Toward Biodegradable Mg–Air Bioelectric Batteries Composed of Silk Fibroin–Polypyrrole Film

Biodegradable active implantable devices can be used to diagnose and/or treat disease and eventually disappear without surgical removal. If an “external” energy source is required for effective operation then a biocompatible and biodegradable battery would be ideal. In this study, a partially biodegradable Mg‐air bioelectric battery (biobattery) is demonstrated using a silk fibroin‐polypyrrole (SF‐PPy) film cathode coupled with bioresorbable Mg alloy anode in phosphate buffered saline (PBS) electrolyte. PPy is chemically coated onto one side of the silk substrate. SF‐PPy film shows a conductivity of ≈1.1 S cm^?1 and a mild catalytic activity toward oxygen reduction. It degrades in a concentrated buffered protease XIV solution, with a weight loss of 82% after 15 d. The assembled Mg‐air biobattery exhibits a discharge capacity up to 3.79 mA h cm^?2 at a current of 10 μA cm^?2 at room temperature, offering a specific energy density of ≈4.70 mW h cm^?2. This novel partially biodegradable battery provides another step along the route to biodegradable batteries.