Revealing the chemical compatibility of common solvents and electrolytes with Mo2TiC2-based MXenes and their interfaces in aluminum-ion batteries (AIBs) through first-principles molecular dynamics simulations

Abstract

Using the first-principles molecular dynamics simulations and CI-NEB calculations, we performed a systematic and comprehensive investigation on the chemical compatibility of various solvents (carbonate esters, aromatic solvents, ethers, carboxylic esters, water, DMSO and ionic liquids) and electrolytes (DMC–Al(OTF)₃, DME–Al(OTF)₃, GBL–Al(OTF)₃, H₂O–Al₂(SO₄)₃, DMSO–Al(OTF)₃, [EMIm]⁺Cl⁻–[AlCl₃] and urea–AlCl₃) with Mo₂TiC₂-based MXenes, evaluating their possible use as solvents, additives and electrolytes in aluminum-ion batteries (AIBs). Among the investigated solvents, carbonate ester (DMC), chain ether (DME), aromatic hydrocarbons (benzene, toluene), chain carboxylic ester (GBL), DMSO, ionic liquids ([EMIm]⁺Cl⁻, [DMPI]⁺Cl⁻ and [BMP]⁺Cl⁻) and urea showed very low reactivity towards both bare Mo₂TiC₂ and Al-terminated structures (Mo₂TiC₂Al₂ and Mo₂TiC₂Al₆ monolayers), indicating their excellent chemical compatibility between these solvents and the MXene cathode. Besides the Mo₂TiC₂ monolayer, a relatively low chemical reactivity was predicted for Al-terminated MXenes after their contact with almost all the solvents considered in this work, even with the relatively more reactive carbonate esters (PC and EC) and ethers (G2 and THF). The electrolytes DMC–Al(OTF)₃ and ionic liquid ([EMIm]⁺Cl⁻–AlCl₃) exhibited high chemical compatibility with Mo₂TiC₂-based MXenes and exhibited promising electrochemical reactivity at the interface between the electrolyte and electrode. Alternatively, either the decomposition of the electrolyte components or the low electrochemical reactivity of Al³⁺ was observed in other electrolyte systems (DME–Al(OTF)₃, GBL–Al(OTF)₃, H₂O–Al₂(SO₄)₃, DMSO–Al(OTF)₃ and urea–AlCl₃), indicating poor reversibility and cyclic performance of AIBs.