High-Safety and Long-Life Silicon-Based Lithium-Ion Batteries via a Multifunctional Binder

Lithium-ion batteries with high energy density and good safety are in urgent demand nowadays. Silicon has the advantages of high theoretical capacity, low cost, and vast reserves. It is regarded as an ideal anode material for high-energy lithium-ion batteries. Unfortunately, its huge volume change during cycling results in unstable cycle behavior and limits its application. To develop a robust electrode by employing effective binders is still a big challenge. Furthermore, both conventional binders and organic liquid electrolytes bring serious safety risks due to their flammability. Herein, a flame-retardant binder is designed and prepared by cross-linking polyacrylic acid (PAA) with a flame-retardant epoxy resin (FREP) containing phosphorus and nitrogen elements. Compared with PAA, it has better wettability to liquid electrolytes. Moreover, the three-dimensional PAA-FREP polymer binder not only provides sufficient mechanical strength to buffer the volume change of Si powders but also enhances the interfacial adhesion between the active film and Cu current collector via epoxy groups. Most importantly, the FREP component in the binder leads to admirable flame retardance. In these ways, the multifunctional binder exhibits excellent mechanical, electrochemical, and safety performances.