MgMn2O4/multiwalled carbon nanotubes composite fabricated by electrochemical conversion as a high-performance cathode material for aqueous rechargeable magnesium ion battery

This work reports a composite material consisting of MgMn 2 O 4 particles and multi-walled carbon nanotubes (MWCNTs) for aqueous magnesium ion batteries (AMIBs), which is prepared with electrochemical conversion method. The electrochemical conversion method has the advantages of easy accessibility, mild condition and small structural failure of electrode material. The obtained MgMn 2 O 4 /MWCNTs displays good surface integrity and structure stability, which improves electrochemical performance. Simultaneously, MWCNTs network serves as the pathways of Mg 2+ ions and electrons not only shorts the ion migration path but also enlarges the interface of electrode/electrolyte. The MgMn 2 O 4 /MWCNTs exhibites the advantages of high conductivity, large charge-discharge capacity and good rate performance. The obtained MgMn 2 O 4 /MWCNTs shows a high discharge capacity of 412.9 mAh g −1 at 50 mA g −1 , which is close to two times of that for the MgMn 2 O 4 obtained by sol-gel method, and the capacity retention is 73.3% after 1000 cycles at 1000 mA g −1 . In addition, the MgMn 2 O 4 /MWCNTs//AC system is firstly assembled, which displays a specific discharge capacity of 94.5 mA h g −1 at 50 mA g −1 . Furthermore, the relevant electrochemical mechanism of Mg 2+ ion insertion/extraction can be explained by the change of manganese valence, which is investigated with ex-situ XRD and XPS measurements. This work expands the compound method of high-performance electrode material for rechargeable aqueous magnesium ion battery.