Insight into the Inhibition of Shuttle by Metal-Modified Covalent Triazine Frameworks and Graphene Composites with the Solvent Interaction in Lithium Sulfur Batteries

The shuttle effect of lithium polysulfides is a key problem that has degraded the performance and limited the commercialization of lithium sulfur batteries. Currently, the composites with covalent triazine frameworks (M-CTFs) modified by metals in the fourth period and graphene (M-CTF/G, M = Li, Ti similar to Zn) were designed as host cathodes and are expected to inhibit the shuttling effect through the modification by the polar metal. Using density functional theory, it was demonstrated that M-CTF/G displayed synergistic adsorption performance of Li2S4 with unsaturated metal-N3 coordinated groups as active sites in the M-CTF. In addition, three solvents with different dielectric constants and polarity, namely, dioxolane, dimethoxyethane dimethyl, and tetramethylurea, were used to investigate the solvent effect, and the effective adsorption energy range of Li2S4 on M-CTF/G was evaluated in the presence of solvents. The theoretical results obtained in this work provide guidance in the design of the cathode and understanding of solvent effects in lithium sulfur batteries.

Automated summary

In this study, composites of covalent triazine frameworks modified by metals and graphene were designed as host cathodes for lithium sulfur batteries to inhibit the shuttle effect of lithium polysulfides. The solvation effect was investigated using solvents with different dielectric constants and polarity, and the effective adsorption energy range of lithium polysulfides on the material was evaluated.