Direct Calculation of Li-Ion Transport in the Solid Electrolyte Interphase
- 5 September 2012
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 134 (37), 15476-15487
- https://doi.org/10.1021/ja305366r
Abstract
The mechanism of Li+ transport through the solid electrolyte interphase (SEI), a passivating film on electrode surfaces, has never been clearly elucidated despite its overwhelming importance to Li-ion battery operation and lifetime. The present paper develops a multiscale theoretical methodology to reveal the mechanism of Li+ transport in a SEI film. The methodology incorporates the boundary conditions of the first direct diffusion measurements on a model SEI consisting of porous (outer) organic and dense (inner) inorganic layers (similar to typical SEI films). New experimental evidence confirms that the inner layer in the ∼20 nm thick model SEI is primarily crystalline Li2CO3. Using density functional theory, we first determined that the dominant diffusion carrier in Li2CO3 below the voltage range of SEI formation is excess interstitial Li+. This diffuses via a knock-off mechanism to maintain higher O-coordination, rather than direct-hopping through empty spaces in the Li2CO3 lattice. Mesoscale diffusion equations were then formulated upon a new two-layer/two-mechanism model: pore diffusion in the outer layer and knock-off diffusion in the inner layer. This diffusion model predicted the unusual isotope ratio 6Li+/7Li+ profile measured by TOF-SIMS, which increases from the SEI/electrolyte surface and peaks at a depth of 5 nm, and then gradually decreases within the dense layer. With no fitting parameters, our approach is applicable to model general transport properties, such as ionic conductivity, for SEI films on the surface of other electrodes, from the atomic scale to the mesoscale, as well as aging phenomenon.Keywords
This publication has 53 references indexed in Scilit:
- Direct Observation of Inhomogeneous Solid Electrolyte Interphase on MnO Anode with Atomic Force Microscopy and SpectroscopyNano Letters, 2012
- The Solid Electrolyte Interphase – The Most Important and the Least Understood Solid Electrolyte in Rechargeable Li BatteriesZeitschrift für Physikalische Chemie, 2009
- Building better batteriesNature, 2008
- Nonaqueous Liquid Electrolytes for Lithium-Based Rechargeable BatteriesChemical Reviews, 2004
- Advances in Lithium-Ion BatteriesPublished by Springer Science and Business Media LLC ,2002
- Issues and challenges facing rechargeable lithium batteriesNature, 2001
- In situ investigation of electrochemical lithium intercalation into graphite powderJournal of Electroanalytical Chemistry, 2000
- Capacity Fade Mechanisms and Side Reactions in Lithium‐Ion BatteriesJournal of the Electrochemical Society, 1998
- A Comparative Study of Synthetic Graphite and Li Electrodes in Electrolyte Solutions Based on Ethylene Carbonate‐Dimethyl Carbonate MixturesJournal of the Electrochemical Society, 1996
- The Correlation Between the Surface Chemistry and the Performance of Li‐Carbon Intercalation Anodes for Rechargeable ‘Rocking‐Chair’ Type BatteriesJournal of the Electrochemical Society, 1994