JP6879803B2 - Method for producing lithium metal composite oxide - Google Patents

Description

The present invention relates to a method for producing a lithium metal composite oxide.

Lithium composite oxides are used as positive electrode active materials for lithium secondary batteries. Lithium secondary batteries have already been put into practical use not only in small power sources for mobile phones and notebook computers, but also in medium- and large-sized power sources for automobiles and power storage.

The method for producing a lithium composite metal oxide generally includes a raw material mixing step, a firing step, a cleaning step, and a heat treatment step. For example, Patent Document 1 describes a method of performing a heat treatment step after washing at 120 ° C. to 550 ° C. and a heating rate of 120 to 600 ° C./hr.

Republished WO2014 / 189108

As the application fields of lithium secondary batteries are expanding, the positive electrode active material of lithium secondary batteries is further improved in battery characteristics such as high power capacity (described later in "Calculation of power capacity") retention rate. Desired.
In the lithium composite metal oxide manufacturing process, the heat treatment step after the cleaning step is a step necessary for removing the cleaning liquid and drying it. In order to remove water, it is preferable to heat-treat at a temperature of 120 ° C. to 550 ° C. as described in Reference 1. However, there is a problem that the power capacity retention rate is lowered depending on the heat treatment temperature.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a lithium composite metal oxide having a high power capacity retention rate while removing water.

That is, the present invention includes the following inventions [1] to [7].
[1] A method for producing a lithium metal composite oxide containing at least nickel, which can be doped and dedoped with lithium ions, and comprises a mixing step of mixing a metal composite compound containing at least nickel and a lithium compound to obtain a mixture. The mixture comprises a firing step of calcining the mixture in an oxygen-containing atmosphere to obtain a calcined product, a cleaning step of cleaning the calcined product to obtain a cleaned product, and a heat treatment step of heat-treating the cleaned product. In the step, the mixture is mixed so that the ratio (molar ratio) of lithium in the lithium compound to the metal element in the metal composite compound exceeds 1, and the heat treatment step is performed at a heating rate of 100 ° C./hr or more. A method for producing a lithium metal composite oxide, which comprises a holding temperature of more than 550 ° C. and a holding temperature of 900 ° C. or lower.
[2] The method for producing a lithium metal composite oxide according to [1], wherein the heat treatment step is performed at a heating rate of 600 ° C./hr or less.
[3] The method for producing a lithium composite metal oxide according to [1] or [2], wherein the lithium metal composite oxide has an α-NaFeO _{type 2 crystal structure represented by the following composition formula (I).
Li [Li x (Ni (1} -y-z-w) Co y Mn z M w) 1-x] O 2 ··· (I)
(In the formula (I), 0 <x ≦ 0.2, 0 <y ≦ 0.5, 0 ≦ z ≦ 0.5, 0 ≦ w ≦ 0.1, y + z + w <1, M is Mg, Ca, Sr. , Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V, W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd Represents one or more metals selected from the group consisting of, In, and Sn.)
[4] The method for producing a lithium metal composite oxide according to [3], wherein y + z + w ≦ 0.3 in the composition formula (I).
[5] After the cleaning step and before the heat treatment step, the lithium metal composite oxide and Al ₂ O ₃ are mixed, and in the heat treatment step, Al is formed on the particle surface of the lithium metal composite oxide. The method for producing a lithium metal composite oxide according to any one of [1] to [4], which forms a coating layer.
[6] When the lithium metal composite oxide was subjected to powder X-ray diffraction measurement using CuKα rays, the integrated intensity A at the peak within the range of 2θ = 18.7 ± 1 ° and 2θ = 44. The lithium metal according to any one of [1] to [5], wherein the ratio (A / B) to the integrated intensity B at the peak within the range of 6 ± 1 ° is 1.20 or more and 1.29 or less. Method for producing composite oxide.
[7] The method for producing a lithium metal composite oxide according to any one of [1] to [6], wherein the specific surface area of the lithium metal composite oxide is 1.2 m ^{2 / g or less.}

According to the present invention, it is possible to provide a method for producing a lithium composite metal oxide that removes water and has a high power capacity retention rate.

It is a schematic block diagram which shows an example of a lithium ion secondary battery.

<Manufacturing method of lithium metal composite oxide>
The present invention is a method for producing a lithium metal composite oxide containing at least nickel, which can be doped and dedoped with lithium ions.
The present invention includes a mixing step of mixing at least a metal composite compound containing nickel and a lithium compound, a firing step of firing in an oxygen-containing atmosphere, a cleaning step of cleaning the lithium metal composite oxide, and a heat treatment step.
Hereinafter, each step will be described.

In the method for producing a lithium composite metal oxide of the present invention, first, a metal other than lithium, that is, an essential metal composed of Ni and Co, and Mn, Mg, Ca, Sr, Ba, Zn, B, Al, One of Ga, Ti, Zr, Ge, Fe, Cu, Cr, V, W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn. It is preferable to prepare a metal composite compound containing the above optional metal and to calcin the metal composite compound with an appropriate lithium salt. As the metal composite compound, a metal composite hydroxide or a metal composite oxide is preferable. Hereinafter, an example of a method for producing a lithium composite metal oxide will be described separately for a step of producing the metal composite compound and a step of mixing the metal composite compound and the lithium compound.

(Manufacturing process of metal composite compound)
The metal composite compound can be produced by a commonly known batch coprecipitation method or continuous coprecipitation method. Hereinafter, the production method thereof will be described in detail by taking a metal composite hydroxide containing nickel, cobalt and manganese as an example.

First co-precipitation method, in particular by a continuous method described in 2002-201028 JP-nickel salt solution, cobalt salt solution, is reacted manganese salt solution and a complexing _{agent, Ni a Co b Mn c (} OH) ₂ (In the formula, a + b + c = 1) is produced as a composite metal hydroxide.

The nickel salt which is the solute of the nickel salt solution is not particularly limited, and for example, any one of nickel sulfate, nickel nitrate, nickel chloride and nickel acetate can be used. As the cobalt salt which is the solute of the cobalt salt solution, for example, any one of cobalt sulfate, cobalt nitrate, and cobalt chloride can be used. As the manganese salt which is the solute of the manganese salt solution, for example, any one of manganese sulfate, manganese nitrate, and manganese chloride can be used. The above metal salts are used in a ratio corresponding to the composition ratio of _{the above Ni a} Co _b Mn _c (OH) _2. Also, water is used as the solvent.

The complexing agent can form a complex with ions of nickel, cobalt, and manganese in an aqueous solution, and includes, for example, an ammonium ion feeder (ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, etc.), hydrazine, and the like. Examples include ethylenediammonium tetraacetic acid, nitrilotriacetic acid, uracil diacetic acid, and glycine.

At the time of precipitation, alkali metal hydroxides (for example, sodium hydroxide and potassium hydroxide) are added if necessary in order to adjust the pH value of the aqueous solution.

When a complexing agent is continuously supplied to the reaction vessel in addition to the nickel salt solution, the cobalt salt solution, and the manganese salt solution, nickel, cobalt, and manganese react with each other, and Ni _a Co _b Mn _c (OH) ₂ Is manufactured. In the reaction, the temperature of the reaction vessel is controlled in the range of, for example, 20 ° C. or higher and 80 ° C. or lower, preferably 30 to 70 ° C., and the pH value in the reaction vessel is, for example, pH 9 or higher and pH 13 or lower, preferably pH 11 to 13. Controlled within, the substances in the reaction vessel are appropriately agitated. The reaction vessel is of a type in which the formed reaction precipitate overflows for separation.

By appropriately controlling the concentration of the metal salt supplied to the reaction vessel, the stirring speed, the reaction temperature, the reaction pH, the firing conditions described later, etc., the finally obtained lithium metal composite oxide is controlled to have desired physical properties. Can be done.

After the above reaction, the obtained reaction precipitate is washed with water and then dried to isolate nickel cobalt manganese hydroxide as a nickel cobalt manganese composite compound. Further, if necessary, it may be washed with a weak acid water or an alkaline solution containing sodium hydroxide or potassium hydroxide. In the above example, the nickel-cobalt-manganese composite hydroxide is produced, but the nickel-cobalt-manganese composite oxide may be prepared.

The present embodiment is not limited to the case where a metal composite hydroxide containing nickel, cobalt and manganese is used as the metal, and the metal composite hydroxide containing nickel, cobalt and aluminum is used as the metal and nickel. , Metal composite hydroxides containing cobalt, manganese and aluminum can also be used. In this case, for example, aluminum sulfate can be used as the aluminum salt.

(Mixing process)
The metal composite oxide or hydroxide is dried and then mixed with a lithium salt. The drying conditions are not particularly limited, but for example, conditions under which the metal composite oxide or hydroxide is not oxidized or reduced (the oxide is maintained as an oxide, the hydroxide is maintained as a hydroxide). , The condition that the metal composite hydroxide is oxidized (the hydroxide is oxidized to the oxide) and the condition that the metal composite oxide is reduced (the oxide is reduced to the hydroxide) Good. Inert gas such as rare gas such as nitrogen, helium and argon may be used for the condition that oxidation / reduction is not performed, and oxygen or air may be used as an atmosphere under the condition that hydroxide is oxidized. Good. Further, as a condition for reducing the metal composite oxide, a reducing agent such as hydrazine or sodium sulfite may be used in an inert gas atmosphere. As the lithium salt, any one or a mixture of lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium hydroxide hydrate, and lithium oxide can be used.

After drying the metal composite oxide or hydroxide, classification may be carried out as appropriate. The above lithium salt and metal composite metal hydroxide are used in consideration of the composition ratio of the final target product.
In the present embodiment, the mixture is mixed so that the ratio (molar ratio) of lithium in the lithium compound to the metal element in the metal composite compound exceeds 1.
For example, when using a nickel-cobalt-manganese composite hydroxide, lithium salt and the composite metal _{hydroxide, Li [Li x (Ni (} 1-y-z) Co y Mn z) 1-x] O 2 ( wherein Medium, it is used at a ratio corresponding to a composition ratio of 0 <x).

(Baking process)
A lithium-nickel-cobalt-manganese composite oxide is obtained by calcining a mixture of a nickel-cobalt-manganese composite metal hydroxide and a lithium salt. An oxygen atmosphere is used for firing, and if necessary, a plurality of heating steps are performed.

The firing temperature of the metal composite oxide or hydroxide and a lithium compound such as lithium hydroxide or lithium carbonate is not particularly limited, but is preferably 600 ° C. or higher and 1100 ° C. or lower, and is 650 ° C. or higher and 1050 ° C. or higher. The temperature is more preferably 700 ° C. or higher, and further preferably 700 ° C. or higher and 1025 ° C. or lower.

The firing time is preferably 3 hours to 50 hours. If the firing time exceeds 50 hours, the battery performance tends to be substantially inferior due to the volatilization of lithium. If the firing time is less than 3 hours, crystal development tends to be poor and battery performance tends to be poor. It is also effective to perform temporary firing before the above firing. The temperature of such temporary firing is preferably in the range of 300 to 850 ° C. for 1 to 10 hours.

(Washing process)
After firing, the obtained fired product is washed. Pure water or an alkaline cleaning solution can be used for cleaning.
Examples of the alkaline cleaning solution include LiOH (lithium hydroxide), NaOH (sodium hydroxide), KOH (potassium hydroxide), Li ₂ CO ₃ (lithium carbonate), Na ₂ CO ₃ (sodium carbonate), and K ₂ CO _3. Examples thereof include an aqueous solution of one or more hydroxides selected from the group consisting of (potassium carbonate) and (NH ₄ ) ₂ CO _{3 (ammonium carbonate) and hydrates thereof.} Ammonia can also be used as the alkali.

In the cleaning step, as a method of bringing the cleaning liquid into contact with the lithium composite metal compound, a method of adding a lithium composite metal compound into the aqueous solution of each cleaning liquid and stirring the mixture, or a method of using the aqueous solution of each cleaning liquid as shower water and lithium composite metal. The method of applying the compound or the lithium composite metal compound is added to the aqueous solution of the cleaning solution and stirred, and then the lithium composite metal compound is separated from the aqueous solution of each cleaning solution, and then the aqueous solution of each cleaning solution is used as shower water for separation. A method of applying to a later lithium composite metal compound can be mentioned.

(Heat treatment process)
After the above cleaning step, the cleaning material is separated from the cleaning liquid by filtration or the like. After that, the washed product is heat-treated at a heating rate of 100 ° C./hr or more, a holding temperature of more than 550 ° C., and 900 ° C. or less.
The heat treatment step is a step of removing water from the washed product after the washing step. In order to dry and remove the water content, the cleaned product may be heat-treated at a temperature of around 400 ° C., but the present inventors heat-treat at a temperature of around 400 ° C. on the particle surface of the lithium composite metal oxide. We have discovered the problem that the nickel component is oxidized and the formation of the nickel oxide layer is promoted. It is speculated that the formation of the nickel oxide layer causes a decrease in the power capacity retention rate.
Therefore, in the present embodiment, it is possible to remove water while suppressing the formation of the nickel oxide layer by raising the temperature to a high temperature in a short time and shortening the residence time in the temperature region where the nickel oxide layer is formed. it can.

In the present embodiment, the heating rate is calculated from the time from the start of the temperature rise to the time when the temperature is reached, which will be described later, in the firing apparatus. The rate of temperature rise is preferably 110 ° C./hr or higher, more preferably 120 ° C./hr or higher, and particularly preferably 130 ° C./hr or higher.
Further, the upper limit of the heating rate is not particularly limited, and the temperature can be increased up to the maximum heating rate of the apparatus to be used. , 400 ° C./hr or less is particularly preferable.
By setting the temperature rise rate within the above-mentioned specific range, the residence time in the temperature region where the nickel oxide layer is formed can be shortened, and the formation of the nickel oxide layer on the particle surface of the lithium composite metal oxide can be suppressed. It is inferred that.

In the present embodiment, the holding temperature is a temperature held at a specific set temperature for 1 hour or more in the firing apparatus, and the actual temperature may be slightly changed (± 5 ° C.). The holding temperature in the heat treatment step is preferably 570 ° C. or higher, more preferably 600 ° C. or higher, and particularly preferably 650 ° C. or higher. The holding temperature is preferably 850 ° C. or lower, more preferably 800 ° C. or lower, and particularly preferably 750 ° C. or lower.
By performing the heat treatment step at a temperature equal to or higher than the above lower limit value, it is possible to sufficiently remove water while suppressing the formation of the nickel oxide layer. Further, by performing the heat treatment step at a temperature equal to or lower than the above upper limit value, it is possible to suppress the collapse of the layer structure of the lithium composite metal oxide.

In the present embodiment, when a metal composite hydroxide containing nickel, cobalt, manganese and aluminum is used as the metal, the integrated intensity ratio (A / B) tends to be easily controlled within the preferable range of the present invention. If the holding temperature of the heat treatment step is adjusted to 680 ° C. or higher and 720 ° C. or lower, the integrated strength ratio (A / B) tends to be easily controlled within the preferable range of the present invention.

After the above heat treatment step, it is appropriately classified after pulverization to obtain a positive electrode active material applicable to a lithium secondary battery.

(Formation of coating layer)
In the present embodiment, after the cleaning step and before the heat treatment step, the lithium metal composite oxide and Al ₂ O ₃ are mixed, and in the heat treatment step, the particles of the lithium metal composite oxide are mixed. It is preferable to form an Al coating layer on the surface. By forming the Al coating layer, the water content of the lithium composite metal oxide can be reduced.

Further, it is preferable to have a drying step after the washing step and before the heat treatment step. The drying step may be blast drying, vacuum drying, or the like, and these may be further combined. When performed by heat treatment, the heating temperature is preferably 50 ° C. to 300 ° C., more preferably 100 ° C. to 200 ° C.

When forming a coating particle or a coating layer, the coating material raw material and the lithium composite metal compound are mixed and heat-treated as necessary to form a lithium-containing metal on the surface of the primary particle or the secondary particle of the lithium composite metal compound. Coating particles or coating layers made of composite oxides can be formed.

As the coating material raw material, oxides, hydroxides, carbonates, nitrates, sulfates, halides, oxalates or alkoxides can be used, and oxides are preferable.

In order to more efficiently coat the surface of the lithium composite metal compound with the coating material raw material, the coating material raw material is preferably fine particles as compared with the secondary particles of the lithium composite metal compound. Specifically, the average secondary particle size of the coating material raw material is preferably 1 μm or less, more preferably 0.5 μm or less, and further preferably 0.2 μm or less.

The coating material raw material and the lithium composite metal compound may be mixed in the same manner as in the mixing at the time of producing the lithium composite metal compound. A method of mixing using a mixing device that does not include a mixing medium such as a ball and does not involve strong pulverization, such as a method of mixing using a powder mixer having a stirring blade inside, is preferable. Further, the coating layer can be more firmly adhered to the surface of the lithium composite metal compound by holding the mixture in an atmosphere containing water after mixing.

By performing the heat treatment step after mixing the coating material raw material and the lithium composite metal compound, coating particles or a coating layer made of a lithium-containing metal composite oxide can be formed on the surface of the primary particles or secondary particles of the lithium composite metal compound. ..

A lithium composite metal compound having a coating layer on the surface of the primary particles or secondary particles of the lithium composite metal compound is appropriately crushed and classified to be a positive electrode active material for a lithium secondary battery.

In the present embodiment, the lithium metal composite oxide powder preferably has _{an α-NaFeO type 2 crystal structure represented by the following composition formula (I).
Li [Li x (Ni (1} -y-z-w) Co y Mn z M w) 1-x] O 2 ··· (I)
(In the formula (I), 0 <x ≦ 0.2, 0 <y ≦ 0.5, 0 ≦ z ≦ 0.5, 0 ≦ w ≦ 0.1, y + z + w <1, M is Mg, Ca, Sr. , Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V, W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd Represents one or more metals selected from the group consisting of, In, and Sn.)

From the viewpoint of obtaining a lithium secondary battery having high cycle characteristics, x in the composition formula (I) is preferably more than 0, more preferably 0.01 or more, and further preferably 0.02 or more. .. Further, from the viewpoint of obtaining a lithium secondary battery having a higher initial coulombic efficiency, x in the composition formula (I) is preferably 0.1 or less, more preferably 0.08 or less, and 0.06. The following is more preferable.
The upper limit value and the lower limit value of x can be arbitrarily combined.

Further, from the viewpoint of obtaining a lithium secondary battery having a low battery resistance, y in the composition formula (I) is preferably 0.005 or more, more preferably 0.01 or more, and 0.05 or more. It is more preferable to have. Further, from the viewpoint of obtaining a lithium secondary battery having high thermal stability, y in the composition formula (I) is more preferably 0.35 or less, and further preferably 0.33 or less.
The upper limit value and the lower limit value of y can be arbitrarily combined.

Further, from the viewpoint of obtaining a lithium secondary battery having high cycle characteristics, z in the composition formula (I) is preferably 0.01 or more, more preferably 0.02 or more, and 0.1 or more. It is more preferable to have. Further, from the viewpoint of obtaining a lithium secondary battery having high storage characteristics at a high temperature (for example, in an environment of 60 ° C.), z in the composition formula (I) is preferably 0.4 or less, preferably 0.38 or less. More preferably, it is more preferably 0.35 or less.
The upper limit value and the lower limit value of z can be arbitrarily combined.

Further, from the viewpoint of obtaining a lithium secondary battery having a low battery resistance, w in the composition formula (I) is preferably more than 0, more preferably 0.0005 or more, and more preferably 0.001 or more. More preferred. Further, from the viewpoint of obtaining a lithium secondary battery having a high discharge capacity at a high current rate, w in the composition formula (I) is preferably 0.09 or less, more preferably 0.08 or less, and 0. It is more preferably .07 or less.
The upper limit value and the lower limit value of w can be arbitrarily combined.

The y + z + w in the composition formula (I) is preferably less than 1, more preferably 0.3 or less. According to the method for producing a lithium composite metal oxide of the present embodiment, it is presumed that the production of nickel oxide can be suppressed, so that a lithium composite metal oxide having a high nickel content can be preferably produced.

M in the composition formula (I) is Mg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V, W, Mo, Sc, Y, Nb, La. , Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn represents one or more metals selected from the group.

Further, from the viewpoint of obtaining a lithium secondary battery having high cycle characteristics, M in the composition formula (I) is one or more metals selected from the group consisting of Ti, Mg, Al, W, B and Zr. Is preferable, and from the viewpoint of obtaining a lithium secondary battery having high thermal stability, one or more metals selected from the group consisting of Al, W, B, and Zr are preferable.

The lithium metal composite oxide powder of the present embodiment has an integrated intensity A at a peak within the range of 2θ = 18.7 ± 1 ° and 2θ = 44.4 ± when measured by powder X-ray diffraction using CuKα rays. The ratio (A / B) to the integrated intensity B at the peak within the range of 1 ° is preferably 1.20 or more. The A / B is preferably 1.29 or less, more preferably 1.25 or less, and even more preferably 1.24 or less.
The upper limit value and the lower limit value of A / B can be arbitrarily combined.

The integrated strength A and the integrated strength B of the lithium metal composite oxide of the present embodiment can be confirmed as follows.
First, for a lithium metal composite oxide, a diffraction peak within the range of 2θ = 18.7 ± 1 ° (hereinafter, may be referred to as peak A') is determined in powder X-ray diffraction measurement using CuKα ray. .. The diffraction peak within the range of 2θ = 44.4 ± 1 ° (hereinafter, may be referred to as peak B') is determined.
Further, the integrated intensity A of the determined peak A'and the integrated intensity B of the peak B'are calculated, and the ratio (A / B) of the integrated intensity A and the integrated intensity B is calculated.

(BET specific surface area)
^{In the present embodiment, the BET specific surface area (m 2} / g) of the ^{lithium metal composite oxide is 1.2 m 2} / g from the viewpoint of obtaining a positive electrode active material for a lithium secondary battery having a high discharge capacity at a high current rate. The following is preferable, 0.8 m ² / g or less is more preferable, and 0.5 m ² / g or less is particularly preferable. It is not limited lower limit in particular, and an example, is preferably 0.1 m ² / g or more, more preferably 0.15 m ² / g or more and 0.20 m ² / g or more Is even more preferable.
The upper and lower limits of the BET specific surface area (m ^{2 / g) of the lithium metal composite oxide can be arbitrarily combined.}

(Layered structure)
The crystal structure of the lithium nickel composite oxide is a layered structure, and more preferably a hexagonal crystal structure or a monoclinic crystal structure.

Hexagonal crystal structures are P3, P3 ₁ , P3 ₂ , R3, P-3, R-3, P312, P321, P3 ₁ 12, P3 ₁ 21, P3 ₂ 12, P3 ₂ 21, R32, P3 m1, P31m, P3c1, P31c, R3m, R3c, P-31m, P-31c, P-3m1, P-3c1, R-3m, R-3c, P6, P6 ₁ , P6 ₅ , P6 ₂ , P6 ₄ , P6 _{3 , P6, P6 / m, P6} 3 / m, P622, P6 1 22, P6 5 22, P6 2 22, P6 4 22, P6 3 22, P6mm, P6cc, P6 3 cm, P6 3 mc, P- It belongs to any one space group selected from the group consisting of 6m2, P-6c2, P-62m, P-62c, P6 / mmm, P6 / mcc, P6 ₃ / mcm, and P6 _{3 / mmc.}

The monoclinic crystal structure is P2, P2 ₁ , C2, Pm, Pc, Cm, Cc, P2 / m, P2 ₁ / m, C2 / m, P2 / c, P2 ₁ / c, C2 /. It belongs to any one space group selected from the group consisting of c.

Of these, from the viewpoint of obtaining a lithium secondary battery having a high discharge capacity, the crystal structure is a hexagonal crystal structure belonging to the space group R-3m or a monoclinic crystal structure belonging to C2 / m. It is particularly preferable to have a crystal structure.

The lithium compound used in the present invention is used by using any one or a mixture of lithium carbonate, lithium nitrate, lithium sulfate, lithium acetate, lithium hydroxide, lithium oxide, lithium chloride and lithium fluoride. can do. Among these, either one or both of lithium hydroxide and lithium carbonate is preferable.
From the viewpoint of improving the handleability of the positive electrode active material for a lithium secondary battery, the lithium carbonate component contained in the lithium metal composite oxide powder is preferably 0.4% by mass or less, and preferably 0.39% by mass or less. Is more preferable, and 0.38% by mass or less is particularly preferable.
Further, from the viewpoint of improving the handleability of the positive electrode active material for the lithium secondary battery, the lithium hydroxide component contained in the lithium metal composite oxide powder is preferably 0.35% by mass or less, preferably 0.25% by mass or less. Is more preferable, and 0.2% by mass or less is particularly preferable.

From the viewpoint of obtaining a positive electrode active material for a lithium secondary battery having high thermal stability, the lithium metal composite oxide of the present embodiment has Li and X (X) on the surface of the primary particles or secondary particles of the lithium composite metal compound. Represents one or more elements selected from the group consisting of B, Al, Ti, Zr and W) and preferably comprises coated particles or a coating layer made of a lithium-containing metal composite oxide.

(Coating particles or coating layer)
The coating particles or coating layer contain a lithium-containing metal composite oxide of Li and X. X is one or more selected from B, Al, Ti, Zr and W, and is preferably Al or W.

When Al is selected as X, the coating particles or the coating layer are preferably _{LiAlO 2.}
When W is selected as X, the coating particles or the coating layer are preferably one or more of _{Li 2} WO ₄ and Li ₄ WO _5.

From the viewpoint of enhancing the effect of the present invention, the ratio of the atomic ratio of X in the coated particles or the coating layer to the sum of the atomic ratios of Ni, Co, Mn and M in the lithium metal composite oxide (X / (Ni + Co + Mn + M). )) Is preferably 0.05 mol% or more and 5 mol% or less. The upper limit of (X / Ni + Co + Mn + M) is more preferably 4 mol% and particularly preferably 3 mol%. The lower limit of (X / Ni + Co + Mn + M) is more preferably 0.1 mol% and particularly preferably 1 mol%. The above upper limit value and lower limit value can be arbitrarily combined.

In the present embodiment, the composition of the coating layer can be confirmed by using STEM-EDX element line analysis, inductively coupled plasma emission analysis, electron probe microanalyzer analysis, etc. of the secondary particle cross section. The crystal structure of the coating layer can be confirmed by using powder X-ray diffraction or electron diffraction.

<Lithium secondary battery>
Next, while explaining the configuration of the lithium secondary battery, a positive electrode using the lithium metal composite oxide of the present invention as a positive electrode active material of the lithium secondary battery, and a lithium secondary battery having this positive electrode will be described.

An example of the lithium secondary battery of the present embodiment has a positive electrode and a negative electrode, a separator sandwiched between the positive electrode and the negative electrode, and an electrolytic solution arranged between the positive electrode and the negative electrode.

FIG. 1 is a schematic view showing an example of the lithium secondary battery of the present embodiment. The cylindrical lithium secondary battery 10 of the present embodiment is manufactured as follows.

First, as shown in FIG. 1A, a pair of strip-shaped separators 1, a strip-shaped positive electrode 2 having a positive electrode lead 21 at one end, and a strip-shaped negative electrode 3 having a negative electrode lead 31 at one end are combined with the separator 1 and the positive electrode. 2. The separator 1 and the negative electrode 3 are laminated in this order and wound to form an electrode group 4.

Next, as shown in FIG. 1 (b), after accommodating the electrode group 4 and an insulator (not shown) in the battery can 5, the bottom of the can is sealed, the electrode group 4 is impregnated with the electrolytic solution 6, and the positive electrode 2 and the positive electrode 2 are formed. An electrolyte is placed between the negative electrode 3 and the negative electrode 3. Further, the lithium secondary battery 10 can be manufactured by sealing the upper part of the battery can 5 with the top insulator 7 and the sealing body 8.

The shape of the electrode group 4 is, for example, a columnar shape such that the cross-sectional shape when the electrode group 4 is cut in the direction perpendicular to the winding axis is a circle, an ellipse, a rectangle, or a rectangle with rounded corners. Can be mentioned.

Further, as the shape of the lithium secondary battery having such an electrode group 4, the shape defined by IEC60086 or JIS C8500, which is a standard for batteries defined by the International Electrotechnical Commission (IEC), can be adopted. .. For example, a cylindrical shape, a square shape, or the like can be mentioned.

Further, the lithium secondary battery is not limited to the above-mentioned winding type configuration, and may have a laminated configuration in which a laminated structure of a positive electrode, a separator, a negative electrode, and a separator is repeatedly laminated. Examples of the laminated lithium secondary battery include so-called coin-type batteries, button-type batteries, and paper-type (or sheet-type) batteries.

Hereinafter, each configuration will be described in order.
(Positive electrode)
The positive electrode of the present embodiment can be manufactured by first preparing a positive electrode mixture containing a positive electrode active material, a conductive material, and a binder, and supporting the positive electrode mixture on a positive electrode current collector.

(Conductive material)
A carbon material can be used as the conductive material contained in the positive electrode of the present embodiment. Examples of the carbon material include graphite powder, carbon black (for example, acetylene black), and fibrous carbon material. Since carbon black is fine and has a large surface area, adding a small amount to the positive electrode mixture can increase the conductivity inside the positive electrode and improve charge / discharge efficiency and output characteristics, but if too much is added, it depends on the binder. Both the binding force between the positive electrode mixture and the positive electrode current collector and the binding force inside the positive electrode mixture decrease, which causes an increase in internal resistance.

The ratio of the conductive material in the positive electrode mixture is preferably 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the positive electrode active material. When a fibrous carbon material such as graphitized carbon fiber or carbon nanotube is used as the conductive material, this ratio can be reduced.

(binder)
A thermoplastic resin can be used as the binder contained in the positive electrode of the present embodiment. The thermoplastic resin includes polyvinylidene fluoride (hereinafter, may be referred to as PVdF), polytetrafluoroethylene (hereinafter, may be referred to as PTFE), ethylene tetrafluoride, propylene hexafluoride, and vinylidene fluoride. Fluororesin such as copolymer, propylene hexafluoride / vinylidene fluoride-based copolymer, ethylene tetrafluoride / perfluorovinyl ether-based copolymer; and polyolefin resin such as polyethylene and polypropylene; can be mentioned.

Two or more kinds of these thermoplastic resins may be mixed and used. Fluororesin and polyolefin resin are used as binders, and the ratio of fluororesin to the entire positive electrode mixture is 1% by mass or more and 10% by mass or less, and the ratio of polyolefin resin is 0.1% by mass or more and 2% by mass or less. It is possible to obtain a positive electrode mixture having high adhesion to the current collector and high bonding force inside the positive electrode mixture.

(Positive current collector)
As the positive electrode current collector included in the positive electrode of the present embodiment, a band-shaped member made of a metal material such as Al, Ni, or stainless steel can be used. Of these, Al is used as a forming material and processed into a thin film because it is easy to process and inexpensive.

Examples of the method of supporting the positive electrode mixture on the positive electrode current collector include a method of pressure molding the positive electrode mixture on the positive electrode current collector. Further, the positive electrode mixture is made into a paste using an organic solvent, and the obtained positive electrode mixture paste is applied to at least one surface side of the positive electrode current collector, dried, pressed and fixed to the positive electrode current collector. The mixture may be carried.

When the positive electrode mixture is made into a paste, the organic solvents that can be used include amine solvents such as N, N-dimethylaminopropylamine and diethylenetriamine; ether solvents such as tetrahydrofuran; ketone solvents such as methyl ethyl ketone; methyl acetate. Ester-based solvents such as dimethylacetamide and amide-based solvents such as N-methyl-2-pyrrolidone (hereinafter, may be referred to as NMP);

Examples of the method of applying the paste of the positive electrode mixture to the positive electrode current collector include a slit die coating method, a screen coating method, a curtain coating method, a knife coating method, a gravure coating method and an electrostatic spray method.

The positive electrode can be manufactured by the method described above.
(Negative electrode)
The negative electrode of the lithium secondary battery of the present embodiment may be capable of doping and dedoping lithium ions at a lower potential than that of the positive electrode, and a negative electrode mixture containing a negative electrode active material is supported on the negative electrode current collector. An electrode made of an electrode and an electrode made of a negative electrode active material alone can be mentioned.

(Negative electrode active material)
Examples of the negative electrode active material of the negative electrode include carbon materials, chalcogen compounds (oxides, sulfides, etc.), nitrides, metals, or alloys, which can be doped and dedoped with lithium ions at a potential lower than that of the positive electrode. Be done.

Examples of the carbon material that can be used as the negative electrode active material include graphites such as natural graphite and artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and calcined organic polymer compounds.

Oxides that can be used as the negative electrode active material include silicon oxides represented by the formula SiO _x (where x is a positive real number) _{such as SiO 2} , SiO; the formula TiO _{x such as TiO 2} and TiO (here). , X is a positive real number) titanium oxide; V ₂ O ₅ , VO _2, etc. Formula VO _x (where x is a positive real number) vanadium oxide; Fe ₃ O ₄ , Fe ₂ O ₃ , FeO, etc. _{Iron oxide represented by the formula FeO x} (where x is a positive real number); SnO ₂ , SnO, etc. Formula SnO _x (where x is a positive real number) Oxides of tin; oxides of tungsten represented by the composition formula WO _x (where x is a positive real number) _{such as WO 3} and WO ₂ ; lithium and titanium such as _{Li 4} Ti ₅ O ₁₂ and LiVO _2. Alternatively, a composite metal oxide containing vanadium; can be mentioned.

Sulfides that can be used as the negative electrode active material include Ti ₂ S ₃ , TiS ₂ , TiS, and other _{titanium sulfides represented by the formula TiS x} (where x is a positive real number); V ₃ S ₄ , VS. _2. VS, etc. _{The sulfide of vanadium represented by the formula VS x} (where x is a positive real number); Fe ₃ S ₄ , FeS ₂ , FeS, etc. formula FeS _x (where x is a positive real number) sulfides of iron _represented; Mo ₂ S 3, MoS _2, etc. formula MoS _x (wherein, x represents a positive real number) sulfides of molybdenum represented _{by; SnS} 2, SnS formula SnS _x (wherein such, Tin sulfide represented by x is a positive real number); WS _{2 and the} like formula WS _x (where x is a positive real number) and represented by tungsten sulfide; Sb ₂ S _{3 and the} like formula SbS _x (here) in, x is antimony represented by a positive real _{number); Se 5 S 3, SeS} 2, SeS formula SeS _x (wherein such, sulfide selenium x is represented by a positive real number); the Can be mentioned.

Nitridees that can be used as the negative electrode active material include Li ₃ N and Li _3-x A _x N (where A is either or both of Ni and Co, and 0 <x <3). Such as lithium-containing nitrides can be mentioned.

These carbon materials, oxides, sulfides, and nitrides may be used alone or in combination of two or more. Further, these carbon materials, oxides, sulfides and nitrides may be either crystalline or amorphous.

Examples of the metal that can be used as the negative electrode active material include lithium metal, silicon metal, and tin metal.

Alloys that can be used as the negative electrode active material include lithium alloys such as Li-Al, Li-Ni, Li-Si, Li-Sn, and Li-Sn-Ni; silicon alloys such as Si-Zn; Sn-Mn, Sn. Tin alloys such as −Co, Sn—Ni, Sn—Cu, Sn—La; alloys such as Cu ₂ Sb, La ₃ Ni ₂ Sn ₇ ; can also be mentioned.

These metals and alloys are mainly used alone as electrodes after being processed into a foil, for example.

Among the above negative electrode active materials, the potential of the negative electrode hardly changes from the uncharged state to the fully charged state during charging (potential flatness is good), the average discharge potential is low, and the capacity retention rate when repeatedly charged and discharged is high. A carbon material containing graphite as a main component, such as natural graphite or artificial graphite, is preferably used because of its high value (good cycle characteristics). The shape of the carbon material may be, for example, a flaky shape such as natural graphite, a spherical shape such as mesocarbon microbeads, a fibrous shape such as graphitized carbon fiber, or an agglomerate of fine powder.

The negative electrode mixture may contain a binder, if necessary. Examples of the binder include thermoplastic resins, and specific examples thereof include PVdF, thermoplastic polyimide, carboxymethyl cellulose, polyethylene and polypropylene.

(Negative electrode current collector)
Examples of the negative electrode current collector included in the negative electrode include a band-shaped member made of a metal material such as Cu, Ni, or stainless steel as a forming material. Among them, Cu is used as a forming material and processed into a thin film because it is difficult to form an alloy with lithium and it is easy to process.

As a method of supporting the negative electrode mixture on such a negative electrode current collector, as in the case of the positive electrode, a method by pressure molding, a paste using a solvent or the like, coating on the negative electrode current collector, drying and pressing are performed. A method of crimping can be mentioned.

(Separator)
Examples of the separator included in the lithium secondary battery of the present embodiment include a porous film, a non-woven fabric, and a woven fabric made of a material such as a polyolefin resin such as polyethylene and polypropylene, a fluororesin, and a nitrogen-containing aromatic polymer. A material having the above can be used. Further, two or more kinds of these materials may be used to form a separator, or these materials may be laminated to form a separator.

In the present embodiment, the separator has an air permeation resistance of 50 seconds / 100 cc or more and 300 seconds / 100 cc according to the Garley method defined by JIS P 8117 in order to allow the electrolyte to permeate well when the battery is used (during charging / discharging). It is preferably 50 seconds / 100 cc or more, and more preferably 200 seconds / 100 cc or less.

The porosity of the separator is preferably 30% by volume or more and 80% by volume or less, and more preferably 40% by volume or more and 70% by volume or less. The separator may be a stack of separators having different porosities.

(Electrolytic solution)
The electrolytic solution contained in the lithium secondary battery of the present embodiment contains an electrolyte and an organic solvent.

The electrolytes contained in the electrolytic solution include LiClO ₄ , LiPF ₆ , _{LiAsF 6} , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiN. (SO ₂ CF ₃ ) (COCF ₃ ), Li (C ₄ F ₉ SO ₃ ), LiC (SO ₂ CF ₃ ) ₃ , Li ₂ B ₁₀ Cl ₁₀ , LiBOB (where BOB is bis (oxalato) boronate) ), LiFSI (where FSI stands for bis (fluorosulfonyl) image), lower aliphatic carboxylic acid lithium salts, lithium salts _{such as LiAlCl 4,} and mixtures of two or more of these. May be used. Among them, the electrolyte is at least selected from the group consisting of _{LiPF 6} , _{LiAsF 6} , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ and LiC (SO ₂ CF ₃ ) _{3 containing fluorine.} It is preferable to use one containing one type.

Examples of the organic solvent contained in the electrolytic solution include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one, 1,2-di. Carbonates such as (methoxycarbonyloxy) ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropylmethyl ether, 2,2,3,3-tetrafluoropropyldifluoromethyl ether, tetrahydrofuran, 2- Ethers such as methyl tetrahydrofuran; esters such as methyl formate, methyl acetate, γ-butyrolactone; nitriles such as acetonitrile and butyronitrile; amides such as N, N-dimethylformamide, N, N-dimethylacetamide; 3-methyl Carbamates such as -2-oxazolidone; sulfur-containing compounds such as sulfolane, dimethylsulfoxide, and 1,3-propanesartone, or those in which a fluoro group is further introduced into these organic solvents (1 of the hydrogen atoms of the organic solvent). The above is replaced with a fluorine atom).

As the organic solvent, it is preferable to use a mixture of two or more of these. Of these, a mixed solvent containing carbonates is preferable, and a mixed solvent of cyclic carbonate and acyclic carbonate and a mixed solvent of cyclic carbonate and ethers are more preferable. As the mixed solvent of the cyclic carbonate and the acyclic carbonate, a mixed solvent containing ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is preferable. An electrolytic solution using such a mixed solvent has a wide operating temperature range, is not easily deteriorated even when charged and discharged at a high current rate, is not easily deteriorated even when used for a long time, and is made of natural graphite as an active material of a negative electrode. It has many features that it is resistant to decomposition even when a graphite material such as artificial graphite is used.

Further, as the electrolytic solution, it is preferable to use an electrolytic solution containing a lithium salt containing fluorine such as _{LiPF 6} and an organic solvent having a fluorine substituent because the safety of the obtained lithium secondary battery is enhanced. A mixed solvent containing ethers having a fluorine substituent such as pentafluoropropylmethyl ether and 2,2,3,3-tetrafluoropropyldifluoromethyl ether and dimethyl carbonate has a capacity even when charged and discharged at a high current rate. It is more preferable because of its high maintenance rate.

A solid electrolyte may be used instead of the above electrolytic solution. As the solid electrolyte, an organic polymer electrolyte such as a polyethylene oxide-based polymer compound, a polymer compound containing at least one of a polyorganosiloxane chain or a polyoxyalkylene chain can be used. Further, a so-called gel type compound in which a non-aqueous electrolytic solution is retained in a polymer compound can also be used. The _{Li 2 S-SiS 2, Li} 2 S-GeS 2, Li 2 S-P 2 S 5, Li 2 S-B 2 S 3, Li 2 S-SiS 2 -Li 3 PO 4, Li 2 S-SiS _{2 -Li 2 SO 4, Li 2} S-GeS 2 -P 2 S 5 inorganic solid electrolytes containing a sulfide, and the like, may be used a mixture of two or more thereof. By using these solid electrolytes, the safety of the lithium secondary battery may be further enhanced.

Further, in the lithium secondary battery of the present embodiment, when a solid electrolyte is used, the solid electrolyte may serve as a separator, and in that case, the separator may not be required.

Since the positive electrode active material having the above configuration uses the lithium-containing composite metal oxide of the present embodiment described above, the life of the lithium secondary battery using the positive electrode active material can be extended.

Further, since the positive electrode having the above configuration has the positive electrode active material for the lithium secondary battery of the present embodiment described above, the life of the lithium secondary battery can be extended.

Further, since the lithium secondary battery having the above configuration has the above-mentioned positive electrode, it is a lithium secondary battery having a longer life than the conventional one.

Next, the present invention will be described in more detail with reference to Examples.

In this example, the evaluation of the lithium metal composite oxide and the production evaluation of the positive electrode for the lithium secondary battery and the lithium secondary battery were carried out as follows.

<BET specific surface area measurement>
After drying 1 g of the lithium metal composite oxide powder in a nitrogen atmosphere at 105 ° C. for 30 minutes, the measurement was carried out using Macsorb (registered trademark) manufactured by Mountec.

<Powder X-ray diffraction measurement>
The powder X-ray diffraction measurement was performed using an X-ray diffractometer (X'Pert PRO manufactured by PANalytical). A powder X-ray diffraction pattern was obtained by filling a dedicated substrate with a lithium metal composite oxide powder and measuring in a diffraction angle range of 2θ = 10 ° to 90 ° using a Cu-Kα radiation source. .. Using the powder X-ray diffraction pattern comprehensive analysis software JADE5, the half width A of the diffraction peak within the range of 2θ = 18.7 ± 1 ° and the range of 2θ = 44.4 ± 1 ° from the powder X-ray diffraction pattern. The full width at half maximum B of the diffraction peak of the above was obtained, and A / B was calculated.
Diffraction peak of full width at half maximum: 2θ = 18.7 ± 1 °
Diffraction peak of full width at half maximum: 2θ = 44.4 ± 1 °

<Composition analysis>
The composition analysis of the lithium metal composite oxide powder produced by the method described below is carried out by dissolving the obtained lithium metal composite oxide powder in hydrochloric acid and then inductively coupled plasma emission spectrometry (SI Nanotechnology Co., Ltd.). Manufactured by SPS3000).

<Manufacturing positive electrodes for lithium secondary batteries>
The lithium metal composite oxide obtained by the production method described later is used as the positive electrode active material, and the positive electrode active material, the conductive material (acetylene black) and the binder (PVdF) are used as the positive electrode active material for the lithium secondary battery: conductive material: binder. A paste-like positive electrode mixture was prepared by adding and kneading so as to have a composition of = 92: 5: 3 (mass ratio). N-methyl-2-pyrrolidone was used as an organic solvent when preparing the positive electrode mixture.

The obtained positive electrode mixture was applied to an Al foil having a thickness of 40 μm as a current collector and vacuum dried at 150 ° C. for 8 hours to obtain a positive electrode for a lithium secondary battery. The electrode area of the positive electrode for the lithium secondary battery was 1.65 cm ² .

<Manufacturing of lithium secondary battery (coin type half cell)>
The following operations were performed in a glove box with an argon atmosphere.
Place the positive electrode for the lithium secondary battery manufactured in "Manufacturing the positive electrode for the lithium secondary battery" on the lower lid of the part for the coin-type battery R2032 (manufactured by Hosen Co., Ltd.) with the aluminum foil surface facing down. A laminated film separator (a heat-resistant porous layer laminated (thickness 16 μm) on a porous polyethylene film) was placed on the laminated film separator. 300 μl of the electrolytic solution was injected therein. The electrolytic solution is ethylene carbonate (hereinafter, may be referred to as EC), dimethyl carbonate (hereinafter, may be referred to as DMC), and ethyl methyl carbonate (hereinafter, may be referred to as EMC) at 30:35. A mixture of 35 (volume ratio) in which LiPF ₆ was dissolved at 1 mol / l (hereinafter, _{may be referred to as LiPF 6} / EC + DMC + EMC) was used.

Using lithium metal as the negative electrode, place the negative electrode on the upper side of the laminated film separator, cover it with a gasket, and crimp it with a caulking machine to obtain a lithium secondary battery (coin-type battery R2032, hereinafter referred to as "coin-type half cell". It may be referred to as).

<Rate test>
Using the coin-type half cell produced in <Preparation of lithium secondary battery (coin-type half cell)>, a rate test was carried out under the conditions shown below.

<0.2C charge / discharge test conditions>
Test temperature: 25 ° C
Maximum charging voltage 4.3V, charging time 6 hours, charging current 1.0CA, constant current constant voltage charging Minimum discharge voltage 2.5V, discharge time 5 hours, discharge current 0.2CA, constant current discharge <3C charge / discharge test conditions ＞
Test temperature: 25 ° C
Maximum charging voltage 4.3V, charging time 6 hours, charging current 1.0CA, constant current constant voltage charging Minimum discharge voltage 2.5V, discharge time 5 hours, discharge current 3.0CA, constant current discharge <Calculation of power capacity>
The 0.2C power capacity was calculated by multiplying the 0.2C discharge capacity by the 0.2C average discharge voltage.
The 3.0C power capacity was calculated by multiplying the 3.0C discharge capacity by the 3.0C average discharge voltage.
The 0.2C and 3.0C average discharge voltages are the average values of the voltages extracted every 10 seconds or 10 mV.
<Calculation of power capacity maintenance rate>
It was calculated by 3C power capacity ÷ 0.2C power capacity × 100.

<Measurement of water content>
The water content was measured using a Karl Fischer titer (831 Coulometer, manufactured by Metrohm) by the coulometric method.

(Example 1)
Production of Lithium Metal Composite Oxide 1 [Nickel Cobalt Manganese Aluminum Composite Hydroxide Production Process]
After putting water in a reaction vessel equipped with a stirrer and an overflow pipe, an aqueous sodium hydroxide solution was added to maintain the liquid temperature at 50 ° C.

A mixed raw material solution is prepared by mixing an aqueous solution of nickel sulfate, an aqueous solution of cobalt sulfate, an aqueous solution of manganese sulfate, and an aqueous solution of aluminum sulfate so that the atomic ratio of nickel atom, cobalt atom, manganese atom, and aluminum atom is 75:10:14: 1. Was prepared.

Next, the mixed raw material solution and the ammonium sulfate aqueous solution were continuously added as a complexing agent into the reaction vessel under stirring, and nitrogen gas was continuously aerated. An aqueous sodium hydroxide solution was added dropwise at appropriate times so that the pH of the solution in the reaction vessel became 12.0 to obtain nickel-cobalt manganese-aluminum composite hydroxide particles, washed with the sodium hydroxide solution, and then dehydrated with a centrifuge. It was isolated and dried at 105 ° C. to obtain Nickel Cobalt Manganese Aluminum Composite Hydroxide 1.

[Mixing process]
The nickel cobalt manganese aluminum composite hydroxide 1 obtained as described above and the lithium hydroxide powder were weighed and mixed so that Li / (Ni + Co + Mn + Al) = 1.07.

[Baking process]
Then, the mixture obtained in the above mixing step was calcined at 820 ° C. for 6 hours in an oxygen atmosphere to obtain a calcined product 1.

[Washing process]
Then, the obtained fired product 1 was washed with water. The washing step was carried out by adding the fired product 1 to pure water, stirring the slurry-like liquid obtained for 10 minutes, and dehydrating the liquid.

[Drying process]
Then, the wet cake obtained in the above washing step was dried at 105 ° C. for a time to obtain a lithium composite oxide washing and drying powder 1.

[Heat treatment process]
After the drying step, the lithium metal composite oxide washing and drying powder 1 was heated from room temperature to 700 ° C. at a heating rate of 160 ° C./hour and heat-treated for 5 hours to obtain a lithium metal composite oxide 1.

Evaluation of Lithium Metal Composite Oxide 1 The composition of the obtained lithium metal composite oxide 1 was analyzed and corresponded to the composition formula (I). As a result, x = 0.03, y = 0.10, z = 0. 14, w = 0.01.

(Example 2)
Production of Lithium Composite Metal Oxide 2 [Nickel Cobalt Manganese Composite Hydroxide Production Process]
After putting water in a reaction vessel equipped with a stirrer and an overflow pipe, an aqueous sodium hydroxide solution was added to maintain the liquid temperature at 50 ° C.

A mixed raw material solution was prepared by mixing an aqueous solution of nickel sulfate, an aqueous solution of cobalt sulfate, and an aqueous solution of manganese sulfate so that the atomic ratio of nickel atom, cobalt atom, and manganese atom was 75:10:15.

Next, the mixed raw material solution and the ammonium sulfate aqueous solution were continuously added as a complexing agent into the reaction vessel under stirring, and nitrogen gas was continuously aerated. An aqueous sodium hydroxide solution was added dropwise at appropriate times so that the pH of the solution in the reaction vessel became 12.0 to obtain nickel-cobalt-manganese composite hydroxide particles, washed with the sodium hydroxide solution, and then dehydrated with a centrifuge. It was isolated and dried at 105 ° C. to obtain nickel-cobalt-manganese composite hydroxide 2.

[Mixing process]
The nickel-cobalt-manganese composite hydroxide 2 obtained as described above and the lithium hydroxide powder were weighed and mixed so that Li / (Ni + Co + Mn) = 1.07.

[Baking process]
Then, the mixture obtained in the above mixing step was calcined at 820 ° C. for 6 hours in an oxygen atmosphere to obtain a calcined product 2.

[Washing process]
Then, the obtained fired product 2 was washed with water. The washing step was carried out by adding the fired product 2 to pure water, stirring the slurry-like liquid obtained for 10 minutes, and dehydrating the liquid.

[Drying process]
Then, the wet cake obtained in the washing step was dried at 105 ° C. for a time to obtain a lithium composite metal oxide washing and drying powder 2.

[Heat treatment process]
After the drying step, the lithium composite metal oxide washing and drying powder 2 was heated from room temperature to 850 ° C. at a heating rate of 200 ° C./hour and heat-treated for 5 hours to obtain a lithium composite metal oxide 2.

Evaluation of Lithium Composite Metal Oxide 2 The composition of the obtained lithium composite metal oxide 2 was analyzed and made to correspond to the composition formula (I). As a result, x = 0.04, y = 0.10, z = 0. 15, w = 0.00.

(Example 3, Comparative Examples 1 to 3)
The lithium composite metal oxide cleaning and drying powder 2 was subjected to the heat treatment step at the heating rate and holding temperature shown in Table 1 below by the same method as in Example 2, and the lithium composite metal oxides 3 and H1 to H1. H3 was manufactured.

Evaluation of Lithium Composite Metal Oxide 3 The composition of the obtained lithium composite metal oxide 3 was analyzed and made to correspond to the composition formula (I). As a result, x = 0.04, y = 0.10, z = 0. 15, w = 0.00.

Evaluation of Lithium Composite Metal Oxide H1 The composition of the obtained lithium composite metal oxide H1 was analyzed and made to correspond to the composition formula (I). As a result, x = 0.05, y = 0.10, z = 0. 15, w = 0.00.

Evaluation of Lithium Composite Metal Oxide H2 The composition of the obtained lithium composite metal oxide H2 was analyzed and made to correspond to the composition formula (I). As a result, x = 0.01, y = 0.10, z = 0. 15, w = 0.00.

Evaluation of Lithium Composite Metal Oxide H3 The composition of the obtained lithium composite metal oxide H3 was analyzed and made to correspond to the composition formula (I). As a result, x = 0.04, y = 0.10, z = 0. 15, w = 0.00.

(Example 4)
Production of Lithium Composite Metal Oxide 4 [Nickel Cobalt Manganese Aluminum Composite Hydroxide Production Process]
After putting water in a reaction vessel equipped with a stirrer and an overflow pipe, an aqueous sodium hydroxide solution was added to maintain the liquid temperature at 50 ° C.

A mixed raw material solution is prepared by mixing an aqueous solution of nickel sulfate, an aqueous solution of cobalt sulfate, an aqueous solution of manganese sulfate, and an aqueous solution of aluminum sulfate so that the atomic ratio of nickel atom, cobalt atom, manganese atom, and aluminum atom is 90: 7: 2: 1. Was prepared.

Next, the mixed raw material solution and the ammonium sulfate aqueous solution were continuously added as a complexing agent into the reaction vessel under stirring, and nitrogen gas was continuously aerated. An aqueous sodium hydroxide solution was added dropwise at appropriate times so that the pH of the solution in the reaction vessel became 12.0 to obtain nickel-cobalt manganese-aluminum composite hydroxide particles, washed with the sodium hydroxide solution, and then dehydrated with a centrifuge. , Isolated and dried at 105 ° C. to obtain Nickel Cobalt Manganese Aluminum Composite Hydroxide 4.

[Mixing process]
The nickel cobalt manganese aluminum composite hydroxide 4 obtained as described above and the lithium hydroxide powder were weighed and mixed so that Li / (Ni + Co + Mn + Al) = 1.07.

[Baking process]
Then, the mixture obtained in the above mixing step was calcined at 820 ° C. for 6 hours in an oxygen atmosphere to obtain a calcined product 4.

[Washing process]
Then, the obtained fired product 4 was washed with water. The washing step was carried out by adding the fired product 4 to pure water, stirring the obtained slurry-like liquid for 10 minutes, and dehydrating the liquid.

[Drying process]
Then, the wet cake obtained in the drying step was dried at 105 ° C. for a time to obtain a lithium composite metal oxide washing and drying powder 4.

[Heat treatment process]
After the drying step, the lithium composite metal oxide washing and drying powder 4 was heated from room temperature to 740 ° C. at a heating rate of 170 ° C./hour and heat-treated for 5 hours to obtain a lithium composite metal oxide 4.

Evaluation of Lithium Composite Metal Oxide 4 The composition of the obtained lithium composite metal oxide 4 was analyzed and made to correspond to the composition formula (I). As a result, x = 0.04, y = 0.07, z = 0. 02, w = 0.01.

(Example 5)
As a result of the ICP composition analysis of the lithium composite metal oxide washing and drying powder 4, the atomic ratio was Ni: Co: Mn: Al = 90: 7: 2: 1. Before the heat treatment step, the lithium composite metal oxide cleaning and drying powder 4 has an atomic number ratio of Al contained in _{Al 2} O ₃ of 0.015 to the number of atoms of Ni + Co + Mn + Al contained in the lithium composite metal oxide cleaning and drying powder 4. The lithium composite metal oxide 5 was produced by the same method as in Example 4 except that the mixture was weighed and mixed.

Cross-sectional STEM-EDX analysis of the obtained lithium composite metal oxide 5 particles revealed that a coating layer was provided on the surface of the secondary particles of the lithium composite metal oxide (core material). Further, the ICP composition analysis and crystal structure analysis of the lithium composite metal oxide 5, the coating layer contains a LiAlO _2, for number of atoms of Ni + Co + Mn + Al contained in the core material of the lithium composite metal oxide 5, Al in the coating layer The atomic number ratio of was 0.015.

Cross-sectional STEM-EDX analysis and ICP composition analysis of the lithium composite metal oxide (core material) particles contained in the obtained lithium composite metal oxide 5 were carried out, and when they corresponded to the composition formula (I), x = 0. 01, y = 0.07, z = 0.02, w = 0.01.

(Comparative Example 4)
Lithium composite metal oxide H4 was produced by the same method as in Example 4 except that the heat treatment step of the lithium composite metal oxide 4 was carried out at the heating rate and holding temperature shown in Table 1 below.

The composition of the obtained lithium composite metal oxide H4 was analyzed and corresponding to the composition formula (I). As a result, x = 0.01, y = 0.07, z = 0.02, w = 0.01. there were.

Table 1 summarizes the compositions of Examples 1 to 5 and Comparative Examples 1 to 4, the rate of temperature rise, the holding temperature, the capacity after 0.2C and after 3C, and the capacity retention rate. If coated, describe the composition of the core material.

Table 2 summarizes the integrated intensities A and B, the integrated intensity ratio (A / B), and the BET specific surface area of Examples 1 to 5 and Comparative Examples 1 to 4.

As shown in Table 1 above, Examples 1 to 5 to which the present invention was applied had a higher power capacity retention rate of 85% or more than Comparative Examples 1 to 4 to which the present invention was not applied. This is considered to mean that the formation of the nickel oxide layer on the surface of the lithium composite metal compound could be suppressed when the present invention was applied.

1 ... Separator, 2 ... Positive electrode, 3 ... Negative electrode, 4 ... Electrode group, 5 ... Battery can, 6 ... Electrolyte, 7 ... Top insulator, 8 ... Seal, 10 ... Lithium secondary battery, 21 ... Positive lead, 31 … Negative lead

Claims (6)

A method for producing a lithium metal composite oxide containing at least nickel, which can be doped and dedoped with lithium ions.
A mixing step of mixing a metal composite compound containing at least nickel and a lithium compound to obtain a mixture,
A firing step of calcining the mixture in an oxygen-containing atmosphere to obtain a calcined product,
A cleaning step of cleaning the fired product to obtain a cleaned product, and
A heat treatment step of heat-treating the washed material and
Have,
In the mixing step, the mixture is mixed so that the ratio (molar ratio) of lithium in the lithium compound to the metal element in the metal composite compound exceeds 1.
A method for producing a lithium metal composite oxide, which comprises performing the heat treatment step at a heating rate of 100 ° C./hr or more and 600 ° C./hr or less , and a holding temperature of more than 550 ° C. and 900 ° C. or less. The method for producing a lithium metal composite oxide according to claim 1, wherein the lithium metal composite oxide has an α-NaFeO _{type 2} crystal structure represented by the following composition formula (I).
_{Li [Li x (Ni (1} -y-z-w) Co y Mn z M w) 1-x] O 2 ··· (I)
(In the formula (I), 0 <x ≦ 0.2, 0 <y ≦ 0.5, 0 ≦ z ≦ 0.5, 0 ≦ w ≦ 0.1, y + z + w <1, M is Mg, Ca, Sr. , Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V, W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd Represents one or more metals selected from the group consisting of, In, and Sn.) The method for producing a lithium metal composite oxide according to claim 2 , wherein y + z + w ≦ 0.3 in the composition formula (I). After the cleaning step and before the heat treatment step, the lithium metal composite oxide and Al ₂ O ₃ are mixed, and in the heat treatment step, an Al coating layer is formed on the particle surface of the lithium metal composite oxide. The method for producing a lithium metal composite oxide according to any one of claims 1 to 3 to be formed. When the lithium metal composite oxide is subjected to powder X-ray diffraction measurement using CuKα rays, the integrated intensity A at the peak within the range of 2θ = 18.7 ± 1 ° and 2θ = 44.6 ± 1 The production of the lithium metal composite oxide according to any one of claims 1 to 4 , wherein the ratio (A / B) to the integrated intensity B at the peak in the range of ° is 1.20 or more and 1.29 or less. Method. The method for producing a lithium metal composite oxide according to any one of claims 1 to 5 , wherein the specific surface area of the lithium metal composite oxide is 1.2 m ² / g or less.

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