Supercapacitors Using n and p-Type Conductive Polymers Exhibiting Metallic Conductivity

Solid State Bi-polar Supercapacitors Utilizing Electroactive Polymers
Patrick J. Kinlen*, Young-Gi Kim, Sabina Besic, June-Ho Jung and Michael Birschbach
Crosslink, 950 Bolger Court, Fenton, MO 63026 - 636-349-0050

Figure 1: PANI-DNNSA

Energy storage devices such as supercapacitors require a superior, safe and reliable performance over a broad range of temperature combined with high energy and high power densities. Development of improved high performance supercapacitors is important for fulfilling the energy and power needs of hybrid electric vehicles, portable electronics, and specialized pulse-power systems required by the military. To meet this need, Crosslink has developed supercapacitors based on inherently conductive polymers (ICPs) and polymer gel electrolytes. The highly conductive ICP electrodes combine both the beneficial redox behavior of the ICP coating and a low equivalent series resistance. In our developmental effort, highly-conductive (> 1000 S/cm) polyaniline (PANI) electrodes are used to fabricate high performance supercapacitors to obtain enhanced charge transfer and redox activity. Typically, soluble PANI is produced as the salt of dinonylnaphthalene sulfonic acid (DNNSA, Figure 1) and cast as a thin film. The PANI-DNNSA film is further treated with secondary dopants such as thymol, p-toluene sulfonic acid (PTSA) and p-toluenesulfonamide (TSAm) to achieve near metallic conductivity.

Figure 2: CV of PANI-DNNSA before and after secondary doping


Table 1: Role of PANI conductivity on device performance

The cyclic voltammogram (cv) of a PANI-DNNSA (PAC1003) film before and after secondary doping (Figure 2) clearly reveals the enhancement of redox activity achieved with the secondary doping process.

Table 1 illustrates the effect of conductivity on specific capacitance and energy density for a Type I coin cell using an ionic liquid electrolyte (1-ethyl-3-methyl-1-H-imidazolium bis(trifluoromethanesulfonyl)imide (EMI-IM)). Clearly, higher electronic conductivity results in higher specific capacitance and higher energy density.

To facilitate the construction of solid state supercapacitors, we have developed new free-standing solid state polymer gel electrolytes (PGEs) that exhibit high ionic conductivity and thermal stability (Figure 3).

The solid state polymer based framework allows the construction of bipolar modules that are designed to function with high energy and power densities, cycle life, and extreme temperature tolerance while keeping production costs low. A rolled up version of a solid state Type I PANI-Bipolar device is shown in Figure 4:

Using the solid state design roll-up architecture we have succeeded in constructing Type I bipolar PANI capacitors with energy densities up to 10 WH/Kg and power densities of 5000 W/Kg. To enhance energy density further, we are working to build TYPE IV systems containing both n and p dopable ICPs.

Figure 3: Free standing polymer gel electrolyte

Figure 4: PANI bipolar supercapacitor (4 inches long)

Acknowledgments:
We thank Missouri State University (Center for Applied Science and Engineering) for assistance in device fabrication and express our gratitude to Hai-Long Nguyen of the US Army ARDEC for continued support of this project. This research is being conducted for Army-ARDEC under the contract number W15QKN-07-C-0121.

Downloads:
Crosslink offers these associated product data sheets and MSDS’s on Energy Storage Materials

EMPAC-1003-071307 (pdf)

EMPAC-1007-071307 (pdf)

Presentations

International Seminar 2010 {pdf)

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