Electrochemical properties of two-dimensional zirconium nitrogen anode materials for K-ion battery by first-principles insights

As a class of two-dimensional transition metal compounds, MXene has become the most potential alternative electrode materials because of its fascinating properties. In this contribution, the electrochemical properties of Zr₂N with O and S groups for K-ion battery are explored. The O and S functional groups have high electronegativity and high affinity with K-ion; the results show that the most stable adsorption site of Zr₂NO₂ and Zr₂NS₂ models is on the bottom Zr atom; with regard to the Zr₂N model, it is located at above the N atom; and the corresponding adsorption energy on the surface of Zr₂NO₂ and Zr₂NS₂ models is far less than that Zr₂N model. The differential charge density map and atomic population indicated obvious electron transfer between the adsorbed atom and monolayer, which proved that there is some chemisorption. With regard to the electrochemical performance, K-ion has low open-circuit voltage and high theoretical specific capacity on Zr₂N, Zr₂NO₂, and Zr₂NS₂ models, and the migration barrier is smaller than that of common two-dimensional materials. A series of results suggest that Zr₂N, Zr₂NO₂, and Zr₂NS₂ can be applied as potential anode materials for K-ion batteries.