Surface reactivity of graphite materials and their surface passivation during the first electrochemical lithium insertion |
| |
| Affiliation: | 1. TIMCAL Ltd., CH-6743 Bodio, Switzerland;2. Electrochemistry Laboratory, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland;3. Swiss Federal Institute of Technology (ETH Zürich), Laboratory of Inorganic Chemistry, CH-8093 Zurich, Switzerland;4. Institut de Chimie des Surfaces et Interfaces, CNRS UPR 9069, F-68057 Mulhouse Cedex, France;1. Institute for Materials Research (IMO), Hasselt University,Wetenschapspark 1, 3590 Diepenbeek, Belgium;2. Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, 40237 Düsseldorf, Germany;3. Center for Electrochemical Sciences — CES, Universität Bochum, Universitätsstraße 150, 44780 Bochum, Germany;4. Centro de Investigacion y Estudios Avanzados del IPN, MX-76001 Santiago de Querétaro, Mexico;5. Physics Department, West Virginia University, White Hall, Box 6315, WV-26506-6315 Morgantown, USA;1. School of Materials Science and Engineering, Shanghai University, Shanghai 200072, China;2. Ningbo Institute of Materials Technology & Engineering Chinese Academy of Sciences, 1219 Zhongguan Road, Zhenhai District, Ningbo 315201, China |
| |
| Abstract: | The surface passivation of TIMREX® SLX50 graphite powder was studied as received and after heat treatment at 2500 °C in an inert gas atmosphere by differential electrochemical mass spectrometry in electrochemical lithium half-cells. 1 M LiPF6 in ethylene carbonate and either a dimethyl carbonate, propylene carbonate or 1-fluoro ethylene carbonate co-solvent was used as electrolyte systems in these half-cells. The SEI-film formation properties of both graphite materials were correlated with their active surface area (ASA), being responsible for the interactions between the carbon and the electrolyte system. The active surface area was determined from the amount of CO and CO2 gas desorbed at temperatures up to 950 °C from the graphite material surface after chemisorption of oxygen at 300 °C. The structural ordering at the graphite surface increased significantly during the heat treatment of the SLX50 graphite material as indicated by the significant decrease of the ASA value. The increased surface crystallinity was confirmed by krypton gas adsorption, Raman spectroscopy as well as temperature-programmed desorption. This increased structural ordering seemed to be the parameter being responsible for a hindered passivation of the heat-treated SLX50 causing partial exfoliation of the graphite structure during the first electrochemical lithium insertion in the ethylene carbonate/dimethyl carbonate electrolyte. In the case of the ethylene carbonate/1-fluoro ethylene carbonate electrolyte system, primarily the fluoro compound is responsible for the graphite passivation. In this electrolyte system, pristine SLX50 and the less reactive, heat-treated SLX50 graphite showed significantly different SEI-film formation mechanisms. In contrast, no difference in the passivation mechanism could be identified for different graphite surfaces in the ethylene carbonate electrolyte system with propylene carbonate as co-solvent. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
