Key points for selecting materials for lithium battery pack casings

The material selection of the lithium battery pack casing, as a key component protecting the internal cells and circuit system, directly affects the safety, durability and performance of the battery. When choosing the shell material, the following core factors should be comprehensively considered:

Mechanical strength and impact resistance

The shell needs to have sufficient rigidity and toughness to withstand the impact force when subjected to external squeezing, dropping or collision. If the material strength is insufficient, it may cause the shell to deform or even crack, which in turn may lead to short circuits or leakage of the internal battery cells. For instance, in the application of electric vehicles, battery packs need to withstand vibrations and collisions during vehicle operation, and the casing materials must pass strict impact tests (such as drop weight tests).

2. Flame retardancy and high-temperature resistance

When lithium batteries are overcharged, short-circuited or have thermal runaway, they may generate high temperatures or even open flames. The casing material needs to have flame-retardant properties to delay the spread of fire. Common requirements include passing the UL 94 V-0 flame retardant test (the material self-extinguishes within 10 seconds in the vertical burning test). In addition, the material needs to maintain stability in high-temperature environments to prevent seal failure due to thermal deformation.

3. Chemical stability and corrosion resistance

The casing needs to be in long-term contact with the electrolyte, gas inside the battery and chemical substances in the external environment (such as acid rain and salt spray), and the material must have corrosion resistance. For instance, some plastics may swell or degrade in the electrolyte, and metal materials need surface treatment (such as anodizing) to enhance their corrosion resistance.

4. Insulation and electromagnetic shielding

The casing needs to effectively isolate the internal circuit from the external conductor to prevent the risk of short circuit. Meanwhile, in high-frequency applications (such as drone batteries), the casing may need to have electromagnetic shielding functions to reduce interference. In such cases, conductive coatings or metal composite materials should be selected.

5. Lightweight and heat dissipation performance

In portable devices such as mobile phones and drones, the casing needs to take into account both lightweight and structural strength. In addition, the material should have a certain degree of thermal conductivity to assist in heat dissipation and prevent the battery from experiencing performance degradation due to overheating. For instance, the aluminum alloy shell can enhance the heat dissipation efficiency by optimizing the design of the heat dissipation fins.

6. Sealing performance and water and dust resistance

The casing needs to pass the IP rating test (such as IP67) to ensure normal operation in damp or dusty environments. The sealing design needs to take into account the compatibility between the material and the sealing element to avoid sealing failure caused by thermal expansion and contraction.

Key points for the design of lithium battery pack enclosures

Structural strength optimization

Reinforcing rib design: Enhance the bending resistance by increasing the wall thickness of the shell or setting reinforcing ribs.

Modular splicing: Adopting a split design (such as upper and lower covers) facilitates assembly and maintenance, while ensuring the strength of the splicing points.

2. Heat dissipation design

Thermal conduction path optimization: Fill thermal conductive silicone gel between the metal casing and the battery cell to enhance the thermal conduction efficiency.

Ventilation hole design: Heat dissipation holes should be set up in non-critical areas, and dust-proof nets should be used in conjunction to prevent foreign objects from entering.

3. Electrical safety design

Insulation layer setting: Add insulating gaskets between the metal casing and the internal circuit to prevent short circuits.

Grounding design: The metal casing must be reliably grounded to prevent the accumulation of static electricity and the resulting electric arc.

4. Sealing and protective design

Selection of sealing ring material: Prioritize the use of silicone or fluororubber that is resistant to aging and chemical corrosion.

Waterproof and breathable valve: In scenarios where it is necessary to balance the pressure difference between the inside and outside (such as high-altitude environments), install a waterproof and breathable valve to prevent water vapor from entering.

5. Convenience of installation and maintenance

Standardized interfaces: The casing should reserve standardized interfaces such as fixed holes and cable outlets to facilitate integration with the equipment.

Detachable design: In scenarios requiring regular maintenance, the casing should be designed with an easily detachable structure (such as snap fasteners or screw fixation).

Comparison of common materials and applicable scenarios

Metal materials (aluminum alloy, steel)

Advantages: High strength, good heat dissipation, strong electromagnetic shielding.

Disadvantages: Heavy weight, prone to corrosion (surface treatment required), and relatively high cost.

Applicable scenarios: Electric vehicles, energy storage systems and other fields with high requirements for strength and heat dissipation.

Engineering plastics (PC, ABS, PP)

Advantages: Lightweight, low cost, and easy to process and form.

Disadvantages: Poor flame retardancy and weak high-temperature resistance.

Applicable scenarios: consumer electronics, small portable devices.

Composite materials (carbon fiber, glass fiber reinforced plastic)

Advantages: High strength, lightweight, and corrosion resistance.

Disadvantages: High cost and difficult processing.

Applicable scenarios: high-end unmanned aerial vehicles, aerospace battery packs.