Lemaire Pierre, Dargon Thomas, Alves Dalla Corte Daniel, Sel Ozlem, Perrot Hubert, Tarascon Jean-Marie
Chimie du Solide et de l'Energie, UMR 8260, Collège de France, 11 Place Marcelin Berthelot, 75231 cedex 05 Paris, France.
Sorbonne Université, 4 Place Jussieu, 75005 Paris, France.
Anal Chem. 2020 Oct 20;92(20):13803-13812. doi: 10.1021/acs.analchem.0c02233. Epub 2020 Sep 29.
Numerous sophisticated diagnostic techniques have been designed to monitor electrode-electrolyte interfaces that mainly govern the lifetime and reliability of batteries. Among them is the electrochemical quartz crystal microbalance (EQCM) that offers valuable insights of the interfaces once the required conditions of the deposited film in terms of viscoelastic and hydrodynamic properties are fulfilled. Herein, we propose a friendly protocol that includes the elaboration of a homogeneous deposit by spray coating followed by QCM measurements at multiharmonic frequencies to ensure the film flatness and rigidity for collecting meaningful data. Moreover, for easiness of the measurements, we report the design of a versatile and airtight EQCM cell setup that can be used either with aqueous or non-aqueous electrolytes. We also present, using a model battery material, LiFePO, how dual frequency and motional resistance monitoring during electrochemical cycling can be used as a well-suitable indicator for achieving reliable and reproducible electrogravimetric measurements. We demonstrate through this study the essential role of the solvent assisting lithium-ion insertion at the LiFePO interface with a major outcome of solvent-dependent interfacial behavior. Namely, in aqueous media, we prove a near-surface desolvation of lithium ions from their water solvation shell as compared with organic molecules. This spatial dissimilarity leads to a smoother Li-ion transport across the LFP-HO interface, hence accounting for the difference in rate capability of LFP in the respective electrolytes. Overall, we hope our analytical insights on interfacial mechanisms will help in gaining a wider acceptance of EQCM-based methods from the battery community.
众多精密的诊断技术已被设计用于监测电极 - 电解质界面，该界面主要决定电池的使用寿命和可靠性。其中包括电化学石英晶体微天平（EQCM），一旦满足沉积膜在粘弹性和流体动力学性质方面的所需条件，它就能提供有关界面的有价值见解。在此，我们提出一种简便的方案，包括通过喷涂制备均匀沉积物，然后在多谐波频率下进行QCM测量，以确保膜的平整度和刚性，从而收集有意义的数据。此外，为了便于测量，我们报告了一种通用且气密的EQCM电池装置的设计，该装置可用于水性或非水性电解质。我们还展示了，使用模型电池材料LiFePO，在电化学循环过程中双频和运动电阻监测如何可作为实现可靠且可重复的电重量测量的合适指标。通过这项研究，我们证明了溶剂在LiFePO界面协助锂离子插入的重要作用，其主要结果是溶剂依赖性界面行为。具体而言，在水性介质中，与有机分子相比，我们证明锂离子从其水合壳层发生近表面去溶剂化。这种空间差异导致锂离子在LFP - H₂O界面的传输更顺畅，从而解释了LFP在各自电解质中的倍率性能差异。总体而言，我们希望我们对界面机制的分析见解将有助于电池领域更广泛地接受基于EQCM的方法。
