JP2013041807A - Positive electrode for lithium secondary battery and lithium secondary battery including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a positive electrode for a lithium secondary battery, capable of achieving both enhanced capacity/output and elongated lifetime of a lithium secondary battery; and a lithium secondary battery including the positive electrode for a lithium secondary battery.SOLUTION: A positive electrode for a lithium secondary battery contains an active material, a conductive material and a binding material. In the positive electrode for a lithium secondary battery, the conductive material has a nitrogen absorption specific surface area (NSA) of 70 m/g or more, and, when S represents the nitrogen absorption specific surface area (NSA, unit: m/g) of the conductive material, and M represents a weight average molecular weight of the binding material, the following expression (1) is satisfied. (S×M)/10,000≤7,500...(1)

Description

  The present invention relates to a positive electrode for a lithium secondary battery used for a lithium secondary battery and the like, and a lithium secondary battery using the positive electrode for a lithium secondary battery.

  In recent years, along with the reduction in size and weight and the increase in functionality of electronic devices, development of lithium secondary batteries used in these devices has been promoted. The positive electrode used in these lithium secondary batteries usually requires an active material having a function of storing and releasing electrons. However, this active material does not necessarily have high electron conductivity, and the electron conductivity during use. In many cases, the active material alone does not function well. Therefore, in order to take a conductive path between the active materials or between the active material and the current collector, a conductive material having an electron transfer function is usually mixed with the active material.

As the conductive material, a highly conductive carbonaceous material obtained by burning or baking organic substances at a high temperature is usually used. It is known that the physical properties greatly affect the performance of the positive electrode and thus the lithium secondary battery.
Although a lithium secondary battery will be described below as an example, the type of the lithium secondary battery of the present invention is not limited as long as the effect of the conductive material is not impaired.

Among lithium secondary batteries, secondary batteries called lithium secondary batteries or lithium ion secondary batteries are excellent in energy density and power density, and can be reduced in size and weight. It is used as a power source for portable devices such as telephones and handy video cameras, and hybrid electric vehicles.
As the positive electrode active material of the lithium secondary battery, a compound capable of inserting and extracting lithium is used. More specifically, lithium transition metal oxides such as lithium manganese oxide having a spinel structure and lithium cobalt oxide having a layered structure are usually used for the positive electrode active material.

As the positive electrode, a material obtained by attaching these active materials to a current collector together with a conductive material and a binder is used. In particular, since the positive electrode has a low electronic conductivity of the active material and does not work well without a conductive material, it is necessary to add a conductive material.
As the conductive material, carbon black such as acetylene black and ketjen black is widely used, but acetylene black is mainly used.

However, in recent years, lithium secondary batteries are required to have higher capacity, higher output, and longer life due to demands for further weight reduction of electronic devices and higher performance such as long-time operation. Accordingly, it is necessary to improve the active material used for the positive electrode and the conductive material.
To increase the capacity of the battery means to pack the positive electrode active material, the conductive material and the fixing agent as close as possible to the electrode plate when producing the positive electrode of the battery. For this purpose, it is necessary to make it difficult for cracks to occur during the positive electrode preparation step or winding. Therefore, in order to obtain an electrode plate, it is important to increase the strength of the electrode plate by selecting a specific positive electrode active material and a specific conductive material.

Higher battery output means that even if the battery is charged / discharged at a higher current than before, there is little polarization and a high capacity can be extracted. It is important to sufficiently form the original performance of the active material.
On the other hand, extending the life of the battery means that deterioration of battery performance is suppressed even if the number of repeated charge / discharge cycles is increased. For this purpose, it is important that the positive electrode active material and the conductive material efficiently take a conductive path. Therefore, when the electrode plate is used, it is important to improve the adhesion between the positive electrode surface and the conductive material by selecting a specific positive electrode active material and a specific conductive material.

  In order to solve the problem of improving the physical properties of the powder while improving the load characteristics such as the rate / output characteristics as described in Patent Document 1, the present applicant attempts to improve the bulk density and optimize the specific surface area. As a result of intensive studies, the compounds containing at least one element selected from B and Bi and one or more compounds containing at least one element selected from Mo and W are specified. After the combined addition in proportion, by firing, lithium-containing transition metal compound powder easy to handle and positive electrode preparation can be obtained without impairing the improvement effect described above, as a lithium secondary battery positive electrode material, It is possible to obtain lithium transition metal-based compound powder that exhibits excellent powder physical properties, high load characteristics, high voltage resistance, high safety, and can be reduced in cost. Lithium transition metal based compound powder was found to have a feature peak in a surface enhanced Raman spectrum.

Patent Document 2 discloses a lithium secondary battery that can achieve both high output and long life of a lithium secondary battery by producing a positive electrode using a specific carbon black and a positive electrode active material. It describes that a positive electrode for a secondary battery can be produced.
Patent Documents 3 and 4 describe the use of a low molecular weight binder when producing a positive electrode.

JP 2008-270161 A JP 2006-210007 A JP 2009-37937 A JP 2005-268206 A

As described above, recent lithium secondary batteries are required to have higher capacities, higher outputs or longer lifetimes, and to improve all these characteristics at the same time. Here, since the positive electrode active material as in Patent Document 1 has a high electronic resistance when it is used as a positive electrode and it is important to maintain a conductive path, further improvement in cycle characteristics has been desired.
In contrast, by using a conductive material as in Patent Document 2 for the positive electrode active material as in Patent Document 1, the shape of the conductive material is easy to contact the surface of the positive electrode active material, and the state in which the contact is maintained is maintained. Since it is easy to maintain, it is presumed that the maintenance power of the conductive path is improved.

Patent Documents 3 and 4 describe the use of a low molecular weight binder in the production of the positive electrode, but the features such as a large nitrogen adsorption specific surface area, a small average particle diameter, or a large amount of volatile matter. There is no description about the stability of the positive electrode slurry when using a specific conductive material having, and there is no description that suggests such a technical idea.
In order to satisfy the demands for both high output and long life of a lithium secondary battery, the present invention selects the type of binder when using a specific conductive material. Providing a positive electrode for a lithium secondary battery capable of achieving both higher output and longer life, and providing a lithium secondary battery using the positive electrode for a lithium secondary battery, and a positive electrode slurry to be handled in the manufacturing process The purpose is to improve the stability.

In order to increase the output and extend the life of a lithium secondary battery, the present inventors select a type of binder when using a specific conductive material, so that in a slurry for producing a positive electrode The present inventors have found that pot life can be improved and have reached the present invention.
That is, the gist of the present invention is as follows.
(1) A positive electrode for a lithium secondary battery containing an active material, a conductive material, and a binder,
The conductive material has a nitrogen adsorption specific surface area (N ₂ SA) of 70 m ² / g or more, the nitrogen adsorption specific surface area (N ₂ SA, unit: m ² / g) of the conductive material is S, and the weight of the binder A positive electrode for a lithium secondary battery that satisfies the following formula (1) when the average molecular weight is M.

(S × M) / 10000 ≦ 7500 (1)
(2) A positive electrode for a lithium secondary battery containing an active material, a conductive material, and a binder,
The conductive material has an average particle size of 35 nm or less;
The positive electrode for a lithium secondary battery satisfying the following formula (1) when the nitrogen adsorption specific surface area (N ₂ SA, unit: m ² / g) of the conductive material is S and the weight average molecular weight of the binder is M .

(S × M) / 10000 ≦ 7500 (1)
(3) A positive electrode for a lithium secondary battery containing an active material, a conductive material, and a binder,
The conductive material has a volatile content of 0.8% or more,
The positive electrode for a lithium secondary battery satisfying the following formula (1) when the nitrogen adsorption specific surface area (N ₂ SA, unit: m ² / g) of the conductive material is S and the weight average molecular weight of the binder is M .

(S × M) / 10000 ≦ 7500 (1)
(4) The positive electrode for a lithium secondary battery according to any one of (1) to (3), wherein the binder has a weight average molecular weight of 600,000 or less.
(5) The positive electrode for a lithium secondary battery according to any one of (1) to (4), wherein the binder is PVdF.
(6) The positive electrode for a lithium secondary battery according to any one of (1) to (5), wherein the conductive material has a nitrogen adsorption specific surface area (N ₂ SA) of 70 m ² / g or more.
(7) The positive electrode for a lithium secondary battery according to any one of (1) to (6), wherein the conductive material has an average particle size of 35 nm or less.
(8) The positive electrode for a lithium secondary battery according to any one of (1) to (7), wherein a volatile content of the conductive material is 0.8% or more.
(9) The positive electrode for a lithium secondary battery according to any one of (1) to (8), wherein the conductive material is oil furnace carbon black.
(10) The positive electrode for a lithium secondary battery according to any one of the above (1) to (9), wherein a ratio of the conductive material to the active material weight is 0.5 wt% or more and 15 wt% or less.
(11) The positive electrode for a lithium secondary battery according to any one of (1) to (10), wherein the active material contains a lithium transition metal composite oxide.
(12) active material, the surface-enhanced Raman spectrum, 800 cm ^-1 or more, for a lithium secondary battery according to any one of the above and has a peak at 1000 cm ^-1 (1) to (11) Positive electrode.
(13) A lithium secondary battery including a positive electrode, a negative electrode, and a nonaqueous electrolyte containing a lithium salt,
The lithium secondary battery whose positive electrode is a positive electrode for lithium secondary batteries as described in any one of said (1)-(12).

  According to the present invention, it is possible to improve the performance of a positive electrode for a lithium secondary battery, and hence to improve the performance of the lithium secondary battery. In particular, the positive electrode for a lithium secondary battery can be used as a positive electrode for a lithium secondary battery. When used as, it becomes possible to simultaneously achieve higher output and longer life of a lithium secondary battery, which has been considered difficult in the past.

  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. The content of is not specified.

[Lithium secondary battery]
Examples of the lithium secondary battery in the present invention include a small-sized lithium secondary battery mainly used for electronic devices and the like, and a lithium secondary battery for automobiles that have been actively studied recently.
As described above, the positive electrode used in these lithium secondary batteries usually requires an active material having a function of storing and releasing electrons, but the active material does not necessarily have high electron conductivity or is used. Since there is a decrease in electron conductivity, the active material alone does not function well in many cases. Therefore, in order to take a conductive path between the active materials or between the active material and the current collector, a conductive material having an electron transfer function is generally mixed.

[Positive electrode for lithium secondary battery]
When the positive electrode for lithium secondary batteries of the present invention uses a specific conductive material, a suitable positive electrode-forming slurry can be obtained by selecting the type of binder.
In addition, in the positive electrode for lithium secondary batteries of this invention, 1 type of the below-mentioned carbon black may be used independently as a electrically conductive material, and 2 or more types may be used together.

[Positive electrode for lithium secondary battery]
Next, the positive electrode for a lithium secondary battery of the present invention will be described.
The positive electrode for a lithium secondary battery in the present invention has the following aspects.
(1) A positive electrode for a lithium secondary battery containing an active material, a conductive material, and a binder,
The conductive material has a nitrogen adsorption specific surface area (N ₂ SA) of 70 m ² / g or more, the nitrogen adsorption specific surface area (N ₂ SA, unit: m ² / g) of the conductive material is S, and the weight of the binder A positive electrode for a lithium secondary battery, which satisfies the following formula (1) when the average molecular weight is M.

(S × M) / 10000 ≦ 7500 (1)
(2) A positive electrode for a lithium secondary battery containing an active material, a conductive material and a binder,
The conductive material has an average particle size of 35 nm or less;
Lithium satisfying the following formula (1), where S is the nitrogen adsorption specific surface area (N ₂ SA, unit: m ² / g) of the conductive material, and M is the weight average molecular weight of the binder. Secondary battery positive electrode.

(S × M) / 10000 ≦ 7500 (1)
(3) A positive electrode for a lithium secondary battery containing an active material, a conductive material and a binder,
The conductive material has a volatile content of 0.8% or more,
Lithium satisfying the following formula (1), where S is the nitrogen adsorption specific surface area (N ₂ SA, unit: m ² / g) of the conductive material, and M is the weight average molecular weight of the binder. Secondary battery positive electrode.

(S × M) / 10000 ≦ 7500 (1)
In addition, the positive electrode active material layer is usually a sheet obtained by mixing a conductive material, a positive electrode active material, a binder, and a thickener, which is used as necessary, in a dry manner into a positive electrode current collector. It is produced by pressure bonding, or by dissolving or dispersing these materials in a liquid medium to form a slurry, which is applied to a positive electrode current collector and dried.
The positive electrode active material layer obtained by coating and drying is preferably consolidated by a hand press, a roller press or the like in order to increase the packing density of the positive electrode active material.
The thickness of the positive electrode active material layer is usually about 10 to 200 μm.

[Active material]
[Lithium transition metal compound powder]
As described above, the lithium transition metal-based compound powder for lithium secondary battery positive electrode material of the present invention (hereinafter sometimes referred to as “the positive electrode active material of the present invention”) in the surface-enhanced Raman spectroscopy spectrum, 800 cm ^-1 or more, the peak to 1000 cm ^-1 or less (hereinafter, referred to as peak a) preferably has a.

  Here, surface-enhanced Raman spectroscopy (hereinafter abbreviated as SERS) selectively amplifies the Raman spectrum derived from molecular vibrations on the outermost surface of the sample by depositing a noble metal such as silver on the surface of the sample in a very thin sea-island shape. It is a technique to do. The detection depth in ordinary Raman spectroscopy is about 0.1 to 1 μm. However, in SERS, the signal of the surface layer portion in contact with the noble metal particles occupies most.

In the present invention, having the SERS spectrum, 800 cm ^-1 or more, and peak at 1000 cm ^-1 or less (hereinafter, referred to as peak A) the. Position of the peak A is usually 800 cm ^-1 or more, preferably 810 cm ^-1 or more, more preferably 820 cm ^-1 or more, more preferably 830 cm ^-1 or more, and most preferably at 840 cm ^-1 or more and usually 1000 cm ^-1 or less , Preferably 980 cm ⁻¹ or less, more preferably 960 cm ⁻¹ or less, and most preferably 940 cm ⁻¹ or less. If it deviates from this range, the effects of the present invention may not be sufficiently obtained.

Further, as described above, the positive electrode active material of the present invention preferably has a half width of the peak A of 30 cm ⁻¹ or more, more preferably 60 cm ⁻¹ or more in SERS. The cause of the attribution of such a broad peak having a half-value width is presumed to be that the additive element is derived from a chemical change caused by the interaction with the element in the positive electrode active material, and the half-value width of peak A is in the above range. In other words, if the interaction between the additive element and the element in the positive electrode active material is small, the effects of the present invention may not be sufficiently obtained. In addition, the additive element here is synonymous with the additive element mentioned later.

Furthermore, as described above, the positive electrode active material of the present invention preferably has an intensity of peak A greater than 0.04 relative to the intensity of a peak of 600 ± 50 cm ⁻¹ (hereinafter referred to as peak B) in SERS. More preferably, it is 0.05 or more. Here, the peak B of 600 ± 50 cm ^{−1 is} a peak derived from stretching vibration of M ″ O ₆ (M ″ is a metal element in the positive electrode active material). When the intensity of peak A relative to peak B is small, the effects of the present invention may not be sufficiently obtained.

The lithium transition metal compound powder used in the present invention has an additive-derived element (additive element), that is, B, Bi (additive element 1), and Mo, W (additive element 2) on the surface of the primary particles. It is preferable that at least one element selected from is present in a concentrated state. The active material of the present invention contains a lithium transition metal compound as a main component, and is selected from at least one element selected from B and Bi (hereinafter referred to as “additive element 1”), and Mo and W. Containing at least one element (hereinafter referred to as “additive element 2”), and the surface portion of the primary particles of the active material with respect to the total of Li and metal elements other than additive element 1 and additive element 2 The total molar ratio (atomic ratio) of additive element 1 is preferably 20 times or more of the molar ratio of the entire particle. The lower limit of this ratio is preferably 25 times or more, more preferably 30 times or more, more preferably 40 times or more, and particularly preferably 50 times or more. The upper limit is not particularly limited, but is preferably 500 times or less, 400
It is more preferable that it is not more than twice, particularly preferably not more than 300 times, and most preferably not more than 200 times. If this ratio is too small, the effect of improving powder physical properties is small, while if it is too large, battery performance may be deteriorated.

  Further, the molar ratio of additive element 2 to the total of Li and metal elements other than additive element 1 and additive element 2 (that is, metal elements other than Li, additive element 1 and additive element 2) in the surface portion of the primary particles is usually The molar ratio of the whole particle is 3 times or more. The lower limit of this ratio is preferably 4 times or more, more preferably 5 times or more, and particularly preferably 6 times or more. The upper limit is not particularly limited, but is preferably 150 times or less, more preferably 100 times or less, particularly preferably 50 times or less, and most preferably 30 times or less. If this ratio is too small, the effect of improving battery performance is small, while if too large, battery performance may be deteriorated.

  Analysis of the composition of the surface part of the primary particles of the lithium transition metal compound powder was performed by X-ray photoelectron spectroscopy (XPS), using monochromatic light AlKα as an X-ray source, an analysis area of 0.8 mm diameter, and an extraction angle of 65 °. Perform under the conditions of Although the range (depth) that can be analyzed varies depending on the composition of the primary particles, it is usually 0.1 nm to 50 nm, particularly 1 nm to 10 nm for a positive electrode active material. Therefore, in the present invention, the surface portion of the primary particles of the lithium transition metal-based compound powder indicates a measurable range under these conditions.

  The positive electrode active material used in the present invention contains at least one element selected from B and Bi (hereinafter referred to as a raw material containing a lithium transition metal-based compound having a function capable of insertion / extraction of lithium ions as a main component (hereinafter referred to as “a lithium transition metal compound”). A compound containing “additive element 1” (hereinafter referred to as “additive 1”) and at least one element selected from Mo and W (hereinafter referred to as “additive element 2”). One or more compounds to be contained (hereinafter referred to as “additive 2”), and 0.01 mol% or more in total of additive 1 and additive 2 with respect to the total molar amount of transition metal elements in the raw material It is preferable that it is fired after the combined addition at a ratio of less than 2 mol%.

<Lithium-containing transition metal compound>
The lithium transition metal compound of the present invention is a compound having a structure capable of desorbing and inserting Li ions, and examples thereof include sulfides, phosphate compounds, and lithium transition metal composite oxides. . Examples of sulfides include compounds having a two-dimensional layered structure such as TiS ₂ and MoS ₂ , and strong compounds represented by the general formula Me _x Mo ₆ S ₈ (Me is various transition metals including Pb, Ag, and Cu). Examples thereof include a sugar compound having a three-dimensional skeleton structure. Examples of the phosphate compound include those belonging to the olivine structure, and are generally represented by LiMePO ₄ (Me is at least one or more transition metals), specifically LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , Examples include LiMnPO ₄ . Examples of the lithium transition metal composite oxide include spinel structures capable of three-dimensional diffusion and those belonging to a layered structure capable of two-dimensional diffusion of lithium ions. Those having a spinel structure are generally expressed as LiMe ₂ O ₄ (Me is at least one transition metal), specifically, LiMn ₂ O ₄ , LiCoMnO ₄ , LiNi _0.5 Mn _1.5 O. ₄ , LiCoVO _{4 and the} like. Those having a layered structure are generally expressed as LiMeO ₂ (Me is at least one or more transition metals), specifically, LiCoO ₂ , LiNiO ₂ , LiNi _1-x Co _x O ₂ , LiNi _{1-x. -y Co x Mn y O 2,} LiNi 0.5 Mn 0.5 O 2, Li 1.2 Cr 0.4 Mn 0.4 O 2, Li 1.2 Cr 0.4 Ti 0.4 O 2, Examples include LiMnO ₂ .

The lithium transition metal-based compound powder of the present invention preferably has an olivine structure, a spinel structure, or a layered structure from the viewpoint of lithium ion diffusion. Among these, those having a layered structure or a spinel structure are preferred, and those having a layered structure are particularly preferred from the viewpoint that the expansion and contraction of the crystal lattice accompanying charge / discharge is large and the effect of the present invention is remarkable.
Further, foreign elements may be introduced into the lithium transition metal-based compound powder of the present invention. As the different elements, B, Na, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Ru, Rh, Pd, Ag, In, Sb, Te , Ba, Ta, Mo, W, Re, Os, Ir, Pt, Au, Pb, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Bi , N, F, S, Cl, Br, or I. These foreign elements may be incorporated into the crystal structure of the lithium transition metal compound, or may not be incorporated into the crystal structure of the lithium transition metal compound, and may be a single element or compound on the particle surface or grain boundary. May be unevenly distributed.

In the present invention, as the additive element 1, at least one selected from B and Bi is used. Among these additive elements 1, the additive element 1 is preferably B from the viewpoint that it can be obtained at low cost as an industrial raw material and is a light element.
The type of the compound containing additive element 1 (additive 1) is not particularly limited as long as it exhibits the effects of the present invention, but usually boric acid, oxo acid salts, oxides , Hydroxides and the like are used. Among these additives 1, boric acid and oxides are preferable, and boric acid is particularly preferable from the viewpoint of being inexpensively available as an industrial raw material.

Examples of the additive 1 include BO, B ₂ O ₂ , B ₂ O ₃ , B ₄ O ₅ , B ₆ O, B ₇ O, B ₁₃ O ₂ , LiBO ₂ , LiB ₅ O ₈ , Li ₂ B. ₄ O ₇ , HBO ₂ , H ₃ BO ₃ , B (OH) ₃ , B (OH) ₄ , BiBO ₃ , Bi ₂ O ₃ , Bi ₂ O ₅ , Bi (OH) _{3 and the} like are listed as industrial raw materials. From the viewpoint of being relatively inexpensive and easily available, B ₂ O ₃ , H ₃ BO ₃ , and Bi ₂ O ₃ are preferable, and H ₃ BO ₃ is particularly preferable. These additives 1 may be used individually by 1 type, and 2 or more types may be mixed and used for them.

In the present invention, as the additive element 2, at least one selected from Mo and W is used. Among these additive elements 2, the additive element 2 is preferably W from the viewpoint of great effect.
The type of the compound containing additive element 2 (additive 2) is not particularly limited as long as it exhibits the effects of the present invention, but an oxide is usually used.

Exemplary compounds of the additive _{2, 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 and the} like, which are relatively easily available as industrial raw materials, or From the viewpoint of including lithium, MoO ₃ , Li ₂ MoO ₄ , WO ₃ , and Li ₂ WO ₄ are preferable, and WO ₃ is particularly preferable. These additives 2 may be used alone or in combination of two or more.

  The range of the total amount of additive 1 and additive 2 is generally 0.01 mol% or more and less than 2 mol%, preferably 0. 0%, based on the total molar amount of transition metal elements constituting the main component. They are 03 mol% or more and 1.8 mol% or less, More preferably, they are 0.04 mol% or more and 1.6 mol% or less, Especially preferably, they are 0.05 mol% or more and 1.5 mol% or less. If the lower limit is not reached, the above effect may not be obtained. If the upper limit is exceeded, battery performance may be reduced.

As the range of the addition ratio of additive 1 and additive 2, the molar ratio is usually 10: 1 or more, 1:20 or less, preferably 5: 1 or more, 1:15 or less, more preferably 2: 1 or more, 1:10 or less, particularly preferably 1: 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.
In addition, in the time-of-flight secondary ion mass spectrometry (hereinafter abbreviated as “ToF-SIMS”), the positive electrode active material of the present invention is a fragment in which an additive element and an element constituting the positive electrode active material are combined. It is preferred that a derived peak is observed.

  Here, ToF-SIMS is a method for estimating chemical species present on the outermost surface of a sample by detecting secondary ions generated by irradiating the sample with an ion beam using a time-of-flight mass spectrometer. By this method, it is possible to infer the distribution state of additive elements existing in the vicinity of the surface layer. In the case where there is no peak derived from a fragment in which the additive element is combined with the element in the positive electrode active material, the additive element is not sufficiently dispersed, and the effect of the present invention cannot be sufficiently obtained. there is a possibility.

By the way, the lithium transition metal-based compound powder for a lithium secondary battery positive electrode material of the present invention has BWO ₅ ⁻ and M′BWO ₆ ⁻ (M ′) when B and W are used as additive elements in ToF-SIMS. is an element may take bivalent state), or, BWO ₅ ^- and _Li 2 BWO ₆ ^- preferably that a peak derived is observed. When the above peak is not observed, the additive element is not sufficiently dispersed, and the effect of the present invention may not be sufficiently obtained.

<Average primary particle size>
The average diameter (average primary particle diameter) of the lithium lithium transition metal compound powder of the present invention is not particularly limited, but the lower limit is preferably 0.1 μm or more, more preferably 0.2 μm or more, and most preferably The upper limit is preferably 2 μm or less, more preferably 1.8 μm or less, still more preferably 1.5 μm or less, and most preferably 1.2 μm or less. 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. There is sex. If the lower limit is not reached, there is a possibility that problems such as inferior reversibility of charge / discharge due to the 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.

<Cumulative fraction of particles with median diameter of 5 μm or less>
The median diameter (50% cumulative diameter (D ₅₀ )) of the lithium transition metal-based compound powder of the present invention is usually 2 μm or more, preferably 2.5 μm or more, more preferably 3 μm or more, still more preferably 3.5 μm or more. It is preferably 4 μm or more, usually 20 μm or less, preferably 19 μm or less, more preferably 18 μm or less, still more preferably 17 μm or less, and most preferably 15 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 lowered.

The cumulative fraction of particles of 5 μm or less of the lithium lithium transition metal compound powder of the present invention is usually 70% or less, preferably 50% or less, more preferably 40% or less, and most preferably 30% or less. . If the cumulative fraction of particles of 5 μm or less exceeds the above upper limit, there is a possibility of liquid preparation and application failure during electrode plate preparation.
In the present invention, the median diameter and the 50% cumulative diameter (D ₅₀ ) as the average particle diameter are set to a refractive index of 1.60a-0.10i using a known laser diffraction / scattering particle size distribution measuring device, Measured with the particle diameter standard as the volume standard. 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). Note that ultrasonic dispersion is not performed.

<BET specific surface area>
The lithium-lithium transition metal compound powder of the present invention also has a BET specific surface area of usually 0.2 m ² / g or more, preferably 0.25 m ² / g or more, more preferably 0.3 m ² / g or more, most Preferably it is 0.4 m ² / g or more, usually 3 m ² / g or less, preferably 2.8 m ² / g or less, more preferably 2.5 m ² / g or less, most preferably 2.0 m ² / g or less. is there. 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.

<The bulk density>
The bulk density of the lithium transition metal compound powder of the present invention is usually 1.2 g / cc or more, preferably 1.3 g / cc or more, more preferably 1.4 g / cc or more, most preferably 1.5 g / cc or more. Usually, it is 3.0 g / cc or less, preferably 2.9 g / cc or less, more preferably 2.8 g / cc or less, and most preferably 2.7 g / cc 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 the positive electrode preparation.
In the present invention, the bulk density is 5 to 10 g of lithium transition metal compound powder in a 10 ml glass measuring cylinder and tapped 200 times with a stroke of about 20 mm (tap density) g / Calculate as cc.

<Volume resistivity>
The volume resistivity value when the lithium transition metal-based compound powder of the present invention is compacted at a pressure of 40 MPa is more preferably 1 × 10 ⁵ Ω · cm or more as a lower limit, and 3 × 10 ⁵ Ω · cm or more. Is more preferable, and 5 × 10 ⁵ Ω · cm or more is most preferable. The upper limit is preferably 1 × 10 ⁷ Ω · cm or less, more preferably 8 × 10 ⁶ Ω · cm or less, further preferably 5 × 10 ⁶ Ω · cm or less, and most preferably 3 × 10 ⁶ Ω · cm or less. . 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 volume resistivity of the lithium transition metal based compound powder is such that the four probe / ring electrode, the electrode spacing is 5.0 mm, the electrode radius is 1.0 mm, the sample radius is 12.5 mm, and the applied voltage limiter is 90 V. The volume resistivity measured in a state where the lithium transition metal-based compound powder is compacted at a pressure of 40 MPa. 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.

<Pore characteristics by mercury intrusion method>
The lithium transition metal-based compound powder for a lithium secondary battery positive electrode material of the present invention preferably satisfies a specific condition in measurement by a mercury intrusion method.
The mercury intrusion method employed in the evaluation of the lithium transition metal compound powder of the present invention will be described below.

The mercury intrusion method is a method for obtaining information such as specific surface area and pore size distribution from the relationship between pressure and the amount of mercury intruded into a pore of a sample such as porous particles while applying pressure. It is.
Specifically, first, the container containing the sample is evacuated and filled with mercury. Mercury has a high surface tension, and as it is, mercury does not penetrate into the pores on the sample surface, but when pressure is applied to the mercury and the pressure is gradually increased, the pores increase in size from the smallest to the smallest. Gradually mercury enters the pores. If a change in the mercury liquid level (that is, the amount of mercury intruded into the pores) is detected while the pressure is continuously increased, a mercury intrusion curve representing the relationship between the pressure applied to the mercury and the amount of mercury intruded can be obtained. .

Here, assuming that the shape of the pore is cylindrical, the radius is r, the surface tension of mercury is δ, and the contact angle is θ, the size in the direction of extruding mercury from the pore is −2πrδ (cos θ). (If θ> 90 °, this value is positive). Moreover, since the magnitude of the force in the direction of pushing mercury into the pores under the pressure P is represented by πr ² P, the following formulas (1) and (2) are derived from the balance of these forces. It will be.

-2πrδ (cosθ) = πr ² P (1)
Pr = -2δ (cos θ) (2)
In the case of mercury, values of surface tension δ = 480 dyn / cm and contact angle θ = 140 ° are generally used well. When these values are used, the radius of the pore into which mercury is injected under the pressure P is expressed by the following formula (3).

  That is, since there is a correlation between the pressure P applied to mercury and the radius r of the pore into which mercury enters, the size of the pore radius of the sample and its volume are calculated based on the obtained mercury intrusion curve. A pore distribution curve representing the relationship can be obtained. For example, when the pressure P is changed from 0.1 MPa to 100 MPa, the pores in the range from about 7500 nm to about 7.5 nm can be measured.

Note that the approximate measurement limit of the pore radius by the mercury intrusion method is that the lower limit is about 2 nm or more and the upper limit is about 200 μm or less, and the pores in a relatively large range compared to the nitrogen adsorption method described later. It can be said that it is suitable for analysis of distribution.
Measurement by the mercury intrusion method can be performed using an apparatus such as a mercury porosimeter. Specific examples of the mercury porosimeter include an autopore manufactured by Micromeritics, a pore master manufactured by Quantachrome, and the like.

Lithium transition metal based compound powder according to the present invention, in a mercury intrusion curve obtained by mercury intrusion porosimetry, mercury penetration amount at boosting the pressure 3.86kPa to 413MPa is, 0.1 cm ³ / g or more, 1.5 cm ³ / g or less is preferable. The amount of mercury intrusion is more preferably 0.15 cm ³ / g or more, most preferably 0.2 cm ³ / g or more, more preferably 1.4 cm ³ / g or less, still more preferably 1.3 cm ³ / g or less, Most preferably, it is 1.2 cm ³ / g or less. When the upper limit of this range is exceeded, the voids become excessive, and when the lithium transition metal compound powder of the present invention is used as the positive electrode material, the filling rate of the positive electrode active material into the positive electrode plate becomes low, and the battery capacity is limited. Will be. On the other hand, if the lower limit of this range is not reached, voids between the particles become excessively small. Therefore, when a battery is produced using the lithium transition metal compound powder of the present invention as a positive electrode material, lithium diffusion between particles is inhibited. As a result, the load characteristics deteriorate.

In the lithium transition metal-based compound powder of the present invention, when a pore distribution curve is measured by the mercury intrusion method described above, a specific main peak described below usually appears.
In the present specification, the “pore distribution curve” refers to the total pore volume per unit weight (usually 1 g) of pores having a radius equal to or larger than the radius of the pores on the horizontal axis, The value obtained by differentiating the logarithm of the pore radius is plotted on the vertical axis, and is usually expressed as a graph connecting the plotted points. In particular, a pore distribution curve obtained by measuring the lithium transition metal-based compound powder of the present invention by a mercury intrusion method is referred to as “a pore distribution curve according to the present invention” as appropriate in the following description.

In this specification, “main peak” refers to the largest peak among the peaks of the pore distribution curve, and “sub peak” refers to a peak other than the main peak of the pore distribution curve.
In the present specification, “peak top” refers to the point at which the coordinate value of the vertical axis takes the largest value in each peak of the pore distribution curve.

<Main peak>
The main peak of the pore distribution curve according to the present invention has a peak top with a pore radius of usually 1600 nm or more, more preferably 1700 nm or more, most preferably 1800 nm or more, and usually 3000 nm or less, preferably 2900 nm or less, More preferably, it exists in 2800 nm or less, More preferably, it is 2700 nm or less, Most preferably, it exists in the range of 2600 nm or less. When the upper limit of this range is exceeded, when a battery is made using the lithium transition metal compound powder of the present invention as the positive electrode material, lithium diffusion in the positive electrode material is inhibited, or the conductive path is insufficient, resulting in load characteristics. May be reduced. On the other hand, below the lower limit of this range, when a positive electrode is produced using the lithium transition metal compound powder of the present invention, the required amount of conductive material and binder increases, and the positive electrode plate (positive electrode current collector) increases. The active material filling rate into the body) is restricted, and the battery capacity may be restricted. In addition, with the formation of fine particles, the mechanical properties of the coating film at the time of coating become hard or brittle, and there is a possibility that the coating film is likely to be peeled off during the winding process during battery assembly.

In addition, the pore volume of the peak having a peak top at a pore radius of 1600 nm or more and 3000 nm or less, which the pore distribution curve according to the present invention has, is preferably usually 0.10 cm ³ / g or more, preferably 0. .15cm ³ / g or more, more preferably 0.18 cm ³ / g or more, most preferably 0.20 cm ³ / g or more and usually 0.8 cm ³ / g or less, preferably 0.7 cm ³ / g, More preferably, it is 0.6 cm < ³ > / g or less, Most preferably, it is 0.5 cm < ³ > / g or less. When the upper limit of this range is exceeded, the voids become excessive, and when the lithium transition metal compound powder of the present invention is used as the positive electrode material, the filling rate of the positive electrode active material into the positive electrode plate becomes low, and the battery capacity is limited. There is a possibility of being. On the other hand, if the lower limit of the range is not reached, voids between the particles become too small. Therefore, when a battery is produced using the lithium transition metal compound powder of the present invention as a positive electrode material, lithium diffusion between secondary particles is caused. May be hindered and load characteristics may be reduced.

<Sub-peak>
The pore distribution curve according to the present invention may have a plurality of sub-peaks in addition to the above-mentioned main peak, and in particular, a sub-peak in which a peak top exists in a pore radius range of 80 nm or more and less than 1600 nm. It is preferable to have. The peak top of the sub-peak has a pore radius of usually 80 nm or more, more preferably 100 nm or more, most preferably 120 nm or more, and usually less than 1600 nm, preferably 1400 nm or less, more preferably 1200 nm or less, still more preferably 1000 nm or less, most preferably Preferably, it exists in the range of 800 nm or less. If it exists in this range, electrolyte solution osmose | permeates the inside of particle | grains and a rate characteristic improves. When the pore radius is larger than this, the volume also increases, which may cause a decrease in tap density.

The pore volume of the sub-peak where the peak top is present in the pore radius of 80 nm or more and less than 1600 nm of the pore distribution curve according to the present invention is suitably usually 0.001 cm ³ / g or more, preferably 0.003 cm ^3. / g or more, more preferably 0.005 cm ³ / g or more, and most preferably 0.007cm ³ / g or more and usually 0.3 cm ³ / g or less, preferably 0.25 cm ³ / g, more preferably 0.20 cm ³ / g or less, and most preferably not more than 0.18 cm ³ / g. If the upper limit of this range is exceeded, voids between secondary particles become excessive, and when the lithium transition metal-based compound powder of the present invention is used as a positive electrode material, the filling rate of the positive electrode active material into the positive electrode plate becomes low. The battery capacity may be limited. On the other hand, if the lower limit of this range is not reached, voids between secondary particles become excessively small. Therefore, when a battery is produced using the lithium transition metal-based compound powder of the present invention as a positive electrode material, between secondary particles. Lithium diffusion may be hindered and load characteristics may be reduced.

  In the present invention, the pore distribution curve by mercury porosimetry has at least one main peak having a peak top at a pore radius of 1600 nm or more and 3000 nm or less, and a pore radius of 80 nm or more and less than 1600 nm. A lithium transition metal-based compound powder for a lithium secondary battery positive electrode material having a sub-peak in which a peak top is present is preferable.

<Crystal structure>
The lithium transition metal-based compound powder of the present invention preferably contains at least a lithium nickel manganese cobalt-based composite oxide having a layered structure and / or a lithium manganese-based composite oxide having a spinel structure as a main component. Among these, since the expansion and contraction of the crystal lattice is large and the effect of the present invention is remarkable, the main component is a lithium nickel manganese cobalt composite oxide having a layered structure. In the present invention, among lithium nickel manganese cobalt-based composite oxides, lithium nickel manganese-based composite oxides not including cobalt are also included in the term “lithium nickel manganese cobalt-based composite oxide”.
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.
Furthermore, the spinel structure will be described in more detail. As a typical crystal system having a spinel structure, there is a crystal system belonging to the MgAl ₂ O ₄ type such as LiMn ₂ O ₄ , which is a cubic system, and because of its symmetry, the space group.

(Hereinafter sometimes referred to as “spinel-type Fd (−3) m structure”). However, the spinel type LiMeO ₄ is not limited to the spinel type Fd (−3) m structure. In addition, spinel type LiMeO ₄ belonging to a different space group (P4 ₃ 32) also exists.

<composition>
The lithium-containing transition metal compound powder of the present invention is preferably a lithium transition metal compound powder represented by the following composition formula (A) or (B).
Li _{1 + x} MO ₂ (A)
_{Li [Li a M b Mn 2} -b-a] O 4 + δ ··· (B)
Further, in the layered compound, the amount of Mn eluted is relatively small compared to the spinel type compound, and the influence of Mn on the cycle characteristics is small. Therefore, the effect of the present invention appears as a clear difference. Therefore, the present invention is more preferably a lithium transition metal compound powder represented by the following composition formula (A).
1) In the case of a lithium transition metal compound powder represented by the following composition formula (A)

Li _{1 + x} MO ₂ (A)
However, x is usually 0 or more, preferably 0.01 or more, more preferably 0.02 or more, most preferably 0.03 or more, usually 0.5 or less, preferably 0.4 or less, more preferably 0.3. Hereinafter, it is most preferably 0.2 or less. M is an element composed of Ni and Mn, or Ni, Mn and Co, and the Mn / Ni molar ratio is usually 0.1 or more, preferably 0.3 or more, more preferably 0.5 or more, Preferably 0.6 or more, more preferably 0.7 or more, still more preferably 0.8 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 1.5 or less. The Ni / M molar ratio 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 0.05 or more, usually 0.50 or less, preferably 0. .49 or less, more preferably 0.48 or less, still more preferably 0.47 or less, and most preferably 0.45 or less. The Co / M molar ratio 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 0.05 or more, usually 0.50 or less, preferably 0. .40 or less, more preferably 0.30 or less, still more preferably 0.20 or less, and most preferably 0.15 or less. In addition, the rich portion of Li represented by x may be replaced with the transition metal site M.

In the composition formula (A), the molar ratio (atomic ratio) of the oxygen amount is described as 2 for convenience, but there may be some non-stoichiometry. When there is nonstoichiometry, the molar ratio (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. The range is ± 0.10, particularly preferably 2 ± 0.05.
In addition, the lithium transition metal-based compound powder of the present invention is preferably obtained by firing at a high temperature in an oxygen-containing gas atmosphere in order to increase the crystallinity of the positive electrode active material.

In particular, the lower limit of the firing temperature is usually 950 ° C. or higher, preferably 960 ° C. or higher, more preferably 970 ° C. or higher, most preferably 980 ° C., in the lithium transition metal compound having the composition represented by the composition formula (A). The upper limit is 1200 ° C. or lower, preferably 1175 ° C. or lower, more preferably 1150 ° C. or lower, and most preferably 1125 ° C. or lower. If the firing temperature is too low, heterogeneous phases are mixed, and the lattice distortion increases without developing a crystal structure. Moreover, the specific surface area becomes too large. Conversely, if the firing temperature is too high, the primary particles grow excessively, sintering between the particles proceeds too much, and the specific surface area becomes too small.
2) A lithium transition metal compound represented by the following composition formula (B).

_{Li [Li a M b Mn 2} -b-a] O 4 + δ ··· (B)
However, M is an element composed of at least one of transition metals selected from Ni, Cr, Fe, Co, Cu, Zr, Al and Mg, and among these, the charge / discharge capacity at a high potential is From the point of view, Ni is most preferable.
The value of b is usually 0.4 or more, preferably 0.425 or more, more preferably 0.45 or more, further preferably 0.475 or more, most preferably 0.49 or more, usually 0.6 or less, preferably 0. .575 or less, more preferably 0.55 or less, still more preferably 0.525 or less, and most preferably 0.51 or less.

If the value of b is in this range, the energy density per unit weight in the lithium transition metal compound is high, which is preferable.
The value of a is usually 0 or more, preferably 0.01 or more, more preferably 0.02 or more, further preferably 0.03 or more, most preferably 0.04 or more, usually 0.3 or less, preferably 0. .2 or less, more preferably 0.15 or less, still more preferably 0.1 or less, and most preferably 0.075 or less.

If the value of a is within this range, the energy density per unit weight in the lithium transition metal-based compound is not significantly impaired, and good load characteristics can be obtained, which is preferable.
Furthermore, the value of δ is usually in the range of ± 0.5, preferably in the range of ± 0.4, more preferably in the range of ± 0.2, still more preferably in the range of ± 0.1, particularly preferably ± 0.05. Range.

If the value of δ is within this range, the stability as a crystal structure is high, and the cycle characteristics and high-temperature storage of a battery having an electrode produced using this lithium transition metal compound are favorable.
Here, the chemical meaning of the lithium composition in the lithium nickel manganese composite oxide, which is the composition of the lithium transition metal compound of the present invention, will be described in more detail below.

In order to obtain a and b in the composition formula of the lithium transition metal compound, each transition metal and lithium are analyzed with an inductively coupled plasma emission spectrometer (ICP-AES) to obtain a ratio of Li / Ni / Mn. It is calculated by the thing.
From a structural point of view, it is considered that lithium related to a is substituted for the same transition metal site. Here, due to the lithium according to a, the average valence of M and manganese becomes larger than 3.5 due to the principle of charge neutrality.

<Contained carbon concentration C>
The carbon concentration C (wt%) value of the lithium transition metal compound powder 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 Preferably it is 0.02% by weight or more, usually 0.25% by weight or less, preferably 0.2% by weight or less, more preferably 0.15% by weight or less, still more preferably 0.1% by weight or less, most preferably Is 0.07% by weight or less. If the lower limit is not reached, battery performance may be reduced. If the upper limit is exceeded, swelling due to gas generation when the battery is produced may increase or battery performance may be reduced.

In the present invention, the carbon concentration C of the lithium nickel manganese cobalt-based composite oxide powder is determined by measurement using an oxygen gas combustion (high-frequency heating furnace type) infrared absorption method, as shown in the Examples section below. It is done.
In addition, the carbon component contained in the lithium nickel manganese cobalt composite oxide powder obtained by 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.
<Preferred composition>
In the lithium transition metal composite oxide powder for a lithium secondary battery positive electrode material of the present invention, the atomic configuration in the M site in the composition formula (A) is represented by the following formula (I) or the following formula (I ′). Those are particularly preferred.

M = Li _{z / (2 + z)} {(Ni _{(1 + y) / 2} Mn _{(1-y) / 2} ) _1-x Co _x } _{2 / (2 + z)} (I)
(However, in the above formula (I),
0 ≦ x ≦ 0.1,
−0.1 ≦ y ≦ 0.1,
(1-x) (0.05-0.98y) ≤z≤ (1-x) (0.20-0.88y)
It is. )
M = Li _{z ′ / (2 + z ′)} {(Ni _{(1 + y ′) / 2} Mn _{(1-y ′) / 2} ) _{1-x ′} Co _{x ′} } _{2 / (2 + z ′)} (I ′) (however, In the composition formula (I ′),
0.1 <x ′ ≦ 0.35
−0.1 ≦ y ′ ≦ 0.1
(1-x ′) (0.02-0.98y ′) ≦ z ′ ≦ (1-x ′) (0.20-0.88y ′))
In the above formula (I), 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 the above formula (I ′), the value of x ′ is usually larger than 0.1, preferably 0.15 or more, more preferably 0.2 or more, still more preferably 0.25 or more, most preferably 0.30 or more. Usually, it is 0.35 or less, preferably 0.345 or less, and most preferably 0.34 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 ′) (0.02−0.98y ′) or more, preferably (1−x ′) (0.03−0.98y) or more, more preferably (1−x ') (0.04-0.98y') or more, most preferably (1-x ') (0.05-0.98y') 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 (1- x ′) (0.16-0.88y ′) or less. If z ′ is less than this lower limit, the conductivity will be reduced, and if it exceeds the upper limit, the amount of substitution to transition metal sites will be too much and the battery capacity will be reduced. there is a possibility. 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 the composition range of the above formulas (I) and (I ′), as the z and z ′ values are closer to the lower limit, which is a constant ratio, the battery tends to have lower rate characteristics and output characteristics. The closer the z and z ′ values are to the upper limit, the higher the rate characteristics and output characteristics of the battery, but there is a tendency for the capacity to decrease. In addition, the lower the y and y ′ values, that is, the smaller the manganese / nickel molar ratio (atomic ratio), the lower the charging voltage, but the lower the cycle characteristics and the safety of the battery with a higher charging voltage. On the contrary, as the y and y ′ values are closer to the upper limit, the cycle characteristics and safety of the battery set at a higher charge voltage improve, while the discharge capacity, rate characteristics, and output characteristics tend to decrease. It is done. Also, the closer the x and x ′ values are to the lower limit, the lower the load characteristics such as the rate characteristics and the output characteristics of the battery, and conversely, the closer the x and x ′ values are to the upper limit, However, if this upper limit is exceeded, cycle characteristics and safety when set at a high charge voltage will be reduced, and raw material costs will be increased. It is an important component of the present invention that the composition parameters x, x ', y, y', z, and z 'are within a specified range.

Here, the chemical meaning of the Li composition (z, z ′ and x, x ′) in the lithium nickel manganese cobalt composite oxide, which is a preferred composition of the lithium transition metal compound powder of the present invention, will be described in more detail below. explain.
As described above, the layered structure is not necessarily limited to the R (-3) m structure, but is preferably one that can be attributed to the R (-3) m structure from the viewpoint of electrochemical performance.

In order to obtain x, x ′, y, y ′, z, and z ′ of the composition formula of the lithium transition metal compound, each transition metal and Li are analyzed with an inductively coupled plasma emission spectrometer (ICP-AES). Thus, the ratio is calculated by determining the ratio of Li / Ni / Mn / Co.
From a structural point of view, it is considered that Li related to z and z ′ is substituted for the same transition metal site. Here, due to Li relating to z and z ′, the average valence of Ni becomes larger than divalent (trivalent Ni is generated) by the principle of charge neutrality. Since z and z ′ increase the Ni average valence, they are indicators of the Ni valence (the ratio of Ni (III)).

  When the Ni valence (m) accompanying the change of z and z ′ is calculated from the above composition formula, the Co valence is trivalent and the Mn valence is tetravalent, Become.

  This calculation result means that the Ni valence is not determined only by z and z ', but is a function of x, x' and y, y '. If z, z '= 0 and y, y' = 0, the Ni valence remains divalent regardless of the values of x, x '. When z and z ′ are negative values, it means that the amount of Li contained in the active material is less than the stoichiometric amount, and those having a very large negative value are effective for the present invention. It may not come out. On the other hand, even if the z and z ′ values are the same, the Ni valence increases as the composition is rich in Ni (y, y ′ values are large) and / or Co rich (large in x, x ′ values). This means that when used in a battery, 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 the upper and lower limits of the z and z 'values are more preferably defined as functions of x, x' and y, y '.

In addition, 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 was used as a lithium secondary battery designed to be charged at a high charging potential. In some cases, charge / discharge capacity, cycle characteristics, and safety are improved.
On the other hand, if the x ′ value is in the range of 0.10 <x ′ ≦ 0.35 and the amount of Co is relatively large, when used as a lithium secondary battery, the charge / discharge capacity, cycle characteristics, load characteristics, safety Improved in a balanced manner.

<Powder X-ray diffraction peak>
In the present invention, the lithium nickel manganese cobalt composite oxide powder having a composition satisfying the composition formulas (I) and (II) has a diffraction angle 2θ of 64.5 in a powder X-ray diffraction pattern using CuKα rays. When the half width of the (110) diffraction peak existing in the vicinity of ° is FWHM (110), it is preferably in the range of 0.1 ≦ FWHM (110) ≦ 0.3.

In general, since the half width of the X-ray diffraction peak is used as a measure of crystallinity, the present inventors have conducted intensive studies on the correlation between crystallinity and battery performance. As a result, it has been found that when the half-value width of the (110) diffraction peak having a diffraction angle 2θ of around 64.5 ° is within the specified range, good battery performance is exhibited.
In the present invention, the FWHM (110) is usually 0.01 or more, preferably 0.05 or more, more preferably 0.10 or more, still more preferably 0.12 or more, most preferably 0.14 or more, usually 0.3. Hereinafter, it is preferably 0.28 or less, more preferably 0.26 or less, further preferably 0.24 or less, and most preferably 0.22 or less.

In the present invention, the lithium nickel manganese cobalt based composite oxide powder having a composition satisfying the composition formulas (I) and (II) has a diffraction angle 2θ of 64 in powder X-ray diffraction measurement using CuKα rays. In the (018) diffraction peak existing at around 0 °, the (110) diffraction peak around 64.5 °, and the (113) diffraction peak around 68 °, a different phase is present on the higher angle side than the peak top. In the case of having no diffraction peak derived from or having a diffraction peak derived from a different phase, the integrated intensity ratio of the different phase peak to the diffraction peak of the original crystal phase is preferably in the following range, respectively.

0 ≦ I ₀₁₈ ^* / I ₀₁₈ ≦ 0.20 0 ≦ I ₁₁₀ ^* / I ₁₁₀ ≦ 0.25
0 ≦ I ₁₁₃ ^* / I ₁₁₃ ≦ 0.30 (where I ₀₁₈ , I ₁₁₀ , and I ₁₁₃ represent the integrated intensities of the diffraction peaks of (018), (110), and (113), respectively, and I ₀₁₈ ^* , (I ₁₁₀ ^* and I ₁₁₃ ^* represent the integrated intensities of the diffraction peaks derived from different phases appearing at higher angles than the peak tops of the (018), (110), and (113) diffraction peaks, respectively.)

By the way, although the details of the causative substance of the diffraction peak derived from this heterogeneous phase are not clear, when a heterogeneous phase is included, the capacity, rate characteristics, cycle characteristics, etc. when it is made into a battery are lowered. For this reason, the diffraction peak may have a diffraction peak that does not adversely affect the battery performance of the present invention, but is preferably a ratio in the above range, and the diffraction peak derived from a different phase with respect to each diffraction peak. The integrated intensity ratio is usually I ₀₁₈ ^* / I ₀₁₈ ≦ 0.20, I ₁₁₀ ^* / I ₁₁₀ ≦ 0.25, I ₁₁₃ ^* / I ₁₁₃ ≦ 0.30, preferably I ₀₁₈ ^* / I ₀₁₈ ≦ 0. 15, I ₁₁₀ ^* / I ₁₁₀ ≦ 0.20, I ₁₁₃ ^* / I ₁₁₃ ≦ 0.25, more preferably I ₀₁₈ ^* / I ₀₁₈ ≦ 0.10, I ₁₁₀ ^* / I ₁₁₀ ≦ 0.15, I ₁₁₃ ^* / _{I 113} ≦ 0.20, more preferably ^{_{I 018 * / I 018 ≦ 0.05}} , I 110 * / I 110 ≦ 0.10, an _{I 113 * / I 113 ≦ 0.15} , It is particularly preferred is also preferably no diffraction peaks derived from heterogeneous phases.

<Chemical adsorption points detected by AFM>
The lithium transition metal-based compound powder of the present invention desirably has many chemical adsorption points on the surface of the active material particles. The chemical adsorption point here is measured by the following method. First, by using AFM (Nanoscope III manufactured by Bruker AXS Co., Ltd.) using a probe chemically modified with polyacrylic acid, an arbitrary portion on the surface of the active material is 4 μm
Scan with an area of × 4 μm to obtain image data (height image and phase image). Probe modification is performed according to the following procedure. First, a probe made of silicon is left in a 0.1 wt% polyacrylic acid aqueous solution for 2 to 3 hours, and then the probe is taken out of the aqueous solution and air-dried for about one day, so that the polyacrylic acid is attached to the probe. Qualify. Further, scanning in AFM is performed under the following conditions. Image data is acquired with a scanning speed of 1 Hz and a number of observation points of 512 × 512 points.

Next, among the acquired image data, the phase image is subjected to flattening processing and automatic threshold extraction processing of chemical adsorption points using image analysis software ImageProPlus (manufactured by Media Cybernetics, Inc., Japan Roper) Count the number. (The flattening process mentioned here is a method in which a background image is created from an image and a background image is subtracted from the original image to smooth the background of the non-uniform image and make it flat. in adsorption point extraction method, the acquired image, bright concentration, the area is 1000nm ² ~20000nm ^2, a circularity of 0.0 to 3.0, an ellipse short length axis ratio of 1.0 The number of points on the image having an inhomogeneity of ~ 3.0 and a non-homogeneity of 0.05 to 1.0 was counted as a chemical adsorption point. Perform the flattening process and count the number of chemical adsorption points in the acquired and acquired images, find the average value of the counted number of chemical adsorption points, and use that value to determine the chemical state When the value is calculated, the value is preferably 10 or more because the binding strength with the conductive material or the binder is increased, more preferably 20 or more, and particularly preferably 30 or more. preferable.

[Method for producing lithium transition metal compound powder for positive electrode material of lithium secondary battery]
The method for producing the lithium transition metal compound powder of the present invention is not limited to a specific production method, but at least selected from lithium compounds and V, Cr, Mn, Fe, Co, Ni, and Cu. One or more transition metal compounds, additive 1 and additive 2 are pulverized in a liquid medium, and a slurry preparation step for obtaining a slurry in which these are uniformly dispersed, and spray for drying the obtained slurry It is preferably produced by the method for producing a lithium transition metal compound powder for a lithium secondary battery positive electrode material of the present invention comprising a drying step and a firing step of firing the resulting spray-dried product.

For example, a lithium nickel manganese cobalt composite oxide powder will be described as an example. A lithium compound, a nickel compound, a manganese compound, a cobalt compound, and a slurry in which additive 1 and additive 2 are dispersed in a liquid medium. A spray-dried product obtained by spray-drying can be produced by firing in an oxygen-containing gas atmosphere.
Hereinafter, the method for producing a lithium transition metal-based compound powder of the present invention will be described in detail by taking as an example the method for producing a lithium nickel manganese cobalt-based composite oxide powder which is a preferred embodiment of the present invention.

<Slurry preparation process>
Among the raw material compounds used in the preparation of the slurry in producing the lithium transition metal-based compound powder by the method of the present invention, the lithium compounds include Li ₂ CO ₃ , LiNO ₃ , LiNO ₂ , LiOH, LiOH · H _2. Examples include O, LiH, LiF, LiCl, LiBr, LiI, CH ₃ OOLi, Li ₂ O, Li ₂ SO ₄ , dicarboxylic acid Li, citric acid Li, fatty acid Li, and alkyl lithium. Among these lithium compounds, lithium compounds that do not contain nitrogen, sulfur, or halogen atoms are preferred because they do not generate harmful substances such as SO _x and NO _x during the firing treatment. It is a compound that easily forms voids by generating cracked gas in the secondary particles of the spray-dried powder by generating cracked gas. Taking these points into consideration, Li ₂ CO ₃ , LiOH, LiOH.H ₂ O is preferable, and Li ₂ CO ₃ is particularly preferable. 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 .BR> QH ₂ O, Ni (NO ₃ ) _{2 · 6H 2 O, NiSO 4,} NiSO 4 · 6H 2 O, fatty nickel, nickel halides 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, a decomposition gas is generated at the time of firing. 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.

  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.

The additive 1 is as described above. The additive 2 is as described above.
The method for mixing the raw materials is not particularly limited, and may be wet or dry. For example, the method of using apparatuses, such as a ball mill, a vibration mill, and a bead mill, is mentioned. 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, a ball mill (wet or dry) usually takes about 1 to 2 days, and a bead mill (wet continuous method) has 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 0.7 μm or less, preferably 0.6 μm or less, more preferably 0.55 μm or less, most preferably Preferably, it is 0.5 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 the cost of pulverization, so that the average particle size is usually 0.01 μm or more, preferably 0.02 μm or more, more preferably 0.05 μm or more. It ’s fine. A means for realizing such a degree of pulverization is not particularly limited, but a wet pulverization method is preferable. Specific examples include dyno mill.

  In 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>
After the wet mixing, it is then usually subjected to a drying process. The drying method is not particularly limited, but spray drying is preferable from the viewpoints of uniformity of the generated particulate matter, powder fluidity, powder handling performance, and efficient production of dry particles.
(Spray-dried powder)
In the method for producing a lithium transition metal-based compound powder such as lithium nickel manganese cobalt-based composite oxide powder of the present invention, a slurry obtained by wet-grinding a raw material compound, additive 1 and additive 2 is sprayed. By drying, a powder obtained by agglomerating primary particles to form secondary particles is obtained. The spray-dried powder formed by agglomerating primary particles to form secondary particles is a geometric 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 firing precursor of lithium transition metal based compound powder such as lithium nickel manganese cobalt based composite oxide powder of the present invention (in this case, measured without applying ultrasonic dispersion) The value is usually 25 μm or less, more preferably 20 μm or less, still more preferably 18 μm or less, and most preferably 16 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 4 μm or more, more preferably 5 μm or more. In the case of producing a particulate material by the spray drying method, the particle size can be controlled by appropriately selecting the spray format, the pressurized gas flow supply rate, the slurry supply rate, the drying temperature, and the like.

  That is, for example, a lithium compound, a nickel compound, a manganese compound, and a slurry in which a cobalt compound, additive 1 and additive 2 are dispersed in a liquid medium are spray-dried, and the obtained powder is fired to obtain lithium nickel. In producing the manganese cobalt-based composite oxide powder, 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), Spray drying is performed under conditions where the slurry viscosity V is 50 cp ≦ V ≦ 10000 cp and the gas-liquid ratio G / S is 500 ≦ G / S ≦ 10000.

  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 10000 cp or less, preferably 7500 cp or less, more preferably. Is 6500 cp or less, most preferably 6000 cp or less.

  Further, when the gas-liquid ratio G / S is lower than the lower limit, the secondary particle size is coarsened or the drying property is liable to be lowered. When the upper limit is exceeded, the productivity may be lowered. Therefore, the gas-liquid ratio G / S is usually 400 or more as a lower limit, preferably 600 or more, more preferably 700 or more, most preferably 800 or more, and the upper limit is usually 10,000 or less, preferably 9000 or less, Preferably it is 8000 or less, most preferably 7500 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.
In the method of the present invention, the above-mentioned gas-liquid ratio G / S is satisfied by controlling the slurry supply amount and gas supply amount that meet the above-mentioned slurry viscosity V (cp) and that are suitable for the specifications of the spray drying apparatus to be used. Spray drying may be performed within a range, and other conditions are appropriately set according to the type of apparatus to be used, but it is preferable to select the following conditions.

  That is, 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 230. It is preferable to carry out the reaction at a temperature of ℃ or less, most preferably 210 ℃ or less. 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.

<Baking process>
The fired precursor thus obtained 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, primary particles grow excessively, sintering between the particles proceeds too much, and the specific surface area becomes small. Pass. On the other hand, if it is too low, heterogeneous phases are mixed, and the lattice distortion increases without developing the crystal structure. Moreover, the specific surface area becomes too large. The firing temperature is usually 1050 ° C. or higher, preferably 1060 ° C. or higher, more preferably 1070 ° C. or higher, further preferably 1080 ° C. or higher, most preferably 1090 ° C. or higher, and the upper limit is 1200 ° C. or lower, preferably 1190 ° C. or lower. More preferably, it is 1180 ° C. or less, and most preferably 1170 ° 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.

  When firing is performed in two stages, the first stage is preferably maintained at a temperature not lower than the temperature at which the Li raw material begins to decompose and below the melting temperature. For example, when lithium carbonate is used, the first stage is preferably maintained at 400 ° C. or higher. More preferably, it is 450 ° C. or higher, more preferably 500 ° C. or higher, most preferably 550 ° C. or higher, usually 850 ° C. or lower, more preferably 800 ° C. or lower, more preferably 780 ° C. or lower, most preferably 750 ° C. or lower. is there.

  In the temperature raising step leading to the maximum temperature holding step, the temperature in the furnace is usually raised at a temperature raising rate of 1 ° C./min to 15 ° 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 heating rate is preferably 2 ° C./min or more, more preferably 3 ° C./min or more, preferably 10 ° C./min or less, more preferably 8 ° 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, most preferably 3 hours or longer within the above-mentioned temperature range. Time 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 transition metal-based compound powder with 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 usually decreased at a temperature decreasing rate of 0.1 ° C./min to 15 ° 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 10 ° C./min or less, more preferably 8 ° C./min or less.

Since the firing atmosphere has an appropriate oxygen partial pressure region depending on the composition of the lithium transition metal-based compound powder to be obtained, appropriate various 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 transition metal-based compound powder of the present invention, for example, the lithium nickel manganese cobalt-based composite oxide powder having the specific composition, the production conditions are constant. When preparing a slurry in which a lithium compound, a nickel compound, a manganese compound, and a cobalt compound, and additive 1 and additive 2 are dispersed in a liquid medium, by adjusting the mixing ratio of each compound, It is possible to control the molar ratio of Li / Ni / Mn / Co.
According to the lithium transition metal-based compound powder of the present invention such as lithium nickel manganese cobalt-based composite oxide powder thus obtained, the capacity is high, the low-temperature output characteristics and the storage characteristics are excellent, and the performance balance is high. A positive electrode material for a lithium secondary battery is provided.

[Conductive material]
Conventionally known carbonaceous materials as conductive materials such as carbon black increase the amount of dehydrogenation when trying to increase the nitrogen adsorption specific surface area, and conversely when trying to keep the dehydrogenation amount low. Therefore, the 24M4DBP absorption amount is also reduced, and it is difficult to improve the life while increasing the conductivity of the conductive material itself.
In the present invention, by adjusting the production conditions of carbon black and achieving the above-mentioned range of nitrogen adsorption specific surface area and 24M4DBP absorption amount, the conductivity can be increased to cope with high output, and electrochemical A positive electrode with a long life, and thus a lithium secondary battery with high output and long life is realized.
Below, the physical property parameter of the electrically conductive material in this invention is demonstrated.

<Nitrogen adsorption specific surface area _(N 2 SA)>
The nitrogen adsorption specific surface area (N ₂ SA) is defined based on JIS K6217 (unit: m ² / g).
Regarding the nitrogen adsorption specific surface area (N ₂ SA) of carbon black used in the present invention, the lower limit is usually 70 m ² / g or more, preferably 80 m ² / g or more, more preferably 100 m ² / g or more, More preferably, it is 150 m < ² > / g or more. The upper limit is usually 300 m ² / g or less, preferably 290 m ² / g or less, more preferably 280 m ² / g or less.

In order to secure a conductive path between the active materials in the positive electrode of the lithium secondary battery and to obtain performance at high output, it is preferable that the specific surface area of the conductive material is large. On the other hand, if the specific surface area is too large, there may be a problem in forming the positive electrode, an irreversible reaction due to an electrochemical side reaction or the like tends to occur, and the life may be shortened.
Therefore, the nitrogen adsorption specific surface area (N ₂ SA) of carbon black as the conductive material is preferably within the above range.

<Average particle size>
In addition, the average particle diameter in this invention is an average diameter observed with the scanning electron microscope (SEM).
The average particle size of the carbon black of the present invention has a lower limit of 10 nm or more, preferably 12 nm or more, particularly preferably 15 nm or more, and an upper limit of 35 nm or less, preferably 33 nm or less, particularly preferably 31 nm or less. If this average particle size is too small, the solid content concentration becomes low during dispersion in the positive electrode slurry, and a large amount of solvent is required during slurry adjustment. On the other hand, if it is too large, the adhesion to the positive electrode active material may decrease.

<Volatile matter>
The lower limit of the volatile content of carbon black as the conductive material of the present invention is usually 0.8% or more, preferably 0.9% or more, particularly preferably 1.0% or more, and the upper limit is usually 5% or less. , Preferably 4% or less, particularly preferably 3% or less. If the volatile content is too small, the interaction with the active material is small, and the adhesion between the conductive material and the active material may be insufficient. On the other hand, if it is too large, the stability of the slurry at the time of producing the positive electrode is insufficient, and disadvantages such as the tendency of the slurry to easily aggregate may occur.

<24M4 DBP absorption and DBP absorption>
DBP absorption amount is an amount that is defined in conformity with JIS K6217 (unit ^cm 3 / 100g).
24M4DBP absorption is the DBP absorption is another parameter, in compliance with DBP absorption as well as JIS K6217, a DBP absorption amount of the compression sample (units also ^cm 3 / 100g).

Carbon black in the present invention, 24M4DBP absorption is generally 100 cm ^3/100 g or more, preferably 105 cm ^3/100 g, more preferably not less than 110 cm ^3/100 g.
If the amount of 24M4DBP absorption is less than the above lower limit, the structure is easily broken due to stress at the time of positive electrode creation, cycle or stress at the time of storage. The path may be broken and the life may be reduced. The upper limit of the 24M4DBP absorption is not particularly limited, in terms of the positive electrode creating readiness in handling, usually less than 200 cm ^3/100 g.

  In general, carbon black forms secondary particles composed of a chain called a unique structure (aggregate structure) in which primary particles are arranged in a kitchen shape. Therefore, it is preferable that the carbon black has a developed structure because it is easy to secure a conductive path. Further, the conductivity is improved by reducing the primary particle size of carbon black. Furthermore, the conductivity is improved by reducing the amount of functional groups (oxygen compounds) on the surfaces of the primary particles of carbon black.

Since DBP (dibutyl phthalate) is absorbed in the voids of the kitchen chain structure of the carbon black structure, the 24M4 DBP absorption amount and DBP absorption amount are important index values indicating the degree of structure development of the carbon black. is there.
Unlike normal DBP absorption by absorbing DBP while carbon black is intact, 24M4 DBP absorption is measured by absorbing DBP after stressing carbon black and breaking easily broken parts. It is. When carbon black is used for the positive electrode, the carbon black is usually subjected to various stresses during the mixing process with the active material and during the molding of the positive electrode. Therefore, the 24M4DBP absorption is more important than the DBP absorption to show the carbon black structure. it is conceivable that.

The amount of 24M4DBP absorbed by carbon black correlates with the amount of effective structure that forms a conductive path in the positive electrode, so it correlates with the improvement of the battery, and the cycle characteristics and storage characteristics of the lithium secondary battery. Therefore, it is considered to represent the abundance of a structure that is not easily destroyed even when the active material or the positive electrode expands or contracts. That is, it is considered that these electrochemical characteristics are difficult to extract unless the 24M4DBP absorption amount is large to some extent.
For this reason, in the present invention, the 24M4DBP absorption amount of carbon black is set to be equal to or greater than the predetermined value.

<(1500 ° C. × 30 minutes) Dehydrogenation amount>
(1500 ° C. × 30 minutes) The amount of dehydrogenation is the amount of hydrogen in the gas generated during heating of carbon black at 1500 ° C. for 30 minutes in a vacuum, and is specifically measured as described below. The
The amount of dehydrogenation of carbon black (hereinafter also simply referred to as “carbon black”), which is a conductive material in the present invention, is usually 1.8 mg / g or less, preferably 1.7 mg / g or less, more preferably 1.6 mg. / G or less is preferable.

  The amount of dehydrogenation is greatly related to the thermal history received by the carbon black. If the heat treatment is insufficient, a large amount of hydrogen remains, which is considered to be largely related to conductivity. In the case of a large amount of dehydrogenation, carbonization on the surface of carbon black has not progressed, so that the conductivity cannot be improved in the electrode, and it is considered that an output cannot be obtained. In addition, when used in a battery, it also affects the electrochemical stability and is considered to influence the life. From these facts, it is generally considered that a smaller amount of dehydrogenation of carbon black is preferable. However, since it will lead to the cost increase at the time of manufacturing industrially when too small, generally it is 0.1 mg / g or more normally, More preferably, 0.3 mg / g or more is good.

(Measurement method)
About 0.5g of carbon black is precisely weighed, put in an alumina tube, depressurized to 0.01 Torr (1.3 Pa), then the decompression system is closed, and it is kept in an electric furnace at 1500 ° C. for 30 minutes. Decomposes and volatilizes oxygen and hydrogen compounds. Volatile components are collected in a fixed-capacity gas collection tube through a quantitative suction pump. The amount of gas is determined from the pressure and temperature, the composition is analyzed by gas chromatography, the amount of hydrogen (H ₂ ) generated (mg) is determined, and the value converted to the amount of hydrogen per gram of carbon black is calculated (the unit is mg / g).

<Crystallite size Lc>
The carbon black used in the present invention has a lower limit of the crystallite size Lc of 10 mm or more, more preferably 13 mm or more, and an upper limit of 40 mm or less, preferably 25 mm or less, and more preferably 17 mm or less. In carbon black, the conductivity of the positive electrode can be maximized by setting the crystallite size Lc within this specific range. If this value is too large or too low, sufficient conductivity may not be obtained.

  The crystallite size Lc according to the present invention is measured using an X-ray diffractometer (RINT-1500 type, manufactured by Rigaku Corporation). The measurement conditions are such that Cu is used for the tube, tube voltage is 40 KV, and tube current is 250 mA. The carbon black sample is filled in a sample plate attached to the apparatus, the measurement angle (2θ) is 10 ° to 60 °, the measurement speed is 0.5 ° / min, and the peak position and half width are calculated by the software of the apparatus. Further, silicon for X-ray standard is used for calibration of the measurement angle. Using the results thus obtained, Scherrer's formula; (Lc (ｃ) = K × λ / (β × cos θ) (where K: form factor constant 0.9, λ: wavelength of characteristic X-ray CuKα 1.5418 (Å), β: half width (radian), θ: peak position (degrees))).

  In the present invention, carbon black having a Dmod / 24M4DBP in the range of 0.6 to 0.9 is more preferable. As described above, carbon black is composed of secondary particles (aggregates) in which a plurality of primary particles are connected, and 24M4DBP absorption is used as an indicator of the degree of development of the aggregate structure (structure). As another index for measuring the characteristics of carbon black, the Stokes diameter is known. The Stokes diameter is generally a diameter (mode diameter; Dmod) obtained by centrifugal sedimentation (DCP) on the assumption that a carbon black aggregate is a pseudosphere according to Stokes' law, and a distribution index of Dmod. The half-width of Dmod (D1 / 2) is used.

Conventionally, using these indices, their ratio (D1 / 2 / Dmod), and other physical property values as the physical property indices of carbon black, improvements in the physical properties and processability of carbon black itself, rubber, and resin compositions have been made. I came. However, conventionally, these numerical values are only evaluated individually, and the characteristics of carbon black have not been sufficiently grasped. For example, since only the Stokes mode diameter (Dmod) of carbon black does not uniquely determine the development of its structure, there is a difference in conductivity even when the carbon black has the same Dmod. There has been a problem that the carbon black added to is not sufficiently improved.

  Therefore, as a result of intensive studies by the present inventors, carbon black whose Dmod is in a specific numerical range with respect to the amount of 24M4DBP absorption indicating the degree of structure development, that is, carbon black whose Dmod / 24M4DBP value is in a specific range. It has been found that a conductive resin composition having an extremely excellent balance between conductivity and fluidity can be realized by using it as a filler of a conductive resin composition.

  The numerical value shown by Dmod / 24M4DBP indicates the size of the aggregate diameter with respect to the degree of carbon black structure development. The lower this value, that is, the higher the degree of development of the structure with respect to the aggregate size of the same size, the more dense the carbon black primary particles are. If this value is too low, the fluidity of the resin composition may decrease due to a decrease in familiarity with the resin, and the conductivity of the resin composition may decrease due to a decrease in the dispersibility of carbon black in the resin composition. Conversely, if it is too high, the conductivity of the carbon black itself will decrease, and the mechanical properties of the resin composition will decrease due to an increase in the amount of carbon black added to the conductive resin composition to give the desired conductivity. There is a case. Therefore, in the carbon black of the present invention, it is preferable that Dmod / 24M4DBP is 0.6 or more and 0.9 or less.

  Furthermore, the carbon black of the present invention preferably has a narrow aggregate diameter distribution with respect to the degree of structure development. Specifically, it is preferable that the numerical value indicated by the ratio (D1 / 2 / 24M4DBP) of the Stokes mode half width (D1 / 2) to the 24M4DBP absorption amount is smaller. If this value is too high, the conductivity of the carbon black itself will decrease, and the mechanical properties of the resin composition will decrease due to the increase in the amount of carbon black added to the conductive resin composition to give the desired conductivity. There is a case. Therefore, D1 / 2 / 24M4DBP in the carbon black of the present invention is preferably 0.9 or less. The lower limit is not particularly limited, but is preferably 0.45 or more for reasons such as production economics.

Furthermore, in the present invention, the CTAB adsorption specific surface area of the carbon black is preferably 120 to 220 m ² / g, particularly 150 to ²⁰⁰ m ² / g. By setting this specific range, both the electrical conductivity and fluidity of the resin composition can be further enhanced. If the CTAB specific surface area is too small, the conductivity may be reduced, whereas if too large, the dispersibility in the resin composition may be reduced.

In addition to the above, in the present invention, the oxygen-containing functional group density defined by the following formula is preferably 3 μmol / m ² or less.
Oxygen-containing functional group density (μmol / m ² )
= [CO generation amount (μmol / g) + CO ₂ generation amount (μmol / g)] / Nitrogen adsorption specific surface area (m ² / g)

Here, this numerical value will be described. Carbon black has a certain amount of surface functional groups. When heated, carbon monoxide (CO) / carbon dioxide (CO ₂ ) is generated. For example, if a carbonyl group (ketone, quinone, etc.) is present, CO is mainly generated by decomposition, and if a carboxyl group and derivatives thereof (ester, lactone, etc.) are present, CO ₂ is similarly generated. That is, the amount of functional groups present on the surface of carbon black can be estimated by determining the amount of gas generated. On the other hand, it is conventionally known that a small amount of these functional groups is desirable for improving the conductivity of carbon black. However, numerical values based on the amount of gas generated per weight of carbon black have been conventionally used for these functional groups. In other words, it has been a conventional wisdom that the amount of functional groups relative to the weight of carbon black affects the conductivity.

On the other hand, as a result of further intensive studies, the present inventors have determined that the amount of these functional groups is not a numerical value per unit weight of carbon black, but rather a unit per unit surface area. Has been found to be effective in achieving both the electrical conductivity of the resin composition, and thus the electrical conductivity and fluidity.
Although the details of the reason are not clear, when an electric current flows through the resin composition, the functional group localized on the surface of the carbon black inhibits the electron transfer between the carbon black secondary particles. It is considered that the number per unit surface area (concentration) affects the conductivity rather than the amount.

That is, since the oxygen-containing functional group density indicates the number of functional groups per unit surface area of carbon black, this value is preferably low. When this numerical value is high, the conductivity of the resin composition containing carbon black decreases due to such a reason. Note that the lower the value, the better from the viewpoint of conductivity. However, if the value is too low, as described above, the dispersibility may be lowered and the conductivity and fluidity may be deteriorated. It is disadvantageous for reasons such as industrial economy. Therefore, the oxygen-containing functional group density is preferably 0.1 μmol / m ² or more.

<Manufacturing method>
The method for producing carbon black as the conductive material of the present invention is arbitrary, and examples thereof include ketjen black by an oil furnace method, an acetylene method, and an activation method. Among these, the oil furnace method is preferable because it can be manufactured at low cost and with high yield.
A specific method for synthesizing carbon black having the above specific physical properties is as described in Japanese Patent Application Laid-Open No. 2006-52237.

  An apparatus for producing carbon black by an oil furnace method is installed following a first reaction zone for burning a fuel to generate a high-temperature combustion gas flow, and a carbon black raw material hydrocarbon (hereinafter referred to as “oil”). A second reaction zone for introducing a carbon black production reaction and a cooling means for stopping the carbon black production reaction, which is subsequently installed in the second reaction zone. Reaction zone.

In order to produce carbon black by this carbon black production apparatus, a high-temperature combustion gas flow is generated in the first reaction zone, and carbon black raw material hydrocarbon (oil) is sprayed in the second reaction zone. Carbon black is produced in the reaction zone. The gas stream containing carbon black is introduced into the third reaction zone, and is rapidly cooled by receiving water spray from the spray nozzle in the third reaction zone. The gas stream containing carbon black in the third reaction zone is then introduced into a collecting means such as a cyclone or a bag filter via a flue to collect the carbon black.
Oil furnace carbon black can be manufactured by controlling the design and manufacturing conditions of such a manufacturing apparatus, the physical properties can be controlled relatively easily, and when used for the positive electrode of a lithium secondary battery. It is more advantageous than other conductive materials in terms of physical property design.

For example, by adjusting the position of the carbon black raw material introduction nozzle in the second reaction zone described above and the position of the cooling water supply nozzle in the third reaction zone to make the carbon black residence time in the furnace a specific range, As described above, the carbon black 24M4DBP absorption amount and specific surface area are within a specific range, the crystallite size Lc is not excessively increased to a specific small value, and the dehydrogenation of the carbon black particle surface has progressed. That's fine. More specifically, the furnace temperature is usually 1500 ° C. to 2000 ° C., preferably 1600 ° C. to 1800 ° C., and the residence time of carbon black in the furnace, that is, the time required to move from the raw material introduction point to the reaction stop position ( The time required for moving the carbon black raw material introduction position distance and the reaction stop position distance) is usually 40 milliseconds to 500 milliseconds, preferably 50 milliseconds to 200 milliseconds. Further, in the case where the temperature in the furnace is lower than 1500 ° C., the residence time in the furnace exceeds 500 milliseconds and is 5 seconds or less, preferably 1 to 3 seconds.

  Since the carbon black according to the present invention has a particularly small amount of dehydrogenation, its production is carried out by a method in which the temperature of the high-temperature combustion gas flow in the furnace is set to a high temperature of 1700 ° C. or more, or downstream of the carbon black raw material supply nozzle. Further, it is preferable to introduce oxygen into the furnace to burn hydrogen or the like on the surface of the carbon black and to extend the residence time at a high temperature with this reaction heat. Such a method is preferable because crystallization in the vicinity of the surface of the carbon black and dehydrogenation inside the carbon black can be effectively performed.

[Method of making positive electrode]
The positive electrode active material layer is usually pressure-bonded to a positive electrode current collector obtained by mixing a positive electrode material used in the present invention, a conductive material used in the present invention, a binder and a thickener in a dry form into a sheet. 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.

<Mixing ratio of positive electrode active material and conductive material>
The mixing ratio of the positive electrode active material and the conductive material of the present invention (= the mass of the conductive material / the mass of the positive electrode active material) is usually 0.1% or more, preferably 0.5% or more, more preferably 1% or more, It is particularly preferably 1.5% or more, usually 20% or less, preferably 18% or less, more preferably 15% or less, and particularly preferably 10% or less. This range is preferable because a sufficient conductive path can be secured while maintaining the charge / discharge capacity.

[Binder]
The binder used for manufacturing the positive electrode active material layer is not particularly limited, and in the case of a coating method, any material that dissolves or disperses in the liquid medium used at the time of manufacturing the positive electrode may be used. , Polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitrocellulose, and other resin polymers, SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluorine rubber, isoprene rubber, butadiene Rubber, rubbery polymer such as ethylene / propylene rubber, styrene / butadiene / styrene block copolymer and its hydrogenated product, EPDM (ethylene-propylene-diene terpolymer), styrene / ethylene / butadiene / ethylene copolymer Polymer, styrene / isopre Thermoplastic elastomeric polymers such as styrene block copolymers and hydrogenated products thereof, syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymers, propylene / α-olefin copolymers, etc. Fluorine polymers such as soft resinous polymers, polyvinylidene fluoride (PVdF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymers, alkali metal ions (especially lithium ions) Examples thereof include a polymer composition having ion conductivity. 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 lower limit of the weight average molecular weight of the binder of the present invention is usually preferably 200,000 or more, more preferably 250,000 or more, more preferably 270,000 or more, and 280,000 or more. Most preferably it is. Further, if the weight average molecular weight is too large, the slurry becomes unstable at the time of producing the positive electrode. Therefore, the upper limit is usually preferably 600,000 or less, more preferably 550,000 or less, and more preferably 500,000 or less. More preferably, it is most preferably 450,000 or less.

  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 3% 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. On the other hand, if it is too high, the battery capacity and the conductivity may be reduced.

<Conductive material>
The above-mentioned carbon black is used as the conductive material, but in combination with it, there is no metal material such as copper or nickel, graphite such as natural graphite or artificial graphite, carbon black such as acetylene black, needle coke, etc. One or more carbon materials such as regular carbon may be used in combination.
In order to sufficiently obtain the effect of the carbon black according to the present invention, when the conductive material includes a conductive material other than the carbon black described above, the ratio is preferably 90% by weight or less of the total conductive material amount. .

[Combination of conductive material and binder]
The positive electrode of the present invention satisfies the following formula (1) when the nitrogen adsorption specific surface area (N ₂ SA, unit: m ² / g) of the conductive material is S and the weight average molecular weight of the binder is M. It is characterized by that.

(S × M) / 10000 ≦ 7500 (1)
The lower limit of (S × M) / 10000 is preferably 1500 or more, more preferably 1700 or more, and more preferably 1900 or more because the electrode plate strength of the positive electrode needs to be sufficiently maintained. More preferably, it is most preferably 1930 or more. Moreover, since it is necessary to ensure sufficient slurry stability at the time of producing the positive electrode, the upper limit is usually 7500 or less, more preferably 7300 or less, and more preferably 7100 or less. Preferably, it is most preferably 7000 or less.

<Liquid medium>
As a liquid medium for forming the slurry, a lithium nickel composite oxide powder, which is a positive electrode active material, a conductive material, a binder, and a thickener used as necessary may be dissolved or dispersed. As long as it is a possible solvent, the type is not particularly limited, and either an aqueous solvent or an organic solvent may be used. Examples of the aqueous solvent include water and alcohol. Examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N -N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran (THF), toluene, acetone, dimethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, etc. Can be mentioned. In particular, when an aqueous solvent is used, it is preferable to add a dispersant in addition to the thickener and make a slurry using a latex such as SBR.
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.

<Current collector>
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. Etc. Among these, metal thin films are preferable because they are currently used in industrialized products. In addition, you may form a thin film suitably in mesh shape.

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

  The content of the lithium transition metal-based compound powder of the present invention as the positive electrode material in the positive electrode active material layer is usually 10% by weight or more, preferably 30% by weight or more, more preferably 50% by weight or more, and usually 99%. .9% by weight or less, preferably 99% by weight or less. If the proportion of the lithium transition metal compound powder in the positive electrode active material layer is too large, the strength of the positive electrode tends to be insufficient, and if it is too small, the capacity may be insufficient.

The thickness of the positive electrode active material layer is usually about 10 to 200 μm.
As the electrode density after pressing of the positive electrode, the lower limit is usually 2.2 g / cm ³ or more, preferably 2.4 g / cm ³ or more, particularly preferably 2.6 g / cm ³ or more, and the upper limit is usually , 4.2 g / cm ³ or less, preferably 4.0 g / cm ³ or less, particularly preferably 3.8 g / cm ³ or less.
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 can be prepared.

<Reason why the positive electrode of the present invention provides the above-mentioned effect>
The reason why the positive electrode of the present invention brings about the above-described effect is presumed as follows.
When the conductive material used in the present invention is mixed with an active material and slurried in a solvent using a normal molecular weight binder, gelation occurs.
On the other hand, if it is the combination of the binder used for this invention and an electrically conductive material, gelatinization when it is set as a positive electrode slurry can be prevented. Although it is not yet clear as a reason which can prevent gelation, it is guessed as follows. That is, when a conductive material having a large nitrogen adsorption specific surface area, a small average particle diameter, or a large amount of volatile matter is used, the amount of moisture brought into the positive electrode slurry from the conductive material increases, and therefore, NMP contained in the positive electrode slurry, etc. The solubility of the binder in the organic solvent is reduced. At this time, if the molecular weight of the binder is high, sufficient solubility in the organic solvent is not ensured, and the binder is precipitated or crystallized, thereby causing a decrease in pot life such as aggregation of slurry. In addition, the reaction area increases due to the large nitrogen adsorption specific surface area of the conductive material and the average particle size is small, or even if the reaction area is similar, the conductive material and the binder are chemically separated due to the high volatile content. The bonding reaction is promoted and the positive electrode slurry is likely to be aggregated. At this time, if the molecular weight of the binder is high, the dispersion in the slurry is easily hindered even if the number of bonding points with the conductive material is small, so that the pot life is reduced. In order to solve these problems, when using a conductive material having a large nitrogen adsorption specific surface area, a small average particle diameter, or a large amount of volatile matter, a low molecular weight within a range that can sufficiently ensure the electrode plate strength of the positive electrode. By using the binder, the stability of the positive electrode slurry can be improved.

[Negative electrode for lithium secondary battery]
Next, the negative electrode for lithium secondary batteries among the positive electrodes for lithium secondary batteries of this invention is demonstrated.
The negative electrode for a lithium secondary battery in the present invention is usually constituted by forming a negative electrode active material layer on a negative electrode current collector, similarly to the above-described positive electrode for a lithium secondary battery.

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

<Active material>
The negative electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions, but it can usually occlude and release lithium from the viewpoint of high safety. A carbon material is used.
Although there is no restriction | limiting in particular as a carbon material, Graphite (graphite), such as artificial graphite and natural graphite, and the thermal decomposition thing of organic substance on various thermal decomposition conditions are mentioned. Examples of pyrolysis products of organic matter include coal-based coke, petroleum-based coke, coal-based pitch carbide, petroleum-based pitch carbide, or carbide obtained by oxidizing these pitches, needle coke, pitch coke, phenol resin, crystalline cellulose, etc. And carbon materials obtained by partially graphitizing these, pitch-based carbon fibers, and the like. Among them, graphite is preferable, and particularly preferable is artificial graphite, purified natural graphite, or graphite material containing pitch in these graphites, which is manufactured by subjecting easy-graphite pitch obtained from various raw materials to high-temperature heat treatment. Therefore, those subjected to various surface treatments are mainly used. One of these carbon materials may be used alone, or two or more thereof may be used in combination.

When a graphite material is used as the negative electrode active material, the d value (interlayer distance) of the lattice plane (002 plane) obtained by X-ray diffraction by the Gakushin method is usually 0.335 nm or more, and usually 0.340 nm or less, particularly What is 0.337 nm or less is preferable.
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, it is detected in the range of 1350 ^-1 that intensity ratio _I a / _{I B} of the intensity _{I B} of a peak _{P B} is what is preferably 0 to 0.5. Further, the half width of the peak _{P A} is preferably 26cm ^-1 or less, 25 cm ^-1 or less is more preferable.

  In addition to the various carbon materials described above, other materials capable of inserting and extracting lithium can be used as the negative electrode active material. Specific examples of the negative electrode active material other than the carbon material include elements such as tin and silicon that form an alloy with lithium and a compound thereof, and lithium alloys such as lithium simple substance and lithium aluminum alloy. 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.

<Current collector>
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.

[Lithium secondary battery]
Next, the lithium secondary battery of the present invention will be described.
The lithium secondary battery includes a positive electrode, a negative electrode, and a non-aqueous electrolyte using a lithium salt as an electrolytic salt, and the positive electrode is the above-described positive electrode for a lithium secondary battery of the present invention.
The lithium secondary battery of the present invention may further include a separator that holds the nonaqueous electrolyte between the positive electrode and the negative electrode. In order to effectively prevent a short circuit due to contact between the positive electrode and the negative electrode, it is desirable to interpose a separator in this way.
The lithium secondary battery of the present invention is usually produced by assembling the above-described positive electrode and / or negative electrode for the lithium secondary battery of the present invention, 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.

<Electrolytes>
As the electrolyte, for example, known organic electrolytes, polymer solid electrolytes, gel electrolytes, inorganic solid electrolytes, and the like can be used. Among them, organic electrolytes are preferable. The organic electrolytic solution is configured by dissolving a solute (electrolyte) in an organic solvent.
Here, the type of the organic solvent is not particularly limited. For example, carbonates, ethers, ketones, sulfolane compounds, lactones, nitriles, chlorinated hydrocarbons, amines, esters, amides, phosphoric acid An ester compound or the like can be used. Typical examples are dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, ethylene carbonate, vinylene carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 4-methyl-2-pentanone, 1, 2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile, benzonitrile, Examples include butyronitrile, valeronitrile, 1,2-dichloroethane, dimethylformamide, dimethyl sulfoxide, trimethyl phosphate, triethyl phosphate, and the like alone or in combination. 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 electrolytic solution is preferably 10% by weight or more, more preferably 20% 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.

The type of the electrolytic salt is not particularly limited, and any conventionally known solute can be used. Specific examples include LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , LiCl, LiBr, CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, LiN (SO ₂ CF ₃ ) _2. , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , LiN (SO ₃ CF ₃ ) _{2 and the} like. Any one of these electrolytic salts may be used alone, or two or more thereof may be used in any combination and ratio.

The lithium salt of the electrolytic salt is usually contained in the electrolytic solution so as to be 0.5 mol / L or more and 1.5 mol / L or less. Even if this concentration 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. In particular, the lower limit is preferably 0.75 mol / L or more and the upper limit is 1.25 mol / L or less.
In addition, the electrolytic solution is good for enabling efficient charge and discharge of lithium ions on the negative electrode surface such as gas such as vinylene carbonate, vinyl ethylene carbonate, CO ₂ , N ₂ O, CO, SO ₂ , and polysulfide S _x ²⁻ A small amount of an additive for forming a thick film may be added.

Furthermore, in organic electrolytes, additives such as lithium difluorophosphate that are effective in improving cycle life and output characteristics, and additives that are effective in suppressing high-temperature storage gases such as propane sultone and propene sultone May be added at an arbitrary ratio.
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.

<shape>
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.

<Charge potential of the positive electrode when fully charged>
In the following examples, the lithium secondary battery of the present invention is used at a charging potential of the positive electrode in a fully charged state of less than 4.4 V, but becomes 4.4 V (vs. Li ^/ Li ⁺ ) or more. It is also possible to use with a battery that is designed in such a way. That is, even when the lithium nickel manganese cobalt based composite oxide powder for a lithium secondary battery positive electrode material of the present invention is used as a lithium secondary battery designed to be charged at a high charging potential, the effect of the present invention is achieved. Should be effective.
The general embodiment of the lithium secondary battery of the present invention has been described above. However, the lithium secondary battery of the present invention is not limited to the above-described embodiment, and various modifications are possible as long as the gist thereof is not exceeded. Can be implemented.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
[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.

[Active material]
[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)>
It was determined by ICP-AES analysis.

<Quantification of additive elements (Mo, W, Nb, B, Sn)>
It was determined by ICP-AES analysis.
<Composition analysis of primary particle surface by X-ray photoelectron spectroscopy (XPS)>
The measurement was performed under the following conditions using an X-ray photoelectron spectrometer “ESCA-5700” manufactured by Physical Electronics.

X-ray source: Monochromatic AlKα
Analysis area: 0.8mm diameter
Extraction angle: 65 °
Determination _{method: Bls, Mn2p 1/2, Co2p 3/2} , Ni2p 3/2, corrected sensitivity coefficient and the area of W4f each peak.

<Median diameter of secondary particles and d50>
Using a known laser diffraction / scattering particle size distribution measuring apparatus, the refractive index was set to 1.60a-0.10i, and the particle diameter standard was measured as the volume standard. The dispersion medium is 0.1% by weight.
Measurement was performed using a sodium hexametaphosphate aqueous solution. Note that ultrasonic dispersion is not performed.

<Average primary particle size>
It calculated | required from the SEM image of 30,000 times.
<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.
<Volume resistivity>
Using a powder resistivity measurement device (Dia Instruments: Lorester GP powder low efficiency measurement system PD-41), the sample weight is 3 g, and a powder probe unit (four probe / ring electrode, electrode spacing 5.0 mm) The electrode resistivity is 1.0 mm, the sample radius is 12.5 mm, and the applied voltage limiter is 90 V. The volume resistivity [Ω · cm] of the powder under various pressures is measured, and the volume resistivity under a pressure of 40 MPa is measured. The values were compared.

<Surface enhanced Raman spectrum (SERS) measurement>
Apparatus: Nicolet Almega XR manufactured by Thermo Fisher Scientific
Pretreatment: Silver deposition (10nm)
Excitation wavelength: 532 nm
Excitation output: 0.1 mW or less at sample position
Analysis method: Measure the height and half-value width excluding the linear background from each peak
Spectral resolution: 10 cm ⁻¹

<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. Further, a 0.1 wt% aqueous solution of sodium hexametaphosphate was used as a dispersion medium, and measurement was performed after 5 minutes of ultrasonic dispersion (output 30 W, frequency 22.5 kHz).

<Median Diameter as Average Particle Diameter of Raw Material Li ₂ CO ₃ Powder>
Using a known laser diffraction / scattering particle size distribution measuring apparatus (LA-920, manufactured by Horiba, Ltd.), the refractive index was set to 1.24, and the particle diameter standard was measured as a volume standard. Further, ethyl alcohol was used as a dispersion medium, and measurement was performed after ultrasonic dispersion for 5 minutes (output 30 W, frequency 22.5 kHz).

<Physical properties of particulate powder obtained by spray drying>
The form was confirmed by SEM observation and cross-sectional SEM observation. The median diameter and 90% cumulative 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 (LA-920, manufactured by Horiba, Ltd.) The particle diameter standard was measured using the volume standard. Further, a 0.1 wt% sodium hexametaphosphate aqueous solution was used as a dispersion medium, and measurement was performed after 0 minutes, 1 minute, 3 minutes, and 5 minutes of ultrasonic dispersion (output 30 W, frequency 22.5 kHz). 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.

<Chemical adsorption points detected by AFM>
An arbitrary portion of the active material surface is scanned with an area of 4 μm × 4 μm by AFM (Nanoscope III manufactured by Bruker AXS) using a probe chemically modified with polyacrylic acid, and image data (height image and phase image) ). The modification of the probe was performed according to the following procedure. First, a probe made of silicon is left in a 0.1 wt% polyacrylic acid aqueous solution for 2 to 3 hours, and then the probe is taken out of the aqueous solution and air-dried for about one day, so that the polyacrylic acid is attached to the probe. Qualified. Further, scanning in AFM is performed under the following conditions. Image data was acquired with a scanning speed of 1 Hz and a number of observation points of 512 × 512 points.

Next, among the acquired image data, the phase image is subjected to flattening processing and automatic threshold extraction processing of chemical adsorption points using image analysis software ImageProPlus (manufactured by Media Cybernetics Co., Ltd., Japan Roper). The number was counted. (The flattening process mentioned here is a method in which a background image is created from an image and a background image is subtracted from the original image to smooth the background of the non-uniform image and make it flat. in adsorption point extraction method, the acquired image, bright concentration, the area is 1000nm ² ~20000nm ^2, a circularity of 0.0 to 3.0, an ellipse short length axis ratio of 1.0 The number of points on the image having an inhomogeneity of ~ 3.0 and a non-homogeneity of 0.05 to 1.0 was counted as a chemical adsorption point. Perform the flattening process and count the number of chemical adsorption points in the acquired and acquired images, find the average value of the counted number of chemical adsorption points, and use that value to determine the chemical state And the value at the time of the value.

[Production of lithium transition metal compounds]
(Synthesis of active material)
Li ₂ CO ₃ , NiCO ₃ , Mn ₃ O ₄ , CoOOH, H ₃ BO ₃ , WO ₃ are mixed with Li: Ni: Mn: Co: B: W = 1.15: 0.45: 0.45: 0. After weighing and mixing to a molar ratio of 10: 0.0025: 0.015, pure water was added thereto to prepare a slurry. While stirring the slurry, the solid content in the slurry was pulverized to a median diameter of 0.5 μm using a circulating medium agitation type wet pulverizer.

Next, this slurry (solid content 50 wt%, viscosity 5500 cp) was spray dried using a four-fluid nozzle type spray dryer (Fujisaki Electric Co., Ltd .: MDP-690 type). The drying inlet temperature was 200 ° C. The median diameter of the particulate powder obtained by spray drying with a spray dryer was 17 μm. This powder was put into an alumina baking pot, fired at 650 ° C. for 2 hours in an air atmosphere (heating rate 7.7 ° C./min.), And further fired at 1125 ° C. for 3.5 hours (heating temperature rate 7. 7 ° C./min.) And then crushed to obtain a lithium nickel manganese cobalt composite oxide having a layered structure with a composition of Li _1.15 (Ni _0.45 Mn _0.45 Co _0.10 ) O ₂ (x = 0.1, y = 0.00, z = 0.15). The average primary particle diameter was 1 μm, the median diameter was 10.0 μm, the bulk density was 2.1 g / cc, and the BET specific surface area was 1.0 m ² / g.

Moreover, when the surface enhancement Raman spectrum (SERS) measurement was performed about this sample, it confirmed having a peak top in 900 cm < ^-1 > vicinity. Moreover, the half value width was 78 cm < ^-1 >. 600 800 cm ^-1 or more to the intensity of the peak around ± 50 cm ^-1, the intensity of the 1000 cm ^-1 or less at the peak was 0.65. Further, the B and W concentrations on the surface were measured by XPS, and the overall B and W concentrations were calculated from the composition ratio of the preparations. When these were compared, the B was 50 times and the W was 10 times.
Furthermore, the chemical adsorption point detected by AFM was 86.6.

[Preparation of slurry (Examples and Comparative Examples)]
(Example B1)
A conductive material, a binder, and NMP were mixed with the produced positive electrode active material using Nawataro Awatori (manufactured by THINKY) to prepare a positive electrode slurry.

HIBLACK 40 B1 (manufactured by Evonik Degussa Japan) is used as the conductive material, PVdF binder # 1120 (manufactured by Kureha) is used as the binder, and the positive electrode active material / conductive material / binder is 92/5/3 by weight. Weighed so that However, PVdF binder # 1120 was weighed so that the solid content dissolved in NMP was 3 wt% with respect to the total solid content weight of the positive electrode slurry.
As the mixing order, first, the conductive material and NMP were mixed, then the binder was mixed, and finally the positive electrode active material was mixed. In all steps, mixing was performed at 1000 rpm for 3 minutes. The NMP mixed with the conductive material first was weighed so that the final N / V ratio of the positive electrode slurry was 60% including the amount of NMP brought in from the PVdF binder.

(Example B2)
A positive electrode slurry was prepared in the same manner as in Example B1, except that powdered acetylene black (manufactured by Nippon Chemical Industry Co., Ltd.) was used as the conductive material and PVdF binder # 7208 (manufactured by Kureha) was used as the binder.
(Comparative Example B1)
A positive electrode slurry was prepared in the same manner as in Example B1, except that PVdF binder # 1710 (manufactured by Kureha) was used as the binder.
(Comparative Example B2)
A positive electrode slurry was prepared in the same manner as in Example B1, except that PVdF binder # 7208 (manufactured by Kureha) was used as the binder.

[Measurement of elastic change behavior of slurry]
The elastic change behavior in the prepared slurry was measured with a rheometer (manufactured by Rheometric Scientific). In the rheometer measurement, Strain = 100
%, Frequency = 10, and the elastic change rate from immediately after preparation to 15 minutes was measured. The elasticity (A) in the slurry immediately after the preparation and the elasticity (B) in the slurry after 15 minutes from the preparation were compared, and the rate of change was calculated by the following equation (1).
Formula (1) B / A × 100
Table 1 shows values obtained by calculating the viscosity behavior change rates of the slurries prepared in Examples 1 and 2 and Comparative Examples 1 and 2 using Equation (1).

  From Table 1, it can be seen that the viscosity increase rate, which was low in the examples, is so high that it cannot be explained by the correlation with the integrated value in the comparative example. This is due to the gelation of the slurry.

  The use of the lithium secondary battery using the lithium transition metal-based composite oxide powder 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 notebook, calculator, memory card, portable tape recorder, radio, backup power supply, motor, lighting equipment, toy, game machine, clock, strobe, camera, pacemaker, electric tool, automotive power source, track vehicle power source, artificial Examples include a power source for satellites.

Claims (13)

A positive electrode for a lithium secondary battery containing an active material, a conductive material and a binder,
The conductive material has a nitrogen adsorption specific surface area (N ₂ SA) of 70 m ² / g or more, the nitrogen adsorption specific surface area (N ₂ SA, unit: m ² / g) of the conductive material is S, and the weight of the binder A positive electrode for a lithium secondary battery that satisfies the following formula (1) when the average molecular weight is M.
(S × M) / 10000 ≦ 7500 (1) A positive electrode for a lithium secondary battery containing an active material, a conductive material and a binder,
The conductive material has an average particle size of 35 nm or less;
The positive electrode for a lithium secondary battery satisfying the following formula (1) when the nitrogen adsorption specific surface area (N ₂ SA, unit: m ² / g) of the conductive material is S and the weight average molecular weight of the binder is M .
(S × M) / 10000 ≦ 7500 (1) A positive electrode for a lithium secondary battery containing an active material, a conductive material and a binder,
The conductive material has a volatile content of 0.8% or more,
The positive electrode for a lithium secondary battery satisfying the following formula (1) when the nitrogen adsorption specific surface area (N ₂ SA, unit: m ² / g) of the conductive material is S and the weight average molecular weight of the binder is M .
(S × M) / 10000 ≦ 7500 (1)   The positive electrode for a lithium secondary battery according to any one of claims 1 to 3, wherein the binder has a weight average molecular weight of 600,000 or less.   The positive electrode for a lithium secondary battery according to any one of claims 1 to 4, wherein the binder is PVdF. The positive electrode for a lithium secondary battery according to claim 1, wherein the conductive material has a nitrogen adsorption specific surface area (N ₂ SA) of 70 m ² / g or more.   The positive electrode for a lithium secondary battery according to any one of claims 1 to 6, wherein the conductive material has an average particle size of 35 nm or less.   The positive electrode for a lithium secondary battery according to claim 1, wherein the conductive material has a volatile content of 0.8% or more.   The positive electrode for a lithium secondary battery according to claim 1, wherein the conductive material is oil furnace carbon black.   The ratio of the electrically conductive material with respect to the active material weight is 0.5 to 15 weight%, The positive electrode for lithium secondary batteries of any one of Claims 1-9.   The positive electrode for a lithium secondary battery according to any one of claims 1 to 10, wherein the active material contains a lithium transition metal composite oxide. Active material, the surface-enhanced Raman spectrum, 800 cm ^-1 or more, a positive electrode for a lithium secondary battery according to any one of claims 1 to 11 and has a peak at 1000 cm ^-1 or less. A lithium secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte containing a lithium salt,
The lithium secondary battery whose positive electrode is a positive electrode for lithium secondary batteries of any one of Claims 1-12.