Evaluating the behaviour of deep eutectic solvent electrolytes on 2D Ca2C MXene anode for the Li-ion batteries

Abstract

Rechargeable Li-ion batteries (LIBs) are one of the green energy storage devices that have been utilized in large-scale devices. Hence, improving the LIBs performance plays a crucial role in many industrial sectors. Herein, we introduce a novel electrode and electrolytes for improving the LIBs efficiency. The deep eutectic solvents (DESs) electrolytes based on lithium bis[(trifluoromethyl)sulfonyl] imide (Li[TFSI]) and two different ratios of 2,2,2-trifluoroacetamide (TFA): (Li[TFSI] : 2TFA and Li[TFSI] : 4TFA), and the calcium carbide monolayer (Ca₂C-ML) MXene were used as an anode in the LIBs. The molecular dynamics (MD) simulation and density functional theory (DFT) calculations are performed to evaluate the interaction and orientation of DESs on Ca₂C-ML. The density profiles, pair correlation functions, mean square displacement (MSD), diffusion coefficient, ionic conductivity, molecular orientation, and charge density profiles analyses are performed to determine the behavior of DESs on Ca₂C-ML. The results indicate that in both DESs, the adsorption of Li⁺ cations and TFA species on the Ca₂C surface is more than that of the [TFSI]⁻ anions. However, the interaction of Li⁺ cations on the Ca₂C surface in Li[TFSI]:2TFA is stronger than in Li[TFSI]:4TFA. Because the adsorption of Li⁺ on the Ca₂C occurs favorably, the low intercalation potential of Li⁺ on the Ca₂C anode can be predicted. Additionally, the simulations are carried out at higher temperatures (333.15 K, 353.15 K, and 373.15 K), and the enhancement in MSD, diffusion coefficient, and ionic conductivity is observed by increasing the temperature. Meanwhile, the low open-circuit voltage (0.30 V) during the Li-ion intercalation processes further shows the advantages of Ca₂C MXene as a potential candidate for LIB anodes. Overall, it is hoped that these findings will provide guidance for the future design of high efficiency LIBs using the Li-based DESs electrolytes and novel MXene anodes.