Unraveling a High-Performance Self-Supported Flexible Zinc-Ion Battery Cathode with Tailored Electrospun MnO_x/N-Doped Carbon Nanofibers

The increasing demand for wearable and bendable electronics has generated significant interest in flexible zinc-ion batteries. However, their development has been hindered by the inadequate capacity and cycling stability of flexible electrodes under repeated mechanical deformation. Herein, we present a self-supported, binder-free, and flexible manganese oxide-based cathode for flexible zinc-ion batteries. This innovation leverages an optimum amount of well-dispersed manganese oxide nanoparticles within a nitrogen-doped carbon nanofiber matrix, achieved by fine-tuning the mass ratio of polyacrylonitrile and manganese acetate during electrospinning. The optimum sample exhibits mechanical robustness and a desirable nanofiber morphology without any bead formations. The synergistic interfaces between manganese oxide nanoparticles and a nitrogen-doped carbon nanofiber matrix facilitate rapid charge transfer and minimize active material detachment, leading to an unprecedented combination of high-rate capability and stability. Consequently, the free-standing cathode can deliver a high specific capacity of 392 mA h g^-1 at 0.1 A g^-1 and maintain stable capacity (∼200 mA h g^-1) for up to 1800 cycles at a high current density of 2.0 A g^-1. Furthermore, employing the obtained cathode with a quasi-solid gel electrolyte, flexible zinc-ion batteries achieve stable performance with a high average capacity of ∼186 mA h g^-1 over 140 cycles, even under extreme bending angles of 180°. This finding surpasses the performance of the existing flexible zinc-ion batteries and offers a promising path for the development of advanced energy storage solutions in flexible electronics.