Nitrogen-Doped Porous Carbon Nanosheets with Ultrahigh Capacity and Quasicapacitive Energy Storage Performance for Lithium and Sodium Storage Applications

One of the great challenges in the development of rechargeable batteries is developing electrode materials with high capacities and good rate performance. Herein, thin carbon nanosheets with hierarchical porous structure and high nitrogen content (10.6 at%) are elaborately designed and fabricated from phenolic resin through a two-step method including N₂ carbonization and NH₃ annealing. The as-obtained nitrogen-doped porous carbon nanosheets (NPCNs) exhibit abundant electroactive sites from large surface area and nitrogen species for lithium/sodium storage, and short diffusion channels from unique porous 2D structure for rapid charge transfer. As a result, the optimal NPCNs show outstanding lithium storage capacities of 2065 and 300 mAh g⁻¹ at current densities of 0.05 and 200 A g⁻¹, respectively, as well as good cycle stability. Moreover, the NPCNs also carry out an excellent sodium storage performance of 222 and 134 mAh g⁻¹ at 1 and 10 A g⁻¹, respectively. Further electrochemical analysis demonstrates that the superior rate capability of NPCNs might attribute to the surface-dominated energy storage process. A new route for the preparation and development of high-performance electrode materials for new-generation energy storage devices is provided.