Electrical and electrochemical properties of Li 2 M(WO 4 ) 2 (M = Ni, Co and Cu) compounds.

Li 2 M(WO 4 ) 2 (M = Co, Cu or Ni) materials have been synthesized using the solid-state reaction method. X-ray diffraction measurements confirmed the single phase of the synthesized compounds in the triclinic crystal system (space group P 1̄). The SEM analyses revealed nearly spherical morphology with the particle size in the range of 1-10 μm. The IR spectra confirm the presence of all modes of WO 4 2- . The impedance spectroscopy measurements showed the presence of grain boundaries and allow determination of the conductivity of the synthesized materials at room temperature. As positive electrode materials for lithium ion batteries, Li 2 M(WO 4 ) 2 (M = Co, Cu or Ni) cathode materials deliver initial discharge capacities of 31, 33 and 30 mA h g -1 for cobalt, nickel, and copper, respectively.