沸石基锂离子电池隔膜的制备及性能

针对传统聚烯烃类锂电隔膜的耐温性差和电解液亲和性差的问题,以沸石粒子、硅溶胶和乙二胺四乙酸为主要原料,通过烧结工艺制备综合性能优异的沸石基锂离子电池隔膜。结果表明:与商用聚乙烯膜相比,本实验制备的沸石隔膜具有发达的孔道结构,其耐热性和电解液润湿性得到显著提升;经过160℃,0.5h的热处理后,沸石隔膜的热收缩率为0,而聚乙烯膜已经完全融化,沸石隔膜的电解液接触角接近0°,聚乙烯膜的接触角高达35°。受益于良好的孔道结构和电解液亲和性,沸石隔膜所装配电池在倍率放电容量和循环放电容量等方面均优于传统聚烯烃膜。     

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。     

同轴静电共喷纺及其在锂离子电池复合隔膜改性中的应用

文中介绍了一种制备纳米复合膜的方法——同轴静电共喷纺。首先组装了由外喷嘴和内喷嘴构成的同轴共喷纺装置,将静电纺丝与静电喷涂结合起来,利用该技术制备纳米纤维/颗粒复合膜。将聚偏氟乙烯(PVDF)/SiO₂溶于N,N-二甲基甲酰胺(DMF)中,从外喷口制备颗粒;PVDF溶于DMF和丙酮混合物中,从内喷口制备纤维,成功制备了同时含颗粒和纤维的PVDF&PVDF/SiO₂复合膜,复合膜中颗粒的平均粒径为2.01μm,纤维平均直径为0.43μm。然后将PVDF&PVDF/SiO₂复合膜原位涂覆在商用超高分子量聚乙烯(UHMWPE)隔膜上,从而制备了一种新型锂离子电池复合隔膜。测试结果表明,该复合隔膜的孔隙率为85.96%,比UHMWPE基材膜的37.85%有明显的提高,纵向收缩率由7.28%降低到5.26%,复合隔膜接触角由48.55°降低到14.93°。与未改性的商用隔膜相比,同轴静电共喷纺制备的复合隔膜首次充放电比容量由107.8 m Ah/g提高到122.4 mAh/g,经50次循环后,仍具有良好的循环稳定性...     

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。     

静电纺丝法制备PVDF锂离子电池隔膜工艺条件的研究

主要研究静电纺丝法制备PVDF锂离子电池隔膜的最佳纺丝条件。实验表明:纺丝浓度18%(wt,质量分数,下同),纺丝电压22kV,纺丝速率0.0007mm/s为静电纺丝制备PVDF隔膜的最佳纺丝条件。静电纺丝法制备PVDF锂离子电池隔膜与Celgard的PP/PE/PP三层隔膜相对比,静电纺丝法制备PVDF锂离子电池隔膜形貌较好,串珠结构更少。     

PVDF/PMMA/PEG型聚合物隔膜的制备

为提高锂离子电池聚偏氟乙烯(PVDF)基聚合物隔膜对电解液体系的亲和性和导电性,引入聚甲基丙烯酸甲酯(PMMA)与聚偏氟乙烯(PVDF)进行共混,并添加有机增塑剂聚乙二醇PEG-400对PVDF基聚合物隔膜进行改性研究。采用先干法后湿法的相转化方法制备PVDF/PMMA/PEG型聚合物隔膜。通过对制备的聚合物隔膜的孔隙率、吸液率、微观形貌和电化学性能的分析研究,确定制膜的最佳工艺条件为聚合物占溶剂质量百分比为8%,PVDF∶PMMA=7∶3,增塑剂含量为30%,非溶剂含量为3%,反应温度为45℃,在此最佳工艺条件下制备的PVDF/PMMA/PEG隔膜的离子电导率可达2.848 m S/cm,对电解液体系的亲和性和导电性得到显著提高。     

锂离子电池用PVDF/P(MMA-co-DMAEMA)共混隔膜的制备与性能

首先合成了甲基丙烯酸甲酯(MMA)与甲基丙烯酸-N,N-二甲胺乙酯的共聚物P(MMA-co-DMAE-MA),与聚偏氟乙烯(PVDF)共混经溶液相转化法制备了PVDF/P(MMA-co-DMAEMA)隔膜。研究发现,相对于纯PVDF隔膜,共混隔膜的孔隙率增加,结晶度降低,电解液吸收稳定性显著提高。共混隔膜具有"活性"隔膜的性质,隔膜-电解液组成的电解质体系表现出凝胶电解质特征,隔膜中PVDF/P(MMA-co-DMAE-MA)质量比为10/1时,隔膜吸液率在420%以上,活化后凝胶电解质膜离子电导率可达到1.8×10-3S/cm。研究结果表明,采用溶液相转化法制备PVDF/P(MMA-co-DMAEMA)共混隔膜,是一种制备凝胶锂离子电池用高性能活性隔膜的有效方法。     

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。     

聚苯硫醚无纺布基耐高温复合电池隔膜的制备与性能

采用耐高温工程塑料聚苯硫醚(PPS)制备的无纺布为基底膜,聚偏氟乙烯(PVDF)和Si O2纳米粒子为表面涂覆材料构建耐高温复合电池隔膜(记作PVDF@Si O2/PPS)。研究发现,与商业隔膜PP/PE/PP相比,隔膜PVDF@Si O2/PPS具有较高的离子电导率和放电比容量。这主要与复合隔膜较高的孔隙率、透气性、较强的电解液浸润能力及吸液能力有关。另外,热处理实验结果表明,PPS无纺布基复合隔膜具有较强的耐热性,在250℃仍可保持较高的尺寸稳定性。可见,采用PPS无纺布构建电池隔膜为高功率高安全锂离子电池的开发提供了可能。     

PVDF/PMMA/TiO_2型聚合物隔膜的制备

为提高锂离子电池聚偏氟乙烯(PVDF)基聚合物隔膜的导电性和降低PVDF基聚合物隔膜的结晶度,引入聚甲基丙烯酸甲酯(PMMA)与聚偏氟乙烯(PVDF)进行共混,掺杂无机纳米材料TiO_2,采用相转化方法制备PVDF/PMMA/TiO_2型聚合物隔膜。通过对制备的PVDF/PMMA/TiO2型多孔膜吸液率、微观形貌和电化学性能的分析研究,确定制膜的最佳工艺条件为聚合物浓度为5%,PVDF∶PMMA为72∶28,纳米TiO_2添加量为5%,非溶剂添加量为3%,水浴温度为55℃。该方案下制备的多孔膜结晶度较纯PVDF薄膜结晶度降低,吸液率达到109.76%,离子电导率为2.64mS/cm,电化学稳定窗口为4.86V,高于4.5V,能够满足锂离子电池正常工作需要。     

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.     

静电纺丝与静电喷雾技术共纺制备PPESK/PVDF复合锂电池隔膜

为了改善传统静电纺丝无纺布纤维膜力学性能较差的缺点,采用静电纺丝和静电喷雾技术相结合的方法,同时进行静电纺PPESK浓溶液和PVDF稀溶液,制备得到PPESK纤维/PVDF珠粒复合锂电池隔膜,并在160℃进行热压后处理。通过扫描电子显微镜、万能拉伸试验机、电化学工作站及充放电测试仪等表征复合锂电池隔膜的微观结构、力学性能、离子电导率和相应的电池充放电性能。结果表明,该复合隔膜具有良好的电解液润湿性,室温下离子电导率达到1.92mS·cm^-1,PVDF珠粒均匀地分布在PPESK纤维中,珠粒经热压产生微熔融有效增强了纤维之间的黏结力,使复合膜的力学强度提高到13.2MPa。此外,使用复合隔膜装配的电池展现出较高的放电比容量和稳定的循环性能。     

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.     

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.     

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。     

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.     

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。      

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。     

静电纺PMMA/EVOH-SO3Li锂离子电池隔膜复合材料的制备及性能

以聚甲基丙烯酸甲酯（PMMA）和聚乙烯-乙烯醇磺酸锂（EVOH-SO₃Li）为原料,通过高压静电纺丝法进行交替纺丝,制备PMMA/EVOH-SO₃Li锂离子电池隔膜复合材料。通过FTIR、SEM、万能拉伸试验仪、TGA、IM6型电化学工作站和电池循环测试设备对PMMA/EVOH-SO₃Li隔膜复合材料的性能进行检测表征。结果表明：PMMA/EVOH-SO₃Li隔膜复合材料具有清晰的三维网状结构,与EVOH-SO₃Li隔膜材料相比,改性后PMMA/EVOH-SO₃Li隔膜复合材料的孔隙率、吸液率和拉伸强度分别提高至80%、340%和3.18 MPa,起始热分解温度升高至294℃,热收缩率也有所降低,并表现出良好的电化学性能。其中电化学稳定窗口由5.0V增加到5.6 V,界面阻抗由420.69 Ω降低至262.31 Ω,离子电导率则由1.560×10^-3 S/cm提高至2.089×10^-3 S/cm,并且经过100次循环充放电后,容量保持率仍高达93.7%。