Prismatic battery

Abstract

To provide a prismatic battery where pressure is less likely to concentrate on a joint of a case.SOLUTION: According to the present invention, there is provided a prismatic battery which includes: a rectangular case having a case body that has a first surface, a second surface and an opening, and a sealing plate that seals the opening; and a laminated electrode assembly having a positive electrode plate and a negative electrode plate 24. The negative electrode plate 24 has a negative electrode active material layer 24a including a Si-containing material. The negative electrode active material layer 24a has: a sealing plate side region A3 provided at an end portion on the sealing plate side; and a central region A2 provided in a band shape at a center thereof in a first direction Z. The sealing plate side region A3 is free of the Si-containing material, or has a content of the Si-containing material lower than that in the central region A2.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a prismatic battery. [Background technology]

[0002] Conventionally, there has been known an electricity storage device that includes a case having a case body with an opening and a sealing plate that seals the opening, and an electrode body housed inside the case (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-040684 [Patent Document 2] International Publication No. 2021 / 261358 Summary of the Invention [Problem to be solved by the invention]

[0004] As described in Patent Document 1, for example, the electrode assembly may expand due to repeated charging and discharging. In such cases, in prismatic batteries with prismatic cases, the pressure applied to the case tends to be uneven, with relatively large pressure being applied to surfaces with large areas. As a result, the case of prismatic batteries is more likely to deform or break than, for example, cylindrical batteries or laminated batteries.

[0005] Furthermore, according to the inventor's findings, in recent years, the outer dimensions of the electrode assembly have been made approximately the same as the inner dimensions of the case, in order to improve energy density, etc. In particular, unlike wound electrode assemblies, laminated electrode assemblies do not have curved portions (R portions), and therefore tend to press strongly against the corners of the case when they expand due to repeated charging and discharging, etc. In particular, when the negative electrode plate contains a Si-containing material in order to increase capacity, the expansion of the laminated electrode assembly becomes more pronounced. This poses a problem in that pressure tends to concentrate particularly at the joint between the case body and the sealing plate.

[0006] The present invention has been made in view of the above circumstances, and its main object is to provide a prismatic battery in which pressure is less likely to concentrate at the joints of the case. [Means for solving the problem]

[0007] The present invention provides a prismatic battery comprising: a prismatic case having a substantially rectangular first surface with a pair of long sides and a pair of short sides; a pair of second surfaces extending from the pair of long sides and having a larger area than the first surface; a case body having one or more openings; and one or more sealing plates sealing the one or more openings; and a laminated electrode assembly housed inside the case and having a positive electrode plate and a negative electrode plate arranged substantially parallel to the second surface. The negative electrode plate comprises a negative electrode active material layer containing a Si-containing material as a negative electrode active material. The negative electrode active material layer has one or more sealing plate-side regions formed in a strip shape at one or more end portions on the sealing plate side, and a strip-shaped central region formed in the center in a first direction perpendicular to the sealing plate. The sealing plate-side regions do not contain the Si-containing material, or have a lower content of the Si-containing material than the central region.

[0008] In the present invention, the sealing plate side region of the negative electrode plate does not contain any Si-containing material or has a lower content of Si-containing material than the central region. This prevents pressure from concentrating at the joint between the case body and the sealing plate, thereby preventing damage to the joint. Furthermore, by relatively increasing the content of Si-containing material in the central region of the negative electrode plate, the energy density can be improved. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view that schematically shows a prismatic battery 100 according to one embodiment. [Figure 2] FIG. 2 is a schematic vertical cross-sectional view taken along line II-II in FIG. [Figure 3] FIG. 3 is a schematic plan view of the negative electrode plate. [Figure 4]FIG. 4 is a view corresponding to FIG. 1 according to a modified example. [Figure 5] FIG. 5 is a schematic vertical cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 6 is a view corresponding to FIG. 3 according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the technology disclosed herein will be described below with reference to the drawings as appropriate. It should be noted that matters other than those specifically mentioned in this specification that are necessary for implementing the technology disclosed herein (for example, the general configuration and manufacturing process of a prismatic battery that does not characterize the technology disclosed herein) can be understood as design matters for those skilled in the art based on prior art in the relevant field. The technology disclosed herein can be implemented based on the content disclosed in this specification and common technical knowledge in the relevant field. Furthermore, the expression "A to B" indicating a range in this specification means greater than or equal to A and less than or equal to B, and also encompasses the meanings of "preferably greater than A" and "preferably smaller than B."

[0011] FIG. 1 is a perspective view of a prismatic battery 100. FIG. 2 is a schematic longitudinal cross-sectional view taken along line II-II in FIG. 1. In the following description, components and parts that perform the same function are designated by the same reference numerals, and redundant descriptions may be omitted or simplified. The reference numerals F, Rr, L, R, U, and D in the drawings represent front, rear, left, right, top, and bottom, respectively. The reference numerals X, Y, and Z in the drawings represent the short side direction (thickness direction) of the prismatic battery 100, the long side direction perpendicular to the short side direction, and the up-down direction perpendicular to the short side and long side directions, respectively. The up-down direction Z typically corresponds to the vertical direction. However, these directions are merely used for convenience of explanation and do not limit the installation form of the prismatic battery 100.

[0012] As shown in FIG. 2, the prismatic battery 100 includes a prismatic case 10, a laminated electrode assembly 20, a positive electrode terminal 30, and a negative electrode terminal 40. Although not shown, the prismatic battery 100 further includes an electrolyte. The prismatic battery 100 is a nonaqueous electrolyte secondary battery. The prismatic battery 100 is preferably a lithium-ion secondary battery. In this specification, the term "secondary battery" refers to any power storage device that can be repeatedly charged and discharged, and is a concept that encompasses secondary batteries such as lithium-ion secondary batteries and nickel-metal hydride batteries, as well as capacitors that utilize chemical reactions, such as lithium-ion capacitors and pseudo-capacitor capacitors.

[0013] The case 10 is a housing that houses the laminated electrode assembly 20 and the electrolyte. As shown in FIG. 1, the case 10 has a flat, bottomed, rectangular parallelepiped (square) outer shape. The case 10 has a size that corresponds to the size of the laminated electrode assembly 20, etc. The material of the case 10 may be the same as that conventionally used, and is not particularly limited. The case 10 is preferably made of metal, and more preferably made of, for example, aluminum, an aluminum alloy, iron, an iron alloy, or the like.

[0014] As shown in FIG. 2 , in this embodiment, the case 10 includes a bottomed, rectangular (box-shaped) case body 12 having an opening 12h on one side (here, the upper side) and a sealing plate (lid) 14 that seals the opening 12h of the case body 12. Here, the case body 12 has only one opening 12h and one sealing plate 14. The case 10 is integrated by joining the sealing plate 14 to the periphery of the opening 12h of the case body 12. In this embodiment, the case body 12 and the sealing plate 14 are integrated by welding the seam between them, for example, by laser welding. A joint (more specifically, a welded joint WP) is formed at the boundary between the periphery of the opening 12h of the case body 12, specifically, the long side surface 12b (second side, see FIG. 1 ) and the short side surface 12c of the case body 12, which will be described later, and the sealing plate 14. The case 10 is hermetically sealed (sealed).

[0015] As shown in FIG. 1, the case body 12 has a substantially rectangular bottom surface 12a having a pair of long sides and a pair of short sides, a pair of long side surfaces 12b extending from the pair of long sides of the bottom surface 12a and facing each other, and a pair of short side surfaces 12c extending from the pair of short sides of the bottom surface 12a and facing each other. The bottom surface 12a faces the sealing plate 14. The bottom surface 12a is an example of a "first surface." The long side surfaces 12b are the surfaces with the largest area. In other words, the long side surfaces 12b have an area larger than that of the bottom surface 12a. The long side surfaces 12b have an area larger than that of the short side surfaces 12c. The long side surfaces 12b are an example of a "second surface."

[0016] In this specification, the term "approximately rectangular" refers not only to a perfect rectangular shape (rectangular shape), but also to shapes such as those in which the corners connecting the long and short sides of the rectangle are rounded, or those in which the corners have notches.

[0017] The sealing plate 14 is a plate-like member that closes the opening 12h of the case body 12. Here, the sealing plate 14 faces the bottom surface 12a (first surface) of the case body 12. The sealing plate 14 has a substantially rectangular shape. As shown in FIG. 2, the sealing plate 14 is provided with a liquid inlet 15, a gas release valve 17, and two terminal holes 18 and 19. The liquid inlet 15 is a through-hole for injecting electrolyte into the case 10 after the sealing plate 14 is assembled to the case body 12. The liquid inlet 15 is sealed with a sealing member 16 after the electrolyte is injected. The gas release valve 17 is configured to break when the pressure inside the case 10 exceeds a predetermined value, thereby releasing the pressure inside the case 10 to the outside. The terminal holes 18 and 19 are formed at both ends of the sealing plate 14 in the long side direction Y. The terminal lead-out holes 18 and 19 each penetrate the sealing plate 14 in the vertical direction Z.

[0018] The positive electrode terminal 30 is disposed at one end of the sealing plate 14 in the long side direction Y (the left end in FIGS. 1 and 2). As shown in FIG. 2, the positive electrode terminal 30 extends from the inside to the outside of the sealing plate 14 through the terminal lead-out hole 18. Here, the positive electrode terminal 30 is fixed by crimping to the peripheral portion of the sealing plate 14 surrounding the terminal lead-out hole 18. A crimped portion 30c is formed at the end of the positive electrode terminal 30 on the case body 12 side (the lower end in FIG. 2). Inside the case 10, the positive electrode terminal 30 is electrically connected to the positive electrode plate 22 of the laminated electrode assembly 20 via a positive electrode current collecting member 50 and a positive electrode tab 22t (described later). The positive electrode terminal 30 is preferably made of metal, more preferably aluminum or an aluminum alloy. The positive electrode terminal 30 is insulated from the sealing plate 14 by a gasket 92 and an internal insulating member 94.

[0019] The negative electrode terminal 40 is disposed at the other end of the sealing plate 14 in the long side direction Y (the right end in FIGS. 1 and 2). As shown in FIG. 2, the negative electrode terminal 40 extends from the inside to the outside of the sealing plate 14 through the terminal lead-out hole 19. Here, the negative electrode terminal 40 is fixed by crimping to the peripheral portion of the sealing plate 14 surrounding the terminal lead-out hole 19. A crimped portion 40c is formed at the end of the negative electrode terminal 40 on the case body 12 side (the lower end in FIG. 2). Inside the case 10, the negative electrode terminal 40 is electrically connected to the negative electrode plate 24 of the laminated electrode assembly 20 via a negative electrode current collecting member 60 and a negative electrode tab 24t (described later). The negative electrode terminal 40 is preferably made of metal, more preferably copper or a copper alloy. The negative electrode terminal 40 is insulated from the sealing plate 14 by a gasket 92 and an internal insulating member 94.

[0020] The electrolyte solution is accommodated inside the case 10. The electrolyte solution may be the same as conventional ones and is not particularly limited. The electrolyte solution is typically a non-aqueous electrolyte solution containing a non-aqueous solvent and a supporting salt (electrolyte salt). However, in other embodiments, the electrolyte solution may be an aqueous electrolyte solution containing an aqueous solvent. Examples of non-aqueous solvents include carbonates such as ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. Examples of supporting salts include fluorine-containing lithium salts such as lithium hexafluorophosphate (LiPF6). The electrolyte solution may further contain additives as necessary. In still other embodiments, the electrolyte solution may be in a solid state (solid electrolyte) and integrated with the laminated electrode body 20.

[0021] As shown in FIG. 2, the laminated electrode body 20 is housed inside the case 10. Here, the laminated electrode body 20 is housed inside the case 10 while covered with a resin insulating sheet (electrode body holder) 29. The laminated electrode body 20 has a positive electrode tab 22t and a negative electrode tab 24t, and is therefore arranged relatively lower (toward the bottom surface 12a (first surface)) inside the case 10. In other words, the gap d1 between the bottom surface 12a (first surface) and the lower end of the laminated electrode body 20 is smaller than the gap d3 between the sealing plate 14 and the upper end of the laminated electrode body 20 (i.e., d1 <d3)。

[0022] The laminated electrode body 20 has positive electrode plates 22 and negative electrode plates 24 arranged (stacked) substantially parallel to the long side surface 12b (second surface) of the case 10. The laminated electrode body 20 typically has a plurality of positive electrode plates 22 and a plurality of negative electrode plates 24. Here, the positive electrode plates 22 and the negative electrode plates 24 are each square-shaped (more specifically, rectangular). The positive electrode plates 22 and the negative electrode plates 24 are arranged such that their long sides extend along the long-side direction Y and their short sides extend along the up-down direction Z. The positive electrode plates 22 and the negative electrode plates 24 are insulated from each other via a separator or the like (not shown) and face each other in the short-side direction X (stacking direction).

[0023] In this specification, the term "substantially parallel" does not mean parallel in the strict sense, but rather allows for an inclination of several degrees, and means that, for example, the angle between the extension direction of the long side surface 12b (second surface) and the extension direction of the positive electrode plate 22 or the negative electrode plate 24 is 10° or less.

[0024] The positive electrode plate 22 has a positive electrode tab 22t that protrudes toward the sealing plate 14 and a positive electrode active material layer 22a. The positive electrode tab 22t protrudes upward from the laminated electrode body 20. Here, the positive electrode tab 22t is part of the positive electrode current collector. More specifically, the positive electrode tab 22t is a convex portion where the positive electrode active material layer 22a is not formed and the positive electrode current collector is exposed. Here, the positive electrode tab 22t is electrically connected to the positive electrode terminal 30 via a positive electrode current collector 50. The positive electrode tab 22t (positive electrode current collector) is preferably made of metal foil, and particularly preferably made of aluminum foil or aluminum alloy foil. However, in other embodiments, the positive electrode tab 22t may be a member separate from the positive electrode plate 22.

[0025] The positive electrode active material layer 22a is fixed to at least one surface (preferably both surfaces) of the positive electrode current collector in the short side direction X. The configuration of the positive electrode active material layer 22a may be the same as that of a conventional positive electrode active material layer, and is not particularly limited. The positive electrode active material layer 22a contains a positive electrode active material capable of reversibly absorbing and releasing charge carriers. A lithium transition metal composite oxide is preferable as the positive electrode active material, and an example thereof is a lithium nickel cobalt manganese composite oxide. The positive electrode active material layer 22a may contain optional components other than the positive electrode active material, such as a conductive material, a positive electrode binder, various additive components, etc. A carbon material such as acetylene black (AB) is preferable as the conductive material. A polyvinylidene fluoride (PVdF) is preferable as the positive electrode binder.

[0026] The negative electrode plate 24 has a negative electrode tab 24t that protrudes toward the sealing plate 14 and a negative electrode active material layer 24a. The negative electrode tab 24t protrudes upward from the laminated electrode body 20. Here, the negative electrode tab 24t is part of the negative electrode current collector. More specifically, the negative electrode tab 24t is a convex portion where the negative electrode active material layer 24a is not formed and the negative electrode current collector is exposed. Here, the negative electrode tab 24t is electrically connected to the negative electrode terminal 40 via the negative electrode current collector member 60. The negative electrode tab 24t (negative electrode current collector) is preferably made of metal foil, and particularly preferably made of copper foil or copper alloy foil. However, in other embodiments, the negative electrode tab 24t may be a member separate from the negative electrode.

[0027] The negative electrode active material layer 24a is fixed to at least one surface (preferably both surfaces) of the negative electrode current collector in the short side direction X. The configuration of the negative electrode active material layer 24a may be the same as that of a conventional negative electrode active material layer and is not particularly limited. The negative electrode active material layer 24a contains a negative electrode active material capable of reversibly absorbing and releasing charge carriers. The negative electrode active material layer 24a contains at least a Si-containing material as the negative electrode active material. The Si-containing material may be Si or a silicon-containing compound such as silicon oxide, silicon carbide, or silicon nitride. The negative electrode active material layer 24a preferably further contains a carbon material such as graphite as the negative electrode active material. The graphite may be natural graphite, artificial graphite, or amorphous carbon-coated graphite in which core graphite particles are coated with an amorphous carbon material.

[0028] The negative electrode active material layer 24a may contain optional components other than the negative electrode active material, such as a negative electrode binder, a conductive material, various additives, etc. Examples of the negative electrode binder include rubbers such as styrene butadiene rubber (SBR) and celluloses such as carboxymethyl cellulose (CMC). Carbon materials are preferred as conductive materials.

[0029] FIG. 3 is a schematic plan view of the negative electrode plate 24. As shown in FIG. 3, the negative electrode active material layer 24a has multiple portions with different compositions in the vertical direction Z. The vertical direction Z is an example of a "first direction perpendicular to the sealing plate." In this embodiment, the negative electrode active material layer 24a is divided into three regions in the vertical direction Z: a ​​sealing plate side region A3, a central region A2, and a bottom side region A1. However, in other embodiments, the negative electrode active material layer 24a (electrode active material layer) may have further regions (fourth region and fifth region), for example, between the bottom side region A1 and the central region A2 or between the sealing plate side region A3 and the central region A2. The sealing plate side region A3 is a band-shaped region provided at the end (upper end) on the sealing plate 14 side. The central region A2 is a band-shaped region provided in the center in the vertical direction Z. The central region A2 is a region including the center of the negative electrode active material layer 24a in the up-down direction Z (first direction). Here, the central region A2 is a region provided between the bottom surface side region A1 and the sealing plate side region A3. The bottom surface side region A1 is a band-shaped region provided at the end (lower end) on the bottom surface 12a (first surface) side. The bottom surface side region A1 is an optional region and may not be present, as described in the modified examples described below, for example. The bottom surface side region A1 is an example of a "first surface side region."

[0030] In some embodiments, it is preferable that the properties (e.g., density and thickness) of each region of the negative electrode active material layer 24a (here, the sealing plate side region A3, the central region A2, and the bottom side region A1) are all the same. Note that, in this specification, "density" refers to the amount of solid content (g / cm) per unit volume of the negative electrode active material layer 24a. 3 The density can be determined by dividing the mass of the negative electrode active material layer 24a by the apparent volume of the negative electrode active material layer 24a.

[0031] In this embodiment, the sealing plate side region A3 does not contain any Si-containing material, or the content (proportion of Si-containing material) of the Si-containing material is lower than that of the central region A2. The laminated electrode body 20 expands in the short side direction X (stacking direction) due to repeated charge and discharge, etc. According to the inventor's knowledge, the expansion of the laminated electrode body 20 increases as the content of Si-containing material increases. Therefore, in the technology disclosed herein, the content of Si-containing material in the sealing plate side region A3 of the negative electrode plate 24 is relatively low. This prevents pressure from concentrating on the welded joint WP between the case body 12 and the sealing plate 14 of the case 10. This in turn prevents damage to the welded joint WP of the case 10. Furthermore, by relatively increasing the content of Si-containing material in the central region A2 of the negative electrode plate 24, the weight per unit cell of the prismatic battery 100 can be relatively increased, thereby improving the energy density.

[0032] In some embodiments, the bottom surface side region A1 (first surface side region) does not contain any Si-containing material or has a lower content of Si-containing material than the central region A2. This prevents pressure from concentrating at the boundary (lower corner) between the long side surface 12b (second surface) and the bottom surface 12a (first surface) of the case 10. This in turn prevents deformation and breakage of the case 10.

[0033] In this embodiment, the negative electrode active material layer 24a preferably further contains graphite as a negative electrode active material, and the graphite content in the sealing plate side region A3 is preferably higher than that in the central region A2. Furthermore, the graphite content in the bottom side region A1 is preferably higher than that in the central region A2. This can mitigate the difference in charge / discharge reaction between the regions of the negative electrode active material layer 24a.

[0034] The sealing plate side region A3 may or may not contain a Si-containing material. The negative electrode active material in the sealing plate side region A3 may be composed of, for example, a Si-containing material and graphite, or may consist solely of graphite. From the viewpoint of increasing capacity, the sealing plate side region A3 preferably contains a Si-containing material, and even more preferably contains a Si-containing material and graphite. Although not particularly limited, the content of the Si-containing material in the entire negative electrode active material in the sealing plate side region A3 is preferably less than 20 mass%, more preferably 1 to 18 mass%, and even more preferably 5 to 15 mass%. By setting the content of the Si-containing material to a predetermined value or less, pressure is further prevented from concentrating on the welded joint WP of the case 10, thereby enabling the effects of the technology disclosed herein to be exerted to a high level. Furthermore, by setting the content of the Si-containing material to a predetermined value or more, a high energy density of the prismatic battery 100 can be achieved.

[0035] In addition, in the sealing plate side region A3, the content of graphite in the entire negative electrode active material is preferably higher than that of the Si-containing material, more preferably 50 mass % or more, further preferably 80 to 100 mass %, and particularly preferably 85 to 95 mass %.

[0036] The central region A2 essentially contains a Si-containing material. The negative electrode active material in the central region A2 may be composed of, for example, a Si-containing material and graphite, or may consist solely of a Si-containing material. Although not particularly limited, the content of the Si-containing material in the overall negative electrode active material in the central region A2 is preferably 20% by mass or more, more preferably 20 to 60% by mass, and, for example, 50% by mass or less, even more preferably 20 to 30% by mass. By ensuring that the content of the Si-containing material is a predetermined value or more, the energy density of the prismatic battery 100 can be increased. Furthermore, by ensuring that the content of the Si-containing material is a predetermined value or more, strong pressure is less likely to be applied to the long side surface 12b (second surface) of the case 10, which effectively prevents deformation and damage to the case 10 and allows the effects of the technology disclosed herein to be exerted to a high level.

[0037] In addition, in the central region A2, the content of graphite in the entire negative electrode active material is preferably higher than that of the Si-containing material, more preferably 40% by mass or more, even more preferably 40 to 80% by mass, and particularly preferably, for example, 50% by mass or more, 70 to 80% by mass.

[0038] The bottom side region A1 may or may not contain a Si-containing material. The negative electrode active material in the bottom side region A1 may be composed of, for example, a Si-containing material and graphite, or may consist solely of graphite. From the viewpoint of increasing capacity, the bottom side region A1 preferably contains a Si-containing material, and even more preferably contains a Si-containing material and graphite. The content of the Si-containing material in the bottom side region A1 may be the same as that in the sealing plate side region A3, or may be different. Although not particularly limited, the content of the Si-containing material in the entire negative electrode active material in the bottom side region A1 is preferably less than 20 mass%, more preferably 1 to 18 mass%, and even more preferably 5 to 15 mass%. By setting the content of the Si-containing material to a predetermined value or less, pressure is further prevented from concentrating on the welded joint WP of the case 10, thereby enabling the effects of the technology disclosed herein to be exerted to a high level. Furthermore, by setting the content of the Si-containing material to a predetermined value or more, a high energy density of the prismatic battery 100 can be achieved.

[0039] In the bottom side region A1, the content of graphite in the entire negative electrode active material is preferably higher than that of the Si-containing material, more preferably 50 mass % or more, further preferably 80 to 100 mass %, and particularly preferably 85 to 95 mass %.

[0040] In each region of the negative electrode active material layer 24a (here, the sealing plate side region A3, the central region A2, and the bottom side region A1), the proportion of the negative electrode active material preferably occupies 95% by mass or more of the whole, and more preferably occupies 98% by mass or more. In this case, the content rate of the Si-containing material in the above-mentioned "whole negative electrode active material" is substantially equal to the content rate in the whole of each region. Therefore, in some embodiments, in the sealing plate side region A3, the content rate of the Si-containing material in the whole sealing plate side region A3 is preferably less than 20% by mass, more preferably 1 to 18% by mass, and still more preferably 5 to 15% by mass. In the central region A2, the content rate of the Si-containing material in the whole central region A2 is preferably 20% by mass or more, more preferably 20 to 60% by mass, and still more preferably 20 to 30% by mass. In the bottom side region A1, the content rate of the Si-containing material in the whole bottom side region A1 is preferably less than 20% by mass, more preferably 1 to 18% by mass, and still more preferably 5 to 15% by mass.

[0041] Although not particularly limited, as shown in FIG. 3, in the vertical direction Z (the first direction), when the total width Wa of the negative electrode active material layer 24a is taken as 100%, the width ratio W3 (%) of the sealing plate side region A3 and the width ratio W1 (%) of the bottom side region A1 are preferably smaller than the width ratio W2 (%) of the central region A2, respectively (that is, W3 < W2 and W1 < W2). By suppressing the width ratios W3 and W1 of the sealing plate side region A3 and the bottom side region A1, where the content rate of the Si-containing material is relatively low, to be small, it is possible to achieve a high energy density of the square battery 100.

[0042] The ratio W3 of the width of the sealing plate side region A3 and the ratio W1 of the width of the bottom side region A1 may be the same or different from each other. Although not particularly limited, the ratio W3 of the width of the sealing plate side region A3 and the ratio W1 of the width of the bottom side region A1 are each preferably 5% or more, and more preferably 10% or more. Thereby, since pressure is less likely to concentrate on the corners of the long side surface 12b (second surface) of the case 10, deformation and breakage of the case 10 can be better suppressed. The ratio W3 of the width of the sealing plate side region A3 is more preferably 15 to 30%. The ratio W1 of the width of the bottom side region A1 is more preferably 10 to 30%. By setting the ratios W3 and W1 of the widths of the sealing plate side region A3 and the bottom side region A1 to a predetermined value or less, a high energy density of the prismatic battery 100 can be achieved.

[0043] When the negative electrode active material layer 24a is divided into three regions as in the present embodiment, the ratio W2 of the width of the central region A2 can be calculated by the following formula: 100 - (W1 + W3); The ratio W2 of the width of the central region A2 is preferably larger than the ratio W1 of the width of the bottom side region A1 and the ratio W3 of the width of the sealing plate side region A3, preferably 20% or more, more preferably 30% or more, still more preferably 40% or more, for example, preferably 40 to 80%, and particularly preferably 40 to 75%. By setting the ratio W2 of the width of the central region A2 to a predetermined value or more, a high energy density of the prismatic battery 100 can be achieved.

[0044] In some embodiments, when the laminated electrode body 20 is disposed relatively closer to the bottom surface 12a (first surface) side in the vertical direction Z (first direction), the ratio W1 of the width of the bottom side region A1 is preferably larger than the ratio W3 of the width of the sealing plate side region A3 (that is, W3 < W1). Thereby, pressure is less likely to concentrate on the corners on the bottom surface 12a (first surface) side close to the laminated electrode body 20, and deformation and breakage of the case 10 can be better suppressed. For the negative electrode active material layer 24a, it is more preferable that the width ratios W1 to W_{3} satisfy W3 < W1 < W2. Thereby, the effects of the technology disclosed herein and high energy density can be achieved at a higher level.

[0045] Prismatic battery 100 can be used for a variety of purposes, but is preferably used, for example, as a power source (driving power source) for motors mounted on vehicles such as passenger cars, trucks, etc. The type of vehicle is not particularly limited, but examples include plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs), battery electric vehicles (BEVs), etc.

[0046] Although the preferred embodiment of the present invention has been described above, the above embodiment is merely an example. The present invention can be implemented in various other forms. The present invention can be implemented based on the contents disclosed in this specification and the technical common sense in the relevant field. The technology described in the claims includes various modifications and alterations of the above-exemplified embodiment. For example, it is possible to replace part of the above-described embodiment with other modifications, or to add other modifications to the above-described embodiment. Furthermore, if a technical feature is not described as essential, it may be deleted as appropriate.

[0047] For example, in the embodiment shown in FIGS. 1 and 2, the case body 12 has one opening 12h and one sealing plate 14. However, this is not limited to this. FIG. 4 is a view corresponding to FIG. 1 relating to a modified example. FIG. 5 is a schematic longitudinal cross-sectional view taken along line VV in FIG. 4. The prismatic battery 200 shown in FIGS. 4 and 5 includes a prismatic case 110, a laminated electrode assembly 120, a positive electrode terminal 130, and a negative electrode terminal 140. As shown in FIG. 5, the case 110 includes a rectangular cylindrical case body 112 having a pair of openings 112h at both ends in the long side direction Y, and two sealing plates 114 that close the pair of openings 112h of the case body 112. That is, in this modified example, the case body 112 has two openings 112h and two sealing plates 114.

[0048] 4, the case body 112 includes a substantially rectangular bottom surface 112a (first surface) having a pair of long sides and a pair of short sides, a pair of long side surfaces 112b (second surfaces) extending from the pair of long sides of the bottom surface 112a and facing each other, and a top surface 112c facing the bottom surface 112a. The case body 112 is formed, for example, by bending a single metal plate into a rectangular cylindrical shape and joining the seams (for example, by welding). The two sealing plates 114 are provided facing each other so as to be perpendicular to the bottom surface 112a (first surface) and the long side surfaces 112b (second surfaces).

[0049] The positive electrode terminal 130 is provided on the first sealing plate 114 (on the right side in FIGS. 4 and 5), and the negative electrode terminal 140 is provided on the second sealing plate 114 (on the left side in FIGS. 4 and 5). The electrolyte injection hole 115 is provided on the first sealing plate 114 together with the positive electrode terminal 130. The electrolyte injection hole 115 is sealed with a sealing plug 116.

[0050] The laminated electrode body 120 is housed inside the case 110 and has a positive electrode plate 122 and a negative electrode plate 124 arranged substantially parallel to the long side surface 112b (second surface). The positive electrode plate 122 (positive electrode tab 122t) is electrically connected to the positive electrode terminal 130 via a positive electrode current collector 150. The negative electrode plate 124 (negative electrode tab 124t) is electrically connected to the negative electrode terminal 140 via a negative electrode current collector 160.

[0051] FIG. 6 is a diagram corresponding to FIG. 3 according to a modified example and is a schematic plan view of a negative electrode plate 124. In this modified example, the long side direction Y is the "first direction perpendicular to the sealing plate." As shown in FIG. 6, the negative electrode active material layer 124a of the negative electrode plate 124 is divided into a sealing plate side region A3 and a central region A2. In the negative electrode plate 124, the sealing plate side region A3 is provided at the end on the first sealing plate 114 side (on the right side in FIGS. 4 and 5) and the end on the second sealing plate 114 side (on the left side in FIGS. 4 and 5). In this case, the central region A2 is a region that includes the center of the long side direction Y (first direction) of the negative electrode active material layer 124a, and is more preferably provided symmetrically with respect to the center of the long side direction Y.

[0052] The composition and width ratios W3 and W2 of the sealing plate side region A3 and the central region A2 to the overall width Wa in the long side direction Y (first direction) may be the same as those in the above-described embodiment. For example, when the overall width Wa of the negative electrode active material layer 124a in the long side direction Y (first direction) is taken as 100%, the width ratio W3 (%) of each of the two sealing plate side regions A3 is preferably smaller than the width ratio W2 (%) of the central region A2. Furthermore, it is more preferable that the width ratio W3 of each of the two sealing plate side regions A3 is 10% or greater.

[0053] As described above, specific aspects of the technology disclosed herein include those described in the following sections. Item 1: A prismatic battery comprising: a prismatic case having a substantially rectangular first surface having a pair of long sides and a pair of short sides, a pair of second surfaces extending from the pair of long sides, each having a larger area than the first surface, and one or more openings; and one or more sealing plates sealing the one or more openings; and a laminated electrode assembly housed inside the case and having a positive electrode plate and a negative electrode plate arranged substantially parallel to the second surface, wherein the negative electrode plate comprises a negative electrode active material layer containing a Si-containing material as a negative electrode active material, and the negative electrode active material layer has one or more sealing plate-side regions provided in a strip shape at one or more end portions on the sealing plate side, and a strip-shaped central region provided in a central portion in a first direction perpendicular to the sealing plate, and the sealing plate-side regions do not contain the Si-containing material or have a lower content of the Si-containing material than the central region. Item 2: The prismatic battery according to Item 1, wherein the negative electrode active material layer further contains graphite as the negative electrode active material, and the sealing plate side region has a higher graphite content than the central region. Item 3: The prismatic battery according to Item 1 or 2, wherein the proportion of the Si-containing material in the entire negative electrode active material in the sealing plate side region is less than 20 mass %, and the proportion of the Si-containing material in the entire negative electrode active material in the central region is 20 mass % or more. Item 4: The prismatic battery according to any one of Items 1 to 3, wherein the opening of the case body and the sealing plate are each one, the sealing plate facing the first surface, the negative electrode active material layer further has a first surface side region provided in a strip shape at an end portion on the first surface side, and the first surface side region does not contain the Si-containing material or has a lower content of the Si-containing material than the central region. Item 5: The prismatic battery according to item 4, wherein, in the first direction, when the overall width of the negative electrode active material layer is 100%, the width ratio of the sealing plate side region and the width ratio of the first surface side region are each smaller than the width ratio of the central region. Item 6: The prismatic battery according to Item 4 or 5, wherein the width ratio of each of the two sealing plate side regions is 10% or more. Item 7: A prismatic battery according to any one of items 4 to 6, wherein the laminated electrode body is positioned closer to the first surface than the sealing plate in the first direction, and the width ratio of the first surface side region is greater than the width ratio of the sealing plate side region. Item 8: The prismatic battery according to any one of Items 1 to 3, wherein the case body has two openings and two sealing plates, the two sealing plates are arranged opposite each other so as to be perpendicular to the first surface and the second surface, and the sealing plate side regions are respectively arranged at the end on the side of the first sealing plate and the end on the side of the second sealing plate. Item 9: The prismatic battery according to item 7, wherein, in the first direction, when the overall width of the negative electrode active material layer is 100%, the proportions of the widths of the two sealing plate side regions are each smaller than the proportion of the width of the central region. Item 10: The prismatic battery according to item 7 or 8, wherein the width ratios of the two sealing plate side regions are each 10% or more. [Explanation of symbols]

[0054] 10, 110 cases 12a, 112a Bottom (first side) 12b, 112b long side (second side) 14, 114 Sealing plate 20, 120 laminated electrode body 22, 122 positive plate 24, 124 negative plate 24a, 124a Negative electrode active material layer 24t, 124t negative electrode tab 100, 200 square batteries Z: vertical direction (first direction in the embodiment) Y Long side direction (first direction in modified example)

Claims

1. a case body having a substantially rectangular first surface having a pair of long sides and a pair of short sides, a pair of second surfaces extending from the pair of long sides and having an area larger than that of the first surface, and one or more openings; one or more sealing plates that seal the one or more openings; a rectangular case having a laminated electrode body housed inside the case and having a positive electrode plate and a negative electrode plate arranged substantially parallel to the second surface; Equipped with the negative electrode plate has a negative electrode active material layer containing a Si-containing material as a negative electrode active material, The negative electrode active material layer is one or more sealing plate side regions provided in a strip shape at one or more of the sealing plate side end portions; a central region provided in a strip shape at a central portion in a first direction perpendicular to the sealing plate; and the sealing plate side region does not contain the Si-containing material or has a lower content of the Si-containing material than the central region; Square battery.

2. the negative electrode active material layer further contains graphite as the negative electrode active material, The sealing plate side region has a higher graphite content than the central region. The prismatic battery according to claim 1 .

3. In the sealing plate side region, the proportion of the Si-containing material in the entire negative electrode active material is less than 20 mass %, In the central region, the proportion of the Si-containing material in the entire negative electrode active material is 20 mass% or more. The prismatic battery according to claim 2 .

4. The opening and the sealing plate of the case body are each one the sealing plate faces the first surface, the negative electrode active material layer further has a first surface side region provided in a strip shape at an end portion on the first surface side, the first surface side region does not contain the Si-containing material or has a lower content of the Si-containing material than the central region; The prismatic battery according to any one of claims 1 to 3.

5. In the first direction, when the entire width of the negative electrode active material layer is taken as 100%, a ratio of the width of the sealing plate side region and a ratio of the width of the first surface side region are each smaller than a ratio of the width of the central region. The prismatic battery according to claim 4.

6. The width ratios of the two sealing plate side regions are each 10% or more. The prismatic battery according to claim 5 .

7. the laminated electrode body is disposed closer to the first surface than the sealing plate in the first direction, the width ratio of the first surface side region is greater than the width ratio of the sealing plate side region; The prismatic battery according to claim 5 .

8. The case body has two openings and two sealing plates, the two sealing plates are provided opposite to each other so as to be perpendicular to the first surface and the second surface, the sealing plate side region is provided at a first end portion on the sealing plate side and a second end portion on the sealing plate side, The prismatic battery according to any one of claims 1 to 3.

9. In the first direction, when the entire width of the negative electrode active material layer is taken as 100%, the proportions of the widths of the two sealing plate side regions are each smaller than the proportion of the width of the central region. The prismatic battery according to claim 8.

10. The width ratios of the two sealing plate side regions are each 10% or more. The prismatic battery according to claim 9.

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