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Nano Scale Electrode Architectures For Lithium Ion Batteries
October 1, 2013 | 4 Comments
Shadi Dayeh, a professor in the Department of Electrical and Computer Engineering at the UC San Diego Jacobs School of Engineering leads a team of researchers in creating nanowires that block diffusion of lithium (Li) across their silicon surface and promote layer-by-layer axial lithiation of the nanowire’s germanium core.
TEM image of Silicon Germanium Nanowire Lithiation. Image credit: UCSD. Click image for more info.
Dayeh explains the work may lead to “an effective way to tailor volume expansion of lithium ion battery electrodes which could potentially minimize their cracking, improve their durability, and perhaps influence how one could think about different electrode architectures.” It is a problem bedeviling lithium-ion battery research in many electrode constructions, especially those working on the very high potential silicon electrode
By coating germanium nanowires with silicon, the researchers stopped nearly all surface diffusion of lithium ions into the nanowires. Instead, lithium diffusion, known as lithiation, occurred layer by layer along the axis of the nanowire. This is in contrast to lithiation from the surface of nanowires not covered with silicon.
The Dayeh team, working with the collaborators at Sandia National Laboratories, prepared a YouTube video showing the lithium build up on silicon-coated nanowires germanium cores, and the diffusion of the lithium into an uncoated germanium nanowire.
A quote from the research paper says, “These results demonstrate for the first time that interface and bandgap engineering of electrochemical reactions can be utilized to control the nanoscale ionic transport / insertion paths and thus may be a new tool to define the electrochemical reactions in Li-ion batteries,” the researchers write in their Nano Letters paper.
This work builds on research demonstrating excellent control over germanium / silicon (Ge/Si) heterostructuring, which Dayeh and colleagues recently published as a cover article in Applied Physics Letters and a cover letter in the journal Nano Letters.
Dayeh grew the nanowires during his time as a postdoctoral researcher at Los Alamos National Laboratory (LANL). The lithiation experiments were performed by two postdoctoral researchers from Sandia National Laboratories, Drs. Yang Liu and Xiaohua Liu, and Dayeh’s postdocdoral researchers working at LANL. Dayeh formulated the mechanism and performed the analysis and simulations after joining the faculty of the Electrical and Computer Engineering Department at the UC San Diego Jacobs School of Engineering.
The work is another example of the ingenuity of the human mind. The idea is so new that it’s not possible to estimate the commercial value yet. But if the charge and discharge cycle count is extraordinary or some breakthrough in production appears the idea might get some legs. Most of all, the technology for nanoscale coatings has a new process that may well benefit other research in ways not yet thought about.
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