¹ Beijing Laboratory of New Energy Storage Technology, School of Energy Power and Mechanical Engineering, North China Electric Power University, Beijing 102206, China;

² Fujian Provincial Key Laboratory of Eco-Industrial Green Technology, Key Laboratory of Green Chemical Technology of Fujian Province University, Wuyi University, Wuyishan, Fujian Province, 354300, China;

³ Key Laboratory of Green Chemical Technology of Fujian Province University, College of Ecology and Resources Engineering, Wuyi University, Wuyishan 354300, China;

⁴ State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China;

⁵ China Electric Power Research Institute, Beijing 100192, China;

⁶ Extreme Materials Research Center, Korea Institute of Science and Technology (KIST), 14-gil 5 Hwarang-ro, Seongbuk-gu, Seoul, 02792, Republic of Korea;

⁷ Department of Physics, Dongguk University, Seoul, 04620, Republic of Korea.

* Correspondence: gcliu@ncepu.edu.cn

With the rapid development of the flexible electronics industry, energy storage devices with excellent electrochemical performance and flexibility have become a research hot spot. Polyaniline (PANI) has become a core electrode material for flexible energy storage devices due to its advantages of abundant raw materials, high conductivity, and good reversibility. This paper systematically reviews the research status and development prospects of PANI-based flexible energy storage devices. First, the basic properties and core energy storage mechanisms of PANI are described. Then, the latest research progress of PANI-based flexible supercapacitors and flexible rechargeable batteries is summarized. Meanwhile, the key bottlenecks in this field are pointed out, including low energy density, poor cycling stability, and immature device fabrication technology. Three targeted optimization strategies are concluded: molecular engineering and doping system optimization, nanostructure regulation and composite design, interface engineering and compatibility improvement. In addition, the emerging application of PANI in photo-enhanced flexible energy storage devices is introduced. As a p-type semiconductor, PANI can form heterojunctions with photoactive components to realize photo-assisted charging. Relevant studies have achieved breakthroughs in aqueous zinc-ion batteries, realizing performance improvement and multi-mode operation. Finally, the future development of PANI-based flexible energy storage devices is prospected, aiming to provide systematic theoretical reference and guidance for the rational design and industrial application of PANI-based energy storage materials.