Flexible Nb₄N₅/rGO electrode for high-performance solid state supercapacitors

Flexible supercapacitors (SCs) are desirable for elastic and clothing electronic products owning to their considerable safety, high foldability and outstanding power density. Herein, multilayered films composed of alternating mesoporous Nb4N5 nanobelts and rGO nanosheets (Nb₄N₅/rGO) are designed and fabricated exhibiting good flexibility. The folding Nb₄N₅/rGO film electrode reveals an areal capacitance of 141 mF cm^-2 (at 1 mA cm^-2) along with remarkable cycling stability (the capacitance retention is 90% after 6,000 cycles). The flexible SCs devices were constructed by interlayer couple films of Nb₄N₅/rGO electrodes with PVA/H₂SO₄ gel as the electrolyte, which exhibited huge volumetric capacitance of 19 F cm^-3 (at 0.1 A cm^-3) and a considerable energy density of 0.98 mW h cm^-3 with a power density of 0.029 W cm^-3. Additionally, the as-obtained folding devices bode outstanding cycling stability with capacitance retention of 89% after 4,000 cycles measured by cyclic voltammetry method (at 100 mV s^-1). Above results about niobium nitride based flexible electrodes and devices exploit a platform for wearable electronics and flexible devices.