电解质对Fe_(3)O_(4)/石墨烯复合材料电化学性能影响的研究

Research on the effects of electrolyte on the electrochemical performance of Fe_(3)O_(4)/graphene composites

采用溶剂热法制得Fe_(3)O_(4)纳米片层垂直均匀生长在石墨烯表面的Fe_(3)O_(4)/石墨烯复合材料,并用XRD、BET、SEM、TEM等表征手段对复合材料的结构进行表征,用CV和GCD等方法对复合材料在KOH、Na_(2)SO_(3)和Na_(2)SO_(4)水溶液中的电化学性能进行测试,分析考察了电解质种类和浓度对Fe_(3)O_(4)/石墨烯复合材料电化学性能的影响。结果显示,不同种类的电解质具有不同的离子半径,离子半径的大小通过影响离子在电极材料中嵌入/嵌出,进而使得Fe_(3)O_(4)/石墨烯复合材料在不同种类电解质中的比电容大小不同,3种电解质中比电容的大小顺序依次为KOH电解质>Na_(2)SO_(3)电解质>Na_(2)SO_(4)电解质,且在0.9 mol/L KOH电解质中比电容达到最大值(330 F/g,电流密度0.4 A/g);不同浓度的KOH电解质具有不同的粘度和电导率,电解质的粘度和电导率将影响离子的迁移速度,进而对Fe_(3)O_(4)/石墨烯复合材料的电容性能产生影响。

Fe_(3)O_(4)/graphene composites with Fe_(3)O_(4) nanosheets vertically and uniformly grown on the surface of graphene are prepared by solvothermal method.XRD,BET,SEM,TEM and other characterization methods are used to characterize the structure of the composites.CV and GCD are used to test the electrochemical performance of the composites using KOH,Na_(2)SO_(3) and Na_(2)SO_(4) aqueous solution as electrolyte.The effects of the type and concentration of electrolyte on the electrochemical performance of Fe_(3)O_(4)/graphene composites are analyzed.The results show that different types of electrolytes have different ionic radii,and the size of the ionic radius affects the insertion/extraction of ions in the electrode material,so the capacitance of Fe_(3)O_(4)/graphene composites in different types of electrolytes behaves differently.The order of specific capacitance of Fe_(3)O_(4)/graphene composites in three different electrolytes from large to small is:KOH electrolyte>Na_(2)SO_(3) electrolyte>Na_(2)SO_(4) electrolyte,and the specific capacitance reaches the maximum in 0.9 mol/L KOH electrolyte(330 F/g,current density is 0.4 A/g).Different concentrations of KOH electrolyte have different viscosities and electrical conductivity.The viscosity and conductivity of the electrolyte will affect the migration speed of ions,further affecting the capacitance performance of Fe_(3)O_(4)/graphene composites.