Study On The Mechanism Of Action Of Different Regimen Dispersants On Cathode Slurry Of Lithium-Ion Battery

Chemical dispersion is an important method used to obtain uniformly dispersed lithium-ion battery slurry.Its essence is to use the steric hindrance or electrostatic repulsion of dispersant to act on the particle surface,and change the physical or chemical properties of the particle surface to inhibit the agglomeration of particles in the slurry.have done a lot of research on the performance and dosage of dispersants with different mechanisms,but there is little discussion on the action mechanism of dispersants in slurry.Therefore,based on different dispersion mechanisms,three representative dispersants,polyethylene glycol octyl phenyl ether(Triton X-100,sterically hindered dispersant),polyvinylpyrrolidone(PVP,sterically hindered dispersant)and sodium carboxymethyl cellulose(CMC,electrostatic repulsive dispersant)are selected in this design,in order to explore the action mechanism of different dispersants on particles in cathode slurry and their influence on internal structure.Electrochemical Impedance Spectroscopy(EIS)and Scanning Electron Microscopy(SEM)are selected as the methods to evaluate the electrochemical and apparent morphological properties of the cathode slurry,and both methods are used to characterize the cathode slurry.In order to obtain a more accurate conclusion of dispersant mechanisms,the following two aspects are studied in this paper:The first is the quantitative study of three dispersants under set experimental conditions to obtain the optimal amount of dispersants.Four dosages of each dispersant are set and made into cathode slurries,which are then characterized electrochemically using EIS method.The experimental results showed that the impedance of the slurries is smallest and the electrochemical performance is best when the contents of Triton X-100 and CMC are 0.5wt%and 1.5wt%,respectively;and the peak resistance and electrical resistance of the cathode slurry made with different contents of PVP are higher than those without dispersant,so it is concluded that the dispersant has the effect of promoting CB dispersion and inhibiting the formation of CB-coated LiCoO2 structure.The inhibition effect is weakest when the content is 0.5wt%.Therefore,the optimal amounts of the three dispersants are selected as 0.5wt%,0.5wt%and 1.5wt%,respectively.Secondly,the optimal amount of dispersants are applied to specific component slurries(PVDF-NMP solution,LiCoO2 slurry,CB slurry and cathode slurry),so as to investigate the ef fect of dispersants on slurry by EIS and infer the mechanism of dispersant action.In order to ensure the rationality and accuracy of the experimental conclusions,the 10-parameter equivalent circuit method and the SEM method are used for comparative studies.It is found that all three methods show that the dispersant Triton X-100 acts on the surface of CB particles in the cathode slurry with a spatial site resistance dispersion mechanism,which effectively prevents the formation of secondary agglomerates between CB particles of the slurry and promotes the formation of CB-covered LiCoO2 structure in the slurry,and the dispersion and electrochemical performance of the slurry are enhanced;the dispersant PVP acts on the surface of CB particles with a spatial site resistance dispersion mechanism and effectively prevents the formation of secondary agglomerates between CB particles.The dispersant CMC ionizes in the slurry to produce ions and adsorbs on the surface of the particles,and when the particles of the same species are close to each other,electrostatic repulsion is generated due to the consistent surface charge,which achieves stable dispersion of the slurry and improves the electrochemical performance of the slurry.The electrochemical performance of the slurry is improved.In summary,this study clarifies the mechanism of the three dispersants commonly used in lithium-ion battery research on the cathode slurry through experiments,which in turn provides theoretical support for the application of dispersants in cathode slurry,and also provides theoretical basis and scientific guidance for the industrial production of lithium-ion batteries.