A Model-Based Insight into Electrolyte Behaviour in Aqueous Zinc-Ion Batteries

Kurzfassung

Next-generation batteries strive for the optimal fit in performance, cost, and environmental safety. Within recent times, a whole playground of different material systems and working principles were investigated. Consumer alkaline batteries with a metallic zinc anode and manganese dioxide cathode achieve excellent energy densities, yet their development stalled due to their limited rechargeability. Switching the aqueous electrolyte from alkaline KOH to, for example, mild electrolytes, however, showed a reversible charge/discharge mechanism at the cathode. This achievement highly increased the research interest in zinc-ion batteries in the last decade, and many successful systems were proposed. Aqueous metal batteries face a series of challenges. The limited stability window of water, as well as unwanted precipitation reactions, deteriorate the battery performance and increase aging reactions. The electrolytes composition and the concentration-dependent complex formation governs its performance. Within Zinc-air batteries, we performed model-based optimization studies of pH adjusted electrolytes. Yet, to our knowledge, there is no modelling work done for zinc-ion batteries. Within our contribution, we combine a description of complex formation with a dynamic cell model. The electrolyte speciation significantly influences the transport properties of the electrolyte as well as its stability. With our cell model, we predict the performance and rate-dependent behavior of commonly used materials. With this, we identify system-requirements and pitfalls in the ongoing optimization of aqueous zinc-ion batteries.