Energy storage devices
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- PRIME PLANET ENERGY & SOLUTIONS INC
- Filing Date
- 2025-01-22
- Publication Date
- 2026-08-03
Smart Images
Figure 2026125455000001_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to a power storage device.
Background Art
[0002] Patent Document 1 discloses a technique of bringing at least a part of an electrode tab group into contact with an electrolytic solution (excess electrolytic solution) outside the electrode body in order to make it difficult for a lithium salt to precipitate in the vicinity of the electrode tab group. Patent Document 2 discloses a technique of adjusting the height of the excess electrolytic solution within a predetermined range in order to suppress temperature unevenness in the height direction of the electrode body.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Patent Document 2
Summary of the Invention
Problems to be Solved by the Invention
[0004] By the way, in a power storage device including an electrode body having a wide shape, the electrolytic solution extruded outside the electrode body during rapid charge and discharge may be difficult to return into the electrode body. As a result, the salt concentration of the electrolytic solution becomes non-uniform within the electrode body, and by continuing operation under rapid charge and discharge conditions, the deterioration of the power storage device may be accelerated. As a result of the study by the present inventor, it has been found that one of the reasons why the electrolytic solution is difficult to return into the electrode body is the thermal expansion of the electrolytic solution due to a temperature rise of the electrolytic solution. The present inventor is proceeding with the development of a power storage device including an electrode body having electrode tabs on the side surface rather than on the upper part of the electrode body. The present inventor wants to suppress the thermal expansion of the electrolytic solution in such a power storage device.
Means for Solving the Problems
[0005] One aspect of this technology is an energy storage device comprising an electrode body including a first electrode and a second electrode, an electrolyte, a case housing the electrode body and the electrolyte, and a first current collector electrically connected to the first electrode. The case comprises a bottom wall, a pair of side walls extending from the edge of the bottom wall and facing each other in the width direction, and a top wall facing the bottom wall in the height direction. The electrode body includes a group of first electrode tabs, each containing a plurality of first electrode tabs protruding from a first end face in one of the width directions, and a group of second electrode tabs, each containing a plurality of second electrode tabs protruding from a second end face in the other of the width directions. The first current collector is joined to the group of first electrode tabs via a first joint. The length of the electrode body in the width direction is at least twice the length of the electrode body in the height direction. The electrolyte includes excess electrolyte present between the electrode body and the case. When the length of the first end face of the electrode body in the height direction is H, the length of the first electrode tab group in the height direction is 1 / 5H or more and less than 1 / 2H. When the bottom wall is positioned vertically downward and the SOC (state of charge) is 95% or more, the height from the bottom wall of the excess electrolyte to the liquid surface is 1 / 100H or more and 1 / 10H or less, and the distance between the liquid surface of the excess electrolyte and the lower end of the first electrode tab group is 1 / 2H or more.
[0006] In an energy storage device with this configuration, the heat generated in the first electrode tab group is less likely to be transferred to the excess electrolyte, thus suppressing the thermal expansion of the electrolyte. [Brief explanation of the drawing]
[0007] [Figure 1] Figure 1 is a perspective view of the energy storage device 100. [Figure 2] Figure 2 is a schematic diagram of the section taken along line II-II in Figure 1. [Figure 3] Figure 3 is a schematic diagram of the section taken along line III-III in Figure 1. [Figure 4] Figure 4 is a schematic diagram of the section along line IV-IV in Figure 1. [Figure 5] Figure 5 is an exploded view schematically showing the configuration of the electrode body 20. [Figure 6] Figure 6 is a schematic perspective view showing the electrode body 20 to which the first current collector 52 and the third current collector 62 are attached. [Figure 7] Figure 7 is a schematic perspective view showing the electrode body 20 attached to the sealing body 14. [Figure 8] Figure 8 is a schematic diagram corresponding to Figure 2 of a modified example, the energy storage device 100A. [Modes for carrying out the invention]
[0008] Hereinafter, several preferred embodiments of the technology disclosed herein will be described with reference to the drawings. Matters other than those specifically mentioned herein but necessary for the implementation of this disclosure (e.g., general configurations and manufacturing processes of energy storage devices not characterizing this disclosure) can be understood as design matters for those skilled in the art based on the prior art. This disclosure can be implemented based on the content disclosed herein and common technical knowledge in the art. Furthermore, the following description is not intended to limit the technology disclosed herein to the following embodiments. In this specification, the notation "A to B" (where A and B are arbitrary numbers) means "A or greater and B or less," and also encompasses the meanings of "greater than A and less than B," "greater than A and less than or equal to B," and "A or greater and less than B."
[0009] In this specification, "energy storage device" refers to a device capable of charging and discharging. Energy storage devices include batteries such as secondary batteries (non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries) and capacitors (physical batteries) such as electric double-layer capacitors. The present technology will be described in detail below using energy storage device 100, which is a lithium-ion secondary battery, as an example.
[0010] Figure 1 is a perspective view of the energy storage device 100. Figure 2 is a schematic diagram of the section taken along line II-II in Figure 1. Figure 3 is a schematic diagram of the section taken along line III-III in Figure 1. Figure 4 is a schematic diagram of the section taken along line IV-IV in Figure 1. In the following description, the symbols L, R, F, Rr, U, and D in the drawings represent left, right, front, back, top, and bottom, respectively, and the symbols X, Y, and Z in the drawings represent the thickness direction, the width direction perpendicular to the thickness direction, and the height direction perpendicular to the thickness direction and width direction of the energy storage device 100, respectively. However, these are merely directions for the convenience of explanation and do not limit the installation configuration of the energy storage device 100 in any way. Note that each drawing is schematic, and the dimensional relationships (height, width, thickness, etc.) do not necessarily reflect the actual dimensional relationships. In addition, in the drawings described below, the same symbols are used for members and parts that perform the same function, and redundant explanations may be omitted or simplified.
[0011] As shown in Figures 1 and 2, the energy storage device 100 comprises a case 10, an electrode body 20, and an electrolyte. In this embodiment, the energy storage device 100 further comprises a first electrode terminal 30, a first electrode external conductive member 32, a second electrode terminal 40, a second electrode external conductive member 42, a second electrode current collector 60, an internal insulating member 70, a gasket 90, and an external insulating member 92. The electrolyte exists inside the case 10, mainly inside the electrode body 20 and between the electrode body 20 and the case 10. In this specification, the electrolyte present between the electrode body 20 and the case 10 is referred to as excess electrolyte 80.
[0012] Case 10 is a housing for the electrode body 20. Case 10 has a flattened, bottomed rectangular parallelepiped (square) shape. The material of case 10 can be the same as that used conventionally, and there are no particular restrictions. It is preferable that case 10 be made of a metal having a predetermined strength. Examples of this type of metal material include aluminum, aluminum alloy, iron, iron alloy, etc.
[0013] The case 10 has a bottom wall 12a, a pair of first side walls 12b, a pair of second side walls 12c, and an upper wall 14. In the present embodiment, the case 10 includes a case body 12 having a bottom wall 12a, a pair of first side walls 12b, and a pair of second side walls 12c, a sealing body as the upper wall 14 (hereinafter also referred to as "sealing body 14"), and a gas discharge valve 17.
[0014] The case body 12 is a flat rectangular (hexahedron shape) container with one face being an opening 12h. The bottom wall 12a has a substantially rectangular shape having a long side extending in the width direction Y and a short side extending in the thickness direction X. The pair of first side walls 12b face each other in the thickness direction X and extend upward U from the short side which is an edge of the bottom wall 12a. The pair of second side walls 12c face each other in the width direction Y and extend upward U from the long side which is an edge of the bottom wall 12a. Here, the area of the second side wall 12c is smaller than the area of the first side wall 12b. 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.
[0015] The sealing body 14 is attached to the case body 12 so as to seal the opening 12h of the case body 12. The sealing body 14 is a plate material having a substantially rectangular shape in plan view. The sealing body 14 faces the bottom wall 12a of the case body 12 in the height direction Z.
[0016] The case 10 is formed by joining (for example, welding) the sealing body 14 to the peripheral edge of the opening 12h of the case body 12. The joining of the sealing body 14 can be performed by welding such as laser welding.
[0017] Note that in some embodiments, the sealing body 14 may be arranged as the bottom wall 12a, the first side wall 12b, or the second side wall 12c instead of the upper wall 14 of the case 10.
[0018] As shown in FIGS. 1 and 2, the gas discharge valve 17 is provided in the sealing body 14. The gas discharge valve 17 is configured to open when the pressure in the case 10 reaches a predetermined value or more and discharge the gas in the case 10.
[0019] In addition to the gas discharge valve 17, the sealing body 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 10 and is a through hole provided for injecting an electrolytic solution in the manufacturing process of the power storage device 100. The liquid injection hole 15 is sealed by a sealing member 16. As such a sealing member 16, for example, a blind rivet is suitable. Thereby, the sealing member 16 can be firmly fixed inside the case 10.
[0020] In the present embodiment, the liquid injection hole 15, the gas discharge valve 17, and the terminal insertion holes 18 and 19 are provided in the sealing body 14, but their positions are not particularly limited. In some embodiments, these may be provided in the case body 12 of the case 10 respectively, or may be omitted.
[0021] As shown in FIG. 3, in the present embodiment, a plurality (here, three) of electrode bodies 20 are accommodated inside the case 10. The number of electrode bodies 20 accommodated inside one case 10 is not particularly limited, and may be one, or two or more (plural).
[0022] Each of the plurality of electrode bodies 20 is connected in parallel. However, the plurality of electrode bodies 20 may be connected in series.
[0023] The electrode body 20 may be accommodated inside the case body 12 of the case 10 in a state covered with a resin sheet. The resin sheet may be, for example, in a bag shape or a box shape, or may be formed into a box shape by folding one or a plurality of sheets. The resin sheet may be, for example, a polyamide resin, a polyolefin resin (for example, polypropylene, polyethylene), or the like. The resin sheet can prevent the electrode body 20 and the case 10 from being electrically connected.
[0024] Figure 5 is an exploded view schematically showing the configuration of the electrode body 20. As shown in Figure 5, the electrode body 20 comprises a first electrode 22 and a second electrode 24. Here, the electrode body 20 includes a separator 26 that insulates the first electrode 22 and the second electrode 24. The electrode body 20 is a wound electrode body in which a strip-shaped first electrode 22 and a strip-shaped second electrode 24 are stacked with two strip-shaped separators 26 in between, and wound around a winding axis WL. The longitudinal directions of the first electrode 22, the second electrode 24 and the separator 26 are aligned, and the winding axis WL coincides with the short direction perpendicular to the longitudinal direction. However, the structure of the electrode body is not limited to the technology disclosed herein. For example, the electrode body may be a laminated electrode body in which a plurality of rectangular first electrodes and a plurality of rectangular second electrodes are stacked in an insulated state.
[0025] The first electrode 22 and the second electrode 24 have one side being the positive electrode and the other the negative electrode. In this embodiment, the first electrode 22 is the positive electrode and the second electrode 24 is the negative electrode.
[0026] In this embodiment, the electrode body 20 has a flattened shape. As shown in Figure 3, the electrode body 20 has a pair of curved portions (R portions) 20r and a flat portion 20f connecting the pair of curved portions 20r. Also, as shown in Figure 2, the electrode body 20 has a first end face 20a at one end in the winding axis WL direction and a second end face 20b at the other end. The electrode body 20 is arranged inside the case 10 with the winding axis WL oriented substantially parallel to the width direction Y of the case 10. That is, in this embodiment, the direction of the winding axis WL of the electrode body 20 housed in the energy storage device 100 can also be rephrased as the width direction Y. The first end face 20a and the second end face 20b of the electrode body 20 are arranged opposite a pair of second side walls 12c. The pair of curved portions 20r are formed at the upper and lower ends of the electrode body 20 in the height direction Z. The pair of curved sections 20r are positioned opposite the upper wall (sealing body) 14 and the bottom wall 12a of the case 10, respectively. The flat section 20f is positioned opposite the first side wall 12b.
[0027] The first end face 20a and the second end face 20b are the surfaces on which the edges of the first electrode 22 and the second electrode 24 are located. In the electrode body 20, which is a wound electrode body, the first end face 20a and the second end face 20b are the surfaces that intersect perpendicularly with the winding axis WL, respectively.
[0028] As shown in Figure 2, the electrode body 20 has a wide shape that extends more in the width direction Y than in the height direction Z. The length of the electrode body 20 in the width direction is, for example, 2 times or more, 2.5 times or more, or 3 times or more, the length in the height direction. The length of the electrode body 20 in the width direction Y is not particularly limited, but for example, it may be 10 times or less, or 5 times or less. The energy storage device 100 can increase its capacity by providing a wide electrode body 20. On the other hand, the wider the shape, the more difficult it is for excess electrolyte 80 to enter the inside of the electrode body 20, and there is a trade-off relationship in that salt concentration unevenness is likely to occur inside the electrode body 20. This technology suppresses the thermal expansion of the electrolyte by suppressing the temperature rise of the excess electrolyte 80, and makes it easier for the excess electrolyte 80 to enter the electrode body 20 even if the electrode body 20 has a wide shape.
[0029] In this specification, the length in the width direction Y of the electrode body 20 refers to the length from the first end face 20a to the second end face 20b. More specifically, the length in the width direction Y of the electrode body 20 refers to the length in the width direction of the separator 26 (in the case of a wound electrode body, the length in the short direction of the strip-shaped separator 26), and does not include the length of the first electrode tab group 23 and the second electrode tab group 25. The length in the height direction of the electrode body 20 is the distance from the upper end to the lower end of the electrode body 20, and here it refers to the length between the vertices of the pair of curved portions 20r when the electrode body 20 is viewed from the width direction Y (see Figure 3).
[0030] As shown in Figure 5, the first electrode 22 (positive electrode) comprises a first electrode current collector 22c, a first electrode active material layer 22a fixed to at least one surface of the first electrode current collector 22c, and a first electrode protective layer 22p. However, the first electrode protective layer 22p is not essential and can be omitted in some embodiments. The first electrode current collector 22c is strip-shaped. The first electrode current collector 22c is made of a conductive metal such as aluminum, aluminum alloy, nickel, or stainless steel. In this case, the first electrode current collector 22c is a metal foil, specifically an aluminum foil.
[0031] The first electrode active material layer 22a is provided in a strip shape along the longitudinal direction of the strip-shaped first electrode current collector 22c. The first electrode active material layer 22a contains an active material (for example, a lithium transition metal composite oxide such as lithium nickel cobalt manganese composite oxide) that can reversibly intercept and release charge carriers. The first electrode active material layer 22a may also contain optional components other than the active material, such as conductive materials, binders, and various additives. As a conductive material, for example, a carbon material such as acetylene black (AB) can be used. As a binder, for example, polyvinylidene fluoride (PVdF) can be used.
[0032] As shown in Figure 5, the first electrode protective layer 22p is provided at the boundary between the first electrode current collector 22c and the first electrode active material layer 22a in the width direction Y. Here, the first electrode protective layer 22p is provided at one end (the left end in Figure 5) in the axial direction of the winding axis WL of the first electrode current collector 22c. The first electrode protective layer 22p is provided in a strip shape along the first electrode active material layer 22a. The first electrode protective layer 22p contains an inorganic filler (e.g., alumina). The first electrode protective layer 22p may also contain optional components other than the inorganic filler, such as conductive materials, binders, various additives, etc. The conductive material and binder may be the same as those exemplified as those that may be included in the first electrode active material layer 22a.
[0033] Multiple first electrode tabs 22t are provided on one axial edge of the first electrode current collector 22c in the direction of the winding axis WL (on the side of the first end face 20a of the electrode body 20). The multiple first electrode tabs 22t are provided at intervals (intermittently) along the longitudinal direction of the strip-shaped first electrode 22. The multiple first electrode tabs 22t protrude from the edge of the first electrode current collector 22c in the direction of the winding axis WL and protrude outward from the separator 26. The first electrode tabs 22t are part of the first electrode current collector 22c and are made of metal foil (aluminum foil). However, the first electrode tabs 22t may be made of a different material from the first electrode current collector 22c. At least a portion of the first electrode tabs 22t is provided with a first electrode current collector exposed region in which the first electrode active material layer 22a and the first electrode protective layer 22p are not formed and the first electrode current collector 22c is exposed. The exposed region of the first electrode current collector is electrically connected to the first electrode current collector 50 via the first joint J1.
[0034] The shape of the first electrode tab 22t is not particularly limited and may be rectangular, trapezoidal, triangular, semicircular, etc.
[0035] Multiple first electrode tabs 22t are stacked at one end in the axial direction of the winding axis WL (the left end in Figure 5) to form a first electrode tab group 23. As shown in Figures 2 and 3, the first electrode tab group 23 is located on one side of the second side wall 12c of the case body 12 (the left side in Figure 2). The first electrode tab group 23 protrudes from the first end face 20a toward the second side wall 12c opposite the first end face 20a. Each of the multiple first electrode tabs 22t constituting the first electrode tab group 23 is joined to the first electrode current collector 50 (specifically, the first current collector member 52) in a bent state. This allows the size of the main body of the electrode body 20 housed in the case 10 to be increased, thereby enabling a higher energy density for the energy storage device 100. In some embodiments, each of the multiple first electrode tabs 22t does not need to be bent.
[0036] Through the inventors' research, it was confirmed that the parts of the energy storage device 100 that are prone to generating heat during charging and discharging are the first electrode tab group 23 and the second electrode tab group 25 of the electrode body 20. In particular, heat is more easily generated at the positive electrode than at the negative electrode during charging and discharging. Therefore, it is especially effective to suppress the thermal expansion of the electrolyte due to the heat generated at the first electrode tab group 23, which is the positive electrode tab.
[0037] As shown in Figure 2, when the length of the first end face 20a of the electrode body 20 in the height direction Z is H, the length L1 of the first electrode tab group 23 in the height direction Z is preferably 1 / 5H or more, and may also be 1 / 4H or more. The longer the length L1 of the first electrode tab group 23 in the height direction Z, the lower the resistance, and the more heat is suppressed in the first electrode tab group 23. On the other hand, if the length L1 of the first electrode tab group 23 in the height direction Z is too long, the distance between the excess electrolyte 80 and the first electrode tab group 23 decreases, and the heat from the first electrode tab group 23 is more easily transferred to the excess electrolyte 80. For this reason, the length L1 of the first electrode tab group 23 in the height direction Z is preferably, for example, less than 1 / 2H or 1 / 3H or less. In this specification, the length L1 of the first electrode tab group 23 in the height direction Z refers to the length at the boundary portion (base) with the first end face 20a of the electrode body 20. Furthermore, the height length H of the first end face 20a of the electrode body 20 is the distance from the upper end to the lower end of the first end face 20a of the electrode body 20, and in this embodiment, it coincides with the height length Z of the electrode body 20.
[0038] The lower end 23b of the first electrode tab group 23 is preferably positioned above the halfway point of the electrode body 20 (towards the upper wall 14 of the case 10) in the height direction Z, and more preferably within the upper 2 / 5 of the height of the electrode body 20. This increases the distance between the first electrode tab group 23 and the excess electrolyte 80, thereby suppressing the rise in the temperature of the excess electrolyte 80 due to the heat of the first electrode tab group 23. In this specification, the lower end 23b of the first electrode tab group 23 refers to the part that is closest to the liquid surface 80h of the excess electrolyte 80 under normal operating conditions.
[0039] The distance between the upper end 23a of the first electrode tab group 23 and the upper end of the first end face 20a of the electrode body 20 is, for example, often 1 / 4H or less, and preferably 1 / 5 or less. This makes it difficult for the heat generated in the first electrode tab group 23 to be transferred by the excess electrolyte 80. The upper end 23a of the first electrode tab group 23 refers to the part that is closest to the upper wall 14 of the case 10 (the sealing body 14 in this embodiment).
[0040] The second electrode 24 (here referred to as the negative electrode) has, as shown in Figure 5, a second electrode current collector 24c and a second electrode active material layer 24a fixed to at least one surface of the second electrode current collector 24c. The second electrode current collector 24c is strip-shaped. The second electrode current collector 24c is made of a conductive metal such as copper, copper alloy, nickel, or stainless steel. In this case, the second electrode current collector 24c is a metal foil, specifically a copper foil.
[0041] As shown in Figure 5, the second electrode active material layer 24a is provided in a strip shape along the longitudinal direction of the strip-shaped second electrode current collector 24c. The second electrode active material layer 24a contains an active material (for example, a carbon material such as graphite) that can reversibly absorb and release charge carriers. The second electrode active material layer 24a may also contain optional components other than the active material, such as a binder, a dispersant, and various additives. As a binder, for example, rubbers such as styrene-butadiene rubber (SBR) can be used. As a dispersant, for example, celluloses such as carboxymethylcellulose (CMC) can be used.
[0042] Multiple second electrode tabs 24t are provided on one axial edge of the second electrode current collector 24c (on the second end face 20b side of the electrode body 20) along the winding shaft WL. The second electrode tabs 24t are provided on the opposite side of the first electrode tab 22t in the axial direction of the winding shaft WL. The multiple second electrode tabs 24t are provided at intervals (intermittently) along the longitudinal direction of the strip-shaped second electrode 24. The second electrode tabs 24t protrude from the edge of the second electrode current collector 24c in the direction of the winding shaft WL and protrude outward from the separator 26. The second electrode tabs 24t are part of the second electrode current collector 24c and are made of metal foil (copper foil). However, the second electrode tabs 24t may be a separate component from the second electrode current collector 24c. At least a portion of the second electrode tab 24t is provided with a second electrode current collector exposed region in which the second electrode active material layer 24a is not formed and the second electrode current collector 24c is exposed. The second electrode current collector exposed region is electrically connected to the second electrode current collector 60 via the second junction J2.
[0043] The shape of the second electrode tab 24t is not particularly limited and may be rectangular, trapezoidal, triangular, semicircular, etc.
[0044] Multiple second electrode tabs 24t are stacked at one end of the winding shaft WL in the axial direction (the right end in Figure 5) to form a second electrode tab group 25. As shown in Figures 2 and 3, the second electrode tab group 25 is located on the other side of the second side wall 12c of the case body 12 (the right side in Figure 2). The second electrode tab group 25 protrudes from the second end face 20b toward the second side wall 12c opposite the second end face 20b. Each of the multiple second electrode tabs 24t constituting the second electrode tab group 25 is joined to the second electrode current collector 60 (specifically, the third current collector member 62) in a bent state. This allows the size of the main body of the electrode body 20 housed in the case 10 to be increased, thereby enabling a higher energy density for the energy storage device 100. In some embodiments, each of the multiple second electrode tabs 24t does not need to be bent.
[0045] In the height direction Z of the energy storage device 100, the lower end 25b of the second electrode tab group 25 is at the same height as the lower end 23b of the first electrode tab group 23, or is located above the lower end 23b of the first electrode tab group 23 (towards the upper wall 14). That is, the lower end 23b of the first electrode tab group 23 may be located below the lower end 25b of the second electrode tab group 25 (towards the bottom wall 12a). In this embodiment, the first electrode tab group 23 and the second electrode tab group 25 are provided at the same height (symmetrical positions).
[0046] The range of length L2 in the height direction Z of the second electrode tab group 25 can correspond to the length L1 in the height direction Z of the first electrode tab group 23 described above. Also, the position of the lower end 25b of the second electrode tab group 25 can correspond to the position of the lower end 23b of the first electrode tab group 23 described above.
[0047] As shown in Figure 5, the separator 26 is a component that insulates the first electrode 22 and the second electrode 24. For the separator 26, a porous sheet made of polyolefin resin such as polyethylene (PE) or polypropylene (PP) is preferred. The separator 26 may have a base material made of a porous sheet made of resin, and a heat-resistant layer (HRL) containing an inorganic filler, provided on at least one surface of the base material. Examples of inorganic fillers include alumina, boehmite, aluminum hydroxide, and titania.
[0048] The first electrode current collector 50 is the part that is electrically connected to the first electrode 22 of the electrode body 20. In this embodiment, the first electrode current collector 50 comprises a first current collector member 52 and a second current collector member 54. The first current collector member 52 and the second current collector member 54 are conductive and are, for example, made of metal. Preferably, the first current collector member 52 and the second current collector member 54 are made of the same type of metal as the first electrode current collector body 22c, and can be made of, for example, aluminum, an aluminum alloy, etc.
[0049] The first current collector member 52 is a member joined to the first electrode tab group 23. In this embodiment, the first current collector member 52 forms a conductive path between the first electrode tab group 23 and the second current collector member 54. As shown in Figure 2, the first current collector member 52 is a plate-shaped member in this embodiment. In this embodiment, the first current collector member 52 extends along the inner surface (in the height direction Z) of the second side wall 12c of the case 10. The lower part of the first current collector member 52 is joined to the first electrode tab group 23 via a first joint J1. The first joint J1 may be, for example, an ultrasonic joint, a resistance weld, or a laser weld. The upper part of the first current collector member 52 is connected to the second current collector member 54. The method of connecting the first current collector member 52 and the second current collector member 54 is not particularly limited, but may be, for example, via an ultrasonic joint, a resistance weld, a laser weld, or the like.
[0050] The first junction J1 is preferably located above the halfway point of the first electrode tab group 23 (towards the upper wall 14 of the case 10) in the height direction Z, and more preferably within the upper 1 / 3 of the first electrode tab group 23. The first junction J1 is a part where current tends to concentrate during charging and discharging, and is particularly prone to generating heat. Therefore, the further the first junction J1 is from the excess electrolyte 80, the more the thermal expansion of the electrolyte can be suppressed. In this specification, the position of the first junction J1 refers to the center point connecting the upper end and lower end of the first junction J1 in the height direction Z.
[0051] The second current collector member 54 is a plate-shaped member. The second current collector member 54 has a first region extending along the inner surface of the sealing body 14 and a second region extending along the inner surface of the second side wall 12c of the case 10. The first region is connected to the first electrode terminal 30. The second region is connected to the first current collector member 52.
[0052] The first electrode terminal 30 is inserted through a terminal insertion hole 18 formed at one end of the sealing body 14 in the width direction Y (the left end in Figure 2). The first electrode terminal 30 is connected to the second current collector 54 by crimping its lower end to the second current collector 54 inside the case 10. The first electrode terminal 30 is preferably made of metal, and more preferably of aluminum or an aluminum alloy. At least a portion of the first electrode terminal 30 is exposed on the outer surface of the case 10. Outside the case 10, the first electrode terminal 30 is electrically connected to a plate-shaped first electrode external conductive member 32. The first electrode external conductive member 32 is a member to which external members such as busbars may be attached. In some embodiments, the first electrode external conductive member 32 may be omitted. Also, in some embodiments, the first electrode terminal 30 may be located on the first side wall 12b, the second side wall 12c, or the bottom wall 12a.
[0053] The first electrode terminal 30 is insulated from the sealing body 14 by an internal insulating member 70 and a gasket 90. The internal insulating member 70 comprises a base portion 70a interposed between the second current collector 54 and the sealing body 14, and a projection 70b protruding from the base portion 70a toward the electrode body 20. The projection 70b restricts the movement of the electrode body 20, preventing contact between the sealing body 14 and the electrode body 20. An external insulating member 92 is positioned between the first electrode external conductive member 32 and the outer surface of the sealing body 14. The external insulating member 92 insulates the first electrode external conductive member 32 from the sealing body 14. The first electrode external conductive member 32 and the external insulating member 92 are not essential components and may be omitted as appropriate. The internal insulating member 70, the gasket 90, and the external insulating member 92 may be made of, for example, fluoropolymer resins such as perfluoroalkoxyalkanes (PFA) and polytetrafluoroethylene (PTFE), or synthetic resin materials such as polyphenylene sulfide (PPS).
[0054] As shown in Figure 2, the second electrode tab group 25 is electrically connected to the second electrode terminal 40 via the second electrode current collector 60. The second electrode current collector 60 here comprises a third current collector member 62 and a fourth current collector member 64. The third current collector member 62 and the fourth current collector member 64 are preferably made of the same metal species as the second electrode current collector 24c, and may be made of a conductive metal such as copper or a copper alloy.
[0055] The third current collector member 62 is a member that is joined to the second electrode tab group 25. In this embodiment, the third current collector member 62 forms an electrical path between the second electrode tab group 25 and the fourth current collector member 64. The lower part of the third current collector member 62 is joined to the second electrode tab group 25 via a second joint J2. The second joint J2 may be, for example, an ultrasonic joint, a resistance weld, or a laser weld. The other configurations of the third current collector member 62 can be configured in accordance with the configuration of the first current collector member 52 described above. Similarly, the configuration of the fourth current collector member 64 can be configured in accordance with the configuration of the second current collector member 54 described above.
[0056] The second electrode terminal 40 is inserted into a terminal insertion hole 19 formed at one end of the sealing body 14 in the width direction Y (the right end in Figure 2). The second electrode terminal 40 is connected to the fourth current collector 64 by crimping its lower end to the fourth current collector 64 inside the case 10. The second electrode terminal 40 is preferably made of metal, and more preferably of copper or a copper alloy. At least a portion of the second electrode terminal 40 is exposed on the outer surface of the case 10. Outside the case 10, the second electrode terminal 40 is electrically connected to a plate-shaped second electrode external conductive member 42. The second electrode external conductive member 42 is a member to which external members such as busbars may be attached. In some embodiments, the second electrode external conductive member 42 may be omitted. Also, in some embodiments, the second electrode terminal 40 may be located on the first side wall 12b, the second side wall 12c, or the bottom wall 12a.
[0057] The second electrode terminal 40 is insulated from the sealing body 14 by an internal insulating member 70 and a gasket 90. Details of the internal insulating member 70 are the same as those described above for the first electrode terminal 30, so their explanation is omitted. An external insulating member 92 is positioned between the second electrode external conductive member 42 and the outer surface of the sealing body 14. The external insulating member 92 insulates the second electrode external conductive member 42 from the sealing body 14. Note that the second electrode external conductive member 42 and the external insulating member 92 are not essential components and may be omitted as appropriate.
[0058] The electrolyte is, for example, a non-aqueous electrolyte containing an organic solvent and a supporting salt. As the organic solvent, aprotic solvents such as carbonates, esters, and ethers can be used. Among these, carbonates such as ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) can be suitably used. Alternatively, fluorinated solvents such as monofluoroethylene carbonate (MFEC), difluoroethylene carbonate (DFEC), monofluoromethyldifluoromethyl carbonate (F-DMC), and trifluorodimethyl carbonate (TFDMC) can be suitably used. Such organic solvents can be used individually or in appropriate combinations of two or more. As the supporting salt, lithium salts such as LiPF6, LiBF4, and LiClO4 can be suitably used. The concentration of the supporting salt is not particularly limited, but it is preferably, for example, between 0.7 mol / L and 1.3 mol / L. Furthermore, the electrolyte may contain components other than the organic solvent and supporting salt mentioned above, as long as they do not significantly impair the effectiveness of this technology. For example, it may contain various additives such as gas generators, film-forming agents, dispersants, and thickeners.
[0059] The energy storage device 100 is typically used with the bottom wall 12a of the case 10 positioned vertically downwards. In this specification, this usage condition is also referred to as the "normal usage condition." In the normal usage condition, the electrolyte contains excess electrolyte 80 present between the electrode body 20 and the case 10. The excess electrolyte 80 accumulates on the bottom wall 12a side of the case 10.
[0060] When the energy storage device 100 is in a charged state, the negative electrode (e.g., the negative electrode active material) expands, and electrolyte tends to be discharged from inside the electrode body 20. Conversely, when the energy storage device 100 is in a discharge state, the negative electrode (e.g., the negative electrode active material) contracts, and excess electrolyte 80 tends to enter inside the electrode body 20. Therefore, the liquid level 80h of the excess electrolyte 80 may fluctuate depending on the state of charge (SOC) of the energy storage device 100. In this specification, a state in which the SOC is 95% or more and 100% or less is also referred to as a "fully charged state," and a state in which the SOC is 0% or more and 15% or less (including SOC 0%) is also referred to as a "discharged state."
[0061] Under normal operating conditions and in a fully charged state, the height from the bottom wall 12a of the case 10 containing the excess electrolyte 80 to the liquid surface 80h is preferably, for example, 1 / 10H or less, 1 / 15H or less, or 1 / 20H or less (where "H" refers to the length H in the height direction Z of the first end face 20a of the electrode body 20 as described above). This allows the distance between the first electrode tab group 23 and the excess electrolyte 80 to be increased. Also, under normal operating conditions and in a fully charged state, the height from the bottom wall 12a of the case 10 containing the excess electrolyte 80 to the liquid surface 80h is preferably, for example, 1 / 100H or more, or 1 / 50H or more. This prevents insufficient electrolyte from entering the electrode body 20 during discharge.
[0062] Under normal operating conditions and in a fully charged state, the distance between the liquid level 80h of the excess electrolyte 80 and the lower end 23b of the first electrode tab group 23 is, for example, 1 / 2H or more, preferably 3 / 5H or more. This makes it difficult for the heat generated in the first electrode tab group 23 during discharge to be transferred to the excess electrolyte 80.
[0063] Under normal operating and discharge conditions, the distance between the liquid level 80h of the excess electrolyte 80 and the lower end 23b of the first electrode tab group 23 is, for example, 1 / 2H or more, preferably 3 / 5H or more, and more preferably 1 / 3H or more. This makes it difficult for the heat generated in the first electrode tab group 23 during charging to be transferred to the excess electrolyte 80.
[0064] In this specification, the height of the liquid level 80h of the excess electrolyte 80 refers to the height from the inner surface of the bottom wall 12a when the surface temperature of the energy storage device 100 is 40°C. The height of the liquid level 80h of the excess electrolyte 80 can be measured, for example, by image analysis measured by CT or by a sensor inside the case 10. The surface temperature of the energy storage device 100 refers to the temperature at the center of the side wall with the largest area (in this case, the first side wall 12b) of the energy storage device 100. The surface temperature of the energy storage device 100 can be measured, for example, by a thermocouple.
[0065] The positional relationship between the second electrode tab group 25 and the excess electrolyte 80 can be similar to the positional relationship between the first electrode tab group 23 and the excess electrolyte 80 described above.
[0066] An example of a method for manufacturing the energy storage device 100 is described below, but this does not limit the method of manufacturing the energy storage device 100. The method for manufacturing the energy storage device 100 may include, for example, a forming step of forming the electrode body 20, a construction step of constructing a battery assembly, and an injection step of injecting an electrolyte. Furthermore, the manufacturing method disclosed herein may include other steps at any stage, the order of the steps may be changed as appropriate, and steps may be omitted as appropriate.
[0067] The formation process may be the same as that of a known method. A strip-shaped first electrode 22, a strip-shaped second electrode 24, and two strip-shaped separators 26 are prepared. Next, the first electrode 22 and the second electrode 24 are stacked so that the separators 26 are placed between them. At this time, the stacking is done so that the longitudinal directions of each are aligned. Then, the electrode body 20 is fabricated by winding the stack around the winding axis WL (see Figure 5). In the formation process, the arrangement of the first electrode tab group 23 and the second electrode tab group 25 can be adjusted as appropriate.
[0068] The construction process may be the same as that of a known method. Figure 6 is a schematic perspective view showing the electrode body 20 to which the first current collector 52 and the third current collector 62 are attached. Figure 7 is a schematic perspective view showing the electrode body 20 attached to the sealing body 14. An example of construction is shown below, but the order of construction is not limited, and the construction described below can be performed before or after other processes. For example, first, the first electrode terminal 30 is attached to the terminal insertion hole 18 of the sealing body 14. At this time, the gasket 90 is placed between the first electrode terminal 30 and the sealing body 14. Next, the second current collector 54 and the internal insulating member 70 are placed on the inner surface of the sealing body 14. At this time, the internal insulating member 70 is placed between the inner surface of the sealing body 14 and the second current collector 54. Then, the end of the first electrode terminal 30 protruding from the inner surface of the sealing body 14 is crimped (riveted) to fix the second current collector 54 and the internal insulating member 70 to the sealing body 14. The same procedure is followed for the second electrode terminal 40, which is inserted into the terminal insertion hole 19, and the gasket 90, the fourth current collector 64, and the internal insulating member 70 are fixed to the sealing body 14. On the outer surface of the sealing body 14, an external insulating member 92 is placed around the gasket 90 attached to the first electrode terminal 30. The first electrode external conductive member 32 is attached to the placed external insulating member 92, and the first electrode terminal 30 and the first electrode external conductive member 32 are electrically connected. The same procedure is followed for the second electrode external conductive member 42 as for the first electrode external conductive member 32, so a detailed explanation is omitted.
[0069] In the construction process, the first current collector 52 is joined to the first electrode tab group 23 of the electrode body 20. The third current collector 62 is joined to the second electrode tab group 25. This creates an electrode body 20 with the first current collector 52 and the third current collector 62 attached, as shown in Figure 6. The joining method is not particularly limited and may be ultrasonic bonding, resistance welding, laser welding, etc. After that, the second current collector 54 attached to the sealing body 14 and the first current collector 52 attached to the electrode body 20 are joined. Similarly, the fourth current collector 64 attached to the sealing body 14 and the third current collector 62 attached to the electrode body 20 are joined to create an assembly as shown in Figure 7. The joining method is not particularly limited and may be ultrasonic bonding, resistance welding, laser welding, etc.
[0070] Next, the assembly shown in Figure 7 is inserted into the case body 12. At this time, the first electrode tab group 23 is positioned on one side of the second side wall 12c, and the second electrode tab group 25 is positioned on the other side of the second side wall 12c. Then, the case body 12 and the sealing body 14 are attached by joining (for example, laser welding) the sealing body 14 to the periphery of the opening 12h of the case body 12. In this way, the energy storage device assembly is manufactured.
[0071] In the electrolyte injection process, the electrolyte is injected into the case 10 through the injection hole 15 according to a known method. At this time, by adjusting the amount of electrolyte injected, the positional relationship between the excess electrolyte 80 and the first electrode tab group 23 can be achieved as described above. After injection, the injection hole 15 is sealed with the sealing member 16.
[0072] Subsequently, a usable energy storage device 100 is manufactured by performing initial charging, aging treatment, etc., under predetermined conditions.
[0073] The energy storage device 100 can be used for various applications, for example, as a battery for vehicles. The type of vehicle is not particularly limited, but examples include plug-in hybrid vehicles (PHEVs), hybrid electric vehicles (HEVs), and battery electric vehicles (BEVs). Furthermore, the energy storage device 100 can also be suitably used as a battery pack in which multiple energy storage devices 100 are arranged in a predetermined direction.
[0074] Although several embodiments of this disclosure have been described above, these embodiments are merely examples. This disclosure can be implemented in various other forms. This disclosure can be implemented based on the content disclosed herein and common technical knowledge in the art. The technology described in the claims includes various modifications and changes to the embodiments illustrated above. For example, it is possible to replace parts of the above embodiments with other modifications, and to add other modifications to the above embodiments. Furthermore, technical features that are not described as essential may be deleted as appropriate.
[0075] For example, in the embodiment described above, as shown in Figure 2, the lower end of the first current collector 52 was located below the lower end 23b of the first electrode tab group 23. However, since the first current collector 52 also generates heat during charging and discharging, it is preferable that the distance between the first current collector 52 and the excess electrolyte 80 be greater. Figure 8 is a schematic diagram corresponding to Figure 2 of a modified energy storage device 100A. The energy storage device 100A includes a first current collector 52A joined to the first electrode tab group 23 via a first joint J1. The lower end 52Ab of the first current collector 52A is located above (towards the upper wall 14) the lower end 23b of the first electrode tab group 23 in the height direction Z. This makes it difficult for heat from the first current collector 52A to be transferred to the excess electrolyte 80, thereby suppressing thermal expansion of the electrolyte. Furthermore, the energy storage device 100A includes a third current collector member 62A joined to the second electrode tab group 25 via a second joint J2. In the third current collector member 62A, it is preferable that the lower end 62Ab is located above the lower end 25b of the second electrode tab group 25 in the height direction Z. Note that the lower end 52Ab of the first current collector member 52A and the lower end 62Ab of the third current collector member 62A both refer to the part that is closest to the liquid surface 80h of the excess electrolyte 80 under normal operating conditions.
[0076] Furthermore, in the embodiments described above, for example, the first electrode current collector 50 comprises a first current collector member 52 and a second current collector member 54, thereby electrically connecting the first electrode tab group 23 of the electrode body 20 to the first electrode terminal 30, but the invention is not limited to this. For example, the first current collector member joined to the first electrode tab group 23 of the electrode body 20 may be directly connected to the first electrode terminal 30. In addition, in some embodiments, the first electrode terminal 30 may be omitted, and the first current collector member connected to the first electrode tab group 23 may itself be configured as the first electrode terminal. For example, a part of the first current collector member may be joined to the first electrode tab group 23, and another part may be directly connected to an external member such as a busbar.
[0077] As described above, specific embodiments of the technology disclosed herein include those described in the following sections. Section 1: An electrode body including a first electrode and a second electrode, Electrolyte and A case for housing the electrode body and the electrolyte, A first current collector member electrically connected to the first electrode and A power storage device comprising, The above case is, The bottom wall and, A pair of side walls extending from the edge of the bottom wall and facing each other in the width direction, In the height direction, the upper wall opposite the bottom wall and Equipped with, The electrode body described above is A group of first electrode tabs including a plurality of first electrode tabs protruding from a first end face in one of the width directions, A group of second electrode tabs including a plurality of second electrode tabs protruding from the second end face on the other side in the width direction, Includes, The first current collector is joined to the first electrode tab group via the first joint, The length of the electrode body in the width direction is at least twice the length of the electrode body in the height direction. The above electrolyte includes the excess electrolyte present between the electrode body and the case. When the length of the first end face of the electrode body in the height direction is H, the length of the first electrode tab group in the height direction is 1 / 5H or more and less than 1 / 2H. When the above bottom wall is positioned vertically downwards, and the SOC (state of charge) is 95% or higher, The height from the bottom wall to the liquid surface of the above excess electrolyte is between 1 / 100H and 1 / 10H. The distance between the liquid level of the excess electrolyte and the lower end of the first electrode tab group is 1 / 2H or more. Energy storage device. Section 2: The lower end of the first electrode tab group is positioned above half of the electrode body in the height direction. The energy storage device as described in item 1. Section 3: The energy storage device according to item 1 or 2, wherein, when the SOC is 15% or less, the distance between the liquid surface of the excess electrolyte and the lower end of the first electrode tab group is 1 / 2H or more. Section 4: The energy storage device according to any one of items 1 to 3, wherein the distance between the upper end of the first electrode tab group and the upper end of the first end face of the electrode body is 1 / 4H or less. Section 5: An energy storage device according to any one of items 1 to 4, wherein the above-mentioned first electrode is the positive electrode. Item 6: The energy storage device according to any one of items 1 to 5, wherein the first joint is provided above half of the first electrode tab group in the height direction. Section 7: The energy storage device according to any one of items 1 to 6, wherein the lower end of the first current collector is positioned above the lower end of the first electrode tab group in the height direction. [Explanation of Symbols]
[0078] 10 cases 12 Case body 12a Bottom wall 12b 1st side wall 12c 2nd side wall 14 Upper wall (sealing body) 20 Electrode body 20a 1st end face 20b 2nd end face 22 1st electrode 23 First electrode tab group 24 2nd electrode 25 Second electrode tab group 30 1st electrode terminal 40 2nd electrode terminal 52 First current collector 80 Excess electrolyte 80h liquid level 100 Energy Storage Devices
Claims
1. An electrode body including a first electrode and a second electrode, Electrolyte and A case for housing the electrode body and the electrolyte, A first current collector member electrically connected to the first electrode and A power storage device comprising, The aforementioned case is, The bottom wall and, A pair of side walls extending from the edge of the bottom wall and facing each other in the width direction, In the height direction, the upper wall opposite the bottom wall and Equipped with, The electrode body is A group of first electrode tabs including a plurality of first electrode tabs protruding from a first end face in one of the width directions, A group of second electrode tabs including a plurality of second electrode tabs protruding from the second end face on the other side in the width direction, Includes, The first current collector is joined to the first electrode tab group via a first joint, The length of the electrode body in the width direction is at least twice the length of the electrode body in the height direction. The electrolyte includes the excess electrolyte present between the electrode body and the case. When the length of the first end face of the electrode body in the height direction is H, the length of the first electrode tab group in the height direction is 1 / 5H or more and less than 1 / 2H. With the bottom wall positioned vertically downwards, and with a State of Charge (SOC) of 95% or more, The height from the bottom wall to the liquid surface of the excess electrolyte is 1 / 100H or more and 1 / 10H or less. The distance between the liquid level of the excess electrolyte and the lower end of the first electrode tab group is 1 / 2H or more. Energy storage device.
2. The lower end of the first electrode tab group is positioned above half of the electrode body in the height direction. The energy storage device according to claim 1.
3. The energy storage device according to claim 1 or 2, wherein, when the SOC is 15% or less, the distance between the liquid surface of the excess electrolyte and the lower end of the first electrode tab group is 1 / 2H or more.
4. The energy storage device according to claim 1 or 2, wherein the distance between the upper end of the first electrode tab group and the upper end of the first end face of the electrode body is 1 / 4H or less.
5. The energy storage device according to claim 1 or 2, wherein the first electrode is a positive electrode.
6. The energy storage device according to claim 1 or 2, wherein the first joint is provided above half of the first electrode tab group in the height direction.
7. The energy storage device according to claim 1 or 2, wherein the lower end of the first current collector is positioned above the lower end of the first electrode tab group in the height direction.