JP2014002984A - Nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous secondary battery having high capacity and excellent charge-discharge cycle characteristics and storage characteristics.SOLUTION: A nonaqueous secondary battery contains, as positive active materials, a lithium nickel cobalt manganese composite oxide and a lithium cobalt composite oxide containing a dissimilar metal element other than lithium, nickel, cobalt, and manganese. The lithium cobalt composite oxide uses a lithium cobalt composite oxide (A) having an average particle diameter greater than 10 μm and less than or equal to 30 μm and a lithium cobalt composite oxide (B) having an average particle diameter greater than or equal to 1 μm and less than or equal to 10 μm so as to satisfy relation of A-B≥5. The lithium cobalt composite oxide (B) has a larger ratio of the dissimilar metal element with respect to a total amount of the cobalt and the dissimilar metal element than the lithium cobalt composite oxide (A). The average particle diameter of the lithium nickel cobalt manganese composite oxide is larger than that of the lithium cobalt composite oxide.

Description

  The present invention relates to a non-aqueous secondary battery having a high capacity and good charge / discharge cycle characteristics and storage characteristics.

  As portable electronic devices such as mobile phones and notebook computers become smaller, lighter, and have higher performance, there is a demand for higher capacity of non-aqueous secondary batteries such as lithium-ion secondary batteries as power sources. Increasingly.

  As the positive electrode of the nonaqueous secondary battery, for example, one having a structure in which a positive electrode mixture layer containing a positive electrode active material or the like is provided on at least one surface of a current collector is used. In increasing the capacity of such a non-aqueous secondary battery, for example, it is conceivable to increase the filling amount of the positive electrode active material in the positive electrode mixture layer or increase the charging voltage.

  For example, Patent Document 1 discloses that the positive electrode active layer in the positive electrode mixture layer is increased by using two or more lithium-containing transition metal oxides having different average particle diameters as the positive electrode active material to increase the density of the positive electrode mixture layer. In order to suppress the deterioration of the positive electrode active material even if the charging amount of the battery is increased and the charging voltage of the battery is increased, among the lithium-containing transition metal oxides, the minimum average particularly inferior in stability In addition to increasing the capacity of a non-aqueous secondary battery by adding a specific metal element to a particle having a particle size, a technique for improving the charge / discharge cycle characteristics has been proposed.

Further, in order to increase the capacity of the non-aqueous secondary battery, in addition to the above method, LiCoO ₂ which is currently widely used as a positive electrode active material also uses a lithium-containing composite oxide containing Ni having a large capacity. It is also being considered.

JP 2007-287658 A

  However, the lithium-containing composite oxide having a high Ni content also has a property that easily causes gas generation that causes battery swelling, for example, when the battery is stored in a charged state, particularly when the particle size is small. ing. Therefore, by using a lithium-containing composite oxide having a high Ni content and applying a technique such as that described in Patent Document 1, the amount of the positive electrode active material in the positive electrode mixture layer is increased, and a high capacity is obtained. In order to obtain a battery having excellent discharge cycle characteristics, it is also desired to suppress the gas generation and enhance its storage characteristics.

  This invention is made | formed in view of the said situation, The objective is to provide a high capacity | capacitance and a non-aqueous secondary battery with favorable charging / discharging cycling characteristics and storage characteristics.

  The non-aqueous secondary battery of the present invention that has achieved the above object has a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator, and the positive electrode comprises a positive electrode mixture layer containing a positive electrode active material, A current collector has one or both surfaces, and as the positive electrode active material, a lithium nickel cobalt manganese composite oxide and a lithium cobalt composite oxide containing different metal elements other than lithium, nickel, cobalt and manganese In addition, the lithium cobalt composite oxide includes a lithium cobalt composite oxide (A) having an average particle diameter of more than 10 μm and 30 μm or less, and a lithium cobalt composite oxide (B) having an average particle diameter of 1 μm or more and 10 μm or less. In the total amount of cobalt and a different metal element in the lithium cobalt composite oxide (B) Lithium nickel cobalt manganese composite oxide used as a positive electrode active material, wherein the ratio of the different metal element is larger than the ratio of the different metal element in the total amount of cobalt and the different metal element in the lithium cobalt composite oxide (A) When the average particle diameter is C (μm), C> B.

  According to the present invention, it is possible to provide a non-aqueous secondary battery that has a high capacity and good charge / discharge cycle characteristics and storage characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows typically an example of the non-aqueous secondary battery of this invention, (a) is the top view, (b) is the fragmentary longitudinal cross-sectional view. It is a perspective view of the non-aqueous secondary battery shown in FIG.

  The positive electrode according to the non-aqueous secondary battery of the present invention has a structure having a positive electrode mixture layer containing a positive electrode active material on one side or both sides of a current collector.

  As the positive electrode active material, a lithium nickel cobalt manganese composite oxide and a lithium cobalt composite oxide containing a different metal element other than lithium, nickel, cobalt, and manganese are used.

  The lithium cobalt composite oxide includes a lithium cobalt composite oxide (A) having an average particle size A (μm) of more than 10 μm and 30 μm or less, and a lithium cobalt composite oxide having an average particle size B (μm) of 1 μm or more and 10 μm or less. The difference (A−B) between the average particle size A of the lithium cobalt composite oxide (A) and the average particle size B of the lithium cobalt composite oxide (B) is 5 at this time. (Μm) or more. In the lithium nickel cobalt manganese composite oxide, when the average particle diameter is C (μm), the relationship with the average particle diameter B of the lithium cobalt composite oxide (B) is C> B. Is used.

  By using the lithium cobalt composite oxide (A) and the lithium cobalt composite oxide (B) as described above in combination with the lithium nickel cobalt manganese composite oxide, the lithium cobalt composite oxide ( A) and the lithium nickel cobalt manganese composite oxide particles can be filled with the lithium cobalt composite oxide (B) having a small particle diameter, so that the density of the positive electrode mixture layer is increased and the positive electrode in the positive electrode mixture layer. The amount of active material can be increased.

Moreover, the lithium nickel cobalt manganese composite oxide used as the positive electrode active material has higher stability under a high voltage than, for example, LiCoO _2. Further, the lithium cobalt composite oxide (A) and the lithium cobalt composite oxide (B ) Is improved in stability under a higher voltage than, for example, LiCoO ₂ by the action of the different metal element. Therefore, even when the nonaqueous secondary battery of the present invention is used in a method of performing constant current-constant voltage charging at a final voltage of 4.3 V or higher, the positive electrode active material is unlikely to deteriorate.

  In the nonaqueous secondary battery of the present invention, excellent charge / discharge cycle characteristics are ensured while increasing the capacity by these actions.

  The lithium nickel cobalt manganese composite oxide tends to cause gas generation in the battery, particularly when the particle size is small. However, in the non-aqueous secondary battery of the present invention, the positive electrode active material having a small particle size that enters the gap between the positive electrode active material particles having a large particle size generates more gas in the battery than the lithium nickel cobalt manganese composite oxide. Since the lithium cobalt composite oxide (B) that is difficult to cause is used, for example, the occurrence of swelling during storage can be suppressed. Therefore, the non-aqueous secondary battery of the present invention also has good storage characteristics.

  The average particle diameter A of the lithium cobalt composite oxide (A) is more preferably 17 μm or more, and more preferably 24 μm or less. Furthermore, the average particle diameter B of the lithium cobalt composite oxide (B) is more preferably 5 μm or more, and more preferably 10 μm or less.

  The average particle size of the lithium nickel cobalt manganese composite oxide is preferably 10 μm or more, more preferably 11 μm or more, and preferably 17 μm or less, more preferably 16 μm or less. .

  In the nonaqueous secondary battery of the present invention, the average particle diameter A of the lithium cobalt composite oxide (A), the average particle diameter B of the lithium cobalt composite oxide (B), and the average of the lithium nickel cobalt manganese composite oxide The particle diameter C (μm) preferably satisfies the relationship A ≧ C> B, and more preferably satisfies the relationship A> C> B. In this case, the effect of increasing the filling amount of the positive electrode active material by improving the density of the positive electrode mixture layer, the effect of improving the charge / discharge cycle characteristics accompanying the improvement of the stability of the positive electrode active material, the particle size of the lithium nickel cobalt manganese composite oxide The effect of improving the storage characteristics by increasing the amount to some extent can be secured more favorably.

The average particle size of the lithium cobalt composite oxide (A), lithium cobalt composite oxide (B), and lithium nickel cobalt manganese composite oxide referred to in this specification is the Nikkiso Co., Ltd. Microtrac particle size distribution measuring device “HRA9320”. It is a 50% diameter value (d ₅₀ ) median diameter in the volume-based integrated fraction when the integrated volume is obtained from particles having a small particle size distribution measured by use.

  In the lithium cobalt composite oxide used for the positive electrode according to the nonaqueous secondary battery of the present invention, the proportion of the different metal element in the total amount of cobalt and the different metal element is lithium cobalt composite oxide (A). The lithium cobalt composite oxide (B) is larger than that.

  As the particle size of the lithium cobalt composite oxide is smaller, the stability under high voltage and the stability against heat are inferior. Therefore, in the non-aqueous secondary battery of the present invention, the lithium cobalt composite oxide (B) having a smaller average particle diameter contains a large amount of the different metal element having an effect of improving the stability. In addition, charging / discharging and stability of heat of the battery are improved, and good charge / discharge cycle characteristics and storage characteristics can be secured.

  However, since the dissimilar metal element is a component that cannot contribute to the capacity of the lithium cobalt composite oxide, when the amount in the lithium cobalt composite oxide increases, the capacity of the lithium cobalt composite oxide decreases. Therefore, in the lithium cobalt composite oxide (A) having a larger average particle size and higher stability, the content of the dissimilar metal element is reduced, and the capacity reduction due to the inclusion of the dissimilar metal element is minimized. Suppresses the balance between stability and capacity.

  The lithium cobalt composite oxide (A) and the lithium cobalt composite oxide (B) are preferably those represented by the following general composition formula (1).

Li _{1 + y} Co _z M ¹ _1-z O ₂ (1)
[In the general composition formula (1), −0.3 ≦ y ≦ 0.3, 0.95 ≦ z <1.0, and M ¹ is selected from the group consisting of Mg, Zr, Al, and Ti. At least one element. ]

In the general composition formula (1), M ¹ corresponds to the different metal element. Different metal elements M ¹ containing a lithium cobalt composite oxide (A) and lithium cobalt composite oxide (B) is, as described above, Mg, Zr, Al, it may be any of Ti, 1 kind or of these Two or more types may be used, but since the lithium cobalt composite oxide (A) and the lithium cobalt composite oxide (B) are more effective in increasing the stability and thermal stability under high voltage, Mg And / or Zr is more preferred.

Incidentally, the lithium-cobalt composite oxide (A) and lithium cobalt composite oxide in (B), Co While a component contributing to the capacity increase, different metal elements M ¹ may not contribute to the capacity increase. Therefore, in the general composition formula (1) representing the lithium cobalt composite oxide (A) and the lithium cobalt composite oxide (B), the amount z of Co is set to 0.95 from the viewpoint of keeping these capacities high. The above is preferable. Further, in the general composition formula (1), the amount of Co z is less than 1.0, but from the viewpoint of better ensuring the above effect by containing the different metal element M ¹ , the different metal element The amount “1-z” of M ¹ is more preferably 0.005 or more, and therefore the amount z of Co is more preferably 0.995 or less.

When the lithium cobalt composite oxide (A) and the lithium cobalt composite oxide (B) are represented by the general composition formula (1), the lithium cobalt composite oxide (A) and the lithium cobalt composite oxide ( B) and, as the different metal elements M ^1, also contain the same elements may contain different elements, lithium cobalt composite oxides the amount of different metal elements M ¹ containing the (a) and "1-z1", lithium-cobalt composite oxide the amount of different metal elements ^{M 1} containing the (B) is taken as "1-z2", the relationship of (1-z1) <(1 -z2) It only has to satisfy. More specifically, “1-z1” is more preferably 0.01 or more, and further preferably 0.02 or less. “1-z2” is more preferably 0.02 or more, and further preferably 0.03 or less.

  The lithium cobalt composite oxide (A) and the lithium cobalt composite oxide (B) have a higher true density and a higher energy volume density, particularly when the composition is close to the stoichiometric ratio. Specifically, in the composition formula, it is preferable to satisfy −0.3 ≦ y ≦ 0.3, and by adjusting the value of y in this way, the true density and reversibility at the time of charge / discharge are improved. Can do.

Lithium cobalt composite oxide (A) and lithium cobalt composite oxide (B) is, Li-containing compound (lithium hydroxide, etc.), Co-containing compound (such as cobalt sulfate), and compounds containing different metallic element M ¹ (oxidation Compound, hydroxide, sulfate, etc.) and the raw material mixture can be fired. In order to synthesize lithium cobalt composite oxide (A) and lithium cobalt composite oxide (B) with higher purity, a composite compound (hydroxide, oxide, etc.) containing Co and a different metal element M ¹ is used. It is preferable to mix a Li-containing compound and the like and to fire this raw material mixture.

  The firing conditions of the raw material mixture for synthesizing the lithium cobalt composite oxide (A) and the lithium cobalt composite oxide (B) can be, for example, 800 to 1050 ° C. for 1 to 24 hours. It is preferable to preheat by heating to lower temperature (for example, 250-850 degreeC) and hold | maintaining at that temperature, and to raise temperature to a calcination temperature after that, and to advance reaction. Although there is no restriction | limiting in particular about the time of preheating, Usually, what is necessary is just to be about 0.5 to 30 hours. The atmosphere during firing can be an atmosphere containing oxygen (that is, in the air), a mixed atmosphere of an inert gas (such as argon, helium, or nitrogen) and oxygen gas, or an oxygen gas atmosphere. The oxygen concentration (volume basis) is preferably 15% or more, and more preferably 18% or more.

  When forming the positive electrode mixture layer relating to the positive electrode of the nonaqueous secondary battery of the present invention, when the total of the lithium cobalt composite oxide (A) and the lithium cobalt composite oxide (B) is 100% by mass The content of the lithium cobalt composite oxide (A) is preferably 50% by mass or more, more preferably 70% by mass or more, and preferably less than 100% by mass, 90% by mass. The following is more preferable.

  The lithium nickel cobalt manganese composite oxide used for the positive electrode according to the nonaqueous secondary battery of the present invention is preferably represented by the following general composition formula (2).

Li _{1 + s} M ² O ₂ (2)
[In the general composition formula (2), −0.3 ≦ s ≦ 0.3, and M ² is a group of three or more elements including at least Ni, Co, and Mn, and each of which constitutes M ² 30 <a <65, 5 <b <35, and 15 <c <50, where the ratios (mol%) of Ni, Co, and Mn in the element are a, b, and c, respectively. ]

In the lithium-nickel-cobalt-manganese composite oxide represented by the general formula (2), Ni is a component that contributes to the capacity increase of the lithium-nickel-cobalt-manganese composite oxide, 100 mol the total number of elements in the element group M ² %, The Ni ratio a is preferably over 30 mol%, more preferably 50 mol% or more. Further, in the lithium-nickel-cobalt-manganese composite oxide represented by the general formula (2), from the viewpoint of satisfactorily ensuring the effect of containing an element other than Ni, the total number of elements in the element group M ² 100 mol %, The Ni ratio a is preferably less than 65 mol% and more preferably 60 mol% or less.

  In the lithium nickel cobalt manganese composite oxide represented by the general composition formula (2), Co is a component that contributes to an increase in the capacity of the lithium nickel cobalt manganese composite oxide as well as Ni, and is filled in the positive electrode mixture layer. While it works to improve density, too much may cause an increase in cost and a decrease in safety. In addition to these reasons, from the viewpoint of satisfactorily securing the action of stabilizing the average valence of Mn described later, the total number of elements in the element group M in the general composition formula (2) representing the lithium nickel cobalt manganese composite oxide Is 100 mol%, the Co ratio b is preferably more than 5 mol%, more preferably 20 mol% or more, and preferably less than 35 mol%, and 30 mol% or less. Is more preferable.

Furthermore, in a lithium-nickel-cobalt-manganese composite oxide, when the total number of elements in the element group ^{M 2} in the general formula (2) and 100 mol%, the ratio c of Mn, that is greater than 15 mol% preferably 20 mol% or more, more preferably less than 50 mol%, and even more preferably 30 mol% or less. By including Mn in the amount as described above in the lithium nickel cobalt manganese composite oxide, and making sure that Mn is present in the crystal lattice, the thermal stability of the lithium nickel cobalt manganese composite oxide can be improved. A highly safe battery can be configured.

  Furthermore, in the lithium nickel cobalt manganese composite oxide, Co acts together with Mn to suppress fluctuations in the valence of Mn due to Li doping and dedoping during battery charging / discharging. Therefore, the average valence of Mn can be stabilized at a value in the vicinity of tetravalence, and the reversibility of charge / discharge can be further enhanced. Therefore, by using such a lithium nickel cobalt manganese composite oxide, it becomes possible to constitute a battery having more excellent charge / discharge cycle characteristics.

In the lithium-nickel-cobalt-manganese composite oxide, the element group ^{M 2} is, Ni, may be composed only of Co and Mn, with these elements, Mg, Ti, Zr, Nb , Mo, W, Al, It may contain at least one element selected from the group consisting of Si, Ga, Ge, and Sn. However, when the total number of elements in the element group ^{M 2} was 100mol%, Mg, Ti, Zr , Nb, Mo, W, Al, Si, Ga, total proportion d of Ge and Sn are the following 5 mol% It is preferably 1 mol% or less. Elements other than Ni, Co and Mn in the element group M ² may be uniformly distributed in the lithium nickel cobalt manganese composite oxide, or may be segregated on the particle surface or the like.

The lithium nickel cobalt manganese composite oxide having the above composition has a large true density of 4.55 to 4.95 g / cm ³ and is a material having a high volume energy density. The true density of the lithium nickel cobalt manganese composite oxide containing Mn in a certain range varies greatly depending on its composition. However, the structure is stabilized and the uniformity can be improved in the narrow composition range as described above. For example, it is considered to be a large value close to the true density of LiCoO ₂ . Moreover, the capacity | capacitance per mass of lithium nickel cobalt manganese complex oxide can be enlarged, and it can be set as the material excellent in reversibility.

The lithium nickel cobalt manganese composite oxide has a higher true density especially when the composition is close to the stoichiometric ratio. Specifically, in the general composition formula (2), −0.3 ≦ s It is preferable that ≦ 0.3, and the true density and reversibility can be improved by adjusting the value of s in this way. s is more preferably −0.05 or more and 0.05 or less. In this case, the true density of the lithium nickel cobalt manganese composite oxide is set to a higher value of 4.6 g / cm ³ or more. Can do.

The lithium nickel cobalt manganese composite oxide represented by the general composition formula (2) includes a Li-containing compound (such as lithium hydroxide), a Ni-containing compound (such as nickel sulfate), a Co-containing compound (such as cobalt sulfate), and a Mn-containing compound. compound (such as manganese sulfate), and the element group M compound containing other elements contained in ² (oxides, hydroxides, sulfates, etc.) can be produced by, for example, mixing, calcining. Further, in synthesizing the lithium-nickel-cobalt-manganese composite oxide with a higher purity, a composite compound containing a plurality of elements included in the element group M ² (hydroxides, such as an oxide) and mixing the Li-containing compound It is preferable to fire.

  Firing conditions can be, for example, 800 to 1050 ° C. for 1 to 24 hours, but once heated to a temperature lower than the firing temperature (for example, 250 to 850 ° C.) and maintained at that temperature, preheating is performed. After that, it is preferable to raise the temperature to the firing temperature to advance the reaction. Although there is no restriction | limiting in particular about the time of preheating, Usually, what is necessary is just to be about 0.5 to 30 hours. The atmosphere during firing can be an atmosphere containing oxygen (that is, in the air), a mixed atmosphere of an inert gas (such as argon, helium, or nitrogen) and oxygen gas, or an oxygen gas atmosphere. The oxygen concentration (volume basis) is preferably 15% or more, and more preferably 18% or more.

  In forming the positive electrode mixture layer relating to the positive electrode of the nonaqueous secondary battery of the present invention, the lithium cobalt composite oxide (A), the lithium cobalt composite oxide (B), and the lithium nickel cobalt manganese composite oxide When the total is 100% by mass, the content of the lithium nickel cobalt manganese composite oxide is preferably 15% by mass or more, more preferably 20% by mass or more, and 45% by mass or less. It is preferable that it is 30 mass% or less.

As the positive electrode active material, other active materials can be used together with the lithium nickel cobalt manganese composite oxide, the lithium cobalt composite oxide (A), and the lithium cobalt composite oxide (B). Examples of such other active materials include LiCoO ₂ ; lithium manganese oxides such as LiMnO ₂ and Li ₂ MnO ₃ ; lithium having a spinel structure such as LiMn ₂ O ₄ and Li _4/3 Ti _5/3 O _4. Olivine-structured lithium-containing composite oxides such as LiFePO ₄ ; oxides obtained by substituting the above-mentioned oxides with basic elements and various elements; and one or more of these can be exemplified. Can be used.

  However, from the viewpoint of ensuring the effect of the present invention satisfactorily, the content of the other active material in the total amount of the positive electrode active material is preferably 10% by mass or less, and more preferably 5% by mass or less. preferable.

  The positive electrode mixture layer usually contains a binder and a conductive additive in addition to the positive electrode active material.

  As the binder for the positive electrode, any thermoplastic resin or thermosetting resin can be used as long as it is chemically stable in the non-aqueous secondary battery. For example, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyhexafluoropropylene (PHFP), styrene butadiene rubber (SBR), tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene -Hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene -Tetrafluoroethylene copolymer (ETFE resin), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-te Lafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer (ECTFE), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer Or an ethylene-acrylic acid copolymer, an ethylene-methacrylic acid copolymer, an ethylene-methyl acrylate copolymer, an ethylene-methyl methacrylate copolymer, and a Na ion crosslinked product of these copolymers. These may be used alone or in combination of two or more. Among these, considering the stability in the non-aqueous secondary battery and the characteristics of the non-aqueous secondary battery, PVDF, PTFE, and PHFP are preferable, and these are used in combination or formed of these monomers. A copolymer may be used.

  Any conductive aid for the positive electrode may be used as long as it is chemically stable in the non-aqueous secondary battery. For example, graphitic carbon materials such as natural graphite and artificial graphite; carbon blacks such as acetylene black, ketjen black (trade name), channel black, furnace black, lamp black, and thermal black; conductivity such as carbon fiber and metal fiber Fibers; Metal powders such as aluminum powders; Fluorinated carbon; Zinc oxide; Conductive whiskers made of potassium titanate; Conductive metal oxides such as titanium oxide; Organic conductive materials such as polyphenylene derivatives; These may be used alone or in combination of two or more. Among these, highly conductive graphite and carbon black excellent in liquid absorption are preferable. Further, the form of the conductive auxiliary agent is not limited to primary particles, and secondary aggregates and aggregated forms such as chain structures can also be used. Such an assembly is easier to handle and has better productivity.

  The positive electrode is prepared, for example, by adding a positive electrode active material, a binder, a conductive additive or the like to a solvent such as N-methyl-2-pyrrolidone (NMP) to prepare a paste-like or slurry-like positive electrode mixture-containing composition, This can be produced by applying it onto a current collector by various coating methods, drying it, and adjusting the thickness and density of the positive electrode mixture layer by pressing.

  Examples of the coating method for applying the positive electrode mixture-containing composition onto the current collector include a substrate pulling method using a doctor blade; a coater method using a die coater, comma coater, knife coater, etc .; screen printing, letterpress Printing methods such as printing can be adopted.

  In the positive electrode mixture layer, it is preferable that the positive electrode active material is 80 to 99% by mass, the binder is 0.5 to 10% by mass, and the conductive additive is 0.5 to 10% by mass. Moreover, it is preferable that the thickness of a positive mix layer is 15-200 micrometers per single side | surface of a collector.

In addition, as described above, the positive electrode mixture layer uses a small particle size lithium cobalt composite oxide (B) together with a relatively large particle size lithium cobalt composite oxide (A) or lithium nickel cobalt manganese composite oxide. for to those, the density of the positive electrode mixture layer, for example, 3.6 g / cm ³ or higher, preferably 3.7 g / cm ³ or more, more preferably enhances well with 3.8 g / cm ³ or more, The filling amount of the active material in the positive electrode mixture layer can be increased. However, if the density of the positive electrode mixture layer is too high, for example, the permeability of the non-aqueous electrolyte is deteriorated, and the effect of increasing the capacity may be reduced. Therefore, the density of the positive electrode mixture layer is preferably 4 g / cm ³ or less.

  The density of the positive electrode mixture layer in the present specification is a value determined by the following measurement method. The positive electrode is cut out in a predetermined area, and its mass is measured using an electronic balance having a minimum scale of 1 mg, and the mass of the positive electrode mixture layer is calculated by subtracting the mass of the current collector from this mass. Further, the total thickness of the positive electrode was measured at 10 points with a micrometer having a minimum scale of 1 μm, and the volume of the positive electrode mixture layer was calculated from the average value and the area obtained by subtracting the thickness of the current collector from this thickness. The density of the positive electrode mixture layer is calculated by dividing the mass of the positive electrode mixture layer.

  The material of the current collector of the positive electrode is not particularly limited as long as it is a chemically stable electron conductor in the constructed nonaqueous secondary battery. For example, in addition to aluminum or aluminum alloy, stainless steel, nickel, titanium, carbon, conductive resin, etc., a composite material in which a carbon layer or a titanium layer is formed on the surface of aluminum, aluminum alloy, or stainless steel can be used. . Among these, aluminum or an aluminum alloy is particularly preferable. This is because they are lightweight and have high electron conductivity. For the positive electrode current collector, for example, a foil, a film, a sheet, a net, a punching sheet, a lath body, a porous body, a foamed body, a molded body of a fiber group, or the like made of the above-described material is used. In addition, the surface of the current collector can be roughened by surface treatment. Although the thickness of a collector is not specifically limited, Usually, it is 1-500 micrometers.

  In addition, a positive electrode is not limited to what was manufactured by the said manufacturing method, The thing manufactured by the other manufacturing method may be used. Moreover, you may form the lead body for electrically connecting with the other member in a non-aqueous secondary battery according to a conventional method as needed.

  The non-aqueous secondary battery of the present invention has a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator, and the positive electrode only needs to be the positive electrode, and there is no particular limitation on the other configuration and structure. Various configurations and structures employed in known non-aqueous secondary batteries such as lithium ion secondary batteries can be applied.

  For the negative electrode, for example, a negative electrode active material, a binder, and, if necessary, a negative electrode mixture layer comprising a negative electrode mixture containing a conductive additive can be used on one or both sides of the current collector. .

  Examples of the negative electrode active material include graphitic carbon materials [natural graphite such as flaky graphite; graphitized carbon such as pyrolytic carbons, mesophase carbon microbeads (MCMB) and carbon fibers at 2800 ° C. or higher. Artificial graphite; etc.], pyrolytic carbons, cokes, glassy carbons, fired bodies of organic polymer compounds, mesocarbon microbeads, carbon fibers, activated carbon, metals that can be alloyed with lithium (Si, Sn, etc.) ) Or alloys thereof, oxides, and the like, and one or more of them can be used.

Among the negative electrode active materials, in order to increase the capacity of the non-aqueous secondary battery, in particular, a material containing Si and O as constituent elements (however, the atomic ratio x of O to Si is 0.5 ≦ x ≦ 1.5 (hereinafter referred to as “SiO _x ”).

The SiO _x may contain Si microcrystal or amorphous phase. In this case, the atomic ratio of Si and O is a ratio including Si microcrystal or amorphous phase Si. That is, SiO _x includes a structure in which Si (for example, microcrystalline Si) is dispersed in an amorphous SiO ₂ matrix, and this amorphous SiO ₂ is dispersed in the SiO ₂ matrix. It is sufficient that the atomic ratio x satisfies 0.5 ≦ x ≦ 1.5 in combination with Si. For example, in the case of a material in which Si is dispersed in an amorphous SiO ₂ matrix and the material has a molar ratio of SiO ₂ to Si of 1: 1, x = 1, so that the structural formula is represented by SiO. The In the case of a material having such a structure, for example, in X-ray diffraction analysis, a peak due to the presence of Si (microcrystalline Si) may not be observed, but when observed with a transmission electron microscope, the presence of fine Si Can be confirmed.

Then, SiO _x is preferably a complex complexed with carbon materials, for example, it is desirable that the surface of the SiO _x is coated with a carbon material. Since SiO _x has poor conductivity, when it is used as a negative electrode active material, from the viewpoint of securing good battery characteristics, a conductive material (conductive aid) is used, and SiO _x and conductive material in the negative electrode are used. Therefore, it is necessary to form a good conductive network by mixing and dispersing with each other. If complexes complexed with carbon material SiO _x, for example, simply than with a material obtained by mixing a conductive material such as SiO _x and the carbon material, good conductive network in the negative electrode Formed.

The complex of the SiO _x and the carbon material, as described above, other although the surface of the SiO _x coated with carbon material, such as granules of SiO _x and the carbon material can be cited.

In addition, since the composite in which the surface of SiO _x is coated with a carbon material is further combined with a conductive material (carbon material or the like), a better conductive network can be formed in the negative electrode. Thus, it is possible to realize a non-aqueous secondary battery with higher capacity and better battery characteristics (for example, charge / discharge cycle characteristics). The complex of the SiO _x and the carbon material coated with a carbon material, for example, like granules the mixture was further granulated with SiO _x and the carbon material coated with a carbon material.

Further, as SiO _x whose surface is coated with a carbon material, the surface of a composite (for example, a granulated body) of SiO _x and a carbon material having a smaller specific resistance value is further coated with a carbon material. Those can also be preferably used. In the non-aqueous secondary battery having a negative electrode containing SiO _x as a negative electrode active material, it is possible to form a better conductive network when SiO _x and the carbon material are dispersed inside the granule. Battery characteristics such as load discharge characteristics can be further improved.

Preferred examples of the carbon material that can be used to form a composite with SiO _x include carbon materials such as low crystalline carbon, carbon nanotubes, and vapor grown carbon fibers.

The details of the carbon material include at least one selected from the group consisting of fibrous or coiled carbon materials, carbon black (including acetylene black and ketjen black), artificial graphite, graphitizable carbon, and non-graphitizable carbon. A seed material is preferred. Fibrous or coil-like carbon materials are preferable in that they easily form a conductive network and have a large surface area. Carbon black (including acetylene black and ketjen black), graphitizable carbon, and non-graphitizable carbon have high electrical conductivity and high liquid retention, and even if SiO _x particles expand and contract. This is preferable in that it has a property of easily maintaining contact with the particles.

When SiO _x is used as the negative electrode active material, it is preferable to use a graphitic carbon material in combination as the negative electrode active material as will be described later. This graphitic carbon material is used as a carbon related to a composite of SiO _x and a carbon material. It can also be used as a material. Graphite carbon material, like carbon black, has high electrical conductivity and high liquid retention, and even when SiO _x particles expand and contract, they easily maintain contact with the particles. Therefore, it can be preferably used for forming a complex with SiO _x .

Among the carbon materials exemplified above, a fibrous carbon material is particularly preferable for use when the composite with SiO _x is a granulated body. Fibrous carbon material can follow the expansion and contraction of SiO _x with the charging and discharging of the battery due to the high shape is thin threadlike flexibility, also because bulk density is large, many and SiO _x particles It is because it can have a junction. Examples of the fibrous carbon include polyacrylonitrile (PAN) -based carbon fiber, pitch-based carbon fiber, vapor-grown carbon fiber, and carbon nanotube, and any of these may be used.

The fibrous carbon material can also be formed on the surface of the SiO _x particles by, for example, a vapor phase method.

The specific resistance value of SiO _x is usually 10 ³ to 10 ⁷ kΩcm, while the specific resistance value of the carbon material exemplified above is usually 10 ^{−5 to} 10 kΩcm. The composite of SiO _x and the carbon material may further have a material layer (a material layer containing non-graphitizable carbon) that covers the carbon material coating layer on the particle surface.

When a composite of SiO _x and a carbon material is used for the negative electrode, the ratio of SiO _x and the carbon material is based on SiO _x : 100 parts by mass from the viewpoint of satisfactorily exerting the effect of the composite with the carbon material. The carbon material is preferably 5 parts by mass or more, and more preferably 10 parts by mass or more. Further, in the composite, if the ratio of the carbon material to be combined with SiO _x is too large, it may lead to a decrease in the amount of SiO _x in the negative electrode mixture layer, and the effect of increasing the capacity may be reduced. SiO _x: relative to 100 parts by weight, the carbon material, and more preferably preferably not more than 50 parts by weight, more than 40 parts by weight.

The composite of the SiO _x and the carbon material can be obtained, for example, by the following method.

First, a manufacturing method in the case of combining SiO _x will be described. A dispersion liquid in which SiO _x is dispersed in a dispersion medium is prepared, and sprayed and dried to produce composite particles including a plurality of particles. For example, ethanol or the like can be used as the dispersion medium. It is appropriate to spray the dispersion in an atmosphere of 50 to 300 ° C. In addition to the above method, similar composite particles can be produced also by a granulation method by a mechanical method using a vibration type or planetary type ball mill or rod mill.

Incidentally, the SiO _x, in the case of manufacturing a granulated body with small carbon material resistivity value than SiO _x is adding the carbon material in the dispersion liquid of SiO _x are dispersed in a dispersion medium, the dispersion by using a liquid, by a similar method to the case of composite of SiO _x may be a composite particle (granule). Further, by granulation process according to the similar mechanical method, it is possible to produce a granular material of the SiO _x and the carbon material.

Next, when the surface of SiO _x particles (SiO _x composite particles or a granulated body of SiO _x and a carbon material) is coated with a carbon material to form a composite, for example, the SiO _x particles and the hydrocarbon-based material The gas is heated in the gas phase, and carbon generated by pyrolysis of the hydrocarbon-based gas is deposited on the surface of the particles. As described above, according to the vapor deposition (CVD) method, the hydrocarbon-based gas spreads to every corner of the composite particle, and the surface of the particle and the pores in the surface are thin and contain a conductive carbon material. Since a uniform film (carbon material coating layer) can be formed, the SiO _x particles can be imparted with good conductivity with a small amount of carbon material.

In the production of SiO _x coated with a carbon material, the processing temperature (atmosphere temperature) of the vapor deposition (CVD) method varies depending on the type of hydrocarbon gas, but usually 600 to 1200 ° C. is appropriate. Among these, the temperature is preferably 700 ° C. or higher, and more preferably 800 ° C. or higher. This is because the higher the treatment temperature, the less the remaining impurities, and the formation of a coating layer containing carbon having high conductivity.

  As the liquid source of the hydrocarbon-based gas, toluene, benzene, xylene, mesitylene and the like can be used, but toluene that is easy to handle is particularly preferable. A hydrocarbon-based gas can be obtained by vaporizing them (for example, bubbling with nitrogen gas). Moreover, methane gas, acetylene gas, etc. can also be used.

In addition, after the surface of SiO _x particles (SiO _x composite particles or a granulated body of SiO _x and a carbon material) is covered with a carbon material by a vapor deposition (CVD) method, a petroleum-based pitch or a coal-based pitch is used. At least one organic compound selected from the group consisting of a thermosetting resin and a condensate of naphthalene sulfonate and aldehydes is attached to a coating layer containing a carbon material, and then the organic compound is attached. The obtained particles may be fired.

Specifically, a dispersion liquid in which a SiO _x particle (SiO _x composite particle or a granulated body of SiO _x and a carbon material) coated with a carbon material and the organic compound are dispersed in a dispersion medium is prepared, The dispersion is sprayed and dried to form particles coated with the organic compound, and the particles coated with the organic compound are fired.

  An isotropic pitch can be used as the pitch, and a phenol resin, a furan resin, a furfural resin, or the like can be used as the thermosetting resin. As the condensate of naphthalene sulfonate and aldehydes, naphthalene sulfonic acid formaldehyde condensate can be used.

As a dispersion medium for dispersing the SiO _x particles coated with the carbon material and the organic compound, for example, water or alcohols (ethanol or the like) can be used. It is appropriate to spray the dispersion in an atmosphere of 50 to 300 ° C. The firing temperature is usually 600 to 1200 ° C., preferably 700 ° C. or higher, and more preferably 800 ° C. or higher. This is because the higher the processing temperature, the less the remaining impurities, and the formation of a coating layer containing a high-quality carbon material with high conductivity. However, the processing temperature needs to be lower than the melting point of SiO _x .

When SiO _x (preferably a composite of SiO _x and a carbon material) is used for the negative electrode active material, it is preferable to use a graphitic carbon material in combination. SiO _x has a high capacity compared to a carbon material that is widely used as a negative electrode active material of a non-aqueous secondary battery. On the other hand, the volume change amount associated with charging / discharging of the battery is large, so that the content ratio of SiO _x is high. In a nonaqueous secondary battery using a negative electrode having a negative electrode mixture layer, the negative electrode (negative electrode mixture layer) deteriorates due to a large volume change due to repeated charge and discharge, and the capacity decreases (that is, the charge / discharge cycle characteristics decrease). There is a risk. Graphite carbon material is widely used as a negative electrode active material for non-aqueous secondary batteries, and has a relatively large capacity, while its volume change associated with charging / discharging of the battery is smaller than that of SiO _x . Therefore, by using SiO _x and a graphitic carbon material in combination with the negative electrode active material, it is possible to suppress the battery capacity improvement effect from decreasing as the amount of SiO _x used decreases as much as possible. Since deterioration of charge / discharge cycle characteristics can be satisfactorily suppressed, a non-aqueous secondary battery having higher capacity and more excellent charge / discharge cycle characteristics can be obtained.

Examples of the graphitic carbon material used as the negative electrode active material together with the SiO _x include natural graphite such as scale-like graphite; graphitizable carbon such as pyrolytic carbons, mesophase carbon microbeads (MCMB), and carbon fibers. And artificial graphite graphitized at 2800 ° C. or higher.

When using a composite of SiO _x and a carbon material and a graphitic carbon material in combination with the negative electrode active material, from the viewpoint of favorably securing the effect of increasing the capacity by using SiO _x , The content of the composite of SiO _x and carbon material in is preferably 0.01% by mass or more, more preferably 1% by mass or more, and more preferably 3% by mass or more. Further, from the viewpoint of better avoiding the problem due to the volume change of SiO _x due to charge / discharge, the content of the composite of SiO _x and the carbon material in the entire negative electrode active material is 20% by mass or less. Preferably, it is 15 mass% or less.

  As the binder and the conductive auxiliary agent related to the negative electrode mixture layer, the same materials as those exemplified above as those that can be used for the positive electrode mixture layer can be used.

  For the negative electrode, for example, a negative electrode active material, a binder, and a conductive auxiliary agent used as necessary are prepared in a paste-like or slurry-like negative electrode mixture-containing composition in which a solvent such as NMP or water is dispersed. (However, the binder may be dissolved in a solvent), which is applied to one or both sides of the current collector, dried, and then subjected to a calendering process as necessary. However, the negative electrode is not limited to those manufactured by the above manufacturing method, and may be manufactured by other methods.

  Moreover, you may form in the negative electrode the lead body for electrically connecting with the other member in a non-aqueous secondary battery according to a conventional method as needed.

  The thickness of the negative electrode mixture layer is preferably 10 to 100 μm per one surface of the current collector, for example. Moreover, as a composition of a negative mix layer, it is preferable that a negative electrode active material shall be 80.0-99.8 mass% and a binder shall be 0.1-10 mass%, for example. Furthermore, when making a negative mix layer contain a conductive support agent, it is preferable that the quantity of the conductive support agent in a negative mix layer shall be 0.1-10 mass%.

  As the current collector for the negative electrode, a foil made of copper or nickel, a punching metal, a net, an expanded metal, or the like can be used, but a copper foil is usually used. In the negative electrode current collector, when the thickness of the entire negative electrode is reduced in order to obtain a battery having a high energy density, the upper limit of the thickness is preferably 30 μm, and the lower limit is 5 μm in order to ensure mechanical strength. Is desirable.

  The separator according to the non-aqueous secondary battery of the present invention is a porous material composed of polyolefin such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer; polyester such as polyethylene terephthalate and copolymer polyester; A membrane is preferred. In addition, it is preferable that a separator has the property (namely, shutdown function) which the hole obstruct | occludes in 100-140 degreeC. Therefore, the separator has a melting point, that is, a thermoplastic resin having a melting temperature measured using a differential scanning calorimeter (DSC) of 100 to 140 ° C. in accordance with JIS K 7121 as a component. Preferably, it is a single layer porous film mainly composed of PE, or a laminated porous film comprising a porous film such as a laminated porous film in which 2 to 5 layers of PE and PP are laminated. Is preferred. When mixing and laminating PE and a resin having a higher melting point than PE, such as PP, PE is preferably 30% by mass or more, and 50% by mass or more as a resin constituting the porous film. Is more desirable.

  As such a resin porous membrane, for example, a porous membrane composed of the above-mentioned exemplified thermoplastic resin used in a conventionally known non-aqueous secondary battery or the like, that is, a solvent extraction method, a dry type Alternatively, an ion-permeable porous film manufactured by a wet stretching method or the like can be used.

  As the non-aqueous electrolyte, a solution in which an electrolyte salt is dissolved in an organic solvent can be used. Examples of the solvent include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), γ-butyrolactone, 1, 2 -Dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivatives, Sulfolane, 3-methyl-2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, diethyl ether, 1,3-propane sultone, etc. Aprotic organic solvents, and the like, may be used these alone, or in combination of two or more of these. Also, amine imide organic solvents, sulfur-containing or fluorine-containing organic solvents, and the like can be used.

As the electrolyte salt related to the non-aqueous electrolyte, a salt of a fluorine-containing compound such as lithium perchlorate, lithium organic boron, trifluoromethanesulfonate, imide salt, or the like is preferably used. Specific examples of the electrolyte salt, for _{example, LiClO 4, LiPF 6, LiBF} 4, LiAsF 6, LiSbF 6, LiCF 3 SO 3, LiC 4 F 9 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 (Rf ₃ OSO ₂ ) ₂ [where Rf Represents a fluoroalkyl group. These may be used alone or in combination of two or more thereof. Among these, LiPF ₆ and LiBF ₄ are more preferable because of good charge / discharge characteristics. This is because these fluorine-containing organic lithium salts have a large anionic property and are easily ion-separated, so that they are easily dissolved in the solvent. The concentration of the electrolyte salt in the nonaqueous electrolytic solution is not particularly limited, but is usually 0.5 to 1.7 mol / L.

  In addition, in order to improve battery safety, charge / discharge cycle performance, and high-temperature storage characteristics, halogen-substituted cyclic carbonates such as 4-fluoro-1,3-dioxolan-2-one (FEC), triethylphospho Additives such as phosphonoacetates such as noacetate (TEPA), vinylene carbonates such as vinylene carbonate (VC), 1,3-propane sultone, diphenyl disulfide, cyclohexylbenzene, biphenyl, fluorobenzene, t-butylbenzene Can also be added to the non-aqueous electrolyte.

  Further, as the non-aqueous electrolyte, a gelled gel (gel electrolyte) can be used by adding a known gelling agent.

  The non-aqueous secondary battery of the present invention, for example, produces a laminated electrode body in which the positive electrode and the negative electrode are laminated via the separator, and a wound electrode body in which this is wound in a spiral shape. And such an electrode body and the said nonaqueous electrolyte solution are enclosed in an exterior body according to a conventional method, and are comprised. As the form of the battery, similarly to the conventionally known non-aqueous secondary battery, a cylindrical battery using a cylindrical (cylindrical or rectangular) outer can, or a flat (circular in plan view) A flat battery using a rectangular flat-shaped outer can, a soft package battery using a metal-deposited laminated film as an outer package, and the like. The outer can can be made of steel or aluminum.

The non-aqueous secondary battery of the present invention comprises a positive electrode active material, a lithium nickel cobalt manganese composite oxide having high stability under high voltage, and a lithium cobalt composite having higher stability under high voltage than LiCoO _2. Since the oxide (A) and the lithium cobalt composite oxide (B) are used, the cathode active material is deteriorated even if it is repeatedly used by a method of performing constant current-constant voltage charging at a final voltage of 4.3 V or more, for example. It is possible to suppress a decrease in capacity and the like. Therefore, the non-aqueous secondary battery of the present invention can be preferably used even in the method of charging under the above-described conditions, thereby maintaining good charge / discharge cycle characteristics while increasing the capacity. .

  The non-aqueous secondary battery of the present invention is preferably used for various applications to which conventional non-aqueous secondary batteries are applied, including power supply applications for various electronic devices such as portable electronic devices such as mobile phones and laptop computers. be able to.

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

Example 1

<Synthesis of lithium nickel cobalt manganese composite oxide>
Aqueous ammonia whose pH was adjusted to about 12 by adding sodium hydroxide was placed in a reaction vessel, and while vigorously stirring, nickel sulfate, cobalt sulfate and manganese sulfate were each added to 2.0 mol / dm ^3. , 0.8 mol ^/ dm 3, a mixed aqueous solution containing a concentration of 1.2 mol / dm ^3, and aqueous ammonia 25% strength by weight, respectively, 23cm ³ / min at a rate of 6.6 cm ³ / min, The solution was added dropwise using a metering pump to synthesize a coprecipitation compound of Ni, Co, and Mn (spherical coprecipitation compound). At this time, the temperature of the reaction solution is kept at 50 ° C., and a sodium hydroxide aqueous solution having a concentration of 6.4 mol / dm ³ is dropped at the same time so that the pH of the reaction solution is maintained around 12. Further, nitrogen gas was bubbled at a flow rate of 1 dm ³ / min.

The coprecipitated compound was washed with water, filtered and dried to obtain a hydroxide containing Ni, Co and Mn in a molar ratio of 5: 2: 3. 0.196 mol of this hydroxide and 0.204 mol of LiOH.H ₂ O were dispersed in ethanol to form a slurry, and then mixed with a planetary ball mill for 40 minutes and dried at room temperature to obtain a mixture. . Next, the mixture is put in an alumina crucible, heated to 600 ° C. in a dry air flow of 2 dm ³ / min, kept at that temperature for 2 hours for preheating, further heated to 900 ° C. and heated to 12 ° C. Lithium nickel cobalt manganese composite oxide was synthesized by firing for a period of time.

  The lithium nickel cobalt manganese composite oxide was washed with water, then heat-treated in the atmosphere (oxygen concentration of about 20 vol%) at 850 ° C. for 12 hours, and then pulverized in a mortar to obtain a powder. The lithium nickel cobalt manganese composite oxide after pulverization was stored in a desiccator.

About the said lithium nickel cobalt manganese complex oxide, the composition analysis was performed as follows using ICP method. First, 0.2 g of the lithium nickel cobalt manganese composite oxide was sampled and placed in a 100 mL container. Thereafter, 5 mL of pure water, 2 mL of aqua regia, and 10 mL of pure water were added in order and dissolved by heating. After cooling, the mixture was further diluted 25 times and analyzed by ICP (“ICP-757” manufactured by JARRELASH) (calibration). Line method). From the obtained results, the composition of the lithium nickel cobalt manganese composite oxide was derived and found to be a composition represented by Li _1.02 Ni _0.5 Co _0.2 Mn _0.3 O ₂ . . Moreover, the average particle diameter of the said lithium nickel cobalt manganese complex oxide was 15 micrometers.

<Synthesis of lithium cobalt composite oxide (A)>
Co (OH) ₂ , Mg (OH) ₂ , Al (OH) ₃ and Li ₂ CO ₃ were mixed at a molar ratio of 1.97: 0.02: 0.01: 1.02. The mixture was heat-treated at 950 ° C. for 12 hours in the atmosphere (oxygen concentration of about 20 vol%) to synthesize lithium cobalt composite oxide (A), and then pulverized in a mortar to obtain a powder. The lithium cobalt composite oxide (A) after pulverization was stored in a desiccator.

For the lithium cobalt composite oxide (A), that the composition analysis is a composition represented by _{Li 1.0 Co 0.985 Mg 0.01 Al 0.005} O 2 was performed using the ICP method There was found. The average particle size of the lithium cobalt composite oxide (A) was 20 μm.

<Synthesis of lithium cobalt composite oxide (B)>
Co _{(OH) 2} and Mg _{(OH) 2} and Al _{(OH) 3} and a molar ratio of the ZrO ₂ and _{Li 2 CO 3 1.946: 0.03:} 0.02: 0.004: 1.02 The mixture was heat-treated at 950 ° C. for 12 hours to synthesize lithium cobalt composite oxide (B) in the atmosphere (oxygen concentration of about 20 vol%), and then pulverized in a mortar to obtain a powder. . The lithium cobalt composite oxide (B) after pulverization was stored in a desiccator.

The lithium-cobalt composite oxide for (B), the composition analysis, is represented by _{Li 1.0 Co 0.973 Mg 0.015 Al 0.01} Zr 0.002 O 2 was performed using the ICP method It turned out to be a composition. Moreover, the average particle diameter of the said lithium cobalt complex oxide (A) was 8 micrometers.

<Preparation of positive electrode>
63 parts by mass of a mixture obtained by mixing the lithium cobalt composite oxide (A) and the lithium cobalt composite oxide (B) at a mass ratio of 80:20, and 15 parts by mass of the lithium nickel cobalt manganese composite oxide. Using a biaxial kneader, an NMP solution containing PVDF as a binder at a concentration of 10% by mass: 20 parts by mass, artificial graphite as a conductive auxiliary agent: 1 part by mass and Ketjen black: 1 part by mass The mixture was kneaded and further NMP was added to adjust the viscosity to prepare a positive electrode mixture-containing paste.

After coating the positive electrode mixture-containing paste on both surfaces of an aluminum foil (positive electrode current collector) having a thickness of 15 μm, vacuum drying is performed at 120 ° C. for 12 hours to form a positive electrode mixture layer on both surfaces of the aluminum foil. did. Thereafter, press treatment was performed to adjust the thickness and density of the positive electrode mixture layer, and a nickel lead body was welded to the exposed portion of the aluminum foil to produce a strip-like positive electrode having a length of 375 mm and a width of 43 mm. . The positive electrode mixture layer in the obtained positive electrode had a thickness of 55 μm per side, and the density of the positive electrode mixture layer was 3.85 g / cm ³ .

<Production of negative electrode>
A composite in which the surface of SiO having an average particle diameter D50% of 8 μm, which is a negative electrode active material, is coated with a carbon material (the amount of the carbon material in the composite is 10% by mass), and graphite having an average particle diameter D50% of 16 μm A mixture in which the amount of the composite whose SiO surface is coated with a carbon material is 3.75% by mass: 97.5 parts by mass, SBR as a binder: 1.5 parts by mass, and a thickener Certain carboxymethyl cellulose: 1 part by mass of water was added and mixed to prepare a negative electrode mixture-containing paste.

  After applying the negative electrode mixture-containing paste to both sides of a copper foil (negative electrode current collector) having a thickness of 8 μm, vacuum drying is performed at 120 ° C. for 12 hours to form a negative electrode mixture layer on both sides of the copper foil. did. Thereafter, press treatment was performed to adjust the thickness and density of the negative electrode mixture layer, and a nickel lead body was welded to the exposed portion of the copper foil to produce a strip-shaped negative electrode having a length of 380 mm and a width of 44 mm. . The negative electrode mixture layer in the obtained negative electrode had a thickness of 65 μm per one surface.

<Battery assembly>
The belt-like positive electrode is stacked on the belt-like negative electrode through a microporous polyethylene separator (porosity: 41%) having a thickness of 16 μm, wound in a spiral shape, and then pressed so as to be flat. An electrode winding body having a flat winding structure was formed, and the electrode winding body was fixed with an insulating tape made of polypropylene. Next, the electrode winding body is inserted into a rectangular battery case made of aluminum alloy having an outer dimension of 4.0 mm in thickness, 34 mm in width, and 50 mm in height to weld the lead body, and a lid made of aluminum alloy The plate was welded to the open end of the battery case. Thereafter, LiPF ₆ was dissolved in a non-aqueous electrolyte (a solvent in which EC, MEC, and DEC were mixed at a volume ratio = 1: 1: 1) to a concentration of 1.1 mol / l from an inlet provided on the cover plate. The solution was added in an amount of 2.0% by mass of FEC and 1.0% by mass of VC), and allowed to stand for 1 hour, after which the inlet was sealed. Thus, the nonaqueous secondary battery having the structure shown in FIG. 1 and the appearance shown in FIG. 2 was obtained.

  Here, the battery shown in FIGS. 1 and 2 will be described. FIG. 1A is a plan view, and FIG. 1B is a partial cross-sectional view thereof. As shown in FIG. 2 is spirally wound through the separator 3 and then pressed to form a flat shape to form a flat wound electrode body 6 in a rectangular (square tube) battery case 4 together with a non-aqueous electrolyte. Contained. 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 battery case 4 is made of an aluminum alloy and constitutes an outer package of the battery. The battery case 4 also serves as a positive electrode terminal. And the insulator 5 which consists of PE sheets is arrange | positioned at the bottom part of the battery case 4, and it connects to each one end of the positive electrode 1 and the negative electrode 2 from the flat wound electrode body 6 which consists of the positive electrode 1, the negative electrode 2, and the separator 3. The positive electrode lead body 7 and the negative electrode lead body 8 thus drawn are drawn out. A stainless steel terminal 11 is attached to a sealing lid plate 9 made of aluminum alloy for sealing the opening of the battery case 4 via a polypropylene insulating packing 10, and an insulator 12 is attached to the terminal 11. A stainless steel lead plate 13 is attached.

  And this cover plate 9 is inserted in the opening part of the battery case 4, and the opening part of the battery case 4 is sealed by welding the joint part of both, and the inside of the battery is sealed. Further, in the battery of FIG. 1, a non-aqueous electrolyte inlet 14 is provided in the cover plate 9, and a sealing member is inserted into the non-aqueous electrolyte inlet 14, for example, laser welding or the like. As a result, the battery is sealed by welding. Further, the lid plate 9 is provided with a cleavage vent 15 as a mechanism for discharging the internal gas to the outside when the temperature of the battery rises.

  In the battery of this Example 1, the outer can 5 and the cover plate 9 function as a positive electrode terminal by directly welding the positive electrode lead body 7 to the lid plate 9, and the negative electrode lead body 8 is welded to the lead plate 13, The terminal 11 functions as a negative electrode terminal by conducting the negative electrode lead body 8 and the terminal 11 through the lead plate 13, but depending on the material of the battery case 4, the sign may be reversed. There is also.

  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.

Examples 2-5 and Comparative Examples 1-7
The lithium cobalt composite oxide [lithium cobalt composite oxide (A)] having the composition shown in Table 1, the lithium cobalt composite oxide [lithium cobalt composite oxide (B)] having the composition shown in Table 2, and the composition shown in Table 3 A positive electrode was produced in the same manner as in Example 1 except that lithium nickel cobalt manganese composite oxide was used, and a nonaqueous secondary battery was produced in the same manner as in Example 1 except that these positive electrodes were used. Each lithium nickel cobalt manganese composite oxide shown in Table 1, each lithium cobalt composite oxide (A) shown in Table 2, and each lithium cobalt composite oxide (B) shown in Table 3 are used as necessary. The synthesis was carried out in the same manner as in Example 1 except that the type and amount of were changed.

  In Tables 1 and 2, and in the above description relating to Tables 1 and 2 in this specification, and in the following description, the lithium cobalt composite oxide used in the comparative example is lithium in terms of composition and average particle size. From the viewpoint of facilitating the comparison with the examples even if the cobalt composite oxide (A) and the lithium cobalt composite oxide (B) are not applicable, for the sake of convenience, the lithium cobalt composite oxide (A) and It is described as a lithium cobalt composite oxide (B). Tables 1 and 2 show the compositions of the lithium cobalt composite oxide (A) and the lithium cobalt composite oxide (B) in accordance with the general composition formula (1), and Table 3 shows lithium nickel cobalt manganese composite oxidation. The composition of the product is expressed in accordance with the general composition formula (2).

  The following evaluation was performed about the non-aqueous secondary battery of the Example and the comparative example. These results are shown in Table 4. Table 4 also shows the density of the positive electrode mixture layer used for each non-aqueous secondary battery.

<Battery capacity>
About each battery of an Example and a comparative example, it charges until it reaches 4.4V with a constant current of 1C at the normal temperature (25 ° C.) after the first charge / discharge, and then charges with a constant voltage of 4.4V-constant-constant Voltage charge (total charge time: 2.5 hours) was performed, and then 0.2 C constant current discharge (discharge end voltage: 3.0 V) was performed, and the obtained discharge capacity (mAh) was defined as the battery capacity.

<Storage characteristics (battery expansion)>
About each battery of an Example and a comparative example, it charged on the same conditions as the measurement of battery capacity after initial charge / discharge. After charging, measured in advance thickness T ₁ of the battery outer can, then, stored for 24 hours in a constant temperature bath set at 85 ° C. the cells, taken out from the thermostatic bath, after 3 hours standing at ambient temperature, to measure the thickness T ₂ of the battery outer can again. The battery outer can thickness referred to in this test means the thickness between the wide surfaces of the side surfaces of the outer can. The thickness of the battery outer can was measured in units of 1/100 mm using a vernier caliper ("CD-15CX" manufactured by Mitutoyo Corporation), with the central portion of the wide surface as the measurement target.

The battery swelling was evaluated from the rate of change to the outer can thickness T ₁ and T ₂ before and after storage relative to the outer can thickness T ₁ before storage at 85 ° C. That is, the battery swelling (%) was obtained by the following formula.
Battery swelling (%) = 100 × (T ₂ −T ₁ ) / (T ₁ )

<Charge / discharge cycle characteristics>
About each battery of an Example and a comparative example, after initial charge / discharge, charging / discharging is repeated by making a series of operation of charge and discharge of the same conditions as measurement of battery capacity into 1 cycle, and with respect to the discharge capacity obtained at the 1st cycle. The number of cycles when the discharge capacity was 80% was examined.

  As the positive electrode active material, lithium nickel cobalt manganese composite oxide, lithium cobalt composite oxide (A) and lithium cobalt composite oxide (B) having an appropriate composition are used, and the average particle diameter and the relationship thereof are determined. Appropriate non-aqueous secondary batteries of Examples 1 to 5 have a high capacity, battery swelling during storage is suppressed, storage characteristics are good, and the number of cycles during charge / discharge cycle characteristics evaluation is high. Many have excellent charge / discharge cycle characteristics.

  On the other hand, the battery of Comparative Example 1 in which the average particle size of the lithium cobalt composite oxide (A) used for the positive electrode is too small and the relationship with the average particle size of the lithium cobalt composite oxide (B) is inappropriate is the positive electrode. The mixture layer has a low filling property (density), a small capacity, and a low stability of the lithium cobalt composite oxide (A), which causes a large swelling during storage, resulting in poor storage characteristics. The battery of Comparative Example 2 in which the average particle diameter of the lithium cobalt composite oxide (A) used for the positive electrode is too large has a low filling capacity (density) of the positive electrode mixture layer, a small capacity, and lithium cobalt Since the resistance in the particles of the composite oxide (A) is large, the charge / discharge cycle characteristics are inferior.

The content of different metal elements M ¹ of the lithium-cobalt composite oxide used for the positive electrode (A) is a battery of a lithium-cobalt composite oxide (B) from greater Comparative Example 3 is inferior capacity. The battery of Comparative Example 4 in which the average particle diameter of the lithium cobalt composite oxide (B) used for the positive electrode is too large and the relationship with the average particle diameter of the lithium cobalt composite oxide (A) is inappropriate is the positive electrode mixture layer. Fillability (density) is low and capacity is inferior.

The battery of Comparative Example 5 in which the average particle size of the lithium cobalt composite oxide (B) used for the positive electrode is too small has a large swelling during storage because the lithium cobalt composite oxide (B) has low heat stability. The storage characteristics are inferior. Lithium cobalt composite oxide used for the positive electrode (B) is the battery of Comparative Example 6 containing no different metal element M ¹ has low stability in the lithium cobalt composite oxide (B) with respect to charging and discharging, charging and discharging Cycle characteristics are inferior.

  The battery of Comparative Example 7 in which the relationship between the average particle size of the lithium nickel cobalt manganese composite oxide used for the positive electrode and the average particle size of the lithium cobalt composite oxide (B) is inadequate is the fillability (density) of the positive electrode mixture layer. ) Is low, the capacity is small, and since the lithium nickel cobalt manganese composite oxide has low heat stability, the swelling during storage is large and the storage characteristics are poor.

1 Positive electrode 2 Negative electrode 3 Separator

Claims (10)

A non-aqueous secondary battery having a positive electrode, a negative electrode, a non-aqueous electrolyte and a separator,
The positive electrode has a positive electrode mixture layer containing a positive electrode active material on one side or both sides of a current collector,
As the positive electrode active material, including lithium nickel cobalt manganese composite oxide and lithium cobalt composite oxide containing different metal elements other than lithium, nickel, cobalt and manganese,
The lithium cobalt composite oxide includes a lithium cobalt composite oxide (A) having an average particle size A (μm) of more than 10 μm and 30 μm or less, and a lithium cobalt composite oxide having an average particle size B (μm) of 1 μm or more and 10 μm or less. The object (B) is used so as to satisfy the relationship of AB ≧ 5,
The ratio of the different metal element in the total amount of cobalt and the different metal element in the lithium cobalt composite oxide (B) is different in the total amount of cobalt and the different metal element in the lithium cobalt composite oxide (A). Greater than the proportion of metallic elements,
A non-aqueous secondary battery, wherein C> B, where C (μm) is the average particle size of the lithium nickel cobalt manganese composite oxide used as the positive electrode active material.   The average particle diameter A (μm) of the lithium cobalt composite oxide (A), the average particle diameter B (μm) of the lithium cobalt composite oxide (B), and the average particle diameter C (μm of the lithium nickel cobalt manganese composite oxide) ) Satisfies the relationship of A ≧ C> B. The lithium cobalt composite oxide (A) and the lithium cobalt composite oxide (B) have the following general composition formula (1):
Li _{1 + y} Co _z M ¹ _1-z O ₂ (1)
[In the general composition formula (1), −0.3 ≦ y ≦ 0.3, 0.95 ≦ z <1.0, and M ¹ is selected from the group consisting of Mg, Zr, Al, and Ti. The non-aqueous secondary battery according to claim 1, wherein the non-aqueous secondary battery is at least one element. The nonaqueous secondary battery according to claim 3, wherein M ¹ in the general composition formula (1) is Mg and / or Zr. The lithium nickel cobalt manganese composite oxide has the following general composition formula (2)
Li _{1 + s} M ² O ₂ (2)
[In the general composition formula (2), −0.3 ≦ s ≦ 0.3, and M ² is a group of three or more elements including at least Ni, Co, and Mn, and each of which constitutes M ² 30 <a <65, 5 <b <35, and 15 <c <50 when the ratio (mol%) of Ni, Co, and Mn in the element is a, b, and c, respectively. The nonaqueous secondary battery according to any one of claims 1 to 4. The general composition formula element group ^{M 2} in (2), Mg, Ti, Zr, Nb, Mo, W, Al, Si, Ga, at least one element selected from the group consisting of Ge and Sn When the total ratio (mol%) of Mg, Ti, Zr, Nb, Mo, W, Al, Si, Ga, Ge, and Sn in each element constituting M ² is d, d <5 The nonaqueous secondary battery according to claim 5.   When the total of the lithium cobalt composite oxide (A) and the lithium cobalt composite oxide (B) used in the positive electrode mixture layer is 100% by mass, the content of the lithium cobalt composite oxide (A) is 50% by mass. The nonaqueous secondary battery according to claim 1, wherein the nonaqueous secondary battery is at least%.   When the total of the lithium cobalt composite oxide (A), lithium cobalt composite oxide (B) and lithium nickel cobalt manganese composite oxide used in the positive electrode mixture layer is 100% by mass, the lithium nickel cobalt manganese composite oxide The nonaqueous secondary battery according to any one of claims 1 to 7, wherein the content of is 15 mass% or more and 45 mass% or less.   The negative electrode is a composite of a material containing Si and O as constituent elements (however, the atomic ratio x of O to Si is 0.5 ≦ x ≦ 1.5) and a carbon material, and a graphitic carbon material The nonaqueous secondary battery according to claim 1, wherein the current collector has a negative electrode mixture layer containing the negative electrode active material on one side or both sides of the current collector.   The nonaqueous secondary battery according to claim 1, wherein constant current-constant voltage charging is performed at a final voltage of 4.3 V or more before use.

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