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Restraining the polarization increase of Ni-rich and low-Co cathodes upon cycling by Al-doping
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2020/03/08 , DOI: 10.1039/d0ta00260g Chunfang Zhang 1, 2, 3, 4 , Jiajia Wan 2, 3, 5, 6, 7 , Yixiao Li 2, 3, 5, 6, 7 , Shiyao Zheng 8, 9, 10 , Ke Zhou 2, 3, 5, 6, 7 , Donghao Wang 1, 2, 3, 4 , Danfeng Wang 2, 3, 5, 6, 7 , Chaoyu Hong 2, 3, 5, 6, 7 , Zhengliang Gong 1, 2, 3, 4 , Yong Yang 1, 2, 3, 4, 5
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2020/03/08 , DOI: 10.1039/d0ta00260g Chunfang Zhang 1, 2, 3, 4 , Jiajia Wan 2, 3, 5, 6, 7 , Yixiao Li 2, 3, 5, 6, 7 , Shiyao Zheng 8, 9, 10 , Ke Zhou 2, 3, 5, 6, 7 , Donghao Wang 1, 2, 3, 4 , Danfeng Wang 2, 3, 5, 6, 7 , Chaoyu Hong 2, 3, 5, 6, 7 , Zhengliang Gong 1, 2, 3, 4 , Yong Yang 1, 2, 3, 4, 5
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Ni-rich and low-Co cathodes (LiNixCoyMn1−x−yO2, x > 0.9, y ≤ 0.03) have the advantages of high capacity and low cost. However, the sharp increase in polarization upon cycling is unfavorable to the cycling performance. Herein, the mechanism of polarization increase is explored in detail, and Al-doping is proposed to restrain the polarization increase upon cycling. First, the electrochemistry test, in situ XRD, GITT and EIS are combined to provide new insights for understanding the polarization increase process. In addition, the mechanism of Al-doping which suppresses the polarization increase is also investigated. During cycling, the main cause for the increased polarization of Al-free LiNi0.94Co0.03Mn0.03O2 (NCM 94) cathodes is attributed to kinetic reasons. It is worth noting that the change of Li dynamics and charge-transfer impedance is more obvious at high SOC, which is consistent with the evolution of polarization. In contrast, because of the stabilizing effect of Al-doping on the structure, Al-doped LiNi0.92Co0.03Mn0.03Al0.02O2 (NCMA 92) cathodes can alleviate polarization increase during prolonged cycling. In detail, Al-doping reduces mechanical strain and relieves the accumulation of local internal stress at high SOC, which is conducive to improving the structural stability, maintaining the connection between primary particles, reducing the surface degradation along microcracks, and thus suppressing the deterioration of the electrochemical kinetics during cycling. Benefiting from the alleviative polarization increase, the NCMA 92 cathodes demonstrate a capacity retention of 92% after 100 cycles, while the NCM 94 only 69%. In this article, the insights on the polarization increase process of Ni-rich and low-Co cathodes will further help in the understanding of their cycling behavior and contribute to the efforts of improving their electrochemical performance.
中文翻译：
铝掺杂循环抑制富镍和低钴阴极的极化增加
富Ni和低钴阴极（的LiNi X钴ý锰1- X - Ý ø 2，X > 0.9，ÿ ≤0.03）具有的高容量和低成本的优点。但是，循环时极化的急剧增加不利于循环性能。在本文中，详细探讨了极化增加的机理，并提出了Al掺杂以抑制循环时极化增加。一，电化学测试，原位XRD，GITT和EIS相结合，为理解极化增加过程提供了新的见解。另外，还研究了Al掺杂抑制极化增加的机理。在循环过程中，无铝LiNi 0.94 Co 0.03 Mn 0.03 O 2（NCM 94）阴极极化增加的主要原因是动力学原因。值得注意的是，在高SOC下，Li动力学和电荷转移阻抗的变化更为明显，这与极化的发展是一致的。相反，由于铝掺杂对结构的稳定作用，铝掺杂的LiNi 0.92 Co 0.03 Mn 0.03 Al 0.02Ø 2（NCMA 92）阴极可以减轻长时间循环过程中的极化增加。详细地讲，Al掺杂降低了机械应力并减轻了高SOC下的局部内应力的累积，这有利于改善结构稳定性，维持一次颗粒之间的连接，减少沿微裂纹的表面降解，从而抑制了Sr的劣化。循环过程中的电化学动力学。受益于缓解的极化增加，NCMA 92阴极在100个循环后的容量保持率达到92％，而NCM 94阴极仅达到69％。在本文中，对富镍低钴阴极的极化增加过程的见解将进一步帮助他们理解其循环行为，并有助于改善其电化学性能。
更新日期：2020-04-08
中文翻译：
铝掺杂循环抑制富镍和低钴阴极的极化增加
富Ni和低钴阴极（的LiNi X钴ý锰1- X - Ý ø 2，X > 0.9，ÿ ≤0.03）具有的高容量和低成本的优点。但是，循环时极化的急剧增加不利于循环性能。在本文中，详细探讨了极化增加的机理，并提出了Al掺杂以抑制循环时极化增加。一，电化学测试，原位XRD，GITT和EIS相结合，为理解极化增加过程提供了新的见解。另外，还研究了Al掺杂抑制极化增加的机理。在循环过程中，无铝LiNi 0.94 Co 0.03 Mn 0.03 O 2（NCM 94）阴极极化增加的主要原因是动力学原因。值得注意的是，在高SOC下，Li动力学和电荷转移阻抗的变化更为明显，这与极化的发展是一致的。相反，由于铝掺杂对结构的稳定作用，铝掺杂的LiNi 0.92 Co 0.03 Mn 0.03 Al 0.02Ø 2（NCMA 92）阴极可以减轻长时间循环过程中的极化增加。详细地讲，Al掺杂降低了机械应力并减轻了高SOC下的局部内应力的累积，这有利于改善结构稳定性，维持一次颗粒之间的连接，减少沿微裂纹的表面降解，从而抑制了Sr的劣化。循环过程中的电化学动力学。受益于缓解的极化增加，NCMA 92阴极在100个循环后的容量保持率达到92％，而NCM 94阴极仅达到69％。在本文中，对富镍低钴阴极的极化增加过程的见解将进一步帮助他们理解其循环行为，并有助于改善其电化学性能。
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