Scalable production of graphene inks via wet-jet milling exfoliation for screen-printed micro-supercapacitors

TL;DR

This paper presents a scalable wet-jet milling method to produce graphene inks for flexible, waterproof micro-supercapacitors with high capacitance, stability, and suitability for wearable electronics.

Contribution

It introduces a cost-effective, high-throughput exfoliation process for graphene and demonstrates its application in screen-printed, flexible, and washable micro-supercapacitors.

Findings

Achieved high areal and volumetric capacitance in printed MSCs.

Demonstrated excellent cycling and mechanical stability.

Produced waterproof MSCs suitable for wearable devices.

Abstract

The miniaturization of energy storage units is pivotal for the development of next-generation portable electronic devices. Micro-supercapacitors (MSCs) hold a great potential to work as on-chip micro-power sources and energy storage units complementing batteries and energy harvester systems. The scalable production of supercapacitor materials with cost-effective and high-throughput processing methods is crucial for the widespread application of MSCs. Here, we report wet-jet milling exfoliation of graphite to scale-up the production of graphene as supercapacitor material. The formulation of aqueous/alcohol-based graphene inks allows metal-free, flexible MSCs to be screen-printed. These MSCs exhibit areal capacitance (Careal) values up to 1.324 mF cm-2 (5.296 mF cm-2 for a single electrode), corresponding to an outstanding volumetric capacitance (Cvol) of 0.490 F cm-3 (1.961 F cm-3 for a single electrode). The screen-printed MSCs can operate up to power density above 20 mW cm-2 at energy density of 0.064 uWh cm-2. The devices exhibit excellent cycling stability over charge-discharge cycling (10000 cycles), bending cycling (100 cycles at bending radius of 1 cm) and folding (up to angles of 180{\deg}). Moreover, ethylene vinyl acetate-encapsulated MSCs retain their electrochemical properties after a home-laundry cycle, providing waterproof and washable properties for prospective application in wearable electronics.