Insights of the Electrochemical Reversibility of P2-Type Sodium Manganese Oxide Cathodes via Modulation of Transition Metal Vacancies,ACS Applied Materials & Interfaces

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Insights of the Electrochemical Reversibility of P2-Type Sodium Manganese Oxide Cathodes via Modulation of Transition Metal Vacancies
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2021-08-04 , DOI: 10.1021/acsami.1c09544
Zhumei Xiao ₁ , Wenhua Zuo _{1,

2} , Xiangsi Liu ₁ , Jisheng Xie ₁ , Huajin He ₁ , Yuxuan Xiang ₁ , Haodong Liu ₃ , Yong Yang _{1,

4}

Affiliation

Among cathode materials for sodium-ion batteries, Mn-based layered oxides have attracted enormous attention owing to their high capacity, cost-effectiveness, and fast transport channels. However, their practical application is hindered by the unsatisfied structural stability and the deficient understanding of electrochemical reaction mechanisms. Among these issues, the research of transition metal (TM) vacancy remains highly active due to their modulation roles on the anionic redox reactions, but their effects on structural and electrochemical stability remain obscure. Herein, based on Al-substituted P2-type Na_2/3MnO₂, we comprehensively investigate the effects of TM vacancies on the corresponding layered oxides. With several characterization techniques such as neutron diffraction, superconducting quantum interferometry, in situ X-ray diffraction, ex situ solid-state nuclear magnetic resonance techniques, and X-ray photoelectron spectroscopy, we determined the TM vacancy content and further revealed that higher content of TM vacancies (7.8%) in the transition layer is beneficial to mitigate the structure evolutions and maintain the P2 structure during cycling in voltage range 1.5–4.5 V, while the oxides with lower content of TM vacancies (1.6%) deliver higher discharge capacity but experience complicated phase transition, including stacking faults and P2–P2′ transitions. It is demonstrated that regulating the contents of TM vacancies can be utilized as an effective strategy to tune the structure stability and electrochemical performances of layered sodium oxide cathodes.

中文翻译：

通过调节过渡金属空位对 P2 型钠锰氧化物阴极的电化学可逆性的洞察

在钠离子电池正极材料中，锰基层状氧化物由于其高容量、成本效益和快速传输通道而引起了极大的关注。然而，它们的实际应用受到不满意的结构稳定性和对电化学反应机制的理解不足的阻碍。在这些问题中，过渡金属（TM）空位的研究由于其对阴离子氧化还原反应的调节作用而保持高度活跃，但它们对结构和电化学稳定性的影响仍不清楚。在此，基于Al取代的P2型Na _2/3 MnO ₂，我们全面研究了 TM 空位对相应层状氧化物的影响。通过中子衍射、超导量子干涉、原位 X 射线衍射、非原位固态核磁共振技术和 X 射线光电子能谱等多种表征技术，我们确定了 TM 空位含量，并进一步揭示了较高含量的过渡层中的 TM 空位 (7.8%) 有利于缓解结构演变并在 1.5-4.5 V 电压范围内循环期间保持 P2 结构，而具有较低 TM 空位含量 (1.6%) 的氧化物提供更高的放电容量，但经历复杂的相变，包括堆垛层错和 P2-P2' 转变。

更新日期：2021-08-19

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