Amorphous cobalt hydroxysulfide nanosheets with regulated electronic structure for high-performance electrochemical ener
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Published online 28 June 2020 | https://doi.org/10.1007/s40843-020-1362-1
Amorphous cobalt hydroxysulfide nanosheets with regulated electronic structure for high-performance electrochemical energy storage 1,2
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Kun Xiang , Xuewan Wang , Wen You , Zhikun Peng , Jing-Li Luo ABSTRACT Pseudocapacitors with high power density, longterm durability, as well as reliable safety, play a key role in energy conversion and storage. Designing electrode materials combing the features of high specific capacitance, excellent rate performance, and outstanding mechanical stability is still a challenge. Herein, a facile partial sulfurization strategy has been developed to modulate the electronic structure and crystalline texture of cobalt hydroxide nanosheets (denoted as Co(OH)2) at room temperature. The resultant cobalt hydroxysulfide nanosheet (denoted as CoSOH) electrode with abundant low-valence cobalt species and amorphous struc−1 ture, exhibits a high specific capacitance of 2110 F g at −1 1 A g with an excellent capability retention rate of 92.1% at −1 10 A g , which is much larger than that of Co(OH)2 precursor −1 −1 −1 (916 F g at 1 A g and 80% retention at 10 A g ). Furthermore, the fabricated asymmetric supercapacitor device constructed with CoSOH and active carbon displays a −1 considerable high energy density of 44.9 W h kg at a power −1 density of 400 W kg , and exceptional stability after 8000 cycles. Keywords: hydroxysulfide, amorphous, supercapacitor, electronic structure, nanosheet
INTRODUCTION High-efficiency energy storage devices play a vital role in alleviating the global energy crisis and environmental pollution. Supercapacitor with high power density, good operational safety and long lifespan, is particularly desirable for potential applications where a large amount of
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and Xian-Zhu Fu
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energy needs to be either quickly stored or delivered, such as electric vehicles, portable electronic devices, subway systems and so on [1–6]. Generally, supercapacitors can be classified into two types on the basis of energy storage principle: electrochemical double layer capacitors (EDLCs) and pseudocapacitors. The EDLC has high power density and long cycle stability due to the rapid charge transfer during the charge and discharge process, resulting from the physically adsorbed ions on the electrode. However, the low charge storage capacity of EDLC seriously limits the practical application. In the case of pseudocapacitor, the presence of Faradaic redox reaction between the electrode surface and electrolyte as illustrated in battery endows the pseudocapacitor with merits of superior energy density, which makes it have received much more attention than EDLC [7]. To optimize the electrochemical properties of pseudocapacitor, design and fabrication of advanced electrode materials are the key factor. Up to date, a variety of electrode materials, such as metal oxides/hydroxides [8–10], phosphides [11], chalcogenides [12], nitrides [13], borides [14], polymers [15] and heteroatom-doped carbon [16], have been devel
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