Enhanced High-Temperature Cyclic Stability of Al-Doped Manganese Dioxide and Morphology Evolution Study Through in situ NMR under High Magnetic Field

Abstract

In this work, Al-doped MnO (Al-MO) nanoparticles have been synthesized by a simple chemical method with the aim to enhance cycling stability. At room temperature and 50 °C, the specific capacitances of Al-MO are well-maintained after 10 000 cycles. Compared with pure MnO nanospheres (180.6 F g at 1 A g), Al-MO also delivers an enhanced specific capacitance of 264.6 F g at 1 A g. During the cycling test, Al-MO exhibited relatively stable structure initially and transformed to needlelike structures finally both at room temperature and high temperature. In order to reveal the morphology evolution process, in situ NMR under high magnetic field has been carried out to probe the dynamics of structural properties. The Na spectra and the SEM observation suggest that the morphology evolution may follow pulverization/reassembling process. The Na intercalation/deintercalation induced pulverization, leading to the formation of tiny MnO nanoparticles. After that, the pulverized tiny nanoparticles reassembled into new structures. In Al-MO electrodes, doping of Al could slow down this structure evolution process, resulting in a better electrochemical stability. This work deepens the understanding on the structural changes in faradic reaction of pseudocapacitive materials. It is also important for the practical applications of MnO-based supercapacitors.

Doping-driven electronic structure and conductivity modification of nickel sulfide

“…Ni atoms were replaced with doped atoms (Co/Mn/Ag) to construct substitution models. 22 3. Results and discussion…”

Oxygen Defects in Promoting the Electrochemical Performance of Metal Oxides for Supercapacitors: Recent Advances and Challenges

“…It has been verified that the oxygen vacancies can vary significantly with the doping of different metal elements such as earth metals, [ 107–109 ] rare earths, [ 110–116 ] transition metal, [ 67,117–133 ] or even noble metal. [ 134–139 ] From all the aforementioned classes of metals, the dopants with comparable ionic size and highly soluble feature offers a vast variety of doping element options in MOs.…”

Experimental and Theoretical Investigation of the Effect of Oxygen Vacancies on the Electronic Structure and Pseudocapacitance of MnO2

“…Recently, numerous researchers have focused on MnO 2 ‐based composites or the doping of MnO 2 with metals (e.g., Al, Zn, Ce, Co and Fe) to improve their intrinsic conductivity . For example, Cakici et al.…”

“…Recently,n umerous researchers have focused on MnO 2based composites or the doping of MnO 2 with metals (e.g.,A l, Zn, Ce, Co and Fe) to improve their intrinsic conductivity. [23][24][25][26][27][28][29] For example, Cakici et al prepared ac arbon fiberf abric/corallike MnO 2 nanostructure by using ag reen hydrothermal method,w hich displayed ac apacitance of 467 Fg À1 at 1Ag À1 . [30] Zhou and co-workers reported Al-doped a-MnO 2 , which showed enhancede lectrochemical performance owing Defect engineering is an effective way to modulate the intrinsic physicochemical properties of materials.…”