All-solid-state lithium ion batteries are considered to be one of the best candidates for next generation batteries due to the high safety and energy density, but there is still a severe challenge for seeking the high-performance solid electrolytes with high ionic conductivity. Most importantly, the huge resistance at the electrode/electrolyte interface limits their applications. In this work, we investigate an in situ building method of a solid electrolyte, which constructs a composite electrolyte on the cathode by UV-curing and reduces the interfacial impedance by 69.1%. The solid electrolyte shows a decent ionic conductivity of 2.21 × 10–5 S cm–1 at 25 °C and presents a wide electrochemical stability window (>4.7 V vs Li+/Li). The all-solid-state LiFePO4/Li cell displays a high discharge capacity of 147 mAh g–1 and good capacity retention of ∼82% in 100 cycles under 0.1 C at room temperature. The strategy for in situ fabrication of a composite polymer electrolyte shows a promising way for the application of all-solid-state lithium batteries.

Oxygen-containing groups can be introduced to carbon paper surfaces by acidification. They improve the electrochemical performances and affect the charge-discharge behaviors of the MnO2/CP cathode by reducing the interface resistance.

The addition of ceramic fillers can weaken the interaction between different polymers and make organic and inorganic components contact directly, which inhibit the segregation of solid electrolyte components.

A polycarboxylic/ether composite polymer electrolyte derived from two-arm monomer and polyethylene oxide (PEO) was in situ synthesized on the cathode. The composite electrolyte exhibits a high ionic conductivity of 3.6 × 10 −5 S cm –1 , high oxidation stability, excellent stability towards Li metal and makes Li/LiFePO 4 present good cyclic and rate performance at 25°C.