A multifunctional cathode sodiation additive for high-performance sodium-ion batteries

Abstract

Sodium-ion batteries (SIBs) demonstrate great application prospects for large-scale energy storage owing to the merits of low cost and abundant sodium resources. Nevertheless, the low initial coulombic efficiency of anode materials inevitably consumes the limited Na⁺ from the cathode, leading to the loss of reversible capacity and inferior energy density of the full-cell. Herein, a multifunctional cathode sodiation additive, 1,2,4-triazole sodium (TS), is first proposed to offset the Na loss in sodium ion full-cells. The energy density of the as-constructed hard carbon//Na₃V₂(PO₄)₃ full cell with 10 wt% TS is obviously improved from 180 to 196 W h kg⁻¹ based on the total mass of the cathode, additive, and anode. More importantly, this TS additive demonstrates multifunctional effects on the electrode. It can further modify the conductive framework in the electrode and build a desirable NaF-rich cathode electrolyte interface on the surface of the cathode, thus accelerating the sodiation/desodiation process. Furthermore, this additive can also enable the facile fabrication of a flexible Na₃V₂(PO₄)₃ electrode with high performance. This work provides a new-type of cathode sodiation additive with multiple roles for advanced SIBs.