Achieving a Stable Solid Electrolyte Interphase and Enhanced Thermal Stability by a Dual-Functional Electrolyte...

Li metal batteries with high-capacity cathodes emerge as promising candidates for next-generation battery technologies. However, the poor reversibility of the Li deposition/stripping process severely reduces its lifespan, and safety also remains a major issue for the Li metal anodes. Herein, we propose (ethoxy)-penta-fluoro-cyclo-triphosphazene (DFA) as a dual-functional electrolyte additive to solve the engineering problem of balancing the cycle life and thermal stability of Li metal batteries. The NCM811/lithium metal pouch batteries (2900 mA h) are assembled using the commercial high areal capacity cathode (3.5 mA h cm^-2). Compared with the NCM811/Li batteries without DFA, the heat generation and heat generation power of lithium metal batteries with DFA are significantly reduced by half during charging. Moreover, the NCM811/Li pouch batteries with DFA show excellent stability in both hot-oven and adiabatic rate calorimeter experiments. Furthermore, a nonlinear phase field simulation is carried out for mechanism investigation, which confirms that the stable solid electrolyte interphase formed by DFA will improve the cycle life of the NCM811/Li pouch. The DFA is verified to be an effective additive to improve the cycle stability and safety simultaneously, providing new opportunities for developing high energy density Li metal batteries.