Facile fabrication of Ni, Fe-doped δ-MnO 2 derived from Prussian blue analogues as an efficient catalyst for stable Li-CO 2 batteries.

Rechargeable Li-CO 2 batteries are regarded as an ideal new-generation energy storage system, owing to their high energy density and extraordinary CO 2 capture capability. Developing a suitable cathode to improve the electrochemical performance of Li-CO 2 batteries has always been a research hotspot. Herein, Ni-Fe-δ-MnO 2 nano-flower composites are designed and synthesized by in situ etching a Ni-Fe PBA precursor as the cathode for Li-CO 2 batteries. Ni-Fe-δ-MnO 2 nanoflowers composed of ultra-thin nanosheets possess considerable surface spaces, which can not only provide abundant catalytic active sites, but also facilitate the nucleation of discharge products and promote the CO 2 reduction reaction. On the one hand, the introduction of Ni and Fe elements can improve the electrical conductivity of δ-MnO 2 . On the other hand, the synergistic catalytic effect between Ni, Fe elements and δ-MnO 2 will greatly enhance the cycling performance and reduce the overpotential of Li-CO 2 batteries. Consequently, the Li-CO 2 battery based on the Ni-Fe-δ-MnO 2 cathode shows a high discharge capacity of 8287 mA h g -1 and can stabilize over 100 cycles at a current density of 100 mA g -1 . The work offers a promising guideline to design efficient manganese-based catalysts for Li-CO 2 batteries.