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 300th-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.