Multilayer NiO@Co3O4@graphene quantum dots hollow spheres for high-performance lithium-ion batteries and supercapacitors

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 7; no. 13; pp. 7800 - 7814
• Main Authors: Yin, Xiaojie, Chuanwei Zhi, Sun, Weiwei, Li-Ping, Lv, Wang, Yong
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 2019
• Subjects: anodes; Batteries; Capacitance; cathodes; Chemical reactions; cobalt oxide; Cobalt oxides; Digital imaging; Electrochemistry; energy density; Flux density; Graphene; Hybrid structures; Lithium; lithium batteries; Lithium-ion batteries; Multilayers; nickel oxide; Nickel oxides; Polarity; potassium; Quantum dots; Rechargeable batteries; Supercapacitors; surface area
• DOI: 10.1039/c8ta11982a
• ISSN: 2050-7488; 2050-7496

In the present study, we designed and prepared multilayer NiO@Co3O4 hollow spheres decorated with graphene quantum dots (NiO@Co3O4@GQDs) through a rational solvothermal treatment. The decoration of the GQDs endowed the hybrid structure with excellent electrochemical behaviors in lithium-ion batteries (LIBs) and supercapacitors (SCs). The core–shell NiO@Co3O4 hollow structure was designed based on the stepwise lithium storage mechanism (first in the Co3O4 shell and then in the NiO core). The carboxyl-functionalized GQDs led to reduced interfacial resistance and increased surface area for electrochemical reactions. The high polarity of the carboxyl functionalized GQDs also showed a strong affinity to the Li+ in LIBs and K+/OH− in SCs. As an anode for LIBs, it demonstrated a large reversible capacity of 1158 mA h g−1 (NiO@Co3O4 contribution: ∼1327 mA h g−1) after 250 cycles at 0.1 A g−1. As a SC cathode, it held an impressive high specific capacitance of 1361 F g−1 (748.5 C g−1) at 1 A g−1, and retained 76.4% capacitance after 3000 cycles. Moreover, the assembled all-solid-state asymmetric supercapacitors (ASCs) (NiO@Co3O4@GQDs//AC) could deliver an energy density of 38.44 W h kg−1 and a superior cyclability (84.3% retention after 10 000 cycles).