Fe-57 Mossbauer study of the electrochemical reaction of lithium with triclinic iron vanadate

The electrochemical reaction of lithium with triclinic FeVO4 (a = 6.714(1) Angstrom, b = 8.060(2) Angstrom, c = 9.352(2) Angstrom, alpha = 96.678(1)de grees, beta = 106.641(1)degrees, and gamma = 101.523(1)degrees, P-1) has be en investigated by means of Fe-57 Mossbauer spectroscopy in order to comple ment the previous X-ray diffraction and X-ray absorption near edge structur e studies on the same system. A complex Fe-III --> Fe-II --> Fe-0 or Fe-III --> Fe-II, Fe-0 reduction process has been detected upon the first dischar ge of the battery down to 0.02 V, with in addition the iron reoxidation dur ing the next charge step. A mechanism based on "lithium adsorption" is prop osed in order to explain this unexpected behavior.