Evaluation of Li nucleation. (a) Optimized geometrical structures of Li binding to POF from the top view and the side view. The hydrogen, lithium, carbon, and nitrogen atoms are marked with white, green, brown, and blue, respectively. (b) Binding energy of Li with G, NG, and POF. (c) Voltage–time curves of Li nucleation at the current density of 0.50 mA cm−2 and (d) Li nucleation overpotentials at different current densities on Cu, G, NG, and G@POF electrodes.