金属锂负极溶剂化结构调控的研究进展

金属锂负极具有极高的理论比容量和极低的氧化还原电位,被认为是二次电池体系中负极材料的最终选择.但在实际应用过程中,不稳定的电极/电解液界面会造成大量的锂枝晶生长,导致容量损失乃至热失控等安全问题.调控锂离子溶剂化结构,可促进有益的固态电解质界面膜(SEI)成膜组分在电极表面优先分解,进而稳定电极界面并可诱导锂离子均匀沉积,是提升液态和准固态金属锂电池电化学性能的重要手段.本文综合评述了近年来从液态到准固态电解质中锂离子溶剂化结构调控的策略和设计原则,探讨了溶剂化结构改变对电极/电解质界面的影响,并对准固态电解质的研究前景进行了展望.     

多酚类化合物—丹宁酸用作锂金属负极电解液成膜添加剂

As the application of lithium-ion batteries in advanced consumer electronics, energy storage systems, plug-in hybrid electric vehicles, and electric vehicles increases, there has emerged an urgent need for increasing the energy density of such batteries. Lithium metal anode is considered as the "Holy Grail" for high-energy-density electrochemical energy storage systems because of its low reduction potential (-3.04 V vs standard hydrogen electrode) and high theoretical specific capacity (3860 mAh·g^-1). However, the practical application of lithium metal anode in rechargeable batteries is severely limited by irregular lithium dendrite growth and high reactivity with the electrolytes, leading to poor safety performance and low coulombic efficiency. Recent research progress has been well documented to suppress dendrite growth for achieving long-term stability of lithium anode, such as building artificial protection layers, developing novel electrolyte additives, constructing solid electrolytes, using functional separator, designing composite electrode or three-dimensional lithium-hosted material. Among them, the use of electrolyte additives is regarded as one of the most effective and economical methods to improve the performance of lithium-ion batteries. As a natural polyphenol compound, tannic acid (TA) is significantly cheaper and more abundant compared with dopamine, which is widely used for the material preparation and modification in the field of lithium-ion batteries. Herein, TA is first reported as an efficient electrolyte film-forming additive for lithium metal anode. By adding 0.15% (mass fraction, wt.) TA into the base electrolyte of 1 mol·L^-1 LiPF₆-EC/DMC/EMC (1 : 1 : 1, by wt.), the symmetric Li|Li cell exhibited a more stable cyclability of 270 h than that of only 170 h observed for the Li|Li cell without TA under the same current density of 1 mA·cm^-2 and capacity of 1 mAh·cm^-2 (with a cutoff voltage of 0.1 V). Electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV), and energy-dispersive X-ray spectroscopy (EDS) analyses demonstrated that TA participated in the formation of a dense solid electrolyte interface (SEI) layer on the surface of the lithium metal. A possible reaction mechanism is proposed here, wherein the small amount of added polyphenol compound could have facilitated the formation of LiF through the hydrolysis of LiPF₆, following which the resulting phenoxide could react with dimethyl carbonate (DMC) through transesterification to form a cross-linked polymer, thereby forming a unique organic/inorganic composite SEI film that significantly improved the electrochemical performance of the lithium metal anode. These results demonstrate that TA can be used as a promising film-forming additive for the lithium metal anode.     

非水体系锂-空气电池研究进展

锂-空气电池是目前已知具有最高能量密度的二次电池,有望成为未来电动汽车的动力电源。由于其能量密度高、环境友好以及成本较低,成为广大科研工作者研究的热点,在过去二十年间与之有关的研究已经在反应机理、电极结构、催化剂及电解液等各方面都取得了很大进展,但受诸多因素限制,其实用化仍然任重道远。本文总结了近几年来非水体系锂-空气电池在反应机理、正极材料、催化剂、电解液以及锂负极等方面的最新研究进展,并在此基础上展望其未来的发展方向。     

锂金属负极界面修饰及其在硫化物全固态电池中的应用

随着我国新能源产业的快速发展,全固态电池由于其理论上的高能量密度和高安全性受到广泛关注,而硫化物全固态电池具有离子电导率高的优势成为目前的研发热点,但是金属锂负极的锂枝晶生长和与硫化物电解质之间的不稳定性严重阻碍了硫化物全固态电池的研发.本工作在高温150℃下制备了均匀的LiF界面层来抑制金属锂负极/硫化物电解质之间的界面反应和锂枝晶.LiF/Li之间具有较高的界面能,所以可以有效抑制锂枝晶的生长.LiNbO₂@LiCoO₂//Li₆PS₅Cl//LiF@Li (LNO@LCO//LPSCl//LiF@Li)全电池0.05 C, 0.1 C, 0.2 C和0.5 C倍率的正极放电克容量分别为138.4 mAh/g, 105.0 mAh/g, 80.3 mAh/g和60.4 mAh/g, 0.05 C循环50周后,正极容量保持率为80.2%.该方法为后续金属锂负极在全固态电池中的应用提供了新的方案.     

金属锂二次电池锂负极改性

本文综述了金属锂二次电池中提高锂负极性能的研究进展。分别介绍了以下改性方法:对金属锂表面进行预处理,使其表面预先形成性能良好的固体电解质界面膜,或直接在其表面制备保护膜;在电解液中加入添加剂对锂电极进行表面改性;采用新型有机溶剂、离子液体、聚合物电解质、玻璃态固体电解质、塑晶固体电解质等电解质体系提高界面相容性;改进金属锂电极的制备工艺,如制备金属锂粉末多孔电极和电沉积锂电极、制备全固态薄膜锂电池以及利用物理方法处理锂电极。并在此基础上对今后的发展趋势进行了展望。     

锂氧电池关键技术研究

锂氧电池是一种用金属锂作负极,以氧气作为正极反应物的金属空气电池,由于其具备较高的理论比能量且环境友好等优势,近年来开始备受关注。本文主要概述了锂氧电池关键技术的最新研究进展,包括正极材料、催化剂、电解质、负极及电池结构等,并在此基础上对其未来发展趋势进行了展望,以期对其他金属空气电池的研究提供新思路和手段。     

多孔金属有机框架材料作为锂金属负极保护层助力长寿命锂氧气电池

在众多能源储存系统中,锂氧气电池以其高达3500 Wh·kg^-1的理论能量密度有望在性能上超越商用锂离子电池.然而,在电池充放电过程中,金属锂不可控的枝晶生长和严重的腐蚀问题极大地阻碍了锂氧气电池的发展.为了解决以上问题,制备了一种具有高比表面积、丰富孔道结构的金属有机框架材料（MOF-801）,并将其设计成金属锂负极的保护层应用在锂氧气电池中.在本工作中,成功合成了具有高达762.9 m²·g^-1比表面积,边长约为800 nm的立方体状纯净MOF-801材料.并且这种材料表现出对于有机电解液体系（四乙二醇二甲醚1 mol·L^-1三氟甲基磺酸锂）和强还原性的金属锂都具有很好的稳定性.得益于该材料丰富的孔道结构以及高比表面积,锂离子得以更均匀地分布在电极表面促进金属锂均匀沉积,有效避免了由于枝晶刺破隔膜而导致的短路甚至火灾事故.此外,MOF-801保护层本身的阻隔作用和材料捕捉水的特性可以帮助减少污染物质（水、氧气、强氧化性物质等）的穿梭效应带来的副反应,缓解锂氧气电池中金属锂负极的腐蚀情况.因此,将经过保护的金属锂组装成的对称电池进行测试,循环寿命长达800 h,同时充/放电过电势仅为0.023 V（未经保护的电池寿命仅为254 h,最终充/放电过电势高达5 V）,且循环阻抗大大降低,证明了这种策略有效地稳定了金属锂/电解液界面.将经过MOF材料保护的电极实际应用在锂氧气电池中,在限容量1000 mAh·g^-1,限电流500 mA·g^-1条件下,可以实现长达170圈的稳定长寿命的循环（是未经保护的电池寿命的2.88倍）.使用MOF-801保护层的锂氧气电池还表现出了高达8935 mAh·g^-1的高比容量.因此,本工作所报道的保护层策略为未来的碱金属空气电池负极保护领域提供了新颖的视角.     

氟代溶剂在锂金属电池中的应用

近年来,锂金属电池由于具有较高的能量密度而成为储能领域的研究热点。电解液作为锂金属电池的“血液”发挥着至关重要的作用。在传统锂离子电池电解液中,锂金属负极与电解液之间的界面副反应严重并伴随着锂枝晶生长,从而导致安全隐患以及循环寿命缩短等问题。在解决锂金属负极问题上,电解液调控策略具有易操作性和有效性,因而在推动锂金属电池发展方面具有举足轻重的地位。氟代电解液是目前重要的研究方向,氟代电解液在循环过程中能够在电极表面形成富含LiF的固体电解质界面膜(SEI);该界面膜不仅可以有效抑制负极锂枝晶的形成,并且在正极方面能够大幅提高电解液的氧化稳定性,从而提升高电压正极的适配性和锂金属电池的循环稳定性。氟代电解液中氟代溶剂/氟代锂盐的分子结构对电解液的溶剂化结构有重要影响。当氟代溶剂分子中氟原子的位置与数量不同时,氟代溶剂的物理化学性质也会随之发生变化,进而改变了电解液与电极的界面反应性。因此,氟代溶剂能够起到调制SEI膜成分和结构的作用,是决定电池性能的关键因素。本文总结了应用于锂金属电池的主要氟代溶剂,尤其是近几年来发展的新型氟代溶剂;着重介绍了高度氟代的溶剂分子作为局域超浓电解液的稀释剂,以及对溶剂进行精准分子设计得到的部分氟代溶剂等。此外,本文还分析探讨了氟代溶剂分子与电池性能之间的构效关系,展望了构建新型氟代溶剂分子的策略,希望能对电解液溶剂分子的结构设计以及构效关系的评估有一定的启发意义。     

氟代溶剂在锂金属电池中的应用

Lithium metal batteries, which use lithium metal as the anode, have attracted tremendous research interest in recent years, owing to their high energy density and potential for future energy storage applications. Despite their advantages such as high energy density, the safety concerns and short lifespan significantly impede their practical applications in transportation and electronic devices. Tremendous efforts have been devoted to overcoming these problems, including materials design, interface modification, and electrolyte engineering. Among these strategies, electrolyte regulation plays a key role in improving the efficiency, stability, and safety of lithium metal anodes. As an important class of electrolyte components, fluorinated solvents, which can decompose to form LiF-rich interphase layers on both anode and cathode, have been proven to enhance the stability of lithium metal anodes and improve the oxidative stability of the electrolytes. Meanwhile, the spatial structure of fluorinated solvents, such as the number and sites of fluorine atoms, can influence the physicochemical properties of the electrolytes and the compositions/structure of the solid-electrolyte interphase, which eventually dictates the cycling performance of Li metal batteries. Recently, many fluorinated solvents with different molecular structures have been designed to regulate the solvation structure of electrolytes, and these solvents exhibit novel electrochemical properties in lithium metal batteries. However, there are few comprehensive reviews that summarize the fluorinated solvents used in Li metal batteries and discuss their functions in electrolytes and their physicochemical properties. This review summarizes the novel fluorinated solvents used in lithium metal batteries in recent years, which have been classified into three parts: diluents, traditional solvents, and novel molecules, based on their functions in the electrolytes. In every part, the understanding of the interactions between fluorinated solvents and Li ions, the decomposition mechanism of fluorinated solvents at the interface of the electrode, the functions of fluorinated solvents in the electrolytes, and the structure-activity relationship between the fluorinated solvents and battery performance have been comprehensively summarized and discussed. Moreover, the advantages and disadvantages of fluorinated solvents have been discussed, and the importance of precisely controlling the number of fluorine atoms and the structure of fluorinated solvents has been emphasized. At the end of this review, a perspective for designing new fluorinated solvents has been proposed. We believe that this review can provide insights on designing novel fluorinated solvents for high-performance Li metal batteries.      

固态锂金属电池中原位聚合电解质的研究进展

在下一代电池体系中,固态金属锂电池具有高能量密度潜力,同时有望避免目前电池面临的燃烧、爆炸等安全隐患.其中,固态电解质和电极材料之间的固-固界面接触差是其实用化面临的重要挑战.近年来,经电池内部原位聚合反应制得的原位聚合电解质用于固态锂金属电池具备界面一体化提升固-固界面相容性、抑制枝晶的形成、抑制正极过渡金属离子/多硫化物/氧化还原介质的溶解/穿梭并提升电池电化学性能多种优势.本文首先讨论了聚合电解质的反应机理,然后分析了电池内部常见电解质的原位聚合原理,总结了固态锂金属电池中原位聚合电解质的最新研究进展.最后,对未来原位聚合电解质的发展方向和商业化应用进行了展望.     

人工界面层在金属锂负极中的应用

金属锂具有极高的比容量(3860 mAh·g^?1)和最低的电化学反应电位(相对标准氢电位为?3.040 V),被认为是高能量密度二次电池最具潜力的负极材料。然而金属锂负极界面稳定性差、不可控的枝晶生长、沉积/剥离过程中巨大的体积变化等严重阻碍了金属锂负极的商业化应用。在金属锂表面构建一层物理化学性质稳定的人工界面保护层被认为是解决金属锂负极界面不稳定和枝晶生长,缓解体积膨胀带来的界面波动等一系列问题的有效手段。本综述依据界面传导性质,从离子导通而电子绝缘的人工固态电解质界面(SEI)层、离子/电子混合传导界面、纳米界面钝化层三个部分对人工界面保护层进行了归纳总结。分析了人工界面保护层的物质结构与性能之间的构效关系,探讨了如何提高人工界面保护层的物理化学稳定性、界面离子输运、界面强度与柔韧性、界面兼容性等。最后,指出用于金属锂负极的人工界面保护层目前面临的主要挑战,并对其未来的发展进行了展望。     

一种有助于稳定锂金属循环的富氟化位点框架结构

锂金属是下一代高能量密度二次电池的理想负极材料,然而它的应用仍然受制于较差的循环稳定性。近期,二维氟化界面被广泛用于改善锂金属负极的成核机制、沉积形貌和循环稳定性。本工作通过将体积缩小化的氟化石墨颗粒与锂离子传导网络结合,获得了一种富氟化位点的三维框架结构。实验结果证明此类三维氟化结构可显著提升锂金属负极在不同电流密度和容量下的循环稳定性,且优于二维氟化界面结构。通过本工作的研究,证明了相较于单纯的二维氟化界面,三维锂离子传导网络和富氟化位点的合理结合可以成为一种改进的界面结构用于锂金属负极保护,为高能量密度锂金属电池的负极保护提供了新的设计思路。     

Recent progress in liquid electrolytes for lithium metal batteries

Li metal batteries are revived as the next-generation batteries beyond Li-ion batteries. The Li metal anode can be paired with intercalation-type cathodes LiMO₂ and conversion-type cathodes such as sulfur and oxygen. Then, energy densities of Li/LiMO₂ and Li/S,O₂ batteries can reach 400 Whkg^?1 and more than 500 Whkg^?1, respectively, which surpass that of the state-of-the-art LIB (280 Whkg^?1). However, replacing the intercalation-type graphite anode with the Li metal anode suffers from low coulombic efficiency during repeated Li plating/stripping processes, which leads to short cycle lifetime and potential safety problems. The key solution is to construct a stable and uniform solid electrolyte interphase with high Li⁺ transport and high elastic strength on the Li metal anode. This review summarizes recent progress in improving the solid electrolyte interphase by tailoring liquid electrolytes, a classical but the most convenient and cost-effective strategy.     

Recent progress in the application of in situ atomic force microscopy for rechargeable batteries

High energy density batteries are urgently required for sustainable life. The intrinsic understanding of the reaction mechanism at the interfaces is essential for the progress. In this short overview, recent advances in rechargeable batteries by in situ atomic force microscopy are summarized, providing nanoscale information on the solid product evolution and metal plating/stripping inside working batteries. Besides, the multifunctional imaging of the morphology along with mechanical and electrical properties can be achieved to assist further interfacial design. Extensive applications of in situ atomic force microscopy are encouraged to explore the electrochemical mechanism and advanced engineering.     

Recent Progress and Perspectives of Sodium Metal Anodes for Rechargeable Batteries

Sodium metal anodes have attracted significant attention due to their high specific capacity,low redox potential and abundant resources.However,the dendrites and unstable solid electrolyte interphase(SEI)of sodium anodes restrict the development of sodium metal batteries.This review includes the recent progress on the Na anode protection in sodium metal batteries.The strategies are summarized as modified three-dimensional current collectors,artificial solid electrolyte interphases,and electrolyte modifications.Conclusions and perspectives are envisaged for the further understanding and development of Na metal anodes.     

基于表界面反应及优化的锂金属电池研究进展

金属锂具有高理论比容量和低还原电位, 是锂电池阳极的理想材料之一. 但在长期循环充放电过程中, 金属锂因锂枝晶生长会导致出现界面恶化及能量损失严重等问题, 对锂金属电极与电解质表界面反应的优化是一个重要研究方向. 本文介绍了锂枝晶产生的危害, 从分析及抑制锂枝晶沉积两方面综合评述了为解决这一问题所采取的方法, 包括固态电解质界面形成机制和保护机理、 表面改性、 三维锂阳极和液态/固态电解质等方法, 总结了各种方法的优劣势, 并展望锂金属电池在能源领域的研究前景.     

可充电镁电池负极改性策略

可充电镁电池具有理论体积比容量大、 地壳丰度高、 成本低、 环境友好及更为安全等优点, 是未来高能量存储系统发展的重要方向之一. 在大多数传统电解液中, 镁金属负极表面形成的钝化膜会阻碍镁的可逆沉积溶解过程, 从而限制了可充电镁电池的商业化应用. 由于存在成本高、 合成步骤复杂、 离子电导率低及难以同时与正负极兼容等问题, 聚焦于解决镁负级钝化问题的电解液研究陷入瓶颈. 因此, 通过对镁电池负极进行修饰改性, 使其在传统电解液中实现可逆过程是一种具有发展前景的策略. 本文从合金负极及人工界面形成两方面总结了近年来用于可充电镁电池负极改性的策略, 并在分析对比的基础上提出了进一步发展的结论和展望.     

Studies on the Anode/Electrolyte Interfacein Lithium Ion Batteries

Summary.  Rechargeable lithium ion cells operate at voltages of 3.5–4.5 V, which is far beyond the thermodynamic stability window of the battery electrolyte. Strong electrolyte reduction and anode corrosion has to be anticipated, leading to irreversible loss of electroactive material and electrolyte and thus strongly deteriorating cell performance. To minimize these reactions, anode and electrolyte components have to be combined that induce the electrolyte reduction products to form an effectively protecting film at the anode/electrolyte interface, which hinders further electrolyte decomposition reactions, but acts as membrane for the lithium cations, i.e. behaving as a solid electrolyte interphase (SEI). This paper focuses on important aspects of the SEI. By using key examples, the effects of film forming electrolyte additives and the change of the active anode material from carbons to lithium storage alloys are highlighted. Received May 30, 2000. Accepted June 14, 2000