Mechanically Robust Polyimide Binder Realizes Stable and High Electrochemical Performance for Micro-Silicon Anodes in Lithium-Ion Batteries

Silicon anodes have been considered one of the most promising candidates for Li-ion batteries due to their high theoretical specific capacity. However, the practical use of silicon anodes is impeded due to side reactions and volumetric change (from 300~400%) charge/discharge process. Binders played a crucial role in Li-ion batteries by effectively mitigating the stress resulting from the volumetric expansion in silicon-based anodes. Herein, we developed a mechanically stable polyimide binder PI-CF₃ that introduced trifluoromethyl and hydroxyl groups for commercial microparticular silicon anodes. With a highest Young′s modulus of ~921.1 MPa, the binder presented the maximum resilience during the charging and discharging of Micro-Si, integrating the morphology, and reducing the degree to which the electrode disrupted ion and electric pathways. Moreover, −OH and −CF₃ groups of the binder could potentially interact with oxide layer at the surface of silicon through hydron bonds, and thereby results in a cross-linking network to improve interface stability during cycling. The as-prepared PI-CF₃ binder with excellent intrinsic mechanical and electro-rich groups stabilizes the electrode structure and facilitates fast Li⁺ transportation. Consequently, micro-Si anode delivered initial specific capacity of 1838 mAh g⁻¹ (at 0.6 A g⁻¹), and at high mass (Si loading = 0.78 mg cm⁻²) these was retained about 1219 mAh g⁻¹ after 330 cycles (only −0.061% capacity reduction per cycle).