Origin of Anion-Rich Solvation Structures in Siloxane Electrolytes

High-voltage lithium (Li) metal batteries (LMBs) are promising next-generation high-energy-density rechargeable batteries. Siloxane electrolytes exhibit excellent performance in high-voltage LMBs. Herein, the mechanisms responsible for the Li metal compatibility and high-voltage resistance of siloxane electrolytes were probed by classical molecular dynamics (MD) simulations, first-principles calculations, and experimental characterizations. Siloxane electrolytes have been demonstrated to deliver anion-rich solvation structures, which are induced by weak Li ion (Li⁺)-solvent interactions and strong Li⁺-anion interactions. The silicon (Si)─oxygen (O) bond energy of siloxane is larger than that of carbon (C)─O of C-siloxane (replacing Si atoms in siloxane with C atoms) because the atomic radius of Si is larger than that of C, and the Pauli exclusion of Si is smaller than that of C. Additionally, ab initio molecular dynamics (AIMD) simulations revealed that the decomposition of siloxane produces substances containing Si─O fragments on Li metal surfaces, which is beneficial for interfacial stability. This work reveals the mechanism of interfacial stability and intrinsic stability of siloxane electrolytes, providing a theoretical basis for the practical application of siloxane electrolytes in high-voltage LMBs.