聚阴离子纤维素盐在锂电池材料上的应用研究

发布时间：2018-02-15 14:50

本文关键词： 淤浆法聚阴离子纤维素盐静电纺丝锂电池水性粘结剂　出处：《北京理工大学》2015年博士论文　论文类型：学位论文

【摘要】：本文利用核磁、化学分析等方法与手段对捏合法和淤浆法制备的聚阴离子纤维素钠(CMC-Na)的取代基在葡萄糖单元(AGU)及链上基团结构分布做了分析比较。发现淤浆法制备的产品C6位上的长链结构要多于捏合法,断裂伸长率基本在12%左右,比捏合法生产的产品8%要高,链柔顺性更高。采用淤浆法产品两步制备新的聚阴离子纤维素盐—羧甲基纤维素锂(CMC-Li),在35℃下用20%的酸进行酸化2h得到CMC-H,再在50℃下碱化2h得到CMC-Li,优化制备工艺,建立测试方法。CMC-Li比CMC-Na具有更明显的非牛顿流体的特性,热稳定性能相当。采用聚环氧乙烷(PEO)作为共溶剂与淤浆法制备的聚阴离子纤维素盐在纯水中形成电纺液,在电压为30~36KV,纺丝距离为15cm,浓度4%,速率为1~4ml/h,聚阴离子纤维素盐的分子量小于10万时能得到表面光滑,直径较小(约70nm)且均一的纳米纤维材料;利用静电纺丝技术包覆碳量子点荧光材料得到具有荧光特性的CMC-Na无纺布,发射波长为510nm;利用静电喷雾技术制备CMC-Na微球,形貌较好,单分散性较好;通过同轴静电纺丝技术,成功制备了CMC-Na中空的纳米纤维。通过静电纺丝将CMC-Li电纺液和铝粉(Al)颗粒共同电纺,制备Al/CMC-Li纳米复合纤维。通过SEM、TEM表征了所得到的各种纤维材料的形貌及包覆颗粒分散情况。研究利用静电纺丝技术,将纳米纤维的优良特性和聚阴离子纤维素盐的结构特性结合,实现了聚阴离子纤维素盐新溶剂电纺法,拓展延伸了纤维素衍生物的应用范围。利用静电纺丝技术制备了CMC-Li和锂电池正极材料磷酸铁锂(LiFePO4,LFP)颗粒混合纤维,并进行高温碳化改性,得到新型改性电极材料。将CMC-Li/LFP纳米纤维复合材料进行285℃预氧化2h控制碳含量在10%以下,在600℃进行氮气保护下高温碳化1h,CMC-Li最终以碳纳米纤维(CNFs)、Li+氧化物盐的形式存在,与LFP颗粒进行充分的混合,形成CNFs/LFP/Li+盐(简称CLL)充分混合的新型改性电极材料。以PVDF为粘结剂,LFP和CLL分别为电极材料组装成锂电池进行性能测试,发现CLL电极材料基电池的首次充放电比容量最高分别达到了168 mAh g-1和161 mAh g-1,分别比未经改性的LFP电极提高了15.1%和11.8%,经过200圈0.1C充放电循环以后,几乎没有损耗。当放电倍率从0.1C、0.2C增大到5C,电池的比容量依旧达到了120.5 mAh g-1,当放电倍率再从5C降低到0.1C,锂电池的比容量可迅速回到167.5mAh g-1。CV的氧化还原峰比较尖锐对称,差值最小达到0.25V。这些表明,通过这种方法能有效的提高正极材料的导电性,缩短锂离子的扩散路径,降低极化程度和增强电化学性能。首次将制备的含锂离子的水性粘结剂CMC-Li应用到正极材料LFP上,建立CMC-Li材料中锂离子脱出和嵌入移动的模型。结果表明,CMC-Li粘结剂基的电池其首次充放电比容量达到183.8 mAh g-1和179.5 mAh g-1,分别比以油溶性PVDF粘结剂提高了22.2%和27.5%,经过200圈循环以后,放电比容量达到175mAh g-1,比容量损耗3.31%,不同倍率0.1C到5C之间的循环性能较优,CV测试的差值最小达到0.22V,EIS性能较小都体现出较优的电化学活性较。实现以低分子量CMC-Li静电纺丝改性LFP,形成了纳米纤维熔融层包裹LFP的改性电极CLL,并以高分子量的CMC-Li作为粘结剂组装成锂电池复合电极进行性能测试,对增强锂电池性能的过程机理进行了理论分析与探究。结果表明,CMC-Li-6作为粘结剂和CLL-3作为活性物质的复合电极材料颗粒形貌成微球型,电解液浸润更充分,首次0.1C充放电比容量最高为179.5 mAh g-1和176.8 mAh g-1,经过100圈循环以后,比容量没有减少,反而增加,最终充放电比容量分别为181.7 mAh g-1和180.6mAh g-1,并且循环效率一直接近100%。当进行大倍率5C进行充放电,依旧能保持在115 mAh g-1、CV峰之间的差值为0.20V,属于电化学性能优良的新型电池。
[Abstract]:In this paper, using NMR, chemical analysis methods and means of kneading and slurry prepared by polyanionic cellulose sodium (CMC-Na) substituent in glucose unit (AGU) and chain group structure distribution is analysed and compared. It is found that slurry prepared by C6 products on the chain structure than kneading, fracture the elongation is about 12%, higher than the kneading products 8%, the chain flexibility is higher. The slurry products two step preparation of new polyanionic cellulose carboxymethyl cellulose lithium salt (CMC-Li), under the temperature of 35 DEG C with 20% acid acidification 2H CMC-H, then at 50 DEG C Solonetzic 2H CMC-Li, optimizing the preparation process, the establishment of.CMC-Li test method has more obvious non Newtonian properties than CMC-Na, thermal stability. Using polyethylene oxide (PEO) as co solvent and slurry prepared by polyanionic cellulose salt in water In the formation of electro spinning solution, the voltage is 30~36KV, the spinning distance is 15cm, the concentration of 4%, rate of 1~4ml/h, the molecular weight of poly anionic cellulose salt is less than 100 thousand can get smooth surface, smaller diameter (about 70nm) nano fiber material and uniform; using electrospinning coated carbon quantum dot fluorescent material CMC-Na non-woven fabric with fluorescence, the emission wavelength is 510nm; CMC-Na microsphere preparation, the use of electrostatic spraying technology for satisfactory morphology and good monodispersity; through coaxial electrospinning technology, CMC-Na hollow nanofibers were prepared by electrospinning. The electrospun CMC-Li liquid and powder (Al) particles electrospinning system preparation of Al/CMC-Li nano composite fiber. By SEM, TEM was characterized by a variety of fiber morphology and dispersion of coated particles. Using the electrospinning technique, the excellent properties of nano fiber and poly anionic fiber In combination with the structural properties of salt, the salt of polyanionic cellulose solvent electrospinning method, expand the scope of application of cellulose derivatives. The CMC-Li lithium battery and lithium iron phosphate cathode material prepared by electrospinning (LiFePO4, LFP) particles mixed fiber, and the high temperature carbonization modification, new change electrode materials. CMC-Li/LFP nano fiber composite materials was 285 DEG C pre oxidation of 2H to control the carbon content below 10%, are under the protection of nitrogen high temperature carbonization at 600 C for 1H CMC-Li with carbon nano fiber (CNFs), Li+ oxide salt, thoroughly mixed with LFP particles, the formation of salt (referred to as CNFs/LFP/Li+ CLL) new modified electrode materials are fully mixed. Using PVDF as binder, LFP and CLL respectively as the electrode material assembled into lithium battery performance testing, found that the first discharge electrode materials of CLL based battery capacity than most The high reached 168 mAh g-1 and 161 mAh g-1 respectively than without LFP modified electrodes increased by 15.1% and 11.8%, after 200 cycles of 0.1C charge discharge cycle, almost no loss. When the discharge rate from 0.1C, 0.2C increased to 5C, the specific capacity of the battery still reached 120.5 mAh g-1, when the discharge then the ratio decreased from 5C to 0.1C, the ratio of lithium battery capacity can be quickly returned to the 167.5mAh g-1.CV of the redox peak sharp symmetry, the minimum value reached 0.25V. this shows that through this method can effectively improve the electrical conductivity of the cathode, shorten the diffusion path of lithium ion, reduce the degree of polarization and enhance the electrochemical performance of system for the first time. The preparation of lithium ion containing water binder CMC-Li applied to the LFP cathode material, a lithium ion insertion and extraction of mobile model CMC-Li materials. The results showed that CMC-Li binder based battery charge and discharge volume for the first time The amount of up to 183.8 mAh g-1 and 179.5 mAh g-1, respectively, compared with oil soluble PVDF binder increased by 22.2% and 27.5%, after 200 cycles, the discharge capacity reached 175mAh g-1, more than 3.31% capacity loss, different ratio of 0.1C to 5C between the cycle performance is better than the CV test the difference reached 0.22V, EIS the performance of small shows better electrochemical activity. In order to achieve the low molecular weight CMC-Li electrospinning modified LFP formed electrode modified with nano CLL fiber melting layer package LFP, and the molecular weight of CMC-Li as binder assembled into composite electrode of lithium battery performance testing, to enhance the process performance of lithium batteries the analysis and Research of the theory. The results show that CMC-Li-6 as a binder and CLL-3 as composite electrode active material particle morphology of microspheres, the electrolyte infiltration more fully, the first charge discharge capacity highest 0.1C 179.5 mAh g-1 and 176.8 mAh g-1, after 100 cycles, the capacity ratio did not decrease, but increased, the final charge discharge were 181.7 mAh g-1 and 180.6mAh g-1 than the capacity and cycle efficiency has been close to 100%. when the rate of 5C charge and discharge, still can be maintained at 115 mAh g-1, the difference between CV peaks for the 0.20V, is a new type of battery with excellent electrochemical properties.

【学位授予单位】：北京理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：O636.11;TM912

【共引文献】