Electrochemical approach to prepare integrated air electrodes for highly stretchable zinc-air battery array with tunable output voltage and current for wearable electronics

Efficient stretchable and flexible energy devices are urgently required due to their promising application in wearable devices. Although flexible solid-state zinc-air batteries have been developed in previous studies, no stretchable Zn-air batteries with large stretchability (> 20%) have been reported. We first present a planar rechargeable stretchable and flexible Zn-air battery array fabricated by layer-by-layer assembly of 2 x 2 electrode arrays, a polymer gel electrolyte, serpentine-shaped copper circuits, and a rubber substrate. Vertical Co3O4 nanosheets were fabricated by a binder-free and simple manner and were grown in situ on carbon cloth as an integrated cathode. The Zn-air battery array displayed stable electrochemical behaviors, with a large tensile strain of 100%. Furthermore, the battery array could be discharged stably at 1 V at a high current density of 2 mA cm(-2) under high-frequency dynamic stretching (similar to 100% strain per second) and bending conditions. In addition, by redesigning the arrangement of the electrode array, the stretchable Zn-air battery array could be configured to provide a wide range of output voltages, specifically from 1 to 4 V. The resulting Zn-air battery array was sewn onto cloth and applied to power a green light band (3.0 V) with 60 light-emitting diodes (LEDs), proving the feasibility of its application in wearable energy-storage electronics.