By Daniel Condrich on 6/9/2025

Die-Cut Cell Separator Materials: Optimizing Safety and Performance for EV and BESS Battery Packs

Die-Cut EV Battery Cell Separators | JBC Technologies

Whether it’s electric vehicle batteries or grid-level industrial and commercial battery storage, proper cell-to-cell protection is critical for mitigating damage in dangerous thermal runaway events, insulating cells from electrical arcing, and dampening vibration and mechanical stress. Die-cut battery cell separators, gaskets, and compression pads can be tailored for a range of applications, providing scalable solutions that can be seamlessly integrated into your battery system.

However, battery cell separators are not one-size-fits-all. Just as every battery pack is different, die-cut battery cell separators come in many shapes and sizes, made from a wide range of flexible materials like foams, papers, and ceramic materials. Navigating these material options can be daunting, which is why it’s important to work with a converting partner to understand the needs of your project and how to meet them with high-performance material converting solutions.

Today, we’ll be highlighting the important role battery separators play in battery safety and performance, as well as how to navigate the different types of separator materials. With safety and product performance on the line, battery cell separators should never be an afterthought.

Let’s take a closer look at why…

Battery Separators vs. Compression Pads vs. Gaskets

Before we jump in, it’s important to clarify the differences between battery cell separators, compression pads, and gaskets.

Battery separator is a broad term that includes cell dividers, spacers, and compression pads that exist both inside and outside of the battery cell. Separators inside each individual cell are thin membranes that sit directly between the anode and cathode to prevent electrical arcing and thermal events from within the cell. In this blog, we’re specifically focusing on the battery separators that sit outside of each individual cell, which provide external protection and prevent propagation between cells.
Dividers and spacers mainly provide thermal and electrical protection by keeping cells properly spaced to reduce heat transfer and electrical arcing.
Compression pads focus on vibration and shock absorption, accommodating cell expansion during charge-discharge cycles.
Gaskets are much broader. Gaskets seal and protect components from environmental factors like moisture, dust, and debris in many places around the battery pack.

For this blog, we’ll be focusing on external cell spacers, dividers, and compression pads.

What Makes a Good Battery Cell Separator?

Battery packs are complex ecosystems. Amidst thermal, mechanical, and electrical stress, battery cells must function without fail. Cell-dividers maintain balance by:

Ensuring thermal management

The right cell separator prevents hotspots, mitigates thermal runaway damage, and prevents heat flow in cascading thermal events.
Ask yourself: Does it insulate or conduct? Can it withstand thermal runaway?

Providing Electrical Insulation

In high-voltage, densely packed systems, spacers prevent electrical arcing and short circuits by isolating cells.
Ask yourself: Is it dielectric? Can it prevent arcing or shorting between cells?

Absorbing Mechanical Stress

Especially relevant in EV applications, spacers cushion cells against vibration and shocks, which can damage and rupture cells.
Ask yourself: How does it hold up to vibration, compression, or impact? Does it return to its original shape after compression?

Resisting Moisture and Chemical Contamination

For a spacer to be a viable long-term solution, it must be able to resist humidity and be able to withstand repeated battery cycling without losing its shape.
Ask yourself: Will it degrade in a humid, corrosive, or fire-prone environment?

Balancing Cost with Performance

Balancing the cost of a material with its performance capabilities is important for hitting your budget and performance goals.
Ask yourself: Does the performance of this material justify the price tag for my specific application?

Selecting the Right Battery Spacer Material

Selecting the right spacer material is a balancing act between many different factors. Whether the priority is mitigating the spread of heat, preventing electrical arcing, absorbing shock and vibration, or a combination of these, weighing the strengths and limitations of different materials is an important step.

Common Battery Spacer Materials + Examples

Material	Pros	Cons	Ideal Use
Polyethylene (PE) Foam Zotefoams Plastazote®	-Lightweight -Chemically inert -Good cushioning	-Not inherently flame retardant or thermally resistant -Can compress under long-term load	Non-critical cushioning spacers, vibration dampeners, and pack sealing
Polypropylene (PP) Foam Sekisui Alveosoft	-High chemical resistance -Low compression set -Electrical insulation	-Less thermally stable than silicone & ceramics -Lower impact resistance than PE	Thin, form-fitting spacers around cells in mid-temperature environments
Ethylene Vinyl Acetate (EVA) Foamtec EVA Foam	-Soft and compressible -Good vibration absorption	-Low thermal resistance -Moderate dielectric strength	Flexible vibration isolating pads in medium temperature environments
Nomex® DuPont™ Nomex® 410	-High dielectric strength -High thermal resistance	-Can be brittle at tight tolerances -More difficult to convert -Less cost-effective than foams	Electrical and thermal insulation between cells/modules
Cork Composites Amorim’s Cork FiberCork	-Sustainable -Low compression set -Good thermal and acoustic insulation	-Not inherently flame resistant -Not moisture resistant without additional treatment -Low structural durability	Cell cushioning and vibration dampening in low thermal environments
Ceramic Materials Morgan Thermal EST™ Compression Papers	-Great thermal protection -Stable at extreme temperatures -Low smoke/toxicity output	-Brittle -High costs -Not compressible	Fire barriers between cells and thermal shielding in module housing
Silicone Foams Saint Gobain Norseal® F-15	-Wide temperature range -High flame resistance -Low compression set -UL 94 V-0 Rated	-High costs -Low tensile strength	High temperature compression pads, gaskets, and seals for high-heat areas
Advanced Composites AIS Contraflame® FCP Series	-Forms protective char above 200°C -Fire retardant -High dielectric strength -Easily converted	-High costs	Thermal runaway barriers to stop the spread of heat between cells

Thermal Protection in Practice: AIS Contraflame® FCP

It’s one thing to talk about the dangers of thermal runaway, but it’s another thing to see it. Check out how AIS Contraflame® handles the heat in this simulated thermal battery event.

Solving Cell-to-Cell Protection with Custom Die-Cutting

For challenges that demand custom solutions...

PRecision/Tight tolerances:

The challenge: In many battery modules, especially EV batteries, where weight and space are a concern, tight battery packs and dense cell clusters are the norm. For battery spacers, even small dimensional errors in these cramped spaces can lead to uneven protection and weak spots in insulation.

The solution: With multi-step precision rotary die-cutting machines, a converting partner can fabricate thousands of dimensionally identical components for even coverage and improved safety, even in densely packed battery modules.

SCalability

The challenge: What works in small-volume prototyping batches may not be feasible to produce at scale.

The solution: With a team of dedicated engineers, JBC applies years of process engineering expertise to assist in optimizing both the design and manufacturing process of your part to help you transition from small-volume prototyping with dieless digital cutting to high-volume manufacturing smoothly.

Multi-Layer Laminates

The challenge: Sometimes, one material just isn’t enough for the job. Some challenges require comprehensive material solutions that solve multiple challenges at once.

The solution: By laminating multiple high-performance materials together, a converter can create a custom material solution that’s greater than the sum of its parts.

In-Line Vision Systems

The challenge: Even small, almost imperceivable defects like tears, bubbles, surface contamination, and missing features can compromise the performance of a part, leading to overall product failures and dangerous thermal runaway events.

The solution: A converting partner, like JBC Technologies, with inline vision defect detection systems, can detect a wide range of defects in real time, allowing for process adjustments and traceability for quality audits, preventing production setbacks before they happen.

JBC Technologies: Small Solutions for Big Challenges

Spacers are more than just a die-cut part; they enable innovation by extending battery life, improving customer safety, and product performance. But without a converting partner to transform performance materials into these high-performance parts, they’re just raw potential…

JBC Technologies is an ISO 9001-certified die-cutter and flexible materials converter with over 35 years of experience converting raw materials into functional EV battery and battery storage solutions. From EV battery compression pads and thermal/electrical insulation to custom-cut attachment tapes and EMI/RFI shielding, JBC is your go-to battery converting partner. Founded on the pillars of supply chain optimization, engineering innovation, and manufacturing excellence, JBC provides full life-cycle product support from rapid prototyping through dieless digital cutting capabilities all the way to high-volume automated production on rotary die-cutting presses.