Optimization of Cation−Anion Dynamics in Cationic Polymer Electrolytes for Boosting the Performance of All‐Solid‐State Lithium−Metal Battery

ABSTRACT Lithium dendrite formation and low ionic conductivity of solid polymer electrolytes (SPEs) are the main challenges that plague the long cycle life and capacity retention of lithium‐metal batteries. To address these challenges, poly(crown ether piperidinium) (PCEP)/poly(ethylene oxide) (PEO) based SPEs with synergistic regulation of cation−anion functions are designed and prepared. The crown ether moieties within PCEP enable coordination with Li + , reducing the Li + coordination number and enhancing the ionic conductivity of SPEs to 4.2 × 10 −4 S cm −1 at 60°C. Concurrently, piperidinium units effectively immobilize TFSI − ions through electrostatic adsorption, resulting in an elevated Li + transference number (0.7) and a concomitant reduction in lithium dendrite growth. Consequently, a coin cell using a PCEP‐based SPE with a lithium iron phosphate cathode displayed a high cycle life of 2000 cycles at 1.0C with a commendable final discharge capacity of 117.9 mAh g −1 , corresponding to 79.4% capacity retention. Furthermore, lithium−sulfur coin cells utilizing PCEP‐based SPEs exhibit a specific discharge capacity of 671.8 mAh g −1 after 80 cycles at 0.2C, corresponding to 80.7% of the initial capacity, outperforming SPEs without PCEP. This research work introduces a synergistic cation−anion regulation strategy for the advancement of solid‐state energy conversion/storage systems.