Synthesis and characterization of a series of fluorine-substituted phenylene-thienyl polymers for battery applications

A series of fluorine-substituted phenylene-thienyl-based monomers (1,4-bis(2-thienyl)-benzene (THB), 1,4-bis(2-thienyl)-2-fluorophenylene (TFP),1,4-bis(2-thienyl)-2,5-difluorophenylene (TF2P), and 1,4-bis(2-thienyl)-2,3,5,6-tetrafluorophenylene (TF4P)) has been synthesized. Thin films of the polymers were deposited by controlled electropolymerization of the monomers, and the doping densities and cycling efficiencies were determined from electrochemical measurements. The polymers poly-1,4-bis(2-thienyl) -benzene (pTHB), poly-1,4-bis(2-thienyl)-2-fluorophenylene (pTFP), and poly-1,4-bis(2-thienyl)-2,5-difluorophenylene (pTF2P) exhibited reversible p-doping and n-doping, with doping densities in the range 0.12 to 0.45 electrons per monomer unit. The cycling efficiencies were higher for p-doping than for n-doping, with values in the range of 99.58 to 99.70% charge retained per cycle.