Doping-induced polymorph transformation to boost ultrafast sodium storage in hierarchical CoSe₂-carbon arrays

Transition metal dichalcogenides (TMDs) are regarded as the most potential candidates of anode materials for sodium-ion batteries (SIBs) owing to their high theoretical capacity, while the sluggish kinetics and huge volume variation that are accompanied by sodium-ion insertion/extraction cause inferior electrochemical performance. Herein, a P-doping-induced polymorph transformation strategy is proposed to modulate the electronic structure of CoSe₂ anode toward fast sodium storage. Density functional theory (DFT) calculations verify the unique effect of doping-induced polymorph engineering on modulating the electronic structure of CoSe₂. Therefore, due to the optimal electronic structure, improved ionic diffusion kinetics, and numerous exposure of reactive sites from hierarchical arrays, the P-CoSe₂/NC anode exhibits impressive rate capability (459 mA h g⁻¹ at 2 A g⁻¹) when used as an anode for SIBs. Our doping-induced polymorph engineering may be applicable to other advanced electrodes toward energy storage applications.