比克-三元正极材料锂离子电池_EPDF

1、三元正极材料动力锂离子电池的安全性保障-”失效-保护”系统Fail-Safe System for NMC Cathode Power Li-Ion Battery 比克电池BAK Battery Inc. 毛焕宇Huanyu Mao, Ph.D.2013/04/08内容提要现实的需要-用三元材料三元材料与磷酸铁锂的比较三元材料电芯的安全性问题Fail Safe 概念的提出如何才能达成Fail -Safe China National Requirements for Automotive Batteries2015年，动力电池模块比能量达到150瓦时/公斤以上By 2015, power b

2、attery energy density to be above 150 wh/kg at module level成本降低至2元/瓦时Reduce the cost to 2 RMB/wh(US$317/kwh“China New Energy Automotive Industrial Develop Plan” Proposed by China MIIT and Passed on April 18, 2012 by State Council节能与新能源汽车产业发展规划, 国务院于2012年04月18日讨论通过高能量密度和低成本High energy density and low

3、 cost成本与能量密度的关系Cost Reduction and Energy Density需要Need 2000pcs原材料Material电池生产流程电池生产流程Process制造成本几乎完全相同Process cost almost the same原材料Material20kwh Pack20Wh/cellCell cost reduction by 50%每台车电芯成本台车电芯成本下降约电芯成本下降约一半下降约一半需要Need1000pcs原材料成本基本相同Similarmaterial cost提升电池能量密度能够大幅度降低单位成本Cost can be substantial

4、ly reduced byincrease energy density 正极材料能量密度计算 材料实际比能量密度 = 比容量 X 电压 X 压实密度 X 活性物质含量 LiCoO2: 148 mAh/g x 3.8V x 4.1 g/cc x 98% =2.260Wh/cc (18650 容量2.6Ah, 约205Wh/kg Li(NMCO2：160 mAh/g x 3.7V x 3.55 g/cc x 97% =2.038Wh/cc (18650 容量2.2Ah, 约176Wh/kg LiMn2O4: 120 mAh/g x 3.9V x 2.9 g/cc x 95% =1.289 Wh/

5、cc (18650 容量1.5Ah, 约120Wh/kg LiFePO4: 140 mAh/g x 3.3V x 2.3 g/cc x 90% =0.956 Wh/cc (18650 容量1.3Ah, 约100Wh/kg 首次充放电效率也是一个重要因素，但是可以通过调整N/P比来改善 正极原材料性能对比 110% 100% 占 90% 比 80% % 70% 60% 50% 克容量 Specific capacity 电压 Volt LiCoO2 Li(NMCO2 LiMn2O4 LiFePO4 压实密度 活性物质含量 Compressed density Active mart.% 实际压实

6、密度与晶体密度的关系 5.3 LiCoO2, 5.05; 4.1 5.1 4.9 晶体计算密度 （g/c.c. Li(NMC, 4.77; 3.5 4.7 4.5 4.3 4.1 3.9 3.7 3.5 2 2.5 3 3.5 4 4.5 实际压实密度 （g/c.c. LiFePO4, 3.6; 2.3 LiMn2O4; 4.18; 2.9 原材料选择 要满足模块150wh/kg 要满足模块150wh/kg 磷酸铁锂(电芯能量密度120wh/kg将很难被 采用 其他正极材料如锰酸锂以及混合材料的循环性 能和能量密度都达不到要求 新型材料如富锰富锂有诸多带根本性的性能问 题未解决，尚未产业化，应

7、用经验不足 要在2015年前完成任务，三元材料及其衍生 化合物是较现实的选择 负极将适量采用微粒分散型硅碳复合材料，可 以提高负极能量密度 两种正极材料的比较 Comparison of 2 typical cathode material Advantages High safety Good Cell cycle life Disadvantages Low energy density (120Wh/kg Poor low T performance Difficult to control and detect self-discharge cells Lower yield LiFe

8、PO4 Li(NMCO2 High energy density(180Wh/kg Good Cell cycle life Good low T performance 80% Easy to detect and control selfdischarge cells Higher yield Easy on SOC indication Poor cell safety Main battery location Auxiliary Power Unit (APU battery location 起火和烟雾，电池内部碳化变黑、 重量减轻5公斤 on the right side Cel

9、ls on the left side Cells 8 7 6 5 4 3 2 1 Substantial thermal damage Moderate thermal damage 13 事故调查 196 mm (including terminal 75 Ah 50 mm Cell specs 75 Ah/3.7V 2.72kg 132 mm 结论：电池内短路! 结论：电池内短路! Conclusion: Internal Short Circuit! Hole 15 CT 扫描图 千万不要小看电池的能量美式MK II 手雷填装57g TNT用电池能量单位来算只有一个三元材料的18Ah3

10、.7V的放电能量 汤浅电池包的放电能量相当于32个手雷电池包无 失效一种安全性模型(无失效-保护A Safety ModelPossibility of InternalShort Circuit 内短路可能性Internal Short Circuit occurs 重物weight火种kindling stone 内短路发生Battery Pack without Fail-Safe s-保护 系统重物weightSafe system重物weight 爆炸火种kindling stoneexplosion电池包具备 失效-保护 系统Battery Pack with Fail-Safe

11、syst system一种安全性模型(有失效-保护A Safety ModelPossibility ofInternal Short Circuit 内短路可能性Fail-Safe System “失效-保护”系统Internal Short Circuit occurs 内短路发生Fail-Safe Systemworks“失效-保护”系统发挥作用重物weight重物weight重物weight火种kindling stone 火种kindling stone 火种kindling stone三元材料的电池包都必须具备“失效-保护”系统 What cause a safety incide

12、nt什么原因引起电池安全事故？Bad connections in a battery packElectrolyte leakingto cause “second-fire”with excess heat around the cellsInternal shortOther extreme conditions电池内部短路是最常见而最难以完全杜绝的现象，难以完全杜绝的现象，特别是在中国大多数生产厂家。是在中国大多数生产厂家。必须要有“必须要有“Fail-Safe”的措施才能完全避免恶性安全事故的发生。的发生。Internal short is the most common and m

13、ost difficult to prevent case，we must take a “Fail-Safe” approach to prevent safety incidences from happening. Demonstration of an Internal Short负极燃烧时热传递的速度 Fire Propagation Rate on AnodeFire spot starts from 0mm to 80 mm in 0.8 sec. Temperature over 600 C 外部引发的内短路 External Trigged Internal Short 6

14、cell Pack ExperimentThermo couplesCells are fully charged Cell vented with fire violentlyLinear heat propagation 直线的热传递过程 #1 #2 #3 #4 #5 #6 被短路的#3电池发热传递给旁边的两电池#2和#4 Cell #3 started the heating and pass the heat to adjacent cell #2 and #4 #2和#4获得能量后爆炸，并将热传递给#1和#5， #2 and #4 exploded after gaining hea

15、t from #3 and pass heat to #1 and #5 #6获得#5的能量后爆炸， #6 exploded after gaining heat from #5 并联电池之间的电传递 Electrical energy surge by inter cell current feeding for cells with parallel connection Brian Barnett, Tiax LLC, Mar 13, 2012, Ft Lauderdale, Florida 万一有内短路发生时，我们必须： In the event of an internal shor

16、t circuit, we must: 切断电池间热传导,终止连锁反应 Cut thermal propagation between cells 切断电池间的电传导 Cut electric feeding between cells or electrode plates 相当于4个 手雷的 爆炸威力 75 Ah 热能传导当量 = 5Ah 约1/5 个手雷的爆炸威力 Termination of heat propagation is possible 热传递过程可以终止 5Ah Heat insulation 绝热墙 _ 75 Ah + 电能传导无法阻止 PTC fuse 电能传导可以有

17、效阻止 5Ah 小结 Conclusion 电池内部短路总是源于很小的一个点，因此也总是首先发生在单个电池中 Internal short always starts from ONE very small pin-point, therefore, internal short always start in one cell. 如果电池之间的热传递能够有效终止，电池包整体就是安全的 overall cell pack maybe safe, IF heat propagation between cells can be effectively stopped 对于尺寸较小的电池比较容易终

18、止热传递，但对于尺寸大的电池实现起来非 常困难 heat propagation is easier to manage for smaller cells and more difficult for larger cells 发生内短路时，小电池之间的电能传递可以采用许多的方式避免，但对于大 电池对于内短路点的电能传递无法避免 In case of an internal short, electric energy feeding between smaller cells can be stopped by proper external measures, but electric energy feeding into the internal short spot through inside connections is not possible to stop 比克电池的”Fail-Safe”系统 的实况视频 Video of BAK Battery Pack “Fail-Safe”System Summary 三元正极材料动力锂离子电池必须具备“失效-安 三元正极材料动力锂离子电池必须具备“失效全”系统 NMC cathode Li-Ion battery must b