Micro-sized FeS2@FeSO4 core-shell composite for advanced lithium storage

Abstract Core-shell structures with resilient shells and high energy density cores are demonstrated to exhibit good chemical diffusion of Li+, high conductivity and cycling stability. Hence, a simple and novel method has been proposed at the first time to synthesize the micro-sized FeS2@FeSO4 core-shell composite. The cubic FeS2 with a rough surface and a size of 1–2 μm is homogeneously covered by a layer of FeSO4, which is formed via slow oxidation. The distinct core-shell structure not only effectively alleviates the huge volume expansion of FeS2, but also improves the reaction kinetics of the electrode. Therefore, the micro-sized FeS2@FeSO4 core-shell composite displays excellent reversible capacity and stable cycling performance as an anode material for lithium storage. In particular, the composite anode delivers a superior cycling performance of 1171 mAh g−1 and capacity retention of 90.8% after 200 cycles at 0.2 A g−1. Even under a current density of 4 A g−1, the micro-sized FeS2@FeSO4 core-shell composite anode achieves a high rate capacity of 744 mAh g−1. Overall, the micro-sized FeS2@FeSO4 core-shell composite has been demonstrated as an ultrafast charge-discharge electrode material for next-generation LIBs. Furthermore, the simple and environment-friendly method opens a door for preparing other transition metal sulfide composites.