Understanding the correlation between ion transport and side chains in polymer electrolyte

Abstract

The rise of the new energy market has driven the rapid development of solid-state batteries (SSBs). Polymer electrolytes, due to their excellent interfacial compatibility and high safety, have brought new opportunities to SSBs. We report a polymer side-chain design strategy that combines ionic liquids and low-molecular-weight ether-based molecules into a copolymer electrolyte (CPE). Using nuclear magnetic resonance (NMR) techniques, we investigated the spatial distribution of lithium ions (Li⁺) and the correlations between anions of different conformations in the CPE. This study found that the introduced ionic liquids and high-freedom ether groups enable rapid ion migration, resulting in an ion conductivity of 1.44 × 10^–4 S cm^-1 at 25 °C. The dual lithium symmetric battery based on CPE can cycle more than1000 h at a current density of 0.3 mA cm^-2, while the LFP|CPE|Li full battery presents high retention after 120 cycles even at ultra-high loading (12.9 mg cm^-2) and a high current density of 1 C.