Ti3AlC2中位点选择性钇取代实现Ti3C2Tx正极的层间工程与锂传输，用于高功率储能

中文摘要 AI 辅助

在本工作中，我们引入了一种前驱体级策略，通过在自下而上的MAX制备过程中，将少量钇替代性掺杂到Ti3AlC2 MAX前驱体中。这使得结构发生永久性改变，并在所得的Ti3C2Tx MXene中得以保留。密度泛函理论（DFT）计算确定，在本文所用的富铝合成条件下，面向Al层的外侧Ti(4f)位点是Y的优先掺入位点，而非内侧Ti(2a)或Al(2b)位点。这种位点特异性取代与实验观察到的晶格膨胀和碳化物类Y键合一致，并为所得Ti3C2Tx MXene中保留的结构变化提供了微观基础。Y的掺入因羟基表面终止基团数量的增加而扩大了MXene的层间距，为锂离子传输创造了更有利的路径。全面的结构表征（包括XRD、XPS和TEM）证实了这些改性。结果表明，Y掺杂的Ti3C2Tx正极表现出扩散控制的电荷存储，锂扩散系数为10-9-10-11 cm2/s。在0.2 C倍率下，其可逆容量约为130 mAh/g，在2 C倍率下循环1000次后仍保持74 mAh/g，库仑效率接近100%。该电极还实现了高达3970 W/kg的功率密度，优于未掺杂的MXene和先前报道的多层MXene正极。这些结果表明，对MAX前驱体进行替代性掺杂是控制MXene层间结构和改善离子传输的一种有前景的策略，为开发高功率储能电极提供了新途径。

英文摘要

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.

发表机构

• ICMUV, Instituto de Ciencia de Materiales, Universidad de Valencia（瓦伦西亚大学材料科学研究所）
• King Danylo University（丹尼洛国王大学）
• Department of Applied Physics and Electromagnetism, University of Valencia（瓦伦西亚大学应用物理与电磁学系）

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