Preparation of block copolymer electrolytes and its electrochemical performance

Abstract

The diblock copolymer electrolyte PEGMEMAm-GMAn-Br （PGA-Br）， a copolymer of poly（ethylene glycol methyl ether methacrylate） （PEGMEMA）， and glycidyl methacrylate （GMA） were synthesised by designing the molecular structure of the polymer and using thermally-initiated free-radical polymerisation. The electrochemical performance were investigated. The results show that the ionic conductivity of polymer electrolyte is improved by PGA block or grafting on polymer electrolyte， and the ionic conductivity at room temperature reaches 1.05×10-4 S·cm-1. At the same time， PGA-Br block copolymer electrolytes exhibit a low glass transition temperature （-65 ℃）， a high thermal decomposition temperature， an electrochemical stability window of up to 5.1 V， and flame-retardant property. The Li|Li symmetrical solid-state battery assembled with PGA-Br copolymer electrolyte exhibits an enhanced electrode/electrolyte solid-solid interface， which can achieve uniform deposition of lithium metal and effectively inhibit the lithium dendrites growth. The LiNi0.8Co0.1Mn0.1O2 （NCM811） |PGA-Br|Li solid-state battery based on PGA-Br block copolymer electrolyte can achieve a high first cycle discharge specific capacity of 160.1 mAh/g at 0.1 C， and the capacity retention rate is as high as 91.5% after 100 cycles， and with a stable Coulombic efficiency of over 98.5%.

Keywords

• solid-state lithium metal battery
• block copolymer electrolyte
• lithium metal anode
• lithium dendrite
• thermal initiation polymerization