Stability and Kinetics Enhancement of Hydrated Vanadium Oxides via Chemical Pre-intercalation for Aqueous Zinc-Ion Batteries

Abstract

Aqueous zinc ion batteries (ZIBs) are promising candidates for large‐scale energy storage due to their cost‐effectiveness, environmental friendliness, intrinsic safety, and competitive energy density. However, strong electrostatic interactions between divalent zinc ions and host materials pose challenges for transport kinetics and structural stability during cycling. This dissertation investigates the enhancement of hydrated vanadium oxides (V2O5·nH2O, VOH) as cathode materials for ZIBs through chemical pre-intercalation strategies. The focus is on understanding the mechanisms and benefits of chemical pre-intercalation, as well as identifying key factors determining pre-intercalation effects and influencing overall electrochemical performance for both metal and organic cation pre-intercalated vanadium oxides. The modified VOH usually shows increased capacity, reduced voltage polarization, improved rate capability, and enhanced electrochemical reversibility and stability. Key findings include: (1) metal cations can be favorably intercalated into the VOH structure, replacing hydrogen bonded water (H3O+) between bilayers, resulting in changes in interlayer distance, structure water amount, and V4+ content. (2) The formation of additional chemical bonds between pre-intercalated metal cations and the V–O lattice contributes to the improved structural and electrochemical stability. (3) Pre-inserting organic cations (trimethylphenylammonium, TMPA+) benefits the effects of both ionic and molecular pre-intercalation, reducing electrostatic interactions between Zn2+ and the V–O lattice, improving structural stability and reaction kinetics during cycling. (4) Interlayer spacing of metal cation pre-intercalated MxV2O5·nH2O materials is influenced by interlayer water content/hydration number, while interlayer spacing of organic cation pre-intercalated (Org)xV8O20·nH2O materials is determined by the ionic radius of organic cations. (5) No direct correlations exist between interlayer spacing and cycling stability or rate performance for both MxV2O5·nH2O and (Org)xV8O20·nH2O materials. (6) The electrochemical stability and kinetics of (Org)xV8O20·nH2O are primarily influenced by the polarity of organic cations. Weaker-polarized methylammonium (MA+) ions facilitate easier Zn2+ ion transport, similar to singly charged ion-stabilized VOH; while the effects of stronger-polarized tetramethylammonium (TMA+) ions align more closely with Mg2+ and Al3+ ions, which exert stronger electrostatic interactions with Zn2+ ions.