Secondary battery

Abstract

To suppress deterioration of battery characteristics.SOLUTION: The laminated electrode body 20 and the electrolytic solution 15 are accommodated in the case body 12. A positive electrode plate 22 and a negative electrode plate 24 are laminated, and a separator 26 is sandwiched between the positive electrode plate 22 and the negative electrode plate 24 and folded. The positive electrode plates 22 and the negative electrode plates 24 are opposed to a pair of opposed side face parts 12b inside the cylindrical case body 12, and the positive electrode plates 22 and the negative electrode plates 24 are alternately arranged. A first end portion 26e1 and a second end portion 26e2 are formed on the laminated electrode body 20. The position of the lower end 26 e D of the second end portion 26e2 is disposed above the liquid surface 15a of the electrolytic solution 15.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] International Publication No. 2019 / 064740 discloses a stacked secondary battery that suppresses adverse effects such as electrode deformation caused by folds in the separator. In this secondary battery, the separator is folded back at the end of the electrode. In the secondary battery disclosed in this publication, the folds in the separator and the end of the negative electrode are separated by a predetermined distance. This prevents adverse effects caused by the folds in the separator. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 064740 Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors of the present invention would like to suppress the deterioration of battery characteristics. [Means for solving the problem]

[0005] The secondary battery disclosed herein includes an electrode assembly including a plurality of first electrode plates, a plurality of second electrode plates having a polarity different from that of the first electrode plates, and a separator; an electrolyte; a cylindrical case body that accommodates the electrode assembly and the electrolyte; a first sealing plate attached to an opening on a first side of the case body; and a second sealing plate attached to an opening on a second side of the case body. the case body has a pair of opposing side surfaces, the plurality of first electrode plates and the plurality of second electrode plates face the pair of opposing side surfaces inside the case body, and the first electrode plates and the second electrode plates are arranged alternately, the separator is strip-shaped and is folded back in order to pass between the first electrode plates and the second electrode plates in order to be arranged between the first electrode plates and the second electrode plates, a first end of the separator is arranged on the outer periphery of the electrode body in which the plurality of first electrode plates and the plurality of second electrode plates face each other alternately, and a second end of the separator is arranged on the outer periphery of the electrode body in which the plurality of first electrode plates and the plurality of second electrode plates face each other alternately, and is overlapped on the outside of the first end and fastened to the outer periphery of the electrode body with tape, and when the pair of opposing side surfaces of the case body are placed vertically, a lower end of the tape is arranged above the liquid surface of the electrolyte outside the electrode body in the case body.

[0006] Such a secondary battery can suppress deterioration of battery characteristics. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view of an electricity storage device 100 according to the first embodiment. [Figure 2] FIG. 2 is a schematic vertical cross-sectional view taken along the line AA in FIG. [Figure 3] FIG. 3 is a cross-sectional view of the laminated electrode body 20. As shown in FIG. [Figure 4] FIG. 4 is a schematic diagram showing the positive electrode plate 22 and the negative electrode plate 24. As shown in FIG. [Figure 5] FIG. 5 is a schematic diagram showing the inside of the case main body 12. As shown in FIG. [Figure 6] FIG. 6 is a rear view of the laminated electrode body 20. As shown in FIG. [Figure 7] FIG. 7 is a schematic diagram showing the inside of the case body 12 when the electricity storage device 100 is being charged. [Figure 8]FIG. 8 is a schematic diagram showing the inside of the case body 12 when the electricity storage device 100 is being discharged. [Figure 9] FIG. 9 is a view corresponding to FIG. 3 according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Preferred embodiments of the technology disclosed herein will be described below with reference to the drawings as appropriate. 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 an electricity storage device 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, in the following drawings, components and parts that perform the same function are designated by the same reference numerals, and duplicate explanations may be omitted or simplified.

[0009] First Embodiment <Electricity storage device 100> FIG. 1 is a perspective view of an electricity storage device 100 according to a first embodiment. FIG. 2 is a schematic longitudinal cross-sectional view taken along line AA in FIG. 1, illustrating the internal structure of the electricity storage device 100. As shown in FIG. 1, the electricity storage device 100 has a polygonal shape (more specifically, a rectangular parallelepiped shape) formed of hexahedrons. The electricity storage device 100 is installed as shown in FIG. 1 when actually used. In the following description, the symbols F, Rr, L, R, U, and D in the drawings represent front, rear, left, right, top, and bottom, and the symbols X, Y, and Z in the drawings represent the width direction of the electricity storage device 100, the thickness direction perpendicular to the width direction, and the up-down direction perpendicular to the width and thickness directions, respectively.

[0010] As shown in FIG. 1 or 2, the electricity storage device 100 includes a case 10, a stacked electrode assembly 20, a positive electrode terminal 30, a negative electrode terminal 40, and an electrolyte solution 15. Here, the electricity storage device 100 is a non-aqueous electrolyte secondary battery, such as a lithium-ion secondary battery. The electricity storage device 100 is configured by accommodating the stacked electrode assembly 20 and the electrolyte solution 15 in a case 10 to which the positive electrode terminal 30 and the negative electrode terminal 40 are attached. In this specification, the term "electricity storage device" refers to a general 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, and capacitors such as lithium-ion capacitors and electric double layer capacitors.

[0011] Case 10 As shown in FIG. 2, the case 10 is a housing that houses the stacked electrode assembly 20 and the electrolyte solution 15. Here, the outer shape of the case 10 is a flat, bottomed rectangular parallelepiped (rectangular). The material of the case 10 is not particularly limited. The case 10 can be made of a metal such as aluminum or an aluminum alloy. The case 10 includes a case main body 12, a first sealing plate 14, and a second sealing plate 16.

[0012] <Case body 12> The case body 12 is a cylindrical member that houses the stacked electrode body 20 and the electrolyte solution 15. In this embodiment, the case body 12 is a cylindrical member that is open at both ends. The case body 12 can be formed, for example, by bending a single metal plate into a rectangular tube shape and joining the seams (for example, by welding). The case body 12 may also be formed by joining multiple metal plates together.

[0013] As shown in FIG. 2, the case body 12 has a pair of narrow faces 12a and a pair of wide faces 12b. The narrow faces 12a are substantially rectangular. The pair of narrow faces 12a face each other in the Z direction and form the upper and lower faces of the case body 12. The narrow faces 12a extend in the X and Y directions. In this embodiment, the narrow face 12a on one side in the Z direction (here, the lower side) is also referred to as a bottom face portion 12aa. The narrow face 12a on the other side in the Z direction (here, the upper side) is also referred to as a top face portion 12ab. The dimensions of the bottom face portion 12aa and the top face portion 12ab along the width direction X are longer than the dimensions along the thickness direction Y.

[0014] The pair of wide surfaces 12b are an example of a pair of opposing side surfaces in the present invention. In the following description, the "wide surfaces 12b" will also be referred to as "side surface portions 12b." The pair of wide surfaces 12b are approximately rectangular. The pair of wide surfaces 12b are disposed between the pair of narrow surfaces 12a and are continuous with the pair of narrow surfaces 12a. Here, the long sides of the pair of wide surfaces 12b are connected to the long sides of the pair of narrow surfaces 12a. The pair of wide surfaces 12b face each other in the X direction and form the front and rear surfaces of the case body 12. The wide surfaces 12b extend in the Y and Z directions. The front side of the side surface portions 12b will also be referred to as side surface portion 12ba. The rear side of the side surface portions 12b will also be referred to as side surface portion 12bb.

[0015] As shown in FIG. 2, openings 12h1 and 12h2 are formed at both ends (ends 12e1 and 12e2) of the case body 12 in the width direction X. The openings 12h1 and 12h2 are formed by the short sides of the bottom surface portion 12aa, the side surfaces 12ba and 12bb, and the top surface portion 12ab. The opening 12h1 is formed at the end 12e1 on the first side (right side) of the case body 12. The opening 12h2 is formed at the end 12e2 on the second side (left side) of the case body 12. The openings 12h1 and 12h2 are substantially rectangular. The stacked electrode body 20 is inserted through the openings 12h1 and 12h2.

[0016] <First sealing plate 14, second sealing plate 16> The first sealing plate 14 is a member attached to the opening 12h1 on the first side of the case body 12. The second sealing plate 16 is a member attached to the opening 12h2 on the second side of the case body 12. The first sealing plate 14 and the second sealing plate 16 are joined to the peripheral edges of the openings 12h1 and 12h2 of the case body 12. The first sealing plate 14 and the second sealing plate 16 are substantially rectangular plate-shaped members. The first sealing plate 14 and the second sealing plate 16 are joined to the peripheral edges of the openings 12h1 and 12h2 after the stacked electrode body 20 is housed in the case body 12. The first sealing plate 14 and the second sealing plate 16 joined to the case body 12 face each other in the width direction X. A positive electrode terminal 30 is provided on the first sealing plate 14. A negative electrode terminal 40 is provided on the second sealing plate 16. The distance between the first sealing plate 14 and the second sealing plate 16 in the width direction X is longer than the length of the stacked electrode body 20 in the width direction X. Therefore, a gap GP is formed between the stacked electrode body 20 and the first sealing plate 14 and second sealing plate 16.

[0017] In this embodiment, as shown in FIG. 1 , a gas exhaust valve 13 is provided on the bottom surface 12aa. The gas exhaust valve 13 is configured to break when the pressure inside the case 10 reaches or exceeds a predetermined value, thereby exhausting gas inside the case 10 to the outside. Note that, although the number of gas exhaust valves 13 is one in this embodiment, the number of gas exhaust valves 13 may be two or more. The gas exhaust valve 13 may be provided on a surface other than the bottom surface 12aa, such as the side surface 12b or the top surface 12ab. The area of ​​the gas exhaust valve 13 is arbitrary. In this embodiment, the gas exhaust valve 13 is a cross-shaped notch. However, the shape of the gas exhaust valve 13 is not particularly limited. The gas exhaust valve 13 may be, for example, a linear notch (only vertical or horizontal lines), or may be a conventionally known elliptical valve (with a notch therein) or a circular valve (with a notch therein). The dimensions (length, depth) of the notch are arbitrary and can be determined appropriately taking into consideration the pressure resistance of the case 10, for example.

[0018] In this embodiment, as shown in FIG. 1, the liquid inlet 17 is formed in the first sealing plate 14. However, the liquid inlet 17 may also be formed in the second sealing plate 16. The liquid inlet 17 may also be formed in the case main body 12. Furthermore, in this embodiment, the liquid inlet 17 is formed on a different surface from the gas release valve 13, but it may also be formed on the same surface as the gas release valve 13. The liquid inlet 17 is a hole for injecting the electrolyte 15 (see FIG. 2) into the inside of the case 10 after the first sealing plate 14 and the second sealing plate 16 are assembled to the case main body 12. The liquid inlet 17 is sealed with the sealing member 18 after the electrolyte 15 has been injected.

[0019] The positive electrode terminal 30 is provided on the first sealing plate 14. The positive electrode terminal 30 is an example of the first terminal of the present invention. The positive electrode terminal 30 is preferably made of metal, and more preferably made of, for example, aluminum or an aluminum alloy. The positive electrode terminal 30 is electrically connected to a positive electrode plate 22 (see also FIG. 3 ), which will be described later, inside the case 10 via a positive electrode current collector 32. The positive electrode terminal 30 may be attached via, for example, an insulator (not shown) or a gasket (not shown).

[0020] The negative electrode terminal 40 is provided on the second sealing plate 16. The negative electrode terminal 40 is an example of the second terminal of the present invention. The negative electrode terminal 40 is preferably made of metal, and more preferably made of, for example, copper or a copper alloy. The negative electrode terminal 40 is electrically connected to a negative electrode plate 24 (see also FIG. 3 ), which will be described later, inside the case 10 via a negative electrode current collector 42. The negative electrode terminal 40 may be attached via, for example, an insulator (not shown) or a gasket (not shown).

[0021] The electrolyte solution 15 is accommodated inside the case 10 together with the laminated electrode assembly 20. A portion of the electrolyte solution 15 is impregnated into the laminated electrode assembly 20. The electrolyte solution 15 is, for example, a non-aqueous electrolyte solution containing a non-aqueous solvent (organic solvent) and a supporting salt (electrolyte salt, such as a lithium salt or a sodium salt). 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 15 is typically liquid, but may also be gel-like. Although not particularly limited, it is preferable that excess electrolyte solution 15 exists between the case 10 and the laminated electrode assembly 20. In this embodiment, the excess electrolyte solution 15 is stored in the gap GP.

[0022] <Laminated electrode body 20> The laminated electrode body 20 is housed inside the case main body 12. In this embodiment, two laminated electrode bodies 20 are housed inside one case main body 12. The two laminated electrode bodies 20 are arranged side by side in the thickness direction Y (see FIG. 5). The number of laminated electrode bodies 20 arranged inside one case main body 12 may be one, or may be three or more. The laminated electrode body 20 may be housed inside the case 10 covered with a resin insulating sheet (electrode body holder).

[0023] FIG. 3 is a cross-sectional view of the laminated electrode body 20. As shown in FIG. 3, the laminated electrode body 20 includes a plurality of positive electrode plates 22, a plurality of negative electrode plates 24 having a polarity opposite to that of the positive electrode plates 22, a separator 26, and adhesive layers 28 interposed between the positive electrode plates 22 and the separator 26 and between the negative electrode plates 24 and the separator 26 in the thickness direction Y. However, the adhesive layer 28 may be provided between the separator 26 and either one of the positive electrode plates 22 or the negative electrode plates 24. The positive electrode plates 22 and the negative electrode plates 24 face a pair of opposing side surface portions 12b (see FIG. 1) inside the cylindrical case body 12, and the positive electrode plates 22 and the negative electrode plates 24 are alternately arranged. The separator 26 is formed in a strip shape. The separator 26 is folded back in order and passes between the positive electrode plate 22 and the negative electrode plate 24 in order, thereby being disposed between the positive electrode plate 22 and the negative electrode plate 24. The surfaces of the positive electrode plate 22 and the negative electrode plate 24 that face the pair of wide surfaces 12b of the positive electrode plate 22 and the negative electrode plate 24 are stacked with the separator 26 interposed therebetween. The separator 26 is folded in a so-called zigzag manner. The stacking direction of the multiple positive electrode plates 22 and the multiple negative electrode plates 24 is the thickness direction Y here. In the following description, the thickness direction Y will also be referred to as the stacking direction Y.

[0024] FIG. 4 is a schematic diagram showing the positive electrode plate 22 and the negative electrode plate 24. Note that the separator 26 (see FIG. 3) is not shown in FIG. 4. As shown in FIG. 4, a positive electrode active material layer 22b is formed on the positive electrode plate 22, and a negative electrode active material layer 24b is formed on the negative electrode plate 24. Therefore, in the stacked electrode body 20, the positive electrode plate 22 and the negative electrode plate 24 are stacked such that the positive electrode active material layer 22b and the negative electrode active material layer 24b face each other while being insulated from each other. The positive electrode active material layer 22b and the negative electrode active material layer 24b are insulated from each other by the separator 26 (see FIG. 3). In this embodiment, as shown in FIG. 3, the side surface of the stacked electrode body 20 to which a tape 29 (described later) is attached is referred to as the side surface 20Rr. In this embodiment, the rear surface of the stacked electrode body 20 is referred to as the side surface 20Rr. The front surface of the stacked electrode body 20 is referred to as the side surface 20F.

[0025] As shown in FIG. 4, the positive electrode plate 22 typically includes a positive electrode current collector foil 22a and a positive electrode active material layer 22b formed on at least one surface (both surfaces in this example) of the positive electrode current collector foil 22a. The positive electrode current collector foil 22a is preferably a metal foil. In this embodiment, the positive electrode current collector foil 22a is made of, for example, aluminum or an aluminum alloy. The positive electrode active material layer 22b contains a positive electrode active material capable of reversibly absorbing and releasing charge carriers. The positive electrode active material may be a conventional material and is not particularly limited. An example of the positive electrode active material is a lithium transition metal composite oxide containing nickel, cobalt, and manganese. The positive electrode active material layer 22b may contain optional components other than the positive electrode active material, such as a binder or a conductive material. As shown in FIG. 3, both surfaces of the positive electrode plate 22 in the stacking direction Y are bonded to separators 26 via adhesive layers 28. As shown in FIG. 4, an uncoated portion 22c that does not have a positive electrode active material layer 22b is formed at one end in the width direction X of the positive electrode current collector foil 22a (here, the right side in the width direction X).

[0026] The negative electrode plate 24 typically includes a negative electrode current collector foil 24a and a negative electrode active material layer 24b formed on at least one surface (both surfaces in this example) of the negative electrode current collector foil 24a. The negative electrode current collector foil 24a is preferably a metal foil. In this embodiment, the negative electrode current collector foil 24a is made of, for example, copper or a copper alloy. The negative electrode active material layer 24b contains a negative electrode active material capable of reversibly absorbing and releasing charge carriers. The negative electrode active material may be a conventional material and is not particularly limited. Examples of negative electrode active materials include carbon materials such as graphite and silicon-based materials. The negative electrode active material layer 24b may contain optional components other than the negative electrode active material, such as a binder, a thickener, and a dispersant. As shown in FIG. 3 , both surfaces of the negative electrode plate 24 in the width direction X are bonded to separators 26 via adhesive layers 28. As shown in FIG. 4, in this embodiment, an uncoated portion 24c that does not have a negative electrode active material layer 24b is formed at one end in the width direction X of the negative electrode current collector foil 24a (here, the left side in the width direction X).

[0027] 3 is an insulating sheet having a plurality of fine through-holes formed therein through which charge carriers can pass. By interposing the separator 26 between the positive electrode plate 22 and the negative electrode plate 24, contact between the positive electrode plate 22 and the negative electrode plate 24 is prevented and charge carriers (e.g., lithium ions) can be transferred between the positive electrode plate 22 and the negative electrode plate 24. The thickness of the separator 26 is not particularly limited, but is about 20 μm in this embodiment.

[0028] As shown in FIG. 3 , the separator 26 has a first end 26e1 and a second end 26e2. The first end 26e1 is disposed on the outer periphery of the stacked electrode body 20, in which a plurality of positive electrode plates 22 and a plurality of negative electrode plates 24 are alternately arranged opposite each other. The second end 26e2 is disposed on the outer periphery of the stacked electrode body 20, in which a plurality of positive electrode plates 22 and a plurality of negative electrode plates 24 are alternately arranged opposite each other, and is overlapped on the outside of the first end 26e1 and fastened to the outer periphery of the stacked electrode body 20 with tape 29. The first end 26e1 and the second end 26e2 are located behind the portion where the positive electrode plates 22 and the negative electrode plates 24 are stacked. The first end 26e1 and the second end 26e2 are folded back at approximately right angles from the portion where the positive electrode plates 22 and the negative electrode plates 24 are stacked to the outer periphery and extend in the up-down direction Z. That is, the first end 26e1 and the second end 26e2 are formed in a substantially L-shape in side view. In FIG. 3, a gap is formed between the first end 26e1 and the second end 26e2 in the thickness direction Y, but in reality, the gap is relatively narrow. At a portion fastened to the outer periphery of the stacked electrode body 20 with tape 29 (described later), the second end 26e2 of the separator 26 is longer than the first end 26e1. Therefore, the lower end 26eD of the second end 26e2 is located lower than the first end 26e1. In this embodiment, when the pair of opposing side surface portions 12b of the case body 12 is placed vertically, the separator 26 is folded back on the bottom surface 12aa side of the case body 12 (see FIG. 2) so as to cover the negative electrode plate 24. At this time, the positive electrode plate 22 is not covered by the separator 26 on the bottom surface 12aa side. The portion of the laminated electrode body 20 where the first end 26e1 and the second end 26e2 are formed is formed thicker in the thickness direction Y than other portions of the laminated electrode body 20 by the thickness of the first end 26e1 and the second end 26e2. In this embodiment, the first end 26e1 and the second end 26e2 are formed in the lower part of the laminated electrode body 20. Although not particularly limited, in this embodiment, the length of the first end 26e1 and the second end 26e2 in the up-down direction Z is approximately 3 to 30 mm. For convenience of explanation, the first end 26e1 and the second end 26e2 are illustrated in an exaggerated manner.

[0029] The separator 26 includes a resin separator substrate and one or more heat-resistant layers (HRLs) 26a containing a metal oxide such as alumina (Al2O3). In this embodiment, the separator 26 has the heat-resistant layer 26a formed on at least one surface. Here, the heat-resistant layer 26a is formed on the inside of the second end 26e2 of the separator 26 at a portion that is fastened to the outer periphery of the stacked electrode body 20 with tape 29, which will be described later.

[0030] The heat-resistant layer 26a typically contains an inorganic filler and a heat-resistant layer binder. The heat-resistant layer 26a suppresses thermal shrinkage of the separator 26, contributing to improved safety of the electricity storage device 100 (see FIG. 1). As the inorganic filler, ceramic particles such as alumina, zirconia, boehmite, aluminum hydroxide, silica, and titania are preferred, and from the viewpoint of suppressing thermal shrinkage of the separator 26, compounds containing aluminum are particularly preferred. As the heat-resistant layer binder, acrylic resins, fluorine-based resins, urethane resins, ethylene vinyl acetate resins, epoxy resins, and the like can be mentioned.

[0031] FIG. 6 is a rear view of the laminated electrode body 20. As described above, the tape 29 fastens the second end 26e2. As shown in FIG. 6, the tape 29 is composed of a first tape 29a, a second tape 29b, and a third tape 29c, which are arranged intermittently along the lower end 26eD of the second end 26e2. In this embodiment, the lower end 26eD of the second end 26e2 extends in the width direction X. Therefore, the first tape 29a, the second tape 29b, and the third tape 29c are aligned along the width direction X. In this embodiment, the tape 29 is composed of the first tape 29a, the second tape 29b, and the third tape 29c, but the number of tapes that make up the tape 29 is not particularly limited. In the following description, unless otherwise specified, "tape 29" refers to the first tape 29a, the second tape 29b, and the third tape 29c. As shown in FIG. 5, in this embodiment, the lower end 29D of the tape 29 is positioned above the liquid surface 15a of the electrolyte solution 15. The thickness of the tape 29 is not particularly limited, but is approximately 50 μm in this embodiment. As shown in FIG. 3, the portion of the stacked electrode body 20 to which the tape 29 is fastened is formed to have a long length in the thickness direction Y of the stacked electrode body 20. The portion where the first end 26e1, the second end 26e2, and the tape 29 overlap in the stacking direction Y is the thickest portion of the stacked electrode body 20. In the following description, the portion of the stacked electrode body 20 where the first end 26e1, the second end 26e2, and the tape 29 overlap in the stacking direction Y is referred to as the "thickest portion."

[0032] FIG. 5 is a schematic diagram showing the inside of the case body 12. As shown in FIG. 5, the two stacked electrode bodies 20 are arranged side by side in the thickness direction Y. When the pair of opposing side surface portions 12b of the case body 12 is placed vertically as shown in FIG. 5, the position of the lower end 26eD of the second end 26e2 of the separator 26 fastened with tape 29 is positioned above the liquid surface 15a of the electrolyte solution 15 outside the stacked electrode body 20 inside the case body 12. "When the pair of opposing side surface portions 12b are placed vertically" refers to the case where the case body 12 is placed so that one of the pair of narrow surfaces 12a (here, the bottom surface portion 12aa) is on the lower side, and the pair of wide surfaces (the pair of opposing side surfaces) 12b are approximately perpendicular to one of the pair of narrow surfaces 12a, as shown in FIG. Here, the height of the liquid level 15a of the electrolyte solution 15 varies depending on the SOC (States Of Charge) of the electricity storage device 100. In this embodiment, when the SOC of the electricity storage device 100 is 75% or higher, the lower end 26eD of the second end 26e2 is located above the liquid level 15a of the electrolyte solution 15. That is, when the SOC of the electricity storage device 100 is 75% or higher, the first end 26e1 and the second end 26e2 of the separator 26 fastened with tape 29 are located above the liquid level 15a of the electrolyte solution 15. For convenience of explanation, a gap is shown between the stacked electrode body 20 and the side surface portion 12b in FIG. 5, but the stacked electrode body 20 and the side surface portion 12b may be in contact with each other. Note that "SOC of 75% or higher" refers to an SOC of 75% or higher when the electricity storage device 100 is new or relatively close to new.

[0033] 5, the side surfaces 20Rr of the two laminated electrode bodies 20 to which the tape 29 is attached are arranged facing the same side surface with respect to the pair of opposing side surface portions 12b of the case body 12. In this embodiment, the side surfaces 20Rr of the two laminated electrode bodies 20 are both arranged facing the side surface portion 12bb. Note that the side surfaces 20Rr of the two laminated electrode bodies 20 may also be arranged facing the side surface portion 12ba.

[0034] As shown in FIG. 2, the positive electrode plate 22 has a positive electrode tab 23 that extends toward the first sealing plate 14 and is connected to the positive electrode terminal 30. Each of the multiple positive electrode plates 22 has a positive electrode tab 23. The positive electrode tab 23 is a portion of the positive electrode current collector foil 22a (see FIG. 4) that protrudes from the region where the positive electrode active material layer 22b (see FIG. 4) and the negative electrode active material layer 24b (see FIG. 4) are overlapped. The positive electrode tab 23 is formed by overlapping the uncoated portion 22c (see FIG. 4). The positive electrode tab 23 is electrically connected to the positive electrode terminal 30 via the positive electrode current collector portion 32. The negative electrode plate 24 has a negative electrode tab 25 that extends toward the second sealing plate 16 and is connected to the negative electrode terminal 40. Each of the multiple negative electrode plates 24 has a negative electrode tab 25. The negative electrode tab 25 is a portion of the negative electrode current collector foil 24a (see FIG. 4) that protrudes from the region where the negative electrode active material layer 24b (see FIG. 4) and the negative electrode active material layer 24b (see FIG. 4) are overlapped. The negative electrode tab 25 is formed by overlapping the uncoated portion 24c (see FIG. 4). The negative electrode tab 25 is electrically connected to the negative electrode terminal 40 via the negative electrode current collector portion 42.

[0035] The adhesive layer 28 shown in Fig. 3 is interposed between at least one of the positive electrode plate 22 and the negative electrode plate 24 and the separator 26, bonding them together. This prevents misalignment of the positive electrode plate 22 and the negative electrode plate 24, thereby preventing misalignment of the stacked electrode body 20. In Fig. 3, both surfaces of the positive electrode plate 22 and both surfaces of the negative electrode plate 24 are bonded to the opposing separators 26 via the adhesive layer 28 in the stacking direction Y.

[0036] The adhesive layer 28 is typically the layer containing the adhesive layer binder at the highest mass ratio. Examples of adhesive layer binders include fluorine-based resins, acrylic resins, urethane resins, ethylene vinyl acetate resins, and epoxy resins. The adhesive layer binder may be the same type as the heat-resistant layer binder described above, or may be a different type. The adhesive layer 28 may further contain other materials (e.g., inorganic fillers, etc.).

[0037] The configuration of the electricity storage device 100 according to this embodiment has been described above. When the electricity storage device 100 is charged and discharged, the positive electrode active material layer 22b (see FIG. 4) and the negative electrode active material layer 24b (see FIG. 4) expand and contract, causing the stacked electrode body 20 to expand and contract. When the stacked electrode body 20 expands, a portion of the electrolyte solution 15 impregnated in the stacked electrode body 20 is extruded. When the stacked electrode body 20 contracts, a portion of the electrolyte solution 15 is absorbed into the stacked electrode body 20. When the extrusion and absorption of the electrolyte solution 15 is repeated, depending on the shape of the stacked electrode body 20, there is a possibility that portions of the stacked electrode body 20 will become deficient in the electrolyte solution 15 (so-called liquid depletion). When liquid depletion occurs, the battery characteristics of the electricity storage device 100 will deteriorate. The present inventors wish to prevent the battery characteristics from deteriorating when the extrusion and absorption of the electrolyte solution 15 is repeated.

[0038] Next, the electrolyte 15 inside the electricity storage device 100 when the electricity storage device 100 is charged and discharged will be described.

[0039] First, charging of the electricity storage device 100 will be described. The electricity storage device 100 is charged by a conventionally known method. FIG. 7 is a schematic diagram showing the inside of the case body 12 when the electricity storage device 100 is being charged. When the electricity storage device 100 is charged, the positive electrode active material layer 22b (see FIG. 4) and the negative electrode active material layer 24b (see FIG. 4) expand, as described above. As described above, the positive electrode plates 22 and the negative electrode plates 24 are stacked along the thickness direction Y. At this time, as shown in FIG. 7, the positive electrode plates 22 and the negative electrode plates 24 curve so as to expand toward the outside of the stacked electrode body 20. Therefore, the stacked electrode body 20 expands so as to expand in the thickness direction Y.

[0040] When the laminated electrode body 20 expands, the laminated electrode body 20 presses the pair of opposing side surface portions 12b outward in the thickness direction Y. At this time, the laminated electrode body 20 receives a normal force from the pair of side surface portions 12b. Here, of the two laminated electrode bodies 20 lined up, the rearmost laminated electrode body 20 (hereinafter referred to as the "rear laminated electrode body 20") has its thickest portion facing the side surface portion 12bb, so the tape 29 comes into contact with the side surface portion 12bb. Furthermore, the side surface 20F of the rear laminated electrode body 20 comes into contact with the tape 29 of the frontmost laminated electrode body 20 (hereinafter referred to as the "front laminated electrode body 20") of the two laminated electrode bodies 20 lined up. Therefore, the rear laminated electrode body 20 is likely to be subjected to a force inward in the thickness direction Y near its thickest portion. Here, the vicinity of the thickest part refers to a range of the laminated electrode body 20 that includes at least one of the first end 26e1, the second end 26e2, and the tape 29. In this embodiment, the vicinity of the thickest part refers to the position of the lower end 29D of the tape 29 and a range above the lower end 29D of the tape 29 in the vertical direction Z of the laminated electrode body 20.

[0041] The tape 29 of the front laminated electrode body 20 is in contact with the rear laminated electrode body 20. The most expanding portion of the side surface 20F of the front laminated electrode body 20 is in contact with the side surface portion 12ba. Here, the side surface 20F is in contact with the side surface portion 12ba near the center in the vertical direction Z. Therefore, in the front laminated electrode body 20, the side surface 20F is likely to be subjected to a force inward in the thickness direction Y near the center in the vertical direction Z, while the side surface 20Rr is likely to be subjected to a force inward in the thickness direction Y near the thickest portion. Because the first end portion 26e1, the second end portion 26e2, and the tape 29 are absent in the region of the laminated electrode body 20 below the tape 29, the region of the laminated electrode body 20 is thinner in the thickness direction Y than the other regions of the laminated electrode body 20. Therefore, the force acting inward in the thickness direction Y is relatively small in the region of the laminated electrode body 20 below the tape 29.

[0042] When a force is applied to each of the two stacked electrode bodies 20 inward in the thickness direction Y, the electrolyte 15 impregnated in the stacked electrode bodies 20 is pushed out. Because the stacked electrode bodies 20 are pushed inward in the thickness direction Y, the electrolyte 15 is pushed outward in the width direction X. In this embodiment, because the force is applied near the thickest part of the stacked electrode body 20, the electrolyte 15 impregnated near the thickest part is easily pushed out. The pushed-out electrolyte 15 is stored inside the case body 12. More specifically, the pushed-out electrolyte 15 is stored in the lower part of the case body 12 due to gravity. Therefore, as shown in FIG. 2, the electrolyte 15 is stored in the lower part of the case body 12. At this time, the electrolyte 15 is also stored in the gaps GP (see FIG. 2) on the right and left sides of the stacked electrode body 20. In the area of ​​the laminated electrode body 20 below the tape 29, the force acting inward in the thickness direction Y is relatively small, so the electrolyte 15 is less likely to be pushed out than in the vicinity of the thickest part.

[0043] Next, the discharge of the electricity storage device 100 will be described. The electricity storage device 100 is discharged, for example, when a vehicle (not shown) equipped with the electricity storage device 100 is running. FIG. 8 is a schematic diagram showing the inside of the case body 12 when the electricity storage device 100 is being discharged. When the electricity storage device 100 is discharged, the positive electrode active material layer 22b (see FIG. 4) and the negative electrode active material layer 24b (see FIG. 4) contract as described above. At this time, as shown in FIG. 8, the positive electrode plate 22 and the negative electrode plate 24 curve inward in the thickness direction Y. Therefore, the stacked electrode body 20 contracts in the thickness direction Y.

[0044] When the laminated electrode body 20 contracts, the electrolyte solution 15 stored inside the case main body 12 is absorbed by the laminated electrode body 20. In this embodiment, the separator 26 is attached so as to cover the positive electrode plate 22 and the negative electrode plate 24 in the thickness direction Y. Therefore, the positive electrode plate 22 and the negative electrode plate 24 are not covered by the separator 26 in the width direction X. Therefore, the laminated electrode body 20 mainly absorbs the electrolyte solution 15 stored in the gaps GP (see FIG. 2 ) on the left and right sides of the laminated electrode body 20. Because the electrolyte solution 15 is stored in the lower part of the case main body 12, it is absorbed from the lower part of the laminated electrode body 20. Here, as described above, when the electricity storage device 100 is charged, the electrolyte solution 15 impregnated near the thickest part is pushed out. Therefore, the electrolyte solution 15 absorbed from the lower part of the laminated electrode body 20 gradually impregnates upward toward the thickest part.

[0045] As described above, in the electricity storage device 100 of this embodiment, the case body 12 accommodates the stacked electrode body 20 and the electrolyte 15. The stacked electrode body 20 is formed by stacking positive electrode plates 22 and negative electrode plates 24, and the separator 26 is sandwiched between the positive electrode plates 22 and the negative electrode plates 24 and folded back. The positive electrode plates 22 and the negative electrode plates 24 face a pair of opposing side surface portions 12b inside the cylindrical case body 12, and the positive electrode plates 22 and the negative electrode plates 24 are arranged alternately. When the electricity storage device 100 is charged and discharged, the electrolyte 15 impregnated in the stacked electrode body 20 is pushed out or absorbed mainly in the width direction X. That is, when the electricity storage device 100 is charged and discharged, the electrolyte 15 is pushed out into the gaps GP, and the electrolyte 15 stored in the gaps GP is absorbed by the stacked electrode body 20. The stacked electrode body 20 has a first end 26e1 and a second end 26e2. Tape 29 is fastened to the second end 26e2. Therefore, when the electricity storage device 100 is charged and the stacked electrode body 20 expands and contacts the pair of side surface portions 12b, a relatively large force is applied to the stacked electrode body 20 near the thickest portion. This makes it easy for the electrolyte 15 to be pushed out from near the thickest portion of the stacked electrode body 20. Furthermore, the lower end 26eD of the second end 26e2 is positioned above the liquid level 15a of the electrolyte 15. Therefore, the electrolyte 15 pushed out from near the thickest portion when the electricity storage device 100 is charged is accumulated in the lower part of the case body 12 due to gravity. Thereafter, when the stacked electrode body 20 contracts due to discharge of the electricity storage device 100, the electrolyte 15 is absorbed from the lower part of the stacked electrode body 20, and the absorbed electrolyte 15 gradually rises toward the vicinity of the thickest part. That is, the electrolyte 15 is pushed out from the vicinity of the thickest part and absorbed from the lower part of the stacked electrode body 20 toward the vicinity of the thickest part, moving so as to be distributed throughout the entire stacked electrode body 20. This prevents the occurrence of liquid depletion in the stacked electrode body 20. Therefore, in the electricity storage device 100, deterioration of battery characteristics due to liquid depletion during charge and discharge is suppressed.

[0046] In the electricity storage device 100 of this embodiment, the separator 26 is folded back on the bottom surface 12aa side of the case body 12 so as to cover the negative electrode plate 24. Here, between the positive electrode active material layer 22b and the negative electrode active material layer 24b, the negative electrode active material layer 24b expands and contracts more due to the insertion and extraction of lithium ions. Therefore, during charging and discharging of the electricity storage device 100, the negative electrode plate 24 expands and contracts more than the positive electrode plate 22, and a greater force is applied to the negative electrode plate 24. Therefore, during charging and discharging of the electricity storage device 100, the negative electrode active material layer 24b is likely to peel off from the negative electrode plate 24. In this embodiment, the bottom surface 12aa side of the negative electrode plate 24 is covered by the separator 26. Therefore, even if the negative electrode active material layer 24b peels off, the negative electrode active material layer 24b is deposited on the separator 26 covering the negative electrode plate 24. Therefore, it is possible to prevent the peeled negative electrode active material layer 24b from becoming free inside the electricity storage device 100 as conductive foreign matter.

[0047] The above describes the power storage device 100 according to the first embodiment. However, the above-described first embodiment is merely an example, and the present invention can be embodied in various other forms.

[0048] Second Embodiment 9 is a view corresponding to FIG. 3 according to the second embodiment. In the following description of the second embodiment, the same reference numerals as in the first embodiment are used for components that perform the same functions as in the first embodiment. Furthermore, duplicated descriptions will be omitted or simplified.

[0049] As shown in Fig. 3, the stacked electrode body 20A includes a separator 26A. In this embodiment, the separator 26A is folded back so as to cover the positive electrode plate 22 on the side of the bottom surface 12aa (see Fig. 2) of the case body 12 when the pair of opposing side surface portions 12b (see Fig. 1) of the case body 12 is placed vertically. In this case, the negative electrode plate 24 is not covered by the separator 26A on the side of the bottom surface 12aa.

[0050] In the electricity storage device 100 according to the second embodiment, the separator 26A is folded back on the bottom surface 12aa side of the case body 12 so as to cover the positive electrode plate 22. It is known that the negative electrode plate 24 absorbs the electrolyte solution 15 more quickly than the positive electrode plate 22. In this embodiment, the negative electrode plate 24 is not covered by the separator 26A on the bottom surface 12aa side, and therefore the surface area of ​​the negative electrode plate 24 that comes into contact with the electrolyte solution 15 is larger than the surface area of ​​the positive electrode plate 22 that comes into contact with the electrolyte solution 15. This increases the amount of electrolyte solution 15 absorbed into the laminated electrode body 20A. That is, when the electrolyte solution 15 is absorbed, the electrolyte solution 15 is more likely to spread throughout the entire laminated electrode body 20A. This further reduces the occurrence of liquid depletion in the laminated electrode body 20.

[0051] The invention disclosed herein has been described in various ways. Unless otherwise specified, the embodiments described herein do not limit the present invention. Furthermore, the embodiments of the invention disclosed herein can be modified in various ways, and each component and each process described herein can be omitted or combined as appropriate, unless a particular problem arises.

[0052] As described above, this specification includes the disclosures set forth in the following sections.

[0053] Section 1: an electrode assembly including a plurality of first electrode plates, a plurality of second electrode plates having a polarity different from that of the first electrode plates, and a separator; An electrolyte; a cylindrical case body that accommodates the electrode assembly and the electrolyte; a first sealing plate attached to an opening on a first side of the case body; a second sealing plate attached to the opening on the second side of the case body; and A secondary battery comprising: The case body has a pair of opposing side surfaces, the plurality of first electrode plates and the plurality of second electrode plates face the pair of opposing side surface portions inside the case body, and the first electrode plates and the second electrode plates are alternately arranged; the separator is in a strip shape, and is disposed between the first electrode plate and the second electrode plate by being folded back in order and passing between the first electrode plate and the second electrode plate in order; The first end of the separator is the plurality of first electrode plates and the plurality of second electrode plates are arranged on the outer periphery of the electrode body so as to face each other alternately; The second end of the separator is the plurality of first electrode plates and the plurality of second electrode plates are arranged on the outer periphery of the electrode body, facing each other alternately, and are overlapped on the outside of the first end portion and fastened to the outer periphery of the electrode body with tape; When the pair of opposing side surfaces of the case body are placed vertically, a lower end of the tape is disposed above a liquid level of the electrolyte outside the electrode body in the case body. Secondary battery.

[0054] Section 2: the first electrode plate is a positive electrode plate in which a positive electrode active material layer is formed on a positive electrode current collecting foil, the second electrode plate is a negative electrode plate in which a negative electrode active material layer is formed on a negative electrode current collector foil, Item 2. The secondary battery according to item 1, wherein the separator is folded back so as to cover the negative electrode plate on the bottom side of the case body when the pair of opposing side surfaces of the case body are placed vertically.

[0055] Section 3: the first electrode plate is a positive electrode plate in which a positive electrode active material layer is formed on a positive electrode current collecting foil, the second electrode plate is a negative electrode plate in which a negative electrode active material layer is formed on a negative electrode current collector foil, Item 2. The secondary battery according to item 1, wherein the separator is folded back so as to cover the positive electrode plate on the bottom side of the case body when the pair of opposing side surfaces of the case body are placed vertically. [Explanation of symbols]

[0056] 10 cases 12 Case body 12a narrow side 12aa bottom part 12ab Top section 12b Wide surface (a pair of opposing side surfaces) 12ba,12bb side part 12e1,12e2 End 12h1 First side opening 12h2 Second side opening 15 Electrolyte 15a Liquid level 20,20A laminated electrode body 20F,20Rr side 22 Positive electrode plate 22a Positive electrode current collector foil 22b Positive electrode active material layer 22c Uncoated area 23 Positive electrode tab 24 negative electrode plate 24a Negative current collector foil 24b Negative electrode active material layer 24c Uncoated area 25 Negative electrode tab 26 Separator 26a Heat-resistant layer 26eD bottom edge 28 Adhesive layer 29 Tape 29D bottom end 30 Positive terminal 32 Positive electrode current collector 40 Negative terminal 42 Negative electrode current collector 100 Energy storage device GP Gap

Claims

1. an electrode assembly including a plurality of first electrode plates, a plurality of second electrode plates having a polarity different from that of the first electrode plates, and a separator; An electrolyte; a cylindrical case body that accommodates the electrode assembly and the electrolyte; a first sealing plate attached to an opening on a first side of the case body; a second sealing plate attached to the opening on the second side of the case body; A secondary battery comprising: The case body has a pair of opposing side surfaces, the plurality of first electrode plates and the plurality of second electrode plates face the pair of opposing side surface portions inside the case body, and the first electrode plates and the second electrode plates are alternately arranged; the separator is in a strip shape, and is folded back in order to pass between the first electrode plate and the second electrode plate in order, thereby being disposed between the first electrode plate and the second electrode plate; The first end of the separator comprises: the plurality of first electrode plates and the plurality of second electrode plates are arranged on the outer periphery of the electrode body so as to face each other alternately; The second end of the separator is the plurality of first electrode plates and the plurality of second electrode plates are arranged on the outer periphery of the electrode body so as to face each other alternately, and are overlapped on the outside of the first end portion and fastened to the outer periphery of the electrode body with tape; When the pair of opposing side surfaces of the case body are placed vertically, a position of a lower end of the tape is disposed above a liquid level of the electrolyte outside the electrode body in the case body. Secondary battery.

2. the first electrode plate is a positive electrode plate in which a positive electrode active material layer is formed on a positive electrode current collector foil, the second electrode plate is a negative electrode plate in which a negative electrode active material layer is formed on a negative electrode current collector foil, 2. The secondary battery according to claim 1, wherein the separator is folded back so as to cover the negative electrode plate on the bottom side of the case body when the pair of opposing side surfaces of the case body are placed vertically.

3. the first electrode plate is a positive electrode plate in which a positive electrode active material layer is formed on a positive electrode current collector foil, the second electrode plate is a negative electrode plate in which a negative electrode active material layer is formed on a negative electrode current collector foil, 2. The secondary battery according to claim 1, wherein the separator is folded back so as to cover the positive electrode plate on the bottom side of the case body when the pair of opposing side surfaces of the case body are placed vertically.

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