Battery cell, method for shaping a battery cell and use thereof

Abstract

The application provides an electric core and a shaping method and application thereof, and the shaping method comprises the following steps: after the electric core is injected with electrolyte once, the electric core is placed and formed, then the electric core is injected with electrolyte again and heated and placed, and the shaping of the electric core is completed; the mixed solution used in the second injection of electrolyte comprises electrolyte, polymer and catalyst. The shaping method injects the electrolyte containing polymer in the second injection process of the electric core, uses the volume expansion of the cross-linking reaction of the polymer to shape the concave electric core, improves the flatness of the electric core, avoids the use of large shaping equipment, and ensures the uniformity of the electric core glue and the electrochemical performance.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and relates to a battery cell and its shaping method and application. Background Technology

[0002] With the rapid development of the battery industry, in order to improve the specific energy of power batteries for new energy vehicles, integrated battery pack solutions without modular structures have become the trend. The use of bolt fasteners is decreasing, and structural adhesives are used more often for structural fastening. Therefore, the spreading effect of the structural adhesive coated inside the battery pack plays a crucial role in the application of the battery pack.

[0003] In battery manufacturing, to ensure smooth core insertion into the casing, the thickness margin of the core is generally designed to be between 85% and 95%. However, in the electrolyte injection process, the negative pressure environment created by vacuuming the battery's interior is used to effectively inject the electrolyte and allow it to permeate into the gaps between the cells, further wetting and penetrating the separator, positive and negative electrode materials, and active materials on the electrodes. During this process, due to the battery's structure leading to varying strengths in different directions, and the use of negative pressure for electrolyte injection, the aluminum-cased battery casing is prone to indentation in the thickness direction, causing cell deformation. Severe deformation can affect the uniform spreading of the structural adhesive coated inside the battery pack, impacting bonding strength and potentially leading to module safety incidents. Therefore, it is necessary to reshape batteries exhibiting bulging after plastic deformation.

[0004] In existing technologies, battery cells are generally shaped by pressure. Most battery shaping devices are simple devices that can only shape a single cell, resulting in low shaping efficiency and failing to meet production needs. Alternatively, they are large mechanical shaping devices that can shape batteries in batches, but only cells of the same size. Devices that can shape batteries of different sizes are bulky, complex to operate, and require a high level of expertise from operators. More importantly, shaping equipment is generally suitable for convex cells, and the shaping effect on concave cells is generally poor. To achieve a certain shaping effect, high pressure is often required, but high pressure can damage the cell casing.

[0005] Based on the above research, there is a need to provide a shaping method for battery cells. This shaping method is simple to implement, low in cost, and does not require the use of large shaping equipment. It can significantly improve the flatness of the battery cells, ensure the uniformity of adhesive application during the battery cell assembly process, reduce the amount of adhesive used, and improve the performance of the battery cells. Summary of the Invention

[0006] The purpose of this invention is to provide a battery cell and its shaping method and application. The shaping method involves injecting an electrolyte containing a polymer during the secondary electrolyte injection process of the battery cell, and utilizing the volume expansion during the cross-linking reaction of the polymer to shape the concave battery cell, thereby improving the flatness of the battery cell, avoiding the use of large shaping equipment, and ensuring the uniformity of the adhesive coating and the electrochemical performance of the battery cell.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for shaping a battery cell, the method comprising the following steps:

[0009] After the first electrolyte injection, the battery cell is left to stand and form, then a second electrolyte injection and heating are performed to complete the shaping of the battery cell.

[0010] The mixed solution used in the secondary injection includes electrolyte, polymer and catalyst.

[0011] This invention involves a second electrolyte injection process after the initial electrolyte injection of the battery cell. This second injection allows the electrolyte to fully wet the cell and form a stable SEI film before a second electrolyte injection, filling the voids within the cell. The solution used in this second injection, based on the electrolyte, also includes polymers and a catalyst. Subsequent heating and settling allow the polymers in the cell voids to undergo a cross-linking reaction under the influence of the heat and catalyst, forming a solid filler with a certain degree of elasticity that fully fills the voids. Therefore, this invention avoids the need for large-scale forming equipment and solves the problem of large-area concavity in the battery cell without increasing the cell manufacturing process. This not only saves costs and ensures the electrochemical performance of the cell, but also improves the uniformity of adhesive application during the cell module assembly process and reduces the amount of adhesive used.

[0012] This invention does not impose specific limitations on the internal structure and composition of the battery cell, the composition of the electrolyte, or the formation conditions; those skilled in the art can make reasonable selections according to their needs.

[0013] Preferably, the polymer comprises polymer A and polymer B.

[0014] Preferably, the viscosity ratio of polymer A and polymer B is (0.8-1.2):(0.8-1.2), for example, it can be 0.8:1, 1:1, 1.2:1 or 1:0.8, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] The polymers described in this invention are two polymers with similar viscosities. Polymer A and polymer B can crosslink under the action of heat and a catalyst. That is, this invention uses a semi-prepolymer method to prepare a solid elastic polymer in the cell voids to solve the problem of cell concavity. Since the viscosities of polymer A and polymer B are similar, the materials in the mixed solution can be easily mixed evenly, thereby improving the yield of crosslinking products. If the viscosity difference between polymer A and polymer B is large, since the viscosity of polymers is affected by the molecular weight of polymers, that is, the molecular weights of the two will differ greatly, the yield of the crosslinked polymer obtained from the reaction will be reduced, and the cell cannot be effectively shaped.

[0016] Preferably, the viscosity of polymer A is 20-50 mPas, for example, it can be 20 mPas, 25 mPas, 30 mPas, 35 mPas, 40 mPas, 45 mPas or 50 mPas, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] Preferably, the viscosity of polymer B is 20-50 mPas, for example, it can be 20 mPas, 25 mPas, 30 mPas, 35 mPas, 40 mPas, 45 mPas or 50 mPas, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] The viscosity of polymer A and polymer B in this invention refers to the melt viscosity. Both are in a molten state at room temperature. Therefore, the viscosity is the melt viscosity at room temperature.

[0019] The viscosities of polymer A and polymer B described in this invention are similar, but their viscosities must be within a specific range to ensure the shaping effect of the battery cell. If the viscosity is too high, the resulting mixed solution will have an excessively high viscosity, affecting the wettability of the electrolyte during secondary injection and preventing the mixed solution from fully filling the gaps, thus reducing the shaping effect. If the viscosity is too low, the molecular weight of both polymers will be too low, and polymer A and polymer B will not be able to form or will form fewer solid cross-linked products, thereby affecting the shaping effect.

[0020] Preferably, the temperature for heating and settling is 35-60°C, for example, it can be 35°C, 40°C, 45°C, 50°C, 55°C or 60°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] Preferably, the heating and settling time is 12-48 hours, for example, it can be 12 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours or 48 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] In this invention, after secondary liquid injection, the cell is heated and allowed to stand. The conditions of the standing period will affect the formation of cross-linking products. If the temperature of heating and standing is too low or the time is too short, the cross-linking reaction will be insufficient and an effective solid elastic polymer will not be formed, thus failing to support the concave surface of the shell. If the temperature of heating and standing is too high, the reaction between polymer A and polymer B will be too fast, causing the reaction to run out of control, resulting in local bulging and preventing the cell from being effectively shaped.

[0023] Preferably, the solution used in the first injection consists only of electrolyte.

[0024] This invention adds polymers and catalysts only during the secondary electrolyte injection process. The primary electrolyte injection process only injects electrolyte to fully wet and form an SEI film. If polymers and catalysts are added to the solution during the primary electrolyte injection, the addition of polymers A and B, both of which have a certain viscosity, will affect the wetting of the electrodes by the electrolyte. Furthermore, the products generated by their reaction will further increase the internal resistance of the cell, causing interface deterioration and affecting electrical performance. However, by adding polymers A, B, and the catalyst during the secondary electrolyte injection, the cell has already completed internal wetting and formation, generating a stable SEI film. This ensures the integrity of the battery interface and performance. The components in the secondary electrolyte injection mainly fill the gaps between the shell and the core, minimizing the impact on the internal interface of the core and ensuring battery performance.

[0025] Preferably, the process includes a cell vacuuming step before the initial electrolyte injection.

[0026] Preferably, the temperature at which the battery cell is left to stand after one injection is 30-60°C, for example, 35°C, 40°C, 45°C, 50°C, 55°C or 60°C, and the time is 12-48h, for example, 12h, 15h, 20h, 25h, 30h, 35h, 40h, 45h or 48h, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, the method for preparing the mixed solution includes: mixing an electrolyte, polymer A, polymer B, and a catalyst to obtain the mixed solution.

[0028] Preferably, the mass ratio of the electrolyte, polymer A, polymer B and catalyst is (88-92):(3-8):(3-8):(0.008-0.015), for example, it can be 90:5:5:0.01, 88:3:8:0.008 or 92:8:8:0.015, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, the mixing temperature is 0-20℃, for example, it can be 0℃, 3℃, 5℃, 7℃, 9℃, 11℃, 13℃, 15℃, 17℃, 19℃ or 20℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 10-15℃.

[0030] In the preparation process of the mixed solution used in the secondary injection of the present invention, polymer A, polymer B, catalyst and electrolyte can be mixed evenly at a relatively low mixing temperature. At the same time, the mixing temperature should be controlled within a reasonable range to avoid premature reaction of polymer A and polymer B during the mixing process.

[0031] Preferably, the mixing speed is 600-800 r / min, for example, 600 r / min, 700 r / min or 800 r / min, and the time is 1-3 h, for example, 1 h, 2 h, 2.5 h or 3 h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] Preferably, polymer A comprises a polymer with hydroxyl groups at the end.

[0033] Preferably, polymer A comprises a polyether polyol, more preferably a polyoxypropylene ether polyol with a molecular weight distribution of 2000-6000. For example, polymer A comprises a polyoxypropylene ether diol.

[0034] Preferably, the polymer B comprises a polymer with -N=C=O end groups.

[0035] The terminal hydroxyl groups in polymer A and the terminal -N=C=O groups in polymer B of the present invention react to form an ester polymer. The resulting cross-linked polymer structure has high stability, does not swell or corrode in the electrolyte, can exist stably in the electrolyte, does not react with the electrolyte, and does not affect the normal use of the battery cell.

[0036] Preferably, the -N=C=O content in polymer B is 5-10.05wt%, for example, it can be 5wt%, 6wt%, 7wt%, 8wt%, 9wt% or 10.05wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] Preferably, the polymer B is obtained by reacting a polyether polyol with an isocyanate compound.

[0038] Preferably, the preparation of polymer B includes: mixing 88-92 parts of polytetrahydrofuran ether polyol, 8-12 parts of polyether polyol and 102-106 parts of 4,4-diphenylmethane diisocyanate, heating to 50-75°C for 1-2 hours, and then cooling to below 25°C to obtain polymer B.

[0039] The temperature is raised to 50-75℃, for example, 50℃, 55℃, 65℃, 70℃ or 75℃, and the reaction is carried out for 1-2 hours, for example, 1 hour, 1.5 hours or 2 hours. The temperature is then lowered to below 25℃, for example, 25℃, 20℃, 15℃, 10℃ or 5℃, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] Preferably, the catalyst comprises an organotin catalyst.

[0041] Preferably, the organotin compound includes dibutyltin dilaurate and / or stannous octoate.

[0042] Preferably, before the first and second injections, the temperature is kept below 25°C, for example, 25°C, 20°C, 15°C or 10°C, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] Preferably, the secondary injection followed by heating and settling is performed in a fixed fixture.

[0044] As a preferred embodiment of the shaping method of the present invention, the shaping method includes the following steps:

[0045] (1) After vacuuming the cell, perform one liquid injection, then let it stand and form to obtain the cell after one liquid injection;

[0046] The solution used in the first injection only includes electrolyte;

[0047] (2) The battery cell after the first liquid injection in step (1) is injected with liquid a second time, and heated and left to stand at 35-60°C in a fixed fixture for 12-48 hours to complete the shaping of the battery cell;

[0048] The temperature of the battery cell is kept below 25°C before the first and second electrolyte injections.

[0049] The preparation method of the mixed solution used in the secondary injection includes: mixing electrolyte, polymer A, polymer B and catalyst at a mass ratio of (88-92):(3-8):(3-8):(0.008-0.015) at a stirring speed of 600-800 r / min for 1-3 h at a temperature of 10-15℃ to obtain the mixed solution;

[0050] The viscosity ratio of polymer A to polymer B is (0.8-1.2):(0.8-1.2). Polymer A is a polyoxypropylene ether polyol with a molecular weight distribution of 2000-6000 and a viscosity of 20-50 mPas. Polymer B is a polymer with a -N=C=O content of 5-10.05 wt% and a viscosity of 20-50 mPas.

[0051] In a second aspect, the present invention provides a battery cell obtained by the shaping method described in the first aspect.

[0052] Thirdly, the present invention provides a battery module comprising the battery cells as described in the second aspect.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] (1) The solution used in the secondary injection of the present invention is based on electrolyte and also contains polymer and catalyst. After subsequent heating and standing, the polymer can undergo cross-linking reaction to form a solid filler with a certain elasticity, which fully fills the gaps in the battery cell. Therefore, the present invention can avoid the use of large-scale shaping equipment and solve the problem of large-area concavity of the battery cell without increasing the battery cell preparation process. It not only saves costs and ensures the electrochemical performance of the battery cell, but also improves the uniformity of adhesive coating during the battery cell module assembly process and reduces the amount of adhesive used.

[0055] (2) In this invention, polymers and catalysts are added only during the secondary liquid injection process, while only electrolyte is injected during the primary liquid injection process. Since the cell has already completed internal wetting and formation during the primary liquid injection, and a stable SEI film has been generated, the addition of polymers during the secondary liquid injection ensures that the interface and performance of the battery are intact. The components in the secondary liquid injection mainly fill the gaps between the shell and the core, which can minimize the impact on the internal interface of the core and ensure the performance of the battery. This avoids the impact on the internal resistance and interface of the cell caused by adding polymers and catalysts to the solution during the primary liquid injection. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the concave battery cell described in Embodiment 1 of the present invention;

[0057] Figure 2 This is a side view of the shaped battery cell as described in Embodiment 1 of the present invention;

[0058] Among them, 1-cell large surface, 2-cell large surface concave surface, 3-cell electrode, 4-wound core, 5-crosslinked polymer. Detailed Implementation

[0059] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0060] The battery cells described in the following examples and comparative examples include an LFP positive electrode, a graphite negative electrode, and a PE separator. The electrolyte includes 1 mol / L LiPF6 / EC+DMC+EMC (EC is ethylene carbonate, EMC is ethyl methyl carbonate, DMC is dimethyl carbonate, and the volume ratio of EC, DMC, and EMC is 1:1:1). The above description of the battery cells and electrolyte is only for the purpose of more completely illustrating the technical solution of the present invention and should not be regarded as a specific limitation of the present invention.

[0061] Example 1

[0062] This embodiment provides a method for shaping a battery cell, the method comprising the following steps:

[0063] (1) After the cell is evacuated, it is injected with liquid once, and then it is left to stand at 50°C for 24 hours before formation to obtain the cell after one injection.

[0064] The solution used in the first injection only includes electrolyte;

[0065] The battery cell after the first injection is as follows: Figure 1 The concave battery cell shown has a battery cell terminal 3 at its upper end and a concave surface 2 on the large surface 1 of the battery cell.

[0066] (2) After the cell has undergone a second electrolyte injection as described in step (1), it is heated and left to stand at 45°C for 24 hours in a fixed fixture to complete the shaping of the cell. The side structure diagram of the shaped cell is shown below. Figure 2 As shown, the interior includes a core 4, and a cross-linked polymer 5 exists between the core 4 and the outer shell;

[0067] The temperature of the battery cell is maintained at 25°C before the first and second electrolyte injections.

[0068] The preparation method of the mixed solution used in the secondary injection includes: mixing electrolyte, polymer A, polymer B and dibutyltin dilaurate at a mass ratio of 90:5:5:0.01 at 13°C and a stirring speed of 700 r / min for 2.5 h to obtain the mixed solution;

[0069] The viscosity ratio of polymer A to polymer B is 1:1, and polymer A is a polyoxypropylene ether diol with a molecular weight distribution of 3000-5000 and a viscosity of 30 mPas.

[0070] Polymer B is a polymer with an -N=C=O content of 8wt% and a viscosity of 30 mPas. The preparation method includes the following steps: 90 parts of polytetrahydrofuran ether diol with an average functionality of 2 and a number average molecular weight of 2000, 10 parts of polyoxypropylene ether diol with an average functionality of 3 and a number average molecular weight of 6000, and 104 parts of 4,4-diphenylmethane diisocyanate are mixed, heated to 60℃ and reacted for 1.5 h, and then cooled to 50℃ to obtain polymer B.

[0071] Example 2

[0072] This embodiment provides a method for shaping a battery cell, the method comprising the following steps:

[0073] (1) After the cell is evacuated, it is injected with liquid once, and then it is left to stand at 30°C for 48 hours before formation to obtain the cell after one injection.

[0074] The solution used in the first injection only includes electrolyte;

[0075] (2) After the cell has been injected with electrolyte once in step (1), it is heated at 60°C in a fixed fixture and left to stand for 12 hours to complete the shaping of the cell.

[0076] The temperature of the battery cell is maintained at 20°C before the first and second electrolyte injections.

[0077] The preparation method of the mixed solution used in the secondary injection includes: mixing electrolyte, polymer A, polymer B and dibutyltin dilaurate at a mass ratio of 88:8:8:0.015 at 20°C and stirring at 800 r / min for 2 h to obtain the mixed solution.

[0078] The viscosity ratio of polymer A to polymer B is 1.2:1, and polymer A is a polyoxypropylene ether diol with a molecular weight distribution of 2000-6000 and a viscosity of 25 mPas.

[0079] Polymer B is a polymer with an -N=C=O content of 10.05 wt% and a viscosity of 20.8 mPas. The preparation method includes the following steps: 88 parts of polytetrahydrofuran ether diol with an average functionality of 2 and a number average molecular weight of 2000, 12 parts of polyoxypropylene ether diol with an average functionality of 3 and a number average molecular weight of 6000, and 106 parts of 4,4-diphenylmethane diisocyanate are mixed, heated to 75°C and reacted for 1 h, and then cooled to 45°C to obtain polymer B.

[0080] Example 3

[0081] This embodiment provides a method for shaping a battery cell, the method comprising the following steps:

[0082] (1) After the cell is evacuated, it is injected with liquid once, and then it is left to stand at 60°C for 12 hours before formation to obtain the cell after one injection.

[0083] The solution used in the first injection only includes electrolyte;

[0084] (2) After the cell has been injected with electrolyte once in step (1), it is heated and left to stand at 35°C for 48 hours in a fixed fixture to complete the shaping of the cell.

[0085] The temperature of the battery cell is maintained at 25°C before the first and second electrolyte injections.

[0086] The method for preparing the mixed solution used in the secondary injection includes: mixing electrolyte, polymer A, polymer B and stannous octoate at a mass ratio of 92:3:3:0.008 at 5°C and stirring at 600 r / min for 3 h to obtain the mixed solution.

[0087] The viscosity ratio of polymer A to polymer B is 0.8:1.2, and polymer A is a polyoxypropylene ether diol with a molecular weight distribution of 2000-6000 and a viscosity of 33.3 mPas.

[0088] Polymer B is a polymer with a -N=C=O content of 5wt% and a viscosity of 50 mPas. The preparation method includes the following steps: 92 parts of polytetrahydrofuran ether diol with an average functionality of 2 and a number average molecular weight of 2000, 12 parts of polyepoxypropylene ether diol with an average functionality of 3 and a number average molecular weight of 6000, and 106 parts of 4,4-diphenylmethane diisocyanate are mixed, heated to 50°C and reacted for 2 hours, and then cooled to 40°C to obtain polymer B.

[0089] Example 4

[0090] This embodiment provides a method for shaping a battery cell. Except for the viscosity change of polymer A and polymer B in step (2) to make their viscosity ratio 0.7:1.3 and to make their molecular weight adaptably changed, the shaping method is the same as in embodiment 1.

[0091] Example 5

[0092] This embodiment provides a method for shaping a battery cell. Except for the viscosity change of polymer A and polymer B in step (2) to make their viscosity ratio 1.3:0.7 and to make their molecular weight adaptably changed, the shaping method is the same as in embodiment 1.

[0093] Example 6

[0094] This embodiment provides a method for shaping a battery cell. Except for step (2), where the viscosity of polymer A and polymer B is 55 mPas and the molecular weight of the two polymers is changed adaptively, the shaping method is the same as in embodiment 1.

[0095] Example 7

[0096] This embodiment provides a method for shaping a battery cell. Except for step (2), where the viscosity of polymer A and polymer B is 15 mPas and the molecular weight of the two polymers is changed adaptively, the shaping method is the same as in Example 1.

[0097] Example 8

[0098] This embodiment provides a method for shaping a battery cell. Except for the heating and settling temperature of 30°C in step (2), the shaping method is the same as that in embodiment 1.

[0099] Example 9

[0100] This embodiment provides a method for shaping a battery cell. Except for the heating and settling temperature of 70°C in step (2), the shaping method is the same as that in embodiment 1.

[0101] Example 10

[0102] This embodiment provides a method for shaping a battery cell. Except for the method of preparing the mixed solution in step (2), which is carried out at 30°C, the shaping method is the same as that in Example 1.

[0103] Comparative Example 1

[0104] This comparative example provides a method for shaping a battery cell, the method comprising the following steps:

[0105] (1) After the cell is evacuated, it is injected with liquid once, and then it is left to stand at 50°C for 24 hours before formation to obtain the cell after one injection.

[0106] The solution used in the first injection only includes electrolyte;

[0107] (2) After the cell has been injected with electrolyte once in step (1), it is heated at 45°C and left to stand for 24 hours to complete the shaping of the cell.

[0108] The solution used in the secondary injection only includes electrolyte.

[0109] Comparative Example 2

[0110] This comparative example provides a method for shaping a battery cell. Except for the solution used in step (1) for the first injection, which is the mixed solution described in step (2), the shaping method is the same as that in Example 1.

[0111] The above embodiments and comparative examples show the deformation of the battery cell obtained after shaping. The deformation size is the vertical distance from the lowest point of the depression or the highest point of the convexity to the plane of the large surface. At the same time, the 100-cycle capacity retention rate of the battery cell is tested.

[0112] The test results are shown in Table 1:

[0113] Table 1

[0114]

[0115] In the table above, negative values ​​represent concave cells, and positive values ​​represent convex cells.

[0116] As can be seen from Table 1:

[0117] (1) The shaping method provided by the present invention does not add any additional steps to the original cell preparation process, which can solve the defect of concavity after cell injection and ensure the performance of the cell. As can be seen from Examples 1 and 4-5, the viscosity ratio of polymer A and B affects the formation of cross-linked polymer, thus affecting the shaping effect. As can be seen from Examples 1 and 6-7, if the viscosity of polymer A and polymer B is too high or too low, it will also affect the formation of cross-linked polymer and reduce the shaping effect. As can be seen from Examples 1 and 8-9, the present invention requires heating and standing at a specific temperature after secondary injection to ensure the reaction of polymer A and polymer B and improve the shaping effect. As can be seen from Examples 1 and 10, the present invention requires low temperature when preparing the mixed solution of secondary injection to avoid the premature reaction of polymer A and polymer B due to excessively high temperature, which would affect the shaping effect. However, it is necessary to ensure that the temperature is above 0°C to ensure the fluidity of the electrolyte.

[0118] (2) As can be seen from Example 1 and Comparative Example 1, when conventional preparation process is used for secondary liquid injection without adding polymer A, polymer B and catalyst, the cell will have a concave surface and the performance of the cell cannot be guaranteed, which is lower than that of Example 1. As can be seen from Example 1 and Comparative Example 2, when polymer A, polymer B and catalyst are added during the first liquid injection, the cell cannot be shaped, but will increase the internal resistance of the cell, deteriorate the cell interface and affect the cell performance. However, when polymer A, polymer B and catalyst are added during the secondary liquid injection of the present invention, the cross-linked polymer can fill the gap between the shell and the core, minimize the impact on the internal interface of the core and ensure the performance of the battery.

[0119] In summary, the present invention provides a battery cell, its shaping method and application. The shaping method involves injecting an electrolyte containing a polymer during the secondary electrolyte injection process of the battery cell, utilizing the volume expansion during the cross-linking reaction of the polymer to shape the concave battery cell, thereby improving the flatness of the battery cell, avoiding the use of large shaping equipment, and ensuring the uniformity of the adhesive coating and electrochemical performance of the battery cell.

[0120] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for shaping a battery cell, characterized in that, The plastic surgery method includes the following steps: After the first electrolyte injection, the battery cell is left to stand and form, then a second electrolyte injection and heating are performed to complete the shaping of the battery cell. The mixed solution used in the secondary injection includes electrolyte, polymer and catalyst; The polymers include polymer A and polymer B; The viscosity ratio of polymer A to polymer B is (0.8-1.2):(0.8-1.2); The viscosity of polymer A is 20-50 mPas; The viscosity of polymer B is 20-50 mPas; The polymer A comprises a polyether polyol, and the polymer B is obtained by reacting a polyether polyol with an isocyanate compound. The catalyst includes organotin catalysts; The solution used in the first injection only includes electrolyte; The mass ratio of the electrolyte, polymer A, polymer B and catalyst is (88-92):(3-8):(3-8):(0.008-0.015).

2. The shaping method according to claim 1, characterized in that, The temperature for heating and settling is 35-60℃.

3. The shaping method according to claim 1, characterized in that, The heating and settling time is 12-48 hours.

4. The shaping method according to claim 1, characterized in that, The process of vacuuming the battery cell is also included before the initial electrolyte injection.

5. The shaping method according to claim 1, characterized in that, The method for preparing the mixed solution includes: mixing an electrolyte, polymer A, polymer B, and a catalyst to obtain the mixed solution.

6. The shaping method according to claim 5, characterized in that, The mixing temperature is 0-20℃.

7. The shaping method according to claim 5, characterized in that, The mixing temperature is 10-15℃.

8. The shaping method according to claim 5, characterized in that, The mixing speed is 600-800 r / min, and the mixing time is 1-3 h.

9. The shaping method according to claim 1, characterized in that, The polymer A comprises polyoxypropylene ether polyols with a molecular weight distribution of 2000-6000.

10. The shaping method according to claim 1, characterized in that, The polymer B includes polymers with -N=C=O end groups, and the content of -N=C=O in the polymer B is 5-10.05 wt%.

11. The shaping method according to claim 1, characterized in that, Before the first and second injections, the temperature should be kept below 25°C.

12. The shaping method according to claim 1, characterized in that, The second injection is followed by heating and settling in a fixed fixture.

13. The shaping method according to claim 1, characterized in that, The plastic surgery method includes the following steps: (1) After vacuuming the cell, perform one liquid injection, then let it stand and form to obtain the cell after one liquid injection; The solution used in the first injection only includes electrolyte; (2) After the cell has been injected with electrolyte once in step (1), it is heated and left to stand at 35-60°C in a fixed fixture for 12-48 hours to complete the shaping of the cell. The temperature of the battery cell is kept below 25°C before the first and second electrolyte injections. The preparation method of the mixed solution used in the secondary injection includes: mixing electrolyte, polymer A, polymer B and catalyst at a mass ratio of (88-92):(3-8):(3-8):(0.008-0.015) at a stirring speed of 600-800 r / min for 1-3 h at a temperature of 10-15℃ to obtain the mixed solution; The viscosity ratio of polymer A to polymer B is (0.8-1.2):(0.8-1.2). Polymer A is a polyoxypropylene ether polyol with a molecular weight distribution of 2000-6000 and a viscosity of 20-50 mPas. Polymer B is a polymer with a -N=C=O content of 5-10.05 wt% and a viscosity of 20-50 mPas.

14. A battery cell, characterized in that, The battery cell is obtained using the shaping method described in any one of claims 1-13.

15. A battery module, characterized in that, The battery module includes the battery cell as described in claim 14.

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