Core-Shell Co₂VO₄/Carbon Composite Anode for Highly Stable and Fast-Charging Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are promising candidates for large-scale energy storage systems due to the abundance and wide distribution of sodium resources. Various solutions have been successfully applied to revolve the large-ion-size-induced battery issues at the mid-to-low current density range. However, the fast-charging properties of SIBs are still in high demand to accommodate the increasing energy needs at large to grid scales. Herein, a core-shell Co₂VO₄/carbon composite anode is designed to tackle the fast-charging problem of SIBs. The synergetic effect from the stable spinel structure of Co₂VO₄, the size of the nanospheres, and the carbon shell provide enhanced Na⁺ ion diffusion and electron transfer rates and outstanding electrochemical performance. With an ultrahigh current density of 5 A g^-1, the Co₂VO₄@C anode achieved a capacity of 135.1 mAh g^-1 and a >98% capacity retention after 2000 cycles through a pseudocapacitive dominant process. This study provides insights for SIB fast-charging material design and other battery systems such as lithium-ion batteries.