双添加剂低浓度水系硫酸盐电解液用于2V碳-碳超级电容器

Low-Concentration Aqueous Sulfate Electrolytes with Dual Additives for 2 V Carbon-Carbon Supercapacitors

为了解决水系电解液在超级电容器中电压窗口低、能量密度小的问题,研究了含有0.5 mol/L硫酸钾(K_(2)SO_(4))以及聚乙二醇(PEG)和碱金属碘化物(AMI)双添加剂的低浓度中性水系电解液在碳-碳超级电容器中的应用。首先在0.5 mol/L K_(2)SO_(4)中添加PEG,由于H2O-PEG之间的相互作用,3%质量分数的PEG添加剂使得0.5 mol/L K_(2)SO_(4)电解液的电化学稳定窗口达到4.70 V。该0.5 mol/L K_(2)SO_(4)+3%PEG电解液应用于以商业活性炭YP-50F作为电极材料的碳-碳超级电容器中,可在2V条件下稳定循环10000次。进一步添加AMI(LiI、NaI或KI)氧化还原添加剂来增大比电容和能量密度,使法拉第反应的比电容进一步提高到400 F·g^(-1)以上,是原始0.5 mol/L K_(2)SO_(4)+3%PEG电解液的3.5倍,能量密度达到50 W·h·kg^(-1)以上。此外,根据电双层电容器的离子孔尺寸匹配理论,LiI和NaI被证明是比KI更有效的添加剂,它们能使得YP-50F丰富的亚纳米孔得到更有效的利用。因此,PEG和AMI的协同作用为超级电容器水系电解液的开发提供了一种可行的方案。

To solve the problems of low voltage window and low energy density of aqueous electrolytes in supercapacitors,low-concentration neutral aqueous electrolytes with 0.5 mol/L potassium sulfate(K_(2)SO_(4))and dual additives of polyethylene glycol(PEG)and an alkali metal iodide(AMI)were studied for application in carbon-carbon supercapacitors.PEG was firstly added to 0.5 mol/L K_(2)SO_(4).Due to the H2O-PEG interaction,the PEG additive of 3%mass fraction results in an electrochemical stabilization window of 4.70 V for the 0.5 mol/L K_(2)SO_(4)electrolyte.The 0.5 mol/L K_(2)SO_(4)+3%PEG electrolyte was applied to carbon-carbon supercapacitors with commercial activated carbon YP-50F as the electrode material for 10000 times stable cycles at 2 V.The redox additive of AMI(LiI,NaI or KI)was further added to increase the specific capacitance and energy density.Thus,the specific capacitance of Faradic reaction is increased above 400 F·g^(-1),which is 3.5 times that of the original 0.5 mol/L K_(2)SO_(4)+3%PEG electrolyte,and the energy density reaches above 50 W·h·kg^(-1).Moreover,according to the ion-pore size matching theory for electric double-layer capacitors,LiI and NaI are proved more efficient than KI,and can allow the abundant sub-nanopores of YP-50F to be used more efficiently.The synergistic effect of PEG and AMI provides a feasible scheme for the development of supercapacitor aqueous electrolyte.