Supercapacitors are efficient electric energy storage devices with a wide range of possible applications. In this study, a natural cellulose-activated carbon composite material that can be used as an electrode in a flexible supercapacitor is prepared using a phase inversion technique. The composite material preparation and testing methodology are described and the electrochemical characteristics of the composite material are analysed as a function of the activated carbon (AC) to natural cellulose (NC) mass ratio. Analysis of the influence of the AC/NC mass ratio on the electrochemical characteristics of the composite material demonstrated the importance of optimal mass ratio determination prior to manufacture. To prove an applicability of the NC binder, the electrochemical characteristics of the composite material prepared with a NC binder are compared with those of a composite material with a standard poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) binder. The experimental results confirm the applicability of using NC as a binder in the preparation of a composite material that can be used as a flexible self-standing supercapacitor electrode. (C) 2016 Elsevier Ltd. All rights reserved.