Zha Xian-Hu, Ma Xiufang, Luo Jing-Ting, Fu Chen
Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
Nanoscale. 2022 Jul 28;14(29):10549-10558. doi: 10.1039/d2nr02271k.
Sodium ion batteries (SIBs) have attracted increasing attention due to their low cost and abundant reserves of sodium, but their ideal anode materials still need to be explored. MXenes could be candidate electrode materials due to their excellent electrical conductivity and large specific surface area. In this work, the theoretical performance of Ti- and Zr-containing MXenes TiCT (T = O, F, OH) and ZrCT (T = O, F, OH, S) as SIB anode materials is investigated. The influence of the Hubbard correction is discussed, and the behaviour at the MXene surface with the partial occupation of sodium atoms is considered. Including the weight and volume of adsorbed sodium atoms, TiCO presents the best performance among the seven MXenes studied. Its mass and volumetric capacities are 299 mA h g and 993 mA h cm respectively, and the migration barrier and open circuit voltage are 0.138 eV and 0.421 V. Both ZrCO and ZrCS can adsorb double layers of sodium atoms on both sides, and the former shows a higher capacity because of its lower weight and smaller volume. The mass and volumetric capacities of ZrCO are 254 mA h g and 913 mA h cm respectively. More importantly, the surface potential is determined to be an effective descriptor for selecting electrode materials. The migration barrier is proportional to the fluctuation amplitude of the surface potential. A low surface potential generally implies a high capacity. A large open circuit voltage is prone to appear in the structure with a large fluctuation amplitude and a low average value of its surface potential.
钠离子电池（SIBs）因其低成本和钠储量丰富而受到越来越多的关注，但其理想的负极材料仍有待探索。MXenes因其优异的导电性和大比表面积，可能成为候选电极材料。在这项工作中，研究了含钛和锆的MXenes TiCT（T = O、F、OH）和ZrCT（T = O、F、OH、S）作为SIB负极材料的理论性能。讨论了哈伯德修正的影响，并考虑了钠原子部分占据时MXene表面的行为。包括吸附钠原子的重量和体积，TiCO在所研究的七种MXenes中表现出最佳性能。其质量容量和体积容量分别为299 mA h g和993 mA h cm，迁移势垒和开路电压分别为0.138 eV和0.421 V。ZrCO和ZrCS都可以在两侧吸附双层钠原子，前者由于其较低的重量和较小的体积而表现出更高的容量。ZrCO的质量容量和体积容量分别为254 mA h g和913 mA h cm。更重要的是，表面电位被确定为选择电极材料的有效描述符。迁移势垒与表面电位的波动幅度成正比。低表面电位通常意味着高容量。在表面电位波动幅度大且平均值低的结构中容易出现大的开路电压。
