JP4175026B2 - Method for producing lithium transition metal composite oxide and positive electrode material for lithium secondary battery, positive electrode for lithium secondary battery, and lithium secondary battery - Google Patents

Description

【００８４】
上記の結果から、粗粉のみからなる正極活物質(実施例５)は容量は大きいがレート特性に劣り、また、微粉のみからなる正極活物質(実施例８)は容量は小さいがレート特性に優れていることがわかる。
上記の実施例１〜４の結果及び実施例５〜８の結果をもとに正極活物質中の粗粉の割合と容量の関係をグラフに示すと図３及び図４のようになる。図３及び図４から明らかなように、容量、レート特性は混合割合で加成性が成り立つので、粗粉と微粉を任意の割合で混合することにより、トライ&エラーを繰り返すことなく容量とレート特性のバランスを自由に選ぶことが出来る。
【００８５】
【発明の効果】
本発明により、レート特性と容量のさまざまなバランスのリチウム二次電池用正極材料を容易に製造できる。
【図面の簡単な説明】
【図１】本発明の実施例の非水電解液二次電池用活物質の製造法の試験に用いたコイン型電池の縦断面図
【図２】 900℃焼成後の粗粉と微粉の粒度分布を示す図
【図３】実施例１〜４の正極活物質中の微粉の割合と容量の関係を示す図
【図４】実施例５〜８の正極活物質中の微粒の割合と容量の関係を示す図
【符号の説明】
１ 正極缶
２ 正極
３ セパレーター
４ ガスケット
５ 負極（対極)
６ スペーサー
７ 負極缶[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a lithium transition metal composite oxide and a positive electrode material for a lithium secondary battery, a positive electrode for a lithium secondary battery, and a lithium secondary battery.
[0002]
[Prior art]
By using a carbon material or the like capable of occluding and releasing lithium ions instead of metallic lithium as the negative electrode active material, the safety has been greatly improved, and the lithium secondary battery has entered the practical stage.
Meanwhile, as a positive electrode active material of a lithium secondary battery, LiCoO₂And LiNiO₂, LiMn₂O_FourLithium transition metal composite oxides such as are now in practical use.
[0003]
For battery applications, large current is not required but large capacity is desired to be used for a long time (mobile phone, portable audio, etc.), large current can be taken out in a short time (rate characteristics are excellent) Applications (power tools, uninterruptible power supplies, etc.) and applications where it is desired that both be in an appropriate balance (hybrid vehicles, electric assist bicycles, etc.) There is a need for batteries.
[0004]
Therefore, in the past, when manufacturing a positive electrode material (lithium transition metal composite oxide) for a lithium secondary battery, various manufacturing conditions were examined according to various balances of the required rate characteristics and capacity, and lithium secondary batteries of each specification were examined. The manufacturing conditions were changed for each positive electrode material for secondary batteries. Examination of manufacturing conditions at that time was based on repeated trial and error, and development of each spec required a great deal of labor.
[0005]
[Problems to be solved by the invention]
Therefore, a method for easily producing positive electrode materials for lithium secondary batteries having various balances between rate characteristics and capacities has been demanded.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present inventors have studied a method for controlling the balance between the rate and capacity of a positive electrode material containing a lithium manganese composite oxide as an active material. As a result, the lithium manganese composite oxide has a large particle size. It has been found that the above problems can be solved by separating them into small ones and mixing them arbitrarily, and the present invention has been solved.
[0007]
That is, the gist of the present invention resides in the following (1) to (25).
(1) A lithium transition metal composite oxide, in which a part of the transition metal may be substituted with another metal element, is passed through a classifier and separated into a large particle size and a small particle size, and a large particle size A small material is blended at a weight ratio of 0: 100 to 100: 0, and a method for producing a positive electrode material for a lithium secondary battery.
(2) A slurry obtained by mixing a lithium compound, a transition metal compound, and a transition metal substitution metal element compound in the presence of a solvent in the presence of a solvent is spray-dried. A method for producing a lithium-transition metal composite oxide, characterized in that it is separated into small ones and a large particle size and a small one are blended in a weight ratio of 0: 100 to 100: 0.
(3) A slurry obtained by mixing a lithium compound, a transition metal compound, and a transition metal substitution metal element compound in the presence of a solvent in the presence of a solvent is spray-dried. A method for producing a lithium-transition metal composite oxide comprising: mixing a large particle size and a small particle size in a weight ratio of 0: 100 to 100: 0.
(4) A slurry obtained by mixing a lithium compound, a transition metal compound, and, optionally, a transition metal substitution metal element compound in the presence of a solvent is spray-dried, and a product having a large particle size and a material having a small particle size by an air classifier. A method for producing a lithium-transition metal composite oxide, comprising: mixing a large particle size and a small particle size at a weight ratio of 0: 100 to 100: 0, followed by firing.
(5) A raw material obtained by mixing a lithium compound with a dry product obtained by spray-drying a slurry obtained by mixing a transition metal compound or a transition metal substitution metal element compound in the presence of a solvent in the presence of a solvent. After obtaining the mixture, it is fired and separated into a large particle size and a small particle size by an air classifier, and the large particle size and the small particle size are blended at a weight ratio of 0: 100 to 100: 0. A method for producing a lithium transition metal composite oxide, comprising:
(6) A transition product obtained by spray-drying a slurry obtained by mixing a transition metal compound or a transition metal substitution metal element compound in the presence of a solvent in the presence of a solvent. And a mixture of lithium compounds in each, followed by firing to produce a lithium transition metal composite oxide having a large particle size and a lithium transition metal composite oxide having a small particle size, A method for producing a lithium transition metal composite oxide comprising blending at a weight ratio of 0: 100 to 100: 0.
(7) Separation of large and small particles is the equilibrium separation particle size D_h= 1-10 micrometers, The manufacturing method in any one of (1), (2) and (5) performed.
(8) Separation between large and small particles is the equilibrium separation particle size D_h= The manufacturing method in any one of (3), (4) and (6) performed by 1-10 micrometers. (However, the equilibrium separation particle diameter D_hIs the particle size when fired at 900 ° C. )
(9) The production method according to any one of (1) to (8), wherein the lithium transition metal composite oxide is a lithium manganese composite oxide.
(10) The lithium transition metal composite oxide is
[0008]
[Chemical 3]
Li_bMn_2-aAl_aO_Four
The manufacturing method in any one of (1)-(8) represented by (0 <a <= 1.0, 0.9 <= b <= 1.1).
(11) The production method according to any one of (2) to (10), wherein the transition metal compound is a manganese compound.
(12) The production method according to (11), wherein the mixing ratio of the lithium compound and the manganese compound is a quantitative ratio such that Li / Mn = 0.4 to 0.6 in terms of Li atom and Mn atom.
(13) Manganese substituted metal element compounds selected from B, Al, Fe, Sn, Cr, Cu, Ti, Zn, Co, and Ni, oxides, hydroxides, nitrates, carbonates, dicarboxylates The method according to (11) or (12), which is a fatty acid salt or an ammonium salt.
(14) The mixing ratio of the substituted metal element compound of manganese is a quantitative ratio in which the metal element other than manganese is 2.5 to 30 mol% of Mn in terms of a metal atom other than Mn atom and manganese. The manufacturing method as described.
(15) The production method according to any one of (1) to (8), wherein the lithium transition metal composite oxide is a lithium nickel composite oxide.
(16) The lithium transition metal composite oxide is
[0009]
[Formula 4]
Li_xNi_1-yM_yO_2-δ
(0.8 ≦ x ≦ 1.3, 0 <y ≦ 0.5, and M is Co, Mn, Fe, Cr, V, Ti, Cu, Al, Ga, Bi, Sn, Zn, Mg, It represents at least one element selected from the group consisting of Ge, Nb, Ta, Be, B, Ca, Sc and Zr, δ corresponds to oxygen deficiency or oxygen excess, and −0.1 <δ <0.1 The manufacturing method in any one of (1)-(8) represented by.
(17) The production method according to any one of (2) to (10), wherein the transition metal compound is a nickel compound.
(18) The mixing ratio of the total number of total atoms of the lithium compound, the nickel compound, and the substitution element thereof is Li / (Ni + M) = 1.1 to 0.00 in terms of the total of Li atoms, Ni atoms, and substitution atoms (M). 9. The production method according to (17), wherein the production ratio is 9.
(19) The substituted metal element compound of nickel is Co, Mn, Fe, Cr, V, Ti, Cu, Al, Ga, Bi, Sn, Zn, Mg, Ge, Nb, Ta, Be, B, Ca, Sc And a production method according to (17) or (18), which is an oxide, hydroxide, nitrate, carbonate, dicarboxylate, fatty acid salt or ammonium salt of a metal selected from the group consisting of Zr.
(20) A lithium transition metal composite oxide positive electrode material for a lithium secondary battery produced by the production method of (1).
(21) A lithium transition metal composite oxide produced by the production method according to any one of (2) to (19).
(22) A positive electrode for a lithium secondary battery comprising a lithium transition metal composite oxide positive electrode material for a lithium secondary battery and a binder produced by the production method of (1).
(23) A positive electrode for a lithium secondary battery, comprising a lithium transition metal composite oxide produced by the production method according to any one of (2) to (19) and a binder.
(24) A lithium secondary battery having a positive electrode for a lithium secondary battery, a negative electrode, and an electrolyte using the lithium transition metal composite oxide positive electrode material for a lithium secondary battery produced by the production method of (1).
(25) A lithium secondary battery having a positive electrode, a negative electrode, and an electrolyte containing the lithium transition metal composite oxide produced by the production method according to any one of (2) to (19).
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The feature of the present invention is that the lithium transition metal composite oxide is passed through a classifier and separated into a product having a large particle size and a product having a small particle size, and a material having a large particle size and a material having a small particle size are arbitrarily blended. Specifically, the lithium transition metal composite oxide is passed through a classifier and separated into a large particle size and a small particle size, and the large particle size and the small particle size are 0: 100 to 100: 0. It is characterized by blending with.
[0011]
The capacity and rate characteristics are additive by the mixing ratio of the large particle size and the small particle size. Therefore, the lithium transition metal composite oxide can be combined with a large particle size and a small particle size. What is necessary is just to mix in arbitrary ratios according to the property calculated | required. Specifically, for example, as shown in FIG. 3 in the embodiment of the present invention, a diagram showing the relationship between the mixing ratio of the large particle size and the small particle size and the capacity / rate characteristics is prepared. Based on this, the mixing ratio of the large particle size and the small particle size may be determined. The mixing ratio may be arbitrarily selected as a mixture having a large particle size by weight ratio: a small particle size = 0: 100 to 100: 0, but in the present invention, it is arbitrarily selected from 1:99 to 99: 1. It is preferable to select.
[0012]
Examples of the lithium transition metal composite oxide in the present invention include composite oxides of lithium and transition metals such as Co, Ni, Mn, V, Fe, Ti, Cr, Sc, and Y. (2) Lithium manganese composite oxide, (2) Lithium nickel composite oxide.
(1) Explanation of lithium manganese composite oxide
Typically LiMn₂O_FourSpinel structure lithium manganate having a basic composition of Li and basic composition LiMnO₂In particular, spinel type lithium manganate is preferable in terms of ease of production and cycle characteristics.
[0013]
The lithium manganese composite oxide may further contain other elements in addition to lithium, manganese and oxygen. Examples of the metal element include B, Al, Fe, Sn, Cr, Cu, Ti, Zn, Co, and Ni, and Al is preferable. That is, in a preferred embodiment, the lithium manganese composite oxide is composed of a composite oxide containing lithium, manganese, and aluminum. Such other elements have a function of stabilizing the crystal structure, for example, by substituting a part of the manganese site with the other elements. Examples of the substitution element for the manganese site include metal elements such as B, Al, Fe, Sn, Cr, Cu, Ti, Zn, Co, and Ni as described above. Of course, it can be replaced with multiple elements. A preferred substitution element is Al. In addition, part of the oxygen atoms can be replaced with a halogen element such as fluorine.
[0014]
Such other element substitution type lithium manganese composite oxide is usually in the case of a lithium manganese composite oxide having a spinel structure, for example.
[0015]
[Chemical formula 5]
Li_bMn_2-a Me_aO_Four
(Me is a substitution element, 0 ≦ b ≦ 1.5, 0 <a ≦ 1). Here, the preferred substitution element Me is Al. However, the type and composition ratio of the substitution elements are not limited to this as long as the crystal structure can be stabilized. The composition of the particularly preferred lithium manganese composite oxide is
[0016]
[Chemical 6]
Li_bMn_2-aAl_aO_Four
(0 <a ≦ 1.0, 0.9 ≦ b ≦ 1.1).
[0017]
In any of the above compositional formulas, the amount of oxygen includes the case where it has nonstoichiometry. Furthermore, in any of the above cases, it is also possible to replace part of the manganese atom site with lithium, for example, by using a stoichiometric amount or more of lithium as a raw material.
▲ 2 ▼Description of lithium nickel composite oxide
Various structures can be considered as the lithium nickel composite oxide, but LiNiO having a hexagonal layered rock salt structure.₂However, it is suitable for a positive electrode material for a lithium ion secondary battery.
[0018]
The lithium nickel composite oxide may further contain other elements in addition to lithium, nickel and oxygen. Examples of the metal element include Co, Mn, Fe, Cr, V, Ti, Cu, Al, Ga, Bi, Sn, Zn, Mg, Ge, Nb, Ta, Be, B, Ca, Sc, and Zr. Is preferably Co or Al. That is, in a preferred embodiment, the lithium nickel composite oxide is composed of a composite oxide containing lithium, nickel, Co, or Al.
[0019]
For example, in the case of a lithium nickel composite oxide having a hexagonal layered rock salt structure, such other element substitution type lithium nickel composite oxide is usually used.
Li_xNi_1-yM_yO_2-δ
(0.8 ≦ x ≦ 1.3, 0 <y ≦ 0.5, and M is Co, Mn, Fe, Cr, V, Ti, Cu, Al, Ga, Bi, Sn, Zn, Mg, It represents at least one element selected from the group consisting of Ge, Nb, Ta, Be, B, Ca, Sc and Zr, δ corresponds to oxygen deficiency or oxygen excess, and −0.1 <δ <0.1 It can be expressed by the composition of Here, preferred substitution elements M are Co and Al. However, the type and composition ratio of the substitution elements are not limited to this as long as the crystal structure can be stabilized.
・ Explanation of lithium transition metal complex oxide production
Lithium transition metal composite oxides can be produced by various conventionally known methods. For example, when substituting a part of the transition metal with lithium and the transition metal with another substitution element, the substitution element is changed. It can manufacture by baking and cooling in oxygen presence after mixing the starting raw material to contain.
[0020]
In the above production method, a lithium transition metal composite oxide in which transition metal sites are not substituted without using a starting material containing a substitution element is produced, and the lithium transition metal composite oxide is used as a starting material containing a substitution metal element. After reacting in the raw material aqueous solution, molten salt or steam, if necessary, the transition metal site is replaced with the replacement element by performing a heat treatment again in order to diffuse the substitution element into the lithium transition metal composite oxide particles. May be.
[0021]
Moreover, it can also manufacture by mixing the starting material containing a transition metal and a substitution element, mixing with the starting material containing lithium, and baking and cooling.
・ Lithium compounds
Lithium compounds used as starting materials include Li₂CO_Three, LiNO_Three, LiOH, LiOH · H₂O, LiOH, LiCl, LiI, CH_ThreeCOOLi, Li₂O, dicarboxylic acid Li, fatty acid Li, alkyl lithium, etc. are mentioned.
[0022]
Among these, Li₂CO_Three, LiNO_Three, LiOH · H₂O, LiOH and CH_ThreeCOOLi and the like are preferable, and LiOH.H is particularly preferable.₂O, LiOH. In order to prevent generation of harmful substances such as NOx and SOx in the subsequent firing step, it is preferable that N and S are not included.
・ Transition metal compounds
Examples of the transition metal compound used as a starting material include a manganese compound, specifically, Mn₂O_Three, MnO₂Manganese oxides such as MnCO_Three, Mn (NO_Three)₂ , MnSO_FourAnd manganese salts such as manganese acetate, manganese dicarboxylate, manganese citrate, and fatty acid manganese, oxyhydroxides, halides, and the like. Mn₂O_ThreeAs MnCO_ThreeAnd MnO₂You may use what was produced by heat-processing such compounds.
[0023]
Further, as the nickel compound, specifically, nickel oxide such as NiO, Ni (OH)₂Nickel hydroxide such as NiOOH, oxyhydroxide such as NiOOH, NiCl₂Halides such as NiCO_ThreeAnd nickel carbonate.
・ Substitute element compounds
Examples of the substitution element compound include oxides, hydroxides, nitrates, carbonates, dicarboxylates, fatty acid salts, and ammonium salts.
・ Mixing of starting materials
These starting materials are usually mixed by methods such as wet mixing, dry mixing, ball milling, and coprecipitation. A pulverization step may be added before and after mixing and during mixing. In addition, if necessary, the lithium compound is separately added to the powder obtained by wet mixing and spray-drying granulation of only the nickel compound and the transition metal compound without mixing the nickel compound, the transition metal compound and the lithium compound at once. Things are also possible.
・ Baking
A mixture of a nickel compound, a transition metal compound, and a lithium compound is fired under predetermined conditions to form a positive electrode material for a lithium ion secondary battery. Specific conditions are described below.
[0024]
The firing temperature is usually 500 ° C. or higher, preferably 550 ° C. or higher, and usually 1000 ° C. or lower, preferably 900 ° C. or lower. If the firing temperature is too low, it is difficult to obtain a lithium nickel composite oxide with good crystallinity. If the firing temperature is too high, a phase other than the intended lithium nickel composite oxide may be produced, or a lithium nickel composite oxide having many defects may be produced. In addition, when raising the temperature of the above reaction from room temperature to a temperature, in order to perform the reaction more uniformly, for example, the temperature is gradually raised at a temperature of 5 ° C. or less per minute, or the temperature is temporarily stopped halfway. In addition, a holding time at a constant temperature may be included.
[0025]
The firing time during the firing treatment is usually 1 hour to 100 hours, preferably 2 hours to 50 hours. If the time is less than the above range and the time is too short, it is difficult to obtain a lithium nickel composite oxide with good crystallinity, and a reaction time that is too long beyond this range is industrially inappropriate.
The atmosphere during the baking treatment is usually performed in the presence of oxygen. Specifically, firing can be performed in air or in a gas atmosphere having an oxygen concentration of 20% or more. When firing in air, it is preferable to use decarboxylated air. Preferably, it is in decarboxylated air or in a gas atmosphere having an oxygen concentration of 20% or more, more preferably a quasi-oxygen atmosphere.
[0026]
In order to obtain a lithium nickel composite oxide with few defects, it is preferable to cool slowly to a certain temperature after the above firing, and gradually cool to 600 ° C., preferably 400 ° C. at a cooling rate of 5 ° C. or less per minute. It is preferable.
The heating device 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.
[0027]
As a method for firing and cooling the lithium manganese oxide, for example, after calcination, the firing is performed in an oxygen atmosphere at a temperature of about 600 to 900 ° C., and then gradually reduced to about 500 ° C. or less at a rate of 10 ° C./min or less. Examples thereof include a method of cooling, and a method of performing calcination in air or an oxygen atmosphere at a temperature of about 600 to 900 ° C. after calcination, and then annealing in an oxygen atmosphere at a temperature of about 400 ° C. The firing and cooling conditions are described in detail in JP-A-9-306490, JP-A-9-306493, JP-A-9-259880, and the like.
[0028]
As a preferred method for producing a lithium transition metal compound, a slurry in which a lithium compound, a transition metal compound, and a substituted metal element compound of a transition metal are further mixed in the presence of a solvent is spray dried and fired (hereinafter referred to as “spray dry method”). ”).
As another preferred production method, a transition metal compound, or a dried product obtained by spray-drying a slurry or a solution in which a transition metal substitution metal element compound is further mixed in the presence of a solvent in some cases, and lithium Examples thereof include a method in which a compound mixture is obtained to obtain a raw material mixture and then fired (hereinafter sometimes referred to as “post-Li addition spray drying method”).
[0029]
Hereinafter, specific embodiments of the production method of the present invention will be described.
・ For spray drying method
In the case of this manufacturing method, the following three methods can be considered as the manufacturing method of the present invention.
(I) A slurry obtained by mixing a lithium compound, a transition metal compound, and, optionally, a transition metal substitution metal element compound in the presence of a solvent, is spray-dried, and after firing, an article having a large particle size is obtained by an air classifier. A method for producing a lithium-transition metal composite oxide, characterized in that it is separated into small ones and a large particle size and a small one are blended in a weight ratio of 0: 100 to 100: 0.
[0030]
(Ii) A slurry obtained by mixing a lithium compound, a transition metal compound, and, optionally, a transition metal substitution metal element compound in the presence of a solvent, is spray-dried, and a product having a large particle size and a material having a small particle size by an air classifier A method for producing a lithium-transition metal composite oxide comprising: mixing a large particle size and a small particle size in a weight ratio of 0: 100 to 100: 0.
[0031]
(Iii) A slurry obtained by mixing a lithium compound, a transition metal compound, and, optionally, a transition metal substitution metal element compound in the presence of a solvent, is spray-dried, and a product having a large particle size and a material having a small particle size by an air classifier A method for producing a lithium-transition metal composite oxide comprising: separating a material having a large particle size and a material having a small particle size in a weight ratio of 0: 100 to 100: 0, followed by firing.
[0032]
In the above, the mixing ratio of the lithium compound and the transition metal compound is specifically described in the case where the transition metal compound is a manganese compound and the lithium transition metal composite oxide is a lithium manganese composite oxide. Usually, Li / Mn = 0.4 to 0.6, preferably 0.45 to 0.55, and more preferably 0.5 to 0.55. If Li is too much or too little, a sufficient capacity cannot be obtained.
[0033]
Further, when the transition metal compound is a nickel compound and the lithium transition metal composite oxide is a lithium nickel composite oxide, it will be explained in detail. Usually Li / Ni = 0.9 to 1.2 in terms of Li atom and Ni atom. The ratio is preferably 0.95 to 1.10, more preferably 1.0 to 1.05. If the amount of Li is too much or too little, good battery characteristics cannot be obtained.
[0034]
When the lithium transition metal composite oxide is a lithium transition metal composite oxide of other element substitution type, the slurry is a metal that becomes a substitution metal element of a transition metal other than manganese in addition to the lithium compound and the transition metal compound manganese compound. A compound containing an element (substitution element) is mixed.
When the transition metal is manganese, the mixing ratio of the compound containing a metal element other than manganese is, in terms of a metal atom other than Mn atom and manganese, the metal element other than manganese is 2.5 mol% or more of Mn, preferably It is 5 mol% or more of Mn, usually 30 mol% or less of Mn, and preferably 20 mol% or less of Mn. When there are too few metal elements other than manganese, the improvement effect of the high temperature cycle may not be sufficient, and when there are too many, the capacity | capacitance at the time of making a battery may fall. In this case, the quantitative ratio (Li / Mn) is a quantitative ratio of Li / (Mn + metal atom other than manganese). (That is, mixing ratio of lithium compound and manganese compound: Li atom, Mn atom, and metal atom other than manganese, usually Li / (Mn + metal atom other than manganese) = 0.4 to 0.6, preferably 0.45 The amount ratio is 0.55, more preferably 0.5 to 0.55.)
When the transition metal is nickel, the mixing ratio of the compound containing a metal element other than nickel is 2.5 mol% or more of Ni, preferably Ni. Is usually 30 mol% or less of Ni, preferably 20 mol% or less of Ni. If the amount of metal elements other than Ni is too much or too little, the effect of improving the high temperature cycle may not be sufficient. In this case, the quantitative ratio (Li / Ni) is a quantitative ratio of Li / (Ni + metal atom other than nickel). (That is, the mixing ratio of lithium compound and nickel compound is usually Li / (metal atom other than Ni + nickel) in terms of metal atoms other than Li atom, Ni atom and nickel) = 0.8 to 1.2, preferably 0.9 to 1.1, and more preferably 1.0 to 1.05.
As the dispersion medium used in the slurry, various organic solvents and aqueous solvents can be used, but water is preferred.
[0035]
The solid content concentration of the slurry indicates the ratio of the weight of the solid contained in the slurry with respect to the weight of the whole slurry, and is usually 10% by weight or more, preferably 12.5% by weight or more, usually 50% by weight or less, preferably Is 35% by weight or less. When the solid content concentration is less than the above range, the slurry concentration is extremely dilute, so that the spherical particles generated by spray drying may become unnecessarily small or breakage. When the saturation solubility is exceeded, the raw materials cannot be completely dissolved and the uniformity of the slurry cannot be maintained, or the fluidity of the slurry is lowered, and drying and granulation by spray drying tend to be difficult.
[0036]
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 is particularly remarkable when trying to produce granulated particles having an average particle diameter of 50 μm or less. Further, since it is not preferable to make particles smaller than necessary because it leads to an increase in the cost of pulverization, the average particle size of the solid is usually 0.01 μm or more, preferably 0.05 μm or more, more preferably 0.1 μm or more. To do. In addition, when a part of solid content at the time of raw material preparation has dissolved in the dispersion medium, “average particle diameter of solid content in slurry” means “undissolved solid content in slurry” Mean particle diameter ".
[0037]
As a method for controlling the average particle size of the solid matter in the slurry, the raw material powder is previously dry pulverized by a ball mill, a jet mill, etc., and this is dispersed in a dispersion medium by stirring, etc., the raw material powder is stirred in a dispersion medium, etc. And a method of wet pulverization using a medium stirring pulverizer after dispersion. In the present invention, it is preferable to use a method in which the raw material powder is dispersed in a dispersion medium and then wet pulverized using a medium stirring pulverizer or the like. The effect of the present invention is remarkably exhibited by wet pulverization.
[0038]
In the present invention, the average particle size of undissolved solids in the slurry is measured by a laser diffraction / scattering type particle size distribution measuring device. The slurry or powder is dispersed in a dispersion medium, the sample solution is irradiated with laser light, and the scattered light 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 diameter 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 to be used, for example, a 0.2% sodium hexametaphosphate aqueous solution is used, but is not limited thereto.
[0039]
Further, the viscosity of the slurry in the state subjected to spray drying 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 1000 mPa · s or less, Particularly preferably, it is 800 mPa · s or less. When the viscosity is below the above range, the spherical particles produced by spray drying become unnecessarily small or easily damaged, whereas when the viscosity exceeds the above range, the tube pump used for transporting the slurry during spray drying is used. Manufacturing problems such as inability to suction may occur. In the present invention, the viscosity is measured using a BM viscometer. In a room temperature atmosphere, a specific metal rotor is rotated, the rotor is rotated with the rotor immersed in slurry, and the viscosity is calculated from the resistance force (torsional force) applied to the rotating shaft. However, the room temperature atmosphere refers to a normally considered laboratory-level environment with a temperature of 10 ° C. to 35 ° C. and a humidity of 20% to 80%. Hereinafter, in the present specification, this condition may be referred to as room temperature atmosphere.
[0040]
The resulting slurry is subjected to spray drying. 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. There is no restriction | limiting in particular as gas supplied as a gas flow, Although air, nitrogen, etc. can be used, Usually, it is easy to use air. However, among these, in the presence of carbon dioxide or the like, since lithium tends to form lithium carbonate, the burden for conversion to oxide by subsequent baking tends to increase, so the concentration of carbon dioxide gas is low. Those such as nitrogen gas, decarboxylated air, and argon are desirable. These are preferably used under pressure. The gas flow is injected at a gas linear velocity of usually 100 m / s or more, preferably 200 m / s or more, more preferably 300 m / s or more. If it is too small, it is difficult to form appropriate droplets. However, since it is difficult to obtain a linear velocity that is too high, the normal injection speed is 1000 m / s 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. The scattered droplets are dried. As described above, an appropriate temperature, air blowing, or the like is applied so as to quickly dry the scattered droplets. Preferably, the drying gas is introduced from the upper part of the drying tower to the lower part in a downward flow. Is preferred. By adopting such a structure, the processing amount per unit capacity of the drying tower can be greatly improved. 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 the temperature is too high, the resulting granulated particles have a lot of hollow structures, and the powder packing density tends to decrease, whereas if it is too low, the powder adheres due to moisture condensation at the powder outlet. Problems such as blockage may occur.
[0041]
The dried product (granulated particles) can be obtained by spray drying in this manner, and the granulated particle size is preferably 50 μm or less, more preferably 30 μm or less in terms of average particle size. 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.
[0042]
The obtained dried product is then subjected to a firing treatment. The firing temperature is usually 500 ° C. or higher and usually 1000 ° C. or lower, although it varies depending on the type of transition metal and substitution element used as a raw material. If the temperature is too low, a long baking time tends to be required in order to obtain a lithium transition metal composite oxide having good crystallinity. In addition, if the temperature is too high, a crystal phase other than the target lithium transition metal composite oxide is generated, or a lithium transition metal composite oxide with many defects is generated. Or degradation due to the collapse of the crystal structure due to charge / discharge.
[0043]
On the other hand, although the firing time varies depending on the temperature, it is usually 30 minutes or more and 50 hours or less in 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.
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, 5 ° C./min. It is preferable to slowly cool at the following cooling rate.
[0044]
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 compound to be produced. For example, when producing a lithium manganese composite oxide having a layered structure, it is preferably performed in a vacuum or in an inert atmosphere such as nitrogen or argon.₂System, LiNiO₂When producing a system or spinel type lithium manganese oxide or the like, it is preferable to carry out in an oxygen-containing atmosphere such as air or oxygen at least in the slow cooling process.
[0045]
The heating device 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.
・ Spray drying method after Li addition
In the case of this manufacturing method, the following two methods can be considered as the manufacturing method of the present invention, for example.
(I) A transition metal compound, or, optionally, a transition metal substitution metal element compound mixed with a lithium compound and a dried material obtained by spray drying a slurry obtained by mixing a transition metal in the presence of a solvent, and a raw material After obtaining the mixture, it is fired and separated into a large particle size and a small particle size by an air classifier, and the large particle size and the small particle size are blended at a weight ratio of 0: 100 to 100: 0. A method for producing a lithium transition metal composite oxide, comprising:
(ii) A dried product obtained by spray-drying a slurry obtained by mixing a transition metal compound or a transition metal substitution metal element compound in the presence of a solvent in the presence of a solvent, and having a large particle size by classification. And a mixture of lithium compounds in each, followed by firing to produce a lithium transition metal composite oxide having a large particle size and a lithium transition metal composite oxide having a small particle size, A method for producing a lithium transition metal composite oxide comprising blending at a weight ratio of 0: 100 to 100: 0.
[0046]
The difference between the post-Li addition spray drying method and the above-described spray drying method is that a lithium compound is mixed with a transition metal compound, or, optionally, a slurry obtained by mixing a transition metal substitution metal element compound in the presence of a solvent. The dried product obtained by drying is mixed with a lithium compound before firing. The properties of the slurry such as the transition metal compound, the transition metal substitution metal element compound, the lithium compound, the slurrying solvent, and the solid content concentration are the same as in the spray drying method described above.
[0047]
The particle size of the lithium compound to be mixed with the dried product is usually 500 μm or less, preferably 100 μm or less, more preferably 100 μm or less in terms of average particle size in order to improve the mixing property with the dried product and to improve battery performance. Is 50 μm or less, most preferably 20 μm or less. On the other hand, those having a too small particle size have an average particle size of 0.01 μm or more, preferably 0.1 μm or more, more preferably 0.2 μm or more, and most preferably 0. 5 μm or more.
[0048]
The dried product and lithium compound are usually mixed to obtain a mixed powder. 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 for mixing may be air, but it is more preferable to mix in an inert gas in order to prevent carbon dioxide absorption in the atmosphere. The mixing composition ratio of the powder to be mixed is appropriately selected according to the composition of the target lithium transition metal nickel composite oxide.
[0049]
The mixed powder can be further mixed with other compounds as required. For example, when no other element compound is contained in the slurry or solution, the slurry or solution can be mixed with the lithium compound after drying and then further mixed with the other element compound. Moreover, when a part of other element compound is contained in the slurry or solution, after the slurry or solution is dried and mixed with the lithium compound, the remaining other element compound can be further mixed. In this case as well, there is no particular limitation on the mixing method, but it is preferable from the viewpoint of uniformity to mix using a powder mixing apparatus used industrially.
[0050]
The obtained mixed powder is then subjected to a firing treatment. The firing temperature, firing time, cooling rate, firing atmosphere, and heating apparatus used for firing are the same as those in the spray drying method.
・ Characteristics of lithium transition metal composite oxide
The obtained lithium transition metal composite oxide has an average primary particle size of usually 0.01 μm or more, preferably 0.02 μm or more, more preferably 0.1 μm or more, usually 30 μm or less, preferably 3 μm or less, more preferably Is 0.5 μm or less. The average secondary particle size is usually 1 μm or more, preferably 4 μm or more, and usually 60 μm or less. Furthermore, the specific surface area by nitrogen adsorption is 0.1-5 m.²/ G is preferable.
[0051]
The size of the primary particles can be controlled by the firing temperature, the firing time, and the like. By increasing one or more of these, the particle size of the primary particles can be increased.
The particle diameter of the secondary particles can be controlled by spraying conditions such as a gas-liquid ratio in the spray drying process.
[0052]
The specific surface area can be controlled by the primary particle size and the secondary particle size, and decreases by increasing the primary particle size and / or the secondary particle size.
The powder packing density is a tap density (after 200 taps), and is usually 0.80 g / cc or more, preferably 1.50 g / cc or more. The higher the powder packing density is, the larger the energy density per unit volume can be, but in reality it is 3.00 g / cc or less.
[0053]
In the case of the manufacturing method other than the spray drying method described above (mixing starting materials containing lithium, transition metal and substitution element, followed by firing and cooling in the presence of oxygen), the manufactured lithium transition metal composite oxide is sintered. Therefore, it is preferably pulverized before being applied to a classifier. Examples of the pulverization method include a jet mill, a dry ball mill, and a dry bead mill.
[0054]
The degree of pulverization is preferably such that the average particle diameter of the lithium transition metal composite oxide is 0.1 to 30 μm, more preferably 0.3 to 10 μm. If the particle size is too small, the cycle deterioration of the battery tends to increase. If the particle size is too large, the internal resistance of the battery may increase and output may be difficult to output.・ Classification and particle composition
The classifier in the present invention is not particularly limited as long as it can separate the lithium transition metal composite oxide into those having a large particle size and those having a small particle size. As the dry type, a dry type includes 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.
[0055]
  There is no particular limitation on the classification method, and the particle size may be divided into two groups or three or more groups with any particle size, but industrially, the equilibrium separation particle size is set so as to obtain desired characteristics. It is advantageous to decide. The equilibrium separation particle size is usually 1 to 10 μm, preferably 2 to 6 μm. By selecting the equilibrium separation particle size, it is possible to separate into those having excellent rate characteristics and those having a large capacity. Relatively particle sizebigContributes to higher capacity and has a relatively small particle size.smallThis contributes to improving the rate characteristics.
[0056]
In the present invention, the equilibrium separated particle size means the amount of coarse powder (“large particle size” in the present invention) brought to the fine powder (“small particle size” in the present invention) side and the coarse powder side. It is the particle size in which the amount of fine powder is equal (Powder Technology Pocket Book P.61: edited by Tsunemi Hayashi, Industrial Research Committee (1996)). When classifying spray-dried slurry mixed with lithium compound and transition metal compound in a solvent, the actual equilibrium separation particle size should be selected so that it can be classified within the range set when calcined at 900 ° C. That's fine.
[0057]
  The classified particle group can be blended at an arbitrary ratio in consideration of the rate characteristics and the capacity, and the battery characteristics can be optimized.
  As a specific blending ratio, a material having a large particle size and a material having a small particle size, in which the equilibrium separation particle size Dh is usually 1 to 10 μm, preferably 2 to 6 μm, in a weight ratio of 0: 100 to It can be blended at an arbitrary ratio of 100: 1. Among them, the weight ratio of the large particle size is 5% by weight or more, particularly 10% by weight or more, based on the total weight of the large particle size and small items. 50% by weight or less, especially 30% by weight or less, the specific surface area becomes excessive, the bulk densityButAppropriate valueYoIt is preferable because it is not low.
[0058]
In addition, in this invention, the other Li transition metal complex oxide produced separately can also be mixed. Although there is no particular limitation on the timing of blending, usually in the present invention, after making the Li transition metal composite oxide (after the firing treatment), prior to classification, or at the time of blending the particles after classification or after. Mixing may be mentioned. Moreover, it cannot be overemphasized that it can also mix | blend, after classifying the other Li transition metal complex oxide itself produced separately.
[0059]
The positive electrode material of the present invention can be used as a positive electrode for a lithium secondary battery.
The positive electrode is usually formed by forming an active material layer containing the positive electrode material, a binder, and a conductive agent on a current collector. In the present invention, the positive electrode active material is a lithium nickel composite oxide and a lithium manganese composite oxide. 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.
[0060]
The proportion of the positive electrode material of the present invention 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. It is as follows. If the amount of the positive electrode 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.
[0061]
As the binder used for the positive electrode, in addition to fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and fluorine rubber, EPDM (ethylene-propylene-diene ternary copolymer) is used. 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 is too large, the capacity may be insufficient. If the amount is too small, the strength may be insufficient.
[0062]
Moreover, as a solvent used when preparing a slurry, the organic solvent which melt | dissolves or disperse | distributes 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.
[0063]
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.
[0064]
The lithium secondary battery of the present invention usually has the positive electrode, the negative electrode, and a non-aqueous electrolyte.
As a negative electrode material that can be used in the lithium secondary battery of the present invention, a carbon material is preferably used. Such carbon materials include natural or artificial graphite, petroleum coke, coal coke, petroleum pitch carbide, coal pitch carbide, phenolic resin / crystalline cellulose resin carbide and some of these carbonized. Examples thereof include carbon materials, furnace black, acetylene black, pitch-based carbon fibers, PAN-based carbon fibers, or a mixture of two or more thereof. 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 conductive agent that can be used for the negative electrode are the same as those used for the positive electrode.
[0065]
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.
Examples of the non-aqueous electrolyte solution that can be used in the lithium secondary battery of the present invention include those obtained by dissolving various electrolytic salts in a non-aqueous solvent.
[0066]
Examples of the non-aqueous solvent include carbonates, ethers, ketones, sulfolane compounds, lactones, nitriles, halogenated hydrocarbons, amines, esters, amides, phosphate ester compounds, and the like. 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, and either alone or two or more kinds of mixed solvents such as triethyl phosphate may be used.
[0067]
Among the above non-aqueous solutions, 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.
[0068]
As the electrolytic salt, any conventionally known salt can be used, and LiClO._Four, LiAsF₆, LiPF₆, LiBF_Four, LiB (C₆H_Five)_Four, LiCl, LiBr, LiCH_ThreeSO_ThreeLi, LiCF_ThreeSO_Three, LiN (SO₂CF_Three)₂, LiN (SO₂C₂F_Five)₂, LiC (SO₂CF_Three)_Three, LiN (SO_ThreeCF_Three)₂And lithium salts such as
[0069]
CO₂, N₂O, CO, SO₂Such as gas and polysulfide Sx^2-In addition, an additive such as vinylene carbonate or catechol carbonate may be present in the electrolyte solution at an arbitrary ratio to form a good film that enables efficient charge and discharge of lithium ions on the negative electrode surface.
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. In the lithium secondary battery of the present invention, an electrolyte layer can be provided between the positive electrode and the negative electrode using various materials as described above.
[0070]
Usually, a separator is 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. Moreover, 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, the polymer is preferably a polyolefin polymer, 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.
[0071]
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. On the other hand, 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.
[0072]
【Example】
  Hereinafter, the present invention will be described more specifically with reference to examples.
  [Battery assembly, capacity and rate measurement] 75 layers of positive electrode active materialamount%, 20% by weight of acetylene black and 5% by weight of polytetrafluoroethylene powder are thoroughly mixed in a mortar, made into a thin sheet, and punched with a 9 mmφ punch. At this time, the total weight is adjusted to about 8 mg each. This was crimped to Al expanded metal to obtain a positive electrode.
[0073]
A coin-type cell having the configuration shown in FIG. 1 was assembled using the positive electrode as a test electrode and Li metal as a counter electrode, and the battery performance was evaluated. That is, a positive electrode 2 is placed on a positive electrode can 1, a 25 μm porous polyethylene film is placed thereon as a separator 3, pressed by a polypropylene gasket 4, a counter electrode 5 is placed, and a spacer 6 for adjusting the thickness is placed. After that, as a non-aqueous electrolyte solution, 1 mol / liter lithium hexafluorophosphate (LiPF₆) Dissolved in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 3: 7, and this was added to the battery and sufficiently impregnated. Then, a negative electrode can was placed and the battery was sealed. .
[0074]
0.5mA / cm²Constant current charging, that is, a reaction for releasing lithium ions from the positive electrode at an upper limit of 4.35 V, and then 0.5 mA / cm²Constant current discharge, that is, the initial charge capacity per unit weight of the positive electrode active material when the test for occluding lithium ions in the positive electrode at a lower limit of 3.2 V is Qs (C) mAh / g, and the initial discharge capacity is Qs (D) Set to mAh / g.
Further, constant current charge / discharge for rate evaluation is performed in the voltage range described above. As a condition, constant current charging is 0.5 mA / cm.²At a constant current discharge of 0.5 mA / cm²1mA / cm²3mA / cm²5mA / cm², 7mA / cm²9mA / cm²11mA / cm²11mA / cm²The discharge capacity when discharged at is Ql (D) mAh / g.
[0075]
Example 1
Mn₂O_Three, AlOOH, LiOH · H₂Each of O was weighed so as to be Li: Mn: Al = 1.04: 1.84: 0.12 (molar ratio) with the composition in the final spinel type lithium manganese composite oxide. Water was added to prepare a slurry having a solid concentration of 30% by weight. While stirring this slurry, a circulating medium stirring wet pulverizer is used to grind until the average particle size of the solid content in the slurry reaches 0.5 μm, and then a nozzle having a droplet refining mechanism is provided. Spray drying was carried out using a spray dryer (manufactured by Fujisaki Electric Co., Ltd., Micro Mist Dryer MDP-050, nozzle type circle edge nozzle, drying tower dimensions 2500 mmφ × 4800 mmH).
[0076]
The amount of dry gas introduced at this time is 23 m.^Three/ Min, the drying gas inlet temperature was 90 ° C. Also, as the spray nozzle, use a type that can be sprayed horizontally in the 360 ° (annular) direction with a diameter of 30mmφ, the nozzle slurry outlet clearance is 600μm, and the pressurized gas outlet clearance for making the slurry finer Set to 350 μm. The slurry supply rate was 700 g / min, and the pressurized gas flow supply rate was 1300 L / min (the gas linear velocity of the gas flow was 330 m / s). The exhaust gas temperature when spray-dried under these conditions was 45 ° C.
[0077]
The dried granulated particles are passed through a cyclone classifier, and the equilibrium separation particle size D_hIt was separated into a product having a large particle size (hereinafter referred to as “coarse powder”) and a small particle size (hereinafter referred to as “fine powder”) at 4.2 μm. This D_hIs measured after firing at 900 ° C. The particle size distribution after firing at 900 ° C. is shown in FIG.
Only the coarse powder was fired at 900 ° C. to obtain a positive electrode active material. The evaluation results of the battery are shown in Table 1.
[0078]
Example 2
The coarse powder and fine powder obtained in Example 1 were mixed at 87:13 and then fired at 900 ° C. to obtain a positive electrode active material. The evaluation results of the battery are shown in Table 1.
Example 3
The coarse powder and fine powder obtained in Example 1 were each fired at 900 ° C. and mixed at 87:13 to obtain a positive electrode active material. The evaluation results of the battery are shown in Table 1.
[0079]
Example 4
Only the fine powder obtained in Example 1 was fired at 900 ° C. to obtain a positive electrode active material. The evaluation results of the battery are shown in Table 1.
Example 5
NiO, Co (OH)₂, And AlOOH were weighed so that Ni: Co: Al = 0.80: 0.15: 0.05 (molar ratio) with the composition in the final layered rock salt type lithium nickel composite oxide. Pure water was added to the slurry to prepare a slurry having a solid content concentration of 30% by weight. While stirring this slurry, a circulating medium stirring type wet pulverizer is used to grind until the average particle size of the solid content in the slurry becomes 0.3 μm, and then a nozzle having a droplet refining mechanism is provided. Spray drying was performed using a spray dryer (manufactured by Fujisaki Electric Co., Ltd., Micro Mist Dryer MDP-050, the nozzle type was a circle edge nozzle, and the drying tower size was 2500 mmφ × 4800 mmH).
[0080]
The amount of dry gas introduced at this time is 23 m.^Three/ Min, the drying gas inlet temperature was 105 ° C. Also, as the spray nozzle, use a type that can be sprayed horizontally in the 360 ° (annular) direction with a diameter of 30mmφ, the nozzle slurry outlet clearance is 600μm, and the pressurized gas outlet clearance for making the slurry finer Set to 350 μm. The slurry supply rate was 700 g / min, and the pressurized gas flow supply rate was 1800 L / min (the gas linear velocity of the gas flow was 450 m / s). The exhaust gas temperature when spray-dried under these conditions was 60 ° C.
[0081]
The dried granulated particles are passed through a cyclone classifier, and the equilibrium separation particle size D_hIt was separated into a product having a large particle size (hereinafter referred to as “coarse powder”) and a small particle size (hereinafter referred to as “fine powder”) at 4.2 μm. LiOH powder was added to each separated powder so that Li: Ni: Co: Al = 1.05: 0.80: 0.15: 0.05 (molar ratio), and a powder mixer was used. And mixed. Each powder was fired in an oxygen stream at 740 ° C. and pulverized to produce a lithium transition metal oxide powder.
[0082]
Table 1 shows the evaluation results of the battery with only coarse powder.
Example 6
After mixing the coarse powder and fine powder obtained in Example 5 at 87:13, Li: Ni: Co: Al = 1.05: 0.80: 0.15: 0.05 (molar ratio). LiOH powder was added to the mixture, and the same firing as in Example 5 was performed to obtain a positive electrode active material. The evaluation results of the battery are shown in Table 1.
Example 7
LiOH powder was added to each of the coarse powder and fine powder obtained in Example 5 so that Li: Ni: Co: Al = 1.05: 0.80: 0.15: 0.05 (molar ratio). The same firing as in Example 5 was performed, and a positive electrode active material prepared from coarse particles and a positive electrode active material prepared from fine particles were mixed at 87:13 to obtain a positive electrode active material. The evaluation results of the battery are shown in Table 1.
Example 8
LiOH powder was added to the powder containing only fine powder obtained in Example 1 so that Li: Ni: Co: Al = 1.05: 0.80: 0.15: 0.05 (molar ratio). Firing was performed in the same manner as in Example 5 to obtain a positive electrode active material. The evaluation results of the battery are shown in Table 1.
[0083]
[Table 1]

[0084]
From the above results, the positive electrode active material consisting only of coarse powder (Example 5) has a large capacity but inferior in the rate characteristic, and the positive electrode active material consisting only of fine powder (Example 8) has a small capacity but the rate characteristic. It turns out that it is excellent.
FIG. 3 and FIG. 4 are graphs showing the relationship between the ratio of the coarse powder in the positive electrode active material and the capacity based on the results of Examples 1 to 4 and Examples 5 to 8. As apparent from FIGS. 3 and 4, the capacity and rate characteristics are additive by the mixing ratio, so by mixing coarse powder and fine powder at an arbitrary ratio, the capacity and rate can be repeated without repeating trial and error. You can freely choose the balance of characteristics.
[0085]
【The invention's effect】
According to the present invention, positive electrode materials for lithium secondary batteries having various balances of rate characteristics and capacity can be easily manufactured.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a coin-type battery used in a test of a method for producing an active material for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention.
[Figure 2] Figure showing the particle size distribution of coarse and fine powder after firing at 900 ° C
FIG. 3 is a graph showing the relationship between the proportion of fine powder in the positive electrode active materials of Examples 1 to 4 and the capacity.
4 is a graph showing the relationship between the proportion of fine particles in the positive electrode active materials of Examples 5 to 8 and the capacity. FIG.
[Explanation of symbols]
1 Positive electrode can
2 Positive electrode
3 Separator
4 Gasket
5 Negative electrode (counter electrode)
6 Spacer
7 Negative electrode can

Claims (15)

  Lithium transition metal composite oxide, in which part of the transition metal may be substituted with other metal elements, is passed through a classifier, and separated into a large particle size and a small particle size with an equilibrium separation particle size Dh = 1 to 10 μm Then, a method for producing a positive electrode material for a lithium secondary battery, wherein a material having a large particle size and a material having a small particle size are blended at a weight ratio of 0: 100 to 100: 0.   Under spraying conditions such that the equilibrium separation particle diameter Dh after firing a slurry obtained by mixing a lithium compound, a transition metal compound, and a transition metal substitution metal element compound in the presence of a solvent in the presence of a solvent is 1 to 10 μm. After spray-drying and separating with an airflow classifier into a large particle size and a small particle size with an equilibrium separation particle size Dh = 1 to 10 μm and then calcining each, a large particle size and a small particle size by weight ratio The manufacturing method of the positive electrode material for lithium secondary batteries characterized by mix | blending by 0: 100-100: 0.   Under spraying conditions such that the equilibrium separation particle diameter Dh after firing a slurry obtained by mixing a lithium compound, a transition metal compound, and a transition metal substitution metal element compound in the presence of a solvent in the presence of a solvent is 1 to 10 μm. Spray dried and separated by an airflow classifier into a large particle size and a small particle size with an equilibrium separation particle size Dh = 1 to 10 μm, and a large particle size and a small particle size in a weight ratio of 0: 100 to 100: A method for producing a positive electrode material for a lithium secondary battery, characterized by comprising mixing at 0 and then firing.   Spray drying under spray conditions such that the equilibrium separation particle diameter Dh after firing of a slurry obtained by mixing a transition metal compound or, optionally, a transition metal substitution metal element compound in the presence of a solvent, is 1 to 10 μm The obtained dried product is separated by separation into a product having a large particle size and a product having a small particle size at an equilibrium separation particle size Dh = 1 to 10 μm, mixed with a lithium compound, and then calcined. A lithium transition metal composite oxide having a large particle size and a lithium transition metal composite oxide having a small particle size are prepared and then blended at a weight ratio of 0: 100 to 100: 0. Manufacturing method of positive electrode material.   The manufacturing method according to claim 1, wherein the positive electrode material is a lithium manganese composite oxide. The positive electrode material

The manufacturing method in any one of Claims 1 thru | or 5 represented by these.   The production method according to claim 2, wherein the transition metal compound is a manganese compound.   The manufacturing method according to claim 7, wherein the mixing ratio of the lithium compound and the manganese compound is an amount ratio such that Li / Mn = 0.4 to 0.6 in terms of Li atom and Mn atom.   Manganese substituted metal element compound is an oxide, hydroxide, nitrate, carbonate, dicarboxylate, fatty acid salt of a metal selected from B, Al, Fe, Sn, Cr, Cu, Ti, Zn, Co, Ni Or a production method according to claim 7 or 8, which is an ammonium salt.   10. The production according to claim 9, wherein the mixing ratio of the substituted metal element compound of manganese is such that the metal element other than manganese is 2.5 to 30 mol% of Mn in terms of metal atoms other than Mn atom and manganese. Method.   The manufacturing method according to claim 1, wherein the positive electrode material is a lithium nickel composite oxide. The positive electrode material

M is a group consisting of Co, Mn, Fe, Cr, V, Ti, Cu, Al, Ga, Bi, Sn, Zn, Mg, Ge, Nb, Ta, Be, B, Ca, Sc and Zr Represents at least one element selected from: δ corresponds to oxygen deficiency or oxygen excess, and represents −0.1 <δ <0.1. The manufacturing method in any one of Claims 1 thru | or 4 represented by these.   The production method according to claim 2, wherein the transition metal compound is a nickel compound.   The mixing ratio of the total number of the total number of atoms of the lithium compound, the nickel compound, and the substitution element thereof is such that the total amount of Li atom, Ni atom, and substitution atom M is Li / (Ni + M) = 1.1 to 0.9. The manufacturing method according to claim 13.   Nickel substitution metal element compounds are Co, Mn, Fe, Cr, V, Ti, Cu, Al, Ga, Bi, Sn, Zn, Mg, Ge, Nb, Ta, Be, B, Ca, Sc and Zr. The production method according to claim 13 or 14, which is an oxide, hydroxide, nitrate, carbonate, dicarboxylate, fatty acid salt or ammonium salt of a metal selected from the group consisting of:

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