Title: "Battery Desalination using Embedded, Micro-Interdigitated Flow Fields"

Kyle Smith

University of Illinois Urbana-Champaign

Host: Robbyn Anand

Abstract: We demonstrate how the >5 molar solid-state concentration swings afforded battery-type cation intercalation materials can electrically produce desalination using Faradaic deionization (FDI).  Our first-of-a-kind demonstration of seawater-level desalination using Prussian blue analogs (PBAs) is enabled by efficiently pumping feed water through ~1 µm electrode pores using embedded, micro-interdigitated flow fields (eµ-IDFFs) that shorten flow paths through pores by ~100X.  PBA electrodes patterned with eµ-IDFFs are shown to produce near-potable water from 500 mM NaCl feeds with energy efficiencies approaching 10% [Energy Environ. Sci., 16 (2023)], which is 50X higher than without eµ-IDFFs.  These low-pressure eµ-IDFFs are also shown to enable efficient brackish water desalination without costly ion-exchange membranes [Environ. Sci. & Tech., 59 (2025)].

However, quasi-1D theory of eµ-IDFF flow kinematics reveals dead zones of stagnant water that result from increased channel hydraulic resistance when up-scaling straight channels, while also revealing that salt back-diffusion produces reaction hot spots at the inlet of high-pressure channels.  Such theory is then used to eliminate dead zones by introducing certain non-linear tapering of channel cross-sections along their lengths [Electrochim. Acta, 514 (2025)], while jointly operating below a threshold residence time to eliminate hot spots [J. Electrochem. Soc., 172 (2025)].  We harness such tapering in conjunction with the observed dependence of electrode permeability on flow-path length to result in eµ-IDFFs with further increased efficiency in seawater and brackish water desalination [Electrochim. Acta, 514 (2025)].  Finally, we explore scalable means of manufacturing these eµ-IDFF-patterned electrodes that balance precision with areal loading and electrochemical performance.

Biosketch: Kyle C. Smith joined the faculty of Mechanical Science and Engineering at UIUC in 2014 after completing his PhD in mechanical engineering (Purdue, 2012) and his post-doc in materials science and engineering (MIT, 2014).  His group uses understanding of flow, transport, and thermodynamics in electrochemical devices and materials to innovate toward separations, energy storage, and conversion.  For his research he was awarded the 2018 ISE-Elsevier Prize in Applied Electrochemistry of the International Society of Electrochemistry and the 2024 Dean’s Award for Early Innovation as an Associate Professor by UIUC’s Grainger College, having authored 60 journal papers and 12 patents and patents pending.