Synthesis And Supercapacitive Performance Of Biomass Carbon Material /Transition Metal Compound Composites

Supercapacitor as one of most popular energy storage device s has attracted wide attention owing to its ultra-high power density,ultra-long cycle life and fast charge-discharge capabilities.The electrode material is the key component of supercapacitor since it plays an important role on the performances of supercapacitor.Therefore,exploring the electrode material is the core research content of supercapcitor.Carbon material is a popular kind of electrode material for supercapacitor and reducing its production cost is considered important and valuable.But the supercapacitive performance of a single-component electrode material trends to be restricted to its shortcomings.Therefore,preparation of composite materia l to synergy the advantages of two or more kinds of material is a hotspot of current research.In this paper,in order to reduce the production cost and improve the electrochemical capacitance performance of electrode material,the composites of biomass carbon material and cheap,non-toxic transition metal compounds are synthesised and their electrochemical performance are studied.The specific works and results are showed as follow:（1）The porous carbons（PCs）are synthesized by carbonization,activation two-steps method with bean meal as carbon precursor.And then the manganite/porous carbons（MnOOH/PCs）are prepared by hydrothermal method.The results show that the activation temperature and the amount of KOH have a great influence on the capacitance properties of porous carbon.When the temperature is 900 ^oC,the mass ratio of pre-carbonization carbon and KOH is 1:4,the PC₄-900 exhibits the optimal electrochemical capacitance performance.Its specific surface area is 2050 m² g^-1,and its specific capacitance is 215.4 F g^-1 at the current density is 1 A g^-1.In 6 M KOH electrolyte,the MnOOH_2.5/PC₄-900 exhibits excellent electrochemical capacitance performance.Its specific capacitance is 300 F g^-1 at 1 A g^-1,while its specific capacitance is 287 F g^-1 at 9 A g^-1.Its capacitance retention remains 95.0%after 2000cycles(at 1 A g^-1).The symmetrical supercapacitor presents the highest energy density(14.6 Wh kg^-1)when its power density is 500 W kg^-1,and its energy density is10.5 Wh kg^-1 when its power density is 4.5 kW kg^-1.（2）The N,B-CNS is prepared by annealing method with gelatin as precursor,boric acid as boron source and template.And then the N,B-CNS/MnO₂ is synthesized by hydrothermal method.The results show that the N,B-CNS with high nitrogen content can be prepared by annealing method,and its nitrogen content and boron content is 8.3%and 3.6%,respectively.In 1 M H₂SO₄ electrolyte,the N,B-CNS/MnO₂ exhibits excellent electrochemical capacitance performance.Its specific capacitance is 329 F g^-1 at 1 A g^-1,while its specific capacitance is 261 F g^-1at 9A g^-1.Its capacitance retention remains 92.3%after 5000 cycles(at 50 mV s^-1).The symmetrical supercapacitor presents the highest energy density(14.9 Wh kg^-1)when its power density is 500 W kg^-1,and its energy density is 11.9 Wh kg^-1 when its power density is 4.5 kW kg^-1.（3）The carbon nanotube/nickel foam（CNT/NF）is prepared by annealing method with bean meal as carbon source,melamine as nitrogen source and nickel foam as current collector,and then the nickel sulfide/carbon nanotube/nickel foam（NiS_x/CNT/NF）is synthesized by hydrothermal sulfuration method with thiacetamide as sulfurizing reagent.It is binder-free and no need conductive agent used as the electrode of supercapacitor.The results show that the mass ratio of carbon source and nitrogen source has a great influence on the morphology structures of CNT/NF,the CNT/NF possesses the optimal morphology structure.In 6 M KOH electrolyte,the NiS_x/CNT/NF exhibits excellent electrochemical capacitance performance.Its area specific capacitance is 21.9 F cm^-2 at 10 mA cm^-2,while its specific capacitance is16.8 F cm^-2 at 50 mA cm^-2.Its capacitance retention remains 89.6%after 2000 cycles(at 10 mA cm^-2).