Core-shell structured Li[(Ni_0.8Co_0.1Mn_0.1)_0.7(Ni_0.45Co_0.1Mn_0.45)_0.3]O₂ cathode material for high-energy lithium ion batteries

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• 作者：Hua Shi ; Xiaoqing Wang ; Peiyu Hou ; Enlou Zhou ; Jian Guo ; Jun Zhang ; Dongge Wang ; Fenxia Guo ; Dawei Song ; Xixi Shi ; Lianqi Zhang
• 关键词：Lithium ion batteries ; Cathode materials ; Core&ndash ; shell structure ; Co-precipitation
• 刊名：Journal of Alloys and Compounds
• 出版年：25 February, 2014
• 年：2014
• 卷：587
• 期：Complete
• 页码：710-716
• 全文大小：2299 K

文摘

The comparative investigations between core-shell and non-core-shell structured layered materials with a same composition are seldom reported and extremely necessary. Li[Ni_0.7Co_0.1Mn_0.2]O₂ is firstly redesigned into core-shell structured Li[(Ni_0.8Co_0.1Mn_0.1)_0.7(Ni_0.45Co_0.1Mn_0.45)_0.3]O₂ and the detailed comparative investigations between them are performed in this work. In this core-shell structure, Li[Ni_0.8Co_0.1Mn_0.1]O₂ with high capacity is encapsulated completely with Li[Ni_0.45Co_0.1Mn_0.45]O₂ as a stable layer. Transition metal hydroxide precursors were synthesized by coprecipitation method. The core-shell structure of hydroxide precursor as designed was identified by particle size analysis, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and derivative thermogravimetric analysis (DTG). The obtained core-shell precursor was calcined with stoichiometric Li₂CO₃ (nLi:nM = 1.05:1) at 850 掳C for 16 h to get lithiated oxide. XRD results showed that lithiated oxide can be indexed to a typical layered structure with a R-3m space group. EDS analysis from the cross-section of core-shell material particles revealed somewhat diffusion of cations in core-shell structure resulting in a concentration gradient layer, however, the core-shell structure of lithiated oxide was still remained. The electrochemical and differential scanning calorimetry (DSC) tests showed that core-shell structured Li[Ni_0.7Co_0.1Mn_0.2]O₂ displayed remarkably improved cyclability and thermal stability compared with the non-core-shell structured one. These results can clarify the function of core-shell structure in core-shell structured layered materials by excluding the effects of composition variation.