Performance variation of Li rechargeable cells having polypyrrole cathodes doped with different anions

Kp Vidanapathirana,Kumudu Perera

doi:10.4038/jnsfsr.v42i2.6997

Abstract

Electrochemically synthesized polymers such as polypyrrole (PPy), polyaniline (PANI) and polyNmethyl pyrrole (PNMP) are considered as one of the most promising polymer electrode material groups for the development of advanced electrochemical devices such as electrochemical cells, super capacitors, electrochromic devices and solar cells. The properties of electrochemically synthesized polymers are known to be largely dependent on the dopant anion used and hence, their performance in applications also depend greatly upon the dopants. In this study, the role of the anion used to dope the PPy cathode on the performance of a lithium (Li) rechargeable cell is reported. Anions were varied from small inorganic anions (CF3SO3 -) to large anions (alkilsulphonate, AS- and dodeclybenzenesulphonate, DBS-). PPy was electropolymerized and the cells were fabricated with a polyacrylonitrile (PAN) based solid polymer electrolyte (SPE) while Li served as the anode. Cyclic voltammetry and continuous charge discharge tests were carried out to characterize the cells. The cycling results showed better cycling charge and long cycle life with the cells fabricated with PPy doped with large anions. The cells with large anions showed higher cycle numbers while the cells with inorganic anions could not be cycled over 350 cycles. Even with electrodes having larger anions, better results can be obtained with slow scan rates. Scanning electron microscopy (SEM) studies revealed that electrodes have a porous morphology with smaller anions and a dense morphology with larger anions, which also affect the performance variations. DOI: http://dx.doi.org/10.4038/jnsfsr.v42i2.6997 J.Natn.Sci.Foundation Sri Lanka 2014 42 (2): 143-147

Highlights

Synthesized polymers or conjugated polymers (CP) are considered as one of the most promising polymer electrode material groups for the development of advanced electrochemical devices since they have interesting features such as appreciable electronic conductivity, low cost, easy handling and environmental friendliness (Cheng et al, 2006; Huang, 2006; Wang et al, 2006; Green et al, 2010)
During the synthesizing of CPs, different anions are introduced to the polymer backbone and it has been found that the properties of such polymer electrodes vary depending on the type of the anions used (Skaarup et al, 2000; 2003)
The cathodic peak of the cyclic voltammogram is assigned to the reduction and the anodic peak is assigned to the oxidation (Tang et al, 2010), i.e. peaks at cyclic voltammograms exhibit the potentials at which redox reactions of the cells at charging and discharging take place

Summary

Introduction

Synthesized polymers or conjugated polymers (CP) are considered as one of the most promising polymer electrode material groups for the development of advanced electrochemical devices since they have interesting features such as appreciable electronic conductivity, low cost, easy handling and environmental friendliness (Cheng et al, 2006; Huang, 2006; Wang et al, 2006; Green et al, 2010). During the synthesizing of CPs, different anions are introduced to the polymer backbone and it has been found that the properties of such polymer electrodes vary depending on the type of the anions used (Skaarup et al, 2000; 2003). The role of the anion used to dope the PPy cathode for the performance of Li rechargeable cells is reported. The structure of the cell is Li / gel polymer electrolyte / PPy cathode doped with different anions. The gel polymer electrolyte consists of polyacrylonitrile (PAN), ethylene carbonate (EC), propylene carbonate (PC) and lithiumtrifluoromethanesulfonate (LiCF3SO3)

Methods

Results

Conclusion