Enhanced anodic performance of CTF0 monolayer for Li-ion batteries through F and Si co-doping: A DFT insight

Abstract

Covalent triazine frameworks (CTFs) have been identified as promising electrode materials for Li-ion batteries (LIBs) because of their high surface area, adjustable conjugated structures, and good chemical/thermal stability. However, their low electrical conductivity limits electron and ion conduction, leading to poor electrochemical performance. In this work, a novel CTF-based monolayer, namely F and Si co-doped CTF₀ (F,Si-CTF₀), was designed using density functional theory (DFT) calculations. The results demonstrated that the co-doping of F and Si atoms on the CTF₀ surface creates more accessible adsorption sites for Li-ion adsorption. The energy analysis confirmed the stability of the F,Si-CTF₀ monolayer, which exhibits a notable adsorption energy of −3.53 eV for Li-ion. The F,Si-CTF₀ monolayer can accommodate five Li-ions, providing a theoretical specific capacity of 462 mAh g⁻¹ and a positive redox potential of 2.57 V. adsorption of Li ions on the F,Si-CTF₀ monolayer leads to a transition from a semiconducting to a metallic state, resulting in a notable enhancement in electronic conductivity. Moreover, the monolayer undergoes minor lattice variations (1.3 %) throughout the lithiation/delithiation process, demonstrating excellent cycling performance. Finally, Li-ion diffuses rapidly on the monolayer surface with a very small diffusion energy barrier of 0.078 eV. The findings suggest that the F,Si-CTF₀ monolayer can be used as a viable anode material in next-generation LIBs. This research shows that F and Si co-doping is an effective and viable strategy for designing two-dimensional CTF-based materials as efficient electrodes for LIBs.