Active electrode material

A phosphorus niobium oxide active electrode material has the composition M1aPx-aM2bNb9-bO25-c-dQd, wherein: M1 is selected from Na, K, Mg, Ca, Sr, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, B, Al, Ga, Si, Ge, Sn, Bi, Sb, and mixtures thereof; M2 is selected from Na, K, Mg, Ca, Sr, Y, Ti, Zr, Hf, V, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, B, Al, Ga, Si, Ge, Sn, Bi, P, Sb, and mixtures thereof; Q is selected from F, Cl, Br, I, N, S, Se, and mixtures thereof; 0 ≤ a ≤ 0.5; 0 ≤ b ≤ 2; -0.5 ≤ c ≤ 1.25; 0 ≤ d ≤ 5; 1 ≤ x ≤ 2; and one or more of a, b, c, and d does not equal 0; with the proviso that if M1 consists of Nb and if M2 consists of P then c is > 0. The electrochemical properties of a PNb9O25-based material are improved by cationic substitution for P and/or Nb, anionic substitution for O, and/or by providing an oxygen deficiency or excess. Such materials are of interest as active electrode materials, especially anode materials, in lithium-ion or sodium-ion batteries, since they have significantly improved capacity retention at high C-rates compared to PNb9O25.