Polytriphenylamine derivative with high free radical density as the novel organic cathode for lithium ion batteries

Polytriphenylamine derivative, poly[N,N,N,N-tetraphenylphenylenediamine] (PDDP), with a high free radical density, has been synthesized and studied as a cathode material for organic free radical batteries for the first time. The chemical structure, morphology, and electrochemical properties of the prepared polymers were characterized by Raman spectra (RS), electron spin resonance (ESR), ultraviolet visible spectroscopy (UV-Vis), scanning electron microscopy (SEM), cyclic voltammograms (CV), and electrochemical impedance spectra (EIS), respectively. In addition, the charge–discharge properties of the prepared polymers were studied by galvanostatic charge–discharge testing. Compared to polytriphenylamine (PTPA), the fabricated lithium ion half-cells based on PDDP as the cathode exhibited two well-defined plateaus at two discharge voltages of 3.8 and 3.3 V vs. Li/Li+ and an improved capacity of 129.1 mA h g−1, which was very close to its theoretical capacity (130 mA h g−1). The excellent electrochemical performances of the PDDP electrode were due to its stable chemical structure and high free radical density, which makes the PDDP a promising free radical cathode material for organic lithium secondary batteries.