Ultrathin Zinc-Air Batteries Used In Wearable Flexible Electronics

Rechargeable flexible Zn–air batteries are attracting a great deal of attention and regarded as high-energy-density power supplies for powering next-generation flexible electronics. For the flexible Zn–air battery, the flexible air electrode with high-performance oxygen reduction reaction (ORR) during the discharge and oxygen evolution reaction (OER) during the charge plays a vital role in the performance of a battery, such as energy efficiency, capacity retention, and cycling life. Co₃O₄ loaded on the carbon cloth without binder has been considered to be the promising air electrode due to its high-performance bifunctional activity and durability in alkaline solutions.

Recently, Xu Chen, Bin Liu, Cheng Zhong, and co-workers develop a high-performance, flexible air electrode for the Zn–air battery by devising a simple fabrication technique. This technique involves a simple yet quick electrodeposition with the heat-treatment to in-situ and horizontally grow ultrathin mesoporous Co₃O₄ layers on the surface of carbon fibers in the carbon cloth (ultrathin Co₃O₄/CC).

Meanwhile, the ultrathin Co₃O₄ layers have a maximum contact area on the conductive support. This helps to facilitate the rapid electron transport and prevent aggregation of the ultrathin layers.

The mass activity for ORR and OER of the as-prepared electrode is more than 10 times higher than that of the carbon cloth loaded with commercial Co₃O₄ nanoparticles due to the high utilization degree of active materials and rapid charge transport. The as-assembled flexible Zn–air battery based on the ultrathin Co₃O₄/CC electrode exhibits excellent rechargeability (≈1.03 V discharge voltage and ≈1.95 V charge voltage at 2 mA cm^–2).

The specific capacity normalized to the mass of consumed Zn is 542 mAh g⁻¹, corresponding to a high charge density of 546 Wh kg^–1. Moreover, whether after 10 hours of galvanostatic discharge–charge testing or after 300 mechanical bending cycles, there is no obvious fading in performance, which confirms the battery has a high cycling stability.

Furthermore, the authors integrate a flexible display into the device as a first prototype. Despite repeated bending, twisting, even being cut by ceramic scissors, the device maintains its brightness. Benefiting from the signaling safe and reliable operation even if the device is damaged，the device is promising in the future.

The study, Ultrathin Co3O4 Layers with Large Contact Area on Carbon Fibers as High-Performance Electrode for Flexible Zinc–Air Battery Integrated with Flexible Display was recently published in the journal Advanced Energy Materials. Xu Chen is the first author and Cheng Zhong is the corresponding author.