Insight into the Redox Reaction Heterogeneity within Secondary Particles of Nickel-Rich Layered Cathode Materials,ACS Applied Materials & Interfaces

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Insight into the Redox Reaction Heterogeneity within Secondary Particles of Nickel-Rich Layered Cathode Materials
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2021-06-04 , DOI: 10.1021/acsami.1c05819
Jiyang Li ₁ , Jingxin Huang ₁ , Hongyang Li ₂ , Xiangbang Kong ₁ , Xue Li ₃ , Jinbao Zhao ₁

Affiliation

Nickel-rich LiNi_xCo_yMn_1–x–yO₂ (nickel-rich NCM, 0.6 ≤ x < 1) cathode materials suffer from multiscale reaction heterogeneity within the electrode during the electrochemical energy storage process. However, owing to the lack of appropriate diagnostic tools, the systematic understanding and observation on the redox reaction heterogeneity at the individual secondary-particle level is still limited. Raman spectroscopy can not only reflect the depth of the redox reaction through probing the vibrational information on the metal–oxygen coordination structure but also sensitively detect the local structure changes of different regions within the secondary particle with suitable spatial resolution. Therefore, Raman spectroscopy is applied here to conveniently conduct the high-resolution and in-depth analysis of the rate-dependent reaction heterogeneity within nickel-rich NCM secondary particles. It is found that, under high-rate conditions, the oxidation/reduction reaction mainly occurs in the surface region of the particles and the cause of this particle-scale reaction heterogeneity is the limitation of the slow solid-phase Li⁺ diffusion and the transient charging/discharging processes. In addition, this reaction heterogeneity would aggravate the structural instability of the material continuously during the charging/discharging cycles, thus resulting in a slowdown in the kinetics of Li⁺ de/intercalation and the apparent capacity decay. This work can not only provide fundamental insight into the rational modification of high-power nickel-rich NCM materials but also guide the setting of electrochemical operating conditions for high-power lithium-ion batteries (LIBs).

中文翻译：

深入了解富镍层状阴极材料次级粒子内的氧化还原反应异质性

富镍 LiNi _x Co _y Mn _{1– x – y} O ₂（富镍 NCM，0.6 ≤ x< 1) 在电化学储能过程中，正极材料在电极内存在多尺度反应异质性。然而，由于缺乏合适的诊断工具，对个体二级粒子水平的氧化还原反应异质性的系统理解和观察仍然有限。拉曼光谱不仅可以通过探测金属-氧配位结构的振动信息来反映氧化还原反应的深度，还可以以合适的空间分辨率灵敏地检测次级粒子内不同区域的局部结构变化。因此，这里应用拉曼光谱可以方便地对富镍 NCM 二次粒子内的速率相关反应异质性进行高分辨率和深入分析。⁺扩散和瞬态充电/放电过程。此外，这种反应异质性会在充放电循环过程中不断加剧材料的结构不稳定性，从而导致锂^离子脱嵌动力学放缓和表观容量衰减。这项工作不仅可以为高功率富镍 NCM 材料的合理改性提供基本见解，还可以指导大功率锂离子电池 (LIBs) 电化学操作条件的设置。

更新日期：2021-06-16

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