L-ascorbic acid coupled graphene double carbon coating enhances the electrochemical properties of Na3V2(PO4)3 cathode materials

Abstract

Sodium vanadium phosphate (NVP) cathode material is highly regarded for its low cost and high current charge-discharge capabilities. However, its poor cycle performance hinders its application. In this paper, the carbon coating NVP is studied with L-Ascorbic acid (KC) as a carbon source, and the double carbon coating design is realized with reduced graphene oxide(rGO) to improve its electrochemical performance. The obtained materials are characterized by XRD, Raman, BET, XPS, SEM, EDS and TEM. The electrochemical performance of the samples is characterized by assembling into batteries. The results show that the amount of ascorbate can greatly affect the electrochemical performance of the electrode material. When n_V:n_C= 1:4.5, the obtained composite NVP@C_KC-4.5 has the best electrochemical performance. The initial specific discharge capacity is up to 109.8 mAh·g⁻¹ at 0.1 C. And its capacity retention rate after 100 cycles at 0.5 C rate is about 94.5 %. On this basis, graphene (in the form of graphene oxide) is introduced. When the amount of graphene oxide is 0.6 % of the total weight, the obtained NVP@C_KC-4.5@rGO-3 composite has the best electrochemical performance. Its half battery charge and discharge rate, its initial discharge capacity increases to 115.4 mAh·g⁻¹ at 0.1 C, and its capacity retention rate is up to 95.2 % at 0.5 C after 100 cycles, showing good electrochemical performance.