Boron-Doped Trimetallic Cu-Ni-Co Oxide Nanoneedles for Supercapacitor Application

Doping has been one of the efficient ways in incorporating potential elements to further increase electrode efficiencies. The introduction of boron as a dopant reinforces transition metal to oxide bonding and makes it stable during the cycling process. Herein, we prepared Cu-Ni-Co oxide (CNCO) with agglomerated nanoneedle-like structures in the first step and then structurally doped it with boron (CNCO-D-SD) in the second step. The agglomerated nanoneedle-like structures with merged tips were retained with boron doping, but stability was decreased. Then, we evaluated the incorporation of boron in one step, and, interestingly, it resulted to self-organized, boron-doped Cu-Ni-Co oxide (CNCO-D-SO) one-dimensional (1D) vertically aligned nanoneedle-like structures. Herein, boric acid acted as a dopant as well as a structural-directing agent. The CNCO-D-SO exhibited superior overall electrochemical performance to the CNCO and CNCO-D-SD. Interestingly, the as-assembled hybrid supercapacitor (HSC) device made from CNCO-D-SO//rGO showed outstanding stability (87% after 8,000 cycles) compared to CNCO-D-SD//rGO (46% after 5,000 cycles) and bare CNCO//rGO (53% after 5,000 cycles). This study demonstrates that doping can improve the stability and/or capacity of Cu-Ni-Co oxide, but the nature of the active materials is also equally important for achieving satisfactory performance. Furthermore, this study suggests a more efficient as well as time-, energy-, and cost-saving preparation of structured electrodes. Overall, the outcomes showed that the as-assembled CNCO-D-SO//rGO HSC device had higher storage capacity, better stability and conductivity, and scalable time-saving fabrication, suggesting that it has great potential in next-generation energy storage applications.