Aparicio Pablo A, de Leeuw Nora H
School of Chemistry, Cardiff University, Main Building Park Place, Cardiff CF10 3AT, UK.
Phys Chem Chem Phys. 2020 Mar 28;22(12):6653-6659. doi: 10.1039/c9cp05559b. Epub 2020 Mar 11.
Sodium-ion batteries are considered one of the most promising alternatives to lithium-ion batteries owing to the low cost and wide abundance of sodium. Phosphate compounds are promising materials for sodium-ion batteries because of their high structural stability, energy densities and capacities. Vanadium phosphates have shown high energy densities, but their sodium-ion diffusion and cation doping properties are not fully rationalized. In this work, we combine density functional theory calculations and molecular dynamics simulations to study the electronic structure, ion diffusion and cation doping properties of the NaVO(PO) compound. The calculated Na-ion activation energy of this compound is 0.49 eV, which is typical for Na-based cathode materials, and the simulations predict a Na-ion diffusion coefficient of 5.1 × 10 cm s. The cell voltage trends show a voltage of 3.3 V vs. Na/Na. Partial substitution of vanadium atoms by other metals (Al, Co, Fe, Mn, Ni or Ti) increases the cell voltage up to 1.1 V vs. Na/Na. These new insights will help us to understand the ion transport and electrochemical behaviour of potential phosphate cathode materials for sodium-ion batteries.
由于钠成本低且储量丰富，钠离子电池被认为是锂离子电池最有前景的替代方案之一。磷酸盐化合物因其高结构稳定性、能量密度和容量，是钠离子电池很有前景的材料。磷酸钒已显示出高能量密度，但其钠离子扩散和阳离子掺杂特性尚未完全得到合理解释。在这项工作中，我们结合密度泛函理论计算和分子动力学模拟，研究了NaVO(PO)化合物的电子结构、离子扩散和阳离子掺杂特性。该化合物计算出的钠离子活化能为0.49电子伏特，这对于钠基正极材料来说是典型的，模拟预测钠离子扩散系数为5.1×10厘米/秒。电池电压趋势显示相对于Na/Na的电压为3.3伏。用其他金属（铝、钴、铁、锰、镍或钛）部分替代钒原子会使相对于Na/Na的电池电压增加高达1.1伏。这些新见解将有助于我们理解钠离子电池潜在磷酸盐正极材料的离子传输和电化学行为。
