The separator material is an important part of a lithium polymer battery.
Main functions of the battery separator material.
It can reduce the distance between the positive and negative electrodes while effectively preventing the connection between the positive and negative electrodes, thereby reducing the impedance of the battery.
Battery application’s requirements for separator
Lithium-ion polymer batteries have high requirements for separator materials.
First, they must meet the basic requirements of general chemical power sources, including:
- It must have a certain mechanical strength to ensure that they do not break under the condition of battery deformation;
- Good ion permeability to reduce the internal resistance of the battery;
- Excellent electronic insulation to ensure effective isolation between the electrodes;
- Chemical and electrochemical corrosion resistance, good stability in the electrolyte;
- Strong ability to absorb electrolyte; low cost, suitable for large-scale industrial production;
- Less impurity content, uniformed performance,
In addition, there are some other special requirements:
- a, The thickness of the film must be very thin to reduce the impedance of the battery;
- b, does not absorb water;
- c, Great special hot melt performance, when the battery is abnormal, the lithium battery separator material can melt itself under the required temperature, close the micropores, become an ionic insulator, and make the battery cut off.
The separator materials for lithium ion polymer batteries are mainly porous polyolefins, such as polypropylene separators produced by Celgard, as well as later polyethylene films, copolymers of ethylene and propylene. These materials have high porosity, low electrical resistance, high tear strength, good acid and alkali resistance, Nice elasticity and ability to retain aprotic solvents.
Manufacturing of lithium polymer battery separator.
There are two main methods for preparing lithium ion battery separators, namely, melt drawing (MSCS) and thermally induced phase separation (TIPS). The MSCS process is relatively simple and has no pollution during the production process. It is the main method for producing diaphragm materials in the world. The TIPS method requires the addition and removal of diluents during the production process, which is costly and accompanied by secondary pollution.