Uncovering Temperature‐Insensitive Feature of Phase Change Thermal Storage Electrolyte for Safe Lithium Battery

Abstract Lithium‐ion batteries (LIBs) have emerged as highly promising energy storage devices due to their high energy density and long cycle life. However, their safety concern, particularly under thermal shock, hinders their widespread applications. Herein, a temperature‐insensitive electrolyte (TI‐electrolyte) with exceptional resistance to thermal stimuli is presented to address the safety issues arising from the lack of thermal abuse tolerance in LIBs. The TI‐electrolyte is composed of two phase‐change polymers with differentiation melting points (60 and 35°C for polycaprolactone and polyethylene glycol respectively), delivering a wide temperature‐resistant range. It is demonstrated that the TI‐electrolyte possesses a heat capacity of 27.3 J g ⁻¹ . The crystalline region in the TI‐electrolyte shrinks when confronted with above‐ambient temperature, absorbing heat to unlock molecular chains fixed in the crystal lattice, becoming amorphous. Notably, the Li||LFP pouch cell delays 3 valuable minutes to achieve the same temperature as conventional liquid electrolytes (LE) when subjected to thermal shocks, paralleling with the simulation results. Moreover, symmetrical Li||Li cell cycles stably for over 600 h at 0.1 mA cm ⁻² , and Li||LFP full cell demonstrates excellent electrochemical performance, with a capacity of 142.7 mAh g ⁻¹ at 0.5 C, thus representing a critical approach to enhancing the safety of LIBs.