Temperature Influence on Electrical Properties of Carbon Nanotubes Modified Solid Electrolyte-Based Structural Supercapacitor

In the present work, we report on structural supercapacitors which are based on NASICON-type solid electrolyte Li_1.4Al_0.4Ti_1.6(PO₄)₃ (LATP). The nanostructured electrodes incorporate single-wall carbon nanotubes (SWCNTs) mixed with the LATP electrolyte. The complete energy storage devices are manufactured in a sandwich structure consisting of two nanostructured electrode layers which are separated by a pure LATP layer. The as-prepared specimens are embedded in composite materials with Airstone 880/886H epoxy resin as matrix. Their electrical properties are characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). At ambient temperature, the addition of 6.5 wt. % SWCNTs results in a distinct improvement by reducing the total resistance of the embedded devices and enhances the capacitance from 0.025 mF g⁻¹ to 3.160 mF g⁻¹ at a scan rate of 5 mV s⁻¹. Electrical measurements of two types of specimens are then applied under different temperatures from ambient temperature to 80 °C. It is observed that the equivalent series resistance (ESR) of device with SWCNTs decreases greatly and capacitance increases comparing with the device without SWCNTs. As a conclusion, the structural supercapacitors acquire excellent performance through high efficient double layer effects realized by nanostructured electrode/electrolyte interphase (large surface electrode areas).