Hi Gh-Performance Li/Na Hybrid-Ion Batteries with Nonstoichiometric Li2.7v2.1(Po4)3/C As Cathode Material

A novel structure for Li/Na hybrid-ion batteries with unique two-stage electrochemical reactions is proposed, using nonstoichiometric Li2.7V2.1(PO4)3/C materials as the cathode and Na foil as the anode with a Li-ion electrolyte. A discharge specific capacity of 132.99 mAh·g−1 is delivered at a current density of 100 mA·g−1 in the range of 2.5–4.2 V. Besides, when the current density increases to 1000 mA·g−1, the specific density can reach a value of 108.50 mAh·g−1, which indicates superior rate performance. After 800 cycles, a discharge capacity of 87.11 mAh·g−1 is still observed at 1000 mA·g−1 in a voltage range of 3.0–4.3 V, maintaining a retention rate of 80.42%. This simple design strategy for Li/Na hybrid-ion batteries harvests the synergetic contribution of Li+ and Na+ ions and provides an efficient solution to further improve hybrid-ion battery performance.