Vanadium oxides obtained by chimie douce reactions: The influences of transition metal species on crystal structures and electrochemical behaviors in zinc–ion batteries

Rechargeable aqueous zinc-ion batteries (RAZIBs) have received increasing attention due to cost-effectiveness and inherent safety. A wide variety of advanced cathode materials have been revealed with promising performance in RAZIBs. However, these materials usually require sophisticated procedures at high temperatures, which greatly limit further practical application. Herein, a chimie douce approach is adopted to prepare vanadium oxides from V2O5 suspension with the addition of various transition metal cations (Mn2+, Zn2+, Ag+, and Fe3+) by simple liquid-solid mixing under ambient conditions. For the cases of Mn2+ and Zn2+, the dissolution-recrystallization process takes place leading to layered Mn0.31V3O7·1.40H2O (MnVO) and Zn0.32V3O7·1.52H2O (ZnVO). The use of Ag+ forms tunneled Ag0.33V2O5 (AgVO), and the present of Fe3+ stays mainly unreacted V2O5. The underlying reaction chemistries are proposed, for which the pH values of precursor solutions are found to be a key factor. Among the prepared materials, layered vanadium oxides exhibit promising battery performance. Particularly, MnVO delivers 340 and 217 mAh g-1 at 1 and 8 A g-1, respectively. A specific capacity of 164 mAh g-1 can be retained after 500 cycles at 1 A g-1. By contrast, AgVO and FeVO demonstrate inferior performance with retaining only 89 and 20 mAh g-1 after 500 cycles.