Fe3S4@Li7P3S11 nanocomposites as cathode materials for all-solid-state lithium batteries with improved energy density and low cost

All-solid-state lithium batteries are considered as one of the most promising alternatives to traditional lithium-ion batteries because of their high safety and high energy density. In order to further improve the energy density of all-solid-state lithium batteries, sulfide electrodes with high theoretical capacities and solid electrolytes with high ionic conductivities have been widely explored and successfully demonstrated in all-solid-state lithium batteries. However, the interfacial resistance arising from poor interfacial compatibility and loose contact seriously hinders the electrochemical performances of all-solid-state lithium batteries. Fe3S4 ultrathin nanosheets with a thickness of 15 nm are synthesized by a facile polyvinyl alcohol-assisted precipitation method. In order to achieve intimate contact between sulfide electrodes and sulfide solid electrolytes, Fe3S4 nanosheets are in situ coated with Li7P3S11 and employed as cathode materials in Li/75% Li2S-24% P2S5-1% P2O5/Li10GeP2S12/Fe3S4@Li7P3S11 all-solid-state lithium batteries to investigate their electrochemical performances. Fe3S4@Li7P3S11 nanocomposite electrodes exhibit higher discharge capacity and better rate capability than pristine Fe3S4 nanosheets. After 200 cycles, the discharge capacity remained at a high value of 1001 mA h g(-1) at a current density of 0.1 A g(-1). The superior cycling stability could be ascribed to intimate contact and low charge transfer resistance at the interface between electrodes and solid electrolytes.