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Developing appropriate sulfur cathode materials in carbonate‐based electrolyte is an important research subject for lithium‐sulfur batteries. Although several microporous carbon materials as host for sulfur reveal the effect, methods for producing microporous carbon are neither easy nor well controllable. Moreover, due to the complexity and limitation of microporous carbon in their fabrication process, there has been rare investigation of influence on electrochemical behavior in the carbonate‐based electrolyte for lithium‐sulfur batteries by tuning different micropore size(0–2 nm) of carbon host. Here, we demonstrate an immediate carbonization process, self‐activation strategy, which can produce microporous carbon for a sulfur host from alkali‐complexes. Besides, by changing different alkali‐ion in the previous complex, the obtained microporous carbon exhibits a major portion of ultramicropore (<0.7 nm, from 54.9% to 25.8%) and it is demonstrated that the micropore structure of the host material plays a vital role in confining sulfur molecule. When evaluated as cathode materials in a carbonate‐based electrolyte for Li‐S batteries, such microporous carbon/sulfur composite can provide high reversible capacity, cycling stability and good rate capability.  相似文献   

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Ti3C2Tx, a typical representative among the emerging family of 2D layered transition metal carbides and/or nitrides referred to as MXenes, has exhibited multiple advantages including metallic conductivity, a plastic layer structure, small band gaps, and the hydrophilic nature of its functionalized surface. As a result, this 2D material is intensively investigated for application in the energy storage field. The composition, morphology and texture, surface chemistry, and structural configuration of Ti3C2Tx directly influence its electrochemical performance, e.g., the use of a well‐designed 2D Ti3C2Tx as a rechargeable battery anode has significantly enhanced battery performance by providing more chemically active interfaces, shortened ion‐diffusion lengths, and improved in‐plane carrier/charge‐transport kinetics. Some recent progresses of Ti3C2Tx MXene are achieved in energy storage. This Review summarizes recent advances in the synthesis and electrochemical energy storage applications of Ti3C2Tx MXene including supercapacitors, lithium‐ion batteries, sodium‐ion batteries, and lithium–sulfur batteries. The current opportunities and future challenges of Ti3C2Tx MXene are addressed for energy‐storage devices. This Review seeks to provide a rational and in‐depth understanding of the relation between the electrochemical performance and the nanostructural/chemical composition of Ti3C2Tx, which will promote the further development of 2D MXenes in energy‐storage applications.  相似文献   

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Lithium–sulfur (Li–S) batteries have been intensively concerned to fulfill the urgent demands of high capacity energy storage. One of the major unsolved issues is the complex diffusion of lithium polysulfide intermediates, which in combination with the subsequent paradox reactions is known as the shuttle effect. Nanocarbon with homogeneous nonpolar surface served as scaffolding materials in sulfur cathode basically cannot afford a sufficient binding and confining effect to maintain lithium polysulfides within the cathode. Herein, a systematical density functional theory calculation of various heteroatoms‐doped nanocarbon materials is conducted to elaborate the mechanism and guide the future screening and rational design of Li–S cathode for better performance. It is proved that the chemical modification using N or O dopant significantly enhances the interaction between the carbon hosts and the polysulfide guests via dipole–dipole electrostatic interaction and thereby effectively prevents shuttle of polysulfides, allowing high capacity and high coulombic efficiency. By contrast, the introduction of B, F, S, P, and Cl monodopants into carbon matrix is unsatisfactory. To achieve the strong‐couple effect toward Li2Sx, the principles for rational design of doped carbon scaffolds in Li–S batteries to achieve a strong electrostatic dipole–dipole interaction are proposed. An implicit volcano plot is obtained to describe the dependence of binding energies on electronegativity of dopants. Moreover, the codoping strategy is predicted to achieve even stronger interfacial interaction to trap lithium polysulfides.  相似文献   

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The sulfur content in carbon–sulfur hybrid using the melt‐diffusion method is normally lower than 70 wt%, which greatly decreases the energy density of the cathode in lithium–sulfur (Li‐S) batteries. Here, a scalable method inspired by the commercialized production of Na2S is used to prepare a hierarchical porous carbon–sulfur hybrid (denoted HPC‐S) with high sulfur content (≈85 wt%). The HPC‐S is characterized by the structure of sulfur nanodots naturally embedded in a 3D carbon network. The strategy uses Na2SO4 as the starting material, which serves not only as the sulfur precursor but also as a salt template for the formation of the 3D carbon network. The HPC‐S cathode with such a high sulfur content shows excellent rate performance and cycling stability in Li–S batteries because of the sulfur nanoparticles, the unique carbon framework, and the strong interaction between them. The production method can also be readily scaled up and used in practical Li–S battery applications.  相似文献   

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Lithium–sulfur (Li–S) batteries are considered as a substitute for conventional batteries as they are the most promising next‐generation energy‐storage system due to their high energy densities. However, their short cycling life, limited sulfur loading, severe polysulfide shuttling, and low sulfur utilization critically impede grid‐level‐storage energy techniques in Li–S batteries. The lithium shuttle effect results in rapid capacity fading and battery failure. The design and fabrication of sulfur hosts are key points to eliminate the aforementioned issues, especially the shuttle effect. In the past decade, spatial encapsulation and chemical interaction have improved the adsorption capacity of lithium polysulfides for the sulfur hosts and thus prolonged the lifetime of Li–S batteries. In an attempt to promote future research on the sulfur cathode and foster breakthroughs in Li–S batteries, recent achievements are highlighted, mechanical insights are discussed, and the remaining challenges and future research directions in the innovation of sulfur cathodes are identified.  相似文献   

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Lithium–sulfur (Li–S) batteries have arousing interest because of their high theoretical energy density. However, they often suffer from sluggish conversion of lithium polysulfides (LiPS) during the charge/discharge process. Single nickel (Ni) atoms on nitrogen‐doped graphene (Ni@NG) with Ni–N4 structure are prepared and introduced to modify the separators of Li–S batteries. The oxidized Ni sites of the Ni–N4 structure act as polysulfide traps, efficiently accommodating polysulfide ion electrons by forming strong Sx 2????Ni? N bonding. Additionally, charge transfer between the LiPS and oxidized Ni sites endows the LiPS on Ni@NG with low free energy and decomposition energy barrier in an electrochemical process, accelerating the kinetic conversion of LiPS during the charge/discharge process. Furthermore, the large binding energy of LiPS on Ni@NG also shows its ability to immobilize the LiPS and further suppresses the undesirable shuttle effect. Therefore, a Li–S battery based on a Ni@NG modified separator exhibits excellent rate performance and stable cycling life with only 0.06% capacity decay per cycle. It affords fresh insights for developing single‐atom catalysts to accelerate the kinetic conversion of LiPS for highly stable Li–S batteries.  相似文献   

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To suppress the shuttle effect and improve the sulfur utilization in lithium–sulfur battery, a novel hollow carbon nitride‐based spheres material (HCNx ) has been synthesized via polymerization of ethylenediamine and carbon tetrachloride on silica spheres and used as a sulfur host. The rational designed structure of HCNx retards diffusion of lithium polysulfides by both chemisorption and physical confinement. The enhanced conductivity of HCNx improves the utilization of the sulfur. As a result, the S/HCNx exhibits a discharge capacity of 579 mA h g−1 after 500 cycles with a fade rate of 0.076% per cycle at 0.5 C. Even at 2 C, the S/HCNx cathode still exhibits a reversible discharge capacity of 658 mA h g−1.  相似文献   

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Lithium–sulfur (Li‐S) batteries have been considered as a promising next‐generation energy storage system. However, practical application of Li‐S batteries is hindered by the nonconductive nature of sulfur (S) and continuous capacity fading during cycling. Here, a simple but effective strategy is proposed to fabricate high‐performance Li‐S batteries by in situ polymerization of polyaniline (PANi)/S/carbon nanofiber (CNF) cathode. Compared to traditional carbon black/S cathodes and other cathode materials with PANi polymer, this effective three‐dimensional (3D) cathode design has several advantages: (i) the interconnected and highly conductive CNF/PANi network structure facilitates the electron transfer between the insulating S and conductive CNF mat; (ii) the CNF/PANi network structure, with abundant oxygen and nitrogen heteroatoms, offers strong adsorption for the polysulfides; (iii) the 3D architecture of CNF/S/PANi helps accommodate the volume change of S during cycling and maintain the structural integrity of the cathode; (iv) the easy and simple fabrication process minimizes the time and energy costs; and (v) the freestanding composite cathode without additional polymer binder contributes to higher energy density of Li‐S batteries. With all the advantages mentioned above, Li‐S cells present a high S utilization with stable cycling performance for over 300 cycles with a low capacity decay rate of 0.08% cycle−1.  相似文献   

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A multifunctional interlayer, composed of molybdenum diphosphide (MoP2) nanoparticles and a carbon nanotube (CNT) film, is introduced into a lithium–sulfur (Li–S) battery system to suppress polysulfide migration. Molybdenum diphosphide acts as the catalyst and can capture polysulfides and improve the polysulfide conversion activity during the discharge/charge processes. The CNT film acts as a conductive skeleton to support the MoP2 nanoparticles and to ensure their uniform distribution. The CNT film physically hinders polysulfide migration, acts as a current collector, and provides abundant electron pathways. The Li–S battery containing the multifunctional MoP2/CNT interlayer exhibits excellent electrochemical performance. It delivers a reversible specific capacity of 905 mA h g?1 over 100 cycles at 0.2 C, with a capacity decay of 0.152% per cycle. These results suggest the introduction of the multifunctional CNT/MoP2 interlayer as an effective and practical method for producing high‐performance Li–S batteries.  相似文献   

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The Li–air battery represents a promising power candidate for future electronics due to its extremely high energy density. However, the use of Li–air batteries is largely limited by their poor cyclability in ambient air. Herein, Li–air batteries with ultralong 610 cycles in ambient air are created by combination of low‐density polyethylene film that prevents water erosion and gel electrolyte that contains a redox mediator of LiI. The low‐density polyethylene film can restrain the side reactions of the discharge product of Li2O2 to Li2CO3 in ambient air, while the LiI can facilitate the electrochemical decomposition of Li2O2 during charging, which improves the reversibility of the Li–air battery. All the components of the Li–air battery are flexible, which is particularly desirable for portable and wearable electronic devices.  相似文献   

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Owing to the high theoretical specific capacity (1675 mA h g?1) and low cost, lithium–sulfur (Li–S) batteries offer advantages for next‐generation energy storage. However, the polysulfide dissolution and low electronic conductivity of sulfur cathodes limit the practical application of Li–S batteries. To address such issues, well‐designed yolk–shelled carbon@Fe3O4 (YSC@Fe3O4) nanoboxes as highly efficient sulfur hosts for Li–S batteries are reported here. With both physical entrapment by carbon shells and strong chemical interaction with Fe3O4 cores, this unique architecture immobilizes the active material and inhibits diffusion of the polysulfide intermediates. Moreover, due to their high conductivity, the carbon shells and the polar Fe3O4 cores facilitate fast electron/ion transport and promote continuous reactivation of the active material during the charge/discharge process, resulting in improved electrochemical utilization and reversibility. With these merits, the S/YSC@Fe3O4 cathodes support high sulfur content (80 wt%) and loading (5.5 mg cm?2) and deliver high specific capacity, excellent rate capacity, and long cycling stability. This work provides a new perspective to design a carbon/metal‐oxide‐based yolk–shelled framework as a high sulfur‐loading host for advanced Li–S batteries with superior electrochemical properties.  相似文献   

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