JP2017062974A - Negative electrode active material for nonaqueous electrolyte secondary battery, method for manufacturing negative electrode active material for nonaqueous electrolyte secondary battery, and negative electrode material for nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a negative electrode active material for a nonaqueous electrolyte secondary battery, which exhibits a superior initial efficiency, a superior discharge capacity and a superior cycle characteristic (cycle retaining rate) when used as a negative electrode material for a nonaqueous electrolyte secondary battery.SOLUTION: A negative electrode active material for a nonaqueous electrolyte secondary battery comprises: a ceramic composite material including a SiOC ceramic, and a metal silicon and SiC dispersed in the SiOC ceramic. Supposing that in X-ray diffraction with CuKα characteristic X-rays, the peak intensity of a (111)plane diffraction line of the metal silicon is b1, and the peak intensity of a (111)plane diffraction line of the SiC is b2, a ratio expressed by b1/b2 is 0.20-10.00. When compressed with a pressure of 30 MPa, the ceramic composite material is 1.2-1.8 g/cmin density.SELECTED DRAWING: None

Description

  The present invention relates to a negative electrode active material for a nonaqueous electrolyte secondary battery, a method for producing a negative electrode active material for a nonaqueous electrolyte secondary battery, and a negative electrode material for a nonaqueous electrolyte secondary battery.

Non-aqueous electrolyte secondary batteries such as lithium secondary batteries are high-power, high-capacity secondary batteries, portable devices such as mobile phones, personal computers and PDAs (personal information terminals), standby power supplies, and driving for vehicles. It is expected that the demand will continue to increase in the future.
In these applications, there is a strong demand for smaller size, lighter weight, and higher capacity, and in order to meet those demands, various parts and materials of secondary batteries are actively being improved. The development of negative electrode active materials is becoming increasingly important.

Currently, carbon (graphite) -based materials are mainly used as the negative electrode active material, and a discharge capacity of about 350 mAh / g to 360 mAh / g and a value close to the theoretical capacity of graphite (372 mAh / g) have been put into practical use. However, it is impossible to exceed the theoretical capacity of graphite.
Metallic silicon, on the other hand, is expected to be a negative electrode active material that can replace graphite because it has a theoretical capacity as large as 4200 mAh / g, but the negative electrode material deteriorates due to expansion and contraction associated with charge and discharge, and the cycle life of the battery is short. There was a technical problem.

On the other hand, silicon oxycarbide (SiOC) ceramics have attracted attention for the purpose of improving the cycle characteristics of the battery while increasing the discharge capacity.
SiOC ceramics is a silicon compound obtained by polymerizing and firing using a silicon-containing organic substance and a carbon source resin. Mass production is possible and cost reduction is expected, and the voltage is uniform until the end of discharge. Therefore, the capacity of the battery can be directly obtained from the voltage measurement as in the case of the carbon (graphite) -based material.

  On the other hand, a negative electrode material made of SiOC ceramics is inferior in initial efficiency and discharge capacity as compared with a negative electrode material made of metal silicon and the like, and particularly when used as a negative electrode material of a lithium secondary battery, the discharge voltage is as high as 3V. Furthermore, since the discharge capacity is insufficient to obtain a sufficient operating voltage, no device that can exhibit practically sufficient performance has been proposed.

  For this reason, although a negative electrode material for a non-aqueous electrolyte secondary battery in which metallic silicon or the like is coated with SiOC ceramics or the like has been proposed (see cited document 1 (Japanese Patent Laid-Open No. 2004-335334)), it is described in cited document 1 There is a technical problem that not only can the battery characteristics be exhibited sufficiently even using a negative electrode material made of the above negative electrode material, but the gelation time during the formation of the negative electrode material is long, resulting in high manufacturing costs (lead time costs). Was.

JP 2004-335334 A

  Under such circumstances, the present invention is for a non-aqueous electrolyte secondary battery that exhibits excellent initial efficiency, discharge capacity, and cycle characteristics (cycle retention rate) when used as a negative electrode material for a non-aqueous electrolyte secondary battery. Negative electrode active material, method capable of industrially mass-producing the negative electrode active material for non-aqueous electrolyte secondary battery easily and at low cost, and non-aqueous electrolyte secondary battery including the negative electrode active material for non-aqueous electrolyte secondary battery The object is to provide a negative electrode material.

As a result of diligent investigations by the present inventors, metal silicon and SiC are dispersed in SiOC ceramics, and the peak intensity of the (111) plane diffraction line of the metal silicon in X-ray diffraction using CuKα characteristic X-rays is obtained. b1, when the peak intensity of the (111) plane diffraction line of SiC is b2, the ratio represented by b1 / b2 is 0.20 to 10.00, and the density when compressed at 30 MPa is 1. by 2g ^/ cm 3 ~1.8g / cm negative active material for a non-aqueous electrolyte secondary battery comprising a ceramic composite material which is ^3, found that it is possible to solve the above technical problem, completed the present invention based on this finding It came to do.

That is, the present invention
(1) Metallic silicon and SiC are dispersed in SiOC ceramics,
In the X-ray diffraction using CuKα characteristic X-ray, b1 / b2 where b1 is the peak intensity of the (111) plane diffraction line of the metal silicon and b2 is the peak intensity of the (111) plane diffraction line of the SiC. The ratio represented by is 0.20 to 10.00,
Negative active material for a nonaqueous electrolyte secondary battery having a density characterized by comprising the ceramic composite material is 1.2g ^/ cm ³ ~1.8g ^/ cm 3 when compressed at 30 MPa,
(2) The particle size D50 of 50% in the integrated particle size distribution in the volume-based integrated particle size distribution of the metal silicon is d1, and the particle size D50 of 50% in the volume-based integrated particle size distribution of the ceramic composite material is d2. The negative electrode active material for a nonaqueous electrolyte secondary battery according to (1) above, wherein the ratio represented by d1 / d2 is 0.01 to 0.40,
(3) The nonaqueous electrolyte secondary battery according to (1) or (2) above, wherein a 50% particle diameter D50 in the volume-based cumulative particle size distribution of the ceramic composite material is 0.5 μm to 50 μm. Negative electrode active material,
(4) The negative electrode active material for a nonaqueous electrolyte secondary battery according to any one of (1) to (3), wherein the ceramic composite material has an average circularity of 0.90 to 1.0,
(5) negative active material for a nonaqueous electrolyte secondary battery according to any one of the nitrogen adsorption specific surface area of the ceramic composite material is ^{0.1m 2 / g~50m 2 / g (} 1) ~ (4) ,
(6) non-water according to any one of the ceramic 1000 taps density when subjected to tapping of the composite material is 0.4g ^/ cm ³ ~1.3g ^/ cm 3 (1) to (5) Negative electrode active material for electrolyte secondary battery,
(7) The non-conducting material according to any one of (1) to (6), wherein the ceramic composite material further contains 1 to 30% by mass of at least one metal atom selected from Mn, Fe, Co, Ni, and Li. Negative electrode active material for water electrolyte secondary battery,
(8) The negative electrode active material for a nonaqueous electrolyte secondary battery according to any one of (1) to (7), wherein the surface portion of the ceramic composite material has a core-shell structure having a carbon content higher than that of the central portion.
(9) The negative electrode active material for a non-aqueous electrolyte secondary battery according to any one of (1) to (8), wherein the ceramic composite material has a carbon film on the surface,
(10) A carbon precursor solution obtained by mixing a carbon precursor and a solvent, a silicon-containing organic substance, and a metal silicon powder are mixed, and then the obtained mixed solution is polymerized, and further, the solvent is removed to obtain a ceramic composite material precursor. Next, after primary firing at 400 ° C. to 800 ° C., pulverization and classification, secondary firing at 1200 ° C. to 1350 ° C. to prepare a ceramic composite material (1) to ( 9) The method for producing a negative electrode active material for a nonaqueous electrolyte secondary battery according to any one of
(11) A negative electrode material for a non-aqueous electrolyte secondary battery comprising the negative electrode active material for a non-aqueous electrolyte secondary battery according to any one of (1) to (9) and a carbon active material. It is to provide.

  According to the present invention, when used as a negative electrode material for a nonaqueous electrolyte secondary battery, a negative electrode active material for a nonaqueous electrolyte secondary battery that exhibits excellent initial efficiency, discharge capacity, and cycle characteristics (cycle retention rate), Provided is a method for industrially mass-producing the negative electrode active material for a nonaqueous electrolyte secondary battery in a simple and low-cost manner and a negative electrode material for a nonaqueous electrolyte secondary battery including the negative electrode active material for the nonaqueous electrolyte secondary battery. can do.

It is a figure which shows the example of a form of the ceramic composite material which comprises the negative electrode active material for nonaqueous electrolyte secondary batteries of this invention. It is an example of the ceramic composite material X-ray diffraction spectrum which comprises the negative electrode active material for nonaqueous electrolyte secondary batteries of this invention. It is a simplified diagram for explaining the structure of a battery manufactured in an example of the present invention.

  First, the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention will be described.

The negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention is obtained by dispersing metallic silicon and SiC in SiOC ceramics, and (111) plane diffraction of the metallic silicon in X-ray diffraction using CuKα characteristic X-rays. When the peak intensity of the line is b1 and the peak intensity of the (111) plane diffraction line of SiC is b2, the ratio represented by b1 / b2 is 0.20 to 10.00 and when compressed at 30 MPa density of those characterized by comprising a ceramic composite material is ^{1.2g / cm 3 ~1.8g / cm 3} .

The ceramic composite material constituting the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention is formed by dispersing metallic silicon and SiC in SiOC ceramics.
The dispersion form of metallic silicon and SiC in the SiOC ceramic is not particularly limited. For example, as schematically shown in FIG. 1, metallic silicon (Si) and SiC are uniformly dispersed in a matrix made of SiOC ceramic. The form can be mentioned.

The ceramic composite material constituting the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention preferably has a SiOC ceramic content of 30 to 90% by mass, more preferably 35 to 85% by mass. 40 to 80% by mass is more preferable.
The ceramic composite material constituting the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention preferably has a metal silicon content of 1 to 69% by mass, and preferably 3 to 65% by mass. More preferred is 5-60% by mass, and particularly preferred is 5-30% by mass.
Furthermore, the ceramic composite material constituting the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention preferably has a SiC content of 1 to 40% by mass, more preferably 3 to 35% by mass. What is 5-30 mass% is more preferable.

When the ceramic composite material contains SiOC ceramics and metal silicon in the above proportions, excellent initial efficiency and discharge capacity are easily achieved when used as a negative electrode active material for a non-aqueous electrolyte secondary battery. be able to.
For example, when a Si / SiOC composite material obtained by sintering an organosilicon compound and metal silicon is used as a negative electrode active material for a non-aqueous electrolyte secondary battery, the metal silicon is likely to expand and cycle characteristics (cycle retention rate). In the negative electrode active material for nonaqueous electrolyte secondary batteries of the present invention, the ceramic composite material contains SiC in the above proportion, so that the negative electrode active material for nonaqueous electrolyte secondary batteries can be reduced. When used as, it is possible to easily achieve excellent cycle characteristics (cycle maintenance ratio) by suppressing expansion of metallic silicon.

  In the ceramic composite material constituting the negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, the content ratio of SiOC ceramics, metal silicon and SiC depends on the amount of raw materials used at the time of preparing the ceramic composite material and the X-ray of the ceramic composite material. It can be determined from the diffraction spectrum.

In the ceramic composite material constituting the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention, b1 represents the peak intensity of the (111) plane diffraction line of the metal silicon in the X-ray diffraction using CuKα characteristic X-ray, When the peak intensity of the (111) plane diffraction line of SiC is b2, the ratio represented by b1 / b2 is 0.20 to 10.00.
The ratio represented by b1 / b2 is preferably 0.30 to 8.00, and more preferably 0.40 to 6.00.

  In the ceramic composite material constituting the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention, the peak intensity ratio b1 / b2 means the ratio of metallic silicon to SiC, and the peak intensity ratio b1 / b2 is within the above range. As a result, metal silicon and SiC can be contained in a desired ratio. For this reason, when used as a negative electrode active material for a non-aqueous electrolyte secondary battery, the expansion and contraction of metal silicon is suppressed, which is excellent. The cycle retention ratio can be achieved, the resistance of the entire electrode and the amount of active material to be deactivated can be suppressed, and the capacity of the entire negative electrode can be easily improved.

  When the ratio represented by b1 / b2 is more than 10.00, it is difficult to suppress the expansion and contraction of Si in the ceramic composite material, and the cycle maintenance rate is liable to decrease, and the ratio is represented by b1 / b2. When the ratio is less than 0.2, the resistance of the entire electrode and the amount of active material to be deactivated increase, and the capacity of the entire negative electrode tends to decrease.

In this application document, the X-ray diffraction spectrum measured using CuKα characteristic X-ray means one measured according to the method defined in JIS K 0131: 1996.
Specifically, a sample horizontal multipurpose X-ray diffractometer (Ultima IV manufactured by Rigaku Corporation) is used as the X-ray diffractometer, light source: CuKα ray, divergence slit: 2/3 °, and scattering slit: 2/3 °. , Applied voltage: 40 kV, applied current: 40 mA, divergence limiting slit: 10 mm, and light receiving slit: 0.3 mm.

  In this application document, the ratio represented by the peak intensity b2 of the (111) plane diffraction line of the (111) plane diffraction line of the (111) plane diffraction line of metallic silicon in the X-ray diffraction using the CuKα characteristic X-ray. Means specifically calculated by the following method.

  That is, the X-ray diffraction spectrum shown in FIG. 2 will be described by using an example of the X-ray diffraction spectrum of the ceramic composite material constituting the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention shown in FIG. Interpolated between points using a cubic spline function, the horizontal axis indicates the Bragg angle (2θ), and the vertical axis indicates the X-ray diffraction intensity (intensity / au (arbitrary unit, arbitrary unit)) The diffraction line peak observed at 27 ° in the Bragg angle (2θ ± 2 °) indicated by “Si” in the figure is the (111) plane diffraction line peak of the Si crystal, and the Bragg angle indicated by “SiC” in the figure. The diffraction line peak observed at (2θ ± 2 °) 35 ° can be identified as the SiC crystal (111) plane diffraction line peak.

  In the X-ray diffraction spectrum shown in FIG. 2, the height from the base line to the peak top of the (111) plane diffraction line peak of metallic silicon (Si crystal) observed at a Bragg angle (2θ ± 2 °) of 27 °. Is the peak intensity b1, and the height from the base line to the peak top of the (111) plane diffraction line peak of SiC that is also observed at a Bragg angle (2θ ± 2 °) of 35 ° is the peak intensity b2, and the ratio b1 between the two / B2 can be obtained.

Ceramic composite material constituting the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention has density when compressed at 30MPa is ^{1.2g / cm 3 ~1.8g / cm 3} , 1. preferably it has a ^{3g / cm 3 ~1.7g / cm 3} , it is more preferable at ^{1.4g / cm 3 ~1.6g / cm 3} .

  When the density of the ceramic composite material constituting the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention is within the above range, a secondary material having a desired electrode density while using a general carbon-based active material. A negative electrode for a battery can be easily produced.

  In the present application document, the density of the ceramic composite material means a value measured according to the contents specified in JIS Z 2058: 2004.

  The ceramic composite material constituting the negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention has a 50% cumulative particle size D50 in the volume-based cumulative particle size distribution of metallic silicon in the ceramic composite material as d1. The ratio represented by d1 / d2 is preferably 0.01 to 0.40, where d2 is a 50% particle diameter D50 in the volume-based cumulative particle size distribution of the material, and 0.02 What is -0.25 is more preferable, and what is 0.03-0.16 is further more preferable.

  Ratio expressed by d1 (50% particle size D50 in the integrated particle size distribution of metal silicon) / d2 (50% particle size in the integrated particle size distribution of ceramic composite material D50) When the ceramic composite material is used as a negative electrode active material for a non-aqueous electrolyte secondary battery, the influence of expansion and contraction of silicon particles during charge and discharge is suppressed, and excellent cycle characteristics ( Cycle maintenance ratio) can be easily exhibited.

When the ratio represented by d1 / d2 is more than 0.40, the volume ratio of metal silicon in the ceramic composite material increases, and the structure of the ceramic composite material collapses due to the expansion and contraction of metal silicon. As a result, the cycle maintenance factor and the charge / discharge efficiency are likely to decrease.
When the ratio represented by the particle diameter ratio d1 / d2 is less than 0.01, the metal silicon surface is oxidized and the conductivity tends to be lowered, so that the battery characteristics are easily lowered, and the inert gas Since it is required to manufacture the ceramic composite material below, the production cost is likely to increase.

The d1 (50% particle diameter D50 in the volume-based cumulative particle size distribution of metal silicon) is preferably 0.1 to 5.0 μm, more preferably 0.2 to 4.0 μm. More preferably, the thickness is 0.3 to 3.0 μm.
Further, the d2 (50% particle diameter D50 in the volume-based cumulative particle size distribution of the ceramic composite material) is preferably 0.5 to 50 μm, more preferably 1 to 30 μm, More preferably, it is 20 μm.

When d1 is within the above range, the direction of expansion and contraction of metallic silicon in the ceramic composite material is made uniform, the influence of expansion and contraction on the entire active material is reduced, and cycle characteristics (cycle maintenance ratio) are improved. A product with high initial efficiency and capacity can be obtained.
Further, since d2 is within the above range, an increase in irreversible capacity and side reactions during charging / discharging are suppressed, electrode density is easily improved, and destruction of ceramic composite material particles during electrode sheet pressing is suppressed. It is easy to suppress the generation of fine powder.

In addition, in this application document, d1 and d2 mean the value measured with the laser diffraction type particle size distribution measuring apparatus according to the prescription | regulation of JISZ8825-2: 2001.
Specifically, for 50 ml of water, add 2 cups of ultra-small spatula and 2 drops of non-ionic surfactant (Triton-X) to the metal silicon or ceramic composite material used as a raw material for more than 3 minutes It means a value measured using a laser diffraction particle size distribution measuring device (SALD2000 manufactured by Shimadzu Corporation) using a sample dispersed by sonic wave as a measurement sample.

The ceramic composite material constituting the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention preferably has an average circularity of 0.90 to 1.0, and preferably 0.91 to 1.00. More preferred is 0.92 to 1.00.
When the average circularity of the ceramic composite material constituting the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention is within the above range, an increase in ceramic composite material particles having many edge portions is suppressed, and the ceramic composite material particles Interaction between each other can be suppressed, and the packing density and the electrode density can be easily improved.

In this application document, the average circularity of the ceramic composite material is 20 g of purified water after adding 10 drops of 1% surfactant (Lion Mama Lemon) aqueous solution to 20 mg of the ceramic composite material. And using a flow type particle image analyzer (manufactured by Sysmex Corporation: model FPIA-3000) to determine the perimeter of the projected image of the ceramic composite material particles. Measure and calculate the perimeter (equivalent circle diameter) of a circle with the same area as the projected image.
Circularity = Equivalent average diameter when the circularity of 20000 to 30000 ceramic composite material particles is obtained from the equivalent circle diameter / peripheral length of the projected image of the particles.

Ceramic composite material constituting the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention, the nitrogen adsorption specific surface ^area, preferably those which are ^{0.1m 2 / g~50m 2 / g,} 0.5m 2 / g ~45m more preferably those which are ² / ^g, more preferably those which are 1m ² / g~40m 2 / g.

In the ceramic composite material constituting the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention, when the nitrogen adsorption specific surface area exceeds 50 m ² / g, it is necessary to add a considerable amount of binder, Since the amount of the ceramic composite material, which is a substance, decreases, the battery capacity tends to decrease.
On the other hand, when the nitrogen adsorption specific surface area exceeds 50 m ² / g, the surface activity of the ceramic composite material particles increases, and the Coulomb efficiency tends to decrease due to decomposition of the electrolytic solution and the like.
When the nitrogen adsorption specific surface area is less than 0.1 m ² / g, the reaction surface area at the time of charge / discharge reaction decreases, so the reaction resistance at the time of charge / discharge increases, and the input / output characteristics and the battery capacity tend to decrease.

  In the present application documents, the nitrogen adsorption specific surface area of the ceramic composite material means a value measured according to the provisions of JIS Z 8830, and specifically, a fully automatic surface area measuring device manufactured by Shimadzu Corporation Gemini V Is a value calculated by the BET multipoint method at 6 points in the range of relative pressure of 0.05 to 0.2 on the nitrogen adsorption isotherm.

Ceramic composite material constituting the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention, the tap density when subjected to 1000 times ^tapping, those which are 0.40g / cm ³ ~1.30g / cm 3 ^preferably, more preferably those which are ^{0.45g / cm 3 ~1.00g / cm 3} , more preferably those wherein ^{0.50g / cm 3 ~0.80g / cm 3} .

When the tap density is less than 0.4 g / cm ³ , the ceramic composite materials are easily aggregated during electrode sheet preparation, and it is difficult to uniformly mix the electrodes, and the electrode plate density of the electrode is lowered, so that the energy density is easily lowered. .
When the tap density exceeds 1.3 g / cm ³ , the density at the time of compression of the mixed powder tends to decrease, the electrode density is difficult to increase when the electrode sheet is pressed, the conductive path is easily dissociated, and the energy density is likely to decrease. Become.

  In this application document, the tap density of the ceramic composite material means a value measured according to JIS Z 2512: 2012.

  The ceramic composite material constituting the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention preferably further contains 1 to 30% by mass of at least one metal atom selected from Mn, Fe, Co, Ni and Li. More preferably, it contains 2 to 25% by mass, more preferably 3 to 20% by mass of at least one metal atom selected from Mn, Fe, Co, Ni and Li.

When the ceramic composite material constituting the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention contains at least one metal atom selected from Mn, Fe, Co, Ni, and Li in the above ratio, When used as a negative electrode active material for a secondary battery, it is possible to easily exhibit excellent conductivity and to easily suppress a decrease in charge / discharge capacity of the electrode.
When the content ratio of at least one metal atom selected from Mn, Fe, Co, Ni and Li is less than 1% by mass, the effect of addition is small, and when it exceeds 30% by mass, the battery capacity tends to decrease. .

  In the present application document, the content ratio of at least one metal atom selected from Mn, Fe, Co, Ni, and Li means a value measured by emission spectroscopy (ICP-AES).

  The ceramic composite material constituting the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention preferably has a core-shell structure in which the surface portion of the ceramic composite material has a higher carbon content than the center portion.

  In the present application documents, the surface portion (shell portion) of the ceramic composite material preferably has an average thickness of 10 to 500 nm, more preferably 2 to 400 nm, and even more preferably 3 to 300 nm.

When the surface portion (shell portion) of the ceramic composite material has a higher carbon content than the center portion (core portion), the surface portion (shell portion) of the ceramic composite material is more than the center portion (core portion). 10% by mass carbon content is preferred, 20% by mass carbon content is more preferred than the central part (core part), and 30% by mass carbon content is greater than the central part (core part). Is more preferable.
The surface portion of the ceramic composite material has a higher carbon content than the center portion, so that the decomposition of the electrolytic solution is suppressed when the ceramic composite material is used as a negative electrode active material for a non-aqueous electrolyte secondary battery. In addition, the loss of the internal resistance can be reduced, and as a result, the cycle maintenance ratio and the input / output characteristics can be easily improved.

The surface portion (shell portion) of the ceramic composite material has a higher carbon content than the center portion (core portion). The surface portion (shell portion) of the ceramic composite material is more SiOC ceramic than the center portion (core portion). And the total content of SiC is high.
In this case, the surface portion (shell portion) of the ceramic composite material preferably contains 0.1 to 50% by mass of metal silicon, more preferably 0.5 to 45% by mass, and 1 to 40% by mass. Is more preferable.
When the content ratio of metal silicon in the surface portion (shell portion) of the ceramic composite material is less than 0.1% by mass, discharge is caused when the ceramic composite material is used as a negative electrode active material for a non-aqueous electrolyte secondary battery. When the capacity tends to decrease and the content ratio of metal silicon in the surface portion of the ceramic composite material is more than 50% by mass, when the ceramic composite material is used as a negative electrode active material for a non-aqueous electrolyte secondary battery, Cycle characteristics (cycle maintenance rate) are likely to be reduced.

  When the center portion of the ceramic composite material has a silicon content higher than that of the surface portion, the composition of the surface portion and the center portion can be measured by an energy dispersive X-ray analyzer (EDS).

  The ceramic composite material constituting the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention is preferably such that a carbon film is further formed on the outer surface.

In the present application document, the carbon film means a layered film in which the mass ratio of carbon atoms is preferably 1 to 100 mass%, more preferably 5 to 99 mass%, and still more preferably 10 to 98 mass%. .
The carbon film may be a material containing SiOC ceramics. In this case, the carbon film preferably has an atomic ratio of Si atoms of 10 to 50%, more preferably 12 to 45%, and still more preferably 15 to 40%. When the Si atom content exceeds 50%, when the porous SiOC ceramic composite material of the present invention is used as the negative electrode active material of a non-aqueous electrolyte secondary battery, the cycle characteristics (cycle retention rate) are likely to be lowered. Become.
The carbon film containing silicon oxycarbide ceramics preferably has an O atom atomic ratio content of 10 to 50 atm%, more preferably 12 to 45 atm%, and even more preferably 15 to 40 atm%.
In the present application documents, the atomic ratio of Si atom, O atom, and carbon atom means a value specified by the method described in Solid state ionics, 225 (2012) p.522-526, specifically, This means a value calculated by identifying the carbon atom and oxygen atom amounts with the carbon analyzer (LECO, C-200) and N / O analyzer (LECO, TC-436) and setting the remaining amount as Si atoms. .

In the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention, when the ceramic composite material has a carbon film further formed on the outer surface, the average thickness of the carbon film is preferably 10 to 500 nm. -400 nm is more preferable, and 3-300 nm is more preferable.
The average thickness of the carbon film can be measured by transmission electron microscope (TEM) image analysis of a cross section of the negative electrode active material for a nonaqueous electrolyte secondary battery according to the present invention.

  Since the ceramic composite material has a carbon film formed on the outer surface, it can suppress the decomposition of the electrolyte when the ceramic composite material is used as a negative electrode active material for a non-aqueous electrolyte secondary battery. In addition, the loss of the internal resistance can be reduced, and as a result, the cycle maintenance ratio and the input / output characteristics can be easily improved.

  According to the present invention, a negative electrode active material for a nonaqueous electrolyte secondary battery that exhibits excellent initial efficiency, discharge capacity, and cycle characteristics (cycle retention rate) when used as a negative electrode material for a nonaqueous electrolyte secondary battery is provided. Can be provided.

Next, the manufacturing method of the negative electrode active material for nonaqueous electrolyte secondary batteries which concerns on this invention is demonstrated.
The method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention is obtained by mixing a carbon precursor solution obtained by mixing a carbon precursor and a solvent, a silicon-containing organic material, and metal silicon powder, and then obtaining the mixture. The liquid is polymerized and the solvent is further removed to obtain a ceramic composite material precursor, followed by primary firing at 400 ° C. to 800 ° C., pulverization and classification, and then secondary firing at 1200 ° C. to 1350 ° C. It is characterized by preparing.

  In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, examples of the carbon precursor used as a raw material for the ceramic composite material include a resin having an OH group. Is preferably a resin having two or more OH groups, and the resin having two or more OH groups may be one or more selected from phenol resins such as resol type phenol resins or novolac type phenol resins, and furan resins. More preferably.

  In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, when the carbon-containing compound is a resin having an OH group, the mass average molecular weight Mw is preferably 200 to 20000, and 500 to 15000. It is more preferable that it is 1000-3000.

  When the mass average molecular weight Mw is less than 200, the polymer is silicified by water generated by dehydration condensation between resins, and therefore when the obtained ceramic is used as a negative electrode active material for a non-aqueous electrolyte secondary battery, The discharge capacity of the negative electrode material tends to decrease. When the mass average molecular weight Mw exceeds 20000, it becomes difficult to dissolve in a solvent, and it becomes difficult to perform a polymerization reaction with a silicon-containing organic substance.

  In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, the solvent for dispersing the carbon precursor is not particularly limited as long as the carbon precursor can be dispersed. For example, methanol, ethanol, Polar solvents such as propanol, butanol, acetone, methyl ketone, tetrahydrofuran, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, acetonitrile, diols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, ethylene glycol monoisopropyl ether And at least one selected from soloselves such as triethylene glycol monobutyl ether and ethylene glycol diethyl ether.

  A carbon precursor solution can be prepared by mixing an amount of a solvent capable of dissolving the carbon precursor with a desired amount of the carbon precursor.

In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, examples of the silicon-containing organic material include siloxane (a silicon-containing organic compound having an —O—Si—O— structure as a main skeleton). The silicon-containing organic compound having a —O—Si—O— structure as the main skeleton is preferably an alkoxysilane compound having two or more alkoxy groups and the main skeleton having a —O—Si—O— structure. As an alkoxysilane compound having an alkoxy group and a main skeleton having an —O—Si—O— structure, a tetraalkoxysilane monomer or oligomer is preferable, and a tetramethoxysilane monomer, a tetraethoxysilane monomer, a tetramethoxysilane oligomer, More preferably, it is at least one selected from tetraethoxysilane oligomers. Arbitrariness.
In the method for producing the porous SiOC ceramic of the present invention, the silicon-containing organic substance preferably has an SiO ₂ equivalent of 28% by mass or more, more preferably an SiO ₂ equivalent of 30% by mass or more, and SiO 2 More preferably, the equivalent of ₂ is 35% by mass or more.

In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, the metal silicon preferably has a particle size of 1 nm to 3 μm, more preferably 10 nm to 2 μm, and more preferably 100 nm to 1 μm. Is more preferred.
When the particle diameter of metallic silicon exceeds 3 μm, silicon particles are not formed in the SiOC structure, and when the obtained ceramic composite material is used as a negative electrode active material for a non-aqueous electrolyte secondary battery, The influence on the electrode is increased, and the cycle characteristics are liable to deteriorate. Further, when the particle size of the metal silicon is less than 1 nm, the pulverization cost is high, and the surface of the particles is easily oxidized. Therefore, when the obtained ceramic composite material is used as a negative electrode active material for a nonaqueous electrolyte secondary battery. , Characteristic deterioration is likely to occur.
The particle diameter of the metal silicon can be adjusted by performing a pulverization process such as pulverization in a ball mill using a non-aqueous solvent and a classification process such as centrifugation or filtration.

  In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, the carbon precursor solution, the silicon-containing organic material, and the metal silicon powder are mixed.

In the above mixing treatment, the carbon precursor is preferably 10 to 100 parts by mass, more preferably 12 to 75 parts by mass, and further preferably 15 to 50 parts by mass with respect to 100 parts by mass of the silicon-containing organic matter in terms of solid content. It is desirable to do so.
When the content of the carbon precursor is less than 10 parts by mass with respect to 100 parts by mass of the silicon-containing organic material, the conductivity after firing is reduced, and a post-treatment such as a carbon coat is necessary. When it is more than 50 parts by mass with respect to part by mass, it becomes difficult to use as a negative electrode material because of its low capacity.
The mixing treatment is preferably 1 to 60 parts by mass, more preferably 5 to 55 parts by mass, in terms of solid content, when the total amount of the silicon-containing organic substance and the carbon precursor is 100 parts by mass. Part, more preferably 10 to 50 parts by mass.
When the mixed amount of metal silicon is less than 1 part by mass when the total amount of silicon-containing organic substance and carbon precursor is 100 parts by mass, the ceramic composite material is used as a negative electrode active material for a non-aqueous electrolyte secondary battery In addition, when the total amount of silicon-containing organic substance and carbon precursor is 100 parts by mass, and the amount of metal silicon mixed is more than 60 parts by mass, the ceramic composite material can be used as a nonaqueous electrolyte. When used as a negative electrode active material for a secondary battery, the cycle retention rate tends to decrease.

  In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, the carbon precursor solution, the silicon-containing organic material, and the metal silicon powder are mixed so that the shear rate is 1 / second or more. It is more preferable to carry out so that it may become 10 / sec-300,000 / sec.

In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, the mixing of the carbon precursor solution, the silicon-containing organic material, and the metal silicon powder and the polymerization treatment described below are preferably performed in an inert atmosphere. .
Examples of the inert atmosphere include a rare gas atmosphere such as a nitrogen atmosphere or an argon atmosphere.
In particular, when moisture exists in the atmosphere, the characteristics of the ceramic composite material obtained due to the progress of silicification tend to deteriorate.

  In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, the mixed solution obtained by mixing the carbon precursor solution, the silicon-containing organic material, and the metal silicon powder is subjected to polymerization treatment.

The temperature during the polymerization treatment is preferably 0 ° C to 300 ° C, more preferably 10 ° C to 300 ° C, and further preferably 20 ° C to 300 ° C.
When the polymerization temperature is less than 0 ° C., the polymerization rate tends to decrease and the yield tends to decrease.

  In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, the polymerization time is preferably 1 to 240 hours, more preferably 2 to 220 hours, and still more preferably 3 to 200 hours. If the polymerization time is 1 hour or less, the yield tends to be low, and if it is 240 hours or more, the production cost is high.

In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, after completion of the polymerization treatment, the mixed solution is subjected to solvent removal to obtain a ceramic composite material precursor.
It is desirable to remove the solvent under vacuum or in an inert atmosphere. The solvent removal temperature is desirably 30 ° C to 300 ° C, more desirably 50 ° C to 300 ° C, and further desirably 7 ° C to 300 ° C. When the solvent removal temperature is less than 30 ° C., it takes a long time to remove the solvent, and thus the production efficiency tends to be lowered.

In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, the ceramic composite material precursor obtained by removing the solvent from the mixed solution is subjected to an average particle size of 100 μm prior to the subsequent firing step. It is preferable to grind to the following.
As a pulverizer used at the time of pulverization, known mechanical pulverization apparatuses such as a hammer mill, a pin mill, a jet mill, a bevel impactor, a turbo mill, a knife hammer mill, a rotary cutter mill, and a roll crusher can be used. Further, classification may be performed using a classifier such as a wind type or a mechanical type.

  In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, a mixture obtained by mixing the carbon precursor solution, the silicon-containing organic material, and the metal silicon powder is polymerized at the temperature. By performing the treatment, the carbon precursor and the silicon-containing organic material can be easily uniformly polymerized. As a result, a polymer (ceramic composite material precursor) having a high yield can be obtained, and a firing treatment described later is further performed. By performing this, a fired product having a high charge capacity can be obtained.

  In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, the ceramic composite material precursor is primarily fired at 400 ° C to 800 ° C.

The primary firing is preferably performed under a temperature condition of 400 ° C to 800 ° C, more preferably performed under a temperature condition of 450 ° C to 750 ° C, and further preferably performed under a temperature condition of 400 ° C to 700 ° C. preferable.
By performing the primary firing within the above temperature range, the ceramic composite material precursor can have an appropriate hardness, and the yield during pulverization described later can be improved.

  The firing time for performing the primary firing is preferably 1 minute to 48 hours, more preferably 2 minutes to 20 hours, and even more preferably 3 minutes to 15 hours.

  The atmosphere during the primary firing is preferably an inert atmosphere or a vacuum atmosphere, and examples of the inert atmosphere include a rare gas atmosphere such as a nitrogen atmosphere or an argon atmosphere.

  The primary firing can be performed using a known firing furnace such as a tunnel furnace, an electric (electric heater) furnace, an induction heating furnace, an electromagnetic heating furnace, an electric furnace / an electromagnetic hybrid furnace, or the like.

  In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, the primary fired product obtained by the primary firing treatment is pulverized and classified.

The primary baked product can be pulverized using a known pulverizer. The pulverizer includes hammer mill, pin mill, jet mill, bevel impactor, turbo mill, knife hammer mill, rotary cutter mill, roll crusher. Etc.
In the production method of the present invention, the pulverization may be performed by combining a plurality of the above pulverizers.
The pulverization conditions may be appropriately adjusted so that a powder having desired characteristics and the like can be obtained.

In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, the pulverized product obtained by the above pulverization treatment is classified.
Examples of the classifier include a rotor classifier, a vibration sieve, and an airflow classifier.

  In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, the pulverization and classification can be performed by a shape processing apparatus capable of simultaneously applying shear, compression, and collision stress. Examples of processing equipment include ball-type kneaders such as a rotary ball mill, wheel-type kneaders such as edge runners, hybridization systems (manufactured by Nara Machinery Co., Ltd.), mechanofusion (manufactured by Hosokawa Micron), Nobilta (Hosokawa Micron) And COMPOSI (manufactured by Nihon Coke Kogyo Co., Ltd.).

  In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, the pulverization treatment and the classification treatment are the same as the above-described method for measuring the average circularity of the ceramic composite material in the pulverization treatment and the classified product. The average circularity measured by the method is preferably 0.90 to 1.0, more preferably 0.91 to 1.0, and 0.92 to 0.92. More preferably, the treatment is carried out to 1.0.

  When the ceramic composite material to be obtained further contains 1 to 30% by mass of at least one metal atom selected from Mn, Fe, Co, Ni and Li, classification treatment obtained by classification treatment after the above pulverization It can be prepared by mixing at least one metal atom selected from Mn, Fe, Co, Ni and Li into the product and then subjecting it to secondary firing described later.

  In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, the pulverization treatment, the pulverization treatment obtained by the classification treatment, and the classified product are then subjected to a secondary firing treatment at 1200 to 1350 ° C. .

The firing temperature during the secondary firing is 1200 ° C to 1350 ° C, preferably 1200 ° C to 1300 ° C, and more preferably 1250 ° C to 1300 ° C.
When the firing temperature at the time of secondary firing is within the above range, excellent initial efficiency and discharge capacity can be exhibited when used as a negative electrode material for a nonaqueous electrolyte secondary battery.

  The firing time in performing the secondary firing is preferably 1 minute to 48 hours, more preferably 2 minutes to 20 hours, and even more preferably 3 minutes to 15 hours.

  The atmosphere for performing the secondary firing is preferably an inert atmosphere or a vacuum atmosphere, and examples of the inert atmosphere include a rare gas atmosphere such as a nitrogen atmosphere and an argon atmosphere. Further, the inert atmosphere may contain a reducing gas such as hydrogen gas.

  The secondary firing can be performed using a known firing furnace such as a tunnel furnace, an electric (electric heater) furnace, an induction heating furnace, an electromagnetic heating furnace, an electric furnace / an electromagnetic hybrid furnace, or the like.

A part of the SiOC ceramic is converted to SiC by the secondary firing treatment. The amount of SiC produced can be controlled by adjusting the firing temperature, firing time, etc. during secondary firing.
As described above, when part of the SiOC ceramic is converted to SiC and dispersed in the ceramic composite material, it suppresses the expansion of metallic silicon when used as the negative electrode active material for non-aqueous electrolyte secondary batteries. Thus, excellent cycle characteristics (cycle maintenance ratio) can be easily achieved.

  In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, the surface portion (shell portion) of the ceramic composite material to be obtained has a core-shell structure having a higher carbon content than the center portion (core portion). The primary baked product obtained by the above primary calcination treatment, or the pulverized and classified product obtained by pulverizing and classifying the primary baked product, the primary baked product or pulverized Then, after coating the carbon precursor, the silicon silicon and the silicon-containing organic substance-containing coating compound blended so that the carbon content is higher than that of the classification-treated product, a secondary firing treatment is performed.

Examples of the carbon precursor and silicon-containing organic substance constituting the coating agent include the same ones as described above.
The composition of the coating agent may be determined so as to correspond to the composition of the surface portion to be obtained, and the coating amount of the coating agent is appropriately determined so as to correspond to the thickness of the surface portion to be obtained. Just decide.

The coating of the above-mentioned coating agent on the primary baked product, pulverized and classified product can be performed by melt-mixing the above coating material on the primary baked product, pulverized and classified product.
The melt mixing can be performed by a known mixer capable of heating the object to be mixed.
As the mixer for performing melt mixing, a mixer that has a stirring shaft inside and is equipped with a stirring blade attached to the stirring shaft for mixing is preferable. Specifically, a Henschel mixer (manufactured by Nippon Coke Industries Co., Ltd.), High A speed mixer (manufactured by Fukae Powtech Co., Ltd., Redige mixer (manufactured by Matsubo Co., Ltd.), etc. can be used, and examples of the mixer for melt mixing include a kneader and a universal mixer.
The treatment temperature at the time of melt mixing is preferably a temperature not lower than the melting temperature of the carbon precursor binder constituting the coating agent and lower than the carbonization temperature, specifically, preferably 80 ° C. to 180 ° C., 100 ° C. More preferably, it is -160 degreeC.
The melt mixing time is preferably 1 minute to 20 minutes, more preferably 1 minute to 15 minutes, and further preferably 1 minute to 10 minutes.

  In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, when the ceramic composite material to be obtained has a carbon film on the surface, classification obtained by classification after the above pulverization A carbonaceous layer such as a resin layer is formed on the surface of the treated product, and then a secondary firing treatment is performed, or a carbon film formation treatment is further performed on the secondary firing treatment product obtained by the secondary firing treatment. As a result, the intended carbon film can be formed.

  Examples of the method for forming the carbon film include a method of mixing an organic material such as pitch with the secondary fired product, a method of performing thermal CVD treatment of an organic compound gas such as methane, and the like.

  When organic matter such as pitch is mixed with the secondary fired product, examples of the organic matter include coal tar, coal tar pitch, petroleum-based pitch, fluid cracking bottom oil (FCC-DO), ethylene bottom oil (EHC), and the like. And one or more selected from petroleum-based, coal-based or synthetic pitches and tars, and acrylic resins such as phenol resins, furan resins, polyacrylonitrile, poly (α-halogenated acrylonitrile), polyamides One or more types selected from thermoplastic resins such as imide resins, polyamide resins, and polyimide resins, thermosetting resins, and sugars can be used. As said organic substance, a pitch or a phenol resin can be used conveniently on a cost or the battery characteristic.

In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, the ceramic composite material to be obtained further contains at least one metal atom selected from Mn, Fe, Co, Ni and Li in an amount of 1 to When containing 30% by mass or containing SiOC ceramics, the organic material is further the same as described above as a raw material for forming at least one metal atom selected from Mn, Fe, Co, Ni and Li and SiOC ceramics. It is preferable to use an organic mixture in which a desired amount is mixed beforehand.
When the ceramic composite material to be obtained further contains 1 to 30% by mass of at least one metal atom selected from Mn, Fe, Co, Ni and Li, it is selected from Mn, Fe, Co, Ni and Li It is preferable to mix 2 to 60 parts by mass, more preferably 5 to 40 parts by mass, and more preferably 5 to 20 parts by mass with respect to 100 parts by mass of the secondary fired product. Is more preferable.

  When mixing an organic substance such as pitch or an organic mixture with the secondary baked product, the mixing treatment is preferably performed by a known mixer capable of heat treatment. And a mixer for mixing by attaching a stirring blade to the stirring shaft. Specifically, a Henschel mixer (manufactured by Nihon Coke Industries Co., Ltd.), a high speed mixer (manufactured by Fukae Powtech Co., Ltd., Ready) Examples include Gemixer (manufactured by Matsubo Co., Ltd.), kneaders, and universal mixers.

  The mixing treatment is preferably performed so that the shear rate is 1 to 20000 (1 / second), more preferably 2 to 17500 (1 / second), and 3 to 15000 (1 / second). More preferably, it is performed so that

The mixing treatment can be performed under heating conditions or non-heating conditions, and the mixing treatment temperature is preferably 0 ° C to 200 ° C, more preferably 10 ° C to 200 ° C, and further preferably 20 ° C to 200 ° C. The mixing time is preferably 0.01 hours to 240 hours, more preferably 0.05 hours to 220 hours, and further preferably 0.1 hours to 200 hours.
The mixing treatment is preferably performed in an inert atmosphere, and examples of the inert atmosphere include a rare gas atmosphere such as a nitrogen atmosphere and an argon atmosphere.

  By mixing the organic matter or organic mixture with the secondary baked product, a coating layer composed of the organic matter or organic mixture is formed on the surface of the secondary particles, and by mixing under heating or non-heating conditions, the above An organic substance or an organic mixture can be polymerized to suitably form a coating film. When the said mixing temperature is less than 0 degreeC, the polymerization rate of an organic substance or an organic mixture will fall easily.

When the organic compound gas such as methane is subjected to thermal CVD treatment for the secondary baked product, the organic compound gas includes methane, ethane, ethylene, acetylene, propane, butane, butene, pentane, isobutane, hexane and other hydrocarbons. Single or mixture, aromatic hydrocarbons such as benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, anthracene, phenanthrene, or any mixture thereof 1 type or more chosen from is mentioned. Moreover, 1 or more types chosen from the gas light oil obtained by a tar distillation process, creosote oil, anthracene oil, naphtha decomposition | disassembly tar oil, or any mixture thereof can be mentioned.
As the organic compound gas, methane or propane can be suitably used in terms of cost or battery characteristics.

In addition, as a reaction apparatus that performs the thermal CVD (thermochemical vapor deposition process), a reaction apparatus having a heating mechanism in a non-oxidizing atmosphere is preferable, and a continuous process and a process that can be performed by a batch process are more preferable. Specifically, a fluidized bed reaction furnace, a rotary furnace, a vertical moving bed reaction furnace, a tunnel furnace, a batch furnace, a rotary kiln, or the like can be appropriately selected according to the purpose. The atmosphere during the heat CVD processing may be only an organic compound gas, Ar, the He, H _2, is preferably treated in a non-oxidizing gas atmosphere such as N _2.

  The details of the negative electrode active material for a nonaqueous electrolyte secondary battery obtained by the production method of the present invention are as described above.

  According to the present invention, a negative electrode active material for a nonaqueous electrolyte secondary battery that exhibits excellent initial efficiency, discharge capacity, and cycle characteristics (cycle retention rate) when used as a negative electrode material for a nonaqueous electrolyte secondary battery is provided. It is possible to provide a method that can be industrially mass-produced simply and at low cost.

Next, the negative electrode material for a nonaqueous electrolyte secondary battery according to the present invention will be described.
The negative electrode material for a non-aqueous electrolyte secondary battery according to the present invention includes the negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention and a carbon active material.

  In the negative electrode material for a nonaqueous electrolyte secondary battery according to the present invention, the carbon active material includes carbon blacks such as acetylene black, ketjen black, furnace black, and thermal black, carbon nanotubes, carbon fibers, expanded graphite, and artificial graphite. And one or more selected from conductive graphite materials such as natural graphite, hard carbon, and soft carbon.

The non-aqueous electrolyte negative electrode material according to the present invention comprises a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention or a negative electrode active material for a non-aqueous electrolyte secondary battery obtained by the production method according to the present invention. Those containing 30% by mass are preferred, those containing 2-25% by mass are more preferred, and those containing 3-20% by mass are more preferred.
Further, the amount of the non-aqueous electrolyte negative electrode material according to the present invention is desirably 70 to 99% by mass, more desirably 75 to 98% by mass, and further desirably 80 to 97% by mass of the carbon active material. . When the content ratio of the carbon active material is less than 70% by mass, the effect of addition is small, and when it exceeds 99% by mass, the battery capacity decreases.

  ADVANTAGE OF THE INVENTION According to this invention, the negative electrode material for nonaqueous electrolyte secondary batteries which exhibits the outstanding initial efficiency, discharge capacity, and cycling characteristics (cycle maintenance factor) can be provided.

Next, embodiments of the negative electrode material for a nonaqueous electrolyte secondary battery according to the present invention will be described.
Examples of the negative electrode for a nonaqueous electrolyte secondary battery using the negative electrode material for a nonaqueous electrolyte secondary battery according to the present invention include, for example, a negative electrode material for a nonaqueous electrolyte secondary battery according to the present invention on a negative electrode current collector. And a film formed with a binder.

Although it does not restrict | limit especially as said binder, A fluorine-type resin (Polyvinylidene fluoride, polytetrafluoroethylene, etc.), a styrene-butadiene resin, a polyimide resin etc. can be illustrated.
The usage-amount of a binder is not specifically limited, It is preferable that it is 1-30 mass parts with respect to 100 mass parts of negative electrode active materials for nonaqueous electrolyte secondary batteries, and it is 1-20 mass parts. Is more preferable.
When the amount of the binder used is out of the above range, for example, the adhesion strength of the ceramic composite material or the like on the current collector surface becomes insufficient, and an insulating layer that causes an increase in electrode internal resistance is formed. There is a case.

The film containing the negative electrode material for a nonaqueous electrolyte secondary battery according to the present invention and a binder formed on the negative electrode current collector may contain any additive.
As said additive, negative electrode active materials, such as a conductive support agent and graphite, can be mentioned, for example.
Examples of the conductive aid include carbon black (Ketjen black, acetylene black, etc.), carbon fiber, carbon nanotube, natural graphite (scale, scale, plate or block), artificial graphite (petroleum coke, coal pitch coke). 1 or more selected from petroleum needle coke or mesophase pitch).
Although the usage-amount of a conductive support agent is not restrict | limited in particular, It is preferable that it is 5-30 mass parts with respect to 100 mass parts of negative electrode active materials for nonaqueous electrolyte secondary batteries of this invention, and is 5-20 mass parts. It is more preferable.
Since the film containing the negative electrode material for a nonaqueous electrolyte secondary battery according to the present invention and a binder formed on the negative electrode current collector contains a conductive additive, it exhibits excellent conductivity and is charged with an electrode. A reduction in discharge capacity can be suppressed.
Further, the negative electrode may contain graphite or the like as any other additive, and as graphite, naturally produced graphite in scale, scale, plate and block, petroleum coke, coal pitch coke, Examples thereof include artificial graphite made from petroleum needle coke and mesophase pitch.

  The film thickness of the film containing the negative electrode material for a nonaqueous electrolyte secondary battery and the binder formed on the negative electrode current collector is, for example, preferably 10 to 300 μm, and more preferably 20 to 200 μm. In forming the electrodes, terminals may be combined as necessary.

  In addition, in this application document, when the film thickness of the film containing the negative electrode material for a nonaqueous electrolyte secondary battery and the binder according to the present invention is 50 points measured with a field emission scanning electron microscope (FE-SEM). Specifically, using an electrolytic emission scanning electron microscope (FE-SEM (JSM-6340F) manufactured by JEOL Co., Ltd.), the sample for measurement was ion milled (Gatan Corporation). This means an arithmetic average value when the cross section cut by Model 691) is observed, the film containing the porous SiOC ceramics and the binder is specified, and the film thickness at 50 points is measured.

  The negative electrode current collector is not particularly limited, and specific examples include a plate, a mesh, a foil, and the like made of copper, nickel, or an alloy thereof.

  The negative electrode is formed, for example, by mixing the negative electrode material for a non-aqueous electrolyte secondary battery of the present invention with a binder and a solvent to form a paste, and the obtained paste is pressed on a current collector. Or after apply | coating on a collector, it can produce by the method of drying and setting it as an electrode.

Specific examples of the binder include those described above. Moreover, the usage-amount of a binder is also the same as the mixing | blending ratio of the binder mentioned above.
When the amount of the binder is outside the above range, the adhesion strength on the surface of the negative electrode current collector tends to be insufficient, and an insulating layer that causes an increase in electrode internal resistance may be formed.

As the solvent for forming the paste-like material, a solvent that can dissolve or disperse the binder is usually used, and specific examples thereof include organic solvents such as N-methylpyrrolidone and N, N-dimethylformamide. it can.
The amount of the solvent used is not particularly limited as long as a paste-like material can be formed. For example, the negative electrode active material for a nonaqueous electrolyte secondary battery according to the present invention or the nonaqueous electrolyte secondary obtained by the production method of the present invention. The amount is preferably 0.01 to 500 parts by weight, more preferably 0.01 to 400 parts by weight, and further preferably 0.01 to 300 parts by weight with respect to 100 parts by weight of the negative electrode active material for a battery. preferable.

  Arbitrary additives may be blended with the paste-like material, and specific examples of additives and blending ratios of the additives are as described above.

  The method for preparing the paste-like product is not particularly limited, and examples thereof include a method of mixing the negative electrode material for a nonaqueous electrolyte secondary battery according to the present invention with a mixed liquid (or dispersion liquid) of a binder and a solvent. Can do.

The thickness of the paste applied to the negative electrode current collector is preferably 30 to 500 μm, and more preferably 50 to 300 μm.
After applying the paste, it is preferable to appropriately perform a drying process, and the drying means is not particularly limited, but a heating vacuum drying process is preferable.

  Nonaqueous electrolyte secondary batteries include those having battery components such as a positive electrode capable of occluding and releasing lithium, an electrolyte, a separator, a current collector, a gasket, a sealing plate, and a case together with the negative electrode. These battery components can be assembled and manufactured by conventional methods.

  In the nonaqueous electrolyte secondary battery, the positive electrode is not particularly limited, and examples thereof include a positive electrode current collector, a positive electrode active material, a conductive material, and the like.

Examples of the positive electrode current collector include aluminum.
The positive electrode active material is not particularly limited as long as it can occlude / desorb an electrolytic solution such as lithium ion, and examples thereof include TiS ₂ , MoS ₃ , NbSe ₃ , FeS, VS ₂ , and VSe ₂ . Metal chalcogenide having a layered structure, CoO ₂ , Cr ₃ O ₅ , TiO ₂ , CuO, V ₃ O ₆ , Mo ₃ O, V ₂ O ₅ (· P ₂ O ₅ ), Mn ₂ O (· Li ₂ O ), LiCoO ₂ , LiNiO ₂ , LiMn ₂ O _{4 and} other metal oxides, iron phosphate-based materials, and the like.
Examples of the positive active _material, LiCoO _2, LiNiO 2, one or more selected from lithium composite oxide such as LiMn ₂ O ₄ are preferred.
Examples of the conductive material used for the positive electrode active material include the same materials as described above, and it is preferably at least one selected from graphite, carbon nanotubes, carbon nanofibers, carbon black, and the like.

In the non-aqueous electrolyte secondary battery, the electrolytic solution is not particularly limited, and examples thereof include a solution in which an electrolyte is dissolved in an organic solvent.
As the electrolyte, for _{example, LiPF 6, LiClO 4, LiBF} 4, LiClF 4, LiAsF 6, LiSbF 6, LiAlO 4, LiAlCl 4, LiCl, can be exemplified one or more selected from lithium salts such as LiI.
Examples of the organic solvent include carbonates (propylene carbonate, ethylene carbonate, diethyl carbonate, etc.), lactones (γ-butyrolactone, etc.), chain ethers (1,2-dimethoxyethane, dimethyl ether, diethyl ether, etc.). ), Cyclic ethers (tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane, 4-methyldioxolane, etc.), sulfolanes (sulfolane, etc.), sulfoxides (dimethylsulfoxide, etc.), nitriles (acetonitrile, propionitrile, benzonitrile, etc.) And one or more selected from aprotic solvents such as amides (N, N-dimethylformamide, N, N-dimethylacetamide, etc.), polyoxyalkylene glycols (diethylene glycol, etc.) Rukoto can.
For example, the electrolyte concentration is preferably one containing 0.3 to 5 mol of electrolyte, more preferably 0.5 to 3 mol, and more preferably 0.8 to 1.5 mol in 1 L of the electrolyte solution. Further preferred.

  In the nonaqueous electrolyte secondary battery, the separator is not particularly limited, and examples thereof include one or more selected from polyolefin-based porous membranes such as porous polypropylene nonwoven fabric and porous polyethylene nonwoven fabric. Can do.

The non-aqueous electrolyte secondary battery can take various forms such as a laminated form, a pack form, a button form, a gum form, an assembled battery form, and a square form.
Examples of the non-aqueous electrolyte secondary battery include lithium secondary batteries, capacitors, hybrid capacitors (redox capacitors), organic radical batteries, and dual carbon batteries, with lithium secondary batteries being particularly preferred.
Since the non-aqueous electrolyte secondary battery contains the negative electrode material for a non-aqueous electrolyte secondary battery of the present invention, it is lightweight, has a high capacity, and has a high energy density. Therefore, a video camera, a personal computer, a word processor, It can be suitably used as a power source and auxiliary power source for portable small electronic devices such as radio cassettes and mobile phones, a driving power source for vehicles, and an auxiliary power source.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by the following examples.

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples. Negative electrode characteristics and battery characteristics were measured and evaluated by the following methods.
Example 1
Under an argon gas flow, 18.6 g of novolak type phenolic resin (manufactured by Gunei Chemical Industry Co., Ltd., PSM4261) was dissolved in 60 ml of polyethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.) to prepare a carbon precursor solution. Further, 10 g of 2 μm metal silicon particles (2 μm of 50% particle size (D50) in the cumulative particle size distribution in the volume-based cumulative particle size distribution) were added to the resin solution, and then the tetraethoxysilane ( 108.6 g of TEOS 45) manufactured by Tama Chemical Industry Co., Ltd. was added dropwise. Thereafter, 4.68 g of p-toluenesulfonic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added as an acid catalyst to initiate polymerization. At this time, the temperature of the solution subjected to the polymerization treatment was 85 ° C.
After heating to 85 ° C. and holding at the same temperature for 20 hours, the temperature was raised to 120 ° C., and heating and curing were carried out by holding in vacuum for 24 hours, and a solvent removal treatment was performed.

(Primary firing, grinding, classification, secondary firing)
The polymer obtained by the solvent removal treatment was subjected to primary calcination by maintaining at 600 ° C. for 1 hour in an argon gas atmosphere. After firing, coarse particles were removed by grinding with a cutter mill and classification with a 270 mesh sieve. A powdered ceramic composite material in which metallic silicon and SiC are dispersed in SiOC ceramics is obtained by subjecting the classified material from which coarse particles have been removed to secondary firing by holding at 1250 ° C. for 3 hours in an argon gas atmosphere. Obtained.

(Powder characteristics)
X-ray diffraction measurement (XRD measurement) using CuKα rays was performed on this powdery ceramic composite material. An X-ray diffraction spectrum is shown in FIG. As shown in FIG. 2, a plurality of Si and SiC-derived peaks were observed. The peak intensity ratio obtained from the (111) plane diffraction line peak intensity b1 of metal Si observed near a Bragg angle of 27 ° and the (111) plane diffraction line peak intensity b2 of SiC similarly observed near a Bragg angle of 35 ° b1 / b2 was 0.48.
The powdered ceramic composite material has a SiOC ceramic content of 80 mass% and a metal silicon content of 6.5 mass based on the amount of raw materials used in the preparation of the ceramic composite material and the X-ray diffraction spectrum of the ceramic composite material. %, And the content ratio of SiC was calculated to be 13.5% by mass.
The powdery ceramic composite material has a density of 1.49 g / cm ³ when compressed at a pressure of 30 MPa, a nitrogen adsorption specific surface area of 8 m ² / g, and a particle size D50 obtained from the volume-based cumulative particle size distribution. The tap density obtained by tapping 13 μm and 1000 times was 0.54 g / cm ³ , and the average circularity obtained from the circularity calculated by flow type particle image analysis was 0.932.
In the powdery ceramic composite material obtained in Example 1, the XRD peak intensity ratio b1 / b2, the density (g / cm ³ ) when compressed at a pressure of 30 MPa, the metal silicon particle diameter D50 (d1), ceramics The particle diameter D50 (d2), particle diameter ratio d1 / d2, nitrogen adsorption specific surface area (m ² / g), tap density (g / cm ³ ) and average circularity when tapped 1000 times are shown. It is shown in 1.

<Production of lithium ion secondary battery>
(Preparation of negative electrode)
1 g of the above powdery ceramic composite material and 9 g of artificial graphite as a carbon-based active material were mixed to obtain a negative electrode material for a lithium ion secondary battery.
To the negative electrode material, 0.71 g of acetylene black, 8.33 g of polyvinylidene fluoride and 6 g of N-methyl-2-pyrrolidone as a solvent were added and stirred for 5 minutes to prepare a negative electrode mixture paste.
The obtained negative electrode mixture paste was applied onto a copper foil (current collector) having a thickness of 18 μm with a doctor blade, heated to 130 ° C. in a vacuum to completely evaporate the solvent, and contained about 50 μm containing the active material. An electrode sheet was obtained.
The obtained electrode sheet was rolled with a roller press and punched with a punch to prepare a 2 cm ² negative electrode (working electrode). The electrode plate density is 1.50 g / cm ³ by measuring the thickness of the active material layer with a micrometer and calculating the density of the active material layer from the weight of the active material excluding the binder and the volume of the active material layer. A negative electrode (working electrode) was produced.
In addition, a positive electrode (counter electrode) was produced by indenting a lithium metal foil into a nickel mesh (current collector) having a thickness of 270 μm punched with a punch under an inert atmosphere.

(Production of evaluation lithium secondary battery)
As an electrolytic solution, a 1: 1 mixed solution of ethylene carbonate (EC) in which 1 mol / dm ³ of a lithium salt LiPF ₆ is dissolved and diethyl carbonate (DEC) is used. As shown in FIG. 2, in the case 1, the positive electrode (counter electrode) 4, the separator 5, the negative electrode (working electrode) 8, and the spacer 7 are stacked in the nickel mesh (current collector) 3. By assembling and sealing with a sealing lid (cap) 2 via a spring 6, a button-type evaluation lithium secondary battery a having the form shown in FIG. 1 is produced. The measurement (1st discharge capacity, initial efficiency) and cycle characteristics (3 times maintenance ease, 50 times maintenance rate) were measured.
As a result, the first discharge capacity was 437 mAh / g, the initial efficiency was 85%, and the cycle characteristics were a 3-time maintenance rate of 100% and a 50-time maintenance rate of 95%. The results are also shown in Table 2.

<Measurement method of initial battery measurement (1st discharge capacity, initial efficiency)>
For initial battery measurement, constant current charging was performed at 0.405 mA and a final voltage of 5 mV, and then a constant potential was maintained until the lower limit current was 0.0405 mA. Next, constant current discharge was performed at 0.405 mA to a final voltage of 1.5 V, and the discharge capacity after the end of one cycle was defined as the rated capacity (reversible capacity (mAh / g)). The above measurement was performed for each of six batteries, and the average value was defined as the 1st discharge capacity.
The initial efficiency of the obtained lithium secondary battery for evaluation a was determined by the following equation using the first charge capacity and discharge capacity.
Initial efficiency (%) = (first discharge capacity (mAh / g) / first charge capacity (mAh / g)) × 100

<Measurement method of cycle characteristics (maintenance rate for 3 times, maintenance rate for 50 times)>
Regarding the cycle characteristics, the rated capacity calculated in the initial measurement was set to 1 C, and constant current charging was performed at 0.1 C with a final voltage of 5 mV, and then the constant potential was maintained until the lower limit current became 0.01 C. Next, constant current discharge was performed at 0.1 C up to a final voltage of 1.5 V, and the test was performed up to 50 cycles. The 3-times maintenance ratio and the 50-times maintenance ratio were each calculated as an average value of the measured values of two batteries.
Cycle characteristics (three-time maintenance ratio (%)) = (third discharge capacity (mAh / g) / first discharge capacity (mAh / g)) × 100
Cycle characteristics (50-time maintenance rate (%)) = (50th discharge capacity (mAh / g) / first discharge capacity (mAh / g)) × 100

For high input characteristics, the rated capacity calculated in the initial measurement was set to 1 C, and constant current charging was performed at 0.1 C with a final voltage of 5 mV or a final time of 10 hours to obtain a 0.1 C charge capacity. Next, constant current discharge was performed at a final voltage of 1.5 V at 0.1 C or a final time of 10 hours.
Thereafter, constant current charging was performed at 1 C with a termination voltage of 5 mV or a termination time of 1 hour to obtain a 1 C charging capacity, and the charging rate was determined from the following formula. In addition, the high input characteristic was calculated as an average of the measurement of each four batteries.

(Example 2)
Except for changing the secondary firing temperature to 1200 ° C., the content ratio of SiOC ceramics is 80% by mass and the content ratio of metal silicon is the same as in Example 1 in which metal silicon and SiC are dispersed in SiOC ceramics. A powdery ceramic composite material having 11.3% by mass and SiC content of 8.7% by mass was produced.
In the obtained powdered ceramic composite material, XRD peak intensity ratio b1 / b2, density (g / cm ³ ) when compressed at a pressure of 30 MPa, metal silicon particle diameter D50 (d1), ceramic composite material particles The diameter D50 (d2), the particle diameter ratio d1 / d2, the nitrogen adsorption specific surface area (m ² / g), the tap density (g / cm ³ ) when tapped 1000 times, and the average circularity are the same as in Example 1. Measured. The results are shown in Table 2.
Next, an evaluation lithium secondary battery was prepared in the same manner as in Example 1 using the obtained powdered ceramic composite material, and evaluated in the same manner as in Example 1.
As a result, the first discharge capacity was 458 mAh / g, the initial efficiency was 85%, and the cycle characteristics were 3 times maintenance rate 100% and 50 times maintenance rate 93%. The results are also shown in Table 2.

(Example 3)
Except for changing the secondary firing temperature to 1300 ° C., the content ratio of the SiOC ceramic is 80% by mass and the content ratio of the metal silicon is the same as in Example 1 in which metal silicon and SiC are dispersed in the SiOC ceramic. A powdery ceramic composite material having 12.1% by mass and SiC content of 7.9% by mass was produced.
In the obtained powdered ceramic composite material, XRD peak intensity ratio b1 / b2, density (g / cm ³ ) when compressed at a pressure of 30 MPa, metal silicon particle diameter D50 (d1), ceramic composite material particles The diameter D50 (d2), the particle diameter ratio d1 / d2, the nitrogen adsorption specific surface area (m ² / g), the tap density (g / cm ³ ) when tapped 1000 times, and the average circularity are the same as in Example 1. Measured. The results are shown in Table 1.
Next, an evaluation lithium secondary battery was prepared in the same manner as in Example 1 using the obtained powdered ceramic composite material, and evaluated in the same manner as in Example 1.
As a result, the first discharge capacity was 418 mAh / g, the initial efficiency was 84%, and the cycle characteristics were 3 times maintenance rate 100% and 50 times maintenance rate 96%. The results are also shown in Table 2.

Example 4
Except for changing the secondary firing temperature to 1350 ° C., the content ratio of SiOC ceramic is 80% by mass, and the content ratio of metal silicon is formed by dispersing metal silicon and SiC in the SiOC ceramic in the same manner as in Example 1. A powdery ceramic composite material having a content of 3.3% by mass and a SiC content of 16.7% by mass was produced.
In the obtained powdered ceramic composite material, XRD peak intensity ratio b1 / b2, density (g / cm ³ ) when compressed at a pressure of 30 MPa, metal silicon particle diameter D50 (d1), ceramic composite material particles The diameter D50 (d2), the particle diameter ratio d1 / d2, the nitrogen adsorption specific surface area (m ² / g), the tap density (g / cm ³ ) when tapped 1000 times, and the average circularity are the same as in Example 1. Measured. The results are shown in Table 1.
Next, an evaluation lithium secondary battery was prepared in the same manner as in Example 1 using the obtained powdered ceramic composite material, and evaluated in the same manner as in Example 1.
As a result, the first discharge capacity was 410 mAh / g, the initial efficiency was 84%, and the cycle characteristics were 3 times maintenance rate 100% and 50 times maintenance rate 98%. The results are also shown in Table 2.

(Example 5)
Except for changing the metal silicon to be used to one having a particle diameter D50 of 1 μm, in the same manner as in Example 1, the content of the SiOC ceramic is 80% by mass, in which the metal silicon and SiC are dispersed in the SiOC ceramic. A powdery ceramic composite material having a silicon content of 11.9% by mass and a SiC content of 8.1% by mass was produced.
In the obtained powdered ceramic composite material, XRD peak intensity ratio b1 / b2, density (g / cm ³ ) when compressed at a pressure of 30 MPa, metal silicon particle diameter D50 (d1), ceramic composite material particles The diameter D50 (d2), the particle diameter ratio d1 / d2, the nitrogen adsorption specific surface area (m ² / g), the tap density (g / cm ³ ) when tapped 1000 times, and the average circularity are the same as in Example 1. Measured. The results are shown in Table 1.
Next, an evaluation lithium secondary battery was prepared in the same manner as in Example 1 using the obtained powdered ceramic composite material, and evaluated in the same manner as in Example 1.
As a result, the first discharge capacity was 452 mAh / g, the initial efficiency was 88%, and the cycle characteristics were 3 times maintenance rate 100% and 50 times maintenance rate 97%. The results are also shown in Table 2.
By reducing the size of the metal silicon particles, the initial efficiency is improved with a decrease in the Li diffusion distance when used in a secondary battery compared to the ceramic composite material obtained in Example 1. It can be seen that by reducing the particle size of metallic silicon, the influence of expansion and contraction due to metallic silicon is reduced, and the cycle retention rate is also improved.

(Example 6)
Except for changing the metal silicon to be used to one having a particle diameter D50 of 0.5 μm, the content ratio of the SiOC ceramic formed by dispersing metal silicon and SiC in the SiOC ceramic in the same manner as in Example 1 is 80% by mass. A powdered ceramic composite material having a metal silicon content of 14% by mass and a SiC content of 6% by mass was produced.
In the obtained powdered ceramic composite material, XRD peak intensity ratio b1 / b2, density (g / cm ³ ) when compressed at a pressure of 30 MPa, metal silicon particle diameter D50 (d1), ceramic composite material particles The diameter D50 (d2), the particle diameter ratio d1 / d2, the nitrogen adsorption specific surface area (m ² / g), the tap density (g / cm ³ ) when tapped 1000 times, and the average circularity are the same as in Example 1. Measured. The results are shown in Table 1.
Next, an evaluation lithium secondary battery was prepared in the same manner as in Example 1 using the obtained powdered ceramic composite material, and evaluated in the same manner as in Example 1.
As a result, the first discharge capacity was 449 mAh / g, the initial efficiency was 87%, and the cycle characteristics were a 3-time maintenance rate of 100% and a 50-time maintenance rate of 98%. The results are also shown in Table 2.
By reducing the size of the metal silicon particles, the initial efficiency is improved with a decrease in the Li diffusion distance when used in a secondary battery compared to the ceramic composite material obtained in Example 1. It can be seen that by reducing the particle size of metallic silicon, the influence of expansion and contraction due to metallic silicon is reduced, and the cycle retention rate is improved.

(Example 7)
Example 1 except that coarse particles were removed by pulverization with a cutter mill after primary firing and classification with a precision air classifier (turbo classifier manufactured by Nissin Engineering Co., Ltd.) instead of a 270 mesh sieve. The silicon silicon and SiC are dispersed in the SiOC ceramic, the SiOC ceramic content is 80% by mass, the metal silicon content is 6.9% by mass, and the SiC content is 13.1% by mass. A powdery ceramic composite material was prepared.
In the obtained powdered ceramic composite material, XRD peak intensity ratio b1 / b2, density (g / cm ³ ) when compressed at a pressure of 30 MPa, metal silicon particle diameter D50 (d1), ceramic composite material particles The diameter D50 (d2), the particle diameter ratio d1 / d2, the nitrogen adsorption specific surface area (m ² / g), the tap density (g / cm ³ ) when tapped 1000 times, and the average circularity are the same as in Example 1. Measured. The results are shown in Table 1.
Next, an evaluation lithium secondary battery was prepared in the same manner as in Example 1 using the obtained powdered ceramic composite material, and evaluated in the same manner as in Example 1.
As a result, the first discharge capacity was 440 mAh / g, the initial efficiency was 86%, and the cycle characteristics were a 3-time maintenance rate of 100% and a 50-time maintenance rate of 95%. The results are also shown in Table 2.
By changing the classification conditions after primary firing and pulverization, compared to the ceramic composite material obtained in Example 1, when used in a secondary battery, the specific surface area of the whole molecule is reduced, and the initial efficiency It can be seen that is improved.

(Example 8)
After the primary firing, instead of the cutter mill, coarse particles were removed by grinding with a super rotor, and the secondary firing temperature was changed to 1200 ° C. In the same manner as in Example 1, metallic silicon and SiC were incorporated into the SiOC ceramic. A powdery ceramic composite material having a SiOC ceramic content of 80% by mass, a metal silicon content of 11.3% by mass, and a SiC content of 8.7% by mass was prepared.
In the obtained powdered ceramic composite material, XRD peak intensity ratio b1 / b2, density (g / cm ³ ) when compressed at a pressure of 30 MPa, metal silicon particle diameter D50 (d1), ceramic composite material particles The diameter D50 (d2), the particle diameter ratio d1 / d2, the nitrogen adsorption specific surface area (m ² / g), the tap density (g / cm ³ ) when tapped 1000 times, and the average circularity are the same as in Example 1. Measured. The results are shown in Table 1.
Next, an evaluation lithium secondary battery was prepared in the same manner as in Example 1 using the obtained powdered ceramic composite material, and evaluated in the same manner as in Example 1.
As a result, the first discharge capacity was 460 mAh / g, the initial efficiency was 84%, and the cycle characteristics were 3 times maintenance rate 100% and 50 times maintenance rate 95%. The results are also shown in Table 2.
Compared with the ceramic composite material obtained in Example 1 by changing the pulverization conditions after the primary firing, the conductive path between the active material particles when used in a secondary battery. It can be seen that the first discharge capacity is improved.

Example 9
After the polymerization treatment and the solvent removal treatment in the same manner as in Example 1, the polymer obtained by the solvent removal treatment in the same manner as in Example 1 was subjected to primary firing, pulverization / classification treatment, and a classified treatment product was obtained. .
Lithium carbonate was added to the classified product obtained by the classification treatment so that the content thereof was 10% by mass, and after dry mixing at 2000 rpm (rotation / min) for 90 seconds, an argon gas atmosphere Secondary baking is performed by maintaining at 1250 ° C. for 3 hours, and the content ratio of SiOC ceramic is 72 mass% and the content ratio of metal silicon is 5.8 mass%, in which metallic silicon and SiC are dispersed in the SiOC ceramic. A powdered ceramic composite material having a SiC content of 12.2% by mass was produced.
In the obtained powdered ceramic composite material, XRD peak intensity ratio b1 / b2, density (g / cm ³ ) when compressed at a pressure of 30 MPa, metal silicon particle diameter D50 (d1), ceramic composite material particles The diameter D50 (d2), the particle diameter ratio d1 / d2, the nitrogen adsorption specific surface area (m ² / g), the tap density (g / cm ³ ) when tapped 1000 times, and the average circularity are the same as in Example 1. Measured. The results are shown in Table 1.
Next, an evaluation lithium secondary battery was prepared in the same manner as in Example 1 using the obtained powdered ceramic composite material, and evaluated in the same manner as in Example 1.
As a result, the first discharge capacity was 450 mAh / g, the initial efficiency was 90%, and the cycle characteristics were 3 times maintenance rate 100% and 50 times maintenance rate 95%. The results are also shown in Table 2.

(Example 10)
After the polymerization treatment and the solvent removal treatment in the same manner as in Example 1, the polymer obtained by the solvent removal treatment in the same manner as in Example 1 was subjected to a primary firing treatment to obtain a primary fired product.
On the other hand, under an argon gas flow, 18.6 g of novolak-type phenol resin (manufactured by Gunei Chemical Industry Co., Ltd., PSM4261) was dissolved in 20 ml of polyethylene glycol (manufactured by Wako Pure Chemical Industries (wako) Co., Ltd.) to obtain a carbon precursor. A solution was prepared, and 1.86 g of tetraethoxysilane (manufactured by Tama Chemical Co., Ltd., TEOS45) was added dropwise while stirring at about 130 rpm. Thereafter, 0.75 g of p-toluenesulfonic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added as an acid catalyst to initiate polymerization. After heating to 85 ° C. and holding at the same temperature for 20 hours, the above primary fired product is charged, stirred with a stirrer for 30 minutes, then heated to 120 ° C. and heated and cured in vacuum for 24 hours. Together with this, a solvent removal treatment was performed.
By subjecting the processed product obtained by the heating effect and the solvent removal treatment to pulverization, classification, and secondary firing in the same manner as in Example 1, metallic silicon and SiC are dispersed in the SiOC ceramic. A powdery ceramic composite material having a SiOC ceramic content of 80% by mass, a metal silicon content of 6.0% by mass, and a SiC content of 14.0% by mass was prepared.
The obtained ceramic composite material had a core-shell structure in which the surface portion had a higher carbon content than the center portion.
In the obtained powdered ceramic composite material, XRD peak intensity ratio b1 / b2, density (g / cm ³ ) when compressed at a pressure of 30 MPa, metal silicon particle diameter D50 (d1), ceramic composite material particles The diameter D50 (d2), the particle diameter ratio d1 / d2, the nitrogen adsorption specific surface area (m ² / g), the tap density (g / cm ³ ) when tapped 1000 times, and the average circularity are the same as in Example 1. Measured. The results are shown in Table 1.
Next, an evaluation lithium secondary battery was prepared in the same manner as in Example 1 using the obtained powdered ceramic composite material, and evaluated in the same manner as in Example 1.
As a result, the first discharge capacity was 430 Ah / g, the initial efficiency was 86%, and the cycle characteristics were 3 times maintenance rate 100% and 50 times maintenance rate 98%. The results are also shown in Table 2.

(Example 11)
After the polymerization treatment and the solvent removal treatment in the same manner as in Example 1, the polymer obtained by the solvent removal treatment in the same manner as in Example 1 was subjected to primary firing, pulverization / classification treatment, and a classified treatment product was obtained. .
On the other hand, 100 g of methanol was dissolved in 10 g of novolak-type phenol resin (manufactured by Gunei Chemical Co., PSM4261), and 1 g of hydrochloric acid was further added as a curing agent, followed by stirring at room temperature for 1 hour to prepare a resin coating solution. 100 g of the classified product was added to the obtained resin coating solution, and stirred for 30 minutes to impregnate, thereby forming a resin layer on the surface of the classified product. By removing the resin coating solution with a filter, the classified material having a resin layer formed on the surface is isolated, then cured at 200 ° C. for 4 hours, and held at 1250 ° C. in an argon gas atmosphere for 3 hours for secondary firing. After being crushed with a cutter mill and classified with a 270 mesh sieve, the silicon silicon and SiC are dispersed in the SiOC ceramic, the content ratio of the SiOC ceramic is 80% by mass, the metal silicon A powdery ceramic composite material having a content ratio of 6.6% by mass and a content ratio of SiC of 13.4% by mass was produced.
The obtained ceramic composite material had a carbon film with an average thickness of 100 nm on the surface.
In the obtained powdered ceramic composite material, XRD peak intensity ratio b1 / b2, density (g / cm ³ ) when compressed at a pressure of 30 MPa, metal silicon particle diameter D50 (d1), ceramic composite material particles The diameter D50 (d2), the particle diameter ratio d1 / d2, the nitrogen adsorption specific surface area (m ² / g), the tap density (g / cm ³ ) when tapped 1000 times, and the average circularity are the same as in Example 1. Measured. The results are shown in Table 1.
Next, an evaluation lithium secondary battery was prepared in the same manner as in Example 1 using the obtained powdered ceramic composite material, and evaluated in the same manner as in Example 1.
As a result, the first discharge capacity was 436 mAh / g, the initial efficiency was 88%, and the cycle characteristics were a 3-time maintenance rate of 100% and a 50-time maintenance rate of 97%. The results are also shown in Table 2.

(Comparative Example 1)
Except for changing the secondary firing temperature to 1100 ° C., the same as in Example 1, the SiOC ceramic content is 80% by mass, the metal silicon content is 20% by mass, and the SiC content is 0% by mass. A powdery ceramic composite material was prepared.
In the obtained powdered ceramic composite material, XRD peak intensity ratio b1 / b2, density (g / cm ³ ) when compressed at a pressure of 30 MPa, metal silicon particle diameter D50 (d1), ceramic composite material particles The diameter D50 (d2), the particle diameter ratio d1 / d2, the nitrogen adsorption specific surface area (m ² / g), the tap density (g / cm ³ ) when tapped 1000 times, and the average circularity are the same as in Example 1. Measured. The results are shown in Table 1.
In Comparative Example 1, since the secondary firing temperature is as low as 1100 ° C., the generation of SiC is small, and the peak intensity b2 of the (111) plane diffraction line of (111) plane diffraction line of metallic silicon The represented ratio was 10.7.
Next, an evaluation lithium secondary battery was prepared in the same manner as in Example 1 using the obtained powdered ceramic composite material, and evaluated in the same manner as in Example 1.
As a result, the first discharge capacity was 448 mAh / g, the initial efficiency was 85%, and the cycle characteristics were a 3-time maintenance rate of 98% and a 50-time maintenance rate of 88%. The results are also shown in Table 2.

(Comparative Example 2)
Except that the secondary firing temperature was changed to 1500 ° C., the content ratio of SiOC ceramics was 80 mass%, the content ratio of metallic silicon was 1.8 mass%, and the content ratio of SiC was 18. A powdery ceramic composite material of 2% by mass was produced.
In the obtained powdered ceramic composite material, XRD peak intensity ratio b1 / b2, density (g / cm ³ ) when compressed at a pressure of 30 MPa, metal silicon particle diameter D50 (d1), ceramic composite material particles The diameter D50 (d2), the particle diameter ratio d1 / d2, the nitrogen adsorption specific surface area (m ² / g), the tap density (g / cm ³ ) when tapped 1000 times, and the average circularity are the same as in Example 1. Measured. The results are shown in Table 1.
Next, an evaluation lithium secondary battery was prepared in the same manner as in Example 1 using the obtained powdered ceramic composite material, and evaluated in the same manner as in Example 1.
As a result, the first discharge capacity was 370 mAh / g, the initial efficiency was 77%, and the cycle characteristics were a 3-time maintenance rate of 100% and a 50-time maintenance rate of 90%. The results are also shown in Table 2.

From Table 1 and Table 2, the negative electrode active materials for non-aqueous electrolyte secondary batteries obtained in Examples 1 to 11 are formed by dispersing metallic silicon and SiC in SiOC ceramics, and using CuKα characteristic X-rays. In the X-ray diffraction, when the peak intensity of the (111) plane diffraction line of metallic silicon is b1 and the peak intensity of the (111) plane diffraction line of SiC is b2, the ratio represented by b1 / b2 is 0. It is 20 to 10.00, and the density when compressed at 30 MPa is 1.2 g / cm ^{3 to} 1.8 g / cm ^3, which is excellent when used for a negative electrode material for non-aqueous secondary batteries. It can be seen that the initial efficiency, discharge capacity, and cycle characteristics (cycle retention rate) are exhibited.

  From Table 1 and Table 2, since the negative electrode active material for a nonaqueous electrolyte secondary battery obtained in Comparative Example 1 has a low secondary firing temperature and a small amount of SiC, the peak intensity ratio b1 / b2 is 10 It can be seen that the deterioration begins at the initial stage of charge and discharge, and the cycle characteristics deteriorate.

  From Tables 1 and 2, the negative electrode active material for a nonaqueous electrolyte secondary battery obtained in Comparative Example 2 has a large amount of SiC and the peak intensity ratio b1 / b2 is less than 0.20. It can be seen that the first discharge capacity is greatly reduced, and the initial efficiency is also greatly reduced due to side reactions and the like.

  According to the present invention, when used as a negative electrode material for a nonaqueous electrolyte secondary battery, a negative electrode active material for a nonaqueous electrolyte secondary battery that exhibits excellent initial efficiency, discharge capacity, and cycle characteristics (cycle retention rate), Provided is a method for industrially mass-producing the negative electrode active material for a nonaqueous electrolyte secondary battery in a simple and low-cost manner and a negative electrode material for a nonaqueous electrolyte secondary battery including the negative electrode active material for the nonaqueous electrolyte secondary battery. can do.

1 Case 2 Sealing lid (cap)
3 Current collector 4 Positive electrode 5 Separator 6 Spring 7 Spacer 8 Negative electrode 9 Gasket

Claims (11)

Metal silicon and SiC are dispersed in SiOC ceramics,
In the X-ray diffraction using CuKα characteristic X-ray, b1 / b2 where b1 is the peak intensity of the (111) plane diffraction line of the metal silicon and b2 is the peak intensity of the (111) plane diffraction line of the SiC. The ratio represented by is 0.20 to 10.00,
Negative active material for a density non-aqueous electrolyte secondary battery characterized by comprising the ceramic composite material is 1.2g ^/ cm ³ ~1.8g ^/ cm 3 when compressed at 30 MPa.   When the particle size D50 of 50% in the integrated particle size distribution in the volume-based integrated particle size distribution of the metal silicon is d1, and the particle size D50 of 50% in the integrated particle size distribution of the ceramic composite material is d2, 2. The negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the ratio represented by d1 / d2 is 0.01 to 0.40.   3. The negative electrode active material for a nonaqueous electrolyte secondary battery according to claim 1, wherein a 50% particle diameter D50 in the volume-based cumulative particle size distribution of the ceramic composite material is 0.5 μm to 50 μm.   4. The negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the ceramic composite material has an average circularity of 0.90 to 1.0. 5. Negative electrode active material for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 4 nitrogen adsorption specific surface area of the ceramic composite material is 0.1m 2 ^/ g~50m 2 ^{/ g.} 1000 non-aqueous electrolyte secondary battery according to any one of claims 1 to 5 tap density when performing tapping is 0.4g ^/ cm ³ ~1.3g ^/ cm 3 of the ceramic composite material Negative electrode active material.   The non-aqueous electrolyte secondary according to any one of claims 1 to 6, wherein the ceramic composite material further contains 1 to 30% by mass of at least one metal atom selected from Mn, Fe, Co, Ni, and Li. Negative electrode active material for batteries.   The negative electrode active material for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 7, wherein a surface portion of the ceramic composite material has a core-shell structure having a carbon content higher than that of a center portion.   The said ceramic composite material has a carbon film on the surface, The negative electrode active material for nonaqueous electrolyte secondary batteries in any one of Claims 1-8. After mixing a carbon precursor solution obtained by mixing a carbon precursor and a solvent, a silicon-containing organic material, and a metal silicon powder, the obtained mixed solution is polymerized, and further the solvent is removed to obtain a ceramic composite material precursor. Next, primary firing is performed at 400 ° C to 800 ° C, pulverization and classification treatment, and then secondary firing is performed at 1200 ° C to 1350 ° C to prepare a ceramic composite material. A method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1.   A negative electrode material for a nonaqueous electrolyte secondary battery comprising the negative electrode active material for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 9 and a carbon active material.