Density functional theory study has been performed on NaMnTiO to evaluate its application feasibility as an electrode in Na ion battery. Two types of void in the structure of NaMnTiO, viz., Z shaped tunnel and polyhedral pentagonal void, has been observed that act as guest sites for reversible migration of Na ions. It is also noted that electrochemically active sites are placed in Z shaped tunnel that act as host for Na during anodic response while it acts as the Na donor during cathodic response. The Mn atom, located in the Z-shape tunnel, acts as redox active site for both cathodic and anodic response via formation of redox couple Mn/Mn and Mn/Mn respectively. On the other hand, Mn atom present at square pyramidal site remains inert during charge–discharge process. The redox action in NaMnTiO, occurring due to intercalation and de-intercalation of 2Na ions per formula unit, has been noted to exhibit voltage ∼2.63 V and 3.82 V respectively. The theoretical capacity ∼128 mAhg has been estimated corresponding to migration of 2Na in NaMnTiO structure. The present simulation study indicates the possibility of electrode action in NaMnTiO for sodium ion battery application.

中文翻译：

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钠离子电池电极用Na4Mn4Ti5O18的密度泛函理论分析

对 NaMnTiO 进行了密度泛函理论研究，以评估其作为钠离子电池电极的应用可行性。 NaMnTiO 结构中的两种类型的空隙，即 Z 形隧道和多面体五边形空隙，已被观察到充当 Na 离子可逆迁移的客体位点。还值得注意的是，电化学活性位点位于 Z 形隧道中，在阳极响应期间充当 Na 的主体，而在阴极响应期间充当 Na 供体。位于 Z 形隧道中的 Mn 原子分别通过形成氧化还原对 Mn/Mn 和 Mn/Mn 充当阴极和阳极响应的氧化还原活性位点。另一方面，存在于四角锥体位置的Mn原子在充放电过程中保持惰性。 NaMnTiO 中的氧化还原作用是由于每个分子式单元 2 个 Na 离子的嵌入和脱嵌而发生的，已注意到电压分别为 ∼2.63 V 和 3.82 V。理论容量约为 128 mAhg，对应于 NaMnTiO 结构中 2Na 的迁移。目前的模拟研究表明了 NaMnTiO 电极作用在钠离子电池中的应用的可能性。