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All-solid-state flexible supercapacitor using graphene/ g-C3N4 composite capacitor electrodes Yuanduo Qu1, Xueyu Zhang1,2,*

1 2

, Wei Lu¨1, Nianjun Yang2, and Xin Jiang2,*

School of Material Science and Engineering, Changchun University of Technology, Changchun 130012, China Institute of Materials Engineering, University of Siegen, 57076 Siegen, Germany

Received: 14 May 2020

ABSTRACT

Accepted: 21 August 2020

Flexible supercapacitors using graphene have been intensively investigated due to their potential applications for wearable and smart devices. In order to avoid stacking between graphene layers, spacers such as carbon fibers and metal oxide particles are often introduced. Such composites enhance effectively the specific surface area of the electrodes and eventually supercapacitor performance. In present work, the graphene/g-C3N4 composite is fabricated and further employed as the supercapacitor electrode. The atomic interaction between C and N of g-C3N4 and O of graphene oxide during the post-reduction in graphene oxide is found to affect device performance. The devices fabricated using the graphene/g-C3N4 composite electrode exhibit a specific area capacitance of 1500 mF cm-2, and 95% of initial capacitance after 5000 cycles and a maximum energy density of 0.075 mWh cm-2. These all-solid-state flexible supercapacitors are thus promising for miniaturized electronics.

Published online: 28 August 2020

Ó

Springer Science+Business

Media, LLC, part of Springer Nature 2020

Introduction Wearable and flexible energy storage devices are attracting more and more attention since they provide a commitment of designable, bendable and portable with the minimization of mass and volume [1, 2]. To fabricate these devices, graphene has been recognized as one of the most promising electrode materials [3, 4]. In particular, it attracts attention for the supercapacitor construction due to its unique

features: extraordinarily high surface area, excellent electrical conductivity, great stability, light and ecofriend [5, 6]. To meet the requirement of flexible supercapacitor devices, orderly graphene sheets have been synthesized with different methods [7–10]. Among them, graphene films or graphene papers assembled from laminar graphene sheets perform outstanding, originating from their high specific area capacitance and facile process [11–14]. However, the p–p stacking caused by strong Van der Waals force between graphene oxide layers induces irreversible

Handling Editor: Mark Bissett.

Address correspondence to E-mail: [email protected]; [email protected]

https://doi.org/10.1007/s10853-020-05156-7

16335

J Mater Sci (2020) 55:16334–16346

agglomeration of thin graphene layers. Such compact stacking reduces their surface areas, and weakens its ability to store energy [15–18]. To alleviate the stacking tendency, spacers are introduced between graphene layers. The reported spacers include carbon fiber [19], carbon nanotubes [20], high molecular polymer [21], metal oxides [22] and even gas [23]. These spacers feature o