Preparation Of NiCo₂S₄ And Its Application In Lithium Secondary Batteries

Spinel Ni Co2S4 has aroused extensive research across the world for its high conductivity and redox activity.However,the preparation process of Ni Co 2S4 is not uniform and its own chemical properties are unknown,and the field of study is limited to capacitors and lithium-ion batteries while no related to lithium-ion batteries catalyst.In the study of lithium-ion batteries the research methods and directions are relatively simple where it can not effectively contribute the property.NiCo2S4 powder and NiCo2S4 nanosheets which are controllable prepared by improved hydrothermal method respectively realize the first application for lithium air batteries catalysts and anode materials for lithium ion batteries in the oxygen.Finally,the properties of NiCo2S4 as lithium ion batteries material is further analyzed by the comparative study and the computer theory simulation by first principle.The Ni Co2S4 powder under the optimum reaction conditions is prepared by hydrothermal method for lithium air batteries catalysts,which is with mesoporous structure,and it is urchin-like that have the diameter of ~5 μm and specific surface area of 10.85 m2/g.Electrochemical performance tests show that the first discharge specific capacity is 6660 mAh/g which is higher than 4868 mAh/g of pure conductive agent Super P in charge-discharge tests limited voltage under the current density of 100 mA/g.However,in the charge-discharge tests limited capacity NiCo2S4 powder does not show some advantages.It can be attributed to the polyvalency of Ni and Co for specific capacity and the increasing of resistance in charge-discharge processes for the decreasing of cycle performance.NiCo2S4 nanosheets with three-dimensional structure is prepared on foam nickel by impored low temperature hydrothermal method with the design of reaction mold and applied to the anode materials of lithium ion batteries.Ni Co2S4 nanosheets will grow in four stages with the increase of reaction time where the nanosheets exhibit different structural stability so that the batteries show a different cycle performance.Electrochemical performance tests show that in the pure oxygen the battery has the discharge specific capacity of 10334 mAh/g under the current density of 100 mA/g while the less number of cycles.When under the larger current density of 1000 mA/g,the specific capacity of the discharge is reduced to 3611 mAh/g and the number of cycles increase to 50 times.Through the characterization of the materials before and after the charge-discharge,oxygen promote the phase transition and transformation of the crystal of SEI film which can increase specific capacity.The compared tests are carried out for lithium-ion batteries in the sealed environment and the model of Ni Co2S4 was established by computer software for analysing the band structure and density of states.The results show that in the sealed environment the batteries can realize the normal charge-discharge tests at high current density.The number of cycles is much higher than that in the pure oxygen while the charge-discharge capacity is opposite.And the physical characterization shows the effects oxygen to SEI film.The computer theory simulation analysis show that NiCo2S4 has the characteristics of conductor,which deepens the understanding of this material.Finally,Market analysis Ni Co2S4 which is respectively as a lithium air battery catalyst and lithium ion battery anode material is conducted.The results show that NiCo2S4 material is cheap and has high utilization rate of raw materials and broad market prospects in the field of secondary batteries.