JP2005336004A - Nickel manganese cobalt composite oxide, layered lithium nickel manganese cobalt composite oxide, positive electrode material for lithium secondary battery, positive electrode for lithium secondary battery using the same, and lithium secondary battery - Google Patents

Abstract

Kind Code: A1 A nickel manganese cobalt composite oxide and a layered lithium nickel manganese cobalt composite oxide capable of realizing a lithium secondary battery with high capacity, excellent rate characteristics, excellent high temperature cycle characteristics, and good performance balance. Provide industrial advantage.
A layered lithium nickel manganese cobalt composite oxide obtained by using a nickel manganese cobalt composite oxide, which is a single phase of a composite oxide having a spinel structure represented by the following formula (I), as a precursor: The primary particles are aggregated to form secondary particles, the standard deviation s of the average primary particle size is 0.15 or less, and nickel, manganese, and cobalt elements are uniformly dispersed. Secondary battery positive electrode material. (Ni _x Mn _x Co _1-2x ) ₃ O ₄ (I) (provided that 0.3 ≦ x ≦ 0.5)
[Selection] Figure 1

Description

  The present invention relates to a nickel manganese cobalt composite oxide and a method for producing the same, a layered lithium nickel manganese cobalt composite oxide using the nickel manganese cobalt composite oxide, a method for producing the same, and the layered lithium nickel manganese cobalt. The present invention relates to a positive electrode for a lithium secondary battery using a lithium-based composite oxide, and a lithium secondary battery including the positive electrode for a lithium secondary battery.

  Lithium secondary batteries are excellent in energy density and output density, and are effective for miniaturization and weight reduction. Therefore, the demand for lithium secondary batteries as a power source for portable devices such as notebook computers, mobile phones and handy video cameras is growing rapidly. Show. Lithium secondary batteries are also attracting attention as power sources for electric vehicles and power load leveling.

  In lithium secondary batteries, lithium-manganese composite oxides, and lithium-based composite oxides of lithium and transition metals, in which some of the transition metals of these composite oxides are replaced with other metals, are usually used as positive electrode active materials. Is 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. Among them, one preferred 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.

  Conventionally, as a method for producing a lithium nickel manganese cobalt-based composite oxide having a layered structure, a method of baking a solid phase mixture comprising a lithium compound, a nickel compound, a manganese compound and a cobalt compound at 850 ° C. in an oxygen atmosphere or in air. Has been proposed (Patent Documents 1 and 2).

  In the lithium nickel manganese cobalt composite oxide having a layer structure as the positive electrode active material, it is important that each element of nickel, manganese, and cobalt is highly uniformly dispersed (compositional uniformity).

  However, the lithium nickel manganese cobalt based composite oxide having a layered structure obtained by the methods of Patent Documents 1 and 2 is directly mixed with each raw material and fired, so that the reactivity of each raw material is different, resulting in poor composition. There is a problem that homogenization tends to occur, and it has been difficult to obtain sufficiently satisfactory battery performance.

  Therefore, from the viewpoint of uniform composition, nickel manganese cobalt coprecipitated composite hydroxide obtained by the technique of uniformly dispersing three transition metal elements at the atomic level by coprecipitation method to form a solid solution is used as a precursor. The manufacturing method which bakes the mixture of this and a lithium compound is disclosed (patent document 3).

  However, the method of Patent Document 3 has an industrial problem in terms of equipment and production volume in addition to the need for advanced technology, and therefore a more industrially advantageous method of uniformizing the composition is desired. It was rare.

In producing a lithium nickel composite oxide having nickel as a main constituent element as a transition metal component, the formula Ni _v M _w O (M is selected from the group consisting of Co, Mn, Cr, Fe, Mg). A mixture of an oxide precursor represented by 0.7 ≦ v ≦ 0.95, v + w = 1) and lithium hydroxide or a hydrate thereof with at least one metal element, and lithium nickel and manufacturing method for obtaining the system composite _{oxide, LiNi 1-u M u O} 2 ( where, M is Co, Al, Mg, Mn, Ti, Fe, Cu, Zn, at least one selected from the group consisting of Ga Nickel obtained by heat-treating a nickel composite hydroxide in which M is dissolved or added in producing a lithium nickel composite oxide represented by 0.25 ≧ u ≧ 0) with the above metal elements Complex acid The manufacturing method which mixes a compound and a lithium compound, and heat-processes and obtains a lithium nickel type complex oxide is disclosed (patent documents 4 and 5).

  However, the nickel-based composite oxide precursor used here has a rock salt type crystal structure, and is not a spinel structure like the nickel manganese cobalt-based composite oxide of the present invention described later. In the nickel manganese cobalt composite oxide composition of the present invention represented by the formula (I) described later, it is extremely difficult to obtain a single phase having a rock salt structure.

On the other hand, in order to improve the characteristics of a lithium nickel cobalt manganese composite oxide having a specific composition, a production method for firing a mixture of a nickel cobalt manganese composite oxide precursor and a lithium compound is also disclosed (Patent Document 6). ). However, at the firing temperature described in the claims of Patent Document 6, a single phase having a spinel structure like the nickel manganese cobalt composite oxide of the present invention described later cannot be obtained, and phases having different compositional metal composition ratios are obtained. There is a high possibility of mixing. Therefore, it is not preferable in terms of uniform composition, and it is considered that sufficiently satisfactory battery performance is not exhibited.
JP-A-8-37007 Japanese Patent Laid-Open No. 5-242891 JP 2003-17052 A JP-A-10-188987 JP 2003-168428 A JP 2003-242976 A

  The present invention is a nickel manganese cobalt composite oxide and a layered lithium nickel manganese cobalt composite oxide capable of realizing a lithium secondary battery with high capacity, excellent rate characteristics, excellent high temperature cycle characteristics, and good performance balance. Is provided industrially advantageously.

  As a result of intensive studies, the present inventor preferably spinel obtained by firing a spray-dried product of a highly pulverized raw material slurry containing a nickel compound, a manganese compound, and a cobalt compound under specific firing conditions. A lithium secondary battery is produced in an industrially advantageous manner by using a nickel manganese cobalt composite oxide having a single phase of the structure as a precursor, mixing this precursor and a lithium compound, and firing the mixture under specific firing conditions. The inventors have found that a layered lithium nickel manganese cobalt based composite oxide powder capable of exhibiting excellent performance as a positive electrode material can be obtained, and the present invention has been completed.

The nickel manganese cobalt based composite oxide of the present invention is a single phase of a composite oxide having a spinel structure represented by the following formula (I).
_{(Ni x Mn x Co 1-2x)} 3 O 4 ... (I)
(However, 0.3 ≦ x ≦ 0.5)

  The precursor for producing a lithium secondary battery positive electrode material of the present invention is characterized by comprising the nickel manganese cobalt composite oxide of the present invention.

  The method for producing a nickel manganese cobalt based composite oxide of the present invention is a method for producing this nickel manganese cobalt based composite oxide, wherein a mixture containing a nickel raw material, a manganese raw material, and a cobalt raw material is placed in an oxygen gas atmosphere. [(2500/3) x + 400] ° C. or higher and [(7000/3) x−50] ° C. or lower, and firing in a temperature range determined by parameters according to the composition.

  The layered lithium nickel manganese cobalt based composite oxide of the present invention is a layered lithium nickel manganese cobalt based composite oxide obtained using the nickel manganese cobalt based composite oxide according to the present invention as a precursor, and the primary particles are aggregated. Secondary particles are formed, the standard deviation s of the average particle diameter of the primary particles is 0.15 or less, and nickel, manganese, and cobalt elements are uniformly dispersed.

The layered lithium nickel manganese cobalt composite oxide preferably has a composition represented by the following formula (II).
_{Li 1 + y Ni z Mn z} Co 1-2z O 2 ... (II)
(However, 0 ≦ y ≦ 0.2, 0.3 ≦ z ≦ 0.5)

  The lithium secondary battery positive electrode material of the present invention is characterized by comprising the layered lithium nickel manganese cobalt composite oxide of the present invention.

  The method for producing the layered lithium nickel manganese cobalt based composite oxide of the present invention is a method for producing such a layered lithium nickel manganese cobalt based composite oxide, comprising a precursor comprising a nickel manganese cobalt based composite oxide, The mixture with the lithium compound is calcined in an oxygen gas-containing atmosphere at a temperature range of 800 ° C. or [3000 × -450] ° C., whichever is higher, and 1100 ° C. or less.

  In this method, the lithium compound is preferably lithium hydroxide which may be hydrated.

  The positive electrode for a lithium secondary battery of the present invention is characterized by having a positive electrode active material layer containing the layered lithium nickel manganese cobalt-based composite oxide according to the present invention and a binder.

  The lithium secondary battery of the present invention includes the positive electrode for a lithium secondary battery 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.

  According to the present invention, a positive electrode material for a lithium secondary battery capable of realizing a lithium secondary battery with high capacity, excellent rate characteristics, excellent high-temperature cycle characteristics, and good performance balance is industrially advantageous. Provided to.

  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 of the present invention. The content of is not specified.

[Nickel manganese cobalt complex oxide]
First, the nickel manganese cobalt based composite oxide of the present invention (hereinafter sometimes referred to as “spinel structure composite oxide”) will be described.

The nickel manganese cobalt-based composite oxide of the present invention is a composite oxide having a single phase having a spinel structure represented by the following formula (I).
_{(Ni x Mn x Co 1-2x)} 3 O 4 ... (I)
(However, 0.3 ≦ x ≦ 0.5)

  In the above formula (I), the value of x is usually 0.3 or more, preferably 0.33 or more, more preferably 0.4 or more, most preferably 0.42 or more as the lower limit, and usually 0 as the upper limit. 0.5 or less, preferably 0.48 or less, more preferably 0.47 or less, and most preferably 0.45 or less. If the value of x is below this lower limit, it is difficult to obtain a single phase, which is not preferable.

  It is important that the nickel manganese cobalt based composite oxide of the present invention has a single phase having a spinel structure. By using such a single phase precursor having a spinel structure, each element is highly uniformly dispersed. That is, a layered lithium nickel manganese cobalt composite oxide having a uniform composition can be obtained. Here, the degree of composition homogeneity can be known by, for example, quantitatively comparing and estimating from the value of crystal strain by Hall plot based on powder X-ray diffraction measurement, or by neutron diffraction measurement.

  Making a nickel-manganese-cobalt composite oxide into a single phase with a spinel structure can be realized, for example, by firing in a specific temperature range in an oxygen gas atmosphere. A diffraction pattern by powder X-ray diffraction by a vibration method can be analyzed and confirmed.

  Such a nickel manganese cobalt based composite oxide of the present invention can be produced by, for example, mixing raw material compounds and, if necessary, pulverizing mixed powder obtained by firing under specific conditions described later. it can.

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

As manganese compounds, manganese oxides such as Mn ₂ O ₃ , MnO ₂ , Mn ₃ O ₄ , MnCO ₃ , Mn (NO ₃ ) ₂ , MnSO ₄ , manganese acetate, manganese dicarboxylate, manganese citrate, manganese fatty acid And manganese salts such as oxyhydroxide, manganese chloride and the like. Among these manganese compounds, MnO ₂ , Mn ₂ O ₃ , and Mn ₃ O ₄ do not generate gases such as NO _X, SO _X , and CO ₂ during the firing process, and can be obtained at low cost as industrial raw materials. Therefore, it is preferable. These manganese compounds may be used individually by 1 type, and may use 2 or more types together.

Cobalt compounds include Co (OH) ₂ , CoOOH, CoO, Co ₂ O ₃ , Co ₃ O ₄ , Co (OCOCH ₃ ) ₂ .4H ₂ O, CoCl ₂ , Co (NO ₃ ) ₂ .6H _2. O, Co (SO ₄ ) ₂ · 7H ₂ O, and the like. Among them, Co (OH) ₂ , CoOOH, CoO, Co ₂ O ₃ , and Co ₃ O ₄ are preferable, and more preferably industrial in that no harmful substances such as NO _X and SO _X are generated during the firing process. Co (OH) ₂ and CoOOH are inexpensive and can be obtained at a low cost. These cobalt compounds may be used individually by 1 type, and may use 2 or more types together.

  The method for mixing the raw materials is not particularly limited, and may be wet or dry. For example, a method using an apparatus such as a ball mill, a vibration mill, or a bead mill can be used. Wet mixing is preferable because more uniform mixing is possible and the reactivity of the mixture can be increased in the firing step.

  In the case of wet mixing, it is preferable to pulverize a slurry prepared by mixing the above-described nickel compound, manganese compound, and cobalt compound together with a solvent using a wet bead mill, a ball mill, or the like. Alternatively, the solid raw material compound may be dry pulverized first and then mixed with a solvent to form a slurry.

  As the solvent used for preparing the slurry, various organic solvents and aqueous solvents can be used, but water is preferred.

  The slurry concentration is not particularly limited, and the lower limit of the concentration is usually 1% by weight or more, preferably 5% by weight or more, more preferably 10% by weight or more, and particularly preferably 15% by weight or more. When the slurry concentration is too low, productivity is lowered and the bulk density of particles obtained by spray drying tends to be reduced. The upper limit of the slurry concentration is usually 50% by weight or less. If the slurry concentration is too high, the viscosity of the slurry becomes high, and there is a possibility that it cannot be sprayed with a nozzle. The preferred slurry concentration is 45% by weight or less, particularly 40% by weight or less.

  The mixing time varies depending on the mixing method, but it is sufficient that the raw materials are uniformly mixed at the particle level. For example, in a ball mill (wet or dry type), usually about 1 to 2 days, and in a bead mill (wet continuous method), a residence time. Is usually about 0.1 to 6 hours.

  In the case of wet mixing, it is then usually subjected to a drying process. The drying method is not particularly limited, but spray drying is preferable from the viewpoints of uniformity of the generated particulate matter, powder flowability, powder handling performance, and the ability to efficiently form spherical secondary particles.

  The spray drying is preferably performed so as to obtain a spray-dried powder having an average particle diameter of the particulate matter of 50 μm or less, and further 40 μm or less. However, since it tends to be difficult to obtain a particle size that is too small, the average particle size of the spray-dried powder is usually 4 μm or more, preferably 5 μm or more. In the case of producing a particulate material by the spray drying method, the particle size can be controlled by appropriately selecting the spray format, the pressurized gas flow supply rate, the slurry supply rate, the drying temperature, and the like.

  The degree of pulverization after mixing is an index of the particle diameter of the raw material particles after pulverization, but the average particle diameter is usually 0.5 μm or less, preferably 0.3 μm or less, more preferably 0.2 μm or less. If the average particle size is too large, the reactivity in the firing step is lowered, and it is difficult to make the composition uniform. In addition, in the case of wet mixing, the sphericity of the dry powder in spray drying described later tends to decrease, and the final powder filling density tends to decrease. This tendency becomes particularly remarkable when trying to produce granulated particles having an average particle diameter of 50 μm or less. It should be noted that making particles smaller than necessary leads to an increase in pulverization cost, so that the average particle size is usually 0.01 μm or more, preferably 0.02 μm or more, more preferably 0.05 μm or more. It ’s fine.

  The mixture containing the nickel raw material, manganese raw material, and cobalt raw material thus obtained is preferably [(2500/3) x + 400] ° C. or higher, [(7000/3) x−50] in an oxygen gas atmosphere. A nickel manganese cobalt-based composite oxide having a single phase with a spinel structure can be obtained by maintaining and firing within a temperature range determined by a parameter corresponding to the composition, which is shown at or below C. In particular, when a particulate material obtained by wet mixing-spray drying is fired, spherical secondary particles formed by sintering primary particles can be obtained. Spherical secondary particles formed by sintering the primary particles are preferable because they have good powder properties and filling properties, and battery performance when used as an electrode active material.

  Here, the “oxygen gas atmosphere” refers to an atmosphere of 100% oxygen.

  When firing at a temperature outside the above temperature range, a single phase having a spinel structure may be difficult to obtain. However, even within the above temperature range, when the firing temperature is high, the specific surface area of the obtained spinel structure composite oxide tends to decrease, and in preparing the layered lithium nickel manganese cobalt composite oxide which is the next step, lithium The reactivity with the compound is reduced. Therefore, in order to obtain a precursor having a specific surface area as high as possible, firing is performed at a temperature close to the lower limit temperature in the temperature range, for example, [(2500/3) x + 400] ° C. or higher and [(3500/3) x + 300] ° C. or lower. It is preferable to do.

  In addition, even when firing in an atmosphere containing oxygen gas such as air other than the oxygen gas atmosphere, by firing at an optimum temperature range different from the firing temperature range in the oxygen gas atmosphere described above, the spinel structure is simple. One phase can be obtained. However, in the spinel structure composite oxide represented by the above formula (I), the ease of generation of the spinel phase varies depending on the firing atmosphere. As an atmosphere at the time of baking, the one where oxygen concentration is higher is preferable, The atmosphere whose oxygen concentration is 10-100 volume% is preferable, More preferably, it is an atmosphere whose oxygen concentration is 50-100 volume%. If the oxygen concentration in the firing atmosphere is too low, it may be difficult to form a spinel single phase.

  For firing, for example, a box furnace, a tubular furnace, a tunnel furnace, a rotary kiln or the like can be used.

  Firing is usually divided into three steps: temperature increase, maximum temperature retention, and temperature decrease. The second maximum temperature holding step is not necessarily a single step, and two or more steps may be included depending on the purpose, which means that aggregation is eliminated to the extent that secondary particles are not destroyed. The temperature raising, maximum temperature holding, and temperature lowering steps may be repeated twice or more with a crushing step or a pulverization step which means crushing to primary particles or even fine powder.

  In the temperature raising step, the temperature in the furnace is usually raised at a temperature raising rate of 1 to 10 ° C./min. If the heating rate is too slow, it takes time and is industrially disadvantageous. However, if the heating rate is too fast, the furnace temperature does not follow the set temperature depending on the furnace.

  The holding time in the maximum temperature holding step is usually selected from a wide range of 1 hour or more and 100 hours or less. However, if the firing time is too short, it is difficult to obtain a complex oxide with good crystallinity.

  In the temperature lowering step, the temperature in the furnace is usually decreased at a temperature decreasing rate of 0.1 to 10 ° C./min. If the rate of temperature drop is too slow, it takes time and is industrially disadvantageous. However, if it is too fast, the uniformity of the target product tends to be lacking or the deterioration of the container tends to be accelerated.

The nickel manganese cobalt composite oxide of the present invention having a single phase having a spinel structure thus obtained is highly reactive with a lithium compound in the production process of the layered lithium nickel manganese cobalt composite oxide of the present invention described later. From the viewpoint of obtaining properties, the BET specific surface area is usually 0.3 m ² / g or more, preferably 0.5 m ² / g or more. The upper limit of this BET specific surface area is usually 150 m ² / g or less, preferably 50 m ² / g or less, more preferably 30 m ² / g or less.

[Layered lithium nickel manganese cobalt composite oxide]
Next, the layered lithium nickel manganese cobalt composite oxide of the present invention will be described.

  The layered lithium nickel manganese cobalt composite oxide of the present invention is obtained from the nickel manganese cobalt composite oxide of the present invention or the spinel structure composite oxide produced by the method for producing the spinel structure composite oxide of the present invention. The primary particles are aggregated to form secondary particles.

  The layered lithium nickel manganese cobalt composite oxide of the present invention is characterized by little variation in primary particle diameter. The degree of variation is indicated by, for example, a standard deviation s calculated by the following equation used when estimating the standard deviation of the population from sample data extracted from the population.

  The standard deviation s of the primary particle diameter of the layered lithium nickel manganese cobalt composite oxide of the present invention is preferably as low as possible, but is usually about 0.01. Moreover, as an upper limit, it is 0.15 or less normally, Preferably it is 0.10 or less, More preferably, it is 0.05 or less. When the above upper limit is exceeded, the filling property to the positive electrode active material layer is lowered, and it is difficult to increase the electrode density per volume. Therefore, the electrode plate strength is lowered, the energy density is lowered, and the life characteristics are further reduced. This is not preferable because it is likely to cause a decrease in the temperature.

  The layered lithium nickel manganese cobalt composite oxide of the present invention has an average primary particle size (average primary particle size) of usually 0.1 μm or more, preferably 0.2 μm or more, more preferably 0.3 μm or more, It is 3 μm or less, preferably 1 μm or less, more preferably 0.6 μm or less. If the above upper limit is exceeded, it is difficult to form spherical secondary particles, which adversely affects the powder filling property, and the specific surface area is greatly reduced, so there is a high possibility that the battery performance such as rate characteristics and output characteristics will deteriorate. Therefore, it is not preferable. Below the lower limit, the crystal is undeveloped, which may cause problems such as poor reversibility of charge / discharge, which is not preferable.

  The primary particle size of the layered lithium nickel manganese cobalt composite oxide can be measured by an SEM image of about 30,000 times. For example, the average primary particle size and its standard deviation from 20 randomly selected primary particle samples. s can be obtained.

  The median diameter of the secondary particles of the layered lithium nickel manganese cobalt composite oxide of the present invention is 5 μm or more, preferably 9 μm or more, 20 μm or less, preferably 15 μm or less. If the above lower limit is not reached, a high bulk density product may not be obtained, and if the upper limit is exceeded, battery performance may be deteriorated, or there may be a problem in applicability during the formation of the positive electrode active material layer. .

  The median diameter of the secondary particles of the layered lithium nickel manganese cobalt based composite oxide can be measured by setting a refractive index of 1.24 using a known laser diffraction / scattering particle size distribution measuring device. In the present invention, a 0.1 wt% sodium hexametaphosphate aqueous solution was used as a dispersion medium used in the measurement, and the measurement was performed after ultrasonic dispersion for 5 minutes.

The layered lithium nickel manganese cobalt composite oxide of the present invention is preferably a composite oxide having a layered structure having a composition represented by the following formula (II).
_{Li 1 + y Ni z Mn z} Co 1-2z O 2 ... (II)
(However, 0 ≦ y ≦ 0.2, 0.3 ≦ z ≦ 0.5)

  In the above formula (II), the value of y is usually 0 or more, preferably 0.01 or more, more preferably 0.02 or more, usually 0.2 or less, preferably 0.15 or less, more preferably 0. 1 or less. Below this lower limit, unreacted substances remain, the crystal structure tends to become unstable, and when the upper limit is exceeded, heterogeneous phases are likely to be formed, or the amount of substitution to transition metal sites becomes too large. There is a possibility that the performance of the secondary battery is reduced.

  The value of z is usually 0.3 or more, preferably 0.33 or more, more preferably 0.4 or more, most preferably 0.42 or more as the lower limit, and usually 0.5 or less, preferably 0 as the upper limit. .48 or less, more preferably 0.47 or less, and most preferably 0.45 or less. If z is less than the above lower limit, it is difficult to obtain a single-phase spinel structure composite oxide as a raw material.

  In the layered lithium nickel manganese cobalt composite oxide of the present invention, a substitution element M may be introduced into the structure thereof as long as the characteristics of the layered lithium nickel manganese cobalt composite oxide of the present invention are not impaired. The substitution element M is selected from any one or more selected from the group consisting of Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, Nb, and Zr.

The layered lithium nickel manganese cobalt composite oxide of the present invention also has a BET specific surface area of 0.2 m ² / g or more, preferably 0.3 m ² / g or more, more preferably 0.4 m ² / g or more, and 4 .0m ² / g or less, preferably 2.5 m ² / g or less, still more preferably not more than ^2m 2 / g. If the BET specific surface area is smaller than this range, the battery performance tends to be lowered.

  In addition, the BET specific surface area of the above-mentioned spinel structure composite oxide and the layered lithium nickel manganese cobalt composite oxide is measured by a known BET type powder specific surface area measuring device. Specifically, nitrogen is used for the adsorption gas and helium is used for the carrier gas, and BET one-point method measurement is performed by a continuous flow method. First, a powder sample is heated and deaerated with a mixed gas at a temperature of 150 ° C., and then cooled to a liquid nitrogen temperature to adsorb the mixed gas. This is heated to room temperature with water and the adsorbed nitrogen gas is desorbed, the amount is detected by a thermal conductivity detector, and the specific surface area of the sample is calculated therefrom.

  The layered lithium nickel manganese cobalt composite oxide of the present invention can be obtained by firing a mixture of the spinel structure composite oxide of the present invention and a lithium compound in an oxygen gas-containing atmosphere. In particular, it can be preferably obtained by baking in an oxygen gas-containing atmosphere in a temperature range of 800 ° C. or [3000 × −450] ° C., whichever is higher, but not higher than 1100 ° C.

Here, as a lithium compound mixed with the spinel structure composite oxide of the present invention, Li ₂ CO ₃ , LiNO ₃ , LiNO ₂ , LiOH, LiOH.H ₂ O, LiH, LiF, LiCl, LiBr, LiI, CH ₃ OOLi, Li ₂ O, Li ₂ SO ₄ , dicarboxylic acid Li, citric acid Li, fatty acid Li, alkyl lithium and the like can be mentioned. Preferred among these lithium compounds in that it does not generate harmful substances such as NO _X and SO _X during the firing process, a lithium compound containing no nitrogen atom and a sulfur atom, LiOH, LiOH · H ₂ O Is preferred. These lithium compounds may be used alone or in combination of two or more.

  As the particle diameter of such a lithium compound, in order to increase the mixing property with the spinel structure composite oxide of the present invention and to improve battery performance, the average particle diameter is usually 500 μm or less, preferably 100 μm or less, More preferably, it is 50 micrometers or less, Most preferably, it is 20 micrometers or less. On the other hand, those having a too small particle diameter have an average particle diameter of usually 0.01 μm or more, preferably 0.1 μm or more, more preferably 0.2 μm or more, and most preferably 0 because of low stability in the atmosphere. .5 μm or more.

  Although there is no restriction | limiting in particular in the mixing method of the lithium compound to the spinel structure complex oxide of this invention, It is preferable to use the powder mixing apparatus generally used as an industrial use. The atmosphere in the mixed system is preferably an inert gas atmosphere in order to prevent carbon dioxide absorption in the air.

  The mixed powder thus obtained is then fired. This firing condition depends on the composition, the lithium compound raw material to be used, and the firing atmosphere, but as a tendency, if the firing temperature is too high, the primary particles grow too much. Is too big. Accordingly, the firing temperature is usually higher than 800 ° C. or [3000x-450] ° C., which is the higher firing temperature in an oxygen gas-containing atmosphere, preferably in the air (in the air), preferably 1100 ° C. or less. Is 1075 ° C. or lower.

  For firing, for example, a box furnace, a tubular furnace, a tunnel furnace, a rotary kiln or the like can be used.

  Firing is usually divided into three steps: temperature increase, maximum temperature retention, and temperature decrease. The second maximum temperature holding step is not necessarily a single step, and two or more steps may be included depending on the purpose, which means that aggregation is eliminated to the extent that secondary particles are not destroyed. The temperature raising, maximum temperature holding, and temperature lowering steps may be repeated twice or more with a crushing step or a pulverization step which means crushing to primary particles or even fine powder.

  In the temperature raising step, the temperature in the furnace is usually raised at a temperature raising rate of 1 to 10 ° C./min. If the rate of temperature increase is too slow, it takes time and is industrially disadvantageous. However, if it is too fast, the furnace temperature does not follow the set temperature depending on the furnace.

  The holding time in the maximum temperature holding step varies depending on the firing temperature, but is usually 30 minutes or more and 50 hours or less in the above-described temperature range. If the firing time is too short, it becomes difficult to obtain a lithium nickel manganese cobalt composite oxide powder with good crystallinity, and therefore it is preferably 5 hours or longer, more preferably 10 hours or longer. On the other hand, it is not very practical to be too long. In addition, if the firing time is too long, then it becomes necessary to crush or it becomes difficult to crush, so it is preferably 25 hours or less, more preferably 20 hours or less.

  In the temperature lowering step, the temperature in the furnace is usually decreased at a temperature decreasing rate of 0.1 to 10 ° C./min. If the rate of temperature drop is too slow, it takes time and is industrially disadvantageous. However, if it is too fast, the uniformity of the target product tends to be lacking or the deterioration of the container tends to be accelerated.

  As the atmosphere during firing, an atmosphere containing oxygen gas such as air can be used. Usually, the atmosphere has an oxygen concentration of 1 to 100% by volume, and an atmosphere having an oxygen concentration of 10 to 50% by volume is preferable in consideration of the crystallinity and particle properties of the product, industrial convenience, manufacturing safety, and the like. In particular, air is preferred.

  According to the layered lithium nickel manganese cobalt composite oxide of the present invention thus obtained, a positive electrode material for a lithium secondary battery with high capacity, excellent rate characteristics, and excellent high-temperature cycle characteristics is provided. Provided.

[Positive electrode for lithium secondary battery]
Next, the positive electrode for a lithium secondary battery of the present invention will be described.

  The positive electrode for a lithium secondary battery of the present invention is obtained by forming a positive electrode active material layer containing a powder of a layered lithium nickel manganese cobalt composite oxide of the present invention and a binder on a current collector. The positive electrode for a lithium secondary battery of the present invention is formed by forming a positive electrode active material layer containing a powder of a layered lithium nickel manganese cobalt composite oxide produced by the production method of the present invention and a binder on a current collector. It is made.

  The positive electrode active material layer is usually a positive electrode current collector obtained by mixing a positive electrode material (positive electrode active material), a binder, and a conductive material and a thickener, which are used as necessary, in a dry form to form a sheet. It is prepared by pressure bonding to a body, or by dissolving or dispersing these materials in a liquid medium to form a slurry, which is applied to a positive electrode current collector and dried.

  As the material for the positive electrode current collector, metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum, and carbon materials such as carbon cloth and carbon paper are usually used. Of these, metal materials are preferable, and aluminum is particularly preferable. As for the shape, in the case of a metal material, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foam metal, etc., and in the case of a carbon material, a carbon plate, a carbon thin film, a carbon cylinder Etc. Among these, metal thin films are preferable because they are currently used in industrialized products. In addition, you may form a thin film suitably in mesh shape.

  When a thin film is used as the positive electrode current collector, its thickness is arbitrary, but it is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 100 mm or less, preferably 1 mm or less, more preferably 50 μm or less. The range of is preferable. If the thickness is thinner than the above range, the strength required for the current collector may be insufficient. On the other hand, if it is thicker than the above range, the handleability may be impaired.

  The binder used in the production of the positive electrode active material layer is not particularly limited, and in the case of a coating method, any material that is stable with respect to the liquid medium used during electrode production may be used. Specific examples include polyethylene, Resin polymers such as polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitrocellulose, SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluorine rubber, isoprene rubber, butadiene rubber, ethylene・ Rubber polymers such as propylene rubber, styrene / butadiene / styrene block copolymer and hydrogenated products thereof, EPDM (ethylene-propylene-diene terpolymer), styrene / ethylene / butadiene / ethylene copolymer, Styrene / isoprene styrene bromide Copolymer and its hydrogenated thermoplastic elastomeric polymer, syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer, etc. Fluorine polymers such as soft resinous polymers, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymers, ion conductivity of alkali metal ions (especially lithium ions) And a polymer composition having the same. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

  The ratio of the binder in the positive electrode active material layer is usually 0.1% by weight or more, preferably 1% by weight or more, more preferably 5% by weight or more, and usually 80% by weight or less, preferably 60% by weight or less. More preferably, it is 40% by weight or less, and most preferably 10% by weight or less. If the ratio of the binder in the positive electrode active material layer is too low, the positive electrode active material cannot be sufficiently retained and the positive electrode has insufficient mechanical strength, which may deteriorate battery performance such as cycle characteristics. If it is too high, the battery capacity and conductivity may be reduced.

  The positive electrode active material layer usually contains a conductive material in order to increase conductivity. There are no particular restrictions on the type, but specific examples include metal materials such as copper and nickel, graphite such as natural graphite and artificial graphite, carbon black such as acetylene black, and amorphous carbon such as needle coke. And carbon materials. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios. The proportion of the conductive material in the positive electrode active material layer is usually 0.01% by weight or more, preferably 0.1% by weight or more, more preferably 1% by weight or more, and usually 50% by weight or less, preferably 30%. % By weight or less, more preferably 15% by weight or less. If the proportion of the conductive material in the positive electrode active material layer is too low, the conductivity may be insufficient, and conversely if it is too high, the battery capacity may be reduced.

  As a liquid medium for forming the slurry, the layered lithium nickel manganese cobalt composite oxide powder of the present invention, which is a positive electrode material, a binder, and a conductive material and a thickener used as necessary are dissolved. Or if it is a solvent which can be disperse | distributed, there will be no restriction | limiting in particular in the kind, You may use either an aqueous solvent or an organic solvent. Examples of the aqueous solvent include water and alcohol. Examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N -N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran (THF), toluene, acetone, dimethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, etc. Can be mentioned. In particular, when an aqueous solvent is used, a dispersant is added together with the thickener, and a slurry such as SBR is slurried. In addition, these solvents may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The content of the layered lithium nickel composite oxide powder of the present invention as the positive electrode material in the positive electrode active material layer is usually 10% by weight or more, preferably 30% by weight or more, more preferably 50% by weight or more, Usually, it is 99.9% by weight or less, preferably 99% by weight or less. If the ratio of the layered lithium nickel composite oxide powder in the positive electrode active material layer is too large, the strength of the positive electrode tends to be insufficient, and if it is too small, the capacity may be insufficient.

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

  Thus, the thickness of the positive electrode active material layer formed is about 10-200 micrometers normally.

[Lithium secondary battery]
Next, the lithium secondary battery of the present invention will be described.

  The lithium secondary battery of the present invention includes the above-described positive electrode for a lithium secondary battery of the present invention capable of occluding and releasing lithium, a negative electrode capable of occluding and releasing lithium, and a non-aqueous electrolyte using a lithium salt as an electrolytic salt, Is provided. Further, a separator for holding a nonaqueous electrolyte may be provided between the positive electrode and the negative electrode. In order to effectively prevent a short circuit due to contact between the positive electrode and the negative electrode, it is desirable to interpose a separator in this way.

  The negative electrode is usually configured by forming a negative electrode active material layer on a negative electrode current collector, similarly to the positive electrode.

  As the material of the negative electrode current collector, metal materials such as copper, nickel, stainless steel, nickel-plated steel, and carbon materials such as carbon cloth and carbon paper are used. For example, in the case of metal materials, metal foil, metal cylinder When a metal coil, a metal plate, a metal thin film, etc. are carbon materials, a carbon plate, a carbon thin film, a carbon cylinder, etc. are mentioned. Among these, metal thin films are preferable because they are currently used in industrialized products. In addition, you may form a thin film suitably in mesh shape. When a metal thin film is used as the negative electrode current collector, the preferred thickness range is the same as the range described above for the positive electrode current collector.

  The negative electrode active material layer includes a negative electrode active material. The negative electrode active material is not particularly limited as long as it is capable of electrochemically occluding and releasing lithium ions, but is usually a carbon that can occlude and release lithium in terms of safety. Material is used.

  Although there is no restriction | limiting in particular as a carbon material, Graphite (graphite), such as artificial graphite and natural graphite, and the thermal decomposition thing of organic substance on various thermal decomposition conditions are mentioned. Examples of pyrolysis products of organic matter include 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, crystalline cellulose, etc. And carbon materials obtained by partially graphitizing these, furnace black, acetylene black, pitch-based carbon fibers, and the like. Among them, graphite is preferable, and particularly preferable is artificial graphite, purified natural graphite, or graphite material containing pitch in these graphites, which is manufactured by subjecting easy-graphite pitch obtained from various raw materials to high-temperature heat treatment. Therefore, those subjected to various surface treatments are mainly used. One of these carbon materials may be used alone, or two or more thereof may be used in combination.

  When a graphite material is used as the negative electrode active material, the d value (interlayer distance) of the lattice plane (002 plane) determined by X-ray diffraction by the Gakushin method is usually 0.335 nm or more, and usually 0.34 nm or less, preferably Is preferably 0.337 nm or less.

  Further, the ash content of the graphite material is usually 1% by weight or less, particularly 0.5% by weight or less, and particularly preferably 0.1% by weight or less, based on the weight of the graphite material.

  Further, 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, and particularly preferably 100 nm or more.

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

Moreover, 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, and further preferably 1.5 m ² / g. or more, and usually 25.0 m ² / g or less, preferably 20.0 m ² / g, more preferably 15.0 m ² / g or less, still more preferably 10.0 m ² / g or less.

Further, when performing Raman spectroscopy using argon laser light for graphite material, and strength _{I A} of the peak _{P A} is detected in the range of 1580～1620Cm ^-1, is detected in the range of 1350 ^-1 that intensity ratio _I a / _{I B} of the intensity _{I B} of a peak _{P B} is what is preferably 0 to 0.5. Further, the half value width is preferably 26cm ^-1 or less of the peak _{P A,} 25 cm ^-1 or less is more preferable.

  In addition to the above-mentioned various carbon materials, it can also be used as a negative electrode active material of other materials capable of inserting and extracting lithium. Specific 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. One of these materials other than the carbon material may be used alone, or two or more thereof may be used in combination. Moreover, you may use in combination with the above-mentioned carbon material.

  As in the case of the positive electrode active material layer, the negative electrode active material layer is usually prepared by slurrying the above-described negative electrode active material, a binder, and optionally a conductive material and a thickener in a liquid medium. It can manufacture by apply | coating to a negative electrode electrical power collector, and drying. As the liquid medium, the binder, the thickener, the conductive material and the like forming the slurry, the same materials as those described above for the positive electrode active material layer can be used at the same ratio.

  As the electrolyte, for example, known organic electrolytes, polymer solid electrolytes, gel electrolytes, inorganic solid electrolytes, and the like can be used. Among them, organic electrolytes are preferable. The organic electrolytic solution is configured by dissolving a solute (electrolyte) in an organic solvent.

  Here, the type of the organic solvent is not particularly limited. For example, carbonates, ethers, ketones, sulfolane compounds, lactones, nitriles, chlorinated hydrocarbons, ethers, amines, esters, amides. A phosphoric acid ester compound or the like can be used. Typical examples are dimethyl carbonate, diethyl carbonate, propylene carbonate, ethylene 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 and the like, and these can be used alone or in combination of two or more.

  The organic solvent described above preferably contains a high dielectric constant solvent in order to dissociate the electrolytic salt. 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 ethylene carbonate, propylene carbonate, and compounds in which hydrogen atoms thereof are substituted with other elements such as halogen or alkyl groups are contained in the electrolytic solution. The proportion of the high dielectric constant solvent 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. If the content of the high dielectric constant solvent is less than the above range, desired battery characteristics may not be obtained.

The type of the electrolytic salt is not particularly limited, and any conventionally known solute can be used. 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. Any one of these electrolytic salts may be used alone, or two or more thereof may be used in any combination and ratio. Further, 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 S _x ^2- , at an arbitrary ratio May be added.

  The lithium salt of the electrolytic salt is usually contained in the electrolytic solution so as to have a concentration of 0.5 mol / L to 1.5 mol / L. Even if this content is less than 0.5 mol / L or more than 1.5 mol / L, the electrical conductivity may be lowered, and the battery characteristics may be adversely affected. The lower limit is preferably 0.75 mol / L or more and the upper limit is 1.25 mol / L or less.

Even when a polymer solid electrolyte is used, the type thereof is not particularly limited, and any known crystalline / amorphous inorganic substance can be used as the solid electrolyte. Examples of the crystalline inorganic solid electrolyte include LiI, Li ₃ N, Li _{1 + m} J _m Ti _2-m (PO ₄ ) ₃ (J = Al, Sc, Y, La), Li _0.5-3n RE _{0. .5 + n} 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.

  When the above-described organic electrolyte is used as the electrolyte, a separator is interposed 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 not particularly limited, but those that are stable with respect to the organic electrolyte used, have excellent liquid retention properties, and can reliably prevent short-circuiting between electrodes are preferable. Preferable examples include microporous films, sheets, nonwoven fabrics and the like made of various polymer materials. Specific examples of the polymer material include polyolefin polymers such as nylon, cellulose acetate, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, polypropylene, polyethylene, and polybutene. In particular, from the viewpoint of chemical and electrochemical stability, which is an important factor for separators, polyolefin polymers are preferable. From the viewpoint of self-occluding temperature, which is one of the purposes of use of separators in batteries, polyethylene is preferred. Is particularly desirable.

  When using a separator made of polyethylene, it is preferable to use ultra-high molecular weight polyethylene from the viewpoint of maintaining high-temperature shape, and the lower limit of the molecular weight is preferably 500,000, more preferably 1,000,000, and most preferably 1,500,000. On the other hand, the upper limit of the molecular weight is preferably 5 million, more preferably 4 million, and most preferably 3 million. This is because if the molecular weight is too large, the fluidity becomes too low and the pores of the separator may not close when heated.

  Using the above-described positive electrode for a lithium secondary battery of the present invention, the lithium secondary battery of the present invention is manufactured by assembling a negative electrode, an electrolyte, and a separator used as necessary into an appropriate shape. Can do. Furthermore, other components such as an outer case can be used as necessary.

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

  The general embodiment of the lithium secondary battery of the present invention has been described above. However, the lithium secondary battery of the present invention is not limited to the above-described embodiment, and various modifications are possible as long as the gist thereof is not exceeded. Can be implemented.

  Hereinafter, the present invention will be described more specifically with reference to experimental examples, examples, and comparative examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

  In the following, phases of nickel manganese cobalt composite oxide and lithium nickel manganese cobalt composite oxide were identified by a powder X-ray diffraction (XRD) pattern.

  The specific surface areas of the nickel manganese cobalt composite oxide and the lithium nickel manganese cobalt composite oxide were determined by the BET method.

  Moreover, the primary particle diameter of the lithium nickel manganese cobalt based composite oxide was measured with an SEM image of 30,000 times, and the average primary particle diameter and standard deviation s of 20 randomly selected primary particle samples were obtained.

  The median diameter of the secondary particles is set to a refractive index of 1.24 using a known laser diffraction / scattering type particle size distribution analyzer, and a 0.1 wt% sodium hexametaphosphate aqueous solution is used as a dispersion medium for 5 minutes. Measured after ultrasonic dispersion.

(Experimental example 1)
Ni (OH) ₂ , Mn ₃ O _4, and Co (OH) ₂ are weighed and mixed so as to have a predetermined molar ratio, and then pure water is added thereto to make a slurry having a concentration of 10 to 15.5 wt%. Was prepared. While stirring this slurry, the solid content in the slurry was pulverized to an average particle size of 0.15 to 0.19 μm using a circulating medium agitation type wet pulverizer (Shinmaru Enterprises Co., Ltd .: Dynomill KDL A type). did. About 5 g of particulate powder obtained by spray-drying the slurry with a spray dryer is charged into an alumina crucible with a volume of about 30 mL, and the firing temperature (maximum holding temperature during firing) is changed under an oxygen flow of 1 L / min. Baking was performed for 20 hours (temperature increase / decrease rate of 5 ° C./min) to obtain a nickel manganese cobalt composite oxide having a predetermined composition.

  About the obtained nickel manganese cobalt type complex oxide, the XRD pattern was investigated and the relationship between the value of x in said Formula (I) and the crystal phase with respect to a calcination temperature was shown to FIGS.

1 to 5, there is a correlation between the firing temperature and the crystal phase of the obtained nickel-manganese-cobalt composite oxide according to x in the formula (I), and depending on the firing temperature, it is a basic phase. In addition to the M ₃ O ₄ phase, the MO phase and M ₂ O ₃ phase, which are other phases, may be observed, and are defined in the present invention under an oxygen gas atmosphere [(2500/3). It was confirmed that a spinel single phase can be obtained by firing in a temperature range determined by parameters depending on the composition, which is represented by x + 400] ° C. or more and [(7000/3) x−50] ° C. or less.

(Example 1)
Ni (OH) ₂ , Mn ₃ O ₄ and Co (OH) ₂ were weighed and mixed so as to have a molar ratio of Ni: Mn: Co = 1: 1: 1, and then pure water was added thereto. A slurry having a concentration of 15.5% by weight was prepared. While stirring this slurry, the solid content in the slurry was pulverized to an average particle size of 0.19 μm using a circulating medium agitation type wet pulverizer (Shinmaru Enterprises Co., Ltd .: Dynomill KDL A type).

About 100 g of particulate powder obtained by spray-drying this slurry with a spray drier is charged into an alumina crucible having a volume of about 784 mL, and calcined at 675 ° C. for 20 hours under a flow of 1 L / min of oxygen gas (heating rate 5) C./min) to obtain a single-phase nickel manganese cobalt composite oxide powder having a spinel structure represented by (Ni _1/3 Mn _1/3 Co _1/3 ) ₃ O ₄ . The spinel structure composite oxide powder had a BET specific surface area of 13.7 m ² / g.

LiOH powder pulverized to an average particle size of 20 μm or less was added to the pulverized spinel structure composite oxide powder so that the molar ratio of Li was 1.05 with respect to (Ni + Mn + Co), and mixed well. About 13 g of this pre-firing mixture was charged in an alumina crucible with a volume of 30 mL, fired at 850 ° C. for 10 hours under an air flow of 9 L / min (heating rate 5 ° C./min) and then crushed to obtain a composition formula A lithium nickel manganese cobalt based composite oxide having a layered structure of Li _1.05 Ni _1/3 Mn _1/3 Co _1/3 O ₂ was obtained. The average primary particle size was 0.37 μm and the standard deviation s was 0.06. The median diameter of the secondary particles was 8.8 μm, and the BET specific surface area was 2.2 m ² / g.

(Example 2)
Ni (OH) ₂ , Mn ₃ O ₄ and Co (OH) ₂ were weighed and mixed so as to have a molar ratio of Ni: Mn: Co = 4: 4: 2, and then pure water was added thereto. A slurry having a concentration of 13% by weight was prepared. While stirring this slurry, the solid content in the slurry was pulverized to an average particle size of 0.15 μm using a circulating medium agitation type wet pulverizer (Shinmaru Enterprises Co., Ltd .: Dynomill KDL A type).

About 100 g of the particulate powder obtained by spray-drying this slurry with a spray drier is charged into an alumina crucible having a volume of about 784 mL, and calcined at 750 ° C. for 20 hours under an oxygen gas flow of 1 L / min (heating rate 5) C / min) to obtain a single-phase nickel manganese cobalt composite oxide powder having a spinel structure represented by (Ni _0.4 Mn _0.4 Co _0.2 ) ₃ O ₄ . The spinel structure composite oxide powder had a BET specific surface area of 5.9 m ² / g.

LiOH powder pulverized to an average particle size of 20 μm or less was added to the pulverized spinel structure composite oxide powder so that the molar ratio of Li was 1.05 with respect to (Ni + Mn + Co), and mixed well. About 13 g of this pre-firing mixture was charged in an alumina crucible with a volume of 30 mL, fired at 900 ° C. for 10 hours under an air flow of 9 L / min (temperature raising / lowering speed 5 ° C./min), and then crushed to obtain a composition formula A lithium nickel manganese cobalt based composite oxide having a layered structure of Li _1.05 Ni _0.4 Mn _0.4 Co _0.2 O ₂ was obtained. The average primary particle size was 0.39 μm and the standard deviation s was 0.05. The median diameter of the secondary particles was 9.0 μm, and the BET specific surface area was 1.9 m ² / g.

(Example 3)
Ni (OH) ₂ , Mn ₃ O ₄ and Co (OH) ₂ were weighed and mixed so that the molar ratio of Ni: Mn: Co = 9: 9: 2 was added, and then pure water was added thereto. A slurry having a concentration of 12% by weight was prepared. While stirring this slurry, the solid content in the slurry was pulverized to an average particle size of 0.15 μm using a circulating medium agitation type wet pulverizer (Shinmaru Enterprises Co., Ltd .: Dynomill KDL A type).

About 60 g of particulate powder obtained by spray-drying this slurry with a spray drier is charged into an alumina crucible having a volume of about 784 mL, and calcined at 775 ° C. for 20 hours under a flow of 1 L / min of oxygen gas (heating rate 5) C./min.) To obtain a single-phase nickel manganese cobalt composite oxide powder having a spinel structure represented by (Ni _0.45 Mn _0.45 Co _0.1 ) ₃ O ₄ . The spinel structure composite oxide powder had a BET specific surface area of 5.3 m ² / g.

LiOH powder pulverized to an average particle size of 20 μm or less was added to the pulverized spinel structure composite oxide powder so that the molar ratio of Li was 1.05 with respect to (Ni + Mn + Co), and mixed well. About 13 g of this pre-firing mixture was charged in an alumina crucible with a volume of 30 mL, fired at 950 ° C. for 10 hours under a flow of 9 L / min (heating rate 5 ° C./min), and then crushed to obtain a composition formula A lithium nickel manganese cobalt based composite oxide having a layered structure of Li _1.05 Ni _0.45 Mn _0.45 Co _0.1 O ₂ was obtained. The average primary particle size was 0.56 μm and the standard deviation s was 0.12. The median diameter of the secondary particles was 7.7 μm, and the BET specific surface area was 1.2 m ² / g.

(Comparative Example 1)
Example 1 except that the pulverized LiOH powder was directly mixed with the particulate powder obtained by spray-drying the slurry with a spray dryer without going through the nickel manganese cobalt-based composite oxide. In the same manner as above, a lithium nickel manganese cobalt based composite oxide having a layered structure with a composition formula of Li _1.05 Ni _1/3 Mn _1/3 Co _1/3 O ₂ was obtained. The average primary particle diameter was 0.31 μm and the standard deviation s was 0.17. The median diameter of the secondary particles was 9.0 μm, and the BET specific surface area was 2.7 m ² / g.

(Comparative Example 2)
Example 2 except that the pulverized LiOH powder was directly mixed with the particulate powder obtained by spray drying the slurry with a spray dryer without going through the nickel manganese cobalt based composite oxide. In the same manner as above, a lithium nickel manganese cobalt based composite oxide having a layered structure with a composition formula of Li _1.05 Ni _0.4 Mn _0.4 Co _0.2 O ₂ was obtained. The average primary particle size was 0.46 μm and the standard deviation s was 0.19. The median diameter of the secondary particles was 8.8 μm, and the BET specific surface area was 1.5 m ² / g.

(Comparative Example 3)
Example 3 except that the pulverized LiOH powder was directly mixed with the particulate powder obtained by spray-drying the slurry with a spray dryer without going through the nickel manganese cobalt-based composite oxide. In the same manner as above, a lithium nickel manganese cobalt based composite oxide having a layered structure with a composition formula of Li _1.05 Ni _0.45 Mn _0.45 Co _0.1 O ₂ was obtained. The average primary particle diameter was 0.63 μm and the standard deviation s was 0.23. The median diameter of the secondary particles was 7.2 μm, and the BET specific surface area was 1.2 m ² / g.

  BET specific surface area of spinel structure composite oxide powder produced in Examples 1 to 3 and various powder physical properties of layered lithium nickel manganese cobalt composite oxide powder produced in Examples 1 to 3 and Comparative Examples 1 to 3 The measurement results are summarized in Table 1.

<Production and evaluation of battery>
Using the layered lithium nickel manganese cobalt based composite oxide powder produced in Examples 1 to 3 and Comparative Examples 1 to 3, batteries were produced and evaluated by the following methods.

(1) Production of positive electrode and initial charge / discharge capacity and rate test:
What weighed 75% by weight of layered lithium nickel manganese cobalt based composite oxide powder prepared in Examples 1 to 3 and Comparative Examples 1 to 3, 20% by weight of acetylene black, and 5% by weight of polytetrafluoroethylene powder. Were mixed thoroughly in a mortar, and a thin sheet was punched out using a 9 mmφ punch. At this time, the total weight was adjusted to about 8 mg. This was pressure-bonded to an aluminum expanded metal to obtain a 9 mmφ positive electrode.

A 9 mmφ positive electrode was used as a test electrode, a lithium metal plate as a counter electrode, and 1 mol of LiPF ₆ in a solvent of EC (ethylene carbonate): DMC (dimethyl carbonate): EMC (ethyl methyl carbonate) = 3: 3: 4 (volume ratio). A coin-type cell was assembled using a 25 μm-thick porous polyethylene film as a separator using an electrolytic solution dissolved at / L.

With respect to the obtained coin-type cell, a charge / discharge two-cycle test was conducted at a constant current of 0.2 mA / cm ² with a charge upper limit voltage of 4.3 V and a discharge lower limit voltage of 3.0 V. 10th cycle, constant current charge of 0.5 mA / cm ² , 0.2 mA / cm ² , 0.5 mA / cm ² , 1 mA / cm ² , 3 mA / cm ² , 5 mA / cm ² , 7 mA / cm ² , 9 mA / cm ^2, and were tested at each discharge of 11 mA / cm ^2. Initial discharge capacity at 0.2 mA / cm ² in the first cycle at this time (mAh / g), and high-rate discharge capacity at the 10th cycle at 11 mA / cm ² a (mAh / g) was measured, the results It is shown in Table 2.

(2) High temperature cycle test:
A. Preparation of positive electrode and capacity check:
What weighed 75% by weight of layered lithium nickel manganese cobalt based composite oxide powder prepared in Examples 1 to 3 and Comparative Examples 1 to 3, 20% by weight of acetylene black, and 5% by weight of polytetrafluoroethylene powder. Were mixed thoroughly in a mortar, and a thin sheet was punched out using 9 mmφ and 12 mmφ punches. At this time, the total weight was adjusted to about 8 mg and about 18 mg, respectively. This was pressure-bonded to an aluminum expanded metal to obtain positive electrodes of 9 mmφ and 12 mmφ.

A 9 mmφ positive electrode was used as a test electrode, a lithium metal plate as a counter electrode, and 1 mol of LiPF ₆ in a solvent of EC (ethylene carbonate): DMC (dimethyl carbonate): EMC (ethyl methyl carbonate) = 3: 3: 4 (volume ratio). A coin-type cell was assembled using a 25 μm-thick porous polyethylene film as a separator using an electrolytic solution dissolved at / L. This was subjected to a constant current / constant voltage charging / discharging of 0.2 mA / cm ² , that is, a reaction for releasing lithium ions from the positive electrode at an upper limit of 4.2 V. Subsequently, the initial charge capacity per unit weight of the positive electrode active material when a constant current discharge of 0.2 mA / cm ² , that is, a reaction of occluding lithium ions in the positive electrode was performed at a lower limit of 3.0 V was Qs (C) [mAh / g], and the initial discharge capacity was Qs (D) [mAh / g].

B. Production of negative electrode and capacity check:
Graphite powder having an average particle size of 8 to 10 μm (d ₀₀₂ = 3.35 Å) was used as the negative electrode active material, and polyvinylidene fluoride was used as the binder, and these were weighed at a weight ratio of 92.5: 7.5. Were mixed in an N-methylpyrrolidone solution to obtain a negative electrode mixture slurry. This slurry was applied to one side of a 20 μm thick copper foil, dried to evaporate the solvent, punched to 12 mmφ, and pressed at 0.5 ton / cm ² (49 MPa) to form a negative electrode.

In addition, the negative electrode active material unit when the negative electrode was used as a test electrode, a battery cell was assembled using lithium metal as a counter electrode, and a test for occluding lithium ions in the negative electrode at a constant current of 0.5 mA / cm ² was performed at a lower limit of 0 V The initial storage capacity per weight was defined as Qf [mAh / g].

C. Battery assembly:
A test battery was assembled using a coin cell, and the battery performance was evaluated. That is, on the positive electrode can of the coin cell, the above-mentioned positive electrode prepared using the layered lithium nickel manganese cobalt based composite oxides of Examples 1 to 3 and Comparative Examples 1 to 3 was placed, and a separator having a thickness of 25 μm was placed thereon. The porous polyethylene film was placed and pressed with a polypropylene gasket, and then EC (ethylene carbonate): DMC (dimethyl carbonate): EMC (ethyl methyl carbonate) = 3: 3: 4 (volume ratio) as a non-aqueous electrolyte. An electrolyte solution in which LiPF ₆ was dissolved at 1 mol / L in a solvent of the above was added into a can and sufficiently impregnated into a separator, and then a negative electrode can was placed and sealed to form a coin-type lithium secondary battery (Example) 1 to 3 and Comparative Examples 1 to 3). At this time, the balance between the weight of the positive electrode active material and the weight of the negative electrode active material was set so as to satisfy the following expression.
Positive electrode active material weight [g] / Negative electrode active material weight [g]
= (Qf [mAh / g] /1.2) Qs (C) [mAh / g]

D. High temperature cycle test In order to compare the high temperature characteristics of the batteries using the layered lithium nickel manganese cobalt based composite oxides of Examples 1 to 3 and Comparative Examples 1 to 3 thus obtained, the hourly rate current value of the battery, that is, 1C Was set as shown below, and the following tests were conducted.
1C [mA] = Qs (D) × positive electrode active material weight [g] / h

  First, a constant current 0.2C charge / discharge cycle and a constant current 1C charge / discharge cycle were performed at room temperature. Next, a constant current 0.2 C charge / discharge cycle was conducted at a high temperature of 60 ° C., and then a constant current 1 C charge / discharge cycle 100 was tested. The upper limit of charging was 4.1 V, and the lower limit voltage was 3.0 V.

At this time, the ratio of the discharge capacity Qh (100) at the 100th cycle to the discharge capacity Qh (100) at the 100th cycle in the 1C charge / discharge 100 cycle test at 60 ° C. is defined as the high-temperature cycle capacity maintenance rate P. Based on the high temperature characteristics of the batteries were compared. That is, P is represented by the following formula.
P [%] = {Qh (100) / Qh (1)} × 100

  Table 2 shows the high-temperature cycle capacity retention rate P in the 1C charge / discharge 100 cycle test at 60 ° C. in the batteries using the layered lithium nickel manganese cobalt based composite oxides of Examples 1 to 3 and Comparative Examples 1 to 3. Show.

  In Table 2, by comparing (Example 1, Comparative Example 1), (Example 2, Comparative Example 2), and (Example 3, Comparative Example 3), which are the same composition ratios, respectively, according to the present invention. For example, it can be seen that a positive electrode material for a lithium secondary battery having a high capacity, excellent rate characteristics, excellent high-temperature cycle characteristics, and good performance balance is provided.

  The use of the lithium secondary battery provided by the present invention is not particularly limited, and can be used for various known uses. Specific examples include notebook computers, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copy, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, minidiscs, and transceivers. Electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, lighting equipment, toys, game machines, watches, strobes, cameras, automobile power sources, and the like.

In Experimental Example 1, it is a graph showing the produced _{(Ni x Mn x Co 1-2x)} 3 O 4 (x = 0.33) calcining temperature and XRD pattern of nickel manganese cobalt-based composite oxide. In Experimental Example 1, it is a graph showing the produced _{(Ni x Mn x Co 1-2x)} 3 O 4 (x = 0.4) calcining temperature and XRD pattern of nickel manganese cobalt-based composite oxide. In Experimental Example 1, it is a graph showing the produced _{(Ni x Mn x Co 1-2x)} 3 O 4 (x = 0.45) calcining temperature and XRD pattern of nickel manganese cobalt-based composite oxide. In Experimental Example 1, it is a graph showing the produced _{(Ni x Mn x Co 1-2x)} 3 O 4 (x = 0.475) calcining temperature and XRD pattern of nickel manganese cobalt-based composite oxide. In Experimental Example 1, it is a graph showing the produced _{(Ni x Mn x Co 1-2x)} 3 calcining temperature O ₄ (x = 0.5) of the nickel-manganese-cobalt composite oxide and the XRD pattern.

Claims (12)

A nickel manganese cobalt-based composite oxide, which is a single phase of a composite oxide having a spinel structure represented by the following formula (I):
_{(Ni x Mn x Co 1-2x)} 3 O 4 ... (I)
(However, 0.3 ≦ x ≦ 0.5)   A precursor for producing a positive electrode material for a lithium secondary battery, comprising the nickel manganese cobalt-based composite oxide according to claim 1.   According to the composition, the mixture containing the nickel raw material, the manganese raw material, and the cobalt raw material is represented by [(2500/3) x + 400] ° C. or higher and [(7000/3) x−50] ° C. or lower in an oxygen gas atmosphere. The method for producing a nickel-manganese-cobalt composite oxide according to claim 1, wherein the firing is performed in a temperature range determined by the parameters.   A layered lithium nickel manganese cobalt composite oxide obtained by using the nickel manganese cobalt composite oxide according to claim 1 as a precursor, wherein primary particles aggregate to form secondary particles, A layered lithium nickel manganese cobalt based composite oxide having a standard deviation s of an average particle diameter of 0.15 or less and nickel, manganese, and cobalt elements uniformly dispersed.   A layered lithium nickel manganese cobalt-based composite oxide obtained from the nickel-manganese cobalt-based composite oxide manufactured by the method for manufacturing a nickel-manganese-cobalt-based composite oxide according to claim 3, wherein primary particles are aggregated to form a secondary The layered lithium nickel manganese is characterized by comprising particles, wherein the standard deviation s of the average particle diameter of the primary particles is 0.15 or less, and each element of nickel, manganese, and cobalt is uniformly dispersed Cobalt complex oxide. 6. The layered lithium nickel manganese cobalt composite oxide according to claim 4 or 5, wherein the layered lithium nickel manganese cobalt composite oxide has a composition represented by the following formula (II).
_{Li 1 + y Ni z Mn z} Co 1-2z O 2 ... (II)
(However, 0 ≦ y ≦ 0.2, 0.3 ≦ z ≦ 0.5)   A lithium secondary battery positive electrode material comprising the layered lithium nickel manganese cobalt composite oxide according to any one of claims 4 to 6.   A mixture of a precursor comprising a nickel manganese cobalt based composite oxide and a lithium compound is heated in an oxygen gas-containing atmosphere to a temperature range of 800 ° C or [3000x-450] ° C, whichever is higher, and 1100 ° C or less. The method for producing a layered lithium nickel manganese cobalt-based composite oxide according to any one of claims 4 to 6, characterized in that firing is performed.   The method for producing a layered lithium nickel manganese cobalt based composite oxide according to claim 8, wherein the lithium compound is lithium hydroxide which may be hydrated.   A lithium secondary material comprising a positive electrode active material layer containing a layered lithium nickel manganese cobalt-based composite oxide according to any one of claims 4 to 6 and a binder on a current collector. Battery positive electrode.   A positive electrode active material layer containing, on a current collector, a layered lithium nickel manganese cobalt-based composite oxide produced by the method for producing a layered lithium nickel manganese cobalt-based composite oxide according to claim 8 or 9, and a binder. A positive electrode for a lithium secondary battery, comprising:   A lithium secondary battery comprising the positive electrode for a lithium secondary battery according to claim 10 or 11, a negative electrode capable of inserting and extracting lithium, and a nonaqueous electrolyte containing a lithium salt as an electrolytic salt.

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