Sub-micron sized LiNi0.8Co0.15Al0.05O2 cathode materials with improved electrochemical performance caused by the reduced cationic disordering in Li slab were synthesized through a solid state reaction routine. 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. Then 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 target cathode materials. XRD investigation revealed a hexagonal layered structure without impurity phase for all samples and significant increase in the diffraction intensity ratio of I(003)/I(104) was observed. Rietveld refinement further 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 electrochemical testing showed an improvement in electrochemical behavior for those pressing treated samples. The calculation of diffusion coefficients using EIS data showed improved Li diffusion coefficient after pressing treatment. The sample S4 presented a diffusion coefficient of 4.36 × 10−11 cm2·s−1, which is almost 3.5 times the value of untreated sample.

Rubidium doped cathode materials Rb x Li 1.27-x Cr 0.2 Mn 0.53 O 2 (x = 0, 0.01, 0.03 and 0.05) were prepared via a solid state reaction method. The influences of the amount of Rb + incorporated in the cathodes on the electrochemical performance were investigated in detail. It was found that the initial specific capacity, coulombic efficiency and rate performance were improved by Rb doping. Among the prepared cathode samples, the Rb 0.03 Li 1.24 Cr 0.2 Mn 0.53 O 2 material presented the best results. The material showed an initial discharging capacity of 224.9 mAh • g −1 , a capacity retention of 98.8% after 50 cycles and excellent high-rate performance of 92.0 mAh • g −1 at 5C rate. The improved diffusion coefficient of Li ions in the Rb + incorporated cathodes was confirmed by electrochemical impedance measurement. The changes in diffusion coefficient are in good accordance with the changes in lattice parameter of c axis obtained from XRD Rietveld refinement. With the increase in Rb concentration, the interlayer spacing increases, then the diffusion of Li ions is enhanced and finally the electrochemical properties is improved. However, when x reaches 0.05, the lattice distorsion happened, c axis begins to shrink, the Li ion diffusion is restricted, and therefore the electrochemical performance is reduced with further increase in Rb concentration.

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