Effects Of Surface Modification On Electrochemical Kinetic Properties Of Cathode Materials Of Lithium Ion Batteries

With the rapid development of high technology and the increasing attraction on environmental protection,the applications of mobile electronic devices and electric vehicles are increased accordingly.On the other hand,the traditional energy storage equipment cannot satisfy the as-increased requirements.In this work,we designed and fabricated a series of composites of two commonly used cathode materials?Lithium iron phosphate?LiFePO₄?and Li-Ni-Co-Mn-O?through surface modification.It was illustrated that their electrical and lithium ion conductivities of the cathode materials had improved The detailed research contents and results are:-In order to improve the electrochemical kinetic properties of the LiFePO₄,chemically reduced graphene oxide and conductive polymer films are chemically coated on the LiFePO₄ powder surface.FE-SEM,XPS and Raman methods were used to characterize the composition,morphology,and structure of the as-prepared composites.The electrochemical measurements showed that the specific capacity of the as-prepared cathode materials at 10 C could reach to 110 mAh g^-1 and the capacity retention was 90.2%after 500 cycles.The kinetic parameters of the LiFePO₄ electrodes were investigated by electrochemical impedance spectroscopy,cyclic voltammograms and potential static step charge measurements.The mechanisms of the effects of chemically reduced graphene oxide/conductive polymer on LiFePO₄ were discussed.-To get three-dimensional network structure of GO sheets on the surface of Li-Ni-Co-Mn-O,graphene oxide,water soluble magnesium salt were reacted with the Li-Ni-Co-Mn-O.It was found that the GO and the magnesium ions could be coated uniformly on the cathode material that enhances their electronic and ionic conductivities correspondingly.The specific capacity of Li-Ni-Co-Mn-O after modification is of 103.9 mAh g^-1and only 10%of initial capacity fading after 100 cycles.The research results envisage that the chemically reduced graphene oxide and its composite materials can effectively improve the electrochemical kinetic properties of the cathode materials of lithium ion batteries,which hold great potentials for practical applications.