Mediating Solid Electrolyte Interphase Formation Kinetics on SiO x Anodes Using Proton Acceptors

Silicon (Si)-based anodes offer high energy density but suffer from significant volume variations, leading to an unstable solid electrolyte interphase (SEI). To enhance SEI stability, numerous electrolyte additives have been designed to decompose on the anode and form desirable SEI components (e.g., LiF). However, their electrochemical reduction kinetics on the anode surface competes with other electrolyte components, leading to suboptimal interfacial decomposition efficiency and a less stable SEI structure. Here, inspired by bioremediation strategies in petroleum pollution treatment, we introduce a proton acceptor that reacts with fluoroethylene carbonate (FEC), a commercially established additive, to generate an intermediate. Such an intermediate lowers the reduction kinetic barrier, accelerating the formation of LiF and enriching it in the inner layer of the SEI. Compared to the randomly distributed LiF structure, the resulting SEI exhibits better mechanical stability and lithium-ion conduction, effectively accommodating volume changes and mitigating stress concentration caused by local overlithiation. As a result, the electrochemical performance surpasses that of previously reported works. This intermediate-based strategy significantly improves the utilization efficiency of commercial additives, offering a practical direction for future electrolyte design.