WO2017149731A1 - Negative-electrode material for lithium-ion battery, lithium-ion battery, and method for manufacturing negative-electrode material for lithium-ion battery - Google Patents

Abstract

A negative-electrode material 100 for one lithium-ion battery according to the present invention is silicon fine particles 201 having a volume distribution in which the modal diameter and the median diameter are not more than 50 nm, or alternatively, an aggregate or collection of the silicon fine particles 201. Some of the silicon fine particles 201 that are folded in the shape of multilayered petals or ramenta or a part of the aggregate or collection of the silicon fine particles 201 are in contact with, or are embedded in, a carbon base material 101. A lithium-ion battery having superior charge/discharge cycle characteristics can be achieved by employing this negative-electrode material 100.

Description

Negative electrode material for lithium ion battery, lithium ion battery, and method for producing negative electrode material for lithium ion battery

The present invention relates to a negative electrode material for a lithium ion battery, a lithium ion battery, and a method for producing a negative electrode material for a lithium ion battery.

Conventionally used lithium ion batteries use a negative electrode material and a negative electrode active material (hereinafter also referred to as “negative electrode material”) graphite (natural graphite, artificial graphite, etc.) as a binder on the negative electrode side. And a negative electrode having a mixture layer mixed together. Stoichiometric composition when filled with lithium ions in its graphite is LiC _6. The calculated theoretical capacity is 372 mAh / g.

On the other hand, when silicon is employed as the negative electrode material, the stoichiometric composition when the silicon is filled with lithium ions is Li ₁₅ Si ₄ or Li ₂₂ Si ₅ . The calculated value of the theoretical capacity is 3577 mAh / g or 4197 mAh / g. Accordingly, when silicon is employed as the negative electrode material, it is theoretically possible to store lithium about 9.6 times or about 11.3 times that of graphite, so silicon (particularly, particulate silicon) Is a very attractive material.

For example, as an example of the production of silicon particles, a powder having a diameter of about 38 microns (μm) or less formed by pulverizing single crystal silicon in a mortar and classifying with a mesh is used in an argon atmosphere at 30 ° C./min. What was heated to 150 degreeC (attainment temperature) by the temperature increase rate is disclosed (patent document 1). As another example, by supplying liquid silicon tetrachloride in high-temperature and high-concentration zinc gas and reacting at a high temperature of 1050 ° C. or higher, silicon tetrachloride is reduced to form silicon particles, Fine silicon is crystallized and agglomerated at 1000 ° C. or lower, particularly 500 to 800 ° C., and the size of the formed silicon particles is adjusted and collected in an aqueous zinc chloride solution. It is disclosed that high-purity silicon particles having a particle size of about 1 to 100 μm can be obtained by this work, and that it is used (Patent Document 2).

However, when lithium ion is charged into particulate silicon, the volume of silicon expands to about 2.7 times to about 3.1 times. Therefore, repeating the filling and releasing of lithium ions repeats the expansion and contraction of the silicon particles, so that the silicon particles are dynamically destroyed over time. When silicon particles are destroyed, the fine silicon particles formed by the destruction are electrically isolated. In addition, a new electrochemical coating layer will be formed on the fracture surface of these fine silicon particles. As a result, the irreversible capacity is increased, and the charge / discharge cycle characteristics are significantly deteriorated.

In response to the above technical problems, silicon particles refined to about 10 nm even when the volume distribution is a median diameter (50% crystallite diameter) should be used as a part of a negative electrode material of a lithium ion battery. Discloses a technique for suppressing or preventing the influence associated with the filling and releasing of lithium ions (Patent Document 3).

JP 2005-032733 A JP 2012-101998 A International Publication No. WO2015 / 189926 Pamphlet

However, in the case of the silicon particles disclosed in the above-mentioned Patent Documents 1 and 2, since it is necessary to perform a high-temperature synthesis and collection process, the manufacturing process until obtaining silicon particles as a negative electrode material becomes extremely complicated. As a result, it is unavoidable that productivity is lowered and manufacturing costs are increased. Further, the technique disclosed in Patent Document 3 is effective in that a part of silicon particles is considered not to be electrically isolated by, for example, expansion and contraction, but there is still room for improvement. Yes. In other words, development of lithium ion batteries using silicon particles is still halfway.

In order to find a higher-performance negative electrode material that can be adapted to the mechanism of a lithium ion battery, without limiting the material used as the negative electrode material only to silicon particles, in light of the above technical problem, Repeated research and analysis.

As a result, the inventors of the present application have achieved higher performance by making the most of their usefulness while utilizing certain characteristic silicon fine particles as a secondary material to the carbon base material. The knowledge that a negative electrode material can be realized was obtained. The present invention was created based on the above viewpoint.

The present invention greatly contributes to the realization of a higher performance negative electrode material of a lithium ion battery and a method for producing the same for a lithium ion battery, which is expected to greatly reduce carbon dioxide gas as the use expands.

In the negative electrode material of one lithium ion battery of the present invention, silicon fine particles having a volume distribution with a mode diameter and a median diameter of less than 50 nm, or aggregates or aggregates thereof, are folded into a multi-layer petal shape or a scale shape. A part of the above-mentioned silicon fine particles in an overlapped state or a part of the aggregate or the aggregate of the above-described silicon fine particles is in contact with or embedded in the carbon base material.

By adopting this negative electrode material for lithium ion batteries, it is possible to prevent the silicon fine particles from being electrically isolated with higher accuracy. For example, the charge / discharge cycle characteristics can be improved, and the life of the lithium ion battery can be extended. It can be realized.

Moreover, the manufacturing method of the negative electrode material of one lithium ion battery of this invention is a mode diameter and a median diameter of less than 50 nm by grind | pulverizing the crystalline silicon | silicone which is the chip or cutting waste scraped off by a fixed abrasive wire. A pulverization step for forming silicon fine particles having a volume distribution of the above or an aggregate or aggregate thereof, and a part of the silicon fine particles or the aggregate or aggregate described above being in contact with the carbon substrate, Or a mixing step of mixing the carbon substrate with the silicon fine particles or the aggregates or aggregates so as to be embedded in the carbon substrate.

According to this method for producing a negative electrode material for a lithium-ion battery, characteristic silicon fine particles formed by the above-described pulverization process or aggregates or aggregates thereof, starting from crystalline silicon that is chips or cutting waste Is mixed with the carbon substrate. As a result, the silicon fine particles or the agglomerates or a part of the aggregates are in contact with the carbon substrate or embedded in the carbon substrate (eg, appear to pierce). Therefore, it is possible to manufacture a negative electrode material for a lithium ion battery that is more accurate and in which silicon fine particles are not electrically isolated. Therefore, by adopting the negative electrode material manufactured by the negative electrode material manufacturing method of the lithium ion battery, for example, the charge / discharge cycle characteristics can be improved and the life of the lithium ion battery can be extended.

According to the negative electrode material of one lithium ion battery of the present invention, the silicon fine particles can be prevented from being electrically isolated with higher accuracy. For example, the charge / discharge cycle characteristics are improved, and the length of the lithium ion battery is improved. It is possible to achieve a long life.

In addition, by adopting the negative electrode material manufactured by the negative electrode material manufacturing method of one lithium ion battery of the present invention, for example, it is possible to improve the charge / discharge cycle characteristics and extend the life of the lithium ion battery. It becomes.

It is the conceptual diagram which showed typically the negative electrode material 100 of 1st Embodiment. It is a conceptual diagram of the carbon base material 101 of 1st Embodiment. It is a flowchart which shows the manufacturing process of the silicon fine particle 201 which comprises a part of negative electrode material of 1st Embodiment, or its aggregate or aggregate. It is a schematic diagram which shows the manufacturing apparatus and manufacturing process of the silicon | silicone fine particle 201 of 1st Embodiment, or its aggregate or aggregate. It is a SEM image of an example of the silicon fine particle of 1st Embodiment, its aggregate, or an aggregate. It is a figure which shows the SEM image of an example of the expanded silicon | silicone fine particle or its aggregate or aggregate | assembly in 1st Embodiment. In the first embodiment, (a) an SEM image of another example of an aggregate or aggregate of silicon fine particles, and (b) an enlarged view of a part of (a). It is a figure which shows the TEM image of the silicon | silicone fine particle of 1st Embodiment. It is a graph which shows the crystallite diameter distribution in (a) number distribution, and the (b) crystallite diameter distribution in volume distribution with respect to the crystallite diameter of the silicon | silicone fine particle of 1st Embodiment. It is a schematic diagram of the structure which coat | covered the silicon fine particle etc. 201 of 1st Embodiment using the carbon coating layer 301. FIG. It is the conceptual diagram which showed typically the apparatus structure for forming the carbon coating layer 301. FIG. Schematic structure of the first embodiment in which the entire structure in which silicon fine particles 201 or the like are brought into contact with or embedded in the surface of the carbon substrate 101 or further partially covered with the carbon coating layer 302 is used. FIG. 2 is a scanning electron micrograph of the negative electrode material of Example 1. FIG. 2 is a further enlarged scanning electron micrograph of the negative electrode material of Example 1. It is a scanning electron micrograph which shows the example of the structure which removed some silicon fine particles 201 etc. among the structures shown in FIG. 14, and was easy to see. It is the result of calculating the silicon weight ratio dependence of electric capacity. It is a structure conceptual diagram of the lithium ion battery of 2nd Embodiment. 4 is a graph showing the results of evaluating each lithium ion battery of Example 1 and Comparative Example 1. It is a schematic diagram which shows the manufacturing apparatus and manufacturing process of the silicon | silicone fine particle 201 or its aggregate or aggregate | assembly of other embodiment.

1 Chips, etc. 2,201 Silicon fine particles 10 Washing machine (cleaning and preliminary grinding machine)
11 Ball type 13a Pot 13b Lid 15 Rotating shaft 20 Crusher 21 Inlet 22 Processing chamber 24 Discharge 25 Filter 30 Dryer 40 Rotary evaporator 50 Oxide film removal tank 55 Hydrofluoric acid or ammonium fluoride aqueous solution 57 Stirrer 58 Centrifugal Separator 100 Negative electrode material 101 Carbon substrate 301, 301 Carbon coating layer 500 Lithium ion battery negative electrode material and negative electrode manufacturing apparatus 1000 Lithium ion battery 1101 Positive electrode 1102 Separator 1103 Negative electrode 1104 Battery can 1105 Positive electrode current collecting tab 1106 Negative electrode current collecting tab 1107 Inner lid 1108 Pressure release valve 1109 Gasket 1110 Positive temperature coefficient resistance element 1111 Battery lid

Embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this description, common parts are denoted by common reference symbols throughout the drawings unless otherwise specified. In the drawings, each element of each embodiment is not necessarily shown in a scale ratio. Moreover, in order to make each drawing easy to see, some reference numerals may be omitted.

<First Embodiment>
1. Negative Electrode Material (Negative Electrode Active Material) FIG. 1 is a conceptual diagram schematically showing the negative electrode material 100. The negative electrode material 100 of the present embodiment is formed using the carbon base material 101 and the silicon fine particles 201 or aggregates or aggregates thereof, and the silicon fine particles 201 in a state of being folded into a multi-layer petal shape or a scale shape. Or the agglomerates or aggregates of silicon fine particles 201. Further, a part of the silicon fine particles 201 or a part of the aggregate or aggregate of the silicon fine particles 201 in a state of being folded into a multi-layered petal shape or a scale shape is in contact with and attached to the carbon base material 101 or carbon. It is buried in the base material 101. Note that, as will be described later, the silicon fine particles of the present embodiment or the aggregates or aggregates thereof have a volume distribution with a mode diameter and a median diameter of less than 50 nm.

Further, it is considered that the silicon fine particles 201 or a part of the aggregates or aggregates thereof are attached to the surface of the carbon base material 101 by van der Waals force. In addition, the silicon fine particles 201 or the aggregates or aggregates thereof can also form a multilayer structure (for example, a multilayer petal-like structure) by contacting or adhering to each other by van der Waals force. Thus, since the multilayer structure is formed, the contact area between the silicon fine particles can be made larger than, for example, the contact surface between the spherical silicon fine particles. As a result, the lithium ion battery is temporarily charged and discharged. Even when expansion and contraction occur, it is possible to realize a negative electrode material that is difficult to isolate silicon fine particles and has high conductivity. Note that some of the silicon fine particles 201 or aggregates or aggregates thereof appear to be inserted so as to pierce the carbon substrate 101, as will be described later.

In this embodiment, it is considered that the role of occlusion and release of lithium ions is mainly played by the silicon fine particles 201 or aggregates or aggregates thereof. A part of the silicon fine particles 201 or a part of the aggregate or aggregate of the silicon fine particles 201 is in contact with, adheres to, or is embedded in the carbon base material 101, thereby providing high conductivity. Can be realized.

2. Regarding Carbon Base Material FIG. 2 is a conceptual diagram of the carbon base material 101 that constitutes a part of the negative electrode material of the present embodiment. The carbon base material 101 of this embodiment is particulate. Artificial graphite, natural graphite, or graphite material processed from them can be used as the carbon substrate 101 of the present embodiment.

The average of the longest particle diameter (longest particle diameter) of the carbon substrate 101 is 1 μm or more and 50 μm or less, and more preferably 5 μm or more and 30 μm or less. When the longest particle diameter is 1 μm or less, it is considered that the curvature of the surface of the carbon base material 101 increases due to the size being too small. As a result, it becomes difficult to contact or embed a portion of the silicon fine particles 201 or the aggregates or aggregates thereof, which will be described later, on the surface or inside thereof.

Further, contact, adhesion, or part of the silicon fine particles 201 or aggregates or aggregates thereof (hereinafter collectively referred to as “silicon fine particles 201”) on the surface of the carbon substrate 101 or inside thereof. In order to realize the embedding with higher accuracy, it is desirable that the longest particle diameter is 5 μm or more. When the longest particle size is 50 μm or more, the specific surface area becomes too small. As a result, it is necessary to make many silicon fine particles 201 or aggregates or aggregates thereof contact, adhere to, or partially embed on the surface of the carbon substrate 101 or inside thereof. However, when a large number of silicon fine particles 201 or aggregates or aggregates thereof are brought into contact with each other, adhered, or partially embedded, electrical resistance between the silicon fine particles 201 or aggregates or aggregates thereof may be an obstacle. In other words, since things other than the silicon fine particles 201 near the surface of the carbon substrate 101 cannot be efficiently used as the negative electrode active material, the life characteristics of the lithium ion battery may be deteriorated as a result. From the viewpoint of more efficiently using the silicon fine particles 201 or the like that are brought into contact with, attached to, or partially embedded in the surface of the carbon base material 101, it is preferable that the longest particle size is 30 μm or less. It is one mode.

3. Silicon Fine Particles or Aggregates or Aggregates thereof FIG. 3 is a flow diagram showing a manufacturing process of silicon fine particles 201 or aggregates or aggregates thereof constituting a part of the negative electrode material of the present embodiment. FIG. 4 is a schematic diagram showing a manufacturing apparatus and manufacturing process for silicon fine particles 201 or aggregates or aggregates thereof.

The manufacturing method of the silicon fine particles 201 or the aggregates or aggregates thereof according to the present embodiment is silicon that is normally regarded as waste in the cutting process of silicon in the production process of silicon wafers used for semiconductor products such as solar cells. And various kinds of processes using, as an example of a starting material, cutting chips, silicon cutting scraps or polishing scraps (hereinafter also referred to as “silicon cutting chips” or “cutting chips”). Further, the chips and the like include fine scraps obtained by pulverizing a silicon wafer to be discarded by a known pulverizer. As shown in FIG. 1, the manufacturing method of the lithium ion battery of this embodiment includes the following steps (1) and (2). Moreover, the manufacturing method of the silicon | silicone fine particle 201 of this embodiment, or its aggregate or aggregate | assembly can include the following processes (3) as another aspect which can be employ | adopted.
(1) Cleaning step (S1)
(2) Grinding step (S2)
(3) Oxide film removal step (S3)

As shown in FIG. 4, the negative electrode material and negative electrode manufacturing apparatus 500 of the lithium ion battery of the present embodiment mainly includes a cleaning machine (cleaning and preliminary pulverizer) 10, a pulverizer 20, and a dryer (not shown). The rotary evaporator 40 is provided. Moreover, the negative electrode material of the lithium ion battery of this embodiment and the negative electrode manufacturing apparatus 500 can include an oxide film removal tank 50 and a centrifuge 58 as another aspect that can be employed. Note that only the pulverizer 20 described above, or the washing machine 10 and the pulverizer 20 are referred to as a pulverization unit in the present embodiment.

(1) Cleaning step (S1)
In the cleaning step (S1) of the present embodiment, for example, it is formed in the cutting process of single crystal or polycrystalline silicon, that is, a crystalline silicon lump or ingot (n-type crystalline silicon lump or ingot). Silicon chips and the like are cleaned. Typical silicon chips and the like are chips and the like in which a silicon ingot is cut out by a known wire or the like (typically, a fixed abrasive wire). Therefore, in the present embodiment, since the silicon fine particles constituting the negative electrode material of the lithium ion battery are formed using silicon chips, which have been conventionally regarded as waste, as the starting material, the manufacturing cost and / or the raw material Excellent in terms of easy procurement and resource utilization.

The cleaning step (S1) of the present embodiment is mainly for the purpose of removing organic substances adhering in the formation process of the above-described silicon chips, typically organic substances such as coolants and additives used in the cutting process. And In this embodiment, as shown in FIG. 3, first, after the chips 1 to be cleaned are weighed, the chips 1, the predetermined first liquid, and the ball 11 have a bottomed cylindrical shape. It is introduced into the pot 13a. After sealing the inside of the pot 13a using the lid 13b, the two cylindrical rotating bodies 15 included in the ball mill which is the cleaning machine (cleaning and preliminary pulverizing machine) 10 are rotated, thereby rotating the rotary body 15 on the rotary body 15. The pot 13a is rotated. As a result, in the pot 13a, the chips 1 to be cleaned are dispersed in the first liquid, whereby the chips 1 are cleaned and preliminarily pulverized.

Here, the ball mill machine of this embodiment uses the steel balls, magnetic balls, cobblestones and the like stored in the pot 13a and the lid 13b as the ball type 11 (grinding medium), and rotates the pot 13a and the lid 13b. It is a crusher that gives a physical impact force. A suitable example of the first liquid is acetone. Moreover, in one more specific aspect, for example, 300 milliliters (mL) of acetone is added to 100 grams (g) of silicon chips and the like, and a ball mill machine (in this embodiment, manufactured by MASUDA, Silicon chips and the like were dispersed in acetone by stirring in a pot 13a and a lid 13b placed on a rotating body 15 (Universal BALL MILL) for about 1 hour. Ball types of the ball mill machine were alumina balls having a particle diameter of φ10 millimeters (mm) and alumina balls having a particle diameter of φ20 mm. In the cleaning step (S1) of the present embodiment, the dispersion process is performed by pre-grinding and stirring silicon chips and the like in the first liquid in the ball mill. Accordingly, since the cleaning efficiency is remarkably improved as compared with the treatment of simply immersing in the first liquid, silicon particles suitable for improving the negative electrode characteristics of the lithium ion battery, particularly for improving the charge / discharge cycle characteristics, are used. Can be obtained.

After the washing step (S1), the lid 13b is opened to discharge the silicon particles together with the first liquid, and then the first liquid is removed by suction filtration with a known vacuum filtration means to become a waste liquid. On the other hand, the remaining silicon particles are dried in a known dryer. If necessary, the silicon particles obtained after the drying treatment are again preliminarily crushed and washed in the washing machine (washing / preliminary pulverizer) 10 in the same process. In addition, the example of the other washing | cleaning method which can be employ | adopted in washing | cleaning process (S1) is the washing | cleaning using the RCA washing | cleaning method, or the washing | cleaning using water (a pure water is included).

(2) Grinding step (S2)
Thereafter, in the pulverization step (S2), a predetermined second liquid is added to the washed silicon particles, and the silicon particles are pulverized in the bead mill. Therefore, in this embodiment, the silicon particles that have undergone the cleaning step (S1) are further finely pulverized by the bead mill used after the above-described ball mill, in other words, after the above-described ball mill. Become.

A suitable example of the second liquid of this embodiment is IPA (isopropyl alcohol). As a pretreatment of the pulverization step, the silicon particles obtained in the second liquid and the washing step (S1) are placed in the pot 13a so that the second liquid is 95% of the silicon particles and 95% of the second liquid. After storing, a preliminary pulverization process is performed by rotating a cleaning machine (cleaning and preliminary pulverizer) 10. After relatively coarse particles are removed by passing the slurry containing silicon particles that have been subjected to pre-grinding treatment through a mesh having an opening of 180 microns, the obtained slurry containing silicon particles is used as a bead mill (this embodiment). , The finely pulverizing treatment is performed using a model star mill LMZ015 manufactured by Ashizawa Finetech. More specifically, a slurry containing silicon particles from which silicon chips having a particle diameter of 180 microns or more are removed is introduced into the inlet 21 of the pulverizer 20, and the slurry is processed by the bead mill using the pump 28. A fine pulverization process is performed in the chamber 22. A specific example of the bead type of the bead mill is zirconia beads having a particle diameter of φ0.5 mm. After collecting the slurry containing finely pulverized silicon particles, the second liquid is removed using a rotary evaporator 40 that automatically performs vacuum distillation to obtain finely pulverized silicon fine particles as a result. It is done.

In this embodiment, silicon fine particles can be obtained by introducing about 450 g of zirconia beads having a particle diameter of φ0.5 mm and performing a pulverization process at a rotational speed of 2900 rpm for 4 hours. Further, in the pulverization step (S2), it is also possible to perform the pulverization treatment by any one of the pulverizers other than those described above, or a combination of two or more of the pulverizers composed of a ball mill, a bead mill, a jet mill, and a shock wave pulverizer. Another aspect that can be achieved. In addition, as a pulverizer used in the pulverization step (S2), not only an automatic pulverizer but also a manual pulverizer may be employed. However, from the viewpoint of forming agglomerates or aggregates of silicon fine particles that are highly accurate and folded into a multi-layered petal shape or scale shape, which will be described later, a pulverization step (S2) consisting of processing by a bead mill, or a bead mill It is preferable to employ a pulverization step (S2) including the treatment by. In addition, by adopting at least a treatment with a bead mill, the silicon particles are not only pulverized, but also the formed silicon fine particles or aggregates or aggregates thereof are more accurately dispersed so that the silicon fine particles are “dama”. Can be prevented.

In addition, using a known reiki machine (as a typical reiki machine, manufactured by Ishikawa Factory Co., Ltd., Model 20D), the silicon fine particles obtained by the above-described crushing step (S2) can be further crushed. This is another preferred embodiment that can be adopted. Since this disintegration treatment improves the dispersibility when forming the negative electrode of the lithium ion battery, it is possible to highly reliably prevent or suppress destruction of the negative electrode due to insertion and extraction of lithium. .

(3) Oxide film removal step (S3)
In the present embodiment, an oxide film removing step (S3) is performed as a preferred embodiment. However, even if this oxide film removal step (S3) is not performed, at least a part of the effects of the present embodiment can be achieved.

In the oxide film removing step (S3) of the present embodiment, the silicon fine particles 2 obtained by the pulverizing step (S2) are brought into contact with hydrofluoric acid or an aqueous ammonium fluoride solution. The silicon fine particles 2 obtained by the pulverization step (S2) are dispersed by being immersed in an aqueous solution of hydrofluoric acid or ammonium fluoride. Specifically, in the oxide film removal tank 50, the silicon fine particles 2 are dispersed in a hydrofluoric acid or ammonium fluoride aqueous solution 55 by using a stirrer 57, whereby an oxide (on the surface of the silicon fine particles 2 ( Mainly silicon oxide) is removed.

Thereafter, the silicon fine particles from which part or all of the surface oxide has been removed are separated from the hydrofluoric acid aqueous solution by the centrifuge 58. Thereafter, the silicon fine particles are immersed in a third liquid such as an ethanol solution. By removing the third liquid, silicon fine particles from which part or all of the oxide (or oxide film) on the surface that was originally formed are removed can be obtained.

In the oxide film removal step (S3) of this embodiment, the silicon fine particles are immersed in hydrofluoric acid or an aqueous ammonium fluoride solution to bring the hydrofluoric acid into contact with the silicon fine particles. A step of bringing hydrofluoric acid or an aqueous ammonium fluoride solution into contact with the silicon fine particles by the above method can also be employed. For example, spraying a hydrofluoric acid aqueous solution onto silicon fine particles like a so-called shower is another aspect that can be employed.

<Other processes>
By the way, the silicon fine particles obtained by the above-described cleaning step (S1) and pulverizing step (S2) or by the cleaning step (S1), pulverizing step (S2), and oxide film removing step (S3) are, for example, In order to reduce the variation in the number distribution and / or volume distribution of the crystallite diameter of each silicon fine particle, it can be classified.

<Analysis results of silicon fine particles obtained in the first embodiment>
A. Analysis of fine silicon particles by SEM and TEM images

FIG. 5 is an SEM (scanning electron microscope) image of an example of silicon fine particles or aggregates or aggregates thereof after the crushing step (S2) of the first embodiment. FIG. 6 is a view showing an SEM image of an example of enlarged silicon fine particles or aggregates or aggregates thereof after the crushing step (S2) of the first embodiment. FIG. 7 is a diagram showing (a) an SEM image of another example of an aggregate or aggregate of silicon fine particles and (b) a partially enlarged view of (a) in the first embodiment. is there. In addition, FIG. 8 is a diagram showing a transmission electron microscope (TEM) image of the silicon fine particles of the first embodiment.

As shown in FIG. 5, not only individual silicon fine particles but also silicon fine particles indicated by Y1 and Y2, or aggregates or aggregates thereof were confirmed. Interestingly, when analyzed in more detail, as shown in FIG. 6 and the Z portion in FIGS. 7A and 7B, silicon fine particles or aggregates thereof are, so to speak, thin layered silicon fine particles. It was confirmed that it was an aggregate or aggregate in a state of being folded into a multi-layer petal shape or a scale shape. In more detail, for example, the range of the length (major axis) when the width (minor axis) of one or a group of scaly silicon fine particles is 1, is 3.3 to 12.9. there were.

Also, another interesting finding was obtained from the TEM image shown in FIG. 8 focusing on individual silicon fine particles. Specifically, it was confirmed that the individual silicon fine particles shown by the region surrounded by the white line in FIG. 8 were crystalline, that is, single crystal silicon. In addition, it was confirmed that at least some of the silicon fine particles were amorphous polygonal crystallites having a size of about 2 nm to about 10 nm in a cross-sectional view. In FIG. 8, the crystal plane orientation is shown in each region surrounded by a white line.

B. Analysis of crystallite size distribution of silicon fine particles by X-ray diffraction method FIG. 9 shows a crystallite size indicating (a) number distribution with respect to the crystallite size in the Si (111) direction of the silicon fine particles of the first embodiment. It is a graph which shows distribution and crystallite diameter distribution which shows (b) volume distribution. FIG. 9 shows the results obtained by analyzing the crystallite size distribution of the silicon fine particles after the pulverization step (S2) using the X-ray diffraction method. In each of FIGS. 9A and 9B, the horizontal axis represents the crystallite diameter (nm), and the vertical axis represents the frequency.

From the results shown in FIGS. 9A and 9B, in the number distribution, the mode diameter was 1.6 nm, and the median diameter (50% crystallite diameter) was 2.6 nm. In the volume distribution, the mode diameter was 6.3 nm and the median diameter was 9.9 nm. Accordingly, it was confirmed that the number distribution was 5 nm or less regardless of the mode diameter or the median diameter, and more specifically, a value of 3 nm or less was realized. It should be noted that the volume distribution was confirmed to be at least less than 50 nm, particularly 30 nm or less (more specifically, less than 20 nm), regardless of the mode diameter or median diameter. . Furthermore, in the example shown in FIG. 9, it was confirmed that an extremely small value of 10 nm or less was realized.

From the results shown in FIGS. 9A and 9B, the silicon fine particles obtained after the pulverization step (S2) using the bead mill method have an average crystallite diameter of about 20 nm or less, more specifically 10 nm. It was confirmed to be about 9.8 nm, which realizes the following. The crystallite size distribution of the silicon fine particles after the oxide film removing step (S3) is almost the same as that in FIG.

Accordingly, if the results of FIG. 9 and the results of FIGS. 5 to 7 are combined and analyzed, an aggregate or aggregate of silicon fine particles at least after the pulverization step (S2) or the oxide film removal step (S3). The product can be said to be in a state in which so-called thin layer silicon fine particles having a major axis of about 100 nm or less are folded into a multi-layer petal shape or a scale shape. As can be seen from FIGS. 8 and 9, the silicon fine particles are mainly composed of crystallites having a major axis of about 20 nm or less, more narrowly 10 nm or less.

Also, it can be seen that the silicon fine particles of the present embodiment include silicon fine particles having a crystallite diameter of 1 nm or less as shown in FIG. Interestingly, it was also confirmed that the average crystallite size in the volume distribution of the silicon fine particles of the present embodiment is about 10 nm. This numerical value can be said to be a very small value. Further, as described above, by further investigation, it was confirmed that the apparent volume diameter of the silicon fine particles was in the range of about 100 nm or less. In particular, ultrafine silicon particles having a major axis of about 20 nm or less, more narrowly 10 nm or less, particularly 5 nm or less in a narrow sense, or aggregates or aggregates thereof are formed on the surface of the carbon substrate 101. Alternatively, the charge / discharge cycle characteristics as a negative electrode material of a lithium ion battery, which will be described later, can be improved with higher accuracy by contacting, adhering, or embedding a part thereof. As will be described later, the fact that at least part of the surface of these fine silicon particles is covered with carbon increases the electrical conductivity between the silicon fine particles, and higher charge capacity value and discharge capacity value, In addition, this contributes to realizing excellent charge / discharge cycle characteristics.

In addition, as shown in FIG. 8, about the silicon | silicone fine particle after the grinding | pulverization process (S2) of this embodiment, the crystalline silicon | silicone fine particle whose surface orientation is (111) mainly has a multilayer petal shape or scale shape. It can be said that they are aggregates or aggregates in a state of being folded in multiple layers. Further, according to the study by the present inventor, very interestingly, the intensity of the diffraction peak attributed to Si (111) near 2θ = 28.4 ° after the pulverization step (S2) is the intensity of other diffraction peaks. It is confirmed that it is larger than (for example, the peak intensity of Si (220) or Si (311)). In addition, the arrangement interval of Si (111) in the crystal lattice of the silicon fine particles after the pulverization step (S2) is 0.31 nm (3.1 cm) as shown in FIG.

The fine silicon particles after the crushing step (S2) or the oxide film removing step (S3) of the present embodiment or the aggregates or aggregates thereof are brought into contact with and attached to the surface of the carbon substrate 101 or inside thereof, or By embedding a part, high performance of the negative electrode material of the lithium ion battery can be realized. More specifically, when lithium ions (Li ⁺ ) ionized from the positive electrode material of the lithium ion battery reached the negative electrode, the lithium ions (Li ⁺ ) folded in multiple layers in a multi-layered petal shape or scale shape. A unique effect can be obtained in that it easily enters and exits the gap between the aggregates or aggregates in the state.

4). Regarding the method for coating silicon fine particles or aggregates or aggregates thereof on a carbon substrate In the present embodiment, the above-described carbon substrate 101 and the above-mentioned silicon fine particles 201 or aggregates or aggregates thereof (that is, silicon) A mixing step of mixing the fine particles 201) is performed. Specifically, using the bead mill (pulverizer 20) used in the pulverization step (S2), without introducing beads, the carbon substrate 101 and the silicon fine particles 201 and the like described above Was mixed for about 1 hour. According to the inventors, the mixing ratio of the carbon base material 101 and silicon fine particles 201 or the like, or the amount of carbon covering the surface of the silicon fine particles 201 or the like, or silicon fine particles or the like, as will be described later. The knowledge that the electric capacity can be adjusted by adjusting the amount of carbon that covers the entire structure in which 201 is brought into contact with the surface of the carbon base material 101 or inside thereof, or a part of the structure is embedded therein, is known. Has been obtained. In the present embodiment, the “coating” of the silicon fine particles 201 on the carbon base material 101 means that the silicon fine particles 201 are in contact with and adhere to the carbon base material 101 or in the carbon base material 101. It means that it is buried.

Specifically, a total of 150 g of the object to be processed, in which the carbon material 101 and silicon fine particles 201 are mixed by 50 wt%, together with IPA (isopropyl alcohol) as a solvent, is combined with a bead mill (in this embodiment, , Manufactured by Ashizawa Finetech Co., Ltd., model DMS65). At this time, the mixing ratio of the object to be processed and IPA was 70 wt% (350 g) for IPA with respect to 30 wt% for the object to be processed. Thereafter, treatment with a bead mill for about 2 hours (for example, by carrying out a rotation speed of 2800 rpm, the carbon substrate was coated with silicon fine particles or aggregates or aggregates thereof.

By the way, since the silicon fine particles 201 or aggregates or aggregates thereof (that is, silicon fine particles 201) have a multi-layered petal-like or scale-like shape as shown in FIG. There is a possibility that it is big and is easy to get rid of. Therefore, in order to disperse this more accurately, the silicon fine particles 201 and the bead mill are mixed and stirred before the mixing step of mixing the carbon substrate 101 and the silicon fine particles 201 is performed. Employing the process is a preferred embodiment. In addition, this stirring process leads not only to dispersion of silicon fine particles or aggregates or aggregates thereof but also to further pulverization by appropriately changing the conditions.

5. FIG. 10 is a conceptual diagram of a structure in which silicon fine particles 201 or aggregates or aggregates thereof are coated with carbon. FIG. As shown in FIG. 10, covering the surface of silicon fine particles 201 or the like with a carbon coating layer 301 is also a preferred embodiment that can be adopted.

Since the carbon coating layer 301 of the present embodiment has electrical conductivity, electrical conduction between particles such as silicon fine particles 201 can be improved with high accuracy. Although FIG. 10 shows a state in which the entire surface of the silicon fine particles 201 or the like is covered with the carbon coating layer 301, the present embodiment is not limited to such a mode. For example, even if a part of the surface of the silicon fine particle 201 or the like is covered with the carbon coating layer 301, at least a part of the effect can be achieved.

FIG. 11 is a conceptual diagram schematically showing a device configuration for forming the carbon coating layer 301.

As shown in FIG. 11, silicon fine particles 201 or aggregates or aggregates thereof placed on a sample boat are accommodated in a reactor, and the sample boat is installed near the center of the reactor. An example of the reaction furnace of this embodiment is a quartz tube. The size of the reactor of this embodiment is 5 cm in diameter and 40 cm in length.

Using the hydrogen gas (H ₂ ) line shown in FIG. 11, hydrogen gas was flowed at a flow rate of 200 mL / min, and the temperature of the reactor was increased from room temperature to 1000 ° C. at a rate of 10 ° C./min. . Then, it hold | maintained on 1000 degreeC temperature conditions for 1 hour. By this heat treatment step, it is possible to reduce the natural oxide film formed on the surface of the silicon fine particles 201 or their aggregates or aggregates.

Thereafter, the hydrogen line was closed using a cock, and argon gas (Ar) was flowed at a flow rate of 200 mL / min, and the temperature was lowered to 800 ° C. at a rate of 10 ° C./min. When the temperature reached 800 ° C., the carbon coating layer 301 was grown for 1 hour by introducing propylene gas (C ₃ H ₆ ) at a flow rate of 10 mL / min and introducing a flow rate of argon gas at 190 mL / min. . Thereafter, the propylene gas line was closed, and the argon gas was kept at a flow rate of 200 mL / min for 15 minutes, and then naturally cooled. By these treatments, it is possible to form a structure in which silicon fine particles 201 or a part or all of aggregates or aggregates thereof are covered with a carbon coating layer 301 (film thickness 5 nm) having a nanographene multilayer structure.

6). FIG. 12 shows a method of coating the entire structure in which silicon fine particles 201 or the like are brought into contact with or embedded in the surface of the carbon base material 101. FIG. Or it is the schematic diagram of the structure which coat | covered the whole structure which contacted the inside or embedded the part further using the carbon coating layer 302. FIG.

In FIG. 12, a structure in which silicon fine particles 201 or the like are brought into contact with the surface of carbon substrate 101 or inside thereof, or a part of the structure is embedded (or inserted) is further covered with carbon coating layer 302. Is conceptually depicted. The structure shown in FIG. 12 can be manufactured, for example, by forming the carbon covering layer 302 after manufacturing the structure shown in FIG. In this way, by further covering with the carbon coating layer 302, further improvement in electrical conductivity can be realized.

Silicon fine particles or the like 201 (or a structure in which the surface of silicon fine particles or the like 201 is covered with the carbon coating layer 301) is brought into contact with the surface of the carbon substrate 101 or inside thereof, or a part thereof is embedded (or inserted). ) A method of further forming the carbon coating layer 302 on the structure is as follows.

A typical example is the same method as the method of providing the carbon coating layer 301 on the surface of the silicon fine particle 201 or the like already described, and therefore a duplicate description can be omitted.

First, silicon fine particles 201 (or a structure in which the surface of the silicon fine particles 201 is covered with the carbon coating layer 301) is brought into contact with the surface of the carbon substrate 101 or the inside thereof on the sample boat shown in FIG. A partially embedded (or inserted) structure is placed, and the sample boat is installed near the center of the reactor.

Thereafter, similarly to the method of providing the carbon coating layer 301 on the surface of the silicon fine particles 201 or the like, a heat treatment at 1000 ° C. in an atmosphere of hydrogen gas, and a temperature lowering treatment to 800 ° C. in a state where argon gas is introduced into the reaction furnace. In addition, a growth process of the carbon coating layer 302 is performed for one hour in a state where propylene gas and argon gas are introduced into the reaction furnace. Finally, the propylene gas line is closed, and the argon gas is kept at a flow rate of 200 mL / min for 15 minutes, and then naturally cooled. As a result, silicon fine particles 201 or the like (or a structure in which the surface of the silicon fine particles 201 is covered with the carbon coating layer 301) is brought into contact with or embedded in the surface of the carbon substrate 101 (or A structure in which a part or all of the (inserted) structure is covered with the carbon coating layer 302 having a nanographene multilayer structure can be formed.

FIG. 13 is a scanning electron micrograph of the negative electrode material of Example 1. In Example 1, the structure in which the surface of the silicon fine particle 201 or the like shown in FIG. 10 is covered with the carbon coating layer 301 is brought into contact with or partially on the surface of the carbon base material 101 which is an artificial graphite particle. The entire structure is embedded. The longest diameter of the artificial graphite particles in Example 1 is 33 μm.

FIG. 14 is a further enlarged scanning electron micrograph of the negative electrode material of Example 1. FIG. 14 is an enlarged view of the silicon fine particles 201 attached to the surface of the carbon substrate 101 (artificial graphite particles) shown in FIG. 13 or a part of the aggregate or aggregate thereof. In this example, the average thickness of the silicon fine particles 201 or aggregates or aggregates thereof is 30 nm, and the average longest diameter is 300 nm. The reason why the silicon microparticles 201 shown in FIG. 9 are used as a starting material is that the silicon microparticles 201 are mixed with each other in the process of mixing the silicon microparticles 201 with the carbon substrate 101. Furthermore, it is considered that it is because of aggregation or aggregation.

FIG. 15 is a scanning electron micrograph showing an example of the structure shown in FIG. 14 that is easy to see by removing some of the silicon fine particles 201 and the like. In FIG. 15, a portion where the silicon fine particles 201 or the aggregates or aggregates thereof are considered to be in contact with or partially embedded in the surface of the carbon substrate 101 or inside thereof is indicated by arrows. By forming the structure shown in this photograph, the bond between the carbon base material 101 and the silicon fine particles 201 or the aggregates or aggregates thereof is strengthened. In addition, the bonding state between the carbon substrate 101 and the silicon fine particles 201 can be maintained.

Further, silicon fine particles 201 existing in the vicinity of the surface of the carbon substrate 101 can be further bonded to the surrounding silicon fine particles 201 or aggregates or aggregates thereof by van der Waals force. As a result, even if the silicon fine particles 201 and the like are located away from the carbon base material 101, a sufficient bonding state with the carbon base material 101 can be maintained without being electrically independent. Note that FIG. 15 shows a state in which a part of the silicon fine particles 201 or the like bonded by van der Waals force is removed.

In order to obtain the above-described structure, the silicon fine particles 201 or aggregates or aggregates thereof are brought into contact with the surface of the carbon base material 101 or the inside thereof in a state of being almost uniformly dispersed without becoming “dama”. It is a preferred embodiment that a part or a part is embedded. When the silicon fine particles 201 are dispersed as finer particles, it is considered that a state is formed in which the carbon base material 101 is more easily contacted and embedded in the carbon base material 101 (for example, easily pierced). . As already described, in order to disperse the silicon fine particles 201 with higher accuracy, it is preferable to carry out a process such as stirring and dispersing the silicon fine particles 201 together with a bead mill or the like.

FIG. 16 shows the result of calculating the silicon weight ratio dependency of the electric capacity. In the calculation, the carbon (C) is assumed to have a stoichiometric composition of LiC ₆ when charged with lithium ions, and its electric capacity is 372 mAh / g. As for silicon (Si), assuming that the stoichiometric composition at the time of filling with lithium ions is Li ₁₅ Si ₄ and its electric capacity is 3577 mAh / g (broken line in FIG. 16), Li Assuming ₂₂ Si ₅ , the calculation was made for both the case where the electric capacity was 4197 mAh / g (solid line in FIG. 16). Note that the horizontal axis Si / (Si + C) Si in FIG. 16 represents the weight of the silicon fine particles 201 and the like, and the horizontal axis C in FIG. 16 represents the total weight of the carbon base material 101, the carbon coating layers 301, 302, and the like. It is.

As shown in FIG. 16, it was found that by changing the weight ratio of the silicon fine particles 201 and the like, it is possible to control a wide range from a carbon specific capacitance to a silicon specific capacitance. A suitable numerical range that can be actually used is a silicon weight ratio of 5 wt% or more and 95 wt% or less. However, from the viewpoint of higher accuracy and improving the coverage with carbon, it is a preferred embodiment that a numerical range of 5 wt% or more and 50 wt% or less is adopted.

<Second Embodiment>
1. About Structure and Manufacturing Method of Lithium Ion Battery In this embodiment, the structure and manufacturing method of the lithium ion battery 1000 shown in FIG. 17 will be described.

As shown in FIG. 17, the lithium ion battery 1000 of this embodiment includes a positive electrode 1101, a separator 1102, a negative electrode 1103, a battery can 1104, a positive electrode current collector tab 1105, a negative electrode current collector tab 1106, an inner lid 1107, and an internal pressure release valve 1108. , A gasket 1109, a positive temperature coefficient (TPC) resistance element 1110, and a battery lid 1111. Note that the battery lid 1111 of this embodiment is an integrated part including an inner lid 1107, an internal pressure release valve 1108, a gasket 1109, and a temperature coefficient resistance element 1110.

For example, the positive electrode 1101 can be manufactured by the following procedure. In this example, LiMn ₂ O ₄ is employed as the positive electrode active material.

First, 7.0 wt% and 2.0 wt% of graphite powder and acetylene black are added as conductive materials to 85.0 wt% of the positive electrode active material, respectively. Further, a 6.0 wt% polyvinylidene fluoride (hereinafter abbreviated as PVDF) solution in 1-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) was added as a binder, and a planetary mixer was used. And mix.

Thereafter, air bubbles in the slurry are removed under vacuum to prepare a homogeneous positive electrode mixture slurry. This slurry is uniformly and evenly applied to both surfaces of an aluminum foil having a thickness of 20 μm using a known applicator. After the application, compression molding is performed using a roll press so that the electrode density is 2.55 g / cm ³ . After compression molding, the positive electrode 1101 having a thickness of 100 μm, a length of 900 mm, and a width of 54 mm can be manufactured by cutting using a cutting machine.

For example, the negative electrode 1103 can be manufactured by the following procedure. In this example, as the negative electrode material (negative electrode active material), the negative electrode material made of the carbon material coated with the silicon fine particles 201 or the aggregates or aggregates thereof described in the first embodiment may be adopted. it can.

First, 5.0 wt% PVDF (solution dissolved in NMP) is added as a binder to 95.0 wt% of the negative electrode material. They are mixed using a planetary mixer.

Thereafter, a uniform negative electrode mixture slurry is prepared by removing bubbles in the slurry under vacuum. This slurry is uniformly and evenly applied to both surfaces of a rolled copper foil having a thickness of 10 μm using a known applicator. After the application, compression molding is performed using a roll press. The electrode density at this time is 1.3 g / cm ³ . After compression molding, the negative electrode 1103 having a thickness of 110 μm, a length of 950 mm, and a width of 56 mm can be produced by cutting with a cutting machine.

The positive electrode current collecting tab 1105 and the negative electrode current collecting tab 1106 are ultrasonically welded to the uncoated portions (current collector exposed surfaces) of the positive electrode 1101 and the negative electrode 1103 manufactured by the above-described manufacturing method, respectively. Note that an aluminum lead piece can be used for the positive electrode current collecting tab 1105, and a nickel lead piece can be used for the negative electrode current collecting tab 1106.

Thereafter, a separator 1102 made of a porous polyethylene film having a thickness of 30 μm is inserted into the positive electrode 1101 and the negative electrode 1103, whereby the positive electrode 1101, the separator 1102, and the negative electrode 1103 are wound to produce a wound body. After the wound body is stored in the battery can 1104, the negative electrode current collecting tab 1106 is connected to the bottom of the battery can 1104 using a resistance welder. On the other hand, the positive electrode current collecting tab 1105 is connected to the bottom surface of the inner lid 1107 by ultrasonic welding.

Before attaching the upper battery lid 1111 to the battery can 1104, a non-aqueous electrolyte is injected. The solvent of the electrolyte solution of this embodiment consists of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC), for example. An example of the volume ratio of the three materials mentioned above is 1: 1: 1. Further, the electrolyte of the present embodiment is LiPF ₆ having a concentration of 1 mol / L (about 0.8 mol / kg). After the electrolytic solution is dropped from above the wound body, the battery lid 1111 is caulked and sealed in the battery can 1104, whereby the lithium ion battery 1000 can be manufactured.

2. About the evaluation result of a lithium ion battery The measurement of the discharge capacity and the maintenance factor of the lithium ion battery 1000 was performed under conditions of a constant current mode at a speed of 1C.

[Comparative Example 1]
Here, as Comparative Example 1, instead of the carbon-coated silicon fine particles 201 employed in Example 1, carbon-coated spherical silicon nanoparticles were employed, and the same method as in Example 1 was used. evaluated.

The average major axis of artificial graphite as the carbon substrate 101 is 20 μm, and the average major axis of the silicon fine particles 201 is 60 nm. An example of the silicon weight ratio in the lithium ion battery 1000 is 15.6 wt%. In addition, charging / discharging was performed at a speed of 1C. A composite material of the carbon base material 101 (artificial graphite) and silicon fine particles 201 of the present embodiment, more specifically, a part of the silicon fine particles 201 or the aggregate or aggregate of the silicon fine particles 201 When a part of the structure in contact with the carbon base material 101 or embedded in the carbon base material 101 was used, the capacity retention rate after 100 cycles was 91.0%. On the other hand, the capacity retention rate of the composite material of artificial graphite and carbon-coated spherical silicon nanoparticles was 48.7%.

Table 1 shows the results of evaluating the lithium ion batteries of Example 1 and Comparative Example 1. FIG. 18 is a graph showing the results of evaluating the lithium ion batteries of Example 1 and Comparative Example 1. As a result, it was revealed that the maintenance rate of the lithium ion battery 1000 of Example 1 was markedly superior to that of Comparative Example 1. More specifically, in Example 1, it was found that even when the number of cycles reached 100, the maintenance rate could be 90% or more, more specifically 91% or more. . In addition, it can be seen that the maintenance rate of the lithium ion battery 1000 of Example 1 achieves a maintenance rate that is 40% or more higher than the result of Comparative Example 1.

<Other embodiment (1)>
By the way, in each of the above-described embodiments, as a starting material, a single-crystal or polycrystalline silicon lump or silicon chips formed in the cutting process of an ingot is exemplified, but other forms of silicon are exemplified. It is another aspect in which chips and the like are used as a starting material. Specifically, silicon chips and the like are not necessarily formed in the cutting process of silicon ingots in the production process of semiconductor products. It is also possible to cut them randomly or randomly. In addition, so-called silicon waste materials such as silicon chips and silicon polishing scraps that are normally discarded can be used as starting materials for the silicon fine particles in each of the above-described embodiments. Also, fine waste obtained by pulverizing a waste wafer or the like may be included. Further, fine silicon particles using a starting material such as metallic silicon chips or metallic silicon polishing scraps or other metallic silicon particles may be employed.

<Other embodiment (2)>
Further, the impurity concentration of the n-type crystalline silicon in each of the above embodiments is not particularly limited. Further, not only n-type but also p-type crystalline silicon can be employed. Furthermore, crystalline silicon which is a genuine semiconductor can also be employed as the crystalline silicon in each of the embodiments described above. Note that since movement of electrons in the negative electrode material of the lithium ion battery is emphasized, it is more preferable to use crystalline silicon containing an n-type impurity.

<Other embodiment (3)>
Further, as an alternative device to the negative electrode material and negative electrode manufacturing apparatus 500 shown in FIG. 3 in the first embodiment, the negative electrode manufacturing apparatus 200 of the lithium ion battery shown in FIG. 19 is adopted. Also good. Specifically, from the viewpoint of simplification of equipment and / or reduction of manufacturing cost, in the negative electrode manufacturing apparatus 200 for a lithium ion battery, a cleaning machine for cleaning silicon chips formed in the cutting process of silicon. Reference numeral 10 denotes an aspect also serving as a pulverizer 20 that forms fine silicon particles by pulverizing washed silicon chips and the like. Accordingly, in the apparatus / method shown in FIG. 19, for example, a relatively large-diameter bead is used in the cleaning process, and a relatively small-diameter bead is used in the pulverization process, so that the negative electrode material of the lithium ion battery is used. Silicon fine particles will be obtained. However, in order to obtain the silicon fine particles described in the first embodiment with higher accuracy, the silicon fine particles are formed by the bead mill machine after the processing using the ball mill machine as in the first embodiment. It is preferable to do.

The disclosure of each of the above-described embodiments is described for explaining the embodiments, and is not described for limiting the present invention. In addition, modifications that exist within the scope of the technical idea of the present invention including other combinations of the embodiments are also included in the scope of the claims.

The negative electrode material of the lithium ion battery and the lithium ion battery including the same of the present invention include, for example, various power generation or power storage devices (including small household power storage devices and large power storage systems), smartphones, portable information terminals, and portable electronics. Equipment (cell phones, portable music players, notebook computers, digital cameras / videos), electric vehicles, hybrid electric vehicles (HEV) or plug-in hybrid electric vehicles (PHEV), motorcycles powered by motors, motors The present invention can be applied to various devices or apparatuses including a motor tricycle as a power source, other transport machines or vehicles.

Claims (14)

1. Silicon fine particles having a volume distribution with a mode diameter and median diameter of less than 50 nm, or aggregates or aggregates thereof, a part of the silicon fine particles in a state of being folded into a multi-layer petal shape or a scale shape, or the silicon A part of the aggregate or aggregate of fine particles is in contact with or embedded in the carbon substrate;
   A negative electrode material for lithium ion batteries.
2. The carbon substrate includes artificial graphite or natural graphite,
   The negative electrode material of the lithium ion battery according to claim 1.
3. The mode diameter and median diameter of the silicon fine particles or aggregates or aggregates thereof have a volume distribution of less than 20 nm.
   The negative electrode material of the lithium ion battery according to claim 1 or 2.
4. The average longest particle diameter of the carbon substrate is 1 μm or more and 50 μm or less,
   The negative electrode material of the lithium ion battery according to claim 1 or 2.
5. The average longest particle diameter of the carbon substrate is 5 μm or more and 30 μm or less.
   The negative electrode material of the lithium ion battery according to claim 1 or 2.
6. The weight ratio of the silicon fine particles to the total weight of the silicon fine particles and the carbon substrate is 5 wt% or more and 95 wt% or less.
   The negative electrode material of the lithium ion battery according to claim 1 or 2.
7. The silicon fine particles or the aggregates or aggregates thereof are formed by pulverizing crystalline silicon that is chips or cutting scraps cut by a fixed abrasive wire.
   The negative electrode material of the lithium ion battery according to claim 1 or 2.
8. The silicon fine particles or aggregates or aggregates thereof are coated with carbon,
   The negative electrode material for a lithium ion battery according to any one of claims 1 to 7.
9. The carbon substrate and the silicon fine particles or aggregates or aggregates thereof are all coated with carbon.
   The negative electrode material for a lithium ion battery according to any one of claims 1 to 7.
10. A positive electrode and a negative electrode are provided, and the negative electrode has the negative electrode material for a lithium ion battery according to any one of claims 1 to 9.
    Lithium ion battery.
11. By pulverizing crystalline silicon, which is a chip or cutting scraped by a fixed abrasive wire, silicon fine particles having a volume distribution with a mode diameter and a median diameter of less than 50 nm, or aggregates or aggregates thereof are formed. Crushing process;
    The carbon substrate and the silicon fine particles or the aggregate so that a part of the silicon fine particle or the aggregate or the aggregate is in contact with the carbon substrate or embedded in the carbon substrate. Or a mixing step of mixing the assembly.
    A method for producing a negative electrode material for a lithium ion battery.
12. The silicon fine particles or the aggregates or the aggregates have a volume distribution with a mode diameter and a median diameter of less than 20 nm.
    The manufacturing method of the negative electrode material of the lithium ion battery of Claim 11.
13. In the pulverization step, the silicon fine particles or the aggregates or the aggregates are formed by pulverizing the crystalline silicon with a bead mill.
    The manufacturing method of the negative electrode material of the lithium ion battery of Claim 11 or Claim 12.
14. The method further includes a stirring step of mixing and stirring the silicon fine particles or the aggregates or the aggregates and the bead mill before the mixing step.
    The method for producing a negative electrode material for a lithium ion battery according to any one of claims 11 to 13.

Images