One step in situ synthesis of ZnS/N and S co-doped carbon composites via salt templating for lithium-ion battery applications
Herein, we report a simple in situ synthetic route to prepare ZnS/carbon composites (ZnS/NSC-x) by using a eutectic salt mixture (LiCl/ZnCl2) as a template and 2-amino-4-phenyl thiazole as a precursor for carbon materials. The structural and morphological characterization reveals the presence of cubic ZnS (9 nm) nanoparticles embedded in the carbon material. These synthesized heteroatom co-doped composites (ZnS/NSC-x) with moderate surface area, when used as the positive electrode in a lithium-ion battery, gave better performance than pure ZnS both in terms of cycling stability and rate performance. The capacity retention at the high current density of 1500 mA g−1 is 65% with respect to the capacity obtained at 250 mA g−1 for ZnS/NSC-800, whereas pure ZnS retained only 28% of the capacity at the same current density. The charge transfer resistance values are also found to be very low for the synthesized composites, which is responsible for their improved kinetics. The heteroatom co-doped carbon matrix besides improving the electronic conductivity also relieved the stress induced by cycling; therefore, the electrode with a high mass loading of up to 4 mg cm−2 gave stable capacity with 90% of the initial capacity retained over 200 cycles (at 250 mA g−1) for the same electrode at which the rate performance was carried out.