Partially Neutralized Polyacrylic Acid/Poly(vinyl alcohol) Blends as Effective Binders for High-Performance Silicon Anodes in Lithium-Ion Batteries

Polymer binders are a key component for long-lasting silicon (Si)-based electrodes, and they should be mechanically robust and electrochemically stable, with the ability to accommodate the large volume expansion of Si during the lithiation/delithiation process. The combination of poly(acrylic acid) (PAA) and poly(vinyl alcohol) (PVA) utilizes the strong adhesion properties of PAA and mechanical robustness of PVA, which can potentially overcome the current technical challenges faced by the traditional polyvinylidene-fluoride-based binder systems, e.g., poor interfacial adhesion, brittleness, and short service life. This study has investigated the PAA/PVA (60/40 wt %) blend for Si anodes and compared its performance with the effects of PAA and partially neutralized PAA/PVA (60/40 wt %). The PAA/PVA blends were further thermally cross-linked in order to improve the mechanical properties. The PAA/PVA binder shows higher stiffness, adhesion strength, and electrochemical performance (100 cycles with 240 mA/g and 40 cycles with 400 mA/g) compared with those of unmodified PAA (38 cycles with 240 mA/g and 25 cycles with 400 mA/g). The partially neutralized PAA/PVA blend shows further improved performance (over 140 cycles with 240 mA/g and over 60 cycles with 400 mA/g). The working mechanism of the partially neutralized PAA/PVA binder is discussed.