Synergistic effect of fluorine doping and oxygen vacancies on electrochemical performance of ZnCo2O4 for advanced supercapacitors and Zn-ion batteries

Abstract

Defects in nanomaterials have been widely used to introduce new properties of pristine materials for electrochemical energy storage. However, most of the research has focused on the effect of single defect while ignoring the synergy of multifold defects on enhancing electrochemical performance. Herein, we have modeled bulk phase oxygen substitution and surface oxygen vacancy on ZnCo2O4 nanowires grown on nickel foam for the first time (F-ZnCo2O4-x), revealing the role of double defects and providing new insights into the effects of electrochemical properties. The enhanced oxygen vacancy concentration and increased active sites enable rapid and sufficient redox reaction of the active components. Therefore, the representative F-ZnCo2O4-x electrode achieves a high specific capacity of 664 mAh·g−1 at 1 A·g−1. Moreover, high energy density (EHSC, 60 Wh·kg−1) and good cycle stability (90.44% capacity retention after 10000 cycles) could be provided as a battery-type electrode of hybrid supercapacitor. The electrodes also have high energy density (Ecell, 692 Wh·kg−1) and good durability (capacity retention of 98.8% after 2000 cycles) when used as zinc ion batteries. This work supplies a new avenue on the universality of defect engineering to design bimetallic oxide with high electrochemical performance.