Dual-functional hosts derived from metal-organic frameworks reduce dissolution of polyselenides and inhibit dendrite growth in a sodium-selenium battery

Selenium-based cathodes for sodium-ion batteries have attracted considerable attention due to their high electronic conductivity and volumetric capacity compared to sulfur-based cathodes. However, the use of sodium-selenium batteries has been hindered due to the low selenium reaction activity towards sodium, rapid capacity fading caused by the shuttle effect of polyselenides, and the formation of sodium dendrites on the Na anodes. Herein, starting from the nitrogen and oxygen-containing ligands, two precursors of Ni&Zn-MOF and Zn-MOF were used to fabricate the cathode and anode, respectively. A N,O-codoped porous carbon host decorated with well-dispersed Ni single-atom catalyst was derived from the Ni&Zn-MOF for Se storage. When applied as a cathode in Na-Se batteries, this composite accelerated the reaction kinetics of Se and Na+, and at the same time weakened the Se-Se bond owing to its high adsorption to the Se8 ring, which resulted in a significant improvement of the cycle stability. Meanwhile, a dendrite-free anode was realized by using Zn-MOF derived N,O-codoped porous carbon host, which showed a strong sodiophilic ability for Na metal. As a result, the Na-Se battery employing these two composites as the cathode and anode showed an excellent cycle stability and improved safety.