Flexible interdigitated symmetric solid-state micro-supercapacitors with higher energy density for wearable electronics

Planar interdigitated solid-state supercapacitors are one of the most promising energy storage devices as they offer the merit of fast ionic transportation with minimal charge transfer resistance due to the narrow gap between the interdigitated isolated electrode fingers. This study focuses on fabricating flexible symmetric solid-state supercapacitor devices with high energy and power densities. Specifically, a symmetric SnO2‖PVA-LiClO4‖SnO2 solid-state supercapacitor (SSC) device was fabricated using the electron beam evaporation (e-beam) technique on thin, flexible electrodes in interdigitated (ISSC) and stacked (SSSC) configurations and their electrochemical performances were compared. The ISSC exhibiting pseudo-capacitive behavior achieved a maximum volumetric capacitance of 439.5 F cm−3 at a scan rate of 5 mV S−1. Quantitative calculation of the device's charge storage dynamics reveals that the diffusion-limited Lithium insertion processes predominantly contribute to the capacitance of ISSC. Comparatively, the ISSC outperformed the SSSC with a diffusion coefficient of 2.55 × 10−13 m2s−1 and ac conductivity of 2.2 × 10−2 S m−1, demonstrating excellent energy density and power density values. Furthermore, the ISSC with no adverse effect on its capacitance even when bent at various angles suggesting its suitability for flexible wearable electronic devices.