JP4228659B2 - Method for producing lithium transition metal composite oxide - Google Patents

Description

【００８２】
【発明の効果】
本発明によれば、充填率の高いリチウム遷移金属複合酸化物を製造することができ、このリチウム遷移金属複合酸化物を正極活物質として用いることにより、単位体積当たりの電池容量が高いリチウム二次電池を提供することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a lithium transition metal composite oxide.
[0002]
[Prior art]
By using a carbon material or the like capable of occluding and releasing lithium ions in place of metallic lithium as the negative electrode active material, the safety of lithium secondary batteries has been greatly improved and has entered the practical stage.
On the other hand, as a positive electrode active material for a lithium secondary battery, the standard composition is LiCoO.₂And LiNiO₂, LiMn₂O₄Lithium transition metal composite oxides such as indicated above are now in practical use. In particular, LiMn₂O₄Manganese positive electrode active materials composed of lithium manganese composite oxides, etc., have the advantage that manganese, which is a component, has a large amount of reserves compared to cobalt and nickel, is inexpensive, and has high safety in overcharging. Have.
[0003]
As a method for producing a lithium transition metal composite oxide, for example, Patent Document 1 describes a method for producing a lithium transition metal composite oxide by spray drying a slurry containing a lithium compound and a transition metal compound and then firing the slurry. However, the present inventors have found that in this method, the lithium transition metal composite oxide obtained in some cases becomes hollow particles, and the battery capacity per unit volume is reduced.
[0004]
That is, as shown in Comparative Example 1 described later, a slurry is formed with a transition metal compound using lithium hydroxide monohydrate, which is well known as a lithium source of a lithium transition metal composite oxide, and spray-dried. When fired, there is a problem that hollow particles are easily generated.
[0005]
[Patent Document 1]
JP 2001-48547 A
[0006]
[Problems to be solved by the invention]
Accordingly, the present invention provides a method for preventing the formation of hollow particles during spray drying in a method for producing a lithium transition metal composite oxide by spray drying a slurry containing a lithium compound and a transition metal compound and then firing the slurry. It is something to try.
[0007]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventors have determined that the lithium transition metal composite oxide particles obtained by spray drying and firing are hollow particles by setting the concentration of dissolved salts in the slurry to a certain level or less. The present invention has been completed by finding that it can be suppressed.
[0008]
  That is, the gist of the present invention is a slurry containing at least one transition metal compound selected from a manganese compound, a cobalt compound and a nickel compound, and a lithium compound, and further containing a metal compound other than these. Spray dried and then firedA hexagonal layered rock salt structure or a spinel structure containing at least one transition metal selected from the group consisting of manganese, nickel and cobalt and lithium, wherein a part of the transition metal may be substituted with another transition metalIn a method for producing a lithium transition metal composite oxide,Of the lithium compound, transition metal compound, and other metal compounds other than these used as the slurry raw material, measured by the following measurement method, dissolved in the solventThe concentration in the slurry,A method for producing a lithium transition metal composite oxide, characterized by comprising 5% by weight or less based on the total solid content.
(Measuring method)
A part of the slurry (about 50 g) is centrifuged at 300 rpm for 20 minutes, and a clear supernatant is collected. After measuring the weight (W1) of the collected supernatant, it is evaporated to dryness at 150 ° C., and the weight (W2) of the residue is measured. Therefore, the concentration S (% by weight) of the dissolved salts in the liquid is S = (W2 / W1) × 100.
On the other hand, the solvent used in the slurry preparation and the weight of the metal compound are W3 and W4, respectively, and the concentration A (wt%) of the dissolved salts with respect to the total solid content in the slurry is defined by the following equation.
[Expression 1]
A = {(W3 × S / 100) / W4} × 100
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, the manganese compound, nickel compound, cobalt compound and lithium compound used for the preparation of the slurry to be spray-dried are appropriately selected from those known to be used as raw materials for lithium transition metal composite oxides. Can be used. Specific examples include oxides of manganese, nickel, cobalt, and lithium; hydroxides; halides; inorganic acid salts such as carbonates, sulfates, and nitrates; organic acid salts such as acetates. Preferably, a compound hardly soluble in water is used.
In the present invention, “poorly soluble in water” means that the solubility in 100 g of water at 25 ° C. is 5.0 g or less, preferably 2.0 or less.
[0010]
As a manganese compound, Mn₂O₃, MnO₂, Mn_ThreeO_FourManganese oxides such as MnCO₃, Mn (NO₃)₂ , MnSO₄And manganese salts such as manganese acetate, manganese dicarboxylate, manganese citrate, and fatty acid manganese, oxyhydroxides, halides, and the like. Mn₂O₃As MnCO₃And MnO₂You may use what produced and heat-processed compounds, such as. Preferably, Mn₂O_Three, Mn_ThreeO_Four, MnO₂Oxides such as Mn (OH)₂A compound which is hardly soluble in water, such as a hydroxide such as, is used.
Specific examples of nickel compounds include NiO and NiO.₂Oxides such as Ni (OH)₂NiOOH; NiCl₂Halides such as NiCO_ThreeEtc. Preferably, an oxide such as NiO, Ni (OH)₂Such a compound that is hardly soluble in water is used.
[0011]
As a cobalt compound, Co (OH)₂Hydroxides such as CoO, Co₂O_ThreeOxides such as CoCl₂Halides such as Co (NO_Three)₂・ 6H₂Nitrates such as O, Co (SO_Four)₂・ 7H₂And sulfates such as O. Preferably, a poorly soluble compound such as cobalt hydroxide or cobalt carbonate is used.
[0012]
Examples of the lithium compound include lithium hydroxide, lithium carbonate, lithium nitrate, lithium sulfate, lithium acetate salt, etc., preferably lithium carbonate, lithium sulfate, and particularly preferably lithium carbonate.
[0013]
In the slurry, at least one transition metal compound selected from a manganese compound, a cobalt compound, and a nickel compound, and a metal compound other than a lithium compound are contained, and finally a lithium transition metal composite oxide obtained is obtained. Metals other than manganese, cobalt, nickel, and lithium can also be contained.
[0014]
Such metals other than manganese, cobalt, nickel and lithium are not particularly limited as long as they can enter the structure of the lithium transition metal composite oxide. Specifically, 2A group elements such as Be, Mg and Ca, 3A group elements such as Sc, 4A group elements such as Ti and Zr, 5A group elements such as V, Nb and Ta, 6A group elements such as Cr, Metals such as Group 8 elements such as Fe, Group 1B elements such as Cu, Group 2B elements such as Zn, Group 3B elements such as B, Al, and Ga, Group 5B elements such as Bi, and Group 4B elements such as Ge and Sn Elements. Preferable examples include V, Nb, Cr, Fe, Bi, and Al.
[0015]
Lithium transition metal composite oxides containing these metals often have better performance as positive electrode active materials for lithium secondary batteries than the original composite oxides. It is considered that the transition metal selected from nickel and nickel is substituted to exist in the structure of the lithium transition metal composite oxide and the structure is stabilized.
[0016]
The basic composition of the lithium transition metal composite oxide is composed of any one of transition metals of manganese, nickel, and cobalt and lithium. However, a part of this transition metal can be replaced with another transition metal. In many cases, the performance of the lithium transition metal composite oxide as a positive electrode active material is often improved as in the case of substituting with a metal other than the transition metal. When a part is substituted with another transition metal, the atomic ratio is preferably 50% or less, particularly preferably 30% or less.
[0017]
When the transition metal is Ni, the metals that substitute for a part thereof are usually Co, Mn, Fe, Cr, V, Ti, Cu, Al, Ga, Bi, Sn, Zn, Mg, Ge, Nb, Ta, Examples include at least one element selected from the group consisting of Be, B, Ca, Sc and Zr, preferably those selected from the group consisting of Co, Al, Fe, Mg and Mn, and particularly preferably Co. Al. Further, when the transition metal is Mn, the metal that replaces a part thereof is usually at least one element selected from the group consisting of B, Al, Fe, Sn, Cr, Cu, Ti, Zn, Co, and Ni A preferable example is Al. When the transition metal is Co, the metal for substituting a part thereof is usually selected from the group consisting of Co, Al, Fe, Mg and Mn, and preferably Al and Ni.
[0018]
A metal that substitutes a part of the transition metal atom may be contained in the slurry as an oxide, hydroxide, nitrate, carbonate, dicarboxylate, fatty acid salt, ammonium salt, or the like, like the transition metal. Preferably, a compound hardly soluble in water, for example, an oxide, a hydroxide, an oxyhydroxide and the like can be used. When the other metal is aluminum, AlOOH is preferably used.
[0019]
As the solvent used for preparing the slurry, various organic solvents and aqueous solvents can be used, but water is preferred.
In the present invention, a lithium compound, a transition metal compound, and other metal compounds used in combination as required are mixed with a solvent to obtain a slurry. Next, the slurry is preferably pulverized by a ball mill or the like. Alternatively, the solid raw material may be pulverized first and then mixed with a solvent to form a slurry.
[0020]
The slurry concentration is not particularly limited, and is usually 1% by weight or more, preferably 5% by weight or more, more preferably 10% by weight or more, and particularly preferably 20% by weight or more. When the slurry concentration is too low, productivity is lowered and the bulk density of particles obtained by spray drying tends to be reduced. The upper limit of the slurry concentration is usually 50% by weight or less. If the slurry concentration is too high, the viscosity of the slurry becomes high, and there is a possibility that it cannot be sprayed with a nozzle. The preferred slurry concentration is 45% by weight or less, particularly 40% by weight or less.
[0021]
Further, the viscosity of the slurry is usually 100 mPs · s or more, preferably 300 mPs · s or more, and usually 1000 mPs · s or less, preferably 800 mPs · s or less. If the viscosity of the slurry is too low, composition deviation tends to occur inside the droplets when sprayed, and if it is too high, it may not be possible to spray with a nozzle.
[0022]
The ratio of metals to each other in the slurry may be generally matched with the composition of the lithium transition metal composite oxide to be finally obtained, and is usually ± 20% with respect to the standard composition of the lithium transition metal composite oxide. Within 10%, preferably within ± 10%. The preferred atomic ratio of lithium to the sum of metals other than lithium in the slurry (ie, transition metals and other metals optionally present to replace some of the transition metals in the lithium transition composite oxide) It depends on the metal.
[0023]
In the present invention, a slurry in which the ratio of dissolved salts to the total solid content is 5% by weight or less is subjected to spray drying.
The dissolved salt refers to a metal compound dissolved in a solvent constituting the slurry. Specifically, the lithium salt, transition metal compound, and other metal compounds other than these used as a solvent for the slurry are used as a solvent. It means the dissolved one.
[0024]
In the present invention, the concentration of dissolved salts with respect to the total solid content in the slurry is measured by the following method.
First, a part (about 50 g) of the slurry is centrifuged at 300 rpm for 20 minutes, and a transparent supernatant is collected. After measuring the weight (W1) of the collected supernatant, it is evaporated to dryness at 150 ° C., and the weight (W2) of the residue is measured. Accordingly, the concentration S (% by weight) of the dissolved salts in the liquid is S = (W2 / W1) × 100.
[0025]
On the other hand, the solvent used in the slurry preparation and the weight of the metal compound are W3 and W4, respectively, and the concentration A (% by weight) of the dissolved salts relative to the total solid content in the slurry is defined by
[0026]
【number2]
  A = {(W3 × S/ 100) / W4} × 100
[0027]
The reason why the resulting lithium transition metal composite oxide is less likely to be hollow by reducing the ratio of the dissolved salts in the slurry used for spray drying to the total solid content is not clear, but is presumed as follows. In the droplet formed by spraying, the dissolved salts in the slurry are dissolved in the droplet at a substantially uniform concentration. As drying progresses and moisture evaporates from the droplet surface, the dissolved salts are transported from the inside to the droplet surface and concentrate on the droplet surface. When the concentration progresses and the dissolved salt exceeds the saturation concentration, the dissolved salt begins to precipitate on the surface of the droplet and forms a film on the surface of the lithium transition metal composite oxide particle. Even after this film is formed, the temperature inside the droplet continues to rise and the liquid is gasified. When the generation rate of this gas exceeds the desorption rate, it is presumed that the internal pressure increases, the coating bursts, and hollow particles are generated.
Therefore, if the concentration of the dissolved salt is low, a continuous skin film sufficient to contain the generated gas is not formed, so that no particle rupture occurs, and therefore, no hollow particle is generated.
[0028]
According to the present inventors' study, in order to suppress the formation of hollow particles, the concentration of dissolved salts relative to the total solid content in the slurry to be spray-dried is 5 wt% or less, preferably 4.5 wt% or less. To do. The lower the concentration of the dissolved salt relative to the total solid content in the slurry, the more preferable it is because the formation of a film by the dissolved salt can be suppressed, but it is usually not necessary to make it 0.05% by weight or less.
[0029]
If the concentration of dissolved salts can be controlled within the above range, a lithium compound, a transition metal compound, a metal compound replacing the transition metal and a compound other than a solvent, such as a compound that is easily soluble in water, may be added to the slurry. Also good. For example, a low melting point compound such as boric acid or lithium borate that acts as a firing aid may be added in an amount of about 0.2 to 1% by weight based on the solid content in the slurry.
[0030]
The slurry is preferably spray-dried so that the resulting spray-dried powder has an average particle size of 1 to 100 μm, particularly 3 to 30 μm. The drying gas is preferably introduced into the spraying device at 80 to 300 ° C. and discharged from the device at 45 to 250 ° C.
The obtained spray-dried powder is fired and converted into a lithium transition metal composite oxide. The firing conditions are not particularly limited. For example, the methods described in JP-A-9-306490, JP-A-9-306493, JP-A-9-259880 and the like can be used.
[0031]
The firing temperature for obtaining a lithium manganese composite oxide whose main transition metal is manganese (hereinafter sometimes referred to as “lithium manganese composite oxide”) is usually 600 ° C. or higher, usually 1000 ° C. or lower, preferably 950 ° C. Below, it is 900 degrees C or less especially preferably. If the firing temperature is too low, it is difficult to obtain a lithium manganese composite oxide with good crystallinity. On the other hand, if the firing temperature is too high, the lithium compound is diffused, so that a lithium manganese composite oxide having the composition of the target compound cannot be obtained.
[0032]
The firing time is usually 1 hour or more, preferably 2 hours or more, and usually 100 hours or less, preferably 50 hours or less. If the firing time is too short, it is difficult to obtain a lithium-nickel composite oxide with good crystallinity. Conversely, it is meaningless to make the firing time longer than necessary.
[0033]
Firing is usually performed in air, but can also be performed in other oxygen-containing gases. In addition, when baking in air, it is preferable to use air from which carbon dioxide has been previously removed.
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. It is also preferable to keep the temperature constant so that the entire temperature becomes uniform.
[0034]
In order to obtain a lithium-manganese composite oxide with few defects, it is preferable to cool slowly after the above baking, and it is preferable to slowly cool at a cooling rate of 100 ° C. or less up to 700 ° C., preferably up to 500 ° C. per hour. .
The lithium manganese composite oxide produced by firing is basically LiMn.₂O_FourSpinel structure lithium manganate or LiMnO₂Is a layered structure lithium manganate having a reference composition.
[0035]
The firing temperature in the case of a lithium transition metal composite oxide whose main transition metal is nickel (hereinafter sometimes referred to as “lithium nickel composite oxide”) is usually 500 ° C. or higher, preferably 550 ° C. or higher. Usually, it is 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. However, it is preferable to maintain the temperature constant so that the entire temperature becomes uniform.
[0036]
The firing time is usually 1 hour or more, preferably 2 hours or more, and usually 100 hours or less, preferably 50 hours or less. If the firing time is too short, it is difficult to obtain a lithium nickel composite oxide with good crystallinity. Conversely, a reaction time that is too long is industrially meaningless.
Firing is usually performed in air, but can also be performed in other oxygen-containing gases. In addition, when baking in air, it is preferable to use air from which carbon dioxide has been previously removed.
[0037]
In order to obtain a lithium-nickel composite oxide with few defects, it is preferable to cool slowly after the above firing, and it is preferable to slowly cool to 600 ° C., preferably 400 ° C. at a cooling rate of 5 ° C. or less per minute. . The lithium nickel composite oxide produced by firing preferably has a hexagonal layered rock salt structure.
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 is used regardless of the type of transition metal. Can
[0038]
Specifically, as a lithium manganese composite oxide produced by firing, LiMn₂O₄Spinel structure lithium manganate, LiMnO₂And lithium manganate having a layered structure with a basic composition of Spinel structure type lithium manganate is preferable because it is easy to manufacture and has excellent cycle characteristics when used as a positive electrode active material.
[0039]
One of the preferable compositions of the spinel structure lithium manganese composite oxide is represented by the following formula.
[0040]
[Chemical 3]
Li_aMn_2-b M_bO₄
[0041]
M represents a metal element other than Li and Mn, and usually represents at least one element selected from the group consisting of B, Al, Fe, Sn, Cr, Cu, Ti, Zn, Co and Ni, preferably Al It is.
[0042]
a is usually 0.8 or more, preferably 1.0 or more, and usually 1.5 or less, preferably 1.2 or less. B is usually greater than 0, preferably 0.05 or more, and usually 1 or less, preferably 0.5 or less.
Particularly preferred are those represented by the following formula.
[0043]
[Formula 4]
Li_aMn_2-bAl_bO₄
[0044]
a is usually 0.9 or more, preferably 1 or more, and usually 1.1 or less, preferably 1.05 or less. B is usually larger than 0, preferably 0.05 or more, usually 1.0 or less, preferably 0.5 or less.
[0045]
In any of the above formulas, the amount of oxygen can vary. It is also possible to replace a part of the manganese atom site with lithium, for example, by using a stoichiometric amount or more of lithium as a raw material.
[0046]
One of the preferable compositions of the lithium composite oxide having a hexagonal layered rock salt structure formed by firing is represented by the following formula.
[0047]
[Chemical formula 5]
Li_c(Ni_dMn_eCo_fM_g) O₂
[0048]
In the formula, M represents a metal element other than Li, Ni, Mn, and Co, and usually Fe, Cr, V, Ti, Cu, Al, Ga, Bi, Sn, Zn, Mg, Ge, Nb, Ta, and Be. And at least one element selected from the group consisting of B, Ca, Sc and Zr, preferably at least one element selected from the group consisting of Al, Fe and Mg.
[0049]
c is 0.8 or more and 1.3 or less, preferably 1.2 or less. D is a number of 0 or more and 1 or less, e is a number of 0 or more and 1 or less, f is a number of 0 or more and 1 or less, g is a number of 0 or more and 1 or less, and d, e, f And the sum of g is 1.
Also, any of d, e, and f is preferably 0.5 or more and less than 1.
[0050]
Specific examples of the lithium nickel composite oxide generated by firing include a lithium nickel composite oxide having a hexagonal layered rock salt structure, and the lithium nickel composite oxide having a hexagonal layered rock salt structure is represented by the following general formula. expressed.
[0051]
[Chemical 6]
Li_xNi_1-yM_yO₂
[0052]
M represents a metal element other than Li and Ni, and usually Co, Mn, Fe, Cr, V, Ti, Cu, Al, Ga, Bi, Sn, Zn, Mg, Ge, Nb, Ta, Be, B , At least one element selected from the group consisting of Ca, Sc and Zr, preferably at least one element selected from the group consisting of Co, Al, Fe, Mg and Mn, particularly preferably Co, Al It is.
x is usually 0.8 or more and usually 1.3 or less, preferably 1.2 or less. Moreover, y is usually larger than 0, preferably 0.1 or more, and usually 0.5 or less, preferably 0.4 or less.
[0053]
In any of the above formulas, the amount of oxygen can vary. The fluctuation amount of oxygen, that is, oxygen deficiency or oxygen excess (δ) is usually greater than 0.1, preferably 0.07 or more, usually less than 0.1, preferably 0.05 or less. To express.
The filling rate of the lithium transition metal composite oxide obtained by the method of the present invention is usually 90 vol% or more, preferably 95 vol% or more, and the filling rate is high, and the hollow portion is very small. A filling rate is 100 vol% or less normally. The filling rate is obtained by the following method.
[0054]
The lithium transition metal composite oxide was embedded in a resin and cured, then cut with a diamond cutter, and an electron micrograph was taken of the cross section. Of the 10 particles in an electron micrograph (1000x magnification) magnified 1000 times, the longest length to the outer shell of each of the 10 particles selected in order from the largest is the diameter of each particle. Volume of the sphere (V_p) Was calculated. In addition, for particles in which the hollow portion is visually recognized, the longest length to the outer shell of the hollow portion is defined as the diameter of each hollow portion, and the volume of the sphere corresponding to the diameter (V_c) Was calculated. From this result, the filling rate (V_R) Is calculated by the following equation.
[0055]
【number3]
V_R= (ΣV₁-ΣV_c/ ΣV₁) × 100
[0056]
The lithium transition metal composite oxide obtained by the production method of the present invention can be used as a positive electrode of a lithium secondary battery.
The positive electrode is usually formed by forming an active material layer containing the lithium transition metal composite oxide, a binder, and a conductive agent on a current collector. In the present invention, the positive electrode active material is a lithium transition metal 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.
[0057]
The proportion of the lithium transition metal composite oxide 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. 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.
[0058]
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.
[0059]
Moreover, as a binder used for a positive electrode, besides fluorinated polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and fluorine rubber, EPDM (ethylene-propylene-diene terpolymer) , 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. Is 40% by 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.
[0060]
Moreover, as a solvent used when preparing the slurry for forming the active material layer of a positive electrode, 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.
The thickness of the active material layer of the positive electrode is usually about 10 to 200 μm.
[0061]
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.
[0062]
The lithium secondary battery of the present invention usually has the above positive electrode, negative electrode and 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, etc. 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 a 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.
[0063]
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.
[0064]
Examples of the electrolyte that can be used in the lithium secondary battery of the present invention include an electrolytic solution, a polymer solid electrolyte, and a semi-solid electrolyte.
The electrolyte solution is preferably a non-aqueous electrolyte solution. Examples of the non-aqueous electrolyte include those obtained by dissolving various electrolytic salts in a non-aqueous solvent.
[0065]
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.
[0066]
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.
[0067]
As the electrolytic salt, any conventionally known salt can be used, and LiClO.₄, LiAsF₆, LiPF₆, LiBF₄, LiB (C₆H₅)₄, LiCl, LiBr, LiCH₃SO₃Li, LiCF₃SO₃, LiN (SO₂CF₃)₂, LiN (SO₂C₂F₅)₂, LiC (SO₂CF₃)₃, LiN (SO₃CF₃)₂And lithium salts such as
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.
[0068]
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.
[0069]
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.
[0070]
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.
[0071]
【Example】
Examples The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
[0072]
<Example 1>
Put 81.4kg of water into the tank, and add Tosoh MnO₂Was baked at 850 ° C., and 25 kg of self-manufactured dimanganese trioxide, 6.475 kg of lithium carbonate (manufactured by Honjo Chemical Co., Ltd.), and 1.210 kg of boehmite (AlOOH, trade name PURAL200, manufactured by Condia Corporation) were added. This was subjected to wet bead mill pulverization for 3 hours under stirring to prepare a slurry having a viscosity of 580 mPa · s.
[0073]
50 g of this slurry was collected, the solid content of the slurry was settled with a centrifugal settling machine, and the upper transparent liquid was collected. This solution was evaporated to dryness at 150 ° C., and the weight of the residue was measured. The concentration of the dissolved salt in the liquid was determined to be 0.45% by weight as the salt dissolved in the liquid. Therefore, the concentration of dissolved salts with respect to the total solid content in the slurry is (81.4 × 0.45 × 10^-2/32.685)×100=1.127% by weight.
[0074]
Next, this slurry was spray-dried under the conditions of a dry air temperature of 105 ° C., a slurry supply rate of 560 cc / min, and an amount of spray air of 1200 L / min to obtain spray-dried powder. The obtained spray-dried powder was fired at 900 ° C. for 10 hours to obtain a lithium transition metal composite oxide.
[0075]
The lithium transition metal composite oxide was embedded in a resin and cured, and then cut with a diamond cutter, and a cross-sectional electron micrograph was taken. Of the 10 particles in the electron micrograph (magnification 1000 times), the longest length to the outer shell is taken as the diameter of each particle, and the volume of the sphere corresponding to the diameter (V_p) Was calculated. In addition, for particles in which the hollow portion is visually recognized, the longest length to the outer shell of the hollow portion is defined as the diameter of each hollow portion, and the volume of the sphere corresponding to the diameter (V_c) Was calculated. From this result, it was 99.6 vol% when the filling factor was calculated by the following formula. The results are shown in Table-1.
[0076]
【number4]
V_R= (ΣV₁-ΣV_c/ ΣV₁) × 100
[0077]
<Example 2>
76.8 kg of water is put in the tank, and this is added to dimanganese trioxide (Mn₂O_Three) 25 kg, lithium carbonate 4.858 kg, lithium hydroxide monohydrate (LiOH.H)₂O, manufactured by Honjo Chemical Co., Ltd.) and 1.839 kg of boehmite (AlOOH) were added, and slurry preparation, spray drying and firing were performed in the same manner as in Example 1 to obtain a lithium transition metal composite oxide. Were manufactured and evaluated in various ways.
The viscosity of the slurry is 1300 mPa · s, the dissolved salt concentration with respect to the solvent in the slurry is 1.08% by weight, and the dissolved salt concentration with respect to the total solid content in the slurry is (76.8 × 1.08 × 10^-2/32.907)×100=2.547 wt%.
Moreover, the filling factor of the obtained lithium transition metal composite oxide was 99.3 vol%. The results are shown in Table-1.
[0078]
<Example 3>
A tank is charged with 77.3 kg of water, and this is mixed with dimanganese trioxide (Mn).₂O_Three) 25 kg, lithium carbonate 3.239 kg, lithium hydroxide monohydrate (LiOH.H)₂O) 3.676 kg and boehmite (AlOOH) 1.210 kg were added, and in the same manner as in Example 1, slurry preparation, spray drying, and firing were performed to produce a lithium transition metal composite oxide, and various evaluations were made. Went.
The viscosity of the slurry is 940 mPa · s, the dissolved salt concentration with respect to the solvent in the slurry is 1.55% by weight, and the dissolved salt concentration with respect to the total solid content in the slurry is (77.3 × 1.55 × 10^-2/33.125)×100=3.674% by weight.
Moreover, the filling factor of the obtained lithium transition metal composite oxide was 99.9 vol%. The results are shown in Table-1.
[0079]
<Example 4>
77.8 kg of water is put in the tank, and this is added to dimanganese trioxide (Mn₂O_Three) 25 kg, lithium carbonate 1.619 kg, lithium hydroxide monohydrate (LiOH.H)₂O) 5.515 kg and boehmite (AlOOH) 1.210 kg were added, and in the same manner as in Example 1, slurry preparation, spray drying, and firing were performed to produce a lithium transition metal composite oxide, and various evaluations were made. Went.
The viscosity of the slurry is 740 mPa · s, the dissolved salt concentration with respect to the solvent in the slurry is 1.81 wt%, and the dissolved salt concentration with respect to the total solid content in the slurry is (77.8 × 1.81 × 10^-2/33.344)×100=4.301% by weight.
Moreover, the filling factor of the obtained lithium transition metal composite oxide was 99.9 vol%. The results are shown in Table-1.
[0080]
<Comparative Example 1>
Put 81.4kg of water in the tank, and add manganese trioxide (Mn₂O_Three) 25 kg, Lithium hydroxide monohydrate (LiOH · H)₂O) Except that 7.350 kg and boehmite 1.210 kg were added, slurry preparation, spray drying, and firing were performed in the same manner as in Example 1 to produce a lithium transition metal composite oxide, and various evaluations were performed. It was.
The slurry has a viscosity of 350 mPa · s, the dissolved salt concentration with respect to the solvent in the slurry is 2.35 wt%, and the dissolved salt concentration with respect to the total solid content in the slurry is (81.4 × 2.35 × 10^-2/33.56)×100=5.837% by weight.
Moreover, the filling factor of the obtained lithium transition metal composite oxide was 74.5 vol%. The results are shown in Table-1.
[0081]
[Table 1]

[0082]
【The invention's effect】
According to the present invention, a lithium transition metal composite oxide having a high filling rate can be produced. By using this lithium transition metal composite oxide as a positive electrode active material, a lithium secondary battery having a high battery capacity per unit volume can be obtained. A battery can be provided.

Claims (9)

A slurry containing at least one transition metal compound and a lithium compound selected from a manganese compound, a cobalt compound and a nickel compound, and further containing a compound of a metal other than these, is spray-dried, and then fired. A hexagonal layered rock salt structure or a spinel structure containing at least one transition metal selected from the group consisting of manganese, nickel and cobalt and lithium, wherein a part of the transition metal may be substituted with another transition metal In the method for producing a lithium transition metal composite oxide, the lithium compound used as a slurry raw material, the transition metal compound, and other metal compounds other than these dissolved in a solvent, measured by the following measurement method, in the slurry lithium transition characterized by a concentration, 5% by weight relative to the total solids Method for producing a genus composite oxide.
(Measuring method)
A part of the slurry (about 50 g) is centrifuged at 300 rpm for 20 minutes, and a clear supernatant is collected. After measuring the weight (W1) of the collected supernatant, it is evaporated to dryness at 150 ° C., and the weight (W2) of the residue is measured. Therefore, the concentration S (% by weight) of the dissolved salts in the liquid is S = (W2 / W1) × 100.
On the other hand, the solvent used in the slurry preparation and the weight of the metal compound are W3 and W4, respectively, and the concentration A (wt%) of the dissolved salts with respect to the total solid content in the slurry is defined by the following equation.
[Expression 1]
A = {(W3 × S / 100) / W4} × 100   The production method according to claim 1, wherein the lithium compound is a lithium compound hardly soluble in water.   60% by weight or more of the metal constituting the transition metal compound is a manganese compound, and the atomic ratio of lithium to the total of metals other than lithium in the slurry is 0.4 to 0.6. The manufacturing method of the lithium transition metal complex oxide of Claim 1 or 2. The method for producing a lithium transition metal composite oxide according to any one of claims 1 to 3, wherein the lithium transition metal composite oxide is a compound having a standard composition represented by the following formula.
[Chemical 1]
Li _a Mn _2-b Al _b O ₄ (in the formula, 0.9 ≦ a ≦ 1.1 and 0 <b ≦ 1.0) The method for producing a lithium transition metal composite oxide according to claim 1 or 2, wherein the lithium transition metal composite oxide is a compound having a standard composition represented by the following formula.
[Chemical formula 2]
_{Li c (Ni d Mn e Co} f M g) O 2 ( where, M is Fe, Cr, V, Ti, Cu, Al, Ga, Bi, Sn, Zn, Mg, Ge, Nb, Ta, Be, At least one element selected from the group consisting of B, Ca, Sc and Zr, 0.8 ≦ c ≦ 1.2, 0 ≦ d ≦ 1, 0 ≦ e ≦ 1, 0 ≦ f ≦ 1, 0 ≦ g ≦ 1, d + e + f + g = 1.)   Either manganese, cobalt or nickel accounts for 60% by weight or more of the metal constituting the transition metal compound, and the total atomic ratio other than the transition metal and lithium with respect to the transition metal is 2.5 to 30%. It exists, The manufacturing method of the lithium transition metal complex oxide in any one of Claims 1-5 characterized by the above-mentioned.   The lithium transition metal complex oxide manufactured by the manufacturing method in any one of Claims 1-6.   A positive electrode for a lithium secondary battery, comprising the lithium transition metal composite oxide according to claim 7 and a binder.   A lithium secondary battery comprising the positive electrode according to claim 8, a negative electrode, and an electrolyte.