Lithium vanadyl phosphate (LiVOPO₄) is an attractive cathode for lithium ion batteries with a high operating voltage 4.0V in phosphate poly-anion cathode materials and good theoretical capacity of 166mAh/g. LiVOPO₄ exist mainly in two different crystallographic phases, one is orthorhombic β-LiVOPO₄ another is triclinic α-LiVOPO₄. Among these phases, β-LiVOPO₄ is widely studied in view of lithium ion intercalation, and it shows better electrochemical performance than α-LiVOPO₄. K. Nagamine et al. presented that the orthorhombic crystals have a three-dimensional Li ion pathway consisting of interconnected VO₆ octahedral and PO₄ tetrahedral units that consequently create channels for Li⁺ion movement. However, the main defects such as poor electrical conductivity and low lithium ionic conductivity are drawback for its application in lithium ion batteries. To improve the poor electrical conductivity, many researches have been studied by carbon coating and composite method.

While, the studies are extremely rate to enhance lithium ion conductivity and lithium ion diffusion coefficient technique. In this study, we have investigated that the diffusion coefficient of lithium ion in β-LiVOPO₄ by SSCV (slow scan cyclic voltammetry), EIS (Electrochemical impedance spectroscopy), GITT (Galvanostatic intermittent titration technique) and PITT (Potentiostatic intermittent titration technique) to compare lithium diffusion value according to four techniques. And we have optimized diffusion technique in β-LiVOPO₄. The synthesis of β-LiVOPO₄ was carried out by sol-gel method. Firstly, oxalic acid and V₂O₅ in stoichiometric ratio were dissolved in deionized water with magnetic stirring at 70°C. After a clear blue solution formed, a mixture of stoichiometric NH₄H₂PO₄ and LiNO₃ was added to the solution while stirring for 4h and the green gel formed. Finally, the dried gel was decomposed at 300°C for 4h and the obtained product was sintered at 500 °C for 4h in air. As a result, SSCV, GITT, PITT techniques relatively indicated similar lithium ion diffusion coefficient value. But, low lithium ion diffusion coefficient value was obtained by EIS technique. Due to the accuracy for calculating needed. The chemical diffusion coefficient of EIS depends on the fitting of experimental impedance with an equivalent circuit model. While, the GITT and PITT techniques were obtained under deviation from equilibrium conditions. Because the between current and voltage and time more exactly reflected the diffusion property. So, among the four techniques, GITT and PITT were more reliable in β-LiVOPO₄ cathode material.