Technical Analysis of Die-Cut Insulation Materials for New Energy Vehicle Power Batteries: A Guide to Material Selection, Processing Techniques, and Reliability Design

As core components characterized by high voltage and high energy density, power battery systems in new energy vehicles (NEVs) impose stringent requirements regarding internal insulation, protection, thermal management, and electromagnetic compatibility. With the advent of 800V high-voltage platforms, fast-charging technologies, and high-power drive systems, battery packs must not only meet basic electrical isolation needs but also deliver comprehensive performance-including heat resistance, flame retardancy, aging resistance, and long-term operational reliability.

 

Die-cut insulation materials are critical auxiliary components in NEV battery systems. They primarily include polycarbonate (PC) insulation sheets, polyester (PET) films, polyimide (PI) films, insulating tapes, silicone pads, flame-retardant foams, and conductive shielding materials. Through precision die-cutting, lamination, and structural design, these materials are applied between battery cells, in high-voltage connection zones, on busbar assemblies, within control modules, and inside battery housings, providing stable and reliable insulation protection for the power battery system.

 

In NEV electrical connection systems, insulation materials typically function in tandem with high-voltage conductive components-such as conductive connectors within battery modules, power connection structures, and busbar systems for energy transmission. Certain high-performance insulation structures integrate with electrical connection solutions (e.g., EV capacitor busbars), incorporating comprehensive designs for insulation clearance, spatial constraints, and voltage withstand capabilities to ensure safety under complex operating conditions.

 

 

 

Based on their specific functions, insulation materials used within NEV power batteries can be categorized into several groups, including high-strength insulation films, elastic cushioning materials, adhesive composite materials, and electromagnetic shielding materials.

 

High-strength insulation films primarily serve to provide electrical isolation and voltage withstand protection. Among them, PC insulation sheets-characterized by high mechanical strength and dimensional stability-are commonly used for battery module side plates, bottom insulation zones, and structural protection points. Their advantages include superior impact resistance, enabling them to withstand the vibrations encountered during vehicle operation.

 

PET films are widely used as insulation materials in power batteries, valued for their moderate cost, excellent processability, and high dimensional stability.

 

They are frequently employed for insulation and isolation between battery cells, protection of internal circuitry, and insulation coverage in conductive connection areas. For battery modules operating at standard temperatures, PET materials can meet most insulation requirements.

 

Due to their excellent high-temperature resistance and electrical stability, PI (polyimide) films are widely used in high-temperature zones-such as near high-voltage connectors, electrical interfaces, and heat-generating components. With a long-term operating temperature often exceeding 200°C, they are well-suited for applications in new energy vehicles that demand high reliability.

 

Inside power battery packs, high-voltage electrical connection components typically require insulation structures for safety protection. For instance, in automotive busbar applications, the insulation design surrounding the busbar must account for voltage ratings, creepage distances, and mechanical assembly space to prevent insulation failure during high-voltage operation.
 

 

In addition to rigid insulation sheets, elastic materials are crucial components of battery systems in new energy vehicles.

 

Silicone pads are commonly placed between battery cells and cooling structures, serving the dual purposes of insulation, thermal conduction, and cushioning. During operation, these pads reduce mechanical stress and facilitate heat transfer from the cells to the cooling system, thereby enhancing thermal stability.

 

Flame-retardant foam is primarily used to fill internal gaps within battery modules; it absorbs vibrations generated during vehicle operation while providing a degree of flame-retardant isolation. Common materials include PU (polyurethane), CR (chloroprene rubber), and PE (polyethylene) foams.

 

For power batteries in new energy vehicles, foam materials must possess not only elasticity but also meet specific flame-retardancy standards.

 

As the energy density of battery systems continues to rise, safety regarding thermal runaway has become a key design priority. Consequently, internal insulation and cushioning materials generally must meet the UL94 V-0 flame-retardancy rating and pass reliability tests involving high temperatures, high humidity, and thermal cycling.

 

In high-power new energy vehicles, battery output terminals often connect to complex electrical systems-such as EV busbars that must transmit high currents within limited spaces. Therefore, the surrounding insulation materials must exhibit excellent heat and voltage resistance.
 

 

 

Insulation tapes and composite die-cut parts are primarily used for securing components, providing protection, and enhancing localized insulation.

PET double-sided tapes, PI tapes, and other high-temperature adhesive materials are frequently used to secure insulation sheets, protect circuitry, and assist in the installation of Battery Management System (BMS) components. Compared to traditional manual application methods, precision die-cut adhesive components ensure dimensional consistency and enhance the efficiency of automated assembly.

 

Multi-layer composite insulation components are becoming increasingly common in battery pack manufacturing. For instance, composite structures comprising PET, PI, foam, and adhesive layers can simultaneously meet requirements for insulation, protection, cushioning, and structural fixation.

 

Regarding high-voltage electrical connection structures in new energy vehicles-such as film capacitor busbars for HEV/EV motor control units-insulation layers must not only ensure electrical safety but also withstand the electromagnetic fluctuations and thermal cycling associated with high-speed switching operations.

 

 

As the level of electronic integration in new energy vehicles rises, electromagnetic compatibility (EMC) issues are garnering increasing attention.

 

Fluctuations in high-voltage current within the power battery system generate a certain degree of electromagnetic interference; consequently, specific areas require shielding using materials such as conductive fabric, conductive foam, copper foil tape, and aluminum foil.

 

Conductive shielding materials are typically employed around BMS control zones, high-voltage connection areas, and signal lines. By forming a continuous conductive shield, they mitigate the impact of external interference on control systems.

 

Furthermore, the power systems of new energy vehicles involve high-speed electrical energy conversion between components such as capacitors, motor controllers, and high-voltage busbars. For example, copper busbar structures for EV DC-link film capacitors must simultaneously satisfy requirements for low impedance, highly reliable connections, and insulation safety.

 

 

Selecting insulation materials requires a comprehensive assessment that goes beyond mere cost considerations, taking into account voltage ratings, operating temperatures, mechanical environments, and long-term reliability.

 

The first factor is voltage withstand capability.

 

With the development of 800V platforms in new energy vehicles, the operating voltage of power battery systems is rising, necessitating insulation materials with higher dielectric strength. Factors such as material thickness, structural spacing, and edge design all influence the final insulation performance.

 

In high-voltage battery systems, insulation design must account for requirements regarding creepage distance and clearance. For high-voltage connection structures-such as copper busbars for electric vehicle capacitors-designs must ensure adequate insulation distance between conductive components.

 

The second factor is flame retardancy. Internal materials for power batteries must withstand extreme safety scenarios; consequently, insulation sheets, foams, and adhesives typically need to meet UL94 V-0 flame retardancy standards. Certain high-end applications may also undergo additional testing, such as glow-wire tests, smoke density tests, and long-term thermal aging tests.

 

The third factor is thermal management capability.

 

During the operation of new energy vehicles, the internal temperature of the battery fluctuates with charging and discharging states. Insulation materials located near heat sources must possess excellent temperature resistance and maintain their performance despite long-term thermal cycling.

 

For instance, in the assembly of copper busbars and film capacitors connecting the battery to power electronics systems, the surrounding insulation materials must withstand combined thermal, electrical, and mechanical stresses.

 

 

 

The internal space of new energy vehicle batteries is highly compact; therefore, the machining precision of die-cut insulation components directly affects assembly reliability.

 

High-precision die-cutting ensures a precise fit between insulation sheets and battery structures, preventing installation interference or reductions in creepage distance caused by dimensional deviations.

 

Typically, dimensional tolerances for power battery insulation components must be controlled within ±0.1 mm, while some precision structures require tolerances as tight as ±0.05 mm.

 

Key aspects to control during the manufacturing process include:

First, the formation of burrs on die-cut edges must be prevented. Metal debris or burrs can cause localized electric field concentration, thereby compromising insulation reliability.

 

Second, material deformation must be controlled. Ultra-thin materials, such as polyimide (PI) films, are particularly prone to curling or dimensional changes during processing.

 

Finally, the bond strength between composite layers must be ensured. For multi-layer insulation structures, the long-term adhesion stability between different materials must be verified.

 

 

As new energy vehicles evolve toward higher voltages, higher power outputs, and greater integration, insulation materials are also advancing toward lightweight designs, high performance, and multifunctional composites.

 

In the future, insulation structures within power battery systems will transcend their role as simple isolation materials; instead, they will become integral components that facilitate safety, thermal management, electromagnetic compatibility, and structural optimization. For instance, components such as copper busbars for EV film capacitors and power distribution bars in the high-voltage powertrains of new energy vehicles require the synergistic design of insulating materials and conductive elements to achieve higher efficiency, lower losses, and superior safety standards.

 

Furthermore, the advancement of hydrogen-powered vehicles, electric construction machinery, and intelligent transportation equipment-along with the specialized operating environments they entail-is driving the development of insulating materials capable of withstanding higher temperatures and voltages. Applications such as copper busbars for DC-link film capacitors in hydrogen-fueled vehicles, for example, impose stricter requirements regarding the long-term reliability of insulation systems.

 

Future developments in die-cutting technology for new energy vehicle battery insulation will focus on three key areas:

First, material performance upgrades: enhancing system safety by developing materials with high heat resistance, flame retardancy, and dielectric strength.

 

Second, manufacturing process upgrades: improving mass-production consistency through automated die-cutting, precision lamination, and intelligent inspection.

 

Third, structural integration: achieving more compact and efficient battery system layouts through the synergistic design of insulating parts and conductive components.

 

As a critical foundation for the safe operation of high-voltage systems, the performance of die-cut insulation materials for new energy vehicle power batteries directly impacts the reliability of the entire vehicle. Through appropriate material selection, precision processing, and systematic validation, the safety, stability, and service life of power batteries can be effectively enhanced, providing reliable support for the sustainable development of the new energy vehicle industry.