JP5737513B2 - Positive electrode active material powder for non-aqueous electrolyte secondary battery, method for producing the same, and non-aqueous electrolyte secondary battery - Google Patents

Description

  An excellent positive electrode active material particle powder for a non-aqueous electrolyte secondary battery having a high discharge voltage, a high discharge capacity, and a reduced side reaction with an electrolytic solution, a method for producing the same, and a non-aqueous electrolyte secondary battery provide.

  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 into practical use, and the demand for a lithium ion secondary battery having excellent storage characteristics as a large-scale application is increasing. Under such circumstances, lithium ion secondary batteries having high energy having the advantage of high discharge voltage or large discharge capacity have attracted attention. In particular, lithium ion secondary batteries can be charged and discharged quickly. Excellent rate characteristics are required for use in the required electric tools and electric vehicles.

Conventionally, as a positive electrode active material useful for a lithium ion secondary battery having a voltage of 4 V class, spinel type LiMn ₂ O ₄ , zigzag layered structure LiMnO ₂ , layered rock salt type structure LiCoO ₂ , LiNiO _2, etc. In general, lithium ion secondary batteries using LiNiO ₂ have attracted attention as batteries having a high discharge capacity.

However, since LiNiO ₂ has a low discharge voltage and is inferior in thermal stability, cycle characteristics, and rate characteristics during charging, further improvement in characteristics is required. There is also a problem that the structure is destroyed when high voltage charging is performed to obtain a high capacity.

LiMn ₂ O ₄ is excellent in rate characteristics and cycle characteristics, but has a low discharge capacity and is hardly a high-energy positive electrode active material.

Therefore, in recent years, a positive electrode active material having a high discharge voltage has attracted attention. Representative examples include LiNi _0.5 Mn _1.5 O ₄ , LiCoMnO ₄ , Li _1.2 Cr _0.4 Mn _0.4 O ₄ , Li _1.2 Cr _0.4 Ti _0.4 O ₄ , LiCoPO ₄ , LiFeMnO ₄ , LiNiVO _{4 and the} like are known.

Among them, LiNi _0.5 Mn _1.5 O ₄ has a high discharge voltage in which a discharge plateau region is present at 4.5 V or more, and is excellent in rate characteristics and cycle characteristics. Attention has been paid.

  From the viewpoint of energy density, a positive electrode active material that has a higher capacity at a high voltage and can reduce side reactions with the electrolyte has been a continuous requirement that has continued since the past.

Conventionally, the _composition: LiNi _{0.5 Mn} 1.5 _{O 4} with respect to the positive electrode active material particles having, various improvements have been made (Patent Document 1 to 7 and Non-Patent Documents 1 and 2).

JP 2000-515672 A JP-A-9-147867 JP 2001-110421 A JP 2001-185145 A JP 2002-158007 A JP 2003-81637 A JP 2004-349109 A

48th Battery Discussion Meeting (2007) 2A16 J. et al. Electrochem. Society, 148 (7) A723-A729 (2001)

  A positive electrode active material for a non-aqueous electrolyte secondary battery that has a high discharge voltage, excellent discharge capacity, and good cycle characteristics is currently the most demanded, but a material that satisfies the necessary and sufficient requirements is still available. It is not done.

  That is, even with the techniques of Patent Documents 1 to 7 and Non-Patent Document 1, high voltage is excellent, discharge capacity is excellent, and further, improvement in long-term stability by reducing side reactions with the electrolyte is not sufficient. .

  According to Patent Document 1, nickel-containing lithium manganate particles in which Ni is uniformly dissolved in a sol-gel method in which manganese nitrate, nickel nitrate, and lithium nitrate are dissolved in ethanol, carbon black is added and mixed with an ammonia solution are obtained. Although there are reports, it is difficult to produce a large amount from an industrial viewpoint, and the discharge capacity is less than 100 mAh / g, which is not practical.

Patent Document 2 reports that a positive electrode active material that can be operated at a high voltage by a solid phase method by mixing electrolytic manganese dioxide, nickel nitrate, and lithium hydroxide and has excellent cycle characteristics is obtained. In the discharge curve, a plateau considered to be derived from Mn ³⁺ can be confirmed in the vicinity of 4 V, and the capacity due to the plateau exceeds 10 mAh / g. Therefore, it is unstable and not practical as a positive electrode material for high voltage. .

In Patent Document 3, a positive electrode active material is produced by ball-mixing lithium carbonate, MnO ₂ and nickel nitrate with an ethanol solvent to produce a gel-like precursor, followed by firing. Positive electrode active in which elements such as F, Cl, Si, and S have a concentration gradient toward the outside of the particles by subjecting a material such as F, Cl, Si, and S to surface treatment and firing. There is a report that the characteristics of the battery can be maintained by suppressing the reaction with the electrolyte in the battery in the high voltage operation due to the effect of the element, but in this method, F, Cl, Si and S become resistance components, and as a result, the charge / discharge capacity may be reduced as compared with unadded products.

  In patent document 4, when co-precipitating with a manganese compound, a nickel compound, and an ammonium compound to obtain a spherical precursor whose primary particles are acicular, Ni and Mn are mixed with a Li compound and fired. Although it has been reported that residual Ni (NiO) that can become an impurity phase can be reduced and can be reduced in an impurity phase, high voltage operation and a large discharge capacity have been obtained, but only discussion on the initial discharge capacity, No mention is made of stability due to suppression of side reactions with the electrolyte by improving the surface properties of the particles. Further, the positive electrode active material described in Patent Document 4 may contain a large amount of impurities during precursor generation, and the impurities may cause instability in battery operation.

In patent document 5, after obtaining the spherical manganese nickel precursor which is a precursor by slowly dripping the solution which mixed ammonia as manganese sulfate, nickel sulfate, and a complex material in sodium hydroxide solution, this precursor is obtained. The mixture of the body and the Li compound is subjected to main firing in a temperature range of 850 ° C. or higher, and then an annealing process is performed to obtain a high-voltage positive electrode active material. However, since the crystallinity of the precursor is low, Li It is necessary to calcinate at a temperature close to 1000 ° C. in the main calcination after mixing with the compound, and as a result, Mn ³⁺ is generated for valence compensation by oxygen deficiency from the shape of the charge / discharge curve. In addition, in this production method, a large amount of sodium and sulfur remain in the spherical particles, which may make the battery unstable.

  Patent Document 6 reports that after mixing lithium nitrate, manganese nitrate, and nickel nitrate, PVA was dropped and granulated, and then a high-capacity cathode material was obtained by firing at a maximum of 500 ° C. Since the firing temperature is low, it is difficult to increase the crystallinity, and it is considered that a side reaction with the electrolytic solution is likely to occur due to the low crystallinity, and long-term characteristics may not be obtained.

  In Patent Document 7, a mixture of manganese sulfate and nickel sulfate in a sodium hydroxide aqueous solution is pH-controlled and slowly dropped to produce spherical manganese nickel hydroxide with small primary particles without using a complexing material. The positive electrode active material in which Ni was uniformly dissolved in the particles by heat-treating the hydroxide at 900 ° C. and the nickel-manganese composite oxide having a high tap density was obtained and reacted with the Li compound was reported. However, since the precursor described in Patent Document 7 does not use a complexing material, the shape of the agglomerated secondary particles becomes distorted (from the SEM image), and sufficient tap density can be obtained even if the precursor is heat-treated at high temperature. Is not obtained.

  Non-Patent Document 1 describes that it has the crystal structure described in this specification, but does not describe a specific manufacturing method or its shape.

  Further, Non-Patent Document 2 discusses heat generation / endotherm associated with low-temperature phase transition due to oxygen deficiency of lithium manganate, but influence of oxygen deficiency of nickel-containing lithium manganate and substitution of Mn sites with Ni. There is no discussion of the behavior at low temperatures when such factors are added.

  In the present invention, a positive electrode active material particle powder for a non-aqueous electrolyte secondary battery having a high discharge voltage, a high discharge capacity, and a reduced side reaction with an electrolytic solution, a method for producing the same, and a non-aqueous electrolyte A secondary battery is provided.

That is, the present invention is a composite oxide particle powder having a spinel structure and containing at least Li, Ni, and Mn as main components, an average primary particle diameter of 1.0 to 4.0 μm, an average secondary particle diameter ( D50) is 4 to 30 μm, the BET specific surface area is 0.3 to 1.0 m ² / g, and the product of the average secondary particle diameter (D50) of the composite oxide powder and the BET specific surface area is y In this case, it is a positive electrode active material particle powder for a non-aqueous electrolyte secondary battery, wherein y ≦ 10.0 × 10 ⁻⁶ m ³ / g (Invention 1).

  Further, the present invention provides a book in which z ≦ 0.230 degree when the half width of the peak of the (400) plane in the X-ray diffraction of the positive electrode active material particle powder for a nonaqueous electrolyte secondary battery is z. It is positive electrode active material particle powder for nonaqueous electrolyte secondary batteries of invention 1, (Invention 2).

  Moreover, the present invention uses the positive electrode active material particle powder for a non-aqueous electrolyte secondary battery and a secondary battery using lithium metal as a counter electrode, and at the initial charge, the battery capacity at 4.8 V charge And the battery capacity at the time of 5.0V charge is b, and the ratio represented by (b−a) / b is less than 10%, the positive electrode for a non-aqueous electrolyte secondary battery according to the present invention 1 or 2 Active material particle powder (Invention 3).

  In addition, the present invention uses the positive electrode active material particle powder for a nonaqueous electrolyte secondary battery and has a charge / discharge efficiency of 90% or more when the secondary battery uses lithium metal as a counter electrode. It is the positive electrode active material particle powder for nonaqueous electrolyte secondary batteries in any one of -3 (this invention 4).

  Further, the present invention provides a method for producing a positive electrode active material particle powder for a non-aqueous electrolyte secondary battery, wherein a composite compound containing Mn and Ni as main components and a Li compound are mixed and 680 ° C. to 1050 ° C. in an oxidizing atmosphere. The positive electrode active material particle powder for a non-aqueous electrolyte secondary battery according to any one of the present inventions 1 to 4, which is calcined (1) and subsequently calcined (2) at 500 to 700 ° C. This is a method (Invention 5).

  Moreover, this invention is a nonaqueous electrolyte secondary battery using the positive electrode active material particle powder for nonaqueous electrolyte secondary batteries in any one of this invention 1-4 (this invention 6).

  The positive electrode active material particle powder for a nonaqueous electrolyte secondary battery according to the present invention has a high discharge voltage, a high discharge capacity, and an excellent positive electrode for a nonaqueous electrolyte secondary battery with reduced side reaction with the electrolyte Active material particle powder.

2 is an X-ray diffraction pattern of a positive electrode active material particle powder for a non-aqueous electrolyte secondary battery obtained in Example 1. FIG. 2 is a charge / discharge curve of a positive electrode active material particle powder for a non-aqueous electrolyte secondary battery obtained in Example 1. FIG. 2 is a SEM image of positive electrode active material particle powder for a non-aqueous electrolyte secondary battery obtained in Example 1. FIG. 4 is a SEM image of positive electrode active material particle powder for nonaqueous electrolyte secondary battery obtained in Comparative Example 1.

  The configuration of the present invention will be described in more detail as follows.

  The positive electrode active material particle powder for non-aqueous electrolyte secondary battery according to the present invention (hereinafter referred to as “positive electrode active material particle powder”) has at least a cubic spinel structure, and Mn and Ni as main components are composite. It is a compound that is oxidized and contains Li, Ni, and Mn.

The positive electrode active material particle powder according to the present invention has an average primary particle diameter of 1.0 to 4.0 μm, an average secondary particle diameter (D50) of 4.0 to 30 μm, and a BET specific surface area of 0. in the range of .3~1.0m ² / g, and the average product y of the secondary particle diameter and (D50) and the BET specific surface area is less ^{10.0 × 10 -6 m 3 / g} (y ≦ 10.0 × 10 ⁻⁶ m ³ / g).

  When the average primary particle diameter of the positive electrode active material particle powder according to the present invention is out of the range of the present invention, the reactivity with the electrolytic solution is improved and becomes unstable.

  Moreover, when the average secondary particle diameter (D50) of the positive electrode active material particle powder according to the present invention is less than 4.0 μm, the contact area with the electrolytic solution is excessively increased, so that the reactivity with the electrolytic solution is increased, and charging is performed. Time stability may be reduced. When the average secondary particle diameter (D50) exceeds 30 μm, the resistance in the electrode increases, and the charge / discharge rate characteristics may be deteriorated. The average secondary particle diameter is more preferably 4.0 to 20 μm, and still more preferably 5.0 to 15 μm.

The specific surface area (BET specific surface area method) of the positive electrode active material particle powder according to the present invention is preferably 0.3 to 1.00 m ² / g. If the specific surface area is too small, the contact area with the electrolytic solution becomes too small and the discharge capacity decreases, and if it is too large, the positive electrode active material particle powder reacts with the electrolytic solution and gas generation and initial efficiency decrease. The specific surface area is preferably 0.35 to 0.80 m ² / g, more preferably 0.43 to 0.75 m ² / g.

In the positive electrode active material particle powder according to the present invention, the product y of the average secondary particle diameter (D50) and the BET specific surface area is 10.0 × 10 ⁻⁶ m ³ / g or less. When the value of the product is larger than 10.0 × 10 ⁻⁶ m ³ / g, a secondary battery is formed using the positive electrode active material particle powder. In this case, it may be considered that the gas reacts with the electrolytic solution and gas generation and battery characteristics deteriorate. The product y of the average secondary particle diameter (D50) and the BET specific surface area is preferably 9.5 × 10 ⁻⁶ m ³ / g or less, more preferably 1.0 × 10 ^{−6 to} 9.0 × 10 ^−6. m ³ / g, still more preferably 2.0 × 10 ^{−6 to} 8.8 × 10 ⁻⁶ m ³ / g.

The y, which is the product of the average secondary particle size and the BET specific surface area, is m ³ / g (reciprocal of density) in units, which is considered to indicate the volume of secondary particles per unit weight. In other words, the minimum surface area can be found from the diameter (secondary particle diameter) and shape. Usually, it has a surface area greater than that value, and its value y is a parameter resulting from the surface condition. As a result, this number is considered to be a parameter indicating the surface property of the particles. When the number increases, the surface of the particle has a lot of unevenness, and when it becomes smaller, the unevenness of the particle surface is reduced and it is considered that the particle surface is approaching a smooth state. When y is within the range of the present invention, it is considered that the particle surface properties are good and side reactions with the electrolyte can be reduced.

  In the X-ray diffraction of the positive electrode active material particle powder according to the present invention, when the half-value width (FWMH (400)) of the (400) plane is z, z ≦ 0.230 ° is preferable. When the half width z of the peak of the (400) plane exceeds 0.230 °, the crystal becomes unstable, and as a result, the battery characteristics may deteriorate. A more preferable range is z ≦ 0.220 °, and further preferably 0.044 ° ≦ z ≦ 0.180 °.

  Further, the half width of the peak of the (111) plane in the X-ray diffraction of the positive electrode active material particle powder according to the present invention is preferably 0.15 ° or less, more preferably 0.053 ° to 0.12 °, 311) The full width at half maximum of the plane peak is preferably 0.18 ° or less, more preferably 0.044 ° to 0.14 °, and the full width at half maximum of the (440) plane is preferably 0.25 ° or less, More preferably, it is 0.045 ° to 0.20 °.

The positive electrode active material particle powder according to the present invention has a chemical formula: Li _{1 + x} Mn _{2 -yz} Ni _y M _z O ₄ (x range is −0.05 ≦ x ≦ 0.10, y range is 0.4. ≦ y ≦ 0.6, and the range of z is 0 ≦ z ≦ 0.20).
Further, as the different element M, one or more selected from Mg, Al, Si, Ca, Ti, Co, Zn, Sb, Ba, W and Bi may be substituted. The content of the different element M is preferably 20 mol% or less based on the compound having the spinel structure. Since the positive electrode active material particle powder according to the present invention has a spinel structure, even if it is charged at a high voltage of 5 V, the structure does not collapse and a charge / discharge cycle can be performed. Moreover, oxygen may be accompanied by oxygen deficiency within the range of common sense (the description in the chemical formula is omitted).

  Next, the manufacturing method of the positive electrode active material particle powder according to the present invention will be described.

  That is, the positive electrode active material particle powder according to the present invention is prepared by mixing a composite compound containing manganese and nickel as main components and a lithium compound at a predetermined molar ratio, and then firing at 680 ° C. to 1050 ° C. in an oxidizing atmosphere (1 And then firing (2) at 500 to 700 ° C.

  The composite compound mainly composed of Mn and Ni used in the present invention includes a hydroxide, an oxide organic compound, etc., preferably a composite oxide of Mn and Ni, more preferably a cubic spinel structure. It is a complex oxide of Mn and Ni.

  The complex oxide has a spinel structure belonging to the space group of Fd-3m, and is an oxide in which Mn and Ni as main components are uniformly distributed in the 8a site and / or the 16d site. Further, the composite oxide may be a composite oxide in which an element other than Mn and Ni is introduced. Moreover, it is preferable that it is substantially single phase.

  The manganese nickel composite oxide in the present invention preferably has an average primary particle size of 1.0 to 4.0 μm. Further, the tap density is preferably 1.8 g / ml or more, and the half-width of the strongest peak by X-ray diffraction is preferably in the range of 0.15 ° to 0.25 °.

The composition of the manganese nickel composite oxide is represented by the following chemical formula (2).
Chemical formula (2)
(Mn _1-yz Ni _y M _z ) ₃ O ₄
0.2 ≦ y ≦ 0.3, 0 ≦ z ≦ 0.10
M: One or more selected from Mg, Al, Si, Ca, Ti, Co, Zn, Sb, Ba, W, Bi

  Further, the manganese nickel composite oxide used in the present invention preferably has a sodium content of 100 to 2000 ppm, a sulfur content of 10 to 1000 ppm, and a total of impurities of 4000 ppm or less.

  If the manufacturing method of the said composite oxide particle powder can manufacture the manganese nickel composite oxide particle powder which satisfy | fills the said characteristic, after co-precipitating various raw materials in the solid-phase reaction or aqueous solution which mixes and bakes various raw materials, Any manufacturing method such as a wet reaction for firing may be used and is not particularly limited. For example, it can be obtained by the following manufacturing method.

  That is, the composite oxide particle powder in the present invention is neutralized with an aqueous manganese salt solution using an alkaline aqueous solution in excess of the equivalent of manganese to form an aqueous suspension containing manganese hydroxide, , A primary reaction for obtaining trimanganese tetroxide core particles by performing an oxidation reaction in a temperature range of 60 to 100 ° C., and a predetermined amount of a manganese raw material and a nickel raw material with respect to the reaction solution after the primary reaction, if necessary A wet reaction step of obtaining a manganese nickel composite compound using trimanganese tetroxide particles as a base material by a secondary reaction that performs an oxidation reaction using an aqueous solution in which an M element material is dissolved, and a manganese nickel composite compound after the wet reaction step Can be washed and dried, and then calcined at 900 to 1000 ° C. in an oxidizing atmosphere.

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

  The lithium compound to be used preferably has an average particle size of 50 μm or less. More preferably, it is 30 μm or less. When the average particle size of the lithium compound exceeds 50 μm, mixing of the composite compound of manganese and nickel becomes non-uniform and the characteristics are deteriorated.

  Further, at the time of synthesizing the positive electrode active material particle powder according to the present invention, it is selected from Mg, Al, Si, Ca, Ti, Co, Zn, Sb, Ba, W and Bi together with the composite oxide particle powder and the lithium compound. An additive element may be introduced into the positive electrode active material particle powder by mixing at least one elemental nitrate, oxide, hydroxide, carbonate or the like.

  The mixing treatment of the composite compound particle powder of manganese and nickel and the lithium compound may be either dry or wet as long as it can be uniformly mixed.

  In the firing step of the present invention, firing at 680 ° C. to 1050 ° C. is preferably performed as firing (1) in an oxidizing atmosphere. By firing (1), the manganese nickel composite compound and the Li compound react to obtain positive electrode active material particle powder in an oxygen deficient state. When the temperature is lower than 680 ° C., the reactivity is poor and the composite is not sufficiently formed. Also, the particle surface properties are not optimized. When the temperature exceeds 1050 ° C., sintering proceeds too much, or Ni comes out of the lattice and precipitates as Ni oxide. More preferable baking temperature is 700-1000 degreeC, More preferably, it is 740-950 degreeC. The firing time is preferably 2 to 50 hours.

  Subsequent to the firing (1), similarly, a heat treatment for firing (2) is performed at 500 to 700 ° C. in an oxidizing atmosphere. By firing (2), it is possible to obtain positive electrode active material particle powder that compensates for oxygen deficiency and has a stable crystal structure. The more preferable temperature range of baking (2) is 550-650 degreeC.

  Next, the positive electrode containing the positive electrode active material particle powder according to the present invention will be described.

  When manufacturing the positive electrode containing the positive electrode active material particle powder according to the present invention, a conductive agent and a binder are added and mixed according to a conventional method. As the conductive agent, acetylene black, carbon black, graphite and the like are preferable, and as the binder, polytetrafluoroethylene, polyvinylidene fluoride and the like are preferable.

  The secondary battery manufactured using the positive electrode containing the positive electrode active material particle powder which concerns on this invention is comprised from the said positive electrode, a negative electrode, and electrolyte.

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

  In addition to the combination of ethylene carbonate and diethyl carbonate, an organic solvent containing at least one of carbonates such as propylene carbonate and dimethyl carbonate and ethers such as dimethoxyethane can be used as the solvent for the electrolytic solution.

  Further, as the electrolyte, in addition to lithium hexafluorophosphate, at least one lithium salt such as lithium perchlorate and lithium tetrafluoroborate can be dissolved in the above solvent and used.

  The non-aqueous electrolyte secondary battery manufactured using the positive electrode containing the positive electrode active material particle powder according to the present invention has a discharge capacity of 3.0 V or higher by an evaluation method described later of 130 mAh / g, more preferably 135 mAh / g or more.

  In addition, the non-aqueous electrolyte secondary battery manufactured using the positive electrode containing the positive electrode active material particle powder according to the present invention has a charge capacity of 4.8 V at the time of initial charge when lithium metal is used for the counter electrode. When a is 5.0 and the charge capacity of 5.0V is b, the ratio of (ba) / b is smaller than 10%.

  When charging at 4.5 V or higher, decomposition of the electrolytic solution generally occurs, so that apparent charging capacity due to this decomposition reaction is added at charging at 4.8 V or higher. As a result of intensive research, the inventor has found that by optimizing the surface properties of the positive electrode active material particles, the decomposition of the electrolytic solution is reduced, so that the apparent charge capacity due to the decomposition of the electrolytic solution is reduced. . By using the positive electrode active material particle powder according to the present invention, it is considered that the decomposition of the electrolytic solution can be suppressed, and the ratio of (b−a) / b described above can be made smaller than 10%.

  When a secondary battery in which the positive electrode active material particle powder according to the present invention is used as a positive electrode and the counter electrode is lithium metal is assembled and a charge / discharge test is performed at a cut-off voltage of 3.0V-5.0V, initial charge / discharge is performed. The efficiency is 90% or more. As described above, it is considered that the apparent charge capacity generated excessively is reduced by reducing the decomposition of the electrolytic solution, and as a result, the charge / discharge efficiency is improved.

  In the secondary battery using the positive electrode active material particle powder according to the present invention, since the decomposition reaction of the electrolyte solution by the positive electrode active material is suppressed, for example, gas generation due to deterioration of the electrolyte solution or decomposition of the electrolyte solution, It is considered that the deterioration of the positive electrode itself can be suppressed. As a result, the secondary battery using the positive electrode active material particle powder according to the present invention is considered to have excellent long-term stability.

  A typical embodiment of the present invention is as follows.

  The average primary particle diameter was observed using a scanning electron microscope SEM-EDX with an energy dispersive X-ray analyzer [manufactured by Hitachi High-Technologies Corporation], and the average value was read from the SEM image.

  The average secondary particle diameter (D50) is a volume-based average particle diameter measured by a wet laser method using a laser type particle size distribution measuring device Microtrac HRA [manufactured by Nikkiso Co., Ltd.].

  The BET specific surface area was measured by using MONOSORB [manufactured by Yuasa Ionics Co., Ltd.] after drying and deaeration of the sample under nitrogen gas at 120 ° C. for 45 minutes.

  The X-ray diffraction of the sample was measured using SmartLab manufactured by Rigaku Corporation. Measurement conditions were 10 to 90 degrees at 2θ / θ by 0.02 degree step scan (0.6 second hold).

  The composition and the amount of impurities were as follows: 0.2 g sample was heated and dissolved in 25 ml of a 20% hydrochloric acid solution, and after cooling, pure water was added to a 100 ml volumetric flask to prepare an adjustment solution. For measurement, ICAP [SPS-4000 Seiko Electronics Each element was quantified and determined using Kogyo Co., Ltd.].

  The packing density of the positive electrode active material particle powder was weighed 40 g, put into a 50 ml measuring cylinder, and the volume when tapped 500 times with a tap denser (manufactured by Seishin Enterprise Co., Ltd.) was read and the packing density (TD 500 times) was calculated. did.

  S content was measured using "HORIBA CARBON / SULFUR ANALYZER EMIA-320V (HORIBA Scientific)".

  About the positive electrode active material particle powder which concerns on this invention, battery evaluation was performed using CR2032-type coin cell.

For coin cells related to battery evaluation, 85% by weight of composite oxide as positive electrode active material particle powder, 5% by weight of acetylene black as a conductive material, 5% by weight of graphite, and polyvinylidene fluoride dissolved in N-methylpyrrolidone as a binder After mixing 5% by weight, it was applied to an Al metal foil and dried at 120 ° C. This sheet was punched out to 14 mmΦ, and then pressure-bonded at 1.5 t / cm ² was used as the positive electrode. A 2032 type coin cell was manufactured using a solution in which EC and DMC mixed with 1 mol / L LiPF ₆ dissolved in a volume ratio of 1: 2 were used as the negative electrode made of metallic lithium having a thickness of 500 μm punched to 16 mmΦ.

  Charging / discharging characteristics were as follows: charging was performed at a current density of 0.1 C up to 5.0 V in an environment set to 25 ° C. in a thermostatic chamber (CC-CV operation, termination condition 1/100 C), and then discharging was performed at 3.0 V. Up to 0.1 C current density (CC operation). In the initial charging, the charging capacity at 4.8V was a, and the charging capacity at 5.0V was b.

  After the initial charge up to 5.0V was obtained and the initial charge capacity b was obtained, the battery was discharged at a current density of 0.1C up to 3.0V (CC operation). At this time, it was set as the discharge capacity c when it was set to 3.0V. The initial charge / discharge efficiency was calculated by the equation c / b × 100.

Example 1
A sodium hydroxide aqueous solution was adjusted so that the excess alkali concentration after the reaction was 2.5 mol / L under nitrogen flow, and the manganese sulfate aqueous solution was adjusted so that the manganese concentration was 0.6 mol / L. An aqueous suspension containing manganese hydroxide particles was obtained by adding the oxide to the reaction vessel to make the total amount 600 L and neutralizing. The aqueous suspension containing the obtained manganese hydroxide particles was switched from nitrogen aeration to air aeration, and an oxidation reaction was performed at 90 ° C. (primary reaction). After the completion of the primary reaction, switching to nitrogen aeration, 0.37.3 mol / L manganese sulfate solution 117.3 L and 1.5 mol / L nickel sulfate solution 39.4 L were added in the same reaction tank to produce the primary reaction. An aqueous suspension containing manganese oxide, a manganese compound, and a nickel compound (such as manganese hydroxide and nickel hydroxide) was obtained. The resulting solution was switched from nitrogen aeration to air aeration and an oxidation reaction was performed at 60 ° C. (secondary reaction). After completion of the secondary reaction, the resultant was washed with water and dried to obtain a manganese nickel composite compound using spinel-structured Mn ₃ O ₄ particles as a base material. The manganese nickel composite compound was fired at 950 ° C. in the atmosphere for 20 hours to obtain manganese nickel composite oxide particle powder.

It was confirmed by X-ray diffraction that the obtained manganese nickel composite oxide particle powder had a cubic spinel structure belonging to the space group of Fd-3m. Its composition was (Mn _0.75 Ni _0.25 ) ₃ O ₄ . The average primary particle size is 2.6 μm, the tap density (500 times) is 2.12 g / ml, the half-width of the strongest peak in X-ray diffraction is 0.20 °, and the Na content is 252 ppm, The S content was 88 ppm and the total amount of impurities was 1589 ppm.

  The obtained manganese nickel composite oxide particle powder and lithium carbonate are weighed so that Li: (Mn + Ni) = 0.50: 1.00 and dry-mixed with a ball mill for 1 hour to obtain a uniform mixture. It was. Thereafter, using an electric furnace, firing was performed at 750 ° C. for 15 hours in the atmosphere (firing (1)), followed by firing at 600 ° C. for 10 hours (firing (2)) to obtain positive electrode active material particle powder. .

The obtained positive electrode active material particle powder was confirmed to have a cubic spinel structure by X-ray diffraction (SmartLab manufactured by Rigaku). The X-ray diffraction pattern of the obtained positive electrode active material particle powder is shown in FIG. The composition is Li _1.0 (Mn _0.75 Ni _0.25 ) ₂ O ₄ , the average primary particle diameter is 3.5 μm, the average secondary particle diameter (D50) is 11.6 μm, and the BET specific surface area is 0. .74m a ² / g, a product of BET specific surface area and average secondary particle size (D50) of was ^{8.6 × 10 -6 m 3 / g} . Further, the half width of (400) was 0.171 °.

  In addition, a 2032 coin-type battery manufactured using lithium metal as a counter electrode and using the positive electrode active material particle powder has a charge capacity a up to 4.8 V at initial charge of 140.2 mAh / g and 5.0 V The charge capacity b was 155.2 mAh / g, and the ratio of (ba) / b was 9.6% as shown in FIG. The initial charge / discharge efficiency was 92.8%.

Example 2 to Example 5
A positive electrode active material particle powder was obtained by the same operation as in Example 1 except that the firing temperature of firing (1) was variously changed.

  Table 1 shows the production conditions of the positive electrode active material particle powder and various characteristics of the obtained positive electrode active material particle powder.

Comparative Example 1
A positive electrode active material particle powder was obtained in the same manner as in Example 1 except that the firing temperature of firing (1) was 650 ° C.

Comparative Example 2
14 L of water was put into the sealed reaction tank, and kept at 50 ° C. while circulating nitrogen gas. Furthermore, 1.5 mol / L Ni, Mn mixed sulfate aqueous solution, 0.8 mol / L sodium carbonate aqueous solution, and 2 mol / L continuously with vigorous stirring so that pH = 8.2 (± 0.2). L Ammonia aqueous solution was added. During the reaction, only the filtrate was discharged out of the system by a concentrating device, and the solid content was retained in the reaction tank. After reacting for 40 hours, a slurry of the coprecipitation product was collected. The collected slurry was filtered and washed with pure water. Thereafter, it was dried at 105 ° C. overnight to obtain precursor particle powder. As a result of the X-ray diffraction measurement, the obtained precursor particle powder was mainly composed of carbonate.

  The obtained precursor particle powder and lithium hydroxide were weighed so that Li: (Mn + Ni) = 0.50: 1.00 and mixed sufficiently. The mixture was baked in an electric furnace at 850 ° C. for 8 hours in the atmosphere, and then baked at 600 ° C. for 6 hours to obtain positive electrode active material particle powder.

  Table 1 shows the production conditions of the positive electrode active material particle powder and various characteristics of the obtained positive electrode active material particle powder.

Comparative Example 3
The precursor particle powder obtained in Comparative Example 2 and lithium hydroxide were weighed so as to be Li: Me = 0.50: 1.00 and mixed well. The mixture was baked in an electric furnace at 1000 ° C. for 8 hours in the atmosphere, and then baked at 600 ° C. for 6 hours to obtain positive electrode active material particle powder.

  Table 1 shows the production conditions of the positive electrode active material particle powder and various characteristics of the obtained positive electrode active material particle powder.

  A scanning electron micrograph of the positive electrode active material particle powder obtained in Example 1 is shown in FIG. 3, and a scanning electron micrograph of the positive electrode active material particle powder obtained in Comparative Example 1 is shown in FIG. As is clear from FIGS. 3 and 4, the positive electrode active material particles of Example 1 were confirmed to have reduced irregularities on the particle surface of the secondary particles compared to the positive electrode active material particles of Comparative Example 1.

  From the above results, it was confirmed that the positive electrode active material particle powder according to the present invention is effective as a positive electrode active material for a non-aqueous electrolyte secondary battery having a small side reaction with the electrolytic solution and excellent long-term stability.

The positive electrode active material particle powder according to the present invention is suitable as a positive electrode active material particle powder for a non-aqueous electrolyte secondary battery because it has excellent long-term stability because of a small side reaction with the electrolytic solution.

Claims (6)

A composite oxide particle powder having a spinel structure and containing at least Li, Ni, and Mn as main components, an average primary particle diameter of 1.0 to 4.0 μm, and an average secondary particle diameter (D50) of 4 to 30 μm. , Where the BET specific surface area is 0.3 to 1.0 m ² / g and the product of the average secondary particle diameter (D50) and the BET specific surface area of the composite oxide powder is y <10.0 * 10 < ^-6 > m < ³ > / g The positive electrode active material particle powder for nonaqueous electrolyte secondary batteries characterized by the above-mentioned. 2. The non-aqueous solution according to claim 1, wherein the x-ray diffraction of the positive electrode active material particle powder for a non-aqueous electrolyte secondary battery is in a range of z ≦ 0.230 degree, where z is the half width of the peak of the (400) plane. Positive electrode active material particle powder for electrolyte secondary battery. When the positive electrode active material particle powder for a non-aqueous electrolyte secondary battery is used and a secondary battery using a lithium metal as a counter electrode is used, the battery capacity at the time of 4.8 V charge is a, 5.0 V at the time of initial charge. The positive electrode active material particle powder for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein a ratio represented by (ba) / b is smaller than 10%, where b is a battery capacity during charging. The initial charge and discharge efficiency is 90% or more when a secondary battery using the positive electrode active material particle powder for a nonaqueous electrolyte secondary battery and using lithium metal as a counter electrode is used. The positive electrode active material particle powder for non-aqueous electrolyte secondary batteries as described. In the method for producing a positive electrode active material particle powder for a non-aqueous electrolyte secondary battery, a composite compound mainly composed of Mn and Ni and a Li compound are mixed and fired at 680 ° C. to 1050 ° C. in an oxidizing atmosphere (1). The method for producing positive electrode active material particle powder according to any one of claims 1 to 4, wherein the method is followed by firing (2) at 500 to 700 ° C. The nonaqueous electrolyte secondary battery using the positive electrode active material particle powder for nonaqueous electrolyte secondary batteries in any one of Claims 1-4.