A smart polymer electrolyte coordinates the trade-off between thermal safety and energy density of lithium batteries

In this article, we develop a smart polymer electrolyte through in-situ radical random polymerization of the cyclic carbonate urethane methacrylate monomer and the 2-isocyanatoethyl methacrylate monomer, which coordinates the trade-off between thermal safety and energy density of lithium batteries. It is demonstrated that the as-developed polymer electrolyte can incur the battery thermal shutdown before reaching the thermal runaway temperature. This originates from the highly crosslinking network caused by the nucleophilic addition of carbamate to isocyanate in the polymer matrix under the elevated temperature exceeding 170 °C. Besides, superior cycle performance of 4.5 V-class LiNi0.6Co0.2Mn0.2O2/Li batteries can be achieved, with a capacity retention of 80% after 200 cycles at 0.5 C and 30 °C, owing to enhanced interface compatibility of this polymer electrolyte. Noting that this polymer electrolyte possesses a superior water-scavenging ability, which helps improve the moisture resistance and battery cycle performance. Impressively, this polymer electrolyte can achieve improved energy density and superior safety characteristic of lithium batteries under high cut-off voltage.