Multi-scale synergistic regulation of hierarchical porous Ni@NiSe cathodes with low voltage gap, high capacity and long-term cycling stability in Li–CO₂ battery

The Li–CO₂ battery often suffers from high overpotential and limited capacity due to the challenges associated with the adsorption of Li⁺ and CO₂ and the decomposition of Li₂CO₃. Herein, hexagonal rich-stepped NiSe crystals are in situ achieved on a three-dimensional (3D) free-standing porous Ni skeleton with double continuous channel architecture (namely p-Ni@NiSe-50) through an in situ selenization process. Structural characterization and theoretical calculation are applied to demonstrate the synergistic effects of marco/microstructural design and electronic band structure regulation. As a result, the adsorption/desorption of Li⁺ and CO₂ and the formation/decomposition of Li₂CO₃ are effectively promoted, simultaneously, enabling an enhanced capacity and reversibility of p-Ni@NiSe-50 as the cathode of Li–CO₂ battery. An ultra-low overpotential of 0.46 V and a remarkably high energy efficiency of 83.8% (20 μA cm⁻²) are achieved, along with a high full discharge specific capacity of 8844 μAh cm⁻². Excellent long-term cycling stability (cycles up to 1000 h at a voltage gap of 1.14 V) of p-Ni@NiSe-50 is also obtained. The results of this work would provide a new insight and strategy to develop high-performance alkali metal-air batteries.

Multi-scale synergistic effect of combining the cathode macroscopic structure design and the microscopic band structure design of NiSe was demonstrated to promote the adsorption of Li⁺ and CO₂, as well as the decomposition of Li₂CO₃, so as to achieve ultra-low voltage gap and high capacity of Li-CO₂ batteries.