Amorphous Ni–Mn–O microspheres with high energy density and ultralong-term stability up to 100, 000 cycles for aqueous pseudo-capacitors

A novel freestanding electrode of porous and amorphous NiMn 1.57 O 4.13 microspheres is prepared for aqueous pseudo-capacitor. The NiMn 1.57 O 4.13 microsphere has both cathodic site and anodic site so that it can be easily assembled as symmetric pseudo-capacitor, showing a great outlook for application. The SPC presents a superior stability and ability to withstand current fluctuations, which exhibits a high energy density of 122.8 Wh kg −1 with a retention of 106.1% at 5 A g −1 after 100,000 cycles. Moreover, the energy density is as high as 44.3 Wh kg −1 even at the ultra-high power density of 18,750.0 W kg −1 , presenting an excellent charge/discharge rate.