Carbon-Sphere Supported Cu9S5/NiS2 Involving Inter-Doping to Promote Fast and Stable Potassium Ion Storage

Potassium ion batteries (PIBs) are highly anticipated beside lithium-ion batteries (LIBs) owing to the abundant K resources, comparable standard electrode potential, and high theoretical capacity & high energy density, while the large radius of K⁺ ion usually results in the anode materials challenged by structural collapse, sluggish kinetics, and fast capacity decay. Herein, a composite with Cu₉S₅/NiS₂ nanoparticle (≈15 nm) uniformly inlaid on hollow carbon-sphere (NCS) is designed, where the firmly anchored Cu₉S₅/NiS₂ particle and sturdy carbon-sphere skeleton synergistically endow high structural-stability and satisfactory electron/ion accessibility for the NCS composite and inter-doping for Cu₉S₅/NiS₂ from the introduction of highly conductive copper have further improved the conductivity of NCS composite for conversion reactions during potassiation/depotassiation. The structural features enable the NCS electrode to achieve a high capacity of ≈600 mAh g⁻¹ even at a mass loading of 3.76 mg cm⁻², stable cyclic performance for 1500 cycles, and fast electrochemical kinetics in half-cell, and the full-cell has also demonstrated a high capacity of ≈600 mAh g⁻¹ and long-term cyclic performance for 550 cycles. The electrochemical mechanism has also been revealed experimentally and theoretically, providing an instructive strategy for the construction of highly stable and fast electrode materials for potassium ion storage.