Research On Ni-Co Bimetallic Sulfide And N-Doped Carbon For Supercapacitors

Due to the rapid development of new energy in recent years,high-efficiency and high-quality energy storage devices have been urgently required.As one of the research hotspots in the new energy field,supercapacitors are gradually being studied and paid more attention by researchers.Based on the work of previous researchers,this dissertation has prepared a new type of asymmetric supercapacitor positive/negative electrode material,which increases the working voltage window and specific capacity,thereby increasing the energy and power density of the supercapacitor.The main research contents are as follows:?1?A two-step hydrothermal method was used to prepare transitional bimetallic sulfide NiCo₂S₄with a hollow microsphere structure,The final target product NiCo₂S₄was obtained,and physical characterization analysis was performed on the morphology,crystal morphology,chemical composition and valence of NiCo₂S₄and its precursors.The first step of hydrothermally obtained nickel-cobalt precursors has a solid urchin-like morphology.The sulfurized NiCo₂S₄exhibits a unique surface porous hollow microsphere structure with a BET specific surface area of 5.5 m²/g,The specific capacity of NiCo₂S₄at current density of 1 A/g is as high as 1688 F/g?areal capacity is 2.70 F/cm²at current density of 1.6 m A/cm²?.After kinetic analysis,the electrochemical reaction occurring on the electrode is a diffusion control reaction.When the current density is increased from 1 A/g to 20 A/g,the capacity retention rate is 84.6%,At a high current density of 10 A/g,after 10,000 charge and discharge cycles,the initial capacity retention rate reached 72.5%,indicating that NiCo₂S₄has excellent rate performance and cycle stability.This is mainly due to the synergistic effect of its unique surface porous hollow microsphere structure and the electrochemical properties of the transition bimetal sulfide itself.?2?The polyaniline/melamine composite was used as the carbon source,and the melamine was used as the template and nitrogen source.The product obtained by hydrothermal treatment was subjected to high-temperature calcination treatment.Finally,the carbon material obtained by high-temperature calcination was activated by different mass ratios of KOH to obtain a nitrogen-doped porous carbon material.The physical morphology,structure and crystals of the material were obtained through physical characterization.Analysis of morphology and element content.The NC-4activated carbon material prepared from polyaniline/melamine has a hierarchical porous structure with a BET specific surface area of 1393.9 m²/g and a nitrogen content of up to 4.72%.The NC-4 electrode has a specific capacity of 208 F/g at a current density of 1 A/g?areal capacity is 208 m F/cm²at current density of 1m A/cm²?;When the current density is increased from 1 A/g to 20 A/g,the capacity retention rate is 69%,and after charging and discharging 10,000 times under a large current density of 5 A/g,the specific capacity is still maintained at 91.7%.The above test results show that the NC-4 activated carbon material has excellent electrochemical performance.These results are mainly due to the high specific surface area and high nitrogen content of the nitrogen-doped carbon material prepared from the polyaniline/melamine composite.?3?NiCo₂S₄and commercial rice husk activated carbon?RHAC?are used as positive/negative materials to assemble NiCo₂S₄//RHAC ASCs as asymmetric supercapacitors with an operating voltage of 1.6 V and an energy density of 41.1Wh/kg at a power density of 400 W/kg At a current density of 5 A/g,after 10,000long cycles,the capacity retention rate reaches 62%,and it still maintains good charge and discharge performance,and has good cycle stability.The above results show that NiCo₂S₄//RHAC ASCs have excellent electrochemical performance of supercapacitors.This is due to the large working potential window of the assembled asymmetric supercapacitors,and the use of NiCo₂S₄with a high specific capacity as the asymmetric supercapacitor positive electrode.The material also greatly increases the specific capacity of the supercapacitor,which further makes the supercapacitor have a higher energy density.Polyaniline/melamine-based carbon materials are used as positive/negative materials to assemble symmetrical supercapacitor NC-4//NC-4,the working potential window is 1.2 V,and the power density is up to 400 W/kg.8.28Wh/kg,at a current density of 5 A/g,after a long cycle of 10,000 times,the capacity remains at 84.5%,which has good charge-discharge cycle stability.The above results show that NC-4//NC-4 symmetrical supercapacitor have excellent electrochemical performance.The experimental results and data show that both NiCo₂S₄and NC-4 electrode materials exhibit excellent electrochemical performance.Applying NiCo₂S₄and NC-4to asymmetric supercapacitors and symmetrical supercapacitors,respectively,both show good supercapacitor performance.This indicates that NiCo₂S₄and NC-4 have broad application prospects as electrode materials for supercapacitors.