Electrolyte reduction on cathodes to enhance the performance of high-energy batteries

The remarkable success of Li-ion batteries originates from the formation of solid electrolyte interphases through electrolyte reduction on anodes. Transferring electrolyte reduction to the cathode could generate cathode-electrolyte interphases that could further improve battery performances, but the implementation has been challenging. Here we introduce a bimolecular nucleophilic substitution reaction-assisted electrolyte reduction strategy that elevates the reduction potential of electrolytes and enables the formation of either passivating or non-passivating LiF-rich cathode-electrolyte interphases. Spectroscopic studies revealed that the passivation behaviour of these interphases is governed by the diffusivity of sulfite-based solvent reduction products and the fluoroborate anion type involved in the reaction. Guided by this principle, we have developed electrolytes that can either enhance the energy and power of primary batteries or extend the cycle life in rechargeable batteries. We also extend this electrolyte design principle from fluoroborate anions to SiCl₄. Collectively, this work establishes a universal approach for electrolyte and interphase design that spans organic chemistry, interfacial chemistry and electrochemistry.