Process Study Of Lithium-sulfur Batter On Cathode Material Synthesis And Structural Design

The cathode material of lithium-sulfur battery has advantages of low cost,environmental friendliness and high energy density,which allow them become one of the most popular cathode materials for power batteries.This article aims at the application of industrial expanded graphite in lithium-sulfur battery cathode material,its feasibility and the suitable preparation process of expanded graphite/sulfur cathode material are studied and discussed.On this basis,a process route for fabricating a metal film coating structure for a positive electrode of a lithium-sulfur battery using a magnetron sputtering process is proposed.The effects of different metal film cladding structures on discharge specific capacity and cycle retention rate are compared and discussed.Under the conditions of this study,the main findings are as follows.(1)Expanded graphite(EG)can be used as sulfur-bearing material for lithium-sulfur batteries.Expanded graphite/sulfur(EG/S)composites have a good skeleton structure and good electrochemical performance.The initial specific capacity is 1451 m Ah/g at the current density of 100 m A/g.After 50 cycles,the specific capacity is 646 m Ah/g.Its electrochemical performance is superior to conventional acetylene black/sulfur composite cathode materials.(2)A suitable preparation process for expanded graphite/sulfur(EG/S)is:Lithium hydroxide is used to activate the expanded graphite and CS₂ is used as a solvent to chemically melt sulfur.Sulfur is melted under the negative pressure at 200°C.Finally,sulfur is burned at300°C and returned at 90°C.The prepared EG/S composite cathode material has a specific capacitance of 1338 m Ah/g at a current density of 200 m A/g.After 100 cycles,the specific capacity is 522 m Ah/g at 1C rate.(3)The EG/S positive pole piece with a titanium metal film cladding structure has significantly improved the cycle retention rate.The discharge specific capacity after circulated at1 C rate 100 times is 675 m Ah/g,the performance increased by about 153 m Ah/g,the cycle retention rate is 89.2%,and the performance increased by about 8.7%.