Preparation And Electrochemical Properties Of Nickel Sulfide/Biomass Carbon Composites For Supercapacitor

In recent years,environmental pollution and energy shortage have become major problems that human can't ignore.In order to alleviate the severe environmental resources situation,clean energy has become the hottest research direction in the world,electrochemical energy storage technology is the most widely used.Supercapacitors occupy a place in energy storage devices with their ultra-high power density.Supercapacitors are mainly divided into two types according to the principle of energy storage:pseudo-capacitors?PS?and electric double layer capacitors?EDLS?.As a typical PS material,nickel sulfide?NiS?has a theoretical specific capacitance of up to 590 mAh g^-1,however,it has been reported that the NiS electrode exhibitsserious capacitance fading because of its low structural stability induced by the electrosorption and intercalation reaction process,which produces an acute internal mechanical stress during the charge-discharge cycling;in contrast,the biomass carbon material is used as the carbon material.One has the typical characteristics of EDLS,which has the advantage of good cycle stability,but its specific capacitance is low.This experiment will improve their electrochemical performance by combining of two materials.The main findings are as follows:In this paper,two kinds of biomass carbon materials were synthesized by high temperature solid phase method:chestnut shell-based biomass carbon material?LC?and celery-based biomass carbon material?QC?.Two kinds of biomass carbon materials were scanned by scanning electron microscopy?SEM?.Characterization,there are a large number of micropores and mesopores on the surface;X-ray diffraction?XRD?and Raman spectroscopy analysis show that both biochars are amorphous carbon;FT-IR proves that both biochar materials are carbonaceous contains nitrogen oxide functional groups.The chestnut shell biomass carbon with a mass ratio of chestnut shell to potassium hydroxide of 1:3?LC-3?has a specific surface area of 1410 m² g^-1 and an average pore diameter of3.06 nm in 6 M KOH,1 M H₂SO₄,and 3 M KOH electrolytes is 258 F g^-1,375 F g^-1,198 F g^-1,,respectively.Long cycling stability with 100%of capacitance retained after 10000cycles under conditions of 3 M KOH and 5 A g^-1.On the basis of LC-3,the NiS/LC composites were synthesized by hydrothermal method,and the effects of reactant concentration and hydrothermal time of the composites were explored.By optimizing the hydrothermal process,we get the sample NiS/40wt%LC which has best electrochemical performance after 12 hours of reaction.The highest specific capacitance was 868.1 F g^-1 when the current density was 1 A g^-1 in 3 M KOH.The retention rate was 90.1%.