Zhang Jian, Liu Yongchang, Zhao Xudong, He Lunhua, Liu Hui, Song Yuzhu, Sun Shengdong, Li Qiang, Xing Xianran, Chen Jun
Beijing Advanced Innovation Center for Materials Genome Engineering, Department of Physical Chemistry, University of Science and Technology Beijing, Beijing, 100083, China.
Beijing Advanced Innovation Center for Materials Genome Engineering, Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing, 100083, China.
Adv Mater. 2020 Mar;32(11):e1906348. doi: 10.1002/adma.201906348. Epub 2020 Feb 9.
Sodium-ion batteries (SIBs) have attracted incremental attention as a promising candidate for grid-scale energy-storage applications. To meet practical requirements, searching for new cathode materials with high energy density is of great importance. Herein, a novel Na superionic conductor (NASICON)-type Na MnCr(PO ) is developed as a high-energy cathode for SIBs. The Na MnCr(PO ) nanoparticles homogeneously embedded in a carbon matrix can present an extraordinary reversible capacity of 160.5 mA h g with three-electron reaction at ≈3.53 V during the Na extraction/insertion process, realizing an unprecedentedly high energy density of 566.5 Wh kg in the phosphate cathodes for SIBs. It is intriguing to reveal the underlying mechanism of the unique Mn /Mn , Mn /Mn , and Cr /Cr redox couples via X-ray absorption near-edge structure spectroscopy. The whole electrochemical reaction undergoes highly reversible single-phase and biphasic transitions with a moderate volume change of 7.7% through in situ X-ray diffraction and ex situ high-energy synchrotron X-ray diffraction. Combining density functional theory (DFT) calculations with the galvanostatic intermittent titration technique, the superior performance is ascribed to the low ionic-migration energy barrier and desirable Na-ion diffusion kinetics. The present work can offer a new insight into the design of multielectron-reaction cathode materials for SIBs.
钠离子电池（SIBs）作为一种有前景的用于电网规模储能应用的候选者，已引起越来越多的关注。为满足实际需求，寻找具有高能量密度的新型阴极材料至关重要。在此，一种新型的钠超离子导体（NASICON）型NaMnCr(PO₄)₃被开发为SIBs的高能量阴极。均匀嵌入碳基体中的NaMnCr(PO₄)₃纳米颗粒在钠脱嵌/嵌入过程中，在≈3.53 V时可呈现出160.5 mA h g的非凡可逆容量以及三电子反应，在用于SIBs的磷酸盐阴极中实现了前所未有的566.5 Wh kg的高能量密度。通过X射线吸收近边结构光谱揭示独特的Mn³⁺/Mn²⁺、Mn⁴⁺/Mn³⁺和Cr³⁺/Cr²⁺氧化还原对的潜在机制很有趣。通过原位X射线衍射和非原位高能同步辐射X射线衍射，整个电化学反应经历高度可逆的单相和双相转变，体积变化适中，为7.7%。结合密度泛函理论（DFT）计算和恒电流间歇滴定技术，优异的性能归因于低离子迁移能垒和理想的钠离子扩散动力学。目前的工作可为SIBs多电子反应阴极材料的设计提供新的见解。
