JP2014089855A - Negative electrode active material for nonaqueous secondary battery use, and nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-aqueous secondary battery having a high capacity and good storage characteristics and a negative electrode active material for constituting the non-aqueous secondary battery.
SOLUTION: A material containing Si and O as constituent elements, an average particle diameter D _50% obtained by a laser diffraction scattering method is 6 to 10 μm, and obtained by an X-ray diffraction method using CuKα rays. A negative active material for a non-aqueous secondary battery, wherein the half-value width of a Si (220) diffraction peak is 0.6 to 1.0 °, the negative active material for a non-aqueous secondary battery, and graphite The above-mentioned problems are solved by a nonaqueous secondary battery using a carbon material as a negative electrode active material.
[Selection figure] None

Description

  The present invention relates to a non-aqueous secondary battery having a high capacity and good storage characteristics, and a negative electrode active material for constituting the non-aqueous secondary battery.

  Non-aqueous secondary batteries such as lithium ion secondary batteries are widely used as power sources for various portable devices because of their high voltage and high capacity. In recent years, the use of medium- and large-sized power tools such as electric tools, electric vehicles, and electric bicycles has been spreading.

In particular, batteries used in mobile phones and game machines that are becoming smaller and more multifunctional are required to have higher capacities, and as a means for this, electrode active materials that exhibit high charge / discharge capacity are required. Research and development are progressing. Among them, as the active material material of the negative electrode, more lithium (ion) such as silicon (Si) and tin (Sn) can be used instead of carbonaceous materials such as graphite, which are used in conventional lithium ion secondary batteries. ) Has been attracting attention. In particular, it has been reported that SiO _x having a structure in which ultrafine particles of Si are dispersed in SiO ₂ has characteristics such as excellent load characteristics (see Patent Documents 1 and 2).

However, since the SiO _x has a large volume expansion / contraction due to the charge / discharge reaction, particles are pulverized every charge / discharge cycle of the battery, and Si deposited on the surface reacts with the non-aqueous electrolyte solvent to have an irreversible capacity. It is also known that problems such as an increase or a gas generated in the battery due to this reaction cause the battery can to swell.

Under such circumstances, the SiO _x utilization rate is limited to suppress volume expansion / contraction due to charge / discharge reactions, or halogen-substituted cyclic carbonates (for example, 4-fluoro-1,3-dioxolane-2- Technologies that improve the charge / discharge cycle characteristics of the battery or suppress the expansion of the battery can due to gas generation have been proposed by using a non-aqueous electrolyte solution to which a gas etc. is added (patent document) 3).

Furthermore, in the non-aqueous secondary battery using SiO _x for the negative electrode, improvement of storage characteristics is also an issue. Patent Document 4 discloses a composite in which SiO _x is used as a core and the surface thereof is coated with carbon, and the degree of carbon coating in the composite and the crystalline state of Si in SiO _x are specified. A technique that achieves this improvement is disclosed.

Japanese Patent Laid-Open No. 2004-047404 Japanese Patent Laid-Open No. 2005-259697 JP 2008-210618A International Publication No. 2012/036127

  The inventors of the present invention have studied the technique described in Patent Document 4 in order to further improve the storage characteristics of the nonaqueous secondary battery. That is, an object of the present invention is to provide a non-aqueous secondary battery having a high capacity and good storage characteristics, and a negative electrode active material for constituting the non-aqueous secondary battery.

The negative electrode active material for a non-aqueous secondary battery of the present invention contains a material containing Si and O as constituent elements, an average particle diameter D _50% determined by a laser diffraction scattering method is 6 to 10 μm, and CuKα The full width at half maximum of the (220) diffraction peak of Si obtained by the X-ray diffraction method using a line is 0.6 to 1.0 °.

  The non-aqueous secondary battery of the present invention is a non-aqueous secondary battery having a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator and a non-aqueous electrolyte. The negative electrode active material for a non-aqueous secondary battery of the present invention and a graphitic carbon material are used.

  According to the present invention, it is possible to provide a nonaqueous secondary battery having a high capacity and good storage characteristics, and a negative electrode active material for constituting the nonaqueous secondary battery.

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

  As described above, the present inventors have studied the technique described in Patent Document 4 in order to further improve the storage characteristics of the nonaqueous secondary battery. As a result, in the material containing Si and O used as the negative electrode active material of the nonaqueous secondary battery as constituent elements, the half width of the (220) diffraction peak of Si obtained by the X-ray diffraction method is within a specific range. In this case, when the average particle diameter of the material takes a specific value, it has been found that the storage characteristics of the non-aqueous secondary battery can be enhanced to a high degree, and the present invention has been completed. Hereinafter, the present invention will be described in detail.

<Negative electrode active material for non-aqueous secondary battery>
The negative electrode active material for a non-aqueous secondary battery of the present invention contains a material containing Si and O as constituent elements. If it is a negative electrode active material containing such a material, a high capacity | capacitance non-aqueous secondary battery can be comprised.

Moreover, the negative electrode active material for non-aqueous secondary batteries of the present invention has an average particle diameter D _50% determined by a laser diffraction scattering method of 6 to 10 μm, and Si determined by an X-ray diffraction method using CuKα rays. The full width at half maximum of the (220) diffraction peak is 0.6 to 1.0 °. In the negative electrode active material for a non-aqueous secondary battery containing a material containing Si and O as constituent elements, the average particle diameter D is _50% , and the half width of the (220) diffraction peak of Si is By making it become a value, in a non-aqueous secondary battery using this, it is possible to suppress a decrease in capacity when stored in a charged state while maintaining a high capacity, and to ensure high storage characteristics. .

That is, if the average particle diameter D _{50% of the} negative electrode active material for a non-aqueous secondary battery is too small, the capacity tends to decrease when a non-aqueous secondary battery using this is stored in a charged state. Further, if the average particle diameter D _{50% of the} negative electrode active material for a non-aqueous secondary battery is too large, the vicinity of the center of the negative electrode active material particles becomes difficult to participate in the charge / discharge reaction of the battery. The capacity of the secondary battery itself becomes small.

  Furthermore, if the half-width of the (220) diffraction peak of Si in the negative electrode active material for a non-aqueous secondary battery is too small, the capacity of the non-aqueous secondary battery using this will be small. And when the half width of the (220) diffraction peak of Si in the negative electrode active material for a non-aqueous secondary battery is too large, when the non-aqueous secondary battery using this is stored in a charged state, the capacity is likely to decrease. Become.

In addition to the (220) diffraction peak, the (111) diffraction peak is known as the main Si-derived peak observed during the measurement by the X-ray diffraction method, but the (220) diffraction peak is ( For example, the half-value width is easier to obtain than the 111) diffraction peak because it is not affected by a broad peak derived from SiO ₂ . Therefore, in the present invention, the negative electrode active material for a non-aqueous secondary battery has a half value width of the (220) diffraction peak of Si as a specific value.

As described above, the average particle diameter D _50% of the negative electrode active material for a non-aqueous secondary battery in the present specification is a value determined by the laser diffraction scattering method. More specifically, the laser scattering particle size distribution meter (For example, “LA-920” manufactured by Horiba, Ltd.), and the particle size at 50% of the volume-based integrated fraction measured by dispersing the negative electrode active material in a medium that does not dissolve.

The negative electrode active material for nonaqueous secondary battery of the present invention, D ₁₀ from the viewpoint of enhancing the storage characteristics of the non-aqueous secondary battery using the better is determined by the average particle diameter D _50% in the same way _% (Particle diameter at 10% of the volume-based integrated fraction) is preferably 4 μm or more.

Furthermore, the negative electrode active material for a non-aqueous secondary battery of the present invention is a non-aqueous secondary battery using the same, from the viewpoint of improving the reliability by suppressing the damage of the separator due to the negative electrode active material. It is preferable that D _90% (particle diameter at 90% of the volume-based integrated fraction) obtained by the same method as the particle diameter D _50% is 14 μm or less.

  The material containing Si and O as constituent elements may be a composite oxide of Si and another metal in addition to an Si oxide, and may contain a microcrystalline or amorphous phase of Si or another metal. You may go out.

Among materials containing Si and O as constituent elements, a material having a structure in which minute Si phases are dispersed in an amorphous SiO ₂ matrix is particularly preferable. This material is represented by the general composition formula SiO _x (where 0.5 ≦ x ≦ 1.5). For example, when Si is dispersed in an amorphous SiO ₂ matrix and the molar ratio between SiO ₂ and Si is 1: 1, the composition formula is expressed as SiO.

SiO _x is preferably a composite that is combined with a carbon material. For example, the surface of SiO _x is preferably coated with the carbon material. Since SiO _x has poor conductivity, when it is used as a negative electrode active material, a conductive aid such as a carbon material is required from the viewpoint of securing good battery characteristics. If complexes complexed with carbon material SiO _x, for example, simply than with a material obtained by mixing a conductive assistant such as SiO _x and the carbon material, good conductive network in the negative electrode The load characteristics of the battery can be enhanced.

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. A fibrous or coiled carbon material 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.

When configuring the non-aqueous secondary battery using a negative active material for a nonaqueous secondary battery of the present invention, graphitic carbon material is also used as a negative electrode active material, the graphite carbon material, and SiO _x It can also be used as a carbon material related to a composite with a carbon material. Graphite carbon materials, like carbon black, have high electrical conductivity and high liquid retention properties, 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.

In complex with SiO _x and the carbon material, the ratio between the SiO _x and the carbon material, from the viewpoint of satisfactorily exhibiting action by complexation with carbon materials, SiO x: relative to ₁₀₀ parts by mass, a carbon material The amount 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.

SiO _x can be obtained, for example, by the following method.

SiO _x can be obtained by a method in which a mixture of Si and SiO ₂ is heated, and the generated silicon oxide gas is cooled and deposited. Moreover, D50 _% , D10 _%, and _D90% can be made into the said value by grind | pulverizing and classifying obtained SiOx. The classification may be performed after the CVD process described later.

By adjusting the temperature and time when heat-treating SiO _x in an inert gas atmosphere, the half width of the (220) diffraction peak of Si can be controlled to the above value. The heat treatment temperature is preferably 900 to 1400 ° C., and the heat treatment time is preferably 0.1 to 10 hours.

When the SiO _x after the heat treatment is measured by the X-ray diffraction method using CuKα rays, the intensity I _{a of the} diffraction peak derived from Si in which 2θ is found at a position of 28.4 ° and 2θ are It is preferable that the ratio I _a / I _{b of} the diffraction peak intensity I _b derived from SiO ₂ observed at a position near 21.2 ° is 2.7 to 3.9. It can be seen that if I _a / I _b is SiO _x satisfying the above values, the SiO ₂ molecules are arranged better as the Si particles grow. That is, if I _a / I _b is SiO _x satisfying the above values, it is heat-treated well, and the effect of improving storage characteristics of a non-aqueous secondary battery using this is improved.

The intensity I _a of diffraction peaks derived from Si to 2 [Theta] in this specification is found at the position of 28.4 ° is the peak height at a position where the peak top of the diffraction peak is present, also, 2 [Theta] is The intensity I _b of the diffraction peak derived from SiO ₂ observed at a position near 21.2 ° means the peak height at the position where the peak top of the diffraction peak exists.

Further, a complex with said 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.

Further, in controlling the half-value width of the Si (220) diffraction peak in SiO _x to the above value, a heat treatment in this CVD method may be used instead of the above heat treatment. It is more preferable because it can be reduced. When the half width of the Si (220) diffraction peak is controlled to the above value by the heat treatment in the CVD method, the processing temperature in the CVD method is preferably 900 ° C. or higher.

  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 .

A composite of SiO _x and a carbon material (especially SiO _x coated with a carbon material) is 510 cm ⁻ derived from Si in a Raman spectrum obtained by Raman spectroscopic analysis using a measurement laser having a wavelength of 532 nm. the intensity _{I 510} of the ^first peak, the ratio _I 510 _{/ I 1343} of the peak intensity _{I 1343} of 1343cm ^-1, which derived from the carbon is preferably 0.25 or less.

More specifically, I ₅₁₀ / I ₁₃₄₃ is a microscopic Raman spectroscopy, mapping measurement (80 × 80 μm range, 2 μm step) of the complex, and averaging all spectra within the measurement range to obtain the peak of Si each intensity of peak (1343Cm around ^-1) of (510 cm around ^-1) and carbon (C) was measured, determined by calculating these ratios.

If I ₅₁₀ / _{I 1343} is of a complex between SiO _x and the carbon material which satisfies the values of the, of the SiO _x particle surface is exposed locations (SiO _x particulate surface that is not coated with the carbon material Therefore, the effect of improving conductivity by combining SiO _x and the carbon material is more remarkably exhibited. Therefore, in the manufacture of the composite of SiO _x and carbon material, the conditions (for example, in the case of the CVD method, the processing temperature and the processing time are set so that I ₅₁₀ / I ₁₃₄₃ satisfies the above value. It is desirable to adjust the liquid source concentration of the carbon material in the processing environment.

<Non-aqueous secondary battery>
The non-aqueous secondary battery of the present invention has a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator, and a non-aqueous electrolyte. The non-aqueous secondary battery of the present invention is used as a negative electrode active material. As long as the negative electrode active material and the graphitic carbon material are used, there is no particular limitation on the other configurations and structures, and various configurations and configurations adopted in conventionally known non-aqueous secondary batteries Structure can be applied.

(Negative electrode)
For the negative electrode according to the non-aqueous secondary battery of the present invention, for example, a negative electrode mixture layer containing a negative electrode active material and a binder is used on one side or both sides of a current collector.

  As described above, the negative electrode active material of the present invention is used in combination with the negative electrode active material for a non-aqueous secondary battery and a graphitic carbon material.

  The negative electrode active material for a non-aqueous secondary battery of the present invention has a higher capacity than a carbon material widely used as a negative electrode active material for a non-aqueous secondary battery. In a non-aqueous secondary battery using a negative electrode having a negative electrode mixture layer with a high content of the negative electrode active material for a non-aqueous secondary battery according to the present invention, the negative electrode (negative electrode mixture layer) is formed by repeated charge and discharge. There is a risk that the volume is greatly changed and deteriorated, and the capacity is lowered (that is, the charge / discharge cycle characteristics are lowered). Graphite carbon material is widely used as a negative electrode active material for non-aqueous secondary batteries, and has a relatively large capacity. However, the amount of volume change accompanying charging / discharging of the battery is negative electrode active materials for non-aqueous secondary batteries of the present invention. Smaller than the substance. Therefore, by using the negative electrode active material for non-aqueous secondary battery of the present invention and the graphitic carbon material in combination with the negative electrode active material, the amount of the negative electrode active material for non-aqueous secondary battery of the present invention is reduced. Since it is possible to satisfactorily suppress the deterioration of the charge / discharge cycle characteristics of the battery while suppressing the decrease in the capacity improvement effect of the battery as much as possible, the capacity is higher and the charge / discharge cycle characteristics are excellent. A water secondary battery can be obtained.

  As the graphitic carbon material, those conventionally used for negative electrode active materials of non-aqueous secondary batteries are preferably used. Specifically, natural graphite such as flake graphite; pyrolytic carbon And artificial graphite obtained by graphitizing easily graphitized carbon such as mesophase carbon microbeads (MCMB) and carbon fibers at 2800 ° C. or higher.

  In the negative electrode according to the nonaqueous secondary battery of the present invention, the nonaqueous secondary battery of the present invention is used from the viewpoint of satisfactorily securing the effect of increasing the capacity by using the negative electrode active material for a nonaqueous secondary battery of the present invention. The content of the negative electrode active material for batteries in the total negative electrode active material is 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 volume change of the negative electrode active material for non-aqueous secondary battery of the present invention, the content of the negative electrode active material for non-aqueous secondary battery of the present invention in all negative electrode active materials is 20% by mass or less, and more preferably 15% by mass or less.

  Specific examples of the binder used for the negative electrode mixture layer include, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), and the like.

  Moreover, you may further add an electroconductive material as a conductive support agent to a negative mix layer. 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 assistant is, for example, 0.01 μm or more in terms of the average particle size (D _50% ) measured by the same method as the negative electrode active material for non-aqueous secondary battery of the present invention. Is preferably 0.02 μm or more, more preferably 10 μm or less, and even more preferably 5 μm or less.

  The negative electrode contains, for example, a negative electrode active material, a binder, and, if necessary, a paste-like or slurry-like negative electrode mixture in which a conductive additive is dispersed in a solvent such as N-methyl-2-pyrrolidone (NMP) water. The composition is prepared (however, the binder may be dissolved in a solvent), applied to one or both sides of the current collector, dried, and then subjected to a pressing process as necessary. The However, the negative electrode is not limited to those manufactured by the above manufacturing method, and may be manufactured by other manufacturing methods.

The thickness of the negative electrode mixture layer is preferably 10 to 100 μm per one side of the current collector. The density of the negative electrode mixture layer is calculated from the mass and thickness of the negative electrode mixture layer per unit area laminated on the current collector, and is preferably 1.0 to 1.9 g / cm ³ . Moreover, as a composition of a negative mix layer, it is preferable that the total amount of a negative electrode active material is 80-99 mass%, for example, it is preferable that the quantity of a binder is 1-20 mass%, and uses a conductive support agent. When it does, it is preferable that the quantity is 1-10 mass%.

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

(Positive electrode)
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.

For the positive electrode mixture layer, a Li-containing transition metal oxide capable of occluding and releasing Li (lithium) ions is used. Examples of the Li-containing transition metal oxide include those conventionally used for non-aqueous secondary batteries, specifically, Li _y CoO ₂ (where 0 ≦ y ≦ 1.1). Li _z NiO ₂ (where 0 ≦ z ≦ 1.1), Li _e MnO ₂ (where 0 ≦ e ≦ 1.1), Li _a Co _b M ¹ _1-b O ₂ (However, M ¹ is at least one metal element selected from the group consisting of Mg, Mn, Fe, Ni, Cu, Zn, Al, Ti, Ge, and Cr, and 0 ≦ a ≦ 1.1. , 0 <b <1.0), Li _c Ni _1-d M ² _d O ₂ (wherein M ² is Mg, Mn, Fe, Co, Cu, Zn, Al, Ti, Ge and At least one metal element selected from the group consisting of Cr, 0 ≦ c ≦ 1.1, 0 <d Is _{1.0.), Li f Mn g} Ni h Co 1-g-h O 2 ( where is 0 ≦ f ≦ 1.1,0 <g < 1.0,0 <h <1.0 Li) -containing transition metal oxides having a layered structure such as.), And only one of these may be used, or two or more may be used in combination.

  As the binder for the positive electrode mixture layer, the same binders as those exemplified above as the binder for the negative electrode mixture layer can be used. In addition, as the conductive auxiliary agent related to the positive electrode mixture layer, for example, graphite (graphite carbon material) such as natural graphite (flaky graphite), artificial graphite; acetylene black, ketjen black, channel black, furnace black, Carbon materials such as carbon black such as lamp black and thermal black; carbon fiber;

  For the positive electrode, for example, a paste-like or slurry-like positive electrode mixture-containing composition in which a positive electrode active material, a binder, and a conductive additive are dispersed in a solvent such as NMP is prepared (however, the binder is dissolved in the solvent). It may be manufactured through a step of applying a press treatment as necessary after applying this to one or both sides of the current collector and drying it. However, the positive electrode is not limited to those manufactured by the above manufacturing method, and may be manufactured by other manufacturing methods.

The thickness of the positive electrode mixture layer is preferably, for example, 10 to 100 μm per one side of the current collector, and the density of the positive electrode mixture layer is the mass of the positive electrode mixture layer per unit area laminated on the current collector. Calculated from the thickness, it is preferably 3.0 to 4.5 g / cm ³ . Moreover, as a composition of a positive mix layer, it is preferable that the quantity of a positive electrode active material is 60-95 mass%, for example, it is preferable that the quantity of a binder is 1-15 mass%, and the quantity of a conductive support agent. Is preferably 3 to 20% by mass.

  As the current collector for the positive electrode, the same one as used for the positive electrode of a conventionally known non-aqueous secondary battery can be used. For example, an aluminum foil having a thickness of 10 to 30 μm is preferable.

(Separator)
As the separator according to the nonaqueous secondary battery of the present invention, it is preferable that the separator has sufficient strength and can hold a large amount of nonaqueous electrolyte, and has a thickness of 5 to 50 μm and an opening ratio of 30 to 70%. Or a microporous membrane made of polyolefin such as polypropylene (PP). The microporous membrane constituting the separator may be, for example, one using only PE or one using only PP, may contain an ethylene-propylene copolymer, and may be made of PE. A laminate of a membrane and a PP microporous membrane may be used.

  In addition, the separator according to the non-aqueous secondary battery includes a porous layer (A) mainly composed of a resin having a melting point of 140 ° C. or lower and a resin having a melting point of 150 ° C. or higher or an inorganic filler having a heat resistance temperature of 150 ° C. or higher. A laminated separator composed of a porous layer (B) included as a main body can be used. Here, “melting point” means a melting temperature measured using a differential scanning calorimeter (DSC) in accordance with the provisions of JIS K 7121. “Heat resistant temperature is 150 ° C. or higher” means at least 150 ° C. This means that no deformation such as softening is observed.

  The porous layer (A) according to the laminated separator is mainly for ensuring a shutdown function, and the melting point of the resin, which is a component in which the nonaqueous secondary battery is the main component of the porous layer (A). When the above is reached, the resin related to the porous layer (A) melts and closes the pores of the separator, thereby causing a shutdown that suppresses the progress of the electrochemical reaction.

  Examples of the resin having a melting point of 140 ° C. or lower as the main component of the porous layer (A) include PE, and the form thereof is a substrate such as a microporous film used in a non-aqueous secondary battery or a nonwoven fabric. And PE particles coated thereon. Here, in all the constituent components of the porous layer (A), the volume of the resin having a main melting point of 140 ° C. or less is 50% by volume or more, and more preferably 70% by volume or more. When the porous layer (A) is formed of the PE microporous film, the volume is 100% by volume.

  The porous layer (B) according to the laminated separator has a function of preventing a short circuit due to direct contact between the positive electrode and the negative electrode even when the internal temperature of the non-aqueous secondary battery is increased, Its function is ensured by a resin having a melting point of 150 ° C. or higher or an inorganic filler having a heat resistant temperature of 150 ° C. or higher. That is, when the battery becomes high temperature, even if the porous layer (A) shrinks, the porous layer (B) which does not easily shrink can directly generate positive and negative electrodes that can be generated when the separator is thermally contracted. It is possible to prevent a short circuit due to the contact of. Moreover, since this heat-resistant porous layer (B) acts as a skeleton of the separator, thermal contraction of the porous layer (A), that is, thermal contraction of the entire separator itself can be suppressed.

  When the porous layer (B) is formed mainly of a resin having a melting point of 150 ° C. or higher, the form thereof is, for example, a microporous film formed of a resin having a melting point of 150 ° C. or higher (for example, a battery made of PP as described above) The composition for forming a porous layer (B) containing fine particles of a resin having a melting point of 150 ° C. or higher is applied to the porous layer (A). And a coating layer type in which a porous layer (B) containing fine particles of a resin having a melting point of 150 ° C. or higher is laminated.

  As the resin constituting the fine particles of the resin having a melting point of 150 ° C. or more, crosslinked polymethyl methacrylate, crosslinked polystyrene, crosslinked polydivinylbenzene, crosslinked styrene-divinylbenzene copolymer, polyimide, melamine resin, phenol resin, benzoguanamine- And various cross-linked polymers such as formaldehyde condensates; heat-resistant polymers such as PP, polysulfone, polyether sulfone, polyphenylene sulfide, PTFE, polyacrylonitrile, aramid, and polyacetal.

The particle diameter of the fine particles of the resin having a melting point of 150 ° C. or higher is an average particle diameter D _50% measured by the same method as that of the negative electrode active material for a non-aqueous secondary battery of the present invention, for example, 0.01 μm or more. Is preferably 0.1 μm or more, more preferably 10 μm or less, and even more preferably 2 μm or less.

  Since the amount of the fine particles of the resin having a melting point of 150 ° C. or higher is mainly contained in the porous layer (B), the total volume of the constituent components of the porous layer (B) (the total volume excluding pores) ), It is preferably 50% by volume or more, preferably 70% by volume or more, more preferably 80% by volume or more, and still more preferably 90% by volume or more.

  When the porous layer (B) is mainly composed of an inorganic filler having a heat resistant temperature of 150 ° C. or higher, a composition for forming the porous layer (B) containing an inorganic filler having a heat resistant temperature of 150 ° C. or higher (coating liquid) ) Is applied to the porous layer (A), and a porous layer (B) containing an inorganic filler having a heat resistant temperature of 150 ° C. or higher is laminated.

  The inorganic filler according to the porous layer (B) has a heat-resistant temperature of 150 ° C. or higher, is stable with respect to the non-aqueous electrolyte of the non-aqueous secondary battery, and is oxidized and reduced within the operating voltage range of the non-aqueous secondary battery. Any electrochemically stable material that is difficult to be treated may be used, but fine particles are preferable from the viewpoint of dispersion and the like, and alumina, silica, and boehmite are preferable. Alumina, silica, and boehmite have high oxidation resistance, and the particle size and shape can be adjusted to desired values, etc., making it easy to accurately control the porosity of the porous layer (B). It becomes. In addition, as for the inorganic filler whose heat-resistant temperature is 150 degreeC or more, the thing of the said illustration may be used individually by 1 type and may use 2 or more types together, for example. Also, an inorganic filler having a heat resistant temperature of 150 ° C. or higher and a resin fine particle having a melting point of 150 ° C. or higher may be used in combination.

  There is no restriction | limiting in particular about the shape of the inorganic filler whose heat-resistant temperature which concerns on a porous layer (B) is 150 degreeC or more, A substantially spherical shape (a true spherical shape is included), a substantially ellipsoid shape (an ellipsoid shape is included), plate shape, etc. Various shapes can be used.

Moreover, if the average particle diameter of the inorganic filler having a heat resistant temperature of 150 ° C. or higher (the average particle diameter of the plate-like filler and the other shape filler. The same applies hereinafter) of the porous layer (B) is too small, the ion permeability is high. Since it falls, it is preferable that it is 0.3 micrometer or more, and it is more preferable that it is 0.5 micrometer or more. In addition, if the inorganic filler having a heat resistant temperature of 150 ° C. or higher is too large, the electrical characteristics are likely to be deteriorated. Therefore, the average particle diameter is preferably 5 μm or less, and more preferably 2 μm or less. The average particle diameter of the inorganic filler having a heat resistant temperature of 150 ° C. or higher as used herein is an average particle diameter (D _50% ) determined by the same method as the average particle diameter of the negative electrode active material.

  Since the inorganic filler having a heat resistant temperature of 150 ° C. or higher in the porous layer (B) is mainly contained in the porous layer (B), the amount in the porous layer (B) is the amount of the porous layer (B). Is 50% by volume or more, preferably 70% by volume or more, more preferably 80% by volume or more, and 90% by volume or more. More preferably it is. By making the content of the inorganic filler in the porous layer (B) high as described above, the thermal contraction of the entire separator can be satisfactorily suppressed even when the non-aqueous secondary battery becomes high temperature. The occurrence of a short circuit due to direct contact between the positive electrode and the negative electrode can be better suppressed.

  In the case where the inorganic filler having a heat resistant temperature of 150 ° C. or higher and the fine particles of the resin having a melting point of 150 ° C. or higher are used in combination, it is sufficient that both of them form the main body of the porous layer (B). Specifically, the total amount of these components may be 50% by volume or more in the total volume of the constituent components of the porous layer (B) (total volume excluding the pores), and 70% by volume or more. It is preferable to make it 80% by volume or more, more preferably 90% by volume or more. Thereby, the effect similar to the case where the inorganic filler in a porous layer (B) is made into high content as mentioned above is securable.

  In the porous layer (B), fine particles of a resin having a melting point of 150 ° C. or higher or inorganic fillers having a heat resistant temperature of 150 ° C. or higher are bound, or the porous layer (B) and the porous layer (A) For example, an organic binder is preferably contained in order to integrate them. Examples of organic binders include ethylene-vinyl acetate copolymers (EVA, those having a structural unit derived from vinyl acetate of 20 to 35 mol%), ethylene-acrylic acid copolymers such as ethylene-ethyl acrylate copolymers, and fluorine-based binders. Examples include rubber, SBR, CMC, hydroxyethyl cellulose (HEC), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP), cross-linked acrylic resin, polyurethane, and epoxy resin. A heat-resistant binder having a heat-resistant temperature is preferably used. As the organic binder, those exemplified above may be used singly or in combination of two or more.

  Among the organic binders exemplified above, highly flexible binders such as EVA, ethylene-acrylic acid copolymer, fluorine-based rubber, and SBR are preferable. Specific examples of such highly flexible organic binders include Mitsui DuPont Polychemical's “Evaflex Series (EVA)”, Nihon Unicar's EVA, Mitsui DuPont Polychemical's “Evaflex-EAA Series (Ethylene). -Acrylic acid copolymer) ", Nippon Unicar EEA, Daikin Industries" DAI-EL Latex Series (Fluororubber) ", JSR" TRD-2001 (SBR) ", Nippon Zeon" BM-400B " (SBR) ".

  When the organic binder is used in the porous layer (B), it may be used in the form of an emulsion dissolved or dispersed in a solvent of a composition for forming a porous layer (B) described later.

  The coating laminate type separator is, for example, a composition for forming a porous layer (B) containing a fine resin particle having a melting point of 150 ° C. or higher or an inorganic filler having a heat resistant temperature of 150 ° C. or higher (a liquid composition such as a slurry). Etc.) may be applied to the surface of the microporous membrane for constituting the porous layer (A) and dried at a predetermined temperature to form the porous layer (B).

  The composition for forming the porous layer (B) contains fine particles of a resin having a melting point of 150 ° C. or higher or an inorganic filler having a heat resistant temperature of 150 ° C. or higher, and, if necessary, an organic binder and the like. Including the medium. The same shall apply hereinafter.) The organic binder can be dissolved in a solvent. The solvent used in the composition for forming the porous layer (B) is not particularly limited as long as it can uniformly disperse the inorganic filler and can uniformly dissolve or disperse the organic binder. Common organic solvents such as hydrocarbons, furans such as tetrahydrofuran, and ketones such as methyl ethyl ketone and methyl isobutyl ketone are preferably used. In addition, for the purpose of controlling the interfacial tension, alcohols (ethylene glycol, propylene glycol, etc.) or various propylene oxide glycol ethers such as monomethyl acetate may be appropriately added to these solvents. In addition, when the organic binder is water-soluble or used as an emulsion, water may be used as a solvent. In this case, alcohols (methyl alcohol, ethyl alcohol, isopropyl alcohol, ethylene glycol, etc.) are appropriately added. It is also possible to control the interfacial tension.

  The composition for forming the porous layer (B) has a solid content including, for example, 10 to 80% by mass of resin fine particles having a melting point of 150 ° C. or higher, an inorganic filler having a heat resistant temperature of 150 ° C. or higher, and an organic binder. It is preferable to do.

  In the laminated separator, the porous layer (A) and the porous layer (B) do not have to be one each, and a plurality of layers may be present in the separator. For example, the porous layer (A) may be arranged on both sides of the porous layer (B), or the porous layer (B) may be arranged on both sides of the porous layer (A). However, increasing the number of layers may increase the thickness of the separator and increase the internal resistance of the battery or decrease the energy density. Therefore, it is not preferable to increase the number of layers. The total number of layers of the porous layer (A) and the porous layer (B) is preferably 5 or less.

  The thickness of the separator (a separator made of a microporous membrane made of polyolefin or the laminated separator) according to the non-aqueous secondary battery is more preferably 10 to 30 μm.

  In the laminated separator, the thickness of the porous layer (B) [when the separator has a plurality of porous layers (B), the total thickness thereof] is determined by each of the functions of the porous layer (B). From the viewpoint of exhibiting more effectively, it is preferably 3 μm or more. However, if the porous layer (B) is too thick, the energy density of the battery may be lowered. Therefore, the thickness of the porous layer (B) is preferably 8 μm or less.

  Further, in the laminated separator, the thickness of the porous layer (A) [when the separator has a plurality of porous layers (I), the total thickness thereof. same as below. ] Is preferably 6 μm or more, more preferably 10 μm or more, from the viewpoint of more effectively exerting the above-described action (particularly the shutdown action) due to the use of the porous layer (A). However, if the porous layer (A) is too thick, there is a possibility that the energy density of the battery may be lowered. In addition, the force that the porous layer (A) tends to shrink is increased, and the heat of the entire separator is increased. There is a possibility that the action of suppressing the shrinkage becomes small. Therefore, the thickness of the porous layer (A) is preferably 25 μm or less, more preferably 20 μm or less, and further preferably 14 μm or less.

The porosity of the separator as a whole is preferably 30% or more in a dried state in order to secure the amount of electrolyte solution retained and to improve ion permeability. On the other hand, from the viewpoint of securing separator strength and preventing internal short circuit, the separator porosity is preferably 70% or less in a dry state. The porosity of the separator: P (%) can be calculated by obtaining the sum for each component i from the thickness of the separator, the mass per area, and the density of the constituent components using the following equation (1).
P = {1- (m / t) / (Σa _i · ρ _i )} × 100 (1)
Here, in the above formula, a _i : ratio of component i when the total mass is 1, ρ _i : density of component i (g / cm ³ ), m: mass per unit area of the separator (g / cm ² ), t: thickness of separator (cm).

In the case of the multilayer separator, in the formula (1), m is the mass (g / cm ² ) per unit area of the porous layer (A), and t is the thickness of the porous layer (A) ( cm), the porosity: P (%) of the porous layer (A) can also be obtained using the formula (1). It is preferable that the porosity of the porous layer (A) calculated | required by this method is 30 to 70%.

Further, in the case of the laminated separator, in the formula (1), m is the mass per unit area (g / cm ² ) of the porous layer (B), and t is the thickness of the porous layer (B) ( cm), the porosity: P (%) of the porous layer (B) can also be obtained using the formula (1). It is preferable that the porosity of the porous layer (B) calculated | required by this method is 20 to 60%.

  The separator preferably has high mechanical strength. For example, the puncture strength is preferably 3N or more. As described above, the negative electrode active material for a non-aqueous secondary battery according to the present invention has a large volume expansion / contraction during charging / discharging, and is mechanically applied to the separator facing the negative electrode due to expansion / contraction of the entire negative electrode by repeated charging / discharging cycles. Damage will be added. If the piercing strength of the separator is 3N or more, good mechanical strength is ensured, and mechanical damage to the separator can be reduced.

  Examples of the separator having a puncture strength of 3N or more include the above-described laminated separator, and in particular, an inorganic filler having a heat resistant temperature of 150 ° C. or higher in the porous layer (A) mainly composed of a resin having a melting point of 140 ° C. or lower. A separator in which a porous layer (B) containing as a main component is laminated is preferable. This is probably because the mechanical strength of the inorganic filler is high, so that the mechanical strength of the entire separator can be increased by supplementing the mechanical strength of the porous layer (A).

  The puncture strength can be measured by the following method. A separator is fixed on a plate having a hole with a diameter of 2 inches so as not to be wrinkled or bent, and a semispherical metal pin having a tip diameter of 1.0 mm is lowered onto a measurement sample at a speed of 120 mm / min. Measure the force when making a hole in the separator 5 times. And an average value is calculated | required about the measurement of 3 times except the maximum value and the minimum value among the said measurement values of 5 times, and this is made into the piercing strength of a separator.

(Nonaqueous electrolyte)
As the non-aqueous electrolyte solution according to the non-aqueous secondary battery of the present invention, a solution in which a lithium salt is dissolved in an organic solvent containing a phosphonoacetate compound satisfying the general formula (2) is used. It is preferable.

In the general formula (2), R ¹ , R ² and R ³ each independently represent an alkyl group, alkenyl group or alkynyl group having 1 to 12 carbon atoms which may be substituted with a halogen atom, and n Represents an integer of 0-6.

  Examples of the phosphonoacetate compound include the following compounds.

<Compound with n = 0 in the general formula (2)>
Trimethyl phosphonoformate, methyl diethylphosphonoformate, methyl dipropylphosphonoformate, methyl dibutylphosphonoformate, triethyl phosphonoformate, ethyl dimethylphosphonoformate, ethyl dipropylphosphonoformate, ethyl Dibutyl phosphonoformate, tripropyl phosphonoformate, propyl dimethylphosphonoformate, propyl diethylphosphonoformate, propyl dibutylphosphonoformate, tributyl phosphonoformate, butyl dimethylphosphonoformate, butyl diethylphospho Noformate, butyl dipropylphosphonoformate, methyl bis (2,2,2-trifluoroethyl) phosphonoformate, ethyl bis (2 2,2-trifluoroethyl) phosphonoacetate formate, propyl bis (2,2,2-trifluoroethyl) phosphonoacetate formate, and butyl bis (2,2,2-trifluoroethyl) phosphonoacetate formate.

<Compound with n = 1 in the general formula (2)>
Trimethyl phosphonoacetate, methyl diethyl phosphonoacetate, methyl dipropyl phosphonoacetate, methyl dibutyl phosphonoacetate, triethyl phosphonoacetate, ethyl dimethylphosphonoacetate, ethyl dipropylphosphonoacetate, ethyl dibutylphosphonoacetate, tripropyl Phosphonoacetate, propyl dimethylphosphonoacetate, propyl diethylphosphonoacetate, propyl dibutylphosphonoacetate, tributyl phosphonoacetate, butyldimethylphosphonoacetate, butyldiethylphosphonoacetate, butyldipropylphosphonoacetate, methylbis (2 , 2,2-trifluoroethyl) phosphonoacetate, ethyl bis (2,2,2-trifluoroethyl) phos No acetate, propyl bis (2,2,2-trifluoroethyl) phosphonoacetate, butyl bis (2,2,2-trifluoroethyl) phosphonoacetate, allyl dimethylphosphonoacetate, allyl diethylphosphonoacetate, 2 -Propinyl dimethylphosphonoacetate, 2-propynyl (diethylphosphono) acetate, etc.

<Compound with n = 2 in the general formula (1)>
Trimethyl 3-phosphonopropionate, methyl 3- (diethylphosphono) propionate, methyl 3- (dipropylphosphono) propionate, methyl 3- (dibutylphosphono) propionate, triethyl 3-phosphonopropionate, ethyl 3- (dimethylphosphono) propionate, ethyl 3- (dipropylphosphono) propionate, ethyl 3- (dibutylphosphono) propionate, tripropyl 3-phosphonopropionate, propyl 3- (dimethylphosphono) propionate, Propyl 3- (diethylphosphono) propionate, propyl 3- (dibutylphosphono) propionate, tributyl 3-phosphonopropionate, butyl 3- (dimethylphosphono) propionate, butyl 3- (diethylphosphono) prop Pionate, butyl 3- (dipropylphosphono) propionate, methyl 3- (bis (2,2,2-trifluoroethyl) phosphono) propionate, ethyl 3- (bis (2,2,2-trifluoroethyl) phosphono ) Propionate, propyl 3- (bis (2,2,2-trifluoroethyl) phosphono) propionate, butyl 3- (bis (2,2,2-trifluoroethyl) phosphono) propionate, and the like.

<Compound with n = 3 in the general formula (2)>
Trimethyl 4-phosphonobutyrate, methyl 4- (diethylphosphono) butyrate, methyl 4- (dipropylphosphono) butyrate, methyl 4- (dibutylphosphono) butyrate, triethyl 4-phosphonobutyrate, ethyl 4- (Dimethylphosphono) butyrate, ethyl 4- (dipropylphosphono) butyrate, ethyl 4- (dibutylphosphono) butyrate, tripropyl 4-phosphonobutyrate, propyl 4- (dimethylphosphono) butyrate, propyl 4- (Diethylphosphono) butyrate, propyl dibutylphosphono) butyrate, tributyl 4-phosphonobutyrate, butyl 4- (dimethylphosphono) butyrate, butyl 4- (diethylphosphono) butyrate, butyl 4- (dipropylphosphono) ) Butyrate etc.

  The content of the phosphonoacetate compound represented by the general formula (2) in the non-aqueous electrolyte used in the non-aqueous secondary battery improves battery swelling particularly when stored at high temperature in a high-voltage charge state. From the viewpoint of ensuring a good suppressing effect, the content is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more. On the other hand, if the amount of the phosphonoacetate compound in the non-aqueous electrolyte is too large, the load characteristics, charge / discharge cycle characteristics, and storage characteristics of the battery may be degraded. Therefore, the content of the phosphonoacetate compound represented by the general formula (2) in the nonaqueous electrolytic solution used for the nonaqueous secondary battery is preferably 5% by mass or less, and 2.5% by mass. The following is more preferable.

  Moreover, it is preferable to contain a 1, 3- dioxane in the non-aqueous electrolyte used for a non-aqueous secondary battery. When a non-aqueous electrolytic solution containing 1,3-dioxane is used, the load characteristics and high-temperature storage characteristics of the non-aqueous secondary battery when charged at a high voltage can be enhanced by its action. Further, 1,3-dioxane is more preferably used in combination with the phosphonoacetate compound represented by the general formula (2). In that case, the charge / discharge cycle characteristics of the non-aqueous secondary battery are further improved. It becomes possible.

  The content of 1,3-dioxane in the non-aqueous electrolyte used in the non-aqueous secondary battery increases the load characteristics of the battery when charged at a high voltage and the capacity recovery after high-temperature storage, and the general formula From the viewpoint of securing the effect of enhancing the charge / discharge cycle characteristics of the battery by the combination with the phosphonoacetate compound represented by (2), it is preferably 0.1% by mass or more, and 0.5% by mass or more. More preferably. On the other hand, if the amount of 1,3-dioxane in the nonaqueous electrolytic solution is too large, the load characteristics, charge / discharge cycle characteristics, and storage characteristics of the battery may be degraded. Therefore, the content of 1,3-dioxane in the nonaqueous electrolytic solution used for the nonaqueous secondary battery is preferably 5% by mass or less, and more preferably 2.5% by mass or less.

  In addition, it is preferable to use a non-aqueous electrolyte containing a halogen-substituted cyclic carbonate. The halogen-substituted cyclic carbonate acts on the negative electrode and has an action of suppressing the reaction between the negative electrode and the non-aqueous electrolyte component. Therefore, a nonaqueous secondary battery with better charge / discharge cycle characteristics can be obtained by using a nonaqueous electrolytic solution that also contains a halogen-substituted cyclic carbonate.

  As the halogen-substituted cyclic carbonate, a compound represented by the following general formula (3) can be used.

In the general formula (3), R ⁴ , R ⁵ , R ⁶ and R ⁷ represent hydrogen, a halogen element or an alkyl group having 1 to 10 carbon atoms, and a part or all of the hydrogen of the alkyl group is halogen. may be substituted with an ^element, at least one of R ^4, R 5, ^{R 6} and ^{R 7} are ^halogen, R ^4, R 5, ^{R 6} and ^{R 7} have different respective Two or more may be the same. When R ⁴ , R ⁵ , R ⁶ and R ⁷ are alkyl groups, the smaller the number of carbon atoms, the better. As the halogen element, fluorine is particularly preferable.

  Among the cyclic carbonates substituted with such a halogen element, 4-fluoro-1,3-dioxolan-2-one (FEC) is particularly preferable.

  The content of the halogen-substituted cyclic carbonate in the non-aqueous electrolyte used for the non-aqueous secondary battery is preferably 0.1% by mass or more from the viewpoint of ensuring better the effect of its use. More preferably, it is 5% by mass or more. However, if the content of the halogen-substituted cyclic carbonate in the non-aqueous electrolyte is too large, the effect of improving storage characteristics may be reduced. Therefore, the content of the halogen-substituted cyclic carbonate in the non-aqueous electrolyte used for the non-aqueous secondary battery is preferably 10% by mass or less, and more preferably 5% by mass or less.

  Further, it is preferable to use a non-aqueous electrolyte containing vinylene carbonate (VC). VC acts on a negative electrode (in particular, a negative electrode using a carbon material as a negative electrode active material) and has an action of suppressing a reaction between the negative electrode and a non-aqueous electrolyte component. Therefore, a nonaqueous secondary battery having better charge / discharge cycle characteristics can be obtained by using a nonaqueous electrolytic solution that also contains VC.

  The content of VC in the non-aqueous electrolyte used for the non-aqueous secondary battery is preferably 0.1% by mass or more, more preferably 1.0% by mass or more, from the viewpoint of better securing the effect of the use. It is more preferable that However, if the content of VC in the non-aqueous electrolyte is too large, the effect of improving storage characteristics may be reduced. Therefore, the content of VC in the non-aqueous electrolyte used for the non-aqueous secondary battery is preferably 10% by mass or less, and more preferably 4.0% by mass or less.

The lithium salt used in the non-aqueous electrolyte is not particularly limited as long as it is dissociated in a solvent to form Li ⁺ ions and hardly causes a side reaction such as decomposition in a voltage range used as a battery. For example, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ and other inorganic lithium salts, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li ₂ C ₂ F ₄ (SO ₃ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiC _n F _{2n + 1} SO ₃ (n ≧ 2), LiN (RfOSO ₂ ) ₂ [where Rf is a fluoroalkyl group] and the like can be used. .

  The concentration of the lithium salt in the non-aqueous electrolyte is preferably 0.5 to 1.5 mol / l, and more preferably 0.9 to 1.25 mol / l.

  The organic solvent used for the non-aqueous electrolyte is not particularly limited as long as it dissolves the lithium salt and does not cause a side reaction such as decomposition in a voltage range used as a battery. For example, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, chain carbonates such as dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; chain esters such as methyl propionate; cyclic esters such as γ-butyrolactone; dimethoxyethane, Chain ethers such as diethyl ether, 1,3-dioxolane, diglyme, triglyme and tetraglyme; cyclic ethers such as 1,4-dioxane, tetrahydrofuran and 2-methyltetrahydrofuran; acetonitrile, propionitrile, methoxypropionitrile and the like Nitriles; sulfites such as ethylene glycol sulfite; and the like. These may be used in combination of two or more. In order to obtain a battery with better characteristics, it is desirable to use a combination that can obtain high conductivity, such as a mixed solvent of ethylene carbonate and chain carbonate.

  Non-aqueous electrolytes used for non-aqueous secondary batteries include acid anhydrides and sulfonate esters for the purpose of further improving charge / discharge cycle characteristics and improving safety such as high-temperature storage and overcharge prevention. , Dinitrile, 1,3-propane sultone, diphenyl disulfide, cyclohexylbenzene, biphenyl, fluorobenzene, t-butylbenzene, and other additives (including these derivatives) can also be added as appropriate.

  Further, as the non-aqueous electrolyte of the non-aqueous secondary battery, a gel (gel electrolyte) obtained by adding a known gelling agent such as a polymer to the non-aqueous electrolyte can be used.

(Battery form)
There is no restriction | limiting in particular as a form of the non-aqueous secondary battery of this invention. 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 addition, when the negative electrode active material for a non-aqueous secondary battery of the present invention is used, a rectangular (square tube) outer can, a flat outer can, a laminated film outer casing, etc. having a small thickness with respect to the width are used. However, in the case of the non-aqueous secondary battery of the present invention, since the occurrence of such battery swelling can be satisfactorily suppressed, the rectangular shape having the exterior body (exterior can) as described above. In the case of a battery or a flat battery, the effect is particularly remarkable.

  In introducing the positive electrode, the negative electrode, and the separator into the nonaqueous secondary battery of the present invention, a laminated electrode body in which the positive electrode and the negative electrode are laminated via the separator, or the positive electrode and the negative electrode are laminated via the separator, Can be used as a spirally wound electrode body. Further, depending on the form of the battery, a plurality of positive electrodes and negative electrodes can be used in these laminated electrode bodies and wound electrode bodies.

  In the laminated electrode body and the wound electrode body used in the non-aqueous secondary battery, when the laminated separator is used, the porous layer (A) mainly composed of a resin having a melting point of 140 ° C. or lower is used. When using a separator in which a porous layer (B) mainly containing an inorganic filler having a heat resistant temperature of 150 ° C. or higher is used, it is preferable to dispose the porous layer (B) so as to face at least the positive electrode. . In this case, since the porous layer (B) having an inorganic filler having a heat-resistant temperature of 150 ° C. or higher as a main component and more excellent in oxidation resistance faces the positive electrode, the oxidation of the separator by the positive electrode can be suppressed better, It is also possible to improve storage characteristics and charge / discharge cycle characteristics of the battery at high temperatures. Further, when an additive such as vinylene carbonate or cyclohexylbenzene is added to the non-aqueous electrolyte, there is a possibility that the battery characteristics may be remarkably deteriorated by forming a film on the positive electrode side and clogging the pores of the separator. Therefore, an effect of suppressing clogging of the pores can be expected by causing the relatively porous porous layer (B) to face the positive electrode.

  On the other hand, when one surface of the laminated separator is the porous layer (A), it is preferable that the porous layer (A) faces the negative electrode, and thus, for example, the porous separator is porous during shutdown. The thermoplastic resin melted from the layer (A) is suppressed from being absorbed by the electrode mixture layer, and can be efficiently used to close the pores of the separator.

  In the electrode body used in the non-aqueous secondary battery (the above-mentioned laminated electrode body or wound electrode body), the mass of the positive electrode active material contained in the positive electrode is p, and the mass of the negative electrode active material contained in the negative electrode is n. P / n is preferably 1.0 to 3.6. By setting the p / n ratio to 3.6 or less, the utilization rate of the negative electrode active material can be reduced to limit the charge electric capacity. Therefore, the material containing Si and O used as the negative electrode active material as constituent elements can be reduced. In addition, the expansion and contraction of the volume accompanying the charging / discharging of the battery can be suppressed, and the deterioration of the charging / discharging cycle characteristics of the battery due to the pulverization of the material particles can be suppressed better. Moreover, a higher battery capacity can be ensured by setting the ratio of p / n to 1.0 or more.

  Since the non-aqueous secondary battery of the present invention has various battery characteristics including storage characteristics, it has been known for a long time for use in power supplies of small and multifunctional portable devices. It can be preferably used for various applications to which the used non-aqueous secondary battery is applied.

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

<Synthesis of lithium-containing composite oxide A containing Ni>
Aqueous ammonia whose pH was adjusted to about 12 by adding sodium hydroxide was placed in a reaction vessel, and while vigorously stirring, nickel sulfate, cobalt sulfate and manganese sulfate were each added to 2.4 mol / dm ^3. , 0.8 mol ^/ dm 3, a mixed aqueous solution containing a concentration of 0.8 mol / dm ^3, and aqueous ammonia 25% strength by weight, respectively, 23cm ³ / min at a rate of 6.6 cm ³ / min, The solution was added dropwise using a metering pump to synthesize a coprecipitation compound of Ni, Co, and Mn (spherical coprecipitation compound). At this time, the temperature of the reaction solution is kept at 50 ° C., and a sodium hydroxide aqueous solution having a concentration of 6.4 mol / dm ³ is dropped at the same time so that the pH of the reaction solution is maintained around 12. Further, nitrogen gas was bubbled at a flow rate of 1 dm ³ / min.

The coprecipitated compound was washed with water, filtered and dried to obtain a hydroxide containing Ni, Co and Mn in a molar ratio of 6: 2: 2. 0.196 mol of this hydroxide and 0.204 mol of LiOH.H ₂ O were dispersed in ethanol to form a slurry, and then mixed with a planetary ball mill for 40 minutes and dried at room temperature to obtain a mixture. . Next, the mixture is put in an alumina crucible, heated to 600 ° C. in a dry air flow of 2 dm ³ / min, kept at that temperature for 2 hours for preheating, further heated to 900 ° C. and heated to 12 ° C. Lithium-containing composite oxide A was synthesized by firing for a period of time.

  The obtained lithium-containing composite oxide A 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 A after pulverization was stored in a desiccator.

About the said lithium containing complex oxide A, the composition analysis was performed as follows using ICP method. First, 0.2 g of the lithium-containing composite oxide A was sampled and placed in a 100 mL container. Thereafter, 5 mL of pure water, 2 mL of aqua regia, and 10 mL of pure water were added in order and dissolved by heating. After cooling, the mixture was further diluted 25 times and analyzed by ICP (“ICP-757” manufactured by JARRELASH) (calibration). Line method). From the obtained results, the composition of the lithium-containing composite oxide A was derived and found to be a composition represented by Li _1.02 Ni _0.6 Co _0.2 Mn _0.2 O ₂ .

<Synthesis of lithium-containing composite oxide B containing Ni>
Aqueous ammonia whose pH was adjusted to about 12 by adding sodium hydroxide was placed in a reaction vessel, and while vigorously stirring, nickel sulfate, manganese sulfate, and cobalt sulfate were each added to 3.76 mol / dm ^3. , 0.21 mol ^/ dm 3, a mixed aqueous solution containing a concentration of 0.21 mol / dm ^3, and aqueous ammonia 25% strength by weight, respectively, 23cm ³ / min at a rate of 6.6 cm ³ / min, The mixture was added dropwise using a metering pump to synthesize a coprecipitation compound of Ni, Mn, and Co (spherical coprecipitation compound). At this time, the temperature of the reaction solution is maintained at 50 ° C., and a sodium hydroxide aqueous solution having a concentration of 6.4 mol / dm 3 is also dropped at the same time so that the pH of the reaction solution is maintained near 12. In order to react under an inert atmosphere, nitrogen gas was bubbled at a flow rate of 1 dm ³ / min.

The coprecipitated compound was washed with water, filtered and dried to obtain a hydroxide containing Ni, Mn and Co in a molar ratio of 90: 5: 5. 0.196 mol of this hydroxide, 0.204 mol of LiOH.H ₂ O and 0.001 mol of TiO ₂ were dispersed in ethanol to form a slurry, and then mixed for 40 minutes with a planetary ball mill. And dried to obtain a mixture. Next, the mixture is put in an alumina crucible, heated to 600 ° C. in a dry air flow of 2 dm ³ / min, held at that temperature for 2 hours for preheating, further heated to 800 ° C. and heated to 12 ° C. Lithium-containing composite oxide B was synthesized by firing for a period of time. The obtained lithium-containing composite oxide B was pulverized into a powder in a mortar and then stored in a desiccator.

For the lithium-containing composite oxide B, where the composition analysis was performed by a calibration curve method using the ICP method described above, the results obtained have been derived composition of the lithium-containing complex oxide B, Li _1.02 It was found that the composition was represented by Ni _0.895 Co _0.05 Mn _0.05 Ti _0.005 O ₂ .

Example 1
<Preparation of positive electrode>
LiCoO _{2 as a} positive electrode active material: 70 parts by mass, LiMn _0.2 Ni _0.6 Co _0.2 O ₂ : 30 parts by mass as the lithium-containing composite oxide A, and artificial graphite as a conductive auxiliary agent: 1 Part by mass and Ketjen Black: 1 part by mass and PVDF as a binder: 10 parts by mass were mixed so as to be uniform using NMP as a solvent to prepare a positive electrode mixture-containing paste. The positive electrode mixture-containing paste is intermittently applied to both surfaces of a current collector made of an aluminum foil having a thickness of 15 μm by adjusting the thickness, dried, and then subjected to a calendar treatment so that the total thickness becomes 130 μm. The thickness of the mixture layer was adjusted, and the positive electrode was produced by cutting so that the width was 54.5 mm. Further, a tab was welded to the exposed portion of the aluminum foil of the positive electrode to form a lead portion.

<Production of negative electrode>
5 is a material in which the surface of SiO is coated with carbon (the amount of carbon in the composite is 20% by mass; hereinafter referred to as “SiO / carbon composite”) and graphitic carbon having an average particle diameter D ₅₀ of 16 μm. : Mixture mixed at a mass ratio of 95: 98 parts by mass, CMC aqueous solution having a concentration of 1% by mass adjusted to a viscosity of 1500 to 5000 mPa · s: 1.0 part by mass, and SBR: 1.0 part by mass Was mixed with ion-exchanged water having a specific conductivity of 2.0 × 10 ⁵ Ω / cm or more as a solvent to prepare an aqueous negative electrode mixture-containing paste.

The SiO / carbon composite is obtained by subjecting SiO having a particle size distribution adjusted by pulverization and classification under the conditions of a treatment temperature of 1100 ° C. and a treatment time of 4 hours using toluene as a liquid source. The SiO / carbon composite obtained after the CVD treatment has a D _10% of 5 μm, a D _50% of 9 μm, a D _90% of 13 μm, a half width of the Si (220) diffraction peak of 0.8 °, and I _a / _Ib is 3.3 and _I510 / _I1343 is 0.10.

  The negative electrode mixture-containing paste is intermittently applied to both sides of a current collector made of a copper foil having a thickness of 8 μm while adjusting the thickness, dried, and then subjected to a calendar process so that the total thickness becomes 110 μm. The thickness of the mixture layer was adjusted, and the negative electrode was produced by cutting so that the width was 55.5 mm. Further, a tab was welded to the exposed portion of the copper foil of the negative electrode to form a lead portion.

<Preparation of separator>
Add 5 kg of ion-exchanged water and 0.5 kg of a dispersant (aqueous polycarboxylic acid ammonium salt, solid content concentration 40 mass%) to 5 kg of boehmite with an average particle diameter D of _50% of 1 μm. Dispersion was prepared by crushing for 10 hours with a ball mill at times / minute. The treated dispersion was vacuum-dried at 120 ° C. and observed with a scanning electron microscope (SEM). As a result, the boehmite was almost plate-shaped.

  To 500 g of the above dispersion, 0.5 g of xanthan gum as a thickener and 17 g of a resin binder dispersion (modified polybutyl acrylate, solid content 45% by mass) as a binder are added and stirred with a three-one motor for 3 hours to form a uniform slurry. [Slurry for forming porous layer (B), solid content ratio 50 mass%] was prepared.

PE microporous separator for non-aqueous secondary battery [porous layer (A): thickness 12 μm, porosity 40%, average pore diameter 0.08 μm, PE melting point 135 ° C.] on one side corona discharge treatment (discharge amount 40 W · min / m ² ), and a slurry for forming a porous layer (B) is applied to the treated surface by a micro gravure coater and dried to form a porous layer (B) having a thickness of 4 μm, and then laminated. A mold separator was obtained. The mass per unit area of the porous layer (B) in this separator was 5.5 g / m ² , the boehmite volume content was 95% by volume, and the porosity was 45%.

<Preparation of non-aqueous electrolyte>
In a mixed solvent in which EC, MEC and DMC were mixed at a volume ratio of 1: 1: 1, LiPF ₆ as a lithium salt was dissolved at a concentration of 1.1 mol / dm ³ , and FEC was further added at 2.0 mass%. In such an amount that the VC is 2.0% by mass, the 2-propynyl (diethylphosphono) acetate is 1.0% by mass, and the 1,3-dioxane is 1.0% by mass. A solution added in an amount was prepared.

<Battery assembly>
The positive electrode and negative electrode obtained as described above were overlapped with the separator porous layer (B) facing the positive electrode and wound in a spiral shape to produce a wound electrode body. The obtained wound electrode body was crushed into a flat shape, placed in an aluminum alloy outer can having a thickness of 5 mm, a width of 42 mm, and a height of 61 mm, and the non-aqueous electrolyte was injected.

  After injecting the non-aqueous electrolyte, the outer can was sealed to produce a non-aqueous secondary battery having the structure shown in FIG. 1 and the appearance shown in FIG. This battery includes a cleavage vent for lowering the pressure when the internal pressure rises at the top of the can.

  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 as described above, and then pressed so as to be flattened and accommodated in a rectangular tube-shaped outer can 4 together with the electrolyte as a flat wound electrode body 6 Has been. 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. Also, the separator layers are not shown separately.

  The outer can 4 is made of an aluminum alloy and constitutes an outer casing of the battery. The outer can 4 also serves as a positive electrode terminal. And the insulator 5 which consists of PE sheets is arrange | positioned at the bottom part of the armored can 4, and it connects to each one end of the positive electrode 1 and the negative electrode 2 from the flat wound electrode body 6 which consists of the positive electrode 1, the negative electrode 2, and the separator 3. The positive electrode lead body 7 and the negative electrode lead body 8 thus drawn are drawn out. A stainless steel terminal 11 is attached to a sealing lid plate 9 made of aluminum alloy for sealing the opening of the outer can 4 through a PP insulating packing 10, and an insulator 12 is attached to the terminal 11. A stainless steel lead plate 13 is attached.

  And this cover plate 9 is inserted in the opening part of the armored can 4, and the opening part of the armored 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, a non-aqueous electrolyte inlet 14 is provided in the cover plate 9, and a sealing member is inserted into the non-aqueous electrolyte inlet 14, for example, laser welding or the like. (See FIG. 1 and FIG. 2, in practice, the non-aqueous electrolyte inlet 14 is actually sealed with the non-aqueous electrolyte inlet.) Although it is a member, for ease of explanation, it is shown as a non-aqueous electrolyte inlet 14). Further, the lid plate 9 is provided with a cleavage vent 15 as a mechanism for discharging the internal gas to the outside when the temperature of the battery rises.

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

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

Examples 2-5 and Comparative Examples 1-4
A negative electrode was produced in the same manner as in Example 1 except that the SiO / carbon composite was changed to the one shown in Table 1, and the nonaqueous secondary battery was made in the same manner as in Example 1 except that these negative electrodes were used. Was made. Incidentally, the carbon content of the SiO / carbon composite was adjusted by the CVD processing time. Specifically, the CVD processing time in the SiO / carbon composite used in Example 3 is 2.4 hours, and the CVD processing time in the SiO / carbon composite used in Comparative Example 1 is 3 hours.

Example 6
A positive electrode was produced in the same manner as in Example 1 except that the lithium-containing composite oxide B was used in place of the lithium-containing composite oxide A, and the non-aqueous solution was used in the same manner as in Example 1 except that this positive electrode was used. A secondary battery was produced.

  The following storage tests (25 ° C. 7 day storage test, 45 ° C. 7 day storage test and 45 ° C. 30 day storage test) were performed on each of the nonaqueous secondary batteries of Examples and Comparative Examples.

<25 ° C 7 days storage test>
About each battery of an Example and a comparative example, after performing constant current-constant voltage charge (total charge time: 3 hours) by a constant current of 1 C and a constant voltage of 4.35 V at 25 ° C., a constant current at 1 C Discharge (discharge end voltage: 2.7 V) was performed, and the initial discharge capacity (mAh) was measured.

  Each battery after the initial discharge capacity measurement was subjected to constant current-constant voltage charging (total charging time: 1 hour) at a constant current of 0.5 C and a constant voltage of 4.35 V at 25 ° C., and then at 25 ° C. Stored in a thermostatic bath for 7 days. Then, each battery was taken out from the thermostat and constant current discharge (discharge end voltage: 2.7 V) was performed at 1C.

  In order to confirm the discharge capacity of each battery after storage, constant current-constant voltage charge and constant current discharge were performed under the same conditions as when measuring the initial discharge capacity, and the discharge capacity after storage at 25 ° C. for 7 days was obtained. It was. The capacity retention rate was calculated by expressing the discharge capacity after storage at 25 ° C. for 7 days by the initial discharge capacity as a percentage.

<45 ° C 7 day storage test>
About each battery of Example and Comparative Example (battery different from that subjected to storage test at 25 ° C. for 7 days), the same as the storage test at 25 ° C. for 7 days, except that the storage temperature in the thermostatic bath was changed to 45 ° C. The initial discharge capacity and the discharge capacity after storage at 45 ° C. for 7 days were measured by the method, and the capacity retention rate was calculated.

<45 ° C 30 day storage test>
Except for changing the storage time in the thermostatic bath to 30 days for each of the batteries of Examples and Comparative Examples (batteries different from those subjected to a storage test at 25 ° C. for 7 days and a storage test at 45 ° C. for 7 days), 45 The initial discharge capacity and the discharge capacity after storage at 45 ° C. for 30 days were measured by the same method as the storage test at 7 ° C., and the capacity retention rate was calculated.

  The structure of the SiO / carbon composite used for the negative electrode is shown in Table 1, and the evaluation results are shown in Table 2. The initial discharge capacity in Table 2 shows the value measured during the storage test at 25 ° C. for 7 days as a relative value when the value in the nonaqueous secondary battery of Example 1 is 100.

As is clear from Tables 1 and 2, Examples 1 to 2 in which SiO having an average particle diameter D of _50% and a Si (220) diffraction peak half-value width appropriate for the negative electrode active material and graphitic carbon were used in combination. The non-aqueous secondary battery of No. 6 has a large initial discharge capacity, and has a high capacity retention rate after storage at 25 ° C. for 7 days, 45 ° C. for 7 days, and 45 ° C. for 30 days, and has excellent storage characteristics. doing.

On the other hand, the battery of Comparative Example 1 using SiO with an average particle diameter D of _50% too small and the battery of Comparative Example 3 using SiO with a half-width of the (220) diffraction peak of Si being too large are 45 ° C. The capacity retention rate after storage for 30 days is low, and the storage characteristics are inferior. The battery of Comparative Example 2 using SiO FWHM of (220) diffraction peak of Si is too small, and the average cell diameter D _50% is Comparative Example 4 using the SiO too large, the initial discharge capacity small.

1 Positive electrode 2 Negative electrode 3 Separator

Claims (7)

It contains a material containing Si and O as constituent elements, has an average particle diameter D _50% of 6 to 10 μm determined by a laser diffraction scattering method, and Si determined by an X-ray diffraction method using CuKα rays ( 220) A negative electrode active material for a non-aqueous secondary battery, wherein a half-value width of a diffraction peak is 0.6 to 1.0 °. 2. The negative electrode active material for a non-aqueous secondary battery according to claim 1, wherein D _10% and D _90% obtained by a laser diffraction scattering method are D _10% : 4 μm or less and D _90% : 14 μm or less. The non-aqueous two-component material according to claim 1 or 2, wherein the material containing Si and O as constituent elements is a material represented by a general composition formula SiO _x (where 0.5 ≦ x ≦ 1.5). Negative electrode active material for secondary battery. When X-ray diffraction measurement using CuKα rays is performed, the intensity I _{a of the} diffraction peak derived from Si observed at a position where 2θ is 28.4 °, and 2θ at a position near 21.2 ° The negative electrode active material for a non-aqueous secondary battery according to claim 3, wherein the ratio I _a / I _b to the observed diffraction peak intensity I _b derived from SiO ₂ is 2.7 to 3.9.   The negative electrode active material for nonaqueous secondary batteries according to any one of claims 1 to 4, which forms a composite with a carbon material. In the Raman spectrum obtained when wavelength is Raman spectroscopy using a measuring laser 532 nm, and the peak intensity _{I 510} of the 510 cm ^-1 derived from Si, the intensity of the peak of 1343cm ^-1, which derived from the carbon _{I 1343} The negative electrode active material for a non-aqueous secondary battery according to claim 5, wherein the ratio I ₅₁₀ / I ₁₃₄₃ to 0.25 is 0.25 or less. A non-aqueous secondary battery having a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator and a non-aqueous electrolyte,
A nonaqueous secondary battery using the negative electrode active material for a nonaqueous secondary battery according to any one of claims 1 to 6 and a graphitic carbon material as the negative electrode active material.

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