三元层状正极材料中位错演变的电子显微分析

三元层状正极材料中位错演变的电子显微分析

韩  笑，闫鹏飞^*，隋曼龄^*

（北京工业大学，材料与制造学部，北京 100124）

摘  要 锂电池层状过渡金属氧化物正极材料在循环过程中发生的体相衰退备受关注，但对其发生衰退的机理仍缺乏深度的理解。位错作为一种常见线缺陷普遍存在于原始和循环后的层状正极材料中，对材料的循环稳定性以及其它缺陷的产生（比如裂纹等）有重要影响，因而也对层状正极材料的电化学性能有重要影响。基于此，本文通过先进透射电子显微镜，从原子尺度揭示了层状正极材料中常见的三种不同类型位错（(003)刃位错、(102)刃位错和(003)螺位错的原始构型及其在充放电循环后的演变。作者发现(003)刃位错的位错核在循环后会发生明显的晶格重构，而(102)刃位错和(003)螺位错具有稳定的位错核结构。电镜观察的统计结果表明(003)和(102)刃位错均可诱发裂纹产生。然而，(003)刃位错区域发生的重构，一方面会阻碍锂离子的扩散，影响其电化学性能；另一方面可以有效地钉扎位错滑移和裂纹形核，对材料的稳定性有积极的作用。研究结果有助于深入理解位错等缺陷对锂离子存储与迁移，以及正极材料稳定性的影响，对电池材料中的缺陷进行精准调控可以进一步改善其综合性能。

关键词 锂离子电池；三元层状氧化物正极；透射电子显微镜；位错；晶格

中图分类号：TG11；TM911；TG115.21⁺5.3  文献标识码：A     doi:10.3969/j.issn.1000-6281.2024.01.001

Electron microanalysis of dislocation evolution in layered ternary cathodes

HAN Xiao, YAN Peng-fei^*, SUI Man-ling^*

(Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing 100124, China)

Abstract  Bulk degradations of layered lithium transition metal oxide are drawing great attention but still lacking in-depth understanding. Dislocation is one of the major bulk defects in both pristine and cycled particles. It is closely related to cracking and phase transition. Thus, it plays an important role in affecting the electrochemical performance of layered-structure cathodes. Herein, by virtue of transmission electron microscopy, we examined three types of dislocations in layered cathodes. We found that the core structure of (003) edge dislocation was highly disordered after high voltage cycling. Considering the high density of dislocations, such dislocation-associated disordered phases were supposed to block Li ion diffusion pathways and consequently plunged energy storage capability. While the screw dislocations and the (102) edge dislocations had stable dislocation cores. Our work demonstrated that intrinsic dislocation defects played an important role in affecting cycling stability. Engineering of intrinsic defects, such as point defects, line defects, and planar defects, could provide plenty of room to improve battery performance.

Keywords   lithium ion battery; layered cathode; transmission electron microscopy; dislocation; lattice structure

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