Na(+)/vacancy disordering promises high-rate Na-ion batteries.
Na(+)/vacancy disordering promises high-rate Na-ion batteries.
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钠/空位无序有望实现高倍率钠离子电池
DOI：
10.1126/sciadv.aar6018
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发表时间：
2018-03
期刊：
影响因子：
13.6
通讯作者：
Guo YG
中科院分区：
文献类型：
--
作者：
Wang PF;Yao HR;Liu XY;Yin YX;Zhang JN;Wen Y;Yu X;Gu L;Guo YG
我们证明了p2型层状阴极的Na+/空位无序确保了快速的Na迁移和低Na扩散势垒。作为Na离子电池（NIBs）最具吸引力的阴极候选材料之一，p2型Na层状氧化物通常表现出不同的单相畴，伴随着不同的Na+/空位有序超结构，这取决于在有限的电化学窗口中探索的Na浓度。因此，它们在高速率下的Na+动力学和循环稳定性受到这些上层结构的影响，在电化学曲线上产生明显的电压高原，作为nib正极材料的电池性能不足。我们发现，通过合理的结构调制，在Na层内构建一个完全无序的Na空位排列，可以有效地消除这一问题。扫描透射电子显微镜、非原位x射线吸收光谱和operando x射线衍射实验的综合分析，加上密度泛函数理论计算，表明过渡金属氧化物板之间的Na+/空位无序保证了p2型化合物的快速Na迁移率（10−10 ~ 10−9 cm2 s−1）和低Na扩散势垒（170 meV）。因此，设计的P2-Na2/3Ni1/3Mn1/3Ti1/3O2具有超长的循环寿命（在1℃下循环500次后容量保留率为83.9%）和前所未有的倍率能力（在20℃的高倍率下容量保留率为77.5%）。这些发现为精确设计可充电nib的高倍率阴极材料开辟了一条新途径。
We demonstrate that Na+/vacancy disordering of P2-type layered cathodes ensures both fast Na mobility and a low Na diffusion barrier. As one of the most fascinating cathode candidates for Na-ion batteries (NIBs), P2-type Na layered oxides usually exhibit various single-phase domains accompanied by different Na+/vacancy-ordered superstructures, depending on the Na concentration when explored in a limited electrochemical window. Therefore, their Na+ kinetics and cycling stability at high rates are subjected to these superstructures, incurring obvious voltage plateaus in the electrochemical profiles and insufficient battery performance as cathode materials for NIBs. We show that this problem can be effectively diminished by reasonable structure modulation to construct a completely disordered arrangement of Na-vacancy within Na layers. The combined analysis of scanning transmission electron microscopy, ex situ x-ray absorption spectroscopy, and operando x-ray diffraction experiments, coupled with density functional theory calculations, reveals that Na+/vacancy disordering between the transition metal oxide slabs ensures both fast Na mobility (10−10 to 10−9 cm2 s−1) and a low Na diffusion barrier (170 meV) in P2-type compounds. As a consequence, the designed P2-Na2/3Ni1/3Mn1/3Ti1/3O2 displays extra-long cycle life (83.9% capacity retention after 500 cycles at 1 C) and unprecedented rate capability (77.5% of the initial capacity at a high rate of 20 C). These findings open up a new route to precisely design high-rate cathode materials for rechargeable NIBs.
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影响因子：
13.6
作者：
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