Secondary battery

Abstract

The present invention provides a secondary battery which suppresses deterioration of battery characteristics. In the laminated electrode body (20), the laminated electrode body (20) and an electrolyte (15) are accommodated in a case main body (12). The positive electrode plate (22) and the negative electrode plate (24) are laminated, and the separator (26) is sandwiched between the positive electrode plate (22) and the negative electrode plate (24) and folded back. The positive electrode plates (22) and the negative electrode plates (24) face the pair of facing side surface portions (12b) inside the cylindrical case main 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 upper portion of the laminated electrode body (20). The position of the lower end (26eD) of the second end portion (26e2) is disposed above the liquid surface (15a) of the electrolyte (15).

Description

Technical Field

[0001] This invention relates to secondary batteries. Background Technology

[0002] International Publication No. 2019 / 064740 discloses a secondary battery for a stacked type that suppresses negative effects such as electrode deformation caused by creases in the separator. In this secondary battery, the separator is folded back at the electrode ends. In the secondary battery disclosed in this publication, the creases in the separator are separated from the end of the negative electrode by a predetermined length. Therefore, the negative effects caused by creases in the separator can be suppressed.

[0003] Patent Document 1: International Publication No. 2019 / 064740

[0004] However, the inventors of this application wish to suppress the degradation of battery characteristics. Summary of the Invention

[0005] The secondary battery disclosed herein comprises: an electrode body including a separator, a plurality of first electrode plates, and a plurality of second electrode plates with polarities different from the first electrode plates; an electrolyte; a casing body, which is cylindrical and houses the electrode body and the electrolyte; a first sealing plate installed on an opening on a first side of the casing body; and a second sealing plate installed on an opening on a second side of the casing body. The casing body has a pair of opposing side portions, and the plurality of first electrode plates and the plurality of second electrode plates are arranged alternately inside the casing body, with the first electrode plates and the second electrode plates being strip-shaped and sequentially bonded by… The membrane is folded back and passes sequentially between the first electrode plate and the second electrode plate, thereby being disposed between the first electrode plate and the second electrode plate. The first end of the diaphragm is disposed on the outer periphery of the electrode body formed by the alternating opposition of the plurality of first electrode plates and the plurality of second electrode plates. The second end of the diaphragm is disposed on the outer periphery of the electrode body formed by the alternating opposition of the plurality of first electrode plates and the plurality of second electrode plates, and is fixed to the outer periphery of the electrode body by tape in a manner that overlaps with the outer side of the first end. When the pair of opposing side portions of the housing body are placed vertically, the lower end of the tape is positioned above the electrolyte surface on the outer side of the electrode body inside the housing body.

[0006] Based on this secondary battery, the degradation of battery characteristics can be suppressed. Attached Figure Description

[0007] Figure 1This is a perspective view of the energy storage device 100 according to the first embodiment.

[0008] Figure 2 It is along Figure 1 A schematic longitudinal section view of line A-A.

[0009] Figure 3 This is a cross-sectional view of the stacked electrode body 20.

[0010] Figure 4 This is a schematic diagram showing the positive electrode plate 22 and the negative electrode plate 24.

[0011] Figure 5 This is a schematic diagram showing the interior of the main body 12 of the housing.

[0012] Figure 6 This is a rear view of the stacked electrode body 20.

[0013] Figure 7 This is a schematic diagram showing the interior of the housing body 12 when the energy storage device 100 is being charged.

[0014] Figure 8 This is a schematic diagram showing the interior of the housing body 12 when the energy storage device 100 is discharging.

[0015] Figure 9 It is related to the second embodiment. Figure 3 A fairly accurate diagram.

[0016] Explanation of reference numerals in the attached figures:

[0017] 10…shell; 12…shell body; 12a…narrow section; 12aa…bottom section; 12ab…top section; 12b…wide section (a pair of opposing side sections); 12ba, 12bb…side sections; 12e1, 12e2…ends; 12h1…opening on the first side; 12h2…opening on the second side; 15…electrolyte; 15a…liquid surface; 20, 20A…layered electrode body; 20F, 20Rr…side section; 22…positive electrode plate; 22a…positive electrode current collector foil; 22b…Positive electrode active material layer; 22c…Uncoated part; 23…Positive electrode tab; 24…Negative electrode plate; 24a…Negative electrode current collector foil; 24b…Negative electrode active material layer; 24c…Uncoated part; 25…Negative electrode tab; 26…Separator; 26a…Heat-resistant layer; 26eD…Lower end; 28…Adhesive layer; 29…Tape; 29D…Lower end; 30…Positive terminal; 32…Positive current collector; 40…Negative terminal; 42…Negative current collector; 100…Energy storage device; GP…Gap. Detailed Implementation

[0018] Hereinafter, preferred embodiments of the technology disclosed herein will be described with appropriate reference to the accompanying drawings. Matters requiring implementation of the technology disclosed herein, other than those specifically mentioned in this specification (e.g., the general structure and manufacturing process of energy storage devices that do not represent the technology disclosed herein), can be grasped by those skilled in the art based on prior art. The technology disclosed herein can be implemented based on the content disclosed in this specification and common technical knowledge in the field. Furthermore, in the following drawings, the same reference numerals are sometimes used to denote components or parts that perform the same function, and repeated descriptions are omitted or simplified.

[0019] <First Embodiment>

[0020] <Electric Storage Devices 100>

[0021] Figure 1 This is a perspective view of the energy storage device 100 according to the first embodiment. Figure 2 It is along Figure 1 A schematic longitudinal sectional view along line A-A shows the internal structure of the energy storage device 100. For example... Figure 1 As shown, the energy storage device 100 is square in shape (more specifically, cuboid in shape) composed of hexahedrons. In actual use, the energy storage device 100 is as follows... Figure 1 That is how it is set up. In addition, in the following description, the reference numerals F, Rr, L, R, U, and D in the attached drawings represent front, back, left, right, top, and bottom, respectively, and the reference numerals X, Y, and Z in the attached drawings represent the width direction, the thickness direction orthogonal to the width direction, and the up and down direction orthogonal to both the width and thickness directions of the energy storage device 100, respectively.

[0022] like Figure 1 or Figure 2 As shown, the energy storage device 100 includes a housing 10, a stacked electrode body 20, a positive terminal 30, a negative terminal 40, and an electrolyte 15. Here, the energy storage device 100 is a non-aqueous electrolyte secondary battery, such as a lithium-ion secondary battery. The energy storage device 100 is constructed by housing the stacked electrode body 20 and the electrolyte 15 within the housing 10, which houses the positive terminal 30 and the negative terminal 40. Furthermore, in this specification, the term "energy storage device" is a term that represents all devices capable of repeated charging and discharging, including secondary batteries such as lithium-ion secondary batteries and nickel-metal hydride batteries, and capacitors such as lithium-ion capacitors and double-layer capacitors.

[0023] <Shell 10>

[0024] like Figure 2As shown, the housing 10 is a frame that houses the stacked electrode body 20 and the electrolyte 15. Here, the housing 10 has a flat, bottomed cuboid shape (square). The material of the housing 10 is not particularly limited. The housing 10 can be made of metals such as aluminum or aluminum alloy. The housing 10 includes a housing body 12, a first sealing plate 14, and a second sealing plate 16.

[0025] <Shell Body 12>

[0026] The housing body 12 is a cylindrical component that houses the stacked electrode body 20 and the electrolyte 15. In this embodiment, the housing body 12 is a cylindrical component with openings at both ends. The housing body 12 can be formed, for example, by bending a single metal plate into a square tube shape and joining the seams (e.g., by welding). The housing body 12 can also be formed by joining multiple metal plates.

[0027] like Figure 2 As shown, the housing body 12 has a pair of narrow surfaces 12a and a pair of wide surfaces 12b. The narrow surfaces 12a are generally rectangular. The pair of narrow surfaces 12a are opposite each other in the Z direction, forming the upper and lower surfaces of the housing body 12. The narrow surfaces 12a extend in the X and Y directions. In this embodiment, the narrow surface 12a on one side in the Z direction (here, the lower side) is also referred to as the bottom surface 12aa. The narrow surface 12a on the other side in the Z direction (here, the upper side) is also referred to as the top surface 12ab. In the bottom surface 12aa and the top surface 12ab, the dimension along the width direction X is longer than the dimension along the thickness direction Y.

[0028] The pair of wide surfaces 12b is one example of a pair of opposing side surfaces in this invention. In the following description, "wide surface 12b" will also be referred to as "side surface 12b". The pair of wide surfaces 12b is generally rectangular. The pair of wide surfaces 12b is disposed between and 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 are opposed in the X direction, forming the front and rear surfaces of the housing body 12. The wide surfaces 12b extend in the Y and Z directions. The front side surface 12b of the side surface 12b is also referred to as side surface 12ba. Furthermore, the rear side surface 12b of the side surface 12b is also referred to as side surface 12bb.

[0029] like Figure 2As shown, openings 12h1 and 12h2 are formed at both ends (ends 12e1 and 12e2) of the housing body 12 in the width direction X. Openings 12h1 and 12h2 are formed by the short sides of the bottom portion 12aa, the side portions 12ba and 12bb, and the top portion 12ab. Opening 12h1 is formed at the end 12e1 on the first side (right side) of the housing body 12. Opening 12h2 is formed at the end 12e2 on the second side (left side) of the housing body 12. Openings 12h1 and 12h2 are generally rectangular. A stacked electrode body 20 can be inserted through openings 12h1 and 12h2.

[0030] <Seal plate 14, seal plate 2>

[0031] The first sealing plate 14 is a component fitted to the opening 12h1 on the first side of the housing body 12. The second sealing plate 16 is a component fitted to the opening 12h2 on the second side of the housing body 12. The first sealing plate 14 and the second sealing plate 16 engage with the periphery of the openings 12h1 and 12h2 of the housing body 12. The first sealing plate 14 and the second sealing plate 16 are generally rectangular plate-shaped components. After the stacked electrode body 20 is housed in the housing body 12, the first sealing plate 14 and the second sealing plate 16 engage with the periphery of the openings 12h1 and 12h2. The first sealing plate 14 and the second sealing plate 16, which are engaged with the housing body 12, are opposite each other in the width direction X. A positive terminal 30 is provided on the first sealing plate 14. A negative 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 first sealing plate 14 and the second sealing plate 16 and the stacked electrode body 20.

[0032] In this embodiment, such as Figure 1 As shown, an exhaust valve 13 is provided on the bottom surface 12aa. The exhaust valve 13 is configured to break when the pressure inside the housing 10 reaches a predetermined value, thereby venting the gas inside the housing 10 to the outside. Furthermore, in this embodiment, there is one exhaust valve 13, but there may be two or more. The exhaust valve 13 may also be provided on a surface other than the bottom surface 12aa, such as the side surface 12b, the top surface 12ab, etc. The area of ​​the exhaust valve 13 is arbitrary. In this embodiment, the exhaust valve 13 has a cross-shaped cut. However, the shape of the exhaust valve 13 is not particularly limited. The exhaust valve 13 may be, for example, a linear cut (only vertical or horizontal lines), or a conventionally known elliptical valve (with a cut inside), circular valve (with a cut inside), etc. Furthermore, the size (length, depth) of the cut is arbitrary, and can be appropriately determined, for example, by considering the pressure resistance of the housing 10.

[0033] In this embodiment, such as Figure 1 As shown, an injection hole 17 is formed on the first sealing plate 14. However, the injection hole 17 may also be formed on the second sealing plate 16. The injection hole 17 may also be formed on the housing body 12. In addition, in this embodiment, the injection hole 17 is formed on a different surface from the exhaust valve 13, but it may also be formed on the same surface as the exhaust valve 13. The injection hole 17 is used to inject electrolyte 15 into the interior of the housing 10 after the first sealing plate 14 and the second sealing plate 16 are assembled into the housing body 12 (see reference). Figure 2 The injection hole 17 is sealed by the sealing component 18 after the electrolyte 15 is injected.

[0034] The positive terminal 30 is disposed on the first sealing plate 14. The positive terminal 30 is an example of the first terminal in this invention. The positive terminal 30 is preferably made of metal, for example, more preferably aluminum or an aluminum alloy. The positive terminal 30 is connected inside the housing 10 to the positive electrode plate 22 (also see below) via the positive current collector 32. Figure 3 Electrical connection. Furthermore, the positive terminal 30 can also be installed, for example, via an insulator (not shown) or a washer (not shown).

[0035] The negative terminal 40 is disposed on the second sealing plate 16. The negative terminal 40 is an example of the second terminal in this invention. The negative terminal 40 is preferably made of metal, for example, more preferably of copper or a copper alloy. The negative terminal 40 is connected inside the housing 10 to the negative electrode plate 24 (also see below) via the negative current collector 42. Figure 3 Electrical connection. Additionally, the negative terminal 40 can also be installed via, for example, an insulator (not shown) or a washer (not shown).

[0036] The electrolyte 15 and the stacked electrode body 20 are housed together inside the housing 10. A portion of the electrolyte 15 permeates the stacked electrode body 20. The electrolyte 15 is, for example, a non-aqueous electrolyte containing a non-aqueous solvent (organic solvent) and a supporting salt (electrolyte salt, such as lithium salt, sodium salt). Examples of non-aqueous solvents include carbonates such as ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. Examples of supporting salts include fluorinated lithium salts such as lithium hexafluoride phosphate (LiPF6). Typically, the electrolyte 15 is liquid, but it can also be gel-like. While not particularly limited, it is preferable that excess electrolyte 15 exists between the housing 10 and the stacked electrode body 20. In this embodiment, excess electrolyte 15 accumulates in the gap GP.

[0037] <Layered Electrode Body 20>

[0038] The stacked electrode body 20 is housed inside the housing body 12. In this embodiment, two stacked electrode bodies 20 are housed inside one housing body 12. The two stacked electrode bodies 20 are arranged in the thickness direction Y (see reference). Figure 5 Furthermore, the number of stacked electrode bodies 20 disposed inside a single housing body 12 can be one or more. Additionally, the stacked electrode bodies 20 can also be housed inside the housing 10 covered by a resin insulating sheet (electrode body holder).

[0039] Figure 3 This is a cross-sectional view of the stacked electrode body 20. (Example) Figure 3 As shown, the stacked electrode body 20 includes multiple positive electrode plates 22, multiple negative electrode plates 24 with different polarities from the positive electrode plates 22, a separator 26, and an adhesive layer 28 sandwiched 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 also be provided between either the positive electrode plate 22 or the negative electrode plate 24 and the separator 26. The positive electrode plate 22 and the negative electrode plate 24 are located inside the cylindrical housing body 12 and on a pair of opposing side portions 12b (see reference). Figure 1 The positive electrode 22 and the negative electrode 24 are arranged alternately, facing each other. The separator 26 is formed in a strip shape. The separator 26 is arranged between the positive electrode 22 and the negative electrode 24 by being folded back in sequence. In the positive electrode 22 and the negative electrode 24, the surfaces of the positive electrode 22 and the negative electrode 24 that face the pair of wide surfaces 12b are overlapped by the separator 26. The separator 26 is folded into a so-called zigzag shape. Here, the stacking direction of the multiple positive electrode 22 and the multiple negative electrode 24 is the thickness direction Y. In the following description, the thickness direction Y is also referred to as the stacking direction Y.

[0040] Figure 4 This is a schematic diagram showing the positive electrode plate 22 and the negative electrode plate 24. Furthermore, in Figure 4 In the text, the diaphragm 26 is omitted (see reference). Figure 3 The illustration is shown below. Figure 4 As shown, 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, the positive electrode plate 22 and the negative electrode plate 24 of the stacked electrode body 20 overlap in an opposing manner while the positive electrode active material layer 22b and the negative electrode active material layer 24b are insulated from each other. The positive electrode active material layer 22b and the negative electrode active material layer 24b are separated by a separator 26 (see reference). Figure 3 And insulation. In this embodiment, such as Figure 3As shown, the side of the laminated electrode body 20 on which the adhesive tape 29 (described later) is fixed is designated as side surface 20Rr. In this embodiment, the rear surface of the laminated electrode body 20 is side surface 20Rr. Furthermore, the front surface of the laminated electrode body 20 is designated as side surface 20F.

[0041] like Figure 4 As shown, typically, the positive electrode plate 22 includes a positive electrode current collector foil 22a and a positive electrode active material layer 22b on at least one surface (here, both surfaces) on which the positive electrode current collector foil 22a is formed. 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 can be the same as conventional materials and is not particularly limited. One example of a positive electrode active material is a lithium transition metal composite oxide containing nickel, cobalt, and manganese. The positive electrode active material layer 22b may also contain any component other than the positive electrode active material, such as a binder, conductive material, etc. Figure 3 As shown, the positive electrode plate 22 is bonded to the separator 26 on both sides in the stacking direction Y via an adhesive layer 28. Figure 4 As shown, an uncoated portion 22c without a positive electrode active material layer 22b is formed at one end of the positive electrode current collector foil 22a in the width direction X (here, the right side of the width direction X).

[0042] Typically, the negative electrode plate 24 includes a negative electrode current collector foil 24a and a negative electrode active material layer 24b on at least one surface (here, both surfaces) on which the negative electrode current collector foil 24a is formed. The negative electrode current collector foil 24a is preferably a metal foil. In this embodiment, the negative electrode current collector foil 24a is, for example, made of 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 can be the same as conventional materials 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 also contain any components other than the negative electrode active material, such as binders, thickeners, dispersants, etc. Figure 3 As shown, the negative electrode plate 24 is bonded to the separator 26 on both sides in the width direction X via an adhesive layer 28. Figure 4 As shown, in this embodiment, an uncoated portion 24c without a negative electrode active material layer 24b is formed at one end of the negative electrode current collector foil 24a in the width direction X (here, the left side in the width direction X).

[0043] Figure 3The separator 26 shown is an insulating sheet with multiple tiny through-holes that allow charge carriers to pass through. By sandwiching 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 can be prevented, and charge carriers (e.g., lithium ions) can move between the positive electrode plate 22 and the negative electrode plate 24. The thickness of the separator 26 is not particularly limited, but in this embodiment it is about 20 μm.

[0044] like Figure 3 As shown, the diaphragm 26 has a first end 26e1 and a second end 26e2. The first end 26e1 is disposed on the outer periphery of a stacked electrode body 20 formed by alternating positive electrode plates 22 and negative electrode plates 24. The second end 26e2 is disposed on the outer periphery of the stacked electrode body 20 formed by alternating positive electrode plates 22 and negative electrode plates 24, and is fixed to the outer periphery of the stacked electrode body 20 by tape 29 in a manner overlapping the outer side of the first end 26e1. The first end 26e1 and the second end 26e2 are located rearward from the portion formed by the stacking of positive electrode plates 22 and negative electrode plates 24. The first end 26e1 and the second end 26e2 extend in the vertical direction Z by folding back approximately at right angles from the portion formed by the stacking of positive electrode plates 22 and negative electrode plates 24 on the outer periphery. That is, the first end 26e1 and the second end 26e2 are generally L-shaped when viewed from the side. exist Figure 3 In the thickness direction Y, a gap is formed between the first end 26e1 and the second end 26e2, but this gap is actually quite narrow. At the portion of the laminated electrode body 20 that is fixed to the outer periphery by the tape 29 (described later), the second end 26e2 of the diaphragm 26 is longer than the first end 26e1. Therefore, the lower end 26eD of the second end 26e2 is located below the first end 26e1. In this embodiment, when the pair of opposing side portions 12b of the housing body 12 are placed facing vertically, the diaphragm 26 is located on the bottom portion 12aa side of the housing body 12 (refer to...). Figure 2 The electrode is folded back to cover the negative electrode plate 24. At this time, the positive electrode plate 22 is not covered by the diaphragm 26 on the bottom surface 12aa side. In the stacked electrode body 20, the portion where the first end 26e1 and the second end 26e2 are formed is formed in the thickness direction Y by an amount that is thicker than the other portion of the stacked electrode body 20 than 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 stacked electrode body 20. Although not particularly limited, in this embodiment, the length of the first end 26e1 and the second end 26e2 in the vertical direction Z is about 3 to 30 mm. In addition, for ease of explanation, the first end 26e1 and the second end 26e2 are exaggeratedly shown in the diagram.

[0045] The diaphragm 26 includes one or more heat-resistant layers (HRLs) 26a comprising a resin-based diaphragm substrate and a metal oxide such as alumina (Al2O3). In this embodiment, the diaphragm 26 has a heat-resistant layer 26a formed on at least one side. Here, at the portion of the laminated electrode body 20 that is fixed by the tape 29 described later, a heat-resistant layer 26a is formed on the inner side of the second end 26e2 of the diaphragm 26.

[0046] Typically, the heat-resistant layer 26a contains inorganic fillers and a heat-resistant adhesive. By incorporating the heat-resistant layer 26a, thermal shrinkage of the diaphragm 26 can be suppressed, contributing to improvements in the energy storage device 100 (see reference). Figure 1 Safety of the membrane 26 is ensured. As inorganic fillers, ceramic particles such as alumina, zirconium oxide, boehmite, aluminum hydroxide, silica, and titanium dioxide are preferred. From the viewpoint of suppressing thermal shrinkage of the membrane 26, aluminum-containing compounds are particularly preferred. As adhesives for the heat-resistant layer, examples include acrylic resins, fluorinated resins, urethane resins, ethylene vinyl acetate resins, and epoxy resins.

[0047] Figure 6 This is a rear view of the stacked electrode body 20. As described above, tape 29 secures the second end 26e2. Figure 6 As shown, tape 29 is composed of a first tape 29a, a second tape 29b, and a third tape 29c intermittently arranged 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 arranged in the width direction X. In this embodiment, tape 29 is composed of the first tape 29a, the second tape 29b, and the third tape 29c, but the number of tapes constituting 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. Figure 5 As shown, in this embodiment, the lower end 29D of the tape 29 is positioned above the liquid surface 15a of the electrolyte 15. The thickness of the tape 29 is not particularly limited, but in this embodiment, it is approximately 50 μm. Figure 3 As shown, in the portion of the laminated electrode body 20 where the adhesive tape 29 is fixed, the length of the laminated electrode body 20 in the thickness direction Y is relatively long. The portion where the first end 26e1, the second end 26e2, and the adhesive tape 29 overlap in the lamination direction Y is the thickest portion of the laminated electrode body 20. In the following description, the portion where the first end 26e1, the second end 26e2, and the adhesive tape 29 overlap in the lamination direction Y of the laminated electrode body 20 will be referred to as the "thickest portion".

[0048] Figure 5 This is a schematic diagram showing the interior of the main body 12 of the casing. (For example...) Figure 5 As shown, two stacked electrode bodies 20 are arranged in the thickness direction Y. Figure 5 As shown, when the two stacked electrode bodies 20 are vertically placed with one pair of opposing side portions 12b of the housing body 12, the lower end 26eD of the second end 26e2 of the diaphragm 26, which is fixed by tape 29, is positioned above the electrolyte surface 15a on the outside of the stacked electrode bodies 20 within the housing body 12. The phrase "when the one pair of opposing side portions 12b are vertically placed" refers to... Figure 5 As shown, this refers to the case where the housing body 12 is positioned such that one of the pair of narrow surfaces 12a (here, the bottom surface 12aa) is positioned downwards, and the pair of wide surfaces (a pair of opposing side surfaces) 12b are positioned approximately perpendicular to one of the pair of narrow surfaces 12a. Here, the height of the electrolyte level 15a varies depending on the SOC (States of Charge) of the energy storage device 100. In this embodiment, when the SOC of the energy storage device 100 is 75% or higher, the lower end 26eD of the second end 26e2 is positioned above the electrolyte level 15a. That is, when the SOC of the energy storage device 100 is 75% or higher, the first end 26e1 and the second end 26e2 of the diaphragm 26, which is fixed by the tape 29, are positioned above the electrolyte level 15a. Furthermore, for ease of explanation, Figure 5 In the diagram, a gap is shown between the stacked electrode body 20 and the side portion 12b, but the stacked electrode body 20 and the side portion 12b can also be in contact. Furthermore, the phrase "SOC of 75% or more" refers to the situation where the energy storage device 100 has an SOC of 75% or more when it is in a new condition or in a condition close to new.

[0049] like Figure 5 As shown, the side 20Rr of the two stacked electrode bodies 20 on the side where the adhesive tape 29 is fixed is arranged facing the same side relative to the pair of opposing side portions 12b of the housing body 12. In this embodiment, the side 20Rr of each of the two stacked electrode bodies 20 is arranged facing the side portion 12bb. Alternatively, the side 20Rr of each of the two stacked electrode bodies 20 may also be arranged facing the side portion 12ba.

[0050] like Figure 2 As shown, the positive electrode plate 22 has a positive electrode tab 23 extending towards the first sealing plate 14 and connected to the positive terminal 30. Multiple positive electrode plates 22 each have a positive electrode tab 23. The positive electrode tab 23 is a positive current collector foil 22a (see reference). Figure 4 From the positive electrode active material layer 22b (reference) Figure 4 ) and negative electrode active material layer 24b (refer to) Figure 4 The overlapping area extends outwards. The positive electrode tab 23 extends through the uncoated portion 22c (see reference). Figure 4 The positive electrode tab 23 is formed by overlapping. The positive electrode tab 23 is electrically connected to the positive terminal 30 via the positive current collector 32. The negative electrode plate 24 has a negative electrode tab 25 extending towards the second sealing plate 16 and connected to the negative terminal 40. Multiple negative electrode plates 24 each have a negative electrode tab 25. The negative electrode tab 25 is a negative current collector foil 24a (see reference). Figure 4 From the negative electrode active material layer 24b (refer to) Figure 4 ) and negative electrode active material layer 24b (refer to) Figure 4 The overlapping area extends outwards. The negative electrode tab 25 extends through the uncoated portion 24c (refer to...). Figure 4 The negative electrode tab 25 is formed by overlapping. The negative electrode current collector 42 is electrically connected to the negative terminal 40.

[0051] Figure 3 The adhesive layer 28 shown is sandwiched between at least one of the positive electrode plate 22 and the negative electrode plate 24 and the separator 26, bonding the two together. This suppresses positional misalignment of the positive electrode plate 22 and the negative electrode plate 24. Furthermore, it suppresses lamination misalignment of the stacked electrode body 20. Figure 3 In the stacking direction Y, the two sides of the positive electrode plate 22 and the two sides of the negative electrode plate 24 are bonded to the opposing diaphragm 26 via the adhesive layer 28.

[0052] Typically, adhesive layer 28 is a layer containing adhesive in the highest possible mass proportion. Examples of adhesives include fluoropolymers, acrylic resins, urethane resins, ethylene vinyl acetate, and epoxy resins. The adhesive can be of the same type as the heat-resistant layer adhesive described above, or it can be different. Adhesive layer 28 may also further contain other materials (e.g., inorganic fillers).

[0053] The structure of the energy storage device 100 according to this embodiment has been described above. However, when the energy storage device 100 is charged and discharged, the positive electrode active material layer 22b (refer to...) Figure 4 ) and negative electrode active material layer 24b (refer to Figure 4The stacked electrode body 20 expands and contracts due to the expansion and contraction of the electrolyte. When the stacked electrode body 20 expands, a portion of the electrolyte 15 impregnated within it is forced out. When the stacked electrode body 20 contracts, a portion of the electrolyte 15 is absorbed by it. If this process of force-out and absorption of the electrolyte 15 is repeated, areas of insufficient electrolyte 15 (so-called liquid drying) may occur due to the shape of the stacked electrode body 20. If liquid drying occurs, the battery characteristics of the energy storage device 100 deteriorate. The inventors of this application aim to suppress battery characteristic deterioration by repeatedly force-out and absorption of the electrolyte 15.

[0054] Next, the electrolyte 15 inside the energy storage device 100 during charging and discharging will be described.

[0055] First, the charging of the energy storage device 100 will be explained. The charging of the energy storage device 100 is carried out using existing, known methods. Figure 7 This is a schematic diagram showing the interior of the housing body 12 when the energy storage device 100 is being charged. When the energy storage device 100 is being charged, as described above, the positive electrode active material layer 22b (refer to...) Figure 4 ) and negative electrode active material layer 24b (refer to Figure 4 Expansion. As described above, the positive electrode plate 22 and the negative electrode plate 24 are stacked along the thickness direction Y. At this time, as... Figure 7 As shown, the positive electrode 22 and the negative electrode 24 are bent in a manner that extends outward toward the stacked electrode body 20. Therefore, the stacked electrode body 20 expands in a manner that extends in the thickness direction Y.

[0056] If the stacked electrode body 20 expands, it pushes against the pair of opposing side portions 12b outward in the thickness direction Y. At this time, the stacked electrode body 20 receives vertical resistance from the pair of side portions 12b. Here, the thickest part of the rear stacked electrode body 20 (hereinafter referred to as "rear stacked electrode body 20") is opposite to the side portion 12bb, so the tape 29 contacts the side portion 12bb. In addition, the side portion 20F of the rear stacked electrode body 20 contacts the tape 29 of the front stacked electrode body 20 (hereinafter referred to as "front stacked electrode body 20"). Therefore, the rear stacked electrode body 20 is easily subjected to an inward force in the thickness direction Y near its thickest part. Here, "near the thickest part" refers to the area within the laminated electrode body 20 that includes at least one of the first end 26e1, the second end 26e2, or the tape 29. In this embodiment, "near the thickest part" refers to the position of the lower end 29D of the tape 29 in the vertical direction Z and the area above the lower end 29D of the tape 29 in the laminated electrode body 20.

[0057] The tape 29 of the front laminated electrode body 20 contacts the rear laminated electrode body 20. Furthermore, the most bulging portion of the side surface 20F of the front laminated electrode body 20 contacts the side surface 12ba. Here, the side surface 12ba contacts the side surface 20F near the center in the vertical direction Z. Therefore, in the front laminated electrode body 20, the side surface 20F is easily subjected to an inward force in the thickness direction Y near the center in the vertical direction Z, and the side surface 20Rr is easily subjected to an inward force in the thickness direction Y near its thickest portion. Furthermore, in the region of the laminated electrode body 20 below the tape 29, the first end 26e1, the second end 26e2, and the tape 29 are absent, thus forming a thinner layer in the thickness direction Y compared to the region of the laminated electrode body 20 excluding this region. Therefore, the region of the laminated electrode body 20 below the tape 29 experiences less inward force in the thickness direction Y.

[0058] If a force is applied to each of the two stacked electrode bodies 20 towards the inside in the thickness direction Y, the electrolyte 15 impregnated in the stacked electrode bodies 20 will be forced out. Because the stacked electrode bodies 20 are pressed towards the inside in the thickness direction Y, the electrolyte 15 is forced out towards the outside in the width direction X. In this embodiment, because a force is applied near the thickest part of the stacked electrode body 20, the electrolyte 15 impregnated near the thickest part is easily forced out. The forced-out electrolyte 15 accumulates inside the housing body 12. More specifically, the forced-out electrolyte 15 accumulates in the lower part of the housing body 12 due to gravity. Therefore, as... Figure 2As shown, electrolyte 15 accumulates in the lower part of the housing body 12. At this time, electrolyte 15 also accumulates in the gaps GP on the right and left sides of the stacked electrode body 20 (see reference). Figure 2 In the laminated electrode body 20, the area below the tape 29 experiences less force towards the inside in the thickness direction Y, making it more difficult to expel the electrolyte 15 compared to the area near the thickest part.

[0059] Next, the situation when the energy storage device 100 is discharged will be explained. The energy storage device 100 discharges, for example, when a vehicle (not shown) equipped with the energy storage device 100 is in motion. Figure 8 This is a schematic diagram showing the interior of the main body 12 of the casing when the energy storage device 100 is discharging. When the energy storage device 100 discharges, the positive electrode active material layer 22b (refer to...) will... Figure 4 ) and negative electrode active material layer 24b (refer to Figure 4 Contraction. At this time, as... Figure 8 As shown, the positive electrode 22 and the negative electrode 24 are bent inwards towards the thickness direction Y. Therefore, the stacked electrode body 20 shrinks in the thickness direction Y.

[0060] If the stacked electrode body 20 contracts, the electrolyte 15 accumulated inside the housing body 12 is absorbed by the stacked electrode body 20. In this embodiment, the diaphragm 26 is installed such that it covers 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 diaphragm 26 in the width direction X. Therefore, the stacked electrode body 20 mainly absorbs the electrolyte 15 accumulated in the gap GP between the left and right sides of the stacked electrode body 20 (see reference). Figure 2 The electrolyte 15 is stored in the lower part of the housing body 12. Since the electrolyte 15 is stored in the lower part of the stacked electrode body 20, it is absorbed from the lower part of the stacked electrode body 20. Here, as described above, when the energy storage device 100 is charged, the electrolyte 15 that has permeated near the thickest part is forced out. Therefore, the electrolyte 15 absorbed from the lower part of the stacked electrode body 20 slowly permeates upwards towards the vicinity of the thickest part.

[0061] As described above, the energy storage device 100 according to this embodiment houses a stacked electrode body 20 and an electrolyte 15 within a housing body 12. In the stacked electrode body 20, a positive electrode plate 22 and a negative electrode plate 24 are stacked, with a diaphragm 26 sandwiched between the positive and negative electrode plates 22 and folded back. The positive and negative electrode plates 22 and 24 are positioned opposite a pair of opposing side portions 12b inside the cylindrical housing body 12, and are arranged alternately. When the energy storage device 100 is charged and discharged, the electrolyte 15 impregnated in the stacked electrode body 20 is extruded or absorbed primarily in the width direction X. That is, during charging and discharging of the energy storage device 100, the electrolyte 15 is extruded into the gap GP, and the electrolyte 15 accumulated in the gap GP is absorbed by the stacked electrode body 20. A first end 26e1 and a second end 26e2 are formed on the stacked electrode body 20. Adhesive tape 29 is fixed to the second end 26e2. Therefore, when the energy storage device 100 is charged, the stacked electrode body 20 expands and comes into contact with the pair of side portions 12b. A relatively large force is applied near the thickest part of the stacked electrode body 20. Therefore, the electrolyte 15 is easily expelled from near the thickest part of the stacked electrode body 20. Furthermore, the lower end 26eD of the second end 26e2 is positioned above the liquid surface 15a of the electrolyte 15. Therefore, the electrolyte 15 expelled from near the thickest part due to the charging of the energy storage device 100 accumulates in the lower part of the interior of the housing body 12 due to gravity. Subsequently, if the stacked electrode body 20 contracts due to discharge, electrolyte 15 is absorbed from the lower part of the stacked electrode body 20, and the absorbed electrolyte 15 slowly rises towards the vicinity of the thickest part. That is, electrolyte 15 is forced out from the vicinity of the thickest part and absorbed from the lower part of the stacked electrode body 20 towards the vicinity of the thickest part, so that electrolyte 15 moves in a manner that covers the entire stacked electrode body 20. As a result, the occurrence of liquid drying in the stacked electrode body 20 can be suppressed. Therefore, the degradation of battery characteristics caused by liquid drying during charging and discharging in the energy storage device 100 can be suppressed.

[0062] In the energy storage device 100 based on this embodiment, the separator 26 is folded back on the bottom part 12aa side of the housing body 12 to cover the negative electrode plate 24. Here, among 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 significantly with the insertion and extraction of lithium ions. Therefore, during the charging and discharging of the energy storage device 100, the expansion and contraction of the negative electrode plate 24 is greater than that of the positive electrode plate 22, and the force applied to the negative electrode plate 24 is greater. Therefore, during the charging and discharging of the energy storage device 100, the negative electrode active material layer 24b is prone to peeling off in the negative electrode plate 24. In this embodiment, since the bottom part 12aa side of the negative electrode plate 24 is covered by the separator 26, even if the negative electrode active material layer 24b peels off, the negative electrode active material layer 24b still accumulates on the separator 26 covering the negative electrode plate 24. Therefore, it is possible to suppress the situation where the stripped negative electrode active material layer 24b, as a conductive foreign object, becomes free inside the energy storage device 100.

[0063] The energy storage device 100 according to the first embodiment has been described above. However, the first embodiment described above is only an example, and the present invention can be implemented in various other ways.

[0064] <Second Embodiment>

[0065] Figure 9 It is related to the second embodiment. Figure 3 Corresponding figures. In the following description of the second embodiment, components that perform the same functions as in the first embodiment are referred to using the same reference numerals as in the first embodiment. Furthermore, repeated descriptions are omitted or simplified.

[0066] like Figure 9 As shown, the stacked electrode body 20A includes a diaphragm 26A. In this embodiment, the diaphragm 26A is provided on one pair of opposing side portions 12b of the housing body 12 (see reference). Figure 1 When placed vertically, the diaphragm 26A is located on the bottom part 12aa side of the main body 12 (refer to...). Figure 2 The plate is folded back to cover the positive electrode plate 22. At this time, the negative electrode plate 24 is not covered by the diaphragm 26A on the bottom surface 12aa side.

[0067] Based on the energy storage device 100 according to the second embodiment, the diaphragm 26A is folded back on the bottom part 12aa side of the housing body 12 to cover the positive electrode plate 22. Here, among the positive electrode plate 22 and the negative electrode plate 24, it is known that the negative electrode plate 24 absorbs the electrolyte 15 faster. In this embodiment, since the negative electrode plate 24 on the bottom part 12aa side is not covered by the diaphragm 26A, the surface area of ​​the negative electrode plate 24 in contact with the electrolyte 15 is larger than the surface area of ​​the positive electrode plate 22 in contact with the electrolyte 15. As a result, the amount of electrolyte 15 absorbed by the stacked electrode body 20A increases. That is, when absorbing the electrolyte 15, the electrolyte 15 is more easily distributed throughout the entire stacked electrode body 20A. Therefore, it is possible to further suppress the occurrence of liquid drying in the stacked electrode body 20.

[0068] The invention disclosed herein has been described above in various ways. Unless otherwise specified, the embodiments described herein are not intended to limit the invention. Furthermore, the embodiments of the invention disclosed herein can be modified in various ways, and unless special problems arise, the constituent elements and processes mentioned herein can be appropriately omitted or appropriately combined.

[0069] As described above, the disclosures contained in the following items are included in this specification.

[0070] Item 1:

[0071] A secondary battery, comprising:

[0072] An electrode body comprising a diaphragm, a plurality of first electrode plates, and a plurality of second electrode plates having a polarity different from that of the first electrode plates;

[0073] Electrolyte;

[0074] The housing body is cylindrical and houses the electrode body and the electrolyte.

[0075] A first sealing plate, which is installed at the opening on the first side of the aforementioned housing body; and

[0076] The second sealing plate is installed at the opening on the second side of the aforementioned housing body.

[0077] in,

[0078] The aforementioned shell body has a pair of opposing side portions.

[0079] The aforementioned plurality of first electrode plates and the aforementioned plurality of second electrode plates are located inside the aforementioned housing body and are opposed to the aforementioned pair of opposing side portions, and the aforementioned first electrode plates and the aforementioned second electrode plates are arranged alternately.

[0080] The aforementioned diaphragm is strip-shaped and is sequentially folded back between the first electrode plate and the second electrode plate, thereby being disposed between the first electrode plate and the second electrode plate.

[0081] The first end of the aforementioned diaphragm is disposed on the outer periphery of the aforementioned electrode body, which is formed by alternating opposition of the aforementioned plurality of first electrode plates and the aforementioned plurality of second electrode plates.

[0082] The second end of the aforementioned diaphragm is disposed on the outer periphery of the electrode body, which is formed by alternating opposition of the plurality of first electrode plates and the plurality of second electrode plates, and is fixed to the outer periphery of the electrode body by adhesive tape in a manner that overlaps with the outer side of the first end.

[0083] When the pair of opposing side portions of the housing body are placed vertically, the lower end of the tape is positioned above the electrolyte surface on the outside of the electrode body inside the housing body.

[0084] Item 2:

[0085] In the secondary battery described in item 1,

[0086] The first electrode plate mentioned above is a positive electrode plate on which a layer of positive active material is formed on the positive current collector foil.

[0087] The second electrode plate mentioned above is a negative electrode plate on which a layer of negative electrode active material is formed on the negative electrode current collector foil.

[0088] When the pair of opposing side portions of the main body of the housing are placed vertically, the diaphragm is folded back on the bottom side of the main body of the housing in a manner that covers the negative electrode plate.

[0089] Item 3:

[0090] In the secondary battery described in item 1,

[0091] The first electrode plate mentioned above is a positive electrode plate on which a layer of positive active material is formed on the positive current collector foil.

[0092] The second electrode plate mentioned above is a negative electrode plate on which a layer of negative electrode active material is formed on the negative electrode current collector foil.

[0093] When the pair of opposing side portions of the main body of the housing are placed vertically, the diaphragm is folded back on the bottom side of the main body of the housing in a manner that covers the positive electrode plate.

Claims

1. A secondary battery, comprising: An electrode body comprising a diaphragm, a plurality of first electrode plates, and a plurality of second electrode plates having a polarity different from that of the first electrode plates; Electrolyte; The housing body is cylindrical and houses the electrode body and the electrolyte. A first sealing plate, which is installed at an opening on a first side of the housing body; as well as A second sealing plate, which is installed at the opening on the second side of the housing body. The secondary battery is characterized in that... The main body of the housing has a pair of opposing side portions. The plurality of first electrode plates and the plurality of second electrode plates are positioned inside the housing body opposite the pair of opposing side portions, and the first electrode plates and the second electrode plates are arranged alternately. The diaphragm is strip-shaped and is sequentially folded back between the first electrode plate and the second electrode plate, thereby being disposed between the first electrode plate and the second electrode plate. The first end of the diaphragm is disposed on the outer periphery of the electrode body, which is formed by alternating opposition of the plurality of first electrode plates and the plurality of second electrode plates. The second end of the diaphragm is disposed on the outer periphery of the electrode body, which is formed by alternating opposition of the plurality of first electrode plates and the plurality of second electrode plates, and is fixed to the outer periphery of the electrode body by adhesive tape in a manner that overlaps with the outer side of the first end. When the pair of opposing side portions of the housing body are placed vertically, the lower end of the tape is positioned above the electrolyte surface on the outside of the electrode body inside the housing body.

2. The secondary battery according to claim 1, characterized in that, The first electrode plate is a positive electrode plate on which a layer of positive active material is formed on the positive current collector foil. The second electrode plate is a negative electrode plate on which a layer of negative electrode active material is formed on the negative electrode current collector foil. When the pair of opposing side portions of the housing body are placed vertically, the diaphragm is folded back on the bottom side of the housing body to cover the negative electrode plate.

3. The secondary battery according to claim 1, characterized in that, The first electrode plate is a positive electrode plate on which a layer of positive active material is formed on the positive current collector foil. The second electrode plate is a negative electrode plate on which a layer of negative electrode active material is formed on the negative electrode current collector foil. When the pair of opposing side portions of the housing body are placed vertically, the diaphragm is folded back on the bottom side of the housing body to cover the positive electrode plate.

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