Wearable eutectic gallium-indium liquid fuel cells

Abstract With the rapid growth of wearable electronics, the development of wearable fuel cells as a smart power source is receiving ever more attention due to their high energy conversion efficiency, modest operating temperature, and ease of handling. To address the most notable limiting factor, the rigid electrodes, of fuel cells, herein, a eutectic gallium-indium liquid metal with excellent deformability and redox ability has been employed to wearable and rechargeable fuel cells with high performance. Thanks to the optimized Ga/In ratio, which is achieved by balancing the anticorrosion and electrochemical activity of the liquid metal anode, the power density of the fuel cell is as high as 72.8 mW cm−2; to our knowledge, this is the highest power density among existing wearable liquid fuel cells at room temperature. Due to the stable redox properties of liquid metal, the fuel cell was stably cycled for 96 h at 2 mA cm−2 as a rechargeable metal-air battery. Meanwhile, running in feed mode to maintain the proportion of Ga in the anode, the fuel cell and the rechargeable liquid metal fuel cell exhibited stable discharging and cycling performances, respectively, and delivered exemplary performances under various flexibility and stretchability measurements. Based on the fluent and renewable liquid metal anode, this novel high-performance wearable liquid fuel cell shows great promise as a shape-variable energy supply for bionic soft robots and wearable devices.