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CN-122026002-A - Lithium ion battery diaphragm with difunctional coating and preparation method thereof

CN122026002ACN 122026002 ACN122026002 ACN 122026002ACN-122026002-A

Abstract

The invention discloses a lithium ion battery diaphragm with a difunctional coating and a preparation method thereof, and belongs to the technical field of lithium ion battery diaphragms. The diaphragm is formed by coating a layer of double-function composite coating consisting of PSSLi and PFPE on the surface of the PE base film on the negative electrode side. The PSSLi is used as a single ion conductor, the desolvation process of lithium ions is effectively promoted by using a strong electrostatic field generated by fixed sulfonate anions, the interface reaction energy barrier is reduced, PFPE is subjected to preferential reduction decomposition on the surface of a negative electrode, and a stable solid electrolyte interface layer rich in lithium fluoride is constructed in situ. The synergistic effect of the two realizes the rapid transmission and uniform deposition of lithium ions, and fundamentally inhibits the growth of lithium dendrites. The composite coating diaphragm prepared by the invention can remarkably improve the ion migration number, critical current density, cycle life and coulombic efficiency of a lithium metal battery, has excellent multiplying power performance and interface stability, has simple preparation process and is suitable for large-scale production.

Inventors

  • MA YUE
  • ZHANG JUNYU
  • LIU TING

Assignees

  • 西北工业大学

Dates

Publication Date
20260512
Application Date
20260413

Claims (10)

  1. 1. The preparation method of the lithium ion battery diaphragm with the difunctional coating is characterized by comprising the following steps: s1, PSSLi, preparing slurry, namely dissolving PAA in deionized water to form uniform glue solution, adding PSSLi powder, and stirring and ball-milling to obtain uniform PSSLi slurry; S2, PSSLi, coating and drying the slurry, namely coating one side of the PSSLi slurry obtained in the step S1 on the surface of the PE diaphragm to form a wet film, drying and curing to form a PSSLi coating, and winding to obtain a finished diaphragm; S3, PFPE synthesis, namely dissolving PFPE-OH, TEA and 4-DMAP into the TFT under the argon atmosphere, dropwise adding a BIBB solution dissolved in the TFT under the ice bath condition, standing at room temperature for reaction after the dropwise adding is finished, and carrying out aftertreatment after the reaction is finished to obtain a brown oily product PFPE; s4, preparing PFPE slurry, namely dissolving the PFPE obtained in the step S3 into a TFT to form uniform PFPE slurry; and S5, drying the PFPE slurry coating, namely coating the PFPE slurry obtained in the step S4 on the surface of the PSSLi coating of the finished membrane obtained in the step S2 to form a wet membrane, drying and curing to form a PFPE coating, and rolling to obtain the lithium ion battery membrane with the PSSLi/PFPE dual-function coating.
  2. 2. The preparation method of the lithium ion battery diaphragm with the bifunctional coating layer, as claimed in claim 1, is characterized in that in the step S1, the mass ratio of PSSLi to PAA is (8:1) - (25:1), and the solid content of the obtained slurry is 5% -15%.
  3. 3. The preparation method of the lithium ion battery separator with the difunctional coating layer according to claim 1 is characterized in that in the step S2, the drying temperature is 40-80 ℃, the drying time is 5-50h, and the thickness of the PSSLi coating layer is 1-4 μm.
  4. 4. The preparation method of the lithium ion battery separator with the bifunctional coating layer, as claimed in claim 1, is characterized in that in the step S3, the mass ratio of PFPE-OH to TEA is (10:1) - (2:1), the mass ratio of the total mass of PFPE-OH and TEA to 4-DMAP is (50:1) - (100:1), and the mass ratio of BIBB to TFT is (5:1) - (10:1).
  5. 5. The preparation method of the lithium ion battery separator with the bifunctional coating layer, as claimed in claim 1, is characterized in that in the step S3, the ice bath temperature is 0 ℃, and the room temperature reaction time is 15-25h.
  6. 6. The method for preparing the lithium ion battery diaphragm with the dual-function coating according to claim 1, wherein in the step S3, the specific post-treatment steps are that after the reaction is finished, 1M sodium hydroxide solution and distilled water are sequentially used for washing twice, the obtained organic phase is dried by anhydrous magnesium sulfate and then filtered, the filtrate is concentrated and collected, the concentrated product is dissolved in TFT, the TFT solution is dripped into methanol under the condition of stirring, and finally the upper layer liquid is collected and concentrated.
  7. 7. The method of manufacturing a lithium ion battery separator with a bifunctional coating layer as claimed in claim 6, wherein the mass ratio of the concentrated product to TFT is (1:3) - (1:10), and the volume ratio of the TFT solution to methanol is (1:5) - (1:15).
  8. 8. The method of claim 1, wherein in step S4, the volume ratio of PFPE to TFT is (1:5) - (1:15).
  9. 9. The method for preparing the lithium ion battery separator with the difunctional coating according to claim 1, wherein in the step S5, the drying temperature is 40-80 ℃, the drying time is 5-50h, and the thickness of the PFPE coating is 0.5-1.5 μm.
  10. 10. A lithium ion battery diaphragm with a bifunctional coating layer, which is characterized in that the diaphragm is prepared by the preparation method of any one of claims 1-9.

Description

Lithium ion battery diaphragm with difunctional coating and preparation method thereof Technical Field The invention relates to the technical field of lithium ion battery diaphragms, in particular to a lithium ion battery diaphragm with a bifunctional coating and a preparation method thereof. Background With the rapid development of electric vehicles and large-scale energy storage fields, more urgent demands are put forward on the energy density of lithium ion batteries. Among various types of negative electrode materials, metallic lithium is considered as an important candidate for realizing the next generation of high energy density battery system due to its extremely high theoretical specific capacity (3860 mAh/g) and extremely low electrode potential (only-3.04V relative to a standard hydrogen electrode). However, to realize large-scale application, the battery still needs to overcome a plurality of key challenges, on one hand, lithium ions are easily unevenly distributed on the surface of the negative electrode in the circulation process to deposit, so that lithium dendrites are formed, and if dendrites continuously grow, the dendrites possibly penetrate through a diaphragm to cause internal short circuit of the battery, and safety risks are brought. On the other hand, lithium metal has higher chemical activity to organic electrolyte, and after the lithium metal contacts with the organic electrolyte, the lithium metal spontaneously reacts at an interface to generate a layer of solid electrolyte interface film (SEI film). The SEI film is often poor in mechanical property and uneven in components, cracking and reconstruction are easy to occur in circulation, active lithium and electrolyte with limited continuous loss are continuously consumed, and the interfacial instability directly causes reduction of battery coulomb efficiency and deterioration of circulation performance. In addition, at the electrode interface, solvated lithium ions need to be first stripped of the solvent shell before they can pass through the SEI film and deposit as metallic lithium. The desolvation process is generally large in kinetic resistance and slow in reaction, and a high energy barrier leads to remarkable lithium deposition overpotential and poor deposition uniformity. Polyolefin separators (e.g., PE separators) are widely used for their good electrochemical stability and mechanical strength, but are inert themselves and cannot regulate the electrode interface, so researchers have attempted to modify the separator. In the prior art, there are reports of coating a separator with a single functional coating, such as coating a fast ion conductor (e.g., lithium Lanthanum Zirconium Oxide (LLZO), lithium thiophosphate (Li 3PS4)) to promote ion conductivity, but its chemical composition control on SEI is limited, coating inorganic particles (e.g., alumina (Al 2O3), silica (SiO 2)) to promote mechanical strength of the separator, physically blocking dendrites, but not promoting interfacial transport kinetics of lithium ions. The fluorine-containing polymer is introduced to generate LiF-rich SEI, liF has high interface energy and electron tunneling strength, and can effectively guide uniform deposition of lithium and stabilize an interface, however, a simple fluorine-containing additive is difficult to effectively solve the problem of slow desolvation of lithium ions. Accordingly, the prior art lacks a comprehensive separator modification scheme capable of simultaneously solving rapid desolvation of lithium ions and constructing a stable and firm SEI film. Disclosure of Invention The invention aims to provide a lithium ion battery diaphragm with a difunctional coating and a preparation method thereof, and the difunctional composite coating can synergistically reduce a lithium ion interface transmission energy barrier and construct optimal SEI chemical composition in situ, so that the performance of a lithium metal battery is comprehensively improved, and the problems of unstable interface, serious dendrite growth and short cycle life of the lithium metal battery in the prior art are solved. In order to achieve the above purpose, the invention provides a preparation method of a lithium ion battery diaphragm with a bifunctional coating, which comprises the following steps: S1, PSSLi, preparing slurry, namely dissolving polyacrylic acid (PAA) in deionized water to form uniform glue solution, adding lithium polystyrene sulfonate (PSSLi) powder, and stirring and ball-milling to obtain uniform PSSLi slurry; S2, PSSLi, coating and drying the slurry, namely coating one side of the PSSLi slurry obtained in the step S1 on the surface of a Polyethylene (PE) diaphragm to form a wet film, drying and curing to form a PSSLi coating, and rolling to obtain a finished diaphragm; S3, PFPE synthesis, namely dissolving perfluoro polyether alcohol (PFPE-OH), triethylamine (TEA) and 4-dimethylaminopyridine (4-DMAP) in benzotrifluoride (TFT) under the arg