Unraveling the Anchoring Effect of MXene-Supported Single Atoms as Cathodes for Aluminum–Sulfur Batteries

Abstract

As an alternative energy storage system, the stable cycle and high-rate performance of aluminum–sulfur (Al–S) batteries are increasingly affected by the dissolution of intermediate Al polysulfide (Al2S n ) into the electrolyte. Introducing anchoring materials that can promote Al2S n conversion is an effective way to solve this problem. However, the lack of an interaction mechanism between Al2S n and anchoring materials hinders the design of anchoring materials. Here, we used single-atom-loaded MXene (SA@MXene) as a representative anchoring material to systematically investigate the binding strength between SA@MXene and Al2S n , the sulfur reduction process on MXene, and their geometric configurations, stabilities, and electronic structures. We evaluated the reaction activity of the various SA@MXene nanosheets and discovered four high-performance cathode candidates for Al–S batteries (SA = Y, Nb, Mo, Tc) with a minimum reaction energy barrier of 0.23 eV. Importantly, to unravel the interaction mechanism between Al2S n and the anchoring material, we proposed an activity volcano by consolidating the decisive S8*, Al2S8*, and Al2S12* binding strengths, which provides a significant roadmap for designing cathodes for Al–S batteries. The proposed study of the Al–S conversion process will benefit the understanding of sulfur chemistry and provide valuable inspiration for the design of other catalytic reaction processes.

Aprotic Sulfur–Metal Batteries: Lithium and Beyond

“…As far as we know, all reports about Ca-S cells have exploited simple sulfur–carbon composites at the positive side by applying mesoporous carbon materials . On the contrary, in the case of Al-S systems, where the shuttle effect of PS is remarkable, the majority of publications have exploited sulfur host structures based, for example, on activated carbon, MOFs, M-Xenes, and doped graphene . Ai et al developed a TiN@N-doped graphene catalyst for use as the sulfur cathode in Al-S batteries, which suppressed the Al-PS shuttle effect, improved the redox kinetics, and reduced the decomposition barrier, being able to deliver ∼993 mAh g –1 in the first cycle and to maintain a capacity of ∼500 mAh g –1 after 200 cycles (see Figure e) .…”

“…On the computational side, an extensive DFT study was carried out by Wang et al in order to unravel the anchoring properties of SAC-decorated (SA@Ti 3 C 2 O 2 ) M-Xenes by screening several SAC metals. Their analysis showed that SAC = Y, Nb, Mo, and Tc are potential candidates for high-performance cathodes, showing good adsorption energies for Al-PS and low reaction barriers (see Figure e) …”

“…Their analysis showed that SAC = Y, Nb, Mo, and Tc are potential candidates for high- performance cathodes, showing good adsorption energies for Al-PS and low reaction barriers (see Figure 3e). 68 ■ TOWARDS A SUITABLE ELECTROLYTE FOR…”

“…Right: binding energies of S 8 and Al 2 S n PSs on different SA@Ti 3 C 2 O 2 nanosheets and relative free energy of conversion. [Adapted with permission from ref . Copyright 2021 American Chemical Society.…”

Modified Solid Electrolyte Interphases with Alkali Chloride Additives for Aluminum–Sulfur Batteries with Enhanced Cyclability

“…In this context, elemental sulfur with high specific capacity (1672 mAh g −1 ) and low cost is a promising cathode material for high-energy-density AMBs, that is, Al-S batteries. [11][12][13][14][15][16] When the sulfur cathode is dis-/charged in a potential window <1.8 V versus Al 3+ / Al with the [AlCl 3 ] 1.3 [EmimCl] 1 electrolyte, the reaction mechanism can be described by the following reactions: [17][18][19] Anode : Al 7AlCl 4Al Cl 3e 4 2 7…”