Abstract
We investigated the chemistry and structure of the solid electrolyte interphase (SEI) grown over a silicon anode as a function of the lithium salt concentration. In these experiments, in situ neutron reflectivity measurements were performed to measure the thickness and composition of the SEI formed from 1.0 and 5.5 M lithium bis(trifluoromethane)sulfonimide (LiTFSI) in standard ethylene carbonate:dimethyl carbonate electrolytes. These measurements reveal the formation of a 350+ Å thick SEI layer that is predominantly organic (∼80%) and dimensionally stable when using a 1.0 M salt solution. In contrast, increasing the salt concentration to 5.5 M resulted in an SEI that exhibited thickness changes from 100 to 375 Å and became up to 30% inorganic. These compositional and structural changes point to the role of salt speciation on the resulting passivation of silicon electrodes and indicate the need to form more organic-like passivation layers to promote the calendar life of silicon anodes.
| Original language | English |
|---|---|
| Pages (from-to) | 16364-16375 |
| Number of pages | 12 |
| Journal | ACS Applied Energy Materials |
| Volume | 8 |
| Issue number | 21 |
| DOIs | |
| State | Published - Nov 10 2025 |
Funding
This research was supported by the U.S. Department of Energy’s Vehicle Technologies Office under the Silicon Consortium Project, directed by Carine Steinway, Nicolas Edison, Thomas Do, and Brian Cunningham and managed by Anthony Burrell. A portion of this research used resources at the Spallation Neutron Source (Liquids Reflectometer), a DOE Office of Science user facility operated by the Oak Ridge National Laboratory (J.F.B., M.D.) on proposal number IPTS-27342.1 and 27342.2. The authors would like to thank Dr. Joshua Kim for his help with cell design and experimental data collection at the beamline. This manuscript has been authored in part by UT-Battelle, LLC, under contract DEAC05- 00OR22725 with the U.S. Department of Energy (DOE). The publisher, by accepting the article for publication, acknowledges that the U.S. government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. government purposes. The DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doepublic-accessplan).
Keywords
- electrode passivation
- interface
- neutron reflectometry
- silicon anode
- solid electrolyte interphase