Garnet materials for Li secondary batteries and methods of making and using garnet materials
Set forth herein are garnet material compositions, e.g., lithium-stuffed garnets and lithium-stuffed garnets doped with alumina, which are suitable for use as electrolytes and catholytes in solid state battery applications. Also set forth herein are lithium-stuffed garnet thin films having fine grains therein. Disclosed herein are novel and inventive methods of making and using lithium-stuffed garnets as catholytes, electrolytes and/or anolytes for all solid state lithium rechargeable batteries. Also disclosed herein are novel electrochemical devices which incorporate these garnet catholytes, electrolytes and/or anolytes. Also set forth herein are methods for preparing novel structures, including dense thin (<50 um) free standing membranes of an ionically conducting material for use as a catholyte, electrolyte, and, or, anolyte, in an electrochemical device, a battery component (positive or negative electrode materials), or a complete solid state electrochemical energy storage device. Also, the methods set forth herein disclose novel sintering techniques, e.g., for heating and/or field assisted (FAST) sintering, for solid state energy storage devices and the components thereof.
1. A bilayer comprising:
a metal foil or metal powder positioned in contact with a lithium-stuffed garnet thin film; wherein the lithium-stuffed garnet thin film is a thin sintered garnet film, wherein the lithium-stuffed garnet thin film thickness is less than 50 μm and greater than 10 nm, and wherein the lithium-stuffed garnet thin film is bonded to the metal or metal powder on at least one side of the film;
wherein the lithium-stuffed garnet is characterized by one of the following formula:
Li A La B M′ C M″ D Zr E O F , Li A La B M′ C M″ D Ta E O F , Li A La B M′ C M″ D Nb E O F , wherein 4<A<8.5, 1.5<B<4, 0≤C≤2, 0≤D≤2; 0≤E<2, 10<F≤13, and M′ and M″ are each, independently in each instance selected from Al, Mo, W, Nb, Sb, Ca, Ba, Sr, Ce, Hf, Rb, or Ta;
Li a La b Zr c Al d Me″ e O f , wherein 5<a<7.7; 2<b<4; 0<c≤2.5; 0≤d<2; 0≤e<2, 10<f≤13 and Me″ is a metal selected from Nb, Ta, V, W, Mo, or Sb;
Li A La B M′ C M″ D Zr E O F , wherein the molar ratio of Al 2 O 3 :lithium-stuffed garnet is between 0.05 and 0.7; or
Li g La 3 Zr 2 O 12 —Al 2 O 3 , wherein 5.5<g<8.5 and the molar ratio of Al 2 O 3 :lithium-stuffed garnet is between 0.05 and 1.0.
2. The bilayer of claim 1 , wherein the metal is Ni; Al; Fe; stainless steel; an alloy of Ni, Cu, Al, or Fe; or a combination of Ni, Cu, Al, or Fe.
3. An electrochemical stack comprising at least two or more bilayers of claim 1 .
4. The bilayer of claim 1 , wherein the lithium-stuffed garnet thin film has a thickness of 1 μm to 150 μm.
5. The bilayer of claim 1 , wherein the bilayer comprises a metal foil and the metal foil is a current collector.
6. A trilayer comprising the bilayer of claim 1 , further comprising a second lithium-stuffed garnet thin film in contact with the metal foil or metal powder of the bilayer.
7. The bilayer of claim 1 , wherein the thickness of the lithium-stuffed garnet thin film is less than 20 μm.
8. The bilayer of claim 1 , wherein the lithium-stuffed garnet thin film has a surface roughness of less than 5 μm.
9. The bilayer of claim 1 , wherein the lithium-stuffed garnet thin film has a median grain size of between 0.1 μm to 10 μm.
10. The bilayer of claim 1 , wherein the lithium-stuffed garnet thin film has a median grain size of between 1.0 μm to 5.0 μm.
11. A process for sintering a thin and free standing lithium-stuffed garnet film, wherein the lithium-stuffed garnet film is the bilayer of claim 1 , comprising the following steps:
providing a green tape by casting a garnet slurry;
wherein the slurry comprises lithium-stuffed garnet or lithium-stuffed garnet chemical precursors, and at least one member selected from the group consisting of a binder, a solvent, a plasticizer, a dispersant, and combinations thereof; and
sintering the green tape between setter plates;
wherein the sintering is heat, spark plasma, or field assisted sintering; and
wherein the lithium concentration in the setter plates is at least 10 atomic percent of the setter.
12. The process of claim 11 , wherein sintering includes applying pressure to the film with the setter plates, wherein the pressure applied is between 0.001 MPa to 200 MPa.
13. The process of claim 11 , wherein the slurry comprises milled and calcined lithium-stuffed garnet.
14. The process of claim 11 , wherein the solid loading of the green tape is at least 30% w/w, or at least 40% w/w, or at least 50% w/w, or at least 60% w/w, or at least 65% w/w.
15. The process of claim 11 , wherein a source of Li is placed in proximity of the sintered film during sintering.
16. The process of claim 11 , wherein the film is sintered directly onto a metal wherein the metal is a metal powder or a metal foil, wherein the metal powder comprises Ni or Cu powder, and wherein the metal powder is between and in contact with one side of the green tape and one setter plate.
17. The process of claim 11 , wherein the setter plates comprise lithium-stuffed garnet, zirconia, porous zirconia, or nickel.
18. The process of claim 11 , wherein the setter plates are porous setter plates.