Abstract
Understanding how lithium-ion batteries function down to the atomic level during charge and discharge cycling can provide valuable guidance to optimize structure-property relationships and to design and understand new electrode materials. Lithium insertion and reactions with the electrodes during charge and discharge cycling can occur via metastable structures with complex ordering and related non-equilibrium phenomena. Remarkably, these processes remain still poorly understood despite their significance in the operation of lithium battery systems in critical technologies. In this communication, we present the dynamics of lithium insertion into Co3O4 and the evolution of metastable phases as probed by in-situ transmission electron microscopy, in concert with first principles density functional theory calculations. We show that the initial lithium intercalation reaction occurs with the formation of several metastable and intermediate phases, followed by a sequence of conversion reactions that perturb and expand the cubic-close-packed oxygen array, ultimately generating an end-product of finely dispersed cobalt metal clusters within a Li2O matrix. The calculated non-equilibrium lithiation pathways corroborate with the experimental lithiation voltages, and explain the significant hysteresis that occurs during electrochemical cycling. The data provide new insights into the complexity of solid state lithium electrochemistry in metal oxides that are relevant to advancing lithium battery technology.
Original language | English (US) |
---|---|
Pages (from-to) | 15-22 |
Number of pages | 8 |
Journal | Nano Energy |
Volume | 44 |
DOIs | |
State | Published - Feb 2018 |
Funding
This work was supported as part of the Center for Electrochemical Energy Science, an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences under Award # DEAC02-06CH11357 , and the Initiative for Sustainability and Energy at Northwestern (ISEN). This work was also supported by the NU ANCE Center at Northwestern University, using the EPIC facility that receives support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF NNCI-1542205 ); the MRSEC program (NSF DMR-1121262 ) at the Materials Research Center; the International Institute for Nanotechnology (IIN); the Keck Foundation ; and the State of Illinois, through the IIN. MMT was funded by the DOE Office of Vehicle Technologies where complementary research on Li-Co-Ni-O spinels is being undertaken. Nanocomposite samples were prepared by Professor Junming Xu at Hangzhou Dianzi University, China. We acknowledge the computing resources from: 1) the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract DE-AC02-05CH11231. 2) Blues, a high-performance computing cluster operated by the Laboratory Computing Resource Center at Argonne National Laboratory.
Keywords
- Conversion reaction electrode
- DFT calculation
- In-situ lithiation
- In-situ transmission electron microscopy
- Lithium-ion battery
- Metastable phase transformations
ASJC Scopus subject areas
- Renewable Energy, Sustainability and the Environment
- General Materials Science
- Electrical and Electronic Engineering