Abstract
Observations of the initial lithiation of NiO electrodes demonstrate how to seed conversion reactions using interfaces in a thin film Ni/NiO bilayer architecture. Operando X-ray reflectivity (XRR) reveals that structural changes in a NiO film begin at potentials near the theoretical reduction potential (1.8-2.0 V) with detectable lithiation of both the buried Ni/NiO interface and the outer NiO surface that occur prior to the reaction of the NiO film. This initial conversion reaction is most pronounced in ultrathin NiO films (∼20 Å) with only small changes to the NiO film surface for thicker films (∼67 Å). The limited reactivity of thicker NiO films probed using operando grazing incidence small-angle X-ray scattering (GISAXS) shows the growth of nanoparticles at the electrode/electrolyte interface during initial lithium ion insertion, with a 16-20 Å average radius. Ex situ X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and scanning transmission electron microscopy/electron energy loss spectroscopy (STEM/EELS) confirm our conclusions about the morphological changes accompanying initial stage of lithiation in these conversion reaction electrodes. The present study reveals the interconnected challenges of solid-solid transitions, overpotentials, interfacial nucleation and kinetics, and transition metal dissolution in conversion-type electrodes that are critical for their use as electrodes in lithium-ion batteries.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 8897-8905 |
| Number of pages | 9 |
| Journal | Physical Chemistry Chemical Physics |
| Volume | 21 |
| Issue number | 17 |
| DOIs | |
| State | Published - 2019 |
Funding
This research was supported by the Center for Electrochemical Energy Science, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. We thank the beamline staff at 33BM and 12ID, Advanced Photon Source (APS), which provided valuable assistance. The samples were grown in the Northwestern University Materials Research Center Pulsed Laser Deposition Facility supported by the National Science Foundation MRSEC program (DMR-1720139). The electron microscopy and XPS/ToF-SIMS work made use of the EPIC and Keck-II facilities of Northwestern University’s NUANCE Center, which is supported by the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205); the MRSEC program (NSF DMR-1720139) at the Materials Research Center; the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois, through the IIN. We also acknowledge the use of the X-ray Diffraction Facility also supported by MRSEC and SHyNE.
ASJC Scopus subject areas
- General Physics and Astronomy
- Physical and Theoretical Chemistry
