JP2005257171A - Baking container, and manufacturing method of lithium-transition metal composite oxide for lithium secondary battery electrode material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide mass production of lithium-transition metal composite oxide for a lithium secondary battery electrode material of certain high quality by baking an object to be baked containing a lithium compound and a transition metal compound. <P>SOLUTION: The lithium-transition metal composite oxide for the lithium secondary battery electrode material is manufactured by housing the object to be baked containing the lithium compound and the transition metal compound in the baking container having a vent hole in a part other than a top face, and baking it. Since the vent hole is in a part other than the top face, intrusion of impurities such as foreign matter, bulky particles, or the like during baking is prevented. Since atmospheric gas can be smoothly communicated from a vent part, the lithium-transition metal composite oxide satisfying required performance in a high level for lithium secondary battery application can be industrially massively produced at constant high quality. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention provides a firing container suitable as a firing container for producing a lithium transition metal composite oxide for a lithium secondary battery electrode material by firing an object to be fired containing a lithium compound and a transition metal compound, and the firing container. The present invention relates to a method for producing a lithium transition metal composite oxide for a lithium secondary battery electrode material used.

  Conventionally, lithium transition metal composite oxides are known as electrode materials for lithium secondary batteries. Lithium transition metal composite oxides for lithium secondary battery electrode materials are manufactured by firing and compounding a mixture of a lithium compound and a transition metal compound or optionally other metal compounds (for example, patents). Reference 1).

  Lithium secondary batteries are used over a long period of time and are repeatedly charged and discharged for various purposes, so various characteristics such as cycle characteristics and storage characteristics are required. Capacity is being demanded. On the other hand, industrial mass production of lithium secondary batteries is required as consumer electronics such as mobile phones and personal computers and the demand for lithium secondary batteries for vehicles are rapidly expanding.

For this reason, even in the industrial production of lithium transition metal composite oxides as electrode materials for lithium secondary batteries, high-quality products required for lithium secondary batteries must always be mass-produced with constant quality. Is becoming required.
Japanese Patent No. 3,334,179

  However, in the past, sufficient studies have not been made on the improvement of an industrial firing process for mass production of a constant high quality lithium transition metal composite oxide for lithium secondary battery electrode materials.

  The present invention has been made in view of the above-described conventional situation, and has a high quality lithium transition metal composite oxide for lithium secondary battery electrode material that is made constant by firing an object to be fired containing a lithium compound and a transition metal compound. It is an object of the present invention to provide a firing container capable of industrially mass-producing a product, and a method for producing a lithium transition metal composite oxide for a lithium secondary battery electrode material using the firing container.

  The inventors have determined that the firing conditions for producing a lithium transition metal composite oxide for a lithium secondary battery electrode material by firing a to-be-fired object containing a lithium compound and a transition metal compound are the lithium transition metal composite oxide. As a result, the following two findings were obtained.

  (1) During firing, foreign materials such as metals and coarse particles are mixed into the material to be fired from the furnace material and firing atmosphere, and remain as impurities in the resulting composite oxide. In an electrode formed using such a complex oxide containing impurities, dendrite is generated due to metal impurities, and coarse particles protrude to the electrode surface. This causes damage to the separator, short-circuiting, and Reduce safety.

  (2) If the circulation of the atmospheric gas during firing is insufficient, a desired crystal phase cannot be formed, and defects occur in the crystal structure of the resulting composite oxide. For example, if it is necessary to incorporate oxygen into the crystal during firing, but oxygen does not spread due to insufficient circulation of the atmospheric gas, the resulting composite oxide has oxygen deficient portions due to lack of oxygen, and the desired crystal phase Cannot be obtained. Conversely, if you want to release oxygen from the object to be fired during firing (when the raw material contains more oxygen than the desired amount of oxygen), there must be enough inert gas to drive out the oxygen. Although it is desirable to calcinate under pressure, if the gas flow is insufficient, the desired crystal phase due to excess oxygen cannot be obtained. If a desired crystal phase cannot be obtained and the complex oxide has a defective crystal structure, the cycle characteristics of a lithium secondary battery using the complex oxide are liable to deteriorate.

  As a result of further diligent investigations based on the above knowledge, the present inventors have devised the shape of the baking container to suppress the mixing of impurities such as foreign matters and coarse particles during baking, and smoothly distribute the atmospheric gas. Thus, the present inventors have found that a lithium transition metal composite oxide satisfying the required performance at a high level for lithium secondary battery applications can be industrially mass-produced with a certain high quality, and the present invention has been completed.

  That is, the firing container of the present invention is a firing container for firing an object to be fired containing a lithium compound and a transition metal compound, and has a ventilation portion in addition to the upper surface.

  This firing container has a ventilation part in addition to the upper surface, so that impurities such as foreign matter and coarse particles are prevented from being mixed into the object to be fired during firing, and the atmosphere gas is smoothly circulated from this ventilation part. Therefore, it is possible to industrially mass-produce a lithium transition metal composite oxide satisfying a required performance at a high level for use in a lithium secondary battery with a certain high quality.

  The firing container of the present invention preferably has a ventilation portion on the side surface (Claim 2), and in particular, a container body whose upper surface is opened so as to put in and out the object to be fired from the upper surface, and a lid body detachably attached to the container body. The vent is provided on the side surface of the container body, and the lid body covers the upper surface of the container body and has a size that protrudes laterally from the side surface of the container body. It is preferable that a canopy portion and a hanging portion that hangs down from the periphery of the canopy portion are provided, and the hanging portion is spaced apart from the side portion of the container main body to the outer side (Claim 3).

  It is preferable that the lower end of the hanging portion hangs downward from the lower end of the ventilation portion of the container body (Claim 4) and has a size facing the entire ventilation portion (Claim 5).

  The ratio of the opening area of the ventilation portion to the area of the side surface portion of the container body is 1% or more and 20% or less (Claim 6), and the container body has at least one pair of opposite side surfaces, It is preferable that a ventilation part is provided in a pair of opposing side surfaces (Claim 7).

  In the firing container of the present invention, the distance between the ventilation part of the container body and the hanging part of the lid body is preferably 1 mm or more and 50 mm or less (Claim 8). It is preferable that the crossing corner between the canopy portion and the hanging portion of the lid body is formed of a concave curved surface or an inclined surface.

The firing container of the present invention is preferably made of at least one metal oxide selected from the group consisting of SiO ₂ , Al ₂ O ₃ , ZrO ₂ , MgO, SiC, and CaO. ), The porosity is preferably 70% or less (claim 11).

  The firing container of the present invention is suitable as a firing container for producing a lithium transition metal composite oxide for a lithium secondary battery electrode material by firing an object to be fired (claim 12).

  The method for producing a lithium transition metal composite oxide for a lithium secondary battery electrode material according to the present invention is for a lithium secondary battery electrode material by containing a fired product containing a lithium compound and a transition metal compound in a firing container and firing. In the method for producing a lithium transition metal composite oxide, the firing container according to the present invention is used as the firing container, and contamination of impurities such as foreign matters and coarse particles during firing is suppressed. At the same time, it is possible to industrially mass-produce lithium transition metal composite oxides with a certain high quality by smoothly circulating the atmospheric gas and satisfying the required performance at a high level for lithium secondary battery applications.

  According to the method for producing a lithium transition metal composite oxide for a firing container and a lithium secondary battery electrode material of the present invention, a lithium transition metal composite oxide satisfying a required performance at a high level for use in a lithium secondary battery can be produced at a constant high level. It can be mass produced industrially with quality.

  Therefore, the lithium transition metal composite oxide for a lithium secondary battery electrode material produced according to the present invention provides a high-performance lithium secondary battery excellent in cycle characteristics, storage characteristics, safety, and the like.

Hereinafter, embodiments of the present invention will be described in detail.
[Baking container]
First, the firing container of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a container body and a lid body showing an embodiment of the firing container of the present invention, FIG. 2 is a front view of the container body, and FIG. 3 is a state in which the container body of this firing container is covered with a lid body FIG.

  The firing container 1 shown in the present embodiment is composed of a container body 2 whose upper surface is opened so that an object to be fired can be taken in and out from the upper surface, and a lid 3 detachably attached to the container body 2.

  The container body 2 has a rectangular bottom surface 20 and rectangular side wall portions 21 to 24 rising from four sides of the bottom surface 20. Ventilation portions 21A to 24A made up of cutout portions are provided on the upper end sides of the side wall portions 21 to 24. In the present embodiment, the ventilation portions 21 </ b> A to 24 </ b> A have a rectangular shape when viewed from the front of the container main body as viewed from the side wall surface of the container main body 2. Ventilation parts 21A-24A are arranged near the middle in the longitudinal direction (width direction) of side wall parts 21-24.

  The ratio of the opening area of the ventilation parts 21A to 24A to the area of the side wall parts 21 to 24 of the container body 2 (including the area of the ventilation part), that is, the area of the side wall part 21 of the container body 2 in FIG. The ratio of the opening area (A × B) of the ventilation portion 21A to the ventilation portion (hereinafter sometimes referred to as “side opening area ratio”) is usually 1% or more, preferably 5% or more, more preferably 7% or more. Usually, it is 20% or less, preferably 15% or less. If this side opening area ratio is too small, the circulation of the atmospheric gas during firing becomes insufficient, and a lithium transition metal composite oxide having a desired crystal structure may not be obtained. On the other hand, if the size is too large, the material to be fired cannot be filled in the portion of the side of the container body where the vents are present. The amount of the fired product is small, and the total amount of the material to be fired packed in the furnace or kiln used for firing is reduced, leading to an increase in firing cost.

  In addition, although the vertical and horizontal lengths (C in FIG. 2) of the container body 2 are not particularly defined, the vertical and horizontal lengths are usually 2 m or less in consideration of the cost for producing the baking container. The height of the container body 2 (D in FIG. 2) is not particularly specified, but is usually 2 m or less in consideration of the cost of producing the firing container, and the height of the material to be fired to be packed in the container body 2 is determined by the ventilation portions 21A to 21A. What is necessary is just to make it the height which added the depth (B of FIG. 2) of 24 A of notches.

  The length (A in FIG. 2) on the upper side of the vent portions 21A to 24A of the container body 2 is the horizontal length of the side wall portions 21 to 24 where the notches of the vent portions 21A to 24A of the container body 2 are present (C in FIG. 2). 30% or more and 90% or less. If this ratio is smaller than 30%, the depth of the notches (B in FIG. 2) of the ventilation portions 21A to 24A for making the ventilation portion of a predetermined size increases, so that the container body 2 can be packed. The filling amount of the fired product is reduced, leading to an increase in firing cost. When this ratio is greater than 90%, the portion of the container body 2 that supports the lid 3 and the stacked baking containers is reduced, and the container body 2 is damaged by the weight of the lid 3 and the weight of the stacked baking containers. There is a risk.

  What is necessary is just to determine the depth (B of FIG. 2) of the notch of ventilation part 21A-24A from the area of the required ventilation part. The depths of the cutouts of the ventilation portions 21A to 24A provided in the side wall portions 21 to 24 of the container body 2 are usually the same depth.

  The shape of the ventilation part is not limited to the rectangular shape as shown in FIGS. In the case of a trapezoid, the ratio of the length of the upper base and the lower base is arbitrary. Further, the ventilation portion is not necessarily limited to the notch, and may be a hole penetrating in the thickness direction of the side wall portion of the container body. A plurality of ventilation portions may be provided on one side wall portion of the container body. However, from the viewpoint of forming the ventilation part in the production of the baking container and the strength and stability of the container body having the ventilation part, the ventilation part was cut out from the upper side of the side wall of the container body as shown in FIGS. A notch shape is preferred.

  As shown in FIGS. 1 to 3, the ventilation portion is preferably provided on the opposite side wall portion when the container body has the opposite side wall portion. That is, in FIGS. 1 to 3, the container body 2 has two pairs of opposite side wall portions, that is, a side wall portion 21 and a side wall portion 23, and a side wall portion 22 and a side wall portion 24. In such a container main body 2, it is preferable that a ventilation part is provided in at least one pair of opposing side wall parts, preferably two pairs of opposing side wall parts. By providing the ventilation portions on the side wall portions facing each other in this manner, the atmosphere in the firing container is uniformly replaced with a desired firing atmosphere during firing, and a uniform single-phase crystalline oxide can be obtained. . On the other hand, if a ventilation part is not provided in the opposite side wall part, the part by which atmosphere substitution is not carried out uniformly will generate | occur | produce in a container main body, and it will be difficult to obtain a uniform single phase.

As the material of the container body 2, since the firing temperature of the material to be fired according to the present invention is usually 300 ° C. or higher and 1300 ° C. or lower as described later, the reaction resistance with the material to be fired is excellent at this temperature. The material is required not to crack at this temperature. Such a material is preferably at least one metal oxide or composite oxide selected from the group consisting of SiO ₂ , Al ₂ O ₃ , ZrO ₂ , MgO, SiC, and CaO.

  Further, the porosity of the container body 2 is preferably 70% or less. If the porosity of the container body 2 is greater than 70%, the static bending strength becomes weak, and the thickness of the container body for obtaining the required strength increases, leading to an increase in cost. On the other hand, if the porosity is higher than 70%, the surface roughness of the container main body becomes high, so that it is difficult to take out the lithium transition metal composite oxide after firing from the container main body. That is, usually, after firing, the container body is inverted and the fired product is taken out. At this time, if the porosity of the container body is low and the surface is smooth, the baked product is less likely to adhere to the inner wall surface of the container body and can be taken out immediately even if it adheres, but the porosity is large and the surface roughness is high. And a baked product adheres to an inner wall surface, and a baked product is difficult to take out.

  The lower limit of the porosity of the container body 2 is not particularly specified, but when the object to be fired is packed in the container body and heated with a heating device, the temperature is raised or lowered at a rate of 100 ° C. or more per minute. It is preferably 2% or more. That is, if the porosity is less than 2%, the container main body 2 may be cracked due to thermal shock during temperature increase or decrease.

  Here, the porosity is expressed as a percentage in terms of the specific gravity obtained from the density when there is no pore determined from the composition of the material, and the actual specific gravity as a numerator. The same applies to the porosity of the lid described later.

  The thickness of the container body 2 is appropriately determined so as to obtain the required strength according to its material and porosity, but is usually about 1 to 50 mm.

  The lid 3 is provided with a canopy portion 30 that covers the upper surface of the container body 2 and projects to the side of the side surface of the container body 2, and hanging portions 31 to 34 that hang from the periphery of the canopy portion 30. It becomes.

  The hanging parts 31 to 34 preferably have a size that faces the entirety of the ventilation parts 21A to 24A of the container body 2, and the lower ends thereof are preferably suspended below the lower ends of the ventilation parts 21A to 24A. In particular, the hanging parts 31 to 34 are preferably 1 mm or more, particularly 3 mm or more and 5 cm or less, particularly 3 cm or less, downward from the lower ends of the ventilation parts 21A to 24A (that is, in FIG. 3, E is 1 mm or more). In particular, it is preferably 3 mm or more and 5 cm or less, particularly 3 cm or less, and in the following, this E may be referred to as “hanging width”.

  If the drooping width E is smaller than 1 mm, there is a risk that foreign materials introduced from the furnace material and the firing atmosphere of the heating apparatus charged with the firing container 1 will enter the firing container from the vent, and if it exceeds 5 cm, the cost of the lid will increase. Leads to.

  Further, if the area of the drooping portion (F × G in FIG. 3) covering the container body of the lid is larger than the opening area (A × B in FIG. 2) of the ventilation portion of the side wall portion of the container body, The foreign material introduced from the material and the firing atmosphere is preferable because it is less likely to enter the firing container from the ventilation portion.

  Note that the lower ends of the hanging portions 31 to 34 of the lid body 3 must be above the lower end surface (bottom surface) of the container body 2 for the circulation of the atmospheric gas into the firing container 1.

  Further, the hanging parts 31 to 34 of the lid body 3 are spaced laterally outward from the side wall parts 21 to 24 of the container body 2, and as shown in FIG. 3, between the hanging parts 31 to 34 and the side wall parts 21 to 24. A gap is preferably formed, and the gap t (hereinafter sometimes referred to as “lid / body gap”) is 1 mm or more, particularly 3 mm or more, 5 cm or less, particularly 3 cm or less. Is preferred. If this gap is too small, the circulation of the atmospheric gas into the firing container becomes insufficient, and a lithium transition metal composite oxide having a desired crystal structure may not be obtained. On the other hand, if the size is too large, the outer size of the lid becomes large, and the number of stuffed furnaces and kilns used for firing decreases, leading to an increase in firing costs.

  Further, as shown in FIG. 4A, the crossing corner 30A between the canopy 30 and the hanging parts 31 to 34 of the lid 3 is preferably a concave curved surface, and the radius of curvature of the concave curved surface is as described above. As described above, the gap t between the side wall portion of the container body and the hanging portion of the lid body is 1 mm or more, preferably 3 mm or more, so that it is inevitably 1 mm or more, preferably 3 mm or more. When the crossing corner 30A of the lid 3 is not a concave curved surface, as shown in FIGS. 6 (a) and 6 (b), when the lid 3 applied to the container body 2 is displaced due to the furnace being inclined, Although some of the ventilation portions of the side walls of the container body 2 may be blocked by the lid 3 that is in close contact with the container body 2 (X in FIG. 6B), When the crossing corner 30A is a concave curved surface, as shown in FIG. 4B, even when the lid 3 is displaced, the lid 3 is not in close contact with the side wall of the container main body 2, and The ventilation part of the side wall part is not blocked by the lid 3 and good ventilation can be achieved (Y in FIG. 4B). The upper limit of the radius of curvature of the concave curved surface of the intersection corner 30A is not particularly defined. As shown in FIGS. 5 (a) and 5 (b), even if the crossing corner 30A of the lid 3 is an inclined surface, the same effect as that of a concave curved surface can be obtained. The corner portion of the surface of the lid 3 that does not contact the container body 2 may be a right angle, a concave curved surface, or an inclined surface.

The material of the lid 3 can be equivalent to the material of the container body _{2, SiO 2, Al 2 O} 3, ZrO 2, MgO, SiC, and at least one metal oxide or composite selected from the group consisting of CaO Although an oxide is preferable, it is not always necessary to use the same material as that of the container body, and a material having a lower cost than the container body can be used. Specifically, even when the material of the container main body is mainly composed of SiC, the material of the lid body can be mainly composed of lower cost Al ₂ O ₃ .

  The porosity of the lid 3 is preferably 70% or less. If the porosity is higher than 70%, the static bending strength is reduced as in the case of the container body, so that the necessary thickness of the lid is increased and the cost is increased. The lower limit of the porosity of the lid is not particularly defined, but for the same reason as the lower limit of the porosity of the container body described above, the temperature is raised and lowered at a rate of 100 ° C. or more per minute when the object to be fired is fired. In such a case, the content is preferably 2% or more.

  The thickness of the lid 3 is also appropriately determined so as to obtain the required strength according to the material and the porosity as in the case of the thickness of the container body 2, but is usually about 1 to 50 mm.

[Method for producing lithium transition metal composite oxide for lithium secondary battery electrode material]
Next, the manufacturing method of the lithium transition metal complex oxide for lithium secondary battery electrode materials of this invention using such a baking container is demonstrated.

<Starting material>
Examples of the lithium compound used as a starting material in the present invention include Li ₂ CO ₃ , LiNO ₃ , LiOH, LiOH · H ₂ O, LiH, LiCl, LiF, LiBr, LiI, Li ₂ O, lithium sulfate, lithium nitrite, Examples include lithium acetate, lithium dicarboxylate, lithium citrate, fatty acid lithium, alkyl lithium, lithium halide and the like. Among these lithium compounds, water-soluble lithium compounds such as Li ₂ CO ₃ , LiNO ₃ , LiOH · H ₂ O, and lithium acetate are preferable. For example, these water-soluble compounds can be easily dissolved in a slurry using water as a dispersion medium to prepare a calcined raw material to easily obtain a lithium transition metal composite oxide having good characteristics. Moreover, the lithium compound which does not contain a nitrogen atom or a sulfur atom is preferable at the point which does not generate | occur | produce harmful substances, such as NOX and SOX, in the baking process. The most preferable lithium raw material is LiOH.H ₂ O which is also water-soluble and does not contain a nitrogen atom or a sulfur atom. These lithium compounds may be used individually by 1 type, and may use multiple types together.

  Examples of the transition metal compound used as a starting material include a manganese compound, a nickel compound, and a cobalt compound.

Specifically, manganese compounds such as Mn ₂ O ₃ , MnO ₂ , Mn ₃ O ₄ , manganese oxides, MnCO ₃ , Mn (NO ₃ ) ₂ , MnSO ₄ , manganese acetate, manganese dicarboxylate, manganese citrate And manganese salts such as fatty acid manganese, halides such as oxyhydroxide and manganese chloride, and the like. Among these manganese compounds, Mn ₂ O ₃ and Mn ₃ O ₄ are preferable because they have valences close to the manganese oxidation number of the composite oxide that is the final target product. Further, Mn ₂ O ₃ is particularly preferable from the viewpoint of being inexpensively available as an industrial raw material and having a high reactivity. As Mn ₂ O ₃ , a material prepared by heat-treating a compound such as MnCO ₃ or MnO ₂ may be used. These manganese compounds may be used individually by 1 type, and may use multiple types together.

Examples of nickel compounds include Ni (OH) ₂ , NiO, NiOOH, NiCO ₃ .2Ni (OH) ₂ .4H ₂ O, NiC ₂ O ₄ .2H ₂ O, Ni (NO ₃ ) ₂ .6H ₂ O, NiSO _4. , NiSO ₄ .6H ₂ O, fatty acid nickel, nickel halide and the like. Among these, Ni (OH) ₂ , NiO, NiOOH, NiCO ₃ .2Ni (OH) ₂ .4H that do not contain nitrogen atoms or sulfur atoms in that no harmful substances such as NOX and SOX are generated during the firing treatment. Nickel compounds such as ₂ O and NiC ₂ O ₄ .2H ₂ O are preferred. Further, Ni (OH) ₂ , NiO, and NiOOH are particularly preferable from the viewpoint of being available as an industrial raw material at low cost and having high reactivity. These nickel compounds may be used individually by 1 type, and may use multiple types together.

Cobalt compounds include Co (OH) ₂ , CoO, Co ₂ O ₃ , Co ₃ O ₄ , Co (OCOCH ₃ ) ₂ .4H ₂ O, CoCl ₂ , Co (NO ₃ ) ₂ .6H ₂ O, Co ( SO ₄ ) ₂ · 7H ₂ O and the like. Among these, Co (OH) ₂ , CoO, Co ₂ O ₃ , and Co ₃ O ₄ are preferable in that no harmful substances such as NOX and SOX are generated during the firing process, and more preferably, they are industrially available at low cost. It is Co (OH) _{2 in} that it can be made and has high reactivity. These cobalt compounds may be used individually by 1 type, and may use multiple types together.

  In the case of introducing an element for substituting these transition metals, the source of the substitution element (hereinafter referred to as “substitution metal compound”) includes oxyhydroxides, oxides, hydroxides and halides of substitutional metals. And inorganic acid salts such as carbonates, nitrates and sulfates, and organic acid salts such as acetates, oxalates, dicarboxylates and fatty acid salts.

  In addition, as a starting material, in addition to the metal compound as described above, the metal itself may be used as in the case of the coprecipitation method described later.

<Preparation of object to be fired>
The lithium transition metal composite oxide for lithium secondary battery electrode material was prepared by the following method, for example, using the above-described lithium compound, transition metal compound, and substituted metal compound used as necessary as a starting material. It can manufacture by baking a to-be-fired thing.
(1) The above-mentioned raw material compounds are mixed in a dry method at a ratio corresponding to a desired ratio (dry mixing method).
(2) After mixing the raw material compounds described above in a wet manner (that is, in a slurry), this is spray dried (spray drying method).
In addition, when mixing by a wet, the lithium compound may not be contained in a slurry, but the spray-dried material and lithium compound of the slurry of other compounds may be dry-mixed. When mixing in a dry process to make a raw material for firing, calcination, crushing, and main firing are performed in this order, and firing is performed a plurality of times, and a crushing step is performed between the two firings to generate impurities. Is preferable in terms of suppressing the above and improving the capacity.
(3) An aqueous solution or colloidal solution containing a metal compound in a dissolved or colloidal state is prepared, and then the pH is controlled to produce a coprecipitate containing these two or more metals. In this case, preferably, a coprecipitate of a metal compound other than the lithium compound is generated, and this is mixed with the lithium compound to obtain a fired product (coprecipitation method).

  Hereinafter, each method (1), (2) and (3) will be described in more detail.

  In the following description, the average particle size of the mixed and pulverized product, the average particle size of the solid content in the slurry, the average particle size of the granulated particles after spray drying, and the average particle size of the lithium transition metal composite oxide Is measured by a known laser diffraction / scattering particle size distribution analyzer. The measurement principle of this method is as follows. That is, a sample solution obtained by dispersing slurry or powder in a dispersion medium is irradiated with laser light, and scattered light that is incident on the particles and scattered (diffracted) is detected by a detector. The scattering angle θ (angle between the incident direction and the scattering direction) of the detected scattered light is forward scattering (0 <θ <90 °) for large particles, and side scattering or backscattering (90 for small particles). ° <θ <180 °). From the measured angular distribution value, the particle size distribution is calculated using information such as the incident light wavelength and the refractive index of the particles. Further, the average particle size is calculated from the obtained particle size distribution. As a dispersion medium used in the measurement, for example, an aqueous 0.1 wt% sodium hexametaphosphate solution can be mentioned.

(1) Dry mixing method A lithium compound, a transition metal compound, and a substituted metal compound used as necessary are mixed in a dry method at a ratio corresponding to a desired ratio, and the mixture is pulverized in a dry pulverizer. Mixing and grinding may be performed simultaneously.

  Examples of the dry pulverizer include a ball mill, a jet mill, and a pin mill. Usually, the degree of pulverization of the mixture is such that the particle size is preferably 0.1 μm or more, more preferably 1 μm or more, preferably 100 μm or less, more preferably 50 μm or less.

  What was dry-mixed and pulverized in this way is used as the material to be fired in the next firing step.

(2) Spray drying method First, raw material compounds are mixed in a wet process. At this time, various organic solvents and aqueous solvents can be used as the dispersion medium used for preparing the slurry, but water is preferred.

  Total weight ratio of lithium compound, transition metal compound and optionally substituted metal compound to the weight of the entire slurry (if the slurry does not contain a lithium compound, the transition metal compound and, if necessary, the weight of the entire slurry The total weight ratio of substituted metal compounds used in the above is usually 10% by weight or more, preferably 12.5% by weight or more, and usually 50% by weight or less, preferably 35% by weight or less. When this weight ratio is less than the above range, the slurry concentration is extremely dilute, so that the spherical particles generated by spray drying become unnecessarily small or easily broken. On the other hand, when the slurry concentration exceeds the above range, it becomes difficult to maintain the uniformity of the slurry.

  The average particle size of the solid matter in the slurry is usually 2 μm or less, preferably 1 μm or less, more preferably 0.5 μm or less. When the average particle size of the solid matter in the slurry is too large, not only the reactivity in the firing step is lowered, but also the sphericity is lowered and the final powder filling density tends to be lowered. This tendency becomes particularly remarkable when trying to produce granulated particles having an average particle diameter of 50 μm or less. Further, making particles smaller than necessary leads to an increase in pulverization cost, so that the average particle size of the solid is usually 0.01 μm or more, preferably 0.05 μm or more, and more preferably 0.1 μm or more.

  As a method for controlling the average particle size of the solid matter in the slurry, the raw material compound is preliminarily dry pulverized by a ball mill, a jet mill, etc., and this is dispersed in a dispersion medium by stirring, etc., the raw material compound is stirred in a dispersion medium, etc. And a method of performing wet pulverization using a medium stirring pulverizer, etc. after dispersion, and a method of performing wet pulverization using a medium stirring pulverizer after dispersing the raw material compound in a dispersion medium. It is preferable to use it.

  The viscosity of the slurry is usually 50 mPa · s or more, preferably 100 mPa · s or more, particularly preferably 200 mPa · s or more, usually 3000 mPa · s or less, preferably 2000 mPa · s or less, particularly preferably 1600 mPa · s or less. is there. When the viscosity is less than the above range, a large load is applied to drying before firing, or spherical particles generated by drying become unnecessarily small or easily broken. On the other hand, if the viscosity exceeds the above range, handling becomes difficult, for example, suction with a tube pump used for slurry transportation during drying becomes impossible. The viscosity of the slurry can be measured using a known BM type viscometer. The BM viscometer is a measurement method that employs a method of rotating a predetermined metal rotor in the room temperature atmosphere. The viscosity of the slurry is calculated from the resistance force (twisting force) applied to the rotating shaft when the rotor is rotated with the rotor immersed in the slurry. However, the room temperature atmosphere refers to an environment at a laboratory level which is normally considered to have a temperature of 10 to 35 ° C. and a relative humidity of 20 to 80% RH.

  The slurry obtained as described above is usually dried and then subjected to a firing treatment as a fired product. As a drying method, spray drying is preferable. By performing spray drying, a spherical lithium transition metal composite oxide can be obtained by a simple method, and as a result, the packing density can be improved. The method of spray drying is not particularly limited. For example, a droplet of a slurry component from the nozzle by flowing a gas flow and a slurry into the tip of the nozzle (in this specification, this may be simply referred to as “droplet”). And the droplets scattered using an appropriate drying gas temperature and air flow rate can be dried quickly. Air, nitrogen, or the like can be used as the gas supplied as the gas flow, but air is usually used. These are preferably used under pressure. The gas flow is ejected at a gas linear velocity of usually 100 m / second or more, preferably 200 m / second or more, more preferably 300 m / second or more. If this linear velocity is too low, it is difficult to form appropriate droplets. However, since a too high linear velocity is difficult to obtain, the normal injection speed is 1000 m / sec or less. The shape of the nozzle to be used is not limited as long as it can discharge a minute droplet, and a conventionally known one, for example, a droplet as described in Japanese Patent No. 2797080 can be miniaturized. Such nozzles can also be used. The droplets are preferably sprayed in an annular shape from the viewpoint of improving productivity. The scattered droplets are dried. As described above, an appropriate temperature, air blowing, or the like is performed so as to quickly dry the dispersed droplets, but it is preferable to introduce a dry gas in a downward flow from the upper part of the drying tower to the lower part. By setting it as such a structure, the processing amount per unit capacity of a drying tower can be improved significantly. In addition, when spraying droplets in a substantially horizontal direction, it is possible to greatly reduce the diameter of the drying tower by suppressing the droplets sprayed in the horizontal direction with a downflow gas, and to manufacture inexpensively and in large quantities. Is possible. The drying gas temperature is usually 50 ° C. or higher, preferably 70 ° C. or higher, and usually 120 ° C. or lower, preferably 100 ° C. or lower. If this temperature is too high, the resulting granulated particles have a lot of hollow structures, and the powder packing density tends to decrease. On the other hand, if it is too low, the powder adheres due to moisture condensation at the powder outlet.・ Problems such as blockage may occur.

  Thus, the granulated particle used as a to-be-fired material is obtained by spray-drying. The granulated particle diameter is preferably 50 μm or less, more preferably 30 μm or less in terms of average particle diameter. However, since it tends to be difficult to obtain a too small particle size, it is usually 4 μm or more, preferably 5 μm or more. The particle diameter of the granulated particles can be controlled by appropriately selecting the spray format, pressurized gas flow supply rate, slurry supply rate, drying temperature, and the like.

  In addition, when a lithium compound is not contained in a slurry, a lithium compound is mixed with this spray-dried material. Although there is no restriction | limiting in particular in the mixing method, It is preferable to use the powder mixing apparatus generally used for industrial use. The atmosphere in the system to be mixed is preferably mixed in an inert gas in order to prevent carbon dioxide absorption in the air.

(3) Coprecipitation method An aqueous solution or colloidal solution containing a transition metal compound and a substituted metal compound used as necessary in a dissolved or colloidal state is prepared, and then the pH is controlled to remove these two or more metals. A coprecipitate is produced, which is mixed with a lithium compound to form a fired product. In this case, the aqueous solution containing the transition metal compound and the substituted metal compound used as necessary dissolves the transition metal compound selected from manganese, cobalt and nickel and the substituted metal compound used as necessary in water. Is obtained.

  When the transition metal compound or the substituted metal compound is a compound hardly soluble in water, it may be dissolved using an acid. In this case, an inorganic acid such as hydrochloric acid, sulfuric acid or nitric acid is usually used as the acid.

Specific examples of the method for preparing the aqueous solution include the following methods.
(i) If both the transition metal compound and the substituted metal compound are water-soluble, they are added to water and dissolved.
(ii) If both the transition metal compound and the substituted metal compound are hardly soluble in water, they are added to the acid and dissolved.
(iii) when one of the transition metal compound and the substituted metal compound is water-soluble and the other is sparingly soluble in water, an aqueous solution in which the water-soluble compound is dissolved in water, and an aqueous solution in which the sparingly soluble compound is dissolved in acid Mix. During mixing, colloids may be formed from a solution of a poorly soluble metal compound, but precipitation must be avoided.

  Examples of transition metal compounds used in the preparation of aqueous solutions include manganese, nickel and cobalt carbonates, chlorides, sulfates, and other inorganic acid salts, oxalates, acetates, citrates, and fatty acids. Organic acid salts such as salts, oxides, hydroxides, oxyhydroxides and the like are used. Further, the metal itself may be dissolved in an acid.

  A colloidal solution in which a transition metal compound and a substituted metal compound exist in a colloidal state, that is, a sol can be produced by, for example, hydrolyzing an organic solvent solution of a metal alkoxide. Moreover, it can also be set as a sol by adding an alkali or water to the aqueous solution prepared by melt | dissolving a sparingly soluble metal compound in an acid, or removing an acid from aqueous solution by an ion exchange resin process.

  The concentration of the metal compound in the aqueous solution is arbitrary as long as the aqueous solution is stable and a uniform coprecipitate is produced in the subsequent coprecipitate production step. It is preferable that it is as dark as possible so that the composition of the coprecipitates matches.

  When producing a substituted lithium transition metal composite oxide using a substituted metal compound, the atomic ratio of the transition metal to the substituted metal in the aqueous solution is usually the final substituted lithium transition metal composite oxide to be obtained. To match the composition of In this case, the atomic ratio of the substituted metal to the transition metal is usually 2.5% or more, preferably 5% or more, and usually 30% or less, preferably 20% or less. If the atomic ratio of the substituted metal is too small, the effect of improving the high-temperature cycle may not be sufficient, and if it is too large, the capacity of the battery may be reduced.

  In order to produce a coprecipitate as a hydroxide from an aqueous solution or colloidal solution containing two or more metals, an alkali such as sodium hydroxide, lithium hydroxide, or potassium hydroxide is added to form a coprecipitate. What is necessary is just to adjust to pH. The pH value at which the coprecipitate is generated varies depending on the metal to be coprecipitated, but is usually 7 to 10. When these metals are coprecipitated as carbonates, carbonates such as sodium carbonate are added. When these metals are coprecipitated as oxalates, oxalic acid is added. Thus, a coprecipitate can also be generated.

  The obtained coprecipitate containing any one of the transition metals of manganese, nickel and cobalt and the substitution metal is mixed with the above-mentioned lithium compound and fired, so that a part of the transition metal is substituted with another metal. In addition, a substitutional lithium transition metal composite oxide can be produced.

  The mixing ratio of the coprecipitate and the lithium compound is such that the atomic ratio of lithium to the total of transition metal and substitution metal in the coprecipitate matches the composition of the substitutional lithium transition metal composite oxide to be finally obtained. It is usually within ± 20%, preferably within ± 10% with respect to the standard composition of the lithium transition metal composite oxide. When the atomic ratio of lithium is too large or too small, the obtained substitutional lithium transition metal composite oxide does not give a battery having a predetermined large capacity when used as an active material of a positive electrode of a secondary battery. .

  Mixing of the coprecipitate and the lithium compound may be either dry mixing or wet mixing.

  In the case of dry mixing, the coprecipitate is removed from the reaction solution, dried, and then mixed with the lithium compound. First, the coprecipitate is separated from the mother liquor by centrifugation, filter press or the like. In order to reduce the content of dissolved salts in the mother liquor contained in the coprecipitate, the separation is preferably performed with the water content of the coprecipitate as low as possible. In addition, the salt content can be further reduced by washing the separated coprecipitate with water. The coprecipitate may be dried according to a conventional method.

  The dried coprecipitate is mixed with a lithium compound. Various dry mixers are used for mixing. As the dry mixer, any mixer that can uniformly mix these powders may be used. Specifically, a rotary rocking mixer, a paddle mixer, an airflow mixer, a screw rotary blade mixer, A rotary disk type mixer can be used. A pulverizer such as a ball mill, a roll mill, or a jet mill can also be used as a machine having a function having both the pulverization step and the mixing step. It is preferable that the coprecipitate and the lithium compound have a finer particle size in advance because they can be easily mixed uniformly. Specifically, the particle diameter is 100 μm or less, more preferably 50 μm or less, and still more preferably 10 μm or less in terms of average particle diameter.

  In the case of wet mixing, even if the dried coprecipitate is mixed with a lithium compound and a solvent to prepare a slurry, the coprecipitate is not taken out from the mother liquor, and the lithium compound is added to the suspension comprising the coprecipitate and the mother liquor. A slurry may be prepared by mixing. Preferably, the decantation is repeated to sufficiently remove salts coexisting with the coprecipitate, followed by mixing with the lithium compound.

  The solvent is not particularly limited as long as it dissolves the lithium compound, and specifically includes water, methanol, ethanol, N-methylpyrrolidone and the like, and preferably water is used.

  The slurry obtained by wet mixing is pulverized after being spray-dried by a spray-drying method or the like, or evaporated to dryness to obtain a dry powder.

  The dry powder containing the coprecipitate and lithium obtained by dry mixing or wet mixing is then subjected to baking as a material to be fired.

<Baking>
The conditions for firing the material to be fired (firing raw material) obtained by the above method are important in controlling the specific surface area and powder packing density of the obtained lithium transition metal composite oxide. The firing temperature depends on the raw material composition, but the tendency is that if the firing temperature is too high, the tap density of the resulting lithium transition metal composite oxide will be too large, and conversely if it is too low, the tap density will be small and the specific surface area will be low. Is too big. The firing temperature varies depending on the type of lithium compound, transition metal compound and the like used as a raw material, but is usually 300 ° C. or higher, preferably 700 ° C. or higher, more preferably 750 ° C. or higher, particularly preferably 800 ° C. or higher. Moreover, it is 1300 degrees C or less normally, Preferably it is 1200 degrees C or less, More preferably, it is 1100 degrees C or less.

  Although the firing time varies depending on the temperature, it is usually 30 minutes or longer and 100 hours or shorter, particularly 50 hours or shorter within the above-mentioned temperature range. If the firing time is too short, it becomes difficult to obtain a lithium transition metal composite oxide having good crystallinity, and it is not practical to be too long. If the firing time is too long, it is not efficient in production, and is preferably 25 hours or less, more preferably 20 hours or less.

  In order to obtain a lithium transition metal composite oxide with few crystal defects, it is preferable to cool slowly after the firing reaction, for example, to cool slowly at a cooling rate of 5 ° C./min or less.

  The atmosphere during firing can be an oxygen-containing gas atmosphere such as air or an inert gas atmosphere such as nitrogen or argon, depending on the composition and structure of the lithium transition metal composite oxide to be produced. In addition, when baking in air, it is preferable to use air from which carbon dioxide has been previously removed.

  The heating apparatus used for firing is not particularly limited as long as the above temperature and atmosphere can be achieved. For example, a box furnace, a tubular furnace, a tunnel furnace, a rotary kiln, or the like can be used.

  In the present invention, when firing such a material to be fired, the above-mentioned firing container of the present invention is used as a firing container, and this firing container is filled with the material to be fired and fired under the above conditions. More specifically, the object to be fired is filled into the container body 2 of the firing container 1 as shown in FIGS. 1 to 3, the cover body 3 is covered with the lid body 3, and this is loaded into a heating device and fired. .

  In this firing, it is preferable that the above-mentioned atmospheric gas flow from the top to the bottom of the firing container 1 covered with the lid 3. By doing so, it is possible to effectively prevent foreign materials from the furnace material of the heating device and the firing atmosphere from entering the firing container. That is, for example, when foreign matter has fallen on the floor surface in the furnace of the heating device, the foreign matter on the floor surface is entrained in the atmospheric gas flow by flowing the atmospheric gas from above to the side surface portion 21 of the container body 2. ˜24 and the hanging parts 31 to 34 of the lid 3 can be prevented from entering the container body 2 from the vents 21 </ b> A to 24 </ b> A.

  The flow rate of the atmospheric gas is usually 0.1 cm / second or more, preferably 0.5 cm / second or more, and usually 30 cm / second or less, preferably 10 cm / second or less. If the lower limit is not reached, the atmosphere in the firing container may not be sufficiently replaced with the atmospheric gas. If the upper limit is exceeded, foreign matter is caught by the atmosphere gas flow from around the firing container and enters the firing container. , Foreign matters are likely to be mixed into the object to be fired.

  Note that if the rate of temperature rise and fall is too high, the firing container may be damaged, so it is 100 ° C./min or less, preferably 50 ° C./min or less. In order to prevent crystal defects in the obtained lithium transition metal composite oxide, the temperature is preferably 5 ° C./min or less.

<Disintegration / Classification>
The lithium transition metal composite oxide obtained after firing is crushed. Examples of means for crushing the lithium transition metal composite oxide include a ball mill, a jet mill, and a pin mill. The degree of crushing of the lithium transition metal composite oxide is such that the particle size is 100 μm or less, more preferably 50 μm or less.

  Next, the crushed lithium transition metal composite oxide is classified. The classification means is not particularly limited as long as the lithium transition metal composite oxide can be separated into those having a large particle size and those having a small particle size. A dry type is preferable, and examples of the dry type include a sieve and an air classifier, and an air classifier is particularly preferable. Examples of the air classifier include gravity classification, inertial force classification, and centrifugal force classification, and preferably centrifugal force classification.

  Further, the upper limit of the classification range may be 100 μm or less, preferably 50 μm or less.

[Lithium secondary battery]
The lithium transition metal composite oxide obtained by the production method of the present invention can be used as an active material for a positive electrode of a lithium secondary battery.

  Hereinafter, a lithium secondary battery using the lithium transition metal composite oxide according to the present invention as a positive electrode active material will be described. A lithium secondary battery is composed of at least a positive electrode, a negative electrode, and a non-aqueous electrolyte, and a separator and other materials are used as necessary.

<Positive electrode>
For the positive electrode, an active material layer containing a lithium transition metal composite oxide (hereinafter sometimes referred to as “positive electrode active material”), which is a positive electrode material, a binder and a conductive agent is usually formed on the current collector. Do it. The active material layer can be usually obtained by preparing a slurry containing the above components and applying and drying the slurry on a current collector.

  The ratio of the positive electrode active material in the active material layer is usually 10% by weight or more, preferably 30% by weight or more, more preferably 50% by weight or more, and usually 99.9% by weight or less, preferably 99% by weight or less. is there. If the amount of the positive electrode active material is too large, the strength of the positive electrode tends to be insufficient. If the amount is too small, the capacity may be insufficient.

  Examples of the conductive agent used for the positive electrode include natural graphite, artificial graphite, carbon black such as acetylene black, and amorphous carbon such as needle coke. The proportion of the conductive agent in the active material layer is usually 0.01% by weight or more, preferably 0.1% by weight or more, more preferably 1% by weight or more, and usually 50% by weight or less, preferably 20% by weight or less. More preferably, it is 10% by weight or less. If the amount of the conductive agent is too large, the capacity may be insufficient, and if the amount is too small, the electrical conductivity may be insufficient.

  In addition, as a binder used for the positive electrode, in addition to fluoropolymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and fluororubber, EPDM (ethylene-propylene-diene ternary copolymer) Coalesced), SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), polyvinyl acetate, polymethyl methacrylate, polyethylene, nitrocellulose and the like. The ratio of the binder in the active material layer is usually 0.1% by weight or more, preferably 1% by weight or more, more preferably 5% by weight or more, and usually 80% by weight or less, preferably 60% by weight or less, More preferably, it is 40 weight% or less. If the amount of the binder is too large, the capacity may be insufficient, and if the amount is too small, the strength may be insufficient.

  Moreover, as a solvent used when preparing a slurry, the organic solvent which can melt | dissolve or disperse | distribute a binder normally is used. For example, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran and the like can be mentioned. In some cases, a dispersant, a thickener, or the like is added to water and slurried with a latex such as SBR.

  The thickness of the active material layer is usually about 10 to 200 μm.

  As the material of the current collector used for the positive electrode, metals such as aluminum, stainless steel, nickel-plated steel, etc. are used, and preferably aluminum.

  The active material layer obtained by coating and drying is preferably consolidated by a roller press or the like in order to increase the packing density of the electrode material.

<Negative electrode>
A carbon material is preferably used as the negative electrode material. Carbon materials include natural or artificial graphite, petroleum coke, coal coke, petroleum pitch carbide, coal pitch carbide, phenolic resin / crystalline cellulose resin carbide, etc., and partially carbonized carbon materials, Examples thereof include furnace black, acetylene black, pitch-based carbon fiber, PAN-based carbon fiber, and a mixture of two or more of these. The negative electrode material is usually formed as an active material layer on the current collector together with a binder and, if necessary, a conductive agent. Moreover, lithium metal itself or lithium alloys, such as a lithium aluminum alloy, can also be used as a negative electrode. Examples of the binder and the conductive agent that can be used for the negative electrode can be the same as those used for the positive electrode, and the use ratio is also equivalent.

  The thickness of the active material layer of the negative electrode is usually about 10 to 200 μm. Formation of the active material layer of a negative electrode can be performed according to the formation method of the active material layer of the said positive electrode.

  As the material for the current collector of the negative electrode, metals such as copper, nickel, stainless steel, nickel-plated steel and the like are usually used, and copper is preferable.

<Non-aqueous electrolyte>
As the non-aqueous electrolytic solution, various electrolytic salts dissolved in a non-aqueous solvent can be used.

  As the non-aqueous solvent, for example, carbonates, ethers, ketones, sulfolane compounds, lactones, nitriles, halogenated hydrocarbons, amines, esters, amides, phosphate ester compounds, etc. may be used. it can. Typical examples of these are propylene carbonate, ethylene carbonate, chloroethylene carbonate, trifluoropropylene carbonate, butylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, vinylene carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, 1, 4-dioxane, 4-methyl-2-pentanone, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, Sulfolane, methyl sulfolane, acetonitrile, propionitrile, benzonitrile, butyronitrile, valeronitrile, 1,2-dichloroethane, dimethylformamide, dimethyl Sulfoxides, trimethyl phosphate, include alone or a mixture of two or more solvents such as triethyl phosphate.

  Among the above non-aqueous solvents, it is preferable to use a high dielectric constant solvent in order to dissociate the electrolyte. The high dielectric constant solvent means a compound having a relative dielectric constant of about 20 or more at 25 ° C. Among the high dielectric constant solvents, it is preferable that the electrolyte solution contains ethylene carbonate, propylene carbonate, and compounds obtained by substituting hydrogen atoms thereof with other elements such as halogen or alkyl groups. When such a high dielectric constant solvent is used, the proportion of the high dielectric constant solvent in the electrolytic solution is usually 20% by weight or more, preferably 30% by weight or more, and more preferably 40% by weight or more. If the content of the high dielectric constant solvent is small, desired battery characteristics may not be obtained.

As the electrolytic salt, any conventionally known salt may be used, and LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , LiCl, LiBr, LiCH ₃ SO ₃ Li, LiCF Examples of the lithium salt include ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , and LiN (SO ₃ CF ₃ ) ₂ .

Also, a good film that enables efficient charge and discharge of lithium ions on the negative electrode surface, such as gas such as CO ₂ , N ₂ O, CO, SO ₂ , polysulfide S _X ²⁻ , vinylene carbonate, catechol carbonate, etc. is generated. Additives may be present in the electrolyte in any proportion.

  Instead of the electrolytic solution, a polymer solid electrolyte that is a conductor of an alkali metal cation such as lithium ion can be used. Alternatively, the electrolyte solution can be made non-fluidized with a polymer to use a semi-solid electrolyte.

<Separator>
A separator is usually provided between the positive electrode and the negative electrode. As the separator, a microporous polymer film is used, and the material is nylon, polyester, cellulose acetate, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, tetrafluoroethylene, polypropylene, polyethylene, polybutene, etc. The polyolefin-type polymer | macromolecule can be mentioned. Further, a nonwoven fabric filter such as glass fiber, a composite nonwoven fabric filter of glass fiber and polymer fiber, and the like can also be used. The chemical and electrochemical stability of the separator is an important factor, and from this point, a polyolefin polymer is preferable as the material, and in particular, it is made of polyethylene from the viewpoint of the self-blocking temperature, which is one of the purposes of the battery separator. Preferably there is.

  In the case of a polyethylene separator, ultrahigh molecular weight polyethylene is preferable from the viewpoint of maintaining high-temperature shape, and the lower limit of the molecular weight is preferably 500,000, more preferably 1,000,000, and most preferably 1.5 million. The upper limit of the molecular weight is preferably 5 million, more preferably 4 million, and most preferably 3 million. This is because if the molecular weight is too large, the pores of the separator may not close when heated because the fluidity is too low.

<Battery shape>
The lithium secondary battery is manufactured by assembling the positive electrode, the negative electrode, the electrolyte, and the separator used as necessary into an appropriate shape. Furthermore, other components such as an outer case can be used as necessary.

  The shape of the lithium secondary battery can be appropriately selected from various shapes generally employed according to the application. Examples of commonly used shapes include a cylinder type with a sheet electrode and separator in a spiral shape, a cylinder type with an inside-out structure combining a pellet electrode and a separator, and a coin type with stacked pellet electrodes and a separator. Can be mentioned. The method for assembling the battery is not particularly limited, and can be appropriately selected from various commonly used methods according to the shape of the target battery.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.
<Example 1>
Mn ₂ O ₃ , AlOOH, and LiOH.H ₂ O are compositions in the final spinel type lithium manganese composite oxide, respectively: Li: Mn: Al = 1.10: 1.88: 0.12 (molar ratio) Then, pure water was added thereto to prepare a slurry having a solid content concentration (slurry concentration) of 29.2% by weight and a viscosity of 600 mPa · s. The slurry was pulverized with stirring using a circulating medium agitation type wet pulverizer until the average particle size of the solid content in the slurry became 0.3 μm. After the raw material was wet pulverized, spray drying (gas linear speed 330 m / sec, drying temperature 105 ° C.) was performed using a spray dryer. As the drying air of the spray dryer, air passed through a HEPA filter that captures 99.7% or more of particles of 0.3 μm or more was used. The dried granulated particles (average particle size 11.2 μm) were collected by a cyclone and used as a firing raw material.

The firing raw material (substance to be fired) thus obtained was fired using the firing container 1 shown in FIGS. This fired container 1 is made of a ceramic whose material is Al ₂ O ₃ 91.0 wt%, SiO ₂ 8.0 wt% for both the container main body 2 and the lid 3, and the porosity is 24.5%. The shape and dimensions are as follows.
Bottom surface 20 of container body 2: Square with side of 153 mm Side wall parts 21 to 24 of container body 2: Rectangle with width C = 153 mm and height D = 80 mm Wall thickness of container body 2 and lid 3: 5 mm
Ventilation portions 21A to 21B of the container body 2: width A = 90 mm, cutout depth B = 12 mm
Rectangular side opening area ratio: 8.8%
Lid / main body distance t: 5 mm
Hanging width E: 5 mm
Crossing corner 30A of lid 3 shown in FIG. 4: concave curved surface with a radius of curvature of 5 mm

  As the firing atmosphere, air passed through a HEPA filter was used, and the atmosphere air was flowed from above the firing container downward to a flow rate of 8 cm / second. The firing conditions were a temperature increase rate of 2 ° C./min, 900 ° C. for 10 hours, and a cooling rate of 1 ° C./min.

  The fired lithium transition metal composite oxide was sieved with a sieve having an opening of 45 μm.

The lithium transition metal composite oxide thus obtained was subjected to powder XRD measurement under the following measurement conditions, and the results are shown in Table 1.
(Measurement conditions for X-ray diffraction)
X-ray source: CuKα ray (CuKα = 1.5418Å)
Divergence slit: 1 °
Scattering slit: 1 °
Receiving slit: 0.2mm
Step width: 0.05 °

Further, the number of metal foreign objects was measured by the following method, and the results are shown in Table 1.
(Measuring method of the number of metallic foreign objects)
1 g of lithium transition metal composite oxide and 40 ml of ion-exchanged water were placed in a 100 ml beaker and stirred for 60 minutes with an Alnico magnet having a size of 50 mm × 10 mm × 10 mm and a magnetic flux density of 2200 gauss coated with resin. By confirming the surface of this magnet with SEM-EDX, the number of metal foreign matters having a major axis of 10 μm or more in the lithium transition metal composite oxide was examined.

<Comparative Example 1>
In Example 1, a lithium transition metal composite oxide was produced in the same manner except that the firing was performed using only the container body without using the lid of the firing container, and the powder XRD measurement and the number of metal foreign objects were measured. The results are shown in Table 1.

  From Table 1, it can be seen that according to the present invention, a lithium transition metal composite oxide with few foreign substances can be produced.

It is a perspective view of a container main part and a lid which show an embodiment of a baking container of the present invention. It is a front view of the container main body of the baking container of FIG. It is a front view which shows the state which covered the cover body on the container main body of the baking container of FIG. It is explanatory drawing which shows the relationship between the shape of the crossing corner part of the top cover part and crossing corner part of a cover body, and the shift | offset | difference of a cover body. It is explanatory drawing which shows the relationship between the shape of the crossing corner part of the top cover part and crossing corner part of a cover body, and the shift | offset | difference of a cover body. It is explanatory drawing which shows the relationship between the shape of the crossing corner part of the top cover part and crossing corner part of a cover body, and the shift | offset | difference of a cover body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Firing container 2 Container main body 3 Cover body 20 Bottom face 21, 22, 23, 24 Side wall part 21A, 22A, 23A, 24A Ventilation part 30 Canopy part 31, 32, 33, 34 Hanging part

Claims (13)

  A firing container for firing an object to be fired containing a lithium compound and a transition metal compound, wherein the firing container has a ventilation portion in addition to the upper surface.   The baking container according to claim 1, wherein the baking container has a ventilation portion on a side surface. In Claim 1, the baking container comprises a container body whose upper surface is opened so as to put in and out the object to be fired from the upper surface, and a lid body detachably attached to the container body.
The vent is provided on the side of the container body,
The lid body is provided with a canopy portion that covers the upper surface of the container main body and projects laterally from the side surface of the container main body, and a hanging portion that hangs down from the periphery of the canopy portion,
The firing container, wherein the hanging part is spaced apart from the side part of the container body to the outside of the side.   4. The firing container according to claim 3, wherein the hanging portion has a lower end depending on a lower side than a lower end of the ventilation portion of the container body.   5. The firing container according to claim 3, wherein the drooping portion has a size facing the whole of the ventilation portion.   The firing container according to any one of claims 3 to 5, wherein a ratio of an opening area of the ventilation portion to an area of a side surface portion of the container main body is 1% or more and 20% or less.   The firing according to any one of claims 3 to 6, wherein the container body has at least one pair of facing side surfaces, and the ventilation portion is provided on the at least one pair of facing side surfaces. container.   The firing container according to any one of claims 3 to 7, wherein a distance between the ventilation portion of the container body and the hanging portion of the lid is 1 mm or more and 50 mm or less.   The firing container according to any one of claims 3 to 8, wherein a crossing corner portion of the lid portion and the hanging portion of the lid body is formed by a concave curved surface or an inclined surface. 10. The material according to claim 1, wherein the material of the firing container is at least one metal oxide selected from the group consisting of SiO ₂ , Al ₂ O ₃ , ZrO ₂ , MgO, SiC, and CaO. The baking container characterized by the above-mentioned.   The firing container according to any one of claims 1 to 10, wherein the porosity of the firing container is 70% or less.   The firing container according to any one of claims 1 to 11, which is a firing container for producing a lithium transition metal composite oxide for a lithium secondary battery electrode material by firing the object to be fired.   13. A method for producing a lithium transition metal composite oxide for a lithium secondary battery electrode material by containing a fired product containing a lithium compound and a transition metal compound in a firing container and firing the same, wherein the firing container is used as the firing container. A method for producing a lithium transition metal composite oxide for a lithium secondary battery electrode material, wherein the firing container according to any one of the above is used.

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