Cyclopentadithiophene-Terephthalic Acid Copolymers: Synthesis Via Direct Arylation And Saponification And Applications In Si-Based Lithium-Ion Batteries

This study investigates conjugated polymers comprising of cyclopentadithiophene and dimethyl terephthalate or terephthalic acid units for use in Si-based lithium-ion batteries. Cyclopentadithiophene tethered with 2-ethylhexyl or triethylene glycol side chains and 2,5-dibromoterephthalate are copolymerized via palladium-complex-catalyzed direct arylation. The dimethyl ester groups in the dimethyl terephthalate unit are converted to the carboxyl groups via saponification. The polymers are mixed with Si nanoparticles to fabricate an anode electrode for use in lithium-ion batteries. Compared with polymers before saponification, the batteries with the electrodes incorporating the saponified polymers have greater specific capacities of up to 2500 mA h g(-1)(for total anode weight) at a second cycle and greater stability. Electrolyte uptake test and scanning electron microscopy are used to verify the battery performance.