Impacts of distorted local chemical coordination on electrochemical performance in hydrated vanadium pentoxide.

Modulating and elevating the operating voltage of a given cathode is a significant challenge to enhance the energy density of secondary batteries without sacrificing power output. The chemical coordination strongly influences the energy levels of d-orbitals of redox cations in cathode materials, which tie to their operating voltage. In contrast to concentrated studies on enhancing the specific capacity, in this study, we choose bi-layered hydrated vanadium pentoxide as the model to modulate the d-orbital energy levels through local chemical coordination manipulation, achieving a higher operating voltage in rechargeable aqueous zinc ion batteries. Here we show that, by employing X-ray absorption spectroscopy (XAS) and pair distribution function (PDF) techniques, we can analyze the distortion of [VO] octahedra and extract chemical bond information, deciphering the correlation between the chemical coordination and operating voltage in cathode materials. The fundamentals could guide the designing and developing RAZIBs with higher energy and power density.