Porous carbon nanotubes improved sulfur composite cathode for lithium-sulfur battery

Porous multi-walled carbon nanotubes (PCNTs) with multiple mesopores structure are synthesized through activation of multi-walled carbon nanotubes (MWCNTs) by potassium hydroxide. The potassium hydroxide activation process results in a significantly enhanced specific surface area with numerous small pores. The as-obtained PCNTs are employed as the conductive matrix for sulfur in the sulfur cathode. Compared with the composite sulfur cathode based on the original MWCNTs, the sulfur-PCNTs cathode shows a significantly improved cycle performance and columbic efficiency. The reversible capacity is 530 mAh?g^?1 and columbic efficiency is 90 % after 100 cycles at a current density of 100 mA?g^?1. The improvement in the electrochemical performance for S-PCNT is mainly attributed to the enlarged surface area and the porous structure of the unique mesopores carbon nanotube host, which cannot only facilitate transport of electrons and Li⁺ ions, but also trap polysulfides, retard the shuttle effect during charge/discharge process.     

Enhanced cyclability of sulfur cathodes in lithium-sulfur batteries with Na-alginate as a binder

Na-alginate as a binder in an aqueous solvent has been applied in the preparation of sulfur cathodes for lithium-sulfur batteries.Their electrochemical performances have been investigated by a charge-discharge cycle test and electrochemical impedance spectroscopy (EIS).The EIS tests indicated that the alginate sulfur cathode had lower resistance and better kinetic characteristics than those of the poly (vinylidene fluoride) (PVDF) sulfur cathode using PVDF as a binder in a N-methy-2-pyrrolidone (NMP) solvent.The charge-discharge tests showed that the discharge capacity and the capacity retention rate of Na-alginate sulfur cathode were 508 mAh·g-1and 65.4% at the 50th cycle with a current density of 335 mA·g-1.Compared with PVDF sulfur cathode,the alginate sulfur cathode showed a remarkably better cycle performance.These results show that the alginate binder has promising potential for lithium-sulfur battery applications.     

High capacity vertical aligned carbon nanotube/sulfur composite cathodes for lithium-sulfur batteries

Binder free vertical aligned (VA) CNT/sulfur composite electrodes with high sulfur loadings up to 70 wt% were synthesized delivering discharge capacities higher than 800 mAh g(-1) of the total composite electrode mass.     

Hybrid cathode materials for lithium-sulfur batteries

This review demonstrates the approaches to fabricate hybrid cathode materials for lithium-sulfur batteries. This short review does not claim to cover all recently published data; instead, an effort is aimed to show how the critical issues on carbon – sulfur hybrid are addressed based on selected articles in last couple of years. The influence of porous structure of carbon, the confinement effect of polysulfides in narrow micropores, and importance of hierarchical porosity are explained. Besides, the heteroatom doping on carbon in carbon–sulfur hybrids plays a vital role on improvement of bulk electronic conductivity of electrode. This review presents the twin polymerization strategy for direct preparation of nanoscale intermixed hybrid materials. Finally, the formation of sulfur containing copolymers by reacting sulfur melt with functional vinyl monomers are shown in this review with selected examples postulating the respective potential for future generation energy storage technology from the viewpoint of industrial applications.     

CNTs@S composite as cathode for all-solid-state lithium-sulfur batteries with ultralong cycle life

The main challenges in development of traditional liquid lithium-sulfur batteries are the shuttle effect at the cathode caused by the polysulfide and the safety concern at the Li metal anode arose from the dendrite formation. All-solid-state lithium-sulfur batteries have been proposed to solve the shuttle effect and prevent short circuits. However, solid-solid contacts between the electrodes and the electrolyte increase the interface resistance and stress/strain, which could result in the limited electrochemical performances.In this work, the cathode of all-solid-state lithium-sulfur batteries is prepared by depositing sulfur on the surface of the carbon nanotubes(CNTs@S) and further mixing with Li_(10) Ge P_2 S_(12) electrolyte and acetylene black agents. At 60 °C, CNTs@S electrode exhibits superior electrochemical performance, delivering the reversible discharge capacities of 1193.3, 959.5, 813.1, 569.6 and 395.5 m Ah g~(-1) at the rate of 0.1, 0.5,1, 2 and 5 C, respectively. Moreover, the CNTs@S is able to demonstrate superior high-rate capability of660.3 m Ah g~(-1) and cycling stability of 400 cycles at a high rate of 1.0 C. Such uniform distribution of the CNTs, S and Li_(10) Ge P_2 S_(12) electrolyte increase the electronic and ionic conductivity between the cathode and the electrolyte hence improves the rate performance and capacity retention.     

Hierarchical nanostructured composite cathode with carbon nanotubes as conductive scaffold for lithium-sulfur batteries

Carbon nanotubes (CNTs) are excellent scaffolds for advanced electrode materials, resulting from their intrinsic sp2 carbon hybridization, interconnected electron pathway, large aspect ratio, hierarchical porous structures, and low cost at a large-scale production. How to make full utilization of the mass produced CNTs as building blocks for nanocomposite electrodes is not well understood yet. Herein, a composite cathode containing commercial agglomerated multi-walled CNTs and S for Li-S battery was fabricated by a facile melt-diffusion strategy. The hierarchical CNT@S coaxial nanocables exhibited a discharging capacity of 1020 and 740 mAh g-1 at 0.5 and 2.0 C, respectively. A rapid capacity decay of 0.7% per cycle at the initial 10 cycles and a slow decay rate of 0.14% per cycle for the later 140 cycles were detected. Such hierarchical agglomerated CNT@S cathodes show advantages in easy fabrication, environmentally benign, low cost, excellent scalability, and good Li ion storage performance, which are extraordinary composites for high performance Li-S battery.     

Electrochemical evaluation of different graphene/sulfur composite synthesis routes in all-solid-state lithium-sulfur batteries

Journal of Solid State Electrochemistry - The preparation of different cathode composites with intimate contact between the components is of great importance to obtain batteries with better...     

Room temperature Na/S batteries with sulfur composite cathode materials

Sodium/sulfur (Na/S) batteries were assembled with a sodium metal anode, liquid electrolyte and a sulfur composite cathode. Their electrochemical characteristics have been investigated at room temperature. Their charge/discharge curves indicate that sodium can reversibly react with sulfur at room temperature. The specific capacity of the sulfur composite cathode material in the first cycle was initially about 655 mA h g⁻¹ and stayed at about 500 mA h g⁻¹ up to the 18th cycle with about 100% charge/discharge efficiency.     

Well-dispersed sulfur anchored on interconnected polypyrrole nanofiber network as high performance cathode for lithium-sulfur batteries

Preparation of novel sulfur/polypyrrole (S/PPy) composite consisting well-dispersed sulfur particles anchored on interconnected PPy nanowire network was demonstrated. In such hybrid structure, the as-prepared PPy clearly displays a three-dimensionally cross-linked and hierarchical porous structure, which was utilized in the composite cathode as a conductive network trapping soluble polysulfide intermediates and enhancing the overall electrochemical performance of the system. Benefiting from this unique structure, the S/PPy composite demonstrated excellent cycling stability, resulting in a discharge capacity of 931 mAh g⁻¹ at the second cycle and retained about 54% of this value over 100 cycles at 0.1 C. Furthermore, the S/PPy composite cathode exhibits a good rate capability with a discharge capacity of 584 mAh g⁻¹ at 1  C.     

Electrochemical performance of sulfur composite cathode materials for rechargeable lithium batteries

The structure and characteristic of carbon materials have a direct influence on the electrochemical performance of sulfur-carbon composite electrode materials for lithium-sulfur battery.In this paper,sulfur composite has been synthesized by heating a mixture of elemental sulfur and activated carbon,which is characterized as high specific surface area and microporous structure.The composite,contained 70%sulfur,as cathode in a lithium cell based on organic liquid electrolyte was tested at room temperature....     

In-situ polymerized cross-linked binder for cathode in lithium-sulfur batteries

Volume expansion and polysulfide shuttle effect are the main barriers for the commercialization of lithium-sulfur(Li-S) battery.In this work,we in-situ polymerized a cross-linked binder in sulfur cathode to solve the aforementioned problems using a facile method under mild conditions.Polycarbonate diol(PCDL),triethanolamine(TEA) and hexamethylene diisocyanate(HDI) were chosen as precursors to prepare the cross-linked binder.The in-situ polymerized binder(PTH) builds a strong network in sulfur cathode,which could restrain the volume expansion of sulfu r.Moreover,by adopting functional groups of oxygen atoms and nitrogen atoms,the binder could effectively facilitate transportation of Li-ion and adsorb polysulfide chemically.The Li-S battery with bare sulfur and carbon/sulfur composite cathodes and cross-linked PTH binder displays much better electrochemical performance than that of the battery with PVDF.The PTH-bare S cathode with a mass loading of 5.97 mg/cm^2 could deliver a capacity of 733.3 mAh/g at 0.2 C,and remained 585.5 mAh/g after 100 cycles.This in-situ polymerized binder is proved to be quite effective on restraining the volume expansion and suppressing polysulfide shuttle effect,then improving the electrochemical performance of Li-S battery.     

Confining sulfur in double-shelled hollow carbon spheres for lithium-sulfur batteries

Going into their shell: A novel carbon-sulfur nanocomposite has been synthesized by confining sulfur in double-shelled "soft" carbon hollow spheres with high surface area and porosity. This carbon-sulfur nanocomposite shows outstanding electrochemical performance when evaluated as a cathode material for lithium-sulfur batteries.     

Engineering the morphology/porosity of oxygen-doped carbon for sulfur host as lithium-sulfur batteries

Despite the intriguing merits of lithium-sulfur(Li-S)systems,they still suffer from the notoriousshuttling-effectof polysulfides.Herein,carbon materials with ...     

Core-shell meso/microporous carbon host for sulfur loading toward applications in lithium-sulfur batteries

Lithium-sulfur(Li-S) batteries belong to one of the promising technologies for high-energy-density rechargeable batteries.However,sulfur cathodes suffer from inherent problems of its poor electronic conductivity and the shuttling of highly dissoluble lithium polysulfides generated during the cycles.Loading sulfur into porous carbons has been proved to be an effective approach to alleviate these issues.Mesoporous and microporous carbons have been widely used for sulfur accommodation,but mesoporous carbons have poor sulfur confinement,whereas microporous carbons are impeded by low sulfur loading rates.Here,a core-shell carbon,combining both the merits of mesoporous carbon with large pore volume and microporous carbon with effective sulfur confinement,was prepared by coating the mesoporous CMK-3 with a microporous carbon(MPC) shell and served as the carbon host(CMK-3 @MPC) to accommodate sulfur.After sulfur infusion,the as-obtained S/(CMK-3@MPC) cathode delivered a high initial capacity of up to 1422 mAh·g~(-1) and sustained 654 mAh·g~(-1) reversible specific capacity after 36 cycles at 0.1 C.The good performance is ascribed to the unique core-shell structure of the CMK-3@MPC matrix,in which sulfur can be effectively confined within the meso/microporous carbon host,thus achieving simultaneously high electrochemical utilization.     

Facile synthesis and performance of polypyrrole-coated sulfur nanocomposite as cathode materials for lithium/sulfur batteries

In situ chemical oxidation polymerization of pyrrole on the surface of sulfur particles was carried out to synthesize a sulfur/polypyrrole （SIPPy） nanocomposite with core-shell structure. The composite was characterized by elemental analysis, X-ray diffraction, scanning/transmission electron microscopy, and electrochemical measurements. XRD and FTIR results showed that sulfur well dispersed in the core-shell structure and PPy structure was successfully obtained via in situ oxidative polymerization of pyrrole on the surface of sulfur particles. TEM observation revealed that PPy was formed and fixed to the surface of sulfur nanoparticle after polymerization, developing a well-defined core-shell structure and the thickness of PPy coating layer was in the range of 20-30 nm. In the composite, PPy worked as a conducting matrix as well as a coating agent, which confined the active materials within the electrode. Consequently, the as prepared SIPPy composite cathode exhibited good cycling and rate performances for rechargeable lithium/sulfur batteries. The resulting cell containing SIPPy composite cathode yields a discharge capacity of 1039 mAh·g^-1 at the initial cycle and retains 59% of this value over 50 cycles at 0.1 C rate. At 1 C rate, the SIPPy composite showed good cycle stability, and the discharge capacity was 475 mAh·g^-1 after 50 cycles.     

Regulation of carbon distribution to construct high-sulfur-content cathode in lithium-sulfur batteries

Lithium-sulfur(Li-S)battery is regarded as one of the most promising next-generation energy storage systems due to the ultra-high theoretical energy density of 2600 Wh kg^-1.To address the insulation nature of sulfur,nanocarbon composition is essential to afford acceptable cycling capacity but inevitably sacrifices the actual energy density under working conditions.Therefore,rational structural design of the carbon/sulfur composite cathode is of great significance to realize satisfactory electrochemical performances with limited carbon content.Herein,the cathode carbon distribution is rationally regulated to construct high-sulfur-content and high-performance Li-S batteries.Concretely,a double-layer carbon(DLC)cathode is prepared by fabricating a surface carbon layer on the carbon/sulfur composite.The surface carbon layer not only provides more electrochemically active surfaces,but also blocks the polysulfide shuttle.Consequently,the DLC configuration with an increased sulfur content by nearly 10 wt%renders an initial areal capacity of 3.40 mAh cm^-2 and capacity retention of 83.8%during 50 cycles,which is about two times than that of the low-sulfur-content cathode.The strategy of carbon distribution regulation affords an effective pathway to construct advanced high-sulfur-content cathodes for practical high-energy-density Li-S batteries.     

Concrete-like high sulfur content cathodes with enhanced electrochemical performance for lithium-sulfur batteries

Nowadays,lithium-sulfur batteries have attracted numerous attention due to their high specific capacity,high energy density,low cost and environmental benignancy.However,there are some critical challenges to be overcome such as low electronic conductivity and capacity fading caused by shuttle effect.Many attempts have been conducted to improve the electrochemical performance by designing effective sulfur hosts.In this paper,we synthesize a concrete-like sulfur/carbon cathode with high sulfur content(84%)by using 3D macroporous hosts with high pore volume.Sophisticated strategies of using polarized carbon framework and polymer coating are applied to synergistically control the dissolution of polysulfides so that the capacity retention and high rate performance can be remarkably enhanced.As a result,the composite exhibits a specific discharge capacity of 820 mAhg~(-1)at a discharge current of 800 mAg~(-1)(approximate to 0.5 C)after 100 cycles,calculated on the integrated mass of composite,which is superior to most report results.