JP5759307B2 - Carbon particle for electrode, negative electrode material for lithium ion secondary battery, and method for producing carbon particle for electrode - Google Patents

Description

The present invention provides a carbon particle for an electrode having a high lithium storage / release capacity and capable of producing a long-life negative electrode material for a lithium ion secondary battery with little decrease in lithium storage / release capacity even after continuous charge / discharge, and The present invention also relates to a negative electrode material for a lithium ion secondary battery using the carbon particles for an electrode. Moreover, it is related with the manufacturing method of this carbon particle for electrodes.

Carbon materials made of carbonaceous fired bodies are used for electrode materials such as lithium ion secondary batteries, electric double layer capacitors, and capacitors.
For example, in a lithium ion secondary battery, a carbon material is used as a negative electrode active material, lithium is occluded (intercalated) into the carbon material in an ionic state when the battery is charged, and released as ions (deintercalation) during discharge. It uses a “rocking chair type” battery configuration.

As electronic devices are rapidly becoming smaller or higher in performance, there is a growing demand for higher energy density in lithium ion secondary batteries. However, since graphite constituting the carbon material has a theoretical lithium storage / release capacity limited to 372 mAh / g, a negative electrode material having a larger lithium storage / release capacity is required.

In contrast, a method using a silicon material instead of a carbon material having a low charge / discharge capacity has been studied. However, the lithium ion secondary battery using a silicon material has a problem that the charge / discharge capacity is extremely reduced by repeating continuous charge / discharge, and the life is short. Therefore, carbon-silicon composite materials have also been studied (for example, Patent Documents 1 to 4). However, even with these carbon-silicon composite materials, the problem of the lifespan is still not fully solved.

JP 2004-259475 A JP 2003-187798 A JP 2001-160392 A JP-A-2005-123175

The present invention provides a carbon particle for an electrode having a high lithium storage / release capacity and capable of producing a long-life negative electrode material for a lithium ion secondary battery with little decrease in lithium storage / release capacity even after continuous charge / discharge, and An object of the present invention is to provide a negative electrode material for a lithium ion secondary battery using the carbon particles for an electrode.

The present invention is a carbon particle for an electrode in which composite metal oxide particles formed by firing composite particles of silicon or silicon oxide and a lithium oxide precursor are encapsulated in a matrix made of carbon.
The present invention is described in detail below.

As a result of intensive studies, the inventor contains composite metal oxide particles obtained by firing composite particles of silicon or silicon oxide and a lithium oxide precursor instead of the conventional silicon material or carbon-silicon composite material. A lithium ion secondary battery using carbon particles for electrodes as a negative electrode material has a high lithium storage / release capacity and a long life with little decrease in the lithium storage / release capacity even after continuous charge / discharge. Completed the invention.

The carbon particles for electrodes of the present invention contain composite metal oxide particles obtained by firing composite particles of silicon or silicon oxide and a lithium oxide precursor.
As a result, compared with conventional carbon particles for electrodes containing silicon material or carbon-silicon composite material, it has a high lithium occlusion / discharge capacity, and the decrease in lithium occlusion / discharge capacity is small even when continuous charge / discharge is performed. A long-life negative electrode material for a lithium ion secondary battery can be obtained.
Although the reason for this is not clear, when lithium or a composite particle of silicon oxide and a lithium oxide precursor is fired to decompose the lithium oxide precursor to produce lithium oxide, the lithium oxide is converted to silicon or silicon oxide. Reacts with silicon to form a kind of alloy, for example, lithium silicate such as lithium silicate (Li ₄ SiO ₄ ), and the lithium silicate such as lithium silicate undergoes volume expansion and contraction accompanying lithium occlusion and release of silicon during charge and discharge. It is thought that this contributes to a longer life.

In this specification, the lithium oxide precursor means a compound that decomposes by heating to generate lithium oxide.
Examples of the lithium oxide precursor include lithium carbonate, lithium acetate, lithium citrate, lithium polyacrylate, lithium peroxide, lithium hydroxide, and lithium nitrate. Of these, lithium carbonate is preferred because it decomposes by heating to produce lithium oxide and harmless carbon dioxide.

The silicon oxide is not particularly limited, and examples thereof include silicon monoxide and silicon dioxide.

The method for producing the composite particles of silicon and lithium oxide precursor is not particularly limited, and examples thereof include the following methods.
That is, first, a silicon raw material such as a silicon scrap wafer is roughly pulverized by a planetary ball mill or the like. Next, the coarsely pulverized silicon and lithium oxide precursor are placed in a suitable dispersion medium such as isopropyl alcohol, and sufficiently stirred with a planetary ball mill or the like, to thereby disperse the composite particles of silicon and lithium oxide precursor. To prepare. And the composite particle of a silicon and a lithium oxide precursor can be obtained by isolate | separating the obtained dispersion liquid with a centrifuge.

The method for producing the composite particles of the silicon oxide and the lithium oxide precursor is not particularly limited, and examples thereof include the following methods.
Silicon oxide particles such as commercially available silicon monoxide particles and silicon dioxide particles and a lithium oxide precursor are placed in a suitable dispersion medium such as isopropyl alcohol, and sufficiently stirred with a planetary ball mill or the like to obtain silicon oxide particles and A dispersion of composite particles with a lithium oxide precursor is prepared. And the composite particle of a silicon oxide and a lithium oxide precursor can be obtained by isolate | separating the obtained dispersion liquid with a centrifuge.

In the composite particles of silicon or silicon oxide and lithium oxide precursor, the preferable lower limit of the blending amount of the lithium oxide precursor with respect to 100 parts by weight of the silicon or silicon oxide is 5 parts by weight, and the preferable upper limit is 95 parts by weight. If the blending amount of the lithium oxide precursor is less than 5 parts by weight, the effect of extending the life may not be obtained, and if it exceeds 95 parts by weight, a high lithium storage / release capacity may not be obtained. The more preferable lower limit of the blending amount of the lithium oxide precursor is 10 parts by weight, and the more preferable upper limit is 90 parts by weight.

The surface of the composite particles of silicon or silicon oxide and lithium oxide precursor may be treated with a pigment dispersant. Dispersibility in the monomer-containing mixture described later is improved by treating the surface with the pigment dispersant.
Examples of the pigment dispersant include high molecular weight polyester acid amide amine salts, acrylic polymers, aliphatic polyvalent carboxylic acids, polyester amine salts, polyvinyl alcohol, polyvinyl pyrrolidone, and methyl cellulose.
The pigment dispersant may be added to the monomer mixture together with the silicon or the composite particles of silicon oxide and lithium oxide precursor.

The composite metal oxide particles can be obtained by firing the composite particles of silicon or silicon oxide and a lithium oxide precursor. Although the said baking may be performed only for the said composite metal oxide particle manufacture, it is preferable to be performed by the baking process at the time of the carbon particle production for electrodes mentioned later. By using the carbon particles for electrodes obtained by firing the composite particles of silicon or silicon oxide and a lithium oxide precursor at the same time in the firing step when producing the carbon particles for electrodes, particularly excellent high-speed charge / discharge characteristics (high rate characteristics) A negative electrode material for a lithium ion secondary battery can be obtained. This is because when the composite particles of silicon or silicon oxide and a lithium oxide precursor are fired, carbon dioxide released from the lithium oxide precursor is diffused to activate the obtained carbon particles for an electrode. This is considered to be because the BET specific surface area is remarkably increased.

A preferable upper limit of the average particle diameter of the composite metal oxide particles is 1 μm. When the average particle diameter of the composite metal oxide particles exceeds 1 μm, the lithium storage / release capacity of the obtained carbon particles for electrodes may be lowered.

The preferable lower limit of the content of the composite metal oxide particles in the electrode carbon particles of the present invention is 1% by weight. When the content of the composite metal oxide particles is less than 1% by weight, a high lithium storage / release capacity may not be exhibited. The minimum with more preferable content of the said composite metal oxide particle is 5 weight%.
The upper limit of the content of the composite metal oxide particles is not particularly limited. The higher the amount of the composite metal oxide particles, the higher the lithium storage / release capacity. However, if the content of the composite metal oxide particles is too large, the carbon material may be easily damaged due to a volume change of the composite metal oxide particles during continuous charge and discharge. The upper limit with preferable content of the said composite metal oxide particle is 95 weight%.

In the carbon particles for electrodes of the present invention, the composite metal oxide particles are encapsulated in a matrix made of carbon.
The matrix made of carbon may have a solid structure without voids inside or a hollow structure with voids inside. Especially, when the matrix made of carbon is composed of a large number of fine particles made of carbon gathered together, and a plurality of pores connected to each other are formed in the gaps between the fine particles to form an open cell hollow structure. In addition to being able to obtain lightweight carbon particles for an electrode, it is possible to exert an excellent effect that it is less likely to be broken and has a longer life when subjected to continuous charge and discharge. This is because even when a volume change of the composite metal oxide particles occurs during continuous charge / discharge, the voids can disperse and absorb the stress due to the volume change, and thus the damage is not reached. It is thought that there is not. Furthermore, the carbon particles for an electrode having such a continuous cell hollow structure have a high BET specific surface area and can be used as a negative electrode material for a lithium ion secondary battery excellent in high rate characteristics.
Silicon or silicon oxide and lithium oxide precursor are formed into carbon particles that are composed of a large number of fine particles made of carbon and have a plurality of pores connected to each other in the gaps between the fine particles to form a continuous cell hollow structure. Carbon particles for electrodes containing composite metal oxide particles obtained by firing composite particles with a body (hereinafter also referred to as “composite metal oxide particle-containing open cell hollow carbon particles”) are also used in the present invention. One.

In the composite metal oxide particle-containing continuous hollow carbon particles, the composite metal oxide particles may be contained in the matrix portion or in the void portion. When the metal forming the composite metal oxide particles is contained in the void portion, it is important that the metal is disposed so as to contact the matrix portion. Without contact with the matrix portion, it cannot contribute to occlusion and release of lithium.

A schematic diagram for explaining the structure of the composite metal oxide particle-containing continuous cell hollow carbon particles is shown in FIG.
FIG. 1 is an example in which composite metal oxide particles are contained in void portions in composite metal oxide particle-containing continuous cell hollow carbon particles. The mixed metal oxide particle-containing continuous cell hollow carbon particle 1 is formed by gathering a large number of fine grains (matrix made of carbon) 11, and a plurality of holes 12 connected to each other are formed in the gaps between the grains 11. Has been. The composite metal oxide particles 13 are contained inside the plurality of holes 12 connected to each other so as to be in contact with fine grains (matrix made of carbon) 11.

The minimum with the preferable porosity of the said composite metal oxide particle containing continuous cell hollow carbon particle is 5%, and a preferable upper limit is 95%. When the porosity of the composite metal oxide particle-containing continuous cell hollow carbon particles is less than 5%, the volume change of the composite metal oxide particles during continuous charge / discharge cannot be sufficiently absorbed and the carbon particles are easily damaged. In some cases, if it exceeds 95%, the strength of the resulting carbon particles may be low, or the carbon content may be too low, resulting in a decrease in conductivity.

The carbon particles for an electrode of the present invention preferably contain at least one conductive aid selected from the group consisting of carbon black, carbon nanotubes, graphene, and fullerene. By containing the conductive aid, the conductivity of the carbon particles for an electrode of the present invention can be further improved.

The electrode carbon particles of the present invention are prepared, for example, by mixing a monomer and a composite particle of silicon or silicon oxide and a lithium oxide precursor to prepare a monomer-containing mixture, and dispersing the monomer-containing mixture in an aqueous phase. A step of preparing a suspension in which oil droplets of the monomer-containing mixture are dispersed, a step of polymerizing oil droplets in the suspension to prepare resin particles, and a step of firing the resin particles. It can manufacture with the manufacturing method of the carbon particle for electrodes which has. Such a method for producing carbon particles for an electrode is also one aspect of the present invention.
The method for producing carbon particles for an electrode according to the present invention will be described in more detail by taking as an example the method for producing the composite metal oxide particle-containing continuous cell hollow carbon particles.

The above-mentioned mixed metal oxide particle-containing open-cell hollow carbon particles include a monomer having low compatibility with the obtained polymer, an organic solvent having low compatibility with the obtained polymer, and silicon or silicon oxide and a lithium oxide precursor. Mixing the composite particles to prepare a monomer-containing mixture; dispersing the monomer-containing mixture in an aqueous phase to prepare a suspension in which oil droplets of the monomer-containing mixture are dispersed; and in the suspension It can manufacture by the manufacturing method of the carbon particle for electrodes which has the process of polymerizing the oil droplet of this, and preparing the resin particle, and the process of baking the said resin particle. Such a method for producing carbon particles for an electrode is also one aspect of the present invention.

The method for producing carbon particles for an electrode according to the present invention includes a monomer having low compatibility with the obtained polymer, an organic solvent having low compatibility with the obtained polymer, and composite particles of silicon or silicon oxide and a lithium oxide precursor To prepare a monomer-containing mixture (hereinafter, “low compatibility with the resulting polymer” is also simply referred to as “low compatibility”).
In this specification, “low compatibility with the obtained polymer” means that the difference between the solubility parameter (SP value) of the monomer or organic solvent and the solubility parameter (SP value) of the polymer is 1.5 or more. Means.
In the present specification, the solubility parameter (SP value) means a value calculated by the Fedors equation.

The monomer having low compatibility constitutes a carbon component of the obtained carbon particles for an electrode by firing after polymerization. By using the low compatibility monomer together with the low compatibility organic solvent, the resulting carbon particles for electrodes are formed by gathering a large number of fine particles made of carbon. It has an open cell hollow structure in which a plurality of holes connected to each other are formed in the gap.

Examples of the low compatibility monomer include divinylbenzene, vinyl chloride, acrylonitrile and the like.

The said organic solvent with low compatibility plays a role of a hollow agent in the manufacturing method of the carbon particle for electrodes of this invention.
As the organic solvent having low compatibility, an appropriate organic solvent is selected in accordance with the monomer having low compatibility. For example, when divinylbenzene is used as the monomer having low compatibility, examples thereof include linear hydrocarbons such as n-heptane and alicyclic hydrocarbons such as cyclohexane.

In the monomer-containing mixture, the preferable lower limit of the blending amount of the low compatibility organic solvent with respect to 100 parts by weight of the low compatibility monomer is 5 parts by weight, and the preferable upper limit is 75 parts by weight. When the blending amount of the organic solvent is less than 5 parts by weight, sufficient voids are not formed inside the obtained carbon particles for electrodes, and the volume change of the composite metal oxide particles during continuous charge / discharge cannot be absorbed. The electrode carbon particles may be easily damaged. When the blending amount of the organic solvent exceeds 75 parts by weight, the strength of the obtained carbon particles for electrodes may be lowered, or it may be difficult to maintain the particle shape. The more preferable lower limit of the amount of the organic solvent is 10 parts by weight, and the more preferable upper limit is 70 parts by weight.

In the monomer-containing mixture, the preferred lower limit of the compounding amount of the composite particles of silicon or silicon oxide and lithium oxide precursor with respect to 100 parts by weight of the monomer having low compatibility is 1 part by weight. When the compounding amount of the composite particles of silicon or silicon oxide and a lithium oxide precursor is less than 1 part by weight, the obtained carbon particles for an electrode may not exhibit a high lithium storage / release capacity. A more preferable lower limit of the compounding amount of the composite particles of silicon or silicon oxide and a lithium oxide precursor is 5 parts by weight. The upper limit of the compounding amount of the composite particles of silicon or silicon oxide and lithium oxide precursor is not particularly limited. The larger the amount of the composite particles of silicon or silicon oxide and lithium oxide precursor, the higher the carbon particles for electrodes that can exhibit a high lithium storage / release capacity. However, if the amount of the composite particles of silicon or silicon oxide and a lithium oxide precursor is too large, the conductivity of the resulting carbon particles for electrodes may be insufficient. The upper limit with preferable compounding quantity of the composite particle of the said silicon or silicon oxide, and a lithium oxide precursor is 95 weight part.

The monomer-containing mixture contains a polymerization initiator.
As said polymerization initiator, conventionally well-known polymerization initiators, such as an organic peroxide, an azo compound, a metal ion redox initiator, a photoinitiator, a persulfate, can be used, for example.
A necessary amount of the polymerization initiator in the monomer-containing mixture may be blended. However, if the polymerization initiator is too small, the monomer may not be sufficiently polymerized and particles may not be formed. If it is added excessively, the molecular weight will not increase, and the post-treatment of the resulting carbon particles for electrodes will be hindered. Sometimes.

The monomer-containing mixture may contain other additives as necessary. For example, you may further contain the at least 1 sort (s) of conductive support agent selected from the group which consists of graphite, carbon black, a carbon nanotube, graphene, and fullerene. By containing the conductive aid, the conductivity of the obtained electrode carbon particles can be further improved. Especially, when the said monomer containing mixture contains graphite, in addition to the role as a conductive support agent, the increase effect of discharge capacity can also be anticipated.

The composite particles of silicon or silicon oxide and lithium oxide precursor are separately prepared in advance by the above-described method.

As a method for preparing the monomer-containing mixture, for example, a monomer having low compatibility, an organic solvent having low compatibility, composite particles of silicon or a silicon oxide and a lithium oxide precursor, and addition as necessary For example, the additive may be mixed and ultrasonically dispersed.

The method for producing electrode carbon particles of the present invention includes a step of dispersing the monomer-containing mixture in an aqueous phase to prepare a suspension in which oil droplets of the monomer-containing mixture are dispersed.
Examples of the aqueous medium constituting the aqueous phase include water, alcohol, and ketones.
The aqueous medium preferably contains a dispersant such as polyvinyl alcohol, methyl cellulose, polyvinyl pyrrolidone, insoluble inorganic fine particles, and a polymer surfactant.

The aqueous phase is preferably blended with a slight amount of a lithium oxide precursor and a buffer component such as citric acid for the purpose of adjusting pH.
The oil phase contains composite particles of the silicon or silicon oxide and a lithium oxide precursor. Of these, the lithium oxide precursor may slightly elute into the aqueous phase. When the aqueous phase is alkaline, it reacts with the silicon particles or silicon oxide particles, the surface is alkali-etched, and hydrogen gas is generated. To do. Thus, by adding a lithium oxide precursor to the aqueous phase in advance, the elution of the lithium oxide precursor from the oil phase is prevented, and the pH is adjusted with a buffer such as citric acid, so that the silicon particles or silicon oxide particles are Can be prevented from being deteriorated by alkali.

As a method for preparing the suspension, for example, the monomer-containing mixture is added to an aqueous medium, and a stirring device such as a homogenizer, a static static mixer, an ultrasonic mixer, an ultrasonic homogenizer, a shirasu porous filter, a stirring blade, or the like. The method of stirring with is mentioned.
By controlling the size of the oil droplets of the monomer-containing mixture in the suspension under the above stirring conditions, the particle diameter of the obtained carbon particles for electrodes can be adjusted.

The method for producing carbon particles for an electrode according to the present invention includes a step of preparing resin particles by polymerizing oil droplets in the suspension.
Examples of polymerization conditions for preparing resin particles by polymerizing the oil droplets include a method of stirring the suspension in a nitrogen stream at 30 to 95 ° C. for about 1 to 50 hours.
The obtained resin particles are separated from the suspension, and subjected to subsequent steps through operations such as washing with water, drying, and classification.

The manufacturing method of the carbon particle for electrodes of this invention has the process of baking the said resin particle. In addition, the composite particle of the said silicon or a silicon oxide, and a lithium oxide precursor turns into a composite metal oxide particle by this baking process. At this time, carbon dioxide and the like released from the lithium oxide precursor are diffused, whereby the obtained carbon particles for electrodes are activated, and the BET specific surface area is remarkably increased.
The firing conditions may be appropriately selected depending on the resin particles.
The firing temperature may be 1000 ° C. or lower, 1000 to 2500 ° C., or 2500 ° C. or higher.
When the firing temperature is 1000 ° C. or lower, when the obtained carbon particles for an electrode are used as a negative electrode material for a lithium ion secondary battery, an extremely high lithium storage / release capacity can be exhibited and a high output can be obtained. . However, the output of the lithium ion secondary battery may become unstable.
When the firing temperature is 1000 to 2500 ° C., stable output characteristics and cycle life can be exhibited when the obtained carbon particles for an electrode are used as a negative electrode material for a lithium ion secondary battery. However, the lithium storage / release capacity becomes low, and a high-power lithium ion secondary battery may not be obtained.
When the firing temperature is 2500 ° C. or higher, when the obtained electrode carbon particles are used as a negative electrode material for a lithium ion secondary battery, a very high lithium storage / release capacity can be exhibited and a high output can be obtained. .

The carbon particles for electrodes of the present invention are obtained by using composite metal oxide particles obtained by firing composite particles of silicon or silicon oxide and a lithium oxide precursor, instead of conventional silicon materials or carbon-silicon composite materials. In addition, a long-life negative electrode material for a lithium ion secondary battery having a high lithium storage / release capacity and a small decrease in the lithium storage / release capacity even when continuous charge / discharge is performed can be obtained. Furthermore, if the carbon particles for electrodes obtained by firing the composite particles of silicon or silicon oxide and a lithium oxide precursor in the firing step when producing the carbon particles for electrodes are used, lithium ions particularly excellent in high-rate characteristics A negative electrode material for a secondary battery can be obtained.
The negative electrode material for a lithium ion secondary battery containing the carbon particles for an electrode of the present invention and a binder resin is also one aspect of the present invention.

The binder resin serves as a binder for bonding the electrode particles of the present invention, and plays a role of forming into an arbitrary shape. However, if a binder resin is added in a large amount, the conductivity of the obtained negative electrode material for a lithium ion secondary battery may be lowered.
Examples of the binder resin include fluorine-containing resins such as polyvinylidene fluoride and polytetrafluoroethylene, and styrene butadiene rubber.

The negative electrode material for a lithium ion secondary battery of the present invention preferably further contains at least one conductive aid selected from the group consisting of graphite, carbon black, carbon nanotubes, graphene, and fullerene. By mix | blending the said conductive support agent, the electroconductivity of the negative electrode material for lithium ion secondary batteries of this invention can be improved more.

A preferable lower limit of the blending amount of the conductive assistant is 1% by weight, and a preferable upper limit is 90% by weight. If the blending amount of the conductive aid is less than 1% by weight, a sufficient conductivity improving effect may not be obtained, and if it exceeds 90% by weight, the lithium storage capacity may be lowered.
In addition, when the said conductive support agent is mix | blended to some extent, the role of the binder which couple | bonds the particle | grains for electrodes can also be exhibited. When the said conductive support agent exhibits the role of a binder, the compounding quantity of binder resin can be reduced and higher electroconductivity can be exhibited.

The method for producing the negative electrode material for a lithium ion secondary battery of the present invention includes, for example, a method of molding after mixing the electrode particles of the present invention, a conductive additive and a binder resin to obtain a mixture.
The mixture may contain an organic solvent so that it can be easily molded.
The organic solvent is not particularly limited as long as it is a poor solvent for the binding resin contained in the electrode particles and can dissolve the binder resin. For example, N-methylpyrrolidone, N, N- Examples include dimethylformamide.

According to the present invention, a carbon particle for an electrode having a high lithium storage / release capacity and capable of producing a long-life anode material for a lithium ion secondary battery with little decrease in lithium storage / release capacity even after continuous charge / discharge. And the negative electrode material for lithium ion secondary batteries which uses this carbon particle for electrodes can be provided.

It is a schematic diagram explaining the structure of a composite metal oxide particle containing continuous cell hollow carbon particle.

Hereinafter, embodiments of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
(1) Preparation of composite particles of silicon and lithium carbonate 150 g of silicon scrap wafer (Shin-Etsu Semiconductor), φ20 mm zirconia balls are put in a special zirconia container, and planetary ball mill (FRISCH, P-6) is 400 rpm for 30 minutes. The silicon scrap wafer was coarsely pulverized under the conditions.
50 g of the coarsely pulverized silicon obtained, 50 g of lithium carbonate (manufactured by Wako Pure Chemical Industries, Ltd.), 120 g of isopropyl alcohol, and φ1 mm zirconia beads were put into a dedicated zirconia container, and 400 rpm, 120 using a planetary ball mill (manufactured by FRITSCH, P-6). To obtain an isopropyl alcohol dispersion of composite particles of silicon and lithium carbonate having an average particle diameter of about 100 nm.
The resulting isopropyl alcohol dispersion of composite particles of silicon and lithium carbonate was separated and collected by a centrifugal separator to obtain composite particles of silicon and lithium carbonate (isopropanol wet cake: solid content 66%).

(2) Manufacture of carbon particles for electrodes (complex metal oxide particle-containing continuous hollow carbon particles) As oil phase components, 70 parts by weight of divinylbenzene as a monomer, 30 parts by weight of normal heptane as a hollow agent, silicon and carbonic acid 21 parts by weight of composite particles with lithium and 10.5 parts by weight of a pigment dispersant (manufactured by Enomoto Kasei Co., Ltd., DA-7301) were mixed and ultrasonically dispersed, and then 0.7 weight of an organic peroxide as a polymerization initiator. Part was added to prepare a monomer mixture.
On the other hand, 500 parts by weight of pure water as a water phase component, 5 parts by weight of polyvinyl alcohol, 6.4 parts by weight of lithium carbonate, and 5 parts by weight of citric acid as a dispersant were mixed.

The obtained oil phase component and aqueous phase component were mixed and stirred and dispersed with a homogenizer to prepare a suspension. The obtained suspension was polymerized by stirring and holding at 80 ° C. for 2 hours under a nitrogen stream. The particles obtained by polymerization were dried to obtain resin particles.
The obtained resin particles were heat-treated at 300 ° C. for 3 hours in an air atmosphere, and then fired at 1000 ° C. for 3 hours in an argon atmosphere to obtain carbon particles for electrodes.
The obtained carbon particles for an electrode had an average particle size of 10 μm and a Cv value of the particle size of 40%. The average particle size and Cv value were determined by observing about 100 arbitrary particles using an electron microscope (S-4300SE / N, manufactured by Hitachi High-Technology Corporation).

(Examples 2 and 3)
Example 1 except that the compounding amount of lithium carbonate in the composite particles of silicon and lithium carbonate (preparation amount, weight%) and the content of the composite metal oxide particles in the carbon particles for electrodes are as shown in Table 1. Thus, carbon particles for electrodes were obtained.

Example 4
(1) Preparation of composite particles of silicon monoxide and lithium carbonate 70 g of silicon monoxide (Osaka Titanium Technologies, average particle size 45 μm or less), 30 g of lithium carbonate (Wako Pure Chemical Industries), 120 g of isopropyl alcohol, φ1 mm The zirconia beads are put into a special zirconia container and pulverized with a planetary ball mill (FRITSCH, P-6) at 400 rpm for 120 minutes, and isopropyl as a composite particle of silicon monoxide and lithium carbonate having an average particle diameter of about 100 nm. An alcohol dispersion was obtained.
Isopropyl alcohol dispersion of the obtained composite particles of silicon monoxide and lithium carbonate is separated and collected by a centrifugal separator, and composite particles of silicon monoxide and lithium carbonate (isopropanol wet cake, solid content 66%) are collected. Obtained.

(2) Manufacture of carbon particles for electrodes (complex metal oxide particle-containing continuous hollow carbon particles) As oil phase components, 70 parts by weight of divinylbenzene as a monomer, 30 parts by weight of normal heptane as a hollow agent, silicon monoxide 21 parts by weight of composite particles of particles and lithium carbonate and 10.5 parts by weight of a pigment dispersant (manufactured by Enomoto Kasei Co., Ltd., DA-7301) are mixed and ultrasonically dispersed, and then an organic peroxide 0 is added as a polymerization initiator. .7 parts by weight were added to prepare a monomer mixture.
On the other hand, 500 parts by weight of pure water as a water phase component, 5 parts by weight of polyvinyl alcohol, 6.4 parts by weight of lithium carbonate, and 5 parts by weight of citric acid as a dispersant were mixed.

The obtained oil phase component and aqueous phase component were mixed and stirred and dispersed with a homogenizer to prepare a suspension. The obtained suspension was polymerized by stirring and holding at 80 ° C. for 2 hours under a nitrogen stream. The particles obtained by polymerization were dried to obtain resin particles.
The obtained resin particles were heat-treated at 300 ° C. for 3 hours in an air atmosphere, and then fired at 1000 ° C. for 3 hours in an argon atmosphere to obtain carbon particles for electrodes.
The obtained carbon particles for an electrode had an average particle size of 10 μm and a Cv value of the particle size of 40%. The average particle size and Cv value were determined by observing about 100 arbitrary particles using an electron microscope (S-4300SE / N, manufactured by Hitachi High-Technology Corporation).

(Example 5)
70 g of silicon dioxide (manufactured by Nacalai Tesque), 30 g of lithium carbonate (manufactured by Wako Pure Chemical Industries, Ltd.), 120 g of isopropyl alcohol, and φ1 mm zirconia beads are put into a special zirconia container, and 400 rpm with a planetary ball mill (manufactured by FRITSCH, P-6). The mixture was pulverized for 120 minutes to obtain an isopropyl alcohol dispersion of composite particles of silicon dioxide and lithium carbonate having an average particle size of about 100 nm.
The resulting isopropyl alcohol dispersion of composite particles of silicon dioxide and lithium carbonate was separated and collected by a centrifugal separator to obtain composite particles of silicon dioxide and lithium carbonate (isopropanol wet cake, solid content 66%). .
Electrode particles were obtained in the same manner as in Example 4 except that the obtained composite particles of silicon dioxide and lithium carbonate were used.

(Comparative Example 1)
Electrode particles were obtained in the same manner as in Example 1 except that the composite particles of silicon and lithium carbonate were not blended.

(Comparative Example 2)
Instead of the composite particles of silicon and lithium carbonate, electrode particles were obtained in the same manner as in Example 1 except that silicon (silicon nanopowder manufactured by Aldrich) was used.

(Comparative Example 3)
Graphite (manufactured by Wako Pure Chemical Industries, average particle size 20 μm, Cv value 50% of particle size) was used as electrode particles.

(Comparative Example 4)
Activated carbon (Norit SX Plus, Norit SX Plus, average particle size 160 μm, particle size Cv value 120%) was used as the electrode particles.

(Comparative Example 5)
Silicon (Aldrich, silicon nanopowder) was used as the electrode particles.

(Comparative Example 6)
Electrode particles were obtained in the same manner as in Comparative Example 2 except that normal heptane as a hollow agent was not added.

(Comparative Example 7)
Mesocarbon microbeads (MCMB particles, manufactured by Ningbo Shanshan New Material Tech, G15) were used as electrode particles.

(Comparative Example 8)
Hard carbon particles (manufactured by Kureha Corp., Carbotron P (J)) were used as the electrode particles.

(Evaluation)
The electrode particles obtained in Examples and Comparative Examples were evaluated as follows. However, Comparative Example 5 tried to be evaluated but could not be measured.
The results are shown in Tables 1 and 2.

(1) Measurement of active material capacity of electrode particles (4) The maximum discharge capacity in 100 cycles of half-cell evaluation of a lithium ion secondary battery is defined as the active material capacity of electrode particles.

(2) As an apparatus for measuring and measuring the BET specific surface area of the electrode particles, an automatic specific surface area measuring apparatus (BET, manufactured by Shimadzu Corporation, Gemini 2375) is used, the adsorption gas is N ₂ , and the measurement equilibrium pressure is 1 to 15 kPa (relative pressure). Was measured under the condition of 0.005 to 0.5).
A sample tube that had been heated and dried under vacuum was weighed, and an appropriate amount of sample was added thereto, followed by vacuum drying at room temperature for 1 hour, followed by vacuum drying at 80 ° C. for 1 hour. The sample was cooled to room temperature and weighed, and the weight of the sample tube was subtracted to obtain the sample weight. Next, nitrogen gas was fed into the sample tube to obtain a BET plot and converted to a specific surface area.

(3) Full Cell Evaluation of Lithium Ion Secondary Battery (3-1) Fabrication of Lithium Ion Secondary Battery Carbon Black (# 3230B, manufactured by Mitsubishi Chemical Co., Ltd.) 10 wt. A mixture was prepared by mixing 10 parts by weight of polyvinylidene fluoride as a binder resin and N-methylpyrrolidone as an organic solvent.
The obtained liquid mixture is applied to one side of a 18 μm thick Cu foil so as to be 1.5 mAh / cm ² or more, dried, and then press-molded with a press roll to form a negative electrode material for a lithium ion secondary battery. This was punched out into a disk shape with a diameter of 16 mm to produce a negative electrode sheet.

A coin-type model cell was produced using the obtained negative electrode sheet.
That is, the obtained negative electrode sheet having a diameter of 16 mm and a counter electrode lithium metal having a diameter of 16 mm were laminated via a separator. After impregnating the separator with the electrolytic solution, these were caulked with an upper can and a lower can through a gasket. The upper can and the lower can were contacted by the negative electrode and the positive electrode, respectively.
As the separator, a polyethylene microporous film having a thickness of 25 μm and a diameter of 24 mm was used. As the electrolyte, a mixed solvent of ethylene carbonate and dimethyl carbonate in a volume ratio of 1: 2 was used, and LiPF ₆ was used as the electrolyte at a concentration of 1 mol. A solution dissolved so as to be / L was used.
The theoretical capacity of the obtained coin-type model cell is 3.0 mAh, and the battery (discharge) capacity for full cell evaluation is represented by mAh.

(3-2) The charge / discharge conditions were as follows: after 1 hour of rest at current 0, the voltage rose to 4.2 V at a current corresponding to current rates 1C and 10C, and then held for 0.5 hours and charged. After resting for 10 minutes, the battery was discharged at a current rate of 1C and 10C until the voltage reached 2.7V. After resting for 10 minutes, this discharging was repeated. The charge / discharge capacity was determined from the amount of electricity applied during that time.

(4) Half-cell evaluation charging / discharging conditions of the lithium ion secondary battery were rested for 4 hours at a current of 0, then dropped to 0.002 V at a current corresponding to 1 C, held for 0.5 hours and charged. After resting for 10 minutes, the battery was discharged at a current of 1 C until the voltage reached 3V. After resting for 10 minutes, this discharging was repeated. The charge / discharge capacity was determined from the amount of electricity applied during that time.
Further, the initial charge / discharge efficiency (%) and the second cycle charge / discharge efficiency (%) were calculated from the following formula. In this test, the process of occluding lithium into the negative electrode material was charged and the process of detaching was defined as discharge.
Initial charge / discharge efficiency (%)
= (Discharge capacity of the first cycle / Charge capacity of the first cycle) × 100
Second cycle charge / discharge efficiency (%)
= (Discharge capacity of the second cycle / Charge capacity of the second cycle) × 100
10th cycle charge / discharge efficiency (%)
= (Discharge capacity of 10th cycle / Charge capacity of 10th cycle) × 100
20th cycle charge / discharge efficiency (%)
= (20th cycle discharge capacity / 20th cycle charge capacity) x 100
100th cycle charge / discharge efficiency (%)
= (100th cycle discharge capacity / 100th cycle charge capacity) x 100

The above cycle was repeated 10 times, 20 times and 100 times, and the cycle characteristics were calculated using the following formula.
Capacity maintenance rate (%) from 2nd cycle to 10th cycle
= (Discharge capacity in the 10th cycle / discharge capacity in the 2nd cycle) × 100
Capacity maintenance rate from the 2nd cycle to the 20th cycle (%)
= (Discharge capacity in 20th cycle / Discharge capacity in 2nd cycle) × 100
Capacity maintenance rate from the 2nd cycle to the 100th cycle (%)
= (Discharge capacity in the 100th cycle / discharge capacity in the second cycle) × 100

According to the present invention, a carbon particle for an electrode having a high lithium storage / release capacity and capable of producing a long-life anode material for a lithium ion secondary battery with little decrease in lithium storage / release capacity even after continuous charge / discharge. And the negative electrode material for lithium ion secondary batteries which uses this carbon particle for electrodes can be provided.

1 Composite Metal Oxide Particle Containing Cystic Hollow Carbon Particles 11 Fine Grain (Carbon Matrix)
12 A plurality of holes 13 connected to each other 13 Composite metal oxide particles

Claims (5)

Silicon or silicon oxide and lithium oxide precursor are formed into carbon particles that are composed of a large number of fine particles made of carbon and have a plurality of pores connected to each other in the gaps between the fine particles to form a continuous cell hollow structure. A method for producing carbon particles for an electrode containing composite metal oxide particles obtained by firing composite particles with a body,
A step of preparing a monomer-containing mixture by mixing a monomer having low compatibility with the obtained polymer, an organic solvent having low compatibility with the obtained polymer, and composite particles of silicon or silicon oxide and a lithium oxide precursor; A step of dispersing the monomer-containing mixture in an aqueous phase to prepare a suspension in which oil droplets of the monomer-containing mixture are dispersed; and a step of polymerizing the oil droplets in the suspension to prepare resin particles; , possess a step of firing the resin particles,
The difference in solubility parameter (SP value) calculated by the Fedors equation is 1 between the monomer having low compatibility with the obtained polymer and the organic solvent having low compatibility with the obtained polymer, and the obtained polymer. A method for producing carbon particles for an electrode, characterized by having 5 or more . The method for producing carbon particles for an electrode according to claim 1 , wherein the lithium oxide precursor is lithium carbonate. An electrode carbon particle obtained by the method for producing an electrode carbon particle according to claim 1 or 2. A negative electrode material for a lithium ion secondary battery, comprising the carbon particles for an electrode according to claim 3 and a binder resin. 5. The negative electrode material for a lithium ion secondary battery according to claim 4, wherein at least one conductive aid selected from the group consisting of graphite, carbon black, carbon nanotubes, graphene and fullerene is blended.

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