Construction And Electrochemical Performance Of Self-supporting Lithium Sulfide Electrode Based On Bacterial Cellulose

Lithium sulfur battery(LSB)is a new type battery with great development prospect.However,the extremely low electronic conductivity of elemental sulfur,the lithium sulfide(Li₂S_x,4?x?8)is easily dissolved and diffused during charging and discharging,the volume change of sulfur positive electrode,leading to low specific capacity,poor cycling constancy and low coulombic efficiency of the battery,limiting the commercial use of LSB severely.In this paper,the purpose of research is to develop a new electrode to inhibit the dissolution of polysulfides and improve the application performance of lithium-sulfur batteries,and construct a reinforced concrete composite of Li₂S,carbon nanospheres and carbon nanofibers structure.Specific research contents and results include the following parts:(1)By hydrothermal method with a carbon nanosphere(CNS)hydrogel structure,can make the CNS of the coated electrode active material,after freeze drying,high temperature carbonization steps,such as the bacterial cellulose into carbon nanofibers(CNF),get Li₂S@CNS@CNS composite cathode material,and do the electrochemical performance test.The test results show that when its lithium sulfide loading is high,reaching 2.68mg cm^-2,the composite material shows a good electrochemical performance.With the current rate of 0.2C to carry out charging and discharging test,the initial specific capacity can get 733m Ah g^-1.After 600 cycles,it still has478m Ah g^-1discharge capacity,about 65.2%of the initial value.(2)By correlation method,Li₂S@PC@CNF freestanding composite anode material was been made.The results display that with the current rate of 0.2C to carry out charging and discharging test,the first specific capacity can arrive 377m Ah g^-1.And after 600 times,its specific capacity was only 235m Ah g^-1.(3)In order to further improve the performance of the battery,the bacterial cellulose aerogel was into CNF,which was used as a current collector and combined with the structure of Li₂S@CNS@CNF.With the electrochemical results,the discharge specific capacity of the first turn of the battery at 0.2C is about 1024m Ah g^-1,and after 600 cycles,it still contains the specific capacity of 576m Ah g^-1,the capacity and stability of the battery have been greatly enhanced.