Understanding Polyacrylic Acid and Lithium Polyacrylate Binder Behavior in Silicon Based Electrodes for Li-Ion Batteries

Silicon nano-particle based electrodes are attractive for implementation in lithium ion batteries due to the improvement in specific capacity over the currently used graphite based electrodes. Here we investigate polyacrylic acid (PAA) and lithium polyacrylate (Li-PAA) polymer binders' role in the electrochemical performance of silicon nanoparticle based electrodes. The binders are evaluated in comparison to sodium carboxymethyl cellulose (Na-CMC), and polyether imide (PEI). Large variations in the cumulative irreversible capacity is observed for the different binders after 20 cycles while limiting the alloying capacity to 1000 mA h g(-1). Coulombic efficiencies at the first cycle and upon cycling are optimized for PAA and Li-PAA binders considering the binder proportion and the molecular weight. Coulombic efficiencies greater than 99% are obtained after 5 cycles. In depth physico-chemical characterizations of the binders, electrode slurries, and electrodes are performed. From these characterizations the polymers' mechanical properties, binder partitioning in the electrode, and binder interactions with the silicon particles are elucidated. Through correlation of these results with electrochemical performance, the basis for PAA and Li-PAA binders' behavior is proposed in silicon nano-particle electrodes. (c) 2017 The Electrochemical Society. All rights reserved.