Hollow coaxial graphene/polyaniline hybrid fibers for high performance cable-type iodine ion batteries

A hollow coaxial graphene/polyaniline hybrid fiber was fabricated using wet spinning and subsequent electrodeposition methods for the purpose of creating fiber-shaped iodine ion cathode. This hybrid fiber consists of an oriented hollow internal graphene shell and a porous external structure made of reduced graphene oxide/polyaniline (rGO/PANI). The hollow structure serves as an electrolyte reservoir, enhancing the accessibility of electrolyte ions, while the oriented graphene shell acts as a pathway for charge transfer, improving conductivity. Additionally, the external porous rGO/PANI structure provides numerous active sites for the adsorption of iodine species. The optimized hybrid fiber demonstrates a high specific capacity of 129 mAh g-1 at a current density of 0.5 mA cm-1, along with excellent cycling stability, retaining 91 % of its capacity after 1200 cycles. The specific capacity can be increased to 185 mAh g-1 at a current density of 0.5 mA cm-1 by introducing highly conductive electrochemically exfoliated graphene oxide into the internal graphene shell. Furthermore, the cable-type iodine ion battery also exhibits a capacity of 184 mAh g-1 (based on the cathode) at a current density of 0.5 mA cm-1, with exceptional cycling stability. It retains 80 % of its capacity after 3000 cycles and 74 % of its capacity after 10,000 cycles.