The reason why dry separators are less used in the ternary power battery market is thickness, because thinner separators can reserve more space for the battery to accommodate active materials, thereby increasing energy density. After the dry-process separator is thinned, if the strength is reduced, there will be a safety hazard in the lithium battery.
However, with the improvement of technology and technology, dry-process diaphragms are gradually transitioning to a thinner trend. The dry-process diaphragm used in power batteries was 32 μm initially, and then gradually evolved into 25 μm, 24 μm, and 22 μm. At this stage, the mainstream model is 20 μm.
The unanimous opinion of the industry is that in 2019, the trend of dry-process diaphragms will be dominated by products below 20 μm. With the large-scale mature application of 16 μm dry-process single-drawing (equal to the current wet process + coating thickness), coupled with its core cost advantage (The cost is half of the wet diaphragm), which is attractive enough for power battery companies.
However, the use of thinner diaphragms not only tests the technical strength and mass production capabilities of diaphragm companies, but also tests the technical research and development and engineering strength of power battery companies.
A senior executive of a diaphragm company said that the dry-process diaphragm is composed of a crystalline region and an amorphous region and is fibrous. This kind of fibrous material will experience stress reduction in the electrolyte, and the stress reduction will eventually cause the diaphragm to wrinkle. This problem is not very obvious when the separator is thicker, such as more than 20 μm, but it will soon appear when it is thinner.Also read:10kwh lithium battery 48v
"Previously, no power battery company has used a 16μm single-layer dry diaphragm. Some hidden problems will start to enlarge due to the thinning of the diaphragm, and the wrinkling of the diaphragm has become the most troublesome problem for battery companies using a 16μm single-layer film." The above mentioned high-level said.
At present, a small number of separator companies in China have large-scale mass production capabilities for 16μm separator products, and have entered the verification system of first-line power battery companies with R&D capabilities.
The "fueling the flames" of cost reduction and high pressure
In the traditional impression, dry-process separators are suitable for lithium iron phosphate batteries, and wet-process separators are suitable for ternary batteries. In fact, there is no strict technical route distinction between the two, such as BAK battery, Funeng Technology and other ternary battery companies. The dry-process diaphragm has been used all the time; the wet-process diaphragm is used in some lithium iron phosphate batteries such as BYD and Guoxuan Hi-Tech.
Each power battery company has different technical processes and uses different material systems, which are mainly related to the company's technical system and usage habits. Since the new energy vehicle industry belongs to the policy market, subsidies have been reduced to withdrawn. Under the requirement of battery cost reduction, it is not impossible for battery enterprises to shift their material system. "A chief engineer of a power battery company explained.
In the face of the sharp decline in subsidy policies, car companies have shifted from blindly pursuing energy density to get subsidies, and started to be fully market-oriented. Based on the comprehensive consideration of cost and performance, power battery companies are also actively cooperating with car companies. .
In addition to converting some wet-process diaphragms to dry-process diaphragms to reduce costs, localization substitution has also become an important idea for power battery companies to reduce costs.see more:600ah lifepo4 battery
Gaogong Lithium Battery has noticed that the dry-process diaphragms used by domestic ternary power battery companies are mainly imported. In order to meet the cost reduction needs of domestic new energy vehicles, the dry-process diaphragms of power batteries are gradually turning to domestic production.
On January 28, Funeng Technology and Xingyuan Materials signed a cooperation agreement. The two parties agreed that the supply guarantee demand for lithium battery separator products in 2019 will be no less than 40 million square meters, and the total annual purchase amount is allowed to be adjusted within 20%. If the guaranteed supply of the agreement is fully implemented, the estimated contract value is about 102 million yuan.
In addition, the increase in demand for dry-process diaphragms this year also comes from the heating up of the energy storage market. At the same time, the demand for lithium iron phosphate batteries in subdivisions such as A00-class models, electric logistics vehicles, 48V micro-hybrid systems, electric online car-hailing, and electric forklifts has increased significantly, which has also driven the starting quantity of dry-process separators.
Wang Xiangdong, CTO of Zhongke Science and Technology, said that thanks to the company's early rooting and cultivation of the energy storage market, the heating up of the domestic and foreign energy storage markets this year has brought considerable incremental benefits to the company's dry-process double-drawn diaphragm, and this part of the market's Both the repayment and the account period are better than those in the power field.
It is worth noting that domestic dry-process diaphragm faucets are still maintaining the pace of expansion of dry-process production capacity while adding new wet-process capacity. The expansion of production capacity of dry-process diaphragm faucets and large-scale manufacturing are bound to drive further reductions in product costs.Also read:lifepo4 battery 500ah
In 2018, Xingyuan Materials used the technical experience accumulated in the field of lithium-ion battery dry-process separators for many years to plan and build 8 new-generation lithium-ion battery dry-process separator production lines. After the project is put into production, it will form an annual production capacity of 400 million square meters of dry-process separators for lithium-ion batteries. According to data from GGII, China's lithium battery separator shipments in 2018 were 2.02 billion square meters, a year-on-year increase of 39.7%. Among them, the shipment of wet-process diaphragms was 1.31 billion square meters, a year-on-year increase of 66.4%; the dry-process diaphragm shipments were 706 million square meters, a year-on-year increase of 7.8%, and the growth rate was much lower than that of wet methods.
The launch of the new subsidy policy in 2019, the "cut in half" style of decline and the increased emphasis on product safety performance have forced the new energy vehicle and power battery industry chain to return to market-oriented thinking. As a result, dry-process diaphragms with low cost, excellent performance, and thinner thickness are also expected to usher in a "counterattack" in the market.
Gaogong Lithium Battery understands that the current dry-process single-pulled separator used in power batteries on a large scale is 20 μm, and 18 μm and 16 μm are already on the road to large-scale application. In 2018, the price of dry-process single-strand film fell by more than 40% year-on-year. This year, the average price of some low-end dry-process single-strand film has fallen below 1 yuan/square meter (wet-process diaphragm is 1.8-2 yuan/square meter).
"Currently, the mainstream of ternary power batteries adopts wet-coated separators with a thickness of 12+4 (12 μm base film + 4 μm coating), and the trend of dry-process single pull this year is less than 20 μm. Some power battery companies have begun to cut into 18 μm, The use of 16μm products." The above-mentioned person said that once 16μm products are used on a large scale, with the cost advantage, the dry-process single-pull diaphragm will erode the wet-process diaphragm market to a certain extent.