Improving the Ionic Conductivity of PEGDMA-Based Polymer Electrolytes by Reducing the Interfacial Resistance for LIBs

Polymer electrolytes (PEs) based on poly(ethylene oxide) (PEO) have gained increasing interest in lithium-ion batteries (LIBs) and are expected to solve the safety issue of commercial liquid electrolytes due to their excellent thermal and mechanical stability, suppression of lithium dendrites and shortened battery assembly process. However, challenges, such as high interfacial resistance between electrolyte and electrodes and poor ionic conductivity (σ) at room temperature (RT), still limit the use of PEO-based PEs. In this work, an in situ PEO-based polymer electrolyte consisting of polyethylene glycol dimethacrylate (PEGDMA) 1000, lithium bis(fluorosulfonyl)imide (LiFSI) and DMF is cured on a LiFePO₄ (LFP) cathode to address the above-mentioned issues. As a result, optimized PE shows a promising σ and lithium-ion transference number (t_Li⁺) of 6.13 × 10^-4 S cm^-1 and 0.63 at RT and excellent thermal stability up to 136 °C. Moreover, the LiFePO₄//Li cell assembled by in situ PE exhibits superior discharge capacity (141 mAh g^-1) at 0.1 C, favorable Coulombic efficiency (97.6%) after 100 cycles and promising rate performance. This work contributes to modifying PEO-based PE to force the interfacial contact between the electrolyte and the electrode and to improve LIBs' performance.