Synthesis And Electrochemical Performances Of Nano-size Nca Materials

In order to solve the problem that a large amount of waste water needs to be treated in the conventional co-precipitation method,we have designed a new method for preparing NCA.We determined the optimal synthetic process through exploring the ball milling time,the oxygen flow and sintering temperature.In a typical process,spherical precursor powder was prepared by spray drying of a uniform suspension obtained from the ball-milling of the mixture of the starting raw materials.The precursor powders were pressed into tablets under different pressures and crushed into powder.The pressing treated powders were finally calcinated under oxygen atmosphere to obtain the NCA.Rietveld refinement confirmed the reduced cationic disordering in Li slab by such pressing treatment,and the smallest disordering was observed for sample S4 with only 1.3%Ni ions on Li lattice position.The initial discharge specific capacity of sample S4 was 201.2 mAh·g^-1 at 0.1C rate,and the specific capacity was 124 mAh·g^-1 after 100 cycles at 5C,and the capacity retention rate was 79.08%.On the basis of the optimal synthetic route,we synthesize the rubidium modified NCA cathode materials and explore the influence of x value on electrochemical properties.The Rietveld refinement results revealed that the Rb-ions were incorporated into the bulk lattice by replacing the original Li ions,which resulted in the enlarging of Li layer spacing and the reducing of the thickness of the transition metal slab.Such changes in crystal structure led to the decrease in the activation energy for the migration of Li⁺,and thus an improved electrochemical performance was observed.The Rb_0.01Li_0.99Ni_0.8Co_0.15Al_0.05O₂ sample exhibits the highest initial specific discharge capacity and the best rate performance.It delivers specific discharge capacities of 190.5mAh·g^-1 at 0.1C.It also shows the best cycle stability with capacity retention of 91.31%after 100 cycles at 2C.