Direct solid-state synthesis and large-capacity anode operation of Li3−xFexN

Abstract

A direct solid-state synthesis route to Li_3−xFe_xN (x < 0.4) was developed and its electrochemical properties as an anode material for lithium-ion batteries were investigated. In order to stabilize the lower valence state of Fe(I) in the layered structure of Li_1−xFe_xN against Fe(III) in the competent phase of anti-fluorite Li₃FeN₂, an argon flow was used during the sintering process instead of the nitrogen or ammonia typically used in the synthesis of nitride compounds. This stabilized Li_3−xFe_xN at moderate temperatures around 600 °C without segregation of Fe metal or melting, and enabled a simple one-step solid state reaction. The largest reversible capacity of ca.700 mAh/g was obtained at x = 0.2 below 1.3 V versusLi/Li⁺.