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[up knowledge] an article to understand the new energy vehicle power battery structure bonding materials

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A large number of materials are needed in the battery system to realize the battery cell grouping. The requirements of each material are different, which can be basically divided into structural bonding materials, thermal conductive materials, insulating materials, thermal insulation materials and sealing materials.

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A large number of materials are needed in the battery system to realize the battery cell grouping. The requirements of each material are different, which can be basically divided into structural bonding materials, thermal conductive materials, insulating materials, thermal insulation materials and sealing materials.

Structural bonding material: Generally speaking, it is divided into structural adhesive or double-sided adhesive tape, which is mainly used for bonding battery core and battery core, battery core and foam, battery core and module shell, etc. Its main function is to integrate battery core and module to meet the requirements of vibration, impact and drop of module.

· Thermal conductive material: mainly used to conduct the heat of the battery cell and transfer the heat of the module to the outside.

Insulation material: This material is often combined with the requirements of other materials. The main goal is to place the single cell in a state of leakage or other damage, and the entire battery will cause short circuit or insulation problems on the metal conductive material.

Insulation material: The main requirement is to isolate external heat from entering the battery system. There are two types of cold and hot. I will further introduce the actual requirements of the fire experiment and the temperature drop experiment for the battery system.

Sealing material: mainly to achieve the requirements of battery system sealing, to achieve the role of IP67.

Figure 1 Overview of materials used in the battery system

We compare the differences in terms of square shells, soft bags and cylinders:

Part I Square Shell Battery

Fixing of square shell batteries in the module: bonding and positioning between batteries, bonding of side plates and end plates. The square shell battery core body is relatively heavy, so the first task needs to fix the battery core. According to the expansion of the battery core, it is necessary to consider leaving sufficient buffer in the module, so higher strength glue needs to be considered here. The surface to be bonded here is:

Aluminum alloy shell insulation film coating

Insulating gasket

· Outer frame aluminum

In general, the bonding between the above two different substrates needs to have sufficient strength, and at the same time, it needs to be resistant to vibration after the bonding is completed. In terms of environmental characteristics, it is in the temperature range of -40°C to 85°C, and the temperature shock resistance is good. The operation time of the whole glue needs to be controlled. When choosing tape and glue, there are some differences.

If glue is selected, the high-strength bonding between the cells is mainly considered, and additional elastic materials are used for buffering.

The adhesive tape bonding method of viscoelastic body mainly uses the characteristics of shock absorption and energy absorption of the adhesive tape, and the strength is to ensure that the impact test of the battery core meets the requirements.

Fig. 2 Requirements for Adhesive Adhesive

Experience summary recommend: bonding between square shell cells: two-component polyurethane DP6310NS,VHBTM double-sided adhesive tape: 4914-02, GTM715

The second part of the soft pack battery

Fixation between soft pack battery core and aluminum shell: bonding positioning, thermal conductivity, good adhesion with PET film and aluminum plate.

Due to the need to fix the battery core, it is also necessary to consider the design of sufficient buffer inside to form the overall situation, so it is necessary to consider the high strength of the glue here, and has a certain thermal conductivity, so that the use of bonding in the module has enough heat transfer. Half of the two-component polyurethane thermal conductive adhesive or high hardness thermal conductive VHBTM double-sided tape is considered. The basic consideration coefficient mainly includes thermal aspect and structural aspect, which is divided into thermal conductivity (W/m.k) and bonding strength; further consideration, it needs to be stable under various environmental conditions, such as high and low temperature characteristics and alternating temperature, and can also meet the requirements of shock and vibration.

Figure 3 Structural Adhesive and VHBTM Double-Sided Tape

Experience summary: bonding between soft-pack batteries: FB49, bonding foam: 468MP,9448A,55236

Part III Material Application of Cylindrical Battery Pack

The bonding between the battery core and the base: acrylic structural adhesive, with strong bonding strength, play a good role in fixing;

It includes a base for placing the cells side by side. The base is provided with a fixed component for fixing the two poles of the side-by-side cells, an adjusting component for pushing the side-by-side cells to be closely arranged, a gel promoting component and a push plate component for guiding and moving the glued cells to the position of the gel promoting component. Due to the characteristics of the cylindrical battery core, it is necessary to emphasize the adhesive force, shear strength, aging resistance, life and other performance indicators of the glue, and after the surface of the battery core is treated, it is also necessary to consider the thermal conductivity, aging resistance, electrical insulation, flame retardancy and other performance indicators of the glue.

Experience recommend: cylindrical battery and PC bracket: two-component epoxy DP125UV;PC bracket and busbar aluminum sheet: two-component acrylic DP8805

In actual operation, for the material of the structural adhesive, especially according to the design requirements of the above module, when going down to the actual characteristics of the glue, the characteristics of the glue need to be considered. In terms of room temperature characteristics, the bonding guarantees stable bonding at room temperature, while satisfying the characteristics of vehicle operation, and also has excellent aging resistance in high temperature and low temperature environments. Here it needs to be verified by the actual glue and the selected material test. Here to 3M VHBTM tape battery bonding performance test report to talk about the actual test method:

Step 1: Paste the blue PETfilm aluminum plate covered with 4914-02 and another blue PET film aluminum plate

Step 2: Bonding the PC insulating cover with 4914-02 and the black PET insulating cover with 4914-02

Step 3: PET steel mold and aluminum plate with 4914-02 bonding

Step 4: After rolling all the test pieces, one group is placed in a high and low temperature aging oven for aging test.

Step 5: Test the dynamic shear speed of the sample after high and low temperature aging and the sample after 72 hours in the constant temperature and humidity test chamber, and the shear speed is 2in/min.

Using the test data of this glue also requires simulation and testing at the module level. We think it is very important to achieve communication and data coupling between the following components and materials for your reference.

Source: Network