Electrochemical Mg²⁺ Displacement Driven Reversible Copper Extrusion/Intrusion Reactions for High‐Rate Rechargeable Magnesium Batteries

Abstract

Rechargeable magnesium batteries (RMBs) based on metal Mg anodes have shown great potential owing to the abundant natural resources, high volumetric capacity, and low safety hazard. Nevertheless, the development of RMBs is hampered by the sluggish kinetics of Mg2+ diffusion and the limited cyclability of cathode materials. Herein, nonstoichiometric copper selenide (Cu2–xSe) are synthesized via a solution‐based method and exploited as a durable cathode material based on ionic displacement mechanism for RMBs. The copper ions in the Se2− based sub‐lattices are reversibly exchanged by Mg2+ ions without causing lattice collapse. Owing to the same face‐centered cubic Se2− sub‐lattices and similar unit cell size of Cu2–xSe and MgSe, the energy barrier for lattice reconstruction during cycling processes is very low, significantly improving the rate performance, structural stability, and cycle life of the Cu2–xSe cathode. Moreover, metal Cu is in situ generated during discharging, thus greatly facilitating electron transport. Comprehensive characterizations confirm that the Cu2–xSe cathode undergoes reversible copper ion extrusion/reinjection during the discharge−charge steps. This work suggests the great potential for exploring high‐performance electrode materials based on ionic displacement mechanism for advanced multivalent‐ion secondary batteries.

A Pyrite Iron Disulfide Cathode with a Copper Current Collector for High‐Energy Reversible Magnesium‐Ion Storage

“…d) Specific capacity and gravimetric energy density values of the as-prepared FeS 2 cathode and some previously reported metal chalcogenide cathodes in RMBs or hybrid batteries using Mg metal anode. [4,[16][17][18][19][20][21][22]33,59,[65][66][67][68][69][70][71][72][73][74][75] e) Cycling performance of the FeS 2 cathodes at 200 or 400 mA g −1 after activation of 15 cycles at 50 mA g −1 .…”

“…[8][9][10] However, the design of high-energy-density RMBs requires the development of high-performance magnesium-free cathode materials by using the Mg metal anode. [11,12] Various cathode materials, including transition metal oxides, [13][14][15] transition metal chalcogenides, [16][17][18][19][20][21][22][23] chalcogens, [24][25][26][27] transition metal halides, [28] halogens, [29] and polyanion-based compounds, [30,31] have been investigated for magnesium storage. Considering the strong polarization effect of the multivalent magnesium ion with a small ionic radius, cathode materials of chalcogens (e.g., S and Se) [27,32] and chalcogenides (e.g., TiS 2 , Cu 2 Se, CuS, and VS 4 ) [18,19,22,33] have attracted considerable attention due to the lower electronegativity of chalcogen anions.…”

“…[11,12] Various cathode materials, including transition metal oxides, [13][14][15] transition metal chalcogenides, [16][17][18][19][20][21][22][23] chalcogens, [24][25][26][27] transition metal halides, [28] halogens, [29] and polyanion-based compounds, [30,31] have been investigated for magnesium storage. Considering the strong polarization effect of the multivalent magnesium ion with a small ionic radius, cathode materials of chalcogens (e.g., S and Se) [27,32] and chalcogenides (e.g., TiS 2 , Cu 2 Se, CuS, and VS 4 ) [18,19,22,33] have attracted considerable attention due to the lower electronegativity of chalcogen anions. In particular, the elemental sulfur-based cathodes have garnered increased interest due to the impressively high theoretical energy density by the combination of sulfur and magnesium electrodes with characteristics of low costs and resource abundance.…”

Bimetallic sulfide NiCo2S4 yolk–shell nanospheres as high-performance cathode materials for rechargeable magnesium batteries

“…The difficulty lies in the strong coulombic interaction between highly polarized Mg 2+ ions and the cathode host, which might inevitably result in sluggish solid-state diffusion of the latter and slow interfacial charge transfer, thus causing poor electrochemical performance of RMBs. Besides the intercalation-type cathodes which have been studied extensively but yield a relatively low specific capacity and poor cycling life, 11 conversion-type materials, such as CuS, 12 CuSe, 13 CoS, 14 Ag 2 S, 15 and AgCl, 16 are promising cathode candidates for RMBs considering their high theoretical capacity and appropriate voltage platform. Nevertheless, conversion-type materials for RMBs still suffer from several drawbacks including poor intrinsic electrical conductivity, huge volume expansion, and nanoparticle aggregation, which imperatively need to be further resolved.…”

Encapsulating Metal-Organic-Framework Derived Nanocages into a Microcapsule for Shuttle Effect-Suppressive Lithium-Sulfur Batteries

“…In order to address those issues, many studies have been reported, in which the synthesis of yolk-shell structure hosts is considered to be a potential strategy [8][9][10]. Zhang et al reported a yolk-shell ZnO by using a hydrothermal method, which provided a specific capacity of 1406 mAh g −1 at 0.1C [11].…”