Self-supporting electrodes for high-performance flexible solid-state supercapacitors: Recent advances and perspectives

[Display omitted] •The principles and advantages of self-supporting electrodes and flexible solid-state supercapacitors.•Various substrates used to design flexible self-supporting electrodes.•Free-standing thin film electrodes without substrate.•Perspectives of self-supporting electrodes for flexible solid-state supercapacitors. Due to their exceptional power density and long-term cycling stability as electrical energy storage systems, supercapacitors (SCs) have been wildly and intensively investigated over the past few decades. In recent years, flexible solid-state SCs (FSSCs) have attracted tremendous research interests due to the increasing demand for flexible and wearable electronic devices. However, the utilization of conventional electrode materials in fabricating SC electrodes through slurry-casting method necessitates the incorporation of binders and conductive additives, which fails to meet the mechanical and electrochemical performance requirements for FSSCs. In contrast, self-supporting electrodes enable the direct growth of electroactive materials on flexible substrates circumvent binders and conductive additives introduction, exhibiting advantages such as reduced weight, lower resistance, higher energy density, enhanced flexibility, and mechanical reliability. In this context, this review comprehensively summarizes the latest advancements in self-supporting electrodes suitable for FSSCs. These include metal substrates, carbon substrates, cellulose (paper), non-conductive polymers, and other substrates that can be utilized to fabricate high-performance flexible SCs. Furthermore, the study also encompasses free-standing electrodes without the need for substrates. Finally, it discusses the future challenges and development prospects of bendable substrate-based flexible SCs along with their applications.