LITHIUM ION CONDUCTIVE MATERIAL AND METHOD FOR PRODUCING THE SAME

Abstract

The present disclosure relates to a lithium ion conductive material, preferably a lithium ion conductive glass ceramic, the material including a garnet-type crystalline phase content and an amorphous phase content. The material has a sintering temperature of 1000° C. or lower, preferably 950° C. or lower and an ion conductivity of at least 1*10.sup.−5 S/cm, preferably at least 2*10.sup.−5 S/cm, preferably at least 5*10.sup.−5 S/cm, preferably at least 1*10.sup.−4 S/cm, and the amorphous phase content includes boron and/or a composition including boron.

Claims

1. A lithium ion conductive material comprising: a garnet-type crystalline phase; and an amorphous phase, wherein the material has a sintering temperature of 1000° C. or lower, and an ion conductivity of at least 1*10.sup.−5 S/cm, and wherein the amorphous phase comprises boron and/or a composition comprising boron.

2. The lithium ion conductive material according to claim 1, wherein the lithium ion conductive material is lithium ion conductive glass ceramic.

3. The lithium ion conductive material according to claim 1, wherein the amorphous phase is less than 35 vol-% of the total composition of the material.

4. The lithium ion conductive material according to claim 1, wherein the amorphous phase is between 0.5 vol-% and 5 vol-% of the total composition of the material.

5. The lithium ion conductive material according to claim 1, wherein the amorphous phase content comprises lithium oxide and at least one doping agent.

6. The lithium ion conductive material according to claim 5, wherein the doping agent is at least one of based on niobium, aluminum, tantalum.

7. The lithium ion conductive material according to claim 1, wherein the garnet-type crystalline phase is boron-free.

8. The lithium ion conductive material according to claim 1, wherein the material is free of at least one of: transition metals and compounds thereof, alkali metals except lithium and compositions thereof, halogenides and compositions thereof, selenium and compositions thereof, sulfur and compositions thereof, lead and compositions thereof, cadmium and compositions thereof, and tellurium and compositions thereof.

9. The lithium ion conductive material according to claim 1, wherein the garnet-type crystalline phase has the formula:
Li.sub.7-3x+y-zAl.sub.xM.sub.y.sup.IIM.sub.3-y.sup.IIIM.sub.2-z.sup.IVM.sub.z.sup.VO.sub.12±δ, wherein M.sup.II is a bivalent cation, M.sup.III is a trivalent cation, M.sup.IV is a quadrivalent cation and M.sup.V is a pentavalent cation, wherein x+z>0, and wherein δ<0.5 represents potential oxygen vacancies.

10. The lithium ion conductive material according to claim 9, wherein the trivalent cation comprises a lanthanide, and wherein the quadrivalent cation comprises zircon and the pentavalent cation comprising niobium and/or tantalum.

11. The lithium ion conductive material according to claim 1, wherein the garnet-type crystalline phase is a cubic garnet-type inorganic solid electrolyte.

12. The lithium ion conductive material according to claim 12, wherein the cubic garnet-type inorganic solid electrolyte is lithium lanthanum zirconium oxide (LLZO) doped with at least one of niobium and aluminum.

13. The lithium ion conductive material according to claim 1, wherein the amorphous phase comprises the composition comprising boron, and wherein the composition further comprises at least one refining agent selected from the group consisting of arsenic oxide, antimony oxide, cerium oxide, tin oxide, and any combinations thereof.

14. The lithium ion conductive material according to claim 1, wherein the material has a sintering temperature of 950° C. or lower.

15. The lithium ion conductive material according to claim 1, wherein the material has an ion conductivity of at least 1*10.sup.−4 S/cm.

16. The lithium ion conductive material according to claim 1, wherein the material has an electronic conductivity that is smaller than 10.sup.−5 S/cm.

17. The lithium ion conductive material according to claim 1, wherein the material has an electronic conductivity that is smaller than 10.sup.−6 S/cm.

18. A method for providing the lithium ion conductive material of claim 1, comprising the steps of; melting precursor materials to obtain a molten mass; homogenizing the molten mass; and cooling of the homogenized molten mass to obtain a final mass in form of the lithium ion conductive material.

19. The method of claim 18, wherein the cooling step comprises ceramizing the cooled mass.

20. The method according to claim 18, further comprising the step of milling the final mass provide a powder.

21. The method according to claim 20, wherein the particles of the powder have a particle size of d.sub.50=10 micrometer or smaller, and wherein the particles comprise the respective content parts of the material with a deviation of less than 50% of the content of each component of the material.

22. The method of claim 21, wherein the particles of the powder have a particle size of d.sub.50=1 micrometer or smaller.

23. The method of claim 21, wherein the particles comprise the respective content parts of the material with a deviation of less than 20% of the content of each component of the material

24. The method according to claim 20, further comprising the step of sintering the powder at a temperature below 1000° Celsius.

25. A component comprising a material according to claim 1, wherein the component is a separator of a battery, an electrode of a battery, or a membrane, and wherein the material of claim 1 is co-sintered with at least one other material to obtain the component.

26. A battery comprising a component according to claim 25.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] FIG. 1 shows steps of part of a method according to an embodiment of the present disclosure, showing method steps for providing a sintered component.

DETAILED DESCRIPTION OF THE DISCLOSURE

[0046] In the following, a method for producing a glass ceramic according to an embodiment of the present disclosure is described.

[0047] Melting takes place in a so-called skull crucible, as described in DE 199 39 782 C1, which is herein incorporated by reference. The LLZO glass ceramics production is preferably according to methods as described in EP 3097060 B1, which is herein incorporated by reference.

[0048] The resulting glass-ceramics were used to produce samples for X-ray diffraction (XRD) investigations. In order to avoid degradation of the samples in contact with water, the sample preparation was carried out without water.

[0049] To determine the conductivity as a function of the sintering temperature, the material solidified as a solid block was further processed as follows:

[0050] In a first step T1, the block was cut into smaller fragments using a hammer and chisel. These were then fed into a jaw crusher in a further step T2 in one or more passes until fragments of a maximum size of less than 15 mm were produced in the longest dimension. These were ground in a further step T3 to a size d.sub.99<2 mm on a disk mill.

[0051] The obtained coarsely ground powder, here LLZO powder, sintering at low temperatures with a particle size <2 mm was finely ground in a further step T4 on a pilot dry classifier mill. 10 wt.-% of the particles in the resulting powder had a diameter of less than 0.2-0.5 μm, 50 wt.-% had a diameter of less than 0.6-1.6 μm, 90 wt.-% had a diameter of less than 2.0-2.8 μm, and 99 wt.-% had a diameter of 3.2-4.8 μm.

[0052] The obtained finely ground powder was then pressed in a further step T5 into cylindrical specimens having a diameter of 10 mm and a thickness of 1 mm and then in a further step T6 sintered at various temperatures and holding times. This resulted in the relative densities and conductivity values for the corresponding sintered specimens listed in the table below.

TABLE-US-00001 Example 1* 2* 3 4 5 6 7 8 9 Wt % Li.sub.2O 14.65 13.15 14.44 14.89 13.43 14.45 14.36 15.17 13.69 La.sub.2O.sub.3 56.37 57.36 55.58 54.15 56.32 55.6 55.26 55.12 53.96 ZrO.sub.2 21.32 21.69 21.02 17.75 22.72 21.03 20.9 20.85 23.13 SiO.sub.2 — — 0.21 0.2 0.21 — 0.21 0.2 — Al.sub.2O.sub.3 — — — — — 0.58 — — 1.13 Nb.sub.2O.sub.5 7.66 7.8 7.56 10.31 6.13 7.56 7.52 7.49 — Ta.sub.2O.sub.5 — — — — — — — — 7.32 B.sub.2O.sub.3 — — 1.19 2.7 1.21 0.79 1.78 1.18 0.77 Amorphous Phase Li 2 Li 1 Li 2 Li 2.7 Li 1.2 Li 2 Li 2 Li 2.5 Li 1.6 (calculated, cations (Li.sup.+, B.sup.3+, B 0.3 B 0.7 B 0.3 B 0.2 B 0.45 B 0.3 B 0.2 Al.sup.3+, Si.sup.4+, P.sup.5+) are Si 0.03 Si 0.03 Al 0.1 Si 0.03 Si 0.03 Al 0.2 charge balanced by oxygen (O.sup.2−), pfu) 1130° C., 0.5 h rel. density in % 99.3 94.6 99.1 97.6 94.5 97 96.7 conductivity 8.0* 6.4* 5.24* 2.1* 4.5* 6.7* 4.8* [S/cm] 10.sup.−4   10.sup.−4   10.sup.−4   10.sup.−4   10.sup.−4   10.sup.−4   10.sup.−4  1000° C., 5 h rel. density in % 63.9 66.8 90.5 88.9 86.2 96.3 89.3 conductivity 2.0E−06 5.0E−06 3.3* 1.2* 1.5* 5.0* 1.3* [S/cm] 10.sup.−4   10.sup.−4   10.sup.−4   10.sup.−4   10.sup.−4   900° C., 5 h rel. density in % 76.7 nb 78.2 84.3 74.8 80 76.7 conductivity 8.0* nb 5.0* 1.3* 3.2* 1.2* 4.0* [S/cm] 10.sup.−5   10.sup.−5   10.sup.−4   10.sup.−4   10.sup.−4   10.sup.−5  Example 10 11 12 13 14 15 16 Wt % Li.sub.2O 14.50 15.17 12.22 14.53 12.94 12.42 12.47 La.sub.2O.sub.3 55.81 55.16 51.41 55.92 50.11 50.77 50.99 Gd.sub.2O.sub.3 5.30 5.16 5.23 5.25 Y.sub.2O.sub.3 0.66 0.64 0.65 0.65 ZrO.sub.2 21.11 20.86 28.81 21.15 28.08 28.45 28.57 SiO.sub.2 0.21 0.14 0.14 0.21 Al.sub.2O.sub.3 0.40 1.19 1.74 1.76 1.77 Nb.sub.2O.sub.5 7.59 7.50 7.60 B.sub.2O.sub.3 0.79 0.90 0.41 0.80 1.19 0.16 0.08 P.sub.2O.sub.5 0.41 Amorphous Phase Li 2 Li 2.5 Li 0.6 Li 2 Li 1.2 Li 0.8 Li 0.8 (calculated, cations (Li.sup.+, B 0.2 B 0.23 B 0.1 B 0.2 B 0.3 B 0.04 B 0.02 B.sup.3+, Al.sup.3+, Si.sup.4+, P.sup.5+) are Si 0.03 Al 0.07 Al 0.1 Al 0.1 Al 0.1 charge balanced by oxygen Si 0.02 Si 0.02 Si 0.03 (O.sup.2−), pfu) P 0.05 1130° C., 0.5 h rel. density in % 94.0 96.3 96.5 98.5 99.4 conductivity [S/cm] 5.8* 2.7* 1.0* 3.5* 1.5* 10.sup.−4   10.sup.−4   10.sup.−4   10.sup.−4   10.sup.−4   1000° C., 5 h rel. density in % conductivity [S/cm] 900° C., 5 h rel. density in % 83.2 85.0 74.6 conductivity [S/cm] 2.0* 9.0* 5.0* 10.sup.−4   10.sup.−5   10.sup.−5  

[0053] The weighed-in composition of the examples according to embodiments of the present disclosure is summarized in Table 1 in percent by weight. The chemical analysis of the samples/examples may reveal additionally HfO.sub.2, which is a common impurity in ZrO.sub.2. Moreover, the Li.sub.2O content can be reduced due to Li loss by evaporation during the synthesis.

[0054] The composition of the amorphous phase is calculated based on the composition of the glass ceramic by the following assumptions:

[0055] Li.sub.2O, La.sub.2O.sub.3, Gd.sub.2O.sub.3, Y.sub.2O.sub.3, ZrO.sub.2, Nb.sub.2O.sub.5, Ta.sub.2O.sub.5 form the stoichiometric garnet.

[0056] In the absence of Nb.sub.2O.sub.5 and Ta.sub.2O.sub.5, Al.sub.2O.sub.3 enters the garnet and substitutes Li.sub.2O until 0.6 pfu Li+ are replaced by 0.2 pfu Al.sup.2+. Surplus Li.sub.2O and Al.sub.2O.sub.3, as well as any SiO.sub.2, B.sub.2O.sub.3 and P.sub.2O.sub.5 and further glass formers are ascribed to the amorphous phase. In other words, the given composition is divided into the stoichiometric garnet, which may contain several dopants,

Li.sub.7-3x+y-zAl.sub.xM.sub.y.sup.IIM.sub.3-y.sup.IIIM.sub.2-z.sup.IVM.sub.z.sup.VO.sub.12±δ,

and an amorphous phase, which comprises the glass formers e.g. SiO.sub.2, B.sub.2O.sub.3, Al.sub.2O.sub.3, and P.sub.2O.sub.5, as well as surplus Li.sub.2O. Divalent ions M.sup.II would be ascribed to the crystalline garnet for the sake of clarity, even though the one skilled in the art is aware that divalent cations can also act as glass formers and would be found at least partially in the amorphous phase. It is to be understood that this calculation does not give a precise, actual composition of the amorphous phase, which can deviate due the assumptions made in this calculation and Li loss during the synthesis, but more so elucidates its compositional range and highlights the influence of boron in this phase on the sintering behavior. The composition of the amorphous phase in the Table above is given in pfu (parts per formula unit) with regard to LLZO. The amorphous phase is oxidic and thus the elements/cations are charge-balanced by oxygen (O.sup.2−).

[0057] Comparative Examples 1* and 2* correspond to the previous state of the art with a glass phase without boron.

[0058] In Example 1* and 2*, the amorphous phase, calculated by subtracting all components that can crystallize as stoichiometric garnet, comprises only Li.sub.2O. Based on a theoretical garnet structure in example 1*, there are 2 mol Li per formula unit, in Example 2*, there is only 1 mol Li per formula unit. In both cases, good conductivities are found during sintering at 1130° C., but even if the sintering temperature is lowered to 1000° C., the sintering temperature drops to below 10.sup.−5 S/M.

[0059] In contrast, Examples 3-16 show the effect of high conductivity at low sintering temperatures according to embodiments of the present disclosure. In addition to the conductivities and density at sintering temperatures of 1130° C., 1000° C., and 900° C., the calculated composition of the amorphous phase is also presented. It can be seen that for all glass ceramics comprising boron in the amorphous phase, conductivities in the order of 10.sup.−4 S/cm are achieved at sintering temperatures of 1000° C. Even if the sintering temperatures are further reduced to 900° C., the conductivities are still in the range of 3.2×10.sup.−5 S/cm to 1.3×10.sup.−4 S/cm providing a high conductivity compared to conventional glass ceramics.

[0060] To summarize, embodiments of the present disclosure provides and/or enables the following features and/or advantages: [0061] low sintering temperature [0062] easy and cheap manufacturing [0063] easy implementation [0064] less resources necessary [0065] high conductivity [0066] scalability [0067] reduced manufacturing time

[0068] Many modifications and other embodiments of the disclosure set forth herein will come to mind to the one skilled in the art to which the disclosure pertains having the benefit of the teachings presented in the foregoing description and the associated drawings. Therefore, it is to be understood that the disclosure is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

LIST OF REFERENCE SIGNS

[0069] T1-T6 Steps of part of a method