Search

EP-4735659-A1 - BATTERY FOIL

EP4735659A1EP 4735659 A1EP4735659 A1EP 4735659A1EP-4735659-A1

Abstract

The invention relates to a battery foil (current collector) comprising an aluminum alloy, with the following composition: Si: 0.1 - 0.2wt-%, Fe: 0.5 - 0.6wt-%, Cu: 0.1 - 0.2wt-%, Mn: 0.03 - 0.05wt-%, Mg: 0.0 - 0.05wt-% Zn: 0.0-0.1wt-% Ti: 0.0 - 0.05wt-%, with 3-4 times as much Fe as Si, with at least 4 times as much Cu as Ti, wherein the aluminum alloy may have impurities of Cd with a max 20ppm, Pb with a max 100ppm and Hg with a max 5ppm, the sum of Pb, Hg, Cd and CrVI being ≤100ppm, the others (not mentioned) individually <0.05wt-% and the sum of the others ≤0.15wt-%, with the rest of the alloy being Al, and, wherein the battery cathode foil has intermetallic phases having an average circle diameter of 0.5µm or more and their number density being on average 1.3×104particles/mm² or more.

Inventors

  • HOFINGER, Matthias
  • HONARAMOOZ, Mohammad Taha
  • KORNFELD, MARTIN

Assignees

  • Constantia Teich GmbH

Dates

Publication Date
20260506
Application Date
20250902

Claims (14)

  1. 1. Battery foil, comprising an aluminum alloy, wherein the aluminum alloy has the following composition: Si: 0.1 - 0.2wt-%, Fe: 0.5 - 0.6wt-%, Cu: 0.1 - 0.2wt-%, Mn: 0.03 - 0.05wt-%, Mg: 0.0 - 0.05wt-% Zn: 0.0-0. lwt-% Ti: 0.0 - 0.05wt-%, wherein there has to be 3-4 times as much Fe as Si, wherein there has to be >4 times as much Cu as Ti, wherein the aluminum alloy may have impurities of Cd with a max 20ppm, Pb with a max lOOppm and Hg with a max 5ppm, the sum of Pb, Hg, Cd and CrVI being <100ppm, the others, not mentioned, individually <0.05wt-% and the sum of the others <0.15wt-%, with the rest of the alloy being Al, and, wherein the battery cathode foil has intermetallic phases having an average circle diameter of 0.5pm or more and their number density being on average 1.3xl0 4 particles/mm 2 or more.
  2. 2. Battery cathode foil according to claim 1, wherein the Si content is 0.14 - 0.2wt-%.
  3. 3. Battery cathode foil according to claim 1 or 2, wherein the Si content is 0.14 - 0.18wt-%.
  4. 4. Battery cathode foil according to any of the preceding claims, wherein the battery cathode foil has intermetallic phases having an average circle diameter of 0.65pm or more.
  5. 5. Battery cathode foil according to any of the preceding claims, wherein the battery cathode foil has a UTS in the rolling direction at room temperature of at least 245MPa after a heat treatment of 100°C for 24 hours.
  6. 6. Battery cathode foil according to any of the preceding claims, wherein the battery cathode foil has a UTS in the rolling direction at room temperature of at least 260MPa after a heat treatment of 130°C for 2 minutes.
  7. 7. Battery cathode foil according to any of the preceding claims, wherein the battery cathode foil has a tensile strength of at least 235 MPa in the rolling direction at 70°C after exposing the aluminum foil to 70°C for 30 seconds.
  8. 8. Battery cathode foil according to any of the preceding claims, wherein the battery cathode foil has a tensile strength of at least 240 MPa transverse to the rolling direction at 70°C after exposing the aluminum foil to 70°C for 30 seconds.
  9. 9. Battery cathode foil according to any of the preceding claims, wherein the measurement of the average circle diameter and the number density has been done using a SEM.
  10. 10. Battery cathode foil according to claim 9, wherein the measurement of the average circle diameter and the number density has been done using a Thermo Fisher Phenom ProX tabletop SEM.
  11. 11. Battery cathode foil according to any of the preceding claims, wherein the battery cathode foil was produced by the process of a) Smelting and casting of the aluminum alloy, b) Hot rolling of the aluminum alloy with temperatures of below 500°C, c) Cold rolling at room temperature with a reduction in thickness per pass of 40% to 60%, d) Foil rolling in 4 to 6 steps at room temperature with a reduction in thickness per pass of 40% to 60%.
  12. 12. Production of a battery cathode foil according to one of the preceding claims consisting of e) Smelting and casting of the aluminum alloy, f) Hot rolling of the aluminum alloy with temperatures of below 500°C, g) Cold rolling at room temperature with a reduction in thickness per pass of 40% to 60%, h) Foil rolling in 4 to 6 steps at room temperature with a reduction in thickness per pass of 40% to 60%.
  13. 13. Production according to claim 12, characterized in that neither an intermediate annealing nor a final annealing is performed.
  14. 14. Use of a battery cathode foil according to any of the preceding claims for batteries suitable for battery electric vehicles.

Description

Battery foil The invention relates to a battery foil, a thin aluminum foil used as a current collector in batteries, in particular for high-temperature applications, according to claim 1. Improving the mechanical properties of battery components has always been a priority. The increasing use of batteries in electric vehicles (battery electric vehicles, BEV) has given these properties even greater importance in recent years. Numerous attempts have been made to improve the mechanical properties of thin aluminum foils, and there are numerous patents in this area. Since the operating temperature of batteries can be as high as 60-70°C, and this temperature range is increasing due to the growing demand for fast charge and super-fast charge batteries where the current collectors are more often exposed to high temperatures, there is an increasing emphasis on how well the mechanical properties of the batteries perform at high temperatures. As the cathode current collector foil is a safety critical component of the battery, it is critical to have high mechanical properties not only at room temperature, but also at these elevated operating temperatures. For example, there currently are market requirements for racing car batteries, which means that battery components must be thermally stable, as racing cars sometimes operate under extremely high loads and temperatures. This begins during the manufacturing process of today's LFP or NMC lithium-ion batteries (LIBs), where the active material is applied as slurry with NMP (N-methyl-2-pyrrolidone) as a solvent to wet the current collector foil. This solvent must be removed by evaporation by heating the foil to high temperatures. Directly in-line after this heating step, the active material is compressed onto the current collector foil by a calendaring process. The cathode current collector foil must be able to withstand these high forces at elevated temperatures in order to avoid plastic deformation and wrinkles at the coil edges or even breakage during rewinding and further production. WO 2019/101723 shows an aluminum foil that is suitable as an electrode foil in a battery but has a very low tensile strength and poor thermal stability, which can lead to problems in battery production, resulting in production interruptions and high costs. WO 2019/101730 also shows an aluminum foil that is suitable as an electrode foil in a battery. However, this battery foil also has unsatisfactory long-term thermal stability. JP 6775335 B2 mentions that the tensile strength of the aluminum foil is 261MPa or more. However, the high Mn content results in very low electrical conductivity, which in turn leads to thermal runaway and an increase in battery temperature. In addition, the tensile strength of 261 MPa was achieved after cold rolling in which the entire thickness reduction is 98.3% or more. CN 116706080 A discloses a thin aluminum foil (<= 13pm) with a tensile strength of 265~270MPa. However, the patent nowhere mentions specific chemical compositions. In addition, the patent requires an intermediate annealing step during foil production, which is neither sustainable nor cost-effective. CN 105658826 B discloses an aluminum foil with a tensile strength of 220MPa or more and an electrical conductivity of over 50% IACS. However, the tensile strength should be higher than 220MPa to avoid wrinkles and cracks during battery cell production. EP 2843 067 Al discloses an aluminum foil and its production process, coming to a high tensile strength. Specific amounts for Si, Fe, Cu and Mn are given, other components are only mentioned as “impurities”. The publication “Aluminum Casting Alloys and Casting Processes”, a technical and processual overview from 2018, discloses a great number of alloys and gives general advice component to component, e.g. describing Cd as volatile and toxic, Hg as hard to bring into the alloy due to its low boiling point, Pb as actually being replaced more and more by Sn due to its toxicity; and so on. Therefore, current collector foils that can withstand high temperatures without compromising their mechanical properties at high temperatures are required. According to the invention, this is achieved by a thin aluminum foil made of an aluminum alloy to be used as a current collector (cathode current collector, battery foil) in batteries according to claim 1 of the invention. In other words, the present invention has a specific chemical composition with, in wt-%, Si between 0.1-0.2 and Fe 0.5-0.6, with 3-4 times as much iron as silicon in the alloy, Cu between 0.1 and 0.2, Mn between 0.03 and 0.05, Mg between 0.00 and 0.05, Ti between 0.00 and 0.05, with at least 4 times as much copper as titan in the alloy, Zn between 0.0 and 0.1, furthermore Cd with a max 20ppm, Pb with a max lOOppm and Hg with a max 5ppm, the sum of Pb, Hg, Cd and CrVI are <100ppm, the others (not mentioned) individually <0.05 and the sum of the others <0.15wt-%, the rest being Al. A specific rollin