Structure and electrochemical performance of LiNi_(0.6)Co_(0.1)Mn_(0.2)Fe_(0.1)O_2 tetrad cathode material for Li-battery

摘要

In the study, the (Ni0.6Co0.1Mn0.2Fe0.1)C2O4 precursor was synthesized according to the oxalate co-precipitation method under different pH values and then layered Ni-rich LiNi0.6Co0.1Mn0.2Fe0.1O2 (6121) materials were prepared by calcinating the mixture of oxalate precursor and LiOHH2O in an oxygen atmosphere. The crystal structure, morphology, chemical compositions, and electrochemical behaviors of the tetrad cathode materials were explored respectively by XRD, SEM, HRTEM, EDS, and electrochemical charge-discharge tests. The XRD results revealed that the ratios of c/a and I-(003)/I-(104) respectively increased from 4.989 to 1.47 to 5.000 and 1.61 after Fe substituted Co in LiNi0.6Co0.2Mn0.2O2 (622). SEM images showed that spherical particles were more uniform and that the particle diameter decreased from 15 mu m to 10 mu m after the introduction of Fe. The results of charge/discharge tests indicated that the LiNi0.6Co0.1Mn0.2Fe0.1O2 sample had the lower polarization (10% at 0.1C), the higher cycling retention (86% after 100 cycles at 1C), and the enhanced rate performance. The LiNi0.6Co0.1Mn0.2Fe0.1O2 sample showed the better reversibility, smaller impedance parameters and a larger Li+ diffusion coefficient in CV and EIS analyses. This study provides a promising tetrad cathode material with the better crystal structure, higher columbic efficiency and better cycle performance. The new tetrad cathode material is expected to become part and parcel of cathode materials.