TWI488827B - Cover - Google Patents

Description

Cover

The present invention relates to a cover for powder baking which is excellent in thermal shock resistance and corrosion resistance.

The positive electrode material of the secondary electrode typified by a metal lithium battery, a lithium ion battery, a lithium polymer battery, or the like includes lithium cobaltate (LiCoO ₂ ), lithium manganate (LiMnO ₂ ), and lithium nickelate ( A lithium-containing transition metal composite oxide such as LiNiO ₂ ) or lithium iron phosphate (LiFePO ₄ ).

For example, in the case of producing lithium manganate which has been particularly demanded in recent years, a mixture of a lithium compound (lithium hydroxide or lithium nitrate) as a raw material and a manganese compound (manganese oxide, manganese hydroxide or manganese carbonate) is placed. The firing container (generally referred to as a jacket or a crucible) formed of a heat resistant ceramic material is fired in a temperature range of about 1000 ° C or lower in an oxygen atmosphere.

When lithium manganate is produced at the firing temperature, the lithium compound is melted during the firing, and the lithium element derived from the compound is evaporated under high temperature conditions, and the heat-resistant ceramic material constituting the container for firing is invaded. . Therefore, in order to produce a container for firing a positive electrode material such as a lithium ion battery, it is required to have high corrosion resistance for diffusion of the positive electrode material at the time of firing.

As a technique for improving the corrosion resistance of the diffusion of lithium, a technique for increasing the content of the magnesium oxide component has been disclosed (for example, Patent Document 1).

However, since the magnesium oxide component increases the thermal expansion coefficient of the cover, it is easy to cause cracks in the firing container during the forced cooling of the furnace temperature in the firing process of the positive electrode material, and the thermal shock resistance is low. The problem of low strength of the cover.

Leading patent documents: [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2003-165767

The object of the present invention is to solve the above problems and to provide an improvement in corrosion resistance of lithium diffusion due to a magnesium oxide component and an increase in thermal expansion coefficient of a sheath due to inclusion of a magnesium oxide component. In addition, it is possible to effectively avoid a coating for powder burning which is caused by a problem of low thermal shock resistance due to an increase in thermal expansion rate or a problem of low product strength.

The cover of the present invention which is prepared to solve the above problems is a cover for firing a lithium compound powder, which is characterized in that it is an aggregate and contains a spinel having a particle diameter of 1 mm or less and a particle diameter of 0.5 mm. The following magnesia, the composition ratio of the crystalline phase is: cordierite: periclase: spinel: corundum: mullite = 1: (0.1 ~ 0.7): (0.03 ~ 0.4): (0.01 ~ 0.15): (0.06~1.10).

In the invention described in the second aspect of the patent application, the thermal expansion coefficient of the substrate at 25 ° C to 1000 ° C is 5.0 × 10 ^-6 / ° C or less.

The invention described in the third aspect of the invention is the coating layer according to the first aspect of the invention, which has a coating layer having a good peeling property from the fired powder on the surface of the substrate.

The invention according to claim 4, wherein the coating layer contains at least one of zirconia, corundum, mullite, and spinel.

The cover for powder baking according to the present invention is a cover comprising cordierite having excellent thermal shock resistance as a main component, and the crystal layer contains periclase (MgO) and spinel (MgAl). ₂ O ₄ ) As an aggregate, it seeks to improve the corrosion resistance of lithium diffusion. From the viewpoint of corrosion resistance, it is preferable to select periclase (MgO) rather than spinel (MgAl ₂ O ₄ ), but the crystal of disintegration of the cristobalite in the crystal structure containing cordierite as a main component The Young's modulus is smaller than the Young's modulus after the spinel is dispersed. Therefore, from the viewpoint of ensuring strength, it is preferred to use a magnesium oxide component derived from spinel in combination. In the present invention, in particular, as the aggregate, a spinel having a particle diameter of 1 mm or less and a rhombohedral having a particle diameter of 0.5 mm or less, by making the composition ratio of these components in the crystal phase, cordierite : Periclase: Spinel = 1: (0.1 ~ 0.7): (0.03 ~ 0.4), and can ensure the best balance between corrosion resistance and thermal shock resistance and product strength for lithium diffusion. Furthermore, in the crystal phase, it is not only sought to be composed of cordierite: periclase: spinel: corundum = 1: (0.1 to 0.7): (0.03 to 0.4): (0.01 to 0.15). Adhesion prevention and by cordierite: periclase: spinel: corundum: mullite = 1: (0.1 ~ 0.7): (0.03 ~ 0.4): (0.01 ~ 0.15): (0.06 ~ 1.10) The product contains mullite and seeks strength. According to the present invention, it is possible to improve the corrosion resistance of the lithium diffusion caused by the magnesium oxide component, and to suppress the increase in the thermal expansion coefficient of the cover due to the inclusion of the magnesium oxide component. Further, it is possible to effectively avoid a coating for powder burning which is caused by a problem of low thermal shock resistance due to an increase in thermal expansion rate or a problem of low product strength.

When the positive electrode material and the cover are dissolved, it is difficult to remove the positive electrode material from the cover after firing, and the yield of the product is lowered, and a part of the surface of the cover (reactive substance of lithium or cobalt and a constituent component of the cover) adheres. In the positive electrode material to be produced, the positive electrode material cannot be used as a product, and the invention described in claim 3 can avoid the post-baking positive electrode by having a coating layer on the surface of the covering sleeve. The problem of the material adhering to the surface of the cover.

The present invention is suitable for use in a baking treatment of a composite oxide of one or more elements selected from cobalt, manganese, nickel, iron, and phosphorus, and a composite oxide of lithium, and is excellent in corrosion resistance, strength, and thermal shock resistance. Invented with the invention related to the cover.

Hereinafter, an embodiment of a cover suitable for powder baking of a lithium composite oxide according to the present invention will be described.

The cover according to the present invention, as an aggregate, contains spinel (MgAl ₂ O ₄ ) having a particle diameter of 1 mm or less, and a composition ratio of a crystal phase having a particle diameter of 0.5 mm or less, MgO, It is in cordierite: periclase: spinel: corundum: mullite = 1: (0.1~0.7): (0.03~0.4): (0.01~0.15): (0.06~1.10). The crystal phase composition ratio related to the present invention is an X-ray diffraction device (RINT 1100K) manufactured by Rigaku Electric Co., Ltd., at a tube voltage: 40 kV, a tube current: 20 mA, a divergence slit of 1°, and a scattered slit of 1°. The measurement was carried out under conditions of a light slit of 0.3 mm, and the integrated intensity was obtained by the JADE integrated intensity method.

As a composition of the crystal phase, when the composition ratio of the periclase (MgO) is 0.1 or less, the corrosion resistance to lithium is not preferable. When the composition ratio of the periclase (MgO) is 0.7 or more, the thermal shock resistance is lowered.

From the viewpoint of corrosion resistance to lithium, it is desirable that the magnesium oxide component in the crystal layer is all derived from periclase (MgO), but the coefficient of thermal expansion of periclase (MgO) is very large. Further, the Young's modulus between cordierite and periclase in crystallization is smaller than the Young's modulus between cordierite and spinel, and therefore, in the present invention, from the viewpoint of ensuring strength, spinel is used in combination. The magnesium oxide component derived from stone (MgAl ₂ O ₄ ).

Specifically, by selecting periclase (MgO) having a particle diameter of 0.5 mm or less, not only the characteristics excellent in corrosion resistance to lithium but also the absolute value of the thermal expansion length are reduced by making the particle diameter small. The suppression of the influence of the coefficient of thermal expansion is sought. Further, in the case of firing of the cover, the occurrence of microcracks is originally caused on the surface of MgO having a high expansion ratio, whereby the expansion ratio of the cover is also reduced.

Further, by selecting spinel (MgAl ₂ O ₄ ) having a particle diameter of 1 mm or less, clogging of fine particles around the spinel aggregate can be improved, and the strength of the product can be ensured. However, if the composition ratio of the spinel is 0.4 or more, the hot punching property is lowered, which is not preferable.

Further, in the crystal phase, corundum is contained by a composition ratio of cordierite: periclase: spinel: corundum = 1: (0.1 to 0.7): (0.03 to 0.4): (0.01 to 0.15), Not only to prevent adhesion and by cordierite: periclase: spinel: corundum: mullite = 1: (0.1 ~ 0.7): (0.03 ~ 0.4): (0.01 ~ 0.15): (0.06 ~ 1.10) The composition contains mullite and seeks to increase its strength. However, if the aforementioned composition of mullite is 1.1 or more, the corrosion resistance to lithium is not preferable.

Further, in order to ensure the moldability of the cover, in addition to the above components, an additive having plasticity is added as an external component. As an additive having plasticity, clay or polysaccharide can be used. Here, as an additive having plasticity, when a clay containing a high reactivity of SiO ₂ is used, it is preferable to use a corundum as a composition of a crystal phase. Thereby, the SiO ₂ component is used for the promotion of the mullite of the corundum, and the instability of the cover due to the presence of SiO ₂ can be eliminated. The amount of corundum added may be appropriately adjusted depending on the amount of SiO ₂ contained in the clay. However, if the composition ratio is 0.15 or more, the thermal shock resistance is lowered.

The coefficient of thermal expansion of the cover is preferably 5.0×10 ^-6 /° C or less. In the present invention, from the viewpoint of corrosion resistance, it contains spinel (MgAl ₂ O ₄ ) and periclase (MgO), and On the other hand, since it has a characteristic of a high coefficient of thermal expansion, in order to make the coefficient of thermal expansion within the above range, cordierite having a low coefficient of thermal expansion coexists, and the entire coefficient of thermal expansion is in the above range.

Moreover, from the viewpoint of corrosion resistance, the choice of periclase (MgO) is better than the selection of spinel (MgAl ₂ O ₄ ), but the Young's modulus between cordierite and periclase in the crystallization is sharp. Since the Young's modulus between the spar and the periclase is small, it is preferable to use a magnesium oxide component derived from the combination of spinel from the viewpoint of ensuring strength. In the present invention, in particular, as the aggregate, a spinel having a particle diameter of 1 mm or less and a rhombohedral having a particle diameter of 0.5 mm or less, by making the composition ratio of these components in the crystal phase, cordierite : Periclase: Spinel = 1: (0.1 ~ 0.7): (0.03 ~ 0.4), and can ensure the best balance between corrosion resistance and thermal shock resistance and product strength for lithium diffusion.

When the particle size of the periclase is 0.5 mm or less, it is possible to obtain a coating property on the surface of the MgO having a high thermal expansion coefficient at the time of firing the cover. The thermal expansion rate can form an optimum amount of microcracks. If the particle size of the periclase is too small, the microcracks are small, and the desired effect of lowering the coefficient of thermal expansion cannot be obtained. On the other hand, if the particle size of the periclase is too large, the microcracks become excessive, and the suspense of the product strength is not good.

In addition, if the positive electrode material and the cover are dissolved, it is difficult to remove the positive electrode material from the cover after firing, and the yield of the product is lowered, and a part of the surface of the cover (reactive substance of lithium or cobalt and the constituent components of the cover) The problem is that the positive electrode material cannot be used as a product, and in the present invention, by having a coating layer on the surface of the covering, the positive electrode material can be avoided after the firing. Set of surface problems.

Hereinafter, a method of manufacturing the cover of the present invention will be described.

The cover of the present invention is used as an aggregate in a cover after firing, and contains spinel (MgAl ₂ O ₄ ) having a particle diameter of 1 mm or less and periclite (MgO) having a particle diameter of 0.5 mm or less. The composition ratio of the crystal phase is contained in cordierite: periclase: spinel: corundum: mullite = 1: (0.1 ~ 0.7): (0.03 ~ 0.4): (0.01 ~ 0.15): (0.06 ~ 1.10) Within the range, the mixture of each raw material is kneaded and kneaded.

The coating after the baking is further added with a molding aid in a mixture to be a predetermined composition ratio, and is mixed in a water or an organic solvent in a wet manner by a stirrer or the like. As a forming aid, it is preferred to use high purity clay. By using high-purity clay, the problem of forming a glass layer from impurities contained in the clay can be avoided.

Further, as the raw material powder of the periclite, it is preferred to use a mineral having a pericloid crystal structure having a particle size range of from 10 to 99% by mass and a purity of 98% by mass. As the raw material powder of the spinel, it is preferred to use a mineral having a particle size range of 10 to 99% by mass and a purity of 98% by mass or more. Each of the raw material powders may be subjected to a pulverization treatment before use to adjust to a predetermined average particle diameter.

Next, the mixture of the niobium raw materials is formed (for example, press-formed by a friction press or the like) and dried (for example, naturally dried), and then fired. The firing temperature and time can be appropriately set to a suitable temperature and time, for example, 1300 ° C to 1420 ° C, more preferably 1330 ° C to 1380 ° C for several hours, and more preferably 2 hours to 5 hours for firing. In order to prevent the decomposition of cordierite, the firing temperature is below 1420 °C.

In order to avoid the problem that the positive electrode material after the baking adheres to the covering, it is preferable to form the coating layer on the specific surface of the molded body obtained as described above. As the raw material of the coating layer, at least one of spinel, mullite, corundum, and zirconia may be used, and the construction method may be a burnt coating or a spray coating.

[Preferred Embodiment for Carrying Out the Invention]

[Examples 1 to 4, Comparative Examples 1 to 5]

The mixture of the respective raw materials was kneaded and fired to prepare a sample having a composition ratio shown in Table 1 (200 mm × 200 mm, thickness: 10 mm). The magnesium oxide raw material used is a substance having a purity of 99% or more. After PVA was added to the molding system, it was carried out by hydraulic press molding, and the firing was carried out at 1,350 °C.

(crystal phase composition ratio)

Each of the samples after the calcination was measured under the following conditions using an X-ray diffraction apparatus (RINT 1100K) manufactured by Rigaku Electric Co., Ltd., and the crystal phase composition ratio was examined.

Tube voltage: 40 kV, tube current: 20 mA, divergence slit 1°, scattered slit 1°, and light-slit slit 0.3 mm. The integrated intensity is obtained by the JADE integrated intensity method.

(thermal shock evaluation)

The test piece (120 × 120 × 11 t) cut out from the obtained sample was heated at 200 ° C for 1 hour, and the furnace body of the thermal shock furnace was pulled up and put into water. Thereafter, the heating temperature was gradually increased every 100 degrees, and the temperature at which cracks occurred in the test piece was measured and evaluated.

(bending strength evaluation)

It is based on the JIS cell R1601.

(Lithium resistance evaluation)

The obtained test piece (20×20×5t) cut out from each sample and 5 g of LiCO ₂ and 5 g of MnO _{2 were} placed in an alumina crucible, and kept at 900 ° C for 5 hours in the atmosphere for one cycle, and repeated. . The size of the test piece before and after the heating was measured, and the number of times the change in the thickness of the test piece due to the reaction was 10%.

(Examples 1 to 4)

Included in cordierite: periclase: spinel: corundum: mullite = 1: (0.1~0.7): (0.03~0.4): (0.01~0.15): (0.06~1.10) 1 to 4, all show excellent lithium reactivity. Further, the coefficient of thermal expansion is small, and the bending strength and the thermal shock resistance also show good values.

(Comparative examples 1 to 3)

As a result of the inclusion of periclase or spinel in an excess ratio, the cordierite content ratio is reduced. In either case, the coefficient of thermal expansion is large, and the thermal shock resistance is problematic. The bending strength is also low, which is not good from the strength surface.

(Comparative Example 4)

In the case where the mullite is contained in an excess ratio, the cordierite content ratio is reduced. The coefficient of thermal expansion is large, and the thermal shock resistance is problematic. Lithium resistance is also poor.

(Comparative Example 5)

In the case of not containing periclase and spinel, lithium reactivity is problematic.

The mixture of the respective raw materials was kneaded and fired to obtain a sample (200 mm × 200 mm, thickness: 10 mm) having the respective composition ratios shown in Table 2 and the aggregate diameter. The magnesium oxide raw material used is a substance having a purity of 99% or more. After PVA was added to the molding system, it was carried out by hydraulic press molding, and the firing was carried out at 1,350 °C.

(crystal phase composition ratio)

Each of the samples after the calcination was measured under the following conditions using an X-ray diffraction apparatus (RINT 1100K) manufactured by Rigaku Electric Co., Ltd., and the crystal phase composition ratio was examined.

Tube voltage: 40 kV, tube current: 20 mA, divergence slit 1°, scattered slit 1°, and light-slit slit 0.3 mm. The integrated intensity is obtained by the JADE integrated intensity method.

(thermal shock evaluation)

The test piece (120 × 120 × 11 t) cut out from the obtained sample was heated at 200 ° C for 1 hour, and the furnace body of the thermal shock furnace was pulled up and put into water. Thereafter, the heating temperature was gradually increased every 100 degrees, and the temperature at which cracks occurred in the test piece was measured and evaluated.

(bending strength evaluation)

It is based on the JIS cell R1601.

(Lithium resistance evaluation)

The obtained test piece (20×20×5t) cut out from each sample and 5 g of LiCO ₂ and 5 g of MnO _{2 were} placed in an alumina crucible, and kept at 900 ° C for 5 hours in the atmosphere for one cycle, and repeated. . The size of the test piece before and after the heating was measured, and the number of times the change in the thickness of the test piece due to the reaction was 10%.

(Examples 5 to 7)

As the aggregate, it includes an example of spinel having a particle diameter of 1 mm or less and periclase having a particle diameter of 0.5 mm or less. Both the bending strength and the thermal shock resistance show good values.

(Comparative Example 6)

As the aggregate, it includes an example of spinel having a particle diameter of 1 mm or more and periclase having a particle diameter of 0.5 mm or more. Compared to Examples 5 to 7, bending strength or thermal shock resistance was observed.

Claims (4)

A cover for firing a lithium compound powder, characterized in that it is a bone material and contains a spinel having a particle diameter of 1 mm or less, and a composition ratio of a crystal phase having a particle diameter of 0.5 mm or less is 堇Bluestone: Periclite: Spinel: Corundum: Mullite = 1: (0.1 ~ 0.7): (0.03 ~ 0.4): (0.01 ~ 0.15): (0.06 ~ 1.10). For example, the cover of the first application of the patent scope, wherein the thermal expansion coefficient of the substrate is from 5 ° C to 1000 ° C is 5.0 × 10 ^-6 / ° C or less. The cover of the first aspect of the patent application, wherein the surface of the substrate has a coating layer having good peelability from the fired powder. The cover of claim 3, wherein the coating layer contains at least one of zirconia, corundum, mullite, and spinel.