Lithium–sulfur battery is recognized as one of the most promising energy storage devices, while the application and commercialization are severely hindered by both the practical gravimetric and volumetric energy densities due to the low sulfur content and tap density with lightweight and nonpolar porous carbon materials as sulfur host. Herein, for the first time, conductive CoOOH sheets are introduced as carbon‐free sulfur immobilizer to fabricate sulfur‐based composite as cathode for lithium–sulfur battery. CoOOH sheet is not only a good sulfur‐loading matrix with high electron conductivity, but also exhibits outstanding electrocatalytic activity for the conversion of soluble lithium polysulfide. With an ultrahigh sulfur content of 91.8 wt% and a tap density of 1.26 g cm−3, the sulfur/CoOOH composite delivers high gravimetric capacity and volumetric capacity of 1199.4 mAh g−1‐composite and 1511.3 mAh cm−3 at 0.1C rate, respectively. Meanwhile, the sulfur‐based composite presents satisfactory cycle stability with a slow capacity decay rate of 0.09% per cycle within 500 cycles at 1C rate, thanks to the strong interaction between CoOOH and soluble polysulfides. This work provides a new strategy to realize the combination of gravimetric energy density, volumetric energy density, and good electrochemical performance of lithium–sulfur battery. Conductive cobalt oxyhydroxide (CoOOH) sheets are prepared as the carbon‐free immobilizer for Li–S batteries for the first time. The S/CoOOH composite exhibits outstanding electrochemical performance resulting from the remarkable conductive framework and electrocatalytic activity contributed by the CoOOH sheets. Moreover, such composite delivers high gravimetric and volumetric energy densities, owing to the high sulfur content and tap density.
Sulfurized−poly(acrylonitrile) composite cathode materials provide high specific capacity, deprive the dissolution of polysulfides and shuttling effect. However, these materials have intrinsic problems such as low sulfur loading and poor rate capability at high C−rate due to the moderate conductivity of the composites. Here, we synthesize a wrapped S/rSP@SPAN composite using a dissolution−reprecipitation method followed by the thermal treatment. The idea is that the dissolution−reprecipitation of SP@PAN augments the surface area of the composite, which provides high sulfur loading and improves the composite−electrolyte contact, and conductivity of cathode material. As a result, the electrochemical performance of the as−fabricated S/rSP@SPAN cathode material yields excellent cyclability and high rate capability of 492 mAh g even at a high C−rate (10 C) with high sulfur loading (54.5%).
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 surfacemediated 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.
Herein we report a simple approach for the preparation of graphene oxide-carbon nanotube-sulfur composites. The self-standing composites can be easily prepared by freeze drying a frozen graphene oxide-carbon nanotube suspension, and then impregnated with sulfur by melt diffusion. Composites obtained in this way are physicochemically characterized by elemental analysis, X-ray diffractometry (XRD), electron microscopy and gas adsorption, showing a three dimensional macroporous graphene-based architecture in which sulfur is homogeneously distributed. The performance of self-standing composites with sulfur loadings over 4.0 mg cm is evaluated as binder-free positive electrodes for Lithium-Sulfur (Li-S) batteries. Results show that the incorporation of just 2 wt.% of CNTs significantly improves both the specific capacity and capacity retention compared to the results shown by the CNT-free samples, and slightly improves the performance of thermally reduced samples. More importantly, reversible specific capacity values over 500 mAh g at a rate of 0.1C after 100 charge/discharge cycles are obtained for either thermally reduced and CNT containing samples, which in terms of areal capacity correspond to values over 2.0 mAh cm .
Lithium–sulfur (Li–S) batteries have attracted much attention in the field of electrochemical energy storage due to their high energy density and low cost. However, the “shuttle effect” of the sulfur cathode, resulting in poor cyclic performance, is a big barrier for the development of Li–S batteries. Herein, a novel sulfur cathode integrating sulfur, flexible carbon cloth, and metal–organic framework (MOF)‐derived N‐doped carbon nanoarrays with embedded CoP (CC@CoP/C) is designed. These unique flexible nanoarrays with embedded polar CoP nanoparticles not only offer enough voids for volume expansion to maintain the structural stability during the electrochemical process, but also promote the physical encapsulation and chemical entrapment of all sulfur species. Such designed CC@CoP/C cathodes with synergistic confinement (physical adsorption and chemical interactions) for soluble intermediate lithium polysulfides possess high sulfur loadings (as high as 4.17 mg cm–2) and exhibit large specific capacities at different C‐rates. Specially, an outstanding long‐term cycling performance can be reached. For example, an ultralow decay of 0.016% per cycle during the whole 600 cycles at a high current density of 2C is displayed. The current work provides a promising design strategy for high‐energy‐density Li–S batteries. A flexible sulfur cathode integrating sulfur, flexible carbon cloth, and N‐doped carbon nanoarrays with embedded CoP is successfully designed. Due to the artful structure and synergistic confinement for soluble lithium polysulfides, it displays an outstanding long‐term cycling performance and an ultralow decay of 0.016% per cycle during the whole 600 cycles at 2C.
Room‐temperature sodium–sulfur (RT‐Na/S) batteries hold significant promise for large‐scale application because of low cost of both sodium and sulfur. However, the dissolution of polysulfides into the electrolyte limits practical application. Now, the design and testing of a new class of sulfur hosts as transition‐metal (Fe, Cu, and Ni) nanoclusters (ca. 1.2 nm) wreathed on hollow carbon nanospheres (S@M‐HC) for RT‐Na/S batteries is reported. A chemical couple between the metal nanoclusters and sulfur is hypothesized to assist in immobilization of sulfur and to enhance conductivity and activity. S@Fe‐HC exhibited an unprecedented reversible capacity of 394 mAh g−1 despite 1000 cycles at 100 mA g−1, together with a rate capability of 220 mAh g−1 at a high current density of 5 A g−1. DFT calculations underscore that these metal nanoclusters serve as electrocatalysts to rapidly reduce Na2S4 into short‐chain sulfides and thereby obviate the shuttle effect. Enhancing sulfur: Transition‐metal nanoclusters (ca. 1.2 nm) wreathed on hollow carbon nanospheres as S hosts were applied to enhance conductivity and activity of sulfur. These nanoclusters chemisorb the resultant polysulfide and electrocatalyze these into short‐chain sulfides, thus achieving excellent cycling stability and rate performance for room‐temperature sodium–sulfur batteries.
•Flower-like MoS2/CNTs-S composites with mesoporous structures for Li–S batteries were prepared.•The flower-like MoS2 NPs act as hosts of sulfur and have strong affinity toward polysulfides.•The MoS2/CNTs-S cathode exhibits a high reversible capacity of 855.5 mA h g−1 with 88.0% sulfur utilization. Lithium–sulfur (Li–S) batteries have attracted an increasing attention for advanced energy storage devices, because of their high energy density, low cost and lower environmental impacts. However, their commercial applications are still hampered with the low conductivity and sulfur utilization, the low sulfur loading and the serious capacity fading at a high current rate. Herein, we prepared flower-like molybdenum disulfide and carbon nanotubes (MoS2/CNTs) composites with mesoporous structures for high sulfur utilization cathodes. The flower-like MoS2 can immobilize sulfur and obstruct the solubility of polysulfide within the structures. The MoS2/CNTs-S cathode with 2.6 mg cm−2 sulfur loading and capacity per area of 3.83 mA h cm−2 delivers an initial specific discharge capacity of 1473 mA h g−1 with 88.0% sulfur utilization and maintains a reversible capacity of 855.5 mA h g−1 with coulombic efficiency up to 96.6% after 50 cycles at the current rate of 0.2 C (335.0 mA g−1). Impressively, the MoS2/CNTs-S cathode at 5 C shows the high specific capacity of 1254 mA h g−1 with 76.0% sulfur utilization and maintains 384.0 mA h g−1 with an average coulombic efficiency of 91% after 200 cycles. The MoS2/CNTs-S cathode could be a good candidate for high-performance Li–S battery.