Embedding hollow Co₃O₄ nanoboxes into a three-dimensional macroporous graphene framework for high-performance energy storage devices

Carbon materials are widely used for supercapacitor applications thanks to their high surface area, good rate capability, and excellent cycling stability. However, the development of high energy density carbon supercapacitors still remains a challenge. In this work, hollow Co₃O₄ nanoboxes have been embedded into three-dimensional macroporous laser-scribed graphene (LSG) to produce composite electrodes with improved electrochemical performance. Here, Co₃O₄ provides high capacity through fast and reversible redox reactions, while LSG serves as a conductive network to maintain high power. The open nanobox morphology is a unique solution for extracting the maximum capacity from Co3O4, resulting in electrodes whose surfaces, both internal and external, are accessible to the electrolyte. The electrochemical performance of the composite material is promising with a volumetric capacity of 60.0 C/cm³ and a specific capacity of 542.3 C/g, corresponding to 682.0 C/g of the constituent Co₃O₄. With a low equivalent series resistance of 0.9 Ω, the Co₃O₄/LSG electrode is able to maintain 113.1% of its original capacity after 10, 000 cycles. This work provides new insights into the design of high-performance carbon/metal oxide nanocomposites for next-generation energy storage devices.