锂离子电池凝胶聚合物隔膜的研究进展

作为锂离子电池重要组分,隔膜由多孔聚烯烃高分子材料组成;电解质体系由有机碳酸酯和六氟磷酸锂混合组成,虽具有高离子电导率,但因液态碳酸酯的易燃特性给锂离子电池带来了安全隐患。利用能够将液态电解质体系凝胶化的聚合物制备得到的凝胶聚合物隔膜,结合了液态电解质体系高电导率和固态电解质高安全性的优点。凝胶聚合物隔膜的研究从简单微孔凝胶聚合物隔膜开始,经历了引入少量纳米无机颗粒的掺杂凝胶聚合物隔膜,到引入大量纳米颗粒的凝胶陶瓷隔膜的发展历程。本文详细介绍这三种类型凝胶聚合物隔膜的物理化学特性,最后展望凝胶聚合物隔膜的发展趋势。     

金属锂电池的热失控与安全性研究进展

锂离子电池在便携式储能器件及电动汽车领域得到了广泛应用,然而频繁发生的电池起火爆炸事故,使热失控和热安全问题备受人们关注,目前已有多篇综述报道了缓解锂离子电池热失控的措施。相比于已经接近理论比能极限的锂离子电池,金属锂负极具有更高的比容量、更低的电势和高反应活性,但是不可控的锂枝晶生长,使得金属锂电池的热失控问题更为复杂和严重。针对金属锂电池的热失控问题,本文首先介绍了热失控的诱因及基本过程和阶段,其次从材料层面综述了提高电池热安全性的多种策略,包括使用阻燃性电解质、离子液体电解质、高浓电解质和局域高浓电解质等不易燃液态电解质体系,开发高热稳定性隔膜、热响应隔膜、阻燃性隔膜和具有枝晶检测预警与枝晶消除功能的新型智能隔膜,以及研究热响应聚合物电解质,最后对金属锂电池热失控在未来的进一步研究进行了展望。     

Separator technologies for lithium-ion batteries

Although separators do not participate in the electrochemical reactions in a lithium-ion (Li-ion) battery, they perform the critical functions of physically separating the positive and negative electrodes while permitting the free flow of lithium ions through the liquid electrolyte that fill in their open porous structure. Separators for liquid electrolyte Li-ion batteries can be classified into porous polymeric membranes, nonwoven mats, and composite separators. Porous membranes are most commonly used due to their relatively low processing cost and good mechanical properties. Although not widely used in Li-ion batteries, nonwoven mats have the potential for low cost and thermally stable separators. Recent composite separators have attracted much attention, however, as they offer excellent thermal stability and wettability by the nonaqueous electrolyte. The present paper (1) presents an overview of separator characterization techniques, (2) reviews existing technologies for producing different types of separators, and (3) discusses directions for future investigation. Research into separator fabrication techniques and chemical modifications, coupled with the numerical modeling, should lead to further improvements in the performance and abuse tolerance as well as cost reduction of Li-ion batteries.     

A Nano‐shield Design for Separators to Resist Dendrite Formation in Lithium‐Metal Batteries

Lithium dendrite growth during repeated charge and discharge cycles of lithium‐metal anodes often leads to short‐circuiting by puncturing the porous separator. Here, a morphological design, the nano‐shield, for separators to resist dendrites is presented. Through both mechanical analysis and experiment, it is revealed that the separator protected by the nano‐shield can effectively inhibit the penetration of lithium dendrites owing to the reduced stress intensity generated and therefore mitigate the short circuit of Li metal batteries. More than 110 h of lithium plating life is achieved in cell tests, which is among the longest cycle life of lithium metal anode and five times longer than that of blank separators. This new aspect of morphological and mechanical design not only provides an alternative pathway for extending lifetime of lithium metal anodes, but also sheds light on the role of separator engineering for various electrochemical energy storage devices.     

The use of polymers in Li‐S batteries: A review

Recent developments in the use of polymeric materials as device components in lithium sulfur (Li‐S) batteries are reviewed. Li‐S batteries have generated tremendous interest as a next generation battery exhibiting charge capacities and energy densities that greatly exceed Li‐ion battery technologies. In this Highlight, the first comprehensive review focusing on the use of polymeric materials throughout these devices is provided. The key role polymers play in Li‐S technology is presented and organized in terms of the basic components that comprise a Li‐S battery: the cathode, separator, electrolyte, and anode. After a straightforward introduction to the construction of a conventional Li‐S device and the mechanisms at work during cell operation, the use of polymers as binders, protective coatings, separators, electrolytes, and electroactive materials in Li‐S batteries will be reviewed. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1635–1668     

Polymer/colloid dual-phase electrolyte membrane for rechargeable lithium batteries

In this work, a polymer/ceramic phase-separation porous membrane is first prepared from polyvinyl alcohol–polyacrylonitrile water emulsion mixed with fumed nano-SiO₂ particles by the phase inversion method. This porous membrane is then wetted by a non-aqueous Li–salt liquid electrolyte to form the polymer/colloid dual-phase electrolyte membrane. Compared to the liquid electrolyte in conventional polyolefin separator, the obtained electrolyte membrane has superior properties in high ionic conductivity (1.9 mS?cm^?1 at 30 °C), high Li⁺ transference number (0.41), high electrochemical stability (extended up to 5.0 V versus Li⁺/Li on stainless steel electrode), and good interfacial stability with lithium metal. The test cell of Li/LiCoO₂ with the electrolyte membrane as separator also shows high-rate capability and excellent cycle performance. The polymer/colloid dual-phase electrolyte membrane shows promise for application in rechargeable lithium batteries.     

Improving the properties of HDPE based separators for lithium ion batteries by blending block with copolymer PE-b-PEG

To improve the performances of HDPE-based separators, polyether chains were incorporated into HDPE membranes by blending with poly(ethylene-block-ethylene glycol) (PE-b-PEG) via thermally induced phase separation (TIPS) process. By measuring the composition, morphology, crystallinity, ion conductivity, etc, the influence of PE-b-PEG on structures and properties of the blend separator were investigated. It was found that the incorporated PEG chains yielded higher surface energy for HDPE separator and improved affinity to liquid electrolyte. Thus, the stability of liquid electrolyte trapped in separator was increased while the interfacial resistance between separator and electrode was reduced effectively. The ionic conductivity of liquid electrolyte soaked separator could reach 1.28 × 10-3 S.cm-1 at 25℃, and the electrochemical stability window was up to 4.5 V (versus Li + /Li). These results revealed that blending PE-b-PEG into porous HDPE membranes could efficiently improve the performances of PE separators for lithium batteries.     

高安全性阻燃动力锂离子电池隔膜

逐年加剧的能源短缺以及日益严重的环境污染问题使得发展电动汽车日益迫切.电动汽车安全问题对动力锂离子电池在大功率输出和高安全性能等方面提出了更高的要求.隔膜电解质体系是制约动力锂离子电池快速发展的重要瓶颈之一,因此,开发高性能的隔膜对提高动力锂离子电池的综合性能至关重要.本文综述了近年来隔膜材料的种类、制备工艺、性能以及本课题组在高安全性阻燃动力锂离子电池隔膜方面的研究进展,并对未来电池隔膜的发展方向进行了预期和展望.     

Recent Progress in High-Performance Lithium Sulfur Batteries: The Emerging Strategies for Advanced Separators/Electrolytes Based on Nanomaterials and Corresponding Interfaces

Lithium-sulfur (Li−S) batteries, possessing excellent theoretical capacities, low cost and nontoxicity, are one of the most promising energy storage battery systems. However, poor conductivity of elemental S and the “shuttle effect” of lithium polysulfides hinder the commercialization of Li−S batteries. These problems are closely related to the interface problems between the cathodes, separators/electrolytes and anodes. The review focuses on interface issues for advanced separators/electrolytes based on nanomaterials in Li−S batteries. In the liquid electrolyte systems, electrolytes/separators and electrodes system can be decorated by nano materials coating for separators and electrospinning nanofiber separators. And, interface of anodes and electrolytes/separators can be modified by nano surface coating, nano composite metal lithium and lithium nano alloy, while the interface between cathodes and electrolytes/separators is designed by nano metal sulfide, nanocarbon-based and other nano materials. In all solid-state electrolyte systems, the focus is to increase the ionic conductivity of the solid electrolytes and reduce the resistance in the cathode/polymer electrolyte and Li/electrolyte interfaces through using nanomaterials. The basic mechanism of these interface problems and the corresponding electrochemical performance are discussed. Based on the most critical factors of the interfaces, we provide some insights on nanomaterials in high-performance liquid or state Li−S batteries in the future.     

聚烯烃锂离子电池隔膜的研究进展

随着信息技术时代的发展,锂离子电池被广泛应用,电池隔膜作为锂离子电池的重要组成部分越发引起大家的重视。聚烯烃锂离子电池隔膜由于其优异的机械性能和化学稳定性,以及相对廉价的特点,在锂离子电池发展初期就被研发应用,已成为锂离子电池隔膜的主流。本文综述了聚烯烃锂离子电池隔膜的制备方法,主要介绍了干法和湿法,及相关的产品。重点阐述了聚烯烃锂离子电池隔膜的性能需求和改性方法,主要包括隔膜的孔隙率、隔膜对电解液的亲和性以及热稳定性等方面。     

A multilayer composite separator consisting of non-woven mats and ceramic particles for use in lithium ion batteries

Battery separator is a porous membrane that is placed between the positive and negative electrodes to avoid their electric contact, while maintaining a good ionic flow through the liquid electrolyte filled in its pores. Non-woven mats have been evaluated as battery separators due to their highly porous structures. In this study, composite non-woven mats were fabricated through electrospinning and lamination with a ceramic layer, and evaluated as lithium ion battery separators. The lamination with the ceramic layer provides not only improved separator dimensional stability at elevated temperatures but also the potential to increase the production rate of electrospun separators. The electrospun mats keep ceramic particles from dropping avoiding the non-uniform current density distribution caused by the loss of the ceramic particles. The composite separators enabled good ionic conductivity when saturated with a liquid electrolyte. Coin cells with this type of separators showed not only stable cycling performance but also good rate capabilities at room temperature.     

锂硫电池多功能涂层隔膜的研究进展与展望

先进储能系统的开发对于满足电动汽车、便携式设备和可再生能源存储不断增长的需求至关重要. 锂硫（Li-S）电池具有比能量高、原材料成本低和环境友好等优点,是新型高性能电池研究领域中的热点. 然而,锂硫电池面向实际应用还存在许多问题,如可溶性多硫化物中间体的穿梭效应、锂枝晶生长以及锂硫电池在使用过程中的热稳定性和安全性等. 设计开发多功能涂层隔膜是改善锂硫电池上述不足的有效策略之一,在本综述中,详细论述了锂硫电池多功能涂层隔膜的研究进展. 包括聚合物材料、碳材料、氧化物材料、催化纳米粒子改性的功能化涂层隔膜及增强电池热稳定性、安全性的特种功能隔膜,对其作用特性进行了系统分析,并对未来研究发展提出展望.     

A redox‐active polythiophene‐modified separator for safety control of lithium‐ion batteries

A potential‐sensitive separator is prepared simply by incorporating a redox‐active poly(3‐butylthiophene) (P3BT) into the micropores of a commercial porous polyolefin film and tested for overcharge protection of LiFePO₄/Li₄Ti₅O₁₂ lithium‐ion batteries. The experimental results demonstrate that owing to the reversible p‐doping and dedoping of the redox‐active P3BT polymer embedded in the separator with the changes of the cathode potential from an overcharge state to a normal operating state, this type of separator can reversibly switch between electronically insulating state and conductive state to maintain the charge voltage of LiFePO₄/Li₄Ti₅O₁₂ cells at a safety value of ≤2.4 V, and thus protecting the cell from voltage runaway. As this type of the separators works reversibly and has no negative impact on the battery performances, it can be used as an internal and self‐protecting mechanism for commercial lithium‐ion batteries and other rechargeable batteries. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1487–1493     

纤维素微孔锂电隔膜的制备及性能研究

为了改善锂电隔膜的亲液性和耐高温性,以醋酸纤维素为成膜材料,利用相转化法制备了新型锂电隔膜,通过形貌和孔道结构表征、亲液性能和耐热性能测试对醋酸纤维素隔膜的基本性能进行研究,并将该隔膜装配成锂离子电池进行充放电性能测试. 结果表明,醋酸纤维素隔膜具有均匀的微孔结构,孔隙率达到65%,约为传统聚烯烃隔膜的1.5倍;纤维素材料的良好亲液性和高孔隙率结构改善了隔膜的吸液性能,其吸液率达到285%;该隔膜在150 ^oC、30 min的热处理条件下未发生明显的热收缩. 鉴于上述优点,相对于市售PE隔膜,醋酸纤维素隔膜所装配锂离子电池显示出更优的循环性能和倍率性能.     

A Nano-shield Design for Separators to Resist Dendrite Formation in Lithium-Metal Batteries

Lithium dendrite growth during repeated charge and discharge cycles of lithium-metal anodes often leads to short-circuiting by puncturing the porous separator. Here, a morphological design, the nano-shield, for separators to resist dendrites is presented. Through both mechanical analysis and experiment, it is revealed that the separator protected by the nano-shield can effectively inhibit the penetration of lithium dendrites owing to the reduced stress intensity generated and therefore mitigate the short circuit of Li metal batteries. More than 110 h of lithium plating life is achieved in cell tests, which is among the longest cycle life of lithium metal anode and five times longer than that of blank separators. This new aspect of morphological and mechanical design not only provides an alternative pathway for extending lifetime of lithium metal anodes, but also sheds light on the role of separator engineering for various electrochemical energy storage devices.     

A Review on Lithium-Ion Battery Separators towards Enhanced Safety Performances and Modelling Approaches

In recent years, the applications of lithium-ion batteries have emerged promptly owing to its widespread use in portable electronics and electric vehicles. Nevertheless, the safety of the battery systems has always been a global concern for the end-users. The separator is an indispensable part of lithium-ion batteries since it functions as a physical barrier for the electrode as well as an electrolyte reservoir for ionic transport. The properties of separators have direct influences on the performance of lithium-ion batteries, therefore the separators play an important role in the battery safety issue. With the rapid developments of applied materials, there have been extensive efforts to utilize these new materials as battery separators with enhanced electrical, fire, and explosion prevention performances. In this review, we aim to deliver an overview of recent advancements in numerical models on battery separators. Moreover, we summarize the physical properties of separators and benchmark selective key performance indicators. A broad picture of recent simulation studies on separators is given and a brief outlook for the future directions is also proposed.     

Understanding the separator pore size inhibition effect on lithium dendrite via phase-field simulations

Dendrite growth in lithium-ion batteries may bring thermal run-away especially at high current densities,which remains the major bottleneck to implement safe and fast charging for portable electronic devices or electronical vehicles. Designing dendrite inhibition separators with proper pore size is considered to be one of the most promising strategies to guarantee the battery safety. However, due to the impossible observation of lithium-ion distribution under separator by experiments, the underl...     

Towards K‐Ion and Na‐Ion Batteries as “Beyond Li‐Ion”

Li‐ion battery commercialized by Sony in 1991 has the highest energy‐density among practical rechargeable batteries and is widely used in electronic devices, electric vehicles, and stationary energy storage system in the world. Moreover, the battery market is rapidly growing in the world and further fast‐growing is expected. With expansion of the demand and applications, price of lithium and cobalt resources is increasing. We are, therefore, motivated to study Na‐ and K‐ion batteries for stationary energy storage system because of much abundant Na and K resources and the wide distribution in the world. In this account, we review developments of Na‐ and K‐ion batteries with mainly introducing our previous and present researches in comparison to that of Li‐ion battery.     

X‐ray Absorption Near‐Edge Structure and Nuclear Magnetic Resonance Study of the Lithium–Sulfur Battery and its Components

Understanding the mechanism(s) of polysulfide formation and knowledge about the interactions of sulfur and polysulfides with a host matrix and electrolyte are essential for the development of long‐cycle‐life lithium–sulfur (Li–S) batteries. To achieve this goal, new analytical tools need to be developed. Herein, sulfur K‐edge X‐ray absorption near‐edge structure (XANES) and ^6,7Li magic‐angle spinning (MAS) NMR studies on a Li–S battery and its sulfur components are reported. The characterization of different stoichiometric mixtures of sulfur and lithium compounds (polysulfides), synthesized through a chemical route with all‐sulfur‐based components in the Li–S battery (sulfur and electrolyte), enables the understanding of changes in the batteries measured in postmortem mode and in operando mode. A detailed XANES analysis is performed on different battery components (cathode composite and separator). The relative amounts of each sulfur compound in the cathode and separator are determined precisely, according to the linear combination fit of the XANES spectra, by using reference compounds. Complementary information about the lithium species within the cathode are obtained by using ⁷Li MAS NMR spectroscopy. The setup for the in operando XANES measurements can be viewed as a valuable analytical tool that can aid the understanding of the sulfur environment in Li–S batteries.     

A Selection Rule for Hydrofluoroether Electrolyte Cosolvent: Establishing a Linear Free‐Energy Relationship in Lithium–Sulfur Batteries

Hydrofluoroethers (HFEs) have been adopted widely as electrolyte cosolvents for battery systems because of their unique low solvating behavior. The electrolyte is currently utilized in lithium‐ion, lithium–sulfur, lithium–air, and sodium‐ion batteries. By evaluating the relative solvating power of different HFEs with distinct structural features, and considering the shuttle factor displayed by electrolytes that employ HFE cosolvents, we have established the quantitative structure–activity relationship between the organic structure and the electrochemical performance of the HFEs. Moreover, we have established the linear free‐energy relationship between the structural properties of the electrolyte cosolvents and the polysulfide shuttle effect in lithium–sulfur batteries. These findings provide valuable mechanistic insight into the polysulfide shuttle effect in lithium–sulfur batteries, and are instructive when it comes to selecting the most suitable HFE electrolyte cosolvent for different battery systems.