Interlayer Doping in Layered Vanadium Oxides for Low-cost Energy Storage: Sodium-ion Batteries and Aqueous Zinc-ion Batteries

Advantages concerns about abundant resources, low cost and high safety have promoted sodium-ion batteries (SIBs) and aqueous zinc-ion batteries (AZIBs) as the most promising candidates for next generation of low-cost large-scale energy storage. However, the state-of-the-art cathode materials are far from meeting the commercial requirements. Considering the unique open framework, layered vanadium oxides have attracted wide attention due to the high energy density and power density, while they also face critical issues such as low stability and sluggish diffusion kinetics. The interlayer doping defects, as the most common method modulating layered materials, are believed to solve these problems which will be highlighted in this review. Firstly, the characteristics and current states of various vanadium oxides in SIBs and AZIBs are summarized. Then, the research efforts related to different types of interlayer doping defects, including ionic, molecular doping, etc., are discussed. Finally, it is pointed out that it is not enough to merely achieve satisfactory performances. Hence, some perspectives about the deep understanding and interrelationship are provided for the subsequent rational design of defective layered vanadium oxides for low-cost energy storage systems.