Years of research and development have not yet been applied on a large scale. Does the non-woven lithium battery separator have development prospects?

It has been 7 years since the product was developed, and the beautiful non-woven fabric lithium battery diaphragm has not yet been commercialized on a large scale. Why? The lithium battery diaphragm matrix materials mainly include polyolefin materials and non-woven fabric materials. Polyolefin separators have excellent mechanical properties, chemical stability and relatively cheap characteristics, but polypropylene/polyethylene materials have limited temperature resistance, and the appropriate working temperature is lower than 150℃; in order to further increase the specific energy of lithium batteries, it needs to be reduced The thickness of the film reduces the liquid absorption rate of the two-dimensional pore structure diaphragm, which again affects the safety of the battery. Therefore, in order to meet the high safety and high-power fast charge and discharge requirements of power lithium batteries, non-woven materials with three-dimensional pore structures have become a research hotspot. Non-woven diaphragm substrates usually use polyethylene terephthalate (PET), polyimide (PI), aramid, etc., which have obvious advantages in heat resistance. At the same time, due to its three-dimensional pore structure, it can effectively avoid the short-circuit phenomenon caused by acupuncture and improve the liquid retention rate. Domestic and foreign companies have carried out a lot of research and development work on non-woven diaphragms. Ø In August 2010, DuPont announced the development of a polyimide diaphragm. In 2010, Shougang Corporation and the Institute of Physics and Chemistry of the Chinese Academy of Sciences jointly established the first spray thinning technology, using the polyimide nanofiber diaphragm technology developed by the Wu Dayong technical team of the Institute of Physics and Chemistry Implement industrialization. In January 2012, the 300,000 square meter/year pilot line was completed and put into operation. In March 2011, Jiangxi Xiancai announced a plan to build a polyimide diaphragm production base with an annual output of 200 million square meters. In July 2014, the semi-annual report of Shenzhen Huicheng, the parent company of Jiangxi Xianma, showed that the progress of the polyimide diaphragm production line equipment installation project was 8.20%, and the cumulative actual investment amount was 5.91 million yuan. In February 2012, Japan Hirose Paper Exhibited a lithium battery separator made of PVA (polyvinyl alcohol) nanofibers spun with polyolefin non-woven fabrics. In 2013, Zhejiang Dadongnan Co., Ltd. signed an agreement with the Institute of Chemistry, Chinese Academy of Sciences for joint research and development Electrospinning was used to prepare lithium battery nanofiber diaphragms, and pilot production was realized in 2015. Evonik Degussa coated ceramic materials on PET non-woven fabrics to make lithium battery diaphragms. Ø In 2016 CIBF, Freudenberg demonstrated the use of ceramic coating PET non-woven membrane battery. Freudenberg stated that because the product can be produced at a higher temperature, the drying process and the electrolyte impregnation process are accelerated, thereby shortening the battery cell preparation process. Ø Japan Special Tokai Paper claims to have developed a cellulose separator material technology Ø Dreamweaver of the United States developed a non-woven membrane based on a mixture of nano- and micro-cellulose Ø Porous Power Technology developed a PET membrane filled with PVDF and Al2O3 Ø Japan's Oji Paper formed a wet-laid non-woven fabric substrate through a papermaking method. Coating PU, PET or PTFE resin on the substrateØ Mitsubishi Paper and Tokyo Institute of Technology have developed PET non-woven membrane technologyØ Ningbo Atmic Lithium Technology Co., Ltd. has launched a nanofiber separator with closed-cell characteristicsØ The joint venture between Toray and Tonen Chemical has developed a microporous aramid film with aramid resin as the substrate with excellent heat resistance and dimensional stability. Ø Japan’s Teijin announced the development in February 2012 Aramid fiber separators used in polymer laminated lithium-ion batteries. All of the above-mentioned non-woven lithium battery separators that look very good, they have one thing in common, that is, they have not achieved large-scale commercial applications. ASIACHEM believes that the main reason is price. The cost of non-woven membranes is often more than 10 yuan/square meter, and the price of medium and high-grade membranes after coating at this stage is about 5-6 yuan. Under the industry trend of more and more stringent lithium battery cost control, non-woven diaphragms lack price competitiveness. In addition, the following factors affect the popularization and application of non-woven diaphragms. 1. Non-woven diaphragms generally have low tensile strength and are difficult to apply to high-speed winding processes. The lamination process has relatively low requirements for the tensile strength of the diaphragm, and the non-woven diaphragm is more suitable for the lamination process. 2. The pore size of the non-woven diaphragm is too large, and the larger pore size brings excellent rate performance, but at the same time it will also cause the battery self-discharge to be too large, and have a potential impact on high temperature and storage performance. 3. The application of non-woven diaphragms requires changes in the existing lithium battery production process, and the diaphragm cutting, baking temperature, and liquid injection volume need to be adjusted. So, does the non-woven lithium battery separator have no prospects for development? ASIACHEM believes that it is also not the case. The reasons are as follows: 1. Large-scale power lithium battery with ternary cathode material is an important development trend of new energy vehicle power source, and its safety is of particular concern. In the large-scale ternary power lithium battery produced by the laminated process, the non-woven diaphragm has advantages over the polyolefin diaphragm in terms of safety, rate performance and service life. With the development of the power lithium battery industry in the future, the performance of the diaphragm will be further improved, and non-woven diaphragms can occupy a place. 2. With the increase in output, the cost of non-woven diaphragms has room to drop.