The "Three Musketeers" of Lithium Batteries: Lithium Battery Packaging Film, Lithium Battery Separator and Battery Cell Blue Film

The "Three Musketeers" of Lithium Batteries: Lithium Battery Packaging Film, Lithium Battery Separator and Battery Cell Blue Film

Lithium battery packaging film

The patron saint of electronic products

1. Structure and characteristics of lithium battery packaging film

Lithium battery packaging film usually consists of three layers of aluminum foil (nylon layer) ON/Al/CPP or four layers (nylon layer) ON/Al/PA/CPP. The outer nylon layer mainly plays a protective role to prevent the aluminum foil layer from being scratched. The outer material is required to be puncture-resistant and impact-resistant. The middle aluminum foil layer, as a base material, plays a waterproof and barrier role to prevent moisture from invading and block oxygen to protect the contents of the battery. The main function of the inner heat-sealing layer (CPP) is heat sealing. Based on the multi-layer structure, it has the functions of corrosion resistance, puncture resistance, aging resistance, insulation, and moisture resistance. It is an ideal packaging material for electronic products. The industry also calls it "aluminum-plastic film". In addition to the above properties, the recyclable characteristics of battery separator film, combined with the concept of green environmental protection, adapt to the trend of the times.

Lithium battery-material-diaphragm technology route and development

Lithium-ion batteries are mainly composed of five parts: positive electrode material, negative electrode material, diaphragm, electrolyte and packaging material. The lithium-ion battery diaphragm is a porous film with uniformly distributed micropores. It is located between the positive electrode material and the negative electrode material of lithium battery. It plays a role in preventing direct contact between positive and negative electrodes, preventing battery short circuit and transmitting ions. It is a key material to ensure battery safety and affect battery performance. Although the diaphragm does not directly participate in the electrochemical reaction of the battery, its performance affects the interface structure, internal resistance and other properties of the battery, and thus affects the battery's energy density, cycle life and rate performance; the thermal stability of the diaphragm also determines the battery's operating temperature tolerance range and battery safety. An ideal battery diaphragm should have good insulation, mechanical strength, electrochemical stability and thermal stability, as well as high porosity and appropriate pore size, and good wettability and adsorption properties for the electrolyte.

▲Lithium-ion battery (cylindrical) structure and lithium battery diaphragm

Summary of high performance resin materials used in diaphragms!

The diaphragm plays two main roles in lithium-ion batteries. First, the diaphragm material needs to have good insulation and a certain strength to avoid direct contact between the positive and negative electrodes in the battery, and can effectively prevent short circuits caused by punctures such as burrs and dendrites, and ensure that there is no significant dimensional change under sudden high temperature conditions, thereby ensuring the safety of the battery. Second, the porous structure of the diaphragm can provide a good migration channel for lithium ions, ensuring stable and efficient operation of the battery.

Brief introduction to lithium battery diaphragms

In the structure of lithium batteries, battery separator refers to a layer of separator material between the positive and negative electrodes of the battery. It is a very critical part of the battery and has a direct impact on the safety and cost of the battery. Its main function is to isolate the positive and negative electrodes and prevent the electrons in the battery from passing freely, so that the ions in the electrolyte can pass freely between the positive and negative electrodes. The performance of the separator determines the interface structure and internal resistance of the battery, which directly affects the battery's capacity, cycle and safety performance. According to the differences in physical and chemical properties, lithium-ion battery separators can be divided into several categories: woven membranes, non-woven membranes (non-woven fabrics), microporous membranes, composite membranes, separator paper, rolled membranes, etc. Although there are many types, the main commercial lithium-ion battery separator materials are polyethylene and polypropylene microporous membranes. Polyolefin materials have excellent mechanical properties, chemical stability and relatively low prices. Therefore, polyolefin microporous membranes such as polyethylene and polypropylene have been used as lithium-ion battery separators in the early stages of lithium-ion battery research and development.