Hayoung Park1,Hyeokjun Park2,1,Sungsu Kang1,Yonggoon Jeon1,Jihoon Kim1,Kisuk Kang1,Jungwon Park1
Seoul National University1,Korea Research Institue of Standards and Science2
Hayoung Park1,Hyeokjun Park2,1,Sungsu Kang1,Yonggoon Jeon1,Jihoon Kim1,Kisuk Kang1,Jungwon Park1
Seoul National University1,Korea Research Institue of Standards and Science2
Nickel-rich layered oxides are regarded as promising next-generation cathode materials for high-energy lithium-ion batteries. However, their commercialization has been hampered by their inferior cycle stability, which stems from chemo-mechanical failures ranging from primary to secondary particle. In this work, we investigate the solid-state synthesis of LiNi<sub>0.6</sub>Co<sub>0.2</sub>Mn<sub>0.2</sub>O<sub>2</sub> in real-time to better understand the structural and/or morphological changes during phase evolution. Multi-length-scale observations (aberration-corrected transmission electron microscopy (TEM), in situ heating TEM and in situ X-ray diffraction, etc.) reveal that the kinetic competition between the intrinsic thermal decomposition of the transition metal hydroxide at the core and the topotactic lithiation near the interface determines the overall synthesis, which results in spatially heterogeneous intermediates at the low temperature. The thermal oxidation of the precursor leads to the formation of intergranular voids and intragranular nanopores which are destructive to cyclability. Furthermore, we demonstrate that the pseudo-equilibrium synthetic pathway which promotes topotactic lithiation can mitigate the generation of defective structures and effectively suppress the chemo-mechanical failures.