Molten-NaNH₂ activated carbon cloth with high areal capacitance and exceptional rate stability for flexible asymmetric supercapacitors

An effective strategy was proposed to obtain molten-NaNH₂ activated carbon cloth (MACC) for the manufacture of flexible asymmetric supercapacitors. First, the commercial carbon cloth is oxidized by wet chemical treatment and then activated in molten-NaNH₂. The obtained MACC possess many advantages, including moderate oxygen functional groups and nitrogen heteroatoms, excellent wettability, large surface area, high conductivity and excellent mechanical strength and flexibility. As electrode, the MACC demonstrates a high areal capacitance of 744.5 mF cm⁻² at a current density of 1 mA cm⁻², and 692.0 mF cm⁻² at a high current density of 50 mA cm⁻² with the capacitance retention as high as 92.93% in 6 M KOH. Furthermore, the flexible asymmetrical supercapacitors are fabricated based on the MACC electrode and Co(OH)₂ electrode using aqueous electrolytes. The assembled aqueous supercapacitors can release an areal capacitance of 373.9 mF cm⁻² under the current density of 2 mA cm⁻², and the corresponding energy density is up to 1.49 mW cm⁻³ at the power density of 19.45 mW cm⁻³. The impressive results reveal that the as-prepared MACC is a potential electrode for the flexible supercapacitors.