Manipulating Electrocatalytic Li₂S Redox via Selective Dual‐Defect Engineering for Li–S Batteries

Abstract

Lithium–sulfur (Li–S) batteries are promising candidates for next‐generation energy storage, yet they are plagued by the notorious polysulfide shuttle effect and sluggish redox kinetics. While rationally designed redox mediators can facilitate polysulfide conversion, favorable bidirectional sulfur electrocatalysis remains a formidable challenge. Herein, selective dual‐defect engineering (i.e., introducing both N‐doping and Se‐vacancies) of a common MoSe2 electrocatalyst is used to manipulate the bidirectional Li2S redox. Systematic theoretical prediction and detailed electrokinetic analysis reveal the selective electrocatalytic effect of the two types of defects, thereby achieving a deeper mechanistic understanding of the bidirectional sulfur electrochemistry. The Li–S battery using this electrocatalyst exhibits excellent cyclability, with a low capacity decay rate of 0.04% per cycle over 1000 cycles at 2.0 C. More impressively, the potential for practical applications is highlighted by a high areal capacity (7.3 mAh cm−2) and the construction of a flexible pouch cell. Such selective electrocatalysis created by dual‐defect engineering is an appealing approach toward working Li–S systems.

Synergetic Anion Vacancies and Dense Heterointerfaces into Bimetal Chalcogenide Nanosheet Arrays for Boosting Electrocatalysis Sulfur Conversion

“…The introduction of anion vacancies provides another effective strategy to enhance the electrocatalytic activity of TMCs toward boosted Li−S battery upon discharging/charging process. [ 25–27 ] Electrons in the Se‐defect can be excited into the conduction band, producing a low bandgap in the conduction band which is favorable to the sulfur conversion reaction. [ 28 ] Moreover, sulfur‐vacancies (S‐vacancies) can regulate the electronic structure of adjacent atoms, thus reducing the decomposition energy barrier of the reaction intermediate.…”

“…Although promising progress has been made, electrocatalytic activity is still unsatisfactory for a wellfunctioning Li−S battery in terms of boosting the entire sulfur conversion reaction.The introduction of anion vacancies provides another effective strategy to enhance the electrocatalytic activity of TMCs toward boosted Li−S battery upon discharging/charging process. [25][26][27] Electrons in the Se-defect can be excited into the conduction band, producing a low bandgap in the conduction band which is favorable to the sulfur conversion reaction. [28] Moreover, sulfurvacancies (S-vacancies) can regulate the electronic structure of adjacent atoms, thus reducing the decomposition energy barrier Vacancy and interface engineering are regarded as effective strategies to modulate the electronic structure and enhance the activity of metal chalcogenides.…”

Ultra‐Small Ferromagnetic Fe3O4 Nanoparticles Modified Separator for High‐Rate and Long Cycling Lithium‐Sulfur Batteries

“…To further investigate the catalytic activity of Fe 3 O 4 for polysulfide reduction, potentiostatic nucleation of Li 2 S in polysulfides was performed at 2.05 V. As shown in Figure S10 (a and b), Fe 3 O 4 @CNTs possesses a higher discharging current of 0.81 mA, compared to that of CNTs (0.42 mA). Correspondingly, Fe 3 O 4 @CNTs shows a higher Li 2 S precipitation capacity of 38 mAh g −1 (light blue area in Figure S10b) than those of CNTs cathode (14 mAh g −1 , yellow area in Figure S10a), suggesting that Fe 3 O 4 @CNTs layers can accelerate to the nucleation and deposition of Li 2 S 2 /Li 2 S on their surface [39] . Besides, the Tafel curves for initial lithiation of symmetrical Li 2 S 6 –Li 2 S 6 cells with CNTs/PP, FC‐6/PP, FC‐12/PP, and FC‐20/PP separators are shown in Figure S11.…”

Customized Structure Design and Functional Mechanism Analysis of Carbon Spheres for Advanced Lithium–Sulfur Batteries

“…NHCS through the capture-diffusion-nucleation mechanism (Figure 14e) as reported. [12] Recently, polar catalytic materials such as metal carbides (Fe 3 C, [307] Fe 3−x C, [261] Mo 2 C, [189,308,309] NbC [310] ), nitrides (Co 4 N, [258] Co 5.47 N x , [311] VN, [259] NbN [280] ), phosphides (FeP [312] ), selenides (MoSe 2 [313,314] ), and heterostructures have been continuously tried to be introduced into LSBs to promote the redox reaction kinetics of LiPSs, thereby reducing the accumulation of LiPSs. [315,316] It is worth to mention that for the first time, Jin et al [307] proposed a new method for simultaneously achieving the controllable growth of ultrafine Fe 3 C nanocrystals and the construction of homogenous multistage pore channels of the ordered micro-mesoporous carbon nanospheres.…”

“…The MoSe 2 nanosheets can chemically restrain the LiPSs and meantime catalyze their rapid redox conversion. Recently, Sun et al [314] further manipulated the bidirectional Li 2 S redox by introducing N-doping and Se-vacancy in MoSe 2 . Impressively, the high area capacity (7.3 mAh cm −2 ) and the construction of a flexible pouch cell highlight the potential for practical application.…”