A compact aqueous K-ion Micro-battery by a Self-shrinkage assembly strategy

Micro-batteries are promising power sources to drive miniaturized or portable electronic devices due to their higher energy density than micro-supercapacitors. Current micro-batteries still suffer from relatively large footprint and unsatisfactory areal electrochemical performance caused by loose electrode structure. Here, we develop a compact aqueous K-ion micro-battery through the self-shrinking of reduced graphene oxide hydrogel to realize small footprint and high areal capacity at the same time. With a volume of as small as 0.00381 cm⁻³, this micro-battery delivers the highest areal capacity (5.1 mAh cm⁻²) and energy density (4.78 mWh cm⁻²) among all reported micro-batteries. Meanwhile, this micro-battery can be prepared into different shapes and attached onto a range of animals (ants, crabs and butterflies, etc.) for wide applications.