Non-aqueous electrolyte secondary battery

Abstract

A nonaqueous electrolyte secondary battery includes an electrode body including a positive electrode plate and a negative electrode plate, a square-shaped exterior body having an opening and housing the electrode body, a sealing plate closing the opening, and an electrode terminal provided on the sealing plate. The positive electrode plate includes a positive electrode core and a positive electrode active material coated on both surfaces of the positive electrode core, and the circumference of the coated portion of the positive electrode active material on the positive electrode core per unit capacity of the battery is 0.28 m / Ah or less.

Description

[0001] This application is a divisional application of the application filed on February 8, 2021 (entering the Chinese national phase on September 15, 2022), with international application number PCT / JP2021 / 004630 (national application number: 202180022097.4) and invention title "Non-aqueous electrolyte secondary battery". Technical Field

[0002] This disclosure relates to a non-aqueous electrolyte secondary battery. Background Technology

[0003] Non-aqueous electrolyte secondary batteries such as lithium-ion batteries have a structure in which the electrode body is housed in an outer casing with an opening, and the opening is sealed with a sealing plate. The electrode body is structured as follows: the positive electrode and the negative electrode are overlapped in such a way that a separator is sandwiched between the positive electrode and the negative electrode.

[0004] In recent years, the demand for lithium-ion batteries for automotive applications has been gradually increasing. These batteries, especially those used in EVs, are required to possess a variety of characteristics, including high capacity, fast charging capability, high capacity recovery rate, and high safety. For example, if a lithium-ion battery is charged and the vehicle is stored away for a period of time without being used, the battery capacity will decrease. Therefore, it is necessary to improve the characteristics that prevent this capacity reduction.

[0005] Patent Document 1: Japanese Patent Publication No. 2019-160587

[0006] Patent Document 2: Japanese Patent Publication No. 2012-43752 Summary of the Invention

[0007] In the past, improvements were made to address the reduction in battery capacity caused by long-term storage. However, with the increasing performance of lithium-ion batteries for EVs, there is a need to further improve their characteristics.

[0008] The non-aqueous electrolyte secondary battery disclosed herein includes: an electrode body comprising a positive electrode plate and a negative electrode plate; a square outer casing having an opening and housing the electrode body; a sealing plate closing the opening; and electrode terminals disposed on the sealing plate. The non-aqueous electrolyte secondary battery is configured such that the positive electrode plate comprises a positive electrode core and a positive electrode active material coated on at least one surface of the positive electrode core, wherein the perimeter of the coated portion of the positive electrode active material on the positive electrode core per unit capacity of the battery is less than 0.28 m / Ah. More preferably, the perimeter of the coated portion of the positive electrode active material on the positive electrode core per unit capacity of the battery is less than 0.11 m / Ah.

[0009] It should be noted that when positive active material is coated on both sides of the positive electrode core, the perimeter of the coated portion of the positive active material on the positive electrode core refers to the sum of the perimeters of the two sides.

[0010] Alternatively, the electrode body may have a shape formed by winding the positive and negative electrode plates together after they are positioned opposite each other.

[0011] Alternatively, the negative electrode plate may include a negative electrode core and a negative electrode active material coated on the negative electrode core. In the electrode body, the positive electrode plate and the negative electrode plate are overlapped by a diaphragm sandwiched between the positive electrode plate and the negative electrode plate. In the negative electrode plate, the area of ​​the portion of the negative electrode active material coating that is opposite to the coating portion of the positive electrode active material is 85% to 95% of the total area of ​​the coating portion of the negative electrode active material.

[0012] Alternatively, the non-aqueous electrolyte secondary battery may include one or more of the aforementioned electrode bodies, each of which has a capacity of 30 Ah or more.

[0013] Alternatively, the battery capacity per unit area of ​​the coating portion of the positive electrode active material on the positive electrode core can be 40 Ah / m³. 2 The above. When positive electrode active material is coated on both sides of the positive electrode core, the area of ​​the coated part of the positive electrode active material on the positive electrode core refers to the sum of the coating areas on both sides.

[0014] Preferably, the non-aqueous electrolyte secondary battery includes: a first current collector disposed between the electrode body and the sealing plate and connected to the electrode terminal; a second current collector disposed between the electrode body and the side wall of the square outer casing and connected to the first current collector; and a tab assembly extending from the electrode body toward the side wall and connected to the second current collector, the second current collector being a flat plate having a surface parallel to the side wall, the tab assembly having a positive tab assembly and a negative tab assembly, and on the connection side connected to the second current collector, the tab assembly being bent in a manner parallel to the side wall, the positive tab assembly being formed by bundling together a plurality of positive tabs extending from the positive electrode plate, and the negative tab assembly being formed by bundling together a plurality of negative tabs extending from the negative electrode plate.

[0015] In the non-aqueous electrolyte secondary battery of this disclosure, the perimeter of the coating portion of the positive electrode active material per unit capacity of the battery is less than 0.28 m / Ah. Therefore, it is possible to reduce the proportion of lithium ions present in the region opposite to the positive electrode in the negative electrode after charging that diffuse to the region not opposite to the positive electrode during storage. In this way, the battery capacity recovery rate can be improved. Attached Figure Description

[0016] Figure 1 This is a perspective view showing a non-aqueous electrolyte secondary battery according to an embodiment of the present disclosure;

[0017] Figure 2 yes Figure 1 A cross-sectional view of the battery;

[0018] Figure 3 This is a diagram illustrating the second current collector according to an embodiment of the present disclosure;

[0019] Figure 4 This is a top view of the positive electrode plate according to an embodiment of the present disclosure;

[0020] Figure 5 This is a top view of the negative electrode plate according to the embodiments of this disclosure;

[0021] Figure 6 This is a top view of the electrode body according to the embodiments of this disclosure;

[0022] Figure 7 It is a schematic three-dimensional view showing the positive and negative plates of a non-aqueous electrolyte secondary battery;

[0023] Figure 8 It is a three-dimensional diagram that schematically shows the state of the negative electrode after charging, without showing the positive electrode.

[0024] Figure 9 It is a three-dimensional diagram schematically showing the state of the negative electrode plate after charging but not discharging, and instead left for a long time without showing the positive electrode plate.

[0025] Figure 10 This is a schematic diagram showing the process from [the point where] the positive electrode is not shown. Figure 9 A three-dimensional diagram of the state of the negative electrode plate after it has just been discharged.

[0026] Figure 11 This is a schematic diagram showing the process from [the point where] the positive electrode is not shown. Figure 10 A 3D diagram of the negative electrode plate that has been placed in a certain state.

[0027] Figure 12 This diagram shows the area near the connection between the second current collector and the tab assembly before the tab assembly is bent;

[0028] Figure 13 This diagram shows the area near the connection between the second current collector and the tab assembly after the tab assembly is bent.

[0029] Figure 14This is a perspective view showing the electrode body connected to the second current collector before bending the electrode assembly;

[0030] Figure 15 This is a diagram showing a group of electrode bodies including multiple electrode bodies;

[0031] Figure 16 This diagram shows a group of multiple electrode bodies and a sealing plate interconnected by a first current collector and a second current collector. Detailed Implementation

[0032] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings. The following description of preferred embodiments is merely illustrative of the nature of this disclosure and is not intended to limit the disclosure, its application, or its uses. In the following drawings, for the sake of simplicity, the same symbols are used to indicate constituent units that have substantially the same function.

[0033] <Battery Overall Structure>

[0034] Figure 1 This is a perspective view showing the non-aqueous electrolyte secondary battery involved in this disclosure. Figure 2 It is cut along a direction parallel to the paper. Figure 1 A cross-sectional view of the battery. (e.g.) Figure 1 , Figure 2 As shown, the non-aqueous electrolyte secondary battery 20 includes a battery casing 100, which is composed of a bottomed rectangular outer body 1 with an opening and a sealing plate 2 that closes the opening of the rectangular outer body 1.

[0035] The square outer casing 1 has a bottom 1a, a pair of first sidewalls 1b and 1c, and a pair of second sidewalls 1d and 1e. The pair of first sidewalls 1b and 1c are arranged in opposite directions. The pair of second sidewalls 1d and 1e are arranged in opposite directions. The pair of first sidewalls 1b and 1c are perpendicular to the long side of the sealing plate 2, and the area of ​​the pair of first sidewalls 1b and 1c is smaller than the area of ​​the pair of second sidewalls 1d and 1e.

[0036] The electrode body 3 and the electrolyte are housed together within a square outer casing 1. The electrode body 3 includes a positive electrode plate 4 and a negative electrode plate 5. In this embodiment, the electrode body 3 is a flat electrode body formed by winding the positive electrode plate 4 and the negative electrode plate 5 together with a diaphragm sandwiched between them. The winding axis of the electrode body 3 extends perpendicular to the first sidewalls 1b and 1c and parallel to the second sidewalls 1d and 1e. It should be noted that the electrode body 3 is not limited to a wound electrode body; for example, it can also be a stacked electrode body formed by stacking multiple positive electrode plates 4 and negative electrode plates 5 with a diaphragm sandwiched between them.

[0037] It should be noted that, in Figure 2In the diagram, symbol 10 represents the external insulating component arranged between the sealing plate 2 and the positive terminal 8, and symbol 12 represents the external insulating component arranged between the sealing plate 2 and the negative terminal 9. Symbol 11 represents the internal insulating component arranged between the sealing plate 2 and the first positive current collector 61, and symbol 13 represents the internal insulating component arranged between the sealing plate 2 and the first negative current collector 71. Symbol 14 represents a box-shaped or bag-shaped insulating sheet arranged inside the square outer casing 1 and housing the electrode body 3. Symbol 15 represents an electrolyte injection hole provided on the sealing plate 2. Symbol 16 represents a sealing component sealing the electrolyte injection hole 15. Symbol 17 represents an exhaust valve provided on the sealing plate 2.

[0038] In the non-aqueous electrolyte secondary battery 20, one side of the electrode body 3 extending along the winding shaft is designated as the positive electrode side, and the other side as the negative electrode side. The following mainly describes the positive electrode side, and sometimes omits the description of the negative electrode side.

[0039] <Structure of the Electrode>

[0040] like Figure 4 As shown, the positive electrode plate 4 is a long strip, and the positive electrode plate 4 has regions on both sides of the positive electrode core (e.g., aluminum foil) where a positive electrode active material layer 4a is formed. Multiple positive electrode tabs 4b protrude convexly from one end of the positive electrode core in the short-side direction of the positive electrode plate 4. The surface of the positive electrode core at one end of the positive electrode plate 4 in the short-side direction and its vicinity is covered by a protective layer 4c. That is, a protective layer 4c is provided with a certain width from one side (end) of the positive electrode plate 4 extending along the long-side direction toward the central axis of the long-side of the positive electrode plate 4. Furthermore, a protective layer is also provided at the root portion of the positive electrode tabs 4b. The protective layer 4c contains an insulating material; for example, the protective layer 4c can be a resin-based insulating layer, or it can be a layer containing inorganic oxides, i.e., ceramics, and a resin binder. As an example of the protective layer 4c, a layer containing alumina powder, a carbon material as a conductive material, and polyvinylidene fluoride as a binder can be cited. It should be noted that the 4c ​​protective layer can also be omitted.

[0041] like Figure 5 As shown, the negative electrode plate 5 is a long strip, and the negative electrode plate 5 has regions on both sides of the negative electrode core (e.g., copper foil) where a layer of negative electrode active material 5a is formed. Multiple negative electrode tabs 5b extend convexly from one end of the negative electrode core in the short side direction of the negative electrode plate 5.

[0042] like Figure 6 As shown, the positive electrode plate 4 and the negative electrode plate 5 overlap with a diaphragm sandwiched between them, and are wound together to form the electrode body 3. In the electrode body 3, the winding axis is along the direction connecting the positive electrode tab group 40 and the negative electrode tab group 50. Figure 6 Extending laterally, in the end face of the electrode body 3 perpendicular to the winding axis, the positive electrode tab group 40 is located on one end face, and the negative electrode tab group 50 is located on the other end face opposite to the aforementioned one end face. This positional relationship, as described above, easily prevents short circuits within the battery.

[0043] <Relationship between positive and negative plates>

[0044] In batteries, to ensure safety and achieve long lifespan, the capacity of the active material in the negative electrode is usually designed to be greater than that in the positive electrode. Moreover, in batteries where the positive and negative electrodes are overlapped in opposite directions, the coating area of ​​the active material in the positive electrode is designed to fall within the coating area of ​​the active material in the negative electrode, and the coating portion of the negative electrode active material is designed to extend beyond (protrude from) the coating portion of the positive electrode active material.

[0045] Figure 7 This diagram schematically illustrates the positive electrode 44 and negative electrode 55 of a non-aqueous electrolyte secondary battery. Active material is disposed on the entire surface of both the positive electrode 44 and the negative electrode 55. The area of ​​the negative electrode 55 is larger than that of the positive electrode 44, and the entire surface of the positive electrode 44 facing the negative electrode 55 is opposite to the surface of the negative electrode 55. However, there is a non-opposing region 57 on the negative electrode 55 that is not opposite to the positive electrode 44.

[0046] Figure 8 The diagram schematically shows the state of the negative electrode plate 55 immediately after charging (the positive electrode plate 44 is not shown). During charging, lithium ions 48 move from the positive electrode plate 44 to the negative electrode plate 55. The diffusion rate of lithium ions 48 within the negative electrode plate 55 is not very high; therefore, immediately after charging, lithium ions 48 are only present in the opposite region 56 to the positive electrode plate 44. It should be noted that... Figure 8 The outer perimeter line 46, representing the outer perimeter of the positive electrode plate 44, is shown by a dashed line. The opposite region 56 is the area enclosed by the outer perimeter line 46.

[0047] If it is left uncharged for a long time after charging, then... Figure 9 (Not shown with positive electrode 44) As shown, lithium ions 48 diffuse within the negative electrode 55, so that the probability of the presence of lithium ions 48 is equal in any part of the negative electrode 55. That is, the distribution ratio of lithium ions 48 is equal in both the relative region 56 and the non-relative region 57.

[0048] Figure 10(The positive electrode plate 44 is not shown.) The diagram shows the state of the negative electrode plate 55 after it has been charged but not discharged, and then fully discharged. During discharge, all the lithium ions 48 present in the relative region 56 move towards the positive electrode plate 44, thus eliminating lithium ions 48 from the relative region 56. On the other hand, the lithium ions 48 present in the non-relative region 57 cannot move to the positive electrode plate 44 during discharge due to the diffusion rate of lithium ions 48, and therefore remain in the non-relative region 57. If further processing is performed in this state, i.e., it is left to stand without charging or discharging, then... Figure 11 (Not shown with positive electrode plate 44) As shown, a portion of the lithium ions 48 move (diffuse) from the non-relative region 57 into the relative region 56.

[0049] Based on the above explanation, it can be understood that when a battery is stored after charging, its capacity decreases compared to when it is immediately after charging. To reduce the rate of capacity reduction mentioned above and thus increase the capacity recovery rate, it is necessary to reduce the length of the outer perimeter 46 per unit capacity of the battery (more precisely, the perimeter of the coating portion of the positive electrode active material on the positive electrode core in the positive electrode plate). That is, from... Figure 8 Towards Figure 9 During progress, if the outer perimeter 46 of the battery per unit capacity is shorter, fewer lithium ions 48 will move into the non-relative region 57, thus increasing the capacity recovery rate.

[0050] Specifically, if the perimeter of the coating portion of the positive electrode active material on the positive electrode core per unit capacity of the battery is 0.28 m / Ah or less, the capacity recovery rate will reach a sufficiently high rate for a battery used in EVs. If the perimeter of the coating portion of the positive electrode active material on the positive electrode core per unit capacity of the battery is 0.11 m / Ah or less, the capacity recovery rate can be further improved. Furthermore, in the negative electrode plate 55, the ratio of the relative area to (relative area + non-relative area) is preferably 85% to 95%. It should be noted that the ratio of the relative area to (relative area + non-relative area) is more accurately the ratio of the area of ​​the coating portion of the negative electrode active material to the total area of ​​the coating portion of the negative electrode active material, wherein the aforementioned portion is the portion opposite to the coating portion of the positive electrode active material. In addition to the perimeter of the coating portion of the positive electrode active material per unit capacity as disclosed herein, the ratio of the area of ​​the relative region to the area of ​​the non-relative region in the negative electrode plate 55 is set to 85% to 95%, thereby enabling suppression Figure 9 The diffusion region of lithium ions shown during long-term storage can improve the capacity recovery rate.

[0051] The capacity of each electrode is preferably 30 Ah or more. Furthermore, the capacity per unit area of ​​the coating portion of the positive electrode active material on the positive electrode core is preferably 40 Ah / m². 2 The above. In particular, the purpose of this disclosure is to improve the capacity recovery rate in lithium-ion batteries for EVs, and in these batteries, the energy density is increased by configuring them as described above, thereby extending the EV's driving range.

[0052] It should be noted that Patent Document 1 discloses a battery with a capacity of 8.4 Ah, a coating width of 11.0 cm for the positive electrode active material, and a positive electrode plate length of 440 cm. In this battery, the perimeter of the positive electrode active material coating area per unit capacity is 1.07 m / Ah. Furthermore, Patent Document 2 discloses a battery with a capacity of 4.6 Ah, a coating width of 50 mm for the positive electrode active material, and a positive electrode plate length of 3000 mm. In this battery, the perimeter of the positive electrode active material coating area per unit capacity is 1.33 m / Ah.

[0053] <Structure of current collector in electrode body>

[0054] On the sealing plate 2, there are positive terminals 8 and negative terminals 9, which are electrode terminals facing outwards. The positive terminal 8 is electrically connected to the positive electrode tab group 40 via a positive current collector 6, which is composed of a first positive current collector 61 and a second positive current collector 62. The negative terminal 9 is electrically connected to the negative electrode tab group 50 via a negative current collector 7, which is composed of a first negative current collector 71 and a second negative current collector 72.

[0055] The first positive current collector 61 has an approximately L-shaped cross-section and is arranged between the electrode body 3 and the sealing plate 2. Specifically, the first positive current collector 61 has a first region arranged along the sealing plate 2 and a second region bent from the end of the first region. The second region extends along the first sidewall 1b toward the bottom 1a. The first positive current collector 61 is connected to the positive terminal 8. The negative terminal side is configured in the same way.

[0056] The second positive current collector 62 is disposed between the electrode body 3 and the first sidewall 1b of the square outer casing 1. Specifically, the second positive current collector 62 is composed of a flat plate having a surface parallel to the first sidewall 1b, and extends along the first sidewall 1b toward the bottom 1a. The second positive current collector 62 is connected to the first positive current collector 61. The negative side is configured in the same way.

[0057] Figure 3The second positive current collector 62 is shown. The second positive current collector 62 has a structure formed by bending a portion of an approximately rectangular flat plate, and includes a current collector connection portion 62a, an inclined portion 62b, and a tab connection portion 62c. The current collector connection portion 62a is connected to the first positive current collector 61. The positive tab assembly 40 is connected to the tab connection portion 62c. The inclined portion 62b connects the current collector connection portion 62a and the tab connection portion 62c, and is inclined relative to both.

[0058] A recess 62d is provided in the current collector connection portion 62a. A through hole 62e is provided in the recess 62d. The current collector connection portion 62a is connected to the first positive current collector 61 in the recess 62d. Furthermore, a fuse portion 66 is provided in the second positive current collector 62.

[0059] Next, the bending of the positive electrode tab group 40 and the connection between the positive electrode tab group 40 and the second positive current collector 62 will be explained. It should be noted that since the negative electrode side has almost the same configuration and structure as the positive electrode side, only the positive electrode side will be described below. Figure 12 The area near the connection between the second positive current collector 62 and the positive current collector 40 before the positive current collector 40 is bent is shown. Figure 14 The electrode body 3 is shown before bending the positive electrode tab group 40 and the negative electrode tab group 50, with the positive electrode tab group 40 connected to the second positive current collector 62 and the negative electrode tab group 50 connected to the second negative current collector 72.

[0060] The positive electrode tab assembly 40 is connected to the tab connection portion 62c in the second positive electrode current collector 62. Specifically, as follows: Figure 12 As shown, before bending the positive electrode tab assembly 40, the positive electrode tab assembly 40 is placed on the tab connection portion 62c in the second positive electrode current collector 62, and the tab connection portion 62c and the positive electrode tab assembly 40 are joined (welded) to form the connection portion 63.

[0061] Here, as Figure 12 As shown, the positive electrode tab group 40 is located on one side of the plate constituting the second positive electrode current collector 62 in the width direction. Figure 12 On the right side of the plate, the connection 63 between the positive electrode tab group 40 and the tab connection 62c is connected to the tab connection portion 62c of the second positive current collector 62. That is, the connection portion 63 between the positive electrode tab group 40 and the tab connection portion 62c is near the root side (width direction side) of the positive electrode tab group 40 in the width direction of the plate. Figure 9 (Right side of the middle). Therefore, when bending the positive electrode tab group 40, a bending shape can be formed more reliably and stably near the root of the positive electrode tab group 40.

[0062] Figure 13This diagram shows the area near the connection between the second positive current collector 62 and the positive electrode tab assembly 40 after the positive electrode tab assembly 40 has been bent. By bending the positive electrode tab assembly 40, it is possible to arrange the first main surface 3a and the second main surface 3b of the electrode body 3 approximately parallel to each other (see reference). Figure 12 , Figure 14 The tab connection portion 62c in the second positive current collector 62 is oriented approximately perpendicular to the winding axis of the electrode body 3. That is, the positive electrode tab assembly 40 is bent parallel to the first sidewall 1b on the side of the connection portion 63 that connects to the second positive current collector 62. The bent positive electrode tab assembly 40 is fixed to the electrode body 3 using tape 80.

[0063] With the configuration described above, the positive electrode tab assembly 40 can be bent without bending the second positive electrode current collector 62. Therefore, a non-aqueous electrolyte secondary battery with high volumetric energy density can be manufactured using a simple method.

[0064] It should be noted that, as mentioned above, the negative electrode side is configured in the same way as the positive electrode side. Figure 14 72a represents the current collector connection part, 72b represents the inclined part, and 72c represents the electrode connection part.

[0065] The non-aqueous electrolyte secondary battery involved in this embodiment can achieve a high volumetric energy density battery without bending the second current collectors 62 and 72 by bending the positive electrode tab group 40 and the negative electrode tab group 50. Since one end 5e of the negative electrode plate 5 is arranged in a position opposite to the protective layer 4c of the positive electrode plate 4, short circuits in the battery can be prevented.

[0066] (Example)

[0067] <Example 1>

[0068] [Manufacturing of the positive electrode plate]

[0069] A positive electrode active material layer slurry was prepared by mixing lithium nickel cobalt manganese composite oxide as the positive electrode active material, polyvinylidene fluoride (PVdF) as the binder, carbon material as the conductive material, and N-methyl-2-pyrrolidone (NMP) as the dispersion medium so that the mass ratio of lithium nickel cobalt manganese composite oxide:PVdF:carbon material reached 97.5:1:1.5.

[0070] A protective layer slurry was prepared by mixing alumina powder, carbon material as a conductive material, polyvinylidene fluoride (PVdF) as a binder, and N-methyl-2-pyrrolidone (NMP) as a dispersion medium to achieve a mass ratio of alumina powder:carbon material:PVdF of 83:3:14.

[0071] Using a die coater, a positive electrode active material layer slurry and a positive electrode protective layer slurry, manufactured by the above method, are coated on both sides of the aluminum foil serving as the positive electrode core. At this time, the positive electrode active material layer slurry is coated to the center of the positive electrode core in the width direction. Furthermore, the positive electrode protective layer slurry is coated at the ends in the width direction of the area where the positive electrode active material layer slurry is coated.

[0072] The positive electrode core, coated with both the positive active material layer slurry and the positive protective layer slurry, is dried to remove NMP contained in these materials. This forms the positive active material layer and the positive protective layer. The positive active material layer is then compressed and used as the primary positive electrode plate. This primary plate is cut into rectangular shapes with an active material layer coating of 88 mm width and 4600 mm length, and used as the positive electrode plate. It should be noted that the positive electrode plate can be cut using energy rays such as lasers, molds, or cutting tools.

[0073] [Manufacturing of the negative electrode plate]

[0074] A negative electrode active material slurry was prepared by mixing graphite as the negative electrode active material, styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) as binders, and water as the dispersion medium to achieve a graphite:SBR:CMC mass ratio of 98:1:1.

[0075] Using a metal coating machine, a negative electrode active material layer slurry manufactured by the above method was coated on both sides of the copper foil, which serves as the negative electrode core.

[0076] The negative electrode core coated with the negative electrode active material slurry is dried to remove water contained in the slurry. This forms the negative electrode active material layer. The negative electrode active material layer is then compressed and used as the negative electrode substrate. This substrate is cut into sections with an active material layer coating width of 92 mm and a length of 4900 mm, and used as the negative electrode plate. It should be noted that the negative electrode substrate can be cut using energy rays such as lasers, molds, or cutting tools.

[0077] [Manufacturing of Electrodes]

[0078] A flat, wound electrode body is manufactured by winding a strip-shaped positive electrode plate and a strip-shaped negative electrode plate, which are produced according to the above method, with a strip-shaped separator made of polyolefin sandwiched between them. The electrode body has a flat region in the center and curved portions at both ends of the flat region.

[0079] At one end of the electrode body extending along the winding axis, a positive electrode tab assembly composed of multiple stacked positive electrode tabs is provided. At the other end of the electrode body extending along the winding axis, a negative electrode tab assembly composed of multiple stacked negative electrode tabs is provided. It should be noted that, in a direction perpendicular to the winding axis of the electrode body and perpendicular to the thickness direction of the electrode body, the centers of the positive electrode tab assembly and the centers of the negative electrode tab assembly are arranged at positions offset to the same side relative to the winding axis.

[0080] [Battery manufacturing]

[0081] like Figure 14 As shown, the second positive current collector 62 is connected to the positive electrode tab group 40, and the second negative current collector 72 is connected to the negative electrode tab group 50. Furthermore, as... Figure 15 , 16 As shown, two electrode bodies 3, with the positive electrode tab group 40 and the negative electrode tab group 50 bent respectively, are fixed with tape 90. Each positive electrode tab group 40 is arranged on the same side, and each negative electrode tab group 50 is arranged on the same side. Furthermore, in each electrode body 3, the positive electrode tab groups 40 are bent in the same direction. Similarly, in each electrode body 3, the negative electrode tab groups 50 are bent in the same direction.

[0082] In the stacking direction of the electrode bodies 3, the second positive current collectors 62 mounted on each electrode body 3 are arranged at intervals and connected to the second region 61b of the first positive current collector 61. The second negative current collectors 72 are the same.

[0083] The two electrode bodies 3 described above are inserted into the square outer casing 1. Then, the sealing plate 2 is attached to the square outer casing 1 to close the opening of the square outer casing 1. Electrolyte is injected through the electrolyte injection hole 15 provided on the sealing plate 2, and the electrolyte injection hole 15 is sealed with the sealing member 16. Thus, a non-aqueous electrolyte secondary battery 20 is formed.

[0084] [Initial charge / discharge conditions]

[0085] The aforementioned non-aqueous electrolyte secondary battery was charged and discharged at 0.5C to adjust the SOC (State of Charge) to below 20%, thereby reaching a state ready for shipment. It was then used as the battery in Example 1.

[0086] [High-Temperature Storage Test Conditions]

[0087] The point at which the above-mentioned non-aqueous electrolyte secondary batteries that can be shipped out are charged to 90% of their SOC is set as the storage period of 0 days. The discharge capacity after being placed in an environment of 60℃ for 56 days and 300 days is confirmed. The proportion when the discharge capacity before storage is assumed to be 100% is set as the capacity recovery rate after storage.

[0088] <Example 2>

[0089] A battery was manufactured using the same method as in Example 1, except that the width of the active material layer coating portion of the positive electrode plate was 262 mm and the length was 2900 mm, and the width of the active material layer coating portion of the negative electrode plate was 272 mm and the length was 3100 mm. A high-temperature storage test was then conducted. This battery was used as Example 2.

[0090] <Comparative Example>

[0091] Batteries were manufactured using the same method as in Examples 1 and 2, except that the width of the active material layer coating portion of the positive electrode plate was 76 mm and the length was 4600 mm, and the width of the active material layer coating portion of the negative electrode plate was 80 mm and the length was 4900 mm. High-temperature storage tests were then conducted. These were used as comparative examples.

[0092] The embodiments involved in this disclosure will now be described in detail using Table 1.

[0093] [Table 1]

[0094]

[0095] Table 1 shows the perimeter of the positive electrode active material coating portion per unit capacity of the non-aqueous electrolyte secondary batteries of Examples 1 and 2 and the comparative examples, the ratio of the area of ​​the opposite portion of the positive electrode active material coating portion to the total area of ​​the negative electrode active material coating portion, the capacity of each electrode body, the capacity per unit area of ​​the positive electrode active material coating portion, and the capacity recovery rate after high-temperature storage test for the non-aqueous electrolyte secondary batteries described above.

[0096] It can be seen that if, as in Example 1, the perimeter of the positive electrode active material coating area per unit capacity of the battery is less than 0.28 m / Ah, then even after 300 days of storage, an 80% capacity recovery rate can be maintained. It should be noted that even after 300 days of storage at 60°C, the capacity recovery rate exceeds 80%, which is preferable for EV batteries. Furthermore, if, as in Example 2, the perimeter of the positive electrode active material coating area per unit capacity of the battery is less than 0.11 m / Ah, then even after 300 days of storage, the capacity recovery rate reaches 86%, further improving storage durability.

[0097] On the other hand, when the perimeter of the positive electrode active material coating portion per unit capacity of the battery is greater than 0.28 m / Ah, as in the comparative example, the capacity recovery rate after 300 days of storage is reduced to 78%, which does not meet the performance level required for EV batteries.

[0098] (Other implementation methods)

[0099] The above-described embodiments are examples of the invention of this application. The invention of this application is not limited to the above examples, and may also combine common knowledge, conventional technology, and known technology, or replace some of them in the above examples. In addition, improvements that can be easily conceived by those skilled in the art are also included in the invention of this application.

[0100] The non-aqueous electrolyte secondary battery 20 may also include multiple electrode bodies 3. In this case, the capacity of each electrode body is preferably 30 Ah. Figure 15 This is a diagram showing an electrode group 300 comprising multiple electrode bodies 3. (See diagram below.) Figure 15 As shown, the non-aqueous electrolyte secondary battery 20 includes multiple (two) electrode bodies 3. A second current collector 62 is connected to the positive electrode tab group 40 of each electrode body 3. By arranging multiple electrode bodies 3,3 and fixing them together with adhesive tape 90, an electrode body group 300 is formed. Figure 16 This is a diagram showing the electrode group 300 and the sealing plate 2 interconnected by the first positive current collector 61 and the second positive current collector 62.

[0101] - Symbol Explanation -

[0102] 1 square outer casing

[0103] 1b First sidewall (sidewall)

[0104] 1c First sidewall (sidewall)

[0105] 2 sealing plates

[0106] 3-electrode body

[0107] 4 positive plates

[0108] 4b Positive electrode tab

[0109] 5 negative plates

[0110] 5b negative electrode tab

[0111] 8 Positive terminals (electrode terminals)

[0112] 9 negative terminals (electrode terminals)

[0113] 20 Non-aqueous electrolyte secondary battery

[0114] 40 Positive Electrode Group (Electrode Group)

[0115] 50 negative electrode tabs (tab group)

[0116] 61 First positive current collector (first current collector)

[0117] 62 Second positive current collector (second current collector)

[0118] 71 First negative current collector (first current collector)

[0119] 72 Second negative current collector (second current collector)

Claims

1. A non-aqueous electrolyte secondary battery, the non-aqueous electrolyte secondary battery comprising: An electrode body, the electrode body comprising a positive electrode plate and a negative electrode plate; A square outer casing having an opening and housing the electrode body; Sealing plate, the sealing plate closing the opening; and Electrode terminals, which are disposed on the sealing plate. The non-aqueous electrolyte secondary battery is characterized by: The positive electrode plate includes a positive electrode core and a positive electrode active material coated on at least one surface of the positive electrode core. The perimeter of the coating portion of the positive electrode active material on the positive electrode core per unit capacity of the battery is less than 0.28 m / Ah. The non-aqueous electrolyte secondary battery includes one or more of the aforementioned electrode elements, each of which has a capacity of 30 Ah or more. The battery capacity per unit area of ​​the coating portion of the positive electrode active material on the positive electrode core is 40 Ah / m³. 2 above, The negative electrode plate includes a negative electrode core and a negative electrode active material coated on the negative electrode core. In the electrode body, the positive electrode plate and the negative electrode plate overlap by a diaphragm sandwiched between them. In the negative electrode plate, the area of ​​the portion of the negative electrode active material coating that is opposite to the positive electrode active material coating is 85% to 95% of the total area of ​​the negative electrode active material coating.

2. The non-aqueous electrolyte secondary battery according to claim 1, characterized in that: The perimeter of the coating portion of the positive electrode active material on the positive electrode core per unit capacity of the battery is less than 0.11 m / Ah.

3. The non-aqueous electrolyte secondary battery according to claim 1 or 2, characterized in that: The electrode body has a shape formed by winding the positive electrode plate and the negative electrode plate together after they are facing each other.

4. The non-aqueous electrolyte secondary battery according to claim 1 or 2, characterized in that: The non-aqueous electrolyte secondary battery includes: A first current collector is disposed between the electrode body and the sealing plate and is connected to the electrode terminal; A second current collector, disposed between the electrode body and the sidewall of the square outer casing and connected to the first current collector; and A tab assembly, which extends from the electrode body toward one side of the sidewall and is connected to the second current collector. The second current collector is composed of a flat plate having a surface parallel to the sidewall. The electrode assembly has a positive electrode assembly and a negative electrode assembly, and on the connection side connected to the second current collector, the electrode assembly is bent in a manner parallel to the side wall. The positive electrode assembly is formed by bundling together a plurality of positive electrode tabs extending from the positive electrode plate, and the negative electrode assembly is formed by bundling together a plurality of negative electrode tabs extending from the negative electrode plate.

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