Stretchable and Biodegradable Batteries with High Energy and Power Density

Abstract Realizing a sustainable, technologically advanced future will necessitate solving the electronic waste problem. Biodegradable forms of electronics offer a viable path through their environmental benignity. With both the sheer number of devices produced every day as well as their areas of application ever increasing, new concepts of degradable batteries able to sustain the high power demands of modern electronics must be developed. Simultaneously, integration of electronics in close interaction with its user or powering soft robotic devices necessitates high degrees of compliance, rendering stretchable batteries indispensable. Here, a concept for merging intrinsically stretchable materials with engineered stretchability by kirigami‐patterning on a component level is shown to yield high‐power biodegradable batteries with reversible elasticity up to 35% when stretched uniaxially and 20% for biaxial extension. Using a combination of molybdenum metal foils, a molybdenum trioxide paste, and magnesium metal foils as electrode materials, a peak power output of 196 µW cm –2 and an energy density of 1.72 mWh cm –2 is achieved. The biodegradable batteries are used to power an on‐skin biomedical sensor patch, enabling monitoring of sodium concentration in sweat. This concept provides a versatile route for high‐power biodegradable batteries, enabling untethered soft electronic devices in a sustainable future.