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September 3, 2019, Research Highlights

Shedding X‑ray Light on the Interfacial Electrochemistry of Silicon Anodes for Li-Ion Batteries

First lithiation of c-Si(100). (a) (i) Measured and fitted XRR of selected data sets, color-coded to show the three lithiation steps; (ii) fit-derived electron density profiles (EDP). (b) Best-fit parameters of (i) thickness of top-SEI, (ii) ED of top-SEI, (iii) product of the thickness and ED of top-SEI, (iv) thicknesses of bottom-SEI and LixSi, and (v) EDs of bottom-SEI and LixSi. (iv) Galvanostatic electrochemistry 25 μA/cm2. (c) Mechanistic model of SEI growth and three-step lithiation of Si electrode.

Scientific Achievement

Our results shed light on the interfacial electrochemistry of silicon anodes for Lithium-ion batteries (LiBs), providing  important mechanistic insight into nanometer scale phenomena and how these influence battery performance.

Significance and Impact

This work motivates further fundamental model-system-based studies of LIB components, of both experimental and computational as well as theoretical nature, and we anticipate that such studies can aid in achieving our goals of improved battery materials.

Research Details

  • Model battery anode consisting of a native oxide terminated single crystalline Si wafer
  • Observed growth of two inorganic SEI layers, LixSiOy (Lithiation of electrode-adjacent) and LiF (electrolyte-adjacent)
  • Crystalline Si (c-Si) is a layer-by-layer, reaction-limited, two-phase process
  • Delithiation of LixSi and the lithiation of amorphous Si (a-Si) are reaction-limited, single-phase processes
  • Unraveled the influences of current density and the Si crystallographic orientation

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DOI: 10.1021/acs.accounts.9b00233

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