N,P co-doped porous carbon/MnO2 composites for zinc-ion hybrid capacitors
Environmental problems caused by the use of fossil fuels have become increasingly serious,and the development of clean energy devices and renewable energy has become an inevitable trend.In this paper,coffee grounds carbon/MnO2 composite was prepared by a simple one-step activation method,and its application in zinc-ion hybrid capacitors(ZHSC)field was discussed.BET test shows that the specific surface area of coffee grounds carbon/MnO2 composite is 550.25 m2/g,and the total pore volume is 0.6284 cm3/g.Electrochemical tests show that electrode displayed excellent specific capacitance of 401.5 F/g at a current density of 0.5 A/g and 264 F/g at a cur-rent density of 20 A/g,which revealed good rate capability.Meanwhile,ZHSC reaches 74.2 mA·h/g,energy density is 39.1 W·h/kg and power density is 4 264 W/kg at 0.5 A/g current density.Furthermore,the capaci-tance retention rate is 98％and the Coulomb efficiency is 98.7％after 5 000 charge-discharge cycles,at the current density of 10 A/g,which indicating it has good cyclic stability and reversibility.Therefore,coffee grounds carbon/MnO2 composites provide a new idea for the exploration of biomass carbon and MnO2 composites.
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