Peanut Shell-Derived Nitrogen–Oxygen Co-Doped Carbon Microsheets for High-Performance Ionic Liquid-Based Aluminum-Ion Batteries

Abstract Rechargeable Ionic liquid-based aluminum-ion batteries (IL-AIBs) have emerged as highly competitive next-generation large-scale energy storage candidates, owing to their low cost, abundant aluminum reserves, ultrahigh theoretical volumetric capacity (8056 mAh cm–3), and inherent safety (nonvolatile and nonflammable ionic liquids). Carbon materials are regarded as promising cathode materials for IL-AIBs due to their excellent electrical conductivity, inherent structural stability, and highly tunable architectures. Herein, a peanut-shell-derived nitrogen–oxygen codoped carbon microsheets (NO-PSCMs) cathode is synthesized via a facile high-temperature pyrolysis. The nitrogen-doped hierarchical micro/nano architecture of NO-PSCMs synergistically boosts conductivity and structural stability, enlarges interlayer spacing, and accelerates Al-ion transport kinetics. The NO-PSCMs exhibit a reversible capacity of 185.7 mAh g–1 after 400 cycles at a current density of 235 mA g–1, which is much higher than that of commercial graphite (87.8 mAh g–1) and still maintain a capacity of 95 mAh g–1 after 2000 cycles at a current density of 1000 mA g–1. To elucidate the energy storage mechanism of NO-PSCMs, we employ a combined approach utilizing in situ Raman spectroscopy and density functional theory (DFT). Raman spectroscopy results indicate the intercalation and extraction of AlCl4– during the charge/discharge processes for the NO-PSCMs. Density functional theory (DFT) calculations further confirm that nitrogen–oxygen doping promotes the adsorption of Al-ions, which thereby contributes to the increase in specific capacity. This work provides a cost-effective and sustainable strategy for fabricating IL-AIBs cathodes from biomass-derived carbon, offering new perspectives for the development of high-performance IL-AIBs in scalable energy storage applications.