A lithium-ion battery consists of four main parts: positive electrode material, negative electrode material, separator, and electrolyte. Among them, the separator is a thin film with a microporous structure and is the most technologically challenging key inner component in the lithium-ion battery industry chain.
As one of the four key materials in lithium-ion batteries, the separator, although not involved in the electrochemical reactions, directly affects crucial battery performance characteristics such as capacity, cycle life, and charge/discharge current density. So, what are the requirements for separators in lithium-ion batteries?
The requirements for separators in lithium-ion batteries include:
1. It has electronic insulation properties, ensuring mechanical isolation between the positive and negative electrodes;
2. It has a certain pore size and porosity, ensuring low resistance and high ionic conductivity, and good permeability to lithium ions;
3. It is resistant to electrolyte corrosion and has sufficient chemical and electrochemical stability, due to the fact that the electrolyte solvent is a highly polar organic compound;
4. It has good wettability in electrolytes and strong liquid absorption and moisture retention capabilities;
5. High mechanical stability, including puncture strength and tensile strength, but with the thickness as small as possible;
6. Good spatial stability and flatness;
7. Excellent thermal stability and automatic shutdown protection performance;
8. The thermal shrinkage rate should be small, otherwise it will cause a short circuit and lead to battery thermal runaway.
The above is a brief introduction to the requirements of lithium batteries for separators. Currently, new energy vehicle batteries and power batteries have put forward higher requirements for the performance of separators in terms of high-power fast charging and discharging and safety. This has led to the development of the main materials used in lithium battery separators from polyolefin materials to multiple materials and composite materials, and the structure has also developed from simple structure to complex structure.
