High‐Rate and Long Cycle‐Life Alloy‐Type Magnesium‐Ion Battery Anode Enabled Through (De)magnesiation‐Induced Near‐Room‐Temperature Solid–Liquid Phase Transformation

Abstract

alternative electrochemical energy storage systems are desirable to satisfy our growing demand for energy. Magnesiumion batteries (MIBs) offer many distinct advantages over their LIB and sodiumion battery (SIB) counterparts, including the earth-abundance of magnesium (Mg), the reversible dendrite-free deposition of Mg, [2,[6][7][8][9][10][11] the divalent nature of Mg ion and its smaller ionic radius compared to lithium (Li) and sodium (Na) ions, [12][13][14] and finally the fact that metallic Mg is less reactive and therefore safer than Li and Na metals. [8,[15][16][17][18][19] Despite these remarkable features, progress toward the development of practical MIBs has been impeded partly by the absence of suitable electrolytes that are compatible with Mg metal as the anode. [7,15,[20][21][22] Typically, common salts and organic solvent combinations like those used in LIBs and SIBs yield a Mg-ion-blocking film on the Mg metal anode. [7,[20][21][22][23][24] A promising way to circumvent this electrolyte issue involves the use of Mg alloy as the anode instead of pure Mg metal. Bismuth (Bi) and tin (Sn) are two promising candidate materials used as alloy-type MIB anodes, in which Mg is reversibly stored to make Mg 3 Bi 2 and Mg 2 Sn alloys, respectively. [1,[25][26][27] Unfortunately, state-of-the-art alloy-type MIB anodes can only be reversibly (dis)charged up to 200 cycles with acceptable capacity retention, [28] which is far below the 1000 cycles or more required for practical battery applications. In general, the capacity of MIB electrodes decays rapidly during cycling due to gradual material failure caused by massive volume expansions (up to 300%), and significant mechanical stresses, [27][28][29][30] which arise during solid-solid phase transformations. This occurs when a solid host MIB anode material (e.g., Bi, rhombohedral crystal structure) stores Mg to form a new solid phase material with a completely different crystal structure (e.g., β-Mg 3 Bi 2 , cubic crystal structure). [16,25] During the reverse process, Mg is removed from this new phase and transforms back to the initial host material. In doing so, the materials cracks and pulverizes into fragments, failing to restore its original shape and causing the battery to die within a few cycles. This issue represents a fundamental challenge in alloytype anodes. [31] In this work, we propose to overcome this challenge by taking advantage of the self-healing property of some Resources used in lithium-ion batteries are becoming more expensive due to their high demand, and the global cobalt market heavily depends on supplies from countries with high geopolitical risks. Alternative battery technologies including magnesium-ion batteries are therefore desirable. Progress toward practical magnesium-ion batteries are impeded by an absence of suitable anodes that can operate with conventional electrolyte solvents. Although alloy-type magnesium-ion battery anodes are compatible with common electrolyte solvents, they suffer from severe failure associated with huge volume ...

Revealing the Magnesium‐Storage Mechanism in Mesoporous Bismuth via Spectroscopy and Ab‐Initio Simulations

“…Alloy-type anodes such as Bi, [7] Sn, [8] Sb [9] and Ga [10] have been investigated in Mg-based batteries.Bismuth is attractive because of its relatively high theoretical volumetric capacity (1949 mAh cm À3 for Mg 3 Bi 2 ). [11] Additionally,B ic an be coupled with conventional carbonate electrolyte,a nd has been demonstrated to be applicable in high-voltage MIBs due to the flat and low redox potential of Bi/Bi 3+ .…”

“…Alloy‐type anodes such as Bi, [7] Sn, [8] Sb [9] and Ga [10] have been investigated in Mg‐based batteries. Bismuth is attractive because of its relatively high theoretical volumetric capacity (1949 mAh cm −3 for Mg 3 Bi 2 ) [11] .…”

Density Functional Theory Calculations for the Evaluation of FePS3 as a Promising Anode for Mg Ion Batteries

“…Many efforts have been devoted to developing cathode materials, such as Mo 6 S 8 [15], TiS 2 [16], and V 2 O 5 [17], but a few works have designed anode materials, such as Ga [18], Sn [19], and Bi [20,21], to replace Mg metal.…”

Alloy Anode Materials for Rechargeable Mg Ion Batteries

“…It can form Mg 2 Ga 5 , MgGa 2 , MgGa, Mg 2 Ga, and Mg 5 Ga 2 alloys with Mg which theoretical specific capacities are 307, 384, 768, 1536, and 1920 mAh g −1 , respectively. Wang et al [ 119 ] have recently reported a high‐performance Mg 2 Ga 5 alloy anode with an unprecedented long life of 1000 cycles and a relatively high rate performance of 3 C (current density: 922.5 mA g −1 ), as shown in Figure 5 . They fabricated Mg 2 Ga 5 alloy anodes by simply melting Ga and Mg chips at the stoichiometric ratio, using a graphite boat in a muffle furnace under argon environment.…”

“…Mg alloy anodes based on Bi and Sn have also shown compatibility with a variety of conventional electrolyte solutions, what provides a strong impetus to continue with the efforts of developing high energy density MIB prototypes based on Mg alloy anodes and conventional electrolyte systems. Very recently, Wang et al [ 119 ] have reported the compatibility of the Mg 2 Ga 5 anodes with conventional electrolyte solutions based on common solvents (e.g., AN, PC, and DME) and simple Mg salts (e.g., Mg(TSFI) 2 and Mg(ClO 4 ) 2 ) using cells based on demagnesiated Mg 2 Sn//conventional electrolyte solutions//Mg 2 Ga 5 configuration. They concluded that the Mg 2 Ga 5 and Mg 2 Sn electrodes can be compatible with AN‐based electrolytes based on Mg(TSFI) 2 and Mg(ClO 4 ) 2 salts while cannot work well with conventional electrolyte solutions based on PC and DME solvents.…”