JP6396938B2 - Heat treatment container for positive electrode active material of lithium battery - Google Patents

Description

  The present invention relates to a heat treatment container for a positive electrode active material of a lithium battery used when producing a positive electrode active material of a lithium battery.

  Various compounds, particularly inorganic compounds, are produced through a heat treatment step. The heat treatment (heating) is usually performed in a state where a heat-treated compound (an inorganic compound or a raw material thereof) is arranged in a heat-resistant heat treatment container. The heat treatment container is required not only to have heat resistance but also to be stable with respect to the heat treatment compound.

One of the inorganic compounds produced through the heat treatment step is a compound containing lithium. This lithium-containing compound is, for example, a LiMnO ₂ -based compound, a LiNi _1/3 Co _1/3 Mn _1/3 O ₂ -based compound, or LiMn ₂ O ₄ that is used in a positive electrode active material of a lithium battery or a lithium ion battery. Compounds, LiCoO ₂ compounds, and LiNiO ₂ compounds. Hereinafter, batteries using a lithium-containing compound such as a lithium battery or a lithium ion battery as a positive electrode active material are collectively referred to as a lithium battery.

  A positive electrode active material (lithium-containing compound) of a lithium battery is produced by firing raw material powder. The heat treatment (firing) of the raw material powder of this lithium-containing compound is generally a heat treatment container (heat treatment container, mortar) fired mainly using a material having heat resistance such as alumina, mullite, cordierite, spinel, etc. ).

  Since cordierite has high thermal shock resistance, it is effective for repeated heat treatment. However, cordierite is highly reactive with lithium-containing compounds, and as a result of the reaction, lithium moves to the heat treatment container, the lithium concentration of the lithium-containing compound decreases, or the surface layer of the heat treatment container peels off into a lithium-containing compound. There was a problem that impurities were mixed. In particular, in the positive electrode active material of a lithium battery, the battery performance of the lithium battery may be deteriorated due to the reaction with the heat treatment container.

Although spinel has low reactivity with lithium-containing compounds, there is a problem that the thermal expansion coefficient is high, and the higher the content rate, the more easily cracking occurs due to thermal shock. That is, it becomes impossible to use the heat treatment container by repeated heating and cooling in a short period. As a result, it has been difficult to increase the spinel content.
Such heat treatment containers are described in Patent Documents 1 and 2, for example.

  In Patent Document 1, when the total mass is 100%, 5-45% alumina powder, 0-35% mullite powder, 5-40% cordierite powder, 5-30% A heat treatment container formed by firing a mixed powder having spinel powder is described.

Patent Document 2 contains 40% to 60% by weight of spinel, 20% to 40% by weight of cordierite, 0% to 40% by weight of mullite, and 56% by weight of Al ₂ O ₃ component. 65 wt%, the MgO component 14 wt% to 23 wt%, and the SiO ₂ component contained 15 wt% to 25 wt%, _Al 2 _{O 3} component, a total of MgO component and SiO ₂ component is 95 mass% or more There is described a mortar with a porosity of 30% or less.

JP 2014-227327 A JP 2011-117663 A

The conventional heat treatment container is made of an inorganic material having low reactivity with the lithium-containing compound, thereby improving the reaction resistance. However, the conventional heat treatment container has a problem that cracking occurs due to low thermal shock resistance when repeated firing is performed. For this reason, it is calculated | required by heat processing container to suppress the crack which generate | occur | produces by repeated use.
The present invention has been made in view of the above circumstances, and provides a heat treatment container for a positive electrode active material of a lithium battery having excellent reaction resistance and thermal shock resistance and having resistance to cracking (excellent crack resistance). The task is to do.

  In order to solve the above-mentioned problems, the present invention was completed as a result of repeated studies on heat treatment containers.

The heat treatment container for the positive electrode active material of the lithium battery of the present invention (hereinafter also referred to as the heat treatment container of the present invention) is a mixed powder obtained by mixing cordierite powder, alumina powder and mullite powder with spinel powder, or cordierite powder. The inorganic material powder composed of a mixed powder obtained by mixing alumina powder and mullite powder, and the ratio of 0.1 to 1 part by mass when the mass of the inorganic material powder is 100 parts by mass, the maximum particle size of the inorganic material powder It consists of a sintered body of alumina long fibers having a fiber length of 1.2 to 5 times.

  The heat treatment container of the present invention is composed of a fired body of inorganic material powder and alumina long fiber, and maintains high reaction resistance against lithium-containing compounds and high thermal shock resistance against rapid temperature rise and fall, while repeating heat It suppresses the occurrence of cracking due to impact (heat treatment container with excellent crack resistance).

It is an enlarged schematic diagram which shows typically the structure of the baking body of the heat processing container of embodiment. It is a perspective view which shows a tank-shaped heat processing container.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to each embodiment, and can be implemented with various modifications.
[Embodiment]
The heat treatment container of this embodiment is 1.2 to 5 times the maximum particle size of the inorganic material powder at a ratio of 0.1 to 1 part by mass when the mass of the inorganic material powder and the inorganic material powder is 100 parts by mass. It consists of a fired body of alumina long fibers having a fiber length of.

The inorganic material powder forming the heat treatment container (fired body) of this embodiment is preferably made of a ceramic powder containing alumina (Al ₂ O ₃ ) in the molecular formula. Examples of such inorganic material powder include alumina (Al ₂ O ₃ ), mullite (3Al ₂ O ₃ .2SiO _{2 to} 2Al ₂ O ₃ .SiO ₂ ), spinel (Al ₂ O ₃ .MgO), cordierite (2MgO). One or more ceramic powders selected from (2Al ₂ O ₃ · 5SiO ₂ ) can be mentioned.
The inorganic material powder may be composed of one kind of these ceramic powders, or may be a mixture of two or more kinds.

  In the heat treatment container of this embodiment, the composition (or inorganic material powder) of the fired body can be properly used depending on the type of lithium-containing compound. For lithium-containing compounds with high reactivity, it is necessary to use a spinel powder that exhibits resistance to resistance, a mixture of cordierite powder, alumina powder, and mullite powder that is molded and fired. preferable. For lithium-containing compounds with low reactivity, it is preferable to use a compound comprising a fired body of a mixed powder obtained by mixing an alumina powder and a mullite powder in a cordierite powder that enhances thermal shock resistance. By using a fired body manufactured from a mixed powder of these ceramic powders, the heat treatment container of this embodiment has resistance to reaction and thermal shock.

  The fired body forming the heat treatment container of this embodiment is preferably composed of a coarse part composed of particles of 500 μm or more and a matrix part composed of an aggregate of particles of 100 μm or less. The coarse portion exhibits a function of suppressing the erosion of the lithium-containing compound or a function of improving the thermal shock resistance, and an inorganic material powder can be appropriately selected. If reaction resistance is required, spinel or alumina is preferably selected. If thermal shock resistance is required, cordierite or mullite is preferably selected. The matrix portion is present around the coarse portion to increase the strength of the heat treatment container, and although the material is not limited, alumina and spinel are preferably selected.

  It is preferable that the ratio of the coarse grain part (ratio of the area of the coarse grain part in the area of a cut surface) to a coarse grain part and a matrix part is 20 to 80% in the cut surface of a sintered body. If it is less than 20%, the effect of having a coarse portion cannot be sufficiently exhibited, and if it exceeds 80%, the matrix portion cannot surround the coarse portion and the strength is lowered. The ratio of a preferable coarse-grain part is 30 to 70%, More preferably, it is 40 to 70%.

  The fired body of the heat treatment container of this embodiment contains alumina long fibers. Thereby, the thermal shock resistance and crack resistance of the heat treatment container of this embodiment are improved and can be repeatedly used for synthesis of the positive electrode active material of the lithium battery.

  Known alumina fibers (alumina fibers) can be used as the alumina long fibers, and for example, crystalline fibers containing 60% or more of alumina can be used. The alumina long fiber is a fiber having a crystal layer made of alumina or mullite and having a general size of fiber diameter of 5 to 30 μm and length of 200 μm or more.

  The alumina long fiber in this embodiment has a fiber length of 1.2 to 5 times the maximum particle size of the inorganic material powder. As the fiber length of the alumina long fiber becomes longer than the maximum particle diameter of the inorganic material powder, the alumina long fiber 12 is contained in the matrix portion 11 or coarsely as shown in the schematic diagram of FIG. It is arranged so as to straddle two or more particles of the matrix part 11 along the outer periphery of the particles of the grain part 10, and the progress of cracks generated in the matrix part 11 or the cracks at the interface between the coarse grain part 10 and the matrix part 11 It will be a structure to stop the progress of. That is, it becomes a structure that reduces thermal shock. If the fiber length is less than 1.2 times, the alumina long fiber 12 cannot be disposed so as to straddle the particles of the two matrix portions 11, and thus the thermal shock cannot be sufficiently relaxed, and the crack resistance is lowered. In addition, when the fiber length is longer than 5 times, it becomes difficult to uniformly mix the alumina long fiber and the inorganic material powder, leading to a decrease in moldability, or the alumina long fiber forms a lump, and the lump becomes a defect. Cause cracks.

  The alumina long fiber is mixed with the inorganic material powder at a ratio of 0.1 to 1 part by mass when the mass of the inorganic material powder is 100 parts by mass. By mixing the alumina long fibers at this ratio, the above effect of adding the alumina long fibers can be exhibited. In 0.1 mass part, the addition amount of an alumina long fiber is too small, and the effect of addition cannot be exhibited. Moreover, when it exceeds 1 mass part, the moldability of the molded object for forming a sintered compact will fall.

  The fiber length of the alumina long fiber is preferably 1 to 10 mm. When the fiber length is 1 mm or less, the effect of suppressing the progress of cracks in the matrix portion is not sufficiently exerted, and when the fiber length is 10 mm or more, the fibers are entangled with each other and uniform mixing cannot be performed, leading to a decrease in moldability and the cause of cracks. Although it does not specifically limit about the diameter of an alumina long fiber, Commercially available or a well-known 5-30 micrometers long fiber can be used.

  The porosity of the heat treatment container of this embodiment is not limited. For example, it may be adjusted to such an extent that cracks due to thermal shock and erosion of lithium-containing compounds do not occur when used for heat treatment. The porosity is preferably 10 to 40%, more preferably 25 to 35%. When the porosity is lower than these ranges, cracking due to thermal shock is likely to occur.When the porosity is higher than these ranges, the positive electrode active material is eroded and easily reacts with the heat treatment container. Cause.

[Production method]
Although the manufacturing method of the heat treatment container of this embodiment is not limited, for example, the following manufacturing method can be used.
First, the inorganic material powder and the alumina long fiber are weighed so as to have a predetermined ratio and mixed uniformly. When the inorganic material powder is composed of a plurality of ceramic powders, either a plurality of ceramic powders are uniformly mixed and then mixed with alumina long fibers, or a plurality of ceramic powders and alumina long fibers are simultaneously mixed. But it ’s okay.

  In mixing the inorganic material powder and the alumina long fiber, an additive which does not affect the properties when the heat treatment container is produced may be added. Examples of the additive include Kibushi clay, Sasame clay, an organic binder, and an inorganic binder.

  The heat treatment container of this embodiment can be manufactured by subjecting the mixture of the inorganic material powder and the alumina long fiber to the molding and firing steps.

The atmosphere is not limited, and firing may be performed in an oxidizing gas atmosphere or an inert gas atmosphere, and is preferably performed in an air atmosphere (oxidizing gas atmosphere).
In addition, before the heat treatment is performed, a drying process or a degreasing process performed at the time of firing the conventional molded body may be performed.

[Effect of this embodiment]
(First effect)
The heat treatment container of this embodiment is 1.2 to 5 times the maximum particle size of the inorganic material powder at a ratio of 0.1 to 1 part by mass when the mass of the inorganic material powder and the inorganic material powder is 100 parts by mass. It consists of a fired body of alumina long fibers having a fiber length of.
With this configuration, the heat treatment container of the present embodiment is a heat treatment container having reaction resistance and thermal shock resistance and excellent crack resistance.

(Second effect)
According to this embodiment, the alumina long fiber has a fiber length of 1 to 10 mm. With this configuration, the effect of thermal shock relaxation can be reliably exhibited.

(Third effect)
According to this embodiment, the inorganic material is at least one selected from alumina, mullite, spinel, and cordierite. With this configuration, the above-described effects can be reliably exhibited.

(Other effects)
The fired body of the heat treatment container of this embodiment is composed of a coarse grain portion that imparts reaction resistance and thermal shock resistance, a matrix portion that improves strength, and alumina long fibers that relieve thermal shock. As a result, the heat treatment container of this embodiment is a heat treatment container having reaction resistance and thermal shock resistance and excellent crack resistance.

Hereinafter, the present invention will be specifically described with reference to examples.
As an example of the present invention, a tank-shaped heat treatment container (so-called mortar) shown in FIG. 2 was produced. The tank-shaped mortar shown in FIG. 2 has a tank-shaped part 20 having an opening at the top, and a lid member 21 that covers the opening of the tank-shaped part 20. In addition, although the tank-shaped mortar was specifically used in the present Example, if the shape can arrange | position (hold | maintain) the positive electrode active material of a lithium battery at the time of heat processing, the shape will be specifically limited. It is not a thing. For example, a positive electrode active material powder of a lithium battery is arranged (held or fixed) on the upper surface thereof in a substantially plate shape (so-called setter), a tank shape (cylindrical shape) having an open top or side, Examples of the shape include a closed shape (so-called mortar) that covers a tank-shaped (tubular) opening with a lid member.
Example 1
As the inorganic material powder, 40 parts by mass of alumina powder, 20 parts by mass of cordierite powder, 20 parts by mass of mullite powder, and 20 parts by mass of spinel powder are weighed. The grain size screened according to JIS standard sieve (JIS Z 8801) was used, and the coarse grain part used a grain size of nominal opening of 1.00 mm-500 μm (16-32 mesh). The maximum particle size of the inorganic material powder measured with a particle size distribution measuring device (MT3300II manufactured by Microtrack Bell) was 1 mm.

Fiber length: 1.5 mm long alumina fibers are prepared at a ratio of 0.2 parts by mass when the mass of the inorganic material powder is 100 parts by mass. The ratio of the alumina long fibers to the maximum particle size of the inorganic material powder is 1.5. The alumina long fiber used was a chopped product obtained by cutting a commercially available product (manufactured by Nichibi Co., Ltd., trade name: Nichibi Alpha Yarn (fiber diameter) 7 μm) to a predetermined length.
The prepared inorganic material powder and the alumina long fiber are mixed uniformly by adding kibushi clay and an organic binder, and then kneaded uniformly by adding water.

  The mixture was pressurized at a pressure of 20 MPa to form a mortar shape, dried, and then fired at 1350 ° C. in an atmospheric atmosphere for 5 hours to produce a heat treatment container of this example.

  The heat treatment container of this example had a porosity of 27.8% as measured by the measurement method described in JIS R 2205. The bending strength measured by the measuring method described in JIS R 1601 was 6.9 MPa, and the elastic modulus measured by the measuring method described in the resonance method of JIS R 1602 was 10.5 GPa.

(Example 2)
This example is a heat treatment container similar to that of Example 1 except that an alumina long fiber having a fiber length of 2 mm was used. The ratio of the alumina long fibers to the maximum particle size of the inorganic material powder is 2.
The heat treatment container of this example had a porosity of 28.0%, a bending strength of 6.2 MPa, and an elastic modulus of 9.0 GPa.

(Example 3)
This example is a heat treatment container similar to that of Example 1 except that an alumina long fiber having a fiber length of 3 mm is used. The ratio of the alumina long fibers to the maximum particle size of the inorganic material powder is 3.
The heat treatment container of this example had a porosity of 28.0%, a bending strength of 6.4 MPa, and an elastic modulus of 10.1 GPa.

(Example 4)
This example is a heat treatment container similar to that of Example 1 except that an alumina long fiber having a fiber length of 5 mm is used. The ratio of the alumina long fibers to the maximum particle size of the inorganic material powder is 5.
The heat treatment container of this example had a porosity of 28.6%, a bending strength of 6.1 MPa, and an elastic modulus of 9.2 GPa.

(Comparative Example 1)
This example is a heat treatment container similar to that of Example 1 except that alumina long fibers are not used.
The heat treatment container of this example had a porosity of 26.0%, a bending strength of 8.4 MPa, and an elastic modulus of 11.8 GPa.

(Comparative Example 2)
This example is a heat treatment container similar to that of Example 1 except that an alumina long fiber having a fiber length of 1 mm is used. The ratio of the alumina long fibers to the maximum particle size of the inorganic material powder is 1.
The heat treatment container of this example had a porosity of 26.3%, a bending strength of 8.9 MPa, and an elastic modulus of 14.2 GPa.

[Evaluation]
As the evaluation of the heat treatment container in each example, the thermal shock resistance, thermal shock damage resistance, and elastic modulus reduction rate were evaluated as follows. The evaluation results are shown in Table 1.
Table 1 also shows the evaluation of formability during the manufacture of the heat treatment containers of each example.

(Heat shock resistance)
The heat treatment container of each example (fired body forming) is processed into a 100 × 50 × 10 mm rectangular parallelepiped (block-shaped test piece), and heated (heated) to an air atmosphere of 1000 ° C. in a heating furnace.
After 30 minutes at a furnace temperature of 1000 ° C., the heat treatment container of each example is taken out from the heating furnace, put into water at a temperature of 15 ° C., and rapidly cooled (water cooled).
After quenching, the presence or absence of cracks is confirmed. If no cracks can be confirmed, the test piece is dried at 100 ° C. for 12 hours and then placed in the heating furnace again.

  This temperature increase (heating) to a predetermined heating temperature and water cooling (rapid cooling) were repeated five times, and the presence or absence of cracks in the heat treatment container (block-shaped test piece) was visually observed. Table 1 shows the number of times the crack was confirmed. In addition, the example which was not able to confirm a crack even if it repeated 5 times was described as "5 times or more."

(Thermal shock damage resistance)
Thermal shock damage resistance is known as a value serving as an index for suppressing the progress of cracks when cracks occur. The higher this value is, the more difficult it is to generate a crack that is unusable when a crack occurs due to thermal shock. Thermal shock damage resistance assumes that there is no difference in fracture energy between materials,
R ′ ″ = E / σ ^ 2 / (1-ν)
This was calculated using the following formula. Here, E is an elastic modulus, Σ is a bending stress, and ν is a Poisson's ratio.

(Elastic modulus decrease rate)
The elastic modulus reduction rate evaluates the presence of microcracks generated by a thermal shock test that cannot be visually confirmed by the reduction in elastic modulus. It can be inferred that the more the cracks are generated, the greater the decrease in elastic modulus (the smaller the elastic modulus decrease rate).
The elastic modulus reduction rate was measured by the resonance method before and after the thermal shock test, and the elastic modulus reduction rate was calculated from (elastic modulus after test) / (elastic modulus before test).

(Formability)
The evaluation of formability is to confirm that the raw material is evenly raised to the top of the side surface during press molding and to measure the bending strength of the bottom and side portions of the mortar shape. A bending strength of 80% or more is acceptable and the following is unacceptable. The evaluation results are indicated by “◯” for pass, “△” for fail, and “x” for those that could not keep the shape after molding.

As shown in Table 1, the heat treatment container of each example has an equivalent porosity.
In addition, the heat treatment container of each example has a lower elastic modulus than the heat treatment container of each comparative example, and the flexibility of the heat treatment container is improved by adding a predetermined amount of alumina long fibers. Moreover, since the heat treatment container of each Example is simultaneously reduced in strength, it is difficult to interpret that the thermal shock resistance has increased. However, in the thermal shock test, cracks were confirmed in Comparative Example 1 which did not contain alumina long fibers 4 times, and in Comparative Example 2 where the fiber length of the alumina long fibers was short 5 times. In each of the Examples using the long fiber length of alumina long fibers, no cracks could be confirmed even after repeated thermal shocks 5 times. This is considered to be because the predetermined alumina long fiber relaxes the thermal shock. In addition, each example has a higher thermal shock resistance coefficient than the comparative example, so that even if a small crack occurs due to thermal shock, the alumina long fiber straddles two or more matrices along the outer periphery of the matrix portion or the coarse grain. It is considered that the structure has a structure in which cracks are difficult to progress because of the arrangement.
This is the same from the result of the elastic modulus reduction rate.
As mentioned above, it can confirm that the heat processing container of each Example is excellent in thermal shock resistance and crack resistance.

(Example 5)
As the inorganic material powder, alumina powder: 20 parts by mass, cordierite powder: 40 parts by mass, mullite powder: 30 parts by mass, and clay mineral (kaolin) powder: 10 parts by mass are prepared. The coarse grain part used the particle size of nominal opening 2.36mm -1.00mm (8-16 mesh). The maximum particle size of the inorganic material powder measured with a particle size distribution measuring device was 2.5 mm.

Fiber length: 3 mm alumina long fibers are prepared at a ratio of 0.2 parts by mass when the mass of the inorganic material powder is 100 parts by mass. The alumina long fiber is the same as in Example 1 except that the fiber length is different. The ratio of the long alumina fibers to the maximum particle size of the inorganic material powder is 1.2.
Thereafter, in the same manner as in Example 1, the inorganic material powder and the alumina long fiber were mixed, kneaded, molded (dried), and fired to produce a heat treatment container of this example.
The heat treatment container of this example had a porosity of 29.0%, a bending strength of 7.3 MPa, and an elastic modulus of 13.4 GPa.

(Example 6)
This example is a heat treatment container similar to that of Example 5 except that an alumina long fiber having a fiber length of 5 mm was used. The ratio of the alumina long fibers to the maximum particle size of the inorganic material powder is 2.
The heat treatment container of this example had a porosity of 29.6%, a bending strength of 7.2 MPa, and an elastic modulus of 12.8 GPa.

(Example 7)
This example is a heat treatment container similar to that of Example 5 except that an alumina long fiber having a fiber length of 10 mm is used. The ratio of the alumina long fibers to the maximum particle size of the inorganic material powder is 4.
The heat treatment container of this example had a porosity of 30.6%, a bending strength of 6.5 MPa, and an elastic modulus of 10.5 GPa.

(Comparative Example 3)
This example is a heat treatment container similar to that of Example 5 except that alumina long fibers are not used.
The heat treatment container of this example had a porosity of 27.6%, a bending strength of 9.1 MPa, and an elastic modulus of 14.7 GPa.

(Comparative Example 4)
This example is a heat treatment container similar to that of Example 5 except that an alumina long fiber having a fiber length of 2 mm was used. The ratio of the long alumina fibers to the maximum particle size of the inorganic material powder is 0.8.
The heat treatment container of this example had a porosity of 29.2%, a bending strength of 7.6 MPa, and an elastic modulus of 11.9 GPa.

(Comparative Example 5)
This example is a heat treatment container similar to that of Example 5 except that an alumina long fiber having a fiber length of 15 mm was used. The ratio of the long alumina fibers to the maximum particle size of the inorganic material powder is 6.
The heat treatment container of this example had a porosity of 35.2%, a bending strength of 5.2 MPa, and an elastic modulus of 5.5 GPa.

[Evaluation]
As the evaluation of the heat treatment container of each example, the thermal shock resistance, the thermal shock damage resistance, the elastic modulus reduction rate and the moldability were evaluated in the same manner as described above. The evaluation results are shown in Table 2.

Similar to the results in Table 1, even when the maximum particle size of the inorganic material powder is changed, the alumina long fibers are longer than the maximum particle size, and the thermal shock resistance and thermal shock damage resistance are high and the decrease in elastic modulus is small. It can be confirmed that it has excellent thermal shock resistance and crack resistance.
It can be seen that Comparative Example 3 which does not contain alumina long fibers cannot relax the thermal shock as in Comparative Example 1. In Comparative Example 4, the thermal shock damage resistance is high and the elastic modulus decrease is small, but it is considered that the thermal shock is not sufficiently relaxed because the fiber length is short.

  Further, in Comparative Example 5 using the alumina long fiber having an excessively long fiber length, the bending strength of the side surface is low and the moldability is reduced to Δ. On the other hand, in each Example, all are evaluated as (circle). From this, it can be seen that if the fiber length of the alumina long fibers becomes excessively long, the fibers become entangled and become a lump, thereby reducing the moldability.

(Example 8)
This example is a heat treatment container similar to that of Example 5 except that the content of the alumina long fibers is 0.1 parts by mass. The ratio of the long alumina fibers to the maximum particle size of the inorganic material powder is 1.2.
The heat treatment container of this example had a porosity of 29.2%, a bending strength of 7.6 MPa, and an elastic modulus of 13.3 GPa.

Example 9
This example is a heat treatment container similar to that of Example 5, except that the content of the alumina long fibers is 0.5 parts by mass.
The heat treatment container of this example had a porosity of 32.3%, a bending strength of 6.2 MPa, and an elastic modulus of 12.5 GPa.

(Example 10)
This example is a heat treatment container similar to that of Example 5 except that the content of the alumina long fibers is 1 part by mass.
The heat treatment container of this example had a porosity of 35.0%, a bending strength of 5.6 MPa, and an elastic modulus of 11.8 GPa.

(Comparative Example 6)
This example is a heat treatment container similar to that of Example 5, except that the content of the alumina long fibers is 2 parts by mass.
The heat treatment container of this example had a porosity of 48.5%, a bending strength of 4.8 MPa, and an elastic modulus of 9.6 GPa.

(Comparative Example 7)
This example is a heat treatment container similar to that of Example 5 except that the content of the alumina long fibers is 0.05 parts by mass.
The heat treatment container of this example had a porosity of 28.2%, a bending strength of 8.6 MPa, and an elastic modulus of 14.6 GPa.

[Evaluation]
As the evaluation of the heat treatment container of each example, the thermal shock resistance, the thermal shock damage resistance, the elastic modulus reduction rate and the moldability were evaluated in the same manner as described above. The evaluation results are shown in Table 3. Table 3 also shows Example 5 and Comparative Example 3 similar to Example 5 except that no alumina long fiber was included.

In each Example, since the thermal shock resistance is high and the decrease in elastic modulus is small, it can be seen that the thermal shock resistance is excellent when the content ratio of the alumina long fibers is in the range of 0.1 parts by mass to 1 part by mass. Further, the thermal shock damage resistance increases as the alumina long fiber content increases, and the crack resistance increases as the amount of alumina long fibers increases.
However, in the case of 2 parts by mass of the alumina long fibers in Comparative Example 6, the thermal shock damage resistance is increased, but the bulk of the raw material increases with the alumina long fibers, so that the formability is reduced and the alumina long fibers are dispersed. When the lump increases, the portion becomes a defect, and the strength and thermal shock resistance are reduced. Also, the porosity is very high at 48.5%, and the erosion of the lithium-containing compound is increased.
Therefore, it turns out that the function as a heat processing container cannot be fulfilled when the content rate of an alumina long fiber increases excessively.

On the other hand, when the content of alumina long fibers in Comparative Example 7 is 0.05 parts by mass, both the thermal shock damage resistance and the elastic modulus decrease rate are reduced, and the thermal shock resistance test results are divided by 4 times. It can be seen that when the amount is small, the effect of the alumina continuous fiber that suppresses thermal shock relaxation and crack progress is reduced. The same applies to Comparative Example 3 in which there is no alumina long fiber.
As described above, it can be confirmed that the firing jig of each example is excellent in thermal shock resistance and crack resistance.

1: Firing body 10: Coarse grain part 11: Matrix part 12: Alumina long fiber 2: Heat treatment container 20: Tank-like part 21: Lid member

Claims (3)

Spinel powder mixed with cordierite powder, alumina powder and mullite powder, or cordierite powder mixed with alumina powder and mullite powder , inorganic material powder, and mass of the inorganic material powder It is made of a fired body of alumina long fibers having a fiber length of 1.2 to 5 times the maximum particle diameter of the inorganic material powder at a ratio of 0.1 to 1 parts by mass when the amount is 100 parts by mass. A heat treatment container (2) for a positive electrode active material of a lithium battery, which is characterized.   The heat treatment container for a positive electrode active material of a lithium battery according to claim 1, wherein the alumina long fibers have a fiber length of 1 to 10 mm. The inorganic material powder is composed of coarse particles of 500 μm or more and fine particles of 100 μm or less,
In any one of Claims 1-2 in which the said sintered body is comprised with the coarse-grain part which consists of the said coarse particle, and the matrix part which is formed from the said fine particle, and contains the said alumina continuous fiber. The heat processing container for positive electrode active materials of lithium battery of description.

Images