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

doi:10.19799/j.cnki.2095-4239.2020.0131

Abstract

Abstract:

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.

Key words: supercapacitor, graphene, carbon nanotubes, surface distance, diameter

CLC Number:

TM 538

Lanfang ZHU, Bing LIU. Influence of graphene surface distance and carbon nanotube diameter on capacitance of a double layer capacitor[J]. Energy Storage Science and Technology, 2020, 9(6): 1720-1728.

Figures/Tables 14

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References 14

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面间距/nm	测量位置与极板的距离Z/nm	K⁺与其结合水间的相互作用能/kJ·mol^-1	K⁺与壁面间的相互作用能/kJ·mol^-1	H₂O与壁面间的相互作用能/kJ·mol^-1	K⁺的结合水与其结合水间的相互作用能/kJ·mol^-1
0.55	0.1375	-114.661	0.949	8.433	-7.427
0.55	0.2750	-151.324	0.864	6.345	-15.019
0.6	0.1500	-240.247	-46.142	-2.648	-7.332
0.6	0.3000	-240.714	-41.470	-2.123	-15.505

面间距/nm	测量位置与极板的距离Z/nm	K⁺与其结合水间的相互作用能/kJ·mol^-1	K⁺与壁面间的相互作用能/kJ·mol^-1	H₂O与壁面间的相互作用能/kJ·mol^-1	K⁺的结合水与其结合水间的相互作用能/kJ·mol^-1
0.9936	0.2340	-552.668	2.580	-0.287	-5.610
0.9936	0.2997	-370.242	5.079	-3.047	-18.490
1.1199	0.2997	-370.242	5.079	-3.047	-18.490
1.1199	0.5994	132.873	5.438	-3.088	-2.322

面间距/nm	测量位置与极板的距离Z/nm	K⁺与其结合水间的相互作用能/kJ·mol^-1	K⁺与壁面间的相互作用能/kJ·mol^-1	H₂O与壁面间的相互作用能/kJ·mol^-1	K⁺的结合水与其结合水间的相互作用能/kJ·mol^-1
0.6608	1.521	-65.548	40.616	32.810	37.033
0.6608	3.041	-2065.220	6.506	34.756	77.843

面间距/nm	1.203	1.08	0.936	0.803	0.6	0.55	0.5	0.4
比电容/μF·cm^-2	0.485	0.470	0.677	3.303	0.798	0.667	0.290	2.598
圆孔直径/nm	11.99	10.86	9.36	7.97	6.08	5.50	5.19	4.52
比电容/μF·cm^-2	0.929	0.519	1.067	0.428	1.014	16.138	1.588	10.027

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