The effect of doped elementals on the electrochemical behavior of hexagonal Li2.6Co0.4N

Although Li2.6Co0.4N with hexagonal structure demonstrates promising electrochemical properties as a negative electrode for lithium-ion batteries, its capacity retention upon long cycles still seems poor. In this work the electrochemical behavior of the layered lithium metal (transition) nitrides has been extensively investigated according to the tradeoffs based on the ternary Li2.6M0.4N (M = Co, Ni, and Cu). Results reveal that the existence of Co in the nitrides is highly essential, and a suitable amount of doped Cu, Ni in place of part Co in Li2.6Co0.4N can significantly improve cycling performance. Enhanced electrochemical stability and interfacial compatibility may take this consequence. A suitable formula of the codoped lithium metal nitrides is Li2.6Co0.4-x-yCuxNiyN (0.1 less than or equal to x less than or equal to 0.2, 0 less than or equal to y less than or equal to 0.1, 0.1 less than or equal to x + y less than or equal to 0.2). Li2.6Co0.2Cu0.2N has proven to be the compound with the best cyclability in this family, but it suffers a little capacity loss. The appropriate content of Cu substituted by Fe in the Li2.6Co0.2Cu0.2N can remarkably increase the reversible capacity to ca. 800 mAh g(-1) with retained cycling stability. This work may greatly motivate the development of lithium metal nitride as anodes in lithium-ion batteries. (C) 2004 The Electrochemical Society.