Applying Non-Metallic Halogen Ions to Boost Aqueous Zn-Based Battery Performance
DescriptionMany smart phones, electric vehicles and grid-storage stations use Li-ion batteries (LIBs) as a power source. However, LIB technology is suboptimal, as it relies on the use of flammable organic electrolytes (e.g., hydrocarbon-based solvents) that cause LIB explosion. Thus, a key challenge for the battery community is to develop an alternative battery technology with an improved safety profile.The most straightforward and effective strategy to address this issue is to substitute volatile organic electrolytes with aqueous counterparts that are intrinsically safe and reliable. Indeed, the aqueous battery research and development field has grown considerably to keep pace with demand from sectors such as human wearable electronics that have stringent safety requirements.The safe battery market is of huge commercial importance. For example, the global flexible battery market is projected to reach USD 296 million by 2025 (up from USD 98 million in 2020) with an annual growth rate of 24.7%. By developing safe aqueous batteries, companies could therefore corner a significant fraction of this market. In addition, aqueous batteries can be produced at lower manufacturing costs and in less stringent manufacturing environments than LIBs, which require low moisture and low oxygen conditions.Although the safety and cost efficiency of aqueous batteries are two inherent advantages over their LIB counterparts, one disadvantage is their compromised energy density when compared to organic batteries. This is mainly due to their low output voltages, which can be up to 60% lower than the mid-point voltage of an LIB. The low output voltage is generally attributed to the confinement of aqueous electrolytes with a narrow electrochemical stability window. To realize the potential of aqueous batteries at the industrial scale thus requires a significant improvement to their energy density.In turn, energy density can be improved by enlarging output voltage and specific capacity. We have profoundly studied the merits and chemistries of aqueous batteries. In contrast to the widely used metal-ion charge carriers (MCC), non-metallic charge carrier (NMCC)-based batteries have great potential to deliver improved performance, especially in terms of energy density and power density. In this project, we propose to use the non-metallic halogen ions iodide (I) and bromide (Br) as charge carriers/cathode materials. The scientific challenges associated with manufacturing high-performance aqueous batteries and the strategies that could be used to overcome them will be thoroughly discussed. Our preliminary results strongly suggest that the objectives can be accomplished within the proposed duration of the project. The output of the project will be functional flexible/wearable devices that run on high-performance and ultra-safe batteries.
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