| AVS 66th International Symposium & Exhibition | |
| Advanced Ion Microscopy and Ion Beam Nano-engineering Focus Topic | Thursday Sessions |
| Session HI+NS-ThA |
| Session: | Emerging Ion Sources, Optics, and Applications |
| Presenter: | Evgheni Strelcov, National Institute of Standards and Technology (NIST) |
| Authors: | W.R. McGehee, National Institute of Standards and Technology (NIST) E. Strelcov, National Institute of Standards and Technology (NIST) V. Oleshko, National Institute of Standards and Technology (NIST) C. Soles, National Institute of Standards and Technology (NIST) N.B. Zhitenev, National Institute of Standards and Technology (NIST) J.J. McClelland, National Institute of Standards and Technology (NIST) |
| Correspondent: | Click to Email |
Improving the performance of Li-ion batteries requires understanding and controlling nanoscale ion transport at the level of interfaces, grain boundaries and defects. While in the last decades a range of electron and scanning probe microscopy techniques have been developed for probing local transport, no reliable method exists for quantitative and controllable nanoscale lithiation. Moreover, wet-cell electrochemical lithiation is significantly complicated by electrolyte decomposition, formation of solid-electrolyte interfacial (SEI) layer and parasitic reactions running in parallel to lithium insertion.
Building on our previous work,1 here we introduce a new method of direct-write quantitative lithiation of battery-relevant materials in vacuo, in the absence of SEI or liquid electrolyte. To benchmark the technique, we use a focused, several keV Li+-ion beam to inject lithium into 35-nm thick crystalline Si membranes with a sub-micron lateral precision. The lithiated regions, undergoing morphological, structural, chemical and functional transformations, were characterized with a combination of electron and scanning probe microscopy techniques. We observed saturation of interstitial lithium in the silicon membrane at ≈ 10 % dopant number density and spill-over of excess lithium onto the membrane’s surface. The implanted Li+ remains electrochemically active, and the spill-over effect can possibly be avoided by cooling the sample. The presented method is especially useful for probing non-equilibrium and low-concentration phases of lithiated materials that form because of incomplete lithium extraction or during initial states of pristine anode lithiation. Focused ion beam lithiation will enable controlled studies and improved understanding of Li+ ion interaction with local defect structures and interfaces in electrode and solid-electrolyte materials.
E.S. acknowledges support under the Cooperative Research Agreement between the University of Maryland and the National Institute of Standards and Technology Center for Nanoscale Science and Technology, Award 70NANB14H209, through the University of Maryland.
W.R.M. and E.S. contributed equally.
1. Takeuchi, S.; McGehee, W. R.; Schaefer, J. L.; Wilson, T. M.; Twedt, K. A.; Chang, E. H.; Soles, C. L.; Oleshko, V. P.; McClelland, J. J. Journal of The Electrochemical Society 2016, 163, (6), A1010-A1012.