CuCo2O4 nanoparticles wrapped in a rGO aerogel composite as an anode for a fast and stable Li-ion capacitor with ultra-high specific energy

Abstract

To meet practical application requirements, high specific energy and specific power and excellent cyclability are highly desired. Herein, we design and synthesize fine CuCo₂O₄ nanoparticles wrapped in a conductive rGO aerogel network as a robust conductive anode for Li-ion capacitors (LICs). The nanostructure of the resulting CuCo₂O₄/rGO composite provides a high capacity of 1285 mA h g⁻¹ at a small current density of 0.1 A g⁻¹. Moreover, the conductive anode was combined with an activated carbon (AC) cathode (denoted as CuCo₂O₄/rGO//AC) to construct high-performance LICs. The as-prepared device (CuCo₂O₄/rGO//AC LIC) exhibits capacitance of 49.5 F g⁻¹ at 1 A g⁻¹ and retained capacitance of 34.0 F g⁻¹ when the current density increased to 4 A g⁻¹, demonstrating outstanding rate performance. Excitingly, our fabricated CuCo₂O₄/rGO//AC LIC exhibits ultra-high specific energy and specific power (396 W h kg⁻¹/8 kW kg⁻¹) with excellent cyclability (∼100% retention after 16 000 cycles) for the first time. We demonstrate that a single LIC cell could light a blue LED with sufficient illumination for 100 s, opening the way to possible realistic applications. Additionally, based on the synergistic effect of the conductive rGO aerogel matrix and the downsized CuCo₂O₄ particles of the CuCo₂O₄/rGO anode, the superior electrochemical performance was attributable to increased conductivity and structural integrity during Li⁺ insertion/extraction.