Abstract: All-solid-state lithium batteries (ASSLBs) are important for enhancing safety across various applications related to lithium-ion batteries (LIBs). Lithium iron phosphate (LiFePO₄) is a widely utilized commercial cathode in LIBs, prized for its stable cycling performance, thermal stability, and low cost. However, low electronic conductivity and slow ion diffusion kinetics limit its application at high rates and low temperatures. Herein, Ti₃C₂T_x MXene nanosheets (NSs) are introduced into the LiFePO₄ cathode. The continuous electron-conducting networks are constructed due to the high electrical conductivity of Ti₃C₂T_x NSs. Meanwhile, the coordination environment of lithium ions in the cathode is weakened by the oxygenated end groups of Ti₃C₂T_x NSs, and thus efficient ion-percolating networks are constructed. Therefore, the ionic and electronic conductivities of the modified cathode are significantly improved. Assembled all-solid-state LiFePO₄/Li full cells with poly(ethylene oxide) as electrolyte exhibits high initial discharged capacities of 91.5 mAh g^-1 at 10 C, and capacities of 155.1 mAh g^-1 after 1000 cycles at 1 C with a retention rate of 93.8 %. Furthermore, the cells still deliver excellent performance at high loading, room temperature, and low temperature. This work offers a facile and scalable strategy for designing high-performance ASSLBs.

Key words: Lithium-ion batteries, Solid-state batteries, LiFePO₄ cathode, Conductive networks, Ionic transport