Katherine Jungjohann2 Katharine Harrison1 Subrahmanyam Goriparti2 Andrew Leenheer3 Nathan Hahn1 Kevin Zavadil1

2, Sandia National Laboratories, Albuquerque, New Mexico, United States
1, Sandia National Laboratories, Albuquerque, New Mexico, United States
3, Sandia National Laboratories, Albuquerque, New Mexico, United States

Advancement in Li-ion battery technology is dependent on the development of new materials/electrolytes that can enable high capacity and provide stable, enhanced charge transfer across the electrode-electrolyte interface. To achieve these metrics, we have explored Li-metal anodes to understand the current limitations in their commercial use due to heterogenous morphology (dendrites) and performance within a solvent-in-salt electrolyte. We implement nanoscale imaging to understand the environmental and electrochemical parameters that control the Li morphology and solid electrolyte interphase structure, which determine the overall performance of the electrode. In-situ scanning/transmission electron microscopy (S/TEM) has enabled the exploration of the initial stages of Li deposition which can provide the baseline structure upon which the electrode evolution occurs [1].
All results were achieved using a custom microfabricated liquid-cell, developed at Sandia National Laboratories and offered through the user program at the Center for Integrated Nanotechnologies, the Electrochemical TEM Discovery Platform [2]. This platform provides customization of 10 electrodes within a single experimental cell, for multiple experiments within the same environment. Integration of Li-containing counter and reference electrodes provides the ability to cycle anode materials as part of a full cell, to monitor electrochemical processes at relevant potentials.
Many in-situ TEM cells suffer from side reactions with contaminants within the cell, due to electrode processing conditions or non-standard electrode materials for battery technologies. In this presentation, the challenges that are faced for using in-situ liquid-cell S/TEM to study processes relevant to bulk-scale battery processes will be discussed. In addition to electron beam effects, as these experiments were performed with the whole of the working electrodes being imaged to directly correlate the electrochemical data to the structural changes on the electrode surface. The real-time observation of Li deposition and stripping dynamics at the nanoscale has been used to identify the dominant factor in non-uniform Li morphology and has highlighted the complication of self-discharge as a potential barrier to commercialization. Our comparison of microscale electrochemcial observations in the TEM as compared to macroscale coin cell electrochemcial data for Li-metal anodes will be discussed [3,4].
[1] A. J. Leenheer et al, ACS Nano 9 (2015), p. 4379.
[2] A. J. Leenheer et al, J. Microelectromech. S. 99 (2015), p. 1061.
[3] K. L. Harrison et al, ‘Lithium Self-Discharge and its Prevention,’ submitted.
[4] Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.