ELECTRICAL STORAGE SYSTEM COMPRISING A SHEET-TYPE DISCRETE ELEMENT, DISCRETE SHEET-TYPE ELEMENT, METHOD FOR THE PRODUCTION THEREOF, AND USE THEREOF

Abstract

An electrical storage system is provided that has a thickness of less than 2 mm, where the system includes at least one sheet-type discrete element, the sheet-type discrete element exhibiting high resistance to an attack of alkali metals or alkali metal ions, in particular lithium, wherein the sheet-type discrete element has a low content of TiO.sub.2, the TiO.sub.2 content preferably being less than 2 wt %, preferably less than 0.5 wt %, and preferably free of TiO.sub.2.

Claims

1. An electrical storage system, comprising: at least one sheet-type discrete element having a thickness of less than 2 mm and being made of glass, wherein the at least one sheet-type discrete element exhibits high resistance to an attack of alkali metals or alkali metal ions, wherein the at least one sheet-type discrete element comprises a compostion comprising a TiO.sub.2 in a content of at most 2 wt % and a compositional range selected from the group consisting of, in wt %: TABLE-US-00030 Component No. 1 No. 2 No. 3 No. 4 SiO.sub.2 58-65 55-75  75-85 50-65 B.sub.2O.sub.3   6-10.5  8-18 0-6 Al.sub.2O.sub.3 14-25 0-15 0.5-4.5 15-20 Li.sub.2O 0-7 0-6 Na.sub.2O 0-15 1.5-5.5  8-15 K.sub.2O 0-14 0-2 0-5 MgO 0-5 0-4  0-5 CaO 0-9 3-12 0-7 BaO 0-8 0-15 SrO 0-8 ZnO 0-2 0-5  0-4 TiO.sub.2 0-2  0-1 ZrO.sub.2 0-4 Total of MgO,  8-18 CaO, SrO, and BaO

2. The electrical storage system as claimed in claim 1, further comprising additional constituents in the form of impurities or of necessary processing-related additives and/or refining agents, with a total of the additional constituents amounting to not more than 2 wt %.

3. The electrical storage system as claimed in claim 1, wherein the compositional range comprises range No. 1 and wherein the BaO content is between 3 wt % and 8 wt %.

4. The electrical storage system as claimed in claim 1, wherein the sheet-type discrete element has an Li.sub.2O content of at least 0.1 wt %.

5. The electrical storage system as claimed in claim 1, wherein the at least one sheet-type discrete element has at least one surface that is inert and/or permeable to a reduced degree and/or impermeable to materials coming into contact with the at least one surface.

6. The electrical storage system as claimed in claim 5, wherein the at least one surface is a barrier layer.

7. The electrical storage system as claimed in claim 6, wherein the barrier layer is a barrier against a diffusion of metals.

8. The electrical storage system as claimed in claim 6, wherein the barrier layer is a barrier against a diffusion of alkali metals.

9. The electrical storage system as claimed in claim 8, wherein the barrier layer is formed by doping or overdoping with at least one alkali metal.

10. The electrical storage system as claimed in claim 5, wherein the barrier layer is a barrier to lithium.

11. The electrical storage system as claimed in claim 1, wherein the the at least one sheet-type discrete element comprises a thickness variation of not more than 25 μm based on wafer or substrate size in a range of >100 mm in diameter.

12. The electrical storage system as claimed in claim 1, wherein the at least one sheet-type discrete element comprises a water vapor transmission rate (WVTR) of <10.sup.−3 g/(m.sup.2.Math.d).

13. The electrical storage system as claimed in claim 1, wherein the at least one sheet-type discrete element has a thickness of not more than 100 μm.

14. The electrical storage system as claimed in claim 1, wherein the at least one sheet-type discrete element has a specific electrical resistance at a temperature of 350° C. and at alternating current with a frequency of 50 Hz of greater than 1.0*10.sup.6 Ohm.Math.cm.

15. The electrical storage system as claimed in claim 1, wherein the at least one sheet-type discrete element comprises a maximum load temperature θ.sub.Max of at least 300° C.

16. The electrical storage system as claimed in claim 1, wherein the at least one sheet-type discrete element has a coefficient of linear thermal expansion a in a range from 2.0*10.sup.−6/K to 10*10.sup.−6/K.

17. The electrical storage system as claimed in claim 1, wherein the at least one sheet-type discrete element further comprises a relationship of a product of a maximum load temperature (θ.sub.Max) and a coefficient of linear thermal expansion (α) of 600.Math.10.sup.−6≦θ.sub.Max.Math.α≦8000.Math.10.sup.−6.

18. The electrical storage system as claimed in claim 1, wherein the at least one sheet-type discrete element further comprises a relationship of a product of a maximum load temperature (θ.sub.Max) and a coefficient of linear thermal expansion (α) of 800.Math.10.sup.−6≦θ.sub.Max.Math.α≦5000.Math.10.sup.−6.

19. A sheet-type discrete element made, comprising: a high resistance to an attack of alkali metals or alkali metal ions; and a composition comprising a TiO.sub.2 content of at most 2 wt % and a compositional range selected from the group consisting of, in wt %: TABLE-US-00031 Component No. 1 No. 2 No. 3 No. 4 SiO.sub.2 58-65 55-75  75-85 50-65 B.sub.2O.sub.3   6-10.5  8-18 0-6 Al.sub.2O.sub.3 14-25 0-15 0.5-4.5 15-20 Li.sub.2O 0-7 0-6 Na.sub.2O 0-15 1.5-5.5  8-15 K.sub.2O 0-14 0-2 0-5 MgO 0-5 0-4  0-5 CaO 0-9 3-12 0-7 BaO 0-8 0-15 SrO 0-8 ZnO 0-2 0-5  0-4 TiO.sub.2 0-2  0-1 ZrO.sub.2 0-4 total of MgO,  8-18 CaO, SrO, and BaO

20. The sheet-type discrete element as claimed in claim 19, further comprising additional constituents in the form of impurities or of necessary processing-related additives and/or refining agents, with a total of the additional constituents amounting to not more than 2 wt %.

21. The sheet-type discrete element as claimed in claim 19, wherein the compositional range comprises range No. 1 and wherein the BaO content is between 3 wt % and 8 wt %.

22. The sheet-type discrete element as claimed in claim 19, wherein the composition has an Li.sub.2O content of at least 0.1 wt %.

23. The sheet-type discrete element as claimed in claim 19, further comprising at least one surface that is inert and/or permeable to a reduced degree and/or impermeable to materials coming into contact with the at least one surface.

24. The sheet-type discrete element as claimed in claim 23, wherein the at least one surface is a barrier layer.

25. The sheet-type discrete element as claimed in claim 24, wherein the barrier layer is a barrier against a diffusion of metals.

26. The sheet-type discrete element as claimed in claim 24, wherein the barrier layer is a barrier against a diffusion of alkali metals.

27. The sheet-type discrete element as claimed in claim 26, wherein the barrier layer is formed by doping or overdoping with at least one alkali metal.

28. The sheet-type discrete element as claimed in claim 19, further comprising a thickness variation of not more than 25 μm based on wafer or substrate sizes in a range of >100 mm in diameter.

29. The sheet-type discrete element as claimed in claim 19, further comprising a thickness of less than 2 mm.

30. The sheet-type discrete element as claimed in claim 19, further comprising a water vapor transmission rate (WVTR) of <10.sup.−3 g/(m.sup.2.Math.d).

31. The sheet-type discrete element as claimed in claim 19, further comprising a specific electrical resistance at a temperature of 350° C. and at alternating current with a frequency of 50 Hz of greater than 1.0*10.sup.6 Ohm.Math.cm.

32. The sheet-type discrete element as claimed in claim 19, further comprising a maximum load temperature θ.sub.Max of at least 300° C.

33. The sheet-type discrete element as claimed in claim 19, further comprising a coefficient of linear thermal expansion a in a range from 2.0*10.sup.−6/K to 10*10.sup.−6/K.

34. The sheet-type discrete element as claimed in claim 19, further comprising a relationship of a product of a maximum load temperature (UMax) and a coefficient of linear thermal expansion (α) of 600.Math.10.sup.−6≦θ.sub.Max.Math.α8000.Math.10.sup.−6.

35. The sheet-type discrete element as claimed in claim 19, wherein the sheet-type discrete element is configured for a use elected from the group consisting of a substrate in an electrical storage system, a superstrate in an electrical storage system, and a cover in an electrical storage system.

36. A method for producing a sheet-type discrete element for use in an electrical storage system, comprising: melting a composition comprising a TiO.sub.2 content of at most 2 wt % and a compositional range selected from the group consisting of, in wt %: TABLE-US-00032 Component No. 1 No. 2 No. 3 No. 4 SiO.sub.2 58-65 55-75  75-85 50-65 B.sub.2O.sub.3   6-10.5  8-18 0-6 Al.sub.2O.sub.3 14-25 0-15 0.5-4.5 15-20 Li.sub.2O 0-7 0-6 Na.sub.2O 0-15 1.5-5.5  8-15 K.sub.2O 0-14 0-2 0-5 MgO 0-5 0-4  0-5 CaO 0-9 3-12 0-7 BaO 0-8 0-15 SrO 0-8 ZnO 0-2 0-5  0-4 TiO.sub.2 0-2  0-1 ZrO.sub.2 0-4 total of MgO,  8-18 CaO, SrO, and BaO and subsequently hot shaping the melted composition.

37. The method as claimed in claim 36, wherein the hot shaping comprises drawing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0145] FIG. 1 shows contact stability of specific exemplary embodiments (EE) for sheet-type discrete elements according to the invention and comparative examples (CE) of non-inventive sheet-type discrete elements;

[0146] FIG. 2 shows a schematic view of an electrical storage element;

[0147] FIG. 3 is a schematic view of a sheet-type discrete element;

[0148] FIGS. 4 through 6 are scanning electron micrographs of discrete sheet-type elements; and

[0149] FIG. 7a through 7e shows photographs of sheet-type discrete elements after exposure to metallic lithium.

DETAILED DESCRIPTION

[0150] FIG. 2 schematically shows an electrical storage system 1 according to the present invention. It comprises a sheet-type discrete element 2 which is used as a substrate. A sequence of different layers is applied on the substrate. By way of example and without being limited to the present example, first the two collector layers are applied on the sheet-type discrete element 2, cathode collector layer 3, and anode collector layer 4. Such collector layers usually have a thickness of a few micrometers and are made of a metal, for example of copper, aluminum, or titanium. Superimposed on collector layer 3 is cathode layer 5. If the electrical storage system 1 is a lithium-based thin film battery, the cathode is made of a lithium-transition metal compound, preferably an oxide, for example of LiCoO.sub.2, of LiMnO.sub.2, or else of LiFePO.sub.4. Furthermore, the electrolyte 6 is applied on the substrate and is at least partially overlapping cathode layer 5, and in the case of a lithium-based thin film battery, this electrolyte is mostly LiPON, a compound of lithium with oxygen, phosphorus, and nitrogen. Furthermore, the electrical storage system 1 comprises an anode 7 which may for instance be made of lithium titanium oxide or else of metallic lithium. Anode layer 7 is at least partially overlapping electrolyte layer 6 and collector layer 4. Furthermore, the battery 1 comprises an encapsulation layer 8.

[0151] In the context of the present invention, any material which is capable of preventing or greatly reducing the attack of fluids or other corrosive materials on the electrical storage system 1 is considered as an encapsulation or sealing of the electrical storage system 1.

[0152] FIG. 3 schematically illustrates a sheet-type discrete element according to the present invention, here in the form of a sheet-type shaped body 10. In the context of the present invention, a shaped body is referred to as being of sheet type or a sheet if its dimension in one spatial direction is not more than half of that in the two other spatial directions. A shaped body is referred to as a ribbon in the present invention if it has a length, width, and thickness for which the following relationship applies: the length is at least ten times larger than the width which in turn is at least twice as large as the thickness.

[0153] FIG. 4 is a scanning electron micrograph showing the breaking edge of a sheet-type discrete element with the composition according to Exemplary Embodiment 5 (EE5) after contact of the surface of the sheet-type discrete element with lithium metal. The breaking edge of the sheet-type discrete element is uniform both at the surface and in the bulk material. There has thus been occurred no degradation of the surface of the sheet-type discrete element due to the contact with lithium metal.

[0154] FIG. 5 shows the surface of a sheet-type discrete element corresponding to the composition of Comparative Example 1 (CE1) prior to the contact with lithium metal.

[0155] FIG. 6 shows the surface of a sheet-type discrete element corresponding to the composition of Comparative Example 1 (CE1) after contact with lithium metal. Clearly visible, the surface of the sheet-type discrete element has been strongly degraded, resulting in chipping at the surface and considerable roughening thereof.

[0156] FIGS. 7a through 7e show photographs of different sheet-type discrete elements after a stress test in which the surface of the sheet-type discrete element was coated with lithium metal by vapor deposition. After having been coated with lithium metal by vapor deposition, the respective samples were stored in a glove box under an inert atmosphere. After this storage, the lithium layer was wiped off.

[0157] In the case of FIGS. 7a and 7b, which have a composition corresponding to Comparative Examples (CE) 1 and 3, respectively, it has been found that the surface of the samples is changed after removal of the metallic lithium, in particular it exhibits haze or is discolored. By contrast, in case of the examined samples of the Exemplary Embodiments (EE) 31, 32, and 28 shown in FIGS. 7c, 7d, and 7e, respectively, such change, in particular discoloration, has not occurred. According to the inventors, this absence of discoloration is attributable to the absence of a titanium content in the samples, in contrast to the Comparative Examples 1 and 3 in FIGS. 7a and 7b, respectively.

LIST OF REFERENCE NUMERALS

[0158] 1 Electrical storage system [0159] 2 Sheet-type discrete element used as a substrate [0160] 3 Cathode collector layer [0161] 4 Anode collector layer [0162] 5 Cathode [0163] 6 Electrolyte [0164] 7 Anode [0165] 8 Encapsulation layer [0166] 10 Sheet-type discrete element in the form of a sheet-type shaped body