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Sulfide electrolyte all-solid-state lithium batteries (ASLBs) with uncoated Li-NixMnyCo1−x−yO2(NMC) cathodes suffer from a large capacity loss during initial cycling and an increase in cell impedance. Decomposition reactions are known to occur at the Li6PS5Cl-NMC111 interface due to incompatibility between the two materials. If a stabilizing coating is applied to the NMC, it delivers full capacity during initial charge. However, the loss in capacity during discharge still occurs. The interface was studied byμXANES and through EIS analysis. A chemically-formed interphase was detected byμXANES, evident from reduction of Co at an uncoated NMC particle surface. This interphase was produced by decomposition at rest. To study the effect of the interphase on electrochemically active surface area, piecewise in situ EIS was performed and the data was modeled using a transmission line model (TLM). The charge transfer resistance RCTwas used to estimate the volume specific active surface area (aact). The median value for aactwas 296 cm−1, a factor of 7.5 lower than the theoretical value of 2216 cm−1. This provided evidence of a lower electrochemically active surface area in the ASLB.
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Quantifying and elucidating the effect of CO 2 on the thermodynamics, kinetics and charge transport of AEMFCs
It has been long-recognized that carbonation of anion exchange membrane fuel cells (AEMFCs) would be an important practical barrier for their implementation in applications that use ambient air containing atmospheric CO 2 . Most literature discussion around AEMFC carbonation has hypothesized: (1) that the effect of carbonation is limited to an increase in the Ohmic resistance because carbonate has lower mobility than hydroxide; and/or (2) that the so-called “self-purging” mechanism could effectively decarbonate the cell and eliminate CO 2 -related voltage losses during operation at a reasonable operating current density (>1 A cm −2 ). However, this study definitively shows that neither of these assertions are correct. This work, the first experimental examination of its kind, studies the dynamics of cell carbonation and its effect on AEMFC performance over a wide range of operating currents (0.2–2.0 A cm −2 ), operating temperatures (60–80 °C) and CO 2 concentrations in the reactant gases (5–3200 ppm). The resulting data provide for new fundamental relationships to be developed and for the root causes of increased polarization in the presence of CO 2 to be quantitatively probed and deconvoluted into Ohmic, Nernstian and charge transfer components, with the Nernstian and charge transfer components controlling the cell behavior under conditions of practical interest.
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- Award ID(s):
- 1803189
- PAR ID:
- 10174741
- Date Published:
- Journal Name:
- Energy & Environmental Science
- Volume:
- 12
- Issue:
- 9
- ISSN:
- 1754-5692
- Page Range / eLocation ID:
- 2806 to 2819
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1039/C9EE01334B
