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Tracking the Influence of Thermal Expansion and Oxygen Vacancies on the Thermal Stability of Ni-Rich Layered Cathode Materials.
Advanced Science ( IF 15.1 ) Pub Date : 2020-04-24 , DOI: 10.1002/advs.201902413
Eunkang Lee 1 , Shoaib Muhammad 1, 2 , Taewhan Kim 1 , Hyunchul Kim 3 , Wontae Lee 1 , Won-Sub Yoon 1
Affiliation  

The ever‐growing demand for high‐energy lithium‐ion batteries in portable electronics and electric vehicles has triggered intensive research efforts over the past decade. An efficient strategy to boost the energy and power density of lithium‐ion batteries is to increase the Ni content in the cathode materials. However, a higher Ni content in the cathode materials gives rise to safety issues. Herein, thermal expansion and oxygen vacancies are proposed as new critical factors that affect the thermal stability of charged Ni‐rich cathode materials based on a systematic synchrotron‐based X‐ray study of Li0.33Ni0.5+x Co0.2Mn0.3‐x O2 (x = 0, 0.1, 0.2) cathode materials during a heating process. Charged cathode materials with higher Ni contents show larger thermal expansion, which accelerates transition metal migration to the Li layers. Oxygen vacancies are formed and accumulate mainly around Ni ions until the layered‐to‐spinel phase transition begins. The oxygen vacancies also facilitate transition metal migration to the Li layers. Thermal expansion and the presence of oxygen vacancies decrease the energy barrier for cation migration and facilitate the phase transitions in charged cathode materials during the heating process. These results provide valuable guidance for developing new cathode materials with improved safety characteristics.

中文翻译:

跟踪热膨胀和氧空位对富镍层状阴极材料热稳定性的影响。

便携式电子产品和电动汽车中对高能锂离子电池的需求不断增长,在过去十年中引发了深入的研究工作。提高锂离子电池能量和功率密度的有效策略是增加正极材料中的Ni含量。然而,正极材料中较高的Ni含量引起安全问题。本文基于Li 0.33 Ni 0.5+ x Co 0.2 Mn 0.3- x O的基于同步加速器的系统X射线研究,提出了热膨胀和氧空位作为影响带电富镍阴极材料热稳定性的新关键因素。2x= 0、0.1、0.2)的阴极材料在加热过程中。Ni含量较高的带电阴极材料显示出较大的热膨胀,从而加速了过渡金属向Li层的迁移。氧空位的形成并主要在Ni离子周围积累,直到层状至尖晶石相变开始。氧空位还促进过渡金属向Li层的迁移。热膨胀和氧空位的存在降低了阳离子迁移的能垒,并在加热过程中促进了带电阴极材料中的相变。这些结果为开发具有改进安全特性的新型阴极材料提供了有价值的指导。
更新日期:2020-06-24
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