AgNa(VO2F2)2: a trioxovanadium fluoride with unconventional electrochemical properties

J Am Chem Soc. 2013 Jul 3;135(26):9898-906. doi: 10.1021/ja404189t. Epub 2013 Jun 24.

Abstract

We present structural and electrochemical analyses of a new double-wolframite compound: AgNa(VO2F2)2 or SSVOF. SSVOF is fully ordered and displays electrochemical characteristics that give insight into electrode design for energy storage beyond lithium-ion chemistries. The compound contains trioxovanadium fluoride octahedra that combine to form one-dimensional chain-like basic building units, characteristic of wolframite (NaWO4). The 1D chains are stacked to create 2D layers; the cations Ag(+) and Na(+) lie between these layers. The vanadium oxide-fluoride octahedra are ordered by the use of cations (Ag(+), Na(+)) that differ in polarizability. In the case of sodium-ion batteries, thermodynamically, the use of a sodium anode introduces a 300 mV loss in overall cell voltage as compared to a lithium anode; however, this can be counter-balanced by introduction of fluoride into the framework to raise the reduction potentials via an inductive effect. This allows sodium-ion batteries to have comparable voltages to lithium systems. With SSVOF as a baseline compound, we have identified new materials design rules for emerging sodium-ion systems that do not apply to lithium-ion systems. These strategies can be applied broadly to provide materials of interest for fundamental structural chemistry and appreciable voltages for sodium-ion electrochemistry.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Coordination Complexes / chemistry*
  • Electrochemical Techniques*
  • Models, Molecular
  • Vanadium / chemistry*

Substances

  • Coordination Complexes
  • Vanadium