Poly(phenylacetylene)s bearing thianthrene groups as high-voltage organic cathode materials for lithium batteries

Abstract Thianthrene-containing acetylenic monomers, thianthrene-1-ylmethyl 4-ethynylbenzoate (M1) and bis(thianthrene-1-ylmethyl)-4-ethynylphthalate (M2) were synthesized and polymerized with [(nbd)RhCl]2/Et3N catalyst to give polymers P1 and P2 with high molecular weight (Mn = 33 × 103 and 44 × 103) in high yields (96.2% and 95.0%). Thermogravimetric analysis revealed that the onset temperature weight loss of the polymers were over 240 °C, indicating relatively high thermal stability. Both polymers displayed reversible redox reactions in composite electrodes. The P1 and P2-based cathodes showed initial specific capacities of 33 and 100 mA h/g, respectively, at a high charge/discharge potential of 4.1 V vs Li/Li+. While the capacity fading in both systems occurred during cycling test, the high specific energy capacity of P2-based battery (240 mW h/g after 20 test cycles) at a high potential and potentially rapid charge/discharge processes make this polymer highly interesting as cathode-active materials.