Progress in Rechargeable Magnesium Battery Technology

Abstract

Rechargeable magnesium batteries were first presented about seven years ago. [1][2][3] Their components included magnesium metal or a Mg alloy anode, Mg x Mo 6 S 8 (0 < x < 2) Chevrel phase cathodes, and electrolyte solutions that contained an ether solvent and a complex electrolyte, a product of the reaction between a MgBu 2 Lewis base and an AlCl 2 Et Lewis acid (Bu = butyl, Et = ethyl). These systems, while demonstrating impressive cycleability, suffered from several drawbacks:i) The micrometric size Mg 0-2 Mo 6 S 8 Chevrel phase cathode suffers from some kinetic limitation and the phenomenon of partial charge trapping (of Mg ions) at low temperatures. [4,5] ii) The electrochemical window of the first generation of electrolyte solutions, THF/Mg(AlCl 2 BuEt) 2 was around 2.2 V, which limited the possible use of cathode materials with a higher redox potential (and higher capacity) than Chevrel phases. iii) For practical use, the synthesis of the components of rechargeable Mg batteries needs simplification. Chevrel phases (CPs), M x Mo 6 T 8 (M = metal, T = S, Se), are of great interest owing to their remarkable electromagnetic, thermoelectric, and catalytic properties [6][7][8][9] . Exceptionally fast cation transport for multi-valent ions (compared to any other inorganic host material) made these materials unique cathodes in Mg batteries. [1][2][3] However, the kinetics of Mg diffusion in the CPs is strongly affected by their composition and temperature. At ambient temperature, the selenide shows excellent Mg mobility in the full intercalation range from 0 to 2 Mg 2+ ions per formula unit, [4] while Mg trapping occurs in the sulfide. During the first magnesiation of Mo 6 S 8 , 2 Mg ions are inserted (i.e., the full theoretical capacity is realized), upon further electrochemical deintercalation of Mg x Mo 6 S 8 , part of the Mg 2+ ions (20-25 %) are trapped and can be removed from the crystal structure, only at elevated temperatures (i.e., only 75-80 % of the theoretical capacity is involved in reversible cycling at low temperatures).[5]Detailed studies [10,11] of the crystal structure of the Mg-containing CPs made it clear that the trapping in the sulfide is caused by a unique ring arrangement of closely located cation sites with low potential energy. The triclinic distortion in the selenide changes the geometry of the cation sites, resulting in the degeneracy of the effect. It can be suggested that the presence of relatively small amounts of Se will be sufficient to improve the kinetics of the Mg 2+ cations in CPs. In fact, in addition to compounds with a single anion, the Chevrel family includes also solid solutions where sulfur and selenium atoms form a common anion framework. [12] Thus, in order to optimize the cathode composition in Mg batteries, it is of great importance to study the influence of the S-Se substitution in the host on the electrochemical behavior. Mg insertion into the binary hosts occurs in two stages: [1][2][3]

Magnesium-sulfur battery: its beginning and recent progress

“…1(a)], a conductivity of 5 mS/cm (30°C) and a cycling efficiency of almost 100%. [22] Spectroscopic analysis revealed that these solutions contain multiple species, including MgCl + , Mg 2 Cl 3 + as electrochemical active species, Ph n AlCl 4−n − (n = 1-3), MgCl 2 , Ph 2 Mg, and PhMgCl resulting from various transmetalations of the ligands and the Schlenk equilibrium [ Fig. 1(b)].…”

The Chevrel phase In4.07Mo15S11.87Se7.13with mixed chalcogenide occupancy

“…For applications, see: Suresh et al (2008); Aurbach et al (2007). For the syntheses and crystal structures of Chevrel phases with various cations, see : Salloum, Gautier et al (2004) ;.…”

“…The classical Chevrel phases, containing blocks of Mo 6 X 8 , have been in interest for both structural respects and application to rechargeable batteries (Suresh, et al, 2008;Aurbach, et al, 2007). The new Chevrel phases In x Mo 15 Se 19 (x=2.9 and 3.3) also have been studied by X-ray single-crystal method (Grüttner et al, 1979).…”

Study on the Electrolyte Containing AlBr3 and KBr for Rechargeable Aluminum Batteries

“…High specific energy density is an essential factor for EV applications, and can be realized by increasing voltage or/and capacity. Recently, new rechargeable batteries with high theoretical specific energy density like air-metal batteries (Kraytsberg & Ein-Eli, 2011;Kumar et al, 2010) and multivalent cation batteries (Mizrahi et al, 2008;Aurbach et al, 2007;Jayaprakash et al, 2011) have attracted attention. Both batteries have lower theoretical electromotive force than LIBs, but they have much higher theoretical specific capacity than LIBs, greatly improving specific energy density.…”

“…Both batteries have lower theoretical electromotive force than LIBs, but they have much higher theoretical specific capacity than LIBs, greatly improving specific energy density. Magnesium is being investigated as a promising negative electrode active material for multivalent cation batteries because it has larger specific capacity and is easy to handle and abundant on the earth (Mizrahi et al, 2008;Aurbach et al, 2007).…”