithium salts such as LiPF6, LiBF4, lithium bis(fluorosulfonyl)imide (LiFSI) (preferably LiPF6) can be preferably used. The concentration of the supporting salt is preferably 0.7 mol / L or more and 1.3 mol / L or less.

[0032] In addition, as long as the effects of the present invention are not significantly impaired, the non-aqueous electrolyte may contain components other than the above-described components, for example, film-forming agents such as oxalato complexes; gas generators such as biphenyl (BP) and cyclohexylbenzene (CHB); thickeners; and various other additives.

[0033] Although not particularly limited, the viscosity of the non-aqueous electrolyte (non-aqueous electrolyte solution) can generally be about 10 to 100 mPa·s (for example, about 20 to 50 mPa·s). Such viscosity can be measured, for example, using a commercially available viscometer.

[0034] As shown in FIG. 2, the positive electrode terminal 30 is inserted into a terminal insertion hole 18 formed at one end (the left end in FIG. 2) in the long side direction Y of the sealing plate 14. The positive electrode terminal 30 is preferably made of metal, and more preferably made of, for example, aluminum or an aluminum alloy. On the other hand, the negative electrode terminal 40 is inserted into a terminal insertion hole 19 formed at the other end (the right end in FIG. 2) in the long side direction Y of the sealing plate 14. The negative electrode terminal 40 is preferably made of metal, and more preferably made of, for example, copper or a copper alloy. These electrode terminals (positive electrode terminal 30, negative electrode terminal 40) protrude from the same surface (specifically, the sealing plate 14) of the case 10 here. However, the positive electrode terminal 30 and the negative electrode terminal 40 may protrude from different surfaces of the case 10, respectively. Further, the electrode terminals (positive electrode terminal 30, negative electrode terminal 40) inserted into the terminal insertion holes 18 and 19 are preferably fixed to the sealing plate 14 by caulking or the like.

[0035] As described above, as shown in FIG. 2, the positive electrode terminal 30 is electrically connected to the positive electrodes 22 (see FIG. 7) of the respective wound electrode bodies 20a, 20b, 20c inside the case body 12 via the positive electrode current collecting portions 50 (the first positive electrode current collecting portion 51 and the second positive electrode current collecting portion 52). The positive electrode terminal 30 is insulated from the sealing plate 14 by the positive electrode internal insulating member 70 and the gasket 90. The positive electrode internal insulating member 70 includes a base portion 70a interposed between the first positive electrode current collecting portion 51 and the sealing plate 14, and a protruding portion 70b protruding from the base portion 70a toward the wound electrode body 20a side. The positive electrode terminal 30 exposed outside the case 10 through the terminal insertion hole 18 is connected to the positive electrode external conductive member 32 outside the sealing plate 14. On the other hand, as shown in FIG. 2, the negative electrode terminal 40 is electrically connected to the negative electrodes 24 (see FIG. 7) of the respective wound electrode bodies 20a inside the case body 12 via the negative electrode current collecting portions 60 (the first negative electrode current collecting portion 61 and the second negative electrode current collecting portion 62). The negative electrode terminal 40 is insulated from the sealing plate 14 by the negative electrode internal insulating member 80 and the gasket 90. Similar to the positive electrode internal insulating member 70, the negative electrode internal insulating member 80 also includes a base portion 80a interposed between the first negative electrode current collecting portion 61 and the sealing plate 14, and a protruding portion 80b protruding from the base portion 80a toward the wound electrode body 20a side. The negative electrode terminal 40 exposed outside the case 10 through the terminal insertion hole 19 is connected to the negative electrode external conductive member 42 outside the sealing plate 14. An external insulating member 92 is interposed between the above-described external conductive members (the positive electrode external conductive member 32 and the negative electrode external conductive member 42) and the outer surface of the sealing plate 14. The external insulating member 92 can insulate the external conductive members 32 and 42 from the sealing plate 14.

[0036] Further, the protruding portions 70b and 80b of the above-described internal insulating members (the positive electrode internal insulating member 70 and the negative electrode internal insulating member 80) are disposed between the sealing plate 14 and the wound electrode body 20a. The protruding portions 70b and 80b of the internal insulating member can restrict the upward movement of the wound electrode body 20a and prevent contact between the sealing plate 14 and the wound electrode body 20a.

[0037] Next, the configuration characterizing the battery 100 according to the present embodiment will be described. First, as described above, the battery 100 according to the present embodiment includes wound electrode bodies 20a, 20b, 20c in which a strip-shaped positive electrode 22 and a strip-shaped negative electrode 24 are wound via a strip-shaped separator 26, a non-aqueous electrolyte 13, and a battery case 10 that houses the wound electrode bodies 20a, 20b, 20c and the non-aqueous electrolyte 13. Further, the positive electrode 22 includes a positive electrode active material layer 22a, and the negative electrode 24 includes a negative electrode active material layer 24a. The length (corresponding to S in FIG. 7) of the negative electrode active material layer 24a in the direction in which the winding axis WL of the wound electrode bodies 20a, 20b, 20c extends (corresponding to the winding axis direction WD in FIG. 7) is 200 mm or more. Also, the liquid penetration rate of the non-aqueous electrolyte in the negative electrode active material layer 24a is 0.02 μL / s to 0.05 μL / s. In the direction in which the winding axis extends (i.e., the winding axis direction WD), the distance (corresponding to B in FIG. 8) between the end of the positive electrode active material layer 22a and the end of the negative electrode active material layer 24a is greater than 0 mm and 5 mm or less. And in the fully charged state (i.e., SOC 100%), the ratio of the volume of the non-aqueous electrolyte to the volume of the voids in the positive electrode active material layer 22a and the negative electrode active material layer 24a in the wound electrode bodies 20a, 20b, 20c is 130% or less.

[0038] According to the study by the present inventors, particularly in the case of a large-sized non-aqueous electrolyte secondary battery as described above, due to the wide electrode width, the movement path of the non-aqueous electrolyte (the path between the center of the electrode body and the outside of the electrode body) becomes long, and the high-rate characteristics are likely to deteriorate (in other words, high-rate degradation is likely to occur). Here, such high-rate degradation can be caused by the following factors. First, when the battery is charged, the electrode expands, and in an environment where the change in the thickness direction of the battery is restricted (for example, when it is in a battery case or when an external pressure is applied to suppress the expansion and contraction of the battery), the non-aqueous electrolyte contained between the electrodes is extruded. Also, when the battery is discharged, the electrode contracts, and the extruded non-aqueous electrolyte returns, but if charging is started again before it can fully return, the non-aqueous electrolyte will be extruded again. By repeating this, the movement of the non-aqueous electrolyte cannot keep up with the expansion and contraction of the electrode, and a concentration gradient occurs in the non-aqueous electrolyte (in other words, salt concentration unevenness occurs). Due to such a concentration gradient, high-resistance portions (for example, both end portions in the winding axis direction of the wound electrode body) may occur in the battery, and Li precipitation and deterioration of the electrode active material may occur at those portions. In this way, high-rate degradation can occur. And according to the study by the present inventors, it has been found that such high-rate degradation is more likely to occur as the support salt in the non-aqueous electrolyte is more dispersed (for example, in the non-aqueous electrolyte, the non-facing portions between the positive electrode and the negative electrode, etc.). For example, in FIG. 8, the facing portion between the positive electrode 22 and the negative electrode 24 is designated as A, the non-facing portion between the positive electrode 22 and the negative electrode 24 is designated as B, and the region where no electrode exists is designated as C. In particular, it is said that the non-aqueous electrolyte is likely to accumulate and the support salt is likely to be dispersed in the region B. Also, it has been found that salt concentration unevenness is more likely to occur between the central portion of the wound electrode body and the end portion in the winding axis direction. And such salt concentration unevenness is also related to the liquid penetration rate (immersion rate) of the electrode, and it has also been found that it is likely to occur when a negative electrode with a slow liquid penetration rate is used. This may be due to the fact that high-rate degradation is likely to occur due to the non-aqueous electrolyte not returning in a negative electrode with a slow liquid penetration rate of the non-aqueous electrolyte.

[0039] Therefore, the inventor of the present invention focused on a wound electrode body provided with a non-aqueous electrolyte secondary battery having a length of the negative electrode active material in the winding axis direction of the negative electrode active material layer of 200 mm or more, which is likely to cause such high-rate deterioration, and a liquid penetration rate of the non-aqueous electrolyte in the negative electrode active material layer of 0.02 μL / s to 0.05 μL / s. As a result of intensive studies, the amount of the non-aqueous electrolyte was set to an appropriate amount (specifically, in a fully charged state (i.e., SOC100%), the ratio of the volume of the non-aqueous electrolyte to the volume of the voids in the positive electrode active material layer and the negative electrode active material layer in the wound electrode body was 130% or less), and the unopposed portions of the positive electrode and the negative electrode were set within an appropriate range (specifically, in the direction in which the winding axis extends, the distance between the end of the positive electrode active material layer and the end of the negative electrode active material layer was greater than 0 mm and 5 mm or less). By doing so, it was found that high-rate deterioration is preferably suppressed, and the present disclosure was completed. Note that the above description is the inventor's consideration based on experimental results, and the technology disclosed herein is not construed as being limited to the above description.

[0040] As described above, from the viewpoint of being suitable as an object to which the technology of the present disclosure is applied (in other words, being likely to cause high-rate deterioration), the length (corresponding to S in FIG. 7) of the negative electrode active material layer 24a in the direction in which the winding axis WL of the wound electrode body 20a (20b, 20c) extends (i.e., the winding axis direction WD) is defined to be 200 mm or more. From the viewpoint of being more suitable as an embodiment to which the technology of the present disclosure is applied, the length S of the negative electrode active material layer 24a is preferably 300 mm or more, and may be, for example, 400 mm or more. Further, the upper limit of the length S of the negative electrode active material layer 24a may be, for example, 600 mm or less, or 500 mm or less. Note that the length S of the negative electrode active material layer 24a can be measured, for example, with a ruler.

[0041] As described above, from the viewpoint of being suitable as an object to which the technology of the present disclosure is applied, the liquid penetration rate of the non-aqueous electrolyte in the negative electrode active material layer 24a is defined to be 0.02 μL / s to 0.05 μL / s. From the viewpoint of being more suitable as an embodiment to which the technology of the present disclosure is applied, such a liquid penetration rate is preferably 0.03 μL / s to 0.05 μL / s. Note that, for example, the method for measuring the liquid penetration rate of the non-aqueous electrolyte can be referred to in the corresponding column of the examples described later. Further, the liquid penetration rate of the non-aqueous electrolyte in the negative electrode active material layer 24a can be easily adjusted, for example, by changing the electrode density of the negative electrode active material layer 24a. Alternatively, it can also be easily adjusted by appropriately changing the type of the negative electrode active material, etc.

[0042] Here, FIG. 8 is a schematic cross-sectional view taken along line VIII-VIII in FIG. 2. As described above, in the technology disclosed herein, from the viewpoint of preferably suppressing high-rate deterioration, in the direction in which the winding axis WL extends (i.e., the winding axis direction WD), the distance between the end of the positive electrode active material layer 22a and the end of the negative electrode active material layer 24a (corresponding to B in FIG. 8) is defined to be greater than 0 mm and 5 mm or less. In the non-facing portion of the negative electrode 24, since there is no facing positive electrode 22 and it is difficult to apply pressure, there is a tendency to more easily hold the non-aqueous electrolyte than in the facing portion. Therefore, by making such a non-facing portion as small as possible and reducing the amount of the non-aqueous electrolyte that can be held in the non-facing portion, unevenness in salt concentration (i.e., suppressing high-rate deterioration) can be reduced. The distance between the end of the positive electrode active material layer 22a and the end of the negative electrode active material layer 24a may be, for example, 1 mm or more, or may be 1.5 mm or more. Further, the upper limit of such a distance may be, for example, 4 mm or less, or may be 3 mm or less. Such a distance can be measured, for example, with a ruler or the like. Further, when the positive electrode 22 and the negative electrode 24 have the positive electrode tab 22t and the negative electrode tab 24t, respectively, as in the present embodiment, the ends of the positive electrode active material layer 22a and the negative electrode active material layer 24a are those excluding the positive electrode tab 22t and the negative electrode tab 24t, respectively. Note that in FIG. 8, the base material layer is denoted as 27 and the heat-resistant layer is denoted as 28.

[0043] Also, as described above, in the technology disclosed herein, from the viewpoint of suitably suppressing high-rate deterioration, the ratio of the volume of the non-aqueous electrolyte to the volume of the voids in the positive electrode active material layer 22a and the negative electrode active material layer 24a in the wound electrode body 20a (20b, 20c) is defined to be 130% or less in a fully charged state (i.e., SOC 100%). In other words, in a fully charged state, when the volume of the voids in the positive electrode active material layer 22a and the negative electrode active material layer 24a in the wound electrode body 20a (20b, 20c) is taken as 100%, the ratio of the volume of the non-aqueous electrolyte is defined to be 130% or less. The volume of such non-aqueous electrolyte means the non-aqueous electrolyte present inside and outside the wound electrode body in a fully charged state. If the amount of the non-aqueous electrolyte is too large, the non-aqueous electrolyte present inside and outside the wound electrode body increases, and thus the supporting salt tends to escape easily, which is not preferable. Therefore, the ratio of the volume of the non-aqueous electrolyte present inside and outside the wound electrode body is defined to be 130% or less. The ratio of the volume of such non-aqueous electrolyte may be, for example, 120% or less, or may be 115% or less. Further, from the viewpoint of allowing the charge and discharge in the battery 100 to proceed smoothly, the upper limit of the ratio of the volume of such non-aqueous electrolyte is preferably 100% or more.

[0044] Here, the volume of the voids in the positive electrode active material layer 22a and the negative electrode active material layer 24a (hereinafter, also simply referred to as "the volume of the electrode voids") can be calculated, for example, by measurement using a mercury intrusion porosimeter or by calculation from the electrode density and the true density of the electrode active material and auxiliary materials. The measurement using such a mercury intrusion porosimeter can be carried out according to this kind of conventionally known method. Further, the method of calculating by calculation from the electrode density and the true density of the electrode active material and auxiliary materials can be carried out, for example, as follows. Specifically, the volume of the voids in the negative electrode active material layer 24a can be calculated by dividing the weight of the negative electrode active material layer 24a by the value obtained by subtracting the density of the negative electrode active material layer 24a from the true density of the negative electrode active material and auxiliary materials (for example, various additives other than the negative electrode active material) constituting the negative electrode active material layer 24a. Also, the volume of the voids in the positive electrode active material layer 22a can be calculated by dividing the weight of the positive electrode active material layer 22a by the value obtained by subtracting the density of the positive electrode active material layer 22a from the true density of the positive electrode active material and auxiliary materials (for example, various additives other than the positive electrode active material) constituting the positive electrode active material layer 22a. Then, by summing the volume of the voids in the negative electrode active material layer 24a and the density of the positive electrode active material layer 22a, the volume of the electrode voids can be obtained.

[0045] Also, for example, regarding a pre-assembled battery, the volume / electrode void volume (%) of the non-aqueous electrolyte can be calculated as follows. First, disassemble the battery in a fully charged state, recover the non-aqueous electrolyte outside the wound electrode body, and measure its volume. Then, for the non-aqueous electrolyte inside the wound electrode body, calculate its volume from the weight difference before and after drying the wound electrode body. Regarding the method for obtaining the weight difference before and after drying, if it is directly dried, there is a risk that the indicator salt will remain in the wound electrode body. Therefore, after measuring the weight before drying, wash it with a solvent (e.g., dimethyl carbonate (DMC), etc.) to ensure that no supporting salt remains, and then dry it and measure the weight. Then, the volume of the non-aqueous electrolyte can be calculated by summing the volume of the non-aqueous electrolyte outside the wound electrode body and the volume calculated from the weight difference before and after drying the wound electrode body. Note that the volume of the non-aqueous electrolyte can be the value measured at room temperature (e.g., 25°C). And the volume of the electrode voids can be measured using a mercury intrusion porosimeter or the like on the wound electrode body after drying.

[0046] Also, for example, as an example of a method for making the volume / electrode void volume (%) of the non-aqueous electrolyte X% at full charge (i.e., SOC 100%), the following method can be mentioned. First, calculate the density of the electrode voids by the method described above in advance, and when injecting the liquid, inject the non-aqueous electrolyte so that the volume / electrode void volume (%) of the non-aqueous electrolyte becomes X%. Thereby, at full charge, the non-aqueous electrolyte can be adjusted so that the volume / electrode void volume of the non-aqueous electrolyte = X%.

[0047] In one aspect of suitability, in a fully charged state (i.e., SOC 100%), the ratio of the volume of the non-aqueous electrolyte to the volume of the space within the battery case 10 is 65 to 80%. The volume of such non-aqueous electrolyte means the non-aqueous electrolyte present inside and outside the wound electrode body in the fully charged state. According to such a configuration, the amount of supporting salt that escapes into the non-aqueous electrolyte present inside and outside the wound electrode body can be preferably suppressed, which is preferable from the viewpoint of suppressing high-rate deterioration. The ratio of the volume of such non-aqueous electrolyte may be, for example, 70% or more, and may be 77% or less (for example, 75% or less). The volume of the space of the battery case 10 is obtained by subtracting the volume of the wound electrode bodies 20a, 20b, 20c, the volume of each member present in the battery case 10 (for example, electrode current collecting parts, insulating members, etc.), and the volume of the non-aqueous electrolyte from the sum of the volume of the battery case 10, the volume of the electrode voids, and the volume of the voids inside the separator 26. Also, as the volume of such non-aqueous electrolyte, the volume value measured, for example, at room temperature (for example, 25°C) can be adopted by disassembling the fully charged battery and recovering the non-aqueous electrolyte inside and outside the wound electrode body.

[0048] Also, for example, as an example of a method of making the volume of the non-aqueous electrolyte / volume of the space in the battery case (%) = Y% at full charge (i.e., SOC 100%), the following method can be mentioned. First, the volume of the space in the battery case is calculated in advance by the method as described above, and at the time of liquid injection, the non-aqueous electrolyte is injected so that the volume of the non-aqueous electrolyte / volume of the space in the battery case (%) = Y%. Thereby, at full charge, the non-aqueous electrolyte can be adjusted so that the volume of the non-aqueous electrolyte / volume of the space in the battery case = Y%.

[0049] Here, FIG. 9 is an explanatory diagram for explaining the relationship between the liquid level height of the non-aqueous electrolyte 13 and the height of the wound electrode body 20a (20b, 20c). Note that the height of the wound electrode body 20a (20b, 20c) is set such that the lower end is 0% and the upper end is 100% in the vertical direction with respect to the bottom wall 12a of the battery case 10. Also, the height of the wound electrode body 20a (20b, 20c) can be, for example, the length in a direction perpendicular to the winding axis direction WD and perpendicular to the thickness direction X. In a preferred embodiment, when the height of the wound electrode body 20a (20b, 20c) (corresponding to P in FIG. 9) is 100% in the fully charged state (i.e., SOC 100%), the liquid level height of the non-aqueous electrolyte 13 (corresponding to Q in FIG. 9) is 10% or less. If there is a large amount of the non-aqueous electrolyte 13 existing outside the wound electrode body 20a (20b, 20c), it becomes easier for the supporting salt to escape, which is not preferable from the viewpoint of suppressing high-rate deterioration. Therefore, as described above, for example, at the time of full charge, it is preferable that the liquid level height Q of the non-aqueous electrolyte 13 is adjusted within an appropriate range (in other words, the amount of the non-aqueous electrolyte 13 existing outside the wound electrode bodies 20a, 20b, 20c is adjusted within an appropriate range). From such a viewpoint, in the fully charged state, the liquid level height Q of the non-aqueous electrolyte 13 is more preferably 7% or less, and even more preferably 5% or less and 3% or less. Also, in the fully charged state, the liquid level height Q of the non-aqueous electrolyte 13 can be, for example, 0.5% or more and 1% or more. Those skilled in the art can adjust the amount of the non-aqueous electrolyte 13 injected during injection by conducting preliminary tests, etc. in advance, so that when the height of the wound electrode body 20a (20b, 20c) is 100% in the fully charged state (i.e., SOC 100%), the liquid level height Q of the non-aqueous electrolyte 13 can be adjusted to 10% or less.

[0050] In a preferred embodiment, when the height of the wound electrode body 20a (20b, 20c) (corresponding to P in FIG. 9) is taken as 100% at SOC 20% (during discharge), the liquid level height of the non-aqueous electrolyte 13 (corresponding to Q in FIG. 9) is 7% or less. If there is a large amount of the non-aqueous electrolyte 13 existing outside the wound electrode bodies 20a, 20b, and 20c, the supporting salt is more likely to escape, which is not preferable from the viewpoint of suppressing high-rate deterioration. Therefore, as described above, for example, at SOC 20%, it is preferable that the liquid level height Q of the non-aqueous electrolyte 13 is adjusted within an appropriate range (in other words, the amount of the non-aqueous electrolyte 13 existing outside the wound electrode bodies 20a, 20b, and 20c is adjusted within an appropriate range). From such a viewpoint, at SOC 20%, the liquid level height Q of the non-aqueous electrolyte 13 is more preferably 5% or less, and even more preferably 3% or less and 1% or less. Also, at SOC 20%, the liquid level height Q of the non-aqueous electrolyte 13 can be, for example, 0.1% or more and 0.5% or more. The liquid level height Q of the non-aqueous electrolyte 13 at SOC 20% is preferably measured, for example, after leaving it for a sufficient time (for example, about one week) after charge and discharge when the movement of the non-aqueous electrolyte is completely finished. Those skilled in the art can adjust the amount of the non-aqueous electrolyte injected during injection by performing preliminary tests or the like in advance, so that when the height of the wound electrode body 20a (20b, 20c) is taken as 100% at SOC 20% (during discharge), the liquid level height of the non-aqueous electrolyte 13 can be adjusted to 7% or less.

[0051] Also, the liquid level height Q of the non-aqueous electrolyte in the fully charged state (or SOC 20%) can be measured by performing a CT scan or the like on the battery 100.

[0052] The technology disclosed herein can be applied to batteries other than large batteries, for example, but large batteries (e.g., high-capacity batteries) are particularly suitable as the application target. Here, as an example of the outer dimensions of the wound electrode body included in such a large battery, length: 50 mm to 100 mm, width: 200 mm to 300 mm, thickness: 10 mm to 40 mm can be mentioned. Note that the above-mentioned length, width, and thickness are, taking the wound electrode body 20a as an example, the length in the short side direction of the wound electrode body 20a (the length in the Z direction in FIG. 7), the length in the long side direction of the wound electrode body 20a (the length in the Y direction in FIG. 7), and the thickness of the wound electrode body 20a (the thickness in the X direction in FIG. 6), respectively. Further, the capacity of the battery 100 is, for example, 50 Ah or more, preferably 100 Ah or more, and can also be 150 Ah or more, 200 Ah or more.

[0053] <Method for manufacturing a battery> Next, an example of the manufacturing method of the battery 100 according to the present embodiment will be described. In the production of the battery 100 according to the present embodiment, the length of the negative electrode active material layer 24a in the direction in which the winding axis WL extends is 200 mm or more, the liquid penetration rate of the non-aqueous electrolyte in the negative electrode active material layer 24a is 0.02 μL / s to 0.05 μL / s, and in the direction in which the winding axis WL extends, the distance between the end of the positive electrode active material layer 22a and the end of the negative electrode active material layer 24a is greater than 0 mm and 5 mm or less. The battery 100 according to the present embodiment can be manufactured, for example, by preparing wound electrode bodies 20a, 20b, and 20c, inserting them into the case 10, and sealing them. More specifically, first, as shown in FIG. 5, a second positive current collector 52 is joined to the positive tab group 23 of each electrode body, and a second negative current collector 62 is joined to the negative tab group 25. Then, as shown in FIG. 4, each electrode body is arranged such that the flat portions face each other. A sealing plate 14 is disposed above each electrode body, and the positive tab group 23 of each electrode body is bent so that the second positive current collector 52 faces one side surface 20e of the electrode body. As a result, the first positive current collector 51 and the second positive current collector 52 are connected. Similarly, the negative tab group 25 of each electrode body 20 is bent so that the second negative current collector 62 faces the other side surface 20h of the electrode body. As a result, the first negative current collector 61 and the second negative current collector 62 are connected. As a result, the electrode body is attached to the sealing plate 14 via the positive current collector 50 and the negative current collector 60. Next, each electrode body attached to the sealing plate 14 is covered with an electrode body holder 29 (see FIG. 3) and then housed inside the case body 12. As a result, the flat portion of the electrode body 20 faces the long side wall 12b of the case body 12 (i.e., the flat surface of the case 10). Also, the upper curved portion 20r faces the sealing plate 14, and the lower curved portion 20r faces the bottom wall 12a of the case body 12. Then, after closing the opening 12h on the upper surface of the case body 12 with the sealing plate 14, the case 10 is constructed by joining (welding) the case body 12 and the sealing plate 14. Thereafter, a predetermined amount of non-aqueous electrolyte is injected into the case 10 through the liquid injection hole 15 of the sealing plate 14, and the liquid injection hole 15 is closed with a sealing member 15a. The battery 100 can be obtained as described above.

[0054] <Battery Applications> Although the battery 100 can be used for various applications, for example, it can be suitably used as a power source (driving power source) for a motor mounted on vehicles such as passenger cars and trucks. The type of vehicle is not particularly limited, and examples include plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs), battery electric vehicles (BEVs), and the like. Since the variation in battery reaction of the battery 100 is reduced, it can be suitably used for constructing a battery pack.

[0055] As described above, one embodiment of the present disclosure has been described, but the above embodiment is merely an example. The present disclosure can be implemented in various other forms. The present disclosure can be implemented based on the content disclosed herein and common general knowledge in the art. The technology described in the claims includes various modifications and changes of the above-exemplified embodiments. For example, it is possible to replace a part of the above-described embodiment with another modified form, and it is also possible to add another modified form to the above-described embodiment. Further, if the technical feature is not described as essential, it can be appropriately deleted.

[0056] As described above, specific aspects of the technology disclosed herein include those described in the following items. Item 1: A wound electrode body in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound with a strip-shaped separator interposed therebetween, a non-aqueous electrolyte solution, and a battery case that houses the wound electrode body and the non-aqueous electrolyte solution. The positive electrode includes a positive electrode active material layer, the negative electrode includes a negative electrode active material layer, the length of the negative electrode active material layer in the direction in which the winding axis of the wound electrode body extends is 200 mm or more, the liquid penetration rate of the non-aqueous electrolyte solution in the negative electrode active material layer is 0.02 μL / s to 0.05 μL / s, and in the direction in which the winding axis extends, the distance between the end of the positive electrode active material layer and the end of the negative electrode active material layer is greater than 0 mm and 5 mm or less. In a fully charged state, the ratio of the non-aqueous electrolyte solution to the voids of the positive electrode active material layer and the negative electrode active material layer in the wound electrode body is 130% or less. A non-aqueous electrolyte secondary battery. Item 2: The non-aqueous electrolyte secondary battery according to Item 1, wherein in a fully charged state, the ratio of the volume of the non-aqueous electrolyte solution to the volume of the space in the battery case is 65 to 80%. Item 3: The non-aqueous electrolyte secondary battery according to Item 1 or Item 2, wherein in a fully charged state, when the height of the wound electrode body is taken as 100%, the liquid level height of the non-aqueous electrolyte solution is 10% or less. Item 4: The non-aqueous electrolyte secondary battery according to any one of Items 1 to 3, wherein at SOC 20%, when the height of the wound electrode body is taken as 100%, the liquid level height of the non-aqueous electrolyte solution is 7% or less.

[0057] Hereinafter, test examples related to the present invention will be described, but the present invention is not intended to be limited to those shown in such test examples.

[0058] [Test Example]

[0059] [Preparation of Each Sample] (Preparation of Separator) As the separator, a wet microporous polyethylene sheet with a thickness of 12 μm was prepared. Further, heat-resistant layers with a thickness of 2 μm were formed on both surfaces of such a separator.

[0060] (Preparation of Negative Electrode Plate) Graphite as the negative electrode active material, styrene-butadiene rubber (SBR) as the binder, and carboxymethyl cellulose (CMC) were mixed so that the weight ratio of the negative electrode active material: CMC: SBR was 98.3: 0.7: 1, and an appropriate amount of ion-exchanged water was added as a solvent to prepare a slurry for forming a negative electrode active material layer. Then, a negative electrode plate was obtained by drying and roll pressing. For each sample, the pressing pressure of the roll pressing was changed to vary the electrode density of the negative electrode active material layer, and it was adjusted so that the liquid penetration rate of the non-aqueous electrolyte shown in Table 1 was obtained respectively.

[0061] The liquid penetration rate of the non-aqueous electrolyte in the negative electrode active material layer was measured as follows. Specifically, at room temperature (for example, 25 ° C) and under a predetermined pressure (for example, under 0.1 MPa), 1 μL of the non-aqueous electrolyte was dropped onto one side of the negative electrode active material layer with a microsyringe, and the time until such a liquid droplet penetrated into the negative electrode active material layer (that is, the liquid droplet on the negative electrode active material layer disappeared) was measured and calculated as the penetration rate of 1 μL of the non-aqueous electrolyte.

[0062] (Fabrication of the positive electrode plate) Lithium nickel cobalt manganese composite oxide (LiNi 0.6 Co 0.2 Mn 0.2 O2, NCM622) as the positive electrode active material, acetylene black (AB) as the conductive material, and polyvinylidene fluoride (PVDF) as the binder were mixed so that the positive electrode active material: conductive material: binder = 97.5: 1.5: 1, and an appropriate amount of N-methyl-2-pyrrolidone (NMP) was added as a solvent to prepare a slurry for forming a positive electrode active material layer. This slurry for forming a positive electrode active material layer was applied onto a positive electrode current collector made of aluminum foil so that the basis weight was 10 mg / cm 2 Then, drying and roll pressing were performed to obtain a positive electrode plate.

[0063] Next, a wound electrode body was obtained by laminating a positive electrode plate and a negative electrode plate with a separator interposed therebetween and pressing them into a flat shape. As the two separators, those prepared above were both used. For each sample, the distance between the end of the positive electrode active material layer and the end of the negative electrode active material layer was adjusted to be the distance shown in Table 1, respectively. Then, after welding a current collector plate to the wound electrode body, the wound electrode body was housed in a rectangular battery case, and a non-aqueous electrolyte was injected. As the non-aqueous electrolyte, LiPF6 was dissolved as a supporting salt at a concentration of 1.1 mol / L in a mixed solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of EC:EMC:DMC = 3:4:3. For each sample, the non-aqueous electrolyte was injected so that the volume of the non-aqueous electrolyte / the volume of the electrode voids (%) was the value shown in Table 1 at the time of injection. The volume of such an electrode density was calculated here from the density of the electrode active material layer and the true density of the electrode active material and auxiliary materials as described above. Then, by sealing the battery case, an evaluation lithium-ion secondary battery according to each sample was obtained. Regarding the volume of the non-aqueous electrolyte / the volume of the space in the battery case (%) at full charge, it was calculated from the space in the battery case measured in advance and the volume of the injected non-aqueous electrolyte. The results were described in the column of "Volume of non-aqueous electrolyte / Volume of space in battery case (%)" in Table 1.

[0064] <Evaluation of each lithium-ion secondary battery for evaluation> Each lithium secondary battery for evaluation prepared as described above was placed in a thermostat at 25°C and the first charge was performed. For the first charge, each lithium secondary battery for evaluation was charged at a constant current of 0.3C up to 4.1V. Then, it was discharged at a constant current of 0.3C down to 3.0V. Further, constant current-constant voltage charging (charged at a constant current of 0.2C up to 4.1V and then charged at a constant voltage until the current value became 1 / 50C) was performed on each such lithium secondary battery for evaluation to bring it to a fully charged state. Then, it was discharged at a constant current of 0.2C down to 3.0V. The discharge capacity at this time was measured and used as the initial capacity.

[0065] (Evaluation of cycle characteristics) Each lithium-ion secondary battery for evaluation was placed in a thermostat at 25°C. For each lithium-ion secondary battery for evaluation, charge-discharge cycles were repeated 200 times, where a constant current charge up to 4.1 V at 2C and a constant current discharge down to 3.0 V at 2C were defined as one cycle. Thereafter, the discharge capacity was measured in the same manner as above, and the discharge capacity at this time was determined as the battery capacity after 200 charge-discharge cycles. The capacity retention rate (%) was determined as (battery capacity after 200 charge-discharge cycles / initial capacity) × 100. The results were shown in the column of "Cycle characteristics" in Table 1.

[0066] (Evaluation of high-rate characteristics) To evaluate the high-rate characteristics (high-rate tolerance) of each lithium-ion secondary battery for evaluation, the resistance increase rate (%) was measured. Such measurement was carried out at 25°C. Specifically, after adjusting the SOC of each lithium-ion secondary battery for evaluation to 60%, a high-rate cycle test was performed by repeating 30 charge-discharge cycles of charging at a constant current of 10C (40A) for 10 seconds and discharging at a constant current of 2C (8A) for 400 seconds. Then, based on the IV resistance after such high-rate cycle test and the initial IV resistance, the resistance increase rate (=[IV resistance after high-rate cycle test / initial IV resistance] × 100) was calculated. The IV resistance was determined from the slope of the linear approximation of the current (I)-voltage (V) plot values when discharging at 10C for 10 seconds. Such measurement was carried out at room temperature (for example, 25°C). The results were shown in the column of "Resistance increase rate" in Table 1. Also, based on the value of such resistance increase rate, the evaluation of the high-rate characteristics was carried out. Specifically, when the resistance increase rate was 1.05 times or less, it was evaluated as "◎", when it was more than 1.05 times and less than 1.10 times, it was evaluated as "〇", and when it was 1.10 times or more, it was evaluated as "×". The results were shown in the column of "High-rate characteristics" in Table 1.

[0067]

Table 1

[0068] As shown in Table 1, the length of the negative electrode active material layer in the winding axis direction is 200 mm or more, the liquid penetration rate of the non-aqueous electrolyte in the negative electrode active material layer is 0.02 μL / s to 0.05 μL / s, and in the winding axis direction, the distance between the end of the positive electrode active material layer and the end of the negative electrode active material layer is greater than 0 mm and 5 mm or less. Further, in the fully charged state, the ratio of the non-aqueous electrolyte to the voids of the positive electrode active material layer and the negative electrode active material layer in the wound electrode body is 130% or less (alternatively, in the fully charged state, the volume ratio of the non-aqueous electrolyte to the space in the battery case is in the range of 65 to 80%). According to the evaluation lithium ion secondary batteries according to Samples 1 to 4, in the fully charged state, the ratio of the non-aqueous electrolyte to the voids of the positive electrode active material layer and the negative electrode active material layer in the wound electrode body is more than 130% (alternatively, in the fully charged state, the volume ratio of the non-aqueous electrolyte to the space in the battery case is outside the range of 65 to 80%). Comparing with the evaluation lithium ion secondary battery according to Sample 5 and the evaluation lithium ion secondary battery according to Sample 6 where the distance between the end of the positive electrode active material layer and the end of the negative electrode active material layer in the winding axis direction is more than 5 mm, it was confirmed that high rate deterioration can be more preferably suppressed.

[0069] Further, in the evaluation lithium ion secondary batteries according to Samples 7 and 8, since the liquid penetration rate of the non-aqueous electrolyte in the negative electrode active material layer is excellent at 0.07 μL / s, it can be seen that there are no problems regarding high rate characteristics (high rate tolerance). That is, it can be said that non-aqueous electrolyte secondary batteries in which the liquid penetration rate of the non-aqueous electrolyte in the negative electrode active material layer is less than 0.07 μL / s (specifically, 0.02 μL / s to 0.05 μL / s) are suitable as the object to which the technology disclosed here is applied. On the other hand, regarding the cycle characteristics (here, the capacity retention rate after 200 cycles), it can be seen that there are problems because it is lower than that of the evaluation lithium ion secondary batteries according to Samples 1 to 4.

Explanation of Signs

[0070] 10 Battery case 12 Case body 14 Sealing plate 15 Liquid injection hole 15a Sealing member 17 Gas discharge valve 18, 19 Terminal insertion holes 20 Electrode body group 20a - 20c Wound electrode bodies 22 Positive electrode 23 Positive electrode tab group 24 Negative electrode 25 Negative electrode tab group 26 Separator 27 Base material layer 28 Heat - resistant layer 30 Positive electrode terminal 32 Positive electrode external conductive member 40 Negative electrode terminal 42 Negative electrode external conductive member 50 Positive electrode current collector 60 Negative electrode current collector 70 Positive electrode internal insulating member 80 Negative electrode internal insulating member 90 Gasket 92 External insulating member 100 Battery (non - aqueous electrolyte secondary battery)

Claims

1. A wound electrode body in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound with a strip-shaped separator interposed therebetween, a non-aqueous electrolyte, a battery case that houses the wound electrode body and the non-aqueous electrolyte, comprising: the positive electrode includes a positive electrode active material layer, the negative electrode includes a negative electrode active material layer, the length of the negative electrode active material layer in the direction in which the winding axis of the wound electrode body extends is 200 mm or more, the liquid penetration rate of the non-aqueous electrolyte in the negative electrode active material layer is 0.02 μL / s to 0.05 μL / s, in the direction in which the winding axis extends, the distance between the end of the positive electrode active material layer and the end of the negative electrode active material layer is greater than 0 mm and 5 mm or less, in a fully charged state, a non-aqueous electrolyte secondary battery in which the ratio of the volume of the non-aqueous electrolyte to the volume of the voids in the positive electrode active material layer and the negative electrode active material layer in the wound electrode body is 130% or less.

2. in a fully charged state, the ratio of the volume of the non-aqueous electrolyte to the volume of the space in the battery case is 65 to 80%, the non-aqueous electrolyte secondary battery according to claim 1.

3. in a fully charged state, the wound electrode body is disposed in the battery case such that the winding axis of the wound electrode body is parallel to the bottom wall of the battery case, when the height of the wound electrode body in the direction perpendicular to the bottom wall is taken as 100%, the liquid level height of the non-aqueous electrolyte in the direction perpendicular to the bottom wall is 10% or less, the non-aqueous electrolyte secondary battery according to claim 1 or 2.

4. at SOC 20%, the wound electrode body is disposed in the battery case such that the winding axis of the wound electrode body is parallel to the bottom wall of the battery case, when the height of the wound electrode body in the direction perpendicular to the bottom wall is taken as 100%, the liquid level height of the non-aqueous electrolyte in the direction perpendicular to the bottom wall is 7% or less, the non-aqueous electrolyte secondary battery according to claim 1 or 2.

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