Centre for Advanced Optoelectronic Functional Materials Research and Key Laboratory for UV Light-Emitting Materials and Technology of Ministry of Education , Northeast Normal University , Changchun 130024 , China.
J Am Chem Soc. 2018 May 9;140(18):5962-5968. doi: 10.1021/jacs.8b02016. Epub 2018 May 1.
Sodium-ion batteries (SIBs) have attracted considerable attention due to the intrinsic safety and high abundance of sodium. However, the lack of high-performance anode materials becomes a main obstacle for the development of SIBs. Here, we identify an ideal anode material, a metallic TiC monolayer with not only remarkably high storage capacity of 1278 mA h g but also low barrier energy and open-circuit voltage, through first-principles swarm-intelligence structure calculations. TiC still keeps metallic after adsorbing two-layer Na atoms, ensuring good electrical conductivity during the battery cycle. Besides, high melting point and superior dynamical stability are in favor of practical application. Its excellent performance can be mainly attributed to the presence of an unusual n-biphenyl unit in the TiC monolayer. High cohesive energy, originating from multibonding coexistence (e.g., covalent, ionic, and metal bonds) in the TiC monolayer, provides strong feasibility for experimental synthesis. In comparison with TiC, functionalized TiC with oxygen shows a higher storage capacity; meanwhile, it keeps nearly the same barrier energy. This is in sharp contrast with metal-rich MXenes. These intriguing properties make the TiC monolayer a promising anode material for SIBs.
钠离子电池（SIBs）由于钠的固有安全性和高丰度而引起了相当大的关注。然而，缺乏高性能的阳极材料成为 SIBs 发展的主要障碍。在这里，我们通过第一性原理群智能结构计算，确定了一种理想的阳极材料，即具有 1278 mA h g 高存储容量、低势垒能和开路电压的金属 TiC 单层。TiC 在吸附两层 Na 原子后仍保持金属性，确保了电池循环过程中的良好导电性。此外，高熔点和优异的动力学稳定性有利于实际应用。其优异的性能主要归因于 TiC 单层中存在不寻常的 n-联苯单元。TiC 单层中多键共存（如共价键、离子键和金属键）产生的高内聚能为实验合成提供了很强的可行性。与 TiC 相比，功能化 TiC 具有氧，显示出更高的存储容量；同时，它保持几乎相同的势垒能。这与富金属 MXenes 形成鲜明对比。这些有趣的特性使 TiC 单层成为 SIBs 有前途的阳极材料。
