An all-in-one free-standing single-ion conducting semi-solid polymer electrolyte for high-performance practical Li metal batteries

Abstract

Single-ion conducting polymer electrolytes, characterized by effective Li⁺ transport and dendrite mitigation, are emerging as promising candidates for the highly demanded lithium metal batteries. However, despite the promise, their current ionic conductivity and Li⁺ transference number fall short of application requirements. Herein, we have developed a free-standing single-ion conducting semi-solid polymer electrolyte (PBSIL), engineered through the synergistic interaction between anion acceptors and solvated ionic liquids. This innovative chemical synergy significantly enhances the complete dissociation of lithium salts while immobilizing anions, thus facilitating rapid Li⁺ transport. As a result, the PBSIL electrolyte exhibits enhanced ionic conductivity of 8.0 × 10⁻⁴ S cm⁻¹, and an improved Li⁺ transference number of 0.75. These features effectively mitigate concentration polarization and dendrite growth, ensuring long-term cell stability. Moreover, Li|PBSIL|LiNi_0.8Co_0.1Mn_0.1O₂ cells demonstrate an ultra-long cycle life of 1300 cycles, with a high discharge capacity of 183 mA h g⁻¹ and excellent capacity retention of 75%. Additionally, PBSIL has been successfully integrated for the first time into the production of winding-processed semi-solid state cylindrical and Z-stacked pouch lithium metal batteries. Through the synergistic regulation of Li⁺ transport and anion immobilization, PBSIL provides an effective design strategy for free-standing semi-solid polymer electrolytes, showcasing superior electrochemical performance and contributing to the development and industrialization of long-cycling lithium metal batteries.