Preparation And Properties Of Flexible Packaging Materials For Lithium-ion Batteries

Compared with traditional steel shell packaging, the flexible packaging materials could reduce the weight of lithium-ion batteries(LIB) greatly, and seized the lithium-ion packaging market rapidly. This thesis obtained appropriate heat-seal materials by investigated the cast polypropylene film (CPP) for inner layer material of LIB, and analyzed their anti-contents penetrability and long-term sealing properties. The flexible packaging materials for LIB were prepared and their overall properties were studied. The research content was as follows:(1) The structure of the innermost layer of flexible packaging materials was designed. The cast polypropylene film was selected as the innermost layer of material and the structure was determined as composite layer/support layer/heat-sealing layer. Moreover, the properties of CPP films were analyzed.(2) The structure of the flexible packaging materials was designed and determined as ON15/DL/A140/Ac/EL/CPP50, which was produced by dry complex and extrusion compound process. Furthermore, the properties of flexible laminate material were analyzed.It was found that:(1) CPP films have good properties, which were produced by high-speed. CPPP is more suitable for the flexible packaging materials of LIB than other types of CPP films. The optimum heat-sealing time is 1 s for 50μm CPPβby the heat-sealing test, and its seal property is excellence for solvent. The structure of CPP(3 is similar to that of the innermost of flexible packaging materials, and CPP(3 is suitable for continuous production for its wide melting range.(2) Tensile strength, breaking elongation, tear strength and peel strength of flexible packaging materials are changed little with long-term, while the tensile strength, elongation at break and tear strength decreased slightly. The peel strength between layers changed significantly within a week, subsequently, the composite properties of essentially were unchangeable. Furthermore, the peel strength of the as-prepared flexible packaging materials is equivalent to the commercial ones after immersion.The heat-sealing strength of flexible packaging for LIB were heat-sealed without solvent is similar to that with DMC. For the as-prepared flexible packaging materials, the heat-sealing range is wide and the performance is stable. The landscape orientation seal strength is slightly higher than the portrait seal strength, and the optimal conditions for the heat-sealing temperature, pressure sealing and time are 170℃,180kPa and 3s, respectively. Moreover, the heat-sealing strength under the optimal condition meets the requirements (≥40N/15mm) of the flexible packaging industry for the LIB.The flexible packaging was simulated to package by DMC, and the change of the innermost material was investigated by FT-IR. The results revealed that the ratio of weight loss is low and the heat-sealing effect is good. After DMC packaging, the surface of the inner material is oxidized, and no obvious change is obtained a year later.