Enabling Si‐dominant Anodes: Influence of Neutralization Degree of Polyacrylic Acid on Low‐Cost Micron‐Sized Silicon Anode in High‐Energy Li‐Ion Full Cell

Abstract

Micron‐sized silicon is a promising low‐cost, abundant material to increase the energy density of lithium‐ion batteries. Nevertheless, significant volume change and therefore excessive solid electrolyte interphase (SEI) growth lead to fast capacity fading. In this work, polyacrylic acid (PAA) with different neutralization degrees is used for the fabrication of Si anodes for practical applications. The electrochemical performance in full pouch cells reveals that the increase in neutralization degree of PAA up to 70% enhances the overall performance by improved electrode properties, higher first cycle efficiency (FCE up to 78.1% at C/3) and better capacity retention (85.4% after 150 cycles at 1C) over cycling, while with even higher neutralization degrees (such as 80%) the performance declines. Since proper mixing of the slurry is another important factor, we optimized the mixing procedure by increasing the solid content of the slurry, which has shown positive influence on the electrochemical performance and electrode properties. To summarize, this work shows full cell 1C cycling until capacity retention of 85% after 150 cycles with pure Si microparticle anodes for 70% neutralized PAA as well as increased C‐rate performance up to 5C. Post‐mortem, less degradation on electrode and particle level is observed.