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

The effect of low‐level chromium substitution in Na 3 V 2‐ x Cr x (PO 4 ) 3 (0≤ x ≤0.4), 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 V 5+ /V 4+ redox couple at approximately 4 V is remarkable for the samples containing chromium. A reversible capacity of 107 mAh g −1 with a coulombic efficiency of 99 % was determined for Na 3 V 1.9 Cr 0.1 (PO 4 ) 3 after 40 cycles. The observed performance correlates with a good kinetic response, resulting from low charge‐transfer resistance and high diffusion coefficient.