Selective sulfur conversion with surface engineering of electrocatalysts in a lithium–sulfur battery

Abstract

The sluggish kinetics of multiphase sulfur conversion with homogeneous and heterogeneous electrochemical processes, causing the "shuttle effect" of soluble polysulfide species (PSs), is the challenges in terms of lithium-sulfur batteries (LSBs). In this paper, a Mn 3 O 4−x catalyst, which has much higher activity for heterogeneous reactions than for homogeneous reactions (namely, preferentialactivity catalysts), is designed by surface engineering with rational oxygen vacancies. Due to the rational design of the electronic structure, the Mn 3 O 4−x catalyst prefers to accelerate the conversion of Li 2 S 4 into Li 2 S 2 /Li 2 S and optimize Li 2 S deposition, reducing the accumulation of PSs and thus suppressing the "shuttle effect." Both density functional theory calculations and in situ X-ray diffraction measurements are used to probe the catalytic mechanism and identify the reaction intermediates of MnS and Li y Mn z O 4−x for fundamental understanding. The cell with Mn 3 O 4−x delivers an ultralow attenuation rate of 0.028% per cycle over 2000 cycles at 2.5 C. Even with sulfur loadings of 4.93 and 7.10 mg cm −2 in a lean electrolyte (8.4 µL mg s −1 ), the cell still shows an initial areal capacity of 7.3 mAh cm −2 . This study may provide a new way to develop preferential-activity heterogeneous-reaction catalysts to suppress the "shuttle effect" of the soluble PSs generated during the redox process of LSBs.

Recent advances in modified commercial separators for lithium–sulfur batteries

“…Surface engineering has been used to improve the catalytic activity for multiple LiPS species instead of specific LiPSs. Zhu et al 306 created oxygen vacancies in Mn 3 O 4 to reduce the activation energy of converting soluble long-chain LiPS into insoluble short-chain LiPS. Due to the oxygen vacancies, strong Mn–S bonds were formed between the catalyst and long-chain LiPS, whereas short-chain LiPS formed more Li–O bonds.…”

“…182 Surface engineering has been used to improve the catalytic activity for multiple LiPS species instead of specic LiPSs. Zhu et al 306 Multi-metal oxide heterostructures are promising for LiPS adsorption owing to their abundant defects providing oxygen vacancies. Hu et al 303 decorated MWCNTs with N, F, and B codoped CoFe 2 O 4−x and coated a Celgard separator (Fig.…”

Dynamic evolution of electrocatalytic materials for Li–S batteries

“…135,136 For example, by calculating the binding energy between electrocatalysts and different sulfur species, Zhang et al proposed the selective catalytic mechanism. 82 In addition, Zeng et al combined theoretical calculations with experiments to propose a dynamic energy-level matching mechanism during the reduction process. 77 However, such a catalytic mechanism combined with theoretical calculations is only applicable to specific electrocatalyst evolution processes owing to the differences in electronic structures.…”

“…2. 73,[77][78][79][80][81][82] With the associated progress of multifarious characterization techniques to decouple the dynamic evolution of electrocatalysts, the real-time trace and accurate identification of true electrocatalytic active sites provides an ideal platform for elaborating the structure-property relationship at the molecular level. Finally, a future outlook is provided to lay the foundation for engineering high-performance electrocatalysts.…”

Ordered Mesoporous Carbon Grafted MXene Catalytic Heterostructure as Li-Ion Kinetic Pump toward High-Efficient Sulfur/Sulfide Conversions for Li–S Battery

“…To mitigate these deficiencies, researchers have proposed a variety of well-established strategies, such as designing structurally diverse conductive sulfur cathodes, − developing multifunctional separator coatings, − protecting lithium anodes, − and tuning electrolyte compositions, − among which modifying the separator can make a difference due to the high capability of capturing and conversing isolated LiPSs. Therefore, various separator coating materials are proposed from physical confinement and chemical adsorption to popular electrocatalytic conversion, displaying exciting achievements. − To the best of our knowledge, the catalytic efficiency of sulfur species relies on both electronically conductive matrix and ionic highway in the electrode/electrolyte interface.…”