Benzoate anions-intercalated cobalt-nickel layered hydroxide nanobelts as high-performance electrode materials for aqueous hybrid supercapacitors.

Layered metal hydroxide salts (LHSs) have recently gained extensive interests as an efficient electrode material for supercapacitors (SCs). Herein, we report, for the first time ever, the synthesis of a cobalt-nickel layered hybrid organic-inorganic LHS that was intercalated with benzoate anions (B-CoNi-LHSs) and observe a high performance as electrode materials for hybrid supercapacitors (HSCs). B-CoNi-LHSs were synthesized by using a co-precipitation method, where sodium benzoate was added dropwise to cobalt and nickel salt solution, without the addition of any organic solvent or surfactant. Due to the intercalation of anions and synergistic interactions of the multi-metallic components, the B-CoNi-LHSs electrode showed a high specific capacity of 570 C g (specific capacitance of 1267 F·g) at 1 A g, excellent rate performance (65% from 1 to 10 A g) and outstanding cycling performance (81.09% over 8000 cycles), in comparison to the mono-metallic counterparts. An HSC device, assembled by using B-CoNi-LHSs as the positive electrode and activated carbon (AC) as the negative one, exhibited a power density of 780 W kg at the energy density of 31.7 Wh kg, and 8543 W kg at 18.1 Wh kg. Results from this study show that the organic-inorganic hybrids of layered dual-metal hydroxides intercalated with benzoate anions may be a viable candidate as electrode materials for high-performance SCs.