Synthesis Of High Performance And Low Cost Activated Carbon For Supercapacitors

Supercapacitors are one type of the most important energy storage devices,which show higher power and longer lifetime comparing with second batteries.In recent years,the research of electrode materials has been focused on carbon materials,conducting polymers and transition metal oxides.Comparing with pseudocapacitance materials,activated carbon materials possess absolute advantages in high power,long lifetime and low cost.However,the cost and of activated carbon materials are greatly affected by the preparation method.Therefore,the preparation method was optimized to improve electrochemical properties and reduce the cost of activated carbon materials.The main contents and results of the paper are as follows:?1?Using commercial activated carbon YP50f as raw materials,potassium permanganate was used to enlarge pore size with a certain scale.In order to the micro-pores could effectively accommodate neutral electrolyte ions,and mesopores could be used as a fast transport channel for ions.The oxidant etching was more facile and economical method,giving the sample?KYP50f?a specific capacitance of 132 F g^–1,which was 40%higher than that of YP50f.Combing with MnO₂ as positive electrode,the asymmetrical supercapacitor with a high voltage of 1.8 V exhibits a maximum specific capacitance of 50 F g^–1and specific energy of 22.5 Wh kg^–1.Moreover,they present a high power density of 9000 W kg^–1at 13.05 Wh kg^–1.?2?Activated carbon was synthesized by a simple and low cost one-step calcination of deoxygenated agar in a hot KOH aqueous solution,in which KOH plays both deoxidant and activation agent.The deoxygenation course of soluble agar in the hot KOH solution omits high temperature carbonization in the conventional technology and leads to molecular level activation of agar in subsequent one-step calcination.As a result the maximum specific capacitance of 226 F g^–1in the KOH electrolyte was obtained for AC-1 was higher than 164 F g^–1for AC-2.The maximum specific capacitance of the symmetrical AC-1 cell was 57 F g^–1for a single electrode at 0.25 A g^–1.88.6%of the initial capacitance can be retained for AC-1 in the 6 mol L^–1KOH at 1A g^–1after the 20000.?3?In order to explore the one-step activation mechanism,glucose was used as the probe.When organic molecules contain groups such as epoxy group,hydroxyl group and aldehyde group,molecular bonds would break under the action of alkali liquor,and then small molecular products would be generated,which provides a theoretical basis for the selection and treatment of biomass precursors.Activated carbon AC-12h had excellent electrochemical properties.the capacitance only decreases to 242 F g^–1at 10 A g^–1,having a superb capacitive retention of 90%relative to 268 F g^–1at 1 A g^–1.91.7%of the initial capacitance can be retained for AC-1 in the 6 mol L^–1KOH at 1 A g^–1after the 10000.