Amorphous Cobalt Hydroxide with Superior Pseudocapacitive Performance

Abstract

Cobalt hydroxide (Co(OH)2) has received extensive attention for its exceptional splendid electrical properties as a promising supercapacitor electrode material. Co(OH)2 study so far prefers to crystal instead of amorphous, in spite of amorphous impressive electrochemical properties including the ability to improve the electrochemical efficiency based on the disorder structure. The amorphous Co(OH)2 nanostructures with excellent electrochemical behaviors were successfully synthesized by a simple and green electrochemistry. Our as-prepared Co(OH)2 electrode exhibited ultrahigh capacitance of 1094 F g(-1) and super long cycle life of 95% retention over 8000 cycle numbers at a nominal 100 mV s(-1) scan rate. The united pseudo-capacitive performances of the amorphous Co(OH)2 nanostructures in electrochemical capacitors are totally comparable to those of the crystalline Co(OH)2 nanomaterials. These findings actually open a door to applications of amorphous nanomaterials in the field of energy storage as superior electrochemical pseudocapacitors materials.

A Simple Electrochemical Route to Access Amorphous Mixed‐Metal Hydroxides for Supercapacitor Electrode Materials

“…[ 21,22 ] However, the ternary amorphous phase exhibits the best long-term cycling stability among all amorphous metal hydroxides in our studies. Therefore, these experimental results suggest that an amorphous phase with mixed metals seems to be good for the longterm cycling stability.…”

“…It has been shown that the integrated electrochemical performance of amorphous metal hydroxides, such as Ni(OH) 2 and Co(OH) 2 , is commensurate with the crystallinity of the materials in the supercapacitor. [ 21,22 ] Considering the excellent electrochemical performance of crystalline mixed-metal hydroxide electrodes several benefi ts should be realizable by the development of amorphous mixed-metal hydroxide electrodes. However, commonly used methods for the production of amorphous oxide materials are not typically amenable to amorphous mixed-metal hydroxides.…”

Tailoring the shape of amorphous nanomaterials: recent developments and applications

“…The reaction process was facile and efficient, simply involving heating the reactants under reflux in ethylene glycol for 1 h. Yang and colleagues [76][77][78] have also contributed to the synthesis of amorphous hydroxide materials by preparing flower-like spherical nanostructures using a unique electrochemical technique that is simple, green and inexpensive. These spheres and hollow structures are interesting candidates for use in energy storage [94].…”

“…The large number of under-coordinated atoms (good electron acceptors) and reactive sites at the surface means that amorphous materials also have the advantage over crystalline ones in their contact with the electrolyte and active substances (electron donors), which favors electrochemical processes. In regard to the merits discussed above, amorphous nanomaterials have already demonstrated their superior performance over bulk crystalline materials in various electrochemical applications, including lithium-and/or sodium-ion batteries [51,62,66,71,79,84,[96][97][98][99][100], super-or pseudo-capacitors [77,78,83], electrochemical water splitting [59] and sensors [72,81]. The amorphous CoSnO 3 @C nanoboxes reported by Wang et al [79] showed high initial discharge and charge capacities of around 1,410 and 480 mA h g −1 , respectively, as revealed in Fig.…”

“…The integrated electrochemical performance of the amorphou s Ni(OH) 2 nanospheres is comparable with that of crystalline Ni(OH) 2 materials in supercapacitors. The same group also synthesized amorphous Co(OH) 2 flower-like nanospheres by a similar method [78]. The as-prepared Co(OH) 2 electrode exhibited an ultrahigh capacitance of 1,094 F g −1 and extremely long cycle life with 95% charge retention after 8,000 cycles at a nominal scan rate of 100 mV s −1 .…”