WO2016171081A1 - Positive electrode active material for non-aqueous electrolyte secondary battery and method for manufacturing same, and non-aqueous electrolyte secondary battery using said positive electrode active material - Google Patents

Positive electrode active material for non-aqueous electrolyte secondary battery and method for manufacturing same, and non-aqueous electrolyte secondary battery using said positive electrode active material Download PDF

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WO2016171081A1
WO2016171081A1 PCT/JP2016/062139 JP2016062139W WO2016171081A1 WO 2016171081 A1 WO2016171081 A1 WO 2016171081A1 JP 2016062139 W JP2016062139 W JP 2016062139W WO 2016171081 A1 WO2016171081 A1 WO 2016171081A1
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Prior art keywords
positive electrode
electrode active
active material
lithium
composite oxide
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PCT/JP2016/062139
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French (fr)
Japanese (ja)
Inventor
佑樹 古市
小向　哲史
広将 戸屋
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住友金属鉱山株式会社
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Priority claimed from JP2015212404A external-priority patent/JP6978182B2/en
Application filed by 住友金属鉱山株式会社 filed Critical 住友金属鉱山株式会社
Priority to EP16783102.3A priority Critical patent/EP3288104B1/en
Priority to KR1020177032607A priority patent/KR20170136601A/en
Priority to KR1020207002590A priority patent/KR102364783B1/en
Priority to CN201680023670.2A priority patent/CN107534144B/en
Priority to US15/568,567 priority patent/US10797302B2/en
Publication of WO2016171081A1 publication Critical patent/WO2016171081A1/en
Priority to US17/007,707 priority patent/US11056681B2/en

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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
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    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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Definitions

  • the present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery, a manufacturing method thereof, and a non-aqueous electrolyte secondary battery using the positive electrode active material.
  • This lithium ion secondary battery is composed of a negative electrode, a positive electrode, an electrolyte, and the like, and a material capable of desorbing and inserting lithium is used as the active material of the negative electrode and the positive electrode.
  • lithium ion secondary batteries are currently being actively researched and developed. Among them, lithium ion secondary batteries using a layered or spinel type lithium metal composite oxide as a positive electrode material are among them. Since a high voltage of 4V class can be obtained, practical use is progressing as a battery having a high energy density.
  • the materials mainly proposed so far include lithium cobalt composite oxide (LiCoO 2 ), which is relatively easy to synthesize, lithium nickel composite oxide (LiNiO 2 ) using nickel, which is cheaper than cobalt, and lithium nickel.
  • lithium cobalt composite oxide LiCoO 2
  • nickel composite oxide LiNiO 2
  • lithium nickel composite oxide LiNiO 2
  • lithium nickel nickel composite oxide
  • lithium nickel nickel
  • cobalt manganese composite oxide LiNi 1/3 Co 1/3 Mn 1/3 O 2
  • lithium manganese composite oxide LiMn 2 O 4
  • lithium nickel composite oxide and lithium nickel cobalt manganese composite oxide are attracting attention as materials that have good cycle characteristics and can provide high output with low resistance. In recent years, it is important to reduce resistance required for high output. Is being viewed. Addition of foreign elements is used as a method for realizing the low resistance, and transition metals capable of taking high numbers such as W, Mo, Nb, Ta, Re, etc. are particularly useful.
  • Patent Document 1 contains at least one element selected from Mo, W, Nb, Ta, and Re in an amount of 0.1 to 5 mol% with respect to the total molar amount of Mn, Ni, and Co.
  • Lithium transition metal compound powder for a lithium secondary battery positive electrode material has been proposed, and Mo, W, Nb, Ta, and Li in the surface portion of primary particles and the total of metal elements other than Mo, W, Nb, Ta, and Re
  • the total atomic ratio of Re is preferably 5 times or more of the atomic ratio of the entire primary particle.
  • the lithium transition metal compound powder is obtained by pulverizing raw materials in a liquid medium, spray-drying a slurry in which these are uniformly dispersed, and firing the resulting spray-dried body. Therefore, a part of different elements such as Mo, W, Nb, Ta, and Re is replaced with Ni arranged in a layer form, and there is a problem that battery characteristics such as battery capacity and cycle characteristics are deteriorated. .
  • Patent Document 2 discloses a positive electrode active material for a non-aqueous electrolyte secondary battery having at least a layered lithium transition metal composite oxide, the lithium transition metal composite oxide being composed of primary particles and aggregates thereof.
  • a positive electrode active material for a secondary battery has been proposed.
  • a positive electrode active material for a non-aqueous electrolyte secondary battery having excellent battery characteristics even under a more severe use environment can be obtained, and in particular, the surface of the particle is composed of molybdenum, vanadium, tungsten, boron and fluorine.
  • the initial characteristics are improved without impairing the improvement of thermal stability, load characteristics and output characteristics.
  • the effect of at least one additive element selected from the group consisting of molybdenum, vanadium, tungsten, boron and fluorine is considered to be an improvement in initial characteristics, that is, initial discharge capacity and initial efficiency, and refers to output characteristics. is not.
  • the additive element is mixed with the hydroxide that has been heat-treated at the same time as the lithium compound and fired, a part of the additive element is replaced with nickel arranged in layers. There is a problem that causes deterioration of battery characteristics.
  • Patent Document 3 discloses a metal including at least one selected from Ti, Al, Sn, Bi, Cu, Si, Ga, W, Zr, B, and Mo around the positive electrode active material and / or a plurality of these.
  • a positive electrode active material coated with an intermetallic compound and / or oxide obtained by a combination has been proposed. Such a coating can absorb oxygen gas and ensure safety, but no output characteristics are disclosed.
  • the disclosed manufacturing method is a method of coating using a planetary ball mill, and such a coating method has a problem of causing physical damage to the positive electrode active material and deteriorating its battery characteristics. .
  • Patent Document 4 a composite oxide particle mainly composed of lithium nickelate is subjected to heat treatment by adhering a tungstic acid compound, and the content of carbonate ions is 0.15% by weight or less.
  • a positive electrode active material has been proposed. According to this proposal, there is a tungstic acid compound or a decomposition product of the tungstic acid compound on the surface of the positive electrode active material, and the oxidation activity on the surface of the composite oxide particles in a charged state is suppressed. Although gas generation can be suppressed, the output characteristics are not disclosed at all.
  • the disclosed production method preferably comprises a composite oxide particle heated to a boiling point or higher of a solution in which an adherent component is dissolved, and a sulfuric acid compound, a nitric acid compound, a boric acid compound, or a phosphoric acid compound as well as a tungstate compound. Since the solution dissolved in the solvent is applied as the adhering component, and the solvent is removed in a short time, the tungsten compound is not sufficiently dispersed on the surface of the composite oxide particles, so that there is a problem that it is not uniformly applied. .
  • Patent Document 5 discloses a lithium metal composite oxide composed of primary particles and secondary particles formed by aggregation of the primary particles, and Li 2 WO 4 , on the surface of the lithium metal composite oxide,
  • a positive electrode active material for a non-aqueous electrolyte secondary battery having fine particles containing lithium tungstate represented by either Li 4 WO 5 or Li 6 W 2 O 9 has been proposed, and high output is obtained with high capacity. ing.
  • demands for high capacity and high output are increasing, and further improvements are required.
  • the present invention provides a positive electrode active material for a non-aqueous electrolyte secondary battery that, when used in a positive electrode material, has a high capacity and suppresses an increase in the amount of gas generated, while obtaining a higher output.
  • the purpose is to do.
  • the present inventors diligently studied the influence on the positive electrode resistance of a battery using a lithium metal composite oxide used as a positive electrode active material for a non-aqueous electrolyte secondary battery.
  • a lithium metal composite oxide used as a positive electrode active material for a non-aqueous electrolyte secondary battery.
  • the lithium-metal composite oxide powder is immersed in an alkaline solution containing tungsten and then subjected to solid-liquid separation to heat-treat the compound containing tungsten and lithium formed on the primary particle surface with lithium.
  • the inventor has obtained the knowledge that it can be formed even between metal composite oxide particles, and has completed the present invention.
  • the manufacturing method of the first cathode active material for a non-aqueous electrolyte secondary battery which is the invention of the present invention have the general formula Li z Ni 1-x-y Co x M y O 2 ( however, 0 ⁇ x ⁇ 0 .35, 0 ⁇ y ⁇ 0.35, 0.95 ⁇ z ⁇ 1.30, and M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti, and Al)
  • a lithium metal composite oxide powder having a layered structure composed of primary particles and secondary particles formed by agglomeration of primary particles has a tungsten concentration of 0.1 to 2 mol / L in which a tungsten compound is dissolved.
  • the lithium metal composite oxide is obtained by mixing and immersing the lithium metal composite oxide powder in the alkali solution in a range of 200 to 2500 g / L in the solid-liquid ratio with respect to the amount of water in the alkali solution, followed by solid-liquid separation.
  • a positive electrode active for a non-aqueous electrolyte secondary battery is characterized by having a water washing step of washing the lithium metal composite oxide powder with water before performing the first step in the first invention. It is a manufacturing method of a substance.
  • the amount of tungsten contained in the tungsten mixture in the first and second inventions is based on the total number of atoms of Ni, Co and M contained in the lithium metal composite oxide powder to be mixed. 3.0 atomic% or less, a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery.
  • a nonaqueous electrolyte secondary characterized in that the tungsten concentration in the alkaline solution in which the tungsten compound in the first to third aspects is dissolved is 0.05 to 2 mol / L. It is a manufacturing method of the positive electrode active material for batteries.
  • the alkaline solution according to the first to fourth aspects is a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein a tungsten compound is dissolved in an aqueous lithium hydroxide solution. It is a manufacturing method.
  • the heat treatment in the second step according to the first to sixth aspects is performed at 100 to 600 ° C. in an oxygen atmosphere or a vacuum atmosphere. It is a manufacturing method of a positive electrode active material.
  • the eighth invention of the present invention is a lithium metal comprising a primary particle and a secondary particle formed by agglomeration of the primary particle, having a layered crystal structure, and a compound containing tungsten and lithium on the surface of the primary particle made from the composite oxide powder represented by the general formula: Li z Ni 1-x- y Co x M y W a O 2 + ⁇ (although, 0 ⁇ x ⁇ 0.35,0 ⁇ y ⁇ 0.35,0.95 ⁇ z ⁇ 1.30, 0 ⁇ a ⁇ 0.03, 0 ⁇ ⁇ ⁇ 0.15, and M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti, and Al)
  • a positive electrode active material for a non-aqueous electrolyte secondary battery wherein the cross section of the secondary particle of the lithium metal composite oxide is observed at a constant magnification using a scanning electron microscope, and at least two or more different observation fields 50 or more arbitrarily extracted in When observing the secondary particles
  • a non-aqueous system wherein the compound containing tungsten and lithium according to the eighth aspect is present on the primary particle surface of the lithium metal composite oxide as fine particles having a particle diameter of 1 to 200 nm. It is a positive electrode active material for electrolyte secondary batteries.
  • the compound containing tungsten and lithium according to the eighth aspect of the present invention is present on the primary particle surface of the lithium metal composite oxide as a film having a thickness of 1 to 150 nm. It is a positive electrode active material for electrolyte secondary batteries.
  • the compound containing tungsten and lithium according to the eighth aspect of the present invention provides primary particles of the lithium metal composite oxide in both forms of fine particles having a particle diameter of 1 to 200 nm and coatings having a thickness of 1 to 150 nm.
  • the amount of tungsten contained in the compound containing tungsten and lithium in the eighth to eleventh aspects is the number of Ni, Co and M atoms contained in the lithium metal composite oxide particles.
  • a thirteenth aspect of the present invention is a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the compound containing tungsten and lithium according to the eighth to twelfth aspects of the present invention is present in the form of lithium tungstate. .
  • a fourteenth aspect of the present invention is a non-aqueous electrolyte secondary battery comprising a positive electrode including a positive electrode active material for a non-aqueous electrolyte secondary battery according to the eighth to thirteenth aspects.
  • the positive electrode active material for nonaqueous electrolyte secondary batteries which can implement
  • the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention may be referred to as primary particles and secondary particles formed by aggregation of primary particles (hereinafter, simply referred to as secondary particles).
  • a lithium metal composite oxide having a layered crystal structure and a compound containing tungsten and lithium on the surface of the primary particle, the composition of the positive electrode active material is represented by the general formula: Li z Ni 1-x- y Co x M y W a O 2 + ⁇ (although, 0 ⁇ x ⁇ 0.35,0 ⁇ y ⁇ 0.35,0.95 ⁇ z ⁇ 1.30,0 ⁇ a ⁇ 0.03,0 ⁇ ⁇ ⁇ 0.15, M represents at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al), and a scanning electron microscope of the cross section of the secondary particle of the lithium metal composite oxide In observation, arbitrary 50 or more secondary particles were observed.
  • the base material as the base material, its composition formula Li z Ni 1-x-y Co x M y O 2 ( however, 0 ⁇ x ⁇ 0.35,0 ⁇ y ⁇ 0.35,0.95 ⁇ z ⁇ 1 .30, M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al), and a lithium metal composite oxide having a layered crystal structure is used. A discharge capacity is obtained. In order to obtain a higher charge / discharge capacity, it is preferable to satisfy x + y ⁇ 0.2 and 0.95 ⁇ z ⁇ 1.10.
  • a lithium metal composite oxide powder composed of primary particles and secondary particles formed by agglomeration of primary particles (hereinafter referred to as “lithium metal combined with secondary particles and primary particles present alone”).
  • a compound containing tungsten (W) and lithium (Li) formed on the surface of the primary particle hereinafter also referred to as “LW compound”.
  • W tungsten
  • Li lithium
  • the output characteristics are improved while maintaining the charge / discharge capacity.
  • the surface of the positive electrode active material is completely covered with a different compound, the movement (intercalation) of lithium ions is greatly limited, resulting in a high capacity of the lithium nickel composite oxide. The advantages are erased.
  • an LW compound is formed on the surface of the lithium metal composite oxide particles and the surface of the primary particles inside, but this LW compound has high lithium ion conductivity and prevents movement of lithium ions. There is an urging effect. For this reason, since the LW compound is formed on the surface of the lithium metal composite oxide particles and the surface of the internal primary particles, a Li conduction path is formed at the interface with the electrolytic solution. (Hereinafter, also referred to as “positive electrode resistance”) is reduced to improve the output characteristics of the non-aqueous electrolyte secondary battery.
  • the voltage lost in the non-aqueous electrolyte secondary battery (hereinafter sometimes simply referred to as “battery”) is reduced, and the voltage actually applied to the load side is reduced. Since it becomes relatively high, a high output can be obtained. Further, since the voltage applied to the load side is increased, lithium is sufficiently inserted and extracted from the positive electrode, so that the charge / discharge capacity (hereinafter also referred to as “battery capacity”) is also improved.
  • the surface of the primary particle in the present invention refers to the surface of the primary particle exposed on the outer surface of the secondary particle and the space near and inside the surface of the secondary particle that can penetrate the electrolyte solution through the outside of the secondary particle.
  • the surface of the primary particle exposed to the surface of the primary particle, and the surface of the primary particle present alone are included. Furthermore, even a grain boundary between primary particles is included as long as the primary particles are not completely bonded and the electrolyte solution can penetrate.
  • the contact with the electrolytic solution is not limited to the outer surface of the secondary particles formed by agglomeration of the primary particles, but also the gap between the primary particles in the vicinity of the inner surface of the secondary particles and the incomplete grain boundary.
  • it since it occurs, it is necessary to form an LW compound also on the surface of the primary particles and promote the movement of lithium ions. Therefore, the reaction resistance of the lithium metal composite oxide particles can be further reduced by forming the LW compound on most of the primary particle surfaces that can be contacted with the electrolytic solution.
  • the form of the LW compound on the primary particle surface is such that when the surface of the primary particle is coated with a layered material, the contact area with the electrolytic solution is reduced. It tends to result in concentration on the surface of specific primary particles. Therefore, although the layered material as the coating has high lithium ion conductivity, the effects of improving the charge / discharge capacity and reducing the reaction resistance can be obtained, but there is room for improvement. Therefore, in order to obtain a higher effect, the LW compound is preferably present on the primary particle surface of the lithium metal composite oxide as fine particles having a particle diameter of 1 to 200 nm.
  • the contact area with the electrolytic solution can be made sufficient, and lithium ion conduction can be effectively improved, so that the battery capacity can be improved and the positive electrode resistance can be reduced more effectively.
  • the particle diameter is less than 1 nm, fine particles may not have sufficient lithium ion conductivity.
  • the particle diameter exceeds 200 nm, the formation of the fine particles on the surface becomes non-uniform, and the higher effect of reducing the positive electrode resistance may not be obtained.
  • the fine particles do not need to be completely formed on the entire surface of the primary particles, and may be scattered.
  • the fine particles are formed on the primary particle surfaces exposed on the outer surface and the internal voids of the lithium metal composite oxide particles, the effect of reducing the positive electrode resistance can be obtained. Further, it is not necessary for all the fine particles to be present as fine particles having a particle diameter of 1 to 200 nm. Preferably, 50% or more of the fine particles formed on the surface of the primary particles are formed in a particle diameter range of 1 to 200 nm. High effect can be obtained.
  • the conduction path of Li can be formed at the interface with the electrolyte while suppressing the decrease in specific surface area, and the effect of higher battery capacity and reduced positive electrode resistance Is obtained.
  • the surface of the primary particle is coated with such a thin film-like LW compound, it is preferably present on the surface of the primary particle of the lithium metal composite oxide as a film having a thickness of 1 to 150 nm. If the film thickness is less than 1 nm, the film may not have sufficient lithium ion conductivity. On the other hand, when the film thickness exceeds 150 nm, the lithium ion conductivity is lowered, and the higher effect of reducing the positive electrode resistance may not be obtained.
  • this coating may be partially formed on the primary particle surface, and the film thickness range of all coatings may not be 1 to 150 nm. If a film having a film thickness of 1 to 150 nm is formed at least partially on the primary particle surface, a high effect can be obtained.
  • the LW compound is formed on the surface of the primary particles, it is possible to suppress the generation of excess lithium on the surface of the lithium metal composite oxide and to suppress the generation of gas from the surface of the positive electrode material.
  • the excess lithium amount is preferably 0.05% by mass or less, more preferably 0.035% by mass or less, based on the total amount of the positive electrode active material.
  • the LW compound when the LW compound is formed non-uniformly between the lithium metal composite oxide particles, the movement of lithium ions between the lithium metal composite oxide particles becomes non-uniform. It is easy to cause deterioration of cycle characteristics and increase of reaction resistance.
  • the secondary particle in which the LW compound is not formed on the surface of the primary particle inside the secondary particle even if the fine particle is formed on the surface of the secondary particle, the LW compound is formed on the surface of the primary particle inside. Compared to secondary particles, it is more likely to be loaded and deteriorated. Therefore, by reducing the secondary particles in which the LW compound is not formed on the primary particle surface inside the secondary particles, the positive electrode resistance can be reduced and the output characteristics and battery capacity can be improved, and the cycle characteristics are also good. Can be.
  • the secondary particle having an LW compound on the surface of the primary particle inside the secondary particle.
  • the battery characteristics as described above can be improved.
  • lithium metal composite oxide particles that is, a positive electrode active material powder is embedded in a resin and processed so that the cross section of the particles can be observed, and then in at least two different visual fields.
  • the cross-section of a total of 50 or more secondary particles is observed at a constant magnification of 5000 times using a field emission scanning electron microscope, and observation is performed by observing 50 or more secondary particles.
  • the positive electrode active material having the effect of eliminating the above error and forming the LW compound in the secondary particles can be accurately determined.
  • the LW compound in this invention should just contain W and Li, it is preferable that it is a form of lithium tungstate.
  • the lithium ion conductivity is further increased, and the effect of reducing the reaction resistance is further increased.
  • lithium tungstate from the viewpoint of lithium ion conductivity, Li 2 WO 4 , Li 4 WO 5 , Li 6 W 2 O 9 , Li 6 WO 6 , 7 (Li 2 WO 4 ) ⁇ 4H 2 O It is preferable to include one or more compounds selected from the group consisting of Li 2 WO 4 or Li 4 WO 5 or a mixture thereof.
  • the amount of tungsten contained in this LW compound is 3.0 atomic% or less, and 0.05 to 3.0 atomic% with respect to the total number of Ni, Co and M atoms contained in the lithium metal composite oxide. Preferably, it is 0.05 to 2.0 atom%, more preferably 0.08 to 1.0 atom%.
  • the effect of improving the output characteristics can be obtained by adding 3.0 atomic% or less of tungsten.
  • the amount of LWO formed is sufficient to reduce the positive electrode resistance, and a sufficient primary particle surface that can be contacted with the electrolyte is secured. It is possible to achieve a higher battery capacity and output characteristics at the same time.
  • the amount of tungsten is less than 0.05 atomic%, the effect of improving the output characteristics may not be sufficiently obtained.
  • the amount of tungsten exceeds 3.0 atomic%, the amount of the LW compound to be formed increases so that lithium Lithium conduction between the metal composite oxide particles and the electrolytic solution may be inhibited, and the battery capacity may be reduced.
  • the amount of lithium contained in the LW compound is not particularly limited, and if it is contained in the LW compound, an effect of improving lithium ion conductivity can be obtained.
  • surplus lithium is present on the surface of the lithium metal composite oxide particles, and the amount of lithium supplied to the LW compound by the surplus lithium when mixed with the alkaline solution may be sufficient, but is sufficient to form lithium tungstate. It is preferable to make it an amount.
  • the total amount of lithium in the positive electrode active material is such that the ratio “Li / Me” of the number of Ni, Co and Mo atoms in the positive electrode active material (Me) to the number of Li atoms is 0.95 to 1. 30, preferably 0.97 to 1.25, more preferably 0.97 to 1.20.
  • the Li / Me of the lithium metal composite oxide particles as the core material is 0.95 to 1.25, more preferably 0.95 to 1.20, and a high battery capacity is obtained and sufficient for the formation of the LW compound. A sufficient amount of lithium can be secured.
  • Li / Me of the positive electrode active material as a whole is 0.95 to 1.15, and Li / Me of the lithium metal composite oxide particles is 0.95 to 1.10.
  • the core material is lithium metal composite oxide particles that do not contain an LW compound, and becomes a positive electrode active material by forming an LW compound on the primary particle surface of the lithium metal composite oxide particles. If the Li / Me is less than 0.95, the reaction resistance of the positive electrode in the non-aqueous electrolyte secondary battery using the obtained positive electrode active material increases, and the output of the battery decreases. On the other hand, when Li / Me exceeds 1.30, the initial discharge capacity of the positive electrode active material decreases and the reaction resistance of the positive electrode also increases.
  • the positive electrode active material of the present invention is an improvement in output characteristics by forming an LW compound on the primary particle surface of the lithium metal composite oxide, and the powder properties such as the particle size and tap density as the positive electrode active material are: What is necessary is just to be in the range of the positive electrode active material used normally.
  • the effect of adhering the LW compound to the primary particle surface of the lithium metal composite oxide is, for example, a powder such as lithium cobalt composite oxide, lithium manganese composite oxide, lithium nickel cobalt manganese composite oxide,
  • the present invention can be applied not only to the positive electrode active material described in the present invention but also to a commonly used positive electrode active material for a lithium secondary battery.
  • a lithium metal composite oxide powder composed of primary particles and secondary particles formed by agglomeration of primary particles is mixed with an alkaline solution in which a tungsten compound is dissolved (hereinafter, an alkaline solution in which a tungsten compound is dissolved).
  • an alkaline solution in which a tungsten compound is dissolved This is a step of obtaining a tungsten mixture by solid-liquid separation after immersion in an alkaline solution (W).
  • W can be uniformly dispersed to the surface of the primary particles inside the secondary particles.
  • the solid-liquid ratio of the lithium metal composite oxide powder to the alkali solution (W) and the amount of water in the alkali solution (W) is in the range of 200 to 2500 g / L, preferably 500. It is necessary to mix and immerse in a range of ⁇ 2000 g / L. Furthermore, the W concentration of the alkaline solution (W) is 0.1 to 2 mol / L, preferably 0.1 to 1.5 mol / L.
  • the alkaline solution (W) having an appropriate concentration is infiltrated to the primary particle surface in the secondary particles, and the primary particle surface
  • the amount of W that forms the LW compound as described above can be dispersed.
  • the amount of W contained in the tungsten mixture is determined by the amount of W in the alkaline solution (W) remaining in the lithium metal composite oxide powder after solid-liquid separation.
  • the amount required to form the compound can be determined from the moisture content after solid-liquid separation.
  • the amount of W contained in the tungsten mixture can be controlled by the W concentration of the alkaline solution (W) and the degree of solid-liquid separation.
  • W the W concentration of the alkaline solution
  • the degree of solid-liquid separation In a solid-liquid separation method that is normally performed, the amount of liquid remaining after solid-liquid separation is 5 to 15% by mass with respect to the cake obtained by solid-liquid separation, and is stable depending on the conditions of solid-liquid separation. Therefore, if the remaining liquid amount (water content) is obtained by a preliminary test or the like, it can be easily controlled.
  • the amount of W contained in the tungsten mixture is equal to the amount of tungsten contained in the compound in the obtained positive electrode active material. Therefore, the amount of W contained in the tungsten mixture is preferably 3.0 atomic% or less with respect to the total number of Ni, Co and M atoms contained in the lithium metal composite oxide powder to be mixed. It is more preferably from 05 to 3.0 atomic%, further preferably from 0.05 to 2.0 atomic%, particularly preferably from 0.08 to 1.0 atomic%.
  • the amount of tungsten to be dissolved in the alkaline solution may be determined in anticipation of the decrease, that is, 5 to 20 atomic% with respect to the added amount of tungsten.
  • the solid-liquid ratio is controlled in the range of 200 to 2500 g / L.
  • the solid-liquid ratio is less than 200 g / L, the amount of Li eluted from the lithium metal composite oxide is excessively obtained. The characteristics of the battery obtained using the active material are deteriorated.
  • the solid-liquid ratio exceeds 2500 g / L, the alkaline solution (W) cannot be uniformly mixed with the tungsten mixture, and secondary particles that do not penetrate the alkaline solution (W) to the primary particle surface inside the particles increase. To do.
  • the W concentration of the alkaline solution (W) is 0.1 to 2 mol / L.
  • the W concentration of the alkaline solution (W) is less than 0.1 mol / L, the amount of W contained in the tungsten mixture decreases. The characteristics of the battery using the positive electrode active material obtained are not improved.
  • the alkaline solution (W) remaining in the tungsten mixture is ubiquitous, so the lithium metal composite oxide particles The amount of W contained between the particles increases, and secondary particles in which no LW compound is formed on the surface of the primary particles inside the particles increase.
  • the W concentration of the alkaline solution (W) exceeds 2 mol / L, the amount of W contained in the tungsten mixture increases so that the characteristics of the battery using the obtained positive electrode active material deteriorate.
  • the tungsten compound is first dissolved in an alkali solution.
  • the dissolution method may be a normal powder dissolution method.
  • the tungsten compound is stirred while the solution is stirred using a reaction vessel equipped with a stirrer. What is necessary is just to add and melt
  • the tungsten compound is not particularly limited as long as it can be dissolved in an alkali solution, and it is preferable to use a tungsten compound that is easily soluble in alkali, such as tungsten oxide, lithium tungstate, and ammonium tungstate.
  • the alkali used for the alkaline solution (W) in order to obtain a high charge / discharge capacity, a general alkaline solution that does not contain impurities harmful to the positive electrode active material is used.
  • Ammonia and lithium hydroxide, which are free of impurities, can be used, but lithium hydroxide is preferably used from the viewpoint of not inhibiting Li intercalation.
  • the amount of lithium contained in the positive electrode active material after mixing must be within the range of Li / Me in the above general formula.
  • the atomic ratio is preferably 3.5 to 10.0, more preferably 3.5 or more and less than 4.5. Li is eluted and supplied from the lithium metal composite oxide. By using lithium hydroxide in this range, an amount of Li sufficient to form an LW compound can be supplied.
  • the alkaline solution (W) is preferably an aqueous solution.
  • W is preferably an aqueous solution.
  • any solvent that can sufficiently penetrate into the secondary particles may be used. If a solvent such as alcohol having high volatility is used, there are many losses due to volatilization, which is undesirable in terms of cost.
  • many impurities present on the secondary particles and the surface of the primary particles are water-soluble, and it is preferable to use an aqueous solution from the viewpoint of removing the impurities and improving the characteristics of the positive electrode active material.
  • the pH of the alkaline solution may be any pH at which the tungsten compound dissolves, but is preferably 9-12.
  • the pH is less than 9, the amount of lithium eluted from the lithium metal composite oxide becomes too large, and the battery characteristics may be deteriorated.
  • pH exceeds 12, there exists a possibility that the excessive alkali which remains in lithium metal complex oxide may increase too much, and a battery characteristic may deteriorate.
  • the lithium metal composite oxide particles used as the core material of the obtained positive electrode active material are lithium metal composite oxide as a base material, that is, lithium metal composite oxide mixed with an alkaline solution (W). Since the lithium content is eluted from the powder into the alkaline solution (W), the lithium metal composite oxide as a base material has a known composition of the general formula Li z Ni 1-x from the viewpoint of high capacity and low reaction resistance.
  • M is, Mn, V, Mg, Mo , Nb, Lithium metal composite oxide represented by at least one element selected from Ti and Al is used. That is, z which is Li / Me of the base material is 0.95 ⁇ z ⁇ 1.30, preferably 0.97 ⁇ z ⁇ 1.25, more preferably 0.97 ⁇ z ⁇ 1.20, and still more preferably.
  • a high battery capacity and low reaction resistance can be achieved by controlling the amount of lithium in the lithium metal composite oxide particles as the core material after cleaning to an appropriate amount. Can be made possible.
  • increasing the contact area with the electrolytic solution is advantageous for improving the output characteristics, so that the primary particles and secondary particles formed by aggregation of the primary particles are formed. It is preferable to use a lithium metal composite oxide powder having voids and grain boundaries that can be penetrated.
  • the lithium metal composite oxide powder is added, mixed and immersed. If the tungsten compound is easily soluble, the lithium metal composite oxide powder may be mixed with a solvent such as water to form a slurry, and then the tungsten compound may be added and dissolved and immersed. Further, the alkaline solution (W) can be circulated, supplied to the lithium metal composite oxide powder, and immersed.
  • the alkaline solution (W) can be circulated between the lithium metal composite oxide particles to penetrate into the secondary particles.
  • the mixing is preferably performed at a temperature of 50 ° C. or lower. By mixing at a temperature of 50 ° C. or lower, excessive Li elution from the lithium metal composite oxide particles can be suppressed.
  • Mixing of the lithium metal composite oxide powder and the alkali solution (W) may be performed by infiltrating the alkali solution (W) into the secondary particles.
  • a stirred reaction vessel or the like can be used.
  • the mixing ratio is high in a stirred reaction tank where the solid-liquid ratio is high, the shape of the lithium metal composite oxide powder is not destroyed by using a mixer such as a shaker mixer, a Laedige mixer, a Julia mixer, or a V blender. What is necessary is just to fully mix with an alkali solution (W) to the extent. Thereby, W in the alkaline solution (W) can be uniformly distributed on the primary particle surface of the lithium metal composite oxide.
  • Solid-liquid separation After immersing the alkaline solution (W), solid-liquid separation is performed to obtain a tungsten mixture. Solid-liquid separation may be performed by a commonly used apparatus, such as a suction filter, a centrifuge, or a filter press.
  • the lithium metal composite oxide powder as a base material can be further washed with water before the first step.
  • This washing with water may be performed by a known method and conditions as long as lithium is not excessively eluted from the lithium metal composite oxide powder and the battery characteristics are not deteriorated.
  • a method of drying and mixing with the alkali solution (W) or a method of mixing with the alkali solution (W) without drying only by solid-liquid separation may be used.
  • the tungsten concentration after immersion in the alkaline solution (W) is diluted by the water contained in the lithium metal composite oxide powder, so the amount of water remaining after solid-liquid separation is taken into account in advance. What is necessary is just to calculate the density
  • the second step is a step of heat-treating the tungsten mixture.
  • an LW compound is formed from W supplied from the alkaline solution (W) and Li supplied from the alkaline solution (W) or lithium elution from the lithium metal composite oxide.
  • a positive electrode active material for a non-aqueous electrolyte secondary battery having an LW compound on the primary particle surface is obtained.
  • the heat treatment method is not particularly limited, but heat treatment is performed at a temperature of 100 to 600 ° C. in an oxygen atmosphere or a vacuum atmosphere in order to prevent deterioration of battery characteristics when used as a positive electrode active material for a non-aqueous electrolyte secondary battery. Is preferred.
  • the heat treatment temperature is less than 100 ° C., the evaporation of moisture is not sufficient, and the LW compound may not be sufficiently formed.
  • the heat treatment temperature exceeds 600 ° C., the lithium metal composite oxide particles are sintered and a part of W is dissolved in the layered structure of the lithium metal composite oxide. May decrease.
  • the atmosphere during the heat treatment is preferably an oxidizing atmosphere such as an oxygen atmosphere or a vacuum atmosphere in order to avoid a reaction with moisture or carbonic acid in the atmosphere.
  • the heat treatment time is not particularly limited, but is preferably 5 to 15 hours in order to sufficiently evaporate the water in the alkaline solution (W) to form fine particles.
  • Non-aqueous electrolyte secondary battery of the present invention includes a positive electrode, a negative electrode, a non-aqueous electrolyte solution, and the like, and includes the same components as those of a general non-aqueous electrolyte secondary battery.
  • the embodiment described below is merely an example, and the nonaqueous electrolyte secondary battery of the present invention can be variously modified based on the knowledge of those skilled in the art based on the embodiment described in the present specification. It can be implemented in an improved form. Moreover, the use of the nonaqueous electrolyte secondary battery of the present invention is not particularly limited.
  • a positive electrode of a non-aqueous electrolyte secondary battery is produced as follows. First, a powdered positive electrode active material, a conductive material, and a binder are mixed, and, if necessary, a target solvent such as activated carbon and viscosity adjustment is added and kneaded to prepare a positive electrode mixture paste.
  • a target solvent such as activated carbon and viscosity adjustment
  • Each mixing ratio in the positive electrode mixture paste is also an important factor for determining the performance of the non-aqueous electrolyte secondary battery.
  • the content of the positive electrode active material is 60 to 95 parts by mass in the same manner as the positive electrode of a general non-aqueous electrolyte secondary battery, and the conductive material
  • the content of is desirably 1 to 20 parts by mass
  • the content of the binder is desirably 1 to 20 parts by mass.
  • the obtained positive electrode mixture paste is applied to, for example, the surface of a current collector made of aluminum foil, and dried to disperse the solvent. If necessary, pressurization may be performed by a roll press or the like to increase the electrode density. In this way, a sheet-like positive electrode can be produced.
  • the sheet-like positive electrode can be cut into an appropriate size or the like according to the target battery and used for battery production.
  • the method for manufacturing the positive electrode is not limited to the illustrated one, and other methods may be used.
  • the conductive agent for example, graphite (natural graphite, artificial graphite, expanded graphite, etc.), carbon black materials such as acetylene black, ketjen black (registered trademark), and the like can be used.
  • the binder plays a role of anchoring the active material particles.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • fluorine rubber ethylene propylene diene rubber
  • styrene butadiene cellulosic resin
  • An acid or the like can be used.
  • a positive electrode active material, a conductive material, and activated carbon are dispersed, and a solvent that dissolves the binder is added to the positive electrode mixture.
  • an organic solvent such as N-methyl-2-pyrrolidone can be used as the solvent.
  • Activated carbon can be added to the positive electrode mixture in order to increase the electric double layer capacity.
  • Negative electrode A negative electrode mixture in which a negative electrode active material capable of occluding and desorbing lithium ions is mixed with a binder and an appropriate solvent is added to the negative electrode. Is applied to the surface of a metal foil current collector such as copper, dried, and compressed to increase the electrode density as necessary.
  • the negative electrode active material for example, natural graphite, artificial graphite, a fired organic compound such as phenol resin, and a powdery carbon material such as coke can be used.
  • a fluorine-containing resin such as PVDF can be used as the negative electrode binder, as in the case of the positive electrode, and a solvent for dispersing these active materials and the binder can be N-methyl-2-pyrrolidone or the like.
  • Organic solvents can be used.
  • (C) Separator A separator is interposed between the positive electrode and the negative electrode.
  • the separator separates the positive electrode and the negative electrode and retains the electrolyte, and a thin film such as polyethylene or polypropylene and a film having many minute holes can be used.
  • Non-aqueous electrolyte The non-aqueous electrolyte is obtained by dissolving a lithium salt as a supporting salt in an organic solvent.
  • the organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and trifluoropropylene carbonate, chain carbonates such as diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, and dipropyl carbonate, tetrahydrofuran, 2- One kind selected from ether compounds such as methyltetrahydrofuran and dimethoxyethane, sulfur compounds such as ethylmethylsulfone and butanesultone, phosphorus compounds such as triethyl phosphate and trioctyl phosphate, etc. are used alone or in admixture of two or more. be able to.
  • the non-aqueous electrolyte solution may contain a radical scavenger, a surfactant, a flame retardant, and the like.
  • the shape of the non-aqueous electrolyte secondary battery of the present invention composed of the positive electrode, negative electrode, separator and non-aqueous electrolyte described above can be various, such as a cylindrical type and a laminated type. Can be.
  • the positive electrode and the negative electrode are laminated via a separator to form an electrode body, and the obtained electrode body is impregnated with a non-aqueous electrolyte and communicated with the positive electrode current collector and the outside.
  • the positive electrode terminal and the negative electrode current collector and the negative electrode terminal communicating with the outside are connected using a current collecting lead or the like and sealed in a battery case to complete a non-aqueous electrolyte secondary battery. .
  • the nonaqueous electrolyte secondary battery using the positive electrode active material of the present invention has a high capacity and a high output.
  • the non-aqueous electrolyte secondary battery using the positive electrode active material according to the present invention obtained in a particularly preferred form is, for example, a high initial discharge capacity of 165 mAh / g or more and a low positive electrode when used for the positive electrode of a 2032 type coin battery. Resistance is obtained, and further, high capacity and high output. Moreover, it can be said that it has high thermal stability and is excellent in safety.
  • FIG. Is An example of the method for measuring the positive electrode resistance in the present invention is as follows.
  • the frequency dependence of the battery reaction is measured by a general AC impedance method as an electrochemical evaluation method
  • the Nyquist diagram based on the solution resistance, the negative electrode resistance and the negative electrode capacity, and the positive electrode resistance and the positive electrode capacity is shown in FIG. Is obtained as follows.
  • the battery reaction at the electrode consists of a resistance component accompanying the charge transfer and a capacity component due to the electric double layer. When these are expressed as an electric circuit, it becomes a parallel circuit of resistance and capacity. It is represented by an equivalent circuit in which circuits are connected in series. Fitting calculation is performed on the Nyquist diagram measured using this equivalent circuit, and each resistance component and capacitance component can be estimated.
  • the positive electrode resistance is equal to the diameter of the semicircle on the low frequency side of the obtained Nyquist diagram.
  • the positive electrode resistance can be estimated by performing AC impedance measurement on the manufactured positive electrode and performing fitting calculation with the equivalent circuit on the obtained Nyquist diagram.
  • the performance (initial stage discharge capacity, positive electrode resistance) was measured.
  • the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
  • the coin battery 1 includes a case 2 and an electrode 3 accommodated in the case 2.
  • the case 2 has a positive electrode can 2a that is hollow and open at one end, and a negative electrode can 2b that is disposed in the opening of the positive electrode can 2a.
  • a space for accommodating the electrode 3 is formed between the negative electrode can 2b and the positive electrode can 2a.
  • the electrode 3 includes a positive electrode 3a, a separator 3c, and a negative electrode 3b, which are stacked in this order.
  • the positive electrode 3a contacts the inner surface of the positive electrode can 2a
  • the negative electrode 3b contacts the inner surface of the negative electrode can 2b. As shown in FIG.
  • the case 2 includes a gasket 2c, and relative movement is fixed by the gasket 2c so as to maintain a non-contact state between the positive electrode can 2a and the negative electrode can 2b. Further, the gasket 2c also has a function of sealing a gap between the positive electrode can 2a and the negative electrode can 2b to block the inside and outside of the case 2 in an airtight and liquid tight manner.
  • the coin battery 1 shown in FIG. 3 was manufactured as follows. First, 52.5 mg of a positive electrode active material for a non-aqueous electrolyte secondary battery, 15 mg of acetylene black, and 7.5 mg of polytetrafluoroethylene resin (PTFE) are mixed, and press-molded to a diameter of 11 mm and a thickness of 100 ⁇ m at a pressure of 100 MPa. A positive electrode 3a was produced. The produced positive electrode 3a was dried at 120 ° C. for 12 hours in a vacuum dryer. Using the positive electrode 3a, the negative electrode 3b, the separator 3c, and the electrolytic solution, the above-described coin-type battery 1 was produced in a glove box in an Ar atmosphere in which the dew point was controlled at ⁇ 80 ° C.
  • PTFE polytetrafluoroethylene resin
  • the negative electrode 3b a negative electrode sheet in which graphite powder having an average particle diameter of about 20 ⁇ m punched into a disk shape with a diameter of 14 mm and polyvinylidene fluoride were applied to a copper foil was used.
  • the separator 3c a polyethylene porous film having a film thickness of 25 ⁇ m was used.
  • the electrolytic solution an equivalent mixed solution (manufactured by Toyama Pharmaceutical Co., Ltd.) of ethylene carbonate (EC) and diethyl carbonate (DEC) using 1M LiClO 4 as a supporting electrolyte was used.
  • the initial discharge capacity and positive electrode resistance showing the performance of the manufactured coin battery 1 were evaluated as follows.
  • the battery capacity was evaluated based on the initial discharge capacity.
  • the initial discharge capacity is measured by allowing the coin-type battery 1 to stand for about 24 hours, and after the open circuit voltage OCV (Open Circuit Voltage) is stabilized, the current density with respect to the positive electrode is cut off at 0.1 mA / cm 2.
  • OCV Open Circuit Voltage
  • the capacity when the battery was charged to a voltage of 4.3 V and discharged to a cut-off voltage of 3.0 V after a pause of 1 hour was defined as the initial discharge capacity.
  • the positive electrode resistance is determined by charging the coin-type battery 1 at a charging potential of 4.1 V and measuring it by an alternating current impedance method using a frequency response analyzer and a potentiogalvanostat (manufactured by Solartron, 1255B). A plot is obtained. Since this Nyquist plot is represented as the sum of the solution resistance, the negative electrode resistance and its capacity, and the characteristic curve indicating the positive electrode resistance and its capacity, the fitting calculation was performed using an equivalent circuit based on this Nyquist plot, and the positive resistance The value of was calculated.
  • each sample of the reagent special grade manufactured by Wako Pure Chemical Industries, Ltd. was used for producing the composite oxide, producing the positive electrode active material, and the secondary battery.
  • a lithium metal composite represented by Li 1.030 Ni 0.82 Co 0.15 Al 0.03 O 2 obtained by a known technique of mixing and baking oxide powder containing Ni as a main component and lithium hydroxide Oxide powder was used as a base material.
  • This lithium metal composite oxide powder had an average particle size of 12.4 ⁇ m and a specific surface area of 0.3 m 2 / g.
  • the average particle diameter was evaluated using the volume integrated average value in the laser diffraction scattering method, and the specific surface area was evaluated using the BET method based on nitrogen gas adsorption.
  • the obtained mixture was put into a SUS baking vessel, heated to 210 ° C. at a heating rate of 2.8 ° C./min in a vacuum atmosphere, heat-treated for 13 hours, and then cooled to room temperature.
  • a positive active material having a compound containing W and Li on the surface of primary particles was prepared by crushing through a sieve having an opening of 38 ⁇ m.
  • the tungsten content and Li / M of the obtained positive electrode active material were analyzed by the ICP method, it was found that the tungsten content had a composition of 0.5 atomic% with respect to the total number of Ni, Co and M atoms. As a result, the Li / Me was 0.994.
  • a positive electrode active material for a non-aqueous electrolyte secondary battery was obtained and evaluated under the same conditions as in Example 1 except that the LiOH used was 3.8 g and the WO 3 was 10.5 g. It is shown in 1.
  • a positive electrode active material for a non-aqueous electrolyte secondary battery was obtained and evaluated under the same conditions as in Example 1 except that 7.0 g of LiOH and 19.3 g of WO 3 were used. It is shown in 1.
  • Comparative Example 2 Although it was washed with pure water in the same manner as in Comparative Example 1, the evaluation was performed in the same manner as in Example 1 except that it was not immersed in the alkaline solution (W). The results are shown in Table 1.
  • This composite oxide particles 100 parts by weight of ammonium paratungstate ((NH 4) 10 W 12 O 41 ⁇ 5H 2 O) and 1.632 parts by weight was added and the mixture was thoroughly mixed in a mortar, a stream of oxygen, After baking at 700 degreeC for 4 hours and cooling to room temperature, it took out and grind
  • Example 1 which was carried out under the preferable conditions of the added tungsten amount and the tungsten concentration of the alkaline solution, had even better initial discharge capacity and positive electrode resistance, and was more suitable as a positive electrode active material for a nonaqueous electrolyte secondary battery. It has become.
  • the obtained positive electrode active material is composed of primary particles and secondary particles formed by agglomeration of primary particles. It is confirmed that an LW compound (black arrow) is formed on the primary particle surface. In Example 2 with a small amount of added tungsten, the formed LW compound is too small. From this, the positive electrode resistance increases from Example 1, and the excess Li also increases. Furthermore, in Example 3 with a large amount of added tungsten, since the formed LW compound is excessive, the positive electrode resistance is increased from that in Example 1, but the excess Li is decreased.
  • Comparative Example 1 the amount of tungsten with respect to the number of Ni, Co, and M atoms contained in the lithium metal composite oxide powder is similar to that in Example 1, but the method of adding and mixing the solution uniformly The dispersion of the compound containing tungsten and lithium is not dispersed, and the positive electrode resistance is increased from that in Example 1, and the excess Li is also increased.
  • Comparative Example 2 since the LW compound according to the present invention is not formed on the primary particle surfaces, the positive electrode resistance is significantly increased, and it is difficult to meet the demand for higher output.
  • the nonaqueous electrolyte secondary battery using the positive electrode active material of the present invention has a high initial discharge capacity and a low positive electrode resistance, and is a battery having excellent characteristics.
  • the non-aqueous electrolyte secondary battery of the present invention is suitable for a power source of a small portable electronic device (such as a notebook personal computer or a mobile phone terminal) that always requires a high capacity, and an electric vehicle battery that requires a high output. Also suitable.
  • the nonaqueous electrolyte secondary battery of the present invention has excellent safety, and can be downsized and increased in output, and thus is suitable as a power source for an electric vehicle subject to restrictions on mounting space.
  • the present invention can be used not only as a power source for an electric vehicle driven purely by electric energy but also as a power source for a so-called hybrid vehicle used in combination with a combustion engine such as a gasoline engine or a diesel engine.

Abstract

The purpose of the present invention is to provide a positive electrode active material for a non-aqueous electrolyte secondary battery which is capable of high capacity and high output when said material is used. The method of manufacturing a positive electrode active material for a non-aqueous electrolyte secondary battery comprises: a first step for mixing an Li metal complex oxide powder comprising primary particles represented by the general formula LizNi1-x-yCoxMyO2 (wherein: 0 ≤ x ≤ 0.35,0 ≤ y ≤ 0.35, 0.97 ≤ z ≤ 1.30; and M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al) and secondary particles formed by aggregation of the primary particles with an alkali solution produced by dissolving a W compound so that the W concentration is 0.1 to 2 mol/L, at a solid/liquid ratio of the complex oxide powder to the water content of the solution in the range of 200 to 2500 g/L, and after immersion, separating the solid from the liquid so as to produce a W mixture in which W is uniformly dispersed on the surfaces of the primary particles of the complex oxide; and a second step for forming a compound including W and Li on the surfaces of the primary particles of the complex oxide powder by heat treating the mixture.

Description

非水系電解質二次電池用正極活物質とその製造方法、および該正極活物質を用いた非水系電解質二次電池Positive electrode active material for non-aqueous electrolyte secondary battery, method for producing the same, and non-aqueous electrolyte secondary battery using the positive electrode active material
　本発明は、非水系電解質二次電池用正極活物質とその製造方法、および該正極活物質を用いた非水系電解質二次電池に関するものである。 The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery, a manufacturing method thereof, and a non-aqueous electrolyte secondary battery using the positive electrode active material.
　近年、携帯電話やノート型パソコンなどの携帯電子機器の普及に伴い、高いエネルギー密度を有する小型で軽量な非水系電解質二次電池の開発が強く望まれている。また、ハイブリット自動車を始めとする電気自動車用の電池として高出力の二次電池の開発が強く望まれている。
　このような要求を満たす二次電池として、リチウムイオン二次電池がある。このリチウムイオン二次電池は、負極および正極と電解液等で構成され、負極および正極の活物質は、リチウムを脱離および挿入することの可能な材料が用いられている。 In recent years, with the widespread use of portable electronic devices such as mobile phones and laptop computers, development of small and lightweight non-aqueous electrolyte secondary batteries having high energy density is strongly desired. In addition, development of a high output secondary battery is strongly desired as a battery for electric vehicles including hybrid vehicles.
As a secondary battery satisfying such requirements, there is a lithium ion secondary battery. This lithium ion secondary battery is composed of a negative electrode, a positive electrode, an electrolyte, and the like, and a material capable of desorbing and inserting lithium is used as the active material of the negative electrode and the positive electrode.
　このようなリチウムイオン二次電池は、現在研究、開発が盛んに行われているところであるが、その中でも、層状またはスピネル型のリチウム金属複合酸化物を正極材料に用いたリチウムイオン二次電池は、４Ｖ級の高い電圧が得られるため、高いエネルギー密度を有する電池として実用化が進んでいる。 Such lithium ion secondary batteries are currently being actively researched and developed. Among them, lithium ion secondary batteries using a layered or spinel type lithium metal composite oxide as a positive electrode material are among them. Since a high voltage of 4V class can be obtained, practical use is progressing as a battery having a high energy density.
　これまで主に提案されている材料としては、合成が比較的容易なリチウムコバルト複合酸化物（ＬｉＣｏＯ２）や、コバルトよりも安価なニッケルを用いたリチウムニッケル複合酸化物（ＬｉＮｉＯ２）、リチウムニッケルコバルトマンガン複合酸化物（ＬｉＮｉ１／３Ｃｏ１／３Ｍｎ１／３Ｏ２）、マンガンを用いたリチウムマンガン複合酸化物（ＬｉＭｎ２Ｏ４）などを挙げることができる。 The materials mainly proposed so far include lithium cobalt composite oxide (LiCoO 2 ), which is relatively easy to synthesize, lithium nickel composite oxide (LiNiO 2 ) using nickel, which is cheaper than cobalt, and lithium nickel. Examples thereof include cobalt manganese composite oxide (LiNi 1/3 Co 1/3 Mn 1/3 O 2 ) and lithium manganese composite oxide (LiMn 2 O 4 ) using manganese.
　このうちリチウムニッケル複合酸化物およびリチウムニッケルコバルトマンガン複合酸化物は、サイクル特性が良く、低抵抗で高出力が得られる材料として注目されており、近年では高出力化に必要な低抵抗化が重要視されている。
　上記低抵抗化を実現する方法として異元素の添加が用いられており、とりわけＷ、Ｍｏ、Ｎｂ、Ｔａ、Ｒｅなどの高価数をとることができる遷移金属が有用とされている。 Among these, lithium nickel composite oxide and lithium nickel cobalt manganese composite oxide are attracting attention as materials that have good cycle characteristics and can provide high output with low resistance. In recent years, it is important to reduce resistance required for high output. Is being viewed.
Addition of foreign elements is used as a method for realizing the low resistance, and transition metals capable of taking high numbers such as W, Mo, Nb, Ta, Re, etc. are particularly useful.
　例えば、特許文献１には、Ｍｏ、Ｗ、Ｎｂ、Ｔａ及びＲｅから選ばれる１種以上の元素が、Ｍｎ、Ｎｉ及びＣｏの合計モル量に対して０．１～５モル％含有されているリチウム二次電池正極材料用リチウム遷移金属系化合物粉体が提案され、一次粒子の表面部分のＬｉ並びにＭｏ、Ｗ、Ｎｂ、Ｔａ及びＲｅ以外の金属元素の合計に対するＭｏ、Ｗ、Ｎｂ、Ｔａ及びＲｅの合計の原子比が、一次粒子全体の該原子比の５倍以上であることが好ましいとされている。 For example, Patent Document 1 contains at least one element selected from Mo, W, Nb, Ta, and Re in an amount of 0.1 to 5 mol% with respect to the total molar amount of Mn, Ni, and Co. Lithium transition metal compound powder for a lithium secondary battery positive electrode material has been proposed, and Mo, W, Nb, Ta, and Li in the surface portion of primary particles and the total of metal elements other than Mo, W, Nb, Ta, and Re The total atomic ratio of Re is preferably 5 times or more of the atomic ratio of the entire primary particle.
　この提案によれば、リチウム二次電池正極材料用リチウム遷移金属系化合物粉体の低コスト化及び高安全性化と高負荷特性、粉体取り扱い性向上の両立を図ることができる。
　しかし、上記リチウム遷移金属系化合物粉体は、原料を液体媒体中で粉砕し、これらを均一に分散させたスラリーを噴霧乾燥し、得られた噴霧乾燥体を焼成することで得ている。そのため、Ｍｏ、Ｗ、Ｎｂ、Ｔａ及びＲｅなどの異元素の一部が層状に配置されているＮｉと置換してしまい、電池の容量やサイクル特性などの電池特性が低下してしまう問題がある。 According to this proposal, it is possible to achieve both low cost and high safety of the lithium transition metal compound powder for the lithium secondary battery positive electrode material, high load characteristics, and improved powder handling properties.
However, the lithium transition metal compound powder is obtained by pulverizing raw materials in a liquid medium, spray-drying a slurry in which these are uniformly dispersed, and firing the resulting spray-dried body. Therefore, a part of different elements such as Mo, W, Nb, Ta, and Re is replaced with Ni arranged in a layer form, and there is a problem that battery characteristics such as battery capacity and cycle characteristics are deteriorated. .
　また、特許文献２には、少なくとも層状構造のリチウム遷移金属複合酸化物を有する非水電解質二次電池用正極活物質であって、そのリチウム遷移金属複合酸化物は、一次粒子およびその凝集体である二次粒子の一方または両方からなる粒子の形態で存在し、その粒子の少なくとも表面に、モリブデン、バナジウム、タングステン、ホウ素およびフッ素からなる群から選ばれる少なくとも１種を備える化合物を有する非水電解質二次電池用正極活物質が提案されている。 Patent Document 2 discloses a positive electrode active material for a non-aqueous electrolyte secondary battery having at least a layered lithium transition metal composite oxide, the lithium transition metal composite oxide being composed of primary particles and aggregates thereof. A non-aqueous electrolyte having a compound which is present in the form of a particle composed of one or both of secondary particles and has at least one selected from the group consisting of molybdenum, vanadium, tungsten, boron and fluorine on at least the surface of the particle A positive electrode active material for a secondary battery has been proposed.
　これにより、より一層厳しい使用環境下においても優れた電池特性を有する非水電解質二次電池用正極活物質が得られるとされ、特に、粒子の表面にモリブデン、バナジウム、タングステン、ホウ素およびフッ素からなる群から選ばれる少なくとも１種を有する化合物を有することにより、熱安定性、負荷特性および出力特性の向上を損なうことなく、初期特性が向上するとしている。 As a result, it is said that a positive electrode active material for a non-aqueous electrolyte secondary battery having excellent battery characteristics even under a more severe use environment can be obtained, and in particular, the surface of the particle is composed of molybdenum, vanadium, tungsten, boron and fluorine. By having a compound having at least one selected from the group, the initial characteristics are improved without impairing the improvement of thermal stability, load characteristics and output characteristics.
　しかしながら、モリブデン、バナジウム、タングステン、ホウ素およびフッ素からなる群から選ばれる少なくとも１種の添加元素による効果は、初期特性、すなわち初期放電容量および初期効率の向上にあるとされ、出力特性に言及したものではない。
　また、開示されている製造方法によれば、添加元素をリチウム化合物と同時に熱処理した水酸化物と混合して焼成するため、添加元素の一部が層状に配置されているニッケルと置換してしまい電池特性の低下を招く問題がある。 However, the effect of at least one additive element selected from the group consisting of molybdenum, vanadium, tungsten, boron and fluorine is considered to be an improvement in initial characteristics, that is, initial discharge capacity and initial efficiency, and refers to output characteristics. is not.
Further, according to the disclosed manufacturing method, since the additive element is mixed with the hydroxide that has been heat-treated at the same time as the lithium compound and fired, a part of the additive element is replaced with nickel arranged in layers. There is a problem that causes deterioration of battery characteristics.
　さらに、特許文献３には、正極活物質の周りにＴｉ、Ａｌ、Ｓｎ、Ｂｉ、Ｃｕ、Ｓｉ、Ｇａ、Ｗ、Ｚｒ、Ｂ、Ｍｏから選ばれた少なくとも一種を含む金属及びまたはこれら複数個の組み合わせにより得られる金属間化合物、及びまたは酸化物を被覆した正極活物質が提案されている。
　このような被覆により、酸素ガスを吸収させ安全性を確保できるとしているが、出力特性に関しては全く開示されていない。また、開示されている製造方法は、遊星ボールミルを用いて被覆するものであり、このような被覆方法では、正極活物質に物理的なダメージを与え、その電池特性を低下させてしまう問題がある。 Further, Patent Document 3 discloses a metal including at least one selected from Ti, Al, Sn, Bi, Cu, Si, Ga, W, Zr, B, and Mo around the positive electrode active material and / or a plurality of these. A positive electrode active material coated with an intermetallic compound and / or oxide obtained by a combination has been proposed.
Such a coating can absorb oxygen gas and ensure safety, but no output characteristics are disclosed. Further, the disclosed manufacturing method is a method of coating using a planetary ball mill, and such a coating method has a problem of causing physical damage to the positive electrode active material and deteriorating its battery characteristics. .
　また、特許文献４には、ニッケル酸リチウムを主体とする複合酸化物粒子にタングステン酸化合物を被着させて加熱処理を行ったもので、炭酸イオンの含有量が０．１５重量％以下である正極活物質が提案されている。
　この提案によれば、正極活物質の表面にタングステン酸化合物またはタングステン酸化合物の分解物が存在し、充電状態における複合酸化物粒子表面の酸化活性を抑制するため、非水電解液等の分解によるガス発生を抑制することができるとしているが、出力特性に関しては全く開示されていない。 In Patent Document 4, a composite oxide particle mainly composed of lithium nickelate is subjected to heat treatment by adhering a tungstic acid compound, and the content of carbonate ions is 0.15% by weight or less. A positive electrode active material has been proposed.
According to this proposal, there is a tungstic acid compound or a decomposition product of the tungstic acid compound on the surface of the positive electrode active material, and the oxidation activity on the surface of the composite oxide particles in a charged state is suppressed. Although gas generation can be suppressed, the output characteristics are not disclosed at all.
　さらに、開示されている製造方法は、好ましくは被着成分を溶解した溶液の沸点以上に加熱した複合酸化物粒子に、タングステン酸化合物とともに硫酸化合物、硝酸化合物、ホウ酸化合物またはリン酸化合物を被着成分として溶媒に溶解した溶液を被着させるものであり、溶媒を短時間で除去するため、複合酸化物粒子表面にタングステン化合物が十分に分散されず、均一に被着されないという問題点がある。 Furthermore, the disclosed production method preferably comprises a composite oxide particle heated to a boiling point or higher of a solution in which an adherent component is dissolved, and a sulfuric acid compound, a nitric acid compound, a boric acid compound, or a phosphoric acid compound as well as a tungstate compound. Since the solution dissolved in the solvent is applied as the adhering component, and the solvent is removed in a short time, the tungsten compound is not sufficiently dispersed on the surface of the composite oxide particles, so that there is a problem that it is not uniformly applied. .
　また、リチウムニッケル複合酸化物の高出力化に関する改善も行われている。
　例えば、特許文献５には、一次粒子および前記一次粒子が凝集して構成された二次粒子からなるリチウム金属複合酸化物であって、前記リチウム金属複合酸化物の表面に、Ｌｉ２ＷＯ４、Ｌｉ４ＷＯ５、Ｌｉ６Ｗ２Ｏ９のいずれかで表されるタングステン酸リチウムを含む微粒子を有する非水系電解質二次電池用正極活物質が提案され、高容量とともに高出力が得られるとされている。
　しかしながら、高容量と高出力に対する要求は高まっており、更なる改善が求められている。 Improvements have also been made with regard to higher output of lithium nickel composite oxide.
For example, Patent Document 5 discloses a lithium metal composite oxide composed of primary particles and secondary particles formed by aggregation of the primary particles, and Li 2 WO 4 , on the surface of the lithium metal composite oxide, A positive electrode active material for a non-aqueous electrolyte secondary battery having fine particles containing lithium tungstate represented by either Li 4 WO 5 or Li 6 W 2 O 9 has been proposed, and high output is obtained with high capacity. ing.
However, demands for high capacity and high output are increasing, and further improvements are required.
特開２００９‐２８９７２６号公報JP 2009-289726 A 特開２００５‐２５１７１６号公報JP 2005-251716 A 特開平１１‐１６５６６号公報Japanese Patent Laid-Open No. 11-16566 特開２０１０‐４０３８３号公報JP 2010-40383 A 特開２０１３－１２５７３２号公報JP 2013-125732 A
　本発明はかかる問題点に鑑み、正極材に用いられた場合に高容量とともに、ガス発生量の増加を抑制しながら、更なる高出力が得られる非水系電解質二次電池用正極活物質を提供することを目的とする。 In view of the above problems, the present invention provides a positive electrode active material for a non-aqueous electrolyte secondary battery that, when used in a positive electrode material, has a high capacity and suppresses an increase in the amount of gas generated, while obtaining a higher output. The purpose is to do.
　本発明者らは、上記課題を解決するため、非水系電解質二次電池用正極活物質として用いられているリチウム金属複合酸化物を用いた電池の正極抵抗に対する影響について鋭意研究したところ、リチウム金属複合酸化物粉末を構成する二次粒子内部の一次粒子表面にタングステンおよびリチウムを含む化合物を形成させること、そのリチウム金属複合酸化物粒子間にタングステンおよびリチウムを含む化合物を均一に形成させることで、電池の正極抵抗を低減して出力特性を向上させることが可能であることを見出した。
　さらに、その製造方法として、タングステンを含むアルカリ溶液にリチウム金属複合酸化物粉末を浸漬させた後に固液分離したものを熱処理することで、一次粒子表面に形成されるタングステンおよびリチウムを含む化合物をリチウム金属複合酸化物粒子間でも均一に形成させることが可能であるとの知見を得て、本発明を完成させるに至った。 In order to solve the above-mentioned problems, the present inventors diligently studied the influence on the positive electrode resistance of a battery using a lithium metal composite oxide used as a positive electrode active material for a non-aqueous electrolyte secondary battery. By forming a compound containing tungsten and lithium on the surface of the primary particles inside the secondary particles constituting the composite oxide powder, and uniformly forming a compound containing tungsten and lithium between the lithium metal composite oxide particles, It has been found that the output characteristics can be improved by reducing the positive electrode resistance of the battery.
Furthermore, as a manufacturing method thereof, the lithium-metal composite oxide powder is immersed in an alkaline solution containing tungsten and then subjected to solid-liquid separation to heat-treat the compound containing tungsten and lithium formed on the primary particle surface with lithium. The inventor has obtained the knowledge that it can be formed even between metal composite oxide particles, and has completed the present invention.
　すなわち、本発明の第１の発明である非水系電解質二次電池用正極活物質の製造方法は、一般式ＬｉｚＮｉ１－ｘ－ｙＣｏｘＭｙＯ２（ただし、０≦ｘ≦０．３５、０≦ｙ≦０．３５、０．９５≦ｚ≦１．３０、Ｍは、Ｍｎ、Ｖ、Ｍｇ、Ｍｏ、Ｎｂ、ＴｉおよびＡｌから選ばれる少なくとも１種の元素）で表される一次粒子および一次粒子が凝集して形成された二次粒子で構成された層状構造の結晶構造を有するリチウム金属複合酸化物粉末を、タングステン化合物を溶解させたタングステン濃度が０．１～２ｍｏｌ／Ｌのアルカリ溶液に、前記アルカリ溶液中の水分量に対するリチウム金属複合酸化物粉末の固液比が２００～２５００ｇ／Ｌの範囲で混合、浸漬させた後に固液分離することにより、前記リチウム金属複合酸化物の一次粒子表面にタングステンを均一に分散させたタングステン混合物を得る第１工程と、そのタングステン混合物を、熱処理することによりタングステンおよびリチウムを含む化合物を、リチウム金属複合酸化物の一次粒子表面に形成する第２工程を有することを特徴とする非水系電解質二次電池用正極活物質の製造方法である。 That is, the manufacturing method of the first cathode active material for a non-aqueous electrolyte secondary battery which is the invention of the present invention have the general formula Li z Ni 1-x-y Co x M y O 2 ( however, 0 ≦ x ≦ 0 .35, 0 ≦ y ≦ 0.35, 0.95 ≦ z ≦ 1.30, and M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti, and Al) A lithium metal composite oxide powder having a layered structure composed of primary particles and secondary particles formed by agglomeration of primary particles has a tungsten concentration of 0.1 to 2 mol / L in which a tungsten compound is dissolved. The lithium metal composite oxide is obtained by mixing and immersing the lithium metal composite oxide powder in the alkali solution in a range of 200 to 2500 g / L in the solid-liquid ratio with respect to the amount of water in the alkali solution, followed by solid-liquid separation. One thing A first step of obtaining a tungsten mixture in which tungsten is uniformly dispersed on the surface of the secondary particles, and a heat treatment of the tungsten mixture to form a compound containing tungsten and lithium on the primary particle surface of the lithium metal composite oxide. It is a manufacturing method of the positive electrode active material for non-aqueous electrolyte secondary batteries characterized by having 2 processes.
　本発明の第２の発明は、第１の発明における第１工程を実施する前に、リチウム金属複合酸化物粉末を水洗する水洗工程を有することを特徴とする非水系電解質二次電池用正極活物質の製造方法である。 According to a second aspect of the present invention, a positive electrode active for a non-aqueous electrolyte secondary battery is characterized by having a water washing step of washing the lithium metal composite oxide powder with water before performing the first step in the first invention. It is a manufacturing method of a substance.
　本発明の第３の発明は、第１及び第２の発明におけるタングステン混合物に含まれるタングステン量が、混合するリチウム金属複合酸化物粉末に含まれるＮｉ、ＣｏおよびＭの原子数の合計に対して、３．０原子％以下とすることを特徴とする非水系電解質二次電池用正極活物質の製造方法である。 In the third invention of the present invention, the amount of tungsten contained in the tungsten mixture in the first and second inventions is based on the total number of atoms of Ni, Co and M contained in the lithium metal composite oxide powder to be mixed. 3.0 atomic% or less, a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery.
　本発明の第４の発明は、第１から第３の発明におけるタングステン化合物を溶解させたアルカリ溶液中のタングステン濃度が、０．０５～２ｍｏｌ／Ｌであることを特徴とする非水系電解質二次電池用正極活物質の製造方法である。 According to a fourth aspect of the present invention, there is provided a nonaqueous electrolyte secondary characterized in that the tungsten concentration in the alkaline solution in which the tungsten compound in the first to third aspects is dissolved is 0.05 to 2 mol / L. It is a manufacturing method of the positive electrode active material for batteries.
　本発明の第５の発明は、第１から第４の発明におけるアルカリ溶液が、水酸化リチウム水溶液にタングステン化合物を溶解させたものであることを特徴とする非水系電解質二次電池用正極活物質の製造方法である。 According to a fifth aspect of the present invention, the alkaline solution according to the first to fourth aspects is a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein a tungsten compound is dissolved in an aqueous lithium hydroxide solution. It is a manufacturing method.
　本発明の第６の発明は、第１から第５の発明におけるタングステン化合物を溶解させたアルカリ溶液とリチウム金属複合酸化物粉末との混合が、タングステン化合物を溶解させたアルカリ溶液が液体で、かつ５０℃以下の温度で行うことを特徴とする非水系電解質二次電池用正極活物質の製造方法である。 According to a sixth aspect of the present invention, there is provided a mixture of the alkaline solution in which the tungsten compound is dissolved and the lithium metal composite oxide powder in the first to fifth aspects, wherein the alkaline solution in which the tungsten compound is dissolved is liquid, and It is a manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries characterized by performing at the temperature of 50 degrees C or less.
　本発明の第７の発明は、第１から第６の発明における第２工程における熱処理が、酸素雰囲気あるいは真空雰囲気中において、１００～６００℃で行うことを特徴とする非水系電解質二次電池用正極活物質の製造方法である。 According to a seventh aspect of the present invention, the heat treatment in the second step according to the first to sixth aspects is performed at 100 to 600 ° C. in an oxygen atmosphere or a vacuum atmosphere. It is a manufacturing method of a positive electrode active material.
　本発明の第８の発明は、一次粒子および一次粒子が凝集して形成された二次粒子からなり、層状構造の結晶構造を有し、一次粒子表面にタングステンおよびリチウムを含む化合物を有するリチウム金属複合酸化物粉末からなり、一般式：ＬｉｚＮｉ１－ｘ－ｙＣｏｘＭｙＷａＯ２＋α（ただし、０≦ｘ≦０．３５、０≦ｙ≦０．３５、０．９５≦ｚ≦１．３０、０＜ａ≦０．０３、０≦α≦０．１５、Ｍは、Ｍｎ、Ｖ、Ｍｇ、Ｍｏ、Ｎｂ、ＴｉおよびＡｌから選ばれる少なくとも１種の元素）で表される非水系電解質二次電池用正極活物質であって、そのリチウム金属複合酸化物の二次粒子の断面を、走査型電子顕微鏡を用いた定倍率による観察において、任意の少なくとも２以上の異なる観察視野における任意に抽出した５０個以上の前記二次粒子を観察した際に、前記二次粒子内部の一次粒子表面にタングステンおよびリチウムを含む化合物を有する二次粒子の数が、観察した二次粒子数の９０％以上であることを特徴とする非水系電解質二次電池用正極活物質である。 The eighth invention of the present invention is a lithium metal comprising a primary particle and a secondary particle formed by agglomeration of the primary particle, having a layered crystal structure, and a compound containing tungsten and lithium on the surface of the primary particle made from the composite oxide powder represented by the general formula: Li z Ni 1-x- y Co x M y W a O 2 + α ( although, 0 ≦ x ≦ 0.35,0 ≦ y ≦ 0.35,0.95 ≦ z ≦ 1.30, 0 <a ≦ 0.03, 0 ≦ α ≦ 0.15, and M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti, and Al) A positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the cross section of the secondary particle of the lithium metal composite oxide is observed at a constant magnification using a scanning electron microscope, and at least two or more different observation fields 50 or more arbitrarily extracted in When observing the secondary particles, the number of secondary particles having a compound containing tungsten and lithium on the surface of the primary particles inside the secondary particles is 90% or more of the observed number of secondary particles. A positive electrode active material for a non-aqueous electrolyte secondary battery.
　本発明の第９の発明は、第８の発明におけるタングステンおよびリチウムを含む化合物が、粒子径１～２００ｎｍの微粒子として前記リチウム金属複合酸化物の一次粒子表面に存在することを特徴とする非水系電解質二次電池用正極活物質である。 According to a ninth aspect of the present invention, there is provided a non-aqueous system wherein the compound containing tungsten and lithium according to the eighth aspect is present on the primary particle surface of the lithium metal composite oxide as fine particles having a particle diameter of 1 to 200 nm. It is a positive electrode active material for electrolyte secondary batteries.
　本発明の第１０の発明は、第８の発明におけるタングステンおよびリチウムを含む化合物が、膜厚１～１５０ｎｍの被膜として前記リチウム金属複合酸化物の一次粒子表面に存在することを特徴とする非水系電解質二次電池用正極活物質である。 According to a tenth aspect of the present invention, the compound containing tungsten and lithium according to the eighth aspect of the present invention is present on the primary particle surface of the lithium metal composite oxide as a film having a thickness of 1 to 150 nm. It is a positive electrode active material for electrolyte secondary batteries.
　本発明の第１１の発明は、第８の発明におけるタングステンおよびリチウムを含む化合物が、粒子径１～２００ｎｍの微粒子及び膜厚１～１５０ｎｍの被膜の両形態として前記リチウム金属複合酸化物の一次粒子表面に存在することを特徴とする非水系電解質二次電池用正極活物質である。 In an eleventh aspect of the present invention, the compound containing tungsten and lithium according to the eighth aspect of the present invention provides primary particles of the lithium metal composite oxide in both forms of fine particles having a particle diameter of 1 to 200 nm and coatings having a thickness of 1 to 150 nm. A positive electrode active material for a non-aqueous electrolyte secondary battery, characterized by being present on the surface.
　本発明の第１２の発明は、第８から第１１の発明におけるタングステンおよびリチウムを含む化合物中に含有されるタングステン量が、リチウム金属複合酸化物粒子に含まれるＮｉ、ＣｏおよびＭの原子数の合計に対してＷの原子数が０．０５～２．０原子％であることを特徴とする非水系電解質二次電池用正極活物質である。 In a twelfth aspect of the present invention, the amount of tungsten contained in the compound containing tungsten and lithium in the eighth to eleventh aspects is the number of Ni, Co and M atoms contained in the lithium metal composite oxide particles. A positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the number of W atoms is 0.05 to 2.0 atomic% with respect to the total.
　本発明の第１３の発明は、第８から第１２の発明におけるタングステンおよびリチウムを含む化合物が、タングステン酸リチウムの形態で存在することを特徴とする非水系電解質二次電池用正極活物質である。 A thirteenth aspect of the present invention is a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the compound containing tungsten and lithium according to the eighth to twelfth aspects of the present invention is present in the form of lithium tungstate. .
　本発明の第１４の発明は、第８から第１３の発明に係る非水系電解質二次電池用正極活物質を含む正極を有することを特徴とする非水系電解質二次電池である。 A fourteenth aspect of the present invention is a non-aqueous electrolyte secondary battery comprising a positive electrode including a positive electrode active material for a non-aqueous electrolyte secondary battery according to the eighth to thirteenth aspects.
　本発明によれば、電池の正極材に用いられた場合に高容量とともに高出力が実現可能な非水系電解質二次電池用正極活物質が得られる。
　さらに、その製造方法は容易で、工業的規模での生産に適したものであり、その工業的価値は極めて大きい。 ADVANTAGE OF THE INVENTION According to this invention, when used for the positive electrode material of a battery, the positive electrode active material for nonaqueous electrolyte secondary batteries which can implement | achieve high output with a high capacity | capacitance is obtained.
Furthermore, the manufacturing method is easy and suitable for production on an industrial scale, and its industrial value is extremely large.
インピーダンス評価の測定例と解析に使用した等価回路の概略説明図である。It is a schematic explanatory drawing of the measurement example of impedance evaluation, and the equivalent circuit used for analysis. 本発明のリチウム金属複合酸化物の断面ＳＥＭ写真（観察倍率５０００倍）である。It is a cross-sectional SEM photograph (observation magnification 5000 times) of the lithium metal complex oxide of this invention. 電池評価に使用したコイン型電池１の概略断面図である。It is a schematic sectional drawing of the coin-type battery 1 used for battery evaluation.
　以下、本発明について、まず本発明の正極活物質について説明した後、その製造方法と本発明による正極活物質を用いた非水系電解質二次電池について説明する。 Hereinafter, after describing the positive electrode active material of the present invention first, the production method and the nonaqueous electrolyte secondary battery using the positive electrode active material according to the present invention will be described.
（１）正極活物質
　本発明の非水系電解質二次電池用正極活物質は、一次粒子および、一次粒子が凝集して形成された二次粒子（以下、単に二次粒子と称することがある。）からなり、層状構造の結晶構造を有し、一次粒子表面にタングステンおよびリチウムを含む化合物を有するリチウム金属複合酸化物であって、正極活物質の組成が一般式：ＬｉｚＮｉ１－ｘ－ｙＣｏｘＭｙＷａＯ２＋α（ただし、０≦ｘ≦０．３５、０≦ｙ≦０．３５、０．９５≦ｚ≦１．３０、０＜ａ≦０．０３、０≦α≦０．１５、Ｍは、Ｍｎ、Ｖ、Ｍｇ、Ｍｏ、Ｎｂ、ＴｉおよびＡｌから選ばれる少なくとも１種の元素）で表され、そのリチウム金属複合酸化物の二次粒子の断面の走査型電子顕微鏡観察において、任意の５０個以上の二次粒子を観察した際に、二次粒子内部の一次粒子表面にタングステン（Ｗ）およびリチウム（Ｌｉ）を含む化合物を有する二次粒子が、観察された粒子数の９０％以上であることを特徴とするものである。 (1) Positive electrode active material The positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention may be referred to as primary particles and secondary particles formed by aggregation of primary particles (hereinafter, simply referred to as secondary particles). A lithium metal composite oxide having a layered crystal structure and a compound containing tungsten and lithium on the surface of the primary particle, the composition of the positive electrode active material is represented by the general formula: Li z Ni 1-x- y Co x M y W a O 2 + α ( although, 0 ≦ x ≦ 0.35,0 ≦ y ≦ 0.35,0.95 ≦ z ≦ 1.30,0 <a ≦ 0.03,0 ≦ α ≦ 0.15, M represents at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al), and a scanning electron microscope of the cross section of the secondary particle of the lithium metal composite oxide In observation, arbitrary 50 or more secondary particles were observed. The one in which secondary particles having a compound to the primary particle surfaces containing tungsten (W) and lithium (Li) of the internal secondary particles, characterized in that it is observed the number of 90% or more particles.
　すなわち母材として、その組成が一般式ＬｉｚＮｉ１－ｘ－ｙＣｏｘＭｙＯ２（ただし、０≦ｘ≦０．３５、０≦ｙ≦０．３５、０．９５≦ｚ≦１．３０、Ｍは、Ｍｎ、Ｖ、Ｍｇ、Ｍｏ、Ｎｂ、ＴｉおよびＡｌから選ばれる少なくとも１種の元素）で表され層状構造の結晶構造を有するリチウム金属複合酸化物を用いることにより、高い充放電容量を得るものである。さらに高い充放電容量を得るためには、上記一般式において、ｘ＋ｙ≦０．２、０．９５≦ｚ≦１．１０とすることが好ましい。
　さらに、その母材が一次粒子および一次粒子が凝集して形成された二次粒子で構成されたリチウム金属複合酸化物粉末（以下、二次粒子と単独で存在する一次粒子を合わせて「リチウム金属複合酸化物粒子」ということがある。）の形態を採り、その一次粒子の表面に形成されたタングステン（Ｗ）およびリチウム（Ｌｉ）を含む化合物（以下、「ＬＷ化合物」ということがある。）により、充放電容量を維持しながら出力特性を向上させるものである。
　一般的に、正極活物質の表面が異種化合物により完全に被覆されてしまうと、リチウムイオンの移動（インターカレーション）が大きく制限されるため、結果的にリチウムニッケル複合酸化物の持つ高容量という長所が消されてしまう。 That is, as the base material, its composition formula Li z Ni 1-x-y Co x M y O 2 ( however, 0 ≦ x ≦ 0.35,0 ≦ y ≦ 0.35,0.95 ≦ z ≦ 1 .30, M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al), and a lithium metal composite oxide having a layered crystal structure is used. A discharge capacity is obtained. In order to obtain a higher charge / discharge capacity, it is preferable to satisfy x + y ≦ 0.2 and 0.95 ≦ z ≦ 1.10.
Further, a lithium metal composite oxide powder composed of primary particles and secondary particles formed by agglomeration of primary particles (hereinafter referred to as “lithium metal combined with secondary particles and primary particles present alone”). A compound containing tungsten (W) and lithium (Li) formed on the surface of the primary particle (hereinafter also referred to as “LW compound”). Thus, the output characteristics are improved while maintaining the charge / discharge capacity.
In general, when the surface of the positive electrode active material is completely covered with a different compound, the movement (intercalation) of lithium ions is greatly limited, resulting in a high capacity of the lithium nickel composite oxide. The advantages are erased.
　対して、本発明においては、リチウム金属複合酸化物粒子の表面及び内部の一次粒子の表面にＬＷ化合物を形成させているが、このＬＷ化合物は、リチウムイオン伝導性が高く、リチウムイオンの移動を促す効果がある。このため、リチウム金属複合酸化物粒子の表面及び内部の一次粒子の表面に上記ＬＷ化合物を形成させることで、電解液との界面でＬｉの伝導パスを形成することから、正極活物質の反応抵抗（以下、「正極抵抗」ということがある。）を低減して非水系電解質二次電池の出力特性を向上させるものである。
　すなわち、正極抵抗が低減されることで、非水系電解質二次電池（以下、単に「電池」ということがある。）内で損失される電圧が減少し、実際に負荷側に印加される電圧が相対的に高くなるため、高出力が得られる。また、負荷側への印加電圧が高くなることで、正極でのリチウムの挿抜が十分に行われるため、充放電容量（以下、「電池容量」ということがある。）も向上するものである。 On the other hand, in the present invention, an LW compound is formed on the surface of the lithium metal composite oxide particles and the surface of the primary particles inside, but this LW compound has high lithium ion conductivity and prevents movement of lithium ions. There is an urging effect. For this reason, since the LW compound is formed on the surface of the lithium metal composite oxide particles and the surface of the internal primary particles, a Li conduction path is formed at the interface with the electrolytic solution. (Hereinafter, also referred to as “positive electrode resistance”) is reduced to improve the output characteristics of the non-aqueous electrolyte secondary battery.
That is, by reducing the positive electrode resistance, the voltage lost in the non-aqueous electrolyte secondary battery (hereinafter sometimes simply referred to as “battery”) is reduced, and the voltage actually applied to the load side is reduced. Since it becomes relatively high, a high output can be obtained. Further, since the voltage applied to the load side is increased, lithium is sufficiently inserted and extracted from the positive electrode, so that the charge / discharge capacity (hereinafter also referred to as “battery capacity”) is also improved.
　電池の正極活物質として用いられた際の電解液との接触は、一次粒子表面で起こるため、一次粒子表面にタングステン酸リチウムが形成されていることが重要である。ここで、本発明における一次粒子表面とは、二次粒子の外面で露出している一次粒子の表面と二次粒子外部と通じて電解液が浸透可能な二次粒子の表面近傍および内部の空隙に露出している一次粒子の表面、さらに単独で存在する一次粒子の表面を含むものである。さらに、一次粒子間の粒界であっても一次粒子の結合が不完全で電解液が浸透可能な状態となっていれば含まれるものである。
　この電解液との接触は、一次粒子が凝集して形成された二次粒子の外面のみでなく、上記二次粒子の表面近傍および内部の一次粒子間の空隙、さらには上記不完全な粒界でも生じるため、上記一次粒子表面にもＬＷ化合物を形成させ、リチウムイオンの移動を促すことが必要である。したがって、電解液との接触が可能な一次粒子表面の多くにＬＷ化合物を形成させることで、リチウム金属複合酸化物粒子の反応抵抗をより一層低減させることが可能となる。 Since the contact with the electrolytic solution when used as the positive electrode active material of the battery occurs on the surface of the primary particle, it is important that lithium tungstate is formed on the surface of the primary particle. Here, the surface of the primary particle in the present invention refers to the surface of the primary particle exposed on the outer surface of the secondary particle and the space near and inside the surface of the secondary particle that can penetrate the electrolyte solution through the outside of the secondary particle. The surface of the primary particle exposed to the surface of the primary particle, and the surface of the primary particle present alone are included. Furthermore, even a grain boundary between primary particles is included as long as the primary particles are not completely bonded and the electrolyte solution can penetrate.
The contact with the electrolytic solution is not limited to the outer surface of the secondary particles formed by agglomeration of the primary particles, but also the gap between the primary particles in the vicinity of the inner surface of the secondary particles and the incomplete grain boundary. However, since it occurs, it is necessary to form an LW compound also on the surface of the primary particles and promote the movement of lithium ions. Therefore, the reaction resistance of the lithium metal composite oxide particles can be further reduced by forming the LW compound on most of the primary particle surfaces that can be contacted with the electrolytic solution.
　さらに、ＬＷ化合物の一次粒子表面上における形態は、一次粒子表面を層状物で被覆した場合には、電解液との接触面積が小さくなってしまう、また、層状物を形成すると、化合物の形成が特定の一次粒子表面に集中するという結果になり易い。したがって、被覆物としての層状物が高いリチウムイオン伝導性を持っていることにより、充放電容量の向上、反応抵抗の低減という効果が得られるものの、十分ではなく改善の余地がある。
　したがって、より高い効果を得るため、ＬＷ化合物は、粒子径１～２００ｎｍの微粒子としてリチウム金属複合酸化物の一次粒子表面に存在することが好ましい。 Further, the form of the LW compound on the primary particle surface is such that when the surface of the primary particle is coated with a layered material, the contact area with the electrolytic solution is reduced. It tends to result in concentration on the surface of specific primary particles. Therefore, although the layered material as the coating has high lithium ion conductivity, the effects of improving the charge / discharge capacity and reducing the reaction resistance can be obtained, but there is room for improvement.
Therefore, in order to obtain a higher effect, the LW compound is preferably present on the primary particle surface of the lithium metal composite oxide as fine particles having a particle diameter of 1 to 200 nm.
　このような形態を採ることにより、電解液との接触面積を十分なものとして、リチウムイオン伝導を効果的に向上できるため、電池容量を向上させるとともに正極抵抗をより効果的に低減させることができる。その粒子径が１ｎｍ未満では、微細な粒子が十分なリチウムイオン伝導性を有しない場合がある。また、粒子径が２００ｎｍを超えると、微粒子の表面における形成が不均一になり、正極抵抗低減のより高い効果が得られない場合がある。
　ここで、微粒子は完全に一次粒子表面の全てにおいて形成されている必要はなく、点在している状態でもよい。点在している状態でも、リチウム金属複合酸化物粒子の外面および内部の空隙に露出している一次粒子表面に微粒子が形成されていれば、正極抵抗の低減効果が得られる。また、微粒子は、全てが粒子径１～２００ｎｍの微粒子として存在する必要がなく、好ましくは一次粒子表面に形成された微粒子の個数で５０％以上が、１～２００ｎｍの粒子径範囲で形成されていれば高い効果が得られる。 By adopting such a form, the contact area with the electrolytic solution can be made sufficient, and lithium ion conduction can be effectively improved, so that the battery capacity can be improved and the positive electrode resistance can be reduced more effectively. . If the particle diameter is less than 1 nm, fine particles may not have sufficient lithium ion conductivity. On the other hand, when the particle diameter exceeds 200 nm, the formation of the fine particles on the surface becomes non-uniform, and the higher effect of reducing the positive electrode resistance may not be obtained.
Here, the fine particles do not need to be completely formed on the entire surface of the primary particles, and may be scattered. Even in the scattered state, if the fine particles are formed on the primary particle surfaces exposed on the outer surface and the internal voids of the lithium metal composite oxide particles, the effect of reducing the positive electrode resistance can be obtained. Further, it is not necessary for all the fine particles to be present as fine particles having a particle diameter of 1 to 200 nm. Preferably, 50% or more of the fine particles formed on the surface of the primary particles are formed in a particle diameter range of 1 to 200 nm. High effect can be obtained.
　一方、一次粒子表面を薄膜で被覆すると、比表面積の低下を抑制しながら、電解液との界面でＬｉの伝導パスを形成させることができ、より高い電池容量の向上、正極抵抗の低減という効果が得られる。このような薄膜状のＬＷ化合物により一次粒子表面を被覆する場合には、膜厚１～１５０ｎｍの被膜としてリチウム金属複合酸化物の一次粒子表面に存在することが好ましい。
　その膜厚が１ｎｍ未満では、被膜が十分なリチウムイオン伝導性を有しない場合がある。また、膜厚が１５０ｎｍを超えると、リチウムイオン伝導性低下し、正極抵抗低減のより高い効果が得られない場合がある。
　しかし、この被膜は、一次粒子表面上で部分的に形成されていてもよく、全ての被膜の膜厚範囲が１～１５０ｎｍでなくてもよい。一次粒子表面に少なくとも部分的に膜厚が１～１５０ｎｍの被膜が形成されていれば、高い効果が得られる。 On the other hand, when the surface of the primary particles is coated with a thin film, the conduction path of Li can be formed at the interface with the electrolyte while suppressing the decrease in specific surface area, and the effect of higher battery capacity and reduced positive electrode resistance Is obtained. When the surface of the primary particle is coated with such a thin film-like LW compound, it is preferably present on the surface of the primary particle of the lithium metal composite oxide as a film having a thickness of 1 to 150 nm.
If the film thickness is less than 1 nm, the film may not have sufficient lithium ion conductivity. On the other hand, when the film thickness exceeds 150 nm, the lithium ion conductivity is lowered, and the higher effect of reducing the positive electrode resistance may not be obtained.
However, this coating may be partially formed on the primary particle surface, and the film thickness range of all coatings may not be 1 to 150 nm. If a film having a film thickness of 1 to 150 nm is formed at least partially on the primary particle surface, a high effect can be obtained.
　さらに、微粒子形態と薄膜の被膜形態が混在して一次粒子表面に化合物が形成されている場合にも、電池特性に対する高い効果が得られる。
　また、ＬＷ化合物が一次粒子表面に形成されることで、リチウム金属複合酸化物表面への余剰リチウムの生成を抑え、正極材表面からのガス発生を抑制する効果も得られる。余剰リチウム量は、正極活物質全量に対して０．０５質量％以下であることが好ましく、０．０３５質量％以下であることがより好ましい。 Further, even when the fine particle form and the thin film form are mixed and a compound is formed on the surface of the primary particle, a high effect on the battery characteristics can be obtained.
In addition, since the LW compound is formed on the surface of the primary particles, it is possible to suppress the generation of excess lithium on the surface of the lithium metal composite oxide and to suppress the generation of gas from the surface of the positive electrode material. The excess lithium amount is preferably 0.05% by mass or less, more preferably 0.035% by mass or less, based on the total amount of the positive electrode active material.
　一方、リチウム金属複合酸化物粒子間で不均一にＬＷ化合物が形成された場合は、リチウム金属複合酸化物粒子間でのリチウムイオンの移動が不均一となるため、特定のリチウム金属複合酸化物粒子に負荷がかかり、サイクル特性の悪化や反応抵抗の上昇を招きやすい。特に、二次粒子内部の一次粒子表面にＬＷ化合物が形成されていない二次粒子は、二次粒子表面に微粒子が形成されていても、内部の一次粒子表面にまでＬＷ化合物が形成されている二次粒子と比べて負荷がかかりやすく、劣化しやすい。
　したがって、二次粒子内部の一次粒子表面にＬＷ化合物が形成されていない二次粒子を少なくすることで、正極抵抗を低減して出力特性や電池容量を向上させることができ、サイクル特性も良好なものとすることができる。 On the other hand, when the LW compound is formed non-uniformly between the lithium metal composite oxide particles, the movement of lithium ions between the lithium metal composite oxide particles becomes non-uniform. It is easy to cause deterioration of cycle characteristics and increase of reaction resistance. In particular, in the secondary particle in which the LW compound is not formed on the surface of the primary particle inside the secondary particle, even if the fine particle is formed on the surface of the secondary particle, the LW compound is formed on the surface of the primary particle inside. Compared to secondary particles, it is more likely to be loaded and deteriorated.
Therefore, by reducing the secondary particles in which the LW compound is not formed on the primary particle surface inside the secondary particles, the positive electrode resistance can be reduced and the output characteristics and battery capacity can be improved, and the cycle characteristics are also good. Can be.
　具体的には、リチウム金属複合酸化物粒子の断面の走査型電子顕微鏡観察において、任意の５０個以上の二次粒子を観察した際に、二次粒子内部の一次粒子表面にＬＷ化合物を有する二次粒子が、観察された粒子数の９０％以上、好ましくは９５％以上とすることで、上記のような電池特性の向上が可能である。
　この走査型電子顕微鏡観察は、例えば、リチウム金属複合酸化物粒子、すなわち正極活物質の粉末を樹脂に埋め込んで粒子の断面が観察可能なように加工した後、少なくとも２視野以上の異なる観察視野における合計５０個以上の二次粒子の断面を、電界放射型走査電子顕微鏡を用いた５０００倍の一定倍率で観察することにより行うものであり、５０個以上の二次粒子を観察することで、観察上の誤差を排除して二次粒子内部にＬＷ化合物を形成させたことによる効果を有する正極活物質を精度よく判定できる。 Specifically, in observation with a scanning electron microscope of a cross section of a lithium metal composite oxide particle, when any 50 or more secondary particles are observed, the secondary particle having an LW compound on the surface of the primary particle inside the secondary particle. By making the secondary particles 90% or more, preferably 95% or more of the number of particles observed, the battery characteristics as described above can be improved.
In this scanning electron microscope observation, for example, lithium metal composite oxide particles, that is, a positive electrode active material powder is embedded in a resin and processed so that the cross section of the particles can be observed, and then in at least two different visual fields. The cross-section of a total of 50 or more secondary particles is observed at a constant magnification of 5000 times using a field emission scanning electron microscope, and observation is performed by observing 50 or more secondary particles. The positive electrode active material having the effect of eliminating the above error and forming the LW compound in the secondary particles can be accurately determined.
　本発明におけるＬＷ化合物は、ＷおよびＬｉを含むものであればよいが、タングステン酸リチウムの形態となっていることが好ましい。
　このタングステン酸リチウムが形成されることで、リチウムイオン伝導性がさらに高まり、反応抵抗の低減効果がより大きなものとなる。さらに、タングステン酸リチウムとしては、リチウムイオン伝導率の観点から、Ｌｉ２ＷＯ４、Ｌｉ４ＷＯ５、Ｌｉ６Ｗ２Ｏ９、Ｌｉ６ＷＯ6、７（Ｌｉ２ＷＯ４）・４Ｈ２Ｏからなる群から選択される１種類以上の化合物を含むことが好ましく、Ｌｉ２ＷＯ４またはＬｉ４ＷＯ５もしくはこれらの混合物であることが好ましい． Although the LW compound in this invention should just contain W and Li, it is preferable that it is a form of lithium tungstate.
By forming this lithium tungstate, the lithium ion conductivity is further increased, and the effect of reducing the reaction resistance is further increased. Further, as lithium tungstate, from the viewpoint of lithium ion conductivity, Li 2 WO 4 , Li 4 WO 5 , Li 6 W 2 O 9 , Li 6 WO 6 , 7 (Li 2 WO 4 ) · 4H 2 O It is preferable to include one or more compounds selected from the group consisting of Li 2 WO 4 or Li 4 WO 5 or a mixture thereof.
　このＬＷ化合物に含まれるタングステン量は、リチウム金属複合酸化物に含まれるＮｉ、ＣｏおよびＭの原子数の合計に対して、３．０原子％以下であり、０．０５～３．０原子％とすることが好ましく、０．０５～２．０原子％とすることがより好ましく、０．０８～１．０原子％とすることがさらに好ましい。３．０原子％以下のタングステンを添加することで、出力特性の改善効果が得られる。さらに、０．０５～２．０原子％とすることにより、ＬＷＯの形成量を正極抵抗を低減させるために十分な量とするとともに、電解液との接触が可能な一次粒子表面を十分に確保できる量とすることができ、より高い電池容量と出力特性を両立することができる。
　タングステン量が０．０５原子％未満では、出力特性の改善効果が十分に得られない場合があり、タングステン量が３．０原子％を超えると、形成される上記ＬＷ化合物が多くなり過ぎてリチウム金属複合酸化物粒子と電解液の間のリチウム伝導が阻害され、電池容量が低下することがある。 The amount of tungsten contained in this LW compound is 3.0 atomic% or less, and 0.05 to 3.0 atomic% with respect to the total number of Ni, Co and M atoms contained in the lithium metal composite oxide. Preferably, it is 0.05 to 2.0 atom%, more preferably 0.08 to 1.0 atom%. The effect of improving the output characteristics can be obtained by adding 3.0 atomic% or less of tungsten. Furthermore, by setting it to 0.05 to 2.0 atomic%, the amount of LWO formed is sufficient to reduce the positive electrode resistance, and a sufficient primary particle surface that can be contacted with the electrolyte is secured. It is possible to achieve a higher battery capacity and output characteristics at the same time.
When the amount of tungsten is less than 0.05 atomic%, the effect of improving the output characteristics may not be sufficiently obtained. When the amount of tungsten exceeds 3.0 atomic%, the amount of the LW compound to be formed increases so that lithium Lithium conduction between the metal composite oxide particles and the electrolytic solution may be inhibited, and the battery capacity may be reduced.
　このＬＷ化合物に含まれるリチウム量は、特に限定されるものではなく、ＬＷ化合物に含まれればリチウムイオン伝導性の向上効果が得られる。通常、リチウム金属複合酸化物粒子の表面には余剰リチウムが存在し、アルカリ溶液との混合時に、その余剰リチウムによりＬＷ化合物に供給されるリチウム量でよいが、タングステン酸リチウムを形成させるのに十分な量とすることが好ましい。 The amount of lithium contained in the LW compound is not particularly limited, and if it is contained in the LW compound, an effect of improving lithium ion conductivity can be obtained. Usually, surplus lithium is present on the surface of the lithium metal composite oxide particles, and the amount of lithium supplied to the LW compound by the surplus lithium when mixed with the alkaline solution may be sufficient, but is sufficient to form lithium tungstate. It is preferable to make it an amount.
　また、正極活物質全体のリチウム量が、正極活物質中のＮｉ、ＣｏおよびＭｏの原子数の和（Ｍｅ）とＬｉの原子数との比「Ｌｉ／Ｍｅ」が、０．９５～１．３０であり、０．９７～１．２５であることが好ましく、０．９７～１．２０であることがより好ましい。これにより、芯材としてのリチウム金属複合酸化物粒子のＬｉ／Ｍｅを０．９５～１．２５、より好ましくは０．９５～１．２０として高い電池容量を得るとともに、ＬＷ化合物の形成に十分な量のリチウムを確保することができる。より高い電池容量を得るためには、正極活物質全体のＬｉ／Ｍｅを０．９５～１．１５、リチウム金属複合酸化物粒子のＬｉ／Ｍｅを０．９５～１．１０とすることがさらに好ましい。ここで、芯材とはＬＷ化合物を含まないリチウム金属複合酸化物粒子であり、リチウム金属複合酸化物粒子の一次粒子表面にＬＷ化合物が形成されることで正極活物質となる。
　そのＬｉ／Ｍｅが０．９５未満であると、得られた正極活物質を用いた非水系電解質二次電池における正極の反応抵抗が大きくなるため、電池の出力が低くなってしまう。また、Ｌｉ／Ｍｅが１．３０を超えると、正極活物質の初期放電容量が低下するとともに、正極の反応抵抗も増加してしまう。 The total amount of lithium in the positive electrode active material is such that the ratio “Li / Me” of the number of Ni, Co and Mo atoms in the positive electrode active material (Me) to the number of Li atoms is 0.95 to 1. 30, preferably 0.97 to 1.25, more preferably 0.97 to 1.20. As a result, the Li / Me of the lithium metal composite oxide particles as the core material is 0.95 to 1.25, more preferably 0.95 to 1.20, and a high battery capacity is obtained and sufficient for the formation of the LW compound. A sufficient amount of lithium can be secured. In order to obtain a higher battery capacity, it is preferable that Li / Me of the positive electrode active material as a whole is 0.95 to 1.15, and Li / Me of the lithium metal composite oxide particles is 0.95 to 1.10. preferable. Here, the core material is lithium metal composite oxide particles that do not contain an LW compound, and becomes a positive electrode active material by forming an LW compound on the primary particle surface of the lithium metal composite oxide particles.
If the Li / Me is less than 0.95, the reaction resistance of the positive electrode in the non-aqueous electrolyte secondary battery using the obtained positive electrode active material increases, and the output of the battery decreases. On the other hand, when Li / Me exceeds 1.30, the initial discharge capacity of the positive electrode active material decreases and the reaction resistance of the positive electrode also increases.
　本発明の正極活物質は、リチウム金属複合酸化物の一次粒子表面にＬＷ化合物を形成させて出力特性を改善したものであり、正極活物質としての粒径、タップ密度などの粉体特性は、通常に用いられる正極活物質の範囲内であればよい。 The positive electrode active material of the present invention is an improvement in output characteristics by forming an LW compound on the primary particle surface of the lithium metal composite oxide, and the powder properties such as the particle size and tap density as the positive electrode active material are: What is necessary is just to be in the range of the positive electrode active material used normally.
　リチウム金属複合酸化物の一次粒子表面に、ＬＷ化合物を付着させることによる効果は、たとえば、リチウムコバルト系複合酸化物、リチウムマンガン系複合酸化物、リチウムニッケルコバルトマンガン系複合酸化物などの粉末、さらに本発明で掲げた正極活物質だけでなく一般的に使用されるリチウム二次電池用正極活物質にも適用できる。 The effect of adhering the LW compound to the primary particle surface of the lithium metal composite oxide is, for example, a powder such as lithium cobalt composite oxide, lithium manganese composite oxide, lithium nickel cobalt manganese composite oxide, The present invention can be applied not only to the positive electrode active material described in the present invention but also to a commonly used positive electrode active material for a lithium secondary battery.
（２）正極活物質の製造方法
　以下、本発明の非水系電解質二次電池用正極活物質の製造方法を工程ごとに詳細に説明する。 (2) Method for Producing Positive Electrode Active Material Hereinafter, the method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention will be described in detail for each step.
［第１工程］
　第１工程は、一次粒子および一次粒子が凝集して形成された二次粒子から構成されたリチウム金属複合酸化物粉末を、タングステン化合物を溶解したアルカリ溶液（以下、タングステン化合物を溶解したアルカリ溶液をアルカリ溶液（Ｗ）という。）に浸漬後、固液分離してタングステン混合物を得る工程である。
　この工程により、二次粒子内部の一次粒子表面にまでＷを均一に分散させることができる。 [First step]
In the first step, a lithium metal composite oxide powder composed of primary particles and secondary particles formed by agglomeration of primary particles is mixed with an alkaline solution in which a tungsten compound is dissolved (hereinafter, an alkaline solution in which a tungsten compound is dissolved). This is a step of obtaining a tungsten mixture by solid-liquid separation after immersion in an alkaline solution (W).
By this step, W can be uniformly dispersed to the surface of the primary particles inside the secondary particles.
　ここで、リチウム金属複合酸化物粉末を、アルカリ溶液（Ｗ）と、アルカリ溶液（Ｗ）中の水分量に対するリチウム金属複合酸化物粉末の固液比を２００～２５００ｇ／Ｌの範囲、好ましくは５００～２０００ｇ／Ｌの範囲で混合、浸漬させることが必要である。さらに、アルカリ溶液（Ｗ）のＷ濃度を０．１～２ｍｏｌ／Ｌ、好ましくは０．１～１．５ｍｏｌ／Ｌとする。 Here, in the lithium metal composite oxide powder, the solid-liquid ratio of the lithium metal composite oxide powder to the alkali solution (W) and the amount of water in the alkali solution (W) is in the range of 200 to 2500 g / L, preferably 500. It is necessary to mix and immerse in a range of ˜2000 g / L. Furthermore, the W concentration of the alkaline solution (W) is 0.1 to 2 mol / L, preferably 0.1 to 1.5 mol / L.
　この第１工程では、アルカリ溶液（Ｗ）にリチウム金属複合酸化物粉末を浸漬することで、二次粒子内の一次粒子表面まで適度な濃度のアルカリ溶液（Ｗ）を浸透させ、一次粒子表面に上述のようなＬＷ化合物が形成される量のＷを分散させることができる。また、タングステン混合物に含まれるＷ量は、固液分離した後にリチウム金属複合酸化物粉末に残留するアルカリ溶液（Ｗ）中のＷ量によって決定される。 In this first step, by immersing the lithium metal composite oxide powder in the alkaline solution (W), the alkaline solution (W) having an appropriate concentration is infiltrated to the primary particle surface in the secondary particles, and the primary particle surface The amount of W that forms the LW compound as described above can be dispersed. The amount of W contained in the tungsten mixture is determined by the amount of W in the alkaline solution (W) remaining in the lithium metal composite oxide powder after solid-liquid separation.
　すなわち、第１工程では、アルカリ溶液（Ｗ）への浸漬後に固液分離を行うため、固液分離後のタングステン混合物に残留するアルカリ溶液（Ｗ）中に含まれるＷ分が、リチウム金属複合酸化物の二次粒子表面や一次粒子表面に分散、付着するため、化合物を形成させるために必要な量を固液分離後の水分率から求めることができる。 That is, in the first step, solid-liquid separation is performed after immersion in the alkaline solution (W), so that the W content contained in the alkaline solution (W) remaining in the tungsten mixture after solid-liquid separation is the lithium metal composite oxidation. In order to disperse and adhere to the secondary particle surface or primary particle surface of the product, the amount required to form the compound can be determined from the moisture content after solid-liquid separation.
　したがって、アルカリ溶液（Ｗ）のＷ濃度と固液分離の程度によりタングステン混合物に含まれるＷ量を制御することが可能である。通常に実施される固液分離方法では、固液分離後に残留する液量は、固液分離によって得られたケーキに対して５～１５質量％であり、固液分離の条件によって安定したものとなるので、予備試験等により残留する液量（水分率）を求めておけば容易に制御することができる。 Therefore, the amount of W contained in the tungsten mixture can be controlled by the W concentration of the alkaline solution (W) and the degree of solid-liquid separation. In a solid-liquid separation method that is normally performed, the amount of liquid remaining after solid-liquid separation is 5 to 15% by mass with respect to the cake obtained by solid-liquid separation, and is stable depending on the conditions of solid-liquid separation. Therefore, if the remaining liquid amount (water content) is obtained by a preliminary test or the like, it can be easily controlled.
　タングステン混合物に含まれるＷ量は、得られる正極活物質中の前記化合物中に含有されるタングステン量と等しくなる。したがって、タングステン混合物に含まれるＷ量は、混合するリチウム金属複合酸化物粉末に含まれるＮｉ、ＣｏおよびＭの原子数の合計に対して、３．０原子％以下とすることが好ましく、０．０５～３．０原子％とすることがより好ましく、０．０５～２．０原子％とすることがさらに好ましく、０．０８～１．０原子％とすることが特に好ましい。 The amount of W contained in the tungsten mixture is equal to the amount of tungsten contained in the compound in the obtained positive electrode active material. Therefore, the amount of W contained in the tungsten mixture is preferably 3.0 atomic% or less with respect to the total number of Ni, Co and M atoms contained in the lithium metal composite oxide powder to be mixed. It is more preferably from 05 to 3.0 atomic%, further preferably from 0.05 to 2.0 atomic%, particularly preferably from 0.08 to 1.0 atomic%.
　後工程の熱処理後にリチウム金属複合酸化物粉末を解砕する場合は、二次粒子表面上に形成されたＷおよびＬｉを含む化合物が剥離して、得られる正極活物質のタングステン含有量が減少することがある。このような場合は、減少分、すなわち、添加するタングステン量に対して５～２０原子％を見越してアルカリ溶液に溶解させるタングステン量を決めればよい。 When the lithium metal composite oxide powder is crushed after the heat treatment in the post-process, the compound containing W and Li formed on the surface of the secondary particles peels off, and the tungsten content of the obtained positive electrode active material decreases. Sometimes. In such a case, the amount of tungsten to be dissolved in the alkaline solution may be determined in anticipation of the decrease, that is, 5 to 20 atomic% with respect to the added amount of tungsten.
　第１工程では、前記固液比を２００～２５００ｇ／Ｌの範囲で制御するが、固液比が２００ｇ／Ｌ未満では、リチウム金属複合酸化物から溶出するＬｉ量が多くなり過ぎて得られる正極活物質を用いて得られる電池の特性が低下する。前記固液比が２５００ｇ／Ｌを超えると、アルカリ溶液（Ｗ）がタングステン混合物と均一に混合できなくなり、粒子内部の一次粒子表面にまでアルカリ溶液（Ｗ）が浸透されていない二次粒子が増加する。 In the first step, the solid-liquid ratio is controlled in the range of 200 to 2500 g / L. When the solid-liquid ratio is less than 200 g / L, the amount of Li eluted from the lithium metal composite oxide is excessively obtained. The characteristics of the battery obtained using the active material are deteriorated. When the solid-liquid ratio exceeds 2500 g / L, the alkaline solution (W) cannot be uniformly mixed with the tungsten mixture, and secondary particles that do not penetrate the alkaline solution (W) to the primary particle surface inside the particles increase. To do.
　また、アルカリ溶液（Ｗ）のＷ濃度を０．１～２ｍｏｌ／Ｌとするが、アルカリ溶液（Ｗ）のＷ濃度が０．１ｍｏｌ／Ｌ未満になると、タングステン混合物に含まれるＷ量が少なくなり、得られる正極活物質を用いた電池の特性が改善されない。さらに、固液分離後に残留する液量を増加させてタングステン混合物に含まれるＷ量を増加させても、タングステン混合物中に残留するアルカリ溶液（Ｗ）が遍在するため、リチウム金属複合酸化物粒子間で含有されるＷ量の変動が大きくなり、粒子内部の一次粒子表面にＬＷ化合物が形成されない二次粒子が増加する。アルカリ溶液（Ｗ）のＷ濃度が２ｍｏｌ／Ｌを超えると、タングステン混合物に含まれるＷ量が多くなり過ぎて、得られる正極活物質を用いた電池の特性が低下する。 Further, the W concentration of the alkaline solution (W) is 0.1 to 2 mol / L. However, when the W concentration of the alkaline solution (W) is less than 0.1 mol / L, the amount of W contained in the tungsten mixture decreases. The characteristics of the battery using the positive electrode active material obtained are not improved. Further, even if the amount of W remaining in the tungsten mixture is increased by increasing the amount of liquid remaining after the solid-liquid separation, the alkaline solution (W) remaining in the tungsten mixture is ubiquitous, so the lithium metal composite oxide particles The amount of W contained between the particles increases, and secondary particles in which no LW compound is formed on the surface of the primary particles inside the particles increase. When the W concentration of the alkaline solution (W) exceeds 2 mol / L, the amount of W contained in the tungsten mixture increases so that the characteristics of the battery using the obtained positive electrode active material deteriorate.
　第１工程では、まず、タングステン化合物をアルカリ溶液に溶解するが、その溶解方法は、通常の粉末の溶解方法でよく、例えば、撹拌装置付の反応槽を用いて溶液を撹拌しながらタングステン化合物を添加して溶解すればよい。タングステン化合物は、アルカリ溶液に完全に溶解させることが、分散の均一性から好ましい。
　このタングステン化合物は、アルカリ溶液に溶解可能なものであればよく、酸化タングステン、タングステン酸リチウム、タングステン酸アンモニウムなど、アルカリに対して易溶性のタングステン化合物を用いることが好ましい。 In the first step, the tungsten compound is first dissolved in an alkali solution. The dissolution method may be a normal powder dissolution method. For example, the tungsten compound is stirred while the solution is stirred using a reaction vessel equipped with a stirrer. What is necessary is just to add and melt | dissolve. It is preferable from the uniformity of dispersion that the tungsten compound is completely dissolved in an alkaline solution.
The tungsten compound is not particularly limited as long as it can be dissolved in an alkali solution, and it is preferable to use a tungsten compound that is easily soluble in alkali, such as tungsten oxide, lithium tungstate, and ammonium tungstate.
　アルカリ溶液（Ｗ）に用いるアルカリとしては、高い充放電容量を得るため、正極活物質にとって有害な不純物を含まない一般的なアルカリ溶液を用いる。不純物混入の虞がないアンモニア、水酸化リチウムを用いることができるが、Ｌｉのインターカレーションを阻害しない観点から水酸化リチウムを用いることが好ましい。
　水酸化リチウムを用いる場合には、混合後の上記正極活物質に含有されるリチウム量が、上記一般式のＬｉ／Ｍｅの範囲内とする必要があるが、水酸化リチウム量をＷに対して原子比で３．５～１０．０とすることが好ましく、３．５以上、４．５未満とすることがより好ましい。Ｌｉはリチウム金属複合酸化物から溶出して供給されるが、この範囲の水酸化リチウムを用いることで、ＬＷ化合物を形成させるのに十分な量のＬｉを供給することができる。 As the alkali used for the alkaline solution (W), in order to obtain a high charge / discharge capacity, a general alkaline solution that does not contain impurities harmful to the positive electrode active material is used. Ammonia and lithium hydroxide, which are free of impurities, can be used, but lithium hydroxide is preferably used from the viewpoint of not inhibiting Li intercalation.
When lithium hydroxide is used, the amount of lithium contained in the positive electrode active material after mixing must be within the range of Li / Me in the above general formula. The atomic ratio is preferably 3.5 to 10.0, more preferably 3.5 or more and less than 4.5. Li is eluted and supplied from the lithium metal composite oxide. By using lithium hydroxide in this range, an amount of Li sufficient to form an LW compound can be supplied.
　また、アルカリ溶液（Ｗ）は水溶液であることが好ましい。
　Ｗを一次粒子表面全体に分散させるためには、二次粒子内部の空隙および不完全な粒界にも浸透させる必要があり、二次粒子内にも十分に浸透可能な溶媒であればよいが、揮発性が高いアルコールなどの溶媒を用いると、揮発によるロスも多く、コスト的に望ましくない。また、二次粒子や一次粒子表面に存在する不純物は水溶性のものが多く、不純物を除去して正極活物質の特性を向上させる観点からも、水溶液を用いることが好ましい。 The alkaline solution (W) is preferably an aqueous solution.
In order to disperse W over the entire surface of the primary particles, it is necessary to penetrate the voids and imperfect grain boundaries inside the secondary particles, and any solvent that can sufficiently penetrate into the secondary particles may be used. If a solvent such as alcohol having high volatility is used, there are many losses due to volatilization, which is undesirable in terms of cost. In addition, many impurities present on the secondary particles and the surface of the primary particles are water-soluble, and it is preferable to use an aqueous solution from the viewpoint of removing the impurities and improving the characteristics of the positive electrode active material.
　アルカリ溶液のｐＨは、タングステン化合物が溶解するｐＨであればよいが、９～１２であることが好ましい。ｐＨが９未満の場合には、リチウム金属複合酸化物からのリチウム溶出量が多くなり過ぎて電池特性が劣化する虞がある。また、ｐＨが１２を超えると、リチウム金属複合酸化物に残留する過剰なアルカリが多くなり過ぎて電池特性が劣化する虞がある。 The pH of the alkaline solution may be any pH at which the tungsten compound dissolves, but is preferably 9-12. When the pH is less than 9, the amount of lithium eluted from the lithium metal composite oxide becomes too large, and the battery characteristics may be deteriorated. Moreover, when pH exceeds 12, there exists a possibility that the excessive alkali which remains in lithium metal complex oxide may increase too much, and a battery characteristic may deteriorate.
　本発明の製造方法においては、得られる正極活物質の芯材となるリチウム金属複合酸化物粒子は、母材とするリチウム金属複合酸化物、すなわちアルカリ溶液（Ｗ）と混合するリチウム金属複合酸化物粉末からアルカリ溶液（Ｗ）中にリチウム分が溶出するため、母材のリチウム金属複合酸化物は、高容量と低反応抵抗の観点より、公知であるその組成が一般式ＬｉｚＮｉ１－ｘ－ｙＣｏｘＭｙＯ２（ただし、０≦ｘ≦０．３５、０≦ｙ≦０．３５、０．９５≦ｚ≦１．３０、Ｍは、Ｍｎ、Ｖ、Ｍｇ、Ｍｏ、Ｎｂ、ＴｉおよびＡｌから選ばれる少なくとも１種の元素）で表されるリチウム金属複合酸化物が用いられる。
　すなわち、母材のＬｉ／Ｍｅであるｚを０．９５≦ｚ≦１．３０、好ましくは０．９７≦ｚ≦１．２５、より好ましくは０．９７≦ｚ≦１．２０、さらに好ましくはより好ましくは０．９７≦ｚ≦１．１５とすることで、洗浄後においても芯材となるリチウム金属複合酸化物粒子中のリチウム量を適正な量に制御して高い電池容量と低反応抵抗を可能とすることができる。
　また、電解液との接触面積を多くすることが、出力特性の向上に有利であることから、一次粒子および一次粒子が凝集して形成された二次粒子から構成され、二次粒子に電解液の浸透可能な空隙および粒界を有するリチウム金属複合酸化物粉末を用いることが好ましい。 In the production method of the present invention, the lithium metal composite oxide particles used as the core material of the obtained positive electrode active material are lithium metal composite oxide as a base material, that is, lithium metal composite oxide mixed with an alkaline solution (W). Since the lithium content is eluted from the powder into the alkaline solution (W), the lithium metal composite oxide as a base material has a known composition of the general formula Li z Ni 1-x from the viewpoint of high capacity and low reaction resistance. -y Co x M y O 2 (however, 0 ≦ x ≦ 0.35,0 ≦ y ≦ 0.35,0.95 ≦ z ≦ 1.30, M is, Mn, V, Mg, Mo , Nb, Lithium metal composite oxide represented by at least one element selected from Ti and Al is used.
That is, z which is Li / Me of the base material is 0.95 ≦ z ≦ 1.30, preferably 0.97 ≦ z ≦ 1.25, more preferably 0.97 ≦ z ≦ 1.20, and still more preferably. More preferably, by setting 0.97 ≦ z ≦ 1.15, a high battery capacity and low reaction resistance can be achieved by controlling the amount of lithium in the lithium metal composite oxide particles as the core material after cleaning to an appropriate amount. Can be made possible.
In addition, increasing the contact area with the electrolytic solution is advantageous for improving the output characteristics, so that the primary particles and secondary particles formed by aggregation of the primary particles are formed. It is preferable to use a lithium metal composite oxide powder having voids and grain boundaries that can be penetrated.
　次に、調製したアルカリ溶液（Ｗ）を撹拌しながらリチウム金属複合酸化物粉末を添加して混合、浸漬する。タングステン化合物が易溶性であれば、リチウム金属複合酸化物粉末を水などの溶媒と混合してスラリー化した後、タングステン化合物を添加して溶解し浸漬してもよい。さらにアルカリ溶液（Ｗ）を循環させてリチウム金属複合酸化物粉末に供給して浸漬することもできる。 Next, while stirring the prepared alkaline solution (W), the lithium metal composite oxide powder is added, mixed and immersed. If the tungsten compound is easily soluble, the lithium metal composite oxide powder may be mixed with a solvent such as water to form a slurry, and then the tungsten compound may be added and dissolved and immersed. Further, the alkaline solution (W) can be circulated, supplied to the lithium metal composite oxide powder, and immersed.
　すなわち、リチウム金属複合酸化物粒子間にアルカリ溶液（Ｗ）を流通させて二次粒子内部まで浸透させることができればよい。
　その混合は、５０℃以下の温度で行うことが好ましい。５０℃以下の温度で混合することで、リチウム金属複合酸化物粒子からの過剰なＬｉの溶出を抑制することができる。 That is, it suffices if the alkaline solution (W) can be circulated between the lithium metal composite oxide particles to penetrate into the secondary particles.
The mixing is preferably performed at a temperature of 50 ° C. or lower. By mixing at a temperature of 50 ° C. or lower, excessive Li elution from the lithium metal composite oxide particles can be suppressed.
　リチウム金属複合酸化物粉末とアルカリ溶液（Ｗ）の混合は、二次粒子内までアルカリ溶液（Ｗ）を浸透させればよく、スラリー状の場合は撹拌反応槽などを用いることができる。
　また、固液比が高く撹拌反応槽では混合が十分でない場合は、例えばシェーカーミキサーやレーディゲミキサー、ジュリアミキサー、Ｖブレンダーなどの混合機を用いてリチウム金属複合酸化物粉末の形骸が破壊されない程度でアルカリ溶液（Ｗ）と十分に混合してやればよい。これにより、アルカリ溶液（Ｗ）中のＷを、リチウム金属複合酸化物の一次粒子表面に均一に分布させることができる。 Mixing of the lithium metal composite oxide powder and the alkali solution (W) may be performed by infiltrating the alkali solution (W) into the secondary particles. In the case of a slurry, a stirred reaction vessel or the like can be used.
In addition, when the mixing ratio is high in a stirred reaction tank where the solid-liquid ratio is high, the shape of the lithium metal composite oxide powder is not destroyed by using a mixer such as a shaker mixer, a Laedige mixer, a Julia mixer, or a V blender. What is necessary is just to fully mix with an alkali solution (W) to the extent. Thereby, W in the alkaline solution (W) can be uniformly distributed on the primary particle surface of the lithium metal composite oxide.
　アルカリ溶液（Ｗ）を浸漬させた後、固液分離してタングステン混合物を得る。固液分離は、通常用いられる装置でよく、吸引濾過機、遠心機、フィルタープレスなどが用いられる。 After immersing the alkaline solution (W), solid-liquid separation is performed to obtain a tungsten mixture. Solid-liquid separation may be performed by a commonly used apparatus, such as a suction filter, a centrifuge, or a filter press.
　本発明の製造方法においては、正極活物質の電池容量および安全性を向上させるために、第１工程の前に、さらに母材であるリチウム金属複合酸化物粉末を水洗することができる。
　この水洗は、公知の方法および条件でよく、リチウム金属複合酸化物粉末から過度にリチウムが溶出して電池特性が劣化しない範囲で行えばよい。水洗した場合には、乾燥してからアルカリ溶液（Ｗ）と混合しても、固液分離のみで乾燥せずにアルカリ溶液（Ｗ）と混合しても、いずれの方法でもよい。 In the production method of the present invention, in order to improve the battery capacity and safety of the positive electrode active material, the lithium metal composite oxide powder as a base material can be further washed with water before the first step.
This washing with water may be performed by a known method and conditions as long as lithium is not excessively eluted from the lithium metal composite oxide powder and the battery characteristics are not deteriorated. In the case of washing with water, either a method of drying and mixing with the alkali solution (W) or a method of mixing with the alkali solution (W) without drying only by solid-liquid separation may be used.
　固液分離のみの場合は、アルカリ溶液（Ｗ）への浸漬後のタングステン濃度は、リチウム金属複合酸化物粉末に含まれる水分により薄められるため、予め固液分離後に残留する水分量を加味して浸漬させるアルカリ溶液（Ｗ）の濃度を計算すればよい。また、アルカリ溶液（Ｗ）を用いてリチウム金属複合酸化物粉末を水洗し、水洗とアルカリ溶液（Ｗ）への浸漬を同時に実施し、その後に固液分離することも可能である。 In the case of solid-liquid separation only, the tungsten concentration after immersion in the alkaline solution (W) is diluted by the water contained in the lithium metal composite oxide powder, so the amount of water remaining after solid-liquid separation is taken into account in advance. What is necessary is just to calculate the density | concentration of the alkaline solution (W) to immerse. It is also possible to wash the lithium metal composite oxide powder with an alkaline solution (W), perform water washing and immersion in the alkaline solution (W) at the same time, and then perform solid-liquid separation.
［第２工程］
　第２工程は、タングステン混合物を熱処理する工程である。これにより、アルカリ溶液（Ｗ）より供給されたＷとアルカリ溶液（Ｗ）、もしくはリチウム金属複合酸化物からのリチウムの溶出により供給されたＬｉから、ＬＷ化合物を形成し、リチウム金属複合酸化物の一次粒子表面に、ＬＷ化合物を有する非水系電解質二次電池用正極活物質が得られる。 [Second step]
The second step is a step of heat-treating the tungsten mixture. As a result, an LW compound is formed from W supplied from the alkaline solution (W) and Li supplied from the alkaline solution (W) or lithium elution from the lithium metal composite oxide. A positive electrode active material for a non-aqueous electrolyte secondary battery having an LW compound on the primary particle surface is obtained.
　その熱処理方法は特に限定されないが、非水系電解質二次電池用正極活物質として用いたときの電池特性の劣化を防止するため、酸素雰囲気あるいは真空雰囲気中で１００～６００℃の温度で熱処理することが好ましい。
　熱処理温度が１００℃未満では、水分の蒸発が十分ではなく、ＬＷ化合物が十分に形成されない場合がある。一方、熱処理温度が６００℃を超えると、リチウム金属複合酸化物粒子が焼結を起こすとともに一部のＷがリチウム金属複合酸化物の層状構造に固溶してしまうために、電池の充放電容量が低下することがある。 The heat treatment method is not particularly limited, but heat treatment is performed at a temperature of 100 to 600 ° C. in an oxygen atmosphere or a vacuum atmosphere in order to prevent deterioration of battery characteristics when used as a positive electrode active material for a non-aqueous electrolyte secondary battery. Is preferred.
When the heat treatment temperature is less than 100 ° C., the evaporation of moisture is not sufficient, and the LW compound may not be sufficiently formed. On the other hand, when the heat treatment temperature exceeds 600 ° C., the lithium metal composite oxide particles are sintered and a part of W is dissolved in the layered structure of the lithium metal composite oxide. May decrease.
　熱処理時の雰囲気は、雰囲気中の水分や炭酸との反応を避けるため、酸素雰囲気などのような酸化性雰囲気あるいは真空雰囲気とすることが好ましい。
　熱処理時間は、特に限定されないが、アルカリ溶液（Ｗ）の水分を十分に蒸発させて微粒子を形成するために５～１５時間とすることが好ましい。 The atmosphere during the heat treatment is preferably an oxidizing atmosphere such as an oxygen atmosphere or a vacuum atmosphere in order to avoid a reaction with moisture or carbonic acid in the atmosphere.
The heat treatment time is not particularly limited, but is preferably 5 to 15 hours in order to sufficiently evaporate the water in the alkaline solution (W) to form fine particles.
（３）非水系電解質二次電池
　本発明の非水系電解質二次電池は、正極、負極および非水系電解液などからなり、一般の非水系電解質二次電池と同様の構成要素により構成される。
　なお、以下で説明する実施形態は例示に過ぎず、本発明の非水系電解質二次電池は、本明細書に記載されている実施形態を基に、当業者の知識に基づいて種々の変更、改良を施した形態で実施することができる。また、本発明の非水系電解質二次電池は、その用途を特に限定するものではない。 (3) Non-aqueous electrolyte secondary battery The non-aqueous electrolyte secondary battery of the present invention includes a positive electrode, a negative electrode, a non-aqueous electrolyte solution, and the like, and includes the same components as those of a general non-aqueous electrolyte secondary battery.
The embodiment described below is merely an example, and the nonaqueous electrolyte secondary battery of the present invention can be variously modified based on the knowledge of those skilled in the art based on the embodiment described in the present specification. It can be implemented in an improved form. Moreover, the use of the nonaqueous electrolyte secondary battery of the present invention is not particularly limited.
（ａ）正極
　先に述べた非水系電解質二次電池用正極活物質を用いて、例えば、以下のようにして、非水系電解質二次電池の正極を作製する。
　まず、粉末状の正極活物質、導電材、結着剤を混合し、さらに必要に応じて活性炭、粘度調整等の目的の溶剤を添加し、これを混練して正極合材ペーストを作製する。 (A) Positive electrode Using the positive electrode active material for a non-aqueous electrolyte secondary battery described above, for example, a positive electrode of a non-aqueous electrolyte secondary battery is produced as follows.
First, a powdered positive electrode active material, a conductive material, and a binder are mixed, and, if necessary, a target solvent such as activated carbon and viscosity adjustment is added and kneaded to prepare a positive electrode mixture paste.
　その正極合材ペースト中のそれぞれの混合比も、非水系電解質二次電池の性能を決定する重要な要素となる。溶剤を除いた正極合材の固形分の全質量を１００質量部とした場合、一般の非水系電解質二次電池の正極と同様、正極活物質の含有量を６０～９５質量部とし、導電材の含有量を１～２０質量部とし、結着剤の含有量を１～２０質量部とすることが望ましい。 Each mixing ratio in the positive electrode mixture paste is also an important factor for determining the performance of the non-aqueous electrolyte secondary battery. When the total mass of 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 to 95 parts by mass in the same manner as the positive electrode of a general non-aqueous electrolyte secondary battery, and the conductive material The content of is desirably 1 to 20 parts by mass, and the content of the binder is desirably 1 to 20 parts by mass.
　得られた正極合材ペーストを、例えば、アルミニウム箔製の集電体の表面に塗布し、乾燥して、溶剤を飛散させる。必要に応じ、電極密度を高めるべく、ロールプレス等により加圧することもある。このようにして、シート状の正極を作製することができる。シート状の正極は、目的とする電池に応じて適当な大きさに裁断等をして、電池の作製に供することができる。ただし、正極の作製方法は、例示のものに限られることなく、他の方法によってもよい。 The obtained positive electrode mixture paste is applied to, for example, the surface of a current collector made of aluminum foil, and dried to disperse the solvent. If necessary, pressurization may be performed by a roll press or the like to increase the electrode density. In this way, a sheet-like positive electrode can be produced. The sheet-like positive electrode can be cut into an appropriate size or the like according to the target battery and used for battery production. However, the method for manufacturing the positive electrode is not limited to the illustrated one, and other methods may be used.
　正極の作製にあたって、導電剤としては、例えば、黒鉛（天然黒鉛、人造黒鉛、膨張黒鉛など）や、アセチレンブラック、ケッチェンブラック（登録商標）などのカーボンブラック系材料などを用いることができる。 In producing the positive electrode, as the conductive agent, for example, graphite (natural graphite, artificial graphite, expanded graphite, etc.), carbon black materials such as acetylene black, ketjen black (registered trademark), and the like can be used.
　結着剤は、活物質粒子をつなぎ止める役割を果たすもので、例えば、ポリフッ化ビニリデン（ＰＶＤＦ）、ポリテトラフルオロエチレン（ＰＴＦＥ）、フッ素ゴム、エチレンプロピレンジエンゴム、スチレンブタジエン、セルロース系樹脂、ポリアクリル酸などを用いることができる。
　なお、必要に応じ、正極活物質、導電材、活性炭を分散させ、結着剤を溶解する溶剤を正極合材に添加する。溶剤としては、具体的には、Ｎ－メチル－２－ピロリドン等の有機溶剤を用いることができる。また、正極合材には、電気二重層容量を増加させるために、活性炭を添加することができる。 The binder plays a role of anchoring the active material particles. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluorine rubber, ethylene propylene diene rubber, styrene butadiene, cellulosic resin, polyacrylic. An acid or the like can be used.
If necessary, a positive electrode active material, a conductive material, and activated carbon are dispersed, and a solvent that dissolves the binder is added to the positive electrode mixture. Specifically, an organic solvent such as N-methyl-2-pyrrolidone can be used as the solvent. Activated carbon can be added to the positive electrode mixture in order to increase the electric double layer capacity.
（ｂ）負極
　負極には、金属リチウムやリチウム合金等、あるいは、リチウムイオンを吸蔵および脱離できる負極活物質に、結着剤を混合し、適当な溶剤を加えてペースト状にした負極合材を、銅等の金属箔集電体の表面に塗布し、乾燥し、必要に応じて電極密度を高めるべく圧縮して形成したものを使用する。 (B) Negative electrode A negative electrode mixture in which a negative electrode active material capable of occluding and desorbing lithium ions is mixed with a binder and an appropriate solvent is added to the negative electrode. Is applied to the surface of a metal foil current collector such as copper, dried, and compressed to increase the electrode density as necessary.
　負極活物質としては、例えば、天然黒鉛、人造黒鉛、フェノール樹脂等の有機化合物焼成体、コークス等の炭素物質の粉状体を用いることができる。この場合、負極結着剤としては、正極同様、ＰＶＤＦ等の含フッ素樹脂等を用いることができ、これらの活物質および結着剤を分散させる溶剤としては、Ｎ－メチル－２－ピロリドン等の有機溶剤を用いることができる。 As the negative electrode active material, for example, natural graphite, artificial graphite, a fired organic compound such as phenol resin, and a powdery carbon material such as coke can be used. In this case, a fluorine-containing resin such as PVDF can be used as the negative electrode binder, as in the case of the positive electrode, and a solvent for dispersing these active materials and the binder can be N-methyl-2-pyrrolidone or the like. Organic solvents can be used.
（ｃ）セパレータ
　正極と負極との間には、セパレータを挟み込んで配置する。セパレータは、正極と負極とを分離し、電解質を保持するものであり、ポリエチレン、ポリプロピレン等の薄い膜で、微少な孔を多数有する膜を用いることができる。 (C) Separator A separator is interposed between the positive electrode and the negative electrode. The separator separates the positive electrode and the negative electrode and retains the electrolyte, and a thin film such as polyethylene or polypropylene and a film having many minute holes can be used.
（ｄ）非水系電解液
　非水系電解液は、支持塩としてのリチウム塩を有機溶媒に溶解したものである。
　有機溶媒としては、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、トリフルオロプロピレンカーボネート等の環状カーボネート、また、ジエチルカーボネート、ジメチルカーボネート、エチルメチルカーボネート、ジプロピルカーボネート等の鎖状カーボネート、さらに、テトラヒドロフラン、２－メチルテトラヒドロフラン、ジメトキシエタン等のエーテル化合物、エチルメチルスルホン、ブタンスルトン等の硫黄化合物、リン酸トリエチル、リン酸トリオクチル等のリン化合物等から選ばれる１種を単独で、あるいは２種以上を混合して用いることができる。 (D) Non-aqueous electrolyte The non-aqueous electrolyte is obtained by dissolving a lithium salt as a supporting salt in an organic solvent.
Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and trifluoropropylene carbonate, chain carbonates such as diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, and dipropyl carbonate, tetrahydrofuran, 2- One kind selected from ether compounds such as methyltetrahydrofuran and dimethoxyethane, sulfur compounds such as ethylmethylsulfone and butanesultone, phosphorus compounds such as triethyl phosphate and trioctyl phosphate, etc. are used alone or in admixture of two or more. be able to.
　支持塩としては、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣｌＯ４、ＬｉＡｓＦ６、ＬｉＮ（ＣＦ３ＳＯ２）２等、およびそれらの複合塩を用いることができる。
　さらに、非水系電解液は、ラジカル捕捉剤、界面活性剤および難燃剤等を含んでいてもよい。 As the supporting salt, LiPF 6 , LiBF 4 , LiClO 4 , LiAsF 6 , LiN (CF 3 SO 2 ) 2 , or a composite salt thereof can be used.
Furthermore, the non-aqueous electrolyte solution may contain a radical scavenger, a surfactant, a flame retardant, and the like.
（ｅ）電池の形状、構成
　以上のように説明してきた正極、負極、セパレータおよび非水系電解液で構成される本発明の非水系電解質二次電池の形状は、円筒型、積層型等、種々のものとすることができる。
　いずれの形状を採る場合であっても、正極および負極を、セパレータを介して積層させて電極体とし、得られた電極体に、非水系電解液を含浸させ、正極集電体と外部に通ずる正極端子との間、および、負極集電体と外部に通ずる負極端子との間を、集電用リード等を用いて接続し、電池ケースに密閉して、非水系電解質二次電池を完成させる。 (E) Battery shape and configuration The shape of the non-aqueous electrolyte secondary battery of the present invention composed of the positive electrode, negative electrode, separator and non-aqueous electrolyte described above can be various, such as a cylindrical type and a laminated type. Can be.
In any case, the positive electrode and the negative electrode are laminated via a separator to form an electrode body, and the obtained electrode body is impregnated with a non-aqueous electrolyte and communicated with the positive electrode current collector and the outside. The positive electrode terminal and the negative electrode current collector and the negative electrode terminal communicating with the outside are connected using a current collecting lead or the like and sealed in a battery case to complete a non-aqueous electrolyte secondary battery. .
（ｆ）特性
　本発明の正極活物質を用いた非水系電解質二次電池は、高容量で高出力となる。
　特により好ましい形態で得られた本発明による正極活物質を用いた非水系電解質二次電池は、例えば、２０３２型コイン電池の正極に用いた場合、１６５ｍＡｈ／ｇ以上の高い初期放電容量と低い正極抵抗が得られ、さらに高容量で高出力である。また、熱安定性が高く、安全性においても優れているといえる。 (F) Characteristics The nonaqueous electrolyte secondary battery using the positive electrode active material of the present invention has a high capacity and a high output.
The non-aqueous electrolyte secondary battery using the positive electrode active material according to the present invention obtained in a particularly preferred form is, for example, a high initial discharge capacity of 165 mAh / g or more and a low positive electrode when used for the positive electrode of a 2032 type coin battery. Resistance is obtained, and further, high capacity and high output. Moreover, it can be said that it has high thermal stability and is excellent in safety.
　なお、本発明における正極抵抗の測定方法を例示すれば、次のようになる。電気化学的評価手法として一般的な交流インピーダンス法にて電池反応の周波数依存性について測定を行うと、溶液抵抗、負極抵抗と負極容量、および正極抵抗と正極容量に基づくナイキスト線図が図１のように得られる。 An example of the method for measuring the positive electrode resistance in the present invention is as follows. When the frequency dependence of the battery reaction is measured by a general AC impedance method as an electrochemical evaluation method, the Nyquist diagram based on the solution resistance, the negative electrode resistance and the negative electrode capacity, and the positive electrode resistance and the positive electrode capacity is shown in FIG. Is obtained as follows.
　電極における電池反応は、電荷移動に伴う抵抗成分と電気二重層による容量成分とからなり、これらを電気回路で表すと抵抗と容量の並列回路となり、電池全体としては溶液抵抗と負極、正極の並列回路を直列に接続した等価回路で表される。
　この等価回路を用いて測定したナイキスト線図に対してフィッティング計算を行い、各抵抗成分、容量成分を見積もることができる。正極抵抗は、得られるナイキスト線図の低周波数側の半円の直径と等しい。 The battery reaction at the electrode consists of a resistance component accompanying the charge transfer and a capacity component due to the electric double layer. When these are expressed as an electric circuit, it becomes a parallel circuit of resistance and capacity. It is represented by an equivalent circuit in which circuits are connected in series.
Fitting calculation is performed on the Nyquist diagram measured using this equivalent circuit, and each resistance component and capacitance component can be estimated. The positive electrode resistance is equal to the diameter of the semicircle on the low frequency side of the obtained Nyquist diagram.
　以上のことから、作製される正極について、交流インピーダンス測定を行い、得られたナイキスト線図に対し等価回路でフィッティング計算することで、正極抵抗を見積もることができる。 From the above, the positive electrode resistance can be estimated by performing AC impedance measurement on the manufactured positive electrode and performing fitting calculation with the equivalent circuit on the obtained Nyquist diagram.
　本発明により得られた正極活物質を用いた正極を有する二次電池について、その性能（初期放電容量、正極抵抗）を測定した。
　以下、本発明の実施例を用いて具体的に説明するが、本発明は、これらの実施例によって何ら限定されるものではない。 About the secondary battery which has a positive electrode using the positive electrode active material obtained by this invention, the performance (initial stage discharge capacity, positive electrode resistance) was measured.
Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
（電池の製造および評価）
　正極活物質の評価には、図３に示す２０３２型コイン電池１（以下、コイン型電池と称す）を使用した。
　図３に示すように、コイン型電池１は、ケース２と、このケース２内に収容された電極３とから構成されている。 (Battery manufacture and evaluation)
For the evaluation of the positive electrode active material, a 2032 type coin battery 1 (hereinafter referred to as a coin type battery) shown in FIG. 3 was used.
As shown in FIG. 3, the coin battery 1 includes a case 2 and an electrode 3 accommodated in the case 2.
　ケース２は、中空かつ一端が開口された正極缶２ａと、この正極缶２ａの開口部に配置される負極缶２ｂとを有しており、負極缶２ｂを正極缶２ａの開口部に配置すると、負極缶２ｂと正極缶２ａとの間に電極３を収容する空間が形成されるように構成されている。
　電極３は、正極３ａ、セパレータ３ｃおよび負極３ｂとからなり、この順で並ぶように積層されており、正極３ａが正極缶２ａの内面に接触し、負極３ｂが負極缶２ｂの内面に接触するようにケース２に収容されている。 The case 2 has a positive electrode can 2a that is hollow and open at one end, and a negative electrode can 2b that is disposed in the opening of the positive electrode can 2a. When the negative electrode can 2b is disposed in the opening of the positive electrode can 2a, A space for accommodating the electrode 3 is formed between the negative electrode can 2b and the positive electrode can 2a.
The electrode 3 includes a positive electrode 3a, a separator 3c, and a negative electrode 3b, which are stacked in this order. The positive electrode 3a contacts the inner surface of the positive electrode can 2a, and the negative electrode 3b contacts the inner surface of the negative electrode can 2b. As shown in FIG.
　なお、ケース２はガスケット２ｃを備えており、このガスケット２ｃによって、正極缶２ａと負極缶２ｂとの間が非接触の状態を維持するように相対的な移動が固定されている。また、ガスケット２ｃは、正極缶２ａと負極缶２ｂとの隙間を密封してケース２内と外部との間を気密液密に遮断する機能も有している。 The case 2 includes a gasket 2c, and relative movement is fixed by the gasket 2c so as to maintain a non-contact state between the positive electrode can 2a and the negative electrode can 2b. Further, the gasket 2c also has a function of sealing a gap between the positive electrode can 2a and the negative electrode can 2b to block the inside and outside of the case 2 in an airtight and liquid tight manner.
　この図３に示すコイン型電池１は、以下のようにして製作した。
　まず、非水系電解質二次電池用正極活物質５２．５ｍｇ、アセチレンブラック１５ｍｇ、およびポリテトラフッ化エチレン樹脂（ＰＴＦＥ）７．５ｍｇを混合し、１００ＭＰａの圧力で直径１１ｍｍ、厚さ１００μｍにプレス成形して、正極３ａを作製した。作製した正極３ａを真空乾燥機中１２０℃で１２時間乾燥した。
　この正極３ａと、負極３ｂ、セパレータ３ｃおよび電解液とを用いて、上述したコイン型電池１を、露点が－８０℃に管理されたＡｒ雰囲気のグローブボックス内で作製した。 The coin battery 1 shown in FIG. 3 was manufactured as follows.
First, 52.5 mg of a positive electrode active material for a non-aqueous electrolyte secondary battery, 15 mg of acetylene black, and 7.5 mg of polytetrafluoroethylene resin (PTFE) are mixed, and press-molded to a diameter of 11 mm and a thickness of 100 μm at a pressure of 100 MPa. A positive electrode 3a was produced. The produced positive electrode 3a was dried at 120 ° C. for 12 hours in a vacuum dryer.
Using the positive electrode 3a, the negative electrode 3b, the separator 3c, and the electrolytic solution, the above-described coin-type battery 1 was produced in a glove box in an Ar atmosphere in which the dew point was controlled at −80 ° C.
　なお、負極３ｂには、直径１４ｍｍの円盤状に打ち抜かれた平均粒径２０μｍ程度の黒鉛粉末とポリフッ化ビニリデンが銅箔に塗布された負極シートを用いた。
　セパレータ３ｃには膜厚２５μｍのポリエチレン多孔膜を用いた。電解液には、１ＭのＬｉＣｌＯ４を支持電解質とするエチレンカーボネート（ＥＣ）とジエチルカーボネート（ＤＥＣ）の等量混合液（富山薬品工業株式会社製）を用いた。 As the negative electrode 3b, a negative electrode sheet in which graphite powder having an average particle diameter of about 20 μm punched into a disk shape with a diameter of 14 mm and polyvinylidene fluoride were applied to a copper foil was used.
As the separator 3c, a polyethylene porous film having a film thickness of 25 μm was used. As the electrolytic solution, an equivalent mixed solution (manufactured by Toyama Pharmaceutical Co., Ltd.) of ethylene carbonate (EC) and diethyl carbonate (DEC) using 1M LiClO 4 as a supporting electrolyte was used.
　製造したコイン型電池１の性能を示す初期放電容量、正極抵抗は、以下のように評価した。
　電池容量は初期放電容量により評価した。初期放電容量の測定は、コイン型電池１を製作してから２４時間程度放置し、開回路電圧ＯＣＶ（Ｏｐｅｎ Ｃｉｒｃｕｉｔ Ｖｏｌｔａｇｅ）が安定した後、正極に対する電流密度を０．１ｍＡ／ｃｍ２としてカットオフ電圧４．３Ｖまで充電し、１時間の休止後、カットオフ電圧３．０Ｖまで放電したときの容量を初期放電容量とした。 The initial discharge capacity and positive electrode resistance showing the performance of the manufactured coin battery 1 were evaluated as follows.
The battery capacity was evaluated based on the initial discharge capacity. The initial discharge capacity is measured by allowing the coin-type battery 1 to stand for about 24 hours, and after the open circuit voltage OCV (Open Circuit Voltage) is stabilized, the current density with respect to the positive electrode is cut off at 0.1 mA / cm 2. The capacity when the battery was charged to a voltage of 4.3 V and discharged to a cut-off voltage of 3.0 V after a pause of 1 hour was defined as the initial discharge capacity.
　また、正極抵抗は、コイン型電池１を充電電位４．１Ｖで充電して、周波数応答アナライザおよびポテンショガルバノスタット（ソーラトロン製、１２５５Ｂ）を使用して交流インピーダンス法により測定すると、図１に示すナイキストプロットが得られる。
　このナイキストプロットは、溶液抵抗、負極抵抗とその容量、および、正極抵抗とその容量を示す特性曲線の和として表しているため、このナイキストプロットに基づき等価回路を用いてフィッティング計算を行い、正極抵抗の値を算出した。 In addition, the positive electrode resistance is determined by charging the coin-type battery 1 at a charging potential of 4.1 V and measuring it by an alternating current impedance method using a frequency response analyzer and a potentiogalvanostat (manufactured by Solartron, 1255B). A plot is obtained.
Since this Nyquist plot is represented as the sum of the solution resistance, the negative electrode resistance and its capacity, and the characteristic curve indicating the positive electrode resistance and its capacity, the fitting calculation was performed using an equivalent circuit based on this Nyquist plot, and the positive resistance The value of was calculated.
　なお、本実施例では、複合酸化物製造、正極活物質および二次電池の作製には、和光純薬工業株式会社製試薬特級の各試料を使用した。 In this example, each sample of the reagent special grade manufactured by Wako Pure Chemical Industries, Ltd. was used for producing the composite oxide, producing the positive electrode active material, and the secondary battery.
　Ｎｉを主成分とする酸化物粉末と水酸化リチウムを混合して焼成する公知技術で得られたＬｉ１．０３０Ｎｉ０．８２Ｃｏ０．１５Ａｌ０．０３Ｏ２で表されるリチウム金属複合酸化物粉末を母材とした。
　このリチウム金属複合酸化物粉末の平均粒径は１２．４μｍであり、比表面積は０．３ｍ２／ｇであった。なお、平均粒径はレーザー回折散乱法における体積積算平均値を用い、比表面積は窒素ガス吸着によるＢＥＴ法を用いて評価した。 A lithium metal composite represented by Li 1.030 Ni 0.82 Co 0.15 Al 0.03 O 2 obtained by a known technique of mixing and baking oxide powder containing Ni as a main component and lithium hydroxide Oxide powder was used as a base material.
This lithium metal composite oxide powder had an average particle size of 12.4 μm and a specific surface area of 0.3 m 2 / g. In addition, the average particle diameter was evaluated using the volume integrated average value in the laser diffraction scattering method, and the specific surface area was evaluated using the BET method based on nitrogen gas adsorption.
　１００ｍｌの純水に５．６ｇの水酸化リチウム（ＬｉＯＨ）を溶解した水溶液中に、１５．６ｇの酸化タングステン（ＷＯ３）を添加して撹拌することにより、タングステンを含有したアルカリ溶液（Ｗ）を得た。 An alkaline solution (W) containing tungsten by adding 15.6 g of tungsten oxide (WO 3 ) to an aqueous solution in which 5.6 g of lithium hydroxide (LiOH) is dissolved in 100 ml of pure water and stirring. Got.
　次に、母材のリチウム金属複合酸化物粉末７５ｇを、作製したアルカリ溶液（Ｗ）に浸漬し、さらに攪拌することで十分に混合すると同時にリチウム金属複合酸化物粉末の水洗も実施した。その後、ヌッチェを用いたろ過により固液分離し、アルカリ溶液（Ｗ）とリチウム金属複合酸化物粉末から形成されたタングステン混合物を得た。 Next, 75 g of the lithium metal composite oxide powder as a base material was immersed in the prepared alkaline solution (W) and sufficiently mixed by stirring, and at the same time, the lithium metal composite oxide powder was washed with water. Thereafter, solid-liquid separation was performed by filtration using a Nutsche to obtain a tungsten mixture formed from the alkaline solution (W) and the lithium metal composite oxide powder.
　その得られた混合物を、ＳＵＳ製焼成容器に入れ、真空雰囲気中において、昇温速度２．８℃／分で２１０℃まで昇温して１３時間熱処理し、その後室温まで炉冷した。
　最後に目開き３８μｍの篩にかけ解砕することにより、一次粒子表面にＷおよびＬｉを含む化合物を有する正極活物質を作製した。 The obtained mixture was put into a SUS baking vessel, heated to 210 ° C. at a heating rate of 2.8 ° C./min in a vacuum atmosphere, heat-treated for 13 hours, and then cooled to room temperature.
Finally, a positive active material having a compound containing W and Li on the surface of primary particles was prepared by crushing through a sieve having an opening of 38 μm.
　得られた正極活物質のタングステン含有量およびＬｉ／ＭをＩＣＰ法により分析したところ、タングステン含有量はＮｉ、ＣｏおよびＭの原子数の合計に対して０．５原子％の組成であることが確認され、そのＬｉ／Ｍｅは０．９９４であった。 When the tungsten content and Li / M of the obtained positive electrode active material were analyzed by the ICP method, it was found that the tungsten content had a composition of 0.5 atomic% with respect to the total number of Ni, Co and M atoms. As a result, the Li / Me was 0.994.
　［ＬＷ化合物の形態分析］
　得られた正極活物質を、樹脂に埋め込み、クロスセクションポリッシャ加工を行ったものについて、倍率を５０００倍とした電界放射型走査電子顕微鏡（ＳＥＭ）による断面観察を行ったところ、一次粒子および一次粒子が凝集して形成された二次粒子から構成され、一次粒子表面にＬＷ化合物の微粒子が形成されていることを確認し、その観察した微粒子の粒子径は２０～１８０ｎｍであった。
　また、正極活物質を樹脂に埋め込んで断面加工した後、電界放射型走査電子顕微鏡を用いて任意の５０個以上の二次粒子の断面を５０００倍で観察したところ、二次粒子内部の一次粒子の表面にＬＷ化合物を有する二次粒子の観察した二次粒子数に対する割合(化合物存在率)は、９７％であった。
　さらに、得られた正極活物質の一次粒子の表面付近を透過型電子顕微鏡（ＴＥＭ）により観察したところ、一次粒子の表面に膜厚２～１０５ｎｍのタングステン酸リチウムの被覆が形成され、化合物はタングステン酸リチウムであることを確認した。 [Morphological analysis of LW compounds]
When the obtained positive electrode active material was embedded in a resin and subjected to cross section polishing, cross-sectional observation was performed with a field emission scanning electron microscope (SEM) with a magnification of 5000 times, primary particles and primary particles It was confirmed that fine particles of LW compound were formed on the surface of the primary particles, and the observed particle size of the fine particles was 20 to 180 nm.
Moreover, after embedding the positive electrode active material in a resin and processing the cross section, the cross section of any 50 or more secondary particles was observed at a magnification of 5000 using a field emission scanning electron microscope. The ratio (compound abundance) of the secondary particles having the LW compound on the surface to the observed number of secondary particles was 97%.
Further, when the vicinity of the surface of the primary particles of the obtained positive electrode active material was observed with a transmission electron microscope (TEM), a coating of lithium tungstate with a film thickness of 2 to 105 nm was formed on the surface of the primary particles, and the compound was tungsten. It was confirmed to be lithium acid lithium.
［電池評価］
　得られた正極活物質を使用して作製された正極を有する図３に示すコイン型電池１の電池特性を評価した。なお、正極抵抗は実施例１を１００とした相対値を評価値とした。初期放電容量は２０４．６ｍＡｈ／ｇであった。
　以下、実施例２～３および比較例１～２については、上記実施例１と変更した物質、条件のみを示す。また、実施例１～３および比較例１～２の初期放電容量および正極抵抗の評価値を表１に示す。 [Battery evaluation]
The battery characteristics of the coin-type battery 1 shown in FIG. 3 having a positive electrode produced using the obtained positive electrode active material were evaluated. In addition, the positive electrode resistance used the relative value which set Example 1 as 100 as the evaluation value. The initial discharge capacity was 204.6 mAh / g.
Hereinafter, for Examples 2 to 3 and Comparative Examples 1 and 2, only the substances and conditions changed from those of Example 1 are shown. Table 1 shows evaluation values of initial discharge capacities and positive electrode resistances of Examples 1 to 3 and Comparative Examples 1 and 2.
［余剰リチウム分析］
　得られた正極活物質中の余剰リチウムの存在状態について、正極活物質から溶出してくるＬｉを滴定することにより評価した。
　得られた正極活物質に純水を加えて一定時間攪拌後、ろ過したろ液のｐＨを測定しながら塩酸を加えていくことにより出現する中和点から溶出するリチウムの化合物状態を評価したところ、余剰リチウム量は、正極活物質の全量に対して０．０１８質量％であった。 [Surplus lithium analysis]
The presence state of excess lithium in the obtained positive electrode active material was evaluated by titrating Li eluted from the positive electrode active material.
After adding pure water to the obtained positive electrode active material and stirring for a certain period of time, when evaluating the compound state of lithium eluted from the neutralization point that appears by adding hydrochloric acid while measuring the pH of the filtered filtrate The excess lithium amount was 0.018% by mass relative to the total amount of the positive electrode active material.
　用いたＬｉＯＨを３．８ｇ、ＷＯ３を１０．５ｇとした以外は、実施例１と同様の条件にて、非水系電解質二次電池用正極活物質を得るとともに評価を行い、その結果を表１に示す。 A positive electrode active material for a non-aqueous electrolyte secondary battery was obtained and evaluated under the same conditions as in Example 1 except that the LiOH used was 3.8 g and the WO 3 was 10.5 g. It is shown in 1.
　用いたＬｉＯＨを７．０ｇ、ＷＯ３を１９．３ｇとした以外は、実施例１と同様の条件にて、非水系電解質二次電池用正極活物質を得るとともに評価を行い、その結果を表１に示す。 A positive electrode active material for a non-aqueous electrolyte secondary battery was obtained and evaluated under the same conditions as in Example 1 except that 7.0 g of LiOH and 19.3 g of WO 3 were used. It is shown in 1.
（比較例１）
　純水５ｍｌに０．６ｇのＬｉＯＨを溶解した水溶液中に、１．４ｇのＷＯ３を添加して攪拌することにより、タングステンを含有したアルカリ溶液（Ｗ）を得た。
　母材とするリチウム金属複合酸化物粉末７５ｇを純水１００ｍｌに浸漬して攪拌することで水洗を実施し、ヌッチェを用いてろ過する固液分離処理をした後に、作製したアルカリ溶液（Ｗ）を添加、混合した以外は、実施例１と同様の条件にして、非水系電解質二次電池用正極活物質を得るとともに評価を行い、その結果を表１に示す。
　純水１００ｍｌに浸漬した後に固液分離した状態で水分率は８．５質量％であり、アルカリ溶液（Ｗ）と混合した際の固液比は６５９０ｇ／Ｌとなった。 (Comparative Example 1)
1.4 g of WO 3 was added to an aqueous solution in which 0.6 g of LiOH was dissolved in 5 ml of pure water and stirred to obtain an alkali solution (W) containing tungsten.
75 g of lithium metal composite oxide powder used as a base material was immersed in 100 ml of pure water and stirred, washed with water and filtered using a Nutsche, and then the prepared alkaline solution (W) A positive electrode active material for a nonaqueous electrolyte secondary battery was obtained and evaluated under the same conditions as in Example 1 except for addition and mixing. Table 1 shows the results.
The moisture content was 8.5% by mass in the state of solid-liquid separation after immersion in 100 ml of pure water, and the solid-liquid ratio when mixed with the alkaline solution (W) was 6590 g / L.
（比較例２）
　比較例１と同様に純水で水洗を実施したが、アルカリ溶液（Ｗ）に浸漬しなかった以外は実施例１と同様にしてその評価を行った。
　その結果を表１に示す。 (Comparative Example 2)
Although it was washed with pure water in the same manner as in Comparative Example 1, the evaluation was performed in the same manner as in Example 1 except that it was not immersed in the alkaline solution (W).
The results are shown in Table 1.
（従来例）
　特許文献４に開示される実施例と同様の方法を用いて、硫酸ニッケルと硫酸コバルトとアルミン酸ナトリウムとを水中に溶解し、さらに十分に攪拌させながら水酸化ナトリウム溶液を加えて、ＮｉとＣｏとＡｌとのモル比がＮｉ：Ｃｏ：Ａｌ＝７７：２０：３となるようにして生成したニッケル－コバルト－アルミニウム複合共沈水酸化物の共沈物を水洗、乾燥させた後、水酸化リチウム一水和塩を加え、モル比がＬｉ：（Ｎｉ＋Ｃｏ＋Ａｌ）＝１０５：１００となるように調整して前駆体を作製した。
　次に、それらの前駆体を酸素気流中、７００℃で１０時間焼成し、室温まで冷却した後に粉砕して組成式Ｌｉ１．０３Ｎｉ０．７７Ｃｏ０．２０Ａｌ０．０３Ｏ２で表されるニッケル酸リチウムを主体とした複合酸化物粒子を作製した。 (Conventional example)
Using a method similar to the example disclosed in Patent Document 4, nickel sulfate, cobalt sulfate, and sodium aluminate are dissolved in water, and a sodium hydroxide solution is added to the mixture while stirring sufficiently. The nickel-cobalt-aluminum composite coprecipitated hydroxide coprecipitate formed so that the molar ratio of Al to Al was Ni: Co: Al = 77: 20: 3 was washed with water and dried, and then lithium hydroxide A precursor was prepared by adding a monohydrate salt and adjusting the molar ratio to be Li: (Ni + Co + Al) = 105: 100.
Next, these precursors were calcined at 700 ° C. for 10 hours in an oxygen stream, cooled to room temperature, and then pulverized to be represented by the composition formula Li 1.03 Ni 0.77 Co 0.20 Al 0.03 O 2 . Composite oxide particles mainly composed of lithium nickelate were prepared.
　この複合酸化物粒子１００重量部に、パラタングステン酸アンモニウム（（ＮＨ４）１０Ｗ１２Ｏ４１・５Ｈ２Ｏ）を１．６３２重量部を加え、乳鉢で十分混合した混合物を、酸素気流中、７００℃で４時間焼成して室温まで冷却した後、取り出して粉砕し、従来例の正極活物質を作製した。
　得られた正極活物質を使用して実施例１と同様にして評価した。その結果を表１に示す。なお従来例では、ＬＷ化合物の形態分析を行わなかった。 This composite oxide particles 100 parts by weight of ammonium paratungstate ((NH 4) 10 W 12 O 41 · 5H 2 O) and 1.632 parts by weight was added and the mixture was thoroughly mixed in a mortar, a stream of oxygen, After baking at 700 degreeC for 4 hours and cooling to room temperature, it took out and grind | pulverized and the positive electrode active material of the prior art example was produced.
Evaluation was performed in the same manner as in Example 1 using the obtained positive electrode active material. The results are shown in Table 1. In the conventional example, morphological analysis of the LW compound was not performed.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
［評価］
　表１から明らかなように、実施例１～３の複合酸化物粒子および正極活物質は、本発明に従って製造されたため、従来例に比べて初期放電容量が高く、正極抵抗も低いものとなっており、優れた特性を有する電池が得られるものである。特に、添加したタングステン量、アルカリ溶液のタングステン濃度を好ましい条件で実施した実施例１は、初期放電容量と正極抵抗がさら良好であり、非水系電解質二次電池用正極活物質として一層好適なものとなっている。 [Evaluation]
As is apparent from Table 1, since the composite oxide particles and the positive electrode active materials of Examples 1 to 3 were manufactured according to the present invention, the initial discharge capacity and the positive electrode resistance were lower than those of the conventional examples. Thus, a battery having excellent characteristics can be obtained. In particular, Example 1, which was carried out under the preferable conditions of the added tungsten amount and the tungsten concentration of the alkaline solution, had even better initial discharge capacity and positive electrode resistance, and was more suitable as a positive electrode active material for a nonaqueous electrolyte secondary battery. It has become.
　また、図２に示す本発明の実施例で得られた正極活物質の断面ＳＥＭ観察結果の一例からは、得られた正極活物質が一次粒子および一次粒子が凝集して構成された二次粒子からなり、その一次粒子表面にＬＷ化合物（黒矢印）を形成していることが確認される。
　なお、添加したタングステン量が少ない実施例２では、形成されたＬＷ化合物が過少となっている。このことから、その正極抵抗は実施例１より増加し、余剰Ｌｉも増加している。
　さらに、添加したタングステン量が多い実施例３では、形成されたＬＷ化合物が過多となっているため、その正極抵抗は実施例１より増加しているが、余剰Ｌｉは減少している。 Further, from the example of the cross-sectional SEM observation result of the positive electrode active material obtained in the example of the present invention shown in FIG. 2, the obtained positive electrode active material is composed of primary particles and secondary particles formed by agglomeration of primary particles. It is confirmed that an LW compound (black arrow) is formed on the primary particle surface.
In Example 2 with a small amount of added tungsten, the formed LW compound is too small. From this, the positive electrode resistance increases from Example 1, and the excess Li also increases.
Furthermore, in Example 3 with a large amount of added tungsten, since the formed LW compound is excessive, the positive electrode resistance is increased from that in Example 1, but the excess Li is decreased.
　一方、比較例１はリチウム金属複合酸化物粉末に含まれるＮｉ、ＣｏおよびＭの原子数に対するタングステンの量が、実施例１と同程度ではあるが、液を添加して混合する方法では均一に分散されず、タングステンおよびリチウムを含む化合物の形成に偏りが生じることで、その正極抵抗が実施例１より増加し、余剰Ｌｉについても増加している。
　また比較例２では、一次粒子表面に本発明に係るＬＷ化合物が形成されていないため、その正極抵抗が大幅に高くなり、高出力化の要求に対応することは困難である。 On the other hand, in Comparative Example 1, the amount of tungsten with respect to the number of Ni, Co, and M atoms contained in the lithium metal composite oxide powder is similar to that in Example 1, but the method of adding and mixing the solution uniformly The dispersion of the compound containing tungsten and lithium is not dispersed, and the positive electrode resistance is increased from that in Example 1, and the excess Li is also increased.
In Comparative Example 2, since the LW compound according to the present invention is not formed on the primary particle surfaces, the positive electrode resistance is significantly increased, and it is difficult to meet the demand for higher output.
　従来例は、固体のタングステン化合物と混合したため、タングステンの分散が十分でないことと化合物中へのリチウムの供給がないため、その正極抵抗が大幅に高い結果となっていた。
　以上の結果より、本発明の正極活物質を用いた非水系電解質二次電池は、初期放電容量が高く、正極抵抗も低いものとなり、優れた特性を有した電池となることが確認できる。 Since the conventional example was mixed with a solid tungsten compound, the dispersion of tungsten was not sufficient and there was no supply of lithium into the compound, resulting in a significantly high positive electrode resistance.
From the above results, it can be confirmed that the nonaqueous electrolyte secondary battery using the positive electrode active material of the present invention has a high initial discharge capacity and a low positive electrode resistance, and is a battery having excellent characteristics.
　本発明の非水系電解質二次電池は、常に高容量を要求される小型携帯電子機器（ノート型パーソナルコンピュータや携帯電話端末など）の電源に好適であり、高出力が要求される電気自動車用電池にも好適である。
　また、本発明の非水系電解質二次電池は、優れた安全性を有し、小型化、高出力化が可能であることから、搭載スペースに制約を受ける電気自動車用電源として好適である。なお、本発明は、純粋に電気エネルギーで駆動する電気自動車用の電源のみならず、ガソリンエンジンやディーゼルエンジンなどの燃焼機関と併用するいわゆるハイブリッド車用の電源としても用いることができる。 The non-aqueous electrolyte secondary battery of the present invention is suitable for a power source of a small portable electronic device (such as a notebook personal computer or a mobile phone terminal) that always requires a high capacity, and an electric vehicle battery that requires a high output. Also suitable.
In addition, the nonaqueous electrolyte secondary battery of the present invention has excellent safety, and can be downsized and increased in output, and thus is suitable as a power source for an electric vehicle subject to restrictions on mounting space. The present invention can be used not only as a power source for an electric vehicle driven purely by electric energy but also as a power source for a so-called hybrid vehicle used in combination with a combustion engine such as a gasoline engine or a diesel engine.
　１　　コイン型電池
　２　　ケース
　２ａ　正極缶
　２ｂ　負極缶
　２ｃ　ガスケット
　３　　電極
　３ａ　正極
　３ｂ　負極
　３ｃ　セパレータ
  DESCRIPTION OF SYMBOLS 1 Coin type battery 2 Case 2a Positive electrode can 2b Negative electrode can 2c Gasket 3 Electrode 3a Positive electrode 3b Negative electrode 3c Separator

Claims (14)

  1. 　一般式ＬｉｚＮｉ１－ｘ－ｙＣｏｘＭｙＯ２（ただし、０≦ｘ≦０．３５、０≦ｙ≦０．３５、０．９５≦ｚ≦１．３０、Ｍは、Ｍｎ、Ｖ、Ｍｇ、Ｍｏ、Ｎｂ、ＴｉおよびＡｌから選ばれる少なくとも１種の元素）で表される一次粒子および一次粒子が凝集して形成された二次粒子から構成された層状構造の結晶構造を有するリチウム金属複合酸化物粉末を、タングステン化合物を溶解させたタングステン濃度が０．１～２ｍｏｌ／Ｌのアルカリ溶液に、前記アルカリ溶液中の水分量に対するリチウム金属複合酸化物粉末の固液比が２００～２５００ｇ／Ｌの範囲で混合し、浸漬させた後に、固液分離することにより、前記リチウム金属複合酸化物の一次粒子表面にタングステンを均一に分散させたタングステン混合物を得る第１工程と、
    　前記タングステン混合物を、熱処理することによりタングステンおよびリチウムを含む化合物を、前記リチウム金属複合酸化物の一次粒子表面に形成する第２工程を有することを特徴とする非水系電解質二次電池用正極活物質の製造方法。     Formula Li z Ni 1-x-y Co x M y O 2 ( however, 0 ≦ x ≦ 0.35,0 ≦ y ≦ 0.35,0.95 ≦ z ≦ 1.30, M is, Mn, At least one element selected from V, Mg, Mo, Nb, Ti and Al), and a crystal structure of a layered structure composed of secondary particles formed by aggregation of primary particles Lithium metal composite oxide powder is dissolved in an alkaline solution having a tungsten concentration of 0.1 to 2 mol / L in which a tungsten compound is dissolved, and the solid-liquid ratio of the lithium metal composite oxide powder to the amount of water in the alkaline solution is 200 to First step of obtaining a tungsten mixture in which tungsten is uniformly dispersed on the primary particle surface of the lithium metal composite oxide by mixing and immersing in the range of 2500 g / L and then solid-liquid separation. When,
    A positive electrode active material for a non-aqueous electrolyte secondary battery comprising a second step of forming a compound containing tungsten and lithium on a primary particle surface of the lithium metal composite oxide by heat-treating the tungsten mixture. Manufacturing method.
  2. 　前記第１工程を実施する前に、前記リチウム金属複合酸化物粉末を水洗する水洗工程を有することを特徴とする請求項１に記載の非水系電解質二次電池用正極活物質の製造方法。 The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, further comprising a water washing step of washing the lithium metal composite oxide powder with water before performing the first step.
  3. 　前記タングステン混合物に含まれるタングステン量が、混合するリチウム金属複合酸化物粉末に含まれるＮｉ、ＣｏおよびＭの原子数の合計に対して、３．０原子％以下とすることを特徴とする請求項１又は２に記載の非水系電解質二次電池用正極活物質の製造方法。 The amount of tungsten contained in the tungsten mixture is 3.0 atomic% or less with respect to the total number of Ni, Co and M atoms contained in the lithium metal composite oxide powder to be mixed. The manufacturing method of the positive electrode active material for non-aqueous electrolyte secondary batteries of 1 or 2.
  4. 　前記タングステン化合物を溶解したアルカリ溶液中のタングステン濃度が、０．０５～２ｍｏｌ／Ｌであることを特徴とする請求項１～３のいずれか１項に記載の非水系電解質二次電池用正極活物質の製造方法。 The positive electrode active for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the tungsten concentration in the alkaline solution in which the tungsten compound is dissolved is 0.05 to 2 mol / L. A method for producing a substance.
  5. 　前記アルカリ溶液が、水酸化リチウム水溶液にタングステン化合物を溶解させたものであることを特徴とする請求項１～４のいずれか１項に記載の非水系電解質二次電池用正極活物質の製造方法。 The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the alkaline solution is obtained by dissolving a tungsten compound in an aqueous lithium hydroxide solution. .
  6. 　前記タングステン化合物を溶解させたアルカリ溶液とリチウム金属複合酸化物粉末との混合が、前記タングステン化合物を溶解したアルカリ溶液が液体で、かつ５０℃以下の温度で行うことを特徴とする請求項１～５のいずれか１項に記載の非水系電解質二次電池用正極活物質の製造方法。 2. The mixing of the alkaline solution in which the tungsten compound is dissolved and the lithium metal composite oxide powder is performed at a temperature of 50 ° C. or less, wherein the alkaline solution in which the tungsten compound is dissolved is liquid. 6. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 5.
  7. 　前記第２工程における熱処理が、酸素雰囲気あるいは真空雰囲気中において、１００～６００℃で行うことを特徴とする請求項１～６のいずれか１項に記載の非水系電解質二次電池用正極活物質の製造方法。 7. The positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1, wherein the heat treatment in the second step is performed at 100 to 600 ° C. in an oxygen atmosphere or a vacuum atmosphere. Manufacturing method.
  8. 　一次粒子および一次粒子が凝集して形成された二次粒子から構成され、層状構造の結晶構造を有し、一次粒子表面にタングステンおよびリチウムを含む化合物を有するリチウム金属複合酸化物粉末からなり、一般式：ＬｉｚＮｉ１－ｘ－ｙＣｏｘＭｙＷａＯ２＋α（ただし、０≦ｘ≦０．３５、０≦ｙ≦０．３５、０．９５≦ｚ≦１．３０、０＜ａ≦０．０３、０≦α≦０．１５、Ｍは、Ｍｎ、Ｖ、Ｍｇ、Ｍｏ、Ｎｂ、ＴｉおよびＡｌから選ばれる少なくとも１種の元素）で表される非水系電解質二次電池用正極活物質であって、
    　前記リチウム金属複合酸化物の二次粒子の断面を、走査型電子顕微鏡を用いた定倍率による観察において、任意の少なくとも２以上の異なる観察視野における任意に抽出した５０個以上の前記二次粒子を観察した際に、前記二次粒子内部の一次粒子表面にタングステンおよびリチウムを含む化合物を有する二次粒子の数が、観察した二次粒子数の９０％以上であることを特徴とする非水系電解質二次電池用正極活物質。     Consists of lithium metal composite oxide powder composed of primary particles and secondary particles formed by agglomeration of primary particles, having a layered crystal structure, and having a compound containing tungsten and lithium on the primary particle surface. formula: Li z Ni 1-x- y Co x M y W a O 2 + α ( although, 0 ≦ x ≦ 0.35,0 ≦ y ≦ 0.35,0.95 ≦ z ≦ 1.30,0 <a ≦ 0.03, 0 ≦ α ≦ 0.15, wherein M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al) An active material,
    In observation of the cross section of the secondary particles of the lithium metal composite oxide at a constant magnification using a scanning electron microscope, 50 or more secondary particles arbitrarily extracted in any at least two different observation fields are obtained. When observed, the number of secondary particles having a compound containing tungsten and lithium on the surface of primary particles inside the secondary particles is 90% or more of the observed number of secondary particles, Positive electrode active material for secondary battery.
  9. 　前記タングステンおよびリチウムを含む化合物が、粒子径１～２００ｎｍの微粒子として前記リチウム金属複合酸化物の一次粒子表面に存在することを特徴とする請求項８に記載の非水系電解質二次電池用正極活物質。 9. The positive electrode active for a non-aqueous electrolyte secondary battery according to claim 8, wherein the compound containing tungsten and lithium is present as fine particles having a particle diameter of 1 to 200 nm on the primary particle surface of the lithium metal composite oxide. material.
  10. 　前記タングステンおよびリチウムを含む化合物が、膜厚１～１５０ｎｍの被膜として前記リチウム金属複合酸化物の一次粒子表面に存在することを特徴とする請求項８に記載の非水系電解質二次電池用正極活物質。 9. The positive electrode active for a non-aqueous electrolyte secondary battery according to claim 8, wherein the compound containing tungsten and lithium is present on the primary particle surface of the lithium metal composite oxide as a film having a thickness of 1 to 150 nm. material.
  11. 　前記タングステンおよびリチウムを含む化合物が、粒子径１～２００ｎｍの微粒子及び膜厚１～１５０ｎｍの被膜の両形態として前記リチウム金属複合酸化物の一次粒子表面に存在することを特徴とする請求項８のいずれか１項に記載の非水系電解質二次電池用正極活物質。 9. The compound according to claim 8, wherein the compound containing tungsten and lithium is present on the primary particle surface of the lithium metal composite oxide in both forms of fine particles having a particle diameter of 1 to 200 nm and a film having a thickness of 1 to 150 nm. The positive electrode active material for nonaqueous electrolyte secondary batteries of any one of Claims 1.
  12. 　前記タングステンおよびリチウムを含む化合物に含有されるタングステン量が、リチウム金属複合酸化物粒子に含まれるＮｉ、ＣｏおよびＭの原子数の合計に対してＷの原子数が０．０５～２．０原子％であることを特徴とする請求項８～１１のいずれか１項に記載の非水系電解質二次電池用正極活物質。 The amount of tungsten contained in the compound containing tungsten and lithium is 0.05 to 2.0 atoms with respect to the total number of Ni, Co, and M atoms contained in the lithium metal composite oxide particles. The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 8 to 11, wherein the positive electrode active material is a non-aqueous electrolyte secondary battery.
  13. 　前記タングステンおよびリチウムを含む化合物が、タングステン酸リチウムの形態で存在することを特徴とする請求項８～１２のいずれか１項に記載の非水系電解質二次電池用正極活物質。 13. The positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 8, wherein the compound containing tungsten and lithium is present in the form of lithium tungstate.
  14. 　請求項８～１３のいずれか１項に記載の非水系電解質二次電池用正極活物質を含む正極を有することを特徴とする非水系電解質二次電池。 A nonaqueous electrolyte secondary battery comprising a positive electrode comprising the positive electrode active material for a nonaqueous electrolyte secondary battery according to any one of claims 8 to 13.
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