Polyethylene Diaphragm Of Fluoride And Its Performance Study In Lithium-ion Battery

Lithium-ion battery, a kind of high performance second green battery, has been widely used in all kinds of portable electronic products and communication tools. Diaphragm material which is an important part of lithium-ion battery get increasing attention of researcher.Regarding of thermal stability, mechanical performance and heat resistance, polyolefin diaphragms are not be good enough so that they lead to unstability in lithium-ion battery performance, thus development of polyethylene membrane materials with better performance for the lithium-ion battery production is a challenge. In this research, polyethylene membrane is proposed to be fluorinated which could improve polyethylene diaphragm regarding its heat resistance, and the fluorinated polyethylene diaphragm was then applied to make lithium-ion battery, the effect of fluorinated polyethylene diaphragm on electrochemical performance of lithium-ion batteries was explored. Results of the research show that heat shrinkable performance of fluorinated polyethylene diaphragm is better, on the direction of TD, the heat shrinkage rate is 0 %, the heat shrinkage rate is reduced by 0.5 % on the direction of MD, improve the safety performance of lithium-ion batteries, results of nail experiments and thermal shock experiments can prove it.Although permeability and porosity of fluorinated polyethylene membrane have a certain degree of decline, but internal resistance and K valu of lithium-ion battery by using fluorinated polyethylene diaphragm change little,rate performance is better,can be use for requirements of the production.At the same time, H group of the polyethylene diaphragm was replaced by the F group in the process of fluorination, make the polarity of polyethylene diaphragm stronger, which enhance affinity with the polarity of the electrolyte ability. F group of Polyethylene diaphragm is easily forming coordination bond with the PVDF on the positive plate and CMC of negative piece, the van der Waals force between the molecules and the coordination bond make bonding foece increase between the diaphragm and pole piece, which reduce the thickness of the lithium-ion battery and promote the capacity of the lithium-ion battery.To further enhance the heat shrinkable performance of polyethylene membrane, the fluorinated polyethylene diaphragm is deeply researched in this paper. Deposition C,and Ti on one side of the fluorinated polyethylene diaphragm by magnetron sputtering method.At room temperature deposition C, Ti on the surface of fluorinated polyethylene membrane by 5 min, 10 min, 30 min. Results of Basic performance test show that thermal contraction performance of the diaphragm performance is further ascension, the thickness and surface density of the diaphragm have a certain degree of rise, but permeability and porosity was decline, especially permeability and porosity of deposition C fluorided decline largerly.With the increase of deposition time, C or Ti layer of C, Ti deposition fluorided polyvinyl membrane distribution is more homogeneous.C, Ti deposition fluorinated polyethylene membrane production sample amount is limited which can not be use for battery production, so make button battery taking the place of lithium-ion battery. Testing results of button batterys show that the g capacity efficiency and g capacity retention of button batterys which are made by C deposition fluorinated polyethylene membrane are short of the button batterys made by fluorided polyvinyl diaphragm, so C deposition fluorided polyvinyl diaphragm is failing. G capacity efficiency of button batterys producted by Ti deposition 30 min diaphragm is agreement with button batterys made by fluorinated polyethylene membrane, and g capacity retention is better. It shows that Ti deposition 30 min diaphragm is more successful.At the same time testing results showe that deposition layer on the surface of C, Ti deposition fluorided polyvinyl membrane can be embedded and taking off lithium-ion.