Transient and Sustainable Batteries: Materials and Emerging Bio‐Based Pathways

The rapid expansion of portable and distributed electronics, combined with the escalating environmental burden of waste electrical and electronic equipment (WEEE), demands energy-storage systems designed from the outset to be sustainable and degradable. This chapter provides a comprehensive overview of transient batteries (TBats), covering the transformation of conventional materials into degradable components, the development of metal-based transient systems, and the emergence of entirely organic and bio-hybrid strategies. We first discuss material-adaptation approaches that enable controlled corrosion of traditionally nondegradable metals through biodegradable matrices. Subsequently, we examine TBats based on Mg, Zn, Mn, Mo, and biodegradable alloys, highlighting their electrochemical performance, degradation pathways, and applications in wearable, implantable, and disposable electronics. Organic redox-active molecules, hydrogels, plant-derived polymers, and microbial systems are then analyzed as sustainable routes toward metal-free and programmable degradation. Finally, we outline the key challenges and future opportunities, particularly integrating artificial intelligence-driven materials screening and circular-economy principles, emphasizing TBats' potential to enable environmentally responsible energy storage for next-generation electronics.