Unveiling the Molecular Structures and Interactions in Boronic Acid Functionalized Aniline Oligomers for Application in Self-Healing Battery Electrodes

This study delves into the structural and electronic properties of the ground and excited states of a series of n-B@PANI (boronic acid-functionalized polyaniline) oligomers with varying chain lengths. These oligomers are particularly interesting as self-healing components for high-capacity silicon anode binders in Li-ion batteries. The role of binders for silicon anodes is to repair the structural damage induced by the enormous volume expansion occurring during charge and discharge cycles. We elucidate the specific impact of the boronic acid functionalization on the oligomer structure and electronic properties by comparing functionalized and pristine PANI oligomers. Using accurate Density Functional Theory simulations, we provide insight into the structural modifications induced by the presence of the boronic acid radical and its interaction with the amine group, and show that this interaction plays a key role in determining the oligomer chain growth pattern and stability. Furthermore, we employ a comprehensive theoretical approach, including Bader's AIM analysis, to investigate the number, kind, and strength of the long-range intra-molecular and inter-chain interactions (mainly hydrogen bonds and van der Waals) and found a clear correlation with the length and conformation of the oligomers. The presence and the number of dynamic hydrogen bonds are important for combining n-B@PANI with different polymers and designing new binders for the silicon anodes. These insights provide a solid foundation for the rational design of advanced PANI-based materials with tailored properties for energy storage and self-repair applications.