Mesoporous Spinel NiMn2O4-Embedded Carbon Nanofibers for Binder-Free Flexible Symmetric Supercapacitors

Abstract

The continuous evolution of energy storage technologies necessitates electrode materials capable of delivering high energy density, mechanical flexibility, and long-term stability. Nevertheless, the development of flexible supercapacitors is hindered by the inherent challenge of integrating mechanically robust substrates with high-performance electroactive materials without compromising overall device functionality. Herein, a binder-free flexible electrode is fabricated via electrospinning followed by carbonization, enabling the in situ formation of spinel NiMn2O4 within a continuous and conductive carbon nanofibers framework. This integrated architecture overcomes the common issue of weak interfacial contact in conventional oxide carbon systems, ensuring efficient charge transport and structural stability. The resulting material exhibits a high surface area of 221.68 m2 g–1 with a mesoporous structure (4.648 nm), facilitating rapid ion diffusion. The assembled flexible symmetric pseudocapacitor based on NiMn2O4 carbon nanofiber electrodes delivers a high areal capacitance of 804.9 mF cm–2 at 2 mA cm–2, energy densities of 514.1–327.0 μWh cm–2 at power densities of 2.2–7.7 mW cm–2, and excellent cycling stability, retaining 95.84% of its initial capacitance after 12,000 cycles. Notably, the interconnected nanofibers network enables mechanical durability, with negligible performance degradation under bending. This work establishes a robust strategy for constructing intrinsically integrated spinel oxide carbon nanofibers electrodes, providing a viable pathway toward high-performance flexible energy storage systems.