Cation-Tuned Reaction Mechanisms in Metal Dicyanamide Anodes for Lithium-Ion Batteries with High Reversible Capacity.
basic_science · Level V
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- Record sourced from PubMed, PMID 41699821.
- Also identified by DOI 10.1021/acsnano.5c19344.
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Abstract
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)<sub>2</sub><sup>-</sup>, through strategic incorporation of metal cations─specifically by replacing Mn<sup>2+</sup> with Ni<sup>2+</sup> and Co<sup>2+</sup>─thereby enabling a transition from conversion-type for Mn[N(CN)<sub>2</sub>]<sub>2</sub> with compromised cycling performance to intercalation-type lithium storage mechanisms for Ni[N(CN)<sub>2</sub>]<sub>2</sub> and α-Co[N(CN)<sub>2</sub>]<sub>2</sub> including superior cycling performance. Ni[N(CN)<sub>2</sub>]<sub>2</sub> and α-Co[N(CN)<sub>2</sub>]<sub>2</sub> exhibit high specific capacities and cycling stability, maintaining reversible capacities of about 500 mAh·g<sup>-1</sup> over 200 cycles and 600 mAh·g<sup>-1</sup> over 400 cycles, respectively. These values notably surpass those of established negative electrode materials such as graphite (≈372 mAh·g<sup>-1</sup>), offering compelling performance comparisons. In addition, advanced characterization techniques reveal an intercalation mechanism facilitated by the N(CN)<sub>2</sub><sup>-</sup> 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)<sub>2</sub><sup>-</sup> complex anion, electrostatically attached to Li<sup>+</sup>. 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.