Measuring the permeability of lithium-protective membranes

Meddings, Nina (2017) Measuring the permeability of lithium-protective membranes. International Battery Association 2017, Nara, Japan, Nara, Japan. 05 - 10 Mar 2017.

Abstract

Lithium ion conducting membranes (LICMs) are important to protect the lithium metal electrode and act as a barrier to crossover species such as redox mediators in Li-O2 cells, polysulphides in Li-S systems or impurities formed by oxidation reactions in high voltage Li-ion materials [1]. We present an in-situ method and cell design for measuring permeability of LICMs to mediator (or other) species. The method employs a ‘Swagelok’ cell design equipped with four electrode connections (Figure 1a). Mediator species are placed initially in the counter electrode compartment only. Permeability through the LICM (which separates working and counter electrodes) is determined using a square wave voltammetry (SWV) technique that allows evaluation of the concentration of crossover species over time. Figure 1b shows SWV scans recorded at a glassy carbon electrode in a Swagelok cell containing an LICM and an ethyl viologen mediator. Additional experiments have shown that: the cell is well-sealed with gaskets, ruling out any ‘leakage’ of mediator species around the membrane; glassy carbon is better (more sensitive) than other materials as a working electrode; pulsed voltammetry is better (more sensitive and stable) than cyclic voltammetry in detecting crossover species. Relative to previous approaches to studying permeability which employed H-type cells and/or ex-situ techniques such as XRD and XPS of the lithium metal surface or elemental analysis of the electrolyte [2-4], the new cell design and method offer advantages in terms of low electrolyte volume, facile and in-situ measurement, and, thanks to the four electrode connections, ability to take measurements before and after passing current lithium ion current through the membrane.
REFERENCES
[1] Y. Sun, Nano Energy 2 (2013) 801–816.
[2] J-Q. Huang, Q. Zhang, H.J. Peng, X.Y. Liu, W.Z. Qian, F. Wei, Energy Environ. Sci. 7 (2014) 347–353.
[3] B.G. Kim, J-S. Kim, J. Min, Y-H. Lee, J.H. Choi, M.C. Jang, S.A. Freunberger, J.W. Choi, Adv. Funct. Mater. 26 (2016) 1747–1756.
[4] K. Juttner, C. Ehrenbeck, J Solid State Electrochem 2 (1998) 60-6.

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Contributors

Author: Nina Meddings

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