Understanding and engineering lithium stripping in ionic liquid electrolytes

Lithium-ion technology is ubiquitous in our contemporary society in varied applications. This is primarily because of their high volumetric and gravimetric energy density, which is unmatched by any other alkali metal ion. State-of-the art cells today reach nearly 700 Wh/L and further ambitions for next generation batteries target 1000 Wh/L, which can be realised through Li metal anodes in conjunction with solid state electrolytes. At the heart of this futuristic technology is the process of continuous plating and stripping of Lithium during cycling of the battery. Owing to the highly reactive nature of Li, this is a complicated process shadowed with several complications during both plating (for e.g., dendrite formation and growth, dead lithium, continuous interface change, short circuit etc.) and stripping (void formation, pitting, broken interface layers etc.). Electrode architecture, choice of electrolytes and the interface layers formed because of the electrolyte reduction are some of the key factors that affect electrochemical performance of Li anode.

Here at imec, we are evaluating various Ionic liquid-based electrolytes (ILEs) for successfully mitigating the issues faced by Li anodes, reducing environmental impact and improving user safety. Of importance here is the electrical double layer (EDL) that is formed at the vicinity of the reactive Li metal. The nature and properties of the EDL can be controlled by changing the composition of the ILEs (concentration of the salt, cosolvent) as well as by chemical/electrochemical preconditioning. In this thesis, we will study the exact process that limits lithium stripping performance by means of experiments and modelling. The prospective student will be guided by imec researchers to uncover the mechanism of this complex process and to use this knowledge to improve the stripping performance using a systematic approach of adding well-chosen additives.

Required background: (Analytic) Chemistry, Electrochemistry, Modelling

Type of work: Computational / Experimental

Supervisor: Philippe Vereecken

Daily advisor: Simon Vandersnickt