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CN-122000614-A - Pre-lithiated diaphragm and preparation method and application thereof

CN122000614ACN 122000614 ACN122000614 ACN 122000614ACN-122000614-A

Abstract

The invention provides a pre-lithiated diaphragm and a preparation method and application thereof, and relates to the technical field of lithium ion batteries. A preparation method of a prelithiation membrane comprises the following steps of S1, soaking the membrane in a solvent to obtain an immersed membrane, S2, soaking the immersed membrane in an oxidant solution under a protective gas atmosphere, heating for reaction to obtain a hydroxylation membrane, S3, soaking the hydroxylation membrane in a solution containing vinylamide compounds under the protective gas atmosphere, heating for reaction to obtain an amidated membrane, S4, soaking the amidated membrane in an alkaline solution under the protective gas atmosphere to obtain a carboxylated membrane, and S5, soaking the carboxylated membrane in a solution containing lithium compounds to obtain the prelithiation membrane. The pre-lithiated diaphragm prepared by the preparation method has obviously improved wettability to electrolyte, and can effectively improve the rate capability of a lithium ion battery.

Inventors

  • CHENG LIANG
  • HE HUALONG
  • LI SHUAI
  • Shen Xianhe

Assignees

  • 合肥国轩高科动力能源有限公司

Dates

Publication Date
20260508
Application Date
20260114

Claims (10)

  1. 1. A method of preparing a pre-lithiated separator, comprising the steps of: S1, soaking a diaphragm in a solvent to obtain an immersed diaphragm; s2, soaking the immersed diaphragm in an oxidant solution in a protective gas atmosphere, and heating for reaction to obtain a hydroxylation diaphragm; S3, soaking the hydroxylated diaphragm in a solution containing vinylamide compounds in a protective gas atmosphere, and heating for reaction to obtain an amidated diaphragm; S4, soaking the amidated diaphragm in an alkaline solution in a protective gas atmosphere to obtain a carboxylated diaphragm; S5, soaking the carboxylated diaphragm in a lithium-containing compound solution to obtain the pre-lithiated diaphragm.
  2. 2. The preparation method of the composite material according to claim 1, wherein in the step S1, the membrane is selected from one or more of a polyethylene membrane and a polypropylene membrane, the solvent is selected from one or more of methanol and water, and the soaking time is 2-5h.
  3. 3. The preparation method of the catalyst according to claim 1, wherein in the step S2, the mass concentration of the oxidant in the oxidant solution is 3-30wt%, the oxidant is one or more selected from potassium persulfate, hydrogen peroxide and potassium permanganate, and the heating temperature is 40-90 ℃ and the heating time is 0.5-3h.
  4. 4. The preparation method of the ethylene amide compound according to claim 1, wherein in the step S3, the solution containing the ethylene amide compound further comprises nitric acid and ceric ammonium nitrate, and the molar ratio of the nitric acid to the ceric ammonium nitrate is (10-40): 1.
  5. 5. The preparation method according to claim 1, wherein in the S3, the mass concentration of the vinylamide compound in the vinylamide compound-containing solution is 1wt% to 5wt%, and the vinylamide compound is selected from one or more of acrylamide, but-3-enamide, pent-4-enamide, 2-methylbut-3-enamide, 2-dimethylbut-3-enamide, 2-methylpent-4-enamide, 3-methylpent-4-enamide, 2, 3-dimethylpent-4-enamide, 2-trifluoromethyl-but-3-enamide, 2-bis (trifluoromethyl) but-3-enamide, 2-trifluoromethyl-pent-4-enamide, 3-trifluoromethyl-pent-4-enamide, and 2, 3-bis (trifluoromethyl) pent-4-enamide.
  6. 6. The preparation method of the water-soluble magnesium sulfate composite material according to claim 1, wherein in the step S4, the alkaline solution is one or more selected from a sodium hydroxide solution, a potassium hydroxide solution and a sodium carbonate solution, the alkaline solution is heated, the temperature of the alkaline solution is 40-70 ℃, the concentration of the alkaline solution is 0.5-2mol/L, and the soaking time is 0.5-3h.
  7. 7. The preparation method of claim 1, wherein in the step S5, the lithium-containing compound is selected from one or more of lithium hydroxide, lithium nitrate and lithium carbonate, the concentration of the lithium-containing compound solution is 0.5-2mol/L, and the soaking time is 0.5-3h.
  8. 8. The preparation method according to claim 1, wherein the shielding gas in S2, S3, S4 is one or more selected from nitrogen, argon, and helium.
  9. 9. A pre-lithiated polyolefin separator film produced by the production process of any one of claims 1 to 8.
  10. 10. Use of the pre-lithiated polyolefin separator of claim 9 or the pre-lithiated polyolefin separator produced by the production method of any one of claims 1 to 8 in a lithium ion battery.

Description

Pre-lithiated diaphragm and preparation method and application thereof Technical Field The invention relates to the technical field of lithium ion batteries, in particular to a pre-lithiated diaphragm and a preparation method and application thereof. Background The battery diaphragm is used as a key material in a lithium ion battery, and plays a role in preventing positive and negative electrodes from being in direct contact and isolating the circulation of electrons, but allowing lithium ions to pass freely. Currently, the commercial lithium ion battery separator mainly comprises polyolefin materials such as polyethylene or polypropylene. The material is nonpolar, has very poor wettability to polar electrolyte and lower liquid retention capacity, thereby reducing the speed of lithium ion transmission, increasing electrochemical impedance and having larger influence on the multiplying power performance of the lithium ion battery. The high ion conductivity is an important index of the electric performance of the diaphragm, and the improvement of the ion conductivity can effectively improve the multiplying power quick charge performance and the long-term circulation stability of a lithium ion battery system, reduce the energy loss caused by high internal resistance and further improve the electric performance of the battery. Therefore, improving the ionic conductivity is an important means for improving the electrical performance of lithium ion batteries currently. Meanwhile, in the early-stage chemical composition and later-stage circulation process of the battery, lithium in the battery is continuously consumed by formation and side reaction of the SEI film, so that the capacity of the battery is continuously reduced, and the capacity of the battery can be improved and the service life of the battery can be prolonged by supplementing lithium. Disclosure of Invention Based on the technical problems in the background technology, the invention provides a pre-lithiated diaphragm and a preparation method and application thereof. The invention provides a preparation method of a pre-lithiated diaphragm, which comprises the following steps: S1, soaking a diaphragm in a solvent to obtain an immersed diaphragm; s2, soaking the immersed diaphragm in an oxidant solution in a protective gas atmosphere, and heating for reaction to obtain a hydroxylation diaphragm; S3, soaking the hydroxylated diaphragm in a solution containing vinylamide compounds in a protective gas atmosphere, and heating for reaction to obtain an amidated diaphragm; S4, soaking the amidated diaphragm in an alkaline solution in a protective gas atmosphere to obtain a carboxylated diaphragm; S5, soaking the carboxylated diaphragm in a lithium-containing compound solution to obtain the pre-lithiated diaphragm. According to the invention, hydroxylation, amidation, carboxylation and lithiation are sequentially carried out on the diaphragm to obtain the pre-lithiated diaphragm, so that the multiplying power performance of the assembled lithium ion battery is improved. Preferably, in the step S1, the separator is one or more selected from a polyethylene separator and a polypropylene separator. Preferably, in the step S1, the solvent is one or more selected from methanol and water. More preferably, the volume ratio of the methanol to the water is (20-80): 20-80. Preferably, in the step S1, the soaking time is 2-5h. The membrane is soaked in a solvent, so that the soaked membrane is obtained to facilitate the next hydroxylation treatment. Preferably, in the step S2, the mass concentration of the oxidant in the oxidant solution is 3wt% to 30wt%. The mass concentration of the oxidant in the oxidant solution is in a certain range, which is helpful for surface hydroxylation treatment, the modification effect is insufficient due to the too low concentration, and the membrane matrix structure is damaged due to the too high concentration, so that the mechanical strength ‌ is reduced. Preferably, in the step S2, the oxidizing agent is one or more selected from potassium persulfate, hydrogen peroxide and potassium permanganate. Preferably, in the step S2, the heating temperature is 40-90 ℃ and the heating time is 0.5-3h. Soaking the soaking diaphragm in oxidant solution, controlling the heating temperature and time, and hydroxylating the surface of the soaking diaphragm. Preferably, after S2, the method further comprises washing and drying the hydroxylated membrane. More preferably, the cleaning solvent is deionized water, the drying temperature is 40-80 ℃, and the drying time is 2-8 hours. The effect of cleaning and drying the hydroxylation diaphragm is to effectively remove reaction residues, and avoid the residues interfering with the subsequent modification process and affecting the modification effect. Preferably, in the S2, S3, S4, the shielding gas is one or more selected from nitrogen, argon, and helium. Preferably, in the step S3, the mass concentration of the