WS₂-MoS₂-biocarbon heterostructure for high-performance potassium ion storage

Potassium ion batteries (PIBs) have attracted increasing attention due to their inexpensive elemental potassium resources and excellent theoretical electrochemical properties. Two-dimensional metal sulfides exhibit a high specific capacity as potassium ion hosts, but the high diffusion barriers for potassium ions lead to a poor reversibility of the reaction and make the theoretical capacity difficult to achieve. Here, the sulphide MoS₂ was introduced into WS₂ nanosheets to construct layered WS₂/MoS₂ heterostructures anchored on a biogenic carbon (BioC) framework. The MoS₂ in the framework served as an anchoring site to stabilise the intermediate product K_xS_y and to increase the WS₂ layer spacing. Interfacial electric fields and potassium ion migration channels with high conversion reversibility were also formed in the layered heterostructures. The results confirmed that the reversibility of the reaction and the potassium ion diffusion rate were improved. As a result, the WS₂-MoS₂-BioC electrode achieves high specific capacity and diffusion rate, with a reversible specific capacity of up to 517.1 mAh g⁻¹ at 0.1 A g⁻¹, and a three order of magnitude improvement in potassium ion diffusion performance compared to that of MoS₂-BioC. This heterostructure design strategy provides ideas for the development of metal sulphide anodes for potassium ion batteries.