Topic 01-19 : Triggering the formation of a passivating interface to enhance the performance of aqueous batteries

At the heart of the success story of Li-ion batteries is the early realization that one single solvent could not provide the required chemical properties (solvation strength with Li+ and controlled chemical reactivity), while ensuring the optimal physical properties for the application (viscosity, thermal stability, etc.). Therefore, a blend of linear and cyclic carbonates, such as dimethylcarbonate (DMC) and ethylcarbonate (EC), respectively, is used. EC, owing to its large dielectric constant, preferentially solvates Li+ ions and its reactivity is responsible for the formation of a passivating layer protecting the negative electrode. In contrast, DMC ensures salt and EC solubility while maintaining a low viscosity to the overall electrolyte. One can thus postulate that a promising route to develop aqueous electrolytes for batteries route would consist in suppressing water from the solvation shell of Li+ in order to suppress its reactivity at the negative electrode while using water as non-coordinating solvent - akin to the idea of localized highly concentrated electrolytes (LHCEs). Achieving such configuration for water would be a first and would certainly unlock the usage of aqueous solutions for high energy density rechargeable batteries that we aim for in this project by the use of organic molecules with large dielectric constant, as well as large solvation and/or chelation power will be used.

Toward that ambitious goal, the knowledge of the Chalmers team in terms of solvation structure and electrolyte structuration will be crucial. The student will therefore spend 3-6 months at Chalmers under the guidance of Prof. Patrik Johansson to study by the use of spectroscopical and modelling approaches the complex solvation structure of these electrolytes. Indeed, only combining these tools with electrochemical measurements will ensure a perfect understanding of how solvent structuration impacts water reactivity at electrochemical interfaces and can trigger the formation of a passivating layer for aqueous batteries.