Recent progress in energy storage and conversion of flexible symmetric transducers

With the advancement of modern wearable electronics, flexible symmetric transducers have become frontrunners in energy technology by virtue of their flexibility, light weight, facile integration, high power density, and long cycle life. In recent years, a wide range of achievements in flexible symmetric transducers have been reported, and many impressive wearable applications have been demonstrated. Herein, a timely review on the latest advances in flexible symmetric transducers has been summarized. Firstly, a fundamental understanding of device configuration, working mechanisms, and evaluation methods are presented. Secondly, some emerging flexible materials for electrodes and electrolytes of the devices are provided, including conductive polymers, carbon nanotubes, graphene, graphitic carbon nitride, metal-organic frameworks, and other derived nanomaterials. Thirdly, critical fabrication techniques, different device shapes, impressive wearable applications, and safety issues concerning flexible symmetric transducers are discussed comprehensively. Finally, critical challenges and future research directions are also highlighted for flexible symmetric transducers.