Toward high-performance flexible micro-supercapacitors: in situ construction of 2D porous carbon nanosheets with a unique polycrystalline-like micro-morphological feature

Abstract

High areal capacitance or energy density is still a challenging issue for carbon-based micro-supercapacitors (MSCs). Herein, porous carbon nanosheets with a unique polycrystalline-like micro-morphological feature (PL-PCN) are in situ constructed for the first time through a two-step fabrication strategy, which is realized by the synthesis of 2D polycrystalline titanium carbide (TiC) nanosheets (P–TiC) using graphene nanosheets (GNS) as the template and the subsequent high-temperature chlorination of P–TiC. Interestingly, the resultant PL-PCN has the characteristics of a high specific surface area (up to 1649.97 m² g⁻¹), superb wettability to electrolytes, and a unique hierarchical micro- and meso-porous structure, in which the mesopores existing in the form of “grain boundary” and the micropores inside the “grain” can effectively provide abundant ion transport channels and accessible electrochemically active sites, respectively. Arising from these advantages, the all-solid-state MSC built by using PL-PCN as the electrode material delivers exceptional electrochemical performances, such as an ultrahigh areal capacitance of 108.88 mF cm⁻² and energy density of 14.73 μW h cm⁻², both of which, to the best of our knowledge, are among the highest values reported so far for carbon-based MSCs. Furthermore, the fabricated MSC also possesses superb mechanical flexibility, and the capacitive output and voltage can be easily regulated by connecting multiple MSC devices in parallel and series. Hence, this work provides a new insight to design and fabricate a carbon electrode material for high-performance micro-supercapacitors.