Because of their high theoretical energy density and low cost, lithium–sulfur (Li–S) batteries are promising next-generation energy storage devices. The electrochemical performance of Li–S batteries largely depends on the efficient reversible conversion of Li polysulfides to Li2S in discharge and to elemental S during charging. Here, we report on our discovery that monodisperse cobalt atoms embedded in nitrogen-doped graphene (Co–N/G) can trigger the surface-mediated reaction of Li polysulfides. Using a combination of operando X-ray absorption spectroscopy and first-principles calculation, we reveal that the Co–N–C coordination center serves as a bifunctional electrocatalyst to facilitate both the formation and the decomposition of Li2S in discharge and charge processes, respectively. The S@Co–N/G composite, with a high S mass ratio of 90 wt %, can deliver a gravimetric capacity of 1210 mAh g–1, and it exhibits an areal capacity of 5.1 mAh cm–2 with capacity fading rate of 0.029% per cycle over 100 cycles at 0.2 C at S loading of 6.0 mg cm–2 on the electrode disk.

Highly concentrated electrolytes (HCEs) significantly improve the stability of lithium metal anodes, but applications are often impeded by their limitation of density, viscosity, and cost. Here, fluorobenzene (FB), an economical hydrocarbon with low density and low viscosity, is demonstrated as a bifunctional cosolvent to obtain a novel FB diluted highly concentrated electrolyte (FB‐DHCE). First, the addition of FB suppresses the decomposition of dimethoxyethane (DME) on the Li metal by strengthening the interactions of DME and FSI− around Li+. Second, FB efficiently elevates the content of LiF in the solid electrolyte interphase (SEI) based on its electrochemical reduction reaction. The unique solvation and interfacial chemistry of FB‐DHCE enable dendrite‐free deposition of lithium with high Coulombic efficiency (up to 99.3%) and prolong cycling life (over 500 cycles at 1 mA cm−2). The performance of FB‐DHCE is further demonstrated in full cells under practical conditions, including ambient to low temperature (–20 °C), high areal capacity (7.6 mAh cm−2), high current density (3 mA cm−2), limited excess Li (20 µm Li), and lean electrolyte (3 g Ah−1). Employing FB as a cosolvent not only opens a novel pathway to stabilize Li metal anodes, but also could greatly advance the development of Li metal batteries.

Lithium-metal anodes are recognized as the most promising next-generation anodes for high-energy-storage batteries.H owever,l ithium dendrites lead to irreversible capacity decayi nl ithium-metal batteries (LMBs). Besides, the strict assembly-environment conditions of LMBs are regarded as ac hallenge for practical applications.I nt his study,aworkable lithium-metal anode with an artificial hybrid layer composed of ap olymer and an alloy was designed and prepared by as imple chemical-modification strategy.T reated lithium anodes remained dendrite-free for over 1000 hinaLi-Li symmetric cell and exhibited outstanding cycle performance in high-areal-loading Li-S and Li-LiFePO 4 full cells.M oreover,t he treated lithium showed improved moisture stability that benefits from the hydrophobicity of the polymer,t hus retaining good electrochemical performance after exposure to humid air.

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Room temperature (RT) sodium–sulfur batteries suffer from slow reaction kinetics and polysulfide dissolution, resulting in poor performance. Sulfurized polyacrylonitrile is a unique sulfur cathode which is suggested to involve only S3–4 and shows high specific capacity. Herein, the designed Te0.04S0.96@pPAN with 4 mol % Te used as eutectic accelerator exhibits significantly enhanced reaction kinetics and excellent sulfur utilization, leading to a high performance RT Na–S battery. Te0.04S0.96@pPAN delivers capacities of 1236 and 629 mA h g–1 and 1111 and 601 mA h g–1 at 0.1 and 6 A g–1 in carbonate and ether electrolytes, respectively. Furthermore, UV–vis spectra and the shuttle current test reveal diminished sodium polysulfides in ether electrolyte, attributed to the fast kinetics enabled by Te doping. More significantly, the spectral technique and electrochemical analysis demonstrate a two-step reaction pathway in which Na2S3 and Na2S are the main intermediate and final discharge product, respectively. This method provides a promising approach toward applicable RT Na–S batteries.