锂离子电池隔膜用非织造材料研究进展

电池隔膜是锂离子电池的核心组件之一,随着锂离子电池的发展而逐渐完善、创新。由于商品化程度最高的聚烯烃类微孔膜受到性能限制,亟需开发新的工艺制备综合性能优异的电池隔膜,优化隔膜的产业结构。综述了近年来使用非织造技术制备的锂离子电池隔膜,包括熔喷法、纺粘法、湿法非织造工艺及静电纺丝法,评价电池隔膜的性能及制备工艺,列举针对各个制备工艺获得的隔膜的改性方法,对锂离子电池隔膜的发展方向做出了设想与展望。     

PPTA锂离子电池隔膜材料研究进展

随着锂离子电池性能的不断提升，对隔膜的性能要求也越来越严格。传统的锂离子电池隔膜材料还存在许多亟待解决的问题，特别是与电池的安全性能方面相关的问题，因此则需要制备具有更加稳定的耐高温和更好机械强度的高分子膜材料。聚对苯二甲酰对苯二胺(PPTA)由于其良好的亲水性、机械性能、耐热性和耐溶剂性，被认为是一类极具发展潜力的新型高性能隔膜材料。然而，如何将PPTA制成具有较高孔隙率的薄膜材料，是目前该领域面临的一大难题。从技术进步的角度，对锂离子电池隔膜制备技术的发展进行了详细的总结，并进行了技术对比分析PPTA电池隔膜的样式。研究表明，PPTA纳米纤维技术可以生产出厚度、孔隙率和电池性能都很好的锂离子电池的隔膜，表明其具有很好的应用潜力。     

湿法制备锂离子电池隔膜的高性能化改性研究

锂离子电池因具有能量密度高、循环寿命长、质量轻、无记忆效应等特性,以及快速充放电等优点,因此成为近年来新型电源技术研究的热点,在高能量和高功率领域备受关注。作为锂离子电池的核心材料之一,隔膜的主要功能是使电池的正、负极分隔开来,阻止电子通过。隔膜性能的优劣直接影响着电池内阻、放电容量、循环使用寿命和电池安全性能的好坏。隔膜越薄、孔隙率越高、电池内阻越小,其高倍率放电性能就越好。     

同轴静电纺丝法制备纤维素基复合纳米纤维及其性能研究

采用同轴静电纺丝技术,以聚偏氟乙烯-六氟丙烯(PVDF-HFP)为壳层,醋酸纤维素(CA)为芯层,制备高效CA/PVDF-HFP复合纳米纤维膜,然后采用0.05mol/L的LiOH溶液对复合纳米纤维膜进行水解,得到纤维素/PVDFHFP复合纤维膜。分别采用差示扫描量热法、扫描电镜、透射电镜、接触角测量仪以及电化学工作站等对样品的性能进行了表征。结果表明:所得复合纳米纤维为壳核结构,并且其热稳定性好、孔隙率高、对电解液亲和性优良,将其用作锂离子电池隔膜,隔膜与锂电极之间的界面电阻低,因此可以推断,该复合纤维膜在锂离子电池隔膜领域的应用前景广泛。     

动力/储能锂离子电池隔膜制备先进技术及研究进展

锂离子电池主要由电极、隔膜、电解液三大部分构成。其中隔膜作为电池的关键部件之一,极大地影响着电池的综合性能。商业聚烯烃隔膜由于润湿性与耐温性差、孔隙率低等缺点,很难满足高性能锂离子电池隔膜的要求。因此,隔膜的制备技术与材料急需进行深入的研究与探索。本文从近期隔膜的研究热点出发,分别从商业聚烯烃隔膜的改性、静电纺丝法及相分离法制备等方面对动力/储能锂离子电池隔膜最新研究成果进行综述,并指出了未来隔膜的发展方向。     

无纺布型锂离子电池隔膜的研究进展

锂离子电池隔膜是隔离正、负极,同时能够让锂离子在正负极间自由通过的多孔隔膜材料.综述了无纺布型锂离子电池隔膜的结构性能特点,以及该材料制备过程中的孔径控制、热闭合作用等关键技术的研究进展.     

锂离子电池隔膜的研究与开发

介绍了锂离子电池隔膜材料的研究与进展，重点综述了聚烯烃锂离子电池隔膜材料的制备方法、孔径结构、孔隙率，透气率，自关闭性能等，认为多层复合隔膜既具有一定的强度又具有较低的自关闭温度，较适合作为锂离子电池隔膜，固体聚合物电解质在锂离子电池中作为电解质的同时还可以起隔膜的作用，表现出良好的应用前景。     

聚烯烃型隔膜的表面亲液改性

为提高锂离子电池聚烯烃多孔膜的亲电液性,增加其离子导电性能,采用辐射聚合甲氧基聚氧化乙烯丙烯酸酯对聚烯烃隔膜进行表面改性。改性后的隔膜对高极性电解液具有良好的湿润性。由于对电解液更高的吸附作用,通过吸附更多的液态电解液,使膜更易传导锂离子。改性膜作为隔膜制备的碳/正极材料锂离子电池不仅具有优良的容量保持性,也具有良好的倍率放电性能。     

基于专利分析的锂离子电池隔膜技术发展趋势研究

对锂离子电池隔膜技术在中、美、欧的专利申请进行了检索、去噪，在此基础上梳理锂离子电池隔膜技术发展生命周期、主要专利权人、技术研发方向，并通过技术功效分析，找到锂离子电池隔膜技术分布和技术效果。从专利分析的结果来看，锂离子电池隔膜技术经历3个阶段，即技术起步期、技术缓慢发展期以及技术快速增长期；锂离子电池隔膜领域的专利主要集中在H01M2/14、H01M2/16、C08J9/00及B32B27/32四大类，主要涉及隔膜的结构、材质及制备工艺；从整体来看，锂离子电池隔膜未来发展方向主要集中在提高隔膜耐热性、研制超薄隔膜、提高隔膜的吸液性能以及研发聚合物电解质隔膜、纤维隔膜等新型隔膜上；并对标东丽、旭化成、帝人、Celgard、住友化学等全球锂离子电池隔膜技术领先公司，建议我国相关研究单位充分发挥在湿法基膜、改性涂布膜研发上的技术优势，优化湿法制膜工艺、拉伸工艺、涂覆改性工艺，提高隔膜安全性、充放电高效性、使用寿命，抢占制高点，针对技术疏松区或技术空白区进行突破。     

一维纳米材料在锂离子电池中的研究进展

主要评述了近年来纳米棒、纳米管、纳米带、纳米纤维等一维纳米材料在锂离子电池正负极、隔膜及全固态电池固态电解质中的应用。一维纳米材料的比表面积大、孔隙率高,能为锂离子提供更短的嵌入脱出路径,还能有效缓解电池工作时产生的体积效应,从而大大提高锂离子电池的性能。介绍了不同方法制备的一维纳米材料在锂离子电池中对电化学性能的优化及提升,并重点介绍了具有产业化前景的静电纺丝法制备用于锂离子电池的一维材料近年的发展;展示了一维纳米材料在锂离子电池中的研究进展,并展望了其发展方向。     

Lithium-Ion Battery Separators for Ionic-Liquid Electrolytes: A Review

Ionic liquids (ILs) are widely studied as a safer alternative electrolyte for lithium-ion batteries. The properties of IL electrolytes compared to conventional electrolytes make them more thermally stable, but they also have poor wetting with commercial separators. In a lithium-ion battery, the electrolyte should completely wet out the separator and electrodes to reduce the cell internal resistance. Investigations of cell materials with IL electrolytes have shown that the wetting issues in IL–electrolyte cells are most likely due to poor separator compatibility, not electrode compatibility. A compatible separator must be developed before IL electrolytes can be used in commercial lithium-ion batteries. Herein, separators for IL electrolytes, including commercial and novel separators, are reviewed. Separators with different processing methods, polymers, additives, and different IL electrolytes are considered. Collated, the separator studies show a strong correlation between ionic conductivity and membrane porosity, even more than the electrolyte type. The challenge of a suitable separator for IL electrolytes is not solved yet. Herein, it is revealed that a separator for IL electrolytes will most likely require a combination of high thermal and mechanical stability polymer, ceramic additives, and an optimized manufacturing process.     

基于离子选择性迁移策略的动力/储能电池隔膜的研究进展

随着锂离子电池等新能源电池在动力/储能领域的不断发展,传统商业聚烯烃隔膜由于润湿性与离子选择性差、孔隙率低等缺点已不能满足高性能锂电池的发展需要。近年来学者针对提升隔膜离子导电性能方面做了大量研究,然而锂电池充放电过程中通常只有阳离子传输参与氧化还原反应,二元电解质中锂离子通常被溶剂分子包围形成较大的溶剂鞘导致阴离子的移动能力反而强于锂离子,电池内部低的阳离子传输效率导致电池出现浓差极化、锂枝晶等问题,限制电池在高倍率下的应用,因此设计抑制阴离子穿梭促进阳离子快速迁移的新型电池隔膜在提升电池综合性能方面具有优异的发展前景。本文从近期的研究热点出发,主要从基团功能化设计、路易斯酸的俘获效应、空间筛分等策略详细介绍基于提升阳离子迁移能力的新型隔膜在电池领域的发展,最后总结指出电池隔膜领域存在的挑战和未来的发展方向。      

Functionalized separator for next-generation batteries

Advancements in battery technology have dramatically increased demand for improvements in separator design, as the separator plays a critical role in ensuring the safety and electrochemical performance of the cells. Current separators, either in commercial usage or under investigation, have yet to meet the high stability and lifespan performance standards necessary to prevent deterioration in the efficiency and reliability of the battery technologies. Recently, considerable effort has been devoted to developing functionalized separators, ranging from designing a variety of new materials and modification methods, and increasingly, to optimizing advanced preparation processes. In order to understand how the mechanisms of separator performance are affected by different properties, we will first summarize recent research progress and then have in-depth discussions regarding the separator’s significant contribution to enhancing the safety and performance of the cell. We then provide our design strategy for future separators, which not only meets the requirements of different type of batteries, but also aims for multifunctionality. We hope such a perspective could provide new inspiration in the development of separator research for future battery technologies.     

Preparation of poly(vinyl alcohol)-based separator with pore-forming additive for lithium-ion batteries

In this work, poly(vinyl alcohol) (PVA)-based separators with microporous structure were prepared from a casting solution composed of PVA resin, water as solvent, and poly(vinyl pyrrolidone) (PVP) polymer as pore controlling additive by non-solvent induced phase separation (NIPS) wet-process and investigated in lithium-ion batteries. The effects of PVP on the morphology and properties of the separator, such as porosity, electrolyte wettability, thermal stability and battery performance (discharge capacity, C-rate capability and cycleability) were systematically analyzed. Results show that PVP induced more pores on the bottom surfaces and the electrolyte uptake, ionic conductivity was further improved. Finally, a 10 wt% PVA-based separator with PVP solid content of 6 wt% exhibited greatly improved porosity, electrolyte uptake, ion conductivity and thermal resistance, resulting in the cell with high safety performance and matched electrochemical performance. The results demonstrated that the PVA-based separator with PVP as pore controlling additive can be a successful candidate serving as an effective separator for lithium-ion battery. Additionally, the present method of producing the microporous separator for LIBs is simple, environmentally benign and economically viable.     

Separator with Nitrogen–Phosphorus Flame-Retardant for LiNixCoyMn1−x−yO2 Cathode-Based Lithium-Ion Batteries

With the pursuit of high-energy-density for lithium-ion batteries (LIBs), the hidden safety problems of batteries have gradually emerged. LiNi_xCo_yMn_1−x−yO₂ (NCM) is considered as an ideal cathode material to meet the urgent needs of high-energy-density batteries. However, the oxygen precipitation reaction of NCM cathode at high temperature brings serious safety concerns. In order to promote high-safety lithium-ion batteries, herein, a new type of flame-retardant separator is prepared using flame-retardant (melamine pyrophosphate, MPP) and thermal stable Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP). MPP takes the advantage of nitrogen–phosphorus synergistic effect upon the increased internal temperature of LIBs, including the dilution effect of noncombustible gas and the rapidly suppression of undesirable thermal runaway. The developed flame-retardant separators show negligible shrinkage over 200 °C and it takes only 0.54 s to extinguish the flame in the ignition test, which are much superior to commercial polyolefin separators. Moreover, pouch cells are assembled to demonstrate the application potential of PVDF-HFP/MPP separators and further verify the safety performance. It is anticipated that the separator with nitrogen–phosphorus flame-retardant can be extensively applied to various high-energy-density devices owing to simplicity and cost-effectiveness.     

Toward stretchable batteries: 3D-printed deformable electrodes and separator enabled by nanocellulose

The needs for stretchable batteries surge as wearable and epidermal electronics emerge. The development of stretchable batteries, however, remains a grand challenge, as the battery components are intrinsically brittle and fracture easily under mechanical loading. Existing efforts to increase the stretchability of battery components often involve complex fabrication processes and thus are not viable for scalable and cost-effective manufacturing. To address this challenge, herein a facile yet effective strategy is developed to fabricate stretchable electrodes and separator for Li-ion batteries using extrusion-based 3D printing of active materials mixed with nanofibrillated cellulose. The resulting electrodes and separator can achieve reversible stretchability of 50%. After 50 stretching cycles, the resistance of the electrodes under 50% stretch only increases by 3%. The origin of the exceptional mechanical and electrical performances of the 3D-printed battery components is twofold: (i) excellent deformability enabled by the 3D-printed serpentine structure at the component level; (ii) the robust nanoscale structure due to the high aspect ratios of nanofibrillated cellulose and carbon nanotubes and the strong interactions between nanofibrillated cellulose and carbon nanotubes or among the individual cellulose fibers at the material structure level. The facile 3D printing of the patterned electrodes/separator leads to low-cost manufacturing of high-performance stretchable Li-ion batteries, demonstrating its promising potential to enable stretchable energy storage devices for wearable and epidermal electronics.     

Recent Development in Separators for High‐Temperature Lithium‐Ion Batteries

Lithium‐ion batteries (LIBs) are promising energy storage devices for integrating renewable resources and high power applications, owing to their high energy density, light weight, high flexibility, slow self‐discharge rate, high rate charging capability, and long battery life. LIBs work efficiently at ambient temperatures, however, at high‐temperatures, they cause serious issues due to the thermal fluctuation inside batteries during operation. The separator is a key component of batteries and is crucial for the sustainability of LIBs at high‐temperatures. The high thermal stability with minimum thermal shrinkage and robust mechanical strength are the prime requirements along with high porosity, ionic conductivity, and electrolyte uptake for highly efficient high‐temperature LIBs. This Review deals with the recent studies and developments in separator technologies for high‐temperature LIBs with respect to their structural layered formation. The recent progress in monolayer and multilayer separators along with the developed preparation methodologies is discussed in detail. Future challenges and directions toward the advancement in separator technology are also discussed for achieving remarkable performance of separators in a high‐temperature environment.     

MOFs及衍生复合材料在锂硫电池中的设计应用

在能源危机与环境问题日益凸显的背景下,电化学储能技术得到了迅速发展。在“超越锂”储能领域的竞争者中,锂硫电池(Li-S)因其具有高理论比容量、高质量能量密度并且环境友好、价格低廉等优点,成为最有前途的新储能技术。但是,锂硫电池的发展仍存在一些瓶颈问题需要解决,例如正极材料导电性能差、多硫化物穿梭效应及在充放电过程中电极体积膨胀等。作为锂硫电池的关键组成部分,电极和隔膜材料的设计和制备对解决这些问题及电池整体性能提升起到了重要的作用。金属有机骨架(MOFs)及衍生的复合材料作为锂硫电池电极或隔膜修饰材料,具有质量轻、电子和离子传导性好、孔道丰富和活性位点均匀分布等优势。此外,这类复合材料还具备形貌和组分可控、来源丰富和孔径可调等特性,从而便于机制研究。本文全面介绍了锂硫电池组成、工作原理并综述了近几年MOFs及衍生复合材料在锂硫电池中的研究进展,重点讨论了其在正极材料和隔膜材料中的应用,并对未来该材料在锂硫电池研究方向上的前景和突破进行了展望。