尖晶石
材料科学
锂(药物)
锰
阴极
微晶
相(物质)
氧化物
化学工程
杂质
无机化学
冶金
化学
物理化学
医学
内分泌学
有机化学
工程类
作者
Faxing Wang,Peng Zuo,Zhichen Xue,Yijin Liu,Chongmin Wang,Guoying Chen
出处
期刊:ACS energy letters
[American Chemical Society]
日期:2024-02-27
卷期号:: 1249-1260
标识
DOI:10.1021/acsenergylett.3c02697
摘要
Lithium- and manganese-rich (LMR) layered oxides are promising high-energy cathodes for next-generation lithium-ion batteries, yet their commercialization has been hindered by a number of performance issues. While fluorination has been explored as a mitigating approach, results from polycrystalline-particle-based studies are inconsistent and the mechanism for improvement in some reports remains unclear. In the present study, we develop an in situ fluorination method that leads to fluorinated LMR with no apparent impurities. Using well-defined single-crystal Li1.2Ni0.2Mn0.6O2 (LNMO) as a platform, we show that a high fluorination level leads to decreased oxygen activities, reduced side reactions at high voltages, and a broadly improved cathode performance. Detailed characterization reveals a particle-level Mn3+ concentration gradient from the surface to the bulk of fluorinated-LNMO crystals, ascribed to the formation of a Ni-rich LizNixMn2–xO4–yFy (x > 0.5) spinel phase on the surface and a “spinel-layered” coherent structure in the bulk where domains of a LiNi0.5Mn1.5O4 high-voltage spinel phase are integrated into the native layered framework. This work provides fundamental understanding of the fluorination effect on LMR and key insights for future development of high-energy Mn-based cathodes with an intergrown/composite crystal structure.
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