Luo Lingxiao, Tan Shuangshuang, Gao Zhipeng, Yang Xiaofang, Xu Junyao, Huang Guangsheng, Wang Jingfeng, Pan Fusheng
College of Materials Science and Engineering, Chongqing University, Chongqing 400044, P. R. China.
National Engineering Research Centre for Magnesium Alloys, Chongqing University, Chongqing 400044, China.
Phys Chem Chem Phys. 2023 Oct 4;25(38):26289-26297. doi: 10.1039/d3cp02422a.
Rechargeable magnesium batteries (RMBs) are considered as highly promising energy storage systems. However, the lack of cathode materials with fast Mg diffusion kinetics and high energy density severely hinders the development of RMBs. Herein, a two-dimensional (2D) VO/VS heterostructure as a RMB cathode material is proposed by introducing an O-V-O layer in VS to improve the discharge voltage and specific capacity while keeping the fast Mg diffusion kinetics. Based on first principle calculations, the geometric structures, electronic characteristics of the VO/VS heterostructure, and the adsorption properties and diffusion behaviors of Mg in VO/VS are systematically studied. The metallic properties of VO/VS and a relatively low diffusion barrier of Mg (0.6 eV) in VO/VS enable a large potential in delivering high rate performance in actual RMBs. Compared with traditional VS materials (1.25 V), the average discharge platform of VO/VS could be increased to 1.7 V. The theoretical capacities of the layered VS and VO/VS are calculated as 233 and 301 mA h g, respectively. Thus, the VO/VS heterostructure exhibits a high theoretical energy density of 511.7 W h kg, significantly surpassing that of VS (291.3 W h kg). This work provides important guidance for designing high-energy and high-rate 2D heterostructure cathode materials for RMBs and other multivalent ion batteries.
可充电镁电池（RMBs）被认为是极具前景的储能系统。然而，缺乏具有快速镁扩散动力学和高能量密度的阴极材料严重阻碍了可充电镁电池的发展。在此，通过在VS中引入O-V-O层，提出了一种二维（2D）VO/VS异质结构作为可充电镁电池的阴极材料，以提高放电电压和比容量，同时保持快速的镁扩散动力学。基于第一性原理计算，系统研究了VO/VS异质结构的几何结构、电子特性以及镁在VO/VS中的吸附特性和扩散行为。VO/VS的金属特性以及镁在VO/VS中相对较低的扩散势垒（0.6 eV）使其在实际的可充电镁电池中具有实现高倍率性能的巨大潜力。与传统的VS材料（1.25 V）相比，VO/VS的平均放电平台可提高到1.7 V。层状VS和VO/VS的理论容量分别计算为233和301 mA h g。因此，VO/VS异质结构表现出511.7 W h kg的高理论能量密度，显著超过VS（291.3 W h kg）。这项工作为设计用于可充电镁电池和其他多价离子电池的高能量和高倍率二维异质结构阴极材料提供了重要指导。
