Electrochemical Deposition Enables Freestanding CoNi Layered Double Hydroxide/MnOX Electrode with Enhanced Electrochemical Properties for Asymmetric Supercapacitors

A carbon fiber paper (CFP)-supported CoNi layered double hydroxide (LDH)/MnOX or MnOX nanomaterial is prepared by a simple and effective two-step electrochemical deposition process. The binder-free CoNi LDH/MnOX/CFP exhibits enhanced electrochemical properties than that of MnOX/CFP, with a maximum capacitance of 1460 F g(-1) at 1 A g(-1), and an excellent capacitance retention of 87% at 4 A g(-1). Notably, the CoNi LDH/MnOX composite exhibits a remarkable cycling stability with 82% capacitance retention over 20 000 cycles even at a high current density of 32 A g(-1). The outstanding electrochemical performance of the CoNi LDH/MnOX/CFP can contribute to the synergistic effects of the freestanding electrode with improved electrical conductivity, electrochemical activity, and material utilization than pure MnOX. Furthermore, an asymmetric supercapacitor (ASC) fabricated with a CoNi LDH/MnOX/CFP positive electrode and active carbon (AC)/CFP negative electrode displays a high energy density of 28.1 Wh kg(-1) at a power density of 400 W kg(-1). These encouraging results indicate that the low-cost CoNi LDH/MnOX/CFP composite shows great potential for high-performance energy storage applications.