Stretchable Plant-Based Redox-Diffusion Battery

Stretchable batteries are essential for the realisation of autonomous and conformable wearable electronics that interface intimately with the human body. In existing battery designs, the predominant use of unsustainable transition metal-based active materials and non-biodegradable petroleum-based elastomers contribute to the environmental problem of e-waste and the mining of finite resources. Moreover, increasing the active material content often leads to stiffer electrodes with poor mechanical properties. Here, we developed a stretchable battery design – the redox-diffusion (RD) battery - based on soluble plant-based redox-active biomolecules infiltrated within a cellulose-based 3D porous electrode scaffold. The redox reaction is mediated by diffusion of dissolved biomolecules within the pores of the 3D scaffold. It decouples the active material loading from the mechanical structure of the electrodes to afford high mass loadings (> 40 mg cm^-2) of the redox-active biomolecules. The electrode achieved a high capacity of 28.6 mAh/cm³ with a skin-like Young’s modulus of 110 kPa and stretchability up to 200 % strain. The RD design is facilitated by the development of a stretchable ion-selective membrane separator to allow the utilisation of two separate redox couples while preventing crossovers. This enabled a full cell with stable electrochemical performance under stretching. The utilisation of plant-based materials for the battery components (electrode, separator, current collector, and encapsulation) enabled the full degradation of the cell into benign products. The work emphasises on the importance to encompass not only high battery performance but considers the human and environmental impact of the materials used and disposal of the cell at the end-of-life.