Research On Carbon And Membrane Materials Of Lignocellulose Based On Hydrated ZnCl₂ System

Wood material is one of the most abundant renewable resources in nature.At present,the development and utilization of wood materials has penetrated into the micro field of wood materials,such as cellulose,the application of individual components of lignin has been relatively mature.Cellulose as one of the main components of woody materials,the difficulty of its dissolution largely limits the development and utilization of cellulosic materials.To address the dissolution problem of cellulose,a series of cellulolytic systems have been developed,such as alkali urea element system and ionic liquid solution system.Compared to the other dissolved systems,the dissolution system of high concentration salt solution has the advantages of simple operation,low cost,safety,no pollution and recycling.Based on the above background,the cellulose extraction and utilization of waste wood with zinc chloride as cellulose dissolution system,we developed two products of cellulose carbon material and cellulose membrane material under this system,and made an in-depth performance test characterization and mechanism research.The specific study results are as follows:（1）Natural cellulose was extracted from the discarded wood board to explore the optimal conditions of the hydrate zinc chloride-cellulose dissolution system.The optimal water salt concentration of zinc chloride was 3-3.5 crystalline water,and 5 wt%of cellulose was completely dissolved in 3.2H₂O·Zn Cl₂ solution at 90℃.Hydrated zinc chloride-cellulose solution has a strong viscosity,which is positively correlated with the cellulose concentration,and negatively correlated with the temperature of the solution.When the cellulose concentration is 5 wt%,the solution at room temperature（25℃）will be extremely viscosity,presenting a solid transparent gel substance.（2）By utilizing the strong crystallinity destruction effect of zinc chloride hydrate on cellulose solution,a hard carbon material was prepared by using hydrothermal pre-carbonization and high-temperature secondary carbonization.Zinc chloride hydrate acts as a dehydrating agent for cellulose only during the pre-carbonization stage.The hard carbon material was characterized and analyzed by a series of testing methods such as scanning electron microscopy and transmission electron microscopy.The effects of hydrothermal temperature,secondary carbonization temperature,and melamine addition on hard carbon were investigated.It was found that the graphitization degree of the hard carbon material prepared by carbonization of cellulose treated with zinc chloride hydrate was significantly reduced compared to that of untreated carbon material.The higher the hydrothermal pre-carbonization temperature,the more complete the decomposition of cellulose.The treatment with zinc chloride hydrate can make the carbonization decomposition of cellulose more complete and completely destroy the crystalline structure between cellulose molecules.The higher the secondary carbonization temperature,the higher the graphitization degree of the hard carbon material.The addition of melamine can inhibit the graphitization degree of hard carbon material to a certain extent and provide nitrogen source for carbon material.（3）In order to explore the application value of cellulose hard carbon materials,lithium-ion batteries were prepared using hard carbon materials as negative electrode materials.The performance of the battery was characterized by electrochemical performance analysis.The results showed that HC-X（Hard Carbon-X）electrode materials prepared under different conditions all showed a specific capacity higher than that of theoretical graphite negative electrode materials(372.0 m Ah g^-1 at a current density of 0.1 A/g).Among them,HC-600M05negative electrode material had a specific capacity of 432.56 m Ah g^-1 at a current density of 0.1A/g,and its specific capacity did not decay after 200 cycles,showing extremely high cycle stability.This indicates that this hard carbon material has high performance advantages in energy storage and has certain utilization and reference value in the field of smart home energy storage.At the same time,by analyzing the pore size distribution and specific surface area of cellulose hard carbon materials,the application prospects of modified adsorbent materials in the home field were prospected.（4）A cellulose membrane was prepared by phase conversion,and the membrane was characterized by SEM,FTIR,and the effect of treatment conditions on the properties of cellulose membrane was studied.The tensile strength of the film is about 35 m Pa,which has the characteristics of hydrophilic,high transparency,compact and flexible tensile strength.In addition,when a certain amount of melamine is added to the membrane casting,the transparency of the membrane will be reduced,but the light transmittance is unchanged.According to the above characteristics,the application of cellulose film is discussed,modeling a lamp using the membrane as the lampshade material,which shows that the cellulose film prepared in this study has application potential in packaging materials and home materials.