Liu Huibing, Zhang Guoxing, Li Dawei, Zhang Junqian
Shanghai Institute of Applied Mathematics and Mechanics, School of Mechanics and Engineering Science, Shanghai University, Shanghai 200444, China.
School of Mechanical Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China.
Nanomaterials (Basel). 2022 Dec 14;12(24):4448. doi: 10.3390/nano12244448.
The in situ curvature measurement of bilayer beam electrodes is widely used to measure the lithium concentration-dependent material properties of lithium-ion battery electrodes, and further understand the mechano-electrochemical coupling behaviors during electrochemical cycling. The application of this method relies on the basic assumption that lithium is uniformly distributed along the length and thickness of the curved active composite layer. However, when the electrode undergoes large bending deformation, the distribution of lithium concentration in the electrolyte and active composite layer challenges the reliability of the experimental measurements. In this paper, an improved experiment for simultaneously measuring the partial molar volume and the elastic modulus of the graphite composite electrode is proposed. The distance between the two electrodes in the optical electrochemical cell is designed and graphite composite electrodes with four different thickness ratios are measured. The quantitative experimental data indicate that the improved experiment can better satisfy the basic assumptions. The partial molar volume and the elastic modulus of the graphite composite electrode evolve nonlinearly with the increase of lithium concentration, which are related to the phase transition of graphite and also affected by the other components in the composite active layer. This improved experiment is valuable for the reliable characterization of the Li concentration-dependent material properties in commercial electrodes, and developing next-generation lithium batteries with more stable structures and longer lifetimes.
双层梁电极的原位曲率测量被广泛用于测量锂离子电池电极中与锂浓度相关的材料特性，并进一步了解电化学循环过程中的机械-电化学耦合行为。该方法的应用依赖于一个基本假设，即锂在弯曲的活性复合层的长度和厚度方向上均匀分布。然而，当电极发生较大弯曲变形时，电解质和活性复合层中锂浓度的分布对实验测量的可靠性提出了挑战。本文提出了一种同时测量石墨复合电极偏摩尔体积和弹性模量的改进实验。设计了光电化学池中两个电极之间的距离，并测量了四种不同厚度比的石墨复合电极。定量实验数据表明，改进后的实验能更好地满足基本假设。石墨复合电极的偏摩尔体积和弹性模量随锂浓度的增加呈非线性变化，这与石墨的相变有关，也受到复合活性层中其他成分的影响。这种改进的实验对于可靠地表征商业电极中与锂浓度相关的材料特性，以及开发结构更稳定、寿命更长的下一代锂电池具有重要价值。
