High rate and ultralong cyclelife fiber‐shaped sodium dual‐ion battery based on bismuth anodes and polytriphenylamine cathodes

Abstract Fiber‐shaped sodium dual‐ion batteries (FSDIBs) have attracted considerable attention in wearable electronics because of their low cost and natural abundance and intrinsic flexibility, as well as high working voltage and energy density. Thus, exploration of an electrode material with good flexibility and more accommodative spaces for the reversible shuttle of large anions and Na+ cations is quite necessary but challenging. Herein, Bi nanoparticles anchored on a carbon nanotube fiber are homogeneously fabricated and used as anodes to assemble FSDIBs with carbon fiber‐coated polytriphenylamine cathodes. A series of in situ/ex situ characterizations are conducted to investigate the corresponding battery reaction mechanism of anodes, revealing a reversible reaction process of mixed insertion‐alloying behavior. Owing to excellent electrochemical properties and electrode match, the FSDIBs show ultralong cycle stability for 5000 cycles at 5 A g−1 and remarkable rate capability ranging from 2.5 to 20 A g−1. Moreover, the FSDIBs also show good flexibility under different bending deformations. This work paves the way for development of flexible energy storage devices for wearable devices.