JP6362033B2 - Cathode active material for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery composed of a lithium manganese nickel composite oxide having few oxygen defects and having an “Fd-3m” structure. The present invention also relates to a non-aqueous electrolyte secondary battery using this positive electrode active material for a non-aqueous electrolyte secondary battery.

  In recent years, with the widespread use of portable electronic devices such as mobile phones and notebook computers, there is an increasing demand for small and lightweight secondary batteries having high energy density. In addition, development of a high-power secondary battery is strongly desired as a power source for electric vehicles including hybrid vehicles.

As a secondary battery satisfying such requirements, there is a lithium ion secondary battery which is a kind of non-aqueous electrolyte secondary battery. This lithium ion secondary battery is composed of a negative electrode, a positive electrode, an electrolytic solution, and the like, and a material capable of desorbing and inserting lithium is used as an active material used as a material for the negative electrode and the positive electrode.
Currently, research and development of such lithium ion secondary batteries are actively conducted. Among them, a lithium ion secondary battery using a lithium metal composite oxide as a positive electrode material is capable of being used as a battery having a high energy density because a voltage of 4 V class can be obtained.

Specifically, lithium cobalt composite oxide (LiCoO ₂ ) particles that are relatively easy to synthesize, lithium nickel composite oxide (LiNiO ₂ ) particles using nickel that is cheaper than cobalt, lithium nickel cobalt manganese composite oxide ( LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) particles, lithium manganese composite oxide (LiMn ₂ O ₄ ) particles using manganese, lithium nickel manganese composite oxide (LiNi _0.5 Mn _0.5 O ₂ ) Lithium composite oxide particles such as particles have been proposed.

Among these, lithium manganese composite oxide particles having a spinel type crystal structure that can realize a secondary battery excellent in thermal stability without using cobalt with a small reserve amount, in particular, a part of manganese is made of Ni. In recent years, substituted lithium manganese nickel composite oxide (LiMn _1.5 Ni _0.5 O ₄ ) particles have attracted attention as a material having a high energy density capable of realizing an operating voltage of 4.5 V or higher.

  Here, in order for the lithium ion secondary battery to have excellent output characteristics, the positive electrode needs to have low resistance. For this reason, research on various modifications to lithium manganese nickel composite oxide particles has been conducted, but further improvement in output characteristics is required in order to cope with the recent high performance of portable electronic devices and electric vehicles. ing.

In such lithium manganese nickel composite oxide, Non-Patent Document 1 shows that there are two types of crystal structures.
One is a structure having a regular arrangement of manganese and nickel of the space group “P4 ₃ 32”, and the other is a structure in which manganese and nickel of the space group “Fd-3m” are randomly arranged. Non-Patent Document 1 discloses that a manganese nickel oxide having a “P4 ₃ 32” structure is obtained by annealing a manganese nickel oxide having a “Fd-3m” structure at 700 ° C., and the difference between them is the “FT-IR spectrum”. "Is distinguished by the difference in the number of peaks.

In Patent Document 1, lithium manganese is subjected to an annealing treatment in the range of 650 ° C. to 800 ° C., and a peak characteristic of the “P4 ₃ 32” structure is detected at a wave number of 400 to 800 cm ⁻¹ of the “FT-IR spectrum”. It is disclosed that a charge / discharge curve showing a flat voltage can be obtained with a nickel composite oxide with little polarization.
Therefore, as a result of an independent study on improvement of the output characteristics of the secondary battery using the lithium manganese nickel composite oxide as the positive electrode active material, the present inventor found that the manganese nickel oxide having the “Fd-3m” structure was better. , And found to have a lower resistance than the “P4 ₃ 32” structure.
However, since the lithium manganese nickel oxide having the “Fd-3m” structure includes a large number of defects caused by high-temperature firing in the crystal structure, it has been simultaneously confirmed that the charge / discharge capacity is low and not suitable for practical use.

Patent Document 2 evaluates the strain in the crystal structure of the composite oxide containing at least lithium, nickel, and manganese using the Williamson-Hall plot from the XRD pattern, and the strain value is 3.0 × 10 ^−4. It is disclosed that a high discharge capacity is obtained when it is ˜20.0 × 10 ⁻⁴ . However, since these manufacturing processes also include an annealing process, the crystal structure “P4 ₃ 32” structure is formed, so that it is considered to be a high-resistance material.

  Thus, the positive electrode active material for non-aqueous secondary batteries having a high voltage, a high capacity, and a low resistance has not yet been realized and has not been put into practical use.

JP 2002-158007 A JP 2012-216548 A

Journal of the Electrochemical Society, 151, A296-A303, (2004).

  An object of the present invention is to provide lithium manganese nickel composite oxide particles having a high capacity and high output when used as a positive electrode active material of a secondary battery. Furthermore, an object of the present invention is to provide a non-aqueous electrolyte secondary battery using the lithium manganese nickel composite oxide particles as a positive electrode active material.

That is, the first invention of the present invention is lithium (Li), manganese (Mn), nickel (Ni), magnesium (Mg), aluminum (Al), silicon (Si), titanium (Ti), chromium (Cr), A positive electrode active material for a non-aqueous electrolyte secondary battery containing at least one element M selected from iron (Fe), cobalt (Co), copper (Cu), and zinc (Zn), each element The molar ratio of Li: Mn: Ni: M = t: 2-xy: x: y (where 0.96 ≦ t ≦ 1.25, 0.40 ≦ x ≦ 0.60, 0 ≦ y) ≦ 0.20). From the diffraction pattern obtained by XRD measurement, the lattice strain obtained by Rietveld analysis based on the spinel crystal structure of “Fd-3m” structure If the value is less than or equal 0.070 percent, crystallite diameter 1000 Above, below 8000 Å, from the FT-IR spectrum obtained by FT-IR measurements of the non-aqueous electrolyte solution positive electrode active material for a secondary battery, the maximum absorbance between wave number 493～513Cm ^-1, wave number 480～ divided by the minimum value of absorbance between 490 cm ^-1 is 1.30 or less, the maximum absorbance between wave number 549～559Cm ^-1, the value obtained by dividing the minimum value of absorbance between wave number 560～570Cm ^-1 1.30, the maximum absorbance between wave number 584～594Cm ^-1, nonaqueous electrolysis divided value is to der Rukoto wherein 1.20 at minimum absorbance between wave number 606～616Cm ^-1 It is a positive electrode active material for liquid secondary batteries.

According to a second aspect of the present invention, the specific surface area of the positive electrode active material for a non-aqueous electrolyte secondary battery according to the first aspect is 0.30 to 1.50 m ² / g. It is a positive electrode active material for liquid secondary batteries.

  According to a third aspect of the present invention, there is provided a positive electrode using the positive electrode active material for a non-aqueous electrolyte secondary battery according to the first and second aspects, a negative electrode, a separator, and a non-aqueous electrolyte. This is a non-aqueous electrolyte secondary battery.

ADVANTAGE OF THE INVENTION According to this invention, when it uses as a positive electrode active material of a secondary battery, the lithium manganese nickel composite oxide particle which can make high output can be provided.
Further, according to the present invention, it is possible to provide a production method capable of easily obtaining such lithium manganese nickel composite oxide particles in industrial scale production.
Furthermore, according to the present invention, a non-aqueous electrolyte secondary battery using the lithium manganese nickel composite oxide particles as a positive electrode active material can be provided, and the industrial significance of the present invention is extremely large.

FIG. 4 is a diagram showing an “FT-IR spectrum” of an “Fd-3m” structure, and is an FT-IR spectrum diagram of the positive electrode active material of Example 1. It is a figure which shows the "FT-IR spectrum" of a "P4 ₃ 32" structure, and is a FT-IR spectrum figure of the positive electrode active material of the comparative example 3. It is sectional drawing of the 2032 type coin battery used for evaluation of the positive electrode active material in the Example.

1. Positive electrode active material for non-aqueous electrolyte secondary battery The positive electrode active material for non-aqueous electrolyte secondary battery of the present invention includes lithium (Li), manganese (Mn), nickel (Ni), magnesium (Mg), aluminum ( Including at least one element M selected from Al), silicon (Si), titanium (Ti), chromium (Cr), iron (Fe), cobalt (Co), copper (Cu), and zinc (Zn), The molar ratio of each element is Li: Mn: Ni: M = t: 2-xy: x: y (where 0.96 ≦ t ≦ 1.25, 0.40 ≦ x ≦ 0.60, 0 ≦ y ≦ 0.20).

Further, the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is a lattice obtained by Rietveld analysis based on a spinel crystal structure of “Fd-3m” structure from a diffraction pattern obtained by XRD measurement. The maximum value of absorbance between wave numbers 493 to 513 cm ^{−1 and} the minimum value of absorbance between wave numbers 480 to 490 cm ⁻¹ from the FT-IR spectrum obtained by FT-IR measurement with a strain value of 0.070% or less. divided by the value 1.30 or less, the maximum absorbance between wave number 549～559Cm ^-1, divided by the minimum value of absorbance between wave number 560～570Cm ^-1 is 1.30 or less, wavenumber 584~594cm absorbance maxima between ^-1, lithium-manganese-nickel composite oxide which divided by the minimum value of absorbance between wave number 606～616Cm ^-1 is characterized that 1.20 or less It is.

[Crystal structure]
The cause of the decrease in the discharge capacity is oxygen defects, and it is desirable that the amount of oxygen defects is small in the positive electrode active material of the present invention.
The amount of oxygen defects can be evaluated by lattice distortion calculated by the Rietveld method from the XRD pattern. At this time, the lattice distortion indicates a standard deviation of the ratio of the deviation of each surface interval to the average surface interval. In the vicinity of oxygen defects, the interplanar spacing changes from a normal crystal. As the number of oxygen vacancies increases, the interplanar spacing takes various values, and the value of lattice strain increases.
The range of lattice strain is 0.070% or less, more preferably 0.035% or less. When it exceeds 0.070%, the capacity | capacitance of a positive electrode active material will fall.

When the lattice strain is calculated from the XRD pattern by the Rietveld method, the crystallite diameter can be evaluated at the same time.
The crystallite diameter is preferably 1,000 to 8,000.
When the range of the lattice strain is 1000 mm or less, the crystal growth is insufficient and many defects are included, so that the material becomes a high resistance material. When the lattice strain exceeds 8000 mm, the diffusion distance in the crystal becomes long and the resistance increases.

Whether the crystal structure of the positive electrode active material is the “P4 ₃ 32” structure or the “Fd-3m” structure is distinguished from the XRD measurement results because of the difference in the X-ray scattering ability due to the arrangement of manganese and nickel. Difficult to do.

Therefore, if the crystal structure of the positive electrode active material is the “P4 ₃ 32” structure, the “FT-IR spectrum” shown in FIG. 1 falls within the range of wave numbers 400 to 800 cm ⁻¹ of the “FT-IR spectrum” as shown in FIG. More peaks than structure can be observed. FIG. 1 shows an “FT-IR spectrum” having an “Fd-3m” structure, and FIG. 2 shows an “FT-IR spectrum” having a “P4 ₃ 32” structure.

By the way, since it is preferable that the crystal structure of the positive electrode active material which consists of lithium manganese nickel oxide in this invention is a "Fd-3m" structure, the FT-IR measurement was carried out for the produced positive electrode active material which consists of lithium manganese nickel oxide. Te, in _"P4 3 32" structure, particularly characteristic about ^{500cm -1, 555cm -1,} if it can be confirmed that the peak intensity is lower in the three wavenumber of 590 cm ^-1, the lithium manganese nickel oxide prepared crystals It can be confirmed that the structure is an “Fd-3m” structure. Therefore, three types of peak intensity ratios are used.

First of all, in order to confirm that the peak intensity at a wave number of about 500 cm ⁻¹ is low, the maximum absorbance between wave numbers 493 to 513 cm ⁻¹ is set to the minimum absorbance between wave numbers 480 to 490 cm ^−1. Confirm that the value divided by is 1.30 or less.

For the wave number in the second to confirm that low peak intensity of about 555cm ^-1 is the maximum absorbance between wave number 549～559Cm ^-1, divided by the minimum value of absorbance between wave number 560～570Cm ^-1 Confirm that the value is 1.30 or less.

Third, in order to confirm that the peak intensity at a wave number of about 590 cm ⁻¹ is low, the maximum absorbance between wave numbers 584 to 594 cm ⁻¹ is set to the minimum absorbance between wave numbers 606 to 616 cm ^−1. Check that the divided value is 1.20 or less.

The reason why the peak position has a certain width at the above three points is that the peak may be shifted by several cm ⁻¹ due to the nature of measurement in FT-IR.
When the peak intensity ratio of the “FT-IR spectrum” is out of the above range, the crystal structure of the lithium manganese nickel oxide is “P4 ₃ 32”, and it can be determined that it is not preferable because it has high resistance as a battery positive electrode.

  FT-IR is easily and preferably measured by the “KBr tablet method”. However, depending on the mixing ratio of the positive electrode active material and KBr, the spectrum becomes unsuitable for evaluation, so care should be taken. The positive electrode active material and KBr are weighed so that the weight ratio is 0.2 to 0.6: 100, and after mixing well in a mortar, the thickness is adjusted to 0.2 to 0.4 mm with a tablet molding machine. When it is molded, a spectrum suitable for evaluation can be obtained.

[composition]
In addition to lithium (Li), manganese (Mn), and nickel (Ni), the positive electrode active material for non-aqueous electrolyte secondary battery of the present invention includes element M (element M is magnesium (Mg), aluminum (Al), silicon ( Si), titanium (Ti), chromium (Cr), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn)), and the moles of each element The ratio is Li: Mn: Ni: M = t: 2-xy: x: y (provided that 0.96 ≦ t ≦ 1.25, 0.40 ≦ x ≦ 0.60, 0 ≦ y ≦ 0. 20) Spinel type oxide.

The value of t indicating the lithium (Li) content is 0.96 to 1.25, preferably 0.98 to 1.20, and more preferably 1.00 to 1.20.
By regulating the value of t within the above range, the output characteristics and capacity characteristics of a secondary battery configured using this positive electrode active material for the positive electrode can be improved. On the other hand, if the value of t is less than 0.96, the positive electrode resistance of the secondary battery is increased, so that the output characteristics cannot be improved. On the other hand, if it exceeds 1.25, the initial discharge capacity decreases.

Nickel (Ni) is an element that contributes to higher potential and higher capacity of the secondary battery.
The value of x indicating the amount of nickel added is 0.40 or more and 0.60 or less, preferably 0.40 or more and 0.56 or less, more preferably 0.40 or more and 0.53 or less.
If the value of x is less than 0.40, the battery capacity at a voltage of 5 V class is reduced in a secondary battery configured using the positive electrode active material having the composite hydroxide particles as a precursor for the positive electrode. On the other hand, when the value of x exceeds 0.60, it becomes impossible to obtain a positive electrode active material composed of a single phase of spinel structure.

In addition, the positive electrode active material of the present invention may contain a predetermined amount of additive element M in addition to the metal element.
Examples of the additive element M include magnesium (Mg), aluminum (Al), silicon (Si), titanium (Ti), chromium (Cr), iron (Fe), cobalt (Co), copper (Cu), and zinc. At least one element selected from (Zn) can be used.

These additive elements M are appropriately selected according to the use of the secondary battery configured using the positive electrode active material and the required performance.
Since M itself does not contribute to the redox reaction, the value of y indicating the amount of M added is 0.20 or less, preferably 0.15 or less, more preferably 0.10 or less.

[Specific surface area]
When the specific surface area of the particles measured by BET method utilizing nitrogen adsorption, it is preferable 0.30~1.50m ² / g, more preferably 0.50~1.50m ² / g.
Lithium ion desorption / insertion that occurs in the positive electrode active material during charging / discharging of the battery occurs on the surface of the positive electrode active material, so that the resistance increases when the specific surface area is less than 0.30 m ² / g. On the other hand, when it exceeds 1.50 m ² / g, the electrolytic solution decomposed by a side reaction occurring at the interface between the positive electrode active material and the electrolytic solution is deposited, which causes an increase in resistance.

[Particle structure]
The form of the positive electrode active material of the present invention is 3.0 to 5.0 μm, which is formed by aggregation of a large number of primary particles having a particle size of 0.1 to 2.0 μm when observed with an electron microscope such as SEM or TEM. Secondary particles, single primary particles having a particle size of 1.0 to 7.0 μm, or a mixture thereof. Each particle may have a space or void surrounded by one or more primary particles.

[Particle size distribution]
If the particle size distribution of the particles is measured with a laser light diffraction / scattering type particle size distribution meter, the volume average particle size is adjusted to be 2 to 8 μm, preferably 3 to 8 μm, more preferably 3 to 6 μm. In the battery using the positive electrode active material for the positive electrode, the battery capacity per volume can be increased, and excellent battery characteristics such as high safety and high output can be obtained.

2. Manufacturing method The manufacturing process of the positive electrode active material of this invention consists of the following three processes.
First stage: [Precursor crystallization process]
Second stage: [Oxidation roasting process]
Third stage: [Lithium synthesis process]

[Precursor crystallization process]
In this step, a mixed aqueous solution is prepared using a water-soluble raw material so that the molar ratio of each element is “Mn: Ni: M = (2-xy): x: y”, and an alkali metal This is a step of obtaining a manganese nickel composite hydroxide precursor by reacting with an aqueous solution or the like in a reaction vessel.

[Oxidation roasting process]
This step is a step of obtaining a manganese nickel composite oxide by firing the hydroxide precursor obtained in the previous step at a temperature of 800 to 1000 ° C. in an air atmosphere.

[Lithium synthesis process]
In this step, the composite oxide obtained in the previous step is mixed with a lithium compound and fired at a temperature of 600 to 850 ° C. in an oxygen atmosphere.

Below, an example of the manufacturing method of lithium manganese nickel complex oxide is shown.
[Precursor crystallization process]
First, a plurality of metal compounds containing manganese are dissolved in water at a predetermined ratio to prepare a mixed aqueous solution. The composition ratio of each metal at this time is the same as the composition ratio of the composite hydroxide particles finally obtained. Therefore, the ratio of the metal compound dissolved in water is adjusted so that the composition ratio of each metal in the mixed aqueous solution is the same as the composition ratio of each metal in the composite hydroxide particles of the present invention. This mixed aqueous solution is prepared. The metal compound may be water-soluble, and sulfate is preferable from the viewpoint of cost. In addition, when the water-soluble suitable raw material is not found by the additive element M etc., it does not add to mixed aqueous solution.

Next, water is put into the reaction tank, an appropriate amount of aqueous sodium hydroxide and aqueous ammonia are added, the pH value in the reaction tank is 11.2 to 12.2 based on the liquid temperature of 25 ° C., and the ammonia concentration is 2 to 2. Prepare to be 15 g / L.
If the pH range at that time is less than 11.2, a large amount of impurities due to anions constituting the raw metal compound are mixed in the composite hydroxide particles, which is not preferable. On the other hand, if the pH exceeds 12.2, the composite hydroxide particles become fine particles, which is not preferable.

  Furthermore, when the ammonia concentration is less than 2 g / L, the composite hydroxide particles do not take a spherical shape, which is not preferable. On the other hand, when the ammonia concentration exceeds 15 g / L, the solubility of nickel forming the ammonia complex is increased, and the composition in the composite hydroxide particles is not as intended.

  The atmosphere in the reaction vessel is preferably a non-oxidizing atmosphere (oxygen concentration: 1% by volume or less). When the oxygen concentration exceeds 1% by volume, oxidized manganese is precipitated as fine particles, which is not preferable.

The temperature of the reaction vessel is set to 40 to 60 ° C, preferably 45 to 55 ° C.
Since the temperature of the reaction vessel naturally rises due to reaction heat and stirring energy, an attempt to maintain the temperature below 40 ° C. consumes extra energy for cooling, which is not preferable. Exceeding 60 ° C. is not preferable because the amount of ammonia evaporation increases and it becomes difficult to maintain the target ammonia concentration.

After adjusting the reaction tank, the mixed aqueous solution was dropped into the reaction tank at a constant rate to obtain a reaction aqueous solution.
At this time, 25% by mass aqueous ammonia and 25% by mass aqueous sodium hydroxide solution were also added dropwise at a constant rate. The pH value of the reaction aqueous solution was 11.2-12. The manganese nickel composite hydroxide particles (hereinafter referred to as “composite hydroxide particles”) were crystallized by controlling so as to be maintained at 15 g / L.

  Thereafter, the slurry containing the manganese nickel composite hydroxide particles recovered from the overflow provided in the reaction vessel is filtered and dried, whereby powdered manganese nickel composite hydroxide particles are obtained.

[Oxidation roasting process]
This step is a step in which the composite hydroxide prepared in the previous step is baked in an air atmosphere at a temperature of 800 to 1000 ° C. for 5 to 24 hours and then cooled to room temperature to obtain a manganese nickel composite oxide. .

  At this time, the compound containing additive element M that could not be co-precipitated in the precursor crystallization step in the previous step may be added to the composite hydroxide and fired so as to have the same composition ratio as the target. The compound containing the additive element M to be added is not particularly limited, and for example, an oxide, hydroxide, carbonate, or a mixture thereof can be used.

If the firing temperature is less than 800 ° C., the specific surface area becomes large and exceeds the preferred range of the specific surface area, which is not preferable. When the firing temperature exceeds 1000 ° C. , the specific surface area becomes small, which is not preferable because it does not satisfy the preferable range of the specific surface area.
If the firing time is less than 5 hours, the temperature in the firing container is not uniform, which is not preferable. On the other hand, firing for more than 24 hours is not preferable from the viewpoint of energy efficiency because the obtained manganese nickel composite oxide particles are the same as when fired for 24 hours.
In addition, when mild sintering is seen in the manganese nickel composite oxide particles, a crushing treatment may be added.
When the crystal structure of the manganese-nickel composite oxide produced as described above is measured by XRD, it can be confirmed that it is a spinel crystal structure.

[Lithium synthesis process]
By adding and mixing a lithium compound to the manganese nickel composite oxide particles such that the lithium content is 46 to 62.5 atomic% with respect to the total number of metal atoms contained in the particles, A lithium mixture is obtained.
The lithium compound to be added is not particularly limited, and for example, lithium hydroxide, lithium nitrate, lithium carbonate, or a mixture thereof can be used. In particular, lithium hydroxide having a low melting point and high reactivity is preferably used.

Next, the obtained lithium mixture is fired in an oxygen atmosphere at a temperature of 600 to 850 ° C. for 5 to 36 hours, and then cooled to room temperature to obtain a lithium manganese nickel composite oxide.
If the oxygen concentration in the atmosphere is less than 80%, oxygen defects are likely to occur, which is not preferable. Moreover, if the firing temperature is less than 600 ° C., the crystal structure of the lithium manganese nickel composite oxide does not grow sufficiently, which is not preferable. Exceeding 850 ° C. is not preferable because oxygen deficiency occurs.
If the firing time is less than 5 hours, the temperature in the firing container is not uniform, which is not preferable. On the other hand, firing for more than 36 hours is not preferable from the viewpoint of energy efficiency because the obtained lithium manganese nickel composite oxide particles are the same as when fired for 36 hours.
In addition, when light sintering is seen in lithium manganese nickel complex oxide, you may add a crushing process.

3. Non-aqueous electrolyte secondary battery The non-aqueous electrolyte secondary battery of the present invention comprises a positive electrode, a negative electrode, a separator, a non-aqueous electrolyte, and the like, and is composed of the same components as a general non-aqueous electrolyte secondary battery. The The embodiments described below are merely examples, and the non-aqueous electrolyte secondary battery of the present invention can be used in various ways based on the knowledge of those skilled in the art based on the embodiments described in this specification. It can be implemented in a form that has been changed or improved. Moreover, the use of the non-aqueous electrolyte secondary battery of the present invention is not particularly limited.

(1) Positive electrode Using the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention, for example, a positive electrode of a non-aqueous electrolyte secondary battery is produced as follows.
First, a powdered positive electrode active material, a conductive material, and a binder are mixed, and activated carbon and a target solvent such as viscosity adjustment are added as necessary, and this is kneaded to prepare a positive electrode mixture paste. . Each mixing ratio in the positive electrode mixture paste is appropriately selected according to the use of the secondary battery and the required performance, and is not particularly limited, but the positive electrode mixture excluding the solvent is not limited. When the solid content is 100 parts by mass, the content of the positive electrode active material is 60 parts by mass to 95 parts by mass, and the content of the conductive material is 1 part by mass, like the positive electrode of a general non-aqueous electrolyte secondary battery. It is desirable that the content of the binder is 1 to 20 parts by mass.

  The obtained positive electrode mixture paste is applied to, for example, the surface of a current collector made of aluminum foil and dried to disperse the solvent. If necessary, pressurization may be performed by a roll press or the like to increase the electrode density. In this way, a sheet-like positive electrode can be produced. The sheet-like positive electrode can be cut into an appropriate size according to the target battery and used for battery production. However, the method for manufacturing the positive electrode is not limited to the above-described examples, and other methods may be used.

In producing the positive electrode, as the conductive material, for example, graphite (natural graphite, artificial graphite, expanded graphite and the like), and carbon black materials such as acetylene black and ketjen black (registered trademark) can be used.
The binder plays a role of anchoring the active material particles. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluorine rubber, ethylene propylene diene rubber, styrene butadiene, cellulosic resin, and polyacrylic are used. An acid can be used.

If necessary, a positive electrode active material, a conductive material, and activated carbon are dispersed, and a solvent that dissolves the binder is added to the positive electrode mixture.
Specifically, an organic solvent such as N-methyl-2-pyrrolidone can be used as the solvent. Activated carbon can be added to the positive electrode mixture in order to increase the electric double layer capacity.

(2) Negative electrode The negative electrode composite material in which the negative electrode is made of metal lithium, lithium alloy, or the like, or a negative electrode active material capable of occluding and desorbing lithium ions, mixed with a binder, and added with an appropriate solvent to form a paste. Is applied to the surface of a metal foil current collector such as copper, dried, and compressed to increase the electrode density as necessary.

  As the negative electrode active material, for example, organic compound fired bodies such as natural graphite, artificial graphite and phenol resin, and powdery bodies of carbon materials such as coke can be used. In this case, a fluorine-containing resin such as PVDF can be used as the negative electrode binder, as in the case of the positive electrode, and an organic material such as N-methyl-2-pyrrolidone can be used as a solvent for dispersing these active materials and the binder. A solvent can be used.

(3) Separator A separator is interposed between the positive electrode and the negative electrode.
The separator separates the positive electrode and the negative electrode and retains an electrolyte, and a thin film such as polyethylene or polypropylene and a film having many minute holes can be used.

(4) Non-aqueous electrolyte The non-aqueous electrolyte is obtained by dissolving a lithium salt as a supporting salt in an organic solvent.
Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and trifluoropropylene carbonate, chain carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and dipropyl carbonate, and tetrahydrofuran, 2- One kind selected from ether compounds such as methyltetrahydrofuran and dimethoxyethane, sulfur compounds such as ethylmethylsulfone and butanesultone, phosphorus compounds such as triethyl phosphate and trioctyl phosphate, etc. are used alone or in admixture of two or more. be able to.

As the supporting salt, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , and complex salts thereof can be used.
Further, the non-aqueous electrolyte may contain a radical scavenger, a surfactant, a flame retardant, and the like in order to improve battery characteristics.

(5) Battery shape and configuration The non-aqueous electrolyte secondary battery of the present invention composed of the positive electrode, the negative electrode, the separator and the non-aqueous electrolyte described above has various shapes such as a cylindrical shape and a laminated shape. It can be shaped. In any case, the positive electrode and the negative electrode are laminated through a separator to form an electrode body, and the obtained electrode body is impregnated with a non-aqueous electrolyte, and the positive electrode current collector communicates with the outside. Connect between the terminals and between the negative electrode current collector and the negative electrode terminal leading to the outside using a current collecting lead, etc., and seal the battery case to complete the non-aqueous electrolyte secondary battery. .

(6) Characteristics A non-aqueous electrolyte secondary battery using the positive electrode active material of the present invention has a high capacity and excellent output characteristics while having a high operating potential.
Specifically, the positive electrode active material of the present invention is used as a positive electrode to form a 2032 type coin battery, with a current density of 0.1 mA / cm ² , charged to a cutoff voltage of 5.0 V, and rested for 1 hour. Thereafter, when discharged to a cutoff voltage of 3.0 V, an initial discharge capacity of 125 mAh / g or more, preferably 130 mAh / g or more is obtained. Moreover, the positive electrode resistance of this 2032 type coin battery can be 28Ω or less, preferably 25Ω or less.

(7) Use of non-aqueous electrolyte secondary battery The non-aqueous electrolyte secondary battery of the present invention has the above-mentioned characteristics, so that it is a small portable electronic device (a notebook personal computer or a mobile phone terminal) that always requires a high capacity. Etc.). Further, since the nonaqueous electrolyte secondary battery of the present invention can be reduced in size and increased in output, it is also suitable as a power source for an electric vehicle subject to restrictions on the mounting space.
The non-aqueous electrolyte secondary battery of the present invention is not only a power source for an electric vehicle driven purely by electric energy but also a power source for a so-called hybrid vehicle used in combination with a combustion engine such as a gasoline engine or a diesel engine. Can also be used.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

[Preparation of lithium manganese nickel composite oxide]
(A) Precursor crystallization step First, the temperature in the tank was set to 40 ° C. while stirring the water in a reaction tank (5 L) up to a half amount. The inside of the reaction vessel at this time was a nitrogen atmosphere (oxygen concentration: 1% by volume or less).

  Appropriate amounts of 25% by mass aqueous sodium hydroxide and 25% by mass aqueous ammonia are added to the water in the reaction vessel, the pH value in the reaction vessel is 11.5 based on the liquid temperature of 25 ° C., and the ammonia concentration is 5 g / L was prepared. At the same time, manganese sulfate and nickel sulfate were dissolved in pure water so that the molar ratio of manganese to nickel was Mn: Ni = 1.50: 0.50 to prepare a 2.0 mol / L raw material aqueous solution. .

  This raw material aqueous solution was dropped into the reaction vessel at a constant rate to obtain a reaction aqueous solution. At this time, 25% by mass aqueous ammonia and 25% by mass aqueous sodium hydroxide solution were also added dropwise at a constant rate, and the pH value of the aqueous reaction solution was maintained at 11.5 based on the liquid temperature of 25 ° C. and the ammonia concentration was maintained at 5 g / L. Thus, manganese nickel composite hydroxide particles (hereinafter referred to as “composite hydroxide particles”) were crystallized.

  Thereafter, the slurry containing the composite hydroxide particles recovered from the overflow provided in the reaction tank is filtered, and water-soluble impurities are washed and removed with ion-exchanged water, followed by drying to obtain a powdery composite hydroxide. Product particles were obtained.

(B) Oxidation roasting step After firing the produced composite hydroxide particles in an air atmosphere at 900 ° C. for 12 hours using an atmosphere firing furnace (manufactured by Siliconit Co., Ltd., BM-50100M), it is cooled to room temperature. Manganese nickel composite oxide particles were obtained. In addition, since mild sintering was seen in this manganese nickel composite oxide, it pulverized using the hammer mill (MF10 by IKA Japan Co., Ltd.).

(C) Lithium synthesis step The manganese nickel composite oxide particles were weighed such that the lithium content was 50 atomic% with respect to the total number of manganese and nickel atoms contained in the composite oxide particles. Lithium oxide monohydrate was added and mixed using a tumbler shaker mixer (Dalton Co., Ltd., T2F) to obtain a lithium mixture.
The resulting lithium mixture was baked at 700 ° C. for 20 hours in an atmosphere of 90% or more of oxygen using an atmosphere firing furnace (manufactured by Siliconit Co., Ltd., BM-50100M), cooled to room temperature, and lithium manganese nickel Composite oxide particles were obtained.

[Evaluation of lithium manganese nickel composite oxide particles]
The following evaluation was performed on the lithium manganese nickel composite oxide thus obtained.

(A) Composition According to an analysis using an ICP emission spectroscopic analyzer (Varian, 725ES), this positive electrode active material has a molar ratio of Li, Mn, and Ni: Li: Mn: Ni = 1.00: 1. It was confirmed that it was represented by 50: 0.50.

(B) Crystal structure When the crystal structure of the lithium manganese nickel composite oxide particles was measured using XRD (manufactured by PANALYTICAL, X'Pert, PROMRD), an XRD pattern of a spinel crystal structure was detected. The XRD pattern was indexed with the Fd-3m structure, and Rietveld analysis was performed using Rietveld analysis software (manufactured by PANALYTICAL, High Score Plus Ver. 3.0d). It was confirmed that the lattice strain was 0.027% and the crystallite diameter was 3813 mm.

In addition, whether the crystal structure of the lithium manganese nickel composite oxide particles is “Fd-3m” structure or “P4 ₃ 32” structure is measured by “FT-IR (manufactured by PerkinElmer, using Frontier Gold)”. confirmed.

"FT-IR spectrum" is obtained in FIG. 1, divided by the minimum value of absorbance at wave number 480～490Cm ^-1 absorbance maxima of the peaks of wavenumber 493～513Cm ^-1 1.02 wavenumber 549～ divided by the minimum value of absorbance maximum wavenumbers 560～570Cm ^-1 absorbance 559cm ^-1 is 1.02, the maximum value of absorbance at wave number 584～594Cm ^-1 absorbance wavenumber 606～616Cm ^-1 The value divided by the minimum value was 1.04, and it was confirmed that the crystal structure was the “Fd-3m” structure.

(C) BET specific surface area, average particle diameter The BET specific surface area of the lithium manganese nickel composite oxide particles was measured using a fully automatic BET specific surface area measuring apparatus (manufactured by Mountech Co., Ltd., Macsorb). The result confirmed that it was 1.08 m < ² > / g.
Moreover, when the volume reference | standard average particle diameter was calculated | required using the laser diffraction scattering type particle size distribution measuring apparatus (the Nikkiso Co., Ltd. make, Microtrac HRA), it confirmed that it was 5.55 micrometers.

[Production of secondary battery]
For the evaluation of the obtained positive electrode active material, a 2032 type coin battery 1 (hereinafter referred to as “coin type battery”) shown in FIG. 3 was used.
The coin-type battery 1 includes a case 2 and an electrode 3 accommodated in the case 2.
The case 2 has a positive electrode can 2a that is hollow and open at one end, and a negative electrode can 2b that is disposed in the opening of the positive electrode can 2a. When the negative electrode can 2b is disposed in the opening of the positive electrode can 2a, A space for accommodating the electrode 3 is formed between the negative electrode can 2b and the positive electrode can 2a.

The electrode 3 includes a positive electrode 3a, a separator 3c, and a negative electrode 3b, which are stacked in this order. The positive electrode 3a contacts the inner surface of the positive electrode can 2a, and the negative electrode 3b contacts the inner surface of the negative electrode can 2b. It is accommodated in the case 2 so as to come into contact. The case 2 includes a gasket 2c, and relative movement is fixed by the gasket 2c so as to maintain a non-contact state between the positive electrode can 2a and the negative electrode can 2b.
Further, the gasket 2c also has a function of sealing a gap between the positive electrode can 2a and the negative electrode can 2b to block the inside and outside of the case 2 in an airtight and liquid tight manner.

Such a coin-type battery 1 was produced as follows.
First, 52.5 mg of the obtained positive electrode active material, 15 mg of acetylene black, and 7.5 mg of polytetrafluoroethylene resin (PTFE) were mixed and thinned to a weight of about 10 mg with a diameter of 10 mm, and the positive electrode 3a This was dried in a vacuum dryer at 120 ° C. for 12 hours.

Next, using the positive electrode 3a, the coin-type battery 1 was produced in a glove box in an Ar atmosphere in which the dew point was controlled at −80 ° C. At this time, as the negative electrode 3b, a lithium foil punched into a disk shape having a diameter of 14 mm, or a negative electrode sheet in which graphite powder having an average particle size of about 20 μm and polyvinylidene fluoride were applied to a copper foil was used.
The separator 3c is a polyethylene porous film having a film thickness of 25 μm, and the electrolyte is a 3: 7 mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) using 1M LiPF ₆ as a supporting electrolyte (Toyama Chemical). Kogyo Co., Ltd.) was used.

[Evaluation of secondary battery]
The initial discharge capacity and the positive electrode resistance showing the performance of the coin-type battery 1 were evaluated as follows.
The initial discharge capacity is about 24 hours after the coin-type battery 1 using lithium foil as the negative electrode is manufactured, and after the open circuit voltage OCV (Open Circuit Voltage) is stabilized, the current density with respect to the positive electrode is 0.1 mA / Evaluation was made by measuring the capacity (initial discharge capacity) when charging to a cutoff voltage of 5.0 V as cm ² and discharging to a cutoff voltage of 3.0 V after a pause of 1 hour. The measurement result was 141 mAh / g.

Positive electrode resistance was evaluated by measuring DC-IR resistance.
Specifically, the coin-type battery 1 is charged to 60% of the initial discharge capacity, sandwiched for 1 minute, discharged at a current density of 0.4 mA / cm ² for 10 seconds, and then sandwiched again for 1 minute. The battery was charged for 10 seconds at a current density of 0.4 mA / cm ² . This operation was repeated under the conditions of 1.3 mA / cm ² , 4.0 mA / cm ² and 6.6 mA / cm ² to measure the difference between the voltage at the start of discharge and the voltage until the end of discharge at each current density. .

Next, the current density was plotted on the vertical axis and the voltage difference was plotted on the horizontal axis, and the obtained linear relationship was found to have a slope by first-order linear approximation, and this slope was taken as the positive electrode resistance (DC-IR resistance).
The measurement result was 25.1Ω.

Lithium manganese nickel composite oxide particles were obtained by the same production method as in Example 1 except that the firing temperature in the lithium synthesis step was 850 ° C.
Various evaluation results are shown in Tables 1 and 2.

In the crystallization process, manganese sulfate, nickel sulfate, and iron sulfate are dissolved in pure water so that the molar ratio of manganese, nickel, and iron is Mn: Ni: Fe = 1.50: 0.45: 0.05. Then, lithium manganese nickel iron composite oxide particles were obtained by the same production method as in Example 1 except that a 2.0 mol / L raw material aqueous solution was prepared.
Various evaluation results are shown in Tables 1 and 2.

In the crystallization process, manganese sulfate, nickel sulfate, and cobalt sulfate are dissolved in pure water so that the molar ratio of manganese, nickel, and cobalt is Mn: Ni: Co = 1.50: 0.45: 0.05. Then, lithium manganese nickel cobalt composite oxide particles were obtained by the same production method as in Example 1 except that a 2.0 mol / L raw material aqueous solution was prepared.
Various evaluation results are shown in Tables 1 and 2.

In the crystallization process, the manganese sulfate, nickel sulfate, and titanium sulfate solution is purified into pure water so that the molar ratio of manganese, nickel, and titanium is Mn: Ni: Ti = 1.45: 0.50: 0.05. Lithium manganese nickel titanium composite oxide particles were obtained by the same production method as in Example 1 except that a 2.0 mol / L raw material aqueous solution was prepared by dissolution.
Various evaluation results are shown in Tables 1 and 2.

In the crystallization process, manganese sulfate, nickel sulfate, and aluminum sulfate are dissolved in pure water so that the molar ratio of manganese, nickel, and aluminum is Mn: Ni: Al = 1.50: 0.45: 0.05. Then, lithium manganese nickel aluminum composite oxide particles were obtained by the same production method as in Example 1 except that a 2.0 mol / L raw material aqueous solution was prepared.
Various evaluation results are shown in Tables 1 and 2.

In the crystallization step, manganese sulfate, nickel sulfate, iron sulfate, and cobalt sulfate have a molar ratio of manganese, nickel, iron, and cobalt, Mn: Ni: Fe: Co = 1.50: 0.40: 0.05: Lithium manganese nickel iron cobalt composite oxide particles were obtained in the same manner as in Example 1 except that the raw material aqueous solution of 2.0 mol / L was prepared by dissolving in pure water to 0.05. .
Various evaluation results are shown in Tables 1 and 2.

(Comparative Example 1)
Lithium manganese nickel composite oxide particles were obtained by the same production method as in Example 1 except that the firing temperature in the lithium synthesis step was set to 900 ° C.
Various evaluation results are shown in Tables 1 and 2.

(Comparative Example 2)
Lithium manganese nickel composite oxide particles were obtained by the same production method as in Example 1 except that the firing atmosphere in the lithium synthesis step was air.
Various evaluation results are shown in Tables 1 and 2.

(Comparative Example 3)
Lithium manganese nickel composite oxide particles obtained by the same production method as in Example 1 were baked at 600 ° C. for 18 hours in an air atmosphere, then cooled to room temperature and annealed lithium manganese nickel composite oxide particles. Obtained.
In the FT-IR measurement, a shape close to that of FIG. 2 was shown, and it was confirmed that the structure was “P4 ₃ 32”.
Various evaluation results are shown in Tables 1 and 2.

DESCRIPTION OF SYMBOLS 1 Coin type battery 2 Case 2a Positive electrode can 2b Negative electrode can 2c Gasket 3 Electrode 3a Positive electrode 3b Negative electrode 3c Separator

Claims (3)

Lithium (Li), manganese (Mn), nickel (Ni), magnesium (Mg), aluminum (Al), silicon (Si), titanium (Ti), chromium (Cr), iron (Fe), cobalt (Co) , A positive electrode active material for a non-aqueous electrolyte secondary battery containing at least one element M selected from copper (Cu) and zinc (Zn),
The molar ratio of each element is Li: Mn: Ni: M = t: 2-xy: x: y (where 0.96 ≦ t ≦ 1.25, 0.40 ≦ x ≦ 0.60) , 0 ≦ y ≦ 0.20).
From the diffraction pattern obtained by XRD measurement, the value of the lattice strain obtained by Rietveld analysis based on the spinel type crystal structure of “Fd-3m” structure is 0 . 070% or less, the crystallite diameter is 1000 to 8000 mm ,
From the FT-IR spectrum obtained by the FT-IR measurement,
The maximum absorbance between wave number 493～513Cm ^-1, divided by the minimum value of absorbance between wave number 480～490Cm ^-1 is 1.30 or less,
The maximum absorbance between wave number 549～559Cm ^-1, divided by the minimum value of absorbance between wave number 560～570Cm ^-1 is 1.30 or less,
The maximum absorbance between wave number 584~594cm ^-1, for a non-aqueous electrolyte secondary battery by dividing a value is to der Rukoto wherein 1.20 at minimum absorbance between wave number 606～616Cm ^-1 Positive electrode active material. 2. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein a specific surface area of the positive electrode active material for the non-aqueous electrolyte secondary battery is 0.30 to 1.50 m ² / g. material.   The nonaqueous electrolyte solution according to claim 1, comprising a positive electrode using the positive electrode active material for the nonaqueous electrolyte secondary battery, a negative electrode, a separator, and a nonaqueous electrolyte solution. Next battery.

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