Electrocatalyst Modulation toward Bidirectional Sulfur Redox in Li–S Batteries: From Strategic Probing to Mechanistic Understanding

Abstract

Electrocatalyst design has stimulated considerable attention and strenuous effort to tackle a multitude of detrimental issues in lithium–sulfur (Li–S) systems, mainly pertaining to the severe polysulfide shuttle effect and sluggish sulfur redox kinetics. In this context related advances in expediting bidirectional sulfur reactions have lately surged. Nonetheless, the structure–activity correlation and electrocatalytic mechanism remain rather elusive, as a result of elusory active sites, complicated aprotic environments, and multistep conversion pathways. This review summarizes burgeoning strategies in the modulation of heterogeneous and homogeneous electrocatalysts, wherein the advanced electrokinetic measurements, operando instrumental probing, and theoretical simulations are elucidated with an emphasis on deciphering bidirectional sulfur electrochemistry. Notably, a “3s” electrocatalysis model is proposed to deepen the mechanistic understanding in this realm. Finally, a development roadmap is sketched and future research layouts are discussed, aiming in essence, to realize favorable bidirectional redox kinetics and ultimately bridge the gap between reality and ideal systems in working Li–S batteries.

Direct-Chemical Vapor Deposition-Enabled Graphene for Emerging Energy Storage: Versatility, Essentiality, and Possibility

“…Rationalizing the electrocatalyst design has emerged as a promising and essential remedy to combat the severe polysulfide shuttling and sluggish redox kinetics in Li–S batteries. − In this sense, the full exposure and uniform distribution of active sites in nanomaterials are important for the promotion of an electrocatalytic effect. − Admittedly, the 3D free-standing electrodes are expected to accommodate high-loading sulfur and alleviate volume change during the electrochemical cycling process. − Nonetheless, the controllable growth and structural modulation of on-site nanocatalysts remains a huge challenge, in which the morphologic uniformity is difficult to realize with limited loading density, thereby giving rise to the mediocre electrocatalytic activity. To this end, VG skeleton derived by direct-CVD growth harnesses the hierarchical array structure and large specific surface area to elevate the density and homogeneity of the electrocatalytic active sites.…”

Advanced Nanostructured Materials for Electrocatalysis in Lithium–Sulfur Batteries

“…Therefore, making the catalyst more defective while reducing its overall size can form more active sites and increase the specific activity of the catalyst [ 156 ]. Based on this theory, single-atom catalysts (SACs) obtained by combining individual metal atoms with catalyst supports can achieve the most efficient utilization of catalyst specific surface area and metal atoms, and their adverse effects on energy density can be minimized due to the light weight of SACs [ 157 , 158 , 159 ], which together prove that the SACs is a promising research direction in the field of Li-S battery electrocatalysis.…”

Environmental applications of immobilized and bio-resourced redox mediators: A Review

“…However, the complex procedures of these immobilization processes, the time-consuming lab work to select suitable process conditions and unaffordable carriers always limited their wide applications (Rocha-Martín et al 2021;Wang et al 2021). To overcome these raised issues, data-driven approaches such as machine learning algorithms have been attempted to predict and optimize those complex procedures and to obtain feasible immobilization conditions (Shi et al 2022). Moreover, some natural biomass and/or their derivatives such as biochar would be expected to be good and low-cost alternatives because of the renewable raw materials.…”