Nanostructure engineering of cobalt-nickel glycerate (CoNi-G) spheres as anodes for constructing high-performance lithium-ion capacitors
Ai‐Jun Jiao, You‐Kang Duan, Zhiwei Li, Shichun Zhang, Yongming Zhang, Tong Su, Zhen‐Hai Fu
Abstract
Electrode materials with heterogeneous structure and favorable morphology can increase the contact with the electrolyte while accelerating the ion transport. Here, we prepared Co 2 NiO 4 /NiO solid spheres and CoNi 2 S 4 hollow spheres by high-temperature calcined oxidation and solvent-thermal vulcanization , with cobalt-nickel glycerate (CoNi-G) solid spheres as precursors, respectively. The specific capacities of Co 2 NiO 4 /NiO and CoNi 2 S 4 as anodes after 170 and 570 cycles at 0.1 A g −1 are 1260.9 mAh g −1 and 495.0 mAh g −1 respectively, and even after 3000 cycles at 2 A g −1 , their specific capacities can reach 168.9 mAh g −1 and 211.1 mAh g −1 respectively. The initial specific capacities of both materials are higher, but the solid structure is more stable than the hollow structure. Density Functional Theory (DFT) calculations show that the constructed Co 2 NiO 4 /NiO heterojunction has reduced Li + embedding formation energy and enhanced conductivity. Finally, the assembled Co 2 NiO 4 /NiO//AC and CoNi 2 S 4 //AC lithium-ion capacitors have maximum energy densities of 106.7 Wh kg −1 and 73.6 Wh kg −1 (at 205 W kg −1 and 95 W kg −1 ), and maximum power densities of 20.5 kW kg −1 and 19.0 kW kg −1 (at 10.8 Wh kg −1 and 19.5 Wh kg −1 ). Improved electrode structures via precursor treatments enhance lithium-ion capacitors performance, suggesting new avenues for material research.