Thermal behavior of overcharged Ni/MH battery is studied with microcalorimeter. The battery is in-stalled in a special device in a microcalorimeter with a quartz frequency thermometer. Quantity of heat and heat capaci...Thermal behavior of overcharged Ni/MH battery is studied with microcalorimeter. The battery is in-stalled in a special device in a microcalorimeter with a quartz frequency thermometer. Quantity of heat and heat capacity of the battery charged at different state of charge (SOC) at different rates are meas-ured by the microcalorimeter. Based on a series of assumputions, heat transfer equation is set up. Ex-pression of heat generation is attained by curve fitting instead of theoretical calculation. Thermal model is used to simulate thermal behavior of the battery in charging period , results of calculation and ex-periment match very well. The temperature distribution is non-uniform because the poor conductivity limits the heat transfer during charging process. It is difficult to greatly improve the heat conductivity of the battery because it is related to materials inside the battery including electrodes, separators and so on. Therefore, high rate charge should be avoided in actual use. It may cause some damage to the battery.展开更多
Large-format lithium-ion(Li-ion) batteries with high energy density for electric vehicles are prone to thermal runaway(or even explosion) under abusive conditions. In this study, overcharge induced explosion behaviors...Large-format lithium-ion(Li-ion) batteries with high energy density for electric vehicles are prone to thermal runaway(or even explosion) under abusive conditions. In this study, overcharge induced explosion behaviors of large-format Li-ion pouch cells with Li[NiCoMn]Ocathode at different current rates(C-rates)(0.5C, 1C, 2C) were investigated. The explosion characteristics of the cells were elucidated by discussing the evolution of the cell voltage, the surface temperature and the shock wave pressure.Generally, the whole overcharge process could be divided into four stages according to the evolution of several key parameters and the overcharge behaviors;the overcharge C-rate has a great influence on cells’ thermal behaviors. The experimental results showed that the thermal runaway process of Liion cells caused by overcharging consisted of two kinds of explosions, physical explosion and chemical explosion. The existence of observable negative pressure zone in the pressure curves indicated that the Li-ion cells are not a self-supplying oxygen system during the explosion. Further, the explosion dynamics parameters were matched. An explosion TNT-equivalent conversion strategy that depended on the pressure of the shock wave was utilized to evaluate the released energy and its hazards. In addition, with respect to the overcharge of Li-ion pouch cells, a safety assessment method and a safety management method were proposed based on the explosion behaviors. From the perspective of battery safety, this study is of great significance for the safety design of Li-ion cells and can provide guidance for engineers to optimize the safety function of battery packs.展开更多
基金Supported by the National Key Basic Research and Development Program of China (Grant No. 2002CB211800)
文摘Thermal behavior of overcharged Ni/MH battery is studied with microcalorimeter. The battery is in-stalled in a special device in a microcalorimeter with a quartz frequency thermometer. Quantity of heat and heat capacity of the battery charged at different state of charge (SOC) at different rates are meas-ured by the microcalorimeter. Based on a series of assumputions, heat transfer equation is set up. Ex-pression of heat generation is attained by curve fitting instead of theoretical calculation. Thermal model is used to simulate thermal behavior of the battery in charging period , results of calculation and ex-periment match very well. The temperature distribution is non-uniform because the poor conductivity limits the heat transfer during charging process. It is difficult to greatly improve the heat conductivity of the battery because it is related to materials inside the battery including electrodes, separators and so on. Therefore, high rate charge should be avoided in actual use. It may cause some damage to the battery.
基金sponsored by the China Postdoctoral Science Foundation(China National Postdoctoral Program for Innovative Talents,BX2021036)the National Natural Science Foundation of China(52072040,U21A20170)supported by the Department of Energy(DOE),Office of Electricity(OE)at Oak Ridge National Laboratory managed by UL-Battelle LLC(DE-AC0500OR22725)。
文摘Large-format lithium-ion(Li-ion) batteries with high energy density for electric vehicles are prone to thermal runaway(or even explosion) under abusive conditions. In this study, overcharge induced explosion behaviors of large-format Li-ion pouch cells with Li[NiCoMn]Ocathode at different current rates(C-rates)(0.5C, 1C, 2C) were investigated. The explosion characteristics of the cells were elucidated by discussing the evolution of the cell voltage, the surface temperature and the shock wave pressure.Generally, the whole overcharge process could be divided into four stages according to the evolution of several key parameters and the overcharge behaviors;the overcharge C-rate has a great influence on cells’ thermal behaviors. The experimental results showed that the thermal runaway process of Liion cells caused by overcharging consisted of two kinds of explosions, physical explosion and chemical explosion. The existence of observable negative pressure zone in the pressure curves indicated that the Li-ion cells are not a self-supplying oxygen system during the explosion. Further, the explosion dynamics parameters were matched. An explosion TNT-equivalent conversion strategy that depended on the pressure of the shock wave was utilized to evaluate the released energy and its hazards. In addition, with respect to the overcharge of Li-ion pouch cells, a safety assessment method and a safety management method were proposed based on the explosion behaviors. From the perspective of battery safety, this study is of great significance for the safety design of Li-ion cells and can provide guidance for engineers to optimize the safety function of battery packs.
