Recent progress and future perspectives for the development of micro-supercapacitors for portable/wearable electronics applications

The rapid development of ultra-thin, lightweight, and flexible energy storage systems for portable/wearable electronic devices has been significantly stimulated due to an increase in the demand for flexible and wearable electronic systems in various sectors. Various energy storage systems such as batteries and supercapacitors (SCs) are widely used in portable/wearable electronics applications, but SCs have attracted considerable attention due to their long cyclability, high power density, and fast charge-discharge rate. Moreover, flexible micro-supercapacitors (MSCs) with their unique merits like flexibility, their light weight, and shape conformability have fulfilled the current requirement for portable and flexible wearable electronics systems in energy storage markets. Further, in-plane interdigitated electrode designs based on various material systems such as graphene, carbon nanotubes, and transition metal oxides and sulfides for MSCs provide the flexibility and ease with which to integrate them with portable and flexible wearable electronics systems. In this review, various material systems, active electrode fabrication techniques, integration and applications of flexible MSCs in portable/wearable electronics systems along with their current challenges and future perspectives have been comprehensively analyzed.