Oxygen-containing groups assist in enhancing Li+/K+ storage: Balancing adsorption and intercalation mechanisms

Porous carbon nanosheets were prepared using a high-temperature solid-phase method and subsequently modified through oxidative acid treatment to introduce oxygen-containing groups. The application and performance of these nanosheets as anodes in lithium-ion and potassium-ion batteries were investigated. The results indicated that the oxidative acid treatment successfully enhanced the porous carbon nanosheets' capacity for storing Li⁺/K⁺. Electrochemical analysis revealed that the oxygen-containing groups balanced intercalation and surface storage behaviors, optimizing the nanosheets' storage performance. These modified porous carbon nanosheets (termed SN@PCNs) demonstrated significantly boosted reversible Li⁺ and K⁺ storage capacities, achieving 1038.1 mAh⋅g⁻¹ and 371.7 mAh⋅g⁻¹ at 0.1 A g⁻¹, respectively, while maintaining capacities of 443.3 mAh⋅g⁻¹ for Li⁺ and 153.9 mAh⋅g⁻¹ for K⁺ at 5.0 A g⁻¹. Furthermore, the study emphasized the significance of a balanced surface capacitance and solid-phase diffusion storage mechanism in attaining high storage capacity and cycle stability. Moderate oxidation and the introduction of oxygen-containing groups were identified as crucial factors in optimizing performance. Additionally, potassium adsorption storage exhibited an advantage over lithium adsorption storage, and the impact of oxygen-containing groups on potassium storage performance was even more pronounced.