用于锂硫电池高效硫载体的Co-N-C@KB复合材料的规模化制备策略（英文）

硫正极较差的性能严重阻碍了锂硫电池的商业化进程,这些因素包括较低的导电能力以及在促进多硫化物转化方面较差的催化活性。我们开发了一种基于配体调控合成和低温热解的规模化策略来制备高效的正极复合材料(Co-N-C@KB),这种材料由富含Co-N-C活性位点的科琴黑(KB)组成。原子级分散的Co-N-C活性位点被证明有利于多硫化物在正极的转化,因而可以提高锂硫电池的容量和循环寿命。基于此,Co-N-C@KB作为正极可以使锂硫电池获得高达1 442 mAh·g-1的初始放电容量,并且该电池在长时间的稳定性测试中具有出色的容量保持能力。     

高容量硫/碳复合正极材料

以锂为负极、硫为正极的锂/硫二次电池,由于其较高的理论能量密度(2 600Wh/kg),而成为最具发展潜力的新型高能化学电源体系.但是,硫正极材料存在的活性物质利用率偏低和循环性能较差等缺点制约了锂/硫电池的快速发展.本文主要综述了基于多孔碳材料负载硫来构筑硫/碳复合材料,进而改善硫电极材料电化学性能的研究进展,多孔碳...     

锂硫电池硫碳复合正极材料研究现状及展望

二次锂硫电池被视为最具有发展潜力的下一代高能量密度二次电池之一. 但由于正极硫的电导率低（5×10^-30 S·cm^-1）,且在放电过程中产生的中间体多硫化物易溶于有机电解液,致使锂硫电池活性物质利用率降低,溶解后的多硫化物还会迁移到负极,被还原成不溶物Li2S2/Li2S而沉积于负极锂,使电极结构遭受破坏,造成电池容量大幅衰减,循环性能差,从而限制了进一步的开发应用. 研究表明,以碳作为导电骨架的硫碳复合正极材料能在不同程度上解决上述问题,从而有效提高了锂硫电池的放电容量和循环性能. 本文综述了近年来国内外报道的各种锂硫电池正极材料的研究进展,结合作者课题组的研究,重点探讨了硫碳复合正极材料,并对其今后的发展趋势进行了展望.     

高比能锂-硫电池研究进展

随着全球经济快速发展对高效绿色能源需求的不断增长,锂-硫电池因具有较高的能量密度,成为了下一代高能量密度二次电池研发的重点.然而,锂-硫电池面临的循环寿命短、库仑效率低、安全性能差、较高自放电等问题,使其目前还很难实现商品化.锂-硫电池存在的这些问题主要与正极活性硫材料的高绝缘性、放电过程中产生的多硫化物溶解于电解液、硫正极在充放电过程中的体积膨胀与收缩、以及锂负极支晶化等有关.通过从锂-硫电池硫复合正极、电解液、黏结剂和负极等4个方面综述了高比能锂-硫电池的最新研究进展,其中重点介绍了硫正极复合材料的进展情况.     

过渡金属硫化物改性锂硫电池正极材料

锂硫电池(LSBs)由于单质硫正极具有超高能量密度(2600 Wh/kg)和超高理论比容量(1675 mAh/g),且环境友好、成本低廉,被认为是最有前景的储能体系之一。然而,硫正极的绝缘性和严重体积膨胀以及多硫化物(LiPSs)的“穿梭效应”等问题导致活性物质利用率低、循环稳定性差及电化学反应动力不足,严重阻碍了LSBs的商业化发展。最新研究表明,过渡金属硫化物作为载体或添加剂能够显著改善LSBs正极材料的电化学性能。本文从等效/共正极作用、导电性增强作用、LiPSs吸附作用和电化学反应催化作用四个方面梳理了过渡金属硫化物在LSBs正极材料中的改性机理,并指出多元过渡金属硫化物复合﹑纳米结晶和量子化作为增加比表面积和活性位点的方法是过渡金属硫化物用于锂硫电池正极材料的重要发展方向,可大幅提升LSBs的电化学性能。     

辐照交联制备低分子量聚丙烯腈纤维锂硫电池正极材料及其储硫机理

通过γ射线辐照交联异型聚丙烯腈(PAN)纤维解决了低分子量聚丙烯腈半碳化中的熔融坍塌问题, 提高了PAN的半碳化稳定性; 采用傅里叶变换红外光谱、 元素分析及核磁共振波谱确定了辐照交联机理. 同时, 根据辐照产生的不同交联度与PAN硫化后载硫量的变化关系, 探讨了硫化聚丙烯腈(SPAN)锂硫电池正极材料的储硫机理. 利用拉曼光谱及X射线光电子能谱等分析手段表征了SPAN中硫原子的反应位置, 说明PAN主链上的亚甲基所在的碳为与硫化学结合的活性位点, 为探究SPAN结构提供了新的依据. 交联度升高对硫化后所形成的SPAN正极材料的电化学稳定性起促进作用, 容量保持率可提升至98%.     

锂硫电池硫正极催化转换反应的研究进展

单质硫作为电池的正极材料,其电化学过程历经多个步骤,完全放电生成最终产物是一个2电子反应. 低阶多硫化锂的生成需克服一定的能垒,且由Li₂S₂得到一个电子还原生成Li₂S的反应是速控步骤. 硫正极的反应动力学是决定锂硫电池电化学性能,如比能量、比功率、低温性能等的关键因素. 提高速控步骤的反应动力学还能加速可溶性多硫化锂Li₂S₄向不溶性Li₂S₂和Li₂S的转化,有利于减缓或消除多硫化锂的“穿梭效应”. 近年,已有大量的过渡金属氧化物、硫化物、碳化物、氮化物、磷化物,单原子催化剂和氧化还原电子中继体等被应用于催化硫正极反应,提高了电极的电化学性能和循环稳定性. 但是,目前详细的催化反应机制尚不完全清晰. 本文重点综述了这些化合物在硫正极反应中的作用机制,总结了近年来的研究进展,并对硫正极催化转换反应的研究和发展进行了展望.     

氧化还原媒介体分子调控锂-硫电池硫正极性能研究进展

锂-硫(Li-S)电池具有较高的理论比容量(约1 675 mAh·g^-1)和能量密度(约2 600 Wh·g^-1),被认为是继锂离子电池之后最有前途的下一代高能量密度电池.Li-S电池在实现产业化之前需要克服硫正极诸多技术瓶颈,主要有硫的导电性差、多硫化物的穿梭效应与硫电极体积膨胀等.本文着重梳理了氧化还原媒介体分子在硫正极改性研究上的进展,并对硫正极的未来发展趋势进行了展望.     

锂硫电池正极材料研究进展

总结了近几年来锂硫电池正极材料的研究进展,简要阐释了锂硫电池正极材料的研究现状、存在的问题及其面临的挑战.通过碳材料的引入,导电聚合物的复合,金属氧化物的添加均不同程度地提高了硫电极材料的电导率,有效抑制了多硫化物的溶解,为体积膨胀提供了空间,从而改善了锂硫电池的活性物质利用率和循环稳定性.简化工艺,降低成本,提高硫的负载量,这将是下一阶段锂硫电池研究的重点.     

金属单原子催化剂增强硫正极动力学的研究进展

单质硫具有理论能量密度高(2600 Wh·kg-1)、放电比容量高(1672mAh·g-1)、成本低等优势,是锂硫电池的理想正极材料。然而,在充放电过程中硫正极迟缓的反应动力学显著地限制了锂硫电池的性能。金属单原子催化剂(SMACs)具有独特的电子结构、金属含量低、理论上100%的原子利用率、催化活性高等优势,其不仅有效地促进了不同中间相的转化反应,而且可为含硫物质提供丰富的锚定位点,从而显著优化硫正极氧化还原反应动力学、多硫化物的穿梭行为和锂硫电池电化学性能。本文以剖析金属单原子催化剂与硫正极间的相互作用为出发点,结合其催化效应表征技术,重点解析了不同类型单原子催化剂的构筑策略、活性调控及其优化硫正极氧化还原行为的机制,展望了金属单原子催化剂在锂硫电池领域面临的挑战和未来发展方向。     

Enhanced Adsorption of Polysulfides on Carbon Nanotubes/Boron Nitride Fibers for High-Performance Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are one of the most promising high-energy-density storage systems. However, serious capacity attenuation and poor cycling stability induced by the shuttle effect of polysulfide intermediates can impede the practical application of Li-S batteries. Herein we report a novel sulfur cathode by intertwining multi-walled carbon nanotubes (CNTs) and porous boron nitride fibers (BNFs) for the subsequent loading of sulfur. This structural design enables trapping of active sulfur and serves to localize the soluble polysulfide within the cathode region, leading to low active material loss. Compared with CNTs/S, CNTs/BNFs/S cathodes deliver a high initial capacity of 1222 mAh g⁻¹ at 0.1 C. Upon increasing the current density to 4 C, the cell retained a capacity of 482 mAh g⁻¹ after 500 cycles with a capacity decay of only 0.044 % per cycle. The design of CNTs/BNFs/S gives new insight on how to optimize cathodes for Li-S batteries.     

Bidirectionally polarizing surface chemistry of heteroatom-doped carbon matrix towards fast and longevous lithium-sulfur batteries

Herein, a bidirectional polarization strategy is proposed for hosting efficient and durable lithium-sulfur battery (Li-S) electrochemistry. By co-doping electronegative N and electropositive B in graphene matrix (BNrGO), the bidirectional electron redistribution enables a higher polysulfide affinity over its mono-doped counterparts, contributing to strong sulfur immobilization and fast conversion kinetics. As a result, BNrGO as the cathode host matrix realizes excellent cycling stability over 1000 cycles with a minimum capacity fading of 0.027% per cycle, and superb rate capability up to 10 C. Meanwhile, decent areal capacity (6.46 mAh/cm²) and cyclability (300 cycles) are also achievable under high sulfur loading and limited electrolyte. This work provides instructive insights into the interaction between doping engineering and sulfur electrochemistry for pursuing superior Li-S batteries.     

Spinel-type bimetal sulfides derived from Prussian blue analogues as efficient polysulfides mediators for lithium−sulfur batteries

More and more attentions have been attracted by lithium-sulfur batteries (Li-S), owing to the high energy density for the increasingly advanced energy storage system. While the poor cycling stability, due to the inherent polysulfide shuttle, seriously hampered their practical application. Recently, some polar hosts, like single metal oxides and sulfides, have been employed as hosts to interact with polysulfide intermediates. However, due to the inherent poor electrical conductivity of these polar hosts, a relatively low specific capacity is obtained. Herein, a spinel-type bimetal sulfide NiCo₂S₄ through a Prussian blue analogue derived methodology is reported as the novel host of polysulfide, which enables high-performance sulfur cathode with high Coulombic efficiency and low capacity decay. Notably, the Li-S battery with NiCo₂S₄-S composites cathode still maintains a capacity of 667 mAh/g at 0.5 C after 300 cycles, and 399 mAh/g at 1 C after 300 cycles. Even after 300 cycles at the current density of 0.5 C, the capacity decays by 0.138% per cycle at high sulfur loading about 3 mg/cm². And the capacity decays by 0.026% per cycle after 1000 cycles, when the rate is 1 C. More importantly, the cathode of NiCo₂S₄-S composite shows the outstanding discharge capacity, owing to its good conduction, high catalytic ability and the strong confinement of polysulfides.     

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.     

纳米CoSe修饰氮掺杂多孔碳的可控制备及其锂硫电池多硫化物的催化转化效应

锂硫电池中较差的循环稳定性和倍率性能是实现锂硫电池商业化的技术障碍,其主要原因之一是多硫化物在硫电极内的电化学转化动力学较为缓慢。为此,我们以ZIF-9为前驱体,采用先碳化,再酸化刻蚀,最后硒化的方法合成了含少量催化剂的CoSe修饰氮掺杂多孔碳(CoSe/NC)电极材料,以期提高硫电极内多硫化物的电化学转化动力学性能,并通过流动液相三电极体系对该材料进行电化学动力学表征。结果显示,相较于对比材料,CoSe/NC能够加快多硫化物的氧化还原反应速率,在 0.2mA·cm^-2电流密度下,多硫化物氧化还原反应在CoSe/NC电极上有最小的反应过电位;同时,在0.1 V过电位下,各氧化还原反应也有最大的响应电流。因此,将 CoSe/NC作为硫宿主材料组装电池展现了优异的电化学性能：在 1C(1C=1 675 mA·g^-1)下初始放电比容量为1 068 mAh·g^-1,经过500次循环后,可逆容量仍保持在693 mAh·g^-1。另外,在3C的高电流密度下,放电比容量可高达819 mAh·g^-1。     

锂-硫二次电池界面反应的特殊性与对策分析

锂-硫电池是在现有锂离子电池基础上最可能实现储能密度大幅提升的实用二次电池体系. 然而,这一电池体系的电化学利用率与循环稳定性仍然难以满足应用要求. 造成锂-硫电池性能不稳定的原因在于硫正极和锂负极的材料结构和反应环境始终处于变化之中,如在充放电过程中,硫-碳反应界面的电化学阻塞、中间产物的溶解流失、正负极之间的穿梭效应等副反应导致正极与负极均难形成稳定的电化学反应界面。针对这些特殊问题,本文简要分析了影响能量利用率和循环稳定性的化学与电化学机制,并提出了构建稳定锂负极与高效硫正极的若干可行性技术.     

纳米CoSe修饰氮掺杂多孔碳的可控制备及其锂硫电池多硫化物的催化转化效应

锂硫电池中较差的循环稳定性和倍率性能是实现锂硫电池商业化的技术障碍,其主要原因之一是多硫化物在硫电极内的电化学转化速率较为缓慢。为此,我们以ZIF-9为前驱体,采用先碳化,再酸化刻蚀,最后硒化的方法合成了含少量催化剂的CoSe修饰氮掺杂多孔碳(CoSe/NC)电极材料,以期提高硫电极内多硫化物的电化学转化动力学性能,并通过流动液相三电极体系对该材料进行电化学动力学表征。结果显示,相较于对比材料,CoSe/NC能够加快多硫化物的氧化还原反应速率,在0.2mA·cm-2电流密度下,多硫化物氧化还原反应在CoSe/NC电极上有最小的反应过电位;同时,在0.1 V过电位下,各氧化还原反应也有最大的响应电流。因此,将CoSe/NC作为硫宿主材料组装电池展现了优异的电化学性能：在1C(1C=1 675 mA·g^-1)下初始放电比容量为1 068 mAh·g^-1,经过500次循环后,可逆容量仍保持在693 mAh·g^-1。另外,在3C的高电流密度下,放电比容量可高达819 mAh·g-1。     

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.     

Dual Dopamine Derived Polydopamine Coated N-Doped Porous Carbon Spheres as a Sulfur Host for High-Performance Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries are considered to be one of the most promising energy storage systems owing to their high energy density and low cost. However, their wide application is still limited by the rapid capacity fading. Herein, polydopamine (PDA)-coated N-doped hierarchical porous carbon spheres (NPC@PDA) are reported as sulfur hosts for high-performance Li-S batteries. The NPC core with abundant and interconnected pores provides fast electron/ion transport pathways and strong trapping ability towards lithium polysulfide intermediates. The PDA shell could further suppress the loss of lithium polysulfide intermediates through polar–polar interactions. Benefiting from the dual function design, the NPC/S@PDA composite cathode exhibits an initial capacity of 1331 mAh g⁻¹ and remains at 720 mAh g⁻¹ after 200 cycles at 0.5 C. At the pouch cell level with a high sulfur mass loading, the NPC/S@PDA composite cathode still exhibits a high capacity of 1062 mAh g⁻¹ at a current density of 0.4 mA cm⁻².     

Beyond the Polysulfide Shuttle and Lithium Dendrite Formation: Addressing the Sluggish Sulfur Redox Kinetics for Practical High-Energy Li-S Batteries

Electrolyte modulation simultaneously suppresses polysulfide the shuttle effect and lithium dendrite formation of lithium–sulfur (Li-S) batteries. However, the sluggish S redox kinetics, especially under high S loading and lean electrolyte operation, has been ignored, which dramatically limits the cycle life and energy density of practical Li-S pouch cells. Herein, we demonstrate that a rational combination of selenium doping, core–shell hollow host structure, and fluorinated ether electrolytes enables ultrastable Li stripping/plating and essentially no polysulfide shuttle as well as fast redox kinetics. Thus, high areal capacity (>4 mAh cm⁻²) with excellent cycle stability and Coulombic efficiency were both demonstrated in Li metal anode and thick S cathode (4.5 mg cm⁻²) with a low electrolyte/sulfur ratio (10 μL mg⁻¹). This research further demonstrates a durable Li-Se/S pouch cell with high specific capacity, validating the potential practical applications.