One-dimensional lithium ion capacitor in core-shell wire shape construction for wearable applications

Abstract

Flexible wire shaped energy storage devices grab tremendous attention due to the emergence of wearable and portable electronics markets. Herein, the design principles (fabrication and assembly process) and device performance (electrochemical performance in static and bending conditions) of the lithium-ion capacitor in core-shell wire topology are described. The wire shaped lithium-ion capacitor (WSLIC) assembly consists of multi-walled carbon nanotubes coated carbon fibers (CNT-CFs) core electrode, polymer electrolytes, lithium titanium oxide (LTO) composite outer electrode, helically wrapped current collectors and protective outer covering. This 2.7 V device exhibits a maximum energy density of 1.85 mWh/cm3, comparable to the energy densities of other reported wire-shaped batteries. WSLIC exhibits excellent safety at a high temperature of 60 °C due to plasticized polymer electrolytes of non-volatile composition, challenges may arise if flammable organic electrolytes were employed. The device also exhibits excellent electrochemical performance under different deforming and repeated bending conditions, attributed to unique properties of CNT-CF core electrode and helically wrapped current collectors. Therefore, WSLIC has excellent potential for implementation in wearable applications.