Uniform-dispersed ZnS quantum dots loading on graphene as a promising anode for potassium-ion batteries

The potassium-ion batteries (PIBs) have become the promising energy storage devices due to their relatively moderate cost and plenteous potassium resources. Whereas, the main drawback of PIBs is unsatisfactory electrochemical performance induced by the larger ionic radius of potassium ion. Herein, we report a well-designed, uniform-dispersed, and morphology-controllable zinc sulfide (ZnS) quantum dots loading on graphene as an anode in the PIBs. The directed uniform dispersion of the in-situ growing ZnS quantum dots (∼2.8 nm in size) on graphene can mitigate the volume effect during the insertion-extraction process and shorten the migration path of potassium ions. As a result, the battery exhibits superior cycling stability (350.4 mAh/g over 200 cycles at 0.1 A/g) and rate performance (98.8 mAh/g at 2.0 A/g). We believe the design of active material with quantum dot-minimized size provides a novel route into PIBs and contributes to eliminating the major electrode failure issues of the system.