Smart Electrolytes for Lithium Batteries with Reversible Thermal Protection at High Temperatures

Abstract Battery safety is a multifaceted concern, with thermal runaway standing out as a primary issue. In this work, we introduce a novel temperature‐responsive, self‐protection electrolyte governed by the phase separation dynamics of poly (butyl methacrylate) (PBMA) in lithium salt/tetraglyme (G4) blends. This innovation effectively mitigates the risks associated with thermal runaway in lithium batteries. Our electrolyte exhibits a temperature‐responsive‐recovery characteristic, imparting intelligent capabilities to lithium batteries. At temperatures of >105 °C, the electrolyte transitions from a homogeneous phase to a segregated state, comprising a PBMA‐rich phase with low conductivity and a high conductivity phase containing dissolved lithium salt in G4. The deposition of the PBMA‐rich phase on the electrode surface obstructs the ion transport, thereby averting a thermal runaway. Subsequently, upon returning to room temperature of 25 °C, the electrolyte reverts to its homogeneous, highly conductive state, with battery capacity resuming at approximately 94 %. Thus, our electrolyte offers a robust, reversible, smart self‐protection for batteries. Additionally, it demonstrates exceptional cycling performance at room temperature. Our findings open new avenues for thermo‐reversible and self‐protective electrolytes, advancing the safe and widespread adoption of lithium‐ion batteries.