JP7225854B2 - Positive electrode active material for non-aqueous electrolyte secondary batteries - Google Patents

Description

The present invention relates to a positive electrode active material for non-aqueous electrolyte secondary batteries.

In recent years, with the spread of mobile electronic devices such as mobile phones and notebook personal computers, there is a demand for the development of small and lightweight secondary batteries with high energy density. There is also a demand for the development of high-output secondary batteries as batteries for electric vehicles such as hybrid vehicles. Lithium ion secondary batteries are known as non-aqueous electrolyte secondary batteries that satisfy such requirements.

A lithium ion secondary battery is composed of, for example, a negative electrode, a positive electrode, an electrolytic solution, and the like, and a material capable of desorbing and intercalating lithium is used as an active material for the negative electrode and the positive electrode.

Lithium-ion secondary batteries using lithium composite oxides, especially lithium-cobalt composite oxides, which are relatively easy to synthesize, as positive electrode materials can obtain a high voltage of the 4V class, so they are expected to have high energy densities. Practical use is progressing. Batteries using lithium-cobalt composite oxides have been extensively developed to obtain excellent initial capacity characteristics and cycle characteristics, and various results have already been obtained.

However, since lithium-cobalt composite oxide uses an expensive cobalt compound as a raw material, the unit price per capacity of a battery using this lithium-cobalt composite oxide is significantly higher than that of a nickel-metal hydride battery, and the applicable applications are quite large. Limited.

For this reason, it is necessary to reduce the cost of positive electrode materials for small secondary batteries for mobile devices and large secondary batteries for power storage and electric vehicles, and to make it possible to manufacture cheaper lithium ion secondary batteries. There are high expectations for this technology, and its realization is of great industrial significance.

As a new active material for lithium-ion secondary batteries, a lithium-nickel composite oxide using nickel, which is cheaper than cobalt, can be mentioned. Since this lithium-nickel composite oxide exhibits a lower electrochemical potential than the lithium-cobalt composite oxide, decomposition due to oxidation of the electrolytic solution is less likely to be a problem, and higher capacity can be expected. Therefore, it is actively developed.

However, when a lithium-nickel composite oxide synthesized purely from nickel is used as a positive electrode material to produce a lithium-ion secondary battery, the cycle characteristics are inferior to those of the cobalt-based battery, and the use and storage in a high-temperature environment is also difficult. Therefore, it has a drawback that the battery performance is relatively likely to be impaired. For this reason, lithium-nickel composite oxides in which a portion of nickel is replaced with other elements such as cobalt and aluminum are generally known.

For example _, in Patent Document 1, it has a layered crystal structure and has _the following formula _{LixNiaCobMcO2} (0.8≤x≤1.2 _, 0.01≤a≤0.99 _, 0.01 ≤b≤0.99, 0.01≤c≤0.3, 0.8≤a+b+c≤1.2, M is at least one element selected from Al, V, Mn, Fe, Cu, and Zn) A positive electrode active material for a lithium secondary battery is proposed, which is characterized by comprising a lithium-containing composite oxide represented by:

JP-A-08-213015

However, in recent years, there has been a demand for further improvement in the performance of non-aqueous electrolyte secondary batteries. For this reason, positive electrode active materials for non-aqueous electrolyte secondary batteries are also in demand for materials capable of improving performance when used in non-aqueous electrolyte secondary batteries. Specifically, there is a demand for a positive electrode active material for non-aqueous electrolyte secondary batteries that can improve the output characteristics of non-aqueous electrolyte secondary batteries when used in the non-aqueous electrolyte secondary batteries.

Therefore, in view of the above-described problems of the prior art, in one aspect of the present invention, a non-aqueous electrolyte secondary battery that can provide a non-aqueous electrolyte secondary battery with excellent output characteristics when used in a non-aqueous electrolyte secondary battery An object of the present invention is to provide a positive electrode active material for a battery.

In order to solve the above problems, according to one aspect of the present invention,
A positive electrode active material for a non-aqueous electrolyte secondary battery containing lithium-nickel composite oxide particles,
The lithium-nickel composite oxide particles are
Li (lithium), Ni (nickel), Co (cobalt), and Al (aluminum),
Li: Ni: Co: Al = a: 1-xy: x: y (where 0.8 ≤ a ≤ 1.2, 0.03 ≤ x ≤ 0.20, 0 .01 ≤ y ≤ 0.10) containing a lithium nickel composite oxide,
The lithium-nickel composite oxide particles are secondary particles in which primary particles are aggregated,
In the cross section of the secondary particles of the lithium-nickel composite oxide particles, 250,000 measurement points are set in a strip-shaped measurement area of 2.5 μm × 12.5 μm, and the crystal orientation is aligned with the measurement points. When allocating
Provide a positive electrode active material for a non-aqueous electrolyte secondary battery , wherein the (001) plane accounts for 40% or more of the (001) plane, the (100) plane, and the (110) plane at the measurement point do.

ADVANTAGE OF THE INVENTION According to one aspect of the present invention, it is possible to provide a positive electrode active material for a non-aqueous electrolyte secondary battery that can provide a non-aqueous electrolyte secondary battery with excellent output characteristics when used in a non-aqueous electrolyte secondary battery. .

Explanatory drawing of the cross-sectional structure of the coin-type battery produced in an Example and a comparative example. Schematic explanatory drawing of the equivalent circuit used for the measurement example of impedance evaluation, and analysis.

Hereinafter, the embodiments for carrying out the present invention will be described with reference to the drawings. Various modifications and substitutions can be made to.
(1) Positive Electrode Active Material for Non-Aqueous Electrolyte Secondary Batteries Hereinafter, one structural example of the positive electrode active material for non-aqueous electrolyte secondary batteries according to the present embodiment will be described.

The positive electrode active material for non-aqueous electrolyte secondary batteries of the present embodiment (hereinafter also simply referred to as "positive electrode active material") can contain lithium-nickel composite oxide particles.
The lithium-nickel composite oxide particles contain Li (lithium), Ni (nickel), Co (cobalt), and Al (aluminum), and the material amount ratio of each element is Li:Ni:Co:Al = a:1-xy:x:y lithium nickel composite oxides.
In addition, a, x, and y in the above formula preferably satisfy 0.8≦a≦1.2, 0.03≦x≦0.20, and 0.01≦y≦0.10.
Moreover, the lithium-nickel composite oxide particles are preferably secondary particles in which primary particles are aggregated. Then, in the cross section of the secondary particles of the lithium-nickel composite oxide particles, the ratio of the (001) plane among the (001) plane, the (100) plane, and the (110) plane is 40% or more. can be done.

The positive electrode active material of the present embodiment can contain lithium-nickel composite oxide particles as described above. In addition, the positive electrode active material of the present embodiment can be composed only of lithium-nickel composite oxide particles. Even in this case, inclusion of unavoidable components mixed in the manufacturing process or the like is not excluded. Moreover, the positive electrode active material of the present embodiment can contain lithium-nickel composite oxide particles in the form of lithium-nickel composite oxide powder, which is an aggregate thereof.

The lithium-nickel composite oxide particles contain Li, Ni, Co, and Al, and the material amount ratio (molar ratio) of each element is Li:Ni:Co:Al=a:1-x- Lithium-nickel composite oxides in which y:x:y can be included. The lithium-nickel composite oxide particles can be composed of the lithium-nickel composite oxide described above, but even in this case, it is not excluded that they contain unavoidable components mixed in during the manufacturing process or the like.

In the formula showing the substance amount ratio of each element contained in the lithium nickel composite oxide, a, x, and y are 0.8 ≤ a ≤ 1.2, 0.03 ≤ x ≤ 0.20, and 0, respectively. It is preferable to satisfy .01≤y≤0.10.

Co and Al replace part of Ni in the lithium-nickel composite oxide. It is preferable that x indicating the substitution ratio of Co is 0.20 or less, and y indicating the substitution ratio of Al is 0.10 or less. This is a non-aqueous non-aqueous system using a positive electrode active material containing particles of the lithium nickel composite oxide, by sufficiently increasing the proportion of lithium nickel oxide by setting the substitution ratio of Ni to Co and Al within the above ranges, respectively. This is because the charge/discharge capacity of the electrolyte secondary battery can be increased, and the stability can be particularly enhanced.

Further, it is preferable that x indicating the substitution ratio of Co is 0.03 or more, and y indicating the substitution ratio of Al is 0.01 or more. This is because by setting the substitution ratio of Ni to Co and Al within the above ranges, the cycle characteristics and stability of the non-aqueous electrolyte secondary battery using the positive electrode active material containing the particles of the lithium-nickel composite oxide can be improved. This is because it can enhance sexuality.

The lithium-nickel composite oxide particles contained in the positive electrode active material of the present embodiment are preferably secondary particles in which primary particles are aggregated. Then, in the cross section of the secondary particles of the lithium-nickel composite oxide particles, the (001) plane accounts for 40% or more of the (001) plane, the (100) plane, and the (110) plane. preferable.

The ratio of each plane in the cross section of the secondary particles of the lithium-nickel composite oxide particles, that is, the crystal orientation can be evaluated using electron backscatter diffraction (EBSD). EBSD uses a scanning electron microscope (SEM) to irradiate a sample with an electron beam and analyze the Kikuchi pattern caused by the electron beam diffraction phenomenon occurring on the surface of the sample to be measured. It is a method that can measure the crystal orientation etc. By analyzing the crystal orientation measured by EBSD, it is possible to evaluate the crystal orientation in a specific direction.

Then, in the observed cross section, more specifically, in the direction perpendicular to the observed cross section, the (001) plane of the (001) plane, the (100) plane, and the (110) plane measured using EBSD The ratio is preferably 40% or more, more preferably 50% or more. When the ratio (orientation ratio) of the (001) plane in the (001) plane, the (100) plane, and the (110) plane in the direction perpendicular to the observed cross section (orientation ratio) is within the above range, the lithium nickel composite oxide particles are included. The output characteristics of a non-aqueous electrolyte secondary battery using the positive electrode active material are improved.

The lithium-nickel composite oxide has a hexagonal crystal structure, and has a layered structure in which transition metal ion layers such as nickel and lithium ion layers are alternately stacked in the c-axis direction. During charging and discharging of the secondary battery, the lithium ions in the crystal of the lithium-nickel composite oxide contained in the positive electrode active material move in the [100] axial direction or the [110] axial direction (ab plane), Lithium ions are intercalated and deintercalated. Therefore, when the orientation ratio of the (001) plane in the (001) plane, the (100) plane, and the (110) plane in the direction perpendicular to the observed cross section is within the above range, the lithium nickel composite contained in the positive electrode active material It is considered that lithium ions are inserted and detached more smoothly in the oxide particles. Therefore, in a non-aqueous electrolyte secondary battery using the positive electrode active material of the present embodiment containing particles of such a lithium-nickel composite oxide, the output characteristics can be improved. Specifically, for such a non-aqueous electrolyte secondary battery, it is thought that, for example, the positive electrode resistance can be reduced and the initial discharge capacity can be increased.

On the other hand, for example, in lithium nickel composite oxide particles having a structure in which primary particles are randomly aggregated, (001) occupies the (001) plane, the (100) plane, and the (110) plane in the direction perpendicular to the observed cross section. The plane ratio becomes less than 40%, and the orientation ratio in the c-axis direction increases. In this case, lithium ion insertion/extraction becomes difficult to proceed, so that the output characteristics of the non-aqueous electrolyte secondary battery using the positive electrode active material containing the lithium-nickel composite oxide particles are degraded.

For the evaluation by EBSD, three or more secondary particles having a volume average particle diameter (MV) of 80% or more are first selected in the cross-sectional observation of the secondary particles of the lithium-nickel composite oxide. Then, the ratio of the (001) plane to the (001) plane, the (100) plane, and the (110) plane in the direction perpendicular to the observed cross section of each selected particle is measured and averaged. can be done.

Specifically, from the ratio R ₀₀₁ of the (001) plane, the ratio R ₁₀₀ of the (100) plane, and the ratio R ₁₁₀ of the (110) plane measured by EBSD, the (001) plane is obtained by the following formula (1). , (100) plane, and (110) plane, the orientation ratio R of the (001) plane can be calculated.
R=100×R ₀₀₁ /[R ₀₀₁ +R ₁₀₀ +R ₁₁₀ ] (1)
Moreover, as a specific evaluation method by EBSD, the method described in Examples described later can be used.

According to the positive electrode active material of the present embodiment described above, when used in a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery having excellent output characteristics can be obtained.
(2) Method for producing a positive electrode active material for non-aqueous electrolyte secondary batteries Next, a method for producing a positive electrode active material for non-aqueous electrolyte secondary batteries according to the present embodiment (hereinafter, also referred to as "a method for producing a positive electrode active material") ) will be explained. In addition, according to the manufacturing method of the positive electrode active material of this embodiment, the above-mentioned positive electrode active material can be manufactured. Therefore, some of the items already explained will be omitted.

The method for producing a positive electrode active material of the present embodiment can have at least the following nickel composite hydroxide preparation step, mixing step, and firing step.

A nickel composite hydroxide preparation step for preparing a nickel composite hydroxide.
A mixing step of mixing a nickel composite hydroxide and a lithium compound to prepare a raw material mixture.
A firing step of filling the raw material mixture in a firing vessel and heat-treating to produce a positive electrode active material containing lithium-nickel composite oxide particles.
Each step will be described below.
[Nickel composite hydroxide preparation step]
In the nickel composite hydroxide preparation step, it is preferable to prepare the nickel composite hydroxide by, for example, a crystallization method. Therefore, the nickel composite hydroxide preparation step can have a crystallization step of crystallizing the nickel composite hydroxide.

In the crystallization step, salts containing Ni, Co, and Al, respectively, can be neutralized and co-precipitated in the aqueous reaction solution in the reaction vessel.

Specifically, in the crystallization step, for example, an aqueous solution containing a metal component such as an aqueous solution containing Ni, an aqueous solution containing Co, and an aqueous solution containing Al, and a neutralizing agent are supplied to the reaction vessel, and the reaction obtained is In an aqueous solution, nickel composite hydroxide can be produced by co-precipitation. During the crystallization step, it is preferable to stir and mix the aqueous solution containing the metal component and the reaction aqueous solution containing the neutralizing agent and the like supplied into the reaction tank.

In the crystallization step, either a batch crystallization method or a continuous crystallization method can be employed. Here, the continuous crystallization method is a crystallization method in which the mixed aqueous solution is continuously supplied and a neutralizing agent is supplied to control the pH, and the nickel composite hydroxide particles generated by the overflow are recovered. be. In the continuous crystallization method, particles with a wide particle size distribution can be obtained, and particles with high packing property can be easily obtained, as compared with the batch-type crystallization method. Further, the continuous crystallization method is suitable for mass production and is an industrially advantageous production method. For example, when the crystallization step is performed by a continuous crystallization method, the packing property (tap density) of the resulting nickel composite hydroxide particles can be further improved, and nickel composite water having higher packing property and sparse density can be obtained. Oxides can be produced easily and in large quantities.

Before starting the crystallization step, pure water, for example, can be put into the reaction vessel to adjust the conditions in the reaction vessel to match the conditions in the crystallization step. Specifically, for example, the atmosphere and temperature in the reaction tank, the strength of stirring by a stirrer, and the like can be adjusted. After starting the crystallization step, an aqueous solution containing a metal component such as an aqueous solution containing Ni can be supplied into the reaction tank as described above.

The aqueous solution containing Ni, the aqueous solution containing Co, and the aqueous solution containing Al can be individually supplied to the reaction vessel, but some or all of them are mixed in advance to form a mixed aqueous solution, and then supplied to the reaction vessel. You can also

As the mixed aqueous solution, an aqueous solution containing Ni, Co, and Al, that is, an aqueous solution in which at least nickel salt, cobalt salt, and aluminum salt are dissolved can be used. At least one salt selected from the group consisting of sulfates, nitrates, and chlorides can be used as the nickel salt, cobalt salt, and aluminum salt, for example. Among these, it is preferable to use sulfate from the viewpoint of cost and waste liquid treatment.

Even if aqueous solutions containing each metal component, such as an aqueous solution containing Ni, are separately used and supplied instead of a mixed aqueous solution, when preparing an aqueous solution containing each metal component, It is preferred to use the various metal salts mentioned above.

Although the concentration of the mixed aqueous solution is not particularly limited, for example, the total concentration of the dissolved metal salts is preferably 1.0 mol/L or more and 2.4 mol/L or less, and 1.2 mol/L or more and 2.2 mol/L. More preferably: By setting the total concentration of the dissolved metal salts in the mixed aqueous solution to 1.0 mol/L or more, the primary particles constituting the obtained nickel composite hydroxide can be sufficiently grown.

In addition, by setting the total concentration of dissolved metal salts in the mixed aqueous solution to 2.4 mol/L or less, excessive reprecipitation of crystals is suppressed in the crystallization step, and clogging of pipes and the like is prevented. can be prevented more reliably. Furthermore, by setting the concentration of the mixed aqueous solution to 2.4 mol/L or less, an excessive increase in the amount of nucleation of the primary particles can be suppressed, and the proportion of fine particles in the resulting nickel composite hydroxide particles can be suppressed. preferable.

Here, the composition of the metal elements contained in the mixed aqueous solution supplied to the reaction tank in the crystallization step substantially matches the composition of the metal elements contained in the resulting nickel composite hydroxide. Therefore, it is preferable to prepare the composition of the metal elements in the mixed aqueous solution so as to be the same as the target composition of the metal elements of the nickel composite hydroxide.

In addition, when the aqueous solutions containing the metal components are added individually without being mixed, the total composition of the metal elements contained in the aqueous solution containing each added metal component is contained in the resulting nickel composite hydroxide. It almost matches the composition of the metal elements that are used. For this reason, it is preferable to adjust the concentration of the aqueous solution containing each metal component and the addition amount in accordance with the target composition of the metal elements of the nickel composite hydroxide.

A complexing agent can also be added to the mixed aqueous solution in conjunction with the neutralizing agent in the crystallization step. The complexing agent is not particularly limited as long as it can bind to a metal element such as Ni ion, Co ion, Al ion in an aqueous solution to form a complex. A supplier may be mentioned. The ammonium ion donor is not particularly limited, but at least one selected from the group consisting of aqueous ammonia, aqueous ammonium sulfate solution, and aqueous ammonium chloride solution can be used, for example. Among these, it is preferable to use ammonia water from the viewpoint of ease of handling. When using an ammonium ion donor, the concentration of ammonium ions in the reaction aqueous solution is preferably in the range of 5 g/L or more and 25 g/L or less.

As the neutralizing agent, for example, an alkaline solution can be used, and for example, it is preferable to use a general alkaline metal hydroxide aqueous solution such as sodium hydroxide or potassium hydroxide. Among these, it is more preferable to use an aqueous sodium hydroxide solution from the viewpoint of cost and ease of handling. Although the alkali metal hydroxide can be added directly to the reaction aqueous solution, it is preferable to add it as an aqueous solution for ease of pH control. In this case, the concentration of the aqueous alkali metal hydroxide solution is preferably 12% by mass or more and 30% by mass or less, more preferably 20% by mass or more and 30% by mass or less. This is because, by setting the concentration of the alkali metal hydroxide aqueous solution to 12% by mass or more, the amount of the neutralizing agent supplied to the reaction tank can be suppressed, and the particles can be grown particularly sufficiently. On the other hand, by setting the concentration of the aqueous alkali metal hydroxide solution to 30% by mass or less, it is possible to suppress the local increase in the pH value of the reaction aqueous solution depending on the addition position of the aqueous alkali metal hydroxide solution, resulting in the generation of fine particles. can be suppressed.

In the crystallization step, the dissolved oxygen concentration, the dissolved nickel concentration, and the stirring intensity in the reaction aqueous solution are preferably set within predetermined ranges. According to the studies of the inventors of the present invention, when a positive electrode active material is prepared using a nickel composite hydroxide crystallized with the dissolved oxygen concentration etc. within a predetermined range, the plane orientation in the secondary particle cross section Thus, the positive electrode active material containing the lithium-nickel composite oxide particles having the properties described above can be obtained more reliably. Preferred conditions such as dissolved oxygen concentration in the crystallization step will be described below.

(Dissolved oxygen concentration)
The dissolved oxygen concentration in the reaction aqueous solution in the crystallization step is preferably 0.2 mg/L or more and 4.6 mg/L or less. By controlling the dissolved oxygen concentration within the above range, it is possible to obtain a nickel composite hydroxide suitable as a precursor of the aforementioned positive electrode active material. Also, during the crystallization step, the dissolved oxygen concentration is preferably controlled within a certain range. The fluctuation range of the dissolved oxygen concentration is, for example, preferably within ±0.2 mg/L, more preferably within ±0.1 mg/L.

The dissolved oxygen concentration can be measured by a winkler method (chemical analysis method), a membrane permeation method (electrochemical measurement method), a fluorescence measurement method, or the like. Since equivalent dissolved oxygen concentration values can be obtained using any of the above methods, any of the above methods may be used to measure the dissolved oxygen concentration. The dissolved oxygen concentration in the reaction aqueous solution can be controlled by, for example, introducing an inert gas (e.g., _N2 gas, Ar gas, etc.), air, or a gas such as oxygen into the reaction vessel, and controlling the flow rate and composition of these gases. can be adjusted by The gas for controlling the dissolved oxygen concentration may be flowed into the space inside the reaction vessel or may be blown directly into the aqueous reaction solution. Further, the dissolved oxygen concentration in the entire reaction aqueous solution can be made more uniform by appropriately stirring the reaction aqueous solution with a stirring device such as a stirring blade at a stirring intensity described later.

(dissolved nickel concentration)
During the crystallization step, the dissolved nickel concentration in the aqueous reaction solution is, for example, preferably 600 mg/L or more and 1400 mg/L or less, and preferably 700 mg/L or more and 1200 mg/L or less, based on the temperature of the reaction aqueous solution. more preferred. Also, during the crystallization step, the dissolved nickel concentration is preferably controlled to be within a certain range. The fluctuation range of the dissolved nickel concentration is preferably within ±20 mg/L, for example. The dissolved nickel concentration can be measured, for example, by chemically analyzing the amount of Ni in the liquid component of the reaction aqueous solution by ICP emission spectroscopy.

(stirring power)
The stirring power applied to the reaction aqueous solution is preferably adjusted in the range of 3 kW/m ³ or more and 15 kW/m ³ or less, more preferably 3 kW/m ³ or more and 14 kW/m ³ or less, and 4.5 kW. /m ³ or more and 12 kW/m ³ or less is more preferable. Moreover, during the crystallization step, the stirring power is preferably controlled within a certain range. The fluctuation width of the stirring power is preferably within ±0.2 kW/m ³ , for example.

Further, the stirring power may be, for example, in the range of 7 kW/m ³ or less, or may be in the range of 6.5 kW/m ³ or less. The stirring power can be controlled within the above range by adjusting the size, rotation speed, etc. of a stirring device such as a stirring blade provided in the reaction vessel.

(reaction temperature)
The temperature of the reaction aqueous solution in the crystallization reaction tank is preferably in the range of 35°C or higher and 60°C or lower, and more preferably in the range of 38°C or higher and 50°C or lower.

By setting the temperature of the reaction aqueous solution to 60° C. or lower, it is possible to suppress an excessive increase in the priority of nucleation over particle growth in the reaction aqueous solution. Therefore, the primary particles constituting the nickel composite hydroxide can be sufficiently grown, and the filling property of the positive electrode active material produced using the nickel composite hydroxide can be improved.

On the other hand, by setting the temperature of the reaction aqueous solution at 35° C. or higher, it is possible to suppress excessive preference for particle growth over nucleation in the reaction aqueous solution. Therefore, it is possible to suppress excessive growth of the primary particles and secondary particles that constitute the nickel composite hydroxide. Furthermore, it is possible to prevent the inclusion of large coarse particles in the positive electrode active material produced using the nickel composite hydroxide.

Further, by setting the temperature of the reaction aqueous solution at 35° C. or higher, the residual amount of metal ions in the reaction aqueous solution can be suppressed, and the reaction efficiency can be enhanced. Furthermore, contamination of impurity elements can be suppressed.

(pH value)
The pH value of the reaction aqueous solution is preferably in the range of 10.0 or more and 13.0 or less based on the liquid temperature of 25°C.

By setting the pH value to 10.0 or more, the production rate of the nickel composite hydroxide is sufficiently increased, and the nickel composite hydroxide having the target composition can be obtained more reliably.

On the other hand, by setting the pH value to 13.0 or less, the particle growth rate and the amount of nucleation are kept within a predetermined range, and the particle size and sphericity of the nickel composite hydroxide are particularly suitable for producing a positive electrode active material. can get things.

The nickel composite hydroxide preparation process can also have arbitrary steps other than the crystallization step. The nickel composite hydroxide preparation step preferably has a washing step, for example after the crystallization step. The cleaning step is a step of cleaning impurities contained in the nickel composite hydroxide obtained in the crystallization step. Pure water is preferably used as the cleaning solution. Also, the amount of the cleaning solution is preferably 1 L or more with respect to 300 g of nickel composite hydroxide. By setting the ratio of the cleaning solution to 1 L or more with respect to 300 g of the nickel composite hydroxide, impurities can be sufficiently suppressed from remaining in the nickel composite hydroxide after cleaning, which is preferable. As a washing method, for example, a washing solution such as pure water may be passed through a filtering machine such as a filter press that collects and filters the nickel composite hydroxide obtained in the crystallization step. If it is desired to further wash the sulfate group (SO ₄ ) remaining in the nickel composite hydroxide, it is preferable to use sodium hydroxide, sodium carbonate, or the like as the washing solution.

The nickel composite hydroxide obtained in the nickel composite hydroxide preparation step contains Ni, Co, and Al, and the material amount ratio of each element is Ni:Co:Al=1-xy:x:y is preferably
Note that x and y in the above formula preferably satisfy 0.03≦x≦0.20 and 0.01≦y≦0.10.
Although the physical properties of the powder of nickel composite hydroxide are not particularly limited, for example, the average particle size is preferably 5 μm or more and 20 μm or less, more preferably 6 μm or more and 15 μm or less. By setting the average particle size to 5 μm or more, the handling of the nickel composite hydroxide can be improved, so that the production efficiency and the positive electrode active material obtained using the nickel composite hydroxide as a raw material can be improved. This is because it is possible to improve the coatability of the slurry when forming the electrode. In addition, by setting the average particle size to 20 μm or less, the smoothness of the electrode surface can be improved when an electrode is produced using the positive electrode active material obtained using the nickel composite hydroxide as a raw material. is.

The bulk density of the nickel composite hydroxide can be, for example, 1 g/cc or more and 2 g/cc or less.

In addition, the nickel composite hydroxide obtained in the nickel composite hydroxide preparation step can also be subjected to roasting or the like to obtain a nickel composite oxide, and then subjected to the mixing step. In this case, the mixing step involves mixing the nickel composite oxide and the lithium compound.
[Mixing process]
In the mixing step, the nickel composite hydroxide and the lithium compound can be mixed to obtain a raw material mixture.

The mixing ratio of the nickel composite hydroxide and the lithium compound is not particularly limited, and can be selected according to the composition of the positive electrode active material to be produced.

The ratio (Li/Me) of the number of lithium atoms (Li) to the number of metal atoms (Me) other than lithium in the raw material mixture hardly changes before and after the firing step. That is, Li/Me in the raw material mixture to be subjected to the firing step is almost the same as Li/Me in the obtained lithium metal composite oxide powder. Therefore, it is preferable to mix so that Li/Me in the raw material mixture prepared in the mixing step is the same as Li/Me in the lithium-nickel composite oxide to be obtained.

For example, in the mixing step, the ratio (Li/Me) of the number of atoms (Me) of metals other than lithium in the mixture and the number of atoms (Li) of lithium is 0.8 or more and 1.2 or less. It is preferable to mix to By setting Li/Me to 0.8 or more, it is possible to suppress the occurrence of Li deficiency at the Li site in the crystal of the lithium-nickel composite oxide and the contamination of metal elements other than Li, thereby producing a lithium-nickel composite oxide. The charge/discharge capacity of the battery can be particularly increased.

In addition, by setting the Li/Me ratio to 1.2 or less, it is possible to prevent unreacted Li from remaining and to particularly increase the ratio of the lithium-nickel composite oxide in the positive electrode active material.

Although the lithium compound to be subjected to the mixing step is not particularly limited, for example, one selected from lithium hydroxide, lithium carbonate, etc., or a mixture thereof can be used.

When lithium hydroxide is used as the lithium compound, it is preferable to use lithium hydroxide anhydrate by dehydration treatment.

In the mixing step, a general mixer can be used as a mixing means for mixing the lithium compound and the nickel composite hydroxide. Just do it.
[Baking process]
The firing step is a step of firing the raw material mixture obtained in the mixing step to obtain a positive electrode active material. When the raw material mixture is fired in the firing step, lithium in the lithium compound diffuses into the nickel composite hydroxide to form a lithium-nickel composite oxide.

During the firing process, it is preferable to be in an oxygen-containing atmosphere continuously, preferably in an oxygen-containing atmosphere having an oxygen concentration of 60% by volume or more. This is because the occurrence of oxygen vacancies can be suppressed by performing the firing step in an oxygen-containing atmosphere having an oxygen concentration of 60% by volume or more. Since the firing step can be performed in an oxygen-only atmosphere, the oxygen concentration in the oxygen-containing atmosphere can be 100% by volume or less.

The firing temperature is preferably, for example, 600° C. or higher and 950° C. or lower. By setting the firing temperature to 600° C. or higher, diffusion of lithium can be sufficiently advanced, and lithium-nickel composite oxide particles having a uniform composition can be obtained more reliably. On the other hand, by setting the temperature to 950° C. or lower, it is possible to suppress the progress of sintering between particles of the lithium-nickel composite oxide particles, which is preferable.

The furnace used for the heat treatment is not particularly limited as long as it can fire the raw material mixture in an oxygen-containing atmosphere, but from the viewpoint of maintaining a uniform atmosphere in the furnace, an electric furnace that does not generate gas is preferable. Either batch or continuous furnaces can be used.

Aggregation or mild sintering may occur in the positive electrode active material obtained by the firing step. In this case, it may be pulverized.

Here, crushing means to apply mechanical energy to an agglomerate composed of a plurality of secondary particles generated by sintering necking between secondary particles during firing, and destroy most of the secondary particles themselves. It is an operation to separate secondary particles and loosen agglomerates.
(3) Non-aqueous electrolyte secondary battery Next, one structural example of the non-aqueous electrolyte secondary battery of the present embodiment will be described.

The non-aqueous electrolyte secondary battery of the present embodiment can have a positive electrode using the positive electrode active material described above as a positive electrode material.

First, a configuration example of the structure of the non-aqueous electrolyte secondary battery of the present embodiment will be described.

The non-aqueous electrolyte secondary battery of the present embodiment can have substantially the same structure as a general non-aqueous electrolyte secondary battery, except that the positive electrode active material described above is used as the positive electrode material.

Specifically, the non-aqueous electrolyte secondary battery of the present embodiment can have a structure including, for example, a case, and a positive electrode, a negative electrode, a non-aqueous electrolytic solution, and a separator housed in the case.

More specifically, a positive electrode and a negative electrode can be laminated with a separator interposed to form an electrode body, and the obtained electrode body can be impregnated with a non-aqueous electrolytic solution. Then, the positive electrode current collector of the positive electrode and the positive electrode terminal connected to the outside, and the negative electrode current collector of the negative electrode and the negative electrode terminal connected to the outside are connected using a current collecting lead or the like, respectively, and are attached to the case. It can have a closed structure.

Needless to say, the structure of the non-aqueous electrolyte secondary battery of the present embodiment is not limited to the above example, and various external shapes such as a cylindrical shape and a laminated shape can be adopted.

A configuration example of each member will be described below.
[Positive electrode]
First, the positive electrode will be explained.

The positive electrode is a sheet-like member, and can be formed, for example, by applying and drying the positive electrode mixture paste containing the above-described positive electrode active material on the surface of a current collector made of aluminum foil. In addition, the positive electrode is appropriately processed according to the battery to be used. For example, it is possible to perform a cutting process to form the material into a suitable size according to the intended battery, and a pressure compression process such as a roll press to increase the electrode density.

The positive electrode mixture paste described above can be formed by adding a solvent to the positive electrode mixture and kneading the mixture. The positive electrode mixture can be formed by mixing the powdered positive electrode active material, the conductive material, and the binder.

The conductive material is added in order to give suitable conductivity to the electrode. Although the material of the conductive material is not particularly limited, graphite such as natural graphite, artificial graphite and expanded graphite, and carbon black materials such as acetylene black and ketjen black can be used.

The binder plays a role of binding the positive electrode active material. The binder used in the positive electrode mixture is not particularly limited, but examples include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluororubber, ethylene propylene diene rubber, styrene butadiene, cellulose resin, polyacrylic One or more selected from acids and the like can be used.

Note that activated carbon or the like can also be added to the positive electrode mixture. By adding activated carbon or the like to the positive electrode mixture, the electric double layer capacity of the positive electrode can be increased.

The solvent has a function of dissolving the binder and dispersing the positive electrode active material, the conductive material, the activated carbon, and the like in the binder. Although the solvent is not particularly limited, organic solvents such as N-methyl-2-pyrrolidone can be used.

Moreover, the mixing ratio of each substance in the positive electrode mixture paste is not particularly limited, and can be, for example, the same as in the case of the positive electrode of a general non-aqueous electrolyte secondary battery. For example, when the solid content of the positive electrode mixture excluding the solvent is 100 parts by mass, the content of the positive electrode active material is 60 parts by mass or more and 95 parts by mass or less, and the content of the conductive material is 1 part by mass or more and 20 parts by mass or less. , the content of the binder can be 1 part by mass or more and 20 parts by mass or less.

The manufacturing method of the positive electrode is not limited to the above method. For example, the positive electrode can be manufactured by press-molding the positive electrode mixture and then drying it in a vacuum atmosphere.
[Negative electrode]
The negative electrode is a sheet-like member formed by applying a negative electrode mixture paste to the surface of a current collector made of metal foil such as copper, and drying the paste.

The negative electrode is formed by substantially the same method as the above-described positive electrode, although the components that make up the negative electrode mixture paste, the composition thereof, the material of the current collector, etc. are different, and various treatments are performed as necessary in the same manner as the positive electrode. done.

The negative electrode mixture paste can be made into a paste by adding an appropriate solvent to a negative electrode mixture obtained by mixing a negative electrode active material and a binder.

As the negative electrode active material, for example, a material containing lithium such as metallic lithium or a lithium alloy, or an occluding material capable of intercalating and deintercalating lithium ions can be employed.

The occluding substance is not particularly limited, but one or more selected from, for example, natural graphite, artificial graphite, baked organic compounds such as phenol resin, and powdery carbon substances such as coke can be used.

When such a storage material is used as the negative electrode active material, a fluorine-containing resin such as PVDF can be used as the binder in the same manner as the positive electrode. Organic solvents such as N-methyl-2-pyrrolidone can be used.

The manufacturing method and structure of the negative electrode are not limited to the above examples, and lithium metal processed into a predetermined shape, a lithium alloy, or the like can also be used as the negative electrode.
[Separator]
The separator is sandwiched between the positive electrode and the negative electrode as necessary, and has the function of separating the positive electrode and the negative electrode and retaining the electrolyte.

As a material for the separator, a thin film such as polyethylene or polypropylene having a large number of fine pores can be used.
[Non-aqueous electrolyte]
The non-aqueous electrolytic solution is obtained by dissolving a lithium salt as a supporting salt in an organic solvent.

Examples of organic solvents include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and trifluoropropylene carbonate; chain carbonates such as diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, and dipropyl carbonate; Ether compounds such as methyltetrahydrofuran and dimethoxyethane; sulfur compounds such as ethylmethylsulfone and butane sultone; and phosphorus compounds such as triethyl phosphate and trioctyl phosphate. be able to.

As the supporting salt, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN(CF ₃ SO ₂ ) ₂ and their composite salts can be used.

In addition, the non-aqueous electrolytic solution may contain radical scavengers, surfactants, flame retardants, and the like in order to improve battery characteristics.
Although the configuration of the non-aqueous electrolyte secondary battery has been described above using a non-aqueous electrolytic solution as the non-aqueous electrolyte, the non-aqueous electrolyte secondary battery of the present embodiment is not limited to such a form. For example, a so-called all-solid battery using a solid electrolyte as the non-aqueous electrolyte can also be used.
Solid electrolytes have the property of withstanding high voltages. Solid electrolytes include inorganic solid electrolytes and organic solid electrolytes.
Examples of inorganic solid electrolytes include oxide-based solid electrolytes and sulfide-based solid electrolytes.
The oxide-based solid electrolyte is not particularly limited, and for example, one containing oxygen (O) and having lithium ion conductivity and electronic insulation can be preferably used. Examples of oxide-based solid electrolytes include lithium phosphate (Li ₃ PO ₄ ), Li ₃ PO ₄ N _x , LiBO ₂ N _x , LiNbO ₃ , LiTaO ₃ , Li ₂ SiO ₃ , Li ₄ SiO ₄ -Li _{3 PO4} , _Li4SiO4 - _Li3VO4 , _{Li2O - B2O3 - P2O5} , _{Li2O - SiO2 , Li2O} - _{B2O3 -} ZnO, Li1 _{+X AlXTi 2-X} (PO ₄ ) ₃ (0≦X≦1), Li _1+X Al _X Ge _2-X (PO ₄ ) ₃ (0≦X≦1), LiTi ₂ (PO ₄ ) ₃ , Li _3X La _{2/ 3-X} TiO ₃ (0≦X≦2/3), Li ₅ La ₃ Ta ₂ O ₁₂ , Li ₇ La ₃ Zr ₂ O ₁₂ , Li ₆ BaLa ₂ Ta ₂ O ₁₂ , Li _3.6 Si _0.6 One or more selected from P _0.4 O ₄ and the like can be mentioned.
The sulfide-based solid electrolyte is not particularly limited, and for example, one containing sulfur (S) and having lithium ion conductivity and electronic insulation can be preferably used. Examples of sulfide solid electrolytes include Li ₂ SP ₂ S ₅ , Li ₂ S—SiS ₂ , LiI—Li ₂ S—SiS ₂ , LiI—Li ₂ SP ₂ S ₅ , LiI—Li ₂ S—B ₂ S ₃ , Li ₃ PO ₄ —Li ₂ S—Si ₂ S, Li ₃ PO ₄ —Li ₂ S—SiS ₂ , LiPO ₄ —Li ₂ S—SiS, LiI—Li ₂ S—P ₂ O ₅ , LiI—Li ₃ PO ₄ —P ₂ S ₅ and the like.
Inorganic solid electrolytes other than those described above may be used, such as Li ₃ N, LiI, Li ₃ N--LiI--LiOH, and the like.
The organic solid electrolyte is not particularly limited as long as it is a polymer compound exhibiting ion conductivity. For example, polyethylene oxide, polypropylene oxide, copolymers thereof, and the like can be used. Moreover, the organic solid electrolyte may contain a supporting salt (lithium salt).
In the case of an all-solid battery using a solid electrolyte, the configuration other than the positive electrode active material can be changed as necessary.

The non-aqueous electrolyte secondary battery of the present embodiment includes a positive electrode using the positive electrode active material described above as a positive electrode material. Therefore, a non-aqueous electrolyte secondary battery with excellent output characteristics can be obtained.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.
[Example 1]
A positive electrode active material was prepared and evaluated by the following procedure.
(Nickel composite hydroxide preparation step)
A predetermined amount of pure water was put into a reaction tank (50 L), the stirring power was adjusted to 6.0 kW/m ² , and the temperature in the tank was set to 42° C. while stirring. At this time, N ₂ (nitrogen) was supplied into the reaction vessel to create a non-oxidizing atmosphere (oxygen concentration: 1 vol%), and the dissolved oxygen concentration in the reaction aqueous solution was adjusted to 1.0 mg/L. The stirring power, the temperature in the tank, and the dissolved oxygen concentration in the reaction aqueous solution were kept constant during the crystallization step.

In addition, nickel sulfate, cobalt sulfate, and aluminum sulfate were dissolved in pure water in advance so that the molar ratio of nickel:cobalt:aluminum was 82:15:3, and the total concentration of the dissolved metal salts was 2.0 mol/ A mixed aqueous solution of L was prepared.

Then, the mixed aqueous solution, a 25% by mass sodium hydroxide aqueous solution as an alkaline solution as a neutralizer, and 25% by mass ammonia water as a complexing agent are simultaneously and continuously added into the reaction tank to form a reaction aqueous solution. bottom. At this time, the pH value and the ammonium ion concentration were adjusted so that the dissolved nickel concentration in the reaction aqueous solution was constant at 800 mg/L. At this time, the pH value in the reaction tank was 11.8 at 25° C., and the ammonium ion concentration was in the range of 12 g/L or more and 15 g/L or less. After the neutralization and crystallization reaction was stabilized, a slurry containing nickel composite hydroxide (nickel-cobalt-aluminum composite hydroxide) was recovered from the overflow port, and then subjected to suction filtration to obtain a cake of nickel composite hydroxide ( crystallization step).

Impurities were washed by passing 1 L of pure water through 140 g of the nickel composite hydroxide in the filtration machine to obtain the nickel composite hydroxide (washing step).
(Mixing process)
A raw material mixture was prepared by mixing the nickel composite hydroxide (Ni _0.82 Co _0.15 Al _0.03 (OH) ₂ ) prepared in the nickel composite hydroxide preparation step and a lithium compound.

As the lithium compound, lithium hydroxide anhydrate obtained by dehydrated commercially available lithium hydroxide monohydrate (LiOH.H ₂ O) by vacuum drying was used.

The lithium hydroxide anhydrate and the nickel composite hydroxide were weighed so that the ratio of the molar amount of lithium to the total molar amount of nickel, cobalt, and aluminum was 1.03, and then sufficiently mixed. . The nickel composite hydroxide had an average particle size of 14 μm and a bulk density of 1.1 g/ml.
(Baking process)
The resulting mixture is charged into a ceramic firing vessel, and is heated to a maximum temperature of 750°C in an atmosphere with an oxygen concentration of 80% by volume using a roller hearth kiln, which is a continuous firing furnace. Firing was performed according to a temperature pattern of heating and holding at 750° C. for 220 minutes. The time required for the mixture to exit from the kiln was 8.0 hours.

The fired product obtained was pulverized using a pin mill with such a strength that the secondary particle shape was maintained.

Through _the above procedure, a positive electrode active _material composed of lithium-nickel _{composite oxide} particles (lithium-nickel composite oxide powder) represented by _{Li1.03Ni0.82Co0.15Al0.03O2} was obtained.
(Evaluation of positive electrode active material)
(1) Ratio of (001) plane among (001) plane, (100) plane, and (110) plane Perpendicular to the particle cross section of the lithium-nickel composite oxide particles contained in the obtained positive electrode active material Among the (001), (100), and (110) planes in the direction, the ratio of the (001) plane was evaluated by EBSD (electron backscatter diffraction method). When the sample to be measured was installed in the measuring apparatus, the sample to be measured was fixed to the holder using a conductive paste (colloidal carbon paste) from the viewpoint of maintaining the conductivity of the sample to be measured.

As a measuring device, a scanning electron microscope (SEM) device (manufactured by Carl Zeiss: Ultra 55) equipped with a computer capable of crystal orientation analysis was used. The acceleration voltage of the electron beam irradiated to the sample to be measured was set to about 15 kV, and the current amount was set to about 20 nA.

In addition, in the cross section of the sample to be measured, the area (surface to be measured) where the crystal orientation is measured is to acquire the orientation information in the z-axis direction in a strip shape of 2.5 μm × 12.5 μm, and the number of measurement points is A total of 250,000 points were awarded.

In order to make it easier to photograph the scattered electron beam (Kikuchi ray) with a camera installed in the SEM, the sample to be measured (specifically, the surface to be measured which is a cross section) is tilted from the horizontal by about 70°. It was installed so that the scattered electron beam was directed toward the camera.

The crystal orientation of the material obtained by EBSD changes depending on what direction the observer places the reference axis. Usually, the crystal orientation distribution map is expressed with reference to any one of orthogonal coordinate axes consisting of x-axis, y-axis and z-axis. Hereinafter, the crystal orientation distribution diagrams based on the x-axis, y-axis, and z-axis are referred to as IPF-X, IPF-Y, and IPF-Z, respectively. IPF-X is the crystal orientation with reference to the horizontal direction on the same plane when the observed cross section is the plane of the paper. IPF-Y is referenced to the vertical direction on the same plane. On the other hand, IPF-Z is a crystal orientation based on the direction perpendicular to the observed cross section.

In the case of a positive electrode material, the edge of the positive electrode material particle where lithium ions are exchanged with the electrolyte such as electrolyte is viewed from the particle surface, and the outside from the center of the particle, which is the path through which lithium ions within the particle desorb. It is thought that crystal orientation information in the radial direction is important. Therefore, when evaluating the orientation in the z-axis direction with respect to the radial direction of the particles, the IPF-Z analysis results corresponding to the crystal orientation observed from these directions were used for the crystal orientation analysis.

The scattered electron beam (Kikuchi line) was observed with a camera, and the data of the Kikuchi pattern observed with the camera was sent to a computer, the Kikuchi pattern was analyzed, and the crystal orientation was determined. For the determined crystal orientation data of the sample to be measured, the coordinates (z) and the Euler angles (φ1, φ and φ2) representing the crystal orientation were obtained for each measurement point.

Each measurement point having an Euler angle value obtained by evaluating the sample was assigned to each crystal orientation as a zone axis according to the following conditions.

<001> axis: φ1=0°±30°, Φ=0°±30°, φ2=0°±30°
<100> axis: φ1=0°±30°, φ=90°±30°, φ2=60°±30°
<110> axis: φ1=0°±30°, φ=90°±30°, φ2=120°±30°
Following the rules above, it is possible to determine in which crystal orientation each measurement point is included.

After performing the above sorting, the ratio of each crystal orientation in the surface to be measured was calculated from the number of measurement points sorted to each crystal orientation.

This step was performed using commercially available EBSD analysis software (Oxford Instruments EBSD analysis software: Project Manager-Tango).

For the measurement by EBSD, first, three secondary particles having a volume average particle diameter (MV) of 80% or more of the previously measured lithium-nickel composite oxide particles were selected. Then, the ratio of (001) planes among (001) planes, (100) planes, and (110) planes in the direction perpendicular to the observed cross section of each selected grain was measured by EBSD as described above. Specifically, from the ratio R ₀₀₁ of the (001) plane, the ratio R ₁₀₀ of the (100) plane, and the ratio R ₁₁₀ of the (110) plane measured by EBSD, the (001) plane is obtained by the following formula (1). , (100) plane, and (110) plane, the orientation ratio R of the (001) plane was calculated.
R=100×R ₀₀₁ /[R ₀₀₁ +R ₁₀₀ +R ₁₁₀ ] (1)
Next, by averaging the measured values of the three particles, the (001) plane, (100) plane, and (110) plane in the particle cross section of the lithium-nickel composite oxide particles subjected to measurement, The ratio of (001) faces was calculated.

Further, when the lithium-nickel composite oxide particles were observed when measuring the EBSD, it was confirmed that the primary particles were aggregated secondary particles.
(2) Initial discharge capacity, positive electrode resistance For a secondary battery having a positive electrode using the lithium-nickel composite oxide particles (powder) prepared in this example as a positive electrode active material, the performance (initial discharge capacity, positive electrode resistance) was measured. evaluated. First, a 2032-type coin battery 10 shown in FIG. 1 was produced by the method described below, and charge/discharge evaluation and positive electrode resistance evaluation were performed.

A 2032-type coin battery 10 is composed of a case 11 and an electrode 12 housed in the case 11 .

The case 11 has a positive electrode can 111 which is hollow and one end is open, and a negative electrode can 112 arranged in the opening of the positive electrode can 111. When the negative electrode can 112 is arranged in the opening of the positive electrode can 111, , a space for accommodating the electrode 12 is formed between the negative electrode can 112 and the positive electrode can 111 .

The electrode 12 is composed of a positive electrode 121, a separator 122 and a negative electrode 123, which are stacked in this order so that the positive electrode 121 is in contact with the inner surface of the positive electrode can 111 and the negative electrode 123 is in contact with the inner surface of the negative electrode can 112. is accommodated in the case 11.

The case 11 is provided with a gasket 113, and the positive electrode can 111 and the negative electrode can 112 are fixed by the gasket 113 so as to maintain an electrically insulated state. The gasket 113 also has the function of sealing the gap between the positive electrode can 111 and the negative electrode can 112 to airtightly and liquidtightly isolate the inside of the case 11 from the outside.

A 2032-type coin battery was produced by the following procedure. 52.5 mg of the positive electrode active material, 15 mg of acetylene black, and 7.5 mg of PTFE are mixed and press-molded to a diameter of 11 mm and a thickness of 100 μm at a pressure of 100 MPa, and dried at 120° C. for 12 hours in a vacuum dryer. Thus, the positive electrode 121 was produced.

Lithium metal with a diameter of 17 mm and a thickness of 1 mm is used for the negative electrode 123 of the 2032 type coin battery 10, and ethylene carbonate (EC) and diethyl carbonate (DEC) with 1 M LiClO ₄ as the supporting electrolyte are used as the non-aqueous electrolyte. (manufactured by Toyama Pharmaceutical Co., Ltd.) was used. A polyethylene porous film having a film thickness of 25 μm was used for the separator 122 .

Using the positive electrode 121, the separator 122, and the negative electrode 123 described above, the 2032-type coin battery 10 having the structure shown in FIG.

After the 2032 type coin battery was produced, it was left at room temperature for about 24 hours, and after the open circuit voltage OCV (Open Circuit Voltage) was stabilized, the current density for the positive electrode was 0.1 mA / cm ² and the cutoff voltage was 4. A charging/discharging test was performed to measure the discharge capacity when the battery was charged at 3 V, rested for 1 hour, and discharged at a cut-off voltage of 3.0 V to determine the initial discharge capacity. As a result, the initial discharge capacity was 185.5 mAh/g. A multi-channel voltage/current generator (R6741A, manufactured by Advantest Co., Ltd.) was used to measure the initial discharge capacity.

A 2032-type coin battery charged at a charging potential of 4.1 V was used to measure the resistance value by the AC impedance method. A frequency response analyzer and a potentiogalvanostat (manufactured by Solartron) were used for the measurement, and a Nyquist plot as shown in FIG. 2(a) was obtained. Since the plot appears as the sum of characteristic curves showing solution resistance, negative electrode resistance and capacity, and positive electrode resistance and capacity, fitting calculations were performed using the equivalent circuit shown in FIG. was calculated. Since the positive electrode resistance varies greatly depending on the configuration and materials of the battery, in the evaluation of the positive electrode resistance in Examples and Comparative Examples, the positive electrode resistance (Ω) of Example 1 was set to 100, and the positive electrode resistance of Comparative Example was evaluated as a relative value. .
[Example 2]
Nickel was prepared in the same manner as in Example 1, except that the N ₂ flow rate and the pH value were adjusted so that the dissolved nickel concentration in the reaction aqueous solution in the crystallization step was 680 mg/L and the dissolved oxygen concentration was 2.4 mg/L. A composite hydroxide and a positive electrode active material were produced.
Each evaluation was performed in the same manner as in Example 1.
In this example, the positive _electrode active _material composed of lithium-nickel _composite oxide particles (lithium-nickel composite _oxide powder) represented by _{Li1.03Ni0.82Co0.15Al0.03O2} was Got. Further, when the lithium-nickel composite oxide particles were observed when measuring the EBSD, it was confirmed that the primary particles were aggregated secondary particles.
Table 1 shows the evaluation results.
[Example 3]
Nickel was prepared in the same manner as in Example ₁ , except that the N flow rate and the pH value were adjusted so that the dissolved nickel concentration in the reaction aqueous solution in the crystallization step was 850 mg/L and the dissolved oxygen concentration was 0.4 mg/L. A composite hydroxide and a positive electrode active material were produced.
Each evaluation was performed in the same manner as in Example 1.
In this example, the positive _electrode active _material composed of lithium-nickel _composite oxide particles (lithium-nickel composite _oxide powder) represented by _{Li1.03Ni0.82Co0.15Al0.03O2} was Got. Further, when the lithium-nickel composite oxide particles were observed when measuring the EBSD, it was confirmed that the primary particles were aggregated secondary particles.
Table 1 shows the evaluation results.
[Comparative Example 1]
The stirring power in the crystallization step was adjusted to 5.5 kW/ ^m3 , and the _N2 flow rate and pH value were adjusted so that the dissolved nickel concentration in the reaction aqueous solution was 400 mg/L and the dissolved oxygen concentration was 5.8 mg/L. A nickel composite hydroxide and a positive electrode active material were produced in the same manner as in Example 1, except that the

Each evaluation was performed in the same manner as in Example 1.

Table 1 shows the evaluation results.
[Comparative Example 2]
Nickel was prepared in the same manner as in Comparative Example 1, except that the N ₂ flow rate and the pH value were adjusted so that the dissolved nickel concentration in the reaction aqueous solution in the crystallization step was 550 mg/L and the dissolved oxygen concentration was 4.0 mg/L. A composite hydroxide and a positive electrode active material were produced.
Each evaluation was performed in the same manner as in Example 1.
Table 1 shows the evaluation results.

実施例１～実施例３で得られた正極活物質を用いたコイン型電池の評価結果によると、比較例１、比較例２と比較して、正極抵抗が低く、初期放電容量が高くなることを確認できた。すなわち、出力特性に優れた非水系電解質二次電池が得られていることを確認できた。

According to the evaluation results of the coin batteries using the positive electrode active materials obtained in Examples 1 to 3, the positive electrode resistance was lower and the initial discharge capacity was higher than in Comparative Examples 1 and 2. could be confirmed. That is, it was confirmed that a non-aqueous electrolyte secondary battery with excellent output characteristics was obtained.

From the above results, the secondary particles of the lithium-nickel composite oxide particles having a predetermined composition are included, and in the cross section of the secondary particles of the lithium-nickel composite oxide particles, the (001) plane, the (100) plane, and the (110) plane It was confirmed that the positive electrode resistance can be suppressed and the initial discharge capacity can be increased by setting the ratio of the (001) plane to 40% or more. That is, it was confirmed that a non-aqueous electrolyte secondary battery having excellent output characteristics can be obtained.

Claims (1)

A positive electrode active material for a non-aqueous electrolyte secondary battery containing lithium-nickel composite oxide particles,
The lithium-nickel composite oxide particles are
Li (lithium), Ni (nickel), Co (cobalt), and Al (aluminum),
Li: Ni: Co: Al = a: 1-xy: x: y (where 0.8 ≤ a ≤ 1.2, 0.03 ≤ x ≤ 0.20, 0 .01 ≤ y ≤ 0.10) containing a lithium nickel composite oxide,
The lithium-nickel composite oxide particles are secondary particles in which primary particles are aggregated,
In the cross section of the secondary particles of the lithium-nickel composite oxide particles, 250,000 measurement points are set in a strip-shaped measurement area of 2.5 μm × 12.5 μm, and the crystal orientation is aligned with the measurement points. When allocating
A positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the (001) plane accounts for 40% or more of the (001) plane, the (100) plane, and the (110) plane at the measurement point .

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