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

Abstract

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 (MnO 2 ) 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 MnO 2 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 MnO 2 samples are 2.9 and 2.8 times than that of pure-MnO 2 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.

Oxygen Vacancy‐Induced Dielectric Polarization Prevails in the Electromagnetic Wave‐Absorbing Mechanism for Mn‐Based MOFs‐Derived Composites

“…Transition metal elements (Ni (3d 8 4s 2 ) and Co (3d 7 4s 2 )) have uncoordinated electrons in the 3d orbitals, which can attract electrons in carbon atoms to form complexes, thus reducing the activation energy required for graphitization. [ 49 ] In particular, more unpaired electrons were present in the Ni atom, which suggests that Ni/MnO@C is more capable of catalyzing graphitization than Co/MnO@C.…”

Recent advances of biomass derived carbon-based materials for efficient electrochemical energy devices

“…The chemical activation method is to form pores through a series of cross-linking polycondensation reactions by inserting chemical reagents into the internal structure of carbon. 61 This method can easily prepare hierarchical porous carbon materials with ultra-high specific surface areas, but it is challenging to obtain ordered nanoporous structures. Although the thermal treatment temperature is relatively low, the environmental pollution and the corrosion of equipment are relatively serious.…”

Pseudocapacitive storage in cathode materials of aqueous zinc ion batteries toward high power and energy density

“…Recently, Xiang et al investigated how electrochemical activation can significantly facilitate the pseudocapacitive effects of δ-MnO 2 . 69 On the one hand, the positive voltage can generate O vacancies in δ-MnO 2 , which facilitates the transport of cations. On the other hand, the negative voltage can promote the insertion of cations in the electrolyte into the interlayers, which stabilizes the structure and improves conductivity.…”