Application of Atomic Force Microscopy in Research of Li-ion Batteries
Lithium-ion batteries (LIBs) are currently the most promising high-efficiency chemical energy storage power sources due to their high specific energy, long cycle life, high safety performance, and environmental protection. In recent years, the research direction of LIBs has mainly focused on the research and development of new high-efficiency positive and negative electrode materials, improving battery safety performance by changing the electrolyte, and improving the stability of the solid electrolyte interface film (solid electrolyte interface, SEI) on the negative electrode material. The SEI film refers to a passivation layer covering the surface of the electrode material formed by the reaction of the electrolyte and the electrode material at the solid-liquid phase interface during the first charging and discharging process of LIBs. The SEI film is an electronic insulator with the characteristics of a solid electrolyte, but it is also an excellent conductor of lithium ions, allowing lithium ions to be freely intercalated and extracted in this layer, and its stability has a great impact on the cycle performance and safety of lithium-ion batteries LIBs. big impact. Usually, electrochemical impedance spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, AFM, etc. are used to study the formation, change and function of SEI films, among which AFM plays an extremely important role in studying the formation, deformation and rupture of SEI films. important role.
In 1982, the advent of the scanning tunneling microscope (STM) made it possible for the first time to observe in real time the arrangement of individual atoms on the surface of a substance and the physical and chemical properties related to the surface electron density function. However, the working principle of STM is to use the tunneling current that changes exponentially with the distance between the probe and the conductive surface for imaging. Therefore, the materials that STM can detect must be conductive, which limits its application. In order to make up for this deficiency, in 1986, BINNIG and others invented the atomic force microscope (AFM) using the probe principle of STM. AFM can not only detect conductors, semiconductor materials, but also insulator materials, and can analyze different physical properties in the atmosphere, vacuum, liquid and other environments. Therefore, it has great significance in the research of surface science, material science, life science and other fields. Great significance and broad application prospects.
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Due to its high energy density, high cycle life, safety and many other advantages, lithium-ion batteries are the most popular portable power sources in modern life and have broad application prospects. In order to give full play to the potential of lithium-ion batteries and promote their practical application, it is necessary to study the electrode reaction process in depth. As a powerful assistant in the research of lithium-ion batteries, atomic force microscopy (AFM) can detect the microscopic morphology of the electrode surface in real time through the interaction between the atoms at the tip of the electrode and the atoms on the electrode surface, and provide physical and chemical information on the electrode surface at the nanometer scale. It provides an experimental basis for the optimization and modification of electrode materials and electrolytes. This paper reviews the latest application progress of AFM in the research of lithium-ion batteries, including the morphology changes, nanomechanical properties and electrical properties of electrode materials under electrochemical reaction conditions, indicating that AFM will further promote the research progress of lithium-ion batteries.
Since the emergence of AFM technology, it has been widely used in the analysis of Li-ion battery LIBs. Its low-destructive ability to detect the evolution of morphology and properties at the nanometer scale is helpful for a deeper understanding of Li-ion battery LIBs. The structure and related properties of the anode material and SEI film have laid a solid foundation for the development and research of LIBs for lithium-ion batteries, and further promoted the development of lithium-ion batteries. In this paper, the application and research progress of AFM in the research of positive and negative electrode materials and SEI films are reviewed from the aspects of morphology, mechanical properties and electrochemical properties. These studies indicate that AFM still has a lot of room for development in the research and application of Li-ion batteries. In addition, a large number of studies have found that the mechanical measurement of AFM has great advantages over other in situ characterization techniques, and this method has great potential in observing the mechanical and structural evolution of interphase and electrodes under different battery operating conditions. Finally, the development of additional scanning modes in conjunction with other detection techniques opens up new vistas for the application of AFM.
