S-functionalized MXenes as electrode materials for Li-ion batteries

• Zr2CS2 MXenes are promising electrode materials for Li-ion batteries.
• S groups can be introduced by reaction with CS2 in solution.
• S groups reduce the Li diffusion barrier as compared to O groups.

MXenes are promising electrode materials for Li-ion batteries because of their high Li capacities and cycling rates. We use density functional theory to investigate the structural and energy storage properties of Li decorated Zr2C and Zr2CX2 (X = F, O and S). We find for Zr2C and Zr2CS2 high Li specific capacities and low diffusion barriers. To overcome the critical drawbacks of the OH, F, and O groups introduced during the synthesis we propose substitution by S groups and demonstrate that an exchange reaction is indeed possible. Zr2CS2 shows a similar Li specific capacity as Zr2CO2 but a substantially reduced diffusion barrier.

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