Probing Kinetics of Water-in-Salt Aqueous Batteries with Thick Porous Electrodes

Abstract

Aqueous electrochemical systems suffer from a low energy density due to a small voltage window of water (1.23 V). Using thicker electrodes to increase the energy density and highly concentrated “water-in-salt” (WIS) electrolytes to extend the voltage range can be a promising solution. However, thicker electrodes produce longer diffusion pathways across the electrode. The highly concentrated salts in WIS electrolytes alter the physicochemical properties which determine the transport behaviors of electrolytes. Understanding how these factors interplay to drive complex transport phenomena in WIS batteries with thick electrodes via deterministic analysis on the rate-limiting factors and kinetics is critical to enhance the rate-performance in these batteries. In this work, a multimodal approach—Raman tomography, operando X-ray diffraction refinement, and synchrotron X-ray 3D spectroscopic imaging—was used to investigate the chemical heterogeneity in LiV 3 O 8 –LiMn 2 O 4 WIS batteries with thick porous electrodes cycled under different rates. The multimodal results indicate that the ionic diffusion in the electrolyte is the primary rate-limiting factor. This study highlights the importance of fundamentally understanding the electrochemically coupled transport phenomena in determining the rate-limiting factor of thick porous WIS batteries, thus leading to a design strategy for 3D morphology of thick electrodes for high-rate-performance aqueous batteries.

Elucidating a dissolution–deposition reaction mechanism by multimodal synchrotron X-ray characterization in aqueous Zn/MnO2 batteries

“…These techniques provide a holistic multimodal characterization approach that can be used to study complex issues involving morphological, chemical, and structural changes at various length scales in energy storage materials, as well as in other electrochemical systems. [19][20][21][22][23] The comprehensive information obtained from these techniques is crucial for understanding the underlying principles and mechanisms of battery operation and contributing towards developing new strategies for improving battery performance and sustainability in the future.…”

Vertically assembled nanosheet networks for high-density thick battery electrodes

“…Each mapping dataset was automatically filtered to remove spectra containing cosmic peaks. NMF was used to unmix the Raman signals from various chemical components of the electrodes as previously described ( 49 – 51 ).…”

ACS Central Science Virtual Issue on Advanced Materials and Processes for Building Low-Carbon Energy Systems

“…However, the physicochemical characteristics of WIS electrolytes are different from those of dilute electrolytes. In the investigation by Ge, Chen-Wiegart et al, 18 a comprehensive approach combining Raman tomography, operando X-ray diffraction refinement, and synchrotron X-ray 3D spectroscopic imaging is employed to investigate the chemical heterogeneity in LiV 3 O 8 -LiMn 2 O 4 batteries utilizing WIS electrolytes and thick porous electrodes. The findings consistently highlight ionic diffusion in the electrolyte as the primary bottleneck impeding the performance of thick porous WIS batteries.…”