Nie Lu, Liang Chao, Chen Shaojie, He Yingjie, Liu Weiyan, Zhao Haojie, Gao Tianyi, Sun Zhetao, Hu Qilin, Zhang Yue, Yu Yi, Liu Wei
School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China.
ACS Appl Mater Interfaces. 2021 Mar 24;13(11):13281-13288. doi: 10.1021/acsami.1c00723. Epub 2021 Mar 12.
Lithium-rich layered oxide cathodes with high specific energy have become one of the most popular cathode materials for high-performance lithium-ion batteries. However, spinel phase formation due to the migration of transition metals and the release of lattice oxygen leads to the degradation of electrochemical performance. Here, we develop a synthesis approach for Li-rich layered oxide cathodes by a two-step heat-treatment process, which includes precursor calcination and pellet sintering. Compared with the sample prepared by the traditional one-step calcination, the oxide particles prepared by the two-step heat treatment show increased grain size from 217 to 425 nm. The Li-rich layered oxide cathodes with larger crystal grains indicate a mitigated formation of spinel phase and reduced voltage decay, which result in improved specific capacity, cycle stability, and rate capability. In addition, the thermal stability of the oxides is also improved. The improved electrochemical performance is because of the large single grains having a reduced contact area with a liquid electrolyte and the stable crystal lattice during cycling. Our strategy not only provides a simple and effective way to enhance the stability of the Li-rich layered oxide cathodes but also extends to the preparation of oxide powders with large grains.
具有高比能量的富锂层状氧化物阴极已成为高性能锂离子电池最受欢迎的阴极材料之一。然而，过渡金属迁移和晶格氧释放导致的尖晶石相形成会导致电化学性能下降。在此，我们通过两步热处理工艺开发了一种富锂层状氧化物阴极的合成方法，该工艺包括前驱体煅烧和颗粒烧结。与传统一步煅烧制备的样品相比，两步热处理制备的氧化物颗粒的晶粒尺寸从217 nm增加到425 nm。具有较大晶粒的富锂层状氧化物阴极表明尖晶石相的形成得到缓解，电压衰减降低，从而提高了比容量、循环稳定性和倍率性能。此外，氧化物的热稳定性也得到了提高。电化学性能的改善是由于大单晶粒与液体电解质的接触面积减小以及循环过程中晶格稳定。我们的策略不仅提供了一种简单有效的方法来提高富锂层状氧化物阴极的稳定性，而且还扩展到了大晶粒氧化物粉末的制备。
