Method and system for improving electrolyte wettability of battery cell
By coating the electrolyte and binder solution during the cell manufacturing process and combining it with appropriate drying, liquid injection and wetting treatments, the problem of poor electrolyte wettability is solved, and uniform diffusion of the electrolyte in the center of the electrode group is achieved, thereby improving the service life and safety of the cell.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SVOLT ENERGY TECHNOLOGY CO LTD
- Filing Date
- 2024-12-24
- Publication Date
- 2026-06-26
AI Technical Summary
In the existing technology, the electrolyte has poor wettability during the cell manufacturing process, which makes it difficult for the electrolyte to spread evenly to the center of the electrode group, thus affecting the cell's service life.
A shaped electrode assembly is prepared using an electrolyte membrane, a positive electrode sheet, and a negative electrode sheet. By coating an electrolyte and a binder to form a first solution, combined with appropriate drying, liquid injection, and wetting treatments, the electrolyte is ensured to diffuse evenly to the center of the electrode assembly.
This improves the diffusion effect of the electrolyte, ensuring that the electrolyte is evenly diffused to the center of the electrode assembly, thereby enhancing the lifespan and safety performance of the battery cell.
Smart Images
Figure CN119650873B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of battery technology, and more specifically, to a method and system for improving the wettability of electrolyte in battery cells. Background Technology
[0002] In recent years, lithium-ion batteries have been widely used in digital products, vehicles, and energy storage. With consumers' urgent demand for longer driving ranges of lithium-ion products, the range of pure electric vehicles has gradually increased from 200km to 400km, and then to 500km and above, corresponding to increasingly larger battery cell capacities. Similarly, in energy storage, especially in large-scale or commercial and industrial storage applications, cell capacity has increased from 280Ah for the first generation to 314Ah for the second generation, and the third generation has reached over 600Ah. This rapid increase in lithium-ion cell capacity has brought new difficulties and challenges to the cell manufacturing process. Larger cell sizes, higher cell mass and energy density, and higher positive and negative electrode pressure densities require longer electrolyte wetting times, leading to longer manufacturing processes and higher cell production costs. Conversely, insufficient electrolyte wetting time will result in insufficient electrolyte retention, affecting the cell's lifespan.
[0003] In existing battery cell manufacturing methods, the electrolyte consists of an electrolyte and a solvent. The viscosity of the electrolyte usually increases dramatically, making it difficult for the electrolyte to wet the cells. In pursuit of higher capacity and higher energy density, the surface density and compaction of the positive and negative electrodes are becoming increasingly higher, and the electrode sizes are becoming wider and longer, further exacerbating the difficulty of electrolyte wetting in the battery cell.
[0004] In view of this, the present invention is hereby proposed. Summary of the Invention
[0005] One objective of this invention is to provide a method for improving the wettability of electrolyte in battery cells, thereby solving the technical problem of poor electrolyte wettability in the battery cell manufacturing process in the prior art. The method of this invention can effectively improve the diffusion of electrolyte, ensure that the electrolyte is evenly diffused to the center of the electrode assembly, and improve the service life of the battery cell.
[0006] Another object of the present invention is to provide a system for implementing the method for improving the wettability of the electrolyte in a battery cell, which is characterized by high efficiency and safety.
[0007] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:
[0008] A method for improving the wettability of electrolyte in a battery cell includes the following steps:
[0009] A shaped electrode assembly is prepared using an electrolyte membrane, a positive electrode sheet, and a negative electrode sheet. The electrolyte membrane is obtained by coating the membrane with a first solution comprising an electrolyte, a binder, and a first solvent, followed by a first drying process. The shaped electrode assembly is then subjected to a shell-mounting process, a second drying process, a liquid injection process, and a wetting process. The liquid injection process uses an injection liquid comprising a second solvent.
[0010] In some embodiments, the electrolyte includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(oxalato)borate, and lithium tetrafluoroborate.
[0011] In some embodiments, the adhesive includes at least one of polyvinylidene fluoride and polytetrafluoroethylene.
[0012] In some embodiments, the first solvent includes at least one of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and vinylene carbonate.
[0013] In some embodiments, the mass ratio of the electrolyte to the binder is m:1-m, where m is 90%-98%.
[0014] In some embodiments, the coating areal density D of the electrolyte membrane is calculated from the unit area capacity A of the positive electrode, the liquid injection coefficient k, and the electrolyte mass ratio m. m is 90%-98%.
[0015] In some embodiments, the coating includes spraying and / or roller coating.
[0016] In some embodiments, the temperature of the first drying is 60–90°C.
[0017] In some embodiments, the temperature of the second drying is 70–95°C, and the drying time is 6–24 hours.
[0018] In some embodiments, the second solvent includes at least one of dimethyl carbonate, ethylene carbonate, ethyl methyl carbonate, and vinylene carbonate.
[0019] In some embodiments, the temperature of the immersion treatment is 35–50°C, and the immersion treatment time is 12–48 hours.
[0020] In some embodiments, the method for preparing the shaped electrode assembly specifically includes: stacking or winding the electrolyte membrane, positive electrode sheet and negative electrode sheet to obtain the electrode assembly, and then performing a shaping process to obtain the shaped electrode assembly.
[0021] In some embodiments, the shaping process of the shaped electrode assembly is carried out by hot pressing or cold pressing.
[0022] In some embodiments, the method further includes welding the shaped electrode assembly.
[0023] In some embodiments, the process of inserting the casing further includes peripheral welding.
[0024] The system used in implementing the method for improving the wettability of the battery cell electrolyte includes an electrolyte membrane preparation section, an electrode assembly preparation section, a casing and welding section, a drying section, a liquid injection section, and a wetting section. The electrolyte membrane preparation section is used to prepare an electrolyte membrane. The shaped electrode assembly preparation section is used to prepare a shaped electrode assembly. The casing and welding section is used to perform casing treatment on the shaped electrode assembly and welding treatment during the preparation process. The drying section is used to perform a second drying on the shaped electrode assembly after casing. The liquid injection section is used to perform liquid injection treatment. The wetting section is used to perform wetting treatment.
[0025] In some embodiments, the electrolyte membrane preparation unit includes a mixing device, a coating device, and a first drying device. The mixing device is used to mix the electrolyte and a first solvent to obtain a first solution. The coating device is used to coat the membrane with the first solution. The first drying device is used to perform a first drying on the membrane coated with the first solution.
[0026] In some embodiments, the shaped electrode assembly preparation unit includes an electrode assembly device and a shaping device; the electrode assembly device includes a stacking device or a winding device.
[0027] In some embodiments, the drying section includes a second drying device.
[0028] In some embodiments, the immersion portion includes a heating device.
[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0030] (1) The method of the present invention first uniformly coats the electrolyte and binder onto the surface of the diaphragm, and then injects the second solvent. In combination with other steps, it can effectively improve the diffusion of the electrolyte, ensure that the electrolyte is uniformly diffused to the center of the electrode group, and improve the service life of the battery cell.
[0031] (2) The system of the present invention is characterized by high efficiency and safety, and can effectively improve the wettability of the electrolyte in the battery cell, and improve the cycle life and safety performance of the battery cell. Attached Figure Description
[0032] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0033] Figure 1 This is a schematic diagram of the system for improving the wettability of the electrolyte in the battery cell according to the present invention.
[0034] Figure label:
[0035] 1-Electrolyte membrane preparation unit, 101-Mixing device, 102-Coating device, 103-First drying device, 2-Shaped electrode assembly preparation unit, 201-Electrode assembly device, 202-Shaping device, 3-Shell insertion and welding unit, 4-Drying unit, 5-Liquid injection unit, 6-Wetting unit. Detailed Implementation
[0036] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.
[0037] According to one aspect of the present invention, the present invention relates to a method for improving the wettability of electrolyte in a battery cell, comprising the following steps:
[0038] A shaped electrode assembly is prepared using an electrolyte membrane, a positive electrode plate, and a negative electrode plate. The electrolyte membrane is obtained by coating a membrane with a first solution comprising an electrolyte, a binder, and a first solvent, followed by a first drying process. The shaped electrode assembly is then subjected to a casing treatment, a second drying process, a liquid injection treatment, and a wetting treatment. The liquid injection treatment uses an injection solution comprising a second solvent.
[0039] The method of the present invention first mixes the electrolyte and binder evenly and coats them onto the surface of the separator, and then injects the second solvent. In coordination with other steps, it can effectively improve the diffusion of electrolyte, ensure that the electrolyte is evenly diffused to the center of the electrode group, and improve the service life of the cell.
[0040] In some embodiments, the electrolyte includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(oxalato)borate, and lithium tetrafluoroborate.
[0041] In some embodiments, the adhesive includes at least one of polyvinylidene fluoride and polytetrafluoroethylene.
[0042] In some embodiments, the first solvent includes at least one of ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and vinylene carbonate (VC).
[0043] In some embodiments, the mass ratio of the electrolyte to the binder is m:1-m, where m is 90%-98%, such as 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, etc.
[0044] In some embodiments, the coating areal density D of the electrolyte membrane is calculated from the unit area capacity A of the positive electrode, the liquid injection coefficient k, and the electrolyte mass ratio m. m is 90%-98%.
[0045] In some embodiments, the coating includes spraying. Spraying allows the first solution to be evenly distributed on the surface and inside the membrane, which is more conducive to improving the uniform dispersion of the electrolyte in the membrane.
[0046] In some embodiments, the first drying temperature is 60–90°C. In some embodiments, the first drying temperature includes, but is not limited to, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, or 90°C, or any range between two of these. This invention uses a suitable first drying temperature to allow the first solvent on the membrane to evaporate while maintaining the physicochemical properties of the membrane.
[0047] In some embodiments, the method for preparing the shaped electrode assembly specifically includes: stacking or winding the electrolyte membrane, positive electrode sheet, and negative electrode sheet to obtain the electrode assembly, and then performing a shaping process to obtain the shaped electrode assembly. The shaping process is carried out by hot pressing or cold pressing. Further, the shaped electrode assembly is subjected to welding processing, which includes pre-welding and final welding. After casing processing, peripheral welding processing is also included.
[0048] In some embodiments, the temperature of the second drying is 70–95°C, such as 70°C, 75°C, 80°C, 85°C, 90°C, or 95°C, or any range between two. The drying time is 6–24 hours, such as 6 hours, 8 hours, 10 hours, 12 hours, 15 hours, 18 hours, 20 hours, or 24 hours, or any range between two.
[0049] In some embodiments, the second solvent includes at least one selected from dimethyl carbonate, ethylene carbonate, methyl ethyl carbonate, and vinylene carbonate. In some embodiments, the second solvent includes dimethyl carbonate, ethylene carbonate, methyl ethyl carbonate, or vinylene carbonate, or a combination of dimethyl carbonate and ethylene carbonate, a combination of ethylene carbonate and methyl ethyl carbonate, a combination of ethylene carbonate, methyl ethyl carbonate, and vinylene carbonate, etc.
[0050] In some embodiments, the immersion treatment temperature is 35–50°C, for example, 35°C, 40°C, 45°C, 50°C, or any value between the two. The immersion treatment time is 12–48 hours, for example, 12 hours, 15 hours, 18 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 42 hours, 45 hours, or 48 hours, or any value between the two. This invention employs suitable immersion treatment conditions, which are more conducive to the full diffusion of the electrolyte, ensuring that the electrolyte is uniformly diffused to the center of the electrode assembly, thus improving the service life of the battery cell.
[0051] According to another aspect of the present invention, the present invention also relates to a system used in implementing the method for improving the wettability of the electrolyte in a battery cell, comprising an electrolyte membrane preparation section, an electrode assembly preparation section, a casing and welding section, a drying section, a liquid injection section, and a wetting section; the electrolyte membrane preparation section is used to prepare an electrolyte membrane; the shaped electrode assembly preparation section is used to prepare a shaped electrode assembly; the casing and welding section is used to perform casing treatment on the shaped electrode assembly and welding treatment during the preparation process; the drying section is used to perform a second drying on the shaped electrode assembly after casing; the liquid injection section is used to perform a liquid injection treatment; and the wetting section is used to perform a wetting treatment.
[0052] The system of the present invention can effectively improve the wettability of the electrolyte in the battery cell, thereby further improving the cycle life and safety performance of the battery cell.
[0053] In some embodiments, the electrolyte membrane preparation unit includes a mixing device, a coating device, and a first drying device. The mixing device is used to mix the electrolyte and a first solvent to obtain a homogeneous first solution; the mixing device may include a homogenizing tank and a stirrer. The coating device is used to coat the membrane with the first solution; the coating device includes a coating machine and a spraying device. The membrane is placed on the coating machine for unwinding, and the first solution is uniformly sprayed onto the membrane using the spraying machine. The first drying device is used to perform a first drying on the membrane coated with the first solution. The first drying device may be a conventional drying device, such as an oven.
[0054] In some embodiments, the shaped electrode assembly preparation unit includes an electrode assembly device and a shaping device; the electrode assembly device includes a stacking device or a winding device. A shaping device is further employed for shaping processing. The shaping device includes a press.
[0055] In some embodiments, the drying section includes a second drying device, such as an oven.
[0056] In some embodiments, the immersion portion includes a heating device, such as an oven.
[0057] In some implementations, the method further includes: forming and grading the impregnated cells.
[0058] In some embodiments, the battery cells of the present invention include pouch cells, aluminum-cased cells, and cylindrical cells, including but not limited to LFP and NCM material systems.
[0059] In a preferred embodiment, the method for improving the wettability of the battery cell electrolyte includes the following steps:
[0060] (a) The coating density D of the electrolyte membrane is calculated based on the positive electrode unit area capacity A, the liquid injection coefficient k, and the electrolyte mass ratio m.
[0061] Electrolyte diaphragms are prepared using an electrolyte diaphragm preparation unit: electrolytes and binders are mixed in proportion, and a first solvent is added and stirred evenly in a mixing device to form a first solution; the electrolyte is lithium hexafluorophosphate, the binder is polyvinylidene fluoride, and the first solvent is dimethyl carbonate; a roll of diaphragm is placed on a coating head for unwinding, and the first solution is evenly coated onto the diaphragm, and then a first drying device is used for first drying at a temperature of 60-90℃ to allow the solvent to evaporate and obtain the electrolyte diaphragm.
[0062] (b) Preparation of a shaped electrode assembly using a shaped electrode assembly preparation unit: The electrolyte diaphragm, positive electrode sheet and negative electrode sheet are assembled using an electrode assembly device, for example, by alternating stacking or winding, to form an electrode assembly, and then hot-pressed and shaped using a shaped device to obtain a shaped electrode assembly.
[0063] Housing insertion and welding treatment: The shaped electrode assembly is pre-welded and final-welded, and then the perimeter is welded after housing insertion.
[0064] Drying process: The cells are placed in a constant temperature oven for a second drying process. The second drying temperature is 70-95℃ and the time is 6-24 hours to control the overall moisture content of the cells.
[0065] Liquid Injection Processing Section: The battery cells processed by the drying section are subjected to liquid injection processing, and the injection liquid used in the liquid injection processing is a second solvent.
[0066] Immersion treatment: After injection, immersion treatment is performed at a temperature of 35-50℃ for 12-48 hours.
[0067] The following explanation, in conjunction with specific embodiments, further clarifies the situation.
[0068] Example 1
[0069] A method for improving the wettability of electrolyte in a battery cell includes the following steps:
[0070] (a) The unit area capacity A of the positive electrode of the LFP cell is taken as 3.0 mAh / cm². 2 The injection coefficient k is 0.35 g / Ah, the electrolyte mass ratio m in the first solution is 94%, and the coating surface density D of the resulting electrolyte diaphragm is 1.117 mg / cm³. 2 .
[0071] Based on an electrolyte mass ratio (m) of 94%, the electrolyte and binder are mixed uniformly at a ratio of 94:6. An appropriate amount of the first solvent is added and stirred in a homogenizing tank to form the first solution. The electrolyte is lithium hexafluorophosphate, the binder is polyvinylidene fluoride, and the first solvent is DMC. A roll of diaphragm is placed on the coating machine head for unwinding, and the first solution is uniformly coated onto the diaphragm. The coating amount is adjusted, and then the diaphragm undergoes a first drying process at 75°C to allow the solvent to evaporate, resulting in an areal density of 1.117 mg / cm³. 2 Electrolyte membrane.
[0072] (b) The above-mentioned electrolyte separator, lithium iron phosphate positive electrode sheet and graphite negative electrode sheet are alternately stacked to form an electrode assembly, and then hot-pressed to shape it to obtain a shaped electrode assembly; the shaped electrode assembly is pre-welded and final-welded, and after being placed in the shell, it is welded around the perimeter; then it is placed in a constant temperature oven for a second drying at a temperature of 90°C for 12 hours; then it is injected with a second solvent (DMC) as the injection liquid; then it is impregnated at a temperature of 45°C for 24 hours.
[0073] Example 2
[0074] A method for improving the wettability of electrolyte in a battery cell includes the following steps:
[0075] (a) The unit area capacity A of the positive electrode of the LFP cell is taken as 3.25 mAh / cm². 2 The injection coefficient k is 0.35 g / Ah, the electrolyte mass ratio m in the first solution is 94%, and the coating surface density D of the resulting electrolyte diaphragm is 1.210 mg / cm³. 2 .
[0076] Based on an electrolyte mass ratio (m) of 94%, the electrolyte and binder are mixed uniformly at a ratio of 94:6. An appropriate amount of the first solvent is added and stirred in a homogenizing tank to form the first solution. The electrolyte is lithium hexafluorophosphate, the binder is polyvinylidene fluoride, and the first solvent is DMC. A roll of diaphragm is placed on the coating machine head for unwinding, and the first solution is uniformly coated onto the diaphragm. The coating amount is adjusted, and then the diaphragm undergoes a first drying process at 80℃ to allow the solvent to evaporate, resulting in an areal density of 1.210 mg / cm³. 2 Electrolyte membrane.
[0077] (b) The above-mentioned electrolyte separator, lithium iron phosphate positive electrode sheet and graphite negative electrode sheet are alternately stacked to form an electrode assembly, and then hot-pressed to shape it to obtain a shaped electrode assembly; the shaped electrode assembly is pre-welded and final-welded, and after being placed in the shell, it is peripherally welded; then it is placed in a constant temperature oven for a second drying at a temperature of 90°C for 12 hours; then it is injected with a second solvent, which is EC, EMC and DMC in a volume ratio of 1:1:1; then it is impregnated at a temperature of 45°C for 36 hours.
[0078] Example 3
[0079] A method for improving the wettability of electrolyte in a battery cell includes the following steps:
[0080] (a) The unit area capacity A of the positive electrode of the LFP cell is taken as 3.25 mAh / cm². 2 The injection coefficient k is 0.35 g / Ah, the electrolyte mass ratio m in the first solution is 98%, and the surface density D of the resulting electrolyte on the diaphragm is 1.161 mg / cm³. 2 .
[0081] Based on an electrolyte mass ratio (m) of 98%, the electrolyte and binder are mixed evenly at a ratio of 98:2. An appropriate amount of the first solvent is added and stirred in a homogenizing tank to form the first solution. The electrolyte is lithium hexafluorophosphate, the binder is polyvinylidene fluoride, and the first solvent is DMC. A roll of diaphragm is placed on the coating machine head for unwinding, and the first solution is evenly coated onto the diaphragm. The coating amount is adjusted, and then the diaphragm undergoes a first drying process at 85℃ to allow the solvent to evaporate, resulting in an areal density of 1.161 mg / cm³. 2 Electrolyte membrane.
[0082] (b) The above-mentioned electrolyte membrane, lithium iron phosphate positive electrode sheet and graphite negative electrode sheet are alternately stacked to form an electrode assembly, and then hot-pressed to shape it to obtain a shaped electrode assembly; the shaped electrode assembly is pre-welded and final-welded, and after being placed in the shell, it is welded around the perimeter; then it is placed in a constant temperature oven for a second drying at a temperature of 75°C for 24 hours; then it is injected with a second solvent, which is EC, EMC and DMC in a volume ratio of 1:1:1; then it is impregnated at a temperature of 50°C for 12 hours.
[0083] Example 4
[0084] A method for improving the wettability of electrolyte in a battery cell includes the following steps:
[0085] (a) The unit area capacity A of the positive electrode of the LFP cell is taken as 3.25 mAh / cm². 2 The injection coefficient k is 0.35 g / Ah, the electrolyte mass ratio m in the first solution is 90%, and the surface density D of the resulting electrolyte on the diaphragm is 1.264 mg / cm³. 2 .
[0086] Based on an electrolyte mass ratio (m) of 90%, the electrolyte and binder are mixed uniformly at a ratio of 90:10. An appropriate amount of the first solvent is added and stirred in a homogenizing tank to form the first solution. The electrolyte is lithium bis(fluorosulfonyl)imide, the binder is polyvinylidene fluoride, and the first solvent is DMC. A roll of diaphragm is placed on the coating head for unwinding, and the first solution is uniformly coated onto the diaphragm. The coating amount is adjusted, and then the diaphragm undergoes a first drying process at 90°C to allow the solvent to evaporate, resulting in an areal density of 1.264 mg / cm³. 2 Electrolyte membrane.
[0087] (b) The above-mentioned electrolyte membrane, lithium iron phosphate positive electrode sheet and graphite negative electrode sheet are alternately stacked to form an electrode assembly, and then hot-pressed to shape it to obtain a shaped electrode assembly; the shaped electrode assembly is pre-welded and final-welded, and after being placed in the shell, it is welded around the perimeter; then it is placed in a constant temperature oven for a second drying at a temperature of 75°C for 24 hours; then it is injected with a second solvent, which is EC, EMC and DMC in a volume ratio of 1:1:1; then it is impregnated at a temperature of 50°C for 12 hours.
[0088] Example 5
[0089] A method for improving the wettability of electrolyte in a battery cell includes the following steps:
[0090] (a) The unit area capacity A of the positive electrode of the LFP cell is taken as 3.25 mAh / cm². 2The injection coefficient k is 0.35 g / Ah, the electrolyte mass ratio m in the first solution is 94%, and the surface density D of the obtained electrolyte on the diaphragm is 1.210 mg / cm³. 2 .
[0091] Based on an electrolyte mass ratio (m) of 94%, the electrolyte and binder are mixed uniformly at a ratio of 94:6. An appropriate amount of the first solvent is added and stirred in a homogenizing tank to form the first solution. The electrolyte is lithium hexafluorophosphate, the binder is polyvinylidene fluoride, and the first solvent is DMC. A roll of diaphragm is placed on the coating machine head for unwinding, and the first solution is uniformly coated onto the diaphragm. The coating amount is adjusted, and then the diaphragm undergoes a first drying process at 90℃ to allow the solvent to evaporate, resulting in an areal density of 1.210 mg / cm³. 2 Electrolyte membrane.
[0092] (b) The above-mentioned electrolyte membrane, lithium iron phosphate positive electrode sheet and graphite negative electrode sheet are wound to form an electrode assembly, and then hot-pressed to shape it to obtain a shaped electrode assembly; the shaped electrode assembly is pre-welded and final-welded, and after being placed in the shell, it is welded around the perimeter; then it is placed in a constant temperature oven for a second drying at a temperature of 90°C for 15 hours; then it is injected with a second solvent, which is EC, EMC and VC in a volume ratio of 1:1:1; then it is impregnated at a temperature of 45°C for 36 hours.
[0093] Example 6
[0094] The system used in implementing the method for improving the wettability of the electrolyte in battery cells as described in Examples 1-5 is as follows: Figure 1 As shown, it includes an electrolyte membrane preparation section 1, an electrode assembly preparation section 2, a shell insertion and welding section 3, a drying section 4, a liquid injection section 5, and an immersion section 6.
[0095] The electrolyte membrane preparation unit 1 is used to prepare an electrolyte membrane; the electrolyte membrane preparation unit 1 includes a mixing device 101, a coating device 102 and a first drying device 103. The mixing device 101 is used to mix an electrolyte and a first solvent to obtain a first solution. The coating device 102 is used to coat the membrane with the first solution. The first drying device 103 is used to perform a first drying on the membrane coated with the first solution.
[0096] The shaping electrode assembly preparation unit 2 is used to prepare the shaping electrode assembly; the shaping electrode assembly preparation unit 2 includes an electrode assembly device 201 (stack device) and a shaping device 202.
[0097] The housing and welding section 3 is used for housing the shaped electrode assembly and for welding during the manufacturing process.
[0098] The drying section 4 is used to perform a second drying on the shaped electrode assembly after it has been placed in the shell; the drying section 4 includes a second drying device.
[0099] The injection section 5 is used to perform injection treatment; the wetting section 6 is used to perform wetting treatment; the wetting section 6 includes a heating device.
[0100] Comparative Example 1
[0101] The unit area capacity A of the positive electrode of the LFP battery cell is 3.25 mAh / cm². 2 The lithium iron phosphate positive electrode sheet and the graphite negative electrode sheet are alternately stacked to form an electrode assembly, which is then hot-pressed and shaped to obtain a shaped electrode assembly. The shaped electrode assembly is pre-welded and final-welded, and after being placed in the casing, it is welded around the perimeter. Then it is placed in a constant temperature oven for a second drying at 90°C for 12 hours. Next, it is injected with a 1.0 mol / L lithium hexafluorophosphate electrolyte, and the electrolyte solvent is EC, EMC and DMC in a volume ratio of 1:1:1. Finally, it is immersed in a solution at 45°C for 36 hours.
[0102] Test case
[0103] Wetting effect test
[0104] (1) Lithium element distribution test: The battery cell after the above impregnation treatment was disassembled, and the center and edge parts of the middle layer negative electrode sheet were taken. The difference in lithium element content between the center and the edge of the negative electrode sheet was tested by ICP. The smaller the difference in lithium element content between the center and the edge, the better the wettability.
[0105] (2) Interface observation: The cell after the above impregnation treatment was subjected to formation treatment, and then charged to 3.8V at a rate of 0.5C. The color difference between the center and the edge of the negative electrode was observed after disassembly. The smaller the color difference between the fully charged interface between the center and the edge, the better the wettability.
[0106] The test results are shown in Table 1.
[0107] Table 1 Test Results
[0108]
[0109] As shown in Table 1, the method of the present invention first uniformly coats the electrolyte and binder onto the surface of the separator, and then implements the subsequent injection of the second solvent. In combination with other steps, it can effectively improve the diffusion of the electrolyte, ensure that the electrolyte is uniformly diffused to the center of the electrode group, and improve the service life of the cell.
[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for improving the wettability of electrolyte in a battery cell, characterized in that, Includes the following steps: A shaped electrode assembly is prepared using an electrolyte membrane, a positive electrode sheet, and a negative electrode sheet. The electrolyte membrane is obtained by coating a membrane with a first solution formed by an electrolyte, a binder, and a first solvent, followed by a first drying process. The shaped electrode assembly undergoes a shell-mounting process, a second drying process, a liquid injection process, and an immersion process. The liquid injection process uses a second solvent as the injection liquid. The electrolyte is at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(oxalato)borate, and lithium tetrafluoroborate. The mass ratio of the electrolyte to the binder is m:1-m, where m is 90%~98%; The coating density D of the electrolyte membrane is calculated from the unit area capacity A of the positive electrode, the liquid injection coefficient k, and the electrolyte mass ratio m. m is 90%~98%; The second drying temperature is 70~95℃, and the second drying time is 6~24h; The temperature for the immersion treatment is 35~50℃; The method for preparing the shaped electrode assembly specifically includes: stacking or winding the electrolyte membrane, positive electrode sheet and negative electrode sheet to obtain the electrode assembly, and then performing a shaping process to obtain the shaped electrode assembly; During the preparation of the shaped electrode assembly, the shaping process is carried out by hot pressing or cold pressing.
2. The method for improving the wettability of the electrolyte in a battery cell according to claim 1, characterized in that, It includes at least one of the following features (1) to (2): (1) The adhesive includes at least one of polyvinylidene fluoride and polytetrafluoroethylene; (2) The first solvent includes at least one of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate and vinylene carbonate.
3. The method for improving the wettability of the electrolyte in a battery cell according to claim 1, characterized in that, The coating includes spraying and / or roller coating.
4. The method for improving the wettability of the electrolyte in a battery cell according to claim 1, characterized in that, The temperature for the first drying process is 60~90℃.
5. The method for improving the wettability of the electrolyte in a battery cell according to claim 1, characterized in that, The second solvent is at least one of dimethyl carbonate, ethylene carbonate, ethyl methyl carbonate, and vinylene carbonate.
6. The method for improving the wettability of the electrolyte in a battery cell according to claim 1, characterized in that, The soaking treatment time is 12~48h.
7. The method for improving the wettability of the electrolyte in a battery cell according to claim 1, characterized in that, It includes at least one of the following features (1) to (2): (1) It also includes: welding the shaped electrode assembly; (2) After the shell-in process, the process also includes: peripheral welding.
8. The system used in implementing the method for improving the wettability of the electrolyte in a battery cell according to any one of claims 1 to 7, characterized in that, It includes an electrolyte membrane preparation section, an electrode assembly preparation section, a shell insertion and welding section, a drying section, a liquid injection section, and an impregnation section; The electrolyte membrane preparation section is used to prepare the electrolyte membrane; the shaped electrode assembly preparation section is used to prepare the shaped electrode assembly; the shell insertion and welding section is used to perform shell insertion treatment on the shaped electrode assembly and welding treatment during the preparation process; the drying section is used to perform a second drying on the shaped electrode assembly after shell insertion; the liquid injection section is used to perform liquid injection treatment; and the wetting section is used to perform wetting treatment.
9. The system according to claim 8, characterized in that, It includes at least one of the following features (1) to (4): (1) The electrolyte membrane preparation unit includes a mixing device, a coating device and a first drying device. The mixing device is used to mix the electrolyte and the first solvent to obtain a first solution. The coating device is used to coat the membrane with the first solution. The first drying device is used to perform a first drying on the membrane coated with the first solution. (2) The shaping electrode assembly preparation unit includes an electrode assembly device and a shaping device; the electrode assembly device includes a stacking device or a winding device; (3) The drying section includes a second drying device; (4) The immersion part includes a heating device.