Low-temperature synthesis in the dittmarite–sodium acetate trihydrate system: electrochemical activity of M3+/M2+ redox couples in AMPO4 (A = Na, Li; M = Mn, Mn/Fe)

Phase-pure NaMPO₄ (M = Mn, Mn/Fe; isotypic to triphylite) and Li(Mn/Fe)PO₄ were isolated as a result of the low- temperature reaction between NH₄MPO₄·H₂O (M = Mn, Mn/Fe) and AcONa·3H₂O or AcOLi, respectively. Electrochemical tests in half-cells revealed that Na-based compounds exhibit poor electrochemical activity vs. metallic Na, while the similarly synthesized Li counterpart demonstrates decent cycling in Na cells. The synthetic features, crystal structures and properties of related members of the olivine family are discussed.