Electrochemically Induced Phase Transformation in Vanadium Oxide Boosts Zn-Ion Intercalation

Vanadium oxides are excellent cathode materials with large storage capacities for aqueous zinc-ion batteries, but their further development has been hampered by their low electronic conductivity and slow Zn 2+ diffusion. Here, an electrochemically induced phase transformation strategy is proposed to mitigate and overcome these barriers. In situ X-ray diffraction analysis confirms the complete transformation of tunnel-like structural V 6 O 13 into layered V 5 O 12 ·6H 2 O during the initial electrochemical charging process. Theoretical calculations reveal that the phase transformation is crucial to reducing the Zn 2+ migration energy barrier and facilitating fast charge storage kinetics. The calculated band structures indicate that the bandgap of V 5 O 12 ·6H 2 O (0.0006 eV) is lower than that of V 6 O 13 (0.5010 eV), which enhanced the excitation of charge carriers to the conduction band, favoring electron transfer in redox reactions. As a result, the transformed V 5 O 12 ·6H 2 O delivers a high capacity of 609 mA h g –1 at 0.1 A g –1, superior rate performance (300 mA h g –1 at 20 A g –1 ), fast-charging capability (<7 min charging for 465 mA h g –1 ), and excellent cycling stability with a reversible capacity of 346 mA h g –1 at 5 A g –1 after 5000 cycles.