Collaborative engineering of Se vacancies, hierarchical nanoarrays, and binder-free structure enabling high-performance CuO@NiCo-Se electrodes for supercapacitors

A binder-free VSe-CuO@NiCo-Se electrode with selenium-rich vacancy (VSe) and hierarchical nanoarrays is constructed. • The interconnected hierarchical nanoarray structure effectively alleviate volume expansion and facilitate rapid electron/ion transport. • Se vacancies significantly enhances the electrical conductivity and creates abundant redox active sites of electrode material. • The series connection of two VSe-CuO@NiCo-Se//AC devices successfully addresses high-voltage application requirements. Sluggish kinetics and poor cycling stability of battery-type electrode materials are two major bottlenecks that limit the large-scale application of supercapacitors (SCs) in energy storage systems. To address these challenges, we designed and constructed a binder-free V Se -CuO@NiCo-Se electrode with hierarchical selenium-vacancy (V Se ) nanoarrays directly grown on a highly conductive copper foam (CF) substrate. Systematic characterizations combined with theoretical calculations reveal that the three-dimensional porous CF structure serves dual functions as both a current collector and a Cu source, which not only alleviates the agglomeration of electrode materials and but also eliminates the degradation of electrochemical performance caused by insulating binders and additives. Moreover, the interconnected hierarchical nanoarray structure effectively alleviate volume expansion during charge-discharge processes while facilitating rapid electron/ion transport. Most notably, the introduction of Se vacancies significantly enhances the electrical conductivity and creates abundant redox active sites of electrode material. As anticipated, the V Se -CuO@NiCo-Se electrode displays elevated specific capacity of 441.6 mAh g –1 (2890.9 F g –1 ) at 3 A g –1 , excellent rate capability (94.8% capacity retention at 20 A g –1 ), and long cycling stability (82% capacity retention after 10,000 cycles). Furthermore, the V Se -CuO@NiCo-Se//AC quasi-solid-state asymmetric supercapacitor device achieves an energy density of 38.4 Wh kg –1 at 800 W kg –1 . Importantly, the series connection of dual devices successfully addresses high-voltage application requirements. The strategic integration of Se vacancies, hierarchical nanoarrays, and a binder-free structure is a highly effective approach for developing high-performance electrodes, thereby advancing the practical application of SCs in energy storage. The hierarchical CuO@NiCo-Se nanoarray electrode material with Se vacancies (V Se -CuO@NiCo-Se) shows high specific capacity, excellent rate performance, and substantial durability. In addition, a quasi-solid-state asymmetric supercapacitor (ASC) constructed with V Se -CuO@NiCo-Se functioning as the positive electrode and activated carbon (AC) serving as the negative electrode manifests outstanding cyclability (75.3% capacity retention after 5000 cycles). Download: Download high-res image (258KB) Download: Download full-size image