The Origin of the Reduced Reductive Stability of Ion-Solvent Complexes on Alkali and Alkaline Earth Metal Anodes

The intrinsic instability of organic electrolytes seriously impedes practical applications of high-capacity metal (Li, Na) anodes. Ion-solvent complexes can even promote the decomposition of electrolytes on metal anodes. Herein, first-principles calculations were performed to investigate the origin of the reduced reductive stability of ion-solvent complexes. Both ester and ether electrolyte solvents are selected to interact with Li⁺ , Na⁺ , K⁺ , Mg²⁺ , and Ca²⁺ . The LUMO energy levels of ion-ester complexes exhibit a linear relationship with the binding energy, regulated by the ratio of carbon atomic orbital in the LUMO, while LUMOs of ion-ether complexes are composed by the metal atomic orbitals. This work shows why ion-solvent complexes can reduce the reductive stability of electrolytes, reveals different mechanisms for ester and ether electrolytes, and provides a theoretical understanding of the electrolyte-anode interfacial reactions and guidance to electrolyte and metal anode design.