Wang Hansen, Kim Sang Cheol, Rojas Tomás, Zhu Yangying, Li Yanbin, Ma Lin, Xu Kang, Ngo Anh T, Cui Yi
Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States.
Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States.
J Am Chem Soc. 2021 Feb 10;143(5):2264-2271. doi: 10.1021/jacs.0c10587. Epub 2021 Jan 28.
Temperature coefficients (TCs) for either electrochemical cell voltages or potentials of individual electrodes have been widely utilized to study the thermal safety and cathode/anode phase changes of lithium (Li)-ion batteries. However, the fundamental significance of single electrode potential TCs is little known. In this work, we discover that the Li-ion desolvation process during Li deposition/intercalation is accompanied by considerable entropy change, which significantly contributes to the measured Li/Li electrode potential TCs. To explore this phenomenon, we compare the Li/Li electrode potential TCs in a series of electrolyte formulations, where the interaction between Li-ion and solvent molecules occurs at varying strength as a function of both solvent and anion species as well as salt concentrations. As a result, we establish correlations between electrode potential TCs and Li-ion solvation structures and further verify them by molecular dynamics simulations. We show that measurements of Li/Li electrode potential TCs provide valuable knowledge regarding the Li-ion solvation environments and could serve as a screening tool when designing future electrolytes for Li-ion/Li metal batteries.
电化学电池电压或单个电极电位的温度系数（TCs）已被广泛用于研究锂离子电池的热安全性和阴极/阳极相变。然而，单个电极电位温度系数的基本意义却鲜为人知。在这项工作中，我们发现锂沉积/嵌入过程中的锂离子去溶剂化过程伴随着相当大的熵变，这对测量的Li/Li电极电位温度系数有显著贡献。为了探究这一现象，我们比较了一系列电解质配方中的Li/Li电极电位温度系数，其中锂离子与溶剂分子之间的相互作用强度随溶剂和阴离子种类以及盐浓度的变化而变化。结果，我们建立了电极电位温度系数与锂离子溶剂化结构之间的相关性，并通过分子动力学模拟进一步验证了它们。我们表明，Li/Li电极电位温度系数的测量提供了有关锂离子溶剂化环境的有价值信息，并可作为设计未来锂离子/锂金属电池电解质时的筛选工具。
