Tunable hetero-assembly of 2D NiFeCr-LDH and MnO2 nanosheets for high-energy quasi-solid-state ammonium-ion asymmetric supercapacitors

Abstract

The development of high-performance quasi-solid-state ammonium-ion asymmetric supercapacitors (QSSAIAS) has recently attracted significant research interest. Nonmetallic ammonium ions, characterized by their high safety, low mass, and small hydrated radius, provide critical advantages for enhancing the performance of ammonium-ion supercapacitors. However, achieving high energy density QSSAIAS remains challenging because of the limited availability of high-capacitance pseudocapacitive cathodes. In this study, we report a high-performance 2D-2D self-assembled layered NiFeCr-LDH-MnO₂ (NFCMn) nanohybrid with pseudocapacitive properties synthesized through an exfoliation-restacking route. The NFCMn nanohybrid achieves a maximum specific capacity of 912 C g⁻¹, a result attributed to its abundant active sites, mesoporous structure, large interlayer gallery, and pronounced synergistic effect of its multi-component layered structure. A full-cell QSSAIAS, assembled using NFCMn nanohybrids as the cathode and activated carbon as the anode, delivers an energy density of 78 Wh kg⁻¹ along with excellent cyclic durability over 15,000 charge–discharge cycles. These findings demonstrate that the self-assembled 2D-2D NFCMn nanohybrid is not only highly effective in enhancing the ammonium-ion supercapacitor performance but also represents a significant step toward developing novel LDH-metal oxide-based hybrid materials with intimate coupling and superior functional properties.