Effect of Substituted Styrene-Butadiene Rubber Binders on the Stability of 4.5 V-Charged LiCoO2 Electrode

The combination of synthetically modified styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC) was studied as an aqueous binder for LiCoO2 composite electrodes under high-voltage operation. Methyl methacrylate (MMA) and 2-vinylpyridine (VP) substituted SBR copolymers were synthesized and examined as functional polymer binders. The electrolyte-solvent uptake of the binder-polymer film was increased by the introduction of the MMA units, but the solubility of the polymer in the solvent remained negligibly low. Hard-X-ray photoelectron spectroscopy revealed the formation of a relatively thick passivation layer on the LiCoO2 surface with MMA-substituted SBR and CMC binder, which suppressed the self-discharge of 4.5 V-charged LiCoO2. The capacity retention during battery cycling experiments was similar for the LiCoO2 electrodes with MMA-modified and unmodified SBR binders. While the effect of VP-substitution was not significant, incorporation of the MMA unit enhanced the stability of the charged LiCoO2 electrode and provided improved self-discharge performance.

Automated summary

The combination of synthetically modified SBR and CMC was studied as an aqueous binder for LiCoO2 composite electrodes under high-voltage operation. Introduction of MMA units increased the electrolyte-solvent uptake of the binder-polymer film and suppressed the self-discharge of charged LiCoO2.