Kinetics and Structural Investigation of Layered Li9V3(P2O7)3(PO4)2 as a Cathode Material for Li-Ion Batteries

Cathode materials with improved safety and energy densities are required for developing next-generation Li-ion battery technology. Among different phosphate-based materials, layered Li9V3(P2O7)3(PO4)2 (LVPP) has recently been explored as a high-voltage cathode. We report the feasibility of multi-electron reactions and the influence of crystallite size on the electrode kinetics. The mechanism of Li extraction/insertion during charge and discharge is investigated and the structural transformations at high voltages are studied by means of in situ and ex situ analysis. The changes induced by electrochemical Li extraction are found to be reversible during cycling in the potential window of 2–4.6 V, whilst voltage profile changes and capacity fading is observed by charging up to 4.8 V, owing to irreversible phase transition and reduction of the interlayer distance. The findings can be applied for optimizing material synthesis as well as the working conditions in Li-ion battery applications.