A dual-carbon structured molybdenum selenide composites controlled via interface engineering and chemical bonding to attain high initial coulombic efficiency and rate capability of potassium-ion batteries

Molybdenum selenide (MoSe2) is considered representative anode material for Potassium-ion batteries (PIBs) by reason of its adjustable forbidden bandwidth and large interlayer spacing allowing the intercalation/deintercalation of large-sized K+. However, its inferior electronic conductivity, substantial volume variation, and aggregation make it difficult to achieve satisfactory cycling performance and rate capability. Herein, we reported a novel composite with MoSe2 nanosheets grown vertically on the surface of N-doped hollow porous carbon bowls and wrapped by ultrathin/wrinkled reduced graphene oxide layers (G-MoSe2/NHPCB) as the anode material for PIBs. The strong chemical bonds between MoSe2 and carbon materials (including C-Mo, C-O-Mo, and C-N-Mo bonds) were profitable for the charge-transfer kinetics and structural durability. The NHPCB substrate, with a large specific surface area, could significantly prohibit the aggregation of MoSe2 nanosheets and shorten the transmission path for electrons and ions. Meanwhile, the ultrathin/wrinkled graphene layers could effectively strengthen the composite structure stability and reinforce the overall conductivity. Benefitting from the distinctive structure, when evaluated as a K-ion half-cell anode, the G-MoSe2/NHPCB electrode exhibited a high discharge capacity of 601.59 mA h g−1 and initial coulombic efficiency (ICE) of 83.4% at 0.1 A/g, exceptional rate capability (261.3 mA h g−1 at 5.0 A/g) and long-term cycling stability (304.3 mA h g−1 at 1.0 A/g after 500 cycles and 214.9 mA h g−1 at 2.0 A/g after 1000 cycles). The electrochemical reaction mechanism and kinetic analysis were investigated using in-situ and ex-situ methods and first-principles calculation. This work demonstrates the advantages of G-MoSe2/NHPCB as KIBs anode materials and provides innovative thinking for the rational design of high-performance transition metal selenides with unique structures.