JP4752244B2 - Layered lithium nickel manganese based composite oxide powder for lithium secondary battery positive electrode material, lithium secondary battery positive electrode using the same, and lithium secondary battery - Google Patents

Description

  The present invention relates to a layered lithium nickel manganese composite oxide powder used as a material for a positive electrode of a lithium secondary battery, a lithium secondary battery positive electrode using the same, and a lithium secondary battery. Specifically, the layered lithium-nickel-manganese based composite oxide for a positive electrode material of a lithium secondary battery that has moderate particle easiness to be crushed, excellent coating film forming ability, and excellent rate characteristics, and lithium The present invention relates to a secondary battery positive electrode and a lithium secondary battery.

  Lithium secondary batteries are excellent in energy density and output density, and can be reduced in size and weight, so that they are rapidly spreading as power sources for portable devices such as laptop computers, mobile phones, and handy video cameras. It is also attracting attention as a power source for electric vehicles and power load leveling.

  A positive electrode used in a lithium secondary battery is generally composed of a current collector and a positive electrode active material layer containing a positive electrode active material, a conductive material, and a binder formed on the surface of the current collector. As a positive electrode active material, a lithium / manganese composite oxide, a lithium / cobalt composite oxide, or a lithium / nickel composite oxide, or a lithium transition in which a part of the transition metal of these composite oxides is replaced with another metal. Metal-based composite oxides are used. Lithium secondary batteries using these lithium-based composite oxides all have the advantage of high voltage and output. In addition, lithium composite oxides having various compositions have been proposed, but one of the preferable ones is a lithium nickel manganese cobalt composite oxide having a layered structure, and a battery using this as a positive electrode active material is It is said that safety is high.

  As a method for producing a lithium nickel manganese cobalt based composite oxide having a layered structure, Patent Document 1 discloses that a raw material powder is obtained by granulating and drying a lithium compound, a nickel compound, a manganese compound and a cobalt compound as raw materials by a spray drying method. Has been proposed that is fired at 970 ° C. in the atmosphere.

  However, the lithium nickel manganese cobalt composite oxide having a layered structure obtained by the above method has a problem in the ability to form a coating film because the secondary particles have low strength. That is, when this is used as a positive electrode active material and mixed with a conductive material and a binder to prepare a coating slurry, or when the prepared coating slurry is applied onto a current collector, the secondary particles are made into one particle unit. As a result, the coated film having sufficient strength cannot be formed. If the strength of the coating film as the positive electrode active material layer is low, the film will be peeled off during battery assembly, and the battery life will be reduced because the network of the conductive material, current collector and active material is weak. Also, it is often difficult to obtain a conductive path. In order to form a coating film having a sufficient strength necessary for battery assembly using such a positive electrode active material having a low secondary particle strength, a conductive material and a binder should be used more than usual when preparing a coating slurry. However, when a large amount of a conductive material or a binder is blended in this way, the proportion of the positive electrode active material is relatively reduced, and the battery density and battery capacity are lowered.

  Patent Document 1 also proposes a method of firing raw material powder obtained by granulation and drying by a coprecipitation method at 970 ° C. in the atmosphere as a comparative example. Lithium nickel manganese cobalt based composite oxide is too strong in the secondary particles, and there is almost no gap for electrolyte to penetrate between the primary particles, so the internal resistance of the particles is high, resulting in the rate characteristics of the resulting battery There is a disadvantage that (output characteristics) are low.

  Patent Document 1 states that “According to such a positive electrode active material for a lithium secondary battery, the cohesive force between the primary particles is weak, so that the primary particles can be easily disintegrated into the primary particles by an appropriate crushing or electrode preparation process. In the process of being crushed and the secondary particles are crushed, the primary particles themselves do not collapse, so that the primary particles are monodispersed (dispersed with most of the particles) while maintaining their size and shape. That is, it is said that the secondary particles are easy to be crushed. “In the positive electrode active material for a lithium secondary battery, the ease with which the secondary particles are crushed is 1 g of powder in a 10.5 mmφ die. In a test in which pressure is applied in a uniaxial direction, it is preferable that the value of d50 of the particle size distribution of the powder when pressure of 2 t is applied is about 70% or less before applying pressure, more preferably Powder when pressure of 1t is applied The d50 value is about 50% or less before the pressure is applied. "Patent Document 1, however, discloses that lithium nickel manganese cobalt based composite oxide satisfying 70% <a≤95%. Is not listed.

1.07ton pressure in Patent Document 1 corresponds to 1.2 ton / cm ² pressure in the particle crushing is easy evaluation a value in the present invention which will be described later. From the viewpoint of the ease of particle crushing evaluation a value according to the present invention, the graph of Patent Document 1 shows that Example 1 of Patent Document 1 is 10 to 12% and that of Comparative Example 1 is 98%. Read from the table. In addition, even if the amount of the active material at the time of measurement is 0.5 g or 1 g, the evaluation of the ease of particle crushing evaluation a value is hardly affected.

That is, in Patent Document 1, when the coprecipitation method as the prior art of Patent Document 1 is adopted, the secondary particles are strong and difficult to be crushed (Comparative Example 1 of Patent Document 1). Since a good positive electrode cannot be formed, the purpose is to completely disperse the secondary particles to primary particles. The technical idea of adjusting to “appropriately easy to be crushed” is disclosed in Patent Document 1. Does not exist.
JP 2004-192846 A

  Accordingly, the present invention has a layered lithium nickel for a lithium secondary battery positive electrode material that has a moderate ease of being crushed and thus can provide a lithium secondary battery excellent in coating film forming ability and excellent in rate characteristics. It is an object of the present invention to provide a manganese-based composite oxide powder, a lithium secondary battery positive electrode and a lithium secondary battery that are high in capacity and have excellent battery performance such as rate characteristics using the same.

  The inventors of the present invention have intensively studied in view of the above problems, and that the ease of crushing of the active material particles is appropriate, that is, the ease of predetermined particle crushing evaluation a value is in an appropriate region. The present inventors have found that a lithium nickel manganese composite oxide powder having a layered structure excellent in rate characteristics and coating film forming ability can be obtained with certainty, and completed the invention.

That is, the gist of the present invention is a powder composed of a layered lithium nickel manganese composite oxide represented by the following composition formula (1), and has a BET specific surface area of 2 m ² / g or less, or a tap density ( Lithium secondary battery positive electrode material, characterized in that the bulk density is 1.3 g / cm ³ or more, and the particle easiness evaluation a value defined below is 70% <a ≦ 95% Layered lithium nickel manganese based composite oxide powder.
_{Li 1 + x Ni 1-y} -z-p Mn y Co z M p O 2 ... (1)
(However, 0 ≦ x ≦ 0.20, 0.25 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.5, 0 ≦ p ≦ 0.2, 0.5 ≦ y + z + p ≦ 0.75, and M Is one or more of Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, Nb, and Zr)
[Evaluation of ease of particle crushing a value]
0.5 g of the powder is sandwiched between two 15 mmφ parallel stainless steel plates, the median diameter b of the powder when pressure of 30 MPa is applied in one axial direction, and the median of the powder before pressure is applied A value calculated from the diameter c by the following equation (2).
a = b / c × 100 (%) (2)

Another gist of the present invention is to have a positive electrode active material layer containing a layered lithium nickel manganese composite oxide powder for a lithium secondary battery positive electrode material of the present invention and a binder on a current collector. The lithium secondary battery positive electrode is characterized.
Still another gist of the present invention is a lithium secondary battery comprising a negative electrode capable of inserting and extracting lithium, a non-aqueous electrolyte containing a lithium salt, and a positive electrode capable of inserting and extracting lithium, wherein The present invention resides in a lithium secondary battery using the positive electrode of the lithium secondary battery of the present invention.

  The layered lithium nickel manganese composite oxide powder for a lithium secondary battery positive electrode material of the present invention is low enough to be pulverized to the primary particle unit excessively when forming a coating film as a positive electrode active material layer. It is not strong, and it has moderate easiness to be crushed, not excessively strong enough that there are almost no gaps between primary particles. For this reason, a coating film having a sufficient strength required for battery production can be formed without using a large amount of a conductive material or a binder, so that the amount of the positive electrode active material in the positive electrode active material layer is sufficiently large. It is possible to secure the battery density and the battery capacity. On the other hand, the rate characteristics can be improved by providing an appropriate gap between the primary particles.

  Therefore, according to the layered lithium nickel manganese composite oxide powder for a lithium secondary battery positive electrode material of the present invention, a lithium secondary battery positive electrode and a lithium secondary battery excellent in battery performance such as high capacity and rate characteristics can be obtained. Can be realized.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to the gist thereof. The content of is not specified.

[Layered lithium nickel manganese based composite oxide powder for lithium secondary battery cathode material]
First, the layered lithium nickel manganese composite oxide powder for a lithium secondary battery positive electrode material of the present invention will be described.

<composition>
The layered lithium nickel manganese composite oxide powder (hereinafter sometimes referred to as “the composite oxide powder of the present invention”) according to the present invention is represented by the following composition formula (1). .
_{Li 1 + x Ni 1-y} -z-p Mn y Co z M p O 2 ... (1)
(However, 0 ≦ x ≦ 0.20, 0.25 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.5, 0 ≦ p ≦ 0.2, 0.5 ≦ y + z + p ≦ 0.75, and M Is one or more of Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, Nb, and Zr)

  In the composition formula (1), x is usually 0 or more, preferably 0.01 or more, more preferably 0.02 or more. When x is smaller than 0, an unreacted compound remains in the composite oxide, and the crystal structure of the composite oxide tends to become slightly unstable. Moreover, x is 0.20 or less normally, Preferably it is 0.15 or less, More preferably, it is 0.10 or less. When x is larger than 0.2, the composite oxide does not become a single crystal phase, and lithium may be replaced with a transition metal site. Therefore, charging / discharging of a lithium secondary battery using this as a positive electrode active material Since the capacity tends to decrease, it is not preferable.

  y is usually 0.25 or more, preferably 0.3 or more, more preferably 0.31 or more, and particularly preferably 0.32 or more. If y is too small, the safety of the battery may be reduced. Further, y is usually 0.5 or less, preferably 0.4 or less, particularly preferably 0.35 or less. If y is too large, the composite oxide does not become a single crystal phase, and the cycle characteristics and charge / discharge capacity of the battery may be reduced.

  z is usually 0 or more, preferably 0.2 or more, more preferably 0.25 or more, and most preferably 0.3 or more. If z is too small, the crystal structure of the complex oxide at the time of charge / discharge may become unstable. Z is usually 0.5 or less, preferably 0.4 or less, particularly preferably 0.35 or less. If z is too large, it becomes expensive and the safety of the battery may be lowered.

  p is usually 0 or more and 0.2 or less, preferably 0.1 or less, more preferably 0.01 or less, and particularly preferably 0. When p is too large, the crystal structure of the composite oxide is unlikely to become a single crystal phase, and the capacity of the battery tends to decrease.

  y + z + p is usually 0.5 or more, preferably 0.6 or more, particularly preferably 0.65 or more. If y + z + p is too small, it is difficult to produce a composite oxide, and the composite oxide tends to absorb carbon dioxide and deteriorate. Moreover, y + z + p is usually 0.75 or less, preferably 0.70 or less, more preferably 0.69 or less, and particularly preferably 0.68 or less. If y + z + p is too large, the battery capacity tends to decrease.

<Ease of particle crushing>
The composite oxide powder of the present invention also has the ease of particle crushing defined below as 70% <a ≦ 95%.
[Evaluation of ease of particle crushing a value]
0.5 g of the powder is sandwiched between two 15 mmφ parallel stainless steel plates, the median diameter b of the powder when a pressure of 1.2 ton / cm ² is applied in one axial direction, and before the pressure is applied The value calculated by the following equation (2) from the median diameter c of the powder.
a = b / c × 100 (%) (2)
In addition, the median diameter here refers to the median diameter of secondary particles measured by a method described later.

  The a value is usually more than 70%, preferably 71% or more, particularly preferably 72% or more, and usually 95% or less, preferably 90% or less, particularly preferably 88% or less, particularly preferably 85% or less. .

  When the value a is smaller than the lower limit, the particles are too scattered when preparing the coating slurry, and only a coating film with low strength can be obtained. As described above, when the film strength is weak, the film is peeled off when the battery is assembled, and the battery life is shortened because the network of the conductive material, the current collector, and the active material is weak. Also, it is often difficult to obtain a conductive path. In order to obtain a coating film having sufficient film strength and a conductive path using particles having an a value smaller than the above lower limit, more conductive material than a predetermined amount, a binder must be added, In this case, the battery density cannot be increased.

  When the a value is larger than the above upper limit, the particles are not easily broken, that is, there are almost no fine cracks or voids between the primary particles constituting the secondary particles. If there are no minute cracks or voids through which the electrolyte solution permeates between primary particles, the internal resistance of the particles is high, and the high rate characteristics (output characteristics at high current) are reduced.

<Median diameter of secondary particles>
The composite oxide of the present invention has a layered structure, and primary particles are aggregated and sintered to form secondary particles.
The average particle diameter (median diameter) of the secondary particles is usually 3 μm or more, preferably 4 μm or more, particularly preferably 5 μm or more. Moreover, it is 20 micrometers or less normally, Preferably it is 15 micrometers or less, Most preferably, it is 10 micrometers or less. If the average particle size of the secondary particles is too small, side reactions occur on the surface of the positive electrode, so that the cycle characteristics are likely to deteriorate. On the other hand, if the average particle size is too large, lithium diffusion is hindered, or the conductive path is insufficient and the rate characteristics and capacity are likely to decrease.
The median diameter of the secondary particles can be measured by a known laser diffraction / scattering particle size distribution measuring apparatus using, for example, a 0.1 wt% sodium hexametaphosphate aqueous solution as a dispersion medium.

<Average primary particle size>
The average primary particle size (average particle size of primary particles) of the composite oxide powder of the present invention is usually 0.1 μm or more, preferably 0.3 μm or more, particularly preferably 0.5 μm or more. Moreover, it is 2 micrometers or less normally, Preferably it is 1.5 micrometers or less, More preferably, it is 1.3 micrometers or less, Most preferably, it is 1.1 micrometers or less. If the average particle size of the primary particles is too small, the cycle characteristics and the safety of the produced battery may be reduced. On the other hand, if the average particle size is too large, the internal resistance increases and a sufficient output may not be obtained.
In addition, the average particle diameter of the primary particle in this invention is an average diameter of the long diameter observed with the scanning electron microscope (SEM), and the long diameter of about 30-50 primary particles is used using an observation photograph of 10,000 times. It can obtain | require as an average value of a measured value.

<BET specific surface area>
The BET specific surface area of the composite oxide powder of the present invention is usually 0.3 m ² / g or more, preferably 0.5 m ² / g or more. Moreover, it is ² m < ² > / g or less normally, Preferably it is 1.5 m < ² > / g or less, More preferably, it is 1.2 m < ² > / g or less. If the BET specific surface area is too small, battery performance may be reduced. On the contrary, if the BET specific surface area is too large, the coating property when forming the positive electrode active material layer is deteriorated, which is not preferable.
The BET specific surface area can be measured by a BET one-point method using N ₂ gas with a known BET type powder specific surface area measuring device.

<Tap density>
The tap density (bulk density) of the composite oxide powder of the present invention is usually 1.3 g / cm ³ or more, preferably 1.5 g / cm ³ or more, more preferably 1.6 g / cm ³ or more, most preferably It is 1.7 g / cm ³ or more, and can be optimized according to the composition ratio and contained elements.

When the tap density of the composite oxide powder is below the above lower limit, the amount of the required dispersion medium increases when the positive electrode active material layer is formed, and the necessary amount of the conductive material and the binder increases. The filling rate of the positive electrode active material is restricted, and the battery capacity may be restricted. By using a complex oxide powder having a high tap density, a high-density positive electrode active material layer can be formed. The tap density is preferably as large as possible, and there is no particular upper limit. However, if the tap density is too large, diffusion of lithium ions using the electrolytic solution in the positive electrode active material layer as a medium becomes rate-determining, and load characteristics may be easily lowered. Usually, it is 2.5 g / cm ³ or less, preferably 2.4 g / cm ³ or less.

  In addition, tap density puts about 8g of complex oxide powders into a 10 ml glass graduated cylinder, and the volume is about 50 to 500 times / minute on a wood table from a position of 1 to 5 cm in height. Determine the volume after tapping until it no longer changes (usually 200 to 800 times).

<Method for producing composite oxide powder of the present invention>
The method for producing the composite oxide powder of the present invention is not particularly limited, but the composite oxide powder of the present invention having the above composition and ease of particle pulverization can be realized, for example, by the following method.
After a predetermined amount of a nickel compound, a manganese compound, a cobalt compound, and an M metal compound is pulverized, sprayed, and granulated by drying, a lithium compound is mixed to prepare a firing precursor mixture, and then this firing precursor mixture is used. Baking in an oxygen-containing gas atmosphere.
At this time, most of the lithium compound used is mixed after forming granulated particles composed of a nickel compound, a manganese compound, a cobalt compound and an M metal compound. However, the lithium compound may be pulverized, sprayed, and dried together with the initial metal compound raw material as long as it is in a trace amount (for example, 0.2 mol% or less with respect to the molar amount of all metal elements excluding lithium). The reason why it is preferable to add the lithium compound after forming the granulated particles is that, if this method is used, the fired particles are unlikely to become hollow particles. On the other hand, in the method in which the lithium compound is first mixed, large voids are often formed between the primary particles after firing. For this reason, the particles are easily crushed and are likely to be separated during the preparation of the coating slurry.

Below, this manufacturing method is demonstrated in detail.
Examples of the lithium compound as a raw material include lithium hydroxides such as LiOH and LiOH.H ₂ O; inorganic lithium compounds such as inorganic lithium salts such as Li ₂ CO ₃ , LiNO ₃ and lithium halides: alkyl lithium; lithium acetate And organic lithium compounds such as carboxylic acid lithium salts. Among these, LiOH or LiOH.H ₂ O is preferable, and LiOH is particularly preferable. These are preferable in that no harmful substances such as NOx and SOx are generated during firing since they do not contain nitrogen element, sulfur element and the like.

Examples of nickel compounds include Ni (OH) ₂ ; NiO; NiOOH; NiCO ₃ .2Ni (OH) ₂ .4H ₂ O, Ni (NO ₃ ) ₂ .6H ₂ O, NiSO ₄ , NiSO ₄ .6H ₂ O. And inorganic nickel compounds such as inorganic nickel salts such as nickel halides; and organic nickel compounds such as nickel acetate and carboxylic acid nickel salts such as NiC ₂ O ₄ .2H ₂ O. Of these, Ni (OH) ₂ , NiO, NiOOH, NiCO ₃ .2Ni (OH) ₂ .4H ₂ O, NiC ₂ O ₄ .2H ₂ O, or the like that does not generate harmful substances such as NOx and SOx during the firing process. preferable. Further preferred is Ni (OH) ₂ , NiO or NiOOH, which is available at a low cost and has high reactivity.

Examples of manganese compounds include manganese oxides such as Mn ₂ O ₃ , MnO ₂ , and Mn ₃ O ₄ ; MnOOH; MnCO ₃ , Mn (NO ₃ ) ₂ , MnSO ₄ , inorganic manganese salts such as manganese halides, etc. Inorganic manganese compounds: Organic manganese compounds such as manganese acetate citric acid, manganese carboxylates such as manganese, and the like. Among these, MnO ₂ , Mn ₂ O ₃ , and Mn ₃ O _{4 that} are inexpensive and can be obtained without causing harmful substances such as NOx and SOx during the firing treatment are preferable.

Examples of the cobalt compound include Co (OH) ₂ ; cobalt oxides such as CoO, Co ₂ O ₃ , and Co ₃ O ₄ ; CoOOH; Co (NO ₃ ) ₂ .6H ₂ O, Co (SO ₄ ) _2. Examples include inorganic cobalt salts such as 7H ₂ O and cobalt halides; and organic cobalt compounds such as carboxylic acid cobalt salts such as Co (OCOCH ₃ ) ₂ .4H ₂ O. Of these, Co (OH) ₂ , CoO, Co ₂ O ₃ , Co ₃ O ₄ , and CoOOH are preferred because no harmful substances such as NOx and SOx are generated during the firing process. More preferable are CoO, Co (OH) ₂ , and CoOOH, which are available at low cost and have high reactivity.

  In addition, a lithium compound, a nickel compound, a manganese compound, and a cobalt compound may each be used individually by 1 type, or may use 2 or more types together.

  The complex oxide powder of the present invention may contain M metal. In this case, as the M metal compound of the M metal raw material, inorganic M metal compounds such as M metal hydroxides; oxides; oxyhydroxides; inorganic salts such as halides, carbonates, nitrates and sulfates: Examples thereof include organic M metal compounds such as mono- and dicarboxylates such as acetate and oxalate. The metal of the M metal compound is Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, or Nb, and Cu is preferable. As for the M metal and the M metal compound, one kind may be used alone, or two or more kinds may be used in combination.

  The above-described nickel compound, manganese compound, cobalt compound, and desired M metal compound are mixed in a wet or dry manner so as to have the composition represented by the composition formula (1), and then a firing precursor mixture of a lithium nickel manganese cobalt based composite oxide. To prepare. The method for preparing the calcined precursor mixture is preferably a method of spray drying after mixing by a wet pulverization method.

  As another example of the wet mixing method, there is a method in which a lithium compound, a nickel compound, a manganese compound, a cobalt compound, and a slurry obtained by dispersing or dissolving a desired M metal compound in a dispersion medium are dried and then fired. Can be mentioned. Preferable is a method in which each metal compound excluding the lithium compound is first dispersed or dissolved in a dispersion medium to form a slurry, dried, and then mixed with the lithium compound and fired. In this method, since it has moderate voids inside and hardly becomes hollow particles, particles having an appropriate secondary particle strength can be obtained.

  As the dispersion medium used in the wet method, either an organic solvent or water can be used, but water is preferably used.

  The average particle size of the lithium compound, nickel compound, manganese compound, cobalt compound, and M metal compound in the slurry is usually 2 μm or less, preferably 1 μm or less, and more preferably 0.5 μm or less. When this average particle diameter is too large, the reactivity in a baking process will fall. Moreover, the sphericity of the obtained composite oxide powder may be reduced, and the bulk density of the composite oxide powder may be lowered. Although the lower limit of the average particle diameter is arbitrary, it is meaningless to make fine particles so that the average particle diameter is less than 0.01 μm because it is expensive. Therefore, the pulverization should be carried out so that the average particle size is usually 0.02 μm or more, preferably 0.1 μm or more. Each metal compound may be pulverized in advance and then dispersed in the dispersion medium, or may be pulverized in the dispersion medium. As a pulverizer, a ball mill, a bead mill, a vibration mill, or the like may be used. It is preferable to grind and mix in a ball mill for about 1 hour to 2 days, and in a bead mill for a residence time of about 0.1 to 6 hours.

  Next, the obtained mixture is dried to obtain a calcined precursor mixture. Drying is preferably performed by a spray drying method, whereby a uniform spherical powder can be obtained. The spray drying is preferably carried out by appropriately selecting the spray device, slurry concentration, and drying temperature so that solid particles having an average particle diameter of 50 μm or less, particularly 40 μm or less are generated. The lower limit of the average particle diameter is arbitrary, but the conditions are usually set to 3 μm or more, preferably 4 μm or more.

  When a metal compound other than the lithium compound is wet-mixed and dried according to the above method and then mixed with the lithium compound to prepare a calcined precursor mixture, the average particle size of the lithium compound used is usually 0.01 μm or more. The thickness is preferably 0.1 μm or more, more preferably 0.2 μm or more, and particularly preferably 0.5 μm or more. Moreover, it is 500 micrometers or less normally, Preferably it is 100 micrometers or less, More preferably, it is 50 micrometers or less, Most preferably, it is 20 micrometers or less. If the average particle size is small, the stability of the lithium compound in the air tends to be low. Conversely, if the average particle size is too large, battery performance may be reduced.

  For mixing the lithium compound and the other metal compound, any commonly used powder mixing apparatus can be used. The mixed atmosphere is preferably mixed in an inert gas atmosphere such as nitrogen or argon so that the metal compound does not react with carbon dioxide in the atmosphere.

  By firing the obtained firing precursor mixture using an apparatus such as a box furnace, a tubular furnace, a tunnel furnace, or a rotary kiln, the composite oxide powder of the present invention can be produced.

  This firing is performed in an oxygen-containing gas atmosphere. Specifically, it can be carried out in an oxygen atmosphere, an air atmosphere, or the like, but an air atmosphere is preferable in terms of economy.

  When this firing temperature is low, the average particle size of the primary particles becomes small, the generation of the lithium nickel manganese cobalt based composite oxide having a layered structure becomes incomplete, and the crystallinity may be inferior. Therefore, the firing temperature is usually 750 ° C. or higher, preferably 800 ° C. or higher, particularly preferably 900 ° C. or higher. Conversely, if the firing temperature is too high, the stability of the crystal phase may be reduced due to oxygen deficiency or the like. Accordingly, the firing is preferably performed at 1100 ° C. or lower.

  The firing time is usually 1 hour or longer, preferably 5 hours or longer, particularly preferably 10 hours or longer. Moreover, it is normally 100 hours or less, Preferably it is 50 hours or less, Most preferably, it is 25 hours or less. If the firing time is short, the reaction may be incomplete. Further, even if firing for a longer time, there is no particular problem, but it is uneconomical.

  The temperature raising operation during firing is preferably performed so that the temperature raising rate is 1 ° C. or more and 10 ° C. or less per minute. It is not practical that the rate of temperature increase is slow. Conversely, if the rate is too high, the furnace temperature may not follow the set temperature. Further, the temperature lowering operation is preferably performed at a rate of 0.1 ° C. to 5 ° C. per minute. It is not practical that the temperature lowering rate is slow, and on the contrary, the uniformity of the obtained composite oxide powder may be inferior if it is too fast. Further, the firing may be either a two-step firing or a one-step firing, and the operation of raising, firing, and lowering the temperature may be repeated twice or more with the crushing process interposed therebetween.

[Lithium secondary battery positive electrode]
The composite oxide powder of the present invention is suitable as a positive electrode material for a lithium secondary battery.
Next, the positive electrode of the lithium secondary battery of the present invention using the composite oxide powder of the present invention will be described.

  The production of the positive electrode using the composite oxide powder of the present invention can be performed by a conventional method. That is, the composite oxide powder of the present invention and a binder, and if necessary, a conductive material and a thickener mixed in a dry form into a sheet form are pressure-bonded to the positive electrode current collector, or these This material is dissolved or dispersed in a dispersion medium to form a slurry, which is applied to a positive electrode current collector and dried to form a positive electrode active material layer on the current collector, whereby a positive electrode can be obtained.

  The content of the composite oxide powder of the present invention in the positive electrode active material layer is usually 10% by weight or more, preferably 30% by weight or more, and particularly preferably 50% by weight or more. Moreover, it is 99.9 weight% or less normally, Preferably it is 99 important% or less. If the content of the composite oxide powder of the present invention in the positive electrode active material layer is low, the electric capacity may be insufficient. Conversely, if the content is too high, the strength of the positive electrode may be insufficient. In addition, the composite oxide powder of this invention may be used individually by 1 type, and may use together 2 or more types from which a different composition or different particle | grains are easy to be crushed by arbitrary combinations and ratios.

  Any binder can be used as long as it is stable to the dispersion medium. Specific examples include polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitrocellulose and other resin-based polymers, SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluororubber, Rubber polymers such as isoprene rubber, butadiene rubber, ethylene / propylene rubber; styrene / butadiene / styrene block copolymer and its hydrogenated product, EPDM (ethylene-propylene-diene terpolymer), styrene / ethylene / Thermoplastic elastomeric polymers such as butadiene / ethylene copolymer, styrene / isoprene styrene block copolymer and hydrogenated products thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene Soft resinous polymers such as vinyl acid copolymers and propylene / α-olefin copolymers; Fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene / ethylene copolymers Polymers: Polymer compositions having ionic conductivity of alkali metal ions (particularly lithium ions), and the like. In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  The binder is usually 0.1% by weight or more, preferably 1% by weight or more, particularly preferably 2% by weight or more, and usually 40% by weight or less, preferably 20% by weight or less, in the positive electrode active material layer. Preferably it is used so that it may become 10 weight% or less. If the content of the binder in the positive electrode active material layer is too small, the positive electrode active material cannot be sufficiently retained, the mechanical strength of the positive electrode is insufficient, and battery performance such as cycle characteristics may be deteriorated. On the other hand, when the content is too large, the amount of the positive electrode active material in the positive electrode active material layer is relatively reduced, and the battery capacity and conductivity may be reduced.

  Examples of the conductive material include metal materials such as copper and nickel: graphite such as natural graphite and artificial graphite (graphite); carbon black such as acetylene black; and carbon materials such as amorphous carbon such as needle coke. In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  The conductive material is usually 0.01% by weight or more, preferably 0.1% by weight or more, particularly preferably 1% by weight or more, and usually 40% by weight or less, preferably 20% by weight or less in the positive electrode active material layer. Especially preferably, it is used so that it may become 10 weight% or less. If the content of the conductive material in the positive electrode active material layer is too small, the conductivity may be insufficient. Conversely, if the content is too large, the battery capacity may decrease.

The dispersion medium used for the preparation of the slurry is not particularly limited as long as it can dissolve or disperse the positive electrode material and the binder, and the conductive material and the thickener. Either of the system media may be used. Examples of the aqueous medium include water and alcohol. Examples of the organic medium include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone. Esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and NN-dimethylaminopropylamine; ethers such as dimethyl ether, ethylene oxide and tetrahydrofuran (THF); N-methylpyrrolidone (NMP) and dimethyl Examples include amides such as formamide and dimethylacetamide; aprotic polar solvents such as hexamethylphosphalamide and dimethylsulfoxide. In particular, when an aqueous medium is used, it is preferable to add a dispersion medium together with the thickener and make a slurry using a latex such as SBR. In addition, these dispersion media may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  Examples of the material of the positive electrode current collector include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and carbon materials such as carbon cloth and carbon paper. Of these, metal materials, particularly aluminum, are preferred.

  Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, and foam metal in the case of a metal material. A thin film, a carbon cylinder, etc. are mentioned. Of these, metal thin films are preferred. In addition, you may form a thin film suitably in mesh shape. The thickness of the thin film is arbitrary, but is usually 1 μm or more, preferably 3 μm or more, particularly preferably 5 μm or more. Moreover, it is 100 micrometers or less normally, Preferably it is 1 mm or less, Most preferably, it is 50 micrometers or less. If the current collector is too thin, the strength required for the current collector may be insufficient. On the other hand, if it is too thick, the handleability is impaired.

  Note that the positive electrode active material layer obtained by applying and drying the application slurry on the current collector is preferably consolidated by a roller press or the like to increase the packing density of the positive electrode active material. The thickness of the positive electrode active material layer thus formed is usually preferably 10 to 200 μm.

[Lithium secondary battery]
Next, the lithium secondary battery of the present invention will be described.
The lithium secondary battery of the present invention has the above-described lithium secondary battery positive electrode of the present invention, a negative electrode capable of inserting and extracting lithium, and a non-aqueous electrolyte containing a lithium salt as an electrolytic salt.

<Negative electrode>
The negative electrode may be produced by forming a negative electrode active material layer on the negative electrode current collector.
Examples of the material for the negative electrode current collector include metal materials such as copper, nickel, stainless steel, and nickel-plated steel; and carbon materials such as carbon cloth and carbon paper. Examples of the shape of the metal material include a metal foil, a metal cylinder, a metal coil, a metal plate, and a metal thin film. Examples of the shape of the carbon material include a carbon plate, a carbon thin film, and a carbon cylinder. Of these, metal thin films are preferred. In addition, you may form a thin film suitably in mesh shape. The thickness of the thin film is arbitrary, but is usually 1 μm or more, preferably 3 μm or more, particularly preferably 5 μm or more. Moreover, it is 1 mm or less normally, Preferably it is 100 micrometers or less, Most preferably, it is 50 micrometers or less. If the current collector is too thin, the strength required for the current collector may be insufficient. On the other hand, if it is too thick, the handleability is impaired.

  The negative electrode active material contained in the negative electrode active material layer may be any material as long as it can electrochemically occlude and release lithium ions, but is usually carbon that can occlude and release lithium from the viewpoint of high safety. Material is used.

  Examples of the carbon material include graphite (graphite) such as artificial graphite and natural graphite, and organic pyrolysis products under various pyrolysis conditions. Examples of pyrolysis products of organic matter include coal-based coke, petroleum-based coke, coal-based pitch carbide, petroleum-based pitch carbide, coal-based or petroleum-based carbonized carbide, needle coke, pitch coke, and phenol resin. And carbides such as crystalline cellulose and the like, carbon materials obtained by partially graphitizing these, furnace black, acetylene black, pitch-based carbon fibers, and the like. Among these, graphite, especially artificial graphite or purified natural graphite produced by subjecting easily graphitizable pitch obtained from various raw materials to high-temperature heat treatment, graphite material containing pitch in these graphite, etc., and various surfaces What processed is preferable. One of these carbon materials may be used alone, or two or more thereof may be used in combination.

  As a graphite material, a d-value (interlayer distance) of a lattice plane (002 plane) obtained by X-ray diffraction by the Gakushin method is usually 0.335 nm or more and 0.34 nm or less, particularly 0.337 nm or less. preferable. The ash content of the graphite material is usually 1% by weight or less, preferably 0.5% by weight or less, more preferably 0.1% by weight or less, based on the weight of the graphite material. The crystallite size (Lc) of the graphite material determined by X-ray diffraction by the Gakushin method is usually 30 nm or more, preferably 50 nm or more, more preferably 100 nm or more.

  The median diameter of the graphite material determined by the laser diffraction / scattering method is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, particularly preferably 7 μm or more, and usually 100 μm or less, preferably 50 μm or less, more preferably. It is 40 μm or less, particularly preferably 30 μm or less.

Further, the BET specific surface area of the graphite material is usually 0.5 m ² / g or more, preferably 0.7 m ² / g or more, more preferably 1.0 m ² / g or more, particularly preferably 1.5 m ² / g. or more, usually 25.0 m ² / g or less, preferably 20.0 m ² / g or less, more preferably 15.0 m ² / g or less, particularly preferably 10.0 m ² / g or less.

The intensity of the Raman spectrum analysis using argon laser beam, the intensity IA of a peak PA detected in the range of 1580～1620Cm ^-1, and intensity IB of a peak PB detected in the range of 1350 ^-1 The ratio IA / IB is preferably 0 or more and 0.5 or less, and the half width of the peak PA is preferably 26 cm ⁻¹ or less, particularly preferably 25 cm ⁻¹ or less.

  Examples of the negative electrode active material other than the carbon material include metal oxides such as tin oxide and silicon oxide; and lithium alloys such as lithium alone and lithium aluminum alloys. These may be used individually by 1 type, may be used in combination of 2 or more types, and may be used in combination with a carbon material.

  The negative electrode active material layer may be formed in the same manner as the positive electrode active material layer. That is, the negative electrode active material and the binder, and optionally a thickener and a conductive material, which are slurried with a dispersion medium, are applied to the negative electrode current collector and dried. As the dispersion medium, the binder, the conductive material, and the thickener used here, the same materials as those described above for the positive electrode active material layer can be used at an equivalent ratio.

<Nonaqueous electrolyte>
Examples of the non-aqueous electrolyte include organic electrolytes, polymer solid electrolytes, gel electrolytes, inorganic solid electrolytes, etc. Among these, organic electrolytes are preferable.

  Any known organic solvent can be used for the organic electrolyte. For example, carbonates such as dimethyl carbonate, diethyl carbonate, propylene carbonate, ethylene carbonate, vinylene carbonate; tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1, Ethers such as 1,3-dioxolane, 4-methyl-1,3-dioxolane and diethyl ether; ketones such as 4-methyl-2-pentanone; sulfolane compounds such as sulfolane and methyl sulfolane; sulfoxide compounds such as dimethyl sulfoxide Lactones such as γ-butyrolactone; nitriles such as acetonitrile, propionitrile, benzonitrile, butyronitrile, and valeronitrile; chlorinated hydrocarbons such as 1,2-dichloroethane; amines Esters, amides such as dimethylformamide; trimethyl phosphate, phosphoric acid ester compounds such as triethyl phosphate. These may be used individually by 1 type, or may use 2 or more types together.

The organic electrolytic solution preferably contains a high dielectric constant solvent having a relative dielectric constant of 20 or more at 25 ° C. in order to dissociate the electrolyte. Among these, it is preferable to include ethylene carbonate, propylene carbonate, and an organic solvent in which hydrogen atoms thereof are substituted with other elements such as halogen or alkyl groups. The ratio of the electrolyte solution of the high dielectric constant solvent to the whole organic electrolyte solution is usually 20% by weight or more, preferably 30% by weight or more, more preferably 40% by weight or more. In addition, in the organic electrolyte, an additive that forms a good film that enables efficient charge and discharge of lithium ions on the negative electrode surface, such as gas such as CO ₂ , N ₂ O, CO, and SO ₂ and polysulfide Sx ²⁻ May be added at an arbitrary ratio.

Any conventionally known lithium salt can be used as the solute. Specific examples include LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , LiCl, LiBr, CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, LiN (SO ₂ CF ₃ ) _2. , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , LiN (SO ₃ CF ₃ ) _{2 and the} like. These solutes may be used alone or in combination of two or more in any combination and ratio.

  The concentration of the lithium salt in the electrolytic solution is usually 0.5 mol / L or more, preferably 0.75 mol / L or more. Moreover, it is 1.5 mol / L or less normally, Preferably it is 1.25 mol / L or less. Whether the concentration is high or low, the conductivity may decrease, and the battery characteristics may deteriorate.

As the inorganic solid electrolyte, any crystalline or amorphous material known to be used as an electrolyte can be used. Examples of the crystalline inorganic solid electrolyte include LiI, Li ₃ N, Li _{1 + x} M _x Ti _2-x (PO ₄ ) ₃ (M = Al, Sc, Y, La), Li _0.5-3x RE _{0. .5 + x} TiO ₃ (RE = La, Pr, Nd, Sm) and the like. Examples of the amorphous inorganic solid electrolyte include oxide glasses such as 4.9LiI-34.1Li ₂ O-61B ₂ O ₅ and 33.3Li ₂ O-66.7SiO ₂ . Any one of these may be used alone, or two or more may be used in any combination and ratio.

<Separator>
The secondary battery preferably includes a separator that holds a nonaqueous electrolyte between the positive electrode and the negative electrode in order to prevent a short circuit between the electrodes.

  The material and shape of the separator are arbitrary as long as they are stable with respect to the organic electrolyte used, have excellent liquid retention, and can reliably prevent short-circuiting between electrodes. Examples thereof include microporous films, sheets and nonwoven fabrics made of various polymer materials. Examples of the polymer material include polyolefin polymers such as nylon, cellulose acetate, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride (PVDF), polypropylene, polyethylene, and polybutene. Polyolefin polymers are preferable from the viewpoint of chemical and electrochemical stability, and polyethylene is preferable from the viewpoint of the self-closing temperature of the battery. As the polyethylene, ultra high molecular weight polyethylene excellent in high temperature shape maintenance is preferable. The molecular weight of polyethylene is usually 500,000 or more, preferably 1,000,000 or more, particularly preferably 1,500,000 or more. Moreover, it is 5 million or less normally, Preferably it is 4 million or less, Most preferably, it is 3 million or less. If the molecular weight is too small, the shape at high temperature may not be maintained. On the other hand, if the molecular weight is too large, the fluidity is lowered, and the hole of the separator may not be closed during heating.

<Battery shape>
The shape of the lithium secondary battery of the present invention can be appropriately selected from various shapes generally employed according to the application. Examples of the shape include a cylinder type in which a sheet electrode and a separator are spiral, a cylinder type having an inside-out structure in which a pellet electrode and a separator are combined, a coin type in which a pellet electrode and a separator are stacked, and the like.
What is necessary is just to assemble a lithium secondary battery by a well-known method according to the shape of the target battery.

  EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist.

Example 1
Ni (OH) ₂ , Mn ₃ O ₄ and Co (OH) ₂ were weighed and mixed so that the molar ratio of Ni: Mn: Co = 0.33: 0.33: 0.33 was obtained. Pure water was added to the slurry to prepare a slurry. While stirring this slurry, the solid content in the slurry was pulverized to an average particle size of 0.18 μm using a circulating medium agitation type wet pulverizer.

The pulverized LiOH powder (average particle diameter of about 8 μm) was added to the particles obtained by spray-drying this slurry with a spray dryer, and mixed well to obtain a calcined precursor mixture. This calcined precursor mixture was calcined at 990 ° C. for 12 hours in an air atmosphere, and then crushed to obtain a lithium nickel manganese cobalt composite oxide powder having a layered structure whose composition formula is Li _1.00 Ni _0.33 Mn _0.33 Co _0.33 O ₂ Got.
About the obtained layered lithium nickel manganese cobalt composite oxide powder, various physical properties and characteristics were measured by the following methods, and the results are shown in Table 1.

<Measurement method of average primary particles>
The average particle size of the primary particles was determined from an image observed with a scanning electron microscope (SEM). The major axis of about 30 to 50 primary particles was measured using a 10,000-fold observation photograph. The average diameter was defined as the average primary particle diameter.

<Measuring method of median diameter of secondary particles>
The average particle diameter of the secondary particles was the median diameter, and was measured using a laser diffraction / scattering particle size distribution analyzer (“LA920” manufactured by Horiba). As the dispersion medium, an aqueous 0.1 wt% sodium hexametaphosphate solution was used. A refractive index of 1.24 (no imaginary term) was selected. The laser diffraction / scattering type particle size distribution measuring apparatus has a great influence on the particle diameter by setting the refractive index. After adding a sample to a dispersion medium, it measured after irradiating an ultrasonic wave for 5 minutes with the ultrasonic irradiation apparatus incorporated in the measuring instrument.

<Method for measuring specific surface area>
The measurement was made using a BET specific surface area meter (model “AMS8000” manufactured by Okura Riken).

<Measurement of tap density>
About 8 g of complex oxide powder is put into a 10 ml glass graduated cylinder, and the volume does not change at an interval of about 50 to 500 times / min. (200 to 800 times) The volume after tapping was measured and determined.

<Measurement method for ease of particle crushing>
On the SUS plate with a diameter of 20 mm, 0.5 g of lithium nickel manganese cobalt composite oxide powder is spread so that the thickness is uniform, and the SUS plate with a diameter of 15 mm and a thickness of 0.6 mm is placed on the SUS plate below. Put it in parallel with the board. From there, uniaxially pressed with a hand press (Riken model “MS05-100” (cylinder area 7.16 cm ² )) for 1 minute at a pressure of 30 MPa (pressure 30 MPa, cylinder area 7.16 cm ^2). Therefore, it corresponds to a load of 2.2 ton, that is, pressing at a pressure of 1.2 ton / cm ² ). The portion protruding from the upper 15 mm diameter SUS plate was removed, and the particle size distribution of only the particles under the load under the 15 mm diameter SUS plate was measured according to the method for measuring the median diameter of the secondary particles. The median diameter before applying pressure was c μm, and the median diameter after applying pressure was b μm.
a = b / c × 100%
The median diameter here refers to the median diameter of the secondary particles.

<Measurement method of coating film strength>
The obtained lithium nickel manganese cobalt composite oxide powder is used as a positive electrode active material, and N-methylpyrrolidone (NMP) is dispersed in a ratio of active material / conductive material / binder = 85/10/5 (wt%). As a coating slurry was prepared. As the conductive material, acetylene black (“DENKA BLACK” manufactured by Denki Kagaku Kogyo Co., Ltd.) was used, and as the binder, polyvinylidene fluoride (“PVDF # 1100” manufactured by Kureha Chemical Industry Co., Ltd.) was used. The ratio of solid content and NMP was a ratio of solid content / (solid content + NMP) = 40 to 43 (% by weight), and mixed well to prepare an NMP slurry. This slurry was vacuum degassed and then applied onto an aluminum foil current collector having a thickness of 20 μm and dried by ventilation drying at 120 ° C. to form a thin film.
About this coating film, based on JISZ0237, the mixture adhesion strength measurement was implemented with the scratch test device (Tribogear, HEIDON-18).

<Measurement method of coating film resistance>
The positive electrode slurry that had been vacuum degassed used to prepare the film for coating film strength measurement was coated on a 100 μm PET film and dried at 120 ° C. to obtain a coating film for resistance measurement. The volume resistivity (Ω · cm) of the thin film was measured with a low resistivity meter (4-terminal four-probe method JIS K7194 compliant: Lorester EP (Mitsubishi Chemical Corporation)). Since active materials having the same composition exhibit approximately the same particle resistance, the lower the volume resistivity of the coating film, the better the conductive material network and the better the conductive path. Such an active material can bring out the performance of the active material with a smaller amount of the conductive material, and can increase the battery capacity.
If the composition of the active material is different, the powder resistance of the particles is different in the order of digits, so a uniform comparison cannot be made. Therefore, this time, only Ni: Mn: Co = 0.33: 0.33: 0.33 composition is compared.

<Measurement method of battery performance>
Lithium nickel manganese cobalt composite oxide powder 75 wt%, acetylene black 20 wt% as a conductive material, polytetrafluoroethylene (PTFE) 5 wt% as a binder are thoroughly mixed in a mortar, and then spread into a sheet. Was punched out in a circular shape so as to have a diameter of 9 mm and 7 mg. An aluminum expanded metal was pressure-bonded to this to obtain a positive electrode.
A Li foil having a thickness of 0.5 mm and a diameter of 12 was used for the negative electrode.
The electrolytic solution is a solution obtained by dissolving LiPF _{6 in} a mixed solvent of ethylene carbonate (EC) / dimethyl carbonate (DMC) / ethyl methyl carbonate (EMC) = 3/3/4 (volume ratio) to a concentration of 1 mol / L. Was used.
A polyethylene film was used as the separator.
A coin-type battery was assembled using these positive electrode, negative electrode, electrolyte, and separator.
Coin cell batteries as the upper limit voltage 4.2 V, lower limit voltage 3.0 V, then charged at 0.2 mA / cm ² constant current constant voltage was carried out 0.2 mA / cm ² constant current discharge (initial discharge capacity (A )). Subsequently, 0.5 mA constant current charge and 11 mA / cm ² constant current discharge were performed as high rate characteristics, and the discharge capacity was measured (11 mA discharge capacity (B)).

(Example 2)
A small amount of Li raw material was added before spray drying, and the remaining Li raw material was added after spray drying to produce lithium nickel manganese cobalt composite oxide powder.
LiOH, NiO, Mn ₃ O ₄ and Co (OH) ₂ are weighed and mixed so as to have a molar ratio of Li: Ni: Mn: Co = 0.05: 0.33: 0.33: 0.33. After that, pure water was added thereto to prepare a slurry. While the slurry was stirred, the solid content in the slurry was pulverized using a circulating medium stirring wet pulverizer.
To the particles obtained by spray-drying this slurry with a spray dryer, pulverized LiOH powder (average particle size 8 μm) with a molar ratio of 1.00 is added to (Ni + Mn + Co), mixed well, and fired. A precursor mixture was obtained. This calcined precursor mixture was calcined at 950 ° C. for 12 hours in an air atmosphere and then crushed to obtain a lithium nickel manganese cobalt composite oxide powder having a layered structure whose composition formula is Li _1.05 Ni _0.33 Mn _0.33 Co _0.33 O ₂ Got.
The obtained lithium nickel manganese cobalt composite oxide powder was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

(Example 3)
A lithium nickel manganese cobalt composite oxide powder was produced in the same manner as in Example 2 except that the cobalt raw material was CoOOH.
The obtained lithium nickel manganese cobalt composite oxide powder was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 4
Ni (OH) ₂ , Mn ₃ O ₄ and CoOOH were weighed and mixed so as to have a molar ratio of Ni: Mn: Co = 0.4: 0.4: 0.2, and then pure water was added thereto. In addition, a slurry was prepared. While stirring this slurry, the solid content in the slurry was pulverized to an average particle size of 0.21 μm using a circulating medium agitation type wet pulverizer.
To the particles obtained by spray-drying this slurry with a spray dryer, pulverized LiOH powder (average particle size 8 μm) with a molar ratio of 1.00 is added to (Ni + Mn + Co), mixed well, and fired. A precursor mixture was obtained. This calcined precursor mixture was calcined at 975 ° C. for 12 hours in an air atmosphere, then crushed, and lithium nickel manganese cobalt composite oxide powder having a layered structure with a composition formula of Li _1.02 Ni _0.40 Mn _0.40 Co _0.20 O ₂ Got.
The obtained lithium nickel manganese cobalt composite oxide powder was evaluated for coating film strength and battery performance in the same manner as in Example 1, and the results are shown in Table 1.

(Comparative Example 1)
The pulverized LiOH powder was added to the coprecipitated particles having a molar ratio of Ni, Mn, and Co of 0.33: 0.33: 0.33 and mixed well to obtain a calcined precursor mixture. This calcined precursor mixture was calcined at 1000 ° C. for 12 hours in an air atmosphere and then crushed to obtain a lithium nickel manganese cobalt composite oxide having a layered structure whose composition formula is Li _1.00 Ni _0.33 Mn _0.33 Co _0.33 O _2. It was.
The obtained lithium nickel manganese cobalt composite oxide powder was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

(Comparative Example 2)
Lithium nickel manganese cobalt composite oxide powder was produced by a method in which all Li raw materials were added before spray drying.
LiOH, NiO, Mn ₃ O ₄ and Co (OH) ₂ are weighed and mixed so as to have a molar ratio of Li: Ni: Mn: Co = 1.05: 0.33: 0.33: 0.33. After that, pure water was added thereto to prepare a slurry. While stirring the slurry, the solid content in the slurry was pulverized to an average particle size of 0.2 μm using a circulating medium agitation type wet pulverizer.
The particles obtained by spray-drying this slurry with a spray dryer are calcined at 950 ° C. for 12 hours in an air atmosphere and then crushed to have a layered structure whose composition formula is Li _1.05 Ni _0.33 Mn _0.33 Co _0.33 O _2. Lithium nickel manganese cobalt composite oxide powder was obtained.
The obtained lithium nickel manganese cobalt composite oxide powder was evaluated for coating film forming ability in the same manner as in Example 1, and the results are shown in Table 1. Since this lithium nickel manganese cobalt composite oxide powder has a low coating film strength, the battery performance was not evaluated.

(Comparative Example 3)
LiOH, NiO, Mn ₃ O ₄ and CoOOH were weighed and mixed so as to have a molar ratio of Li: Ni: Mn: Co = 0.05: 0.65: 0.15: 0.20. Pure water was added to the slurry to prepare a slurry. While stirring the slurry, the solid content in the slurry was pulverized to an average particle size of 0.2 μm using a circulating medium agitation type wet pulverizer.
To the particles obtained by spray-drying this slurry with a spray dryer, pulverized LiOH powder with a molar ratio of 1.00 to (Ni + Mn + Co) was further added and mixed well to obtain a calcined precursor mixture. . This calcined precursor mixture was calcined at 830 ° C. for 12 hours in an air atmosphere, and then crushed, and a lithium nickel manganese cobalt composite oxide having a layered structure with a composition formula of Li _1.05 Ni _0.65 Mn _0.15 Co _0.20 O _2. A material powder was obtained.
For the obtained lithium nickel manganese cobalt composite oxide powder, the coating film strength was examined in the same manner as in Example 1, and the results are shown in Table 1. Since this lithium nickel manganese cobalt composite oxide powder has a low coating film strength, the battery performance was not evaluated.

From Table 1, the following is clear.
In the composite oxide powder of Comparative Example 1 manufactured by the coprecipitation method, since the particle evaluation rate “a” is too large, the capacity retention rate is low and the rate characteristics are inferior.
In the composite oxide powder of Comparative Example 2 manufactured by the method of adding all the Li raw materials before spray drying, the ease of particle crushing evaluation a value is too small, so the strength of the coating film is low. Inferior in film forming ability.
In the composite oxide powder of Comparative Example 3 having a too high Ni content in the composition, the particle evaluation easiness of particle pulverization is small, and the strength of the coating film is also low.
Compared to these comparative examples, in Examples 1 to 4 in which both the particle evaluation easiness of particle crushing and the composition are within the appropriate ranges, the capacity retention rate and the coating film strength are high, and the rate characteristics and the coating film Compatibility with forming ability can be achieved.

  The lithium secondary battery including the positive electrode using the layered lithium nickel manganese based composite oxide powder for the positive electrode material of the lithium secondary battery according to the present invention has a high capacity and excellent rate characteristics. , Mobile PC, electronic book player, mobile phone, mobile fax, mobile copy, mobile printer, headphone stereo, video movie, LCD TV, handy cleaner, portable CD, minidisc, walkie-talkie, electronic notebook, calculator, memory card, mobile tape It can be used for power supplies such as recorders, radios, backup power supplies, motors, lighting equipment, toys, game machines, watches, strobes, cameras, power load leveling, electric bicycles, electric scooters, electric cars and the like.

Claims (7)

A powder composed of a layered lithium nickel manganese composite oxide represented by the following composition formula (1), having a BET specific surface area of 2 m ² / g or less, and evaluation of easiness of particle crushing as defined below A layered lithium nickel manganese based composite oxide powder for a lithium secondary battery positive electrode material, wherein the a value is 70% <a ≦ 95%.
_{Li 1 + x Ni 1-y} -z-p Mn y Co z M p O 2 ... (1)
(However, 0 ≦ x ≦ 0.20, 0.25 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.5, 0 ≦ p ≦ 0.2, 0.5 ≦ y + z + p ≦ 0.75, and M Is one or more of Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, Nb, and Zr)
[Evaluation of ease of particle crushing a value]
0.5 g of the powder is sandwiched between two 15 mmφ parallel stainless steel plates, the median diameter b of the powder when a pressure of 1.2 ton / cm ² is applied in one axial direction, and before the pressure is applied The value calculated by the following equation (2) from the median diameter c of the powder.
a = b / c × 100 (%) (2) A powder composed of a layered lithium nickel manganese composite oxide represented by the following composition formula (1), the tap density (bulk density) is 1.3 g / cm ³ or more, and the particle solution defined below A layered lithium nickel manganese based composite oxide powder for a lithium secondary battery positive electrode material, wherein the ease of crushing evaluation a value is 70% <a ≦ 95%.
_{Li 1 + x Ni 1-y} -z-p Mn y Co z M p O 2 ... (1)
(However, 0 ≦ x ≦ 0.20, 0.25 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.5, 0 ≦ p ≦ 0.2, 0.5 ≦ y + z + p ≦ 0.75, and M Is one or more of Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, Nb, and Zr)
[Evaluation of ease of particle crushing a value]
0.5 g of the powder is sandwiched between two 15 mmφ parallel stainless steel plates, the median diameter b of the powder when a pressure of 1.2 ton / cm ² is applied in one axial direction, and before the pressure is applied The value calculated by the following equation (2) from the median diameter c of the powder.
a = b / c × 100 (%) (2) The layered lithium nickel manganese for a positive electrode material for a lithium secondary battery according to claim 1 or 2, wherein the primary particles are aggregated to form secondary particles, and the median diameter of the secondary particles is 3 to 20 µm. -Based composite oxide powder. 4. The layered lithium nickel manganese based composite oxide powder for a lithium secondary battery positive electrode material according to claim 1, wherein the average primary particle diameter is 0.1 to 2 μm. In any one of claims 1 to 4, a lithium secondary battery positive electrode material, characterized for the layered complex oxide powder that has a BET specific surface area of 0.3~2m 2 / ^g. A positive electrode active material layer containing the layered lithium nickel manganese composite oxide powder for a lithium secondary battery positive electrode material according to any one of claims 1 to 5 and a binder on a current collector. A lithium secondary battery positive electrode characterized by. A lithium secondary battery comprising a negative electrode capable of inserting and extracting lithium, a non-aqueous electrolyte containing a lithium salt, and a positive electrode capable of inserting and extracting lithium, wherein the lithium secondary battery according to claim 6 is used as the positive electrode. A lithium secondary battery using a positive electrode.