Theoretical and Experimental Understanding of Metal Single-Atom Electrocatalysts for Accelerating the Electrochemical Reaction of Lithium–Sulfur Batteries

Abstract

Metal single-atom materials have attracted tremendous attention in the research field of lithium–sulfur (Li–S) batteries because they can effectively improve the reaction kinetics of sulfur cathodes. However, it is still difficult to determine the best metal single-atom catalyst for Li–S batteries, due to the lack of a unified measurement and evaluation method. Herein, a series of metal single-atom- and nitrogen-doped graphene materials (M-NG, M = Fe, Co, Ni, Ir, Ru) have been prepared as the catalysts for promoting the reaction kinetics of the sulfur reduction reaction process. Using rotating disk electrode measurements and density functional theory-based theoretical calculations, Ni-NG was screened out to be the best catalyst. It is found that Ni-NG materials can provide a kinetically favorable pathway for the reversible conversion of polysulfide conversion, thus increasing the utilization of sulfur. By coating the Ni-NG materials on the separator as a multifunctional interlayer, a commercially available sulfur cathode presents a stable specific capacity of 701.8 mAh g–1 at a current rate of 0.5C over 400 cycles. Even with a high sulfur loading of 3.8 mg cm–2, a high areal capacity of 4.58 mAh cm–2 can be achieved. This work will provide a fundamental understanding of efficient single-atom catalyst materials for Li–S batteries.

Interfacial Engineering of Ru Nanocluster-Modified TiO2 Nanotube-Assisted Regulation of Lithium Polysulfide Reactions

“…According to classical kinetic and thermodynamics studies, the process of long-chain polysulfides to short-chain polysulfides was affected by the Gibbs energy barrier. 19,38 For TiO 2 −Ru, it could be seen that the Gibbs free energy of each step and the Gibbs free energy change of each intermediate product conversion were lower than TiO 2 , indicating that Ru nanoclusters with high catalytic activity were more favorable for the sulfur reduction reaction. 39,40 In addition, the Li 2 S nucleation curves of TiO 2 − Ru@S and TiO 2 @S cathodes are shown in Figure S7.…”

Single-atom site catalysis in Li–S batteries

“…Xu et al prepared a series of metal single-atom and nitrogen-doped graphene materials (M-NG, M = Fe, Co, Ni, Ir, Ru) and conducted rotating disk electrode (RDE) measurements and theoretical calculations based on density functional theory. 193 In RDE testing, all five types of M-NG electrodes exhibited higher initial potentials and limited diffusion current density ( j d ) compared to NG. Among the five M-NG electrodes, the Ni-NG electrode showed the highest j d , demonstrating the best catalytic performance of Ni-NG material in facilitating the conversion of molecular sulfur into insoluble discharge products (Fig.…”

“…191,192 Among these functional materials, SASCs with excellent conductivity are the most promising candidates, as they exhibit high LiPS catalytic activity and promote Li + diffusion, among other advantages (Table 2). 112,132,[193][194][195][196][197][198]…”

Non‐trivial Contribution of Carbon Hybridization in Carbon‐based Substrates to Electrocatalytic Activities in Li‐S Batteries

“…However, the synthesized Ni SAC of one research work was screened out to be the best catalyst material among different metal atoms (Fe/Co/Ni). [6] In contrast, the Ni SAC obtained by a different research group exhibited almost no electrocatalytic activity for SRR. [4] Given the same type of specific metal species and prepared by a similar approach in these studies, the origin of the difference in catalytic activity may be derived from different annealing temperatures of the material that results in the change of the carbon supports.…”