Background and influence of deformation problems in Automotive battery aluminum cases

Automotive battery aluminum cases are widely used in fields such as new energy vehicles due to their structural rules and high energy density. However, due to its anisotropic structural characteristics, it is prone to deformation problems such as unevenness in length and width directions during the production process, which can affect the safety and service life of the battery. The occurrence of deformation problems is closely related to multiple aspects such as material properties, manufacturing processes, and internal environmental control of power battery units. Therefore, it is necessary to analyze the reasons from multiple dimensions and implement targeted preventive measures. This article provides an in-depth analysis of the core causes and systematic prevention strategies for the deformation of Aluminum case for new energy cars, providing technical references for industry production practices.

In the production system of lithium-ion batteries, the stability of the Lithium battery aluminum case structure is directly related to product reliability, and deformation problems are often the result of the synergistic effects of multiple factors such as material properties, process control, and internal thermodynamic states. From the perspective of material and structural dimensions, the selection of aluminum shell materials and strength design are fundamental factors. If materials with insufficient tensile strength (such as 3003 aluminum alloy) or shell thickness less than 0.6 mm are used, they are prone to yield deformation under internal pressure and thermal stress.

At the same time, the structural characteristics of the welding area cannot be ignored: the heat affected zone formed during the welding process will reduce local strength by 20% to 30% due to lattice reorganization, becoming a stress concentration area that is prone to deformation during subsequent stress. The rationality of welding process has a decisive impact on the stability of shell structure. Laser welding, as a mainstream process, if the heat input is not properly controlled (such as power exceeding 300 W or welding speed below 30 mm/s), it can cause local temperatures in New energy aluminum battery cases to far exceed the melting point of aluminum (660 ℃), resulting in a deep melt pool and a sharp increase in cooling shrinkage stress; In addition, improper weld bead design (such as the absence of stress relief notches in continuous ring welding and weld bead width less than 0.8 mm) can reduce the load-bearing capacity of the weld and further exacerbate the risk of deformation.

The abnormal internal pressure of the battery is another core thermodynamic cause of deformation in Deep drawn aluminum battery housing. When the temperature exceeds 45 ℃, side reactions such as electrolyte decomposition and abnormal damage to the SEI film inside the battery will accelerate gas production. When the internal pressure exceeds 10 kPa, it will push the shell to deform. At the same time, in a fully charged state, the expansion rate of the negative electrode can reach 20% to 30%. If the gap between the battery cell and the inner wall of the shell exceeds 1.0 mm (industry standard gap is 0.3-0.8 mm), the expansion force cannot be effectively restrained by the Rechargeable aluminum shell, and will turn to higher degrees of freedom in the vertical direction, causing deformation of the cover plate or side wall. In addition, process control deviations during the production process may also cause or exacerbate deformation problems. For example, if the gap between the cover plate and the shell exceeds 0.2 mm during assembly, the thermal stress during welding will superimpose with the gap displacement effect, directly leading to deformation; When the vacuum degree during the sealing stage is too low (below -90 kPa), external atmospheric pressure will directly act on the weak parts of the shell, causing passive compression deformation.

In response to the above deformation mechanism, preventive strategies should be systematically developed from the aspects of material selection, structural design, welding process, and process control. In terms of materials and structure, aluminum alloy materials with higher tensile strength (such as 6063, etc.) should be prioritized, and the thickness of the Pack aluminum housing should be designed reasonably (recommended not less than 0.8 mm). At the same time, the assembly gap between the battery cell and the inner wall of the housing should be optimized, strictly controlled within the range of 0.3-0.8 mm. In terms of welding process, laser welding parameters should be strictly controlled to avoid excessive power or low welding speed.

At the same time, weld bead design should be optimized, stress relief structures should be added to ensure that weld width and penetration are within a reasonable range. In terms of process control, it is necessary to strictly manage the assembly gap between the cover plate and the Battery pack with aluminum housing (not exceeding 0.2 mm), and ensure that the vacuum degree during the sealing stage meets the process requirements (not less than -90 kPa). In addition, it is necessary to strengthen the temperature management of the production environment, avoid the battery from being in a working condition above 45 ℃ for a long time, reduce the production of side reaction gas from the source, and reduce the risk of internal pressure rise.

The above is a systematic review of the deformation mechanism and prevention strategies of Automotive battery aluminum cases. If you encounter technical problems or need further process optimization support in actual production, please feel free to contact us through the platform, and we will provide you with professional solutions and technical consultation.