In-situ polymerized electrolyte enabling high-voltage (4.6 V) full-cell lithium-ion batteries

The commercial deployment of lithium batteries is limited by the safety concerns of liquid electrolytes and the poor ionic conductivity of solid-state electrolytes. In this work, a lithium secondary battery is developed via in-situ polymerization of poly(ethyl 4,4,4-trifluorocrotonate) (PTCA-SPE), yielding an electrolyte with enhanced safety, interfacial compatibility, thermal stability, and high ionic conductivity. When applied in a 4.6 V lithium-rich (OLO)|Gr-Si soft-pack full cell with an energy density of 350 Wh kg⁻¹, the battery exhibits stable electrochemical performance. The thermal runaway threshold is elevated by 20 °C compared to a conventional liquid electrolyte, and capacity retention after 300 cycles at 0.33 C is substantially improved. The coordination between Li⁺ and C=O/C–O functional groups facilitate effective lithium ion dissociation and transport. As a result, PTCA-SPE forms a rapid and well-organized ion transport pathway, delivering a high ionic conductivity of 6.93 × 10⁻³ S cm⁻¹, a lithium-ion transference number of 0.84, and an electrochemical stability window exceeding 6.0 V. Beyond lithium-ion batteries, PTCA-SPE also significantly enhances the cycling stability and thermal safety of sodium-ion batteries and high-voltage NCM-based systems.