A compound comprising a composition Ax(M′1-aM″a)y(XD4)z, Ax(M′1-aM″a)y(DXD4)z, or Ax(M′1-aM″a)y(X2D7)z, and have values such that x, plus y(1-a) times a formal valence or valences of M′, plus ya times a formal valence or valence of M″, is equal to z times a formal valence of the XD4, X2D7, or DXD4 group; or a compound comprising a composition (A1-aM″a)xM′y(XD4)z, (A1-aM″a)xM′y(DXD4)z(A1-aM″a)xM′y(X2D7)z and have values such that (1-a)x plus the quantity ax times the formal valence or valences of M″ plus y times the formal valence or valences of M′ is equal to z times the formal valence of the XD4, X2D7 or DXD4 group. In the compound, A is at least one of an
alkali metal and
hydrogen, M′ is a first-row
transition metal, X is at least one of
phosphorus,
sulfur,
arsenic,
molybdenum, and
tungsten, M″ any of a Group IIA, IIIA, IVA, VA, VIA, VIIA, VIIIA, IB, IIB, IIIB, IVB, VB, and VIB
metal, D is at least one of
oxygen,
nitrogen, carbon, or a
halogen, 0.0001<a≦0.1, and x, y, and z are greater than zero. The compound can have a
conductivity at 27° C. of at least about 10−8 S / cm. The compound can be a doped
lithium phosphate that can intercalate
lithium or
hydrogen. The compound can be used in an electrochemical device including electrodes and storage batteries and can have a gravimetric capacity of at least about 80 mAh / g while being charged / discharged at greater than about C rate of the compound.