软炭负极在锂离子动力电池中的应用研究

发布时间：2018-05-11 16:50

本文选题：软炭 + 倍率性能　；参考：《复旦大学》2014年硕士论文

【摘要】：在电动汽车领域,汽车电池的能量回收对应于电池具有良好的充电倍率性能。而决定锂离子电池倍率充电性能的是负极材料。锂离子负极材料主要有石墨,软炭和硬炭。石墨材料是市场应用最多的负极材料,d002在0.3330-0.3370nm,较高的容量和效率,但是在大倍率充电性能差,安全性低。硬炭材料主要是指难石墨化的碳,d002在0.3700-0.400nm,倍率性能和低温性能较好,但是材料成本高,工艺要求无水无氧环境,整体的生产成本高。软炭材料主要指易石墨化碳,d002在0.342-0.347nm,具备较宽的层间距,良好的倍率充放电性能,低温处于石墨和硬炭之间,材料成本便宜,生产工艺对水氧含量不敏感,已是动力电池的发展方向。但是软炭在负极中的应用还需要解决如下问题：一是材料的开发,开发出倍率和低温性能好的软炭材料；二是比容量低,压实密度低导致的能量密度低；三是工艺的开发,由于软炭在放电时的电压降较大,直流内阻大,产生过多的极化热,造成能量浪费。因此软炭在锂离子电池中的应用开发任务还很重。本论文首先考察了不同粒径的材料具有的倍率性能,材料包覆等方式对低温性能的改善；混合导电石墨,改善压实密度和能量密度；然后在工艺上采取减薄极片尺寸,降低了电池的直流内阻。测试了电池各方面的性能,取得了较好的结果。本论文的主要研究内容如下：1.通过比较不同粒径材料D50=15μm,12μm, 10μm 的 Rs, Rct,发现倍率性能随着粒径的减小而升高,从15μm降低到10μm,Rct减小。减小粒径能缩短锂离子在固相里的传输路径,减小电池反应阻抗；2.通过沥青包覆后的软炭材料的低温放电能力增强,-20℃3C放电比率从未包覆的55%上升到62%,放电平台也大幅提高。3.软炭的首次库仑效率低,在首次嵌锂时消耗大量正极的活性锂,导致了电池的容量低。通过在负极表面添加锂粉,补充了由SEI膜形成和孔隙嵌锂造成的锂损失,提高了电池的首次库仑效率。大大提高了正负极材料比容量的发挥：正极比容量发挥从120mAh/g提高到150mAh/g,负极比容量从207mAh/g提高到257mAh/g。电池的能量密度提高了近25%。解决了由于软炭电池首效低等缺陷影响了电池容量发挥问题。4. 对软炭材料进行工艺优化：通过优化软炭粘结剂,提高了软炭极片与集流体之间的粘结强度,提高了电池的倍率性能；通过导电剂的选择和优化,提高了极片的电导率和压实密度,增大了电池的体积能量密度,增大了电池的倍率充放电性能。优化后的电池具有良好的倍率充放电性能,常温循环和大倍率循环性能,高温循环性能和安全性能。
[Abstract]:In the field of electric automobile , the energy recovery of the automobile battery corresponds to the performance of the battery with good charging multiplying power . The lithium ion negative electrode material mainly refers to graphite , soft carbon and hard carbon . The graphite material is mainly graphite , soft carbon and hard carbon .
secondly , the energy density caused by low specific capacity and low compaction density is low ;
Third is the development of the process , because the voltage drop of the soft carbon in the discharge is large , the direct current internal resistance is large , excessive polarization heat is generated , and energy waste is caused . Therefore , the application development task of the soft charcoal in the lithium ion battery is also very heavy .
mixing conductive graphite to improve compaction density and energy density ;
The results are as follows : 1 . By comparing Rs and Rct of different particle size materials D50 = 15 渭m , 12 渭m , 10 渭m , the rate performance is decreased from 15 渭m to 10 渭m , and Rct is reduced . The reduction of particle size can shorten the transmission path of lithium ion in solid phase and decrease the reaction impedance of the battery .
2 . the low - temperature discharge capacity of the soft carbon material after the asphalt coating is enhanced , the 3C discharge ratio of -20 DEG C is increased from 55 % to 62 % , and the discharging platform is greatly improved . By optimizing the soft carbon binder , the bonding strength between the soft carbon pole piece and the current collector is improved , and the multiplying power performance of the battery is improved ;
Through the selection and optimization of the conductive agent , the electrical conductivity and the compaction density of the pole pieces are improved , the volume energy density of the battery is increased , and the rate and discharge performance of the battery is increased .

【学位授予单位】：复旦大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM912

【参考文献】