A battery

Abstract

The utility model provides a battery, comprising a battery cell, the battery cell comprising a first pole piece and a second pole piece with a polarity opposite to the first pole piece, the first pole piece comprising a first active material layer, and the second pole piece comprising a second active material layer; the battery satisfies 0<S1 / S2-1≤0.2, wherein S1 is the total area of ​​the first active material layer in the battery cell, and S2 is the total area of ​​the second active material layer in the battery cell. The utility model can improve the high temperature performance of the battery.

Description

Technical Field

[0001] The utility model relates to the field of electrochemical energy storage devices, in particular to a battery. Background Art

[0002] Batteries are common electrochemical energy storage devices with a wide range of applications. However, the high-temperature performance of batteries needs to be further improved. For example, lithium-ion batteries are often used and stored at different temperatures, and the electrochemical performance, life and safety of lithium-ion batteries are sensitive to temperature. High-temperature working environments will directly affect the electrochemical performance and safety of batteries. For example, at higher operating temperatures, it is very easy to cause degradation and irreversible damage to battery performance (such as irreversible losses caused by lithium ion migration failure, negative electrode side reactions and positive electrode side reactions), which often reduces battery capacity and shortens battery life, which greatly limits the application of lithium-ion batteries in high-temperature environments. Therefore, it is urgent to improve the high-temperature performance of lithium-ion batteries. Utility Model Content

[0003] The utility model provides a battery, which can improve the high temperature performance of the battery and effectively overcome the defects of the prior art.

[0004] The utility model provides a battery, comprising a battery cell, wherein the battery cell comprises a first pole piece and a second pole piece with a polarity opposite to that of the first pole piece, the first pole piece comprises a first active material layer, and the second pole piece comprises a second active material layer; the battery satisfies 0<S1 / S2-1≤0.2, wherein S1 is the total area of ​​the first active material layer in the battery cell, and S2 is the total area of ​​the second active material layer in the battery cell.

[0005] According to one embodiment of the present invention, 0.05≤S1 / S2-1≤0.2.

[0006] According to one embodiment of the present invention, S2 = (100,000 to 2.3 million) mm 2 ; and / or, S1 = (110,000 to 2.4 million) mm 2 .

[0007] According to one embodiment of the utility model, the battery cell includes a plurality of first electrode sheet layers formed by the first electrode sheet, and a plurality of second electrode sheet layers formed by the second electrode sheet, and the plurality of first electrode sheet layers and the plurality of second electrode sheet layers are stacked; in the battery cell, the number of the first electrode sheet layers is 11 to 73, and the number of the second electrode sheet layers is 10 to 71; preferably, the battery cell is a stacked battery cell, and the first electrode sheet layer is the first electrode sheet; or, the battery cell is a wound battery cell, the first electrode sheet includes the plurality of first electrode sheet layers, and a first bend portion connected between every two adjacent first electrode sheet layers, and the second electrode sheet includes the plurality of second electrode sheet layers, and a second bend portion connected between every two adjacent second electrode sheet layers.

[0008] According to one embodiment of the present invention, the width of the first active material layer is 58 to 130 mm; and / or the width of the second active material layer is 55 to 126 mm.

[0009] According to one embodiment of the utility model, the first pole piece includes a first pole ear, the second pole piece includes a second pole ear, and the first pole ear and the second pole ear are located on the same side of the battery cell; the second pole piece also includes an insulating layer, and the insulating layer is located on the side of the second active material layer facing the second pole ear; preferably, the first active material layer includes an invalid area extending beyond the second active material layer, and the ratio of the width of the insulating layer to the width of the invalid area on the side of the first pole piece where the first pole ear is provided is 1:(1.2~8); preferably, the width of the insulating layer is 0.5mm~5mm; preferably, the ratio of the total thickness of the second active material layer in the second pole piece to the total thickness of the insulating layer is (0.5~12):1; preferably, the total thickness of the insulating layer in the second pole piece is 10μm~100μm; preferably, the insulating layer includes a ceramic coating.

[0010] According to one embodiment of the present invention, the length of the battery core is 40 to 150 mm.

[0011] According to one embodiment of the present invention, the battery satisfies η+k×(S1 / S2-1)≥0.8, preferably 0.8≤η+k×(S1 / S2-1)≤1; wherein the units of s1 and s2 are mm respectively. 2 ; η is the capacity retention rate of the battery in a fully charged state after being placed at a temperature T for n3 days; k = (OCV1-OCV2) / n3, OCV1 is the voltage of the battery in a fully charged state, OCV2 is the voltage of the battery in a fully charged state after being placed at a temperature T for n3 days, and the unit of k is mV / day; 55℃≤T≤65℃, 29≤n3≤31.

[0012] According to one embodiment of the present invention, the battery satisfies k≤0.5, k=(OCV1-OCV2) / n3, wherein the unit of k is mV / day, OCV1 is the voltage of the battery in a fully charged state, OCV2 is the voltage of the battery in a fully charged state after being left at temperature T for n3 days, 55℃≤T≤65℃, 29≤n3≤31; preferably, 0.05≤k≤0.5.

[0013] According to one embodiment of the utility model, the capacity retention rate of the battery in a fully charged state after being left at a temperature T for n3 days is greater than or equal to 93%, 55°C≤T≤65°C, and 29≤n3≤31.

[0014] The battery provided by the utility model satisfies 0<S1 / S2-1≤0.2, which can improve the high temperature performance of the battery, is beneficial to the storage and use of the battery in a high temperature environment, and improves the battery life and cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic structural diagram of a first pole piece according to an embodiment of the utility model;

[0016] Figure 2 This is a structural schematic diagram of the projection of the second pole piece on the first pole piece according to an embodiment of the utility model;

[0017] Figure 3 A structural schematic diagram showing the relative position relationship between the first pole piece and the second pole piece of an embodiment of the utility model;

[0018] Figure 4 A structural schematic diagram showing the relative positional relationship between the first pole piece and the second pole piece of another embodiment of the utility model;

[0019] Figure 5 It is a schematic diagram of the structure of the positive electrode sheet when the extension portion of the second current collector is not cut into the second electrode tab in one embodiment of the utility model;

[0020] Figure 6 This is a schematic diagram of the structure of the positive electrode sheet according to an embodiment of the utility model;

[0021] Figure 7 This is a schematic diagram of the positive electrode structure of another embodiment of the utility model;

[0022] Figure 8 This is a schematic diagram of the positive electrode structure of another embodiment of the utility model;

[0023] Fig. 9 This is a schematic structural diagram of a wound battery cell according to an embodiment of the utility model;

[0024] Fig.10This is a schematic structural diagram of a laminated battery cell according to an embodiment of the utility model;

[0025] Fig.11 It is a schematic diagram of the projection structure of the second pole piece on the first pole piece in the laminated battery cell according to one embodiment of the utility model;

[0026] Fig.12 It is a curve diagram showing the relationship between the high temperature capacity retention rate and the AO value of the battery in the embodiment of the present utility model.

[0027] Explanation of the reference numerals: 1: first pole piece; 11: first current collector; 12: first active material layer; 101: effective area; 102, 102': ineffective area; 1021: outer ring area; 100: first bending portion; 110: first pole piece layer; 111: first pole ear; 2: second pole piece; 21: second current collector; 22: second active material layer; 23: insulating layer; 231: main body; 232: extension portion; 200: second bending portion; 210: second pole piece layer; 211: second pole ear; 211': extension portion of the second current collector; 3: diaphragm; a: first direction; b: second direction; c: third direction; M1, M2: straight line; O1: center of the first pole ear in the first direction; O2: center of the second pole ear in the first direction; w0: width of the ineffective area; w1: width of the first active material layer; w2: width of the second active material layer; w3: width of the insulating layer. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the scheme of the utility model, the utility model is further described in detail below. The specific implementation methods listed below are only for describing the principles and features of the utility model. The examples are only used to explain the utility model and do not limit the scope of the utility model. Based on the embodiments of the utility model, all other implementation methods obtained by ordinary technicians in this field without making creative work are within the scope of protection of the utility model.

[0029] Batteries are common electrochemical energy storage devices with a wide range of applications. However, the high-temperature performance and other properties of batteries need to be further improved. Specifically, lithium-ion batteries are widely used in portable electronic devices and electric vehicles due to their high energy density, long cycle life and low self-discharge performance. However, in practical applications, lithium-ion batteries are often used and stored at different temperatures, and the electrochemical properties, life and safety of lithium-ion batteries are sensitive to temperature. High-temperature working environments will directly affect the electrochemical properties and safety of batteries. For example, at higher operating temperatures, it is very easy to cause degradation of battery performance and irreversible damage (such as irreversible losses caused by lithium ion migration failure, negative electrode side reactions and positive electrode side reactions), which often reduces battery capacity, shortens battery life, and even brings some safety issues, which greatly limits the application of lithium-ion batteries in high-temperature environments. Therefore, it is urgent to improve the high-temperature performance of lithium-ion batteries.

[0030] According to the inventor's long-term research, the capacity loss of lithium-ion batteries at high temperatures mainly comes from the loss of active lithium and the loss of lithium capacity caused by polarization. The loss of active lithium, which is the main influencing factor, is generally caused by the higher specific surface area of ​​the positive electrode, the low graphitization degree of the negative electrode, and the larger area ratio of the pole pieces. Among them, the larger area ratio of the pole pieces is usually mainly due to the larger area ratio of the active material layers of the positive and negative pole pieces, resulting in the existence of invalid areas of the active material layers in the battery cell. During the battery charging and discharging process, lithium ions are deintercalated between the positive and negative poles, and lithium ions are easy to migrate to the invalid area, especially under high temperature conditions, which makes it easier for lithium ions to migrate to the invalid area. Since there is no active material layer of the opposite pole piece directly facing the invalid area in the battery cell, the lithium ions that migrate to the invalid area can no longer return to participate in the lithium ion deintercalation process between the positive and negative poles, thereby causing irreversible lithium loss, affecting the capacity and life of the battery, and causing battery performance degradation.

[0031] In view of this, the present invention provides a battery, such as Figures 1 to 11 As shown, the battery includes a battery cell, the battery cell includes a first electrode sheet 1, and a second electrode sheet 2 with opposite polarity to the first electrode sheet 1, the first electrode sheet 1 includes a first active material layer 12, and the second electrode sheet 2 includes a second active material layer 22; the battery satisfies 0<S1 / S2-1≤0.2, wherein S1 is the total area of ​​the first active material layer 12 in the battery cell, and S2 is the total area of ​​the second active material layer 22 in the battery cell.

[0032] In the embodiment of the present invention, by controlling S1 / S2-1 (referred to as AO value in the present invention, i.e., AO value = S1 / S2-1) to satisfy 0<S1 / S2-1≤0.2 (i.e., 0<(S1-S2) / S2≤0.2), the high temperature performance of the battery can be effectively improved. The reason for this is that by controlling 0<S1 / S2-1≤0.2, the area ratio of the invalid region 102 of the first active material layer 12 in the battery cell is reduced, thereby reducing the proportion of ions in the battery cell that migrate to the invalid region 102, thereby reducing the proportion of irreversible elements generated during the battery charge and discharge process, thereby improving the battery's life and other performance, especially improving the battery's high temperature performance, specifically improving the battery's high temperature storage performance and high temperature cycle performance, etc.

[0033] Specifically, the battery of the embodiment of the utility model may include a lithium-ion battery. By controlling 0<S1 / S2-1≤0.2, the area ratio of the invalid region 102 of the first active material layer 12 in the battery cell can be reduced, thereby reducing the proportion of lithium ions in the battery cell that migrate to the invalid region 102, and further reducing the proportion of irreversible lithium generated during the charging and discharging process of the lithium-ion battery, that is, reducing the irreversible lithium loss, thereby improving the life of the lithium-ion battery and other performance, especially the high temperature performance of the lithium-ion battery, specifically improving the high temperature storage performance and high temperature cycle performance of the battery.

[0034] Specifically, the polarities of the first pole piece 1 and the second pole piece 2 are opposite, that is, the first pole piece 1 is a positive pole piece and the second pole piece 2 is a negative pole piece, or the first pole piece 1 is a negative pole piece and the second pole piece 2 is a positive pole piece.

[0035] Generally speaking, if the area of ​​the positive electrode is larger than that of the negative electrode (i.e. the positive electrode covers the negative electrode), the positive electrode will easily have more lithium ions, while there are not enough sites in the negative electrode to embed these lithium ions, resulting in problems such as lithium dendrites in the negative electrode.

[0036] Therefore, in the embodiment of the utility model, the first electrode sheet 1 is preferably a negative electrode sheet, and the second electrode sheet 2 is a positive electrode sheet. Accordingly, the first active material layer 12 is a negative electrode active material layer (negative electrode paste), and the second active material layer 22 is a positive electrode active material layer (positive electrode paste). This can avoid problems such as the generation of lithium dendrites at the negative electrode, thereby further improving the safety and other performance of the battery.

[0037] Among them, the area of ​​the negative electrode sheet is larger than that of the positive electrode sheet, so that the negative electrode sheet covers the positive electrode sheet, and there is an invalid area 102 in the negative electrode active material layer of the negative electrode sheet (that is, the part of the negative electrode active material layer exceeding the positive electrode active material layer). The embodiment of the utility model can reduce the area ratio of the invalid area 102 of the negative electrode active material layer in the battery cell by controlling 0<S1 / S2-1≤0.2, thereby reducing the amount of lithium ions migrating to the invalid area 102 and the irreversible lithium loss caused thereby, thereby improving the battery life and other performance, especially the high temperature performance of the battery, specifically the high temperature storage performance and high temperature cycle performance of the battery.

[0038] In general, if Figures 9 to 11 As shown, the battery cell includes a plurality of first pole sheet layers 110 formed by the first pole sheet 1 and a plurality of pole sheet layers formed by the second pole sheet 2 , and the plurality of first pole sheet layers 110 and the plurality of second pole sheet layers 210 are stacked.

[0039] Continue to refer Figures 9 to 11 , the width of the first pole sheet layer 110 is greater than the width of the second pole sheet layer 210, the area of ​​the first pole sheet layer 110 is greater than the area of ​​the second pole sheet layer 210, and the projection of the first pole sheet layer 110 along the thickness direction of the battery cell covers the projection of the second pole sheet layer 110 along the thickness direction of the battery cell. The projection along the thickness direction of the battery cell refers to the projection perpendicular to the thickness direction of the battery cell.

[0040] In addition, the battery cell further includes a diaphragm 3, which is located between the first pole piece 1 (first pole piece layer 110) and the second pole piece 2 (second pole piece layer 210) to separate the first pole piece 1 and the second pole piece 2 to prevent the first pole piece 1 and the second pole piece 2 from contacting and short-circuiting. Specifically, in the battery cell, the first pole piece layer 110, the diaphragm 3, and the second pole piece layer 210 are stacked in sequence, and can be stacked along the thickness direction of the battery cell.

[0041] Specifically, Fig.10 and Fig.11 As shown, the battery cell can be a stacked battery cell (stacked core). In this case, the first electrode layer 110 is the first electrode 1, and the second electrode layer 210 is the second electrode 2. That is, the battery cell has multiple first electrode sheets 1 and multiple second electrode sheets 2. These first electrode sheets 1 and second electrode sheets 2 are arranged alternately, and the first electrode sheets 1 and the second electrode sheets 2 are separated by the diaphragm 3.

[0042] Or, if Fig. 9As shown, the battery cell can be a wound battery cell (wound core), that is, the battery cell is formed by stacking a first electrode sheet 1, a diaphragm 3 and a second electrode sheet 2 in sequence and then winding them. The first electrode sheet 1, the diaphragm 3 and the second electrode sheet 2 each have a wound structure. For example, the first electrode sheet 1 includes a plurality of first electrode sheet layers (first straight portions) 110, and a first bent portion 100 connected between every two adjacent first electrode sheet layers 110, and the second electrode sheet 2 includes a plurality of second electrode sheet layers (second straight portions) 210, and a second bent portion 200 connected between every two adjacent second electrode sheet layers 210.

[0043] Continue to refer Figures 1 to 11 The area of ​​the first electrode piece 1 is greater than the area of ​​the second electrode piece 2, so that the first electrode piece 1 covers the second electrode piece 2, so that the first active material layer 12 of the first electrode piece 1 has an invalid area 102 (that is, the first active material layer 12 of the first electrode piece 1 exceeds the part of the second active material layer 22 of the second electrode piece 2 (overhang)).

[0044] Specifically, the first active material layer 12 of the first pole piece 1 includes an effective area 101 and an ineffective area 102. The effective area 101 and the second active material layer 22 of the second pole piece 2 directly face each other through the diaphragm 3 (that is, there is no other film layer or other structure between the two except the diaphragm 3), and the projections of the two on the same plane (the plane is basically perpendicular to the thickness direction of the first pole piece 1 or the second pole piece 2) basically overlap, and the ineffective area 102 does not overlap with the second active material layer 22 of the second pole piece 2, that is, there is no second active material layer 22 in the battery cell that directly faces the ineffective area 102 through the diaphragm 3.

[0045] Generally, in a battery cell, an invalid area 102 exists at at least one of the following locations of the first pole piece 1: (1) an invalid area 102 exists on one side or on two opposite sides in the length direction of the first pole piece 1; (2) an invalid area 102 exists on one side or on two opposite sides in the width direction of the first pole piece 1.

[0046] For example, Figures 1 to 4 yes Fig. 9 The structural diagram of the first pole piece 1 and the second pole piece 2 in the wound battery cell shown in FIG. Figures 1 to 4 As shown, the first active material layer 12 of the first pole piece 1 has a portion (ie, the inactive region 102 ) that exceeds the second active material layer 22 of the second pole piece 2 in both the first direction a and the second direction b.

[0047] In addition, if Fig. 9 As shown, in the wound cell, the outer ring region 1021 of the first pole piece 1 has an ineffective region 102 (i.e. Figures 1 to 4The invalid area 102 on the right side of the first pole piece 1 in the outer ring area 1021 is located from one end of the first pole piece 1 located outside the wound battery cell ( Figures 1 to 4 The right end of the first electrode sheet 1 in the middle) extends along the winding direction of the first electrode sheet 1 from the outside to the inside to at least a part of the area of ​​the nth first electrode sheet layer 110 of the first electrode sheet 1, where n can generally be 1, 2 or 3, that is, the invalid area 102 located in the outer circle area 1021 has the first active material layer 12, but the invalid area 102 is directly facing the first electrode sheet layer 110 of the inner circle closest to the invalid area 102 through the diaphragm 3, and there is no second electrode sheet layer 210 with the second active material layer 22 directly facing the invalid area 102.

[0048] For example, in Fig. 9 In the wound cell shown, n=3, starting from the first electrode layer 110 where the end of the first electrode sheet 1 located outside the cell is located as the first first electrode layer 110, the first first electrode layer 110, the second first electrode layer 110, a partial area of ​​the third first electrode layer 110, and the first bending portion 100 connected between the first first electrode layer 110 and the second first electrode layer 110, and the first bending portion 100 connected between the second first electrode layer 110 and the third first electrode layer 110 are all invalid areas 102, so that There is an invalid area 102 in the outer circle area 1021 of the first pole piece 1, wherein the first first pole sheet layer 110 faces the third first pole sheet layer 110 through the diaphragm 3 (there is no second pole sheet layer 210 between them), the second first pole sheet layer 110 faces the fourth first pole sheet layer 110 through the diaphragm 3 (there is no second pole sheet layer 210 between them), and a partial area (invalid area 102) of the third first pole sheet layer 110 faces the fifth first pole sheet layer 110 (there is no second pole sheet layer 210 between them).

[0049] Due to factors such as the battery manufacturing process, the above-mentioned ineffective area 102 ( Figures 1 to 4 The ineffective area 102 (overhang) in the wound battery cell and the ineffective area 102 in the outer ring area 1021 of the first pole piece 1 in the wound battery cell are inevitable. For example, overhang is related to the volatility of equipment production and cannot be eliminated usually. If the equipment is modified to improve the equipment accuracy and thus reduce the overhang, this will increase the equipment cost and the complexity of battery manufacturing, which is not conducive to actual industrial production. When preparing a wound battery cell, if the outer ring area 1021 of the first pole piece 1 is eliminated, the outer ring pole piece of the wound battery cell will be wrinkled, affecting the process and performance of the battery (for example, the wrinkles produced in the outer ring area 1021 of the second pole piece 2 can easily puncture the diaphragm 3, resulting in safety issues such as short circuit of the positive and negative electrodes).

[0050] In the embodiment of the utility model, by controlling 0<S1 / S2-1≤0.2, the area ratio of the invalid region 102 of the first active material layer 12 in the battery cell is reduced, thereby reducing the proportion of lithium ions that migrate to the invalid region 102 in the battery cell, thereby reducing the proportion of irreversible lithium generated during the battery charging and discharging process, thereby improving the battery life and other performance, especially improving the high temperature performance of the battery, specifically improving the high temperature storage performance and high temperature cycle performance of the battery.

[0051] In addition, compared with the method of reducing overhang by modifying equipment and improving equipment accuracy, the embodiment of the utility model reduces the area ratio of the invalid area 102 by adjusting the AO value, and conventional equipment can be used to manufacture batteries without modifying existing battery manufacturing equipment. Therefore, it also has the advantages of simple battery process and low cost, which is conducive to actual industrial application.

[0052] At the same time, the embodiment of the utility model reduces the area ratio of the invalid area 102 existing in the outer circle area 1021 of the first pole piece 1 in the wound battery cell by adjusting the AO value, and can improve the high temperature performance of the battery without canceling the outer circle area 1021 of the first pole piece 1. That is, the embodiment of the utility model can retain the outer circle area 1021 of the first pole piece 1 while achieving the improvement of the high temperature performance of the battery to avoid wrinkling of the outer circle pole piece, thereby avoiding problems such as the wrinkles of the outer circle pole piece piercing the diaphragm 3 and causing short circuit of the positive and negative electrodes due to the wrinkling of the outer circle pole piece, thereby further ensuring the safety and other performance of the battery.

[0053] Generally, the first active material layer 12 is provided on both the front and back surfaces of the first pole piece 1, and the second active material layer 22 is provided on both the front and back surfaces of the second pole piece 2. Specifically, the first pole piece 1 includes a first current collector 11, and the first active material layer 12 is provided on the surface of the first current collector 11, and specifically, the first active material layer 12 can be provided on both the front and back surfaces of the first current collector 11; the second pole piece 2 includes a second current collector 21, and the second active material layer 22 is provided on the surface of the second current collector 21, and specifically, the second active material layer 22 can be provided on both the front and back surfaces of the second current collector 21.

[0054] like Figures 6 to 11 As shown, the first pole piece 1 is further provided with at least one first pole lug 111 connected to the first current collector 11, and the first pole lug 111 can be arranged on one side or two opposite sides in the width direction of the first current collector 11 and / or on one end or two opposite ends in the length direction of the first current collector 11, and the second pole piece 2 is further provided with at least one second pole lug 211 connected to the second current collector 21, and the second pole lug 211 can be arranged on one side or two opposite sides in the width direction of the second current collector 21 and / or on one end or two opposite ends in the length direction of the second current collector 21. For example, as Figure 6 , Figure 7 and Figure 8 As shown, the second electrode tab 211 is disposed on one side of the second current collector 21 in the width direction.

[0055] In some embodiments, in the battery cell, the first pole tab 111 of the first pole sheet 1 and the second pole tab 211 of the second pole sheet 2 may be located on the same side of the battery cell (eg, Figures 9 to 11 shown).

[0056] Specifically, in the battery cell, at least a portion of each of the first pole sheet layers 110 is provided with a first pole ear 111, and the projections of these first pole ears 111 along the thickness direction of the battery cell (the projection is perpendicular to the thickness direction of the battery cell) at least partially overlap; at least a portion of each of the second pole sheet layers 210 is provided with a second pole ear 211, and the projections of these second pole ears 211 along the thickness direction of the battery cell at least partially overlap.

[0057] In some embodiments, Fig. 9 As shown, a plurality of first pole ears 111 are provided on the first pole sheet 1, and in the wound battery cell, a first pole ear 111 is provided on each first pole sheet layer 110, and the projections of these first pole ears 111 along the thickness direction of the battery cell basically overlap, that is, the centers (middle positions) O1 of these first pole ears 111 in the first direction a are basically on the same straight line M1, and the distance between the center O1 of each first pole ear 111 in the first direction a and the straight line M1 (that is, the misalignment degree of the first pole ear 111) is less than 5 mm.

[0058] Continue to refer Fig. 9 , a plurality of second pole ears 211 are provided on the second pole sheet 2, and in the wound battery cell, a second pole ear 211 is provided on each second pole sheet layer 210, and the projections of these second pole ears 211 along the thickness direction of the battery cell basically overlap, that is, the centers (middle positions) O2 of these second pole ears 211 in the first direction a are basically on the same straight line M2, and the distance between the center O2 of each second pole ear 211 in the first direction a and the straight line M2 (that is, the misalignment degree of the second pole ear 211) is less than 5 mm.

[0059] The direction of the straight line M1 is parallel to the third direction c.

[0060] In other embodiments, Fig.10 As shown, in the stacked battery cell, each first pole sheet 1 is provided with a first pole ear 111, and the projections of the first pole ears 111 of these first pole sheets 1 along the thickness direction of the battery cell basically overlap; each second pole sheet 2 is provided with a second pole ear 211, and the projections of the second pole ears 211 of these second pole sheets 2 along the thickness direction of the battery cell basically overlap.

[0061] Specifically, the first pole ear 111 can be formed by the first current collector 11 extending outward in a direction away from the first active material layer 12, and the portion of the first active material layer 12 extending to the first pole ear 111 (also the portion where the first active material layer 12 and the first pole ear 111 overlap) has a width along the direction from the first active material layer 12 to the first pole ear 111 that is less than or equal to 1 mm (during the preparation of the first pole sheet 1, the first active material layer 12 may be coated on the first pole ear 111, so that the first active material layer 12 extends to the first pole ear 111).

[0062] In addition, the second pole tab 211 can be formed by the second current collector 21 extending outward in a direction away from the second active material layer 22, and the portion of the second active material layer 22 extending to the second pole tab 211 (also the portion where the second active material layer 22 and the second pole tab 211 overlap) has a width along the direction from the second active material layer 22 to the second pole tab 211 that is less than or equal to 1 mm (during the preparation of the second pole sheet 2, the second active material layer 22 may be coated on the second pole tab 211, so that the second active material layer 22 extends to the second pole tab 211).

[0063] For example, if Figure 5 As shown, during the preparation of the second electrode sheet 2, after the second active material layer 22 and other coatings are formed on the second current collector 21, the second current collector 21 is reserved for forming an extension 211' (i.e., an area on the second current collector 21 not covered by the coating) for forming the second electrode tab 211, and then the extension 211' is cut into the second electrode tab 211 (such as Figure 6 As shown), the second contact 211 of the second electrode sheet 2 is formed by the second current collector 21 extending outward in a direction away from the second active material layer 22.

[0064] In addition, the battery further comprises a package body encapsulating the battery cell, a first adapter electrode connected to the first electrode 111 and extending out of the package body, and a second adapter electrode connected to the second electrode 211 and extending out of the package body. In the battery cell, all the first electrode 111 are attached together and connected to the first adapter electrode, specifically by welding; all the second electrode 211 are attached together and connected to the second adapter electrode, specifically by welding.

[0065] In the embodiment of the utility model, the package body may include an aluminum-plastic film, the first transfer tab may include a copper-plated nickel tab, and the second transfer tab may include an aluminum tab, but is not limited thereto.

[0066] Specifically, in the above-mentioned battery cell, the number n1' of the first pole sheet layers 110 can be 11 to 73 (i.e., 11≤n1'≤73), and the number n2' of the second pole sheet layers 210 can be 10 to 71 (i.e., 10≤n2'≤71). That is, when the battery cell is a laminated battery cell, the number of the first pole sheets 1 in the battery cell is n1', and the number of the second pole sheets 2 is n2'; when the battery cell is a wound battery cell, the first pole sheet 1 includes n1' first pole sheet layers 110, and a first bending portion 100 connected between every two adjacent first pole sheet layers 110, and the second pole sheet 2 includes n2' second pole sheet layers 210, and a second bending portion 200 connected between every two adjacent second pole sheet layers 210.

[0067] Specifically, in the above battery cell, at least part (part or all) of the first electrode layer 110 has a first active material layer 12 on both the front and back surfaces, and at least part of the second electrode layer 210 has a second active material layer 22 on both the front and back surfaces.

[0068] Generally speaking, in laminated cells (such as Fig.10 and Fig.11 As shown in FIG. 1 , each first electrode sheet 1 has a first active material layer 12 on both the front and back surfaces, and each second electrode sheet 2 has a second active material layer 22 on both the front and back surfaces. Fig. 9 As shown), at least part of the first pole sheet layer 110 and the front and back surfaces of the first bending portion 100 are provided with a first active material layer 12, and at least part of the second pole sheet layer 210 and the front and back surfaces of the second bending portion 200 are provided with a second active material layer 22.

[0069] For example, Fig. 9 As shown, in the wound battery cell, the outer ring region 1021 of the first electrode sheet 1 (for example, as described above, extending from the end of the first electrode sheet 1 located on the outside of the wound battery cell along the winding direction of the first electrode sheet 1 from the outside to the inside to at least a portion of the nth first electrode sheet layer 110 of the first electrode sheet 1) can be provided with a first active material layer 12. Specifically, one side of the outer ring region 1021 of the first electrode sheet 1 (such as the side facing the inside of the wound battery cell or the side away from the inside of the wound battery cell) is provided with the first active material layer 12, and the other side is not provided with the first active material layer 12 (that is, the other side is an empty foil area, for example, composed of Figure 4 The first electrode sheet 1 and the second electrode sheet 2 are wound together to form a wound battery cell) or the front and back sides of the outer ring area 1021 of the first electrode sheet 1 (i.e., the side facing the inner side of the wound battery cell and the side away from the inner side of the wound battery cell) are respectively provided with a first active material layer 12 (for example, Figure 3The wound battery cell is formed by winding the first pole piece 1 and the second pole piece 2 shown in the figure); except for the outer circle area 1021 of the first pole piece 1, the front and back surfaces of other areas (that is, each other first pole piece layer 110 and the first bending portion 100) are respectively provided with a first active material layer 12.

[0070] Specifically, S1 is the total area of ​​the first active material layer 12 in the battery cell, that is, S1 is the sum of the areas of all the first active material layers 12 in the battery cell; S2 is the total area of ​​the second active material layer 22 in the battery cell, that is, S2 is the sum of the areas of all the second active material layers 22 in the battery cell. The area of ​​the first active material layer 12 refers to the surface area of ​​the first active material layer 12 (that is, the area of ​​the projection of the first active material layer 12 on the first current collector 11), and the area of ​​the second active material layer 22 refers to the surface area of ​​the second active material layer 22 (that is, the area of ​​the projection of the second active material layer 22 on the second current collector 21).

[0071] Specifically, in the above-mentioned battery cell, the number of the first electrode layer 110 having the first active material layer 12 is n1, that is, among the n1 first electrode layers 110, each first electrode layer 110 has the first active material layer 12; among the n1 first electrode layers 110, the number of faces with the first active material layer 12 is m1 (m1≤2×n1, each first electrode layer 110 has two front and back faces, when each first electrode layer 110 has the first active material layer 12 on both the front and back faces, m1=2×n1), and the area of ​​the first active material layer 12 on each face is expressed as S 01 , then S1=S 01 ×m1.

[0072] The number of second electrode layers 210 having the second active material layer 22 is n2, and each of the n2 second electrode layers 210 has the second active material layer 22; the number of faces of the n2 second electrode layers 210 having the second active material layer 22 is m2 (m2≤2×n2, each second electrode layer 210 has two front and back faces, and when the front and back faces of each second electrode layer 210 are provided with the second active material layer 22, m2=2×n2), and the area of ​​the second active material layer 22 on each face is expressed as S 02 , then S2=S 02 ×m2.

[0073] Among them, in the wound battery cell, S1 is the sum of the areas of the first active material layer 12 on the front and back surfaces of the entire first electrode sheet 1, and S2 is the sum of the areas of the second active material layer 22 on the front and back surfaces of the entire second electrode sheet 2. Since the proportion of the first bent portion 100 of the first electrode sheet 1 and the proportion of the second bent portion 200 of the second electrode sheet 2 in the wound battery cell are very small, S1 is basically equal to the sum of the areas of the first active material layer 12 on all the first electrode sheets 110 (i.e., S1=S 01 ×m1), S2 is substantially equal to the sum of the areas of the second active material layers 22 on all the second electrode layers 210 (i.e., S1 = S 01 ×m2).

[0074] In specific implementation, the length of the battery cell can be used as the length of the first electrode layer 110 and the second electrode layer 210 (the length of the first electrode layer 110 and the length of the second electrode layer 210 are substantially equal to the length of the battery cell), and the total area S of the ineffective region 102 can be calculated according to the following formula: 无效 and its area ratio in the positive electrode region (i.e., AO value): the total area S of the ineffective region 102 无效 = S1-S2 = width w1 of the first active material layer 12 × length L of the battery cell × number m1 of the first active material layer 12 in the battery cell - width w2 of the second active material layer 22 × length L of the battery cell × number m2 of the second active material layer 22 in the battery cell; the total area S of the ineffective region 102 无效 The area ratio of the second pole piece 2

[0075] Here, m1=m2+a, that is, a represents the difference between the number of surfaces m1 with the first active material layer 12 and the number of surfaces m2 with the second active material layer 22 in the battery cell.

[0076] Combined with the above AO value calculation process, it can be seen that when m2 increases, the AO value decreases accordingly. Therefore, when the battery capacity or battery thickness increases, the number of folds of the second electrode 2 in the battery (that is, the number of second electrode layers 210) and the number of folds of the first electrode 1 (that is, the number of first electrode layers 110) also increase. At this time, the number of surfaces m2 with the second active material layer 22 and the number of surfaces m1 with the first active material layer 12 also increase accordingly, which reduces the AO value and reduces the area ratio of the invalid region 102 of the second electrode 2 in the battery cell.

[0077] However, if S1 / S2-1 is too small, the number of folds of the first electrode sheet 1 and the second electrode sheet 2 in the battery cell is large, and the electrode tabs are prone to misalignment (such as the misalignment of the first electrode tab 111 is greater than 5 mm, the misalignment of the second electrode tab 211 is greater than 5 mm, etc.), the first active material layer 12 on the first electrode sheet 1 extends too much to the first electrode tab 111 (the width of this part along the direction from the first active material layer 12 to the first electrode tab 111 is greater than 1 mm), the second active material layer 22 on the second electrode sheet 2 extends too much to the second electrode tab 211 (the width of this part along the direction from the second active material layer 22 to the second electrode tab 211 is greater than 1 mm), and the K value of the OCV process in the battery preparation process is too large, resulting in low battery process yield.

[0078] Therefore, by comprehensively considering the high temperature performance of the battery, the battery capacity, the thickness and other dimensions of the battery cell, and the battery manufacturing yield and other factors, 0.05≤S1 / S2-1≤0.2 can be met, which is beneficial to improving the capacity and high temperature performance of the battery, while facilitating the manufacture of the battery and improving the battery manufacturing yield.

[0079] In some embodiments, S2 = (100,000 to 2.3 million) mm 2 , for example 100,000 mm 2 , 120,000mm 2 , 140,000mm 2 , 150,000mm 2 , 170,000 mm 2 , 190,000mm 2 , 250,000mm 2 , 500,000mm 2 , 700,000 mm 2 , 900,000mm 2 , 1 million mm 2 ,1.1 million mm 2 , 1.2 million mm 2 , 1.4 million mm 2 , 1.5 million mm 2 , 1.7 million mm 2 , 1.9 million mm 2 , 2 million mm 2 , 2.3 million mm 2 Or a range consisting of any two of them.

[0080] In some embodiments, S1 = (110,000 to 2.4 million) mm 2 , such as 110,000, 130,000, 150,000, 160,000, 180,000, 190,000, 200,000, 220,000, 300,000, 500,000, 800,000 mm 2 , 1 million mm 2 ,1.1 million mm 2 , 1.3 million mm2 , 1.5 million mm 2 , 1.7 million mm 2 , 2 million mm 2 , 2.3 million mm 2 , 2.4 million mm 2 Or a range consisting of any two of them.

[0081] Specifically, in the battery cell, the number n1 of the first pole sheet layers 110 having the first active material layer 12 is less than or equal to the total number n1' of the first pole sheet layers 110 (i.e., n1≤n1'), and n1-n1' is, for example, 0 or 1. When there is a first pole sheet layer 110 without the first active material layer 12 in the battery cell, n1<n1', and the difference between the two (n1-n1') is the number of the first pole sheet layers 110 without the first active material layer 12 in the battery cell.

[0082] In addition, in the battery cell, the number n2 of the second pole sheet layers 210 having the second active material layer 22 is less than or equal to the total number n2′ of the second pole sheet layers 210 (ie, n2≤n2′), and usually n2=n2′.

[0083] In addition, the difference between n1' and n2' (i.e., n1'-n2') can be an integer of 0 to 2, for example, 0, 1 or 2, and the difference a between the number of faces m1 where the first active material layer 12 exists and the number of faces m2 where the second active material layer 22 exists can be 0 to 2 times of n1'-n2'. For example, in a laminated cell, n1'-n2'=1, a=2; in a wound cell, n1'-n2'=2, a=4.

[0084] Specifically, w1=w2+the total width of the ineffective region 102 (ie, w1=w2+the sum of the widths w0 of the ineffective regions 102 on two opposite sides in the width direction of the first pole piece 1). Figure 1 and Figure 2 As shown, there are portions (i.e., ineffective regions 102) that extend beyond the first active material layer 12 on both sides of the first active material layer 12 in the second direction b, and the total width of the ineffective regions 102 = the width of the portion of the first active material layer 12 that extends beyond the second active material layer 22 on one side of the second direction b (i.e., the width of the ineffective region 102 on one side of the second active material layer 22 in the second direction b) w0 + the width of the portion of the first active material layer 12 that extends beyond the second active material layer 22 on the other side of the second direction b (i.e., the width of the ineffective region 102 on the other side of the second active material layer 22 in the second direction b) w0. The widths w0 of the ineffective regions 102 on the two sides of the first active material layer 12 in the second direction b may be equal or unequal, and are preferably substantially equal.

[0085] Generally, the width of the first active material layer 12 is substantially equal to the width of the first electrode 1 (first electrode layer 110), and the width of the second active material layer 22 is substantially equal to the width of the second electrode 2 (second electrode layer 210). The increase in the width of the battery cell means that the widths of the first electrode 1 and the second electrode 2 in the battery cell become correspondingly larger, which will reduce the proportion of the width of the portion of the first active material layer 12 that exceeds the second active material layer 22 (i.e., the width of the invalid area 102) in the width w2 of the second active material layer 22 (or the first active material layer 12w1), that is, reducing the area proportion of the invalid area 102 of the second electrode 2 in the battery cell, which is beneficial to improving the high temperature performance of the battery.

[0086] Therefore, it is generally preferred that the width w1 of the first active material layer 12 is greater than or equal to 58 mm, and the width w2 of the second active material layer 22 is greater than or equal to 55 mm.

[0087] Taking into further consideration the size of the battery and the manufacturing process of the battery cell, the width w1 of the first active material layer 12 (usually also the width of the first electrode sheet 1 (first electrode sheet layer 110)) can be 58-130 mm, for example, 58 mm, 60 mm, 65 mm, 70 mm, 75 mm, 80 mm, 85 mm, 90 mm, 95 mm, 100 mm, 105 mm, 110 mm, 115 mm, 120 mm, 125 mm, 130 mm or a range consisting of any two of them, which is beneficial to improving the high temperature performance of the battery, while facilitating the manufacture of the battery and improving the manufacturing yield of the battery.

[0088] Taking into further consideration factors such as the size of the battery and the manufacturing process of the battery cell, the width w2 of the second active material layer 22 (usually also the width of the second electrode plate 2 (second electrode plate layer 210)) can be 55-126mm, for example, 55mm, 60mm, 65mm, 70mm, 75mm, 80mm, 85mm, 90mm, 95mm, 100mm, 105mm, 110mm, 115mm, 120mm, 126mm or a range consisting of any two of them, which is beneficial to improving the high temperature performance of the battery, while facilitating the manufacture of the battery and improving the manufacturing yield of the battery.

[0089] In addition, the length L of the battery cell can be 40 to 150 mm, for example, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm or a range consisting of any two thereof.

[0090] In some embodiments, Figure 5 , Figure 6 and Figure 7As shown, the second pole piece 2 may further include an insulating layer 23, and the insulating layer 23 is located on one side or two opposite sides in the width direction of the second active material layer 22. By introducing the insulating layer 23 at the edge of the second pole piece 2, burrs on the second pole piece 2 caused by cutting and other factors, as well as the burrs piercing the diaphragm and causing short circuits between the positive and negative electrodes, can be covered. At the same time, the insulation between the positive and negative electrodes can be further increased. For example, when the diaphragm 3 is small in width or the pole piece is not well coated, the conductive structures such as the first pole ear 111 of the first pole piece 1 can be prevented from crossing the diaphragm 3 and contacting and short-circuiting with the conductive area of ​​the second pole piece 2 (such as the second current collector 21 or the second active material layer 22).

[0091] Specifically, the insulating layer 23 is disposed on the second current collector 21, and specifically, the insulating layer 23 may exist on both the front and back surfaces of the second current collector 21. Figure 6 As shown, on any surface of the second current collector 21 provided with the insulating layer 23 , the insulating layer 23 is in direct contact with the second active material layer 22 , that is, there is no empty foil area or other coating structure between the insulating layer 23 and the second active material layer 22 .

[0092] Specifically, the insulating layer 23 may be a conventional insulating coating in the art, which may be formed on the surface of the second current collector 21 by a conventional method in the art such as coating. For example, the insulating layer 23 includes a ceramic coating, such as an aluminum oxide ceramic coating.

[0093] Continue to refer Figure 6 , the insulating layer 23 can be provided only on the side of the second active material layer 22 facing the second pole ear 211, that is, the insulating layer 23 is located on the side of the second active material layer 22 facing the second pole ear 211, that is, the insulating layer 23 is located between the second active material layer 22 and the second pole ear 211. In this way, the second pole ear 211 and the first pole ear 111 are located on the same side of the battery cell. By providing the insulating layer 23 on the side of the second pole sheet 2 where the second pole ear 211 is provided, the conductive structures such as the first pole ear 111 can be prevented from crossing the diaphragm 3 and contacting the second pole sheet 2 for short circuit. At the same time, the insulating layer 23 is not provided on the other side of the second pole sheet 2, so that more second active material layers 22 can be provided on the second pole sheet 2, thereby increasing the energy density of the second pole sheet 2, thereby improving the safety and capacity of the battery cell.

[0094] As mentioned above, the first active material layer 12 includes an ineffective area 102 that exceeds the second active material layer 22. After further research, the ratio (w3 / w0) of the width w3 of the insulating layer 23 to the width w0 of the ineffective area 102' located on the side of the first pole piece 1 provided with the first pole ear 111 can be 1:(1.2-8), for example, 1:1.2, 1:1.5, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8 or a range composed of any two of them, which is conducive to further improving the safety and cyclability of the battery. Specifically, if w3 / w0 is too small (w3 / w0<1:8), then the insulation layer 23 is not as good as the ineffective area 102'. The insulating layer 23 is too narrow (or even without the insulating layer 23) and the invalid area 102' is too wide, which may easily cause the conductive structure such as the first pole ear 111 to cross the diaphragm 3 and contact the second pole piece 2 to short-circuit. At the same time, the invalid area 102' that is too wide will increase the proportion of lithium ions diffusing laterally to the invalid area 102' during the battery charging and discharging process, which may specifically lead to the formation of SEI film and consume more active lithium, thereby increasing the attenuation of the battery capacity, which is not conducive to the cycle life and high temperature performance of the battery; if w3 / w0 is too large (w3 / w0>1:1.2), the insulating layer 23 is too wide, which will increase the internal resistance of the second pole piece 2 and cause the battery capacity to decay too quickly.

[0095] In some embodiments, the width w3 of the insulating layer 23 may be 0.5 mm to 5 mm, for example, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm or a range consisting of any two thereof.

[0096] Specifically, in the battery cell, the insulating layer 23 in the second pole piece 2 and the invalid area 102' located on the side of the first pole piece 1 where the first pole ear 111 is provided are located on the same side of the battery cell in the second direction b, the width w3 of the insulating layer 23 refers to the width of the insulating layer 23 in the second direction b, and the width w0 of the invalid area 102' located on the side of the first pole piece 1 where the first pole ear 111 is provided is the width of the invalid area 102' in the second direction b.

[0097] In some embodiments, Figure 7 As shown, when the insulating layer 23 is formed, it may be coated on the second pole ear 211, so that the insulating layer 23 may exist on the surface of the second pole ear 211 (the insulating layer 23 coated on the second pole ear 211 is usually very small), that is, the insulating layer 23 includes a main body 231, and an extension portion 232 extending to the surface of the second pole ear 211, the main body 231 and the extension portion 232 are connected, the main body 231 is located between the extension portion 232 and the second active material layer 22, and also between the second pole ear 211 and the second active material layer 22, and the extension portion 232 is located on the surface of the second pole ear 211, that is, the extension portion 232 is located on the side of the main body 231 away from the second active material layer 22.

[0098] Continue to refer Figure 7 The width w3 of the insulating layer 23 refers to the width of the main body 231, that is, when the insulating layer 23 includes an extension portion 232 extending to the surface of the second pole ear 211, the width w3 of the insulating layer 23 refers to the width of the main body 231 in the second direction b, rather than the sum of the width of the main body 231 in the second direction b and the width of the extension portion 232 in the second direction b.

[0099] In addition, the ratio (H1 / H2) of the total thickness H1 of the second active material layer 22 in the second electrode 2 to the total thickness H2 of the insulating layer 23 can be (0.5-12):1, for example, 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1 or a range composed of any two of them, which is beneficial to further improve the preparation yield of the battery, as well as the safety and cyclability of the battery. Specifically, if the ratio of the total thickness of the second active material layer 22 to the total thickness of the insulating layer 23 is too small (<0.5:1), the thickness of the insulating layer 23 is too thick relative to the second active material layer 22, resulting in poor flatness of the second pole piece 2, which has a great impact on the stacked battery cell or the wound battery cell structure, and will reduce the process yield of the battery cell and the battery performance; and if the ratio of the total thickness of the second active material layer 22 to the total thickness of the insulating layer 23 is too large (>12:1), the thickness of the insulating layer 23 is too thin or even there is no insulating layer 23, which has limited effect on covering the burrs on the edge of the second pole piece 2, and easily causes a battery short circuit, which will not only affect the safety of the battery, but also after the battery is short-circuited, its internal resistance will increase linearly with the extension of the use time, thereby causing the battery capacity to gradually decrease, especially making the battery capacity decay faster and the capacity retention rate lower in a high temperature environment.

[0100] In some embodiments, the total thickness of the insulating layer 23 in the second pole piece 2 can be 10 μm to 100 μm, for example, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm or a range consisting of any two thereof.

[0101] Specifically, when one surface of the second current collector 21 has a second active material layer 22, the total thickness of the second active material layer 22 in the second pole piece is the thickness of the second active material layer 22; when both the front and back surfaces of the second current collector 21 have the second active material layer 22, the total thickness of the second active material layer 22 in the second pole piece is the sum of the thicknesses of the second active material layers 22 on the front and back surfaces of the second current collector 21; when one surface of the second current collector 21 has an insulating layer 23, the total thickness of the insulating layer 23 in the second pole piece is the thickness of the insulating layer 23; when both the front and back surfaces of the second current collector 21 have an insulating layer 23, the total thickness of the insulating layer 23 in the second pole piece is the sum of the thicknesses of the insulating layer 23 on the front and back surfaces of the second current collector 21.

[0102] Specifically, the first direction a and the second direction b intersect, and the two can be perpendicular to each other; the third direction c intersects with the first direction a, and the two can be perpendicular to each other; the third direction c intersects with the second direction b, and the two can be perpendicular to each other. Exemplarily, the first direction a, the length direction of the first pole piece 1 (the length direction of the first current collector 11, the length direction of the first active material layer 12), the length direction of the second pole piece 2 (the length direction of the second current collector 21, the length direction of the second active material layer 22), the length direction of the battery cell, the length direction of the first pole piece layer 110, the length direction of the second pole piece layer 210, and the length direction of the insulating layer 23 are parallel to each other; the second direction b, the width direction of the first pole piece 1 (the width direction of the first current collector 11, the width direction of the first active material layer 12), the width direction of the second pole piece 2 (the width direction of the second current collector 21 direction, the width direction of the second active material layer 22), as well as the width direction of the battery cell, the width direction of the first pole sheet layer 110, the width direction of the second pole sheet layer 210, and the width direction of the insulating layer 23 are parallel to each other; the third direction c, the thickness direction of the first pole sheet 1 (the thickness direction of the first current collector 11, the thickness direction of the first active material layer 12), the thickness direction of the second pole sheet 2 (the thickness direction of the second current collector 21, the thickness direction of the second active material layer 22), as well as the thickness direction of the battery cell, the thickness direction of the first pole sheet layer 110, the thickness direction of the second pole sheet layer 210, and the thickness direction of the insulating layer 23 are parallel to each other.

[0103] In addition, the direction from the first active material layer 12 to the first electrode tab 111 may be parallel to the length direction or width direction of the first electrode sheet 1 , and the direction from the second active material layer 22 to the second electrode tab 211 may be parallel to the length direction or width direction of the second electrode sheet 2 .

[0104] The battery of the embodiment of the utility model can satisfy η+k×(S1 / S2-1)≥0.8 and has good performance such as good cyclability. The units of s1 and s2 are mm respectively. 2; η is the capacity retention rate of the battery when it is fully charged and stored at temperature T for n3 days; k = (OCV1-OCV2) / n3, OCV1 is the voltage of the battery when it is fully charged (initial voltage), OCV2 is the voltage of the battery after it is fully charged and stored at temperature T for n3 days (terminal voltage), that is, k represents the daily voltage decay rate of the battery when it is fully charged and stored at temperature T for n3 days, and the unit of k is mV / day; 55℃≤T≤65℃, 29≤n3≤31.

[0105] Furthermore, the above battery can satisfy 0.8≤η+k×(S1 / S2-1)≤1, which is beneficial to further improve the comprehensive performance of the battery.

[0106] Furthermore, the battery may satisfy k≤0.5, specifically, may satisfy 0.05≤k≤0.5, and has a lower daily voltage decay rate at high temperatures.

[0107] Generally, the capacity retention rate η of the above-mentioned battery in a fully charged state after being left at temperature T for n3 days can be greater than or equal to 93%, specifically 93% to 97%, for example, 93%, 94%, 95%, 96%, 97% or a range consisting of any two of them.

[0108] In specific implementation, the voltage daily decay rate k and capacity retention rate η of a battery placed at temperature T (or open circuit) for n3 days in a fully charged state can be measured by the following method: (1) At room temperature (25°C ± 2°C), discharge at a constant current rate of 1C to the discharge termination voltage V 放 , leave it for 30±1min; then charge it at 1C rate with constant current and constant voltage to the charge limit voltage V 充 , cut-off current 0.05C, leave for 30±1min; then discharge at 1C rate constant current to the discharge termination voltage V 放 , get the initial capacity C1 of the battery; (2) then, leave it for 30±1min; fully charge it at 1C constant current and constant voltage; (3) leave it for 30±1min, record the initial voltage OCV1, then leave it for n3 days in a constant temperature environment at temperature T, record the terminal voltage OCV2; (4) then discharge it at 1C constant current to the end voltage V 放 ; Then charge at a constant current and constant voltage rate of 1C to the charge limit voltage V 充 , cut-off current 0.05C, leave for 30±1min, then discharge at 1C rate constant current to the discharge termination voltage V 放 , get the battery capacity C n1 (5) Calculate the voltage daily decay rate k according to the formula k = (OCV1-OCV2) / n3, and calculate the voltage daily decay rate k according to the formula η = C n1 / C1Calculate the high temperature capacity retention rate η.

[0109] For example, when the battery is a lithium iron phosphate battery (i.e., the positive electrode active material is lithium iron phosphate), the battery discharge termination voltage V 放 About 2.2V, charging limit voltage V 充 It is about 3.65V.

[0110] Generally, the positive electrode active material layer includes a positive electrode active material, a conductive agent and a binder, wherein the positive electrode active material can be a conventional positive electrode active material in the art, for example, including at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, a ternary material, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium phosphate, and lithium-rich manganese-based materials. The ternary material can include lithium nickel cobalt manganese oxide and / or lithium nickel cobalt aluminum oxide, etc.

[0111] In addition, the negative electrode active material layer may include a negative electrode active material, a conductive agent and a binder, wherein the negative electrode active material may be a conventional negative electrode active material in the art, for example, including at least one of graphite, mesophase carbon microbeads, soft carbon, hard carbon, silicon material, silicon oxygen material, silicon carbon material, and lithium titanate.

[0112] In addition, in the positive electrode active material layer and the negative electrode active material layer, the conductive agent can be a conventional conductive material in the art, for example, including one or more of conductive carbon black (SP), acetylene black, carbon nanotubes, conductive graphite, and graphene, and the binder can be a conventional binding material in the art, for example, including one or more of polyvinylidene fluoride (PVDF), a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylic acid salt, carboxymethyl cellulose sodium (CMC), polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene and styrene-butadiene rubber (SBR).

[0113] The current collector of the positive electrode sheet may be a conventional positive electrode current collector in the art, such as aluminum foil, and the current collector of the negative electrode sheet may be a conventional negative electrode current collector in the art, such as copper foil.

[0114] In addition, the above-mentioned diaphragm 3 (isolation membrane) can be a conventional diaphragm 3 in the art, for example, including one or more of a polypropylene diaphragm 3 (PP), a polyethylene diaphragm 3 (PE), a polypropylene / polyethylene double-layer composite film (PP / PE), a polyimide electrospinning diaphragm 3 (PI), a polypropylene / polyethylene / polypropylene three-layer composite film (PP / PE / PP), a cellulose non-woven fabric diaphragm, and a diaphragm with a ceramic coating.

[0115] In addition, the above-mentioned battery also includes an electrolyte or an electrolyte solution. The embodiments of the present utility model can adopt conventional electrolyte or electrolyte solution materials in the art.

[0116] For example, the electrolyte includes a non-aqueous electrolyte, which specifically includes an organic solvent and a lithium salt, wherein the organic solvent may include one or more of ethylene carbonate (EC), dimethyl carbonate (DMC), 1,2-propylene glycol carbonate, propylene carbonate (PC), and diethyl carbonate (DEC), and the lithium salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI).

[0117] The battery of the embodiment of the utility model can be manufactured according to the conventional methods in the field. For example, the positive electrode sheet, the separator 3, and the negative electrode sheet can be stacked in sequence, and wound (or laminated) to form a battery core, and then the battery is manufactured after packaging, liquid injection, formation, capacity division, OCV (open circuit voltage test) and other processes. These steps / processes are all conventional operations in the field, and there is no special limitation on this, and they will not be repeated.

[0118] Generally, the OCV process can be carried out at room temperature, which may specifically include: at room temperature, placing the divided battery for 3 days and testing its voltage (denoted as OCV1); then placing the battery for 10 days and testing its voltage again (denoted as OCV2), and calculating the K value based on K value = (OCV1-OCV2) / 10. The K value range is generally 0 to 0.03mV / h (if the K value is greater than 0.03mV / h, it means that the battery is discharged too fast and is a defective product).

[0119] The present invention is further described below through specific embodiments. In the following embodiments, unless otherwise specified, the first pole piece 1 is a negative pole piece, the first active material layer 12 is a negative active material layer (negative electrode paste), and the first pole ear 111 is a negative pole ear, which is formed by extending outward from the first current collector 11 in a direction away from the first active material layer 12; the second pole piece 2 is a positive pole piece, the second active material layer 22 is a positive active material layer (positive electrode paste), and the second pole ear 211 is a positive pole ear, which is formed by extending outward from the second current collector 21 in a direction away from the second active material layer 22.

[0120] Example 1-1

[0121] (1) Preparation of positive electrode

[0122] Lithium iron phosphate, PVDF, and conductive carbon black are mixed in a mass ratio of 93.5:3.5:3, and N-methylpyrrolidone (NMP) is added thereto, and stirred evenly to obtain a positive electrode slurry with a solid content of 58.3wt%; the positive electrode slurry is coated on the front and back surfaces of an aluminum foil, and after drying and roller pressing, a positive electrode active material layer is formed; then, an alumina ceramic coating in contact with the positive electrode active material layer is formed on the front and back surfaces of the aluminum foil, and the alumina ceramic coating is located between the positive electrode active material layer and the epitaxial portion of the aluminum foil (the area on the aluminum foil not covered by the positive electrode active material layer and the alumina ceramic coating), and the epitaxial portion of the aluminum foil is cut into a positive electrode tab to obtain a positive electrode sheet;

[0123] (2) Preparation of negative electrode sheet

[0124] Graphite, SBR and conductive carbon black are mixed in a mass ratio of 95:3:2, and water is added thereto and stirred evenly to prepare a negative electrode slurry with a solid content of 41wt%; the negative electrode slurry is coated on the front and back surfaces of a copper foil, and after drying and roller pressing, a negative electrode active material layer (first active material layer 12) is formed to obtain a negative electrode sheet.

[0125] (3) Battery assembly

[0126] The positive electrode sheet, the separator 3 and the negative electrode sheet are stacked to form a stacked battery cell (bare battery cell, the structure of which is as follows Fig.10 As shown); wherein, the number of layers of the positive electrode sheet is 25 (i.e., the number of the second electrode sheet layers 210 is 25), the number of layers of the negative electrode sheet is 26 (i.e., the number of the first electrode sheet layers 110 is 26), the positive electrode sheets and the negative electrode sheets are arranged alternately, and the positive electrode sheets and the negative electrode sheets are separated by the diaphragm 3; then, after hot pressing the bare battery cell, the aluminum electrode ear (the second transfer electrode ear) connected to the positive electrode sheet and the copper-plated nickel electrode ear (the first transfer electrode ear) connected to the negative electrode sheet are welded; then, after punching the aluminum-plastic film, the bare battery cell is packaged and vacuum-baked at 85°C for 24 hours; after liquid injection, the battery is formed, sorted, and OCV tested to obtain a soft-package battery.

[0127] The electrolyte contains 1 mol / L lithium hexafluorophosphate, and the solvent of the electrolyte is a mixture of ethylene carbonate, dimethyl carbonate, and 1,2-propylene glycol carbonate in a volume ratio of 1:1:1.

[0128] Among them, the length, width and thickness of the battery cell are 70mm×50mm×56.9mm (that is, the length of the battery cell is 70mm, the width is 50mm, and the thickness is 56.9mm);

[0129] Among them, the projections of the negative electrode active material layers on the front and back surfaces of the negative electrode sheet on the copper foil surface basically overlap (such as Figure 3As shown), in the battery cell, both the positive and negative surfaces of each first electrode layer 110 are provided with a negative electrode active material layer.

[0130] Example 1-2: The difference from Example 1-1 is that the number of positive electrode sheets is 30, the number of negative electrode sheets is 31, the length, width and thickness of the battery cell are 70mm×50mm×67.4mm, and the battery parameters such as AO value, total positive electrode paste area S2, and total negative electrode paste area S1 are shown in Table 1. The other conditions are the same as those of Example 1-1.

[0131] Example 1-3: The difference from Example 1-1 is that the number of stacking layers of the positive electrode sheet is 35, the number of stacking layers of the negative electrode sheet is 36, the length, width and thickness of the battery cell are 70mm×50mm×77.8mm, and the parameters such as the AO value of the battery, the total area of ​​the positive electrode paste S2, and the total area of ​​the negative electrode paste S1 are shown in Table 1. The other conditions are the same as those of Example 1-1.

[0132] Example 2-1: The difference from Example 1-1 is that the battery cell is a wound battery cell. The parameters of the battery such as the AO value, the total area of ​​the positive electrode paste S2, and the total area of ​​the negative electrode paste S1 are shown in Table 1. Except for the difference shown in Table 1, the other conditions are the same as those of Example 1-1. The assembly process of the battery in Example 2-1 is as follows: The positive electrode sheet, the separator 3, and the negative electrode sheet are stacked in sequence and then wound to form a wound battery cell (bare battery cell, whose structure is as shown in FIG. Fig. 9 As shown); wherein, the number of winding folds of the positive electrode sheet is 41 (i.e., after the positive electrode sheet forms a wound structure, the number of the second electrode sheet layers 210 is 41), and the number of winding folds of the negative electrode sheet is 43 (i.e., after the negative electrode sheet forms a wound structure, the number of the first electrode sheet layers 110 is 43); then, after hot pressing the bare battery cell, weld the aluminum electrode tab (second transfer electrode tab) connected to the positive electrode sheet and the copper-plated nickel electrode tab (first transfer electrode tab) connected to the negative electrode sheet; then, after punching the aluminum-plastic film, encapsulate the bare battery cell and bake it at a high temperature of 85°C in vacuum for 24 hours; after liquid injection, the battery is formed, sorted, and OCV tested to obtain a soft-package battery (such as Fig. 9 As shown, the battery is a multi-electrode soft-package battery, that is, in its battery cell, the number of first pole ears 111 is multiple, and these first pole ears 111 are welded with the first adapter pole ears after being attached together, and the number of second pole ears 211 is multiple, and these second pole ears 211 are welded with the second adapter pole ears after being attached together); wherein, the length, width and thickness of the battery cell are 140mm×145mm×11mm.

[0133] Example 2-2: The difference from Example 2-1 is that the number of winding folds of the positive electrode sheet is 51, the number of winding folds of the negative electrode sheet is 53, the length, width and thickness of the battery cell are 140mm×145mm×13.6mm, and the parameters such as the AO value of the battery, the total area of ​​the positive electrode paste S2, and the total area of ​​the negative electrode paste S1 are shown in Table 1. The other conditions are the same as those of Example 2-1.

[0134] Example 2-3: The difference from Example 2-1 is that the number of winding folds of the positive electrode sheet is 61, the number of winding folds of the negative electrode sheet is 63, the length, width and thickness of the battery cell are 140mm×145mm×16.2mm, and the parameters such as the AO value of the battery, the total area of ​​the positive electrode paste S2, and the total area of ​​the negative electrode paste S1 are shown in Table 1. The other conditions are the same as those of Example 2-1.

[0135] Example 2-4: The difference from Example 2-1 is that, in the process of preparing the negative electrode sheet, when the negative electrode slurry is coated on the copper foil, one side of the copper foil is completely coated and the other side is partially coated, so that part of the surface area of ​​one side of the prepared negative electrode sheet is a blank foil area (such as Figure 4 As shown), in the battery cell, an outer ring region 1021 of the negative electrode sheet (extending from one end of the negative electrode sheet located on the outside of the wound battery cell along the winding direction of the negative electrode sheet from the outside to the inside to a partial area of ​​the third first electrode sheet layer 110 of the negative electrode sheet) is provided with a negative electrode active material layer on one side and an empty foil area on the other side, and a diaphragm 3 is present on the outside of the outer ring region 1021 of the negative electrode sheet.

[0136] Example 2-5: The difference from Example 2-1 is that the parameters such as AO value are different, see Table 1 for details. Except for the differences shown in Table 1, the other conditions are the same as Example 2-1.

[0137] Comparative Example 1: The difference from Example 1-1 is that the parameters such as AO value are different, see Table 1 for details. Except for the differences shown in Table 1, the other conditions are the same as Example 2-1.

[0138] Among them, in Examples 1-1 to 1-3, Examples 2-1 to 2-5, and Comparative Example 1, the thickness H1 of the positive electrode active material layer was approximately 0.133 mm, the thickness H2 of the insulating layer was approximately 0.070, H1 / H2 was approximately 1.9, the width w3 of the insulating layer was approximately 2.5 mm, the width w0 of the invalid area 102' on the side of the positive electrode sheet where the positive electrode ear was provided was approximately 5.21 mm, and the ratio (w3 / w0) of the width w3 of the insulating layer to the width w0 of the invalid area 102' on the side of the positive electrode sheet where the positive electrode ear was provided was approximately 0.48.

[0139] Examples 2-6 to 2-15: The difference from Example 2-1 is that the width w3 of the insulating layer, and the ratio (w3 / w0) of the width w3 of the insulating layer to the width w0 of the ineffective area 102' located on the side of the positive electrode sheet where the positive electrode ear is provided are different, see Table 2 for details. Except for the differences shown in Table 2, the other conditions (such as battery cell structure, H1, H2, AO value, positive electrode sheet folding number, negative electrode sheet folding number, positive electrode paste area S2, negative electrode paste area S1, etc.) are the same as those in Example 2-1.

[0140] Examples 2-16 to 2-25: The difference from Example 2-1 is that the thickness H2 of the insulating layer and the ratio (H1 / H2) of the thickness H1 of the positive electrode active material layer to the thickness H2 of the insulating layer are different, as shown in Table 3. Except for the differences shown in Table 3, the other conditions (such as battery cell structure, w3, w0, AO value, positive electrode sheet folding number, negative electrode sheet folding number, positive electrode paste area S2, negative electrode paste area S1, etc.) are the same as those of Example 2-1.

[0141] Example 2-26: The difference from Example 2-1 is that no insulating layer is provided on the positive electrode sheet, and the other conditions are the same as those of Example 2-1.

[0142] In each embodiment and comparative example, a plurality of battery cells were prepared, and the battery cell process yield was calculated (battery cell process yield refers to the percentage of good battery cells to the total number of battery cells, the total number of battery cells = good battery cells + defective battery cells), and the results are shown in Table 1. Among them, any of the following (1) to (3) is considered a defective product, and the standards for good and defective products are as follows:

[0143] (1) If one or more of the pole tabs of the wound cell (including the first pole tab 111 and the second pole tab 211) are misaligned by more than or equal to 5 mm, the wound cell is a defective product; if no pole tab is misaligned by more than or equal to 5 mm, the wound cell is a good product (i.e., the misalignment of each first pole tab 111 and each second pole tab 211 is less than 5 mm);

[0144] (2) If, among all the tabs (including the first tab 111 and the second tab 211) of the laminated battery cell, one or more tabs have too much active material layer (i.e., the width of the portion of the active material layer extending to the tab is greater than 1 mm in the direction from the active material layer to the tab), the laminated battery cell is a defective product; a cell in which the width of the active material layer on each tab in the direction from the active material layer to the tab is less than or equal to 1 mm is a good product (i.e., the width of the first active material layer 12 covered on each first tab 111 is less than or equal to 1 mm, and the width of the second active material layer 22 covered on each second tab 211 is less than or equal to 1 mm);

[0145] (3) During the battery preparation process, if the K value of the OCV process is greater than 0.03mV / h, it is a defective product; if the K value of the OCV process is in the range of 0 to 0.03mV / h, it is a good product.

[0146] In addition, the capacity retention rate η of the batteries of each embodiment and comparative example in a fully charged state and placed in an open circuit at 60°C for 30 days was tested according to the following process: (1) at room temperature (25°C±2°C), the batteries were discharged at a constant current rate of 1C to a discharge termination voltage (2.2V) and placed for 30 minutes; then, the batteries were charged at a constant current and constant voltage rate of 1C to a charge limit voltage (3.65V), with a cut-off current of 0.05C, and placed for 30 minutes; then, the batteries were discharged at a constant current rate of 1C to a discharge termination voltage, and the initial capacity C1 of the batteries was obtained; (2 ) Then, leave it for 30 minutes; fully charge it at 1C constant current and constant voltage; (3) leave it for 30 minutes, record the initial voltage OCV1, then leave it in an open circuit at 60℃ for 30 days (T=60℃, n3=30 days), record the terminal voltage OCV2; (4) discharge it at 1C constant current to the discharge termination voltage; then charge it at 1C constant current and constant voltage to the charge limit voltage, with a cutoff current of 0.05C, leave it for 30±1 minutes, then discharge it at 1C constant current to the discharge termination voltage, and record the battery capacity C n1 (5) Calculate the voltage daily decay rate k according to the formula k = (OCV1-OCV2) / n3, and calculate the voltage daily decay rate k according to the formula η = C n1 / C1 calculated the high temperature capacity retention rate η, and the results are shown in Table 1.

[0147] Table 1

[0148]

[0149] As can be seen from Table 1, relative to Comparative Example 1, the AO values ​​of Examples 1-1 to 2-5 are ≤0.2, which can significantly improve the high temperature capacity retention rate of the battery, improve the high temperature performance of the battery, and maintain a relatively high cell process yield. Among them, the batteries in Examples 1-1 to 1-3 and 2-1 to 2-4 further satisfy 0.05≤S1 / S2-1≤0.2, which can improve the high temperature capacity retention rate of the battery while having a higher cell process yield.

[0150] In addition, relative to Example 2-5, the AO values ​​of Example 1-1 to Example 2-4 are within the range of 0.05 to 0.2, which can improve the high temperature performance of the battery while improving the cell manufacturing yield. The reason for this is that the smaller the AO value, the more folds (layers) of the positive and negative electrode sheets in the cell, the more difficult it is to assemble the cell, which will affect the cell manufacturing yield to a certain extent.

[0151] In addition, according to the AO values ​​and high temperature capacity retention rates η of the above-mentioned Examples 1-1 to 2-4, a relationship curve of the high temperature capacity retention rate η changing with the AO value was obtained by fitting. The results are shown in FIG. Fig.12 , combined with Fig.12It can be seen that with the increase of AO value, the capacity retention rate of the battery tends to decrease. When the AO value is greater than 0.2, the high-temperature capacity retention rate is less than 90%, and the high-temperature performance of the battery is poor.

[0152] Table 2

[0153]

[0154] It can be seen from Table 2 that, relative to Example 2-14 (w3 / w0>1:1.2) and Example 2-15 (w3 / w0<1:8), the batteries in Example 2-6 to Example 2-13 satisfy 1:8≤w3 / w0≤1:1.2, which is beneficial to improving the high temperature capacity retention rate of the battery while maintaining a relatively high cell process yield.

[0155] Table 3

[0156] Example <![CDATA[H2(mm)]]> <![CDATA[H1 / H2]]> Voltage daily decay rate k High temperature capacity retention rate η Cell process yield Example 2-16 0.266 0.5 0.315 94.2％ 70％ Example 2-17 0.133 1.00 0.318 94.4％ 77％ Example 2-18 0.067 2.00 0.322 94.6％ 80％ Example 2-19 0.033 4.00 0.319 94.5％ 78％ Example 2-20 0.022 6.00 0.314 94.2％ 75％ Example 2-21 0.017 8.00 0.308 93.7％ 73％ Example 2-22 0.013 10.00 0.304 93.0％ 70％ Example 2-23 0.011 12 0.295 92.2％ 69％ Example 2-24 1.33 0.1 0.23 85％ 62％ Example 2-25 0.003 50 0.18 70％ 40％ Example 2-26 0 / 0.1 50％ 30％

[0157] It can be seen from Table 3 that, relative to Example 2-24 (H1 / H2<0.5:1) and Example 2-25 (H1 / H2>12:1), the batteries in Example 2-16 to Example 2-23 satisfy 0.5:1≤H1 / H2≤12:1, which is beneficial to improving the high temperature capacity retention rate of the battery and the cell process yield.

[0158] In addition, it can be seen from Tables 2 and 3 that, relative to Comparative Example 2-26 (no insulating layer is provided on the positive electrode sheet), in Examples 2-6 to 2-25, by providing an insulating layer on the side of the positive electrode active material layer facing the positive electrode tab, the high temperature capacity retention rate of the battery and the cell process yield can be improved.

[0159] In addition, referring to the relevant parameters of the wound batteries of Examples 2-6 to 2-26, laminated batteries were made (the difference between laminated batteries and wound batteries is that the cells in laminated batteries are laminated cores. In addition, the thickness and width of each coating of the first electrode sheet and the second electrode sheet of the laminated battery, the number of folds of the first electrode sheet, the number of folds of the second electrode sheet, the AO value, the positive electrode paste area S2, the negative electrode paste area S1 and other conditions are the same as those of the core of the wound battery), and the capacity retention rate and other properties of the laminated batteries and the wound batteries were measured. The trends presented are basically the same (the capacity retention rates of the laminated batteries prepared according to the relevant parameters of Examples 2-6 to 2-25 are better than those of the laminated batteries prepared according to the relevant parameters of Example 2-26, and the laminated batteries satisfy 1:8≤w3 / w0≤1:1.2 and / or 0.5:1≤H1 / H2≤12:1, which can further improve the high temperature capacity retention rate and other performances of the battery), wherein the capacity retention rate of the laminated batteries is about 1.7% lower than that of the wound batteries. The voltage daily decay rate k of the laminated batteries prepared according to the parameters of these embodiments is between 0.28 and 0.38, and these laminated batteries all satisfy 0.8≤η+k×(S1 / S2-1)≤1, which is not repeated in Table 1.

[0160] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the utility model.

Claims

1. A battery, characterized in that: The battery cell comprises a first pole piece and a second pole piece having a polarity opposite to that of the first pole piece, wherein the first pole piece comprises a first active material layer, and the second pole piece comprises a second active material layer; The battery satisfies 0<S1 / S2-1≤0.2, wherein S1 is the total area of ​​the first active material layer in the battery cell, and S2 is the total area of ​​the second active material layer in the battery cell.

2. The battery according to claim 1, characterized in that 0.05≤S1 / S2-1≤0.

2.

3. The battery according to claim 1, characterized in that S2 = (100,000~2.3 million) mm 2 ; And / or, S1 = (110,000~2.4 million) mm 2 .

4. The battery according to any one of claims 1 to 3, characterized in that: The battery cell includes a plurality of first pole sheet layers formed by the first pole sheet, and a plurality of second pole sheet layers formed by the second pole sheet, and the plurality of first pole sheet layers and the plurality of second pole sheet layers are stacked; in the battery cell, the number of the first pole sheet layers is 11 to 73, and the number of the second pole sheet layers is 10 to 71.

5. The battery according to claim 4, characterized in that The battery cell is a laminated battery cell, and the first pole sheet layer is the first pole sheet; Alternatively, the battery cell is a wound battery cell, the first pole sheet includes the multiple first pole sheet layers, and a first bend portion connected between every two adjacent first pole sheet layers, and the second pole sheet includes the multiple second pole sheet layers, and a second bend portion connected between every two adjacent second pole sheet layers.

6. The battery according to any one of claims 1 to 3, characterized in that: The width of the first active material layer is 58-130 mm; And / or, the width of the second active material layer is 55-126 mm.

7. The battery according to any one of claims 1 to 3, characterized in that: The first pole piece includes a first pole ear, the second pole piece includes a second pole ear, and the first pole ear and the second pole ear are located on the same side of the battery cell; the second pole piece also includes an insulating layer, and the insulating layer is located on the side of the second active material layer facing the second pole ear.

8. The battery according to claim 7, characterized in that The first active material layer includes an ineffective region extending beyond the second active material layer, and a ratio of a width of the insulating layer to a width of the ineffective region on a side of the first pole piece where the first pole ear is provided is 1:(1.2-8).

9. The battery according to claim 7, characterized in that The width of the insulating layer is 0.5 mm to 5 mm.

10. The battery according to claim 7, characterized in that The ratio of the total thickness of the second active material layer in the second pole piece to the total thickness of the insulating layer is (0.5-12):

1.

11. The battery according to claim 7, characterized in that The total thickness of the insulating layer in the second pole piece is 10 μm to 100 μm.

12. The battery according to claim 7, characterized in that The insulating layer includes a ceramic coating.

13. The battery according to any one of claims 1 to 3, characterized in that: The length of the battery cell is 40-150 mm.

14. The battery according to claim 1, characterized in that The battery satisfies η+k×(S1 / S2-1)≥0.8, The units of s1 and s2 are mm. 2 ; η is the capacity retention rate of the battery when it is fully charged and left at temperature T for n3 days; k=(OCV1-OCV2) / n3, OCV1 is the voltage of the battery in a fully charged state, OCV2 is the voltage of the battery in a fully charged state after being placed at temperature T for n3 days, and the unit of k is mV / day; 55℃≤T≤65℃, 29≤n3≤31.

15. The battery according to claim 14, characterized in that 0.8≤η+k×(S1 / S2-1)≤1.

16. The battery according to claim 1 or 14, characterized in that: The battery satisfies k≤0.5, k=(OCV1-OCV2) / n3, wherein the unit of k is mV / day, OCV1 is the voltage of the battery in a fully charged state, OCV2 is the voltage of the battery after being left at temperature T for n3 days in a fully charged state, 55°C≤T≤65°C, and 29≤n3≤31.

17. The battery according to claim 16, characterized in that 0.05≤k≤0.5。 18. The battery according to claim 1 or 14, characterized in that: The capacity retention rate of the battery when fully charged and placed at temperature T for n3 days is greater than or equal to 93%, 55°C≤T≤65°C, 29≤n3≤31.

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