Synthesis Of Metal Sulfide/Carbon Composites By Sulfide Papermaking Red Liquor And Their Electrochemical Properties

In this thesis,we studied the basic properties of lignin in papermaking red liquor were studied,and the lignin in papermaking red liquor was purified and used as carbon source and biological template to synthesis carbon anode material,cuprous sulfide/carbon anode material,ferrous sulfide/iron/carbon,sodium iron sulfide/carbon anode material.And we studied the effects of different synthesis conditions and synthesis methods on the composition,structure and electrochemical properties ofthe composite.The definite research content is as follows:Using the papermaking red liquor as the carbon source,the carbon anode material was synthesized by purifying and hydrothermal treating the papermaking red liquor with different acids,and explored the structure and electrochemical properties of the carbon anode material simultaneously.The results showed that the organic acid（citric acid）and inorganic acid（sulfuric acid）had little effect on its electrochemical properties in the synthesis of the carbon anode material;while the hydrothermal treatment had a great influence on its structure.The papermaking red liquid was treated with citric acid and subjected to hydrothermal reaction,and after in situ carbon thermal reduction at800℃,a carbon anode with the best electrochemical performance could be obtained.At the current density of 0.5 A g^-1,the first discharge specific capacity reached 297.13 mAh g^-1,and after 150 cycles,the specific discharge capacity kept at 264.01 mAh g^-1,and the Coulombic efficiency was almost 100%.Since the hydrothermal treatment can form a spherical particle structure with a uniform size and a large specific surface area,the carbon material can provide a good ion diffusion channel for lithium ions during charging and discharging,which is beneficial to the storage and transportation of lithium ions,and shortens the transportation distance of lithium ions and electrons,accelerates the transportation rate and improves its electrochemical performance.The Cu_xS/C composite anode material was synthesized by using papermaking red liquor as bio-mould and carbon source.The effects of treatment with citric acid on red liquor and hydrothermal treatment on the structure and electrochemical properties of the prepared material were explored.The results showed that the Cu_xS/C composites synthesized by calcination at 600°C had the best electrochemical performance after treatment with citric acid and hydrothermal reaction.The first discharge was 746.76mAh g^-11 at a current density of 1 A g^-1,and the specific discharge capacity was 386.57mAh g^-11 after 100 cycles,and the Coulombic efficiency was close to 100%.The excellent electrochemical performance of the anode is due to the fact that lignin acts as a template,which makes Cu_xS to form a stable sheet-like space structure,increases the specific surface area of the material,and forms a carbon coating on Cu_xS,which improves the conductivity of the anode.Futhermore,the stable space structure alleviates the effect of Cu_xS due to volume expansion during charging and discharging.FeSNs-Fe/HCMS composite anode materials were synthesized by using papermaking red liquor as biological template and carbon source.The effects of different additions of papermaking red liquor on the structure and properties of the materials under hydrothermal conditions were investigated.The results showed that when 40 ml of papermaking red liquor was added and calcined at 700℃,the synthetic material has uniform nano-FeS spherical particles and flaky mesoporous hard carbon structure,and its specific surface area is high,which facilitates lithium ion intercalation/deintercalation and buffers the damage of the material structure due to volume expansion,which enables it to have excellent electrochemical performance.At the current density of 1A g^-1,the first discharge specific capacity reached 1182 mAh g^-1,and the specific discharge capacity was 881 mAh g^-11 after 100 cycles.We prepared the NaFeS₂/C anode by simple precipitation method and hydrothermal method using ferric oxalate and sodium sulphide as raw materials.And we also modified the NaFeS₂ by using papermaking red liquor as biological template and carbon source.Among them,NaFeS₂ is the by-product of FeS₂ as anode for sodium ion batteries.Futhermore,the effects of different experimental conditions on the phase and electrochemical properties of the anode materials were investigated,and the electrode reaction mechanism of NaFeS₂ as the anode for sodium ion batteries was also studied.The result showed that the NaFeS₂/C anode composite anode materials using the treated papermaking red liquor delivered the first discharging capacity of 864.82 mAh g^-11 at the current density of 0.2 A g^-1,far exceed than the other samples.Papermaking red liquor used as template and carbon resource will provide excellent space structure which is in favor of electrochemical properties.In addition,the result showed that NaFeS₂ used as anode for sodium ion batteries will not lead to the side reaction.