Preparation And Properties Of Lithium Ion Battery Separator Based On Zirconia Fibers And Cellulosic Fibers

Lithium-ion batteries exist in many electronic products used in life,and they support the operation of equipment by virtue of repeated charging and discharging behavior.As one of the important components of lithium-ion batteries,separators play an important role in the electrochemical performance and safety performance of batteries.At present,the commonly used separator of lithium ion battery is polyolefin material.Polyolefin comes from petrochemical oil,which is a non-renewable energy source,and has poor wettability,high temperature resistance and low safety when used as a diaphragm.Therefore,in this paper,zirconia fibers with stable chemical properties and strong heat resistance and green cellulosic fibers with high strength are used to prepare composite network for battery separator,and different additives are used to modify and optimize composite paper,and zirconia fiber/cellulose fiber composite paper is used as lithium ion battery separator.In principle,it is difficult for single zirconia fibers to make papers,but by introducing wood pulp fibers,a shaped composite network can be prepared as a diaphragm substrate.In this work,three different methods were used to improve the bonding ability of zirconia fibers and wood pulp fibers,and the two fibers were complementary to coordinate the shortcomings of each single fibers:（a）the traditional papermaking process was used to prepare composite paper by blending two kinds of fibers,and one side of the base paper was slightly dissolved by using the wood pulp fiber-derived additives（dispersion of wood pulp dissolved in sodium hydroxide/urea system）,and the lithium ion battery separator was constructed by ethanol regeneration;（b）the traditional papermaking process was used to prepare wood pulp base paper,zirconia fibers were added into the slurry as filler,and the separator of lithium ion battery was constructed by adding polyamide polyamine-epichlorohydrin in the wet end;（c）The zirconia fibers/wood pulp fibers composite paper was prepared by traditional papermaking technology,and the surface of composite paper was treated with carboxymethyl cellulose to construct lithium ion battery separator.The main conclusions are as follows:（a）When the amount of zirconia fibers（based on the absolute dry paper）is 40%of the composite paper,the fiber network is treated with fiber-derived additives,and the tensile index increases by about 50%.The porosity decreases from 38.71%to 35.00%,and the composite paper has little effect on the electrolyte absorption rate.After assembling the battery,the ion conductivity of the composite paper is 0.077 S·m^-1,which is about three times that of the polyolefin separator（Celgard 2325）,After 50 cycles at 0.5 C,the capacity retention rate reached about 81%.（b）With 1 g wood pulp fiber paper as raw material,when the content of zirconia fibers is 50%（based on wood pulp fiber）and the content of polyamide polyamine-epichlorohydrin is 3%,the composite paper can have higher porosity at higher strength.Compared with the original composite paper,the tensile index is increased by about 20%,and the ionic conductivity is as high as 0.068 S·m^-1,After 50 cycles at 0.5 C,the capacity retention rate reached about 97%.（c）With 1 g wood pulp fiber paper and 50%zirconia fibers（based on wood pulp fiber）as raw materials,the composite paper can have higher porosity at higher strength when the concentration of carboxymethyl cellulose solution is 2%.At this time,the tensile index of the paper sample is 51.56 N·m·g^-1 and the ionic conductivity is as high as 0.044S·m^-1,After 50 cycles at 0.5 C,the capacity retention rate reached about 75%.Three different kinds of composite papers all show good thermal stability and electrochemical properties.In this work,zirconia fibers and cellulosic fibers are used to prepare the composite network,and the structure and performance of the composite network are modified and improved by different methods,combined with the excellent performance of the two fibers,a composite that can give full play to the advantages of zirconia fiber and wood pulp fiber is constructed for the purpose of being suitable for lithium-ion batteries,and the application of zirconia fiber and wood pulp fiber in the battery field is preliminarily explored in order to build lithium-ion batteries that can be used in more fields and under more conditions.