JP5419093B2 - Non-aqueous secondary battery - Google Patents

Description

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

  Non-aqueous secondary batteries such as lithium ion secondary batteries have high expectations for their development because non-aqueous secondary batteries have high voltage and high capacity. For negative electrode material (negative electrode active material) of non-aqueous secondary battery, natural or artificial graphite (graphitic carbon material) that can insert and desorb Li ions in addition to Li (lithium) and Li alloy is applicable Has been.

  However, recently, there has been a demand for further higher capacity of a battery for a portable device that has been downsized and multifunctional, and in response to this, low crystalline carbon, Si (silicon), Sn (tin), etc. Thus, a material that can accommodate more Li is attracting attention as a negative electrode material (hereinafter, also referred to as “high-capacity negative electrode material”).

As one of such high-capacity negative electrode materials for non-aqueous secondary batteries, SiO _x having a structure in which Si ultrafine particles are dispersed in SiO ₂ has attracted attention (for example, Patent Documents 1 to 3). When this material is used as a negative electrode active material, since Si that reacts with Li is an ultrafine particle, charging and discharging are performed smoothly. On the other hand, the SiO _x particle itself having the above structure has a small surface area, and thus the negative electrode mixture layer The coating property when forming a coating material for forming the electrode and the adhesion of the negative electrode mixture layer to the current collector are also good.

JP 2004-47404 A Japanese Patent Laid-Open No. 2005-259697 JP 2007-242590 A

  By the way, since the volume change accompanying charging / discharging is very large as described above, in a battery using the material, there is a possibility that the battery characteristics may be rapidly deteriorated by repeated charging / discharging. Therefore, from the viewpoint of avoiding such problems, in constructing a battery using the above-described high-capacity negative electrode material, a conventional non-aqueous secondary battery having a negative electrode using a graphitic carbon material as an active material is a negative electrode. It is necessary to greatly change the configuration.

  On the other hand, there is also a request to increase the capacity while adopting the same configuration as the conventional non-aqueous secondary battery, and when this is achieved by using a high capacity negative electrode material, the above-mentioned battery characteristics are deteriorated. Control is required.

  This invention is made | formed in view of the said situation, The objective is to provide the high capacity | capacitance and the non-aqueous secondary battery excellent in charging / discharging cycling 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 negative electrode is 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, the material may be referred to as “SiO _x ”) and a carbon material, and graphitic carbon It has a negative electrode mixture layer containing a material as a negative electrode active material on one or both sides of a current collector, and the positive electrode has the following general composition formula (1)
Li _{1 + y} MO ₂ (1)
[In the general composition formula (1), −0.15 ≦ a <0.15, and M is at least one of Mg, Ba and Zr, and four kinds containing Ni, Co and Mn. When the ratio (mol%) of Ni, Co, Mn, Mg, Ba, and Zr among the elements constituting M is represented as a, b, c, d, e, and f, respectively, 50 ≦ a ≦ 97, b ≦ 49, c ≦ 49, d ≦ 3, e ≦ 3, f ≦ 3 and 3 ≦ b + c + d + e + f ≦ 50]
It has the positive mix layer which contains the lithium containing complex oxide represented by these as a positive electrode active material, It is characterized by having on the single side | surface or both surfaces of a collector.

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

It is a schematic diagram which shows an example of the non-aqueous secondary battery of this invention, (a) Top view, (b) Cross-sectional view. FIG. 2 is a perspective view of FIG. 1.

In the present invention, the conductivity in the negative electrode mixture layer containing SiO _x having poor conductivity can be enhanced by acting as an active material and the above-mentioned SiO _x on the negative electrode active material. By using a graphitic carbon material at a specific ratio to form a negative electrode, it was decided to suppress a decrease in battery characteristics due to a change in volume of SiO _x accompanying charge / discharge.

However, as described above, a negative electrode using both SiO _x and a graphitic carbon material is used, and further, for example, using a positive electrode using lithium cobaltate (LiCoO ₂ ) widely used in non-aqueous secondary batteries. It has become clear that even if the battery is configured, it is not possible to achieve a capacity that is high enough to meet the use of SiO _x .

On the other hand, when a lithium composite oxide containing Ni and Mn having a higher capacity than LiCoO ₂ is used as the positive electrode active material, and this is combined with the negative electrode, a high capacity can be achieved satisfactorily. However, in this case, it has become clear from the study by the present inventors that the charge / discharge cycle characteristics of the battery are likely to deteriorate due to a reason different from the volume change of SiO _x accompanying charge / discharge. The reason for this is, Mn is eluted from the lithium-containing composite oxide with the charging and discharging of the battery, which is selectively deposited on the surface of the SiO _x, the degradation of SiO _x, in order to have caused deterioration of the thus negative It is believed that there is.

  Therefore, in the present invention, a lithium-containing composite oxide capable of suppressing elution of Mn at the time of charge and discharge of the battery is included as a positive electrode active material by including specific additive elements as well as Ni and Mn. By combining this with the negative electrode, it is possible to provide a non-aqueous secondary battery with high capacity and excellent charge / discharge cycle characteristics.

For the negative electrode according to the nonaqueous secondary battery of the present invention, for example, a negative electrode mixture layer containing a negative electrode active material, a binder, or the like is used on one side or both sides of a current collector. Then, the negative active material according to the negative electrode, to complex with SiO _x and the carbon material, and a graphitic carbon material used.

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 a complex complexed with carbon materials, for example, it is desirable that the surface of the SiO _x is coated with a carbon material. As described above, since SiO _x has poor conductivity, when using it as a negative electrode active material, from the viewpoint of securing good battery characteristics, a conductive material (conductive aid) is used, and SiO _x in the negative electrode is used. It is necessary to form an excellent conductive network by mixing and dispersing the material and the conductive material well. 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.

A graphite carbon material used in combination with SiO _x as a negative electrode active material can also be used as a carbon material related to a composite of SiO _x and a carbon 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 .

Examples of the graphitic carbon material used as the negative electrode active material together with the composite of SiO _x and the carbon material include natural graphite such as flake graphite; graphitizable carbon such as pyrolytic carbons, MCMB, and carbon fiber. And artificial graphite obtained by graphitizing at 2800 ° C. or higher.

In the negative electrode according to the present invention, from the viewpoint of satisfactorily ensuring the effect of the high capacity by using a SiO _x, the content of the complex of the SiO _x and the carbon material in the anode active material, 0 It 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 accompanying charge / discharge, the content of the composite of SiO _x and carbon material in the negative electrode active material is preferably 20% by mass or less. More preferably, it is 15 mass% or less.

The negative electrode according to the present invention is sufficiently kneaded by adding an appropriate solvent (dispersion medium) to a mixture (negative electrode mixture) containing a composite of SiO _x and a carbon material, a graphitic carbon material, and a binder. The obtained paste-like or slurry-like negative electrode mixture-containing composition is applied to one side or both sides of the current collector, and the solvent (dispersion medium) is removed by drying or the like, thereby having a predetermined thickness and density. It can be obtained by forming a layer. In addition, the negative electrode which concerns on this invention is not restricted to what was obtained by the said manufacturing method, The thing manufactured by the other manufacturing method may be used.

  Examples of the binder used in the negative electrode mixture layer include starch, polyvinyl alcohol, polyacrylic acid, carboxymethylcellulose (CMC), hydroxypropylcellulose, regenerated cellulose, diacetylcellulose, and other polysaccharides and modified products thereof; polyvinylchloride, Thermoplastic resins such as polyvinylpyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyamide and their modified products; polyimide; ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene Rubber (SBR), butadiene rubber, polybutadiene, fluororubber, polyethylene oxide and other polymers having rubbery elasticity, and modified products thereof. May be used alone or two or more al.

  A conductive material may be further added to the negative electrode mixture layer as a conductive aid. Such a conductive material is not particularly limited as long as it does not cause a chemical change in the non-aqueous secondary battery. For example, carbon black (thermal black, furnace black, channel black, ketjen black, acetylene black) Etc.), carbon fibers, metal powder (copper, nickel, aluminum, silver, etc.), metal fibers, polyphenylene derivatives (described in JP-A-59-20971), and the like are used alone or in combination. be able to. Among these, carbon black is preferably used, and ketjen black and acetylene black are more preferable.

  The particle size of the carbon material used as the conductive auxiliary agent is, for example, an average particle size determined by the method described in Examples described later, preferably 0.01 μm or more, and more preferably 0.02 μm or more. It is preferably 10 μm or less, more preferably 5 μm or less.

In the negative electrode mixture layer, the total amount of the negative electrode active material (the composite of SiO _x and the carbon material and the graphitic carbon material) may be 80 to 99% by mass, and the amount of the binder may be 1 to 20% by mass. preferable. In addition, when a conductive material is separately used as the conductive auxiliary agent, these conductive materials in the negative electrode mixture layer are used in a range in which the total amount of the negative electrode active material and the binder amount satisfy the above-described preferable values. It is preferable.

  The thickness of the negative electrode mixture layer is preferably 10 to 100 μm, for example.

  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.

  For the positive electrode according to the non-aqueous secondary battery of the present invention, for example, a positive electrode mixture layer containing a positive electrode active material, a binder, a conductive additive and the like can be used on one side or both sides of the current collector.

As the positive electrode active material, the lithium-containing composite oxide represented by the general composition formula (1) is used. The combination of the positive electrode containing such a positive electrode active material and the negative electrode described above makes it possible to increase the capacity of the lithium ion secondary battery for the following reason. A battery in which a negative electrode constituted by using SiO _x as a negative electrode active material is combined with a positive electrode constituted by using a positive electrode active material having a relatively small irreversible capacity in charge and discharge, which is widely used for lithium ion secondary batteries such as LiCoO _2. In this case, since the irreversible capacity of SiO _x is large, the effect of increasing the capacity by using SiO _x is hardly exhibited. However, the lithium-containing composite oxide itself represented by the general formula (1), although than LiCoO ₂ is a high capacity, since the irreversible capacity is relatively large, the negative electrode and the positive electrode using the same, the SiO _x When combined with the negative electrode used as the active material, the balance of the irreversible capacity of the positive and negative electrodes becomes good, and the effect of increasing the capacity by using SiO _x is exhibited well.

By the way, in a battery configured by combining a positive electrode having a lithium-containing composite oxide containing Mn as a positive electrode active material, a composite of SiO _x and a carbon material, and a negative electrode having a graphitic carbon material as a negative electrode active material, Compared with a battery configured by combining the positive electrode and a negative electrode using only a carbon material such as a graphitic carbon material as a negative electrode active material, charge / discharge cycle characteristics are deteriorated.

Although it is known that Mn is easily eluted from a positive electrode using a lithium-containing composite oxide containing Mn as a positive electrode active material, a composite of SiO _x and a carbon material and a graphitic carbon material are used as a negative electrode active material. In a battery combined with a negative electrode as a substance, it has been found that Mn is selectively deposited on the surface of a composite of SiO _x and a carbon material. In a negative electrode using a composite of SiO _x and a carbon material and a graphite carbon material as a negative electrode active material, the contribution ratio of SiO _x related to the composite in terms of capacity is larger than that of a graphitic carbon material. It is presumed that the deterioration of SiO _x due to the selective precipitation of the lead leads to the deterioration of the entire negative electrode, thereby impairing the charge / discharge cycle characteristics of the battery.

On the other hand, in the case of the positive electrode using the lithium-containing composite oxide represented by the general composition formula (1) as the positive electrode active material, the composite of SiO _x and the carbon material and the graphitic carbon material are used as the negative electrode active material. Even when combined with the negative electrode, a high capacity can be achieved while improving the charge / discharge cycle characteristics. This is considered to be because in the positive electrode using the lithium-containing composite oxide represented by the general composition formula (1), the elution amount of Mn when charging and discharging are repeated can be reduced.

  In the lithium-containing composite oxide represented by the general composition formula (1), Ni is a component that contributes to the capacity improvement.

  When the total number of elements in the element group M in the general composition formula (1) representing the lithium-containing composite oxide is 100 mol%, the Ni ratio a is 50 mol from the viewpoint of improving the capacity of the lithium-containing composite oxide. % Or more, and more preferably 60 mol% or more. However, if the proportion of Ni in the element group M is too large, for example, the amount of Co or Mn is reduced, and the effects of these may be reduced. Therefore, when the total number of elements in the element group M in the general composition formula (1) representing the lithium-containing composite oxide is 100 mol%, the Ni ratio a is 97 mol% or less.

  In the general composition formula (1) representing the lithium-containing composite oxide, when the total number of elements in the element group M is 100 mol%, the Co ratio b is set to 49 mol% or less, and Co is added to the crystal lattice. When present, the irreversible reaction resulting from the phase transition of the lithium-containing composite oxide due to the insertion and release of Li during charge / discharge of the nonaqueous secondary battery can be mitigated, and the reversibility of the crystal structure of the lithium-containing composite oxide can be improved Therefore, a non-aqueous secondary battery with a long charge / discharge cycle life can be configured. In addition, in order to ensure the above-mentioned effect by containing Co better, when the total number of elements in the element group M is 100 mol% in the general composition formula (1) representing the lithium-containing composite oxide. In addition, the Co ratio b is preferably 1 mol% or more.

  Furthermore, in the general composition formula (1) representing the lithium-containing composite oxide, when the total number of elements in the element group M is 100 mol%, the Mn ratio c is 49 mol% or less, and Mn is contained in the crystal lattice. When present, the layered structure can be stabilized together with the divalent Ni, and the thermal stability of the lithium-containing composite oxide can be improved, so that a safer non-aqueous secondary battery can be configured. It becomes. In addition, in order to ensure the above-mentioned effect by containing Mn more satisfactorily, when the total number of elements in the element group M is 100 mol% in the general composition formula (1) representing the lithium-containing composite oxide. Further, it is preferable that the ratio c of Mn is 1 mol% or more.

  The lithium-containing composite oxide contains at least one element selected from Mg, Ba and Zr as well as Ni, Co and Mn as the element group M.

  In the lithium-containing composite oxide, when Mg is present in the crystal lattice, it is possible to stabilize the crystal structure of the lithium-containing composite oxide, so that it is possible to suppress elution of Mn accompanying the charge / discharge cycle of the battery. It is done. Further, since the thermal stability of the lithium-containing composite oxide can be improved by the effect of stabilizing the crystal structure by Mg, it is possible to configure a safer non-aqueous secondary battery. Furthermore, when the phase transition of the lithium-containing composite oxide occurs due to Li insertion / desorption during charge / discharge of the non-aqueous secondary battery, the irreversible reaction is mitigated by the rearrangement of Mg to the Li site, and the lithium-containing composite Since the reversibility of the crystal structure of the oxide can be increased, the charge / discharge cycle life of the nonaqueous secondary battery can also be improved. In particular, in the general composition formula (1) representing the lithium-containing composite oxide, when y <0 and the lithium-containing composite oxide has a Li-deficient crystal structure, Mg instead of Li becomes a Li site. A lithium-containing composite oxide can be formed in a form that enters, and a stable compound can be obtained.

  However, since Mg has little influence on the charge / discharge capacity, if the content in the lithium-containing composite oxide is increased, the capacity may be reduced. Therefore, in the general composition formula (1) representing the lithium-containing composite oxide, when the total number of elements in the element group M is 100 mol%, the ratio of Mg is preferably 3 mol% or less. In addition, in order to ensure the above-mentioned effect by containing Mg more satisfactorily, in the general composition formula (1) representing the lithium-containing composite oxide, when the total number of elements in the element group M is 100 mol% Furthermore, it is preferable that the Mg ratio is 0.01 mol% or more.

The lithium-containing composite oxide containing Mn tends to be hard to grow primary particles. However, when Ba is contained, the growth of primary particles is promoted and the crystallinity of the lithium-containing composite oxide is improved. In addition, it is considered that the surface of the lithium-containing composite oxide particles thus grown is chemically stable, which can suppress elution of Mn accompanying the charge / discharge cycle of the battery. In addition, by improving the crystallinity due to Ba, the active sites can be reduced, the stability over time when a paint for forming a positive electrode mixture layer (a positive electrode mixture-containing composition described later) is improved, Irreversible reaction with the nonaqueous electrolyte solution of the nonaqueous secondary battery can be suppressed. Furthermore, since these elements are present on the particle surfaces and grain boundaries of the lithium-containing composite oxide, the CO ₂ gas in the battery can be trapped. It can be configured.

  However, since Ba cannot participate in the charge / discharge reaction, if the content in the lithium-containing composite oxide is increased, the capacity may be reduced. Therefore, in the general composition formula (1) representing the lithium-containing composite oxide, when the total number of elements in the element group M is 100 mol%, the Ba ratio e is preferably 3 mol% or less. In addition, in order to ensure the above-mentioned effect by containing Ba more satisfactorily, when the total number of elements in the element group M is 100 mol% in the general composition formula (1) representing the lithium-containing composite oxide. Furthermore, it is preferable that the Ba ratio e is 0.005 mol% or more.

  When the lithium-containing composite oxide contains Zr, the presence of the lithium-containing composite oxide is present at the grain boundaries and surfaces of the lithium-containing composite oxide particles, so that the surface activity of the lithium-containing composite oxide is reduced without impairing the electrochemical properties of the lithium-containing composite oxide. Suppress. Therefore, it is thought that the elution of Mn accompanying the charge / discharge cycle of the battery can be suppressed. In addition, the effect of suppressing the activity of the particle surface by Zr makes it possible to construct a non-aqueous secondary battery with better storage and longer life.

However, since Zr cannot participate in the charge / discharge reaction, if the content in the lithium-containing composite oxide is increased, the capacity may be reduced. Therefore, in the general composition formula (1) representing the lithium-containing composite oxide, when the total number of elements in the element group M is 100 mol%, the Zr ratio f is preferably 3 mol% or less .

  The lithium-containing composite oxide only needs to contain at least one element selected from Mg, Ba, and Zr as the element group M together with Ni, Co, and Mn. Specifically, the lithium-containing composite oxide may contain only one kind of element among Mg, Ba, and Zr, may contain two kinds of elements, or may contain three kinds of elements. In the general composition formula (1), when the total number of elements in the element group M is 100 mol%, the Co ratio b, the Mn ratio c, and the Mg ratio d The sum of the ratio e of Ba and the ratio f of Zr may be 3 mol% or more and 50 mol% or less.

  In addition, it is more preferable that the lithium-containing composite oxide contains a plurality of these Mg, Ba, and Zr. For example, if the crystal structure is strengthened by the effect of Mg and the surface activity is lowered appropriately by containing Zr, the elution of Mn is further reduced, and a non-aqueous secondary battery having excellent charge / discharge cycle characteristics is obtained. It becomes possible to configure.

  The element group M in the general composition formula (1) representing the lithium-containing composite oxide may contain elements other than Ni, Co, Mn, Mg, Ba, and Zr. For example, Cr, Fe, Elements such as Cu, Zn, Ge, Sn, Ca, Sr, Ag, Ta, Nb, Mo, B, P, W, and Ga may be included. However, in order to sufficiently obtain the effects of the present invention, the ratio of elements other than Ni, Co, Mn, Mg, Ba and Zr when the total number of elements in the element group M is 100 mol% is 10 mol% or less. Preferably, it is more preferable to set it as 3 mol% or less. Elements other than Ni, Co, Mn, Mg, Ba, and Zr in the element group M may be uniformly distributed in the lithium-containing composite oxide, or may be segregated on the particle surface or the like.

The lithium-containing 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-containing composite oxide containing Al and Mn in a certain range varies greatly depending on the composition, but can be synthesized stably in the narrow composition range as described above and has a large true density as described above. It is considered a thing. Moreover, the capacity | capacitance per mass of lithium containing complex oxide can be enlarged, and it can be set as the material excellent in reversibility.

The lithium-containing composite oxide has a higher true density especially when the composition is close to the stoichiometric ratio. Specifically, in the general composition formula (1), −0.15 ≦ y ≦ 0. .15 is preferable, and the true density and reversibility can be improved by adjusting the value of y in this way. y is more preferably −0.1 or more and 0.1 or less. In this case, the true density of the lithium-containing composite oxide can be set to a higher value of 4.6 g / cm ³ or more. .

The lithium-containing composite oxide suppresses gas generation in the non-aqueous secondary battery of the present invention by moderately suppressing the activity of the particle surface, and in particular, a battery having a rectangular (rectangular cylindrical) outer package. In such a case, the deformation of the exterior body can be suppressed, and the storability and life can be improved. From the viewpoint of securing such an effect, the lithium-containing composite oxide preferably has the following form. First, the lithium-containing composite oxide is in the form of particles, and the ratio of primary particles having a particle size of 0.7 μm or less in all primary particles is preferably 30% by volume or less, and 15% by volume or less. It is more preferable. Further, BET specific surface area of the lithium-containing composite oxide is preferably at 0.3 m ² / g or less, and more preferably less 0.25 m ² / g.

  That is, in the lithium-containing composite oxide, when the proportion of primary particles having a particle size of 0.7 μm or less in all primary particles is too large or the BET specific surface area is too large, the reaction area is large and the active points are increased. Therefore, an irreversible reaction with the moisture in the atmosphere, the binder used to form the electrode mixture layer, and the nonaqueous electrolyte of the battery is likely to occur, and gas may be generated in the battery to cause deformation of the outer package. In addition, the composition (paste, slurry, etc.) containing the solvent used for forming the positive electrode mixture layer may cause gelation.

The lithium-containing composite oxide may not contain any primary particles having a particle size of 0.7 μm or less (that is, even if the proportion of primary particles having a particle size of 0.7 μm or less is 0% by volume). Good). Further, the BET specific surface area of the lithium-containing composite oxide is preferably 0.1 m ² / g or more in order to prevent the reactivity from being lowered more than necessary. Furthermore, the lithium-containing composite oxide preferably has a number average particle size of 5 to 25 μm.

  The ratio of primary particles having a particle size of 0.7 μm or less contained in the lithium-containing composite oxide, and the number average particle size of the lithium-containing composite oxide (further, the number average particle size of other active materials described later) ) Can be measured by a laser diffraction scattering type particle size distribution measuring device, for example, “Microtrac HRA” manufactured by Nikkiso Co., Ltd. Further, the BET specific surface area of the lithium-containing composite oxide is a specific surface area of the surface of the active material and the micropores, which is obtained by measuring and calculating the surface area using the BET formula, which is a theoretical formula of multimolecular layer adsorption. . Specifically, it is a value obtained as a BET specific surface area using a specific surface area measuring device (“Macsorb HM model-1201” manufactured by Mounttech) by a nitrogen adsorption method.

  The lithium-containing composite oxide particles preferably have a spherical shape or a substantially spherical shape from the viewpoint of increasing the density of the positive electrode mixture layer and further increasing the capacity of the positive electrode and thus the capacity of the nonaqueous secondary battery. . Thus, in the pressing step (details will be described later) at the time of producing the positive electrode, when the lithium-containing composite oxide particles are moved by the pressing process to increase the density of the positive electrode mixture layer, the particles can be moved without difficulty. And the particles are smoothly rearranged. Therefore, since the press load can be reduced, it is possible to reduce the damage to the current collector caused by the press, and it is possible to increase the productivity of the positive electrode and further the productivity of the non-aqueous secondary battery. Further, when the particles of the lithium-containing composite oxide are spherical or substantially spherical, the particles can withstand a larger pressing pressure, so that the positive electrode mixture layer can be made higher in density. .

Furthermore, the lithium-containing composite oxide preferably has a tap density of 2.3 g / cm ³ or more, and preferably 2.8 g / cm ³ or more, from the viewpoint of enhancing the filling property in the positive electrode mixture layer. More preferred. The tap density of the lithium-containing composite oxide is preferably 3.8 g / cm ³ or less. That is, the ratio of the pores is such that the tap density is high and there are no pores inside the particles, or the area ratio of minute pores of 1 μm or less measured by cross-sectional observation of the particles is 10% or less. By setting it as few particle | grains, the filling property of the lithium containing complex oxide in an electrode mixture layer can be improved.

The tap density of the lithium-containing composite oxide is a value determined by the following measurement using “Powder Tester PT-S type” manufactured by Hosokawa Micron. The particles are ground and put into a 100 cm ³ measuring cup, and tapped 180 times while appropriately replenishing the reduced volume. After tapping is completed, excess particles are scraped off with a blade, and then the mass (A) (g) is measured, and the tap density is obtained by the following equation.

    Tap density = (A) / 100

  In synthesizing the lithium-containing composite oxide, it is very easy to obtain a high purity by simply mixing and firing raw material compounds such as a Li-containing compound, a Ni-containing compound, a Co-containing compound, and a Mn-containing compound. Have difficulty. This is because Ni, Mn, and the like have a low diffusion rate in the solid, so that it is difficult to uniformly diffuse them during the synthesis reaction of the lithium-containing composite oxide. It is thought that Ni, Mn, etc. are difficult to distribute uniformly.

  Therefore, when synthesizing the lithium-containing composite oxide according to the present invention, a composite compound containing Ni, Co and Mn as constituent elements, a compound containing at least one element selected from Mg, Ba and Zr, and Li It is preferable to employ a method of firing the containing compound, and by such a method, the lithium-containing composite oxide can be synthesized relatively easily with high purity. That is, a composite compound containing at least Ni, Co, and Mn is synthesized in advance, and this and a compound containing at least one element selected from Mg, Ba, and Zr are fired together with a Li-containing compound, thereby oxidizing. In the product formation reaction, Ni, Co, and Mn are uniformly distributed, and the lithium-containing composite oxide is synthesized with higher purity. The same applies to a compound containing at least one element selected from Mg, Ba and Zr. In order to produce a more uniform lithium-containing composite oxide, Ni, Co and A method may be used in which a composite oxide containing Mn and at least one element selected from Mg, Ba, and Zr is produced and fired together with this Li-containing compound.

  The method for synthesizing the lithium-containing composite oxide according to the present invention is not limited to the above-described method, but depending on what synthesis process is performed, the physical properties of the finally obtained composite oxide, that is, the structure It is estimated that the stability, reversibility of charge / discharge, true density, and the like greatly change.

Here, as the composite compound containing Ni, Co and Mn and at least one element selected from Mg, Ba and Zr, for example, selected from Ni, Co and Mn and Mg, Ba and Zr. Examples thereof include a coprecipitation compound containing at least one element, a hydrothermally synthesized compound, a mechanically synthesized compound, and a compound obtained by heat-treating them, such as Ni _0.69 Co _0.15 Mn _{0. 15} Mg _0.01 (OH) ₂ , Ni _0.69 Co _0.15 Mn _0.15 Mg _0.01 OOH, etc., at least one element selected from Ni, Co and Mg and Mg, Ba and Zr And the hydroxide obtained by heat-treating them are preferable.

  Note that a part of the element group M further includes at least one element selected from Mg, Ba, and Zr, and elements other than Ni, Co, and Mn (for example, Cr, Fe, Cu, Zn, Ge, Sn, At least one element selected from the group consisting of Ca, Sr, Ag, Ta, Nb, Mo, B, P, W, and Ga. These are hereinafter collectively referred to as “element M ′”). The lithium-containing composite oxide is a mixture of a composite compound containing Ni, Co and Mn, at least one element selected from Mg, Ba and Zr, a Li-containing compound and a compound containing the element M ′. And can be synthesized by firing.

  However, in order to obtain a more homogeneous composite oxide, the element M ′ is preferably contained together in a composite compound containing Ni or the like, and a composite compound containing all the constituent elements of the element group M, that is, It is preferable to use a composite compound containing at least one element selected from Mg, Ba and Zr, and Ni, Co, Mn and the element M ′.

  The amount ratio of at least one element selected from Mg, Ba, and Zr, and Ni, Co, Mn, and element M ′ in the composite compound is appropriately adjusted according to the composition of the target lithium-containing composite oxide. do it.

  As the Li-containing compound that can be used for the synthesis of the lithium-containing composite oxide, various lithium salts can be used, for example, lithium hydroxide, lithium nitrate, lithium carbonate, lithium acetate, lithium bromide, lithium chloride, citric acid, and the like. Examples include lithium oxide, lithium fluoride, lithium iodide, lithium lactate, lithium oxalate, lithium phosphate, lithium pyruvate, lithium sulfate, and lithium oxide. Among them, carbon dioxide, nitrogen oxide, sulfur oxide Lithium hydroxide is preferable in that no gas that adversely affects the environment is generated.

  In order to synthesize the lithium-containing composite oxide, first, the various raw material compounds are mixed so that each element contained in these compounds has a ratio approximately corresponding to the composition of the target lithium-containing composite oxide. To do. And the said lithium containing complex oxide can be obtained by baking the obtained raw material mixture at 600-1000 degreeC for 1 to 24 hours, for example.

  When firing the raw material mixture, rather than raising the temperature to a predetermined temperature at one time, once heated to a temperature lower than the firing temperature (for example, 250-850 ° C.), preheating by holding at that temperature, Thereafter, it is preferable to raise the temperature to the firing temperature to advance the reaction, and it is preferable to keep the oxygen concentration in the firing environment constant.

  This is because, in the process of producing the lithium-containing composite oxide according to the present invention, trivalent Ni is unstable, and thus tends to have a non-stoichiometric composition. Therefore, the reaction of various raw material compounds related to the raw material mixture is performed. This is because it is generated stepwise to increase the homogeneity of the resulting lithium-containing composite oxide, and the generated lithium-containing composite oxide can be stably crystal-grown. That is, when the temperature is raised to the firing temperature at once, or when the oxidation concentration of the firing environment decreases during firing, the various raw material compounds related to the raw material mixture are likely to react unevenly and the composition uniformity. Is easily damaged.

  In addition, although there is no restriction | limiting in particular about the time of the said preheating, Usually, what is necessary is just to be about 0.5 to 30 hours.

  In addition, the firing atmosphere of the raw material mixture may be an atmosphere containing oxygen (that is, in the air), a mixed atmosphere of an inert gas (argon, helium, nitrogen, etc.) and oxygen gas, an oxygen gas atmosphere, or the like. However, the oxygen concentration (volume basis) at that time is preferably 15% or more, and more preferably 18% or more. However, from the viewpoint of reducing the production cost of the lithium-containing composite oxide particles and increasing the productivity of the particles and thus the productivity of the electrodes, it is more preferable to perform the firing of the raw material mixture in an atmospheric flow.

The flow rate of the gas during firing of the raw material mixture is preferably 2 dm ³ / min or more per 100 g of the mixture. If the gas flow rate is too low, that is, if the gas flow rate is too slow, the homogeneity of the composition of the lithium-containing composite oxide may be impaired. In addition, it is preferable that the flow rate of the gas at the time of firing the raw material mixture is 5 dm ³ / min or less per 100 g of the mixture.

  In the step of firing the raw material mixture, the dry-mixed mixture may be used as it is, but the raw material mixture is dispersed in a solvent such as ethanol to form a slurry and mixed for about 30 to 60 minutes with a planetary ball mill or the like. It is preferable to use a dried product, and the homogeneity of the lithium-containing composite oxide to be synthesized can be further improved by such a method.

  In the production method described above, a lithium-containing composite oxide satisfying the particle size, the BET specific surface area, the number average particle size, and the tap density can be obtained by appropriately controlling the gas composition and the firing temperature according to the composition. .

The positive electrode active material may be used in combination with a lithium-containing composite oxide other than the lithium-containing composite oxide represented by the general composition formula (1). Examples of such lithium-containing composite oxides include lithium cobalt oxides such as LiCoO ₂ ; lithium manganese oxides such as LiMnO ₂ and Li ₂ MnO ₃ ; lithium nickel oxides such as LiNiO ₂ ; LiCo _1-x NiO Lithium-containing composite oxide having a layered structure such as ₂ ; Lithium-containing composite oxide having a spinel structure such as LiMn ₂ O ₄ and Li _4/3 Ti _5/3 O ₄ ; Lithium-containing composite oxide having an olivine structure such as LiFePO ₄ And oxides having the above-described oxide as a basic composition and substituted with various elements.

As the positive electrode active material, at least the lithium-containing composite oxide represented by the general composition formula (1) is used, but only the lithium-containing composite oxide represented by the general composition formula (1) is used, or, it is more preferable to use a lithium-containing composite oxide and LiCoO ₂ represented by the general formula (1). When the lithium-containing composite oxide represented by the general composition formula (1) and LiCoO ₂ are used in combination, the LiCoO ₂ has a high true density and is charged and discharged at a relatively high potential. A battery having both relatively large capacities can be configured.

  When the lithium-containing composite oxide represented by the general composition formula (1) is used in combination with another lithium-containing composite oxide, the lithium-containing composite oxide represented by the general composition formula (1) From the viewpoint of ensuring a better effect by use, the ratio of the lithium-containing composite oxide represented by the general composition formula (1) is preferably 5% by mass or more of the entire active material, and is preferably 10% by mass or more. More preferably.

  When the lithium-containing composite oxide represented by the general composition formula (1) and another active material are used in combination, these may be used simply by mixing them. More preferably, it is used as an integrated composite particle. In this case, the packing density of the active material in the positive electrode mixture layer is improved, and the contact between the active material particles can be made more reliable. Therefore, the capacity and load characteristics of the non-aqueous secondary battery can be further enhanced.

  When the composite particles are used, the number average particle diameter of either the lithium-containing composite oxide represented by the general composition formula (1) or the other active material is ½ or less of the other number average particle diameter. It is preferable that When composite particles are formed by combining particles having a large number average particle diameter (hereinafter referred to as “large particles”) and particles having a small number average particle diameter (hereinafter referred to as “small particles”). In this case, small particles can be easily dispersed and fixed around the large particles, and composite particles having a more uniform mixing ratio can be formed. Therefore, non-uniform reaction in the electrode can be suppressed, and the charge / discharge cycle characteristics and safety of the electrochemical element can be further enhanced.

  When forming composite particles using large particles and small particles as described above, the number average particle size of the large particles is preferably 10 to 30 μm, and the number average particle size of the small particles is Is preferably 1 to 15 μm.

  The composite particles of the lithium-containing composite oxide represented by the general composition formula (1) and other active materials include, for example, the lithium-containing composite oxide particles represented by the general composition formula (1) and other particles. The particles of the active material can be mixed and mixed by using various kneaders such as a general uniaxial kneader and biaxial kneader, and the particles are slid together to give a share. The kneading is preferably a continuous kneading method in which raw materials are continuously fed in consideration of the productivity of composite particles.

  In the kneading, it is preferable to add a binder to each of the active material particles. Thereby, the shape of the composite particle formed can be kept strong. Further, it is more preferable to add a conductive additive and knead. Thereby, the electroconductivity between active material particles can further be improved.

  As the binder to be added at the time of producing the composite particles, any one of a thermoplastic resin and a 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, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoro Propylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoro Ethylene copolymer (ETFE resin), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoro Ethylene copolymer, ethylene-chlorotrifluoroethylene copolymer (ECTFE), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, or , Ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, and Na ion cross-linked products of these copolymers. 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.

  The amount of the binder added when forming the composite particles is preferably as small as the composite particles can be stabilized. For example, it is preferably 0.03 to 2 parts by mass with respect to 100 parts by mass of the total active material. .

  The conductive auxiliary agent added during the production of the composite particles may be any one that is chemically stable in the non-aqueous secondary battery. For example, graphite such as natural graphite and artificial graphite, acetylene black, ketjen black (trade name), carbon black such as channel black, furnace black, lamp black and thermal black; conductive fiber such as carbon fiber and metal fiber; aluminum Metallic powders such as 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; One species may be used alone, or two or more species may be used in combination. 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 amount of the conductive additive added when forming the composite particles is only required to ensure good conductivity and liquid absorption, for example, 0.1 to 2 parts by mass with respect to 100 parts by mass of the total active material. It is preferable.

  The composite particles preferably have a porosity of 5 to 15%. This is because the composite particles having such a porosity have appropriate contact with the non-aqueous electrolyte and penetration of the non-aqueous electrolyte into the composite particles.

  Further, the shape of the composite particles is preferably spherical or substantially spherical, similarly to the lithium-containing composite oxide represented by the general composition formula (1). Thereby, the density of the positive electrode mixture layer can be further increased.

  The positive electrode is produced, for example, by forming a positive electrode mixture layer containing the lithium-containing composite oxide represented by the general composition formula (1) or the composite particles as an active material on one side or both sides of a current collector. be able to.

  The positive electrode mixture layer includes, for example, a lithium-containing composite oxide represented by the general composition formula (1), the composite particles, a binder, and a conductive additive added to a solvent to form a paste-like or slurry-like positive electrode mixture. It can be formed by preparing a composition, applying it to the surface of the current collector by various coating methods, drying it, and adjusting the thickness and density of the positive electrode mixture layer by a pressing process.

  Here, the presence of a conductive additive and a water-repellent agent such as a fluorine-based resin or a silane compound in the positive electrode mixture layer facilitates the formation of a solid-phase / liquid-phase / gas-phase three-phase interface. Gas absorption becomes easy, and it becomes possible to constitute a non-aqueous secondary battery having further excellent storability and long life.

  Examples of the coating method for applying the positive electrode mixture-containing composition to the surface of the current collector include a substrate lifting 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.

  Examples of the binder and conductive aid that can be used for the preparation of the positive electrode mixture-containing composition include various binders and various conductive aids exemplified as those that can be used for forming the composite particles.

  In the positive electrode mixture layer, the total active material including the lithium-containing composite oxide represented by the general composition formula (1) is 80 to 99% by mass, and a binder (including that contained in the composite particles). Is preferably 0.5 to 10% by mass, and the conductive auxiliary agent (including those contained in the composite particles) is preferably 0.5 to 10% by mass.

Moreover, it is preferable that the thickness of the positive mix layer is 15-200 micrometers per single side | surface of a collector after press processing. Further, after pressing, the density of the positive electrode mixture layer is preferably 3.1 g / cm ³ or more, and more preferably 3.52 g / cm ³ or more. By using an electrode having such a high-density positive electrode mixture layer, higher capacity can be achieved. However, if the density of the positive electrode mixture layer is too large, the porosity becomes small and the permeability of the non-aqueous electrolyte may decrease, so the density of the positive electrode mixture layer after the press treatment is 4 It is preferably 0.0 g / cm ³ or less. In addition, as press processing, it can roll-press with the linear pressure of about 1-100 kN / cm, for example, and it can be set as the electrode mixture layer which has the said density by such processing.

  Further, the density of the positive electrode mixture layer in the present specification is a value measured by the following method. The positive electrode is cut into a predetermined area, its mass is measured using an electronic balance with a minimum scale of 0.1 mg, and the mass of the current collector is subtracted to calculate the mass of the positive electrode mixture layer. On the other hand, 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 obtained by subtracting the thickness of the current collector from these measured values and the area. To do. Then, the density of the positive electrode mixture layer is calculated by dividing the mass of the positive electrode mixture layer by the volume.

  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, the positive electrode which concerns on this invention is not limited to what was manufactured by the said manufacturing method, The thing manufactured by the other manufacturing method may be used. For example, when the composite particle is used as an active material, it is obtained by a method in which the composite particle is fixed as it is on the current collector surface to form a positive electrode mixture layer without using a positive electrode mixture-containing composition. The positive electrode obtained 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 to the positive electrode and negative electrode which concern on this invention.

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

  The separator according to the non-aqueous secondary battery of the present invention is preferably a porous film composed of polyolefin such as polyethylene, polypropylene and ethylene-propylene copolymer; polyester such as polyethylene terephthalate and copolymer polyester; . 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 polyethylene or a laminated porous film comprising a porous film such as a laminated porous film in which 2 to 5 layers of polyethylene and polypropylene are laminated. Is preferred. When a resin having a melting point higher than that of polyethylene such as polyethylene and polypropylene is used by mixing or laminating, it is desirable that polyethylene is 30% by mass or more, and 50% by mass or more as a resin constituting the porous membrane. 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.

  The average pore size of the separator is preferably 0.01 μm or more, more preferably 0.05 μm or more, preferably 1 μm or less, more preferably 0.5 μm or less.

Moreover, as a characteristic of the separator, a Gurley value represented by the number of seconds in which 100 ml of air permeates the membrane under a pressure of 0.879 g / mm ² is 10 to 500 sec. It is desirable to be. If the air permeability is too high, the ion permeability is reduced, whereas if it is too low, the strength of the separator may be reduced. Further, the strength of the separator is desirably 50 g or more in terms of piercing strength using a needle having a diameter of 1 mm. If the piercing strength is too small, a short circuit may occur due to the piercing of the separator when lithium dendrite crystals are generated.

  Even when the inside of the non-aqueous secondary battery is 150 ° C. or higher, the lithium-containing composite oxide represented by the general composition formula (1) is excellent in thermal stability, and therefore, safety is maintained. Can do.

  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. Among these, a mixed solvent of EC, MEC, and DEC is preferable. In this case, it is more preferable to include DEC in an amount of 15% by volume to 80% by volume with respect to the total volume of the mixed solvent. This is because such a mixed solvent can enhance the stability of the solvent during high-voltage charging while maintaining the low temperature characteristics and charge / discharge cycle characteristics of the battery high.

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 such an electrolyte salt include, for example, LiClO ₄ and 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 [wherein 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 solvent is not particularly limited, but is usually 0.5 to 1.7 mol / L.

  In addition, vinylene carbonates, 1,3-propane sultone, diphenyl disulfide, cyclohexyl benzene, biphenyl, and fluorobenzene are used for the purpose of improving the safety, charge / discharge cycleability, and high-temperature storage properties of the non-aqueous electrolyte. An additive such as t-butylbenzene may be added as appropriate. When the lithium-containing composite oxide contains Mn or when an active material containing Mn is used for the composite particles, the surface activity can be stabilized, and therefore an additive containing sulfur element can be added. Particularly preferred.

  The non-aqueous secondary battery of the present invention, for example, produces an electrode laminate in which the negative electrode and the positive electrode are laminated via the separator, and an electrode wound body in which this is wound in a spiral shape. And such an electrode body and the said nonaqueous electrolyte are enclosed and comprised in an exterior body according to a conventional method. 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.

  Since the non-aqueous secondary battery of the present invention has a high capacity and excellent battery characteristics, taking advantage of these characteristics, a power supply for a small and multifunctional portable device has been conventionally used. It can be preferably used for various applications to which known non-aqueous secondary batteries are applied.

Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention. Of the examples described later, Example 2 and Example 5 correspond to examples of the present invention.

Example 1
SiO (volume average particle size 5.0 μm) is heated to about 1000 ° C. in a boiling bed reactor, and the heated particles are brought into contact with a mixed gas of 25 ° C. composed of methane and nitrogen gas, and CVD is performed at 1000 ° C. for 60 minutes. Processed. Thus, carbon (hereinafter also referred to as “CVD carbon”) generated by pyrolyzing the mixed gas is deposited on the composite particles to form a coating layer, and a composite of SiO and a carbon material (carbon-coated SiO) Got.

  The composition of the composite of SiO and carbon material was calculated from the mass change before and after the coating layer was formed, and was SiO: CVD carbon = 85: 15 (mass ratio).

  Next, a negative electrode precursor sheet was prepared using the composite of SiO and a carbon material and graphite. The carbon-coated SiO was mixed with 7% by mass (content in the total solid content, the same applies hereinafter), 91% by mass of graphite, 1% by mass of CMC as a binder, 1% by mass of SBR, and water, and further mixed with negative electrode. A containing slurry was prepared.

  Using a blade coater, the negative electrode mixture-containing slurry was applied to both sides of a current collector made of copper foil having a thickness of 10 μm, dried at 100 ° C., and then compression-molded with a roller press to obtain a thickness per side. Formed a negative electrode mixture layer having a thickness of 60 μm. The electrode having the negative electrode mixture layer formed on the current collector was dried in vacuum at 100 ° C. for 15 hours.

  The dried electrode was further heat-treated at 160 ° C. for 15 hours using a far infrared heater. In the electrode after the heat treatment, the adhesion between the negative electrode mixture layer and the current collector was strong, and the negative electrode mixture layer was not peeled off from the current collector even by cutting or bending.

  Thereafter, the electrode was cut into a width of 37 mm to obtain a strip-shaped negative electrode.

  Moreover, the positive electrode was produced as follows.

First, mixed nickel sulfate, cobalt sulfate and manganese sulfate, magnesium sulfate, ^{respectively,} to ^{1.78mol / dm 3, 0.594mol / dm} 3, 0.594mol / dm 3, at a concentration of 0.03 mol / dm ³ An aqueous solution was prepared. Next, ammonia water whose pH was adjusted to about 12 by addition of sodium hydroxide was put into a reaction vessel, and while stirring it vigorously, the mixed aqueous solution and 25% by mass concentration of ammonia water were respectively added thereto. , 23 cm ³ / min, and 6.6 cm ³ / min at a rate of dropwise addition 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 maintained at 50 ° C., and a 3 mol / dm ³ concentration sodium hydroxide aqueous solution is simultaneously dropped so that the pH of the reaction solution is maintained at around 12, and further nitrogen is added. 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. This hydroxide and LiOH.H ₂ O were dispersed in ethanol at a molar ratio of 1: 1 to form a slurry, and then mixed with a planetary ball mill for 40 minutes and dried at room temperature to obtain a mixture. Obtained. 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. The lithium-containing composite oxide was synthesized by firing for a period of time.

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

About the said lithium containing complex oxide, the composition analysis was performed as follows using ICP (Inductive Coupled Plasma) method. First, 0.2 g of the lithium-containing composite oxide was collected 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). When the composition of the lithium-containing composite oxide was derived from the obtained results, it was a composition represented by Li _1.0 Ni _0.59 Co _0.2 Mn _0.2 Mg _0.01 O _2. found.

The lithium-containing composite oxide had a BET specific surface area of 0.25 m ² / g, and the ratio of primary particles of 0.7 μm or less in all primary particles was 11.7% by volume.

  96% by mass of the lithium-containing composite oxide (content in the total solid content; the same shall apply hereinafter), 2% by mass of Ketjen black as a conductive additive, 2% by mass of PVDF as a binder, and dehydrated N-methyl-2- The positive electrode mixture-containing slurry obtained by mixing pyrrolidone (NMP) was applied to both sides of a current collector made of an aluminum foil having a thickness of 15 μm, dried and pressed to form a positive electrode mixture having a thickness of 70 μm on one side. An agent layer was formed. Thereafter, this was cut into a width of 36 mm to obtain a strip-shaped positive electrode.

Next, the negative electrode and the positive electrode are overlapped via a microporous polyethylene film separator (thickness 18 μm, porosity 50%) and wound into a roll, and then terminals are connected to the positive and negative electrodes. It welded and inserted in the positive electrode can made from aluminum alloy of thickness 49mm, width 42mm, and height 61mm (494261 type), and the lid was welded and attached. Thereafter, non-aqueous electrolysis prepared by further dissolving LiPF ₆ to 1 mol% in a solution in which 3% by mass of vinylene carbonate was dissolved in EC: DEC = 3: 7 (volume ratio) from the liquid inlet of the lid. 3.6 g of the liquid was poured into the container and sealed to obtain a rectangular non-aqueous secondary battery having the structure shown in FIG. 1 and the appearance shown in FIG.

  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 so as to be flattened to form a flat electrode winding body 6 on a rectangular (square tube) positive electrode can 4 together with a non-aqueous electrolyte. Contained. However, in FIG. 1, in order to avoid complication, a metal foil, an electrolytic solution, and the like as a current collector used for manufacturing the positive electrode 1 and the negative electrode 2 are not illustrated.

  The positive electrode can 4 is made of an aluminum alloy and constitutes an outer package of the battery. 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 is connected to one end of each of the positive electrode 1 and the negative electrode 2 from the flat electrode winding body 6 made 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 an aluminum alloy lid (sealing lid plate) 9 for sealing the opening of the positive electrode can 4 via a polypropylene insulating packing 10. A stainless steel lead plate 13 is attached via the body 12.

  And this lid | cover 9 is inserted in the opening part of the 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. Further, in the battery of FIG. 1, an electrolyte inlet 14 is provided in the lid 9, and the electrolyte inlet 14 is welded and sealed by, for example, laser welding in a state where a sealing member is inserted. Thus, the battery hermeticity is ensured (therefore, in the battery shown in FIGS. 1 and 2, the electrolyte inlet 14 is actually an electrolyte inlet and a sealing member. In order to do so, it is shown as an electrolyte inlet 14). Further, the lid 9 is provided with a cleavage vent 15 as a mechanism for discharging the internal gas to the outside when the battery temperature rises.

  In the battery of this Example 1, the positive electrode can 4 and the lid 9 function as a positive electrode terminal by directly welding the positive electrode lead body 7 to the lid 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 connecting the negative electrode lead body 8 and the terminal 11 via 13, but the positive / negative may be reversed depending on the material of the positive electrode can 4. .

  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
First, nickel sulfate, cobalt sulfate and manganese sulfate, ^{respectively, 1.8mol / dm 3, 0.6mol /} dm 3, except that to prepare a mixed aqueous solution containing at a ratio of 0.6 mol / dm ³ to Example 1 Similarly, a hydroxide was prepared. This hydroxide, LiOH.H ₂ O, and BaCO ₃ were dispersed in ethanol so that the molar ratio was 1: 1: 0.001, and the mixture was made into a slurry, and then mixed for 40 minutes with a planetary ball mill. A lithium-containing composite oxide was synthesized in the same manner as in Example 1, except that the mixture was obtained by drying at room temperature.

When the composition of the lithium-containing composite oxide was analyzed by ICP in the same manner as in Example 1, the composition represented by Li _1.0 Ni _0.6 Co _0.2 Mn _0.2 Ba _0.001 O ₂ It turned out to be.

The lithium-containing composite oxide had a BET specific surface area of 0.2 m ² / g, and the proportion of primary particles of 0.7 μm or less in all primary particles was 9.0% by volume.

  A 494261 type square non-aqueous secondary battery was produced in the same manner as in Example 1 except that the positive electrode active material was changed to the lithium-containing composite oxide.

Example 3
First, a hydroxide was prepared in the same manner as in Example 2. This hydroxide, LiOH.H ₂ O, and ZrO ₂ were dispersed in ethanol so as to have a molar ratio of 1: 1: 0.001, and then slurryed, and then mixed for 40 minutes with a planetary ball mill. A lithium-containing composite oxide was synthesized in the same manner as in Example 1, except that the mixture was obtained by drying at room temperature.

When the composition of the lithium-containing composite oxide was analyzed by ICP in the same manner as in Example 1, the composition represented by Li _1.0 Ni _0.6 Co _0.2 Mn _0.2 Zr _0.001 O ₂ It turned out to be.

The lithium-containing composite oxide had a BET specific surface area of 0.28 m ² / g, and the ratio of primary particles of 0.7 μm or less in all primary particles was 13.4% by volume.

  A 494261 type square non-aqueous secondary battery was produced in the same manner as in Example 1 except that the positive electrode active material was changed to the lithium-containing composite oxide.

Example 4
First, a hydroxide was prepared in the same manner as in Example 1. This hydroxide, LiOH.H ₂ O, and ZrO ₂ were dispersed in ethanol so as to have a molar ratio of 1: 1: 0.001, and then slurryed, and then mixed for 40 minutes with a planetary ball mill. A lithium-containing composite oxide was synthesized in the same manner as in Example 1, except that the mixture was obtained by drying at room temperature.

The composition of the lithium-containing composite oxide was analyzed by ICP in the same manner as in Example 1. As a result, Li _1.0 Ni _0.59 Co _0.2 Mn _0.2 Mg _0.01 Zr _0.001 O ₂ It was found to be the represented composition.

The lithium-containing composite oxide had a BET specific surface area of 0.22 m ² / g, and the ratio of primary particles of 0.7 μm or less in all primary particles was 12.5% by volume.

  A 494261 type square non-aqueous secondary battery was produced in the same manner as in Example 1 except that the positive electrode active material was changed to the lithium-containing composite oxide.

Example 5
First, a hydroxide was prepared in the same manner as in Example 1. This hydroxide, LiOH.H ₂ O, and BaCO ₃ were dispersed in ethanol so that the molar ratio was 1: 1: 0.001, and the mixture was made into a slurry, and then mixed for 40 minutes with a planetary ball mill. A lithium-containing composite oxide was synthesized in the same manner as in Example 1, except that the mixture was obtained by drying at room temperature.

When the composition of the lithium-containing composite oxide was analyzed by ICP in the same manner as in Example 1, Li _1.0 Ni _0.59 Co _0.2 Mn _0.2 Mg _0.01 Ba _0.001 O ₂ It was found to be the represented composition.

The lithium-containing composite oxide had a BET specific surface area of 0.18 m ² / g, and the ratio of primary particles of 0.7 μm or less in all primary particles was 4.8% by volume.

  A 494261 type square non-aqueous secondary battery was produced in the same manner as in Example 1 except that the positive electrode active material was changed to the lithium-containing composite oxide.

Example 6
First, mixed nickel sulfate, cobalt sulfate and manganese sulfate, magnesium sulfate, ^{respectively,} to ^{2.38mol / dm 3, 0.297mol / dm} 3, 0.297mol / dm 3, in a proportion of 0.03 mol / dm ³ A hydroxide was prepared in the same manner as in Example 1 except that an aqueous solution was prepared. This hydroxide, LiOH.H ₂ O, and ZrO ₂ were dispersed in ethanol so as to have a molar ratio of 1: 1: 0.001, and then slurryed, and then mixed for 40 minutes with a planetary ball mill. A lithium-containing composite oxide was synthesized in the same manner as in Example 1 except that the mixture was obtained by drying at room temperature.

When the composition of the lithium-containing composite oxide was analyzed by ICP in the same manner as in Example 1, Li _1.0 Ni _0.79 Co _0.099 Mn _0.099 Mg _0.01 Zr _0.001 O ₂ It was found to be the represented composition.

The lithium-containing composite oxide had a BET specific surface area of 0.29 m ² / g, and the ratio of primary particles of 0.7 μm or less in all primary particles was 11.6% by volume.

  A 494261 type square non-aqueous secondary battery was produced in the same manner as in Example 1 except that the positive electrode active material was changed to the lithium-containing composite oxide.

Example 7
The same Li _1.0 Ni _0.59 Co _0.2 Mn _0.2 Mg _0.01 Zr _0.001 O ₂ and LiCoO ₂ as synthesized in Example 4 were in a mass ratio of 3: 7. Weigh and mix for 30 minutes using a Henschel mixer. A 494261 type square non-aqueous secondary battery was produced in the same manner as in Example 1 except that the obtained mixture was used as the positive electrode active material.

Comparative Example 1
First, a hydroxide was prepared in the same manner as in Example 2. This hydroxide and LiOH.H ₂ O were dispersed in ethanol at a molar ratio of 1: 1 to make a slurry, then mixed in a planetary ball mill for 40 minutes and dried at room temperature to obtain a mixture. A lithium-containing composite oxide was synthesized in the same manner as in Example 1 except that it was obtained.

When the composition of the lithium-containing composite oxide was analyzed by ICP in the same manner as in Example 1, it was found to be a composition represented by Li _1.0 Ni _0.6 Co _0.2 Mn _0.2 O _2. found.

The lithium-containing composite oxide had a BET specific surface area of 0.30 m ² / g, and the ratio of primary particles of 0.7 μm or less in all primary particles was 18.7% by volume.

  A 494261 type square non-aqueous secondary battery was produced in the same manner as in Example 1 except that the positive electrode active material was changed to the lithium-containing composite oxide.

Comparative Example 2
A 494261-type square non-aqueous secondary battery was produced in the same manner as in Example 1 except that the positive electrode active material was changed to LiCoO ₂ .

Comparative Example 3
A negative electrode composite prepared by mixing a positive electrode produced in the same manner as in Example 1 except that the positive electrode active material was changed to LiCoO ₂ , 98% by mass of graphite, 1% by mass of CMC as a binder, 1% by mass of SBR and water. A negative electrode produced in the same manner as in Example 1 was used except that the agent-containing slurry was used, and a 494261 type rectangular non-aqueous secondary battery was produced in the same manner as in Example 1.

The configurations of the positive electrode active material and the negative electrode active material used in the nonaqueous secondary batteries of Examples 1 to 7 and Comparative Examples 1 to 3 are shown in Table 1, and the nonaqueous secondary batteries of Examples 1 to 7 and Comparative Example 1 are used. Table 2 shows the compositions of lithium-containing composite oxides other than LiCoO ₂ among the positive electrode active materials used.

  In the non-aqueous secondary battery of Comparative Example 1, only the lithium-containing composite oxide that does not satisfy the general composition formula (1) is used as the positive electrode active material. In the “ratio in the middle”, the amount used is described in the column of “lithium-containing composite oxide represented by the general composition formula (1)”. Moreover, y in Table 2 is y in the general composition formula (1), and a to f mean the proportion of each element included in the element group M in the general composition formula (1). .

  Each battery produced by the above method was stored at 60 ° C. for 7 hours and then subjected to discharge capacity measurement and charge / discharge cycle test at 20 ° C. The battery was charged and discharged in each measurement by the following method. Regarding the discharge capacity measurement, charging was performed at a constant current with a current of 850 mA, and after the charging voltage reached 4.2 V, the charging was performed at a constant voltage until the current became 1/50. The discharge was performed at a constant current with a current of 340 mA, and the final discharge voltage was 2.5V. The series of operations of charging and discharging was defined as one cycle. And the discharge capacity of the battery was evaluated by the discharge capacity at the second charge / discharge cycle. Moreover, about the charging / discharging cycle test, charging was performed at a constant current with a current of 1.7 A, and the charging voltage was 4.2 V after the charging voltage reached 4.2 V. The charging was completed in 2.5 hours from the start of charging. The discharge was performed at a constant current with a current of 1.7 A, and the final discharge voltage was 2.5V. And the series of operation of the said charge and discharge was made into 1 cycle, and the superiority or inferiority of the charge / discharge cycle characteristic was evaluated with the capacity | capacitance maintenance factor of the 500th cycle. The capacity maintenance rate was calculated by the following formula.

Capacity maintenance rate (%)
= (Discharge capacity at 500th cycle / discharge capacity at the second cycle) × 100

  These results are shown in Table 3.

  As is apparent from Table 3, Examples 1 to 1 provided with a positive electrode containing a lithium-containing composite oxide represented by the general composition formula (1) and a negative electrode containing a composite of SiO and a carbon material. The nonaqueous secondary battery of No. 7 has a high capacity and good charge / discharge cycle characteristics.

On the other hand, the battery of Comparative Example 1 using a lithium-containing composite oxide containing Ni, Co, and Mn but not containing any of Mg, Ba, and Zr has inferior charge / discharge cycle characteristics. ing. The battery of Comparative Example 2 that only LiCoO ₂ as a positive electrode active material, and only LiCoO ₂ as the positive electrode active material, and the battery of Comparative Example 3 that the only graphite as a negative electrode active material, capacity than the battery of Example Is small.

1 Positive electrode 2 Negative electrode 3 Separator

Claims (4)

A non-aqueous secondary battery having a positive electrode, a negative electrode, a non-aqueous electrolyte and a separator,
The negative electrode is a composite of a material containing Si and O as constituent elements (provided that the atomic ratio x of O to Si is 0.5 ≦ x ≦ 1.5) and a carbon material, and graphitic carbon A negative electrode mixture layer containing a material as a negative electrode active material has one or both sides of a current collector ,
The positive electrode has the following general composition formula (1)
Li _{1 + y} MO ₂ (1)
[In the general composition formula (1), −0.15 ≦ y <0.15, and M represents a group of four or more elements containing B a , Ni, Co, and Mn; in each element which constitutes, Ni, Co, Mn, and the ratio of Ba to (mol%), when a, b, c, and the e respectively, 50 ≦ a ≦ 97, b ≦ 49, c ≦ 49, e ≦ 3 is a contact and 3 ≦ b + c + e ≦ 50]
A non-aqueous secondary battery comprising a positive electrode mixture layer containing a lithium-containing composite oxide represented by the formula (1) as a positive electrode active material on one side or both sides of a current collector. The nonaqueous secondary battery according to claim 1, further comprising LiCoO ₂ as a positive electrode active material.   3. The non-aqueous secondary battery according to claim 1, wherein the content of the composite of the material containing Si and O as a constituent element and the carbon material in the negative electrode active material is 0.01 to 20 mass%. The lithium-containing composite oxide represented by the general composition formula (1) has a ratio of primary particles having a particle size of 0.7 µm or less in all primary particles of 30 vol% or less. The non-aqueous secondary battery in any one.

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