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

• In-situ polymerization method simplifies the preparation process of polymer electrolytes. • The driving mechanism of lithium ions in polymer electrolytes under the strategy of side-chain design was revealed for the first time using solid-state nuclear magnetic resonance (NMR) technology. • The LFP|CPE|Li full battery can cycle stably even at ultra-high loading (12.9 mg cm -2 ) and a high current density of 1C. 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. We report a polymer side-chain design strategy that incorporates ionic liquids and low molecular weight ether-based molecules into a copolymer electrolyte (CPE). Using nuclear magnetic resonance (NMR) technology, we investigated the spatial distribution of lithium ions and the correlation between different conformations of anions in the CPE. The study found that the introduced ionic liquids and highly mobile ether groups enable rapid ion migration, achieving an ionic conductivity of 1.44 × 10 –4 S cm -1 at 25 °C.