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Research progress of electrochemical cycling stability of Al3+ doped manganese dioxide

wallpapers Tech 2020-06-09
Supercapacitors have the characteristics of high specific capacity, long cycle life, and environmental friendliness. They play the role of green energy in electronic products and hybrid power systems. The supercapacitor electrode material is a crucial factor affecting the electrochemical performance of supercapacitors. Manganese dioxide (MnO2) is not only high in theoretical specific capacity but also rich in raw materials. It is an electrode material with good application prospects. However, due to its poor conductivity and cycle stability, the capacity retention rate during electrochemical cycling needs to be improved. Doping metal ions can improve the electrochemical performance and cycle stability of manganese dioxide.
 
Electrochemical performance analysis was carried out using Al3+ doped MnO2 (Al-MO) and pure MnO2 (MO) electrode materials prepared by chemical precipitation. The test found that the specific capacity of the Al-MO electrode at a current density of 1A/g is 264.6F/g, which is higher than that of the MO electrode (180.6F/g) and has better cycle stability at room temperature and 50°C high temperature. Sex. Observing the micro-morphology of the wire after different cycle times through field emission scanning electron microscope, it was found that the Al-MO electrode gradually changed from granular to the needle-like structure. Still, the crystal form did not change, and the MO electrode was in the process of cycling. At the same time, changes in morphology and crystal form occurred.
 
To further understand the relationship between the evolution of electrode morphology and electrochemical stability, the researchers used in-situ solid-state nuclear magnetic resonance to observe the insertion/deintercalation process of Na+ in Al-MO and MO positive electrodes during different charge and discharge cycles. They found that During the discharge process, the 23Na peak of the MO electrode showed visible changes under different potentials and different periods, indicating that the MO electrode had a structural change in the cycle; the 23Na peak of the Al-MO electrode did not change significantly during the charge and discharge process. There was no change even in the first cycle, indicating that Na+ had a rapid and reversible intercalation/deintercalation reaction on the surface of the Al-MO electrode, which suggested that the structure of the Al-MO electrode was stable.
 
Based on the above test results, the researchers speculate that the morphological evolution of the MO electrode during cycling may follow the "powder-self-assembly" process. The intercalation/deintercalation of Na+ leads to a change in the volume of MnO2 nanoparticles, which results in powdering of the surface. These powdered nanoparticles exhibit morphological changes after reassembly. In the case of weak bond bonding, the reassembled fine particles may break away from the matrix and dissolve in the electrolyte. As the active electrode material is lost, the capacitance will gradually decrease. Al3+ doping of MnO2 can enhance the bonding between powdered particles, which is beneficial to improve the structural stability of MnO2.
 
Trunnano is one of the world's largest producers of manganese dioxide. In addition to manganese dioxide, the company also has nano-oxide products such as manganese trioxide. If you are interested, you can consult Dr. Leo, email: brad@ihpa.net.

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