JP2017199591A - Positive electrode active material particles for nonaqueous electrolyte secondary battery, method for manufacturing the same, and nonaqueous electrolyte secondary battery arranged by use thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide positive electrode active material particles by which stable charge and discharge smaller in degradation owing to the repetition of charge and discharge (cycle characteristics) can be performed.SOLUTION: Positive electrode active material particles comprise a positive electrode active material represented by the following general formula: Li(NiCoAlMnM)O(where 1.0≤a≤1.15, 0<x≤1, 0<y≤1, 0<x+y≤1, 0≤z≤0.05, 0≤b≤0.05, and M is Mg, P, Ca, Ti, Y, Sn, Bi, Ce, Zr, La, Mo, Sc, Nb or W). In a case in which the positive electrode active material particles are used for a positive electrode and Li is used for a negative electrode to assemble a coin cell, and the tilt of crystal planes obtained from a Williamson-Hall plot according to XRD diffraction on the positive electrode active material particles is represented by "a", and the tilt for the positive electrode active material particles in initial charging at 4.3 V is represented by "b", an amount of change calculated according to the formula, (b-a)/a is 10.5 or less.SELECTED DRAWING: None

Description

  The present invention relates to positive electrode active material particles for a non-aqueous electrolyte secondary battery, a method for producing the same, and a non-aqueous electrolyte secondary battery using the same, and more particularly to stable charging with little deterioration against repeated charge and discharge. The present invention relates to positive electrode active material particles capable of discharging, a method for producing the same, and a nonaqueous electrolyte secondary battery using the same.

  In recent years, electronic devices such as AV devices and personal computers are rapidly becoming portable and cordless, and there is an increasing demand for secondary batteries having a small size, light weight, and high energy density as power sources for driving these devices. In recent years, in consideration of the global environment, electric vehicles and hybrid vehicles have been developed and put to practical use, and there is an increasing demand for lithium ion secondary batteries having excellent durability characteristics for large power supply applications. Under such circumstances, a lithium ion secondary battery having excellent repeated charge / discharge life and output characteristics has been attracting attention.

  In order to satisfy such a requirement, means for controlling the interfacial reaction between the electrode active material and the electrolytic solution that accompanies insertion / extraction of Li ions during charging / discharging is usually employed. One example is various surface treatments of the active material, and its effect has been proven.

  In addition, for the purpose of improving the output and durability of the active material, secondary particle design with finer crystallites of the active material and a behavioral unit of those aggregates has become the mainstream, and the effect of this is also the mainstream. Proven. However, a problem peculiar to an active material having such secondary particles as a behavioral unit is the collapse of aggregated forms during charge and discharge, that is, cracking of behavioral particles starting from grain boundaries. Such cracks lead to a decrease in conductive paths and a decrease in electrode density, which in turn leads to a rapid decrease in battery characteristics. Therefore, in order to further improve the performance, it is necessary to solve the problem that the characteristics are gradually impaired due to such peeling of the crystal interface.

  In order to solve such a problem, it has been reported focusing on elemental doping and composition control of crystal grain boundaries formed inside the behavior unit in the particles having secondary particles as the behavior unit.

  For example, examples of the layered oxide positive electrode active material having Ni include those in which Ti is present at the grain boundaries (Patent Document 1), those in which Nb is present at the grain boundaries (Patent Document 2), Ti, Zr, Hf, Examples thereof include a material doped with a compound containing at least one element of Si, Ge, and Sn (Patent Document 3).

JP 2012-28163 A Japanese Patent No. 5505565 JP 2007-317576 A

However, Patent Documents 1 to 3 do not disclose suppression of grain boundary cracking for the purpose of improving battery life, and even if the methods described in Patent Documents 1 to 3 are used. These methods alone cannot sufficiently improve the performance of the positive electrode active material, and it is difficult to obtain a positive electrode that can sufficiently perform stable charge and discharge with little deterioration against repeated charge and discharge. is there.
The present invention has been made in view of the above-mentioned problems, and its purpose is to suppress the above-described grain boundary cracking and growth, and to reduce stability with respect to repeated charge and discharge. It is to obtain positive electrode active material particles that can be charged and discharged and to extend the life of the battery.

  In order to achieve the above object, the present inventors have conducted intensive research. As a result, in the battery assembled using the positive electrode active material particles, the slope of the Williamson-Hall plot with respect to the crystal plane of the positive electrode active material particles is 4.3 V. It was found that the smaller the change before and after the initial charge, the less likely the particle cracking occurred when the cycle test was performed, and the present invention was reached.

Specifically, the positive electrode active material particles according to the present invention has a layered rock salt structure, general _{formula, Li a (Ni x Co y} Al z Mn 1-x-y-z M b) O 2 (1. 0 ≦ a ≦ 1.15, 0 <x ≦ 1, 0 <y ≦ 1, 0 <x + y ≦ 1, 0 ≦ z ≦ 0.05, 0 ≦ b ≦ 0.05, M is Mg, P, Ca, Ti, Y, Sn, Bi, Ce, Zr, La, Mo, Sc, Nb or W) positive electrode active material particles made of a lithium transition metal layered oxide, the positive electrode active material particles being used as a positive electrode Using a 2032 size coin cell with Li as the negative electrode, the initial charge up to 4.3V, assuming the slope of the Williamson-Hall plot for the crystal plane obtained by XRD diffraction in the positive electrode active material particles before initial charge as a. (B−a) / a where b is the inclination after The amount of change calculated in (1) is 10.5 or less.

  According to the positive electrode active material particles according to the present invention, since the change amount of the Williamson-Hall plot of the particles before and after the initial charge up to 4.3 V is as small as 10.5 or less, as described above, the positive electrode active material particles In this case, particle cracking is difficult to occur, and therefore stable charge / discharge with less deterioration can be performed with respect to repeated charge / discharge. As a result, the battery life can be extended.

  The nonaqueous electrolyte secondary battery according to the present invention is characterized by using the positive electrode active material particles.

  According to the non-aqueous electrolyte secondary battery according to the present invention, since the positive electrode active material particles according to the present invention are used, the deterioration is more stable with respect to the cycle test, and the battery life can be extended. .

  A method for producing positive electrode active material particles according to the present invention is a method for producing the positive electrode active material particles, wherein a Ni compound and a Co compound, optionally at least one of an Al compound and a Mn compound, and an M element are co-precipitated simultaneously. A step of obtaining a composite compound precursor comprising Ni and Co and optionally at least one of Al and Mn as main components, and a lithium compound as a precursor having a molar ratio of Li / (Ni + Co + Al + Mn + M) of 1.00 or more 1. A step of mixing to obtain a range of 1.15 or less to obtain a mixture, and a step of baking the mixture at 700 ° C. to 950 ° C. in an oxidizing atmosphere.

  According to the method for producing positive electrode active material particles according to the present invention, positive electrode active material particles having a change amount of the slope of the Williamson-Hall plot before and after initial charging up to 4.3 V as described above are 10.5 or less. be able to. That is, stable charge / discharge with less deterioration can be performed with respect to repeated charge / discharge. As a result, positive electrode active material particles that can extend the life of the battery can be obtained.

  The positive electrode active material particle manufacturing method according to the present invention includes Mg, P, Ca, Ti, Y, Sn, Bi, Ce, Zr, La, Mo, Sc, Nb, and W in the step of obtaining a precursor. A composite compound precursor may be obtained by co-precipitation of a compound containing a plurality of or any one of the metal components together with the Ni compound, the Co compound, and optionally at least one of the Al compound and the Mn compound.

  Alternatively, in the step of obtaining a mixture, the precursor includes Mg, P, Ca, Ti, Y, Sn, Bi, Ce, Zr, La, Mo, Sc, Nb and W together with the lithium compound. A compound containing a plurality of or any metal component may be mixed.

  By using these methods, it is possible to suppress grain boundary cracking due to cycle characteristics, and as a result, it is possible to obtain positive electrode active material particles that are less susceptible to repeated charge / discharge and can be more stably charged / discharged.

  According to the positive electrode active material particle and the method for producing the same according to the present invention, it is possible to perform stable charge and discharge with little deterioration with respect to repeated charge and discharge because cracks and growth of grain boundaries in the particle can be suppressed. Positive electrode active material particles can be obtained. Moreover, according to the nonaqueous electrolyte secondary battery according to the present invention, since the positive electrode active material particles according to the present invention are used, it is possible to extend the life.

  Furthermore, by looking at the amount of change in the Williamson-hall plot in the present invention, it is possible to determine the superiority or inferiority of the cycle characteristics without performing a cycle test, which is also useful as a measurement method.

It is a Williamson-Hall plot of the positive electrode active material particles of Example 1 and Comparative Example 1 of the present invention. It is a cross-sectional SEM image after the end of the cycle test of the positive electrode active material particles of Example 1 and Comparative Example 1 of the present invention.

  Hereinafter, modes for carrying out the present invention will be described. The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the invention, its method of application, or its application.

  First, the positive electrode active material particles for a nonaqueous electrolyte secondary battery according to an embodiment of the present invention will be described.

The positive electrode active material particles according to the present embodiment include Li _a (Ni _x Co _y Al _z Mn _1-xyz M _b ) O ₂ (1.0 ≦ a ≦ 1.15, 0 <x ≦ 1, 0 <y ≦ 1, 0 <x + y ≦ 1, 0 ≦ z ≦ 0.05, 0 ≦ b ≦ 0.05, M is Mg, P, Ca, Ti, Y, Sn, Bi, Ce, Zr, La, It consists of a lithium transition metal layered oxide represented by Mo, Sc, Nb or W).

A more preferable composition of the positive electrode active material particles according to the present embodiment is Li _a (Ni _x Co _y Al _z Mn _1-xyz M _b ) O ₂ , and the range of a is 1.00 ≦ a ≦ 1. .10, the range of x is 0.05 ≦ x ≦ 0.5, and the range of y is 0.1 ≦ y ≦ 0.4.

The lithium transition metal layered oxide has a very small solid solution region of Li unlike a full solid solution such as LiMn ₂ O ₄ spinel oxide. For this reason, the ratio of Li to the transition element (Li / Me) in the crystal immediately after the synthesis of the layered oxide does not greatly deviate from 1.0. Further, in the present embodiment, the positive electrode active material particles have a crystallite size of, for example, 100 nm to 600 nm and are formed by aggregated secondary particles that are aggregates of primary particles, and therefore there are crystal grain boundaries in the particles. To do.

  As described above, the positive electrode active material particles according to the present embodiment contain different kinds of metals such as Mg, P, Ca, Ti, Y, Sn, Bi, Ce, Zr, La, Mo, Sc, Nb, and W. Although preferable, the inclusion form may exist by substituting for the main element in the crystal lattice, or may exist at the grain boundary of the secondary particles.

  In addition, the positive electrode active material particles according to the present embodiment are formed by using a positive electrode active material particle as a positive electrode, assembling a 2032 size coin cell with Li as a negative electrode, and a cutoff voltage of 4. The initial charge when set to 3 V was charged under the condition of a charge rate of 0.1 C (CC-CV). The slope of the Williamson-Hall plot by XRD diffraction of the electrode of the positive electrode active material particle powder before charging is a, and after charging to 4.3 V, the battery using the positive electrode active material particle powder is disassembled, When the slope of the Williamson-Hall plot in the XRD diffraction of the electrode cleaned with DMC is b, the amount of change calculated by (b−a) / a is 10.5 or less. The Williamson-Hall plot is the slope of the straight line obtained by plotting the full width at half maximum at each peak and 2θ / θ in which XRD diffraction is observed on a particle with sin θ on the horizontal axis and β cos θ on the vertical axis. Represents a crystal strain and a section represents a crystallite size. In particular, in the present invention, for example, the (101) plane, the (102) plane, the (104) plane, the (105) plane, the (107) plane, etc. are plotted, and an approximate straight line is obtained for these points using the least square method. Deriving and calculating the slope of the straight line.

  The inventors of the present invention have found that the slope value (hereinafter referred to as WH value) indicating the crystal distortion obtained by the Willamson-Holl plot is an indicator of deterioration of the characteristics of the positive electrode active material particles. Specifically, the amount of change in the WH value before and after 4.3 V initial charging is larger with respect to the battery using the positive electrode active material particles, and the larger the magnitude, the higher the positive electrode active material particles in the cycle test. It was found that cracks were formed at the grain boundaries in the agglomerated particles, and as a result, the cycle characteristics deteriorated (FIG. 2). Therefore, obtaining positive electrode active material particles whose change in WH value is not significantly increased is synonymous with obtaining positive electrode active material particles having high cycle characteristics. In particular, in the positive electrode active material particles according to the present embodiment, the amount of change (ba) / a between the initial WH value (a) and the WH value (b) after the initial charge of 4.3 V is 10.5 or less. , Preferably 10.0 or less.

  Moreover, the average secondary particle diameter of the positive electrode active material particles according to the present embodiment is preferably 3.0 μm to 20 μm. When the upper limit exceeds 20 μm, the diffusion of Li accompanying charge / discharge is hindered, causing a decrease in input / output of the battery. The lower limit is preferably 3.0 μm. Below this, the active material / electrolyte interface increases, leading to an increase in undesirable side reactions. A more preferable average secondary particle diameter is 4.0 μm to 19 μm.

  Next, the manufacturing method of the positive electrode active material particle which concerns on one Embodiment of this invention is described.

  First, a spherical nickel-cobalt-manganese composite compound as a precursor is prepared by a wet coprecipitation reaction by continuously supplying a mixed sulfuric acid aqueous solution of cobalt, nickel, and manganese to an aqueous solution adjusted to an optimum pH value. Get particles. The nickel / cobalt / manganese composite compound particles are preferably a composite compound. Next, a mixture in which the precursor and the lithium compound have a molar ratio of Li / (Ni + Co + Mn) in a predetermined range, for example, about 1.00 to 1.15, is obtained, and this mixture is obtained at 600 ° C. to 950 in an oxidizing atmosphere. Bake at ℃. In addition, it is preferable to anneal at 500 ° C. to 750 ° C. in an oxidizing atmosphere during the cooling after the firing or after the cooling. By performing this annealing, the distortion of the crystal structure can be reduced.

  The lithium compound used in the present embodiment is not particularly limited, and various lithium salts can be used. For example, lithium hydroxide monohydrate, lithium nitrate, lithium carbonate, lithium acetate, lithium bromide, Examples include lithium chloride, lithium citrate, lithium fluoride, lithium iodide, lithium lactate, lithium oxalate, lithium phosphate, lithium pyruvate, lithium sulfate, and lithium oxide.

  In the present embodiment, different metals such as Mg, P, Ca, Ti, Y, Sn, Bi, Ce, Zr, La, Mo, Sc, and W may be added. It may be at the time of reaction or may be added by subsequent dry mixing, and is not particularly limited.

It obtained the complex compound particles, crystallite size 100 nm to 600 nm, as an average secondary particle size 3Myuemu～20myuemu, the specific surface area by the BET method becomes 0.15m ² /g~1.0m ² / g It is preferable to be prepared, and in some cases, a treatment such as pulverization may be performed.

  In this embodiment, the Li / (Ni + Co + Mn) ratio in the mixture of the precursor and the Li compound is 1.00 to 1.15 in molar ratio. When the Li / (Ni + Co + Mn) ratio is smaller than 1.00, Ni is mixed into the Li site of the crystal structure, and a single crystal phase cannot be obtained, which causes a decrease in battery performance. When the Li / (Ni + Co + Mn) ratio is larger than 1.15, an excess amount of Li than the stoichiometric composition becomes a factor of the resistance component and causes a decrease in battery performance. A more preferable Li / (Ni + Co + Mn) ratio is 1.02-1.12 in terms of molar ratio, and even more preferably 1.02-1.08.

  The atmosphere for firing the mixture is an oxidizing atmosphere, and the preferred oxygen content is 20 vol% or more. When the oxygen content is below the above range, Li ions are mixed into the transition metal site, leading to a decrease in battery performance. The upper limit of the oxygen content is not particularly limited.

  The firing temperature is preferably 700 ° C to 950 ° C. When the firing temperature is lower than 700 ° C., the diffusion energy of the element is insufficient, so that the target crystal structure in a thermal equilibrium state cannot be reached and a single layer cannot be obtained. On the other hand, when the firing temperature exceeds 950 ° C., oxygen vacancies in the crystal due to reduction of the transition metal occur, and a single layer having the target crystal structure cannot be obtained.

  When annealing after firing, a temperature range of 500 ° C. to 750 ° C. is preferable, and the atmosphere is preferably an oxidizing atmosphere. When the annealing temperature is less than 500 ° C., the diffusion energy of the element is insufficient, so that excess lithium at the grain boundary cannot be diffused into the crystal, so that the intended composition variation cannot be reduced. When the annealing temperature exceeds 750 ° C., the oxygen activity is insufficient, and a transition metal rock salt structure oxide which is an impurity phase is generated. A more preferable annealing temperature is 550 ° C to 730 ° C, and still more preferably 580 ° C to 700 ° C. By performing the annealing, the distortion of the crystal structure of the positive electrode active material particles can be reduced.

  In the above description, the case where z = 0, that is, the case where Al is not included has been described. Naturally, a complex oxide may be manufactured by adding Al or M element. In that case, Al and M elements can be coprecipitated simultaneously with Ni, Co and Mn.

According to the manufacturing method of the present embodiment, after a Ni compound, a Co compound, and optionally at least one of an Al compound and a Mn compound, and an M element are simultaneously coprecipitated, a precursor having a predetermined raw material composition ratio is obtained. When the mixture containing Li having a predetermined raw material composition ratio is fired and heat-treated under predetermined conditions, the amount of change in the WH value before and after the initial charge of the battery up to 4.3 V is 10 when the battery is used. The positive electrode active material particles of .5 or less can be obtained.
Alternatively, at least one of an Ni compound, a Co compound, and optionally an Al compound and an Mn compound is simultaneously coprecipitated to obtain a precursor having a predetermined raw material composition ratio, and then Li and M elements having a predetermined raw material composition ratio When the mixture containing is baked and heat-treated under predetermined conditions, positive electrode active material particles having a change in WH value before and after the initial charge of the battery of 10.5 or less can be obtained.

  Next, a nonaqueous electrolyte secondary battery according to an embodiment of the present invention will be described.

  The nonaqueous electrolyte secondary battery according to the present invention includes a positive electrode including the positive electrode mixture, a negative electrode, and an electrolyte.

  Although it does not specifically limit as a positive electrode mixture in this invention, For example, it can obtain by knead | mixing by the ratio of active material: conductive agent: binder 90: 6: 4.

  As the negative electrode active material, lithium metal, lithium / aluminum alloy, lithium / tin alloy, silicon, silicon / carbon composite, graphite, or the like can be used.

  In addition to the combination of ethylene carbonate (EC) and diethyl carbonate (DEC), the solvent for the electrolyte solution includes carbonates having a basic structure of propylene carbonate (PC), dimethyl carbonate (DMC), etc., and dimethoxyethane (DME). An organic solvent containing at least one kind of ether such as) can be used.

Further, as the electrolyte, in addition to lithium hexafluorophosphate (LiPF ₆ ), at least one lithium salt such as lithium perchlorate (LiClO ₄ ) or lithium tetrafluoroborate (LiBF ₄ ) is used as the solvent. It can be used by dissolving.

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What is important in the present invention is that the nonaqueous electrolyte secondary battery using the positive electrode active material according to the present invention can perform stable charge and discharge with little capacity deterioration in cycle characteristics from low temperature to high temperature. It is.

In the present invention, positive electrode active material particles that are lithium transition metal oxides having aggregated secondary particles as behavioral units are characterized in that the crystal distortion of the particles is small during repeated charge and discharge. Specifically, it can be seen that in the positive electrode active material particles of the present invention, the amount of change between the WH value after initial charging to 4.3 V and the WH value before charging is small, that is, the occurrence of crystal distortion can be suppressed. As a result, cracks at the grain boundaries are suppressed, battery capacity deterioration due to cycle characteristics can be reduced, and cracks at the grain boundaries within the aggregated particles are reduced, so that the electron conduction path and ion conduction path function sufficiently. In addition, it can be determined before the cycle characteristic test that the deterioration of the battery characteristic can be suppressed.
Thus, since the positive electrode active material particles according to the present invention have a small amount of change by the WH method before and after charging and few cracks in the aggregated particles, the battery material has high stability and high cycle characteristics. Can do.

  A typical embodiment of the present invention is as follows. First, various measurement methods for the positive electrode active material particles in this example will be described.

  The composition of the positive electrode active material particles was prepared by dissolving 1.0 g of a sample in 25 ml of a 20% hydrochloric acid solution by heating, transferring to a 100 ml volumetric flask after cooling, preparing pure water by adding pure water, and measuring the ICAP [Optima 8300. Each element was quantified and determined using Perkin Elmer Co., Ltd.].

  The technique for calculating the slope according to the Williamson-Hall plot is based on the use of an electrode produced by the above-described electrode production method, and an electrode in a coin cell after completion of a cycle characteristic test described later using an X-ray diffractometer [SmartLab Co., Ltd. Made by Rigaku], 2θ / θ was in the range of 10 ° to 120 ° by a step scan of 1.2 ° / min in increments of 0.02 °.

  For repeated charge / discharge characteristic measurement (cycle characteristic test) of the positive electrode material mixture according to the present invention, a charge rate in a range of 3.0V-4.3V in a constant temperature bath at 60 ° C. using a 2032 size coin cell. 501 cycles were performed under the conditions of 1.0 C (CC-CV) and a discharge rate of 1.0 C (CC), and the ratio of the battery capacity between the first cycle and the 501 cycle was calculated.

For coin cells related to battery evaluation, 90% by weight of composite oxide as positive electrode active material powder, 6% by weight of carbon black as conductive agent, and 4% by weight of polyvinylidene fluoride dissolved in N-methylpyrrolidone as binder are mixed. Then, it was applied to an Al metal foil and dried at 110 ° C. The sheet was punched to φ16 mm, and then pressure-bonded at 3.0 t / cm ² was used for the positive electrode. Metal lithium foil was used for the negative electrode. As the electrolytic solution, a coin cell of the above size was prepared by using 1 mol / L LiPF ₆ dissolved in a solvent in which EC and DMC were mixed at a volume ratio of 1: 2.

  Moreover, the initial charge to 4.3V performed the charge by 4.3V (CC-CV) in a 25 degreeC thermostat after assembling the coin cell which used the negative electrode as Li as mentioned above.

  For SEM images, a cross-section polisher (SEM cross-section sample preparation device SM-09010) [JEOL Datum Co., Ltd.] processed sample to observe cross-section SEM, scanning electron with energy dispersive X-ray analyzer Observation was performed using a microscope SEM-EDX [manufactured by Hitachi High-Technologies Corporation].

Example 1
An aqueous sodium hydroxide solution having a pH of 12.0 was prepared in a reactor equipped with a blade-type stirrer. An aqueous ammonia solution was added dropwise so that the ammonia concentration was 0.80 mol / l. A mixed aqueous solution of cobalt sulfate, nickel sulfate and sodium aluminate was continuously fed to the reactor at a molar ratio of Co: Ni: Al = 80: 15: 5. During this time, an aqueous sodium hydroxide solution and an aqueous ammonia solution were continuously supplied so that the reaction solution had a pH of 12 and an ammonia concentration of 0.8 mol / l, and was grown to the target average secondary particle size. During this time, a spherical composite transition metal precipitate was obtained by applying mechanical shearing force to the suspension.

  After the reaction, the suspension taken out was washed with water using a filter press and then dried at 80 ° C. for 12 hours to obtain nickel / cobalt / aluminum compound particles (nickel / cobalt / aluminum composite compound particles). It was. Thereafter, lithium hydroxide and the transition metal mixed spherical compound were calcined at 760 ° C. for 10 hours in an oxidizing atmosphere (Li / Ni + Co + Al = 1.01). This was pulverized to obtain a positive electrode active material powder.

  It was 9.25 as a result of producing 2032 coin cell as above-mentioned with the obtained positive electrode active material particle, and calculating the variation | change_quantity of the WH value before and behind 4.3V initial charge. In addition, the result of the Williamson-Hall plot in a present Example is shown in FIG. Further, FIG. 2 shows a cross-sectional SEM image after the end of the cycle characteristic test of the positive electrode active material particles in this example.

Example 2
An aqueous sodium hydroxide solution having a pH of 12.0 was prepared in a reactor equipped with a blade-type stirrer. An aqueous ammonia solution was added dropwise so that the ammonia concentration was 0.80 mol / l. A mixed aqueous solution of cobalt sulfate, nickel sulfate, manganese sulfate, and sodium aluminate was continuously fed to the reactor at a molar ratio of Co: Ni: Mn: Al = 90: 5: 2: 3. During this time, an aqueous sodium hydroxide solution and an aqueous ammonia solution were continuously supplied so that the reaction solution had a pH of 12 and an ammonia concentration of 0.8 mol / l, and was grown to the target average secondary particle size. During this time, a spherical composite transition metal precipitate was obtained by applying mechanical shearing force to the suspension.

  After the reaction, the suspension taken out was washed with water using a filter press and then dried at 80 ° C. for 12 hours to obtain nickel / cobalt / aluminum / magnesium compound particles (nickel / cobalt / aluminum / magnesium composite compound). Particles). Thereafter, lithium hydroxide and the transition metal mixed spherical compound were mixed and baked in an oxidizing atmosphere at 750 ° C. for 10 hours (Li / Ni + Co + Al + Mn = 1.00). This was pulverized to obtain a positive electrode active material powder.

  It was 9.56 as a result of producing 2032 coin cell as above-mentioned with the obtained positive electrode active material particle, and calculating the variation | change_quantity of WH value before and behind 4.3V initial charge.

Comparative Example 1
An aqueous sodium hydroxide solution having a pH of 12.0 was prepared in a reactor equipped with a blade-type stirrer. An aqueous ammonia solution was added dropwise so that the ammonia concentration was 0.80 mol / l. A mixed aqueous solution of cobalt sulfate and nickel sulfate was continuously supplied to the reactor so that the molar ratio was Co: Ni = 80: 15. During this time, an aqueous sodium hydroxide solution and an aqueous ammonia solution were continuously supplied so that the pH of the reaction solution was 11.8 and the ammonia concentration was 0.8 mol / l, and the reaction solution was grown to the target average secondary particle size. During this time, a spherical composite transition metal precipitate was obtained by applying mechanical shearing force to the suspension.

  After the reaction, the suspension taken out was washed with a filter press and then dried at 80 ° C. for 12 hours to obtain nickel / cobalt compound particles (nickel / cobalt composite compound particles). Thereafter, the transition metal mixed spherical compound was mixed with aluminum hydroxide and lithium hydroxide and fired at 750 ° C. for 10 hours in an oxidizing atmosphere (Ni: Co: Al = 0.80: 0.15: 0). .05, and Li / Ni + Co + Al = 1.01). This was pulverized to obtain a positive electrode active material powder.

  A 2032 coin cell was produced with the obtained positive electrode active material particles as described above, and the amount of change in the WH value before and after 4.3V initial charge was calculated to be 11.07. In addition, the result of the Williamson-Hall plot in this comparative example is shown in FIG. Moreover, the cross-sectional SEM image after the completion of the cycle characteristic test of the positive electrode active material particles in this comparative example is shown in FIG.

Comparative Example 2
An aqueous sodium hydroxide solution having a pH of 12.0 was prepared in a reactor equipped with a blade-type stirrer. An aqueous ammonia solution was added dropwise so that the ammonia concentration was 0.80 mol / l. Cobalt sulfate and nickel sulfate mixed aqueous solution was continuously supplied to the reactor so that the molar ratio was Co: Ni = 85: 12. During this time, an aqueous sodium hydroxide solution and an aqueous ammonia solution were continuously supplied so that the pH of the reaction solution was 11.8 and the ammonia concentration was 0.8 mol / l, and the reaction solution was grown to the target average secondary particle size. During this time, a spherical composite transition metal precipitate was obtained by applying mechanical shearing force to the suspension.

  After the reaction, the suspension taken out was washed with a filter press and then dried at 80 ° C. for 12 hours to obtain nickel / cobalt compound particles (nickel / cobalt composite compound particles). Thereafter, with respect to the composition ratio of the precursor, aluminum hydroxide, lithium hydroxide and the transition metal mixed spherical compound were mixed and baked at 740 ° C. for 10 hours in an oxidizing atmosphere (Ni: Co: Al = 0). 80: 0.12: 0.03, and Li / Ni + Co + Al = 1.01). This was pulverized to obtain a positive electrode active material powder.

  As a result of producing a 2032 coin cell with the obtained positive electrode active material particles as described above and calculating the amount of change in the WH value before and after 4.3 V initial charge, it was 12.31.

  Table 1 below shows the characteristics of the batteries in Examples 1 and 2 and Comparative Examples 1 and 2.

  As described above, from the results shown in Table 1, FIG. 1 and FIG. 2, the secondary batteries (Examples 1 and 2) produced using the positive electrode active material particle powder according to the present invention were subjected to 4.3V initial charging. The amount of change between the WH value and the WH value before charging is small, that is, the occurrence of crystal distortion can be suppressed, cracks at the grain boundaries in the cycle characteristics can be suppressed, and battery capacity deterioration can be reduced. Further, since the grain boundary cracks in the agglomerated particles are reduced, the electron conduction path and the ion conduction path sufficiently function, and the deterioration of the battery characteristics can be suppressed. Thus, it became clear that the positive electrode active material particles according to the present invention are excellent in repeated charge / discharge characteristics.

  Since the positive electrode active material particle powder according to the present invention is excellent in cycle characteristics, it is suitable as a positive electrode active material particle powder for a non-aqueous electrolyte secondary battery.

Claims (5)

Having a layered rock salt structure, general _{formula, Li a (Ni x Co y} Al z Mn 1-x-y-z M b) O 2 (1.0 ≦ a ≦ 1.15,0 <x ≦ 1, 0 <y ≦ 1, 0 <x + y ≦ 1, 0 ≦ z ≦ 0.05, 0 ≦ b ≦ 0.05, M is Mg, P, Ca, Ti, Y, Sn, Bi, Ce, Zr, La, Positive electrode active material particles comprising a lithium transition metal layered oxide represented by Mo, Sc, Nb or W),
The positive electrode active material particles are used as the positive electrode, the negative electrode is Li, a 2032 size coin cell is assembled, and the slope of the Williamson-Hall plot for the crystal plane obtained by XRD diffraction in the positive electrode active material particles before charging is defined as a. The positive electrode active for a non-aqueous electrolyte secondary battery in which the amount of change calculated by (ba) / a is 10.5 or less, where b is the slope after performing 4.3V initial charging. Substance particles.   A non-aqueous electrolyte secondary battery using the positive electrode active material particles according to claim 1 A method for producing the positive electrode active material particles according to claim 1,
By simultaneously co-precipitating Ni compound and Co compound and optionally at least one of Al compound and Mn compound, a composite compound precursor mainly comprising Ni and Co and optionally at least one of Al and Mn is obtained. Steps,
Mixing the lithium compound with the precursor so that the molar ratio of Li / (Ni + Co + Al + Mn) is in the range of 1.00 or more and 1.15 or less to obtain a mixture;
Calcining the mixture at 700 ° C. or higher and 950 ° C. or lower in an oxidizing atmosphere.   In the step of obtaining the precursor, a compound comprising a plurality of Mg, P, Ca, Ti, Y, Sn, Bi, Ce, Zr, La, Mo, Sc, Nb and W, or any metal component. The method for producing positive electrode active material particles according to claim 3, wherein the Ni compound and the Co compound are optionally co-precipitated with at least one of an Al compound and a Mn compound to obtain a composite compound precursor.   In the step of obtaining the mixture, the precursor and the lithium compound together with Mg, P, Ca, Ti, Y, Sn, Bi, Ce, Zr, La, Mo, Sc, Nb and W, or any one of them The method for producing positive electrode active material particles according to claim 3, wherein the compounds containing the metal components are mixed together.