Understanding degradation in water-in-salt batteries

Context.

Developing safer batteries is the ultimate goal of current research in the field of battery technology. Water-based electrolyte could easily replace flammable organic electrolyte providing enhanced safety, a topic so far under investigated in the literature. Unfortunately, water-based electrolyte suffers from poor energy density due to the very narrow electrochemical stability windows.
With aqueous electrolyte, we are facing the oxygen and hydrogen evolution reaction leading to pH fluctuation in the battery causing electroactive materials degradation, and poor electrochemical performance. Based on an interdisciplinary approach, the project will aim to drastically enhanced the safety and the energy density of water-in-salt system with an in-depth investigation of highly concentrated water-in-salt electrolytes to understand the main limitations of such technology.
Cycling an aqueous battery at the edge of the electrochemical stability window over many consecutive cycles is expected to give rise to local pH gradients in the electrolyte over time, and these gradients modify locally the electrochemical stability window as described by the Nernst equation. The electrode materials must be able to tolerate these variations to guarantee long-term cycling stability of the full system. In addition, an understanding of the evolution of pH gradients is critical, as it determines the electrode potentials with respect to the stability window of the electrolyte.
This project aims to understand the water-in-salt approach, especially the pH fluctuation using advanced operando techniques such as scanning electrochemical microscope (SECM) and model electrode materials. The student will deal with the development of specific coating on the top of electroactive material being able to resist pH fluctuation during cycling and understand the pH fluctuation during cycling.

Expected skills

This internship is devoted to a student of the GS program Soft Nanosciences following the master Nanochemistry or the master Physics of Complex Systems. The student should be skilled in chemistry and like to be in the laboratory. A knowledge in material sciences and in electrochemistry is an asset (batteries in particular).

Published on January 27, 2025
Updated on January 27, 2025