Computational Insights into the Interaction between Li2S/Li2S2 and Heteroatom-Doped Graphene Materials

Electrochemical nucleation and deposition of Li2S/Li2S2 is among the major problems hindering the application of lithium-sulfur batteries. Adsorption behavior of Li2Sx (x=1, 2, 4, 8) with nitrogen-doped, boron-doped graphene and reduced graphene oxides (r-GOs) are investigated in this study by DFT method. It is discovered that graphene with pyridinic N doping (PD-N) and pyrrolic N doping (PL-N) are able to benefit the nucleation for short-chain lithium-polysulfides (Li2S/Li2S2) through Li-N interaction. r-GOs can also enhance the nucleation to some extent through Li-O interaction, which is not as good as Li-N interaction. At the same time, pristine graphene, graphene with graphitic N (GRN) and B-doped graphene can only provide Li-C interaction, which is weaker than Li-O and Li-N. This makes the sequence of adsorption strength to be PD-N approximate to PL-D>r-GO>B>GRN approximate to pristine graphene. The unique mechanism of B-doped graphene adsorbed with Li2S/Li2S2 is also discovered.