A Comparative Investigation of Various Binders for Silicon Anodes: Interactions with Other Components, Rheological Property, and Behavior in Operando Dilatometry

Abstract

Benefitting from its outstanding advantages, silicon (Si) has been considered as one of the best candidates of anode materials for next-generation lithium ion batteries (LIBs). Among various influencing factors on the electrochemical performance of Si anodes, binder attracts more and more attention though occupying only a small portion. Well-designed binders play a critical role in improving cycling performance of Si anodes. Herein, sodium carboxymethyl cellulose (CMC), poly (acrylic acid) (PAA), sodium alginate (SA), polyvinylidene difluoride (PVDF), and polyacrylonitrile (PAN) are selected as binders, and their effects on the electrochemical performance are investigated. PAA, CMC, and SA form both dynamic hydrogen bonds and covalent bonds with Si while PAN and PVDF form monotonous hydrogen bonds with Si. Defects of PAA and CMC in slurry mixing and subsequent drying process originated from high modulus and poor liquidity are exposed. The binder influence on expansion/contraction behavior of silicon anodes is innovatively investigated in real time. Electrodes with PAA binder exhibit the greatest expansion but the highest reversibility, which contributes to superior electrochemical performance. This article aims to provide useful information for failure mechanism analysis of binders as well as design of advanced binders for high energy LIBs.