JP2006172753A - Lithium-nickel-manganese-based composite oxide powder for lithium secondary battery positive electrode material, its manufacturing method, positive electrode for lithium secondary battery using it, and lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost lithium-nickel-manganese-based composite oxide reducing a cost and of compatibly establishing enhancement of safety and battery performance improvement when it is used as a lithium secondary battery positive electrode material. <P>SOLUTION: This lithium-nickel-manganese-based composite oxide powder has a composition represented by the following formula (I), wherein contained sulfur concentration is 0.06-0.35 wt.%. The formula (I): Li<SB>1+z</SB>Ni<SB>x</SB>Mn<SB>y</SB>Co<SB>1-x-y</SB>O<SB>2</SB>, where x, y and z are numerals respectively satisfying 0.20≤x≤0.55, 0.20≤y≤0.60, 0.50≤x+y≤1, and 0.02≤z≤0.55. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lithium nickel manganese composite oxide powder used as a lithium secondary battery positive electrode material, a method for producing the same, a positive electrode for a lithium secondary battery using the lithium nickel manganese composite oxide powder, and The present invention relates to a lithium secondary battery including a positive electrode for a lithium secondary battery.

  Lithium secondary batteries are excellent in energy density and output density, and are effective in reducing the size and weight. 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.

  Currently, lithium manganese composite oxides, layered lithium nickel composite oxides, and layered lithium cobalt composite oxides having a spinel structure are used as positive electrode active material materials for lithium secondary batteries. All of the lithium secondary batteries using these lithium-containing composite oxides have advantages and disadvantages in terms of characteristics. That is, a lithium manganese composite oxide having a spinel structure is inexpensive and relatively easy to synthesize, and is excellent in safety when used as a battery, but has a low capacity and inferior high-temperature characteristics (cycle and storage). Layered lithium-nickel composite oxides have high capacity and excellent high-temperature characteristics, but are difficult to synthesize, have poor stability when used as batteries, and have drawbacks such as requiring careful storage. Layered lithium cobalt-based composite oxides are widely used as power sources for portable devices because they are easy to synthesize and have an excellent balance of battery performance. However, they are not sufficient in safety and costly. It is a drawback.

  Under such circumstances, lithium nickel manganese cobalt-based composite oxides having a layered structure are possible candidates for active material materials that can overcome or reduce as much as possible the drawbacks of these positive electrode active material materials and are excellent in battery performance balance. Proposed. In particular, in recent years, demands for cost reduction and safety are increasing, and therefore, they are regarded as promising as positive electrode active material materials that can meet both requirements. However, the cost reduction and the degree of safety vary depending on the composition ratio, particularly the Ni / Mn / Co ratio. Among these, Ni: Mn: Co = x: y: 1-xy (x and y are 0.20 ≦ x ≦ 0, respectively) as a particularly excellent composition ratio from the viewpoint of cost reduction and safety enhancement. 55, 0.20 ≦ y ≦ 0.60, and a number satisfying 0.50 ≦ x + y ≦ 1) are known.

  However, lithium secondary batteries using layered lithium nickel manganese cobalt-based composite oxides with such a low cost and high safety composition range as the positive electrode material have reduced battery performance such as charge / discharge capacity and output characteristics. Therefore, further improvement is necessary for practical use in order to improve battery performance.

  Conventionally, as a technique for improving the battery performance of the lithium nickel manganese cobalt-based composite oxide having the above-described composition region having relatively high safety, a technique described in Patent Document 1 can be cited. This technology improves the battery performance such as rate characteristics and output characteristics without lowering the charge / discharge capacity by slightly increasing the lithium / transition metal (nickel, manganese, cobalt) ratio from 1. .

  However, in the technique described in Patent Document 1, the basicity (pH) of the obtained lithium nickel manganese cobalt-based composite oxide increases with an increase in the lithium / transition metal (nickel, manganese, cobalt) ratio. . When the basicity (pH) of the positive electrode material is increased, problems such as a tendency of battery swelling due to gas generation and a decrease in storage characteristics have been pointed out (see Non-Patent Document 1). Nevertheless, Patent Document 1 describes nothing about measures for suppressing such an increase in basicity (pH).

  Moreover, the technique of patent document 2 and patent document 3 is mentioned as a technique which made the lithium nickel manganese cobalt type complex oxide of the above-mentioned composition range contain a sulfur component and aimed at the improvement of battery performance.

  However, the techniques described in Patent Literature 2 and Patent Literature 3 have problems in improving battery performance or have problems associated with an increase in basicity (pH) as described above.

JP 2002-110167 A Japanese Patent Laid-Open No. 2001-6672 JP 2003-297360 A INTERNATIONAL MEETING ON LITHIUM BATTERIES, 11th MEETING, ABSTRACT No.371, 2002

  From the above background, the lithium nickel manganese cobalt based composite oxide powder having the specific composition range described above, while reducing costs and improving battery performance, at the same time, suppressing the increase in basicity (pH), It has been required to achieve improvement in storage stability.

  The present invention has been made on the basis of the above-mentioned problems. The object of the present invention is to reduce the cost and improve the battery performance when used as a positive electrode material for a lithium secondary battery, and at the same time, the basic (pH). Lithium-nickel-manganese composite oxide powder capable of suppressing an increase and achieving improved safety and storage stability, a method for producing the same, and a lithium nickel-manganese composite oxide powder using the lithium-nickel-manganese composite oxide powder It aims at providing the positive electrode for secondary batteries, and the lithium secondary battery using this positive electrode for lithium secondary batteries.

  As a result of intensive studies, the present inventors have found that lithium / transition metal (nickel, manganese, cobalt) atoms in a lithium nickel manganese cobalt based composite oxide having a limited composition range (the above-mentioned nickel / manganese / cobalt ratio). When the ratio is set within a predetermined range higher than 1 and a sulfur component having a predetermined concentration coexists, when used as a positive electrode material for a lithium secondary battery, cost reduction and battery performance improvement are achieved. At the same time, it has been found that it is possible to suppress the increase in basicity (pH) and to achieve improvement in safety and storage stability, and the present invention has been completed.

That is, the gist of the present invention is a lithium secondary battery having a composition represented by the following formula (I) and having a sulfur concentration of 0.06 wt% or more and 0.35 wt% or less. It exists in the lithium nickel manganese type complex oxide powder for positive electrode materials (Claim 1).
_{Li 1 + z Ni x Mn y} Co 1-xy O 2 (I)
(In the formula (I), x, y and z are 0.20 ≦ x ≦ 0.55 and 0.20 ≦ y ≦, respectively.
It represents a number satisfying 0.60, 0.50 ≦ x + y ≦ 1, 0.02 ≦ z ≦ 0.55. )

Here, in the formula (I), y / x representing the Mn / Ni atomic ratio is 0.95 ≦ y / x.
It is preferable that ≦ 1.5 (Claim 2).
Moreover, it is preferable that a contained sulfur component consists of a sulfate compound (Claim 3).
Further, the carbon concentration C is preferably 0.012% by weight or less (claim 4).
Moreover, it is preferable that the volume resistivity when it is consolidated at a pressure of 40 MPa is 5 × 10 ⁵ Ω · cm or less.
In addition, the primary particles are aggregated to form secondary particles, the bulk density is 1.5 g / cm ³ or more, the average primary particle diameter is 0.1 μm or more and 3 μm or less, The median diameter is preferably 3 μm or more and 20 μm or less (Claim 6).
The BET specific surface area is preferably 0.2 m ² / g or more and 1.5 m ² / g or less (Claim 7).

  Another gist of the present invention is a method for producing a lithium nickel manganese composite oxide powder for a positive electrode material for a lithium secondary battery, wherein the nickel compound, the manganese compound, the sulfate compound, and, if necessary, A powder obtained by pulverizing a cobalt compound used in a liquid medium to an average particle size of 0.3 μm or less, spray-drying a uniformly dispersed slurry, and agglomerating primary particles to form secondary particles; Thereafter, the powder is sufficiently mixed with a lithium compound, and the mixture is fired in an oxygen-containing gas atmosphere, thereby producing a lithium nickel manganese composite oxide powder for a positive electrode material for a lithium secondary battery The method resides in claim 8.

  Another purpose of the present invention is to provide at least a current collector and a positive electrode active material layer formed on the current collector, and the positive electrode active material layer is lithium nickel for a positive electrode material for a lithium secondary battery described above. The present invention resides in a positive electrode for a lithium secondary battery, characterized by containing at least a manganese-based composite oxide powder and a binder.

  Still another object of the present invention is a lithium secondary battery comprising at least a positive electrode and a negative electrode capable of inserting and extracting lithium, and a non-aqueous electrolyte containing a lithium salt, wherein the positive electrode is the above-described lithium It is a lithium secondary battery, which is a positive electrode for a secondary battery (claim 10).

  When the lithium nickel manganese based composite oxide powder of the present invention is used as a positive electrode material for a lithium secondary battery, it can suppress an increase in basicity (pH) while improving battery performance. Therefore, a lithium secondary battery that is inexpensive and excellent in battery performance, as well as in safety and storage stability is provided.

  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 specified by the contents of these descriptions. It is not a thing.

[I. Lithium nickel manganese composite oxide powder)
The lithium nickel manganese based composite oxide powder for lithium secondary battery positive electrode material of the present invention (hereinafter referred to as “lithium nickel manganese based composite oxide powder” as appropriate) has a composition represented by the following formula (I). .

_{Li 1 + z Ni x Mn y} Co 1-xy O 2 (I)
(In the formula (I), x, y and z are 0.20 ≦ x ≦ 0.55 and 0.20 ≦ y ≦, respectively.
It represents a number satisfying 0.60, 0.50 ≦ x + y ≦ 1, 0.02 ≦ z ≦ 0.55. )

In the formula (I), the value of x is usually 0.20 or more, preferably 0.25 or more, more preferably 0.30 or more, most preferably 0.325 or more, and usually 0.55 or less, Preferably it is 0.50 or less, more preferably 0.45 or less, and most preferably 0.425 or less. If the lower limit of this range is not reached, the battery capacity may be reduced, and if the upper limit of this range is exceeded, the safety tends to decrease.

  The value of y is usually 0.20 or more, preferably 0.25 or more, more preferably 0.30 or more, most preferably 0.325 or more, and usually 0.60 or less, preferably 0.55 or less. More preferably, it is 0.50 or less, and most preferably 0.475 or less. Below the lower limit of this range, the storage stability tends to be degraded and deteriorated, and when the upper limit of this range is exceeded, heterogeneous phases are likely to be generated and battery performance is likely to be degraded.

  The value of x + y is usually 0.50 or more, preferably 0.55 or more, more preferably 0.60 or more, most preferably 0.65 or more, and 1 or less, preferably 0.95 or less, more preferably Is 0.90 or less, and most preferably 0.85 or less. A lower value is preferable because the battery performance is improved, but if the value is below the lower limit of this range, the safety of the battery may be impaired.

  The value of z is usually 0.02 or more, preferably 0.03 or more, more preferably 0.04 or more, still more preferably 0.05 or more, most preferably 0.06 or more, and usually 0.55. In the following, it is preferably 0.45 or less, more preferably 0.30 or less, and most preferably 0.15 or less. If the lower limit of this range is not reached, the conductivity may decrease, and if the upper limit of this range is exceeded, the amount of substitution with transition metal sites becomes too large and the battery capacity becomes low. There is a risk of performance degradation.

In the composition range of the above formula (I), the Li / (Ni + Mn + Co) molar ratio is a constant ratio.
The pH value becomes lower as the value becomes closer to the value, but on the other hand, there is a tendency that the rate characteristic and output characteristic when the battery is used are also lowered, and conversely, the battery becomes higher as the Li / (Ni + Mn + Co) molar ratio becomes larger than the constant ratio. However, there is a tendency that the pH value is also increased. The present invention has been completed as a result of intensive studies to overcome this contradictory tendency, and as described above, the Li / (Ni + Mn + Co) molar ratio is larger than the constant ratio as described above. It is possible to reduce the pH value by containing a sulfur component at a predetermined concentration.

In the formula (I), the atomic ratio of the oxygen amount is described as 2 for convenience, but there may be some non-stoichiometry.

  Moreover, the substitutional element M may be introduced into the structure of the lithium nickel manganese based composite oxide powder of the present invention. Examples of the substitution element M include one or more elements selected from the group consisting of Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, Nb, Zr, Mo, W, and Sn. . The concentration of the substitution element M is not particularly limited, but is usually 5% by weight or less, preferably 3% by weight or less, and more preferably 2% by weight or less. If this range is exceeded, battery performance such as charge / discharge capacity may be reduced.

  The lithium nickel manganese based composite oxide powder of the present invention has a sulfur content (this value is hereinafter referred to as “S value” as appropriate) of 0.06 wt% or more and 0.35 wt% or less. And Among these, the lower limit is preferably 0.10% by weight or more, more preferably 0.15% by weight or more, most preferably 0.18% by weight or more, and the upper limit thereof is preferably 0.30% by weight. Hereinafter, it is more preferably 0.25% by weight or less, and most preferably 0.23% by weight or less. If the lower limit of this range is not reached, there may be an increase in blistering due to gas generation when the battery is made or the safety may be reduced. If the upper limit of this range is exceeded, battery performance such as charge / discharge capacity may be reduced. There is.

  In addition, the lithium nickel manganese composite oxide powder of the present invention has a y / x value representing an Mn / Ni atomic ratio of usually 0.95 or more, particularly from the viewpoint of improving safety and storage stability. From the viewpoint of battery capacity, it is usually 1.5 or less, preferably 1.3 or less, and more preferably 1.1 or less.

  In the lithium nickel manganese composite oxide powder of the present invention, the presence form of the contained sulfur component is not particularly limited, but it is preferably present in the form of a sulfate. In particular, for the lithium nickel manganese based composite oxide powder produced by the production method described later (the production method of the present invention), a numerical value assuming that all the sulfur is derived from sulfate ions from the contained sulfur concentration obtained by sulfur analysis described later. And the sulfate ion concentration analyzed by ion chromatography agree well, it is considered that the sulfur in the lithium nickel manganese composite oxide powder of the present invention is generally present as a sulfate, and therefore the S value is In particular, it can be regarded as indicating information about the content of sulfate compounds.

  In order to obtain a lithium nickel manganese composite oxide powder containing a sulfate compound, a sulfate compound may be used as part of the active material raw material, or a sulfate compound may be added separately. Moreover, you may use the compound which produces | generates a sulfate by baking reaction. The method for introducing the sulfate compound is not limited, but it is preferably added at the stage of mixing the active material raw materials.

  The lithium nickel manganese based composite oxide powder of the present invention has a concentration of carbon (this value is hereinafter referred to as “C value” as appropriate) is usually 0.012% by weight or less, preferably 0.010% by weight. Hereinafter, it is more preferably 0.008% by weight or less. When this upper limit is exceeded, there is a possibility that swelling due to gas generation when the battery is produced increases or battery performance deteriorates.

  For the lithium nickel manganese composite oxide powder produced by the production method described later (the production method of the present invention), from the contained carbon concentration determined by the carbon analysis described later, a numerical value assuming that all the carbon is derived from carbonate ions, Since the carbonate ion concentration analyzed by ion chromatography is in good agreement, it is considered that the carbon in the lithium nickel manganese composite oxide powder of the present invention is generally present as a carbonate. In particular, it can be regarded as indicating information about the amount of lithium carbonate deposited.

  The S value and C value of the lithium nickel manganese based composite oxide powder are determined by, for example, the measurement method shown in the column of Examples described later, that is, combustion in an oxygen stream (high-frequency heating furnace type) -infrared absorption method. It can be determined by measurement.

The volume resistivity value when the lithium nickel manganese composite oxide powder of the present invention is compacted at a pressure of 40 MPa is usually 5 × 10 ⁵ Ω · cm or less, preferably 2 × 10 ⁵ Ω · cm or less. More preferably, it is 1 × 10 ⁵ Ω · cm or less, and particularly preferably 2 × 10 ⁴ Ω · cm or less. When the volume resistivity exceeds this upper limit, there is a possibility that rate characteristics and low-temperature characteristics as a battery may be deteriorated. The lower limit of the volume resistivity is usually 5 × 10 ¹ Ω · cm or more, preferably 1 × 10 ² Ω · cm or more, more preferably 5 × 10 ² Ω · cm or more, and most preferably 1 × 10 ³ Ω · cm. That's it. If the volume resistivity is below this lower limit, the safety of the battery may be reduced.

  In the present invention, the volume resistivity when the lithium nickel manganese composite oxide powder is compacted at a pressure of 40 MPa is a known powder resistivity measuring device (for example, Lorester GP powder resistance manufactured by Dia Instruments Co., Ltd.). For example, measurement can be performed based on the measurement conditions shown in the section of Examples described later.

  The lithium nickel manganese composite oxide powder of the present invention usually has a form in which primary particles are aggregated to form secondary particles. In addition, it can confirm that lithium nickel manganese type complex oxide powder has such a form by SEM (scanning electron microscope) observation or cross-sectional SEM observation, for example.

The bulk density of the lithium nickel manganese based composite oxide powder of the present invention is usually 1.5 g / cm ³ or more, preferably 1.7 g / cm ³ or more, more preferably 1.9 g / cm ³ or more, most preferably 2.0 g / cm ³ or more. Below this lower limit, powder filling properties and electrode preparation are adversely affected, and a positive electrode using this as an active material is not preferable because the capacity density per unit volume becomes too small. Further, the upper limit of the bulk density is usually 3 g / cm ³ or less, preferably 2.8 g / cm ³ or less, more preferably 2.6 g / cm ³ or less. While it is preferable for the bulk density to exceed this upper limit, it is preferable for improving powder filling properties and electrode density. On the other hand, the specific surface area may become too low, which is not preferable because battery performance deteriorates.

  The average primary particle diameter of the lithium nickel manganese composite oxide powder of the present invention is usually 0.1 μm or more, preferably 0.2 μm or more, more preferably 0.3 μm or more, and most preferably 0.4 μm or more. It is 3 μm or less, preferably 2 μm or less, more preferably 1.5 μm or less, and most preferably 1.0 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 median diameter of the secondary particles of the lithium nickel manganese based composite oxide powder of the present invention is usually 3 μm or more, preferably 5 μm or more, more preferably 9 μm or more, most preferably 10 μm or more, and usually 20 μm or less. It is preferably 18 μm or less, more preferably 16 μm or less, and most preferably 15 μm or less. If the lower limit of the range is not reached, a high bulk density product may not be obtained. If the upper limit of the range is exceeded, battery performance may be deteriorated or the coatability at the time of forming the positive electrode active material layer may be problematic. Since there is a possibility, it is not preferable.

The 90% cumulative diameter (D ₉₀ ) of the secondary particles of the lithium nickel manganese composite oxide powder of the present invention is usually 30 μm or less, preferably 26 μm or less, more preferably 23 μm or less, and most preferably 20 μm or less. In addition, it is usually 5 μm or more, preferably 8 μm or more, more preferably 12 μm or more, and most preferably 15 μm or more. If the upper limit of this range is exceeded, battery performance may be deteriorated, and there may be a problem in applicability during the formation of the positive electrode active material layer. If the lower limit of this range is exceeded, high bulk density products cannot be obtained. Since there is a possibility, it is not preferable. The 90% cumulative diameter (D ₉₀ ) of the secondary particles defined here is a value when set at a refractive index of 1.24.

The BET specific surface area of the lithium nickel manganese composite oxide powder of the present invention is usually 0.2 m ² / g or more, preferably 0.3 m ² / g or more, more preferably 0.4 m ² / g or more. In addition, it is usually 1.5 m ² / g or less, preferably 1.2 m ² / g or less, more preferably 0.9 m ² / g or less, and most preferably 0.6 m ² / g or less. When the BET specific surface area is less than the lower limit of this range, the battery performance is likely to deteriorate. When the BET specific surface area exceeds the upper limit of this range, the bulk density is difficult to increase or a problem is likely to occur in the coating property when forming the positive electrode active material.

  The bulk density of the lithium nickel manganese composite oxide powder is, for example, a powder packing density (tap density) when 10 to 11 g of a sample is placed in a 10 ml glass graduated cylinder and tapped 200 times with a stroke of about 20 mm. Can be obtained as Moreover, an average primary particle diameter can be calculated | required from the SEM image observed by 30000 times, for example. The median diameter of the secondary particles can be measured using a known laser diffraction / scattering particle size distribution measuring device, for example, by setting a refractive index of 1.24 and using the particle diameter reference as a volume reference. Specifically, a 0.1 wt% sodium hexametaphosphate aqueous solution is used as a dispersion medium in the measurement, and the measurement can be performed after ultrasonic dispersion for 5 minutes. The specific surface area can be measured by a known BET specific surface area measurement method using a nitrogen adsorption method.

Here, the difference between the technology described in Patent Documents 1 to 3 and the present invention will be described.
In the technique described in Patent Document 1, as described above, the basicity (pH) increases as the lithium ratio increases, and there are problems such as gas generation associated therewith. However, in order to reduce the basicity (pH). No measures are taken, and there is no description regarding the concentration of contained sulfur, which is a requirement for reducing basicity (pH) and improving battery performance of the present invention. Also, a description of the carbon content that affects battery performance by causing side reactions as impurity constituents, or existing on the surface or grain boundary of the positive electrode active material and inhibiting lithium ion storage / release reactions. There is no recognition of the influence of the contained sulfur concentration, volume resistivity, and contained carbon concentration on battery performance.

  In the technique described in Patent Document 2, the Li ratio is limited to 1, which does not satisfy the composition range of the present invention. As a result, the battery performance of the obtained lithium secondary battery is insufficient. Further, this document does not disclose the concept of adding a sulfur component for the purpose of reducing basicity (pH). As described above, the lithium ratio defined in this document is lower than that of the present invention, and therefore, the problem of increase in basicity (pH) that the present invention is based on cannot be generated.

In the technique described in Patent Document 3, Li _1.05 Ni _0.42 Mn _0.53 O ₂ containing a sulfur content is used as the positive electrode active material in the examples. However, the sulfur concentration contained in the positive electrode active material is 0.05% by weight when converted to% by weight, which is less than the concentration range defined by the present invention. When the contained sulfur concentration is within this range, it is difficult to exert the basicity (pH) reduction effect as described above.

  On the other hand, in the present invention, in the lithium nickel manganese composite oxide having the composition ratio (nickel / manganese / cobalt ratio) in the predetermined range, the atomic ratio of lithium / transition metal (nickel, manganese, cobalt) is changed. While being set within a predetermined range higher than 1, a sulfur component (preferably sulfate) having a predetermined concentration coexists. As a result, it is possible to reduce the cost and improve the battery performance, and at the same time, suppress the increase in basicity (pH) and achieve the improvement of safety and storage stability.

In addition, some technical documents relating to conventional lithium secondary batteries disclose that a positive electrode material contains a sulfur content. Examples of those documents are given below.
・ Japanese Patent Laid-Open No. 07-014572, Japanese Patent No. 3444324, Japanese Patent Laid-Open No. 09-245787, Japanese Patent Laid-Open No. 09-283118, Japanese Patent No. 3421510, Japanese Patent No. 3315910, Japanese Patent Laid-Open No. 2000-021402 -JP2000-215895A-JP2002-015739A-JP2004-014296A

  However, all of the techniques described in these documents differ from the lithium nickel manganese composite oxide powder of the present invention in the composition or crystal structure of the positive electrode active material. In addition, these references do not mention reduction of basicity (pH).

[II. Method for producing lithium nickel manganese composite oxide]
The lithium nickel manganese composite oxide powder of the present invention is not limited to a specific production method. For example, a nickel compound, a manganese compound, a cobalt compound used as necessary, and a sulfate compound in a liquid medium. The slurry dispersed in can be spray-dried, mixed with a lithium compound, and the mixture can be fired to produce. Hereinafter, this production method (hereinafter referred to as “the production method of the lithium nickel manganese composite oxide powder of the present invention” or simply “the production method of the present invention”) will be described in detail.

Among the raw material compounds used for the preparation of the slurry in producing the lithium nickel manganese composite oxide by the production method of the present invention, the 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) ₂ .4H ₂ , which does not contain nitrogen atoms or sulfur atoms, does not generate harmful substances such as NO _x during the firing process. Nickel compounds such as 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 are preferable because they do not generate NO _X , CO _{2, and} other gases during the firing process and can be obtained at low cost as industrial raw materials. 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 in terms of not generating harmful substances such as NO _x during the firing process, and more preferably industrially inexpensive. Co (OH) ₂ and CoOOH are available and have high reactivity. These cobalt compounds may be used individually by 1 type, and may use 2 or more types together.

Moreover, as a sulfate compound, as an inorganic salt, ZnSO ₄ , (NH ₄ ) ₂ Zn (SO ₄ ) ₂ , Al ₂ (SO ₄ ) ₃ , (SbO) ₂ .SO ₄ , Sb ₂ (SO ₄ ) ₃ , (NH ₄ ) ₂ SO ₄ , Al (NH ₄ ) (SO ₄ ) ₂ , Na (NH ₄ ) SO ₄ , Y ₂ (SO ₄ ) ₃ , (NH ₄ ) Y (SO ₄ ) ₂ , K ₃ Y (SO ₄ ) ₃ , NaY (SO ₄ ) ₂ , Ir ₂ (SO ₄ ) ₃ , Ir (SO ₄ ) ₂ , CsIr (SO ₄ ) ₂ , In ₂ (SO ₄ ) ₃ , In (NH ₄ ) (SO _{4) 2, CsIn (SO 4} ) 2, CdSO 4, Cd 2 (NH 4) 2 (SO 4) 3, Cd (NH 4) 2 (SO 4) 2, K 2 SO 4, Ga 2 (SO 4) _{3, AlK (SO 4) 2} , Ga (NH 4) (SO 4) 2, IrK (SO 4) 2, IrK 3 (SO 4) 3, CdK 2 (SO 4) 2, GdK (SO 4) 2, _{aK (SO 4) 2, CaK} 2 (SO 4) 2, CrK (SO 4) 2, CoK 2 (SO 4) 3, CoK (SO 4) 2, CsGa (SO 4) 2, CeK (SO 4) 2 _{, ceK 4 (SO 4) 4} , FeK 2 (SO 4) 2, FeK (SO 4) 2, CuK 2 (SO 4) 2, K 2 Ni (SO 4) 2, K 2 Mg (SO 4) 2, K ₂ Mg ₂ (SO ₄ ) ₃ , K ₂ Mn (SO ₄ ) ₂ , KMn (SO ₄ ) ₂ , CaSO ₄ , Ag ₂ SO ₄ , Au ₂ (SO ₄ ) ₃ , CrSO ₄ , Cr ₂ (SO ₄ ) ₃ , Cr (NH ₄ ) (SO ₄ ) ₂ , Cr (NH ₄ ) ₃ (SO ₄ ) ₃ , CrCs (SO ₄ ) ₂ , CoSO ₄ , Co ₂ (SO ₄ ) ₃ , Co (NH ₄ ) ₂ (SO ₄ ) ₂ , Co (NH ₄ ) (SO ₄ ) ₂ , CoCs (SO ₄ ) ₂ , Zr (SO ₄ ) ₂ , Zr (OH) ₂ (SO ₄ ), Zr ₂ (OH ) ₂ (SO ₄ ) ₃ , NH ₄ HSO ₄ , (NO) HSO ₄ , KHSO ₄ , Ca (HSO ₄ ) ₂ , Sr (HSO ₄ ) ₂ , CsHSO ₄ , NaHSO ₄ , Ba (HSO ₄ ) ₂ , ( NH ₃ OH) HSO ₄ , Mg (HSO ₄ ) ₂ , LiHSO ₄ , RbHSO ₄ , Sc ₂ (SO ₄ ) ₃ , KSc (SO ₄ ) ₂ , SnSO ₄ , Sn (SO ₄ ) ₂ , SrSO ₄ , Cs ₂ SO ₄ , AlCs (SO ₄ ) ₂ , Ce ₂ (SO ₄ ) ₃ , Ce (SO ₄ ) ₂ , (NH ₄ ) Ce (SO ₄ ) ₂ , (NH ₄ ) ₄ Ce (SO ₄ ) ₄ , Ta ₂ (SO ₄ ) ₅ , TiO (SO ₄ ), Ti ₂ (SO ₄ ) ₃ , Ti (SO ₄ ) ₂ , (NH ₄ ) Ti ₃ (SO ₄ ) ₅ , CsTi (SO ₄ ) ₂ , FeSO ₄ , Fe _{2 (SO 4) 3, FeSO} 4 · Fe 2 (SO 4) 3, Cs 2 Fe (SO 4) 2, CsFe (S _{4) 2, (NH 4)} 2 Fe (SO 4) 2, Fe (NH 4) (SO 4) 2, Fe (NH 4) 3 (SO 4) 3, Fe (NH 3 OH) (SO 4) 2 , Cu ₂ SO ₄ , CuSO ₄ , Cu (NH ₄ ) ₂ (SO ₄ ) ₂ , Cs ₂ Cu (SO ₄ ) ₂ , Th (SO ₄ ) ₂ , Na ₂ SO ₄ , AlNa (SO ₄ ) ₂ , K ₃ Na (SO ₄ ) ₂ , CaNa ₂ (SO ₄ ) ₂ , Na ₃ Sc (SO ₄ ) ₃ , NaCe (SO ₄ ) ₂ , CuNa ₂ (SO ₄ ) ₂ , Na ₂ Ni (SO ₄ ) ₂ , MgNa ₂ (SO ₄ ) ₂ , MnNa ₂ (SO ₄ ) ₂ , PbSO ₄ , Pb (SO ₄ ) ₂ , Nb ₆ O ₃ (SO ₄ ) ₈ , Nb ₂ O (SO ₄ ) ₄ , NiSO ₄ , Cs ₂ Ni (SO ₄ ) ₂ , (NH ₄ ) ₂ Ni (SO ₄ ) ₂ , Pt (SO ₄ ) ₂ , VSO ₄ , V ₂ (SO ₄ ) ₃ , V (SO ₄ ) ₂ , K ₂ V (SO ₄ ) ₂ , KV (SO ₄ ) ₂ , CsV (SO ₄ ) ₂ , Rb ₂ V (SO ₄ ) ₂ , RbV (SO ₄ ) ₂ , VO (SO ₄ ), (NH ₄ ) ₂ V (SO ₄ ) ₂ , (NH ₄ ) V (SO ₄ ) ₂ , Hf (SO ₄ ) ₂ , PdSO ₄ , BaSO ₄ , Bi ₂ (SO ₄ ) ₃ , (N ₂ H ₅ ) HSO ₄ , (N ₂ H ₅ ) ₂ SO ₄ , Al (N ₂ H ₅ ) (SO ₄ ) ₂ , Cr (N ₂ H ₅ ) (SO ₄ ) ₂ , (NH ₃ OH) ₂ SO ₄ , Al (NH ₃ OH) (SO ₄ ) ₂ , Ga (NH ₃ OH) (SO ₄ ) ₂ , Cr (NH ₃ OH) (SO ₄ ) ₂ , (NH ₄ ) Pr (SO ₄ ) ₂ , K ₃ Pr (SO ₄ ) ₃ , BeSO ₄ , MgSO ₄ , Mg (NH ₄ ) ₂ (SO ₄ ) ₂ , Cs ₂ Mg (SO ₄ ) ₂ , MnSO ₄ , Mn ₂ (SO ₄ ) ₃ , Mn (SO ₄ ) ₂ , Cs ₂ Mn (SO ₄ ) ₂ , CsMn ( SO _{4) 2 Mn (NH 4) 2 (SO} 4) 2, Mn (NH 4) (SO 4) 2, CsMo (SO 4) 2, EuSO 4, Eu 2 (SO 4) 3, La 2 (SO 4) 3, Li ₂ SO ₄ , Ru (SO ₄ ) ₂ , Rb ₂ SO ₄ , AlRb (SO ₄ ) ₂ , IrRb (SO ₄ ) ₂ , GaRb (SO ₄ ) ₂ , CrRb ₂ (SO ₄ ) ₂ , CrRb (SO ₄ ) ₂ , CoRb ₂ (SO ₄ ) ₂ , FeRb ₂ (SO ₄ ) ₂ , FeRb (SO ₄ ) ₂ , MgRb ₂ (SO ₄ ) ₂ , MnRb ₂ (SO ₄ ) ₂ , MnRb (SO ₄ ) ₂ , Rh ₂ (SO ₄ ) ₃ , KRh (SO ₄ ) ₂ , CsRh (SO ₄ ) ₂ , and hydrates thereof. Among organic salts, tetrabutylammonium hydrogen sulfate, trifluoromethanesulfonic acid, 1-naphthylamine-2-sulfonic acid, 1-naphthylamine-5-sulfonic acid, 1-naphthol-3,6-disulfonic acid, p-bromobenzenesulfonic acid , P-anilinesulfonic acid, o-xylene-4-sulfonic acid, dimethylsulfone, o-sulfobenzoic acid, 5-sulfosalicylic acid and the like. These sulfate compounds may be used individually by 1 type, and may use 2 or more types together.

Among these, as the sulfate compound, a compound containing no carbon atom is preferable from the viewpoint of reducing the concentration of carbon contained after the firing treatment as much as possible, and an environmentally destructive substance such as NH ₃ or NO _x during the firing process. The compound which does not contain a nitrogen atom at the point which does not generate | occur | produce is preferable. Specifically, ZnSO ₄ , Al ₂ (SO ₄ ) ₃ , Sb ₂ (SO ₄ ) ₃ , Y ₂ (SO ₄ ) ₃ , CaSO ₄ , Zr (SO ₄ ) ₂ , SnSO ₄ , Sn (SO ₄ ) ₂ , SrSO ₄ , Ce ₂ (SO ₄ ) ₃ , Ce (SO ₄ ) ₂ , TiO (SO ₄ ), Ti ₂ (SO ₄ ) ₃ , Ti (SO ₄ ) ₂ , FeSO ₄ , Fe ₂ (SO ₄ ) ₃ , FeSO ₄ · Fe ₂ (SO ₄ ) ₃ , Cu ₂ SO ₄ , CuSO ₄ , BaSO ₄ , Bi ₂ (SO ₄ ) ₃ , MgSO ₄ , EuSO ₄ , Eu ₂ (SO ₄ ) ₃ , La ₂ (SO ₄ ) ₃ , Li ₂ SO ₄ and their hydrates are preferred.

  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.

  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 raw material mixing stage, it is preferable that the raw material is pulverized in parallel.

  As the degree of pulverization, the particle diameter of the raw material particles after pulverization is an index, but the average particle diameter (median diameter) is usually 0.3 μm or less, preferably 0.25 μm or less, more preferably 0.2 μm or less, most preferably Preferably it is 0.15 μm or less. If the average particle size of the raw material particles after pulverization is too large, the reactivity in the firing step is lowered, and it is difficult to make the composition uniform. However, making particles smaller than necessary leads to an increase in the cost of pulverization, 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. A means for realizing such a degree of pulverization is not particularly limited, but a wet pulverization method is preferable. Specific examples include dyno mill. In addition, the average particle diameter (median diameter) of the pulverized particles in the slurry can be measured by, for example, the method described in the column of Examples described later.

  After the wet mixing, it is then usually subjected to a drying process. The method is not particularly limited, but spray drying is preferable from the viewpoints of uniformity of the generated particulate matter, powder fluidity, powder handling performance, and efficient formation of spherical secondary particles.

  In the method for producing lithium nickel manganese composite oxide powder of the present invention, primary particles are aggregated and solid secondary by pulverizing to an average particle size of 0.3 μm or less by wet pulverization and then spray drying. A powder obtained by forming particles is obtained. A powder formed by agglomerating primary particles to form solid secondary particles is a feature of the product of the present invention. Such shape characteristics are reflected in the lithium nickel manganese composite oxide powder basically obtained by mixing and firing with the Li raw material, though there is a change in the particle size. Examples of the shape confirmation method include SEM observation and cross-sectional SEM observation.

  The average particle diameter (median diameter) of the particulate matter obtained by spray drying is usually 50 μm or less, more preferably 40 μm or less, and most preferably 30 μm or less. However, since it tends to be difficult to obtain a particle size that is too small, it is usually 3 μm or less, preferably 5 μm or more, and more preferably 6 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. In addition, the average particle diameter (median diameter) of the particulate matter after spray drying can be measured by, for example, the method described in the column of Examples described later.

In addition, when the particulate matter obtained by spray drying has a low specific surface area, the reactivity with the lithium compound is reduced in producing a lithium nickel manganese composite oxide by a firing reaction with a lithium compound in the next step. Therefore, as described above, it is preferable that the specific surface area be as high as possible by means such as pulverizing the starting material before spray drying. On the other hand, an excessively high specific surface area is industrially disadvantageous. Accordingly, the spray-dried particles obtained thereby have a BET specific surface area of usually 20 m ² / g or more, preferably 30 m ² / g or more, more preferably 40 m ² / g or more, still more preferably 50 m ² / g or more, Most preferably, it is 60 m ² / g or more, usually 200 m ² / g or less, preferably 150 m ² / g or less.

Examples of the lithium compound to be mixed with the granulated particles obtained by spray drying include 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. Among these lithium compounds, preferred are lithium compounds that do not contain nitrogen atoms or sulfur atoms in that no harmful substances such as NO _x are generated during the firing treatment. From the viewpoint of reducing as much as possible, it is a compound containing no carbon atom, and taking these points into consideration, LiOH and LiOH.H ₂ O are particularly preferable. These lithium compounds may be used individually by 1 type, and may use 2 or more types together.

  The particle diameter of such a lithium compound is usually an average particle diameter (median diameter) in order to improve the mixing performance with a mixture containing a nickel raw material, a manganese raw material, and a cobalt raw material, and to improve battery performance. It is 500 μm or less, preferably 100 μm or less, more preferably 50 μm or less, still more preferably 20 μm or less, and most preferably 10 μm or less. On the other hand, those having a too small particle size have a mean particle size 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 the stability in the air is low. .5 μm or more. In addition, the average particle diameter (median diameter) of the raw material lithium compound particles can be measured, for example, by the method described in the column of Examples described later.

  When specific production conditions are fixed, the Li / (Ni + Mn + Co) molar ratio can be adjusted by adjusting the amount of the lithium compound to the transition metal when the lithium compound is mixed with the granulated particles obtained by spray drying. Can be controlled.

  It is important to sufficiently mix the powder obtained by spray drying and the lithium compound. The mixing method is not particularly limited as long as it can be sufficiently mixed, but it is preferable to use a powder mixing apparatus generally used for industrial purposes. The atmosphere in the system to be mixed is preferably an inert gas atmosphere such as air from which carbon dioxide gas has been removed, nitrogen gas, argon gas, etc. 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 and the lithium compound raw material to be used. However, if the firing temperature is too high, primary particles tend to grow too much. Conversely, if the firing temperature is too low, the bulk density is small. The specific surface area tends to be too large. The firing temperature is usually 800 ° C. or higher, preferably 900 ° C. or higher, more preferably 950 ° C. or higher, and usually 1100 ° C. or lower, preferably 1075 ° C. or lower, more preferably 1050 ° 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. The firing process is usually divided into three parts: temperature increase, maximum temperature retention, and temperature decrease. The second maximum temperature holding portion is not necessarily limited to one time, and may include two or more stages 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.

  As the temperature raising step, the temperature in the furnace is usually raised at a temperature raising rate of 1 ° C./min or more and 10 ° C./min or less. Even if this rate of temperature rise 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.

  Although the holding time in the maximum temperature holding step varies depending on the temperature, it is usually 30 minutes or longer, preferably 5 hours or longer, more preferably 10 hours or longer, 50 hours or shorter, preferably 25 hours within the aforementioned temperature range. Hereinafter, it is more preferably 20 hours or less. If the firing time is too short, it becomes difficult to obtain a lithium nickel manganese cobalt composite oxide powder having good crystallinity, and it is not practical to be too long. If the firing time is too long, it will be disadvantageous because it will be necessary to crush afterwards or it will be difficult to crush.

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

  As an atmosphere during firing, an oxygen-containing gas atmosphere such as air can be used. The oxygen concentration is usually 1% by volume or more, preferably 10% by volume or more, and usually 100% by volume or less, preferably 50% by volume or less.

  According to the lithium nickel manganese composite oxide powder thus obtained (lithium nickel manganese composite oxide powder of the present invention), there is little swelling due to gas generation, high capacity, excellent rate characteristics, A positive electrode material for a lithium secondary battery having excellent low temperature output characteristics and storage characteristics and a well-balanced performance is realized.

[III. (Positive electrode for lithium secondary battery)
The positive electrode for a lithium secondary battery of the present invention is obtained by forming a positive electrode active material layer containing the lithium nickel manganese composite oxide powder of the present invention and a binder on a current collector.

  The positive electrode active material layer is usually formed by mixing a positive electrode material, a binder, and a conductive material and a thickener, which are used if necessary, in a dry form into a sheet shape, and then pressing the positive electrode current collector on the positive electrode current collector. Alternatively, these materials are dissolved or dispersed in a liquid medium to form a slurry, which is applied to the 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, the thickness is arbitrary, but 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. The following ranges are preferred. 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 40% by weight or less, and most preferably 10% by weight or less. If the proportion of the binder is too low, the positive electrode active material cannot be sufficiently retained, and the mechanical strength of the positive electrode may be insufficient, and the battery performance such as cycle characteristics may be deteriorated. There is a possibility that it may lead to a decrease in capacity and conductivity.

  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 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 a slurry, it is possible to dissolve or disperse lithium nickel-based composite oxide powder as a positive electrode material, a binder, and a conductive material and a thickener used as necessary. The solvent is not particularly limited as long as it is a suitable solvent, and either an aqueous solvent or an organic solvent may be used. 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 ratio of the lithium nickel manganese 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, Moreover, it is 99.9 weight% or less normally, Preferably it is 99 weight% or less. If the ratio of the lithium nickel manganese composite oxide powder of the present invention in the positive electrode active material layer is too large, the strength of the positive electrode tends to be insufficient, and conversely if too small, the capacity may be insufficient. .

  The thickness of the positive electrode active material layer is usually about 10 to 200 μm.

  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.

[IV. Lithium secondary battery of the present invention]
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 a material of the negative electrode current collector, a metal material such as copper, nickel, stainless steel, nickel-plated steel, or a carbon material such as carbon cloth or carbon paper is used. Among these, in the case of a metal material, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, etc., and in the case of a carbon material, 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 can electrochemically occlude and release lithium ions, but it can usually occlude and release lithium from the viewpoint of high safety. A carbon 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 graphite material determined 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, more preferably 40 μm or less, especially 40 μm or less. It is preferable that it is 30 micrometers 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, 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, in the case of performing the Raman spectrum analysis using an argon laser beam on the graphite material, the intensity I _A of the peak P _A is detected in the range of 1580～1620Cm ^-1, it 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 width of the peak P _A is preferably 26cm ^-1 or less, 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 that form the slurry, the same materials as those described above for the positive electrode active material layer can be used.

  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. Each of these may be used alone, or two or more kinds may be mixed and used in an arbitrary combination and ratio.

  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 , LiBOB, 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. In addition, any ratio of 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, SO ₂ , and polysulfide S _x ²⁻ You can add it.

  The lithium salt of the electrolytic salt is usually contained in the electrolytic solution so as to be 0.5 mol / L or more and 1.5 mol / L or less. Even if it 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 + x} J _x Ti _2-x (PO ₄ ) ₃ (wherein J is any one of Al, Sc, Y, and La). Li _0.5-3x RE _{0.5 + x} TiO ₃ (wherein RE represents any element of La, Pr, Nd, and Sm), etc. Represents a number satisfying 0 ≦ x ≦ 2.) 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 or more, more preferably 1,000,000 or more, most preferably 1,500,000 or more. It is. On the other hand, the upper limit of the molecular weight is preferably 5 million or less, more preferably 4 million or less, and most preferably 3 million or less. 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.

  The lithium secondary battery of the present invention is produced by assembling the above-described positive electrode for a lithium secondary battery of the present invention, a negative electrode, an electrolyte, and a separator used as necessary into an appropriate shape. 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.

  EXAMPLES Next, although an Example demonstrates this invention still in detail, this invention is not limited at all by these Examples, unless the summary is exceeded.

[Method for measuring physical properties]
The physical properties and the like of lithium nickel manganese composite oxide powders produced in each of Examples and Comparative Examples described later were measured as follows.

Crystal phase: Determined by powder X-ray diffraction pattern.
Specific surface area: determined by the BET method.
Average primary particle size: It was determined from an SEM image of 30000 times.
Median diameter of secondary particles: measured after 5 minutes of ultrasonic dispersion.
Bulk density: 10 to 11 g of the sample powder was placed in a 10 ml glass graduated cylinder, and was determined as the powder packing density when tapped 200 times with a stroke of about 20 mm.

Contained carbon concentration C: An EMIA-520 carbon sulfur analyzer manufactured by Horiba, Ltd. was used. A sample of several tens to 100 mg was weighed into an air-baked porcelain crucible, a combustion aid was added, and C was burned and extracted in a high-frequency heating furnace in an oxygen stream. CO ₂ in the combustion gas was quantified by non-dispersive infrared absorptiometry. For sensitivity calibration, 150-15 low alloy steel No. 1 (C guaranteed value: 0.469% by weight) manufactured by Japan Iron and Steel Federation was used.

Contained sulfur concentration S: An EMIA-520 carbon sulfur analyzer manufactured by Horiba, Ltd. was used. A sample of several tens to 100 mg was weighed into an air-baked porcelain crucible, a combustion aid was added, and S was burned and extracted in a high-frequency heating furnace in an oxygen stream. SO ₂ in the combustion gas was quantified by non-dispersive infrared absorptiometry. For sensitivity calibration, 150-15 low alloy steel No. 1 (S guaranteed value: 0.0295% by weight) manufactured by Japan Iron and Steel Federation was used.

Volume resistivity: Powder resistivity measuring device (Dia Instruments Co., Ltd .: Lorester GP powder low efficiency measurement system PD-41), sample weight of 3 g, powder probe unit (four probe / ring electrode, electrode) The volume resistivity [Ω · cm] of the powder under various pressures was measured at an applied voltage limiter of 90 V with an interval of 5.0 mm, an electrode radius of 1.0 mm, and a sample radius of 12.5 mm. The volume resistivity values were compared.

pH: Weigh 50 g of demineralized water into a beaker and add 5 g of sample while stirring. While monitoring the liquid temperature and the pH value, the pH value and the liquid temperature after 10 minutes from the introduction were measured.

The median diameter of the pulverized particles in the slurry was measured with a known laser diffraction / scattering particle size distribution measuring apparatus with a refractive index of 1.24 and a particle diameter standard as a volume standard. In addition, a 0.1 wt% aqueous sodium hexametaphosphate solution was used as a dispersion medium, and measurement was performed after ultrasonic dispersion for 5 minutes.

Median diameter as average particle diameter of raw material LiOH powder: Using a known laser diffraction / scattering particle size distribution measuring apparatus, the refractive index was set to 1.14, and the particle diameter standard was measured as a volume standard. Further, ethyl alcohol was used as a dispersion medium to make a saturated solution of lithium hydroxide, and measurement was performed after ultrasonic dispersion for 5 minutes.

Physical properties of the particulate powder obtained by spray drying: The morphology was confirmed by SEM observation and cross-sectional SEM observation. The median diameter and 90% cumulative diameter (D ₉₀ ) as the average particle diameter were measured with a known laser diffraction / scattering particle size distribution measuring device with a refractive index of 1.24 and a particle diameter standard as a volume standard. . In addition, a 0.1 wt% aqueous sodium hexametaphosphate solution was used as a dispersion medium, and measurement was performed after ultrasonic dispersion for 5 minutes. The specific surface area was measured by the BET method using the specific surface area standard as the volume standard.

[Production of Lithium Nickel Manganese Complex Oxide Powder (Examples and Comparative Examples)]
Example 1
Ni (OH) ₂ , Mn ₃ O ₄ , Co (OH) ₂ , and Al ₂ (SO ₄ ) ₃ · 14 to 18H ₂ O are mixed with Ni: Mn: Co: SO ₄ = 1/3: 1/3: After weighing and mixing to a molar ratio of 1/3: 0.005, pure water was added to prepare a slurry. While stirring the slurry, the solid content in the slurry was pulverized to a median diameter of 0.14 μm using a circulating medium agitation type wet pulverizer.

Particulate powder obtained by spray-drying the slurry with a spray dryer (powder formed by agglomeration of primary particles to form solid secondary particles. Average particle size: 12.6 μm, BET specific surface area: 43 m ² / G), LiOH powder pulverized to a median diameter of 20 μm or less was added at a Li / (Ni + Mn / Co) molar ratio of 1.10. About 52 g of this pre-mixed powder was placed in a 500 ml wide-mouthed plastic bottle, sealed, and shaken and mixed for 20 minutes at a stroke of about 20 cm and about 160 times per minute. This pre-firing mixture was charged into an alumina crucible and calcined at 975 ° C. for 12 hours under air flow (temperature increase / decrease rate of 5 ° C./min.) And then crushed to have a composition of Li _1.06 Ni _0.325 Mn _0.333 Co _0.342 O. A lithium nickel manganese cobalt composite oxide having a layered structure of ₂ was obtained. The average primary particle diameter is 1.0 μm, the median diameter of the secondary particles is 11.3 μm, the 90% cumulative diameter (D ₉₀ ) is 16.9 μm, the bulk density is 2.0 g / cm ³ , and the BET specific surface area is 0.00. 51 m ² / g, the contained sulfur concentration was 0.184 wt%, the contained carbon concentration was 0.010 wt%, and the volume resistivity was 6.0 × 10 ⁴ Ω · cm. The pH value (liquid temperature) was 10.80 (23.9 ° C.).

(Example 2)
Ni (OH) ₂ , Mn ₃ O ₄ , Co (OH) ₂ , and Al ₂ (SO ₄ ) ₃ · 14 to 18H ₂ O are mixed with Ni: Mn: Co: SO ₄ = 1/3: 1/3: After weighing and mixing to a molar ratio of 1/3: 0.01, pure water was added thereto to prepare a slurry. While stirring the slurry, the solid content in the slurry was pulverized to a median diameter of 0.14 μm using a circulating medium agitation type wet pulverizer.

Particulate powder obtained by spray-drying the slurry with a spray dryer (powder formed by agglomeration of primary particles to form solid secondary particles. Average particle size: 11.8 μm, BET specific surface area: 38 m ² / G), LiOH powder pulverized to a median diameter of 20 μm or less was added at a Li / (Ni + Mn / Co) molar ratio of 1.10. About 52 g of this pre-mixed powder was placed in a 500 ml wide-mouthed plastic bottle, sealed, and shaken and mixed for 20 minutes at a stroke of about 20 cm and about 160 times per minute. This pre-firing mixture was charged into an alumina crucible, fired at 975 ° C. for 12 hours under air flow (temperature raising / lowering rate 5 ° C./min.), And then crushed to have a composition of Li _1.09 Ni _0.328 Mn _0.332 Co _0.340 O. A lithium nickel manganese cobalt composite oxide having a layered structure of ₂ was obtained. The average primary particle diameter is 1.3 μm, the median diameter of the secondary particles is 11.6 μm, the 90% cumulative diameter (D ₉₀ ) is 17.2 μm, the bulk density is 2.0 g / cm ³ , and the BET specific surface area is 0.00. It was 39 m ² / g, the contained sulfur concentration was 0.325 wt%, the contained carbon concentration was 0.008 wt%, and the volume resistivity was 4.6 × 10 ⁴ Ω · cm. The pH value (liquid temperature) was 10.81 (24.2 ° C.).

(Example 3)
Ni (OH) ₂ , Mn ₃ O ₄ , Co (OH) ₂ , and Li ₂ SO ₄ .H ₂ O are mixed with Ni: Mn: Co: SO ₄ = 1/3: 1/3: 1/3: 0. After weighing and mixing so that the molar ratio was 0.005, pure water was added thereto to prepare a slurry. While stirring the slurry, the solid content in the slurry was pulverized to a median diameter of 0.15 μm using a circulating medium agitation type wet pulverizer.

Particulate powder obtained by spray-drying the slurry with a spray dryer (powder formed by aggregation of primary particles to form solid secondary particles. Average particle size: 12.1 μm, BET specific surface area: 44 m ² / G), LiOH powder pulverized to a median diameter of 20 μm or less was added at a Li / (Ni + Mn / Co) molar ratio of 1.10. About 52 g of this pre-mixed powder was placed in a 500 ml wide-mouthed plastic bottle, sealed, and shaken and mixed for 20 minutes at a stroke of about 20 cm and about 160 times per minute. This pre-firing mixture was charged into an alumina crucible and calcined at 975 ° C. for 12 hours under air flow (temperature increase / _decrease rate of 5 ° C./min.) And then crushed to have a composition of Li _1.06 Ni _0.329 Mn _0.325 Co _0.346 O. A lithium nickel manganese cobalt composite oxide having a layered structure of ₂ was obtained. The average primary particle diameter is 0.9 μm, the median diameter of the secondary particles is 11.1 μm, the 90% cumulative diameter (D ₉₀ ) is 16.7 μm, the bulk density is 2.0 g / cm ³ , and the BET specific surface area is 0.00. 57 m ² / g, the contained sulfur concentration was 0.188 wt%, the contained carbon concentration was 0.012 wt%, and the volume resistivity was 3.6 × 10 ⁴ Ω · cm. The pH value (liquid temperature) was 10.83 (24.7 ° C.).

(Comparative 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 was prepared. While stirring the slurry, the solid content in the slurry was pulverized to a median diameter of 0.15 μm using a circulating medium agitation type wet pulverizer.

Particulate powder obtained by spray-drying the slurry with a spray dryer (powder formed by agglomeration of primary particles to form solid secondary particles. Average particle size: 11.7 μm, BET specific surface area: 46 m ² / G), LiOH powder pulverized to a median diameter of 20 μm or less was added at a Li / (Ni + Mn / Co) molar ratio of 1.05. About 256 g of the powder before mixing was placed in a 500 ml wide-mouthed plastic bottle, sealed, and shaken and mixed for 20 minutes at a stroke of about 20 cm and about 160 times per minute. This pre-firing mixture was placed in an alumina crucible, fired at 950 ° C. for 12 hours under air flow (heating / cooling rate 5 ° C./min.), Crushed, and fired again at 950 ° C. for 12 hours (heating / cooling rate 5). C./min.) To obtain a lithium nickel manganese cobalt composite oxide having a layered structure with a composition of Li _1.00 Ni _0.326 Mn _0.329 Co _0.345 O ₂ . The average primary particle diameter is 0.7 μm, the median diameter of the secondary particles is 11.8 μm, the 90% cumulative diameter (D ₉₀ ) is 19.8 μm, the bulk density is 2.3 g / cm ³ , and the BET specific surface area is 0.3. 58 m ² / g, the contained sulfur concentration was 0.024 wt%, and the contained carbon concentration was 0.009 wt%. The volume resistivity was 2.8 × 10 ⁶ Ω · cm. The pH value (liquid temperature) was 10.93 (25.0 ° C.).

(Comparative 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 = 1: 1: 1, and then pure water was added thereto. A slurry was prepared. While the slurry was stirred, the solid content in the slurry was pulverized to a median diameter of 0.21 μm using a circulating medium stirring wet pulverizer.

Particulate powder obtained by spray-drying the slurry with a spray dryer (powder formed by agglomeration of primary particles to form solid secondary particles. Average particle size: 11.8 μm, BET specific surface area: 68 m ² / G), LiOH powder ground to a median diameter of 20 μm or less was added in a Li / (Ni + Mn / Co) molar ratio at a ratio of 1.08. About 3 kg of this pre-mixed powder was used in a high-speed mixer, and the rotational speed of the agitator was 300 rpm / min. The chopper was rotated at 3000 rpm / min and mixed for 1 hour. This pre-firing mixture was charged into an alumina square bowl, fired at 975 ° C. for 12 hours under air flow (temperature raising / lowering rate 5 ° C./min.), Pulverized, and the composition was Li _1.04 Ni _0.337 Mn _0.332 Co _0.331. A lithium nickel manganese cobalt composite oxide having a layered structure of O ₂ was obtained. The average primary particle diameter is 0.9 μm, the median diameter of the secondary particles is 10.3 μm, the 90% cumulative diameter (D ₉₀ ) is 16.7 μm, the bulk density is 2.2 g / cm ³ , and the BET specific surface area is 0.00. 66 m ² / g, the contained sulfur concentration was 0.040 wt%, and the contained carbon concentration was 0.009 wt%. The volume resistivity was 5.5 × 10 ⁴ Ω · cm. The pH value (liquid temperature) was 11.01 (25.0 ° C.).

(Comparative Example 3)
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 was prepared. While the slurry was stirred, the solid content in the slurry was pulverized to a median diameter of 0.21 μm using a circulating medium stirring wet pulverizer.

Particulate powder obtained by spray-drying the slurry with a spray dryer (powder formed by agglomeration of primary particles to form solid secondary particles. Average particle size: 11.8 μm, BET specific surface area: 68 m ² / G), LiOH powder ground to a median diameter of 20 μm or less was added at a Li / (Ni + Mn / Co) molar ratio of 1.12. About 3 kg of this pre-mixed powder was used in a high-speed mixer, and the rotational speed of the agitator was 300 rpm / min. The chopper was rotated at 3000 rpm / min and mixed for 1 hour. This pre-fired mixture was charged into an alumina square bowl, fired at 975 ° C. for 12 hours under air flow (temperature raising / lowering rate 5 ° C./min.), Pulverized, and the composition was Li _1.08 Ni _0.337 Mn _0.332 Co _0.331. A lithium nickel manganese cobalt composite oxide having a layered structure of O ₂ was obtained. The average primary particle diameter is 0.9 μm, the median diameter of the secondary particles is 10.3 μm, the 90% cumulative diameter (D ₉₀ ) is 16.6 μm, the bulk density is 2.1 g / cm ³ , and the BET specific surface area is 0.00. It was 64 m ² / g, the contained sulfur concentration was 0.036 wt%, the contained carbon concentration was 0.015 wt%, and the volume resistivity was 1.2 × 10 ⁴ Ω · cm. The pH value (liquid temperature) was 11.24 (24.9 ° C.).

(Comparative Example 4)
Ni (OH) ₂ , Mn ₃ O ₄ , Co (OH) ₂ , and Al ₂ (SO ₄ ) ₃ · 14 to 18H ₂ O are mixed with Ni: Mn: Co: SO ₄ = 1/3: 1/3: After weighing and mixing to a molar ratio of 1/3: 0.005, pure water was added to prepare a slurry. While stirring the slurry, the solid content in the slurry was pulverized to a median diameter of 0.14 μm using a circulating medium agitation type wet pulverizer.

Particulate powder obtained by spray-drying the slurry with a spray dryer (powder formed by agglomeration of primary particles to form solid secondary particles. Average particle size: 12.6 μm, BET specific surface area: 43 m ² / G), LiOH powder pulverized to a median diameter of 20 μm or less was added at a Li / (Ni + Mn / Co) molar ratio of 1.05. About 51 g of this pre-mixed powder was placed in a 500 ml wide-mouthed plastic bottle, sealed, and shaken and mixed for 20 minutes at a stroke of about 20 cm and about 160 times per minute. This pre-firing mixture was charged into an alumina crucible, fired at 950 ° C. for 10 hours under air flow (temperature raising / lowering rate 5 ° C./min.), Crushed, and the composition was Li _1.01 Ni _0.325 Mn _0.333 Co _0.342 O. A lithium nickel manganese cobalt composite oxide having a layered structure of ₂ was obtained. The average primary particle diameter is 0.5 μm, the median diameter of the secondary particles is 10.3 μm, the 90% cumulative diameter (D ₉₀ ) is 15.8 μm, the bulk density is 2.1 g / cm ³ , and the BET specific surface area is 0.00. 83 m ² / g, contained sulfur concentration was 0.220 wt%, contained carbon concentration was 0.011 wt%, and volume resistivity was not measurable because the resistance value exceeded the measuring range. The pH value (liquid temperature) was 10.29 (24.5 ° C.).

(Comparative Example 5)
Ni (OH) ₂ , Mn ₃ O ₄ , Co (OH) ₂ , and Li ₂ SO ₄ .H ₂ O are mixed with Ni: Mn: Co: SO ₄ = 1/3: 1/3: 1/3: 0. After weighing and mixing so that the molar ratio was 0.005, pure water was added thereto to prepare a slurry. While stirring the slurry, the solid content in the slurry was pulverized to a median diameter of 0.15 μm using a circulating medium agitation type wet pulverizer.

Particulate powder obtained by spray-drying the slurry with a spray dryer (powder formed by aggregation of primary particles to form solid secondary particles. Average particle size: 12.1 μm, BET specific surface area: 44 m ² / G), LiOH powder pulverized to a median diameter of 20 μm or less was added at a Li / (Ni + Mn / Co) molar ratio of 1.05. About 51 g of this pre-mixed powder was placed in a 500 ml wide-mouthed plastic bottle, sealed, and shaken and mixed for 20 minutes at a stroke of about 20 cm and about 160 times per minute. This pre-firing mixture was charged into an alumina crucible, fired at 950 ° C. for 10 hours under air flow (temperature raising / lowering rate 5 ° C./min.), And then crushed to have a composition of Li _1.01 Ni _0.329 Mn _0.325 Co _0.346 O. A lithium nickel manganese cobalt composite oxide having a layered structure of ₂ was obtained. The average primary particle diameter is 0.6 μm, the median diameter of the secondary particles is 10.5 μm, the 90% cumulative diameter (D ₉₀ ) is 16.4 μm, the bulk density is 2.1 g / cm ³ , and the BET specific surface area is 0.00. It was 94 m ² / g, the contained sulfur concentration was 0.218 wt%, the contained carbon concentration was 0.017 wt%, and the volume resistivity was 4.6 × 10 ⁶ Ω · cm. The pH value (liquid temperature) was 10.33 (24.4 ° C.).

[Production and evaluation of batteries]
Using the lithium nickel manganese composite oxide powders produced in Examples 1 to 3 and Comparative Examples 1 to 5 described above as positive electrode materials (positive electrode active materials), a lithium secondary battery was produced by the following method, Evaluation was performed.

(1) Initial charge / discharge capacity:
In a mortar, weighed 75% by weight of lithium nickel manganese composite oxide powders prepared in Examples 1 to 3 and Comparative Examples 1 to 5, 20% by weight of acetylene black, and 5% by weight of polytetrafluoroethylene powder. Thoroughly mixed and made into 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.

Using a 9 mmφ positive electrode as a test electrode and a lithium metal plate as a counter electrode, 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 with a constant current of 0.2 mA / cm ² , a charge upper limit voltage of 4.3 V, and a discharge lower limit voltage of 3.0 V. 10th cycle, constant current charging 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 tests were carried out 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 10 th cycle high-rate discharge capacity at 11 mA / cm ² a (mAh / g) was measured (these Hereinafter, these are simply referred to as “initial charge / discharge capacity” and “high-rate discharge capacity”).

(2) Low temperature load characteristic test:
In a mortar, weighed 75% by weight of lithium nickel manganese composite oxide powders prepared in Examples 1 to 3 and Comparative Examples 1 to 5, 20% by weight of acetylene black, and 5% by weight of polytetrafluoroethylene powder. Thoroughly mixed and made into a thin sheet was punched out using 9 mmφ and 12 mmφ punches. At this time, the total weight was adjusted to be about 8 mmg and about 18 mg, respectively. This was pressure-bonded to an aluminum expanded metal to obtain positive electrodes of 9 mmφ and 12 mmφ.

Using a 9 mmφ positive electrode as a test electrode and a lithium metal plate as a counter electrode, 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.

The obtained coin-type cell was subjected to a constant current / constant voltage charge 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 performing a constant current discharge of 0.2 mA / cm ² , that is, a reaction for occluding lithium ions in the positive electrode at a lower limit of 3.0 V is Qs (C) [mAh / g], and the initial discharge capacity was Qs (D) [mAh / g].

Graphite powder (d ₀₀₂ = 3.35 Å) having an average particle diameter of 8 to 10 μm 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. The 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 to form a negative electrode. At this time, the amount of the negative electrode active material on the electrode was adjusted to be about 5 to 12 mg.

A test in which a negative electrode is used as a test electrode, a battery cell is assembled using lithium metal as a counter electrode, and lithium ions are occluded in the negative electrode by a constant current-constant voltage method (cut current 0.05 mA) of 0.2 mA / cm ² -3 mV. Is the initial storage capacity per unit weight of the negative electrode active material when the lower limit is 0 V, and Qf [mAh / g].

The positive electrode and the negative electrode were combined, a test battery was assembled using a coin cell, and the battery performance was evaluated. That is, the above-described positive electrode prepared is placed on the positive electrode can of the coin cell, a porous polyethylene film having a thickness of 25 μm is placed thereon as a separator, pressed with a polypropylene gasket, and then EC ( Using an electrolytic solution in which LiPF ₆ was dissolved at a concentration of 1 mol / L in a solvent of ethylene carbonate): DMC (dimethyl carbonate): EMC (ethyl methyl carbonate) = 3: 3: 4 (volume ratio), this was added to the can. After fully infiltrating the separator, the above-described negative electrode was placed, the negative electrode can was placed and sealed, and coin-type lithium secondary batteries (the batteries of Examples 1 to 3 and Comparative Examples 1 to 4) were produced. 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]

In order to measure the low temperature load characteristics of the battery thus obtained, the 1 hour rate current value of the battery, that is, 1C, was set as shown in the following equation, and the following tests were performed.
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. The upper limit of charging was 4.1 V, and the lower limit voltage was 3.0 V. Next, when a coin cell adjusted to a charging depth of 40% is held in a low temperature atmosphere of −30 ° C. for 1 hour or longer by 1/3 C constant current charging / discharging and then discharged for 10 seconds at a constant current of 0.5 C [mA]. Assuming that the voltage after 10 seconds is V [mV] and the voltage before discharge is V ₀ [mV], the low-temperature resistance value R [Ω] is calculated from the following equation as ΔV = V−V ₀ .
R [Ω] = ΔV [mV] /0.5C [mA]

〔result〕
Various physical properties of the lithium nickel manganese composite oxide powders of Examples 1 to 3 and Comparative Examples 1 to 5 are shown in Tables 1 to 3 below. In addition, Table 3 below shows characteristics (initial charge / discharge capacity, high rate discharge capacity, low temperature resistance value) measured for lithium secondary batteries prepared using these as positive electrode materials (positive electrode active materials). Regarding the column of “judgment result” in Table 3, the pH of the positive electrode material is 11.00 or less, the initial charge / discharge capacity of the lithium secondary battery is 150 mAh / g or more, the high-rate discharge capacity is 115 mAh / g or more, and the low temperature resistance A criterion that the value is 450Ω or less is provided, and “◯” indicates that all of these criteria are satisfied, and “X” indicates that any one or more of the criteria is not satisfied.

  From the results shown in Tables 1 to 3, the following is clear.

  The lithium nickel manganese composite oxide powders of Comparative Examples 1, 4, and 5 have too little Li content and do not satisfy the provisions of the present invention. Moreover, it turns out that the lithium secondary battery produced using it does not satisfy | fill the above-mentioned reference | standard in the high-rate discharge capacity and low temperature resistance value, and battery characteristics are inadequate.

  The lithium nickel manganese composite oxide powders of Comparative Examples 2 and 3 have a too low sulfur concentration and do not satisfy the provisions of the present invention, and as a result, the pH does not satisfy the above-described criteria. Therefore, it is estimated that the lithium secondary battery obtained by using it has problems such as swelling due to gas generation and storage deterioration.

  On the other hand, the lithium nickel manganese based composite oxide powders of Examples 1 to 3 in which various physical properties such as the composition and the concentration of contained sulfur satisfy the provisions of the present invention have a pH that satisfies the above-mentioned criteria. Therefore, it is estimated that the lithium secondary battery obtained by using it has problems such as swelling due to gas generation and storage deterioration. In addition, the fabricated lithium secondary battery has an initial charge / discharge capacity, a high-rate discharge capacity, and a low-temperature resistance value that all meet the above-mentioned standards, so it has a high capacity and excellent load characteristics and low-temperature output characteristics. I understand that.

The use of the lithium secondary battery of 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.

Claims (10)

A lithium nickel manganese composite for a lithium secondary battery positive electrode material having a composition represented by the following formula (I) and a sulfur concentration of 0.06 wt% or more and 0.35 wt% or less Oxide powder.
_{Li 1 + z Ni x Mn y} Co 1-xy O 2 (I)
(In the formula (I), x, y and z are 0.20 ≦ x ≦ 0.55 and 0.20 ≦ y ≦, respectively.
It represents a number satisfying 0.60, 0.50 ≦ x + y ≦ 1, 0.02 ≦ z ≦ 0.55. ) In the formula (I), y / x representing the Mn / Ni atomic ratio is 0.95 ≦ y / x ≦ 1.5.
The lithium nickel manganese based composite oxide powder for a lithium secondary battery positive electrode material according to claim 1, wherein: 3. The lithium nickel manganese composite oxide powder for a lithium secondary battery positive electrode material according to claim 1, wherein the sulfur component is a sulfate compound. 4. The lithium nickel manganese based composite oxide powder for a lithium secondary battery positive electrode material according to any one of claims 1 to 3, wherein the carbon concentration is 0.012 wt% or less. The lithium nickel for a lithium secondary battery positive electrode material according to any one of claims 1 to 4, wherein the volume resistivity when consolidated at a pressure of 40 MPa is 5 x 10 ⁵ Ω · cm or less. Manganese complex oxide powder. The primary particles are aggregated to form secondary particles, the bulk density is 1.5 g / cm ³ or more, the average primary particle size is 0.1 μm to 3 μm, and the median diameter of the secondary particles The lithium nickel manganese based composite oxide powder for a lithium secondary battery positive electrode material according to claim 1, wherein is 3 μm or more and 20 μm or less. BET specific surface area of 0.2 m ² / g or more, and characterized in that 1.5 m ² / g or less, a lithium secondary battery positive electrode material for a lithium nickel manganese according to any one of claims 1 to 6 -Based composite oxide powder. A method for producing a lithium nickel manganese based composite oxide powder for a lithium secondary battery positive electrode material according to any one of claims 1 to 7,
A nickel compound, a manganese compound, a sulfate compound, and a cobalt compound used as necessary are pulverized in a liquid medium to an average particle size of 0.3 μm or less, and a uniformly dispersed slurry is spray-dried to obtain a primary The powder is formed by agglomerating particles to form secondary particles, the powder is thoroughly mixed with a lithium compound, and the mixture is fired in an oxygen-containing gas atmosphere. The manufacturing method of the lithium nickel manganese type complex oxide powder for secondary battery positive electrode materials. A current collector, and at least a positive electrode active material layer formed on the current collector,
The positive electrode active material layer contains at least the lithium nickel manganese composite oxide powder for a lithium secondary battery positive electrode material according to any one of claims 1 to 7 and a binder. A positive electrode for a lithium secondary battery. A lithium secondary battery comprising at least a positive electrode and a negative electrode capable of inserting and extracting lithium, and a non-aqueous electrolyte containing a lithium salt,
The lithium secondary battery, wherein the positive electrode is a positive electrode for a lithium secondary battery according to claim 9.