Phosphorus–carbon covalent bond induced kinetics modulation of vanadium diphosphide for room- and high-temperature sodium-ion batteries

Abstract

Metal phosphides are of great interest in sodium-ion batteries due to their high capacity in theory and suitable redox potential. However, the large bulk expansion and sluggish diffusion kinetics greatly hinder their development. Herein, the electrochemical reaction kinetics of vanadium diphosphide (VP₂) is regulated by the phosphorus–carbon (P–C) covalent bond to boost the sodium storage performance. Simultaneous coupling of phosphorus with conductive carbon-based materials can also enhance the electronic conductivity and alleviate the huge volumetric expansion further improving the stability of the composite electrode. Specifically, the VP₂/phosphorus/carbon (VP₂/3P/C) composites achieve high specific capacity (550 mA h g⁻¹ at 50 mA g⁻¹), and good rate capability (280 mA h g⁻¹ at 2 A g⁻¹) and cycling stability (more than 200 cycles). Even at a high temperature of 60 °C, the VP₂/3P/C composites exhibit high capacities of 630 mA h g⁻¹ at 50 mA g⁻¹ and 375 mA h g⁻¹ at 5 A g⁻¹, which opens up a wide horizon for sodium-ion battery applications.