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.