面向高性能锂-硫二次电池应用的非对称电极-电解质界面（英文）

锂-硫电池具有高的理论电芯比能量和低成本,是极具应用前景的下一代电化学储能技术,已被广泛研究。实用化锂-硫电池技术目前面临的挑战主要包括正极侧电活性硫物种在充放电过程中的不可逆损失,负极侧枝晶形核生长,以及因活性硫迁移至负极而导致的界面副反应,上述问题会导致电池工况条件下性能迅速衰退,引发电池失效和安全问题。本工作中,我们提出通过设计非对称的电极-电解质界面稳定锂-硫电池正负极电化学,协同促进电极/电解质体相和界面电荷输运,从而延长电池循环寿命,显著提升电化学性能。本文所讨论的策略有望指导电池界面理性设计,助力实现高性能的锂-硫电池。     

锂硫二次电池硫-碳纳米管正极的合成和性能

由单质硫与碳纳米管合成一种新型含碳复合材料.XRD、SEM、BET比表面和孔径分布表征观察硫-碳纳米管复合材料,循环伏安法和电池充放电测试材料的电化学性能.结果表明:以硫-碳纳米管作正极组装的2016型扣式电池有较好的电化学性能,其初始放电比容量达680mAh/g(室温),30次循环放电比容量仍稳定在500mAh/g.     

锂硫二次电池正极研究进展

综述了锂硫电池中硫基正极材料的制备方法、结构特征以及电化学性能. 简述了单质硫正极材料, 重点探讨了有机硫化物、碳/硫复合材料、聚合物/硫复合材料的结构设计、材料制备、反应机理以及充放电特性, 并对其中存在的问题进行了分析, 还介绍了硫化锂正极材料. 最后对硫基正极的进一步发展, 以及锂硫电池的商业化应用进行了展望.     

PEO基锂硫二次聚合物电池

分别对单质硫和PABTH (polyanthra [1 ,9 ,8 -b,c,d,e][4 ,10 ,5 -b ,c ,d ,e ]bis-[1,6,6a(6a-S^Ⅳ)trithia]pentalene)在PEO (polyethylene oxide)基聚合物电解质中的电化学性能进行了研究. 研究发现单质硫和PABTH在PEO基聚合物电解质中都存在放电产物溶解现象, 说明醚基电解液即使以聚合物形式存在(如PEO基聚合物电解质)也不能有效抑制硫电极放电产物的溶解损失. 因此, 必须设计合成具有特定结构的电解质溶剂, 以抑制硫电极放电产物的溶解. 另外, 硫及有机硫化物在PEO基聚合物电解质中的利用率较低, 这主要是由于硫及有机硫化物不是离子导体, Li^＋在硫及有机硫化物中的扩散系数较低, 同时, 传输Li^＋的PEO分子量较大, Li^＋不能被有效传输至材料颗粒的内部. 因此, 全固态聚合物电解质不适合锂硫二次电池, 液态小分子电解质溶剂更有利于锂硫二次电池发挥其高比容量.     

固态锂硫电池研究进展（英文）

固态锂硫电池具有高能量密度和高安全性的潜在优势,被认为是最有前景的下一代储能体系之一。虽然固态电解质的应用有效地抑制了传统锂硫电池存在的“穿梭效应”和自放电现象,固态锂硫电池仍面临着多相离子/电子输运、电极/电解质界面稳定性、化学-机械稳定性、电极结构稳定性和锂枝晶生长等关键问题亟待解决。针对以上问题,本综述对近年来固态电解质、硫基复合正极、锂金属及锂合金负极以及电极/电解质界面的研究进行了详细的论述。作为固态锂硫电池的重要组成部分,固态电解质近年来受到了研究者们的广泛关注。本文首先对在锂硫电池中得到广泛应用的聚合物基、氧化物基、硫化物基固态电解质的种类和性质进行了概述,并对其在固态锂硫电池中的最新应用进行了系统的总结。在此基础上,对以单质硫、硫化锂、金属硫化物为活性物质的复合硫正极、锂金属及锂合金负极的反应机理以及面临的挑战进行了归纳和比较,对其解决策略进行了总结和分析。此外,对制约固态锂硫电池性能的电极/电解质界面离子/电子输运以及界面相容性问题及其改性策略进行了系统的阐述。最后,对固态锂硫电池的未来发展进行了展望。     

锂-空气二次电池关键材料与器件的设计与制备

锂-空气二次电池因拥有超高的理论能量密度及巨大的应用潜力, 有望替代锂离子电池成为下一代高性能化学 电源. 高效、稳定电极的制备以及新型锂-空气电池器件的开发是提升电池电化学性能, 促进其应用的关键. 针对以上 问题, 本文对空气正极材料的开发与设计、锂负极的修饰保护以及锂-空气二次电池器件进行了简要介绍, 并对该领域 进行总结展望     

锂硫电池硫正极粘结剂的比较研究

本文将三类粘结剂体系(PVDF、LA133和CMC+SBR)用于构筑锂硫电池硫正极,表征了不同粘结剂材料的官能团结构、结晶性能、热力学性质、电解液吸收性与粘结强度,考察了粘结剂种类对电极电化学性能的影响。结果表明,由1∶1质量比的CMC+SBR制作的硫电极吸液率低,剥离强度低,循环稳定性较差;无定形LA133支持高的粘结强度,维稳电极结构的能力强;PVDF因半结晶状态制约粘结效果,制作的电极吸液量高,但电荷转移阻抗小。基于PVDF制作的硫正极具有相对最优的电化学性能,其0.2C下循环100周后保留的可逆容量达722mAh·g~(-1),容量保持率达82.9%。     

导电聚合物与锂二次电池

本文对聚合物的锂二次电池原理，发展、应用前景及今后的展望做了评述．     

锂硫（硒）电池中的界面问题与解决途径

由于硫（硒）的导电性差、多硫（硒）化物的溶解、硫（硒）的体积膨胀、锂枝晶等问题,导致构建稳定的界面成为锂硫（硒）电池面临的重大挑战. 本文介绍了锂硫（硒）电池的研究进展,并以本课题组的研究工作为主,着重讨论了纳米限域效应、化学成键、界面吸附、表面包覆、电解液优化、负极改进等技术方案在锂硫（硒）电池中构建稳定界面的可行性.     

聚合物自由基锂二次电池正极材料的合成与电化学性能

合成了一种聚合物自由基聚 4 甲基丙烯酸 2 ,2 ,6 ,6 四甲基哌啶 1 氮氧自由基酯 (PTMA) ,并用红外光谱 (IR)、紫外光谱 (UV)、电子顺磁共振 (ESR)等证实了PTMA的结构 .PTMA的循环伏安曲线 (扫描速度为 5mV·s- 1)显示通过阳极的氧化电量和阴极的还原电量相等且氧化峰电流等于还原峰电流 ,表明PTMA的氧化还原反应可逆性很好 .PTMA的氧化峰电位 (Ea ,p=3 6 6VversusLi Li+ )与还原峰电位 (Ec,p=3 58V)之差为 80mV ,比其它锂二次电池的有机正极材料 (如有机二硫化物 )小得多 ,因此PTMA的氧化还原反应速度比较快 .PTMA的最大放电比容量为 78 4mAh·g- 1(以 0 2C充放电 ) ,是它理论比容量 ( 111mAh·g- 1)的 70 6 % ,它的充放电曲线分别在 3 6 5V和 3 56V处有一个很平稳的平台 ,经过 10 0次充放电循环后电池的放电比容量相对于最大放电比容量只衰减了 2 % ,表明PTMA 锂扣式电池具有优良的循环稳定性 .这些研究结果显示PTMA是一种非常有发展前景的有机聚合物自由基锂二次电池正极材料     

PEO基聚合物电解质及其锂硫电池性能研究

锂硫电池由于具有高的理论比能量引起了广泛关注,然而传统液态锂硫电池由于多硫化物的“穿梭效应”以及安全问题而限制了其应用,全固态锂硫电池可显著提高电池安全性能并有望解决多硫化物的穿梭问题. 本文采用传统的溶液浇铸法制备了具有不同的[EO]/[Li⁺]的PEO-LiTFSI聚合物电解质,并将其应用于锂硫电池. 研究发现,虽然[EO]/[Li⁺] = 8的聚合物电解质具有更高的离子电导率,但是[EO]/[Li⁺] = 20的电解质与金属锂负极间的界面阻抗更低,界面稳定性更好. Li|PEO-LiTFSI([EO]/[Li⁺]=20)|Li对称电池在60 °C,电流密度为0.1 mA·cm^-2时可稳定循环超过300 h,而Li|PEO-LiTFSI ([EO]/[Li⁺]=8)|Li对称电池循环75 h就出现了短路现象. 基于PEO-LiTFSI([EO]/[Li⁺]=20)电解质的锂硫电池首圈放电比容量为934 mAh·g^-1,循环16圈后放电比容量为917 mAh·g^-1以上. 而基于PEO-LiTFSI ([EO]/[Li⁺]=8)电解质的锂硫电池,由于与锂负极较低的界面稳定性不能够正常循环,首圈就出现了严重过充现象.     

锂硫电池隔膜功能化设计

锂硫电池具有较高的理论比容量(以硫计1675 mAh·g^-1和2600 Wh·kg^-1),以及低成本和绿色环保等优势,成为最有前景的下一代可充电储能器件之一。然而,锂硫电池内部严重的多硫化锂穿梭现象导致了电池容量的下降和使用寿命的快速降低。为实现锂硫电池的商业化,其严重的“穿梭效应”亟需改善。普通的商业隔膜有很大的孔径(500 nm),且不具有阻碍多硫化锂迁移的功能。因此,对隔膜进行表面修饰,引入功能化修饰层就成为了一种很有效的策略。本文综述了近年来隔膜表面修饰所遵循的方法以及在此基础上开发的新型隔膜,并对功能化的隔膜在提升锂硫电池性能上的前景进行了展望。     

电化学转换反应及其在二次电池中的应用

电化学转换反应作为一种新的电极反应机制,近年来受到相当多的关注. 转换反应不仅能够利用金属化合物的多价态氧化还原,大幅度提高电化学容量利用率,而且对于主体晶格的结构、嵌脱阳离子的尺寸并无特殊要求,可以应用于众多不同种类的金属化合物,针对不同的金属离子设计高容量正负极活性材料. 因此,基于转换反应构建高容量电极材料正成为二次电池发展的一个新方向. 本文简要分析了电化学转换反应的基本原理和实现条件,并结合作者课题组近年来的研究工作探讨了这类反应在锂离子及钠离子电池中的潜在应用.     

Synergistic Effect of Covalent Bonding and Physical Encapsulation of Sulfur in the Pores of a Microporous COF to Improve Cycling Performance in Li-S Batteries

Lithium-sulfur batteries stands out as a promising technology for energy storage owing to a combination of favorable characteristics including a high theoretical gravimetric capacity, energy density, inexpensive character, and environmental benignity. Covalent organic frameworks (COFs) are a rapidly developing family of functional nanostructures which combine porosity and crystallinity, and which have been already used in these kinds of batteries to build sulfur electrodes, by embedding sulfur into porous COFs in order to enhance cycle lifetimes. In this contribution, this is taken one step forward and a COF endowed with vinyl groups is used, in order to graft sulfur to the COF skeleton through inverse vulcanization. The main aim of the article is to show the synergistic effect of covalent bonding and physical encapsulation of sulfur in the pores of the COF in order to alleviate the fatal redox shuttling process, to improve the cycling performance, and to provide faster ion diffusion pathways. In addition, it is shown how the material with covalently-bound S provides better electrochemical performance under demanding and/or changeable charge conditions than a parent analogue material with sulfur physically confined, but without covalent linkage.     

Multi-Electron Reactions Enabled by Anion-Based Redox Chemistry for High-Energy Multivalent Rechargeable Batteries

The development of multivalent metal (such as Mg and Ca) based battery systems is hindered by lack of suitable cathode chemistry that shows reversible multi-electron redox reactions. Cationic redox centres in the classical cathodes can only afford stepwise single-electron transfer, which are not ideal for multivalent-ion storage. The charge imbalance during multivalent ion insertion might lead to an additional kinetic barrier for ion mobility. Therefore, multivalent battery cathodes only exhibit slope-like voltage profiles with insertion/extraction redox of less than one electron. Taking VS₄ as a model material, reversible two-electron redox with cationic–anionic contributions is verified in both rechargeable Mg batteries (RMBs) and rechargeable Ca batteries (RCBs). The corresponding cells exhibit high capacities of >300 mAh g⁻¹ at a current density of 100 mA g⁻¹ in both RMBs and RCBs, resulting in a high energy density of >300 Wh kg⁻¹ for RMBs and >500 Wh kg⁻¹ for RCBs. Mechanistic studies reveal a unique redox activity mainly at anionic sulfides moieties and fast Mg²⁺ ion diffusion kinetics enabled by the soft structure and flexible electron configuration of VS₄.     

A Perovskite Electrolyte That Is Stable in Moist Air for Lithium‐Ion Batteries

Solid‐oxide Li⁺ electrolytes of a rechargeable cell are generally sensitive to moisture in the air as H⁺ exchanges for the mobile Li⁺ of the electrolyte and forms insulating surface phases at the electrolyte interfaces and in the grain boundaries of a polycrystalline membrane. These surface phases dominate the total interfacial resistance of a conventional rechargeable cell with a solid–electrolyte separator. We report a new perovskite Li⁺ solid electrolyte, Li_0.38Sr_0.44Ta_0.7Hf_0.3O_2.95F_0.05, with a lithium‐ion conductivity of σ_Li=4.8×10^?4 S cm^?1 at 25 °C that does not react with water having 3≤pH≤14. The solid electrolyte with a thin Li⁺‐conducting polymer on its surface to prevent reduction of Ta⁵⁺ is wet by metallic lithium and provides low‐impedance dendrite‐free plating/stripping of a lithium anode. It is also stable upon contact with a composite polymer cathode. With this solid electrolyte, we demonstrate excellent cycling performance of an all‐solid‐state Li/LiFePO₄ cell, a Li‐S cell with a polymer‐gel cathode, and a supercapacitor.     

Multi‐Electron Reactions Enabled by Anion‐Based Redox Chemistry for High‐Energy Multivalent Rechargeable Batteries

The development of multivalent metal (such as Mg and Ca) based battery systems is hindered by lack of suitable cathode chemistry that shows reversible multi‐electron redox reactions. Cationic redox centres in the classical cathodes can only afford stepwise single‐electron transfer, which are not ideal for multivalent‐ion storage. The charge imbalance during multivalent ion insertion might lead to an additional kinetic barrier for ion mobility. Therefore, multivalent battery cathodes only exhibit slope‐like voltage profiles with insertion/extraction redox of less than one electron. Taking VS₄ as a model material, reversible two‐electron redox with cationic–anionic contributions is verified in both rechargeable Mg batteries (RMBs) and rechargeable Ca batteries (RCBs). The corresponding cells exhibit high capacities of >300 mAh g^?1 at a current density of 100 mA g^?1 in both RMBs and RCBs, resulting in a high energy density of >300 Wh kg^?1 for RMBs and >500 Wh kg^?1 for RCBs. Mechanistic studies reveal a unique redox activity mainly at anionic sulfides moieties and fast Mg²⁺ ion diffusion kinetics enabled by the soft structure and flexible electron configuration of VS₄.     

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。     

Enhanced Multiple Anchoring and Catalytic Conversion of Polysulfides by Amorphous MoS3 Nanoboxes for High-Performance Li-S Batteries

The practical implementation of lithium–sulfur batteries is obstructed by poor conductivity, sluggish redox kinetics, the shuttle effect, large volume variation, and low areal loading of sulfur electrodes. Now, amorphous N-doped carbon/MoS₃ (NC/MoS₃) nanoboxes with hollow porous architectures have been meticulously designed as an advanced sulfur host. Benefiting from the enhanced conductivity by the N-doped carbon, reduced shuttle effect by the strong chemical interaction between unsaturated Mo and lithium polysulfides, improved redox reaction kinetics by the catalytic effect of MoS₃, great tolerance of volume variation and high sulfur loading arising from flexible amorphous materials with hollow-porous structures, the amorphous NC/MoS₃ nanoboxes enabled sulfur electrodes to deliver a high areal capacity with superior rate capacity and decent cycling stability. The synthetic strategy can be generalized to fabricate other amorphous metal sulfide nanoboxes.     

The Use of Light in the Study of Interfacial Electrochemical Reactions

Spectroscopic analysis techniques have become particularly important in the study of interfacial electrochemical processes since it has become possible to increase their sensitivity to the extent where changes occurring in the absorption of light by fractions of monolayers can be detected. At the same time the development of new techniques in surface physics, though most of these can only be used in ultra-high vacuum, has also had a considerable influence on electrochemistry since it has enabled studies to be carried out on electrodes after transfer to UHV. The availability of well-defined semiconductors in which photocurrents can be generated by the absorption of light has led to the development of photoelectrochemical methods that can be used for the study of electrode reactions at semiconductors or at metal surfaces which are covered with a semiconducting film. Finally, it has been observed during the study of semiconductor electrodes that redox reactions at an electrode can result in the generation of luminescence. This, in turn, can lead to important information on the mechanism of the charge transfer process. These recent developments are reviewed in the present article.