Systems-Level Investigation of Aqueous Batteries for Understanding the Benefit of Water-in-Salt Electrolyte By Synchrotron Nano-Imaging

The concept of “Water-in-salt” (WIS) electrolyte enabled the application of higher voltage aqueous battery, overcoming the limitation of the narrow voltage window of water (~1.23V) for better safety and environmental sustainability. Recent work in the field has been exploring the electrochemical performance of batteries using WIS electrolytes with different electrode couples as well as the intrinsic electrochemistry and physical chemistry properties of WIS electrolytes. In this work, LiV3O8 anode and LiMn2O4 cathode for aqueous Li-ion batteries are coupled to investigate the mechanism by which WIS electrolyte improves the cycling stability at an extended voltage window. The study probed the morphological evolution of the active electrode particles as a function of the electrochemistry. While delaying the water decomposition process, the WIS electrolyte improves the cycling stability of the battery by suppressing the mechanical damage to the electrode network and dissolution of the electrode particles through the operando observation under synchrotron transmission X-ray microscopy on the LiMn2O4 cathode. As the viscosity of WIS is significantly higher, the reaction heterogeneity of the electrodes cycled with WIS electrolyte is quantified with X-ray absorption spectroscopic imaging, visualizing for the first time the kinetic limitations of the WIS electrolyte. This work furthers the mechanistic understanding of electrode – WIS aqueous electrolyte interactions and paves the way to explore the strategy to mitigate their possible kinetic limitations in 3D architectures. Figure 1