Rate and Composition Dependence on the Structural–Electrochemical Relationships in P2–Na2/3Fe1–yMnyO2 Positive Electrodes for Sodium-Ion Batteries,Chemistry of Materials

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Rate and Composition Dependence on the Structural–Electrochemical Relationships in P2–Na2/3Fe1–yMnyO2 Positive Electrodes for Sodium-Ion Batteries
Chemistry of Materials ( IF 7.2 ) Pub Date : 2018-10-02 00:00:00 , DOI: 10.1021/acs.chemmater.8b02456
Wesley M. Dose ₁ , Neeraj Sharma ₁ , James C. Pramudita _{1,

2} , Maxim Avdeev ₂ , Elena Gonzalo ₃ , Teofilo Rojo _{3,

4}

Affiliation

Structural–electrochemical compositional evolution of attractive cathode candidates for sodium-ion batteries is illustrated. Varying the Fe/Mn ratio plays a significant role in phase evolution, which ranges from a simple solid solution or two-phase transitions to more complex combinations and sequences of phase transitions dependent on the Na concentration. Further complexity is added by the kinetic limitations placed on the compositions with applied current and associated material utilization. This work provides a standardized set of electrochemical and structural data for members of the Na_2/3Fe_1–yMn_yO₂ series, exploring the phase evolution at a selected rate of 15 mA g^–1, comparing this with literature data at various current rates, and focusing on the evolution of the y = 0.9 at higher and lower current rates. The y = 0.8 composition shows the highest capacity, while y = 0.9 shows slightly better capacity retention at 15 mA g^–1. Structurally, the y = 0.8 features a solid-solution evolution throughout the charge–discharge process, while the y = 0.9 shows a solid solution and two-phase evolution, yet shows better capacity retention. Such studies illustrate how chemical tuning and electrochemical current influences structural evolution with sodium insertion/extraction and how this in turn influences electrochemical performance.

中文翻译：

钠离子电池的P2-Na _2/3 Fe _{1- y} Mn _y O ₂正电极中的结构-电化学关系的速率和成分依赖性

说明了钠离子电池有吸引力的阴极候选物的结构-电化学组成演变。Fe / Mn比的变化在相演化中起着重要作用，其范围从简单的固溶体或两相转变到更复杂的组合和相变序列（取决于Na浓度）。通过施加电流和相关材料利用而对组合物施加的动力学限制进一步增加了复杂性。这项工作为Na _2/3 Fe _{1– y} Mn _y O ₂系列的成员提供了一套标准化的电化学和结构数据，探索了以15 mA g ^–1的选定速率进行的相演化。，将其与各种电流速率下的文献数据进行比较，并着重于在较高和较低电流速率下y = 0.9的演变。所述ÿ = 0.8组合物表现出最高的容量，同时ÿ = 0.9示出了稍好的容量保持在15mA克^-1。在结构上，y = 0.8在整个充放电过程中具有固溶演化，而y = 0.9则显示固溶和两相演化，但容量保持率更高。这些研究说明了化学调节和电化学电流如何通过钠的插入/萃取影响结构的演变，以及这又如何影响电化学性能。

更新日期：2018-10-02

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