Fig. 7.

Reversible Li active sites in a 2D-C₃N₄ sheet, and b 1D-C₃N₄ fiber. Green means reversible Li atoms and red means non-reversible Li atoms. c Top and side view of stable intercalation structures of n Li ions into C₃N. Reproduced with permission from Ref. [40]. d Diffusion paths and e corresponding energy barriers of Li migration in C₃N-S2. Reproduced with permission from Ref. [51]. f Binding energy of Li₂S₄/Li₂S₆/Li₂S₈ interacting with G, BN, C₂N, C₃N₄ and DOL/DME solvent, respectively. Reproduced with permission from Ref. [17]. g Isosurfaces of charge density difference of Li₂S, Li₂S₂, Li₂S₄, Li₂S₆, Li₂S₈, and S₈ adsorbed on the surface of C₅N with the isovalue of 0.003 A⁻³. Blue wireframes denote loss of electrons and yellow wireframes denote gain of electrons. Reproduced with permission from Ref. [27]. Copyright permissions from American Chemical Society, Elsevier and Wiley–VCH. (Color figure online)