Thermal runaway-free Ah-level Na-ion battery

Safety is a fundamental criterion for determining rechargeable batteries in energy storage applications1,2. Despite the great efforts in non-flammable electrolytes, they still cannot achieve intrinsic safety so far in Ah-level batteries without thermal runaway3-10, and the relationship between the flame-retardancy of electrolytes and the safety performance of batteries is still unclear. Here, we propose a polymerizable and non-flammable electrolyte (PolyNonflyte or PNE). In addition to the inherent non-flammability, this formulation also leverages the synergistic anion-cation solvation effect and undergoes thermally triggered polymerization, facilitating the optimized electrode-electrolyte interfacial chemistry and a cross-linked barrier that prevents mechanical/chemical interactions between the electrodes with impeded side reactions and reductive gases generation. These features promise PNE to eliminate thermal runaway in Ah-level cylindrical cells even when the temperature rises to 300°C in accelerating rate calorimeter and thermal abuse tests. The nail penetration tests were also passed without fire, smoke, or explosion. Furthermore, batteries with this electrolyte exhibit exceptional temperature adaptability between -40°C and 60°C and a high energy density of 211 Wh/kg at 4.3 V. This work brings a new insight of the battery safety beyond non-flammable electrolyte design and paves the way towards safer and more efficient battery systems for energy storage technology.