Cell design principles for solid-state batteries from a streamlined porous-electrode model
Guanchen Li a, Zeyang Geng b c, Charles Monroe b c
a University of Glasgow, James Watt School of Engineering, United Kingdom
b Department of Engineering Science, University of Oxford, United Kingdom, Parks Road, United Kingdom
c The Faraday Institution, Harwell, Didcot OX11, Reino Unido, Harwell, United Kingdom
nanoGe Fall Meeting
Proceedings of Materials for Sustainable Development Conference (MAT-SUS) (NFM22)
Solid State Batteries: Advances and challenges on materials, processing and characterization
Barcelona, Spain, 2022 October 24th - 28th
Contributed talk, Zeyang Geng, presentation 232
Publication date: 11th July 2022

Solid-state lithium-ion batteries are a promising energy storage solution which promise greater safety with energy and power density comparable to current Li-ion technology. Although many advances have been made recently on the materials level, there still remains a need to understand how the properties of individual parts of the cell (e.g. electrolyte, active material, interfaces) combine to determine device performance on the cell level [1]. Research has focussed on improving solid-state battery performance by tailoring individual properties, such as the electrolyte’s ionic conductivity κ, the cathode active-material conductivity σ, and interface resistances or capacitances. When several materials are brought together to form a porous electrode, the cell performance does not always reflect individual properties in straightforward ways. Optimization of cell designs to achieve satisfactory performance requires an understanding of how the properties of various cell constituents interact. We believe that at this early stage of solid-state battery development, broad and simple design principles are preferable to finely resolved mechanistic models.

To that end, in this work we present a simple model of a planar solid-state battery cell based on the Newman–Tobias theory [2], which illustrates the roles of cathode porosity, interfacial contact, electrolyte ionic conductivity, and active-material electronic conductivity. We show that the current distribution in the porous cathode is governed by a few key dimensionless parameters, including the fraction of the conductivities of the two phases s=σ/(σ+κ) , and the ratio of the kinetic resistance to the bulk resistances. The results show – somewhat counterintuitively – that balancing the bulk conductivities of the interpenetrating cathode phases can lead to improved cell performance, as well as a higher electrode utilization. Insights provided by this approach provide useful guidelines for optimizing solid-state battery design.

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