JWBS105-c01 JWBS105-Scrosati Printer: Yet to Come May 1, 2013 19:50 Trim: 6.125in×9.25in CHAPTER 1 ELECTROCHEMICAL CELLS: BASICS Hubert Gasteiger, Katharina Krischer, and Bruno Scrosati 1 ELECTROCHEMICAL CELLS AND ION TRANSPORT 1 2 CHEMICAL AND ELECTROCHEMICAL POTENTIAL 5 2.1 TEMPERATURE DEPENDENCE OF THE REVERSIBLE CELL VOLTAGE 5 2.2 CHEMICAL POTENTIAL 5 2.3 ELECTROCHEMICAL POTENTIAL 6 2.4 THE NERNST EQUATION 7 2.5 ELECTROCHEMICAL DOUBLE LAYER 11 3 OHMIC LOSSES AND ELECTRODE KINETICS 13 3.1 OHMIC POTENTIAL LOSSES 14 3.2 KINETIC OVERPOTENTIAL 15 3.3 THE BUTLER–VOLMER EQUATION 17 4 CONCLUDING REMARKS 18 1 ELECTROCHEMICAL CELLS AND ION TRANSPORT An electrochemical cell is a device with which electrical energy is converted into chemical energy, or vice versa. We can consider two types: electrolytic cells, in which electric energy is converted into chemical energy (corresponding to the charging of a battery), and galvanic cells, in which chemical energy is converted into electric energy (corresponding to a battery in discharge). In its most basic structure, an electrochemical cell is formed by two electrodes, one positive and one negative, separated by an ionically conductive and electronically insulating electrolyte, which may be a liquid, a liquid imbibed into a porous matrix, an ionomeric polymer, or a solid. At the negative electrode, an oxidation or anodic reaction occurs during discharge (e.g., the release of electrons and lithium ions from a graphite electrode: LiC 6 → C 6 + Li + + e − ), while the process is reversed during charge, when a reduction or cathodic reaction occurs at the negative electrode (e.g., C 6 + Li + + e − → LiC 6 ). Even though the negative electrode is in principle an anode during discharge and a Lithium Batteries: Advanced Technologies and Applications, First Edition. Edited by Bruno Scrosati, K. M. Abraham, Walter van Schalkwijk, and Jusef Hassoun. © 2013 John Wiley & Sons, Inc. Published 2013 by John Wiley & Sons, Inc. 1 COPYRIGHTED MATERIAL