Boosting potassium storage in nanosheet assembled MoSe2 hollow sphere through surface decoration of MoO2 nanoparticles

Considering the suitable redox potential, low price, and abundant resource of potassium, potassium-ion batteries (PIBs) have attracted considerable attention as one of the alternatives to lithium-ion batteries (LIBs), however, the larger ionic radius of potassium ions makes it difficult to select suitable electrode materials. Herein, the MoSe2@MoO2 heterojunction in which MoO2 nanoparticles embedded on MoSe2 nanosheets was synthesized by hydrothermal method and used as a novel anode material for PIBs. The electrochemical performance of the heterojunction was greatly improved as compared with the pure MoSe2 and pure MoO2. At the current density of 500 mA g−1 after 100 cycle, the heterojunction electrode still maintains a capacity of 255 mA h g−1 and the coulomb efficiency is close to 100%. By introducing metallic MoO2 can improve the electrical conductivity, furthermore, the MoSe2@MoO2 heterostructures facilitate interfacial electron transport and built-in electric field makes the diffusion of K-ion easier. In addition, the well dispersed MoO2 nanoparticles prevent the restacking of MoSe2 nanosheets and maintain the structure stability during the charge/discharge process.