1. Typical coordination geometries of metal cyanamides/carbodiimides^[9]

2. SEM (the first three rows), TEM (the fourth row) images of partial metal cyanamides/carbodiimides^{[12,16,18,36,47,48,50,52,53]}

3. Electrochemical performance and charge storage mechanism of FeNCN and CoNCN anode materials for lithium-ion batteries^[19,51]

4. Electrochemical performance and charge storage mechanism of Cr₂(NCN)₃ anode material for lithium-ion battery^[53]

5. (a) Comparison of rate capacities of Sn₂ONCN and SnO₂ anode materials for lithium-ion batteries; (b) Rate capacity of Sn₂ONCN/GN hybrid anode; (c) Cycling performance of Sn₂ONCN/GN hybrid anode at 1 and 2 A/g; (d) Comparison of the specific gravimetric rate capabilities among Sn₂ONCN/GN and the recently reported SnO₂-based materials; Proposed reaction mechanisms of (e) SnO₂ and (f) Sn₂ONCN electrodes during charge/discharge; (g) Schematic diagram, (h) galvanostatic charge-discharge profiles at different rates, (i) rate capacities from 0.5C to 20C and cycling stability at 0.5C rate of lithium-ion full cell assembled by commercial LiCoO₂ cathode and TG/MnNCN hybrid anode^[57,61]

6. (a) Galvanostatic charge-discharge profiles of FeNCN anode for sodium-ion battery at different current densities; (b) Rate capacities at different current densities; (c) Comparison of the specific gravimetric rate capability among FeNCN and the recently reported iron-based inorganic materials; (d) Calculated Na⁺ diffusion barrier along the three directions in FeNCN and the proposed diffusion highway^[60]

Table 1. Crystal structures of partial metal cyanamides/carbodiimides reported in the literature and their applications for electrochemical energy storage^[9]