ε-VOPO4 polyanionic cathode materials for high energy density Li-ion batteries.
As one of the most interesting polyanionic cathode materials, ε-VOPO4 offers a great attractiveness. This material adopts a stable 3D tunnel structure with a theoretical specific capacity of ~2 *158mAh/g (almost double that of LiFePO4). Compared with LiFePO4, ε-VOPO4 has a much higher conductivity and one higher charge/discharge plateau (around 4.0 V), and one lower (around 2.5 V). As ε-VOPO4 has the capability of reversibly intercalating more than one lithium ion into the structure, it would store and deliver more energy than the current batteries in the market. Overall, all these advantages make ε-VOPO4 a great candidate for next generation of high energy density Li-ion batteries.
The precursors can be readily and controllably synthesized with a well-defined stoichiometry, no undesired contaminations being incorporated into the final products. The ε-VOPO4 pure phase can be formed through a short single-step heat treatment under moderate temperature without involving complicated and costly high-temperature vacuum environment. Earth-abundant starting materials, simple processing procedures and cheap equipment would further lower the fabrication cost of ε-VOPO4 based batteries.