Two-dimensional transition metal carbides (MXenes) have received tremendous attention because of their great promise in flexible energy storage. Although surface engineering plays an important role in regulating the properties of MXenes with the development of synthesis technology, an atomistic design of surface diversity for desired functionalities is generally limited by purely unified surface termination. Herein, the Janus MXenes consisting of different surface terminations are proposed for flexible anodes through first-principles calculations. Taking TiC (, = O, F, or OH) as an illustration of Janus MXenes, critical strains, ideal strengths, Li-ion diffusion barriers, equilibrium voltages, and theoretical capacities are determined and used as descriptors to evaluate the properties of flexible anodes. These Janus MXenes exhibit high critical strains and ideal strengths, indicating their mechanical flexibility. The strain-independent Li-ion diffusion barrier of TiCOF suggests its fast Li-ion transport even suffering from mechanical deformation, endowing its application potential in flexible anodes. These results establish a theoretical framework for the comprehensive evaluation of flexible anode materials, providing a theoretical scheme for designing flexible anode materials.

中文翻译：

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通过表面工程制备柔性阳极的二维Janus过渡金属碳化物

二维过渡金属碳化物（MXenes）因其在柔性储能方面的巨大前景而受到了极大的关注。尽管随着合成技术的发展，表面工程在调节 MXene 的性能方面发挥着重要作用，但针对所需功能的表面多样性原子设计通常受到纯粹统一表面终止的限制。在此，通过第一原理计算，提出了由不同表面终端组成的 Janus MXenes 用于柔性阳极。以 TiC (, = O、F 或 OH) 作为 Janus MXenes 的说明，确定临界应变、理想强度、锂离子扩散势垒、平衡电压和理论容量，并将其用作描述符来评估柔性阳极的性能。这些 Janus MXene 表现出高临界应变和理想的强度，表明它们的机械灵活性。 TiCOF 的应变无关的锂离子扩散势垒表明，即使遭受机械变形，其也能快速传输锂离子，赋予其在柔性阳极中的应用潜力。这些结果为柔性负极材料的综合评价建立了理论框架，为柔性负极材料的设计提供了理论方案。