Simulation And Experimental Study On Stirring And Coating Process Of Lithium Battery Slurry

With the rapid development of new energy vehicles,the requirements for lithium-ion batteries,which are the core power components of new energy vehicles,are becoming more and more stringent.The poor consistency and low manufacturing accuracy of single core are the bottlenecks of current technical research.At present,most of the research focuses on the performance of battery materials and battery management system,but there is little research on the precision manufacturing of battery plates,especially in theory.Battery plate manufacturing is the first process in the production of lithium ion batteries.In this paper,the effect of slurry preparation and coating on the consistency of electrodes is studied in depth,aiming at providing theoretical support for precision manufacturing equipment,providing theoretical basis for improving the consistency of plate,guiding actual production and improving the quality of battery products.The research in this paper mainly uses two methods,finite element simulation and experimental research.Firstly,the fluid characteristics of slurry and the principle of agitator are explained,and the kinematics of double planet agitator is analyzed by MATLAB software.Secondly,based on mixing characteristics of high viscosity slurry and double planet mixing mechanism,the three-dimensional simulation of solid-liquid two-phase mixing of negative slurry for lithium ion batteries in the mixing tank was carried out by using Fluent software,and the distribution of the velocity of the flow field,the volume concentration of solid phase,and so on are analyzed.The external flow field of slurry slit extrusion coating process was also simulated in two dimensions.Finally,the lithium ion battery negative electrode slurry was stirred and mixed by vacuum mixer to investigate the effects of different process parameters on the viscosity,solid content and surface morphology of the of battery plate.The results show that the larger the ratio C of the rotational speed to the rotational speed,or the larger the ratio S of the rotational radius to the rotational radius,the greater the crossover and density distribution of the moving points on the impeller,which is more conducive to mixing and shearing of the slurry and can effectively eliminate the "dead angle".The cross-section and density distribution of moving point trajectory can be increased in the same stirring time by choosing the rotating speed ratio C as the non-circulating decimal.The multi-layer helical blade structure of the twin planetary screw agitator can mix the slurry more quickly and efficiently.The higher the rotational speed of the agitator,the shorter the mixing time of the slurry,and the larger the circulation formed by the rotational speed has the effect of mixing the slurry in a wide range,which can weaken the "dead angle" of the agitation.For the slit extrusion coating of lithium-ion battery paste,when the base moving speed is low or the die exit speed is too high,the lithium-ion battery paste accumulates at the edge of the coating die,and the coating thickness is very large and not stable.If the moving speed of the substrate is high or the exit speed of the die is too low,the air will be easily involved between the coating paste and the substrate,and even lead to the fracture of the coating.For slurries with certain density and solid content,when the coating speed,extrusion exit speed and coating width are the same,the coating amount is the same,so the wet thickness of the coating is the same.Experiments show that the shear,friction and impact of the double planetary stirring equipment through the stirring principle of its planetary system make the solid particle distribution of lithium ion battery slurry more uniform and stable.Compared with the traditional single-axis stirring technology,the double planetary stirring equipment not only improves the mixing and dispersion quality of lithium battery slurry,but also greatly shortens the mixing time and improves the production efficiency.The research results of this paper can provide reference for technical research and field production.