A High-Performance Polyurethane–Polydopamine Polymeric Binder for Silicon Microparticle Anodes in Lithium-Ion Batteries

Micro silicon (Si) has been one of the most promising anode materials for lithium-ion batteries (LIBs) due to high theoretical specific capacity and material sources. Nonetheless, an unavoidable huge volume expansion of Si microparticles (SiMPs) and the uncontrolled growth of the solid–electrolyte interphase (SEI) during the cycling still inhibit its commercialization. Among the strategies to overcome these problems, the design of a polymer binder is more feasible. Herein, a binder derived from two of the most common polymers, polyurethane (PU) and polydopamine (PDA), has been synthesized by a simple heating and mixing method for SiMP anodes in LIBs. In the PU–PDA binder, the synergistic effect of PU and PDA enables it to adapt to the volume expansion of SiMPs and maintain the electrode integrity and provides excellent cycling performance and long cycle life. The SiMP anodes with the PU–PDA binder have a capacity retention above 1000 mA h g–1 after 1000 cycles at a current density of 0.2 C and could deliver a discharging specific capacity of 1399 mA h g–1 at 4 C. Our research provides a safe, simple, and efficient PU–PDA polymer binder for SiMP anodes in the next-generation LIBs.