JP5213103B2 - Positive electrode for non-aqueous electrolyte secondary battery, non-aqueous electrolyte secondary battery and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery having a high capacity, superior safety, with battery swelling at the time of high-temperature storage suppressed, to provide a positive electrode capable of constituting the battery, and an electronic apparatus using the battery. <P>SOLUTION: The positive electrode for a nonaqueous electrolyte secondary battery contains as a positive electrode active material a layered complex oxide (A) represented by general formula LiNi<SB>x</SB>Co<SB>(1-x-y)</SB>M<SP>1</SP><SB>y</SB>O<SB>2</SB>(0.65&le;x&le;0.9, 0.01&le;y&le;0.06, an element M<SP>1</SP>is a metal element other than Li, Ni, Co, and includes Al, Mg, Ti, Mn or Zr) and a layered complex oxide (B) represented by general formula LiCo<SB>(1-z)</SB>M<SP>2</SP><SB>z</SB>O<SB>2</SB>(0.002&le;z&le;0.03, an element M<SP>2</SP>is an element other than Li, Ni, Co, and includes Al, Mg, Ti, Mn or Zr), the amount of alkali in the mixture of the (A) and (B) is 0.15 mass% or less, the carbon material being a conductive assistant is 1.0-2.0 pts.mass to the positive electrode active material 100 pts.mass, and a specific surface area of the positive electrode mixture layer is 0.9-1.5 m<SP>2</SP>/g. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a positive electrode capable of constituting a non-aqueous electrolyte secondary battery excellent in safety, a non-aqueous electrolyte secondary battery having the positive electrode, and an electronic device using the non-aqueous electrolyte secondary battery. .

  2. Description of the Related Art In recent years, secondary batteries have become one of the essential components that are indispensable as power sources for personal computers and mobile phones, and as power sources for electric vehicles and output storage. In particular, there is a demand for further miniaturization and weight reduction in small mobile electronic devices such as mobile phones, portable game machines, and PDAs. However, these devices are more compact and lighter due to the high power consumed by the backlight and drawing control of the liquid crystal display panel and the secondary battery capacity is still insufficient. Is in a difficult situation. Therefore, there is an urgent need to increase the power capacity, particularly the discharge capacity when the voltage of the unit cell is 3.3 V or higher.

  A positive electrode used in a non-aqueous electrolyte secondary battery such as a lithium ion battery is obtained by adding an organic solvent such as N-methyl-2-pyrrolidone (NMP) to a positive electrode active material, a conductive additive and a binder, for example. By mixing, a paste-like or slurry-like positive electrode mixture-containing composition is prepared, and this positive electrode mixture-containing composition is applied to the surface of a conductive substrate serving as a current collector, and the solvent is dried and removed. It is manufactured through a process of forming a positive electrode mixture layer having a thickness and density adjusted by a treatment or the like.

  As a method for achieving a higher capacity of the nonaqueous electrolyte secondary battery having such a positive electrode, for example, the positive electrode density (the density of the positive electrode mixture layer) is increased to increase the filling amount of the positive electrode active material in the positive electrode. And a method for increasing the charging voltage. However, in the former method, the permeability of the electrolyte solution into the positive electrode mixture layer is lowered, and problems such as battery manufacturing problems and characteristic deteriorations occur. Furthermore, the latter method has problems such as a decrease in battery safety associated with high voltage charging.

  In addition, lithium-cobalt composite oxide containing lithium (Li) and cobalt (Co) is widely used as the positive electrode active material for non-aqueous electrolyte secondary batteries, but the capacity per unit mass is higher than this. The use of lithium / nickel / cobalt composite oxide to which large nickel (Ni) is added as the positive electrode active material has been studied to increase the capacity of the battery.

  However, the inventors have found that the following problems occur when a battery is configured using a positive electrode using lithium-nickel-cobalt composite oxide as a positive electrode active material. Although the capacity per unit mass of lithium / nickel / cobalt composite oxide increases, the battery capacity does not increase because the chargeability and charge / discharge efficiency decrease compared to lithium / cobalt composite oxide. In addition, lithium / nickel / cobalt composite oxides have low thermal stability, which may lead to battery safety, such as battery ignition or rupture during overcharging or storage at high temperatures, and non-aqueous electrolytes during high voltage charging. Decomposition occurs and the charge / discharge cycle characteristics of the battery deteriorate. In addition, in a battery having a positive electrode using a lithium / nickel / cobalt composite oxide as a positive electrode active material, the battery tends to swell when stored in a charged state, particularly at a high temperature, and the discharge capacity at a low temperature is small. There is also a problem of becoming.

  In addition to the above, there has been proposed a technique aimed at solving the above-described problems in a non-aqueous electrolyte secondary battery using a lithium-cobalt composite oxide as a positive electrode active material. For example, Patent Document 1 discloses an oxide containing (a) lithium cobaltate and (b) at least one element selected from the group consisting of Al, B, Sn and Nb, and Li, Ni and Co. And using a positive electrode in which the mixing ratio [(a) :( b)] of these active materials (a) and (b) is in the range of 20:80 to 80:20 by weight ratio. Batteries have been proposed. In Patent Document 1, it is stated that by adopting the above-described configuration, it is possible to achieve an increase in battery capacity and an improvement in overdischarge characteristics and cycle characteristics.

  Patent Document 2 proposes a battery using, as a positive electrode active material, a mixture of spinel type lithium manganate and lithium cobaltate to which at least one of Zr and Ti (first different element) is added. According to Patent Document 2, in the lithium cobaltate, the addition of the first different element suppresses the elution of cobalt during high-temperature storage of the battery, so that the high-temperature storage characteristics of the battery are improved and the safety is improved. It is described. It is also described that the characteristics of the battery are further improved by using lithium cobalt oxide to which Mg or Al is added as the second different element in addition to the first different element.

JP-A-2005-19086 JP 2005-285720 A

  However, in the technique of Patent Document 1, particularly when the active material ratio of (b) in the positive electrode active material increases, the battery voltage at the end of discharge decreases, so that discharge is required in a high operating voltage region such as a mobile phone. When used as a power source for such a device, the capacity held by the battery may not be sufficiently extracted. In addition, since it is difficult to increase the density of the positive electrode mixture layer and increase the filling amount of the positive electrode active material, it is difficult to say that high capacity can be sufficiently achieved in this respect. Furthermore, it is not always sufficient in terms of improving the safety of the battery.

  In addition, since the technology of Patent Document 2 uses a stable spinel type lithium manganate, it is possible to improve the safety of the battery. However, the spinel type lithium manganate has a capacity per unit mass of lithium. Since it is smaller than the cobalt composite oxide and has a lower true density, it is difficult to increase the capacity.

  Recently, the level required for the capacity and safety of non-aqueous electrolyte secondary batteries has become very high, and the development of technology that can achieve both of these at a high level is required.

  The present invention has been made in view of the above circumstances, and its purpose is that the discharge capacity at room temperature is high, the discharge capacity at low temperature is maintained to the conventional level, and it is excellent in safety and stored at high temperature. To provide a positive electrode capable of constituting a nonaqueous electrolyte secondary battery in which battery swelling is suppressed, a nonaqueous electrolyte secondary battery having the positive electrode, and an electronic device using the nonaqueous electrolyte secondary battery .

The positive electrode for a non-aqueous electrolyte secondary battery of the present invention (hereinafter sometimes simply referred to as “positive electrode”) that has achieved the above object is a positive electrode mixture layer containing a positive electrode active material, a conductive additive, and a binder. As the positive electrode active material, the general formula LiNi _x Co _(1-xy) M ¹ _y O ₂ (0.65 ≦ x ≦ 0.90, 0.01 ≦ y ≦ 0.06, element M ¹ is a metal element other than Li, Ni and Co, and includes at least one element selected from the group consisting of Al, Mg, Ti, Mn and Zr). Oxide (A) and general formula LiCo _(1-z) M ² _z O ₂ (0.002 ≦ z ≦ 0.03, element M ² is a metal element other than Li, Ni and Co, Al, Mg , At least one selected from the group consisting of Ti, Mn and Zr Layered lithium / cobalt composite oxide (B) represented by the above-mentioned layered lithium / nickel / cobalt composite oxide (A) and the layered lithium / cobalt composite oxide (B). And the amount of the carbon material as the conductive additive is 1.0 to 2.0 parts by mass with respect to 100 parts by mass of the positive electrode active material, The positive electrode mixture layer has a specific surface area of 0.9 to 1.5 m ² / g.

  Moreover, the nonaqueous electrolyte secondary battery which has the positive electrode for nonaqueous electrolyte secondary batteries of this invention, and the electronic device using the nonaqueous electrolyte secondary battery of this invention are also contained in this invention.

  When the battery is configured using only the lithium / nickel / cobalt composite oxide as the positive electrode active material, the battery capacity can be reduced by the decrease in the filling rate and the charge / discharge efficiency in the positive electrode mixture layer. On the other hand, when the battery is configured using only the lithium-cobalt composite oxide as the positive electrode active material, the battery capacity is limited due to a decrease in the capacity per unit mass of the positive electrode active material.

  In the present invention, in order to achieve high battery capacity, the layered lithium / nickel / cobalt composite oxide (A) and the layered lithium / cobalt composite oxide (B) are used in combination with the positive electrode active material, Both advantages were exhibited synergistically, and the filling properties in these positive electrode mixture layers were improved.

Further, in the present invention, those using those containing additive elements M ¹ in layered lithium-nickel-cobalt composite oxide (A), and containing an additive element M ² in a layered lithium-cobalt composite oxide (B) Furthermore, the alkali amount in the mixture of the layered lithium / nickel / cobalt composite oxide (A) and the layered lithium / cobalt composite oxide (B) is set to a specific value or less, and the ratio of the positive electrode mixture layer is added. The surface area is limited to a specific range, and these configurations suppress battery swelling during high-temperature storage, and also provide safety under harsh conditions such as overcharging, nail penetration, and leaving in a high-temperature environment. Improved.

  According to the present invention, the discharge capacity at normal temperature is high, the discharge capacity at low temperature is maintained to the same level as before, and the non-aqueous electrolyte secondary battery is excellent in safety and suppressed in battery swelling during high temperature storage. A battery, a positive electrode capable of constituting the nonaqueous electrolyte secondary battery, and an electronic device using the nonaqueous electrolyte secondary battery can be provided.

  In the positive electrode of the present invention, for example, the layered lithium / nickel / cobalt composite oxide (A) as the positive electrode active material and the layered lithium / cobalt composite oxide ( B), having a form in which a positive electrode mixture layer containing a conductive additive and a binder is formed.

The layered lithium / nickel / cobalt composite oxide (A) according to the positive electrode of the present invention (hereinafter sometimes referred to as “compound (A)”) is LiNi _x Co _(1-xy) M ¹ _y O ₂ . It is a compound represented. The ratio x of Ni in the compound (A) is 0.65 or more, preferably 0.75 or more and 0.9 or less. M ¹ in the compound (A) is a metal element other than Li, Ni, and Co, and includes one or more elements selected from the group consisting of Al, Mg, Ti, Mn, and Zr. The ratio y of M ¹ is 0.01 or more, preferably 0.03 or more, and is 0.06 or less, preferably 0.05 or less. In M ¹ , at least one element selected from the group consisting of Al, Mg, Ti, Mn, and Zr is preferably at least 0.01 and at least 0.03, and at least 0.03. More preferably. Further, all of M ¹ may be one or more elements selected from the group consisting of Al, Mg, Ti, Mn, and Zr. By using the compound (A) having such a composition, the capacity of the battery is increased, and a nail penetration test assuming that a metal piece or the like is stuck in the battery (details will be described later in Examples). Safety can be improved.

That is, in the compound (A), if the Ni ratio x is too small, the capacity per unit mass of the positive electrode active material is greatly reduced. If x is too large, the charge / discharge efficiency and charge / discharge cycle characteristics of the battery are deteriorated. Occur. In the compound (A), if the ratio y of M ¹ is too small, the safety of the battery cannot be improved, and if y is too large, the capacity per unit mass of the positive electrode active material is greatly reduced.

The layered lithium-cobalt composite oxide (B) [hereinafter sometimes referred to as “compound (B)”] according to the positive electrode of the present invention is a compound represented by LiCo _(1-z) M ² _z O _2. . M ² in the compound (B) is a metal element other than Li, Ni, and Co, and includes one or more elements selected from the group consisting of Al, Mg, Ti, Mn, and Zr. The ratio z of M ² is 0.002 or more, preferably 0.003 or more, and is 0.03 or less, preferably 0.02 or less. Of M ² , one or more elements selected from the group consisting of Al, Mg, Ti, Mn, and Zr are preferably at least in a ratio z of 0.002 or more, and 0.003 or more. More preferably. Further, all of M ² may be one or more elements selected from the group consisting of Al, Mg, Ti, Mn, and Zr. By using the compound (B) having such a composition, it is possible to suppress the swelling of the battery during high-temperature storage and to improve the high voltage charge / discharge cycle characteristics of the battery. That is, in the compound (B), if the ratio z of M ² is too small, the effect of suppressing swelling during high-temperature storage and the effect of improving high-voltage charge / discharge cycle characteristics cannot be sufficiently obtained, while if z is too large. , Battery capacity decreases.

  The compound (A) and the compound (B) [mixture of the compound (A) and the compound (B)] in the positive electrode mixture layer have an alkali amount of 0.15% by mass or less, preferably 0.11% by mass. % Or less. In the lithium transition metal composite oxide such as compound (A) or compound (B), unreacted substances such as lithium carbonate, cobalt oxide, nickel hydroxide and nickel oxide used as raw materials are mixed as impurities. . Further, during the formation reaction of the lithium transition metal composite oxide or after the completion of the reaction, lithium reacts with moisture in the air to become lithium hydroxide. Thus, alkalis such as lithium carbonate and lithium hydroxide mixed in the compound (A) and the compound (B) are present in the mixture of the compound (A) and the compound (B) in an amount exceeding 0.15% by mass. Then, when the battery is formed or charged, a decomposition reaction of these alkalis occurs to generate carbon dioxide gas or hydrogen gas, which causes the battery to swell.

  The amount of alkali in the mixture of compound (A) and compound (B) is determined by the following neutralization titration method. This neutralization titration method is also called the Warder method or the Winkler method, and is well known as a quantitative analysis method for a mixture of lithium hydroxide and lithium carbonate (for example, Abe, “Analytical Chemistry”, Bafukan, Showa 25 years, 223-224). In this titration, first, phenolphthalein is used as an indicator, half of the total lithium hydroxide and lithium carbonate are neutralized, and the remaining carbonate is neutralized from the phenolphthalein endpoint to the endpoint with methyl orange indicator. Is.

That is, the following formulas (1) to (3);
LiOH + HCl → LiCl + H ₂ O (1)
Li ₂ CO ₃ + HCl → LiCl + LiHCO ₃ (2)
LiHCO ₃ + HCl → LiCl + CO ₂ + H ₂ O (3)
, The total hydrochloric acid titration amount of formula (1), formula (2) and formula (3) is the amount of alkali.

  Actually, the alkali amount is measured as follows. 20 g of a mixture of compound (A) and compound (B) is weighed as a sample and placed in a 200 ml conical flask with a stopcock. 100 ml of pure water is added here, the inside of the flask is replaced with nitrogen gas, and the stopcock is closed. This was stirred for 1 hour with a magnetic stirrer, allowed to stand, then decantated and filtered, 50 ml of the filtrate was precisely weighed, phenolphthalein indicator was added as an indicator, and titrated with 0.2 M hydrochloric acid. The amount (A ml) is determined. Subsequently, methyl orange indicator is added and titrated to determine the second titer (B ml). Then, from these titration amounts A and titration amounts B, the amount of alkali in the sample mixture is calculated.

  In order to obtain the compound (A) and the compound (B) having an alkali amount of 0.15% by mass or less in the case of a mixture, selection of raw materials to be used for producing the compound (A) and the compound (B), and It is only necessary to appropriately control the reaction at the time of manufacture and to perform selection by an analytical test.

Furthermore, in the positive electrode of the present invention, the specific surface area of the positive electrode mixture layer is 1.5 m ² / g or less, preferably 1.2 m ² / g or less. In the positive electrode of the present invention, the specific surface area of the positive electrode mixture layer is kept small as described above, and the safety of the battery (especially the safety during overcharge) is also enhanced by such a configuration. The reason why the safety of the battery is improved by adopting the above configuration is that the specific surface area of the positive electrode mixture layer is reduced, and the battery becomes high voltage (that is, when the battery is overcharged). This is considered to be because the reaction rate at the positive electrode can be lowered, and as a result, the runaway of the battery reaction can be suppressed.

However, if the specific surface area of the positive electrode mixture layer is too small, battery characteristics (especially, discharge capacity at low temperature) are lowered, and therefore the specific surface area of the positive electrode mixture layer is 0.9 m ² / g or more. It is preferably 0 m ² / g or more.

Here, the “specific surface area of the positive electrode mixture layer” referred to in the present specification is about 5 mm × 30 mm × 13 to 16 sheets cut out from the electrode sheet as pretreatment, and after weighing the mass, the sample tube is sealed, Using a high-precision fully automatic gas adsorption device (BET measuring device, “BELSORP36” manufactured by Nippon Bell Co., Ltd.), after vacuum degassing at room temperature, the adsorption isotherm of N ₂ gas in liquid nitrogen (77K) is measured and obtained. This is a value obtained by analyzing the obtained isotherm by the BET multipoint method.

  Compound (A) and Compound (B) have a mean particle size of preferably 8 μm or more, more preferably 10 μm or more, and preferably 80 μm or less, more preferably 30 μm or less, when these are used as a mixture. is there. By using the compound (A) and the compound (B) in which the average particle size of the mixture is as described above, the filling property in the positive electrode mixture layer is reduced by increasing the particle size or decreasing the particle size of the positive electrode active material. It can suppress and can make a battery characteristic favorable. Moreover, although the positive electrode which concerns on the battery of this invention is normally produced through the positive mix layer forming process including the process of apply | coating a positive mix mixture containing composition (a paste, slurry, etc.) to a collector (it mentions later). ), By using the compound (A) and the compound (B) having an average particle size of the mixture as described above, application spots such as streaking when the composition is applied by increasing the particle size of the positive electrode active material Can also be prevented. The average particle size when the compound (A) and the compound (B) are used as a mixture can be controlled by adjusting the average particle size and the use ratio of the compound (A) and the compound (B).

Further, when the compound (A) and the compound (B) are used as a mixture, the specific surface area is preferably 0.2 m ² / g or more, more preferably 0.3 m ² / g or more. Is 0.6 m ² / g or less, more preferably 0.4 m ² / g or less. By using the compound (A) and the compound (B) in which the mixture is in the form as described above, the deterioration of the load characteristics of the battery due to the reduction of the specific surface area of these positive electrode active materials is suppressed, and better battery characteristics are secured. can do. The specific surface area when the compound (A) and the compound (B) are used as a mixture can be controlled by adjusting the use ratio of the compound (A) and the compound (B).

Here, the “average particle diameter of the mixture of the compound (A) and the compound (B)” in the present specification is determined using a laser-type particle size distribution measuring device (“HRA9320-X100” manufactured by Microtrack). This is a value obtained as a particle size (D ₅₀ ) that is 50% by volume frequency integration under the condition of light absorption mode when a sample is dispersed in pure water. The “specific surface area of the mixture of the compound (A) and the compound (B)” in the present specification is a one-point BET measuring device (“Macsorb HM-1201” manufactured by Mountec Co., Ltd.) using N ₂ gas adsorption. ), And as a pretreatment, the value is obtained by measuring after maintaining for 1 hour in an environment of 150 ° C. in an N ₂ gas flow.

  The use ratio of the compound (A) to the compound (B) is such that when the total amount of the compound (A) and the compound (B) is 100% by mass, the content of the compound (A) is preferably 10% by mass. As mentioned above, More preferably, it is 15 mass% or more, Preferably it is 30 mass% or less. In other words, when the total amount of the compound (A) and the compound (B) is 100% by mass, the content of the compound (B) is preferably 70% by mass or more, preferably 90% by mass or less, More preferably, it is 85 mass% or less. When the compound (A) and the compound (B) are used as a mixture, it preferably satisfies the above specific surface area, and preferably satisfies the above average particle size, and is used at such a ratio, so that the battery Higher capacity and improved safety can be achieved better.

  That is, when the content ratio of the compound (A) is small, the filling property of the active material in the positive electrode mixture layer is improved and a high-density positive electrode mixture layer can be formed, but the content ratio of (A) is too high. If it is too small, the capacity per unit mass of the positive electrode active material tends to decrease, and as a result, the battery capacity may decrease. In addition, when the content of the compound (A) is large, the capacity per unit mass of the positive electrode active material is large. However, when the content is too large, the battery voltage at the end of discharge is rapidly decreased, or the active capacity in the positive electrode mixture layer is increased. Since it becomes difficult to increase the filling property of the substance and the battery capacity tends to decrease, it is not preferable.

In the positive electrode of the present invention, at least a carbon material is used as a conductive additive, and the carbon material preferably has a specific surface area of 50 m ² / g or more and 1500 m ² / g or less, for example. If the carbon material has such a specific surface area, it is possible to reduce the content in the positive electrode mixture layer while suppressing deterioration of the battery characteristics, and thus it becomes possible to form a higher density positive electrode mixture layer. Further increase in battery capacity can be achieved. The specific surface area of the carbon material is more preferably 800 m ² / g or less.

  Examples of conductive assistants composed of carbon materials that can be used for the positive electrode include graphites such as natural graphite (flaky graphite, etc.) and artificial graphite; acetylene black, ketjen black, channel black, furnace black, lamp black, thermal Carbon blacks such as black; carbon fibers; In the positive electrode of the present invention, among these carbon materials, those having the above specific surface area are preferable. However, if necessary, those having a specific surface area other than those described above and conductive aids other than the carbon material (for example, metal) Conductive fibers such as fibers; carbon fluoride; metal powders such as aluminum; zinc oxide; conductive whiskers such as potassium titanate; conductive metal oxides such as titanium oxide; organic conductive materials such as polyphenylene derivatives Etc.) may also be used in combination. As the carbon material, acetylene black, ketjen black, and other carbon blacks are particularly preferable because those having the specific surface area are easily available.

  When using together the carbon material which has the said specific surface area, and another conductive support agent (carbon material which has a specific surface area other than the above, or conductive support agents other than a carbon material), in the conductive support agent whole quantity, The carbon material having a specific surface area of, for example, is preferably 30% by mass or more, and more preferably 50% by mass or more. Of course, only the carbon material having the specific surface area (that is, 100% by mass) may be used.

  As the binder used for the positive electrode mixture layer according to the positive electrode of the present invention, it is preferable to use rubber. By using rubber as the binder, it becomes easy to reduce the specific surface area of the positive electrode mixture layer as described above.

  Further, as will be described in detail later, in producing the positive electrode of the present invention, the positive electrode mixture containing the compound (A), the compound (B), the conductive auxiliary agent and the binder is used as N-methyl-2-pyrrolidone. A production method using a positive electrode mixture-containing composition which is dispersed in an organic solvent such as (NMP) (the binder may be dissolved) is usually employed. Therefore, the binder (binder) used for the positive electrode of the present invention is preferably a polymer (rubber) that can be dissolved or dispersed in an organic solvent such as NMP.

  Specific examples of rubbers that can be dissolved or dispersed in organic solvents such as NMP, which are suitable as binders, include poly 1,3-butadiene, polyisoprene, isoprene-isobutylene copolymers, natural rubber, styrene-1,3-butadiene. Copolymer (SBR), styrene-isoprene copolymer, 1,3-butadiene-isoprene-acrylonitrile copolymer, styrene-1,3-butadiene-isoprene copolymer, 1,3-butadiene-acrylonitrile copolymer, styrene-acrylonitrile-1,3-butadiene Methyl methacrylate copolymer, styrene-acrylonitrile-1,3-butadiene-itaconic acid copolymer, styrene-acrylonitrile-1,3-butadiene-methyl methacrylate-fumaric acid copolymer, styrene-1,3- Tadiene-itaconic acid-methyl methacrylate-acrylonitrile copolymer, acrylonitrile-1,3-butadiene-methacrylic acid-methyl methacrylate copolymer, 1,3-butadiene-styrene-methyl methacrylate copolymer, styrene-1,3-butadiene-itacon Diene rubber such as acid-methyl methacrylate-acrylonitrile copolymer, styrene-acrylonitrile-1,3-butadiene-methyl methacrylate-fumaric acid copolymer; Olefin rubber such as ethylene-propylene copolymer, ethylene-propylene-diene copolymer; styrene Ethylene-butadiene copolymer, styrene-butadiene-propylene copolymer, styrene-n-butyl acrylate-itaconic acid-methyl methacrylate-acrylonite And the like; Rukoporima, styrene - acrylate n- butyl - itaconic acid - - Methyl methacrylate styrene rubbers such as acrylonitrile copolymer. These rubbers may be used alone or in combination of two or more.

  In addition to the rubber, other binders can be used for the binder of the positive electrode mixture layer. The binder other than rubber used for the binder of the positive electrode mixture layer is also preferably a polymer that can be dissolved or dispersed in an organic solvent such as NMP. Examples of such polymers include polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene ionomer, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, chlorinated polyethylene, chlorosulfonated polyethylene, and other olefin polymers; polymethyl methacrylate, polymethyl acrylate , Polyethyl acrylate, polybutyl acrylate, acrylate-acrylonitrile copolymer, 2-ethylhexyl acrylate-methyl acrylate-acrylic acid-methoxypolyethylene glycol monomethacrylate, polyacrylic acid, polymethacrylic acid, polyacrylamide, poly-N-isopropylacrylamide (Meth) acrylic polymers such as poly-N, N-dimethylacrylamide; Polyamide and polyimide polymers such as lyamide 6, polyamide 66, polyamide 11, polyamide 12, aromatic polyamide, polyimide; ester polymers such as polyethylene terephthalate and polybutylene terephthalate; polyvinylidene fluoride (PVDF), polytetrafluoroethylene , Polyhexafluoropropylene, vinylidene fluoride-hexafluoropropylene (VDF-HFP) copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene (VDF-HFP-TFE) copolymer, vinylidene fluoride-pentafluoropropylene (VDF-) PFP) copolymer, vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene (VDF-PF) -TFE) copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene (VDF-PFMVE-TFE) copolymer, vinylidene fluoride-chlorotrifluoroethylene (VDF-CTFE) copolymer and other fluorine-based polymers; .

  In addition, polyvinylpyrrolidone, polyethyleneimine, polyoxyethylene, poly (2-methoxyethoxyethylene), poly (3-morphinylethylene), polyvinyl sulfonic acid, and the like can also be used as the binder. In addition, block polymers such as polystyrene-polybutadiene block copolymer, styrene-butadiene-styrene block copolymer, styrene-ethylene-butylene-styrene block copolymer, styrene-isoprene block copolymer, styrene-ethylene-propylene-styrene block copolymer are also available. It can be used as a binder.

  As described above, the positive electrode of the present invention has a positive electrode mixture layer composed of a positive electrode mixture containing a positive electrode active material, a conductive additive, and a binder on one or both surfaces of a conductive substrate serving as a current collector. It has a formed form. The current collector is not particularly limited as long as it is an electron conductor that is substantially chemically stable in the battery that is constructed. For example, as a material constituting the current collector, in addition to aluminum or its alloy, stainless steel, nickel or its alloy, titanium or its alloy, carbon, conductive resin, carbon or titanium on the surface of aluminum or stainless steel What processed this is used. Of these, aluminum and aluminum alloys are particularly preferable. These materials can also be used after oxidizing the surface. Moreover, it is preferable to give an unevenness | corrugation to the collector surface by surface treatment. Examples of the shape of the current collector include films, sheets, nets, punched materials, lath bodies, porous bodies, foamed bodies, and molded bodies of fiber groups, in addition to foils. Although the thickness of a collector is not specifically limited, For example, it is preferable that it is 5-50 micrometers.

  As a method for preparing the positive electrode mixture-containing composition (paste, slurry, etc.), for example, (1) a conductive auxiliary agent, a binder and a solvent are kneaded in advance with a strong shearing dispersion device, and the positive electrode active material is added to this dispersion (2) A mixture of a positive electrode active material, a binder, and a solvent is dispersed to form a dispersion such as a paste. A method of preparing a dispersion by kneading an agent, a binder and a solvent with a strong shearing dispersion device to add another dispersion to the former dispersion, and (3) positive electrode active And a method in which a mixture of a substance, a conductive additive, a binder, and a solvent is kneaded with a high shear disperser.

  In addition, the compound (A) and the compound (B) which are the positive electrode active materials may be used as a mixture in advance, and this mixture may be used for the preparation of the positive electrode mixture-containing composition. The compound (A) and the compound (B) May be used for the preparation of the positive electrode mixture-containing composition without mixing.

Examples of the high shear dispersion device used for preparing the positive electrode mixture-containing composition include, for example, a triaxial planetary mixer having two blades for kneading and one high-speed stirrer; A four-axis planetary mixer equipped with two blades and two high-speed stirrers (such as “Planetary Dispa (trade name)” manufactured by Asada Tekko Co., Ltd.); a three-axis planetar with three blades Lee mixer [Intrie Corporation's "Trimix (trade name)"etc.]; Media mill represented by mill; Kneader; Continuous twin-screw kneader; Colloid mill; Roll mill; Paint (Positive electrode mixture-containing composition) A homogenizer type disperser that generates a jet flow and disperses by shearing between liquid and liquid; high speed rotating homogenizer capable of high speed operation of 3000 to 20000 min ⁻¹ with improved mechanical accuracy Examples include Clairemix (trade name, manufactured by M Technique Co., Ltd.) and universal mixer (trade name, manufactured by POWREC Co., Ltd.).

  The positive electrode of the present invention may be applied, for example, by applying the positive electrode mixture-containing composition prepared by the above technique to one or both sides of the current collector, drying to remove the solvent, and then performing a press treatment such as calendering. Thus, it is manufactured through a step of adjusting the thickness, density and specific surface area of the positive electrode mixture layer. In order to adjust the thickness and density of the positive electrode mixture layer to the appropriate values described below, for example, the linear pressure during the press treatment is preferably set to 700 to 2000 kgf / cm.

In the positive electrode of the present invention thus obtained, the density of the positive electrode mixture layer is, for example, preferably 3.6 g / cm ³ or more, and more preferably 3.7 g / cm ³ or more. At present, a positive electrode using a layered lithium-cobalt composite oxide having a positive electrode mixture layer density of about 3.6 to 3.8 g / cm ³ can be used. Therefore, also in the positive electrode of the present invention, the density of the positive electrode mixture layer is preferably 3.6 g / cm ³ or more from the viewpoint of increasing the capacity. That is, by using a positive electrode having such a high-density positive electrode mixture layer, the capacity of a battery having this positive electrode can be further increased. If the density of the positive electrode mixture layer is too high, the permeability of the electrolytic solution into the positive electrode mixture layer may be reduced, and the battery characteristics may be impaired. Therefore, the density of the positive electrode mixture layer is 4 preferably .3g / cm ³ or less, more preferably 4.2 g / cm ³ or less.

The density of the positive electrode mixture layer here is measured by the following method. First, it cuts a positive electrode to a size of 1 cm × 1 cm, a thickness micrometer _{(l 1),} measuring the mass _{(m 1)} a precision balance. Next, the positive electrode material mixture layer is scraped off, and only the current collector is taken out, and the thickness (l _c ) and mass (m _c ) of the current collector are measured in the same manner as the positive electrode. From the obtained thickness and mass, the positive electrode mixture layer density (d _ca ) is determined by the following formula ( _note that the unit of thickness is cm and the unit of mass is g).
d _ca = (m ₁ −m _c ) / (l ₁ −l _c )

  In addition, the thickness of the positive electrode mixture layer (when the positive electrode mixture layer is formed on both sides of the current collector, the thickness per one surface thereof) is preferably 30 to 80 μm.

  If the amount of the carbon material that is a conductive additive in the positive electrode mixture layer is too small, the specific surface area of the positive electrode mixture layer becomes too small and the battery characteristics (especially low-temperature discharge characteristics) deteriorate. It is 1.0 mass part or more with respect to 100 mass parts of substances, and it is preferable that it is 1.2 mass parts or more. In addition, if the amount of the carbon material in the positive electrode mixture layer is too large, the specific surface area of the positive electrode mixture layer becomes too large, and the safety during overcharging in particular decreases. It is 2.0 mass parts or less with respect to 100 mass parts, and it is preferable that it is 1.5 mass parts or less.

  In the positive electrode of the present invention, a carbon material (preferably a carbon material having the above specific surface area) is used as a conductive aid, thereby reducing the conductive aid content in the positive electrode mixture layer as described above. However, it is possible to ensure very good electrical conductivity, and in addition to this, the content of the binder can be reduced, so that the density of the positive electrode mixture layer can be increased more easily, and the battery can be made higher. It can also be a capacity.

  Moreover, it is preferable that the quantity of the positive electrode active material in the positive mix layer whole quantity is 96-99 mass%. Furthermore, the amount of the binder in the positive electrode material mixture layer is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, preferably 2 parts by mass with respect to 100 parts by mass of the positive electrode active material. 0 parts by mass or less, more preferably 1.5 parts by mass or less.

  Further, the amount of rubber as a binder in the positive electrode mixture layer is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more with respect to 100 parts by mass of the positive electrode active material. By using a sufficient amount of rubber, it becomes easy to reduce the specific surface area of the positive electrode mixture layer as described above. However, if the amount of rubber in the positive electrode mixture layer is too large, the specific surface area of the positive electrode mixture layer becomes too small as described above, which may cause deterioration of the discharge characteristics of the battery, particularly at low temperatures. Therefore, the amount of rubber in the positive electrode mixture layer is preferably 0.6 parts by mass or less, more preferably 0.4 parts by mass or less, with respect to 100 parts by mass of the positive electrode active material.

  The non-aqueous electrolyte secondary battery of the present invention only needs to have the positive electrode of the present invention, and there are no particular restrictions on the other configurations and structures, and it is employed in conventionally known non-aqueous electrolyte secondary batteries. Each configuration / structure can be applied.

  Examples of the negative electrode include those formed by forming a negative electrode mixture layer containing a negative electrode active material on the current collector surface. The negative electrode mixture layer contains, in addition to the negative electrode active material, a binder and, if necessary, a conductive aid, and includes, for example, a negative electrode active material and a binder (further, a conductive aid). A negative electrode mixture-containing composition (slurry etc.) obtained by adding a suitable solvent to the mixture (negative electrode mixture) and kneading thoroughly is applied to the surface of the current collector and dried to obtain a desired thickness. Can be formed.

  Examples of the negative electrode active material include graphite materials such as natural graphite (flaky graphite), artificial graphite, and expanded graphite; graphitizable carbonaceous materials such as coke obtained by calcining pitch; furfuryl alcohol resin ( Carbon materials such as non-graphitizable carbonaceous materials such as amorphous carbon obtained by low-temperature firing of PFA), polyparaphenylene (PPP), and phenol resins. In addition to the carbon material, lithium or a lithium-containing compound can also be used as the negative electrode active material. Examples of the lithium-containing compound include lithium alloys such as Li—Al, and alloys containing elements that can be alloyed with lithium such as Si and Sn. Furthermore, oxide-based materials such as Sn oxide and Si oxide can also be used. The amount of the negative electrode active material in the total amount of the negative electrode mixture is preferably 97 to 99% by mass, for example.

  The conductive aid is not particularly limited as long as it is an electron conductive material, and may not be used. Specific examples of conductive aids include acetylene black; ketjen black; carbon blacks such as channel black, furnace black, lamp black, and thermal black; carbon materials such as carbon fibers; and conductive fibers such as metal fibers. Carbon fluoride, metal powders such as copper and nickel, organic conductive materials such as polyphenylene derivatives, and the like. These may be used alone or in combination of two or more. . Among these, acetylene black, ketjen black and carbon fiber are particularly preferable. However, when a conductive additive is used for the negative electrode, it is desirable that the conductive additive amount in the total amount of the negative electrode mixture be 10% by mass or less in order to increase the capacity.

As a binder concerning a negative mix layer, any of a thermoplastic resin and a thermosetting resin may be sufficient. Specifically, for example, the same material as the binder according to the positive electrode of the present invention, an ethylene-acrylic acid copolymer, a Na ⁺ ion crosslinked product of the copolymer, an ethylene-methacrylic acid copolymer, or the Copolymer Na ⁺ ion cross-linked product, ethylene-methyl acrylate copolymer or Na ⁺ ion cross-linked product of the copolymer, ethylene-methyl methacrylate copolymer or Na ⁺ ion cross-linked product of the copolymer, etc. These materials may be used alone or in combination of two or more.

Among these, PVDF, SBR, ethylene-acrylic acid copolymer or Na ⁺ ion crosslinked product of the copolymer, ethylene-methacrylic acid copolymer or Na ⁺ ion crosslinked product of the copolymer, ethylene-acrylic acid A methyl copolymer or a Na ⁺ ion crosslinked product of the copolymer, an ethylene-methyl methacrylate copolymer or a Na ⁺ ion crosslinked product of the copolymer is particularly preferable. The amount of the binder in the total amount of the negative electrode mixture is preferably 1 to 5% by mass, for example.

  The thickness of the negative electrode mixture layer (when the negative electrode mixture layer is formed on both sides of the current collector, the thickness per one surface thereof) is preferably 30 to 80 μm.

  The current collector used for the negative electrode is not particularly limited as long as it is an electron conductor that is substantially chemically stable in the nonaqueous electrolyte secondary battery. Examples of the material constituting the current collector include stainless steel, nickel or an alloy thereof, copper or an alloy thereof, titanium or an alloy thereof, carbon, conductive resin, carbon, or the like on the surface of copper or stainless steel. A material obtained by treating titanium is used. Among these, copper and copper alloys are particularly preferable. These materials can also be used after oxidizing the surface. Moreover, it is preferable to give an unevenness | corrugation to the collector surface by surface treatment. Examples of the shape of the current collector include films, sheets, nets, punched materials, lath bodies, porous bodies, foamed bodies, and molded bodies of fiber groups, in addition to foils. Although the thickness of a collector is not specifically limited, For example, it is preferable that it is 5-50 micrometers.

  As the non-aqueous electrolyte, for example, a solution (non-aqueous electrolyte) prepared by dissolving a lithium salt in the following non-aqueous solvent can be used.

  Examples of the solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), γ-butyrolactone (γ-BL ), 1,2-dimethoxyethane (DME), tetrahydrofuran (THF), 2-methyltetrahydrofuran, dimethyl sulfoxide (DMSO), 1,3-dioxolane, formamide, dimethylformamide (DMF), dioxolane, acetonitrile, nitromethane, Methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivative, sulfolane, 3-methyl-2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, diethyl Aprotic organic solvents such as ruether and 1,3-propane sultone can be used singly or as a mixed solvent in which two or more are mixed.

The inorganic ion salt according to the non-aqueous electrolyte, for _{example, LiClO 4, LiPF 6, LiBF} 4, LiAsF 6, LiSbF 6, LiCF 3 SO 3, LiCF 3 CO 2, Li 2 C 2 F 4 (SO 3) 2, LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiC _n F _{2n + 1} SO 3 (n ≧ 2), LiN (RfOSO ₂ ) ₂ [where Rf is a fluoroalkyl group] At least one selected from the above. The concentration of these lithium salts in the electrolytic solution is preferably 0.6 to 1.8 mol / l, and more preferably 0.9 to 1.6 mol / l.

  In the non-aqueous electrolyte according to the present invention, it is preferable to use an ester having a C═C double bond outside the ring or an ester having a C═C double bond in the ring.

  The ester having a C═C double bond outside the ring and the ester having a C═C double bond in the ring (hereinafter, both may be collectively referred to as “ester having a C═C double bond”) ) Has a function of forming a surface protective film on the surface of the positive electrode active material during battery charging (particularly during initial charging), and direct contact between the positive electrode and the nonaqueous electrolyte is suppressed by the surface protective film. . In addition, the ester having a C═C double bond has an action of gradually reducing the circuit voltage of the battery when the charged battery is stored at a high temperature, for example. Therefore, when the battery of the present invention has a non-aqueous electrolyte containing an ester having a C═C double bond, the positive electrode formed by the surface protective film can be stored in a charged state, for example, at a high temperature of about 150 ° C. Since the reaction between the positive electrode and the non-aqueous electrolyte is suppressed by the action of suppressing direct contact with the non-aqueous electrolyte and the decrease in battery voltage, the temperature rise of the battery due to such reaction can be suppressed, and further safety It will be excellent.

  Examples of the ester having a C═C double bond outside the ring include vinylethylene carbonate, 4-methyl-4-vinylethylene carbonate, 4-ethyl-4-vinylethylene carbonate, 4-n-propyl-4-vinyl. Examples include ethylene carbonate, 5-methyl-4-vinylethylene carbonate, 4,4-divinylethylene carbonate, 4,5-divinylethylene carbonate, and the like.

  Examples of the ester having a C═C double bond in the ring include vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, 4,5-diethyl vinylene carbonate, methyl ethyl vinylene carbonate, and the like. Can be mentioned.

  The ester having a C═C double bond outside the ring and the ester having a C═C double bond inside the ring are preferably used in combination.

  The addition amount of the ester having a C═C double bond in the ring in the non-aqueous electrolyte is 0.5 mass in the total amount of the non-aqueous electrolyte from the viewpoint of more effectively exerting the action of the addition of these compounds. % Or more, preferably 0.9% by mass or more, and more preferably 1.8% by mass or more. However, if the amount of the ester having a C═C double bond in the ring is too large in the non-aqueous electrolyte, the voltage drop of the battery increases, so the addition of the ester having a C═C double bond in the ring The amount is preferably 5% by mass or less, more preferably 3% by mass or less, and further preferably 2.5% by mass or less in the total amount of the nonaqueous electrolyte. The addition amount of the ester having a C═C double bond outside the ring in the non-aqueous electrolyte is 0.2 mass in the total amount of the non-aqueous electrolyte from the viewpoint of more effectively exerting the effect of the addition of these compounds. % Or more, preferably 0.5% by mass or more, and more preferably 0.8% by mass or more. However, if the amount of the ester having a C═C double bond outside the ring is too large in the non-aqueous electrolyte, the voltage drop of the battery increases, so the addition of the ester having a C═C double bond outside the ring The amount is preferably 3% by mass or less, more preferably 2% by mass or less, and still more preferably 1.5% by mass or less in the total amount of the nonaqueous electrolyte.

  In the non-aqueous electrolyte secondary battery of the present invention, a separator containing the non-aqueous electrolyte is disposed between the positive electrode and the negative electrode. As the separator, an insulating microporous thin film having a large ion permeability and a predetermined mechanical strength is used. Moreover, what has a function which a hole is obstruct | occluded by fusion | melting of a structural material above a fixed temperature (for example, 100-140 degreeC), and raises resistance (namely, what has a shutdown function) is preferable. Specific examples of such a separator include a sheet (porous sheet), a nonwoven fabric or a woven fabric composed of a material such as polyethylene solvent, hydrophobic polymer such as polyethylene, polypropylene, or glass fiber having organic solvent resistance and hydrophobicity; And a porous material in which fine particles of the exemplified polyolefin polymer are fixed with an adhesive. The pore diameter of the separator is preferably such that the active material of the positive and negative electrodes, the conductive auxiliary agent, the binder and the like detached from the positive and negative electrodes do not pass through, and is preferably 0.01 to 1 μm, for example. The thickness of the separator is generally 8-30 μm, but is preferably 10-20 μm in the present invention. Further, the porosity of the separator is determined according to the constituent material and thickness, but is generally 30 to 80%.

  In the nonaqueous electrolyte secondary battery of the present invention thus obtained, the positive electrode (the positive electrode of the present invention) is stable even when charged to a voltage of 4.2 to 4.5 V on the basis of lithium metal, By performing charging at a higher voltage among such voltages, a further increase in capacity can be achieved.

  As described above, the non-aqueous electrolyte secondary battery of the present invention has a high capacity and is excellent in safety and high-temperature storage properties in a state where a metal piece or the like is stuck during overcharge. Taking advantage of these characteristics, various electronic devices such as notebook computers, pen input computers, pocket computers, notebook word processors, pocket word processors, e-book players, mobile phones, cordless phones, pagers, handy terminals, mobile copy, Electronic notebook, calculator, LCD TV, electric shaver, electric tool, electronic translator, car phone, transceiver, voice input device, memory card, backup power supply, tape recorder, radio, headphone stereo, portable printer, handy cleaner, portable CD, Small video movies, navigation systems, etc. Power supply for equipment, refrigerator, air conditioner, TV, stereo, water heater, microwave oven, dishwasher, washing machine, dryer, game machine, lighting equipment, toy, sensor equipment, road conditioner, medical equipment, automobile, electricity It can be used as a power source, auxiliary power source and backup power source for large and medium-sized equipment such as automobiles, golf carts, electric carts, security systems, and power storage systems. In addition to consumer use, it can also be used for space use.

  Among them, the effect of increasing the capacity is increased in a small portable device, and it is particularly desirable to use it for a portable device having a mass of 3 kg or less, and more desirably for a portable device of 1 kg or less. Further, the lower limit of the mass of the portable device is not particularly limited, but in order to obtain a certain effect, it is preferably about the same as the mass of the battery, for example, 10 g or more. The thickness of the device is desirably 30 mm or less, more desirably 20 mm or less, and further desirably 15 mm or less. This is because the effects of battery swelling and heat generation are likely to appear on the surface of the device due to its thinness. Further, in order to be able to incorporate a battery, the device needs to have a certain thickness, and specifically, it is desirable that the thickness is 2 mm or more.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention.

Example 1
<Preparation of positive electrode>
As the positive electrode active material, compound (A): LiNi _0.85 Co _0.10 Al _0.05 O ₂ [average particle diameter 10 μm, BET specific surface area 0.3 m ² / g, alkali amount 0.48 mass%] And compound (B): LiCo _0.997 Al _0.001 Mg _0.001 Ti _0.001 O ₂ [average particle size 18 μm, BET specific surface area 0.3 m ² / g, alkali amount 0.01 mass%] Were used at a mass ratio of 20:80. This positive electrode active material mixture had an average particle diameter of 16 μm, a BET specific surface area of 0.3 m ² / g, and an alkali amount of 0.11% by mass.

The positive electrode active material mixture and acetylene black [Denka Black (trade name) manufactured by Denki Kagaku Kogyo Co., Ltd.], powdered product, average primary particle size (electron microscopy): 40 nm, BET specific surface area : 65 m ² / g, DBP oil absorption: 180 cc / 100 g], a rubber binder “BM720H” manufactured by Nippon Zeon Co., Ltd. as a binder, and PVDF “KF polymer L # 1120 manufactured by Kureha Chemical Co., Ltd. (product) Name) ”is mixed at a solid mass ratio of 100: 1.2: 0.2: 0.8, NMP as a solvent is added, and“ Clearmix CLM0.8 (product) manufactured by M Technique Co., Ltd. ” Name) ”was used for 30 minutes at a rotational speed of 10,000 min ⁻¹ to obtain a paste-like mixture. NMP which is a solvent was further added to this mixture, and the mixture was treated at a rotational speed of 10000 min ⁻¹ for 15 minutes to prepare a positive electrode mixture-containing composition.

The positive electrode mixture-containing composition is applied to both sides of an aluminum foil (thickness: 15 μm), which is a current collector, vacuum-dried at 120 ° C. for 12 hours, and further subjected to a press treatment, whereby both sides of the current collector are applied. In addition, a positive electrode having a positive electrode mixture layer having a thickness of 52 μm was prepared. The density of the positive electrode mixture layer after press treatment determined by the above method was 3.82 g / cm ³ , and the specific surface area of the positive electrode mixture layer was 1.1 m ² / g.

<Production of negative electrode>
Natural graphite: 97.5% by mass, SBR: 1.5% by mass, and carboxymethylcellulose (thickener): 1% by mass were mixed with water to prepare a slurry-like negative electrode mixture-containing composition. . This negative electrode mixture-containing composition was applied to both sides of a copper foil (thickness: 8 μm) as a current collector, vacuum-dried at 120 ° C. for 12 hours, and further subjected to a press treatment to form both sides of the current collector. A negative electrode having a negative electrode mixture layer with a thickness of 63 μm was prepared. The density of the negative electrode mixture layer after the press treatment obtained by the same method as the method for measuring the density of the positive electrode mixture layer was 1.65 g / cm ³ .

<Production of electrode body>
The positive electrode and the negative electrode were overlapped with a separator interposed therebetween, and these were wound to produce an electrode body. As the separator, a polyethylene porous film (air permeability: 300 seconds / 100 cm ³ ) having a thickness of 14 μm was used.

<Preparation of non-aqueous electrolyte>
LiPF ₆ was dissolved at a concentration of 1.2 mol / l in a mixed solvent of methyl ethyl carbonate, diethyl carbonate and ethylene carbonate (volume ratio 2: 1: 3), and vinylene carbonate (VC) 2% by mass, vinyl A non-aqueous electrolyte (non-aqueous electrolyte) was prepared by adding 1% by mass of ethylene carbonate (V-EC).

<Battery assembly>
A prismatic nonaqueous electrolyte secondary battery was assembled using the electrode body and the nonaqueous electrolyte. First, a current collector plate was joined to each end face of the electrode body by welding. Next, the lead part of the current collecting plate was connected to an electrode terminal current collecting mechanism attached to the lid. Then, the electrode body was accommodated inside the positive electrode can, and the lid body was welded and fixed to the opening of the positive electrode can. Finally, a non-aqueous electrolyte is injected into the positive electrode can through the injection hole provided in the lid, and the structure shown in FIG. 1 has a thickness of 4 mm, a width of 34 mm, and a height of 50 mm. A square nonaqueous electrolyte secondary battery was produced.

  Here, the battery shown in FIGS. 1 and 2 will be described. The positive electrode 1 and the negative electrode 2 are formed into a rectangular positive electrode can 4 as the electrode body 6 having a winding structure wound in a spiral shape through the separator 3 as described above. It is housed with a non-aqueous electrolyte. However, in FIG. 1, in order to avoid complication, a metal foil, a non-aqueous electrolyte, or the like as a current collector used for manufacturing the positive electrode 1 and the negative electrode 2 is not illustrated.

  The positive electrode can 4 is made of an aluminum alloy and constitutes a battery exterior material. The positive electrode can 4 also serves as a positive electrode terminal. An insulator 5 made of a polyethylene sheet is arranged at the bottom of the positive electrode can 4, and the positive electrode 1 connected to one end of each of the positive electrode 1 and the negative electrode 2 from the electrode body 6 made of the positive electrode 1, the negative electrode 2 and the separator 3. A current collector plate 7 and a negative electrode current collector plate 8 are drawn out. A stainless steel terminal 11 is attached to an aluminum alloy cover plate 9 that seals the opening of the positive electrode can 4 via a polypropylene insulating packing 10, and an insulator 12 is connected to the terminal 11. A stainless steel lead plate (electrode terminal current collecting mechanism) 13 is attached.

  And this cover plate 9 is inserted in the opening part of the said positive electrode can 4, and the opening part of the positive electrode can 4 is sealed by welding the junction part of both, and the inside of a battery is sealed.

  The lid plate 9 is provided with a liquid injection hole (14 in the figure). When the battery is assembled, a nonaqueous electrolyte is injected into the battery from the liquid injection hole, and then the liquid injection hole. Is sealed. The cover plate 9 is provided with an explosion-proof safety valve 15.

  In the battery of this Example 1, the positive electrode can 4 and the cover plate 9 function as positive terminals by directly welding the positive electrode current collector plate 7 to the cover plate 9, and the negative electrode current collector plate 8 is welded to the lead plate 13. The negative electrode current collector plate 8 and the terminal 11 are connected to each other through the lead plate 13 so that the terminal 11 functions as a negative electrode terminal. Sometimes it becomes.

  FIG. 2 is a perspective view schematically showing the external appearance of the battery shown in FIG. 1. FIG. 2 is shown for the purpose of showing that the battery is a square battery. FIG. 1 schematically shows a battery, and only specific members of the battery are shown. Also in FIG. 1, the inner peripheral portion of the electrode body is not cross-sectional.

Example 2
A positive electrode was produced in the same manner as in Example 1 except that the mixing ratio of the compound (A) and the compound (B) was (A) / (B) = 10/90 (mass ratio) as the positive electrode active material. . The positive electrode active material mixture has an average particle size of 17 μm, a BET specific surface area of 0.3 m ² / g, and an alkali amount of 0.06% by mass. The density of the positive electrode mixture layer after the press treatment is 3.87 g / The specific surface area of cm ³ and the positive electrode mixture layer was 1.1 m ² / g. And the nonaqueous electrolyte secondary battery was produced like Example 1 except having used the said positive electrode.

Example 3
A positive electrode was produced in the same manner as in Example 1 except that the mixture ratio of the compound (A) and the compound (B) was (A) / (B) = 30/70 (mass ratio) as the positive electrode active material. . The positive electrode active material mixture has an average particle size of 15 μm, a BET specific surface area of 0.3 m ² / g, and an alkali amount of 0.15% by mass. The density of the positive electrode mixture layer after press treatment is 3.80 g / The specific surface area of cm ³ and the positive electrode mixture layer was 1.1 m ² / g. And the nonaqueous electrolyte secondary battery was produced like Example 1 except having used the said positive electrode.

Example 4
A positive electrode was produced in the same manner as in Example 1 except that the compound (A) was changed to LiNi _0.65 Co _0.33 Al _0.02 O ₂ . The mixture of the compound (A) and the compound (B) (positive electrode active material mixture) has an average particle diameter of 16 μm, a BET specific surface area of 0.3 m ² / g, and an alkali amount of 0.08% by mass, and is subjected to press treatment. The density of the subsequent positive electrode mixture layer was 3.84 g / cm ³ , and the specific surface area of the positive electrode mixture layer was 1.1 m ² / g. And the nonaqueous electrolyte secondary battery was produced like Example 1 except having used the said positive electrode.

Example 5
A positive electrode was produced in the same manner as in Example 1 except that the compound (A) was changed to LiNi _0.90 Co _0.05 Al _0.05 O ₂ . The mixture of the compound (A) and the compound (B) (positive electrode active material mixture) has an average particle diameter of 16 μm, a BET specific surface area of 0.3 m ² / g, and an alkali amount of 0.12% by mass, and is subjected to press treatment. The density of the subsequent positive electrode mixture layer was 3.82 g / cm ³ , and the specific surface area of the positive electrode mixture layer was 1.1 m ² / g. And the nonaqueous electrolyte secondary battery was produced like Example 1 except having used the said positive electrode.

Example 6
A positive electrode was produced in the same manner as in Example 1 except that the compound (A) was changed to LiNi _0.85 Co _0.10 Mg _0.025 Ti _0.025 O ₂ . The mixture of the compound (A) and the compound (B) (positive electrode active material mixture) has an average particle diameter of 16 μm, a BET specific surface area of 0.3 m ² / g, and an alkali amount of 0.11% by mass, and is subjected to press treatment. The density of the subsequent positive electrode mixture layer was 3.82 g / cm ³ , and the specific surface area of the positive electrode mixture layer was 1.1 m ² / g. And the nonaqueous electrolyte secondary battery was produced like Example 1 except having used the said positive electrode.

Example 7
A positive electrode was produced in the same manner as in Example 1 except that the compound (A) was changed to LiNi _0.85 Co _0.10 Mg _0.025 Zr _0.025 O ₂ . The mixture of the compound (A) and the compound (B) (positive electrode active material mixture) has an average particle diameter of 16 μm, a BET specific surface area of 0.3 m ² / g, and an alkali amount of 0.11% by mass, and is subjected to press treatment. The density of the subsequent positive electrode mixture layer was 3.82 g / cm ³ , and the specific surface area of the positive electrode mixture layer was 1.1 m ² / g. And the nonaqueous electrolyte secondary battery was produced like Example 1 except having used the said positive electrode.

Example 8
A positive electrode was produced in the same manner as in Example 1 except that the compound (B) was changed to LiCo _0.994 Mg _0.005 Ti _0.001 O ₂ . The mixture of the compound (A) and the compound (B) (positive electrode active material mixture) has an average particle diameter of 16 μm, a BET specific surface area of 0.3 m ² / g, and an alkali amount of 0.11% by mass, and is subjected to press treatment. The density of the subsequent positive electrode mixture layer was 3.82 g / cm ³ , and the specific surface area of the positive electrode mixture layer was 1.1 m ² / g. And the nonaqueous electrolyte secondary battery was produced like Example 1 except having used the said positive electrode.

Example 9
A positive electrode was produced in the same manner as in Example 1 except that the amount of the conductive additive (acetylene black) relative to 100 parts by mass of the positive electrode active material was 1.0 part by mass. The density of the positive electrode mixture layer after the press treatment was 3.84 g / cm ³ , and the specific surface area of the positive electrode mixture layer was 0.9 m ² / g. And the nonaqueous electrolyte secondary battery was produced like Example 1 except having used the said positive electrode.

Example 10
A positive electrode was produced in the same manner as in Example 1 except that the amount of the conductive additive (acetylene black) was 2.0 parts by mass and the amount of PVDF was 1.4 parts by mass with respect to 100 parts by mass of the positive electrode active material. The density of the positive electrode mixture layer after the press treatment was 3.75 g / cm ³ , and the specific surface area of the positive electrode mixture layer was 1.5 m ² / g. And the nonaqueous electrolyte secondary battery was produced like Example 1 except having used the said positive electrode.

Example 11
A positive electrode was produced in the same manner as in Example 1 except that the rubber binder amount was 0.5 parts by mass and the PVDF amount was 0.5 parts by mass with respect to 100 parts by mass of the positive electrode active material. The density of the positive electrode mixture layer after the press treatment was 3.80 g / cm ³ , and the specific surface area of the positive electrode mixture layer was 0.9 m ² / g. And the nonaqueous electrolyte secondary battery was produced like Example 1 except having used the said positive electrode.

Example 12
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the amount of V-EC was 0.3% by mass when preparing the nonaqueous electrolyte.

Example 13
Compound (A) obtained by classifying LiNi _0.85 Co _0.10 Al _0.05 O ₂ used in Example 1 [average particle size 4 μm, BET specific surface area 0.4 m ² / g, Obtained by _classifying LiCo _0.997 Al _0.001 Mg _0.001 Ti _0.001 O ₂ used in Example 1 by changing the alkali amount to 0.55% by mass]. A positive electrode was produced in the same manner as in Example 1, except that the average particle size was 10 μm, the BET specific surface area was 0.4 m ² / g, and the alkali amount was 0.02 mass%. The mixture (positive electrode active material mixture) of the compound (A) and the compound (B) has an average particle diameter of 8 μm, a BET specific surface area of 0.4 m ² / g, and an alkali amount of 0.13 mass%, and is subjected to press treatment. The density of the subsequent positive electrode mixture layer was 3.75 g / cm ³ , and the specific surface area of the positive electrode mixture layer was 1.2 m ² / g. And the nonaqueous electrolyte secondary battery was produced like Example 1 except having used the said positive electrode.

Comparative Example 1
A positive electrode was produced in the same manner as in Example 1 except that only the compound (A) used in Example 1 was used as the positive electrode active material. The density of the positive electrode mixture layer after the press treatment was 3.60 g / cm ³ , and the specific surface area of the positive electrode mixture layer was 1.0 m ² / g. And the nonaqueous electrolyte secondary battery was produced like Example 1 except having used the said positive electrode.

Comparative Example 2
A positive electrode was produced in the same manner as in Example 1 except that only the compound (B) used in Example 1 was used as the positive electrode active material. The density of the positive electrode mixture layer after the press treatment was 3.90 g / cm ³ , and the specific surface area of the positive electrode mixture layer was 1.1 m ² / g. And the nonaqueous electrolyte secondary battery was produced like Example 1 except having used the said positive electrode.

Comparative Example 3
A positive electrode was produced in the same manner as in Example 1 except that LiNiO ₂ was used in place of the compound (A). The mixture of LiNiO ₂ and compound (B) (positive electrode active material mixture) has an average particle size of 16 μm, a BET specific surface area of 0.3 m ² / g, and an alkali amount of 0.16% by mass. The density of the positive electrode mixture layer was 3.77 g / cm ³ , and the specific surface area of the positive electrode mixture layer was 1.1 m ² / g. And the nonaqueous electrolyte secondary battery was produced like Example 1 except having used the said positive electrode.

Comparative Example 4
A positive electrode was produced in the same manner as in Example 1 except that LiNi _0.85 Co _0.15 O ₂ was used in place of the compound (A). The mixture of LiNi _0.85 Co _0.15 O ₂ and compound (B) (positive electrode active material mixture) has an average particle diameter of 16 μm, a BET specific surface area of 0.3 m ² / g, and an alkali amount of 0.11 mass. The density of the positive electrode mixture layer after the press treatment was 3.82 g / cm ³ , and the specific surface area of the positive electrode mixture layer was 1.1 m ² / g. And the nonaqueous electrolyte secondary battery was produced like Example 1 except having used the said positive electrode.

Comparative Example 5
A positive electrode was produced in the same manner as in Example 1 except that LiNi _0.65 Co _0.25 Al _0.1 O ₂ was used in place of the compound (A). The mixture (positive electrode active material mixture) of LiNi _0.65 Co _0.25 Al _0.1 O ₂ and the compound (B) has an average particle diameter of 16 μm, a BET specific surface area of 0.3 m ² / g, and an alkali amount. The density of the positive electrode mixture layer after the press treatment was 3.78 g / cm ³ , and the specific surface area of the positive electrode mixture layer was 1.1 m ² / g. And the nonaqueous electrolyte secondary battery was produced like Example 1 except having used the said positive electrode.

Comparative Example 6
A positive electrode was produced in the same manner as in Example 1 except that LiCoO ₂ was used in place of the compound (B). The mixture of the compound (A) and LiCoO ₂ (positive electrode active material mixture) has an average particle size of 16 μm, a BET specific surface area of 0.3 m ² / g, and an alkali amount of 0.12% by mass. The density of the positive electrode mixture layer was 3.82 g / cm ³ , and the specific surface area of the positive electrode mixture layer was 1.1 m ² / g. And the nonaqueous electrolyte secondary battery was produced like Example 1 except having used the said positive electrode.

Comparative Example 7
A positive electrode was produced in the same manner as in Example 1 except that LiCo _0.96 Al _0.2 Mg _0.1 Ti _0.1 O ₂ was used in place of the compound (A). The mixture (positive electrode active material mixture) of LiCo _0.96 Al _0.2 Mg _0.1 Ti _0.1 O ₂ and compound (B) has an average particle diameter of 16 μm and a BET specific surface area of 0.3 m ² / g. The alkali amount was 0.11% by mass, the density of the positive electrode mixture layer after the press treatment was 3.78 g / cm ³ , and the specific surface area of the positive electrode mixture layer was 1.1 m ² / g. And the nonaqueous electrolyte secondary battery was produced like Example 1 except having used the said positive electrode.

Comparative Example 8
A positive electrode was produced in the same manner as in Example 1 except that only LiCoO ₂ was used as the positive electrode active material. The positive electrode active material has an average particle size of 18 μm, a BET specific surface area of 0.3 m ² / g, and an alkali amount of 0.01% by mass. The density of the positive electrode mixture layer after the press treatment is 3.90 g / cm. ³ , the specific surface area of the positive electrode mixture layer was 1.1 m ² / g. And the nonaqueous electrolyte secondary battery was produced like Example 1 except having used the said positive electrode.

Comparative Example 9
A positive electrode was produced in the same manner as in Example 1 except that the amount of the conductive additive (acetylene black) relative to 100 parts by mass of the positive electrode active material was changed to 0.8 parts by mass. The density of the positive electrode mixture layer after the press treatment was 3.82 g / cm ³ , and the specific surface area of the positive electrode mixture layer was 0.6 m ² / g. And the nonaqueous electrolyte secondary battery was produced like Example 1 except having used the said positive electrode.

Comparative Example 10
A positive electrode was produced in the same manner as in Example 1 except that the amount of the conductive additive (acetylene black) was 2.5 parts by mass and the amount of PVDF was 1.6 parts by mass with respect to 100 parts by mass of the positive electrode active material. The density of the positive electrode mixture layer after the press treatment was 3.70 g / cm ³ , and the specific surface area of the positive electrode mixture layer was 1.8 m ² / g. And the nonaqueous electrolyte secondary battery was produced like Example 1 except having used the said positive electrode.

  About the nonaqueous electrolyte secondary battery of Examples 1-13 and Comparative Examples 1-10, the following characteristic evaluation experiment was done.

<Discharge capacity>
For each of the batteries of Examples 1 to 13 and Comparative Examples 1 to 10, after charging at a constant current of 0.2 C up to 4.2 V, the battery was charged at a constant voltage until the total charging time was 8 hours, followed by 0. A constant current discharge was performed until the battery voltage was 3.3 V at 2C, and the discharge capacity at that time was determined. (Note that the lithium-based battery voltage at the time of constant current charging means 4.3 V.) After that, the battery was charged again under the above conditions and held at −10 ° C. for 3 hours, and then at −10 ° C. The battery was discharged until the battery voltage became 3.3 V at 0.5 C, and the discharge capacity at that time was determined. In the table, the discharge capacity after the charge / discharge cycle obtained for each battery is shown as a relative value when the discharge capacity of Comparative Example 8 is 100.

<Battery swelling after high temperature storage>
About each battery of Examples 1-13 and Comparative Examples 1-10, after performing a constant current-constant voltage charge to 4.2V on the same conditions as the said discharge capacity measurement, it stored for 4 hours in 85 degreeC environment, After taking out, the thickness of the battery after cooling for 2 hours in an atmosphere at 20 ° C. was measured to determine the change (swelling) from the battery thickness before storage.

<Overcharge>
Each of the batteries of Examples 1 to 13 and Comparative Examples 1 to 10 was charged at a constant current of 0.2 C up to 4.2 V, and then charged at a constant voltage until the total charging time was 8 hours, and then 1 A Then, constant current charging was performed up to 5.0 V, and after reaching 5.0 V, constant voltage charging was performed at 5.0 V. The test was continued for 240 minutes from the start of constant current charging, and the number of explosion-proof mechanisms (vents) operated during that time was examined.

<Nail penetration test>
About each battery of Examples 1-13 and Comparative Examples 1-10, after charging with a constant current of 0.2C to 4.25V, constant voltage charge was performed until the total charge time was 8 hours. The test was pierced using a 2.5 mmφ nail until it penetrated at a speed of 50 cm / second, and then the number of the battery having reached 120 ° C. or higher was examined.

  Table 1 shows the main structures of the nonaqueous electrolyte secondary batteries of Examples 1 to 13 and Comparative Examples 1 to 10, and Table 2 shows the evaluation results.

  In Table 1, the numerical value in the “carbon material amount” column is the amount with respect to 100 parts by mass of the positive electrode active material, and the numerical value in the “alkaline amount” column is the alkali amount [compound (A) and ( The amount of alkali in the mixture of B) or the total amount of the composite oxide used as the positive electrode active material] is meant.

  In Table 2, the value in the “overcharge test” column is the “number of batteries in which the explosion-proof mechanism was activated in the overcharge test”, and the value in the “nail puncture test” column is “the temperature in the nail puncture test is 120 ° C. The numerical values in the “battery swelling” column for “the number of batteries as described above” mean the battery swelling after the high-temperature storage test.

  As is apparent from Tables 1 and 2, the layered lithium / nickel / cobalt composite oxide [compound (A)] and the layered lithium / cobalt composite oxide [compound (B)] are in a mass ratio of 10:90 to In the batteries of Examples 1 to 3 using the positive electrode active material mixed in the range of 30:70, high capacity at room temperature was achieved, and the discharge capacity at low temperature was maintained high, and after high temperature storage The battery swelled, and the safety during overcharging and nail penetration was also good. On the other hand, the battery of Comparative Example 1 using only the compound (A) has a small discharge capacity at both normal and low temperatures, large swelling during high-temperature storage, easy operation of the explosion-proof mechanism during overcharge, and even during nail penetration. The battery temperature has risen. The swelling during high temperature storage is thought to be due to the increased amount of gas in the battery due to the large amount of alkali in the positive electrode active material. In addition, the amount of gas generated in the battery increased due to the large amount of alkali during overcharging, and in addition to this, gas generation due to positive electrode decomposition during overcharging caused the internal pressure of the battery to increase, and the explosion-proof mechanism was activated. it is conceivable that. In the nail penetration test, it is considered that the battery temperature increased because the calorific value of the lithium / nickel / cobalt composite oxide during 4.25V charging was very large.

  On the other hand, in the batteries of Comparative Examples 2 and 8 using the positive electrode not containing the compound (A), a high capacity battery was not obtained.

  As is clear from Tables 1 and 2, in the batteries of Examples 4 to 13, as in the batteries of Examples 1 to 3, an increase in capacity at room temperature was achieved, and the discharge capacity at low temperature was also high. In addition to being maintained at a high level, the battery swelled after high-temperature storage, as well as excellent safety during overcharging and nail penetration.

In contrast, in the batteries of Comparative Examples 3 and 4 using a compound of lithium-nickel composite oxide containing no added metal M ¹ in place of (A) and lithium nickel cobalt composite oxide, explosion-proof during overcharge The mechanism was easy to operate, and the battery temperature was likely to be high in the nail penetration test. Moreover, in Comparative Example 3 containing no cobalt, battery swelling during high-temperature storage increased. By using these things layered lithium-nickel-cobalt composite oxide containing an additive element M ¹ from the compound (A)], and actuation of the explosion-proof mechanism during overcharge, the battery temperature rise suppression during nail penetration and It can be seen that battery swelling during high temperature storage can be reduced. Moreover, it turns out that the battery swelling at the time of high temperature storage can be reduced by containing cobalt. However, in the battery of Comparative Example 5 in which a lithium / nickel / cobalt composite oxide having a high content of cobalt and additive element M ¹ was used in place of the compound (A), the discharge capacity was reduced, so that the compound ( The ratio y of M ¹ in A) is preferably 0.06 or less.

In addition, the battery of Comparative Example 9 in which the amount of the conductive additive in the positive electrode mixture layer was small and the specific surface area of the positive electrode mixture layer was small was inferior in discharge capacity at low temperatures. On the other hand, the battery of Comparative Example 10 in which the amount of the conductive auxiliary agent in the positive electrode mixture layer is large, the amount of PVDF as the binder is large, and the specific surface area of the positive electrode mixture layer is large is Since the safety at the time was inferior, the specific surface area of the electrode is preferably 0.9 to 1.5 m ² / g or less.

As described above, the layered lithium / nickel / cobalt composite oxide (A) and the layered lithium / cobalt composite oxide (B) obtained by adding the specific metal elements M ¹ and M ² to the positive electrode active material are used. By controlling the specific surface area of the electrode while controlling the form and the amount of alkali contained, and also controlling the amount of conductive auxiliary agent and rubber binder, it is non-water that has high capacity, high safety, and can suppress battery swelling. An electrolyte secondary battery can be provided. The nonaqueous electrolyte secondary battery of the present invention is more preferably applied to a prismatic battery or a laminate battery, which is particularly prone to swelling.

  In addition, although the electronic device using the battery of the embodiment of the small swelling can satisfy all of the capacity, the swelling, and the safety, when the battery of the comparative example is used, any of the capacity, the swelling, and the safety is satisfied. It will be inferior. For example, in an electronic device having a thickness of 15 mm, if the battery of Comparative Example 1 is used, the thickness becomes 16.6 mm and the lid may not close. However, if the battery of Example 1 is used, the thickness is suppressed to 15.4 mm. Can prevent such problems.

It is a figure which shows typically an example of the nonaqueous electrolyte secondary battery which concerns on this invention, (a) is the top view, (b) is the fragmentary longitudinal cross-sectional view. It is a perspective view of the nonaqueous electrolyte secondary battery shown in FIG.

Explanation of symbols

1 Positive electrode 2 Negative electrode 3 Separator

Claims (9)

A positive electrode for a non-aqueous electrolyte secondary battery comprising a positive electrode mixture layer containing a positive electrode active material, a conductive additive and a binder,
As the positive electrode active material, the general formula LiNi _x Co _(1-xy) M ¹ _y O ₂ (0.65 ≦ x ≦ 0.9, 0.01 ≦ y ≦ 0.06, element M ¹ is Li A layered lithium / nickel / cobalt composite oxide represented by a metal element other than Ni and Co and including at least one element selected from the group consisting of Al, Mg, Ti, Mn and Zr) A) and the general formula LiCo _(1-z) M ² _z O ₂ (0.002 ≦ z ≦ 0.03, element M ² is a metal element other than Li, Ni and Co, and includes Al, Mg, A layered lithium-cobalt composite oxide (B) represented by (including at least one element selected from the group consisting of Ti, Mn and Zr),
The amount of alkali in the mixture of the layered lithium / nickel / cobalt composite oxide (A) and the layered lithium / cobalt composite oxide (B) is 0.15% by mass or less,
The amount of the carbon material that is the conductive assistant is 1.0 to 2.0 parts by mass with respect to 100 parts by mass of the positive electrode active material,
A part of the binder is rubber, and the amount of rubber as the binder is 0.1 to 0.6 parts by mass with respect to 100 parts by mass of the positive electrode active material,
A positive electrode for a non-aqueous electrolyte secondary battery, wherein the positive electrode mixture layer has a specific surface area of 0.9 to 1.5 m ² / g.   2. The nonaqueous electrolyte secondary battery according to claim 1, wherein the average particle size of the mixture of the layered lithium / nickel / cobalt composite oxide (A) and the layered lithium / cobalt composite oxide (B) is 8 to 80 μm. Positive electrode. The specific surface area of the mixture of the layered lithium / nickel / cobalt composite oxide (A) and the layered lithium / cobalt composite oxide (B) is 0.2 to 0.4 m ² / g. Positive electrode for non-aqueous electrolyte secondary battery.   Content of layered lithium / nickel / cobalt composite oxide (A) when the total amount of layered lithium / nickel / cobalt composite oxide (A) and layered lithium / cobalt composite oxide (B) is 100 mass% Is 10-30 mass%, The positive electrode for nonaqueous electrolyte secondary batteries in any one of Claims 1-3.   The nonaqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein in the positive electrode mixture layer, the amount of the binder is 0.5 to 2.0 parts by mass with respect to 100 parts by mass of the positive electrode active material. Positive electrode. The positive electrode for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 5, wherein a part of the binder in the positive electrode mixture layer is polyvinylidene fluoride. The density of a positive mix layer is 3.6-4.3 g / cm < ³ >, The positive electrode for nonaqueous electrolyte secondary batteries in any one of Claims 1-6 . Non-aqueous electrolyte secondary battery characterized by having a non-aqueous electrolyte secondary battery positive electrode according to any one of claims 1-7. An electronic apparatus using the nonaqueous electrolyte secondary battery according to claim 8 .

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