Polyvinyl alcohol grafted poly (acrylic acid) as water-soluble binder with enhanced adhesion capability and electrochemical performances for Si anode

Abstract

Polyvinyl alcohol grafted poly (acrylic acid) (PVA-g-PAA) is synthesized through graft polymerization of acrylic acid (AA) onto PVA backbone via a free radical reaction. PVA-g-PAA is used as a water-soluble binder for silicon (Si) anodes in lithium-ion batteries (LIBs). The enhanced adhesion strength, excellent flexibility and high electrolyte uptake after grafting reaction render PVA-g-PAA a robust binder for Si anodes. Compared to linear PVA, PAA and CMC, optimal Si-PVA-g-10PAA electrode exhibits better cycle stability, higher Coulombic efficiency and more excellent rate capability, possessing a high electrical conductivity, low SEI/charge transfer resistance and fast lithium-ion diffusion coefficient. PVA-g-PAA binder not only maintains the electrode's mechanical and electrical integrity, facilitates a favorable electrochemical kinetics, but also assists in forming a stable SEI layer on Si surface upon long-term cycling. Such a strategy sheds light on the design of novel polymer binders for practical applications of high-capacity active materials with great volume change.