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Improving areal capacity of flexible Li–CO2 batteries by constructing a freestanding cathode with monodispersed MnO nanoparticles in N-doped mesoporous carbon nanofibers

High-energy-density batteries are in demand to meet society's immense electricity consumption, especially for wearable and portable devices. Li–CO2 batteries have attracted increasing attention for their high theoretical capacity (1876 W h kg−1) and environmental benignity. Recent research efforts have been mainly focused on improving the performance of powder catalysts; however, the overall energy density is still limited due to the inevitable employment of extra gas diffusion layers (GDLs) in cathodes. Against this backdrop, we report a method of fabricating a freestanding cathode containing ultrafine MnO nanoparticles embedded in mesoporous carbon nanofibers (MnO@NMCNFs) using electrospun Mn metal–organic framework nanofibers as precursors. Benefiting from excellent mechanical strength of the nitrogen-doped carbon nanofiber matrix, abundant mesopores and fully exposed Mn(II) active sites, the obtained cathode guarantees high flexibility, high interface accessibility, high catalytic activity and high conductivity. Therefore, the corresponding Li–CO2 batteries achieved ultrahigh areal capacity (19.07 mA h cm−2), impressively low overpotential (0.73 V) and competitive cycling stability (>50 cycles under cut-off capacity of 1 mA h cm−2). A pouch-type flexible cell based on MnO@NMCNFs steadily lit up commercial LED devices at different bending angles. Our findings advance the application of high-energy Li–CO2 batteries in wearable energy storage systems.