Preparation And Electrochemical Properties Of Anode Materials For Lithium Ion Batteries

Global energy changes are intensifying,and human society’s demand for clean energy is growing.The demand for electric vehicles,large-scale photovoltaic power generation and wind power storage has driven the rapid development of lithium-ion battery technology.The performance of existing lithium-ion batteries needs to be improved,and lithium-ion anode materials need further breakthroughs as the key material for battery technology iteration.On the other hand,people are constantly making new demands for a green and environmentally friendly living space.Industrial waste dyes and polysilicon by-product SiCl₄are a greater threat to a green and safe environment,and the topics of resource utilization of industrial waste and high value-added product development are also of contemporary significance.In this thesis,nitrogen and sulfur co-doped biomass carbon materials were prepared from industrial dye waste containing abundant nitrogen and sulfur sources and silicon tetrachloride as silicon source for lithium-ion battery anode.Through material characterization and electrochemical performance testing,the influencing factors of lithium storage of the materials were investigated and the performance optimization was carried out.The main research results are as follows.（1）Preparation of nitrogen-sulfur self-doped carbon materials and performance of lithium ion batteries.Industrial dye waste has a large potential environmental risk,and the bottom-up synthesis scheme for the preparation of lithium-ion battery anode materials is an effective solution for the resource utilization of dye waste,combined with the characteristics of dye molecular structure.Single industrial dye reactive yellow（FN-2R）waste was used as precursor for the preparation of nitrogen-sulfur co-doped carbon materials,N,S-GC-600,N,S-GC-700,N,S-GC-800,N,S-GC-900,under different temperature conditions.N,S-GC-700 has a maximum layer spacing of 0.422 nm and a high pyrrole nitrogen content,which provides more Li⁺adsorption sites and suitable layer spacing,and therefore has a high Li storage capacity.After electrochemical tests,the first charge/discharge specific capacity of N,S-GC-700 is 542.0/1244.1m Ah/g at 0.1 C and 449.7/449.2 m Ah/g for 100 cycles.（2）Preparation of ZnS/N,S-LGC and Performance of Lithium ion batteries.Dye wastes brought by textile industry are difficult to degrade completely and cause great environmental risks.Dye waste from cotton dyeing process in Xinjiang region exists with dyestuff,lignin and other materials with abundant nitrogen,sulfur and carbon sources.Zn（NO₃）₂was introduced as a graphitic nitrogen inhibitor of the material,and ZnS loaded on nitrogen-sulfur co-doped carbon material（ZnS/N,S-LGC）was prepared by carbon bath method.The XRD data showed that ZnS was also synthesized when the nitrogen-sulfur co-doped carbon material was achieved by ZnS loading on the nitrogen-sulfur co-doped carbon material（ZnS/N,S-LGC）.The XPS data showed that the pyrrole nitrogen content increased by 12.4%and the graphitized nitrogen decreased by 6.7%after the addition of Zn（NO₃）₂.After electrochemical tests,the first charge/discharge specific capacities of ZnS/N,S-LGC materials were660.3/1117.5 m Ah/g at 0.1 C,respectively,with a Coulomb efficiency of 59.1%.After 100 cycles,the charge/discharge capacities of ZnS/N,S-LGC were 527.6/529.5 m Ah/g,respectively,and the Coulomb efficiencies were greater than 99%.（3）Synthesis of Silicon doped carbon materials and performance of Lithium ion batteriesIn Xinjiang,where the photovoltaic industry is booming,the environmental risk of SiCl₄,an industrial by-product of polysilicon production,has increased.The multi-path high value-added utilization of SiCl₄is of great significance to the regional industrial development.SiCl₄as a silicon source and polyhydroxylated biomass glucose as a carbon source were used to prepare precursors（Si O-GLS）by combining the reaction properties of SiCl₄with base compounds and improving the dispersion of silicon by combining the hydroxyl groups of glucose skeleton with spatial anisotropy,followed by roasting treatment at 900℃to prepare Si O-C-900.After electrochemical tests,Si O-C-900 maintained a capacity of 406 m Ah/g after 100cycles at 0.1 C,and its specific capacity was 1.87 times higher than that of GLS-900.The material synthesis temperature and the ratio of precursor silicon to carbon were also initially investigated,and the lithium storage capacity of the material could be increased to more than 530 m Ah/g after optimization of the synthesis process.