German metal foil specialist SCHLENK has developed a line of thin-rolled metal foils based on high-tensile alloys. Used as a current collector foil in batteries, these foils are designed to improve the stability of battery coatings.
Companies have invested a lot of R&D effort in the field
of high-power electrode coatings based on silicon or other additives. This has
led to new challenges for anode and cathode foils.
SCHLENK has 90 years of experience in thin foil production –
its product line includes metals rolled to thicknesses of 6 to 100 microns,
with widths of up to 640 mm. Battery manufacturers are already familiar with SCHLENK’s
rolled-annealed (RA) copper anode foil. In order to enhance the stability of
current collectors, SCHLENK has improved the mechanical strength by rolling
special copper alloys.
In terms of tensile strength, pure copper foils reach a
physical limit of around 400 MPa in thin gauges. The electrical conductivity is
roughly 98% IACS. Forming a metal alloy by adding other elements to copper,
however, changes its properties – tensile strength can be enhanced
significantly at the cost of a slight loss of conductivity.
SCHLENK has tested different materials based on copper
alloys, rolled to thicknesses of 10 to 20 microns. One alloy showed average
tensile strengths of 500 to 600 MPa (70 to 85 ksi) with a conductivity of
approximately 86% IACS. The mechanical strength of this alloy is thus 50%
higher than that of pure copper.
Going even higher in tensile strength is possible, but
reduces conductivity. Tensile strengths of up to 750 MPa can be reached with
conductivity of around 40%. Which specific alloy and specification provides a
suitable compromise depends on the particular battery application.
In the third quarter of 2019, SCHLENK will add new kit
versions with nickel and high-tensile alloy foils. Researchers can test
different aspects of metal foils for capacity and cycle behavior in their
battery configurations. The pure copper version is currently available, with
two thicknesses to choose from: 10 and 18 microns. The width of each roll is
250 mm. SCHLENK’s engineering team is happy to assist customers in choosing the
right sample kit.
SCHLENK will present its battery sample kits together with
rolled metal foils and tabs at the upcoming Battery Show in Novi, Michigan.