New anatase phase VTi2.6O7.2 ultrafine nanocrystals for high-performance rechargeable magnesium-based batteries

Abstract

Magnesium-based batteries are regarded as a potential candidate for next-generation energy storage devices due to their safety and low cost. However, existing cathode materials still suffer from slow ion diffusion kinetics and relatively inferior electrochemical performance. In this work, we design and synthesize a kind of new anatase phase VTi_2.6O_7.2 ultrafine nanocrystal (VTO) with fast intercalation kinetics. As a cathode material for magnesium batteries (MBs), VTO exhibits a capacity of 121.9 mA h g⁻¹ at 20 mA g⁻¹. When applied to magnesium–lithium hybrid batteries (MLHBs), VTO exhibits a high specific capacity (265.2 mA h g⁻¹ at 50 mA g⁻¹), good cycling stability (84.2% capacity retention after 1200 cycles) and high rate capability (64.9 mA h g⁻¹ at 2 A g⁻¹). These good performances are attributed to the enhanced diffusion kinetics, increased cation storage active sites and shortened ion diffusion path. Furthermore, the lithium storage mechanism in VTO was studied via the in situ XRD measurements. These results show that VTO is a promising electrode material for magnesium-based batteries, and constructing a substitutional solid solution is an effective way to exploit and optimize new types of electrode materials with enhanced performances.