Facile fabrication of Ni, Fe-doped δ-MnO2 derived from Prussian blue analogues as an efficient catalyst for stable Li–CO2 batteries

Abstract

Rechargeable Li–CO₂ batteries are regarded as an ideal new-generation energy storage system, owing to their high energy density and extraordinary CO₂ capture capability. Developing a suitable cathode to improve the electrochemical performance of Li–CO₂ batteries has always been a research hotspot. Herein, Ni–Fe-δ-MnO₂ nano-flower composites are designed and synthesized by in situ etching a Ni–Fe PBA precursor as the cathode for Li–CO₂ batteries. Ni–Fe-δ-MnO₂ 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 CO₂ reduction reaction. On the one hand, the introduction of Ni and Fe elements can improve the electrical conductivity of δ-MnO₂. On the other hand, the synergistic catalytic effect between Ni, Fe elements and δ-MnO₂ will greatly enhance the cycling performance and reduce the overpotential of Li–CO₂ batteries. Consequently, the Li–CO₂ battery based on the Ni–Fe-δ-MnO₂ 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–CO₂ batteries.