The Nature of Lithium Bonding in C 2 H 2 Li 2 , C 6 Li 6 , and Lithium Halide Dimers

Liu, Yameng; Peng, Bin; Wang, Xiao; Xie, Yaoming; Schaefer, Henry F.

doi:10.1021/acs.organomet.9b00683

The notorious polysulfide shuttle effect is a crucial factor responsible for the degradation of Li-S batteries. A good way to suppress the shuttle effect is to effectively anchor dissoluble lithium polysulfides (LPSs, Li 2 S n ) on appropriate substrates. Previous studies have revealed that Li of Li 2 S n is prone to interact with the N of N-containing materials to form Li–N bonds. In this work, by means of density functional theory (DFT) computations, we explored the possibility to form Li bonds on ten different N-containing monolayers, including BN, C 2 N, C 2 N 6 S 3 , C 9 N 4 , a covalent triazine framework (CTF), g -C 3 N 4 , p -C 3 N 4 , C 3 N 5 , S -N 2 S, and T -N 2 S, by examining the adsorption behavior of Li 2 S n ( n = 1, 2, 3, 4, 6, 8) on these two-dimensional (2D) anchoring materials (AMs), and investigated the performance of the formed Li bonds (if any) in inhibiting the shuttle effect. By comparing and analyzing the nitrogen content, the N-containing pore size, charge transfer, and Li bonds, we found that the N content and N-containing pore size correlate with the number of Li bonds, and the formed Li–N bonds between LPSs and AMs correspond well with the adsorption energies of the LPSs. The C 9 N 4 and C 2 N 6 S 3 monolayers were identified as promising AMs in Li-S batteries. From the view of Li bonds, this work provides guidelines for designing 2D N-containing materials as anchoring materials to reduce the shuttle effect in Li-S batteries, and thus improving the performance of Li-S batteries.

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