Mangosteen husk-derived porous carbon for quasi solid-state supercapacitor with advanced performances

[Display omitted] •Mangosteen husk-derived porous carbon (MHPC) has foam-like morphology with high specific surface area.•MHPC and KOH gel-electrolyte are assembled in quasi solid-state supercapacitors with cost-effective and highly safety.•High specific capacitance and exceptional cyclability are achieved in coin-type supercapacitor.•Flexible supercapacitor maintains superior capacitive performance under arbitrary bending state. Exploiting advanced electrode materials and electrolytes are two fundamental approaches to enhance the electrochemical performances of supercapacitor. Herein, mangosteen husk-derived porous carbon (MHPC) and KOH gel-electrolyte are prepared and applied in quasi solid-state supercapacitor. In coin-type supercapacitor employing 6 M KOH gel-electrolyte, the MHPC electrode exhibits a high specific capacitance of 285 F g−1 at a current density of 0.2 A g−1, coupled with exceptional cyclability, retaining 88.9 % of its initial capacity after 10,000 cycles. Additionally, the elaborated MHPC electrode and 6 M KOH gel-electrolyte enabled the flexible device in maintaining superior capacitive properties under arbitrary bending angles. Our findings present an avenue in the development of cost-effective and highly safe energy storage devices.