Few-layer graphene via electrochemically cathodic exfoliation for micro-supercapacitors

ZHOU Feng1 TIAN Lijun2 GAO Lei2 WU Zhongshuai1

(1.Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, China 116023)
(2.Great Scientific Research Institute, Datong Coal Mine Group Co., Ltd., Datong, Shanxi, China 037003)

【Abstract】The use of graphite as a raw material for efficient, green, and low-cost preparation of few-layer graphene is of great significance for the large-scale production and application of graphene. However, the efficient exfoliation of graphite to graphene without use of strong oxidants and acids is still a great challenge. Herein, we developed a green and scalable aqueous-based electrochemical cathodic exfoliation approach, in which graphite as a negative electrode can be electrochemically charged and expanded in an electrolyte of 6 mol·L−1 potassium hydroxide (KOH under high current density and exfoliated efficiently into few-layer graphene sheets with the aid of sonication. The obtained few-layer graphene has low oxygen content [1.27% (mass)], few defects (ID/IG < 0.035), a plate size of 5–10 μm, high conductivity of >200 S·cm−1, and good solution additivity. Moreover, such electrochemically exfoliated graphene (EG) nanosheets are readily used to produce highly solution-processable ink (1 mg·mL−1) in ethanol without the need of any surfactants, allowing for the production of large-area EG microelectrodes for EG based micro-supercapacitors (EG-MSCs). Furthermore, the as-fabricated aqueous EG-MSCs show ultrahigh scan rate of 100 000 mV·s−1 and short time constant of only 24 ms. More importantly, using ionic liquids-based electrolyte of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide with bis(trifluoromethanesulfonyl)imide lithium sal (EMIMTFSI/LiTFSI), EG-MSCs can work at a high voltage of 4.0 V, and show high volumetric energy density of 113 mW·h·cm−3, outperforming the most reported MSCs (< 50 mW·h·cm−3).

【Keywords】 electrochemical; cathode exfoliation; graphene; graphite; micro-supercapacitors;

【DOI】

【Funds】 National Natural Science Foundation of China (51872283, 21805273) Graphene Applied Technology Research Program, Datong Coal Mine Group Co., Ltd. National Key R&D Program of China (2016YFA0200200) Program of Dalian National Laboratory For Clean Energy, CAS (DNL180310, DNL180308, DNL201912, DNL201915) DICP (DICP ZZBS201708, DICP ZZB201802) PhD Start-Up Foundation of Liaoning Province (2019-BS-246)

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This Article

ISSN:0438-1157

CN: 11-1946/TQ

Vol 71, No. 06, Pages 2724-2734+2920

June 2020

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Article Outline

Abstract

  • Introduction
  • 1 Analysis of exfoliation mechanism
  • 2 Experimental section
  • 3 Results and discussion
  • 4 Conclusion
  • References