期刊
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
卷 19, 期 16, 页码 10443-10452出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c7cp00378a
关键词
-
资金
- National Research Foundation of Korea (NRF) - Korean government (MSIP) [2012R1A3A2048841]
- Industrial Strategic Technology Development Program [10041589]
- IT R&D Program - Ministry of Trade, Industry & Energy (MOTIE), Republic of Korea
- New & Renewable Energy Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) - Ministry of Trade, Industry & Energy, Republic of Korea [20152020105420]
A fundamental understanding of anomalous redox mechanisms in hexacyanometallate compounds, compared with conventional NaMO2 systems (M: transition metals), is presented based on first-principles calculations and experimental validations. From theoretical calculations, we identified low-spin and high-spin states of Fe ions coordinated by the cyanide group (-CN) with the same oxidation state (Fe2+) in Na2Fe2(CN)(6). Considering the site dependency of d electronic spin configurations based on the crystal field theory (CFT) of transition metals (TMs), we calculated the thermodynamic mixing energy using Na2Fe2(CN)(6) and Na2Mn2(CN)(6) for obtaining a thermodynamically stable phase of Na2FeMn(CN)(6). The phase stabilities of Na2Fe2-xMnx(CN)(6) among many atomic configurations and lattice parameters originating from octahedral structures (i.e., Fe(CN)(6) and Mn(NC)(6)) are highly dependent on the electronic structures of TMs with spin states. From partial density of states (PDOS) and spatial electron distributions, it was observed that Fe2+ in the low-spin state (t(2g)(6)) and Mn2+ in the high-spin states (t(2g)(3) and e(g)(2)) in the stable phase lead to higher redox potentials (similar to 3.55 V vs. Na/Na+) with the removal of Na+ as compared to that of Na2Fe2(CN)(6). In addition, lattice parameters from x = 0 to x = 1 in Na2Fe2-xMnx(CN)(6) are increased due to the larger ionic radius of Mn2+ in the high-spin states. On the other hand, Fe2+ in the high-spin states (t(2g)(4) and e(g)(2)) and Mn2+ in the low-spin state (t(2g)(5)) in the most unstable phase of Na2FeMn(CN)(6) would have lower redox potentials. Based on the fundamental correlation between redox potentials and CFT with spin configurations of TMs, we suggest a material design concept for intercalation compounds with higher energy densities for rechargeable battery systems.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据