Far- and Near-Field Spectroscopy and Imaging of Interfaces and Interphases in Li-Ion Battery Electrodes

Development of new innovative experimental approaches and enabling methodologies to understand the function and mechanism of operation of materials, electrodes and electrochemical interfaces in electrical energy storage systems is critical for clean and/or renewable energy technologies. A better understanding of the underlying principles that govern these phenomena is inextricably linked with successful implementation of high energy density materials.

Several analytical techniques have been implemented for the physico-chemical characterization of the materials, interfaces and interphases. In many cases limitations in studying the real system are imposed by ex situ methods that require excitation or detection of electrons or ions in vacuum environment and/or they suffer from inadequate sensitivity, selectivity and specificity in the in situ environment.

The advent of femtosecond (fs) lasers and near-field optical methods during the past decades has led to the development of new advanced techniques for chemical analysis. This presentation provides a brief overview of novel in and ex situ experimental approaches aimed at probing battery materials and electrodes in electrical storage systems at an atom, molecular or nanoparticulate level.

The presented methodologies exploit the micro and nano-manipulation techniques and single particle model electrodes to provide sufficient sample definition suitable for advanced far- and near-field Raman, FTIR , fluorescence spectral microscopy, pumped laser probes and micro- and nano-electrochemical characterization techniques.

Examples of detailed in situ molecular characterization of electrode surface and bulk processes at the nano-level scale exceeding the diffraction limit will be discussed. These include elemental and molecular depth profiling at nanometer-scale depth resolution of a solid electrolyte interface (SEI) layer formed on Sn polycrystalline and monocrystral model electrodes in an organic carbonate-based electrolyte.

Acknowledgement

Part of this work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy, under contract no. DE-AC02-05CH11231. It has also been supported in part by the Northeastern Center for Chemical Energy Storage, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under award number DESC0001294. This work was also supported in part by the Chemical Science Division, Office of Basic Energy Sciences, Office of Nuclear Nonproliferation, and the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.