Sagger

Abstract

To provide a technique for efficiently heat-treating powder of a lithium positive electrode material.SOLUTION: A sagger includes a box-shaped ceramic part, and a box-shaped metal part. The ceramic part includes an outer bottom surface part, and an outside wall part projecting upward from the outer bottom surface part. The metal part includes an inner bottom surface part, and an inside wall part projecting upward from the inner bottom surface part, and is detachably arranged in the inside of the ceramic part. When the metal part is arranged in the inside of the ceramic part in a normal temperature state, a clearance is formed between the outside wall part and the inside wall part. The outside wall part includes at least a pair of recesses which are recessed from the upper end to the lower end. When the metal part is viewed in plan view, the pair of recesses are provided at opposite positions while sandwiching the center of the metal part therebetween. The metal part includes at least a pair of flange parts extending outward from the upper end of the inside wall part. When the metal part is arranged in the inside of the ceramic part, the pair of flange parts are positioned in the pair of recesses.SELECTED DRAWING: Figure 3

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 technology]

[0002] A heat treatment furnace (for example, a roller hearth kiln, etc.) may be used to heat treat powder that is a raw material for lithium positive electrode material. When the powder of lithium positive electrode material (hereinafter also simply referred to as powder) is heat treated in a heat treatment furnace, the powder is accommodated in a sagger, and the sagger containing the powder is transported in the heat treatment furnace. Since the temperature for heat treating the powder of lithium positive electrode material is high, the powder is generally accommodated in a sagger made of ceramic having high heat resistance. However, in recent years, a technology for heat treating the powder using a metal sagger has been developed. Since the metal sagger has a high thermal conductivity, the powder accommodated in the sagger can be efficiently heated and heat treated when heat treating in a heat treatment furnace. For example, Patent Document 1 discloses an example of a metal sagger. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-137814 A Summary of the Invention [Problem to be solved by the invention]

[0004] In order to improve the productivity of heat-treating powder, multiple saggers are sometimes stacked vertically when heat-treating powder in a heat treatment furnace. However, metal saggers have low durability against vertical loads, making it difficult to stack multiple saggers vertically.

[0005] This specification discloses a technique for efficiently heat treating powder of lithium cathode material. [Means for solving the problem]

[0006] In a first aspect of the technology disclosed in the present specification, the sagger is a sagger for heat-treating a powder of a lithium positive electrode material by being placed in a heat treatment furnace while containing the powder. The sagger includes a box-shaped ceramic part and a box-shaped metal part. The ceramic part includes an outer bottom surface part and an outer wall part protruding upward from the outer bottom surface part, and is open at the top and formed of ceramic. The metal part includes an inner bottom surface part and an inner wall part protruding upward from the inner bottom surface part, and is open at the top and is detachably placed inside the ceramic part. When the metal part is placed inside the ceramic part at room temperature, a clearance is formed between the outer wall part and the inner wall part. The outer wall part includes at least a pair of recesses recessed from the upper end to the lower end. When the metal part is viewed in plan, the pair of recesses are provided at positions facing each other across the center of the metal part. The metal portion has at least a pair of flanges extending outward from an upper end of the inner wall portion. When the metal portion is disposed inside the ceramic portion, the pair of flanges are located within the pair of recesses.

[0007] In the above sagger, since the metal part is disposed inside the ceramic part, when the powder is contained in the sagger, the powder comes into contact with the metal part. Therefore, the powder can be efficiently heated. Furthermore, since the ceramic part is disposed outside the metal part, the ceramic part receives a vertical load, and thus durability against the vertical load is increased. Therefore, a plurality of saggers can be stacked vertically. These features can improve productivity. Furthermore, the metal part is disposed detachably inside the ceramic part, and the flange part of the metal part is located in the recess of the ceramic part. When the powder after the heat treatment is collected from the sagger, for example, the powder contained therein can be dropped and collected by inverting the sagger. For example, if the metal part is bonded to the ceramic part, it is possible to prevent the metal part from dropping when the sagger is inverted, but on the other hand, when the sagger is discarded, it is difficult to remove the reusable metal part from the sagger. Since the flange of the metal part is located within the recess of the ceramic part, the metal part can be prevented from falling off when the sagger is held at the portion where the flange is located and turned over. Therefore, since the flange of the metal part is located within the recess of the ceramic part, the sagger can be easily turned over without the metal part being bonded to the ceramic part and without the metal part being dropped off. Therefore, the powder can be easily recovered and the metal part can be easily removed from the ceramic part when reused. In addition, since the thermal expansion coefficient of metal is higher than that of ceramic, when the sagger is placed under heat treatment conditions (for example, when placed in a heat treatment furnace), the metal is more likely to expand than the ceramic. Since a clearance is formed between the side surface of the ceramic part and the side surface 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]

[0008] [Figure 1] FIG. [Diagram 2] FIG. [Diagram 3] FIG. 2 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a diagram for explaining dimensions of each part of the sagger in the embodiment. [Diagram 5] FIG. 2 is a diagram showing the effects on the saggers and powder when the powder is heat-treated using the saggers of Examples 1 and 2 and Comparative Examples 1 to 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The main features of the embodiments described below are listed below. Note that the technical elements described below are independent technical elements that exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing.

[0010] In a second aspect of the technology disclosed in the present specification, in the first aspect described above, the metal part may be formed of a metal containing aluminum at least on its surface. According to this configuration, a metal containing aluminum is disposed on the surface of the metal part. As a result, when the sagger is placed under heat treatment conditions (for example, when placed in a heat treatment furnace), an alumina coating is formed on the surface of the metal part. This makes it possible to suppress oxidation of the metal part by the powder in the sagger during heat treatment.

[0011] In a third aspect of the technology disclosed in the present specification, in the first aspect, the metal part may be made of a nickel-based alloy containing aluminum. With this configuration, when the sagger is placed under heat treatment conditions (for example, when placed in a heat treatment furnace), an alumina coating is formed on the surface of the metal part, and oxidation of the metal part by the powder in the sagger during heat treatment can be suppressed.

[0012] In a fourth aspect of the technique disclosed in the present specification, in any one of the first to third aspects, the ceramic part and the metal part may have a rectangular shape in a plan view. The outer wall part may include a pair of first outer wall parts and a pair of second outer wall parts perpendicular to the pair of first outer wall parts. The inner wall part may include a pair of first inner wall parts and a pair of second inner wall parts perpendicular to the pair of first inner wall parts. When the metal part is disposed inside the ceramic part, the pair of first outer wall parts and the pair of first inner wall parts may be parallel to each other, and the pair of second outer wall parts and the pair of second inner wall parts may be parallel to each other. When the thermal expansion coefficient of the ceramic part is a, the thermal expansion coefficient of the metal part is b, and the maximum temperature when the powder in the sagger is heat-treated is T, the clearance formed between the first outer wall part and the first inner wall part may be larger than (L1i×b×T)-(L1o×a×T), where the inner dimension of the first outer wall part is L1o and the outer dimension of the first inner wall part is L1i, and the clearance formed between the second outer wall part and the second inner wall part may be larger than (L2i×b×T)-(L2o×a×T), where the inner dimension of the second outer wall part is L2o and the outer dimension of the second inner wall part is L2i. With this configuration, even if the metal part expands when the sagger is placed under heat treatment conditions (for example, when placed in a heat treatment furnace), the metal part fits within the clearance. Therefore, it is possible to preferably avoid the ceramic part being damaged by the metal part.

[0013] In a fifth aspect of the technique disclosed in the present specification, in any one of the first to fourth aspects, when the metal part is disposed inside the ceramic part, the inner bottom surface part may be in contact with the outer bottom surface part. With this configuration, it is possible to prevent the metal part from being deformed by the load of the powder contained in the metal part.

[0014] In a sixth aspect of the technique disclosed in the present specification, in any one of the first to fifth aspects, when the metal part is disposed inside the ceramic part, the upper surface of the flange part may be located below the upper end of the outer wall part. With this configuration, the recessed part can be prevented from being blocked by the inner wall part. Therefore, gas generated from the powder contained in the sagger during heat treatment can be discharged from the recessed part. EXAMPLES

[0015] The sagger 10 will be described with reference to the drawings. The sagger 10 accommodates a powdered material to be treated. In this embodiment, the material to be treated accommodated in the sagger 10 is a powdered lithium positive electrode material (hereinafter, simply referred to as "powder"). A heat treatment furnace (e.g., a roller hearth kiln, etc.) for heat treating the powder is configured to transport the sagger 10 from an entrance to an exit. The sagger 10 is transported through the heat treatment furnace while accommodating the powder.

[0016] As shown in Figs. 1 to 3, the sagger 10 is box-shaped and has a rectangular shape when viewed from above. In this embodiment, the sagger 10 has a substantially square shape when viewed from above. The sagger 10 includes a ceramic part 20 and a metal part 30. The metal part 30 is detachably disposed inside the ceramic part 20.

[0017] The ceramic portion 20 is box-shaped and made of ceramic. The ceramic portion 20 has a substantially square shape when the sagger 10 is viewed from above. The ceramic portion 20 includes an outer bottom surface portion 22 and an outer wall portion 24.

[0018] The outer bottom surface portion 22 has a substantially square flat plate shape. The outer wall portion 24 is disposed along the outer periphery of the outer bottom surface portion 22 and protrudes upward from the outer bottom surface 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 disposed on each side of the outer periphery of the outer bottom surface portion 22. The first outer wall portion 24a and the third outer wall portion 24c are disposed opposite each other, and the second outer wall portion 24b and the fourth outer wall portion 24d are disposed opposite each other. The first outer wall portion 24a to the fourth outer wall portion 24d have substantially the same dimensions in the height direction.

[0019] The first outer wall 24a to the fourth outer wall 24d are provided with recesses 26a to 26d, respectively. The recess 26a is provided on the first outer wall 24a. The recess 26a is recessed downward from the upper end of the first outer wall 24a. The recess 26a is formed near the center of the first outer wall 24a. The recesses 26b to 26d are provided on the second outer wall 24b to the fourth outer wall 24d, respectively, and have the same shape as the recess 26a. Hereinafter, when it is not necessary to distinguish between the recesses 26a to 26d, the suffixed alphabet may be omitted and they may be referred to as recesses 26. By providing the recesses 26 on the outer wall 24, when a plurality of saggers 10 are stacked vertically and heat-treated, gas generated from the powder contained in the saggers 10 by heat treatment can be released from the recesses 26 to the outside of the saggers 10. In addition, a flange portion 36, which will be described later, is disposed in the recessed portion 26.

[0020] The metal part 30 is box-shaped and made of metal. In this embodiment, the metal part 30 is made of stainless steel, and the surface is coated with aluminum (aluminized). The thickness of the metal part 30 is approximately uniform, and in this embodiment, it is approximately 2 mm. The metal part 30 has a substantially square shape when the sagger 10 is viewed from above. The metal part 30 includes an inner bottom surface part 32, an inner wall part 34, and flange parts 36a to 36d.

[0021] The inner bottom surface portion 32 has a generally square flat plate shape. The inner bottom surface portion 32 is smaller than the outer bottom surface portion 22. When the metal portion 30 is disposed in the ceramic portion 20, the inner bottom surface portion 32 is placed on the outer bottom surface portion 22, and the lower surface of the inner bottom surface portion 32 abuts against the upper surface of the outer bottom surface portion 22.

[0022] The inner wall portion 34 is disposed 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 disposed 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 disposed opposite to each other, and the second inner wall portion 34b and the fourth inner wall portion 34d are disposed opposite to each other. The first inner wall portion 34a to the fourth inner wall portion 34d have substantially the same height dimension. In addition, the height dimension of the first inner wall portion 34a to the fourth inner wall portion 34d is smaller than the height dimension of the first outer wall portion 24a to the fourth outer wall portion 24d. Specifically, when the metal part 30 is disposed in the ceramic part 20, the upper ends of the first inner wall part 34a to the fourth inner wall part 34d are located between the lower end of the recess 26 and the upper ends of the first outer wall part 24a to the fourth outer wall part 24d, and are preferably located near the lower end of the recess 26. By having the upper ends of the first inner wall part 34a to the fourth inner wall part 34d located near the lower end of the recess 26, it is possible to prevent the recess 26 from being blocked by the first inner wall part 34a to the fourth inner wall part 34d.

[0023] The flanges 36a to 36d are connected to the first to fourth inner wall portions 34a to 34d, respectively. The flanges 36a are flat and are arranged so as to be perpendicular to the first inner wall portion 34a. The flanges 36a extend from the upper end of the first inner wall portion 34a toward the outside of the sagger 10. The flanges 36a are arranged near the center of the first inner wall portion 34a. The dimension of the flanges 36a extending along the first inner wall portion 34a is smaller than the dimension of the recess 26a. The flanges 36a are located in the recess 26a when the metal portion 30 is arranged in the ceramic portion 20. The flanges 36b to 36d are connected to the second to fourth inner wall portions 34b to 34d, respectively, and have the same configuration as the flanges 36a. Hereinafter, when there is no need to distinguish between the flange portions 36a to 36d, they may be referred to as the flange portion 36 without the alphabetical subscript.

[0024] In the sagger 10 of this 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, the metal part 30 can be removed from the ceramic part 20 by simply lifting the metal part 30. For example, when the sagger 10 becomes unusable due to damage or the like, the metal part 30 can be easily removed from the ceramic part 20. While the ceramic part 20 is often discarded when it becomes unusable, the metal part 30 can be recycled even when it becomes unusable. Since the metal part 30 can be easily separated from the ceramic part 20, the metal part 30 can be easily recycled when the sagger 10 becomes unusable.

[0025] In addition, in the sagger 10 of this embodiment, the flange 36 of the metal part 30 is disposed in the recess 26 of the ceramic part 20. After the powder in the sagger 10 is heat-treated, the powder is often collected from the sagger 10 by inverting the sagger 10. For example, if the metal part is bonded to the ceramic part, the metal part will not fall off even if the sagger is inverted. On the other hand, in the sagger 10 of this embodiment, since the metal part 30 is not bonded to the ceramic part 20, if only the ceramic part 20 is held and inverted, the metal part 30 will fall off. However, in the sagger 10 of this embodiment, the flange 36 of the metal part 30 is disposed in the recess 26 of the ceramic part 20. Therefore, if the sagger 10 is held at the portion where the flange 36 is located, the sagger 10 can be inverted while holding both the ceramic part 20 and the metal part 30. Therefore, it is possible to prevent the metal part 30 from falling when collecting the powder inside the sagger 10, without bonding the metal part 30 to the ceramic part 20. If the flange part 36 protrudes outward beyond the ceramic part 20, the sagger 10 may be turned over by gripping only 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 single unit.

[0026] In this embodiment, the flange portion 36 is provided on each of the first inner wall portion 34a to the fourth inner wall portion 34d, but is not limited to this configuration. For example, the flange portion 36 may be provided on two opposing inner wall portions 34 among the four inner wall portions 34a to 34d, and 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 portions 36 are provided on at least 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 collecting the powder inside the sagger 10. Therefore, if the flange portions 36 are provided on at least the two opposing inner wall portions 34, it is possible to prevent the metal portion 30 from falling when collecting the powder inside the sagger 10.

[0027] Moreover, both the inner bottom surface portion 32 and the outer bottom surface portion 22 are substantially square, and the inner bottom surface portion 32 is smaller than the outer bottom surface portion 22. Therefore, the metal portion 30 can be disposed within the ceramic portion 20. Furthermore, when the metal portion 30 is disposed within the ceramic portion 20, the first inner wall portion 34a to the fourth inner wall portion 34d are disposed parallel to the opposing first outer wall portion 24a to the fourth outer wall portion 24d, respectively. Note that the sagger 10 may be substantially rectangular in shape when viewed from above. When the metal portion 30 is disposed within the ceramic portion 20, a clearance 40 is provided between the outer wall portion 24 and the inner wall portion 34.

[0028] Here, the size of the clearance 40 will be described. As shown in Fig. 3, two clearances 40a, 40b (hereinafter also referred to as a pair of clearances 40a, 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 sum of the size d1 of the clearance 40a and the size d2 of the clearance 40b is set so as to satisfy (d1+d2)>(L1i x b x T)-(L1o x a x T). In addition, L1i indicates 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), L1о indicates 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 indicates the thermal expansion coefficient of the ceramic forming the ceramic portion 20, b indicates the thermal expansion coefficient of the metal forming the metal portion 30, and T indicates the maximum temperature when the powder contained in the sagger 10 is heat-treated.

[0029] In addition, a clearance 40 (not shown) is provided between another pair of opposing outer wall portions 24 and a pair of inner wall portions 34. For example, a clearance 40 is provided between the second inner wall portion 34b and the second outer wall portion 24b, and a clearance 40 is provided between the fourth inner wall portion 34d and the fourth outer wall portion 24d. The sum of the sizes of these clearances 40 is also provided to be larger than (L2i×b×T)-(L2o×a×T). Note that L2i indicates 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 indicates 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).

[0030] For example, the sagger 10 of this embodiment can be formed as follows. The ceramic portion 20 has an outer bottom surface portion 22 with a side of about 330 mm. The outer bottom surface portion 22 and the outer wall portion 24 each have a thickness of about 11 mm. Then, the inner dimension (L10 and L20) of the outer wall portion 24 is about 308 mm. The metal portion 30 has an inner bottom surface portion 32 with a side of about 302 mm. That is, the outer dimension (L1i and L2i) of the inner wall portion 34 is about 302 mm. The sum of the pair of clearances 40 (for example, the sum of the clearance 40a between the first inner wall portion 34a and the first outer wall portion 24a and the clearance 40b between the third inner wall portion 34c and the third outer wall portion 24c) is about 6 mm. 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 part 30 is 15 to 18 × 10 -6 The maximum temperature during the heat treatment of the powder contained in the sagger 10 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 to 4.4327 mm. That is, it is preferable that the total of the pair of clearances 40 is approximately 4 mm or more (each clearance 40 is approximately 2 mm or more). In this embodiment, the total of the pair of clearances 40 is 6 mm, which satisfies the above conditional expression.

[0031] In the sagger 10 of this embodiment, the metal part 30 is disposed in the ceramic part 20. Therefore, when powder is contained in the sagger 10, the powder comes into contact with the metal part 30. The metal part 30 has a higher thermal conductivity than the ceramic part 20. When powder is contained in the sagger 10, the powder comes into contact with the metal part 30, so that the powder can be efficiently heated during heat treatment. In addition, in this embodiment, the metal part 30 is formed of stainless steel and is aluminized. By aluminizing, an alumina coating is formed on the surface of the metal part 30 when the sagger 10 is placed under heat treatment conditions including oxygen (for example, when placed in a heat treatment furnace). This makes it possible to suppress oxidation of the metal part 30 by the powder in the sagger 10 during heat treatment. The metal part 30 may be formed of a nickel-based alloy containing aluminum.

[0032] In addition, in the sagger 10 of this embodiment, the ceramic part 20 is located outside the sagger 10. The metal part 30 has low durability against vertical loads, while the ceramic part 20 has high durability against vertical loads. By having the ceramic part 20 located outside the sagger 10, multiple saggers 10 can be stacked vertically. This improves productivity during heat treatment.

[0033] In addition, in the sagger 10 of this embodiment, a clearance 40 is provided between the outer wall 24 and the inner wall 34. The thermal expansion coefficient of metal is higher than that of ceramic. Therefore, when powder is placed in the sagger 10 and heat treated, the metal part 30 expands more than the ceramic part 20. Since the metal part 30 is disposed inside the ceramic part 20, if there is no clearance 40 between the outer wall 24 and the inner wall 34, the ceramic part 20 may be damaged due to the expansion of the metal part 30. In this embodiment, by providing the clearance 40 between the outer wall 24 and the inner wall 34, even if the metal part 30 expands more than the ceramic part 20 during heat treatment, the metal part 30 suppresses the generation of excessive thermal stress in the ceramic part 20. Therefore, it is possible to avoid the ceramic part 20 being damaged due to the expansion of the metal part 30.

[0034] In this embodiment, it has been confirmed that the powder in the sagger 10 can be suitably heat-treated by the sagger 10 having the above-mentioned configuration. As shown in Figs. 4 and 5, an experiment was conducted to see what effects would occur to the sagger 10 and the powder when the powder was placed in the sagger 10 and heat-treated. In the experiment, the outer diameter (outer diameter of the ceramic part 20) of the sagger 10 when viewed from above was about 330 mm x about 330 mm. 7 kg of positive electrode material (powder) of a lithium-ion battery was placed inside the sagger 10. Then, a plurality of saggers 10 were arranged in four rows and two stages and heat-treated in a roller hearth kiln with a furnace length of 42 m. The heat treatment conditions were an atmospheric temperature of 950°C and an oxygen atmosphere of 96%. The sagger 10 was reused multiple times (three to ten times) for the heat treatment.

[0035] In the sagger 10 of Example 1, the metal part 30 was made of stainless steel and aluminized. The thickness (dimension A) of the metal part 30 was about 2 mm. It was confirmed that the dimension A had no effect even if it was about 3 mm. For this reason, the thickness of the metal part 30 is preferably about 2 to 3 mm, and from the viewpoint of economy, it can be said that about 2 mm is more preferable. 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 part 24 and the inner wall part 34, dimension B) was about 3 mm. The size (dimension C) between the outer surface of the inner bottom part 32 of the metal part 30 and the inner surface of the outer bottom part 22 of the ceramic part 20 was about 0 mm. That is, the inner bottom part 32 of the metal part 30 was in contact with the outer bottom part 22 of the ceramic part 20. The length (dimension D) from the lower end of the recess 26 to the inner wall part 34 (brim part 36) was 3 mm.

[0036] As shown in Fig. 5, even when the sagger 10 of Example 1 was used for ten heat treatments, the quality of the powder after the heat treatment was high, and the powder could be collected without adhering to the surface of the metal part 30. Furthermore, no corrosion of the metal part 30 or deformation of each part (ceramic part 20 and metal part 30) was observed. In other words, it was confirmed that the sagger 10 of Example 1 can suitably heat treat the powder, and has high durability for multiple reuse.

[0037] Moreover, Example 2 differs from Example 1 in that the metal part 30 is a nickel-based alloy containing aluminum. In Example 2, the same results as in Example 1 were obtained, and it was confirmed that the powder could be suitably heat-treated and had high durability against multiple reuse.

[0038] On the other hand, Comparative Examples 1 to 3 show comparative examples of metal parts formed of stainless steel and aluminized. The sagger of Comparative Example 1 was different from the sagger 10 of Example 1 in that the dimension C was 3 mm. That is, the sagger of Comparative Example 1 had 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 was supported by the ceramic part by the flange portion. After ten heat treatments, the metal part 30 of the sagger of Comparative Example 1 was deformed by 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.

[0039] The sagger of Comparative Example 2 differed from the sagger 10 of Example 1 in that the dimension B was 1 mm. That is, the distance between the outer wall 24 and the inner wall 34 of the sagger of Comparative Example 2 was narrower than that of the sagger 10 of Example 1. After only one heat treatment, the ceramic part of the sagger of Comparative Example 2 was pressed against the metal part due to the expansion of the metal part, causing cracks in the ceramic part. Therefore, it can be said that the dimension B should be greater than 1 mm, and preferably greater than 2 mm as described above.

[0040] The sagger of Comparative Example 3 differed from the sagger 10 of Example 1 in that the dimension D was 10 mm. That is, in the sagger of Comparative Example 3, the area of ​​the recess 26 blocked by the inner wall was large. When the results of ten heat treatments were examined for the sagger of Comparative Example 3, there was a problem with the quality of the powder after the heat treatment. This was presumably because ventilation was impaired inside the sagger due to the recess being blocked by the inner wall. Therefore, it can be said that the dimension D should be smaller than 10 mm, and preferably about 3 mm.

[0041] Comparative Examples 4 and 5 show comparative examples of metal parts formed of nickel-based alloys containing aluminum. Comparative Example 4 differs from the sagger 10 of Example 2 in that the dimension B is 1 mm. Comparative Example 5 differs from the sagger 10 of Example 2 in that the dimension C is 3 mm. Comparative Examples 4 and 5 also did not provide favorable results in terms of the quality of the powder after heat treatment, adhesion of the powder to the surface of the metal part, deformation of the metal part, etc. From the above, it was confirmed that the powder in the sagger 10 can be favorably heat-treated by using the sagger 10 of this example.

[0042] Although specific examples of the technology disclosed in this specification have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. Furthermore, the technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings achieves multiple objectives simultaneously, and achieving one of the objectives itself has technical utility. [Explanation of symbols]

[0043] 10: Box 20: Ceramic section 22: Outer bottom part 24:Outer wall 26: Recess 30: Metal part 32: Inner bottom part 34:Inner wall 36: Tsuba section 40: Clearance

Claims

1. A sagger for containing a powder of a lithium positive electrode material and being placed in a heat treatment furnace for heat treating the powder, A box-shaped ceramic portion having an outer bottom surface portion and an outer wall portion protruding upward from the outer bottom surface portion, the box-shaped ceramic portion being open at the top and being made of ceramic; a box-shaped metal part having an inner bottom surface and an inner wall protruding upward from the inner bottom surface, the metal part being open at the top and being detachably disposed inside the ceramic part; a clearance is formed between the outer wall portion and the inner wall portion when the metal portion is disposed inside the ceramic portion at room temperature; The outer wall portion has at least a pair of recesses recessed from an upper end to a lower end, When the metal portion is viewed in a plan view, the pair of recesses are provided at positions facing each other across a center of the metal portion, The metal portion includes at least a pair of flanges extending outward from an upper end of the inner wall portion, A sagger, wherein the pair of flanges are positioned within the pair of recesses when the metal portion is disposed within the ceramic portion.

2. 2. The sagger according to claim 1, wherein at least a surface of the metal portion is formed from a metal containing aluminum.

3. 2. The sagger of claim 1, wherein the metal portion is formed of a nickel-based alloy containing aluminum.

4. The ceramic portion and the metal portion have a rectangular shape in a plan view, The outer wall portion includes a pair of first outer wall portions and a pair of second outer wall portions perpendicular 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 perpendicular 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 and the pair of first inner wall portions are parallel to each other, and the pair of second outer wall portions and the pair of second inner wall portions are parallel to each other, When the thermal expansion coefficient of the ceramic portion is a, the thermal expansion coefficient of the metal portion is b, and the maximum temperature during the heat treatment of the powder in the sagger is T, A clearance formed between the first outer wall portion and the first inner wall portion is larger than (L1i×b×T)−(L1o×a×T), where L1o is an inner dimension of the first outer wall portion and L1i is an outer dimension of the first inner wall portion.

2. The sagger of claim 1, wherein a clearance formed between the second outer wall portion and the second inner wall portion is greater than (L2i×b×T)-(L2o×a×T), where L2o is an inner dimension of the second outer wall portion and L2i is an outer dimension of the second inner wall portion.

5. 2. The sagger of claim 1, wherein the inner bottom surface contacts the outer bottom surface when the metal portion is disposed within the ceramic portion.

6. 2. The sagger of claim 1, wherein an upper surface of said flange is located below an upper end of said outer wall when said metal portion is disposed within said ceramic portion.

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