JP4061879B2 - Nickel-containing slurry and method for producing the same, and method for producing lithium nickel oxide - Google Patents

Description

【００６１】
なお、表―１において、ＮｉＯの半価幅とは、以下の方法で測定されたＸ線回折ピークの００３面の半価幅を意味する。また、実施例及び比較例で使用した酸化ニッケルのＸ線回折パターンを図１〜４に示す。
半価幅の測定方法：
粉末Ｘ線回折装置（フィリップス社ＰＷ１７００）を使用し、集中法に基づくゴニオメータ半径１７３ｍｍを有するＸ線回折計を用い、下の条件で測定した。Ｃｕ管球、出力電圧＝４０ｋＶ、出力電流＝３０ｍＡ、測定モード＝θ−２θカップリングスキャン、走査モード＝連続スキャン、測定範囲（２θ）＝１０°〜９０°、ステップ幅＝０．０５°、走査速度＝３．０°／分、発散スリット＝１．０°、散乱スリット＝１．０°、受光スリット＝０．２０ｍｍ。
【００６２】
半価幅は、プロファイルフィッティング法により求めた。プロファイルフィッティングは、線源である特性Ｘ線に含まれるＫα１、Ｋα２の影響を考慮したピアソン− VII関数の５つの変数（高さ、２θ、半価幅、形定数、非対称）を非対称最小二乗法に基づき精密化、カーブフィッティングピークを行った。用いる半価幅は、Ｋα２を除去したＫα１由来のピーク半価幅とした。
【００６３】
【発明の効果】
本発明方法によれば、増粘の抑制されたニッケル含有スラリーを得ることができる。また、本発明によれば、リチウム二次電池の正極に使用されるリチウムニッケル系酸化物を湿式法で製造する際、スラリーの増粘を抑制した結果、長期の安定性に優れ、且つ取扱が容易となり、生産性高くリチウムニッケル系酸化物を得ることができる。また、得られるスラリーから調製したリチウムニッケル系酸化物は、電池特性や性状において、良好である。従って、本発明方法は、工業的製法として極めて有用である。
【図面の簡単な説明】
【図１】 実施例１で使用した酸化ニッケルのＸ線回折パターン
【図２】 実施例２で使用した酸化ニッケルのＸ線回折パターン
【図３】 実施例３で使用した酸化ニッケルのＸ線回折パターン
【図４】 比較例１で使用した酸化ニッケルのＸ線回折パターン[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a slurry containing a nickel compound and a method for producing the same. In detail, it is related with manufacture of the lithium nickel type oxide used suitably as a positive electrode active material of a lithium secondary battery, the slurry used therefor, and its manufacturing method.
[0002]
[Prior art]
A lithium transition metal composite oxide is considered promising as a positive electrode active material that can provide a lithium secondary battery that can actually be used. Among these lithium transition metal composite oxides, cobalt, nickel, and manganese are used as transition metals. When a lithium cobalt oxide, lithium nickel oxide, or lithium manganese oxide is used as a positive electrode active material, a high performance battery is obtained. It is also known that properties can be obtained. Furthermore, in order to stabilize and increase the capacity of lithium transition metal composite oxides, improve safety, and improve battery characteristics at high temperatures, lithium transition metals in which some of the transition metal sites are replaced with other elements such as aluminum elements It is also known to use complex oxides.
[0003]
As a method for producing a lithium transition metal composite oxide, a dry method in which a raw material lithium compound, a transition metal compound, and other elemental compounds used as necessary are mixed and fired, or the above lithium compound, transition Examples include various methods such as a wet method in which a slurry in which a metal compound and other elemental compounds are dispersed in a dispersion medium such as water is dried and then baked. Among these production methods, the wet method has an advantage that the lithium transition metal composite oxide can be granulated in a spherical shape and the packing density can be increased (the energy density per unit volume can be increased). In other words, when the lithium transition metal composite oxide manufactured by the above method is used, when a battery of the same size is manufactured as compared with the case of using the lithium transition metal composite oxide manufactured by the dry method, A battery having a capacity can be obtained, and a battery having the same energy capacity has advantages such as miniaturization.
[0004]
[Problems to be solved by the invention]
On the other hand, among lithium transition metal composite oxides, a lithium nickel oxide containing nickel as a transition metal is a particularly promising material such as a high capacity as a lithium secondary battery. For example, it has been found that when such a lithium nickel oxide is produced by the above-described wet method, thickening of the slurry is likely to occur. This increase in viscosity impairs the flow of dispersed particles in the slurry, resulting in unstable particle size after drying, resulting in a shift in composition, and eventually becoming difficult to dry, etc. The industrial handling of the slurry becomes difficult. In particular, when solids are pulverized by a wet method in producing a slurry, this tendency is remarkable. As a result, subsequent pulverization becomes difficult and the pulverized particle diameter is not sufficiently refined. There was a problem that got worse.
[0005]
The present invention has been made in view of such circumstances. That is, the present invention provides a highly stable nickel-containing slurry which is suitable for the production of lithium nickel-based oxides and has a high stability and a method for producing the same, and is also produced because the thickening of the slurry is difficult to occur. An object of the present invention is to provide a method for producing a lithium nickel-based oxide having high properties and high packing density.
[0006]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above object, the present inventors have found that the occurrence of thickening of the slurry is caused by the nickel compound used, specifically, nickel oxide most preferably used as the nickel compound. As a result, the inventors have found that thickening can be suppressed by selecting one having higher crystallinity as nickel oxide to be used, and completed the present invention.
[0007]
That is, the first gist of the present invention is that in the method for producing a nickel-containing slurry in which a nickel compound is subjected to a mixing treatment in a solvent to form a slurry, the half width of the 003 plane of the X-ray diffraction peak is 0 as the nickel compound. The present invention resides in a method for producing a nickel-containing slurry characterized by using nickel oxide of 6 degrees or less.
The second gist of the present invention is that a slurry containing a nickel compound, a lithium compound and a solvent is dried and then subjected to a firing treatment, or a slurry containing a nickel compound and a solvent is dried and then mixed with a lithium compound, and further fired. In the method for producing a lithium nickel oxide used for the treatment, nickel oxide having a half-value width of 003 plane of an X-ray diffraction peak of 0.6 degrees or less is used as the nickel compound The manufacturing method.
[0008]
Furthermore, the third gist of the present invention is that a nickel compound and a lithium compound are subjected to a wet pulverization treatment in a solvent to form a slurry, which is then dried and further subjected to a firing treatment. In a method for producing a lithium nickel-based oxide that is subjected to a wet pulverization treatment in a solvent to obtain a slurry, which is then dried, mixed with a lithium compound, and further subjected to a firing treatment. The present invention resides in a method for producing a lithium nickel oxide, wherein nickel oxide having a half width of 003 plane of 0.6 degrees or less is used.
[0009]
Furthermore, the fourth gist of the present invention is that, in a nickel-containing slurry in which a nickel compound is dispersed in a solvent, the nickel compound has an X-ray diffraction peak 003 plane half width of 0.6 degrees or less. A nickel-containing slurry characterized by containing nickel oxide.
[0010]
[Action]
Although the details are not clear, it is estimated that the thickening of the slurry is derived from the exposure of the new surface of the nickel compound crystal in the slurry. That is, the new surface of the nickel compound is exposed in the slurry by wet pulverization or the like, but this new surface is extremely active, so the interaction of the particles in the slurry is strengthened, and as a result, aggregation occurs and the viscosity of the slurry increases. is there.
[0011]
On the other hand, it is presumed that by using a nickel compound having high crystallinity, the activity is suppressed even on the exposed new surface, and as a result, the thickening of the slurry is suppressed.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The raw material nickel oxide used in the present invention has a half-value width of the peak of the 003 plane measured by X-ray diffraction of 0.6 ° or less, preferably 0.5 ° or less. If the half width is too large, the crystallinity of the raw material nickel oxide is lowered, resulting in a significant increase in slurry viscosity. Moreover, in order to suppress the increase in slurry viscosity, it is necessary to lower the solid content concentration in the slurry, which is industrially disadvantageous, such as a reduction in product yield per unit time. The half width is preferably as small as possible. On the other hand, it is difficult to obtain a half width that is too small, so that it is usually 0.01 ° or more, preferably 0.1 ° or more. In general, an X-ray diffractometer generally used cannot easily obtain a half width less than 0.1 ° as a normal measurement limit.
[0013]
Next, the method for measuring the half width will be described.
The half width can be determined by a powder X-ray diffractometer. As detailed measurement conditions usually employed, an X-ray diffractometer having a goniometer radius of 173 mm based on the concentration method is used, and the following conditions are adopted as measurement conditions.
Cu tube, output voltage = 40 kV, output current = 30 mA, measurement mode = θ-2θ coupling scan, scan mode = continuous scan, measurement range (2θ) = 10 ° to 90 °, step width = 0.05 °, Scanning speed = 3.0 ° / min, diverging slit = 1.0 °, scattering slit = 1.0 °, light receiving slit = 0.20 mm.
[0014]
Of the powder X-ray diffraction patterns obtained under the above measurement conditions, the half width of the Bragg diffraction peak of the (003) plane, to which the nickel oxide (NiO) raw material is assigned as the rhombohedral crystal form, is calculated.
The peak on the 003 plane is usually observed at a position of about 2θ = 37.0 to 37.6, but varies depending on the length of the unit cell in the a-axis direction and the length of the unit cell in the c-axis direction.
[0015]
The crystallinity of nickel oxide is considered to depend on the production method, and a thermal decomposition method and a direct firing method are known as the production method. The crystallinity of nickel oxide varies greatly depending on the nickel oxide manufacturer and its items due to the difference in the manufacturing method and the like, and thus nickel oxide used in the present invention can be obtained by appropriately selecting from these.
By setting the half width obtained by the above method to a specific value, the thickening of the slurry can be suppressed.
[0016]
In the slurry, the nickel oxide is dispersed in a solvent, but a nickel compound other than nickel oxide may be dissolved or dispersed in the slurry. In this case, the content of the compound other than nickel oxide with respect to the entire nickel compound is generally 50% or less, preferably 30% or less, and more preferably 10% or less in terms of nickel molar ratio.
As the solvent for the slurry, various organic solvents and inorganic solvents can be used, but it is preferable to use water from the viewpoint of the remarkable effect of the present invention and industrial superiority.
[0017]
The nickel-containing slurry can further contain other components as required. When producing a lithium nickel oxide, a lithium compound is usually required as a raw material, but the lithium compound can be contained in a slurry. In this case, it is possible to obtain a lithium nickel-based oxide having better properties with high productivity and to obtain excellent battery performance. In addition, as a lithium nickel-based oxide, when a compound having other elements other than lithium or nickel is added and nickel sites are substituted with other elements, raw material compounds containing these other elements are contained in the slurry. Can be made. These other components may be dissolved or dispersed in a solvent.
[0018]
Examples of lithium compounds that can be contained in the slurry include lithium oxides, hydroxides, oxyhydroxides, inorganic acid salts such as carbonates, nitrates and sulfates, and organic acids such as acetates. Examples thereof include halides such as salts and chlorides, and hydrates thereof. Among them, preferable examples include lithium hydroxide, lithium hydroxide monohydrate, lithium carbonate, lithium nitrate, lithium organic acid salt and lithium oxide, and more preferable lithium hydroxide, lithium hydroxide monohydrate. Products, lithium carbonate, lithium nitrate and lithium acetate. Most preferred is lithium hydroxide monohydrate. A lithium compound can also use multiple types together.
[0019]
There are no particular restrictions on the elements that can be used as other elements, for example, cobalt, manganese, iron, chromium, vanadium, titanium, copper, aluminum, gallium, bismuth, tin, zinc, magnesium, germanium, niobium, tantalum, zirconium, etc. The various metals can be mentioned. These multiple types can also be used in combination. Other element compounds that can be contained in the slurry when other elements are introduced include the above-mentioned metal oxides, hydroxides, oxyhydroxides, and inorganic acid salts such as carbonates, nitrates and sulfates. And organic acid salts such as acetates and halides such as chlorides.
[0020]
When aluminum is used as the other element, examples of the aluminum compound include aluminum oxides, hydroxides, oxyhydroxides, organic acid salts, chlorides, nitrates, sulfates, and other inorganic acid salts, or their water. Japanese products are listed. Specifically, Al ₂ O _Three , AlOOH, Al (OH) _Three , Al (CH _Three (COO) _Three AlCl _Three , Al (NO _Three ) ・ ₉ H ₂ O, Al ₂ (SO _Four ) _Three , Etc., preferably Al ₂ O _Three , AlOOH, Al (OH) _Three It is.
[0021]
The composition ratio of various components in the slurry is appropriately selected according to the composition of the target lithium nickel oxide. Moreover, although the slurry density | concentration in a slurry changes also with the kind of raw material compound, it is 0.1 to 60 weight% normally, Preferably it is 0.1 to 50 weight%, Most preferably, it is 5 to 40 weight%. If the slurry concentration is too low, the productivity tends to decrease. On the other hand, if the slurry concentration is too high, it is difficult to ensure the uniformity of the slurry composition.
[0022]
In preparing the slurry, it is preferable to sufficiently mix and stir the slurry in order to increase the uniformity and maintain the stability of the slurry in the next step. In that case, as long as mixing and stirring are sufficiently performed, the stirring means is not particularly limited. For example, as the type of the stirrer, for example, from a simple motor stirring to a planetary mixer, a three-axis planetary mixer, a two-axis butterfly mixer, Concentric twin-screw mixers, dissolvers, homomixers, kneaders, etc. can be used. In preparing the slurry, it is more preferable from the viewpoint of the effect of the present invention and the battery performance that the solid content in the slurry is pulverized simultaneously with stirring, that is, wet pulverization. As a stirrer for that purpose, it is preferable to use a stirrer capable of strong stirring accompanied by pulverization of the solid content in the slurry, for example, a medium stirring type wet pulverizer. The medium agitation type wet pulverizer is generally called a bead mill and is a wet pulverizer using beads such as glass, ceramics, and steel as the pulverization media. Fill the vessel with about 70-90% beads as grinding media, rotate the agitator disk and pin at a normal circumferential speed of about 5-15 m / sec to give motion to the beads, and add slurry (crushed material) ) Is pumped and finely pulverized and dispersed by shearing force between beads. Therefore, the properties required for beads include high fracture strength, wear resistance, component content, stability, etc. In addition, for the selection of beads, considering the contamination with the slurry, corrosiveness, etc. It is necessary to choose.
[0023]
The pulverization conditions vary depending on the type of the target lithium nickel oxide, but the average particle size of the solid particles in the slurry after wet pulverization is necessary for the oxide to have a desired secondary particle size. It is preferable to make it as small as possible, usually 2 μm or less, preferably 1 μm or less, more preferably 0.5 μm or less, so that the pulverization conditions can be selected accordingly. However, since it is difficult to obtain solid particles after wet pulverization, the particle size is usually 0.01 μm or more, preferably 0.05 μm or more, and more preferably 0.1 μm or more.
[0024]
The viscosity of the slurry in the present invention is usually 1 to 10,000 mPa · s. When the viscosity of the slurry is too low, the storage stability of the slurry is poor, and problems such as difficulty in obtaining clean granulated particles in the production of a lithium nickel oxide may occur. On the other hand, if the slurry viscosity is too high, smooth transfer does not proceed, causing problems in handling, and problems such as difficulty in obtaining fine particles in drying may occur. The viscosity of the slurry is preferably 1 to 5000 mPa · s, more preferably 1 to 1800 mPa · s, and even more preferably 100 to 1000 mPa · s.
[0025]
The viscosity of the slurry can be measured using a known BM viscometer. The BM viscometer is a measurement method that employs a method of rotating a predetermined metal rotor in the room temperature atmosphere. The viscosity of the slurry is calculated from the resistance force (twisting force) applied to the rotating shaft when the rotor is rotated with the rotor immersed in the slurry. However, room temperature air means an environment having a temperature of 10 ° C. to 35 ° C. and a relative humidity of 20% RH to 80% RH.
[0026]
In obtaining the lithium nickel-based oxide, the obtained slurry is dried to remove the solvent. Although there is no restriction | limiting in particular in the method of drying, Spray drying is preferable. A spherical lithium nickel oxide can be obtained by a simple method by spray drying, and as a result, the packing density can be improved. The method of spray drying is not particularly limited. For example, a droplet of a slurry component from the nozzle by flowing a gas flow and a slurry into the tip of the nozzle (in this specification, this may be simply referred to as “droplet”). And the droplets scattered using an appropriate drying gas temperature and air flow rate can be dried quickly. The gas supplied as a gas flow is air (de-CO 2 ₂ In addition to air), an inert gas such as nitrogen can be used, but usually air is used. 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 from the viewpoint of improving productivity. The scattered droplets are dried. As described above, an appropriate temperature, air blowing, or the like is performed so as to quickly dry the dispersed droplets, but it is preferable to introduce a dry gas in a downward flow from the upper part of the drying tower to the lower part. By 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, usually 300 ° C. or lower, preferably 200 ° C. or lower, more preferably 120 ° C. or lower, and most 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.
[0027]
By drying, granulated particles as a firing raw material are obtained. The granulated particle size (secondary particle size) is preferably 50 μm or less, more preferably 30 μm or less in terms of battery performance in terms of battery performance. However, since it tends to be difficult to obtain a particle size that is too small, it is usually 0.1 μm or more, preferably 1 μm or more, more preferably 4 μm or more, and most preferably 5 μm or more. The particle diameter of the granulated particles can be controlled by appropriately selecting the drying conditions, for example, the spray format in the case of spray drying, the pressurized gas flow supply rate, the slurry supply rate, the drying temperature, and the like.
[0028]
The dried particles are mixed with other compounds as necessary and then subjected to a firing treatment. For example, when a lithium compound or other element compound is not contained in the slurry, the slurry can be dried and mixed with a lithium compound or other element compound, and then subjected to a firing treatment. Moreover, when a part of lithium compound and / or other element compound is contained in the slurry, after the slurry is dried, the remaining lithium compound and / or other element compound is mixed and then subjected to a firing treatment. Can do.
The firing temperature during the firing treatment 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 takes a long reaction time to obtain a lithium nickel oxide having good crystallinity, and the effect of improving the packing density may be reduced. If the firing temperature is too high, a phase other than the target lithium nickel oxide may be generated, or a lithium nickel oxide with many defects may be generated. Further, when raising the temperature from room temperature to the above reaction 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 rise is stopped once in the middle, A holding time at a constant temperature may be included.
[0029]
The firing time is usually 1 hour or more and 100 hours or less, preferably 2 hours or more and 50 hours or less. If the time is less than the above range and the time is too short, it is difficult to obtain a lithium nickel oxide having good crystallinity, and a reaction time that is too long beyond this range is not practical. Firing is usually performed in the presence of oxygen. Specifically, the 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 decarbonized air. Preferably, baking is performed in decarbonated gas air or in a gas atmosphere having an oxygen concentration of 20% or more, and more preferably, baking is performed in a pure oxygen atmosphere.
[0030]
In order to obtain a lithium nickel-based oxide with few crystal defects, it is preferable to cool slowly to a certain temperature after the above baking, and 800 ° C., preferably 600 ° C., 5 ° C./min. It is preferable to slowly cool at the following cooling rate.
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.
[0031]
The lithium nickel-based oxide thus produced is usually formed from secondary particles in which fine primary particles are aggregated. The size of the primary particles can be controlled by the degree of pulverization of the raw material, the calcination temperature, the calcination time, and the like, and the particle size of the secondary particles is determined by the pulverization conditions of the raw material, spray drying conditions, and further calcination It can be controlled by subsequent pulverization, classification conditions, and the like. In order to use a lithium nickel oxide as a positive electrode active material of a lithium secondary battery, it is composed of secondary particles having a particle size of 1 to 100 μm in which primary particles of 0.1 to 10 μm are aggregated, and nitrogen adsorption. Specific surface area by 0.1 to 5m ² / G is preferable.
[0032]
The obtained lithium nickel oxide is usually represented by the following general formula (1).
[0033]
[Chemical 1]
Li _x Ni _1-y M _y O _2- δ (1)
Here, x represents a number of 0.8 to 1.3, preferably 0.9 to 1.1, and y corresponds to a substitution amount with other element M, and is 0 to 0.5, preferably 0 to 0. And M is at least one selected from the group consisting of cobalt, manganese, iron, chromium, vanadium, titanium, copper, aluminum, gallium, bismuth, tin, zinc, magnesium, germanium, niobium, tantalum and zirconium. Δ corresponds to oxygen deficiency or oxygen excess, and represents a number of −0.1 to 0.1, preferably −0.05 to 0.05.
[0034]
The lithium nickel-based oxide represented by the general formula (1) is characterized by excellent battery characteristics such as battery capacity, rate characteristics, cycle characteristics, storage characteristics, and safety.
A lithium secondary battery can be produced using the lithium nickel-based oxide produced by the above method of the present invention as a positive electrode active material.
[0035]
A lithium secondary battery usually has a positive electrode, a negative electrode, and an electrolyte layer. An example of a lithium secondary battery is a secondary battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator. In this case, an electrolyte exists between the positive electrode and the negative electrode, and the separator does not contact the positive electrode and the negative electrode. Placed between them.
The positive electrode usually contains the lithium nickel oxide and a binder. Usually, the positive electrode is formed by forming a positive electrode layer containing the positive electrode material and a binder on a current collector.
[0036]
Such a positive electrode layer can be produced by applying a lithium nickel oxide, a binder and, if necessary, a slurry of a conductive agent or the like in a solvent to a positive electrode current collector and drying.
In the positive electrode layer, LiMn ₂ O _Four LiMnO ₂ LiCoO ₂ LiFePO _Four As described above, an active material capable of occluding and releasing lithium ions other than lithium nickel-based oxides may be further contained.
[0037]
The ratio of the active material in the positive electrode 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 is too large, the mechanical strength of the electrode tends to be inferior. If the amount is too small, the battery performance such as capacity tends to be inferior.
Examples of the binder used for the positive electrode include polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, EPDM (ethylene-propylene-diene terpolymer), and SBR (styrene-butadiene rubber). ), NBR (acrylonitrile-butadiene rubber), fluororubber, polyvinyl acetate, polymethyl methacrylate, polyethylene, nitrocellulose and the like. The ratio of the binder in the positive electrode 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% by weight or less, most preferably 10% by weight or less. If the proportion of the binder is too low, the active material cannot be sufficiently retained, and the mechanical strength of the positive electrode is insufficient, which may deteriorate battery performance such as cycle characteristics. May lower the sex.
[0038]
The positive electrode layer usually contains a conductive agent in order to increase conductivity. Examples of the conductive agent include graphite such as natural graphite and artificial graphite, carbon black such as acetylene black, and carbon materials such as amorphous carbon such as needle coke. The proportion of the conductive agent in the positive electrode 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 30% by weight or less. Preferably it is 15 weight% or less. If the proportion of the conductive agent is too low, the conductivity may be insufficient, and conversely if it is too high, the battery capacity may be reduced.
[0039]
The slurry solvent is not particularly limited as long as it can dissolve or disperse the binder, but an organic solvent or water is usually used. For example, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, water and the like can be mentioned.
[0040]
The thickness of the positive electrode layer is usually about 1 to 1000 μm, preferably about 10 to 200 μm. If it is too thick, the conductivity tends to decrease, and if it is too thin, the capacity tends to decrease.
As the material of the current collector used for the positive electrode, aluminum, stainless steel, nickel-plated steel or the like is used, and preferably aluminum. The thickness of the current collector is usually about 1 to 1000 μm, preferably about 5 to 500 μm. If it is too thick, the capacity of the lithium secondary battery as a whole will decrease, and if it is too thin, the mechanical strength may be insufficient.
[0041]
The positive electrode layer obtained by coating and drying is preferably consolidated by a roller press or the like to increase the packing density of the active material.
The active material of the negative electrode used for the negative electrode of the secondary battery may be a lithium alloy such as lithium or a lithium aluminum alloy, but is preferably a carbon material that has higher safety and can occlude and release lithium.
[0042]
The carbon material is not particularly limited, but graphite, coal-based coke, petroleum-based coke, coal-based pitch carbide, petroleum-based pitch carbide, or carbide obtained by oxidizing these pitches, needle coke, pitch coke, phenol resin, Examples thereof include carbides such as crystalline cellulose, carbon materials obtained by partially graphitizing these, furnace black, acetylene black, pitch-based carbon fibers, and the like.
[0043]
Furthermore, SnO, SnO as a negative electrode active material ₂ , Sn _1-x M _x O (M = Hg, P, B, Si, Ge or Sb, where 0 ≦ x <1), Sn _Three O ₂ (OH) ₂ , Sn _3-x M _x O ₂ (M = Mg, P, B, Si, Ge, Sb or Mn, where 0 ≦ x <3), LiSiO ₂ , SiO ₂ LiSnO ₂ Etc. In addition, you may use 2 or more types of mixtures chosen from these as a negative electrode active material.
[0044]
The negative electrode is usually formed by forming a negative electrode layer on a current collector as in the case of the positive electrode. As the binder used at this time, the conductive agent used as necessary, and the slurry solvent, the same ones used for the positive electrode can be used. In addition, as the negative electrode current collector, copper, nickel, stainless steel, nickel-plated steel, or the like is used, and copper is preferably used.
[0045]
When a separator is used between the positive electrode and the negative electrode, usually a microporous polymer film is used. Polytetrafluoroethylene, polyester, nylon, cellulose acetate, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, polypropylene Those made of polyolefin polymers such as polyethylene and polybutene are used. Moreover, the nonwoven fabric filter, such as glass fiber, and the nonwoven fabric filter of glass fiber and polymer fiber can also be used. The chemical and electrochemical stability of the separator is an important factor. In this respect, a polyolefin-based polymer is preferable, and it is preferable that the polymer is made of polyethylene in view of the self-occluding temperature which is one of the purposes of the battery separator.
[0046]
In the case of a polyethylene separator, ultrahigh molecular weight polyethylene is preferable from the viewpoint of high temperature shape maintenance, and the lower limit of the molecular weight is preferably 500,000, more preferably 1,000,000, and most preferably 1,500,000. On the other hand, the upper limit of the molecular weight is preferably 5 million, more preferably 4 million, and most preferably 3 million. If the molecular weight is too small, the plugging property becomes too high, causing problems in use at high temperatures. If the molecular weight is too large, the fluidity is too low and the pores of the separator may not be blocked when heated.
[0047]
In addition, as the electrolyte forming the electrolyte layer in the lithium secondary battery, for example, a known organic electrolyte, polymer solid electrolyte, gel electrolyte, inorganic solid electrolyte, and the like can be used. Among them, the organic electrolyte is preferable.
The organic electrolyte usually contains an organic solvent and a solute. The organic solvent is not particularly limited, but for example, carbonates, ethers, ketones, sulfolane compounds, lactones, nitriles, chlorinated hydrocarbons, amines, esters, amides, phosphoric acid An ester compound or the like can be used. Specific examples thereof include dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, ethylene carbonate, butylene 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, methylsulfolane, acetonitrile Propionitrile, benzonitrile, butyronitrile, valeronitrile, 1,2-dichloroethane, dimethylformamide, dimethyl sulfoxide, trimethyl phosphate, triethyl phosphate, etc. Rukoto is possible, these alone or two or more kinds of mixed solvents can be used.
[0048]
The above organic solvent preferably contains a high dielectric constant solvent for dissociating the electrolyte. Here, the high dielectric constant solvent means a compound having a relative dielectric constant of 20 or more at 25 ° C. Among the high dielectric constant solvents, it is preferable that the electrolyte solution contains ethylene carbonate, propylene carbonate, γ-butyrolactone, and compounds obtained by substituting those hydrogen atoms with other elements such as halogen or alkyl groups. The proportion of the high dielectric constant compound in the electrolytic solution is preferably 20% by weight or more, more preferably 30% by weight or more, and most preferably 40% by weight or more. This is because if the content of the compound is small, desired battery characteristics may not be obtained.
[0049]
The solute dissolved in this solvent is not particularly limited, but any conventionally known solute can be used, and LiClO. _Four , LiAsF ₆ , LiPF ₆ , LiBF _Four , LiB (C ₆ H _Five ) _Four , LiCl, LiBr, CH _Three SO _Three Li, CF _Three SO _Three Li, LiN (SO ₂ CF _Three ) ₂ , LiN (SO ₂ C ₂ F _Five ) ₂ , LiC (SO ₂ CF _Three ) _Three And at least one of them can be used. CO ₂ , N ₂ O, CO, SO ₂ An additive such as a gas such as polysulfide Sx2- may be added to the above-mentioned single or mixed solvent in an arbitrary ratio to form a good film capable of efficiently charging and discharging lithium ions on the negative electrode surface.
[0050]
Even when a polymer solid electrolyte is used, a known polymer can be used as the polymer. In particular, it is preferable to use a polymer having high ion conductivity with respect to lithium ions. For example, polyethylene oxide, polypropylene oxide, polyethyleneimine, and the like are preferably used. Moreover, it is also possible to add the above solvent to the polymer together with the solute and use it as a gel electrolyte.
[0051]
Even when an inorganic solid electrolyte is used, a known crystalline or amorphous solid electrolyte can be used for this inorganic substance. Examples of crystalline solid electrolytes include LiI, Li _Three N, Li _{1 + x} M _x Ti _2-x (PO _Four ) _Three (However, M = at least one selected from the group consisting of Al, Sc, Y and La), Li _0.5-3x RE _{0.5 + x} TiO _Three (However, at least one selected from the group consisting of RE = La, Pr, Nd and Sm) and the like. Examples of the amorphous solid electrolyte include 4.9LiI-34.1Li ₂ O-61B ₂ O _Five , 33.3Li ₂ O-66.7SiO ₂ Oxide glass such as 0.45LiI-0.37Li ₂ S-0.26B ₂ S _Three , 0.30LiI-.42Li ₂ S-0.28SiS ₂ And sulfide glass. Of these, at least one of them can be used.
[0052]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
In addition, the viscosity of the slurry in an Example was measured with the BM type | mold viscosity meter (made by Tokimec). Measurement is performed at room temperature in the atmosphere, a specific metal rotor is fixed to the rotating shaft of the apparatus body, the rotor is immersed in a slurry liquid, the rotor is rotated, the scale after 3 minutes is read, and a conversion table is used, The slurry viscosity was calculated from the rotor and rotation speed.
<Example 1>
(1) Li _1.05 Ni _0.80 Co _0.15 Al _0.05 O ₂ Manufacturing of
LiOH ・ H ₂ O, NiO (reagent manufactured by Wako Pure Chemical Industries, 003 half-value width = 0.138 degrees), Co (OH) ₂ And AlOOH are compositions in the final layered lithium nickelate composite oxide so that Li: Ni: Co: Al = 1.05: 0.80: 0.15: 0.05 (molar ratio). Then, pure water was added thereto to prepare a slurry having a solid content concentration of 26% by weight. While stirring this slurry, pulverization is carried out using a circulating medium stirring type wet pulverizer (Shinmaru Enterprises Co., Ltd .: Dynomill KDL-A type) until the average particle size of the solid content in the slurry becomes 0.29 μm. did. The time required for grinding was 6 hours. The slurry had a viscosity of 140 mPa · s.
[0053]
Next, the slurry was spray-dried by using a two-fluid nozzle type spray dryer (manufactured by Okawahara Chemical Industries Co., Ltd .: LT-8 type spray dryer). At this time, air was used as the drying gas, the discharge gas introduction amount was 50 L / min, and the drying gas inlet temperature was 90 ° C. Next, the water contained in the spray-dried powder was removed by firing the granulated particles obtained by spray-drying in air at 450 ° C. for 3 hours. Next, it was baked in oxygen at 750 ° C. for 24 hours.
[0054]
As a result, cobalt aluminum substituted lithium nickelate having a molar ratio composition almost as prepared was obtained.
As a result of measuring the particle diameter of the obtained lithium nickelate using a laser diffraction / scattering particle size distribution measuring device (manufactured by Horiba: LA-920 type particle size distribution measuring device), an average secondary particle diameter of 10.7 μm, The particles had a substantially spherical shape with a maximum particle size of 26 μm.
[0055]
The crystallinity of the obtained lithium nickelate composite oxide was measured using a powder X-ray diffractometer (X-ray diffractometer PW1700, manufactured by Philips, Cu tube, output voltage = 40 kV, output current = 30 mA, scan speed = 3 ° / min. 09-0063 (LiNiO) of Joint committee on powder diffraction standards (hereinafter referred to as JCPDS) ₂ ) Is similar to the pattern registered in ₂ LiNiO in which components other than nickel (aluminum and cobalt) other than nickel were uniformly dissolved in nickel. ₂ It was confirmed that it has a similar crystal structure.
(2) Fabrication of lithium secondary battery
Li as a positive electrode active material _1.05 Ni _0.80 Co _0.15 Al _0.05 O ₂ And acetylene black, which is a conductive agent, and Teflon, which is a binder, are mixed at a weight ratio of 75: 20: 5, sufficiently kneaded using an agate mortar, formed into a sheet, and then used for rate characteristic measurement. After being punched into a diameter of 9 mm and a temperature of 12 mm for measuring high temperature cycle characteristics, they were pressure-bonded to an Al current collector having a diameter of 16 mm at a pressure of 14 MPa for a diameter of 9 mm and at a pressure of 20 MPa for a diameter of 12 mm, respectively. After vacuum drying for 3 hours, a positive electrode was obtained.
[0056]
A 2032 type coin battery was assembled with the obtained positive electrode in a glove box in an argon atmosphere. Lithium metal having a diameter of 16 mm and a thickness of 1 mm was used for the negative electrode for rate characteristic measurement. The negative electrode for measuring high-temperature cycle characteristics is a ratio of 92.5: 7.5 by weight of polyvinylidene fluoride with a graphite powder having an average particle diameter of 8 to 10 um as a binder on a copper foil having a thickness of 20 um. And weighed it in N-methylpyrrolidone, and dried the coated one to 12 mm in diameter, 0.5 ton / cm ² What was pressed at a pressure of 1 mm was used. The electrolyte contains 1 mol / liter LiPF ₆ A mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 3: 7 was used.
(3) Battery performance evaluation
A. Initial discharge capacity measurement
The battery manufactured as described above has a rate characteristic measurement condition of 0.2 mA / cm in a voltage range of 3.2 V to 4.2 V. ² The initial discharge capacity (mAh / g) per unit weight of the positive electrode active material when the charge / discharge test was performed at a current density of 5 μm was measured.
B. Measurement of capacity retention rate at 50 ° C and 100 cycles
As a condition for measuring high-temperature cycle characteristics, a cycle test was performed at 50 ° C. with 1 C constant current charge / discharge in a voltage range of 3.0 V to 4.2 V, and discharge at the 100th cycle with respect to the first cycle discharge capacity Qh (1). The ratio of the capacity Qh (100) is defined as the high-temperature cycle capacity maintenance rate P, that is,
[0057]
[Expression 1]
P [%] = {Qh (100) / Qh (1)} × 100
The high temperature characteristics of the batteries were compared with this value.
Table 1 shows the evaluation results of A and B.
<Example 2>
The nickel oxide manufactured by Shodo Chemical Industry Co., Ltd. (003 plane half-value width = 0.192 degrees) was used, the slurry concentration was 25% by weight, and the average particle size of the solid content in the slurry by wet grinding. Lithium nickelate was produced and evaluated in the same manner as in Example 1 except that the thickness was 0.28 μm. At this time, the slurry viscosity was 460 mPa · s.
[0058]
The obtained lithium nickelate composite oxide had a substantially spherical shape with an average secondary particle size of 10.7 μm and a maximum particle size of 26 μm. Also, LiNiO in which components other than nickel (aluminum and cobalt) were uniformly dissolved in nickel by a powder X-ray diffractometer ₂ It was also confirmed to have a similar crystal structure.
The evaluation results as a coin battery are shown in Table-1.
<Example 3>
Sumitomo Metal Mining nickel oxide (003 plane half-value width = 0.311 degrees) was used as nickel oxide, the slurry concentration was 25 wt%, and the average particle size of the solid content in the slurry by wet grinding Lithium nickelate was produced and evaluated in the same manner as in Example 1 except that the thickness was 0.28 μm. At this time, the slurry viscosity was 250 mPa · s.
more than
[0059]
The obtained lithium nickelate composite oxide had a substantially spherical shape with an average secondary particle size of 10.7 μm and a maximum particle size of 26 μm. Also, LiNiO in which components other than nickel (aluminum and cobalt) were uniformly dissolved in nickel by a powder X-ray diffractometer ₂ It was also confirmed to have a similar crystal structure. The evaluation results as a coin battery are shown in Table-1.
<Comparative Example 1>
Nickel oxide PRM-B (003 half-width = 0.664 degrees) made by Pacific Rare Metal handled by Nippon Chemical Industry Co., Ltd. was used as nickel oxide, and the slurry concentration was 25 weight. %, Wet pulverization was performed in the same manner as in Example 1. When pulverization was started, the slurry viscosity increased significantly 20 minutes after the start of pulverization, the internal pressure in the pulverization vessel increased due to clogging, and pulverization could not be continued. The slurry had a viscosity of 1760 Pa · S.
[0060]
[Table 1]

[0061]
In Table 1, the half width of NiO means the half width of the 003 plane of the X-ray diffraction peak measured by the following method. Moreover, the X-ray-diffraction pattern of the nickel oxide used by the Example and the comparative example is shown in FIGS.
Half width measurement method:
Using a powder X-ray diffractometer (Phillips PW1700), an X-ray diffractometer having a goniometer radius of 173 mm based on the concentration method was used and measured under the following conditions. Cu tube, output voltage = 40 kV, output current = 30 mA, measurement mode = θ-2θ coupling scan, scan mode = continuous scan, measurement range (2θ) = 10 ° to 90 °, step width = 0.05 °, Scanning speed = 3.0 ° / min, diverging slit = 1.0 °, scattering slit = 1.0 °, light receiving slit = 0.20 mm.
[0062]
The half width was obtained by a profile fitting method. Profile fitting is an asymmetric least-squares method for five variables (height, 2θ, half-value width, shape constant, and asymmetric) of the Pearson-VII function considering the effects of Kα1 and Kα2 included in the characteristic X-ray source. Based on the above, refinement and curve fitting peak were performed. The half width to be used was the peak half width derived from Kα1 from which Kα2 was removed.
[0063]
【The invention's effect】
According to the method of the present invention, a nickel-containing slurry with suppressed thickening can be obtained. In addition, according to the present invention, when a lithium nickel-based oxide used for a positive electrode of a lithium secondary battery is produced by a wet method, as a result of suppressing the thickening of the slurry, it is excellent in long-term stability and handling. It becomes easy and a lithium nickel oxide can be obtained with high productivity. Moreover, the lithium nickel-type oxide prepared from the obtained slurry is favorable in battery characteristics and properties. Therefore, the method of the present invention is extremely useful as an industrial production method.
[Brief description of the drawings]
1 is an X-ray diffraction pattern of nickel oxide used in Example 1. FIG.
2 is an X-ray diffraction pattern of nickel oxide used in Example 2. FIG.
3 is an X-ray diffraction pattern of nickel oxide used in Example 3. FIG.
4 is an X-ray diffraction pattern of nickel oxide used in Comparative Example 1. FIG.

Claims (8)

  In the method for producing a nickel-containing slurry in which a nickel compound is subjected to wet pulverization treatment and mixing treatment in a solvent to form a slurry, the average particle size of the solid particles after the wet pulverization treatment is 1 μm or less, and as the nickel compound, A method for producing a nickel-containing slurry, wherein nickel oxide having a half-value width of 003 plane of an X-ray diffraction peak of 0.6 degrees or less is used.   The method for producing a nickel-containing slurry according to claim 1, wherein the solvent is water.   The nickel compound and the lithium compound are subjected to a wet pulverization treatment in a solvent to obtain a slurry, and then dried and further subjected to a firing treatment, or the nickel compound is subjected to a wet pulverization treatment in a solvent to obtain a slurry. Then, after drying this and mixing with a lithium compound, the average particle diameter of the solid particle after a wet-grinding process is 1 micrometer or less in the manufacturing method of the lithium nickel type oxide which uses for a baking process, and the said nickel compound As a method for producing a lithium nickel oxide, nickel oxide having a half-value width of 003 plane of an X-ray diffraction peak of 0.6 degrees or less is used.   The method for producing a lithium nickel oxide according to claim 3, wherein the solvent is water.   The lithium nickel according to any one of claims 3 and 4, wherein the lithium compound contains at least one selected from the group consisting of lithium hydroxide, lithium hydroxide monohydrate, lithium carbonate, lithium nitrate, and lithium acetate. A method for producing a system oxide.   The method for producing a lithium nickel oxide according to any one of claims 3 to 5, wherein the drying is performed by spray drying.   The method for producing a lithium nickel oxide according to claim 6, wherein the secondary particle diameter of the particles obtained by spray drying is an average particle diameter of 50 µm or less.   The method for producing a lithium nickel-based oxide according to any one of claims 3 to 7, wherein the firing treatment is performed in a decarbonized gas air atmosphere or an atmosphere having an oxygen concentration of 20% or more.

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