Study On The Construction And Electrochemical Performance Of Sulfur-based Nanomaterials Superlattice Structure

With the increasing market demand for advanced energy storage materials,the research of new lithium-ion battery anode materials is becoming more and more popular.The transition metal sulfide is considered to be one of the most promising anode materials for lithium-ion batteries due to its high theoretical capacity and excellent lithium storage performance,low price and abundant reserves.In this paper,CoS micro-flowers with special three-dimensional flower-like morphologies and degenerate superlattice Ni3(S)1.1(S2)0.9 micro-pyramids were respectively prepared by simple hydrothermal methods,meanwhile their electrochemical performance were studied in detail.The specific research content is as follows:(1)The CoS with three-dimensional flower-like morphology were synthesis by using CoCl2·6H2O and NH2CSNH2 as raw materials with a hydrothermal reaction.Applying this self-assembled three-dimensional interconnection structure to a lithium-ion battery.When the current density is 500 mA/g,the first discharge specific capacity is as high as 1158.5 mAh/g,the second discharge capacity is 1010.4 mAh/g,and the capacity retention rate reaches 87%,but after 10 cycles of charge and discharge,its specific capacity Significantly lower,only 334.5 mAh/g,compared with the first discharge capacity,the capacity retention rate is only 29%.It proves that although the morphology of this pure-phase transition metal sulfide is beneficial to the deintercalation process of lithium ions,its crystal structure is not stable.Therefore,the structure is very easy to collapse during the charge and discharge process,and the electrochemical performance is reduced.(2)The S powder was activated with NaOH solution to obtain alkaline sulfur aqueous solutions with different S22-concentrations.Then,nickel foam was used as the substrate to cause the nickel foam to undergo self-vulcanization reaction through hydrothermal reaction,thereby synthesised Ni3(S)1.1(S2)0.9 micro-pyramid sample.The electrode material was tested by electrochemical impedance spectroscopy,and its ohmic resistance R,was only 0.62 ohm,and the charge-transfer resistance Rct was close to 0 ohm.Used as a negative electrode material in lithium batteries,when the current density is 200 mA/g,the battery specific capacity is as high as 874 mAh/g,when the current density is 500 mA/g,the battery can still maintain a high ratio of 565 mAh/g Capacity.Compared with pure phase CoS,its rate performance and charge-discharge cycle performance have been greatly improved.