JP2014032802A - Nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous secondary battery excellent in cycle characteristics and rapid charging characteristics.SOLUTION: The nonaqueous secondary battery of the present invention which includes a cathode, an anode, a nonaqueous electrolyte, and a separator is characterized in that: the anode includes an anode mixture layer containing, as an anode active material, a material containing an element capable of alloying with lithium; and the nonaqueous electrolyte contains a fluorine-containing organic metal salt having an oxalic acid group. The content of the fluorine-containing organic metal salt having the oxalic acid group in the nonaqueous electrolyte is 0.01 mass% or more and less than 10 mass%.

Description

  The present invention relates to a 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-sized and large-sized power tools such as power tools, electric vehicles, and electric bicycles has been spreading.

  In addition, there is an increasing demand for higher capacities due to the necessity of expanding smartphones and extending the distance that electric vehicles can travel. As a countermeasure for increasing the capacity, as a negative electrode active material, instead of a carbon material such as graphite used in a conventional non-aqueous secondary battery, more lithium such as silicon (Si) or tin (Sn) is used. A material capable of occluding and releasing (Li) ions has been proposed, but capacity reduction due to volume change accompanying charge / discharge is large, and improvement is necessary. Further, when a composite in which the surface of an oxide-based material such as SiO is coated with an electron conductive carbon material is used as the negative electrode active material, the cycle characteristics are further improved, but problems still remain.

  On the other hand, a general charging method for a non-aqueous secondary battery is a predetermined charging with a current of about 0.7 to 1 C, where 1 C is a current value that can discharge a fully charged battery in 1 hour. It is standard to perform constant current charging up to the end voltage, and then switch to constant voltage charging in which the charge current is decreased so as to maintain the charge end voltage after reaching the charge end voltage.

  In addition, there is an increasing need to complete battery charging as soon as possible. For example, taking a lithium secondary battery, which is a non-aqueous secondary battery for a mobile phone, as an example, a conventional lithium secondary battery for a mobile phone can be charged for about 2 to 4 hours at a current value of 1C or less. It was possible to make it fully charged or close to it. However, since the non-aqueous secondary battery is required to have a higher capacity as the application of the non-aqueous secondary battery such as a mobile phone is enhanced, the current value is comparable to the conventional one. In charging at, there is a possibility that the time required for charging exceeds the practical range and becomes longer. In order to avoid this, it is necessary to develop a technology that enables charging with a larger current value, increases the capacity, and shortens the time required for charging.

  In order to meet such demands, for example, a method of improving the quick charge characteristics by using a combination of a plurality of positive electrode active materials (Patent Document 1), and using a lithium titanium composite oxide for the negative electrode, high output (load) (Enhancement of characteristics) and a method of enhancing quick charge characteristics (Patent Document 2), and a method of ensuring good battery characteristics even when rapidly charged by adding an insulating inorganic oxide filler separately from the active material to the negative electrode (Patent Document 3) and the like have been proposed.

In addition, it has been reported that it is effective to use SiO _x having a structure in which ultrafine particles of Si are dispersed in SiO ₂ as the negative electrode active material in terms of simply improving the load characteristics of the non-aqueous secondary battery ( Patent Documents 4 and 5).

  On the other hand, when charging with the battery pack removed from the device body like an electric tool, the battery pack is forcibly cooled by a cooling device provided in the charging device due to a rapid temperature rise due to rapid charging. There has been proposed a method (Patent Document 6) for enabling charging with an excess current and shortening the charging time.

On the other hand, when a material in which SiO _x is coated with a conductive carbon material is used as a negative electrode active material, a method for improving cycle characteristics by adding a specific additive to the electrolytic solution (Patent Document 7) has also been proposed. .

JP 2011-076997 A JP 2010-097551 A JP 2009-054469 A Japanese Patent Laid-Open No. 2004-047404 Japanese Patent Laid-Open No. 2005-259697 JP 2008-104349 A JP 2008-210618A

  However, the methods proposed in the above-mentioned patent documents still do not have sufficient battery cycle characteristics. Further, in improving the quick charge characteristics, for example, it is conceivable to improve the load characteristics of the battery. However, according to the study by the present inventors, when a battery pack using such a battery and having a PTC element, a protection circuit, etc. as applied to a portable device or the like is used, a certain amount of rapid charging is performed. Although improvement in characteristics is recognized, the degree of improvement often does not reach the predicted level, and it has been found that simply increasing the load characteristics of the battery is insufficient.

  The present invention has been made to solve the above problems, and provides a non-aqueous secondary battery excellent in cycle characteristics and quick charge characteristics.

  In order to solve the above problems, the non-aqueous secondary battery of the present invention is a non-aqueous secondary battery including a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator, and the negative electrode is an element that can be alloyed with lithium. And the nonaqueous electrolyte contains a fluorine-containing organometallic salt having an oxalic acid group.

  ADVANTAGE OF THE INVENTION According to this invention, the non-aqueous secondary battery excellent in cycling characteristics and quick charge characteristics can be provided.

FIG. 1 is a circuit diagram showing an example of a non-aqueous secondary battery pack using the non-aqueous secondary battery of the present invention. FIG. 2 is a diagram schematically illustrating an example of the nonaqueous secondary battery of the present invention, in which FIG. 2A is a plan view and FIG. 2B is a cross-sectional view. FIG. 3 is a perspective view showing an example of the appearance of the nonaqueous secondary battery of the present invention.

  The non-aqueous secondary battery of the present invention is a non-aqueous secondary battery including a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator, and the negative electrode includes a material containing an element that can be alloyed with lithium as a negative electrode active material. The non-aqueous electrolyte includes a fluorine-containing organic metal salt having an oxalic acid group. Thereby, cycle characteristics and quick charge characteristics can be improved.

  Hereinafter, each component of the non-aqueous secondary battery of this invention is demonstrated.

<Nonaqueous electrolyte>
The nonaqueous electrolyte according to the nonaqueous secondary battery of the present invention contains a fluorine-containing organometallic salt having an oxalic acid group. Thereby, the cycling characteristics of a battery can be improved. Similar effects can be obtained when a polyvalent organic metal salt is contained in addition to the fluorine-containing organic metal salt having an oxalic acid group. The fluorine-containing organometallic salt having an oxalic acid group or the polyvalent organometallic salt may be added in the negative electrode. In this case, it is added to the negative electrode mixture layer separately from the binder. .

  The fluorine-containing organic metal salt or polyvalent organic metal salt having an oxalic acid group is more likely to cause an oxidation reaction than an organic solvent that is a main component of the nonaqueous electrolyte or another electrolyte. Therefore, during the initial charging of the battery, the fluorine-containing organometallic salt or polyvalent organometallic salt having an oxalic acid group reacts preferentially on the surface of the positive electrode, and the reaction product is deposited on the surface of the positive electrode active material. The direct contact between the positive electrode surface and the nonaqueous electrolyte is prevented by the coating effect on the surface of the positive electrode active material by the film (deposited film) made of this deposit, and the decomposition reaction of the nonaqueous electrolyte is suppressed. As a result, it is possible to suppress a decrease in the cycle characteristics of the battery.

  Also, usually, when a deposition film of a reaction product of an organometallic salt is formed on the surface of the positive electrode active material, the movement of ions on the surface of the positive electrode active material is hindered, and the necessary battery reaction does not proceed sufficiently. There is a risk that the characteristics will deteriorate. However, when the fluorine-containing organic metal salt having a oxalic acid group or a polyvalent organic metal salt is added to the non-aqueous electrolyte, the movement of ions on the surface of the positive electrode active material becomes smooth, and the deterioration of battery characteristics is improved. Can be suppressed.

In the present invention, after the battery was formed, it was decomposed after discharge in an argon dry box, washed with diethyl carbonate (DEC), vacuum dried, and the intensity of the 1S spectrum of carbon (C) near 284-285 eV in the XPS analysis of the negative electrode. intensity ratio I ₆₈₅ / I ₂₈₅ between the intensity I ₆₈₅ of 1S spectrum of fluorine (F) in the vicinity of I ₂₈₅ and 684-686eV of preferably less than 1.5, more preferably less than 1.0, less than 0.7 Further preferred. Since the peak of 685 eV mainly due to F is smaller than the peak of C at 285 eV, the load characteristics and quick charge characteristics of the battery can be further improved. However, if the strength ratio is too small, the storage characteristics of the battery may be impaired, so 0.1 or more is preferable, 0.2 or more is more preferable, and 0.4 or more is more preferable. This intensity ratio can be controlled by adjusting the content of the fluorinated organometallic salt having an oxalic acid group.

In addition, it is preferable that the 1S spectrum peak of C derived from the fluorine-containing organometallic salt having an oxalic acid group exists in the vicinity of 288 eV because the load characteristics can be further improved. When XPS analysis of the composition of the film formed on the negative electrode surface, usually a large amount of organic carbonate such as lithium carbonate is detected, but as the amount of lithium carbonate present in the film formed on the negative electrode surface increases, The load characteristics tend to deteriorate. The presence of CO ₃ ^2- derived from lithium carbonate is confirmed by a peak appearing near 291 eV. In the present invention, when XPS analysis was performed on the film formed on the negative electrode surface, the peak near 291 eV decreased and the peak appeared near 288 eV. The peak near 288 eV indicates the presence of COO derived from a fluorine-containing organometallic salt having an oxalic acid group added to the nonaqueous electrolyte. In other words, in the present invention, the coating on the negative electrode surface contains a reaction product of a fluorinated metal salt having an oxalic acid group, and this coating has ionic conductivity and improves load characteristics. Conceivable.

Examples of the fluorine-containing organic metal salt having an oxalic acid group include, for example, the general formula (PF ₂ (C ₂ O ₄ ) ₂ ) _{b1 Mc 1} , (BF ₂ (C ₂ O ₄ )) _{b1 Mc 1} , M _b1 ( And PF ₄ (C ₂ O ₄ )) _c1 . In the above general formula, M is a metal element such as an alkali metal, an alkaline earth metal, a transition metal, or a group 13 element, preferably a metal element of an alkali metal or an alkaline earth metal, more preferably an alkali metal. is there. Specific examples include at least one metal element selected from the group consisting of Li, Na, K, Mg, Ca, Mn, and Al, and among these, Li is most preferable. b1 and c1 are integers determined by the valence of M and the valence of the anion.

Specific examples of the fluorine-containing organometallic salt having an oxalic acid group include LiPF ₂ (C ₂ O ₄ ) ₂ and LiBF ₂ (C ₂ O ₄ ).

Examples of the polyvalent organic metal salt include those having a plurality of anion sites, such as a salt having a metal ion having a valence of 2 or more, or an organic metal salt having a plurality of monovalent metal ions. Specific examples thereof include divalent, trivalent and tetravalent organometallic salts. Specific examples of the polyvalent organic metal salt include those represented by the general formula [R ¹ (Y) _a ] _b M ¹ _c . In the above general formula, R ¹ is, for example, an organic group such as an alkyl group, an alkylene group, and an aromatic group, and part or all of the hydrogen atoms of these groups may be substituted with a fluorine atom. Y is, for example, a metal base of an acid, specifically, —SO ₃ ⁻ , —CO ₂ ⁻ , —PO ₄ ⁻ , —PF _d Rf _5−d ⁻ [wherein Rf represents all hydrogen atoms Is an alkyl group substituted with a fluorine atom (hereinafter the same), and d is an integer of 5 or less (hereinafter the same). _{], - BF e Rf 3-} e - [ However, e is a 3 an integer (hereinafter the _{same)], - R g PO 4} - [ wherein, R is an organic residue (the same applies hereinafter), R ^It may be bonded to ¹ . g is 0 or 1 (the same applies hereinafter). Etc., and only one of these may be used, or two or more thereof may be used. M ¹ is a metal element such as an alkali metal, an alkaline earth metal, a transition metal, or a group 13 element, preferably a metal element of an alkali metal or an alkaline earth metal, and more preferably an alkali metal. Specific examples include at least one metal element selected from the group consisting of Li, Na, K, Mg, Ca, Mn, and Al, and among these, Li is most desirable. That is, as the polyvalent organic metal salt, a polyvalent organic lithium salt is most desirable. a is an integer of 2 or more. b and c are integers determined by the valence of M ^{1 and} the valence of [R ¹ (Y) _a ].

The polyvalent organic metal salts represented by the general formula [R ¹ (Y) _{a] b} M ¹ _c, the hydroxyl group (-OH) or in R ^1, group (-SO ₃ H, -CO ₂ H) may be included, but since these groups may cause a reaction in the battery, the number is preferably less than the acid metal base, and is 1/10 or less of the number of acid metal bases. More preferably.

In addition, in the polyvalent organometallic salt represented by the general formula [R ¹ (Y) _a ] _b M ¹ _c , if the molecular weight of R ¹ is too large, the positive electrode active material may not be effectively coated. Therefore, 100,000 or less is preferable, 2000 or less is more preferable, and 500 or less is more preferable. On the other hand, the molecular weight of R ¹ is preferably 30 or more, more preferably 50 or more, and even more preferably 70 or more, because if the molecular weight of R ¹ is too small, it may form a deposited film on the surface of the positive electrode active material. R ¹ is an alkylene or aromatic group, or an organic hybrid mainly containing them, such as —CH ₂ CH ₂ CH ₂ CH ₂ —, —CHFCH ₂ CH ₂ CH ₂ —, —CF ₂ CF ₂ CF. _{2 CF 2 - -C h H 2h} -i F i , such as - (. However, h, i is an integer, 1 ≦ h, 0 is ≦ i) alkylene represented as; -C ₆ H _{4 -,> C 6 H 3 -} , - C 6 H 4 -C 6 H 4 -, - C 6 H 3 F -, - C 6 F 4 - , etc. _{- (C 6 H 4-j} F k) l ( C ₆ H _4−m F _n ) _u − (where j, k, l, m, n, u are integers, 0 ≦ j, 0 ≦ k, k ≦ j, 0 ≦ m, 0 ≦ n, n ≦ m, 1 ≦ l + u)); or> C ₆ H ₃ —C (CF ₃ ) ₂ —C ₆ H ₃ <,> C ₆ H ₃ —CF ₃ , − _{C 6 H 4 -C (CF 3} ) 2 -C 6 H 4 -, R 2 (CH 2 C _{2 -C 6 H 4 -.)} N R 3 ( provided that, R ^2, R ³ is an organic group) organic hybrids of or the like. Specifically, LiOOC—CF ₂ CF ₂ CF ₂ CF ₂ —COOLi, LiOOC—C ₆ H ₄ —COOLi, LiOOC—C ₆ H ₄ —SO ₃ Li, LiOOC—C ₆ H ₄ — (C (CF ₃ ) _2- ) -C ₆ H ₄ -COOLi, metal salts such as LiOOC-C ₆ H ₃ F-COOLi can be exemplified. The molecule preferably contains an aromatic ring, and preferably has a —SO ₃ ^— group or a —COO ^— group. This is because the rapid charge effect tends to be increased by having these in the molecule. The molecular weight of the organometallic salt is preferably 150,000 or less, more preferably 2000 or less, and most preferably 500 or less. Moreover, 50 or more are preferable, 70 or more are more preferable, and 90 or more are the most preferable.

  The content of the fluorinated organic metal salt or polyvalent organic metal salt having an oxalic acid group is preferably 0.01% by mass or more, more preferably 0.1% by mass or more in the nonaqueous electrolyte. 2 mass% or more is more preferable. If the content is too high, the battery characteristics deteriorate, so it is preferably less than 10% by mass, more preferably less than 3% by mass, and even more preferably less than 1.5% by mass.

  The non-aqueous electrolyte containing the fluorine-containing organic metal salt having a oxalic acid group or the polyvalent organic metal salt is a non-aqueous electrolyte solution in which an electrolyte salt such as an inorganic lithium salt or an organic lithium salt is dissolved in an organic solvent. Is used.

  Examples of the organic solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate (MEC). , Γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester , Trimethoxymethane, dioxolane derivative, sulfolane, 3-methyl-2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, diethyl Ether, include aprotic organic solvents such as 1,3-propane sultone, may be used those either alone, or in combination of two or more.

Examples of the inorganic lithium _{salt, LiClO 4, LiBF 4, LiPF} 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiB 10 Cl 10, lower aliphatic carboxylic acids Li, LiAlCl _4, LiCl, LiBr , LiI, chloroborane Li, lithium tetraphenylborate and the like, and these may be used alone or in combination of two or more.

Examples of the organic lithium salt include 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 _n1 F _{2n1 + 1} SO ₃ (2 ≦ n1 ≦ 7), LiN (Rf ¹ OSO ₂ ) ₂ [wherein Rf ¹ is a fluoroalkyl group. Etc., and these may be used alone or in combination of two or more. The above Li ₂ C ₂ F ₄ (SO ₃ ) ₂ is a polyvalent organic metal salt, but has high solubility in the electrolyte and can not be expected to have an effect of covering the surface of the positive electrode active material. In the present invention, it is treated as an electrolyte salt.

The concentration of the electrolyte salt in the nonaqueous electrolyte solution, for example, is preferably 0.2~3.0mol / dm ^3, more preferably from 0.5~1.5mol / dm ^3, 0. More preferably, it is 9-1.3 mol / dm ³ .

As the non-aqueous electrolyte, a solvent containing at least one chain carbonate selected from methyl carbonate, diethyl carbonate and methyl ethyl carbonate and at least one cyclic carbonate selected from ethylene carbonate and propylene carbonate, LiPF It is particularly preferable to use a nonaqueous electrolytic solution in which ₆ is dissolved.

In addition, the non-aqueous electrolyte may appropriately contain the following additives for the purpose of improving cycle characteristics, improving safety such as high-temperature storage and preventing overcharge. Examples of the additive include anhydride, sulfonate ester, dinitrile, 1,3-propane sultone, diphenyl disulfide, cyclohexylbenzene, vinylene carbonate (VC), biphenyl, fluorobenzene, t-butylbenzene, and cyclic fluorinated carbonate. [Trifluoropropylene carbonate (TFPC), fluoroethylene carbonate (FEC), etc.], or chain fluorinated carbonate [trifluorodimethyl carbonate (TFDMC), trifluorodiethyl carbonate (TFDEC), trifluoroethyl methyl carbonate (TFEMC) , Etc.], fluorinated ether [Rf ² —OR ⁴ (where Rf ² is an alkyl group containing fluorine, R ⁴ is an organic group which may contain fluorine], phosphoric acid ester [ Ethyl diethylphosphonoacetate _{(EDPA) :( C 2 H 5} O) 2 (P = O) -CH 2 (C = O) OC 2 H 5], trisphosphate (trifluoroethyl) (TFEP) :( CF ₃ CH2O) ₃ P = O, triphenyl phosphate _{(TPP) :( C 6 H 5} O) 3 P = O , etc.] or the like (including derivatives of the above compounds).

  The non-aqueous electrolyte can also be used as a gel electrolyte using a known gelling agent such as a polymer.

<Negative electrode>
For the negative electrode according to the nonaqueous secondary battery of the present invention, for example, a negative electrode mixture layer containing a negative electrode active material, a binder and the like can be used on one or both sides of the current collector.

As the negative electrode active material contained in the negative electrode mixture layer, a material containing an element that can be alloyed with lithium is used. Examples of the material containing an element that can be alloyed with lithium include a metal that can be alloyed with lithium (Si, Sn, etc.) or an alloy thereof, but the general composition formula SiO _x (where the atomic ratio x of O to Si is And 0.5 ≦ x ≦ 1.5.) A material containing Si and O represented by Hereinafter, a material containing Si and O as constituent elements is referred to as “SiO _x ”.

The SiO _x is not limited to an oxide of Si, and may be a complex oxide of Si and another metal (for example, B, Al, Ga, In, Ge, Sn, P, Bi, etc.) Further, it may contain a crystallite or amorphous phase of Si or another metal, and it is sufficient that the atomic ratio x of O to Si satisfies 0.5 ≦ x ≦ 1.5 as a whole.

The aforementioned SiO _x, for example, a SiO ₂ matrix of amorphous Si (e.g., microcrystalline Si) is include the dispersed structure, the SiO ₂ of the amorphous, therein In combination with the dispersed Si, it is sufficient that the atomic ratio x satisfies 0.5 ≦ x ≦ 1.5. For example, in the case of a material having a structure in which Si is dispersed in an amorphous SiO ₂ matrix and the molar ratio of SiO ₂ to Si is 1: 1, x = 1. Is done. In the case of a material having such a structure, for example, in X-ray diffraction analysis, a peak due to the presence of Si (microcrystalline Si) may not be observed, but when observed with a transmission electron microscope, the presence of fine Si Can be confirmed. As the particle size of SiO _x , in order to enhance the effect of compounding with the carbon material described later, and to prevent miniaturization during charge and discharge, a laser diffraction scattering type particle size distribution measuring device, for example, “MICRO As the number average particle diameter measured by “Track HRA” or the like, a particle having a particle diameter of about 0.5 to 10 μm is preferably used.

By the way, since the SiO _x has poor conductivity, when it is used alone as a negative electrode active material, a conductive aid such as a carbon material is required from the viewpoint of ensuring good battery characteristics. However, rather than using a mixture obtained by simply mixing SiO _x with a carbon material as a negative electrode active material, a composite having SiO _x as a core material and a carbon coating layer formed on the surface (hereinafter referred to as SiO _x). / Carbon composite) is preferably used. In this case, a conductive network in the negative electrode is favorably formed, and the load characteristics of the nonaqueous secondary battery can be improved.

Further, when using a SiO _x / carbon composite as the negative electrode active material, the storage characteristics are maintained while maintaining the characteristics of high capacity by optimizing the amount and state of carbon deposited on the surface of the core material. Can be improved.

The above-mentioned SiO _{x serving as the} core material can be produced by a conventionally known method. The SiO _x, other primary particles of SiO _x, and SiO _x composite particles comprising a plurality of particles, for the purpose of increasing the conductivity of the core material, granular material or the like which the SiO _x was granulated with a carbon material Is mentioned.

In addition, the SiO _x / carbon composite may be formed by, for example, heating the SiO _x particles and the hydrocarbon-based gas in a gas phase to convert the carbon generated by the thermal decomposition of the hydrocarbon-based gas to the surface of the SiO _x particles. Obtained by depositing on top. By producing using the vapor phase growth (CVD) method in this way, the hydrocarbon-based gas spreads to every corner of the SiO _x particles, and the conductive carbon material in the surface of the particles and in the pores of the surface Since a thin and uniform film (carbon coating layer) containing can be formed, conductivity can be imparted to the SiO _x particles with good uniformity with a small amount of carbon material.

  About the processing temperature (atmosphere temperature) of the said vapor phase growth (CVD) method, although it changes also with the kind of said hydrocarbon gas, 600-1200 degreeC is suitable normally, and it may be 700 degreeC or more especially. Preferably, the temperature is 800 ° C. or higher. This is because the higher the treatment temperature, the less the remaining impurities, and the formation of a coating layer containing carbon having high conductivity.

  As the liquid source of the hydrocarbon 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 coating the surface of SiO _x particles with a carbon material using the above-mentioned vapor deposition (CVD) method, petroleum pitch, coal pitch, thermosetting resin, and naphthalene sulfonate and aldehydes At least one organic compound selected from the group consisting of condensates may be attached to a coating layer containing a carbon material, and the particles to which the organic compound is attached may be fired. Specifically, a dispersion liquid in which SiO _x particles whose surface is coated with a carbon material and an organic compound are dispersed in a dispersion medium is prepared, and the dispersion liquid is sprayed and dried to obtain particles coated with the organic compound. The particles formed and coated with the organic compound are fired.

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

As the dispersion medium for dispersing the SiO _x particles whose surface is 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 .

If the amount of carbon deposited on the surface of the core material SiO _x is too small, the capacity drop after storage is large, and if it is too large, the effect of using the high capacity SiO _x may not be sufficiently secured. Therefore, 10 to 30% by mass is preferable with respect to the total amount of the composite of SiO _x and the carbon material.

When the surface of the core material is exposed, the capacity tends to decrease after storage, so the higher the ratio of the surface of the core material covered with carbon, the better. For example, when measuring the Raman spectra of the SiO _x / carbon composite at a measurement laser wavelength 532 nm, the peak intensity of 510 cm ^-1 originating from Si: and I _510, a peak intensity of 1343cm ^-1, which derived from the carbon (C): intensity ratio I ₅₁₀ / I ₁₃₄₃ and I ₁₃₄₃ is preferably 0.25 or less. A smaller intensity ratio I ₅₁₀ / I ₁₃₄₃ means a higher carbon coverage.

The intensity ratio I ₅₁₀ / I ₁₃₄₃ of the above Raman spectrum is obtained by mapping the SiO _x / carbon complex by micro Raman spectroscopy (measurement range: 80 × 80 μm, 2 μm step), and averaging all spectra in the measurement range. Te is a value determined by the intensity ratio between the peak (1343cm ^-1) derived from the C-peak (510 cm ^-1) derived from Si.

When the SiO _x / carbon composite is used as the negative electrode active material, if the crystallite size of the Si phase contained in the core material is too small, there is a possibility that the capacity drop after storage may increase, so CuKα radiation was used. The half width of the (111) diffraction peak of Si obtained by the X-ray diffraction method is preferably less than 3.0 °, and more preferably 2.5 ° or less. On the other hand, if the crystallite size of the Si phase is too large, the initial charge / discharge capacity may be reduced. Therefore, the half width of the (111) diffraction peak of Si obtained by the X-ray diffraction method is 0.5. It is preferable that it is more than °.

The SiO _x / mean particle diameter D ₅₀ of the carbon composite material, from the viewpoint of suppressing the reduction capacity after repeated charging and discharging, preferably at 0.5μm or more, from the viewpoint of suppressing the expansion of the negative electrode caused by charging and discharging, It is preferable that it is 20 micrometers or less. The average particle diameter D ₅₀ referred to in this specification is a volume measured by dispersing the material in a medium that does not dissolve the resin using a laser scattering particle size distribution meter (for example, “LA-920” manufactured by Horiba, Ltd.). It is a standard average particle diameter.

The specific resistance value of the SiO _x is usually 10 ³ to 10 ⁷ kΩcm, whereas the specific resistance value of the carbon material covering the SiO _x is usually 10 ^{−5 to} 10 kΩcm.

In the negative electrode according to the nonaqueous secondary battery of the present invention, it is preferable to use a graphitic carbon material together with the above-mentioned SiO _x as the negative electrode active material. As the graphitic carbon material, those used in conventionally known non-aqueous secondary batteries are suitable. For example, natural graphite such as flake graphite; pyrolytic carbons, mesophase carbon micro beads (MCMB) ), And artificial graphite obtained by graphitizing easily graphitized carbon such as carbon fiber at 2800 ° C. or higher.

The content of SiO _x in the negative electrode active material is preferably 0.5% by mass or more in terms of Si from the viewpoint of increasing the capacity of the non-aqueous secondary battery and further improving the quick charge characteristics. The content is more preferably at least 2% by mass, and still more preferably at least 2% by mass. When the content of SiO _x is large, the initial capacity increases, but the capacity decrease due to charging / discharging tends to increase. Therefore, it is necessary to determine the amount of use based on the balance between the required capacity and the cycle characteristics. Therefore, in order to suppress the capacity decrease due to the charge / discharge due to the volume change of SiO _x accompanying the charge / discharge of the battery and improve the cycle characteristics of the battery, the content of SiO _x in the negative electrode active material is increased in the active material. Is preferably 20% by mass or less, more preferably 15% by mass or less, and still more preferably 10% by mass or less.

  Examples of the binder used in the negative electrode mixture layer include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyacrylate, polyimide, and polyamide. Imide and the like are preferably used.

  Moreover, you may add a conductive material to the said negative mix layer as a conductive support agent further. The conductive material is not particularly limited as long as it does not cause a chemical change in the non-aqueous secondary battery, and examples thereof include various carbon blacks such as acetylene black and ketjen black, carbon nanotubes, and carbon fibers. 1 type (s) or 2 or more types can be used.

  The negative electrode according to the present invention includes, for example, a negative electrode active material and a binder, and further, if necessary, a paste or slurry in which a conductive additive is dispersed in a solvent such as N-methyl-2-pyrrolidone (NMP) or water. A negative electrode mixture-containing composition was 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 pressing treatment as necessary. It is manufactured through a process. 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 (calculated from the mass and thickness of the negative electrode mixture layer per unit area laminated on the current collector) is preferably 1.0 to 1.9 g / cm ³ . As a composition of the said negative mix layer, it is preferable that the total amount of a negative electrode active material is 80-99 mass%, it is preferable that the quantity of a binder is 1-20 mass%, and when using a conductive support agent. Is preferably used in such a range that the total amount of the negative electrode active material and the amount of the binder satisfy the above preferred values.

In the negative electrode according to the present invention, the content per unit area of the negative electrode mixture layer of Si element contained in the negative electrode active material is 0.007 mg / cm ² from the viewpoint of further improving the quick charge characteristics of the nonaqueous secondary battery. in is preferably higher, more preferably 0.018 mg / cm ² or more, more preferably 0.1 mg / cm ² or more. If the content of Si element is too large, the initial capacity of the non-aqueous secondary battery is increased, but the cycle characteristics of the battery tend to be lowered. Therefore, the unit of the negative electrode mixture layer of Si element contained in the negative electrode active material The content per area is preferably less than 1.5 mg / cm ² , more preferably less than 1 mg / cm ² , and still more preferably less than 0.5 mg / cm ² .

  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 of the thickness is 5 μm in order to ensure mechanical strength. It is preferable that

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

As the positive electrode active material, 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 used in conventionally known non-aqueous secondary batteries. Specifically, Li _y CoO ₂ (where 0 ≦ y ≦ 1.1), Li _z NiO ₂ (where 0 ≦ z ≦ 1.1), Li _p MnO ₂ (wherein is 0 ≦ p ≦ 1.1.), Li q Co r M 2 1-r O 2 ( however, M ² is, Mg, Mn, Fe, Ni , Cu, Zn, Al, Ti, from Ge and Cr At least one metal element selected from the group consisting of 0 ≦ q ≦ 1.1 and 0 <r <1.0), Li _s Ni _1-t M ³ _t O ₂ (where M ³ is at least one metal element selected from the group consisting of Mg, Mn, Fe, Co, Cu, Zn, Al, Ti, Ge, and Cr, and 0 ≦ s ≦ 1.1, 0 <t < is _{1.0.), Li f Mn v} Ni w Co 1-vw O 2 ( provided that 0 ≦ f ≦ 1.1,0 <v < 1.0,0 <w <1.0.) Layered structure such as Li-containing transition metal oxides and the like having, may be used only one of these may be used in combination of two or more.

  As said binder, the same thing as the various binders illustrated previously as a binder of a negative electrode can be used.

  Examples of the conductive auxiliary include graphite (graphite carbon material) such as natural graphite (flaky graphite, etc.) and artificial graphite; acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black. Carbon black such as carbon fiber; carbon material such as carbon fiber;

  The positive electrode according to the present invention is prepared, for example, by preparing 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. It may be dissolved), and this is applied to one or both sides of the current collector, dried, and then subjected to a step of pressing as necessary. 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. The density of the positive electrode mixture layer is calculated from the mass and thickness of the positive electrode mixture layer per unit area laminated on the current collector, and is preferably 3.0 to 4.5 g / cm ³ . As the composition of the positive electrode mixture layer, for example, the amount of the positive electrode active material is preferably 60 to 95% by mass, the amount of the binder is preferably 1 to 15% by mass, and the amount of the conductive auxiliary agent is It is preferable that it is 3-20 mass%.

  As the current collector of the positive electrode, the same one used for the positive electrode of a conventionally known non-aqueous secondary battery can be used, for example, from aluminum, stainless steel, nickel, titanium or an alloy thereof. Foil, punched metal, expanded metal, net, and the like, and aluminum foil having a thickness of 10 to 30 μm is preferably used.

The negative electrode and the positive electrode are laminated with a separator, which will be described later, sandwiched between them, and a laminated electrode body in which these are opposed via a separator, or a laminated body in which a negative electrode and a positive electrode are laminated via a separator are spirally wound. As a wound electrode body wound in a shape, it is used for a non-aqueous secondary battery. In a non-aqueous secondary battery, the capacity (mAh) is divided by the facing area between the positive electrode mixture layer and the negative electrode mixture layer (the area of the portion facing through the separator. Unit: cm ₂ ). capacitance per unit area obtained Te (hereinafter, referred to as "capacity per electrode facing area".) of preferably less than 3.3mAh / cm ^2, more preferably less than 3.0 mAh / cm ² More preferably, it is less than 2.8 mAh / cm ² . By using the non-aqueous secondary battery having a small capacity per unit area, it is possible to suppress an increase in battery voltage during rapid charging of the non-aqueous secondary battery. However, if the capacity per electrode facing area is too small, the energy density of the non-aqueous secondary battery is lowered. Therefore, the capacity per electrode facing area in the non-aqueous secondary battery is 1 mAh / cm ² or more. Preferably there is.

  The capacity of the nonaqueous secondary battery used for calculating the capacity per electrode facing area is a value determined by the following method. A non-aqueous secondary battery was charged at a constant current at a current value of 1.0 C at 25 ° C., and charged at a constant voltage after reaching a fully charged voltage (4.2 V in the examples described later). When the total charging time is 2.5 hours, the charging is finished. About the non-aqueous secondary battery after charge, it discharged at 0.2 C, and when discharge final voltage (it was set as 3V in the below-mentioned Example), discharge was stopped and discharge electric energy was calculated | required, and this discharge electric energy was calculated | required. Capacity.

  When the positive electrode is smaller than the negative electrode and all of the positive electrode mixture layer faces the negative electrode mixture layer, the capacity per electrode facing area is the capacity of the nonaqueous secondary battery as the area of the positive electrode mixture layer. The value divided by.

  In the present invention, when the mass of the positive electrode active material is P and the mass of the negative electrode active material 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 lowered to limit the charge electric capacity, and the volume change of the negative electrode active material accompanying the above-described charge / discharge can be suppressed, and the negative electrode active material particles It is possible to suppress a decrease in cycle characteristics due to pulverization or the like. Moreover, a high battery capacity is securable by making P / N ratio into 1.0 or more.

<Separator>
As the separator according to the nonaqueous secondary battery of the present invention, a separator having sufficient strength and capable of holding a large amount of nonaqueous electrolyte is preferable. For example, polyethylene having a thickness of 5 to 50 μm and an opening ratio of 30 to 70% A microporous membrane made of polyolefin such as (PE) or polypropylene (PP) can be used. 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.

  Further, as a separator, a porous layer (A) mainly composed of a resin having a melting point of 140 ° C. or lower and a porous layer (B) mainly including 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 a laminated separator composed of) can also be used. The porous layer (A) is mainly for ensuring a shutdown function, and when the non-aqueous secondary battery reaches a temperature equal to or higher than the melting point of the resin that is the main component of the porous layer (A), 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. On the other hand, the porous layer (B) 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 rises, and has a melting point of 150 ° C. The function is ensured by the above resin or the 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. Can prevent short circuit due to contact. 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. Here, the “melting point” means a melting temperature measured using a differential scanning calorimeter (DSC) in accordance with the provisions of Japanese Industrial Standard (JIS) K 7121, and “a heat-resistant temperature is 150 ° C. or higher”. Means that no deformation such as softening is observed at least at 150 ° C.

  The thickness of a separator (a separator made of a microporous membrane made of polyolefin or the above laminated separator) according to the nonaqueous secondary battery of the present invention is more preferably 10 to 30 μm.

  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 and the like may be used.

  In addition, when introducing the positive electrode, the negative electrode, and the separator into the non-aqueous secondary battery, depending on the form of the battery, a laminated electrode body in which a plurality of positive electrodes and a plurality of negative electrodes are stacked via a separator, or a positive electrode and a negative electrode Can be used as a wound electrode body obtained by laminating a film through a separator and then winding it in a spiral shape.

  Hereinafter, a non-aqueous secondary battery pack using the non-aqueous secondary battery of the present invention will be described with reference to the drawings.

  FIG. 1 is a circuit diagram showing an example of a non-aqueous secondary battery pack using the non-aqueous secondary battery of the present invention. The non-aqueous secondary battery pack shown in FIG. 1 has a non-aqueous secondary battery 100, a PTC (Positive Temperature Coefficient) element (PTC thermistor) 101, a protection circuit 102, and external terminals + IN and -IN. These are connected by lead wires, and supply of electric power to the external load or charging from the outside is performed from the positive terminal and the negative terminal of the non-aqueous secondary battery 100 via the external terminals + IN and −IN.

  The PTC element 101 has a function of cutting off current in response to a temperature rise. The protection circuit 102 includes a field effect transistor (FET) 103a which is a switching element for turning on / off a discharge current, a FET 103b which is a switching element for turning on / off a charging current, and a battery voltage at the time of charging / discharging. And a control unit 104 that detects the voltage between the FETs 103a and 103b and controls the operation of the FETs 103a and 103b based on the detected voltage. It has a function for protecting the battery.

  The non-aqueous secondary battery pack may have a structure in which components such as the non-aqueous secondary battery 100, the PTC element 101, and the protection circuit 102 shown in FIG.

  In FIG. 1, an example of a non-aqueous secondary battery pack having one non-aqueous secondary battery 100 is shown. However, the non-aqueous secondary battery pack has a non-aqueous secondary battery 100 according to a required capacity. You may have two or more.

  Here, in this specification, in the charging / discharging path (path between the nonaqueous secondary battery 100 and the external terminals + IN, −IN) so as to provide a function of controlling the charging / discharging current for battery protection. Each element connected to is referred to as a protection element. In FIG. 1, the PTC element 102, the FET 103 a, and the FET 103 b correspond to protection elements, and in the following description, the PTC element 102 and the FETs 103 a and 103 b are collectively described as a protection element group 105. The protection element group refers to the entire element that contributes to the resistance component of the protection element existing between terminals for detecting voltage from the outside by a pack or module.

  Usually, in the constant current-constant voltage charging of the nonaqueous secondary battery pack, the capacity per unit time in the constant current charging period is larger than the charging capacity per unit time in the constant voltage charging period. Therefore, the time from the start of charging the non-aqueous secondary battery pack to the fully charged state can be greatly shortened by increasing the region where constant current charging is possible and increasing the charging current.

  As a result of extensive studies by the present inventors, a battery pack having a capacity of 1.5 Ah was produced using a non-aqueous secondary battery containing a material containing an element that can be alloyed with lithium as a negative electrode active material. The total impedance (hereinafter referred to as the protection element group impedance) corresponding to the ratio of the current impedance due to the non-aqueous secondary battery is changed from 0.08Ω to 0.015Ω, and 1.5C It has been found that when charging at a current value, it can be charged up to 80% of the battery pack capacity by constant current charging. Based on this knowledge, the voltage rise of the non-aqueous secondary battery pack during charging is reduced by adjusting the protection element group impedance and the capacity of the non-aqueous secondary battery to a specific relationship. In such a case, it is possible to secure a constant current charging area that cannot be assumed, and to suppress the attenuation of current as much as possible during charging, greatly increasing its rapid charging characteristics without requiring special operations such as forced cooling, For example, it has been found that the time from the start of charging to the fully charged state can be greatly shortened as compared with the conventional method of charging at a current value of 1 C or less.

  In the non-aqueous secondary battery pack using the non-aqueous secondary battery of the present invention, when the protective element group impedance is PR (Ω) and the capacity of the non-aqueous secondary battery is Q (Ah), the protective element impedance capacity The index is expressed as PR / Q (Ω / Ah). The protective element impedance capacity index PR / Q is preferably 0.03 or less, more preferably 0.02 or less, and still more preferably 0.012 or less. By setting the protective element impedance capacity index to the above value, the constant current charging time during charging of the non-aqueous secondary battery pack can be extended, and the rapid charging characteristics can be improved.

  Further, when the impedance of the non-aqueous secondary battery of the present invention used for the non-aqueous secondary battery pack is CR (Ω) and the capacity of the non-aqueous secondary battery is Q (Ah), the non-aqueous secondary battery The impedance capacity index is expressed as CR / Q (Ω / Ah). Here, when a plurality of batteries are controlled in parallel, CR and Q are expressed as impedance and capacity of the whole battery controlled in parallel. The non-aqueous secondary battery impedance capacity index CR / Q is preferably 0.04 or less, more preferably 0.03 or less, and further preferably 0.025 or less. By setting the non-aqueous secondary battery impedance capacity index to the above value, the resistance component of the non-aqueous secondary battery is reduced, and the constant current charging time during charging of the non-aqueous secondary battery pack can be extended, Rapid charging characteristics can be enhanced.

  The protective element impedance capacity index PR / Q is preferably as small as possible, but is usually 0.002 or more because of technical limitations. Similarly, the non-aqueous secondary battery impedance capacity index CR / Q is preferably as small as possible, but is usually 0.001 or more because of technical limitations.

  The impedance Z for calculating the protective element impedance capacity index PR / Q or the non-aqueous secondary battery impedance capacity index CR / Q is measured using an LCR meter at 25 ° C. and 1 kHz. Use the value.

  Moreover, the value calculated | required with the following method is used for the capacity | capacitance Q of the non-aqueous secondary battery for calculating the said protection element impedance capacity index PR / Q or the said non-aqueous secondary battery impedance capacity index CR / Q. That is, a non-aqueous secondary battery was charged at a constant current at a current value of 1.0 C at 25 ° C., charged at a constant voltage after reaching a full charge voltage (4.2 V in the example), and the total charge time When the battery reaches 2.5 hours, charging is terminated. About the non-aqueous secondary battery after charge, it discharges at 0.2C, and when discharge end voltage (3V in an Example) is reached | attained, discharge is stopped | required and discharge electric charge is calculated | required, and this discharge electric charge is made into the capacity | capacitance Q.

The protective element impedance capacity index PR / Q can be adjusted by adjusting the protective element group impedance PR and the capacity Q of the non-aqueous secondary battery, respectively. Various methods are known as methods for adjusting the capacity Q of the non-aqueous secondary battery. In the present invention, these methods can be employed as long as the effects of the present invention are not impaired. In the non-aqueous secondary battery of the present invention, as described above, the negative electrode is made of, for example, SiO _x or a composite of SiO _x and a carbon material having a higher capacity than a carbon material widely used as a conventional negative electrode active material. Although used for at least a part of the active material, this is also mentioned as a method for adjusting the capacity of the non-aqueous secondary battery.

  Moreover, as a method for adjusting the protection element group impedance PR, there is a method of using a PTC element as a protection element and a FET having a small resistance value for each of the FETs included in the protection circuit. For example, for PTC elements and FETs, conventional non-aqueous secondary battery packs for mobile phones (non-aqueous secondary battery packs with a capacity that can be fully charged if charged for about 1 hour at a current value of 1 C or less) It is preferable to select one having a resistance value lower than that employed in the above. In particular, by using a FET having a low resistance value, or by connecting FETs in parallel to lower the resistance of the entire path, it is possible to greatly contribute to a reduction in impedance of the entire non-aqueous secondary battery pack.

  As described above, in order to improve the quick charge characteristics of the non-aqueous secondary battery pack, it is preferable to increase the charging current value in the constant current-constant voltage charging and to increase the chargeable region by the constant current charging. Specifically, the capacity that can be charged by constant current charging is preferably more than 60%, more preferably 70%, of the capacity of the non-aqueous secondary battery pack.

  The non-aqueous secondary battery pack has a slope k40 at a SOC of 40% of a voltage (mV) -SOC (ratio of charge capacity to standard capacity) (%) curve obtained when charged at a current value of 1.5 C. Is preferably small. The slope k40 is obtained by extending a tangent line at SOC 40% of the voltage-SOC curve from SOC 35% to SOC 45%, obtaining a voltage difference at each SOC, and calculating the value as a voltage increase value (mV) with respect to a change in SOC 10%. ). Therefore, in this specification, the slope k40 is described as a voltage increase value (mV) / 10% SOC.

  It means that the smaller the value of the slope k40, the larger the chargeable capacity because the voltage increase in constant current charging of the non-aqueous secondary battery pack is small. Therefore, the quick charge characteristic of the nonaqueous secondary battery pack can be improved by reducing the value of the slope k40. Specifically, the slope k40 is preferably 90 mV / 10% SOC or less, more preferably 50 mV / 10% SOC or less, still more preferably 10 mV / 10% SOC or less. Further, the inclination k40 is usually larger than 1 mV / 10% SOC.

The inclination k40 can be reduced by using a material containing an element that can be alloyed with lithium, particularly SiO _x , as the negative electrode active material for the non-aqueous secondary battery constituting the non-aqueous secondary battery pack. In addition, when the above SiO _x is used for the negative electrode active material, the slope k40 can be improved more by adjusting the content per unit area of the negative electrode mixture layer of Si contained in the negative electrode active material to the above value. Can be adjusted.

  As described above, the non-aqueous secondary battery pack using the non-aqueous secondary battery of the present invention can secure good quick charge characteristics while increasing the capacity. It can be preferably used for various uses to which a conventionally known non-aqueous secondary battery pack is applied, including the power source of portable devices. For example, when the non-aqueous secondary battery pack using the non-aqueous secondary battery of the present invention is installed in a conventional charging device (constant current / constant voltage charging device, pulse charging device, etc.), rapid charging is possible. It is possible to configure a simple charging system, and it is possible to implement a charging method capable of rapid charging with such a charging system.

  Hereinafter, the present invention will be described in detail using examples. However, the present invention is not limited to the following examples.

Example 1
<Preparation of positive electrode>
LiCoO _{2 as} positive electrode active material: 80 parts by mass and LiMn _0.2 Ni _0.6 Co _0.2 O ₂ : 20 parts by mass, artificial graphite as conductive aid: 1 part by mass and Ketjen black: 1 part by mass, binder PVDF: 10 parts by mass was mixed with NMP as a solvent uniformly to prepare a positive electrode mixture-containing paste. Then, the obtained positive electrode mixture-containing paste was intermittently applied and dried on both sides of a current collector made of an aluminum foil having a thickness of 15 μm, and then calendered to give a total thickness of 120 μm. Then, the thickness of the positive electrode mixture layer was adjusted so that the width was 54.5 mm, and a positive electrode was produced. 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>
Negative electrode active material in which the mean particle size D _50: mixture SiO _x / carbon composite and an average particle diameter D ₅₀ of 5μm was mixed with graphitic carbon is 16μm at a weight ratio 5:95: 98 parts by weight, A binder having a viscosity of 1500 to 5000 mPa · s and a CMC aqueous solution having a concentration of 1% by mass: 1.0 part by mass and SBR: 1.0 part by mass, and a specific conductivity of 2. A water-based negative electrode mixture-containing paste was prepared by mixing with ion exchange water of 0 × 10 ⁵ Ω / cm or more.

The coating amount of carbon in the SiO _x / carbon composite is 20% by mass, the I ₅₁₀ / I ₁₃₄₃ intensity ratio of the Raman spectrum at a measurement laser wavelength of 532 nm is 0.10, and X of SiO _x using CuKα rays The half width of the Si (111) diffraction peak in the line diffraction measurement was 1.0 °.

  Next, the negative electrode mixture-containing paste was intermittently applied and dried on both sides of a current collector made of a copper foil having a thickness of 8 μm, and then subjected to a calendering treatment to a total thickness of 108 μm. The thickness of the negative electrode mixture layer was adjusted so that the width was 55.5 mm, and a negative electrode was produced. Further, a tab was welded to the exposed portion of the copper foil of the negative electrode to form a lead portion.

Area of the negative electrode mixture layer in the negative electrode is 599Cm ^2, the content per unit area of the negative electrode mixture layer of Si element contained in the negative electrode active material was 0.14 mg / cm ^2.

<Preparation of separator>
To 5 kg of boehmite having an average particle diameter D ₅₀ of 1 μm, 5 kg of ion-exchanged water and 0.5 kg of a dispersant (aqueous polycarboxylic acid ammonium salt, solid content concentration of 40% by mass) are added, and the internal volume is 20 L and the number of turns is 40 times. A dispersion was prepared by pulverizing with a ball mill for 10 hours per 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 resin binder dispersion (modified polybutyl acrylate, solid content 45% by mass) as a binder are added and stirred for 3 hours with a stirrer to form a uniform slurry. [Slurry for forming porous layer (B), solid content ratio 50 mass%] was prepared.

Next, a microporous separator made of PE for a non-aqueous secondary battery [porous layer (A): thickness 12 μm, porosity 40%, average pore diameter 0.08 μm, PE melting point 135 ° C.], corona discharge treatment on one side. (Discharge amount 40 W · min / m ² ) is applied, 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. Thus, a laminated 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>
LiPF ₆ as an electrolyte salt is dissolved at a concentration of 1.1 mol / dm ³ in a mixed solvent in which EC, MEC and DEC are mixed at a volume ratio of 1: 0.5: 1.5, and VC, FEC and EDPA, LiPF ₂ (C ₂ O ₄ ) ₂ , which is a fluorine-containing organometallic salt having an oxalic acid group, amounts to 2.5% by mass, 1.75% by mass, 1.00% by mass, and 1.00% by mass, respectively. In addition, a non-aqueous electrolyte was prepared.

<Battery assembly>
The above-described positive electrode and the above-described negative electrode were overlapped with each other so that the porous layer (B) of the separator faced 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, put into an aluminum alloy outer can having a thickness of 5 mm, a width of 42 mm, and a height of 61 mm, and the above non-aqueous electrolyte was injected. Then, after injecting the non-aqueous electrolyte, the outer can was sealed, and a non-aqueous secondary battery having the appearance shown in FIG. 3 with the structure shown in FIGS. 2A and 2B was produced.

  Here, the battery shown in FIGS. 2A, 2B and 3 will be described. FIG. 2A is a plan view, FIG. 2B is a cross-sectional view, and as shown in FIG. After being wound in a spiral shape, it is pressurized so as to be flat and is accommodated in a rectangular tube-shaped outer can 4 together with a non-aqueous electrolyte as a flat wound electrode body 6. However, in FIG. 2B, in order to avoid complication, the metal foil, the electrolytic solution, and the like as the current collector used in the production of 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, From the flat wound electrode body 6 which consists of the positive electrode 1, the negative electrode 2, and the separator 3, it is in each one end of the positive electrode 1 and the negative electrode 2 The connected positive electrode lead body 7 and negative electrode lead body 8 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 the 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. 2A and 2B, the lid plate 9 is provided with a non-aqueous electrolyte inlet 14, and a sealing member is inserted into the non-aqueous electrolyte inlet 14, for example, a laser. The battery is hermetically sealed by welding or the like, so that the battery is sealed. Therefore, in the batteries of FIGS. 2A, 2B, and 3, the non-aqueous electrolyte inlet 14 is actually a non-aqueous electrolyte inlet and a sealing member. An electrolyte inlet 14 is shown. 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 nonaqueous secondary battery of Example 1, the outer can 4 and the cover plate 9 function as a positive electrode terminal by directly welding the positive electrode lead body 7 to the cover plate 9, and the negative electrode lead body 8 is connected to the lead plate 13. The terminal 11 functions as a negative electrode terminal by welding and connecting 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 positive or negative. It may be the opposite.

  FIG. 3 is a perspective view schematically showing the appearance of the battery shown in FIGS. 2A and 2B. FIG. 3 is shown for the purpose of showing that the battery is a square battery. FIG. 3 schematically shows the battery, and only specific members among the members constituting the battery are shown. Not shown. Also, in FIG. 2B, the central portion of the spirally wound electrode body 6 and the separator 3 are not displayed with hatching indicating a cross section.

Regarding the nonaqueous secondary battery of Example 1, the capacity was 1.58 Ah, the capacity per electrode facing area was 2.8 mAh / cm ² , the impedance was 0.033Ω, and the impedance capacity index was 0.021Ω / Ah. .

In addition, the nonaqueous secondary battery of Example 1 was decomposed after discharge in an argon dry box after battery formation, washed with DEC, vacuum dried, and then subjected to XPS analysis of the negative electrode. In this XPS analysis, an X-ray photoelectron spectrometer “ESCA5500MC” manufactured by ULVAC-PHI is used as an instrument, an analysis aperture diameter is 800 μm, an X-ray source is MgKα400W (15 kV), and a photoelectron extraction angle is 45 degrees. , Went without using a neutralizing gun. As a result, the intensity ratio I ₆₈₅ / I ₂₈₅ between the intensity I ₂₈₅ of the 1S spectrum of C near 284-285 eV and the intensity I ₆₈₅ of the 1S spectrum of F near 684-686 eV was 0.5. A peak was detected at 288 eV.

<Assembly of non-aqueous secondary battery pack>
The non-aqueous secondary battery of Example 1 described above, a protection circuit in which two FETs having a resistance value of 0.01Ω are connected in parallel, and a PTC element having a resistance value of 0.01Ω are used. The non-aqueous secondary battery pack of Example 1 was assembled by connecting with lead wires and housed in an exterior body.

  Regarding the nonaqueous secondary battery pack of Example 1, the protective element group impedance was 0.018Ω, and the protective element impedance capacity index was 0.011Ω / Ah.

(Example 2)
The non-aqueous solution of Example 2 was obtained in the same manner as in Example 1 except that the content of LiPF ₂ (C ₂ O ₄ ) ₂ , which is a fluorine-containing organometallic salt having an oxalic acid group, was changed to 0.3% by mass. A secondary battery was produced.

Regarding the nonaqueous secondary battery of Example 2, the capacity was 1.58 Ah, the capacity per electrode facing area was 2.8 mAh / cm ² , the impedance was 0.033Ω, and the impedance capacity index was 0.021Ω / Ah. . Further, after the battery formation, the XPS analysis of the negative electrode was performed in the same manner as in Example 1. As a result, the 1S spectrum intensity I ₂₈₅ in the vicinity of 284-285 eV and the 1S spectrum intensity I _{685 in the} vicinity of 684-686 eV were obtained. The intensity ratio I ₆₈₅ / I ₂₈₅ was 0.6.

  A nonaqueous secondary battery pack of Example 2 was produced in the same manner as Example 1 except that the nonaqueous secondary battery of Example 2 was used.

  Regarding the nonaqueous secondary battery pack of Example 2, the protective element group impedance was 0.018Ω, and the protective element impedance capacity index was 0.011Ω / Ah.

(Example 3)
Example 3 is the same as Example 2 except that LiBF ₂ (C ₂ O ₄ ) is used instead of LiPF ₂ (C ₂ O ₄ ) ₂ as the fluorine-containing organometallic salt having an oxalic acid group. A non-aqueous secondary battery was produced.

Regarding the nonaqueous secondary battery of Example 3, the capacity was 1.58 Ah, the capacity per electrode facing area was 2.8 mAh / cm ² , the impedance was 0.033Ω, and the impedance capacity index was 0.021Ω / Ah. . Further, after the battery formation, the XPS analysis of the negative electrode was performed in the same manner as in Example 1. As a result, the 1S spectrum intensity I ₂₈₅ in the vicinity of 284-285 eV and the 1S spectrum intensity I _{685 in the} vicinity of 684-686 eV were obtained. The intensity ratio I ₆₈₅ / I ₂₈₅ was 0.7.

  A nonaqueous secondary battery pack of Example 3 was produced in the same manner as Example 1 except that the nonaqueous secondary battery of Example 3 was used.

  For the nonaqueous secondary battery pack of Example 3, the protective element group impedance was 0.018Ω, and the protective element impedance capacity index was 0.011Ω / Ah.

Example 4
In the same manner as in Example 2 except that C ₆ H ₄ (COOLi) ₂ was used in place of LiPF ₂ (C ₂ O ₄ ) ₂ as the fluorine-containing organometallic salt having an oxalic acid group, A non-aqueous secondary battery was produced.

Regarding the nonaqueous secondary battery of Example 4, the capacity was 1.58 Ah, the capacity per electrode facing area was 2.8 mAh / cm ² , the impedance was 0.033Ω, and the impedance capacity index was 0.021Ω / Ah. . Further, after the battery formation, the XPS analysis of the negative electrode was performed in the same manner as in Example 1. As a result, the 1S spectrum intensity I ₂₈₅ in the vicinity of 284-285 eV and the 1S spectrum intensity I _{685 in the} vicinity of 684-686 eV were obtained. The intensity ratio I ₆₈₅ / I ₂₈₅ was 0.7.

  A nonaqueous secondary battery pack of Example 4 was produced in the same manner as Example 1 except that the nonaqueous secondary battery of Example 4 was used.

  Regarding the nonaqueous secondary battery pack of Example 4, the protective element group impedance was 0.018Ω, and the protective element impedance capacity index was 0.011Ω / Ah.

(Comparative Example 1)
In a mixture of EC, MEC and DEC at a volume ratio of 1: 0.5: 1.5, LiPF ₆ was dissolved as a lithium salt at a concentration of 1.1 mol / dm ³ , and VC, FEC and EDPA were further added. The non-aqueous electrolyte of Comparative Example 1 was prepared in the same manner as in Example 1 except that 2.5% by mass, 1.75% by mass and 1.00% by mass were respectively added to prepare and use the non-aqueous electrolyte. A secondary battery was produced.

Regarding the nonaqueous secondary battery of Comparative Example 1, the capacity was 1.58 Ah, the capacity per electrode facing area was 2.8 mAh / cm ² , the impedance was 0.033Ω, and the impedance capacity index was 0.021Ω / Ah. . Further, after the battery formation, the XPS analysis of the negative electrode was performed in the same manner as in Example 1. As a result, the 1S spectrum intensity I ₂₈₅ in the vicinity of 284-285 eV and the 1S spectrum intensity I _{685 in the} vicinity of 684-686 eV were obtained. The intensity ratio I ₆₈₅ / I ₂₈₅ was 2.3.

  Further, a nonaqueous secondary battery pack of Comparative Example 1 was produced in the same manner as in Example 1 except that the nonaqueous secondary battery of Comparative Example 1 was used.

  Regarding the nonaqueous secondary battery pack of Comparative Example 1, the protective element group impedance was 0.018Ω, and the protective element impedance capacity index was 0.011Ω / Ah.

(Comparative Example 2)
As the negative electrode active material, instead of the mixture of SiO _x / carbon composite and graphitic carbon material, only the graphite carbon material is used, and the negative electrode capacity is reduced by this, and the negative electrode mixture layer is made thicker. Then, a negative electrode was produced in the same manner as in Example 1 except that the capacity was almost the same as that of the negative electrode produced in Example 1. A nonaqueous secondary battery of Comparative Example 2 was produced in the same manner as Comparative Example 1 except that the size of the outer can was changed in accordance with the change in the thickness of the negative electrode.

Regarding the nonaqueous secondary battery of Comparative Example 2, the capacity was 1.58 Ah, the capacity per electrode facing area was 2.8 mAh / cm ² , the impedance was 0.037Ω, and the impedance capacity index was 0.023Ω / Ah. . Further, after the battery formation, the XPS analysis of the negative electrode was performed in the same manner as in Example 1. As a result, the 1S spectrum intensity I ₂₈₅ in the vicinity of 284-285 eV and the 1S spectrum intensity I _{685 in the} vicinity of 684-686 eV were obtained. The intensity ratio I ₆₈₅ / I ₂₈₅ was 2.4.

  A non-aqueous secondary battery pack of Comparative Example 2 was produced in the same manner as Example 1 except that the non-aqueous secondary battery of Comparative Example 2 was used. With respect to the obtained nonaqueous secondary battery pack, the protective element group impedance was 0.018Ω, and the protective element impedance capacity index was 0.011Ω / Ah.

(Comparative Example 3)
Except for using the non-aqueous secondary battery of Comparative Example 1, a protection circuit including one FET having a resistance value of 0.05Ω, and a PTC element having a resistance value of 0.03Ω, the same as in Example 1, A non-aqueous secondary battery pack of Comparative Example 3 was produced.

  Regarding the nonaqueous secondary battery pack of Comparative Example 3, the protective element group impedance was 0.08Ω, and the protective element impedance capacity index was 0.051Ω / Ah.

(Cycle characteristics)
In order to evaluate the cycle characteristics of the batteries, the nonaqueous secondary batteries of Examples 1 to 4 and Comparative Example 1 were used, charged at a 1C rate, charged at a constant voltage after reaching 4.2V, and current values. Was stopped at the time when the current became 0.05 C (5% current of 1 C), and then the battery was discharged to a voltage value of 3 V at a current value of 1 C. With this as one cycle, 40 charge / discharge cycles were repeated under the above conditions, and the capacities of the nonaqueous secondary batteries of Examples 1 to 4 and Comparative Example 1 after 40 cycles were determined. And the capacity ratio (%) of Examples 1-4 when the comparative example 1 was made into 100% was computed. If the capacity ratio is larger than 100%, it can be evaluated that the cycle characteristics are improved. Moreover, the capacity | capacitance reduction rate of the capacity | capacitance after 40 cycles with respect to the capacity | capacitance after 1 cycle of a charging / discharging cycle was computed about each non-aqueous secondary battery of Examples 1-4. It can be evaluated that the smaller the capacity reduction rate, the higher the effect of improving the cycle characteristics.

  Moreover, in order to confirm the addition effect of the fluorine-containing organometallic salt which has an oxalic acid group, about each non-aqueous secondary battery of Examples 1-4, the addition effect rate (using the capacity | capacitance reduction rate after 40 cycles mentioned above ( %) Was calculated. It can be evaluated that the effect of improving the cycle characteristics is higher as the additive effect rate is larger. For example, in the case of Example 1 to which a fluorine-containing organometallic salt having an oxalic acid group was added, the capacity reduction rate after 40 cycles was 2.7% (Table 1 described later), whereas the oxalic acid group Since the capacity reduction rate of Comparative Example 1 in which the fluorine-containing organometallic salt having γ is not added is 4.5% (Table 1 described later), the addition effect rate in Example 1 is (4.5 -2.7) ÷ 4.5 × 100 = 40 (%).

(Quick charge test)
A charging system was constructed by combining the non-aqueous secondary battery packs of Examples 1 to 4 and Comparative Examples 1 to 3 and the charging / discharging device, and a rapid charging test was performed using the charging method shown below.

  That is, using each of the charging systems described above, at 25 ° C., the voltage is a constant current of 1.5 C (corresponding to 2.37 A in the case of 1.58 Ah) for each capacity, and the charging voltage of the battery (in this case) The battery was charged until the voltage reached 4.2 V), and thereafter, constant current-constant voltage charging (cut-off current value was 0.05 C) was performed with a constant voltage maintaining the voltage. And the constant current charge time (minute) which is time until it switches to a constant voltage mode from charge start, and the time (minute) required for charge from SOC charge to SOC90% were measured.

  For each of the above Examples and Comparative Examples, the type of negative electrode active material and the content of Si per area of the negative electrode mixture layer, the type and content of fluorinated organometallic salt having an oxalic acid group, the capacity ratio after 40 cycles Table 1 shows the rate of decrease in capacity after 40 cycles, the effect of addition of a fluorine-containing organometallic salt having an oxalic acid group, and the slope at 40% SOC of the voltage-SOC curve obtained when charged at a current value of 1.5C. It was.

  “Voltage slope at 40% SOC” in Table 1 means the slope at 40% SOC of the voltage-SOC curve obtained when charging at a current value of 1.5C.

In addition, the impedance of the non-aqueous secondary battery, the capacity of the non-aqueous secondary battery, the impedance capacity index of the non-aqueous secondary battery, the intensity ratio I ₆₈₅ / I ₂₈₅ , the constant current charging time and the SOC 90 for each of the above examples and comparative examples. The time required for charging up to% is shown in Table 2.

From the results of Table 1, in Examples 1 to 4 in which a specific organic metal salt was added to the negative electrode active material using SiO _x / carbon composite, the capacity was higher than that in Comparative Example 1 even after 40 cycles. I understand. Moreover, when the comparative example 1 and Examples 1-4 are compared, it turns out that the capacity | capacitance reduction rate (%) after 40 cycles is significantly reduced rather than the comparative example 1. FIG.

From the results shown in Table 2, the nonaqueous secondary battery using the SiO _x / carbon composite as the negative electrode active material was used, and the impedance capacity index of the nonaqueous secondary battery was set to an appropriate value. It can be seen that the non-aqueous secondary battery pack can shorten the time required for charging up to SOC 90% in the quick charge test as compared with the non-aqueous secondary battery packs of Comparative Examples 1 to 3.

  The non-aqueous secondary battery pack takes a long time until the SOC reaches 90% in a low temperature environment (for example, 5 ° C.). By charging while heating up to (25 ° C.), it was possible to obtain a charging time substantially equivalent to that in the case of charging in a room temperature environment. Therefore, it was found that the non-aqueous secondary battery pack of the present invention can be rapidly charged by heating the pack itself even in a low temperature environment, and can be rapidly charged even in a wide temperature range.

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

100 Nonaqueous secondary battery 101 PTC element 102 Protection circuit 103a, 103b FET
DESCRIPTION OF SYMBOLS 104 Control part 105 Protection element group 1 Positive electrode 2 Negative electrode 3 Separator 4 Outer can 5 Insulator 6 Winding electrode body 7 Positive electrode lead body 8 Negative electrode lead body 9 Sealing lid plate 10 Insulation packing 11 Terminal 12 Insulator 13 Lead plate 14 Non Water electrolyte inlet 15 Cleavage vent

Claims (12)

A non-aqueous secondary battery including a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator,
The negative electrode includes a negative electrode mixture layer containing a material containing an element that can be alloyed with lithium as a negative electrode active material,
The non-aqueous electrolyte includes a fluorine-containing organometallic salt having an oxalic acid group.   2. The non-aqueous secondary battery according to claim 1, wherein a content of the fluorine-containing organometallic salt having an oxalic acid group is 0.01% by mass or more and less than 10% by mass in the non-aqueous electrolyte. In the XPS analysis of the negative electrode, the intensity ratio I ₆₈₅ / I ₂₈₅ between the intensity I ₂₈₅ of the C 1S spectrum near 284-285 eV and the intensity I ₆₈₅ of the 1S spectrum of F near 684-686 eV is less than 1.5 _. The non-aqueous secondary battery according to claim 1 or 2. The fluorine-containing organometallic salt having an oxalic acid group has the general formula (PF ₂ (C ₂ O ₄ ) ₂ ) _{b1 Mc 1} , (BF ₂ (C ₂ O ₄ )) _{b1 Mc 1} or M _b1 (PF ₄ (PF ₄ ( C ₂ O ₄ )) _c1
In the general formula, M is at least one metal element selected from the group consisting of Li, Na, K, Mg, Ca, Mn, and Al, and b1 and c1 are the valence of M and the valence of anions. The non-aqueous secondary battery according to claim 1, wherein the non-aqueous secondary battery is an integer that is determined. Fluorine-containing organic metal salt having the oxalic acid _{groups, LiPF 2 (C 2 O 4} ) 2 or LiBF ₂ (C ₂ O ₄₎ non-aqueous secondary according to claim 1 which is battery.   The non-aqueous secondary battery according to claim 1, wherein the material containing an element that can be alloyed with lithium is a material containing Si and O as constituent elements.   The material containing an element that can be alloyed with lithium is a composite in which a coating layer of carbon is formed on the surface of a core material containing Si and O as constituent elements. A non-aqueous secondary battery according to 1. The material containing Si and O as constituent elements is a material represented by a general composition formula SiO _x ,
8. The non-aqueous secondary battery according to claim 6, wherein x in the general composition formula is 0.5 ≦ x ≦ 1.5. The nonaqueous secondary according to any one of claims 6 to 8, wherein a content of the Si contained in the negative electrode active material per unit area of the negative electrode mixture layer is 0.007 mg / cm ² or more. battery.   The non-aqueous secondary battery according to claim 1, wherein the negative electrode mixture layer further includes a graphitic carbon material as a negative electrode active material. The capacity per unit area obtained by dividing the capacity of the non-aqueous secondary battery by the facing area between the positive electrode mixture layer and the negative electrode mixture layer of the positive electrode is less than 3.0 mAh / cm ^2. The nonaqueous secondary battery according to any one of 1 to 10.   The slope at 40% SOC of the voltage (mV) -SOC (%) curve obtained when charging at a current value of 1.5 C is used, using the voltage increase (mV) per 10% SOC corresponding to the tangent at 40% SOC. The nonaqueous secondary battery according to any one of claims 1 to 11, wherein the slope is 90 mV / 10% SOC or less when expressed as voltage increase (mV) / 10% SOC.

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