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首页> 外文会议>Charging amp; infrastructure symposium 2018 >On the Impact of the Graphite Anode in Parallel Connected Lithium-Ion-Batteries: A Case Study on Tesla Model S 85 Cells
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On the Impact of the Graphite Anode in Parallel Connected Lithium-Ion-Batteries: A Case Study on Tesla Model S 85 Cells

机译：并联阳极锂离子电池中石墨阳极的影响：以特斯拉S 85型电池为例

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摘要

Lithium-ion batteries consist of an anode and a cathode. The potential difference of both electrodes can be measured from the outside. The measurable voltage of lithium-ion-batteries is strongly dependent on the lithium concentration inside of the electrodes, which consist of different sized particles. During usage the lithium distributes unevenly to these particle due to e.g. different active areas of the reaction surface. Thick graphite electrodes which are used in high-energy electric vehicle batteries are especially prone to potential gradients due to growing inhomogeneity in the lithium concentration. Even a small difference in lithium concentration can cause more than 40 mV of potential difference on the graphite electrode. This lateral potential difference can cause a homogenization and redistribution of the lithium on the electrode. Lewerenz et al. [1] used the differential voltage analysis (DVA) as a technique to describe this homogeneity of the lithium distribution and to compare the results over different ageing states. A high peak in the DVA can be interpreted as a high homogeneity of lithium distribution and a small peak therefore as a low homogeneity. In a high homogeneity case the electrode reacts as if it only consists of one particle and the potential response to an applied current is thus synchronized over all particles. A low homogeneity causes the electrode's potential to react like a distribution. Different particles react at different potentials and at different times A low homogeneity can be a sign of an onset of ageing and is of particular interest. However current research has not addressed the effect of homogenization and synchronicity in a parallel connection of lithium-ion batteries. Hence it is researched in this work. In this work a parallel connection of cells from the Tesla Model S 85 are investigated. The car was driven for 25.000 km before being disassembled. 27 specimens were harvested and the 1 kHz impedance was measured at 3.6 V. Afterwards, the specimen were connected to a newly developed measurement device. The device is capable of measuring up to 30 batteries in parallel. The measured values include single cell voltages and currents as well as the surrounding temperature. All measurements are conducted in sync with a sample rate up to 9600 samples per second. The parallel connected batteries are charged and discharged in this experiment with small current rates. To analyze the synchronicity of the batteries a modified differential voltage analysis (DVA) is applied. The DVA is usually applied to small constant current charge or discharge of a single battery [1,2,3,4]. Therefore the time, charge and SOC are connected linearly. However this changes when applying the DVA to parallel connected batteries. The current distribution changes over time and no linear connection between charge and time is present. It is still possible to calculate the DVA over charge for every single battery. Yet, in this DVA the synchronicity of the parallel connected batteries is lost. To overcome this limitation different analysis strategies are introduced. From the results a theory for the homogenization and synchronicity caused by the graphite anode is derived. This poster will present the theory on homogenization in parallel connected lithium-ion batteries as well as the conducted experimental results.
机译：锂离子电池由阳极和阴极组成。可以从外部测量两个电极的电势差。锂离子电池的可测量电压在很大程度上取决于电极内部的锂浓度，该电极由不同尺寸的颗粒组成。在使用期间，由于例如锂的存在，锂不均匀地分布在这些颗粒上。反应表面的不同活性区域。由于锂浓度的不均匀性增加，用于高能电动汽车电池的厚石墨电极特别容易出现电位梯度。即使锂浓度的微小差异也可能导致石墨电极上的电位差超过40 mV。这种横向电势差会导致锂在电极上的均匀化和重新分布。 Lewerenz等。 [1]使用差分电压分析（DVA）作为描述锂分布均匀性并比较不同老化状态下结果的技术。 DVA中的高峰可解释为锂分布的高均一性，因此小峰可解释为低均一性。在高度均匀的情况下，电极会像仅由一个粒子组成一样进行反应，因此对所有粒子的施加电流的电势响应都是同步的。低均匀性会导致电极的电势像分布一样发生反应。不同的粒子在不同的电位和不同的时间反应。低均匀性可能是老化的标志，并且特别令人关注。然而，当前的研究尚未解决锂离子电池并联中的均质化和同步性的影响。因此，在这项工作中进行了研究。在这项工作中，研究了来自Tesla Model S 85的电池的并联连接。拆解前，该车行驶了25,000公里。收获27个样本，并在3.6 V下测量1 kHz阻抗。之后，将样本连接到新开发的测量设备。该设备能够并行测量多达30个电池。测量值包括单电池电压和电流以及周围温度。所有测量均以高达每秒9600个样本的采样速率同步进行。在此实验中，并联的电池以小电流速率充电和放电。为了分析电池的同步性，应用了改进的差分电压分析（DVA）。 DVA通常用于单个电池的小恒定电流充电或放电[1,2,3,4]。因此，时间，电荷和SOC是线性连接的。但是，将DVA应用于并联电池时，情况会发生变化。电流分布随时间变化，并且电荷和时间之间不存在线性关系。仍然有可能为每个电池计算DVA过充电量。然而，在该DVA中，并联电池的同步性丧失。为了克服该限制，引入了不同的分析策略。从结果得出了石墨阳极引起的均质化和同步性的理论。该海报将介绍并联锂离子电池均质化的理论以及进行的实验结果。

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  • 会议地点 Mainz(DE)
  • 作者

    Friedrich Emanuel Hust; Markus Niessen; Xinya Xu; Dirk Uwe Sauer;

  • 作者单位

    RWTH Aachen University, Electrochemical Energy Conversion and Storage Systems Group, Institute for Power Electronics and Electrical Drives (ISEA), Jaegerstrasse 17/19, Aachen, D-52066 Germany;

    RWTH Aachen University, Electrochemical Energy Conversion and Storage Systems Group, Institute for Power Electronics and Electrical Drives (ISEA), Jaegerstrasse 17/19, Aachen, D-52066 Germany,Juelich Aachen Research Alliance, JARA-Energy, Aachen, Germany;

    RWTH Aachen University, Electrochemical Energy Conversion and Storage Systems Group, Institute for Power Electronics and Electrical Drives (ISEA), Jaegerstrasse 17/19, Aachen, D-52066 Germany,Juelich Aachen Research Alliance, JARA-Energy, Aachen, Germany;

    RWTH Aachen University, Electrochemical Energy Conversion and Storage Systems Group, Institute for Power Electronics and Electrical Drives (ISEA), Jaegerstrasse 17/19, Aachen, D-52066 Germany,Juelich Aachen Research Alliance, JARA-Energy, Aachen, Germany,Helmholtz Institute Muenster (HI MS), IEK-12, Forschungszentrum Juelich, Corrensstrasse 46, Muenster, D-48149 Germany;

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