Boehmite-based ceramic separator for lithium-ion batteries

A free-standing ceramic separator for lithium-ion batteries based on synthesized and surface-functionalized boehmite nanoparticles (AlO(OH)) was prepared by means of a pilot coating machine. For this composite membrane, polyvinylidene difluoride (PVdF) homopolymer was used as a binder. The separator displays a homogeneous morphology with a thickness of 22 µm. The mean pore size of the separator is 64 nm and the MacMullin number is 5.1. The constant current cycling behavior and C-rate capability up to 5 C are comparable to those of a commercial tri-layer polyolefin separator. Even though the mechanical properties of the ceramic separator are in some regards comparable to those of the polyolefin separator, however, they need to be improved so that the ceramic separator is able to withstand the stressful cell assembly process. Moreover, the boehmite-based ceramic separator displays a superior wettability and thermal stability compared to state-of-the-art polyolefin separators and is, therefore very promising for application in lithium-ion batteries.