Enhancing high-voltage solid-state lithium-metal battery performance through a stable solid-electrolyte interphase

The development of next-generation batteries relies on addressing critical challenges such as the formation of a robust and stable solid electrolyte interphase (SEI) as well as mitigating lithium dendrite propagation. In this study, we focus on addressing these issues in the preparation of solid polymer electrolytes (SPEs) using poly(ethylene oxide) (PEO) and three different Li-based conductive salts. We investigate the impact of each SPE on the electrochemical performance of solid-state batteries comprising a high-voltage LiNi0.6Mn0.2Co0.2O2 cathode and Li-metal anode. Among the various salts, lithium bis(oxalate)borate (LiBOB) salt stands out, exhibiting a stable voltage profile during charging up to 4.2 V vs. Li/Li+ and preventing the catalytic oxidation of PEO at high-voltage. X-ray photoelectron spectroscopy reveals that LiBOB is reduced into lithium oxalate and other semicarbonate-like species, thereby enhancing the Li metal|SPE interface from the formation of a dense and stable SEI enriched with LiBOB decomposition products. Our findings underscore the significance of the choice of Li-based salts for forming a stable SEI, which is key for an interfacial engineering design that enables the high-performance of next-generation solid-state batteries. The development of next-generation batteries relies on addressing critical challenges such as the formation of a robust and stable solid electrolyte interphase (SEI) as well as mitigating lithium dendrite propagation.