A Mitochondrion‐Inspired Magnesium–Oxygen Biobattery with High Energy Density In Vivo

Abstract Implantable batteries are urgently needed as a power source to meet the demands of the next generation of biomedical electronic devices. However, existing implantable batteries suffer from unsatisfactory energy density, hindering the miniaturization of these devices. Here, a mitochondrion‐inspired magnesium–oxygen biobattery that achieves both high energy density and biocompatibility in vivo is reported. The resulting biobattery exhibits a recorded energy density of 2517 Wh L –1 /1491 Wh kg –1 based on the total volume/mass of the device in vivo, which is ≈2.5 times higher than the current state‐of‐the‐art, and can adapt to different environments for stable discharges. The volume of the magnesium–oxygen biobattery can be as thin as 0.015 mm 3 and can be scaled up to 400 times larger without reducing the energy density. Additionally, it shows a stable biobattery/tissue interface, significantly reducing foreign body reactions. This work presents an effective strategy for the development of high‐performance implantable batteries.