Research On Surface Modification And Electrochemical Properties Of Electrode Materials For Iron-based Lithium Ion Batteries

In order to meet the demand of high-volume energy density and high-quality energy density of lithium-ion batteries in today's society,it is urgent to develop anode materials that can replace commercial graphite.Transition metal oxides with high specific capacity are the research hotspots in the field of anode materials.However,the transition metal oxides have some disadvantages such as low electronic conductivity and low ionic conductivity,resulting in poor rate performance.At the same time,the volume change of the active material during delithiation or lithiation seriously damages the structure of the material,leading to material pulverization and capacity decay,which seriously restricts the commercial application of the transition metal oxide.In this paper,the electrochemical properties of ZnFe₂O₄ materials were improved by co-coating of surface carbon and ZnO.In addition,for the practical problems of thermal runaway safety and high rate performance of power lithium-ion batteries,this paper improves the uniform distribution of heat during high-current charge and discharge of batteries by adding TiN nanoparticles to the electrode material,promoting the battery's high current discharge performance and battery safety.The specific research contents are as follows:Firstly,a zinc ferrite precursor solution with ethylene glycol as a complexing agent was disposed,and a zinc ferrite precursor powder was collected by a spray drying technique.Finally the ZnO/ZnFe₂O₄@C composite material was obtained by calcination under an inert atmosphere.The results show that this composite material has a hollow spherical shell structure.The carbon layer coating effectively inhibit the volume expansion of zinc ferrite powdering during charging and discharging process,thereby improving the electrochemical performance of the material.At the same time,the synergistic effect between ZnO and ZnFe₂O₄ can better exert the lithium storage performance of the composite active material and improve the cycle performance and rate performance of the ZnO/ZnFe₂O₄@C composite material.Secondly,nano-TiN was deposited on the surface of the lithium iron phosphate positive electrode sheet by ultrasonic spray technique,and fabricated into a 2063C8laminated battery.Electrochemical test results show that the electrochemical performance of the battery after TiN modification is significantly improved,and the thermal stability of the battery is also improved,which is mainly attributed to the high conductivity and high thermal conductivity of TiN nanoparticles at the electrode.The internal conductive/thermal conduction network contributes to the rapid transport of electrons and rapid conduction of heat,else.Thereby improving the electrochemical performance of the lithium iron phosphate material and the safety of the battery.