Electrochemical performance of a nickel-rich LiNi0.6Co0.2Mn0.2O2 cathode material for lithium-ion batteries under different cut-off voltages

A spherical-like Ni0.6Co0.2Mn0.2(OH)2precursor was tuned homogeneously to synthesize LiNi0.6Co0.2Mn0.2O2as a cathode material for lithium-ion batteries. The effects of calcination temperature on the crystal structure, morphology, and the electrochemical performance of the as-prepared LiNi0.6Co0.2Mn0.2O2were investigated in detail. The as-prepared material was characterized by X-ray diffraction, scanning electron microscopy, laser particle size analysis, charge–discharge tests, and cyclic voltammetry measurements. The results show that the spherical-like LiNi0.6Co0.2Mn0.2O2material obtained by calcination at 900°C displayed the most significant layered structure among samples calcined at various temperatures, with a particle size of approximately 10 μm. It delivered an initial discharge capacity of 189.2 mAh•g−1at 0.2C with a capacity retention of 94.0% after 100 cycles between 2.7 and 4.3 V. The as-prepared cathode material also exhibited good rate performance, with a discharge capacity of 119.6 mAh•g−1at 5C. Furthermore, within the cut-off voltage ranges from 2.7 to 4.3, 4.4, and 4.5 V, the initial discharge capacities of the calcined samples were 170.7, 180.9, and 192.8 mAh•g−1, respectively, at a rate of 1C. The corresponding retentions were 86.8%, 80.3%, and 74.4% after 200 cycles, respectively. © 2017, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

Tuning Li_(3)PO_(4)modification on the electrochemical performance of nickel-rich LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)

Surface deterioration occurs more easily in nickel-rich cathode materials with the increase of nickel content.To simultaneously pre-vent deterioration of active cathode materials and improve the electrochemical performance of the nickel-rich cathode material,the surface of nickel-rich LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)cathode material is decorated with the stable structure and conductive Li_(3)PO_(4)by a facile method.The LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)-1wt%,2wt%,3wt%Li_(3)PO_(4)samples deliver a high-capacity retention of more than 85%after 100 cycles at 1 C under a high voltage of 4.5 V.The effect of different coating amounts(0-5wt%)for the LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)cathode is analyzed in detail.Results show that 2wt%coating of Li_(3)PO_(4)gives better performance compared to other coating concentrations.Detailed analysis of the structure of the samples during the charge−discharge process is performed by in-situ X-ray diffraction.It is indicated that the modification for LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)cathode could protect the well-layered structure under high voltages.In consequence,the electrochemical performance of modified samples is greatly improved.

Modified disordered carbon prepared from 3,4,9,10-perylenetetracarboxylic dianhydride as an anode material for Li-ion batteries

To prepare an anode material for Li-ion batteries with high discharge capacity and good cycling stability, disordered carbon （DC） formed by calcinations of 3,4,9,10-perylenetetracarboxylic dianhydride was modified via an acid treatment using a mixture of HNO3 and H2SO4. The modified disordered carbon （MDC） was characterized by Fourier-transform infrared （FTIR） spectroscopy, X-ray diffraction （XRD） analysis, Brtmaner-Emmett-Teller （BET） analysis, and scanning electron microscopy （SEM）. FTIR spectra confirm the successful introduction of carbonyl groups onto the DC surface. Some pores appear in the columnar structure of MDC, as observed in SEM micro- graphs. Li＋ ions intercalation/deintercalation is facilitated by the modified morphology. Electrochemical tests show that the MDC exhibits a significant improvement in discharge capacity and cycling stability. These results indicate that the MDC has strong potential for use as an anode material in Li-ion batteries.