Exchanging Anion in CuCo-Carbonate Double Hydroxide for Faradaic Supercapacitors: A Case Study.

A systematic synthetic method involving the anion exchange process was designed and developed to fabricate the superior functioning three-dimensional (3-D) urchin-architectured copper cobalt oxide (CuCo 2 O 4 ; CCO) and copper cobalt sulfide (CuCo 2 S 4 ; CCS) electrode materials from copper-cobalt carbonate double hydroxide [(CuCo) 2 (CO 3 )(OH) 2 ; CCH]. The effective tuning of chemical, crystalline, and morphological properties was achieved during the derivatization process of CCH, based on the anion exchange effect and phase transformation without altering the 3-D spatial assembly. Benefiting from morphological and structural advantages, CCO and CCS exhibited superior electrochemical activity with capacity values of 1508 and 2502 C g -1 at 10 A g -1 to CCH (1182 C g -1 at 10 A g -1 ). The thermal treatment of CCH has generated a highly porous nature in nanospikes of 3-D urchin CCO structures, which purveys betterment in electrochemical phenomena than pristine smooth-surfaced CCH. Meanwhile, the sulfurization reaction induced the anion effect to a greater extent in the CCS morphology, resulting in hierarchical 3-D urchins formed by 1-D nanospikes constituting coaxially swirled 2-D nanosheets with high exposure of active sites, specific surface areas, and 3-D electron/ion transportation channels. The asymmetric supercapacitor was constructed with a superior CCS electrode as a cathode and an activated carbon electrode as an anode, showing a high specific capacity of 287.35 C g -1 at 7 A g -1 and durability for 5000 cycles with 94.2% retention at a high current density of 30 A g -1 . The ultrahigh energy and power density of 135.3 W h kg -1 (10 A g -1 ) and 44.35 kW kg -1 (30 A g -1 ) were harvested during the PC device performance. Our finding proposes an idea about the importance of anions and phase transformation as a versatile tool for engineering high-functioning electrode materials and their endeavor toward overwhelming the major demerit of SCs by aggrandizing the energy density value and rate performance.