Co(OH)2 Nanosheets Coupled With CNT Arrays Grown on Ni Mesh for High-Rate Asymmetric Supercapacitors with Excellent Capacitive Behavior

Abstract

Aqueous asymmetric supercapacitors (ASCs) have been recently designed to improve energy storage density due to their large operation voltage and low cost. However, most reported ASCs (particularly for cobalt/nickel-based materials) always deviate from ideal capacitive behavior. In the present work, Co(OH)2 nanosheets arrays (NAs) are directly loaded on Ni mesh (Co(OH)2 NAs@Ni) via electrodeposition, while coral-like carbon nanotubes (CNTs) are successfully grown on Ni mesh (CNTs@Ni) through chemical vapor deposition (CVD). Using Co(OH)2 NAs@Ni as positive electrode and CNTs@Ni as negative electrode, a novel ASC has been successfully fabricated. Due to the merits of in-situ growth for active materials, the highly-conductive Ni mesh current collector and the positive synergistic effect between the positive and negative electrodes, our Co(OH)2 NAs@Ni//CNTs@Ni ASC exhibits excellent capacitive behavior, which is quite similar to RuO2·xH2O-based supercapacitors. Notably, even when the scan rate rise up to 1Vs−1, the CV curve of the ASC device can still retains an inspiring quasi-rectangle shape from 0 to 1.5V. Furthermore, the ASC demonstrates a high energy density of 19Whkg−1 at 113Wkg−1. More impressively, an ultra-high power density of 45kWkg−1 is achieved at an energy density of 12.5Whkg−1. Besides, the Co(OH)2 NAs@Ni//CNTs@Ni ASC also presents long-term cycling stability (with only 4% capacitance loss after 7000 cycles).