Wang Qiang, Wang Quanyu, Zhang Mingying, Han Bo, Zhou Chenggang, Chen Yanling, Lv Guobin
Faculty of Materials Science and Chemistry, China University of Geosciences Wuhan, 388 Lumo Road, Wuhan, 430074, Hubei, People's Republic of China.
Network & Education Technology Center, China University of Geosciences Wuhan, Wuhan, 430074, Hubei, People's Republic of China.
J Mol Model. 2019 Mar 13;25(4):96. doi: 10.1007/s00894-019-3971-1.
NaV(PO) (NVP) is one of the most promising candidates for use as cathodes in room-temperature sodium ion batteries owing to its high structural stability and rapid Na transportation kinetics. The cationic doping of foreign ions at Na or V sites in the NVP lattice has proven to be an effective approach for enhancing the electrochemical performance of NVP. In this work, we present a first-principles density functional theory investigation of the impact of polyanionic boron doping at P sites on the structural and electrochemical behavior of NVP. Our simulation results suggest that B doping considerably increases the structural stability of NVP while shrinking its lattice size to some extent. Since B donates far fewer electrons to connected O atoms, the surrounding V atoms become more positive, causing the operating voltage to increase with B content. However, the reduction in lattice size is not beneficial for the Na transportation kinetics. As demonstrated by a search for the transition state, a concerted ion-exchange mechanism is preferred for Na transportation, and increased B doping leads to a higher Na diffusion barrier. Improvements in electrochemical performance due to B doping see (Hu et al. Adv Sci 3(12):1600112, 2016) appear to originate mainly from the resulting increased electrical conductivity.
NaV(PO)（NVP）因其高结构稳定性和快速的钠离子传输动力学，是室温钠离子电池阴极最有前景的候选材料之一。在NVP晶格中的钠或钒位点进行外来离子的阳离子掺杂已被证明是提高NVP电化学性能的有效方法。在这项工作中，我们提出了一项基于第一性原理密度泛函理论的研究，探讨在P位点进行聚阴离子硼掺杂对NVP结构和电化学行为的影响。我们的模拟结果表明，硼掺杂显著提高了NVP的结构稳定性，同时在一定程度上缩小了其晶格尺寸。由于硼向相连的氧原子提供的电子少得多，周围的钒原子变得更正电，导致工作电压随硼含量增加。然而，晶格尺寸的减小对钠离子传输动力学不利。通过搜索过渡态表明，协同离子交换机制在钠离子传输中更受青睐，硼掺杂增加会导致更高的钠离子扩散势垒。硼掺杂导致的电化学性能改善（见Hu等人，《先进科学》3(12):1600112，2016）似乎主要源于由此增加的电导率。
