In the structure of a lithium battery, the separator is one of the key internal components. The performance of the lithium battery separator determines the battery's interface structure, internal resistance, and other characteristics, directly affecting the battery's capacity, cycle life, and safety performance. A high-performance separator plays an important role in improving the overall performance of the battery.
What is a lithium battery separator?
The separator in a lithium battery is located between the positive and negative electrodes. Its main function is to separate the active materials of the two electrodes, preventing short circuits caused by contact. Additionally, it maintains the necessary electrolyte and forms channels for ion movement during electrochemical reactions. The separator material is non-conductive, and different types of lithium batteries use different separators.
What are the constituent materials of lithium battery separators?
Based on their different physical and chemical properties, lithium battery separator materials can be classified into several categories, including woven membranes, nonwoven membranes (non-woven fabrics), microporous membranes, composite membranes, separator paper, and rolled membranes.
Polyolefin materials possess excellent mechanical properties, chemical stability, and relatively low cost. Therefore, polyolefin microporous membranes such as polyethylene and polypropylene were used as lithium battery separators in the early stages of lithium battery research and development. Although in recent years, research has been conducted on preparing lithium battery separators using other materials, such as using polyvinylidene fluoride (PVDF) as the bulk polymer in a phase inversion method, and studying cellulose composite membranes as lithium battery separator materials, etc.
However, the membrane materials on the market are mainly polyolefin membranes, primarily made of polyethylene and polypropylene. Polyethylene products are mainly produced by wet processes, while polypropylene products are mainly produced by dry processes.
What types of lithium battery separators are there?
Lithium-ion battery separators can be classified into different types based on their structure and composition. Currently, the three most common types on the market are porous polymer membranes, non-woven fabric separators, and inorganic composite membranes.
Porous polymer membranes refer to lithium battery separators with uniform pore distribution prepared by various methods such as mechanical methods, thermally induced phase separation methods, and immersion precipitation methods.
Non-woven membranes are made of oriented or random fibers and are usually combined with organic materials or ceramic gels to obtain lithium battery membranes with better chemical and physical properties.
Inorganic composite membranes: These are lithium battery separators made by combining inorganic nanoparticles with high polymers.
As an important inner component of lithium batteries, the lithium battery separator has a promising future, and its production technology will also improve accordingly.
