在高度NMC811中,O3到O1相转换在高温下发生
Zachary Ruff1,2, Chloe S Coates1, Katharina Märker1,2
1Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, U.K.
Chemistry of materials : a publication of the American Chemical Society
|July 17, 2023
概括
富含的分层氧化物阴极,如NMC811,可以在高脱状态下可逆地过渡到O1阶段. 这种相位过渡是由温度和时间动态控制的,而不是质子度.
科学领域:
- 材料科学 材料科学 材料科学
- 电化学 电化学 电化学
- 固态化学 固态化学
背景情况:
- 富含的多层氧化物,如NMC811,为商业阴极提供了高的实际容量.
- NMC811的脱化通常遵循固体溶液 (O3结构) 的行为,直到xLi>0.10.
- 进一步的脱化在动力学上是有限的,容易产生副作用.
研究的目的:
- 研究NMC811在高脱状态下的相位行为.
- 探索进入和描述O3之外的新阶段的条件.
- 了解任何观察到的相位过渡的动力学和影响因素.
主要方法:
- 充电小格式的NMC811石墨袋式电池,在高温下达到高电压.
- 在这些条件下长时间保持细胞,以达到高脱化.
- 利用Rietveld在高分辨率衍射数据和选择区域电子衍射 (SAED) 模式索引上的现场精细化.
- 采用1H的NMR光谱来分析质子度.
主要成果:
- 在特定的高压,高温条件下,NMC811经历了部分和可逆的O3到O1相位过渡.
- O1阶段的分数取决于的度,温度和保持时间,表明动力控制.
- 用1H NMR测量的质子度随着O1相分数的增加而下降,并且似乎没有推动过渡.
结论:
- 在NMC811中O3到O1的相位过渡是一个动力控制的现象.
- 高电压和高温可以诱导这种可逆相变,为理解阴极材料提供了新的可能性.
- 观察到的过渡独立于质子度,澄清了潜在的机械路径.
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