Self-assembled CoS₂ nanoparticles wrapped by CoS₂-quantum-dots-anchored graphene nanosheets as superior-capability anode for lithium-ion batteries

For the first time, self-assembled CoS₂ nanoparticles wrapped by CoS₂-quantum-dots anchored graphene nanosheets (CoS₂NP@G-CoS₂QD) are synthesized by a facile L-cysteine-assisted hydrothermal reaction. When the composite is used as anode in lithium-ion batteries (LIBs), it shows superior electrochemical performance: the reversible specific capacity is as large as 1048 mAh g⁻¹; the 300^th-cycle capacity still maintains 831 mAh g⁻¹ even at 1 A g⁻¹; the rate capacity remains 411 mAh g⁻¹ even at 10 A g⁻¹, which is the highest value ever reported at such high current density for CoS₂ based materials. The excellent electrochemical performance is attributed to the unique structure with CoS₂ nanoparticles homogeneously wrapped by highly flexible and conductive few-layer graphene nanosheets adhering abundant CoS₂ quantum dots, which can effectively suppress the aggregation of CoS₂ nanoparticles, accommodate the volume change during the cycle processes and maintain high electrical conductivity of the electrode. The CoS₂NP@G-CoS₂QD composite is promising for superior-capability anode for LIBs and can be further extended to broad applications in supercapacitors, sensors, and catalysis.