3D CNTs/graphene network conductive substrate supported MOFs-derived CoZnNiS nanosheet arrays for ultra-high volumetric/gravimetric energy density hybrid supercapacitor

Abstract With the increasing demand for miniaturization and portable energy storage system, it is an urgent necessary that developing high volumetric energy density supercapacitors with small volumes. Herein, an integrated self-supporting CoZnNiS@CNTs/rGO composite film electrode with the thickness of about 6 μm was designed. In the unique structure, porous CNTs/rGO film is served as conductive substrate to support the CoZn-MOFs derived vertically oriented two-dimensional CoZnNiS nanoarrays. The self-supporting film endows the electrode a high volumetric mass density of 1.28 g cm-3 and superior electron-ion transport channel, which displays a maximum specific capacitance of 1349.2 F g-1 as well as high volumetric capacity of 1727.0 F cm-3 at 1 A g-1. Besides, a porous film of pure carbon materials (carbon spheres integrated graphene) was designed and used as the negative electrode in supercapacitor. When assembled a hybrid supercapacitor based on the above two self-supporting electrodes, the device delivers up an ultra-high volumetric/gravimetric energy density of 65.2 W h L-1 (60.4 W h kg-1) at a power density of 1308 W L-1 (1200 W kg-1). Moreover, the asymmetric supercapacitor also displays an ultra-long lifetime with 90.6% retention after 10,000 cycles. These outstanding performances make the CoZnNiS@CNTs/rGO electrode could be a promising candidate for next-generation high volumetric/gravimetric energy density supercapacitors, especially in the limited space.