Interfacial optimization of FeCoNiS@MXene via in-situ sulfidation for high-capacity lithium-ion battery

High-capacity transition metal sulfides (TMSs) are promising anode materials for high-energy-density lithium-ion batteries (LIBs), but their practical application is hindered by sluggish ion/electron transport. To address these challenges, we developed a high-performance FeCoNiS@MXene composite anode via in-situ growth of FeCoNiS nanoparticles on Ti₃C₂T_x MXene. The heterogeneous interfaces between FeCoNiS and MXene, together with S vacancies, effectively narrow the band gap, thereby enhancing both electronic and ionic conductivity to accelerate conversion reaction kinetics. In addition, the uniformly anchored FeCoNiS nanoparticles suppress aggregation, while the interfacial structure significantly enhances Li⁺ adsorption and migration, boosting high-capacity LIBs. Benefiting from these synergistic effects, the FeCoNiS@MXene anode exhibits excellent rate performance (658.0 mAh g⁻¹ at 5.0 A g⁻¹, 2.1 times higher than that of FeCoNiS-MXene without engineered interfaces and S vacancies) and cycling stability (87.3 % capacity retention with 971.4 mAh g⁻¹ at the 100th cycle). This work demonstrates the effectiveness of interface engineering and offers a feasible approach for designing high-performance TMS-based composite anodes for advanced LIBs.