Enhancing the capacitance and active surface utilization of supercapacitor electrode by graphene nanoplatelets D. Pullini a , V. Siong b,⇑ , D. Tamvakos a , B. Lobato Ortega c , M.F. Sgroi a , A. Veca a , C. Glanz b , I. Kolaric b , A. Pruna d,⇑ a Centro Ricerche Fiat, 50 Strada Torino, 10043 Orbassano, Italy b Fraunhofer Institute for Manufacturing and Automation, 12 Nobelstrasse, 70569 Stuttgart, Germany c Instituto Nacional del Carbón (CSIC), Apartado 73, 33080 Oviedo, Spain d University of Bucharest, 405 Atomistilor Str., 077125 Bucharest-Magurele, Romania article info Article history: Received 20 October 2014 Received in revised form 3 March 2015 Accepted 4 March 2015 Available online 10 March 2015 Keywords: A. Nano composites B. Electrical properties D. Scanning electron microscopy (SEM) D. Raman spectroscopy D. X-ray diffraction (XRD) abstract The potential application of graphene nanoplatelets as electrode material in supercapacitors with high energy density was investigated. The electrode were prepared with commercially available graphene nanoplatelets before and after being functionalized with MnO 2 particles, and with those electrochemi- cally exfoliated from graphite. The morphology, structure and the specific surface area properties of each material were analyzed prior to test the electrochemical performance of the corresponding electrodes under the design constraints of real devices by cyclic-voltammetry (CV) and charge/discharge (CD) measurements. The results indicated that graphene nanoplatelets show potential in replacing activated carbon for the fabrication of supercapacitors with high energy density, while the efficient usage of active surfaces available of the electrode material should be considered. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction The advancements of complex electronics systems over the last years have led to the increasing demand of portable energy usage and storage [1,2]. In this instance, powerful and reliable energy storage systems are sought after as power supply units for emerg- ing applications in the field of electro-mobility. In the automotive field, many applications, such as the device actuation, heating of seats and starting of the engine or energy recuperation during braking require not only a device with high energy density, but also one that is able to deliver/store the energy within a short per- iod of time (i.e. high power and high charging rate). In spite of their low power densities [3], batteries are the most commonly applied solution to the aforementioned challenges thanks to the high energy density they offer [4]. In recent times, supercapacitors are thought to be among promising candidates to replace or to be coupled with batteries for these applications with the aim of enhancing the power densi- ties of the devices [5]. In comparison to batteries, a supercapacitor modus operandi offers higher power densities, faster charging rates and theoretically unlimited cyclability [6]. However, the main drawback of the commercially available supercapacitors is their limited energy densities. Therefore, one of the main focal point of today’s research in this field is oriented at increasing the energy density of supercapacitors. In this aspect, advancements have been assisted by the discovery of novel advanced materials which are capable of bringing the energy density of supercapacitors to a level more comparable to batteries [7,8]. A common approach to enhance the capacitance of a supercapacitor cell, and its energy density lies in providing the electrodes with more active sites for the storage of charge compounds, such as the ions of the elec- trolyte. To achieve this goal, supercapacitors have been fabricated with materials that are able to provide high surface area. Till date, the commercially available supercapacitors constitute mainly of carbon-based electrodes and among them, activated carbon ones are the most commonly employed due to its high specific surface area, ranging from a few hundreds to 1500 m 2 g À1 , low cost and long cycling life [9,10]. However their complex pore structures of irregular pore sizes have been reported to impede the access of electrolyte ions resulting in an increased electrode’s resistance and reduced capacitance [10]. Amid the search for systems with high efficiency, graphene has emerged as one of the most promising alternative for electrode developments in devices including batteries [11], fuel-cells [12] http://dx.doi.org/10.1016/j.compscitech.2015.03.004 0266-3538/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding authors. Tel.: +34 627018518 (A. Pruna). E-mail addresses: victor.siong@yahoo.com (V. Siong), ai.pruna@gmail.com (A. Pruna). Composites Science and Technology 112 (2015) 16–21 Contents lists available at ScienceDirect Composites Science and Technology journal homepage: www.elsevier.com/locate/compscitech