Entangled S-doped LiFePO₄ with carbon network for self-supporting cathode of flexible energy storage devices

This paper describes the development of a highly flexible self-supporting cathode incorporating a network of entangled carbon nanofibers (CNFs) and well-dispersed sulfur-doped lithium iron phosphate (SLFP) particles. Through a spin-on-dopant process, sulfur atoms were successfully incorporated into both the surface carbon layer and inner LFP particles. The resulting S-doped carbon@LFP (SLFP-CNF) flexible electrode featured a unique hybrid composite architecture in which the interconnecting CNF framework considerably enhanced both the physical and electrochemical properties. Notably, the SLFP-CNF electrode maintained its structural integrity even after 5000 flexibility cycles, demonstrating robust mechanical stability. The electrode exhibited a high ionic diffusion rate of 9.14 × 10^–13 cm²/s, which is attributed to the expanded lattice constant of the S-doped LFP particles, which facilitates favorable Li-ion pathways. This contributes to a high specific capacity of 135.82 mAh/g and superior rate performance of 74.16 mAh/g after 1500 cycles (92.4 % retention rate) at a current density of 2000 mA/g. This enhanced performance is further supported by the conductive S-doped carbon layer, which enables rapid electron transport and ensures excellent cyclability. These results indicate that the SLFP-CNF flexible cathode is a promising candidate for next-generation flexible lithium-ion batteries.