| Autor: |
Thorne, J. S., Zheng, Lituo, Lee, Christopher L. D., Dunlap, R. A., Obrovac, M. N. |
| Zdroj: |
ACS Applied Materials & Interfaces; July 2018, Vol. 10 Issue: 26 p22013-22022, 10p |
| Abstrakt: |
The synthesis, structure, and electrochemistry in Na cells of NaFexM1–xO2positive electrode materials with M = Ni, Co0.5Ni0.5, and Co are reported. In particular, the properties of O3-NaFeO2–NaCo0.5Ni0.5O2solid solutions having compositions NaFex(Co0.5Ni0.5)1–xO2with 0 ≤ x≤ 0.5 are explored. It is found that the substitution of Fe in NaNi0.5Co0.5O2causes an increase in first cycle energy density from 320 to 440 mWh/g in a 1.5–4.0 V test. However, capacity retention is generally reduced when xis increased for all M = Ni, Co0.5Ni0.5, and Co. In general, NaFexM1–xO2samples with M = Co had the highest capacity retention for all values of x. Ex situ X-ray diffraction and Mössbauer results of as-prepared and charged materials are directly compared for NaFex(Co0.5Ni0.5)1–xO2and NaFexCo1–xO2(x= 0.4, 0.5). Iron was found to be in the +3 oxidation state in the as-prepared materials. A significant fraction of Fe3+is oxidized to Fe4+in these samples when they are charged to 4.0 V. |
| Databáze: |
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