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

Methyl tetrafluoro-2-(methoxy) propionate as co-solvent for propylene carbonate-based electrolytes for lithium-ion batteries

Methyl tetrafluoro-2-(methoxy) propionate (MTFMP) was evaluated as co-solvent for PC-based electrolytes in combination with graphite electrodes. Already 10 wt% (5.6 mol%) of MTFMP in PC were sufficient to form an effective and stable SEI on graphite as confirmed by battery tests. In the first cycle, the formation of an effective SEI via the decomposition of MTFMP was observed before PC co-intercalation thus preventing the subsequent exfoliation of the graphite. The stability of this SEI was verified by long term cycling tests, which showed that the capacity loss of the graphite-based cell was only 1.3% after 300 cycles at 1 C. The electrolyte, 1 M LiPF 6 in PC:MTFMP (9:1 wt%), showed also a good rate capability up to 5 C on graphite. Therefore, MTFMP can be considered as a new, very promising co-solvent for PC-based electrolytes for use in lithium-ion batteries with graphite anodes. © 2012 Elsevier B.V. All rights reserved