MnO₂ with controlled phase for use in supercapacitors

Abstract

Nanostructured MnO 2 has been synthesized using a simple and rapid microwaveassisted hydrothermal (MHT) technique through the decomposition of KMnO 4 in a hydrochloric acid solution. The effects of hydrothermal temperature and ramp rate were examined and discussed. It was found that a lower temperature (140°C) favors the formation of cauliflower-like d-MnO 2 particles while a higher temperature (160°C, 180°C, or 200°C) favors the formation of a-MnO 2 nanorods. The dimensions of the obtained MnO 2 nanorods were affected by the ramp rate. The cauliflower-like d-MnO 2 particles have higher specific surface areas than the a-MnO 2 nanorods. Supercapacitors having the obtained MnO 2 as the electrodes were evaluated using cyclic voltammetry and electrochemical impedance spectroscopy in a 1 molÁL À1 Na 2 SO 4 solution within a potential window of À0.1-0.9 V. The cauliflower-like d-MnO 2 electrodes give higher capacitance, up to 202 F/g, than the nanorods a-MnO 2 electrodes, at most 61 F/g.

Carbon-Based Quantum Dots for Supercapacitors: Recent Advances and Future Challenges

“…Various methods are used to synthesize SC electrode materials, such as sol-gel, electropolymerization/electrodeposition, in situ polymerization, vacuum filtration technique, chemical vapor deposition (CVD), co-precipitation, hydrothermal, and others. Since pseudocapacitive performance depends on the materials’ structures and properties, optimizing the parameters of various synthesis methods is vital [ 8 , 52 , 63 , 64 ].…”

Electrochemical performance of nanosized MnO2 synthesized by redox route using biological reducing agents

“…Low cost, high theoretical capacity, environmental friendliness, and natural abundance are the main advantages of manganese dioxides, MnO2 (MDOs), which make them promising electrode materials for lithium-ion batteries and supercapacitors [7,8]. However, the practical application of MnO2 as electrode material for lithium-ion batteries is actually limited by the poor conductivity, large volume expansion and aggregation during Li insertion/extraction, which limits its rechargeability.…”

Tailoring carboxyl tubular carbon nanofibers/MnO2 composites for high‐performance lithium‐ion battery anodes

“…Among all the TMOs, MnO 2 has shown its great potential as an energy storage and conversion material. 15,16 It exhibits some outstanding properties when used as an LIB anode material, such as lower discharge plateau and huge theoretical capacity. However, like many other conversion and alloying type oxide anode materials, MnO 2 undergoes large volume expansion and shrink during lithiation/delithiation.…”

“…Transition metal oxides (TMOs) and mixed metal oxides based on conversion reaction mechanism, including MoS 2 , 12 Fe 2 O 3 , 13 and Cu‐Ni oxide 14 have become expected alternative anode materials due to their environment‐friendliness and abundant reserves. Among all the TMOs, MnO 2 has shown its great potential as an energy storage and conversion material 15,16 . It exhibits some outstanding properties when used as an LIB anode material, such as lower discharge plateau and huge theoretical capacity.…”