Acta Phys. -Chim. Sin. ›› 2011, Vol. 27 ›› Issue (02): 449-454.doi: 10.3866/PKU.WHXB20110205

• ELECTROCHEMISTRY AND NEW ENERGY • Previous Articles     Next Articles

Asymmetric Capacitance Behavior Based on the Relationship between Ion Dimension and Pore Size

SUN Gang-Wei, SONG Wen-Hua, LIU Xiao-Jun, QIAO Wen-Ming, LING Li-Cheng   

  1. State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, P. R. China
  • Received:2010-10-15 Revised:2010-11-19 Published:2011-01-25
  • Contact: LING Li-Cheng E-mail:lchling@ecust.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (50730003).

Abstract:

We reported on the capacitive behaviors regarding to the relationship between ion size and pore architecture, using activated carbons with an adjusted pore structure as electrode materials. The results revealed that an asymmetric capacitance response occurred in both electrodes. The gravimetric capacitances for the positive and negative electrodes were 113 and 7 F·g-1, respectively. A significant current decay was presented in the negative region of cyclic voltammetry curve. Experimental and calculated maximum storage charges had a good agreement. This results suggested that the insufficiently developed pore architecture for cation accommodation led to a saturation effect on the active surface, consequently, a deteriorated capacitive performance in the negative electrode. Contrarily, when pore size was larger than tetrafluoroborate dimension, the saturation effect was not found. However, this was at the expense of the lower specific area capacitance in the positive electrode. The poor capacitive behavior of the negative electrode would limit the usable voltage of the cell system and consequently the deliverable energy and power. As a result, an optimal match between the pores size and the ion dimension with respect to each electrode would be considered to obtain the maximum capacitance for the capacitor unit.

Key words: Electrochemical capacitor, Organic electrolyte, Asymmetric capacitance behavior, Pore size distribution, Ion dimension

MSC2000: 

  • O646