Highly Conductive Yarn Cathode Coated with Polypyrrole as a Flexible Battery for Wearables

The practical application of yarn electrode materials has been restricted because of the inherent insulating properties and adverse electrochemical properties of conventional yarns. The aim of the study was to make yarn electrodes with higher specific capacitance and construct a type of yarn-like manganese dioxide (MnO2) electrode. In this work, polyacrylonitrile-wrapped carbon fibers (CFs) core-spun yarn (CFP core spun yarn) was prepared by electrospinning with CF yarn as the base material. The highly conductive yarn (CFPP yarn) was then prepared by depositing polypyrrole nanoparticles by in situ polymerization on top of the CFP cored yarn. Finally, based on CFPP yarn, the CFPP@MnO2 yarn cathode material was prepared by coating MnO2 on CFPP yarn by an impregnation coating method. The CFPP@MnO2 yarn cathode showed outstanding electrochemical performance in the three-electrode system test, maintaining 89.76% of the initial capacity after 100 charge–discharge cycles at a current density of 1 mA cm–1, which indicates that the CFPP@MnO2 yarn cathode has outstanding cycling stability. The yarn cell can therefore be used as the cathode electrode for yarn batteries, providing an effective strategy for applications in smart textiles and wearable electronics.