Porous Spinel Magnesium Manganese Oxide/Multiwalled Carbon Nanotubes Composite Synthesized by Electrochemical Conversion as High-Performance Cathode for Aqueous Magnesium Ion Battery

Abstract

Aqueous magnesium ion batteries (AMIBs) have attracted great interest due to the low manufacture cost and eco-friendliness, but the lack of suitable cathodes with good electrochemical performance obstructs their development. Here, a composite of spinel magnesium manganese oxide (MgMn 2 O 4 ) and multiwalled carbon nanotubes (MWCNTs) with a porous structure is synthesized by electrochemical conversion method and used as the cathode for the AMIB, which improves the inherent low conductivity for MgMn 2 O 4 and enhanced its specific capacity. The electrochemical conversion method helps preserve the surface integrity and structure stability of the electrode, and the MWCNTs network provides the pathway of Mg ion migration among the MgMn 2 O 4 particles. The obtained MgMn 2 O 4 /MWCNTs displays a discharge capacity of 322.3 mAh g −1 at 50 mA g −1 , and the capacity retention is 81.8% after 2000 iterations at 1000 mA g −1 . Further, the MgMn 2 O 4 /MWCNTs//VO 2 system is assembled, which displays a capacity retention rate of near 100%. The electrochemical mechanism of Mg ion insertion/extraction is investigated though the ex situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements. This paper extends synthesis method of the high performance cathode material for AIMB system.