Electrochemical Performance of B-Type Vanadium Dioxide as a Sodium-Ion Battery Cathode: A Combined Experimental and Theoretical Study

B-type vanadium dioxide is a frequently investigated lithium-ion battery material because of its appreciable gravimetric capacity, energy density, rate capability and cycling stability, but investigations of its performance with sodium working metal are scarce. We present a combined experimental-theoretical study exploring the underlying mechanism of the electrochemical sodiation of B-type vanadium dioxide. We find agreement between theoretical and experimental results, which complement each other and map out a detailed mechanistic picture. We are able to identify the sluggish diffusion of sodium ions in the vanadium dioxide host material, especially at low concentrations, as a key obstacle to the utilization of the pristine material as a high-performance cathode for sodium-ion batteries. Our findings provide context for previously reported results and can be used for a more targeted vanadium dioxide electrode design in the future.