Ultrahigh Energy Density and Ultrafast Response in Symmetric Microsupercapacitors with 3D Bicontinuous Pseudocapacitance

Achieving a high storage capability while maintaining good rate performance using symmetric microsupercapacitors (MSCs) remains challenging. Herein, a 3D symmetric MSC based on interdigitated 3D bicontinuous pseudocapacitive electrodes is proposed to simultaneously attain ultrahigh energy density and ultrafast response. The 3D electrodes comprise electrolytically active MnO2 layers conformally coated onto a 3D periodic porous Ni current collector. In this architecture, the low conductivity of MnO2 can be compensated by efficient charge transport and facile charge transfer without compromising its high capacitance. The 3D MSC with a 1-V window exhibits an ultrahigh volumetric energy density of 15.8 mWh cm-3 with a high power density of 4.95 W cm-3, outperforming all previously reported MnO2-based symmetric MSCs. Benefitting from its ultrafast response, the 3D MSC exhibits superiority in terms of the phase angle (-66 degrees), areal capacitance (1400 mu F cm-2), and time constant (0.6 ms) at an alternating-current (AC) frequency of 120 Hz. By using the 3D MSC as a line-filtering capacitor in a real circuit, the AC signal is effectively smoothed with small residual ripples (approximate to 1.35 mV). Additionally, the device achieves excellent performance in an all-solid-state form. A symmetric 3D microsupercapacitor with ultrahigh energy density and ultrafast response is fabricated. The electrodes comprise a 3D architectured Ni current collector conformally coated with pseudocapacitive MnO2 layers. The device exhibited exceptional volumetric energy density and volumetric power density, outperforming most previously reported oxide-based symmetric microsupercapacitors. Additionally, the ultrafast kinetics of the device resulted in excellent AC line-filtering performance. image