A brief introduction to the performance and classification of lithium-ion battery separators. Posted by benzoenergy.com
In the structure of lithium batteries, the separator is one of the key inner layer components. The performance of the lithium-ion battery separator determines the interface structure and internal resistance of the battery, which directly affects the capacity, cycle and safety performance of the battery. The separator with excellent performance plays an important role in improving the overall performance of the battery.
First, the performance of lithium-ion battery separator
The lithium-ion battery
separator is located between the positive electrode and the negative
electrode, 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 and form a channel
for ion movement . The diaphragm material is non-conductive, and the
diaphragm used is different for different types of batteries. For
lithium-ion batteries, since the electrolyte is an organic solvent
system, the separator is required to have the following properties.
1. In the battery system, its chemical stability is better, and the materials used are resistant to organic solvents.
2. High mechanical strength and long service life.
3.
The ionic conductivity of the organic electrolyte is lower than that of
the aqueous system. In order to reduce the resistance, the electrode
area must be as large as possible, so the diaphragm must be very thin.
4.
When an abnormality occurs in the battery system, the temperature
rises. In order to prevent danger, when the rapid heat generation
temperature (120-140°C) begins, the thermoplastic diaphragm melts, the
micropores are closed, and it becomes an insulator to prevent the
electrolyte from passing through, thereby achieve the purpose of
interrupting the current.
5.
From the perspective of lithium batteries, it must be fully impregnated
with organic electrolyte, and can maintain a high degree of
impregnation during repeated charge and discharge.
The
separator materials commonly used in batteries are generally
microporous membranes made of cellulose or braided fabrics and synthetic
resins. Lithium-ion batteries generally use high-strength, thin-film
polyolefin-based porous membranes. Commonly used separators include
polypropylene (PP) and polyethylene (PE) microporous separators, as well
as copolymers of propylene and ethylene, polyethylene homopolymers,
etc. .
Second, the classification of lithium-ion battery separators
According to different physical and chemical properties, lithium battery separator
materials can be divided into: woven film, non-woven film (non-woven
fabric), microporous film, composite film, separator paper, laminated
film and so on. Polyolefin materials have excellent mechanical
properties, chemical stability and relatively cheap characteristics, so
polyolefin microporous membranes such as polyethylene and polypropylene
have been used as lithium battery separators in the early stage of
lithium battery research and development. Although in recent years there
have been studies using other materials to prepare lithium battery
separators, such as using polyvinylidene fluoride (PVDF) as bulk polymer
to prepare lithium battery separators by phase inversion, and studying
cellulose composite membranes as lithium battery separator materials.
However, until now commercial lithium battery separator materials still
mainly use polyethylene and polypropylene microporous membranes.
BENZO Energy Technology Co.,Ltd
UFine Technology Co., Ltd
Site: www.bz-battery.com / www.benzoenergy.com
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