Insight Into Pre-Intercalation of Layered Vanadium Oxide Cathodes: From Precise Control of the Interspace to Related Electrochemical Performance and Beyond

Abstract

Pre-intercalation is the mainstream approach to inhibit the unpredicted structural degradation and the sluggish kinetics of Zn-ions migrating in vanadium oxide cathode of aqueous zinc-ion batteries (AZIBs), which has been extensively explored over the past 5 years. The functional principles behind the improvement are widely discussed but have been limited to the enlargement of interspace between VO layers. As the different types of ions could change the properties of vanadium oxides in various ways, the review starts with a comprehensive overview of pre-intercalated vanadium oxide cathode with different types of molecules and ions, such as metal ions, water molecules, and non-metallic cations, along with their functional principles and resulting performance. Furthermore, the pre-intercalated vanadium cathodes reported so far are summarized, comparing their interlayer space, capacity, cycling rate, and capacity retention after long cycling. A discussion of the relationship between the interspace and the performance is provided. The widest interspaces could result in the decay of the cycling stability. Based on the data, the optimal interspace is likely to be around 12 Å, indicating that precise control of the interspace is a useful method. However, more consideration is required regarding the other impacts of pre-intercalated ions on vanadium oxide. It is hoped that this review can inspire further understanding of pre-intercalated vanadium oxide cathodes, paving a new pathway to the development of advanced vanadium oxide cathodes with better cycling stability and larger energy density.