Square battery

Abstract

The utility model provides a square battery which comprises a square shell provided with a containing cavity, a first surface plane and a second surface plane, the first surface plane and the second surface plane are located on the outer side of the square shell, and the area of the first surface plane and the area of the second surface plane are maximum. The battery cell is positioned in the accommodating cavity; the insulating film covers the outer side of the square shell; wherein an elastic pad is arranged on the first surface plane and / or the second surface plane. According to the utility model, the elastic layer design is carried out on the large surface of the square battery cell shell, so that the square battery can generate pressure and form constraint on the internal battery cell in the whole charging and discharging process, thereby ensuring that the interfaces between the positive electrode and the diaphragm as well as between the negative electrode and the diaphragm are tight, shortening the lithium ion transmission distance and improving the rate capability and the cycle performance of the battery.

Description

Technical Field

[0001] The utility model relates to the technical field of lithium-ion batteries, in particular to a square battery. Background Art

[0002] Lithium-ion batteries, due to their high energy density, long cycle life, and environmental friendliness, are widely used as a power source for new energy vehicles, leading to continuous technological advancement. Currently, the two most common lithium-ion battery structures are square and cylindrical hard-shell cells.

[0003] Unlike the deformable aluminum-plastic film of soft-pack cells and the strong restraint of cylindrical cell casings, the aluminum casing of prismatic cells, due to its square edges, does not deform well. Furthermore, due to its shape, the aluminum casing does not adequately restrain the internal wound or stacked cores. Therefore, structural optimization is required for traditional prismatic cells to ensure that external forces restrain the wound or stacked cores during charge and discharge, especially for systems where the stacked cores expand significantly from empty to full charge.

[0004] The exterior of the current square battery cell is adhered to the aluminum shell with an insulating film to provide insulation and protection. However, inside the square battery cell battery pack, the external force will not constrain the internal winding core and stacked core due to the presence of the square battery edges. During high-current charging and discharging (between 0% SOC and 100% SOC), the expansion and contraction of the negative electrode plate will increase the distance between the plate and the diaphragm, increasing the polarization of the battery cell and hindering long-term cycling.

[0005] Based on this, it is necessary to design a new square battery structure to improve the above problems. Utility Model Content

[0006] The utility model provides a square battery. The utility model designs an "elastic layer" on the large surface of the square battery cell shell, so that the square battery can generate pressure on the internal battery cell during the entire charging and discharging process to form a constraint, thereby ensuring that the interface between the positive electrode and the diaphragm, and the negative electrode and the diaphragm is tight, shortening the lithium ion transmission distance, and improving the battery's rate performance and cycle performance.

[0007] In order to achieve the above purpose, the technical solution adopted by the present utility model is as follows:

[0008] A first aspect of the present invention provides a square battery, comprising:

[0009] A square shell having a receiving cavity and a first surface plane and a second surface plane located on the outer side of the square shell with the largest area;

[0010] A battery cell is located in the accommodating cavity;

[0011] An insulating film, covering the outer side of the square shell;

[0012] Wherein, an elastic pad is provided on the first surface plane and / or the second surface plane.

[0013] Through the above technical solution, the present invention has at least the following advantages compared with the prior art:

[0014] (1) The square battery structure designed in the present invention is provided with elastic pads on the first surface plane and the second surface plane with the largest area on the outside of the square shell. The elastic pads can ensure the binding force of the bare battery cell inside the accommodating cavity of the square battery shell during the entire charging and discharging process, and at the same time ensure the adhesion between the electrode and the diaphragm, so that the interface contact between the positive electrode and the diaphragm, and the interface contact between the negative electrode and the diaphragm is close, reducing the internal resistance of the battery and improving the rate charging and discharging performance of the battery cell.

[0015] (2) The square battery structure designed by the present invention is provided with elastic pads on the first surface plane and the second surface plane with the largest area on the outer side of the square shell. The elastic pads can also ensure that elastic buffering force is provided for the expansion and contraction of the bare battery cell during the charging and discharging process; and in the long cycle process, the close adhesion between the electrode and the diaphragm is always maintained, shortening the transmission distance of lithium ions and improving the cycle life, especially the fast charging and long cycle performance of the battery can be effectively improved.

[0016] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic cross-sectional view of a square battery provided by the present invention Figure 1 .

[0018] Figure 2 A schematic cross-sectional view of a square battery provided by the present invention Figure 2 .

[0019] Figure 3 This is a top view schematic diagram of the square battery provided by the utility model.

[0020] Figure 4 The battery cross-section comparison diagrams are of the battery cell provided by the present invention and the battery cell in the prior art in the empty state (0% SOC) and the fully charged state (100% SOC).

[0021] Description of the reference numerals: square shell 101 , battery cell 102 , insulating film 103 , elastic pad 104 , positive and negative electrode posts 105 . DETAILED DESCRIPTION

[0022] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0023] The first aspect of the present invention provides a square battery, such as Figure 1 and Figure 2 Shown, including:

[0024] A square housing 101 having a receiving cavity and a first surface and a second surface located on the outer side of the square housing with the largest area;

[0025] The battery cell 102 is located in the accommodating cavity;

[0026] An insulating film 103 is coated on the outside of the square housing 101;

[0027] There is an elastic pad 104 on the first surface plane and / or the second surface plane.

[0028] The square battery structure designed by the present invention is provided with elastic pads on the first surface plane and the second surface plane with the largest area on the outer side of the square shell. The elastic pads can ensure the binding force of the bare battery cell inside the accommodating cavity of the square battery shell during the entire charging and discharging process, and at the same time ensure the adhesion force between the electrode piece and the diaphragm, so that the interface contact between the positive electrode and the diaphragm, and the negative electrode and the diaphragm is close, thereby reducing the internal resistance of the battery and improving the rate charging and discharging performance of the battery cell; and the elastic pads can also ensure that an elastic buffering force is provided for the expansion and contraction of the bare battery cell during the charging and discharging process; and in the long cycle process, the close adhesion between the electrode piece and the diaphragm is always maintained, which shortens the transmission distance of lithium ions, thereby effectively improving the cycle life of the square structure battery, especially the fast charging performance and long cycle performance of the square battery can be effectively improved.

[0029] According to the square battery of the present utility model, Figure 2 As shown, the elastic pad 104 is located in the covering cavity formed by the insulating film 103, or as shown Figure 1 As shown, the elastic pad 104 is located outside the covering cavity formed by the insulating film 103 . Figure 1 The square battery structure shown is that the outside of the square shell 101 is first covered with an insulating film 103, and then the elastic pad 104 is bonded on the basis of the insulating film 103; Figure 2The square battery structure shown is that the elastic pad 104 is directly bonded to the square shell 101, and then the insulating film 103 is coated on the outside of the shell containing the elastic pad 104. The elastic pads under the above two coating sequences are both arranged on the first surface plane and the second surface plane with the largest area on the outside of the square shell, and both can play a role in enhancing the binding force of the battery cell inside the square shell accommodating cavity, ensuring close contact between the electrode and the diaphragm; in addition, in the present invention, the elastic pad 104 and the insulating film 103 can also be integrated first, and then coated on the outside of the square shell 101. Specifically, the elastic pad 104 is directly bonded to the insulating film 103. The elastic pad 104 can be arranged on the side of the insulating film 103 close to the square shell 101 or on the side away from the square shell 101, and then coated on the outside of the square shell 101 together, thereby forming two integrated coating methods.

[0030] According to the square battery of the present utility model, Figure 1-Figure 3 As shown, the distance between the outer edge of the projection of the elastic pad 104 on the first surface plane and / or the second surface plane and the outer edge of the square shell 101 is h, 3mm≤h≤20mm, and for example, the value of h can be 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, or 20mm; it should be noted that the vertical distance between the outer edge of the projection of the elastic pad 104 on the first surface plane and / or the second surface plane and the outer edge of the square shell 101 is on the same side, specifically as Figure 3 In the top view schematic diagram of the square battery shown, the outer edges of the projection of the elastic pad 104 on the first surface plane and / or the second surface plane are divided into long edges and short edges, and the outer edges of the square shell 101 are also divided into long edges and short edges, and the distance h is the vertical distance between the outer edges on the same side, that is, the vertical distance between the long edge of the elastic pad and the long edge of the square shell, or the vertical distance between the short edge of the elastic pad and the short edge of the square shell, and the vertical distance h between the edges of different sides can be equal or different, as long as it is adjusted within the range of 3mm≤h≤20mm. In addition, the distance h of the elastic pad located on the first surface plane and the distance h of the elastic pad located on the second surface plane can also be equal or different.

[0031] The utility model can better control the size of the projected area of the elastic pad on the first surface plane and / or the second surface plane by adjusting the distance between the projected outer edge of the elastic pad and the outer edge of the square shell, so that the projected area is slightly smaller than the area of the first surface plane and / or the second surface plane of the square shell. This design can avoid deformation of the square shell under the pressure of the elastic pad, because the edges of the square shell are prone to irreversible deformation when subjected to force. In addition, the elastic pad is set at a certain distance from the edges, which can make the first surface plane and the second surface plane more likely to deform when subjected to force, and is more conducive to providing elastic buffering force for the expansion and contraction of the bare battery cell, ensuring its restraint force inside the accommodating cavity. In a preferred embodiment, 5mm≤h≤10mm. In addition, Figure 3 This is a top view of the square battery provided by the present invention. Positive and negative poles 105 may also be provided on one side of the square shell 101.

[0032] According to the square battery of the present invention, the material of the elastic pad includes one or more of silica gel, polypropylene, polyethylene, polyimide, aromatic polyamide, polyethylene terephthalate, poly(p-phenylene benzobisoxazole), polyurethane, polyvinyl acid, polystyrene, polymethyl methacrylate, melamine resin, self-microporous polymer, organic covalent polymer, conjugated microporous polymer, covalent triazine framework polymer, porous aromatic framework polymer, hyper-crosslinked polymer, and metal-organic framework polymer.

[0033] According to the square battery of the present invention, the square shell is a square aluminum shell.

[0034] According to the square battery of the present invention, the battery cell can be a laminated structure battery cell or a wound structure battery cell.

[0035] According to the square battery of the present invention, the material of the insulating film includes one or more of polypropylene, polyethylene, polyimide, aromatic polyamide, polyethylene terephthalate, poly(p-phenylene benzobisazole), polyurethane, polyvinyl acid, polystyrene, polymethyl methacrylate, and melamine resin.

[0036] According to the square battery of the present invention, the Shore hardness of the elastic pad is 10 degrees to 60 degrees. For example, the Shore hardness of the elastic pad can be 10 degrees, 11 degrees, 12 degrees, 13 degrees, 14 degrees, 14 degrees, 16 degrees, 17 degrees, 18 degrees, 19 degrees, 20 degrees, 25 degrees, 30 degrees, 35 degrees, 40 degrees, 45 degrees, 50 degrees, 55 degrees, and 60 degrees. When the Shore hardness of the elastic pad is less than 10 degrees, the elastic pad will easily deform under the restraining pressure, thereby failing to play a restraining role. When the Shore hardness of the elastic pad is higher than 60 degrees, the elasticity of the elastic pad will disappear, thereby failing to play a rebound role and reducing the cushioning performance. In a preferred embodiment, the Shore hardness of the elastic pad is 20 degrees to 30 degrees. In addition, the Shore hardness of the elastic pad can be measured by a Shore hardness tester.

[0037] According to the square battery of the present invention, the elastic modulus of the elastic pad is 0.1Mpa to 5Mpa. Exemplarily, the elastic modulus of the elastic pad can be 0.1Mpa, 0.2Mpa, 0.3Mpa, 0.4Mpa, 0.5Mpa, 1Mpa, 1.5Mpa, 2Mpa, 2.5Mpa, 3Mpa, 3.5Mpa, 4Mpa, 4.5Mpa, and 5Mpa. The elastic modulus is a physical quantity that measures the material's ability to resist deformation. The present invention regulates the elastic modulus of the elastic pad to ensure that its deformation ability is within an appropriate range, thereby better achieving a buffering effect. In a preferred embodiment, the elastic modulus of the elastic pad is 1.5Mpa to 3.5Mpa. In addition, the elastic modulus of the elastic pad can be measured by compression or tension test methods, and the stress-strain curve is measured, and the elastic modulus is calculated based on the slope of the linear region.

[0038] According to the square battery of the present invention, the thickness of the elastic pad is d, 0.5mm≤d≤5mm. For example, the value of d can be 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, or 5mm. If the thickness of the elastic pad is too thin, it will not play the role of increasing the binding force. If the elastic pad is too thick, it will cause the elastic pad to exert too much pressure on the square shell, which may easily cause a certain degree of deformation damage to the internal bare battery cell and the square shell. Therefore, it is necessary to control the thickness d of the elastic pad within an appropriate range. In a preferred embodiment, 0.5mm≤d≤2.5mm.

[0039] According to the square battery of the present invention, the thickness rebound rate of the battery cell is M, 2.5%≤M≤20%, illustratively, the value of M can be 2.5%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%; in a preferred embodiment, 2.5%≤M≤10%. The thickness rebound rate of the battery cell refers to the thickness a and b of the battery cell measured by a micrometer when the battery cell is empty (0% SOC) and fully charged (100% SOC), and then the thickness rebound rate (%) of the battery cell is calculated by the rebound rate formula M=(ba) / a×100%, as shown in FIG. Figure 4 As shown in Figure a), the thickness of the battery cell 102 is tested in two states respectively, and then the thickness rebound rate R (%) of the battery cell is calculated by the rebound rate formula. According to the thickness rebound rate of the battery cell, an elastic pad of appropriate thickness can be selected to further enhance the cushioning effect and binding force of the elastic pad.

[0040] In addition, if Figure 4 From the comparison of Figure a) and Figure b), it can be seen that the utility model can effectively ensure the binding force of the bare battery cell inside the accommodating cavity of the square battery shell during the entire charging and discharging process by arranging elastic pads on the first surface plane and the second surface plane of the square shell 101, and at the same time ensure the adhesion force between the electrode and the diaphragm, so that the interface contact between the positive electrode and the diaphragm, and the negative electrode and the diaphragm is close; while the battery cell inside the square battery without an elastic pad will expand or contract under different conditions, so that the distance between the electrode and the diaphragm is greatly stretched, the polarization is increased, and it is not conducive to long-term circulation.

[0041] According to the square battery of the present invention, the thickness d of the elastic pad, the thickness rebound rate M of the battery cell, and the thickness a of the battery cell in the empty (i.e., 0% SOC) state, satisfy the relationship: 0.2mm≤da×M≤0.5mm. Exemplarily, the relationship can be 0.2mm, 0.3mm, 0.4mm, and 0.5mm. By controlling this relationship within an appropriate range, the present invention can ensure that the thickness of the elastic pad is slightly greater than the rebound thickness of the bare battery cell, thereby ensuring the presence of restraining pressure and further enhancing the restraining effect of the elastic pad. At the same time, the elastic pad thickness can be reasonably designed according to the thickness and rebound rate of different battery cells to prevent the elastic pad from being too thick and affecting the energy density of the battery pack. In a preferred embodiment, 0.2mm≤da×M≤0.3mm.

[0042] In addition, it should be noted that the thickness of the battery cell can be designed according to the thickness of the square shell, and the thickness of the battery cell must be less than or equal to the thickness of the inner wall of the square shell. Among them, the thickness of the battery cell in the empty (0% SOC) state is a, which can be measured by a micrometer, and its range is 2mm to 60mm.

[0043] According to the square battery of the present invention, the battery cell includes a negative electrode sheet, and the thickness rebound rate of the negative electrode sheet is ≥10%; the thickness rebound rate of the negative electrode sheet is consistent with the thickness rebound rate test method of the battery cell. According to the square battery of the present invention, the negative electrode sheet is a silicon-carbon negative electrode, and the silicon doping content of the negative electrode sheet is 3% to 100%. The square battery structure system of the present invention is suitable for batteries whose negative electrode system is a carbon-silicon negative electrode system, and negative electrode sheets with a silicon doping content in the range of 3% to 100% are suitable for the square battery structure of the present invention. The elastic pad can enhance the binding force and improve the buffering effect, thereby improving the rate performance and cycle performance of the battery.

[0044] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and illustrative of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above-mentioned content of the present invention are encompassed within the scope of protection intended by the present invention.

[0045] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the reagents, materials, etc. used in the following examples are all commercially available unless otherwise specified.

[0046] To make the purpose, technical solutions, and advantages of the present invention more clear, the following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0047] Example 1

[0048] Used to prepare the square battery of the utility model:

[0049] like Figure 1 In the structure shown, the square battery cell shell is an aluminum shell. The length, width and thickness of the square shell (bare battery cell in a fully charged state) are 280mm, 100mm and 25mm respectively (the size of the battery cell is generally slightly smaller than the size of the square shell and can be just installed in the accommodating cavity of the square shell, but since the reduced size is too small, it can be ignored). The battery cell capacity is 120Ah, and the battery cell adopts a stacking process.

[0050] The chemical system of the battery cell is NCM811 high-nickel ternary material for the positive electrode, and a mixed negative electrode of 10% silicon material + 90% graphite for the negative electrode. The thickness rebound rate of the negative electrode sheet from empty to full charge is 30%, and the thickness rebound rate M of the bare battery cell is 10%.

[0051] The elastic pad is made of silicone with an elastic modulus of 1 MPa, a Shore hardness of 20 degrees, a thickness d of 2.5 mm, and a size of 270 mm in length and 90 mm in width.

[0052] The specific steps are as follows: First, coat the prismatic aluminum battery casing with an insulating film (made of PET). Then, adhere two elastic pads to the first and second surfaces of the prismatic battery casing, respectively. Calculations show that the distance h between the outer edge of the projection of the elastic pads onto the first and / or second surfaces and the outer edge of the prismatic casing is 10 mm.

[0053] Then follow the normal battery production process to complete the Figure 1 The battery shown in the figure is made. The square battery is recorded as C1. The thickness of the battery cell in the empty 0% SOC state is tested to be a=22.3mm, and the thickness of the battery cell in the fully charged 100% SOC state is b=25mm as shown above. At this time, the relationship da×M=0.27mm.

[0054] Example 2

[0055] Example 2 is carried out with reference to Example 1, the only difference from Example 1 is that the battery structure is as follows Figure 2 As shown, two elastic pads need to be bonded to the first surface and the second surface of the square aluminum shell first, and then the insulating film is bonded to the outside. The square battery is marked as C2.

[0056] Example 3

[0057] Example 3 is carried out with reference to Example 1. The only difference from Example 1 is that the elastic pad is bonded only on the first surface of the square battery cell shell. This square battery is denoted as C3.

[0058] Example 4

[0059] Example 4 was carried out with reference to Example 1, with the only difference from Example 1 being that the thickness of the elastic pad was changed to 1.5 mm. The square battery was denoted as C4.

[0060] Example 5

[0061] Example 5 was carried out with reference to Example 1, with the only difference from Example 1 being that the thickness of the elastic pad was changed to 0.5 mm. The square battery was denoted as C5.

[0062] Example 6

[0063] Example 6 was carried out with reference to Example 1, with the only difference from Example 1 being that the thickness of the elastic pad was changed to 5 mm. The square battery was denoted as C6.

[0064] Example 7

[0065] Example 7 was carried out with reference to Example 1, with the only difference from Example 1 being that the size of the elastic pad was changed to 275 mm in length and 95 mm in width. The square battery was designated as C7.

[0066] Example 8

[0067] Example 8 was carried out with reference to Example 1, with the only difference from Example 1 being that the size of the elastic pad was changed to 260 mm in length and 80 mm in width. The square battery was designated as C8.

[0068] Example 9

[0069] Example 9 was carried out with reference to Example 1, with the only difference from Example 1 being that the size of the elastic pad was changed to 280 mm in length and 100 mm in width. The square battery was designated as C9.

[0070] Example 10

[0071] Example 10 is carried out with reference to Example 1. The only difference from Example 1 is that the specific silicone material of the elastic pad is changed so that the elastic modulus of the elastic pad becomes 0.1 MPa and the Shore hardness is 10 degrees. The square battery is recorded as C10.

[0072] Example 11

[0073] Example 11 is carried out with reference to Example 1. The only difference from Example 1 is that the specific silicone material of the elastic pad is changed so that the elastic modulus of the elastic pad becomes 5 MPa and the Shore hardness is 60 degrees. This square battery is recorded as C11.

[0074] Example 12

[0075] Example 12 is carried out with reference to Example 1. The only difference from Example 1 is that the negative electrode is changed to a mixed negative electrode of 5% silicon material + 95% graphite. The thickness rebound rate of the negative electrode sheet from empty charge to full charge is 22%, and the thickness rebound rate M of the bare battery cell is 2.5%. The square battery is recorded as C12.

[0076] Example 13

[0077] Example 13 is carried out with reference to Example 1. The only difference from Example 1 is that the negative electrode is changed to a mixed negative electrode of 16% silicon material + 84% graphite. The thickness rebound rate of the negative electrode sheet from empty charge to full charge is 35%, and the thickness rebound rate M of the bare battery cell is 15%. The square battery is recorded as C13.

[0078] Example 14

[0079] Example 14 is carried out with reference to Example 1. The only difference from Example 1 is that the negative electrode is changed to a mixed negative electrode of 25% silicon material + 75% graphite. The thickness rebound rate of the negative electrode sheet from empty charge to full charge is 60%, and the thickness rebound rate M of the bare battery cell is 20%. The square battery is recorded as C14.

[0080] Comparative Example 1

[0081] Comparative Example 1 was carried out with reference to Example 1, with the only difference from Example 1 being that no elastic pads were provided on both sides of the square shell. This square battery was denoted as C15.

[0082] Test Case

[0083] Used to test the square batteries prepared in the above embodiments and comparative examples;

[0084] 1. Determination of the interface bonding between the cell electrode and the diaphragm & lithium plating window:

[0085] Each of the multiple prismatic batteries C1-C15 prepared in Example 1-Comparative Example 1 was cycled 20 times at room temperature (25°C) using constant current and constant voltage charging (CCCV) at 0.33C, 0.5C, 1C, 2C, 3C, 4C, and 5C, respectively, to 4.2V, and then discharged at 0.5C to 2.5V. The cells were fully charged at different rates and then disassembled. The adhesion between the electrode and the separator was observed and recorded (Table 1). The presence of lithium deposition on the negative electrode surface and the severity of the deposition were also determined and recorded (Table 1).

[0086] II. Cell Cycling Test: Prismatic cells C1-C15 were cycled at room temperature (25°C) using two charge-discharge cycles: 1C / 1C and 4C / 1C. The voltage range was 4.2V to 2.75V. The number of cycles required for the cell capacity to decay to 80% of its initial capacity was recorded in Table 2. After cycling, the cells were fully charged and disassembled. The adhesion between the electrode and separator, as well as the presence of lithium deposition on the negative electrode surface, was observed and recorded. The severity of the deposition was determined and recorded in Table 2.

[0087] Table 1

[0088]

[0089]

[0090] like Figure 1 and Figure 2 The prismatic cells C1 and C2 shown in the figure provide a spring force that ensures strong adhesion between the electrode and the separator during charge and discharge. At the same time, the size of the spring pad must also match the prismatic cell. Too small a size, such as in prismatic cell C8, can result in insufficient spring force at the edges, resulting in a strong center and weak edges, which in turn leads to poor adhesion between the electrode and separator.

[0091] Table 1 also shows the lithium deposition conditions for prismatic cells C1-C15 at different charge rates. By using an elastic pad with an insulator film of appropriate thickness, the lithium deposition window for prismatic cells can be increased from 1C (prismatic cell C15) to 5C (prismatic cell C1), depending on the bare cell rebound rate. Furthermore, the size of the elastic pad must be adapted to the size of the bare cell within the square aluminum casing, otherwise it can easily lead to insufficient adhesion between the edge electrode and the separator, resulting in lithium deposition.

[0092] Table 2

[0093] square battery 1C / 1C Lithium analysis 4C / 1C Lithium analysis C1 1454T@80％ none 1231T@80％ none C2 1412T@80％ none 1208T@80％ none C3 882T@80％ Slight lithium deposition 315T@80％ lithium precipitation C4 1213T@80％ none 1021T@80％ lithium precipitation C5 652T@80％ Slight lithium deposition 273T@80％ Severe lithium deposition C6 1394T@80％ none 1202T@80％ none C7 1322T@80％ none 1152T@80％ lithium precipitation C8 1385T@80％ none 1102T@80％ Edge lithium deposition C9 402T@80％ Slight lithium deposition 103T@80％ Severe lithium deposition C10 397T@80％ Slight lithium deposition 86T@80％ Severe lithium deposition C11 404T@80％ Slight lithium deposition 93T@80％ Severe lithium deposition C12 1578T@80％ none 1502T@80％ none C13 591T@80％ Slight lithium deposition 203T@80％ Severe lithium deposition C14 323T@80％ Severe lithium deposition 72T@80％ Severe lithium deposition C15 523T@80％ Severe lithium deposition 90T@80％ Severe lithium deposition

[0094] Table 2 shows the cycling performance and lithium release of cells C1-C15 under the 1C / 1C and 4C / 1C cycles. Compared to conventional prismatic cells, prismatic cells with elastic pad insulation films of appropriate thickness and size exhibit significantly improved cycling performance, particularly fast-charge cycling performance.

[0095] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be considered as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A square battery, characterized in that: include: A square shell having a receiving cavity and a first surface plane and a second surface plane located on the outer side of the square shell with the largest area; A battery cell is located in the accommodating cavity; An insulating film, covering the outer side of the square shell; Wherein, an elastic pad is provided on the first surface plane and / or the second surface plane.

2. The square battery according to claim 1, characterized in that The elastic pad is located in the covering cavity formed by the insulating film, Alternatively, the elastic pad is located outside the covering cavity formed by the insulating film.

3. The square battery according to claim 1, characterized in that A distance between an outer edge of a projection of the elastic pad on the first surface plane and / or the second surface plane and an outer edge of the square shell is h, and 3mm≤h≤20mm.

4. The square battery according to claim 3, characterized in that 5mm≤h≤10mm.

5. The square battery according to claim 1, characterized in that The material of the elastic pad includes one or more of silica gel, polypropylene, polyethylene, polyimide, aromatic polyamide, polyethylene terephthalate, poly(p-phenylene benzobisazole), polyurethane, polyvinyl acid, polystyrene, polymethyl methacrylate, melamine resin, self-microporous polymer, organic covalent polymer, conjugated microporous polymer, covalent triazine framework polymer, porous aromatic framework polymer, hyper-crosslinked polymer, and metal organic framework polymer; And / or, the material of the insulating film includes one or more of polypropylene, polyethylene, polyimide, aromatic polyamide, polyethylene terephthalate, poly(p-phenylene benzobisoxazole), polyurethane, polyvinyl acid, polystyrene, polymethyl methacrylate, and melamine resin; And / or, the square housing is a square aluminum housing; And / or, the battery cell is a laminated structure battery cell or a wound structure battery cell.

6. The square battery according to claim 1, characterized in that The shore hardness of the elastic pad is 10 degrees to 60 degrees.

7. The square battery according to claim 6, characterized in that: The shore hardness of the elastic pad is 20 degrees to 30 degrees.

8. The square battery according to claim 1, characterized in that The elastic modulus of the elastic pad is 0.1Mpa~5Mpa.

9. The square battery according to claim 8, characterized in that The elastic modulus of the elastic pad is 1.5 MPa to 3.5 MPa.

10. The square battery according to claim 1, characterized in that The thickness of the elastic pad is d, 0.5mm≤d≤5mm.

11. The square battery according to claim 10, characterized in that: 0.5mm≤d≤2.5mm.

12. The square battery according to claim 10, characterized in that: The thickness rebound rate of the battery cell is M, 2.5%≤M≤20%.

13. The square battery according to claim 12, characterized in that: 2.5%≤M≤10%。 14. The square battery according to claim 12, characterized in that: The thickness d of the elastic pad, the thickness rebound rate M of the battery cell and the thickness a of the battery cell in an empty state satisfy the relationship: 0.2mm≤da×M≤0.5mm.

15. The square battery according to claim 14, characterized in that: 0.2mm≤da×M≤0.3mm.

16. The square battery according to claim 1, characterized in that The battery cell includes a negative electrode sheet, and the thickness rebound rate of the negative electrode sheet is ≥10%; And / or, the negative electrode sheet is a silicon-carbon negative electrode, and the silicon doping amount of the negative electrode sheet is 3% to 100%.

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