Lithium battery casing material selection analysis: Why is aluminum the industry’s first choice?

Lithium-ion Battery Aluminum Shell is a square or cylindrical battery shell component made of aluminum alloy as a base material through precision stamping, stretching or extrusion molding processes. It is used to accommodate the cells, electrolytes and electrode components of lithium-ion batteries, and provides mechanical protection, sealing insulation and heat conduction functions. As a key structural component of lithium-ion batteries, the aluminum shell is in direct contact with the battery's internal electrode group and participates in the electrical circuit as part of the battery's negative or positive terminals. Therefore, there are strict technical requirements for dimensional accuracy, surface quality, air tightness and mechanical strength. The wall thickness of the aluminum shell is usually between 0.2mm and 1.0mm, which varies according to the battery capacity. In square aluminum-shell batteries, the shell is usually formed one or more times using a deep drawing process, with a rounded corner transition at the bottom, and a crimp or welding structure reserved at the open end for sealing connection with the cover plate. The inner wall of the aluminum shell needs to be treated with an insulating coating or covered with an insulating film to prevent internal short circuits between the battery tabs and the shell. In addition, the surface of the aluminum shell needs to have good electrolyte corrosion resistance, because electrolyte components such as lithium hexafluorophosphate inside the battery are corrosive to metal materials.

 

New Energy Vehicle Aluminum Battery Case specifically refers to aluminum case products used in new energy vehicle power batteries. This type of product has higher requirements for consistency, reliability and safety, and needs to meet national standards such as GB/T 31484 and GB/T 31485 as well as customer-specific vibration, impact and extrusion test requirements. At the cell level, Aluminum Battery Case and Lithium Cell Aluminum Can are different expressions of the same type of product. The former focuses more on the shell function after battery assembly, while the latter emphasizes the form as a single cell container. The explosion-proof notch design on the bottom of the aluminum shell has been an important safety feature in the industry in recent years. When the internal pressure of the battery exceeds the set threshold, the bottom explosion-proof valve will prioritize breaking and releasing the pressure to avoid more serious consequences caused by the overall explosion of the shell. In addition, the thickness uniformity and wall thickness distribution of the aluminum shell directly affect the gravimetric energy density and volumetric energy density of the battery. A shell that is too thick will reduce the energy density, and a shell that is too thin may not provide sufficient mechanical support and safety redundancy.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The product quality of New Energy Vehicle Aluminum Battery Case is reflected in several key details, which directly determine the safety, consistency and assembly efficiency of the battery cells. Wall thickness uniformity is the primary concern. Through precise mold design and multi-pass drawing process control, we ensure that the wall thickness deviation of each part of the aluminum shell side wall is within ±0.02mm, and there is no local thinning in the bottom corner area to avoid local overheating or insufficient mechanical strength caused by uneven wall thickness. The bottom explosion-proof valve is the core safety feature of the power battery aluminum shell. We use high-precision scoring technology to control the remaining thickness of the explosion-proof valve between 0.03mm and 0.08mm. The deviation of the notch depth does not exceed ±0.005mm, and the burst pressure deviation is controlled within ±0.2MPa to ensure that the pressure relief can be accurately and consistently opened when the battery has abnormal internal pressure. The flatness of the open end directly affects the quality of laser welding of the aluminum shell and the cover plate. Our notching process ensures that the flatness of the open end is below 0.05mm, with no burrs, no curling, and no gaps, providing a good contact interface for subsequent welding.

 

The cleanliness of the inner wall is the key to preventing micro-short circuits inside the battery. We use a multi-stage ultrasonic cleaning process, combined with high-temperature hot air circulation drying, to control the residual particulate matter on the inner wall of the aluminum shell to no more than 3 particles above 100 μm per piece. We can also provide cleanliness test reports and particulate matter sample filter membranes according to customer requirements. In terms of external surface quality, the outer wall of the aluminum shell should be smooth without drawing, scratches, pits, or oil spots. For appearance parts or aluminum shells with special customer requirements, we also provide automatic optical inspection of surface defects to eliminate products with visible defects. Dimensional consistency is the basic guarantee for batch assembly. We implement 100% online inspection or high-proportion random inspection of key dimensions such as the length, width, height, open end inner diameter, and bottom thickness of the aluminum shell. The dimensional process capability index Cpk reaches above 1.33 to ensure interchangeability between multiple batches of products.

 

In addition, the roundness of the rolled edge structure and the uniformity of the chamfer radius are also important details that we control. The rolled edge has no cracks or wrinkles, and the chamfers are smooth and have no sharp corners to avoid scratching the diaphragm or tabs during the battery assembly process. The packaging method also reflects detailed management. The aluminum shell is packed in anti-static blister pallets or clean cartons, and the layers are separated by sulfur-free paper or pearl cotton to prevent collisions and scratches during transportation and handling. Each pallet is attached with a batch label and inspection report QR code to achieve full process traceability.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The manufacturing process of Stamping Aluminum Sheet Metal mainly includes coil flattening, blanking, multi-channel stretching, cutting, punching, bottom explosion-proof valve forming, cleaning, drying, inspection and packaging. First, the coil material is flattened and blanked. The aluminum coil is uncoiled and leveled and then fed into the blanking die to punch out round or square blanks (commonly called aluminum discs or aluminum square sheets). The blanking process needs to ensure that the edges of the blank are smooth and burr-free, otherwise scratches or stress concentration points will occur during the subsequent stretching process. Second, multiple stretches. The blanks are fed into multiple drawing presses or multi-station drawing dies in sequence, gradually reducing the diameter and increasing the depth, and finally form the desired shell shape. The number of stretching times depends on the ratio of the depth to diameter of the aluminum shell (aspect ratio). The larger the aspect ratio, the more stretching times are required. After each drawing process, the material becomes harder due to work hardening. For aluminum shells with greater depth, an intermediate annealing treatment needs to be inserted between the two drawing processes. Third, incision and size finishing. The open end of the stretched aluminum shell usually has unevenness or residual stretch marks. It is necessary to cut the open end flat through the cutting process and ensure that the height tolerance of the open end is within ±0.1mm.

 

For aluminum shells that require curling, curling preprocessing is required after incision. Fourth, the bottom explosion-proof valve is formed. The explosion-proof valve structure is processed by scoring or partially thinning the bottom of the aluminum shell. The notching depth and residual thickness of the explosion-proof valve must be precisely controlled to ensure that no leakage occurs under normal operating pressure and that it can reliably rupture and relieve pressure when the internal pressure rises abnormally. Fifth, clean and dry. During the stretching and stamping process of the aluminum shell, stamping oil, aluminum chips and dust will remain, which must be completely removed through ultrasonic cleaning or spray cleaning. The cleaning medium usually uses environmentally friendly water-based cleaning agents. After cleaning, hot air drying is performed, and the cleanliness is tested online. Sixth, inspection and packaging. Use imaging measuring instruments, air tightness detectors, wall thickness measuring instruments and other equipment to conduct full or random inspections of the key dimensions, air tightness and wall thickness distribution of the aluminum shell.

 

After passing the inspection, it is packaged in a clean environment, usually in anti-static pallets or blister boxes, and each layer is separated by dust-free paper to prevent collisions and scratches during transportation. Compared with steel shell stamping, the Aluminum Metal Stamping process has stricter requirements for mold clearance, lubricant selection, and drawing speed control, because aluminum has good ductility but is more prone to mold sticking and scratches. A common problem in Aluminum Sheet Metal Stamping is longitudinal scratches on the side walls of the aluminum shell. This is usually caused by mold surface wear, aluminum chips failing to be blown out in time, or lubricant failure. It needs to be prevented through regular mold repair, online purging and lubricant testing. For consumer electronic aluminum shells with special appearance requirements, surface treatment processes such as polishing, brushing, sandblasting or anodizing will also be added to obtain a specific color or texture. In the field of power batteries, the cleanliness of the aluminum casing is one of the most important quality indicators. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

We focus on the manufacturing of high-precision metal parts, with advanced production equipment and rich industry experience. If you are looking for a reliable partner, please contact us for detailed quotations and technical consultation on Lithium-ion Battery Aluminum Shell.