title: Vertical distribution of overpotentials and irreversible charge losses in lithium ion battery electrodes.
abstract: Porous lithium ion battery electrodes are characterized using a vertical distribution of cross-currents. In an appropriate simplification, this distribution can be described by a transmission line model (TLM) consisting of infinitely thin electrode layers. To investigate the vertical distribution of currents, overpotentials, and irreversible charge losses in a porous graphite electrode in situ, a multi-layered working electrode (MWE) was developed as the experimental analogue of a TLM. In this MWE, each layer is in ionic contact but electrically insulated from the other layers by a porous separator. It was found that the negative graphite electrodes get lithiated and delithiated stage-by-stage and layer-by-layer. Several mass-transport- as well as non-mass-transport-limited processes could be identified. Local current densities can reach double the average, especially on the outermost layer at the beginning of each intercalation stage. Furthermore, graphite particles close to the counter electrode act as "electrochemical sieve" reducing the impurities present in the electrolyte such as water.
authors.affiliation: Analytical Chemistry-Center for Electrochemical Sciences (CES), Ruhr-Universität Bochum, Universitätsstr. 150, 44780 Bochum (Germany).
authors.forename: Stefan
authors.initials: S
authors.lastname: Klink
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schuhmann
authors.forename: Fabio
authors.initials: F
authors.lastname: La Mantia
mesh_terms: D011211:Electric Power Supplies; D004563:Electrochemistry; D004566:Electrodes; D004573:Electrolytes / Q000737:chemistry; D006108:Graphite / Q000737:chemistry; D008094:Lithium / Q000737:chemistry*; D008956:Models, Chemical; D016062:Porosity
chemical_list: D004573:Electrolytes; D006108:Graphite; D008094:Lithium
keywords: electrochemistry; irreversible charge losses; lithium-ion batteries; multi-layered working electrode; porous electrodes