LI DEINTERCALATION AND STRUCTURAL-CHANGE IN THE LITHIUM TRANSITION-METAL NITRIDE LI3FEN2

Li3FeN2 with a non-dimensional structure was prepared by heating a mix ture of Li3N and Fe4N in a 1% H2-99% N2 gas stream. Li ion was easily deintercalated, forming Li3-xFeN2 in a range of 0 less-than-or-equal-t o x less-than-or-equal-to 1.0 in a Li/Li3FeN2 cell. With increasing x, four kinds of phases having orthorhomic symmetry appeared sequentiall y. Electrical resistivity decreased with increasing x. Mossbauer spect ra suggested that Li deintercalation oxidizes Fe(III) to Fe(IV). The L i/Li3FeN2 cell showed a good reversibility, with a high current densit y (500 muA cm-2). Li3FeN2 is thus believed to be a good candidate for an electrode for lithium secondary batteries. (C) 1994 Academic Press, Inc.