Lithium-ion battery aluminum shell packaging casing: industry knowledge overview

Lithium-ion battery aluminum shell is a key structural component used to encapsulate and protect the internal cell structure of the battery. It is an irreplaceable physical barrier and safety component in the battery cell. The casing directly determines the air tightness, cycle life and explosion-proof safety performance of the battery. It is the core interface connecting the battery chemical system and the external use environment. From the perspective of engineering classification, lithium-ion battery casings are mainly divided into three forms: square, cylindrical and soft pack according to different battery packaging forms. Among them, Aluminum shell for Prismatic and cylindrical battery cases is a universal shell solution for prismatic and cylindrical batteries, while Aluminum Laminate Pouch for Li-ion Batteries represents the packaging technology route for soft pack batteries. For professional purchasers and engineering customers, understanding the nature of aluminum shells as a "structure-thermal-electricity" multi-physics coupling interface is the starting point for scientific selection and supplier evaluation.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

First, precise matching of alloy grades. Through the dispersion strengthening of manganese element, 3003 aluminum-manganese alloy can increase the yield strength to 130-150MPa without significantly reducing the elongation, which is exactly in the balance range of "resistant to internal gas bulging" and "satisfied with deep drawing without cracking". This alloy is non-heat treatment strengthened, and its mechanical properties meet the usage requirements after drawing, avoiding the risk of dimensional deformation caused by aging treatment. Second, the uniformity control of grain structure. Coarse grains or mixed crystal structure are the microscopic sources of draw cracking. Professional manufacturers conduct metallographic sampling inspections of each batch of base materials, requiring the average grain size to be controlled at 30-60 μm, and the proportion of equiaxed grains to be no less than 85%. The randomness of the grain orientation is verified through electron backscattered diffraction to avoid differences in drawing performance in different directions due to texture concentration.

 

Third, surface quality and passivation film engineering. The melting point of natural alumina film is as high as 2072°C, which is far higher than that of the aluminum matrix. If it is too thick or unevenly distributed, it will affect the stability of laser welding. High-quality aluminum shell products require that the base material surface roughness Ra be controlled at 0.2-0.4μm, and the oxide film thickness should not exceed 50nm. Chemical passivation treatment can be provided according to demand to form a uniform and controllable artificial passivation film, which can significantly improve the width and consistency of the welding window. Fourth, environmental compatibility and long-life design. Strictly control high-potential impurities such as copper and nickel (copper ≤ 0.05%, nickel ≤ 0.01%) to avoid local micro-battery corrosion. For high-voltage systems or extreme-humidity environments, the inner wall ceramic coating or carbon coating can be customized to further improve chemical inertness. At the same time, the 100% recyclability of the aluminum shell meets the purchasing requirements of European and American customers for carbon footprint and circular economy.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The manufacturing of aluminum shells involves many key process links such as material selection, forming processing, welding sealing and surface treatment. In terms of molding process, the shell mainly uses stamping and stretch forming technology. Except for the shell cover, the aluminum alloy shell can usually be stretched and formed in one step. In order to improve production efficiency and reduce mold jamming and scrap rates, automated blanking components and continuous die stamping devices are commonly used in the industry. For the Aluminum deep drawing stamping battery case, the multi-pass deep drawing process is the core of realizing a high aspect ratio square container - the transformation from a circular blanking piece to a rectangular shell requires precise control of the deformation amount and blank holder force of each drawing pass. The cracking control in the corner area is a difficult process.

 

In terms of welding technology, the welding of the battery casing and cover is the first hurdle to ensure sealing, which directly affects the voltage resistance and cycle life of the battery. Laser welding technology for square aluminum shell top cover sealing has undergone continuous iteration: in the early stage, the welding speed was lower than 100mm/s, and then developed to the 100-200mm/s stage. Technologies such as laser hybrid welding or laser beam high-frequency swing welding were used to improve speed and quality. At the current stage, high-speed welding of 300mm/s and above is being explored, using point-annular spot laser welding and other technologies to significantly improve welding stability and product compatibility. Aluminum alloy laser welding faces engineering difficulties such as pores, hot cracks and spatter, which need to be overcome through precise power control and protective gas management.

 

In terms of sealing and protection technology, sealing design plays a key role in battery voltage resistance reliability. During design, it is necessary to systematically calculate the compression amount of the sealing ring, the structure of the sealing groove, the assembly tolerance and the deformation of the end cover. For applications in deep water or high-humidity environments, a combination design of pressure-resistant cabin structure, internal potting reinforcement and O-ring radial sealing can be used to resist pressure shock. In addition, surface treatment processes such as blue film coating help improve energy density and production yield by optimizing the coating structure (such as arranging the overlapping portion on the corner curved surface).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The new energy vehicle field is the most important application scenario for aluminum shells. Power battery packs have extremely strict requirements on the high strength, lightweight and high safety of the casing. The lithium iron phosphate system corresponding to LiFePo4 LFP Lithium Iron Phosphate battery cells is widely used in battery systems for passenger cars and commercial vehicles because of its excellent thermal stability. The aluminum shell plays multiple roles in heat conduction, mechanical protection and electrical insulation. Large cylindrical battery casings are also rapidly penetrating the new energy vehicle scene due to their high safety and fast charging performance advantages.

 

The field of energy storage systems has put forward differentiated requirements for the reliability, lifespan and cost-effectiveness of aluminum shells. Energy storage scenarios usually require a cycle life of more than 6,000 times, which requires the aluminum shell to maintain good air tightness and structural stability during long-term use, and will not leak due to micro-corrosion or stress fatigue. Large cylindrical batteries generally use aluminum shell packaging solutions. Relying on their lightweight, good thermal conductivity and controllable cost characteristics, they are widely used in energy storage cylindrical batteries.

 

The field of consumer electronics has high requirements for the thinness, lightness, feel and integration of battery cases. Soft-wrapped aluminum-plastic film occupies a dominant position in this field due to its advantages such as light weight, high energy density, and low internal resistance. Aluminum shell for lithium polymer battery cell is oriented to lithium polymer batteries and has unique value in flexible shape adaptation. The field of special equipment has additional protective performance requirements for battery cases. For example, the battery shell used by deep-water robots needs to withstand a water pressure of about 1MPa (corresponding to a water depth of about 100 meters). The design requires systematic calculation of wall thickness, reinforcement ribs, end cover structure and sealing reliability.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

If you need to customize LiFePo4 Prismatic Battery Aluminum Cells for your next high-security energy storage or power project, our engineering team can provide full-process technical support from material selection to structural simulation to ensure that the shell design perfectly matches your system needs.