Enhancing\nEfficiency,\nStability, and Cycle Life of\nLithium Metal Electrodeposition in Dry Solid-State Polymer Electrolytes

Dry solid polymer\nelectrolytes (SPEs), particularly those\nbased\non poly(ethylene oxide) (PEO), hold significant potential for advancing\nsolid-state Li-metal battery (LMB) technology. Despite extensive research\nover the years, a comprehensive evaluation of Coulombic efficiency\n(CE), deposit stability, and cycle life for reversible Li metal electrodeposition\nin SPE-based cells is still lacking. In this study, we systematically\nassess the effect of cycling conditions on the CE of Li|SPE|Cu half\ncells and provide a thorough examination of different electrolyte\nchemistries, highlighting and explaining their performance across\nvarious parameters. While the efficiency of the PEO-based SPEs still\nfalls short of the efficiency benchmark set by liquid and gel electrolytes,\nwe demonstrated >95% CE with Lithium bis(fluorosulfonyl)imide (LiFSI)-based\nSPEs, surpassing previous reports for dry SPEs in a Li|SPE|Cu cells,\nthis result marks a significant breakthrough. Furthermore, our findings\nhighlight the critical impact of the Li-SPE interphase on these performance\nmetrics. The LiFSI-based SPE forms a Li-rich, high-conductivity interphase,\nwhich not only enhances efficiency but also improves cycle life and\nLi deposit stability. These results underscore the importance of selecting\nthe right polymer electrolyte chemistry and concentration to enhance\nSPE performance.