Synthesis and application of single-atom catalysts in sulfur cathode for high-performance lithium–sulfur batteries

Lithium–sulfur(Li-S) batteries are regarded as one of the most promising energy storage devices because of their low cost, high energy density, and environmental friendliness. However, Li-S batteries suffer from sluggish reaction kinetics and serious “shuttle effect” of lithium polysulfides(LiPSs), which causes rapid decay of battery capacity and prevent their practical application. To address these problems, introducing single-atom catalysts(SACs) is an effective method to improve the electroch...     

锂硫电池正极材料的制备及工艺优化

锂硫电池具有能量密度高、价格低等优势,有希望应用于下一代储能领域. 但锂硫电池仍然存在一些问题,如多硫化物穿梭效应、缺乏有效的锂硫电池规模制备工艺等. 为了解决这些问题,作者以不同商用碳材料（乙炔黑、科琴黑与碳纳米管）和单质硫复合作为正极材料,探究正极制备工艺对多硫化物穿梭效应抑制效果及锂硫电池性能的影响. 通过研究,作者得出以下结论：科琴黑作为单质硫的载体,与单质硫球磨8 h后,匹配粘结剂聚乙烯吡咯烷酮（PVP）制备的正极浆料可实现在涂布和辊压后极片的厚度达到500 μm、压实密度达到991.65 mg·cm ^-3. 作者将最终得到的正极极片应用于高硫载量锂硫软包电池,电池首圈放电容量为137.4 mA·h,经过10圈循环后,放电容量为115.5 mA·h,表现出优异的电化学性能. 该碳硫复合正极材料制备工艺有望在锂硫电池的宏量制备中获得应用.     

Effect of cations in ionic liquids on the electrochemical performance of lithium-sulfur batteries

Lithium-sulfur(Li-S) battery is a promising choice for the next generation of high-energy rechargeable batteries, but its application is impeded by the high dissolution of the polysulfides in commonly used organic electrolyte. Room temperature ionic liquids(RTILs) have been considered as appealing candidates for the electrolytes in Li-S batteries. We investigated the effect of cations in RTILs on the electrochemical performance for Li-S batteries. Ex situ investigation of lithium anode for Li-S batteries indicates that during the discharge/charge process the RTIL with N-methyl-N-propylpyrrolidine cations(P13) can effectively suppress the dissolution of the polysulfides, whereas the RTIL with 1-methyl-3-propyl imidazolium cation(PMIM) barely alleviates the shuttling problem. With 0.5 mol L-1 LiTFSI/P13 TFSI as the electrolyte of Li-S battery, the ketjen black/ sulfur cathode material exhibits high capacity and remarkable cycling stability, which promise the application of the P13-based RTILs in Li-S batteries.     

Atomically Dispersed Fe-N4 Sites and Fe3C Particles Catalyzing Polysulfides Conversion in Li-S Batteries

Lithium-sulfur(Li-S) batteries have been puzzled by the “shuttle effect”. In the recent years, catalytic materials present a huge potential for solving this problem. However, the exploitation for catalytic activity was still challenging in Li-S batteries. In this article, we put forward a single atom catalyst (SAC) of FeN₄ coupled with Fe₃C on the N-doped carbon (FeN₄/Fe₃C@NC) by one-step pyrolysis method. The FeN₄ and Fe₃C synergistically catalyze the polysulfides conversion when the N-doped carbon provides the high conductive three-dimensional skeleton in Li-S batteries. As a result, the FeN₄/Fe₃C@NC shows a specific capacity of 1100 mA·h/g at 0.2 C(1 C=1675 mA/g). In addition, the FeN₄/Fe₃C@NC maintains 99.01% of the pristine specific capacity after 100 cycles at 0.5 C, indicating the improved electrochemical performance in Li-S batteries. This work sheds new lights on the design of engineering catalysts for developing high-performance Li-S batteries.     

锂硫电池及关键材料研究进展

锂硫电池因具有远高于传统锂离子电池的理论比容量和质量能量密度,而受到人们的广泛关注,近年来一直是高能锂金属电池领域的研究热点之一. 然而这一体系的一些固有特性问题依然没有得到解决,无法实现稳定理论容量输出,严重阻碍了锂硫电池的实际应用. 其中,比较突出的问题是电池充放电过程中生成可溶性中间产物-多硫化物-对硫基正极、锂基负极和电解液等电池关键组成部分具有深刻的影响. 本综述从多硫化物的热力学和动力学等性质入手,详细介绍了锂硫电池中关键材料的功能化设计和优化策略,并对未来的发展做出展望.     

Non-trivial Contribution of Carbon Hybridization in Carbon-based Substrates to Electrocatalytic Activities in Li-S Batteries

Appling an electrochemical catalyst is an efficient strategy for inhibiting the shuttle effect and enhancing the S utilization of Li-S batteries. Carbon-based materials are the most common conductive agents and catalyst supports used in Li-S batteries, but the correlation between the diversity of hybridizations and sulfur reduction reaction (SRR) catalytic activity remains unclear. Here, by establishing two forms of carbon models, i.e., graphitic carbon (GC) and amorphous carbon (AC), we observe that the nitrogen atom doped in the GC possesses a higher local charge density and a lower Gibbs free energy towards the formation of polysulfides than in the AC. And the GC-based electrode consistently inherits considerably enhanced SRR kinetics and superior cycling stability and rate capability in Li-S batteries. Therefore, the function of carbon in Li-S batteries is not only limited as conductive support but also plays an unignorable contribution to the electrocatalytic activities of SRR.     

高比能锂硫电池正极材料

锂硫电池被认为是最有发展潜力的新型多电子反应的二次电池体系之一.单质硫与锂反应的理论比容量为1675 mA h g?1,质量比能量达2600 W h kg?1,远远高于现行的传统锂离子二次电池材料.同时硫又具有来源丰富、环境友好等优点.然而,仍然有许多问题制约了锂硫电池的发展与广泛应用.本文综述了近年来锂硫电池正极材料的研究进展.     

Few-Layer Boron Nitride with Engineered Nitrogen Vacancies for Promoting Conversion of Polysulfide as a Cathode Matrix for Lithium–Sulfur Batteries

Lithium–sulfur (Li-S) batteries have become one of the most promising candidates as next-generation batteries, owing to their high specific capacity, low cost, and environmental benignity. Although many strategies have been proposed to restrain the shuttle of lithium polysulfides (LiPSs) through physical trapping and chemical binding, the sluggish kinetics of PS conversion still degrade the capacity, rate, and cycling performance of Li-S batteries. Herein, a novel kind of few-layer BN with engineered nitrogen vacancies (v-BN) has been developed as a cathode matrix for Li-S batteries. The positive vacancies in the BN nanosheets not only promote the immobilization and conversion of LiPSs, but also accelerate the lithium ion diffusion in cathode electrodes. Compared with pristine BN, the v-BN cathodes exhibit higher initial capacities from 775 mA h g⁻¹ to 1262 mA h g⁻¹ at 0.1 C and a high average coulombic efficiency of over 98 % during 150 cycles. Upon increasing the current density to 1 C, the cell still preserves a capacity of 406 mA h g⁻¹ after 500 cycles, exhibiting a capacity decay of only 0.084 % per cycle. The new vacancy-engineered material provides a promising method for achieving excellent performance in Li-S batteries.     

Trithiocyanuric acid derived g-C_3N_4 for anchoring the polysulfide in Li-S batteries application

Lithium-sulfur (Li-S) batteries have great potential as an electrochemical energy storage system because of the high theoretical energy density and acceptable cost of financial and environment.However,the shuttle effect leads to severe capacity fading and low coulombic efficiency.Here,graphitic carbon nitride(g-C_3N_4) is designed and prepared via a feasible and simple method from trithiocyanuric acid (TTCA) to anchor the polysulfides and suppress the shuttle effect.The obtained g-C_3N_4 exhibits strong chemical interaction with polysulfides due to its high N-doping of 56.87 at%,which is beneficial to improve the cycling stability of Li-S batteries.Moreover,the novel porous framework and high specific surface area of g-C_3N_4 also provide fast ion transport and broad reaction interface of sulfur cathode,facilitating high capacity output and superior rate performance of Li-S batteries.As a result,Li-S batteries assembled with g-C_3N_4 can achieve high discharge capacity of 1200 mAh/g at 0.2 C and over 800 mAh/g is remained after 100 cycles with a coulombic efficiency more than 99.5%.When the C-rate rises to 5 C,the reversible capacity of Li-S batteries can still maintain at 607mAh/g.     

锂硫电池用石墨烯基材料的研究进展

锂硫电池因其理论能量密度高、资源丰富和环境友好等优势,被认为是最有发展前景的下一代电化学储能系统之一。然而,硫的绝缘性、充放电中间产物多硫化物的溶解和扩散、硫的体积膨胀以及锂负极安全性等问题,严重制约着锂硫电池的商业应用。石墨烯因其具有高导电、高柔性等诸多优异特性而被广泛研究,将其用于锂硫电池的正极载体、隔膜涂层和集流体中,以期实现高比能、高稳定性的锂硫电池。本文综述了石墨烯基材料,包括石墨烯、功能化石墨烯、掺杂石墨烯和石墨烯复合物,在锂硫电池中应用的研究进展,并展望了锂硫电池用石墨烯基材料的未来发展方向。     

Identification of Non‐Carbonaceous Cathodes in Al Batteries: Potential Applicability of Black and Blue Phosphorene Monolayers

In the present era of growing energy demands, low‐dimensional materials are emerging as the suitable choices for energy storage due to their excellent ion transport properties, improved reversible capacity, fine rate performance and good cycling stability. In this context, we have investigated the applicability of black and blue phosphorene monolayers as potential cathodes for Al batteries. Both black and blue phosphorene monolayers show similar electrochemical behavior as that of experimentally reported graphite with a charge transfer from the surface in order to bind the tetrahedral geometry of AlCl₄ during the charging process. The adsorption of AlCl₄ drives semiconductor‐to‐metallic transformation of black/blue phosphorene, which ensures constant conductivity in Al batteries. Following the systematic adsorption of AlCl₄, the voltage for black and blue phosphorene is calculated to be ≈1.50 V and ≈1.80 V with storage capacities of 144 mAh g^?1 and 108 mAh g^?1, respectively. Besides, low diffusion barriers of 0.11 eV and 0.14 eV are predicted for AlCl₄ on the respective systems of black and blue phosphorene monolayers. Our work suggests that both black and blue phosphorene monolayers can be potential cathodes for Al batteries with delivery of high storage capacity and high voltage, respectively.     

Development prospects of metal-based two-dimensional nanomaterials in lithium-sulfur batteries

A lithium-sulfur(Li-S) system is an important candidate for future lithium-ion system due to its low cost and high specific theoretical capacity(1675 m Ah/g, 2600 Wh/kg), which is greatly hindered by the poor conductivity of sulfur, large volume change and dissolution of lithium polysulfides. Two-dimensional(2D)materials with monolayers or few-layers usually have peculiar structures and physical/chemical properties, which can resolve the critical issues in Li-S batteries. Especially, the metal-b...     

Bimetal-organic frameworks derived Co/N-doped carbons for lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries have received extensive attention due to their high theoretical specific energy density. However, the utilization of sulfur is seriously reduced by the shuttle effect of lithium polysulfides and the low conductivity of sulfur and lithium sulfide (Li₂S). Herein, we introduced bimetal-organic frameworks (Co/Zn-ZIF) derived cobalt and nitrogen-doped carbons (Co/N-C) into Li-S batteries through host design and separator modification. The Co/N-C in Li-S batteries effectively limits the shuttle effect through simultaneously serving as polysulfide traps and chemical catalyst. As a result, the Li-S batteries deliver a high reversible capacity of 1614.5 mAh/g and superior long-term cycling stability with a negligible capacity decay of only 0.04% per cycle after 1000 cycles. Furthermore, they have a high area capacity of 5.5 mAh/cm².     

Hollow Micro-/Nanostructure Reviving Lithium-sulfur Batteries

High-energy-density lithium-sulfur(Li-S) batteries are drawing dramatic research interests to fulfill the ever-increasing demands of electrical vehicles. However, challenges with the insulating property of sulfur and its lithiation products and its large volume expansion, and the shuttle effect of lithium polysulfides, hinder the commercial application of Li-S batteries. Lots of material design concepts have been developed to address the failure modes. Among them, hollow micro-/nanostructures with abundant compositional and geometrical feasibility have been proved fruitful in addressing the current obstacles of Li-S batteries. Here, typical examples of designing hollow micro-/nanostructures to address the problems of Li-S batteries and simultaneously improve the practical capacity and lifespan are highlighted. In particular, the great effect of structural engineering on minimizing volume change, inhibiting the shuttle effect and catalyzing polysulfide conversion are discussed systematically. Finally, future directions of hollow nanostructure design to enhance the progress of Li-S batteries are also provided.     

锂硫电池复合正极研究进展

锂硫电池因其超高的理论能量密度被视为极具前景的下一代电化学储能体系,其中高比容量的硫正极提供了锂硫电池的能量密度优势并直接决定了电池的实际性能。经过数十年的发展,最具前景的硫正极体系分别是硫碳复合（S/C）正极和硫化聚丙烯腈（SPAN）正极。本文系统综述了S/C正极和SPAN正极的最新研究进展。首先,简要介绍了两种正极的工作原理并进行了比较。S/C正极发生固-液-固多相转化反应,充放电表现为双平台特征。与之相比,SPAN正极发生固-固反应,充放电曲线为单平台。然后,对两种正极所面临的挑战和目前报道的优化策略进行了系统的分析与讨论。对于S/C正极,主要调控策略包括电极结构修饰、电催化剂设计与辅助氧化还原介体调控;对于SPAN正极,主要调控策略包括电极结构设计、电极形貌调控、杂原子掺杂和外源性氧化还原介体调控。最后,在电池尺度上对S/C正极和SPAN正极进行了综合比较,并对基于S/C正极和SPAN正极的锂硫电池在未来所面对的机遇与挑战进行了展望。     

Towards High-performance Lithium-Sulfur Batteries: the Modification of Polypropylene Separator by 3D Porous Carbon Structure Embedded with Fe3C/Fe Nanoparticles

Lithium-sulfur(Li-S) batteries with high energy densities have received increasing attention. However, the electrochemical performance of Li-S batteries is still far from the satisfactory of the practical application, which can be mainly attributed to the shuttling of polysulfides and the slow reaction kinetics of polysulfide conversion. To address this issue, a 3D porous carbon structure constructed by 2D N-doped graphene and 1D carbon nanotubes with embedded Fe₃C/Fe nanoparticles(NG@Fe₃C/Fe) was designed and prepared by a simple programmed calcination method for the modification of polypropylene(PP) separator. The Fe₃C/Fe nanoparticles demonstrate an excellent catalytic conversion and strong chemisorption towards polysulfides, while the unique architecture of N-doped graphene promotes the Li⁺/electron transfer and the physical adsorption of polysulfides. The electrochemical performance of the Li-S batteries with the NG@Fe₃C/Fe-modified separator is significantly improved. A large discharge capacity of 1481 mA∙h∙g^-1 is achieved at 0.2 C(1 C=1675 mA/g), and a high capacity of 601 mA∙h∙g^-1 is maintained after discharged/charged for 500 cycles at a current rate of 1 C. This work provides a new approach for the development of high-performance Li-S batteries through the modification of the PP separator by rationally designed composites with large adsorption capability to polysulfides, good wettability to the electrolyte and high catalytic property.     

Quaternized polymer binder for lithium-sulfur batteries:The effect of cation structure on battery performance

Lithium-sulfur (Li-S) batteries are great candidates for energy storage systems,but need to overcome the issues of low sulfur utilization and polysulfide shuttling for use in large-scale commercial applications.Recently,quaternized polymers have received much attention for their polysulfide trapping properties due to electrostatic interaction.In this work,we report a series of polyarylether sulfone (PSF) binders with different cation structures including imidazolium (Im),triethylammonium (Tr),and morpholinium(Mo).The ability of the these quaternized binders and the conventional poly(vinylidene fluoride) or PVDF binder to capture polysulfide increases in the order of PVDF PSF-Mo PSF-TrPSF-Im.The delocalized charge on the imidazolium cation may promote the interaction between PSF-Im and polysulfide as indicated by an X-ray photoelectron spectroscopic study.The PSF-Im based cathodes showed the highest capacity retention (77%at 0.2 C after 100 cycles and 84%at 0.5 C after 120 cycles),and the best rate capability.This work demonstrates the importance of the cation structure in the design of efficient quaternized binders for high performance Li-S batteries.     

Impregnated Sulfur in Carbonized Nitrogen-containing Porous Organic Frameworks as Cathode with High Rate Performance and Long Cycle Life for Lithium-sulfur Batteries

The undesirable cycling performance caused by soluble poly sulfides shuttling between anode and cathode has been considered as the main challenge that has hindered its practical applications for lithium-sulfiir(Li-S) batteries. To solve tliis issue effectively, a nitrogen-containing porous carbon, namely JUC-Z2-900,developed from a porous organic framework, namely JUC-Z2, bearing a high surface area(805 m^2/g),small pore size(0.5 mil) and nitrogen doping(2.15%, mass fraction), has been used as a host material for Li-S batteries. The micropores of JUC-Z2-900 can confine the smaller sulfur molecules S2-4, which can essentially alleviate the critical problem of poly sulfide dissolution.Furthermore, nitrogen-containing JUC-Z2-900 can promote chemical adsorption of sulfur. The above two factors can improve the electrochemical performance of Li-S batteries effectively. To compare the eftects of sulfur contents and melt-difiusion strategy in JUC-Z2-900/S composites, a series of JUC-Z2-900/S composites was synthesized and tlieir electrochemical perfbnnances were explored, indicating good rate performance and excellent cycling stability of the composites contributed by both appropriate mass percentage of sulfiir and its confinement in the micropores.     

氧缺位结构介孔二氧化钛/聚乙烯复合隔膜在锂硫电池中的应用

采用两步溶液法合成了一种具有高度氧缺位的黑色介孔二氧化钛, 并将其涂覆在隔膜表面作为锂硫电池复合隔膜, 研究了其在锂硫电池中的电化学性能. 结果表明, 氧缺位的黑色介孔二氧化钛材料不仅展现出良好的导电性, 还能加强对多硫化物的物理和化学吸附能力, 从而显著提高锂硫电池的放电比容量(0.1C倍率下首次放电比容量为1257 mA·h/g)和循环性能(循环100次后放电比容量为821 mA·h/g).     

High performance lithium-sulfur batteries by facilely coating a conductive carbon nanotube or graphene layer

A dual-layer cathode electrode is constituted by facilely coating a conductive carbon nanotube or graphene layer on the pristine sulfur cathode electrode. The conductive layer can effectively improve the conductivity and suppress the polysulfide diffusion, giving rise to an enhanced electrochemical performance for Li-S batteries.