Preparation And Modification Of Silicon-carbon Anode Binder And Lithium-rich Cathode

The rapid development of science and technology has brought convenience to life,but the challenges have become more serious.How to solve the energy problem is urgent.Lithium-ion batteries are widely used in portable electronic products due to their high energy density,good cycle performance,and environmental friendliness.Silicon anodes have a high theoretical specific capacity,which is more ten times than that of graphite anodes,and the storage of silicon is large in the earth.As an alternative to traditional graphite,the silicon materials are expected to be next generation of anode materials.However,silicon anodes have a huge volume expansion during charging and discharging,which causes a rapidly decay of the electrode capacity,limiting their commercial application.In this particle,the research of high-capacity silicon anode materials and lithium-rich cathode materials is taken as the starting points,meanwhile,the modification of their electrochemical performance has been conducted.For silicon anode materials,polyacrylamide is selected as the binder and its cross-linking modification is studied.The spinel-layered structure of lithium-rich cathode material is prepared,and its characterization and electrochemical performance are studied.（1）Compared with uncross-linked polyacrylamide（PAM）binder and traditional polyvinylidene fluoride（PVDF）,the cross-linked polyacrylamide（c-PAM）as the binder of silicon/carbon anode material was synthesized by simple solution polymerization method and had a three-dimensional network structure with enhanced mechanical strength and better thermal stability.The initial specific discharge capacity is 1252 m A h g^-1 at a charging/discharging current density of 100 m A g^-1.After 200 cycles,the discharge capacity of c-PAM electrode is still 622 m A h g^-1,effectively suppress the volume expansion of silicon particles and improve the electrochemical performance of silicon anodes.（2）The electrochemical performance of silicon/carbon anodes with different silicon content by using c-PAM as a binder has been conducted.The higher silicon content can effectively improve the initial specific capacity and the specific discharge capacity after cycling,but has a poor rate performance.（3）In order to improve the rate performance of silicon/carbon anodes,the polyacrylonitrile（PAN）was doped and acted together with c-PAM binder.The Si/C/PAN/c-PAM electrodes have a better spersion surface and adhesive property.When discharged at a current density of 1 A g^-1.The specific discharge capacity is 1058 m A h g^-1,which is higher than 650 m A h g^-1 of the undoped PAN electrodes（Si/C/c-PAM）and the capacity retention is as high as 60%after 200 cycles.（4）0.2Li Ni_0.5Mn_1.5O₄·0.8Li[Li_0.2Ni_0.2Mn_0.6]O₂ as a high-capacity lithium-rich cathodes was synthesized by co-precipitation and heated at high-temperature,and then the influence of different heatig temperatures on structure and electrochemical performance was studied.The results show that the sample of heating at 900℃（s900）has a higher specific discharge capacity.At a discharging rate of 0.1 C,the specific discharge capacity is as high as 276 m A h g^-1 after 60 cycles.