JP4954270B2 - Non-aqueous secondary battery - Google Patents

Description

  The present invention relates to a high capacity non-aqueous secondary battery.

  Since non-aqueous secondary batteries have high voltage and high capacity, there are great expectations for their development. In addition to Li (lithium) and Li alloys, natural or artificial graphite-based carbon materials that can insert and desorb Li ions are applied to the negative electrode material (negative electrode active material) of nonaqueous secondary batteries. .

  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 graphite-based carbon material or the like is an anode. 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 which has a favorable battery characteristic.

The non-aqueous secondary battery of the present invention that has achieved the above object is a non-aqueous secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, and the positive electrode has the following general composition formula (1):
Li _{1 + y + a} Ni _{(1-yz + b) / 2} Mn _{(1-yzb) / 2} M ¹ _z O ₂ (1)
(Wherein, ^{M 1} is represented Co, or a Co, Ti, Cr, Fe, C u, Zn, Al, Ge, Sn, and at least one element selected from the group consisting of Mg and Zr, -0 0.1 ≦ y ≦ 0.1, −0.05 ≦ a ≦ 0.05, 0 < z ≦ 0.4, −0.1 ≦ b ≦ 0.6, and 0.6 ≧ 1-yzz > 0 and 1 ≦ 1-yz + b )
And the negative electrode is 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 (hereinafter, the material may be abbreviated as “SiO _x ”) and a negative electrode mixture layer containing graphite, and constitutes Si and O. The material included in the element forms a composite with the carbon material. In the negative electrode mixture layer, when the total of the material including Si and O and the graphite is 100% by mass, Si and O The ratio of the material containing the above as constituent elements is 3 to 20% by mass.

According to the present invention, a high-capacity non-aqueous secondary battery can be provided. Further, in the nonaqueous secondary battery of the present invention is a high capacity, and while using large SiO _x of volume change during charge and discharge, it is possible to suppress the deterioration of the battery characteristics due to the volume change. Therefore, in the battery of the present invention, for example, good battery characteristics can be ensured without greatly changing the configuration from the conventional non-aqueous secondary battery.

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 graphite in a specific ratio to constitute the negative electrode, it was decided to suppress the deterioration of battery characteristics due to the volume change of SiO _x accompanying charge / discharge.

However, as described above, a battery is configured using a negative electrode using both SiO _x and graphite, and further using, for example, a positive electrode using lithium cobaltate (LiCoO ₂ ) widely used in non-aqueous secondary batteries. Even so, it has been clarified by the present inventors that the capacity cannot be increased to meet the use of SiO _x .

Accordingly, the present inventors have conducted extensive studies, together with the negative electrode, by constituting the battery using the cathode for the Li-containing transition metal oxide represented by the general formula (1) as an active material, The present invention has been completed by finding that the capacity can be increased while suppressing a decrease in battery characteristics such as charge / discharge cycle characteristics resulting from the volume change of SiO _x accompanying charge / discharge.

  The negative electrode according to the nonaqueous secondary battery of the present invention includes 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 material having a negative electrode mixture layer containing graphite is used.

The SiO _x may contain a microcrystalline or amorphous phase of Si. In this case, the atomic ratio of Si and O is a ratio including Si microcrystalline or amorphous phase Si.

That is, the above material, the SiO ₂ matrix of amorphous Si (e.g., microcrystalline Si) is include the dispersed structure, the SiO ₂ of the amorphous, dispersed therein 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.

The SiO _x is preferably a composite that is combined with a conductive material such as a carbon material. For example, the surface of the SiO _x is preferably covered with a conductive material (such as a carbon material). Since SiO _x is an oxide and has poor conductivity, when it is used as a negative electrode active material, a conductive material (conductive aid) is used from the viewpoint of ensuring good battery characteristics, and SiO in the negative electrode is used. _It is necessary to improve the mixing and dispersion of _x and the conductive material to form an excellent conductive network. In the case of a composite in which SiO _x is combined with a conductive material, for example, a conductive network in the negative electrode is formed better than when a mixture obtained by simply mixing SiO _x and a conductive material is used. The

As a composite of SiO _x and a conductive material, as described above, the surface of SiO _x is covered with a conductive material (preferably a carbon material), and SiO _x and a conductive material (preferably a carbon material). And the like.

Further, by using the composite in which the surface of SiO _x is coated with a conductive material (preferably a carbon material) in combination with a conductive material (such as a carbon material), an even better conductive network can be obtained in the negative electrode. Therefore, a non-aqueous secondary battery having a higher capacity and excellent charge / discharge cycle characteristics can be realized. The complex of the SiO _x and a conductive material coated with a conductive material, for example, like granules the mixture was further granulated with SiO _x and a conductive material coated with a conductive material .

As the SiO _x whose surface is coated with a conductive material, a complex with SiO _x and a conductive material resistivity value is less than (e.g. granulate), preferably between SiO _x and the carbon material Those in which the surface of the composite is further coated with a carbon material can be preferably used. When the SiO _x and the conductive material are dispersed inside the granule, a better conductive network can be formed. Therefore, in a non-aqueous secondary battery having a negative electrode using this as a negative electrode material, heavy load discharge characteristics The battery characteristics can be further improved.

Preferred examples of the conductive 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.

Details of the conductive material include a fibrous or coiled carbon material, a fibrous or coiled metal, carbon black (including acetylene black and ketjen black), artificial graphite, graphitizable carbon and non-graphitizable. At least one material selected from the group consisting of carbon is preferred. A fibrous or coiled carbon material or a fibrous or coiled metal is preferable in that it easily forms a conductive network and has 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.

Graphite used in combination with SiO _x as the negative electrode active material can also be used as a conductive material according to a composite of SiO _x and a conductive material. Graphite, like carbon black, has high electrical conductivity and high liquid retention, and also has the property of easily maintaining contact with the SiO _x particles even when they expand and contract. Therefore, it can be preferably used for forming a complex with SiO _x .

Among the conductive materials exemplified above, a fibrous carbon material is particularly preferable as a material used when the composite with SiO _x is a granulated body. The fibrous carbon material has a thin thread shape and high flexibility so that it can follow the expansion and contraction of SiO _x , and because of its high bulk density, it can have many junctions with SiO _x particles. Because it can. 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.

In addition, a fibrous carbon material and a fibrous metal can also be formed on the surface of 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, whereas the specific resistance value of the exemplified conductive material is usually 10 ^{−5 to} 10 kΩcm.

The composite of SiO _x and the conductive material may further include a material layer (a material layer containing non-graphitizable carbon) that covers the carbon material coating layer on the particle surface.

When using a complex of SiO _x and a conductive material, the ratio between the SiO _x and a conductive material, from the viewpoint of satisfactorily exhibiting the effect by compounding the conductive material, SiO x: ₁₀₀ parts by weight On the other hand, the conductive material is preferably 5 parts by mass or more, and more preferably 10 parts by mass or more. In the composite, if the ratio of the conductive material to be combined with SiO _x is too large, the amount of SiO _x in the negative electrode mixture layer may be decreased, and the effect of increasing the capacity may be reduced. , SiO _x : The conductive material is preferably 95 parts by mass or less, more preferably 90 parts by mass or less with respect to 100 parts by mass of SiO _x .

The composite of the SiO _x and the conductive 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 conductive material resistivity value than SiO _x is adding the conductive material into the dispersions SiO _x are dispersed in a dispersion medium, Using this dispersion, composite particles (granulated body) may be formed by the same technique as that for combining SiO _x . Further, by granulation process according to the similar mechanical method, it is possible to produce a granular material of SiO _x and a conductive material.

Next, when the surface of SiO _x particles (SiO _x composite particles or a granulated body of SiO _x and a conductive material) is coated with a carbon material to form a composite, for example, hydrocarbon gas is removed. Heating in the phase causes carbon produced by pyrolysis of the hydrocarbon gas to deposit 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 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. However, it is preferable that it is 700 degreeC or more especially, and it is still more preferable that it is 800 degreeC or more. 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, hexane, cyclohexane 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, ethylene gas, acetylene gas, etc. can also be used.

In addition, after covering the surface of SiO _x particles (SiO _x composite particles, or a granulated body of SiO _x and a conductive material) with a carbon material by a vapor deposition (CVD) method, petroleum pitch, coal-based After attaching at least one organic compound selected from the group consisting of pitch, thermosetting resin, and a condensate of naphthalene sulfonate and aldehydes to a coating layer containing a carbon material, the organic compound is The adhered 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 conductive 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 .

There is no particular limitation on the graphite used as a negative electrode active material with said SiO _x, it is possible to use flake graphite, natural graphite or artificial graphite such as earthy graphite.

The negative electrode according to the present invention includes an appropriate solvent (dispersion medium) in a mixture (negative electrode mixture) containing SiO _x (including a composite of SiO _x and a conductive material), graphite, and a binder (binder). ) And then kneaded thoroughly to apply a paste-like or slurry-like negative electrode mixture-containing composition on one or both sides of the current collector, and the solvent (dispersion medium) is removed by drying or the like. Can be obtained by forming a negative electrode mixture layer having a thickness and density of 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 according to the present invention, in the negative electrode mixture layer, when the graphite is used as the conductive material in the composite of SiO _x and graphite (the composite of SiO _x and conductive material, the amount of graphite used in the composite When the sum of the ratio of SiO _x and graphite is the same hereinafter) is 100 mass%, the ratio of SiO _x is 3 mass% or more, preferably 4 mass% or more. By making the ratio of SiO _x as described above, it is possible to increase the capacity of the non-aqueous secondary battery. However, _if the use ratio of SiO _x is too large, the deterioration of battery characteristics due to the volume expansion of SiO _x accompanying charge / discharge cannot be sufficiently suppressed. Therefore, in the negative electrode mixture layer, when the total of SiO _x and graphite is 100 mass%, the ratio of SiO _x is 20 mass% or less, preferably 18 mass% or less.

Further, in the negative electrode mixture layer, the total amount of the negative electrode active material containing SiO _x and graphite (when graphite was used as the conductive material in the composite of SiO _x and conductive material, this composite was used. The amount of graphite is preferably 80 to 99% by mass, and the amount of the binder is preferably 1 to 20% by mass. In the case of using a conductive material (preferably a carbon material) for forming a composite with SiO _x or other conductive auxiliary agent, these conductive materials in the negative electrode mixture layer are: It is preferable that the total amount of the negative electrode active material and the amount of the binder are used in a range satisfying the above-described preferable values.

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

The positive electrode of the battery of the present invention uses a positive electrode having a positive electrode mixture layer containing the Li-containing transition metal oxide represented by the general formula (1).

By combining such a positive electrode with the negative electrode, it is possible to increase the capacity of the nonaqueous secondary battery for the following reason. When a negative electrode formed by using SiO _x and graphite in combination with a positive electrode formed by using a positive electrode active material commonly used for non-aqueous secondary batteries such as LiCoO ₂ is used as a battery, the irreversibility of SiO _x Since the capacity is large, the effect of increasing the capacity by using SiO _x is hardly exhibited. However, Li-containing transition metal oxide itself represented by the general formula (1), although than LiCoO ₂ is a high capacity, since the irreversible capacity is relatively large, a positive electrode using the same, and SiO _x When combined with the negative electrode using graphite in the above ratio, 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.

  In the general composition formula (1) representing the Li-containing transition metal oxide, it is preferable to increase the ratio of Ni to Mn in order to achieve high capacity, but when b is greater than 0.6, Ni is introduced into the Li site and tends to have a non-stoichiometric composition. In addition, since trivalent Ni is unstable, Ni preferably has an oxidation number lower than that of trivalent. However, when b is greater than 0.6, for example, Ni is baked in the atmosphere. It becomes difficult to control the oxidation number of (a method for synthesizing a Li-containing transition metal oxide will be described later). For these reasons, when b is larger than 0.6 in the general composition formula (1), sufficient theoretical capacity and charge / discharge reversibility cannot be obtained. Therefore, in the Li-containing transition metal oxide represented by the general composition formula (1), the Ni content is adjusted so that −0.1 ≦ b ≦ 0.6.

  In the general composition formula (1) representing the Li-containing transition metal oxide, 1-yz-b> 0, and Mn is always present in the crystal lattice, whereby the Li-containing transition metal oxide particles Therefore, it is possible to configure a safer non-aqueous secondary battery. That is, in the crystal lattice, Mn stabilizes the layered structure together with divalent Ni and improves the thermal stability of the Li-containing transition metal oxide.

Further, in the Li-containing transition metal oxide represented by the general formula (1), by containing the element M ^1, of Mn due to doping and dedoping of Li in the charge and discharge of non-aqueous secondary battery It is possible to suppress valence fluctuation, stabilize the average valence of Mn at a value close to tetravalent, further increase the reversibility of charge / discharge, and obtain a positive electrode excellent in charge / discharge cycle characteristics.

More specifically, wherein the Li-containing transition metal oxide represented by the general formula (1), as the element ^{M 1,} Co, or the Co, Ti, Cr, Fe, C u, Zn, Al, Ge , Sn, are contained and at least one element selected from the group consisting of Mg and Zr. As described above, the element M ¹ is involved in stabilization of the crystal structure and control of reactivity in the Li-containing transition metal oxide, but if it is too much, the capacity may be reduced. Therefore, in the general composition formula (1) representing the Li-containing transition metal oxide, z indicating the amount of the element M ¹ is 0 < z ≦ 0.4. z is more preferably 0.05 or more, and more preferably 0.35 or less. The element M ¹ is more preferably Co, Al, Mg, Ti, or Ge, and particularly preferably Co, Al, or Mg because the above-described effect can be more easily obtained. The element M ¹ may be uniformly distributed in the Li-containing transition metal oxide, or may be segregated on the particle surface or the like.

The Li-containing transition metal oxide having the above composition has a large true density of 4.55 to 4.95 g / cm ³ and becomes a material having a high volume energy density. In addition, although the true density of the Li-containing transition metal oxide containing Mn in a certain range varies greatly depending on its composition, the structure is stabilized and uniformity can be improved in the narrow composition range as described above. For example, it is considered to be a large value close to the true density of LiCoO ₂ . Further, the capacity per mass of the active material can be increased, and a material having excellent reversibility can be obtained.

  In addition, the Li-containing transition metal oxide represented by the general composition formula (1) has a large true density particularly when the composition is close to the stoichiometric ratio. In (1), it is preferable to satisfy −0.1 ≦ y ≦ 0.1 and −0.05 ≦ a ≦ 0.05. By adjusting the values of y and a in this way, the true density and Reversibility can be increased.

Preferable specific examples of the Li-containing transition metal oxide represented by the general composition formula (1) include, for example, Li _1.0 Ni _0.65 Mn _0.15 Co _0.2 O ₂ , Li _1.0 Examples include Ni _0.6 Mn _0.2 Co _0.2 O ₂ and Li _1.0 Ni _0.5 Mn _0.2 Co _0.3 O ₂ .

Further, in the positive electrode according to the present invention, a Li-containing transition metal oxide represented by the following general composition formula (2) may be used together with the Li-containing transition metal oxide represented by the general composition formula (1). it can.

Li _{1 + c} M ² O ₂ (2)
[However, −0.3 ≦ c ≦ 0.3, and M ² Represents at least three element groups including Ni, Mn and Mg, ² 70 ≦ d ≦ 97, 0.5 <e <30, 0.5 <, where the ratios (mol%) of Ni, Mn, and Mg are d, e, and f, respectively. f <30, −10 <ef <10 and −8 ≦ (ef) / f ≦ 8]

The Li-containing transition metal oxide represented by the general formula (2) contains an element group M ² containing at least Ni, Mn and Mg. Ni is a component that contributes to improving the capacity of the Li-containing transition metal oxide.

In the general composition formula (2) representing the Li-containing transition metal oxide, it is preferable to increase the ratio of Ni to Mn or Mg in order to achieve high capacity. For example, when pure LiNiO ₂ is used, Ni Is introduced into the Li site and tends to have a non-stoichiometric composition (referred to as cation mixing), and conversely the capacity decreases. However, since M ² contains a small amount of Mn or Mg in addition to Ni, the structure is stabilized and the caryon mixing is less likely to occur. Therefore, in the Li-containing transition metal oxide represented by the general composition formula (2), when the total number of elements of M ² is 100 mol%, the Ni ratio d is 70 mol% or more and 97 mol% or less. The amount of Ni in the Li-containing transition metal oxide is adjusted.

  In addition, since the electrical conductivity of the Li-containing transition metal oxide improves as the average valence of Ni increases, in the Li-containing transition metal oxide represented by the general composition formula (2), in the examples described later, The average valence (A) of Ni measured by the method shown is preferably 2.5 to 3.2.

  In addition, in the Li-containing transition metal oxide represented by the general composition formula (2), the thermal stability of the Li-containing transition metal oxide can be increased by allowing Mn to be present in the crystal lattice. A safer non-aqueous secondary battery can be configured. That is, in the crystal lattice, Mn stabilizes the layered structure together with divalent Ni and improves the thermal stability of the Li-containing transition metal oxide.

  Furthermore, in the Li-containing transition metal oxide, by adding Mg, the Mn valence fluctuation associated with doping and dedoping of Li during charge / discharge of the non-aqueous secondary battery is suppressed, and the average valence of Mn Can be stabilized at a value close to tetravalent, reversibility of charge / discharge can be further increased, and a positive electrode excellent in charge / discharge cycle characteristics can be obtained.

Thus, Mn and Mg are involved in stabilization of the crystal structure and control of reactivity in the Li-containing transition metal oxide, but if too much, the capacity may be reduced. Therefore, in the general composition formula (2) representing the Li-containing transition metal oxide, when the total number of elements of M ² is 100 mol%, the ratio e of Mn and the ratio f of Mg are 0.5 <e, respectively. <30, 0.5 <f <30, and −10 <ef <10 and −8 ≦ (ef) / f ≦ 8.

In addition, in the Li-containing transition metal oxide represented by the general composition formula (2), from the viewpoint of ensuring the above-described effect by Mn more favorably, the ratio e of Mn in all elements of M ² is 1 mol. % Or more, preferably 2 mol% or more, on the other hand, preferably 10 mol% or less, more preferably 7 mol% or less. In addition, in the Li-containing transition metal oxide represented by the general composition formula (2), from the viewpoint of ensuring the above-described effects of Mg more favorably, the ratio f of Mg in all elements of M ² is 1 mol. % Or more, and more preferably 2 mol% or more. However, as described above, since Mg has little influence on the charge / discharge capacity, if the addition amount is large, the capacity may be reduced. Therefore, in the Li-containing transition metal oxide represented by the general composition formula (2), the Mg ratio f is preferably 15 mol% or less, more preferably 10 mol% or less, and 7 mol% or less. More preferably it is. It is preferable that −3 ≦ e−f ≦ 3, and it is preferable that −2 ≦ (ef) / f ≦ 2.

  Further, in the Li-containing transition metal oxide represented by the general composition formula (2), the average valence of Mn is described below from the viewpoint of stabilizing Mg and effectively exhibiting its action. It is a value measured by the method shown in the example of the above, and it is preferably 3.5 to 4.2.

M ² in the general composition formula (2) representing the Li-containing transition metal oxide contains at least Ni, Mn, and Mg, and may be an element group composed of these three elements.

The M ² may be a group of four or more elements including Co in addition to Ni, Mn and Mg. When M ² contains Co, the presence of Co in the crystal lattice of the Li-containing transition metal oxide causes Li-containing transition metal oxidation due to Li desorption and insertion during charge / discharge of the nonaqueous secondary battery. Since the irreversible reaction resulting from the phase transition of the product can be further relaxed and the reversibility of the crystal structure of the Li-containing transition metal oxide can be increased, a non-aqueous secondary battery having a longer charge / discharge cycle life is formed. It becomes possible.

In Li-containing transition metal oxide represented by the general formula (2), ^{if M 2} comprises Co, with each element which constitutes the ^{M 2,} the ratio of Co g (mol%) is, ^{M 2} configuration It is preferable that 0 <g <30 from the viewpoint of suppressing the effect of these elements from decreasing as the amount of other elements (Ni, Mn, and Mg) decreases. In addition, from the viewpoint of ensuring the above-described effects by Co better, the ratio g of Co in all elements of M ² is more preferably 1 mol% or more.

Further, in the Li-containing transition metal oxide represented by the general composition formula (2), when M ² contains Co, the average valence of Co in the Li-containing transition metal oxide is excellent in the above-described effect due to Co. From the viewpoint of ensuring the above, it is a value measured by the method shown in the examples below, and is preferably 2.5 to 3.2.

Note that M ² in the general composition formula (2) representing the Li-containing transition metal oxide may contain an element other than Ni, Mn, Mg, and Co. For example, Ti, Cr, Fe, Cu, It may contain elements such as Zn, Al, Ge, Sn, Ag, Ta, Nb, Mo, B, P, Zr, and Ga. However, in order to obtain the effect of the present invention sufficiently, when formed into a 100 mol% of the total number of elements in ^{M 2,} Ni, Mn, ratio of elements other than Mg and Co is preferably set to less 15 mol% More preferably, it is 3 mol% or less. Elements other than Ni, Mn, Mg and Co in M ² may be uniformly distributed in the Li-containing transition metal oxide, or may be segregated on the particle surface or the like.

Similarly to the Li-containing transition metal oxide represented by the general composition formula (1), the true density of the Li-containing transition metal oxide represented by the general composition formula (2) is 4.55-4. It becomes a large value of 95 g / cm ³ and becomes a material having a high volume energy density. The true density of the Li-containing transition metal oxide containing Mn in a certain range varies greatly depending on its composition, but the structure is stabilized and the uniformity can be improved in the narrow composition range as described above. Further, the capacity per mass of the active material can be increased, and a material having excellent reversibility can be obtained.

  The Li-containing transition metal oxide represented by the general composition formula (2) is also a composition close to the stoichiometric ratio, like the Li-containing transition metal oxide represented by the general composition formula (1). In this case, the true density increases. Specifically, preferably, −0.3 ≦ c ≦ 0.3, more preferably −0.1 ≦ c ≦ 0.1. True density and reversibility can be increased.

Preferable specific examples of the Li-containing transition metal oxide represented by the general composition formula (2) include, for example, Li _1.0 Ni _0.94 Mn _0.03 Mg _0.03 O ₂ , Li _{1.02 Examples} include Ni _0.92 Co _0.06 Mn _0.01 Mg _0.01 O ₂ and Li _1.02 Ni _0.9 Co _0.05 Mn _0.03 Mg _0.02 O ₂ .

  The Li-containing transition metal oxide represented by the general composition formula (1) and the Li-containing transition metal oxide represented by the general composition formula (2) include a Li-containing compound, a Ni-containing compound, and a Mn-containing compound, It is very difficult to obtain high purity by simply mixing and firing Mg-containing compounds. This is because Ni, Mn, and the like have a low diffusion rate in the solid, so that it is difficult to diffuse them uniformly during the synthesis reaction of the Li-containing transition metal oxide. It is thought that this is because Ni and Mn are difficult to be uniformly distributed therein.

  Therefore, when synthesizing the Li-containing transition metal oxide according to the present invention, at least Ni and Mn, and if necessary, a composite compound containing Mg and Co as constituent elements and a Li-containing compound are fired. It is preferable to adopt a method for the above, and by such a method, the Li-containing transition metal oxide can be synthesized relatively easily with high purity. That is, a composite compound containing Ni and Mn and, if necessary, Mg, Co or the like is synthesized in advance, and this is baked together with a Li-containing compound. Evenly distributed, Li-containing transition metal oxide is synthesized with higher purity.

  The method for synthesizing the Li-containing transition metal 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 Li-containing transition metal oxide to be generated, that is, It is presumed that the stability of the structure, reversibility of charge / discharge, true density, etc. will change greatly.

Here, as a composite compound containing at least Ni and Mn (and Mg and Co as necessary), for example, coprecipitation compounds containing these elements, hydrothermally synthesized compounds, mechanically synthesized compounds And compounds obtained by heat-treating them. More specifically, Ni _0.8 Mn _0.2 (OH) ₂ , NiMn ₂ O ₄ , Ni _0.6 Mn _0.4 OOH and other oxides or hydroxides of Ni and Mn, Ni _0.7 Mn _0.1 Mg _0.2 (OH) ₂ , Ni _0.9 Co _0.05 Mn _0.03 Mg _0.02 (OH) ₂ or other oxides or water of Ni, Mn and Mg Oxides, oxides or hydroxides of Ni, Mn, Mg, and Co are preferable.

Incidentally, as an element, the element ^M 1 (Co, or a Co, Ti, Cr, Fe, C u, Zn, Al, Ge, Sn, and at least one element selected from the group consisting of Mg and Zr) Li-containing transition metal oxide represented by the general formula (1) containing the calcined mixed with complex compound containing at least Ni and Mn, a Li-containing compound, and an element M ¹ containing compound It can be synthesized by, instead of the complex compound and the element M ¹ containing compound containing at least Ni and Mn, at least Ni, it is preferable to use a composite compound containing Mn and the element M ^1. The amount ratio of the Ni in the composite compound, Mn and M ¹ may be appropriately adjusted according to the composition of the Li-containing transition metal oxide of interest.

Further, a part of the element group ^{M 2,} Ni, Mn, elements other than Mg and Co (e.g., Ti, Cr, Fe, Cu , Zn, Al, Ge, Sn, Ag, Ta, Nb, Mo, B, P, at least one element selected from the group consisting of Zr and Ga. hereinafter, Li-containing transition represented by the general formula which collectively contains called.) "element M ^{2 ''} (2) The metal oxide can be synthesized by mixing and firing a composite compound containing at least Ni, Mn, and Mg (and optionally Co), a Li-containing compound, and an element M ² ′ -containing compound. In place of the compound compound containing at least Ni, Mn and Mg (and optionally Co) and the element M ² ′ -containing compound, at least Ni, Mn, Mg and element M ² ′ (and further if necessary) Contains Co) It is preferable to use a composite compound. The amount ratio of Ni, Mn, Mg and M ² ′ in the composite compound and the amount ratio of Ni, Mn, Mg, Co and M ² ′ depend on the composition of the target Li-containing transition metal oxide. What is necessary is just to adjust suitably.

  Examples of the Li-containing transition metal oxide represented by the general composition formula (1) and the Li-containing compound that can be used for the synthesis of the Li-containing transition metal oxide represented by the general composition formula (2) include various lithium salts. For example, lithium hydroxide monohydrate, lithium nitrate, lithium carbonate, lithium acetate, lithium bromide, lithium chloride, lithium citrate, lithium fluoride, lithium iodide, lithium lactate, oxalic acid Lithium, lithium phosphate, lithium pyruvate, lithium sulfate, lithium oxide, etc. are included, and among them, hydroxylated gas is not generated because it does not generate adverse gases such as carbon dioxide, nitrogen oxide, sulfur oxide. Lithium monohydrate is preferred.

In order to synthesize the Li-containing transition metal oxide represented by the general composition formula (1) and the Li-containing transition metal oxide represented by the general composition formula (2), first, the composite compound and Li and containing compound, and an element M ¹ containing compound or element M ^{2 'containing} compound to be used if necessary, are mixed at a ratio roughly corresponding to the composition of the Li-containing transition metal oxide of interest. And the Li containing transition metal oxide represented by the said general composition formula (1) by baking the obtained raw material mixture at 800-1050 degreeC for 1 to 24 hours, for example in the atmosphere containing oxygen Alternatively, a Li-containing transition metal oxide represented by the general composition formula (2) can be obtained.

  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 trivalent Ni is unstable in the formation process of the Li-containing transition metal oxide represented by the general composition formula (1) and the Li-containing transition metal oxide represented by the general composition formula (2). Therefore, the reaction of the raw material mixture is caused in a stepwise manner to increase the homogeneity of the Li-containing transition metal oxide to be produced, and the produced Li-containing transition metal oxide This is for stably growing the crystal. That is, when the temperature is raised to the firing temperature at once, or when the oxidation concentration of the firing environment is lowered during firing, the raw material mixture is likely to react non-uniformly, and the produced Li-containing transition metal oxide contains Li. Uniformity of the composition tends to be impaired, such as easy release.

  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, more preferably 18% or more, further preferably 50% or more, and preferably 80% or more. Particularly preferred (the oxygen concentration may be 100%).

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. When the gas flow rate is too low, that is, when the gas flow rate is too slow, the homogeneity of the composition of the Li-containing transition metal 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 Li-containing transition metal oxide to be synthesized can be further improved by such a method.

The positive electrode according to the battery of the present invention, the generally formula (1) Li-containing transition metal oxide represented by a and a positive electrode mixture layer containing as an active material, the positive electrode mixture layer may include other The active material may also be included. Examples of other active materials other than the Li-containing transition metal oxide 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 ; Li-containing transition metal oxide having a layered structure such as LiCo _1-x NiO ₂ ; Li-containing transition metal oxide having a spinel structure such as LiMn ₂ O ₄ , Li _4/3 Ti _5/3 O ₄ ; Olivine such as LiFePO ₄ Li-containing transition metal oxides having a structure; oxides having the above-described oxide as a basic composition and substituted with various elements; and the like can be used. Moreover, the Li-containing transition metal oxide represented by the general composition formula (1) and the Li-containing transition metal oxide represented by the general composition formula (2) can be used together.

  When using an active material other than the Li-containing transition metal oxide represented by the general composition formula (1) and the Li-containing transition metal oxide represented by the general composition formula (2), In order to clarify the effect, the ratio of the other active material is desirably 30% by mass or less of the entire active material.

  The positive electrode is a paste-like or slurry-like positive electrode mixture obtained by adding an appropriate solvent (dispersion medium) to the mixture (positive electrode mixture) containing the positive electrode active material, the conductive additive and the binder, and sufficiently kneading the mixture. The agent-containing composition can be obtained by applying on one or both sides of the current collector to form a positive electrode mixture layer having a predetermined thickness and density. The positive electrode is not limited to the one obtained by the above-described production method, and may be one produced by another production method.

  As the binder relating to the positive electrode, the above-described binders exemplified as those for the negative electrode can be used. In addition, as for the conductive auxiliary agent related to the positive electrode, the above-described conductive auxiliary agents and graphite (natural graphite such as scale-like graphite and earth-like graphite, artificial graphite, etc.) exemplified for the negative electrode can be used.

  In the positive electrode mixture layer according to the positive electrode, the content of the positive electrode active material is, for example, 79.5 to 99% by mass, and the content of the binder is, for example, 0.5 to 20% by mass. The content of the conductive assistant is preferably, for example, 0.5 to 20% by mass. Moreover, it is preferable that the thickness of a positive mix layer is 15-200 micrometers per single side | surface of a collector.

  The non-aqueous secondary battery of the present invention may be provided with the above-described negative electrode and positive electrode, and there are no particular restrictions on other components and structures, and it is employed in conventionally known non-aqueous secondary batteries. Various components and structures can be applied.

  Examples of the non-aqueous electrolyte used in the non-aqueous secondary battery of the present invention include an electrolyte prepared by dissolving the following inorganic ion salt in the following solvent.

  Examples of the solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate, 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, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, 3 Non-prototypes such as methyl-2-oxazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, diethyl ether, 1,3-propane sultone Sex organic solvents may be used alone or in combination.

As the inorganic ion salt, Li salt, for _{example, LiClO 4, LiBF 4, LiPF} 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiB 10 Cl 10, lower aliphatic carboxylic acids Li, LiAlCl ₄ , LiCl, LiBr, LiI, chloroborane Li, Li tetraphenylborate, or the like can be used alone or in combination.

Among the electrolytic solutions in which the inorganic ion salt is dissolved in the solvent, a solvent containing at least one selected from the group consisting of 1,2-dimethoxyethane, diethyl carbonate, and methyl ethyl carbonate, and ethylene carbonate or propylene carbonate In addition, an electrolytic solution in which at least one inorganic ion salt selected from the group consisting of LiClO ₄ , LiBF ₄ , LiPF ₆ , and LiCF ₃ SO ₃ is dissolved is preferable. An appropriate concentration of the inorganic ion salt in the electrolytic solution is, for example, 0.2 to 3.0 mol / dm ³ .

  As the separator according to the nonaqueous secondary battery of the present invention, a separator having sufficient strength and capable of holding a large amount of electrolyte is preferable. From such a viewpoint, the thickness is 10 to 50 μm and the aperture ratio is 30 to 70%. Of these, a microporous film or a nonwoven fabric containing polyethylene, polypropylene, or ethylene-propylene copolymer is preferable.

  Moreover, in the non-aqueous secondary battery of this invention, there is no restriction | limiting in particular also about the shape. For example, any of a coin shape, a button shape, a sheet shape, a laminated shape, a cylindrical shape, a flat shape, a square shape, a large size used for an electric vehicle, etc. may be used.

  In such a non-aqueous secondary battery of the present invention, the amount of Li in the negative electrode mixture layer in a discharged state is 0.05 to 0.5 times the total amount of Si and C in terms of atomic ratio. High utilization rate of active material and high capacity. In addition, “the amount of Li in the negative electrode mixture layer in the discharge state” referred to in the present specification is derived as follows. The battery discharged to 2.0 V is decomposed in an argon atmosphere, the negative electrode is taken out, and immersed in DEC for 24 hours. Thereafter, 1 g of the negative electrode mixture is taken out from the negative electrode, and the abundance is analyzed by a calibration curve method using fluorescent X-rays for Si and C, and by inductively coupled plasma (ICP) analysis for Li. The atomic ratio of the total amount of C and C is calculated.

  In the non-aqueous secondary battery of the present invention, the initial charge / discharge efficiency (ratio of the discharge capacity to the initial charge capacity) after the battery production in the negative electrode is as high as 80% or more, and high capacity is achieved efficiently. it can.

  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. In addition, the average particle diameter of the various particles in the following examples is a volume average value measured by a laser diffraction particle size distribution measurement method using “MICROTRAC HRA (Model: 9320-X100)” manufactured by Microtrack.

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

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

  Next, a negative electrode precursor sheet was produced using the negative electrode material and graphite. 10% by mass of the carbon-coated SiO (content in the total solid content, hereinafter the same), 80% by mass of graphite, 2% by mass of ketjen black (average particle size 0.05 μm) as a conductive assistant, and as a binder 8% by mass of polyamideimide and dehydrated N-methylpyrrolidone (NMP) were mixed to prepare a negative electrode mixture-containing slurry.

  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, 96% by mass of Li _1.0 Ni _0.6 Co _0.2 Mn _0.2 O ₂ as a positive electrode material (positive electrode active material) (content in the total solid content; the same shall apply hereinafter) and a conductive auxiliary agent A positive electrode mixture-containing slurry obtained by mixing 2% by mass of ketjen black (average particle size 0.05 μm) as a binder, 2% by mass of PVDF as a binder, and dehydrated NMP, and a current collector made of an aluminum foil having a thickness of 15 μm It applied to both surfaces of the body, dried and pressed to form a positive electrode mixture layer having a thickness of 70 μm per one surface. 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 aluminum positive electrode can of thickness 4mm, width 34mm, and height 43mm (463443 type | mold), and the lid was welded and attached. Thereafter, 2.5 g of an electrolytic solution (non-aqueous electrolyte) prepared by dissolving 1 mol of LiPF ₆ in a solvent of EC: DEC = 3: 7 (volume ratio) was poured into the container from the liquid inlet of the lid and sealed. Thus, a rectangular non-aqueous secondary battery having the structure shown in FIG. 1 and the appearance shown in FIG. 2 was obtained.

  Here, the battery shown in FIGS. 1 and 2 will be described. FIG. 1A is a plan view, and FIG. 1B is a partial cross-sectional view thereof. As shown in FIG. 2 is spirally wound through a separator 3 and then pressed to be flattened to form a flat wound electrode body 6 into a rectangular (square tube) positive electrode can 4 with an electrolyte (non-aqueous solution). It is housed together with the electrolyte. 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 wound electrode 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
SiO (average particle size 1 μm), graphite (average particle size 10 μm), and polyethylene resin particles of a binder are put into a 4 L stainless steel container, and further a stainless steel ball is added and mixed in a vibration mill for 3 hours. Grinding and granulation were performed. As a result, composite particles (composite particles of SiO and graphite) having an average particle diameter of 20 μm could be produced. Subsequently, the composite particles are heated to about 950 ° C. in a boiling bed reactor, a mixed gas of 25 ° C. composed of toluene and nitrogen gas is brought into contact with the heated composite particles, and CVD treatment is performed at 950 ° C. for 60 minutes. went. In this manner, carbon produced by the thermal decomposition of the mixed gas was deposited on the composite particles to form a coating layer, thereby obtaining a negative electrode material.

  When the composition of the negative electrode material was calculated from the mass change before and after the coating layer was formed, it was SiO: graphite: CVD carbon = 10: 80: 10 (mass ratio).

  Next, the negative electrode material: 90% by mass (content in the total solid content; the same shall apply hereinafter), ketjen black (average particle size 0.05 μm) as a conductive additive: 2% by mass, and polyamideimide as a binder 8% by mass and dehydrated NMP were mixed to prepare a negative electrode mixture-containing slurry. The negative electrode mixture-containing slurry was prepared in the same manner as in Example 1 except that this negative electrode mixture-containing slurry was used to form the negative electrode mixture layer. Except that this negative electrode was used, in the same manner as in Example 1, a 463443-type square non-aqueous A secondary battery was produced.

Example 3
A negative electrode was prepared in the same manner as in Example 1, except that the binder in the negative electrode mixture was changed to SBR and CMC (mass ratio 1: 1), and the solvent of the negative electrode mixture-containing slurry was changed to water. A 463443-type square non-aqueous secondary battery was produced in the same manner as in Example 1 except that the negative electrode was used.

Example 4
A 463443-type prismatic nonaqueous secondary battery was produced in the same manner as in Example 3 except that the positive electrode material (positive electrode active material) was changed to Li _1.0 Ni _0.6 Al _0.2 Mn _0.2 O ₂ . .

Example 5
463443 square non-aqueous secondary as in Example 3, except that the positive electrode material (positive electrode active material) was changed to Li _1.0 Ni _0.6 Co _0.15 Al _0.05 Mn _0.2 O ₂ A battery was produced.

Example 6
463443 square non-aqueous secondary as in Example 3, except that the positive electrode material (positive electrode active material) was changed to Li _1.0 Ni _0.6 Co _0.15 Mg _0.05 Mn _0.2 O ₂ A battery was produced.

Example 7
463443 square non-aqueous secondary as in Example 3 except that the positive electrode material (positive electrode active material) was changed to Li _1.0 Ni _0.6 Co _0.15 Ge _0.05 Mn _0.2 O ₂ A battery was produced.

Example 8
463443 square non-aqueous secondary as in Example 3 except that the positive electrode material (positive electrode active material) was changed to Li _1.0 Ni _0.6 Co _0.15 Ti _0.05 Mn _0.2 O ₂ A battery was produced.

Example 9
463443 square non-aqueous secondary as in Example 3 except that the positive electrode material (positive electrode active material) was changed to Li _1.0 Ni _0.6 Co _0.15 Cr _0.05 Mn _0.2 O ₂ A battery was produced.

Example 10
463443 square non-aqueous secondary as in Example 3 except that the positive electrode material (positive electrode active material) was changed to Li _1.0 Ni _0.6 Co _0.15 Fe _0.05 Mn _0.2 O ₂ A battery was produced.

Example 11
463443 square non-aqueous secondary as in Example 3 except that the positive electrode material (positive electrode active material) was changed to Li _1.0 Ni _0.6 Co _0.15 Cu _0.05 Mn _0.2 O ₂ A battery was produced.

Example 12
463443 square non-aqueous secondary as in Example 3, except that the positive electrode material (positive electrode active material) was changed to Li _1.0 Ni _0.6 Co _0.15 Zn _0.05 Mn _0.2 O ₂ A battery was produced.

Example 13
463443 square non-aqueous secondary as in Example 3, except that the positive electrode material (positive electrode active material) was changed to Li _1.0 Ni _0.6 Co _0.15 Sn _0.05 Mn _0.2 O ₂ A battery was produced.

Example 14
463443 square non-aqueous secondary as in Example 3, except that the positive electrode material (positive electrode active material) was changed to Li _1.0 Ni _0.6 Co _0.15 Zr _0.05 Mn _0.2 O ₂ A battery was produced.

Example 15
A 463443-type square non-aqueous secondary battery was produced in the same manner as in Example 3 except that the positive electrode material (positive electrode active material) was changed to Li _1.0 Ni _0.5 Co _0.2 Mn _0.3 O ₂ . .

Example 16
463443 square non-aqueous secondary as in Example 3, except that the positive electrode material (positive electrode active material) was changed to Li _1.0 Ni _0.5 Co _0.15 Mg _0.05 Mn _0.3 O ₂ A battery was produced.

Comparative Example 1
A 463443-type square non-aqueous secondary battery was produced in the same manner as in Example 3 except that the positive electrode active material was changed to LiCoO ₂ .

Comparative Example 2
A negative electrode was prepared in the same manner as in Example 3 except that the carbon-coated SiO content in the negative electrode mixture was 40% by mass and the graphite content was 50% by mass. In the same manner as in Example 3, a 463443-type prismatic non-aqueous secondary battery was produced.

Comparative Example 3
A negative electrode was produced in the same manner as in Example 3 except that the carbon-coated SiO content in the negative electrode mixture was 27 mass% and the graphite content was 63 mass%. In the same manner as in Example 3, a 463443-type prismatic non-aqueous secondary battery was produced.

Comparative Example 4
A negative electrode was produced in the same manner as in Example 3 except that the carbon-coated SiO content in the negative electrode mixture was 1% by mass and the graphite content was 89% by mass. In the same manner as in Example 3, a 463443-type prismatic non-aqueous secondary battery was produced.

  For each battery of Examples 1 to 16 and Comparative Examples 1 to 4, the amount of Li in the negative electrode mixture layer in the discharged state (atomic ratio with respect to the total amount of Si and C), the thickness of the battery at the time of charging (of the negative electrode Confirmation of the presence or absence of warping), discharge capacity measurement, and battery characteristics (capacity maintenance rate at the 200th charge / discharge cycle) were evaluated. The composition of the positive electrode active material according to each battery is shown in Tables 1 and 2 in accordance with the description of the general composition formula (1), the configuration of the negative electrode is shown in Tables 3 and 4, and the evaluation results are shown in Tables 5 and 6 respectively.

The amount of Li in the negative electrode mixture layer in the discharged state was determined by the above method. Moreover, the following methods performed charging / discharging of the battery in the measurement of the discharge capacity of a battery and battery characteristic evaluation. Charging was performed at a constant current with a current of 400 mA. After the charging voltage reached 4.2 V, the charging was performed at a constant voltage until the current became 1/10. The discharge was performed at a constant current with a current of 400 mA, and the discharge end 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. Further, the capacity retention rate at the 200th cycle was calculated by the following formula.
Capacity maintenance rate (%)
= (Discharge capacity at 200th cycle / Discharge capacity at 2nd cycle) × 100

  As is clear from Tables 1 to 6, an implementation using a positive electrode constituted by using a Li-containing transition metal oxide having a proper composition and a negative electrode constituted by using SiO and graphite at a proper composition ratio The nonaqueous secondary batteries of Examples 1 to 16 have a high capacity, an increase in thickness during charging is suppressed, and charge / discharge cycle characteristics are good.

On the other hand, the battery of Comparative Example 1 using a positive electrode using LiCoO ₂ and the battery of Comparative Example 4 using a negative electrode in which the amount of SiO used is too small relative to the total amount of SiO and graphite have the capacity. small. In addition, the batteries of Comparative Example 2 and Comparative Example 3 using a negative electrode in which the amount of SiO used is too large relative to the total amount of SiO and graphite, the increase in thickness during charging is large, and the charge / discharge cycle characteristics Is inferior.

1 Positive electrode 2 Negative electrode 3 Separator

Claims (4)

A non-aqueous secondary battery comprising a positive electrode, a negative electrode and a non-aqueous electrolyte,
The positive electrode has the following general composition formula (1)
Li _{1 + y + a} Ni _{(1-yz + b) / 2} Mn _{(1-yzb) / 2} M ¹ _z O ₂ (1)
(Wherein, ^{M 1} is represented Co, or a Co, Ti, Cr, Fe, Cu, Zn, Al, Ge, Sn, and at least one element selected from the group consisting of Mg and Zr, -0. 1 ≦ y ≦ 0.1, −0.05 ≦ a ≦ 0.05, 0 <z ≦ 0.4, −0.1 ≦ b ≦ 0.6 and 0.6 ≧ 1-yz−b> 0, and 1 ≦ 1-yz + b)
A positive electrode mixture layer containing a Li-containing transition metal oxide represented by:
The negative electrode has 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 negative electrode mixture layer containing graphite. And
The material containing Si and O as constituent elements forms a composite with a carbon material,
In the negative electrode mixture layer, when the total of the material containing Si and O as constituent elements and graphite is 100% by mass, the ratio of the material containing Si and O as constituent elements is 3 to 20% by mass. A non-aqueous secondary battery characterized by the above.   The nonaqueous secondary battery according to claim 1, wherein the amount of Li in the negative electrode mixture layer in a discharged state is 0.05 to 0.5 times the total amount of Si and C in atomic ratio.   The nonaqueous secondary battery according to claim 1 or 2, wherein a surface of a composite of a material containing Si and O as constituent elements and a carbon material is coated with the carbon material. The carbon material constituting the composite of the material containing Si and O as constituent elements and the carbon material and / or the carbon material covering the surface of the composite heated the hydrocarbon gas in the gas phase. The non-aqueous secondary battery according to claim 3 , which is generated by thermal decomposition at the time.

Images