Interconnected conductive gel binder for high capacity silicon anode for Li-ion batteries

A new design for conjugation and crosslinking combined with a conjugated polymer and its application for high capacity Li-ion battery are demonstrated. Polyfluorene (PF), poly(phenylene) (PP), with lateral substituents, namely carboxylic acids, as a potential building block for conjugation was synthesized and characterized. The synthesis was achieved through Suzuki polycondensation reaction in the presence of Pd(PPh₃)₄ catalyst by using dibromo benzoic acid in conjunction with dioctylfluorene-diboronic acid bis(1,3-propanediol) ester. Thermal chemical cross-linking between carboxylic acid in the polymer backbone and free hydroxyl groups in poly(vinyl alcohol) (PVA) has been performed in the presence of Si. This approach enables a polymer binder with multi-functionality providing a high electronic conductivity and good cycling stability. Overall, we report on a Si-anode with capacity of 1932 mAh/g at C/3, demonstrating the improvement of the electrode using gel polymer binder.