Oxygen-vacancy engineered Co3O4 cathodes for 3D printing micro-supercapacitor applications

The increasing demand for high-energy–density, customizable Micro-Supercapacitors (MSCs) is driven by the rapid miniaturization, integration, and smart functionalities of electronic devices. The use of 3D printing technology in fabricating high-performance energy storage electrodes opens up novel opportunities for portable and micro-device applications. Through a simple solution reduction method, NaBH₄ is used to adjust the electronic structure of Co₃O₄, producing defects rich in oxygen vacancies (Ovs), increasing electroactive sites, reducing resistance, and thus improving the performance of supercapacitors. By mixing with graphene oxide in a certain proportion to prepare 3D printing ink, a three-dimensional conductive network is formed. In this work, the Micro-Supercapacitor (MSC) fabricated via 3D printing technology demonstrates excellent electrochemical performance. It achieves a high areal specific capacity of 715.6 mF cm⁻² at a current density of 1 mA cm⁻². After 10,000 cycles at a high current density of 9 mA cm⁻², it retains 92.5 % of its initial capacity. Additionally, it delivers an impressive energy density of 254.4 µWh cm⁻² at a power density of 800 µW cm⁻². Mesenchymal stem cells fabricated via 3D printing offer a transformative approach for developing next-generation wearable electronics.