Dual-functional TiN/BN@separator for enhanced electrochemical performance and safety of lithium-ion batteries

As the energy density of lithium-ion batteries continues to increase, the performance requirements for separators have become more stringent. Traditional polyolefin separators offer advantages such as low cost and excellent chemical stability. But they suffer from poor electrolyte wettability, thermal stability, and high interfacial resistance, which hinder the development of high-performance lithium-ion batteries. To address these issues, this study introduces a blending coating method using titanium nitride and boron nitride particles to enhance the overall performance of polypropylene separators. The TiN/BN@PP-15 separator demonstrates superior wettability, thermal stability, and electrochemical performance. Under a high discharge rate of 5C, it achieves an initial discharge capacity of 130.7 mAh g⁻¹. Additionally, batteries assembled with the TiN/BN@PP-15 separator exhibit the lowest interfacial resistance of 79.7 Ω, a high ionic conductivity of 0.466 mS cm⁻¹, and a lithium-ion diffusion coefficient of 11.7 × 10⁻¹⁴ cm² s⁻¹. These results indicate that the co-blending coating of TiN and BN particles not only improves the physicochemical properties of PP separators but also ensures high discharge capacity and cycling stability under high-rate conditions, providing reliable technical support for high energy density and high rate energy storage systems.