The main reasons for lithium batteries to use aluminum shells can be analyzed in detail from the following aspects, namely lightweight, corrosion resistance, good conductivity, good processing performance, low cost, good heat dissipation performance, etc.
1. Lightweight
• Low density: The density of aluminum is about 2.7 g/cm³, which is significantly lower than that of steel, which is about 7.8 g/cm³. In electronic devices that pursue high energy density and lightweight, such as mobile phones, laptops, and electric vehicles, aluminum shells can effectively reduce the overall weight and improve endurance.
2. Corrosion resistance
• Adaptability to high-voltage environments: The working voltage of lithium battery positive electrode materials, such as ternary materials and lithium cobalt oxide, is relatively high (3.0-4.5V). At this potential, aluminum will form a dense aluminum oxide (Al₂O₃) passivation film on the surface to prevent further corrosion. Steel is easily corroded by electrolyte under high pressure, resulting in battery performance degradation or leakage.
• Electrolyte compatibility: Aluminum has good chemical stability to organic electrolytes, such as LiPF₆, and is not prone to reaction during long-term use.
3. Conductivity and structural design
• Current collector connection: Aluminum is the preferred material for positive electrode current collectors (such as aluminum foil). The aluminum shell can be directly connected to the positive electrode, simplifying the internal structure, reducing resistance, and improving energy transmission efficiency.
• Shell conductivity requirements: In some battery designs, the aluminum shell is part of the current path, such as cylindrical batteries, which has both conductivity and protection functions.
4. Processing performance
• Excellent ductility: Aluminum is easy to stamp and stretch, and is suitable for large-scale production of complex shapes, such as aluminum-plastic films for square and soft-pack batteries. Steel shells are difficult to process and have high costs.
• Sealing guarantee: Aluminum shell welding technology is mature, such as laser welding, which can effectively seal the electrolyte, prevent moisture and oxygen from invading, and extend battery life.
5. Thermal management
• High heat dissipation efficiency: The thermal conductivity of aluminum (about 237 W/m·K) is much higher than that of steel (about 50 W/m·K), which helps the battery to dissipate heat quickly when working and reduce the risk of thermal runaway.
6. Cost and economy
• Low material and processing costs: The raw material price of aluminum is moderate, and the processing energy consumption is low, which is suitable for large-scale production. In contrast, materials such as stainless steel are more expensive.
7. Safety design
• Pressure relief mechanism: Aluminum shells can release internal pressure and avoid explosion in the event of overcharge or thermal runaway by designing safety valves, such as the CID flip structure of cylindrical batteries.
8. Industry practices and standardization
• Aluminum shells have been widely adopted since the early days of lithium battery commercialization, such as the 18650 battery launched by Sony in 1991, forming a mature industrial chain and technical standards, further consolidating its mainstream position.
There are always exceptions. In some special scenarios, steel shells are also used:
In some scenarios with extremely high mechanical strength requirements, such as some power batteries or extreme environment applications, nickel-plated steel shells may be used, but the cost is increased weight and cost.
Conclusion
Aluminum shells have become an ideal choice for lithium battery shells due to their comprehensive advantages such as light weight, corrosion resistance, good conductivity, easy processing, excellent heat dissipation and low cost, perfectly balancing performance, safety and economic requirements.
Post time: Feb-17-2025
