Zhou Bo, Shi Hui, Cao Rongfang, Zhang Xiaodong, Jiang Zhenyi
Institute of Modern Physics, Northwest University, Xi'an 710069, People's Republic of China.
Phys Chem Chem Phys. 2014 Sep 14;16(34):18578-85. doi: 10.1039/c4cp02230k.
Several first-principles calculations based on density functional theory have been carried out looking at the key issues of a magnesium battery with a V2O5 cathode. This kind of magnesium battery was reported by D. Aurbach's group in 2013. Our theoretical studies provide explanations for the experimental findings such as higher voltage, slow ion diffusivity and the decrease of the crystallinity. The calculated open circuit voltage of a magnesium battery with a V2O5 cathode is 3.06 V, which is 0.22 V higher than a lithium battery with the same cathode. Electronic band structure calculations suggest that higher electronic conductivity must be expected in a magnesium battery. Elastic constants are obtained, which give information on the stability of the magnesiated cathode. Furthermore, we have also calculated the diffusion barriers of Li and Mg ions in the cathode using the nudged elastic band method. The hopping barrier of Mg ions is 1.26 eV, which is much higher than that of Li ions (0.35 eV). The obtained minimum energy paths show the different hopping processes in the lithium and magnesium batteries, which can explain the phenomenon of slow diffusion in experiments. The possible transition pathway between the α and δ phases is analyzed for the first time, which gives an explanation for the reversibility of Mg ions in the V2O5 cathode.
基于密度泛函理论进行了几项第一性原理计算，研究了采用V2O5阴极的镁电池的关键问题。这种镁电池由D. Aurbach团队于2013年报道。我们的理论研究为诸如较高电压、缓慢的离子扩散率和结晶度降低等实验结果提供了解释。采用V2O5阴极的镁电池的计算开路电压为3.06 V，比采用相同阴极的锂电池高0.22 V。电子能带结构计算表明，镁电池中有望具有更高的电子电导率。获得了弹性常数，其给出了镁化阴极稳定性的信息。此外，我们还使用推挤弹性带方法计算了Li和Mg离子在阴极中的扩散势垒。Mg离子的跳跃势垒为1.26 eV，远高于Li离子的跳跃势垒（0.35 eV）。所获得的最小能量路径显示了锂和镁电池中不同的跳跃过程，这可以解释实验中的缓慢扩散现象。首次分析了α相和δ相之间可能的转变途径，这为Mg离子在V2O5阴极中的可逆性提供了解释。
