Nonaqueous magnesium electrochemistry and its application in secondary batteries

Abstract

A revolution in modern electronics has led to the miniaturization and evolution of many portable devices, such as cellular telephones and laptop computers, since the 1980s. This has led to an increasing demand for new and compatible energy storage technologies. Furthermore, a growing awareness of pollution issues has provided a strong impetus for the science and technology community to develop alternatives with ever-higher energy densities, with the ultimate goal of being able to propel electric vehicles. Magnesium's thermodynamic properties make this metal a natural candidate for utilization as an anode in high-energy-density, rechargeable battery systems. We report herein on the results of extensive studies on magnesium anodes and magnesium insertion electrodes in nonaqueous electrolyte solutions. Novel, rechargeable nonaqueous magnesium battery systems were developed based on the research. This work had two major challenges: one was to develop electrolyte solutions with especially high anodic stability in which magnesium anodes can function at a high level of cycling efficiency; the other was to develop a cathode that can reversibly intercalate Mg ions in these electrolyte systems. The new magnesium batteries consist of Mg metal anodes, an electrolyte with a general structure of Mg(AlX(3-n)R(n)R')(2) (R',R = alkyl groups, X = halide) in ethereal solutions (e.g., tetrahydrofuran, polyethers of the "glyme" family), and Chevrel phases of MgMo(3)S(4) stoichiometry as highly reversible cathodes. With their practical energy density expected to be >60 Wh/Kg, the battery systems can be cycled thousands of times with almost no capacity fading. The batteries are an environmentally friendly alternative to lead-acid and nickel-cadmium batteries and are composed of abundant, inexpensive, and nonpoisonous materials. The batteries are expected to provide superior results in large devices that require high-energy density, high cycle life, a high degree of safety, and low-cost components. Further developments in this field are in active progress.

Solution Structure and Magnesium Deposition Electrochemistry of Mixing Alkylmagnesium Halide with Magnesium Sulfonyl Amide/Glyme Solution

“…[1][2][3] The reversible deposition-dissolution of magnesium, through the negative electrode reaction, is difficult to conduct in conventional non-aqueous electrolytes consisting of magnesium salts dissolved in aprotic polar solvents because of the high reactivity of fresh magnesium metal toward such solvents and the resultant surface passivation layer. The existence of such a passivation layer provides a great degree of difference of potential between magnesium deposition and dissolution.…”

Exploring the Liquid Structure and Ion Formation in Magnesium Borohydride Electrolyte Using Density Functional Theory

“…1,2 These challenges have motivated researchers in recent years to consider alternatives to lithium-ion batteries, such as sodium 3,4 and multivalent 5,6 battery chemistries. Ever since the first prototypes were developed, 7,8 magnesium batteries have attracted much interest from the research community. Compared with lithiumion batteries, magnesium batteries have several advantages, such as their high volumetric capacity (3832 mAh/cm 3 ), which is a result of the divalency of magnesium.…”

“…12,13 There are only a handful of electrolytes known to be stable 14 during battery cycling, due to the reactivity of the Mg anode. 8,15 Lu et al considered different classes of organic solvents; 15 those containing carbonate or nitrile groups led to the formation of surface films on the anode, but ethereal solvents remained inactive. Additionally, salt anions such as ClO 4 − and BF 4 − led to the formation of passivation layers with high impedance.…”

“…Additionally, salt anions such as ClO 4 − and BF 4 − led to the formation of passivation layers with high impedance. Magnesium organohaloaluminates 16,17 popularized by Aurbach et al, 8 and the magnesium aluminum chloride complex 18 are examples of electrolytes which have successfully demonstrated high anodic stability and the capability to reversibly plate magnesium, but they contain halides which are corrosive to some battery parts.…”

Corrosion Resistance of Current Collector Materials in Bisamide Based Electrolyte for Magnesium Batteries

“…Recently Mg batteries have gained large interest due to the high theoretical energy density of Mg (2233 mAh g −1 and 3832 mAh cm −3 , respectively) but also because of the comparable low price, high abundance and the non-toxic properties of Mg. 1,2 In contrast to metallic Li, no dendrite formation has been observed during electrochemical cycling of Mg. 3,4 Thus, the technical application of metallic Mg anodes for secondary batteries with liquid electrolyte is not hampered by safety concerns as they exist for metallic Li. As the energy density of a battery is determined by the capacity of the electrode materials and by the potential difference between the anode and the cathode, both should be as high as possible.…”