Preparation of hierarchical porous carbon sieve through the decomposition-templating of NaHCO3 for high areal energy density micro-supercapacitor.

• We developed an all-solid-state flexible micro-supercapacitor with 145 mF cm−2 areal capacitance and 20.14 μWh cm−2 energy density. • A hierarchical porous carbon material was prepared by a facile method, which was then utilized in 3D-printed micro-supercapacitors. • Hierarchical porous structure can facilitate ion diffusion of supercapacitors and deliver high energy density. • Hierarchical porous carbon material is cheaper and delivers better performance than commonly used electrode materials such as graphene and carbon nanotubes, promoting the commercialization of micro-supercapacitors. Porous carbon proves a crucial electrode material for micro-supercapacitors (MSCs) due to its favourable electrical conductivity, along with chemical and thermal stability. Nevertheless, the low area accessible to ions and the long electron diffusion paths commonly result in a low energy density for carbon-based MSCs. Here, an alga-based carbon sieve with an interconnected and hierarchical porous structure was prepared and employed as the electrode material to construct MSCs by 3D printing. The interconnected and hierarchical structure facilitates electrolyte diffusion and ion transport, resulting in a high specific capacitance of 145 mF cm−2 and an impressive energy density of 20.14 μWh cm−2 for the MSC. Moreover, the device exhibits excellent mechanical properties and long cycle life. These findings demonstrate the potential of devices for application in microelectronic devices. [ABSTRACT FROM AUTHOR]