Tunable Conjugated Porous Polymers with Cyano-Containing Organic Molecules as Anode Materials for High-Performance Li-Ion Batteries

Nitrogen-containing organic compounds have shown great potential in energy storage because the N atom can act as the electrochemical reaction center. However, their high solubility and polarization in the electrolyte lead to unsatisfactory performance. In this study, we report a high-performance anode for lithium-ion batteries (LIBs), with 1,2,4,5-tetracyanobenzene (TCB) used as anode and precursor to form nitrogen-doped carbon (NDC) and conjugated porous polymer (CPP) to further improve the electrochemical performance. The three separate materials effectively utilize the π conjugation between the cyano groups, −C═N groups, and benzene rings, and the initial specific capacities are as high as 1241.61, 1314.85, and 1256.90 mAh g–1, respectively. In particular, the CPP has a better 2D layered structure, which can significantly improve the cycling stability and rate capability, maintaining a high capacity of 597.35 mAh g –1 after 1000 cycles. Furthermore, the charge storage mechanism of TCB, NDC, and CPP was systematically investigated through density functional theory calculations. The cyano groups, −C═N groups, and the π conjugation between the benzene rings were identified as the active centers for Li+ storage. This work provides a molecular design strategy and an effective theoretical reference for the comprehensive utilization of organic molecules as electrode materials.