石墨烯面间距和碳纳米管直径对双电层电容器电容的影响

Influence of graphene surface distance and carbon nanotube diameter on capacitance of a double layer capacitor

双电层电容器作为一种新型储能装置因为功率密度大、使用寿命长、清洁环保等优点在设备储能、电动汽车和电网等领域具有巨大潜力。虽然如此,其能量密度低的缺点却阻碍了其应用。通过增大其电容可提高其能量密度,因此采用分子动力学模拟(MD)的方法研究了石墨烯面间距(狭缝孔径)和碳纳米管直径(圆孔直径)对面积比电容的影响规律,以此间接反映石墨烯面间距和碳纳米管直径对能量密度的影响。通过分析K+和H2O的分布规律,发现在狭缝孔中,当K+呈单层分布(面间距小于0.5 nm)时,电容随着面间距减小而增加;K+呈双层分布(面间距介于0.5~0.803 nm)时则相反;而在圆孔中,电容随直径呈振荡变化,并且由于曲率,其面积比电容比狭缝孔的大得多。

As a new type of energy storage device,double-layer capacitors are gradually replacing traditional batteries because of their advantages of high-power density,long service life,cleanliness,and environmental protection.They also have a wide application prospect.However,their low energy density hinders application.The energy density can be increased by increasing their capacitance.Therefore,a molecular dynamics simulation method is used herein to study the influence of graphene surface spacing(slit pore width)and carbon nanotube diameter(cylinder pole diameter)on the area specific capacitance to indirectly reflect the influence of graphene surface spacing and carbon nanotube diameter on the energy density.An analysis of the K+and H2O distribution shows that when K+is distributed in a single layer(surface spacing:less than 0.5 nm),the capacitance increases with the decrease of the surface spacing.When K+is distributed in a double layer(surface spacing:between 0.5 nm and 0.803 nm),the result implies the opposite.In a circular hole,the capacitance oscillates with the diameter,and the area is much larger than that of the slit hole because of the curvature.