Unraveling the Complex Delithiation and Lithiation Mechanisms of the High Capacity Cathode Material V6O13

V6O13 is a promising Li-ion battery cathode material for use in the high temperature oil field environment. The material exhibits a high capacity, and the voltage profile contains several plateaus associated with a series of complex structural transformations, which are not fully understood. The underlying mechanisms are central to understanding and improving the performance of V6O13-based rechargeable batteries. In this study, we present in situ X-ray diffraction data that highlight an asymmetric six-step discharge and five-step charge process, due to a phase that is only formed on discharge. The LixV6O13 unit cell expands sequentially in c, b, and a directions during discharge and reversibly contracts back during charge. The process is associated with change of Li ion positions as well as charge ordering in LixV6O13. Density functional theory calculations give further insight into the electronic structures and preferred Li positions in the different structures formed upon cycling, particularly at high lithium contents, where no prior structural data are available. The results shed light into the high specific capacity of V6O13 and are likely to aid in the development of this material for use as a cathode for secondary lithium batteries.