Core-shell structured Li[(Ni sub(0.8)Co sub(0.1)Mn sub(0.1)) sub(0.7)(Ni sub(0.45) Co sub(0.1)Mn sub(0.45)) sub(0.3)]O sub(2) cathode material for high-energy lithium ion batteries

• Published in: Journal of alloys and compounds 2014-02, Vol.587, p.710-716
• Main Authors: Shi, Hua, Wang, Xiaoqing, Hou, Peiyu, Zhou, Enlou, Guo, Jian, Zhang, Jun, Wang, Dongge, Guo, Fenxia, Song, Dawei, Shi, Xixi, Zhang, Lianqi
• Format: Article
• Language: English
• Subjects: Core-shell structure; Differential scanning calorimetry; Hydroxides; Layered materials; Lithium-ion batteries; Oxides; Precursors; Scanning electron microscopy; X-ray diffraction
• ISSN: 0925-8388
• DOI: 10.1016/j.jallcom.2013.10.226

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 sub(0.7)Co sub(0.1)Mn sub(0.2)]O sub(2) is firstly redesigned into core-shell structured Li[(Ni sub(0.8)Co sub(0.1)Mn sub(0.1)) sub(0.7)(Ni sub(0.45) Co sub(0.1)Mn sub(0.45)) sub(0.3)]O sub(2) and the detailed comparative investigations between them are performed in this work. In this core-shell structure, Li[Ni sub(0.8)Co sub(0.1)Mn sub(0.1)]O sub(2) with high capacity is encapsulated completely with Li[Ni sub(0.45)Co sub(0.1)Mn sub(0.45)]O sub(2) 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 Li sub(2)CO sub(3) (nLi:nM = 1.05:1) at 850 [degrees]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 sub(0.7)Co sub(0.1)Mn sub(0.2)]O sub(2) 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.