电解质组成对锂-硫电池电化学性能的影响

Effect of electrolyte on electrochemical performance of lithium-sulfur battery

采用恒流充放电、循环伏安等方法并结合电解质的电导率和粘度的测试,研究了电解质对硫电极电化学性能的影响。实验以LiClO4为电解质,选用1,3-二氧戊环(DOL)、乙二醇二甲醚(DME)、四氢呋喃(THF)三种有机溶剂,配制了三种电解质:1mol/LLiClO4/(DOL+THF)(50∶50,体积比)、1mol/LLiClO4/(DME+DOL)(50∶50,体积比)、1mol/LLiClO4/(DME+THF)(50∶50,体积比)。比较了这三种电解质在锂-硫电池中的电化学性能,实验结果表明:在配制的电解质中,硫电极在2.3V和2.0V附近有两个放电电压平台,低电压平台的电位和电解质的粘度密切相关。使用1mol/LLiClO4/(DME+THF)(50∶50,体积比)的电解质时,硫电极有很好的大电流性能,首放比容量高达860mAh/g,当放电电流密度为0.6mA/cm2时,硫电极的充放电效率超过了80%。

The influence of electrolyte on the electrochemical performance of sulfur electrode was investigated by galvanostatic charge-discharge and cycling voltammetry methods combined with conductivity and viscosity measurements. By using LiClO4 as conductive salt, DME, DOL, THF as solvents, three electrolytes were prepared： 1 mol/L LiClO4/ （DOL＋THF） （50 ： 50,vol）, 1 mol/L LiClO4 / （ DME＋DOL ） （50 ： 50,vol）, 1 mol/L LiClO4 / （ DME＋THF ） （50 ： 50,vol）. Electrochemical test of sulfur electrode was conducted in the three electrolytes. Charge-discharge test shows that there are two different voltage plateaus on the discharge profile, 2.3 V and 2.0 V respectively. The voltage of lower voltage plateau is highly dependent on the viscosity of the electrolyte. Sulfur electrode sustaines good discharge performance in 1 mol/L LiClO4/（ DME＋THF ） （50 ： 50,vol） electrolyte, the initial discharge specific capacity is 860 mAh/g. When discharge current density is 0.6 mA/cm^2, efficiency of charge and discharge is above 80%.