Structural perspective on revealing energy storage behaviors of silver vanadate cathodes in aqueous zinc-ion batteries

Exploitation and improvement of electrode materials mainly rely on the understanding of electrochemical reaction mechanisms. Here we provide a comprehensive perspective of Zn2+ storage behaviors in silver vanadates (e.g. Ag0.33V2O5, Ag1.2V3O8, Ag2V4O11, β-AgVO3, Ag4V2O7), which exhibit electrochemical redox multi-mechanisms. Ag0.33V2O5 with stable tunnel structure and low mole ratio of Ag/V demonstrates a combination of reversible displacement/intercalation reaction with good cyclic stability. Ag1.2V3O8 and Ag2V4O11 with layer structure and higher mole ratio of Ag/V show a reversible intercalation/de-intercalation reaction accomplished by an irreversible displacement reaction to form a highly conductive Ag0 matrix, leading to the high rate performance. The chain-like β-AgVO3 and isolated island-like Ag4V2O7 with unstable structure and the highest mole ratio of Ag/V reveal irreversible phase transition mechanism to form the amorphous matrix. The crystal structure is the decisive factor in the basic electrochemical properties, providing a new insight into battery energy storage mechanism.