聚偏氟乙烯-沸石复合锂电隔膜的制备及性能

针对传统聚烯烃类锂离子电池隔膜的耐温性差和电解液亲和性差的问题,本实验以微孔沸石纳米粒子和聚偏氟乙烯树脂(PVDF)为主要原料,通过相转化法制备了综合性能优异的沸石/PVDF复合锂电隔膜。结果表明:与商用聚乙烯(PE)膜相比,所制备的沸石/PVDF复合隔膜具有更加发达的孔道结构,其孔隙率超过70%,约为PE膜的2倍。沸石/PVDF复合膜的耐高温性和电解液润湿性明显优于PE膜和纯PVDF膜,经过160℃、0.5h的高温处理后,复合膜的热收缩率仅为5%,而PE膜已完全融化,收缩率达到100%,PVDF膜收缩率超过50%;沸石/PVDF复合膜的电解液接触角仅为7.4°,而PE膜和PVDF膜的接触角高达42.5°和31.7°。受益于丰富的孔道结构和良好的电解液吸收/保持能力,沸石/PVDF复合膜所装配锂离子电池的倍率放电容量高于PE膜,同时,该复合膜装配电池的循环性能也优于传统聚乙烃隔膜。     

石墨电极表面聚丙烯腈纳米纤维膜的制备及性能

为了充分利用纳米纤维膜的多孔特性,同时克服其低机械强度的缺陷,以聚丙烯腈(PAN)为主要原料,采用静电纺丝法在石墨电极表面制备PAN纳米纤维膜,形成隔膜-电极一体化结构单元(SAA),并对SAA的孔道结构、力学性能、电解液性能、热尺寸稳定性及电池性能进行系统研究.结果表明:SAA中PAN隔膜与石墨电极的粗糙表面结合紧密,PAN隔膜呈现出发达的孔道结构,电解液亲和性良好;在150℃热处理0.5 h,SAA表面隔膜的热收缩率小于2％,显著优于市售聚烯烃隔膜.基于良好的理化特性,SAA装配的钴酸锂全电池表现出优异的循环容量和倍率容量保持性,如在0.2 C下,经历200次循环后电池的放电容量保持率为98％,在32 C下电池的放电容量为0.5 C下的44.3％.因此,电极表面直接制备纳米纤维膜可形成完整的隔膜-电极一体化单元,在充分发挥纳米纤维膜优势的同时,可优化电极与隔膜的界面相容性、改善电池的充放电性能,并能够提高电池的装配效率.     

聚苯醚纳米纤维锂电隔膜的制备

为了改善锂离子电池的高温安全性和充放电性能,以聚苯醚树脂为成膜材料,采用静电纺丝技术制备了纳米纤维锂电隔膜,对隔膜的形貌、结构、电解液亲和性和耐高温性进行了系统测试,并将该纳米纤维膜装配到电池中进行充放电性能测试。结果显示:聚苯醚隔膜的纳米纤维直径约为260nm,纤维交错形成均匀的孔道(平均孔径约500nm),其孔隙率达到74%以上,为聚烯烃隔膜的2倍左右;聚苯醚树脂的电解液亲和性和高孔隙率强化了隔膜的电解液吸收和保持能力,其吸液率约为310%;在150℃,60min的热处理条件下,该隔膜的尺寸收缩率几乎为零。电池性能测试表明,聚苯醚基纳米纤维膜显示出更优的放电倍率性能和循环性能。     

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。     

无纺布基PVDF膜的制备及亲液性能研究

为提高锂离子电池隔膜的亲液性和耐温性,提高锂离子电池的综合性能,采用涂覆方法制备PVDF-无纺布复合隔膜,并对隔膜进行碱处理改性。结果表明,所制备复合膜表面具有发达的海绵状孔道结构,孔径约为2μm。改性后的隔膜对电解液具有良好的亲和性,电解液接触角由PP无纺布的140°降低至40°,吸液率由最初的70%提高到约300%,而复合膜自身的形貌和结构没有发生明显变化。改性后的隔膜对电解液具有更好的吸附作用,由于吸附更多的电解液,锂离子在膜层中的传递阻力更小。因此,改性后的复合膜装配的锂离子电池显示出优良的电池容量保持性。     

用于锂离子电池的复合隔膜

为改善锂离子电池隔膜的耐热安全性,对用于锂离子电池的ZrTiO4/PP陶瓷聚烯烃复合隔膜进行了开发研究,得到的复合膜具有高的多孔性和良好的液体电解液湿润性。膜中陶瓷具有两性特征,将电解液中的酸性副产物HF消耗掉,而HF作为现在锂离子电池所用电解液中的副产物不可避免。复合膜用于制备锂离子电池不仅具有优良的容量保持性、高温安全性,且显示出良好的倍率放电性。     

一种用于锂离子电池的无机复合隔膜

为了替代传统的聚烯烃微孔膜,对用于锂离子电池的Al₂O₃/SiO₂/PAN (聚丙烯腈)复合隔膜进行了研究。复合膜具有高度多孔性和良好液体电解液湿润性。由于高的毛细吸附作用,通过吸附液态电解液,膜极易传导锂离子。膜中Al₂O₃/SiO₂的两性特征,将电解液中的酸性HF(氟化氢)消耗掉,而HF作为现在锂离子电池所用电解液中的杂质是不可避免的。复合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、高温安全性,也显示出良好的倍率放电性和耐过充电保护性能。     

相转化法制备聚苯醚基锂电隔膜及其性能研究

为了改善锂电隔膜的亲液性和耐热性,本研究采用聚苯醚树脂为成膜材料,利用相转化法制备了微孔锂电隔膜,通过膜形貌和结构表征、亲液性和耐热性测试对聚苯醚隔膜的基本性能进行研究,并将该隔膜装配成锂电池进行电化学性能表征。结果表明,聚苯醚隔膜显示出发达的三维孔道结构,孔隙率达到68%,约为传统聚烯烃膜的1.5倍;材料的良好亲液性和高孔隙率结构改善了聚苯醚隔膜的吸液性,其吸液率达到325%;该隔膜在160℃、60min的热处理条件下未发生明显的热收缩。相对于市售聚乙烯隔膜,聚苯醚微孔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。     

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。     

勃姆石纳米片增强锂离子电池隔膜性能研究

采用勃姆石涂覆改性聚烯烃隔膜可以提升锂离子电池的隔膜热稳定性和电解液润湿性。本工作通过简单的水热法合成了平均粒径约为150 nm的勃姆石纳米片, 并采用刮涂法涂覆在聚乙烯(Polyethylene, PE)隔膜表面。该涂覆隔膜的孔隙率达到46.6%、吸液率为138.9%、离子电导率为0.47 mS/cm和锂离子迁移数为0.42, 使得该隔膜组装的锂离子电池具有较好的循环稳定性, 在1C(1C=150 mA/g)的电流密度下循环100次后仍能保留93.7%的放电比容量。同时, 勃姆石纳米片涂覆的隔膜的孔结构分布均匀, 优化了锂离子传输通量, 抑制了锂枝晶。     

Clay-Originated Two-Dimensional Holey Silica Separator for Dendrite-Free Lithium Metal Anode

Lithium metal anode is the ultimate choice to obtain next-generation high-energy-density lithium batteries, while the dendritic lithium growth owing to the unstable lithium anode/electrolyte interface largely limits its practical application. Separator is an important component in batteries and separator engineering is believed to be a tractable and effective way to address the above issue. Separators can play the role of ion redistributors to guide the transport of lithium ions and regulate the uniform electrodeposition of Li. The electrolyte wettability, thermal shrinkage resistance, and mechanical strength are of importance for separators. Here, clay-originated two-dimensional (2D) holey amorphous silica nanosheets (ASN) to develop a low-cost and eco-friendly inorganic separator is directly adopted. The ASN-based separator has higher porosity, better electrolyte wettability, much higher thermal resistance, larger lithium transference number, and ionic conductivity compared with commercial separator. The large amounts of holes and rich surface oxygen groups on the ASN guide the uniform distribution of lithium-ion flux. Consequently, the Li//Li cell with this separator shows stable lithium plating/stripping, and the corresponding Li//LiFePO₄, Li//LiCoO_2, and Li//NCM523 full cells also show high capacity, excellent rate performance, and outstanding cycling stability, which is much superior to that using the commercial separator.     

Flexible,High‐Wettability and Fire‐Resistant Separators Based on Hydroxyapatite Nanowires for Advanced Lithium‐Ion Batteries

Separators play a pivotal role in the electrochemical performance and safety of lithium‐ion batteries (LIBs). The commercial microporous polyolefin‐based separators often suffer from inferior electrolyte wettability, low thermal stability, and severe safety concerns. Herein, a novel kind of highly flexible and porous separator based on hydroxyapatite nanowires (HAP NWs) with excellent thermal stability, fire resistance, and superior electrolyte wettability is reported. A hierarchical cross‐linked network structure forms between HAP NWs and cellulose fibers (CFs) via hybridization, which endows the separator with high flexibility and robust mechanical strength. The high thermal stability of HAP NW networks enables the separator to preserve its structural integrity at temperatures as high as 700 °C, and the fire‐resistant property of HAP NWs ensures high safety of the battery. In particular, benefiting from its unique composition and highly porous structure, the as‐prepared HAP/CF separator exhibits near zero contact angle with the liquid electrolyte and high electrolyte uptake of 253%, indicating superior electrolyte wettability compared with the commercial polyolefin separator. The as‐prepared HAP/CF separator has unique advantages of superior electrolyte wettability, mechanical robustness, high thermal stability, and fire resistance, thus, is promising as a new kind of separator for advanced LIBs with enhanced performance and high safety.     

无机涂层改善锂离子电池聚烯烃隔膜性能研究

为了提高锂离子电池用聚烯烃微孔膜的综合性能, 在商用Celgard膜表面涂布ZrO₂无机涂层, 粘结剂选用电池用聚偏氟乙烯。对比分析涂覆前后的隔膜发现, ZrO₂涂层可以显著提高Celgard膜的热尺寸稳定性和热熔化温度, 对提高锂离子电池安全性起到积极作用。同时无机涂层还能明显改善隔膜对电解液的浸润性, 复合隔膜具有更好的保液能力, 以涂有ZrO₂涂层的Celgard膜作为隔膜组装锂离子电池,可以显著提高长期充放电循环时电池容量保持率。     

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.     

聚硅氧烷/聚苯硫醚无纺布复合电池隔膜的制备与性能

以聚乙烯基硅氧烷（PVS）为涂覆材料,以耐高温聚苯硫醚（PPS）无纺布为支撑材料,通过物理浸涂的方法制备了PVS/PPS无纺布复合锂离子电池隔膜。通过对基本物理性能、电化学性能和电池性能的系统考察,发现与聚烯烃（PP/PE/PP）隔膜相比,PVS/PPS复合隔膜具有较发达的微孔结构、良好的润湿性、较高的离子电导率及良好的界面相容性,有助于降低电池工作时的欧姆极化程度,并使电池表现出较高的放电比容量和良好的循环稳定性（保持率约为100%）。此外研究发现,PVS/PPS复合隔膜具有优异的耐热性,在250℃的高温下热处理1 h后仍能表现出较好的尺寸稳定性。可见,PPS无纺布基复合隔膜在动力型锂离子电池领域具有很大的发展前景。      

Heat-Resistant,Robust, and Hydrophilic Separators Based on Regenerated Cellulose for Advanced Supercapacitors

Separators in supercapacitors (SCs) typically suffer from defects of low mechanical property, limited ion transport, and electrolyte wettability, and poor thermal stability, impeding the development of SCs. Herein, high-performance regenerated cellulose (RC) based separators are designed that are fabricated by effective hydrolytic etching of inorganic CaCO₃ nanoparticles from a filled RC membrane. The as-prepared RC separator displays excellent comprehensive performances such as higher tensile strength (75.83 MPa) and thermal stability (200 °C), which is superior to commercial polypropylene-based separator (Celgard 2500) and sufficient to maintain their structural integrity even at temperatures in excess of 200 °C. Benefiting from its hydrophilicity, high porosity, and outstanding electrolyte uptake rate (208.5%), the RC separator exhibits rapid transport and permeability of ions, which is 2.5× higher than that of the commercial nonwoven polypropylene separator (NKK -MPF30AC-100) validated by electrochemical tests in the 1.0 m Na₂SO₄ electrolyte. Results show that porous RC separator with unique advantages of superior electrolyte wettability, mechanical robustness, and high thermal stability, is a promising separator for SCs with high-performance and safety.     

Preparation and performance of silica/polypropylene composite separator for lithium-ion batteries

In an effort to improve thermal stability and mechanical properties of porous polypropylene (PP) separators for lithium-ion battery, SiO₂/PP/SiO₂ composite separators were prepared by introducing SiO₂ layer on both sides of PP separator through a dip-coating process, with polyvinylidene fluoride–hexafluoropropylene (PVDF–HFP) as binder. SiO₂ nanoparticles are evenly distributed and closely packed in the coated layer, which features a porous honeycomb structure. This unique porous structure was quantitatively analyzed by Gurley value, and it can retain liquid electrolyte, leading to higher electrolyte uptake and ionic conductivity of the composite separator. The introduction of SiO₂-coated layers can not only suppress thermal shrinkage but also improve mechanical properties of the composite separator. C-rate capability and cycle performance of composite separator were also investigated, and compared to those of pristine PP separator.     

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。