Revealing excess Al3+ preinsertion on altering diffusion paths of aluminum vanadate for zinc-ion batteries

Layered metal vanadates have been extensively investigated for aqueous zinc-ion batteries (AZIBs) due to their low cost, crystal structure, and a wide diversity of vanadium valence states. However, research on the number of cationic pre-intercalation layers is almost empty and the effect of Al atomic numbers in H11Al2V6O23.2 (HAVO) on the diffusion path has not been studied even more. The systematic investigation into pre-intercalated ions in electrode materials is fundamental but vital for the further development of high-performance batteries of both the point of academic and industry. In this contribution, we designed and synthesized HAVO with four different layer spacings by simply modulating aluminum content for the first time and combined a range of ex-situ and in-situ complementary techniques to reveal the reaction mechanism of zinc ion storage and its intrinsic relationship with electrochemical performance. The “pillar” effects of stable Al3+ between the interlayers protects the laminate structures from collapse during electrochemical process and effectively widens the layer spacing at the same time. However, based on experiments and calculations we have demonstrated that the appropriate aluminum content can significantly improve the electrochemical properties of the material, while excessive ion intercalation can block the zinc ions diffusion channels. As a result, HAVO with a suitable Al atomic number displays extraordinary electrochemical performance. This work provides further insights into the design and construction of cathodes for pre-inserted ion batteries, and facilitates the exploitation of low-cost and high-safety cathodes.