PNNL

Abstract

The demand for fast-charging, high-energy lithium-ion batteries intensifies interest in silicon (Si) anode. Although carbon coatings, such as carbon nanowires, have been used to enhance the electronic conductivity of the Si anode, the limited ionic conductivity still hinders high-rate applications, especially for high-energy batteries. Here, we report a lithiated polyimide (Li-PI) binder that combines mechanical robustness with enhanced Li? transport for micro-sized, high-loading porous Si anodes. Li-PI is synthesized by partially opening imide rings in a conventional polyimide backbone, introducing immobilized Li?-conducting sites that form continuous ionic transport pathways (“Li?-conductive highways”) while preserving structural integrity. This design suppresses first-cycle irreversibility, improves Coulombic efficiency, and enhances the ionic conductivity of the Si anode. Consequently, Si?LiNi0.6Mn0.2Co0.2O2 full cells achieve 80% state of charge in ~7.5 min when charged at a 7C rate (where 1C = 2.9 mA cm-2) and maintain stable cycling at 6C, outperforming conventional PI binders. This binder-level ion-pathway strategy is extendable to other electrochemical device systems to enhance their high-rate performance.