Abstract
The active species in magnesium electrolytes is regularly assigned as being the thermodynamically stable dinuclear [Mg2Cl3]+ cation. By deliberately targeting other implicated aggregates, their effect on Mg-ion battery performance is easily ascertained.
Highlights
Mg batteries present an attractive and sustainable alternative to Li-ion batteries, wherein magnesium metal as an anode displays a superior theoretical volumetric energy density of 3833 A h L−1 versus 2062 A h L−1 for lithium
An outstanding crucial bottleneck in realising their more widespread uptake is the development of suitable electrolytes, where electrode passivation, a limited electrochemical window, conditioning requirements, low ion mobility and low coulombic efficiencies all contribute to current limitations in Mg batteries
In an area far dominated by the thermodynamically stable [Mg2Cl3]+ dinuclear cation, we present here a novel family of magnesium amidohaloaluminate electrolytes [(Dipp) (SiMe3)2NAlCl3]− [MgxCl2x−1]+ where the magnesium chloride cation aggregation has been tailored (x = 1, 2, 3) by substitution of the coordinating ligand to the Mg2+ centre, and show how directly altering this cation affects battery performance (Dipp = 2,6-diisopropylphenyl, Me = methyl)
Summary
Inorganic Chemistry Frontiers overcome by addition of a group 13 Lewis acid, generating ionic bimetallic complexes such as magnesium aluminates.[5]. We report the battery performances using these compounds as electrolytes in Mg–metal/Mo6S8 battery cells and interpret the different experimental results in order to identify which aggregation is more beneficial to Mg2+ ion transfer, plating/ stripping and intercalation. We have selected the Mo6S8 Chevrel phase as a robust cathode material which has been widely studied in the literature, but it is interesting to note recent developments in high-performance cathodes such as MgTi2S4 which display improved properties.[21,22] We show that all three electrolytes possess individual properties which affect the plating/stripping of Mg, electrochemical stability window, ionic conductivity, gravimetric specific capacity and overpotential of battery cells. The presence of different Lewis donors, tetraamine Me6TREN (tris[2-(dimethylamino)ethyl] amine N(CH2CH2NMe2)3), is suspected to affect the electrochemical window by enhancing the oxidative stability of the electrolyte, with electrolyte conditioning required before achieving optimal performance
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