Flexible fiber-shaped lithium and sodium-ion batteries with exclusive ion transport channels and superior pseudocapacitive charge storage

Abstract

Fiber batteries have become increasingly important in the wearable energy market and thus, great efforts have been devoted to their development with better specific capacities, longer lifetimes, and sufficient flexibility. However, the sluggish kinetics of the ion transport in the electrochemical process has become a limitation for their practical applications. Herein, we directly employed 2D tungstate and graphene nanosheets as building blocks to construct fiber electrodes with 2D nanofluidic channels and 3D interconnected tunnels for exclusive and fast ion transport. These structures could accelerate the ionic transport process, avoiding the limitations from solid-state diffusion in the electrochemical process and finally facilitating efficient pseudocapacitive charge storage. The resulting fiber-shaped lithium- and sodium-ion batteries exhibited extremely high capacities (206 and 178 mA h g⁻¹ for LIBs and SIBs, respectively), excellent rate performance, long-term cycling capability (1000 cycles), and outstanding flexibility (200 bending cycles), which could continuously light an LED even under mechanical deformations. Thus, this work provides new insights into the structural engineering of fiber electrodes, showing great promise for boosting the battery performances in actual wearable applications to new levels.