Investigation On Performances Of High-nickel Ternary Cathode Materials System Lithium-ion Batteries

The cycling performance,rate performance,low tempareture performance and high voltagedischargingperformanceofthehighnickelternarymaterial LiNi_0.6Co_0.2Mn_0.2O₂/graphite systerm lithium ion battery were studied in this paper.The stucture of cathode material at different cycles was studied using X-ray diffraction?XRD?,electrochemical performance of battery at different cycles and different temparetures was examined by electrochemical impedance spectroscopy?EIS?,reaction type of battery in the range of voltage was studied by cyclic voltemmatry?CV?.The study found that graphite whose first coulomb efficiency isn,t lower than high nickel ternary material LiNi_0.6Co_0.2Mn_0.2O_2.The lower inetial coulombic effeciency of the anode material,the less anode material to be used and the higher energy density of the battery.The study found that cycling performance of the battery deteriorated as increasing of density of the electrode surface.According to EIS measurements of the battery,the growth rate of Ohmic resistance and Charge transfer resistance increased as the rise of the electrode surface density.With the increase of cycle number,charge transfer resistance of the battery whose density of electrode surface is 400 g/m² increases significantly.After 600 cycles,the R_S,R_SEI,R_ct and Warburg factor are increased by 65.2%,31.4%,1268.1%,233.8%respectively.According to XRD analysis of the cathode material at different cycle numbers,it is found that the layered structure of cathode material became deteriorated as the cycle number increased,but the mixed cationic of material becomes severe.This demonstrates that the increasing of charger transfer impedance and the change of the cathode material structure are the key reason that cause cycle performance degradation.The rate performance is increased as the reducing of density of the electrode surface and the increasing of conductive agent.According the study of the low tempareture performance of the battery,the ohmic resistance,the charger transfer impedance increase and the warburg factor significantly increases as the temperature decreases.The growth rate of charger transfer impedance decreases as the conductive agent content increases at low tempareture.The high voltage performance of the battery was tested.It is found that cycle performance of the battery is deteriorated as the increasing of the charging voltage?4.2 V-4.4 V?and that the redox current still exists when scaning potential is nearby 4.4 V by cyclic voltammetry measurement,which means that more Ni³⁺transfers to Ni⁴⁺.The cycle performance of the battery at different charging voltage is tested,It is found that cycle performance of the battery is reduced as the increasing of the charging voltage.When the charging voltage is 4.2 V,4.3 V and 4.4 V,capacity retention of the battery is 93.7%,89.9%and 67.1%,respectively,after 200 cycles which means that the battery has better capacity retention when the charging voltage is 4.3 V.It can be used as the design templates in actual production.