3D Printed Gallium Battery with Outstanding Energy Storage: Toward Fully Printed Battery‐on‐the‐Board Soft Electronics

Abstract The last decade observed rapid progress in soft electronics. Yet, the ultimate desired goal for many research fields is to fabricate fully integrated soft‐matter electronics with sensors, interconnects, and batteries, at the ease of pushing a print button. In this work, an important step is taken toward this by demonstrating an ultra‐stretchable thin‐film Silver‐Gallium (Ag‐Ga) battery with an unprecedented combination of areal capacity and mechanical strain tolerance. The Biphasic Gallium‐Carbon anode electrode demonstrates a record‐breaking areal capacity of 78.7 mAh cm⁻², and an exceptional stretchability of 170%, showing clear progress over state‐of‐the‐art. The exceptional theoretical capacity of gallium, along with its natural liquid phase self‐healing, and its dendrite‐free operation permits excellent electromechanical cycling. All composites of the battery including liquid‐metal‐based current collectors, and electrodes are sinter‐free and digitally printable at room temperature, enabling the use of a wide range of substrates, including heat‐sensitive polymer films. Consequently, it is demonstrated for the first time multi‐layer, and multi‐material digital printing of complex battery‐on‐the‐board stretchable devices that integrate printed sensor, multiple cells of printed battery, highly conductive interconnects, and silicone chips, and demonstrate a tailor‐made patch for body‐worn electrophysiological monitoring.