Scanning Electrochemical Microscopy for Chemical Imaging and Understanding Redox Activities of Battery Materials

Abstract

Improving the charge storage capacity and lifetime and charging/discharging efficiency of battery systems is essential for large-scale applications such as long-term grid storage and long-range automobiles. While there have been substantial improvements over the past decades, further fundamental research would help provide insights into improving the cost effectiveness of such systems. For example, it is critical to understand the redox activities of cathode and anode electrode materials and stability and the formation mechanism and roles of the solid−electrolyte interface (SEI) that forms at the electrode surface upon an external potential bias. The SEI plays a critical role in preventing electrolyte decay while still allowing charges to flow through the system while serving as a charge transfer barrier. While surface analytical techniques such as X-ray photoelectron (XPS), X-ray diffraction (XRD), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and atomic force microscopy (AFM) provide invaluable information on anode chemical composition, crystalline structure, and morphology, they are often performed ex situ, which can induce changes to the SEI layer after it is removed from the electrolyte. While there have been efforts to combine these techniques using pseudo-in situ approaches via vacuum-compatible devices and inert atmosphere chambers connected to glove boxes, there is still a need for true in situ techniques to obtain results with improved accuracy and precision. Scanning electrochemical microscopy (SECM) is an in situ scanning probe technique that can be combined with optical spectroscopy techniques such as Raman and photoluminescence spectroscopy methods to gain insights into the electronic changes of a material as a function of applied bias. This Review will highlight the potential of SECM and recent reports on combining spectroscopic measurements with SECM to gain insights into the SEI layer formation and redox activities of other battery electrode materials. These insights provide invaluable information for improving the performance of charge storage devices.

Unravelling air/moisture stability of cathode materials in sodium ion batteries: characterization, rational design, and perspectives

“…Additionally, Raman spectroscopy can be integrated with other microscopy techniques employing micro-sized lasers. 74–76 SEM-Raman analysis allows for the acquisition of high-resolution morphology-correlated Raman spectra. As illustrated in Fig.…”

Scanning electrochemical probe microscopy investigation of two-dimensional materials

“…We foresee exciting prospects in amalgamating SECM/SECCM with the developmental trajectory of 2D materials in sensor innovation. Both SECM and SECCM offer avenues to scrutinize the formation of SEIs on electrodes-a pivotal facet of battery research [203]. Furthermore, by unraveling multiple charge transfer and mass transfer mechanisms in the complex EC systems, SECM/SECCM can directly impact the evolution of more efficient metal-ion batteries [203,204].…”

“…Both SECM and SECCM offer avenues to scrutinize the formation of SEIs on electrodes-a pivotal facet of battery research [203]. Furthermore, by unraveling multiple charge transfer and mass transfer mechanisms in the complex EC systems, SECM/SECCM can directly impact the evolution of more efficient metal-ion batteries [203,204]. The suitability of 2D materials as advanced battery electrode materials stems from their expansive specific surface area, minimized ion diffusion distances, and capacity to mitigate volume fluctuations during repeated charge/discharge cycles [205,206].…”

General Method for Fitting Kinetics from the SECM Images of Reactive Sites on Flat Surfaces

“…The products of this reaction can diffuse back to the ME, creating a feedback loop that leads to an increase or decrease in current at the ME depending on whether or not the surface is reactive or unreactive, respectively . Electrochemical reactions involving corrosion, , energy materials, catalysis, , and biological systems can all be interrogated using this technique.…”