Why is the O3 to O1 phase transition hindered in LiNiO2 on full delithiation?
Why is the O3 to O1 phase transition hindered in LiNiO2 on full delithiation?
复制标题
DOI：
10.1039/d1ta03066c
复制
发表时间：
2021-06-25
影响因子：
11.9
通讯作者：
Yabuuchi, Naoaki
中科院分区：
文献类型：
--
作者：
Ikeda, Naohiro;Konuma, Itsuki;Yabuuchi, Naoaki
富镍层状材料被用作高能锂离子电池的正极材料。由于连续循环后化学计量的LiNiO2的电极可逆性逐渐丧失，Ni离子部分被其他金属离子（Co、Mn、Al等）取代。然而，化学计量LiNiO2劣化的根源仍不完全清楚。此外，仅在高电压区域（>4.1 V）观察到容量损失，这与其他电极材料中观察到的失效模式明显不同。在这里，我们首次报告了劣化的根源，这是通过原位 X 射线衍射研究揭示的。对于完全充电的 NiO2，Ni 离子从 NiO2 板中的原始八面体位点迁移到 Li 层中的共面四面体位点，从而抑制 O3 到 O1 相变。请注意，镍迁移是一个可逆过程，镍离子在放电时迁移回原来的八面体位点。然而，经过连续循环后，Ni迁移的可逆性逐渐丧失，Ni离子部分留在Li层的四面体位置。由于Ni在Li层中占据，电极动力学也会恶化，并且Ni离子在四面体位点的积累导致高电压区域可逆容量的损失。这一发现开辟了设计高容量富镍电极材料的新方法，从而促进了高能锂离子电池的发展。
Ni-enriched layered materials are utilized as positive electrode materials of high-energy Li-ion batteries. Because electrode reversibility is gradually lost for stoichiometric LiNiO2 after continuous cycles, Ni ions are partially substituted by other metal ions (Co, Mn, Al etc.). However, the origin of deterioration in stoichiometric LiNiO2 is still not fully understand yet. Moreover, the loss of capacities is observed only in the high voltage region (>4.1 V), which is obviously different from the failure mode observed in other electrode materials. Here, we report for the first time the origin of deterioration, which is revealed by an in situ X-ray diffraction study. For fully charged NiO2, Ni ions migrate from original octahedral sites in NiO2 slabs to face-sharing tetrahedral sites in Li layers, by which the O3 to O1 phase transition is suppresed. Note that Ni migration is a reversible process, and the Ni ions migrate back to the original octahedral sites on discharge. However, after continuous cycles, the reversibility of Ni migration is gradually lost, and Ni ions are partially left at the tetrahedral sites in Li layers. Electrode kinetics are also deteriorated because of the Ni occupation in Li layers, and the accumulation of Ni ions at tetrahedral sites results in the loss of reversible capacities in the high voltage region. This finding opens a new way to design high-capacity Ni-enriched electrode materials, leading to the development of high-energy Li-ion batteries.