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Atomic-Level Changes during Electrochemical Cycling of Oriented LiMn2O4 Cathodic Thin Films
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2022-01-27 , DOI: 10.1021/acsami.1c18630
Yumi H Ikuhara 1 , Xiang Gao 1 , Kazuaki Kawahara 2 , Craig A J Fisher 1 , Akihide Kuwabara 1 , Ryo Ishikawa 2 , Hiroki Moriwake 1 , Yuichi Ikuhara 1, 2
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2022-01-27 , DOI: 10.1021/acsami.1c18630
Yumi H Ikuhara 1 , Xiang Gao 1 , Kazuaki Kawahara 2 , Craig A J Fisher 1 , Akihide Kuwabara 1 , Ryo Ishikawa 2 , Hiroki Moriwake 1 , Yuichi Ikuhara 1, 2
Affiliation
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Spinel LiMn2O4 is an attractive lithium-ion battery cathode material that undergoes a complex series of structural changes during electrochemical cycling that lead to rapid capacity fading, compromising its long-term performance. To gain insights into this behavior, in this report we analyze changes in epitaxial LiMn2O4 thin films during the first few charge–discharge cycles with atomic resolution and correlate them with changes in the electrochemical properties. Impedance spectroscopy and scanning transmission electron microscopy are used to show that defect-rich LiMn2O4 surfaces contribute greatly to the increased resistivity of the battery after only a single charge. Sequences of {111} stacking faults within the films were also observed upon charging, increasing in number with further cycling. The atomic structures of these stacking faults are reported for the first time, showing that Li deintercalation is accompanied by local oxygen loss and relaxation of Mn atoms onto previously unoccupied sites. The stacking faults have a more compressed structure than the spinel matrix and impede Li-ion migration, which explains the observed increase in thin-film resistivity as the number of cycles increases. These results are used to identify key factors contributing to conductivity degradation and capacity fading in LiMn2O4 cathodes, highlighting the need to develop techniques that minimize defect formation in spinel cathodes to improve cycle performance.
中文翻译：
取向 LiMn2O4 阴极薄膜电化学循环过程中的原子级变化
尖晶石 LiMn 2 O 4是一种极具吸引力的锂离子电池正极材料，在电化学循环过程中会发生一系列复杂的结构变化，导致容量快速衰减，从而影响其长期性能。为了深入了解这种行为，在本报告中，我们以原子分辨率分析了前几个充放电循环中外延 LiMn 2 O 4薄膜的变化，并将它们与电化学特性的变化相关联。阻抗谱和扫描透射电子显微镜用于显示富含缺陷的 LiMn 2 O 4仅在一次充电后，表面对提高电池的电阻率有很大贡献。在充电时还观察到薄膜内的 {111} 堆垛层错序列，随着进一步循环，数量增加。首次报道了这些堆垛层错的原子结构，表明锂脱嵌伴随着局部氧损失和锰原子松弛到先前未占据的位置。堆垛层错具有比尖晶石基质更压缩的结构并阻碍锂离子迁移，这解释了观察到的薄膜电阻率随着循环次数的增加而增加。这些结果用于确定导致 LiMn 2 O 4中电导率下降和容量衰减的关键因素阴极，强调需要开发最大限度地减少尖晶石阴极缺陷形成的技术，以提高循环性能。
更新日期：2022-02-09
中文翻译：
取向 LiMn2O4 阴极薄膜电化学循环过程中的原子级变化
尖晶石 LiMn 2 O 4是一种极具吸引力的锂离子电池正极材料，在电化学循环过程中会发生一系列复杂的结构变化，导致容量快速衰减，从而影响其长期性能。为了深入了解这种行为，在本报告中，我们以原子分辨率分析了前几个充放电循环中外延 LiMn 2 O 4薄膜的变化，并将它们与电化学特性的变化相关联。阻抗谱和扫描透射电子显微镜用于显示富含缺陷的 LiMn 2 O 4仅在一次充电后，表面对提高电池的电阻率有很大贡献。在充电时还观察到薄膜内的 {111} 堆垛层错序列，随着进一步循环，数量增加。首次报道了这些堆垛层错的原子结构，表明锂脱嵌伴随着局部氧损失和锰原子松弛到先前未占据的位置。堆垛层错具有比尖晶石基质更压缩的结构并阻碍锂离子迁移，这解释了观察到的薄膜电阻率随着循环次数的增加而增加。这些结果用于确定导致 LiMn 2 O 4中电导率下降和容量衰减的关键因素阴极，强调需要开发最大限度地减少尖晶石阴极缺陷形成的技术，以提高循环性能。
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