Why do prismatic shell batteries need blue film?

The main reason for wrapping the blue film on the outside of square lithium-ion batteries involves functional requirements and process considerations in many aspects. The following is a detailed explanation:

1. Insulation protection and anti-short circuit design:

The outer shell of prismatic shell batteries is usually made of metal (such as aluminum alloy). Direct contact may cause short circuits between batteries or external components. The blue film acts as an insulating layer to effectively isolate the metal surface and prevent accidental conduction.

Enhanced safety: In scenarios where battery packs are densely arranged, the blue film reduces the risk of short circuits caused by outer shell contact and improves overall safety.

2. Anti-corrosion and sealed environmental protection:

The blue film can isolate corrosive environmental factors such as moisture, salt spray, acidic and alkaline substances, delay oxidation and rust of the metal shell, and extend battery life.

Sealing assistance: Some blue film materials have waterproof and dustproof properties, and cooperate with battery packaging technology to further improve the sealing.

3. Mechanical protection against physical damage:

During transportation, assembly or use, the blue film can reduce the damage to the battery shell caused by scratches and collisions, and avoid the exposure of the internal structure or electrolyte leakage due to shell damage.

Buffering effect: Some blue films are elastic and can absorb slight impacts to protect the structural stability of the internal pole pieces and diaphragms of the battery.

4. Thermal management and auxiliary heat dissipation optimization:

Some blue film materials have added thermal conductive particles (such as ceramics and graphite) to help evenly distribute the surface temperature of the battery and avoid local overheating. At the same time, dark colors (such as blue) may be more conducive to heat radiation.

Insulation function: In extremely high temperature environments, the blue film may serve as an insulation layer to reduce the impact of external heat on the battery.

5. Identification and management model distinction:

Blue is often used to identify specific battery models, capacities or voltage levels, which facilitates quick identification during sorting and maintenance of the production line.

Brand recognition: Manufacturers use unified colors (such as CATL's iconic blue film) to strengthen their brand image and prevent counterfeiting.

Traceability information: Some blue films are printed with QR codes or batch numbers, and the color can be combined to quickly trace production data.

6. Process and cost optimization Automation adaptation:

The blue film has high contrast in the visual inspection system, which is convenient for machine vision positioning, detection of coating integrity, and improved production efficiency.

Material cost: Insulation film materials such as blue PET (polyester) are mature and low-cost, balancing performance and economic benefits.

7. Special functional requirements Flame retardant performance:

Some blue films are added with flame retardants to delay the spread of fire when exposed to high temperatures, meeting battery safety standards.

Anti-ultraviolet: Blue pigments may have better UV resistance, delay film aging, and are suitable for outdoor energy storage scenarios.

Summary

The blue film of prismatic shell batteries is not just a simple packaging, but a key component that integrates insulation, protection, thermal management, and identification.

Its color selection (blue) may be due to technical considerations (such as heat dissipation, detection adaptation), or it may be part of the manufacturer's brand strategy.

In actual applications, the specific characteristics of the blue film will vary depending on the battery application (such as power battery, energy storage battery) and manufacturer design.

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