A new sodium insertion compound, γ'-V₂O₅, was prepared by the chemical oxidation of γ-LiV₂O₅ phase using NO₂BF₄ as oxidizing agent. One sodium ion per mole of γ'-V₂O₅ can be inserted in γ'-V₂O₅ involving a high V^5 +/V^4 + redox potential of 3.5 V vs. Na⁺/Na. A fully reversible capacity of 145 mAh g^− 1 was obtained at C/60, at 50°C (figure 1). The γ'-V₂O₅ electrode can deliver a high discharge capacity of 125 mAh g^{− 1} at C/20 rate at 50°C, stable over 50 cycles. An excellent retention capacity is also demonstrated over 90 cycles at RT: capacities in the range 60-80 mAh. g^-1 in the C/5-C/20 range against 100-125 mAh g^-1 at 50°C were recovered. A discharge capacity of 80 mAh g^{− 1} was still available after 90 cycles at C/20 rate. A two phases mechanism involving the γ'-V₂O₅ / γ-NaV₂O₅ system was evidenced from X-ray diffraction and Raman spectroscopy measurements. The structural features of the fully sodiated γ-NaV₂O₅ phase, with an unusual expansion along the c axis (+2 Å/ γ'-V₂O₅) were solved (inset in figure 1). These results revealed that the γ'-V₂O₅ forms a new competitive cathode for the reversible intercalation of sodium ions.