  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.
