Rationally designed oxygen vacancy for achieving effective and kinetically boosted Na-Se batteries

Abstract

Reasonable chemistry design of selenium hosts to stabilize and transform sodium polyselenide (Na2Sex) is of great significance for high-performance Na-Se batteries. Herein, a hollow nitrogen-doped carbon embedded with oxygen defective Fe2O3 nanoparticles (Fe2O3@NC) has been prepared, which integrates conductivity, polarity and catalytic ability into cooperation and is validated as a suitable selenium host to suppress the Na2Sex shuttling. Fe2O3 not only serves as an efficient Na2Sex reservoir via strong chemisorption between O atoms of Fe2O3 and Na atoms of Na2Sex, but also promotes the transformation of Na2Sex. Moreover, the plentiful oxygen vacancy defects in Fe2O3 phase increases the catalytic conversion efficiency of Na2Sex. Accordingly, the selenium-containing Fe2O3@NC exhibits a reversible capacity of 215.3 mAh g−1 after 2310 cycles at 10 A g−1 with a superior capacity retention of 97.1%. This work clarifies the unique chemical properties of metal oxides, especially analogs with plentiful O vacancies, in promoting the adsorption-conversion process of Na2Sex, which provides a practical way to achieve the design of highly stable Na-Se batteries.