Nanosheet-interwoven structures and ion-electron decoupling storage enable Fe1-xS fast ion transport in Li+/Na+/K+ batteries

Fe_1-xS, known for its high theoretical capacity, abundant resources, and intrinsic safety, has become a focal point as a universal anode for Li⁺/Na⁺/K⁺ batteries. However, its fast-charging capability is unsatisfactory due to sluggish ion transport rate and low electrical conductivity. Furthermore, its Li⁺/Na⁺/K⁺ storage mechanisms are still unclear. Here, we fabricate a single-crystal Fe_1-xS/N-doped carbon composite nanosheet interwoven structure, in which N-doped carbon layers onto surface of Fe_1-xS nanosheets ameliorate the electrical conduction and the interwoven nanosheets form open pore channels that favor permeation of electrolytes to boost ion transport. In-situ magnetometry reveals that ion-electron decoupling storage and transport occur in two-phase composites of Fe/Li₂S, Fe/Na₂S, and Fe/K₂S, in which Fe phase stores and transports electrons and sulfide phase stores and transports ions in a space-charge form, resulting in extra ion storage and fast ion transport. Consequently, the nanosheet interwoven structure delivers high capacities (1320.1/652.2/350.6 mAh g⁻¹), outstanding fast-charging performances (679.6/295.4/106.4 mAh g⁻¹ at 20 A g⁻¹), and long cycling life over 5000 cycles as Li⁺/Na⁺/K⁺ battery anodes, respectively