2D Frameworks of C₂ N and C₃ N as New Anode Materials for Lithium-Ion Batteries

Novel layered 2D frameworks (C₃ N and C₂ N-450) with well-defined crystal structures are explored for use as anode materials in lithium-ion batteries (LIBs) for the first time. As anode materials for LIBs, C₃ N and C₂ N-450 exhibit unusual electrochemical characteristics. For example, C₂ N-450 (and C₃ N) display high reversible capacities of 933.2 (383.3) and 40.1 (179.5) mAh g^-1 at 0.1 and 10 C, respectively. Furthermore, C₃ N shows a low hypothetical voltage (≈0.15 V), efficient operating voltage window with ≈85% of full discharge capacity secured at >0.45 V, and excellent cycling stability for more than 500 cycles. The excellent electrochemical performance (especially of C₃ N) can be attributed to their inherent 2D polyaniline frameworks, which provide large net positive charge densities, excellent structural stability, and enhanced electronic/ionic conductivity. Stable solid state interface films also form on the surfaces of the 2D materials during the charge/discharge process. These 2D materials with promising electrochemical performance should provide insights to guide the design and development of their analogues for future energy applications.