Abstract
Liquid electrolytes composed of lithium salt in a mixture of organic solvents have been widely used for lithium-ion batteries. However, the high flammability of the organic solvents can lead to thermal runaway and explosions if the system is accidentally subjected to a short circuit or experiences local overheating. In this work, a cross-linked composite gel polymer electrolyte was prepared and applied to lithium-ion polymer cells as a safer and more reliable electrolyte. Mesoporous SiO2 nanoparticles containing reactive methacrylate groups as cross-linking sites were synthesized and dispersed into the fibrous polyacrylonitrile membrane. They directly reacted with gel electrolyte precursors containing tri(ethylene glycol) diacrylate, resulting in the formation of a cross-linked composite gel polymer electrolyte with high ionic conductivity and favorable interfacial characteristics. The mesoporous SiO2 particles also served as HF scavengers to reduce the HF content in the electrolyte at high temperature. As a result, the cycling performance of the lithium-ion polymer cells with cross-linked composite gel polymer electrolytes employing methacrylate-functionalized mesoporous SiO2 nanoparticles was remarkably improved at elevated temperatures.
Highlights
The reactive vinyl groups on the surface of the SiO2 particles allowed an in-situ cross-linking reaction with the gel electrolyte precursor by free radical polymerization
The composite membrane with mesoporous methacrylate-functionalized SiO2 (MA-SiO2) nanoparticles was prepared by dipping the fibrous PAN membrane in a solution containing mesoporous MA-SiO2 nanoparticles followed by vacuum drying
The composite membrane was used in the lithium-ion cell, and the cell was injected with gel electrolyte precursor containing a small amount of tri(ethylene glycol) diacrylate (TEGDA) and liquid electrolyte
Summary
The reactive vinyl groups on the surface of the SiO2 particles allowed an in-situ cross-linking reaction with the gel electrolyte precursor by free radical polymerization. These reactive SiO2 particles had a non-porous structure, and Li+ ion transport was blocked by insulating SiO2 particles. The connectivity of the ion-conducting pathway became more tortuous in these composite gel polymer electrolytes. To solve this problem, we synthesized mesoporous SiO2 nanoparticles containing reactive methacrylate groups as inorganic cross-linking sites, and these particles were uniformly dispersed into a fibrous polyacrylonitrile (PAN) membrane. The cycling performance of the cells was evaluated and compared to those of cells assembled with a cross-linked composite gel polymer electrolyte employing non-porous SiO2 nanoparticles
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