MnO2-based composite has attracted wide attention because of its high power density, and long cycle life as electrodes for energy storage devices. However, its instability at lower electrochemical potential limits its operating potential window (OPW) and impedes its further development as a promising electrode material for symmetrical supercapacitors. Herein, flexible MnO2@carbonized cotton textile electrodes (MCCT) is designed and demonstrated via a facile in-situ low-temperature chemical reaction method. Remarkably, an excellent electrochemical stability under negative polarization is obtained, delivering a large OPW of 1.6 V. In addition, the flexible MCCT exhibits a high areal capacitance of 526.25 mF cm(-2) (751.78 F g(-1)) at 1mA cm(-2) coupled with good rate performance (237.6mF cm(-2) at 50 mAcm(-2)), as well as high cycle retention (99.7% after 10000 cycles). The operation voltage of symmetrical supercapacitors is expanded to 1.6 V, revealing a maximum energy density of 5.71mWh cm(-3) (0.057mWh cm(-2)) and a high power density of 3.97Wcm(-3) (39.71mWcm(-2)). As a representative of high operation voltage MnO2 composite electrode, the flexible MCCT has potential for state-of-the-art energy storage devices. (C) 2019 Elsevier Ltd. All rights reserved.