Structural, microstructural and electrochemical studies of layered Lix(Ni0.33Mn0.33Co0.33)1-xO2 as cathode materials for rechargeable lithium ion batteries.

GUSTAVO SUAREZ; MARIELA ORTIZ; MARTINA GAMBA; SILVIA REAL

São Paulo

Congreso; ICC7. 7th International Congress on Ceramics; 2018

University of São Paulo (Polytechnic School)

The enriched lithium ion containing layered oxide cathode materials Lix(Ni0.33Mn0.33Co0.33)1-xO2 (x = 0, 0.07, 0.143 and 0.175) have been prepared, by solid state reactions, from a stoichiometric mixture of Li2CO3, NiO, Co2O3 and MnO2. Starting materials were well mixed in a non-liquid state in an agate ball milling tank at 800 rpm for 270 min. The milled powder containing the mixed raw materials were, in a first step, heated at 10 ºC/min heating rate under air atmosphere up to 400 ºC for 4 h and then, in a second step, up to 800 ºC for 12 h. The obtained materials were left at room temperature and were ground using an agate mortar up to smaller than mesh #325. The phase purity and crystalline structure of the layered oxide materials were determined by X-ray diffraction analysis and Rietveld refinements studies. Surface morphology and elemental analysis have been carried out using scanning electron microscopy. Particle diameters were measured by light scattering experiments. In order to study electrochemical performances, cells were assembled in an argon-filled glove box. For the positive electrodes, 80 wt.% of the synthesized material, 10 wt.% of Super P conductive carbon black and 10 wt.% of poly(vinylidene fluoride) were mixed in n-methylpirrolidone and the obtained paste was spread over an aluminum film. Lithium metal was used as counter and reference electrodes, while the electrolyte was composed of a 1:1 volume ratio of ethylene carbonate (EC), and dimethyl carbonate (DMC) with 1 M LiPF6. The electrochemical behavior of the prepared electrodes was studied employing cyclic voltammetry and charge-discharge curves. These results clearly exhibit that the lithium-enriched cathode material showed a well redox performance at electrode?electrolytic interface. Furthermore, the capacity of the material increased from 90 mAhg-1 for non-rich lithium ion material (x = 0) to 174 mAhg-1 for the highest content of lithium (x = 0.175) at 0.1 C, showing both well cycling stability (i.e., capacity retention: 80% after 20 cycles) at ambient temperature, between 2-4.6 V. These properties allow concluding that these cathode materials can be considered as suitable positive electrodes for the development of rechargeable lithium ion batteries.