Search for: All records

Fourier-transform infrared spectroscopy (FTIR) is a powerful analytical method not only for the chemical identification of solid, liquid, and gas species but also for the quantification of their concentration. However, the chemical quantification capability of FTIR is significantly hindered when the analyte is surrounded by a strong IR absorbing medium, such as liquid solutions. To overcome this limit, here we develop an IR fiber microprobe that can be inserted into a liquid medium and obtain full FTIR spectra at points of interest. To benchmark this endoscopic FTIR method, we insert the microprobe into bulk water covering a ZnSe substrate and measure the IR transmittance of water as a function of the probe–substrate distance. The obtained vibrational modes, overall transmittance vs z profiles, quantitative absorption coefficients, and micro z-section IR transmittance spectra are all consistent with the standard IR absorption properties of water. The results pave the way for endoscopic chemical profiling inside bulk liquid solutions, promising for applications in many biological, chemical, and electrochemical systems. 

Solid-electrolyte interphases (SEIs), oftentimes viewed as the most important yet least understood part of alkali ion/metal batteries, remain a key bottleneck for battery design. Despite extensive research in the past few decades, to date we have only begun to unravel the structure of SEIs, while its dynamic nucleation and growth mechanism is still elusive. Here we discuss the existing progress in characterizing SEIs in the battery community, and propose that SEI growth depends critically on the electrical double layer (EDL) structure, a factor that has been largely hidden or ignored to date. We will further discuss methods for simultaneously characterizing EDL and SEIs, with a particular focus on the emerging electrochemical 3D atomic force microscopy (EC-3D-AFM) and shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) techniques. In the end, we will propose strategies for predictive design of electrolytes to enable controlled EDL and SEI structures and achieve desired battery performance.