Phytic acid-doped and ammonium hydroxide de-doped polyaniline cathodes for rechargeable aluminum ion battery

Abstract

Rechargeable aluminum ion battery (RAIB) is a very promising large-scale energy storage scheme attributed by the advantages of aluminum with large theoretical capacity, high energy density, low cost, abundant earth resources and environment friendliness. The selection and preparation of cathode materials are crucial for the electrochemical performance of RAIB. In this study, the specific capacity and cycle life of RAIB were improved by using polyaniline doped with phytic acid and further optimized by ammonium hydroxide de-doping treatment. Phytic acid doping improves the spatial configuration of polyaniline, making the nanostructure more hierarchical and increasing the specific surface area. More importantly, ammonium hydroxide treatment provides more chemical reaction sites while maintaining hierarchic structural morphology of the material. Due to the advantages above, the de-doped polyaniline cathode obtains an initial discharge-specific capacity of the initial cycle is 78.1 mAh g−1 at a high current density of 1 A g−1. After cycling of 2000, the capacity loss is only 16.7%, and an average decay rate of 0.007% per cycle with the Coulomb efficiency remains about 100% after cycling of 5000. At the same time, the contribution of pseudo capacitance and working mechanism are investigated. The capacity contribution of RAIB has been divided into diffusion-control, surface-control and double-layer, which is more consistent with the actual situation and further deepens the understanding of the charging-discharging mechanism of RAIB. These results are expected to lay a foundation for the future development of RAIB systems for large-scale energy storage using organic polymers as cathode materials.