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

Abstract

would impose restrictions on the penetration of LIBs into these large-volume markets. [3,4] In addition, after 25 years of continuous improvements, the mature LIBs technology is approaching a fundamental limit in terms of energy density (slightly above 300 W h kg −1 ) and costs at the materials level. [4][5][6] With the aforementioned concerns, alternative battery concepts have significantly stimulated research interests to further drive battery technologies to increase both the gravimetric and volumetric energy densities, reduce the cost, and expand the cycling life. [3,6,7] The "beyond Li-ion" technologies such as lithium-air, lithium-sulfur (Li-S), multivalent batteries, and solid-state batteries show the unique feature of using metal anodes that can store more energy via a reversible metal plating/stripping process. Unfortunately, these emerging or reviving technologies involving lithium metal inevitably meet the critical challenges of resource shortage. Furthermore, the high reactivity of lithium metal leads to electrolyte consumption and nonuniform lithium distribution (even dendritic growth) during cycling. These issues still hamper the mainstream commercialization of the lithium-metal-based batteries. [8,9] Rechargeable magnesium (Mg) batteries may offer considerable advantages (see Table 1) over Li-metal batteries because the metallic Mg anode shows double the volumetric capacity, safer and easier processing features, more uniform and nondendritic electroplating during cell charging, and cheaper costs due to its greater abundance in the earth crust. [4,[10][11][12][13] Based on these advantages, intensive attention has been garnered toward the development of new electrolytes, cathodes, and their corresponding mechanistic understandings for the rechargeable Mg batteries. Additionally, several industries including Pellion Technologies (a spin-off company from Massachusetts Institute of Technology), the Toyota Research Institute of North America, and recently Sony Corporation have initiated R&D projects for the rechargeable Mg batteries and tried to find practical application pathways. Nonetheless, developing a high-energy-density Mg battery with long cycle life and high rate capability is still a huge challenge due to the lack of high-performance cathodes and suitable Mg-ion electrolytes. [9,12] It is fair to state that the Chevrel phases, reported by Aurbach et al. in 2000, are still the most attractive Mg-ion Rechargeable magnesium (Mg) batteries are one of the potential contenders to replace current Li-ion batteries to power future electric vehicles with lower cost, higher safety, and extended mileage. To achieve this goal, both high-voltage intercalation-type cathodes and high-capacity conversion-type cathodes are considered. However, there are still no reports to compare rechargeable Mg batteries with the state-of-the art Li-ion batteries in terms of their overall performance. Also, potential cathode materials to deliver higher energy density in rechargeable Mg batteries are rarely summarized. Here, t...

A High‐Rate Rechargeable Mg Battery Based on AgCl Conversion Cathode with Fast Solid‐State Mg2+ Diffusion Kinetics

“…Such a long‐term cyclability is of the highest level as compared with the reported Mg‐storage cathodes (Table S1, Supporting Information). The capacity fading during initial cycles could be due to problems of conversion‐type cathodes, such as large irreversible‐phase transformations and dissolution of MgCl 2 …”

“…Therefore, it is of great significance to explore new type of cathode materials. Electrochemical conversion reaction provides an alternative strategy to widen the options of Mg‐storage cathode, since it is not essentially constrained by the crystal lattice, and thus various kinds of electrode materials could be selected to construct Mg batteries . However, conversion‐type materials usually suffer from high activation energies during conversion reactions, and this issue will become more prominent for Mg batteries because of the bivalent Mg 2+ cation .…”

“…The reversibility of conversion reaction could be well‐explained by hard and soft acids and bases theory. Since X 2 n − anion is bonded with bivalent Mg 2+ ion (hard acid), using soft X 2 n − anions (such as S 2− and Se 2− ) is expected to weaken the Mg—X bonds, and thus could improve the reversibility of conversion reaction . However, selection of M element is also of great significance.…”

A Multifunctional Separator Enables Safe and Durable Lithium/Magnesium–Sulfur Batteries under Elevated Temperature

“…Besides, as revealed by the SEM image of the surface of LLZO-embedded PEO coating layer ( Figure S10c,d, Supporting Information), the macropores of the pristine PI separator have been filled with rigid-flexible composites of LLZO and PEO mixtures, which could further prevent the in situ formed copper sulfides from migrating to anode side. [2,31,32] However, the notorious polysulfide shuttling effects and the sluggish S/MgS conversion severely imped their developments. Nevertheless, the relative content of copper element is only ≈0.25% detected by energy dispersive X-ray spectroscopy (EDS) results even after 100 cycles.…”

Halogenid‐basierte Materialien und Chemie für wiederaufladbare Batterien

“…[162] Viele Bestrebungen, die RMBs entgegengebracht wurden, wurden in Übersichtsartikeln erçrtert und zusammengefasst. [30,31,35,161,[163][164][165][166][167] Ein potenzielles Hindernis in der Umsetzbarkeit von RMBs ist die Notwendigkeit, Elektrolytlçsungen zu entwickeln, die eine reversible Mg-Ablagerung/Auflçsung ermçglichen. [35,168] Die halogenhaltigen Elektrolyten haben sich dabei als geeignet herausgestellt.…”