Synthesis, Characterizations, and Electrochemical Performances of Highly Porous, Anhydrous Co0.5Ni0.5C2O4 for Pseudocapacitive Energy Storage Applications

Neeraj Kumar Mishra; Rakesh Mondal; Thandavarayan Maiyalagan; Preetam Singh

doi:10.1021/acsomega.1c05356

Synthesis, Characterizations, and Electrochemical Performances of Highly Porous, Anhydrous Co_0.5Ni_0.5C₂O₄ for Pseudocapacitive Energy Storage Applications

ACS Omega. 2022 Jan 4;7(2):1975-1987. doi: 10.1021/acsomega.1c05356. eCollection 2022 Jan 18.

Authors

Neeraj Kumar Mishra¹, Rakesh Mondal¹, Thandavarayan Maiyalagan², Preetam Singh¹

Affiliations

¹ Department of Ceramic Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi, Uttar Pradesh 221005, India.
² Electrochemical Energy Laboratory, Department of Chemistry, SRM Institute of Science and Technology, Kattankulathur, Tamilnadu 603203, India.

Abstract

Electrochemical energy storage relies essentially on the development of innovative electrode materials with enhanced kinetics of ion transport. Pseudocapacitors are excellent candidates to bridge the performance gap between supercapacitors and batteries. Highly porous, anhydrous Ni_0.5Co_0.5C₂O₄ is envisaged here as a potential electrode for pseudocapacitor applications, mainly because of its open pore framework structure, which poses inherent structural stability due to the presence of planar oxalate anions (C₂O₄ ^2-), and active participation of Ni^2+/3+ and Co^2+/3+ results in high intercalative charge storage capacity in the aqueous KOH electrolyte. The Ni_0.5Co_0.5C₂O₄ electrode shows specific capacitance equivalent to 2396 F/g at 1 A/g in the potential window of 0.6 V in the aqueous 2 M KOH electrolyte by galvanostatic charge/discharge experiments. Predominant pseudocapacitive mechanism seems to operative behind high charge storage due to active participation of Ni^2+/3+ and Co^2+/3+ redox couple as intercalative (inner) and surface (outer) charges stored by porous anhydrous Co_0.5Ni_0.5C₂O₄ were close to high 38 and 62% respectively. Further, in full cell asymmetric supercapacitors (ASCs) in which porous anhydrous Co_0.5Ni_0.5C₂O₄ was used as the positive electrode and activated carbon (AC) was utilized as the negative electrode, in the operating potential window 1.6 V, the highest specific energy of 283 W h/kg and specific power of ∼817 W/kg were achieved at 1 A/g current rates. Even at a very high power density of 7981 W/kg, the hybrid supercapacitor still attains an energy density of ∼75 W h/kg with high cyclic stability at a 10 A/g current rate. The detailed electrochemical studies confirm higher cyclic stability and a superior electrochemical energy storage property of porous anhydrous Co_0.5Ni_0.5C₂O₄, making it a potential pseudocapacitive electrode for large energy storage applications.