Rhombohedral NASICON-type NaxFe2(SO4)3 for sodium ion batteries: comparison with phosphate and alluaudite phases
Rhombohedral NASICON-type NaxFe2(SO4)3 for sodium ion batteries: comparison with phosphate and alluaudite phases
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DOI：
10.1039/c7ta08606g
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发表时间：
2018-03-07
影响因子：
11.9
通讯作者：
Yamada, Atsuo
中科院分区：
文献类型：
--
作者：
Chung, Sai-Cheong;Ming, Jun;Yamada, Atsuo
Sulfate has attracted considerable interest as an anion for cathode materials in lithium and sodium ion batteries because they induce high voltages. Herein, Fe-2(SO4)(3) in the rhombohedral NASICON phase was examined as a Na-ion cathode. Electrochemical, structural, and theoretical methods were employed. Starting from the charged state, Fe-2(SO4)(3) can be discharged to near theoretical capacity under very slow GITT experimental conditions. However, the available capacity rapidly dropped under high current. First-principles calculations found that one of the alkali metal sites was metastable and a high diffusion barrier of 0.9 eV for Na+ ion migration was found. The NASICON-type structure, with its open framework, is generally considered a good ionic conductor. However, the small size of SO42- anions limit the site availability and the mobility of Na+ ions in the NASICON phase of Fe-2(SO4)(3), which accounted for their inferior properties compared with the recently discovered alluaudite polymorph.
