锂离子电池有机/聚丙烯复合隔膜研究

以单向拉伸的PP隔膜为基膜,PVDF、PTFE、PEK-C、PES和PPSU等多种具有耐高温性能的聚合物为涂层材料,制备了有机/PP复合隔膜.对复合隔膜的形貌、透气性及热稳定性进行了研究,并考察了复合隔膜对电解液的电化学稳定性和电池循环性能的影响.研究发现,有机复合隔膜的透气性能略有降低,但热收缩性能有了明显的改善.电化学性能表明,复合隔膜在锂离子电池工作的电化学窗口性能稳定.电池循环性能发现,采用有机复合隔膜电池的放电容量普遍增加,倍率放电性能也优于使用PP隔膜的电池.     

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.     

锂离子电池安全性保护措施研究进展

锂离子电池最常见的安全性问题主要出现在电解液和隔膜.热失控是导致锂离子电池产生安全事故的主要原因.改变电解液组分、增加电解液组分、引入阻燃添加剂等措施,能够有效缓解并抑制热效应,降低可燃性.改性聚烯烃隔膜是提高隔膜热稳定性的简单方法,使用高熔点的聚合物或无机材料对隔膜进行修饰,其本质类似于给隔膜穿上一层“外骨骼”,用来抵御热冲击和机械冲击.隔膜在保证具备基本功能的同时,还要更加环保,逐步转向可持续的生物质材料.本文针对近年来锂离子电池的安全保护措施进行了综述,主要包括近几年内部保护措施和外部保护措施的相关研究和探索方面的成果.详细介绍了最近报道的不易燃电解液、阻燃添加剂、隔膜、正极材料、限流设备和电池管理系统的作用机理和研究进展,并展望了未来锂离子电池安全性研究的发展方向.     

隔膜对锂-铜电池短路时间的影响

隔膜在锂离子电池中起着防止正负极直接短路和提供离子传输通道的作用，决定着电池的安全性能.在本文中，我们利用锂-铜电池的短路时间建立了一种评价隔膜安全性能的方法 .通过对电池短路时间的研究发现，对于同一种类型的隔膜，短路时间与隔膜厚度和内阻的线性相关度较高，隔膜厚度和内阻的增加均能延长电池的短路时间.同一厚度不同类型的隔膜，其电池的短路时间与隔膜自身的微孔结构相关.电池的短路时间与隔膜的穿刺强度之间的线性相关程度较低，结合电池短路后隔膜表面枝晶形貌的观察，我们推测枝晶是沿隔膜的孔道持续生长最终穿透隔膜，而非刺穿隔膜导致的电池短路.利用不同厚度的隔膜组装锂硫电池，发现循环寿命与隔膜厚度具有显著线性相关性，验证了测试方法在实际电池使用中的有效性.同时，研究也证实，利用功能隔膜调控锂的沉积行为、抑制锂的枝晶沉积能极大延长电池的短路时间，提升电池的安全性能，这为新型高安全性复合隔膜及电池的研究和设计提供了新的思路和理论依据.     

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.     

锂硫电池隔膜材料的研究进展

锂硫电池因其具有较高的理论容量和能量密度、原料丰富、环保性好、成本低等优点,被认为是目前最具发展潜力的新型高性能电池之一.锂硫电池主要由正极材料、电解液、隔膜以及负极材料构成.隔膜作为锂硫电池的重要组成部分之一,其性能优劣对电池整体性能有着重要的影响,高品质隔膜材料开发已是锂硫电池重要研究方向之一.本文全面综述了聚烯烃、聚环氧乙烷、聚偏氟乙烯、共混聚合物等微孔隔膜和纳米纤维多孔膜在锂硫电池隔膜材料中的最新研究进展,并对未来高性能锂硫电池隔膜材料的开发进行了展望.     

锂硫电池先进功能隔膜的研究进展

随着电子设备和电动汽车对储能设备性能要求的不断提高,锂硫电池因其多电子转化化学赋予的高能量密度受到广泛关注.当前锂硫电池的实用化受到库伦效率低、正极容量快速衰减、负极循环性能差等问题的制约.针对锂硫电池上述瓶颈,设计多功能电解质系统有望大幅提升活性材料的利用效率及循环寿命.本文综述了近年来锂硫电池中多功能隔膜系统的研究进展,具体包括面向抑制副反应的选择性透过隔膜、面向正极的低界面电阻隔膜以及面向稳定负极界面的隔膜.并展望了锂硫电池多功能隔膜系统面临的科学挑战与未来发展的机遇.     

隔膜对双电层电容器和混合型电池-超级电容器的电化学性能的影响

隔膜是双电层电容器和混合型电池-超级电容器等电化学储能器件的重要组成元件.本文采用1 mol?L-1四乙基四氟硼酸铵的丙烯碳酸酯电解液制备了基于活性炭的扣式双电层电容器,并采用1 mol?L-1六氟磷酸锂锂离子电解液制备了(LiNi0.5Co0.2Mn0.3O2+活性炭)/石墨体系的混合型电池-超级电容器.研究了不同类型隔膜的物理化学性能,以及其对双电层电容器和混合型电池-超级电容器的电化学性能的影响.四种隔膜分别是无纺布聚丙烯毡、多孔聚丙烯薄膜、Al2O3涂层的聚丙烯薄膜和纤维素纸隔膜.进行了表面形貌、差示扫描量热、电解液吸液量和表观接触角测试表征.电化学测试表明,采用纤维素隔膜的双电层电容器具有最高的比电容和更优的倍率性能,电容器的自放电性能差别不大.而对于混合型电池-超级电容器,采用聚丙烯薄膜和无纺布聚丙烯毡隔膜器件的比容量比其它器件约高20%,且采用纤维素隔膜的器件自放电率最高.     

无机复合锂离子电池隔膜的制备及性能研究

用氧化铝(Al2O3)、硫酸钡(Ba SO4)、锆钛酸铅(PZT)、二氧化钛(Ti O2)、气相二氧化硅R202(RSi O2)、A380(ASi O2)和沉淀相二氧化硅(PSSi O2)7种无机纳米材料制备成分散液,在单向拉伸聚丙烯(PP)隔膜表面单面涂覆制备了复合隔膜.对复合隔膜的形貌、透气性及热稳定性进行了研究,并通过线性扫描曲线和不同倍率下电池充放电循环考察了复合隔膜对电解液的电化学稳定性和电池循环性能的影响.结果表明,7种复合隔膜与空白PP隔膜相比,在140℃下的热收缩率均减小1倍以上,表明其中无机纳米材料对PP隔膜的热收缩性能有很大改善.电池循环性能研究表明,这几种复合隔膜电池循环性能都有不同程度的提高,且在较高倍率下依旧可以发挥优势(ASi O2涂层复合隔膜除外).ASi O2涂层复合隔膜电池在2 C高倍率放电时容量快速衰减,其原因可能是ASi O2过大的比表面积增加了锂离子迁移的阻力.     

具有热关断涂层的锂电池隔膜性能表征

介绍了一种具有热关断涂层的锂电池功能隔膜,利用热关断涂层的耐热特点来降低隔膜的热闭孔温度,当电池内部达到一定的温度时,涂层迅速熔化并覆于极片和隔膜之间,形成绝缘层,阻止锂离子的进一步传输,从而提高锂离子电池的安全性. 实验表明,热关断涂层表观均匀,对电池的内阻、倍率性能和循环性能没有不良影响. 电池的安全测试表明,该功能隔膜可表现出优异的安全防护作用.     

Progresses in Manufacturing Techniques of Lithium‐Ion Battery Separators in China

The cover picture shows a microporous separator which is a key component to determine the safety and performance of lithium‐ion battery (LIB). In China, the LIB separators were totally imported from abroad before 2008. Based on the extensive studies on the pore formation mechanisms, Fu et al. realized the industrialization of LIB separators successfully. Nowadays, China has become the biggest producer of LIB separators in the word. More details are discussed in the article by Fu et al. on page 1207–1215.

     

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.     

Thickness difference induced pore structure variations in cellulosic separators for lithium-ion batteries

The pore structure of the separator is crucial to the performance of a lithium-battery as it affects the cell resistance. Herein, a straightforward approach to vary the pore structure of Cladophora cellulose (CC) separators is presented. It is demonstrated that the pore size and porosity of the CC separator can be increased merely by decreasing the thickness of the CC separator by using less CC in the manufacturing of the separator. As the pore size and porosity of the CC separator are increased, the mass transport through the separator is increased which decreases the electrolyte resistance in the pores of the separator. This enhances the battery performance, particularly at higher cycling rates, as is demonstrated for LiFePO₄/Li half-cells. A specific capacity of around 100 mAh g^?1 was hence obtained at a cycling rate of 2 C with a 10 µm thick CC separator while specific capacities of 40 and close to 0 mAh g^?1 were obtained for separators with thicknesses of 20 and 40 µm, respectively. As the results also showed that a higher ionic conductivity was obtained for the 10 µm thick CC separator than for the 20 and 40 µm thick CC separators, it is clear that the different pore structure of the separators was an important factor affecting the battery performance in addition to the separator thickness. The present straightforward, yet efficient, strategy for altering the pore structure hence holds significant promise for the manufacturing of separators with improved performance, as well as for fundamental studies of the influence of the properties of the separator on the performance of lithium-ion cells.     

Effect of silica nanoparticles/poly（vinylidene fluoride-hexafluoropropylene） coated layers on the performance of polypropylene separator for lithium-ion batteries

In an effort to reduce thermal shrinkage and improve electrochemical performance of porous polypropylene （PP） separators for lithium-ion batteries, a new composite separator is developed by introducing ceramic coated layers on both sides of PP separator through a dip-coating process. The coated layers are comprised of heat-resistant and hydrophilic silica nanoparticles and polyvinylidene fluoride-hexafluoropropylene （PVDF-HFP） binders. Highly porous honeycomb structure is formed and the thickness of the layer is only about 700 nm. In comparison to the pristine PP separator, the composite separator shows significant reduction in thermal shrinkage and improvement in liquid electrolyte uptake and ionic conduction, which play an important role in improving cell performance such as discharge capacity, C-rate capability, cycle performance and coulombic efficiency.     

Recent advances on battery separators based on poly(vinylidene fluoride) and its copolymers for lithium-ion battery applications

Lithium-ion batteries represent one of the most suitable systems for effective energy storage for a wide range of applications, such as smartphones, laptops, electric vehicles, or even home storage systems. Among the different battery components, the separator plays an essential role in the performance of the batteries; its most relevant characteristics are (micro)structure, wettability, thermal and mechanical properties, and ionic conductivity value. This work provides a comprehensive review of the current state of the art in lithium-ion battery separator membranes based on poly(vinylidene fluoride) (PVDF) and its copolymers. The most recent developments in the last two years are presented, focusing on the different separator types that have been developed with the aim of improving wettability, thermal characteristics, and cycling behavior. The most used types of PVDF separators are composites, polymer blends, and the combination of both. Among the most common fillers, metal–organic frameworks, ionic liquids, and ceramic particles have been used for the development of PVDF-based composites and polymers such as poly(m-phenylene isophthalamide), poly(acrylonitrile), poly(tetrafluoroethylene), or poly(methyl methacrylate), for the development of polymer blends. Electrospinning is one of the most used processing techniques to improve wettability, thermal stability, and mechanical properties. The wettability of separators has been also improved by using PVDF as a coating on commercial separators.It is shown that PVDF-based battery separators can play an important role in the next generation of high-performance batteries.     

锂离子二次电池用隔膜的制备及其性质

本文采用倒相法制备了锂离子二次电池用的PVDF HFP共聚物型多孔聚合物隔膜 ,该聚合物膜具有良好的机械性能 ,其孔隙率可达 75% ,吸附电解液后增重 4 50 % ,电导率为 10 - 3S/cm ,组装成电池后表现出良好的循环性能和较低的极化率     

Lithium-ion battery separators: Recent developments and state of art

Lithium-ion battery separators are receiving increased consideration from the scientific community. Single-layer and multilayer separators are well-established technologies, and the materials used span from polyolefins to blends and composites of fluorinated polymers. The addition of ceramic nanoparticles and separator coatings improves thermal and mechanical properties, as well as electrolyte uptake and ionic conductivity. The state-of-art separators are actively involved in the cell chemistry through specific functional groups on their surface. Among the numerous properties, safety features and long cycle life are high-priority requirements for next-generation lithium-ion batteries.     

A roadmap of battery separator development: Past and future

The battery separator is one of the most essential components that highly affect the electrochemical stability and performance in lithium-ion batteries. In order to keep up with a nationwide trend and needs in the battery society, the role of battery separators starts to change from passive to active. Many efforts have been devoted to developing new types of battery separators by tailoring the separator chemistry. In this article, the overall characteristics of battery separators with different structures and compositions are reviewed. In addition, the research directions and prospects of separator engineering are suggested to provide a solid guideline for developing a safe and reliable battery system.     

Flexible,high-wettability and thermostable separator based on fluorinated polyimide for lithium-ion battery

To meet the booming demands for lithium-ion battery (LIB), it is practically significant to promote its electrochemical performance and safety. In our work, a novel kind of flexible membrane as separator for LIB is prepared via phase inversion method with soluble polyimide (SPI) containing trifluoromethyl substituent, which is synthesized from 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (6FAPB) and 4,4′-oxydiphthalic anhydride (ODPA). The SPI separator shows 5% weight loss temperature (T_d5%) of 535 °C and maintains intrinsic dimension even after heating at 200 °C. The SPI membrane depicts a sponge-like structure with abundant interconnected pores and delivers a dominant porosity (67%). The SPI membrane displays desired electrolyte wettability, validated by contact angle tests (16.2° and 46.8° for SPI membrane and PE separator, respectively) and electrolyte uptake tests (420 and 132% for SPI membrane and PE separator, respectively). The LIB with SPI membrane as separator exhibits nice ionic conductivity (0.92 mS cm^?1) than that with PE separator (0.30 mS cm^?1), and therefore affords better electrochemical performance, such as cycling stability and rate capability.     

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.