KR101085611B1 - A silicon-carbon composite negative material for lithium ion battery and the preparation method of the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon-carbon composite negative electrode material for a lithium ion battery and a method for producing the same, wherein the problem to be solved is to improve the specific capacity of the battery. The material of the present invention is based on composite particles of silicon-like particles and carbon-like particles that are spherical or close to the spherical, and are coated with a carbon coating layer. The manufacturing method is as follows. The silicon particles are pulverized, and the composite particles obtained by mixing the silicon particles and the carbon particles are mixed with a precursor of pyrolytic carbon of an organic material, coated, carbonized, crushed and pulverized. Compared with the prior art, the composite negative electrode material coated with the coating layer and based on the composite material of the silicon phase particles and the carbon phase particles has a reversible specific gravity greater than 450 mAh / g, the first round circulating coulomb efficiency is 85% or more, and the second round circulating capacity retention rate This is 80% or more. Since the volumetric effect can be reduced during the inhalation and release of the silicon-containing active material and the diffusion movement of lithium in the active material is improved, the obtained material can be suitably used as a lithium ion battery negative electrode material in portable devices and power tools. have.

Carbon-silicon composite negative electrode material, lithium ion battery

Description

Lithium-ion Battery Silicon-Carbon Composite Negative Electrode Material and Manufacturing Method {A SILICON-CARBON COMPOSITE NEGATIVE MATERIAL FOR LITHIUM ION BATTERY AND THE PREPARATION METHOD OF THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery negative electrode material and a manufacturing method, and a lithium ion battery silicon-carbon composite negative electrode material and a manufacturing method.

Lithium-ion batteries have been rapidly developed since Sony, Japan's first success in researching and developing lithium-ion batteries in 1990, and entering the market. In recent years, lithium ion batteries have been widely used in various fields, such as living and military. On the other hand, with the continuous development of science and technology, consumers' demand for battery characteristics is also increasing. In other words, as electronic products are miniaturized and individually developed, batteries with small volumes and high energy are required. And the energy in the aerospace sector requires batteries with better cycle life, low temperature charge and discharge performance and safety performance. In the field of electric vehicles, there is a demand for batteries with high capacity, low cost and high safety performance. The success of the research and development of lithium ion batteries is mainly due to the electrode materials. In particular, due to the breakthrough development of carbon negative electrode materials, graphite carbon materials have a superior layered structure among many carbon materials, which is suitable for insertion and release of lithium ions. Li-GIC, a graphite lithium compound, has a relatively high specific capacity and is approaching the theoretical specific capacity of 372 mAh / g of LiC ₆ . In addition, lithium ion batteries have superior charge / discharge voltages and relatively low insertion and exit lithium potentials, so a combination with LiCoO ₂ , LiNiO ₂ , LiMn ₂ O _4, etc., provided as a lithium positive electrode material, is suitable, and the average battery voltage is high and the discharge is stable. . Therefore, in the commercialization of lithium ion batteries, a carbon material of graphites is currently used to make a negative electrode material.

However, current graphite materials are already approaching theoretical capacity. In order to realize safe operation under high current density, to reduce the loss of one time irreversible capacity, and to meet the market demand for high energy and high power lithium ion battery in the future, the development of new lithium ion composite electrode material is in urgent situation. to be. Currently, research on the electrode material has been actively conducted. As a result of the research and discovery of the negative electrode material, an alloy metal formed of elements such as Al, Sn, Sb, and Si and lithium is used as a lithium ion battery negative electrode material. The reversible storage capacity far exceeded the graphite negative electrode material. However, the relatively low circulation stability due to the volume effect of these negative electrode materials has caused the system to still have some difference in the degree of practical use. Therefore, the practical use of the materials of the high lithium storage capacity has already emerged as a focus of current lithium ion battery research.

During the study of non-carbon negative electrode materials, silicon materials have a high theoretical lithium storage capacity. For example, the monocrystalline silicon has a lithium capacity of 4200 mAh / g. In addition, silicon has a low insertion lithium potential and shows higher stability than other metals and materials, attracting much attention. If the silicon material application is successful, the negative electrode material of the lithium ion battery will have a significant significance for the development of the lithium ion battery, and also have a significant influence on the development of information and energy fields. However, unlike metallic materials, high volumetric effects exist on silicon materials under high degree of escape insertion conditions, resulting in unstable electrode circulation and high application of lithium ion battery negative electrodes due to high irreversible capacity. Therefore, many researchers are now working to improve and optimize these high lithium storage performance materials. For example, Maxwell of Hitachi, Japan, has improved the structure and conductivity performance of silicon materials by introducing a composite system in which amorphous carbon particles are coated on silicon particle surfaces manufactured using the CVD method. This improved the circulation performance of the material by inhibiting the volume effect during the lithium insertion and removal process at a certain degree. However, it was difficult to control the process of CVD and there were many uncertainties, so mass production could not be realized. The binary composites of silicon and carbon produced by the researchers of CSWang and graphite and silicon powder by spherical milling have a relatively high single-insertion lithium capacity. However, the charging and discharging performance is unstable, and the reduction of the circulating capacity in the early stage is very fast (J. Electrochem. Soc., 8 (1998): 2751-2758). The net structure manufactured by the SBNg et al. (Sol-Gel) method and the composite Si (OCH ₃ ) ₄ of graphite and silicon have a relatively stable mechanical performance, which plays a role in improving circulation performance. As such, the presence of the Si-O net structure inhibited the diffusion of lithium, thereby reducing the amount of lithium intercalated, thereby inhibiting the sufficient display of the high capacity characteristics of silicon (J. Power Sources, 94 (2001): 63-67).

In preparation of the lithium exfoliation during the electrochemical process, silicon has a significant volume effect, and by introducing a volume compensation method, a composite material containing a kind of silicon can be utilized to make use of the high specific-capacity characteristics of silicon. In addition, the volume change of the entire electrode is controlled to a reasonable level to improve circulation stability. In addition, the energy density of the lithium ion electronic negative electrode material is improved, thereby allowing the negative electrode material to have a higher reversible specific capacity than the carbon negative electrode material commonly used in conventional commercials. This can meet increasing battery energy density requirements of various portable electronic equipment.

SUMMARY OF THE INVENTION An object of the present invention is to provide a lithium ion battery silicon-carbon composite negative electrode material and a manufacturing method, and technical problems to be solved are improvement of specific capacity, circulation performance, and high rate discharge performance of a lithium ion battery.

Technical solution of the present invention:

A lithium ion battery composite silicon-carbon negative electrode material characterized by having a composite particle of silicon and carbon as a substrate, having a spherical form or approximating a spherical form, and having a carbon coating layer on the surface of the substrate.

The carbon coating layer of the present invention is an organic pyrolytic carbon coating layer.

The carbon coating layer of the present invention contains conductive carbon.

The coating layer surface of this invention contains a lithium compound.

The coating layer thickness of this invention is 0.1-5 micrometers, the ratio which organic pyrolysis carbon occupies in a negative electrode material is 0.5-20 weight%, and the ratio which conductive carbon occupies in a negative electrode material is 0.5-5 weight%.

The composite silicon-carbon negative electrode material of the present invention has an average particle diameter of 5 to 60 µm, a specific surface area of 1.0 to 4.0 m 2 / g, and a tap density of 0.7 to 2.0 g / cm 3.

The silicon particles of the present invention are single silicon, silicon oxide SiOx, solid solution containing silicon, or intermetallic compound containing silicon, and the proportion of silicon particles in composite particles is 1 to 50% by weight, where 0 <X≤2.

As for the ratio which the silicon particle of this invention occupies in a composite grain | particle, 5-30 weight% is preferable.

The proportion of the silicon particles of the present invention in the composite particles is preferably 10 to 20% by weight.

The silicon-containing solid solution or silicon-containing intermetallic compound of the present invention is any one or two elements of group IIA elements in the silicon and chemical element periodic table, and any one or three elements of transition metal elements. Or any one or two elements of Group IIIA elements, or any one or two elements of Group IVA elements except silicon.

The carbon particles of the present invention are any one or more of one or more of natural scaly graphite, microcrystalline graphite, artificial graphite, carbonaceous mesophase spheres and coke.

The organic pyrolytic carbon of the present invention is water-soluble polyvinyl alcohol, SBR, CMC, polystyrene, polymethyl methacrylate, polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, phenol resin (phenol- Formaldehyde resin, epoxy resin, glucose, sucrose, fructose, fiber, starch or bitumen as a precursor and formed through high temperature carbonization.

The conductive carbon of the present invention is acetylene carbon black, carbon nanotubes, nano CMB, carbon fiber or conductive carbon.

The lithium-containing compound of the present invention is lithium oxide, lithium carbonate, lithium fluoride, lithium chloride, lithium nitrate or lithium hydroxide.

The manufacturing method of the lithium ion battery carbon composite negative electrode material following the following procedure.

1. Grind the silicon particles into 0.1 ~ 1 ㎛ size to make fine particles. Natural graphite having a particle size of 75 μm or less and a carbon content of 95% or more is pulverized, followed by classification, shaping, and purification to obtain carbon particles having a carbon content of 99.9% or more and a particle size of 0.1 to 5 μm.

2. The silicon particles and the carbon particles are mixed to obtain composite particles. 3. The obtained composite particles and a precursor of organic pyrolytic carbon occupying 1 to 25% by weight of the composite particles are mixed or water is added and stirred for about 1 to 12 h. Subsequently, the particles are subjected to gas immersion or coating under conditions of 100 to 400 ° C.

4. Carbonize the particles after coating and heat them at about 450 ~ 1500 ℃ in an inert atmosphere and keep them for 1 ~ 10 hours. The temperature is then lowered to room temperature to form a carbon coating layer.

5. The particles are ground to a size of 5 to 40 μm to produce a lithium ion battery silicon-carbon composite negative electrode material.

In the method of the present invention, the particles are pulverized to a size of 5 to 40 μm, mixed with 1 to 30% by weight of bitumen in powder, and then carbonized to heat 450 to 1500 ° C. in an inert atmosphere. Insulate for about 1 to 10 hours, mix and coat the powder thus obtained and the conductive carbon of powder about 0.5 to 5% by weight, mix for about 1 to 6 hours in a mixing apparatus or a surface coating apparatus, and for 1 to 30 minutes with ultrasonic waves. Disperse about and grind to 5 ~ 60 ㎛ size.

In the method of the present invention, the particles are pulverized to a size of 5 to 60 μm and immersed in a lithium compound, and the composite powder is placed in a compound solution containing lithium in a concentration of 0.2 to 10 wt%, wherein the ratio of solid and liquid Is 0.1 to 2 and immersion time is 1 to 48 hours.

In the method of the present invention, the silicon particles are single silicon, silicon oxide SiOx, solid solution containing silicon or intermetallic compound containing silicon, and silicon particles account for 1-50% by weight of the composite particles, where 0 <x≤ 2, silicon-containing solid solution or silicon-containing intermetallic compound is any one or two elements of group IIA elements of silicon and chemical element periodic table, and any one or three elements of transition metal element And any one or two elements of group IIIA elements, or any one or two elements of group IVA elements other than silicon.

In the method of the present invention, the carbon particles are any one or one or more mixtures of natural scaly graphite, microcrystalline graphite, artificial graphite, mesophase carbon spheres and coke, and the proportion of carbon particles in the composite particles is 50 to 50. 99 wt%.

In the method of the present invention, the proportion of the coating layer in the composite material is 1 to 25% by weight.

In the method of the present invention, the precursor of the organic pyrolytic carbon is water-soluble polyvinyl alcohol, SBR, CMC, polystyrene, polymethyl methacrylate, polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile organic material, phenol resin , Epoxy resins, glucose, sucrose, fructose, fiber or starch.

In the process of the invention the conductive carbon is acetylene carbon black, carbon nanotubes, nano CMB, carbon fiber or conductive carbon.

In the method of the present invention, the lithium compound is lithium oxide, lithium carbonate, lithium fluoride, lithium chloride, lithium nitrate or lithium hydroxide.

In the process of the invention said silicon particle spherical milling is carried out in an inert atmosphere, wherein the inert atmosphere is any one or a mixture of argon, hydrogen or nitrogen.

In the method of the present invention, when the silicon particles and the carbon particles are mixed to form composite particles, they are mixed for 1 to 6 hours in a mixing apparatus.

Compared with the prior art, the present invention uses a composite material of silicon particles and carbon particles and is spherical in shape or close to spherical. The lithium ion battery silicon-carbon composite negative electrode material of the outer coating layer has very high electrochemical lithium adsorption reversible capacity and good circulation stability, the negative electrode material reversible cost is greater than 450 mAh / g, the one-time circulating coulomb efficiency is more than 85%, 200 cycle capacity retention rate is 80% or more. Therefore, the silicon-containing active material significantly reduces the volume effect of inhaling and releasing lithium and improves the diffusion movement of lithium in the active material, thereby improving the efficiency and circulation of the elementary silicon more than elementary substance silicon. In addition, the loss of the positive electrode material was reduced. In addition, since the potential at the time of lithium insertion and removal is higher than that of commercial lithium ion battery negative electrode materials including intermediate phase carbon spheres, it prevents the release of metallic lithium from the surface of the negative electrode and has excellent high current discharge capability. In addition, it is widely used in lithium ion battery negative electrode materials used in various portable devices, electric appliances, etc. due to its advantages such as simple manufacturing technology and easy operation.

1 is an electron micrograph (1000 magnification) of the lithium ion battery composite negative electrode material of Example 1 of the present invention.

2 is an electron micrograph (5000 magnification) of the lithium ion battery silicon composite negative electrode material of Example 1 of the present invention.

3 is a one-time charge and discharge graph of the material of Example 1 of the present invention.

4 is an XRD diagram of a material of Example 1 of the present invention.

The present invention will be described in more detail with reference to the accompanying drawings and examples.

The lithium ion battery composite negative electrode material of this invention is based on the silicon particle and the carbon particle, and the composite carbon coating layer is coat | covered on the surface. The silicon particles in the substrate are simple silicon and silicon oxide SiOx, where 0 <x≤2. The solid solution containing silicon or the intermetallic compound containing silicon may be any one or two elements of silicon and group IIA elements of the periodic table of chemical elements, any one or three elements of transition metal elements, or any of group IIIA elements. It consisted of one or two elements of, or any one or two elements of Group IVA elements other than silicon, with silicon particles accounting for 1-50% by weight of the composite particle substrate. The carbon particles in the substrate are any one or more than one of natural scaly graphite, microcrystalline graphite, artificial graphite, mesophase carbon spheres and coke. The thickness of a coating layer is 0.1-5 micrometers, the ratio which organic pyrolysis carbon occupies in a negative electrode material is 0.5-20 weight%, and the ratio which conductive carbon occupies in a negative electrode material is 0.5-5 weight%. Organic pyrolysis carbon in the coating layer is a pyrolysis carbon formed through high temperature carbonization and is water-soluble polyvinyl alcohol, SBR, CMC, polystyrene, polymethyl methacrylate, polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, Phenolic resin (phenol-formaldehyde resin), epoxy resin (glucose), glucose, sucrose, fructose, fiber, starch or bitumen as a precursor. The conductive carbon in the coating layer is acetylene carbon black, carbon nanotubes, nano CMB, carbon fiber or conductive carbon Super-P, and the surface of the composite particles of the negative electrode material is lithium oxide, lithium carbonate, lithium fluoride, lithium chloride, lithium nitrate, or It is a lithium compound containing lithium hydroxide.

Technical characteristics of the lithium ion battery composite negative electrode material of the present invention are 5 to 60 µm in average particle diameter, 1.0 to 4.0 m 2 / g in specific surface area, and 0.7 to 2.0 g / cm 3 in tap density. The average particle diameter is measured by Malvern's fluorescence particle size analyzer, the specific surface area is measured by a nitrogen-substituted BET method, and the tap density is measured by a Quantachrome AutoTap measuring instrument.

The following procedure is included in producing the lithium ion battery composite negative electrode material of the present invention using the above materials and ratios. 1. The silicon particles are spherically pulverized to a size of 0.1 to 1 탆 in a non-oxidizing atmosphere of air or argon, hydrogen, nitrogen, or any one or several mixed gases, to obtain fine silicon particles. 2. The raw carbon having a particle size smaller than 75 µm and having a carbon content of 95% or more is pulverized in a stage such as classification, molding, and purification to obtain carbon particles having a particle size of 0.1 to 5 µm. 3. The obtained silicon particle and carbon particle | grain are mixed for 1 to 6 hours in a mixed particle granulation apparatus, and a composite particle base material is obtained. 4. The mixture is stirred for 1 to 12 h while spherical grinding or water is applied to the organic particles pyrolyzed carbon precursor that occupies 1 to 25% by weight of the composite particles and the composite particle base, followed by vapor phase deposition or coating under the conditions of 100 to 400 ° C. Make particles. 5. Carbonize the particles after coating, heat them at about 450 ~ 1500 ℃ in inert atmosphere, keep them for 1 ~ 10 hours, lower the temperature to room temperature to form a carbon coating layer and grind them into 5 ~ 40㎛ size. 6. The powder ground to a size of 5 to 40 µm and the bitumen having 1 to 30% by weight of the powder are mixed and coated in a mixing apparatus. 7. After coating the bitumen, carbonize it, but heat it at 450 ~ 1500 ℃ in inert atmosphere, keep it for 1 ~ 10 hours, lower the temperature to room temperature and grind it to 5 ~ 60 ㎛ size. 8. The obtained composite material and conductive carbon having 0.5 to 5% by weight of the powder are mixed and coated, and mixed for 1 to 6 hours in a mixing device or a surface coating device. The ultrasonic wave is dispersed for 1 ~ 30 minutes, but the ultrasonic frequency is 40kHz ~ 28kHz and the ultrasonic power is 50W ~ 3600W. 9. The compound containing lithium is immersed and the composite powder is immersed in a solution containing 0.2 to 10% by weight of lithium containing compound, the ratio of solid and liquid is 0.1 to 2 and the immersion time is 1 to 48 hours. Subsequently, the particle size is adjusted to 5 to 60 mu m to obtain a lithium ion battery silicon-carbon composite negative electrode material.

Silicon combines with lithium to form intermetallic compounds. For example, Li ₂₂ Si ₅ or the like allows lithium to be reversible. In the case of using silicon as a negative electrode material for lithium ion secondary battery, the theoretical charge and discharge capacity of silicon reaches 4200 mAh / g, 9783 mAh / cm 3, and when the specific gravity is calculated as 2.33, the graphite material (the theoretical capacity of 372 mAh / g) is used. Or 844 mAh / g, specific gravity 2.27). However, since the negative electrode material made of silicon is accompanied by a severe volume change of 300% during the lithium extraction process, it causes the silicon negative electrode to crack or cause powdering and the capacity of the negative electrode suddenly drops during the charge and discharge cycle. . Therefore, pure Si cannot be directly used as a next-generation negative electrode material for lithium ion secondary batteries.

In the study of the product and manufacturing method of the present invention, it was found that when the silicon-containing particles are dispersed in the carbon material substrate or the silicon-containing solid solution or intermetallic compound is coated on the surface, the volume change accompanying lithium aspiration is alleviated. Or under certain constraints can prevent electrode differentiation and increase cycle life. In order to fully exhibit such an effect, the silicon particle of small particle size is preferentially needed. In the present invention, silicon particles having a particle size of 1 to 40 µm are ground to 0.1 to 1 µm in an inert atmosphere to obtain fine silicon particles, which are used as negative electrode active materials in the composite material. When the average particle diameter of the silicon particles was larger than 1 µm, the volume absorption reaction of the substrate was weakened and the improvement of the circulation performance of the composite material was affected. When the average particle diameter of the silicon particles is smaller than 0.1 µm, not only the manufacturing difficulty is increased, but also the possibility of the surface oxidation of the active particles is increased by increasing the possibility of surface oxidation of the active particles, which further affects the specific capacity of the negative electrode material. Electron microscope SEM can be used to measure the particle diameter of silicon particles and other methods. For example, the median diameter in the volume particle size distribution measured by the dioptric particle size measuring instrument may be set as the average particle diameter. In the examples, the average particle diameter of the particles was measured using a Malvern Mastersizer 2000 light particle size analyzer in the UK.

In the silicon-carbon composite negative electrode material of the present invention, silicon particles point to 1 to 50% by weight of the composite particle base material. If the proportion of silicon particles exceeds 50% by weight, the substrate cannot effectively alleviate or absorb the volumetric effect of silicon. On the contrary, when the proportion of the silicon particles is smaller than 1% by weight, the capacity of the negative electrode material cannot rise effectively. Therefore, the suitable ratio of silicon particle is 5-30 weight%, and 10-20 weight% is especially preferable.

The silicon particles are intermetallic compounds containing elemental silicon, silicon oxide SiOx, 0 <x≤2, silicon solid solution or silicon. Intermetallic compounds containing silicon solid solution or silicon containing silicon are any one or two elements of silicon and Group IIA elements of the periodic table of chemical elements, any one or three elements of transition metal elements, and group IIIA elements. Any one or two of them, or composed of any one or two of the IVA group elements other than silicon. The element can be used lithium as the active element of the reversible storage to increase the specific capacity of the negative electrode material. On the other hand, some of the elements are inert elements that can not be stored in lithium, but can be used as an active material to mitigate or absorb the volume reaction due to lithium adsorption, or may be used as an element of the conductive performance of the composite material to optimize the circulation stability of the material. When considering various factors such as lithium uptake amount of these elements, relaxation of silicon volume effect, effect of composite conductivity performance and resources, the IIA group elements Mg, Ca, Ba, transition metal elements Ti, Cr, Mn, Fe, Co, Ni, Cu, Mo, Ag, Ce, Nd, Group IIIA elements Al, Ga, In and IVA elements Ge, Sn, Sb are preferred. Among these elements, Mg, Ca, Fe, Co, Ni and Cu are most preferred.

In order to prepare a lithium ion battery composite negative electrode material and to improve the electrochemical performance of the negative electrode material, the present invention has been treated with silicon particles for mixed granulation, composite coating and surface performance improvement.

1 and 2, the lithium ion battery silicon-carbon composite negative electrode material of the present invention is based on a composite material composed of silicon particles and carbon particles, and the surface of the composite material measured by electron microscopy. Has a composite carbon cladding layer and has a spherical or microscopic characteristic close to the spherical. The outer layer is a coating layer composed of organic pyrolysis carbon and conductive carbon, thereby improving compatibility of the graphite material and the electrolyte solution. The coating layer improved the capacity and the large current charge / discharge capacity of the negative electrode material by suppressing the volume effect of the silicon particles, improving the conductive performance, and enabling the reversible insertion and removal of lithium. The relatively large crystalline layer spacing of the coating layer reduced the amount of expansion shrinkage produced during the repeated filling process, prevented breakdown and dropping of the negative electrode material structure, and improved circulation performance.

3 is a one-time charge and discharge curve of the silicon-carbon composite material prepared in Example 1 of the present invention. The high potential of silicon on the charge-discharge curve and about 0.5V vs. Lithium storage of Li / Li ⁺ was increased. This resulted in a relatively large improvement in the lithium adsorption capacity of the composite material.

4 is an X-ray diffraction diagram XRD of the silicon-carbon composite material prepared in Example 1 of the present invention. Among the diffractograms of the composite material compared to the standard powder diffraction data PDF card of the International X-Ray Powder Diffraction Committee are the diffraction rods of carbon PDF card number 41-1487 and silicon PDF card number 27-1402. This means that the silicon-carbon composite material of the present invention is composed of carbon and silicon.

The carbon particles in the substrate may be any one or more mixtures of natural scaly graphite, microcrystalline graphite, artificial graphite, mesophase carbon spheres, and coke, and the proportion of carbon particles in the composite particles is 99 to 50% by weight. To this. Carbon particles are mainly used for absorbing and mitigating the volumetric effect of silicon particles upon lithium adsorption and also provide a constant capacity of lithium insertion. The materials are all flexible carbon materials with relatively good elasticity and relatively high lithium insertion capacity. When the carbon particles are smaller than 50% by weight, the silicon particles cannot be effectively dispersed, and the absorption and relaxation effect of the carbon particles on the volume effect of silicon as the active material is lowered, and the circulation performance of the material is also disadvantageous. On the other hand, when the proportion of carbon particles is greater than 99%, the proportion of silicon, which is the active material, is reduced, which affects the enhancement of the specific amount of the material.

The composite carbon coating layer has a thickness of 0.1 to 5 μm, which is obtained by measuring a particle average particle diameter before and after coating with a Malvern dimming particle size apparatus. The composite carbon coating layer contains organic pyrolysis carbon and conductive carbon and accounts for 1 to 25% by weight of the negative electrode material. Among them, the proportion of organic pyrolytic carbon in the coating layer is 0.5 to 20% by weight, and the proportion of conductive carbon in the coating layer is 0.5 to 5% by weight. When the composite carbon coating layer thickness is less than 0.1 mu m or the proportion of the negative electrode material is less than 1 wt%, a complete coating layer cannot be formed. Therefore, the circulation stability of the negative electrode material is affected. On the other hand, if the coating layer is too thick, for example, larger than 5 μm or the ratio of the coating layer to the negative electrode material is greater than 25% by weight, it will affect the specific capacity and the one-time efficiency of the negative electrode material and the electrochemical performance of the negative electrode material. It is also disadvantageous to improve.

The organic pyrolysis carbon in the coating layer is a pyrolysis carbon formed through high temperature carbonization and is water-soluble polyvinyl alcohol, SBR, CMC, polystyrene, polymethyl methacrylate, polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile. Precursors include, phenol-formaldehyde resin, epoxy resin, glucose, sucrose, fructose, fiber, starch or bitumen. When the organic material is mixed with the composite particle substrate, the tackifier, dispersant, or suspending agent as a precursor or solution system of late pyrolytic carbon is evenly coated on the surface of the composite particle substrate and undergoes pyrolysis reaction and pyrolysis during late pyrolysis carbonization. Create During high temperature pyrolysis, compounds composed of elements such as H, O, and N in organic compounds are decomposed, carbon atoms are continuously cyclized and aromatized, and atoms such as H, O, and N are continuously reduced, and carbon The elements are constantly contracted and concentrated. The organic material is formed of hard graphite through liquid carbonization or solid graphite through solid graphite. All of these pyrolytic carbons are relatively non-graphitized carbons, and thus contain a relatively large amount of minute pores formed during the thermal decomposition of small molecule compounds. As a result, the volume effect of the active material during charge and discharge can be better absorbed and mitigated, and the spacing between the pyrolytic carbon layers is relatively large, which is more advantageous for the insertion and removal of lithium ions. The multilayer structure of the pyrolytic carbon material also improves circulation safety by preventing desorption of the graphite layer due to the incorporation of solventized lithium ions. The conductive carbon in the coating layer is acetylene carbon black, carbon nanotubes, nano CMB, carbon fiber or conductive carbon Super-P.

The method for mixing and coating the composite particle substrate, the precursor of organic pyrolysis carbon, and the conductive carbon is not particularly limited, and any known mixed particle granulation facilities can be used. The mixed coating is mixed spherical grinding or mixed and stirred for 1 to 12 h in the state of adding water, followed by vapor deposition or coating particle formation under conditions of 100 to 400 ° C. When the treatment temperature is lower than 100 ℃, the powder drying rate is relatively slow and the coating effect is also low, which is likely to cause mutual adhesion between the particles, and further affect the production efficiency and product quality. If the treatment temperature is higher than 400 ° C, there is a possibility of causing carbonization or oxidation of the coating layer and affects the coating effect. Subsequently, carbonization is performed on the mixed material, but the temperature is maintained for 1 to 10 hours at a temperature of 450 ° C to 1500 ° C, and the temperature is lowered to room temperature. In order to ensure the denseness of the coating layer, the coating treatment is carried out in two times, wherein the coating material is bitumen and the coating amount is 1 to 30% by weight. The carbonization treatment is carried out in a non-oxidizing atmosphere, for example, nitrogen, argon, helium, neon or a mixture of the above gases, in a vacuum or a reducing atmosphere. The carbonization treatment is performed at a temperature of 450 ° C. to 1500 ° C., but the temperature is maintained for 1 to 10 hours and the temperature is lowered to room temperature again.

The conductive performance is reduced by coating non-graphite organic pyrolytic carbon on the surface of the composite material. Therefore, in order to improve the conductive performance of the negative electrode material and to ensure sufficient stability of the circulation stability and specific amount of the negative electrode material, the present invention performed coating or doping conductive carbon treatment on the surface of the composite material. It points to 0.5-5 weight%. If the amount of the conductive carbon is less than 0.5% by weight, the conductive network cannot be continuously formed and the conductive performance of the material cannot be improved. On the contrary, when the conductive performance is greater than 5% by weight, it may affect the specific amount of the material and the charge / discharge efficiency. Therefore, the ideal conductive dose is 0.5 to 5% by weight.

The method of coating the silicon-carbon composite material and the conductive carbon after the mixed coating treatment is not particularly defined, and a known mixing device can be used. For example, there is a high speed stirring device, a planetary mixing device and the like, and the mixing treatment time is 1 to 6 hours. Ultrasonic treatment is used to treat the suspension of the composite material and the conductive carbon to evenly distribute the conductive carbon, but the ultrasonic treatment time is 1 to 30 minutes, the ultrasonic frequency is 40kHz to 28kHz, and the ultrasonic power is 50W to 3600W.

Solvent and electrolyte salts cause irreversible electrochemical reduction decomposition during one-time charge and discharge of lithium ion batteries. As a result, products such as alkyl lithium carbonate and alkoxy lithium carbonate are deposited on the surface of the negative electrode material to form an SEI film, which is a solid electrolyte film of one layer. This SEI film is insulated against electrons and serves as a conductive part to ions. The nature of the SEI membrane greatly affects the electrochemical performance of the negative electrode material, so that the production of a thin, dense electrode surface passivation film of one layer can prevent the insertion of solvent lithium ions. This ensures that the cell has a relatively high single cycle efficiency and a relatively small cycle savings. The compactness of the passivation film on the surface of the resulting electrode is determined by the base of the carbon microcrystals in the negative electrode material, the relative amounts of the cross-sections, the difference in reactivity and the size of the microcrystals, the constituents of the electrolyte solution, the kinetics of reductive decomposition, and the like.

In the method of the present invention, the silicon-carbon composite negative electrode material is treated using an inorganic or organic solution system of a lithium-containing compound. By generating a single layer of dense lithium ion conductive solid electrolyte membrane on the surface of the negative electrode material, the one-time charge and discharge efficiency and circulation stability of the negative electrode material are improved. A lithium ion battery silicon-carbon composite negative electrode material is obtained later using a method of immersing a lithium-containing compound.

The lithium ion battery obtained through the above treatment uses a silicon-carbon composite negative electrode material with an average particle diameter of 5 to 60 µm, a specific surface area of 1.0 to 4.0 m 2 / g, and a tap density of 0.7 to 2.0 g / cm 3. In the above, the average particle diameter is measured by a Malvern dimming particle size instrument, the specific surface area is measured by a nitrogen-substituted BET method, and the tap density is measured by a Quartachrome AutoTap tap density instrument.

Example 1 Preparation of Silicon-Carbon Composite Negative Electrode Material Si-GC-Li ₂ CO ₃

The silicon powder having a particle size of 75 µm was pulverized into a spherical particle having a size of 0.5 µm in a high speed mechanical grinder in argon gas to obtain a fine silicon powder. Spheroidal graphite having a carbon content of at least 99.9% and a particle diameter of 1 μm was obtained through classification, molding, and crushing treatment on natural graphite having a particle size of 70 μm and a carbon content of 95% or more. The obtained fine silicon powder and spherical graphite were mixed for 6 hours in a double helix stirrer at a ratio of 20% by weight and 80% by weight, respectively, to obtain a composite particle base material. The composite particle base and the 10 wt% phenol resin (phenol-formaldehyde resin) mixture were stirred for 10 h while water was added, followed by drying at 300 ° C. to obtain particles. The composite material after coating the phenol resin was carbonized, heated to 1100 ° C. in argon gas, kept warm for 3 hours, and then lowered to room temperature. It was then dispersed and ground to about 10 μm. The powder after grinding and 10% by weight bitumen were mixed and coated, carbonized, heated to 1200 ° C. in argon gas, kept warm for 2 hours, and then cooled to room temperature. It was then ground to 20 μm and mixed with 0.5 wt% carbon nanotubes in a high speed mill for 4 hours. And it was processed for 5 minutes by the ultrasonic wave of the frequency of 28kHz, 3600W. The 1% Li ₂ CO ₃ solution was immersed for 1 hour and the ratio of solid and liquid of 0.1 was taken to obtain a silicon-carbon composite negative electrode material later. The average particle diameter of the obtained particles was 20.1 µm, the specific surface area was 3.5 m 2 / g, and the tap density was 1.3 g / cm 3.

The electrode was manufactured with the following method about the obtained composite material. An electrode was prepared after 95 g of composite negative electrode material was taken and uniformly mixed with 2.5 g of SBR, 1.5 g of CMC, and 1 g of Super-P conductive agent with an appropriate amount of purified water dispersant. An analog battery was assembled using lithium as an electrode, 1 M LiPF ₆ , EC: DMC: EMC = 1: 1: 1 and v / v solutions, which were three mixed solvents, as an electrolyte solution, and a polypropylene microporous membrane as a diaphragm. A stable current charge / discharge experiment was conducted at a current density of 0.5 mA / cm 2, and the composite material reversible specific capacity was measured under a charge and discharge voltage of 0.02 to 1.5V. Cycling performance was measured using a finished cell, but LiCoO ₂ A finished battery was assembled with a positive electrode, a solution of 1 M LiPF ₆ , EC: DMC: EMC = 1: 1: 1, v / v as an electrolyte, and a polypropylene microporous membrane as a diaphragm. A charge and discharge experiment was conducted at a rate of 1C, and the charge and discharge voltage was limited to 4.2 to 3.0V to measure the capacity retention rate C ₂₀₀ / C ₁ when the battery circulated 200 times.

Example 2 Preparation of Silicon-Carbon Composite Negative Electrode Material Si-Mg-G-C-LiOH

Si-Mg powder having a particle size of 75 µm and containing 50% by weight of silicon was ground in an argon gas at about 0.1 µm with a high speed spherical mill to obtain a fine powder. Natural graphite having a particle size of 70 μm and a carbon content of 95% or more was classified, molded, and purified to obtain spherical graphite having a carbon content of 99.9% or more and a particle size of 3 μm. The obtained 30 weight% Si-Mg powder and 70 weight% spherical graphite were mixed for 1 hour to obtain a composite particle base material. The composite particle substrate and 2.5 wt% SBR were mixed with water for 4 h and then dried under 200 ° C. to form particles. The composite material after coating was carbonized, heated to 700 ° C. in argon gas, warmed for 5 hours, and then ground to a room temperature, and ground to a size of 10 μm. The powdered powder and 12 wt% bitumen were mixed coated and carbonized, heated to 1200 ° C. in argon gas, kept warm for 8 hours, lowered to room temperature, and pulverized to about 15 μm. Subsequently, the mixture was mixed for 1 hour in a high-speed grinder with 1% of nano CMB, and treated for 20 minutes using ultrasonic waves having a frequency of 40 kHz and a power of 50 W. It was immersed in a 5% LiOH solution for 12 hours, at which time the ratio of solid and liquid was 1. This obtained the silicon-carbon composite negative electrode material. The particle size of the particles measured was 15.4 µm, the specific surface area was 2.8 m 2 / g, and the tap density was 1.2 g / cm 3.

For the obtained negative electrode material, an electrode was prepared in the same manner as in Example 1, and electrochemical performance was measured.

Example 3 Preparation of Silicon-Carbon Composite Negative Electrode Material Si-Fe-G-C-LiF

Si-Fe powders having a particle size of 75 μm and containing 75% by weight of silicon were pulverized with a high speed grinder in argon gas to obtain a fine 1 μm Si-Fe powder. Spherical graphite having a carbon content of at least 99.9% and a particle diameter of 5 μm was produced by classifying, molding, and purifying natural graphite having a particle size of 70 μm and a carbon content of 95% or more. The obtained fine Si-Fe powder and spherical graphite were mixed and pulverized in a mill for 6 hours at a ratio of 2% by weight and 98% by weight, respectively, to obtain a composite particle base material. The composite particle substrate and the 1 wt% polyvinyl alcohol solution were mixed and stirred for 10 h while water was added thereto, followed by drying under a temperature of 200 ° C. to form particles. The composite material after coating was carbonized, heated to 1500 ° C. in argon gas, warmed for 1 hour, lowered to room temperature, and ground to about 5 μm. After pulverizing, the powder and 10 wt% bitumen were mixed, coated, carbonized, and heated to 1200 ° C. in argon gas, kept warm for 10 hours, lowered to room temperature, and pulverized to 15 μm. Subsequently, 5% of carbon fiber was mixed for 6 hours in a high-speed mill, treated for 30 minutes with an ultrasonic wave having a frequency of 40 kHz and a power of 50 W, then dried to 100 ° C. to obtain particles. The particles were immersed in 0.2% LiF solution for 48 hours with a solid to liquid ratio of 2. This obtained the silicon-carbon composite negative electrode material. The particles measured had a particle diameter of 15.6 µm, a specific surface area of 1.8 m 2 / g, and a tap density of 1.0 g / cm 3.

For the obtained negative electrode material, an electrode was prepared in the same manner as in Example 1, and electrochemical performance was measured.

Example 4 Preparation of Silicon-Carbon Composite Negative Electrode Material Si-Ca-G-C-LiCl

The Si-Ca powder having a silicon content of 60% by weight and a particle size of 75 μm was pulverized in an argon gas to a size of 0.6 μm by a high speed grinder to obtain a fine Si-Ca powder. Natural graphite having a particle size of 70 µm and a carbon content of 95% or more was pulverized and classified, molded, and purified to obtain spherical graphite having a carbon content of 99.9% or more and a particle diameter of 5 µm. The obtained fine Si-Ca powder and spherical graphite were mixed at a ratio of 40% by weight and 60% by weight, respectively, and mixed in a tapered mixer for 4 hours to form a composite particle substrate. The composite particle substrate and the 10 wt% phenol resin solution were mixed and stirred for 4 h while water was added thereto, and then dried under a temperature of 400 ° C. to obtain particles. The composite material after coating was carbonized, heated to 800 ° C. in argon gas, warmed for 5 hours, lowered to room temperature, and ground to 18 μm. The powder after pulverization and 30% by weight of bitumen were mixed, coated and carbonized, and then heated in an argon gas to 1200 ° C., insulated for 1 hour, lowered to room temperature, and ground to a size of 15 μm. The solid and 1% acetylene carbon black were then mixed for 2 hours in a high speed mill and treated for 20 minutes with ultrasonic waves at a frequency of 40 kHz and a power of 50 W. The particles were immersed in 10% LiCl solution for 24 hours with a solid to liquid ratio of 0.5. This obtained the silicon-carbon composite negative electrode material. The measured particles had a particle diameter of 24.8 µm, a specific surface area of 3.8 m 2 / g, and a tap density of 0.94 g / cm 3.

For the obtained negative electrode material, an electrode was prepared in the same manner as in Example 1, and electrochemical performance was measured.

Example 5 Preparation of Silicon-Carbon Composite Negative Electrode Material SiO-GC-Li ₂ O

SiO powder having a particle size of 75 µm was ground in an argon gas to a size of 0.8 µm with a high speed grinder to obtain a fine SiO powder. Artificial graphite having a particle size of 70 µm and a carbon content of 95% or more was pulverized and subjected to classification, molding, and purification to obtain spherical graphite having a carbon content of 99.9% or more and a particle size of 3 µm. The obtained fine SiO powder and spherical graphite were mixed at a ratio of 15 wt% and 85 wt%, respectively, and mixed in a double helix mixer for 5 hours to form a composite particle substrate. The composite particles and 2.5% by weight of a polyvinyl alcohol solution were mixed and stirred for 4 h while water was added thereto, and then dried under a temperature of 250 ° C. to obtain particles. The composite material after coating was carbonized, heated to 1300 ° C. in argon gas, warmed for 2 hours, lowered to room temperature, and ground to about 5 μm. The powder after pulverization and 8% by weight bitumen were mixed, coated and carbonized, heated to 1100 ° C. in argon gas, kept warm for 10 hours, lowered to room temperature, and ground to a size of 5 μm. The solid was then immersed in 5% Li ₂ O solution for 48 hours with a solid to liquid ratio of 1. This obtained the silicon-carbon composite negative electrode material. The particles measured were 5.8 μm, specific surface area of 3.8 m 2 / g, and tap density of 0.96 g / cm 3.

For the obtained negative electrode material, an electrode was prepared in the same manner as in Example 1, and electrochemical performance was measured.

Example 6 Preparation of Silicon-Carbon Composite Negative Electrode Material Si-GC-LiNO ₃

A Si-Ni powder having a silicon content of 40% by weight and a particle size of 75 µm was ground in an argon gas at about 0.6 µm with a high speed grinder to obtain a fine Si-Ni powder. Artificial graphite having a particle size of 70 µm and a carbon content of 95% or more was pulverized and subjected to classification, molding, and purification to obtain spherical graphite having a carbon content of 99.9% or more and a particle size of 3 µm. The obtained fine Si-Ni powder and spherical graphite were mixed at a ratio of 50 wt% and 50 wt%, respectively, and mixed in a double helix mill for 6 hours to form a composite particle substrate. The composite particles and 2.5 wt% SBR solution were mixed and stirred for 4 h while water was added thereto, and then dried under a temperature of 200 ° C. to obtain particles. The composite material after coating was carbonized, heated to 700 ° C. in argon gas, warmed for 5 hours, lowered to room temperature, and ground to about 10 μm. The powder after pulverization and 12 wt% bitumen were mixed and coated, carbonized, and heated to 1200 ° C. in argon gas, kept warm for 10 hours, and then lowered to room temperature and pulverized to about 5 μm. The solid was then mixed with 1% conductive carbon (Super-P) for 2 hours and treated with ultrasonic waves at a frequency of 35 kHz and an output of 2500 W for 15 minutes. The particles were immersed in 10% LiNO ₃ solution for 36 hours with a solid to liquid ratio of 2. This obtained the silicon-carbon composite negative electrode material. The particle | grains measured were 5.2 micrometers, the specific surface area was 4.0 m <2> / g, and the tap density was 2.0 g / cm <3>.

For the obtained negative electrode material, an electrode was prepared in the same manner as in Example 1, and electrochemical performance was measured.

Example 7: Preparation of Silicon-Carbon Composite Negative Electrode Material SiO ₂ -GC

The SiO ₂ powder has a particle size of 75 ㎛ obtain the SiO ₂ powder were pulverized with a 0.8 minute ㎛ size as the high-speed grinder the air. Artificial graphite having a particle size of 70 µm and a carbon content of 95% or more was pulverized and subjected to classification, molding, and purification to obtain spherical graphite having a carbon content of 99.9% or more and a particle size of 3 µm. The obtained fine SiO ₂ powder and spherical graphite were mixed at a ratio of 10% by weight and 90% by weight, respectively, and mixed for 5 hours in a double helix mill to produce a composite particle substrate. The composite particles and 25% by weight of a phenol-formaldehyde resin solution were mixed and stirred for 4 h while water was added thereto, and then dried under a temperature of 250 ° C. to obtain particles. The composite material after coating was carbonized, heated to 1300 ° C. in a reducing gas containing hydrogen, and warmed for 2 hours, and then lowered to room temperature and ground to 40 μm. The powder after grinding and 5% by weight of bitumen were mixed and coated, and heated in an argon gas to 1100 ° C. through carbonization and kept for 10 hours, and then lowered to room temperature and ground to a size of 60 μm. This obtained the silicon-carbon composite negative electrode material. The particles measured had a particle diameter of 60.4 µm, a specific surface area of 2.8 m 2 / g, and a tap density of 0.98 g / cm 3.

For the obtained negative electrode material, an electrode was prepared in the same manner as in Example 1, and electrochemical performance was measured.

Example 8 Fabrication of Silicon-Carbon Composite Negative Electrode Material Si-G-C

The Si powder having a particle size of 75 µm was ground in an argon gas at about 0.5 µm with a high speed grinder to obtain a fine Si powder. Natural graphite having a particle size of 70 µm and a carbon content of 95% or more was pulverized and subjected to classification, molding, and purification to obtain spherical graphite having a carbon content of 99.9% or more and a particle diameter of 3 µm. The obtained fine Si powder and spherical graphite were mixed at a ratio of 5% by weight and 95% by weight, respectively, and mixed in a rotary mill for 5 hours to form a composite particle base material. The composite particles, 2.5% by weight SBR solution and 1.5% CMC solution were mixed and stirred for 1 h while water was added thereto, and then dried under a temperature of 250 ° C. to obtain particles. The composite material after coating was carbonized, heated to 450 ° C. in argon gas, warmed for 10 hours, lowered to room temperature, and ground to a size of 15 μm. The powder after pulverization and 1% by weight of bitumen were mixed, coated, carbonized, and heated to 1100 ° C. in argon gas, kept warm for 10 hours, lowered to room temperature, and pulverized to a size of 17 μm. This obtained the silicon-carbon composite negative electrode material. The measured particles had a particle diameter of 17.2 µm, a specific surface area of 3.3 m 2 / g, and a tap density of 1.05 g / cm 3.

For the obtained negative electrode material, an electrode was prepared in the same manner as in Example 1, and electrochemical performance was measured.

Example 9 Preparation of Silicon-Carbon Composite Negative Electrode Material Si-G-C

The Si powder having a particle size of 75 µm was ground in an argon gas at about 0.5 µm with a high speed grinder to obtain a fine Si powder. Natural graphite having a particle size of 70 μm and a carbon content of 95% or more was pulverized and classified, molded, and purified to obtain spherical graphite having a carbon content of 99.9% or more and a particle size of 3 μm. The obtained fine Si powder and spherical graphite were mixed at a ratio of 1% by weight and 99% by weight, respectively, and mixed in a rotary mill for 5 hours to form a composite particle substrate. The composite particles, 2.5% by weight of SBR solution and 1.5% of CMC solution were mixed and stirred for 12 h with water, and treated for 5 minutes using ultrasonic waves of 28 kHz and 3600 W, followed by a temperature of 250 ° C. Dry and the particles were obtained. The composite material after coating was carbonized, heated to 450 ° C. in argon gas, warmed for 10 hours, lowered to room temperature, and ground to a size of 15 μm. The powder after pulverization and 6% by weight bitumen were mixed, coated and carbonized, heated to 1100 ° C. in argon gas, kept warm for 10 hours, lowered to room temperature, and ground to a size of 17 μm. This obtained the silicon-carbon composite negative electrode material. The particles measured had a particle diameter of 17.5 μm, a specific surface area of 3.2 m 2 / g, and a tap density of 1.03 g / cm 3.

For the obtained negative electrode material, an electrode was prepared in the same manner as in Example 1, and electrochemical performance was measured.

Example 10 Preparation of Silicon-Carbon Composite Negative Electrode Material Si-Sn-Cu-G-C

The Si—Sn—Cu powder having a particle size of 75 μm was pulverized into 0.5 μm in an argon gas with a high speed grinder at a weight ratio of Si: Sn: Cu = 65: 30: 5 to obtain a fine Si alloy powder. Natural graphite having a particle size of 70 μm and a carbon content of 95% or more was pulverized and classified, molded, and purified to obtain spherical graphite having a carbon content of 99.9% or more and a particle size of 3 μm. The obtained fine Si powder and spherical graphite were mixed at a ratio of 40% by weight and 60% by weight, respectively, and mixed in a rotary mill for 5 hours to form a composite particle base material. The composite particles, 2.5% by weight of SBR solution and 1.5% of CMC solution were mixed and stirred for 12 h while added with water, treated for 5 minutes using ultrasonic waves at a frequency of 28 kHz and 3600 W, followed by drying at a temperature of 250 ° C. And particles were obtained. The composite material after coating was carbonized, heated to 450 ° C. in argon gas, kept warm for 10 hours, lowered to room temperature, and ground to a size of 15 μm. The powder after pulverization and 6% by weight bitumen were mixed, coated, carbonized, and heated to 1100 ° C. in argon gas, kept warm for 10 hours, lowered to room temperature, and pulverized to about 17 μm. This obtained the silicon-carbon composite negative electrode material. The particles measured had a particle diameter of 17.5 µm, a specific surface area of 2.1 m 2 / g, and a tap density of 1.23 g / cm 3.

For the obtained negative electrode material, an electrode was prepared in the same manner as in Example 1, and electrochemical performance was measured.

Example 11 Preparation of Silicon-Carbon Composite Negative Electrode Material Si-Ni-Co-Ag-G-C

Si-Ni-Mg-Ag powder having a particle size of 75 µm was ground in an argon gas in a weight ratio of Si: Ni: Co: Ag = 55: 30: 10: 5 with a high speed mill to about 0.5 µm to obtain a fine Si alloy powder. It was. Natural graphite having a particle size of 70 μm and a carbon content of 95% or more was pulverized and classified, molded, and purified to obtain spherical graphite having a carbon content of 99.9% or more and a particle size of 3 μm. The obtained fine Si powder and spherical graphite were mixed at a ratio of 40% by weight and 60% by weight, respectively, and mixed in a rotary mill for 5 hours to form a composite particle base material. The composite particles, 2.5% by weight of SBR solution and 1.5% of CMC solution were mixed, stirred for 12h, treated with ultrasonic water at a frequency of 28 kHz and 3600W for 5 minutes with water, followed by drying at a temperature of 250 ° C. And particles were obtained. The composite material after coating was carbonized, heated to 450 ° C. in argon gas, warmed for 10 hours, lowered to room temperature, and ground to about 15 μm. The powder after pulverization and 6% by weight bitumen were mixed, coated, carbonized, and heated to 1100 ° C. in argon gas, kept warm for 10 hours, lowered to room temperature, and pulverized to about 17 μm. This obtained the silicon-carbon composite negative electrode material. The particle size of the measured particles was 17.5 µm, the specific surface area was 1.9 m 2 / g, and the tap density was 1.41 g / cm 3.

For the obtained negative electrode material, an electrode was prepared in the same manner as in Example 1, and electrochemical performance was measured.

Comparative example:

Natural spherical graphite having a D ₅₀ = 16 μm was used directly as a negative electrode material without being treated as a negative electrode material. The electrode was prepared according to the same method as in Example 1, and the electrochemical performance was measured.

The electrochemical performance of the negative electrode material measured by the said Example and the comparative example is shown in Table 1.

As can be seen from the examples, the reversible specific capacity of the graphite negative electrode material produced in the present invention is greater than 450 mAh / g and the 200 cycle capacity retention rate is greater than 80%.

As the lithium-ion battery silicon-carbon composite material of the present invention is widely used in various fields such as mobile phones, laptops, cameras, portable electric appliances, electric tools, etc., the cost of the battery is greatly improved, and the weight of the battery in the electric appliance is increased. Also more realistic.

Electrochemical Performance of Negative Electrode Materials Si particles and content in the substrate 1st round
Charging capacity
(mAh / g) 1st round
Discharge capacity
(Ah / g) 200th cycle capacity retention rate
(%) Example 1 Si 20 wt% 765 650 82.3 Example 2 Si-Mg 30 wt% 770 680 87.1 Example 3 Si-Fe 2 wt% 526 452 83.5 Example 4 Si-Ca 40 wt% 806 690 82.1 Example 5 SiO 15 wt% 658 558 82.5 Example 6 Si-Ni 50 wt% 772 654 81.8 Example 7 SiO ₂ 10 wt% 530 450 84.9 Example 8 Si 5 wt% 538 458 89.6 Example 9 Si 1 wt% 421 386 92.1 Example 10 Si-Sn-Cu 40 wt% 965 788 81.2 Example 11 Si-Ni-Co-Ag 40 wt% 915 775 84.3 Comparative example - 401 345 70.0

Claims (25)

delete delete delete It is based on a composite particle of silicon and carbon, the shape of the base material is spherical or approximate to the spherical shape, and there is a carbon coating layer on the surface of the base material, The carbon coating layer is an organic material pyrolysis carbon coating layer, The carbon coating layer contains conductive carbon, A lithium ion battery composite silicon-carbon negative electrode material, wherein the coating layer surface contains a lithium compound. The thickness of the said coating layer is 0.1-5 micrometers, the ratio of organic pyrolysis carbon to a negative electrode material is 0.5 to 20 weight%, and the ratio of conductive carbon to a negative electrode material is 0.5 to 5 weight%. A lithium ion battery composite silicon-carbon negative electrode material. The composite silicon-carbon negative electrode material according to claim 4 or 5, wherein the average particle diameter of the composite silicon-carbon negative electrode material is 5 to 60 µm, the specific surface area is 1.0 to 4.0 m 2 / g, and the tap density is 0.7 to 2.0 g. / Cm 3 It is a lithium ion battery composite silicon-carbon negative electrode material. The method according to claim 6, wherein the silicon particles are single silicon, silicon oxide SiOx, solid solution containing silicon or an intermetallic compound containing silicon, and the proportion of silicon particles in the composite particles is 1 to 50% by weight, wherein 0 <x≤2, The lithium ion battery composite silicon-carbon negative electrode material characterized by the above-mentioned. The lithium ion battery composite silicon-carbon negative electrode material according to claim 6, wherein the proportion of the silicon particles in the composite particles is preferably 5 to 30% by weight. The lithium ion battery composite silicon-carbon negative electrode material according to claim 8, wherein the proportion of the silicon particles in the composite particles is preferably 10 to 20% by weight. delete 10. The method of claim 9, wherein the carbon particles are any one or a mixture of one or more of natural scaly graphite, microcrystalline graphite, artificial graphite, carbonaceous mesophase spheres and coke. Lithium ion battery composite silicon-carbon negative electrode material. The method of claim 11, wherein the organic pyrolysis carbon is water-soluble polyvinyl alcohol, SBR, CMC, polystyrene, polymethyl methacrylate, polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, Lithium-ion battery composite silicon-carbon, characterized in that the phenol-formaldehyde resin, epoxy resin, glucose, sucrose, fructose, fiber, starch or bitumen as a precursor and formed by high temperature carbonization Negative electrode material. The lithium ion battery composite silicon-carbon negative electrode material according to claim 12, wherein the conductive carbon is acetylene carbon black, carbon nanotubes, nano CMB, carbon fiber or conductive carbon. The lithium ion battery composite silicon-carbon negative electrode material according to claim 13, wherein the lithium compound is lithium oxide, lithium carbonate, lithium fluoride, lithium chloride, lithium nitrate or lithium hydroxide. delete delete A method for producing a lithium ion battery silicon-carbon composite negative electrode material following the following procedure. 1. Grind the silicon particles into 0.1 ~ 1 ㎛ size to make fine particles. Natural graphite having a particle size of 75 μm or less and a carbon content of 95% or more is pulverized, followed by classification, shaping, and purification to obtain carbon particles having a carbon content of 99.9% or more and a particle size of 0.1 to 5 μm. 2. The silicon particles and the carbon particles are mixed to obtain composite particles. 3. The obtained composite particles and a precursor of organic pyrolytic carbon occupying 1 to 25% by weight of the composite particles are mixed or water is added and stirred for about 1 to 12 h. Subsequently, the particles are subjected to gas immersion or coating under conditions of 100 to 400 ° C. 4. Carbonize the particles after coating and heat them at about 450 ~ 1500 ℃ in an inert atmosphere and keep them for 1 ~ 10 hours. The temperature is then lowered to room temperature to form a carbon coating layer. 5. Grind the particles into 5-40 ㎛ size. 6. The pulverized particles were mixed and coated with 1-30 wt% of bitumen of the powder, followed by carbonization and heating at 450 to 1500 ° C. in an inert atmosphere, followed by warming for 1 to 10 hours. Powder and powder about 0.5 to 5% by weight of conductive carbon are mixed and coated, mixed for 1 to 6 hours in a mixing device or surface coating device, dispersed for 1 to 30 minutes by ultrasonic wave, and then to the size of 5 to 60 μm. Crush. 7. The pulverized particles are immersed in a lithium compound, and the composite powder is placed in a compound solution containing lithium in a concentration of 0.2 to 10% by weight, wherein the ratio of solid and liquid is 0.1 to 2 and the immersion time is 1 to 48 hours. 18. The method of claim 17, wherein the silicon particles are single silicon, silicon oxide SiOx, a solid solution containing silicon, or an intermetallic compound containing silicon, and silicon particles make up 1-50% by weight of the composite particles, wherein 0 <x ≤ 2, silicon-containing solid solution or silicon-containing intermetallic compound is any one or two of the group IIA elements of the silicon and chemical element periodic table, any one or three of the transition metal elements And any one or two elements of a group IIIA element, or any one or two elements of an IVA group element other than silicon. A method for producing a lithium ion battery silicon-carbon composite negative electrode material. 19. The method according to claim 18, wherein the carbon particles are any one or more mixtures of natural scaly graphite, microcrystalline graphite, artificial graphite, mesophase carbon spheres and coke, and the proportion of carbon particles in the composite particles is 50. It is -99 weight%, The lithium ion battery silicon-carbon composite negative electrode material manufacturing method. The method for producing a lithium ion battery silicon-carbon composite negative electrode material according to claim 19, wherein the proportion of the coating layer in the composite material is 1 to 25% by weight. The polyvinyl alcohol, SBR, CMC, polystyrene, polymethyl methacrylate, polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile organic material, phenol, wherein the precursor of the organic pyrolysis carbon is water-soluble. Resin, epoxy resin, glucose, sucrose, fructose, cellulose or starch, The lithium ion battery silicon-carbon composite negative electrode material manufacturing method characterized by the above-mentioned. The method for producing a lithium ion battery silicon-carbon composite negative electrode material according to claim 21, wherein the conductive carbon is acetylene carbon black, carbon nanotubes, nano CMB, carbon fibers or conductive carbon. The method for producing a lithium ion battery silicon-carbon composite negative electrode material according to claim 22, wherein the lithium compound is lithium oxide, lithium carbonate, lithium fluoride, lithium chloride, lithium nitrate or lithium hydroxide. The lithium ion battery silicon-carbon composite negative electrode according to claim 23, wherein the spherical milling of the silicon particles is performed in an inert atmosphere, wherein the inert atmosphere is any one or a mixture of argon, hydrogen, or nitrogen. Material manufacturing method. The method for producing a lithium ion battery silicon-carbon composite negative electrode material according to claim 24, wherein the silicon particles and the carbon particles are mixed for 1 to 6 hours in a mixing device when the composite particles are mixed.

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