Progress in high-voltage MgMn2O4 oxyspinel cathode materials for Mg batteries

Facile Surface Modification of MgMn2O4 Positive-Electrode Material for Improving Cycle Performance of Magnesium Rechargeable Batteries

“… 5 In the refinement, Zr was not considered because of the very low Zr content ( Table 1 ). Since a previous work suggested a cation mixing (inversion) of Mg and Mn especially at elevated temperature, 21 Mg and Mn occupancies at the tetrahedral (4a) and octahedral (8d) sites were refined while maintaining the metal ratio as an analytical value by ICP-AES. As a result, the Mg occupancy at the octahedral site became slightly negative in the refinement process, indicating that the octahedral site is not occupied by Mg.…”

“…This has prompted material research on MRB-positive electrodes, with several studies in the last decade successfully uncovering novel oxides that can function as positive electrodes. For example, Mg 1+ x M 2– x O 4 ( M = transition metal) with a spinel structure, − Mg M O 2 with a rocksalt structure, ZnMnO 3 with a deficient spinel structure, , and magnesiated layered materials − have been investigated, considering the fact that spinel and layered rocksalt structures provide ion diffusion paths in LIB electrode materials. Among these oxides, spinel-type MgMn 2 O 4 with a high theoretical capacity (270 mA h g –1 for Mg insertion) is promising because it is composed only of abundant elements (Mg, Mn, and O) and can be synthesized by a simple inverse coprecipitation method with subsequent heat treatment. , Indeed, MgMn 2 O 4 can deliver high discharge capacities over 200 mA h g –1 , but its cycle performance in anhydrous electrolytes is supposed to be insufficient for practical use. ,, As is well known, in the case of LIBs and other rechargeable batteries, surface modification and partial substitution of the electrode powders are the good strategies to overcome this drawback. − Currently, however, there are few reports on the surface modification of MRB electrode materials. − …”

Revisiting the Chevrel Phase: Impact of Dispersion Corrections on the Properties of Mo6S8 for Cathode Applications**

“…Multiple cathode materials have been proposed for Mg batteries such as spinels, [11,12,18–21] V 2 O 5 [22–25] or the chevrel phase (CP) [13–16] which are often also used for other multivalent charge carriers such as Zn 2+ [26,27] . However, only in the CP the issues of sluggish insertion kinetics and low reversibility are solved more or less satisfactorily [13–16] .…”

“…[5] As a common problem, the insertion of Mg ions on the cathode side is often sluggish and hard to reverse, which is mainly due to the divalent ions being strongly bound at the cathode side. [17] Multiple cathode materials have been proposed for Mg batteries such as spinels, [11,12,[18][19][20][21] V 2 O 5 [22][23][24][25] or the chevrel phase (CP) [13][14][15][16] which are often also used for other multivalent charge carriers such as Zn 2 + . [26,27] However, only in the CP the issues of sluggish insertion kinetics and low reversibility are solved more or less satisfactorily.…”

Ultraporous, Ultrasmall MgMn2O4 Spinel Cathode for a Room-Temperature Magnesium Rechargeable Battery

“…Here, we demonstrate high-voltage MRB full cells; we fabricate highly porous nanosized oxides to reduce the Mg conduction path in the MMO cathode material, an approach that was previously attempted by many groups. 12 Recently, our group has developed porous MMO nanoparticles (∼8 nm diameter) with a specific surface area (SSA) of ∼250 m 2 g −1 by a sol−gel process, 18 and ultrasmall MMO nanoparticles (<5 nm) with a SSA of ∼150 m 2 g −1 by alcohol reduction process, 19 which all showed a first discharge capacity of 230 mAh g −1 at room temperature. This discharge value, while high among MMO cathodes, was still 85% of the theoretical capacity (270 mAh g −1 ).…”