A layered oxalatophosphate framework as a cathode material for Li-ion batteries

A new lithium containing hybrid inorganic–organic open framework material, Li2(VO)2(HPO4)2(C2O4), has been synthesized and its reversible lithium storage has been investigated. Firstly, the hydrated phase Li2(VO)2(HPO4)2(C2O4)·6H2O (1) was obtained via a hydrothermal route at 120 °C which on dehydration yielded the anhydrous phase. The crystal structure of 1 was solved and refined from its powder X-ray diffraction data and optimized by DFT calculations. The presence of extractable lithium ions in the inter-layer space together with the feasibility of the V4+/5+ redox couple make this compound suitable for cathode applications in Li-ion batteries. Electrochemical properties of this material were studied using galvanostatic charge–discharge cycling, cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and ex situ XRD studies. The material exhibits reversible lithium insertion/extraction during cycling.