Synthesis, characterization and charge-discharge studies of ferrocene-containing poly(fluorenylethynylene) derivatives as organic cathode materials

Two new poly(fluorenylethynylene)s with ferrocene moieties PFFAL1 and PFFAL2 were designed and synthesized. Their structures, molar masses, photophysical properties and thermal characteristics were analyzed by ¹H NMR, Fourier transform infrared (FTIR) spectroscopy, size exclusion chromatography (SEC), ultraviolet-visible (UV-Vis) spectroscopy and thermogravimetric analysis (TGA). The morphologies and electrochemical performances of the polymer-composed cathodes were studied by scanning electron microscopy (SEM), cyclic voltammetry (CV) and galvanostatic charge-discharge test. The results showed that PFFAL1-composed electrode retained over 90% of the initial capacity after 100 cycles at 10 C and PFFAL2-based cathode exhibited a stable discharge capacity of 73 mAh g^-1 at 1 C, which is close to the theoretical value (82.3 mAh g^-1). The stable capacity as well as the good cycle endurance of these polymer-based coin cells revealed their great potential as cathode-active materials for rechargeable lithium batteries.