Crosslinked Ultra High Molecular Polymeric Binder using Boronic Acid for Si Anode in Li Battery

Abstract

Si has received attention as active material in anode due to its high theoretical charge capacity but the Si anode has big challenge result from the large volume expansion,>300% at lithiation. This expansion causes isolated, dead Si and rapidly fading the capacity of electrode. To alleviate this ephemeral ability we introduce boronic acid polymeric cross-linker for stable binding of Si. Boronic acids of cross-linker form stable chemical crosslink with hydroxyl groups of binder. By using polymeric cross-linker, cross-linker can make bond with binder in broader range than simple material. And we use ultrahigh molecular weight polymer binder of PAA-PVA random copolymer due to their high viscosity and abundant functional group. Acrylic acid of binder have good adhesion with Cu foil and Si particle. And Boronic acid of cross-linker and alcohol group of PAA-PVA binder form in situ chemical crosslink by heat treat. By using elastic and entangled polymer, cross-linked binder efficiently grasp expanded Si and prevent isolation of contracted Si. This crosslinking of boronic acid cross-linker and PAA-PVA binder will maintain electrode and improve lifetime and capacity of Li ion battery.