Engineering

Metallurgy

Materials science

Cathode

Vanadate

Power (physics)

Inorganic chemistry

Chemical engineering

Vanadium

Physical chemistry

Thermodynamics

Physics

Organic chemistry

Energy storage

Aqueous solution

Chemistry

Pentoxide

Vanadium oxide

Energy storage materials

Vanadium oxides are promising candidates for cathode materials in aqueous zinc-ion batteries (ZIBs) with low cost and high capacity yet requirements for long cycling necessitate the development of increasingly stable structure. This study reports a structural engineering method by incorporating K+ into hydrated vanadium pentoxide (V2O5·nH2O, VOH) to achieve unique hydrated vanadate (KV12O30-y·nH2O, KVOH). In contrast to previously reported works, K+ introduction leads to a new phase of KVOH with faster ion diffusion kinetics and better long-term cycling stability. This work establishes an understanding of the role of K+ incorporation in KVOH which goes beyond its conventional categorization as an agent for interlayer spacing adjustment, reflecting in maintaining structure flexibility for effective Zn2+ insertion/extraction even at high rates, improving materials conductivity by the electron hoping of V4+/V5+ and acting as a stabilizer to accommodate structural contraction/expansion with smaller voltage hysteresis and higher reversibility. KVOH displays a remarkable capacity of 436 mAh g−1 at 0.05 ​A ​g−1, maintains 227 mAh g−1 at 10 ​A ​g−1, which is better than VOH and the majority of reported monovalent and multivalent metal ions introduced in vanadates. KVOH exhibits excellent cycling stability with 92% capacity retention over 3000 cycles at 5 ​A ​g−1, high energy density (308 ​Wh kg−1) and power density (7502 ​W ​kg−1), as well as improved energy efficiency. These characteristics recommend KVOH cathodes for use in high-performance aqueous ZIBs.

Structural engineering of hydrated vanadium oxide cathode by K+ incorporation for high-capacity and long-cycling aqueous zinc ion batteries