Fabrication of Network Spherical α-Al₂O₃ and Its Application on the Separator of Lithium-Ion Batteries

Ceramic-coated polyolefin separator technology is considered a simple and effective method for the improvement of lithium-ion battery (LIB) safety. However, the characteristics of ceramic powder can adversely affect the surface structure and ion conductivity of the separators. Therefore, it is crucial to develop a ceramic powder that not only improves the thermal stability of the separators but also enhances ion conductivity. Herein, network spherical α-Al₂O₃ (N-Al₂O₃) with a multi-dimensional network pore structure was constructed. Furthermore, N-Al₂O₃ was applied as a coating to one side of polyethylene (PE) separators, resulting in N-Al₂O₃-PE separators that exhibit superior thermal stability and enhanced wettability with liquid electrolytes. Notably, the N-Al₂O₃-PE separators demonstrated exceptional ionic conductivity (0.632 mS cm^-1), attributed to the internal multi-dimensional network pore structures of N-Al₂O₃, which facilitated an interconnected and efficient "highway" for the transport of Li⁺ ions. As a consequence, LiCoO₂/Li half batteries equipped with these N-Al₂O₃-PE separators showcased remarkable rate and cycling performance. Particularly at high current densities, their discharge capacity and capacity retention rate significantly outperformed those of conventional PE separators.