Site-Selective Yttrium Substitution in Ti3AlC2 Enables Interlayer Engineering and Li Transport in Ti3C2Tx cathodes for High-Power Energy Storage

Tetiana Boichuk; Andrii Boichuk; Mahesh Eledath Changarath; Joao Fonseca; Said Agouram; Marie Finas; Alejandro Molina-Sanchez; Juan F. Sanchez-Royo

arXiv · 2609.32707

Site-Selective Yttrium Substitution in Ti3AlC2 Enables Interlayer Engineering and Li Transport in Ti3C2Tx cathodes for High-Power Energy Storage

Tetiana Boichuk·Andrii Boichuk·Mahesh Eledath Changarath·Joao Fonseca·Said Agouram·Marie Finas·Alejandro Molina-Sanchez·Juan F. Sanchez-Royo

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Abstract

In this work, we introduce a precursor-level strategy by substitutionally doping the Ti3AlC2 MAX precursor with a small amount of Yttrium during top-down MAX preparation. This allows permanent structural changes that are retained in the resulting Ti3C2Tx MXene. Density functional theory (DFT) calculations identify the outer Ti(4f) site, facing the Al layer, as the preferred incorporation site for Y under the Al-excess synthesis conditions used here, rather than the inner Ti(2a) or Al(2b) sites. This site-specific substitution is consistent with the experimentally observed lattice expansion and carbide-like Y bonding and provides a microscopic basis for the structural changes retained in the resulting Ti3C2Tx MXene. Y incorporation expands the MXene interlayer spacing due to an increase in the amount of hydroxyl surface terminations, creating more favorable pathways for lithium-ion transport. Comprehensive structural characterization (including XRD, XPS and TEM) confirms these modifications. As a result, the Y-doped Ti3C2Tx cathode shows diffusion-controlled charge storage with a Li diffusion coefficient of 10-9-10-11 cm2/s. It delivers a reversible capacity of about 130 mAh/g at 0.2 C and retains 74 mAh/g after 1000 cycles at 2 C with nearly 100% Coulombic efficiency. The electrode also achieves a high power density of up to 3970 W/kg, outperforming the undoped MXene and previously reported multilayered MXene cathodes. These results show that substitutional doping of the MAX precursor is a promising strategy for controlling the interlayer structure of MXenes and improving ion transport, providing a new route for the development of high-power energy-storage electrodes.

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Tetiana Boichuk, Andrii Boichuk, Mahesh Eledath Changarath, Joao Fonseca, Said Agouram, Marie Finas, Alejandro Molina-Sanchez, Juan F. Sanchez-Royo. 2026-09-26. Site-Selective Yttrium Substitution in Ti3AlC2 Enables Interlayer Engineering and Li Transport in Ti3C2Tx cathodes for High-Power Energy Storage. https://arxiv.org/abs/2609.32707

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