A comparative study of polyacrylic acid (PAA) and carboxymethyl cellulose (CMC) binders for Si-based electrodes

Abstract

This work is a comparative study on two well-known binder systems for silicon-based negative composite electrodes for Li-ion batteries: polyacrylic acid (PAA) and carboxymethyl cellulose/citric acid (CMC/CA). The electrode slurry rheological properties and the dry electrode morphology and physical properties are studied as a function of the binder content. The electrochemical behavior of the electrodes is also studied as a function of the active mass loading (from 1 to 4.5 mg cm⁻²). Increasing the binder content from 4 to 12 wt% improves the 1st cycle efficiency, which is clearly related to its contribution as a pre-formed artificial solid electrolyte interphase (SEI) layer. The enhancement of the mechanical strength of the composites with increasing binder content is reflected in the better cyclability of the electrodes with active mass loading higher than 1 mg cm⁻². CMC/CA is more efficient as a binder at low content while PAA is more efficient at high content, which could be related to their molecular structure. Finally, for both binders the influence of a post-processing treatment of the electrodes (called maturation) is shown to improve the electrochemical performance. This is however more significant with CMC/CA than with PAA.