Effect of Fe3+ on the synthesis and electrochemical performance of nanostructured MnO2

► Fe3+ affects the phase structure evolution and morphologies of MnO2. ► Fe3+ prevents the epitaxial growth and crystallization of MnO2 nucleus. ► KMF-based MnO2 shows better textual characteristics. ► KMF-based MnO2 yields higher specific capacitance in the same condition.