Construction of strong built-in electric field in binary metal sulfide heterojunction to propel high-loading lithium-sulfur batteries

The practical application of lithium-sulfur(Li-S)batteries is greatly hindered by soluble polysulfides shuttling and sluggish sulfur redox kinetics.Rational design of multifunctional hybrid materials with superior electronic conductivity and high electrocatalytic activity,e.g.,heterostructures,is a promising strategy to solve the above obstacles.Herein,a binary metal sulfide MnS-MoS_(2) heterojunction electrocatalyst is first designed for the construction of high-sulfur-loaded and durable Li-S batteries.The MnS-MoS_(2) p-n heterojunction shows a unique structure of MoS_(2) nanosheets decorated with ample MnS nanodots,which contributes to the formation of a strong built-in electric field at the two-phase interface.The MnS-MoS_(2) hybrid host shows strong soluble polysulfide affinity,enhanced electronic conductivity,and exceptional catalytic effect on sulfur reduction.Benefiting from the synergistic effect,the as-derived S/MnS-MoS_(2) cathode delivers a superb rate capability(643 m A h g^(-1)at 6 C)and a durable cyclability(0.048%decay per cycle over 1000 cycles).More impressively,an areal capacity of 9.9 m A h cm^(-2)can be achieved even under an extremely high sulfur loading of 14.7 mg cm^(-2)and a low electrolyte to sulfur ratio of 2.9μL mg^(-1).This work provides an in-depth understanding of the interfacial catalytic effect of binary metal compound heterojunctions on sulfur reaction kinetics.

High sulfur loading and shuttle inhibition of advanced sulfur cathode enabled by graphene network skin and N,P,F-doped mesoporous carbon interfaces for ultra-stable lithium sulfur battery

Achieving high loading of active sulfur yet rational regulating the shuttle effect of lithium polysulfide(LiPS)is of great significance in pursuit of high-performance lithium-sulfur(Li-S)battery.Herein,we develop a free-standing graphene nitrogen(N),phosphorus(P)and fluorine(F)co-doped mesoporous carbon-sulfur(G-NPFMC-S)film,which was used as a binder-free cathode in Li-S battery.The developed mesoporous carbon(MC)achieved a high specific surface area of 921 m^(2)·g^(-1)with a uniform pore size distribution of 15 nm.The inserted graphene network inside G-NPFMC-S cathode can effectively improve its electrical conductivity and simultaneously restrict the shuttle of LiPS.A high sulfur loading of 86%was achieved due to the excellent porous structures of graphene-NPFMC(G-NPFMC)composite.When implemented as a freestanding cathode in Li-S battery,this G-NPFMC-S achieved a high specific capacity(1,356 mAh·g^(-1)),favorable rate capability,and long-term cycling stability up to 500 cycles with a minimum capacity fading rate of 0.025%per cycle,outperforming the corresponding performances of NPFMC-sulfur(NPFMC-S)and MC-sulfur(MC-S).These promising results can be ascribed to the featured structures that formed inside G-NPFMC-S film,as that highly porous NPFMC can provide sufficient storage space for the loading of sulfur,while,the N,P,F-doped carbonic interface and the inserted graphene network help hinder the shuttle of LiPS via chemical adsorption and physical barrier effect.This proposed unique structure can provide a bright prospect in that high mass loading of active sulfur and restriction the shuttle of LiPS can be simultaneously achieved for Li-S battery.

Metal-free two-dimensional phosphorene-based electrocatalyst with covalent P-N heterointerfacial reconstruction for electrolyte-lean lithium-sulfur batteries

The use of lithium-sulfur batteries under high sulfur loading and low electrolyte concentrations is severely restricted by the detrimental shuttling behavior of polysulfides and the sluggish kinetics in redox processes.Two-dimensional(2D)few layered black phosphorus with fully exposed atoms and high sulfur affinity can be potential lithium-sulfur battery electrocatalysts,which,however,have limitations of restricted catalytic activity and poor electrochemical/chemical stability.To resolve these issues,we developed a multifunctional metal-free catalyst by covalently bonding few layered black phosphorus nanosheets with nitrogen-doped carbon-coated multiwalled carbon nanotubes(denoted c-FBP-NC).The experimental characterizations and theoretical calculations show that the formed polarized P-N covalent bonds in c-FBP-NC can efficiently regulate electron transfer from NC to FBP and significantly promote the capture and catalysis of lithium polysulfides,thus alleviating the shuttle effect.Meanwhile,the robust 1D-2D interwoven structure with large surface area and high porosity allows strong physical confinement and fast mass transfer.Impressively,with c-FBP-NC as the sulfur host,the battery shows a high areal capacity of 7.69 mAh cm^(−2) under high sulfur loading of 8.74 mg cm^(−2) and a low electrolyte/sulfur ratio of 5.7μL mg^(−1).Moreover,the assembled pouch cell with sulfur loading of 4 mg cm^(−2) and an electrolyte/sulfur ratio of 3.5μL mg^(−1) shows good rate capability and outstanding cyclability.This work proposes an interfacial and electronic structure engineering strategy for fast and durable sulfur electrochemistry,demonstrating great potential in lithium-sulfur batteries.

Towards full demonstration of high areal loading sulfur cathode in lithium–sulfur batteries

Lithium–sulfur(Li–S)batteries have been recognized as promising substitutes for current energy-storage technologies owing to their exceptional advantages in very high-energy density and excellent material sustainability.The cathode with high sulfur areal loading is vital for the practical applications of Li–S batteries with very high energy density.However,the high sulfur loading in an electrode results in poor rate and cycling performances of batteries in most cases.Herein,we used diameters of 5.0(D5)and 13.0(D13)mm to probe the effect of electrodes with different sizes on the rate and cycling performances under a high sulfur loading(4.5 mg cm^-2).The cell with D5 sulfur cathode exhibits better rate and cycling performances comparing with a large(D13)cathode.Both the high concentration of lithium polysulfides and corrosion of lithium metal anode impede rapid kinetics of sulfur redox reactions,which results in inferior battery performance of the Li–S cell with large diameter cathode.This work highlights the importance of rational matching of the large sulfur cathode with a high areal sulfur loading,carbon modified separators,organic electrolyte,and Li metal anode in a pouch cell,wherein the sulfur redox kinetics and lithium metal protection should be carefully considered under the flooded lithium polysulfide conditions in a working Li–S battery.

Emerging catalytic materials for practical lithium-sulfur batteries

High-energy lithium-sulfur batteries(LSBs)have experienced relentless development over the past decade with discernible improvements in electrochemical performance.However,a scrutinization of the cell operation conditions reveals a huge gap between the demands for practical batteries and those in the literature.Low sulfur loading,a high electrolyte/sulfur(E/S)ratio and excess anodes for lab-scale LSBs significantly offset their high-energy merit.To approach practical LSBs,high loading and lean electrolyte parameters are needed,which involve budding challenges of slow charge transfer,polysulfide precipitation and severe shuttle effects.To track these obstacles,the exploration of electrocatalysts to immobilize polysulfides and accelerate Li-S redox kinetics has been widely reported.Herein,this review aims to survey state-of-the-art catalytic materials for practical LSBs with emphasis on elucidating the correlation among catalyst design strategies,material structures and electrochemical performance.We also statistically evaluate the state-of-the-art catalyst-modified LSBs to identify the remaining discrepancy between the current advancements and the real-world requirements.In closing,we put forward our proposal for a catalytic material study to help realize practical LSBs.

Comprehensive Design of the High-Sulfur-Loading Li–S Battery Based on MXene Nanosheets

The lithium-sulfur battery is the subject of much recent attention due to the high theoretical energy density,but practical applications are challenged by fast decay owing to polysulfide shuttle and electrode architecture degradation.A comprehensive study of the sulfur host microstructure design and the cell architecture construction based on the MXene phase(Ti3C2Tx nanosheets) is performed,aiming at realize stable cycling performance of Li-S battery with high sulfur areal loading.The interwoven KB@Ti3C2Tx composite formed by self-assembly of MXene and Ktej en black,not only provides superior conductivity and maintains the electrode integrality bearing the volume expansion/shrinkage when used as the sulfur host,but also functions as an interlayer on separator to further retard the polysulfide cross-diffusion that possibly escaped from the cathode.The KB@Ti3C2Tx interlayer is only 0.28 mg cm-2 in areal loading and 3 μm in thickness,which accounts a little contribution to the thick sulfur electrode;thus,the impacts on the energy density is minimal.By coupling the robust KB@Ti3C2Tx cathode and the effective KB@Ti3C2Tx modified separator,a stable Li-S battery with high sulfur areal loading(5.6 mg cm-2) and high areal capacity(6.4 mAh cm-2) at relatively lean electrolyte is achieved.

Separator coatings as efficient physical and chemical hosts of polysulfides for high-sulfur-loaded rechargeable lithium–sulfur batteries

Lithium-sulfur batteries(LSBs)are promising alternative energy storage devices to the commercial lithium-ion batteries.However,the LSBs have several limitations including the low electronic conductivity of sulfur(5×10^-30S cm^-1),associated lithium polysulfides(PSs),and their migration from the cathode to the anode.In this study,a separator coated with a Ketjen black(KB)/Nafion composite was used in an LSB with a sulfur loading up to 7.88 mg cm^-2to mitigate the PS migration.A minimum specific capacity(Cs)loss of 0.06%was obtained at 0.2 C-rate at a high sulfur loading of 4.39 mg cm^-2.Furthermore,an initial areal capacity up to 6.70 mAh cm^-2 was obtained at a sulfur loading of 7.88 mg cm^-2.The low Cs loss and high areal capacity associated with the high sulfur loading are attributed to the large surface area of the KB and sulfonate group(SO3^-)of Nafion,respectively,which could physically and chemically trap the PSs.

Critical load of sulfur deposition for ecosystemand its application in China

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Acid deposition critical loads modeling for the simulation of sulfur exceedance and reduction in Guangdong, China

The current acid deposition critical loads in Guangdong, China were calculated using the PROFILE model with a 3 km × 3 km resolution. Calculations were carded out for critical loads of potential acidity, actual acidity, sulfur and nitrogen, with values in extents of 0-3.5, 0-14.0, 0-26.0 and 0-3.5 kmol/（hrnE.year）, respectively. These values were comparable to previously reported results and reflected the influences of vegetation and soil characteristics on the soil acid buffering capacity. Simulations of SO2 emission and sulfur deposition in this study showed that sulfur deposition core areas mirrored SO2 emission centers. The prediction of sulfur deposition after 20% and 40% reduction of SO2 emission suggested that the reduction of area sources contributed greatly to the decrease of sulfur deposition. Thus, abatement of area source emissions could be the primary way to mitigate sulfur deposition in Guangdong to meet both the provincial and national regulations of air pollution control.

Synthesis of glycerin triacetate over molding zirconia-loaded sulfuric acid catalyst

Zirconia-loaded sulfuric acid （SO2-/ZrO2） catalysts were prepared by impregnation method, molded by punch tablet machine and characterized by X-ray diffraction. SO4^2-/ZrO2 catalyst was used to obtain glycerol triacetate （GTA） directly from glycerin. The effect of some factors, such as different temperatures of calcination and catalysts molded or not, on the reusable times of catalysts and the yield of GTA were investigated. The optimum reaction conditions were shown as follows： the reaction temperature was 403 K; the reaction time continued for 8 h; the amount of molded catalysts was 5 wt% of glycerin and the molar ratio of glycerin to acetic acid was 1 ： 8. The yield of GTA was 97.93% under the optimum condition.

高载量锂硫电池正极设计优化

高载量硫正极是研发高能量密度锂硫电池的必要先决条件。然而,硫载量的提高不可避免地会引起正极导电性不良、多硫化物转化动力学缓慢,穿梭效应加剧等问题。本文从化学工程的角度出发,重点关注高载量硫正极中的传质和反应过程,综述了性能优良的高载量锂硫电池正极设计思路。具体而言,从增强电子传导、改善锂离子传质、优化反应动力学、抑制多硫化物穿梭这四种研究思路出发,对比了不同优化策略之间的优劣性,并提出下一代高硫载量硫正极设计的探索方向。分析表明,基于吸附-催化双重功能的三维高导电正极具有巨大发展前景。从应用层面考虑,本文还关注了高载量正极设计中常被忽视的安全性问题,探讨了削弱正极诱导并从源头降低热失效风险的可行性,旨在为研究人员优化高载量(≥4mg/cm^(2))正极设计方案时提供实用指导。

气负荷变化对天然气净化工艺及经济性的影响研究分析

天然气净化装置气负荷变化对装置运行的稳定性和天然气处理成本具有重要的影响。对川西北气矿两个气源气质相似的天然气净化厂的气负荷变化对装置运行的影响及经济性进行研究分析。结果表明:120%超负荷运行的A厂装置运行工艺参数与设计参数偏差不大,装置能够稳定运行,尾气SO_(2)排放浓度稳定且低于国家标准,天然气处理成本为0.014元/m^(3);B厂受气藏储量影响,气负荷持续走低,装置运行稳定性降低,导致尾气SO_(2)排放出现超标情况,装置运行能耗增加,天然气处理成本达到0.092元/m^(3),是A厂处理成本的6.6倍,天然气净化的经济性显著降低。

In situ sulfur-doped graphene nanofiber network as efficient metal-free electrocatalyst for polysulfides redox reactions in lithium–sulfur batteries

The major challenge for realistic application of Li-S batteries lies in the great difficulty in breaking through the obstacles of the sluggish kinetics and polysulfides shuttle of the sulfur cathode at high sulfur loading for continuously high sulfur utilization during prolonged charge-discharge cycles.Here we demonstrate that large percentage of sulfur can be effectively incorporated within a three-dimensional(3D)nanofiber network of high quality graphene from chemical vapor deposition(CVD),through a simple ball-milling process.While high quality graphene network provided continuous and durable channels to enable efficient transport of lithium ions and electrons,the in-situ sulfur doping from the alloying effect of ball milling facilitated desirable affinity with entire sulfur species to prevent sulfur loss and highly active sites to propel sulfur redox reactions over cycling.This resulted in remarkable rate-performance and excellent cycling stability,together with large areal capacity at very high sulfur mass loading(Specific capacity over 666 mAh g-1after 300 cycles at 0.5 C,and areal capacity above 5.2 mAh cm-2at 0.2C at sulfur loading of 8.0 mg cm-2 and electrolyte/sulfur(E/S)ratio of 8μL mg-1;and high reversible areal capacities of 13.1 m Ah cm-2 at a sulfur load of 15 mg cm-2 and E/S of 5μL mg-1).

A strategy to achieve high loading and high energy density Li-S batteries

Lithium-sulfur(Li-S) batteries are one of the most promising rechargeable storage devices due to the high theoretical energy density.However,the low areal sulfur loading impedes their commercial development.Herein,a 3 D free-standing sulfur cathode scaffold is rationally designed and fabricated by coaxially coating polar Ti_3 C_2 T_x flakes on sulfur-impregnated carbon cloth(Ti_3 C_2 T_x@S/CC) to achieve high loading and high energy density Li-S batteries,in which,the flexible CC substrate with highly porous structure can accommodate large amounts of sulfur and ensure fast electron transfer,while the outer-coated Ti_3 C_2 T_x can serve as a polar and conductive protective layer to further promote the conductivity of the whole electrode,achieve physical blocking and chemical anchoring of lithium-polysulfides as well as catalyze their conversion.Due to these advantages,at a sulfur loading of 4 mg cm^(-2),Li-S cells with Ti_3 C_2 T_x@S/CC cathodes can deliver outstanding cycling stability(746.1 mAh g^(-1) after 200 cycles at1 C),superb rate performance(866.8 mAh g^(-1) up to 2 C) and a high specific energy density(564.2 Wh kg^(-1) after 100 cycles at 0.5 C).More significantly,they also show the commercial potential that can compete with current lithium-ion batteries due to the high areal capacity of 6.7 mAh cm^(-2) at the increased loading of 8 mg cm^(-2).

Characteristics of a gold-doped electrode for application in high-performance lithium-sulfur battery

Bulk sulfur incorporating 3 wt% gold nano-powder is investigated as possible candidate to maximize the fraction of active material in the Li-S battery cathode.The material is prepared via simple mixing of gold with molten sulfur at 120℃,quenching at room temperature,and grinding.Our comprehensive study reports relevant electrochemical data,advanced X-ray computed tomography(CT)imaging of the positive and negative electrodes,and a thorough structural and morphological characterization of the S:Au 97:3 w/w composite.This cathode exhibits high rate capability within the range from C/10 to 1C,a maximum capacity above 1300 mAh gs^(-1),and capacity retention between 85%and 91%after 100 cycles at 1C and C/3 rates.The novel formulation enables a sulfur fraction in the composite cathode film as high as 78 wt%,an active material loading of 5.7 mg cm^(-2),and an electrolyte/sulfur(E/S)ratio of 5μL mg^(-1),which lead to a maximum areal capacity of 5.4 mAh cm^(-2).X-ray CT at the micro-and nanoscale reveals the microstructural features of the positive electrode that favor fast conversion kinetics in the battery.Quantitative analysis of sulfur distribution in the porous cathode displays that electrodeposition during the initial cycle may trigger an activation process in the cell leading to improved performance.Furthermore,the tomography study reveals the characteristics of the lithium anode and the cell separator upon a galvanostatic test prolonged over 300 cycles at a 2C rate.

Synthesis of Highly Microporous Sulfur-Containing Activated Carbons by a Multistep Modification Process

The sulfur-containing activated carbons(SACs)were prepared by CO2 activation and sulfur impregnation.The sulfur-containing samples were then oxidized in air.The SACs were characterized by N2 adsorption,elemental analysis,thermogravimetric analysis,X-ray photoelectron spectroscopy,Raman spectroscopy,and X-ray diffraction.The CO2 activation provided precursor carbons with high porosity,which in turn were sulfurized effectively.Oxidation in air at 200℃enlarged pores and redistributed amorphous sulfur in the hierarchical pores.A typical SAC containing 17.89%sulfur exhibited a surface area of 1464 m2/g.This work may open up a valid route to prepare highly microporous SACs with high sulfur loading for applications where the presence of sulfur is beneficial.

高炉水冲渣过程中硫化物排放计算分析

高炉炉料中的硫元素约85%随炉渣排出,对高炉水冲渣过程中的硫化物排放进行了计算分析。计算结果表明:①炉渣与水接触的0.3s内产生大量的H_(2)S和SO_(2),在随蒸汽及气溶胶外排至大气的过程中,有部分H_(2)S转化成SO_(2),温度较低时会生成H_(2)SO_(4);②当人炉硫负荷为4kg/t时,冲渣点烟窗处的硫化物排放如全部折算成SO_(2)为369.96mg/m^(3),如全部折算成H_(2)S为196.54mg/m^(3);③从某1500m^(3)高炉渣处理系统的实测结果来看,硫化物排放峰值高于理论计算值;④有部分H_(2)S和SO_(2)与Ca(OH)2反应生成CaSO_(4)·0.5H_(2)O和CaSO_(4)·2H_(2)O,并在循环过程中结晶析出,是造成滤层板结及管道堵塞的根本原因。

硫负载方式调控碳/硫复合材料结构及锂-硫电池性能研究

碳/硫(C/S)复合材料的硫负载方式调控可以改善聚硫化物的穿梭效应,提升锂-硫电池的容量。物理硫负载法容易导致循环过程中硫的脱落,化学硫负载法不利于倍率性能的提升。采用物理硫负载和化学硫负载相结合的方式,对提升C/S复合材料的循环稳定性和倍率性能具有重要意义。本文控制C/S复合材料的硫负载方式,研究化学硫负载制得的C/S复合材料在热处理前后的结构和性能变化,有利于实现稳定的聚硫化物转化,提升锂-硫电池循环稳定性和倍率性能。结果表明:C/S煅烧后复合电极具有较好的循环稳定性(5C下的容量保持率为60%)和倍率性能(60 mAh·g^(-1)20C),这是因为其具有稳定的聚硫化物转化能力。

一种智能环保硫磺装车系统设计

针对硫磺在装车时自卸车需要频繁进入硫磺堆场内部,车轮粘料而导致港区内污染和硫磺自燃的问题,给出一种智能环保硫磺装车系统设计方案。该系统能够智能检测自卸车位置,自动化程序控制装车皮带机启停及装车漏斗口开合,可通过后方料斗和皮带机直接将物料提升输送至场外自卸车内,实现硫磺装车自动化,可有效提升港区硫磺装车效率。

The role of functional materials to produce high areal capacity lithium sulfur battery

The lithium sulfur batteries(LSBs) are considered as one of the promising next generation energy storage devices due to the high theoretical specific capacity of sulfur(1675 m Ah g-1), naturally available, low cost.However, the practical LSBs are impeded by the well-known "shuttle effect" combined with other technical drawbacks. The "shuttle effect" causes rapid capacity decay, severe self-discharging and low active material utilization. The polysulfide(PS) which has lone pair electrons in each sulfur atom is considered as Lewis base and shows strong affinity to various polar, Lewis acid and catenation interactive materials but very weakly interacts with the non-polar conductive carbons. The "shuttle effect" occurs due to the diffusion of high order PS from the cathode to the anode and then low-order PS back to the cathode. The PS is polar and, due to a lone pair of electrons associated with the sulfur atom, is considered a Lewis base. As such, the PS shows a strong affinity with various polar and Lewis acid materials. In addition, a more novel trapping can be performance through a catenation reaction. For LSBs to compete with the state-of-the-art lithium ion batteries(LIBs), the LSB areal capacity need to be ~6 m Ah cm-2(which is proportional to sulfur loading). To achieve this target the PS shuttling needs to mitigate, which can be achieved through using functional materials. This review addresses the aforementioned phenomena by considering the PS phase interacts with the various functional materials and how this impacts areal capacity and cycling stability of LSBs.