| Compared with other batteries, lithium-ion batteries have those advantages: high energy,capable of second charge and discharge, long life, high voltage, low self-discharge, etc. Nowadays,lithium-ion battery has been widely used in mobile phones, mobile computers and other mobile electronic devices. The shortcomings—lyophilic poor and can’t tolerate high temperature of the currently used polyolefin membrane restrict the further development of lithium-ion batteries.In order to improve the pro liquid performance of lithium-ion battery separator, this paper puts forward using Tencel fiber as raw material, combined with the flexibility to choose non-woven materials, the design structure, etc., as well as a wet papermaking process flexibility and other advantages forming a uniform, non-woven fabric prepared lithium-ion battery separator.Firstly beating process on Tencel fibrillation effect, determine the appropriate fibrillation treatment process.The key issue about non-woven wet-type lithium-ion battery separator is how to control the thickness, while meeting its pore size and mechanical strength requirements. Pure Tencel nonwoven is poor in mechanical strength, especially its low wet strength. Therefore, this paper will discuss from the perspective of the lithium ion battery separator Effects Tencel nonwoven fabric weight, and further research is mixed PET fiber Tencel and improved hot rolling effect.In addition, this paper studied how to improve the security of the separator after coating with the separator obturator effect at high temperatures. Finally, this paper tested the separator sample cell performance and evaluated the performance of the battery. The conclusions are as follows:（1） beating can achieve Tencel fiber fibrillation. With the beating time increases, the fiber pulp beating degree continues to rise, to achieve the best value in 120 min 72 ° RS. Fiber qualityanalysis showed that with the beating time increases, the number of fiber increased significantly,average fiber thickness decreases trend overall. After the beating, the ratio of the bending fibers and fines increased significantly.（2）To make different processing time beating Tencel fibers into nonwoven fabric by wet method. With the growth of beating time, Tencel nonwoven fabric tensile strength increases, the elongation at break decreases. After 150 min treatment, the Tencel fiber nonwoven fabric with best mechanical properties can be achieved. And its tensile breaking strength is 2.15 N. Those treated for 120 min is second to it. And it is 2.02 N. The thickness of Tencel nonwoven fabric increases with increase processing time and gradually reduced. 40 g / m2 Tencel wet nonwoven minimum thickness can reach 159.9um.（3） When the non-woven fabric Tencel pure weight is 10g/m2 and 5g/m2, the thickness of each is 38.4um and 25.2um, basically meet the lithium-ion battery separator thickness requirements. Pure Tencel nonwoven of 5g/m2 is of uniformity, the maximum aperture is up to638.16 um. The diameter of those pure Tencel nonwoven fabric lies 10g/m2 and above can reach about 4.00 um. It is still a little bit far from the required battery separator distance, but it can be treated in a subsequent coating aperture meet the requirements. Liquid absorbing performance and liquid retention performance of the nonwoven fabric Tencel pure is good. Actually it is much better than the commercial PE membrane. However, the wet strength of this material is poor.Improvement is needed.（4） In order to improve the wet-strength of the material. PET fiber is mixed in fiber Tencel,and different proportions of Tencel / PET non-woven fabric thickness, strength and aspiration and other performance have been tested. We found that with the increase in the PET non-woven fiber content, which has increased the thickness, material strength with increasing PET content increased first and then decreased trend. Containing 25% PET mixed nonwoven maximum strength as 2.72N; mix containing 50% PET nonwoven fabric strength is 2.18 N, it is better than pure Tencel woven fabric. Tencel / PET non-woven and non-woven fabric Tencel pure water absorption enhancement compared to liquid retaining performance deteriorated. After subsequent hot rolling PET fiber can provide more entangled web, the higher the content of the more favorable subsequent hot rolling process and therefore selected containing 50% PET mixed nonwoven follow-up study.（5） After hot-rolling process, non-woven fabric of PET fibers melted and deformed. Affected by temperature and pressure Tencel fiber also occurred in some deformation. Due to the effect of hot-rolled, the cloth surface also became smoother. The gap between the fibers became smaller and the non-woven fabric density increases the structure also became closer. In addition, after the hot-rolling, the thickness of non-woven reduced, pore size decreased, the aspiration rate decreased,the intensity increased. When the hot-rolling condition is 180 ℃, 20 s, 2MP, the nonwoven fabric thickness is 24.1um, a porosity of 37.6%, strength 4.12 N, an average pore size of 1.49 um. Under such conditions, Nonwoven fabric gets the best overall performance.（6） Two coatings made of Al2O3 particles and PE powder can reduce pore size. After coating,both commercial battery separator and hot-rolled Tencel fabric/ PET non-woven fabric decreased.Average pore diameter of commercial battery separator decreased from 3.10 um to 0.17 um and0.30 um after coating. Hot-rolled Tencel fabric/ PET non-woven fabric decreased from 1.49 aperture down to 0.13 um and 0.23 um after coating. But the coating porosity membrane declined.The made Diaphragm is pretty good and is with low thermal shrinkage. PE powder in the coating ensured the obturator temperature properties of diaphragm at 120 ℃. After the closed-cell,separator shape does not change significantly. Observed by electron microscopy, PE powder was dissolved after the membrane surface completely covered, which helps to improve the safety performance of the battery. After coating, the hydrophilic membrane increase and the contact with electrolyte became better.（7） Because the lithium-ion batteries assembled by the four kinds of the diaphragm prepared in this paper have performed 50 cycles at 1C charge-discharge condition, its capacity retention rates were 84.4%, 84.2%, 84.5% and 84.0%, close to the commercial battery separator. During the battery rate performance tests, the capacity retention of the five kinds of membrane were 34.2%,34.0%, 27.4%, 24.3% and 23.4%. The performance of all the four membrane prepared in the experiment was slightly better than the commercial battery separator.In summary, Tencel / PET non-woven fabric membrane has excellent performance, and it is expected to become an important supplement to the commercial separator market. |
PDF Full Text Request