Crosslinked Natural binder using boronic acid cross-linker for stable Si anode in Li ion battery

Abstract

Si has received attention as active material in anode due to its high theoretical charge capacity. However the Si anode has big challenge resulted from the large volume expansion (>300%) during the lithiation. This expansion causes isolated Si and rapidly fading the capacity of electrode. To alleviate this ephemeral ability, we introduce boronic acid polymeric cross-linker for stable contact of electrode. Boronic acids of crosslinker form stable chemical crosslink with vicinal hydroxyl groups. We utilize guar gum, natural polymer from seed. It is commercial product and has high viscosity and abundant functional group. Alcohol groups of guar gum form dynamic chemical crosslink with boronic acid group. This bonds are reversible but broken at high temperature and low/high pH. Broken bond can recover by reforming of crosslinking of –OH and Boronic acid at low temperature and mild pH. Cross-linked binder efficiently grasp expanded Si and prevent isolation of contracted Si. This crosslinking of boronic acid and guar gum will maintain integrity of electrode and eventually improve lifetime and retention of Li ion battery.