Insights into the Role of Separators in Lithium-Ion Batteries

According to Stratview Research, rising demand for electric vehicles (EVs) and other lithium-ion battery (LiB)–powered technologies is expected to drive strong growth in the LiB separator market. Sustained progress in raw materials, production techniques, and manufacturing efficiency will remain essential to support this expansion. The market, valued at approximately USD 6.1 billion in 2023, is projected to grow nearly fourfold and exceed USD 24.3 billion by 2030.

Lithium-ion batteries rely on multiple critical components to operate effectively, but the core electrochemical process depends on the cathode and anode working together to generate energy. At the same time, these two electrodes must remain physically separated to prevent short circuits, system failure, or, in extreme cases, thermal events. This function is performed by the battery separator—a thin but essential barrier that supports both safety and performance in modern energy storage systems.

In Li-ion battery architecture, separators serve two primary roles. First, they maintain safety by ensuring physical separation between the battery’s positive and negative electrodes, reducing the risk of electrical short circuits. Second, they enable battery operation by permitting controlled ionic movement. Separators are designed as porous membranes, with microscopic pores that allow lithium ions to pass through while preventing direct electron flow. This balance is fundamental to reliable charging and discharging behavior in lithium-ion batteries.

Polyethylene as the Dominant Separator Material

Lithium-ion batteries face inherent safety risks, including short circuits caused by separator thermal shrinkage under elevated temperatures. This creates a strong requirement for separator materials that offer high tensile strength, dimensional stability, chemical resistance, and consistent electrochemical performance.

Polyolefins such as polyethylene (PE) and polypropylene (PP) are the most widely used separator materials, with each offering distinct performance characteristics. Among these, polyethylene dominates the market. More than 80% of lithium-ion battery separators are produced using PE, particularly ultra-high molecular weight polyethylene (UHMWPE). UHMWPE is favored due to its strong mechanical durability, chemical stability, and reliable electrical insulation properties.

In addition, polyethylene provides effective shutdown behavior. When internal battery temperatures rise to unsafe levels—often due to continuous charging—PE-based separators can restrict ion movement, helping reduce the likelihood of further escalation. This shutdown capability has contributed significantly to polyethylene’s continued leadership in separator production.

Separators are primarily manufactured using two processes: the dry process and the wet process. Among the two, the wet process is more widely adopted because it offers greater control over pore formation and uniformity. This method involves mixing a polymer with a solvent, followed by phase separation to form a porous structure that supports efficient ion transport. Wet-process separators are recognized for low thickness, improved electrolyte interaction, and higher energy density, making them especially suitable for applications that demand compact packaging and high performance.

Wet-process separators typically require high molecular weight polymers. As a result, more than 90% of the raw material used in wet-process separator manufacturing is UHMWPE, reinforcing its importance in the global separator value chain.

Broad and Expanding Applications of LiB Separators

Lithium-ion batteries are used across a wide range of industries, most notably automotive, industrial, and consumer electronics. In everyday applications, LiBs power smartphones, laptops, smartwatches, digital cameras, and many other portable devices due to their high energy density, long service life, and rechargeability.

Beyond consumer goods, lithium-ion batteries serve larger-scale applications such as grid energy storage and industrial backup systems. Additional end-use sectors include aerospace, defence, marine, medical devices, and power systems, further expanding the importance of high-quality separators.

LiBs are valued for their durability and energy storage capability. They typically retain around 80% of original capacity even after extensive use, and their energy density can reach up to 330 Wh/kg. Compared with older technologies such as lead-acid batteries, lithium-ion systems offer significantly lower weight, enabling better portability and performance across multiple platforms.

Among all applications, the automotive industry—led by EV adoption—is the largest demand driver for lithium-ion battery separators. Approximately 65% of total separator demand is generated by the automotive segment. Separators are essential to supporting battery performance, safety, and reliability in battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), and hybrid electric vehicles (HEVs).

EV Adoption Accelerating Separator Demand, with China Leading

Global efforts to reduce emissions and support net-zero objectives are rapidly accelerating EV adoption. Bloomberg New Energy Finance (BNEF) estimates that more than 50% of global passenger vehicle sales could be electric by 2040. Since EVs depend heavily on lithium-ion batteries, the growth trajectory of battery demand directly increases separator requirements.

Multiple studies indicate that global lithium-ion battery demand could exceed 1,748 GWh annually by 2030. Meeting this scale of battery production will require a corresponding expansion in separator manufacturing capacity and technological capability.

The Asia-Pacific region is expected to generate the highest demand for separators due to its strong concentration of EV manufacturing and battery supply chain development, led primarily by China and supported by countries such as India. China, in particular, remains the largest EV producer globally. In 2024, China’s new energy vehicle (NEV) production and sales reportedly exceeded 12 million units, reinforcing its leading role in global EV output. Roughly 60% of global EV volume originates in China, making it the most influential market for lithium-ion batteries and separators.

Europe also plays a major role in driving EV adoption due to policy-led decarbonization initiatives. Through programs such as “Fit for 55,” the European Union targets a 55% reduction in greenhouse gas emissions by 2030 and aims to phase out internal combustion engine (ICE) vehicles by 2035. These commitments strengthen long-term demand fundamentals for lithium-ion batteries and associated separator materials.

North America, meanwhile, is positioned for accelerated growth due to increasing EV production activity and expanded investments in separator manufacturing. In November 2024, Asahi Kasei Battery Separator Corporation announced plans for a new lithium-ion battery separator facility in Canada, with commercial production expected to begin in 2027. ENTEK has also announced significant expansion plans for its U.S.-based separator business, including an initial expansion targeted for completion by 2025, followed by additional capacity increases through 2027 totaling 1.4 billion square meters of annual output. Once fully operational, the initial expansion is expected to supply enough separator material to support approximately 1.4 million EVs.

Based on these developments, North America is projected to register a CAGR exceeding 35% through 2030, outpacing typical market growth rates.

Innovation, Recycling, and Material Shifts

As EV adoption increases, battery recycling and reuse are gaining momentum, driven by government policies in regions such as China, the European Union, and India. Over time, recycling—including separator recovery—could influence demand for newly produced separator materials.

At the same time, sustainability priorities are accelerating interest in recyclable and environmentally friendly separator solutions. This shift is reviving consideration of historical separator materials. Early separators were manufactured using rubber, glass fiber, and cellulose-based materials. Today, cellulose is being reconsidered as a potential alternative to polyolefin separators. While cellulose requires additional modifications to improve performance, several companies—including NIPPON KODOSHI CORPORATION and Celgard—are actively developing cellulose-based separator technologies.

Despite recycling-related considerations, falling lithium-ion battery prices and ongoing innovation remain strong demand accelerators. In 2023, Li-ion battery prices declined by approximately 14% to USD 139/kWh, further supporting adoption across consumer and automotive markets. Technical developments such as nanofiber-based separators and solid-state electrolytes are also strengthening battery performance and safety, supporting continued growth in separator requirements.

In addition, lightweight thin-film batteries represent an emerging trend that drives further innovation in separator design. To support thinner and lighter batteries, advanced separator systems increasingly utilize solid-state electrolytes and ceramic coatings to improve stability and simplify cell architecture.

Market Outlook

Demand for EVs and other lithium-ion battery applications is expected to continue rising over the long term. As a result, separator technologies must evolve in parallel through improved material formulations, optimized manufacturing methods, and scale-driven cost efficiencies. According to Stratview Research, the lithium-ion battery separator market, valued at USD 6.1 billion in 2023, is projected to expand fourfold and exceed USD 24.3 billion by 2030, reinforcing separators as a critical and rapidly growing segment within the global battery value chain.