Sagger

Abstract

Provided is a technique for efficiently heat-treating a powder of a lithium positive electrode material. The sagger is provided with a box-shaped ceramic part and a box-shaped metal part. The ceramic part is provided with an outer bottom surface part and an outer side wall part protruding upwards from the outer bottom surface part. The metal part is provided with an inner bottom surface part and an inner side wall part protruding upwards from the inner bottom surface part, and is detachably arranged in the ceramic part. In a normal temperature state, when the metal part is disposed inside the ceramic part, a clearance is formed between the outer side wall part and the inner side wall part. The outer side wall part is provided with at least a pair of recessed parts which are recessed from the upper end to the lower end. In a plan view of the metal portion, the pair of recesses are provided at positions facing each other with the center of the metal portion therebetween. The metal portion includes at least a pair of flange portions extending outward from an upper end of the inner wall portion. When the metal portion is disposed inside the ceramic portion, the pair of flange portions is located inside the pair of recesses.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a sagger used when heat-treating powder of a lithium positive electrode material. Background Art

[0002] Sometimes a heat treatment furnace (such as a roller hearth furnace, etc.) is used to heat treat the powder as the raw material of the lithium positive electrode material. When the powder of the lithium positive electrode material (hereinafter also referred to as the powder) is heat treated in the heat treatment furnace, the powder is stored in a sagger, and the sagger containing the powder is transported in the heat treatment furnace. The temperature for heat treatment of the powder of the lithium positive electrode material is high temperature, so the powder is usually stored in a sagger formed of ceramics with high heat resistance. However, in recent years, a technology for heat treatment of powder using a metal sagger is being developed. The thermal conductivity of the metal sagger is high, so when heat treatment is performed using a heat treatment furnace, the powder stored in the sagger can be efficiently heated and heat treated. For example, Patent Document 1 discloses an example of a metal sagger.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2015-137814 Summary of the invention

[0006] In order to improve the productivity when heat treating the powder, a plurality of saggers are sometimes overlapped in the vertical direction when heat treating the powder in a heat treatment furnace. However, the durability of metal saggers against vertical loads is low, so it is difficult to overlap a plurality of saggers in the vertical direction.

[0007] This specification discloses a technology for efficiently performing heat treatment on powder of lithium positive electrode material.

[0008] In the first scheme of the technology disclosed in this specification, the sagger is a sagger for heat-treating the powder in a state where the powder of the lithium positive electrode material is stored. The sagger has a box-shaped ceramic part and a box-shaped metal part. The ceramic part has an outer bottom face and an outer side wall protruding upward from the outer bottom face, which is open at the top and formed by ceramic. The metal part has an inner bottom face and an inner side wall protruding upward from the inner bottom face, which is open at the top and is arranged inside the ceramic part in a manner that can be loaded and unloaded. Under normal temperature conditions, when the metal part is arranged inside the ceramic part, a clearance is formed between the outer side wall and the inner side wall. The outer side wall at least has a pair of recessed parts that are recessed from the upper end to the lower end. When the metal part is viewed from above, a pair of recesses are arranged at positions opposite to each other with the center of the metal part sandwiched therebetween. The metal part at least has a pair of flange parts extending outward from the upper end of the inner side wall. When the metal part is arranged inside the ceramic part, a pair of flange parts are located in a pair of recesses.

[0009] In the above-mentioned sagger, a metal part is arranged inside the ceramic part, so when the powder is stored in the sagger, the powder contacts the metal part. Therefore, the powder can be heated efficiently. In addition, since the ceramic part is arranged outside the metal part, the ceramic part bears the vertical load, so that the durability against the vertical load is improved. Therefore, multiple saggers can be overlapped in the up and down direction. Through these features, productivity can be improved. In addition, the metal part is arranged inside the ceramic part in a manner that can be loaded and unloaded, and the flange part of the metal part is located in the recess of the ceramic part. When the powder after heat treatment is recovered from the sagger, for example, the sagger can be turned over to make the stored powder fall and be recovered. For example, if the metal part is bonded to the ceramic part, the metal part can be prevented from falling when the sagger is turned over, but when the sagger is discarded, it is difficult to remove the reusable metal part from the sagger. The flange part of the metal part is located in the recess of the ceramic part. If the sagger is gripped and turned over at the part where the flange part is located, the metal part can be prevented from falling. Therefore, by locating the flange portion of the metal part in the recess of the ceramic part, the sagger can be easily turned over in a manner that the metal part does not fall, even if the metal part is not bonded to the ceramic part. Therefore, the recovery of the powder can be made easy, and the metal part can be easily removed from the ceramic part when it is reused. In addition, the thermal expansion coefficient of metal is higher than that of ceramic, and therefore, when the sagger is placed under heat treatment conditions (for example, when arranged in a heat treatment furnace), the metal is prone to significantly expand compared to ceramic. By forming a clearance between the side of the ceramic part and the side of the metal part, even if the metal part located inside the ceramic part expands, the ceramic part can be prevented from being damaged by the metal part. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a top view of the sagger of the embodiment.

[0011] Figure 2It is a side view of the sagger of the embodiment.

[0012] Figure 3 yes Figure 1 Cross-sectional view at line III-III.

[0013] Figure 4 It is a figure for demonstrating the dimension of each part of the sagger of Example.

[0014] Figure 5 This is a diagram showing the influence on the sagger and the powder when the powder is heat-treated using the saggers of Examples 1 and 2 and Comparative Examples 1 to 5.

[0015] Explanation of symbols

[0016] 10: sagger, 20: ceramic part, 22: outer bottom surface part, 24: outer side wall part, 26: recessed part, 30: metal part, 32: inner bottom surface part, 34: inner side wall part, 36: flange part, 40: clearance. DETAILED DESCRIPTION

[0017] The main features of the embodiments described below are listed in advance. It should be noted that the technical elements described below are independent technical elements, which can exert technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of application.

[0018] The second solution of the technology disclosed in this specification is based on the above-mentioned first solution, and the metal part can be formed of a metal containing aluminum on at least the surface. According to this structure, a metal containing aluminum is arranged on the surface of the metal part. Accordingly, when the sagger is placed under heat treatment conditions (for example, when arranged in a heat treatment furnace), an aluminum oxide film is formed on the surface of the metal part. Thus, it is possible to suppress the oxidation of the metal part due to the powder in the sagger during the heat treatment.

[0019] The third solution of the technology disclosed in this specification is based on the above-mentioned first solution, and the metal part can be formed of a nickel-based alloy containing aluminum. According to this structure, when the sagger is placed under heat treatment conditions (for example, when it is arranged in a heat treatment furnace), an aluminum oxide film is formed on the surface of the metal part, which can inhibit the metal part from being oxidized by the powder in the sagger during the heat treatment.

[0020] The fourth scheme of the technology disclosed in this specification is based on any one of the first to third schemes mentioned above, and the ceramic part and the metal part can have a rectangular shape when viewed from above. The outer wall part can include: a pair of first outer wall parts, and a pair of second outer wall parts orthogonal to the pair of first outer wall parts. The inner wall part can include: a pair of first inner wall parts, and a pair of second inner wall parts orthogonal to the pair of first inner wall parts. When the metal part is arranged inside the ceramic part, it can be: a pair of first outer wall parts and a pair of first inner wall parts are parallel, and a pair of second outer wall parts and a pair of second inner wall parts are parallel. When the thermal expansion coefficient of the ceramic part is set to a, the thermal expansion coefficient of the metal part is set to b, the maximum temperature when the powder in the sagger is heat-treated is set to T, the inner dimension of the first outer wall part is set to L1o, the outer dimension of the first inner wall part is set to L1i, the inner dimension of the second outer wall part is set to L2o, and the outer dimension of the second inner wall part is set to L2i, the clearance formed between the first outer wall part and the first inner wall part can be greater than (L1i×b×T)-(L1o×a×T), and the clearance formed between the second outer wall part and the second inner wall part can be greater than (L2i×b×T)-(L2o×a×T). According to this structure, when the sagger is placed under heat treatment conditions (for example, when it is arranged in a heat treatment furnace), even if the metal part expands, the metal part falls into the clearance. Therefore, it is possible to well avoid the ceramic part from being damaged by the metal part.

[0021] The fifth solution of the technology disclosed in this specification is based on any one of the first to fourth solutions described above, and when the metal part is arranged inside the ceramic part, the inner bottom surface part can contact the outer bottom surface part. According to this structure, the metal part can be prevented from being deformed by the load of the powder contained in the metal part.

[0022] The sixth scheme of the technology disclosed in this specification is based on any one of the first to fifth schemes above, and when the metal part is arranged inside the ceramic part, the upper surface of the flange part can be located below the upper end of the outer wall part. According to this structure, it is possible to prevent the recess from being blocked by the inner wall part. Therefore, the gas generated by the powder stored in the sagger during heat treatment can be discharged from the recess.

[0023] Example

[0024] The sagger 10 is described with reference to the accompanying drawings. The sagger 10 stores the processed object which is a powder. In the present embodiment, the processed object stored in the sagger 10 is a powder of a lithium positive electrode material (hereinafter also referred to as "powder"). A heat treatment furnace (such as a roller hearth furnace, etc.) for heat treating the powder is configured as follows: the sagger 10 is transported from an input port to an output port. The sagger 10 is transported in the heat treatment furnace in a state where the powder is stored.

[0025] like Figure 1 to Figure 3As shown, the sagger 10 is box-shaped and has a rectangular shape when viewed from above. In the present embodiment, the sagger 10 has a substantially square shape when viewed from above. The sagger 10 includes a ceramic portion 20 and a metal portion 30. The metal portion 30 is disposed inside the ceramic portion 20 in a detachable manner.

[0026] The ceramic part 20 is box-shaped and is formed of ceramic. The ceramic part 20 has a substantially square shape when the sagger 10 is viewed from above. The ceramic part 20 includes an outer bottom surface part 22 and an outer side wall part 24 .

[0027] The outer bottom portion 22 has a substantially square flat plate shape. The outer wall portion 24 is arranged along the outer periphery of the outer bottom portion 22 and protrudes upward from the outer bottom portion 22. The outer wall portion 24 has four flat plate-shaped side surfaces (hereinafter also referred to as the first outer wall portion 24a to the fourth outer wall portion 24d). The first outer wall portion 24a to the fourth outer wall portion 24d are respectively arranged on each side of the outer periphery of the outer bottom portion 22. The first outer wall portion 24a and the third outer wall portion 24c are arranged opposite to each other, and the second outer wall portion 24b and the fourth outer wall portion 24d are arranged opposite to each other. The dimensions of the first outer wall portion 24a to the fourth outer wall portion 24d in the height direction are substantially the same.

[0028] Recesses 26a to 26d are provided on the first outer wall portion 24a to the fourth outer wall portion 24d, respectively. The recess 26a is provided on the first outer wall portion 24a. The recess 26a is recessed downward from the upper end of the first outer wall portion 24a. The recess 26a is formed near the center of the first outer wall portion 24a. The recesses 26b to 26d are provided on the second outer wall portion 24b to the fourth outer wall portion 24d, respectively, and have the same shape as the recess 26a. Hereinafter, when it is not necessary to distinguish the recesses 26a to 26d, the subscript letters are sometimes omitted and referred to as the recess 26. By providing the recess 26 on the outer wall portion 24, when a plurality of saggers 10 are overlapped in the vertical direction and heat-treated, the gas generated by the powder contained in the sagger 10 during the heat treatment can be discharged from the recess 26 to the outside of the sagger 10. In addition, the flange portion 36 described later is arranged on the recess 26.

[0029] The metal part 30 is box-shaped and is formed of metal. In the present embodiment, the metal part 30 is formed of stainless steel and is coated with aluminum (aluminum plating) on ​​the surface. The thickness of the metal part 30 is roughly the same, and in the present embodiment, it is about 2 mm. The metal part 30 has a roughly square shape when the sagger 10 is viewed from above. The metal part 30 includes: an inner bottom surface part 32, an inner side wall part 34, and flange parts 36a to 36d.

[0030] The inner bottom surface 32 has a substantially square flat plate shape and is smaller than the outer bottom surface 22. When the metal part 30 is arranged in the ceramic part 20, the inner bottom surface 32 is placed on the outer bottom surface 22, and the lower surface of the inner bottom surface 32 abuts against the upper surface of the outer bottom surface 22.

[0031] The inner wall portion 34 is arranged along the outer periphery of the inner bottom surface portion 32 and protrudes upward from the inner bottom surface portion 32. The inner wall portion 34 has four flat side surfaces (hereinafter also referred to as the first inner wall portion 34a to the fourth inner wall portion 34d). The first inner wall portion 34a to the fourth inner wall portion 34d are respectively arranged on each side of the outer periphery of the inner bottom surface portion 32. The first inner wall portion 34a and the third inner wall portion 34c are arranged opposite to each other, and the second inner wall portion 34b and the fourth inner wall portion 34d are arranged opposite to each other. The dimensions of the first inner wall portion 34a to the fourth inner wall portion 34d in the height direction are substantially the same. In addition, the dimensions of the first inner wall portion 34a to the fourth inner wall portion 34d in the height direction are smaller than the dimensions of the first outer wall portion 24a to the fourth outer wall portion 24d in the height direction. Specifically, when the metal portion 30 is disposed in the ceramic portion 20, the upper ends of the first inner wall portion 34a to the fourth inner wall portion 34d are located between the lower end of the recess 26 and the upper ends of the first outer wall portion 24a to the fourth outer wall portion 24d, preferably located near the lower end of the recess 26. By locating the upper ends of the first inner wall portion 34a to the fourth inner wall portion 34d near the lower end of the recess 26, it is possible to prevent the recess 26 from being blocked by the first inner wall portion 34a to the fourth inner wall portion 34d.

[0032] The flanges 36a to 36d are connected to the first inner wall portion 34a to the fourth inner wall portion 34d, respectively. The flange 36a is flat and is arranged to be orthogonal to the first inner wall portion 34a. The flange 36a extends from the upper end of the first inner wall portion 34a toward the outside of the sagger 10. The flange 36a is arranged near the center of the first inner wall portion 34a. The dimension of the flange 36a extending along the first inner wall portion 34a is smaller than the dimension of the recess 26a. When the metal part 30 is arranged in the ceramic part 20, the flange 36a is located in the recess 26a. The flanges 36b to 36d are connected to the second inner wall portion 34b to the fourth inner wall portion 34d, respectively, and have the same structure as the flange 36a. Hereinafter, when it is not necessary to distinguish the flanges 36a to 36d, the subscript letters are sometimes omitted and referred to as the flange 36.

[0033] In the sagger 10 of the present embodiment, the metal part 30 is placed in the ceramic part 20. That is, the metal part 30 is not bonded to the ceramic part 20. Therefore, as long as the metal part 30 is lifted, the metal part 30 can be removed from the ceramic part 20. For example, when the sagger 10 cannot be used due to damage, the metal part 30 can be easily removed from the ceramic part 20. The ceramic part 20 is discarded when it cannot be used in most cases, but the metal part 30 can be recycled even if it cannot be used. The metal part 30 can be easily separated from the ceramic part 20, and the metal part 30 can be easily recycled when the sagger 10 cannot be used.

[0034] In addition, in the sagger 10 of the present embodiment, the flange portion 36 of the metal part 30 is arranged in the recess 26 of the ceramic part 20. After the powder in the sagger 10 is heat-treated, the sagger 10 is turned over in most cases to recover the powder from the sagger 10. For example, if the metal part is bonded to the ceramic part, the metal part will not fall even if the sagger is turned over. On the other hand, in the sagger 10 of the present embodiment, since the metal part 30 is not bonded to the ceramic part 20, when only the ceramic part 20 is gripped and turned over, the metal part 30 will fall. However, in the sagger 10 of the present embodiment, the flange portion 36 of the metal part 30 is arranged in the recess 26 of the ceramic part 20. Therefore, if the sagger 10 is gripped at the portion where the flange portion 36 is located, the sagger 10 can be turned over in a state where both the ceramic part 20 and the metal part 30 are gripped. Therefore, the metal part 30 can be prevented from falling when the powder in the sagger 10 is recovered without being bonded to the ceramic part 20. It should be noted that when the flange part 36 protrudes to a position closer to the outside than the ceramic part 20, the sagger 10 can be turned over by only holding the flange part 36. In this case, the ceramic part 20 is supported by the flange part 36, and the ceramic part 20 and the metal part 30 can be handled as a whole.

[0035] It should be noted that, in this embodiment, the flange portion 36 is provided on each inner wall portion of the first inner wall portion 34a to the fourth inner wall portion 34d, but the present invention is not limited to this configuration. For example, the flange portion 36 may be provided on two inner wall portions 34 that are opposite to each other among the four inner wall portions 34a to 34d, or may not be provided on the other two inner wall portions 34. That is, if the flange portion 36 is provided on the first inner wall portion 34a and the third inner wall portion 34c, the flange portion 36 may not be provided on the second inner wall portion 34b and the fourth inner wall portion 34d, and if the flange portion 36 is provided on the second inner wall portion 34b and the fourth inner wall portion 34d, the flange portion 36 may not be provided on the first inner wall portion 34a and the third inner wall portion 34c. If the flange 36 is provided at least on the two opposing inner wall portions 34, the two flange portions 36 provided on the two opposing inner wall portions 34 can be gripped together with the ceramic portion 20 when the powder in the sagger 10 is recovered. Therefore, if the flange 36 is provided at least on the two opposing inner wall portions 34, the metal portion 30 can be prevented from falling when the powder in the sagger 10 is recovered.

[0036] In addition, the inner bottom face portion 32 and the outer bottom face portion 22 are both roughly square, and the inner bottom face portion 32 is smaller than the outer bottom face portion 22. Therefore, the metal portion 30 can be arranged in the ceramic portion 20. In addition, when the metal portion 30 is arranged in the ceramic portion 20, the first inner side wall portion 34a to the fourth inner side wall portion 34d are arranged in parallel with the first outer side wall portion 24a to the fourth outer side wall portion 24d opposed. It should be noted that the sagger 10 can be roughly rectangular in shape when viewed from above. When the metal portion 30 is arranged in the ceramic portion 20, a clearance 40 is provided between the outer side wall portion 24 and the inner side wall portion 34.

[0037] Here, the size of the clearance 40 is described. Figure 3As shown, two clearances 40a and 40b (hereinafter also referred to as a pair of clearances 40a and 40b) are provided between the pair of opposing outer wall portions 24 and the pair of inner wall portions 34. For example, the clearance 40a is provided between the first inner wall portion 34a and the first outer wall portion 24a, and the clearance 40b is provided between the third inner wall portion 34c and the third outer wall portion 24c. The total of the size d1 of the clearance 40a and the size d2 of the clearance 40b is set to satisfy (d1+d2)>(L1i×b×T)-(L1o×a×T). It should be noted that L1i represents the outer dimension of the inner wall portion 34 (i.e., the length from the outer surface of the first inner wall portion 34a to the outer surface of the third inner wall portion 34c), L1o represents the inner dimension of the outer wall portion 24 (i.e., the length from the inner surface of the first outer wall portion 24a to the inner surface of the third outer wall portion 24c), a represents the thermal expansion coefficient of the ceramic forming the ceramic portion 20, b represents the thermal expansion coefficient of the metal forming the metal portion 30, and T represents the maximum temperature when the powder stored in the sagger 10 is heat treated.

[0038] In addition, a clearance 40 (not shown) is also provided between another pair of opposing outer wall portions 24 and a pair of inner wall portions 34. For example, a clearance 40 is also provided between the second inner wall portion 34b and the second outer wall portion 24b, and a clearance 40 is also provided between the fourth inner wall portion 34d and the fourth outer wall portion 24d. The total size of these clearances 40 is also set to be larger than (L2i×b×T)-(L2o×a×T). It should be noted that L2i represents the outer dimension of the inner wall portion 34 (i.e., the length from the outer surface of the second inner wall portion 34b to the outer surface of the fourth inner wall portion 34d), and L2o represents the inner dimension of the outer wall portion 24 (i.e., the length from the inner surface of the second outer wall portion 24b to the inner surface of the fourth outer wall portion 24d).

[0039] For example, the sagger 10 of the present embodiment can be formed as follows. In the ceramic portion 20, the side length of the outer bottom portion 22 is about 330 mm. The thickness of the outer bottom portion 22 and the outer wall portion 24 are both about 11 mm. Therefore, the inner dimension (L1o, L2o) of the outer wall portion 24 is about 308 mm. In the metal portion 30, the side length of the inner bottom portion 32 is about 302 mm. That is, the outer dimension (L1i, L2i) of the inner wall portion 34 is about 302 mm. The total of a pair of gaps 40 (for example, the total of the gap 40a between the first inner wall portion 34a and the first outer wall portion 24a and the gap 40b between the third inner wall portion 34c and the third outer wall portion 24c) is about 6 mm. In addition, the thermal expansion coefficient of the ceramic forming the ceramic portion 20 is about 2.5×10 -6 The thermal expansion coefficient of the metal forming the metal portion 30 is 15 to 18×10 -6The maximum temperature of the powder stored in the sagger 10 during heat treatment is about 950°C. Therefore, (L1i×b×T)-(L1o×a×T)={302mm×(15~18×10 -6 )×950}-(308mm×2.5×10 -6 ×950)=3.572-4.4327 mm. That is, the total of the pair of clearances 40 is preferably about 4 mm or more (each clearance 40 is about 2 mm or more). In this embodiment, the total of the pair of clearances 40 is 6 mm, which satisfies the above conditional expression.

[0040] In the sagger 10 of the present embodiment, the metal part 30 is arranged in the ceramic part 20. Therefore, when the powder is stored in the sagger 10, the powder is in contact with the metal part 30. The thermal conductivity of the metal part 30 is higher than that of the ceramic part 20. If the powder is stored in the sagger 10, since the powder is in contact with the metal part 30, the powder can be efficiently heated during heat treatment. In addition, in the present embodiment, the metal part 30 is formed of stainless steel and is plated with aluminum. By aluminizing, when the sagger 10 is placed under heat treatment conditions containing oxygen (for example, when it is arranged in a heat treatment furnace), an aluminum oxide film is formed on the surface of the metal part 30. Thereby, the oxidation of the metal part 30 due to the powder in the sagger 10 during heat treatment can be suppressed. It should be noted that the metal part 30 can be formed of a nickel-based alloy containing aluminum.

[0041] In addition, in the sagger 10 of the present embodiment, the ceramic part 20 is located outside the sagger 10. The durability of the metal part 30 against vertical loads is low, while on the other hand, the durability of the ceramic part 20 against vertical loads is high. By locating the ceramic part 20 outside the sagger 10, a plurality of saggers 10 can be overlapped in the vertical direction. Therefore, productivity can be improved during heat treatment.

[0042] In addition, in the sagger 10 of the present embodiment, a clearance 40 is provided between the outer wall portion 24 and the inner wall portion 34. The thermal expansion coefficient of metal is higher than that of ceramic. Therefore, when the powder is stored in the sagger 10 for heat treatment, the metal portion 30 expands significantly compared with the ceramic portion 20. Since the metal portion 30 is arranged inside the ceramic portion 20, in the absence of the clearance 40 between the outer wall portion 24 and the inner wall portion 34, the ceramic portion 20 may be damaged due to the expansion of the metal portion 30. In the present embodiment, by providing the clearance 40 between the outer wall portion 24 and the inner wall portion 34, even if the metal portion 30 expands significantly compared with the ceramic portion 20 during heat treatment, excessive thermal stress on the ceramic portion 20 caused by the metal portion 30 can be suppressed. Therefore, it is possible to avoid the ceramic portion 20 from being damaged due to the expansion of the metal portion 30.

[0043] In this embodiment, the sagger 10 has the above-mentioned structure, and it can be confirmed that the powder in the sagger 10 can be well heat-treated. Figure 4 and Figure 5 As shown, an experiment was conducted to investigate the effects on the sagger 10 and the powder when the powder was stored in the sagger 10 and subjected to heat treatment. In the experiment, the outer diameter of the sagger 10 when viewed from above (the outer diameter of the ceramic portion 20) was approximately 330 mm × approximately 330 mm. 7 kg of positive electrode material (powder) for lithium-ion batteries was stored inside the sagger 10. Then, a plurality of saggers 10 were heat treated in a roller hearth furnace with a furnace length of 42 m in a 4-row, 2-layer arrangement. The conditions for the heat treatment were as follows: an atmosphere temperature of 950°C and an oxygen atmosphere of 96%. In addition, the sagger 10 was reused multiple times (3 to 10 times) for heat treatment.

[0044] In the sagger 10 of Example 1, the metal part 30 is formed of stainless steel and plated with aluminum. The thickness (dimension A) of the metal part 30 is about 2 mm. It should be noted that, regarding the dimension A, it has been confirmed that there is no effect even if it is set to about 3 mm. Therefore, the thickness of the metal part 30 is preferably about 2 to 3 mm, and from the viewpoint of economic efficiency, it can be said that it is more preferably about 2 mm. In addition, in the sagger 10 of Example 1, the size of one of the pair of clearances 40a, 40b (the distance between the outer wall portion 24 and the inner wall portion 34, dimension B) is about 3 mm. The size (dimension C) between the outer surface of the inner bottom surface portion 32 of the metal part 30 and the inner surface of the outer bottom surface portion 22 of the ceramic part 20 is about 0 mm. That is, the inner bottom surface portion 32 of the metal part 30 is in contact with the outer bottom surface portion 22 of the ceramic part 20. The length (dimension D) from the lower end of the recess 26 to the inner wall portion 34 (flange portion 36) is 3 mm.

[0045] like Figure 5 As shown, even if the sagger 10 of Example 1 is used for 10 heat treatments, the quality of the powder after the heat treatment is high, and the powder can be recovered in a manner that the powder does not adhere to the surface of the metal part 30. In addition, corrosion of the metal part 30 and deformation of each part (ceramic part 20, metal part 30) are not observed. That is, the sagger 10 of Example 1 can heat treat the powder well, and it is confirmed that it has high durability for multiple reuse.

[0046] In addition, Example 2 is different from Example 1 in that the metal part 30 is a nickel-based alloy containing aluminum. Example 2 can also obtain the same results as Example 1, and the powder can be well heat-treated and it can be confirmed that it has high durability for multiple reuse.

[0047] On the other hand, Comparative Examples 1 to 3 show comparative examples of metal parts formed of stainless steel and plated with aluminum. The difference between the sagger of Comparative Example 1 and the sagger 10 of Example 1 is that the dimension C is 3 mm. That is, in the sagger of Comparative Example 1, there is a clearance of about 3 mm between the inner bottom surface portion 32 of the metal part 30 and the outer bottom surface portion 22 of the ceramic part 20. In other words, the sagger of Comparative Example 1 is supported on the ceramic part by the flange portion. With regard to the sagger of Comparative Example 1, after 10 heat treatments, the metal part 30 is deformed due to the load of the powder contained in the metal part 30. Therefore, it can be said that the dimension C is preferably 0 mm, and the inner bottom surface portion 32 of the metal part 30 is preferably in contact with the outer bottom surface portion 22 of the ceramic part 20.

[0048] The difference between the sagger of Comparative Example 2 and the sagger 10 of Example 1 is that the dimension B is 1 mm. That is, in the sagger of Comparative Example 2, the distance between the outer wall portion 24 and the inner wall portion 34 is narrower than that of the sagger 10 of Example 1. With respect to the sagger of Comparative Example 2, after only one heat treatment, the ceramic portion is pressed against the metal portion due to the expansion of the metal portion, and cracks are generated in the ceramic portion. Therefore, it can be said that the dimension B is larger than 1 mm, and as mentioned above, it is preferably larger than 2 mm.

[0049] The difference between the sagger of comparative example 3 and the sagger 10 of embodiment 1 is that the dimension D is 10 mm. That is, in the sagger of comparative example 3, the area where the recess 26 is blocked by the inner wall portion is large. In the sagger of comparative example 3, the results of 10 heat treatments were discussed, and as a result, there were problems with the quality of the powder after the heat treatment. It is presumed that this is because the recess is blocked by the inner wall portion, thereby causing ventilation obstruction in the sagger. Therefore, it can be said that the dimension D is less than 10 mm, preferably about 3 mm.

[0050] In addition, Comparative Examples 4 and 5 show comparative examples of metal parts formed of a nickel-based alloy containing aluminum. The difference between Comparative Example 4 and the sagger 10 of Example 2 is that the dimension B is 1 mm. In addition, the difference between Comparative Example 5 and the sagger 10 of Example 2 is that the dimension C is 3 mm. Regarding Comparative Examples 4 and 5, good results were not obtained in terms of the quality of the powder after heat treatment, the adhesion of the powder to the surface of the metal part, the deformation of the metal part, etc. It was confirmed from the above that by using the sagger 10 of this embodiment, the powder in the sagger 10 can be well heat-treated.

[0051] The specific examples of the technology disclosed in this specification are described in detail above, however, these specific examples are only examples and do not limit the claims. The technology described in the claims includes various modifications and changes to the specific examples illustrated above. In addition, the technical elements described in this specification or the drawings exert technical usefulness alone or in various combinations, and are not limited to the combination described in the claims at the time of application. In addition, the technology illustrated in this specification or the drawings achieves multiple purposes at the same time, and the technology that achieves one of the purposes itself has technical usefulness.

Claims

1. A sagger, which is used to place a powder of a lithium positive electrode material in a heat treatment furnace to heat treat the powder, comprising: a box-shaped ceramic portion, the ceramic portion including an outer bottom surface portion and an outer side wall portion protruding upward from the outer bottom surface portion, the upper side of the ceramic portion being open, and the ceramic portion being formed of ceramic; and A box-shaped metal part, which includes an inner bottom surface and an inner wall portion protruding upward from the inner bottom surface, is open at the top and is disposed inside the ceramic part in a detachable manner. When the metal portion is disposed inside the ceramic portion at room temperature, a clearance is formed between the outer wall portion and the inner wall portion. The outer wall portion has at least a pair of recessed portions that are recessed from the upper end to the lower end. The pair of recesses are provided at positions facing each other with the center of the metal portion sandwiched therebetween when the metal portion is viewed from above. The metal portion includes at least a pair of flange portions extending outward from the upper end of the inner wall portion. When the metal portion is disposed inside the ceramic portion, the pair of flange portions are located inside the pair of recessed portions.

2. The sagger according to claim 1, characterized in that: At least a surface of the metal portion is formed of a metal containing aluminum.

3. The sagger according to claim 1, characterized in that: The metal portion is formed of a nickel-based alloy containing aluminum.

4. The sagger according to claim 1, characterized in that: The ceramic portion and the metal portion have a rectangular shape when viewed from above, The outer wall portion includes: a pair of first outer wall portions and a pair of second outer wall portions orthogonal to the pair of first outer wall portions. The inner wall portion includes: a pair of first inner wall portions and a pair of second inner wall portions orthogonal to the pair of first inner wall portions. When the metal portion is disposed inside the ceramic portion, the pair of first outer wall portions are parallel to the pair of first inner wall portions, and the pair of second outer wall portions are parallel to the pair of second inner wall portions. When the thermal expansion coefficient of the ceramic part is set to a, the thermal expansion coefficient of the metal part is set to b, the maximum temperature when the powder in the sagger is heat-treated is set to T, the inner dimension of the first outer wall is set to L1o, the outer dimension of the first inner wall is set to L1i, the inner dimension of the second outer wall is set to L2o, and the outer dimension of the second inner wall is set to L2i, The clearance formed between the first outer wall portion and the first inner wall portion is greater than (L1i×b×T)-(L1o×a×T), A clearance formed between the second outer wall portion and the second inner wall portion is larger than (L2i×b×T)-(L2o×a×T).

5. The sagger according to claim 1, characterized in that: When the metal portion is disposed inside the ceramic portion, the inner bottom surface portion is in contact with the outer bottom surface portion.

6. The sagger according to claim 1, characterized in that: When the metal portion is arranged inside the ceramic portion, the upper surface of the flange portion is located below the upper end of the outer wall portion.

Images