Influence Of Hot Pressing Parameters And Binder Content On The Performance Of Dry Graphite Anode Electrodes

The dry electrode preparation process for lithium-ion batteries can avoid the consumption of large amounts of NMP in traditional wet electrode preparation,save costs,reduce energy losses,and protect the environment.Some researchers have conducted experimental studies on the dry process using electrostatic spraying and roll-to-roll technology,but the study of the performance of the dry electrode preparation process in terms of hot pressing parameters and binder content is still unclear.In this paper,polyvinylidene fluoride(PVDF)was used as the binder to investigate the effects of hot pressing parameters and binder content on the performance of graphite anodes.The performance of the conventional wet process for graphite anode is compared with that of the dry process.The structure of PVDF was analyzed using X-ray diffraction(XRD)and infrared spectroscopy to find the processing parameters with the highest β crystalline content;the structure of graphite in the mixture of graphite,PVDF,and acetylene black was analyzed using XRD and Raman spectroscopy;and the material mix was determined by scanning electron microscopy(SEM)testing.The blended materials were then made into electrodes under different conditions,and electrochemical experiments were carried out to determine the best-performing dry process ball milling parameters and to explore the effect of different ball milling times and speeds on the blended materials.Dry graphite electrodes were prepared according to the process parameters determined from the above experiments,and dry electrode sheets were produced with binder contents of 10 wt.%,5wt.%,3wt.%,and 1wt.%,respectively.The results of the study show that: the most crystalline type with good electrical properties in PVDF at 180°C;too high a temperature and pressure will cause oxidation of the copper foil;too low a temperature will cause poor adhesion of the active material,conductive agent,and binder;and the final determination of the most suitable hot pressing parameters at 180°C for 15 min and 6 Mpa pressure;ball milling makes the conductive agent and binder uniformly distributed on the carbon surface,and the powder will be more uniform.During the mixing process,the ball mill speed is 180 r/min for 2 hours to homogenize the powder,at which time the graphite structure defects are minimized and the degree of graphitization is the highest,which is beneficial to the battery’s performance.The reduction of the binder content in the dry electrode helps to further improve the electrochemical performance of the dry graphite anode,and the multiplicative performance of the graphite anode is better when the binder content is reduced from 10 wt.% to 5wt.%.