Toward high-performance and flexible all-solid-state micro-supercapacitors: MOF bulk vs. MOF nanosheets

Due to the advantages of ultrahigh power density, long lifespan and easy integration with wearable and microscale electronics, micro-supercapacitors (MSCs) have attracted great interest in recent years. However, new high-performance electrode materials for such micro-electrochemical energy storage devices require deep excavation. Herein, we precisely synthesized a new 3D bulk MOF and new 2D ultrathin MOF nanosheets with a thickness of less than 10 nm, and utilized them as high-capacitance microelectrode materials for sophisticated all-solid-state MSC devices respectively. Notably, the MSCs based on MOF nanosheets displayed a high areal capacitance of 28.3 mF·cm−2, and a volumetric capacitance of 15.7 F·cm−3 at 0.2 mA·cm−2. Especially, our MSCs exhibited remarkable energy density of 8.7 mWh·cm−3 at a power density of 110.3 mW·cm−3, and excellent cycling lifespans with retention of 96.0% after 10,000 cycles, and all performances are better than the MSCs based on MOF bulks. This work provides a new way to further explore the inherent advantages of MOFs and stimulates the synthesis of advanced MOFs materials for application in microscale energy storage.