Ag<sub>4</sub>V<sub>2</sub>O<sub>6</sub>F<sub>2</sub>:  An Electrochemically Active and High Silver Density Phase

Low-temperature hydrothermal techniques were used to synthesize single crystals of Ag<sub>4</sub>V<sub>2</sub>O<sub>6</sub>F<sub>2</sub>. 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 <i>P</i>2<sub>1</sub>/<i>n</i> (No. 14), with <i>a </i>= 8.4034(4) Å, <i>b </i>= 10.548(1) Å, <i>c </i>= 12.459(1) Å, β = 90.314(2)°, and <i>Z</i> = 4. Ag<sub>4</sub>V<sub>2</sub>O<sub>6</sub>F<sub>2</sub> (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, Ag<sub>2</sub>V<sub>4</sub>O<sub>11</sub> (SVO).