Method and system for improving wettability of battery cell electrolyte

Abstract

The invention relates to the technical field of batteries, in particular to a method and a system for improving wettability of a battery cell electrolyte. The method for improving the wettability of the battery cell electrolyte comprises the following steps that an electrolyte diaphragm, a positive plate and a negative plate are adopted to prepare a shaped pole group, and the electrolyte diaphragm is obtained by coating a diaphragm with a first solution formed by an electrolyte, a binder and a first solvent and then performing first drying; and the shaped pole group is subjected to shell entering treatment, second drying, liquid injection treatment and infiltration treatment, and injection liquid adopted in the liquid injection treatment comprises a second solvent. According to the method disclosed by the invention, the electrolyte and the binder are uniformly coated on the surface of the diaphragm to obtain the electrolyte diaphragm, and then the subsequent injection of the second solvent is implemented and coordinated with other steps, so that the diffusion of the electrolyte can be effectively improved, the electrolyte is ensured to be uniformly diffused to the center of a pole piece of a pole group, and the service life of a battery cell is prolonged.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a method and system for improving the wettability of an electrolyte in a battery cell. Background Art

[0002] In recent years, lithium-ion batteries have been widely used in digital products, vehicle terminals and energy storage fields. With consumers' urgent demand for long-range lithium-ion products, the range of pure electric vehicles has gradually increased from 200 km to 400 km, and then to 500 km and above, and the capacity of the corresponding power battery cells has become larger and larger; for the same energy storage battery cells, especially in the field of large storage or industrial and commercial storage, the battery cell capacity has increased from 280 Ah in the first generation to 314 Ah in the second generation, and the capacity of the third generation battery cells has reached more than 600 Ah. The rapid increase in the capacity of lithium-ion batteries has brought new difficulties and challenges to the process of battery cells. The larger the size of the battery cell, the higher the quality and energy density of the battery cell, the higher the density of the positive and negative electrodes, and the longer the time required for the corresponding electrolyte to be infiltrated, the longer the process time, and the higher the corresponding battery cell manufacturing cost. On the contrary, if the electrolyte infiltration time of the battery cell is insufficient, it will first lead to insufficient liquid retention, which will affect the service life of the battery cell.

[0003] In the prior art battery cell preparation method, the electrolyte is composed of electrolyte and solvent, and the viscosity of the electrolyte usually increases sharply, making it difficult for the electrolyte to penetrate. In pursuit of higher capacity and higher energy density, the surface density and compaction of the positive and negative electrodes are getting higher and higher, and the size of the electrode is getting wider and longer, making it more difficult for the electrolyte to penetrate the battery cell.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] One object of the present invention is to provide a method for improving the wettability of electrolyte in battery cells, so as to solve the technical problem of poor wettability of electrolyte in the battery cell preparation process in the prior art; the method of the present invention can effectively improve the diffusion of electrolyte, ensure that the electrolyte is evenly diffused to the center of the electrode group and the electrode sheet, 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 of a battery cell, which has the characteristics of high efficiency and safety.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0008] A method for improving the wettability of a battery cell electrolyte comprises the following steps:

[0009] A shaped electrode group is prepared by using an electrolyte diaphragm, a positive electrode sheet and a negative electrode sheet, wherein the electrolyte diaphragm is obtained by coating the diaphragm with a first solution formed by an electrolyte, a binder and a first solvent and then undergoing a first drying process; the shaped electrode group is subjected to a shelling process, a second drying process, a liquid injection process and an infiltration process, wherein the injection liquid used in the liquid injection process comprises a second solvent.

[0010] In some embodiments, the electrolyte includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(oxalatoborate), and lithium tetrafluoroborate.

[0011] In some embodiments, the binder 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 surface density D of the electrolyte separator is calculated from the unit area capacity A of the positive electrode sheet, the injection coefficient k and the electrolyte mass ratio m. m is 90%-98%.

[0015] In some embodiments, the coating comprises spray coating and / or roller coating.

[0016] In some embodiments, the first drying temperature is 60-90°C.

[0017] In some embodiments, the second drying temperature is 70 to 95° C., and the second drying time is 6 to 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 infiltration treatment is 35 to 50° C., and the time of the infiltration treatment is 12 to 48 hours.

[0020] In some embodiments, the method for preparing the shaped electrode group specifically includes: laminating or winding the electrolyte membrane, the positive electrode sheet and the negative electrode sheet to obtain the electrode group, and then performing a shaping treatment to obtain the shaped electrode group.

[0021] In some embodiments, during the preparation of the shaped electrode group, the shaping treatment is performed by hot pressing or cold pressing.

[0022] In some implementations, the method further includes: welding the shaped electrode group.

[0023] In some implementations, after the shelling process, the process further includes: peripheral welding process.

[0024] The system used to implement the method for improving the wettability of the electrolyte of the battery cell includes an electrolyte membrane preparation part, a pole group preparation part, a shelling and welding part, a drying part, a liquid injection part and an impregnation part; the electrolyte membrane preparation part is used to prepare the electrolyte membrane; the shaped pole group preparation part is used to prepare the shaped pole group; the shelling and welding part is used to perform shelling treatment on the shaped pole group and welding treatment during the preparation process; the drying part is used to perform a second drying on the shaped pole group after shelling; the liquid injection part is used to implement the liquid injection treatment; and the impregnation part is used to implement the impregnation treatment.

[0025] In some embodiments, the electrolyte membrane preparation unit includes a mixing device, a coating device and a first drying device, wherein 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, and the first drying device is used to perform a first drying on the membrane coated with the first solution.

[0026] In some embodiments, the shaping electrode group preparation section includes a pole piece assembly device and a shaping device; the pole piece assembly device includes a lamination device or a winding device.

[0027] In some embodiments, the drying section includes a second drying device.

[0028] In some embodiments, the wetting portion includes a heating device.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The method of the present invention firstly uniformly coats the electrolyte and the binder on the surface of the diaphragm, and then implements the subsequent injection of the second solvent. This method cooperates with other steps to effectively improve the diffusion of the electrolyte, ensure that the electrolyte is uniformly diffused to the center of the electrode group and the electrode sheet, and improve the service life of the battery cell.

[0031] (2) The system of the present invention is highly efficient and safe, and can effectively improve the wettability of the battery cell electrolyte, thereby improving the cycle life and safety performance of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 A schematic diagram of a system for improving the wettability of a battery cell electrolyte according to the present invention.

[0034] Reference numerals:

[0035] 1-electrolyte membrane preparation section, 101-mixing device, 102-coating device, 103-first drying device, 2-molding electrode group preparation section, 201-electrode piece assembly device, 202-molding device, 3-shelling and welding section, 4-drying section, 5-liquid injection section, 6-infiltration section. DETAILED DESCRIPTION

[0036] The embodiments of the present invention will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. If no specific conditions are specified in the examples, the conditions are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially.

[0037] According to one aspect of the present invention, the present invention relates to a method for improving the wettability of a battery cell electrolyte, comprising the following steps:

[0038] The shaped electrode group is prepared by using an electrolyte membrane, a positive electrode sheet and a negative electrode sheet, wherein the electrolyte membrane is obtained by coating the membrane with a first solution including an electrolyte, a binder and a first solvent and then undergoing a first drying process. The shaped electrode group is subjected to a shelling process, a second drying process, a liquid injection process and an impregnation process, wherein the injection liquid used in the liquid injection process includes a second solvent.

[0039] The method of the present invention first mixes the electrolyte and the binder and evenly coats them on the surface of the diaphragm, and then implements the subsequent injection of the second solvent. This is coordinated with other steps to effectively improve the diffusion of the electrolyte, ensure that the electrolyte is evenly diffused to the center of the electrode group and the electrode sheet, and improve the service life of the battery cell.

[0040] In some embodiments, the electrolyte includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(oxalatoborate), and lithium tetrafluoroborate.

[0041] In some embodiments, the binder 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%, for example 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, etc.

[0044] In some embodiments, the coating surface density D of the electrolyte separator is calculated from the unit area capacity A of the positive electrode sheet, the injection coefficient k and the electrolyte mass ratio m. m is 90%-98%.

[0045] In some embodiments, the coating includes spraying. By spraying, the first solution can be evenly distributed on the surface and inside of the separator, which is more conducive to improving the uniform dispersion of the electrolyte in the separator.

[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 the two. The present invention uses a suitable first drying temperature to volatilize the first solvent on the diaphragm while ensuring the physical and chemical properties of the diaphragm.

[0047] In some embodiments, the method for preparing the shaped electrode group specifically includes: laminating or winding the electrolyte membrane, the positive electrode sheet and the negative electrode sheet to obtain an electrode group, and then performing a shaping process to obtain a shaped electrode group. The shaping process is performed by hot pressing or cold pressing. Further, the shaped electrode group is subjected to a welding process, and the welding process includes pre-welding and final welding. After the shelling process, it also includes: peripheral welding process.

[0048] In some embodiments, the second drying temperature is 70-95°C, such as 70°C, 75°C, 80°C, 85°C, 90°C or 95°C, or any range therebetween. The second drying time is 6-24h, such as 6h, 8h, 10h, 12h, 15h, 18h, 20h or 24h, or any range therebetween.

[0049] In some embodiments, the second solvent comprises at least one of dimethyl carbonate, ethylene carbonate, ethyl methyl carbonate and vinylene carbonate. In some embodiments, the second solvent comprises dimethyl carbonate, ethylene carbonate, ethyl methyl carbonate or vinylene carbonate, or a combination of dimethyl carbonate and ethylene carbonate, a combination of ethylene carbonate and ethyl methyl carbonate, a combination of ethylene carbonate, ethyl methyl carbonate and vinylene carbonate, etc.

[0050] In some embodiments, the temperature of the immersion treatment is 35 to 50°C, such as 35°C, 40°C, 45°C, 50°C, etc., or any range between the two. The time of the immersion treatment is 12 to 48h, such as 12h, 15h, 18h, 20h, 25h, 30h, 35h, 40h, 42h, 45h or 48h, etc., or any range between the two. The present invention adopts appropriate immersion treatment conditions, which is more conducive to the full diffusion of the electrolyte, ensuring that the electrolyte is evenly diffused to the center of the pole group pole piece, and 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 to implement the method for improving the wettability of the electrolyte of the battery cell, comprising an electrolyte membrane preparation section, a pole group preparation section, a shelling and welding section, a drying section, a liquid injection section and an infiltration section; the electrolyte membrane preparation section is used to prepare the electrolyte membrane; the shaped pole group preparation section is used to prepare the shaped pole group; the shelling and welding section is used to perform shelling treatment on the shaped pole group and welding treatment during the preparation process; the drying section is used to perform a second drying on the shaped pole group after shelling; the liquid injection section is used to implement the liquid injection treatment; and the infiltration section is used to implement the infiltration treatment.

[0052] The system of the present invention can effectively improve the wettability of the battery cell electrolyte, and further improve 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 the first solvent to obtain a uniform first solution, and the mixing device may include a slurry tank and an agitator. The coating device is used to coat the membrane with the first solution, and 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 evenly sprayed on 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 can use a conventional drying device, such as an oven.

[0054] In some embodiments, the shaping electrode group preparation unit includes a pole piece assembly device and a shaping device; the pole piece assembly device includes a lamination device or a winding device. A shaping device is further used to perform shaping treatment. 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 wetting part includes a heating device, such as an oven.

[0057] In some implementations, the method further includes: forming and dividing the capacity of the battery cell after the infiltration treatment.

[0058] In some embodiments, the battery cell of the present invention includes a soft-pack battery cell, an aluminum shell battery cell, a cylindrical battery cell, including but not limited to LFP and NCM material systems.

[0059] In a preferred embodiment, the method for improving the wettability of the electrolyte of the battery cell comprises the following steps:

[0060] (a) The coating surface density D of the electrolyte membrane is calculated based on the positive electrode unit area capacity A, the injection coefficient k and the electrolyte mass ratio m.

[0061] The electrolyte membrane preparation unit is used to prepare the electrolyte membrane: the electrolyte and the binder are mixed in proportion, and the first solvent is added to the mixing device and stirred and mixed evenly 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 membrane is taken and placed on the coating head to unwind, the first solution is evenly coated on the membrane, and then the first drying device is used for the first drying, and the temperature of the first drying is 60 to 90°C, so that the solvent is volatilized to obtain the electrolyte membrane.

[0062] (b) Preparing a shaped electrode group using a shaped electrode group preparation unit: The electrolyte membrane, positive electrode sheet and negative electrode sheet are assembled using an electrode sheet assembly device, such as alternately stacking or winding to form an electrode group, and then hot-pressed and shaped using a shaping device to obtain a shaped electrode group.

[0063] Shell entry and welding part processing: pre-weld and final weld the shaped pole group, and perform peripheral welding after shell entry.

[0064] Drying treatment: Place in a constant temperature box for second drying, the second drying temperature is 70-95°C, the time is 6-24h, and the overall moisture content of the battery cell is controlled.

[0065] Liquid injection treatment section: the battery cell treated by the drying section is subjected to liquid injection treatment, and the injection liquid used in the liquid injection treatment is the second solvent.

[0066] Wetting treatment: After injection, wetting treatment is carried out. The temperature of the wetting treatment is 35-50°C and the time of the wetting treatment is 12-48 hours.

[0067] The following is further explained in conjunction with specific embodiments.

[0068] Example 1

[0069] A method for improving the wettability of a battery cell electrolyte comprises the following steps:

[0070] (a) The unit area capacity A of the positive electrode sheet of the LFP battery is 3.0 mAh / cm 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 obtained electrolyte membrane is 1.117 mg / cm 2 .

[0071] According to the electrolyte mass ratio m of 94%, the electrolyte and the binder are evenly mixed at a ratio of 94:6, and an appropriate amount of the first solvent is added and stirred in a homogenizing tank to form a 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 head for unwinding, the first solution is evenly coated on the diaphragm, the coating amount is adjusted, and then the first drying is performed. The temperature of the first drying is 75°C, and after the solvent is volatilized, the surface density is 1.117 mg / cm 2 of the electrolyte membrane.

[0072] (b) The electrolyte membrane, lithium iron phosphate positive electrode sheet and graphite negative electrode sheet are alternately stacked to form an electrode group, and then hot-pressed to obtain a shaped electrode group; the shaped electrode group is pre-welded and final-welded, and then the peripheral welding is performed after the shell treatment; then placed in a constant temperature box for a second drying, the second drying temperature is 90°C, and the time is 12 hours; then a liquid injection treatment is performed, and the injection liquid used in the liquid injection treatment is a second solvent (DMC); then an infiltration treatment is performed, the temperature of the infiltration treatment is 45°C, and the time of the infiltration treatment is 24 hours.

[0073] Example 2

[0074] A method for improving the wettability of a battery cell electrolyte comprises the following steps:

[0075] (a) The unit area capacity A of the positive electrode sheet of the LFP battery is 3.25 mAh / cm 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 obtained electrolyte membrane is 1.210 mg / cm 2 .

[0076] According to the electrolyte mass ratio m of 94%, the electrolyte and the binder are evenly mixed at a ratio of 94:6, and an appropriate amount of the first solvent is added and stirred in a homogenizing tank to form a 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 head for unwinding, the first solution is evenly coated on the diaphragm, the coating amount is adjusted, and then the first drying is performed. The temperature of the first drying is 80°C, and after the solvent is volatilized, the surface density is 1.210 mg / cm 2 of the electrolyte membrane.

[0077] (b) The electrolyte membrane, lithium iron phosphate positive electrode sheet and graphite negative electrode sheet are alternately stacked to form an electrode group, and then hot-pressed to obtain a shaped electrode group; the shaped electrode group is pre-welded and final-welded, and then the peripheral welding is performed after the shell treatment; then placed in a constant temperature box for a second drying, the second drying temperature is 90°C, and the time is 12h; then a liquid injection treatment is performed, and the injection liquid used in the liquid injection treatment is the second solvent, and the second solvent is EC, EMC and DMC with a volume ratio of 1:1:1; then an infiltration treatment is performed, the infiltration treatment temperature is 45°C, and the infiltration treatment time is 36h.

[0078] Example 3

[0079] A method for improving the wettability of a battery cell electrolyte comprises the following steps:

[0080] (a) The unit area capacity A of the positive electrode sheet of the LFP battery is 3.25 mAh / cm 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 obtained electrolyte on the separator is 1.161 mg / cm 2 .

[0081] According to the electrolyte mass ratio m of 98%, the electrolyte and the binder are evenly mixed at a ratio of 98:2, and an appropriate amount of the first solvent is added and stirred in a homogenizing tank to form a 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 head for unwinding, the first solution is evenly coated on the diaphragm, the coating amount is adjusted, and then the first drying is performed. The temperature of the first drying is 85°C, and after the solvent is volatilized, the surface density is 1.161 mg / cm 2 of the electrolyte membrane.

[0082] (b) The electrolyte membrane, lithium iron phosphate positive electrode sheet and graphite negative electrode sheet are alternately stacked to form an electrode group, and then hot-pressed to obtain a shaped electrode group; the shaped electrode group is pre-welded and final-welded, and the peripheral welding is performed after the shell treatment; it is then placed in a constant temperature box for a second drying, the second drying temperature is 75°C, and the time is 24 hours; then a liquid injection treatment is performed, and the injection liquid used in the liquid injection treatment is the second solvent, and the second solvent is EC, EMC and DMC with a volume ratio of 1:1:1; then an infiltration treatment is performed, the infiltration treatment temperature is 50°C, and the infiltration treatment time is 12 hours.

[0083] Example 4

[0084] A method for improving the wettability of a battery cell electrolyte comprises the following steps:

[0085] (a) The unit area capacity A of the positive electrode sheet of the LFP battery is 3.25 mAh / cm 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 obtained electrolyte on the separator is 1.264 mg / cm 2 .

[0086] According to the electrolyte mass ratio m of 90%, the electrolyte and the binder are evenly mixed at a ratio of 90:10, and an appropriate amount of the first solvent is added and stirred in a homogenizing tank to form a 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, the first solution is evenly coated on the diaphragm, the coating amount is adjusted, and then the first drying is performed, the temperature of the first drying is 90°C, and after the solvent is volatilized, the surface density is 1.264 mg / cm 2 of the electrolyte membrane.

[0087] (b) The electrolyte membrane, lithium iron phosphate positive electrode sheet and graphite negative electrode sheet are alternately stacked to form an electrode group, and then hot-pressed to obtain a shaped electrode group; the shaped electrode group is pre-welded and final-welded, and the peripheral welding is performed after the shell treatment; it is then placed in a constant temperature box for a second drying, the second drying temperature is 75°C, and the time is 24 hours; then a liquid injection treatment is performed, and the injection liquid used in the liquid injection treatment is the second solvent, and the second solvent is EC, EMC and DMC with a volume ratio of 1:1:1; then an infiltration treatment is performed, the infiltration treatment temperature is 50°C, and the infiltration treatment time is 12 hours.

[0088] Example 5

[0089] A method for improving the wettability of a battery cell electrolyte comprises the following steps:

[0090] (a) The unit area capacity A of the positive electrode sheet of the LFP battery is 3.25 mAh / cm 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 separator is 1.210 mg / cm 2 .

[0091] According to the electrolyte mass ratio m of 94%, the electrolyte and the binder are evenly mixed at a ratio of 94:6, and an appropriate amount of the first solvent is added and stirred in a homogenizing tank to form a 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 head for unwinding, the first solution is evenly coated on the diaphragm, the coating amount is adjusted, and then the first drying is performed. The temperature of the first drying is 90°C, and after the solvent is volatilized, the surface density is 1.210 mg / cm 2 of the electrolyte membrane.

[0092] (b) The electrolyte membrane, lithium iron phosphate positive electrode sheet and graphite negative electrode sheet are wound to form an electrode group, and then hot-pressed to obtain a shaped electrode group; the shaped electrode group is pre-welded and final-welded, and then the peripheral welding is performed after the shell treatment; then placed in a constant temperature box for a second drying, the second drying temperature is 90°C, and the time is 15 hours; then a liquid injection treatment is performed, and the injection liquid used in the liquid injection treatment is a second solvent, and the second solvent is EC, EMC and VC with a volume ratio of 1:1:1; then an infiltration treatment is performed, the infiltration treatment temperature is 45°C, and the infiltration treatment time is 36 hours.

[0093] Example 6

[0094] The system used in the method for improving the wettability of the electrolyte of the battery cell described in Examples 1 to 5 is as follows: Figure 1 As shown, it includes an electrolyte membrane preparation part 1, an electrode group preparation part 2, a shell insertion and welding part 3, a drying part 4, a liquid injection part 5 and an infiltration part 6.

[0095] The electrolyte membrane preparation section 1 is used to prepare an electrolyte membrane; the electrolyte membrane preparation section 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, and the first drying device 103 is used to perform a first drying on the membrane coated with the first solution.

[0096] The shaped electrode group preparation section 2 is used to prepare a shaped electrode group; the shaped electrode group preparation section 2 includes a electrode piece assembly device 201 (a lamination device) and a shaping device 202 .

[0097] The shell insertion and welding part 3 is used for shell insertion processing of the shaped electrode group and welding processing during the preparation process.

[0098] The drying section 4 is used to perform a second drying on the shaped electrode group after entering the shell; the drying section 4 includes a second drying device.

[0099] The injection part 5 is used for performing injection treatment; the infiltration part 6 is used for performing infiltration treatment; and the infiltration part 6 includes a heating device.

[0100] Comparative Example 1

[0101] The unit area capacity A of the positive electrode sheet of the LFP battery is 3.25 mAh / cm 2 , alternately stack the above-mentioned lithium iron phosphate positive electrode sheets and graphite negative electrode sheets to form an electrode group, and then perform hot pressing to shape the electrode group; pre-weld and final weld the shaped electrode group, and perform peripheral welding after shell treatment; then put it into a constant temperature box for a second drying, the second drying temperature is 90°C, and the time is 12h; then perform liquid injection treatment, the injection liquid used in the liquid injection treatment is 1.0 mol / L lithium hexafluorophosphate electrolyte, and the electrolyte solvent is EC, EMC and DMC in a volume ratio of 1:1:1; then perform infiltration treatment, the infiltration treatment temperature is 45°C, and the infiltration treatment time is 36h.

[0102] Test example

[0103] Wettability test

[0104] (1) Lithium distribution test: The battery cell after the above-mentioned impregnation treatment is disassembled, and the center and edge parts of the middle layer negative electrode plate are taken, and the difference in lithium content between the center and edge of the negative electrode plate is tested by ICP. The smaller the difference in lithium content between the center and the edge, the better the wettability.

[0105] (2) Interface observation: The battery cells after the above-mentioned impregnation treatment were subjected to formation treatment, and then charged to 3.8V at a rate of 0.5C. The color difference between the center and edge of the negative electrode sheet was observed. The smaller the color difference between the center and edge of the fully charged interface, the better the wettability.

[0106] The test results are shown in Table 1.

[0107] Table 1 Test results

[0108]

[0109] As can be seen from Table 1, the method of the present invention firstly evenly coats the electrolyte and the binder on the surface of the diaphragm, and then implements the subsequent injection of the second solvent, which cooperates with other steps to effectively improve the diffusion of the electrolyte, ensure that the electrolyte is evenly diffused to the center of the electrode group and the electrode sheet, and improve the service life of the battery cell.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the wettability of a battery cell electrolyte, characterized in that: The following steps are involved: A shaped electrode group is prepared by using an electrolyte membrane, a positive electrode sheet and a negative electrode sheet, wherein the electrolyte membrane is obtained by coating the membrane with a first solution including an electrolyte, a binder and a first solvent and then performing a first drying process; The shaped electrode group is subjected to shelling treatment, second drying, liquid injection treatment and immersion treatment, and the injection liquid used in the liquid injection treatment includes a second solvent.

2. The method for improving the wettability of a battery cell electrolyte according to claim 1, characterized in that: Contains at least one of the following features (1) to (4): (1) The electrolyte comprises at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(oxalatoborate) and lithium tetrafluoroborate; (2) The binder includes at least one of polyvinylidene fluoride and polytetrafluoroethylene; (3) the first solvent comprises at least one of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate and vinylene carbonate; (4) The mass ratio of the electrolyte to the binder is m:1-m, where m is 90% to 98%.

3. The method for improving the wettability of a battery cell electrolyte according to claim 1, characterized in that: Contains at least one of the following features (1) to (2): (1) The coating surface density D of the electrolyte separator is calculated from the unit area capacity A of the positive electrode sheet, the injection coefficient k and the electrolyte mass ratio m. m is 90% to 98%; (2) The coating includes spraying and / or roller coating.

4. The method for improving the wettability of a battery cell electrolyte according to claim 1, characterized in that: The first drying temperature is 60-90°C.

5. The method for improving the wettability of a battery cell electrolyte according to claim 1, characterized in that: The temperature of the second drying is 70 to 95° C., and the time of the second drying is 6 to 24 hours.

6. The method for improving the wettability of a battery cell electrolyte according to claim 1, characterized in that: The second solvent includes at least one of dimethyl carbonate, ethylene carbonate, ethyl methyl carbonate, and vinylene carbonate.

7. The method for improving the wettability of a battery cell electrolyte according to claim 1, characterized in that: The temperature of the infiltration treatment is 35 to 50° C., and the time of the infiltration treatment is 12 to 48 hours.

8. The method for improving the wettability of a battery cell electrolyte according to claim 1, characterized in that: Contains at least one of the following features (1) to (4): (1) The method for preparing the shaped electrode group specifically comprises: laminating or winding the electrolyte separator, the positive electrode sheet and the negative electrode sheet to obtain an electrode group, and then performing a shaping treatment to obtain a shaped electrode group; (2) During the preparation of the shaped electrode group, the shaping treatment is carried out by hot pressing or cold pressing; (3) further comprising: welding the shaped electrode group; (4) After the shelling process, it also includes: peripheral welding process.

9. A system for implementing the method for improving the wettability of a battery cell electrolyte according to any one of claims 1 to 8, characterized in that: It includes electrolyte membrane preparation part, electrode group preparation part, shell insertion and welding part, drying part, liquid injection part and impregnation part; The electrolyte membrane preparation section is used to prepare the electrolyte membrane; the shaped electrode group preparation section is used to prepare the shaped electrode group; the shelling and welding section is used to perform shelling treatment on the shaped electrode group and welding treatment during the preparation process; the drying section is used to perform a second drying on the shaped electrode group after shelling; the liquid injection section is used to implement liquid injection treatment; and the infiltration section is used to implement infiltration treatment.

10. The system according to claim 9, characterized in that Contains 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, wherein 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, and the first drying device is used to perform a first drying on the membrane coated with the first solution; (2) The shaping electrode group preparation unit includes a electrode assembly device and a shaping device; the electrode assembly device includes a lamination device or a winding device; (3) The drying section includes a second drying device; (4) The wetting portion includes a heating device.

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