Quantitative spatiotemporal Li profiling using nanoindentation
Quantitative spatiotemporal Li profiling using nanoindentation
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DOI：
10.1016/j.jmps.2020.104102
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发表时间：
2020-11
影响因子：
5.3
通讯作者：
L. Vasconcelos;Rong Xu;K. Zhao
中科院分区：
文献类型：
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作者：
L. Vasconcelos;Rong Xu;K. Zhao
锂离子电池的倍率性能和寿命在很大程度上取决于电极的组成动力学。我们提出了一种纳米压痕的方法来探测的时空Li配置文件使用的功能依赖于Li组合物的机械性能。这种力学信息的材料动力学使我们能够测量成分依赖的扩散率，评估锂反应的限速过程，并定量评估对锂运输的应力调节。实验结果表明，锂在非晶硅中的扩散系数从原始状态到完全锂化状态呈指数变化，变化幅度为三个数量级。非晶Si中的锂化受到微米级扩散的限制。我们进一步评估的热力学驱动力，锂扩散，包括材料的非理想性和机械应力。通过计算建模，我们发现，在一般情况下，锂扩散率的组成依赖性与脱锂锂的速率能力上创建一个不对称。在Si中，与缓慢且相对平滑的脱锂相比，指数依赖性导致通过陡峭的浓度梯度进行的快速锂化。这种不对称行为似乎是Li捕获和Si中可输送容量损失的根本原因。这项工作揭示了锂输运的热力学和非晶硅的锂化动力学。它展示了操作纳米压痕在机械方面的潜力，了解锂化学和帮助电池研究超越机械测量。
The rate capability and lifetime of Li-ion batteries is largely dictated by the composition dynamics of the electrodes. We set forth a nanoindentation approach to probe the spatiotemporal Li profile using the functional dependence of the mechanical properties on Li composition. This mechanics-informed material dynamics allows us to measure the composition-dependent diffusivity, assess the rate-limiting process in Li reactions, and quantitatively evaluate the stress regulation on Li transport. The experiments show that Li diffusivity in amorphous Si varies exponentially by three orders of magnitude from the pristine to the fully lithiated state. Lithiation in amorphous Si is limited by diffusion at the micron scale. We further evaluate the thermodynamic driving force for Li diffusion by including the material non-ideality and mechanical stresses. Through computational modeling, we find that the composition dependence of the Li diffusivity in general creates an asymmetry on the rate capability during lithiation versus delithiation. In Si, the exponential dependence results in a fast lithiation that proceeds via a steep concentration gradient compared to a slow and relatively smooth delithiation. This asymmetric behavior appears to be a root cause of Li trapping and loss of the deliverable capacity in Si. This work sheds light on the thermodynamics of Li transport and the lithiation kinetics of amorphous Si. It demonstrates the potential of operando nanoindentation in the mechanics-informed understanding of Li chemistry and aiding battery research beyond mechanical measurement.