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Electrode design concepts for stretchable batteries using wood-based materials
- Aiman Rahmanudin
- Considering the exponential growth of the internet-of-things devices by 2035, of which many will be wearables, adopting sustainable practices to mitigate the environmental impact of traditional energy storage solutions while advancing their mechanical functions and battery performance is urgently needed to meet the United Nations Sustainable Development Goals. High-capacity stretchable batteries are crucial for next-generation wearables to enable long-term operation and mechanical conformability with human users. However, in existing battery electrode designs, increasing the active material loading to yield higher capacity often leads to thicker and stiffer electrodes with poor mechanical properties. Majority of reported stretchable and conventional batteries predominantly use unsustainable battery chemistries (Li-ion and toxic organic electrolytes), expensive and finite metal current collectors, and non-biodegradable petroleum-based polymers such as fluorinated polymers, and elastomers such as silicones and styrene block co-polymers as either binders and/or encapsulation layers. We will present a concept that decouples the electrochemical (redox-active material) and mechanical properties of the battery electrode. The key innovation is that the mass loading of the active material and their resulting battery capacity is independent from the overall stiffness of the cell. Such a design enables thicker battery electrodes with higher capacities without a trade-off in mechanical properties. The concept was realised by exploiting the unique functional properties of wood-based materials. The batteries were constructed from plant-based redox-active biomolecules (e.g., lignin), cellulose nanofibers as mechanical scaffolds and biodegradable elastomers as encapsulation layers. We hope that the work inspires future battery designs to address the mechanical, electrochemical, and sustainability challenges simultaneously.
