Nickel-rich layered materials LiNi 1-x-y Mn x Co y O 2 are promising candidates for high-energy-density lithium-ion battery cathodes. Unfortunately, they suffer from capacity fading upon cycling, especially with high-voltage charging. It is critical to have a mechanistic understanding of such fade. Herein, synchrotron-based techniques (including scattering, spectroscopy, and microcopy) and finite element analysis are utilized to understand the LiNi 0.6 Mn 0.2 Co 0.2 O 2 material from structural, chemical, morphological, and mechanical points of view. The lattice structural changes are shown to be relatively reversible during cycling, even when 4.9 V charging is applied. However, local disorder and strain are induced by high-voltage charging. Nano-resolution 3D transmission X-ray microscopy data analyzed by machine learning methodology reveal that high-voltage charging induced significant oxidation state inhomogeneities in the cycled particles. Regions at the surface have a rock salt–type structure with lower oxidation state and build up the impedance, while regions with higher oxidization state are scattered in the bulk and are likely deactivated during cycling. In addition, the development of micro-cracks is highly dependent on the pristine state morphology and cycling conditions. Hollow particles seem to be more robust against stress-induced cracks than the solid ones, suggesting that morphology engineering can be effective in mitigating the crack problem in these materials.
|Journal||Advanced Functional Materials|
|Publication status||Published - 2019 May 2|
Bibliographical noteFunding Information:
Y.M. and X.W. contributed equally to this work. The engineering support from D. Van Campen, V. Borzenets, and D. Day for the TXM experiment at beamline 6-2C of SSRL is gratefully acknowledged. The work done at Brookhaven National Laboratory was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Vehicle Technology Office of the U.S. Department of Energy, through the Advanced Battery Materials Research (BMR) Program, including Battery500 Consortium under Contract No. DE-SC0012704. This research used beamlines 8-ID and 28-ID-2 of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704. Use of the Stanford Synchrotron Radiation Light Source, SLAC National Accelerator Laboratory, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. F.L. and K.Z. acknowledge support from the National Science Foundation under Grant Nos. DMR-1832613 and DMR-1832707, respectively.
© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics