【作者】 郭永兴；

【导师】 李新海；

【作者基本信息】 中南大学 ， 冶金物理化学， 2010， 博士

【摘要】 本文在对锂离子动力电池技术及产业化进展进行充分分析的基础上,研究了正、负极材料微观结构、形貌与电化学性能之间的关系,选定了动力电池的正、负极材料及其它关键材料；在动力电池功能电解液开发,电池结构设计以及制作工艺改进优化的基础上,开发了容量型和功率型锂离子动力电池；分析了动力电池在充放电过程中的热行为,建立了功率型动力电池的表面温度分布模型与散热模型；全面测试了动力电池(组)的电化学性能、安全性能,并对锂离子动力电池生产进行了试制研究。1.功率型动力锂离子电池的研制。以固相法制备了磷酸铁锂(LiFePO4)掺Mg材料,通过对其结构表征,发现在正极材料LiFePO4晶格中掺杂Mg,并且发生Fe位取代后,会引起LiFePO4晶胞体积收缩,晶格参数a、b减少,并增强材料的电子导电性,所制备的样品号为LP3的LiFePO4材料,化学计量比为LiFe0.95Mg0.05PO4,材料颗粒的粒径分布均匀,主要分布在7μm左右,表面形貌光滑,材料颗粒趋于球形,具有良好的电化学性能及倍率性能；负极材料方面,发现比表面积小、颗粒分布适中、循环性以及大电流充放电性能好的中间相碳微球石墨材料适合用于功率型锂离子电池的负极材料。研制功率型动力电池循环1900周(100%DOD)后容量保持率为初始容量的87%,30C放电的容量保持率为1C放电容量的91%,-20℃放电容量保持率为常温下放电容量的62%。2.容量型动力电池的研制。对材料的分析表征发现,晶格参数a<8.21 A、晶体生长完整、颗粒表面平整光滑、比表面积小于1.0m2·g-1、粒度分布比较集中的锰酸锂(LiMn2O4)材料结构稳定,不易引发与电解液的反应及John-Teller效应,具备良好的电化学循环性能及安全性能,是容量型动力电池合适的正极材料。发现在电解液中加入3%的1,3-丙烯磺酸内酯(1,3-PS)和5%的碳酸丙烯酯(PC),能使电池的高温(85℃,4小时)膨胀率由35.11%下降至12.40%；添加O.1M的双草酸硼酸锂(LiBOB)作为电解质盐,锰酸锂动力电池循环寿命在60℃下的循环寿命提高约3倍。发现在电解液中添加2%的环己基苯(CHB)时,电池过充性能明显改善,电池顺利通过3C/10V过充,基本不影响电池的其它性能。通过SEM.FTIR等手段研究发现CHB的防过充机理为阻断机理。研制的容量型电池在0.5C电流进行充放电循环500周后容量保持率为83%；20C倍率下放电,容量保持率为1C倍率放电容量的86%；高温(55℃)放电容量是常温(25℃)放电容量的99%,高温性能良好,低温(-25℃)放电容量是常温放电容量的75%。3.对电池在充放电过程中热量产生的因素进行了全面分析,并以研究制作的磷酸铁锂动力电池F11100120(标称容量：10Ah,标称电压：3.2V)在3C条件下放电表面温度分布数据为基础,建立了方型电池表面温度分布模型,模型如下：t=a+bx+cx2+dx3+ex4+fx5+gy+hy2+iy3+jy4+ky5(其中：x为电池的宽度,y为长度；x,y的系数为常数)根据电池表面温度分布情况,建立了电池表面散热模型,模型如下：Qt=4Qf+2Qs+2Qa+2Qb(其中：Qf为1/4电池正表面散热量,Qs为电池侧面散热量,Qa为电池极耳前端散热量,Qb为电池后端侧面散热量)以QC/T 743-2006“电动汽车用锂离子蓄电池”为标准,对本研究所制备的动力电池分别进行了过充、过放、短路、针刺、挤压、加热等安全性测试,测试过程中无起火、爆炸等现象出现,完全达到标准要求。4.试制生产了容量型M95100170(13Ah)与功率型F11100120(10Ah)两个型号的锂离子动力电池,并对安全性以及一致性工艺进行了重点研究。对试制产品的成品率进行分析,发现M95100170的成品率为97.2%,F11100120的成品率为95.2%。且产品一致性良好；试制生产的动力电池具备了较高的比能量和比功率,其中容量型动力电池M95100170的质量比能量为151Wh.kg-1,体积比能量为330Wh·L-1；功率型F11100120的质量比功率为2100W·kg-1,体积比功率为4000W·L-1,与国内外同类产品比较均达到了较高水平；将M95100170以串联的方式组装成13Ah/36V动力电池组,经500次充放电循环以后,电池组容量保持82%左右。动力电池模块通过了标准为QC/T 743-2006《电动汽车用锂离子蓄电池》的安全性测试。更多还原

【Abstract】 The development of lithium ion power batteries was reviewed in detail. The dependence of electrochemical properties on the microstructure, morphology of anode and cathode materials were comprehensively investigated, and then the key materials for power lithium ion batteries were selected. Several kinds of advanced electrolyte for power batteries were developed. A series of manufacture technologies, such as the optimization of battery structure design, the improvement of safety were achieved. And then lithium ion battery with high energy density and that with high power density were developed. The thermal behaviors of the batteries during charge/discharge were studied, and the model of surface temperature distribution and thermal dissipation were established. The electrochemical properties and safety performances of the batteries were characterized. Finally, the pilot-scale manufacture of high energy density battery and high power density battery were carried out.1. Lithium ion batteries with high power density were developed. LiFe1-xMgxPO4 cathode materials were synthesized by solid-state reaction. According to the results of cathode material characterization, the substitution of Fe with Mg in the LiFePO4 lattice has caused the contraction of unit cell volume and the decrease of lattice parameter a, b, as well as the improvement of electron conductivity. The prepared cathode material LP3, with stoichiometry of LiFe0.95Mgo.osPO4, Characterized with smooth surface and spherical morphology, has relatively concentrated particle size distribution(median size 7μm) and exhibits excellent electrochemical and high power properties. The MCMB (Mesophase Carbon Micro-Beads) samples shows a low specific surface area, narrow particle size distribution, stable cycle property and can be charged/discharged in a large current, which qualifies it to be the anode active material of lithium ion batteries with high power density. And then the lithium ion batteries with high power density were developed. The lithium ion batteries with high power density exhibit excellent electrochemical properties. The capacity retention ratio remains 87% after 1900 cycles. Compared with the discharge capacity at 1C current rate and ambient temperature, the discharge capacity at 30C current rate remains 91% and that at-20℃remains 62%, respectively.2. Synthesis and study of the high energy battery. The results of cathode material characterization indicate that the spinel LiMn2O4, characterized with lattice parameter a<8.21 A, exhibits smooth surface, perfect crystal growth, specific surface area below 1.0m2·g-1 stable structure and well particle size distribution. The John-Teller effect and the undesired reaction between LiMn2O4 and electrolyte decrease. Therefore, the material with typical properties described above is selected as cathode active material for the high energy battery.The advanced electrolyte special for LiMn2O4 power battery was studied. The swell rate of the battery decreases from 35.11% to 12.40% when 3% 1,3-PS and 5%PC used as electrolyte additives. For 0.1M LiBOB mixed with LiPF6 battery, the cycle life of LiMn2O4 power battery is greatly improved about 3 times at 60℃.The safety performance of LiMn2O4 power battery was also investigated. It is found that the addition of 2% CHB will improve the battery overcharge property. The LiMn2O4 battery passed the 3C/10V overcharge without any other expense. The SEM and FTIR characterizations show that the action mechanism of CHB was as ascribed to interdiction with.The capacity retention of the manufactured battery is 86% after 500 cycles, at 0.5C rate. The discharge capacity of the battery retains 86% at 20C, compared to that of 1C. The relatively high temperature (55℃) has little effect on the discharge capacity. However, the capacity retention is only 75% at low temperature (-25℃)..3. The potential factors contributing to the heat production were comprehensively concluded. The dates were collected from the surface temperature of LiFePO4 power battery (Model:F11100120, Nominal Capacity:10Ah, Nominal Voltage:3.2V) discharging at 3C rate, and analysed by fitting soft. The fitting model of temperature distribution of battery is as follow: t= a+bx+cx2+dx3+ex4+fx5+gy+hy2+iy3+jy4+ky5(x, y is the width and length of battery respectively, and the indexes of x, y are constant, t is temperature)The heat dissipation model was also established as follow: Q1=4Qf+2Qs+2Qa+2Qb(Qt is total thermal dissipation, Qf is obverse surface thermal dissipation, Qs, Qa, Qb denote the left and right side, the front side, the rear side thermal dissipation respectively)The safety testing items, including overcharge, overdischarge, short circuit, nail penetration, crush, heating test, were performed according the method of Industry Standard QC/T 743-2006 "Lithium-ion batteries for electric vehicle". All the testing items are satisfied.4. The pilot tests of high energy density battery M95100170 (13Ah) and high power density battery F11100120(10Ah)were carried out respectively. Key-point controls were performed on the safety and consistency technology. The results of pilot product show that the yield of M95100170 and F11100120 is 97.2%,95.2%, respectively. The consistency of pilot product is fairly good. The specific energy density of M95100170 is 151Wh-kg"1 or 330Wh-L"’and the specific power density of F11100120 is 2100W-kg"1, or 4000W-L"1. Both pilot products are in the advanced level, comparing with similar products at international. Furthermore, lithium power battery packs (13 Ah/36V) were assembled with M95100170 cell in series. The capacity retention rate of pack is 82% after 500 cycles. The pack also passed all the safety testing items according the method of Industry Standard QC/T 743-2006 "Lithium-ion batteries for electric vehicle".更多还原