Advantages of Ceramic Materials as Separators for Lithium Batteries

Lithium ion batteries are composed of a positive electrode, a negative electrode, a battery separator, and a battery electrolyte,The function of the separator is to separate the positive and negative poles of the battery, to prevent short circuits caused by contact between the positive and negative poles, and to ensure the smooth passage of electrolyte ions.

As an important component of lithium-ion batteries, the excellent performance of the separator directly affects the capacity, cycling ability, and safety performance of lithium-ion batteries.

Therefore, the lithium battery separator should have uniform thickness, excellent mechanical properties (including tensile strength and puncture resistance), breathability, physical and chemical properties (including wettability, chemical stability, thermal stability, safety, etc.)

The separator for lithium-ion batteries is mainly composed of polyethylene (PE), polypropylene (PP) monolayer membranes, and polyethylene/polypropylene/polyethylene three-layer membranes,

However, due to the low breaking temperature of the above-mentioned membranes, such as about 140 ℃ for PE film and 160 ℃ for PP film, it is easy to cause the membrane to shrink or even melt when the battery is not in use, leading to a short circuit in the battery and causing serious accidents.

In response to this situation, various methods have been adopted to improve the thermal stability of membranes, among which coating a layer of inorganic ceramic particles on PP or PE membranes is considered the most effective and economical method.

Advantages:

1. Good thermal stability. Ceramic materials are distributed in the three-dimensional structure of the diaphragm, forming a specific rigid framework. With extremely high thermal stability, the diaphragm can effectively prevent contraction and melting under Thermal runaway conditions.

2. High safety and low thermal conductivity of ceramic materials can further prevent some Thermal runaway points in the battery from expanding to form an overall Thermal runaway, thus improving the safety of the battery.

3. Improved service life. Ceramic materials are generally amphoteric oxides, and ceramic powder particles in the separator can partially absorb impurities such as HF generated by the presence of trace amounts of water in the electrolyte, further improving the battery's service life.