Tuning solvation structure and derived interphase for high-rate micro-silicon anodes in lithium-ion batteries with high safety using ionic liquid based electrolytes

Ionic liquid electrolytes (ILEs), distinguished by their nonvolatility and high thermal stability, demonstrate considerable compatibility with silicon anodes and thus are an ideal alternative electrolyte for lithium-ion batteries. However, substantial challenges are to be addressed, notably the poor rate capability predominantly due to excessively tight Li+-coordination in the solvation sheath. Here, we introduce an innovative ILE-based electrolyte tailored for micro-sized silicon (μSi) anodes to address the issue of rate capability. By incorporating nonflammable sulfolane molecules into the primary Li+-solvation sheath, we concurrently enhance de-solvation kinetics and ion-conducting capability of solid electrolyte interphase (SEI). The primary sulfolane-mediated Li+-solvation configuration weakens de-solvation barrier and strengthens inorganic-rich SEI, while impeding the precipitation of organic cations in the SEI formation. The μSi electrode with the sulfolane-mediated ILE delivers an impressive rate capability of 782.5 mA h g–1 at a high current density of 12 A g–1 over 500 cycles Accelerating rate calorimetry further verifies remarkable thermal stability of the derived SEI and superior thermal safety of the sulfolane-mediated ILE compared to the commonly used electrolyte. This work provides an effective way to boost the rate capability of μSi anodes based on ILEs without compromising the thermal safety for developing high-performance lithium-ion batteries.