Branched nanosheets-interlaced structure of Co 2+ /Co 3+ -doped Ni(OH) 2 originating from Ni 3 (NO 3 ) 2 (OH) 4 template

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Branched nanosheets-interlaced structure of Co2+/ Co3+-doped Ni(OH)2 originating from Ni3(NO3)2(OH)4 template with significantly boosted electrochemical performance Jing Wang1, Jing Li1, Yuanyuan Liu1, Meiri Wang1, and Hongtao Cui1,* 1

School of Chemistry and Chemical Engineering, Yantai University, Yantai 264005, China

Received: 15 August 2020

ABSTRACT

Accepted: 13 October 2020

The cycling stability of electrode materials is a key for Faraday supercapacitors (FSs), especially the structure-unstable Ni(OH)2. There exist various strategies for stabilizing the structure of Ni(OH)2 such as cobalt ions doping and mechanical support from substrate. However, these strategies have their own disadvantages. On the other hand, the combination of two or more strategies has the serious issues in materials synthesis. In this work, a branched nanosheetsinterlaced structure of Co2?/Co3?-doped Ni(OH)2 is built by a method of precursor template, which effectively applies two strategies including ions doping and self-supportive structure. Due to the synergistic contribution of these two strategies, the cycling stability of as-prepared material is significantly enhanced. This material also presents excellent high-rate capacity, and the as-assembled asymmetric supercapacitors (ASCs) show both high energy and power densities. These results prove that the effective combination of ions doping and selfsupportive structure strategies is a promising route for the preparation of Ni(OH)2-based electrode materials with high performance.

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Springer Science+Business

Media, LLC, part of Springer Nature 2020

Introduction Nickel-based materials are a category of intensively investigated battery-type electrode materials for application in FSs. These materials include Ni(OH)2, nickel-based double-layered hydroxides, nickelbased sulfide, and selenides [1–4]. Ni(OH)2 has been Handling Editor: Yaroslava Yingling.

Address correspondence to E-mail: [email protected]

https://doi.org/10.1007/s10853-020-05446-0

considered as an important electrode material for application in FSs because of its high theoretical capacity [5]. Although Ni(OH)2 has satisfied electrochemical performance in alkaline batteries, it presents poor high-rate performance and cycling stability when it is transplanted directly to FSs. It is widely accepted that the poor performance of Ni(OH)2 in FSs originates from its low ionic/electronic conductivities

J Mater Sci

and low structural instability [6]. To solve these two issues, nanoengineering the structure of Ni(OH)2 has been the only feasible strategy so far [7, 8]. During the charge–discharge cycles, the layerstructured Ni(OH)2 undergoes the following reversible redox reaction in alkaline electrolyte solution: Ni(OH)2 ? OH- $ NiOOH ? H2O ? e- [9]. The cycling phase transformation between Ni(OH)2 and NiOOH results in the cycling volumetric swell and shrink due to their different densities. Based on the theoretical density data [10, 11], it is known that the volumetric change fraction of material because of the phase transf

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