Suppressed oxygen extraction and degradation of LiNixMnyCozO2 cathodes at high charge cut-

Suppressed oxygen extraction and degradation of LiNixMnyCozO2 cathodes at high charge cut-off

voltages

Jianming Zheng;Jiguang Zhang;Pengfei Yan;Jiandong Zhang;Mark H.Engelhard;Zihua Zhu;Bryant J.Polzin;Steve Trask;Jie Xiao;Chongmin Wang

【期刊名称】《纳米研究（英文版）》 【年(卷),期】2017(010)012

【摘要】The capacity degradation mechanism in lithium nickel-manganese-cobalt

oxide

(NMC)

cathodes

(LiNi1nMnv3Co1/3O2

(NMC333) and LiNi0.4Mn0.4Co02O2 (NMC442))during high-voltage (cut-off of 4.8 V) operation has been investigated.In contrast to NMC442,NMC333 exhibits rapid structural changes including severe micro-crack formation and phase transformation from a layered to a disordered rock-salt structure,as well as interfacial degradation during high-voltage cycling,leading to a rapid increase of the electrode resistance and fast capacity decline.The fundamental reason behind the poor structural and interfacial stability of NMC333 was found to be correlated to its high Co content and the significant overlap between the Co3+/4+ t2g and O2-2p bands,resulting in oxygen removal and consequent structural changes at high voltages.In addition,oxidation of the electrolyte solvents by the extracted oxygen species generates acidic species,which then attack the electrode surface and form highly