Modelling Electrolyte Behavior in Aqueous Zinc-Ion Batteries

The transformation of the energy production sector is leading to a drastic increase in demand for stationary battery storage. Battery technologies are competing in the area of energy density, environmental safety, and cost per capacity. Consumer alkaline batteries with zinc anodes and manganese dioxide cathodes achieve energy densities of 440 Wh l-1, yet their development stalled due to the challenge of recharging. Changing the aqueous electrolyte from alkaline KOH to, for example, mild acidic electrolytes, however, shows a reversible charge/discharge at the cathode . This concept boosted the research interest in zinc-ion batteries in the last decade, and many promising systems were proposed. Aqueous metal batteries face a series of challenges. The dynamic electrolyte composition and pH profile heavily influence performance and unwanted side reactions. We have performed model-based optimization studies of pH adjusted electrolytes for zinc-air batteries. However, to our knowledge, there is no modelling work done for zinc-ion batteries. In this contribution, we present a thermodynamically consistent dynamic cell model, which takes into account the complex formation and related transport properties of the electrolyte. Considering this, we can predict the performance and rate-dependent behaviour of commonly used electrolyte and electrode materials. This allows us to identify system-requirements and pitfalls in the ongoing optimization of aqueous zinc-ion batteries