Zhao Wengao, Zou Lianfeng, Zhang Leiting, Fan Xinming, Zhang Hehe, Pagani Francesco, Brack Enzo, Seidl Lukas, Ou Xing, Egorov Konstantin, Guo Xueyi, Hu Guorong, Trabesinger Sigita, Wang Chongmin, Battaglia Corsin
Materials for Energy Conversion, Empa, Swiss Federal Laboratories for Materials, Science and Technology, Dübendorf, 8600, Switzerland.
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 3335 Innovation Boulevard, Richland, WA, 99354, USA.
Small. 2022 Apr;18(14):e2107357. doi: 10.1002/smll.202107357. Epub 2022 Feb 18.
Lithium-ion batteries based on single-crystal LiNi Co Mn O (NCM, 1-x-y ≥ 0.6) cathode materials are gaining increasing attention due to their improved structural stability resulting in superior cycle life compared to batteries based on polycrystalline NCM. However, an in-depth understanding of the less pronounced degradation mechanism of single-crystal NCM is still lacking. Here, a detailed postmortem study is presented, comparing pouch cells with single-crystal versus polycrystalline LiNi Co Mn O (NCM622) cathodes after 1375 dis-/charge cycles against graphite anodes. The thickness of the cation-disordered layer forming in the near-surface region of the cathode particles does not differ significantly between single-crystal and polycrystalline particles, while cracking is pronounced for polycrystalline particles, but practically absent for single-crystal particles. Transition metal dissolution as quantified by time-of-flight mass spectrometry on the surface of the cycled graphite anode is much reduced for single-crystal NCM622. Similarly, CO gas evolution during the first two cycles as quantified by electrochemical mass spectrometry is much reduced for single-crystal NCM622. Benefitting from these advantages, graphite/single-crystal NMC622 pouch cells are demonstrated with a cathode areal capacity of 6 mAh cm with an excellent capacity retention of 83% after 3000 cycles to 4.2 V, emphasizing the potential of single-crystalline NCM622 as cathode material for next-generation lithium-ion batteries.
基于单晶LiNiCoMnO（NCM，1 - x - y≥0.6）正极材料的锂离子电池因其结构稳定性的提高而受到越来越多的关注，与基于多晶NCM的电池相比，其循环寿命更优。然而，目前仍缺乏对单晶NCM不太明显的降解机制的深入理解。在此，我们进行了一项详细的失效分析研究，比较了在与石墨负极进行1375次充/放电循环后，采用单晶和多晶LiNiCoMnO（NCM622）正极的软包电池。在阴极颗粒近表面区域形成的阳离子无序层的厚度在单晶颗粒和多晶颗粒之间没有显著差异，而多晶颗粒出现明显开裂，单晶颗粒则几乎没有。通过飞行时间质谱法对循环后的石墨负极表面进行量化分析，发现单晶NCM622的过渡金属溶解量大幅降低。同样，通过电化学质谱法对前两个循环中CO气体析出量进行量化分析，发现单晶NCM622的析出量也大幅降低。受益于这些优势，展示了石墨/单晶NMC622软包电池，其阴极面积容量为6 mAh/cm²，在3000次循环至4.2 V后具有83%的优异容量保持率，强调了单晶NCM622作为下一代锂离子电池正极材料的潜力。
