Benefits of Chromium Substitution in Na3V2(PO4)3 as a Potential Candidate for Sodium-Ion Batteries

The effect of low-level chromium substitution in Na3V2-xCrx(PO4)(3) (0x0.4), a potential cathode material in Na-ion cells, has been examined. A suitable synthesis procedure is developed to obtain composites of crystalline NASICON phosphate and an amorphous carbon phase to enhance the electrical conductivity of the electrode. The optimized cathode materials were characterized by using X-ray diffraction and spectroscopic techniques. The electrochemical evaluation was carried out by using galvanostatic and potentiostatic methods. The activity of the V5+/V4+ redox couple at approximately 4V is remarkable for the samples containing chromium. A reversible capacity of 107mAhg(-1) with a coulombic efficiency of 99% was determined for Na3V1.9Cr0.1(PO4)(3) after 40cycles. The observed performance correlates with a good kinetic response, resulting from low charge-transfer resistance and high diffusion coefficient.