A composite sealing method and sealing structure for ceramic-to-metal sealing

Abstract

The application discloses a composite sealing method and a sealing structure for ceramic and metal sealing, and the sealing method comprises the following steps: glass sealing the outer side and the inner side of sealing glass with the inner wall of a metal shell and the side surface of a ceramic electrolyte sheet respectively, or glass sealing the outer side of sealing glass with the inner wall of a metal shell; placing a lining ring in the metal shell and on the ceramic electrolyte sheet, and then, placing inorganic salt at the bottom between the lining ring and the metal shell for salt sealing. The sealing structure obtained by using specific sealing materials can realize good sealing of ceramic and metal materials, and has good corrosion resistance to lithium metal, molten salt and the like; and further, the sealing member using the sealing structure can be used in a molten lithium metal battery and other devices in a high-corrosion environment.

Description

Technical Field

[0001] This invention relates to the field of packaging technology for solid electrolyte batteries, and more specifically to a composite sealing method and sealing structure for ceramic and metal sealing. Background Technology

[0002] The sealing of ceramics and metals is a crucial step in the entire production process of lithium-ion batteries, sodium-ion batteries, solid electrolyte fuel cells, and lithium extraction devices based on solid electrolytes. The quality of the sealing performance is critical to the product's performance.

[0003] Traditional ceramic-metal sealing involves high-temperature fusion sealing with sealing glass. This requires the sealing glass to not only have a suitable coefficient of thermal expansion and sealing temperature, but also to withstand corrosion from lithium metal, sodium metal, and molten salts. This sealing glass is typically made of silicate glass.

[0004] In existing technologies, neither high-silicate glass nor low-silicate glass can withstand corrosion from lithium metal, sodium metal, and molten salts for extended periods, leading to seal failure.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a composite sealing method and sealing structure for sealing ceramics and metals. This sealing method can improve the sealing performance and corrosion resistance between the metal shell and the ceramic electrolyte sheet, thereby improving the quality of the prepared product.

[0007] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0008] The first aspect of this invention provides a composite sealing method for sealing ceramics and metals, the sealing method comprising the following steps:

[0009] (a) Seal the outer and inner sides of the sealing glass with the inner wall of the metal casing and the side of the ceramic electrolyte sheet, respectively, or seal the outer side of the sealing glass with the inner wall of the metal casing.

[0010] (b) Place the inner liner ring inside the metal casing and on the ceramic electrolyte sheet, and then place the inorganic salt at the bottom between the inner liner ring and the metal casing for salt sealing.

[0011] Preferably, the inorganic salt has a melting point lower than the softening point of the sealing glass.

[0012] Preferably, the sealing glass can be a silicate-based glass, for example, a low-silicate glass prepared in application number 202210173208.8.

[0013] Preferably, the metal casing material includes, but is not limited to, stainless steel, tungsten, and molybdenum; the stainless steel includes, but is not limited to, 304 stainless steel, 316 stainless steel, and 446 stainless steel.

[0014] Preferably, the ceramic electrolyte sheet is made of materials including but not limited to alumina ceramic, lithium lanthanum zirconium tantalum oxide ceramic, lithium titanium aluminum phosphate ceramic, and lithium lanthanum titanium oxide ceramic.

[0015] Preferably, the inorganic salt is selected from at least one of halides, carbonates, and sulfates.

[0016] Preferably, the carbonates include, but are not limited to, potassium carbonate and lithium carbonate; the halides include, but are not limited to, potassium chloride and lithium chloride.

[0017] More preferably, the inorganic salt is a mixture of potassium carbonate and lithium carbonate, wherein the molar ratio of potassium carbonate to lithium carbonate is (1-7):(1-3); the inorganic salt may also be a mixture of potassium chloride and lithium chloride, wherein the molar ratio of potassium chloride to lithium chloride is 2:(2-4).

[0018] Preferably, the inner liner ring is made of stainless steel or magnesium oxide.

[0019] Preferably, the sealing temperature of the glass sealing is 600-900℃ and the sealing time is 15-25 minutes.

[0020] Preferably, the salt sealing temperature is 350–550°C and the sealing time is 10–20 min.

[0021] Preferably, the inorganic salt is ball-milled before salt sealing;

[0022] Preferably, the ball milling process specifically includes placing the inorganic salt in a ball milling jar and ball milling at 150–300 r / min for 8–12 h.

[0023] A second aspect of the present invention provides a sealing structure for a metal casing and a ceramic electrolyte sheet in a molten lithium metal battery, wherein the sealing structure is obtained by the sealing method described above.

[0024] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0025] This invention provides a novel glass-inorganic salt composite sealing method for ceramic-metal bonding. The method involves first sealing the metal battery casing and ceramic electrolyte with a sealing glass, followed by a second salt sealing process using inorganic salt. Specifically, the sealing glass and inorganic salt can be arranged vertically or horizontally. The sealing glass does not contact lithium metal or molten salt. Since the melting point of the inorganic salt is lower than the softening point of the glass, during the second salt sealing process, the liquid inorganic salt penetrates into the interior of the sealing glass, filling pores and microcracks. Furthermore, the inorganic salt is resistant to corrosion from lithium metal and molten salt, thus protecting the glass from corrosion and improving the overall sealing performance of the device.

[0026] The sealing structure obtained by the present invention using a specific sealing material can achieve good sealing of ceramic and metal materials; at the same time, it has good resistance to corrosion by lithium metal, molten salt, etc.; therefore, the sealing parts using the sealing structure of the present invention can be used in molten lithium metal batteries and other devices in highly corrosive environments. Attached Figure Description

[0027] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0028] Figure 1 These are schematic diagrams of the sealing structures after sealing using the sealing methods in Embodiments 1 and 2 of the present invention.

[0029] Figure 2 This is a schematic diagram of the sealing structure after sealing using the sealing method of Embodiment 3 of the present invention;

[0030] Figure 3 This is a voltage-time curve of a lithium battery assembled from the sealing structure obtained by the sealing method in Embodiment 3 of the present invention.

[0031] Figure 4 This is a schematic diagram of the sealing structure after sealing using the sealing methods of Comparative Examples 1 and 2 of the present invention;

[0032] Figure 5 This is a voltage-time curve of a lithium battery assembled from the sealing structure obtained by the sealing method of Comparative Example 1 of the present invention.

[0033] Figure 6 This is a voltage-time curve of a lithium battery assembled from the sealing structure obtained by the sealing method of Comparative Example 2 of the present invention. Detailed Implementation

[0034] The embodiments of the technical solution of the present invention will be described in detail below with reference to the examples. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and are therefore only examples, and should not be used to limit the scope of protection of the present invention.

[0035] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by those skilled in the art to which this invention pertains.

[0036] The raw materials used in the following embodiments are as follows:

[0037] The sealing glass is a low-silicate glass prepared in Example 1 of application number 202210173208.8.

[0038] Example 1

[0039] This embodiment is a composite sealing method for sealing ceramics and metals, and the sealing method includes the following steps:

[0040] (a) The outer and inner sides of the sealing glass are respectively connected to the inner wall of the 304 stainless steel shell and the side of the LLZTO ceramic electrolyte sheet. The sealing temperature is 700℃ and the sealing time is 20min.

[0041] (b) Weigh K2CO3 and Li2CO3 into a ball mill jar at a molar ratio of 1:1 and ball mill at 200 r / min for 10 h to obtain a uniformly mixed inorganic salt powder.

[0042] (c) Place the magnesium oxide inner ring inside the 304 stainless steel shell and on the LLZTO ceramic electrolyte sheet. Then, place the inorganic salt at the bottom between the magnesium oxide inner ring and the 304 stainless steel shell for salt sealing. The salt sealing temperature is 530°C and the salt sealing time is 15 min.

[0043] The leakage rate of the device after glass sealing in step (a) was tested, and the result was 2.5 × 10⁻⁶. -9 Pa.m 3 / s;

[0044] The leakage rate of the device after salt sealing in step (c) was tested, and the result was 3.2 × 10⁻⁶. -10 Pa.m 3 / s;

[0045] The sealing structure obtained after sealing by the sealing method of the present invention is as follows: Figure 1 As shown in the attached diagram; the sealing glass and inorganic salt are arranged vertically. In the diagram, 1 is the 304 stainless steel outer shell; 2 is the inner liner ring; 3 is the LLZTO ceramic electrolyte sheet; 4 is the inorganic salt; and 5 is the sealing glass.

[0046] The salt-sealed device was placed in molten lithium metal and kept at 300°C for 400 hours. Observation revealed no obvious reaction at the seal, and airtightness testing showed a helium leakage rate of 2.7 × 10⁻⁶. -10 Pa.m 3 / s indicates that the sealing joint has good resistance to molten lithium corrosion;

[0047] After salt sealing, the apparatus was placed in a mixed molten salt of KCl and NaCl and kept at 300°C for 300 hours. Afterwards, no obvious reaction was observed at the sealing point, and the airtightness test showed a helium leakage rate of 1.7 × 10⁻⁶. -10 Pa.m 3 / s indicates that the sealing joint has good resistance to corrosion from a mixture of KCl and NaCl molten salts.

[0048] Example 2

[0049] This embodiment is a composite sealing method for sealing ceramics and metals, and the sealing method includes the following steps:

[0050] (a) The outer and inner sides of the sealing glass are respectively connected to the inner wall of the 304 stainless steel shell and the side of the LLZTO ceramic electrolyte sheet. The sealing temperature is 700℃ and the sealing time is 20min.

[0051] (b) Weigh potassium chloride and lithium chloride into a ball mill jar at a molar ratio of 2:3 and ball mill at 200 r / min for 10 h to obtain a uniformly mixed inorganic salt powder.

[0052] (c) Place the 304 stainless steel inner ring inside the 304 stainless steel outer shell and on the LLZTO ceramic electrolyte sheet. Then, place the inorganic salt at the bottom between the 304 stainless steel inner ring and the 304 stainless steel outer shell for salt sealing. The salt sealing temperature is 400°C and the salt sealing time is 15 min.

[0053] The leakage rate of the device after glass sealing in step (a) was tested, and the result was 2.3 × 10⁻⁶. -9 Pa.m 3 / s;

[0054] The leakage rate of the device after salt sealing in step (c) was tested, and the result was 7.3 × 10⁻⁶. -10 Pa.m 3 / s;

[0055] The sealing structure obtained after sealing by the sealing method of the present invention is as follows: Figure 1 As shown; the sealed glass and inorganic salt are arranged vertically.

[0056] The salt-sealed device was placed in molten lithium metal and kept at 300°C for 400 hours. Observation revealed no obvious reaction at the seal, and airtightness testing showed a helium leakage rate of 5.5 × 10⁻⁶. -10 Pa.m 3 / s indicates that the sealing joint has good resistance to molten lithium corrosion;

[0057] After salt sealing, the device was placed in a mixed molten salt of KBr and NaBr and kept at 300℃ for 300 hours. Afterwards, no obvious reaction was observed at the sealing point, and the airtightness test showed a helium leakage rate of 3.8 × 10⁻⁶. -10 Pa.m 3 / s indicates that the sealing joint has good resistance to corrosion from a mixture of KBr and NaBr molten salts.

[0058] Example 3

[0059] This embodiment is a composite sealing method for sealing ceramics and metals, and the sealing method includes the following steps:

[0060] (a) Seal the outer side of the sealing glass with the inner wall of the 304 stainless steel shell. The sealing temperature is 700°C and the sealing time is 20 minutes.

[0061] (b) Weigh K2CO3 and Li2CO3 into a ball mill jar at a molar ratio of 7:3 and ball mill at 200 r / min for 10 h to obtain a uniformly mixed inorganic salt powder.

[0062] (c) Place the 304 stainless steel inner ring inside the 304 stainless steel outer shell and on the LLZTO ceramic electrolyte sheet. Then, place the inorganic salt at the bottom between the 304 stainless steel inner ring and the 304 stainless steel outer shell for salt sealing. The salt sealing temperature is 550°C and the salt sealing time is 10 min.

[0063] The leakage rate of the device after glass sealing in step (a) was tested, and the result was 4.3 × 10⁻⁶. -9 Pa.m 3 / s;

[0064] The leakage rate of the device after salt sealing in step (c) was tested, and the result was 4.6 × 10⁻⁶. -10 Pa.m 3 / s;

[0065] The sealing structure obtained after sealing by the sealing method of the present invention is as follows: Figure 2 As shown in the attached diagram; the sealing glass and inorganic salt are arranged in a left-right configuration. In the diagram, 1 is the 304 stainless steel outer shell; 2 is the inner liner ring; 3 is the LLZTO ceramic electrolyte sheet; 4 is the inorganic salt; and 5 is the sealing glass.

[0066] The salt-sealed device was placed in molten lithium metal and kept at 300°C for 400 hours. Observation revealed no obvious reaction at the seal, and airtightness testing showed a helium leakage rate of 3.3 × 10⁻⁶. -10 Pa.m 3 / s indicates that the sealing joint has good resistance to molten lithium corrosion;

[0067] After salt sealing, the apparatus was placed in a mixed molten salt of KCl and NaCl and kept at 300°C for 300 hours. Afterwards, no obvious reaction was observed at the sealing point, and the airtightness test showed a helium leakage rate of 2.7 × 10⁻⁶. -10 Pa.m 3 / s indicates that the sealing joint has good resistance to corrosion from a mixture of KCl and NaCl molten salts.

[0068] A lithium battery was assembled using lithium metal as the negative electrode and a mixture of LiAlCl4, LiCl, and brass powder as the positive electrode, following the salt-sealing process described above. The battery operated at 300°C, and its voltage-time curve is shown below. Figure 3 As shown;

[0069] Depend on Figure 3 It can be seen that the battery has been running stably for nearly 500 hours.

[0070] Comparative Example 1

[0071] This comparative example illustrates a composite sealing method for sealing ceramics and metals, which includes the following steps:

[0072] The 304 stainless steel shell, LLZTO ceramic electrolyte sheet and magnesium oxide inner ring were glass-sealed using the same sealing glass as in Examples 1, 2 and 3. The glass sealing temperature was 700°C and the glass sealing time was 20 minutes.

[0073] The sealing structure obtained after sealing by the sealing method of the present invention is as follows: Figure 4 As shown in the attached diagram; 1 is the 304 stainless steel outer shell; 2 is the inner liner ring; 3 is the LLZTO ceramic electrolyte sheet; 5 is the sealing glass; the leakage rate of the device after glass sealing was tested, and the result was 6.1 × 10⁻⁶. -9 Pa.m 3 / s.

[0074] The sealed device was placed in molten lithium metal at 300°C for 400 hours; after the end of the process, the seal was found to have turned black, and the airtightness test showed a helium leakage rate of 3.8 × 10⁻⁶. -7 Pa.m 3 / s indicates that the sealing joint has poor resistance to molten lithium corrosion.

[0075] The sealed apparatus was placed in a mixed molten salt of KCl and NaCl at 300°C for 300 hours. Afterward, the seal was found to have turned gray, and airtightness testing showed a helium leakage rate of 2.2 × 10⁻⁶. -7 Pa.m 3 / s indicates that the sealing joint has poor resistance to corrosion from a mixture of KCl and NaCl molten salts.

[0076] The sealed device was placed in a mixed molten salt of KBr and NaBr, with lithium metal added on top to form a lithium-saturated molten salt. The mixture was then held at 300°C for 300 hours. Afterward, the seal was found to have turned black, and an airtightness test showed a helium leakage rate of 4.3 × 10⁻⁶. -6 Pa.m 3 / s indicates that the sealing joint has poor resistance to corrosion from a mixed molten salt of lithium-saturated KBr and NaBr.

[0077] A lithium battery was assembled using lithium metal as the negative electrode and a mixture of LiAlCl4, LiCl, and brass powder as the positive electrode, following the glass-sealed assembly described above. The battery operated at 300°C, and its charge-discharge curve is shown below. Figure 5 As shown;

[0078] Depend on Figure 5 It can be concluded that the battery experienced a short circuit after operating for 45 hours.

[0079] Comparative Example 2

[0080] This comparative example illustrates a composite sealing method for sealing ceramics and metals, which includes the following steps:

[0081] A high silicate sealing glass (the silicate glass prepared in Example 4 of application number CN03160282.7) was used to seal the 304 stainless steel shell, LLZTO ceramic electrolyte sheet and magnesium oxide inner ring. The sealing temperature was 650℃ and the sealing time was 20min.

[0082] The sealing structure obtained after sealing by the sealing method of the present invention is as follows: Figure 4 As shown; the leakage rate of the device after glass sealing was tested, and the result was 5.9 × 10⁻⁶. -9 Pa.m 3 / s.

[0083] After the glass sealing was completed, the device was placed in molten lithium metal at 300°C for 400 hours. After the end of the process, it was found that the sealing area turned black and leaked during the air tightness test, indicating that the sealing area had very poor resistance to molten lithium corrosion.

[0084] The sealed apparatus was placed in a mixed molten salt of KCl and NaCl and kept at 300℃ for 300 hours. Afterward, the seal was found to have turned black, and an airtightness test showed a helium leakage rate of 8.5 × 10⁻⁶.-6 Pa.m 3 / s indicates that the sealing joint has poor resistance to corrosion from a mixture of KCl and NaCl molten salts.

[0085] After the glass sealing was completed, the device was placed in a mixed molten salt of KBr and NaBr. Lithium metal was added to the top layer of the molten salt to form a lithium-saturated molten salt. The device was kept at 300°C for 300 hours. After the end of the process, it was found that the sealing area turned black and leaked during the air tightness test, indicating that the sealing area had very poor resistance to corrosion by the mixed molten salt of lithium-saturated KBr and NaBr.

[0086] A lithium battery was assembled using lithium metal as the negative electrode and a mixture of LiAlCl4, LiCl, and brass powder as the positive electrode, employing the aforementioned glass-sealed assembly. The battery operated at 300°C, and its charge-discharge curve is shown below. Figure 6 As shown;

[0087] Depend on Figure 6 It can be concluded that the battery experienced a short circuit after operating for 14.5 hours.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A composite sealing method for sealing ceramics and metals, characterized by, The method comprises the following steps: (a) glass-sealing the outer side and the inner side of the sealing glass with the inner wall of the metal shell and the side of the ceramic electrolyte sheet respectively, or glass-sealing the outer side of the sealing glass with the inner wall of the metal shell; (b) placing the inner lining ring in the metal shell and on the ceramic electrolyte sheet, and then filling the inorganic salt between the bottom of the inner lining ring and the metal shell for salt sealing, wherein the liquid inorganic salt penetrates into the interior of the sealing glass during the salt sealing; the inorganic salt is selected from at least one of halide and carbonate, wherein the carbonate is potassium carbonate and lithium carbonate, and the halide is potassium chloride and lithium chloride; the sealing temperature of the glass sealing is 600-900 ℃, and the time is 15-25 min; the sealing temperature of the salt sealing is 350-550 ℃, and the time is 10-20 min.

2. The method of claim 1, wherein the melting point of the inorganic salt is lower than the softening point of the sealing glass.

3. The method of sealing according to claim 1, wherein, the material of the metal shell comprises at least one of stainless steel, tungsten and molybdenum, wherein the stainless steel comprises 304 stainless steel, 316 stainless steel or 446 stainless steel.

4. The method of claim 1 wherein, the material of the ceramic electrolyte sheet comprises at least one of lithium lanthanum zirconium tantalum oxygen ceramic, lithium titanium aluminum phosphate ceramic and lithium lanthanum titanium oxygen ceramic.

5. The method of sealing according to claim 1, wherein the material of the inner lining ring comprises stainless steel or magnesium oxide.

6. The method of sealing according to claim 1, wherein, the inorganic salt is subjected to ball milling before the salt sealing.

7. A seal structure of a metal case and a ceramic electrolyte sheet in a molten lithium metal battery, characterized by, the sealing structure is obtained by the sealing method according to any one of claims 1-6.

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