On the Utility of Spinel Oxide Hosts for Magnesium-Ion Batteries

Abstract

There is immense interest to develop Mg-ion batteries, but finding suitable cathode materials has been a challenge. The spinel structure has many advantages for ion insertion and has been successfully used in Li-ion batteries. We present here findings on the attempts to extract Mg from MgMn2O4-based spinels with acid (H2SO4) and with NO2BF4. The acid treatment was able to fully remove all Mg from MgMn2O4 by following a mechanism involving the disproportionation of Mn(3+), and the extraction rate decreased with increasing cation disorder. Samples with additional Mg(2+) ions in the octahedral sites (e.g., Mg1.1Mn1.9O4 and Mg1.5Mn1.5O4) also exhibit complete or near complete demagnesiation due to an additional mechanism involving ion exchange of Mg(2+) by H(+), but no Mg could be extracted from MgMnAlO4 due to the disruption of Mn-Mn interaction/contact across shared octahedral edges. In contrast, no Mg could be extracted with the oxidizing agent NO2BF4 from MgMn2O4 or Mg1.5Mn1.5O4 as the electrostatic repulsion between the divalent Mg(2+) ions prevents Mg(2+) diffusion through the 16c octahedral sites, unlike Li(+) diffusion, suggesting that spinels may not serve as potential hosts for Mg-ion batteries. The ability to extract Mg with acid in contrast to that with NO2BF4 is attributed to Mn dissolution from the lattice and the consequent reduction in electrostatic repulsion. The findings could provide insights toward the design of Mg hosts for Mg-ion batteries.

Spinel Li4Mn5O12 as 2.0 V Insertion Materials for Mg‐Based Hybrid Ion Batteries

“…Recently, multivalent cation rechargeable batteries using a zinc, [1][2] aluminum, [3][4] magnesium [5][6] anode have received more attention because of the high cost and environmental threats of the by-products of lithium-ion batteries (LIBs). [7][8][9][10] In particular, rechargeable magnesium-ion batteries (MIBs) have an appealing low cost, a high theoretical volumetric capacity (3833 mAh cm À 3 for Mg and 2046 mAh cm À 3 for Li), and a low toxicity.…”

A rechargeable Mg 2+ /Li + hybrid battery based on sheet-like MoSe 2 /C nanocomposites cathode

“…Nevertheless, there are also significant disadvantages such as intrinsic strong coulombic interactions between bivalent Mg 2+ ions and the host materials, which cause the sluggish kinetics for the diffusion of Mg 2+ ions and result in a large polarization, and finally lead to low Mg 2+ intercalation levels and rapid capacity decay. [5,6] The absence of high capacity, high voltage and fast kinetics of Mg 2+…”

Sponge-Like Porous Manganese(II,III) Oxide as a Highly Efficient Cathode Material for Rechargeable Magnesium Ion Batteries

“…Their favorable properties are attributed to fast ion diffusion resulting from the 3D layered structure, high operating voltage, and structural stability. 41,42 Several studies have claimed intercalation of Mg 2+ ions into spinel-structured Mn2O4 (λ-MnO2) in aqueous environments. 43 45,46 Mn3O4 as cathode material for MIB could host about 0.66 Mg ions per formula unit, corresponding to the theoretical capacity of 154 mAh g -1 .…”