Main content:
With the rapid development of battery industry technology, the performance requirements of sodium-ion battery separators are becoming higher and higher. As one of the core components of sodium battery, the characteristics of separator directly affect the safety, energy density and cycle life of the battery. This article will discuss the performance requirements, separator types and future development trend of sodium battery separator, and provide reference for the application of sodium battery technology.
What are the characteristics of a good sodium battery separator?
A good separator should have a rich pore structure, uniform pore size distribution, appropriate thickness, standard mechanical strength, appropriate porosity, good thermal conductivity and iodine chemical stability, which helps to promote sodium ion conduction and increase battery cycle. PP film and PE film are widely used in lithium batteries because of their strong corrosion resistance and high strength. Because sodium battery technology and lithium batteries are in the same vein, so the current sodium battery basically uses lithium battery separator.
Types of sodium ion separator
The types of sodium ion separators mainly include polymer separators and inorganic solid electrolyte separators.
Polymer separator: Polymer separator is composed of polymer material, which has good flexibility and ion transport performance. Polymer separators are widely used in sodium-ion batteries and can be optimized by controlling the pore size and changing the chemical structure.
Inorganic solid state electrolyte separator: Inorganic solid electrolyte separator is composed of inorganic materials with high ionic conductivity, such as oxides, phosphates, etc. These separators have good chemical stability and high temperature resistance, but because of their high rigidity, they need to overcome challenges such as brittleness and blocking properties.
Performance requirements for sodium ion separators
A series of performance requirements are required to ensure the efficient operation and safety of the battery.
Ion transport performance: The separator should have a high sodium ion transport rate and low resistance to provide good battery performance.
Mechanical strength and flexibility: The separator should have sufficient mechanical strength to resist stress changes during the battery cycle, and at the same time have a certain flexibility to adapt to the deformation and expansion of the battery.
Chemical stability: The separator should have good chemical stability and be able to resist chemical reactions in the electrolyte and corrosion in the battery environment.
Thermal stability: The separator should have good thermal stability to avoid expansion, deformation or melting under high temperature conditions.
New polymer materials, nano-composite materials and porous materials have been extensively studied in the field of sodium ion separators to improve ion transport rate, mechanical properties and chemical stability. Research on functional separators, such as those with self-healing properties, flame retardant properties and resistance to polarization, was carried out. At present, the microstructure and pore size distribution optimization of the separator are studied to improve the ion transport efficiency and mechanical strength.
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What are the battery separators that have been commercialized for sodium ion batteries?
Currently commercialized battery separators mainly include polyethylene (PP) and polypropylene (PP) separators, which have excellent mechanical properties, chemical stability and low prices, but due to inherent shortcomings, their thermal stability is poor, the wettability of sodium-ion battery electrolyte is also very poor, not suitable for sodium-ion batteries. The need to find new separators that can match the sodium-ion battery system is particularly important.
The development of low cost, high safety and large-scale production of sodium ion battery separator is worth exploring. It is necessary to explore the relationship between pore distribution in the separator and electrolyte infiltration. The distribution of porous structure in the separator will directly affect its mechanical strength, and then affect the separation effect of the separator on the positive and negative electrodes, and affect the safety of the battery. In addition, the properties of the separator under extreme conditions, such as shrinkage at high temperatures, brittleness at low temperatures, etc., are important factors affecting the application range.
The mainstream market types of sodium ion battery separators include ultra-high molecular weight polyethylene separators, polypropylene separators and nonwovens composite separators. There are relatively few researches on the separator materials of sodium-ion battery in China, mainly focusing on polyolefin composite separator, glass fiber filter paper separator and organic polymer non-woven separator.
The glass fiber filter paper type separator is a kind of fiber separator made of inorganic material, because of its high price, thicker material and low tensile strength, most of it is currently used in laboratory and small-scale pilot test stage. Polyolefin composite separators and organic polymer non-woven separators have been mass-produced and have been tested in terms of safety, but these two materials need to be further explored in terms of thermal stability and electrolyte fusion.
Future development trends of sodium battery separators
Currently commercialized battery separators mainly include polyethylene (PP) and polypropylene (PP) separators, which have excellent mechanical properties, chemical stability and low prices, but due to inherent shortcomings, their thermal stability is poor, the wettability of sodium-ion battery electrolyte is also very poor, not suitable for sodium-ion batteries. The need to find new separators that can match the sodium-ion battery system is particularly important.
The development of low cost, high safety and large-scale production of sodium ion battery separator is worth exploring. It is necessary to explore the relationship between pore distribution in the separator and electrolyte infiltration. The distribution of porous structure in the separator will directly affect its mechanical strength, and then affect the separation effect of the separator on the positive and negative electrodes, and affect the safety of the battery. In addition, the properties of the separator under extreme conditions, such as shrinkage at high temperatures, brittleness at low temperatures, etc., are important factors affecting the application range.
The mainstream market types of sodium ion battery separators include ultra-high molecular weight polyethylene separators, polypropylene separators and nonwovens composite separators. There are relatively few researches on the separator materials of sodium-ion battery in China, mainly focusing on polyolefin composite separator, glass fiber filter paper separator and organic polymer non-woven separator.
The glass fiber filter paper type separator is a kind of fiber separator made of inorganic material, because of its high price, thicker material and low tensile strength, most of it is currently used in laboratory and small-scale pilot test stage. Polyolefin composite separators and organic polymer non-woven separators have been mass-produced and have been tested in terms of safety, but these two materials need to be further explored in terms of thermal stability and electrolyte fusion.
Conclusion
The performance of sodium battery separator directly affects the overall performance of the battery. With the deepening of research and technological progress, the future sodium battery separator will develop in the direction of safer, more stable and lower cost to meet the growing market demand and application scenarios.
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