How Can CPP Resin Unlock New Potential in New Energy Battery Packaging and Printing?

The rapid growth of the new energy vehicle industry is reshaping the entire industrial materials supply chain. According to industry data, China continued to lead the global new energy vehicle market in production and sales in 2025, while power battery installations continued to rise. At the same time, pouch cells are gaining increasing adoption in high-end passenger vehicles and energy storage applications due to their high energy density and safety advantages. As a result, aluminum-plastic film, the key packaging material for pouch cells, is facing extremely demanding requirements for its inner-layer bonding and heat-sealing performance.

1. Special Requirements for Printing Materials in New Energy Battery Packaging

Unlike conventional packaging, new energy battery packaging must meet a range of extremely demanding performance requirements.

First, resistance to electrolyte corrosion. Lithium batteries contain carbonate-based organic electrolytes. In the event of leakage, these electrolytes can attack packaging materials. Printing coatings used for battery labels, housing markings, and similar applications must withstand long-term contact with electrolytes without swelling or delaminating.

Second, resistance to high temperature and high humidity. Batteries generate heat during charging and discharging, and temperatures inside battery packs can exceed 60°C. At the same time, battery packaging materials may need to pass demanding damp-heat aging tests, such as 85°C/85% RH. Under these conditions, printing coatings must retain both their adhesion and functional integrity.

Third, electrical insulation. Printing coatings used in battery packaging must not compromise the electrical insulation of the battery. In particular, between the battery cell and external circuits, any conductive contamination could create a risk of short circuits. As a polymer material, CPP resin typically has a volume resistivity above 10¹⁵ Ω·cm, allowing it to meet the insulation requirements of battery packaging applications.

Fourth, lightweight and thin-gauge construction. As the energy density of power battery packs increases, every component needs to be as lightweight as possible. The bonding layer in aluminum-plastic film is typically only a few to more than ten micrometers thick, while the thickness of printing coatings is also strictly controlled.

Fifth, environmental compliance. Battery packaging materials need to comply with environmental regulations such as RoHS and REACH. At the same time, automotive manufacturers impose strict controls on VOC emissions and solvent residues.

Taken together, these requirements present challenges far beyond those encountered in conventional packaging printing. The molecular structure of CPP resin, however, provides several properties that can help address these challenges.

2. Three Major Applications of CPP in New Energy Battery Packaging

2.1 Application 1: Bonding Layer for Lithium Battery Aluminum-Plastic Film

Aluminum-plastic film is a key packaging material for pouch lithium batteries. Its structure typically consists of "outer nylon + aluminum foil + inner cast polypropylene (CPP) film." It should be noted that the "CPP film" mentioned here refers to Cast Polypropylene Film, which is different from the Chlorinated Polypropylene (CPP) resin discussed in this article. As the heat-sealing layer, the inner layer of aluminum-plastic film comes directly into contact with the electrolyte and must simultaneously provide resistance to electrolyte corrosion, high electrical insulation, and good heat-seal strength.

The application of chlorinated polypropylene resin in aluminum-plastic film is mainly found in the formulation of the bonding layer. Through the "molecular bridging" effect of CPP resin, the adhesion between the aluminum foil and the inner PP film can be enhanced.

The chlorine atoms in the CPP molecular chain introduce a certain degree of polarity, enabling the resin to form good adhesion with the oxide layer on the aluminum foil surface. At the same time, CPP retains the non-polar polypropylene backbone, providing inherent compatibility with the inner PP film. During heat sealing, the CPP layer can achieve good coating and lamination performance at relatively low temperatures, helping protect the aluminum foil and external functional layers from thermal damage.

Bonding materials for aluminum-plastic film have long been dominated by a small number of international companies. In recent years, however, domestic manufacturers have made breakthroughs in gas-phase CPP production technology, providing new options for the localization of aluminum-plastic film materials. Gas-phase CPP offers extremely low solvent residue and a cleaner molecular structure, making it well suited for use in aluminum-plastic film bonding layers.

2.2 Application 2: Marking and Printing on Battery Module Housings

Power battery module housings can be made from a variety of materials, including PP, PP/glass-fiber composites, PA (nylon), and PC/ABS alloys. PP and PP/glass-fiber composites are widely used in battery module housings due to their cost advantages and well-balanced overall performance.

However, these non-polar substrates have very low surface energy, making it difficult for conventional inks to adhere effectively. At the same time, battery housings need to carry brand logos, model information, traceability QR codes, safety warnings, and other markings, which places extremely high demands on ink adhesion.

As an ink binder, CPP resin can form strong physical entanglement with PP substrates through "like-with-like affinity," while its polar groups can also provide good compatibility with pigments and additives in the ink.

Using CPP-based inks for battery housing printing can help ensure that markings remain clear and firmly attached throughout the battery's service life while withstanding vibration, temperature cycling, and changes in humidity.

2.3 Application 3: Electrolyte-Resistant Coatings for Battery Labels

Battery labels are attached to the surface of battery cells or modules. In addition to providing identification, they also contribute to electrical insulation and electrolyte protection. The coating on the label must withstand long-term exposure to electrolytes without swelling or peeling.

By incorporating maleic anhydride-modified CPP resin into the label coating, its chemical bonding capability can be used to form a strong bond with the substrate. At the same time, the inherent chemical resistance of CPP provides the coating with a basic barrier against electrolyte exposure.

For applications requiring higher electrolyte resistance, crosslinkable monomers can also be introduced through copolymer modification, transforming the coating from a thermoplastic system into a thermosetting system and significantly improving its resistance to solvent penetration.

3. Technical Compatibility of CPP in Battery Packaging

The reason CPP resin can play an important role in new energy battery packaging lies primarily in three key advantages provided by its molecular structure.

3.1 "Molecular Bridging" Enables Adhesion Across Different Interfaces

One end of the CPP molecular chain retains the non-polar structure of polypropylene, allowing molecular-level interpenetration with PP substrates. The other end gains polarity through the presence of chlorine atoms, enabling good interaction with aluminum foil, polar resins, and functional fillers.

This unique structure, which can be described as "non-polar affinity on one side and polar affinity on the other," makes CPP an effective "bridge" between different material layers in battery packaging.

3.2 Chemical Basis for Electrolyte Corrosion Resistance

CPP has a certain degree of resistance to dilute acids, dilute alkalis, and organic solvents. In lithium battery electrolyte environments, high-purity CPP combined with appropriate crosslinking modification can effectively resist the penetration of carbonate-based solvents.

The electrical insulation properties of CPP in the bonding layer of aluminum-plastic film can also help prevent internal short circuits within the battery.

3.3 Low Melting Point for Thin-Gauge Processing

The trend toward lightweight battery packaging requires bonding layers and coatings to be as thin as possible. The melting point of CPP resin generally ranges from approximately 80°C to 160°C, with products containing around 30% chlorine typically showing relatively low melting points.

A lower melting point means that uniform coating can be achieved at milder processing temperatures. This makes CPP suitable for the processing of ultra-thin bonding layers while reducing thermal damage to heat-sensitive functional layers.

3.4 Process Advantages for Environmental Compliance

Gas-phase CPP production does not use organic solvents, allowing volatile organic residues in the final product to be reduced to extremely low levels.

For battery products exported to the European Union, the use of gas-phase CPP can help meet REACH requirements and stringent customer requirements for VOC emissions.

4. Three Frequently Asked Questions

Question 1: What is the Main Function of CPP Resin in Aluminum-Plastic Film? 

CPP resin is mainly used as a key component in the formulation of the bonding layer in aluminum-plastic film.

It performs two core functions. First, it enhances the adhesion between the aluminum foil and the inner cast polypropylene film, helping prevent delamination of the aluminum-plastic film during forming and battery assembly. Second, its polar groups can form strong interactions with the oxide layer on the surface of the aluminum foil.

It is important to distinguish between the two similarly named materials. The heat-sealing layer inside aluminum-plastic film is cast polypropylene film (CPP film), whereas chlorinated polypropylene resin (CPP resin) is a functional component used in the bonding layer. Although their names are similar, their functions are different.

The adhesion of CPP resin to aluminum foil and its resistance to electrolytes directly affect the service life of aluminum-plastic film and the safety performance of the battery.

Question 2: What Special Requirements Does Battery Housing Printing Have for CPP Resin? 

Battery housings are commonly made from PP or PP/glass-fiber composites. These materials have low surface energy and high chemical inertness, making adhesion difficult for conventional inks.

The "like-with-like affinity" of CPP resin allows it to form a strong bond with PP substrates. In addition, battery housing printing must meet several specific requirements.

First, it must be resistant to electrolytes to prevent markings from peeling if electrolyte leakage occurs under abnormal battery conditions.

Second, it must withstand high- and low-temperature cycling to accommodate temperature changes during battery charging and discharging.

Third, it must provide adequate electrical insulation so that the coating does not compromise the insulation resistance of the battery module.

Maleic anhydride-modified CPP products are recommended for applications requiring a balance between adhesion and electrolyte resistance.

Question 3:  What Are the Environmental Requirements for CPP Resin Used in New Energy Battery Packaging?

The environmental requirements of the new energy battery industry are generally more stringent than those of conventional packaging.

First, the RoHS Directive restricts hazardous substances such as lead, mercury, cadmium, and hexavalent chromium. CPP resin itself does not contain these heavy metals, but catalyst residues should still be carefully controlled.

Second, the REACH Regulation imposes strict restrictions on Substances of Very High Concern (SVHCs). Battery products exported to the European Union need to provide SVHC declarations where applicable.

Third, automotive manufacturers impose strict controls on VOC emissions. Gas-phase CPP resin is therefore recommended to eliminate the risk of solvent residues at the source.

Fourth, the recyclability of battery packaging materials is receiving increasing attention. Since CPP and the PP inner layer both belong to the polyolefin family, CPP can contribute to the compatibility of the overall material system with recycling and recovery processes.

Conclusion

The rapid development of the new energy battery industry is creating new application opportunities for CPP resin.

From bonding layers in aluminum-plastic film to printing on battery housings and electrolyte-resistant coatings for battery labels, CPP is becoming an increasingly important functional material in battery packaging systems due to its unique "molecular bridging" properties and chemical resistance.

As the localization of aluminum-plastic film accelerates and environmental requirements across the battery industry continue to become more stringent, gas-phase CPP resin is expected to have further application potential in the new energy sector.