期刊
JOURNAL OF MATERIALS CHEMISTRY A
卷 7, 期 9, 页码 4705-4713出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c8ta10980j
关键词
-
资金
- Natural Science Foundation of Shandong Province [ZR2017BEM010, ZR2016JL015]
- National Natural Science Foundation of China [51672109]
High-voltage P2-Na-2/3[Ni1/3Mn2/3]O-2 as a high energy density cathode for sodium-ion batteries (SIBs) has attracted considerable attention. But the unfavorable P2-O2 phase transition and electrode/electrolyte side reactions easily occur when charged above 4.2 V (vs. Na/Na+), resulting in the rapid decay of capacity. Here, for the first time, a nanoscale cobalt gradient substitution is introduced to build a Co-enriched surface and cobalt-substituted interior, in which the cobalt-enriched surface is expected to reduce the side reactions and improve the Na+ kinetics while the cobalt substitution is supposed to mitigate the P2-O2 transition. Correspondingly, this gradient cobalt substituted P2-Na-2/3[Ni1/3Mn2/3]O-2 delivers a large reversible capacity of 164.6 mA h g(-1) with a high median potential of 3.55 V, achieving a high energy density of approximate to 585 W h kg(-1) and is comparable to the LiCoO2 cathode in lithium-ion batteries. As anticipated, it shows a mitigated P2-O2 transition and thus exhibits an improved cycling stability. Besides, it delivers a much higher capacity of 110 mA h g(-1) at a high rate of 10C than reported pristine and modified electrodes by bulk doping and surface coating, indicating better high-rate properties. These gratifying achievements make this nanoscale gradient substitution an effective approach for suppressing the P2-O2 transition and improving the Na+ kinetics of P2-Na-2/3[Ni1/3Mn2/3]O-2 cathodes.
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