| Summary: | Flexible electronics have been limited by inadequate energy storage solutions. Despite extensive research, the energy efficiency and lifespan of current flexible storage devices fall short of commercial standards. Additionally, the high cost of these solutions hampers the scalability of flexible electronics.
Flexible batteries offer a promising energy storage solution, leveraging the success of commercial batteries. While flexible lithium-ion batteries have been investigated, their intrinsic safety hazards limit their broader adoption, particularly in wearable and medical electronics. Flexible zinc-ion batteries have recently garnered attention for their safety, high capacity, and low cost. However, challenges such as shuttling effects, zinc dendrites, and low energy efficiency remain. Although advancements have been made in electrodes, electrolytes, and separators for flexible zinc-ion batteries, further research is needed before they can achieve commercial viability.
This thesis investigates the materials and structural design of flexible aqueous zinc-ion batteries, focusing on methodologies to enhance reaction kinetics and lifespan for potential industrial applications. We first introduce a hydrogel cellulose paper-based separator that integrates seamlessly with electrode materials, facilitating the rapid and straightforward fabrication of large-area flexible zinc-ion batteries, thus supporting scalable production. The hydrogel-reinforced cellulose paper also provides excellent mechanical durability, addressing the issue of repeated bending and enhancing the overall robustness of paper batteries.
In the next chapter, we introduce a layer-expanding strategy to enhance electrodes for aqueous zinc-ion batteries by increasing active sites and facilitating smooth hydrated zinc ion transport. The insertion of n-butylamine expands the interlayer spacing of Zr(HPO4)2•H2O (α-ZrP), creating expanded-interlayer ZrP (EI-ZrP). EI-ZrP is also proved to facilitate electron transport. By combining hydrogel cellulose paper (HCP) as the separator, a paper battery with EI-ZrP in the cathode material is fabricated and proved to be efficiently relieved from shuttling effects.
Furthermore, zinc-air batteries, which use atmospheric oxygen at the cathode, reduce material costs and show immense potential for flexible energy storage applications due to their high capacity and low production cost. This thesis introduces an innovative double-layer electrolyte design that leverages the distinct kosmotropism of different anions to induce phase separation, eliminating the need for a separator. This design enhances zinc utilization and battery lifespan by mitigating side reactions and provides a framework for further advancements in zinc-air batteries and their cost-effective, scalable production.
All proposed solutions for cellulose-based zinc-ion batteries have been demonstrated through integration with practical electronic devices, validating their capability for prolonged use. These experiments offer valuable insights into industrial applications of flexible cellulose-based batteries in wearables, medical devices, and other flexible electronics.
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