Electrochemical growth of alpha-MnO2 on carbon fibers for high-performance binder-free electrodes of supercapacitors

摘要

Cryptomelane-type MnO2 (alpha-MnO2) was directly deposited on carbon fiber paper (CFP) by a simple electrochemical method and evaluated as the active material of binder-free electrodes for supercapacitors. The obtained alpha-MnO2@CFP electrode exhibits a higher capacitance and better rate capability than the epsilon-MnO2@CFP electrode prepared by the conventional electrochemical method. For the alpha-MnO2@CFP electrode, a specific capacitance of 623.9 F g(-1) can be achieved at 2 mV s(-1) and the capacitance retention is up to 75% at 200 mV s(-1). Compared to most of the binder-free MnO2/carbon electrodes reported in previous studies, the electrode also presents a much better rate capability. These superiorities mainly result from the specific tunnel structure of alpha-MnO2 which offers not only facile diffusion paths for cations but also plentiful reactive sites for the inner-surface redox reactions associated with the energy storage process. The fabrication method is facile and readily scalable and thus has great promise in the development of high-performance binder-free MnO2 electrodes for energy storage devices.