Current Progress on Rechargeable Magnesium–Air Battery

Abstract

in reversible oxidation/reduction reaction to achieve a high energy density. (ii) Fast charge transport and high exchanging current density of materials dramatically reduce the polarization and further provide a high power density. (iii) Uniform micro/nanostructures are associated with increased specific surfaces areas and decreased ionic diffusion over distance and time, resulting in a long lifetime and a good cycling stability.Among various energy sources in history, rechargeable cells are lead (Pb)-acid, nickel-chromium (Ni-Cr), nickel-metal hydride (Ni-MH), redox flow, lithiumion, fuel cells and metal-air batteries. [2] In particular, rechargeable metal-air batteries have received great interest due to a huge theoretical specific energy density, deriving from a unique cell structure. In this system, only the metal (Li, Na, Mg, Al, Zn, Si, Fe, Sn, etc.) anode is assembled in the cell, while the active cathode material is oxygen (O 2 ), directly obtained from the atmosphere. [12][13][14][15][16][17] Figure 1a presents a summary of basic theoretical properties and electrochemical reactions in typical metal-air batteries. For instance, rechargeable Li-air batteries can provide a theoretical cell voltage of 2.96 V and a theoretical specific energy density of 3.4 kW h kg −1 . In this particular battery, the decomposition of lithium peroxide (Li 2 O 2 ), despite being an explosive and poisonous compound, plays a vital role in the improved charge transport because it demonstrates a highly reversible reaction between the discharge and charge process. [18,19] The maximum specific capacity of secondary Li-air batteries reaches an initial discharge capacity of 14000 mA h g −1 at a current density of 140 mA g −1 , using Co 3 O 4 /reduced graphene oxide nanocomposites as electrocatalysts. [20] Unfortunately, although they are the focus of numerous investigations, lithium-air batteries are still accompanied by the major drawbacks of the high price of metallic lithium (The USD $160000-180000/ton as of May 2017) and safety issues in an organic electrolyte.Magnesium provides a number of improvements compared to metallic Li, including its abundance in the earth's crust (2.08% for Mg vs 0.0065% for Li) and environmental friendliness. Moreover, rechargeable Mg-O 2 battery allows a theoretical volumetric density and a specific energy density of 14 kW h L −1 and 3.9 kW h kg −1 , respectively, assuming MgO is formed as the discharge product. [21,22] These values are much larger than those of Li-O 2 cells on the basis of Li 2 O 2 (8.0 kW h L −1 and 3.4 kW h kg −1 ). Though a great number of efforts have focused on the widespread studies of Li-air Rechargeable Mg-air batteries are a promising alternative to Li-air cells owing to the safety, low price originating from the abundant resource on the earth, and high theoretical volumetric density (3832 A h L −1 for Mg anode vs 2062 A h L −1 for Li). Only a few works are related to the highly reversible Mg-air batteries. The fundamental scientific difficulties hindering the rapid developmen...

Atomic Fe–Nx Coupled Open‐Mesoporous Carbon Nanofibers for Efficient and Bioadaptable Oxygen Electrode in Mg–Air Batteries

“…Theoretically, Mg–air batteries are capable of providing high‐energy density and discharge voltage in neutral condition; meanwhile, the Mg alloy exhibits good bioresorbability and the produced Mg 2+ ions show no toxicity towards the environment and the human body . However, the high polarization, low coulombic efficiency, and much lower working voltage than theoretical voltage of these Mg–air batteries during operation limit their widespread application . One of the most important scientific challenges reducing the performances of Mg–air batteries is the sluggish kinetics of the oxygen reduction reaction (ORR) at the air cathode …”

Rechargeable Magnesium Batteries using Conversion‐Type Cathodes: A Perspective and Minireview

“…In addition, common challenges and recent advances are particularly discussed in this section. Because of a recent well‐organized Progress Report relating to high‐capacity O 2 or air and conversion‐type oxide of MnO 2 cathodes, we will not discuss these battery chemistries in detail …”

Toward Promising Cathode Catalysts for Nonlithium Metal–Oxygen Batteries

“…Compared with Zn–O 2 batteries, the research on the ORR electrocatalysts for primary Mg–O 2 batteries is very limited, due to the intrinsic passivation of Mg anode . As summarized in Table S1 (Supporting Information), most primary Mg–O 2 batteries show a low OCV of 1.2–1.8 V (vs the theoretical value of 2.95 V) and a low power output below 100 mA cm −2 , which is mainly because of the net corrosion potential originated from the Mg corrosion.…”

“…In contrast, MgO is hard to decompose in the organic electrolytes even at high voltages. Hence, increasing the reactivity of MgO during the charge process is critical for rechargeable Mg–O 2 batteries . Shiga et al successfully established a catalytic pathway for secondary Mg–O 2 batteries with iodine‐dimethylsulfoxide complex (I 2 –DMSO) and 2,2,6,6‐tetramethylpiperidine‐oxyl (TEMPO)–anion complex as the electrocatalyst to decompose MgO (Figure f) .…”