Cellulose-reinforced poly(cyclocarbonate-ether)-based composite polymer electrolyte and facile gel interfacial modification for solid-state lithium-ion batteries

Synthesizing high-performance solid electrolytes with simple methods and common materials has long been a desire for lithium-ion batteries. Here, easy-available composite polymer electrolytes (CPEs) were prepared via UV curing of novel P(VEC-co-EGDMA) matrix and ionic liquid (IL) with commercial cellulose separator (CL). Loose complexation environment enabled cyclic carbonate of vinyl ethylene carbonate (VEC) to have higher Li+ migration capacity than EO, and poly (ethylene glycol) dimethacrylate (PEGDMA) was introduced as a flexible crosslinker to avoid excessively rigid structure. Furthermore, the IL with high voltage stability and CL with polar groups on the surface achieved liquid plasticization and mechanical reinforcement of P(VEC-co-EGDMA) matrix, synergistically improving the electrochemical performance and safety of CPEs. The ionic conductivity, electrochemical stability window and tensile strength of the optimal sample (PI64/CL) even reached 3.60 × 10−4 S cm−1 (25 °C), 5.6 V and 4.50 MPa, respectively. Finally, a 5 μm-thick PEO-LLZTO-IL gel transition layer was added at the electrolyte/cathode interface by a facile casting-curing method to optimize their interfacial contact, enabling the assembled solid-state battery to exhibit impressive rate and cycle performance, its specific capacity reached 151.6 mAh g−1 (1C) at 40 °C with the 89.1% capacity retention rate after 280 cycles, corresponding to 148.6 mAh g−1 (0.5C), 98.7%, 120 cycles at room temperature.