JPWO2016056373A1 - Negative electrode material for lithium ion battery, lithium ion battery, method for manufacturing negative electrode or negative electrode material for lithium ion battery, and apparatus for manufacturing the same - Google Patents

Abstract

The negative electrode material of one lithium ion battery of the present invention has a volume distribution with a mode diameter and a median diameter of less than 50 nm, and at least a part of the surface is covered with carbon fine particles or aggregates or aggregates thereof. It is formed using. Further, the negative electrode material of another lithium ion battery of the present invention is formed using silicon fine particles or aggregates or aggregates thereof, at least part of which is covered with carbon, and has a multi-layer petal shape or The agglomerates or aggregates of the silicon fine particles in a scale-like state are included. By employing each of the negative electrode materials described above, a lithium ion battery with little change in charge / discharge capacity can be obtained even when charge / discharge is repeated.

Description

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

Conventionally adopted lithium-ion batteries use a negative electrode active material (hereinafter also referred to as “negative electrode material”) graphite (natural graphite, artificial graphite, etc.) and a negative electrode material as a binder on the negative electrode side. It has a negative electrode with a mixed material layer. Further, the positive electrode side is formed by binding a positive electrode material and a positive electrode active material lithium (Li) oxide powder (LiCoO ₂ , LiNiO ₂ , LiMnO _2, etc.) and conductive graphite (mainly carbon black, etc.) to a binder (PVDF : Polyvinylidene fluoride, etc.) and a positive electrode provided with a mixture layer formed by coating. The cell container of the lithium ion battery is filled with an electrolytic solution, and a separator (mainly a polyolefin-based porous material or a porous polypropylene sheet) is provided between the negative electrode material and the positive electrode material. It has been.

  The above-described separator is provided so as to allow the electrolyte solution to pass therethrough and cause lithium ions to move, and to separate the electrodes from each other so that an electrical short circuit does not occur.

  Charging and discharging of a lithium ion battery is performed by moving lithium ions between a negative electrode material and a positive electrode material in an electrolytic solution. Lithium ions move to the negative electrode side during charging, and lithium ions move to the positive electrode side during discharging. Charging is performed through an externally connected power source, and discharging is performed through an externally connected resistor (load).

  By the way, in the field of lithium ion batteries, in recent years, a technique has been disclosed in which silicon particles are used as a negative electrode active material instead of the above graphite. For example, as an example of silicon particles, a powder having a diameter of about 38 microns (μm) or less formed by pulverizing single crystal silicon with a mortar and classifying it with a mesh is heated at 30 ° C./min in an argon atmosphere. Some have been heated to a temperature of 150 ° C. (reached temperature) (see 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 less, particularly 500 to 800 ° C., and the particle size of the formed silicon particles is adjusted and collected in an aqueous zinc chloride solution. It has been disclosed that high-purity silicon particles having a particle diameter of about 1 to 100 μm are obtained by this work and that it is used (see Patent Document 2).

JP 2005-032733 A JP 2012-101998 A

  However, in the prior art, when silicon particles are used as the negative electrode material, the electric capacity in charge / discharge can be increased, but on the other hand, lithium is occluded / released into the silicon particles, and the silicon particles change in volume. Or will be destroyed. As a result, there is a problem that the charge / discharge cycle characteristics cannot be maintained.

  In addition, in the case of silicon particles disclosed in the above-mentioned prior art documents, 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. Therefore, the silicon particles disclosed heretofore have a significant problem that the negative electrode characteristics of the lithium ion battery are poor and the industrial utility is not yet sufficient. That is, development of lithium ion batteries using silicon particles is still in progress.

  The present invention solves at least a part of various problems related to charge / discharge cycle characteristics, etc., which a negative electrode material using conventional silicon particles has, and thereby provides a negative electrode material for a high-performance lithium ion battery, a lithium ion battery, It can greatly contribute to the provision of a method for manufacturing a negative electrode or a negative electrode material of a lithium ion battery and a manufacturing apparatus therefor.

  The negative electrode material of one lithium ion battery of the present invention has a volume distribution with a mode diameter and a median diameter of less than 50 nm, and at least a part of the surface is covered with silicon fine particles or aggregates thereof. It is formed using an aggregate.

  Further, the negative electrode material of another lithium ion battery of the present invention is formed using silicon fine particles or aggregates or aggregates thereof, at least part of which is covered with carbon, and has a multi-layer petal shape or The agglomerates or aggregates of the silicon fine particles in a scale-like state are included.

  By adopting each of the above-described negative electrode materials, it is possible to realize a lithium ion battery with little change in charge / discharge capacity even when charge / discharge is repeated, in other words, good charge / discharge cycle characteristics. Alternatively, an increase in charge / discharge capacity can be realized.

  In addition, the silicon fine particles or the aggregates or aggregates thereof, which are the negative electrode materials described above, are usually treated as industrial waste, for example, when a molten or solidified lump of silicon or an ingot is shaved with a fixed abrasive wire. It is worthy of special mention that the chip or cutting waste that has been used can be used as a starting material. In addition, the silicon fine particles formed by pulverizing the chips or chips with a ball mill and / or a bead mill, or aggregates or aggregates thereof, have a high level of charge / discharge cycle characteristics of a lithium ion battery. This is a preferred embodiment for realizing maintenance and / or improvement of characteristics thereof.

  Also, one lithium ion battery of the present invention has a volume distribution with a mode diameter and a median diameter of less than 50 nm, and at least a part of the surface is covered with carbon fine particles or aggregates or aggregates thereof. A negative electrode material formed by using is provided.

  In addition, another lithium ion battery of the present invention is formed using silicon fine particles or aggregates or aggregates thereof, at least a part of which is covered with carbon, and has a multi-layered petal shape or scale shape. A negative electrode material comprising the agglomerates or aggregates of the silicon fine particles in a folded state;

  According to the above-described lithium ion battery, it is possible to reduce the change in charge / discharge capacity even when charge / discharge is repeated. Alternatively, it is possible not only to maintain the charge / discharge cycle characteristics at a high level and / or to improve the characteristics, but also to increase the charge / discharge capacity.

  In addition, the negative electrode material manufacturing apparatus for a lithium ion battery according to the present invention includes a silicon fine particle having a volume distribution with a mode diameter and a median diameter of less than 50 nm, or an aggregate or aggregate thereof by grinding crystalline silicon. And a coating forming part for forming carbon covering at least a part of the surface of the silicon fine particles or the aggregates or the aggregates.

  Further, another apparatus for producing a negative electrode material of a lithium ion battery according to the present invention is a multi-layer petal-like or scaly-like shape by pulverizing crystalline silicon that is a chip or cutting scraped by a fixed abrasive wire. A pulverized portion for forming the silicon fine particles so as to include an aggregate or aggregate of the silicon fine particles in a folded state, and at least a part of the surface of the silicon fine particles or the aggregate or aggregate. A covering forming part for forming carbon to be covered.

  According to the above-described apparatus for producing a negative electrode material for a lithium ion battery, it is possible to realize a lithium ion battery that has little change in charge capacity and / or discharge capacity even when charge and discharge are repeated, in other words, good charge / discharge cycle characteristics. Or contribute to the manufacture of a lithium ion battery that can realize an increase in charge / discharge capacity.

  In addition, the negative electrode manufacturing apparatus of one lithium ion battery according to the present invention pulverizes crystalline silicon so that silicon fine particles or agglomerates thereof, which have a volume distribution with a mode diameter and a median diameter of less than 50 nm, are obtained. A pulverizing part for forming a product or an aggregate, and a coating forming part for forming carbon covering at least a part of the silicon fine particles or the aggregate or the surface of the aggregate.

  Moreover, the manufacturing apparatus of the negative electrode of another lithium ion battery of the present invention is formed into a multi-layer petal shape or a scale shape by pulverizing crystalline silicon which is a chip or cutting waste cut out by a fixed abrasive wire. A pulverized portion for forming the silicon fine particles as a negative electrode material so as to include an aggregate or aggregate of the silicon fine particles in a folded state, and on the surface of the silicon fine particles, the aggregate or the aggregate And a coating forming part for forming carbon covering at least a part thereof.

  According to the negative electrode manufacturing apparatus for a lithium ion battery described above, it is possible to realize a lithium ion battery that has little change in charge capacity and / or discharge capacity even when charge and discharge are repeated, in other words, good charge / discharge cycle characteristics. Or it can contribute to manufacture of the lithium ion battery which can implement | achieve the increase in charging / discharging capacity | capacitance.

  The method for producing a negative electrode material for a lithium ion battery according to the present invention also includes fine silicon particles or aggregates or aggregates thereof having a volume distribution with a mode diameter and a median diameter of less than 50 nm by grinding crystalline silicon. And a coating forming step of forming carbon covering at least part of the surface of the silicon fine particles or the agglomerates or aggregates.

  Moreover, the manufacturing method of the negative electrode material of another lithium ion battery of this invention is a multilayer petal shape or scale shape by grind | pulverizing the crystalline silicon which is the chip or cutting waste scraped off by a fixed abrasive wire. A pulverization step of forming the silicon fine particles so as to include an aggregate or aggregate of silicon fine particles in a state of being folded, and at least a part of the surface of the silicon fine particles or the aggregate or aggregate Forming a covering carbon.

  According to the above-described method for producing a negative electrode material for a lithium ion battery, a change in charge capacity and / or discharge capacity is small even when charge and discharge are repeated, in other words, a lithium ion battery having good charge / discharge cycle characteristics is realized. Or contribute to the manufacture of a lithium ion battery that can realize an increase in charge / discharge capacity.

  In addition, the method for producing a negative electrode of one lithium ion battery according to the present invention is a method of pulverizing crystalline silicon, whereby fine silicon particles or agglomerates thereof serving as a negative electrode material having a volume distribution with a mode diameter and a median diameter of less than 50 nm are obtained. A pulverizing step for forming a product or an aggregate, and a coating forming step for forming carbon covering at least a part of the silicon fine particles or the aggregate or the surface of the aggregate.

  Moreover, the manufacturing method of the negative electrode of another lithium ion battery of the present invention is obtained by pulverizing crystalline silicon which is chips or cutting scraps cut out by a fixed abrasive wire, thereby forming a multi-layer petal shape or a scale shape. A pulverization step for forming the silicon fine particles as a negative electrode material so as to include an aggregate or aggregate of the silicon fine particles in a folded state, and on the surface of the silicon fine particles, the aggregate or the aggregate A coating forming step of forming carbon covering at least part of the carbon.

  According to the above-described method for manufacturing a negative electrode of a lithium ion battery, as the charge / discharge capacity increases, the charge capacity and / or the discharge capacity change little even when charge / discharge is repeated, in other words, the charge / discharge cycle characteristics are good. It can contribute to the manufacture of lithium ion batteries.

  In addition, the means for covering at least a part of the surface of each of the above silicon fine particles or the aggregates or aggregates thereof with carbon is not particularly limited. Representative examples of the means include means using a carbon film formed by thermal decomposition of hydrocarbons such as acetylene, means using a carbon film formed by a furnace method, and formed by a channel method. Means using a carbon film or means using a carbon film formed by plasma treatment.

  Note that the crystalline silicon in each of the above-described inventions includes not only single crystal silicon but also polycrystalline silicon. In addition, metallic silicon can be selected as the crystalline silicon in each of the above-described inventions.

  According to the negative electrode material of one lithium ion battery of the present invention, a change in charge / discharge capacity is small even when charge / discharge is repeated, in other words, a lithium ion battery having good charge / discharge cycle characteristics can be realized. In addition, an increase in charge / discharge capacity can be realized. In addition, according to one lithium ion battery of the present invention, not only can charging / discharging capacity change even if charging / discharging is repeated, in other words, charging / discharging cycle characteristics can be improved, but also charging / discharging. An increase in capacity can be realized. In addition, according to the manufacturing apparatus of one lithium ion battery of the present invention and the manufacturing method of one lithium ion battery of the present invention, even if charging / discharging is repeated, the change in charge / discharge capacity is small, in other words, charging / discharging. This can contribute not only to lithium ion batteries with good discharge cycle characteristics, but also to the manufacture of lithium ion batteries that can realize an increase in charge / discharge capacity.

It is a flowchart which shows the manufacturing process of the negative electrode material of the lithium ion battery of 1st Embodiment. It is a schematic diagram which shows the manufacturing apparatus and manufacturing process of the negative electrode material of the lithium ion battery of 1st Embodiment. It is a figure which shows the TEM (transmission electron microscope) image of an example of the silicon | silicone fine particle which passed through the coating formation process (S4) 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 graph which shows the result ((a) wide range, (b) limited range) of the X-ray-diffraction measurement of the silicon | silicone fine particle of 1st Embodiment, or its aggregate or aggregate. It is a schematic block diagram of the lithium ion battery of 2nd Embodiment. It is a graph which shows an example of the cycle characteristic of charge of the lithium ion battery of a 2nd embodiment. It is a graph which shows an example of the cycle characteristic of the discharge of the lithium ion battery of a 2nd embodiment. It is a graph which shows the cycling characteristics of the charge of the lithium ion battery as a reference example. It is a graph which shows the cycling characteristics of the discharge of the lithium ion battery as a reference example. About the lithium ion battery of 2nd Embodiment, it is a TEM image of the silicon fine particle after the charging / discharging cycle was performed 100 times, or its aggregate or aggregate. It is a schematic diagram which shows the manufacturing apparatus and manufacturing process of the negative electrode material of the lithium ion battery of other embodiment. It is a graph which shows the cycling characteristics of the charge of a lithium ion battery when the quantity of FEC in electrolyte solution in the lithium ion battery of other embodiments is changed. It is a graph which shows the cycling characteristics of the discharge of a lithium ion battery when the quantity of FEC in electrolyte solution in the lithium ion battery of other embodiments is changed. It is a graph which shows the cycle characteristic of charge of a lithium ion battery when the weight ratio of silicon (Si) and carbon (C) is changed in a lithium ion battery of other embodiments. It is a graph which shows the cycling characteristics of the discharge of a lithium ion battery when the weight ratio of silicon (Si) and carbon (C) is changed in the lithium ion battery of other embodiments.

1 Chips, etc. 2 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 60 Coating formation part 70 Mixing part 100 Lithium ion battery negative electrode material and negative electrode manufacturing apparatus 500 Lithium ion battery 510 Container 512 Negative electrode 514 Negative electrode material and negative electrode material 516 Positive electrode 518 Positive electrode material and positive electrode material 520 Separator 530 Electrolyte 540 power supply 550 resistance

  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>
FIG. 1 is a flow diagram showing a manufacturing process of a negative electrode material of the lithium ion battery of this embodiment. FIG. 2 is a schematic diagram showing a negative electrode material manufacturing apparatus and manufacturing process of the lithium ion battery of this embodiment.

A negative electrode material for a lithium ion battery according to the present embodiment, a lithium ion battery including the negative electrode material, and a method for manufacturing the negative electrode material include a silicon cutting process in the production process of a silicon wafer used for a semiconductor product such as a solar battery. Various processes using silicon chips or silicon cutting scraps or polishing scraps (hereinafter also referred to as “silicon chips or the like” or “chips or the like”) as waste materials in Is provided. 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), (2), (4) and (5). Moreover, the manufacturing method of the lithium ion battery of this embodiment can include the following step (3) as another aspect that can be adopted.
(1) Cleaning step (S1)
(2) Grinding step (S2)
(3) Oxide film removal step (S3)
(4) Coating formation process (S4)
(5) Negative electrode forming step (S5)

  As shown in FIG. 2, the negative electrode material and the negative electrode manufacturing apparatus 100 of the lithium ion battery according to the present embodiment mainly include a cleaning machine (cleaning and preliminary pulverizer) 10, a pulverizer 20, and a dryer (not shown). , Rotary evaporator 40, coating formation unit 60 for forming carbon covering at least a part of the surface of silicon fine particles or aggregates or aggregates thereof (hereinafter also referred to as “silicon fine particles”), and lithium The mixing part 70 which bears a part of negative electrode formation of an ion battery is provided. Moreover, the negative electrode material of the lithium ion battery and the negative electrode manufacturing apparatus 100 of the present embodiment can include an oxide film removal tank 50 and a centrifuge 58 as another aspect that can be adopted. 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. 2, 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, The 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 of 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 cleaning 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). Is further pulverized using a star mill LMZ015 manufactured by Ashizawa Fineting. 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 circulated using a pump 28 while the slurry is circulated. At 22 pulverization is performed. 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 fine pulverization process at 2908 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 the above among the pulverizers consisting of a group of ball mill, bead mill, jet mill, and shock wave pulverizer, or a combination of two or more. 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, 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 removal step (S3) of the present embodiment, a process is performed in which the silicon fine particles 2 obtained by the pulverization 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 centrifuge 58 separates the silicon fine particles from which part or all of the surface oxide has been removed from the hydrofluoric acid aqueous solution. 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 addition, when the removal process of the oxide which may exist on the surface of the silicon | silicone fine particle 2 is not performed, the process by the coating formation process (S4) and negative electrode formation process (S5) mentioned later is performed for a silicon | silicone fine particle.

  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.

(4) Coating formation process (S4)
In the present embodiment, a coating forming step is performed in which a part or all of the surface of the silicon fine particles that have passed or not passed through the oxide film removing step (S3) is covered with a carbon film. Therefore, since the silicon fine particles that have undergone the coating formation step (S4) of this embodiment are at least partially covered with carbon, the thickness is increased compared to silicon fine particles that are not covered with carbon. It will be. In addition, when the carbon of this embodiment is provided with conductivity, a negative electrode material having conductivity can be formed. Further, for example, by covering silicon fine particles with carbon having a film thickness of several nm to several μm, not only a thin negative electrode but also a relatively thick negative electrode can be easily formed. FIG. 3 shows a TEM (transmission type) as an example of silicon fine particles (partially enlarged view) or aggregates or aggregates (partially enlarged view) that have undergone the coating formation step (S4) of the present embodiment. (Electron microscope) image. The crystalline silicon shown in FIG. 3 mainly has a crystal plane orientation (111) (also simply referred to as “Si (111)” or “(111)”. The same applies to other plane orientations). Observed.

  In addition, for example, the internal stress of the negative electrode as a whole can be reduced by covering the silicon fine particles with carbon, and more microscopically, the internal stress of the individual silicon fine particles can be reduced. As a result, the production of the lithium ion battery can be made easier, and it can contribute to the improvement of the performance (for example, charge / discharge cycle characteristics) of the lithium ion battery.

  In addition, by forming a negative electrode material for a lithium ion battery using silicon fine particles at least part of which is covered with carbon, a charge capacity value and a discharge capacity compared to silicon fine particles not covered with carbon. It is also possible to increase the value. For example, according to the study by the present inventors, in the case of silicon fine particles not covered with carbon, for example, when the thickness of the negative electrode material is about 30 μm, the charge capacity value and the discharge capacity value are 500 (mAh). / G). However, by using silicon fine particles in which at least a part of the surface is covered with carbon, the charge capacity value and the discharge capacity value are increased more than twice (typically about 3 to about 5 times). be able to.

  By the way, in the coating forming step (S4) of the present embodiment, means for coating a part or all of the surface of the silicon fine particles (in other words, at least a part on the surface) with the carbon film is not particularly limited. . For example, a method of covering at least a part of the surface of the silicon fine particles 2 with carbon by a thermal CVD method which is an example of a chemical vapor deposition method can be employed. Specifically, at least a part on the surface of the silicon fine particles 2 is carbonized by heating the silicon fine particles 2 at about 600 ° C. or more and about 1200 ° C. or less in an atmosphere containing an organic gas and / or its vapor. It can be covered with a film. Therefore, the thermal CVD apparatus which is an example of the chemical vapor deposition apparatus is an aspect of the coating forming unit 60 that can be employed in the coating forming step (S4) of the present embodiment. Examples of materials (or raw materials) that can be employed in the thermal CVD method include one or more selected from the group of methane, ethane, acetylene, ethylene, propane, butane, butene, pentane, isobutane, and hexane. It is a hydrocarbon and / or one or more known aromatic hydrocarbons. In addition, the point which can thermally decompose acetylene at about 400 degreeC by employ | adopting copper or a copper alloy as a catalyst can contribute to the reduction in processing temperature.

  As described above, typically, hydrocarbon gas is pyrolyzed on or in the vicinity of heated silicon fine particles 2 and carbonized, whereby at least a part of the surface of silicon fine particles 2 is carbonized. It can be said that the coating with the film is a technique excellent in productivity and industrial efficiency while realizing an example of a suitable carbon film in the present embodiment. Note that a low-pressure thermal CVD method or a plasma CVD method, which is another example of the chemical vapor deposition method, can also be appropriately employed.

  Another example of a method for covering at least a part of the surface of the silicon fine particle 2 with a carbon film is as follows. First, a known organic compound (such as chlorinated polyethylene elastomer) or a mixture of the organic compound and graphite powder is mixed in the coating forming unit 60 at least in the cleaning step (S1) and the pulverization step ( It adheres to or adsorbs on the silicon fine particles 2 processed in S2). Thereafter, the organic compound is heated to a temperature at which the organic compound is thermally decomposed to carbonize the organic compound, whereby at least a part of the surface is covered with carbon (typically, graphene, graphite, and / or amorphous carbon). The broken silicon fine particles 2 can be formed. In addition, the silicon fine particles 2 once formed may be additionally and / or preliminarily performed in a nitrogen atmosphere or a hydrogen atmosphere, for example, at 400 ° C. to 1200 ° C. It is an aspect of the modified example. From the viewpoint of accurately preventing, suppressing or removing the formation of an oxide film on the surface of the silicon fine particles 2 or their aggregates or aggregates, the silicon fine particles 2 are heated in a hydrogen atmosphere. It is preferable to do.

  Moreover, it is another aspect which can employ | adopt forming the silicon | silicone fine particle 2 by which at least one part on the surface was covered with carbon using another well-known means. For example, a carbon film formed by a known carbon black production method (furnace method or channel method) can be used. The furnace method is a method in which droplets are cooled with water after partial combustion of creosote oil is performed in a predetermined chamber in which creosote oil obtained by distillation of coal tar is turbulently diffused. The channel method is a method of depositing carbon by, for example, causing a flame formed by burning natural gas to collide with a cooling surface of channel steel. However, since a petroleum-derived sulfur component is contained, it is more preferable to employ the above-described thermal CVD method, which is a method in which such an impurity component is hardly mixed. Further, when adopting each of the above-described methods, for example, by applying a known mechanical structure to the silicon fine particles or aggregates or aggregates thereof, and imparting kinetic energy, the silicon fine particles 2 or Employing a method of coating at least a part of the surface of the agglomerates or aggregates with a carbon film is more homogeneous on the surface of the silicon fine particles 2 or the aggregates or aggregates thereof (for example, This is a preferred embodiment because a carbon film can be formed with good uniformity in thickness and / or density. More specifically, ultrasonic vibration is applied to the silicon fine particles 2 or the aggregates or aggregates thereof while rotating the chamber or tube containing the silicon fine particles or the aggregates or aggregates thereof. However, adopting a method of coating at least a part of the surface of the silicon fine particles 2 or the aggregates or aggregates thereof with a carbon film is possible on the surface of the silicon fine particles 2 or the aggregates or aggregates thereof. Furthermore, it is possible to form a carbon film more uniformly, which is a preferred embodiment.

(4) Negative electrode forming step (S5)
The negative electrode material and negative electrode manufacturing apparatus 100 of the lithium ion battery according to this embodiment include silicon fine particles as a negative electrode material processed in the coating formation step (S4), and a member (for example, copper foil) constituting a part of the negative electrode ) With a binder (for example, ammonium carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR), or ammonium carboxymethyl cellulose (CMC) and polyvinyl alcohol (PVA)). . A negative electrode is formed using the mixture layer formed by the mixing unit 70.

<Other processes>
Note that the above-described cleaning step (S1), pulverization step (S2) and (4) coating formation step (S4), or the cleaning step (S1), pulverization step (S2), oxide film removal step (S3) and ( 4) The silicon fine particles obtained by the coating formation step (S4) can be classified, 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.

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

  FIG. 4A 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. Moreover, FIG. 4B is a figure which shows the SEM image of an example of the expanded silicon | silicone fine particle or its aggregate or aggregate after the grinding | pulverization process (S2) of 1st Embodiment. 4C is a diagram showing an SEM image of another example of an aggregate or aggregate of silicon fine particles in the first embodiment, and (b) an enlarged view of a part of (a). is there. In addition, FIG. 5 is a diagram showing a transmission electron microscope (TEM) image of the silicon fine particles of the first embodiment.

  As shown in FIG. 4A, 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. 4B and the Z portion of FIGS. 4C (a) and 4 (b), 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 scale-like silicon fine particles is 1, is 3.3 to 12.9. there were.

  In addition, another interesting finding was obtained from the TEM image shown in FIG. 5 focusing on individual silicon fine particles. Specifically, it has been confirmed that the individual silicon fine particles indicated by the region surrounded by the white line in FIG. 5 are crystalline, that is, single crystal silicon. In addition, it was confirmed that at least a part 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. 5, the crystal plane orientation is shown in each region surrounded by a white line.

2. 6. Analysis of crystallite size distribution of silicon fine particles by X-ray diffraction method FIG. 6 shows (a) the crystallite diameter indicating the 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. 6 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. 6A and 6B, the horizontal axis represents the crystallite diameter (nm), and the vertical axis represents the frequency.

  From the results of FIG. 6A and FIG. 6B, 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 is worthy to note that the volume distribution was confirmed to be at least 50 nm or less, particularly 30 nm or less, regardless of mode diameter or median diameter. Further, in FIG. 6, it was confirmed that an extremely small value of 10 nm or less was realized.

  From the results shown in FIGS. 6A and 6B, 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.

  Therefore, if the result of FIG. 6 and the result of each figure of FIG. 4 are combined and analyzed, the agglomerates or aggregates of silicon fine particles after at least the pulverization step (S2) or the oxide film removal step (S3) are: In other words, it can be said that the thin silicon fine particles having a major axis in the range of about 100 nm or less are folded in a multi-layered petal shape or scale shape. Further, as can be seen from FIGS. 5 and 6, the silicon fine particles are mainly composed of crystallites having a major axis of 10 nm or less.

  Moreover, it turns out that the silicon | silicone fine particle of this embodiment contains the silicon | silicone fine particle of 1 nm or less crystallite diameter, 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, by including a large number of ultrafine silicon particles having a crystallite diameter of 5 nm or less in the major axis, the charge / discharge cycle characteristics derived from the silicon fine particles used as the negative electrode material of the lithium ion battery described later are improved with higher accuracy. Is. In addition, since at least a part of the surface is covered with carbon in the ultrafine silicon particles described above, higher charge capacity value and discharge capacity value, and excellent charge / discharge cycle characteristics can be realized.

3. Analysis of plane orientation of crystallites of silicon fine particles by X-ray diffraction method FIG. 7A shows X-ray diffraction of silicon fine particles or aggregates or aggregates thereof before the pulverization step (S2) of the first embodiment. It is the result of having analyzed the result (Q) of the X-ray-diffraction measurement of the silicon fine particle after the measurement result (P) and the pulverization step (S2) or its aggregate or aggregate in a wide angle range. FIG. 7B is an enlarged view of a part of the result (P) of FIG. 7A, and silicon fine particles or aggregates thereof after the pulverization step (S2) of the first embodiment or It is the result (R) which analyzed the result of the X-ray-diffraction measurement of the aggregate | assembly in the limited angle range. Note that the peak intensities of the C (002) plane and C (003) plane shown in FIG. 7B are about 1 wt% to about 3 wt% of graphite fine particles or silicon fine particles. It shows that it is contained in the aggregate or aggregate. As an example, the size of the fine graphite particles on the C (002) plane is about 50 nm or less, more specifically about 35 nm, and the size of the fine graphite particles on the C (003) plane is about 100 nm. Hereinafter, more specifically, it was about 75 nm.

  As shown in FIGS. 7A and 7B, compared to the diffraction peak attributed to the Si crystal plane (111) near 2θ = 28.4 ° before the pulverization step (S2) of the first embodiment. It was confirmed that the half value width of the diffraction peak attributed to Si (111) after the pulverization step (S2) is large. In addition, the average crystallite diameter calculated using the Scherrer equation from the half width of the Si (111) peak after the pulverization step (S2) was 9.8 nm. Also, very interestingly, the intensity of the diffraction peak attributed to Si (111) near 2θ = 28.4 ° after the crushing step (S2) is the intensity of other diffraction peaks (for example, Si (220) or Si (311) peak intensity) was found to be larger. In addition, as shown in FIG. 5, 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).

  Based on each analysis result described above, for the silicon fine particles after the pulverization step (S2) of the present embodiment, the crystalline silicon fine particles having a plane orientation of (111) mainly have a multi-layer petal shape or a scale shape. It can be said that they are aggregates or aggregates in a state of being folded in multiple layers.

Then, the positive electrode material of the lithium ion battery is obtained by using the silicon fine particles or the aggregates or aggregates thereof after the pulverization step (S2) or the oxide film removal step (S3) of the present embodiment as the negative electrode material of the lithium ion battery. When lithium ions (Li ⁺ ) ionized from inside reach the negative electrode, the lithium ions (Li ⁺ ) enter the gaps between the aggregates or aggregates in a state where the lithium ions (Li ⁺ ) are multi-folded in a multi-layered petal shape or scale shape. A unique effect of being easy to enter and exit.

<Second Embodiment>
The lithium ion battery of this embodiment uses, as a negative electrode material, silicon fine particles produced in the first embodiment and having at least a part of the surface covered with carbon. The configuration other than the negative electrode material is the same as the configuration of a conventional CR2032-type coin cell lithium ion battery.

  FIG. 8 is a schematic configuration diagram of the lithium ion battery 500 of the present embodiment. The lithium ion battery 500 of this embodiment includes a negative electrode 512 that is electrically connected to the negative electrode material and the negative electrode material 514 and a positive electrode that is electrically connected to the positive electrode material and the positive electrode material 518 in the CR5102-type coin cell container 510. 516, a separator 520 that electronically insulates the negative electrode material and negative electrode material 514 from the positive electrode material and positive electrode material 518, and an electrolyte solution 530. Further, the lithium ion battery 500 of the present embodiment has an external circuit including a power source 540 and a resistor 550 connected to the negative electrode 512 and the positive electrode 516 in order to realize charging and discharging.

  Moreover, the manufacturing method of the lithium ion battery 500 of this embodiment is as follows.

  As for the method for producing the negative electrode, first, about 0.3 g of silicon fine particles produced in the first embodiment and having at least a part of the surface covered with carbon, 1 wt% CMC binder aqueous solution, SBR binder aqueous dispersion It is dispersed in a solution of about 10 mL (milliliter) made of (TRD2001, manufactured by JSR Corporation).

  In this embodiment, the dry weight ratio is 67: 11: 13: 9 or 50: 25: 20: 5 in the order of silicon fine particles, carbon black, CMC binder aqueous solution, and SBR binder aqueous dispersion. Blend in. Moreover, in one modification of this embodiment, it mix | blends so that it may become 50: 25: 20: 5 in order of dry weight ratio, silicon fine particle, carbon black, CMC binder aqueous solution, and PVA binder aqueous dispersion. .

  Next, the slurry prepared by mixing using an agate mortar is 15 μm thick and has a thickness of about 30 μm to about 200 μm after drying on one side of a copper foil of about 9 cm (length) × 10 cm (width). After the coating, a drying process is performed on the hot plate in the air at 80 ° C. for about 1 hour. Thereafter, the working electrode is formed by punching the above-described copper foil together with the dry slurry into a circle having a diameter corresponding to the battery standard CR2032 type coin cell of 11.3 mm. After measuring the weight of the working electrode, the material dried again by vacuum heating at 120 ° C. for 6 hours in the glow box is pasted on the inner surface of the negative electrode 512 made of copper foil, whereby A negative electrode is produced.

  Next, as a positive electrode, a positive electrode 516 was formed by punching a lithium substrate into a circle having a diameter of 13 mm in order to evaluate the characteristics of the negative electrode material using a lithium ion battery having a half cell structure. As the positive electrode of the lithium ion battery, a known positive electrode can be used instead of the positive electrode 516 described above.

Further, the separator 520 of the present embodiment is a porous polyprolene sheet. In addition, the electrolytic solution 530 of the present embodiment is prepared by adding 1 mol of lithium hexafluorophosphate (1 L) in a solvent (1 L) of ethylene carbonate (EC) / diethyl carbonate (DEC) mixed at a volume ratio of 1/1. An electrolytic solution in which LiPF ₆ ) is dissolved, or a solution obtained by adding fluoroethylene carbonate (FEC) to the electrolytic solution, and injecting an amount within an amount that satisfies the internal volume (about 1 mL) of the CR2032 type coin cell. is there.

  The positive electrode material and positive electrode material 518, the positive electrode 516, the negative electrode material and negative electrode material 514, the negative electrode 512, the separator 520, and the electrolyte solution 530 are placed in the container 510 of the CR2032-type coin cell. Thereafter, the constituent materials of the separator 520 and the electrolytic solution 530 are sealed in the container 510 in a state where the positive electrode 516 and the negative electrode 512 of the outer frame of the coin cell are insulated in a glove box in an argon atmosphere. Thus, a lithium ion battery 500 of a CR2032-type coin cell was prototyped.

  Examples of the electrolytic solvent constituting the electrolytic solution 530 in this embodiment are ethylene carbonate (EC), propylene carbonate (PC) (polyprolene sheet) cyclic carbonate, dimethyl carbonate (DMC), and diethyl carbonate (DEC). ) And the like. Further, a supporting salt such as lithium hexafluorophosphate (LiPF) or lithium tetrafluoroborate (LiBF) can be used by dissolving in the above-mentioned electrolytic solvent.

<Charge / discharge cycle characteristics of lithium ion battery 500>
By adopting the lithium ion battery 500 having the above-described configuration, the charge capacity value and the discharge capacity value are compared with the case where silicon fine particles whose surface is not covered with carbon are employed (less than about 500 (mAh / g)). The charge capacity value and the discharge capacity value can be increased even if the number of charge / discharge cycles reaches 100 times or more. In any case, it is possible to realize extremely good charge / discharge cycle characteristics that are not so much lowered.

  FIG. 9 is a graph showing cycle characteristics of charging of the lithium ion battery 500 of the present embodiment. FIG. 10 is a graph showing the discharge cycle characteristics of the lithium ion battery 500 of the present embodiment. In addition, the circle mark in each figure shows the example which employ | adopted CMC and PVA as a binder, and the filled square mark shows the example which employ | adopted CMC and SBR as a binder.

  As shown in FIG. 9 and FIG. 10, in both the example employing CMC and PVA and the example employing CMC and SBR, the charge capacity value and the discharge capacity value are stable until the number of charge / discharge is at least 60 times. It can be seen that is maintaining a high value. In addition, the charge capacity value and the discharge capacity value tend to decrease slightly until the number of charge / discharge cycles reaches 100. However, both the example employing CMC and PVA and the example employing CMC and SBR have a high charge capacity value (about 1400 to about 1500 mAh / g) and discharge capacity value ( It was also found to maintain about 1400 to about 1500 mAh / g).

  Interestingly, it was confirmed that the example employing CMC and PVA can maintain higher charge capacity value and discharge capacity value than the example employing CMC and SBR. This is considered to be because when SBR is employed, it is less likely to be uniformly mixed than PVA when mixed with CMC or silicon fine particles.

  As a reference example, the charge / discharge cycle characteristics of a lithium ion battery manufactured in the same manner as the lithium ion battery 500 were measured using the silicon fine particles of this embodiment before the treatment in the coating formation step (S4). The results will be described. FIG. 11 is a graph showing the charge cycle characteristics of the lithium ion battery of the reference example described above. FIG. 12 is a graph showing the discharge cycle characteristics of the lithium ion battery of the above-mentioned reference example. In addition, this reference example is an example which employ | adopted CMC and PVA as a binder.

  As shown in FIGS. 11 and 12, it can be seen that the charge capacity value and the discharge capacity value are relatively low values of less than 500 (mAh / g).

  Therefore, by using the silicon fine particles and / or aggregates (including aggregates) of the first embodiment described above, the lithium ion battery has high capacity and excellent charge / discharge cycle characteristics. It was confirmed that can be realized. In particular, in comparison with the result of the lithium ion battery as a reference example, silicon fine particles and / or aggregates (aggregates thereof) in which at least a part of the surface is covered with carbon by the coating formation step (S4). The lithium ion battery 500 according to the second embodiment that employs (including) is capable of increasing the charge capacity value and the discharge capacity value more than twice (typically about 3 to about 5 times). . In addition, by covering part or all of the silicon fine particles with carbon, the formation of a thick negative electrode material is facilitated, so that the lithium ion battery 500 can be manufactured more easily. In addition, even when a charge / discharge cycle is performed more than 100 times (for example, several hundred to 1000 times), the lithium ion battery 500 is the present embodiment before the treatment by the coating formation step (S4). It can be said that it has a charge capacity value and discharge capacity value and / or charge / discharge cycle characteristics which are significantly superior to those of lithium ion batteries employing silicon fine particles.

  As shown in FIG. 13, for the lithium ion battery 500 of this embodiment, TEM (permeation) of silicon fine particles or aggregates or aggregates constituting the negative electrode material after 100 charge / discharge cycles have been performed. As a result of confirming the image of the scanning electron microscope), a substantially circular crystal (microcrystal) having a diameter of about 4 nm was confirmed as indicated by a region “A” in the figure. Therefore, if a negative electrode material using silicon fine particles obtained by pulverization of crystalline silicon or aggregates or aggregates thereof is employed, even after at least 100 charge / discharge cycles, a part of the crystalline state is obtained. It is another interesting fact that it became clear that it was maintained. Note that the example of the lithium ion battery 500 shown in FIG. 13 is an example in which CMC and PVA are employed as the binder, and about 5 wt% of fluoroethylene carbonate (FEC) described later is added. Further, it is considered that the crystalline silicon in the region “A” in FIG. 13 mainly has Si (111).

<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. Further, the graphite fine particles of about 1 wt% to about 3 wt% indicated by the peak intensities of the C (002) plane and the C (003) plane shown in FIG. 7B are silicon fine particles or silicon fine particles. Since it is contained in the aggregate, some or all of these graphites will be added to the points that can contribute to the improvement of the conductivity of the negative electrode material.

<Other embodiment (3)>
Further, the silicon fine particles of the above-described embodiments and the lithium ion battery including the same are not limited to application to the coin cell type structure introduced in the second embodiment. Therefore, the present invention can be applied to various devices or apparatuses including or using a lithium ion battery having a larger electric capacity than a coin cell type structure. Moreover, it is another one aspect | mode which can employ | adopt what mixed graphite (typically graphite) with the silicon mixed powder of each above-mentioned embodiment as negative electrode material.

<Other embodiment (4)>
Further, as an alternative device to the negative electrode material and negative electrode manufacturing apparatus 100 shown in FIG. 2 in the first embodiment, the negative electrode manufacturing apparatus 200 shown in FIG. 14 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. Therefore, in the apparatus / method shown in FIG. 14, for example, beads having a relatively large diameter are used in the cleaning process, and beads having a relatively small diameter are 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.

<Other embodiment (5)>
In addition, according to the analysis of the inventors of the present application, the amount of fluoroethylene carbonate (FEC) added to the electrolyte solution 530 in the second embodiment depends on the charge capacity value, the discharge capacity value, and the charge / discharge cycle characteristics. It became clear that it could have an impact. FIG. 15A is a graph showing the cycle characteristics of charging of a lithium ion battery when the amount of FEC in the electrolytic solution 530 is changed. FIG. 15B is a graph showing the cycle characteristics of discharge of the lithium ion battery when the amount of FEC in the electrolytic solution 530 is changed. The amount of FEC to be measured is 5 wt%, 10 wt%, and 15 wt%, respectively. For reference, a lithium ion battery to which no FEC was added was also measured. 15A and 15B, carbon (C) was 0.1 when the weight ratio of silicon (Si) was 1. In addition, in FIGS. 15A and 15B, a charge / discharge cycle is performed under the condition of a current value of 180 mA / g up to 5 times of charge / discharge, and a current of 1800 mA / g is obtained when the number of charge / discharge is 6 times or more. The charge / discharge cycle is performed under the condition of the value. This is to form a good (eg, low resistance and / or thin) solid electrolyte interface (SEI) on the surface of the negative electrode material.

  As shown in FIG. 15A and FIG. 15B, when the addition amount (wt%) of FEC is in the range of more than 5% and 15% or less, charging is performed stably even when 100 charge / discharge cycles are performed. It can be seen that the capacity value and the discharge capacity value are maintained at high values (typically about 1500 mAh / g). In particular, it has been clarified that by adding about 10% of FEC, the charge capacity value and the discharge capacity value can be stably maintained at very high values. Therefore, it was found that by adding FEC, a high charge capacity value and a high discharge capacity value can be obtained even when 100 charge / discharge cycles are performed.

<Other embodiment (6)>
In addition, the inventor of the present application provides the weight ratio of carbon (C) to silicon (Si), the charge capacity value and the discharge capacity value, and the characteristics of the charge / discharge cycle in the negative electrode material employed in the second embodiment. The correlation was investigated. FIG. 16A is a graph showing cycle characteristics of charging of a lithium ion battery when the weight ratio of silicon (Si) to carbon (C) is changed. FIG. 16B is a graph showing the cycle characteristics of discharge of the lithium ion battery when the weight ratio of silicon (Si) to carbon (C) is changed. In addition, the weight ratio of silicon (Si) and carbon (C) as measurement targets is four examples shown in the following (1) to (4).
(1) Carbon (C): Silicon (Si) = 0.1: 1
(2) Carbon (C): Silicon (Si) = 0.16: 1
(3) Carbon (C): Silicon (Si) = 0.21: 1
(4) Carbon (C): Silicon (Si) = 0.37: 1

  In FIG. 16A and FIG. 16B, a charge / discharge cycle is performed under the condition of a current value of 180 mA / g until the number of times of charge / discharge is 5 times, and a current value of 1800 mA / g when the number of times of charge / discharge is 6 times or more. The charge / discharge cycle is performed under the conditions of This is to form a good (eg, low resistance and / or thin) solid electrolyte interface (SEI) on the surface of the negative electrode material. 16A and 16B are examples in which about 10 wt% of fluoroethylene carbonate (FEC) is added.

  As shown in FIG. 16A and FIG. 16B, the charge capacity value and the discharge capacity value of the example in which the ratio of carbon (C) is the largest (the above (4)) are slightly lower values, but the other three examples are It can be seen that both of them stably maintain high values of the charge capacity value and the discharge capacity value. Accordingly, when the ratio of carbon (C) (weight ratio) is 0.1 or more and 0.21 or less when silicon (Si) is 1, even when 100 charge / discharge cycles are performed, It has become clear that a particularly high value (typically about 1500 mAh / g) of the charge capacity value and the discharge capacity value can be maintained stably. However, the example of the above (4) is more than the charge capacity value and the discharge capacity value of the lithium ion battery in which at least part of the surface of the silicon fine particles or the aggregates or aggregates thereof is not covered with carbon. It has a charge capacity value and a discharge capacity value that are twice or more (typically about 3 times) higher.

  In this embodiment, the weight ratio of carbon (C) when silicon (Si) is 1 is 0.1, but the weight of carbon (C) when silicon (Si) is 1 is used. If the ratio is 0.05 or more, substantially the same effects as the results of (1) to (3) described above can be achieved. Accordingly, when the ratio of carbon (C) is 0.05 or more and less than 0.37 when silicon (Si) is 1, lithium ions that are stable and have a high charge capacity value and high discharge capacity value. A battery can be obtained.

  In this embodiment, as a result of further detailed analysis by the present inventor, carbon (C) in the case of (1) described above is attached to silicon (Si) according to a TEM (transmission electron microscope) image. The film thickness was about 2 nm to about 3 nm. The film thickness of the portion where carbon (C) is attached to silicon (Si) in the case of (2) above was about 5 nm to about 10 nm. Further, the film thickness of the portion where carbon (C) in the above-mentioned case (3) adheres to silicon (Si) was also about 5 nm to about 10 nm. In addition, the film thickness of the portion where carbon (C) in the above-mentioned case (4) is attached to silicon (Si) was about 50 nm to about 90 nm. Therefore, if the film thickness of carbon (C) attached to silicon (Si) is 1 nm or more and less than 50 nm, in particular, if the film thickness is 2 nm or more and 10 nm or less, the film is stable and has a charge capacity. A lithium ion battery having a high value and a high discharge capacity value can be obtained.

  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 within the scope of the present invention including other combinations of the embodiments are also included in the claims.

  Silicon fine particles and a lithium ion battery including the same according to 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, portable electronic devices (portable devices). Telephone, portable music player, notebook computer, digital camera / video), electric vehicle, hybrid electric vehicle (HEV) or plug-in hybrid electric vehicle (PHEV), motor-driven motorcycle, motor as power source It can be suitable for various devices or apparatuses including a motor tricycle, other transport machines or vehicles.

Claims (31)

The mode diameter and the median diameter are formed using silicon fine particles having a volume distribution of less than 50 nm and at least a part of which is covered with carbon, or aggregates or aggregates thereof.
A negative electrode material for lithium ion batteries. The agglomerates of the silicon fine particles formed using silicon fine particles or aggregates or aggregates thereof, at least a part of which are covered with carbon, and folded in a multi-layered petal shape or scale shape Or including the collection,
A negative electrode material for lithium ion batteries. According to the X-ray diffraction measurement of the silicon fine particles or the aggregates or the aggregates, the intensity of the diffraction peak attributed to Si (111) near 2θ = 28.4 ° is larger than the intensity of other diffraction peaks.
The negative electrode material of the lithium ion battery according to claim 1 or 2. Including the agglomerates or aggregates of the silicon fine particles in a state of being folded into a multi-layer petal shape or a scale shape,
The negative electrode material of the lithium ion battery according to claim 1 or 3. When the silicon in the silicon fine particles is 1, the weight ratio of the carbon is 0.05 or more and less than 0.37.
The negative electrode material for a lithium ion battery according to any one of claims 1 to 4. The film thickness of the carbon is 1 nm or more and less than 50 nm,
The negative electrode material for a lithium ion battery according to any one of claims 1 to 4. A negative electrode material having a volume distribution with a mode diameter and a median diameter of less than 50 nm, and formed using silicon fine particles or aggregates or aggregates thereof at least partially covered with carbon,
Lithium ion battery. The agglomerates of the silicon fine particles formed using silicon fine particles or aggregates or aggregates thereof, at least a part of which are covered with carbon, and folded in a multi-layered petal shape or scale shape Or a negative electrode material comprising the aggregate,
Lithium ion battery. According to the X-ray diffraction measurement of the silicon fine particles or the aggregates or the aggregates, the intensity of the diffraction peak attributed to Si (111) near 2θ = 28.4 ° is larger than the intensity of other diffraction peaks.
The lithium ion battery according to claim 7. Including the agglomerates or aggregates of the silicon fine particles in a state of being folded into a multi-layer petal shape or a scale shape,
The lithium ion battery according to claim 7 or 9. When the silicon in the silicon fine particles is 1, the weight ratio of the carbon is 0.05 or more and less than 0.37.
The lithium ion battery according to any one of claims 7 to 10. The film thickness of the carbon is 1 nm or more and less than 50 nm,
The lithium ion battery according to any one of claims 7 to 10.   The apparatus provided with the lithium ion battery of any one of Claims 7 thru | or 12. By crushing crystalline silicon, a pulverization part that forms 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, and
A coating forming part that forms carbon covering at least a part of the surface of the silicon fine particles or the aggregates or the aggregates,
An apparatus for producing a negative electrode material for a lithium ion battery. By pulverizing crystalline silicon that is chip or cutting scraped by the fixed abrasive wire, it contains agglomerates or aggregates of silicon fine particles that are folded in a multi-layered petal shape or scale shape. A pulverizing part for forming the silicon fine particles;
A coating forming part that forms carbon covering at least a part of the surface of the silicon fine particles or the aggregates or the aggregates,
An apparatus for producing a negative electrode material for a lithium ion battery. The pulverized portion forms the aggregate or the aggregate in a state where the silicon fine particles are folded into a multi-layer petal shape or a scale shape,
The manufacturing apparatus of the negative electrode material of the lithium ion battery of Claim 14. The pulverization unit includes a ball mill and a bead mill used after the ball mill.
The manufacturing apparatus of the negative electrode material of the lithium ion battery of any one of Claim 14 thru | or 16. The coating forming part is a chemical vapor deposition apparatus,
The manufacturing apparatus of the negative electrode material of the lithium ion battery of any one of Claims 14 thru | or 17. According to the X-ray diffraction measurement of the silicon fine particles or the aggregates or the aggregates, the intensity of the diffraction peak attributed to Si (111) near 2θ = 28.4 ° is larger than the intensity of other diffraction peaks.
The manufacturing apparatus of the negative electrode material of the lithium ion battery of any one of Claims 14 thru | or 18. By pulverizing crystalline silicon, a pulverization part that forms silicon fine particles or an aggregate or aggregate thereof as a negative electrode material having a volume distribution with a mode diameter and a median diameter of less than 50 nm,
A coating forming part that forms carbon covering at least a part of the surface of the silicon fine particles or the aggregates or the aggregates,
An apparatus for manufacturing a negative electrode of a lithium ion battery. By pulverizing crystalline silicon that is chip or cutting scraped by the fixed abrasive wire, it contains agglomerates or aggregates of silicon fine particles that are folded in a multi-layered petal shape or scale shape. A pulverizing part for forming the silicon fine particles as a negative electrode material;
A coating forming part that forms carbon covering at least a part of the surface of the silicon fine particles or the aggregates or the aggregates,
An apparatus for manufacturing a negative electrode of a lithium ion battery. The pulverization unit includes a ball mill and a bead mill used after the ball mill.
The apparatus for producing a negative electrode for a lithium ion battery according to claim 20 or claim 21. The coating forming part is a chemical vapor deposition apparatus,
The apparatus for producing a negative electrode for a lithium ion battery according to any one of claims 20 to 22. A pulverization step of forming crystalline silicon particles or aggregates or aggregates thereof having a volume distribution with a mode diameter and a median diameter of less than 50 nm by pulverizing crystalline silicon;
Forming a carbon covering at least part of the surface of the silicon fine particles or the aggregates or the aggregates,
A method for producing a negative electrode material for a lithium ion battery. By pulverizing crystalline silicon that is chip or cutting scraped by the fixed abrasive wire, it contains agglomerates or aggregates of silicon fine particles that are folded in a multi-layered petal shape or scale shape. A pulverizing step for forming the silicon fine particles;
Forming a carbon covering at least a part of the surface of the silicon fine particles or the aggregates or the aggregates,
A method for producing a negative electrode material for a lithium ion battery. In the pulverization step, the crystalline silicon is pulverized by a bead mill after the crystalline silicon is pulverized to form the silicon fine particles or the aggregates or the aggregates.
The manufacturing method of the negative electrode material of the lithium ion battery of Claim 24 or Claim 25. The coating formation step is a step of forming the carbon by chemical vapor deposition.
The method for producing a negative electrode material for a lithium ion battery according to any one of claims 24 to 26. A pulverizing step of forming crystalline silicon particles or aggregates or aggregates thereof as a negative electrode material having a volume distribution with a mode diameter and a median diameter of less than 50 nm by pulverizing crystalline silicon;
Forming a carbon covering at least part of the surface of the silicon fine particles or the aggregates or the aggregates,
A method for producing a negative electrode of a lithium ion battery. By pulverizing crystalline silicon that is chip or cutting scraped by the fixed abrasive wire, it contains agglomerates or aggregates of silicon fine particles that are folded in a multi-layered petal shape or scale shape. Pulverizing step for forming the silicon fine particles to be a negative electrode material,
Forming a carbon covering at least a part of the surface of the silicon fine particles or the aggregates or the aggregates,
A method for producing a negative electrode of a lithium ion battery. In the pulverization step, the crystalline silicon is pulverized by a bead mill after the crystalline silicon is pulverized to form the silicon fine particles or the aggregates or the aggregates.
30. A method for producing a negative electrode for a lithium ion battery according to claim 28 or claim 29. The coating formation step is a step of forming the carbon by chemical vapor deposition.
The method for producing a negative electrode for a lithium ion battery according to any one of claims 28 to 30.