A Universal Voltage Design for Triggering Manganese Dioxide Defects Construction to Significantly Boost the Pseudocapacitance

Electrochemical activation can be appropriate for constructing tunable/controllable defects within the interior of electrode materials. However, the activation mechanisms under different applied electric fields urgently need to be systematically explored. Herein, the electrochemically activated manganese dioxide (MnO2) samples are prepared via applying a positive/negative electric field, and two different activation mechanisms are revealed through a series of characterization methods. During the activation process, it is fascinating to discover that MnO2 mainly generates the O vacancies under positive voltage, whereas the electrolyte cations are embedded in the interlayer under negative voltage. The generated O vacancies and intercalated ions not only act as active sites or participate in the charge‐transport process, but also enhance the transmission capability of carriers. In contrast, the specific capacitances of optimized MnO2 samples are 2.9 and 2.8 times than that of pure‐MnO2 after electrochemical activation under positive and negative voltage, respectively. In addition, the activated samples exhibit excellent cycle stability and resistance to electrochemical corrosion, which can well‐maintain the 3D network structure composed of nanosheets after 5000 cycles. This strategy opens up a promising approach for exploring efficient and corrosion‐resistant electrode materials. The manganese dioxide (MnO2) is activated by applying a positive/negative electric field, and the activation mechanisms under two different electric fields are systematically explored through a series of characterization methods. It is found that oxygen vacancies will be generated under positive voltage, whereas the electrolyte cations will be embedded in the MnO2 interlayer under negative voltage.