In-depth research report on lithium battery separator

1. Basic overview of lithium battery separator
2. Market scale of lithium battery separator
3. The core manufacturers of lithium battery separator
4. Summary

The main materials of lithium-ion batteries include positive electrode materials, negative electrode materials, electrolytes and separators and other components. Among them, the production process of battery separator has high technical requirements and is considered to be the most valuable industry in the lithium-ion battery industry chain.

1. Basic overview of lithium battery separator

During the electrolysis reaction of the lithium battery, the battery separator can be used to separate the positive electrode and the negative electrode to prevent the occurrence of short circuit, while allowing the free passage of electrolyte ions. Electrolyte plays a vital role in battery, and lots of competitive electrolyte manufacturers come out. There is a list of top 10 battery electrolyte companies in China for you to get more relevant knowledge.

The battery separator is immersed in the electrolyte, and there are a large number of micropores on the surface that allow lithium ions to pass through. The material, number and thickness of the micropores will affect the speed of lithium ions passing through the battery separator, which in turn affects the discharge rate, cycle life and other performance of the battery.

The battery separator itself is not conductive, but the battery separator has micropores, which can absorb the electrolyte. Lithium ions pass through the microporous  battery separator from the anode to the cathode for the charging process, and from the cathode to the anode for the discharge process.

The cost of the battery separator accounts for about 10%-20% of the cost of lithium-ion batteries, and the gross profit rate can reach 50%-60%, which is the product with the highest gross profit rate among the four major materials.

The battery separator has good mechanical properties, chemical stability and high temperature self-closing performance, which can improve the comprehensive performance of lithium ion batteries from the aspects of isolating the positive and negative electrodes of the battery, allowing lithium ions to pass through, preventing battery explosion caused by high temperature, etc.

Compared with traditional lead-acid and nickel-cadmium batteries, lithium-ion batteries have obvious advantages in terms of energy density, cycle life, environmental protection and safety. At present, li-ion battery separator is widely used in new energy vehicles, energy storage power stations, electric bicycles, power tools, aerospace, medical and digital electronic products and other fields.

2. Market scale of lithium battery separator

At present, the diaphragm mainly includes two technical routes: wet diaphragm and dry diaphragm. The production process of diaphragm includes many processes such as raw material formulation and rapid formulation adjustment, microporous preparation technology, and independent design of complete sets of equipment. Among them, the micropore preparation technology is the core of the battery separator preparation process.

The production of the diaphragm base film is mainly divided into two types: dry method and wet method according to the pore-forming mechanism of micropores. At present, ternary material power lithium batteries basically use wet-process battery separator. What are the specific manufacturers, we can click on our top 10 ternary power battery manufacturers in China article to see.

And mainstream manufacturers such as CATL and Gotion Hi-Tech also use wet-process battery separator for lithium iron phosphate batteries that also need to continuously improve energy density.

The main steps of the dry process are feeding, casting, heat treatment, pulling and slitting. First, the raw materials such as PP and additives are pretreated according to the formula and then sent to the extrusion system. The pretreated raw materials are melted and plasticized in the extrusion system and then extruded from the die. The melt forms a specific crystal structure after casting.

The base film is heat-treated to obtain a hard elastic film, and then the hard elastic film is cold-stretched and hot-stretched to form a nano-microporous film, and finally the nano-microporous film is cut into a finished film according to the customer’s specifications. 

The main steps of the wet process are feeding, casting, longitudinal pulling, transverse pulling, extraction, shaping and slitting. The traditional wet method is mainly based on the phase inversion method, and in recent years, the tips thermally induced phase separation method is the main method. The raw materials such as PE and pore former are pretreated and transported to the extrusion system according to the formula.

The pretreated raw materials are melted and plasticized in the twin-screw extrusion system and extruded from the die head, and the melt is formed after casting. A casting slab containing a pore-forming agent and the casting slab is longitudinally stretched and then stretched laterally to obtain a base film containing a pore-forming agent.

The base film is solvent-extracted to form a base film that does not contain a pore-forming agent. The base film without pore-forming agent is dried and shaped to obtain a nano-microporous film; the nano-microporous film is cut into a finished film according to the customer’s specifications.

Due to the gradual improvement of the performance requirements of lithium batteries in the downstream industry and the gradual release of the production capacity of wet-process separators, the growth of battery separator shipments in China is mainly reflected in the substantial increase in wet-process battery  separator shipments.

In the future, with the rapid growth of energy storage, it will further bring about an incremental market for wet and dry diaphragms. According to the data, the compound annual growth rate of China’s diaphragm shipments will reach 23.36% from 2022 to 2028, and the annual shipments will reach 33.909 billion square meters by 2028.

3. The core manufacturers of lithium battery separator

The diaphragm is the link with the highest technical barriers among the four major materials. In the micron-scale film formation and pore formation, it is necessary to maintain consistency and stability, and the requirements for equipment and production processes are the highest.

Diaphragm is an asset-heavy industry. The single GWh input is higher than that of negative electrode and electrolyte, but lower than that of positive electrode, and the equipment cost is high. The raw material of diaphragm accounts for only about 35%, and the proportion of depreciation and amortization is high. The diaphragm factory needs to continue to reduce costs to maintain a competitive advantage.

The competition pattern of the diaphragm industry is highly concentrated, and the leading profitability is strong. From the perspective of concentration, the concentration is significantly higher than other materials. During 2017-2018, a fierce price war took place in the diaphragm industry. With the rapid decline in the selling price of diaphragm products, the profitability of first-tier leading and second-tier and third-tier manufacturers was significantly differentiated.

Among them, JEVE has maintained a high gross profit margin through rapid cost reduction through advantages in equipment, technology and production capacity. Although the overall gross profit margin of Senior has not fallen sharply, its wet process diaphragm subsidiaries Hefei Senior and Changzhou Senior are also in a loss situation. The gross profit margin of third-tier manufacturers declined rapidly, and some manufacturers such as Yuntianhua Newmi and MingZhu even suffered gross profit margin losses.

Since 2018, mergers and acquisitions and production stoppages have occurred in the diaphragm industry. Second-tier manufacturers JGP, Yuntianhua Newmi, Tonry and Donghang Optic have been acquired by Yunnan Energy. Chinaly has also been merged and integrated by Sinoma due to its own profit pressure.

According to the data, in 2021, the leading advantages of the diaphragm market will be further strengthened. The cumulative production of the top five manufacturers in China will account for more than 94% of the total annual production. Yunnan Energy has acquired GREEN POWER and Yuntianhua Newmi, and the leading position will be further consolidated under the industry integration.

The market share of production in 2021 will increase to 56.1%, an increase of 6 percentage points compared with the full year of 2020. The production capacity of Senior wet-process diaphragms will run smoothly, and the market share of production in 2021 will increase to 13.1%, showing a competitive advantage. In terms of dry process, Senior maintained its leading position, Wuhan Huiqiang’s dry process production increased year-on-year, and the market share of production increased rapidly.

4. Summary

The cost of diaphragm raw materials accounts for about 41%, and polyethylene PE accounts for a high proportion of raw materials, and the overall price shows a fluctuating upward trend. The raw materials required for diaphragm production include polyethylene, paraffin oil, dichloromethane, etc.

Among them, polyethylene (PE) is the main material, accounting for a relatively large proportion of raw materials. The upstream raw material of polyethylene is crude oil, the upstream crude oil price rises, and the price is transmitted to the downstream polyethylene. The spot price of HDPE has risen from $846/ton at the beginning of 2020 to the current $1,241/ton, and the overall price has risen by a large margin.

In 2021, the prices of dry-process and wet-process diaphragms will rise, with a rise of 5-10% for dry-process diaphragms and 10-15% for wet-process diaphragms. The major diaphragm manufacturers benefited from the strong industry demand and the accelerated release of production capacity. With the expansion of diaphragm shipments, the unit cost of diaphragm enterprises has dropped significantly, and the customer structure has been optimized, and the profitability has increased significantly.

According to the data, the current comprehensive cost of lithium battery wet diaphragm manufacturers is about 7246.26 RMB / 10,000 square meters, and the cost pressure of lithium battery diaphragms will not change much in the short term.

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