Design Principles for Manipulating Electrochemical Interfaces in Solid-State Supercapacitors for Wearable Applications

Abstract

Storage and delivery of electrical energy form the heart of the rapidly expanding domain of wearable electronics, with applications ranging from point-of-care medical diagnostics to Internet-of-Things (IoT). Solid-state, electrochemical, doublelayer-based supercapacitive energy storage devices, with high power density, ability to interface with intermittent energy harvesters, long lifetime, and cyclability, offer attractive possibilities for self-sustaining power sources in such portable applications. This mini-review highlights the need for a multipronged approach involving (a) development of materials for electrodes and electrolyte and (b) utilizing the right kind of design principles, processing techniques, and fabrication approaches to (c) achieve seamless all-solid electrode−electrolyte interfaces providing (d) facile integration onto wearable platforms. Importantly, a comprehensive figure-of-merit (FOM) accounting for both the electrochemical performance and the mechanical robustness of flexible supercapacitors is proposed. This is expected to facilitate uniform comparison of performance across devices differing in their design approaches and materials. Finally, new operando and in situ techniques for probing and understanding such all-solid interfaces are presented. The iterative cycle of scientific understanding, furthering technological advancements, seeks to provide future directions for achieving mechanically robust supercapacitors with enhanced energy density and power density for wearable and portable applications.

3D Printed Supercapacitor: Techniques, Materials, Designs, and Applications

“…As promising candidates for supplying power, [ 175 ] SCs are supposed to possess high properties, as well as provide smart responsive functions, which can response to the variations from either the external circumstance or equipment themselves. [ 176 ] Intelligent functions, including self‐healing, [ 177 ] stretchability, [ 178 ] and shape memory [ 179 ] have been introduced into stimuli‐responsive equipment. [ 180 ]…”

Recent advances in solid‐state supercapacitors: From emerging materials to advanced applications

“…It is worth mentioning that the reported values in the literature are based on the active mass or the volume of electrodes instead of the total device mass or volume, as specified for commercial devices. Hence, SSCs are promising candidates for next-generation energy storage applications, particularly portable and wearable electronics, implementable medical devices, Internet of Things (IoT), 36 and smart textiles. 37,38 Several good reviews have been reported in the literature [37][38][39][40][41][42][43][44][45][46][47][48] ; however, these studies focus particularly on flexible SSCs, instead of giving the complete picture of the technology.…”

“…It is worth mentioning that the reported values in the literature are based on the active mass or the volume of electrodes instead of the total device mass or volume, as specified for commercial devices. Hence, SSCs are promising candidates for next‐generation energy storage applications, particularly portable and wearable electronics, implementable medical devices, Internet of Things (IoT), 36 and smart textiles 37,38 …”

Employing Redox‐Active Additives for Enhanced Charge Polarization and Twofold Higher Energy Density in Supercapacitor

“…[5,6] At a fundamental level, such stringent requirements translate to the holy grail of energy storage: high energy density and power density without compromising the lifetime. [7][8][9][10] Electrochemical double layer-based supercapacitors (EDLCs) operating on the basis of non-Faradic electrostatic charge build-up at the electrode-electrolyte interface and therefore exhibits high-rate capability, short relaxation time constant (τ), long lifetime, and high-power density compared to their Faradic counterparts. However, the low energy density and selfdischarge behavior of such systems severely restricts their usability in tandem with renewables.…”