A heatproof electrospun PES/PVDF composite membrane as an advanced separator for lithium-ion batteries

In the present paper, the physicochemical properties of a novel composite fibrous membrane, based on a mixture of poly(aryl ether sulfone) (PES) and poly(vinylidene fluoride) (PVDF), as separators for lithium-ion batteries are reported and discussed. Compared with the pure PVDF fibrous membrane, the introduction of PES can decrease the PVDF crystallinity while increasing the proportion of α-phase. Meanwhile, the initial thermal decomposition temperature is enhanced by 24°C. Heat shrinkage tests and thermomechanical analyzers indicate the composite membrane has significantly improved thermal-dimensional stability. The shrinkage rate of the composite membrane after heat-treated at 180°C for 2 hr is only 4.8%, which is far below the Celgard separator (82%) and the pure PVDF fibrous membrane (75%). The composite membrane with excellent wettability demonstrates a high ionic conductivity (1.69 × 10⁻³ S cm⁻¹) at room temperature as well as high electrolyte uptake (595%). The cells assembled with the composite membrane exhibit more stable cycle performance, capacity retention, and C-rate capability than that with polyolefin separator. These results suggest that PES/PVDF composite fibrous membrane is an effective separator for high-performance Lithium-ion batteries.     

陶瓷复合锂离子电池隔膜研究进展

相对于传统锂离子电池隔膜,有机-无机陶瓷复合隔膜兼具有机材料的柔韧性、无机材料的耐温性和电解液亲和性。本文对锂离子电池用陶瓷复合隔膜进行综述,首先介绍了此类隔膜相对于传统隔膜的优势,其次对目前研究的陶瓷锂离子电池隔膜的结构形式和主要成膜材料进行了讨论,并介绍了国内外主要公司的陶瓷复合隔膜的研究和发展现状,最后对陶瓷复合隔膜的应用前景和面临的挑战进行了简要分析。鉴于该新型隔膜的优势,随着锂离子电池在高端电子产品以及动力、储能等新兴领域的发展,高安全性陶瓷复合锂离子电池隔膜必将代替传统的聚烯烃隔膜,成为主流隔膜满足人们的需要。     

Electrochemical performance and thermal stability of the electrospun PTFE nanofiber separator for lithium‐ion batteries

Separator is a very important set of lithium‐ion batteries. At present, low porosity and poor thermal stability are two major disadvantages of separator. In this work, we first apply electrospinning method to prepare the Polytetrafluoroethylene (PTFE) nanofiber separator, which has the advantages of electrospinning method and PTFE materials. The effect of the PTFE nanofiber separator is investigated by scanning electron microscope, Capillary Flow Porometer, thermogravimetric–differential scanning calorimeter, linear sweep voltammeter, AC impedance, and charge/discharge cycling tests. The results demonstrate that the PTFE nanofiber separator has a special fiber structure made from PTFE particles gathering one by one along the fibers. Moreover, the PTFE nanofiber separator exhibits several advantages, including suitable pore diameter, uniform pore size distribution, high porosity, and electrolyte uptake, which enhance the ionic conductivity. The thermal stability of the PTFE nanofiber separator is much better than that of the conventional polyolefin separator. The Li/LiCoO₂ cell equipped with PTFE nanofiber separator exhibits excellent rate performance and first charge–discharge specific capacity of 142 and 131 mA h g^?1, respectively, accompanied by relatively stable cycle performance at 0.2 C rate. It is supposed to be a candidate for application in lithium‐ion batteries. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46508.     

聚丙烯腈/聚酯无纺布微孔复合锂电隔膜的制备及性能

为了改善锂电隔膜的耐热性、电解液亲和性和机械性能,本文以聚丙烯腈为主要材料,采用相转化法制备了聚酯无纺布支撑的聚丙烯腈微孔复合锂电隔膜,对隔膜的理化性能（孔道结构、机械性能、电解液性能和耐热性）和电池性能（循环性能、倍率性能）进行系统研究。结果表明,复合隔膜具有均匀的微孔结构,平均孔径约为425nm,孔隙率为74%,拉伸强度为30MPa;电解液亲和性良好,吸液率为385%,接触角接近0°,锂离子电导率较市售隔膜显著提高,达到1.65mS/cm;在150℃、0.5h的热处理条件下,复合隔膜的热收缩率为0。鉴于良好的理化特性,该隔膜所装配的钴酸锂/锂金属电池表现出优异的循环容量和倍率容量保持性,如在0.2C倍率下,经历200次循环后电池的放电容量保持率为95.2%,在10C倍率下电池的放电容量为0.5C倍率下的58.3%。因此,相转化法制备的聚丙烯腈基微孔复合隔膜在锂离子电池中显示出较好的应用前景。     

我国锂离子电池隔膜市场分析

介绍了2012年我国锂离子电池隔膜的生产、消费及价格情况,分析了锂离子电池目前面临的替代形势,提出了相关建议。     

中国锂离子电池隔膜市场潜力巨大

本刊北京消息(2015年4月10日)由中国塑料加工工业协会主办,中国汽车工业协会支持,中国电池工业协会协办,中国塑协双向拉伸聚丙烯薄膜专委会承办的“2015锂电池和隔膜市场与工艺技术发展研讨会暨锂电池关键材料产业链发展论坛”4月9日在中国北京召开.本次会议由德国布鲁克纳机械股份有限公司、德国哈勒集团、南京安顺自动化装备有限公司、诺信塑料工程系统(上海)有限公司、德国比勒(上海)自动化技术有限公司、威海海朝机械有限公司、美国微觉视检测技术(苏州)有限公司、深圳市善营自动化股份有限公司赞助,来自汽车、锂电池、隔膜产业链的200多名中外企业高层人士出席了本次会议.     

A phase inversion based sponge-like polysulfonamide/SiO2 composite separator for high performance lithium-ion batteries

In this work,a sponge-like polysulfonamide(PSA)/SiO_2 composite membrane is unprecedentedly prepared by the phase inversion method,and successfully demonstrated as a novel separator of lithium-ion batteries(LIBs).Compared to the commercial polypropylene(PP) separator,the sponge-like PSA/SiO_2 composite possesses better physical and electrochemical properties,such as higher porosity,ionic conductivity,thermal stability and flame retarding ability.The LiCoO_2/Li half-cells using the sponge-like composite separator demonstrate superior rate capability and cyclability over those using the commercial PP separator.Moreover,the sponge-like composite separator can ensure the normal operation of LiCoO_2/Li half-cell at an extremely high temperature of 90 °C,while the commercial PP separator cannot.All these encouraging results suggest that this phase inversion based sponge-like PSA/SiO_2 composite separator is really a promising separator for high performance LIBs.     

Plasma-modified polyethylene membrane as a separator for lithium-ion polymer battery

The surface of polyethylene (PE) membranes as a separator for lithium-ion polymer battery was modified with acrylonitrile (AN) using the plasma technology. The plasma-induced acrylonitrile coated PE (PiAN-PE) membrane was characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and contact angle measurement. The electrochemical performance of the lithium-ion polymer cell fabricated with the PE and the PiAN-PE membranes were also analyzed. The surface characterization demonstrates that the enhanced adhesion of the PiAN-PE membrane resulted from the increased polar component of surface energy for the PiAN-PE membrane. The presence of the PiAN induced onto the surface of the membrane via the plasma modification plays a critical role in improving the wettability and electrolyte retention, the interfacial adhesion between the electrodes and the separator, the cycle performance of the resulting lithium-ion polymer cell assembly. The PiAN-PE membrane modified by the plasma treatment holds a great potential to be used as a high-performance and cost-effective separator for lithium-ion polymer battery.     

聚乙烯醇交联改性聚乙烯锂离子电池隔膜的制备

将聚乙烯(PE)隔膜用乙醇润湿,然后将其放入聚乙烯醇(PVA)溶液中浸润,使PVA进入隔膜孔结构中,再将隔膜放入交联溶液[pH=2,25%(w)戊二醛]中进行交联反应,制备了PVA交联改性PE隔膜。采用傅里叶变换红外光谱和能量色散X射线光谱对隔膜的表面与断面进行了表征,并研究了改性隔膜的物理性能及电池性能。结果表明:PVA交联改性PE隔膜的表面亲水性和抗高温热收缩性提高,瞬时水接触角由初始的98.6°降至66.5°,且组装的锂离子电池的循环性能和倍率容量均有一定程度的改善,PE隔膜的离子电导率由0.463 mS/cm升至0.864 mS/cm。     

Self-standing integrative cell with an inorganic separator for lithium-ion battery stacks

An integrative cell with a porous Al₂O₃ membrane as both a support and a separator has been fabricated. LiFePO₄ and graphite were coated onto the both sides of the rigid porous Al₂O₃ separator, while an electrolyte was infiltrated inside. The LiFePO₄/graphite integrative cells were evaluated in coin-type cells and exhibited good cycle capacity. The self-standing integrative cell was a simple and promising technology to assemble the battery stacks and meanwhile had an obvious advantage of forming a firm structure, which could avoid inner short circuit during being moved or crashed.     

动力锂离子二次电池聚偏氟乙烯隔膜的制备及性能表征

采用浸没沉淀相转化法,以聚酯(PET)无纺布为底膜,在其上涂覆聚偏氟乙烯(PVDF)制备复合隔膜,应用于动力锂离子二次电池隔膜。将制备的复合隔膜与Celgard隔膜进行了孔结构分析、电化学性质、热性能等理化性质及电池性能检测对比。结果显示,复合隔膜孔径尺寸较大且分布均一,孔隙率达到48.5%,可以承受250.8℃的高温,离子电导率达0.346 mS·cm^-1,使用该隔膜的锂离子电池具有很好的倍率特性,初次放电容量达48.7 mA·h,循环100次后仍保持77.9%的容量,其性能与市售Celgard隔膜基本相当,能满足实际应用的要求。     

Fabrication and characterization of LATP/PAN composite fiber-based lithium-ion battery separators

Lithium aluminum titanium phosphate (LATP)/polyacrylonitrile (PAN) composite fiber-based membranes were prepared by electrospinning dispersions of LATP particles in PAN solutions. The electrolyte uptakes of the electrospun LATP/PAN composite fiber-based membranes were measured and the results showed that the electrolyte uptake increased as the LATP content increased. The lithium ion conductivity, the electrochemical oxidation limit and the interface resistance of liquid electrolyte-soaked electrospun LATP/PAN composite fiber-based membranes were also measured and it was found that as the LATP content increased, the electrospun LATP/PAN composite fiber-based membranes had higher lithium ion conductivity, better electrochemical stability, and lower interfacial resistance with lithium electrode. Additionally, lithium//1 M LiPF₆/EC/EMC//lithium iron phosphate cells using LATP/PAN composite fiber-based membranes as the separator demonstrated high charge/discharge capacity and good cycle performance.     

无机超细粉体改性锂离子电池隔膜的研究进展

综述了近年来无机超细粉体改性锂离子电池隔膜的研究进展,首先介绍了已在锂电隔膜改性上商业应用的Al₂O₃和AlOOH对传统聚烯烃膜和新型静电纺丝膜的改性方法和改性效果,随后又对常规无机材料TiO₂和SiO₂粉体对锂电隔膜的改性进行了叙述,最后对BN等非常规隔膜改性无机材料进行了简介;总结和讨论了无机材料改性后隔膜的组分、结构和性能对锂离子电池综合性能的影响,并对其无机材料改性锂电池隔膜的未来发展趋势进行了展望。     

Electrochemical studies of LiB compound as anode material for lithium-ion battery

Electrochemical studies of LiB compound were carried out for its application as anode for lithium-ion battery. The compound exhibited a reversible discharge-charge behavior between 0 and 0.75 V versus Li/Li⁺ with a first discharge capacity of 293 mA h g⁻¹. Discharging to 1.0 V, the first discharge capacity of LiB compound was 660 mA h g⁻¹, but a part of this capacity was irreversible. Impedance spectra were measured at several potentials corresponding to different discharge plateaus. The impedance spectra obtained below and above 0.8 V presented significantly different features. The solid electrolyte interphase layer (SEI) was formed below 0.8 V and assumed a good performance of LiB electrode in this potential range. The SEI was found to deteriorate above 0.8 V, which might be associated with the irreversible discharge capacity.     

Electrochemical studies of electrospun organic/inorganic hybrid nanocomposite fibrous polymer electrolyte for lithium battery

Poly(vinylidene fluoride-co-hexafluoropropylene) P(VdF-co-HFP)/magnesium aluminate (MgAl₂O₄) hybrid fibrous nanocomposite polymer electrolyte membranes were newly prepared by electrospinning method. The as-prepared electrospun pure and nanocomposite fibrous polymer membranes with various MgAl₂O₄ filler contents were characterized by X ray diffraction, differential scanning calorimetry and scanning electron microscopy techniques. The fibrous nanocomposite polymer electrolytes were prepared by soaking the electrospun membranes in 1 M LiPF₆ in EC:DEC (1:1, v/v). The fibrous nanocomposite polymer electrolyte membrane with 5 wt.% of MgAl₂O₄ show high electrolyte uptake, enhanced ionic conductivity is found to be 2.80 × 10⁻³ S cm⁻¹ at room temperature and good electrochemical stability window higher than 4.5 V. Electrochemical performance of commercial celgard 2320, fibrous pure and nanocomposite polymer electrolyte (PE, NCPE) membranes with different MgAl₂O₄ filler content is evaluated in Li/celgard 2320, PE, NCPE/LiCoO₂ CR 2032 coin cells at current density 0.1 C-rate. The NCPE with 5 wt.% of MgAl₂O₄ delivers an initial discharge capacity of 158 mAhg⁻¹ and stable cycle performance compared with the other cells containing celgard 2320 separator and pure membrane.     

Preparation of porous-structured LiFePO4/C composite by vacuum sintering for lithium-ion battery

The LiFePO₄/C (LFP/C) composite as a cathode material for lithium-ion battery was synthesized by solid-state reaction under vacuum sintering condition (20–5 Pa). The effects of vacuum sintering temperature and time on the phase composition, morphological structure, and electrochemical performance of LFP/C composite were investigated by X-ray diffraction, scanning electron microscopy, galvanostatic charge–discharge cycling test, and electrochemical impedance spectroscopy. The synthetic LFP/C composite possessed uniform particle-size distribution with porous architecture upon sintering at 650 °C for 12 h and thus exhibited the highest discharge capacity and best cycle performance. The complete decomposition of citric acid at a suitable temperature under vacuum condition resulted in the formation of porous structure. Compared with atmospheric argon sintering, vacuum sintering method led to the formation of porous architecture, the porous sample showed excellent cycle performance with less than 2% capacity loss after 80 cycles at 0.2 C, and reached the discharge specific capacity of 87.6 mAh g⁻¹ at 10 C rate, these are better than that of atmospheric argon sintering. The LFP/C composite prepared under vacuum sintering also reduced the optimum sintering temperature by nearly 100 °C compared with that prepared under atmospheric argon sintering.     

钴酸锂电池烤箱热滥用模拟及热行为分析

建立钴酸锂电池烤箱热滥用的热模型,并对不同烤箱温度下的热滥用进行数值模拟。比较分析电芯不同区域的热滥用反应及热行为发现,高温下电池电芯发生热失控的主要热量来自于正电极与电解液的反应,隔离膜区域的热生成量最少。考察不同散热条件和烤箱温度对电芯热行为的影响发现,散热条件和环境温度是影响电芯热行为的关键因素,发生热失控的临界温度随着散热条件的变好而升高,使得电池不发生热失控的临界散热系数随着烤箱温度的升高而增大。     

Electrochemical model of a lithium-ion battery implemented into an automotive battery management system

This paper presents the development of an electrochemical model that can be implemented into automotive battery management systems (BMSs). Compared with empirical models, the electrochemical model features more accurate state estimates over a broader and longer use of the battery. In this work, model implementation schemes are devised to make the electrochemical model uncomplicated enough to be embedded into the BMS. A nonlinear system of partial differential equations in the model is discretized into a linearized system of algebraic equations (AEs). A solver selected to evaluate the resulting system of AEs is modified for its application to the BMS. As the BMS is preoccupied by its existing tasks, the reformulated equations and optimized solver are reorganized such that the limited computational resources of the BMS are appropriately exploited. The electrochemical model is consequently implemented into the BMS, predicting battery behaviors in 1 s intervals while occupying a 14 kB RAM.     

Electrochemical characteristics of nano-sized MoO2/C composite anode materials for lithium-ion batteries

A nano-sized MoO₂/C composite was synthesized using a spray pyrolysis technique, and investigated as an anode material for Li-ion batteries. Spherical MoO₂/C particles with the monoclinic phase were obtained without any impurities, and with a primary particle size in the range 30–50 nm. Structural variation of the prepared MoO₂/C during Li⁺ insertion was examined by in situ X-ray diffraction and selected area electron diffraction analyses. The structural analysis results indicated that no conversion reaction was activated in the MoO₂/C composite. The electrochemical tests demonstrated that the rate-capability and capacity retention of the synthesized materials were improved significantly, which could be attributed to the effective carbon distribution and nano-sized primary particle resulting from the low-synthesis temperature. Therefore, control of the powder morphology and minimization of the primary particle size are found to be essential for achieving the enhanced electrochemical properties in MoO₂ anode materials.