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Grain Boundaries as a Diffusion-Limiting Factor in Lithium-Rich NMC Cathodes for High-Energy Lithium-Ion Batteries
ACS Applied Energy Materials ( IF 5.4 ) Pub Date : 2021-07-01 , DOI: 10.1021/acsaem.1c00872 Artem M. Abakumov 1 , Chen Li 2 , Anton Boev 1 , Dmitry A. Aksyonov 1 , Aleksandra A. Savina 1 , Tatiana A. Abakumova 3 , Gustaaf Van Tendeloo 2 , Sara Bals 2
ACS Applied Energy Materials ( IF 5.4 ) Pub Date : 2021-07-01 , DOI: 10.1021/acsaem.1c00872 Artem M. Abakumov 1 , Chen Li 2 , Anton Boev 1 , Dmitry A. Aksyonov 1 , Aleksandra A. Savina 1 , Tatiana A. Abakumova 3 , Gustaaf Van Tendeloo 2 , Sara Bals 2
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High-energy lithium-rich layered transition metal oxides are capable of delivering record electrochemical capacity and energy density as positive electrodes for Li-ion batteries. Their electrochemical behavior is extremely complex due to sophisticated interplay between crystal structure, electronic structure, and defect structure. Here we unravel an extra level of this complexity by revealing that the most typical representative Li1.2Ni0.13Mn0.54Co0.13O2 material, prepared by a conventional coprecipitation technique with Na2CO3 as a precipitating agent, contains abundant coherent (001) grain boundaries with a Na-enriched P2-structured block due to segregation of the residual sodium traces. The trigonal prismatic oxygen coordination of Na triggers multiple nanoscale twinning, giving rise to incoherent (104) boundaries. The cationic layers at the (001) grain boundaries are filled with transition metal cations being Mn-depleted and Co-enriched; this makes them virtually not permeable for the Li+ cations, and therefore they negatively influence the Li diffusion in and out of the spherical agglomerates. These results demonstrate that besides the mechanisms intrinsic to the crystal and electronic structure of Li-rich cathodes, their rate capability might also be depreciated by peculiar microstructural aspects. Dedicated engineering of grain boundaries opens a way for improving inherently sluggish kinetics of these materials.
中文翻译：
晶界作为高能锂离子电池富锂 NMC 阴极的扩散限制因素
高能富锂层状过渡金属氧化物作为锂离子电池的正极能够提供创纪录的电化学容量和能量密度。由于晶体结构、电子结构和缺陷结构之间复杂的相互作用，它们的电化学行为极其复杂。在这里，我们通过揭示最典型的 Li 1.2 Ni 0.13 Mn 0.54 Co 0.13 O 2材料，通过与 Na 2 CO 3的常规共沉淀技术制备，揭示了这种复杂性的额外水平作为沉淀剂，由于残留钠痕量的分离，含有丰富的连贯 (001) 晶界和富含钠的 P2 结构块。Na 的三角棱柱氧配位触发多个纳米级孪晶，产生不连贯的 (104) 边界。(001)晶界处的阳离子层充满了贫锰和富钴的过渡金属阳离子；这使得它们几乎不能渗透 Li +阳离子，因此它们对 Li 扩散进出球形团聚体产生负面影响。这些结果表明，除了富锂正极的晶体和电子结构固有的机制外，它们的倍率性能也可能因特殊的微观结构方面而降低。晶界的专用工程为改善这些材料固有的缓慢动力学开辟了道路。
更新日期：2021-07-26
中文翻译：
晶界作为高能锂离子电池富锂 NMC 阴极的扩散限制因素
高能富锂层状过渡金属氧化物作为锂离子电池的正极能够提供创纪录的电化学容量和能量密度。由于晶体结构、电子结构和缺陷结构之间复杂的相互作用，它们的电化学行为极其复杂。在这里，我们通过揭示最典型的 Li 1.2 Ni 0.13 Mn 0.54 Co 0.13 O 2材料，通过与 Na 2 CO 3的常规共沉淀技术制备，揭示了这种复杂性的额外水平作为沉淀剂，由于残留钠痕量的分离，含有丰富的连贯 (001) 晶界和富含钠的 P2 结构块。Na 的三角棱柱氧配位触发多个纳米级孪晶，产生不连贯的 (104) 边界。(001)晶界处的阳离子层充满了贫锰和富钴的过渡金属阳离子；这使得它们几乎不能渗透 Li +阳离子，因此它们对 Li 扩散进出球形团聚体产生负面影响。这些结果表明，除了富锂正极的晶体和电子结构固有的机制外，它们的倍率性能也可能因特殊的微观结构方面而降低。晶界的专用工程为改善这些材料固有的缓慢动力学开辟了道路。
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