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problems such as non-conductivity of sulfur, growth of lithium dendrites and the shuttle effect, impeding the process of commercialization. [7][8][9][10] In principle, people generally regard shuttle effect is the core problem that results in the poor cycle performance. For the shuttle effect, the soluble polysulfides from the sulfur cathode dissolve into the electrolyte, shuttle to the anode, and react with the lithium metal, which leads to the rapid capacity fading, low Coulombic efficiency, and a short cycle life. In addition, the polysulfides hinder the electron transport during the electrochemistry process, which brings about sluggish conversion of polysulfides and low sulfur utilization. [11][12][13][14][15] Consequently, it is highly desired to explore an effective strategy to prevent the shuttle effect and facilitate the redox kinetics. Separators play an important role in batteries that facilitates ion transportation, blocks electron and avoids short circuit. Nevertheless, unmodified separators are not able to retard the diffusion of the polysulfides. In recent years, numerous researches have been conducted to investigate functional separators to confine polysulfides and promote kinetics process of the transformation from the immobilized polysulfides to Li 2 S (kinetics conversion of the immobilized lithium polysulfides). It is generally believed that the commercial separator modification by coating functional materials is the most effective approach to design functional separator, which is more convenient and cost-effective than the fabrication of the composite sulfur cathodes. [4,[16][17][18] In the past decades, a series of materials and strategies have been explored to modify separators. Initially, carbon materials were widely used as coating materials to physically adsorb polysulfides due to their high porosity and surface area. Nevertheless, physical adsorption is so weak to some extent that the separation effect is limited. Then chemical adsorption as a more efficient method was developed to adsorb polysulfides because the chemical bonds are stronger to anchor the polysulfides and suppress the shuttle effect. The polar materials such as transition metal oxides, sulfides and nitrides usually possess chemical active sites to adsorb polysulfides. However, these materials possess weak catalytic performance so that the sluggish redox kinetics of polysulfides confined on the active coating has an adverse effect on the cycle performance of the Li-S batteries. Taking metal sulfides as an example, theThe practical application of Li-S batteries is seriously hindered due to its shuttle effect and sluggish redox reaction, which requires a better functional separator to solve the problems. Herein, polypropylene separators modified by MoS 2 nanosheets with atomically dispersed nickel (Ni-MoS 2 ) are prepared to prevent the shuttle effect and facilitate the redox kinetics for Li-S batteries. Compared with pristine MoS 2 nanosheets, Ni-MoS 2 nanosheets exhibit both excellent adsorption and catalysis performance f...

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The severe shuttle effect of polysulfides and sluggish redox kinetics are the main problems that hinder the practical applications of lithium–sulfur (Li–S) batteries. In this study, dual metallic single atom pairs are implanted into carbon nanospheres to address the shuttle effect and facilitate the bi‐directional redox kinetics of sulfur. Fe sites are found to be favorable for the reduction reaction of polysulfides, while Co sites facilitate the dissolution of Li2S experimentally and theoretically, promoting the overall electrochemical performance of Li−S batteries due to the synergetic effect. The sulfur cathode with the dual metallic single atom pairs exhibits an ultrahigh capacity retention of 96.4% after 100 cycles at 0.5 C. More importantly, it demonstrates excellent rate performance (618 mAh g−1 at current density of 10 C) and outstanding cycle performance at 2 C after 2800 cycles with only 0.01% decay per cycle. Impressively, the assembled pouch cell delivers a high discharge capacity of 1385 mAh g−1 and retains 869 mAh g−1 after 100 cycles at 0.2 C. These results demonstrate the potential of dual single atom catalysts for the favorable bi‐directional redox kinetics in Li−S batteries.

Lithium metal is an ideal anode for high-energy-density batteries. However, the low Coulomb efficiency and the generation of dendrites pose a significant limitation to its practical application, while the excess lithium in the battery also generates serious safety concerns. Herein, a layer-by-layer optimized multilayer structure integrating an artificial solid electrolyte interphase (LiF) layer, a lithiophilic (Li x Au alloy) layer, and a lithium compensation layer is reported for a lean-lithium metal battery, where each layer acts synergistically to stabilize the lithium deposition behaviors and enhances the cycling performance of the battery. The optimized anode could effectively induce homogeneous reversible lithium deposition under the synergistic effect of multilayer films and keep the integrity of the morphological structure unbroken during the deposition. The presence of the lithium compensation layer allows the half-cell to have a high initial CE of 158.9%, and the action of the LiF layer and lithiophilic layer maintains an average CE of 98.8% over 160 cycles, which further demonstrates the stability of the structure. As a result, when combined with LiFePO4 cathode, an initial capacity of 148 mAh g–1 and a retention rate of 97.5% over 130 cycles were achieved.