title: The effect of various electrolyte cations on electrochemical performance of polypyrrole/RGO based supercapacitors.
abstract: In this work, polypyrrole/graphene doped by p-toluenesulfonic is prepared as an active material for supercapacitors, and its capacitance performance is investigated in various aqueous electrolytes including HCl, LiCl, NaCl, and KCl with a concentration of 3 M, respectively. A rising trend of capacitance is observed according to the cationic mobility (Li(+) < Na(+) < K(+) < H(+)), which is due to its effect on the ionic conductivity, efficient ion/charge diffusion/exchange and relaxation time. On the other hand, long-term cycling stability is in the following order: KCl < NaCl < LiCl < HCl, corresponding to the decreasing tendency of cation size (K(+) > Na(+) > Li(+) > H(+)). The reason can be attributed to the fact that the insertion/de-insertion of large size cation brings a significant doping level decrease and an over-oxidation increase during the charging-discharging cycles. Hence, we not only obtain good capacitance performance (280.3 F g(-1) at 5 mV s(-1)), superior rate capability (225.8 F g(-1) at 500 mV s(-1)) and high cycling stability (92.0% capacitance retention after 10,000 cycles at 1 A g(-1)) by employing 3 M HCl as an electrolyte, but also reveal that the electrolyte cations have a significant effect on the supercapacitors' electrochemical performance.
authors.affiliation: Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, Xi'an Jiaotong University, Xi'an 710049, P. R. China. ylxuxjtu@mail.xjtu.edu.cn.
authors.forename: Jianbo
authors.initials: J
authors.lastname: Zhu
authors.affiliation: Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, Xi'an Jiaotong University, Xi'an 710049, P. R. China. ylxuxjtu@mail.xjtu.edu.cn.
authors.forename: Youlong
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, Xi'an Jiaotong University, Xi'an 710049, P. R. China. ylxuxjtu@mail.xjtu.edu.cn.
authors.forename: Jie
authors.initials: J
authors.lastname: Wang
authors.affiliation: Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, Xi'an Jiaotong University, Xi'an 710049, P. R. China. ylxuxjtu@mail.xjtu.edu.cn.
authors.forename: Jun
authors.initials: J
authors.lastname: Lin
authors.affiliation: Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, Xi'an Jiaotong University, Xi'an 710049, P. R. China. ylxuxjtu@mail.xjtu.edu.cn.
authors.forename: Xiaofei
authors.initials: X
authors.lastname: Sun
authors.affiliation: Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, Xi'an Jiaotong University, Xi'an 710049, P. R. China. ylxuxjtu@mail.xjtu.edu.cn.
authors.forename: Shengchun
authors.initials: S
authors.lastname: Mao