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CN-122025786-A - Three-dimensional composite crystal polymer electrolyte, preparation method thereof and lithium metal battery

CN122025786ACN 122025786 ACN122025786 ACN 122025786ACN-122025786-A

Abstract

The invention discloses a stereocomplex crystal polymer electrolyte and a preparation method thereof, and a lithium metal battery, wherein the preparation method comprises the steps of grafting dextrorotatory polylactic acid on a flexible polycaprolactone chain segment, and synthesizing to obtain a PDLA-PCL-PDLA triblock copolymer; dissolving PDLA-PCL-PDLA triblock copolymer and L-polylactic acid in chloroform, adding lithium salt to obtain mixed solution, and preparing into a film to obtain the stereocomplex crystal polymer electrolyte which has a stereocomplex crystal structure. The structure-built composite crystal forms a bicontinuous phase structure, can relieve the excessive phase separation of two phases, solves the problems of growth and poor cycle stability of negative electrode side lithium dendrite in the cycle process of lithium metal solid polymer electrolyte, can keep long cycle of more than 1200 circles under high multiplying power of 5C in a charge-discharge cycle test, and has a capacity retention rate as high as 87.7%.

Inventors

  • LIU CHEN
  • Lian Haojian

Assignees

  • 深圳大学

Dates

Publication Date
20260512
Application Date
20260310

Claims (10)

  1. 1. A method for preparing a stereocomplex crystalline polymer electrolyte, comprising: grafting the dextrorotatory polylactic acid on a flexible polycaprolactone chain segment, and synthesizing to obtain a PDLA-PCL-PDLA triblock copolymer; dissolving the PDLA-PCL-PDLA triblock copolymer and the L-polylactic acid in chloroform, and adding lithium salt to obtain a mixed solution; The mixed solution is prepared into a film to obtain the stereocomplex crystal polymer electrolyte, wherein the stereocomplex crystal polymer electrolyte has a stereocomplex crystal structure, and the stereocomplex crystal structure is formed by complexing two spiral chains of the L-polylactic acid and the D-polylactic acid through hydrogen bonds and dipole-dipole interactions.
  2. 2. The method for preparing a stereocomplex crystal polymer electrolyte according to claim 1, wherein the molar ratio of the PDLA-PCL-PDLA triblock copolymer to the lithium salt is 1:5-6.
  3. 3. The method for preparing a stereocomplex crystal polymer electrolyte according to claim 1, wherein the method comprises grafting a polylactic acid with a flexible polycaprolactone segment to synthesize a PDLA-PCL-PDLA triblock copolymer, and specifically comprises: mixing the hydroxy-terminated polycaprolactone, the D-lactide and the stannous isooctanoate, and performing heating treatment under vacuum condition to obtain the PDLA-PCL-PDLA triblock copolymer, wherein the heating temperature is 130-145 ℃ and the heating time is 18-24h.
  4. 4. The method for preparing the stereocomplex crystal polymer electrolyte according to claim 1, wherein the mixed solution is prepared into a film, and the stereocomplex crystal polymer electrolyte is obtained, specifically comprising: pouring the mixed solution into a mold; And (3) placing the die filled with the mixed solution in vacuum equipment, sealing and placing for 15-24 hours, drying, transferring to a glove box, and standing to obtain the stereocomplex crystal polymer electrolyte.
  5. 5. The method for preparing a stereocomplex crystal polymer electrolyte according to claim 4, wherein the drying temperature is 70 to 90 ℃.
  6. 6. A stereocomplex crystalline polymer electrolyte, characterized in that it is prepared by the preparation method of any one of claims 1 to 5.
  7. 7. The stereocomplex crystalline polymer electrolyte of claim 6, wherein the stereocomplex crystalline polymer electrolyte comprises an ion conductive phase and a mechanical support phase, and an interfacial reinforcement layer formed at an interface of the two phases, the interfacial reinforcement layer being composed of a pair of PDLA-PCL-PDLA triblock copolymers, through hydrogen bonding, for anchoring the ion conductive phase and the mechanical support phase, maintaining stability of the bicontinuous phase structure.
  8. 8. A lithium metal battery comprising the stereocomplex crystalline polymer electrolyte of any of claims 6 to 7.
  9. 9. The lithium metal battery of claim 8, wherein the capacity retention is greater than 87% after 1200 cycles at 5C rate.
  10. 10. The lithium metal battery of claim 8, wherein the capacity retention is greater than 81% after 300 cycles of 0.5C paired with NCM811 positive electrode at 4.3V high pressure.

Description

Three-dimensional composite crystal polymer electrolyte, preparation method thereof and lithium metal battery Technical Field The invention relates to the technical field of preparation of a stereocomplex crystal polymer electrolyte, in particular to a stereocomplex crystal polymer electrolyte, a preparation method thereof and a lithium metal battery. Background Solid polymer electrolytes generally suffer from low ionic conductivity due to excessive crystallinity at room temperature, while melting easily occurs at high temperatures, limiting their practical use. It is often difficult to combine multiple requirements of high ionic conductivity, good mechanical strength, and broad electrochemical stability window with a single polymer system. To overcome this limitation, strategies are commonly employed in the art to blend two or more polymer matrices. The strategy does not need complex chemical synthesis, has simple process and lower cost, and can reduce crystallinity by disturbing the regular arrangement of polymer chain segments, thereby improving room temperature ionic conductivity and widening the working temperature range. In the blended polymer electrolyte, the phase separation type solid polymer electrolyte realizes the cooperative optimization of functions by inducing two or more incompatible polymers to form a controllable phase separation structure on a microscopic scale. One phase forms a continuous ion transmission channel, which is beneficial to improving the ion conductivity and migration number, and the other phase forms a high-modulus framework, which provides necessary mechanical strength and toughness, is beneficial to processing and forming, can inhibit the growth of lithium dendrites, and enhances the safety of the battery. Although the electrolyte solves the contradiction that the ion conduction and the mechanical property are difficult to be compatible in the traditional solid polymer electrolyte to a certain extent, in practical application, if the phase separation is excessively developed, the ion conduction region is discontinuous and isolated, so that the problems of ion conductivity reduction, mechanical property degradation, electrode/electrolyte interface stability and the like are caused. Currently, the predominant methods of improving the phase separation structure include the addition of plasticizers or the use of physical electric field induction. Plasticizers, while promoting segmental motion, inhibiting crystallization, and increasing ionic conductivity, can result in a decrease in the modulus of the overall polymer matrix, impairing its ability to inhibit lithium dendrites. The physical electric field induction technology relies on the directional arrangement of an external field on charged molecular chains or ion clusters, needs long-time treatment under specific temperature and electric field conditions, has the problems of complex equipment, high energy consumption, time-consuming process and the like, and is difficult to meet the requirements of large-scale and high-efficiency manufacturing in the battery industry. Disclosure of Invention In order to solve the technical problems, the invention provides a preparation method of a stereocomplex crystal polymer electrolyte and a lithium metal battery, wherein the polylactic acid stereocomplex crystal bicontinuous phase solid polymer electrolyte is designed by a solution casting method to form a bicontinuous phase structure solid polymer electrolyte, and the stereocomplex crystal can form a bridge at a two-phase interface, so that the damage of a structure caused by excessive phase separation is avoided, the ion conductivity and the ion migration number are improved, the growth of lithium dendrites is inhibited, and the problems that the ionic conductivity and the mechanical strength of the stereocomplex solid electrolyte cannot be considered and the long-cycle performance is poor are successfully solved. Specifically: in a first aspect, an embodiment of the present invention provides a method for preparing a stereocomplex crystal polymer electrolyte, including: grafting the dextrorotatory polylactic acid on a flexible polycaprolactone chain segment, and synthesizing to obtain a PDLA-PCL-PDLA triblock copolymer; dissolving the PDLA-PCL-PDLA triblock copolymer and the L-polylactic acid in chloroform, and adding lithium salt to obtain a mixed solution; The mixed solution is prepared into a film to obtain the stereocomplex crystal polymer electrolyte, wherein the stereocomplex crystal polymer electrolyte has a stereocomplex crystal structure, and the stereocomplex crystal structure is formed by complexing two spiral chains of the L-polylactic acid and the D-polylactic acid through hydrogen bonds and dipole-dipole interactions. The following is a preferred technical scheme of the present invention, but not a limitation of the technical scheme provided by the present invention, and the following preferred technical scheme can be