材料科学
水溶液
阴极
空位缺陷
电化学
扩散
钠
无机化学
离子
化学工程
冶金
电极
物理化学
结晶学
热力学
有机化学
化学
工程类
物理
作者
Munseok S. Chae,Arup Chakraborty,Sooraj Kunnikuruvan,Ran Attias,Satyanarayana Maddukuri,Yosef Gofer,Dan Thomas Major,Doron Aurbach
标识
DOI:10.1002/aenm.202002077
摘要
Abstract Aqueous sodium‐ion batteries are expected to be low‐cost, safe, and environmentally friendly systems for large scale energy storage due to the abundance and low cost of sodium. However, only a few candidates have been reported for cathodes and there is a need to develop new practical host materials with improved electrochemical performance. Here, tunnel‐type, calcium‐doped, sodium manganese oxide is demonstrated as a novel cathode material, ultrafast rate capabilities and superior high‐rate cycling stability—98.8% capacity retention at the 1000th cycle—for aqueous sodium‐ion batteries. Advanced structural analysis of the Ca 0.07 Na 0.26 MnO 2 material using X‐ray diffraction and ab initio calculations identify the calcium sites and indicate a plausible sodium diffusion mechanism. Calcium preferentially substitutes at the Na(1) sites among the three different types of Na sites. This substitution creates vacancies at the Na(2) and Na(3) sites. Calculations of the energy barrier for Na ion diffusion indicate that diffusion along the Na(2)‐to‐Na(2) and Na(2)‐to‐Na(3) pathways is the most feasible. These vacancies provide improved diffusion kinetics and show 43% capacity enhancement at 50 C‐rate. The results suggest that Ca 0.07 Na 0.26 MnO 2 is a promising cathode material for aqueous sodium‐ion batteries, and provide an improved fundamental understanding of sodium storage mechanisms.
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