3. Synthesis and Electrochemical Studies of a Novel MOPOF Cathode Material, [Li₂(VO)₂(C₂O₄)(HPO₄)₂]

This chapter deals with the synthesis and ab initio structure determination of a novel lithium containing Metal Organophosphate Open Framework (MOPOF) material, [Li₂(VO)₂(HPO₄)₂(C₂O₄)]·6H₂O. It was synthesized by hydrothermal method at 120 °C and the crystal structure was solved and refined from its powder X-ray diffraction data. The anhydrous phase, [Li₂(VO)₂(HPO₄)₂(C₂O₄)] obtained by dehydration of the hydrated phase at 200 °C was studied as a novel cathode material for Lithium ion batteries. The presence of extractable Li⁺ ions in the inter-layer space together with the feasibility of V⁴⁺/V⁵⁺ redox couple and a good theoretical capacity of 125 mAh g⁻¹ make this compound suitable as a cathode material. Electrochemical properties of the material was investigated using cyclic voltammetry, galvanostatic charge-discharge cycling, electrochemical impedance spectroscopy (EIS) and ex situ XRD studies. The material exhibits reversible lithium insertion at ~4 V with a reversible capacity of 80 mAh g⁻¹ at 0.1 C current rate.