In order to build rechargeable high-energy-density and long-term cycling stability batteries, significant efforts have been dedicated to the development of alternate anodes. Here, we designed two intercalation-type anodes based on the dicyanamide anion, N(CN)2-, through strategic incorporation of metal cations─specifically by replacing Mn2+ with Ni2+ and Co2+─thereby enabling a transition from conversion-type for MnN(CN)22 with compromised cycling performance to intercalation-type lithium storage mechanisms for NiN(CN)22 and α-CoN(CN)22 including superior cycling performance. NiN(CN)22 and α-CoN(CN)22 exhibit high specific capacities and cycling stability, maintaining reversible capacities of about 500 mAh·g-1 over 200 cycles and 600 mAh·g-1 over 400 cycles, respectively. These values notably surpass those of established negative electrode materials such as graphite (≈372 mAh·g-1), offering compelling performance comparisons. In addition, advanced characterization techniques reveal an intercalation mechanism facilitated by the N(CN)2- anion, which contributes to reversible capacity retention. Furthermore, we show, through density functional theory (DFT) calculations and quantum-chemical analysis, that the source of excellent electrical performance lies in the delocalized nature of the π-bonded N(CN)2- complex anion, electrostatically attached to Li+. This mechanism, observed in transition-metal dicyanamides, is likely the key to their exceptional electrochemical performance and provides insight into the design of anode materials.
Qiao et al. (Mon,) studied this question.