Rational design heterostructured bimetallic selenides for high capacity and durability sodium/potassium-ion storage

Transition metal selenides are regarded as a type of promising candidate anode material for sodium/potassium ion batteries owing to their high theoretical specific capacity. However, it is still a challenge to design and construct appropriate nanostructures to address the fatal issue of vast volume variation stemmed from repeated ion intercalation/deintercalation. Herein, simple solvothermal method combined with calcination treatment was applied to synthesis CoSe2-Cu2Se nanospheres encapsulated in nitrogen-doped carbon shells (CoSe2-Cu2Se@NC) as high-performance anode material for sodium/potassium ion batteries. The as obtained CoSe2-Cu2Se@NC electrode features unique heterogeneous structure, uniform carbon coating, large specific surface area and synergistic effects, which ultimately accelerate charge/electron transfer, restrain volume expansion, and thus improve electrochemical performance. Density functional theory results disclose the heterojunctions existed in the CoSe2-Cu2Se interface contribute to the prominent rate capability for the composite. As a result, CoSe2-Cu2Se@NC nanospheres displays good rate performance and improved durability in cycling for sodium/potassium ion batteries. In additional, the depth reaction mechanism of CoSe2-Cu2Se@NC were explored by in-situ and ex-situ XRD analyses.

Automated summary

Transition metal selenides are considered promising anode materials for sodium/potassium ion batteries due to their high theoretical specific capacity, but designing appropriate nanostructures to address volume changes remains a challenge. In this study, high-performance CoSe2-Cu2Se@NC nanospheres were synthesized using a simple solvothermal method and calcination treatment, showing unique structure and improved performance.