Spatial dynamics of lithiation and lithium plating during high-rate operation of graphite electrodes
- National Renewable Energy Laboratory, Golden, USA
- Centre for Materials and Nanotechnology, University of Oslo, 0315 Oslo, Norway
- Electrochemical Innovation Laboratory, Department of Chemical Engineering, University College London, London, UK, The Faraday Institution
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, USA
- ESRF-The European Synchrotron, 38000 Grenoble, France
- MAX IV Laboratory, University of Lund, Lund, Sweden
The principal inhibitor of fast charging lithium ion cells is the graphite negative electrode, where favorable conditions for lithium plating occur at high charge rates, causing accelerated degradation and safety concerns. The local response of graphite, both at the electrode and particle level, when exposed to fast charging conditions of around 6C is not well understood. Consequently, the conditions that lead to the onset of lithium plating, as well as the local dynamics of lithium plating and stripping, have also remained elusive. Here, we use high-speed (100 Hz) pencil-beam X-ray diffraction to repeatedly raster along the depth of a 101 μm thick graphite electrode in 3 μm steps during fast (up to 6C) charge and discharge conditions. Consecutive depth profiles from separator to current collector were each captured in 0.5 seconds, giving an unprecedented spatial and temporal description of the state of the electrode and graphite's staging dynamics during high rate conditions. The electrode is preferentially activated near the separator, and the non-uniformity increases with rate and is influenced by free-energy barriers between graphite's lithiation stages. The onset of lithium plating and stripping was quantified, occurring only within the first 15 μm from the separator. The presence of lithium plating changed the behavior of the underlying graphite, such as causing co-existence of LiC6 and graphite in the fully discharged state. Finally, the staging behavior of graphite at different rates was quantified, revealing a high dependency on rate and drastic hysteresis between lithiation and delithiation.
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Vehicle Technologies Office; The Faraday Institution
- Grant/Contract Number:
- AC36-08GO28308
- OSTI ID:
- 1638545
- Alternate ID(s):
- OSTI ID: 1660156
- Journal Information:
- Energy & Environmental Science, Journal Name: Energy & Environmental Science Journal Issue: 8 Vol. 13; ISSN EESNBY; ISSN 1754-5692
- Publisher:
- Royal Society of ChemistryCopyright Statement
- Country of Publication:
- United Kingdom
- Language:
- English