Research Advances in High Thermal Stability New-Type Separators for Lithium-Ion Batteries
In recent years, with the increasing demand for high-performance lithium-ion batteries, research on high thermal stability separators has made significant progress. The development of new separator materials and technologies aims to enhance the safety, thermal stability, and cycling performance of batteries, especially in high-temperature or high-power application scenarios. The following are some of the main research directions and recent advances:
1. Inorganic Ceramic Coated Separators
Inorganic ceramic materials (such as silica (SiO₂), alumina (Al₂O₃), etc.) are widely used for separator coatings due to their excellent thermal and chemical stability. These materials can significantly improve the electrolyte absorption and ionic conductivity of separators.
Silica Coating: By uniformly coating or chemically depositing silica, a thin and uniform layer can be formed, significantly improving the electrolyte wettability and ionic conductivity of the separator. For example, amino-functionalized silica (N-SiO₂) coatings on polyethylene (PE) separators have demonstrated higher ionic conductivity (0.81 mS cm⁻¹) and lower contact angles (51.3°), effectively suppressing electrolyte decomposition at high temperatures.
Composite Ceramic Coatings: Combining different ceramic materials, such as SiO₂ and Al₂O₃, can further enhance separator performance. These composite ceramic-coated separators have shown excellent electrolyte absorption (over 350%) and ionic conductivity (over 2 mS cm⁻¹), with a capacity retention rate of over 80% after 100 cycles.
2. Inorganic Carbon-Based Nanomaterial Coated Separators
Two-dimensional materials such as graphene oxide (GO) have become popular separator coating materials due to their good electrolyte wettability and ionic conductivity.
Graphene Oxide Coating: GO-coated separators have extremely low contact angles (15°), showing excellent electrolyte wettability. Further functionalization, such as with polyacrylic acid (PAA), can enhance their ionic conductivity and lithium-ion flux uniformity.
Composite Nanomaterial Coatings: Combining GO with other inorganic materials (such as boron nitride) can produce separators with higher ionic conductivity and cycling stability. For example, B/N co-doped reduced graphene oxide/boron nitride nanosheet-coated separators have demonstrated excellent cycling performance in lithium-sulfur batteries (capacity retention rate of 92.3% after 500 cycles).
3. Multi-Material Composite Coated Separators
To further enhance separator performance, researchers have developed multi-material composite coated separators. These separators not only have excellent thermal stability and electrolyte wettability but can also suppress the growth of lithium dendrites.
Porous Structure Coatings: By designing porous structured coating materials, such as Laponite nanosheets and carbon black composite coatings, the ionic conductivity and flexibility of separators can be significantly improved. These coated separators maintain good thermal stability at 160°C, with a contact angle close to 0°.
Functionalized Coatings: Introducing specific functional groups into the coatings can further optimize separator performance. For example, Fe₃N-doped GO-coated separators accelerate lithium-ion transport and regulate lithium-ion flux, effectively suppressing the growth of lithium dendrites.
Future Outlook
Current research trends indicate that the development of high thermal stability separators will continue to move towards multifunctionalization and high performance. By optimizing the composition and structure of coating materials and exploring new coating techniques, researchers are expected to further enhance the comprehensive performance of separators to meet the demands of high-performance lithium-ion batteries in various application scenarios.
