Using Poly(4-Styrene Sulfonic Acid) to Improve the Dispersion Homogeneity of Aqueous-Processed LiFePO4 Cathodes

The dispersion properties of aqueous lithium iron phosphate (LiFePO4) slurries and the electrochemical properties of the corresponding as-prepared cathodes with the addition of a dispersant, poly(4-styrene sulfonic acid) (PSSA), have been investigated. The influence of PSSA on the dispersion behaviors of LiFePO4 and conductive agents, graphite and carbon black, in aqueous suspensions are explored by the analyses of zeta-potential and rheology. The results show that the PSSA adsorbs onto the LiFePO4 and conductive agents so that they can be electrosterically stabilized in aqueous suspensions. Through the observation using a scanning electron microscope, it is shown that the homogeneity and dispersion of the composition distributed in the LiFePO4 electrode sheet are significantly improved with increasing content of PSSA. However, an excess addition of PSSA is detrimental to the electronic conduction and the electrical capacity of the cathode. To obtain a homogeneous electrode with a good cell performance, the optima content of PSSA is suggested to be 2.0 wt % based on the LiFePO4 weight.