WO2016067498A1 - Negative electrode material for lithium ion secondary batteries, method for producing same, negative electrode for lithium ion secondary batteries and lithium ion secondary battery - Google Patents
Negative electrode material for lithium ion secondary batteries, method for producing same, negative electrode for lithium ion secondary batteries and lithium ion secondary battery Download PDFInfo
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- WO2016067498A1 WO2016067498A1 PCT/JP2015/003936 JP2015003936W WO2016067498A1 WO 2016067498 A1 WO2016067498 A1 WO 2016067498A1 JP 2015003936 W JP2015003936 W JP 2015003936W WO 2016067498 A1 WO2016067498 A1 WO 2016067498A1
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- negative electrode
- ion secondary
- lithium ion
- electrode material
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 72
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 72
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Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Definitions
- the present invention relates to a negative electrode material for a lithium ion secondary battery and a method for producing the same, and also relates to a negative electrode and a lithium ion secondary battery using the negative electrode material for the lithium ion secondary battery.
- Patent Documents 1 and 2 Conventionally, as a measure for increasing the capacity of this type of secondary battery, for example, a method of using an oxide such as V, Si, B, Zr, Sn, or a composite oxide thereof as a negative electrode material (for example, Patent Documents 1 and 2). Reference), a method of applying a melt-quenched metal oxide as a negative electrode material (for example, see Patent Document 3), a method of using silicon oxide as a negative electrode material (for example, see Patent Document 4), and Si 2 N 2 O as a negative electrode material And a method using Ge 2 N 2 O (see, for example, Patent Document 5) is known.
- an oxide such as V, Si, B, Zr, Sn, or a composite oxide thereof as a negative electrode material
- Patent Document 3 a method of applying a melt-quenched metal oxide as a negative electrode material
- Patent Document 4 a method of using silicon oxide as a negative electrode material
- Si 2 N 2 O as a negative electrode material
- Ge 2 N 2 O see,
- Patent Document 6 For the purpose of imparting conductivity to the negative electrode material, a method of carbonizing SiO after graphite and mechanical alloying (for example, see Patent Document 6), a method of coating a carbon layer on the surface of silicon particles by a chemical vapor deposition method (for example, And Patent Document 7), and a method of coating the surface of silicon oxide particles with a carbon layer by chemical vapor deposition (for example, see Patent Document 8).
- JP-A-5-174818 Japanese Patent Laid-Open No. 6-60867 JP-A-10-294112 Japanese Patent No. 2999741 JP-A-11-102705 JP 2000-243396 A JP 2000-215887 A Japanese Patent Laid-Open No. 2002-42806
- Patent Document 4 silicon oxide is used as a negative electrode material for a lithium ion secondary battery to obtain a high-capacity electrode.
- the irreversible capacity at the time of initial charge / discharge is still insufficient.
- the technique of imparting conductivity to the negative electrode material also has a problem in Patent Document 6 that a uniform carbon film is not formed because of solid-solid fusion and the conductivity is insufficient.
- Patent Document 8 although improvement in cycle performance is confirmed, the number of cycles of charge / discharge is increased due to insufficient deposition of fine silicon crystals, integration of the carbon coating structure and the base material. As a result, there is a problem that the capacity gradually decreases and then rapidly decreases after a certain number of times, which is still insufficient for a secondary battery.
- the present invention has been made in view of such problems, and an object thereof is to provide a negative electrode material for a negative electrode of a lithium ion secondary battery excellent in cycle characteristics and a method for producing the same. Another object of the present invention is to provide a negative electrode and a lithium ion secondary battery using such a negative electrode material.
- the present invention comprises a step of preparing base particles made of a material containing silicon atoms and capable of occluding and releasing lithium ions, and forming a carbon coating on the surface of the base particles
- the substrate particles were measured with a laser diffraction particle size distribution measurement device in a state where the carbon coating was not formed
- the ratio of particles having a particle size of 1 ⁇ m or less in the volume-based distribution was defined as a%, and the ratio of particles having a particle diameter of 1 ⁇ m or less in the volume-based distribution measured with a laser diffraction particle size distribution measuring device with respect to the coated particles was defined as b%.
- a method for producing a negative electrode material for a lithium ion secondary battery is provided, wherein the step of forming the carbon film is performed so that a / b ⁇ 3.
- the negative electrode material is produced by forming a carbon film so that a / b ⁇ 3, particles having a particle size of 1 ⁇ m or less that existed before the coating with the carbon film (that is, (Fine powder having a relatively small particle diameter) forms secondary particles aggregated with carbon by coating.
- the secondary particles fill the gaps of the large particles and contribute to the reduction of the electric resistance of the negative electrode. This leads to an improvement in capacity retention rate when the charge / discharge cycle is repeated.
- the base particle in the step of preparing the base particle, it is preferable to prepare the base particle having the a% of 0.1% to 30%.
- the base particles have a ratio of particles having a particle size of 1 ⁇ m or less in the volume-based distribution of 0.1% or more and 30% or less, secondary particles can be easily formed.
- the base particles may be silicon particles, particles having a composite structure in which silicon fine particles are dispersed in a silicon-based compound, or a general formula SiOx (0.5 ⁇ x ⁇ 1.6). ), Or a mixture thereof can be prepared.
- the method for producing a negative electrode material of the present invention can be applied to any of the above base material particles.
- the ratio of the mass of carbon contained in the coated particles to the mass of the coated particles is preferably 0.5% by mass or more and 40% by mass or less.
- the base particles may have a cumulative 50% diameter (D 50 ) in a volume reference distribution measured with a laser diffraction particle size distribution measuring device of the base particles of 0.1 ⁇ m. It is preferable to prepare one having a thickness of 30 ⁇ m or less.
- the step of forming the carbon coating is performed such that the cumulative 50% diameter (D 50 ) in the volume reference distribution measured with a laser diffraction particle size distribution measuring device of the coated particles is 1 ⁇ m or more and 30 ⁇ m or less. Is preferred.
- the step of forming the carbon coating is performed by chemical vapor deposition of carbon on the base particle in an organic gas atmosphere that can be pyrolyzed to generate carbon in a temperature range of 600 to 1200 ° C. It is preferable.
- the present invention also provides a negative electrode material for a lithium ion secondary battery manufactured by any one of the above-described methods for manufacturing a negative electrode material for a lithium ion secondary battery.
- the present invention also relates to lithium, which is a coated particle composed of a material containing a silicon atom and comprising a base particle capable of inserting and extracting lithium ions and a carbon coating formed on the surface of the base particle.
- a / b ⁇ 3 where b is the ratio of particles having a particle size of 1 ⁇ m or less in the volume reference distribution measured with a laser diffraction particle size distribution measuring device to the coated particles.
- a negative electrode material for a lithium ion secondary battery There is provided a negative electrode material for a lithium ion secondary battery.
- fine particles having a particle size of 1 ⁇ m or less that existed before the coating with the carbon coating forms secondary particles aggregated with carbon by the coating.
- the secondary particles fill the gaps of the large particles and contribute to the reduction of the electric resistance of the negative electrode. This leads to an improvement in capacity retention rate when the charge / discharge cycle is repeated.
- the present invention also provides a negative electrode for a lithium ion secondary battery using the above negative electrode material for a lithium ion secondary battery.
- the present invention also provides a lithium ion secondary battery using the above negative electrode for a lithium ion secondary battery.
- the presence of the secondary particles contained in the negative electrode material contributes to the reduction of the electric resistance of the negative electrode. This leads to an improvement in capacity retention rate when a charge / discharge cycle of a lithium ion secondary battery using the negative electrode is repeated.
- the negative electrode material for a lithium ion secondary battery of the present invention fine particles having a particle size of 1 ⁇ m or less that existed before the coating with the carbon coating forms secondary particles aggregated with carbon by the coating.
- the secondary particles fill the gaps of the large particles and contribute to the reduction of the electric resistance of the negative electrode. This leads to an improvement in capacity retention rate when the charge / discharge cycle is repeated.
- the negative electrode material of the present invention can have a high capacity.
- the manufacturing method is not particularly complicated, is simple, and can sufficiently withstand industrial scale production.
- FIG. 2 is a particle size distribution chart of base material particles before performing carbon coating by CVD in Examples 1 to 3 and Comparative Example 1.
- FIG. 2 is a particle size distribution chart of coated particles in Example 1.
- FIG. 3 is a particle size distribution chart of coated particles in Example 2.
- 4 is a particle size distribution chart of coated particles in Example 3.
- 6 is a particle size distribution chart of coated particles in Example 4.
- 4 is a particle size distribution chart of coated particles in Comparative Example 1.
- 6 is a particle size distribution chart of base material particles before performing carbon coating by CVD in Comparative Example 2; 6 is a particle size distribution chart of coated particles in Comparative Example 2.
- a negative electrode material for a lithium ion secondary battery according to the present invention is made of a material containing silicon atoms, and base particles capable of inserting and extracting lithium ions, and a carbon coating formed on the surface of the base particles.
- the ratio of particles having a particle size of 1 ⁇ m or less in a volume reference distribution measured with a laser diffraction particle size distribution measuring device with respect to the base material particles in a state where no carbon film is formed is defined as a%.
- the ratio of particles having a particle diameter of 1 ⁇ m or less in the volume reference distribution measured with a laser diffraction particle size distribution measuring device to the coated particles is defined as b%.
- the negative electrode material of the present invention satisfies the relationship of a / b ⁇ 3.
- the inventors set the distribution of the respective particle sizes of the base particles and the coated particles within a specific range, that is, the particles having the above-mentioned a / b of 3 or more as negative electrode materials for lithium ion secondary batteries ( It has been found that a lithium-ion secondary battery having a high capacity and excellent cycle characteristics can be obtained by using it as an active material), and the present invention has been made.
- the definition of the particle size distribution of the particles in the present invention is based on particle size distribution measurement using a laser diffraction method (also referred to as laser diffraction particle size distribution measurement).
- a laser diffraction particle size distribution measuring apparatus for example, SALD-3100 manufactured by Shimadzu Corporation can be used.
- the volume reference distribution measured with a laser diffraction particle size distribution measuring device for specific particles (particle group, powder) is also simply referred to as “volume reference distribution” below.
- the “ratio of particles having a particle size of 1 ⁇ m or less” may be generally referred to as “cumulative 1 ⁇ m”.
- the negative electrode material for a lithium ion secondary battery of the present invention can be produced through the following steps. First, base material particles made of a material containing silicon atoms and capable of inserting and extracting lithium ions are prepared (step A). Next, a carbon film is formed on the surface of the substrate particles to form coated particles (step B). At this time, the carbon coating of the base particles is formed so that the above a and b satisfy a / b ⁇ 3. This manufacturing method is not particularly complicated, is simple, and can sufficiently withstand industrial scale production.
- Base material particles In the present invention, as described above, carbon (coating) is performed on particles (base material particles) made of a material containing silicon atoms and capable of inserting and extracting lithium ions.
- the substrate particles used in the present invention (that is, the substrate particles prepared in step A) are silicon particles, particles having a composite structure in which silicon fine particles are dispersed in a silicon-based compound, and a general formula SiOx (0.5 ⁇ x ⁇ The silicon oxide particles represented by 1.6) or a mixture thereof is preferred.
- the method for producing a negative electrode material of the present invention can be applied to any of the above base particles. By using any of the above as the base particles, a negative electrode material for a lithium ion secondary battery having higher initial charge / discharge efficiency, high capacity, and excellent cycleability can be obtained.
- Silicon oxide in the present invention is a general term for amorphous silicon oxide, and silicon oxide before disproportionation is represented by the general formula SiO x (0.5 ⁇ x ⁇ 1.6).
- x is preferably 0.8 ⁇ x ⁇ 1.3, and more preferably 0.8 ⁇ x ⁇ 1.0.
- This silicon oxide can be obtained, for example, by cooling and precipitating silicon monoxide gas generated by heating a mixture of silicon dioxide and metal silicon.
- Particles having a composite structure in which silicon fine particles are dispersed in a silicon-based compound are, for example, a method of firing a mixture of silicon fine particles and a silicon-based compound, or oxidation before disproportionation represented by the general formula SiO x. It can be obtained by heat-treating silicon particles at a temperature of 400 ° C. or higher, preferably 800 to 1,100 ° C. in an inert non-oxidizing atmosphere such as argon, and performing a disproportionation reaction. In particular, the material obtained by the latter method is suitable because silicon crystallites are uniformly dispersed. By the disproportionation reaction as described above, the size of the silicon nanoparticles can be set to 1 to 100 nm.
- silicon dioxide in the particles having a structure in which silicon nanoparticles are dispersed in silicon oxide is preferably silicon dioxide. Note that it can be confirmed by transmission electron microscopy that silicon nanoparticles (crystals) are dispersed in amorphous silicon oxide.
- a silicon oxide-based material is particularly preferable because it has a low volume expansion coefficient during insertion and extraction of lithium.
- the cycle property is particularly good.
- the physical properties of the base particles used in the present invention can be appropriately selected depending on the target coated particles (composite particles). For example, it is preferable to use a material whose cumulative 50% diameter (D 50 , also referred to as volume average particle diameter) in a volume reference distribution measured with a laser diffraction particle size distribution measuring apparatus is 0.1 ⁇ m or more and 30 ⁇ m or less. it can.
- the lower limit of this range is more preferably 0.2 ⁇ m or more, and further preferably 0.3 ⁇ m or more.
- the upper limit is more preferably 20 ⁇ m or less, and further preferably 10 ⁇ m or less.
- the cumulative 50% diameter (D 50 ) is 0.1 ⁇ m or more, the BET specific surface area described later can be made sufficiently small, and no adverse effect due to the excessively large BET specific surface area is exerted. Further, if the cumulative 50% diameter (D 50 ) is 30 ⁇ m or less, it becomes easy to apply a negative electrode material or the like when producing the negative electrode.
- BET specific surface area of the substrate particles used in the present invention is preferably from 0.5 m 2 / g or more 100 m 2 / g or less, 1 m 2 / g or more 20 m 2 / g or less is more preferable.
- the BET specific surface area is 0.5 m 2 / g or more, the adhesiveness when the negative electrode material is applied to produce the negative electrode can be made sufficient, and the battery characteristics can be improved.
- the BET specific surface area is 100 m 2 / g or less, the ratio of silicon dioxide due to natural oxidation of the particle surface can be reduced. As a result, since silicon dioxide that does not contribute to the battery reaction can be reduced, a decrease in battery capacity can be suppressed when used as a negative electrode material for a lithium ion secondary battery.
- the “a%” of the base particles used in the present invention is preferably 0.1% or more and 30% or less.
- the base particles have a ratio of particles having a particle size of 1 ⁇ m or less in a volume-based distribution of 0.1% or more and 30% or less, the secondary particles described above can be easily formed, and the electric resistance in the negative electrode is reduced. Contribute to.
- Step B a carbon film is formed on the surface of the base material particles to form coated particles. This is for imparting conductivity to the base particles and improving battery characteristics.
- it is essential to form a carbon film on the surface of the substrate particles, but this carbon coating may be performed and mixed with conductive particles such as graphite.
- a method for forming a carbon film on the surface of the substrate particles a method performed by chemical vapor deposition (CVD) is suitable.
- CVD chemical vapor deposition
- a method of performing chemical vapor deposition of carbon in a temperature range of 600 to 1200 ° C. in an organic gas atmosphere that can be pyrolyzed to generate carbon with respect to base particles Is mentioned.
- This chemical vapor deposition can be applied at both normal pressure and reduced pressure, and examples of reduced pressure include reduced pressure of 50 to 30,000 Pa.
- generally known apparatuses such as a batch furnace, a continuous kiln, such as a rotary kiln and a roller hearth kiln, and a fluidized bed, can be used for the apparatus used for the formation process of a carbon film.
- a rotary kiln capable of continuously performing vapor deposition while stirring can efficiently coat carbon more uniformly, and can improve battery characteristics.
- the formation of a carbon film by chemical vapor deposition includes the following various organic substances as the carbon source.
- the thermal decomposition temperature, vapor deposition rate, and the characteristics of the carbon film formed after vapor deposition largely depend on the substance used. May be different.
- the carbon source can be appropriately changed according to the physical properties of the target coated particles. A substance having a low vapor deposition rate is preferred because it tends to make the surface carbon film uniform enough.
- the substance is decomposed at a low temperature, the growth of silicon crystals in the base material particles during vapor deposition is suppressed, so that it is possible to suppress a decrease in discharge efficiency and cycle characteristics.
- the ratio of the mass of carbon contained in the coating particles to the mass of the coating particles is preferably 0.5% by mass or more and 40% by mass or less. This ratio is more preferably 1.0 to 30% by mass. Although it depends on the particles to be coated, by setting the carbon coating amount to 0.5% by mass or more, it is possible to maintain substantially sufficient conductivity, and the cycle characteristics when used as a negative electrode of a nonaqueous electrolyte secondary battery. Can be reliably achieved. In addition, if the carbon coating amount is 40% by mass or less, the effect of imparting conductivity by the carbon coating can be obtained, and a decrease in charge / discharge capacity due to an increase in the proportion of carbon in the negative electrode material can be suppressed. Can do.
- the negative electrode material of the present invention satisfies the relationship of a / b ⁇ 3 in terms of particle size.
- Particles fine powder having a particle size of 1 ⁇ m or less in the volume-based distribution of the base material particles in a state where no carbon coating is formed form secondary particles aggregated with carbon by the coating.
- the secondary particles fill the gaps of the large particles and contribute to the reduction of the electric resistance of the negative electrode (electrode). This leads to an improvement in capacity retention rate when the charge / discharge cycle is repeated.
- the carbon coating is preferably formed so that the 50% cumulative diameter (D 50 ) in the volume reference distribution measured with a laser diffraction particle size distribution measuring device of the coated particles is 1 ⁇ m or more and 30 ⁇ m or less.
- the base material particles in order to make the base material particles have a specific particle size distribution and a particle size range, it can be appropriately adjusted by a treatment such as pulverization or classification.
- a treatment such as pulverization or classification.
- the coated particles on which the carbon coating is formed have a specific particle size distribution and particle size range, it can be appropriately adjusted depending on the coating amount.
- the coating amount of the carbon coating depends on conditions such as the carbon source gas used for CVD, the heat treatment temperature, and the heat treatment time, in addition to the physical properties of the base particles. The relationship between the coating conditions and the coating amount can be easily determined experimentally.
- a known apparatus can be used for pulverizing the particles.
- the apparatus illustrated below can be used.
- a ball mill and a medium agitation mill are exemplified in which a pulverizing medium such as a ball or a bead is moved and an object is pulverized using an impact force, a frictional force, or a compressive force.
- the roller mill which grind
- a jet mill is exemplified in which the object to be crushed collides with the lining material at high speed or particles collide with each other, and pulverization is performed by the impact force of the impact.
- examples include a hammer mill, a pin mill, and a disk mill that pulverize a material to be crushed by using an impact force generated by rotation of a rotor having a hammer, blade, pin, and the like fixed thereto.
- the colloid mill using a shear force is illustrated.
- a high-pressure wet-opposing collision type disperser “Ultimizer” is exemplified. For pulverization, both wet and dry processes can be used.
- dry classification in order to adjust the particle size distribution after pulverization, dry classification, wet classification, sieving classification, or the like can be used.
- dry classification an air stream is mainly used, and dispersion, separation (separation of fine particles and coarse particles), collection (separation of solid and gas), and discharge are sequentially or simultaneously performed.
- pre-treatment adjustment of moisture, dispersibility, humidity, etc.
- pre-treatment adjustment of moisture, dispersibility, humidity, etc.
- pulverization and classification are performed at a time, and a desired particle size distribution can be obtained.
- the above coated particles are used for a negative electrode material (active material) for a lithium ion secondary battery.
- a negative electrode material for a lithium ion secondary battery obtained in the present invention a negative electrode is prepared, and lithium An ion secondary battery can be manufactured.
- conductive agents such as carbon and graphite
- the kind of the conductive agent is not particularly limited, and any electronic conductive material that does not cause decomposition or alteration in the configured battery may be used.
- metal particles such as Al, Ti, Fe, Ni, Cu, Zn, Ag, Sn, Si, metal fibers, natural graphite, artificial graphite, various coke particles, mesophase carbon, vapor grown carbon fiber, pitch Graphite such as carbon-based carbon fiber, PAN-based carbon fiber, and various resin fired bodies can be used.
- Examples of the method for preparing the negative electrode (molded body) include the following methods.
- a paste-like mixture prepared by kneading a solvent such as N-methylpyrrolidone or water with the above-described negative electrode material, a conductive agent as necessary, and other additives such as a binder such as a polyimide resin. And This mixture is applied to the sheet of the current collector.
- a negative electrode current collector any material that is usually used as a negative electrode current collector, such as a copper foil or a nickel foil, can be used without any particular limitation on thickness and surface treatment.
- molds a mixture into a sheet form is not specifically limited, A well-known method can be used.
- the lithium ion secondary battery of this invention is a lithium ion secondary battery using said negative electrode for lithium ion secondary batteries.
- at least a positive electrode and a lithium ion conductive nonaqueous electrolyte are included.
- the lithium ion secondary battery of the present invention is characterized in that it comprises a negative electrode using the negative electrode material composed of the above coated particles, and other positive electrode, electrolyte, separator, and other materials and battery shapes are used.
- the negative electrode material of the present invention has good battery characteristics (charge / discharge capacity and cycle characteristics) when used as a negative electrode material for a lithium ion secondary battery, and is particularly excellent in cycle durability. .
- the positive electrode active material a known material such as an oxide of a transition metal such as LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , V 2 O 5 , MnO 2 , TiS 2 , MoS 2 , lithium, or a chalcogen compound may be used. it can.
- a non-aqueous solution containing a lithium salt such as lithium hexafluorophosphate and lithium perchlorate is used.
- a lithium salt such as lithium hexafluorophosphate and lithium perchlorate
- the non-aqueous solvent one or a combination of two or more of propylene carbonate, ethylene carbonate, diethyl carbonate, dimethoxyethane, ⁇ -butyrolactone, 2-methyltetrahydrofuran and the like are used.
- Various other non-aqueous electrolytes and solid electrolytes can also be used.
- SiOx (x 1.0) coarsely crushed by a jaw crusher (Maekawa Kogyo) was pulverized for 80 minutes by a ball mill (Makino) using alumina balls having a diameter of 10 mm as a medium. These particles were used as substrate particles (Step A).
- a particle size distribution chart of the base particles is shown in FIG.
- the 100 g of the base particles were laid on a tray so that the thickness of the powder layer was 10 mm, and charged into a batch type heating furnace. Then, the pressure in the furnace was increased to 1,000 ° C. at a temperature increase rate of 200 ° C./hr while the pressure in the furnace was reduced by an oil rotary vacuum pump. After reaching 1,000 ° C., methane was passed through the furnace at 0.3 L / min, and carbon coating treatment was performed for 10 hours (step B). After stopping methane, the temperature in the furnace was lowered and cooled to obtain 106 g of black particles.
- ⁇ Battery evaluation> battery evaluation using the obtained coated particles as a negative electrode active material was performed by the following method. First, 45% by mass of the obtained negative electrode material, 45% by mass of artificial graphite (average particle size 10 ⁇ m) and 10% by mass of polyimide were mixed, and N-methylpyrrolidone was further added to form a slurry. This slurry was applied to a copper foil having a thickness of 12 ⁇ m, dried at 80 ° C. for 1 hour, then subjected to pressure molding by a roller press, and the electrode was vacuum-dried at 350 ° C. for 1 hour. Then, it punched out to 2 cm ⁇ 2 > and set it as the negative electrode.
- a lithium foil was used for the counter electrode, and lithium hexafluorophosphate was mixed with ethylene carbonate and diethyl carbonate in a 1/1 (volume ratio) mixture as a non-aqueous electrolyte.
- the prepared lithium ion secondary battery is allowed to stand at room temperature overnight, and then charged with a secondary battery charge / discharge tester (manufactured by Nagano Co., Ltd.) until the voltage of the test cell reaches 0 V / 0.5 mA / cm 2. After reaching 0V, the battery was charged by decreasing the current so as to keep the cell voltage at 0V. The charging was terminated when the current value fell below 40 ⁇ A / cm 2 . The discharge was performed at a constant current of 0.5 mA / cm 2 , and the discharge was terminated when the cell voltage reached 1.4 V, and the discharge capacity was determined.
- the above charge / discharge test was repeated, and a charge / discharge test after 50 cycles of the evaluation lithium ion secondary battery was performed.
- the results are shown in Table 1. It was confirmed that the lithium-ion secondary battery had a high capacity with an initial discharge capacity of 1781 mAh / g, a cycle retention rate of 94% after 50 cycles, and excellent cycle performance.
- the obtained black particles were conductive particles having a carbon coating amount of 21.3% by mass with respect to the black particles.
- D 50 was 5.8 ⁇ m
- the cumulative 1 ⁇ m ratio of particles having a particle size of 1 ⁇ m or less
- b 0.3
- a particle size distribution chart of the coated particles is shown in FIG.
- the particle size distribution of the particles D 50 of 4.4 [mu] m, (the proportion of the particle size 1 ⁇ m or less of the particles) accumulated 1 ⁇ m was 4.9% (i.e., b 4.9).
- a particle size distribution chart of the coated particles is shown in FIG.
- the obtained black particles were conductive particles having a carbon coating amount of 0.3% by mass with respect to the black particles.
- a particle size distribution chart of the coated particles is shown in FIG.
- the base particles were subjected to a carbon coating treatment in the same manner as in Example 1.
- a particle size distribution chart of the coated particles is shown in FIG.
- Table 1 shows a list of the particle sizes and battery characteristics of Examples 1 to 4 and Comparative Examples 1 and 2.
- the present invention is not limited to the above embodiment.
- the above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.
Abstract
The present invention is a method for producing a negative electrode material for lithium ion secondary batteries, wherein base particles formed of a material containing silicon atoms are prepared and a carbon coating film is formed on the surface of each base particle, thereby forming coated particles. In this method for producing a negative electrode material for lithium ion secondary batteries, the formation of the carbon coating film is carried out so that a and b satisfy a/b ≥ 3, where a (%) is the ratio of particles having particle diameters of 1 μm or less in the volume-based distribution of the base particles, the surfaces of which are not covered by carbon coating films, as determined using a laser diffraction particle size distribution measuring instrument, and b (%) is the ratio of particles having particle diameters of 1 μm or less in the volume-based distribution of the coated particles as determined using the laser diffraction particle size distribution measuring instrument. Consequently, the present invention provides: a negative electrode material for lithium ion secondary batteries, which has excellent cycle characteristics; and a method for producing this negative electrode material for lithium ion secondary batteries.
Description
本発明は、リチウムイオン二次電池用負極材及びその製造方法に関し、また、そのリチウムイオン二次電池用負極材を用いた負極及びリチウムイオン二次電池に関する。
The present invention relates to a negative electrode material for a lithium ion secondary battery and a method for producing the same, and also relates to a negative electrode and a lithium ion secondary battery using the negative electrode material for the lithium ion secondary battery.
近年、携帯型の電子機器、通信機器等の著しい発展に伴い、経済性と機器の小型化、軽量化の観点から、高エネルギー密度の二次電池が強く要望されている。
In recent years, with the remarkable development of portable electronic devices, communication devices, etc., there is a strong demand for secondary batteries with high energy density from the viewpoints of economy and downsizing and weight reduction of devices.
従来、この種の二次電池の高容量化策として、例えば、負極材料にV、Si、B、Zr、Sn等の酸化物及びそれらの複合酸化物を用いる方法(例えば、特許文献1、2参照)、溶融急冷した金属酸化物を負極材として適用する方法(例えば、特許文献3参照)、負極材料に酸化珪素を用いる方法(例えば、特許文献4参照)、負極材料にSi2N2O及びGe2N2Oを用いる方法(例えば、特許文献5参照)等が知られている。
Conventionally, as a measure for increasing the capacity of this type of secondary battery, for example, a method of using an oxide such as V, Si, B, Zr, Sn, or a composite oxide thereof as a negative electrode material (for example, Patent Documents 1 and 2). Reference), a method of applying a melt-quenched metal oxide as a negative electrode material (for example, see Patent Document 3), a method of using silicon oxide as a negative electrode material (for example, see Patent Document 4), and Si 2 N 2 O as a negative electrode material And a method using Ge 2 N 2 O (see, for example, Patent Document 5) is known.
また、負極材に導電性を付与する目的として、SiOを黒鉛とメカニカルアロイング後に炭化処理する方法(例えば、特許文献6参照)、珪素粒子表面に化学蒸着法により炭素層を被覆する方法(例えば、特許文献7参照)、酸化珪素粒子表面に化学蒸着法により炭素層を被覆する方法(例えば、特許文献8参照)がある。
Further, for the purpose of imparting conductivity to the negative electrode material, a method of carbonizing SiO after graphite and mechanical alloying (for example, see Patent Document 6), a method of coating a carbon layer on the surface of silicon particles by a chemical vapor deposition method (for example, And Patent Document 7), and a method of coating the surface of silicon oxide particles with a carbon layer by chemical vapor deposition (for example, see Patent Document 8).
しかしながら、上記従来の方法では、充放電容量が上がり、エネルギー密度が高くなるものの、サイクル性が不十分であったり、市場の要求特性には未だ不十分であったりし、必ずしも満足でき得るものではなく、更なるエネルギー密度の向上が望まれていた。
However, in the above conventional method, although the charge / discharge capacity is increased and the energy density is increased, the cycleability is insufficient, or the required characteristics of the market are still insufficient, and are not always satisfactory. However, further improvement in energy density has been desired.
上述のように、従来の負極材にはまだ問題があった。特に、特許文献4では、酸化珪素をリチウムイオン二次電池用負極材として用い、高容量の電極を得ているが、本発明者らが知る限りにおいては、未だ初回充放電時における不可逆容量が大きかったり、サイクル性が実用レベルに達していなかったり等の問題があり、改良する余地がある。
As described above, the conventional negative electrode material still had problems. In particular, in Patent Document 4, silicon oxide is used as a negative electrode material for a lithium ion secondary battery to obtain a high-capacity electrode. However, as far as the present inventors know, the irreversible capacity at the time of initial charge / discharge is still insufficient. There are problems such as large size and poor cycle performance, and there is room for improvement.
また、負極材に導電性を付与した技術についても、特許文献6では固体と固体の融着であるため均一な炭素被膜が形成されず、導電性が不十分であるといった問題がある。特許文献8の方法においては、サイクル性の向上は確認されるものの、微細な珪素結晶の析出、炭素被覆の構造及び基材との融合が不十分であることより、充放電のサイクル数を重ねると徐々に容量が低下し、一定回数後に急激に低下するという現象があり、二次電池用としてはまだ不十分であるといった問題があった。
Also, the technique of imparting conductivity to the negative electrode material also has a problem in Patent Document 6 that a uniform carbon film is not formed because of solid-solid fusion and the conductivity is insufficient. In the method of Patent Document 8, although improvement in cycle performance is confirmed, the number of cycles of charge / discharge is increased due to insufficient deposition of fine silicon crystals, integration of the carbon coating structure and the base material. As a result, there is a problem that the capacity gradually decreases and then rapidly decreases after a certain number of times, which is still insufficient for a secondary battery.
本発明はかかる問題点に鑑みてなされたもので、サイクル特性に優れたリチウムイオン二次電池負極用負極材、及びその製造方法を提供することを目的とする。また、本発明は、そのような負極材を用いた負極及びリチウムイオン二次電池を提供することを目的とする。
The present invention has been made in view of such problems, and an object thereof is to provide a negative electrode material for a negative electrode of a lithium ion secondary battery excellent in cycle characteristics and a method for producing the same. Another object of the present invention is to provide a negative electrode and a lithium ion secondary battery using such a negative electrode material.
上記課題を解決するため、本発明は、珪素原子を含む材料から成り、リチウムイオンを吸蔵及び放出することが可能な基材粒子を準備する工程と、前記基材粒子の表面に炭素被膜を形成して被覆粒子とする工程とを備えるリチウムイオン二次電池用負極材の製造方法において、前記炭素被膜が形成されていない状態で前記基材粒子に対してレーザー回折法粒度分布測定装置で測定した体積基準分布における粒径1μm以下の粒子の割合をa%とし、前記被覆粒子に対してレーザー回折法粒度分布測定装置で測定した体積基準分布における粒径1μm以下の粒子の割合をb%としたときに、a/b≧3となるように、前記炭素被膜を形成する工程を行うことを特徴とするリチウムイオン二次電池用負極材の製造方法を提供する。
In order to solve the above problems, the present invention comprises a step of preparing base particles made of a material containing silicon atoms and capable of occluding and releasing lithium ions, and forming a carbon coating on the surface of the base particles In the method for producing a negative electrode material for a lithium ion secondary battery comprising a step of forming coated particles, the substrate particles were measured with a laser diffraction particle size distribution measurement device in a state where the carbon coating was not formed The ratio of particles having a particle size of 1 μm or less in the volume-based distribution was defined as a%, and the ratio of particles having a particle diameter of 1 μm or less in the volume-based distribution measured with a laser diffraction particle size distribution measuring device with respect to the coated particles was defined as b%. In some cases, a method for producing a negative electrode material for a lithium ion secondary battery is provided, wherein the step of forming the carbon film is performed so that a / b ≧ 3.
このように、a/b≧3になるようにして炭素被膜の形成を行う負極材の製造方法であれば、炭素被膜による被覆を行う前に存在していた粒径1μm以下の粒子(すなわち、比較的粒径の小さい微粉)が、被覆によって炭素で凝集した2次粒子を形成する。負極材により負極を作製した際にこの2次粒子が大粒子の間隙を埋めて負極の電気抵抗の低減に寄与する。これによって充放電サイクルを繰り返したときの容量維持率の向上につながる。
Thus, if the negative electrode material is produced by forming a carbon film so that a / b ≧ 3, particles having a particle size of 1 μm or less that existed before the coating with the carbon film (that is, (Fine powder having a relatively small particle diameter) forms secondary particles aggregated with carbon by coating. When the negative electrode is produced from the negative electrode material, the secondary particles fill the gaps of the large particles and contribute to the reduction of the electric resistance of the negative electrode. This leads to an improvement in capacity retention rate when the charge / discharge cycle is repeated.
この場合、前記基材粒子を準備する工程において、前記基材粒子として、前記a%が0.1%以上30%以下のものを準備することが好ましい。
In this case, in the step of preparing the base particle, it is preferable to prepare the base particle having the a% of 0.1% to 30%.
このように、基材粒子を、体積基準分布における粒径1μm以下の粒子の割合が0.1%以上30%以下のものとすることにより、2次粒子を形成しやすくなる。
Thus, by making the base particles have a ratio of particles having a particle size of 1 μm or less in the volume-based distribution of 0.1% or more and 30% or less, secondary particles can be easily formed.
また、前記基材粒子を準備する工程において、前記基材粒子として、珪素粒子、珪素の微粒子が珪素系化合物に分散した複合構造を有する粒子、一般式SiOx(0.5≦x≦1.6)で表される酸化珪素粒子、又はこれらの混合物であるものを準備することができる。
In the step of preparing the base particles, the base particles may be silicon particles, particles having a composite structure in which silicon fine particles are dispersed in a silicon-based compound, or a general formula SiOx (0.5 ≦ x ≦ 1.6). ), Or a mixture thereof can be prepared.
本発明の負極材の製造方法は、上記のいずれの基材粒子にも適用することができる。
The method for producing a negative electrode material of the present invention can be applied to any of the above base material particles.
また、前記被覆粒子の質量に対する、該被覆粒子に含有される炭素の質量の割合を、0.5質量%以上40質量%以下とすることが好ましい。
In addition, the ratio of the mass of carbon contained in the coated particles to the mass of the coated particles is preferably 0.5% by mass or more and 40% by mass or less.
このような炭素被覆量とすることにより、負極材に十分な導電性を付与し、かつ充放電容量を高くすることができる。
By using such a carbon coating amount, sufficient conductivity can be imparted to the negative electrode material, and the charge / discharge capacity can be increased.
また、前記基材粒子を準備する工程において、前記基材粒子として、前記基材粒子のレーザー回折法粒度分布測定装置で測定した体積基準分布における累積50%径(D50)が、0.1μm以上30μm以下であるものを準備することが好ましい。
In the step of preparing the base particles, the base particles may have a cumulative 50% diameter (D 50 ) in a volume reference distribution measured with a laser diffraction particle size distribution measuring device of the base particles of 0.1 μm. It is preferable to prepare one having a thickness of 30 μm or less.
このような累積50%径を有する基材粒子を用いることにより、負極作製のために負極材を塗布した際にセパレーターを傷付けることなく、また電極の導電性を良好なものとすることができる。
By using such base material particles having a cumulative 50% diameter, it is possible to improve the electrode conductivity without damaging the separator when the negative electrode material is applied for producing the negative electrode.
また、前記炭素被膜の形成を行う工程を、前記被覆粒子のレーザー回折法粒度分布測定装置で測定した体積基準分布における累積50%径(D50)が、1μm以上30μm以下となるように行うことが好ましい。
In addition, the step of forming the carbon coating is performed such that the cumulative 50% diameter (D 50 ) in the volume reference distribution measured with a laser diffraction particle size distribution measuring device of the coated particles is 1 μm or more and 30 μm or less. Is preferred.
被覆粒子の累積50%径をこのような値とすることにより、負極作製のために負極材を塗布した際にセパレーターを傷付けることなく、また電極の導電性を良好なものとすることができる。
By setting the cumulative 50% diameter of the coated particles to such a value, it is possible to improve the conductivity of the electrode without damaging the separator when the negative electrode material is applied for producing the negative electrode.
また、前記炭素被膜の形成を行う工程を、前記基材粒子に対して、熱分解して炭素を生成し得る有機物ガス雰囲気中で600~1200℃の温度範囲で炭素を化学蒸着することにより行うことが好ましい。
In addition, the step of forming the carbon coating is performed by chemical vapor deposition of carbon on the base particle in an organic gas atmosphere that can be pyrolyzed to generate carbon in a temperature range of 600 to 1200 ° C. It is preferable.
このような条件で炭素被覆を行うことにより、良好な炭素被膜の形成を行うことができ、負極材に適切な導電性を付与することができる。
By performing carbon coating under such conditions, a good carbon film can be formed, and appropriate conductivity can be imparted to the negative electrode material.
また、前記熱分解して炭素を生成し得る有機物ガスの原料として、メタン、エタン、エチレン、アセチレン、プロパン、プロピレン、ブタン、ブテン、ペンタン、イソブタン、ヘキサン、ベンゼン、トルエン、キシレン、スチレン、エチルベンゼン、ジフェニルメタン、ナフタレン、フェノール、クレゾール、ニトロベンゼン、クロルベンゼン、インデン、クマロン、ピリジン、アントラセン、フェナントレン、タール蒸留工程で得られるガス軽油、クレオソート油、アントラセン油及びナフサ分解タール油の中から選択される1種以上を用いることが好ましい。
In addition, as a raw material of organic gas that can generate carbon by pyrolysis, methane, ethane, ethylene, acetylene, propane, propylene, butane, butene, pentane, isobutane, hexane, benzene, toluene, xylene, styrene, ethylbenzene, 1 selected from diphenylmethane, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, anthracene, phenanthrene, gas light oil obtained in tar distillation process, creosote oil, anthracene oil and naphtha cracked tar oil It is preferable to use more than one species.
有機物ガスの原料としてはこれらを好適に用いることができる。
These can be suitably used as organic gas raw materials.
また、本発明は、上記のいずれかのリチウムイオン二次電池用負極材の製造方法により製造されたことを特徴とするリチウムイオン二次電池用負極材を提供する。
The present invention also provides a negative electrode material for a lithium ion secondary battery manufactured by any one of the above-described methods for manufacturing a negative electrode material for a lithium ion secondary battery.
また、本発明は、珪素原子を含む材料から成り、リチウムイオンを吸蔵及び放出することが可能な基材粒子と、該基材粒子の表面に形成された炭素被膜とから成る被覆粒子であるリチウムイオン二次電池用負極材であって、前記炭素被膜が形成されていない状態で前記基材粒子に対してレーザー回折法粒度分布測定装置で測定した体積基準分布における粒径1μm以下の粒子の割合をa%とし、前記被覆粒子に対してレーザー回折法粒度分布測定装置で測定した体積基準分布における粒径1μm以下の粒子の割合をb%としたときに、a/b≧3となるものであることを特徴とするリチウムイオン二次電池用負極材を提供する。
The present invention also relates to lithium, which is a coated particle composed of a material containing a silicon atom and comprising a base particle capable of inserting and extracting lithium ions and a carbon coating formed on the surface of the base particle. Proportion of particles having a particle size of 1 μm or less in a volume reference distribution measured with a laser diffraction particle size distribution measuring device with respect to the base particles in a state where the carbon film is not formed in the negative electrode material for an ion secondary battery And a / b ≧ 3, where b is the ratio of particles having a particle size of 1 μm or less in the volume reference distribution measured with a laser diffraction particle size distribution measuring device to the coated particles. There is provided a negative electrode material for a lithium ion secondary battery.
本発明の負極材においては、炭素被膜による被覆を行う前に存在していた粒径1μm以下の微粉が被覆によって炭素で凝集した2次粒子を形成する。負極材により負極を作製した際にこの2次粒子が大粒子の間隙を埋めて負極の電気抵抗の低減に寄与する。これによって充放電サイクルを繰り返したときの容量維持率の向上につながる。
In the negative electrode material of the present invention, fine particles having a particle size of 1 μm or less that existed before the coating with the carbon coating forms secondary particles aggregated with carbon by the coating. When the negative electrode is produced from the negative electrode material, the secondary particles fill the gaps of the large particles and contribute to the reduction of the electric resistance of the negative electrode. This leads to an improvement in capacity retention rate when the charge / discharge cycle is repeated.
また、本発明は、上記のリチウムイオン二次電池用負極材を用いたことを特徴とするリチウムイオン二次電池用負極を提供する。
The present invention also provides a negative electrode for a lithium ion secondary battery using the above negative electrode material for a lithium ion secondary battery.
また、本発明は、上記のリチウムイオン二次電池用負極を用いたことを特徴とするリチウムイオン二次電池を提供する。
The present invention also provides a lithium ion secondary battery using the above negative electrode for a lithium ion secondary battery.
本発明の負極材を用いたリチウムイオン二次電池用負極においては、負極材に含まれる上記の2次粒子の存在が負極の電気抵抗の低減に寄与する。これは、その負極を用いたリチウムイオン二次電池の充放電サイクルを繰り返したときの容量維持率の向上につながる。
In the negative electrode for a lithium ion secondary battery using the negative electrode material of the present invention, the presence of the secondary particles contained in the negative electrode material contributes to the reduction of the electric resistance of the negative electrode. This leads to an improvement in capacity retention rate when a charge / discharge cycle of a lithium ion secondary battery using the negative electrode is repeated.
本発明のリチウムイオン二次電池用負極材においては、炭素被膜による被覆を行う前に存在していた粒径1μm以下の微粉が、被覆によって炭素で凝集した2次粒子を形成する。負極材により負極を作製した際にこの2次粒子が大粒子の間隙を埋めて負極の電気抵抗の低減に寄与する。これによって充放電サイクルを繰り返したときの容量維持率の向上につながる。また、珪素原子を含む材料を基材粒子として用いるので、本発明の負極材は、高容量なものとすることができる。また、その製造方法は特別複雑なものではなく簡便であり、工業的規模の生産にも十分耐え得るものである。
In the negative electrode material for a lithium ion secondary battery of the present invention, fine particles having a particle size of 1 μm or less that existed before the coating with the carbon coating forms secondary particles aggregated with carbon by the coating. When the negative electrode is produced from the negative electrode material, the secondary particles fill the gaps of the large particles and contribute to the reduction of the electric resistance of the negative electrode. This leads to an improvement in capacity retention rate when the charge / discharge cycle is repeated. In addition, since a material containing silicon atoms is used as the base particle, the negative electrode material of the present invention can have a high capacity. In addition, the manufacturing method is not particularly complicated, is simple, and can sufficiently withstand industrial scale production.
以下、本発明について詳細に説明する。
Hereinafter, the present invention will be described in detail.
[リチウムイオン二次電池用負極材]
本発明のリチウムイオン二次電池用負極材は、珪素原子を含む材料から成り、リチウムイオンを吸蔵及び放出することが可能な基材粒子と、該基材粒子の表面に形成された炭素被膜とから成る被覆粒子である。また、本発明の負極材は、炭素被膜の形成前後の粒子が以下の条件を満たすものである。炭素被膜が形成されていない状態で基材粒子に対してレーザー回折法粒度分布測定装置で測定した体積基準分布における粒径1μm以下の粒子の割合をa%とする。また、被覆粒子に対してレーザー回折法粒度分布測定装置で測定した体積基準分布における粒径1μm以下の粒子の割合をb%とする。このとき、本発明の負極材はa/b≧3の関係を満たすものである。 [Anode material for lithium ion secondary battery]
A negative electrode material for a lithium ion secondary battery according to the present invention is made of a material containing silicon atoms, and base particles capable of inserting and extracting lithium ions, and a carbon coating formed on the surface of the base particles. Coated particles consisting of In the negative electrode material of the present invention, the particles before and after the formation of the carbon coating satisfy the following conditions. The ratio of particles having a particle size of 1 μm or less in a volume reference distribution measured with a laser diffraction particle size distribution measuring device with respect to the base material particles in a state where no carbon film is formed is defined as a%. Further, the ratio of particles having a particle diameter of 1 μm or less in the volume reference distribution measured with a laser diffraction particle size distribution measuring device to the coated particles is defined as b%. At this time, the negative electrode material of the present invention satisfies the relationship of a / b ≧ 3.
本発明のリチウムイオン二次電池用負極材は、珪素原子を含む材料から成り、リチウムイオンを吸蔵及び放出することが可能な基材粒子と、該基材粒子の表面に形成された炭素被膜とから成る被覆粒子である。また、本発明の負極材は、炭素被膜の形成前後の粒子が以下の条件を満たすものである。炭素被膜が形成されていない状態で基材粒子に対してレーザー回折法粒度分布測定装置で測定した体積基準分布における粒径1μm以下の粒子の割合をa%とする。また、被覆粒子に対してレーザー回折法粒度分布測定装置で測定した体積基準分布における粒径1μm以下の粒子の割合をb%とする。このとき、本発明の負極材はa/b≧3の関係を満たすものである。 [Anode material for lithium ion secondary battery]
A negative electrode material for a lithium ion secondary battery according to the present invention is made of a material containing silicon atoms, and base particles capable of inserting and extracting lithium ions, and a carbon coating formed on the surface of the base particles. Coated particles consisting of In the negative electrode material of the present invention, the particles before and after the formation of the carbon coating satisfy the following conditions. The ratio of particles having a particle size of 1 μm or less in a volume reference distribution measured with a laser diffraction particle size distribution measuring device with respect to the base material particles in a state where no carbon film is formed is defined as a%. Further, the ratio of particles having a particle diameter of 1 μm or less in the volume reference distribution measured with a laser diffraction particle size distribution measuring device to the coated particles is defined as b%. At this time, the negative electrode material of the present invention satisfies the relationship of a / b ≧ 3.
本発明者らは、基材粒子及び被覆粒子のそれぞれの粒径の分布を特定の範囲にすること、すなわち上記のa/bが3以上となる粒子を、リチウムイオン二次電池用負極材(活物質)として用いることで、高容量で且つサイクル特性に優れたリチウムイオン二次電池が得られることを知見し、本発明をなすに至った。
The inventors set the distribution of the respective particle sizes of the base particles and the coated particles within a specific range, that is, the particles having the above-mentioned a / b of 3 or more as negative electrode materials for lithium ion secondary batteries ( It has been found that a lithium-ion secondary battery having a high capacity and excellent cycle characteristics can be obtained by using it as an active material), and the present invention has been made.
上記のように、本発明における粒子の粒度分布の規定は、レーザー回折法を用いた粒度分布測定(レーザー回折式粒度分布測定とも称する)に基づく。レーザー回折法粒度分布測定装置としては、例えば、島津製作所製のSALD-3100を用いることができる。特定の粒子(粒子群、粉体)についてレーザー回折法粒度分布測定装置で測定した体積基準分布を、以下では単に「体積基準分布」とも称する。なお、「粒径1μm以下の粒子の割合」は、一般に「累積1μm」とも称されることがある。
As described above, the definition of the particle size distribution of the particles in the present invention is based on particle size distribution measurement using a laser diffraction method (also referred to as laser diffraction particle size distribution measurement). As the laser diffraction particle size distribution measuring apparatus, for example, SALD-3100 manufactured by Shimadzu Corporation can be used. The volume reference distribution measured with a laser diffraction particle size distribution measuring device for specific particles (particle group, powder) is also simply referred to as “volume reference distribution” below. The “ratio of particles having a particle size of 1 μm or less” may be generally referred to as “cumulative 1 μm”.
[リチウムイオン二次電池用負極材の製造方法]
本発明のリチウムイオン二次電池用負極材は、以下の工程を経ることにより製造することができる。まず、珪素原子を含む材料から成り、リチウムイオンを吸蔵及び放出することが可能な基材粒子を準備する(工程A)。次に、基材粒子の表面に炭素被膜を形成して被覆粒子とする(工程B)。このとき、上記のaとbとが、a/b≧3となるように、基材粒子の炭素被膜を形成する。この製造方法は特別複雑なものではなく簡便であり、工業的規模の生産にも十分耐え得るものである。 [Method for producing negative electrode material for lithium ion secondary battery]
The negative electrode material for a lithium ion secondary battery of the present invention can be produced through the following steps. First, base material particles made of a material containing silicon atoms and capable of inserting and extracting lithium ions are prepared (step A). Next, a carbon film is formed on the surface of the substrate particles to form coated particles (step B). At this time, the carbon coating of the base particles is formed so that the above a and b satisfy a / b ≧ 3. This manufacturing method is not particularly complicated, is simple, and can sufficiently withstand industrial scale production.
本発明のリチウムイオン二次電池用負極材は、以下の工程を経ることにより製造することができる。まず、珪素原子を含む材料から成り、リチウムイオンを吸蔵及び放出することが可能な基材粒子を準備する(工程A)。次に、基材粒子の表面に炭素被膜を形成して被覆粒子とする(工程B)。このとき、上記のaとbとが、a/b≧3となるように、基材粒子の炭素被膜を形成する。この製造方法は特別複雑なものではなく簡便であり、工業的規模の生産にも十分耐え得るものである。 [Method for producing negative electrode material for lithium ion secondary battery]
The negative electrode material for a lithium ion secondary battery of the present invention can be produced through the following steps. First, base material particles made of a material containing silicon atoms and capable of inserting and extracting lithium ions are prepared (step A). Next, a carbon film is formed on the surface of the substrate particles to form coated particles (step B). At this time, the carbon coating of the base particles is formed so that the above a and b satisfy a / b ≧ 3. This manufacturing method is not particularly complicated, is simple, and can sufficiently withstand industrial scale production.
[基材粒子]
本発明では、上記のように、珪素原子を含む材料から成り、リチウムイオンを吸蔵及び放出することが可能な粒子(基材粒子)に炭素被覆を行う。本発明で用いる基材粒子(すなわち、工程Aで準備する基材粒子)は、珪素粒子、珪素の微粒子が珪素系化合物に分散した複合構造を有する粒子、一般式SiOx(0.5≦x≦1.6)で表される酸化珪素粒子、又はこれらの混合物が好ましい。本発明の負極材の製造方法は、上記のいずれの基材粒子にも適用することができる。基材粒子として上記のいずれかを使用することで、より初回充放電効率が高く、高容量でかつサイクル性に優れたリチウムイオン二次電池用負極材が得られる。 [Base material particles]
In the present invention, as described above, carbon (coating) is performed on particles (base material particles) made of a material containing silicon atoms and capable of inserting and extracting lithium ions. The substrate particles used in the present invention (that is, the substrate particles prepared in step A) are silicon particles, particles having a composite structure in which silicon fine particles are dispersed in a silicon-based compound, and a general formula SiOx (0.5 ≦ x ≦ The silicon oxide particles represented by 1.6) or a mixture thereof is preferred. The method for producing a negative electrode material of the present invention can be applied to any of the above base particles. By using any of the above as the base particles, a negative electrode material for a lithium ion secondary battery having higher initial charge / discharge efficiency, high capacity, and excellent cycleability can be obtained.
本発明では、上記のように、珪素原子を含む材料から成り、リチウムイオンを吸蔵及び放出することが可能な粒子(基材粒子)に炭素被覆を行う。本発明で用いる基材粒子(すなわち、工程Aで準備する基材粒子)は、珪素粒子、珪素の微粒子が珪素系化合物に分散した複合構造を有する粒子、一般式SiOx(0.5≦x≦1.6)で表される酸化珪素粒子、又はこれらの混合物が好ましい。本発明の負極材の製造方法は、上記のいずれの基材粒子にも適用することができる。基材粒子として上記のいずれかを使用することで、より初回充放電効率が高く、高容量でかつサイクル性に優れたリチウムイオン二次電池用負極材が得られる。 [Base material particles]
In the present invention, as described above, carbon (coating) is performed on particles (base material particles) made of a material containing silicon atoms and capable of inserting and extracting lithium ions. The substrate particles used in the present invention (that is, the substrate particles prepared in step A) are silicon particles, particles having a composite structure in which silicon fine particles are dispersed in a silicon-based compound, and a general formula SiOx (0.5 ≦ x ≦ The silicon oxide particles represented by 1.6) or a mixture thereof is preferred. The method for producing a negative electrode material of the present invention can be applied to any of the above base particles. By using any of the above as the base particles, a negative electrode material for a lithium ion secondary battery having higher initial charge / discharge efficiency, high capacity, and excellent cycleability can be obtained.
本発明における酸化珪素とは、非晶質の珪素酸化物の総称であり、不均化前の酸化珪素は、一般式SiOx(0.5≦x≦1.6)で表される。xは0.8≦x<1.3が好ましく、0.8≦x<1.0がより好ましい。この酸化珪素は、例えば、二酸化珪素と金属珪素との混合物を加熱して生成した一酸化珪素ガスを冷却・析出して得ることができる。
Silicon oxide in the present invention is a general term for amorphous silicon oxide, and silicon oxide before disproportionation is represented by the general formula SiO x (0.5 ≦ x ≦ 1.6). x is preferably 0.8 ≦ x <1.3, and more preferably 0.8 ≦ x <1.0. This silicon oxide can be obtained, for example, by cooling and precipitating silicon monoxide gas generated by heating a mixture of silicon dioxide and metal silicon.
珪素の微粒子が珪素系化合物に分散した複合構造を有する粒子は、例えば、珪素の微粒子を珪素系化合物と混合したものを焼成する方法や、一般式SiOxで表される不均化前の酸化珪素粒子を、アルゴン等不活性な非酸化性雰囲気中、400℃以上、好適には800~1,100℃の温度で熱処理し、不均化反応を行うことで得ることができる。特に後者の方法で得た材料は、珪素の微結晶が均一に分散されるため好適である。上記のような不均化反応により、珪素ナノ粒子のサイズを1~100nmとすることができる。なお、珪素ナノ粒子が酸化珪素中に分散した構造を有する粒子中の酸化珪素については、二酸化珪素であることが望ましい。なお、透過電子顕微鏡によってシリコンのナノ粒子(結晶)が無定形の酸化珪素に分散していることを確認することができる。
Particles having a composite structure in which silicon fine particles are dispersed in a silicon-based compound are, for example, a method of firing a mixture of silicon fine particles and a silicon-based compound, or oxidation before disproportionation represented by the general formula SiO x. It can be obtained by heat-treating silicon particles at a temperature of 400 ° C. or higher, preferably 800 to 1,100 ° C. in an inert non-oxidizing atmosphere such as argon, and performing a disproportionation reaction. In particular, the material obtained by the latter method is suitable because silicon crystallites are uniformly dispersed. By the disproportionation reaction as described above, the size of the silicon nanoparticles can be set to 1 to 100 nm. Note that silicon dioxide in the particles having a structure in which silicon nanoparticles are dispersed in silicon oxide is preferably silicon dioxide. Note that it can be confirmed by transmission electron microscopy that silicon nanoparticles (crystals) are dispersed in amorphous silicon oxide.
基材粒子としては、酸化珪素系の材料がリチウムの吸蔵及び放出時の体積膨張率が低く、特に好ましい。基材粒子自体の体積膨張率が低いと、サイクル性が特に良好となる。
As the base particle, a silicon oxide-based material is particularly preferable because it has a low volume expansion coefficient during insertion and extraction of lithium. When the volume expansion coefficient of the base particle itself is low, the cycle property is particularly good.
本発明で用いる基材粒子の物性は、目的とする被覆粒子(複合粒子)によって、適宜選定することができる。例えばレーザー回折法粒度分布測定装置で測定した体積基準分布における累積50%径(D50、体積平均粒径とも称される。)が、0.1μm以上30μm以下であるものを好適に用いることができる。この範囲の下限は0.2μm以上がより好ましく、0.3μm以上がさらに好ましい。上限は20μm以下がより好ましく、10μm以下がさらに好ましい。累積50%径(D50)が0.1μm以上であれば、後述するBET比表面積を十分に小さいものとすることができ、BET比表面積が大きすぎることによる悪影響を及ぼさない。また、累積50%径(D50)が30μm以下であれば、負極を作製する際の負極材の塗布等をしやすくなる。
The physical properties of the base particles used in the present invention can be appropriately selected depending on the target coated particles (composite particles). For example, it is preferable to use a material whose cumulative 50% diameter (D 50 , also referred to as volume average particle diameter) in a volume reference distribution measured with a laser diffraction particle size distribution measuring apparatus is 0.1 μm or more and 30 μm or less. it can. The lower limit of this range is more preferably 0.2 μm or more, and further preferably 0.3 μm or more. The upper limit is more preferably 20 μm or less, and further preferably 10 μm or less. If the cumulative 50% diameter (D 50 ) is 0.1 μm or more, the BET specific surface area described later can be made sufficiently small, and no adverse effect due to the excessively large BET specific surface area is exerted. Further, if the cumulative 50% diameter (D 50 ) is 30 μm or less, it becomes easy to apply a negative electrode material or the like when producing the negative electrode.
本発明で用いる基材粒子のBET比表面積は、0.5m2/g以上100m2/g以下が好ましく、1m2/g以上20m2/g以下がより好ましい。BET比表面積が0.5m2/g以上であれば、負極を作製するために負極材を塗布した際の接着性を十分なものとすることができ、電池特性を向上させることができる。また、BET比表面積が100m2/g以下であれば、粒子表面の自然酸化による二酸化珪素の割合を少なくすることができる。その結果、電池反応に寄与しない二酸化珪素を少なくすることができるので、リチウムイオン二次電池用負極材として用いた際に電池容量の低下を抑制することができる。
BET specific surface area of the substrate particles used in the present invention is preferably from 0.5 m 2 / g or more 100 m 2 / g or less, 1 m 2 / g or more 20 m 2 / g or less is more preferable. When the BET specific surface area is 0.5 m 2 / g or more, the adhesiveness when the negative electrode material is applied to produce the negative electrode can be made sufficient, and the battery characteristics can be improved. Moreover, if the BET specific surface area is 100 m 2 / g or less, the ratio of silicon dioxide due to natural oxidation of the particle surface can be reduced. As a result, since silicon dioxide that does not contribute to the battery reaction can be reduced, a decrease in battery capacity can be suppressed when used as a negative electrode material for a lithium ion secondary battery.
また、本発明で用いる基材粒子の上記「a%」が0.1%以上30%以下であることが好ましい。基材粒子を、体積基準分布における粒径1μm以下の粒子の割合が0.1%以上30%以下のものとすることにより、上記した2次粒子を形成しやすくなり、負極における電気抵抗の低減に寄与する。
In addition, the “a%” of the base particles used in the present invention is preferably 0.1% or more and 30% or less. By making the base particles have a ratio of particles having a particle size of 1 μm or less in a volume-based distribution of 0.1% or more and 30% or less, the secondary particles described above can be easily formed, and the electric resistance in the negative electrode is reduced. Contribute to.
[炭素被膜の形成方法]
本発明においては、上記のように、工程Bにおいて、基材粒子の表面に炭素被膜を形成して被覆粒子とする。これは、上記基材粒子に導電性を付与し、電池特性の向上を図るためである。本発明では、基材粒子の表面に炭素被膜を形成することが必須であるが、この炭素被覆を行うとともに、黒鉛等の導電性のある粒子と混合してもよい。基材粒子の表面に炭素被膜を形成する方法としては、化学蒸着(CVD)により行う方法が好適である。 [Method of forming carbon film]
In the present invention, as described above, in Step B, a carbon film is formed on the surface of the base material particles to form coated particles. This is for imparting conductivity to the base particles and improving battery characteristics. In the present invention, it is essential to form a carbon film on the surface of the substrate particles, but this carbon coating may be performed and mixed with conductive particles such as graphite. As a method for forming a carbon film on the surface of the substrate particles, a method performed by chemical vapor deposition (CVD) is suitable.
本発明においては、上記のように、工程Bにおいて、基材粒子の表面に炭素被膜を形成して被覆粒子とする。これは、上記基材粒子に導電性を付与し、電池特性の向上を図るためである。本発明では、基材粒子の表面に炭素被膜を形成することが必須であるが、この炭素被覆を行うとともに、黒鉛等の導電性のある粒子と混合してもよい。基材粒子の表面に炭素被膜を形成する方法としては、化学蒸着(CVD)により行う方法が好適である。 [Method of forming carbon film]
In the present invention, as described above, in Step B, a carbon film is formed on the surface of the base material particles to form coated particles. This is for imparting conductivity to the base particles and improving battery characteristics. In the present invention, it is essential to form a carbon film on the surface of the substrate particles, but this carbon coating may be performed and mixed with conductive particles such as graphite. As a method for forming a carbon film on the surface of the substrate particles, a method performed by chemical vapor deposition (CVD) is suitable.
化学蒸着(CVD)の方法としては、例えば、基材粒子に対して、熱分解して炭素を生成し得る有機物ガス雰囲気中で600~1200℃の温度範囲で炭素を化学蒸着することにより行う方法が挙げられる。
As a method of chemical vapor deposition (CVD), for example, a method of performing chemical vapor deposition of carbon in a temperature range of 600 to 1200 ° C. in an organic gas atmosphere that can be pyrolyzed to generate carbon with respect to base particles. Is mentioned.
この化学蒸着(CVD)は、常圧、減圧下共に適用可能であり、減圧下としては、50~30,000Paの減圧下が挙げられる。また、炭素被膜の形成工程に使用する装置は、バッチ式炉、ロータリーキルン及びローラーハースキルンといった連続炉、並びに流動層等の一般的に知られた装置が使用可能である。特に、攪拌を行いながら連続して蒸着を行うことができるロータリーキルンは、効率的に、炭素をより均一に被覆することができ、電池特性の向上を図ることができる。
This chemical vapor deposition (CVD) can be applied at both normal pressure and reduced pressure, and examples of reduced pressure include reduced pressure of 50 to 30,000 Pa. Moreover, generally known apparatuses, such as a batch furnace, a continuous kiln, such as a rotary kiln and a roller hearth kiln, and a fluidized bed, can be used for the apparatus used for the formation process of a carbon film. In particular, a rotary kiln capable of continuously performing vapor deposition while stirring can efficiently coat carbon more uniformly, and can improve battery characteristics.
化学蒸着による炭素被膜の形成には、下記のような様々な有機物がその炭素源として挙げられるが、熱分解温度や蒸着速度、また蒸着後に形成される炭素被膜の特性等は、用いる物質によって大きく異なる場合がある。炭素源は、目的とする被覆粒子の物性に従って適宜変更することができる。蒸着速度が小さい物質は、表面の炭素被膜の均一性を十分なものとしやすいため、好ましい。反面分解が低温で行われる物質であれば、蒸着時の基材粒子中の珪素結晶の成長が抑制されるため、放電効率やサイクル特性の低下を抑制することができる。
The formation of a carbon film by chemical vapor deposition includes the following various organic substances as the carbon source. The thermal decomposition temperature, vapor deposition rate, and the characteristics of the carbon film formed after vapor deposition largely depend on the substance used. May be different. The carbon source can be appropriately changed according to the physical properties of the target coated particles. A substance having a low vapor deposition rate is preferred because it tends to make the surface carbon film uniform enough. On the other hand, if the substance is decomposed at a low temperature, the growth of silicon crystals in the base material particles during vapor deposition is suppressed, so that it is possible to suppress a decrease in discharge efficiency and cycle characteristics.
熱分解して炭素を生成し得る有機物ガスの原料として、メタン、エタン、エチレン、アセチレン、プロパン、プロピレン、ブタン、ブテン、ペンタン、イソブタン、ヘキサン、ベンゼン、トルエン、キシレン、スチレン、エチルベンゼン、ジフェニルメタン、ナフタレン、フェノール、クレゾール、ニトロベンゼン、クロルベンゼン、インデン、クマロン、ピリジン、アントラセン、フェナントレン、タール蒸留工程で得られるガス軽油、クレオソート油、アントラセン油及びナフサ分解タール油等が挙げられる。これらは1種単独で又は2種以上を適宜選択して用いることができる。
As raw materials for organic gases that can generate carbon by pyrolysis, methane, ethane, ethylene, acetylene, propane, propylene, butane, butene, pentane, isobutane, hexane, benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, naphthalene Phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, anthracene, phenanthrene, gas light oil obtained in the tar distillation step, creosote oil, anthracene oil, and naphtha cracked tar oil. These can be used singly or in appropriate combination of two or more.
炭素被膜の被覆量については、被覆粒子の質量に対する、該被覆粒子に含有される炭素の質量の割合を、0.5質量%以上40質量%以下とすることが好ましい。この割合は、1.0~30質量%がより好ましい。被覆される粒子にもよるが、炭素被覆量を0.5質量%以上とすることで、概ね十分な導電性を維持することができ、非水電解質二次電池の負極とした際のサイクル性の向上を確実に達成することができる。また、炭素被覆量が40質量%以下であれば、炭素被覆による導電性付与の効果を得ることができるとともに、負極材料に占める炭素の割合が多くなることによる充放電容量の低下を抑制することができる。
Regarding the coating amount of the carbon coating, the ratio of the mass of carbon contained in the coating particles to the mass of the coating particles is preferably 0.5% by mass or more and 40% by mass or less. This ratio is more preferably 1.0 to 30% by mass. Although it depends on the particles to be coated, by setting the carbon coating amount to 0.5% by mass or more, it is possible to maintain substantially sufficient conductivity, and the cycle characteristics when used as a negative electrode of a nonaqueous electrolyte secondary battery. Can be reliably achieved. In addition, if the carbon coating amount is 40% by mass or less, the effect of imparting conductivity by the carbon coating can be obtained, and a decrease in charge / discharge capacity due to an increase in the proportion of carbon in the negative electrode material can be suppressed. Can do.
[負極材の粒径分布及び粒径範囲]
本発明の負極材は、上記のように、粒径の規定がa/b≧3の関係を満たすものである。炭素被覆が形成されていない状態の基材粒子の体積基準分布における粒径1μm以下の粒子(微粉)が、被覆によって炭素で凝集した2次粒子を形成する。負極材により負極を作製した際にこの2次粒子が大粒子の間隙を埋めて負極(電極)の電気抵抗の低減に寄与する。これによって充放電サイクルを繰り返したときの容量維持率の向上につながる。 [Particle size distribution and particle size range of anode material]
As described above, the negative electrode material of the present invention satisfies the relationship of a / b ≧ 3 in terms of particle size. Particles (fine powder) having a particle size of 1 μm or less in the volume-based distribution of the base material particles in a state where no carbon coating is formed form secondary particles aggregated with carbon by the coating. When the negative electrode is produced from the negative electrode material, the secondary particles fill the gaps of the large particles and contribute to the reduction of the electric resistance of the negative electrode (electrode). This leads to an improvement in capacity retention rate when the charge / discharge cycle is repeated.
本発明の負極材は、上記のように、粒径の規定がa/b≧3の関係を満たすものである。炭素被覆が形成されていない状態の基材粒子の体積基準分布における粒径1μm以下の粒子(微粉)が、被覆によって炭素で凝集した2次粒子を形成する。負極材により負極を作製した際にこの2次粒子が大粒子の間隙を埋めて負極(電極)の電気抵抗の低減に寄与する。これによって充放電サイクルを繰り返したときの容量維持率の向上につながる。 [Particle size distribution and particle size range of anode material]
As described above, the negative electrode material of the present invention satisfies the relationship of a / b ≧ 3 in terms of particle size. Particles (fine powder) having a particle size of 1 μm or less in the volume-based distribution of the base material particles in a state where no carbon coating is formed form secondary particles aggregated with carbon by the coating. When the negative electrode is produced from the negative electrode material, the secondary particles fill the gaps of the large particles and contribute to the reduction of the electric resistance of the negative electrode (electrode). This leads to an improvement in capacity retention rate when the charge / discharge cycle is repeated.
また、炭素被膜の形成は、被覆粒子のレーザー回折法粒度分布測定装置で測定した体積基準分布における累積50%径(D50)が、1μm以上30μm以下となるように行うことが好ましい。これにより、負極を作製するために負極材を塗布した際にセパレーターを傷付けることなく、また電極の導電性を良好なものとすることができる。
The carbon coating is preferably formed so that the 50% cumulative diameter (D 50 ) in the volume reference distribution measured with a laser diffraction particle size distribution measuring device of the coated particles is 1 μm or more and 30 μm or less. Thereby, when apply | coating a negative electrode material in order to produce a negative electrode, the electroconductivity of an electrode can be made favorable, without damaging a separator.
本発明において、基材粒子を特定の粒径分布及び粒径範囲とするためには、粉砕や分級等の処理等により適宜調整することができる。また、炭素被膜を形成した被覆粒子を特定の粒径分布及び粒径範囲とするためには、その被覆量等により適宜調整することができる。炭素被膜の被覆量は、基材粒子の物性の他、CVDに用いる炭素源ガスや熱処理温度、熱処理時間等の条件に依存する。被覆を行う際の条件と被覆量との関係は実験的に容易に求めることができる。
In the present invention, in order to make the base material particles have a specific particle size distribution and a particle size range, it can be appropriately adjusted by a treatment such as pulverization or classification. Moreover, in order to make the coated particles on which the carbon coating is formed have a specific particle size distribution and particle size range, it can be appropriately adjusted depending on the coating amount. The coating amount of the carbon coating depends on conditions such as the carbon source gas used for CVD, the heat treatment temperature, and the heat treatment time, in addition to the physical properties of the base particles. The relationship between the coating conditions and the coating amount can be easily determined experimentally.
粒子の粉砕には公知の装置を使用することができる。例えば以下に例示される装置を用いることができる。まず、ボール、ビーズ等の粉砕媒体を運動させ、その運動エネルギーによる衝撃力や摩擦力、圧縮力を利用して被砕物を粉砕するボールミル、媒体撹拌ミルが例示される。また、ローラによる圧縮力を利用して粉砕を行うローラミルが例示される。また、被砕物を高速で内張材に衝突もしくは粒子相互に衝突させ、その衝撃による衝撃力によって粉砕を行うジェットミルが例示される。また、ハンマー、ブレード、ピン等を固設したローターの回転による衝撃力を利用して被砕物を粉砕するハンマーミル、ピンミル、ディスクミルが例示される。また、剪断力を利用するコロイドミルが例示される。また、高圧湿式対向衝突式分散機「アルティマイザー」が例示される。粉砕は、湿式、乾式をともに用いることができる。
A known apparatus can be used for pulverizing the particles. For example, the apparatus illustrated below can be used. First, a ball mill and a medium agitation mill are exemplified in which a pulverizing medium such as a ball or a bead is moved and an object is pulverized using an impact force, a frictional force, or a compressive force. Moreover, the roller mill which grind | pulverizes using the compressive force by a roller is illustrated. In addition, a jet mill is exemplified in which the object to be crushed collides with the lining material at high speed or particles collide with each other, and pulverization is performed by the impact force of the impact. Further, examples include a hammer mill, a pin mill, and a disk mill that pulverize a material to be crushed by using an impact force generated by rotation of a rotor having a hammer, blade, pin, and the like fixed thereto. Moreover, the colloid mill using a shear force is illustrated. Further, a high-pressure wet-opposing collision type disperser “Ultimizer” is exemplified. For pulverization, both wet and dry processes can be used.
さらに、粉砕後に粒度分布を整えるため、乾式分級、湿式分級、及びふるい分け分級等を用いることができる。乾式分級は、主として気流を用い、分散、分離(細粒子と粗粒子の分離)、捕集(固体と気体の分離)、排出のプロセスが逐次又は同時に行われる。また、粒子相互間の干渉、粒子の形状、気流の流れの乱れ、速度分布、静電気の影響等で分級効率を低下させないよう、分級をする前に前処理(水分、分散性、湿度等の調整)を行ったり、使用される気流の水分や酸素濃度を調整して用いられる。また、サイクロン等の乾式で分級機が一体となっているタイプでは、一度に粉砕、分級が行われ、所望の粒度分布とすることが可能となる。
Furthermore, in order to adjust the particle size distribution after pulverization, dry classification, wet classification, sieving classification, or the like can be used. In the dry classification, an air stream is mainly used, and dispersion, separation (separation of fine particles and coarse particles), collection (separation of solid and gas), and discharge are sequentially or simultaneously performed. Also, pre-treatment (adjustment of moisture, dispersibility, humidity, etc.) before classification so as not to reduce classification efficiency due to interference between particles, particle shape, turbulence of air flow, velocity distribution, static electricity, etc. ) Or adjusting the moisture and oxygen concentration of the airflow used. In addition, in a dry type such as a cyclone in which a classifier is integrated, pulverization and classification are performed at a time, and a desired particle size distribution can be obtained.
本発明は、上記被覆粒子をリチウムイオン二次電池用負極材(活物質)に用いるものであり、本発明で得られたリチウムイオン二次電池用負極材を用いて、負極を作製し、リチウムイオン二次電池を製造することができる。
In the present invention, the above coated particles are used for a negative electrode material (active material) for a lithium ion secondary battery. Using the negative electrode material for a lithium ion secondary battery obtained in the present invention, a negative electrode is prepared, and lithium An ion secondary battery can be manufactured.
[負極]
上記リチウムイオン二次電池用負極材を用いて負極を作製する場合、さらにカーボンや黒鉛等の導電剤を添加することができる。この場合においても導電剤の種類は特に限定されず、構成された電池において、分解や変質を起こさない電子伝導性の材料であればよい。具体的にはAl,Ti,Fe,Ni,Cu,Zn,Ag,Sn,Si等の金属粒子や金属繊維又は天然黒鉛、人造黒鉛、各種のコークス粒子、メソフェーズ炭素、気相成長炭素繊維、ピッチ系炭素繊維、PAN系炭素繊維、各種の樹脂焼成体等の黒鉛を用いることができる。 [Negative electrode]
When producing a negative electrode using the said negative electrode material for lithium ion secondary batteries, conductive agents, such as carbon and graphite, can be added further. Also in this case, the kind of the conductive agent is not particularly limited, and any electronic conductive material that does not cause decomposition or alteration in the configured battery may be used. Specifically, metal particles such as Al, Ti, Fe, Ni, Cu, Zn, Ag, Sn, Si, metal fibers, natural graphite, artificial graphite, various coke particles, mesophase carbon, vapor grown carbon fiber, pitch Graphite such as carbon-based carbon fiber, PAN-based carbon fiber, and various resin fired bodies can be used.
上記リチウムイオン二次電池用負極材を用いて負極を作製する場合、さらにカーボンや黒鉛等の導電剤を添加することができる。この場合においても導電剤の種類は特に限定されず、構成された電池において、分解や変質を起こさない電子伝導性の材料であればよい。具体的にはAl,Ti,Fe,Ni,Cu,Zn,Ag,Sn,Si等の金属粒子や金属繊維又は天然黒鉛、人造黒鉛、各種のコークス粒子、メソフェーズ炭素、気相成長炭素繊維、ピッチ系炭素繊維、PAN系炭素繊維、各種の樹脂焼成体等の黒鉛を用いることができる。 [Negative electrode]
When producing a negative electrode using the said negative electrode material for lithium ion secondary batteries, conductive agents, such as carbon and graphite, can be added further. Also in this case, the kind of the conductive agent is not particularly limited, and any electronic conductive material that does not cause decomposition or alteration in the configured battery may be used. Specifically, metal particles such as Al, Ti, Fe, Ni, Cu, Zn, Ag, Sn, Si, metal fibers, natural graphite, artificial graphite, various coke particles, mesophase carbon, vapor grown carbon fiber, pitch Graphite such as carbon-based carbon fiber, PAN-based carbon fiber, and various resin fired bodies can be used.
負極(成型体)の調製方法としては、一例として下記のような方法が挙げられる。
Examples of the method for preparing the negative electrode (molded body) include the following methods.
まず、上述の負極材と、必要に応じて導電剤と、ポリイミド樹脂等の結着剤等の他の添加剤とに、N-メチルピロリドン又は水等の溶剤を混練してペースト状の合剤とする。この合剤を集電体のシートに塗布する。この場合、集電体としては、銅箔、ニッケル箔等、通常、負極の集電体として使用されている材料であれば、特に厚さ、表面処理の制限なく使用することができる。なお、合剤をシート状に成形する成形方法は特に限定されず、公知の方法を用いることができる。
First, a paste-like mixture prepared by kneading a solvent such as N-methylpyrrolidone or water with the above-described negative electrode material, a conductive agent as necessary, and other additives such as a binder such as a polyimide resin. And This mixture is applied to the sheet of the current collector. In this case, as the current collector, any material that is usually used as a negative electrode current collector, such as a copper foil or a nickel foil, can be used without any particular limitation on thickness and surface treatment. In addition, the shaping | molding method which shape | molds a mixture into a sheet form is not specifically limited, A well-known method can be used.
[リチウムイオン二次電池]
本発明のリチウムイオン二次電池は、上記のリチウムイオン二次電池用負極を用いたリチウムイオン二次電池である。負極の他は、少なくとも、正極と、リチウムイオン導電性の非水電解質とを有する。本発明のリチウムイオン二次電池は、上記被覆粒子からなる負極材を用いた負極からなる点に特徴を有し、その他の正極、電解質、セパレータ等の材料及び電池形状等は公知のものを使用することができ、特に限定されない。上述のように、本発明の負極材は、リチウムイオン二次電池用の負極材として用いた場合の電池特性(充放電容量及びサイクル特性)が良好で、特にサイクル耐久性に優れたものである。 [Lithium ion secondary battery]
The lithium ion secondary battery of this invention is a lithium ion secondary battery using said negative electrode for lithium ion secondary batteries. In addition to the negative electrode, at least a positive electrode and a lithium ion conductive nonaqueous electrolyte are included. The lithium ion secondary battery of the present invention is characterized in that it comprises a negative electrode using the negative electrode material composed of the above coated particles, and other positive electrode, electrolyte, separator, and other materials and battery shapes are used. There is no particular limitation. As described above, the negative electrode material of the present invention has good battery characteristics (charge / discharge capacity and cycle characteristics) when used as a negative electrode material for a lithium ion secondary battery, and is particularly excellent in cycle durability. .
本発明のリチウムイオン二次電池は、上記のリチウムイオン二次電池用負極を用いたリチウムイオン二次電池である。負極の他は、少なくとも、正極と、リチウムイオン導電性の非水電解質とを有する。本発明のリチウムイオン二次電池は、上記被覆粒子からなる負極材を用いた負極からなる点に特徴を有し、その他の正極、電解質、セパレータ等の材料及び電池形状等は公知のものを使用することができ、特に限定されない。上述のように、本発明の負極材は、リチウムイオン二次電池用の負極材として用いた場合の電池特性(充放電容量及びサイクル特性)が良好で、特にサイクル耐久性に優れたものである。 [Lithium ion secondary battery]
The lithium ion secondary battery of this invention is a lithium ion secondary battery using said negative electrode for lithium ion secondary batteries. In addition to the negative electrode, at least a positive electrode and a lithium ion conductive nonaqueous electrolyte are included. The lithium ion secondary battery of the present invention is characterized in that it comprises a negative electrode using the negative electrode material composed of the above coated particles, and other positive electrode, electrolyte, separator, and other materials and battery shapes are used. There is no particular limitation. As described above, the negative electrode material of the present invention has good battery characteristics (charge / discharge capacity and cycle characteristics) when used as a negative electrode material for a lithium ion secondary battery, and is particularly excellent in cycle durability. .
正極活物質としてはLiCoO2、LiNiO2、LiMn2O4、V2O5、MnO2、TiS2、MoS2等の遷移金属の酸化物、リチウム及びカルコゲン化合物等の公知のものを用いることができる。
As the positive electrode active material, a known material such as an oxide of a transition metal such as LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , V 2 O 5 , MnO 2 , TiS 2 , MoS 2 , lithium, or a chalcogen compound may be used. it can.
電解質としては、例えば、六フッ化リン酸リチウム、過塩素酸リチウム等のリチウム塩を含む非水溶液が用いられる。非水溶媒としてはプロピレンカーボネート、エチレンカーボネート、ジエチルカーボネート、ジメトキシエタン、γ-ブチロラクトン、2-メチルテトラヒドロフラン等の1種又は2種以上を組み合わせて用いられる。また、それ以外の種々の非水系電解質や固体電解質も使用することができる。
As the electrolyte, for example, a non-aqueous solution containing a lithium salt such as lithium hexafluorophosphate and lithium perchlorate is used. As the non-aqueous solvent, one or a combination of two or more of propylene carbonate, ethylene carbonate, diethyl carbonate, dimethoxyethane, γ-butyrolactone, 2-methyltetrahydrofuran and the like are used. Various other non-aqueous electrolytes and solid electrolytes can also be used.
以下、実施例及び比較例を示して本発明をより具体的に説明するが、本発明は下記の実施例に制限されるものではない。
Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the following examples.
[実施例1]
ジョークラッシャ―(前川工業所製)で粗砕したSiOx(x=1.0)を直径10mmのアルミナボールを媒体としてボールミル(マキノ製)で80分間粉砕した。この粒子を基材粒子とした(工程A)。この基材粒子をレーザー回折法粒度分布測定装置(島津製作所SALD-3100)で屈折率3.90-0.01iの条件で測定したところ、体積基準分布におけるD50(累積50%径)は4.6μm、累積1μm(粒径1μm以下の粒子の割合)は14.8%(すなわち、a=14.8)であった。基材粒子の粒度分布チャートを図1に示した。 [Example 1]
SiOx (x = 1.0) coarsely crushed by a jaw crusher (Maekawa Kogyo) was pulverized for 80 minutes by a ball mill (Makino) using alumina balls having a diameter of 10 mm as a medium. These particles were used as substrate particles (Step A). When this base material particle was measured with a laser diffraction particle size distribution analyzer (SALD-3100, Shimadzu Corporation) under the condition of a refractive index of 3.90-0.01i, D 50 (cumulative 50% diameter) in the volume-based distribution was 4. 0.6 μm and cumulative 1 μm (ratio of particles having a particle diameter of 1 μm or less) were 14.8% (that is, a = 14.8). A particle size distribution chart of the base particles is shown in FIG.
ジョークラッシャ―(前川工業所製)で粗砕したSiOx(x=1.0)を直径10mmのアルミナボールを媒体としてボールミル(マキノ製)で80分間粉砕した。この粒子を基材粒子とした(工程A)。この基材粒子をレーザー回折法粒度分布測定装置(島津製作所SALD-3100)で屈折率3.90-0.01iの条件で測定したところ、体積基準分布におけるD50(累積50%径)は4.6μm、累積1μm(粒径1μm以下の粒子の割合)は14.8%(すなわち、a=14.8)であった。基材粒子の粒度分布チャートを図1に示した。 [Example 1]
SiOx (x = 1.0) coarsely crushed by a jaw crusher (Maekawa Kogyo) was pulverized for 80 minutes by a ball mill (Makino) using alumina balls having a diameter of 10 mm as a medium. These particles were used as substrate particles (Step A). When this base material particle was measured with a laser diffraction particle size distribution analyzer (SALD-3100, Shimadzu Corporation) under the condition of a refractive index of 3.90-0.01i, D 50 (cumulative 50% diameter) in the volume-based distribution was 4. 0.6 μm and cumulative 1 μm (ratio of particles having a particle diameter of 1 μm or less) were 14.8% (that is, a = 14.8). A particle size distribution chart of the base particles is shown in FIG.
この基材粒子100gを粉体層厚みが10mmとなるようトレイに敷き、バッチ式加熱炉内に仕込んだ。そして油回転式真空ポンプで炉内を減圧しつつ、200℃/hrの昇温速度で炉内を1,000℃に昇温した。そして1,000℃に達した後、炉内にメタンを0.3L/minで通気し、10時間の炭素被覆処理を行った(工程B)。メタン停止後、炉内を降温・冷却し、106gの黒色粒子を得た。
The 100 g of the base particles were laid on a tray so that the thickness of the powder layer was 10 mm, and charged into a batch type heating furnace. Then, the pressure in the furnace was increased to 1,000 ° C. at a temperature increase rate of 200 ° C./hr while the pressure in the furnace was reduced by an oil rotary vacuum pump. After reaching 1,000 ° C., methane was passed through the furnace at 0.3 L / min, and carbon coating treatment was performed for 10 hours (step B). After stopping methane, the temperature in the furnace was lowered and cooled to obtain 106 g of black particles.
得られた黒色粒子は、黒色粒子に対する炭素被覆量4.8質量%の導電性粒子であった。またこの粒子の粒度分布を上記と同様に測定したところ、体積基準分布におけるD50は5.3μm、累積1μm(粒径1μm以下の粒子の割合)は2.6%(すなわち、b=2.6)であった。この被覆粒子の粒度分布チャートを図2に示した。
The obtained black particles were conductive particles having a carbon coating amount of 4.8% by mass with respect to the black particles. Further, the particle size distribution of the particles were measured in the same manner as described above, D 50 in the volume-based distribution 5.3 .mu.m, (the ratio of the particle size 1μm or less of the particles) Cumulative 1μm is 2.6% (i.e., b = 2. 6). A particle size distribution chart of the coated particles is shown in FIG.
<電池評価>
次に、以下の方法で、得られた被覆粒子を負極活物質として用いた電池評価を行った。まず、得られた負極材45質量%と人造黒鉛(平均粒子径10μm)45質量%、ポリイミド10質量%を混合し、さらにN-メチルピロリドンを加えてスラリーとした。このスラリーを厚さ12μmの銅箔に塗布し、80℃で1時間乾燥後、ローラープレスにより電極を加圧成形し、この電極を350℃で1時間真空乾燥させた。その後、2cm2に打ち抜き、負極とした。 <Battery evaluation>
Next, battery evaluation using the obtained coated particles as a negative electrode active material was performed by the following method. First, 45% by mass of the obtained negative electrode material, 45% by mass of artificial graphite (average particle size 10 μm) and 10% by mass of polyimide were mixed, and N-methylpyrrolidone was further added to form a slurry. This slurry was applied to a copper foil having a thickness of 12 μm, dried at 80 ° C. for 1 hour, then subjected to pressure molding by a roller press, and the electrode was vacuum-dried at 350 ° C. for 1 hour. Then, it punched out to 2 cm < 2 > and set it as the negative electrode.
次に、以下の方法で、得られた被覆粒子を負極活物質として用いた電池評価を行った。まず、得られた負極材45質量%と人造黒鉛(平均粒子径10μm)45質量%、ポリイミド10質量%を混合し、さらにN-メチルピロリドンを加えてスラリーとした。このスラリーを厚さ12μmの銅箔に塗布し、80℃で1時間乾燥後、ローラープレスにより電極を加圧成形し、この電極を350℃で1時間真空乾燥させた。その後、2cm2に打ち抜き、負極とした。 <Battery evaluation>
Next, battery evaluation using the obtained coated particles as a negative electrode active material was performed by the following method. First, 45% by mass of the obtained negative electrode material, 45% by mass of artificial graphite (
そして、得られた負極の充放電特性を評価するために、対極にリチウム箔を使用し、非水電解質として六フッ化リン酸リチウムをエチレンカーボネートとジエチルカーボネートの1/1(体積比)混合液に1モル/Lの濃度で溶解した非水電解質溶液を用い、セパレータに厚さ30μmのポリエチレン製微多孔質フィルムを用いた評価用リチウムイオン二次電池を作製した。
In order to evaluate the charge / discharge characteristics of the obtained negative electrode, a lithium foil was used for the counter electrode, and lithium hexafluorophosphate was mixed with ethylene carbonate and diethyl carbonate in a 1/1 (volume ratio) mixture as a non-aqueous electrolyte. A lithium ion secondary battery for evaluation using a non-aqueous electrolyte solution dissolved at a concentration of 1 mol / L and a polyethylene microporous film having a thickness of 30 μm as a separator was prepared.
作製したリチウムイオン二次電池を、一晩室温で放置した後、二次電池充放電試験装置((株)ナガノ製)を用いて、テストセルの電圧が0Vに達するまで0.5mA/cm2の定電流で充電を行い、0Vに達した後は、セル電圧を0Vに保つように電流を減少させて充電を行った。そして、電流値が40μA/cm2を下回った時点で充電を終了させた。そして放電は0.5mA/cm2の定電流で行い、セル電圧が1.4Vに達した時点で放電を終了して、放電容量を求めた。
The prepared lithium ion secondary battery is allowed to stand at room temperature overnight, and then charged with a secondary battery charge / discharge tester (manufactured by Nagano Co., Ltd.) until the voltage of the test cell reaches 0 V / 0.5 mA / cm 2. After reaching 0V, the battery was charged by decreasing the current so as to keep the cell voltage at 0V. The charging was terminated when the current value fell below 40 μA / cm 2 . The discharge was performed at a constant current of 0.5 mA / cm 2 , and the discharge was terminated when the cell voltage reached 1.4 V, and the discharge capacity was determined.
以上の充放電試験を繰り返し、評価用リチウムイオン二次電池の50サイクル後の充放電試験を行った。結果を表1に示す。初回放電容量1781mAh/g、50サイクル後のサイクル保持率94%の高容量かつ及びサイクル性に優れたリチウムイオン二次電池であることが確認された。
The above charge / discharge test was repeated, and a charge / discharge test after 50 cycles of the evaluation lithium ion secondary battery was performed. The results are shown in Table 1. It was confirmed that the lithium-ion secondary battery had a high capacity with an initial discharge capacity of 1781 mAh / g, a cycle retention rate of 94% after 50 cycles, and excellent cycle performance.
[実施例2]
実施例1と同じSiOx(x=1.0)粉砕品(基材粒子)を100g、実施例1と同様にバッチ式加熱炉内に仕込んだ。そして油回転式真空ポンプで炉内を減圧しつつ、200℃/hrの昇温速度で炉内を1,100℃に昇温した。そして1,100℃に達した後、炉内にメタンを0.3L/minで通気し、16時間の炭素被覆処理を行った。メタン停止後、炉内を降温・冷却した。 [Example 2]
The same SiOx (x = 1.0) pulverized product (base particle) as in Example 1 was charged in a batch heating furnace in the same manner as in Example 1. Then, the pressure in the furnace was increased to 1,100 ° C. at a temperature increase rate of 200 ° C./hr while the pressure in the furnace was reduced by an oil rotary vacuum pump. After reaching 1,100 ° C., methane was passed through the furnace at 0.3 L / min, and carbon coating treatment was performed for 16 hours. After stopping methane, the temperature in the furnace was lowered and cooled.
実施例1と同じSiOx(x=1.0)粉砕品(基材粒子)を100g、実施例1と同様にバッチ式加熱炉内に仕込んだ。そして油回転式真空ポンプで炉内を減圧しつつ、200℃/hrの昇温速度で炉内を1,100℃に昇温した。そして1,100℃に達した後、炉内にメタンを0.3L/minで通気し、16時間の炭素被覆処理を行った。メタン停止後、炉内を降温・冷却した。 [Example 2]
The same SiOx (x = 1.0) pulverized product (base particle) as in Example 1 was charged in a batch heating furnace in the same manner as in Example 1. Then, the pressure in the furnace was increased to 1,100 ° C. at a temperature increase rate of 200 ° C./hr while the pressure in the furnace was reduced by an oil rotary vacuum pump. After reaching 1,100 ° C., methane was passed through the furnace at 0.3 L / min, and carbon coating treatment was performed for 16 hours. After stopping methane, the temperature in the furnace was lowered and cooled.
得られた黒色粒子は黒色粒子に対する炭素被覆量21.3質量%の導電性粒子であった。この粒子の粒度分布はD50が5.8μm、累積1μm(粒径1μm以下の粒子の割合)は0.3%(すなわち、b=0.3)であった。この被覆粒子の粒度分布チャートを図3に示した。
The obtained black particles were conductive particles having a carbon coating amount of 21.3% by mass with respect to the black particles. As for the particle size distribution of these particles, D 50 was 5.8 μm, and the cumulative 1 μm (ratio of particles having a particle size of 1 μm or less) was 0.3% (that is, b = 0.3). A particle size distribution chart of the coated particles is shown in FIG.
[実施例3]
実施例1と同じSiOx(x=1.0)粉砕品(基材粒子)を、1°に傾斜させてキルン内部を1000℃に昇温させたロータリーキルンに入口側から2kg/hrで供給し、出口側から16体積%に窒素で希釈したメタンを通気した。キルンの回転数は1rpmとした。投入開始から6時間後、出口側から被覆量3.5質量%の導電性粒子を得た。この粒子の粒度分布はD50が5.2μm、累積1μm(粒径1μm以下の粒子の割合)は3.7%(すなわち、b=3.7)であった。この被覆粒子の粒度分布チャートを図4に示した。 [Example 3]
The same SiOx (x = 1.0) pulverized product (base particles) as in Example 1 was supplied at a rate of 2 kg / hr from the inlet side to a rotary kiln in which the inside of the kiln was heated to 1000 ° C. by inclining to 1 °. Methane diluted with nitrogen was vented to 16% by volume from the outlet side. The rotation speed of the kiln was 1 rpm. Six hours after the start of charging, conductive particles having a coating amount of 3.5% by mass were obtained from the outlet side. The particle size distribution of the particles D 50 is 5.2 .mu.m, (the ratio of the particle size 1μm or less of the particles) accumulated 1μm was 3.7% (i.e., b = 3.7). A particle size distribution chart of the coated particles is shown in FIG.
実施例1と同じSiOx(x=1.0)粉砕品(基材粒子)を、1°に傾斜させてキルン内部を1000℃に昇温させたロータリーキルンに入口側から2kg/hrで供給し、出口側から16体積%に窒素で希釈したメタンを通気した。キルンの回転数は1rpmとした。投入開始から6時間後、出口側から被覆量3.5質量%の導電性粒子を得た。この粒子の粒度分布はD50が5.2μm、累積1μm(粒径1μm以下の粒子の割合)は3.7%(すなわち、b=3.7)であった。この被覆粒子の粒度分布チャートを図4に示した。 [Example 3]
The same SiOx (x = 1.0) pulverized product (base particles) as in Example 1 was supplied at a rate of 2 kg / hr from the inlet side to a rotary kiln in which the inside of the kiln was heated to 1000 ° C. by inclining to 1 °. Methane diluted with nitrogen was vented to 16% by volume from the outlet side. The rotation speed of the kiln was 1 rpm. Six hours after the start of charging, conductive particles having a coating amount of 3.5% by mass were obtained from the outlet side. The particle size distribution of the particles D 50 is 5.2 .mu.m, (the ratio of the particle size 1μm or less of the particles) accumulated 1μm was 3.7% (i.e., b = 3.7). A particle size distribution chart of the coated particles is shown in FIG.
[実施例4]
実施例1と同じSiOx(x=1.0)粉砕品(基材粒子)を、1°に傾斜させてキルン内部を1000℃に昇温させたロータリーキルンに入口側から2.8kg/hrで供給し、出口側から16体積%に窒素で希釈したメタンを通気した。キルンの回転数は1rpmとした。投入開始から6時間後、出口側から被覆量2.6質量%の導電性粒子を得た。この粒子の粒度分布はD50が4.4μm、累積1μm(粒径1μm以下の粒子の割合)は4.9%(すなわち、b=4.9)であった。この被覆粒子の粒度分布チャートを図5に示した。 [Example 4]
The same SiOx (x = 1.0) pulverized product (base particles) as in Example 1 was supplied at 2.8 kg / hr from the inlet side to a rotary kiln that was inclined at 1 ° and the temperature inside the kiln was raised to 1000 ° C. Then, methane diluted with nitrogen to 16% by volume was vented from the outlet side. The rotation speed of the kiln was 1 rpm. Six hours after the start of charging, conductive particles having a coating amount of 2.6% by mass were obtained from the outlet side. The particle size distribution of the particles D 50 of 4.4 [mu] m, (the proportion of the particle size 1μm or less of the particles) accumulated 1μm was 4.9% (i.e., b = 4.9). A particle size distribution chart of the coated particles is shown in FIG.
実施例1と同じSiOx(x=1.0)粉砕品(基材粒子)を、1°に傾斜させてキルン内部を1000℃に昇温させたロータリーキルンに入口側から2.8kg/hrで供給し、出口側から16体積%に窒素で希釈したメタンを通気した。キルンの回転数は1rpmとした。投入開始から6時間後、出口側から被覆量2.6質量%の導電性粒子を得た。この粒子の粒度分布はD50が4.4μm、累積1μm(粒径1μm以下の粒子の割合)は4.9%(すなわち、b=4.9)であった。この被覆粒子の粒度分布チャートを図5に示した。 [Example 4]
The same SiOx (x = 1.0) pulverized product (base particles) as in Example 1 was supplied at 2.8 kg / hr from the inlet side to a rotary kiln that was inclined at 1 ° and the temperature inside the kiln was raised to 1000 ° C. Then, methane diluted with nitrogen to 16% by volume was vented from the outlet side. The rotation speed of the kiln was 1 rpm. Six hours after the start of charging, conductive particles having a coating amount of 2.6% by mass were obtained from the outlet side. The particle size distribution of the particles D 50 of 4.4 [mu] m, (the proportion of the particle size 1μm or less of the particles) accumulated 1μm was 4.9% (i.e., b = 4.9). A particle size distribution chart of the coated particles is shown in FIG.
[比較例1]
実施例1と同じSiOx(x=1.0)粉砕品(基材粒子)を100g、同様にバッチ式加熱炉内に仕込んだ。そして油回転式真空ポンプで炉内を減圧しつつ、200℃/hrの昇温速度で炉内を1,000℃に昇温した。そして1,000℃に達した後、炉内にメタンを0.1L/minで通気し、2時間の炭素被覆処理を行った。メタン停止後、炉内を降温・冷却し、127gの黒色粒子を得た。 [Comparative Example 1]
100 g of the same SiOx (x = 1.0) pulverized product (substrate particles) as in Example 1 was charged into a batch-type heating furnace. Then, the pressure in the furnace was increased to 1,000 ° C. at a temperature increase rate of 200 ° C./hr while the pressure in the furnace was reduced by an oil rotary vacuum pump. After reaching 1,000 ° C., methane was passed through the furnace at a rate of 0.1 L / min, and a carbon coating treatment was performed for 2 hours. After the methane was stopped, the temperature in the furnace was lowered and cooled to obtain 127 g of black particles.
実施例1と同じSiOx(x=1.0)粉砕品(基材粒子)を100g、同様にバッチ式加熱炉内に仕込んだ。そして油回転式真空ポンプで炉内を減圧しつつ、200℃/hrの昇温速度で炉内を1,000℃に昇温した。そして1,000℃に達した後、炉内にメタンを0.1L/minで通気し、2時間の炭素被覆処理を行った。メタン停止後、炉内を降温・冷却し、127gの黒色粒子を得た。 [Comparative Example 1]
100 g of the same SiOx (x = 1.0) pulverized product (substrate particles) as in Example 1 was charged into a batch-type heating furnace. Then, the pressure in the furnace was increased to 1,000 ° C. at a temperature increase rate of 200 ° C./hr while the pressure in the furnace was reduced by an oil rotary vacuum pump. After reaching 1,000 ° C., methane was passed through the furnace at a rate of 0.1 L / min, and a carbon coating treatment was performed for 2 hours. After the methane was stopped, the temperature in the furnace was lowered and cooled to obtain 127 g of black particles.
得られた黒色粒子は黒色粒子に対する炭素被覆量0.3質量%の導電性粒子であった。この粒子の粒度分布はD50が4.8μm、累積1μm(粒径1μm以下の粒子の割合)は11.4%(すなわち、b=11.4)であった。この被覆粒子の粒度分布チャートを図6に示した。
The obtained black particles were conductive particles having a carbon coating amount of 0.3% by mass with respect to the black particles. The particle size distribution of the particles D 50 is 4.8 .mu.m, (the ratio of the particle size 1μm or less of the particles) accumulated 1μm was 11.4% (i.e., b = 11.4). A particle size distribution chart of the coated particles is shown in FIG.
[比較例2]
実施例1と同じSiOx(x=1.0)粉砕品を、気流式分級機(日清エンジニアリング(株)製TC-15)で風量2.5Nm3/min、ローター回転数10,000rpmの条件で分級した。分級機下で回収した粗粉側の粒子のD50は6.1μmで、累積1μm(粒径1μm以下の粒子の割合)は1.0%(すなわち、a=1.0)であった。この粉末を、比較例2における基材粒子(炭素被覆を行う対象の粒子)とした。この基材粒子の粒度分布チャートを図7に示した。この基材粒子に対し、実施例1と同様に炭素被覆処理を行った。得られた粒子は炭素被覆量4.2質量%、D50が6.2μm、累積1μm(粒径1μm以下の粒子の割合)は0.7%(すなわち、b=0.7)であった。この被覆粒子の粒度分布チャートを図8に示した。 [Comparative Example 2]
The same SiOx (x = 1.0) pulverized product as in Example 1 was subjected to conditions of an airflow classifier (TC-15 manufactured by Nisshin Engineering Co., Ltd.) with an air volume of 2.5 Nm 3 / min and a rotor rotational speed of 10,000 rpm. Classification with. The D 50 of the coarse particles recovered under the classifier was 6.1 μm, and the cumulative 1 μm (ratio of particles having a particle size of 1 μm or less) was 1.0% (that is, a = 1.0). This powder was used as base material particles (particles to be subjected to carbon coating) in Comparative Example 2. A particle size distribution chart of the substrate particles is shown in FIG. The base particles were subjected to a carbon coating treatment in the same manner as in Example 1. The resulting particles a carbon coating amount 4.2 wt%, D 50 is 6.2 .mu.m, (the ratio of the particle size 1μm or less of the particles) accumulated 1μm was 0.7% (i.e., b = 0.7) . A particle size distribution chart of the coated particles is shown in FIG.
実施例1と同じSiOx(x=1.0)粉砕品を、気流式分級機(日清エンジニアリング(株)製TC-15)で風量2.5Nm3/min、ローター回転数10,000rpmの条件で分級した。分級機下で回収した粗粉側の粒子のD50は6.1μmで、累積1μm(粒径1μm以下の粒子の割合)は1.0%(すなわち、a=1.0)であった。この粉末を、比較例2における基材粒子(炭素被覆を行う対象の粒子)とした。この基材粒子の粒度分布チャートを図7に示した。この基材粒子に対し、実施例1と同様に炭素被覆処理を行った。得られた粒子は炭素被覆量4.2質量%、D50が6.2μm、累積1μm(粒径1μm以下の粒子の割合)は0.7%(すなわち、b=0.7)であった。この被覆粒子の粒度分布チャートを図8に示した。 [Comparative Example 2]
The same SiOx (x = 1.0) pulverized product as in Example 1 was subjected to conditions of an airflow classifier (TC-15 manufactured by Nisshin Engineering Co., Ltd.) with an air volume of 2.5 Nm 3 / min and a rotor rotational speed of 10,000 rpm. Classification with. The D 50 of the coarse particles recovered under the classifier was 6.1 μm, and the cumulative 1 μm (ratio of particles having a particle size of 1 μm or less) was 1.0% (that is, a = 1.0). This powder was used as base material particles (particles to be subjected to carbon coating) in Comparative Example 2. A particle size distribution chart of the substrate particles is shown in FIG. The base particles were subjected to a carbon coating treatment in the same manner as in Example 1. The resulting particles a carbon coating amount 4.2 wt%, D 50 is 6.2 .mu.m, (the ratio of the particle size 1μm or less of the particles) accumulated 1μm was 0.7% (i.e., b = 0.7) . A particle size distribution chart of the coated particles is shown in FIG.
実施例2~4、比較例1、2で得られた粒子について、実施例1と同様に電池評価を行った。
For the particles obtained in Examples 2 to 4 and Comparative Examples 1 and 2, battery evaluation was performed in the same manner as in Example 1.
実施例1~4、比較例1、2の粒度及び電池特性の一覧表を表1に示す。
Table 1 shows a list of the particle sizes and battery characteristics of Examples 1 to 4 and Comparative Examples 1 and 2.
実施例1~4の負極材は、比較例1、2の負極材に比べて明らかに電池特性に優れたリチウムイオン二次電池であることが確認された。
It was confirmed that the negative electrode materials of Examples 1 to 4 were lithium ion secondary batteries that were clearly superior in battery characteristics as compared with the negative electrode materials of Comparative Examples 1 and 2.
なお、本発明は、上記実施形態に限定されるものではない。上記実施形態は例示であり、本発明の特許請求の範囲に記載された技術的思想と実質的に同一な構成を有し、同様な作用効果を奏するものは、いかなるものであっても本発明の技術的範囲に包含される。
Note that the present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.
Claims (12)
- 珪素原子を含む材料から成り、リチウムイオンを吸蔵及び放出することが可能な基材粒子を準備する工程と、
前記基材粒子の表面に炭素被膜を形成して被覆粒子とする工程と
を備えるリチウムイオン二次電池用負極材の製造方法において、
前記炭素被膜が形成されていない状態で前記基材粒子に対してレーザー回折法粒度分布測定装置で測定した体積基準分布における粒径1μm以下の粒子の割合をa%とし、前記被覆粒子に対してレーザー回折法粒度分布測定装置で測定した体積基準分布における粒径1μm以下の粒子の割合をb%としたときに、a/b≧3となるように、前記炭素被膜を形成する工程を行うことを特徴とするリチウムイオン二次電池用負極材の製造方法。 Preparing base particles made of a material containing silicon atoms and capable of inserting and extracting lithium ions;
In the method for producing a negative electrode material for a lithium ion secondary battery, comprising a step of forming a carbon film on the surface of the base particle to form a coated particle,
The ratio of particles having a particle size of 1 μm or less in the volume reference distribution measured with a laser diffraction particle size distribution measuring device with respect to the substrate particles in a state where the carbon coating is not formed is a%, Performing the step of forming the carbon film so that a / b ≧ 3 when the ratio of particles having a particle size of 1 μm or less in the volume reference distribution measured by a laser diffraction particle size distribution analyzer is b%. A method for producing a negative electrode material for a lithium ion secondary battery. - 前記基材粒子を準備する工程において、前記基材粒子として、前記a%が0.1%以上30%以下のものを準備することを特徴とする請求項1に記載のリチウムイオン二次電池用負極材の製造方法。 2. The lithium ion secondary battery according to claim 1, wherein in the step of preparing the base particle, the base particle is prepared such that the a% is 0.1% or more and 30% or less. Manufacturing method of negative electrode material.
- 前記基材粒子を準備する工程において、前記基材粒子として、珪素粒子、珪素の微粒子が珪素系化合物に分散した複合構造を有する粒子、一般式SiOx(0.5≦x≦1.6)で表される酸化珪素粒子、又はこれらの混合物であるものを準備することを特徴とする請求項1又は請求項2に記載のリチウムイオン二次電池用負極材の製造方法。 In the step of preparing the base particles, the base particles are silicon particles, particles having a composite structure in which silicon fine particles are dispersed in a silicon-based compound, and a general formula SiOx (0.5 ≦ x ≦ 1.6). 3. The method for producing a negative electrode material for a lithium ion secondary battery according to claim 1, wherein the silicon oxide particles are expressed or a mixture thereof.
- 前記被覆粒子の質量に対する、該被覆粒子に含有される炭素の質量の割合を、0.5質量%以上40質量%以下とすることを特徴とする請求項1から請求項3のいずれか1項に記載のリチウムイオン二次電池用負極材の製造方法。 The ratio of the mass of carbon contained in the coated particles to the mass of the coated particles is 0.5% by mass or more and 40% by mass or less. The manufacturing method of the negative electrode material for lithium ion secondary batteries as described in any one of.
- 前記基材粒子を準備する工程において、前記基材粒子として、前記基材粒子のレーザー回折法粒度分布測定装置で測定した体積基準分布における累積50%径(D50)が、0.1μm以上30μm以下であるものを準備することを特徴とする請求項1から請求項4のいずれか1項に記載のリチウムイオン二次電池用負極材の製造方法。 In the step of preparing the base material particles, the base material particles have a cumulative 50% diameter (D 50 ) in a volume reference distribution measured by a laser diffraction particle size distribution measuring device of the base material particles of 0.1 μm or more and 30 μm. The following is prepared, The manufacturing method of the negative electrode material for lithium ion secondary batteries of any one of Claims 1-4 characterized by the above-mentioned.
- 前記炭素被膜の形成を行う工程を、前記被覆粒子のレーザー回折法粒度分布測定装置で測定した体積基準分布における累積50%径(D50)が、1μm以上30μm以下となるように行うことを特徴とする請求項1から請求項5のいずれか1項に記載のリチウムイオン二次電池用負極材の製造方法。 The step of forming the carbon coating is performed such that a cumulative 50% diameter (D 50 ) in a volume reference distribution measured with a laser diffraction particle size distribution measuring device of the coated particles is 1 μm or more and 30 μm or less. The method for producing a negative electrode material for a lithium ion secondary battery according to any one of claims 1 to 5.
- 前記炭素被膜の形成を行う工程を、前記基材粒子に対して、熱分解して炭素を生成し得る有機物ガス雰囲気中で600~1200℃の温度範囲で炭素を化学蒸着することにより行うことを特徴とする請求項1から請求項6のいずれか1項に記載のリチウムイオン二次電池用負極材の製造方法。 The step of forming the carbon coating is performed by chemical vapor deposition of carbon on the base particles in an organic gas atmosphere capable of generating carbon by thermal decomposition in a temperature range of 600 to 1200 ° C. The manufacturing method of the negative electrode material for lithium ion secondary batteries of any one of Claims 1-6 characterized by the above-mentioned.
- 前記熱分解して炭素を生成し得る有機物ガスの原料として、メタン、エタン、エチレン、アセチレン、プロパン、プロピレン、ブタン、ブテン、ペンタン、イソブタン、ヘキサン、ベンゼン、トルエン、キシレン、スチレン、エチルベンゼン、ジフェニルメタン、ナフタレン、フェノール、クレゾール、ニトロベンゼン、クロルベンゼン、インデン、クマロン、ピリジン、アントラセン、フェナントレン、タール蒸留工程で得られるガス軽油、クレオソート油、アントラセン油及びナフサ分解タール油の中から選択される1種以上を用いることを特徴とする請求項7に記載のリチウムイオン二次電池用負極材の製造方法。 As a raw material of organic gas capable of generating carbon by pyrolysis, methane, ethane, ethylene, acetylene, propane, propylene, butane, butene, pentane, isobutane, hexane, benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, One or more selected from naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, anthracene, phenanthrene, gas light oil obtained in the tar distillation process, creosote oil, anthracene oil and naphtha cracked tar oil The method for producing a negative electrode material for a lithium ion secondary battery according to claim 7, wherein:
- 請求項1から請求項8のいずれか1項に記載のリチウムイオン二次電池用負極材の製造方法により製造されたことを特徴とするリチウムイオン二次電池用負極材。 A negative electrode material for a lithium ion secondary battery manufactured by the method for manufacturing a negative electrode material for a lithium ion secondary battery according to any one of claims 1 to 8.
- 珪素原子を含む材料から成り、リチウムイオンを吸蔵及び放出することが可能な基材粒子と、
該基材粒子の表面に形成された炭素被膜と
から成る被覆粒子であるリチウムイオン二次電池用負極材であって、
前記炭素被膜が形成されていない状態で前記基材粒子に対してレーザー回折法粒度分布測定装置で測定した体積基準分布における粒径1μm以下の粒子の割合をa%とし、
前記被覆粒子に対してレーザー回折法粒度分布測定装置で測定した体積基準分布における粒径1μm以下の粒子の割合をb%としたときに、
a/b≧3となるものであることを特徴とするリチウムイオン二次電池用負極材。 Base material particles made of a material containing silicon atoms and capable of occluding and releasing lithium ions;
A negative electrode material for a lithium ion secondary battery, which is a coated particle comprising a carbon coating formed on the surface of the substrate particle,
The ratio of particles having a particle size of 1 μm or less in a volume reference distribution measured with a laser diffraction particle size distribution measuring device with respect to the base material particles in a state where the carbon film is not formed is a%,
When the ratio of particles having a particle diameter of 1 μm or less in the volume reference distribution measured with a laser diffraction particle size distribution measuring device to the coated particles is b%,
A negative electrode material for a lithium ion secondary battery, wherein a / b ≧ 3. - 請求項9又は請求項10に記載のリチウムイオン二次電池用負極材を用いたことを特徴とするリチウムイオン二次電池用負極。 A negative electrode for a lithium ion secondary battery using the negative electrode material for a lithium ion secondary battery according to claim 9 or 10.
- 請求項11に記載のリチウムイオン二次電池用負極を用いたことを特徴とするリチウムイオン二次電池。 A lithium ion secondary battery using the negative electrode for a lithium ion secondary battery according to claim 11.
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JP2013191529A (en) * | 2012-02-16 | 2013-09-26 | Hitachi Chemical Co Ltd | Composite material, method for manufacturing composite material, electrode material for lithium ion secondary battery, negative electrode for lithium ion secondary battery, and lithium ion secondary battery |
JP2014519135A (en) * | 2012-05-02 | 2014-08-07 | 昭和電工株式会社 | Negative electrode material for lithium ion battery and its use |
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