Preparation Of Heteroatom-doped Carbon Materials And Its Electrochemical Performance

Supercapacitors,a new and sustainable energy storage device,are widely used due to their advantages such as high power,good cycle stability,and fast charge-discharge rate.The electrochemical performance of the electrode materials is a key factor that determining the performance of supercapacitors.Therefore,the study of electrode materials is the most important task in the whole research work.In the light of the charge storage principles,there mainly are two kinds of electrode materials for supercapacitors: the electric double-layer capacitor materials and the pseudocapacitance materials.Carbon materials are one of the typical electric double-layer electrode materials,which are usually hot research spot in the field of supercapacitor.And the functional carbon materials doped with heteroatom dopants possess pesudocapacitance which further improve the capacitance.However,the preparation and functionalization process often requires more complicated steps.So it is significant to develop some simple methods to prepare heteroatom-doped carbon materials for supercapacitor.This thesis develops two kinds of heteroatom-doped carbon materials which exhibit excellent electrochemical performance in supercapacitor.The structure properties are researched by some characterizations such as XRD,TEM,XPS and the charge storages principles are disscused.The research achievements are as follows:(1)A kind of B/N co-doped carbon material(BNC)was prepared with inexpensive and readily available polyaniline as a precursor and boric acid as boron source.The dosage of boric acid and carbonization temperature for preparing BNC were optimized.When the amount of aniline(2.7 mmol)and ammonium persulfate(2.5 mmol)are constant,the optimum dosage of boric acid is 5 g and 700 ? is optimal according to electrochemical tests.The BNC material achieved under optimum conditions exhibits a specific capacitance of 340.55 F/g at 0.5 A/g which still maintained at 245.6 F/g at a large current density of 20 A/g,exhibiting a capacitance retention rate of 72.12 % with good rate performance.The capacitance retention was still 86.28 % after 5000 cycles of charge and discharge at a current density of 5 A/g,showing a good cycle stability.The symmetrical supercapacitor assembled with BNC-700 as electrode material has a high energy density of 6.0 Wh/kg and a power density of 2500 W/kg at a high current density of 5 A/g.The research expands the application range of B/N co-doped carbon materials in the electrochemical field to a certain extent.(2)With sodium lignosulfonate(SLS)as a precursor and boric acid as template and boron source,a series of B/S co-doped carbon materials(BSC)were synthesized by carbonization.The mass ratio of sodium lignin sulfonate to boric acid and the carbonization temperature were screened.According to electrochemical tests,the optimum mass ratio of sodium lignosulfonate to boric acid was 1:7 and the best carbonization temperature was 700 ?,which endows BSC-700 the best electrochemical performance.The specific capacitance of 309.1 F/g could be obtained at 0.5 A/g,and the specific capacitance was still 191.34 F/g at 20 A/g,and the capacitance retention rate was still 61.9 % at a large current density.100 % capacitance retention is exhibited after 5000 times charge-discharge cycles at a current density of 5 A/g.These results demonstrate that the B/S co-doped carbon material has potential application in the field of supercapacitor.