Short communication Enabling high areal capacitance in electrochemical double layer capacitors by means of the environmentally friendly starch binder Alberto Varzi a, b , Stefano Passerini a, b, * a Helmholtz Institute Ulm (HIU), Helmholtzstrasse 11, 89081, Ulm, Germany b Karlsruhe Institute of Technology (KIT), P.O. Box 3640, 76021, Karlsruhe, Germany highlights  Potatoes starch is proposed as superior water-processable binder for electrochemical double layer capacitors.  The presence of amylopectin provides enhanced mechanical properties and suppresses the cracking of the electrode.  Potatoes starch enables considerably higher electrode loadings resulting on increased areal capacitance. article info Article history: Received 28 May 2015 Received in revised form 15 September 2015 Accepted 16 September 2015 Available online 26 September 2015 Keywords: EDLC Binder Starch Areal capacitance Electrodes Water processing abstract Potatoes starch (PS), a natural polymer obtainable from non-edible sources, is for the first time evaluated as alternative water-processable binder for Electrochemical Double-Layer Capacitor (EDLC) electrodes. Morphological and electrochemical properties of activated carbon (AC)-based electrodes are investigated and compared to those achieved with the state-of-the-art aqueous binder (CMC, i.e. Na-carboxymethyl cellulose). The obtained results suggest substantial benefits of PS, in particular regarding the electrode fabrication process. As a matter of fact, owing to its amylopectin content (moderately branched poly- saccharide), PS displays only minimal shrinkage upon drying, resulting on rather homogeneous elec- trodes not presenting the dramatic surface cracking observed with CMC. Furthermore, owing to the smaller volume of water required for the processing, much higher active material loading per area unit can be achieved. This is reflected on improvements of up to 60% in terms of areal capacitance. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Electrochemical energy storage devices, in particular lithium ion batteries (LIBs) and electrochemical double-layer capacitors (EDLCs), are nowadays being employed in a continuously rising number of applications. Storing energy produced via renewable sources and re-use it on demand has become today's reality while electrically powered vehicles will likely represent the normality in the very next future. This leads to a growing market for such de- vices, raising, at the same time, concerns about the impact their production and disposal could have on the environment. Thus, many efforts are ongoing to develop environmentally friendly de- vices constituted by non-toxic materials that can be safely produced and disposed without using hazardous chemicals. A very effective approach is constituted by the use of water processable binders. Several natural (and naturally derived) polymers have been already proposed for LIBs, such as Na-carboxymethyl cellulose (CMC) [1,2], natural cellulose [3], chitosan [4], alginate [5], Xanthan Gum [6,7], etc. Besides their enhanced environmentally friendli- ness, more appealing is their capability to improve the cyclability of alloying anodes, by retaining the contact among particles, even when the active particles undergo severe volume expansion. Strain associated to faradaic reactions is not an issue in EDLC electrodes, where, theoretically, the charge is simply stored in the double layer. This fact partially justifies the limited attention paid to the binder in EDLCs-related scientific literature. Nevertheless, it has been demonstrated that green binders can provide interesting benefits to EDLC as well [8e11]. Our recent work, for example, demonstrated as natural cellulose enables superior performance than PVdF under prolonged floating conditions at high cell voltages (i.e., 3.7 V for 750 h) [10]. Despite the quite appealing properties, * Corresponding author. Helmholtz Institute Ulm (HIU), Helmholtzstrasse 11, 89081, Ulm, Germany. E-mail address: stefano.passerini@kit.edu (S. Passerini). Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour http://dx.doi.org/10.1016/j.jpowsour.2015.09.065 0378-7753/© 2015 Elsevier B.V. All rights reserved. Journal of Power Sources 300 (2015) 216e222