Employing first-principles calculations, the energy storage properties and ion diffusion dynamics of Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Zn²⁺, and Al³⁺ on bare (Mo_2/3Sc_1/3)₂C and surface-functionalized (Mo_2/3Sc_1/3)₂CT₂ (T = −O, −OH, and −F) i-MXenes are predicted. The investigated i-MXenes show weak adsorption ability to the Zn²⁺ ion regardless of the surface terminations, excluding their use as anodes for Zn ion batteries. The first-principles molecular dynamics simulations indicate that the adsorption of alkaline (earth) metal ions and Al³⁺ on (Mo_2/3Sc_1/3)₂C(OH)₂ and (Mo_2/3Sc_1/3)₂CF₂ causes the surface reaction between metal ions and surface terminations, leading to the formation of metal hydride or fluorite overlayers covering the underneath remaining i-MXenes. We find that the bare (Mo_2/3Sc_1/3)₂C and (Mo_2/3Sc_1/3)₂CO₂ are suitable candidates for use as anodes for alkaline (earth) metal and Al ion batteries. Specifically, both (Mo_2/3Sc_1/3)₂C and (Mo_2/3Sc_1/3)₂CO₂ i-MXenes show good ion storage capacities, ideal open circuit voltages, and fast ion diffusion dynamics for alkaline (earth) metal ions. Notably, the predicted theoretical capacities of (Mo_2/3Sc_1/3)₂C ((Mo_2/3Sc_1/3)₂CO₂) for Li⁺, Mg²⁺, and Al³⁺ are 291 mAh g^–1 (254 mAh g^–1), 490 mAh g^–1 (436 mAh g^–1), and 886 mAh g^–1 (640 mAh g^–1), respectively. In addition, the calculated open circuit voltage profiles of Li⁺, Mg²⁺, and Al³⁺ exhibit the small on-set voltage and the board plateau region. The climbing image-nudged elastic band predicts that the diffusion energies of Li⁺, Na⁺, K⁺, and Ca²⁺ ions on bare (Mo_2/3Sc_1/3)₂C are extremely small (<0.05 eV), and the O-terminated surface show higher diffusion energies for various metal ions. Overall, (Mo_2/3Sc_1/3)₂C and (Mo_2/3Sc_1/3)₂CO₂ are good electrode materials for fast charging alkaline (earth) metal ion batteries and supercapacitors.

中文翻译：

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评估 (Mo2/3Sc1/3)2C 和 (Mo2/3Sc1/3)2CT2 (T = -O、-OH 和 -F) i-MXenes 作为锂和非锂离子电池的高性能电极材料

采用第一性原理计算，Li ⁺、Na ⁺、K ⁺、Mg ²⁺、Ca ²⁺、Zn ²⁺和Al ³⁺在裸（Mo _2/3 Sc _{1/ 3} ) ₂ C 和表面功能化 (Mo _2/3 Sc _1/3 ) ₂ CT ₂ (T = -O、-OH 和 -F) i-MXenes 被预测。所研究的 i-MXenes 对 Zn ^{2+的吸附能力较弱}离子，无论表面终端如何，不包括它们用作锌离子电池的阳极。第一性原理分子动力学模拟表明碱（土）金属离子和Al ³⁺在(Mo _2/3 Sc _1/3 ) ₂ C(OH) ₂和(Mo _2/3 Sc _1/3 )上的吸附₂ CF ₂引起金属离子和表面末端之间的表面反应，导致形成金属氢化物或萤石覆盖层，覆盖下面剩余的 i-MXenes。我们发现裸露的 (Mo _2/3 Sc _1/3 ) ₂ C 和 (Mo _2/3 Sc _1/3) ₂ CO ₂适合用作碱（土）金属和铝离子电池的阳极。具体而言，(Mo _2/3 Sc _1/3 ) ₂ C 和 (Mo _2/3 Sc _1/3 ) ₂ CO ₂ i-MXenes 均显示出良好的离子存储能力、理想的开路电压和快速的碱性离子扩散动力学（土）金属离子。_{值得注意的是，(Mo 2/3} Sc _1/3 ) ₂ C ((Mo _2/3 Sc _1/3 ) ₂ CO ₂ )对Li ⁺ , Mg ²⁺的预测理论容量, 和 Al ³⁺分别为 291 mAh g ^–1 (254 mAh g ^–1 )、490 mAh g ^–1 (436 mAh g ^–1 ) 和 886 mAh g ^–1 (640 mAh g ^–1 )。^{此外，计算的Li +}、Mg ²⁺和Al ³⁺的开路电压分布表现出小的启动电压和电路板平台区域。爬升图像微调弹性带预测 Li ⁺、Na ⁺、K ⁺和 Ca ²⁺离子在裸 (Mo _2/3 Sc _1/3 ) _{2上的扩散能}C 极小（<0.05 eV），O 端面对各种金属离子表现出更高的扩散能。总体而言，(Mo _2/3 Sc _1/3 ) ₂ C 和(Mo _2/3 Sc _1/3 ) ₂ CO ₂是用于快速充电碱（土）金属离子电池和超级电容器的良好电极材料。