Abstract Here, A kind of carbon nanotubes (CNT) wrapping Na0·44MnO2 has been synthesized via a high-temperature solid state method and showed better electro-chemical performance in 1 M Na2SO4 aqueous solution as cathode material for aqueous sodium ion batteries. This rod-like nano-composite exhibited a first charge capacity of 70.1 mA h·g−1 with the reversible capacity retention of about 63.4% after 300 cycles at a current density of 50 mA g−1. It can also remain reversible specific capacity of 53.1, 44.7, 34.8, and 19.7 mA h·g−1 at the current density of 1 C, 2 C, 5 C and 10 C, respectively. The Na+ migration mechanism and kinetics of Na0·44MnO2 are fully investigated by molecular dynamics (MD) and the density functional theory (DFT). A SQS-8 quasi-random structure is used to model the structure of the material. The results show that Na+ is highly vigorous and propagates 1D along the c-axis. A minimum of 0.081 eV and 0.51 eV is required for Na+ to travel through the large S-shaped tunnel and the small tunnel, respectively.

中文翻译：

---

水性钠电池Na0·​​44MnO2-CNT电极电化学性能改善及钠离子迁移机理研究

摘要 在此，采用高温固相法合成了一种包裹Na0·44MnO2的碳纳米管(CNT)，在1 M Na2SO4水溶液中表现出较好的电化学性能，作为水性钠离子电池的正极材料。这种棒状纳米复合材料的首次充电容量为 70.1 mA h·g-1，在 50 mA g-1 的电流密度下循环 300 次后，可逆容量保持率约为 63.4%。它还可以分别在1 C、2 C、5 C和10 C的电流密度下保持53.1、44.7、34.8和19.7 mA h·g-1的可逆比容量。通过分子动力学(MD)和密度泛函理论(DFT)对Na0·44MnO2的Na+迁移机制和动力学进行了充分研究。SQS-8 准随机结构用于模拟材料的结构。结果表明 Na+ 是高度活跃的并且沿 c 轴传播 1D。Na+ 分别穿过大 S 形隧道和小隧道至少需要 0.081 eV 和 0.51 eV。