Polyaniline doped with dimethyl sulfate as a nucleophilic dopant and its electrochemical properties as an electrode in a lithium secondary battery and a redox supercapacitor

The physical properties of polyaniline (PAn) powder, doped by nucleophilic doping of dimethyl sulfate (DMS), were characterized, as well as its electrochemical behaviors, to investigate the possibility of a power source device adopting the PAn-DMS electrodes. It is shown that the nucleophilic addition of DMS into PAn concurrently resulted in an increase of the charge transport properties (e.g., electrical conductivity) and enhanced the processability (e.g., lowering of the melting point). The surface structure of PAn-DMS electrodes showed that the compactness of the electrode surface was helpful in increasing the capacity of lithium rechargeable batteries, whereas the porous behavior was valuable to improve the capacitance of a redox supercapacitor. Depending on the power source devices using the lump- and sheet-type PAn-DMS electrodes, the following optimized performances were obtained: more than 80 mA h g^-1 after 50 cycles for lithium secondary battery use and ∼115 F g^-1 initially and ∼94 F g ^-1 after 5000 cycles at a current density of 2.5 m A cm^-2 for application as a redox supercapacitor, which were the highest reported performances for all PAn-based electrodes.