Nanostructure engineering of cobalt-nickel glycerate (CoNi-G) spheres as anodes for constructing high-performance lithium-ion capacitors

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. • Co 2 NiO 4 /NiO and CoNi 2 S 4 obtained by nanostructure engineering of CoNi-G precursors. • Co 2 NiO 4 /NiO with Heterogeneous and CoNi 2 S 4 hollow structure enhance Li + storage. • DFT calculations revealed that Co 2 NiO 4 /NiO shows enhanced electrical conductivity. • Regulation of LICs performance by mass matching and voltage window matching.