A lithium supplement agent modified battery cell diaphragm and preparation method thereof

Abstract

The present invention discloses a lithium-supplementing agent-modified battery cell separator and a preparation method thereof, relating to the technical field of battery materials. The present invention discloses a method for preparing a lithium-supplementing agent-modified battery cell separator, comprising the following steps: applying a lithium-supplementing agent solution to the surface of a battery cell substrate separator and drying to obtain the lithium-supplementing agent-modified battery cell separator; the lithium-supplementing agent solution is prepared by mixing a lithium-supplementing agent, a conductive agent, a binder, and a solution; and by coating the separator surface with a lithium-supplementing agent layer, the present invention can significantly improve the initial coulombic efficiency and cycle stability of the battery, extend the battery life, and increase the battery energy density.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and in particular to a lithium supplement modified battery core diaphragm and a preparation method thereof. Background Art

[0002] Existing lithium-ion batteries are widely used in portable electronic devices, electric vehicles, and energy storage devices. However, due to their limited performance in energy density and cycle life, they are unable to meet the growing market demand. Polyolefin materials such as polyethylene (PE) and polypropylene (PP) are used as the main materials for lithium battery separators in the early stages of lithium battery research and development due to their excellent properties such as high strength and solution corrosion resistance and low price. However, traditional separators will experience problems such as pore size changes and reduced electrolyte wettability during long-term use of the battery, which will affect the cycle life and safety of the battery. Therefore, there is an urgent need to develop an improved separator material to improve the overall performance of the battery. As one of the key components of the battery, modified separators play an important role in improving battery performance. Current separator modification methods mainly focus on the structural optimization of separator materials and surface coating technology.

[0003] Existing lithium-ion battery separators primarily utilize polyethylene (PE) or polypropylene (PP) materials. While these materials offer excellent chemical stability and mechanical strength, their pore size distribution and electrolyte wettability are poor, impacting overall battery performance. Furthermore, existing technologies have not fully utilized lithium supplementation agents to modify separators, resulting in limited initial coulombic efficiency and cycle performance. This paper proposes a method for preparing a battery cell with a separator modified with a lithium supplementation agent, aiming to address the issues of low initial coulombic efficiency and short cycle life. Summary of the Invention

[0004] The purpose of the present invention is to provide a lithium supplement agent modified battery cell separator and a preparation method thereof, to solve the following technical problems:

[0005] Existing separators are mainly made of polyethylene or polypropylene materials, which have poor pore size distribution and electrolyte wettability, resulting in low initial coulombic efficiency and short cycle life of the battery.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for preparing a lithium supplement agent modified battery cell separator comprises the following steps: applying a lithium supplement agent solution on the surface of a battery cell base separator and drying the solution to obtain the lithium supplement agent modified battery cell separator;

[0008] The preparation method of the lithium supplement solution comprises the following steps: mixing a lithium supplement, a conductive agent, a binder, and a solvent to obtain the lithium supplement solution;

[0009] The preparation method of the lithium supplement comprises the following steps:

[0010] S1: In a nitrogen atmosphere, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, 2,5-dihydroxy-1,4-benzenedicarboxylic acid, o-dichlorobenzene, and 1,4-dioxane were added to a reaction kettle, and acetic acid solution was added to disperse them evenly. The temperature was controlled at 110-130°C, and the reaction was kept warm for 48-72 hours. The mixture was washed and dried to obtain component 1;

[0011] S2: Add lithium tert-butoxide and a portion of N,N-dimethylformamide into a reactor and disperse them evenly. Add 1,3-propane sultone and disperse them evenly. Blend component 1 and another portion of N,N-dimethylformamide and add them into the reactor and disperse them evenly. Control the temperature at 55-65°C, keep the reaction warm for 3-6 hours, wash with acetone, and dry to obtain a lithium supplement.

[0012] As a further embodiment of the present invention, the acetic acid solution in S1 is a 5-8 mol / L acetic acid aqueous solution; the addition ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, 2,5-dihydroxy-1,4-benzenedicarboxylic acid aldehyde, o-dichlorobenzene, 1,4-dioxane, and acetic acid solution is 1 g: 0.45-1.2 g: 25-100 mL: 25-100 mL: 5-15 mL.

[0013] As a further embodiment of the present invention, the addition ratio of lithium tert-butoxide, a portion of N,N-dimethylformamide, 1,3-propane sultone, component 1, and another portion of N,N-dimethylformamide in S2 is 0.05-0.1 g: 25-50 mL: 0.1-0.15 g: 1 g: 25-50 mL.

[0014] As a further solution of the present invention, the coating amount of the lithium supplement solution on the surface of the battery core substrate diaphragm is 0.5-2 mg / cm 2 .

[0015] As a further solution of the present invention: the specific step of drying is: drying the battery base separator coated with the lithium supplement solution at 60-100° C. for 12-24 hours.

[0016] As a further solution of the present invention: the binder is polyvinylidene fluoride.

[0017] As a further solution of the present invention: the conductive agent is obtained by mixing acetylene black and carbon nanotubes in a mass ratio of 1:0.25-1.

[0018] As a further solution of the present invention, the mass ratio of lithium supplement agent: conductive agent: binder in the lithium supplement agent solution is 90-95:3-6:2-4.

[0019] As a further embodiment of the present invention, the solvent is any one of N-methylpyrrolidone and ethanol, and the solvent accounts for 2-10% of the total mass of the lithium supplement solution.

[0020] As a further solution of the present invention: the method of coating the lithium supplement agent on the surface of the battery core substrate diaphragm includes a doctor blade coating method, a transfer coating method, and an electrostatic spinning method.

[0021] As a further solution of the present invention: the battery core base membrane is made of polyolefin material; the polyolefin material includes polyethylene and polypropylene.

[0022] A lithium supplement modified battery cell separator, prepared by any one of the above preparation methods.

[0023] Beneficial effects of the present invention:

[0024] (1) This application uses 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 2,5-dihydroxy-1,4-benzenedicarboxylic acid aldehyde as raw materials and acetic acid solution as catalyst to prepare a porous organic framework material with extremely high specific surface area, porosity and stability, namely component one; component one can limit the diffusion of molecules with its large pore capacity and small window size; this application further uses component one and 1,3-propane sultone as raw materials, and under the action of a strong nucleophilic reagent lithium tert-butoxide, the hydroxyl group of component one undergoes an electrophilic reaction, and the hydrogen atom in the hydroxyl group is replaced by a lithium ion. A porous polymer with lithium alcohol groups is generated, and the oxygen anions and lithium cations in the lithium alcohol groups attack the 1,3-propane sultone ring-opening addition between the cations and lithium ions of component one, respectively, and lithium sulfonate groups are grafted onto component one to obtain a lithium replenisher. The grafted lithium sulfonate in the pores of the lithium replenisher prepared in this application and the abundant lithium salts in the pores provide a rich lithium source and improve the lithium ion conductivity. The single-ion polymer electrolyte properties generated by the interaction between the lithium replenisher and the anions make it easy for lithium ions to leave, which has a positive effect on increasing the lithium ion migration number and can effectively inhibit the growth of lithium dendrites.

[0025] The lithium replenisher prepared in the present application is added to the solution to prepare a coating on the surface of the diaphragm, which not only effectively regulates the problems of pore size change and reduced electrolyte wettability of the diaphragm during battery charging and discharging, but also effectively compensates for the initial irreversible lithium loss of the lithium-ion battery and improves the energy density of the battery; the lithium replenisher can repair the SEI film during the battery cell cycle, and at the same time can significantly improve the initial coulombic efficiency and cycle stability of the battery, extend the battery life, and improve the battery energy density.

[0026] (2) This application uses a composite of acetylene black and carbon nanotubes as a conductive agent. The carbon nanotubes achieve micron-scale connections, and the acetylene black fills the nanoscale pores. The two work together to form a conductive network, thereby reducing the internal resistance of the battery. DETAILED DESCRIPTION

[0027] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0028] Example 1 The preparation method of the lithium supplement comprises the following steps:

[0029] S1: In a nitrogen atmosphere, 1 g of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, 0.45 g of 2,5-dihydroxy-1,4-benzenedicarboxylic acid, 50 mL of o-dichlorobenzene, and 50 mL of 1,4-dioxane were added to a reaction kettle, and 5 mL of a 5 mol / L aqueous acetic acid solution was added to disperse the mixture evenly. The temperature was controlled at 110°C, and the mixture was kept warm for 48 h. The mixture was then washed and dried to obtain component 1.

[0030] S2: Add 0.05 g of lithium tert-butoxide and 25 mL of N,N-dimethylformamide into a reactor and disperse evenly. Add 0.1 g of 1,3-propane sultone and disperse evenly. Blend 1 g of component 1 and 25 mL of N,N-dimethylformamide and add to the reactor and disperse evenly. Control the temperature at 55°C, keep the reaction warm for 3 h, wash with acetone, and dry to obtain a lithium supplement.

[0031] Example 2 The preparation method of the lithium supplement comprises the following steps:

[0032] S1: In a nitrogen atmosphere, 1 g of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, 0.8 g of 2,5-dihydroxy-1,4-benzenedicarboxylic acid, 50 mL of o-dichlorobenzene, and 50 mL of 1,4-dioxane were added to a reaction kettle, and 10 mL of a 5 mol / L aqueous acetic acid solution was added to disperse the mixture evenly. The temperature was controlled at 120°C, and the mixture was kept warm for 48 h. The mixture was then washed and dried to obtain component 1.

[0033] S2: Add 0.08 g of lithium tert-butoxide and 40 mL of N,N-dimethylformamide into a reactor and disperse them evenly. Add 0.12 g of 1,3-propane sultone and disperse them evenly. Blend 1 g of component 1 and 40 mL of N,N-dimethylformamide and add them into the reactor and disperse them evenly. Control the temperature at 60°C, keep the reaction warm for 4.5 h, wash with acetone, and dry to obtain a lithium supplement.

[0034] Example 3 The preparation method of the lithium supplement comprises the following steps:

[0035] S1: In a nitrogen atmosphere, 1 g of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, 1.2 g of 2,5-dihydroxy-1,4-benzenedicarboxylic acid, 50 mL of o-dichlorobenzene, and 50 mL of 1,4-dioxane were added to a reaction kettle, and 15 mL of a 5 mol / L aqueous acetic acid solution was added to disperse the mixture evenly. The temperature was controlled at 130°C and the reaction was kept warm for 72 h. The mixture was then washed and dried to obtain component 1.

[0036] S2: Add 0.1 g of lithium tert-butoxide and 50 mL of N,N-dimethylformamide into a reactor and disperse them evenly. Add 0.15 g of 1,3-propane sultone and disperse them evenly. Blend 1 g of component 1 and 50 mL of N,N-dimethylformamide and add them into the reactor and disperse them evenly. Control the temperature at 65°C, keep the reaction warm for 6 h, wash with acetone, and dry to obtain a lithium supplement.

[0037] Example 4 A method for preparing a lithium supplement agent modified battery cell separator comprises the following steps:

[0038] A1: 84.6 g of the lithium supplement prepared in Example 1, 1.8 g of acetylene black, 1.08 g of carbon nanotubes, 2.52 g of polyvinylidene fluoride, and 10 g of N-methylpyrrolidone were mixed to obtain a lithium supplement solution;

[0039] A2: Use the doctor blade coating method to apply the lithium supplement solution on the surface of Celgard2400 porous polypropylene separator with a coating amount of 1 mg / cm 2 , and dried at 80°C for 15h to obtain a lithium supplement agent modified battery cell separator.

[0040] Example 5 A method for preparing a lithium supplement agent modified battery cell separator comprises the following steps:

[0041] A1: 84.6 g of the lithium supplement prepared in Example 2, 1.8 g of acetylene black, 1.08 g of carbon nanotubes, 2.52 g of polyvinylidene fluoride, and 10 g of N-methylpyrrolidone were mixed to obtain a lithium supplement solution;

[0042] A2: Use the doctor blade coating method to apply the lithium supplement solution on the surface of Celgard2400 porous polypropylene separator with a coating amount of 1 mg / cm 2 , and dried at 80°C for 15h to obtain a lithium supplement agent modified battery cell separator.

[0043] Example 6 A method for preparing a lithium supplement agent modified battery cell separator comprises the following steps:

[0044] A1: 84.6 g of the lithium supplement prepared in Example 3, 1.8 g of acetylene black, 1.08 g of carbon nanotubes, 2.52 g of polyvinylidene fluoride, and 10 g of N-methylpyrrolidone were mixed to obtain a lithium supplement solution;

[0045] A2: Use the doctor blade coating method to apply the lithium supplement solution on the surface of Celgard2400 porous polypropylene separator with a coating amount of 1 mg / cm 2 , and dried at 80°C for 15h to obtain a lithium supplement agent modified battery cell separator.

[0046] Example 7 A method for preparing a lithium-ion battery comprises the following steps:

[0047] B1: Pole sheet preparation: The positive electrode active material is LiFePO4, the conductive agent is acetylene black, and the binder is polytetrafluoroethylene (PTFE). The active material, acetylene black, and PTFE are thoroughly ground at a mass ratio of 75:20:5, mixed evenly, and anhydrous ethanol is added as a dispersant. The positive electrode sheet is pressed into a 100μm thick positive electrode sheet, which is then punched into 8mm diameter discs at 10MPa. The discs are dried in a constant temperature drying oven at 100°C for 24h. Aluminum sheets are used as positive electrode current collectors to obtain the positive electrode sheet.

[0048] B2: Electrolyte preparation: 1M LiPF6 / EC+DMC;

[0049] B3: Battery assembly: This was carried out in an argon-filled glove box (moisture <1 ppm). Metal lithium sheets were used as auxiliary electrodes and reference electrodes (copper sheet current collectors). The separator used was the lithium supplement agent-modified battery cell separator prepared in Example 4. After assembly in a mold, the mold was sealed and allowed to stand at room temperature for 10 h to obtain a battery.

[0050] Example 8 A method for preparing a lithium-ion battery comprises the following steps:

[0051] B1: Pole sheet preparation: The positive electrode active material is LiFePO4, the conductive agent is acetylene black, and the binder is polytetrafluoroethylene (PTFE). The active material, acetylene black, and PTFE are thoroughly ground at a mass ratio of 75:20:5, mixed evenly, and anhydrous ethanol is added as a dispersant. The positive electrode sheet is pressed into a 100μm thick positive electrode sheet, which is then punched into 8mm diameter discs at 10MPa. The discs are dried in a constant temperature drying oven at 100°C for 24h. Aluminum sheets are used as positive electrode current collectors to obtain the positive electrode sheet.

[0052] B2: Electrolyte preparation: 1M LiPF6 / EC+DMC;

[0053] B3: Battery assembly: This was carried out in an argon-filled glove box (moisture content <1 ppm). A metallic lithium sheet was used as the auxiliary electrode and reference electrode (copper sheet current collector). The separator used was the lithium supplement agent-modified battery cell separator prepared in Example 5. After assembly in a mold, the mold was sealed and allowed to stand at room temperature for 10 h to obtain a battery.

[0054] Example 9 A method for preparing a lithium-ion battery comprises the following steps:

[0055] B1: Pole sheet preparation: The positive electrode active material is LiFePO4, the conductive agent is acetylene black, and the binder is polytetrafluoroethylene (PTFE). The active material, acetylene black, and PTFE are thoroughly ground at a mass ratio of 75:20:5, mixed evenly, and anhydrous ethanol is added as a dispersant. The positive electrode sheet is pressed into a 100μm thick positive electrode sheet, which is then punched into 8mm diameter discs at 10MPa. The discs are dried in a constant temperature drying oven at 100°C for 24h. Aluminum sheets are used as positive electrode current collectors to obtain the positive electrode sheet.

[0056] B2: Electrolyte preparation: 1M LiPF6 / EC+DMC;

[0057] B3: Battery assembly: This was carried out in an argon-filled glove box (moisture content <1 ppm). Metal lithium sheets were used as auxiliary electrodes and reference electrodes (copper sheet current collectors). The separator used was the lithium supplement agent-modified battery cell separator prepared in Example 6. After assembly in a mold, the mold was sealed and allowed to stand at room temperature for 10 h to obtain a battery.

[0058] Comparative Example 1 A method for preparing a lithium-ion battery comprises the following steps:

[0059] B1: Pole sheet preparation: The positive electrode active material is LiFePO4, the conductive agent is acetylene black, and the binder is polytetrafluoroethylene (PTFE). The active material, acetylene black, and PTFE are thoroughly ground at a mass ratio of 75:20:5, mixed evenly, and anhydrous ethanol is added as a dispersant. The positive electrode sheet is pressed into a 100μm thick positive electrode sheet, which is then punched into 8mm diameter discs at 10MPa. The discs are dried in a constant temperature drying oven at 100°C for 24h. Aluminum sheets are used as positive electrode current collectors to obtain the positive electrode sheet.

[0060] B2: Electrolyte preparation: 1M LiPF6 / EC+DMC;

[0061] B3: Battery assembly: This was carried out in an argon-filled glove box (moisture content <1 ppm). Lithium metal sheets were used as auxiliary and reference electrodes (copper current collectors). Celgard 2400 porous polypropylene membrane was used as the separator. After assembly in the mold, the mold was sealed and allowed to stand at room temperature for 10 hours. The battery sample was obtained.

[0062] Comparative Example 2 The preparation method of the lithium supplement comprises the following steps:

[0063] S1: In a nitrogen atmosphere, 1 g of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, 0.45 g of 2,5-dihydroxy-1,4-benzenedicarboxylic acid, 50 mL of o-dichlorobenzene, and 50 mL of 1,4-dioxane were added to a reaction kettle, and 5 mL of a 5 mol / L aqueous acetic acid solution was added to disperse the mixture evenly. The temperature was controlled at 110°C, and the mixture was kept warm for 48 h. The mixture was then washed and dried to obtain component 1.

[0064] S2: 0.1 g of lithium methanesulfonate and 1 g of component 1 are mixed to obtain a lithium supplement.

[0065] Comparative Example 3 Comparative Example 3 is compared with Example 5, except that an equal amount of the lithium supplement prepared in Example 2 added in Example 5 is replaced by the lithium supplement prepared in Comparative Example 2. The remaining components and preparation method are completely the same as those in Example 5.

[0066] Comparative Example 4 Compared with Example 8, Comparative Example 4 only replaces the lithium supplement agent modified battery cell separator prepared in Example 5 used in Example 8 with the lithium supplement agent modified battery cell separator prepared in Comparative Example 3. The other components and preparation methods are exactly the same as those in Example 8.

[0067] Comparative Example 5 Comparative Example 5 is compared with Example 5, except that an equal amount of the lithium supplement prepared in Example 2 added in Example 5 is replaced with lithium methanesulfonate, and the remaining components and preparation method are completely the same as those in Example 5.

[0068] Comparative Example 6 Compared with Example 8, Comparative Example 6 only replaces the lithium supplement agent modified battery core separator prepared in Example 5 used in Example 8 with the lithium supplement agent modified battery core separator prepared in Comparative Example 5. The other components and preparation methods are exactly the same as those in Example 8.

[0069] Performance testing

[0070] (1) Electrochemical performance

[0071] ① Electrochemical stability window: Linear sweep voltammetry was used to test the electrochemical stability window of the material using a CHI electrochemical workstation. The working electrode was a stainless steel sheet, and the auxiliary electrode was a lithium sheet. The cells were assembled into a semi-blocked cell (stainless steel sheet / diaphragm (immersed in electrolyte) / stainless steel sheet). The operating parameters were: scan rate 0.002 V / s, sampling interval 0.001 V. The test results are shown in Table 1.

[0072] ② Ionic conductivity: The electrochemical impedance spectroscopy method was used to test the M2273 electrochemical workstation. First, a semi-blocked cell (stainless steel sheet / diaphragm (immersed in electrolyte) / stainless steel sheet) was assembled. The operating parameters were: ambient temperature 20°C, sinusoidal amplitude 5mV, scanning frequency 0.1-10 4 Hz, the impedance spectrum is obtained, and the intersection point of the straight line and the real axis in the impedance spectrum is recorded as the bulk resistance Rb. The ionic conductivity σ is calculated according to the following formula;

[0073] σ=d / (Rb·S)

[0074] Where, σ-ionic conductivity, s / cm; d-film thickness, cm; Rb-film bulk resistance, Ω; S-film area, cm 2 ; The calculation results are shown in Table 1;

[0075] ③ Lithium ion migration number: The AC impedance method and steady-state current were used to test the M2273 electrochemical workstation. First, a semi-blocked battery (stainless steel sheet / diaphragm (immersed in electrolyte) / stainless steel sheet) was assembled. The operating parameters were: polarization potential 10mV, test time 3000s, and the initial state current I0 and the polarization steady-state current value I were obtained from the obtained polarization current curve. s ; respectively in 0.1-10 4 In the Hz frequency range, the AC impedance test is performed on the material before and after polarization to obtain the AC impedance curve, and the initial resistance R0 and the polarization steady-state resistance R ss ; and calculate the lithium ion migration number t according to the following formula Li+ :

[0076] t Li+ =[I s (V-I0R0)] / [I0(VI s R ss )]

[0077] Where, t Li+ -Lithium ion migration number; I0-initial state current, A; I s - steady-state current, A; V-polarization voltage, V; R0-initial state resistance, Ω; R ss Steady-state resistance, Ω; test results are shown in Table 1;

[0078] Table 1: Electrochemical impedance spectroscopy data statistics

[0079]

[0080] As can be seen from Table 1, the diaphragm prepared in the present application has a higher liquid absorption rate and porosity than the existing Celgard2400 porous polypropylene diaphragm, which increases its electrical conductivity; the lithium ion migration number of the diaphragm prepared in the present application is close to 1, which is better than the traditional Celgard2400 porous polypropylene diaphragm.

[0081] (2) Charge and discharge test: The battery was cycled at room temperature using the LAND CT-2001A battery test system; the charge and discharge voltage range was 2.8-4.2 V (vs Li / Li+), and the current density was 1.4 mA / cm 2 ; Charge and discharge cycles were carried out at a charge and discharge rate of 0.5C, and the battery capacity retention rate was tested after 500 cycles; the test results are shown in Table 2;

[0082] Table 2: Statistics of performance test data of Examples 7-9 and Comparative Examples 1, 4 and 6

[0083]

[0084] As can be seen from Table 2, the present application coats a lithium replenisher containing lithium elements on the surface of the diaphragm, which effectively compensates for the initial irreversible lithium loss of the lithium-ion battery, improves the energy density of the battery, and significantly improves the battery energy density and cycle stability of the battery, thereby extending the battery life.

[0085] The above is a detailed description of an embodiment of the present invention. However, the content described is only a preferred embodiment of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A method for preparing a lithium supplement agent modified battery cell separator, characterized in that: The method comprises the following steps: applying a lithium supplement agent solution on the surface of a battery cell base membrane and drying the solution to obtain a lithium supplement agent modified battery cell membrane; The preparation method of the lithium supplement solution comprises the following steps: mixing a lithium supplement, a conductive agent, a binder, and a solvent to obtain a lithium supplement solution; The preparation method of the lithium supplement comprises the following steps: S1: In a nitrogen atmosphere, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, 2,5-dihydroxy-1,4-benzenedicarboxylic acid, o-dichlorobenzene, and 1,4-dioxane were added to a reaction kettle, and acetic acid solution was added to disperse them evenly. The temperature was controlled at 110-130°C, and the reaction was kept warm for 48-72 hours. The mixture was washed and dried to obtain component 1; S2: Add lithium tert-butoxide and a portion of N,N-dimethylformamide into a reactor and disperse them evenly. Add 1,3-propane sultone and disperse them evenly. Blend component 1 and another portion of N,N-dimethylformamide and add them into the reactor and disperse them evenly. Control the temperature at 55-65°C, keep the reaction warm for 3-6 hours, wash with acetone, and dry to obtain a lithium supplement.

2. The method for preparing a lithium supplement agent modified battery cell separator according to claim 1, characterized in that: The acetic acid solution in S1 is a 5-8 mol / L acetic acid aqueous solution; the addition ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, 2,5-dihydroxy-1,4-benzenedicarboxylic acid aldehyde, o-dichlorobenzene, 1,4-dioxane, and acetic acid solution is 1 g: 0.45-1.2 g: 25-100 mL: 25-100 mL: 5-15 mL.

3. The method for preparing a lithium supplement agent modified battery cell separator according to claim 1, characterized in that: The addition ratio of lithium tert-butoxide, a portion of N,N-dimethylformamide, 1,3-propane sultone, component one, and another portion of N,N-dimethylformamide in S2 is 0.05-0.1 g: 25-50 mL: 0.1-0.15 g: 1 g: 25-50 mL.

4. The method for preparing a lithium supplement modified battery cell separator according to claim 1, characterized in that: The coating amount of lithium supplement solution on the surface of the battery base diaphragm is 0.5-2mg / cm 2 .

5. The method for preparing a lithium supplement agent modified battery cell separator according to claim 1, characterized in that: The specific steps of drying are: drying the battery cell base diaphragm coated with the lithium supplement solution at 60-100° C. for 12-24 hours.

6. The method for preparing a lithium supplement modified battery cell separator according to claim 1, characterized in that: The binder is polyvinylidene fluoride.

7. The method for preparing a lithium supplement modified battery cell separator according to claim 1, characterized in that: The conductive agent is obtained by mixing acetylene black and carbon nanotubes in a mass ratio of 1:0.25-1.

8. The method for preparing a lithium supplement modified battery cell separator according to claim 1, characterized in that: The mass ratio of the lithium supplement agent: the conductive agent: the binder in the lithium supplement agent solution is 90-95: 3-6: 2-4.

9. The method for preparing a lithium supplement modified battery cell separator according to claim 1, characterized in that: The solvent is any one of N-methylpyrrolidone and ethanol, and the solvent accounts for 2-10% of the total mass of the lithium supplement solution.

10. A lithium supplement modified battery cell separator, characterized in that: Prepared by the preparation method according to any one of claims 1 to 9.

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