JP2009004310A - Cathode active material for lithium secondary battery, cathode for lithium secondary battery using the same, and lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cathode active material for a lithium secondary battery capable of improving its load characteristics and reducing its cost and performing high-voltage resistance and a high level of safety. <P>SOLUTION: The cathode active material for a lithium secondary battery is provide with a mixture of lithium contained transition metal compound powder A obtained by a manufacturing method including at least a slurry manufacturing process for obtaining uniformly dispersed slurry by crushing a lithium compound, one or more transition metal compounds including at least Mn, Ni, and Co, and an additive for restraining grain growth and sintering in the time of calcination in a liquid medium; a spray drying process for spraying and drying the obtained slurry; and a sintering process for sintering the obtained spray and drying powder: and lithium contained transition metal composite oxide powder B having a spinel structure (a space group Fd-3m (No. 227)) and including Li and at least Mn as transition metal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a positive electrode active material for a lithium secondary battery, a positive electrode for a lithium secondary battery using the positive electrode active material, and a lithium secondary battery including the positive electrode for a lithium secondary battery.

  Lithium secondary batteries are excellent in energy density and output density, and are effective in reducing the size and weight. Therefore, the demand for power supplies for portable devices such as notebook computers, mobile phones, and handy video cameras is growing rapidly. ing. Lithium secondary batteries are also attracting attention as power sources for electric vehicles and power load leveling, and in recent years, demand for power sources for hybrid electric vehicles is rapidly expanding. In particular, in electric vehicle applications, it is necessary to be excellent in low cost, safety, life (particularly under high temperature) and load characteristics, and improvements in materials are desired.

Among the materials constituting the lithium secondary battery, as the positive electrode active material, a substance having a function capable of desorbing and inserting lithium ions can be used. There are various types of these positive electrode active material materials, each having its own characteristics. In addition, a common problem for improving performance is to improve load characteristics, and improvements in materials are strongly desired.
Furthermore, there is a demand for a material with a good performance balance that is excellent in low cost, safety, and life (particularly under high temperatures).

  Currently, lithium manganese composite oxides having a spinel structure, layered lithium nickel composite oxides, layered lithium cobalt composite oxides, and the like have been put into practical use 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 inferior safety 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 with a layered structure have been proposed as promising candidates for active material materials that can overcome or reduce the shortcomings of these positive electrode active material materials and are excellent in battery performance balance. Has been. Particularly, in recent years, demands for lowering costs, higher voltages, and increasing safety demands are promising as positive electrode active material materials that can meet any of the demands.

  However, the degree of cost reduction, higher voltage, and safety will vary depending on the composition ratio. Therefore, for further cost reduction, use with a higher upper limit voltage, and higher safety requirements. Therefore, it is necessary to select and use one having a limited composition range such as a manganese / nickel atomic ratio of approximately 1 or more, or a reduction in the cobalt ratio. However, a lithium secondary battery using a lithium nickel manganese cobalt based composite oxide having such a composition range as a positive electrode material has reduced load characteristics such as rate and output characteristics. It was necessary.

  Therefore, in order to solve the problem of improving the load characteristics such as rate and output characteristics, the present inventor has made the fineness by suppressing the grain growth and sintering while making the active material sufficiently high in the stage of firing. As a result of diligent investigations, especially in layered lithium nickel manganese cobalt-based composite oxides, after adding a compound containing a specific element such as W, firing at a temperature above a certain level Found that lithium transition metal compound powder consisting of fine particles with suppressed grain growth and sintering can be obtained, and as a positive electrode material for lithium secondary batteries, low cost, high voltage resistance, high safety In addition, the load characteristics such as rate and output characteristics can be improved. However, further improvement is necessary to further increase the capacity while taking advantage of the above-mentioned characteristic merit.

  Conventionally, for the lithium-containing transition metal composite oxide powder A (lithium nickel manganese cobalt based composite oxide powder) according to the present invention, the production method indicated by the present invention and “grain growth and sintering during firing”. Although there is no document describing the addition treatment of “suppressing additive”, a compound containing W, Mo, Nb, Ta, Re in lithium nickel manganese cobalt based composite oxide for the purpose of improving the positive electrode active material The following patent documents 1 to 12 and non-patent documents 1 and 2 are disclosed as well-known documents in which addition processing or substitution processing is performed. However, any of these known documents includes a mixture of the lithium-containing transition metal composite oxide powder B (lithium manganese composite oxide powder having a spinel structure) of the present invention and a positive electrode active material for a lithium secondary battery. There is no description of using as a material.

In addition, regarding the layered lithium nickel manganese cobalt-based composite oxide that is the base of the lithium-containing transition metal composite oxide powder A shown in the present invention, for the purpose of improving battery performance, different lithium-containing transition metal composite oxides and The following patent documents 13 to 75 and non-patent documents 3 to 5 are disclosed as known documents describing the use of the mixture.
However, Patent Documents 13 to 46 and Non-Patent Documents 3 to 5 are all mixed with lithium-containing transition metal composite oxide powder B (lithium manganese composite oxide powder having a spinel structure) defined in the present invention. There is no description that the obtained material is used as a positive electrode active material for a lithium secondary battery.

On the other hand, in Patent Documents 47 to 68, a mixture of lithium-containing transition metal composite oxide powder B (lithium manganese composite oxide powder having a spinel structure) defined in the present invention is used as a positive electrode for a lithium secondary battery. Description of use as an active material is recognized.
However, in the lithium-containing transition metal composite oxide powder A (layered lithium nickel manganese cobalt composite oxide powder) used here, the production method indicated by the present invention and “grain growth during firing” In addition, there is no description of the addition treatment of “additive that suppresses sintering”, and addition treatment or substitution treatment of a compound containing W, Mo, Nb, Ta, Re or the like to the layered lithium nickel manganese cobalt based composite oxide There is no mention of what was done.

In Patent Documents 69 to 75, there is no description that the manufacturing method according to the present invention and “additive for suppressing grain growth and sintering during firing” were added, but layered lithium nickel manganese cobalt based composite oxidation There is a description that a compound containing W, Mo, Nb, Ta, Re, or the like is added to or treated in the product. However, these are different from the production methods defined by the present invention, and in terms of words, only one of the above elements is described, and no specific examples are recognized.
Japanese Patent No. 3088716 Japanese Patent No. 3362025 JP 2002-151071 A WO2002-041419 JP 2003-68298 A JP 2004-303673 A JP 2005-235628 A JP-A-2005-251716 JP 2006-164934 A JP 2006-202647 A JP 2006-202702 A JP 2007-18985 A Japanese Patent No. 3869605 Japanese Patent No. 3867030 Japanese Patent No. 3844733 Japanese Patent No. 3793054 Japanese Patent No. 3712251 Japanese Patent No. 3291400 Japanese Patent No. 3079382 JP 2006-344509 A JP 2006-294482 A JP 2006-278078 A JP 2006-236725 A JP 2006-228733 A JP 2006-202529 A JP 2006-156234 A JP 2006-156230 A JP 2006-156004 A JP 2006-147191 A JP 2006-080020 A JP 2005-339970 A JP 2005-317499 A JP 2005-251713 A Japanese Patent Laying-Open No. 2005-019149 JP 2004-134207 A WO2002-040404 JP 2004-047180 A JP 2004-031165 A JP 2004-022239 A JP 2003-229128 A JP 2001-023640 A JP 2002-1003007 A JP 2002-1003006 A JP 2003-173776 A JP 2002-358967 A JP 2002-216755 A Japanese Patent Laid-Open No. 2003-092108 Japanese Patent No. 3683144 Japanese Patent No. 3120789 Japanese Patent No. 3024636 Japanese Patent No. 2996234 JP 2006-278079 A WO 2004-105162 JP 2006-073253 A JP-A-2005-339887 Japanese Patent Laid-Open No. 2005-267956 JP 2004-31423 A JP 2004-259511 A WO2002-086993 JP 2004-179019 A JP 2004-146363 A JP 2004-134245 A JP 2002-075369 A JP 2002-110253 A JP 2002-1003008 A JP 2003-157844 A JP 2003-017060 A JP 2002-270247 A JP 2006-278322 A JP 2006-252895 A JP 2006-252894 A JP 2006-196250 A JP-A-2005-339887 JP-A-2005-340055 JP 2005-339886 A Microelectronics Journal, 36 (2005) 491. J. PowerSources, 162 (2006) 1367. J. Electrochem. Soc., 153 (2006) A935. Electrochim. Acta., 52 (2006) 1457. J. PowerSources, 153 (2006) 345.

  As mentioned above, the present inventors previously added a compound containing a specific element such as W in the layered lithium nickel manganese cobalt-based composite oxide, and then baked at a certain temperature or higher to thereby grow grains. And lithium transition metal compound powder composed of fine particles with suppressed sintering, and based on this knowledge, as a lithium secondary battery positive electrode material, cost reduction, high voltage resistance, high In addition to safety, load characteristics such as rate and output characteristics can be improved at the same time. However, improvements are desired to achieve higher characteristics.

  An object of the present invention is to improve load characteristics such as rate and output characteristics in use as a positive electrode active material for a lithium secondary battery, and more preferably to achieve both low cost, high voltage resistance and high safety. It is intended to provide a positive electrode active material for a lithium secondary battery, a positive electrode for a lithium secondary battery using the positive electrode active material, and a lithium secondary battery including the positive electrode for a lithium secondary battery.

  As a result of intensive studies to solve the problem of further improving load characteristics such as rate and output characteristics in addition to cost reduction, high voltage resistance and high safety, the present inventor has identified W and the like. Layered lithium nickel manganese cobalt based composite oxide powder A composed of fine particles with suppressed grain growth and sintering, and transition metal In combination with a spinel-structured lithium manganese composite oxide powder B containing at least Mn as a mixture, these can be mixed and used to further improve the characteristics without impairing the above-described improvement effect. And found that a positive electrode active material for a lithium secondary battery capable of reducing the cost with high load characteristics, high voltage resistance and high safety can be obtained, and the present invention has been completed. .

  That is, the positive electrode active material for a lithium secondary battery of the present invention includes a lithium compound, at least one transition metal compound containing at least Mn, Ni, and Co, and an additive that suppresses grain growth and sintering during firing. A slurry preparation step for pulverizing the agent in a liquid medium and obtaining a slurry in which these are uniformly dispersed, a spray drying step for spray drying the obtained slurry, and a firing for firing the obtained spray-dried powder Lithium-containing transition metal compound powder A obtained by a production method including at least a process, and lithium having a spinel structure (space group Fd-3m (No. 227)) and containing at least Mn as Li and a transition metal The transition metal composite oxide powder B is mixed (claim 1).

  In the positive electrode active material for a lithium secondary battery of the present invention, the mixing ratio of the lithium-containing transition metal composite oxide powder A and the lithium-containing transition metal composite oxide powder B is 20: 1 to 1:20 by weight ratio. It is preferable that it is the range (Claim 2).

  In addition, the lithium-containing transition metal composite oxide powder A is obtained in the slurry preparation step by using a laser diffraction / scattering type particle size distribution measurement device in a liquid medium containing the lithium compound, the transition metal compound, and the additive. Then, the refractive index is set to 1.24, the particle diameter reference is volume reference, and the mixture is pulverized until the median diameter measured after 5 minutes of ultrasonic dispersion (output 30 W, frequency 22.5 kHz) is 0.4 μm or less, In the spray drying process, when the slurry viscosity during spray drying is V (cp), the slurry supply amount is S (L / min), and the gas supply amount is G (L / min), 50 cp ≦ V ≦ 4000 cp, 1500 ≦ It is obtained by a production method in which spray drying is performed under conditions of G / S ≦ 5000, and the spray-dried powder is fired at 950 ° C. or higher in an oxygen-containing gas atmosphere in the firing step. It is preferable that (claim 3).

  In the lithium-containing transition metal composite oxide powder A, the additive for suppressing grain growth and sintering during firing is one or more elements selected from the group consisting of Mo, W, Nb, Ta, and Re. It is preferable that it is an oxide containing (Claim 4).

  Further, the lithium-containing transition metal composite oxide powder A is preferably composed mainly of a lithium nickel manganese cobalt composite oxide that includes a crystal structure belonging to a layered structure. ).

Further, the lithium-containing transition metal composite oxide powder A has a composition represented by the following composition formula (I) and one or more elements selected from the group consisting of Mo, W, Nb, Ta, and Re. What is contained is preferable (claim 6).
LiMO ₂ (I)
[However, in the above formula (I),
M is an element composed of Li, Ni and Mn, or Li, Ni, Mn and Co. Mn / Ni molar ratio is 0.8 or more and 5 or less Co / (Mn + Ni + Co) molar ratio is 0 or more, 0 .35 or less,
Li molar ratio in M is 0.001 or more and 0.2 or less. ]

Furthermore, in the lithium-containing transition metal composite oxide powder A, M in the composition formula (I) is preferably represented by the following composition formula (II) (claim 7).
M = Liz _{/ (2 + z)} {(Ni _{(1 + y) / 2} Mn _{(1-y) / 2} ) _1-x Co _x } _{2 / (2 + z)} (II)
[However, in the above formula (II),
0 ≦ x ≦ 0.1
−0.1 ≦ y ≦ 0.1
(1-x) (0.05-0.98y) ≤z≤ (1-x) (0.20-0.88y)
It is. ]

The lithium-containing transition metal composite oxide powder B preferably has a composition represented by the following composition formula (III) (claim 8).
_{Li (Mn 2-x'-y} 'Li x' M 'y') O 4 ... (III)
[In the above formula (III), M ′ is at least one metal element that can be substituted with Mn (16d) sites other than Mn and Li, and x ′ is 0.01 to 0.10, y 'Is 0.01 to 0.5. ]

  Here, the positive electrode active material for the lithium secondary battery of the present invention is set to a refractive index of 1.24 using a laser diffraction / scattering type particle size distribution measuring device, and the particle size standard is a volume standard. It is preferable that the median diameter measured after sonic dispersion (output 30 W, frequency 22.5 kHz) is 0.5 μm or more and 10 μm or less (Claim 9).

Furthermore, the positive electrode active material for a lithium secondary battery of the present invention preferably has a BET specific surface area of 0.5 m ² / g or more and 5 m ² / g or less (claim 10).

Furthermore, the positive electrode active material for a lithium secondary battery of the present invention preferably has a bulk density of 0.5 g / cm ³ or more and 2.5 g / cm ³ or less (claim 11).

Furthermore, the positive electrode active material for a lithium secondary battery of the present invention preferably has a volume resistivity of 50 Ω · cm or more and 1 × 10 ⁶ Ω · cm or less when consolidated at a pressure of 40 MPa. ).

  Furthermore, the positive electrode active material for a lithium secondary battery of the present invention preferably has a C value of 0.005 wt% or more and 0.1 wt% or less when the carbon concentration is C (wt%). (Claim 13).

  The positive electrode for a lithium secondary battery of the present invention has a positive electrode active material layer containing at least the positive electrode active material for a lithium secondary battery and a binder on a current collector (claim). 14).

  The lithium secondary battery of the present invention is a lithium secondary battery comprising a negative electrode capable of inserting and extracting lithium, a non-aqueous electrolyte containing a lithium salt, and a positive electrode capable of inserting and extracting lithium. Such a positive electrode for a lithium secondary battery of the present invention is used (claim 15).

  When the positive electrode active material for a lithium secondary battery according to the present invention is used as a positive electrode material for a lithium secondary battery, it is possible to reduce costs, increase safety, and improve load characteristics. Therefore, according to the present invention, a lithium secondary battery that is inexpensive, highly safe, and excellent in performance is provided.

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

[Positive electrode active material for lithium secondary battery]
The positive electrode active material for a lithium secondary battery of the present invention (hereinafter sometimes referred to as “positive electrode active material”) comprises a compound having a structure capable of desorbing and inserting Li ions, and at least a specific material Two types of compounds (the following lithium-containing transition metal composite oxide powder A and lithium-containing transition metal composite oxide powder B) are mixed.

  In the positive electrode active material for a lithium secondary battery of the present invention, the mixing ratio of the lithium-containing transition metal composite oxide powder A and the lithium-containing transition metal composite oxide powder B is usually 20: 1 or more and 1:20 or less, preferably 15: 1 or more and 1:15 or less, more preferably 10: 1 or more and 1:10 or less, and most preferably 5: 1 or more and 1: 5 or less. If it deviates from this range, the effects of the present invention may be difficult to obtain.

<Lithium-containing transition metal compound powder A>
The lithium-containing transition metal composite oxide powder A of the present invention comprises a lithium compound, one or more transition metal compounds containing at least Mn, Ni, and Co, and an additive that suppresses grain growth and sintering during firing. Are prepared in a liquid medium, and a slurry preparation step for obtaining a slurry in which these are uniformly dispersed, a spray drying step for spray-drying the obtained slurry, and a firing step for firing the obtained spray-dried powder And at least Mn, Ni, and Co as transition metals, and further includes elements derived from additives that suppress grain growth and sintering during firing. .

  In producing the lithium-containing transition metal composite oxide powder A, in the slurry preparation step, the lithium compound, the transition metal compound, and the additive are dispersed in a laser diffraction / scattering particle size distribution in a liquid medium. With the measuring device, the refractive index is set to 1.24, the particle diameter reference is the volume reference, and the median diameter measured after 5 minutes of ultrasonic dispersion (output 30 W, frequency 22.5 kHz) is 0.4 μm or less. In the spray drying process, when the slurry viscosity during spray drying is V (cp), the slurry supply amount is S (L / min), and the gas supply amount is G (L / min), 50 cp ≦ V ≦ 4000 cp Spray drying is performed under the condition of 1500 ≦ G / S ≦ 5000, and the spray-dried powder is fired at 950 ° C. or higher in an oxygen-containing gas atmosphere in the firing step. And allows expression particularly excellent performance.

  In addition, the lithium-containing transition metal composite oxide powder A of the present invention preferably includes a crystal structure belonging to a layered structure.

<Lithium-containing transition metal composite oxide powder B>
The lithium-containing transition metal composite oxide powder B of the present invention comprises a composite oxide having a spinel structure containing at least Mn as Li and a transition metal element.
Those having a spinel structure are generally expressed as LiMe ₂ O ₄ (Me is one or more elements including at least Mn), specifically, LiMn ₂ O ₄ , LiMn _2−xy Li _x Al _y. Examples include O ₄ , LiCoMnO ₄ , and LiNi _0.5 Mn _1.5 O ₄ , but the element that substitutes a part of Mn is not limited thereto.

<Additives that suppress grain growth and sintering during firing>
In the present invention, the term “additive that suppresses grain growth and sintering during firing” refers to an active material that suppresses sintering between primary particles or secondary particles during positive electrode active material firing at a high temperature. This refers to those that have the effect of suppressing the growth of particles and achieving high crystallization, and obtaining a fine powder property having a large number of voids.

In the present invention, the specific compound added as an additive that suppresses grain growth and sintering during firing is not clear as to the mechanism that exerts the effect of suppressing grain growth and sintering during firing. Since compounds composed of metal elements that can be pentavalent or hexavalent have common effects, they are different from any of the cationic elements that constitute the lithium transition metal-based compound. It is possible to stably take an expensive number state such as a valence, and as a result of being hardly dissolved by a solid-phase reaction, it is unevenly distributed on the surface or grain boundary of the lithium transition metal compound particles. Therefore, it is presumed that the mass transfer due to the contact between the positive electrode active material particles is inhibited, and the growth and sintering of the particles are suppressed.

  The type of additive is not particularly limited as long as it exhibits the above effects, but an element selected from elements such as Mo, W, Nb, Ta, and Re that are stable in an expensive state (hereinafter referred to as this type). An additive-derived element is sometimes referred to as an “additive element”.) Is preferable, and two or more of these elements may be appropriately used in combination. Usually, an oxide material is used as the additive containing these elements.

Exemplary compounds as an _{additive, MoO, MoO 2, MoO 3} , MoO x, Mo 2 O 3, Mo 2 O 5, Li 2 MoO 4, WO, WO 2, WO 3, WO x, W 2 O 3 , W ₂ O ₅ , W ₁₈ O ₄₉ , W ₂₀ O ₅₈ , W ₂₄ O ₇₀ , W ₂₅ O ₇₃ , W ₄₀ O ₁₁₈ , Li ₂ WO ₄ , NbO, NbO ₂ , Nb ₂ O, Nb ₂ O ₅ , Nb ₄ O, Nb ₆ O, LiNbO ₃ , TaO, TaO ₂ , Ta ₂ O ₅ , LiTaO ₃ , ReO ₂ , ReO ₃ , Re ₂ O _{3 and the} like can be mentioned, preferably MoO ₃ , Li ₂ MoO ₄ , WO _{3, Li 2 WO 4, LiNbO} 3, Ta 2 O 5, LiTaO 3, ReO 3 , and more preferably include include _{WO 3, Li 2 WO 4,} ReO 3, most Mashiku can be mentioned WO _3.

  As the range of the amount of these additives, the ratio of the additive element is usually 0.01 mol with respect to the total molar amount of the transition metal elements constituting the main component raw material of the lithium-containing transition metal composite oxide powder A. % Or more, preferably 0.03 mol% or more, more preferably 0.04 mol% or more, particularly preferably 0.05 mol% or more, usually less than 2 mol%, preferably 1.8 mol% or less, more preferably The amount is 1.5 mol% or less, particularly preferably 1.3 mol% or less. If the additive amount is less than this lower limit, the effect may not be obtained, and if it exceeds the upper limit, battery performance may be deteriorated.

<Preferable composition of lithium-containing transition metal composite oxide powder A>
The lithium-containing transition metal composite oxide powder A of the present invention is represented by the following composition formula (I), and is derived from the additive for suppressing the grain growth and sintering during the firing described above, Mo, W, Nb, Ta And one or more elements selected from the group consisting of Re.

LiMO ₂ (I)
[However, in the above formula (I),
M is an element composed of Li, Ni and Mn, or Li, Ni, Mn and Co. Mn / Ni molar ratio is 0.8 or more and 5 or less Co / (Mn + Ni + Co) molar ratio is 0 or more, 0 .35 or less,
Li molar ratio in M is 0.001 or more and 0.2 or less. ]

In the above formula (I), M is an element composed of Li, Ni and Mn, or Li, Ni, Mn and Co. Mn / Ni molar ratio is usually 0.8 or more, preferably 0.82. Or more, more preferably 0.85 or more, further preferably 0.88 or more, most preferably 0.9 or more, usually 5 or less, preferably 4 or less, more preferably 3 or less, still more preferably 2.5 or less, most preferably Preferably it is 1.5 or less.
The Co / (Mn + Ni + Co) molar ratio is usually 0 or more, preferably 0.01 or more, more preferably 0.02 or more, further preferably 0.03 or more, most preferably 0.05 or more, usually 0.30 or less, preferably Is 0.20 or less, more preferably 0.15 or less, still more preferably 0.10 or less, and most preferably 0.099 or less.
The Li molar ratio in M is usually 0.001 or more, preferably 0.01 or more, more preferably 0.02 or more, still more preferably 0.03 or more, most preferably 0.05 or more, usually 0.2 or less, Preferably it is 0.19 or less, More preferably, it is 0.18 or less, More preferably, it is 0.17 or less, Most preferably, it is 0.15 or less.

  The lithium transition metal-based composite oxide powder A of the present invention is particularly preferably one in which the atomic configuration in the M site in the composition formula (I) is represented by the following composition formula (II).

M = Liz _{/ (2 + z)} {(Ni _{(1 + y) / 2} Mn _{(1-y) / 2} ) _1-x Co _x } _{2 / (2 + z)} (II)
[However, in the above formula (II),
0 ≦ x ≦ 0.1
−0.1 ≦ y ≦ 0.1
(1-x) (0.05-0.98y) ≤z≤ (1-x) (0.20-0.88y)
It is. ]

In the above formula (II), the value of x is usually 0 or more, preferably 0.01 or more, more preferably 0.02 or more, still more preferably 0.03 or more, most preferably 0.04 or more, usually 0.1. Hereinafter, it is preferably 0.099 or less, and most preferably 0.098 or less.
The value of y is usually −0.1 or more, preferably −0.05 or more, more preferably −0.03 or more, most preferably −0.02 or more, usually 0.1 or less, preferably 0.05 or less, More preferably, it is 0.03 or less, and most preferably 0.02 or less.
The value of z is usually (1-x) (0.05-0.98y) or more, preferably (1-x) (0.06-0.98y) or more, more preferably (1-x) (0. 07-0.98y) or more, more preferably (1-x) (0.08-0.98y) or more, most preferably (1-x) (0.10-0.98y) or more, usually (1- x) (0.20-0.88y) or less, preferably (1-x) (0.18-0.88y) or less, more preferably (1-x) (0.17-0.88y), most Preferably, it is (1-x) (0.16-0.88y) or less.

  If z is below this lower limit, the conductivity will decrease, and if it exceeds the upper limit, the amount of substitution to transition metal sites will increase so much that the battery capacity will decrease, leading to a decrease in the performance of lithium secondary batteries using this. There is sex. On the other hand, if z is too large, the carbon dioxide absorbability of the active material powder increases, so that it becomes easy to absorb carbon dioxide in the atmosphere. As a result, it is estimated that the concentration of contained carbon increases.

  In addition, in the composition range of the above formula (II), the closer the z value is to the lower limit that is a constant ratio, the lower the rate characteristics and output characteristics of the battery, and the z value is closer to the upper limit. As the battery is used, the rate characteristics and output characteristics increase, but on the other hand, the capacity tends to decrease. In addition, the lower the y value, that is, the smaller the manganese / nickel atomic ratio, the higher the capacity is obtained at a lower charging voltage. However, the cycle characteristics and safety of batteries set at a higher charging voltage tend to be reduced. As the value is closer to the upper limit, the cycle characteristics and safety of the battery set at a higher charge voltage are improved, while the discharge capacity, rate characteristics, and output characteristics tend to decrease. In addition, the closer the x value is to the lower limit, the lower the load characteristics such as rate characteristics and output characteristics when the battery is used. Conversely, the closer the x value is to the upper limit, the rate characteristics when the battery is used. However, if this upper limit is exceeded, the cycle characteristics and safety when set at a high charge voltage are reduced, and the raw material cost is increased. Setting the composition parameters x, y, and z within a specified range is an important component of the present invention.

  Here, the chemical meaning of the Li composition (z and x) in the lithium nickel manganese cobalt based composite oxide, which is a preferred composition of the lithium-containing transition metal composite oxide powder A of the present invention, will be described in more detail below.

（以下「層状Ｒ（−３）ｍ構造」と表記することがある。）に帰属される。 As described above, the lithium-containing transition metal composite oxide powder A preferably includes a crystal structure belonging to a layered structure.
Here, the layered structure will be described in more detail. As a typical crystal system having a layered structure, there are those belonging to the α-NaFeO ₂ type such as LiCoO ₂ and LiNiO ₂ , which are hexagonal and have a space group due to their symmetry.

(Hereinafter referred to as “layered R (−3) m structure”).

However, the layered LiMeO ₂ is not limited to the layered R (−3) m structure. In addition to this, LiMnO ₂ called so-called layered Mn is an orthorhombic and space-group Pm2m layered compound, and Li ₂ MnO ₃ called so-called 213 phase is Li [Li _1/3 Mn _2/3 ]. O ₂ , which is a monoclinic space group C2 / m structure, is also a layered compound in which a Li layer, a [Li _1/3 Mn _2/3 ] layer, and an oxygen layer are stacked.
Thus, the layered structure is not necessarily limited to the R (−3) m structure, but it is preferable from the aspect of electrochemical performance that it can be attributed to the R (−3) m structure.

  In order to determine x, y, and z in the composition formula (II) of the lithium-containing transition metal composite oxide, each transition metal and Li are analyzed by an inductively coupled plasma emission spectrometer (ICP-AES), and Li / It is calculated by obtaining the ratio of Ni / Mn / Co.

  From a structural point of view, it is considered that Li related to z is substituted for the same transition metal site. Here, due to Li related to z, the average valence of Ni becomes larger than divalent (trivalent Ni is generated) by the principle of charge neutrality. Since z raises the Ni average valence, it becomes an index of the Ni valence (the ratio of Ni (III)).

となる。この計算結果は、Ｎｉ価数はｚのみで決まるのではなく、ｘ及びｙの関数となっていることを意味している。ｚ＝０かつｙ＝０であれば、ｘの値に関係なくＮｉ価数は２価のままである。ｚが負の値になる場合は、活物質中に含まれるＬｉ量が化学量論量より不足していることを意味し、過度に大きな負の値を有するものは本発明の効果が出ない可能性がある。一方、同じｚ値であっても、Ｎｉリッチ（ｙ値が大きい）及び／又はＣｏリッチ（ｘ値が大きい）な組成ほどＮｉ価数は高くなるということを意味し、電池に用いた場合、レート特性や出力特性が高くなるが、反面、容量低下しやすくなる結果となる。このことから、ｚ値の上限と下限はｘ及びｙの関数として規定するのがより好ましいと言える。 From the above composition formula, when calculating the Ni valence (m) accompanying the change of z, the Co valence is trivalent and the Mn valence is tetravalent,

It becomes. This calculation result means that the Ni valence is not determined only by z but is a function of x and y. If z = 0 and y = 0, the Ni valence remains divalent regardless of the value of x. When z becomes a negative value, it means that the amount of Li contained in the active material is less than the stoichiometric amount, and those having an excessively large negative value do not exhibit the effect of the present invention. there is a possibility. On the other hand, even if the z value is the same, it means that the Ni valence becomes higher as the composition is rich in Ni (large y value) and / or rich in Co (large x value). The rate characteristics and output characteristics are improved, but on the other hand, the capacity tends to decrease. From this, it can be said that it is more preferable to define the upper and lower limits of the z value as a function of x and y.

  Here, when the x value is in the range of 0 ≦ x ≦ 0.1 and the amount of Co is small, in addition to reducing the cost, it is used as a lithium secondary battery designed to be charged at a high charging potential. In this case, charge / discharge capacity, cycle characteristics, and safety are improved.

  In the composition formula (I), the atomic ratio of the oxygen amount is described as 2 for convenience, but there may be some non-stoichiometry. In the case of non-stoichiometry, the atomic ratio of oxygen is usually in the range of 2 ± 0.2, preferably in the range of 2 ± 0.15, more preferably in the range of 2 ± 0.12, and even more preferably 2 ± 0.10. And particularly preferably in the range of 2 ± 0.05.

  In addition, as described above, when the lithium-containing transition metal composite oxide powder A is produced, the additive amount for suppressing the grain growth and sintering during firing is determined by the lithium-containing transition metal composite oxide powder A. The ratio of the additive element is usually 0.01 mol% or more, preferably 0.03 mol% or more, more preferably 0.04 mol% or more, relative to the total molar amount of the transition metal elements constituting the main component raw material of Particularly preferably 0.05 mol% or more, usually less than 2 mol%, preferably 1.8 mol% or less, more preferably 1.5 mol% or less, particularly preferably 1.3 mol% or less. Therefore, the lithium-containing transition metal composite oxide powder A of the present invention is usually 0.01 mol% or more with respect to the total molar amount of transition metal elements in the lithium-containing transition metal composite oxide powder A. , Preferably 0.03 mol% or more, More preferably 0.04 mol% or more, particularly preferably 0.05 mol% or more, usually less than 2 mol%, preferably 1.8 mol% or less, more preferably 1.5 mol% or less, particularly preferably 1. The additive element derived from 3 mol% or less additive is included.

  Further, foreign elements may be introduced into the lithium-containing transition metal composite oxide powder A of the present invention. The different elements include B, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Ru, Rh, Pd, Ag, In , Sn, Sb, Te, Ba, Os, Ir, Pt, Au, Pb, Bi, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, N , F, P, S, Cl, Br, and I. These foreign elements may be incorporated into the crystal structure of the lithium-containing transition metal composite oxide powder A, or may not be incorporated into the crystal structure of the lithium-containing transition metal composite oxide powder A, and the particles It may be unevenly distributed as a single substance or a compound on the surface or grain boundary.

<Preferable composition of lithium-containing transition metal composite oxide powder B>
The lithium-containing transition metal composite oxide powder B of the present invention is preferably represented by the following composition formula (III).

_{Li (Mn 2-x'-y} 'Li x' M 'y') O 4 ... (III)
[In the above formula (III), M ′ is at least one metal element that can be substituted with Mn (16d) sites other than Mn and Li, and x ′ is 0.01 to 0.10, y 'Is 0.01 to 0.5. ]

  In the above formula (III), the value of x ′ is usually 0.01 or more, preferably 0.015 or more, more preferably 0.025 or more, usually 0.10 or less, preferably 0.08 or less, more preferably Is 0.05 or less, most preferably 0.04 or less. If x 'is too small, the cycle characteristics may be insufficient, and if it is too large, the charge / discharge capacity tends to decrease significantly.

  The value of y ′ is usually 0.01 or more, preferably 0.05 or more, more preferably 0.08 or more, most preferably 0.10 or more, usually 0.5 or less, preferably 0.4 or less, More preferably, it is 0.3 or less, and most preferably 0.2 or less. If y 'is too large, a problem may occur in terms of a decrease in charge / discharge capacity. If y' is too small, it is difficult to obtain a high-temperature stabilization effect.

  The metal element M ′ is preferably a divalent or higher metal. Specific examples include Cr, Co, Fe, Ni, Cu, Zn, Ga, Al, Mg, B, Nb, Ta, Mo, W, Sn, Zr, and the like, but preferably Cr, Co, Fe Ga and Al, and more preferably Co and Al. A plurality of metals may be used as the metal M ′.

  In the composition formula (III), the atomic ratio of the oxygen amount is described as 4 for convenience, but there may be some non-stoichiometry. When there is non-stoichiometry, the atomic ratio of oxygen is usually in the range of 4 ± 0.5, preferably in the range of 4 ± 0.2, more preferably in the range of 4 ± 0.1, and even more preferably 4 ± 0.05. The range is particularly preferably 4 ± 0.02.

<Median diameter and 90% integrated diameter ( _D90 )>
The median diameter of the positive electrode active material for a lithium secondary battery of the present invention is usually 0.5 μm or more, preferably 1 μm or more, more preferably 1.3 μm or more, further preferably 1.6 μm or more, and most preferably 2 μm or more. Usually, it is 10 μm or less, preferably 9 μm or less, more preferably 8 μm or less, further preferably 7 μm or less, and most preferably 6 μm or less. If the median diameter is less than this lower limit, there is a possibility of causing a problem in applicability at the time of forming the positive electrode active material layer, and if it exceeds the upper limit, battery performance may be deteriorated.

The 90% cumulative diameter (D ₉₀ ) of the secondary particles of the positive electrode active material for a lithium secondary battery of the present invention is usually 20 μm or less, preferably 18 μm or less, more preferably 13 μm or less, and most preferably 10 μm or less. Usually, it is 1 μm or more, preferably 2 μm or more, more preferably 3 μm or more, and most preferably 4 μm or more. If the 90% cumulative diameter (D ₉₀ ) exceeds the above upper limit, the battery performance may be deteriorated, and if it is less than the lower limit, there is a possibility of causing a problem in the coating property when forming the positive electrode active material layer.

In the present invention, the median diameter and the 90% integrated diameter (D ₉₀ ) as the average particle diameter are set to a refractive index of 1.24 using a known laser diffraction / scattering particle size distribution measuring device, and the particle diameter standard is determined. Measured as a volume reference. In the present invention, a 0.1 wt% sodium hexametaphosphate aqueous solution was used as a dispersion medium used in the measurement, and measurement was performed after 5 minutes of ultrasonic dispersion (output 30 W, frequency 22.5 kHz).

<Average primary particle size>
The average primary particle diameter (average primary particle diameter) of the positive electrode active material for a lithium secondary battery of the present invention is not particularly limited, but the lower limit is preferably 0.1 μm or more, more preferably 0.15 μm or more. More preferably, it is 0.2 μm or more, most preferably 0.25 μm or more, and the upper limit is preferably 3 μm or less, more preferably 2.5 μm or less, further preferably 2 μm or less, and most preferably 1.5 μm or less. is there. If the average primary particle size exceeds the above upper limit, it may adversely affect the powder filling property or the specific surface area will decrease, which may increase the possibility that the battery performance such as rate characteristics and output characteristics will decrease. If the value falls below the lower limit, there is a possibility that problems such as inferior reversibility of charge and discharge may occur due to undeveloped crystals.

  In addition, the average primary particle diameter in this invention is an average diameter observed with the scanning electron microscope (SEM), and the average particle diameter of about 10-30 primary particles using a SEM image of 30,000 times. It can be obtained as a value.

<BET specific surface area>
Positive electrode active material for lithium secondary lithium battery of the present invention also includes, BET specific surface area is usually 0.5 m ² / g or more, preferably 0.6 m ² / g or more, more preferably 0.8 m ² / g or more Most preferably, it is 1.0 m ² / g or more, usually 5 m ² / g or less, preferably 4 m ² / g or less, more preferably 3 m ² / g or less, and most preferably 2.7 m ² / g or less. If the BET specific surface area is smaller than this range, the battery performance is likely to be lowered, and if it is larger, the bulk density is difficult to increase, and there is a possibility that a problem is likely to occur in the coating property at the time of forming the positive electrode active material.

  The BET specific surface area can be measured by a known BET type powder specific surface area measuring device. In the present invention, an OMS Riken: AMS8000 type automatic powder specific surface area measuring device was used, nitrogen was used as an adsorption gas, and helium was used as a carrier gas. Specifically, the powder sample was heated and deaerated with a mixed gas at a temperature of 150 ° C., then cooled to liquid nitrogen temperature to adsorb the mixed gas, and then heated to room temperature with water to be adsorbed. Nitrogen gas was desorbed, the amount was detected by a heat conduction detector, and the specific surface area of the sample was calculated therefrom.

<Bulk density>
The bulk density of the positive electrode active material for a lithium secondary battery of the present invention is usually 0.5 g / cm ³ or more, preferably 0.7 g / cm ³ or more, more preferably 0.9 g / cm ³ or more, most preferably 1. in .0g / cm ³ or more, usually 2.5 g / cm ³ or less, preferably 2.3 g / cm ³ or less, more preferably 2.1 g / cm ³ or less, and most preferably is 1.9 g / cm ³ or less . While the bulk density exceeding this upper limit is preferable for improving powder filling properties and electrode density, the specific surface area may become too low, and battery performance may be reduced. If the bulk density is below this lower limit, there is a possibility of adversely affecting the powder filling property and electrode preparation.

In the present invention, the bulk density is determined as the powder packing density (tap density) g / cm ³ when 5 to 10 g of the positive electrode active material is put in a 10 ml glass graduated cylinder and tapped 200 times with a stroke of about 20 mm. .

<Volume resistivity>
The volume resistivity value when the positive electrode active material for a lithium secondary battery of the present invention is consolidated at a pressure of 40 MPa is preferably 50 Ω · cm or more as a lower limit, more preferably 1 × 10 ² Ω · cm or more. 1.5 × 10 ² Ω · cm or more is more preferable. The upper limit is preferably 1 × 10 ⁶ Ω · cm or less, more preferably ⁵ × 10 5 Ω · cm or less, more preferably less than 1 × 10 ⁵ Ω · cm. If this volume resistivity exceeds this upper limit, the load characteristics when used as a battery may be reduced. On the other hand, if the volume resistivity is below this lower limit, the safety of the battery may be reduced.

  In the present invention, the positive electrode active material for the lithium secondary battery has a volume resistivity of four probe / ring electrodes, an electrode interval of 5.0 mm, an electrode radius of 1.0 mm, a sample radius of 12.5 mm, and an applied voltage limiter. Is the volume resistivity measured in a state where the positive electrode active material is compacted at a pressure of 40 MPa, with 90V. The volume resistivity can be measured, for example, by using a powder resistance measuring device (for example, Lorester GP powder resistance measuring system manufactured by Dia Instruments Co., Ltd.) with a powder probe unit on a powder under a predetermined pressure. It can be carried out.

<Contained carbon concentration C>
The carbon concentration C (wt%) value of the positive electrode active material for a lithium secondary battery of the present invention is usually 0.005 wt% or more, preferably 0.01 wt% or more, more preferably 0.015 wt% or more. Most preferably 0.02% by weight or more, usually 0.1% by weight or less, preferably 0.08% by weight or less, more preferably 0.06% by weight or less, and most preferably 0.04% by weight or less. is there. If the C value is below this lower limit, battery performance may be reduced, and if it exceeds the upper limit, swelling due to gas generation when the battery is produced may increase or battery performance may be reduced.

In the present invention, the carbon content C of the positive electrode active material for a lithium secondary battery is determined by measurement using an oxygen gas combustion (high-frequency heating furnace type) infrared absorption method, as shown in the Examples section below. .
In addition, the carbon component contained in the positive electrode active material for a lithium secondary battery obtained by the carbon analysis described later can be regarded as indicating information on the amount of carbonic acid compound, particularly lithium carbonate. This is due to the fact that the carbon amount determined by carbon analysis is assumed to be all derived from carbonate ions, and the carbonate ion concentration analyzed by ion chromatography generally agrees.

  On the other hand, when a composite treatment with conductive carbon is performed as a method for increasing the electron conductivity, a C amount exceeding the specified range may be detected, but such a treatment was performed. The C value in the case is not limited to the specified range.

<Reason why the positive electrode active material for a lithium secondary battery of the present invention brings about the above-mentioned effect>
The reason why the positive electrode active material for a lithium secondary battery of the present invention brings about the above-described effects is considered as follows.
That is, when a mixture obtained by mixing lithium-containing transition metal composite oxide powder A and lithium-containing transition metal composite oxide powder B is used, each single lithium transition metal composite oxide powder is used. Thus, battery performance with improved balance of load characteristics, capacity, and cycle maintenance ratio can be exhibited.

[Method for producing positive electrode active material for lithium secondary battery]
The method for producing a positive electrode active material for a lithium secondary battery according to the present invention suppresses grain growth and sintering during firing, a lithium compound, one or more transition metal compounds containing at least Mn, Co, and Ni. A slurry preparation step for obtaining a slurry in which the additive is pulverized in a liquid medium and uniformly dispersing them, a spray drying step for spray drying the obtained slurry, and firing the obtained spray-dried powder And a lithium-containing transition metal composite oxide powder A produced by including a firing step, a spinel structure (space group Fd-3m (No. 227)), and at least Mn as Li and a transition metal. It is produced by mixing lithium-containing transition metal composite oxide powder B.

Below, the manufacturing method of the positive electrode active material material for lithium secondary batteries of this invention is demonstrated in detail.
First, a method for producing the lithium-containing transition metal composite oxide powder A will be described.

<Slurry preparation process>
Among the raw material compounds used for preparing the slurry for producing the lithium-containing transition metal composite oxide powder A, the lithium compounds 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, citrate Li, fatty acid Li, alkyllithium and the like. Among these lithium compounds, lithium compounds containing no nitrogen atom, sulfur atom, or halogen atom are preferable because they do not generate harmful substances such as SO _x and NO _x during the firing treatment. It is a compound that tends to form voids by generating cracked gas in secondary particles of spray-dried powder due to generation of cracked gas. Considering these points, Li ₂ CO ₃ , LiOH, among others LiOH.H ₂ O is preferable, and Li ₂ CO ₃ is preferable because it is easy to handle and relatively inexpensive. These lithium compounds may be used individually by 1 type, and may use 2 or more types together.

Moreover, as a nickel compound, Ni (OH) ₂ , NiO, NiOOH, NiCO ₃ , 2NiCO ₃ .3Ni (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, nickel fatty acid, nickel halide and the like. Among these, Ni (OH) ₂ , NiO, NiOOH, NiCO ₃ , 2NiCO ₃ .3Ni (OH) ₂ .4H ₂ O, NiC are used in that no harmful substances such as SO _X and NO _X are generated during the firing process. Nickel compounds such as ₂ O ₄ .2H ₂ O are preferred. Further, from the viewpoint that it can be obtained as an industrial raw material at a low cost, and from the viewpoint of high reactivity, Ni (OH) ₂ , NiO, NiOOH, NiCO ₃ , and further generation of decomposition gas during firing, spray-dried powder Ni (OH) ₂ , NiOOH, and NiCO ₃ are particularly preferable from the viewpoint of easily forming voids in the secondary particles. These nickel compounds may be used individually by 1 type, and may use 2 or more types together.

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

Further, as the cobalt compound, 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, CoCO _{3 and the} like. Among them, Co (OH) ₂ , CoOOH, CoO, Co ₂ O ₃ , Co ₃ O ₄ , and CoCO ₃ are preferable, and more preferably, from the viewpoint that no harmful substances such as SO _X and NO _X are generated during the firing process. Co (OH) ₂ and CoOOH are industrially inexpensively available and highly reactive. In addition, Co (OH) ₂ , CoOOH, and CoCO ₃ are particularly preferable from the viewpoint of easily forming voids in the secondary particles of the spray-dried powder due to generation of decomposition gas during firing. These cobalt compounds may be used individually by 1 type, and may use 2 or more types together.

The transition metal compound raw material is not limited to a single element compound, and may be a compound in which a plurality of elements are complexed, such as a complex oxide or a complex hydroxide. Illustrative compounds include (Ni _1-ab Mn _a Co _b ) ₃ O ₄ , (Ni _1-a-b Mn _a Co _b ) (OH) _{2 and the} like.

  In addition to the above Li, Ni, Mn, and Co raw material compounds, other elements are substituted to introduce the above-mentioned foreign elements, and voids in secondary particles formed by spray drying described later are efficiently formed. It is possible to use a group of compounds intended to be used. In addition, the addition stage of the compound used for the purpose of efficiently forming the voids of the secondary particles used here can be selected either before or after mixing the raw materials depending on the property. It is. In particular, it is preferable to add a compound that is easily decomposed due to mechanical shear stress applied by the mixing step after the mixing step.

  As described above, the additive for suppressing grain growth and sintering during firing is not particularly limited as long as it exhibits the desired effect, but Mo and W are stable in an expensive state. A compound containing an element selected from elements such as Nb, Ta, and Re is preferable, and an oxide material is usually used.

Examples of additives that suppress grain growth and sintering during firing include MoO, MoO ₂ , MoO ₃ , MoO _x , Mo ₂ O ₃ , Mo ₂ O ₅ , Li ₂ MoO ₄ , WO, WO ₂ , WO ₃ , WO _x , W ₂ O ₃ , W ₂ O ₅ , W ₁₈ O ₄₉ , W ₂₀ O ₅₈ , W ₂₄ O ₇₀ , W ₂₅ O ₇₃ , W ₄₀ O ₁₁₈ , Li ₂ WO ₄ , NbO, NbO ₂ Nb ₂ O, Nb ₂ O ₅ , Nb ₄ O, Nb ₆ O, LiNbO ₃ , TaO, TaO ₂ , Ta ₂ O ₅ , LiTaO ₃ , ReO ₂ , ReO ₃ , Re ₂ O _{3 and the} like are preferable. Includes MoO ₃ , Li ₂ MoO ₄ , WO ₃ , Li ₂ WO ₄ , LiNbO ₃ , Ta ₂ O ₅ , LiTaO ₃ , ReO ₃ , and particularly preferably WO ₃ , Li ₂ WO ₄ , R eO ₃ is mentioned, and WO ₃ is most preferred. These additives may be used individually by 1 type, and may use 2 or more types together.

The method for mixing the raw materials is not particularly limited, and may be wet or dry. For example, a method using an apparatus such as a ball mill, a vibration mill, or a bead mill can be used. Wet mixing in which the raw material compound is mixed in a liquid medium such as water or alcohol 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 0.4 μm or less, preferably 0.3 μm or less, more preferably 0.25 μm or less, most preferably Preferably, it is 0.2 μm or less. If the average particle size of the pulverized raw material particles is too large, the reactivity in the firing process is lowered, and the composition is difficult to homogenize. However, making particles smaller than necessary leads to an increase in pulverization cost, so that the average particle size is usually 0.01 μm or more, preferably 0.02 μm or more, more preferably 0.05 μm or more. It ’s fine. 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 the present invention, the median diameter of the pulverized particles in the slurry was measured with a known laser diffraction / scattering type particle size distribution measuring apparatus with a refractive index of 1.24 and a particle diameter standard set as a volume standard. Is. In the present invention, a 0.1 wt% sodium hexametaphosphate aqueous solution was used as a dispersion medium used in the measurement, and measurement was performed after 5 minutes of ultrasonic dispersion (output 30 W, frequency 22.5 kHz).

<Spray drying process>
The slurry obtained in the above slurry preparation step is then subjected to a spray drying step. Here, as a drying method, a spray drying method is adopted from the viewpoints of uniformity of the generated particulate matter, powder fluidity, powder handling performance, and efficient production of dry particles.

  In the method for producing the lithium-containing transition metal composite oxide powder A of the present invention, the slurry obtained by wet-grinding the raw material compound and the additive is preferably spray-dried, whereby the primary particles are preferably agglomerated. A powder obtained by forming secondary particles is obtained. A spray-dried powder obtained by agglomerating primary particles to form secondary particles is a suitable shape feature of the spray-dried powder of the present invention. Examples of the shape confirmation method include SEM observation and cross-sectional SEM observation.

  The median diameter of the powder obtained by spray drying which is also a calcined precursor of the lithium-containing transition metal composite oxide powder A of the present invention (here, a value measured without applying ultrasonic dispersion) is usually 15 μm or less, more preferably. Is 12 μm or less, more preferably 9 μm or less, and most preferably 7 μm or less. However, since it tends to be difficult to obtain a too small particle size, it is usually 3 μm or more, preferably 5 μm or more, 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.

  That is, for example, a powder obtained by spray drying a slurry in which a lithium compound, a nickel compound, a manganese compound, a cobalt compound, and an additive that suppresses grain growth and sintering during firing are dispersed in a liquid medium. In producing lithium transition metal-based compound powder such as lithium nickel manganese cobalt-based composite oxide powder by firing, the slurry viscosity during spray drying is V (cp), the slurry supply amount is S (L / min), When the gas supply amount is G (L / min), the slurry viscosity V is 50 cp ≦ V ≦ 4000 cp and the gas-liquid ratio G / S is 1500 ≦ G / S ≦ 5000. Dry.

  If the slurry viscosity V (cp) is too low, it may be difficult to obtain a powder obtained by agglomerating primary particles to form secondary particles. If the slurry viscosity V (cp) is too high, the supply pump may fail or the nozzle may be blocked. is there. Therefore, the slurry viscosity V (cp) is usually 50 cp or more as a lower limit, preferably 100 cp or more, more preferably 300 cp or more, most preferably 500 cp, and the upper limit is usually 4000 cp or less, preferably 3500 cp or less. Is 3000 cp or less, most preferably 2500 cp or less.

Further, when the gas-liquid ratio G / S is lower than the lower limit, the secondary particle size is likely to be coarsened or the drying property is liable to be lowered, and when it exceeds the upper limit, the productivity may be lowered. Therefore, the gas / liquid ratio G / S is usually 1500 or more, preferably 1600 or more, more preferably 1700 or more, most preferably 1800 or more as a lower limit, and usually 5000 or less, preferably 4700 as an upper limit.
Hereinafter, it is more preferably 4500 or less, and most preferably 4200 or less.

  The slurry supply amount S and the gas supply amount G are appropriately set according to the viscosity of the slurry used for spray drying, the specifications of the spray drying apparatus used, and the like.

  When spray drying is performed under such conditions, in the method of the present invention, the slurry supply amount and gas supply amount that satisfy the above-mentioned slurry viscosity V (cp) and are suitable for the specifications of the spray drying apparatus to be used are controlled. Spray drying may be performed within a range satisfying the above-described gas-liquid ratio G / S, and other conditions are appropriately set according to the type of apparatus to be used, but the following conditions should be further selected. Is preferred.

  Spray drying of the slurry is usually 50 ° C. or higher, preferably 70 ° C. or higher, more preferably 120 ° C. or higher, most preferably 140 ° C. or higher, usually 300 ° C. or lower, preferably 250 ° C. or lower, more preferably 200 ° C. or lower. Most preferably, it is performed at a temperature of 180 ° C. or lower. If this temperature is too high, the resulting granulated particles may have a lot of hollow structures, which may reduce the packing density of the powder. On the other hand, if it is too low, problems such as powder sticking and blockage due to moisture condensation at the powder outlet may occur.

  In addition, the spray-dried powder as a firing precursor of the lithium-containing transition metal composite oxide powder A of the present invention is characterized by a weak cohesion between primary particles, and this is a median diameter accompanying ultrasonic dispersion. This can be confirmed by examining changes in Here, the upper limit of the median diameter of spray-dried particles when measured after applying ultrasonic dispersion “Ultra Sonic” (output 30 W, frequency 22.5 kHz) for 5 minutes is usually 4 μm or less, preferably 3.5 μm or less. More preferably, it is 3 μm or less, more preferably 2.5 μm or less, most preferably 2 μm or less, and the lower limit is usually 0.01 μm or more, preferably 0.05 μm or more, more preferably 0.1 μm or more, most preferably It is 0.2 μm or more. Lithium transition metal compound particles calcined using spray-dried particles having a median diameter after ultrasonic dispersion larger than the above value have few voids between the particles, and the load characteristics are not improved. On the other hand, lithium transition metal compound particles fired using spray-dried particles whose median diameter after ultrasonic dispersion is smaller than the above values have too many voids between the particles, resulting in decreased bulk density, There is a possibility that problems such as worsening may occur.

Further, the bulk density of the spray-dried powder as the firing precursor of the lithium-containing transition metal composite oxide powder A of the present invention is usually 0.1 g / cm ³ or more, preferably 0.3 g / cm ³ or more, more preferably Is 0.5 g / cm ³ or more, most preferably 0.7 g / cm ³ or more, usually 1.7 g / cm ³ or less, preferably 1.6 g / cm ³ or less, more preferably 1.5 g / cm ^3. Hereinafter, it is most preferably 1.4 g / cm ³ or less. If the bulk density is below this lower limit, it may adversely affect the powder filling property and powder handling, and it is preferable for the powder filling property and powder handling that the bulk density exceeds this upper limit. The specific surface area may become too low, and the reactivity in the firing step may be reduced.

In addition, if the specific surface area of the spray-dried powder is small, the reactivity between the raw material compounds is reduced in the next firing step. As described above, the starting material is pulverized before spray-drying. It is preferable that the specific surface area be as high as possible. On the other hand, if the specific surface area is excessively increased, not only is industrial disadvantageous, but the lithium-containing transition metal composite oxide powder A of the present invention may not be obtained. Therefore, BET specific surface area of the spray-dry powder is usually ^{10 m} 2 / g or more, preferably ^{20 m} 2 / g or more, further preferably ^{30 m} 2 / g or more, most preferably ^{50 m} 2 / g or more and usually 100 m ² / g or less, preferably 80 m ² / g or less, more preferably 70 m ² / g or less, and most preferably 65 m ² / g or less.

<Baking process>
The spray-dried powder as the firing precursor obtained in the spray-drying process is then fired.
Here, the “firing precursor” in the present invention means a precursor of a lithium transition metal compound such as a lithium nickel manganese cobalt composite oxide before firing obtained by treating a spray-dried powder. For example, the above spray-dried powder may contain a compound that generates or sublimates decomposition gas during the above-described firing to form voids in the secondary particles, and serves as a firing precursor.

  This firing condition depends on the composition and the lithium compound raw material used, but as a tendency, if the firing temperature is too high, the primary particles grow excessively, the sintering between the particles proceeds too much, and the resulting lithium-containing transition The specific surface area of the metal composite oxide powder A becomes too small. On the other hand, if it is too low, heterogeneous phases are mixed, the crystal structure does not develop and the lattice strain increases, and the specific surface area of the resulting lithium-containing transition metal composite oxide powder A becomes too large. Accordingly, the firing temperature (the maximum temperature described later) is usually 700 ° C. or higher, but in the production of the lithium-containing transition metal composite oxide powder A having the composition represented by the composition formulas (I) and (II), The firing temperature is usually preferably 950 ° C. or higher, more preferably 960 ° C. or higher, further preferably 970 ° C. or higher, more preferably 980 ° C. or higher, most preferably 990 ° C. or higher, usually 1200 ° C. or lower, preferably 1175 ° C. Hereinafter, it is more preferably 1150 ° C. or less, most preferably 1125 ° C. or less.

  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 crushing step meaning crushing to primary particles or even fine powder.

  In the temperature raising step, the temperature in the furnace is usually raised at a temperature raising rate of 1 ° C./min to 10 ° C./min. 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. The rate of temperature rise is preferably 1.2 ° C./min or more, more preferably 1.5 ° C./min or more, preferably 7 ° C./min or less, more preferably 5 ° C./min or less.

  Although the holding time in the maximum temperature holding step varies depending on the temperature, it is usually 30 minutes or longer, preferably 1 hour or longer, more preferably 2 hours or longer, more preferably 3 hours or longer, as long as it is within the aforementioned baking temperature range. Preferably it is 5 hours or more, usually 50 hours or less, preferably 25 hours or less, more preferably 20 hours or less, and most preferably 15 hours or less. If the firing time is too short, it becomes difficult to obtain a lithium-containing transition metal composite oxide powder A 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 to 10 ° C./min. If the temperature lowering rate 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 lost or the deterioration of the container tends to be accelerated. The temperature lowering rate is preferably 1 ° C./min or more, more preferably 3 ° C./min or more, preferably 7 ° C./min or less, more preferably 5 ° C./min or less.

Since the firing atmosphere has an appropriate oxygen partial pressure region depending on the composition of the lithium-containing transition metal composite oxide powder A to be obtained, various appropriate gas atmospheres for satisfying the oxygen partial pressure region are used. Examples of the gas atmosphere include oxygen, air, nitrogen, argon, hydrogen, carbon dioxide, and a mixed gas thereof. An oxygen-containing gas atmosphere such as air can be used for the lithium nickel manganese cobalt based composite oxide powder specifically implemented in the present invention. Usually, the atmosphere has an oxygen concentration of 1% by volume or more, preferably 10% by volume or more, more preferably 15% by volume or more, and 100% by volume or less, preferably 50% by volume or less, more preferably 25% by volume or less.

  In such a production method, in order to produce the lithium-containing transition metal composite oxide powder A of the present invention, when the production conditions are constant, for example, a lithium compound, a nickel compound, a manganese compound, and a cobalt compound And a slurry in which an additive that suppresses grain growth and sintering at the time of firing is dispersed in a liquid medium, the target Li / Ni / Mn / The molar ratio of Co and the content ratio of the additive element can be controlled.

<Powder mixing process>
Subsequently, the lithium-containing transition metal composite oxide powder A thus obtained has a spinel structure (space group Fd-3m (No. 227)) and contains at least Mn as Li and a transition metal. The lithium-containing transition metal composite oxide powder B is mixed at the above-mentioned suitable weight ratio to obtain the positive electrode active material for a lithium secondary battery of the present invention.
In addition, there is no restriction | limiting in particular in the manufacturing method of lithium containing transition metal complex oxide powder B.

  In order to mix the lithium-containing transition metal composite oxide powder A and the lithium-containing transition metal composite oxide powder B, dry mixing or wet mixing may be used. Examples of the mixing method include artificial hand shaking mixing and mortar mixing, and mechanically blender, readyge mixer, mechano-fusion, and the like.

  In this way, the positive electrode active material for a lithium secondary battery of the present invention having a high capacity, excellent load characteristics such as rate and output, high temperature cycle characteristics, etc., and good performance balance is provided.

[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 a positive electrode active material for a lithium secondary battery 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, its thickness is arbitrary, but it is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 100 mm or less, preferably 1 mm or less, more preferably 50 μm or less. The range of is preferable. If it 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 copolymers and hydrogenated products thereof, EPDM (ethylene / propylene / diene terpolymers), styrene / ethylene / butadiene / ethylene copolymers, Styrene / isoprene styrene bromide Such as thermoplastic elastomeric polymers such as copolymer and hydrogenated products thereof, syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer, etc. Fluorine polymers such as soft resin-like polymers, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymers, ion conductivity of alkali metal ions (especially lithium ions) And a polymer composition having the same. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

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

  The positive electrode active material layer usually contains a conductive material in order to increase conductivity. There are no particular restrictions on the type, but specific examples include metal materials such as copper and nickel, graphite such as natural graphite and artificial graphite, carbon black such as acetylene black, and amorphous carbon such as needle coke. And carbon materials. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios. The proportion of the conductive material in the positive electrode active material layer is usually 0.01% by weight or more, preferably 0.1% by weight or more, more preferably 1% by weight or more, and usually 50% by weight or less, preferably 30%. % By weight or less, more preferably 20% 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 a lithium transition metal compound powder as a positive electrode material, a binder, and a conductive material and a thickener used as necessary. If it is a solvent, there is no restriction | limiting in particular in the kind, You may use either an aqueous solvent or an organic solvent. Examples of the aqueous solvent include water and alcohol. Examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N , N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran (THF), toluene, acetone, dimethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, etc. be able to. 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 positive electrode active material for a lithium secondary battery of the present invention as the positive electrode material in the positive electrode active material layer is usually 10% by weight or more, preferably 30% by weight or more, more preferably 50% by weight or more, Usually, it is 99.9% by weight or less, preferably 99% by weight or less. If the proportion of the positive electrode active material material for lithium secondary batteries 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 if it is 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.
Thus, the positive electrode for a lithium secondary battery of the present invention is prepared.

[Lithium secondary battery]
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.

<Negative electrode>
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, The 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 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: d ₀₀₂ ) 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. In the following, it is preferable that the thickness is 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.

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

Further, when performing Raman spectroscopy using argon laser light for graphite material, and strength _{I A} of the peak _{P A} is detected in the range of 1580~1620cm ^-1, 135
Intensity ratio _I A / _{I B} of the intensity _{I B} of a peak _{P B} detected in the range of 0～1370Cm ^-1 is intended preferably 0 or more and 0.5 or less. 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 negative electrode active materials other than carbon materials include metal oxides such as tin oxide and silicon oxide, nitrides such as Li _2.6 Co _0.4 N, and lithium alloys such as lithium alone and lithium aluminum alloys. Can be mentioned. 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.

<Nonaqueous electrolyte>
As the non-aqueous electrolyte, for example, known organic electrolytes, polymer solid electrolytes, gel electrolytes, inorganic solid electrolytes, and the like can be used. Of these, 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 include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, ethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 4-methyl-2- Pentanone, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile Benzonitrile, butyronitrile, valeronitrile, 1,2-dichloroethane, dimethylformamide, dimethyl sulfoxide, trimethyl phosphate, triethyl phosphate, etc. Et compounds, hydrogen atoms may be partially substituted with a halogen atom. Moreover, these single or 2 or more types of mixed solvents can be used.

  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 electrolyte is preferably 20% by weight or more, more preferably 25% by weight or more, and most preferably 30% 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.

Further, in the organic electrolyte _{solution, CO 2, N 2 O,} CO, gas and vinylene carbonate such as SO _2, polysulfide _S ^{x 2-like,} good to enable efficient charging and discharging of the lithium ion to the negative electrode surface You may add the additive which forms a film in arbitrary ratios. Among these additives, vinylene carbonate is particularly preferable.

  Furthermore, an additive that exhibits an effect of improving cycle life and output characteristics, such as lithium difluorophosphate, may be added to the organic electrolyte at an arbitrary ratio.

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.

  The lithium salt of the electrolytic salt is usually contained in the electrolytic solution so as to have a concentration of 0.5 mol / L to 1.5 mol / L. Even if the lithium salt concentration in the electrolytic solution is less than 0.5 mol / L or more than 1.5 mol / L, the electric conductivity may be lowered, and the battery characteristics may be adversely affected. The lower limit of this concentration 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 (J = Al, Sc, Y, La), Li _0.5-3x RE _{0. .5 + x} TiO ₃ (RE = La, Pr, Nd, Sm) and the like. Examples of the amorphous inorganic solid electrolyte include oxide glasses such as 4.9LiI-34.1Li ₂ O-61B ₂ O ₅ and 33.3Li ₂ O-66.7SiO ₂ . Any one of these may be used alone, or two or more may be used in any combination and ratio.

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

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

<Battery shape>
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.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples as long as the gist of the present invention is not exceeded.

[Measurement method of physical properties]
The physical properties and the like of lithium transition metal-based compound powders produced in each Example and Comparative Example described below were measured as follows.

<Composition (Li / Ni / Mn / Co) (Li / Ni / Co / Al)
(Li / Co) (Li / Mn / Al)>
It was determined by ICP-AES analysis.

<Quantification of additive element (W)>
It was determined by ICP-AES analysis.

<Median diameter of secondary particles and 90% integrated diameter ( _D90 )>
Using a known laser diffraction / scattering particle size distribution measuring device, the refractive index was set to 1.24, and the particle diameter standard was measured as the volume standard. As a dispersion medium, a 0.1 wt% sodium hexametaphosphate aqueous solution was used, and measurement was performed after 5 minutes of ultrasonic dispersion (output 30 W, frequency 22.5 kHz).

<Bulk density>
4 to 10 g of the sample powder was put into a 10 ml glass graduated cylinder, and the powder packing density when tapped 200 times with a stroke of about 20 mm was obtained.

<Specific surface area>
Obtained by BET method.

<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 magnetic crucible, a combustion aid was added, and carbon was extracted by combustion in a high-frequency heating furnace in an oxygen stream. CO ₂ in the combustion gas was quantified by non-dispersive infrared absorption spectrophotometry. 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.

<Volume resistivity>
Using a powder resistivity measuring device (Dia Instruments: Lorester GP powder low-efficiency measurement system PD-41), the sample weight is set to 2 to 3 g, and a powder probe unit (four probe / ring electrodes, electrode spacing 5) The volume resistivity [Ω · cm] of the powder under various pressures was measured at an applied voltage limiter of 90 V using an electrode radius of 1.0 mm, an electrode radius of 1.0 mm, and a sample radius of 12.5 mm. The rate values were compared.

<Median diameter of pulverized particles in slurry>
Using a known laser diffraction / scattering particle size distribution measuring device, the refractive index was set to 1.24, and the particle diameter standard was measured as the volume standard. As a dispersion medium, a 0.1 wt% sodium hexametaphosphate aqueous solution was used, and measurement was performed after 5 minutes of ultrasonic dispersion (output 30 W, frequency 22.5 kHz).

<Physical properties of particulate powder obtained by spray drying>
The median diameter as the average particle diameter was measured with a known laser diffraction / scattering particle size distribution measuring apparatus (LA-920, manufactured by Horiba, Ltd.) with a refractive index of 1.24 and a particle diameter standard as a volume standard. . Moreover, 0.1 weight% sodium hexametaphosphate aqueous solution was used as a dispersion medium, and it measured after ultrasonic dispersion for 5 minutes. The specific surface area was determined by the BET method. The bulk density was determined as the powder packing density when 4 to 6 g of sample powder was put in a 10 ml glass graduated cylinder and tapped 200 times with a stroke of about 20 mm.

[Production of cathode active material for lithium secondary battery (Examples and Comparative Examples)]
(Example 1)
Li ₂ CO ₃ , Ni (OH) ₂ , Mn ₃ O ₄ , CoOOH, WO ₃ are mixed with Li: Ni: Mn: Co: W = 1.12: 0.45: 0.45: 0.10: 0. After weighing and mixing so as to have a molar ratio of 01, pure water was added thereto to prepare a slurry. While stirring this slurry, the solid content in the slurry was pulverized to a median diameter of 0.23 μm using a circulating medium agitation type wet pulverizer.

Next, this slurry (solid content 16.5% by weight, viscosity 1650 cp) was spray-dried using a four-fluid nozzle type spray dryer (manufactured by Fujisaki Electric Co., Ltd .: MDP-50 type). At this time, air was used as the dry gas, the dry gas introduction amount G was 1600 L / min, and the slurry introduction amount S was 780 mL / min (gas-liquid ratio G / S = 2051). The drying inlet temperature was 200 ° C. Particulate powder obtained by spray-drying with a spray dryer (median diameter: 3.2 μm, bulk density: 1.0 g / cm ³ , BET specific surface area: 53.2 m ² / g), about 370 g of alumina square bowl And fired at 1000 ° C. for 2 hours in an air atmosphere (temperature increase rate: about 1.7 ° C./min., Temperature decrease rate: about 3.3 ° C./min.). And lithium-containing transition metal composite oxide powder A was obtained.

The lithium-containing transition metal oxide powder A, the composition is _{Li (Li 0.053 Ni 0.425 Mn 0.427} Co 0.095) Lithium nickel manganese cobalt composite oxide having a layered structure of _{O 2} (the composition In formulas (I) and (II), x = 0.100, y = −0.002, z = 0.111), and the moles of W contained with respect to the total molar amount of (Ni, Mn, Co) The ratio was 1.0 mol%.

As lithium-containing transition metal oxide powder B, lithium manganese aluminum composite having a spinel structure with a composition of Li (Li _0.03 Mn _1.85 Al _0.12 ) O ₄ as lithium-containing transition metal oxide powder B Oxide powder was used.
This lithium-containing transition metal composite oxide powder A and lithium-containing transition metal composite oxide powder B were sufficiently mixed at a ratio of 1: 1 (weight ratio) to obtain a target mixed powder.

The mixed powder has a volume resistivity of 3.0 × 10 ⁴ Ω · cm, a carbon concentration C of 0.025 wt%, a median diameter of 2.7 μm, a 90% cumulative diameter (D ₉₀ ) of 5.9 μm, The bulk density was 1.3 g / cm ³ and the BET specific surface area was 1.7 m ² / g.

(Comparative Example 1)
The lithium-containing transition metal composite oxide powder A used in Example 1 was evaluated without being mixed with the lithium-containing transition metal composite oxide powder B.
This unmixed powder has a volume resistivity of 6.3 × 10 ⁴ Ω · cm, a carbon concentration C of 0.031 wt%, a median diameter of 2.7 μm, and a 90% integrated diameter (D ₉₀ ) of 4.9 μm. The bulk density was 1.0 g / cm ³ and the BET specific surface area was 2.8 m ² / g.

(Comparative Example 2)
The lithium-containing transition metal composite oxide powder B used in Example 1 was evaluated without being mixed with the lithium-containing transition metal composite oxide powder A.
This unmixed powder has a volume resistivity of 1.3 × 10 ⁴ Ω · cm, a carbon concentration C of 0.001% by weight, a median diameter of 11.7 μm, and a 90% integrated diameter (D ₉₀ ) of 18.0 μm. The bulk density was 1.8 g / cm ³ and the BET specific surface area was 0.7 m ² / g.

(Comparative Example 3)
Instead of the lithium-containing transition metal composite oxide powder B, the same procedure as in Example 1 was used, except that a lithium cobalt composite oxide powder having a layered structure with a composition of Li _1.03 Co _1.00 O ₂ was used. Mixed powder was produced.
The mixed powder has a volume resistivity of 2.3 × 10 ⁴ Ω · cm, a carbon concentration C of 0.041% by weight, a median diameter of 2.6 μm, a 90% integrated diameter (D ₉₀ ) of 5.6 μm, The bulk density was 1.4 g / cm ³ and the BET specific surface area was 1.7 m ² / g.

(Comparative Example 4)
The lithium cobalt composite oxide powder used in Comparative Example 3 was evaluated without being mixed with the lithium-containing transition metal composite oxide powder A.
This unmixed powder has a volume resistivity of 1.3 × 10 ⁴ Ω · cm, a carbon concentration C of 0.026 wt%, a median diameter of 11.6 μm, and a 90% integrated diameter (D ₉₀ ) of 16.9 μm. The bulk density was 2.6 g / cm ³ and the BET specific surface area was 0.7 m ² / g.

  Table 1 summarizes the physical property values of the mixed powder or the non-mixed powder produced in Example 1 and Comparative Examples 1 to 4.

[Production and evaluation of battery]
Using the mixed powder or non-mixed powder produced in Example 1 and Comparative Examples 1 to 4 described above as the positive electrode material (positive electrode active material), a lithium secondary battery was prepared and evaluated by the following method. It was. The results are shown in Table 2.

(1) Initial charge / discharge capacity:
A mortar obtained by weighing 75% by weight of each of the mixed powder or non-mixed powder produced in Example 1 and Comparative Examples 1 to 4, 20% by weight of acetylene black, and 5% by weight of polytetrafluoroethylene powder. Were mixed thoroughly and made into a thin sheet, and 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.

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

The obtained coin-type cell was subjected to a constant current constant voltage charge of 0.2 mA / cm ² at an upper limit voltage of 4.2 V and a constant current discharge test of 0.2 mA / cm ² at a lower limit voltage of 3.0 V to perform initial charge / discharge. The capacity was determined.

  In addition, the initial discharge capacity of the said 1st cycle was set to 125 mAh / g or more as an acceptance criterion of an Example.

(2) Low temperature load characteristic test and high temperature cycle test:
In a mortar, 75% by weight of the mixed powder or unmixed powder produced in Example 1 and Comparative Examples 1 to 4, 20% by weight of acetylene black, and 5% by weight of polytetrafluoroethylene powder were weighed. Thoroughly mixed and made into a thin sheet was punched out using a 12 mmφ punch. At this time, the total weight was adjusted to about 18 mg. This was pressure-bonded to an aluminum expanded metal to obtain a 12 mmφ positive electrode.

  Using the result of charge and discharge in the first cycle in the coin cell test of (1), the initial charge capacity per unit weight of the positive electrode active material is Qs (C) [mAh / g], and the initial discharge capacity is Qs (D) [mAh / g].

Graphite powder having an average particle size of 8 to 10 μm (d ₀₀₂ = 3.35 Å) was used as the negative electrode active material, and polyvinylidene fluoride was used as the binder, and these were weighed at a weight ratio of 92.5: 7.5. Were mixed in an N-methylpyrrolidone solution to obtain a negative electrode mixture slurry. This slurry was applied to one side of a 20 μm thick copper foil, dried to evaporate the solvent, punched to 12 mmφ, and pressed at 0.5 ton / cm ² (49 MPa) to form a negative electrode. 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. The initial occlusion capacity per unit weight of the negative electrode active material at a lower limit of 0 V was defined as 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 ( An electrolytic solution in which LiPF ₆ was dissolved at a rate of 1 mol / L in a solvent of ethylene carbonate): DMC (dimethyl carbonate): EMC (ethyl methyl carbonate) = 3: 3: 4 (volume ratio) was added to the can. After fully infiltrating the separator, the above-described negative electrode was placed, a negative electrode can was placed and sealed, and a coin-type lithium secondary battery was 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] / hour [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 resistance value R [Ω] is calculated from the following equation as ΔV = V−V ₀ .
R [Ω] = ΔV [mV] /0.5C [mA]

Next, a constant current 0.2C charge / discharge cycle was conducted at a high temperature of 60 ° C., followed by a constant current 1C charge / discharge cycle 100. The upper limit of charging was 4.1 V, and the lower limit voltage was 3.0 V. At this time, the ratio of the discharge capacity Qh (100) at the 100th cycle of 1C charge / discharge at 60 ° C. was calculated as the high-temperature cycle capacity retention ratio P by the following formula, and the high-temperature characteristics of the batteries were compared with this value.
P [%] = {Qh (100) / Qh (1)} × 100

  Next, the resistance value R [Ω] after the high-temperature cycle test was calculated in the same manner as described above.

  Table 2 shows the low-temperature resistance values and 60 ° C. cycle capacity retention rates of the batteries using the positive electrode active material materials for lithium secondary batteries of Example 1 and Comparative Examples 1 to 4, respectively. The smaller the resistance value, the better the low temperature load characteristic, and the higher the maintenance ratio, the better the high temperature cycle characteristic. In addition, as a pass criterion for the examples, a low temperature resistance value of 350Ω or less and a cycle capacity maintenance rate of 70% or more were set.

  From Table 2, it can be seen that according to the lithium secondary battery positive electrode active material of the present invention, a lithium secondary battery having an excellent balance of capacity, high temperature cycle characteristics, and load characteristics can be realized.

  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 (15)

A lithium compound, one or more transition metal compounds containing at least Mn, Ni, and Co, and an additive that suppresses grain growth and sintering during firing are pulverized in a liquid medium and uniformly dispersed. A lithium-containing transition metal composite obtained by a production method comprising at least a slurry preparation step for obtaining a slurry, a spray drying step for spray-drying the obtained slurry, and a firing step for firing the obtained spray-dried powder Oxide powder A;
Lithium having a spinel structure (space group Fd-3m (No. 227)) and mixed with Li and a lithium-containing transition metal composite oxide powder B containing at least Mn as a transition metal Positive electrode active material for secondary batteries.   The mixing ratio of the lithium-containing transition metal composite oxide powder A and the lithium-containing transition metal composite oxide powder B is in the range of 20: 1 to 1:20 by weight ratio. Positive electrode active material for lithium secondary battery. The lithium-containing transition metal composite oxide powder A is
In the slurry preparation step, the lithium compound, the transition metal compound, and the additive are set in a liquid medium with a refractive index of 1.24 using a laser diffraction / scattering particle size distribution measurement device, and the particle size reference Crushed until the median diameter measured after ultrasonic dispersion (output 30 W, frequency 22.5 kHz) for 5 minutes is 0.4 μm or less,
In the spray drying process, when the slurry viscosity during spray drying is V (cp), the slurry supply amount is S (L / min), and the gas supply amount is G (L / min), 50 cp ≦ V ≦ 4000 cp, 1500 ≦ Spray drying is performed under the condition of G / S ≦ 5000,
3. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the spray-dried powder is obtained by firing at 950 ° C. or higher in an oxygen-containing gas atmosphere in the firing step. .   4. The oxide according to claim 1, wherein the additive is an oxide containing one or more elements selected from the group consisting of Mo, W, Nb, Ta, and Re. Positive electrode active material for lithium secondary battery.   The lithium-containing transition metal composite oxide powder A is mainly composed of a lithium nickel manganese cobalt composite oxide including a crystal structure belonging to a layered structure. The positive electrode active material for lithium secondary batteries according to any one of the above items. The composition of the lithium-containing transition metal composite oxide powder A is represented by the following composition formula (I) and contains one or more elements selected from the group consisting of Mo, W, Nb, Ta, and Re. The positive electrode active material for a lithium secondary battery according to any one of claims 1 to 5, wherein
LiMO ₂ (I)
[However, in the above formula (I),
M is an element composed of Li, Ni and Mn, or Li, Ni, Mn and Co. Mn / Ni molar ratio is 0.8 or more and 5 or less Co / (Mn + Ni + Co) molar ratio is 0 or more, 0 .35 or less,
Li molar ratio in M is 0.001 or more and 0.2 or less. ] The positive electrode active material for a lithium secondary battery according to claim 6, wherein M in the composition formula (I) is represented by the following composition formula (II).
M = Liz _{/ (2 + z)} {(Ni _{(1 + y) / 2} Mn _{(1-y) / 2} ) _1-x Co _x } _{2 / (2 + z)} (II)
[However, in the above formula (II),
0 ≦ x ≦ 0.1
−0.1 ≦ y ≦ 0.1
(1-x) (0.05-0.98y) ≤z≤ (1-x) (0.20-0.88y)
It is. ] The composition of the lithium-containing transition metal composite oxide powder B is represented by the following composition formula (III), and the positive electrode active for lithium secondary battery according to any one of claims 1 to 7 Material material.
_{Li (Mn 2-x'-y} 'Li x' M 'y') O 4 ... (III)
[In the above formula (III), M ′ is at least one metal element that can be substituted with Mn (16d) sites other than Mn and Li, and x ′ is 0.01 to 0.10, y 'Is 0.01 to 0.5. ]   The median diameter measured after 5 minutes of ultrasonic dispersion (output 30 W, frequency 22.5 kHz) using a laser diffraction / scattering particle size distribution analyzer with a refractive index of 1.24 and a particle size standard as a volume standard. 9. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the material is 0.5 μm or more and 10 μm or less. 10. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the BET specific surface area is 0.5 m ² / g or more and 5 m ² / g or less. 11. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the bulk density is 0.5 g / cm ³ or more and 2.5 g / cm ³ or less. Volume resistivity when compacted at a pressure of 40MPa is 50 [Omega · cm or more, for a lithium secondary battery according to any one of claims 1 to 11, characterized in that 1 × 10 ⁶ Ω · cm or less Positive electrode active material.   13. The lithium according to claim 1, wherein the C value is 0.005 wt% or more and 0.1 wt% or less when the carbon content is C (wt%). Positive electrode active material for secondary batteries.   A lithium secondary battery comprising a positive electrode active material layer containing at least the positive electrode active material material for a lithium secondary battery according to any one of claims 1 to 13 and a binder on a current collector. Battery positive electrode.   A lithium secondary battery comprising a negative electrode capable of inserting and extracting lithium, a nonaqueous electrolyte containing a lithium salt, and a positive electrode capable of inserting and extracting lithium, wherein the lithium secondary battery according to claim 14 is used as the positive electrode. A lithium secondary battery using a positive electrode for a battery.