To achieve the green preparation of electrodes, a self-supporting electrode (SSE) was prepared using cotton fiber, nano-cellulose, sodium carboxymethyl cellulose, and copolyacrylate emulsion as adhesives, carbon black (CB) and carbon fiber (CF) as conductive agents, activated carbon (AC) as the active material, and water as the dispersant. To further enhance the conductivity of the electrode, a self-made CB conductive slurry was used to conductively strengthen the SSE, creating a conductively strengthened self-supporting electrode (CSSE). Characterization through SEM, BET nitrogen adsorption, contact angle, and electrochemical performance tests revealed that the SSE possesses a rich porous structure that allows rapid wetting by the electrolyte. The conductive strengthening effectively improved the conductivity of the electrode, resulting in abundant ionic microchannels and conductive pathways. To further boost the energy density of supercapacitors (SC), AC loaded with manganese dioxide (MnO2@AC) powder was prepared using a simple one-step aqueous carbon reduction method. Subsequently, a CSSE-MnO2 electrode was fabricated and paired with an AC electrode to assemble an asymmetric supercapacitor known as ASC (CSSE-MnO2//AC). Its electrochemical performance was evaluated in both neutral Na2SO4 electrolyte and redox electrolytes. The study found that the addition of redox-active electrolyte ammonium iron citrate to the neutral Na2SO4 electrolyte enables rapid and reversible redox reactions on the electrode surface, further enhancing the electrochemical performance of the ASC within a voltage window of 2.0～2.4 V. The assembled ASC exhibited exceptional areal capacitance (1.5 F/cm2 at a current density of 3～11 mA/cm2), a wide operating voltage window (2.0～2.4 V), satisfactory rate capability (1.2 F/cm2 at a current density of 84 mA/cm2), and outstanding cycling stability (maintaining 80% of its initial capacity after 10,000 cycles at 2 A/g). It achieved a remarkable energy density of 37.6 Wh/kg at a power density of 300 W/kg. The simple and cost-effective preparation process of CSSE offers a novel and feasible strategy for developing inexpensive, and safe energy storage devices.