Zinc Dicyanamide: A Potential High-Capacity Negative Electrode for Li-Ion Batteries

We demonstrate that the beta-polymorph of zinc dicyanamide, Zn[N(CN)(2)](2), can be efficiently used as a negative electrode material for lithium-ion batteries. Zn[N(CN)(2)](2) exhibits an unconventional increased capacity upon cycling with a maximum capacity of about 650 mAh<middle dot>g(-1) after 250 cycles at 0.5C, an increase of almost 250%, and then maintaining a large reversible capacity of more than 600 mAh<middle dot>g(-1) for 150 cycles. Such an increased capacity is primarily attributed to the increased level of activity in the conversion reaction. A combination of conversion-type and alloy-type mechanisms is revealed in this anode material via advanced characterization studies and theoretical calculations. This mechanism, observed here for the first time in transition-metal dicyanamides, is probably responsible for the outstanding electrochemical performance. We believe that this study guides the development of new high-capacity anode materials.