What are the main lithium materials used in lithium-ion battery separators?
The separator is a crucial component of lithium-ion batteries, serving as one of the most critical materials in their structure. Currently, commercially available lithium-ion battery separators are primarily polyolefin-based, and their manufacturing processes are transitioning from dry to wet methods. However, in recent years, separators with different material systems and manufacturing processes have been developed. This article will detail the composition of lithium-ion battery separator materials.
In the structure of lithium-ion batteries, the separator is one of the key internal components. For lithium-ion batteries, the performance of the separator determines the battery's interface structure, internal resistance, and other characteristics, directly affecting the battery's capacity, cycle life, and safety performance. Based on differences in physical and chemical properties, lithium-ion battery separators can be classified into several categories, including woven membranes, non-woven membranes (non-woven fabrics), microporous membranes, composite membranes, separator paper, and rolled membranes. Despite the variety of types, polyethylene and polypropylene microporous membranes are still the most commonly used materials for commercially available lithium-ion battery separators. Polyolefin materials have excellent mechanical properties, chemical stability, and relatively low cost; therefore, polyethylene, polypropylene, and other polyolefin microporous membranes were used as lithium-ion battery separators in the early stages of lithium-ion battery research and development.
Commercially available lithium-ion battery separator materials are primarily polyolefin separators, mainly composed of polyethylene (PE) and polypropylene (PP). PE products are primarily manufactured using wet processes, while PP products are primarily manufactured using dry processes. As for the characteristics of these two lithium-ion battery separator materials...
Overall:
1. PP is more resistant to high temperatures, while PE is more resistant to low temperatures;
2. PP has a lower density than PE;
3. PP has a higher melting point and closed-cell temperature than PE;
4. PP products are more brittle than PE products;
5. PE is more sensitive to environmental stress.
Important lithium-ion battery separator materials include single-layer PP, single-layer PE, PP+ceramic coating, PE+ceramic coating, double-layer PP/PE, double-layer PP/PP, and triple-layer PP/PE/PP. The first two types of products are mainly used in the field of 3C small batteries, while the latter types are mainly used in the field of power lithium-ion batteries.
In the field of separator materials for power lithium-ion batteries, double-layer PP/PP separator materials are mainly produced by Chinese companies and used in mainland my country. This is primarily because, at present, no Chinese company possesses the technology and capability to fabricate a double-layer composite membrane from PP and PE. Globally, separator materials used in automotive power lithium-ion batteries mainly include triple-layer PP/PE/PP, double-layer PP/PE, and PP+ceramic coating and PE+ceramic coating separators.
What types of separators are available for lithium-ion batteries?
Lithium-ion battery separators can be classified into different types based on their structure and composition. Currently, there are three main types commonly found on the market: porous polymer membranes, non-woven fabric membranes, and inorganic composite membranes.
1. Porous polymer membrane: refers to a lithium-ion battery separator with uniform pore distribution prepared by various methods such as mechanical methods, thermally induced phase separation methods, and immersion precipitation methods.
2. Non-woven membrane: It is made of oriented or random fibers and is usually combined with organic materials or ceramic gels to obtain lithium-ion battery membranes with better chemical and physical properties.
3. Inorganic composite membrane: These are lithium-ion battery separators made by combining inorganic nanoparticles and high polymers.
The development of the lithium-ion battery separator industry presents two main trends.
One type focuses on thinner and lighter consumer-grade lithium-ion battery separators, primarily targeting distributed application architectures such as mobile phones, laptops, and IoT applications, to improve the capacity and portability of lithium-ion batteries;
Another type is the power lithium battery separator that tends to use thick film or multi-layer composite separators. It is mainly for large-scale power applications such as electric vehicles and large-scale energy storage power stations. It requires good energy output and power characteristics, and has strict safety requirements. It can balance the capacity and safety performance of lithium-ion batteries.
In summary, the lithium-ion battery separator material industry has a high degree of concentration. The separator is one of the four key components of lithium-ion batteries, and its performance improvement has an undeniable impact on the quality and safety of lithium-ion batteries.
