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

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. ... mehrThis research work introduces a synergistic cation−anion regulation strategy for the advancement of solid-state energy conversion/storage systems.