Simple evaluation method of mechanical strength and mechanical fatigue of negative electrode for lithium-ion battery
Simple evaluation method of mechanical strength and mechanical fatigue of negative electrode for lithium-ion battery
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DOI：
10.1299/mej.19-00545
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发表时间：
2020
影响因子：
4.4
通讯作者：
Y. Kishimoto;Yukiyoshi Kobayashi;T. Ohtsuka;S. Ono;H. Yamazaki;Yuki Tsukagoshi;Kyohei Nakamura
中科院分区：
文献类型：
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作者：
Y. Kishimoto;Yukiyoshi Kobayashi;T. Ohtsuka;S. Ono;H. Yamazaki;Yuki Tsukagoshi;Kyohei Nakamura
锂离子电池有望成为汽车的主要动力源。然而，由于LIBS具有较高的能量密度，因此LIBS极易引发严重事故。对于汽车上的应用，应保证LIBS在各种外部载荷下的可靠性。尤其是汽车引起的振动和热应力，使LIBS不断受到静载荷和循环载荷的作用，LIBS的电极会发生疲劳损伤。在这方面，评估焊条的机械强度和机械疲劳性能，如抗拉强度和S-N曲线是很重要的。本研究提出了一种利用电极的力学模型对LIBS电极的机械强度和疲劳性能进行简单评估的方法。活性物质颗粒的实际排列是随机的，基于实际排列的力学模型过于复杂，无法推导出电极的主要力学因素。所提出的模型将粒子的排列近似为体心立方(BCC)和面心立方(FCC)，这两种晶格是众所周知的晶格。为了验证所提出的方法，对LIBS负极进行了静态拉伸试验和弯曲疲劳试验。从试验结果来看，由所提出的模型估算的负极抗拉强度与实验值基本一致，且BCC模型与FCC模型之间的差异小于实验值的变化。每1周在负极上产生裂纹的应力的估计值与抗拉强度一致。循环次数在对数尺度上随应力幅值的减小而线性增加，106-107周次的应力幅值与抗拉强度的一半相吻合。
Lithium-ion batteries (LIBs) are expected to be main power sources of automobiles. Nevertheless, LIBs easily lead to serious incidents because LIBs have high energy density. For application to automobiles, the reliability of LIBs should be guaranteed against various external loads. Especially, static loads and cyclic loads are constantly applied on LIBs because of vibration and thermal stress induced in automobiles, and fatigue damage occurs in electrodes of the LIBs. In this respect, it is important to evaluate mechanical strength and mechanical fatigue property of electrodes, such as tensile strength and S-N curves. This study has proposed a simple evaluation method of the mechanical strength and the fatigue property of electrodes for LIBs by using mechanical models of the electrodes. The actual alignment of particles of active material is random, and mechanical models based on the actual alignment are too complex to derive the main factor of mechanics of the electrodes. The proposed models approximate the alignment of the particles as the body-centered cubic (bcc) and the face-centered cubic (fcc) which are the well-known crystal lattices. In order to verify the proposed method, static tensile tests and bending fatigue tests of negative electrodes for LIBs have been conducted. From the test results, the tensile strength of the negative electrodes estimated by the proposed models agree with the experimental values, and the difference between the bcc model and the fcc model is smaller than the variation of the experimental values. The estimation value of the stress that initiates a crack on the negative electrodes by 1 cycle agrees with the tensile strength. The number of cycles linearly increases in the log scale with the decrease of the stress amplitude, and the stress amplitude at the 106–107 cycles agrees with the half of the tensile strength.