K0.5V2O5: A novel Li intercalation compound as positive electrode material for rechargeable lithium batteries

We report here for the first time the reversible electrochemical lithium insertion in the potassium vanadium bronze K0.5V2O5 leading to LixK0.5V2O5 with 0 < x ≤ 1.5. Long and thin platelets of K0.5V2O5 are prepared by a fast and facile synthesis route. A specific capacity of 210 mAh g−1 is available at an average voltage of 2.6 V without any significant structural changes even after extended cycling experiments. This vanadium bronze exhibits an excellent capacity retention with still 200 mAh g−1 at C/10 after 70 cycles and a good rate capability with 140 and 120 mAh g−1 at 1 C and 1.4 C respectively. The electrochemical performance of this cathode material is one of the best among vanadium bronzes.