Ag₄V₂O₆F₂:  An Electrochemically Active and High Silver Density Phase

Low-temperature hydrothermal techniques were used to synthesize single crystals of Ag₄V₂O₆F₂. This previously unreported oxide fluoride phase was characterized by single-crystal X-ray diffraction and IR spectroscopy and was also evaluated as a primary lithium battery cathode. Crystal data:  monoclinic, space group P2₁/n (No. 14), with a = 8.4034(4) Å, b = 10.548(1) Å, c = 12.459(1) Å, β = 90.314(2)°, and Z = 4. Ag₄V₂O₆F₂ (SVOF) exhibits two characteristic regions within the discharge curve, an upper plateau at 3.5 V, and a lower sloped region around 2.3 V from reduction of the vanadium oxide fluoride framework. The material has a nominal capacity of 251 mAh/g, with 148 mAh/g above 3 V. The upper discharge plateau at 3.5 V is nearly 300 mV over the silver reduction potential of the commercial primary battery material, Ag₂V₄O₁₁ (SVO).