3D nanostructured conductive PANI/MXene hydrogels for durable aqueous Zn-ion batteries

Abstract

Polyaniline (PANI) hydrogels are promising cathode materials for aqueous zinc-ion batteries (AZIBs) due to their inherent porous structure and redox activity. However, the instability during the repeated charge/discharge process limits their application in commercial battery systems. Herein, PANI/MXene hydrogels are synthesized by grafting the negatively charged MXene with the aniline monomer followed by a rapid chemical oxidative polymerization reaction. After combining MXene nanosheets with the PANI chains, the hybrid hydrogels show a three-dimensional (3D) network structure of MXene nanosheets interconnected with PANI chains through hydrogen bond interactions, thus greatly improving the electrochemical reactivity and stability. Moreover, the 3D PANI/MXene network structure can provide fast transport channels for ions and electrons. Consequently, the PANI/MXene cathodes not only achieve a high capacity of 219.0 mA h g⁻¹ at 0.2 A g⁻¹, but also exhibit outstanding rate performance (147.5 mA h g⁻¹ at 5 A g⁻¹), together with excellent long-term cycling stability (over 5000 cycles with a capacity retention of 88.3%). The Zn²⁺ and CF₃SO₃⁻ insertion/extraction mechanisms are further revealed by ex situ X-ray photoelectron spectroscopy (XPS) measurements. This work demonstrates the availability of conducting polymer hydrogels as cathode materials for high-performance AZIBs.