Functionalized MXenes as effective polyselenide immobilizers for lithium-selenium batteries: a density functional...

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Lithium-selenium (Li-Se) batteries face challenges from polyselenide dissolution (shuttle effect) and inactive deposition, hindering practical applications.
• MXenes, with their high conductivity and mechanical strength, are promising for anchoring polyselenides and improving battery performance.

Purpose of the Study:

• To investigate the binding mechanism of lithium polyselenides (Li2Sen) on graphene and surface-functionalized Ti3C2 MXenes using density functional theory (DFT).
• To evaluate the anchoring capabilities of different functionalized MXenes (Ti3C2X2, where X = S, O, F, Cl) for polyselenides.

Main Methods:

• Density functional theory (DFT) calculations were employed to simulate the adsorption of Li2Sen on graphene and functionalized Ti3C2 MXenes.
• Graphene served as a reference material to compare the binding strengths of Li2Sen on various functionalized Ti3C2 surfaces.
• Density of States (DOS) analysis was used to assess the electronic conductivity of the MXene materials after polyselenide adsorption.

Main Results:

• Ti3C2S2 and Ti3C2O2 demonstrated superior anchoring behavior for Li2Sen compared to graphene, Ti3C2F2, and Ti3C2Cl2.
• The calculated adsorption strengths on S- and O-terminated Ti3C2 were greater than those of common ether-based electrolytes, crucial for suppressing the shuttle effect.
• Functionalized MXenes and graphene maintained structural integrity and conductivity after Li2Sen adsorption, facilitating redox electrochemistry.

Conclusions:

• Ti3C2S2 and Ti3C2O2 exhibit excellent anchoring properties for Li2Sen, offering a promising strategy for advanced Li-Se battery design.
• These findings support the development of carbon-free Ti3C2 MXene-based selenium cathode materials to enhance the electrochemical performance of Li-Se batteries.