JP7315418B2 - Method for producing modified lithium-cobalt-based composite oxide particles - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing modified lithium-cobalt-based composite oxide particles.

2. Description of the Related Art In recent years, as home appliances have rapidly become portable and cordless, lithium ion secondary batteries have been put to practical use as power sources for small electronic devices such as laptop computers, mobile phones, and video cameras. Since Mizushima et al. reported in 1980 that lithium cobalt oxide is useful as a positive electrode active material for lithium ion secondary batteries, research and development on lithium-based composite oxides have been actively promoted, and many proposals have been made.

However, a lithium secondary battery using lithium cobalt oxide has a problem of deterioration of cycle characteristics due to elution of cobalt atoms and the like.

Patent Literature 1 below proposes a lithium secondary battery in which a lithium cobalt-based composite oxide in which the proportion of titanium present on the particle surfaces of lithium cobaltate is 20% or more is used as a positive electrode active material. In addition, Patent Document 2 below proposes a positive electrode active material for a lithium secondary battery comprising a lithium transition metal composite oxide containing 0.20 to 2.00% by weight of Ti atoms, wherein the Ti atoms are present in the depth direction from the particle surface of the lithium transition metal composite oxide, and a lithium cobalt-based composite oxide having a maximum concentration gradient on the particle surface is used as the positive electrode active material. Patent Documents 3 and 4 below propose that a lithium-cobalt-based composite oxide containing Sr atoms and Ti atoms be used as a positive electrode active material.

Japanese Patent Application Laid-Open No. 2005-123111 International publication WO2011/043296 pamphlet JP 2013-182758 A JP 2013-182757 A

In recent years, there has been a demand for further improvement in the energy density of lithium-ion batteries. One of the means for achieving this is to increase the voltage, such as increasing the end-of-charge voltage of the battery. However, even with these prior art methods, there is a problem that cycle characteristics deteriorate when charging and discharging voltages are repeated under a high voltage.

Therefore, an object of the present invention is to provide a method for producing modified lithium-cobalt-based composite oxide particles that can improve cycle characteristics and energy density retention rate under high voltage when used as a positive electrode active material for lithium secondary batteries.

As a result of intensive research in view of the above circumstances, the present invention has found that (1) the use of modified lithium cobalt composite oxide particles having a titanium-containing compound adhered to the particle surface, which is obtained by applying a heat treatment after adhering a titanium chelate compound to the particle surface of a lithium cobalt composite oxide, as a positive electrode active material increases the cycle characteristics and energy density retention rate of a lithium secondary battery under high voltage, and (2) containing Mg in addition to the titanium-containing compound produced using the titanium chelate compound. The inventors have found that the use of modified lithium-cobalt-based composite oxide particles, in which a compound is attached to the particle surface, as a positive electrode active material further enhances the cycle characteristics and energy density retention rate of lithium secondary batteries under high voltage conditions, and have completed the present invention.

That is, the present invention (1) provides a process (A1) for obtaining modified lithium cobalt composite oxide particles (a1) by bringing lithium cobalt composite oxide particles into contact with a surface treatment liquid containing a titanium chelate compound, followed by heat treatment, wherein the temperature of the heat treatment is 600 to 1000° C., and the titanium chelate compound is a titanium chelate compound represented by the following general formula (1).
General formula (1):
Ti(R ¹ ) _m L _n (1)
(In the formula, R ¹ represents an alkoxy group, a hydroxyl group, a halogen atom, an amino group, or a phosphine, and when there are a plurality of them, they may be the same or different. L represents a group derived from hydroxycarboxylic acid, and when there are a plurality of them, they may be the same or different. m represents a number of 0 or more and 3 or less, n represents a number of 1 or more and 3 or less, and m+n is 3 to 6.)

The present invention (2) further provides the method for producing modified lithium-cobalt-based composite oxide particles of (1), comprising a step (A2) of obtaining modified lithium-cobalt-based composite oxide particles (a2) by bringing the modified lithium-cobalt-based composite oxide particles (a1) obtained by performing the step (A1) into contact with a surface treatment liquid containing a Mg-containing compound or a precursor of the Mg-containing compound, followed by heat treatment.

Further, the present invention (3) includes a step (B1) of obtaining lithium cobalt-based composite oxide particles (b1) by contacting the lithium-cobalt-based composite oxide particles with a surface treatment liquid containing a Mg-containing compound or a precursor of the Mg-containing compound and then heat-treating the particles;
A step (B2) of obtaining modified lithium-cobalt-based composite oxide particles (b2) by bringing the Mg-containing compound-attached lithium-cobalt-based composite oxide particles (b1) into contact with a surface treatment liquid containing a titanium chelate compound, followed by heat treatment;
, the temperature of the heat treatment in the step (B2) is 600 to 1000° C., and the titanium chelate compound is a titanium chelate compound represented by the following general formula (1).
General formula (1):
Ti(R ¹ ) _m L _n (1)
(In the formula, R ¹ represents an alkoxy group, a hydroxyl group, a halogen atom, an amino group, or a phosphine, and when there are a plurality of them, they may be the same or different. L represents a group derived from hydroxycarboxylic acid, and when there are a plurality of them, they may be the same or different. m represents a number of 0 or more and 3 or less, n represents a number of 1 or more and 3 or less, and m+n is 3 to 6.)

Further, the present invention (4) comprises a step (C) of obtaining modified lithium cobalt composite oxide particles (c1) by contacting the lithium cobalt composite oxide particles with a surface treatment liquid containing a titanium chelate compound and a Mg-containing compound or a precursor of the Mg-containing compound, followed by heat treatment, wherein the temperature of the heat treatment is 600 to 1000° C., and the titanium chelate compound is a titanium chelate compound represented by the following general formula (1): A method for producing composite oxide particles is provided.
General formula (1):
Ti(R ¹ ) _m L _n (1)
(In the formula, R ¹ represents an alkoxy group, a hydroxyl group, a halogen atom, an amino group, or a phosphine, and when there are a plurality of them, they may be the same or different. L represents a group derived from hydroxycarboxylic acid, and when there are a plurality of them, they may be the same or different. m represents a number of 0 or more and 3 or less, n represents a number of 1 or more and 3 or less, and m+n is 3 to 6.)

The present invention ( 5 ) also provides the method for producing modified lithium-cobalt-based composite oxide particles according to ( 2 ), wherein the heat treatment temperature in step (A2) is 400 to 1000°C.

The present invention ( 6 ) also provides the method for producing modified lithium-cobalt-based composite oxide particles according to (3), wherein the heat treatment temperature in step (B1) is 400 to 1000°C.

The present invention ( 7 ) is characterized in that the lithium-cobalt-based composite oxide particles contain, in addition to Li, Co and O, one or more of M elements (M is Mg, Al, Ti, Zr, Cu, Fe, Sr, Ca, V, Mo, Bi, Nb, Si, Zn, Ga, Ge, Sn, Ba, W, Na, K, Ni or Mn). The present invention provides a method for producing such modified lithium-cobalt-based composite oxide particles.

In addition, the present invention ( 8 ) provides the method for producing modified lithium-cobalt-based composite oxide particles according to ( 7 ), wherein the M element is one or more selected from Ti, Mg and Ca.

According to the present invention, it is possible to provide a method for producing modified lithium-cobalt-based composite oxide particles that can improve cycle characteristics and energy density retention rate under high voltage when used as a positive electrode active material for lithium secondary batteries.

A method for producing modified lithium-cobalt-based composite oxide particles according to the first embodiment of the present invention is a method for producing modified lithium-cobalt-based composite oxide particles, comprising a step (A1) of obtaining modified lithium-cobalt-based composite oxide particles (a1) by contacting the lithium-cobalt-based composite oxide particles with a surface treatment liquid containing a titanium chelate compound, followed by heat treatment.

Step (A1) is a step of bringing lithium cobalt composite oxide particles (particles to be surface-treated in step (A1)) into contact with a surface treatment liquid (a1) containing a titanium chelate compound, followed by heat treatment (heat treatment (a1)) to obtain modified lithium cobalt composite oxide particles (a1).

In the step (A1), first, the lithium-cobalt-based composite oxide particles are brought into contact with the surface treatment liquid (a1). In the step (A1), the lithium-cobalt-based composite oxide particles and the surface treatment liquid (a1) are brought into contact with each other, for example, by mixing the lithium-cobalt-based composite oxide particles and the surface treatment liquid (a1).

In step (A1), the lithium cobalt-based composite oxide particles and the surface treatment liquid (a1) are brought into contact with each other, and then the mixture of the lithium cobalt-based composite oxide particles and the surface treatment liquid (a1) is dried to remove part or all of the solvent in the surface treatment liquid (a1). In drying the mixture, the entire amount of the mixture may be dried using a spray dryer, a rotary evaporator, a fluid bed drying coating apparatus, a vibration drying apparatus, or the like.

In the step (A1), the lithium-cobalt-based composite oxide particles are brought into contact with the surface treatment liquid (a1), dried, and then heat-treated at 400 to 1000°C, preferably 600 to 900°C (a1). By carrying out the heat treatment, the titanium chelate compound in the surface treatment liquid (a1) is oxidatively decomposed into a Ti-containing compound, which strongly adheres to the surface of the lithium-cobalt-based composite oxide particles.

Thus, in the method for producing modified lithium-cobalt-based composite oxide particles of the first embodiment of the present invention, lithium-cobalt-based composite oxide particles (a1) having a Ti-containing compound attached to at least part of the particle surface are obtained as modified lithium-cobalt-based composite oxide particles (a1) by performing the step (A1). The modified lithium-cobalt-based composite oxide particles (a1) obtained by performing the step (A1), that is, the Ti-containing compound-attached lithium-cobalt-based composite oxide particles (a1) are suitably used as a positive electrode active material for lithium secondary batteries.

The method for producing modified lithium-cobalt-based composite oxide particles of the first embodiment of the present invention may further comprise a step (A2) of obtaining modified lithium-cobalt-based composite oxide particles (a2) by bringing the modified lithium-cobalt-based composite oxide particles (a1) obtained by performing the step (A1), that is, the lithium-cobalt-based composite oxide particles (a1) having a Ti-containing compound attached to the surface thereof, into a surface treatment liquid (a2) containing a Mg-containing compound or a precursor of the Mg-containing compound, followed by heat treatment. I can.

The step (A2) is a step of bringing the modified lithium cobalt composite oxide particles (a1) (particles to be surface-treated in step (A2)) into contact with the surface treatment liquid (a2), followed by heat treatment (heat treatment (a2)) to obtain modified lithium cobalt composite oxide particles (a2).

In step (A2), first, the Ti-containing compound-attached lithium-cobalt-based composite oxide particles (a1) are brought into contact with the surface treatment liquid (a2). In the step (A2), the Ti-containing compound-attached lithium cobalt-based composite oxide particles (a2) and the surface treatment liquid (a2) are brought into contact with each other, for example, by mixing the Ti-containing compound-attached lithium cobalt-based composite oxide particles (a1) and the surface treatment liquid (a2).

In step (A2), the Ti-containing compound-attached lithium cobalt-based composite oxide particles (a1) are brought into contact with the surface treatment liquid (a2), and then the Ti-containing compound-attached lithium cobalt-based composite oxide particles (a1) and the surface treatment liquid (a2) are dried to remove part or all of the solvent in the surface treatment liquid (a2). In drying the mixture, the entire amount of the mixture may be dried using a spray dryer, a rotary evaporator, a fluid bed drying coating apparatus, a vibration drying apparatus, or the like.

In the step (A2), the Ti-containing compound-attached lithium cobalt-based composite oxide particles (a1) and the surface treatment liquid (a2) are brought into contact with each other, dried, and then heated at 400 to 1000°C, preferably 600 to 900°C (a2). By performing the heat treatment, the Mg-containing compound in the surface treatment liquid (a2) strongly adheres to the surface of the Ti-containing compound-attached lithium cobalt-based composite oxide particles (a1), and the precursor of the Mg-containing compound is oxidatively decomposed to become a Mg-containing compound, which strongly adheres to the surface of the Ti-containing compound-attached lithium cobalt-based composite oxide particles (a1).

By performing the step (A2) in this way, the lithium cobalt-based composite oxide particles (a2) having the Ti-containing compound and the Mg-containing compound attached to at least a part of the particle surface are obtained as the modified lithium-cobalt-based composite oxide particles (a2). The modified lithium-cobalt-based composite oxide particles (a2) obtained by performing the step (A2), that is, the lithium-cobalt-based composite oxide particles (a2) attached with the Ti-containing compound and the Mg-containing compound are suitably used as a positive electrode active material for lithium secondary batteries.

The method for producing a modified lithium-cobalt-based composite oxide according to the second aspect of the present invention includes a step (B1) of bringing lithium-cobalt-based composite oxide particles into contact with a surface treatment liquid containing a Mg-containing compound or a precursor of the Mg-containing compound, followed by heat treatment to obtain lithium-cobalt-based composite oxide particles (b1) attached to the Mg-containing compound;
A step (B2) of obtaining modified lithium-cobalt-based composite oxide particles (b2) by bringing the Mg-containing compound-attached lithium-cobalt-based composite oxide particles (b1) into contact with a surface treatment liquid containing a titanium chelate compound, followed by heat treatment;
A method for producing modified lithium-cobalt-based composite oxide particles characterized by having

Step (B1) is a step of bringing lithium-cobalt-based composite oxide particles (particles to be surface-treated in step (B1)) into contact with a surface treatment liquid (b1) containing a Mg-containing compound or a precursor of a Mg-containing compound, followed by heat treatment (heat treatment (b1)) to obtain Mg-containing compound-attached lithium-cobalt-based composite oxide particles (b1).

In the step (B1), first, the lithium-cobalt composite oxide particles are brought into contact with the surface treatment liquid (b1). In the step (B1), the lithium-cobalt-based composite oxide particles and the surface treatment liquid (b1) are brought into contact with each other, for example, by mixing the lithium-cobalt-based composite oxide particles and the surface treatment liquid (b1).

In step (B1), after the lithium cobalt-based composite oxide particles and the surface treatment liquid (b1) are brought into contact, the mixture of the lithium cobalt-based composite oxide particles and the surface treatment liquid (b1) is dried to remove part or all of the solvent in the surface treatment liquid (b1). In drying the mixture, the entire amount of the mixture may be dried using a spray dryer, a rotary evaporator, a fluid bed drying coating apparatus, a vibration drying apparatus, or the like.

In the step (B1), the lithium-cobalt-based composite oxide particles are brought into contact with the surface treatment liquid (b1), dried, and then heat-treated at 400 to 1000°C, preferably 600 to 900°C (b1). By performing the heat treatment, the Mg-containing compound in the surface treatment liquid (b1) strongly adheres to the surfaces of the lithium-cobalt-based composite oxide particles, and the Mg-containing compound precursor is oxidatively decomposed to become a Mg-containing compound, which strongly adheres to the surfaces of the lithium-cobalt-based composite oxide particles.

Thus, in the method for producing a modified lithium-cobalt-based composite oxide according to the second aspect of the present invention, step (B1) is performed to obtain lithium-cobalt-based composite oxide particles (b1) having a Mg-containing compound attached to at least a portion of the particle surface.

The step (B2) is a step of bringing the Mg-containing compound-attached lithium-cobalt-based composite oxide particles (b1) (particles to be surface-treated in step (B2)) into contact with a surface treatment liquid (b2) containing a titanium chelate compound, followed by heat treatment (heat treatment (b2)) to obtain modified lithium-cobalt-based composite oxide particles (b2).

In the step (B2), first, the Mg-containing compound-deposited lithium-cobalt-based composite oxide particles (b1) are brought into contact with the surface treatment liquid (b2). In the step (B2), the Mg-containing compound-deposited lithium cobalt-based composite oxide particles (b1) and the surface treatment liquid (b2) are contacted, for example, by mixing the Mg-containing compound-deposited lithium cobalt-based composite oxide particles (b1) and the surface treatment liquid (b2).

In the step (B2), the Mg-containing compound-deposited lithium cobalt-based composite oxide particles (b1) are brought into contact with the surface treatment liquid (b2), and then the mixture of the Mg-containing compound-deposited lithium cobalt-based composite oxide particles (b1) and the surface treatment liquid (b2) is dried to remove part or all of the solvent in the surface treatment liquid (b2). In drying the mixture, the entire amount of the mixture may be dried using a spray dryer, a rotary evaporator, a fluid bed drying coating apparatus, a vibration drying apparatus, or the like.

In the step (B2), the Mg-containing compound-deposited lithium-cobalt-based composite oxide particles (b1) and the surface treatment liquid (b2) are brought into contact with each other, dried, and then heated at 400 to 1000°C, preferably 600 to 900°C (b2). By performing the heat treatment, the titanium chelate compound in the surface treatment liquid (b2) is oxidatively decomposed to become a Ti-containing compound, which strongly adheres to the surfaces of the Mg-containing compound-deposited lithium-cobalt-based composite oxide particles (b1).

By performing the step (B2) in this way, the lithium cobalt-based composite oxide particles (b2) having the Ti-containing compound and the Mg-containing compound attached to at least a part of the particle surface are obtained as the modified lithium-cobalt-based composite oxide particles (b2). The modified lithium-cobalt-based composite oxide particles (b2) obtained by performing the step (B2), that is, the lithium-cobalt-based composite oxide particles (b2) attached with the Ti-containing compound and the Mg-containing compound are suitably used as a positive electrode active material for lithium secondary batteries.

A method for producing modified lithium-cobalt-based composite oxide particles according to a third aspect of the present invention is a method for producing modified lithium-cobalt-based composite oxide particles, comprising a step (C) of obtaining modified lithium-cobalt-based composite oxide particles (c1) by contacting the lithium-cobalt-based composite oxide particles with a surface treatment liquid containing a titanium chelate compound and a Mg-containing compound or a precursor of the Mg-containing compound, followed by heat treatment.

The step (C) is a step of bringing the lithium-cobalt-based composite oxide particles (the particles to be surface-treated in the step (C)) into contact with a surface treatment liquid (c1) containing a titanium chelate compound and a Mg-containing compound or a precursor of the Mg-containing compound, followed by heat treatment (heat treatment (c1)) to obtain modified lithium-cobalt-based composite oxide particles (c1).

In step (C), the lithium-cobalt-based composite oxide particles are brought into contact with the surface treatment liquid (c1). In the step (C), the lithium-cobalt-based composite oxide particles and the surface treatment liquid (c1) are brought into contact with each other, for example, by mixing the lithium-cobalt-based composite oxide particles and the surface treatment liquid (c1).

In step (C), the lithium cobalt-based composite oxide particles and the surface treatment liquid (c1) are brought into contact with each other, and then the mixture of the lithium cobalt-based composite oxide particles and the surface treatment liquid (c1) is dried to remove part or all of the solvent in the surface treatment liquid (c1). In drying the mixture, the entire amount of the mixture may be dried using a spray dryer, a rotary evaporator, a fluid bed drying coating apparatus, a vibration drying apparatus, or the like.

In the step (C), the lithium-cobalt-based composite oxide particles are brought into contact with the surface treatment liquid (c1), dried, and then subjected to heat treatment (c1) at 400 to 1000°C, preferably 600 to 900°C. By performing the heat treatment, the Mg-containing compound in the surface treatment liquid (c1) strongly adheres to the surfaces of the lithium-cobalt-based composite oxide particles, the Mg-compound precursor is oxidatively decomposed to become a Mg-containing compound, and the titanium chelate compound is oxidatively decomposed to become a Ti-containing compound, and is strongly adhered to the surfaces of the lithium-cobalt-based composite oxide particles.

Thus, in the method for producing a modified lithium-cobalt-based composite oxide according to the third embodiment of the present invention, step (C) is performed to obtain lithium-cobalt-based composite oxide particles (c1) having a Ti-containing compound and a Mg-containing compound attached to at least part of the particle surface as modified lithium-cobalt-based composite oxide particles (c1). The modified lithium-cobalt-based composite oxide particles (c1) obtained by performing the step (C), i.e., the lithium-cobalt-based composite oxide particles (c1) with the Ti-containing compound and the Mg-containing compound attached thereto, are suitably used as a positive electrode active material for lithium secondary batteries.

In the method for producing the modified lithium-cobalt-based composite oxide particles of the first aspect of the present invention, the method for producing the modified lithium-cobalt-based composite oxide particles of the second aspect of the present invention, or the method for producing the modified lithium-cobalt-based composite oxide particles of the third aspect of the present invention, the mixture obtained by the mixing treatment of the particles to be surface-treated and the surface treatment liquid may be in the form of powder, paste, or slurry. When the mixture is in the form of powder, paste or slurry, it can be obtained in any form by appropriately adjusting the amount of the surface treatment liquid added to the particles to be surface treated.

In the method for producing modified lithium-cobalt-based composite oxide particles according to the first aspect of the present invention, the method for producing modified lithium-cobalt-based composite oxide particles according to the second aspect of the present invention, or the method for producing modified lithium-cobalt-based composite oxide particles according to the third aspect of the present invention, when the entire mixture of the particles to be treated and the surface treatment liquid is dried, the amount of Mg-containing compound and/or Ti-containing compound attached to the lithium-cobalt-based composite oxide particles is determined by the amount of Mg or Ti in the surface treatment liquid used and the amount of Mg or Ti in the surface treatment liquid used and the amount of contact with the surface treatment liquid. It can be expressed as a theoretical adhesion amount obtained from the amount of lithium-cobalt-based composite oxide particles.

In the method for producing modified lithium-cobalt-based composite oxide particles of the first aspect of the present invention, the method for producing modified lithium-cobalt-based composite oxide particles of the second aspect of the present invention, or the method for producing modified lithium-cobalt-based composite oxide particles of the third aspect of the present invention, in the heat treatment (heat treatment (a1), heat treatment (a2), heat treatment (b1), heat treatment (b2), or heat treatment (c1)), the heat treatment temperature is 400 to 1000 ° C., preferably 600 to 900. °C. If the heat treatment temperature is less than the above range, if the surface treatment liquid contains a precursor of a Mg-containing compound such as an organic acid salt of Mg or a titanium chelate compound or a precursor of a Ti-containing compound, sufficient decomposition and oxidation reactions will not occur. The heat treatment time is not critical in the present production method, and a positive electrode active material for lithium secondary batteries with satisfactory performance can be obtained as long as it is usually 1 hour or more, preferably 2 to 10 hours. The atmosphere of the heat treatment is preferably an oxidizing atmosphere such as air or oxygen gas.

In this way, in the modified lithium cobalt-based composite oxide particles obtained by the method for producing modified lithium cobalt-based composite oxide particles of the first aspect of the present invention, the method for producing modified lithium cobalt-based composite oxide particles of the second aspect of the present invention, or the method for producing modified lithium cobalt-based composite oxide particles of the third aspect of the present invention, the Ti-containing compound and/or the Mg-containing compound are attached to at least a part of the particle surface. The Ti-containing compound and/or Mg-containing compound may cover the entire surface of the lithium-cobalt-based composite oxide particles.

The lithium-cobalt-based composite oxide according to the method for producing the modified lithium-cobalt-based composite oxide particles of the first embodiment of the present invention, the method for producing the modified lithium-cobalt-based composite oxide particles of the second embodiment of the present invention, and the method for producing the modified lithium-cobalt-based composite oxide particles of the third embodiment of the present invention, that is, the object to be subjected to modification of the particle surface is a composite oxide containing at least lithium and cobalt.

In the lithium-cobalt-based composite oxide, the atomic ratio of Li to Co (Li/Co) is preferably 0.90 to 1.20, particularly preferably 0.95 to 1.15. When the molar ratio of Li to Co (Li/Co) in terms of atoms in the lithium-cobalt-based composite oxide is within the above range, the energy density of the positive electrode active material for a lithium secondary battery is increased.

For the purpose of improving performance or physical properties, the lithium-cobalt-based composite oxide can contain any one or more of the M elements shown below, if necessary. The M element optionally contained in the lithium-cobalt-based composite oxide is Mg, Al, Ti, Zr, Cu, Fe, Sr, Ca, V, Mo, Bi, Nb, Si, Zn, Ga, Ge, Sn, Ba, W, Na, K, Ni or Mn.

The lithium-cobalt-based composite oxide preferably contains one or more selected from Ti, Mg, and Ca as the M element, and particularly preferably contains Mg and Ca, in that battery characteristics such as cycle characteristics, operating voltage, and rate characteristics are further improved.

When the lithium cobalt-based composite oxide contains the M element, the atomic conversion mol% of the M element with respect to Co in the lithium cobalt-based composite oxide ((M / Co) × 100) is preferably 0.01 to 5.00 mol%, particularly preferably 0.05 to 2.00 mol%. In the case where the lithium cobalt-based composite oxide contains the M element, the atomic conversion mol% of the M element with respect to Co in the lithium cobalt-based composite oxide ((M / Co) × 100) is in the above range, thereby improving the battery characteristics without impairing the charge and discharge capacity. When the lithium-cobalt-based composite oxide contains two or more M elements, the number of moles of the M elements in terms of atoms, which is the basis for calculating the above mol%, refers to the total number of moles of each M element.

Further, when the lithium-cobalt-based composite oxide contains one or more selected from Ti, Mg and Ca as the M element, in the lithium-cobalt-based composite oxide, the atomic conversion of the M element to Co mol% ((M / Co) × 100) is preferably 0.01 to 5.00 mol%, particularly preferably 0.05 to 2.00 mol%. When the lithium-cobalt-based composite oxide contains one or more selected from Ti, Mg, and Ca as the M element, the atomic conversion mol% of the M element relative to Co in the lithium-cobalt-based composite oxide ((M/Co) × 100) is within the above range, so that battery characteristics such as high charge-discharge capacity, cycle characteristics, operating voltage, load characteristics, and safety can be satisfied at the same time.

When the lithium cobalt-based composite oxide contains Ti as the M element, the atomic conversion mol% of Ti relative to Co in the lithium cobalt-based composite oxide ((Ti/Co) × 100) is preferably 0.01 to 5.00 mol%, particularly preferably 0.05 to 2.00 mol%. When the lithium-cobalt-based composite oxide contains Ti as the M element, the mol% ((Ti/Co) × 100) of Ti in terms of atoms relative to Co in the lithium-cobalt-based composite oxide is within the above range, so that cycle characteristics, operating voltage, and battery characteristics such as load characteristics can be particularly improved.

When the lithium-cobalt-based composite oxide contains Mg as the M element, the atomic conversion mol% of Mg relative to Co in the lithium-cobalt-based composite oxide ((Mg/Co) × 100) is preferably 0.01 to 5.00 mol%, particularly preferably 0.05 to 2.00 mol%. When the lithium-cobalt-based composite oxide contains Mg as the M element, the mol% ((Mg/Co) × 100) of Mg in terms of atoms with respect to Co in the lithium-cobalt-based composite oxide is within the above range, so that the battery characteristics such as cycle characteristics, load characteristics, and safety can be particularly improved.

When the lithium cobalt-based composite oxide contains Ca as the M element, the atomic conversion mol% of Ca relative to Co ((Ca/Co) × 100) in the lithium cobalt-based composite oxide is preferably 0.01 to 5.00 mol%, particularly preferably 0.05 to 2.00 mol%. When the lithium-cobalt-based composite oxide contains Ca as the M element, the lithium-cobalt-based composite oxide has an atom-equivalent mol% of Ca relative to Co ((Ca/Co) × 100) within the above range, so that the battery characteristics such as cycle characteristics, load characteristics, and safety can be particularly improved.

The M element may be present inside the lithium-cobalt-based composite oxide particles, may be present on the surface of the lithium-cobalt-based composite oxide particles, and may be present both inside and on the surface of the lithium-cobalt-based composite oxide particles.

When the M element exists on the surface of the particles of the lithium-cobalt-based composite oxide, the M element may exist in the form of an oxide, composite oxide, sulfate, phosphate, or the like.

The lithium-cobalt-based composite oxide particles are particles of the lithium-cobalt-based composite oxide.

Lithium-cobalt-based composite oxide particles are manufactured by performing, for example, a raw material mixing step of preparing a raw material mixture containing a lithium compound and a cobalt compound, and then a firing step of firing the resulting raw material mixture.

The lithium compound related to the raw material mixing step is not particularly limited as long as it is a lithium compound that is usually used as a raw material for producing a lithium cobalt composite oxide, and examples thereof include lithium oxides, hydroxides, carbonates, nitrates, sulfates and organic acid salts.

The cobalt compound used in the raw material mixing step is not particularly limited as long as it is a cobalt compound that is usually used as a raw material for producing a lithium-cobalt composite oxide, and examples thereof include cobalt oxides, oxyhydroxides, hydroxides, carbonates, nitrates, sulfates, and organic acid salts.

In the raw material mixing step, the mixing ratio of the lithium compound and the cobalt compound is such that, in terms of atoms, the ratio of the number of moles of Li to the number of moles of Co (Li/Co molar ratio) is preferably 0.90 to 1.20, particularly preferably 0.95 to 1.15. When the mixing ratio of the lithium compound and the cobalt compound is within the above range, it becomes easier to obtain a single-phase lithium-cobalt-based composite oxide.

In the raw material mixing step, the raw material mixture can be mixed with a compound containing the M element.

Compounds containing the M element include oxides, hydroxides, carbonates, nitrates, sulfates, fluorides and organic acid salts containing the M element. As the compound containing the M element, a compound containing two or more kinds of the M element may be used.

The lithium compound, the cobalt compound, and the compound containing the M element, which are raw materials, may have any production history, but in order to produce high-purity lithium-cobalt-based composite oxide particles, it is preferable that the content of impurities is as low as possible.

In the raw material mixing step, examples of the method of mixing the lithium compound, the cobalt compound, and the compound containing the M element used as necessary include a mixing method using a ribbon mixer, a Henschel mixer, a super mixer, a Nauta mixer, or the like. At the laboratory level, a home-use mixer is sufficient as a mixing method.

The firing step is a step of firing the raw material mixture obtained by performing the raw material mixing step to obtain a lithium-cobalt-based composite oxide.

In the firing step, the firing temperature for firing the raw material mixture to react the raw materials is 800 to 1150°C, preferably 900 to 1100°C. By setting the firing temperature within the above range, it is possible to reduce the formation of unreacted cobalt oxide or overheated decomposition products of the lithium-cobalt-based composite oxide, which cause a decrease in the capacity of the lithium-cobalt-based composite oxide.

The firing time in the firing step is 1 to 30 hours, preferably 5 to 20 hours. The firing atmosphere in the firing step is an oxidizing atmosphere such as air or oxygen gas.

The lithium-cobalt-based composite oxide thus obtained may be subjected to a plurality of firing steps, if necessary.

The average particle size of the lithium-cobalt-based composite oxide particles before the Ti-containing compound and the Mg-containing compound are adhered is a particle size (D50) at 50% volume integration in the particle size distribution determined by a laser diffraction/scattering method, and is 0.5 to 30 μm, preferably 3 to 25 μm, particularly preferably 7 to 25 μm. The BET specific surface area of the lithium-cobalt composite oxide particles before the Ti-containing compound and Mg-containing compound are attached is preferably 0.05 to 1.0 m ² /g, particularly preferably 0.15 to 0.6 m ² /g. When the average particle diameter or BET specific surface area of the lithium-cobalt-based composite oxide particles before the Ti-containing compound and Mg-containing compound are adhered is within the above range, the positive electrode mixture can be easily prepared and coated, and an electrode with high fillability can be obtained.

The surface treatment liquid containing the Mg-containing compound or the precursor of the Mg-containing compound used in the method for producing the modified lithium-cobalt-based composite particles of the first aspect of the present invention or the method for producing the modified lithium-cobalt-based composite particles of the second aspect of the present invention is a solution in which the Mg-containing compound or the precursor of the Mg-containing compound is dissolved or dispersed in water and/or an organic solvent.

The surface treatment liquid containing a titanium chelate compound used in the method for producing modified lithium cobalt composite particles of the first aspect of the present invention or the method for producing modified lithium cobalt composite particles of the second aspect of the present invention is a solution in which a titanium chelate compound is dissolved or dispersed in water and/or an organic solvent.

The surface treatment liquid containing the Mg-containing compound or the precursor of the Mg-containing compound and the titanium chelate compound used in the method for producing the modified lithium-cobalt-based composite particles of the third embodiment of the present invention is a solution obtained by dissolving or dispersing the Mg-containing compound or the precursor of the Mg-containing compound and the titanium chelate compound in water and/or an organic solvent.

Examples of Mg-containing compounds include Mg sulfates, Mg oxides, Mg fluorides, composite oxides of Ti and Mg, and the like. Precursors of Mg-containing compounds include organic acid salts of Mg. The precursor of the Mg-containing compound is thermally decomposed on the surface of the lithium-cobalt composite oxide particles by heat treatment at 400 to 1000°C, preferably 600 to 900°C.

The organic acid salt of Mg is preferably a carboxylate, and examples of the carboxylate include monocarboxylic acids such as formic acid, acetic acid, glycolic acid, lactic acid, and gluconic acid; dicarboxylic acids such as oxalic acid, maleic acid, malonic acid, malic acid, tartaric acid, and succinic acid; and carboxylic acid salts having three carboxyl groups, such as citric acid. These organic acid salts of Mg are converted to oxides of Mg by heat treatment to be described later.

A titanium chelate compound is a compound in which one or more hydroxycarboxylic acid molecules are coordinated to a titanium metal atom. As a precursor of the Ti-containing compound, a titanium chelate compound represented by the following general formula (1) is preferable.
Ti(R ¹ ) _m L _n (1)
(In the formula, R ¹ represents an alkoxy group, a hydroxyl group, a halogen atom, an amino group, or a phosphine, and when there are a plurality of them, they may be the same or different. L represents a group derived from hydroxycarboxylic acid, and when there are a plurality of them, they may be the same or different. m represents a number of 0 or more and 3 or less, n represents a number of 1 or more and 3 or less, and m+n is 3 to 6.)

The alkoxy group represented by R ¹ is preferably a linear or branched alkoxy group having 1 to 4 carbon atoms. Halogen atoms include fluorine, chlorine, bromine and iodine atoms. The amino group includes, for example, methylamino group, ethylamino group, propylamino group, isopropylamino group, butylamino group, isobutylamino group, tert-butylamino group, pentylamino group and the like. Examples of phosphines include trimethylphosphine, triethylphosphine, tributylphosphine, tris-tert-butylphosphine, triphenylphosphine and the like.

The hydroxycarboxylic acid-derived group represented by L includes a group in which an oxygen atom of a hydroxyl group in a hydroxycarboxylic acid or an oxygen atom of a carboxyl group in a hydroxycarboxylic acid is coordinated to a titanium atom. In addition, a group in which an oxygen atom of a hydroxyl group in a hydroxycarboxylic acid and an oxygen atom of a carboxyl group in a hydroxycarboxylic acid are bidentately coordinated to a titanium atom is also included. Among these, the oxygen atom of the hydroxyl group in the hydroxycarboxylic acid and the oxygen atom of the carboxyl group in the hydroxycarboxylic acid are preferably bidentate coordinated groups to the titanium atom. When m is 0, m+n is preferably 3, and when m is 1 or more and 3 or less, m+n is preferably 4 or 5.

For the titanium chelate compound, for example, a titanium alkoxide is diluted with a solvent to obtain a diluted solution, and the diluted solution and hydroxycarboxylic acid are mixed to obtain a solution containing the titanium chelate compound (see WO2019/138989 pamphlet). In this production method, the solution containing the titanium chelate compound can be used as it is as the solution containing the organotitanium compound. Also, water may be added to the solution containing the titanium chelate compound. Thereby, a dispersion or solution of the titanium chelate compound in a water-containing solvent can be obtained.

Examples of the titanium alkoxide include tetramethoxytitanium (IV), tetraethoxytitanium (IV), tetra-n-propoxytitanium (IV), tetraisopropoxytitanium (IV), tetra-n-butoxytitanium (IV) and tetraisobutoxytitanium (IV).

Examples of the hydroxycarboxylic acid include monovalent carboxylic acids such as lactic acid, glycolic acid, glyceric acid and hydroxybutyric acid, divalent carboxylic acids such as tartronic acid, malic acid and tartaric acid, and trivalent carboxylic acids such as citric acid and isocitric acid. Among these, lactic acid is preferable from the viewpoint that it becomes a solution easily at room temperature, is easily mixed with the diluted titanium alkoxide solution, and can easily produce a titanium chelate compound.

As the solvent used as the diluent, alcohols such as methanol, ethanol, isopropanol, n-propanol, n-butanol, sec-butanol, tert-butanol and n-pentane can be preferably used.

In addition to the hydroxycarboxylic acid, a ligand compound capable of coordinating to titanium may be added to the mixture of the diluent and the hydroxycarboxylic acid or to the solution containing the titanium chelate compound for the purpose of efficiently obtaining the titanium chelate compound with high productivity. Examples of such ligand compounds include halogen atom-containing compounds, methylamino group, ethylamino group, propylamino group, isopropylamino group, butylamino group, isobutylamino group, t-butylamino group, amines having functional groups such as pentylamino, and phosphines such as trimethylphosphine, triethylphosphine, tributylphosphine, tris-tert-butylphosphine and triphenylphosphine.

Moreover, some titanium chelate compounds are commercially available from Matsumoto Fine Chemical Co., Ltd., and commercial products may be used.

The content of the Mg-containing compound or the precursor of the Mg-containing compound in the surface treatment liquid containing the Mg-containing compound or the precursor of the Mg-containing compound used in the method for producing the modified lithium-cobalt-based composite particles of the first embodiment of the present invention or the method for producing the modified lithium-cobalt-based composite particles of the second embodiment of the present invention is 0.01 to 30.0% by mass, preferably 0.05 to 25.0% by mass, in terms of atoms, as Mg. preferable from this point of view.

The content of the titanium chelate compound in the surface treatment liquid containing the titanium chelate compound used in the method for producing the modified lithium cobalt composite particles of the first embodiment of the present invention or the method for producing the modified lithium cobalt composite particles of the second embodiment of the present invention is preferably 0.01 to 30.0% by mass, preferably 0.05 to 20.0% by mass as Ti, in terms of the stability of the Ti solution and the operability of the coating treatment.

The content of the Mg-containing compound or the precursor of the Mg-containing compound in the surface treatment liquid containing the Mg-containing compound or the precursor of the Mg-containing compound used in the method for producing the modified lithium-cobalt-based composite particles of the third embodiment of the present invention and the titanium chelate compound is preferably 0.01 to 30.0% by mass, preferably 0.05 to 25.0% by mass as Mg in terms of atoms, from the viewpoint of stability of the solution and operability of the coating treatment, and the content of the titanium chelate compound. is 0.01 to 30.0% by mass, preferably 0.05 to 20.0% by mass as Ti in terms of atoms, from the viewpoint of solution stability and coating treatment operability.

In the modified lithium-cobalt-based composite oxide particles obtained by the method for producing the modified lithium-cobalt-based composite oxide particles of the first aspect of the present invention, the method for producing the modified lithium-cobalt-based composite oxide particles of the second aspect of the present invention, or the method for producing the modified lithium-cobalt-based composite oxide particles of the third aspect of the present invention, the Ti-containing compound may adhere to a part of the surface of the lithium-cobalt-based composite oxide particles, or may cover the entire surface of the lithium-cobalt-based composite oxide particles. Further, in the modified lithium cobalt-based composite oxide particles obtained by the method for producing the modified lithium cobalt-based composite oxide particles of the first embodiment of the present invention, the method for producing the modified lithium cobalt-based composite oxide particles of the second embodiment of the present invention, or the method for producing the modified lithium cobalt-based composite oxide particles of the third embodiment of the present invention, the Mg-containing compound may be attached to a part of the surface of the lithium cobalt-based composite oxide particles, or may be attached covering the entire surface of the lithium cobalt-based composite oxide particles. In the modified lithium-cobalt-based composite oxide particles obtained by the method for producing the modified lithium-cobalt-based composite oxide particles of the first aspect of the present invention, the method for producing the modified lithium-cobalt-based composite oxide particles of the second aspect of the present invention, or the method for producing the modified lithium-cobalt-based composite oxide particles of the third aspect of the present invention, the Ti-containing compound and/or the Mg-containing compound is attached to at least a part of the surface of the lithium-cobalt-based composite oxide particles, thereby reducing cycle deterioration and increasing the energy maintenance rate. In the modified lithium-cobalt-based composite oxide particles obtained by the method for producing the modified lithium-cobalt-based composite oxide particles of the first aspect of the present invention, the method for producing the modified lithium-cobalt-based composite oxide particles of the second aspect of the present invention, or the method for producing the modified lithium-cobalt-based composite oxide particles of the third aspect of the present invention, the Mg-containing compound adheres to cover the entire surface of the lithium-cobalt-based composite oxide particles, and the Ti-containing compound adheres to a part of the surface of the lithium-cobalt-based composite oxide particles. It is preferable in that even when charging and discharging are repeated at voltage, cycle deterioration is small, and the positive electrode active material has a high energy density retention rate.

In the modified lithium-cobalt-based composite oxide particles obtained by the method for producing modified lithium-cobalt-based composite oxide particles according to the first aspect of the present invention, the method for producing modified lithium-cobalt-based composite oxide particles according to the second aspect of the present invention, or the method for producing modified lithium-cobalt-based composite oxide particles according to the third aspect of the present invention, the Mg-containing compound adhering to part or all of the surface of the lithium-cobalt-based composite oxide particles is a compound containing Mg. Fluorides of Mg, composite compounds of titanium and magnesium (hereinafter also referred to as “composite oxides of Ti and Mg”), and the like.

The oxide of Mg may be produced by oxidative decomposition of an organic acid salt of Mg at 400 to 1000.degree. C., preferably 600 to 900.degree. The organic acid salt of Mg is preferably a carboxylate, and examples of the carboxylate include monocarboxylic acids such as formic acid, acetic acid, glycolic acid, lactic acid, and gluconic acid; dicarboxylic acids such as oxalic acid, maleic acid, malonic acid, malic acid, tartaric acid, and succinic acid; and carboxylic acid salts having three carboxyl groups, such as citric acid. When an organic acid salt of Mg is used as a raw material for attaching the Mg-containing compound to the surfaces of the lithium-cobalt-based composite oxide particles, the Mg-containing compound attached to the surface of the lithium-cobalt-based composite oxide particles is an oxidative decomposition product of the organic acid salt of Mg.

As the Mg-containing compound, Mg sulfates, Mg oxides, and Ti-Mg composite oxides are preferred because they are highly stable even in a charged state and can contribute to improving battery characteristics. Mg sulfates are particularly preferred because they also have the effect of reducing the pH of lithium-cobalt-based composite oxides.

In the modified lithium-cobalt-based composite oxide particles obtained by further performing the step (A2) in the method for producing modified lithium-cobalt-based composite oxide particles of the first aspect of the present invention, or in the modified lithium-cobalt-based composite oxide particles obtained by the method for producing modified lithium-cobalt-based composite oxide particles of the second aspect of the present invention or the method for producing modified lithium-cobalt-based composite oxide particles of the third aspect of the present invention, the adhesion amount of the Mg-containing compound is, in terms of atoms, from 0.01 to Mg relative to Co in the lithium-cobalt-based composite oxide. It is preferably 5.00 mol %, preferably 0.10 to 2.00 mol %. When the adhesion amount of the Mg-containing compound is within the above range, it is possible to achieve both high charge/discharge capacity and battery characteristics such as cycle characteristics, load characteristics, and safety.

In the modified lithium-cobalt-based composite oxide particles obtained by the method for producing modified lithium-cobalt-based composite oxide particles of the first embodiment of the present invention, the method for producing modified lithium-cobalt-based composite oxide particles of the second embodiment of the present invention, or the method for producing modified lithium-cobalt-based composite oxide particles of the third embodiment of the present invention, the Ti-containing compound attached to a part or all of the surfaces of the lithium-cobalt-based composite oxide particles includes oxides containing titanium, and the like. The oxide containing titanium may be, for example, an oxide of Ti or a composite oxide containing Ti obtained by the present production method. The composite oxide containing Ti includes, for example, a composite oxide of Li and/or M element and Ti derived from Li or M element in the lithium cobalt-based composite oxide, a composite oxide of Mg and Ti derived from a surface treatment liquid containing a Mg-containing compound or a precursor of the Mg-containing compound, and a composite oxide of Li and/or M element derived from Li and/or M element in the lithium cobalt-based composite oxide and Mg derived from a surface treatment liquid containing a Mg-containing compound or a precursor of the Mg-containing compound, Mg, and Ti. etc.

The oxide containing titanium is produced by oxidative decomposition of a titanium chelate compound at 400 to 1000°C, preferably 600 to 900°C. Since the titanium chelate compound is used as a raw material for attaching the Ti-containing compound to the surfaces of the lithium-cobalt-based composite oxide particles, the Ti-containing compound attached to the surfaces of the lithium-cobalt-based composite oxide particles is an oxidative decomposition product of the titanium chelate compound.

In the modified lithium-cobalt-based composite oxide particles obtained by the method for producing the modified lithium-cobalt-based composite oxide particles of the first aspect of the present invention, the method for producing the modified lithium-cobalt-based composite oxide particles of the second aspect of the present invention, or the method for producing the modified lithium-cobalt-based composite oxide particles of the third aspect of the present invention, the Ti-containing compound is an oxide containing titanium that is highly stable even in a charged state, and can contribute to improving battery characteristics.

In the modified lithium-cobalt-based composite oxide particles obtained by the method for producing the modified lithium-cobalt-based composite oxide particles of the first aspect of the present invention, the method for producing the modified lithium-cobalt-based composite oxide particles of the second aspect of the present invention, or the method for producing the modified lithium-cobalt-based composite oxide particles of the third aspect of the present invention, the amount of the Ti-containing compound attached is 0.01 to 5.00 mol%, preferably 0.10 to 2.00 mol% as Ti, based on Co in the lithium-cobalt-based composite oxide, in terms of atoms. Preferred. When the amount of the Ti-containing compound attached is within the above range, it is possible to achieve both high charge/discharge capacity and battery characteristics such as cycle characteristics, load characteristics, and safety.

The average particle size of the modified lithium-cobalt-based composite oxide particles obtained by the method for producing the modified lithium-cobalt-based composite oxide particles of the first aspect of the present invention, the method for producing the modified lithium-cobalt-based composite oxide particles of the second aspect of the present invention, or the method for producing the modified lithium-cobalt-based composite oxide particles of the third aspect of the present invention is 0.5 to 30 μm, preferably 3 to 25 μm, particularly preferably 0.5 to 30 μm, preferably 3 to 25 μm, as a particle diameter (D50) at 50% volume integration in the particle size distribution obtained by a laser diffraction/scattering method. 7 to 25 μm. The BET specific surface area of the modified lithium cobalt composite oxide particles obtained by the method for producing modified lithium cobalt composite oxide particles of the first embodiment of the present invention, the method for producing modified lithium cobalt composite oxide particles of the second embodiment of the present invention, or the method for producing modified lithium cobalt composite oxide particles of the third embodiment of the present invention is preferably 0.05 to 1.0 m ² /g, and particularly preferably 0.15 to 0.6 m ² /g. When the average particle size or BET specific surface area of the modified lithium cobalt composite oxide particles obtained by the method for producing modified lithium cobalt composite oxide particles of the first aspect of the present invention, the method for producing modified lithium cobalt composite oxide particles of the second aspect of the present invention, or the method for producing modified lithium cobalt composite oxide particles of the third aspect of the present invention is in the above range, the positive electrode mixture can be easily prepared and coated, and an electrode with high fillability can be obtained.

A lithium secondary battery comprising a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte containing a lithium salt can be produced by using the modified lithium cobalt composite oxide particles obtained by the method for producing the modified lithium cobalt composite oxide particles of the first embodiment of the present invention, the method for producing the modified lithium cobalt composite oxide particles of the second embodiment of the present invention, or the method for producing the modified lithium cobalt composite oxide particles of the third embodiment of the present invention.

The positive electrode of the lithium secondary battery according to the present invention is formed, for example, by coating and drying a positive electrode material mixture on a positive electrode current collector. The positive electrode mixture is composed of a positive electrode active material, a conductive agent, a binder, a filler added as necessary, and the like. In the lithium secondary battery, the positive electrode is uniformly coated with the modified lithium-cobalt-based composite oxide particles obtained by the method for manufacturing the modified lithium-cobalt-based composite oxide particles of the first embodiment of the present invention, the method for manufacturing the modified lithium-cobalt-based composite oxide particles of the second embodiment of the present invention, or the method for manufacturing the modified lithium-cobalt-based composite oxide particles of the third embodiment of the present invention, as a positive electrode active material. For this reason, the lithium secondary battery according to the present invention has high battery performance, in particular, even when charging and discharging are repeated under high voltage, there is little deterioration in (charge-discharge) capacity, and the energy density retention rate is high.

The content of the positive electrode active material contained in the positive electrode mixture for the lithium secondary battery is desirably 70 to 100% by mass, preferably 90 to 98% by mass.

The positive electrode current collector for the lithium secondary battery is not particularly limited as long as it is an electronic conductor that does not undergo chemical changes in the constructed battery. The surface of these materials may be oxidized before use, or the surface of the current collector may be roughened by surface treatment. Examples of the form of the current collector include foil, film, sheet, net, punched material, lath, porous material, foam, fiber group, non-woven fabric, and the like. Although the thickness of the current collector is not particularly limited, it is preferably 1 to 500 μm.

The conductive agent for lithium secondary batteries is not particularly limited as long as it is an electronically conductive material that does not undergo chemical changes in the constructed battery. Examples include graphite such as natural graphite and artificial graphite; carbon blacks such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber and metal fiber; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; , flaky graphite and earthy graphite. These can be used singly or in combination of two or more. The mixing ratio of the conductive agent is 1 to 50% by mass, preferably 2 to 30% by mass in the positive electrode mixture.

リチウム二次電池に係る結着剤としては、例えば、デンプン、ポリフッ化ビニリデン、ポリビニルアルコール、カルボキシメチルセルロース、ヒドロキシプロピルセルロース、再生セルロース、ジアセチルセルロース、ポリビニルピロリドン、テトラフロオロエチレン、ポリエチレン、ポリプロピレン、エチレン－プロピレン－ジエンターポリマー（ＥＰＤＭ）、スルホン化ＥＰＤＭ、スチレンブタジエンゴム、フッ素ゴム、テトラフルオロエチレン－ヘキサフルオロエチレン共重合体、テトラフルオロエチレン－ヘキサフルオロプロピレン共重合体、テトラフルオロエチレン－パーフルオロアルキルビニルエーテル共重合体、フッ化ビニリデン－ヘキサフルオロプロピレン共重合体、フッ化ビニリデン－クロロトリフルオロエチレン共重合体、エチレン－テトラフルオロエチレン共重合体、ポリクロロトリフルオロエチレン、フッ化ビニリデン－ペンタフルオロプロピレン共重合体、プロピレン－テトラフルオロエチレン共重合体、エチレン－クロロトリフルオロエチレン共重合体、フッ化ビニリデン－ヘキサフルオロプロピレン－テトラフルオロエチレン共重合体、フッ化ビニリデン－パーフルオロメチルビニルエーテル－テトラフルオロエチレン共重合体、エチレン－アクリル酸共重合体またはその（Ｎａ ⁺ ）イオン架橋体、エチレン－メタクリル酸共重合体またはその（Ｎａ ⁺ ）イオン架橋体、エチレン－アクリル酸メチル共重合体またはその（Ｎａ ⁺ ）イオン架橋体、エチレン－メタクリル酸メチル共重合体またはその（Ｎａ ⁺ ）イオン架橋体、ポリエチレンオキシドなどの多糖類、熱可塑性樹脂、ゴム弾性を有するポリマー等が挙げられ、これらは１種または２種以上組み合わせて用いることができる。 When using a compound containing a functional group that reacts with lithium, such as a polysaccharide, it is preferable to deactivate the functional group by adding a compound such as an isocyanate group. The blending ratio of the binder is 1 to 50% by mass, preferably 5 to 15% by mass in the positive electrode mixture.

A filler for a lithium secondary battery suppresses volume expansion and the like of the positive electrode in the positive electrode mixture, and is added as necessary. As the filler, any fibrous material can be used as long as it does not cause a chemical change in the constructed battery. The amount of the filler to be added is not particularly limited, but is preferably 0 to 30% by mass in the positive electrode mixture.

A negative electrode for a lithium secondary battery is formed by coating and drying a negative electrode material on a negative electrode current collector. The negative electrode current collector for the lithium secondary battery of the present invention is not particularly limited as long as it is an electronic conductor that does not cause a chemical change in the constructed battery. Further, the surface of these materials may be oxidized before use, or the surface of the current collector may be roughened by surface treatment. Examples of the form of the current collector include foil, film, sheet, net, punched material, lath, porous material, foam, fiber group, non-woven fabric, and the like. Although the thickness of the current collector is not particularly limited, it is preferably 1 to 500 μm.

The negative electrode material for lithium secondary batteries is not particularly limited, but examples thereof include carbonaceous materials, metal composite oxides, lithium metals, lithium alloys, silicon-based alloys, tin-based alloys, metal oxides, conductive polymers, chalcogen compounds, Li—Co—Ni-based materials, Li ₄ Ti ₅ O ₁₂ , lithium niobate, silicon oxide (SiOx: 0.5≦x≦1.6), and the like. Examples of carbonaceous materials include non-graphitizable carbon materials and graphite-based carbon materials. Examples of metal composite oxides include Sn _p (M ¹ ) _1-p (M ² ) _{q Or} (wherein M ¹ represents one or more elements selected from Mn, Fe, Pb and Ge, M ² represents one or more elements selected from Al, B, P, Si, Groups 1, 2 and 3 of the periodic table and halogen elements, and 0<p≦1, 1≦q≦3, and 1≦r≦8. ), Li _t Fe ₂ O ₃ (0≦t≦1), and Li _t WO ₂ (0≦t≦1). GEO, GEO ₂ , SNO, SNO 2, PBO ₂ , PBO ₂ , PB ₂ O ₃ , SB _{2 O 3, SB 2 O 3 , SB 2 O5} , SB _{2 O5} , BI ₂ O ₃ , BI ₂ O ₄ , BI ₂ O5 _, etc. Examples of conductive polymers include polyacetylene and poly-p-phenylene.

As a separator for a lithium secondary battery, an insulating thin film having a high ion permeability and a predetermined mechanical strength is used. Sheets and non-woven fabrics made of olefin polymers such as polypropylene, glass fibers, or polyethylene are used because of their organic solvent resistance and hydrophobicity. The pore size of the separator may be within a range generally useful for batteries, for example, 0.01 to 10 μm. The thickness of the separator may be within the range for general batteries, for example, 5 to 300 μm. In addition, when a solid electrolyte such as a polymer is used as the electrolyte described later, the solid electrolyte may also serve as a separator.

A non-aqueous electrolyte containing a lithium salt for a lithium secondary battery is composed of a non-aqueous electrolyte and a lithium salt. Non-aqueous electrolytes, organic solid electrolytes, and inorganic solid electrolytes are used as the non-aqueous electrolyte for the lithium secondary battery of the present invention. Non-aqueous electrolytes include, for example, N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, and triphosphate. Esters, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, diethyl ether, 1,3-propanesultone, methyl propionate, solvents mixed with two or more of aprotic organic solvents such as ethyl propionate.

Examples of organic solid electrolytes for lithium secondary batteries include polyethylene derivatives, polyethylene oxide derivatives or polymers containing them, polypropylene oxide derivatives or polymers containing these, phosphate ester polymers, polyphosphazenes, polyaziridines, polyethylene sulfides, polyvinyl alcohol, polyvinylidene fluoride, polymers containing ionic dissociation groups such as polyhexafluoropropylene, and mixtures of polymers containing ionic dissociation groups and the above non-aqueous electrolytes.

Li nitrides, halides, oxates, sulfides, etc. can be used as inorganic solid electrolytes for lithium secondary batteries.₃N, LiI, Li_FiveNI₂, Li₃N-LiI-LiOH, LiSiO_Four, LiSiO_Four-LiI-LiOH, Li₂SiS₃, Li_FourSiO_Four, Li_FourSiO_Four-LiI-LiOH, P₂S._Five, Li₂S or Li₂SP₂S._Five, Li₂S—SiS₂, Li₂S-GeS₂, Li₂S-Ga₂S.₃, Li₂SB₂S.₃, Li₂SP₂S._Five-X, Li₂S—SiS₂-X, Li₂S-GeS₂-X, Li₂S-Ga₂S.₃-X, Li₂SB₂S.₃-X, (where X is LiI, B₂S.₃, or Al₂S.₃at least one selected from) and the like.

更に、無機固体電解質が非晶質（ガラス）の場合は、リン酸リチウム（Ｌｉ ₃ ＰＯ ₄ ）、酸化リチウム（Ｌｉ ₂ Ｏ）、硫酸リチウム（Ｌｉ ₂ ＳＯ ₄ ）、酸化リン（Ｐ ₂ Ｏ ₅ ）、硼酸リチウム（Ｌｉ ₃ ＢＯ ₃ ）等の酸素を含む化合物、Ｌｉ ₃ ＰＯ _4-ｕ Ｎ _2ｕ/3 （ｕは０＜ｕ＜４）、Ｌｉ ₄ ＳｉＯ _4-ｕ Ｎ _2ｕ/3 （ｕは０＜ｕ＜４）、Ｌｉ ₄ ＧｅＯ _4-ｕ Ｎ _2ｕ/3 （ｕは０＜ｕ＜４）、Ｌｉ ₃ ＢＯ _3-ｕ Ｎ _2ｕ/3 （ｕは０＜ｕ＜３）等の窒素を含む化合物を無機固体電解質に含有させることができる。 The addition of this oxygen-containing compound or nitrogen-containing compound widens the gaps in the formed amorphous skeleton, reduces hindrance to the movement of lithium ions, and further improves the ionic conductivity.

As the lithium salt for the lithium secondary battery, one _{that dissolves in the above non-aqueous electrolyte is used. 4 , CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2 ) 2 NLi , lithium chloroborane , lithium lower aliphatic carboxylate , lithium tetraphenylborate , imides , and the like ,} or salts thereof in combination _of two or more thereof.

In addition, the following compounds can be added to the non-aqueous electrolyte for the purpose of improving discharge and charge characteristics and flame retardancy. For example, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinone and N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, polyethylene glycol, pyrrole, 2-methoxyethanol, aluminum trichloride, monomers of conductive polymer electrode active materials, triethylenephosphonamide, trialkylphosphine, morpholine, aryl compounds with carbonyl groups, hexamethylphosphoric triamide and 4-alkylmorpholine, bicyclic tertiary amines, oils, phosphonium salts and tertiary sulfonium salts, phosphazenes, carbonate esters and the like. Moreover, in order to make the electrolyte nonflammable, the electrolyte may contain a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride. In addition, carbon dioxide gas can be contained in the electrolytic solution in order to make it suitable for high-temperature storage.

A lithium secondary battery using as a positive electrode active material the modified lithium cobalt composite oxide particles obtained by the method for producing the modified lithium cobalt composite oxide particles of the first embodiment of the present invention, the method for producing the modified lithium cobalt composite oxide particles of the second embodiment of the present invention, or the method for producing the modified lithium cobalt composite oxide particles of the third embodiment of the present invention is a lithium secondary battery that exhibits little cycle deterioration even when charging and discharging are repeated, especially under high voltage, and has a high energy density maintenance rate. Any shape may be used.

Applications of the lithium secondary battery are not particularly limited, but examples thereof include notebook computers, laptop computers, pocket word processors, mobile phones, cordless child devices, portable CD players, radios, liquid crystal televisions, backup power sources, electric shavers, memory cards, electronic devices such as video movies, and consumer electronic devices such as automobiles, electric vehicles, drones, game devices, and electric tools.

EXAMPLES The present invention will be described in detail below with reference to Examples, but the present invention is not limited to these Examples.

<Preparation of lithium cobalt composite oxide particles (LCO) sample>
<LCO sample 1>
Lithium carbonate (average particle size 5.7 μm), tricobalt tetroxide (average particle size 2.5 μm), titanium dioxide (average particle size 0.4 μm), and calcium sulfate (average particle size 7.3 μm) were weighed and thoroughly mixed in a home mixer to obtain a raw material mixture having a Li/Co molar ratio of 1.04, a Ti/Co molar ratio of 0.01, and a Ca/Co molar ratio of 0.0006.
The raw material mixture thus obtained was then fired in an alumina pot at 1050° C. for 5 hours in the air. After firing, the fired product was pulverized and classified to obtain a lithium-cobalt composite oxide containing 1.00 mol % of Ti and 0.06 mol % of Ca relative to Co.

<LCO sample 2>
Lithium carbonate (average particle size: 5.7 μm) and tricobalt tetroxide (average particle size: 2.5 μm) were weighed and thoroughly mixed in a home mixer to obtain a raw material mixture with a Li/Co molar ratio of 0.997.
The raw material mixture thus obtained was then fired in an alumina pot at 1050° C. for 5 hours in the air. After firing, the fired product was pulverized and classified to obtain a lithium-cobalt composite oxide.

<LCO sample 3>
Lithium carbonate (average particle size: 5.7 μm), tricobalt tetroxide (average particle size: 2.5 μm), magnesium fluoride (average particle size: 2.8 μm), magnesium oxide (average particle size: 0.6 μm), and calcium sulfate (average particle size: 7.3 μm) were weighed and thoroughly mixed in a home mixer to obtain a Li/Co molar ratio of 1.05, a F/Co molar ratio of 0.005, and a Mg/Co molar ratio of 0.005. A raw material mixture having a Ca/Co molar ratio of 0.0013 was obtained.
The resulting raw material mixture was then fired in an alumina pot at 1080° C. for 5 hours in the air. After firing, the fired product was pulverized and classified to obtain a lithium-cobalt composite oxide containing 0.50 mol % of Mg and 0.13 mol % of Ca relative to Co.

<LCO sample 4>
Lithium carbonate (average particle size: 5.7 μm) and tricobalt tetroxide (average particle size: 2.5 μm) were weighed and thoroughly mixed in a home mixer to obtain a raw material mixture with a Li/Co molar ratio of 1.04.
The raw material mixture thus obtained was then fired in an alumina pot at 1050° C. for 5 hours in the air. After firing, the fired product was pulverized and classified to obtain a lithium-cobalt composite oxide.

Table 1 shows various physical properties of the lithium cobalt composite oxide sample (LCO sample) obtained above. The average particle size was determined by the (laser diffraction/scattering) method.

<Preparation of surface treatment liquid>
<Preparation of surface treatment liquid containing magnesium sulfate>
Magnesium sulfate was dissolved in water, and the pH was adjusted to 8.5 with aqueous ammonia to prepare a magnesium sulfate-containing surface treatment liquid having the concentration shown in Table 2 below.

<Preparation of Surface Treatment Liquid Containing Titanium Lactate Chelate>
Tetraisopropoxytitanium (TPT) was added to isopropanol (IPA), lactic acid was added with stirring (TPT/IPA/lactic acid = 1/2/3 in terms of molar ratio), and then water was added to prepare a titanium lactate chelate solution. Further, the pH was adjusted to 8.5 with aqueous ammonia to prepare a surface treatment liquid containing a titanium lactate chelate having a concentration shown in Table 2 below.
The titanium lactate chelate mainly contained a compound in which m = 0 and n = 3 in the general formula (1), and L is a group in which an oxygen atom of a hydroxyl group and an oxygen atom of a carboxyl group in lactic acid are bidentate coordinated to a titanium atom.

<Preparation of titanium lactate chelate/magnesium acetate composite surface treatment liquid>
An aqueous magnesium acetate solution was added to the titanium lactate chelate solution before pH adjustment, and the pH was adjusted to 8.5 with aqueous ammonia to prepare a titanium lactate chelate/magnesium acetate composite surface treatment solution having a concentration shown in Table 2 below.

<Preparation of titanium lactate chelate/ammonium sulfate composite surface treatment liquid>
An ammonium sulfate aqueous solution was added to the titanium lactate chelate solution before pH adjustment, and the pH was adjusted to 8.5 with ammonia water to prepare a titanium lactate chelate/ammonium sulfate composite surface treatment solution having a concentration shown in Table 2 below.

(Example 1-1)
30 g of LCO sample 1 shown in Table 1 was collected in a conical beaker, and 6 g of titanium lactate chelate-containing surface treatment liquid B-1 was added thereto and sufficiently kneaded with a spatula or the like to obtain a paste-like mixture. Then, the entire amount was dried in a dryer at 100 ° C., and the obtained dry powder was baked at 800 ° C. for 5 hours and heat-treated to obtain a Ti-containing compound-adhered lithium cobalt composite oxide particle (positive electrode active material sample) shown in Table 3.

(Example 1-2)
30 g of LCO sample 1 shown in Table 1 was collected in a conical beaker, and 6 g of magnesium sulfate-containing surface treatment liquid A-1 was added thereto and sufficiently kneaded with a spatula or the like to obtain a paste-like mixture.
Next, the entire amount of the magnesium sulfate-adhered LCO obtained was transferred to a conical beaker, and 6 g of the titanium lactate chelate-containing surface treatment liquid B-1 was added thereto and sufficiently kneaded with a spatula or the like to obtain a paste-like mixture.

(Comparative Example 1-1)
The LCO sample 1 shown in Table 1 was sintered as it was at 800° C. for 5 hours and subjected to heat treatment to obtain lithium-cobalt-based composite oxide particles (positive electrode active material sample) shown in Table 3.

(Comparative Example 1-2)
30 g of LCO sample 1 shown in Table 1 was collected in a conical beaker, and 6 g of magnesium sulfate-containing surface treatment liquid A-1 was added thereto and sufficiently kneaded with a spatula or the like to obtain a paste-like mixture.

(Example 2-1)
Using the LCO sample 2 shown in Table 1, the Ti-containing compound-attached lithium-cobalt composite oxide particles (positive electrode active material sample) shown in Table 3 were obtained in the same manner as in Example 1-1.

(Example 2-2)
30 g of LCO sample 2 shown in Table 1 was collected in a conical beaker, and 6 g of titanium lactate chelate/ammonium sulfate composite surface treatment liquid D was added thereto and sufficiently kneaded with a spatula or the like to obtain a paste-like mixture. Then, the entire amount was dried in a dryer at 100 ° C., and the obtained dry powder was baked at 800 ° C. for 5 hours and heat-treated to obtain sulfate and Ti-containing compound-attached lithium cobalt composite oxide particles (positive electrode active material sample) shown in Table 3.

(Example 2-3)
Using the LCO sample 2 shown in Table 1, the Ti-containing compound- and Mg-containing compound-attached lithium-cobalt-based composite oxide particles (positive electrode active material sample) shown in Table 3 were obtained in the same manner as in Example 1-2.

(Example 2-4)
30 g of LCO sample 2 shown in Table 1 was collected in a conical beaker, and 6 g of titanium lactate chelate/magnesium acetate composite surface treatment liquid C was added thereto and sufficiently kneaded with a spatula or the like to obtain a paste-like mixture. After that, the entire amount was dried in a dryer at 100 ° C., and the obtained dry powder was baked at 800 ° C. for 5 hours and heat-treated to obtain lithium-cobalt-based composite oxide particles (positive electrode active material sample) attached with a Ti-containing compound and Mg-containing compound shown in Table 3.

(Comparative Example 2-1)
The LCO sample 2 shown in Table 1 was sintered as it was at 800° C. for 5 hours and subjected to heat treatment to obtain lithium-cobalt composite oxide particles (positive electrode active material sample) shown in Table 3.

(Example 3-1)
30 g of LCO sample 3 shown in Table 1 was collected in a conical beaker, and 6 g of titanium lactate chelate-containing surface treatment liquid B-2 was added thereto and sufficiently kneaded with a spatula or the like to obtain a paste-like mixture. Then, the entire amount was dried in a dryer at 100 ° C., and the obtained dry powder was baked at 1000 ° C. for 5 hours and heat-treated to obtain a Ti-containing compound-adhered lithium cobalt composite oxide particle (positive electrode active material sample) shown in Table 3.

(Example 3-2)
Using LCO sample 3 shown in Table 1, using A-2 as a magnesium sulfate-containing surface treatment liquid and B-2 as a titanium lactate chelate-containing surface treatment liquid, dry powder obtained by drying the entire amount after surface treatment was 1000 ° C. For 5 hours, the same operation as in Example 1-2 was performed, except that the Ti-containing compound and Mg-containing compound-adhered lithium cobalt composite oxide particles (positive electrode active material sample) shown in Table 3 were obtained.

(Comparative Example 3-1)
The LCO sample 3 shown in Table 1 was sintered as it was at 1000° C. for 5 hours and heat-treated to obtain lithium-cobalt-based composite oxide particles (positive electrode active material sample) shown in Table 3.

(Example 4-1)
In the same manner as in Example 1-2, except that LCO sample 4 shown in Table 1 was used, A-3 was used as the magnesium sulfate-containing surface treatment solution, and B-3 was used as the titanium lactate chelate-containing surface treatment solution.

(Comparative Example 4-1)
The LCO sample 4 shown in Table 1 was sintered as it was at 800° C. for 5 hours and heat-treated to obtain lithium-cobalt-based composite oxide particles (positive electrode active material sample) shown in Table 3.

注）付着量は、ＬＣＯ試料中のＣｏに対する原子換算のＭｇ及び／又はＴｉの量をｍｏｌ％で示した。

Note) The adhesion amount indicates the amount of Mg and/or Ti in terms of atoms with respect to Co in the LCO sample in mol%.

A battery performance test was conducted as follows.
<Production of lithium secondary battery>
95% by mass of the positive electrode active material obtained in Examples and Comparative Examples, 2.5% by mass of graphite powder, and 2.5% by mass of polyvinylidene fluoride were mixed to form a positive electrode agent, which was dispersed in N-methyl-2-pyrrolidinone to prepare a kneaded paste. The kneaded paste was applied to an aluminum foil, dried, pressed and punched into a disk having a diameter of 15 mm to obtain a positive electrode plate.
Using this positive electrode plate, a coin-type lithium secondary battery was manufactured using members such as a separator, a negative electrode, a positive electrode, a collector plate, a mounting bracket, an external terminal, and an electrolytic solution. Among them, a metal lithium foil was used as the negative electrode, and a solution prepared by dissolving 1 mol of LiPF ₆ in 1 liter of a 1:1 mixture of ethylene carbonate and methyl ethyl carbonate was used as the electrolyte.
Next, performance evaluation of the obtained lithium secondary battery was performed. The results are shown in Table 4.

<Battery performance evaluation>
The produced coin-type lithium secondary batteries were operated at room temperature under the following test conditions, and the following battery performances were evaluated.
(1-a) Test Conditions for Evaluation of 4.5V Cycle Characteristics First, charging was performed at 0.5C to 4.5V over 2 hours, and then constant current/constant voltage charging (CCCV charging) was performed to hold the voltage at 4.5V for 3 hours. After that, charge and discharge were performed by constant current discharge (CC discharge) to 2.7 V at 0.2 C, and these operations were regarded as one cycle, and the discharge capacity was measured for each cycle. This cycle was repeated for 20 cycles.
(1-b) Test Conditions for Evaluation of 4.6V Cycle Characteristics First, charging was performed at 0.5C to 4.6V over 2 hours, and then constant current/constant voltage charging (CCCV charging) was performed to hold the voltage at 4.6V for 3 hours. After that, charge and discharge were performed by constant current discharge (CC discharge) to 2.7 V at 0.2 C, and these operations were regarded as one cycle, and the discharge capacity was measured for each cycle. This cycle was repeated for 20 cycles.

(2) Initial capacity (per weight of active material), initial charge-discharge efficiency The charge and discharge capacities of the first cycle in the cycle characteristic evaluation are defined as the initial charge capacity and the initial discharge capacity, and the efficiency calculated by the following formula (1) is defined as the initial charge-discharge efficiency.
Initial charge/discharge efficiency (%) = (1st cycle charge capacity/1st cycle discharge capacity) x 100 (1)

(3) Capacity retention rate The capacity retention rate was calculated from the discharge capacity (per active material weight) at the 1st cycle and the 20th cycle in the cycle characteristic evaluation, using the following formula (2).
Capacity retention rate (%) = (discharge capacity at 20th cycle/discharge capacity at 1st cycle) x 100 (2)

(4) Energy Density Retention Rate The energy density retention rate was calculated by the following formula (3) from the Wh capacity (per active material weight) during discharge at the 1st cycle and the 20th cycle in the cycle characteristics evaluation.
Energy density maintenance rate (%) = (Discharge Wh capacity at 20th cycle/Discharge Wh capacity at 1st cycle) x 100 (3)

<LCO sample 5>
Lithium carbonate (average particle size: 5.7 μm) and tricobalt tetroxide (average particle size: 2.5 μm) were weighed and thoroughly mixed in a home mixer to obtain a raw material mixture with a Li/Co molar ratio of 1.04.
Next, the obtained raw material mixture was calcined in an alumina pot at 1000° C. for 5 hours in the air. After firing, the fired product was pulverized and classified to obtain a lithium-cobalt composite oxide.

Table 9 shows various physical properties of the lithium cobalt composite oxide sample (LCO sample) obtained above. The average particle size was determined by the (laser diffraction/scattering) method.

(Example 5-1)
Using LCO sample 5 shown in Table 9, using A-1 as a magnesium sulfate-containing surface treatment liquid and B-1 as a titanium lactate chelate-containing surface treatment liquid, dry powder obtained by drying the entire amount after surface treatment at 800 ° C. A Ti-containing compound and Mg-containing compound-attached lithium cobalt composite oxide particles (positive electrode active material sample) shown in Table 10 were obtained in the same manner as in Example 1-2 except that they were baked for 5 hours and heat-treated.
Then, a battery performance test was conducted in the same manner as described above. The results are shown in Table 11.

(Comparative Example 5-1)
The LCO sample 5 shown in Table 9 was baked as it was at 800° C. for 5 hours and heat-treated to obtain a positive electrode active material sample shown in Table 10.
Then, a battery performance test was conducted in the same manner as described above. The results are shown in Table 11.

注）付着量は、ＬＣＯ試料に対する原子換算のＭｇ及び／又はＴｉの量をｍｏｌ％で示した。

Note) The amount of adhesion indicates the amount of Mg and/or Ti in terms of atoms with respect to the LCO sample in mol%.

Claims (8)

A method for producing modified lithium-cobalt-based composite oxide particles, comprising a step (A1) of bringing lithium-cobalt-based composite oxide particles into contact with a surface treatment liquid containing a titanium chelate compound, followed by heat treatment to obtain modified lithium-cobalt-based composite oxide particles (a1), wherein the temperature of the heat treatment is 600 to 1000° C., and the titanium chelate compound is a titanium chelate compound represented by the following general formula (1).
General formula (1):
Ti(R ¹ ) _m L _n (1)
(In the formula, R ¹ represents an alkoxy group, a hydroxyl group, a halogen atom, an amino group, or a phosphine, and when there are a plurality of them, they may be the same or different. L represents a group derived from hydroxycarboxylic acid, and when there are a plurality of them, they may be the same or different. m represents a number of 0 or more and 3 or less, n represents a number of 1 or more and 3 or less, and m+n is 3 to 6.) 2. The method for producing modified lithium-cobalt-based composite oxide particles according to claim 1, further comprising a step (A2) of obtaining modified lithium-cobalt-based composite oxide particles (a2) by contacting the modified lithium-cobalt-based composite oxide particles (a1) obtained by performing the step (A1) with a surface treatment liquid containing a Mg-containing compound or a precursor of the Mg-containing compound, followed by heat treatment. A step (B1) of obtaining Mg-containing compound-attached lithium-cobalt-based composite oxide particles (b1) by contacting the lithium-cobalt-based composite oxide particles with a surface treatment liquid containing a Mg-containing compound or a precursor of the Mg-containing compound, followed by heat treatment;
A step (B2) of obtaining modified lithium-cobalt-based composite oxide particles (b2) by bringing the Mg-containing compound-attached lithium-cobalt-based composite oxide particles (b1) into contact with a surface treatment liquid containing a titanium chelate compound, followed by heat treatment;
, wherein the temperature of the heat treatment in step (B2) is 600 to 1000 ° C., and the titanium chelate compound is a titanium chelate compound represented by the following general formula (1). A method for producing modified lithium cobalt-based composite oxide particles.
General formula (1):
Ti(R ¹ ) _m L _n (1)
(In the formula, R ¹ represents an alkoxy group, a hydroxyl group, a halogen atom, an amino group, or a phosphine, and when there are a plurality of them, they may be the same or different. L represents a group derived from hydroxycarboxylic acid, and when there are a plurality of them, they may be the same or different. m represents a number of 0 or more and 3 or less, n represents a number of 1 or more and 3 or less, and m+n is 3 to 6.) Lithium cobalt composite oxide particles are brought into contact with a surface treatment liquid containing a titanium chelate compound and a Mg-containing compound or a precursor of the Mg-containing compound, and then subjected to heat treatment to obtain modified lithium cobalt composite oxide particles (c1).
General formula (1):
Ti(R ¹ ) _m L _n (1)
(In the formula, R ¹ represents an alkoxy group, a hydroxyl group, a halogen atom, an amino group, or a phosphine, and when there are a plurality of them, they may be the same or different. L represents a group derived from hydroxycarboxylic acid, and when there are a plurality of them, they may be the same or different. m represents a number of 0 or more and 3 or less, n represents a number of 1 or more and 3 or less, and m+n is 3 to 6.) 3. The method for producing modified lithium cobalt composite oxide particles according to claim 2, wherein the heat treatment temperature in step (A2) is 400 to 1000.degree. 4. The method for producing modified lithium-cobalt-based composite oxide particles according to claim 3, wherein the heat treatment temperature in step (B1) is 400 to 1000.degree. The modified lithium-cobalt-based composite oxide particles according to any one of claims 1 to 6 , wherein the lithium-cobalt-based composite oxide particles contain one or more of M elements (M is Mg, Al, Ti, Zr, Cu, Fe, Sr, Ca, V, Mo, Bi, Nb, Si, Zn, Ga, Ge, Sn, Ba, W, Na, K, Ni, or Mn) in addition to Li, Co, and O. manufacturing method. 8. The method for producing modified lithium-cobalt-based composite oxide particles according to claim 7 , wherein the element M is one or more selected from Ti, Mg and Ca.