Selective synthesis of monodisperse bimetallic nickel-cobalt phosphates with different nanoarchitectures for battery-like supercapacitors

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 12; no. 23; pp. 1445 - 1458
• Main Authors: Wulan Septiani, Ni Luh, Chowdhury, Silvia, Hardiansyah, Andri, Rinawati, Mia, Yeh, Min-Hsin, Nara, Hiroki, Yamauchi, Yusuke, Kaneti, Yusuf Valentino, Yuliarto, Brian
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 11.06.2024
• Subjects: Activated carbon; Bimetals; Butanol; Capacitance; Cobalt; Current density; Diffusion rate; Electrochemical analysis; Electrochemistry; Electrolytes; Ethanol; Fabrication; Intermetallic compounds; Mixtures; Nickel; Phosphate; Phosphates; Roasting; Solvents; Specific capacity; Stability tests; Supercapacitors
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d3ta06584g

This work reports the fabrication of monodisperse nickel-cobalt phosphate particles with varying structures via the solvothermal reaction of nickel-cobalt glycerate spheres with triethyl phosphate (TEP) in different solvents followed by subsequent calcination in air at 600 °C. The choice of solvent affects the morphology of the resulting nickel-cobalt phosphate precursor obtained from the solvothermal reaction. It is found that alcohol-based solvents (pure ethanol and ethanol/butanol mixture) favour the formation of monodisperse plate-like particles, while the use of a water/ethanol mixture promotes the generation of rod-like particles. The optimized amorphous nickel-cobalt phosphate sample prepared using pure ethanol followed by calcination in air at 600 °C (E-NiCo-TEP-600) exhibits a battery-like behaviour with a high specific capacity of 620 C g −1 (specific capacitance of 1550 F g −1 ) in 6.0 M KOH at a current density of 2 A g −1 . Furthermore, the asymmetric supercapacitor (ASC) fabricated using E-NiCo-TEP-600 as the cathode and commercial activated carbon (AC) as the anode (E-NiCo-TEP-600//AC ASC) displays a maximum energy density of 45 W h kg −1 at a power density of 750 W kg −1 . The stability test reveals the good long-term stability of this ASC with a high capacitance retention of ∼100% after 5000 cycles at a high current density of 10 A g −1 . The porous nature along with the high structural disorder and abundant mesopores in the amorphous nickel-cobalt phosphate plate-like particles (E-NiCo-TEP-600) can promote faster diffusion of electrolyte ions and better electrolyte ion penetration, leading to a higher electrochemical performance. These results indicate the promising potential of porous amorphous bimetallic phosphates for supercapacitors. This work reports the selective synthesis of monodisperse nickel-cobalt phosphate particles with different structures for battery-like supercapacitors.