Preparation And Performance Characterization Of Melt-blown Non-woven Fabric For Lithium-ion Battery

Lithium-ion battery is popular in our daily life,but because traditional diaphragm of lithium-ion battery exists some shortcomings of low porosity and absorption,the poor thermal stability,it is unable to fully meet the requirements of lithium-ion battery's fast charge and discharge.How to design a good performance of diaphragm for lithium-ion battery becomes an important issue of this field.On the basis of studying on this issue,this paper took polypropylene melt-blown non-woven fabric which had advantages of higher porosity,mipor and winding structure,high absorption,small pore and small size shrinkage as a diaphragm for lithium-ion battery.At first,this paper took polypropylene melt-blown non-woven fabric as the research object.Testing the physical property and electrochemical property to explore the adhesive way,lamination and composited with nano SiO₂ particles of polypropylene melt-blown non-woven fabric which had an influence on the diaphragm for lithium-ion battery.Secondly,Testing and analyzing synthetically the physical and electrochemical properties of lithium-ion battery separators which were prepared by different process.Studying the microstructure of the separators and comparing the properties of the separators to achieve the optimized process in the prepared process.And providing a theoretical basis and experimental basis for the development and application of polypropylene melt-blown non-woven fabric for lithium-ion battery separator.the main conclusions are as follows:?1?Compared with the hot-rolled samples at room temperature and spot-bonded samples,the hot-rolled samples has higher porosity,higher absorption and ionic conductivity.?2?Discharge specific capacities of battery 1,battery 2 and battery 3 which are respectively installed by hot-rolled samples at room temperature,hot-rolled samples and spot-bonded samples are about 110 mAh/g,130 mAh/g and 115 mAh/g at 0.2 C.Discharge specific capacities of batteries which are installed by above three kind samples are 0 mAh/g,when the current increase to 2.0 C.Although the process of these polypropylene melt-blown non-woven fabrics whichwithstand the current is only 1 C,the battery which is installed by hot-rolled samples has better electrical property.?3?With stacked layers of polypropylene melt-blown non-woven fabric increasing,its thickness,the porosity,absorption and internal resistance increase,the pore size decreases and the distribution of the pore size becomes more uniform.?4?With stacked layers of polypropylene melt-blown non-woven fabric increasing,the first charge/discharge specific capacities and cycle capacities decrease.When the number of stacked layer is 5,discharge specific capacity decreases to 82 mAh/g.With the number of stacked layer increasing,high rate discharge of lithium-ion batteries increase on different degrees.When the number of stacked layers are respectively 1,2,3,4 and 5,the discharge specific capacities of lithium-ion batteries which consist of them are respectively 0.23 mAh/g ? 1.60 m Ah/g ? 60mAh/g ? 63 mAh/g and 43 mAh/g.It shows that: With stacked layers of polypropylene melt-blown non-woven fabric increasing,although high rate discharges of lithium-ion batteries increase,cycle capacities decrease.?5?Coating nano SiO₂ coating solution on the unilateral side of polypropylene melt-blown non-woven fabric which can effectively improve the pore size,the distribution of pore size and thermal stability of polypropylene melt-blown non-woven fabric.When the concentration of SiO₂ coating solution reaches 15%,the composite diaphragm of lithium-ion battery has not changed under the condition of 150? for 0.5 h.?6?Coating nano SiO₂ coating solution on the unilateral side of polypropylene melt-blown non-woven fabric which decreases the resistance of polypropylene melt-blown non-woven fabric,decreasing from 3.71 W to 2.96 W.Testing the electrical performance,the first discharge specific capacity of lithium-ion batteries which are made of polypropylene melt-blown non-woven fabric or composite diaphragm of lithium-ion battery are respectively 105 mAh/g,120 mAh/g,123mAh/g,135 m Ah/g and 99 mAh/g at 5 C.Testing the rate performance,the discharge specific capacity of lithium-ion battery which is made of polypropylene melt-blown non-woven fabric is0 mAh/g at 2 C,the discharge specific capacities of lithium-ion batteries which are made of 5%coated sample,10% coated sample,15% coated sample and 20% coated sample are respectively68 mAh/g,83 mAh/g,89 mAh/g and 36 mAh/g at 5 C.It Shows that the rate performance of lithium-ion battery which is made of composite diaphragm is better.?7?Testing and analyzing synthetically the physical and electrochemical properties of lithium-ion battery separators which were prepared by different process,it shows that filling inorganic particles into polypropylene melt-blown non-woven fabric which not only can improve the pore size,distribution of pore size and thermal stability of polypropylene melt-blown non-woven fabric,and also can improve the electrical performance of lithium-ion battery.But for its high surface density and high thickness,it needs to reduce the surface density and thickness and let it get thinner and lighter,it usually is 25 ?m or 40 ?m.With regard to the problem of large average pore size and uneven distribution,it needs to adjust the relevant parameters of the melt-blown process,the polypropylene melt-blown nonwoven fabric is homogenized.At the same time,in the coating process,it needs to adjust the coating liquid configuration to improve the coating process and it is for uniform coating to achieve the uniform distribution and its average pore size is up to 1 ?m.