CoNi₂ S₄ Nanoparticle/Carbon Nanotube Sponge Cathode with Ultrahigh Capacitance for Highly Compressible Asymmetric...

Compared with other flexible energy-storage devices, the design and construction of the compressible energy-storage devices face more difficulty because they must accommodate large strain and shape deformations. In the present work, CoNi₂ S₄ nanoparticles/3D porous carbon nanotube (CNT) sponge cathode with highly compressible property and excellent capacitance is prepared by electrodepositing CoNi₂ S₄ on CNT sponge, in which CoNi₂ S₄ nanoparticles with size among 10-15 nm are uniformly anchored on CNT, causing the cathode to show a high compression property and gives high specific capacitance of 1530 F g^-1 . Meanwhile, Fe₂ O₃ /CNT sponge anode with specific capacitance of 460 F g^-1 in a prolonged voltage window is also prepared by electrodepositing Fe₂ O₃ nanosheets on CNT sponge. An asymmetric supercapacitor (CoNi₂ S₄ /CNT//Fe₂ O₃ /CNT) is assembled by using CoNi₂ S₄ /CNT sponge as positive electrode and Fe₂ O₃ /CNT sponge as negative electrode in 2 m KOH solution. It exhibits excellent energy density of up to 50 Wh kg^-1 at a power density of 847 W kg^-1 and excellent cycling stability at high compression. Even at a strain of 85%, about 75% of the initial capacitance is retained after 10 000 consecutive cycles. The CoNi₂ S₄ /CNT//Fe₂ O₃ /CNT device is a promising candidate for flexible energy devices due to its excellent compressibility and high energy density.