Assembling a dense grid structure with green polyhydroxyurethane and a high-capacity Si-based anode for lithium ion batteries

Abstract

The practical application of silicon-based anodes in lithium-ion batteries has been hindered by their large volume expansion causing capacity decay and resulting in them being electrically inactive. Designing an integrative structure of rigid and soft polymers addresses this challenge; however, conventional soft polymers as represented by polyurethane lack crosslinkable moieties when prepared using toxic isocyanates. Herein, we design a green polyhydroxyurethane binder with abundant functional groups to crosslink with multiple polyacrylic acid binders and even interact with silicon anodes. This binder synthesized by the free-isocyanate route has the advantage of removing isocyanate which is harmful to both humans and the environment. By constructing a dense three-dimensional grid network structure, electrochemical performances of the Si-based anode greatly improved, exhibiting 79.7% capacity retention after 300 cycles at 1C and enabling the preparation of an ultrahigh mass loading electrode (∼3.84 mA h cm⁻²) in a full-cell with stable capacity retention (∼85.3%) after 400 cycles. This innovative binder structure sheds light on an environmentally friendly yet practical approach to designing crosslinkable binders for high-capacity anode materials.