JP2018181573A - Manufacturing method of negative electrode material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further improve a function of a negative electrode material containing a silicon material.SOLUTION: In a manufacturing method of a negative electrode material in which metal particles are present on particles of a silicon material having a structure in which a plurality of plate silicon bodies are laminated in the thickness direction, the particles of the silicon material is caused to be in contact with a metal salt solution including a solution and at least one metal salt selected from copper formate, nickel acetate, nickel formate, or lead formate and heated to a temperature equal to or higher than the decomposition temperature of the metal salt.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method of manufacturing a negative electrode material.

  As a negative electrode active material for lithium ion secondary batteries, a negative electrode active material containing Si having a high lithium ion storage capacity is known. For example, Patent Document 1 and Patent Document 2 describe a lithium ion secondary battery in which the negative electrode active material is silicon. Patent Document 3 and Patent Document 4 describe lithium ion secondary batteries in which the negative electrode active material is SiO.

  In order to further improve the battery performance of lithium ion secondary batteries, search for new Si-containing negative electrode active materials is in progress. Patent Document 5 discloses a silicon material having a structure in which a plurality of plate-like silicon bodies are stacked in the thickness direction as a new negative electrode active material containing Si, and the silicon material is a lithium ion. It is described that it can be used as a negative electrode active material of a secondary battery.

JP, 2014-203595, A JP, 2015-57767, A JP, 2015-185509, A JP, 2015-179625, A International Publication No. 2014/080608

  By the way, in recent years, the lithium ion secondary battery which is more excellent in battery performance is required. Also for the negative electrode active material for lithium ion secondary batteries, improvement of various functions is desired to contribute to improvement of battery performance of lithium ion secondary batteries. Similarly to the silicon material disclosed in Patent Document 5, further improvement in function is desired.

  The present invention has been made in view of such circumstances, and an object thereof is to further improve the function of a negative electrode material containing a silicon material.

  In view of the above-mentioned circumstances, the inventor of the present invention has obtained an idea of coating a silicon material with a different material in order to improve the function of the silicon material as the negative electrode material. Furthermore, a silicon material is coated with various materials and various methods to manufacture a negative electrode material, and as a result of repeated tests to evaluate the performance of the negative electrode material, a coat capable of improving various functions of the silicon material The present invention has been accomplished by finding that by further coating the silicon material in a specific manner, the function of the silicon material can be further improved.

  That is, according to the method for producing a negative electrode material of the present invention, particles of a silicon material having a structure in which a plurality of plate-like silicon bodies are stacked in the thickness direction are made of copper formate, nickel acetate, nickel formate or lead formate. A method for producing a negative electrode material, wherein metal particles exist on particles of the silicon material, which is brought into contact with a metal salt solution containing at least one selected metal salt and a solvent, and heated to a temperature above the decomposition temperature of the metal salt. It is.

  According to the method for manufacturing a negative electrode material of the present invention, the function of the negative electrode material containing a silicon material can be improved.

3 is a SEM image of the negative electrode material of Example 1; 7 is a SEM image of the negative electrode material of Example 3. 21 is a SEM image of negative electrode material # 10 of Example 6.

The inventors of the present invention conducted intensive studies, and it was considered that it is necessary to further improve the function of the negative electrode material containing a silicon material in the following points.
First, while silicon materials have high theoretical capacity, they have a problem that they are inferior in conductivity to graphite and the like.
Further, since the silicon material is a material having a relatively large amount of expansion and contraction at the time of charge and discharge, fatigue of the silicon material, such as cracking of the silicon material, is estimated when the expansion and contraction associated with the charge and discharge are repeated.

  For example, by metal-coating a silicon material, it is considered that a negative electrode material having excellent conductivity can be obtained. Focusing on the improvement of the durability of the negative electrode material, covering the silicon material with a metal coat and physically reinforcing the silicon material is considered to be advantageous also in suppressing the fatigue.

  However, if the silicon material is covered thoroughly with, for example, a metal coating, it is expected that the metal coating inhibits lithium ion migration. Further, in this case, the amount of the metal coating to the silicon material may be excessive, and the capacity of the lithium ion secondary battery may be reduced.

  In order to solve the problem, the inventor of the present invention intended to form metal particles on particles of a silicon material rather than a film-like metal coat. And the inventor actually manufactured the silicon material which formed the metal coat by various methods, and reached the manufacturing method of the negative electrode material of the above-mentioned this invention mentioned above. According to the method for producing a negative electrode material of the present invention, it is possible to produce a negative electrode material in which metal particles are present on particles of a silicon material. In the negative electrode material, metal particles present on the particles of the silicon material impart excellent conductivity to the negative electrode material, and the silicon material is reinforced. That is, according to the method for producing a negative electrode material of the present invention, a negative electrode material containing a silicon material and having improved function can be obtained.

  Hereinafter, as necessary, the method for producing the negative electrode material of the present invention will be referred to as the production method of the present invention, or simply as the production method. Moreover, the negative electrode material obtained by the method for producing a negative electrode material of the present invention is referred to as the negative electrode material of the present invention, or simply referred to as the negative electrode material.

  In the negative electrode material of the present invention, metal particles are present on particles of a silicon material disclosed in Patent Document 5. The negative electrode material of the present invention can also be rephrased as a negative electrode material in which the silicon material disclosed in Patent Document 5 is coated in a granular form with at least one selected from copper, nickel, and lead.

  In the method for producing a negative electrode material of the present invention, a silicon material is brought into contact with a metal salt solution containing at least one metal salt selected from copper formate, nickel acetate, nickel formate or lead formate and a solvent, Heat to a temperature above the decomposition temperature. When the above process is performed using at least one metal salt selected from copper formate, nickel acetate, nickel formate, or lead formate, metal is formed in the form of particles, not silicides or metal oxides, on particles of silicon material. .

  At the time of heating, the metal salt solution may be in liquid state and in contact with the silicon material, or the metal salt generated from the metal salt solution may be in solid state and in contact with the silicon material. When the particle forming step is performed before heating as described later, part of the metal salt may be already metal at the time of heating. According to the method for producing the negative electrode material of the present invention, the metal salt is heated to a temperature above its decomposition temperature, and metal particles containing at least one metal selected from copper, lead and nickel are formed on the surface of the silicon material.

  The lower limit is not particularly set for the degree of coating of the silicon material with metal particles in the negative electrode material of the present invention, and if metal particles are present in the negative electrode material even a little (that is, metal is present), the present invention The effect of The degree of coating of the silicon material with metal particles can be represented by the content of metal particles in the negative electrode material, and the content of metal in the negative electrode material of the present invention may be more than 0% by mass. However, if the lower limit is set to the content of the metal, the content of the metal is preferably 10% by mass or more, more preferably 15% by mass or more, and 20% by mass or more Is more preferable, and 25% by mass or more is more preferable. In the negative electrode material of the present invention, the upper limit of the content of the metal is also not particularly limited. However, if desired, the content of the metal in the negative electrode material is preferably 50% by mass or less. In addition, what is necessary is just to use known methods, such as ICP emission analysis, ICP mass spectrometry, energy dispersive X ray analysis (EDX), for measurement of metal content.

Therefore, the metal content of the metal salt solution and the amount of metal to silicon material in the method for producing a negative electrode material of the present invention are also not particularly limited. However, if the concentration of the metal salt solution is too low, when trying to coat the desired amount of metal, the amount of metal salt solution to silicon material becomes too large, and only metal particles are formed on the silicon material. In addition, unnecessary metal particles that are made of only a metal salt or only a metal and do not contribute to the battery reaction may be generated separately from the negative electrode material. In consideration of this point, it is considered that the metal content of the metal salt solution is preferably a predetermined amount or more. Specifically, the metal content of the metal salt solution can be 1.0% by mass or more, 2.0% by mass or more, and 3.0% by mass or more.
The amount of metal to silicon material can also be taken as the amount of metal in a slurry comprising particles of silicon material and a metal salt solution. Hereinafter, the slurry containing the particles of the silicon material and the metal salt solution described above is referred to as a raw material slurry, as necessary.

  In the method for producing a negative electrode material of the present invention, the size of the metal particles formed on the silicon material is also not particularly limited, but the metal particles preferably have a small diameter. The range of the preferable particle size of the metal particles may include an average particle diameter of 1 to 100 nm, 2 to 75 nm, and 5 to 50 nm. The average particle size may be measured and calculated from, for example, an SEM image of the negative electrode material. Specifically, 50 metal particles are arbitrarily extracted on the SEM image, the maximum diameter is measured for each of the 50 metal particles, and the average of the measured values is regarded as the average particle diameter of the metal particles. it can.

  The step of contacting the silicon material with the metal salt solution and the step of heating the metal salt and the silicon material to a temperature above the decomposition temperature of the metal salt may be performed simultaneously or separately. In any case, in order to form fine metal particles densely on the silicon material, it is preferable that the metal salt adheres to the silicon material in a dry state and in the form of fine particles during heating. That is, the metal salt is preferably subjected to heating in a dried or semi-dried state on a silicon material. In order to bring the metal salt into such a state, the method for producing the negative electrode material of the present invention preferably has a step of "spray-drying a slurry containing particles of silicon material and a metal salt solution". The said process is called particle | grain formation process. Also, "the step of heating the metal salt and the silicon material to a temperature above the decomposition temperature of the metal salt" is referred to as a heating step. Furthermore, a spray-dried product of the slurry obtained in the particle forming step, which has not been subjected to the heating step, is referred to as coated particles. The method for producing a negative electrode material of the present invention requires a heating step, and preferably further includes a particle forming step.

  In the method for producing a negative electrode material of the present invention, the particle forming step may be performed in one step or in multiple steps. The case of carrying out the particle formation process in multiple steps will be described in detail later.

  The particle forming process may use any apparatus, for example, a known drying apparatus can be used. The spray drying as referred to herein means drying while scattering the raw material slurry in the form of small-diameter particles by utilizing the flow of gas. Therefore, as a drying apparatus that can be used in the particle formation process, one having a spray function and a drying function can be selected. As such a drying device, for example, various drying devices such as a so-called spray drying type drying device, a flash drying device, a fluidized bed drying device and the like can be mentioned.

In the heating step, the raw material slurry may be heated as it is, or the coated particles obtained in the particle forming step may be heated. That is, the heating step may be performed simultaneously with the particle forming step, or may be performed after the particle forming step. The particle forming step may not be performed. In any case, in order to form metal particles, the heating temperature in the heating step is set to a temperature higher than the decomposition temperature of the metal salt. The decomposition temperature is not a temperature at which only a part of the metal salt contained in the coated particles can be decomposed, but a temperature at which all of the metal salt is decomposed to be a metal. The heating temperature may be constant or may vary.
The decomposition temperature of nickel acetate is about 350 ° C., the decomposition temperature of lead formate is about 320 ° C., the decomposition temperature of nickel formate is about 280 ° C., and the decomposition temperature of copper formate is about 220 ° C.

  When the specific temperature is mentioned, the heating temperature in the heating step is preferably in the range of 220 ° C. to 700 ° C., more preferably in the range of 300 ° C. to 600 ° C., although it depends on the type of metal. More preferably, it is in the range of 400 ° C to 500 ° C.

  It is preferable to carry out heating not only in the heating step but also in drying in the particle formation step. The drying temperature, that is, the drying temperature may or may not be constant. For example, the drying temperature may be gradually raised or may be gradually lowered. In any case, the maximum drying temperature is preferably equal to or higher than a predetermined temperature. Drying the raw material slurry at a relatively high temperature, that is, rapidly drying the metal salt solution component in the raw material slurry, is useful for producing small-diameter particulate metal particles in the production method of the present invention. it is conceivable that.

  The maximum drying temperature is preferably a temperature above the decomposition temperature of the metal salt. As demonstrated in the examples described later, this makes it possible to obtain an anode material having fine metal particles. In the case where the maximum temperature of the drying temperature is set to a temperature higher than the decomposition temperature of the metal salt for the purpose of suppressing the total amount of heat acting on the silicon material and suppressing the deterioration of the silicon material, the drying temperature is not constant. It is preferable to include a temperature lower than the decomposition temperature.

  Specifically, the maximum temperature of the drying device in the particle forming step is preferably in the range of 200 ° C. to 700 ° C., more preferably in the range of 250 ° C. to 700 ° C., and in the range of 300 ° C. to 650 ° C. Is more preferred. As a preferable temperature range of the drying apparatus in a particle | grain formation process, the range of 400 degreeC-650 degreeC, 500 degreeC-650 degreeC, and 600 degreeC-650 degreeC can be mentioned further. Here, the maximum temperature of the drying device means, for example, the inlet temperature of the spray drying type drying device.

  In the particle forming step, the drying apparatus is supplied with a gas for spraying and / or drying the raw material slurry. Although the type of gas is not particularly limited, it is preferable to select an inert gas such as argon gas or nitrogen gas in consideration of the reactivity with the raw material slurry and the coated particles. The gas flow rate range in the drying apparatus is 5.0 to 20.0 liters / minute, 7.5 to 15.0 liters / minute, 7.5 to 10.0 liters / minute, and 9.0 to 15 liters / minute. A range of minutes can be mentioned.

  Details of the particles of the silicon material contained in the raw material slurry will be described later.

  The raw material slurry may contain the silicon material and the metal salt described above and a solvent, but may further contain an additive such as a thickener. The blending ratio of the additive to the total of the silicon material, the metal salt and the solvent is preferably in the range of 100: 0 to 80:20 by mass ratio, and is in the range of 100: 0 to 85:15. Is more preferably 100: 0 to 90:10, and still more preferably 100: 0 to 95: 5. The solvent is not particularly limited as long as the metal salt can be dissolved, but is preferably water in view of cost and ease of handling.

  The above-described coated particles and the negative electrode material of the present invention may be in the form of particles, and the size thereof is not particularly limited. However, in consideration of handleability and the like at the time of producing the negative electrode, for example, The diameter is preferably 1.5 to 50.0 μm, more preferably 3.0 to 10.0 μm, and still more preferably 4.0 to 8.5 μm. The preferable range of the average particle diameter of the coated particles is also the same as that of the negative electrode material. In addition, the average particle diameter as used in this specification means D50 at the time of measuring with a general laser diffraction scattering type particle size distribution measuring apparatus.

  In addition, it is preferable that the average particle diameter of the particles of the silicon material which is the raw material of the coated particles is smaller than the average particle diameter of the coated particles. For example, the average particle diameter of the silicon material particles is preferably 0.6 to 30 μm, more preferably 1 to 20 μm, still more preferably 2 to 10 μm, and more preferably 3 to 8 μm. Particularly preferred.

The method for producing a negative electrode material of the present invention may further include a carbon coating step of further carbon-coating the negative electrode material after the heating step. In this case, the heating temperature in the carbon coating step is preferably in the range of 500 to 1000 ° C., more preferably in the range of 600 to 950 ° C., and particularly preferably in the range of 700 to 900 ° C. The purpose is to promote the carbon coating suitably and to suppress the amount of heat acting on the silicon material.

  In the method for producing a negative electrode material of the present invention, the particle forming step may be performed in one step or in multiple steps, but in order to form metal particles uniformly on a silicon material, the particle forming step Is preferably performed in multiple steps.

Hereinafter, the particle formation process of the first step is referred to as a coating process, and the particle formation process of the second and subsequent steps is referred to as a recoating process. The recoating step may also be performed in multiple steps.
The particle formation process comprises a coating process and a recoating process. The coated particles refer to particles after the coating process, and include particles after the coating process and those after the coating process and the recoating process.

In the coating step, a raw material slurry containing particles of a silicon material and a metal salt solution is spray-dried to form coated particles. When the recoating step is performed multiple times, in the first recoating step, the raw material slurry containing the coated particles obtained in the coating step and the metal salt solution is spray-dried to obtain recoated coated particles. In the second recoating step, the raw material slurry containing the coated particles obtained in the first recoating step and the metal salt solution is spray-dried to obtain coated particles which have been recoated twice.
The first coating step, the first recoating step, the second coating step, the second recoating step, the third coating step, the i th recoating step, the (i + 1) th coating step, the i th recoating step Assuming that the coated particles having undergone the process are the (i + 1) -coated particles, the particle forming process having the coating process and the recoating process can also be expressed as Formula 1.

Where k is an i-th step of spray-drying a slurry containing the (i-1) particles obtained in the (i-1) coating step and the metal salt solution to obtain an i-th particle, and n is 2 or more Is an integer of

  When the particle forming process is performed in multiple steps including a coating process and a recoating process, the content of the silicon material in the raw material slurry can be reduced because the amount of metal coated on the silicon material can be reduced per coating process or recoating process. It is possible to Therefore, in this case, it is considered possible to form metal particles uniformly on the silicon material. More preferably, the particle formation process is performed in multiple stages and with a reduced amount of solvent to silicon material.

  When the particle formation process is performed in multiple steps and while reducing the amount of metal salt solution to silicon material, the metal content of the metal salt solution is preferably 1.0% by mass or more, and 2.0% by mass It is more preferable that it is the above, and it is still more preferable that it is 3.0 mass% or more. In this case, the ratio of the silicon material to the solvent in the raw material slurry is preferably in the range of 50: 100 to 150: 100 in mass ratio, and more preferably in the range of 75: 100 to 125: 100. Preferably, the range of 90: 100 to 110: 100 is more preferable. The metal content of the metal salt solution mentioned here and the ratio of the silicon material to the solvent in the raw material slurry are the coating step (that is, the first coating step) and the recoating step (that is, the i-th coating step, i ≧) Common to 2).

  In order to form fine metal particles densely, n is preferably 3 or more, more preferably 5 or more, still more preferably 8 or more, and still more preferably 10 or more. The upper limit of n is not particularly limited, but if it is strong, the range of 50 or less, 30 or less, 25 or less can be mentioned.

  When the method for producing the negative electrode material of the present invention has a coating step and a recoating step, the heating step may be performed simultaneously with the coating step and the recoating step, or after the coating step and all the recoating steps are completed. It may be performed, may be performed after the coating step and every time after each recoating step, or may be performed twice or more in total after one or more coating steps and / or recoating steps. In any case, suitable drying and heating temperatures are as described above.

The details of the silicon material will be described below.
As described above, the silicon material is the silicon material disclosed in Patent Document 5. The silicon material is, for example, a step of reacting CaSi ₂ with an acid to synthesize a layered silicon compound mainly composed of polysilane, and further, a step of heating the layered silicon compound at 300 ° C. or higher to release hydrogen. It can be manufactured through.

It can be as follows when the manufacturing method of the silicon material of patent document 5 is shown with an ideal reaction formula at the time of using hydrogen chloride as an acid.
3CaSi ₂ +6 HCl → Si ₆ H ₆ +3 CaCl ₂
Si ₆ H ₆ → 6Si + 3H ₂ ↑

However, in the upper reaction for synthesizing Si ₆ H ₆ which is polysilane, water is generally used as a reaction solvent from the viewpoint of removal of by-products and impurities. And, since Si ₆ H ₆ can react with water, in the process of synthesizing the layered silicon compound including the reaction in the upper stage, the layered silicon compound is hardly produced as one containing only Si ₆ H ₆ , and the layered silicon compound is layered The silicon compound is represented by Si ₆ H _s (OH) _t X _u (X is an element or group derived from the anion of an acid, s + t + u = 6, 0 <s <6, 0 <t <6, 0 <u <6) Manufactured as In the above chemical formula, unavoidable impurities such as remaining Ca are not taken into consideration. And the silicon material obtained by heating the said layered silicon compound also contains the element derived from the anion of oxygen or an acid.

The silicon material has a structure in which a plurality of plate-like silicon bodies are stacked in the thickness direction. The plate-like silicon body preferably has a thickness in the range of 10 nm to 100 nm, and more preferably in the range of 20 nm to 50 nm for efficient insertion and desorption reaction of charge carriers such as lithium ions. . The length in the longitudinal direction of the plate-like silicon body is preferably in the range of 0.1 μm to 50 μm. The plate-like silicon body preferably has a (longitudinal length) / (thickness) in the range of 2 to 1000. The layered structure of the plate-like silicon body can be confirmed by observation with a scanning electron microscope or the like. Moreover, this laminated structure is considered to be a remnant of the Si layer in the raw material CaSi ₂ .

  The silicon material preferably includes amorphous silicon and / or silicon crystallites. In particular, in the plate-like silicon body, it is preferable that amorphous silicon be a matrix and silicon crystallites be scattered in the matrix. The size of the silicon crystallite is preferably in the range of 0.5 nm to 300 nm, more preferably in the range of 1 nm to 100 nm, still more preferably in the range of 1 nm to 50 nm, and particularly preferably in the range of 1 nm to 10 nm. The size of the silicon crystallite is calculated from the Scheller equation using the half width of the diffraction peak of the Si (111) plane of the obtained X-ray diffraction chart by performing X-ray diffraction measurement on the silicon material. .

  The amount and size of the plate-like silicon body, amorphous silicon and silicon crystallite contained in the silicon material mainly depend on the heating temperature and heating time. The heating temperature is preferably in the range of 350 ° C. to 950 ° C., and more preferably in the range of 400 ° C. to 900 ° C.

  With regard to the silicon material produced by the above method, when the average particle diameter exceeds the above-described preferred range, the silicon material may be pulverized using a general pulverizing apparatus. That is, the manufacturing method of the negative electrode material of this invention may have a grinding process. Further, in order to obtain a silicon material having a more uniform particle diameter, it is preferable to perform the grinding process a plurality of times by changing the grinding apparatus. As a pulverizing apparatus for the pulverizing process, known pulverizing apparatuses such as a jet mill, a hammer mill, a pin mill, a rolling mill, a vibrating mill, a planetary mill, a swinging mill, a horizontal mill, a ball mill and the like can be used.

  The negative electrode material of the present invention can be used as a negative electrode for a lithium ion secondary battery. Hereinafter, the lithium ion secondary battery provided with the negative electrode material of the present invention is referred to as the lithium ion secondary battery of the present invention, as needed. In addition, if necessary, the negative electrode and the positive electrode are collectively referred to as an electrode, the negative electrode active material and the positive electrode active material are collectively referred to as an active material, and the negative electrode active material layer and the positive electrode active material layer are included. It is called an active material layer.

The lithium ion secondary battery of the present invention comprises a negative electrode containing the negative electrode material of the present invention, a positive electrode, an electrolytic solution and, if necessary, a separator. Among these, the negative electrode has a current collector and a negative electrode active material layer formed on the current collector.
The negative electrode active material layer may contain the negative electrode material of the present invention and, if necessary, various additives typified by a binder, a conductive auxiliary, a dispersant and a thickener. Further, the negative electrode active material layer may contain a negative electrode active material for a lithium ion secondary battery in addition to the negative electrode material of the present invention.

The negative electrode active material other than the negative electrode material of the present invention is not particularly limited as long as it is a single body, an alloy or a compound capable of inserting and extracting lithium ions. For example, Li as a negative electrode active material, a Group 14 element such as carbon, silicon, germanium, tin, a Group 13 element such as aluminum or indium, a Group 12 element such as zinc or cadmium, a Group 15 element such as antimony or bismuth, magnesium And alkaline earth metals such as calcium, and Group 11 elements such as silver and gold may be used alone. Specific examples of the alloy or compound include tin-based materials such as Ag-Sn alloys, Cu-Sn alloys, Co-Sn alloys, carbon-based materials such as various types of graphite, and SiO _x (disproportionate into silicon alone and silicon dioxide) Examples thereof include silicon-based materials such as 0.3 ≦ x ≦ 1.6), a simple substance of silicon, or a composite obtained by combining a silicon-based material and a carbon-based material. In addition, as the negative electrode active material, oxides such as Nb ₂ O ₅ , TiO ₂ , Li ₄ Ti ₅ O ₁₂ , WO ₂ , MoO ₂ , Fe ₂ O ₃ or Li _3-x M _x N (M = A nitride represented by Co, Ni, Cu) may be employed. One or more of these can be used as the negative electrode active material.

  The negative electrode active material layer may contain, in addition to the negative electrode active material, if necessary, additives such as a conductive aid, a binder, and a dispersant in an appropriate amount. In addition, since the positive electrode active material layer can also contain these additives in an appropriate amount in addition to the positive electrode active material described later, the following section includes the negative electrode active material layer and the positive electrode active material layer. To explain. Hereinafter, as necessary, the negative electrode and the positive electrode are collectively referred to as an electrode, the negative electrode active material and the positive electrode active material are collectively referred to as an active material, and the negative electrode active material layer and the positive electrode active material layer are collectively included It is said.

  A conductive aid is added to the active material layer as needed to enhance the conductivity of the electrode. The conductive support agent may be any chemically active high electron conductor, and carbon black fine particles such as carbon black, graphite, vapor grown carbon fiber (vapor grown carbon fiber), and various metal particles are exemplified. . Examples of carbon black include acetylene black, ketjen black (registered trademark), furnace black, channel black and the like. These conductive assistants can be added to the active material layer singly or in combination of two or more.

  The binding agent plays a role of fixing the active material and the like to the surface of the current collector. Examples of the binder include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, and alkoxysilyl group-containing resins. be able to. Moreover, you may employ | adopt the polymer which has a hydrophilic group as a binding agent. As a hydrophilic group of the polymer which has a hydrophilic group, a carboxyl group, a sulfo group, a silanol group, an amino group, a hydroxyl group, and a phosphoric acid group are illustrated. Specific examples of the polymer having a hydrophilic group include polyacrylic acid, carboxymethylcellulose, polymethacrylic acid and poly (p-styrenesulfonic acid).

  In addition, as a binder for the negative electrode, a binder is disclosed in WO 2016/063882, which is a crosslinked polymer obtained by crosslinking a carboxyl group-containing polymer such as polyacrylic acid or polymethacrylic acid with a polyamine such as diamine. It may be used as

Examples of the diamine used for the cross-linked polymer include alkylene diamines such as ethylene diamine, propylene diamine and hexamethylene diamine, 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, isophorone diamine, bis (4-aminocyclohexyl) methane and the like. Saturated carbocyclic ring diamine, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylether, bis (4-aminophenyl) sulfone, benzidine, o-tolidine, 2,4- Aromatic diamines such as tolylene diamine, 2,6-tolylene diamine, xylylene diamine and naphthalene diamine can be mentioned.
Well-known additives can be adopted as additives such as a dispersing agent other than the conductive aid and the binder.

  The current collector refers to a chemically inactive electron conductor for keeping current flowing to the electrode during discharge or charge of the lithium ion secondary battery. As the current collector, at least one selected from silver, copper, gold, aluminum, magnesium, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel Etc. can be exemplified.

The current collector may be coated with a known protective layer. What processed the surface of a collector by a well-known method may be used as a collector.
Further, the current collector can take the form of a foil, a sheet, a film, a linear shape, a rod shape, a mesh or the like. Therefore, as the current collector, for example, metal foils such as copper foil, nickel foil, aluminum foil, and stainless steel foil can be suitably used.

  In order to form an active material layer on the surface of a current collector, current collection can be performed using conventionally known methods such as roll coating, die coating, dip coating, doctor blade method, spray coating, curtain coating and the like. An electrode mixture having an active material may be applied to the surface of the body. Specifically, the active material, the solvent, and, if necessary, the binder and the conductive auxiliary agent are mixed to form a slurry-like electrode mixture, and the slurry-like electrode mixture is applied to the surface of the current collector. ,dry. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone and water. The dried one may be compressed to increase the electrode density.

It does not specifically limit about the positive electrode active material used for the positive electrode of the lithium ion secondary battery of this invention, The general positive electrode active material for lithium ion secondary batteries can be used.
As a general positive electrode active material for a lithium ion secondary battery, a general formula of a layered rock salt structure: Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 2, b + c + d + e = 1, 0 ≦ e <1, D is W, Mo, Re, Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Al, Nb, Mg, Ta, Ti, La, Zr, Cu, Ca, Ir, Hf, At least one element selected from Rh, Fe, Ge, Zn, Ru, Sc, Sn, In, Y, Bi, S, Si, Na, K, P, V, and represented by 1.7 ≦ f ≦ 3) And lithium mixed metal oxides, Li ₂ MnO ₃ . In addition, as a positive electrode active material, a metal oxide of spinel structure such as LiMn ₂ O ₄ , a solid solution composed of a mixture of a metal oxide of spinel structure and a layered compound, LiMPO ₄ , LiMVO ₄ or Li ₂ MSiO ₄ M is selected from at least one of Co, Ni, Mn, and Fe), and the like. Furthermore, as the positive electrode active material, tavorite compound (the M a transition metal) LiMPO ₄ F, such as LiFePO ₄ F represented by, Limbo ₃ such LiFeBO ₃ (M is a transition metal) include borate-based compound represented by be able to. Any metal oxide used as a positive electrode active material may have the above composition formula as a basic composition, and one obtained by replacing the metal element contained in the basic composition with another metal element can also be used.

  The negative electrode containing the negative electrode material of the present invention may be placed in a battery container together with a positive electrode and, if necessary, a known separator, and an electrolyte may be injected to form a lithium ion secondary battery.

The electrolytic solution contains an organic solvent and a lithium salt dissolved in the organic solvent.
As the organic solvent, cyclic esters, chain esters, ethers and the like can be used. Examples of cyclic esters include ethylene carbonate, propylene carbonate, butylene carbonate, gamma butyrolactone, vinylene carbonate, 2-methyl-gamma butyrolactone, acetyl-gamma butyrolactone, and gamma valerolactone. Examples of the chain ester include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, ethyl methyl carbonate, alkyl propionic acid ester, malonic acid dialkyl ester, acetic acid alkyl ester and the like. As the ethers, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyethane can be exemplified. For the electrolytic solution, these organic solvents may be used alone or in combination of two or more.

Examples of lithium salts include LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (FSO ₂ ) _{2 and the} like.

As an electrolytic solution, 0.5 mol / l of lithium salt such as LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ and the like in an organic solvent such as ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, dimethyl carbonate A solution dissolved at a concentration of about 1.7 mol / l can be exemplified.

  The embodiments of the method for producing the negative electrode material of the present invention and the negative electrode material of the present invention have been described above, but the present invention is not limited to the above embodiments and may be modified within the scope of the present invention. It can implement in the various form which made the change, improvement, etc. which a maker can make. Moreover, each component shown here including embodiment and the following example can each be extracted arbitrarily, and can be implemented in combination.

  The present invention will be more specifically described below by way of examples. In addition, this invention is not limited by said embodiment and the following example.

<Anode material # 1>
Example 1
(Silicon material manufacturing process)
Under argon atmosphere, 50 g of CaSi ₂ (Ca content: 38.9 wt%) was added to 507 g of a 35 wt% aqueous HCl solution at 0 ° C. and stirred. The molar ratio of CaSi ₂ to HCl was 1:10. After confirming that the reaction solution had ceased bubbling, the mixture was further stirred under the same conditions for a total of 3 hours. Thereafter, the reaction solution was warmed to room temperature and filtered. The filter residue was washed 3 times with 300 mL of distilled water, then with 300 mL of ethanol, dried under reduced pressure, and heated at 900 ° C. for 1 hour under an argon atmosphere containing 1 volume% or less of O ₂ . This is a silicon material.

(Crushing process)
The silicon material obtained by the above-mentioned silicon material manufacturing process was crushed by jet mill NJ-30 (Aisin Nano Technologies Inc.). The average particle diameter D50 of the particles of the silicon material after grinding by a jet mill was 4.335 μm. In addition, D10 of the particle | grains of the said silicon material was 1.404 micrometers, D90 was 9.508 micrometers.

(Particle formation process)
The raw material slurry was prepared by taking particles of water, nickel acetate, and the above silicon material so as to have a mass ratio of 1224: 216: 30. Specifically, particles of silicon material are added to an aqueous solution of nickel acetate in which nickel acetate is dissolved in water, and the liquid mixture is stirred by a stirrer to disperse the particles of silicon material in an aqueous solution of nickel acetate. The raw material slurry was obtained. In addition, nickel acetate tetrahydrate was used as nickel acetate.

  The raw material slurry obtained was spray-dried using a spray drying apparatus (MDL- 015 CM-H manufactured by Fujisaki Electric Co., Ltd.). Nitrogen gas was used as the gas. The spray drying conditions at this time were an inlet temperature of 600 ° C., a slurry feed rate of 16 ml / min, and a nozzle gas flow rate of 34 L / min. The coated particles of Example 1 were obtained through the above steps.

(Heating process)
The coated particles of Example 1 were heated at 400 ° C. for one hour in an argon gas atmosphere to obtain a negative electrode material of Example 1. The heating temperature of 400 ° C. in the heating step is equal to or higher than the decomposition temperature of nickel acetate. The detail of the manufacturing method of the negative electrode material of Example 1 and Example 2-Example 5 mentioned later, and the comparative example 1 is shown in Table 1 mentioned later.

(Example 2)
Negative electrode material of Example 2 in the same manner as in Example 1 except that copper formate tetrahydrate was used as the metal salt, and the mixing ratio of water, metal salt, and particles of silicon material in the raw material slurry I got
In the method of manufacturing the negative electrode material of Example 2, the mixing ratio of water, copper formate tetrahydrate, and particles of silicon material in the raw material slurry was 1320: 180: 30 by mass ratio.

(Example 3)
The use of MDL-015 (C) MGC (-S) manufactured by Fujisaki Electric Co., Ltd. as a spray drying apparatus, that the spray drying conditions were an inlet temperature of 200 ° C., a nozzle gas flow rate of 26 L / min, and ethanol as a solvent A negative electrode material of Example 3 was obtained in the same manner as Example 1, except that the raw material slurry was used and the blending ratio of the solvent, metal salt and particles of silicon material in the raw material slurry.
In the method of manufacturing the negative electrode material of Example 3, the blending ratio of particles of ethanol, nickel acetate tetrahydrate, and silicon material in the raw material slurry was 1360: 240: 50 by mass.

(Example 4)
The same method as in Example 3 except that copper formate tetrahydrate was used as the metal salt, water was used as the solvent, and the blending ratio of the solvent, metal salt, and particles of the silicon material in the raw material slurry Thus, the negative electrode material of Example 4 was obtained.
In the method of manufacturing the negative electrode material of Example 4, the mixing ratio of water, copper formate tetrahydrate and particles of silicon material in the raw material slurry was 550: 75: 75 in mass ratio.

(Example 5)
A negative electrode material of Example 5 was obtained in the same manner as in Example 3 except for the blend ratio of the solvent, metal salt, and particles of the silicon material in the raw material slurry.
In the method of manufacturing the negative electrode material of Example 5, the blending ratio of particles of ethanol, nickel acetate tetrahydrate, and silicon material in the raw material slurry was 240: 60: 50 by mass.

(Comparative example 1)
A negative electrode material of Comparative Example 1 was obtained in the same manner as in Example 1 except that the particle forming step and the heating step were not performed. In other words, the negative electrode material of Comparative Example 1 is the silicon material used in Example 1.

(Evaluation 1-1)
SEM images of the negative electrode materials of Example 1 and Example 3 were taken. The SEM image of the negative electrode material of Example 1 is shown in FIG. 1, and the SEM image of the negative electrode material of Example 3 is shown in FIG.
As shown in FIG.1 and FIG.2, the negative electrode material of the Example is comprised by the particle | grains of a silicon material, and the small diameter metal particle currently formed on the said particle | grain. Further, as shown in FIG. 2, coarse metal particles and fine metal particles are mixed in the negative electrode material of Example 3, but as shown in FIG. 1, fine metal particles are obtained in the negative electrode material of Example 1. The grains are densely formed.

(Evaluation 1-2)
The metal content and the powder resistance of the negative electrode materials of Examples 1 to 3 and Comparative Example 1 were measured. For metal content, nickel content or copper content was measured by EDX. The powder resistance was measured using a resistance measuring apparatus (Mitsubishi Chemical Analytech, trade name MCP-PD51). As a sample for measuring powder resistance, 1 g of each of the negative electrode materials was put in a cylindrical tube of 1 cm in diameter and compressed with a load of 20 kN. The measurement results of the metal content and the powder resistance are shown in Table 2.

  As shown in Table 2, the powder resistances of the negative electrode materials of Examples 1 to 3 were very low, and these negative electrode materials were excellent in conductivity. From this result, it is understood that according to the production method of the present invention, a negative electrode material with low powder resistance can be produced. In addition, since the powder resistance of the negative electrode material of Example 1 is much lower than the powder resistance of the negative electrode material of Example 3, when the inlet temperature of spray drying in the particle forming step is 600 ° C. It can be seen that a negative electrode material excellent in conductivity with low powder resistance can be manufactured as compared to the case of 200 ° C. The inlet temperature of 600 ° C. is a temperature at which the decomposition temperature of nickel acetate is about 350 ° C. or more.

Considering the results shown in Table 2 and the SEM image of Evaluation 1, the negative electrode material in which fine metal particles are densely formed on the surface of the silicon material is obtained by spray-drying the slurry at a high temperature in the particle formation step. It is speculated that the negative electrode material having fine and fine metal particles is excellent in conductivity.
As shown in Table 2, the resistance was too high for the negative electrode material of Comparative Example 1, that is, the silicon material, and the powder resistance could not be detected. From this result, it is understood that according to the manufacturing method of the example, it is possible to manufacture a negative electrode material having excellent conductivity while using a silicon material having high powder resistance and poor conductivity.

  The lithium ion secondary battery of Example 1 and the lithium ion secondary battery of Comparative Example 1 using the negative electrode material of Example 1 and the negative electrode material of Comparative Example 1 were manufactured as follows.

Example 1
72.5 parts by mass of the negative electrode material of Example 1 as a negative electrode active material, 13.5 parts by mass of acetylene black as a conductive additive, and 14 parts by mass of a crosslinked polymer obtained by crosslinking polyacrylic acid with diamine as a binder It was a mixture. The mixture was dispersed in an appropriate amount of N-methyl-2-pyrrolidone to prepare a slurry. A copper foil was prepared as a current collector for the negative electrode. The slurry was applied in the form of a film on the surface of the copper foil using a doctor blade. The copper foil to which the slurry was applied was dried to remove N-methyl-2-pyrrolidone, and then the copper foil was pressed to obtain a joint. The obtained bonded product was dried by heating with a vacuum dryer to produce a negative electrode made of copper foil on which a negative electrode active material layer was formed.

Using the negative electrode of Example 1 as an evaluation electrode, a lithium ion secondary battery (half cell) was manufactured. The counter electrode was a metal lithium foil having a thickness of 500 μm.
The counter electrode was cut into a diameter of 14 mm, and the evaluation electrode was cut into a diameter of 11 mm, and a separator (a glass filter manufactured by Hoechst Celanese and "Celgard 2400" manufactured by Celgard) was interposed between both electrodes to form an electrode body. This electrode body was accommodated in a battery case (CR2032 type coin battery member, manufactured by Takasen Co., Ltd.). A non-aqueous electrolytic solution in which LiPF ₆ is dissolved at a concentration of 1 M in a mixed solvent in which ethylene carbonate and diethyl carbonate are mixed at a volume ratio of 1: 1 is injected into a battery case, and the battery case is closed. A lithium ion secondary battery was manufactured.

(Comparative example 1)
The lithium ion secondary battery of Comparative Example 1 is the same as the lithium ion secondary battery of Example 1 except that the negative electrode material of Comparative Example 1, ie, the silicon material, is used instead of the negative electrode material of Example 1. Manufactured.

(Evaluation 1-3)
(Cycle test)
The lithium ion secondary batteries of Example 1 and Comparative Example 1 were initially charged at a temperature of 25 ° C. and a current of 0.5 mA until the voltage with respect to the counter electrode of the evaluation electrode was 0.01 V. Initial discharge was performed at 2 mA until the voltage to the counter electrode of the evaluation electrode was 1 V.
In the evaluation 1-3, occluding Li in the evaluation electrode is referred to as charging, and releasing Li from the evaluation electrode is referred to as discharging.

Next, for each lithium ion secondary battery, 50 cycles of 1 V-0.01 V charge and discharge cycles were performed under the conditions of a temperature of 25 ° C., discharging to 1 V at a current of 0.5 mA and charging to 0.01 V. The discharge capacity of each lithium ion secondary battery after charge and discharge after 50 cycles was measured under the same conditions as the measurement of the initial discharge capacity. These discharge capacities were taken as post-cycle discharge capacities. The capacity retention rate (%) was determined by the following equation.
Capacity retention rate (%) = (cycle after-discharge capacity / initial discharge capacity) x 100

  As shown in Table 3, the capacity retention ratio of the lithium ion secondary battery of Example 1 after 50 cycles is much larger than that of the lithium ion secondary battery of Comparative Example 1 after 50 cycles. It was a value. Thus, the lithium ion secondary battery of Example 1 is superior in durability to the lithium ion secondary battery of Comparative Example 1. From this result, it is understood that the negative electrode material of the present invention in which the metal particles are formed exhibits excellent durability.

<Anode material # 2>
(Example 6)
(Particle formation process)
(Coating process: 1st coating process)
The first coating step was performed in the same manner as the particle formation step in the production method of Example 1 except for the mixing ratio of water, metal salt, and particles of silicon material in the raw material slurry. Specifically, water and nickel acetate tetrahydrate were mixed to prepare a metal salt solution, and a mixture of the metal salt solution and particles of silicon material was used as a raw material slurry. The blending ratio of particles of water, nickel acetate tetrahydrate, and silicon material was 200: 35.3: 200 by mass ratio. In the first coating step, the metal content of the metal salt solution was about 3.5 mass%, and the ratio of the silicon material to water in the raw material slurry was 100: 100 in mass ratio.
The obtained raw material slurry was spray-dried using a spray-drying apparatus in the same manner as in the particle forming step in the production method of Example 1. Through the above steps, the first particles, which are the coated particles of Example 6, were obtained.

(Recoating step: second to tenth coating steps)
Water, nickel acetate tetrahydrate, and so that the metal content of the metal salt solution is about 3.5% by mass, and the ratio of the first particles to water in the raw material slurry is 100: 100 in mass ratio The raw material slurry mixed with the first particles was spray-dried in the same manner as in the first coating step to obtain second particles which are recoated particles.

  Likewise, in the same manner, the obtained recoat particles are prepared so that the metal content of the metal salt solution is about 3.5% by mass, and the ratio of recoat particles to water in the raw material slurry is 100: 100 in mass ratio The step of mixing to obtain a raw material slurry and repeating the step of spray-drying the raw material slurry in the same manner as in the first coating step was repeated to obtain third to tenth particles which are recoated particles of Example 6. The composition of the raw material slurry in the first coating step to the tenth coating step of Example 6 is shown in Table 4.

(Example 7)
As in Example 6, the nickel content of the metal salt solution is about 3.5% by mass, and the ratio of the particles of silicon material (or the i-th particles) to water in the raw material slurry is 100: 100 in mass ratio The step of spray-drying the raw material slurry in which water, nickel acetate tetrahydrate and particles of silicon material (or i-th particles) are mixed is repeated to obtain first particles to 16th particles of Example 7 Obtained. The composition of the raw material slurry in the first coating step to the sixteenth coating step of Example 7 is shown in Table 5.

(Example 8)
Example 6 using MDL-015 (C) MGC (-S) manufactured by Fujisaki Electric Co., Ltd. as a spray drying apparatus, except that the spray drying conditions were an inlet temperature of 200 ° C. and a nozzle gas flow rate of 26 L / min. And in the same manner as in Example 7, the nickel content of the metal salt solution is about 3.5% by mass, and the ratio of the particles of silicon material (or the i-th particles) to water in the raw material slurry is 100: 100 by mass ratio The step of spray-drying the raw material slurry in which water, nickel acetate tetrahydrate and particles of silicon material (or the i-th particle) are mixed so as to be I got The composition of the raw material slurry in the first coating step to the fourteenth coating step of Example 8 is shown in Table 6.

(Heating process)
The tenth particles of Example 6, the eleventh to sixteenth particles of Example 7, and the eleventh to fourteenth particles of Example 8 were each heated at 400 ° C. for one hour in an argon gas atmosphere. In this step, negative electrode material # 10 of Example 6, negative electrode material # 11 to # 16 of Example 7, and negative electrode material # 11 to # 14 of Example 8 were obtained.

(Evaluation 2-1)
A SEM image of the negative electrode material # 10 of Example 6 obtained by heating the tenth particles of Example 6 was taken. The SEM image of negative electrode material # 10 of Example 6 is shown in FIG.
As shown in FIG. 3, in the negative electrode material # 10 of Example 6, very fine metal particles are formed very densely. Comparing FIG. 3 with FIG. 1, the metal particles in the negative electrode material # 10 of Example 6 are finer and denser than the metal particles in the negative electrode material of Example 1 on the surface of the silicon material. It is formed. From this result, it can be seen that performing repeated recoating steps contributes to the refinement and densification of the metal particles.

(Evaluation 2-2)
The powder resistances of the negative electrode materials # 11 to # 16 of Example 7 and the negative electrode materials # 11 to # 14 of Example 8 were measured. For the negative electrode materials # 11 to # 16 of Example 7 and the negative electrode materials # 11 to # 14 of Example 8, the nickel content and the oxygen content were further measured. The measurement results of the metal content and the powder resistance are shown in Table 7 together with the measurement results of the negative electrode material of Comparative Example 1 described above.

  As shown in Table 7, the negative electrode material of Example 7 had very low powder resistance and was excellent in conductivity. From this result, it is possible to further improve the conductivity of the negative electrode material by repeating the recoating step, and to conduct drying at a high temperature in the particle forming step even when repeating the recoating step. It turns out that it is effective for improvement.

  Similar to the lithium ion secondary battery of Example 1, using the negative electrode material # 10 of Example 6, the negative electrode materials # 11 to # 16 of Example 7, and the negative electrode materials # 11 to # 14 of Example 8, respectively. A lithium ion secondary battery # 10 of Example 6, a lithium ion secondary battery # 11 to # 16 of Example 7, and a lithium ion secondary battery # 11 to # 14 of Example 8 were manufactured.

(Evaluation 2-3)
(Cycle test)
Lithium ion secondary battery of Example 1, lithium ion secondary battery # 10 of Example 6, lithium ion secondary batteries # 11 to # 16 of Example 7, lithium ion secondary batteries # 11 to # of Example 8 The initial charge capacity and the initial discharge capacity of the lithium ion secondary battery of Comparative Example 1 and Comparative Example 1 were measured in the same manner as in Evaluation 1-3, and a cycle test was performed.
The initial efficiency and the capacity retention after 50 cycles for each lithium ion secondary battery are shown in Table 8. The initial efficiency was calculated by (initial discharge capacity / initial charge capacity) × 100.

As shown in Table 8, the lithium ion secondary battery # 10 of Example 6 and the lithium ion secondary batteries # 11 to # 16 of Example 7 were compared with the lithium ion secondary battery of Comparative Example 1. The initial efficiency has improved, and the capacity retention rate has been greatly exceeded. In addition, the initial discharge capacity of the lithium ion secondary battery of each example appears to be apparently lower than that of the lithium ion secondary battery of Comparative Example 1. However, in consideration of the fact that at least 25% of the mass of the negative electrode material in each example is formed of a metal coat, it is considered that the initial discharge capacity per volume of the negative electrode material or the mass per silicon material is also improved. I can say that. From this result, it can be said that the manufacturing methods of Examples 6 and 7 in which the recoating step is repeated, greatly contribute to the improvement of the initial characteristics and the capacity retention rate, that is, the cycle characteristics.
In addition, regarding lithium ion secondary batteries # 11 to # 14 of Example 8 in which the drying in the particle forming step was performed at a relatively low temperature, the initial efficiency was higher than that of the lithium ion secondary battery of Comparative Example 1, The capacity retention rate was lower than that of the lithium ion secondary battery # 10 of Example 6 and the lithium ion secondary batteries # 11 to # 16 of Example 7. From this result, it can be seen that if the drying in the particle formation step is performed at a relatively high temperature, a negative electrode material that can improve the battery characteristics can be obtained.

  Furthermore, compared with the negative electrode material of Example 1 which performed the particle formation process at once, the negative electrode material of Examples 6-8 which repeated the recoating process in the particle formation process was excellent in initial stage efficiency and initial stage discharge capacity. From this result, it is understood that, by repeatedly performing the recoating step, metal particles suitable for a negative electrode material for a lithium ion secondary battery can be formed.

Claims (6)

  A particle of a silicon material having a structure in which a plurality of plate-like silicon bodies are stacked in a thickness direction, a solvent of at least one metal salt selected from copper formate, nickel acetate, nickel formate or lead formate The manufacturing method of the negative electrode material which a metal particle solution exists on the particle | grains of the said silicon material made to contact the metal salt solution containing, and it heats to the temperature more than the decomposition temperature of the said metal salt. And a coating step of spray-drying a slurry containing particles of the silicon material and the metal salt solution to form coated particles containing the particles of the silicon material and the metal salt,
The manufacturing method of the negative electrode material of Claim 1 which heats the said coat particle | grain to the temperature more than the decomposition temperature of the said metal salt in at least one part of the said coating process. A coating step of spray-drying a slurry comprising particles of the silicon material and the metal salt solution to form coated particles comprising the particles of the silicon material and the metal salt;
The method for producing a negative electrode material according to claim 1, comprising a recoating step of spray-drying a slurry containing the coated particles and the metal salt solution.   The manufacturing method of the negative electrode material of Claim 3 which repeats a recoating process with respect to the said coated particle.   The method according to claim 3 or 4, further comprising a heating step of heating the coated particles to a temperature above the decomposition temperature of the metal salt after the coating step or after the recoating step to form the metal particles. Method of manufacturing negative electrode material.   The negative electrode material according to any one of claims 3 to 5, wherein the coated particles are heated to a temperature equal to or higher than the decomposition temperature of the metal salt in at least a part of the coating step and / or the recoating step. Manufacturing method.