Oxysalt-assistant Synthesis Of Fish Scale-derived Porous Carbons For Use In Potassium-ion Capacitor

Due to the hybrid energy-storage mechanism,potassium-ion capacitors have the superiorities of high specific energy,high specific energy and long operation life,which are regarded as a new generation of energy-storage devices that can be widely used.However,the lack of high-performance electrode materials limits the improvement of the overall performance for potassium-ion capacitors.Porous carbons with suitable micro-structures and rich element composition are very promising electrode materials for potassium-ion capacitors.Unfortunately,the regulation methods of their structures and compositions are still faced with many problems,including complex synthesis processes and low regulation effects.In this thesis,collagen within fish scales was extracted by water-soluble potassium phosphate and honeycomb like porous carbons with oxygen/nitrogen/phosphorus heteroatoms were prepared due to the activation,doping,and templating roles of potassium phosphate.The formation mechanisms of the porous carbons were studied by in-situ thermal analysis.The porous carbons were further used as cathode and anode materials for the potassium-ion capacitors,and their electrochemical performance were also evaluated.In addition,the energy storage mechanisms of the porous carbon cathodes and anodes were revealed by in-situ characterization.Finally,a potassium-ion capacitor with high specific energy(107 W h kg-1),high specific power(7.9 kW kg-1)and good operation stability(with a capacity retention of 93%after 6000 cycles at 1 A g-1)was assembled using the optimal cathode and anode.Potassium sulfate was further used as an auxiliary to prepare seaweed clump-like fish scale-derived porous carbons with oxygen/nitrogen/sulfur heteroatoms by the same synthesis processes.The activation,doping,and templating functions of potassium sulfate were deeply studied by in-situ thermal analysis.The as-prepared porous carbons were used as the anode materials for the potassium-ion capacitor and their electrochemical performance was evaluated.Finally,a potassium-ion capacitor was assembled using the optimal anode,showing high specific energy(129 W h kg-1),high specific power(2.3 kW kg-1)and good long-operation stability(with a capacity retention of 76%after 6000 cycles at 1 A g-1).