Predicting Degradation Mechanisms in Lithium Bistriflimide "Water-In-Salt" Electrolytes For Aqueous Batteries.

Aqueous solutions are crucial to most domains in biology and chemistry, including in energy fields such as catalysis and batteries. Water-in-salt electrolytes (WISEs), which extend the stability of aqueous electrolytes in rechargeable batteries, are one example. While the hype for WISEs is huge, commercial WISE-based rechargeable batteries are still far from reality, and there remain several fundamental knowledge gaps such as those related to their long-term reactivity and stability. Here, we propose a comprehensive approach to accelerating the study of WISE reactivity by using radiolysis to exacerbate the degradation mechanisms of concentrated LiTFSI-based aqueous solutions. We find that the nature of the degradation species depends strongly on the molality of the electrolye, with degradation routes driven by the water or the anion at low or high molalities, respectively. The main aging products are consistent with those observed by electrochemical cycling, yet radiolysis also reveals minor degradation species, providing a unique glimpse of the long-term (un)stability of these electrolytes.

Non-aqueous carbon black suspensions for lithium-based redox flow batteries: rheology and simultaneous rheo-electrical behavior.

We report on the rheological and electrical properties of non-aqueous carbon black (CB) suspensions at equilibrium and under steady shear flow. The smaller the primary particle size of carbon black is, the higher the magnitude of rheological parameters and the conductivity are. The electrical percolation threshold ranges seem to coincide with the strong gel rather than the weak gel rheological threshold ones. The simultaneous measurements of electrical properties under shear flow reveal the well-known breaking-and-reforming mechanism that characterises such complex fluids. The small shear rate breaks up the network into smaller agglomerates, which in turn transform into anisometric eroded ones at very high shear rates, recovering the network conductivity. The type of carbon black, its concentration range and the flow rate range are now precisely identified for optimizing the performance of a redox flow battery. A preliminary electrochemical study for a composite anolyte (CB/Li4Ti5O12) at different charge-discharge rates and thicknesses is shown.