Resolving atomic-scale phase transformation and oxygen loss mechanism in ultrahigh-nickel layered cathodes for cobalt-free lithium-ion batteries

By Chunyang Wang, Lili Han, Rui Zhang, H. Cheng, Linqin Mu, K. Kisslinger, Peichao Zou, Yang Ren, P. Cao, Feng Lin and 1 more. Matter, 2021

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By using in situ and 3D electron microscopy, we decipher the chemomechanical degradation pathway of LiNiO 2 -based ultrahigh-nickel layered cathodes for lithium-ion batteries. We reveal that the O1 phase acts as a preferential nucleation site for rock-salt transformation via a two-step pathway involving cation mixing and shear along the (003) plane. Two types of cracks initiating from both the particle surface and interior as well as concurrent rock-salt phase transformation are uncovered. Our results provide deep understanding of the degradation mechanism of LiNiO 2 -derived cathodes. SUMMARY Doped LiNiO 2 has recently become one of the most promising cathode materials for its high specific energy, long cycle life, and reduced cobalt content. Despite this, the degradation mechanism of LiNiO 2 and its derivatives still remains elusive. Here, by combining in situ electron microscopy and first-principles calculations, we elucidate the atomic-level chemomechanical degradation pathway of LiNiO 2 -derived cathodes. We uncover that the O1 phase formed at high voltages acts as a preferential site for rock-salt transformation via a two-step pathway involving cation mixing and shear along (003) planes. Moreover, electron tomography reveals that planar cracks nucleated simultaneously from particle interior and surface propagate along the [100] direction on (003) planes, accom-panied by concurrent structural degradation in a discrete manner. Our results provide an in-depth understanding of the degradation mechanism of LiNiO 2 -derived cathodes, pointing out the concept that suppressing the O1 phase and oxygen loss is key to stabilizing LiNiO 2 for developing next-generation high-energy cathode materials. layered cathodes and point toward new directions in designing more robust high-Ni-content layered cathodes for next-generation high-energy-density LIBs.

Subfields: Automotive Engineering, Electrical and Electronic Engineering, Mechanical Engineering

View Paper: https://www.semanticscholar.org/paper/def687f0f1adb1c718bd17069570c9d635aa498c