JP4539139B2 - Nonaqueous electrolyte secondary battery, positive electrode active material for nonaqueous electrolyte secondary battery, and positive electrode mixture for nonaqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery, a positive electrode active material for a non-aqueous electrolyte secondary battery (hereinafter also simply referred to as a “positive electrode active material”), and a positive electrode for a non-aqueous electrolyte secondary battery. The present invention relates to a mixture (hereinafter also simply referred to as “positive electrode mixture”). Specifically, the present invention relates to a non-aqueous electrolyte secondary battery having a layered lithium transition metal composite oxide, a positive electrode active material, and a positive electrode mixture, with extremely improved battery characteristics.

Non-aqueous electrolyte secondary batteries are characterized by higher operating voltage and higher energy density compared to conventional nickel cadmium secondary batteries, etc. Mobile electronics such as mobile phones, notebook computers, digital cameras, etc. Widely used as a power source for equipment. Examples of the positive electrode active material of the non-aqueous electrolyte secondary battery include lithium transition metal composite oxides typified by LiCoO ₂ , LiNiO ₂ , and LiMn ₂ O _4. Among them, LiCoO ₂ has been conventionally used for mobile electronic devices. It was used, and sufficient battery characteristics were obtained.

At present, however, mobile electronic devices are used in more severe environments due to higher functionality such as the addition of various functions and use at high and low temperatures. Also, application to power sources such as batteries for electric vehicles is expected, and conventional non-aqueous electrolyte secondary batteries using LiCoO ₂ cannot obtain sufficient battery characteristics, and further improvements are required. Yes.

Patent Document 1 describes a positive electrode made of Li _1-x CoO ₂ (0 ≦ x <1) to which zirconium (Zr) is added or a part of cobalt thereof is substituted with another transition metal. Then, the surface of the LiCoO ₂ particles is stabilized by being covered with zirconium oxide (ZrO ₂ ) or a composite oxide of lithium and zirconium, Li ₂ ZrO _3. It is described that a positive electrode active material exhibiting excellent cycle characteristics and storage characteristics can be obtained without causing destruction.
However, this positive electrode active material could not satisfy the load characteristics, low temperature characteristics and thermal stability required for recent non-aqueous electrolyte secondary batteries. There is also room for improvement in cycle characteristics.

JP-A-4-319260

  An object of the present invention is to provide a non-aqueous electrolyte secondary battery, a positive electrode active material for a non-aqueous electrolyte secondary battery, and a positive electrode mixture for a non-aqueous electrolyte secondary battery having excellent battery characteristics even in a more severe use environment. There is to do.

  The present invention provides the following (1) to (5).

(1) Forming a positive electrode active material layer using a positive electrode active material having zirconium in at least a part of a crystallite interface of a layered lithium transition metal composite oxide on at least one surface of a band-shaped positive electrode current collector. A belt-like positive electrode constituted by:
Metallic lithium,
Lithium alloy,
By forming a negative electrode active material layer using a carbon material capable of occluding and releasing lithium ions or a compound capable of occluding and releasing lithium ions as a negative electrode active material on at least one surface of a strip-shaped negative electrode current collector A configured negative electrode,
A strip separator,
A non-aqueous electrolyte secondary battery in which the strip separator is interposed between the strip positive electrode and the strip negative electrode.

  (2) A spiral type in which the belt-like positive electrode and the belt-like negative electrode are wound a plurality of times in a state of being laminated via the belt-like separator, and the belt-like separator is interposed between the belt-like positive electrode and the belt-like negative electrode The non-aqueous electrolyte secondary battery according to (1), wherein the non-aqueous electrolyte secondary battery is configured by forming a wound body.

  (3) A stack body in which the strip-shaped separator is interposed between the strip-shaped positive electrode and the strip-shaped negative electrode is formed by stacking the strip-shaped positive electrode and the strip-shaped negative electrode in a state of being stacked via the strip-shaped separator. The nonaqueous electrolyte secondary battery according to (1) above.

(4) A positive electrode active material for a non-aqueous electrolyte secondary battery having at least a layered lithium transition metal composite oxide,
The lithium transition metal composite oxide is a positive electrode active material for a non-aqueous electrolyte secondary battery having zirconium in at least a part of a crystallite interface thereof.

(5) A positive electrode mixture for a non-aqueous electrolyte secondary battery having a positive electrode active material having at least a layered lithium transition metal composite oxide and a conductive agent,
The lithium transition metal composite oxide has zirconium in at least a part of its crystallite interface,
A positive electrode mixture for a non-aqueous electrolyte secondary battery, wherein zirconium is present between the positive electrode active material and the conductive agent.

The nonaqueous electrolyte secondary battery according to (1) has a strip of a positive electrode active material layer using a positive electrode active material having zirconium in at least a part of a crystallite interface of a layered structure lithium transition metal composite oxide. A belt-like positive electrode is formed by forming the positive electrode current collector.
Since zirconium is present in at least a part of the crystallite interface of the lithium transition metal composite oxide, the interface resistance decreases, and this increases the discharge potential under load at normal and low temperatures. Capacity maintenance rate is improved. That is, it is considered that load characteristics and low temperature characteristics are improved.
Moreover, it is thought that lithium can suppress local precipitation to a negative electrode at the time of charge. For this reason, it is considered that the generation of gas during charging can be suppressed and dry-out can be prevented, so that the cycle characteristics are improved.
Furthermore, it is considered that by having zirconium in at least a part of the crystallite interface, desorption of oxygen is suppressed and thermal stability is improved.
Therefore, a nonaqueous electrolyte secondary battery having improved load characteristics, low temperature characteristics, cycle characteristics, and thermal stability can be obtained.

  The non-aqueous electrolyte secondary battery according to (2) is formed by winding a strip-shaped positive electrode and a strip-shaped negative electrode a plurality of times in a state of being stacked via a strip-shaped separator, and the strip-shaped separator is interposed between the strip-shaped positive electrode and the strip-shaped negative electrode. It forms a spiral wound body. By adopting such a configuration, a nonaqueous electrolyte secondary battery excellent in mass productivity can be obtained without impairing improvements in load characteristics, low temperature characteristics, cycle characteristics, and thermal stability.

  The nonaqueous electrolyte secondary battery according to (3) is a stack in which a belt-like positive electrode and a belt-like negative electrode are stacked in a state of being laminated via a belt-like separator, and the belt-like separator is interposed between the belt-like positive electrode and the belt-like negative electrode Consists of the body. By adopting such a configuration, the internal resistance of the battery can be lowered without impairing improvements in load characteristics, low-temperature characteristics, cycle characteristics, and thermal stability. A battery is obtained.

The positive electrode active material according to (4) has zirconium in at least a part of the crystallite interface of the lithium transition metal composite oxide.
It is considered that the interface resistance is reduced because zirconium is contained in at least a part of the crystallite interface of the lithium transition metal composite oxide. As a result, the discharge potential under load at normal temperature and low temperature is increased, and the capacity retention rate under load is improved. That is, load characteristics and low temperature characteristics are improved.
In addition, it is considered that lithium can be prevented from locally depositing on the negative electrode during charging, and gas generation during charging can be suppressed, thereby preventing dryout. For this reason, cycle characteristics are improved.
Furthermore, it is considered that the elimination of oxygen is suppressed by having zirconium in at least a part of the crystallite interface. For this reason, thermal stability improves.

Since the positive electrode active material described in (5) has zirconium at least part of the crystallite interface of the lithium transition metal composite oxide, as described above, load characteristics, low temperature characteristics, cycle characteristics, and heat Stability is improved.
Further, it is considered that the presence of zirconium between the lithium transition metal composite oxide and the conductive agent makes it difficult to separate the lithium transition metal composite oxide and the conductive agent. Thereby, the application | coating characteristic to the electrical power collector of a positive mix is improved, without impairing said effect.

  Hereinafter, the nonaqueous electrolyte secondary battery, the positive electrode active material for nonaqueous electrolyte secondary battery, and the positive electrode mixture for nonaqueous electrolyte secondary battery according to the present invention will be specifically described. However, the present invention is not limited to this embodiment.

<Positive electrode active material for non-aqueous electrolyte secondary battery>
The positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention comprises at least a layered lithium transition metal composite oxide. The layered structure means that the crystal structure of the lithium transition metal composite oxide is layered.
FIG. 1 is a schematic view showing a crystal structure of a lithium transition metal composite oxide having a layered structure.
The layered structure is not particularly limited, and examples thereof include a layered rock salt structure and a zigzag layered rock salt structure. Among these, a layered rock salt structure is preferable.

  The lithium transition metal composite oxide having a layered structure is not particularly limited. For example, lithium cobaltate, lithium nickelate, lithium chromate, lithium vanadate, lithium manganate, lithium nickel cobaltate, nickel cobalt lithium manganate, nickel cobalt lithium aluminate. Preferable examples include lithium cobaltate, lithium nickel cobaltate, nickel cobalt lithium aluminate and nickel cobalt lithium manganate.

When the composition ratio of Li, Co, and O of lithium cobaltate is represented by the general formula Li _x CoO _y , x represents a number satisfying 0.95 ≦ x ≦ 1.10, and y is 1.8 ≦ y ≦ It is preferable to represent a number satisfying 2.2.
Li of lithium nickel cobaltate, Ni, when represents a composition ratio of Co and O in the general formula _{Li k Ni m Co p O r} , k represents a number satisfying 0.95 ≦ k ≦ 1.10, m Represents a number satisfying 0.1 ≦ m ≦ 0.9, p represents a number satisfying 0.1 ≦ p ≦ 0.9, and r represents a number satisfying 1.8 ≦ r ≦ 2.2. Is preferred.
Nickel cobalt aluminate lithium Li, Ni, Co, when represents a composition ratio of Al and O in the general formula _{Li k Ni m Co p Al (} 1-m-p) O r, k is 0.95 ≦ k ≦ 1.10, m represents a number satisfying 0.1 ≦ m ≦ 0.9, p represents a number satisfying 0.1 ≦ p ≦ 0.9, and m + p represents m + p ≦ 1. It is preferable to represent a number that satisfies, and r represents a number that satisfies 1.8 ≦ r ≦ 2.2.
When the composition ratio of Li, Ni, Co, Mn, and O of lithium nickel cobalt manganate is expressed by the general formula Li _k Ni _m Co _p Mn _(1-mp) O _r , k is 0.95 ≦ k ≦ 1.10, m represents a number satisfying 0.1 ≦ m ≦ 0.9, p represents a number satisfying 0.1 ≦ p ≦ 0.9, and m + p represents m + p ≦ 1. It is preferable to represent a number that satisfies, and r represents a number that satisfies 1.8 ≦ r ≦ 2.2.

In the positive electrode active material of the present invention, the lithium transition metal composite oxide has zirconium in at least a part of its crystallite interface.
A crystallite means the maximum group considered as a single crystal. In general, the crystal grains themselves are composed of a plurality of single crystals. When the crystal orientations of two or more adjacent single crystals coincide with each other, the whole of the two or more single crystals is considered as one crystallite. When the crystal orientations of adjacent single crystals are different, each single crystal becomes a different crystallite.
The presence of zirconium in at least a part of the crystallite interface can be confirmed by various methods. For example, it can be confirmed with a SEM image, a SIM image, a TEM image, a STEM image, or the like. You may confirm the cross section of lithium transition metal complex oxide by a SEM image, a SIM image, a TEM image, a STEM image, etc.

In the positive electrode active material of the present invention, the lithium transition metal composite oxide is usually a particle, but the form is not particularly limited, and may be, for example, a film. The particles may be primary particles, secondary particles, or a mixture of these.
Zirconium is not particularly limited in its form of existence, and can exist as a simple substance or a compound.
As the zirconium compound, zirconium oxide and lithium zirconate are preferable. More preferable zirconium compounds are ZrO ₂ and Li ₂ ZrO ₃ . More preferably, it is Li ₂ ZrO ₃ .

  In the positive electrode active material of the present invention, zirconium is preferably 0.01 mol% or more, more preferably 0.02 mol% or more, and 0.04 mol% or more with respect to the lithium transition metal composite oxide. Is more preferably 2 mol% or less, more preferably 0.3 mol% or less, and further preferably 0.25 mol% or less. If the amount of zirconium is too small, the proportion of zirconium in a part of the crystallite interface decreases, so that it is difficult to obtain the effects of the present invention. When there is too much zirconium, the discharge capacity becomes small.

  Hereinafter, lithium transition metal composite oxides suitably used in the present invention will be exemplified.

(1) When at least one lithium transition metal composite oxide selected from the group consisting of lithium cobaltate, lithium nickel cobaltate, nickel cobalt lithium aluminate, and nickel cobalt lithium manganate is lithium cobaltate or nickel cobaltate, Cycle characteristics are further improved, and a positive electrode active material for a non-aqueous electrolyte secondary battery having excellent load characteristics, low temperature characteristics and thermal stability is obtained. Therefore, the nonaqueous electrolyte secondary battery using this positive electrode active material can be suitably used for applications such as mobile phones and notebook computers.
When the lithium transition metal composite oxide is nickel cobalt lithium aluminate, it becomes a positive electrode active material for a non-aqueous electrolyte secondary battery with further improved load characteristics, low temperature characteristics, output characteristics, cycle characteristics, and thermal stability. Therefore, the nonaqueous electrolyte secondary battery using this positive electrode active material can be suitably used for applications such as electric vehicles, mobile phones, and notebook computers.
When the lithium transition metal composite oxide is nickel cobalt lithium manganate, the load characteristics, low temperature characteristics, output characteristics and cycle characteristics are further improved, and the positive electrode active material for a non-aqueous electrolyte secondary battery is further improved in thermal stability. . Therefore, the nonaqueous electrolyte secondary battery using this positive electrode active material can be suitably used for applications such as mobile phones, electric tools, and electric vehicles.

Nickel cobalt lithium, nickel cobalt lithium lithium and nickel cobalt lithium manganate have a layered crystal structure similar to lithium cobalt oxide.
However, these methods have a problem that a large amount of gas is generated and a potential at the time of discharge is lower than that of lithium cobaltate.
In the present invention, since zirconium is present in at least a part of these crystallite interfaces, it is considered that residual lithium in the raw material is reduced and gas generation during charging can be prevented.
In addition, the interface resistance is reduced, thereby increasing the discharge potential under load at normal temperature and low temperature, and improving the capacity retention rate under load. That is, it is considered that load characteristics and low temperature characteristics are improved.
Further, it is considered that lithium can be prevented from locally depositing on the negative electrode during charging. For this reason, it is considered that the generation of gas during charging can be suppressed and dry-out can be prevented, so that the cycle characteristics are improved.
Further, it is considered that the presence of zirconium in at least a part of the crystallite interface suppresses the desorption of oxygen and improves the thermal stability.
Therefore, the lithium transition metal composite oxide is at least one selected from the group consisting of lithium nickel cobaltate, nickel cobalt lithium aluminate, and nickel cobalt lithium manganate having zirconium at least at part of its crystallite interface. The embodiments are useful.

(2) transition metal that is not the same as cobalt, lithium cobalt oxide containing at least one element selected from the group consisting of Group 2, Group 13 and Group 14 elements of the periodic table, halogen element and sulfur Thus, load characteristics, low temperature characteristics, cycle characteristics and thermal stability are further improved.
Among them, lithium cobaltate is represented by the general formula Li _x CoO _y (wherein x represents a number satisfying 0.95 ≦ x ≦ 1.10 and y represents a number satisfying 1.8 ≦ y ≦ 2.2). .).
Preferred specific examples of the general formula is in _{Li a Co 1-b M b} O c X d S e ( wherein, M is a Group 2 of the transition metal and the periodic table is not identical to the cobalt, the Group 13 and 14 elements of the X represents at least one selected from the group consisting of halogen elements, a represents a number satisfying 0.95 ≦ a ≦ 1.10, and b represents 0 <b ≦ 0.10. C represents a number satisfying 1.8 ≦ c ≦ 2.2, d represents a number satisfying 0 ≦ d ≦ 0.10, and e represents a number satisfying 0 ≦ e ≦ 0.015. Lithium transition metal composite oxide represented by the following formula.

(3) nickel cobalt oxide lithium containing at least one element selected from the group consisting of transition metals that are not identical to nickel and cobalt, elements of groups 2, 13 and 14 of the periodic table, halogen elements and sulfur; nickel And nickel cobalt lithium aluminate containing at least one element selected from the group consisting of transition metals not identical to cobalt, group 2 of the periodic table, group 13 and group 14 elements not identical to aluminum, halogen elements and sulfur; Or a nickel cobalt lithium manganate containing at least one element selected from the group consisting of transition metals not identical to nickel, cobalt and manganese, elements of Groups 2, 13 and 14 of the periodic table, halogen elements and sulfur By including these elements, load characteristics, low temperature characteristics, Further improvement of output characteristics, cycle characteristics and thermal stability can be realized. Therefore, the nonaqueous electrolyte secondary battery using this positive electrode active material can be suitably used for applications such as electric tools, electric vehicles, mobile phones, and notebook computers.

Among them, transition metals that are not identical to Co and Ni (when Z is Mn in the following formula, transition metals that are not identical to Co, Ni, and Mn), Groups 2 and 13 of the periodic table (when Z is Al in the formula below) The general formula is Li _k Ni _m Co _p Z _(1-mp) containing at least one element selected from the group consisting of Group 13 elements not identical to Al) and Group 14 elements, halogen elements and S O _r (wherein Z represents Al or Mn, k represents a number satisfying 0.95 ≦ k ≦ 1.10, m represents a number satisfying 0.1 ≦ m ≦ 0.9, and p represents A number satisfying 0.1 ≦ p ≦ 0.9, m + p representing a number satisfying m + p ≦ 1, and r representing a number satisfying 1.8 ≦ r ≦ 2.2. Metal composite oxides are preferred.

As a preferable specific example, the general formula is Li _k Ni _m Co _p Z _(1-mp) O _r (wherein Z represents Al or Mn, and k satisfies 0.95 ≦ k ≦ 1.10. M represents a number satisfying 0.1 ≦ m ≦ 0.9, p represents a number satisfying 0.1 ≦ p ≦ 0.9, m + p represents a number satisfying m + p ≦ 1, r Represents a number satisfying 1.8 ≦ r ≦ 2.2).

(4) Lithium cobaltate containing at least one element selected from the group consisting of titanium, aluminum, vanadium, zirconium, magnesium, calcium, strontium, and sulfur. It is considered that the cycle characteristics are improved by stabilizing. Moreover, it is thought that cycling characteristics improve by surface modification.
More preferably, it contains at least one element selected from the group consisting of titanium, aluminum, zirconium and magnesium. By including at least one element selected from the group consisting of titanium, aluminum, zirconium and magnesium, the cycle characteristics are further improved. In addition to these effects, the thermal stability is further improved by including magnesium.

In the aspect (4), since the passage of electrons is improved by the presence of sulfur, it is considered that the cycle characteristics and the load characteristics are further improved.
The sulfur content is preferably 0.03 to 0.7% by weight based on the total of the lithium transition metal composite oxide and sulfur. If it is less than 0.03% by weight, it may be difficult to reduce the resistance of electron movement. If it is more than 0.7% by weight, gas generation may occur due to moisture adsorption.

In the aspect (4), sulfur may be present in any form. For example, it may exist in the form of sulfate radicals.
The sulfate radical includes sulfate ions, a group of atoms obtained by removing the electrons from sulfate ions, and a sulfo group. It is preferably based on at least one selected from the group consisting of alkali metal sulfates, alkaline earth metal sulfates, organic sulfates and organic sulfonic acids and salts thereof.
Among them, it is preferable to use at least one selected from the group consisting of alkali metal sulfates and alkaline earth metal sulfates, and more preferable to use alkali metal sulfates. This is because these are chemically stable because they are composed of strong acid strong base bonds.

In the aspect (4), the sulfate radical is preferably present on the surface of the lithium transition metal composite oxide particles. By having sulfate radicals on the surface of the particles, it is considered that the sulfate radicals can easily pass electrons. Therefore, load characteristics are further improved.
Even when the sulfate radical covers the entire particle surface of the lithium transition metal composite oxide, or even when the sulfate radical covers a part of the particle surface of the lithium transition metal composite oxide. Further, load characteristics are improved.

In the aspect (4), when the composition ratio of Li, Co, and O of lithium cobaltate is represented by the general formula Li _x CoO _y , x represents a number satisfying 0.95 ≦ x ≦ 1.10. Preferably represents a number satisfying 1.8 ≦ y ≦ 2.2.

(5) at least a lithium-transition metal composite oxide is represented by the general formula _{Li a Co 1-b M b} O c X d S e (M is Ti, Al, V, Zr, Mg, selected from the group consisting of Ca and Sr X represents at least one element selected from halogen elements, a represents a number satisfying 0.95 ≦ a ≦ 1.10, and b represents a number satisfying 0 ≦ b ≦ 0.10. C represents a number satisfying 1.8 ≦ c ≦ 2.2, d represents a number satisfying 0 ≦ d ≦ 0.10, and e represents a number satisfying 0 ≦ e ≦ 0.015.) An embodiment represented by
It is preferable for the same reason as in the aspect (4).

(5) comprising at least one element selected from the group consisting of titanium, aluminum, vanadium, zirconium, magnesium, calcium, strontium and sulfur, comprising lithium nickel cobaltate, nickel cobalt lithium aluminate and nickel cobalt lithium manganate At least one selected from the group It is considered that the presence of these elements causes a pillar effect and improves the cycle characteristics by stabilizing the crystal structure. Moreover, it is thought that cycling characteristics improve by surface modification.
More preferably, it contains at least one element selected from the group consisting of titanium, aluminum, zirconium and magnesium. By including at least one element selected from the group consisting of titanium, aluminum, zirconium and magnesium, the cycle characteristics are further improved. In addition to these effects, the thermal stability is further improved by including magnesium.

In aspect (5), since the passage of electrons is improved by the presence of sulfur, it is considered that the cycle characteristics and load characteristics are further improved.
The sulfur content is preferably 0.03 to 0.7% by weight based on the total of the lithium transition metal composite oxide and sulfur. If it is less than 0.03% by weight, it may be difficult to reduce the resistance of electron movement. If it is more than 0.7% by weight, gas generation may occur due to moisture adsorption.

In the aspect (5), sulfur may be present in any form. For example, it may exist in the form of sulfate radicals.
The sulfate radical includes sulfate ions, a group of atoms obtained by removing the electrons from sulfate ions, and a sulfo group. It is preferably based on at least one selected from the group consisting of alkali metal sulfates, alkaline earth metal sulfates, organic sulfates and organic sulfonic acids and salts thereof.
Among them, it is preferable to use at least one selected from the group consisting of alkali metal sulfates and alkaline earth metal sulfates, and more preferable to use alkali metal sulfates. This is because these are chemically stable because they are composed of strong acid strong base bonds.

In the aspect (5), it is preferable that the sulfate group exists on the surface of the lithium transition metal composite oxide particles. By having sulfate radicals on the surface of the particles, it is considered that the sulfate radicals can easily pass electrons. Therefore, load characteristics are further improved.
Even when the sulfate radical covers the entire particle surface of the lithium transition metal composite oxide, or even when the sulfate radical covers a part of the particle surface of the lithium transition metal composite oxide. Further, load characteristics are improved.

In the embodiment (5), when expressed Li of lithium nickel cobaltate, Ni, a composition ratio of Co and O in the general formula _{Li k Ni m Co p O r} , k is 0.95 ≦ k ≦ 1.10 M represents a number satisfying 0.1 ≦ m ≦ 0.9, p represents a number satisfying 0.1 ≦ p ≦ 0.9, and r represents 1.8 ≦ r ≦ 2. It is preferable to represent a number satisfying 2.

In the aspect (5), when the composition ratio of Li, Ni, Co, Al, and O of nickel cobalt lithium aluminate is represented by the general formula Li _k Ni _m Co _p Al _(1-mp) O _r , k represents a number satisfying 0.95 ≦ k ≦ 1.10, m represents a number satisfying 0.1 ≦ m ≦ 0.9, and p represents a number satisfying 0.1 ≦ p ≦ 0.9. , M + p represents a number satisfying m + p ≦ 1, and r preferably represents a number satisfying 1.8 ≦ r ≦ 2.2.

In the embodiment (5), Li of lithium nickel cobalt manganese oxide, Ni, Co, when representing the composition ratio of Mn and O in the general formula _{Li k Ni m Co p Mn (} 1-m-p) O r, k represents a number satisfying 0.95 ≦ k ≦ 1.10, m represents a number satisfying 0.1 ≦ m ≦ 0.9, and p represents a number satisfying 0.1 ≦ p ≦ 0.9. , M + p represents a number satisfying m + p ≦ 1, and r preferably represents a number satisfying 1.8 ≦ r ≦ 2.2.

  In the positive electrode active material of the present invention, the lithium transition metal composite oxide may be a mixture of lithium nickel cobaltate and nickel cobalt lithium aluminate, or a mixture of lithium nickel cobaltate and nickel cobalt lithium manganate, It may be a mixture of nickel cobalt lithium aluminate and nickel cobalt lithium manganate. Moreover, the mixture of these and lithium cobaltate may be sufficient.

  In the positive electrode active material of the present invention, the proportion of particles having a volume-based particle diameter of 50 μm or more of the lithium transition metal composite oxide is preferably 10% by volume or less of the total particles. By being a positive electrode active material within this range, it is possible to improve coating characteristics and slurry properties without impairing improvement in cycle characteristics and thermal stability of a high charge potential.

The specific surface area of the lithium transition metal composite oxide is preferably 0.2 to ³ m ² / g.
When the specific surface area is too small, the particle size of the positive electrode active material becomes too large and the battery characteristics deteriorate. When the specific surface area is too large, the oxidative decomposition reaction of the electrolytic solution occurring on or near the surface of the positive electrode active material increases, and the amount of gas generated increases. Within the above range, gas generation can be reduced without impairing improvements in low temperature characteristics, output characteristics and thermal stability, and more excellent cycle characteristics and load characteristics can be obtained.
The specific surface area can be measured by a nitrogen gas adsorption method.

  In the lithium transition metal composite oxide, the proportion of particles having a volume-based particle size of 50 μm or more is preferably 10% by volume or less of the total particles. Within the above range, the coating characteristics and slurry properties can be improved without impairing the improvement of load characteristics, low temperature characteristics, output characteristics and thermal stability.

In the present invention, it is one of preferred embodiments that at least a part of the surface of the lithium transition metal composite oxide is covered with a coating layer made of Al ₂ O ₃ and / or LiTiO ₂ powder.
When the coating layer is made of Al ₂ O ₃ powder, it is considered that the moving speed in the electric double layer can be somewhat lowered, and the moving speed of lithium ions in the crystal lattice can be kept in balance. Therefore, the voltage drop can be improved.
In addition, when the coating layer is made of LiTiO ₂ powder, a unique phenomenon occurs when the lithium ions are exchanged during charging and discharging, so that the load characteristics can be further improved. LiTiO ₂ preferably belongs to the space group Fm3m.

<Method for producing positive electrode active material for non-aqueous electrolyte secondary battery>
Although the manufacturing method of the positive electrode active material of this invention is not specifically limited, For example, it can manufacture as follows (1) and (2) and also (3).

(1) Preparation of raw material mixture The compounds described later are mixed so that each constituent element has a predetermined composition ratio to obtain a raw material mixture. The compound used for the raw material mixture is selected according to the elements constituting the target composition.
The mixing method is not particularly limited, for example, a method of mixing in a slurry form using water and / or an organic solvent, and then drying to obtain a raw material mixture; A method of drying the resulting precipitate to obtain a raw material mixture; a method of using these together.

Below, the compound used for a raw material mixture is illustrated.
Lithium compound is not particularly limited, for _{example, Li 2 CO 3, LiOH,} LiOH · H 2 O, Li 2 O, LiCl, LiNO 3, Li 2 SO 4, LiHCO 3, Li (CH 3 COO), fluoride Examples include lithium, lithium bromide, lithium iodide, and lithium peroxide. Among these, Li ₂ CO ₃ , LiOH, LiOH · H ₂ O, Li ₂ O, LiCl, LiNO ₃ , Li ₂ SO ₄ , LiHCO ₃ , and Li (CH ₃ COO) are preferable.

The cobalt compound is not particularly limited, and examples thereof include cobalt oxide, cobalt hydroxide, cobalt carbonate, cobalt chloride, cobalt iodide, cobalt sulfate, cobalt bromate, and cobalt nitrate. Among these, CoSO ₄ · 7H ₂ O and Co (NO ₃ ) ₂ · 6H ₂ O are preferable.

The nickel compound is not particularly limited, and examples thereof include nickel oxide, nickel hydroxide, nickel carbonate, nickel chloride, nickel bromide, nickel iodide, nickel sulfate, nickel nitrate, and nickel formate. Among these, NiSO ₄ · 6H ₂ O and Ni (NO ₃ ) ₂ · 6H ₂ O are preferable.

The aluminum compound is not particularly limited, and examples thereof include aluminum oxide, aluminum hydroxide, aluminum carbonate, aluminum chloride, aluminum iodide, aluminum sulfate, and aluminum nitrate. Among these, Al ₂ (SO ₄ ) ₃ , Al (NO ₃ ) ₃ , Al ₂ O ₃ , and Al (OH) ₃ are preferable.

The manganese compound is not particularly limited, and examples thereof include manganese oxide, manganese hydroxide, manganese carbonate, manganese chloride, manganese iodide, manganese sulfate, and manganese nitrate. Among these, MnSO ₄ and MnCl ₂ are preferable.

The vanadium compound is not particularly limited, and examples thereof include vanadium oxide, vanadium hydroxide, vanadium chloride, and vanadium sulfate. Among these, V ₂ O ₅ and VCl ₂ are preferable.

The strontium compound is not particularly limited, and examples thereof include strontium oxide, strontium hydroxide, strontium chloride, and strontium sulfate. Of these, SrO and Sr (OH) ₂ are preferable.

The calcium compound is not particularly limited, and examples thereof include calcium oxide, calcium carbonate, calcium hydroxide, calcium chloride, and calcium nitrate. Of these, CaO and CaCO ₃ are preferable.

Although a sulfur containing compound is not specifically limited, For example, sulfide, sulfur iodide, hydrogen sulfide, a sulfuric acid, its salt, and nitrogen sulfide are mentioned. Among these, Li ₂ SO ₄ , MnSO ₄ , (NH ₄ ) ₂ SO ₄ , Al ₂ (SO ₄ ) ₃ , and MgSO ₄ are preferable.

The compound containing a halogen element is not particularly limited. For example, hydrogen fluoride, oxygen fluoride, hydrofluoric acid, hydrogen chloride, hydrochloric acid, chlorine oxide, fluorinated chlorine oxide, bromine oxide, bromine fluorosulfate, hydrogen iodide , Iodine oxide, and periodic acid. Among these, NH ₄ F, NH ₄ Cl, NH ₄ Br, NH ₄ I, LiF, LiCl, LiBr, LiI, MnF ₂ , MnCl ₂ , MnBr ₂ , and MnI ₂ are preferable.

Magnesium compound is not particularly limited, for _{example, MgO, MgCO 3, Mg (} OH) 2, MgCl 2, MgSO 4, Mg (NO 3) 2, Mg (CH 3 COO) 2, magnesium iodide, perchlorate Examples include magnesium. Among these, MgSO ₄ and Mg (NO ₃ ) ₂ are preferable.

The titanium compound is not particularly limited. Examples thereof include titanium fluoride, titanium chloride, titanium bromide, titanium iodide, titanium oxide, titanium sulfide, and titanium sulfate. Of these, TiO, TiO ₂ , Ti ₂ O ₃ , TiCl ₂ , and Ti (SO ₄ ) ₂ are preferable.

The zirconium compound is not particularly limited. Examples thereof include zirconium fluoride, zirconium chloride, zirconium bromide, zirconium iodide, zirconium oxide, zirconium sulfide, zirconium carbonate and the like. Among them _{ZrF 2, ZrCl, ZrCl 2,} ZrBr 2, ZrI 2, ZrO, Z r (OH) 3 and the like are preferable.
Moreover, you may use the compound containing 2 or more types of each element mentioned above.

Below, the suitable method of obtaining a raw material mixture is demonstrated concretely.
(I) Prepared from the cobalt compound, zirconium compound and magnesium compound described above. An aqueous solution containing cobalt ions, zirconium ions and magnesium ions having a predetermined composition ratio is dropped into pure water being stirred. Next, an aqueous sodium hydroxide solution is added dropwise so that the pH is 7 to 11, and the mixture is stirred and reacted at 40 to 80 ° C. and at a rotational speed of 500 to 1500 rpm. After finishing the dropping of the aqueous solution containing cobalt ions, zirconium ions and magnesium ions of a predetermined composition ratio, only the aqueous sodium hydroxide solution was dropped until the pH reached 9 to 10, and the precipitates of cobalt, zirconium and magnesium were added. obtain. Instead of the sodium hydroxide aqueous solution, an alkaline solution such as an ammonium hydrogen carbonate aqueous solution, a sodium hydrogen carbonate aqueous solution, a potassium hydroxide aqueous solution, or a lithium hydroxide aqueous solution can also be used.

  Next, the aqueous solution is filtered to collect a precipitate. The collected precipitate is washed with water and heat-treated, and then mixed with the above-described lithium compound to obtain a raw material mixture.

  (Ii) Prepared from the cobalt compound, nickel compound, manganese compound, and zirconium compound described above. An aqueous solution containing cobalt ions, nickel ions, manganese ions and zirconium ions having a predetermined composition ratio is dropped into pure water being stirred. A sodium hydroxide aqueous solution is dripped here so that it may become pH 8-11, and it is made to react by stirring at 40-80 degreeC and rotation speed 500-1500 rpm. After finishing the dropping of the aqueous solution containing cobalt ions, nickel ions, manganese ions and zirconium ions having a predetermined composition ratio, only the aqueous sodium hydroxide solution was dropped until the pH reached 9 to 10, and cobalt, nickel, manganese and A zirconium precipitate is obtained. Instead of the sodium hydroxide aqueous solution, an alkaline solution such as an ammonium hydrogen carbonate aqueous solution, a sodium hydrogen carbonate aqueous solution, a potassium hydroxide aqueous solution, or a lithium hydroxide aqueous solution can also be used.

  Next, the aqueous solution is filtered to collect a precipitate. The collected precipitate is washed with water and heat-treated, and then mixed with the above-described lithium compound to obtain a raw material mixture.

  (Iii) Prepared from the cobalt compound, nickel compound, aluminum compound and zirconium compound described above. An aqueous solution containing cobalt ions, nickel ions, aluminum ions and zirconium ions having a predetermined composition ratio is dropped into pure water being stirred. A sodium hydroxide aqueous solution is dripped here so that it may become pH 8-11, and it is made to react by stirring at 40-80 degreeC and rotation speed 500-1500 rpm. After dropwise addition of an aqueous solution containing cobalt ions, nickel ions, aluminum ions and zirconium ions of a predetermined composition ratio, only sodium hydroxide aqueous solution is continuously dropped until the pH reaches 9 to 10, and precipitates of cobalt, nickel, manganese and zirconium Get. Instead of the sodium hydroxide aqueous solution, an alkaline solution such as an ammonium hydrogen carbonate aqueous solution, a sodium hydrogen carbonate aqueous solution, a potassium hydroxide aqueous solution, or a lithium hydroxide aqueous solution can also be used.

  Next, the aqueous solution is filtered to collect a precipitate. The collected precipitate is washed with water and heat-treated, and then mixed with the above-described lithium compound to obtain a raw material mixture.

(2) Firing and grinding of raw material mixture Next, the raw material mixture is fired. The firing temperature, time, atmosphere, and the like are not particularly limited, and can be appropriately determined according to the purpose.
The firing temperature is preferably 700 ° C. or higher, more preferably 800 ° C. or higher, and further preferably 850 ° C. or higher. If the firing temperature is too low, unreacted raw materials may remain in the positive electrode active material, and the original characteristics of the positive electrode active material may not be utilized. The firing temperature is preferably 1200 ° C or lower, more preferably 1150 ° C or lower, and further preferably 1100 ° C or lower. If the firing temperature is too high, by-products are likely to be generated, resulting in a decrease in discharge capacity per unit weight, a decrease in cycle characteristics, and a decrease in operating voltage.
The firing time is preferably 1 hour or longer, and more preferably 6 hours or longer. Within the above range, the diffusion reaction between the particles of the mixture proceeds sufficiently.
The firing time is preferably 36 hours or less, and more preferably 30 hours or less. When it is within the above range, the synthesis proceeds sufficiently.

  Examples of the firing atmosphere include air, oxygen gas, a mixed gas of these with an inert gas such as nitrogen gas and argon gas, an atmosphere in which the oxygen concentration (oxygen partial pressure) is controlled, and a weak oxidizing atmosphere.

  After firing, if desired, the powder may be pulverized using a rough mortar, ball mill, vibration mill, pin mill, jet mill or the like to obtain a powder having a desired particle size.

  By using the above production method, the target positive electrode active material of the present invention can be obtained.

Hereinafter, a specific method for producing the positive electrode active material of the present invention will be described.
An aqueous solution containing cobalt ions, nickel ions and zirconium ions having a predetermined composition ratio is dropped into pure water being stirred. Here, a sodium hydroxide aqueous solution is dropped so that pH = 9, and cobalt and nickel are precipitated at 80 ° C. and a rotational speed of 650 rpm to obtain a precipitate of cobalt and nickel. The resulting precipitate is filtered, washed with water, heat-treated, mixed with aluminum oxide and lithium hydroxide monohydrate, and calcined at about 750 ° C. for about 10 hours in an air atmosphere. This is pulverized to obtain a positive electrode active material.
The composition ratio of the obtained positive electrode active material is Li: Ni: Co: Al: Zr = 1.04: 0.7: 0.2: 0.1: 0.01.
When confirmed by a cross-sectional STEM image, it can be seen that zirconium is included in part of the crystallite interface.

An aqueous solution containing cobalt ions, nickel ions, manganese ions and zirconium ions having a predetermined composition ratio is dropped into pure water being stirred. Here, sodium hydroxide aqueous solution is dropped so that pH = 9, and cobalt, nickel, manganese and zirconium are precipitated to obtain a precipitate of cobalt, nickel, manganese and zirconium. The obtained precipitate is filtered, washed with water, heat-treated, mixed with lithium carbonate, and fired at about 950 ° C. for about 10 hours in an air atmosphere. This is pulverized to obtain a positive electrode active material.
The composition ratio of the obtained positive electrode active material is Li: Ni: Co: Mn: Zr = 1.04: 0.33: 0.33: 0.33: 0.01.
When confirmed by a cross-sectional STEM image, it can be seen that zirconium is included in part of the crystallite interface.

<Positive electrode mixture>
Next, the positive electrode mixture of the present invention will be described.
The positive electrode mixture of the present invention has at least a positive electrode active material having a lithium transition metal composite oxide having a layered structure and a conductive agent.
The positive electrode active material used for the positive electrode mixture of the present invention is the above-described positive electrode active material of the present invention.

In the positive electrode mixture of the present invention, the conductive agent is not particularly limited, and examples thereof include carbon materials such as graphite such as Tennobu graphite and artificial graphite, carbon black such as acetylene black, and amorphous carbon such as needle coast. .
Acetylene black and / or artificial graphite are preferable. Since these are excellent in conductivity, cycle characteristics and load characteristics are further improved.

In the positive electrode mixture of the present invention, “between” means between the conductive agent in contact with the lithium transition metal composite oxide.
In the present invention, the positive electrode mixture is not only a paste-like material composed of a positive electrode active material, a conductive agent, a binder, and a solvent for the binder, but also after being applied to the positive electrode current collector and then dried. This includes a state after the solvent is skipped.

  By using the positive electrode active material of the present invention described above, the positive electrode mixture of the present invention improves the coating properties to the current collector without impairing the effect of each positive electrode active material. Thereby, battery characteristics are improved, and a positive electrode mixture with improved coating characteristics is obtained.

  Although the manufacturing method of the positive electrode mixture of the present invention is not particularly limited, for example, it can be manufactured as follows.

(1) Production of positive electrode active material A positive electrode active material can be obtained by the method for producing a positive electrode active material of the present invention described above.

(2) Preparation of positive electrode mixture The positive electrode active material powder is mixed with a carbon-based conductive agent such as acetylene black and graphite, a binder, and a binder solvent or dispersion medium. To prepare.

  The positive electrode active material and the positive electrode mixture of the present invention are suitably used for nonaqueous electrolyte secondary batteries such as lithium ion secondary batteries and lithium ion polymer secondary batteries.

<Nonaqueous electrolyte secondary battery>
The nonaqueous electrolyte secondary battery of the present invention is a nonaqueous electrolyte secondary battery using the above-described positive electrode active material of the present invention. The positive electrode active material of the present invention is suitably used for non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries and lithium ion polymer secondary batteries.

The non-aqueous electrolyte secondary battery may be a known non-aqueous electrolyte secondary battery using the positive electrode active material of the present invention as at least a part of the positive electrode active material, and other configurations are not particularly limited. For example, an electrolytic solution is used for a lithium ion secondary battery, and a solid electrolyte (polymer electrolyte) is used for a lithium ion polymer secondary battery. Examples of the solid electrolyte used in the lithium ion polymer secondary battery include a solid electrolyte described later.
Hereinafter, a lithium ion secondary battery will be described as an example.

  As the negative electrode active material, metallic lithium, a lithium alloy, a carbon material capable of occluding and releasing lithium ions, or a compound capable of occluding and releasing lithium ions can be used. Examples of the lithium alloy include a LiAl alloy, a LiSn alloy, and a LiPb alloy. Examples of the carbon material capable of occluding and releasing lithium ions include carbon materials such as graphite and graphite. Examples of the compound capable of occluding and releasing lithium ions include oxides such as tin oxide and titanium oxide.

The electrolyte solution is not particularly limited as long as it is a compound that does not change or decompose with the operating voltage. The electrolyte includes an electrolytic solution.
Examples of the solvent used in the electrolytic solution include dimethoxyethane, diethoxyethane, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, γ-butyrolactone, 2-methyltetrahydrofuran, dimethyl sulfoxide, Organic solvents such as sulfolane can be mentioned. These can be used alone or in admixture of two or more.

Examples of the electrolyte used for the electrolytic solution include lithium salts such as lithium perchlorate, lithium tetrafluoroborate, lithium hexafluorophosphate, and lithium trifluoromethanoate.
The above-described solvent and electrolyte are mixed to obtain an electrolytic solution. Here, a gelling agent or the like may be added and used as a gel. Moreover, you may make it absorb and use a hygroscopic polymer.
Further, a solid electrolyte having conductivity of inorganic or organic lithium ions may be used.

  Examples of the separator include a porous film made of polyethylene or polypropylene.

  Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, polyamide acrylic resin, and the like.

Using the positive electrode active material of the present invention and the above-described negative electrode active material, electrolyte, separator, and binder, the nonaqueous electrolyte secondary battery of the present invention can be obtained according to a conventional method.

  By using lithium manganate as the positive electrode active material together with the positive electrode active material of the present invention, not only the cycle characteristics, load characteristics and thermal stability are improved, but also the non-aqueous electrolyte having excellent overcharge characteristics and safety. A secondary battery can be obtained.

Represented by the general formula Li _a Mn _3−a O _{4 + f} (a represents a number satisfying 0.8 ≦ a ≦ 1.2, and f represents a number satisfying −0.5 ≦ f ≦ 0.5). Lithium manganate is preferred. The lithium manganate is selected from the group consisting of magnesium, aluminum, calcium, vanadium, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, strontium, zirconium, niobium, molybdenum, boron and tin. It may be substituted with at least one selected from the above.

  The lithium manganate used together with the positive electrode active material of the present invention is a positive electrode active material for a non-aqueous electrolyte secondary battery having at least a lithium transition metal composite oxide having a spinel structure. The following (i) to (vii) are mentioned as preferred embodiments of the lithium transition metal composite oxide.

(I) Formula _{Li 1 + a Mg b Ti c} Mn 2-a-b-c B d O 4 + e (a represents a number satisfying -0.2 ≦ a ≦ 0.2, b is 0.005 ≦ b ≦ 0.10 represents a number satisfying 0.10, c represents a number satisfying 0.005 ≦ c ≦ 0.05, d represents a number satisfying 0.002 ≦ d ≦ 0.02, and e represents −0.5 ≦ e represents a number satisfying e ≦ 0.5.)

Aspect (i) is excellent in cycle characteristics, high temperature cycle characteristics and load characteristics.
In embodiment (i), a is preferably greater than 0. It is considered that the cycle characteristics are improved by substituting a part of manganese with lithium.
In the embodiment (i), b is preferably 0.01 or more, more preferably 0.02 or more, and preferably 0.08 or less, and 0.07 or less. More preferred. If b is too large, + 3-valent manganese ions decrease, and the charge / discharge capacity decreases. If b is too small, elution of transition metal ions increases and gas generation occurs, so that the high temperature characteristics deteriorate.
In the embodiment (i), c is preferably 0.01 or more, more preferably 0.02 or more, and preferably 0.08 or less, and 0.07 or less. More preferred. When c is too large, the charge / discharge efficiency decreases. If c is too small, sufficient load characteristics and cycle characteristics cannot be obtained.
In the embodiment (i), d is preferably 0.003 or more, and is preferably 0.008 or less. If d is too large, the initial capacity decreases. In addition, the elution of transition metal ions increases, causing gas generation, resulting in deterioration of high temperature characteristics. If d is too small, the primary particle size does not grow, and the particle packing property is not improved.

  (Ii) An embodiment in which the lithium transition metal composite oxide is a lithium manganese composite oxide having at least one selected from the group consisting of titanium, zirconium and hafnium.

  By having at least one selected from the group consisting of titanium, zirconium, and hafnium, the lattice constant of the unit cell of the lithium manganese composite oxide particle increases, the mobility of lithium ions in the particle increases, and the impedance decreases. I think it can be done. For this reason, it is thought that output characteristics improve, without impairing improvement of cycling characteristics and high temperature cycling characteristics.

(Iii) The aspect in which the lithium transition metal composite oxide is a lithium manganese composite oxide having at least one selected from the group consisting of titanium, zirconium and hafnium and sulfur.

In the embodiment (iii), it is considered that the cycle characteristics and the load characteristics are further improved since the passage of electrons is improved by the presence of sulfur.
The sulfur content is preferably 0.03 to 0.3% by weight based on the total of the lithium transition metal composite oxide and sulfur. If it is less than 0.03% by weight, it may be difficult to reduce the resistance of electron movement. If it exceeds 0.3% by weight, the battery may swell due to moisture adsorption.

Sulfur may be present in any form. For example, it may exist in the form of sulfate radicals.
The sulfate radical includes sulfate ions, a group of atoms obtained by removing the charge from sulfate ions, and sulfo groups. It is preferably based on at least one selected from the group consisting of alkali metal sulfates, alkaline earth metal sulfates, organic sulfates and organic sulfonic acids and salts thereof.
Among them, it is preferable to use at least one selected from the group consisting of alkali metal sulfates and alkaline earth metal sulfates, and more preferable to use alkali metal sulfates. This is because these are chemically stable because they are composed of strong acid strong base bonds.

In aspect (iii), the reason for containing elements other than sulfur is the same as in aspect (ii).
In the embodiment (iii), by containing each of the above elements, a positive electrode plate having a high charge / discharge capacity and excellent binding properties and surface smoothness can be obtained due to the synergistic effect of each element. .

The lithium transition metal composite oxide may have a sulfate group at least on the surface of the particle.
The presence of the sulfate radical on the surface of the lithium transition metal composite oxide particle makes the electron transfer resistance around the particle extremely small, and as a result, the ease of passing electrons is improved, and the cycle characteristics and load characteristics are improved. It is thought to improve.
In addition, when the positive electrode active material of the present invention is used to form a high voltage battery (for example, a battery using LiMn _1.5 Ni _0.5 O ₄ as a lithium transition metal composite oxide), there is a problem in the conventional high voltage battery. Thus, the decomposition of the electrolyte during charging is suppressed, and as a result, the cycle characteristics are improved. The electrolyte decomposition reaction is thought to occur as a catalyst at the interface between the lithium transition metal composite oxide particles and the electrolyte, but the lithium transition is caused by sulfate radicals that do not function to decompose the electrolyte. By covering all or part of the surface of the metal composite oxide particles, it is considered that the contact area between the electrolyte and the catalyst is reduced, and the above reaction is suppressed.

  In the present invention, the sulfate group exhibits the effect of the present invention regardless of the form of the sulfate group present on the surface of the lithium transition metal composite oxide particles. For example, even when the sulfate radical covers the entire particle surface of the lithium transition metal composite oxide, the sulfate radical covers a part of the particle surface of the lithium transition metal composite oxide. However, cycle characteristics and load characteristics are improved.

Moreover, the sulfate radical should just exist in the surface of particle | grains at least. Therefore, a part of the sulfate radical may exist inside the particle.
Whether or not the sulfate radical is present on the surface of the lithium transition metal composite oxide particles can be analyzed by various methods. For example, it can be analyzed by Auger electron spectroscopy or X-ray photoelectron spectroscopy.
Moreover, various methods can be used for the determination of sulfate radicals. For example, it can be quantified by ICP emission spectrometry or titration.

  (Iv) An embodiment in which the lithium transition metal composite oxide is a lithium manganese composite oxide having at least one selected from the group consisting of titanium, zirconium and hafnium, sulfur, sodium and / or calcium.

In the embodiment (iv), by containing sodium and / or calcium, elution of manganese ions can be further suppressed by a synergistic effect with boron (preferably boron and sulfur), and the practical level is excellent. Cycle characteristics can be realized.
In embodiment (iv), the reason for containing an element other than sodium and / or calcium is the same as in embodiment (ii) and (iii).

  (V) An embodiment in which the lithium transition metal composite oxide is a lithium manganese composite oxide having aluminum and / or magnesium.

  When aluminum and / or magnesium are contained, the crystal structure is stabilized, so that the storage characteristics, load characteristics, and output characteristics are not impaired, and the cycle characteristics are excellent, and the swelling of the battery is further suppressed. it can.

  (Vi) An embodiment in which the lithium transition metal composite oxide is a lithium manganese composite oxide having aluminum and / or magnesium and boron.

  Boron acts as a flux, promotes crystal growth, and further improves cycle characteristics and storage characteristics.

(Vii) The lithium transition metal composite oxide has a general formula of Li _{1 + a} M _b Mn _2- abB _c O _{4 + d} (M represents aluminum and / or magnesium, and a represents −0.2 ≦ a ≦ 0.2. B represents a number satisfying 0 ≦ b ≦ 0.2, c represents a number satisfying 0 ≦ c ≦ 0.02, and d satisfied −0.5 ≦ d ≦ 0.5. A mode represented by a number).

Aspect (vii) is excellent in cycle characteristics, load characteristics, storage characteristics, and charge / discharge capacity, and has less battery swelling.
In embodiment (vii), a is preferably greater than 0. It is considered that the cycle characteristics are improved by substituting a part of manganese with lithium.
In the embodiment (vii), b is preferably larger than 0, more preferably 0.05 or more. When aluminum and / or magnesium is contained, the crystal structure is stabilized, so that the storage characteristics, load characteristics, and output characteristics are not impaired, and the cycle characteristics are excellent, and the swelling of the battery is further suppressed. it can. b is preferably 0.15 or less. When b is too large, the discharge capacity decreases.
In the embodiment (vii), c is preferably larger than 0, and more preferably 0.001 or more. Boron acts as a flux, promotes crystal growth, and further improves cycle characteristics and storage characteristics. c is preferably 0.01 or less. If c is too large, the cycle characteristics deteriorate.

  The production method of the lithium manganate used together with the positive electrode active material of the present invention is not particularly limited, and can be produced, for example, as follows.

A compound is mixed so that each constituent element has a predetermined composition ratio to obtain a raw material mixture. The compound used for the raw material mixture is selected according to the elements constituting the target composition.
The mixing method is not particularly limited, for example, a method of mixing powdery compounds as they are to obtain a raw material mixture; mixing in a slurry form using water and / or an organic solvent, and then drying to obtain a raw material mixture Method: A method in which an aqueous solution of the above-mentioned compound is mixed and precipitated, and the resulting precipitate is dried to obtain a raw material mixture; a method in which these are used in combination.
Next, the raw material mixture is fired to obtain lithium manganate. The firing temperature, time, atmosphere, and the like are not particularly limited, and can be appropriately determined according to the purpose.
After firing, if desired, the powder may be pulverized using a rough mortar, ball mill, vibration mill, pin mill, jet mill or the like to obtain a powder having a desired particle size.

A preferred method for producing a positive electrode using the positive electrode active material of the present invention will be described below.
A positive electrode mixture is prepared by mixing the positive electrode active material powder of the present invention with a carbon-based conductive agent such as acetylene black and graphite, a binder, and a binder solvent or dispersion medium. The obtained positive electrode mixture is made into a slurry or a kneaded product, applied to or supported on a band-shaped current collector such as an aluminum foil, and press-rolled to form a positive electrode active material layer on the band-shaped current collector.
FIG. 2 is a schematic cross-sectional view of the positive electrode. As shown in FIG. 2, the positive electrode 13 is obtained by holding the positive electrode active material 5 on the strip-shaped current collector 12 with the binder 4.

It is considered that the positive electrode active material of the present invention is excellent in mixing with the conductive agent powder and has a low internal resistance of the battery. Accordingly, the charge / discharge characteristics, particularly the discharge capacity, are excellent.
In addition, the positive electrode mixture of the present invention has excellent fluidity when kneaded with the binder, and is easily entangled with the binder polymer and has excellent binding properties.

As a preferred embodiment of the nonaqueous electrolyte secondary battery of the present invention, a strip-shaped positive electrode formed by forming a positive electrode active material layer using the positive electrode active material of the present invention on both surfaces of a strip-shaped positive electrode current collector, and metallic lithium A negative electrode active material layer using one selected from a lithium alloy, a carbon material capable of occluding and releasing lithium ions, or a compound capable of occluding and releasing lithium ions as a negative electrode active material is formed on both sides of a strip-shaped negative electrode current collector Examples include a non-aqueous electrolyte secondary battery that includes a strip-shaped negative electrode and a strip-shaped separator, and the strip-shaped separator is interposed between the strip-shaped positive electrode and the strip-shaped negative electrode.
A positive electrode active material layer using the positive electrode active material of the present invention is formed on both surfaces of a strip-shaped positive electrode current collector, and a negative electrode active material layer using the negative electrode active material is formed on both surfaces of the strip-shaped negative electrode current collector. Thus, a nonaqueous electrolyte secondary battery having a higher charge / discharge capacity can be obtained without impairing the battery characteristics of the present invention.

  Further, as another preferred embodiment of the nonaqueous electrolyte secondary battery of the present invention, a nonaqueous electrolyte secondary battery having a positive electrode, a negative electrode, a separator and a nonaqueous electrolyte, wherein the following I is used as a positive electrode active material of the positive electrode, A non-aqueous electrolyte secondary battery using the following II as a negative electrode active material of the negative electrode can be mentioned. This non-aqueous electrolyte secondary battery is excellent not only in load characteristics, low temperature characteristics, output characteristics and thermal stability, but also in overcharge characteristics and safety.

I: general formula _{Li a Mn 3-a O 4} + f (a is a number satisfying 0.8 ≦ a ≦ 1.2, f is a number satisfying -0.5 ≦ f ≦ 0.5.) And the lithium transition metal composite oxide used in the positive electrode active material of the present invention, the weight of the lithium manganate is A, and the weight of the lithium transition metal composite oxide is B. In some cases, the positive electrode active material for a non-aqueous electrolyte secondary battery is mixed so that 0.2 ≦ B / (A + B) ≦ 0.8.
II: A negative electrode active material comprising at least one selected from the group consisting of metallic lithium, lithium alloys, a carbon material capable of occluding and releasing lithium ions, and a compound capable of occluding and releasing lithium ions.

In the positive electrode active material of I described above, it is preferable to mix so that 0.4 ≦ B / (A + B) ≦ 0.6. This is because, in the range of 0.4 ≦ B / (A + B) ≦ 0.6, not only the load characteristics, the low temperature characteristics, the output characteristics, and the thermal stability, but also the overcharge characteristics and safety are remarkably improved.
In the positive electrode active material of I, a part of lithium manganate is magnesium, aluminum, calcium, vanadium, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, strontium, zirconium, niobium, molybdenum. , May be substituted with at least one selected from the group consisting of boron and tin.
As a compound capable of occluding and releasing lithium ions used for the negative electrode active material of II, a general formula consisting of a spinel structure containing an alkali metal and / or an alkaline earth metal is Li _a Ti _b O _{4 + c} (a is 0.8). ≦ a ≦ 1.5, b represents a number satisfying 1.5 ≦ b ≦ 2.2, and c represents a number satisfying −0.5 ≦ c ≦ 0.5. The negative electrode active material for a non-aqueous electrolyte secondary battery is preferred. At this time, it is possible to obtain a nonaqueous electrolyte secondary battery in which not only load characteristics, low temperature characteristics, output characteristics and thermal stability but also cycle characteristics are greatly improved.

The shape of the nonaqueous electrolyte secondary battery of the present invention is not particularly limited, and may be a cylindrical shape, a coin shape, a square shape, a laminate shape, or the like.
FIG. 3 is a schematic cross-sectional view of a cylindrical battery. As shown in FIG. 3, in the cylindrical battery 20, the positive electrode 13 in which the positive electrode active material layer is formed on the current collector 12, and the negative electrode 11 in which the negative electrode active material layer is formed on the current collector 12. Are repeatedly laminated via the separator 14.
FIG. 4 is a schematic partial cross-sectional view of a coin-type battery. As shown in FIG. 4, in the coin-type battery 30, the positive electrode 13 in which the positive electrode active material layer is formed on the current collector 12 and the negative electrode 11 are stacked via the separator 14.
FIG. 5 is a schematic perspective view of a prismatic battery. As shown in FIG. 5, in the square battery 40, the positive electrode 13 in which the positive electrode active material layer is formed on the current collector 12, and the negative electrode 11 in which the negative electrode active material layer is formed on the current collector 12. However, they are repeatedly laminated via the separator 14.

<Applications of non-aqueous electrolyte secondary batteries>
The use of the nonaqueous electrolyte secondary battery using the positive electrode active material of the present invention is not particularly limited. For example, notebook computers, pen input computers, pocket computers, notebook word processors, pocket word processors, electronic book players, mobile phones, cordless phones, electronic notebooks, calculators, LCD TVs, electric shavers, electric tools, electronic translators, car phones , Portable printer, transceiver, pager, handy terminal, portable copy, voice input device, memory card, backup power supply, tape recorder, radio, headphone stereo, handy cleaner, portable compact disc (CD) player, video movie, navigation system, etc. It can be used as a power source for equipment.
Also, lighting equipment, air conditioner, TV, stereo, water heater, refrigerator, oven microwave, dishwasher, washing machine, dryer, game machine, toy, road conditioner, medical equipment, automobile, electric car, golf cart, It can be used as a power source for electric carts, power storage systems and the like.
Furthermore, the application is not limited to consumer use, and may be used for military use or space.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

1. Preparation of positive electrode active material [Example 1]
A cobalt sulfate aqueous solution and a zirconium oxychloride aqueous solution were dropped into the agitated pure water so as to have a predetermined composition ratio. The zirconium oxychloride aqueous solution was added dropwise so that zirconium was 0.2 mol% with respect to cobalt. Furthermore, sodium hydroxide aqueous solution was dripped so that it might become pH 7-7.5, and it was made to react at 60 degreeC and rotation speed 650rpm. After finishing the dropping of the cobalt sulfate aqueous solution and the zirconium oxychloride aqueous solution, only the sodium hydroxide aqueous solution was continuously dropped until the pH reached 9.4 to 9.6 to precipitate cobalt and zirconium, thereby obtaining a precipitate. The obtained precipitate was filtered, washed with water, heat-treated, mixed with lithium carbonate, and calcined at 995 ° C. for 7 hours in the air. In this way, a positive electrode active material was obtained.

[Example 2]
A cobalt sulfate aqueous solution and a zirconium oxychloride aqueous solution were dropped into the agitated pure water so as to have a predetermined composition ratio. The zirconium oxychloride aqueous solution was added dropwise so that zirconium was 0.04 mol% with respect to cobalt. Furthermore, sodium hydroxide aqueous solution was dripped so that it might become pH 7-7.5, and it was made to react at 60 degreeC and rotation speed 650rpm. After finishing the dropping of the cobalt sulfate aqueous solution and the zirconium oxychloride aqueous solution, only the sodium hydroxide aqueous solution was continuously dropped until the pH reached 9.4 to 9.6 to precipitate cobalt and zirconium, thereby obtaining a precipitate. The obtained precipitate was filtered, washed with water, heat-treated, mixed with lithium carbonate, and calcined at 995 ° C. for 7 hours in the air. In this way, a positive electrode active material was obtained.

[Comparative Example 1]
Lithium carbonate (Li ₂ CO ₃ ), cobalt trioxide (Co ₃ O ₄ ), and zirconium oxide (ZrO ₂ ) were used as the raw material compounds. The compound as the raw material was weighed so as to have a predetermined composition ratio, and dry-mixed to obtain a raw material mixed powder. The obtained raw material mixed powder was fired at 995 ° C. for 7 hours in the air atmosphere. In this way, a positive electrode active material was obtained.

[Comparative Example 2]
An aqueous cobalt sulfate solution was dropped into the stirred pure water so as to obtain a predetermined composition ratio. Here, a sodium hydroxide aqueous solution was added dropwise so that the pH was 7, and cobalt was precipitated at 60 ° C. and a rotation speed of 650 rpm to obtain a precipitate. The obtained precipitate was filtered, washed with water, heat-treated, mixed with lithium carbonate, and calcined at 1045 ° C. for 7 hours in the air. In this way, a positive electrode active material was obtained.

2. Properties of positive electrode active material (1) Configuration of positive electrode active material The positive electrode active materials obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were subjected to ICP spectroscopy.
The positive electrode active material obtained in Example 1 was LiCoO ₂ in which 0.2 mol% of zirconium was present.
Example 1 From a number of particles of the obtained positive electrode active material, a lithium transition metal composite oxide having an average particle diameter was selected, and the particle cross-sectional view of the selected lithium transition metal composite oxide was the maximum diameter. A cross-section was obtained by a method of processing with FIB. When this particle cross-sectional image was represented by a STEM image, it was found that zirconium was present in part of the crystallite interface. This particle cross-sectional STEM image is shown in FIG.
The positive electrode active material obtained in Example 2 was LiCoO ₂ in which 0.04 mol% of zirconium was present.
The positive electrode active material obtained in Example 2 was subjected to cross-section in the same manner as the positive electrode active material obtained in Example 1. When this particle cross-sectional image was represented by a STEM image, it was found that zirconium was present in part of the crystallite interface.
The positive electrode active material obtained in Comparative Example 1 was LiCoO ₂ in which 0.2 mol% of zirconium was present.
The positive electrode active material obtained in Comparative Example 1 was subjected to cross-section in the same manner as the positive electrode active material obtained in Example 1. When this particle cross-sectional image was represented by a STEM image, it was found that zirconium was not present at the crystallite interface. A cross-sectional view of this particle is shown in FIG.
The positive electrode active material obtained in Comparative Example 2 was LiCoO ₂ .

(2) Specific surface area of positive electrode active material The specific surface area of the obtained positive electrode active material was determined by a constant pressure BET adsorption method using nitrogen gas.
The specific surface area of the positive electrode active material obtained in Example 1 was 0.55 m ² / g. The specific surface area of the positive electrode active material obtained in Comparative Example 1 was 0.47 m ² / g.

3. Evaluation of positive electrode active material (1)
(1) Production of Lithium Ion Secondary Battery For each positive electrode active material obtained in Examples 1 and 2 and Comparative Example 1, test secondary batteries were produced and evaluated as follows.
A paste was prepared by kneading 90 parts by weight of the positive electrode active material powder, 5 parts by weight of carbon powder to be a conductive agent, and a normal methylpyrrolidone solution of polyvinylidene fluoride (5 parts by weight of polyvinylidene fluoride). The obtained paste was applied to a positive electrode current collector to prepare a test secondary battery in which the negative electrode was lithium metal.

(2) Load characteristics A discharge load of 0.2 C (where 1 C is a current load that completes discharge in one hour. The same applies hereinafter), a charge potential of 4.3 V, and a discharge potential of 2.75 V. After measuring the discharge capacity, the load discharge capacity was measured under the conditions of a discharge load 1C, a charge potential 4.3V, and a discharge potential 2.75V. The load capacity retention rate (%) at the time of the discharge load 1C was obtained from the following formula.

  Load capacity retention rate (%) = (1C discharge capacity) / (0.2C discharge capacity) × 100

  Next, the high load discharge capacity was measured under the conditions of the discharge load 2C, the charge potential 4.3V, and the discharge potential 2.75V. The load capacity retention rate (%) at the time of the discharge load 2C was obtained from the following formula.

  Load capacity retention rate (%) = (2C discharge capacity) / (0.2C discharge capacity) × 100

(3) Average voltage Initial discharge capacity and electric energy were measured on the conditions of discharge load 0.2C, charge potential 4.3V, and discharge voltage 2.75V. The average voltage was calculated from the following formula.

  Average voltage (V) = electric energy (mWh / g) / capacity (mAh / g)

  The results are shown in Table 1.

As is apparent from Table 1, it can be seen that the positive electrode active materials of the present invention (Examples 1 and 2) are excellent in load characteristics and high load characteristics at a high potential.
On the other hand, the positive electrode active material (Comparative Example 1) having no zirconium at the crystallite interface of the lithium transition metal composite oxide obtained by dry mixing to obtain a raw material mixed powder has a low potential, load characteristics, Inferior to high load characteristics.

4). Evaluation of positive electrode active material (2)
(1) Production of Laminated Battery For each positive electrode active material obtained in Example 1 and Comparative Example 2, a laminated battery was produced and evaluated as follows.
A positive electrode plate was obtained in the same manner as in the case of the test secondary battery. Further, a carbon material was used as the negative electrode active material, and was applied to the negative electrode current collector and dried in the same manner as in the case of the positive electrode plate to obtain a negative electrode plate. A porous polypropylene film was used as the separator. As the electrolytic solution, a solution in which LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate / methyl ethyl carbonate = 3/7 (volume ratio) to a concentration of 1 mol / L was used. A positive electrode plate, a negative electrode plate, and a separator were formed into a thin sheet, laminated and stored in a battery case of a laminate film, and an electrolyte solution was injected into the battery case to produce a laminate battery.

(2) Impedance An impedance measuring device (SI1287 and SI1260, both manufactured by SOLARTRON) was used for the impedance measurement.
The clip of the measuring device was attached to the lead wires provided on the positive and negative electrodes of the laminate battery, and the internal impedance at 0.1 Hz was measured by the AC impedance method under the conditions of SOC 60% and 0 ° C. It can be said that the smaller the impedance, the better the output characteristics.

(3) Thermal stability Using a laminate battery, charging / discharging with a constant current was carried out to make it fit. Thereafter, the battery was charged at a rate of 0.2 C with CC-CV charging, a final voltage of 4.2 V, and a final charge current of 0.02 mA. After the charging was completed, the positive electrode was taken out from the laminated battery, washed with one component solution contained in the electrolytic solution used in the laminated battery and dried, and the positive electrode active material was scraped off from the positive electrode. An aluminum cell was charged with ethylene carbonate used for the electrolyte and the positive electrode active material scraped from the positive electrode in a weight ratio of 0.40: 1.00, and the differential scanning calorific value was measured at a heating rate of 5.0 ° C./min. .
Differential scanning calorimetry (DSC) is a method of measuring a difference in energy input as a function of temperature while changing the temperature of a material and a reference material according to a program. Although the differential scanning calorific value did not change even when the temperature rose in the low temperature part, the differential scanning calorific value greatly increased above a certain temperature. The temperature at this time was defined as the heat generation start temperature. The higher the heat generation start temperature, the better the thermal stability.

(4) Cycle characteristics After measuring the initial discharge capacity under the conditions of a discharge load of 1C, a charge potential of 4.2 V, and a discharge potential of 2.75 V, charging and discharging are repeated under the same conditions, and the discharge capacity after 100 cycles is measured. did. The capacity retention rate (%) was determined from the following formula.

  Capacity retention rate (%) = (discharge capacity after 100 cycles) / (discharge capacity after 1 cycle) × 100

  The results are shown in Table 2.

From Table 2, it can be seen that the positive electrode active material of the present invention (Example 1) has reduced impedance and excellent output characteristics. Moreover, it turns out that it is excellent in thermal stability and cycling characteristics.
Moreover, since the low-temperature impedance is small, the positive electrode active material of the present invention has excellent low-temperature output characteristics and excellent low-temperature load characteristics.

It is a schematic diagram which shows the lithium transition metal complex oxide of a layered structure. It is typical sectional drawing of a positive electrode. It is typical sectional drawing of a cylindrical battery. It is a typical fragmentary sectional view of a coin type battery. It is a typical section perspective view of a square battery. 2 is a cross-sectional STEM image of the lithium transition metal composite oxide of Example 1. FIG. 3 is a cross-sectional STEM image of a lithium transition metal composite oxide of Comparative Example 1.

Explanation of symbols

1 3a site 2 6c site 3 3b site 4 binder 5 active material 6 zirconium 11 negative electrode 12 current collector 13 positive electrode 14 separator 20 cylindrical battery 30 coin-type battery 40 square battery

Claims (4)

At least part of the crystallite interface of the layered lithium transition metal composite oxide obtained by firing a precipitate obtained by reacting an aqueous solution of transition metal ions containing zirconium with an alkaline solution at a pH of 7 to 9 with a lithium compound. A belt-shaped positive electrode comprising a zirconium-containing positive electrode active material layer using a positive electrode active material and formed on at least one surface of the belt-shaped positive electrode current collector;
Metallic lithium,
Lithium alloy,
By forming a negative electrode active material layer using a carbon material capable of occluding and releasing lithium ions or a compound capable of occluding and releasing lithium ions as a negative electrode active material on at least one surface of a strip-shaped negative electrode current collector A configured negative electrode,
A strip separator,
A non-aqueous electrolyte secondary battery in which the strip separator is interposed between the strip positive electrode and the strip negative electrode. A spiral-type winding in which the strip-shaped positive electrode and the strip-shaped negative electrode are wound a plurality of times in a state of being laminated via the strip-shaped separator, and the strip-shaped separator is interposed between the strip-shaped positive electrode and the strip-shaped negative electrode The nonaqueous electrolyte secondary battery according to claim 1, comprising a body. The belt-like positive electrode and the belt-like negative electrode are stacked in a state of being laminated via the belt-like separator, and a stack body in which the belt-like separator is interposed between the belt-like positive electrode and the belt-like negative electrode is formed. 2. The nonaqueous electrolyte secondary battery according to 1. A positive electrode active material for a non-aqueous electrolyte secondary battery having at least a layered lithium transition metal composite oxide,
The lithium transition metal composite oxide is obtained by firing a precipitate obtained by reacting an aqueous solution of transition metal ions containing zirconium and an alkaline solution at pH 7 to 9 with a lithium compound, and at least a part of the crystallite interface thereof A positive electrode active material for a non-aqueous electrolyte secondary battery, having zirconium in it.

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