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US-12620572-B1 - Methods of making lithium metal oxide films and solid-state lithium-based batteries containing the same using wet annealing

US12620572B1US 12620572 B1US12620572 B1US 12620572B1US-12620572-B1

Abstract

A method of making a lithium metal oxide film is disclosed. The method includes wet annealing the lithium metal oxide film in a first phase at a first temperature of 450-750° C. for a first length of time (e.g., at least 0.1 hour), in a first oxygen-containing atmosphere further containing a first concentration or amount of water vapor. The first concentration or amount of water vapor is >0, and the metal in the lithium metal oxide is selected from cobalt, manganese, nickel, titanium and iron. The method may further include a second wet annealing phase, conducted at a second temperature for a second length of time, in a second oxygen-containing atmosphere further containing a second concentration or amount of water vapor. The method may further include dry annealing the lithium metal oxide film at a third temperature for a third length of time, in a third oxygen-containing atmosphere in the absence of water vapor.

Inventors

  • Zhongchun Wang
  • Arvind Kamath

Assignees

  • ENSURGE MICROPOWER ASA

Dates

Publication Date
20260505
Application Date
20230923

Claims (20)

  1. 1 . A method of making a lithium metal oxide film, comprising: flowing an oxygen-containing gas over or through a source of water vapor to prepare a first oxygen-containing atmosphere; wet annealing the lithium metal oxide film in a first phase at a first temperature of 450-750° C. for a first length of time, in the first oxygen-containing atmosphere; and after wet annealing the lithium metal oxide film, dry annealing the lithium metal oxide film at a second temperature greater than the first temperature, for a second length of time, in a second oxygen-containing atmosphere substantially free of water vapor, wherein the metal in the lithium metal oxide film is cobalt (Co), manganese (Mn), nickel (Ni), titanium (Ti) or iron (Fe).
  2. 2 . The method of claim 1 , wherein the first length of time is at least 0.02 hour.
  3. 3 . The method of claim 1 , wherein wet annealing the lithium metal oxide film further comprises a second phase following the first phase, conducted at a third temperature for a third length of time, in a third oxygen-containing atmosphere comprising the oxygen-containing gas bubbled through the source of water vapor.
  4. 4 . The method of claim 3 , wherein the third temperature is 450-750° C.
  5. 5 . The method of claim 3 , wherein the third temperature is the first temperature ±50° C.
  6. 6 . The method of claim 5 , wherein the third temperature is the same as the first temperature.
  7. 7 . The method of claim 3 , wherein the first length of time and the third length of time together are in the range of 0.1-8 hours.
  8. 8 . The method of claim 7 , wherein the first length of time is 0.1-6 hours, the second length of time is 1 hour, and the third length of time is 5-180 minutes.
  9. 9 . The method of claim 1 , wherein the second length of time is less than or equal to the first length of time.
  10. 10 . The method of claim 9 , wherein the second length of time is less than the first length of time and the third length of time combined.
  11. 11 . The method of claim 1 , wherein the oxygen-containing gas comprises clean dry air, clean undried air, filtered air, ambient air, scuba gas, or oxygen.
  12. 12 . The method of claim 1 , further comprising, prior to wet annealing the lithium metal oxide film, increasing a temperature of a furnace in which the lithium metal oxide film is annealed from room temperature to the first temperature at a rate of 1-20° C./min, and the first temperature is 550-690° C.
  13. 13 . The method of claim 1 , wherein the first temperature is 600° C.±50° C., the second temperature is 700° C., the oxygen-containing gas is flowed at a rate of 2-50 standard liters per minute, and the second oxygen-containing atmosphere is clean dry air.
  14. 14 . The method of claim 1 , wherein the source of water vapor comprises a bubbler containing water at a temperature of 80-100° C.
  15. 15 . A method of making a solid-state battery or battery cell, comprising: depositing a lithium metal oxide film on a metal substrate, and annealing the lithium metal oxide film by the method of claim 1 .
  16. 16 . The method of claim 15 , wherein the metal substrate is configured to function as a cathode current collector in the solid-state battery or battery cell.
  17. 17 . The method of claim 16 , further comprising: forming a cathode on the metal substrate when the metal substrate functions as a cathode current collector, the cathode comprising the lithium metal oxide film; forming a solid-phase or solid-state electrolyte layer on the cathode; forming an anode current collector on the electrolyte layer; and forming electrical contacts to the cathode current collector and the anode current collector.
  18. 18 . The method of claim 17 , further comprising encapsulating and/or packaging the solid-state battery or battery cell.
  19. 19 . The method of claim 17 , wherein the cathode comprises lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide or lithium iron phosphate.
  20. 20 . The method of claim 1 , wherein the metal substrate comprises a metal foil, and the metal foil comprises stainless steel, aluminum, copper, nickel, inconel, brass, molybdenum or titanium, the elemental metals of which may be alloyed with up to 10% of one or more other elements.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Pat. Appl. No. 63/377,928, filed Sep. 30, 2022, incorporated herein by reference in its entirety. FIELD OF THE INVENTION The present invention generally relates to the field of solid-state and/or thin film batteries. More specifically, embodiments of the present invention pertain to methods of making a lithium metal oxide film and a lithium-based solid-state battery containing the film. DISCUSSION OF THE BACKGROUND Crystallization of amorphous LiCoO2 on precious metals is known. An example of this crystallization is discussed in Kim et al., “Characteristics of rapid-thermal-annealed LiCoO2 cathode film for an all-solid-state thin film microbattery,” J. Vac. Sci. Technol. A, 22(4), July/August 2004, where an anneal at 700° C. for 20 minutes of an amorphous layer of LiCoO2 deposited on a platinum film on a high-temperature MgO/Si substrate provides for crystallization of the LiCoO2 material, as shown by x-ray diffraction data. In Kim et al., it was shown that such a crystalline film is capable of constituting the lithium-ion-containing cathode layer of a functional all solid-state lithium battery. For the synthesis of LiCoO2 films, various methods have been investigated such as magnetron sputtering, sol-gel synthesis, pulsed laser deposition (PLD), chemical vapor deposition (CVD), and laser ablation. It is important to obtain LiCoO2 films with a beneficial or optimal crystal structure, in order to utilize the beneficial properties of LiCoO2, such as high electronic conductivity and charge capacity. However, obtaining a pure crystal phase in a LiCoO2 film is still challenging, and there is a lack of experimental guidelines on how to obtain an operationally robust and reliable LiCoO2 film. Among the methods known to the present inventors, sputtering followed by post-deposition annealing is the easiest, most scalable, and most applicable technique for the deposition of uniform films. It was found in one study of transparent amorphous In—Ga—Zn—O semiconductor films for thin-film transistors that wet O2 annealing is more effective to decrease electron traps, enhance TFT performance, and homogenize TFT characteristics than dry O2 annealing. Furthermore, the findings were understood to relate to stronger oxidation power of H2O-related species and consequent stabilization of chemical bonds. Oxidation studies of ZrB2 were performed in another study under wet air and dry air conditions at 1200° C., 1400° C., and 1500° C. for 1, 4, and 10 h. Compared to dry air, the presence of water vapor was found to enhance the oxidation kinetics by a factor of 7 to 30, depending on the temperature. Thermodynamic calculations suggested that water vapor promoted the formation of additional volatile species such as boric acid (e.g., HBO2), in addition to boria (B2O3, which is produced in dry air). The boric acid increases the evaporation rate of B2O3. Compared to dry air, the presence of water vapor leads to more rapid evaporation of boria and a transition from parabolic oxidation kinetic behavior (i.e., in which the rate of oxidation is controlled by diffusion of oxidizing species through boria) to linear (i.e., the underlying ZrB2 is directly exposed to the oxidizing environment) at shorter times and lower temperatures. It is also of continuing interest for the manufacture of solid-state lithium batteries to further reduce the thermal budget of any post-deposition anneal, both in time and in temperature, so as to enable the manufacture of such batteries without the need for expensive precious metal nucleation, barrier layers, or expensive high-temperature substrates. The present inventors are unaware of any existing process that allows for production of a cathode film for a battery in which the post-deposition anneal process has a sufficiently low thermal budget to allow production of functional structures for batteries on low-temperature materials such as stainless steel, aluminum, or copper foil. SUMMARY OF THE INVENTION The present invention relates to solid-state and thin film batteries, and more specifically to methods of making a lithium metal oxide film and a lithium-based solid-state battery containing the film. In one aspect, the present invention relates to a method of making a lithium metal oxide film, comprising wet annealing the lithium metal oxide film at a first temperature of 450-750° C. for a first length of time (e.g., of at least 0.02 hour), in a first oxygen-containing atmosphere further containing a first concentration or amount of water vapor. The first concentration or amount of water vapor is >0 (e.g., mol/L, g/L, % by weight or moles of all gases in the first oxygen-containing atmosphere, etc.). The metal may be cobalt (Co), manganese (Mn), nickel (Ni), titanium (Ti) or iron (Fe). In one aspect, wet annealing the lithium metal oxide film may be conducted in first and second phases. The first phase may be as describ