Doctor of Philosophy, Stanford University, MATSC-PHD (2018)
- Solid Electrolyte Interphase on Native Oxide-Terminated Silicon Anodes for Li-Ion Batteries JOULE 2019; 3 (3): 762–81
- The nanoscale structure of the electrolyte-metal oxide interface (vol 11, pg 594, 2018) ENERGY & ENVIRONMENTAL SCIENCE 2018; 11 (4): 996
- The nanoscale structure of the electrolyte-metal oxide interface ENERGY & ENVIRONMENTAL SCIENCE 2018; 11 (3): 594–602
Fluoroethylene Carbonate Induces Ordered Electrolyte Interface on Silicon and Sapphire Surfaces as Revealed by Sum Frequency Generation Vibrational Spectroscopy and X-ray Reflectivity
2018; 18 (3): 2105–11
The cyclability of silicon anodes in lithium ion batteries (LIBs) is affected by the reduction of the electrolyte on the anode surface to produce a coating layer termed the solid electrolyte interphase (SEI). One of the key steps for a major improvement of LIBs is unraveling the SEI's structure-related diffusion properties as charge and discharge rates of LIBs are diffusion-limited. To this end, we have combined two surface sensitive techniques, sum frequency generation (SFG) vibrational spectroscopy, and X-ray reflectivity (XRR), to explore the first monolayer and to probe the first several layers of electrolyte, respectively, for solutions consisting of 1 M lithium perchlorate (LiClO4) salt dissolved in ethylene carbonate (EC) or fluoroethylene carbonate (FEC) and their mixtures (EC/FEC 7:3 and 1:1 wt %) on silicon and sapphire surfaces. Our results suggest that the addition of FEC to EC solution causes the first monolayer to rearrange itself more perpendicular to the anode surface, while subsequent layers are less affected and tend to maintain their, on average, surface-parallel arrangements. This fundamental understanding of the near-surface orientation of the electrolyte molecules can aid operational strategies for designing high-performance LIBs.
View details for PubMedID 29451803
- The Atomic Scale Electrochemical Lithiation and Delithiation Process of Silicon ADVANCED MATERIALS INTERFACES 2017; 4 (22)
- Surface structure of coherently strained ceria ultrathin films PHYSICAL REVIEW B 2016; 94 (20)
In Situ Study of Silicon Electrode Lithiation with X-ray Reflectivity.
Surface sensitive X-ray reflectivity (XRR) measurements were performed to investigate the electrochemical lithiation of a native oxide terminated single crystalline silicon (100) electrode in real time during the first galvanostatic discharge cycle. This allows us to gain nanoscale, mechanistic insight into the lithiation of Si and the formation of the solid electrolyte interphase (SEI). We describe an electrochemistry cell specifically designed for in situ XRR studies and have determined the evolution of the electron density profile of the lithiated Si layer (LixSi) and the SEI layer with subnanometer resolution. We propose a three-stage lithiation mechanism with a reaction limited, layer-by-layer lithiation of the Si at the LixSi/Si interface.
View details for PubMedID 27783514