Alumina modified sodium vanadate cathode for aqueous zinc-ion batteries

Aqueous zinc-ion batteries (ZIBs) have great prospects for widespread application in massive scale energy storage. By virtue of the multivalent state, open frame structure and high theoretical specific capacity, vanadium (V)-based compounds are a kind of the most developmental potential cathode materials for ZIBs. However, the slow kinetics caused by low conductivity and the capacity degradation caused by material dissolution still need to be addressed for large-scale applications. Therefore, sodium vanadate Na₂V₆O₁₆·3H₂O (NVO) was chosen as a model material, and was modified with alumina coating through simple mixing and stirring methods. After Al₂O₃ coating modification, the rate capability and long-cycle stability of Zn//NVO@Al₂O₃ battery have been significantly improved. The discharge specific capacity of NVO@Al₂O₃ reach up to 228 mAh/g (at 4 A/g), with a capacity reservation rate of approximately 68% after 1000 cycles, and the Coulombic efficiency (CE) is close to 100%. As a comparison, the capacity reservation rate of Zn//NVO battery is only 27.7%. Its superior electrochemical performance is mainly attributed to the Al₂O₃ coating layer, which can increase zinc-ion conductivity of the material surface, and to some extent inhibit the dissolution of NVO, making the structure stable and improving the cyclic stability of the material. This paper offers new prospects for the development of cathode coating materials for ZIBs.