Polymer electrolyte composite membrane and preparation method thereof

Abstract

The invention relates to the technical field of lithium-ion batteries, in particular to a polymer electrolyte composite membrane and a preparation method thereof. The polymer electrolyte composite membrane comprises a porous base membrane and an electrolyte membrane dip-coated on the porous base membrane, and the electrolyte membrane is mainly composed of a PVDF modified single lithium-ion conductor polymer, polyethyleneimine and polyoxyethylene according to a weight ratio of (40-70): (1-10): (20-40). The PVDF modified single lithium-ion conductor polymer, the polyethyleneimine and the polyoxyethylene in the polymer electrolyte composite membrane have a synergistic effect, and the polymer electrolyte composite membrane is prepared through the procedures of dissolving, mixing, dip-coating and drying, and has excellent ionic conductivity and tensile strength. The preparation method is simple in process and convenient to operate, and facilitates the quantitative production of the polymerelectrolyte composite membrane.

Description

technical field [0001] The invention relates to the technical field of lithium ion batteries, in particular to a polymer electrolyte composite membrane and a preparation method thereof. Background technique [0002] Lithium-ion batteries on the market mostly use organic liquid electrolytes, which are prone to safety issues such as leakage and flammability during use. Solid polymer electrolytes can overcome the problems of easy leakage and flammability of liquid electrolytes, so more and more researchers are devoting themselves to the research of solid polymer electrolytes. [0003] Traditional polymer electrolytes are generally dual-ion conductors, and current conduction is achieved through the directional migration of lithium ions and their corresponding anions. The lithium ion migration number of the double ion conductor polymer electrolyte is low, generally less than 0.5. During battery charging and discharging, lithium ions and their corresponding anions move in opposi...

AI Technical Summary

Problems solved by technology

For example: ① Most lithium single-ion conductor polymers are prepared by polymerizing monomers with specific structures or modifying branched chains with specific structures on polymers, and then the polymer electrolyte membrane obtained by casting process has a high tensile strength. Low, generally less than 20MPa, difficult to meet the requirements of lithium battery production process

②. Because the dissociation energy between anion and lithium ion on the single ion conductor polymer is relatively large, and the energy required for lithium ion migration is relatively high, the room temperature internal resistance of the single ion conductor polymer is relatively large (> 10 -5 S / cm), its internal resistance and liquid electrolyte (10 -2 -10 -3 S / cm) There is still a big gap compared with

However, PVDF does not contain lithium atoms and has poor affinity with lithium salts. Therefore, the polymer electrolyte prepared by directly adding lithium salt to PVDF has a large internal resistance, which is not suitable for the preparation of polymer electrolytes for lithium-ion batteries. membrane

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