Highly porous silver dendrites on carbon nanotube wrapped copper cobaltite nano-flowers for boosting energy density and cycle stability of asymmetric supercapattery

In the present work, we have demonstrated the rapid synthesis of Ag dendrites on carbon nanotubes (CNTs) wrapped CuCo₂O₄ nanoflowers (CNT-CuCo₂O₄@Ag) by using a two-step chemical approach. The as-synthesized CNT-CuCo₂O₄@Ag is used as an electrode for supercapattery application. Individually, CNT-CuCo₂O₄@Ag electrode shows the exceptional capacity of 590 mAh g⁻¹ at a current density of 0.5 A g⁻¹. This capacity is 1.8 and 1.6 times those of the pure CuCo₂O₄ and CNT-CuCo₂O₄ nanoflower-based electrodes, respectively. Furthermore, an all-solid-state asymmetric supercapattery (ASC), CNT-CuCo₂O₄@Ag//AC, has been fabricated using the CNT-CuCo₂O₄@Ag nanoflowers as the positive electrode and a thermocol-derived activated carbon (AC) as the negative electrode. Interestingly, the ASC device delivers an ultrahigh energy density of 91 Wh kg⁻¹ at the power density of 0.42 kW kg⁻¹; even at the high power density of 18 kW kg⁻¹, the ASC device still maintains an energy density of 50 Wh kg⁻¹. The ASC device also exhibits excellent cyclic stability by showing 98% of capacity retention over 20,000 cycles at a high current density of 10 A g⁻¹. This rapid in situ synthesis strategy for Ag dendrite growth and CNT wrapping is also applicable to other metal oxides and metal sulphides with porous nanostructures containing NH₃ molecules.