Binder Selection Towards Improved Stability of Rechargeable Aqueous Zinc-Ion Batteries with Manganese Oxide Cathodes

Abstract

Rechargeable aqueous zinc-ion batteries are promising alternatives due to its abundance of active materials, safety, and lower cost. However, development of a suitable cathode that is earth abundance, such as manganese oxide, which can also produce high performance battery needs to be further carried out. Binders play a key role in achieving desirable properties, such as mechanical, electrical, electrochemical etc. of a battery. Specifically, selecting the right binder will promote stability throughout operation and enable tuning the thickness of a cathode to load more active materials to increase the capacity. This work explores three different binders, Carboxymethyl cellulose(CMC), Cellulose acetate (CA), and Polyvinylidene fluoride (PVDF), in aqueous electrolyte with ZnSO4 salt to investigate the effect of hydrophilicity level on performance and stability of the battery. The result shows that a cathode with PVDF as a binder yields the highest specific capacity regardless of charge/discharge rate. While, CA cathode works well at low rate and their performance started to drop at higher rates. CMC based cathode yields the lowest capacity from low to medium rate and starts to excel at higher rates. The relationship between different degree of electrolyte wettability on cyclability of the batteries will also be discussed. Further investigation using the Galvanostatic Intermittent Titration Technique (GITT) shows that there are two regions of ionic diffusion in all samples. During high state-of-charge (SOC) all three cathodes behave the same, while at lower SOC, CA based electrode seems to be limited by ionic diffusion. This explains why CA cathode performance dropped a lot at a higher rate. Our binder selection criteria for zinc-ion batteries can be further adapted in wider rechargeable zinc-based batteries for a variety of applications. Figure 1