AEROXIDE® fumed alumina increases the safety of Lithium-ion battery cells
The Challenge
The separator is a crucial element in a Lithium-ion battery cell: A porous, polymeric membrane made of PE or PP separates the electrodes from each other to prevent a short circuit.
A separator should be as thin as possible, and at the same time provide maximum safety. Ceramic coating of separators is state-of-the art to get very thin separators with very high safety. However, the ceramic particles used to build up the coating (mainly alumina and boehmite) are often too large to achieve ultra-thin ceramic coatings.
Evonik’s Smart Solutions
Evonik has developed matching alumina products for water-based and solvent-based separator coating with ultra-thin ceramic layers.
Water-based separator coating:
VP Alu 45 and the related ready-to-use dispersion VP Disp. W 4150 XC6 were specifically designed for the water-based ceramic coating of LIB separators. The small aggregate size and the narrow particle size distribution of these alumina products enable ultra-thin ceramic coatings of <1 µm. Such a thin, nano-structured AEROXIDE® coating provides excellent protection for the separator, because the thermal and mechanical stability is significantly increased.
Solvent-based separator coating:
VP Alu C 711 is a surface modified AEROXIDE® for solvent-based separator coating and features a MEMO functionality on the alumina particle surface. It can be used in applications with a cross-linking reaction: the methacrylate group reacts with other chemicals, and a strong network will be built-up.
VP Alu C 711 is typically applied in solvent-based coating slurries. It is very powerful as an additive or major ingredient in a ceramic coating and protects Lithium-ion battery separators against thermal shrinkage.
