Prelithiated rigid polymer with high ionic conductivity as silicon-based anode binder for lithium-ion battery

Silicon-based electrodes suffer from rapid performance degradation derived from a severe volume expansion during cycling in lithium-ion batteries, and using elaborately designed polymer binders is deemed an efficient tactic to tackle the above thorny issues. In this study, a water-soluble rigid-rod poly(2,2′-disulfonyl-4,4′-benzidine terephthalamide) (PBDT) polymer is described and employed as the binder for Si-based electrodes for the first time. The nematic rigid PBDT bundles wrapped around the Si nanoparticles by hydrogen bonding effectively inhibit the volume expansion of the Si and promote the formation of stable solid electrolyte interfaces (SEI). Moreover, the prelithiated PBDT binder with high ionic conductivity (3.2 × 10−4 S cm−1) not only improves the Li-ions transportation behaviors in the electrode but can also partially compensate for the irreversible Li source consumption during SEI formation. Consequently, the cycling stability and initial coulombic efficiency of the Si-based electrodes with the PBDT binder are remarkably enhanced compared to that with the PVDF binder. This work demonstrates the molecular structure and prelithiation strategy of the polymer binder that play a crucial role in improving the performance of Si-based electrodes with high-volume expansion.