Plasma-Assisted Surface Modification on Electrode Interface for Flexible Fiber-Shaped Zn-Polyaniline Batteries.

A novel flexible fiber-shaped zinc-polyaniline battery (FZPB) is proposed to enhance the electrochemical performance, mass loading, and stability of polyaniline cathodes. To this end, electron-cyclotron-resonance oxygen plasma-modified carbon fibers are employed. During plasma treatment, on the carbon-fiber surface, O2+ plasma breaks the C-C, C-H, and C-N bonds to form C radicals, while the O2 molecules are broken down to reactive oxygen species (O+, O2+, O2+, and O22+). The C radicals and the reactive oxygen species are combined to homogeneously form oxygen functional groups, such as -OH, -COOH, and -C=O. The surface area and total pore volume of the treated carbon fibers increase as the plasma attacks. During electrodeposition, aniline interacts with the oxygen functional groups to form N-O, N-H bonds, and π-π stacking, resulting in a homogeneous and high-loading polyaniline structure, and improved adhesion between polyaniline and carbon fibers. In FZPB, the cathode with plasma-treated carbon fibers and polyaniline loading of 0.158 mg mgCF-1 (i.e., 2.36 mg cmCF-1) exhibits a capacity retention of 95.39% after 200 cycles at 100 mA g-1, and a discharge capacity of 83.96 mA h g-1 at such high current density of 2,000 mA g-1, which are ~1.67 and 1.24 times those of the pristine carbon-fiber-based one, respectively. Furthermore, the FZPB exhibits high flexibility with a capacity retention of 86.4% after bending to radius of 2.5 mm for 100 cycles, as a wearable energy device.