The concentration distributions of binders in dried water-based and organic-based LiCoO 2 electrode sheets are studied, and the effects of binder distributions on the physical, electrical and electrochemical properties of electrodes are also discussed. When the LiCoO 2 slurry is prepared with an organic-based process, the non-uniform distributions of the binder, poly(vinylidene fluoride), and a conductive agent, graphite, are markedly observed in the dried electrode sheet. Nevertheless, these non-uniform distributions of constituents are less significant for the electrode sheet prepared by a water-based process that uses a blend of styrene butadiene rubber and sodium carboxymethyl cellulose as the binder. Beside the experimental results, the binder distributions in the dried electrodes can be accurately predicted via a theoretical calculation based on a migration-controlled drying kinetics. The calculated results show that the organic-based electrode sheet has much higher non-uniformity of binder distribution than the water-based one. Because of the higher non-uniform distributions of binder, the organic-based electrode sheet displays properties of weaker adhesion and higher electrical resistance. Moreover, the electrochemical performance shows that the IR-drop of the organic-based electrode is larger than the water-based one, which has to be reduced by the compression process of electrode sheets.

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The dispersion property of aqueous lithium cobalt oxide ͑LiCoO 2 ͒ slurries and their corresponding cell performance with and without addition of dispersant, ammonium polyacrylic acid ͑PAA-NH 4 ͒, were investigated. The surface chemical properties of LiCoO 2 and graphite powders were characterized by diffuse reflectance using infrared Fourier transform spectrometry. The adsorption effects of PAA-NH 4 and latex binder ͑LA132͒, respectively, on the dispersion behaviors of LiCoO 2 and graphite powders in aqueous suspensions were analyzed by measurements of adsorption behavior, potential, sedimentation property, and rheology. The results showed that the PAA-NH 4 can adsorb onto both the LiCoO 2 and graphite powders to stabilize them in aqueous suspensions, but LA132 binder only adsorbs onto graphite and showed a competitive adsorption with PAA-NH 4 on the graphite surface. By observation of scanning electron microscope, it was shown that the as-prepared LiCoO 2 sheet without PAA-NH 4 addition had significant agglomeration of powders and accumulation of binder around the powder. These undesired coagulations of powder and binder can be diminished by increasing the PAA-NH 4 content. Although the dispersion property of powders was increased with increasing PAA-NH 4 content, too much addition of PAA-NH 4 is detrimental to the electronic conduction, adhesion strength, and electrochemical properties of LiCoO 2 electrode. To simultaneously obtain a well-dispersed and a better electrochemical property of LiCoO 2 electrode sheet, the appropriate amount of PAA-NH 4 was found to be on the order of 0.01 wt % based upon LiCoO 2 .

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