Characterisation of the ambient and elevated temperature performance of a graphite electrode

• Published in: Journal of power sources Vol. 81; pp. 8 - 12
• Main Authors: Andersson, Anna M., Edström, Kristina, Thomas, John O.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Lausanne Elsevier B.V 01.09.1999; Elsevier Sequoia
• Subjects: Applied sciences; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Exact sciences and technology; Graphite electrode; Li-ion battery; Lithium intercalation; SEI layer; Thermal stability; Graphite electrode; SEI layer; Lithium intercalation; Li-ion battery; Thermal stability; Lithium Ions; Battery; Graphite; Secondary cell; Electrode material; Performance
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/S0378-7753(99)00185-8

Thermal stability of the SEI layer on graphite in <Li|liquid electrolyte|graphite> half-cells has been investigated. DSC measurements reveal a two-stage exothermal reaction. The first, corresponding to a breakdown of the SEI layer, begins at 58°C for a 1 M LiBF 4 in EC/DMC 2:1 electrolyte. The second, starting at ∼80°C, corresponds to lithium deintercalation, followed by some irreversible chemical reaction; the heat evolved in the second stage increases for increasing lithium content in the graphite. Precycling at RT to generate the Solid Electrolyte Interface (SEI) layer, followed by storage for 1 week at different temperatures and then continued cycling, brings about a rapid decline in capacity for cells stored above 50°C. XRD could also show that graphite electrodes are partially blocked for subsequent lithium-ion insertion after such treatment. ESCA (XPS) characterisation of the surface of fresh graphite electrodes compared with that of graphite electrodes extracted from these RT precycled/stored cells gives evidence of the formation of a thicker macroscopic layer on the electrode surface of cells stored at 60°C. This layer is not found for half-cells stored at lower temperatures.