Alkali Transition Metal Phosphites as Potential Cathode Materials Grown from Molten Boric Acid

This is the first study on developing six alkali transition metal phosphites as potential candidates of cathode materials grown from molten boric acid, a simple, low energy costing method compared with conventional solid‐state reactions. Li2[Mn(HPO3)2] (1) and Li[V(HPO3)2] (2) are featured with high theoretical capacitance values up to 117 and 123 mAh/g, respectively. With the replacement of Li+ by Na+ or K+, four new compounds with strongly related layer topology Na2[Co4(HPO3)5] (3), K2[Co3(HPO3)4] (4), K2[Mn2(HPO3)3] (5), and K[V(HPO3)2] (6) were prepared. The synthesis mediated by molten boric acid automatically provides reductive atmosphere and helps maintain low valence in metal centers. This is the first study on developing six alkali transition metal phosphites as potential candidates of cathode materials grown from molten boric acid. Compounds 1 and 2 are featured with high theoretical capacitance values up to 117 and 123 mAh/g, respectively. Compounds 3 to 6 are layered and strongly related in topology.