Unveiling potential of thiophene-functionalized C3N3 nanosheet as an anode for Li-ion batteries: A DFT-D3 study

Abstract

Covalent triazine frameworks (CTFs) are a fascinating type of porous organic materials that exhibit numerous distinct features, such as significant specific surface area, outstanding chemical/thermal stability, and structural modifiability at the molecular level. These features make CTFs highly appealing for utilization in Li-ion batteries (LIBs). However, their low electronic conductivity limits their practical applications. In the present study, the potential anode application of thiophene-functionalized C3N3 nanosheet for LIBs was conducted by dispersion-corrected density functional theory (DFT-D3) calculations. It was found that functionalization of the C3N3 nanosheet with six thiophene groups ((THP)6@C3N3) led to the highest reduction (0.19 eV) in the energy gap of the pristine C3N3 nanosheet. A single Li-ion preferably adsorbs between two nitrogen atoms of the triazine ring with an adsorption energy of about 4.59 eV. The absorption of Li-ion resulted in a reduction of the band gap from 1.37 eV to 0.43 eV, indicating enhanced electrical conductivity and superior cycle stability. The fully loaded functionalized nanosheet with nineteen Li-ions at various adsorption sites exhibited a remarkable theoretical specific capacity of 526.55 mAh/g. This configuration also displayed a low open-circuit voltage (0.09 V) and diffusion energy barrier (0.35 eV), ideal as an anode with a rapid charging/discharging rate. Therefore, thiophene-functionalized C3N3 nanosheet demonstrates superior anode performance for LIBs due to its high theoretical specific capacity, small diffusion barrier, and low working voltage. This work can provide insights for the refere development of CTF-based anode materials.