In the structure of lithium batteries, the diaphragm is one of the key internal components. The performance of the lithium battery separator determines the battery's interface structure, internal resistance, etc., which directly affect the battery's capacity, cycle and safety performance. A separator with excellent performance plays an important role in improving the overall performance of the battery.
What is a lithium battery separator?
The lithium battery separator is located between the positive and negative electrodes, and its main function is to separate the positive and negative active materials to prevent the two electrodes from being short-circuited due to contact; in addition, during the electrochemical reaction, it can maintain the necessary electrolyte to form a channel for ion movement . The diaphragm material is non-conductive, and different types of lithium batteries use different diaphragms.
What are the constituent materials of lithium battery separators?
According to different physical and chemical properties, lithium battery separator materials can be divided into woven membranes, non-woven membranes (non-woven fabrics), microporous membranes, composite membranes, membrane paper, laminated membranes, etc.
Polyolefin materials have excellent mechanical properties, chemical stability and relatively inexpensive characteristics. Therefore, in the early stage of lithium battery development, polyolefin microporous membranes such as polyethylene and polypropylene have been used as lithium battery separators. Although in recent years there have been studies using other materials to prepare lithium battery separators, such as the phase inversion method using polyvinylidene fluoride (PVDF) as the bulk polymer to prepare lithium battery separators, and the use of cellulose composite membranes as lithium battery separator materials.
However, the diaphragm materials on the market are mainly polyolefin diaphragms based on polyethylene and polypropylene. Among them, polyethylene products are dominated by wet process, and polypropylene products are dominated by dry process.
What are the types of lithium battery separators?
Lithium battery separators can be divided into different types according to their structure and composition. At present, there are mainly three types that are more common in the market, namely porous polymer membranes, non-woven membranes and inorganic composite membranes.
Porous polymer diaphragm: refers to a lithium battery diaphragm with uniform pore distribution prepared by mechanical method, thermally induced phase separation method, immersion precipitation method and other methods.
Non-woven diaphragm: It is composed of oriented or random fibers, usually combined with organic matter or ceramic gel to obtain a lithium battery diaphragm with better chemical and physical properties.
Inorganic composite membrane: Most lithium battery separators are composed of inorganic nanoparticles and polymers.
As an important internal component of lithium batteries, lithium battery separators have broad development prospects, and their production technology will also be improved.