Dynamic Aspects of Solid Solution Cathodes for Electrochemical Power Sources

Sven Atlung, Keld West, Torben Jacobsen

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Battery systems based on alkali metal anodes and solid solution cathodes,i.e., cathodes based on the insertion of the alkali cation in a "host lattice,"show considerable promise for high energy density storage batteries. Thispaper discusses the interaction between battery requirements, in particularfor vehicle propulsion, and electrochemical and constructional factors. It isargued that the energy obtainable at a given load is limited by saturation ofthe surface layers of cathode particles with cations, and that the time beforesaturation occurs is determined by diffusion of cations and electrons into thehost lattice. Expressions are developed for plane, cylindrical, and sphericalparticles, giving the relation between battery load and the amount of cathodematerial utilized before saturation. The particle shape and a single parameterQ is used to describe cathode performance. Q is the ratio between dischargetime at 100% utilization of the cathode at the given load, and the timeconstant for diffusion through the cathode particles. This description is extendedto cover short peak loads characteristic of vehicle propulsion. On thebasis of estimated parameters for the Li/TiS2 couple with LiClO4-propylene-carbonateelectrolyte the properties of plane cathodes or cathodes consistingof few layers of particles are examined in relation to traction requirements.In this context limiting currents in the electrolyte phase are discussed,and a relation between the maximal allowed values for particle size andelectrode spacing is derived. For nonporous electrodes the limiting factor iscathode surface saturation. A qualitative discussion of porous cathodes indicatesthat the cathode thickness, and thus the over-all specific energy, islimited by cation transport in the pore electrolyte when the cation diffusioncoefficient in the solid exceeds 10–10 cm2 sec–1. On the basis of an approximaterelation between cathode thickness and electrode spacing the specificenergy for the Li/TiS2 system with organic electrolyte is estimated to be 120–150W-hr/kg in agreement with published values. ©1979 The Electrochemical Society, Inc.
Original languageEnglish
JournalJournal of The Electrochemical Society
Issue number8
Pages (from-to)1311-1321
Publication statusPublished - 1979

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Copyright The Electrochemical Society, Inc. [1979]. All rights reserved. Except as provided under U.S. copyright law, this work may not be reproduced, resold, distributed, or modified without the express permission of The Electrochemical Society (ECS).


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