Functionalized Graphene Quantum Dot Modification of Yolk–Shell NiO Microspheres for Superior Lithium Storage

Abstract Yolk–shell NiO microspheres are modified by two types of functionalized graphene quantum dots (denoted as NiO/GQDs) via a facile solvothermal treatment. The modification of GQDs on the surface of NiO greatly boosts the stability of the NiO/GQD electrode during long‐term cycling. Specifically, the NiO with carboxyl‐functionalized GQDs (NiO/GQDsCOOH) exhibits better performances than NiO with amino‐functionalized GQDs (NiO/GQDsNH 2 ). It delivers a capacity of ≈1081 mAh g −1 (NiO contribution: ≈1182 mAh g −1 ) after 250 cycles at 0.1 A g −1 . In comparison, NiO/GQDsNH 2 electrode holds ≈834 mAh g −1 of capacity, while the bald NiO exhibits an obvious decline in capacity with ≈396 mAh g −1 retained after cycling. Except for the yolk–shell and mesoporous merits, the superior performances of the NiO/GQD electrode are mainly ascribed to the assistance of GQDs. The GQD modification can support as a buffer alleviating the volume change, improve the electronic conductivity, and act as a reservoir for electrolytes to facilitate the transportation of Li + . Moreover, the enrichment of carboxyl/amino groups on GQDs can further donate more active sites for the diffusion of Li + and facilitate the electrochemical redox kinetics of the electrode, thus together leading to the superior lithium storage performance.

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