JP2013225502A - Negative electrode material for nonaqueous secondary battery, negative electrode for nonaqueous secondary battery, and nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a negative electrode material for a nonaqueous secondary battery that has both high capacity and high cycle characteristics, a negative electrode for the nonaqueous secondary battery, and the nonaqueous secondary battery.SOLUTION: There is provided a negative electrode material for a nonaqueous secondary battery that includes carbonaceous particles (A) and silicon oxide particles (B), the carbonaceous particles (A) being approximate ellipsoids having an ellipticity (f) of 0.38-0.68 represented by expression (1) of f=1-b/a(1) calculated from a major diameter (a) and a minor diameter (b) found in the following measuring method, where approximate ellipsoid sections are obtained through image analyzing software from respective sectional ellipses of 100 carbonaceous particles in an image of an electrode section photographed by a scanning type electron microscope after an electrode of 6-20 mg/cmin weight of an active material layer obtained by mixing only carbonaceous particles (A) and a binding resin is cut by a cross section polisher while pressed to an active material density of 1.2 to 1.8 g/cmor not pressed, average values of respective major diameters and minor diameters which are thus measured being a major diameter (a) and a minor diameter (b).

Description

  The present invention relates to a negative electrode material for a non-aqueous secondary battery electrode, a negative electrode for a non-aqueous secondary battery using the same, and a non-aqueous secondary battery. Among non-aqueous secondary batteries, it particularly relates to a lithium ion secondary battery.

  In recent years, demand for high-capacity secondary batteries has increased with the downsizing of electronic devices. In particular, non-aqueous secondary batteries having higher energy density and excellent rapid charge / discharge characteristics, particularly lithium ion secondary batteries, are attracting attention as compared to nickel / cadmium batteries and nickel / hydrogen batteries.

A nonaqueous lithium secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and a nonaqueous electrolyte solution in which a lithium salt such as LiPF ₆ or LiBF ₄ is dissolved has been developed and put into practical use.

  Various materials have been proposed as negative electrode materials for this battery. The negative electrode material has a high capacity and excellent discharge potential flatness, and so on, such as natural graphite, artificial graphite obtained by graphitization of coke, graphitized mesophase pitch, graphitized carbon fiber, etc. These carbon materials are used.

  In addition, an amorphous carbon material is also used as the negative electrode material because it is relatively stable with respect to some electrolyte solutions. Further, as the negative electrode material, a carbon material having the characteristics of graphite and amorphous carbon by coating, adhering or adhering amorphous carbon on the surface of the graphite particles is also used.

  For example, Patent Document 1 discloses a spheroidized graphite having a particle shape that is spherical by giving mechanical energy treatment to graphite particles that are originally scaly, lump, or plate. It has been proposed to use particles for negative electrode materials. Graphite particles improve their rapid charge / discharge characteristics by making them spherical. Further, it has been proposed that the graphite particles may be used as a negative electrode material as spheroidized graphite particles having a multilayer structure in which amorphous carbon is coated, adhered, or attached to the surface thereof.

  However, recently, non-aqueous secondary batteries, especially non-aqueous secondary batteries, have been developed for use in applications such as conventional notebook computers, mobile communication devices, portable cameras, portable game consoles, electric tools, Rapid charge / discharge performance, which has been increased in the past, is required for electric vehicles. Furthermore, non-aqueous secondary batteries are desired to have both high capacity and high cycle characteristics.

For example, in Patent Document 2, in order to improve cycle characteristics, carbonaceous particles having a multilayer structure having an R value of 0.2 or more obtained from a Raman spectrum analysis using an argon ion laser beam having a wavelength of 5145 と, A mixture of carbonaceous particles having a single-phase structure with a peak of (002) plane d002 of 3.36 to 3.62 and a specific surface area of 7 m ² / g by X-ray wide angle diffraction Non-aqueous secondary batteries used as materials have been proposed.

  Patent Document 3 proposes a negative electrode material in which coated graphite particles whose surface is coated with amorphous carbon and uncoated graphite particles whose surface is not coated with amorphous carbon are mixed. More specifically, Patent Document 3 discloses that coated graphite particles and uncoated graphite particles are the same type of graphite particles, and that the particle diameters of coated graphite particles and uncoated graphite particles are the same. Yes.

Patent Document 4 proposes using silicon oxide as a negative electrode material together with a carbon material in order to suppress a decrease in discharge capacity due to a side reaction between the carbon material and an electrolytic solution. In addition, in Patent Document 5, in order to maintain a high capacity without deteriorating cycle characteristics, a SiO _x powder having an average particle diameter d50 of 0.2 to 20 μm is used as a nucleus by mechanical surface fusion treatment. There has been proposed a negative electrode material containing graphite and a conductive SiO _x powder in which the surface of the core is covered with a conductive material such as artificial graphite having an average particle diameter d50 of 20 nm to 13 μm.

  Furthermore, in Patent Document 6, in order to improve cycle characteristics while maintaining a high capacity, carbon precursors such as graphite powder, pitch, silicon / silicon compounds / silicon alloys, carbon black, and chain polymer materials are disclosed. Proposed is a negative electrode active material for lithium ion secondary batteries composed of roughly spherical particles having an aspect ratio of 1 to 2 obtained by firing the void-forming agent.

Japanese Patent No. 3534391 Japanese Patent No. 3291756 JP 2005-294011 A JP 11-31518 A JP 2002-373653 A JP 2008-186732 A

  However, even with the negative electrode material disclosed in the above-mentioned document, a non-aqueous secondary battery that satisfies the high capacity targeted by the present inventors cannot be obtained, and the cycle characteristics of the battery cannot be improved.

  Therefore, the present invention has high capacity and high cycle characteristics that can satisfy characteristics required by recent application development, for example, characteristics when used in electric tools and electric vehicles. An excellent non-aqueous secondary battery negative electrode material, a non-aqueous secondary battery negative electrode, and a non-aqueous secondary battery are proposed.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies, and as a result, a negative electrode including carbonaceous particles (A) that are approximate ellipsoids having a flattening ratio f in a specific range and silicon oxide particles (B). By using the material, it was found that a negative electrode material for a non-aqueous secondary battery having high capacity and high cycle characteristics was obtained, and the present invention was completed.

[1] The present invention includes carbonaceous particles (A) and silicon oxide particles (B), and the carbonaceous particles (A) are calculated from a major axis a and a minor axis b determined by the following measurement method. It is related with the negative electrode material for non-aqueous secondary batteries characterized by being an approximate ellipsoid whose flatness f represented by following formula (1) is 0.38-0.68.
f = 1−b / a (1)
(Measurement method)
100 parts by mass of carbonaceous particles (A) and 10 parts by mass or less of the binder resin are mixed to form a slurry in an aqueous or organic medium, and if necessary, a thickener is added and applied to the current collector. Then, an electrode having a basis weight of 6 to 20 mg / cm ² of the active material layer is produced by drying. The obtained electrode was cut out with an active material layer density of 1.2 to 1.8 g / cm ^{3 or} in an unpressed state by a cross section polisher (CP), and was scanned with a scanning electron microscope (SEM). Each cross-sectional ellipse of 100 carbonaceous particles in the photographed electrode cross-sectional image is made into an approximate ellipsoidal cross section using image analysis software, and the length of each major axis and the length of the minor axis are measured from each approximate ellipsoidal section. The average value of the lengths of these major axes and the average value of the minor axis lengths are defined as major axis a and minor axis b.
[2] The present invention relates to the negative electrode material for a non-aqueous secondary battery according to the above [1], wherein the carbonaceous particles (A) include those having a carbon layer on at least a part of the surface of the graphite particles.
[3] In the present invention, the ratio Rs / Rg between the average particle diameter Rg of the carbonaceous particles (A) and the average particle diameter Rs of the silicon oxide particles (B) is 0.001 to 5 [1] ] Or the negative electrode material for non-aqueous secondary batteries according to [2].
[4] The negative electrode for a non-aqueous secondary battery according to [1] to [3], wherein the present invention includes 1 to 50 parts by mass of silicon oxide particles (B) with respect to 100 parts by mass of the carbonaceous particles (A). Regarding materials.
[5] The present invention provides the method according to any one of [1] to [4], wherein the silicon oxide particles (B) are represented by a general formula SiO _x (x is 0.5 ≦ x ≦ 1.6). It is related with the negative electrode material for non-aqueous secondary batteries of description.
[6] The present invention relates to the negative electrode material for a non-aqueous secondary battery according to any one of [1] to [5], wherein the average particle diameter Rg of the carbonaceous particles (A) is 5 to 30 μm.
[7] The nonaqueous system according to any one of [1] to [6], wherein the carbonaceous particles (A) have a major axis a of 5 to 30 μm and a minor axis b of 1 to 25 μm. The present invention relates to a negative electrode material for a secondary battery.
[8] The present invention relates to the negative electrode material for a non-aqueous secondary battery according to any one of [1] to [7], wherein the silicon oxide particles (B) have an average particle diameter Rs of 0.01 to 10 μm. .
[9] The present invention relates to the negative electrode material for a non-aqueous secondary battery according to any one of [1] to [8], further including flaky graphite (A1).
[10] The present invention is a negative electrode for a non-aqueous secondary battery comprising a current collector and an active material layer formed on the current collector, wherein the active material layer is the above-mentioned [1] to [9] A negative electrode for a non-aqueous secondary battery comprising the negative electrode material for a non-aqueous secondary battery according to any one of [9].
[11] The present invention is an ion secondary battery comprising a positive electrode and a negative electrode capable of occluding and releasing ions, and an electrolyte, wherein the negative electrode is the negative electrode for a non-aqueous secondary battery according to [10]. The present invention relates to a non-aqueous secondary battery.

  ADVANTAGE OF THE INVENTION According to this invention, the nonaqueous secondary battery which has the outstanding characteristic which is a high capacity | capacitance and has a high cycle characteristic can be provided.

It is a SEM photograph (500 magnifications) which shows the cross section of the carbonaceous particle (A) which is an approximate ellipsoid concerning this invention. 2 is a SEM photograph (2000 magnification) showing a cross section of a conventional spheroidized graphite particle shown in Comparative Example 1. 4 is a SEM photograph (10,000 magnifications) showing a cross section of a conventional flaky graphite shown in Comparative Example 2.

The present invention includes carbonaceous particles (A) and silicon oxide particles (B), and the carbonaceous particles (A) are calculated from the following formulas calculated from a major axis a and a minor axis b obtained by the following measurement method ( 1) A negative electrode material for a non-aqueous secondary battery, which is an approximate ellipsoid having a flatness ratio f of 0.38 to 0.68.
f = 1−b / a (1)
(Measurement method)
100 parts by mass of the carbonaceous particles (A) and 10 parts by mass or less of the binder resin are mixed to form a slurry with an aqueous or organic medium. If necessary, a thickener is added thereto, the slurry is applied to a current collector, and dried to prepare an electrode having a basis weight of 6 to 20 mg / cm ² of the active material layer. The obtained electrode is cut by a cross section polisher (CP) in a state where it is pressed to an active material layer density of 1.2 to 1.8 g / cm ^{3 or in} an unpressed state. The cut-out electrode cross section is photographed with a scanning electron microscope (SEM). Each cross-sectional ellipse of 100 carbonaceous particles in the photographed electrode cross-sectional image is set as an approximate ellipsoidal cross-section using image analysis software. From the approximate ellipsoidal cross section of each carbonaceous particle (A) in the image of the electrode cross section, the length of the major axis and the length of the minor axis are measured, and the average value of the major axis length and the length of the minor axis are measured. The average value is a major axis a and a minor axis b. As image analysis software for analyzing the cross-sectional ellipse of the carbonaceous particles (A) as an approximate ellipsoidal cross-section, for example, ImageProPlus (manufactured by Japan Cybernetics, Japan Roper) can be used. Here, the active material layer in the electrode for measuring the flatness f of the carbonaceous particles (A) means a mixture containing only the carbonaceous particles (A) and the binder resin (B). The blending ratio of only the carbonaceous particles (A) and the binder resin (only the carbonaceous particles (A): the binder resin) is 100: 0.1 to 10, more preferably 100: 0.2-7. More preferably, it is 100: 0.3-7. Here, “only the carbonaceous particles (A)” means that only the carbonaceous particles (A) are included, and other components such as silicon oxide particles (B) other than the carbonaceous particles (A) are not included. The basis weight of the active material layer of the electrode is preferably 6 to 15 mg / cm ² , more preferably 7 to 12 mg / cm ² , and further preferably 7 to 10 mg / cm ² . As the carbonaceous particles (A), one type of carbonaceous particles may be used alone, or two or more types of carbonaceous particles may be used in combination. As the current collector, for example, a copper foil with a thickness of 18 μm can be used. The thickness and material of the current collector are not particularly limited. The current collector does not affect the flatness of the carbonaceous particles (A) measured by the measurement method described above. In the present specification, the electrode means a negative electrode unless otherwise specified.

  Here, the approximate ellipsoid refers to an ellipse having the same area as the object to be analyzed (carbonaceous particles in the present specification) and having the same first moment and second moment. Here, the primary moment and the secondary moment of the object can be measured using the image analysis software or the like.

  The carbonaceous particles (A) are approximate ellipsoids having an oblateness f of 0.38 to 0.68 derived from the major axis a and the minor axis b measured by the measurement method described above. The carbonaceous particles (A), which are approximate ellipsoids, come into contact with the active material layer of the electrode so that the entry and exit of alkali ions including lithium (Li) ions is ensured, while the silicon oxide particles (B) Create gaps that can exist. The active material layer of the electrode has a structure in which silicon oxide particles (B) are present in the gaps formed by the carbonaceous particles (A). The silicon oxide particles (B) have a larger theoretical capacity than the carbonaceous particles (A). For this reason, the battery has a larger capacity and a higher capacity when it contains carbonaceous particles (A) and silicon oxide particles (B) than when it contains only carbonaceous particles (A). Can be realized. In the active material layer of the electrode, the gap formed by the carbonaceous particles (A) absorbs the volume change of the silicon oxide particles (B) due to the occlusion / release of alkali ions such as Li ions due to charge / discharge. For this reason, the active material layer of the electrode is suppressed from being deteriorated due to repeated charging and discharging accompanied by occlusion / release of alkali ions such as Li ions. For this reason, the battery can improve cycle characteristics. Further, in the active material layer of the electrode, the gap between the carbonaceous particles (A) forms a path of a diffusion path of alkali ions such as Li ions in the electrode, and the carbonaceous particles (A) and silicon oxide particles during charge / discharge Ensuring sufficient entry and exit of alkali ions such as Li ions to (B). For this reason, the battery can improve input / output characteristics.

  The carbonaceous particles (A) that are approximate ellipsoids are often formed by applying mechanical action to graphite particles that are originally scaly to bend the particles or to cut the particle surface. Therefore, the carbonaceous particles (A) that are approximate ellipsoids are highly likely to have stress remaining in the particles. The stress remaining in the carbonaceous particles (A) may be released to the outside due to repeated charge and discharge, and contact between the carbonaceous particles (A) may be separated. In the active material layer of the electrode, the gap formed by the carbonaceous particles (A) absorbs the volume change of the silicon oxide particles (B) accompanying charge / discharge and the residual stress released from the carbonaceous particles (A). And ensuring contact between the carbonaceous particles (A). For this reason, in the active material layer of the battery, disconnection of the conductive path due to repeated charge / discharge is suppressed. Further, the battery can improve cycle characteristics.

[Carbonaceous particles (A)]
The carbonaceous particles (A) used in the present invention are obtained by spheroidizing graphite such as natural graphite into an approximate ellipsoid by optimizing mechanical energy treatment conditions as described in Japanese Patent No. 3534391, for example. Spherical graphite can be used.

<Flatness f of carbonaceous particles (A)>
The flatness f of the carbonaceous particles (A) that are approximate ellipsoids is 0.38 to 0.68. When the flatness f of the carbonaceous particles (A) is less than 0.38, the shape of the carbonaceous particles (A) approaches a perfect circle, and the perfect circles of the carbonaceous particles (A) and the perfect circles. It becomes difficult to make contact between the carbonaceous particles (A) and the silicon oxide particles (B). When the flatness f of the carbonaceous particles (A) exceeds 0.68, the shape of the carbonaceous particles (A) approaches a scaly shape, and the volume change of the silicon oxide particles (B) accompanying the occlusion / release of Li ions, etc. It becomes difficult to form a suitable gap for absorbing the water. Further, if the flatness f of the carbonaceous particles (A) exceeds 0.68, it becomes difficult to secure a path for diffusing alkali ions such as Li ions in the electrode. The flatness f of the carbonaceous particles (A) is preferably 0.40 to 0.66, more preferably 0.42 to 0.64, and still more preferably 0.44 to 0.62.

The flatness f of the carbonaceous particles (A) can be measured by producing an electrode by the method described in Examples when the carbonaceous particles (A) are in powder form. Also, the flatness of the carbonaceous particles (A) in the electrode can be measured according to the measurement method described in this specification.

<Longer diameter a and shorter diameter b of carbonaceous particles (A)>
The carbonaceous particles (A) preferably have a major axis “a” of 5 to 30 μm and a minor axis “b” of 1 to 25 μm. The carbonaceous particles (A) have the major axis a and the minor axis b in this range, and the flatness f derived from the major axis a and the minor axis b is 0.38 to 0.68. In the material layer, the carbonaceous particles (A) can form gaps in which the silicon oxide particles (B) can exist while being in contact with each other so as to ensure the entry and exit of lithium ions.
When the major axis “a” of the carbonaceous particles (A) is less than 5 μm and the numerical value of the minor axis “b” is small, the overall particle size may be small and it may be difficult to suppress an increase in contact interface resistance. When the long diameter a of the carbonaceous particles (A) is less than 5 μm and the numerical value of the short diameter b is large, the shape of the carbonaceous particles (A) approaches a perfect circle, and the flatness f is 0.38 to It becomes difficult to make it the range of 0.68, and it becomes difficult to form a gap that allows the presence of silicon oxide particles (B).
On the other hand, when the major axis a of the carbonaceous particle (A) exceeds 30 μm, when the numerical value of the minor axis b is small, the shape of the carbonaceous particle (A) approaches a scaly shape, and the carbonaceous particle (A) It becomes difficult to form a suitable gap in which the silicon oxide particles (B) and the electrolytic solution are present. In addition, when the major axis “a” of the carbonaceous particles (A) exceeds 30 μm and the numerical value of the minor axis “b” is small, the electrode including the carbonaceous particles (A) has a suitable gap between the carbonaceous particles (A). Is difficult to form, and it may be difficult to secure a diffusion path of alkali ions such as Li ions. Further, when the major axis a of the carbonaceous particle (A) exceeds 30 μm and the numerical value of the minor axis b is large, the entire carbonaceous particle (A) has a large particle diameter, and the increase in the electrode thickness The flatness is impaired, and at the same time, it is difficult to secure a contact between the carbonaceous particles (A) and the silicon oxide particles (B). The approximate ellipsoidal carbonaceous particles (A) in the cross section of the electrode preferably have a major axis a of 10 to 25 μm and a minor axis b of 2 to 22 μm, and more preferably a major axis a of 12 to 22 μm and a minor axis b. The major axis “a” is 15 to 20 μm and the minor axis “b” is 7 to 18 μm.

<Method for producing carbonaceous particles (A)>
A method for producing carbonaceous particles (A), which is an approximate ellipsoid having an aspect ratio f of 0.38 to 0.68, is described below.

  Although there is no restriction | limiting in particular as a method of manufacturing a carbonaceous particle (A), For example, it can manufacture by the manufacturing method described below. In addition, mechanical energy treatment (mechanical action such as impact compression, friction and shear force) is applied to artificial graphite produced by heating petroleum coke, coal pitch coke, coal needle coke, mesophase pitch, etc. to 2500 ° C. or higher. ), Carbonaceous particles (A) can also be produced.

  As a method for producing the carbonaceous particles (A), a method of spheroidizing natural graphite and / or artificial graphite into a substantially perfect circle can be applied. This method includes a method of reducing energy for damaging the surface of the graphite particles as compared with the case of spheroidizing the graphite particles made of natural graphite and / or artificial graphite into a substantially circular shape. For example, there is a method of reducing the energy of damaging the particle surface by reducing the peripheral speed of a rotor having a large number of blades that apply mechanical action to graphite particles. In addition, there is a method of reducing the energy for damaging the surface of the graphite particles by shortening the treatment time. Here, the mechanical action applied to the graphite particles refers to, for example, impact compression, friction or shear force. For example, when carbonaceous particles (A) are produced using a hybridization system manufactured by Nara Machinery Co., Ltd., the circumferential speed of the rotor having a large number of blades is usually 10 to 200 m / second, preferably 25 to 150 m / second. Second, more preferably 30 to 120 m / second, still more preferably 40 to 100 m / second. Further, the graphite particles can be treated by simply passing the graphite particles between a large number of blades, but it is preferable that the graphite particles be circulated or retained between the large numbers of blades for 30 seconds or longer. . The treatment time is more preferably 1 minute or longer. Moreover, the input amount of the graphite particles to the above system is usually set to 10 to 1000 g, preferably 50 to 750 g, more preferably 100 to 500 g. By combining these production conditions and adjusting the energy applied to the graphite particles, carbonaceous particles (A) that are approximate ellipsoids having an aspect ratio f of 0.38 to 0.68 can be produced.

[Composite carbonaceous particles (A)]
The carbonaceous particles (A) include composite-type carbonaceous particles having a carbon layer on at least a part of the surface of spheroidized graphite. The carbon layer is preferably made of amorphous carbon or graphite. Here, “the carbon layer is provided on at least a part of the surface” means that the carbon layer covers not only a part or the whole of the surface of the spheroidized graphite but also a part or the whole of the surface of the carbon layer. It also includes forms that adhere to and attach to the surface. The composite type carbonaceous particles (A) may be provided with a carbon layer so as to cover the entire surface, or provided with a carbon layer so as to cover, adhere or attach a part of the surface. It may be. Preferably, the composite-type carbonaceous particles (A) are provided with a carbon layer covering the entire surface of the spheroidized graphite. The composite-type carbonaceous particles (A) include a carbon layer made of amorphous carbon on at least a part of the surface of the graphite particles (also referred to as “amorphous carbon-coated approximate ellipsoidal graphite”). It is. The composite-type carbonaceous particles (A) are those provided with a carbon layer made of graphite on at least a part of the surface of the graphite particles (also referred to as “graphite-coated approximate ellipsoidal graphite”). As the carbonaceous particles (A), one kind selected from the group consisting of spheroidized graphite which is an approximate ellipsoid and composite type carbonaceous particles may be used alone, or two or more kinds may be used in combination. In addition, the composite-type carbonaceous particle (A) can confirm the carbon layer provided in at least one part of the surface by SEM photography etc., for example.

  In the active material layer of the electrode, the composite type carbonaceous particles (A) form a gap. The active material layer of the electrode has a structure in which highly active silicon oxide particles (B) in which alkali ions such as lithium ions easily enter and exit are present in the gaps formed by the composite type carbonaceous particles (A). . For this reason, the battery can achieve high capacity. In addition, since the composite type carbonaceous particles (A) are provided with a carbon layer made of amorphous or the like on at least a part of the surface, the composite type carbonaceous particles may vary depending on the uneven shape of the surface and the hardness of the particles themselves. A space | gap can be ensured in the active material layer of an electrode with a particle | grain (A) and a silicon oxide particle (B). For this reason, the active material layer of the electrode has a good diffusion path for alkali ions such as lithium ions. In addition, the battery can achieve higher capacity and higher rate. Furthermore, the active material layer of the electrode has a structure in which the silicon oxide particles (B) are present in the gaps between the composite-type carbonaceous particles (A), so that the silicon oxide particles (B) associated with the entry / exit of alkali ions such as lithium ions. The gap formed by the composite type carbonaceous particles (A) can be absorbed by the volume change. For this reason, the electrode is prevented from being cut off by a volume change. Moreover, the capacity | capacitance fall and the fall of a rate characteristic with a conductive path interruption | blocking are suppressed, and a battery can implement | achieve high capacity | capacitance and high rate.

  The coverage of the carbon layer represents the amount of the carbon layer present on the surface of the graphite particles. The coverage of the carbon layer is preferably 0.1 to 10% by mass with respect to 100% by mass of the carbonaceous particles (A). If the coverage of the carbon layer is within this range, it can contribute to improvement of input / output characteristics of alkali ions such as lithium ions in the active material layer of the electrode. The coverage of the carbon layer is more preferably 0.2 to 8% by mass, and still more preferably 0.4 to 5% by mass. The coverage of the carbon layer is expressed by mass% of carbon present on the surface of the graphite particles, and can be measured by the method described later in the examples.

  When the carbon layer is made of amorphous carbon, the coverage of the carbon layer is preferably 0.1 to 10% by mass, more preferably 0.2 to 8% by mass, and still more preferably 0.4 to 5% by mass. %. When the coverage of the carbon layer made of amorphous carbon is 0.1% by mass or more, high acceptability of alkali ions such as lithium ions possessed by amorphous carbon can be fully utilized. Moreover, the fall of the capacity | capacitance by the influence of the magnitude | size of the irreversible capacity | capacitance which amorphous carbon has as the coverage of a carbon layer is 10 mass% or less can be prevented. Thereby, the battery can suppress an increase in contact resistance and improve rate characteristics.

<Coverage of composite type carbonaceous particles (A)>
The coverage of the carbon layer of the carbonaceous particles can be obtained by the following equation.
Coverage (mass%) = 100− (K × D) / ((K + T) × N) × 100
In this equation, K is the mass (Kg) of the graphite particles subjected to mixing with the tar pitch, T is the mass (kg) of the tar pitch that is the coating raw material used for mixing with the graphite particles, and D is the amount of K and T Of the mixture, the amount of the mixture actually subjected to firing, N, indicates the mass of the carbonaceous particles (A) provided with the carbon layer after firing on at least a part of the surface of the graphite particles.

<Method for producing composite carbonaceous particles (A)>
In addition, composite carbonaceous particles (A) having a carbon layer on at least a part of the surface of the graphite particles can be produced by the following method.
For example, petroleum-based or coal-based tar and pitch, polyvinyl alcohol, polyacrylonitrile, phenol resin, cellulose, and other resins are mixed using a solvent if necessary, and this mixture is mixed with the carbonaceous particles (A). Composite-type carbonaceous particles having a carbon layer on at least a part of the surface by firing at 500 ° C. to 3000 ° C. in a non-oxidizing atmosphere, preferably 700 ° C. to 2000 ° C., more preferably 800 to 1500 ° C. A) can be produced.

<Other physical properties of carbonaceous particles (A)>
Below, it describes about the physical property of the carbonaceous particle (A) used for this invention. In addition, when the physical property value of the carbonaceous particles (A) is not particularly specified, the physical property value of the powdery carbonaceous particles (A) before forming the electrode may be used, and the carbonaceous particles (A) taken out from the electrode Or the physical property value of the carbonaceous particles in the electrode.

(A) Average particle diameter Rg
The average particle diameter Rg of the carbonaceous particles (A) is preferably 5 to 30 μm. When the average particle diameter Rg of the carbonaceous particles (A) is 5 to 30 μm, an increase in irreversible capacity due to an increase in specific surface area and an increase in contact interface resistance due to a small particle diameter can be suppressed. Moreover, the increase in the thickness of the electrode due to the large particle size of the carbonaceous particles (A) can be suppressed, and the flatness of the electrode is not impaired. Moreover, when the average particle diameter Rg of the carbonaceous particles (A) is 5 to 30 μm, it is possible to avoid disconnection of the conductive path between the carbonaceous particles (A) and the silicon oxide particles (B). The average particle diameter Rg is more preferably 6 to 28 μm, still more preferably 7 to 26 μm. Here, the average particle diameter Rg refers to a volume-based median diameter measured by laser diffraction / scattering particle size distribution measurement.

(B) Tap density The tap density of the carbonaceous particles (A) is preferably 0.7 g / cm ³ or more, more preferably 0.8 g / cm ³ or more. That the tap density is 0.7 g / cm ³ or more indicates that the carbonaceous particles (A) are approximate ellipsoids having an aspect ratio f of 0.38 to 0.68. A tap density is measured by the method of the Example mentioned later. Also in the case of composite type carbonaceous particles (A), the tap density is preferably 0.7 g / cm ³ or more.

(C) Specific surface area by BET method The specific surface area of the carbonaceous particles (A) by the BET method is preferably 0.5 to ²⁰ m ² / g, more preferably 1 to 18 m ² / g, still more preferably 1.5 to 16 m ² / g. In this specification, the specific surface area by BET method is measured by the method of the Example mentioned later. When the specific surface area of the carbonaceous particles (A) is 0.5 m ² / g or more, the lithium ion acceptability is improved, and when the specific surface area is 20 m ² / g or less, the battery capacity is reduced due to the increase in irreversible capacity. Can be prevented.

(D) 002 plane spacing by X-ray wide angle diffraction method (d002) and Lc
(Di) Interplanar spacing of 002 faces of carbonaceous particles (A) (d002)
The carbonaceous particles (A) preferably have an 002-plane spacing (d002) of 3.37 mm or less and Lc of 900 mm or more by X-ray wide angle diffraction. The fact that the 002 plane spacing (d002) by X-ray wide angle diffraction method is 3.37 mm or less and Lc is 900 mm or more means that the crystallinity of the carbonaceous particles (A) is high. Since the carbonaceous particles (A) have high crystallinity, the capacity of the irreversible capacity as seen in the amorphous carbon material is increased, except for the composite part of the carbon layer made of amorphous carbon. Can be prevented. The inter-surface distance (d002) of the 002 surface by the X-ray wide angle diffraction method is measured by the method described later in the examples.

(D-ii) 002 plane spacing of amorphous carbon (d002)
The interplanar spacing (d002) of the 002 plane according to the X-ray wide angle diffraction method of the carbon layer made of amorphous carbon provided on at least a part of the surface of the composite type carbonaceous particle (A) is 3.40 mm or more, and Lc is 500 mm. The following is preferable. When the 002 plane spacing (d002) is 3.40 mm or more and Lc is 500 mm or less, the acceptability of lithium ions can be improved.

(E) True density The true density of the carbonaceous particles (A) made of spheroidized graphite spheroidized into an approximate ellipsoid is preferably 2.1 g / cm ³ or more. More preferably, it is 2.15 g / cm ³ or more, and further preferably 2.2 g / cm ³ or more. A true density is measured by the method of the Example mentioned later. A true density of 2.1 g / cm ³ or higher indicates that the crystallinity of the main body of spheroidized graphite is high, and a high capacity negative electrode material with a small irreversible capacity can be obtained.

[Scale-like graphite particles (A1)]
Moreover, the negative electrode material of this invention may mix scale-like graphite particle | grains (A1) other than the carbonaceous particle (A) which is an approximate ellipsoid. The scaly graphite (A1) is made of natural graphite highly purified so that the crystallinity of graphite is almost completely crystallized, or made of artificially formed graphite. The scaly graphite particles (A1) are preferably made of natural graphite. In the present specification, scaly means that the average aspect ratio, which is the ratio of the length of the major axis to the minor axis of the scaly graphite (A1), is 2.1 or more.

  In the active material layer of the electrode, scaly graphite (A1) whose surface and edge are in contact with each other is formed in the gap formed by the carbonaceous particles (A), and the scaly graphite (A1) is partially composed of carbonaceous particles (A1). It has a structure that bridges between A). With this structure, in the active material layer of the electrode, volume change occurs in the carbonaceous particles (A) due to occlusion / release of alkali ions such as lithium ions accompanying charging and discharging, and the contacts between the carbonaceous particles (A) are separated. Even in this case, the conductive path between the carbonaceous particles (A) can be secured by the scaly graphite (A1). For this reason, the battery can improve cycle characteristics. The active material layer of the electrode has a structure in which silicon oxide particles (B) are present in the gaps formed by the carbonaceous particles (A) and the scaly graphite (A1). The silicon oxide particles (B) are highly active, easily allowing alkali ions such as Li ions to enter and exit. For this reason, the battery can realize further higher capacity. Further, in the active material layer of the electrode, the gap formed by the carbonaceous particles (A) and the scaly graphite (A1) changes in the volume of the silicon oxide particles due to occlusion / release of alkali ions such as Li ions due to charge / discharge. To absorb. For this reason, the active material layer of the electrode is suppressed from being deteriorated due to repeated charging and discharging accompanied by occlusion / release of alkali ions such as Li ions. Further, the battery can improve cycle characteristics. Furthermore, in the active material layer of the electrode, a diffusion path of alkali ions such as Li ions in the electrode is secured by a gap formed by the carbonaceous particles (A) and the scaly graphite (A1). For this reason, the battery can also improve rate characteristics.

<Physical properties of scale-like graphite (A1)>
(A-2) 50% particle size (d50)
The 50% particle diameter (d50) Rg of the scaly graphite (A1) is preferably 2 to 30 μm, more preferably 3 to 28 μm, and still more preferably 4 to 26 μm. When the 50% particle diameter of the scale-like graphite (A1) is within this range, an increase in irreversible capacity due to an increase in specific surface area can be prevented when an electrode is used. If the 50% particle size (d50) Rg of the flake graphite (A1) is too large, the electrode material mixed with the flake graphite (A1) is applied as a slurry by adding a binder, water, or an organic solvent. In the process, streaks or irregularities due to large particles may occur. Here, the 50% particle diameter (d50) refers to a volume-based median diameter measured by laser diffraction / scattering particle size distribution measurement.

(B-2) Aspect ratio The aspect ratio, which is the ratio of the length of the major axis to the minor axis of the particles, is preferably 2.1 to 10. The aspect ratio is more preferably 2.3 to 9, and still more preferably 2.5 to 8. When the aspect ratio is within this range, the electrode containing carbonaceous particles (A) and scaly graphite (A1) makes point contact while forming a suitable gap in which silicon oxide particles (B) can exist. Between the carbonaceous particles (A), there exists scale-like graphite (A1) whose surface and edge are in contact with each other, and the scale-like graphite (A1) partially spans between the carbonaceous particles (A). ) Can be used as a bridge. With this structure, even when the carbonaceous particles (A) that are in point contact with each other are separated from each other by repetition of charge and discharge, the electrode has carbonaceous particles (A that are bridged by scaly graphite (A1)). ) Is secured. For this reason, the battery can improve cycle characteristics. The aspect ratio of the flaky graphite (A1) can be measured by using the method of Examples described later.

(C-2) Tap density The tap density of the scaly graphite (A2) is preferably 0.1 g / cm ³ or more, more preferably 0.15 g / cm ³ or more. Further, the tap density of the scaly graphite (A1) is preferably 0.2 g / cm ³ or less, more preferably 2.0 g / cm ³ or less, still more preferably 1.6 g / cm ³ or less. When the tap density of the flaky graphite (A1) is within this range, the carbonaceous particles (A) and the flaky graphite (A1) are carbonaceous while forming a gap where the silicon oxide particles (B) can exist. Even when the scaly graphite (A1) bridges between the particles (A), the strength of the electrode is not lowered. The active material layer of the electrode absorbs the volume change of the silicon oxide particles (B), the carbonaceous particles (A), and the flaky graphite (A1) due to charge / discharge, and suppresses the deterioration of the electrode active material caused by the volume change. can do. For this reason, the battery can improve cycle characteristics. A tap density is measured by the method of the Example mentioned later.

(D-2) Specific surface area by BET method The specific surface area by the BET method of the scale-like graphite (A1) is preferably 1 to 40 m ² / g. BET specific surface area of the flake graphite (A1) is more preferably from 2~35m ² / g, and further preferably from 3~30m ² / g. The specific surface area of the scaly graphite (A1) by the BET method improves the acceptability of alkali ions such as lithium ions, and by making it 40 m ² / g or less, it is possible to prevent a decrease in battery capacity due to an increase in irreversible capacity. . The BET method specific surface area is measured by the method of Examples described later.

(E-2) The 002 plane spacing (d002) and the Lc scale-like graphite (A1) 002 plane spacing (d002) by the X-ray wide angle diffraction method are 0.337 nm or less. On the other hand, since the theoretical value of the interplanar spacing of the 002 plane of graphite is 0.335 nm, the interplanar spacing of the 002 plane of graphite is usually 0.335 nm or more. Further, Lc of the scaly graphite (A1) by an X-ray wide angle diffraction method is 90 nm or more, preferably 95 nm or more. When the spacing between the 002 planes (d002) is 0.337 nm or less, the scaly graphite (A1) has high crystallinity, and a negative electrode material that can increase the capacity of the battery can be obtained. Moreover, when Lc is 90 nm or more, it shows that crystallinity is high, and a negative electrode material having a high capacity can be obtained. The interplanar spacing (d002) of the 002 surface by the X-ray wide angle diffraction method and Lc are measured by the method of the example described later.

(F-2) True density The true density of the scale-like graphite (A1) is preferably 2.1 g / cm ³ or more, more preferably 2.15 g / cm ³ or more, and further preferably 2.2 g / cm ³ or more. . If the true density is a highly crystalline graphite having a true density of 2.1 g / cm ³ or more, a high capacity negative electrode material with a small irreversible capacity can be obtained. The true density of the flaky graphite (A1) is measured by the method of the example described later.

(G-2) Length of particle minor axis The length of the minor axis of the scaly graphite (A1) is preferably 15 μm or less, more preferably 10 μm or less, and still more preferably 8 μm or less. The length of the minor axis of the scaly graphite (A1) is preferably 0.9 μm or more. If the length of the minor axis of the scaly graphite (A2) is too large, the volume change of the silicon oxide particles present in the gap may not be sufficiently absorbed. Further, if the length of the minor axis of the flaky graphite (A2) is too small, the contact between the carbonaceous particles (A) and the flaky graphite (A1) may not be maintained, and the conductive path may be cut off. The length of the minor axis of the flaky graphite (A1) can be measured by the same method as the method of measuring the minor axis when measuring the aspect ratio using the method of Examples described later.

<Manufacture of scale-like graphite (A1)>
As long as the flake graphite (A1) has the above-mentioned properties, it can be produced by any method. For example, scaly, massive, or plate-like natural graphite can be used as it is. For example, petroleum coke, coal pitch coke, coal needle coke, mesophase pitch, etc. are heated to 2500 ° C. or higher to produce artificial graphite. You may go and manufacture.

[Mass ratio of carbonaceous particles (A) and scaly graphite (A1)]
The mass ratio of carbonaceous particles (A) to scaly graphite (A1) (carbonaceous particles (A): scaly graphite (A1)) is preferably 95: 5 to 5:95. When the mass ratio of the carbonaceous particles (A) and the flaky graphite (A1) is within this range, the carbonaceous particles (A) and the flaky graphite (A1) are composed of silicon oxide particles (B). The scaly graphite (A1) has a structure in which the carbonaceous particles (A) are in contact with each other across the carbonaceous particles (A) while forming a suitable gap in which the carbonaceous particles (A) can exist. The mass ratio between the carbonaceous particles (A) and the flaky graphite (A1) is more preferably 90:10 to 10:90, and still more preferably 85:15 to 15:85.

[Silicon oxide particles (B)]
The silicon oxide particles (B) are obtained by using silicon dioxide (SiO ₂ ) as a raw material and thermally reducing SiO ₂ using metal silicon (Si) and / or carbon. SiO _x has a value of x. A generic term for particles made of silicon oxide represented by 0 <x <2. Silicon (Si) has a larger theoretical capacity than graphite. Furthermore, amorphous silicon oxide is easy for lithium ions to enter and exit, and a high capacity can be obtained.

The silicon oxide particles (B) used in the present invention are preferably silicon oxide particles (B) represented by the general formula SiO _x (x is 0.5 ≦ x ≦ 1.6). The range of x in the general formula SiO _x is more preferably x is 0.6 ≦ x ≦ 1.5, more preferably x is 1.3 or less, and particularly preferably x is 1.2 or less. When _{x in} the general formula SiO _x is in the range of 0.5 ≦ x ≦ 1.6, highly active amorphous particles in which lithium ions easily enter and exit are obtained. Therefore, the battery can achieve a high capacity and a high cycle maintenance rate. When the value of x in the general formula SiO _x is smaller than 0.5, the proportion of highly active amorphous Si in which Li ions easily enter and exit can be increased, and the capacity of the battery can be increased. Volume change associated with occlusion / release is increased. When the large volume change of the silicon oxide particles (B) having a large proportion of amorphous Si cannot be absorbed, cracks and the like occur in the silicon oxide particles (B) themselves, resulting in deterioration of the cycle characteristics of the battery. There is a case. When _{x in} the general formula SiO _x is larger than 1.6, Li ions and oxygen contained in the silicon oxide particles (B) react to increase the irreversible capacity, leading to a decrease in battery capacity.

  As the silicon oxide particles (B), composite silicon oxide particles (B) having silicon oxide particles as nuclei and a carbon layer made of amorphous carbon on at least a part of the surface may be used. As the silicon oxide particles (B), one type selected from the group consisting of silicon oxide particles not having a carbon layer made of amorphous carbon and composite type silicon oxide particles may be used alone, or two or more types may be used. You may use together. Here, “having a carbon layer made of amorphous carbon on at least a part of the surface” means that the carbon layer covers not only a part or all of the surface of the silicon oxide particles in a layered manner, It includes a form in which the silicon oxide particles are attached to or attached to part or all of the surface of the silicon oxide particles. The composite silicon oxide particles (B) may include a carbon layer that covers the entire surface, or may include a carbon layer that covers, adheres to, or is attached to a part of the surface.

  The physical properties of the silicon oxide particles (B) are described below. Composite-type silicon oxide particles including a silicon layer made of silicon oxide particles and amorphous carbon have the following common physical properties. In addition, the following physical property values may be the physical property values of the powdery material before forming the electrode, the physical property values obtained by taking out from the electrode, or the physical property values in the electrode unless otherwise specified.

<Physical properties of silicon oxide particles (B)>
(F) Average particle diameter Rs of silicon oxide particles (B)
The average particle diameter Rs of the silicon oxide particles (B) is preferably 0.01 to 10 μm, more preferably 0.1 to 9 μm, and still more preferably 0.5 to 8 μm. When the average particle diameter Rs is within this range, the active material layer of the electrode has a structure in which silicon oxide particles (B) are present in the gaps formed by the carbonaceous particles (A). With this structure, the active material of the electrode allows the silicon oxide particles (B) to absorb the volume change of the silicon oxide particles (B) that accompanies occlusion / release of lithium ions due to charge and discharge. ) Due to volume change is suppressed. For this reason, as a result, the battery can improve cycle characteristics. Here, the average particle diameter Rs is a volume-based median diameter measured by laser diffraction / scattering particle size distribution measurement.

(G) a specific surface area by the BET method specific surface area silicon oxide particles by the BET method of the silicon oxide particles (B) (B) is preferably from 0.5 to 100 ² / g, is 1~60m ² / g Is more preferable, and it is still more preferable that it is 1-40 m < ² > / g. When the specific surface area of the silicon oxide particles (B) by the BET method is within this range, the electrode including the carbonaceous particles (A) and the silicon oxide particles (B) has a mobility of lithium ions in the electrolyte solution, and a sufficient charge. Sufficient lithium ions can enter and leave the carbonaceous particles (A) and the silicon oxide particles (B) during discharge. For this reason, the battery can achieve high capacity. When the specific surface area by the BET method of the silicon oxide particles (B) is less than 0.5 m ² / g, the efficiency of input / output of lithium ions decreases, and the silicon oxide particles (B) become relatively large, and the carbonaceous particles (A) The silicon oxide particles (B) are present in the gaps between the two, making it difficult. On the other hand, when the specific surface area exceeds 60 m ² / g, the silicon oxide particles (B) become too small, the irreversible capacity of the battery increases, and the capacity decreases. The BET method specific surface area is measured by the method of Examples described later.

<Method for producing silicon oxide particles (B)>
The silicon oxide particles (B) may be produced by any method as long as they satisfy the characteristics of the present invention. For example, the silicon oxide particles (B) produced by the method described in Japanese Patent No. 3952118 Can be used. Specifically, silicon dioxide powder and metal silicon powder or carbon powder are mixed at a specific ratio, and after filling this mixture into the reactor, the pressure is reduced to normal pressure or a specific pressure, and the temperature is increased to 1000 ° C. or higher. It is heated and held to generate SiO _x gas, and then cooled and precipitated to obtain particles of the general formula SiO _x (x is 0.5 ≦ x ≦ 1.6). The precipitate can be made into particles by applying mechanical energy treatment.

  For mechanical energy treatment, for example, using a device such as a ball mill, a vibrating ball mill, a planetary ball mill, or a rolling ball mill, a raw material charged in the reactor and a moving body that does not react with the raw material are placed, and this is vibrated and rotated. Alternatively, the silicon oxide particles (B) satisfying the above characteristics can be formed by a method of providing a combined movement.

<Method for producing composite silicon oxide particles (B)>
Examples of the method for producing the composite type silicon oxide particles (B) include the following methods. For example, petroleum-based or coal-based tar or pitch, polyvinyl alcohol, polyacrylonitrile, phenol resin, cellulose and other resins are mixed as necessary using a solvent or the like, and this mixture and silicon oxide particles (B) are mixed. Silicon oxide particles (B) can be produced by firing at 500 ° C. to 3000 ° C., preferably 700 ° C. to 2000 ° C., more preferably 800 ° C. to 1500 ° C. in a non-oxidizing atmosphere.

[Ratio Rs / Rg]
In the present invention, the ratio Rs / Rg between the average particle diameter Rg of the carbonaceous particles (A) and the average particle diameter Rs of the silicon oxide particles (B) is preferably 0.001 to 5. The ratio Rs / Rg is more preferably 0.01-4, still more preferably 0.05-3, and particularly preferably 0.1-2. When the ratio Rs / Rg is within this range, the active material layer of the electrode has a structure in which the silicon oxide particles (B) are present in the gaps formed by the carbonaceous particles (A). The silicon oxide particles (B) have a theoretical capacity larger than that of the carbonaceous particles (A), and lithium ions easily enter and exit. Furthermore, since the gap formed by the carbonaceous particles (A) absorbs the volume change of the silicon oxide particles (B) due to the insertion and extraction of lithium ions due to charge and discharge, the active material of the electrode is the silicon oxide particles ( The conduction path break due to the volume change of B) is suppressed. For this reason, as a result, the battery can improve cycle characteristics and achieve a high capacity.

[Mixing ratio]
It is preferable that the negative electrode material for non-aqueous secondary batteries of this invention contains 1-50 mass parts of silicon oxide particles (B) with respect to 100 mass parts of carbonaceous particles (A). When the negative electrode material for a non-aqueous secondary battery contains silicon oxide particles (B) in this range with respect to 100 parts by mass of the carbonaceous particles (A), the active material layer of the electrode has carbonaceous particles ( It has a structure in which silicon oxide particles (B) are present in the gaps formed by A). For this reason, further increase in capacity and cycle characteristics can be improved. The silicon oxide particles (B) are more preferably 1.2 to 40 parts by weight, still more preferably 1.5 to 30 parts by weight, and particularly preferably 2 to 20 parts by weight with respect to 100 parts by weight of the carbonaceous particles (A). Part.

[Tap density of the mixture]
The tap density of the mixture containing 1 to 50 parts by mass of silicon oxide particles (B) with respect to 100 parts by mass of carbonaceous particles (A) is preferably 0.8 to 1.8 g / cm ³ . When the tap density of the mixture of the carbonaceous particles (A) and the silicon oxide particles (B) is within this range, the active material layer of the electrode has an electrolyte and silicon oxide in the gap formed by the carbonaceous particles (A). It has a structure in which particles (B) are present. For this reason, the battery can achieve high capacity. The tap density is more preferably 0.9 to 1.7 g / cm ³ , and still more preferably 1.0 to 1.6 g / cm ³ .

[Electrode pore capacity]
First, a binder resin is added to 100 parts by mass of carbonaceous particles (A) on a negative electrode material for a non-aqueous secondary battery including 100 parts by mass of carbonaceous particles (A) and 1 to 50 parts by mass of silicon oxide particles (B). 10 parts by mass or less is added to the slurry, and an aqueous or organic medium is used as a slurry. If necessary, a thickener is added to the slurry, and the slurry is applied to a current collector and dried to produce an electrode having an active material layer basis weight of 6 to 20 mg / cm ² . The obtained electrode is measured for pore volume by a mercury intrusion method in a state where it is pressed to an active material layer density of 1.2 to 1.8 g / cm ^{3 or in} an unpressed state. The pore volume in the range of 10 nm to 100,000 nm by the mercury intrusion method of the electrode is preferably 0.05 ml / g or more, and more preferably 0.1 ml / g or more. The pore capacity of the electrode is measured by the method of the example described later. By setting the pore volume of the electrode to 0.05 ml / g or more, the electrode can increase the area where alkali ions such as Li ions enter and exit.

[Negative electrode]
In order to produce a negative electrode using the negative electrode material of the present invention, a mixture of a negative electrode material and a binder resin is made into a slurry with an aqueous or organic medium, and if necessary, a thickener is added thereto and applied to a current collector. And then dry.

  As the binder resin, it is preferable to use a resin that is stable with respect to the non-aqueous electrolyte and water-insoluble. For example, rubbery polymers such as styrene, butadiene rubber, isoprene rubber and ethylene / propylene rubber; synthetic resins such as polyethylene, polypropylene, polyethylene terephthalate, polyimide, polyacrylic acid and aromatic polyamide; styrene / butadiene / styrene block Polymers and hydrogenated products thereof, thermoplastic elastomers such as styrene / ethylene / butadiene, styrene copolymers, styrene / isoprene and styrene block copolymers and hydrides thereof; syndiotactic-1,2-polybutadiene, ethylene / Soft resinous polymer such as vinyl acetate copolymer and copolymer of ethylene and α-olefin having 3 to 12 carbon atoms; polytetrafluoroethylene / ethylene copolymer, polyvinylidene fluoride, polypentafluoro Professional Fluorinated polymers such as polyphenylene and poly hexafluoropropylene may be used. Examples of the organic medium include N-methylpyrrolidone and dimethylformamide.

  The binder resin is usually used in an amount of 0.1 parts by mass or more, preferably 0.2 parts by mass or more based on 100 parts by mass of the negative electrode material. By setting the ratio of the binder resin to 0.1 parts by mass or more with respect to 100 parts by mass of the negative electrode material, the binding force between the negative electrode materials and between the negative electrode material and the current collector becomes sufficient, and the current collector to the negative electrode material It is possible to prevent the battery capacity from being reduced and the recycling characteristics from being deteriorated due to the separation of the active material layer.

  The binder resin is preferably 10 parts by mass or less, more preferably 7 parts by mass or less with respect to 100 parts by mass of the negative electrode material. By setting the ratio of the binder resin to 10 parts by mass or less with respect to 100 parts by mass of the negative electrode material, it is possible to prevent a decrease in the capacity of the negative electrode and prevent problems such as preventing lithium ions from entering and exiting the negative electrode material. it can.

  As the thickener added to the slurry, for example, water-soluble celluloses such as carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose, polyvinyl alcohol, polyethylene glycol and the like may be used. Of these, carboxymethylcellulose is preferred. The thickener is preferably used in an amount of usually 0.1 to 10 parts by mass, preferably 0.2 to 7 parts by mass with respect to 100 parts by mass of the negative electrode material.

  As the negative electrode current collector, for example, copper, copper alloy, stainless steel, nickel, titanium, and carbon that are conventionally known to be usable for this purpose may be used. The shape of the current collector is usually a sheet shape, and those having irregularities on the surface thereof, those using nets, punching metals, and the like are also preferable.

After the negative electrode material and the binder resin slurry are applied to the current collector and dried, the negative electrode is pressed to increase the density of the negative electrode active material layer formed on the current collector, thereby It is preferable to increase the battery capacity per unit volume. The density of the negative electrode active material layer in the range of 1.2~1.8g / cm ³ is more preferably preferably 1.3~1.6g / cm ^3.

By setting the density of the negative electrode active material layer to 1.2 g / cm ³ or more, it is possible to prevent a decrease in battery capacity accompanying an increase in electrode thickness. In addition, by setting the density of the negative electrode active material layer to 1.8 g / cm ³ or less, the amount of electrolyte solution held in the voids decreases as the interparticle voids in the electrode decrease, and the movement of alkali ions such as lithium ions moves. It is possible to prevent the rapid charge / discharge performance from being reduced.

  The active material layer of the negative electrode has a structure in which silicon oxide particles (B) are present in the gaps formed by the carbonaceous particles (A). Thereby, the capacity of the battery can be increased, and the cycle characteristics can be improved.

[Non-aqueous secondary battery]
The non-aqueous secondary battery according to the present invention can be produced according to a conventional method except that the negative electrode is used. Examples of the positive electrode material include a lithium cobalt composite oxide whose basic composition is represented by LiCoO ₂ , a lithium nickel composite oxide represented by LiNiO ₂ , and a lithium manganese composite oxide represented by LiMnO ₂ and LiMn ₂ O ₄ . Lithium transition metal composite oxides such as, transition metal oxides such as manganese dioxide, and composite oxide mixtures thereof may be used. Furthermore _{TiS 2, FeS 2, Nb 3} S 4, Mo 3 S 4, CoS 2, V 2 O 5, CrO 3, V 3 O 3, FeO 2, GeO 2 and _{LiNi 0.33 Mn} 0.33 Co _{0 .33} O ₂ , LiFePO _4, or the like may be used.

  The positive electrode can be produced by slurrying a mixture of a positive electrode material and a binder resin with an appropriate solvent, and applying and drying to a current collector. The slurry preferably contains a conductive material such as acetylene black and ketjen black. Moreover, you may contain a thickener as desired.

  As the thickener and the binder resin, those well-known in this application, for example, those exemplified as those used for the production of the negative electrode may be used. As for the compounding ratio with respect to 100 mass parts of positive electrode materials, 0.5-20 mass parts is preferable for a electrically conductive agent, and 1-15 mass parts is especially preferable. The thickener is preferably 0.2 to 10 parts by mass, particularly 0.5 to 7 parts by mass.

  The blending ratio of the binder resin to 100 parts by mass of the positive electrode material is preferably 0.2 to 10 parts by mass, particularly preferably 0.5 to 7 parts by mass when the binder resin is used by slurrying with water. When the binder resin is used in a slurry form with an organic solvent that dissolves the binder resin such as N-methylpyrrolidone, the amount is preferably 0.5 to 20 parts by mass, particularly 1 to 15 parts by mass.

  Examples of the positive electrode current collector include aluminum, titanium, zirconium, hafnium, niobium and tantalum, and alloys thereof. Of these, aluminum, titanium and tantalum and their alloys are preferred, and aluminum and its alloys are most preferred.

  As the electrolytic solution, a solution in which various lithium salts are dissolved in a conventionally known non-aqueous solvent can be used. Examples of the non-aqueous solvent include cyclic carbonates such as ethylene carbonate, fluoroethylene carbonate, propylene carbonate, butylene carbonate and vinylene carbonate, chain carbonates such as dimethyl carbonate, ethylmethyl carbonate and diethyl carbonate, and cyclic esters such as γ-butyrolactone. , Crown ether, 2-methyltetrahydrofuran, tetrahydrofuran, 1,2-dimethyltetrahydrofuran and cyclic ethers such as 1,3-dioxolane, chain ethers such as 1,2-dimethoxyethane, and the like may be used. Usually some of these are used together. Of these, it is preferable to use a cyclic carbonate and a chain carbonate, or another solvent in combination.

  Further, compounds such as vinylene carbonate, vinyl ethylene carbonate, succinic anhydride, maleic anhydride, propane sultone and diethyl sulfone, and difluorophosphates such as lithium difluorophosphate may be added. Furthermore, an overcharge inhibitor such as diphenyl ether and cyclohexylbenzene may be added.

Examples of the electrolyte dissolved in the non-aqueous solvent include LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ CF ₂ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) _3, or the like may be used. The concentration of the electrolyte in the electrolytic solution is usually 0.5 to 2 mol / liter, preferably 0.6 to 1.5 mol / liter.

  For the separator interposed between the positive electrode and the negative electrode, it is preferable to use a porous sheet or non-woven fabric of polyolefin such as polyethylene or polypropylene.

  In the non-aqueous secondary battery according to the present invention, the negative electrode / positive electrode capacity ratio is preferably designed to be 1.01 to 1.5, and more preferably 1.2 to 1.4. The non-aqueous secondary battery is preferably a lithium ion secondary battery including a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte.

  EXAMPLES Next, specific embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

  In the present specification, measurements of the flatness f, average particle diameter, tap density, BET specific surface area, X-ray diffraction, true density, etc. of the approximate ellipsoid were performed as follows.

Flatness ratio: only carbonaceous particles (A) and a binder resin (binder) are blended to form a slurry in an aqueous or organic medium. If necessary, a thickener is added to the slurry and applied to a current collector, followed by drying. Thus, an electrode (negative electrode) having a basis weight of 7 to 8 mg / cm ² of the active material layer was produced. This electrode (negative electrode) was cut out by a cross section polisher (CP) in a state where it was pressed to an active material layer density of 1.2 to 1.8 g / cm ^{3 or in} an unpressed state. The cut electrode cross section was photographed with a scanning electron microscope (SEM). Each cross-sectional ellipse of 100 carbonaceous particles (A) in the photographed electrode cross-sectional image was made into an approximate ellipsoidal cross-section using image analysis software ImageProPlus (manufactured by Media Cybernetics, Japan Roper). The length of the major axis and the length of the minor axis were measured from each approximate ellipsoidal cross section, and the average value of the major axis length and the average value of the minor axis length were defined as major axis a and minor axis b. The oblateness f represented by the following formula (1) was calculated from the major axis a and the minor axis b.
Flatness ratio f = 1−b / a (1)

  Particle size: About 1 ml of 2% (volume) aqueous solution of polyoxyethylene (20) sorbitan monolaurate, about 20 mg of carbon powder, dispersed in about 200 ml of ion-exchanged water, laser diffraction particle size distribution The volume-based particle size distribution was measured using a meter (LA-920, manufactured by Horiba, Ltd.) to determine the median diameter (d50). The measurement conditions are ultrasonic dispersion for 1 minute, ultrasonic intensity 2, circulation speed 2, and relative refractive index 1.50.

  Tap density: For example, it is measured using a powder density measuring instrument tap denser KYT-3000 (manufactured by Seishin Enterprise Co., Ltd.). After dropping carbonaceous particles or the like into a 10 cc tap cell and filling the cell fully, tap with a stroke length of 10 mm was performed 500 times, and the density at that time was defined as the tap density.

  BET specific surface area; measured using AMS-8000 manufactured by Okura Riken Co., Ltd. After pre-drying at 250 ° C. and flowing nitrogen gas for 30 minutes, the BET one-point method by nitrogen gas adsorption was used for measurement.

X-ray diffraction: Reflective diffractometer using a mixture of carbon powder and X-ray standard high-purity silicon powder of about 15% by mass as a material, and using CuKα radiation monochromatized with a graphite monochromator as a radiation source A wide-angle X-ray diffraction curve was measured by this method. The interplanar spacing (d002) and crystallite size (Lc) were determined using the Gakushin method.

  True density: Measured by a liquid phase substitution method (pycnometer method) using butanol using a 0.1% aqueous solution of a surfactant as a medium.

Pore volume (pore volume in the range of 10 nm to 100000 nm): The mercury porosimeter (model name: manufactured by Micromeritics, Autopore 9520) was used to carry out the mercury intrusion method. After pressing, or unpressed electrode sheet 2000 mm ² was accurately cut out and weighed and subjected to pretreatment (degassing) at room temperature (24 ° C.) for 10 minutes under vacuum (50 μm / Hg), then mercury pressure Was increased from 4.0 psia to 40000 psia and then decreased to 15 psia (total number of measurement points 120 points). At the measured 120 points, the intrusion amount of mercury was measured after an equilibration time of 5 seconds until 30 psia, and thereafter 10 seconds for each pressure.
From the mercury intrusion curve thus obtained, the pore distribution was calculated using the Washburn equation (D = − (1 / P) 4γcos ψ). D represents the pore diameter, P represents the pressure, γ represents the surface tension of mercury (using 485 dynes / cm), and ψ represents the contact angle (using 140 °).

Aspect ratio: Take a picture of the negative electrode surface, a cross section cut and polished in a plane parallel to the film surface of the current collector, or a cross section of the negative electrode cut and polished perpendicularly to the film surface of the current collector, More than 50 points of the major axis (longest diameter) and minor axis of the surface (cross section) of the carbonaceous particles (A) or scaly graphite (A1) were measured by image analysis of the photograph of the photographed negative electrode cross section. The average value was calculated | required about each of the measured major axis and minor axis, and ratio of these average major axis and average minor axis was made into the aspect ratio (major axis / minor axis). Further, when the negative electrode active material does not maintain the negative electrode form (for example, in powder form), the negative electrode active material particles are embedded in a resin in a state where they are arranged on a flat plate serving as a substrate such as glass, and are parallel to the flat plate. The long diameter was measured as described above from the cross-sectional photograph. Similarly, the minor axis of the graphite cross section was measured to determine the aspect ratio. Here, since the plate-like particles usually tend to be arranged so that the thickness direction of the particles is perpendicular to the flat plate, the above-mentioned method obtains characteristic long and short diameters of the particles. Can do. In addition, generally the cross-section (or surface) photograph of particle | grains is image | photographed using a scanning electron microscope (Scanning Electron Microscope: SEM). However, when the shape of the carbonaceous particles (A) cannot be specified by the SEM photograph, a cross-sectional (surface) photograph is taken in the same manner as described above using a polarizing microscope or a transmission electron microscope (TEM). Thus, the aspect ratio can be obtained.
In this example, the negative electrode was cut and polished perpendicularly to the film surface of the current collector, a cross-sectional photograph thereof was taken, and the major axis of the cross section of the carbonaceous particles (A) was obtained by image analysis of the photographed photograph. The minor axis was measured at 100 points.

  Length of minor axis of particle: It was measured by the same method as that of measuring the minor axis when measuring the aspect ratio.

The coverage of the carbon layer of the composite type carbonaceous particles;
Coverage (mass%) = 100− (K × D) / ((K + T) × N) × 100
In this equation, K is the mass (Kg) of the graphite particles subjected to mixing with the tar pitch, T is the mass (kg) of the tar pitch that is the coating raw material used for mixing with the graphite particles, and D is the amount of K and T Of the mixture, the amount of the mixture actually subjected to firing, N, indicates the mass of the carbonaceous particles (A) provided with the carbon layer after firing on at least a part of the surface of the graphite particles.

[Example 1]
(Carbonaceous particles (A))
The carbonaceous particles (A) have an average particle diameter Rg of 19 μm, a tap density of 0.95 g / cm ³ , a BET method specific surface area of 5.5 m ² / g, and a surface spacing of 002 planes by an X-ray wide angle diffraction method (d002). ) Is 3.35 mm, Lc is 1000 mm or more, the true density is 2.2 g / cm ³ , the major axis a is 18 μm, the minor axis b is 8.8 μm, and it is an approximate ellipsoid with an oblateness f of 0.51. Graphite was used. The flatness of the carbonaceous particles (A) was measured by the following measurement method. Specifically, with respect to 100 parts by mass of the carbonaceous particles (A), 300 parts by mass of a 1% by mass aqueous solution of carboxymethyl cellulose (CMC) as a binder (binder resin) and 48% by mass aqueous dispersion of styrene butadiene rubber (SBR). 6.25 parts by mass was kneaded with a hybridizing mixer to form a slurry. This slurry was applied onto a rolled copper foil having a thickness of 18 μm by a blade method so as to have a basis weight of 7 to 8 mg / cm ² and dried to obtain a sample negative electrode for measuring the flatness of carbonaceous particles. This negative electrode was cut out by a cross section polisher in an unpressed state, the major axis a and the minor axis b were measured by the above-described measurement method, and the flatness f was calculated from the major axis a and the minor axis b. FIG. 1 shows a photograph of a cross section of a negative electrode for a sample cut out by a cross section polisher in an unpressed state at a magnification of 500 by a scanning electron microscope (SEM).

(Silicon oxide particles (B))
As the silicon oxide particles (B), commercially available SiO particles (SiO _x x = 1) particles (Osaka Titanium Technologies) were used. The SiO particles had a median diameter (d50) Rs of 6 μm and a BET specific surface area of 6 m ² / g.

[Mixture of carbonaceous particles (A) and silicon oxide particles (B)]
Carbonaceous particles (A) were 100 parts by mass and 11 parts by mass of silicon oxide particles (B) were dry mixed to obtain a mixture. Since the average particle diameter Rg of the carbonaceous particles (A) is 19 μm and the average particle diameter Rs of the silicon oxide particles (B) is 6 μm, the ratio Rs / Rg between them is 0.316. Moreover, the tap density of the mixture was 1.1 g / cm ³ .

[Production of battery for performance evaluation]
100 parts by mass of the mixture of carbonaceous particles (A) and silicon oxide particles (B), 300 parts by mass of a 1% by mass aqueous solution of carboxymethyl cellulose (CMC) as a binder (binder resin), and 48% by mass of styrene butadiene rubber (SBR). 6.25 parts by mass of the aqueous dispersion was kneaded with a hybridizing mixer to obtain a slurry. This slurry was applied onto a rolled copper foil having a thickness of 18 μm by a blade method so as to have a basis weight of 7 to 8 mg / cm ² and dried. Then, roll press with a 250 mφ roll press with a load cell so that the electrode density is 1.4 to 1.5 g / cm ³ , punched into a circular shape with a diameter of 12.5 mm, and vacuum dried at 110 ° C. for 2 hours, A negative electrode for evaluation was used. As a result of measuring the pore volume of the electrode with a mercury polysimeter in an unpressed state, it was 0.18 ml / g.

  The battery was fabricated by stacking a negative electrode and a Li foil as a counter electrode through a separator impregnated with an electrolytic solution, to produce a battery for a charge / discharge test. As the electrolytic solution, a solution obtained by dissolving LiPF6 in a mixed solution of ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 3: 3: 4 (weight ratio) to 1 mol / liter was used.

First, the positive electrode and the negative electrode are charged to 5 mV at a current density of 0.12 mA / cm ² , further charged to a current value of 0.012 mA at a constant voltage of 5 mV, and lithium is doped into the negative electrode. The battery was discharged to 1.5 V with respect to the positive electrode and the negative electrode at a current density of .12 mA / cm ² . This cycle was repeated twice for initial adjustment.
After 3 cycles, the positive electrode and the negative electrode are charged to 5 mV at a current density of 0.49 mA / cm ² , and further charged at a constant voltage of 5 mV until the current value becomes 0.049 mA. After doping, the positive electrode and the negative electrode were discharged to 1.5 V at a current density of 0.49 mA / cm ² . Using the battery of Example 1, the following cycle characteristics were evaluated. The results are shown in Table 1.

<Cycle characteristic evaluation>
The battery repeated the charge / discharge cycle after 3 cycles 50 times, calculated | required the capacity | capacitance maintenance factor by following formula (2), and evaluated the charge / discharge efficiency at the time of 50 cycles by following formula (3). The negative electrode active material weight was determined by subtracting the weight of the copper foil punched out to the same area as the negative electrode from the negative electrode weight.

Capacity maintenance rate Capacity maintenance rate (%) = {Discharge capacity at 53 cycles (mAh / g) / 3 Discharge capacity at 3 cycles (mAh / g)} × 100 (2)

Charging / discharging efficiency at 50 cycles Charging / discharging efficiency at 50 cycles (%) = {discharge capacity at 53 cycles (mAh / g) / charge capacity at 53 cycles (mAh / g)} × 100 (3)

[Example 2]
(Carbonaceous particles (A) and silicon oxide particles (B))
The carbonaceous particles (A) have an average particle diameter Rg of 23 μm, a tap density of 1.0 g / cm ³ , a BET method specific surface area of 5.6 m ² / g, and a plane spacing of 002 planes by the X-ray wide angle diffraction method (d002 ) Is 3.35 mm, Lc is 1000 mm or more, true density is 2.2 g / cm ³ , major axis a: 22.1 μm, minor axis b: 11.5 μm, flatness f: 0.48. Some natural graphite was used. As the silicon oxide particles (B), commercially available SiO particles (SiOx x = 1) particles (Osaka Titanium Technologies) were used. The SiO particles had a median diameter (d50) Rs of 6 μm and a BET specific surface area of 6 m ² / g.

[Mixture of carbonaceous particles (A) and silicon oxide particles (B)]
Carbonaceous particles (A) were 100 parts by mass and 11 parts by mass of silicon oxide particles (B) were dry mixed to obtain a mixture. Since the average particle diameter Rg of the carbonaceous particles (A) is 23 μm and the average particle diameter Rs of the silicon oxide particles (B) is 6 μm, the ratio Rs / Rg between them is 0.261. Moreover, the tap density of the mixture was 1.15 g / cm ³ .

[Production of battery for performance evaluation]
A negative electrode for evaluation was produced in the same manner as in Example 1 using a mixture of carbonaceous particles (A) and silicon oxide particles (B). A battery for evaluation was produced in the same manner as in Example 1, and the results of the cycle characteristic evaluation similar to that described above are shown in Table 1.

[Example 3]
(Carbonaceous particles (A) and silicon oxide particles (B))
The carbonaceous particles (A) have an average particle diameter Rg of 17.7 μm, a tap density of 0.7 g / cm ³ , a BET specific surface area of 6.5 m ² / g, and a 002 plane spacing by X-ray wide angle diffraction. Approximate ellipse with (d002) of 3.35 mm, Lc of 1000 mm or more, true density of 2.2 g / cm ³ , major axis a: 17.4 μm, minor axis b: 6.6 μm, flatness ratio f: 0.62 Natural graphite was used.
As the silicon oxide particles (B), commercially available SiO particles (SiO _x x = 1) particles (Osaka Titanium Technologies) were used. The SiO particles had a median diameter (d50) Rs of 6 μm and a BET specific surface area of 6 m ² / g.

[Mixture of carbonaceous particles (A) and silicon oxide particles (B)]
Carbonaceous particles (A) were 100 parts by mass and 11 parts by mass of silicon oxide particles (B) were dry mixed to obtain a mixture. Since the average particle diameter Rg of the carbonaceous particles (A) was 17.7 μm and the average particle diameter Rs of the silicon oxide particles (B) was 6 μm, the ratio Rs / Rg between them was 0.339. Moreover, the tap density of the mixture was 0.8 g / cm ³ .

[Production of battery for performance evaluation]
A negative electrode for evaluation was produced in the same manner as in Example 1 using a mixture of carbonaceous particles (A) and silicon oxide particles (B). A battery for evaluation was produced in the same manner as in Example 1, and the results of the cycle characteristic evaluation similar to that described above are shown in Table 1.

[Example 4]
(Composite carbonaceous particles (A))
The composite type carbonaceous particles (A) have an average particle diameter Rg of 19 μm, a tap density of 0.95 g / cm ³ , a BET specific surface area of 5.5 m ² / g, and a 002 plane by X-ray wide angle diffraction. An approximate ellipsoid with an interval (d002) of 3.35 mm, Lc of 1000 mm or more, a true density of 2.2 g / cm ³ , a major axis a: 18 μm, a minor axis b: 8.8 μm, and an oblateness f: 0.51 Carbon coating was performed on the natural graphite as follows. 100 parts by mass of the carbonaceous particles (A) and 9.4 parts by mass of the coal-derived pitch were put into a kneader having a machiskater type stirring blade previously heated to 128 ° C. and mixed for 20 minutes. The obtained slurry-like mixture was heated in a batch heating furnace in a nitrogen / oxygen mixed atmosphere at 350 ° C. for 1 hour, and then maintained at 900 ° C. and further heat-treated for 1 hour. After cooling in an inert atmosphere, the obtained powder was pulverized to obtain composite-type carbonaceous particles (A) having a carbon layer made of amorphous carbon on at least a part of the surface of the graphite particles. .
The composite-type carbonaceous particles (A) have a carbon layer coverage of 3% by mass, an average particle diameter Rg of 19 μm, an aspect ratio of 1.62, and a 002 surface by an X-ray wide angle diffraction method. The face spacing (d002) was 3.35 mm, Lc was 1000 mm or more, the tap density was 1.10 g / cm ³ , the BET specific surface area was 2.8 m ² / g, and the true density was 2.2 g / cm ³ .
In addition, the pitch derived from coal used alone was fired in a nitrogen atmosphere to 1300 ° C., then cooled to room temperature, and pulverized to obtain a 002 surface by an X-ray wide angle diffraction method of an amorphous carbon single material. The surface separation (d002) was 3.45 mm and Lc was 24 mm.

(Silicon oxide particles (B))
As the silicon oxide particles (B), commercially available SiO particles (SiO _x x = 1) particles (Osaka Titanium Technologies) were used. The SiO particles had a median diameter (d50) Rs of 6 μm and a BET specific surface area of 6 m ² / g.

[A mixture of composite carbonaceous particles (A) and silicon oxide particles (B)]
Carbonaceous particles (A) were dry mixed with 11 parts by mass of silicon oxide particles (B) with respect to 100 parts by mass to obtain a mixture. Since the average particle diameter Rg of the carbonaceous particles (A) is 19 μm and the average particle diameter Rs of the silicon oxide particles (B) is 6 μm, the ratio Rs / Rg between them is 0.316. Moreover, the tap density of the mixture was 1.1 g / cm ³ .

[Production of battery for performance evaluation]
A negative electrode for evaluation was produced in the same manner as in Example 1 by using a mixture of composite type carbonaceous particles (A) and silicon oxide particles (B). A battery for evaluation was produced in the same manner as in Example 1, and the results of the cycle characteristic evaluation similar to that described above are shown in Table 1.

[Example 5]
(Carbonaceous particles (A))
The carbonaceous particles (A) have an average particle diameter Rg of 19 μm, a tap density of 0.95 g / cm ³ , a BET method specific surface area of 5.5 m ² / g, and a surface spacing of 002 planes by an X-ray wide angle diffraction method (d002). ) Is 3.35 mm, Lc is 1000 mm or more, the true density is 2.2 g / cm ³ , the major axis a is 18 μm, the minor axis b is 8.8 μm, and it is an approximate ellipsoid with an oblateness f of 0.51. Graphite was used.

(Composite silicon oxide particles (B))
Silicon oxide particles (B) were obtained by applying carbon coating to commercially available SiO particles (SiO _x x = 1) particles (Osaka Titanium Technologies) (median diameter (d50) Rs: 6 μm, BET specific surface area: 6 m ² / g). Particles were used. Carbon coating was performed by the following procedure. 100 parts by mass of the silicon oxide particles (B) and 9.4 parts by mass of the coal-derived pitch were put into a kneader having a machiskater type stirring blade previously heated to 128 ° C. and mixed for 20 minutes. The obtained slurry-like mixture was heated in a batch heating furnace in a nitrogen / oxygen mixed atmosphere at 350 ° C. for 1 hour, and then maintained at 900 ° C. and further heat-treated for 1 hour. After cooling in an inert atmosphere, the obtained powder was pulverized to obtain composite silicon oxide particles (B) having a carbon layer made of amorphous carbon on at least a part of the surface of the graphite particles. .

[Mixture of carbonaceous particles (A) and composite silicon oxide particles (B)]
Carbonaceous particles (A) were dry mixed with 11 parts by mass of composite silicon oxide particles (B) with respect to 100 parts by mass to obtain a mixture. Since the average particle diameter Rg of the carbonaceous particles (A) is 19 μm and the average particle diameter Rs of the silicon oxide particles (B) is 6 μm, the ratio Rs / Rg between them is 0.316. Moreover, the tap density of the mixture was 1.1 g / cm ³ .

[Production of battery for performance evaluation]
A negative electrode for evaluation was produced in the same manner as in Example 1 using a mixture of carbonaceous particles (A) and composite type silicon oxide particles (B). A battery for evaluation was produced in the same manner as in Example 1, and the results of the cycle characteristic evaluation similar to that described above are shown in Table 1.

[Example 6]
(Carbonaceous particles (A) and silicon oxide particles (B))
The carbonaceous particles (A) have an average particle diameter Rg of 19 μm, a tap density of 0.95 g / cm ³ , a BET method specific surface area of 5.5 m ² / g, and a surface spacing of 002 planes by an X-ray wide angle diffraction method (d002). ) Is 3.35 mm, Lc is 1000 mm or more, the true density is 2.2 g / cm ³ , the major axis a is 18 μm, the minor axis b is 8.8 μm, and it is an approximate ellipsoid with an oblateness f of 0.51. Graphite was used. As the silicon oxide particles (B), SiO particles (x = 0.7 of SiO _x ) particles were used. The SiO particles had a median diameter (d50) Rs of 0.4 μm and a BET specific surface area of 100 m ² / g.

[Mixture of carbonaceous particles (A) and silicon oxide particles (B)]
Carbonaceous particles (A) were dry mixed with 11 parts by mass of silicon oxide particles (B) with respect to 100 parts by mass to obtain a mixture. Since the average particle diameter Rg of the carbonaceous particles (A) is 19 μm and the average particle diameter Rs of the silicon oxide particles (B) is 6 μm, the ratio Rs / Rg between them is 0.316. Moreover, the tap density of the mixture is 0.86 g / cm ³ .

[Production of battery for performance evaluation]
A negative electrode for evaluation was produced in the same manner as in Example 1 using a mixture of carbonaceous particles (A) and silicon oxide particles (B). A battery for evaluation was produced in the same manner as in Example 1, and the results of the cycle characteristic evaluation similar to that described above are shown in Table 1.

[Comparative Example 1]
(Carbonaceous particles (A '))
The carbonaceous particles (A ′) have an average particle diameter Rg of 16 μm, a tap density of 1.0 g / cm ³ , a BET specific surface area of 7 m ² / g, and an interplanar spacing of 002 by X-ray wide angle diffraction (d002). Is 3.35 mm, Lc is 1000 mm or more, true density is 2.2 g / cm ³ , major axis a: 14.7 μm, minor axis b: 9.2 μm, flatness f: 0.37, perfect circle shape Natural graphite close to is used. The major axis a and minor axis b of the carbonaceous particles (A ′) were measured, and the flatness f was measured from the major axis a and minor axis b by the following measuring method.

Specifically, carbonaceous particles (A ′) alone: with respect to 100 parts by mass, 300 parts by mass of a 1% by mass aqueous solution of carboxymethyl cellulose (CMC) as a binder (binder resin) and 48% by mass of styrene butadiene rubber (SBR). 6.25 parts by mass of the aqueous dispersion was kneaded with a hybridizing mixer to obtain a slurry. This slurry was applied onto a rolled copper foil having a thickness of 18 μm by a blade method so as to have a basis weight of 7 to 8 mg / cm ² and dried to obtain a sample negative electrode for measuring the flatness of carbonaceous particles. This negative electrode was cut out by a cross section polisher in an unpressed state. FIG. 2 shows a photograph of a magnification of 2000 magnification by a scanning electron microscope (SEM) of a cross section of the negative electrode for a sample cut out by a cross section polisher in an unpressed state.

(Silicon oxide particles (B))
As the silicon oxide particles (B), commercially available SiO particles (SiO _x x = 1) particles (Osaka Titanium Technologies) were used. The SiO particles had a median diameter (d50) Rs of 6 μm and a BET specific surface area of 6 m ² / g.

[Mixture of carbonaceous particles (A ′) and silicon oxide particles (B)]
Carbonaceous particles (A ′) were dry mixed with 11 parts by mass of silicon oxide particles (B) with respect to 100 parts by mass to obtain a mixture. Since the average particle diameter Rg of the carbonaceous particles (A) was 16 μm and the average particle diameter Rs of the silicon oxide particles (B) was 6 μm, the ratio Rs / Rg between them was 0.375. Moreover, the tap density of the mixture was 1.3 g / cm ³ .

[Production of battery for performance evaluation]
A negative electrode for evaluation was produced in the same manner as in Example 1 using a mixture of carbonaceous particles (A ′) and silicon oxide particles (B). As a result of measuring the pore volume of the electrode with a mercury polysimeter in an unpressed state, it was 0.58 ml / g. Table 1 shows the results of producing a battery for evaluation using the negative electrode in the same manner as in Example 1 and performing the same cycle characteristics evaluation as described above.

[Comparative Example 2]
(Carbonaceous particles (A "))
As the carbonaceous particles (A ″), scaly graphite (manufactured by TIMCAL, trade name UF2) was used. The flatness of the carbonaceous particles (A ″) was measured by the above measurement method. Specifically, the carbonaceous particles (A ″) alone: with respect to 100 parts by mass, 300 parts by mass of a 1% by mass aqueous solution of carboxymethyl cellulose (CMC) as a binder (binder resin) and 48% by mass of styrene butadiene rubber (SBR). 6.25 parts by mass of an aqueous dispersion was kneaded in a hybrid mixer to obtain a slurry, which was applied to a rolled copper foil having a thickness of 18 μm by a blade method, and the basis weight of the active material was 7 to 8 mg / cm ^2. A negative electrode for a sample for measuring the flatness of the carbonaceous particles was obtained by cutting the negative electrode with a cross section polisher, measuring the major axis a and the minor axis b by the measurement method, The oblateness f was calculated from the major axis a and the minor axis b. The carbonaceous particles (A ″) had a major axis a: 5.4 μm, a minor axis b: 1.65 μm, and an oblateness ratio f: 0. .69 and scaly. FIG. 3 shows a photograph at a magnification of 10,000 with a scanning electron microscope (SEM) of a cross section of the negative electrode for a sample cut out by a cross section polisher.

The obtained carbonaceous particles (A ″) have an average particle diameter Rg of 5 μm, a tap density of 0.3 g / cm ³ , a BET specific surface area of 15 m ² / g, and a 002 plane spacing by X-ray wide angle diffraction. (D002) was 3.35 kg, Lc was 1000 kg or more, and the true density was 2.2 g / cm ³ .

(Silicon oxide particles (B))
As the silicon oxide particles (B), commercially available SiO particles (SiO _x x = 1) particles (Osaka Titanium Technologies) were used. The SiO particles had a median diameter (d50) Rs of 6 μm and a BET specific surface area of 6 m ² / g.

[Mixture of carbonaceous particles (A ″) and silicon oxide particles (B)]
100 parts by mass of carbonaceous particles (A ″) and 11 parts by mass of silicon oxide particles (B) were dry mixed to form a mixture. The average particle diameter Rg of the carbonaceous particles (A ″) was 5 μm. Since the average particle diameter Rs of the silicon oxide particles (B) is 6 μm, the ratio Rs / Rg between them was 1.2. Moreover, the tap density of the mixture was 0.37 g / cm ³ .

[Production of battery for performance evaluation]
A negative electrode for evaluation was produced using a mixture of carbonaceous particles (A ″) and silicon oxide particles (B) in the same manner as in Example 1. In an unpressed state, the pores of the electrodes were measured with a mercury polysimeter. As a result of measuring the volume, it was 0.27 ml / g Using the negative electrode, a battery for evaluation was produced in the same manner as in Example 1, and the results of cycle characteristics evaluation similar to the above were shown. It is shown in 1.

[Comparative Example 3]
(Carbonaceous particles (A))
The carbonaceous particles (A) have an average particle diameter Rg of 19 μm, a tap density of 0.95 g / cm ³ , a BET method specific surface area of 5.5 m ² / g, and a surface spacing of 002 planes by an X-ray wide angle diffraction method (d002). ) Is 3.35 mm, Lc is 1000 mm or more, the true density is 2.2 g / cm ³ , the major axis a is 18 μm, the minor axis b is 8.8 μm, and it is an approximate ellipsoid with an oblateness f of 0.51. Graphite was used.

(Commercially available Si particles)
Instead of the silicon oxide particles (B), commercially available Si particles (mountain metal) were used. The Si particles had a median diameter (d50) Rs of 6 μm and a BET specific surface area of 6 m ² / g.

[A mixture of carbonaceous particles (A) and commercially available Si particles]
Carbonaceous particles (A) were dry mixed with 100 parts by mass of silicon oxide particles (B) and 6 parts by mass to obtain a mixture. Since the average particle diameter Rg of the carbonaceous particles (A) was 19 μm and the average particle diameter Rs of the Si particles was 6 μm, the ratio Rs / Rg between them was 0.316. Moreover, the tap density of the mixture was 1.2 g / cm ³ .

[Production of battery for performance evaluation]
A negative electrode for evaluation was produced in the same manner as in Example 1 using a mixture of carbonaceous particles (A) and commercially available Si particles. A battery for evaluation was produced in the same manner as in Example 1, and the results of the cycle characteristic evaluation similar to that described above are shown in Table 1.

In Table 1 below, the capacity retention rates of Examples 1 to 6 and Comparative Examples 1 to 3 and the charge and discharge efficiency at 50 cycles are described.

  As shown in Table 1, a battery using a negative electrode material including carbonaceous particles (A) and silicon oxide particles (B), which are approximate ellipsoids having an aspect ratio f in the range of 0.38 to 0.68, Compared to the batteries using the negative electrode materials of Comparative Example 1 and Comparative Example 2, the capacity retention ratio and the charge / discharge efficiency showed good numerical values, and the cycle characteristics were improved while maintaining a high capacity. When the shape of the carbonaceous particles (A ′) approaches a perfect circle as in Comparative Example 1, the expansion associated with charging / discharging of the silicon oxide particles (B) present in the gaps formed by the carbonaceous particles (A ′). Due to the shrinkage, the contact of the carbonaceous particles (A ′) having a shape close to a perfect circle became difficult to be held, and the capacity retention rate and the charge / discharge efficiency were slightly reduced. Further, as in Comparative Example 2, when the shape of the carbonaceous particles (A) in the cross section of the negative electrode approaches a scaly shape, it becomes difficult to form a gap in which the silicon oxide particles (B) can exist, and the silicon oxide particles (B ) Cannot be present, the capacity retention rate has decreased. In addition, when the carbonaceous particles (A ″) of Comparative Example 2 were used, it became difficult to ensure contact between the carbonaceous particles (A ″) with charge / discharge, and the conductive path was cut, resulting in a decrease in cycle characteristics. . Further, when the commercially available Si particles of Comparative Example 3 were used, even if the particle diameter was the same as that of Example 1 or the like, the Si particles were lithium in comparison with the amorphous silicon oxide particles (B). Since it was difficult for ions to enter and exit and the activity was low, both the capacity retention rate and the charge / discharge efficiency were reduced.

  According to the present invention, it is possible to provide a non-aqueous secondary battery having both high capacity and high cycle characteristics. The non-aqueous secondary battery according to the present invention can satisfy the characteristics required for the use of recent power tools and electric vehicles, and is industrially useful.

Claims (11)

The carbonaceous particles (A) include carbonaceous particles (A) and silicon oxide particles (B), and the carbonaceous particles (A) are represented by the following formula (1) calculated from the major axis a and the minor axis b determined by the following measurement method. A negative electrode material for a non-aqueous secondary battery, wherein the flatness f is an approximate ellipsoid having a flatness ratio f of 0.38 to 0.68.
f = 1−b / a (1)
(Measurement method) 100 parts by mass of carbonaceous particles (A) and 10 parts by mass or less of binder resin are mixed to form a slurry in an aqueous or organic medium, and a thickener is added thereto as necessary to collect current. An electrode having a basis weight of 6 to 20 mg / cm ² of the active material layer is prepared by applying to the body and drying. The obtained electrode was cut out with an active material layer density of 1.2 to 1.8 g / cm ^{3 or} in an unpressed state by a cross section polisher (CP), and was scanned with a scanning electron microscope (SEM). Each cross-sectional ellipse of 100 carbonaceous particles in the photographed electrode cross-sectional image is made into an approximate ellipsoidal cross section using image analysis software, and the length of each major axis and the length of the minor axis are measured from each approximate ellipsoidal section. The average value of the lengths of these major axes and the average value of the minor axis lengths are defined as major axis a and minor axis b.   The negative electrode material for a non-aqueous secondary battery according to claim 1, wherein the carbonaceous particles (A) include those having a carbon layer on at least a part of the surface of the graphite particles.   The ratio Rs / Rg between the average particle diameter Rg of the carbonaceous particles (A) and the average particle diameter Rs of the silicon oxide particles (B) is 0.001 to 5, according to claim 1 or 2. Negative electrode material for secondary batteries.   The negative electrode material for nonaqueous secondary batteries according to any one of claims 1 to 3, comprising 1 to 50 parts by mass of silicon oxide particles (B) with respect to 100 parts by mass of carbonaceous particles (A). The negative electrode for a nonaqueous secondary battery according to any one of claims 1 to 4, wherein the silicon oxide particles (B) are represented by the general formula SiO _x (x is 0.5 ≦ x ≦ 1.6). Wood.   The negative electrode material for a non-aqueous secondary battery according to any one of claims 1 to 5, wherein the average particle diameter Rg of the carbonaceous particles (A) is 5 to 30 µm.   The negative electrode material for nonaqueous secondary batteries according to any one of claims 1 to 6, wherein the carbonaceous particles (A) have a major axis a of 5 to 30 µm and a minor axis b of 1 to 25 µm.   The negative electrode material for a non-aqueous secondary battery according to any one of claims 1 to 7, wherein the silicon oxide particles (B) have an average particle diameter Rs of 0.01 to 10 µm.   Furthermore, the negative electrode material for non-aqueous secondary batteries of any one of Claims 1-8 containing scaly graphite (A1).   It is a negative electrode for non-aqueous secondary batteries provided with the electrical power collector and the active material layer formed on this electrical power collector, Comprising: The said active material layer is any one of Claims 1-9. A negative electrode for a non-aqueous secondary battery comprising the negative electrode material for a non-aqueous secondary battery.   An ion secondary battery comprising a positive electrode and a negative electrode capable of occluding and releasing ions, and an electrolyte, wherein the negative electrode is a negative electrode for a non-aqueous secondary battery according to claim 10, Water-based secondary battery.