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Currently, the application of supercapacitors (SCs) in portable electronic devices and vehicles is limited by their low energy density. Developing high-energy density SCs without sacrificing their advantages, such as their long-term stability and high power density, has thus become an increasing demand but a major challenge. This demand has motivated tremendous efforts, especially towards discovering and optimizing the architecture of novel electrode materials. To this end, we herein report the design, synthesis, and SC application of a new family of two-dimensional (2D) nanoplatelets, i.e., a transition-metal hydroxymethylate complex (Nix Co1–x (OH)(OCH3)). Bimetallic nanoplatelets were synthesized via a cost-effective approach involving a one-step solvothermal procedure. We for the first time tuned the metal composition of these 2D nanoplatelets over the entire molar-fraction range (0–1.0). Tuning the molar ratio of Ni/Co allowed us to optimize the structures and physicochemical properties of the nanoplatelets for SC applications. When tested in a half cell, SC electrodes using the nanoplatelets exhibited high electrochemical performance with a specific capacitance as high as 1, 415 F·g–1 and a 96.1% retention of the initial capacitance over 5, 000 cycles. We exploited the novel 2D nanoplatelets as cathode materials to assemble a hybrid SC for full-cell tests. The resulting SCs operated in a wide potential window of 0–1.7 V, exhibited a high energy density over 50 Wh·kg–1, and sustained their performance over 10, 000 charge–discharge cycles. The results suggest that the novel 2D nanoplatelets are promising alternative materials for the development of high-energy density SCs.

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Publication history

Received: 26 October 2016
Revised: 02 February 2017
Accepted: 05 February 2017
Published: 04 April 2017
Issue date: September 2017

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© Tsinghua University Press and Springer-Verlag Berlin Heidelberg 2017

Acknowledgements

Acknowledgements

This work was supported by China postdoctoral science foundation (No. 2015M580299), Fundamental Research Funds for the Central Universities (Nos. 1514011 and 222201718003), and National Natural Science Foundation of China (No. 21576082). FP7 Staff-exchange for K. K. Z. and Z. T. L. under the ELECTRONANOMAT program (No. PIRSES-GA-2012-318990) sponsored by the Marie-Curie Act program of EU is acknowledged. K. K. Z. and Z. T. L. acknowledge the Danish Agency for Science, Technology and Innovation (No. 5132-00053B) for supporting collaboration with DTU. Q. J. C. acknowledges the Danish Council for Independent Research DFF-FTP (No. 12-127447) and the Danish Agency for Science, Technology and Innovation (No. 5132-00053B) for the financial support. We thank Prof. Xinhua Zhong for helpful discussions.

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Email: nanores@tup.tsinghua.edu.cn

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