Ultrafast rechargeable Zn micro-batteries endowing a wearable solar charging system with high overall efficiency

Wearable solar charging systems are now developing rapidly. However, their insufficient overall efficiency and poor charging rate remain daunting challenges. Herein, we report the rational design of a wearable solar charging unit based on a miniature GaAs solar cell and an ultrafast rechargeable Zn micro-battery. This integrated system demonstrates a high overall efficiency of 23.11%. Upon solar charging for 5 s, the system delivers a continuous supply of power for 110 s at 0.5 mA cm−2, showing favorable fast charging performance characteristics. With the aid of in-depth characterization combined with theoretical simulations, the electrochemical energy storage mechanism of the zinc ion battery is elucidated as the synergy of hydroxyl anion intercalation with surface pseudocapacitive reaction. This work provides an innovative strategy to construct wearable solar charging units with high efficiency and advanced charging capabilities.