Lithium Battery Separator Materials Future Development Trends

What are Lithium Battery Separator Materials

Lithium batteries mainly consist of four key materials: cathode materials, anode materials, electrolytes, and separators, along with other components. The role of the separator is to separate the positive and negative electrodes of the battery, preventing contact and short circuits, while providing microporous channels for electrolyte ions to pass freely. The separator is a critical material that ensures the safety of the battery system and affects battery performance. The performance of the separator determines the battery's interface structure, internal resistance, and directly influences characteristics such as capacity, cycle life, and safety. High-performance separators play an important role in enhancing the overall performance of batteries.

Common Lithium Battery Separator Materials

Generally, high-performance lithium batteries require separators to have uniform thickness and excellent mechanical properties (including tensile strength and puncture resistance), gas permeability, and physicochemical properties (including wettability, chemical stability, thermal stability, and safety). Currently, commercially produced lithium battery separators primarily use PP, PE separators, and coated separators based on these two types. The advantages and disadvantages of different separator materials are summarized in the table below.

Recent Growth of Dry and Wet Process Separators

With the implementation and promotion of the "dual carbon" policy, the rapid development of global new energy vehicles, and the expansion of the lithium battery industry, there is significant market potential for the lithium battery separator industry. Additionally, the rapid growth of the energy storage market has further propelled the development of the lithium battery separator sector.

In recent years, Chinese separator companies have continuously improved their global supply capabilities, resulting in a significant increase in the shipment volume of lithium battery separators. According to data, the shipment volume reached 12 billion square meters in the first three quarters of 2023, a year-on-year increase of 30%. Among these, dry process separators accounted for 3.3 billion square meters, and wet process separators accounted for 8.7 billion square meters, with respective year-on-year increases of 55% and 31%. The demand for dry process separators is growing faster than that for wet process separators, primarily due to the energy storage market's preference for dry process products.

Differences Between Wet and Dry Process Separators

Based on different production processes, separators can be divided into dry and wet processes, with dry processes further classified into uniaxial stretching and biaxial stretching. As downstream applications like power and digital lithium batteries demand high energy density, and since wet process separators are thinner and advantageous for enhancing lithium battery energy density, the Chinese lithium separator market still predominantly utilizes wet process separators.

Future Trend 1: Thinning and Functionalization of Separator Products

The increasing demand for thinner and more functional separators from downstream applications imposes higher performance and functional requirements on separator products.

As the new energy industry develops, the comprehensive indicators such as capacity, performance, and safety in the downstream lithium battery sector continue to improve, leading to further demand for thinner and more functional separators. Thinning remains one of the key focus areas in the lithium separator industry. In the dry process separator field, the large-scale application of separators with a thickness of 10μm or less will be a major focus in the next stage of industry R&D. Meanwhile, with the maturity of various sub-application fields, there will be a more targeted selection of separators in downstream applications, driving the development of functionalized separators.

For instance, in the power battery field, thickness and porosity are key factors that directly relate to the consumer's driving experience. In the energy storage battery field, the focus will be on how separators impact battery cycle life to extend usage time. In high-economic applications, lithium battery manufacturers will increasingly emphasize the cost-performance ratio of separators to ensure their profit margins.

To meet the higher demands of downstream applications, separator manufacturers need to maintain research and improvement on process technologies, continuously innovate in R&D, and provide economically optimal separator products in response to the demands for high performance and functionality.

Furthermore, the gradual development of cutting-edge fields like sodium-ion batteries and semi-solid batteries is also creating new demands for separator applications, necessitating proactive product and technology planning by separator manufacturers.

Future Trend 2: Expanding Applications of Coated Membranes with Differentiated Formulations

Depending on the specific coating materials, coating can effectively enhance the puncture resistance and thermal stability of lithium battery separators, improve liquid absorption capacity, and address issues like electrolyte affinity and membrane wrinkling. In recent years, the application of coated membranes has been expanding.

Commonly used coating materials in the market include inorganic ceramics, PVDF, aramid, etc. The selection of materials is relatively limited, and some raw materials are in short supply. Major separator manufacturers are actively expanding the range of coating materials and developing new coating formulations, including functional coatings and low-cost coatings. It is expected that in the future, companies mastering high-quality core coating formulations and processes will have greater development potential.

Looking ahead, with the acceleration of globalization, the separator materials industry will face competition in the international market. Chinese separator material companies should actively explore international markets to enhance their product competitiveness. By fostering collaboration between industry, academia, and research, companies can improve their technological innovation capabilities and work closely with upstream and downstream enterprises to drive the development of the entire supply chain, accelerating the rise of China's separator materials industry.