  Portable miniaturized energy storage micro-supercapacitor has engrossed
significant attention due to its power source and energy storage capacity,
replacing batteries in ultra-small electronic devices. Fabrication with porous
and 2D graphitic nanomaterials with high conductivity and surface area signify
high performance of micro-supercapacitor. In order to satisfy the fast-growing
energy demands for the next-generation, we report performance and design of a
2D heterostructure of EDLC (g-C$_3$N$_4$) & pseudocapacitive (FeNi$_3$)
resulting low ionic diffusion path and prominent charge storage based on their
synergic functionalities. This heterostructure system shows an enhanced quantum
capacitance (38% enhancement) due to delocalized states near Fermi level.
Having achieved the areal capacitance of 19.21 mFcm$^{-2}$, capacitive
retention (94%), enhanced power density (17 fold) having ultrahigh energy
density of 0.30 Wh.cm$^{-3}$ and stability of the material even without any
obvious degradation after 1000 cycles, this smart heterostructure acts as a new
platform for designing high-performance in-plane micro-supercapacitor.
