Engineering Ultrathin Co(OH)₂ Nanosheets on Dandelion–like CuCo₂O₄ Microspheres for Binder‐Free Supercapacitors

Abstract

A stepwise synthetic approach is developed for large‐scale growth of three‐dimensional branched CuCo2O4@Co(OH)2 core−shell structures on nickel foam as a high‐performance supercapacitor electrode. The synthesis procedure involves the hydrothermal treatment of a bimetallic (Cu, Co) hydroxide precursor on a Ni foam substrate and subsequent thermal transformation to dandelion‐like CuCo2O4 microspheres. The Co(OH)2 shells are then coated onto the branches of as‐prepared CuCo2O4 microspheres by using an electrodeposition method. The loading of Co(OH)2 nanosheets is dependent on the electrodeposition time in Co(NO3)2 solution. The resulting unique core−shell structure promotes fast electron and ion transport, large electroactive surface area, and excellent structural stability. As a result, superior electrochemical performance is achieved with a specific capacitance of 424 F g−1 at a current density of 0.5 A g −1, and good cycling performance (85.8 % retention after 10000 cycles), suggesting its promising application in supercapacitors. These good electrochemical properties could be attributed to the synergic interaction of each component. In addition, the asymmetric supercapacitor exhibits an energy density of 19.2 Wh kg−1 at a power density of 350 W kg−1.

β‐Co(OH)2 Nanosheets: A Superior Pseudocapacitive Electrode for High‐Energy Supercapacitors

“…Recently, β‐Co(OH) 2 has been reported as a promising pseudocapacitor electrode material with various morphological features in the three‐electrode assembly . Layered β‐Co(OH) 2 has a high theoretical specific capacitance, but the lower redox potential hampers its potential use.…”

“…[5,34] Recently, b-Co(OH) 2 has been reporteda sapromisingp seudocapacitor electrode material with various morphological features in the three-electrode assembly. [35][36][37][38][39][40][41][42][43] Layered b-Co(OH) 2 has ahigh theoretical specific capacitance, but the lower redox potentialh ampers its potential use. As mentioned earlier,t he fabrication of asymmetrics upercapacitors with AC is one of the easiest approaches to achieve high energy charges torage devices.A ccordingly,t his b-Co(OH) 2 k AC configurationi sc apable of operating in aw ide potential window (> 1.2 V), and hence,s ignificant enhancement in the energy density is anticipated.…”

Self-Supported Sisal-like CuCo2O4@Ni(OH)2Core–Shell Composites Grown on Ni Foam for High-Performance All-Solid State Supercapacitors

“…Among these materials, a CuCo 2 O 4 @ Co(OH) 2 electrode had been shown to achieve a fairish specific capacitance of 424 F g −1 at 0.5 A g −1 , and outstanding cycling stability with 85.8% retention after 10 000 cycles. 22 A mesoporous CuCo 2 O 4 @MnO 2 electrode delivered a decent capacitance of 850 F g −1 at 1 A g −1 and maintained 94.2% retention over 3000 cycles. 23 A lamellar Co 3 O 4 @Ni(OH) 2 electrode obtained an admirable electrochemical performance that its capacitance reached 1306 F g −1 at 1.2 A g −1 and it also holds ∼90% capacitance after 3000 cycles.…”

One-step sulfuration synthesis of hierarchical NiCo2S4@NiCo2S4 nanotube/nanosheet arrays on carbon cloth as advanced electrodes for high-performance flexible solid-state hybrid supercapacitors

“…[4][5][6] Hybrid supercapacitors (HSCs), which are typically comprised of a faradaic battery-type electrode and an electrical double-layer capacitive (EDLC) electrode as the energy and power sources, respectively, have emerged as one of the most promising candidates, since they can combine the merits of both electrodes with improved energy density and enlarged output voltage window. [7][8][9] As the key component of HSC devices, various battery-type electrode materials, including transition metal oxides (Co 3 O 4 , NiCo 2 O 4 , CuCo 2 O 4 ), [10][11][12][13][14][15][16] hydroxides (Ni(OH) 2 , Ni-Mn LDH, Ni-Co LDH) and their composites, [17][18][19][20] have been widely explored owing to their high theoretical capacity, natural abundance and low cost. However, the typically low conductivity of these materials has greatly restricted their improvement of rate capability and durability.…”