Enhanced Working Voltage in Hydrated Vanadate Cathodes: Insights into [VO₆] Octahedral Distortion and V 3 <i>d</i> Orbital Splitting
Huanhuan Niu, Heng Liu, Wei‐Hsiang Huang, Ting Shen, Menghao Yang, Min‐Hsin Yeh, Long Yang, Chaofeng Liu
Abstract
Abstract The bi‐layered hydrated vanadate is anticipated as a promising next‐generation cathode material for high‐energy zinc‐ion batteries. However, the practical application has been impeded by undesirable voltage fade, which originates from local structure distortion induced by zinc ion (de)intercalation. Herein, V 2 O 5 · n H 2 O pre‐intercalated with various organic cations is investigated to elucidate the relationship between electronic structure modulation and voltage variations during local structure evolution. Microscopic scale observations—using ex situ X‐ray diffraction, synchrotron X‐ray pair distribution function along with X‐ray absorption fine structure spectroscopy—reveal that the electronic structure perturbation is governed by the distortion of [VO 6 ] octahedra, which leads to V 3 d orbitals splitting. Specifically, the structural distortion induces variations in vanadium‐oxygen bond lengths and alters the ligand‐field electronic structure, boosting the operating voltage (44 mV higher midpoint voltage) and cycling stability (91.3% retention after 3000 cycles). These findings reveal a fundamental correlation for the development of high‐energy‐density batteries with superior stability through local structural design.