KR20120041383A - An electrode-active composite comprising an electrically-conductive porous body and a transition metal compound filler, and a method for preparing the same - Google Patents

Abstract

PURPOSE: A composite is provided to have high volume density and small specific surface area, not to generate a sudden increase of viscosity in a slurry dispersion process for manufacturing electrodes, and to remarkably decrease dispersion time. CONSTITUTION: An electrode active composite comprises an electroconductive porous material and a transition metal compound filler, and has a tap density of 1.5 g/cm^3. The weight of the porous material occupies 0.5-50% of the composite weight. The porous material consists of carbon. The ratio(I1355/I1575) of the peak intensity at 1355cm^(-1) to the peak intensity at 1575 cm^(-1) in the Raman spectrum of the carbon is 0.85 or less. A manufacturing method of the composite comprises a step of filling the pores of the electroconductive porous material with transition metal compounds.

Description

A composite having an electrode activity, comprising an electrically conductive porous body and a filler of a transition metal compound, and a method for producing the same.

The present invention relates to a composite comprising an electrically conductive porous body and a filler of a transition metal compound and having an electrode activity, and a method for producing the same.

Transition metal compounds are used as electrode active materials for secondary batteries, and many efforts have been made to improve physicochemical properties such as corrosion resistance and dispersibility, and electrical properties such as electrical conductivity.

 Examples of such efforts include nanonization of transition metal compound particles, solid solution of dissimilar elements, formation of a protective film on the particle surface, and agglomeration of nanometer-sized primary particles into secondary particles.

It has been frequently performed to coat the surface of transition metal compound particles with a carbon-based material or ceramic material which is excellent in corrosion resistance and chemical resistance and improves the electrical conductivity of the electrode material.

Since carbon has advantages such as high electronic conductivity, chemical stability, and the like, the carbon is coated or mixed with the transition metal compound for the purpose of protecting the transition metal compound and improving its function. Rather than simply mixing carbon with a transition metal compound using a mechanical mixing method, the advantage of carbon is more pronounced when carbon is coated on the particle surface of the transition metal compound using chemical vapor deposition or the like. Advantages of carbon include improvement in electrical conductivity of electrode materials, protection of transition metal compound particles from external physicochemical influences, and limitation of excessive growth of transition metal compound particles during heat treatment.

Looking at the chemical stability aspect more specifically, there is a much higher risk of the transition metal compound being exposed to a highly reactive material such as an acidic or alkaline material compared to the case of simply mixing carbon. For example, in the case of a lithium secondary battery, LiPF ₆ is generally used as an electrolyte. When moisture is present in the battery, hydrofluoric acid (HF) is generated by reaction between moisture and LiPF ₆ , and the hydrofluoric acid is a strong acid material. The battery performance is lowered by dissolving and oxidizing it. This problem of dissolution and oxidation by hydrofluoric acid can be remarkably alleviated by coating the surface of the electrode active material with carbon. Therefore, in spite of the cost and complexity of the process compared to the case of mixing carbon, coating is more generally performed.

The general method of coating carbon is to apply carbon precursor to the transition metal compound particles, and then heat-treat the carbon precursor under an inert atmosphere to carbonize it. The crystallinity, electrical conductivity, mechanical strength, etc. of the carbide produced vary depending on the type of carbon precursor and the atmosphere and temperature of the carbonization reaction. In order to achieve complete carbonization in which all hydrogen, oxygen, hydrocarbons, impurity elements, etc. are released through pyrolysis and the carbides have high crystallinity, it is preferable to perform carbonization at 1,000 ° C. or higher. Increasing the heat treatment temperature increases the crystallite size and crystallinity of the carbon, and increasing the crystallinity also increases the mechanical strength and electrical conductivity of the carbides produced.

However, when the temperature for carrying out the carbonization rises above a certain level, the transition metal compound may cause phase transition or thermal decomposition. Therefore, the carbonization temperature is limited to be within the range that does not adversely affect the transition metal compound.

On the other hand, the carbon coating should be thick enough for physicochemical protection of the transition metal compound, and a large amount of carbon precursor should be used to secure sufficient thickness, but a large amount of carbon precursor is used for forming the coating. There is a disadvantage that becomes more likely to form.

In the known art, the carbon precursor was carbonized at low temperature to form a carbon coating, and the carbon coating was not thick enough. For example, US Pat. Nos. 6,855,273 and 6,962,666 coat a particle surface of the electrode material with a carbon-based material, wherein the heat treatment temperature for forming the coating is a low temperature of 800 ° C or lower. As a result of low temperature carbonization, the resulting carbonaceous coating is not highly crystalline. In addition, when using the method of the prior art, it is difficult to completely cover the surface of the individual particles, the particles are fine and dispersibility is lowered by causing a sharp increase in viscosity when dispersed in an organic solvent or water system, the dispersion time is long There are disadvantages such as an excessive amount of binder required for electrode bonding. Furthermore, in the prior art, the carbon-based material is coated on the fine primary particles, and the bulk density of the product is low, and as a result, the electrode density is low, and also when the powdery electrode material is transported or weighed, Problems such as adhesion phenomenon occur.

On the other hand, Korean Patent Application Publication No. 2010-0044713 aggregates fine primary particles to make secondary particles. However, according to the prior art, when the primary particles are not coated with carbon, the primary particles are in direct contact with each other, and when the primary particles are coated with carbon, as shown in FIG. A core-shell structure composed of a core made of a metal compound and a shell, which is a carbon coating, in which case a large amount of empty space is generated between the primary particles. Unlike the prior art, in the present invention, the primary particles and the primary particles are separated by the porous body inner wall, and have a high-density structure in which the empty space inside the porous body is minimized.

The problem to be solved by the present invention is to provide an electrode material with improved physicochemical function and a method of manufacturing the same.

The present invention provides a composite comprising an electrically conductive porous body and a filler of a transition metal compound and having an electrode activity, and also providing a method of manufacturing the same.

In one embodiment of the present invention, there is provided a composite comprising a highly crystalline porous body and a transition metal compound filler.

Another embodiment of the present invention provides a high density porous body / filler composite.

Methods of preparing the porous body / filler composite according to the present invention are largely divided into two. In the first method, a porous body is formed and a filler is formed in its pores. Another method is to make a filler and mix it with the raw material for forming the porous body to form a porous / filler composite. Heat treatment of the composite thus formed enhances crystallinity and mechanical strength.

The composite according to the present invention may be a high density composite with minimal empty space therein. In addition, the porous body according to the present invention has high crystallinity and robustness, and may physically protect the filler and allow the filler to sufficiently express an electrochemical function.

 When the high density composite according to the present invention is used as an electrode active material of a lithium secondary battery, the density of the electrode can be dramatically improved, and accordingly, the energy density of the electrode can be increased. Furthermore, the battery life can be improved by suppressing the volume change of the transition metal compound accompanying the lithium ion insertion and desorption reaction.

In addition, the present invention can significantly improve the problems that occur in the handling process of the powdered electrode material. Since the composite according to the present invention has a high bulk density and a small specific surface area, a sharp increase in viscosity does not occur in the slurry dispersing process for preparing the electrode, and it is easily dispersed to significantly reduce the dispersion time, as well as the solid content of the slurry. It is possible to increase the electrode density by increasing the content. In addition, when packaging, transporting and weighing, problems such as static electricity generation and dust scattering associated with nanometer-sized primary particles can be greatly improved.

The composite having electrode activity according to the present invention can be used as an electrode active material of capacitors and other electrochemical devices, including secondary batteries, memory devices, and hybrid capacitors (P-EDLC), in particular as a cathode active material of secondary batteries. Suitable.

1A is a schematic diagram of a porous body having empty pores. 1B is a schematic diagram of a porous body / filler complex. FIG. 1C is a schematic diagram of a core-shell structure in which transition metal compound particles form a core, and the surface of the core is coated with carbon.
2A is a scanning electron microscope (SEM) photograph of the carbon porous body obtained in step a) of Example 1. FIG. (Magnification of large pictures: 3,000x, magnification of small pictures: 50,000x)
2B is a scanning electron microscope (SEM) photograph of the carbon porous body / lithium iron phosphate composite obtained in Example 2. FIG. (Magnification of large picture: 1,000x, magnification of small picture: 5,000)
FIG. 2C is a scanning electron microscope (SEM) photograph of the carbon-coated lithium iron phosphate secondary particles obtained in Comparative Example 1 measured at a magnification of 10,000 times. FIG.
3 is an X-ray diffraction spectroscopy (XRD) graph of the carbon porous body / lithium cobalt dioxide composite prepared in step b) of Example 1. FIG.
Figure 4 is an X-ray diffraction spectroscopy (XRD) graph of the carbon porous body / lithium iron phosphate composite prepared in Example 2.
5 is an X-ray diffraction spectroscopy (XRD) graph of the carbon porous body / lithium iron phosphate composite prepared in Example 3. FIG.
FIG. 6 is an X-ray diffraction spectrum (XRD) graph of the carbon porous body / lithium iron phosphate nickel manganese cobalt composite prepared in Example 4. FIG.
7 is an X-ray diffraction spectrum (XRD) graph of lithium iron phosphate having a core-shell structure prepared in Comparative Example 1. FIG.
Graph (a) of Figure 8 is a Raman spectrum of the highly crystalline carbon porous body obtained in step a) of Example 1. Graph (b) of Figure 8 is a Raman spectrum of the core-shell structure coated with carbon, obtained in Comparative Example 1.
9 is a carbon porous body / lithium iron phosphate composite of Example 2 using a positive electrode active material
A charge and discharge graph of a lithium secondary battery.

The present invention provides a composite comprising an electrically conductive porous body and a transition metal compound filler and having electrode activity.

In one embodiment of the present invention, the porous body has high crystallinity.

In another embodiment of the present invention, the void space inside the composite is minimized so that the composite has a high density.

Porous body

The porous body constituting the skeleton of the composite according to the present invention can be obtained by various methods. The shape of the porous body and the porous raw material are also not limited to specific ones.

The porous body preferably has open pores connected from the outside to the inside. However, after the porous body / filler composite is formed, an electrically conductive material may be applied to the outer surface of the composite to prevent the filler from being exposed to the outside.

The pores formed inside the porous body are not limited to a particular shape, and may have various shapes such as spherical shape, straight tube shape, curved tube shape, square shape, and atypical shape. The particle size of the transition metal compound, which is a filler filled in such internal pores, is defined by the pore size, so that the size of the pores is controlled or selected so that the filler has the desired size.

When preparing the transition metal compound particles and coating the surface thereof with a carbon-based material as in the prior art, the particle size of the transition metal compound is controlled by the conditions of the process for producing the transition metal compound. According to one embodiment of the present invention, in the case where a porous metal having pores having a desired shape and size is formed in advance, and then a transition metal compound is produced in the pores of the porous body, the shape and size of the transition metal compound is the shape of the pores inside the porous body. And size. That is, a factor that determines the shape of the pores and the like in the process of manufacturing the porous body is a factor that determines the shape of the transition metal compound particles and the like.

In addition, in the present invention, when manufacturing the porous body, it is possible to control the wall thickness between the pores by adjusting the ratio of the amount of the raw material to form the porous skeleton and the amount of pores. In addition, the composite according to the present invention may be formed of a high density composite having a minimum empty space.

When the composite of the present invention is used as an electrode active material of a lithium secondary battery, the size of pores inside the porous body may be about 1 to 1,000 nm, preferably expressed as a diameter of a circle having an equal area for the projection area. 10 to 500 nm, more preferably 10 to 300 nm.

The material forming the porous skeleton is not particularly limited as long as it has high electrical conductivity, high temperature resistance, and excellent chemical and corrosion resistance. For example, carbon-based materials such as crystalline carbon, graphite, activated carbon, and conductive ceramics such as TiO ₂ , TiN, TiB ₂ , SiC, and Al ₂ O ₃ may be used. These materials may be used alone or in combination.

A carbonaceous porous body can also be obtained by the following method.

The first method is to obtain a porous body by carbonizing organic materials existing in nature under appropriate conditions.

The second method is to create a pattern of pores having the size and shape of the porous pores using a material different from the material forming the porous skeleton (ie, a non-carbonaceous material). By mixing with a carbonaceous precursor, heat treating and carbonizing, a pore model / porous body mixture having pores filled with a pore model is formed, and then the pore model is removed from the combination to form a carbonaceous porous body having empty pores.

The carbonaceous porous body may be produced by gas phase carbonization, liquid phase carbonization, or solid phase carbonization, depending on the kind of precursor of the carbon material. The physicochemical properties of the porous skeleton depend on the state of the precursor of the carbonaceous material as a raw material and the intermediates produced during the reaction, and may also be greatly changed by temperature. Precursors of carbonaceous materials include volatile organics, gaseous hydrocarbons (methane, propane, benzene, etc.), molten organics, molten coal, ascorbic acid, cellulose, polyvinyl alcohol (PVA), polyethylene glycol (PEG), phenol formaldehyde. Resins, resorcinol formaldehyde resins, perfuryl alcohol resins, phenol furan resins, coal-based or petroleum-based pitches, coke, anthracene, sucrose, glucose and the like.

The porous body made of a ceramic material can be obtained by, for example, replacing the precursor of the carbonaceous material with the precursor of the ceramic material in the method used for forming the carbonaceous porous body.

Transition Metal Compound Filler

As a transition metal compound which is a filler, it can be used as long as the insertion and desorption of an alkali metal ion can be made reversible. Such transition metal compounds are divided into spinel structure, layer structure and olivine structure according to their crystal structure.

Examples of the spinel structure system include LiMn ₂ O ₄ .

Examples of the layer structural system _{LiCoO 2, Li (Ni 1 -x-} y Co x Al y) O 2, Li (Ni 1 -x- y Mn x Co y) O 2 and Li _{2 -z} (Fe _x Mn _{1 -xy} M _y ) _z O ₂ (M = Ti, Ni, Zn, Mn, etc.).

Examples of the olivine structure system include LiMPO ₄ including LiFePO ₄ (M = Fe, Mn, Ni, Co or a mixture thereof) and the like.

As a manufacturing method of the transition metal compound which is a filler, a well-known solid-phase method, co-precipitation, hydrothermal method, supercritical hydrothermal method, sol-gel method, an alkoxide method, etc. can be used, A manufacturing method is not specifically limited.

Porous / Filler Filler Complex

The appearance of the composite may have a variety of shapes, such as spherical, cylindrical, rectangular and atypical, but is preferably spherical in order to have a high bulk density.

The size of the composite may be 1 to 200 μm, preferably 2 to 50 μm, more preferably 2 to 20 μm. If the size of the composite is too small, the specific surface area is increased, thereby decreasing the flowability of the powder, generating static electricity, making it difficult to transfer or weigh the powder, take a long time to disperse, and require a large amount of binder. Is generated. On the other hand, if the size is too large, there is a problem that the capacity decrease and the particle size exceeds the electrode thickness due to the increase in the ion diffusion distance.

In the composite, the weight of the porous skeleton may comprise 0.3 to 50% of the weight of the composite, preferably 1 to 10%, more preferably 2 to 5%.

In addition, even when filled with a filler, some pores in the composite may remain as empty spaces, and the internal porosity, which is the ratio of the volume of these empty pores based on the volume of the individual composites, is preferably less than 10% by volume. The internal porosity can be obtained from the area ratio of the part occupied by the empty space of the total area from the image of the cross section of the composite particle, or can be obtained by measuring the tap density of the powder. The porous body / filler composite according to the present invention preferably has a tap density of 1.5 g / cm 3 or more.

electrode Combination

The porous body / filler composite according to the present invention can be used for the preparation of an electrode mixture for a lithium secondary battery. The electrode mixture may optionally include a conductive material, a binder, an additive, etc. in addition to the composite as a component thereof.

The conductive material may typically comprise 1 to 30% of the total weight of the electrode mixture. The conductive material does not cause side reactions when the battery is charged and discharged, and may be used as long as it has conductivity. Examples of the conductive material include graphite materials such as natural graphite or artificial graphite; Carbon black, acetylene black, ketjen black, etc .; Fibrous carbon materials; Conductive metal oxides such as titanium oxide; Conductive metal materials such as nickel and aluminum.

The binder is used to bond the composite and the conductive material or the current collector. The binder is added to account for 1 to 30% of the weight of the total electrode mixture. Examples of the binder include cellulose materials such as cellulose, methyl cellulose and carboxymethyl cellulose; Olefin polymer materials such as polyethylene and polypropylene; Polyvinylidene fluoride, polyvinylpyrrolidone, polyvinyl chloride and the like; Rubber components such as EPDM, styrene-butylene rubber and fluorine rubber.

Meanwhile, Additives may be used for the purpose of inhibiting the swelling of the electrode, such additives may be fibrous materials which do not produce electrochemical side reactions, for example olefinic polymers or copolymers such as polyethylene, polypropylene; Glass fibers, carbon fibers, and the like.

electrode

An electrode can be manufactured by coating an electrode mixture on an electrical power collector.

The electrode has a form in which the electrode mixture is coated on a surface of a conductive metal sheet such as aluminum foil. It is preferable that the thickness of an electrical power collector is 2-500 micrometers, and does not involve chemical side reactions when constructing a battery. Examples of the current collector are those in which aluminum, stainless steel, nickel, titanium, silver, and the like are processed in a thin plate form, and the surface of the current collector may be chemically etched or coated with a conductive material.

Secondary battery

By using the composite according to the present invention, a lithium secondary battery composed of a positive electrode, a negative electrode, a separator and a lithium salt-containing non-aqueous electrolyte may be configured.

As a positive electrode, what coat | covered the electrical power collector the electrode mixture containing the porous body / filler composite which concerns on this invention can be used. As a negative electrode, what coat | covered the negative electrode active material mixture on the electrical power collector can be used.

The separator physically separates the positive electrode and the negative electrode, and also provides a migration path for lithium ions. As the separator, those having high ion permeability and mechanical strength and having thermal stability can be used.

The lithium salt-containing non-aqueous electrolyte solution is composed of an electrolyte solution and a lithium salt. As the non-aqueous electrolyte, a non-aqueous organic solvent, an organic solid electrolyte, an inorganic solid electrolyte, and the like are used. As the lithium salt, those which are easy to dissolve in the non-aqueous electrolytic solution, for example, LiCl, LiBr, LiI, LiBF ₄ , LiPF ₆ and the like can be used.

The following describes a method for producing a composite according to the present invention.

Methods of preparing the porous body / filler composite according to the present invention are largely divided into two.

In the first method, a porous body is formed and a filler is formed in its pores. In this case, since the size and shape of the porous pores can be easily controlled, the size and shape of the transition metal compound can also be easily controlled. In addition, a transition metal compound, which is a filler, may be formed in the empty pores inside the porous body having high crystallinity. In the prior art, a carbon precursor is coated on the surface of the transition metal compound particles, and the carbon precursor is carbonized at a temperature lower than a temperature at which the transition metal compound can be phase transitioned or pyrolyzed to form a carbon coating.

The second method is to prepare a filler and mix it with the material for forming the porous body to form a porous body / filler composite, and then heat treatment to strengthen the crystallinity and mechanical strength of the composite. That is, after the transition metal compound is prepared, it is mixed with a material for forming a porous body, and then treated under appropriate conditions to form a porous body / filler composite including the transition metal compound and the porous body. It is to strengthen the strength.

Examples of the method for producing a composite according to the first method is as follows.

(a) Manufacture of Pore Models

A pore model having a shape and a size of pores to be formed inside the porous body is prepared.

As a material for forming the pore model, a material different from the material for forming the porous skeleton is used. When the porous skeleton is carbon-based, silicon dioxide or the like can be used as the material of the pore model.

The pore model may be prepared and used in a desired size and shape, or may be one having a suitable size and shape and dissolved by an acid or basic solution.

(b) formation of porous / pore model conjugates

The pore model obtained in step (a) is mixed with the raw material to form the porous skeleton, the mixture is made to an appropriate size and heat treated to form a combination of the porous body and the pore model.

If the carbon is to form a porous skeleton, the pore model is mixed with the carbon precursor. By performing a carbonization reaction by heat treatment at a temperature of 500 ° C ~ 1,500 ° C according to the type of carbon precursor, to produce a porous body / pore model combination filled with internal pores of the pore model.

In the process of mixing a pore model and a carbon precursor, you may add a crosslinking agent as needed.

Carbonization of the carbon precursor can be carried out according to known gas phase carbonization, liquid phase carbonization or solid phase carbonization.

In order to thermally decompose the carbon precursor to release all hydrogen, hydrocarbons, impurity elements, and the like, carbonization is preferably performed at a temperature of 1,000 ° C. or higher.

(c) Removing the pore model from the porous / pore model combination to form a porous skeleton

By removing the pore model from the porous / pore model conjugate obtained in step (b), a porous backbone with empty pores is obtained. When the pore model is removed, the space occupied by the original pore model remains as empty pores.

When the material forming the pore model is silicon dioxide, pores can be formed in the porous body by dissolving and removing silicon dioxide using an aqueous solution of hydrofluoric acid or sodium hydroxide as a solvent.

(d) Formation of porous / transition metal compound filler complex

A mixture comprising the porous body of step (c), raw materials for forming a transition metal compound, and water is reacted under a condition of a temperature of 200 to 700 ° C. and a pressure of 180 to 550 bar to fill the porous body and a transition metal compound filler. After forming a complex (porous body / transition metal compound filler complex), the complex is washed and dried to obtain a powder.

The raw materials for the formation of the transition metal compound are reacted to produce a precursor of the transition metal compound, from which the transition metal compound is produced.

Specifically, raw materials including a transition metal precursor, an alkali metal salt or a hydroxide, and an alkalizing agent are reacted to produce a precursor of the transition metal compound.

The alkalizing agent is not particularly limited as long as the reaction solution is made alkaline above pH 9. Non-limiting examples of alkalizing agents include alkali metal hydroxides (NaOH, KOH, etc.), alkaline earth metal hydroxides (Ca (OH) ₂ , Mg (OH) _2, etc.), ammonia compounds (ammonia water, ammonium nitrate, etc.), or mixtures thereof. There is this.

The reactants, including transition metal precursors and alkalizing agents, may be mixed with water or mixed with water at one time.

As a preferred example, the transition metal compound may be prepared through process change such as reactant mixing ratio, reaction temperature (50 to 700 ° C.) and reaction pressure (180 to 550 bar) based on hydrothermal synthesis using subcritical or supercritical water. have.

If the reaction temperature is less than 50 ° C, it is unsuitable for obtaining a single-phase high crystalline transition metal compound. If the temperature is higher than 700 ° C, the material cost of the manufacturing apparatus increases.

Alkali metal hydroxides such as lithium, sodium, and potassium have high solubility in water at room temperature and atmospheric pressure, but when the density of water decreases due to high temperature and high pressure, the solubility decreases significantly. In the case of LiOH, it is necessary to maintain a pressure of 180 to 550 bar and a temperature of 200 to 700 ° C. together to significantly reduce the solubility.

The pH of the reaction is preferably greater than 4.0 and less than 9.0. If the pH is less than 4.0, the prepared transition metal compound is not preferable because it is dissolved in a low pH range. Since it needs to be added to the furnace, economical efficiency is reduced because a separate additional process for washing and treatment of the discharge liquid is required.

(e) the output of step (d) Calcination

It is preferable to carry out the step of calcination immediately after step (d) to improve the crystallinity of the result of step (d) and the adhesion between the crystals. If the calcination process is not performed, crystals of the transition metal compound may not be stabilized, resulting in a decrease in electrochemical activity.

As described above, the present invention provides a porous body / filler complex. The material forming the porous skeleton may be a carbon or ceramic material having high crystallinity. The composite may have a large bulk density and control the inner wall thickness of the porous body and the pore size, shape, etc. formed in the porous body. As a result, an electrode material having high electrical conductivity is provided, the transition metal compound as a filler can be effectively protected from physicochemical external forces, the shape, size, etc. of the transition metal compound particles can be easily controlled, and the transition metal compound The volume change of is suppressed and the dispersibility and adhesion of the transition metal compound can be greatly improved.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the following examples serve to illustrate the present invention, and the scope of the present invention is not limited thereto.

[Example]

Example 1 Porous / LiCoO ₂ Composites

Step a): After mixing spherical silicon dioxide primary particles having an average particle size of 0.2 µm with water (weight ratio of water: silicon dioxide is 1: 0.3), spray-drying, and agglomerating primary particles with an average size of 10 µm Phosphorus secondary particles were formed. (A silicon dioxide secondary particle was used as a model of the porous pores, as described below.) After mixing the secondary particle and the petroleum pitch at a weight ratio of 1: 5, for 1 hour in an argon atmosphere of 1,200 ° C. The heat treatment resulted in a porous body / silicon dioxide binder composed of a carbon porous body and a silicon dioxide filler filling the porous pores, with an average particle size of 10 μm.

The binder was poured into 1M aqueous sodium hydroxide solution and stirred for 4 hours to dissolve the silicon dioxide present in the binder, followed by filtration and washing to produce a carbon porous body in which the sites where silicon dioxide was removed remain as empty pores. (FIG. 2A). A carbon porous body obtained Raman (Raman) spectroscopy to obtain a spectrum using a 1355㎝ for the peak intensity 1575㎝ ^{-1 -} was determined the ratio (I ₁₃₅₅ / I ₁₅₇₅₎ of the peak intensity in the ^first, the result is Fig. 9 is shown in the graph (a).

5 g of the porous carbon body was placed in a 1 L volume reactor, and 500 mL of distilled water was added thereto to prepare a carbon porous body slurry.

Step b): 72.7 g of cobalt nitrate hexahydrate (Co (NO ₃ ) ₂ ˜6H ₂ O) was added to the carbon porous slurry prepared in step a) to prepare a first aqueous solution. In addition, 42 g of lithium hydroxide monohydrate (LiOH.H ₂ O) and 200 ml of 28% ammonium hydroxide (NH ₄ OH) solution were mixed, and 200 ml of distilled water was added to prepare a second aqueous solution. The second aqueous solution was added thereto while stirring the first aqueous solution, and when the addition was completed, the reactor was sealed and heated to maintain at 150 ° C. for 4 hours, and then cooled to room temperature. The cooled mixture was removed from the reactor and filtered through a filter having a pore size of 1 μm, followed by washing three times with 500 ml of distilled water. The finished cake-shaped product was dried in an oven at 80 ° C. for 24 hours to obtain a powder. The powder was charged in an argon (Ar) atmosphere, heated to maintain the temperature at 900 ° C. for 10 hours, and then cooled to room temperature to obtain a fired product.

The microstructure was examined using a scanning electron microscope (SEM), and the calcined product was spherical with an average size of 10 μm, and the skeleton was a carbon porous body, and the pores inside the porous body were a composite filled with lithium manganese dioxide (LiMnO ₂ ). It was. Whether or not lithium manganese dioxide was confirmed by X-ray diffraction spectroscopy (XRD) (Fig. 3). The bulk density of the composite powder, which was calculated by measuring tap density, was 2.8 g / cm 3. As a result of measuring the carbon content using an elemental analyzer, it was confirmed that carbon occupies 8.4% of the total weight of the composite.

Example 2 Porous / LiFePO ₄ Composites

69.5 g of iron sulfate heptahydrate [FeSO ₄ .7H ₂ O] and 22.5 g of phosphoric acid (H ₃ PO ₄ ) were added to the carbon porous slurry prepared in step a) of Example 1, thereby preparing a first aqueous solution. After mixing 24 g of lithium hydroxide monohydrate (LiOH.H ₂ O) and 200 ml of 28% ammonium hydroxide (NH ₄ OH) solution, 200 ml of distilled water was added to prepare a second aqueous solution. While stirring the first aqueous solution, a second aqueous solution was added thereto, and when the addition was completed, the reactor was sealed and heated to maintain at 180 ° C. for 4 hours, and then cooled to room temperature. The cooled mixture was removed from the reactor, filtered through a filter having a pore size of 1 μm, and washed three times with 500 ml of distilled water. The finished cake form was dried in an oven at 80 ° C. for 24 hours to obtain a powder. 5% by weight of methyl cellulose was mixed with the powder, charged in an electric furnace in an argon (Ar) atmosphere, and heated to maintain the temperature at 700 ° C. for 10 hours, and then cooled to room temperature to obtain a fired product.

The microstructure was examined using a scanning electron microscope (SEM). The calcined product was spherical with an average size of 10 μm, and the skeleton was a porous body, and the pores inside the porous body were lithium iron phosphate (LiFePO ₄ ) having an olivine structure. It was confirmed that the carbon porous body / lithium iron phosphate complex (Fig. 2b). Whether LiFePO ₄ was confirmed by X-ray diffraction spectroscopy (XRD) (FIG. 4).

The bulk density of the composite powder, calculated by measuring the tap density, was 1.8 g / cm 3. As a result of measuring the carbon content using an elemental analyzer, it was confirmed that carbon occupies 6.3% of the total weight of the composite.

Example 3 Porous / LiFePO ₄ Composites

1 mol of iron sulfate (FeSO ₄ H ₂ O), 1 mol of phosphoric acid, 27.8 g of sugar dissolved in 1.6 L of water, 1.1 mol of ammonia and 2 mol of lithium hydroxide in 1.2 L of water 2 aqueous solution was prepared. The two aqueous solutions were pressurized to 250 bar at room temperature and continuously pumped, and mixed in a mixer to produce a slurry of pH 6.1 containing a lithium iron phosphate precursor.

Ultrapure water heated to about 450 ° C. to the precursor was pumped under pressure to 250 bar and mixed in a mixer. The final mixture was transferred to a reactor maintained at 380 ° C. and 250 bar, and held for 7 seconds to produce lithium iron phosphate, followed by cooling and filtration to obtain a concentrate having 30% of the total weight as solid.

1.5 kg of the concentrated solution was taken and placed in a batch high temperature high pressure reactor, and 13.5 g of sucrose was added thereto, and the reactor was sealed and heated to maintain the temperature at 190 ° C. for 4 hours, and then cooled to room temperature. The cooled mixture was filtered and the filtrate was washed three times with distilled water, and the resulting cake-like result was dried in an oven at 80 ° C. for 24 hours to obtain a powder. The powder was charged in an argon (Ar) atmosphere, heated to maintain the temperature at 700 ° C. for 10 hours, and then cooled to room temperature to obtain a fired product.

The microstructure was examined using a scanning electron microscope (SEM). The calcined product was spherical, having an average size of 5 μm, the skeleton of which was porous, and the pores inside the porous body were lithium iron phosphate (LiFePO ₄ ) of olivine structure. It was confirmed that the filled carbon porous body / lithium iron phosphate complex. Whether LiFePO ₄ was confirmed by X-ray diffraction spectroscopy (XRD) (FIG. 5).

The bulk density of the composite powder, which was calculated by measuring the tap density, was 2.5 g / cm 3. As a result of measuring the carbon content using an elemental analyzer, it was confirmed that carbon occupies 8.2% of the total weight of the composite.

Example 4 Porous Body / LiFeNiMnCoPO ₄ Composite

Example of step 1 a) the porous carbon ferrous sulfate heptahydrate in the slurry prepared in [FeSO ₄ and 7H ₂ O] 34.7g, nickel nitrate _{[Ni (NO 3) 2?} 6H 2 O] 36.3g, manganese nitrate [Mn _{(NO 3) 2? 6H 2} O] 43.7g, cobalt nitrate _{[Co (NO 3) 2?} 6H 2 O] 36.4g and phosphoric acid (H ₃ PO ₄₎ made of a first aqueous solution was added to 48.95g. After mixing 24 g of lithium hydroxide monohydrate (LiOH.H ₂ O) and 200 ml of 28% ammonium hydroxide (NH ₄ OH) solution, 200 ml of distilled water was added to prepare a second aqueous solution. The second aqueous solution was added thereto while stirring the first aqueous solution, and when the addition was completed, the reactor was sealed and heated to maintain at 180 ° C. for 4 hours, and then cooled to room temperature.

The cooled mixture was taken out of the reactor, filtered through a filter having a pore size of 1 μm, and then washed three times with 500 ml of distilled water. The finished cake form was dried in an oven at 80 ° C. for 24 hours to obtain a powder. The powder was charged in an argon (Ar) atmosphere, heated to maintain the temperature at 700 ° C. for 10 hours, and then cooled to room temperature to obtain a fired product.

The microstructure was examined using a scanning electron microscope (SEM), and as a result, the calcined product was spherical with an average size of 10 μm, and the skeleton was a porous body. ₄ ) was confirmed to be a complex filled with. Whether LiFeNiMnCoPO ₄ was confirmed by X-ray diffraction spectroscopy (XRD) (FIG. 6).

The bulk density of the composite powder, calculated by measuring the tap density, was 1.8 g / cm 3. As a result of measuring the carbon content using an elemental analyzer, it was confirmed that carbon occupies 6.5% of the total weight of the composite.

Inductively coupled plasma atomic emission spectroscopy (inductively coupled plasma atomic emission spectroscopy, ICP-AES) using a with respect to the lithium nickel manganese cobalt-iron phosphate Analysis of the specific molar ratio of the composition components, Li _{0 .97 0 .25} Fe Ni ₀ to _5.25 having a composition of Mn _{0 .25} Co _{0 .25} PO ₄ was confirmed.

[Comparative Example]

Comparative Example 1 : Core-Shell Structure

1 mol of iron sulfate (FeSO ₄ H ₂ O), 1 mol of phosphoric acid, 27.8 g of sugar dissolved in 1.6 L of water, 1.1 mol of ammonia and 2 mol of lithium hydroxide in 1.2 L of water 2 aqueous solution was prepared. The two aqueous solutions were pressurized to 250 bar at room temperature and continuously pumped, and mixed in a mixer to produce a slurry of pH 6.1 containing a lithium iron phosphate precursor.

Ultrapure water heated to about 450 ° C. to the precursor was pumped under pressure to 250 bar and mixed in a mixer. The final mixture was transferred to a reactor maintained at 380 ° C. and 250 bar, and held for 7 seconds to produce lithium iron phosphate, followed by cooling and filtration to obtain a concentrate having a solid content of 30% in total weight.

After the sugar was mixed at a weight ratio of 10% by weight of the lithium iron phosphate contained in the concentrate, spray drying and granules were formed through a spray dryer. The formed dry granular particles were heat-treated at 700 ° C. for 10 hours to obtain a fired product having a core-shell structure in which lithium iron phosphate particles form a core and the surface of the core is coated with carbon. .

The calcined product was analyzed by X-ray diffraction spectroscopy (XRD) to confirm that it was lithium iron phosphate (LiFePO ₄ ) having an olivine structure (FIG. 7), and the microstructure was examined using a scanning electron microscope (SEM). It was confirmed that the powder was composed of secondary particles having a large internal space with a size of 10 μm.

The bulk density of the composite powder, calculated by measuring the tap density, was 0.7 g / cm 3. As a result of measuring the carbon content using an elemental analyzer, it was confirmed that carbon occupies 2.8% of the total weight of the composite.

From the Raman spectrum for the carbon in the powder 1355㎝ for the 1575㎝ ^-1 peak intensity ^was measured for ratio (I ₁₃₅₅ / I ₁₅₇₅₎ of the peak intensity in the ^first (graph in Fig. 8 (b)).

Geometry inspection

Figure 2a is a SEM photograph of the carbon porous body obtained in step a) of Example 1 shows a structure having a plurality of empty pores. Figure 2b is a SEM photograph of the carbon porous body / lithium iron phosphate composite obtained in Example 2 shows a state filled with the pores filler. FIG. 2C is a SEM photograph of secondary particles of carbon-coated lithium iron phosphate obtained in Comparative Example 1, showing a structure in which a plurality of empty spaces exist between primary particles constituting secondary particles. From these SEM photographs, it can be seen that the carbon porous body / lithium iron phosphate composite according to Example 3 has a compact structure in which the empty space is reduced compared to the secondary particles of lithium iron phosphate according to Comparative Example 1.

Carbon content, Average particle size , Tap density

The ratio of Raman peak intensity (I ₁₃₅₅ / I ₁₅₇₅ ), carbon content, average particle size, and tap density measured in Examples and Comparative Examples are as follows.

Raman peak intensity ratio (I ₁₃₅₅ / I ₁₅₇₅ ) Carbon content (wt%) Average particle size (㎛) Tap density (g / cm 3) Example 1 0.76 8.4 10.0 2.8 Example 2 6.3 10.0 1.8 Example 3 8.2 10.0 2.5 Example 4 6.5 10.0 1.8 Comparative Example 1 0.92 2.8 10.0 0.7

Crystal Characterization

Graph (a) of Figure 8 is a Raman spectrum of the highly crystalline carbon porous body obtained in step a) of Example 1. Graph (b) of Figure 8 is a Raman spectrum of the core-shell structure coated with carbon, obtained in Comparative Example 1.

In general, the peak of 1575 cm ^-1 (hexagonal plane type) is large in crystalline carbon and the peak of 1355 cm ^-1 (diamond type) is relatively small. As the size of the crystal increases, the Raman peak becomes narrower, and the 1355 cm ⁻¹ peak intensity increases when the size of the carbon crystal decreases or the disorder of the structure in the carbon increases. 1355㎝ for the 1575㎝ ^-1 peak intensity ^- of the peak intensity in the ^first ratio (I ₁₃₅₅ / I ₁₅₇₅ = I _D / I _G ) is inversely proportional to the size and crystallinity of the carbon crystallites. When the electrically conductive porous body according to the present invention consists of carbon, it is preferable that the ratio (I ₁₃₅₅ / I ₁₅₇₅ ) of Raman peak intensity of carbon is 0.85 or less.

The ratio of peak intensity (I ₁₃₅₅ / I ₁₅₇₅ ) shown in graphs (a) and (b) of FIG. 8 shows the crystallinity difference according to the heat treatment temperature difference of the carbon body.

Anode manufacturing

Using the porous body / filler composite obtained in Examples 1 to 4 and the electrode active material obtained in Comparative Example 1, a positive electrode for a secondary battery was prepared as follows.

90 parts by weight of electrode active material particles, 5 parts by weight of super-P (conductive material) and 5 parts by weight of polyvinylidene fluoride (binder, polyvinylidene fluoride, PVDF) were added to N-methyl pyrrolidinone (NMP) And mixed in a mortar to produce a positive electrode mixture slurry. It was coated on one surface of aluminum foil, dried and rolled by pressing to prepare a positive electrode.

Electrode density

The cathodes prepared as described above were cut out into circular specimens having a diameter of 1.4 cm, the weight was measured, and the density of each electrode except the current collector was calculated. The results are as follows.

Electrode active material Electrode Density (g / cm 3) Example 1 2.8 Example 2 2.6 Example 3 2.9 Example 4 2.5 Comparative Example 1 2.0

Charge and Discharge Characterization

A lithium secondary battery was prepared using the carbon porous body / lithium iron phosphate composite prepared in Example 3 as a cathode active material, and battery characteristics were evaluated.

The electrolyte was obtained by dissolving 1 mol of LiPF ₆ in a solvent in which ethylene carbonate (EC): ethyl methyl carbonate (EMC) was mixed at a volume ratio of 1: 2, and a coin half cell type using lithium metal as a negative electrode. The lithium secondary battery was prepared, and the charge and discharge evaluation was performed at a constant current of 0.2C rate using a Maccor series 4000.

9 is a charge / discharge graph of a lithium secondary battery prepared using the composite prepared in Example 2 as an active material, wherein the discharge capacity of the carbon porous body / lithium phosphate composite prepared in Example 2 is 163.58 mAh / g. Show it. The discharge capacity of the lithium iron phosphate according to the prior art is 130 ~ 158 mAh / g, it can be seen that the composite according to the present invention has a very good discharge capacity.

Chemical Stability of Electrode Material

100 g of the powders prepared in Example 2 and Comparative Example 1 were mixed with 1 L of distilled water, respectively, and hydrofluoric acid (HF) was added at a concentration of 100 ppm relative to the weight of the powder, and then the container was sealed. Samples were taken 24 hours, 1 week, 2 weeks and 3 weeks after sealing, filtered, and the filtrate was analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) to calculate the amount of eluted iron (Fe). The result is shown below.

Fe elution amount (ppm) 1 day 1 week 2 weeks 3 weeks Example 3 25 253 315 331 Comparative Example 1 232 1,478 2,236 2,450

As shown in the above table, the electrode material according to Example 3 has a significantly lower amount of iron dissolution than the electrode material according to 1, and it is understood that the former is superior in terms of chemical stability to the latter. Can be.

According to the present invention, a composite comprising an electrically conductive porous body and a filler of a transition metal compound and having electrode activity is used as an electrode active material of capacitors and other electrochemical devices including secondary batteries, memory devices, and hybrid capacitors (P-EDLC). It can be used and it is especially suitable as a positive electrode active material of a secondary battery.

Claims (8)

A composite having electrode activity, comprising an electrically conductive porous body and a transition metal compound filler. The composite of claim 1 wherein the tap density is at least 1.5 g / cm 3. The composite of claim 1, wherein the weight of the porous body comprises 0.5 to 50% of the weight of the composite. The method of claim 1, wherein the porous body is made of carbon, for 1355㎝ of 1575㎝ ^-1 peak intensity in Raman spectrum of the ^carbon-ratio (I ₁₃₅₅ / I ₁₅₇₅₎ of the peak intensity at the ^one is not more than 0.85 Complex. An electrode using the composite according to any one of claims 1 to 4 as an electrode active material. A secondary battery, a memory device, or a capacitor using the composite according to any one of claims 1 to 4 as an electrode active material. A method of manufacturing a composite having an electrode activity and comprising an electrically conductive porous body and a transition metal compound filler, the method comprising filling the pores of the electrically conductive porous body with a transition metal compound. A method of manufacturing a composite having an electrode activity and comprising an electrically conductive porous body and a transition metal compound filler, the method comprising mixing a raw material and a transition metal compound to form an electrically conductive porous body.

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