Utilizing Co(2+)/Co(3+) Redox Couple in P2-Layered Na(0.66)Co(0.22)Mn(0.44)Ti(0.34)O(2) Cathode for Sodium-Ion Batteries.
Utilizing Co(2+)/Co(3+) Redox Couple in P2-Layered Na(0.66)Co(0.22)Mn(0.44)Ti(0.34)O(2) Cathode for Sodium-Ion Batteries.
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在钠离子电池P2层Na0.66Co0.22Mn0.44Ti0.34O2正极中使用Co2/Co3氧化还原对
DOI：
10.1002/advs.201700219
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发表时间：
2017-11
期刊：
影响因子：
--
通讯作者：
Zhou YN
中科院分区：
文献类型：
--
作者：
Wang QC;Hu E;Pan Y;Xiao N;Hong F;Fu ZW;Wu XJ;Bak SM;Yang XQ;Zhou YN
开发用于大规模储能的钠离子电池面临着缺乏高性能正极材料的巨大挑战。本文设计并合成了钠离子电池用新型正极材料Na0.66CoxMn0.66 - xTi0.34O2，旨在降低过渡金属离子有序度、电荷有序度以及Na+和空位有序度。当Co含量从x = 0增加到0.33时，Na0.66CoxMn0.66 - xTi0.34O2的结构发生了有趣的变化，从正方晶向六方晶转变。特别是，具有P2型层状结构的Na0.66Co0.22Mn0.44Ti0.34O2在0.1 C时的可逆容量为120 mAh g−1，当电流密度增加到10 C时，仍然可以获得63.2 mAh g−1的可逆容量，表明有希望的速率能力。在Na0.66Co0.22Mn0.44Ti0.34O2中，低价态Co2+取代形成平均Mn3.7+价态，有效抑制了Mn3+诱导的Jahn-Teller畸变，从而稳定了层状结构。X射线吸收光谱结果表明，Na0.66Co0.22Mn0.44Ti0.34O2在充放电过程中的电荷补偿是由Co2.2+/Co3+和Mn3.3+/Mn4+氧化还原对贡献的。这是第一次在钠离子电池的P2层阴极中观察到高度可逆的Co2+/Co3+氧化还原对。这一发现可能为设计先进的插层型阴极材料开辟新的途径。
Developing sodium‐ion batteries for large‐scale energy storage applications is facing big challenges of the lack of high‐performance cathode materials. Here, a series of new cathode materials Na0.66CoxMn0.66– xTi0.34O2 for sodium‐ion batteries are designed and synthesized aiming to reduce transition metal‐ion ordering, charge ordering, as well as Na+ and vacancy ordering. An interesting structure change of Na0.66CoxMn0.66– xTi0.34O2 from orthorhombic to hexagonal is revealed when Co content increases from x = 0 to 0.33. In particular, Na0.66Co0.22Mn0.44Ti0.34O2 with a P2‐type layered structure delivers a reversible capacity of 120 mAh g−1 at 0.1 C. When the current density increases to 10 C, a reversible capacity of 63.2 mAh g−1 can still be obtained, indicating a promising rate capability. The low valence Co2+ substitution results in the formation of average Mn3.7+ valence state in Na0.66Co0.22Mn0.44Ti0.34O2, effectively suppressing the Mn3+‐induced Jahn–Teller distortion, and in turn stabilizing the layered structure. X‐ray absorption spectroscopy results suggest that the charge compensation of Na0.66Co0.22Mn0.44Ti0.34O2 during charge/discharge is contributed by Co2.2+/Co3+ and Mn3.3+/Mn4+ redox couples. This is the first time that the highly reversible Co2+/Co3+ redox couple is observed in P2‐layered cathodes for sodium‐ion batteries. This finding may open new approaches to design advanced intercalation‐type cathode materials.
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