| The vigorous development of new energy vehicles has a huge demand for power lithium batteries.The consistency of thickness of single cell pole piece seriously affects the safety performance of power battery pack.As one of the key technologies for manufacturing power lithium battery pole piece,ensuring the uniformity and stability of coating is the prerequisite for improving battery performance.Compared with other coating methods,slot coating has more market competitiveness in the field of power lithium battery coating because of its advantages such as fast coating speed,good coating uniformity and wide coating window.However,the research of slot coating technology was first concentrated in the traditional film and paper industry,and the related theories can no longer be applied to the field of power lithium battery coating.Therefore,this paper aims to improve the coating quality of pole pieces to fill the lack of research on slot coating process of power lithium battery in China.Based on the actual engineering situation,the internal and external flow fields of slot coating die are simulated by using the two-phase flow model of Fluent software.The work and main conclusions are as follows:(1)The rheological experiment of lithium ferrous phosphate power lithium battery slurry was carried out.The experiment shows that both positive and negative slurry are pseudoplastic fluid with shear thinning phenomenon,which can provide rheological data for the design of flow channel in coating die.(2)According to the theory of slot coating,the internal and external flow fields of coating die are preliminarily analyzed.It is concluded that the key in the process of slot coating is to keep the coating uniformity in the transverse direction of die and the stability of coating beads by analyzing the process of slurry flow.(3)The flow field in the coating die was numerically simulated to explore the influence of the structural parameters of the gasket on the coating results.The results show that changing the shape and size of the inner edge and central area of the gasket can improve the uniformity of slurry speed at the exit of the die slit,and the coating uniformity of the optimized coating die can be improved from 96.40% to 99.12%.(4)The external flow field of coating die was numerically simulated,and the quantitative relationship between coating process parameters(foil moving speed,coating gap and inlet flow rate)and wet thickness of slurry coating was determined by using full factor analysis method.The flow process of slurry and the causes of coating defects under different operating conditions were analyzed,and the coating window range with stable coating and no defects was determined,which provided theoretical guidance for the selection of coating process parameters in actual production. |
PDF Full Text Request