An In Situ TEM Liquid Cell for Imaging Electrode/Electrolyte Interactions
To test the cell operation, we imaged Li electrodeposition on a nanopatterned Ti working electrode. The liquid electrolyte consisted of 1:1 ethylene carbonate:diethyl carbonate with 1M LiPF6, and a galvanostatic two-electrode charging experiment was performed to deposit Li from the electrolyte onto the working electrode. The TEM was operated in scanning mode (STEM) with a low electron dose to minimize beam effects on the liquid electrolyte. Upon application of a few pA of current, we acquired a characteristic chronopotentiometric curve and saw clear deposition of Li particles in the STEM images and movies (see Figure 1). Following Li deposition, a thick growth of SEI was evident near the Li nanoparticles, consistent with electrolyte decomposition in the presence of reactive Li. We also imaged electrodeposition/stripping of Cu nanoparticles in the same liquid environment and will explore battery-relevant materials such as LiFePO4 and Si nanostructures. Our TEM liquid cell provides a unique, high-resolution view of the electrode/electrolyte interfacial phenomena, and both the challenges in fabrication as well as the successes in imaging electrochemical processes will be presented.
1. Sullivan, J. P. et al. “Real-time Studies of Battery Electrochemical Reactions Inside a Transmission Electron Microscope.” Sandia Technical Report SAND2012-0103 (2012). doi:10.2172/1038174