Unlocking the Potential of Oxygen-Deficient Copper-Doped Co₃O₄Nanocrystals Confined in Carbon as an Advanced Electrode for Flexible Solid-State Supercapacitors

Battery-type materials for supercapacitors have attracted increasing research interest owing to their high energy density. However, their poor electrode kinetics severely limit the utilization of redox-active sites on the electrode surface, resulting in subpar electrochemical performance. Herein, we incorporate both Cu dopants and O vacancies into Co3O4 nanocrystals confined in a carbon matrix (Ov-Cu-Co3O4@C) which are assembled into nanowires. This heterostructured architecture with multifunctional nanogeometries provides a high intercomponent synergy, enabling high accessibility to active species. Moreover, the Cu dopants and O vacancies in Ov-Cu-Co3O4@C synergistically manipulate the electronic states and provide more accessible active sites, resulting in enhanced electrical conductivity and enriched redox chemistry. The Ov-Cu-Co3O4@C achieves a significantly improved specific capacity and rate performance, exceeding those of Co3O4@C. The asymmetric supercapacitors with Ov-Cu-Co3O4@C deliver a high energy density of 64.1 W h kg-1 at 800 W kg-1, exhibiting good flexibility without significant performance degradation under different bending states.