Facile Synthesis of Oxygen-Vacancy-Rich Li-K Coinsertion Vanadate Nanoflakes for High-Performance Zn-Ion Batteries

Aqueous zinc-ion batteries have emerged as viable energy storage solutions owing to their economical pricing, enhanced safety features, environmentally sustainable nature, and remarkable theoretical storage capacity. Metal vanadate has been deeply researched as one of the cathode materials with great promise. However, most of the previous reports of metal vanadates require high energy consumption or a complex synthesis process to ensure high electrochemical performance. Herein, Li-K coinsertion vanadate nanoflake (Li-KVO) was synthesized by a facile method at a low-temperature water bath. When assembled as the cathode, Li-KVO exhibits an excellent Zn2+ storage ability (363 mAh g(-1) at 0.1 A g(-1)), impressive rate performance (212 mAh g(-1) at 5 A g(-1) and 128 mAh g(-1) at 20 A g(-1)), and long cycling stability (81.1% capacity retention under 20 A g(-1) for 10,000 cycles). The in-depth research indicates that the high electrochemical performance originates from the Li+-induced kinetically favorable rich oxygen vacancies and nanoflake structure. Furthermore, ex situ XPS and ex situ XRD prove that the "pillar" effect of Li+ ensures the stability of the V-O layer structure. This strategy broadens the path for the synthesis of layered vanadium oxides and promotes their application as cathode materials for zinc-ion batteries.