Invited: In Situ Analytical Electron Microscopy for Probing Electrochemistry at Interfaces

Significant progress has been made in the past few years on the development of in situ electron microscopy for probing nano-scale electrochemistry. In situ electrochemical operation in the ultra-high vacuum column of a TEM has been pursued by three major strategies. In one strategy, an AFM type tip is used as a current collector and lithium oxide is used as the electrolyte to lithiate materials at low potential, however high voltage charging is not possible due to the low breakdown voltage of lithium oxide. A second strategy involves organic and/or liquid electrolyte, though this approach more closely resembles the actual operation conditions of LIB, it presents significant challenges for in situ cell design for TEM due to the volatility of the organic/liquid electrolyte. To this end, we have developed a novel in situ instrumental system combining analytical electron microscopy with advanced spectroscopy to probe the dynamic phenomena in an all solid-state nano-battery. An “all solid state battery” can be fabricated from an all-solid-state thin film battery using focused ion beam (FIB). The electrolyte is either polymer based or ceramic based without any liquid component. The interfaces between the active electrode material/electrolyte can be clearly observed at nano-scale under TEM imaging, in contrast to the composite electrodes/electrolyte interfaces in conventional lithium ion batteries, where quantitative interface characterization is extremely difficult if not impossible.  In situ electron microscopy can be a versatile technique and provide us answers to questions that could not be provided using other techniques. However in order to fully exploit the capabilities, a very carefully thought-out plan is essential to minimize the beam damage and other artifacts. Io ensure transparency for spectroscopic analysis, the nano-battery must be made very thin, typically less than 100 nm if EELS are to be done quantitatively. Artifacts due to plural scattering can be reduced by increasing the inelastic mean-free-path (by higher kV) or restricting analyses to thin regions of the sample. We will present the main challenges that we have overcome to enable in situ nano-electrochemistry in the (S)TEM.