The impact of local bond stiffness and disorder on the functional properties of electrodes

Synchrotron x-ray absorption spectroscopy (XAS) has played a key role in driving advances and breakthroughs in battery science, owing to its ability to provide information on the electronic structure of the redox-active elements and their local atomic environments. Conventional XAS studies on Li or Na-ion battery electrodes are typically carried out at a single temperature as a function of state-of-charge, to access information on electrochemical behavior and charge-transfer mechanisms during the ions deintercalation and intercalation. However, because the charge-discharge process directly affects the bond length, strength, and disorder, the approach based on temperature dependent extended x-ray absorption fine structure can provide essential information on the realistic correlation between local structure and the battery performance. Indeed, this approach can help in making a clear distinction between static and dynamic disorder apart from providing direct measurement of the local force constants of near-neighbors atoms.Here, we have reviewed the studies based on the above approach and highlighted the critical role of local atomic correlations and disorder that can have in limiting factors for ion diffusion and achievable capacity. Furthermore, we examined how local bond rigidity affects the charge-compensation mechanism and, in turn, the reversibility of anion redox processes in transition-metal oxide cathodes.