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Issue 28, 2016
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The reaction current distribution in battery electrode materials revealed by XPS-based state-of-charge mapping

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Abstract

Morphologically complex electrochemical systems such as composite or nanostructured lithium ion battery electrodes exhibit spatially inhomogeneous internal current distributions, particularly when driven at high total currents, due to resistances in the electrodes and electrolyte, distributions of diffusion path lengths, and nonlinear current–voltage characteristics. Measuring and controlling these distributions is interesting from both an engineering standpoint, as nonhomogenous currents lead to lower utilization of electrode material, as well as from a fundamental standpoint, as comparisons between theory and experiment are relatively scarce. Here we describe a new approach using a deliberately simple model battery electrode to examine the current distribution in a electrode material limited by poor electronic conductivity. We utilize quantitative spatially resolved X-ray photoelectron spectroscopy to measure the spatial distribution of the state-of-charge of a V2O5 model electrode as a proxy measure for the current distribution on electrodes discharged at varying current densities. We show that the current at the electrode–electrolyte interface falls off with distance from the current collector, and that the current distribution is a strong function of total current. We compare the observed distributions with a simple analytical model which reproduces the dependence of the distribution on total current, but fails to predict the correct length scale. A more complete numerical simulation suggests that dynamic changes in the electronic conductivity of the V2O5 concurrent with lithium insertion may contribute to the differences between theory and experiment. Our observations should help inform design criteria for future electrode architectures.

Graphical abstract: The reaction current distribution in battery electrode materials revealed by XPS-based state-of-charge mapping

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Publication details

The article was received on 13 May 2016, accepted on 22 Jun 2016 and first published on 22 Jun 2016


Article type: Paper
DOI: 10.1039/C6CP03271K
Citation: Phys. Chem. Chem. Phys., 2016,18, 19093-19102
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    The reaction current distribution in battery electrode materials revealed by XPS-based state-of-charge mapping

    A. J. Pearse, E. Gillette, S. B. Lee and G. W. Rubloff, Phys. Chem. Chem. Phys., 2016, 18, 19093
    DOI: 10.1039/C6CP03271K

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