At present, the battery pole-ear rubber is imported from Japan. The technical difficulty of polar lug rubber production is that the molecular weight of PP material should be controlled within a narrow range, and the PP rubber produced by domestic technology cannot meet the requirements.
Structure of polar lug rubber: polar lug rubber is generally made of three layers of material hot-pressed, except for the single-layer modified PP produced by Toppan and Showa and the five-layer polar lug rubber produced by Tiansheng. Generally speaking, sheet rubber consists of a skeleton layer in the middle and a modified PP layer on both sides, with the same modified PP material on both sides. In order to pursue ultra-high bonding strength between the rubber layer and the metal strip, Hitachi and Tenson use different modified PP materials on the two surfaces, one is pro-metal modified PP and the other is pro-plastic modified PP.
At present, the frame adhesives used in the domestic market are divided into white, black, yellow and single-layer adhesives. Most of the high-end core customers use single-layer topping 80μm and 50μm white glue. Generally speaking, DNP black glue and DNP yellow glue are used by low- and mid-range customers. White glue with three-layer structure is widely used in Japan and Korea. The core companies in Japan and Korea rarely use single-layer white glue and basically use white glue with three-layer structure. The higher-end core companies in China are also gradually adopting the white rubber with three-layer structure.
The performance of each cell lug rubber
The structure of DNP yellow rubber is the middle functional layer UHR (non-woven structure) and the two surface layers are modified PPa.
The thickness of the UHR layer is 14g/m2≈12μm and the thickness of the surface modified PPa is 44μm.
The melting point of UHR is 310~340℃ and the melting point of PPa is 147℃.
The yellow rubber lugs are in danger of delamination. However, the encapsulation conditions of yellow rubber lugs are easier to adjust than those of white rubber. The disadvantages of yellow rubber were also mentioned by previous Japanese lug suppliers in three ways:
(1) The sheet rubber is made of a middle layer of UHR and two layers of modified PP rubber hot pressed on the surface.
(2) The middle layer is non-woven fabric, moisture will enter the cell from the non-woven fabric through capillary penetration and make the cell bulge.
(3) The non-woven fabric is easy to delaminate, the hot pressing effect is not good, and the battery cell is easy to cause leakage after long-term use or long-term shelving.
The thickness of PEN layer is 12μm, the thickness of surface modified PPa is 44μm. the melting point of PEN is 265℃, the melting point of PPa is 147℃. the functional layer of PEN and PP layer is different material compound, there is a risk of delamination, so high-end customers generally do not use this adhesive.
White glue: white glue is divided into single-layer white glue, three-layer white glue and five-layer white glue.
Single-layer white glue is generally composed of one layer of modified PP, similar to the initial inner layer of aluminum plastic film, with melting point above 140℃, which is close to that of CPP.
Three-layer structure white glue is coextruded from two layers of modified PP and the middle skeleton layer PP on the surface, there is no risk of delamination, high-end customers and power cells generally use this kind of sheet glue.