One-step Cr-doping engineering of MoSe2 nanoflowers for efficient and durable potassium storage

Potassium-ion batteries (PIBs) present a promising, cost-effective alternative to lithium-ion batteries for large-scale energy storage. However, their development is hindered by the lack of high-performance electrode materials that can withstand significant volume expansion and accommodate the large ionic radius of K⁺. This work addresses this challenge by developing a Cr-doping strategy for MoSe₂ anodes. Comprehensive characterization reveals that optimal Cr-doping effectively modulates the electronic structure and expands the interlayer spacing of MoSe₂. These synergistic improvements significantly enhance the electronic conductivity and provide more active sites as well as wider diffusion channels for K⁺. Consequently, the optimized Cr-doped MoSe₂ electrode delivers superior electrochemical performance for PIBs. It exhibits a reversible capacity of 171.1 mAh g⁻¹ after 600 cycles at a current density of 2 A g⁻¹ and achieves a high-rate capacity of 168.4 mAh g⁻¹ at 5 A g⁻¹. Electrochemical kinetics analysis confirms enhanced pseudocapacitive contributions and faster K⁺ diffusion kinetics. Furthermore, density functional theory (DFT) calculations elucidate that Cr-doping strengthens K⁺ adsorption energy and induces metallic-like electronic behavior, thereby improving conductivity. This study demonstrates that rational Cr doping is a highly effective strategy for engineering high-performance MoSe₂-based anodes, offering a viable pathway towards advanced potassium-ion storage systems.