SAGGER RECEIVING ELEMENT, IN PARTICULAR A SAGGER FOR BURNING POWDERY CATHODE MATERIAL FOR LITHIUM-ION ACCUMULATORS, AND MIXTURE THEREFOR

Abstract

A sagger receiving element for burning powdery cathode materials for producing lithium ion accumulators including a rectangular shell comprising four side walls and a base, wherein the sagger receiving element is produced by a burning process from heat-resistant material which withstands temperatures of in particular more than 900° C., and wherein the material of the sagger receiving element is produced on the basis of oxide-bonded SiC, the material having the following chemical composition in percent by weight to a total of 100%: silicon carbide (SiC) content in a range of 40.0%-80.0%, Al.sub.2O.sub.3 content in a range of 10%-43%, total SiO.sub.2 content in a range of 5%-30%, and alkali oxide and iron oxide content of less than 2%.

Claims

1.-15. (canceled)

16. A sagger receiving element for burning powdery cathode materials for producing lithium ion accumulators, comprising: a rectangular shell comprising four side walls and a base; wherein the sagger receiving element is produced by a burning process from heat-resistant material which withstands temperatures of in particular more than 900° C.; and wherein the material of the sagger receiving element is produced on the basis of oxide-bonded SiC, the material having the following chemical composition in percent by weight to a total of 100%: silicon carbide (SiC) content in a range of 40.0%-80.0%; Al.sub.2O.sub.3 content in a range of 10%-43%; total SiO.sub.2 content in a range of 5%-30%; and alkali oxide and iron oxide content of less than 2%.

17. The sagger receiving element according to claim 16, wherein the SiC content is in the range of 50.0%-70.0%.

18. The sagger receiving element according to claim 16, wherein the Al.sub.2O.sub.3 content is in the range of 15%-35%.

19. The sagger receiving element according to claim 18, wherein the Al.sub.2O.sub.3 content is in the range of 20%-30%.

20. The sagger receiving element according to claim 16, wherein the SiO.sub.2 content is in the range of 7%-20%.

21. The sagger receiving element according to claim 20, wherein the SiO.sub.2 content is in the range of 8%-15%.

22. The sagger receiving element according to claim 16, wherein the material of the sagger receiving element has the following chemical composition in percent by weight to the total of 100%: Al.sub.2O.sub.3 content as corundum and mullite in a range of 10.0%-40.0%; mullite (Al.sub.6Si.sub.2O.sub.13); and silica phase of less than 10%.

23. The sagger receiving element according to claim 22, wherein the Al.sub.2O.sub.3 content is in the range of 13.0%-30.0%.

24. The sagger receiving element according to claim 22, wherein the silica phase is less than 8%.

25. The sagger receiving element according to claim 16, wherein the mullite (Al.sub.6Si.sub.2O.sub.13) is provided at a content of less than 25%.

26. The sagger receiving element of claim 25, wherein the mullite (Al.sub.6Si.sub.2O.sub.13) content is less than 20%.

27. The sagger receiving element according to claim 16, wherein the material has the following composition in percent by weight: silicon carbide (SiC) content in a range of 50.0%-70.0%; Al.sub.2O.sub.3 content as corundum in a range of 13.0%-30%; mullite (Al.sub.6Si.sub.2O.sub.13) content of less than 20%; silica phase of less than 7%; and alkali oxide and iron oxide content of less than 1%.

28. The sagger receiving element according to claim 16, wherein an average particle size of an SiC particle size is less than 500 μm.

29. The sagger receiving element according to claim 16, wherein a bulk density of the sagger receiving element is in a range of 2.50 g/cm.sup.3-2.60 g/cm.sup.3.

30. The sagger receiving element according to claim 16, wherein the sagger receiving element has an open porosity in a range of 15%-22%.

31. The sagger receiving element of claim 30, wherein the open porosity range is 18%-21%.

32. A mixture for producing the sagger receiving element according to claim 16, the silicon carbide content in a range of 40.0%-82.0% by weight and an average particle size of <500 μm, the aluminium oxide having a powdery Al.sub.2O.sub.3 content in the range of 10.0%-43.0% by weight, and the silica dioxide having a powdery SiO.sub.2 carrier based on at least 90% SiO.sub.2 and a particle size of <100 μm, is used for a single sagger material in a powder mixture, the remainder being impurities.

33. The mixture of claim 32, wherein the Al.sub.2O.sub.3 content is in the range of 15.0%-35.0%.

34. The mixture of claim 33, wherein the Al.sub.2O.sub.3 content is in the range of 19.5%-26.0%.

35. The mixture of claim 32, wherein the powdery SiO.sub.2 carrier is based on at least 95% SiO.sub.2 by weight.

36. The mixture of claim 32, wherein the powdery SiO.sub.2 carrier particle size is less than 50 μm.

37. The mixture of claim 36, wherein the powdery SiO.sub.2 carrier particle size is less than 45 μm.

38. The mixture according to claim 32, wherein the SiO.sub.2 carrier is present at a content of 5% to 15% by weight.

39. The mixture according to claim 38, wherein the SiO.sub.2 carrier is present at a content of 5%-7% by weight.

40. The mixture according to claim 32, wherein the material is mixed and kneaded with an admixture of water, and, from the plastically deformable material produced therefrom, the nagger receiving element is shaped and burned.

41. The mixture according to claim 32, wherein the SiC content is formed from the mixture having a varied particle size of 3%-9% (% by weight) SiC mesh 80/220 having an average particle size in millimetres of 0.1 mm-0.35 mm, a content of 23%-54% (% by weight) of SiC mesh 30/70 having an average particle size in millimetres in a range of 0.35 mm-0.85 mm, a content of SiC mesh 16/24 of 7%-19% (% by weight) having an average particle size in a range of 0.85 mm-1.5 mm, and an SiC content of 0.5%-1% (% by weight) at an average particle size ≤ 100 μm, the maximum content of SiC being 82% by weight.

42. The mixture of claim 41, wherein the SiC mesh 80/220 has an average particle size of less than 0.25 mm.

43. The mixture of claim 41, wherein the SiC mesh 30/70 has an average particle size of 0.25 mm-0.71 mm.

44. The mixture of claim 41, wherein the SiC mesh 16/24 of has an average particle size of less than 1.0 mm.

45. The mixture of claim 41, wherein the SiC content has an average particle size of greater than or equal to 20 μm.

46. The mixture of claim 45, wherein the SiC content has an average particle size of 20 μm-45 μm.

47. The mixture of claim 46, wherein the SiC content has an average particle size of 30 μm-37 μm.

48. The mixture according to claim 41, wherein the SiC mixture is formed from 4%-8% by weight SiC mesh 80/220, 43%-54% by weight SiC mesh 30/70, 11%-16% by weight SiC mesh 16/24, and SiC extremely fine particulate having a particle size ≤ 100 μm at up to 1% by weight.

49. The mixture according to claim 32, wherein the Al.sub.2O.sub.3 content is formed from corundum and/or clay, comprising 19%-35% by weight clay, at least 12% by weight corundum.

50. The mixture according to claim 49, wherein the clay is 19%-26% by weight.

51. The mixture according to claim 49, wherein the corundum is at least 15% by weight.

52. The mixture according to claim 32, wherein after the burning process, the sagger receiving element comprises silicon carbide at a content of 40%-75% by weight, an SiO.sub.2 content of 5.0%-15.0% by weight, an Al.sub.2O.sub.3 content of 19.0%-26.0% by weight, remainder clay and impurities at at most 1.0% of iron oxide, alkali.

53. The mixture according to claim 52, wherein the content of silica carbide after the burning process is 52.0%-70.0% by weight.

54. The mixture according to claim 52, wherein the SiO.sub.2 content after the burning process is 5.0%-7.0% by weight.

55. The mixture according to claim 52, wherein the Al.sub.2O.sub.3 content after the burning process is 23.0%-26.0% by weight.

56. The mixture according to claim 52, wherein the remainder clay and impurities is less than 0.7% by weight.

Description

[0050] The accompanying FIGS. 1 to 3 show a sagger such as is conventionally used for burning cathode materials for lithium-ion accumulators. It can be seen that this is a shell comprising four peripherally arranged side walls and a base.

[0051] FIG. 1 is a sectional view,

[0052] FIG. 2 is a plan view, and

[0053] FIG. 3 is a perspective view.

[0054] If required, and while remaining within the scope of the invention, conventional burning aids in a shell-shaped structure may be provided with a coating of the above-mentioned materials, whereby the burning of cathode material can also, highly advantageously, be suitably implemented.

[0055] Hereinafter, purely by way of example, suitable material mixtures according to the invention from which the nagger is produced are set out in brief.

TABLE-US-00001 Example 1 (No. 1) SiC 67.0% Clay (Al.sub.2O.sub.3) 25.5% SiO.sub.2 carrier 6.5% Remainder impurities

[0056] The silicon carbide is present in powder form as an oxide-bonded SiC mixture, expediently at a particle size of SiC mesh 80/220 in a range of 4-8%, SiC mesh 30/70 in a range of 43-47%, and SiC mesh 16/24 in a range of 11-16%, extremely fine powder having a size of <100 μm also being present at up to 0.1%, in particular in the form of Totanin powder.

[0057] Clay is present in powder form, expediently at a particle size of 0-0.08 mm, various types of clay being suitable, in particular clay of an average particle size of 3 μm to 5 μm being available.

TABLE-US-00002 Example 2 (No. 2) SiC 74.0% Clay (Al.sub.2O.sub.3) 19.5% SiO.sub.2 carrier 5.0% Remainder impurities

[0058] The silicon carbide is expediently present as an oxide-bonded SiC mixture having a particle size expediently in the following contents: SiC mesh 80/200 in a range of 5-9%, SiC mesh 30/70 in a range of 47-54%, SiC mesh 16/24 in a range of 13-19%, it being possible in this case too for extremely fine particles having a size of <100 μm to be added within a range of up to 2%.

[0059] In particular powdery, highly reactive clay is suitable as the clay.

TABLE-US-00003 Example 3 SiC 54.0% Clay (Al.sub.2O.sub.3) 34.0% SiO.sub.2 carrier 10.0% Remainder impurities

[0060] In this case too, the oxide-bonded SiC is in the form of a powdery SiC mixture, specifically preferably having a particle size content of SiC mesh 80/220 in a range of 3-7%, SiC mesh 30/70 in a range of 33-39%, and SiC mesh 16/24 in a range of 9-13%, it also expediently being possible for the clay to be added in extremely fine particles <100 μm at 0.5-2%.

[0061] As in the above examples, various types of clay are suitable for the Al.sub.2O.sub.3 content of this composition, specifically including those having the trade names set out in the other examples.

TABLE-US-00004 Example 4 SiC 41.0% Clay (Al.sub.2O.sub.3) 42.5% SiO.sub.2 carrier 14.5% Remainder impurities

[0062] The silicon carbide is preferably present in an oxide-bonded SiC mixture, the following ranges being expedient: SiC mesh 80/220 in a range of 3-6%, SiC mesh 30/70 in a range of 23-29%, and SiC mesh 16/24 in a range of 7-11%, as well as extremely fine particles of SiC <100 μm at 0.5-2%, the percentage specifications being given in percent by weight.

[0063] Accordingly, powdery clay is suitable as the clay, expediently having a particle size of 0-0.08 mm, in particular corundum, as well as clay having an average particle size of 5 μm and having an Al.sub.2O.sub.3 content higher than 99.5% by weight, but also other clays, being suitable as the clay. The corresponding selection can readily be made by a person skilled in the art. A plurality of suitable clays are available for this purpose.

[0064] The following table gives a chemical analysis of the material components of the produced naggers for the two mixtures of Examples 1 and 2, including the methods and devices used for the analysis.

TABLE-US-00005 Examples in the No. 1 No. 2 description Example 1 Example 2 Mixture Material composition wt. % wt. % SiC 67 74 Clay (Al.sub.2O.sub.3) 25.5 19.5 SiO.sub.2 carrier 6.5 5.0 Remainder impurities Chemical analysis Method/Standard wt. % wt. % SiC ANSI B74.15-1992-(R2007) 65.5%   72% After calcination at 750° C. without weight recovery Al.sub.2O.sub.3 X-ray fluorescence analysis 24.5% 19.0% Total SiO.sub.2 content X-ray fluorescence analysis  8.9%  8.0% Na.sub.2O + K.sub.2O + Fe.sub.2O.sub.3 + TiO.sub.2 X-ray fluorescence analysis   <1%   <1% CaO + MgO X-ray fluorescence analysis   <1%   <1% Other oxides X-ray fluorescence analysis <0.5% <0.5% Total  100%  100% Silicate phase Chemical analysis 6 wt. % 5 wt. % Milling of sample to 100 μm 1 g powder attacked with hydrofluoric acid (40%) at temperature of −16° C. Filtration and determination of residue by gravimetry Phases measured by D8 Endeavor de BRUKER diffraction analysis HighScoresoftware using X-rays Rietveld refining wt. % wt. % SiC 65 71 Mullite 17 15 Corundum 15 10 Cristobalite 3 4 Method/Standard/Unit of Physical analysis measure Bulk density kg/dm.sup.3 (ISO5017) 2.55 2.58 Open porosity vol. % 21.0 20.5 Standard ISO 5017

[0065] The SiC content was measured using a Horiba EMIA-820, in accordance with Standard ANSI B74.15-1992-(R2007).

[0066] The other elements or oxides, such as the total SiO.sub.2, with the exception of SiC, were measured by X-ray fluorescence analysis.

[0067] The silica phase content was measured by chemical methods. In this context, silica phase means a phase in which silicon dioxide (SiO.sub.2) is not combined with aluminium oxide (Al.sub.2O.sub.3). This may in particular be a pure SiO.sub.2 phase, such as quartz, cristobalite; and/or an SiO.sub.2 glass phase; an SiO.sub.2 phase for example comprising sodium oxide and/or a crystalline phase such as sodium silicates, but in particular without aluminium oxide and in any case with the exception of mullite.

[0068] The sample was milled to a fineness smaller than approximately 100 μm. After an attack by hydrofluoric acid (40% by weight) at a temperature of −16° C., filtration, and measurement of the residue by gravimetry, this silica phase is determined.

[0069] The content of phases such as mullite and corundum was measured by diffraction analysis using X-rays and the Rietveld method.

[0070] In particular the materials available under the trade name Microsilica, in a suitable powdery form, are suitable as an SiO.sub.2 carrier.

[0071] In all the above examples, the SiO.sub.2 carrier is preferably added at an extremely small particle size, in other words at a particle size preferably <100 μm, in particular <50 μm, expediently <45 μm. The SiO.sub.2 carrier is preferably based on 90% SiO.sub.2; remainders of the carrier component are highly desirable as well as normal impurities such as oxides of iron, alkali and alkaline earths and the like.

[0072] In these examples, it has been found that a breaking strength of at least 15 MPa when cold, of approximately 25 MPa at a temperature of 1000° C. and of approximately 15 MPa at a temperature of 1400° C. occurs, this being an indicator of the excellent breaking strength of the saggers produced from the above-mentioned materials. This means that flaking is still prevented when a wide range of cathode material is used and the fracture susceptibility is also greatly reduced, in such a way that the saggers endure much longer operating times.

[0073] Overall, the nagger material or fitting material according to the invention overcomes the drawbacks of the prior art in that much greater strength is achieved and the temperature change resistance is also increased and the risk of fracture susceptibility is reduced. To date, the problem of conventional saggers is that they have to be replaced with new saggers frequently as a result of contamination during the burning process of the cathode material, and this causes a large amount of special waste which can be disposed of by way of expensive recycling processes.