Textured Na2V6O16·3H2O Cathode Tuned via Crystal Engineering Endows Aqueous Zn-Ion Batteries with High Rate Capability and Adequate Lifespan

Abstract

Aqueous zinc-ion batteries (ZIBs) play a vital role in large-scale energy storage for smart grids due to their environmental friendliness, safety, and low cost. Unfortunately, the application of ZIBs has been challenged by the relatively low capacity of cathode materials, especially at higher rates, which originates from the sluggish diffusion of Zn ions. Herein, a crystal engineering strategy is explored for using bernesite, Na2V6O16·3H2O (NVO), for regulating the diffusion-preferable texture, which was beneficial for fostering Zn ions’ diffusion and thus guaranteeing a uniform concentration inside the cathode. An enlarged capacity at a higher rate was obtained, delivering a capacity of 156.9 mAh g–1 at the ultra-high current density of 20 A g–1, of which 140.6 mAh g–1 remained after 5000 cycles. The use of crystal engineering to regulate the texture of cathode materials paves the way to boost the application of NVO in aqueous ZIBs, which could be translated to design state-of-the-art cathodes for other battery systems.