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

Abstract

Silicon is regarded as a highly promising anode material for lithium-ion batteries, attributed to its substantial theoretical specific capacity. The practical implementation of Si-anodes is hindered by side reactions and significant volumetric changes, ~300% to 400%, occurring during the lithiation/delithiation processes. Pertinent binders can effectively mitigate the stress resulting from the volumetric exchange in Si-anodes. Herein, we developed a mechanically stable polyimide binder PI-CF3 and introduced trifluoromethyl and hydroxyl groups for commercial microparticular Si-anodes. With the 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 the oxide layer at the surface of silicon through H-bonds resulting in a cross-linking network to improve interface stability. The as-prepared PI-CF3 binder with excellent intrinsic mechanical and electro-rich groups stabilizes the electrode structure and facilitates fast Li+ transportation. Consequently, at 0.6 Ag-1, the micro-Si anode produced an initial specific capacity of 1838 mAh g-1 at Si 0.66 mg cm-2. Besides, at Si 0.78 mg cm-2 specific capacity retained around 1219 mAh g-1 over 330 cycles.