KR101746424B1 - Electrode Material, Manufacturing Method Thereof and Secondary Battery Using the Same - Google Patents

Electrode Material, Manufacturing Method Thereof and Secondary Battery Using the Same Download PDF

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KR101746424B1
KR101746424B1 KR1020150150929A KR20150150929A KR101746424B1 KR 101746424 B1 KR101746424 B1 KR 101746424B1 KR 1020150150929 A KR1020150150929 A KR 1020150150929A KR 20150150929 A KR20150150929 A KR 20150150929A KR 101746424 B1 KR101746424 B1 KR 101746424B1
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carbon
silicon
electrode material
method
silicon compound
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KR20170049968A (en
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김한수
손명범
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한양대학교 산학협력단
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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of or comprising active material
    • H01M4/36Selection of substances as active materials, active masses, active liquids
    • H01M4/362Composites
    • H01M4/366Composites as layered products
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01GCAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors [EDLCs]; Processes specially adapted for the manufacture thereof or of parts thereof
    • H01G11/04Hybrid capacitors
    • H01G11/06Hybrid capacitors with one of the electrodes allowing ions or anions to be reversibly doped thereinto, e.g. lithium-ion capacitors [LICs]
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/052Li-accumulators
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of or comprising active material
    • H01M4/36Selection of substances as active materials, active masses, active liquids
    • H01M4/38Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386Silicon or alloys based on silicon
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00Batteries for particular applications
    • H01M2220/20Batteries in motive systems, e.g. vehicle, ship, plane
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00Batteries for particular applications
    • H01M2220/30Batteries in portable systems, e.g. mobile phone, laptop
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage
    • Y02E60/12Battery technologies with an indirect contribution to GHG emissions mitigation
    • Y02E60/122Lithium-ion batteries
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage
    • Y02E60/13Ultracapacitors, supercapacitors, double-layer capacitors
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50Manufacturing or production processes characterised by the final manufactured product
    • Y02P70/54Manufacturing of lithium-ion, lead-acid or alkaline secondary batteries
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02TCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00Road transport of goods or passengers
    • Y02T10/60Other road transportation technologies with climate change mitigation effect
    • Y02T10/70Energy storage for electromobility
    • Y02T10/7005Batteries
    • Y02T10/7011Lithium ion battery

Abstract

The present invention relates to an electrode material, a manufacturing method thereof, and a secondary battery using the electrode material. More particularly, the present invention relates to an electrode material capable of effectively suppressing the volume expansion of silicon and having improved lifetime characteristics, The present invention also relates to a technique for applying the same to a secondary battery.
According to the present invention, there is provided an electrode material capable of realizing a carbon-silicon compound having a porous structure without using a harmful substance such as hydrofluoric acid, thereby effectively suppressing the volume expansion of silicon, and a method for manufacturing the electrode material can do.
Also, the electrode material manufactured through the above-described method can improve the charge / discharge capacity and the life characteristics at the same time, and can be applied to a secondary battery, a capacitor, an electric vehicle, a flexible electronic device, and the like.

Description

Technical Field [0001] The present invention relates to an electrode material, a method of manufacturing the electrode material, and a secondary battery using the electrode material.

The present invention relates to an electrode material, a method of manufacturing the electrode material, and a secondary battery using the electrode material. More particularly, the present invention relates to an electrode material capable of effectively suppressing the volume expansion of silicon and having an improved life characteristic, The present invention relates to a technology applied to a battery.

Generally, lithium secondary batteries are currently expanding from small-sized electronic devices such as smart phones to large-scale systems such as renewable energy storage systems, as well as promoting human convenience such as medical robots and drones The role of robot as an energy storage source for robots that can work in extreme situations that can not be done by humans is emerging. Therefore, lithium secondary battery technology can bring about a great change in human life, and on a larger scale, it will become more important in the future to enable innovation of national power grid like smart grid. Conventionally, graphite having a theoretical capacity per unit weight of 372 mAh / g is used as a main anode material for a lithium secondary battery, but lithium secondary batteries using graphite as an anode active material due to a low theoretical capacity have been recently developed It is not suitable for a flexible device and a wearable device requiring a low mass and a small volume. In addition, the distance that a moving means such as an automobile employing an internal combustion engine can be moved at the time of one charging can not satisfy an electric vehicle employing a current lithium secondary battery. Therefore, it is possible to store energy by lithium ionization which becomes an alloy with lithium at the time of charging the battery, and silicone which can release energy by releasing energy by de-lithization at the time of discharging to become lithium and dealloying. An anode active material such as silicon (Si), tin (Sn), and germanium (Ge) is attracting great attention as an important material that can enable high energy density of a lithium secondary battery. However, in the case of a material capable of storing and releasing energy by alloying and de-alloying, there is a disadvantage in that capacity is decreased due to expansion and contraction of volume during lithification and de-lithization. One of the possible methods for solving this problem is to improve the lifetime characteristics of a lithium secondary battery which exhibits a high capacity by using an electrochemically stable compound of an inactive material and a material capable of alloying with lithium as an electrode material have.

In recent years, in order to prevent the deterioration of performance of the lithium secondary battery due to the expansion and contraction of the volume caused by the storage and release of lithium in the silicon, an electrochemically stable inactive material is used as a structure to suppress the volume expansion of silicon / Inactive), it is attempted to reduce the influence of changes in the volume of silicon by producing carbon or metal oxide and silicon compound or by producing a silicon alloy in which an alloy or metal is converted into an electrochemically inactive material. However, It is inevitable that the expansion of the volume occurs simply by covering the silicon with an inactive material, so that the volume expansion of the electrode can not be suppressed.

Particularly, since no pores are contained in the particles of the silicon alloy obtained by the arc melting and the melt spinning method, the volume expansion of the silicon leads to the volume expansion of the entire silicon alloy particles obtained by the above-mentioned arc melting and melt spinning. That is, it is difficult to expect the effect of collapsing the electrochemically inactive alloy or metal which is expected to suppress the volume expansion while covering the silicon. In the case of the compound of carbon and silicon, the case where the surface of the silicon oxide (SiO 2 ) -silicon (Si) compound having a spherical shape is coated with carbon and the silicon oxide is removed by hydrofluoric acid (HF) However, the production of nanoscale silicon or silicon oxides and the use of hydrofluoric acid, which is very harmful to human body, are costly, environmentally unfriendly, and unsuitable for mass production. (Patent Documents 1 and 2)

Accordingly, the present invention provides pores in a carbon-silicon compound at an environmentally-friendly and low cost through etching in an aqueous alkaline solution, thereby effectively improving the volume expansion and contraction of silicon, thereby improving the performance of the lithium secondary battery. Small pores formed on the carbon can impose the structural stability of the carbon structure, and the pores in the carbon structure formed by the etching of the silicon serve to allow the lithium ions through the electrolyte to move easily to the inside of the particles. In addition, the pores in the particles will absorb the bulk expansion of the silicon, thereby suppressing the expansion of the particles as a whole.

Patent Document 1. Korean Patent Laid-Open No. 10-2012-0010211 Patent Document 2: Korean Patent Publication No. 10-1419280

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a carbon-silicon compound having a porous structure without using harmful substances such as hydrofluoric acid, And to provide a method of manufacturing the electrode material.

It is another object of the present invention to provide a secondary battery including the electrode material and having improved charging / discharging capacity and life characteristics at the same time.

According to an aspect of the present invention, there is provided an electrode material comprising silicon particles and a carbon structure surrounding the silicon particles, wherein the carbon structure has pores formed by partially etching the silicon particles.

The carbon structure has pores having a diameter of 250 nm or less.

The present invention also provides a process for producing a carbon-silicon compound, comprising the steps of (A) ball milling silicon particles, (B) adding a carbon precursor to the ball-milled silicon particles to produce a carbon- And a step of applying a solution to the electrode material and etching the electrode material.

The basic solution is characterized in that NaOH, KOH, LiOH, Zn ( OH) 2, Mg (OH) 2, RbOH , and Ca (OH) at least one member selected from among 2.

And the molar concentration (M) of the basic solution is 3 or less.

Wherein the carbon precursor is at least one selected from carbon black, pitch, polydopamine, polyacronitrile, polyvinyl chloride, polyvinyl alcohol, and epoxy resin.

The silicon and the carbon precursor are mixed in a weight ratio of 8: 2 to 2: 8.

The step (A) is performed under an inert gas atmosphere for 20 to 50 hours.

Wherein the step (A) is performed by charging iron balls 10 to 30 times the weight of the silicon particles.

The step (B) is performed by heat-treating the carbon-silicon compound at a temperature of 500 to 1,200 ° C for 1 to 5 hours.

The heat treatment temperature is elevated at a rate of 1 to 10 ° C / min.

And the step (C) is performed for 1 to 3 hours.

The method may further include (D) treating the carbon-silicon compound with an acidic solution to neutralize the carbon-silicon compound, and (E) filtering and drying the neutralized carbon-silicon compound.

The present invention also provides a secondary battery, a capacitor, an electric vehicle, a flexible or wearable electronic device including the electrode material manufactured through the above-described manufacturing method.

According to the present invention, there is provided an electrode material capable of realizing a carbon-silicon compound having a porous structure without using a harmful substance such as hydrofluoric acid, thereby effectively suppressing the volume expansion of silicon, and a method for manufacturing the electrode material can do.

Also, the electrode material manufactured through the above-described method can improve the charge / discharge capacity and the life characteristics at the same time, and can be applied to a secondary battery, a capacitor, an electric vehicle, a flexible electronic device, and the like.

1 is an image showing a result of observation of a silicon particle after ball milling with a scanning electron microscope (SEM), wherein (a) shows a magnification of 5.0 × 10 3 , (b) shows a magnification of 1.5 × 10 5 Represents the magnification.
Figure 2 is the carbon of Preparation 1 to an image showing a result of observation of the particles of the silicon compound with a scanning electron microscope ((a) is a ratio of 5.0 × 10 3, (b) has a magnification of 1.5 × 10 5 .
3 is an image showing a result of observing the electrode material of Example 1 with a scanning electron microscope ((a) shows a magnification of 5.0 × 10 3 , and FIG. 3 (b) shows a magnification of 1.5 × 10 5 ).
4 is an image showing a result of observation of a cross section of the carbon-silicon compound particle of Production Example 1 with a scanning electron microscope.
5 is a graph showing the result of elemental analysis of a part of a cross section of the carbon-silicon compound particle of Production Example 1 by a scanning electron microscope. [(A) Analysis point, (b)
6 is an image showing a result of observation of a cross section of the electrode material of Example 1 by a scanning electron microscope.
7 is a graph showing the result of elemental analysis of a part of a cross section of the electrode material of Example 1 by a scanning electron microscope. [(A) Analysis point, (b) Elemental ratio]
8 is a graph showing the results of thermogravimetry analysis (TGA) of the carbon-silicon compound of Production Example 1 and the porous electrode material of Example 1.
FIG. 9 is a graph showing the results of measurement of the porosity of the carbon-silicon compound of Production Example 1 and the porous electrode material of Example 1. FIG. 9 (a) The size and distribution of pores are measured.
FIG. 10 is a graph showing the results of measurement of charge / discharge capacities of secondary batteries of Comparative Example 1 and Example 2. FIG. 10 (a) shows the results in the first cycle, and FIG. 10 And the results of measurement of charge / discharge capacity are shown.
Fig. 11 is a graph showing the results of the charge / discharge of the secondary batteries of Comparative Example 1 and Example 2, and showing the cross section of the electrode material when it was subjected to Pristine, Lithiated and De-lithiated (A) shows Comparative Example 1, and (b) shows Example 2 with an image (x 100 탆) showing the result of observation with an electron microscope.

Hereinafter, various aspects and various embodiments of the present invention will be described in more detail.

The present invention relates to an electrode material comprising a silicon particle and a carbon structure surrounding the silicon particle, wherein the carbon structure has a porosity greater than that of the silicon particle.

The carbon structure is characterized by having pores having a diameter of 250 nm or less, preferably pores having a diameter of 50 to 250 nm. If the diameter of the pores is less than 50 nm, the specific surface area of carbon increases and the amount of the solid electrolyte interface generated on the surface increases, and the initial efficiency decreases. Also, as the cycle progresses, the by-products of the accumulated surface fill up the pores to interfere with or prevent the migration of Li + , which is undesirable as it will result in a decrease in rate capability and a reduction in available silicon If the thickness exceeds 250 nm, the carbon structure will not be able to suppress the pulverization of silicon because it exceeds the critical range at which the silicon particles and rupture of the silicon particles do not occur during charging and discharging, And short-circuiting between the carbon and the carbon.

That is, the carbon structure has a structure surrounding the silicon particles, and serves as a structure of the electrode material.

The carbon structure may be one selected from the group consisting of carbon black, pitch, poly-dopamine, polyacrylonitrile, polyvinyl chloride, polyvinyl alcohol and epoxy resin However, the present invention is not limited thereto, and any organic precursor material capable of carbonization through ananalization can be used.

Particularly, the electrode material can form finer pores through chemical etching using a basic solution. The carbon structure serves as a structure to maintain the structure, that is, the pore structure, . ≪ / RTI >

10, which shows the charge-discharge capacity measurement results of the secondary battery according to Example 2 according to an embodiment of the present invention. As shown in FIG. 10, in the case of Example 2, after 100 cycles It can be seen that the decrease in charge / discharge capacity is insignificant. That is, it can be confirmed that the life characteristics of the battery are improved.

The electrode material has a specific surface area of 100 to 150 m 2 / g as measured by a BET method.

The present invention also provides a process for producing a carbon-silicon compound, comprising the steps of (A) ball milling silicon particles, (B) adding a carbon precursor to the ball milled silicon particles to produce a carbon- And then etching the electrode material.

The method may further include (D) treating the carbon-silicon compound with an acidic solution to neutralize the carbon-silicon compound, and (E) filtering and drying the neutralized carbon-silicon compound.

The present invention is characterized in that silicon particles are ball-milled to miniaturize silicon of a large size, and the thus formed silicon particles are formed so as to surround the silicon structure, the silicon particles are accumulated and then some silicon particles are etched with a basic aqueous solution It is possible to form a carbon-silicon compound having a porous structure by forming pores in the carbon structure.

The carbon having such a porous structure is effective for suppressing the volume expansion of silicon. Particularly, in the present invention, the porous structure can be obtained by using the basic solution having a low concentration without using harmful substances such as hydrofluoric acid, Silicon particles can be realized.

The step (A) is a step of ball milling the silicon particles, which is a step of refining the silicon of a large size. The carbon structure is injected without subjecting the silicon particles to a ball milling process and an etching process using a basic solution The carbon-silicon compound can be formed. However, when the battery is charged or discharged, the carbon structure may collapse due to the size of the large silicon particles. This phenomenon can not solve the problems of the prior art because the carbon structure can not suppress the volume expansion of the silicon particles.

Therefore, the present invention can achieve the effects according to the present invention only when the pre-processing for ball milling the silicon particles and the subsequent etching for the basic solution are performed.

Specifically, the silicon is preferably in the form of powder, and the ball milling is preferably carried out by introducing iron balls 10 to 30 times the weight of the silicon powder. However, as described above, But is not limited thereto.

Preferably, the ball milling is performed in an inert gas atmosphere for 20 to 50 hours. However, the ball milling machine may be manufactured by a ball milling machine, a material of a ball mill vial, a ball-to-power ratio to a ball mill vial, The result is not limited to the above time range.

However, when the time is less than 20 hours, the ball may collide with the silicon particles, resulting in insufficient number of incidents in which pulverization may occur. Therefore, the loaded silicon may remain, and if it exceeds 50 hours, Fe) may be precipitated and impurities may be mixed in the resultant product. The size of silicon is not continuously decreased because the ball milling time is long, and it is more preferable that the size of silicon is within 50 hours because it converges to a specific size.

The ball milling may further include a step of dispersing the silicon particles in a solvent. The solvent may be distilled water or ethanol, but is not limited thereto. It is more preferable to perform ultrasonic treatment for several minutes in order to more efficiently disperse the silicon particles.

The step (B) is a step of preparing a carbon-silicon compound by injecting a carbon precursor into the silicon particle, and the carbon-silicon compound is preferably prepared by heat-treating the carbon-silicon compound at 500 to 1200 ° C for 1 to 5 hours .

The heat treatment is performed by carbonizing the organic raw material to form a carbon structure and accumulating the silicon particles, and the rate of raising the temperature to reach the heat treatment temperature is preferably 1 to 10 ° C / min.

The silicon and the carbon precursor are preferably mixed in a weight ratio of 8: 2 to 2: 8. If the amount of the carbon precursor is too small, it is difficult to aggregate the silicon particles. When the amount of the carbon precursor is too large, In many cases, the capacity is greatly reduced, which is undesirable.

The step (C) is a step of applying a basic solution to the carbon-silicon compound to ultrasonically treat the carbon-silicon compound, thereby effectively forming fine pores in the carbon-silicon compound.

The basic solution is preferred that at least one member selected from the group consisting of 2 NaOH, KOH, LiOH, Zn (OH) 2, Mg (OH) 2, RbOH , and Ca (OH), hydroxide ions (OH -) in aqueous solution to release the Any substance can be used. More preferably, the basic solution has a molar concentration (M) of 0.1 to 3.

If the molar concentration is less than 0.1, the treatment time is increased due to the low hydroxide ion concentration, the silicon is not sufficiently etched, and the pores in the carbon structure can not be secured. The etching is performed by reacting two hydroxide ions and one silicon atom as shown in the following reaction formula.

[Reaction Scheme]

Si + 2NaOH + H 2 O - > Na 2 SiO 3 + 2H 2

Conventionally, a porous structure is realized by distributing sacrificial particles such as silicon dioxide (SiO 2 ) to a carbon structure and etching the silicon particles using a strong acid harmful to human body such as hydrofluoric acid. However, the strong acid such as hydrofluoric acid is very harmful to the human body and has a problem of requiring additional manufacturing process and treatment facility for treating the strong acid.

In order to solve the above problems, the present invention uses a basic solution instead of a harmful substance such as strong acid, and the silicon particle itself is etched with a basic solution as a sacrificial particle to impart porosity to the carbon structure, The porous structure of the carbon-silicon compound can be realized.

More specifically, the step (C) is preferably performed for 1 to 3 hours. If the etching time is less than 1 hour, the silicon is not sufficiently etched, and pores for relaxing the volume expansion of silicon are not sufficiently formed, And if it exceeds 3 hours, the amount of silicon capable of expressing the capacity is remarkably decreased, which is not preferable.

In the step (D), after the chemical etching using the basic solution is completed, neutralization is carried out by introducing at least one acidic solution selected from HCl, HF, H 2 SO 4 , HNO 3 and CH 3 COOH, To suppress the etching reaction to terminate the reaction and to remove impurities. In addition to the above, the acidic solution may be any substance that releases hydrogen ions (H + ) in an aqueous solution state.

In the step (E), the neutralized carbon-silicon compound is filtered and dried. Preferably, the compound is filtered at a reduced pressure and dried at a temperature of 50 to 100 ° C.

The present invention also provides a secondary battery including the electrode material. As shown in FIG. 10, the secondary battery including the electrode material according to the present invention has improved charge / discharge capacity and lifetime characteristics.

Hereinafter, the present invention will be described in detail with reference to examples.

(Preparation Example 1: Production of carbon-silicon compound)

Silicon powder and iron balls were charged into a stainless steel vial, filled with argon gas and ball milled for 36 hours in an inert atmosphere, mixed with pitch, and heat-treated at 800 DEG C for 2 hours under a nitrogen atmosphere to prepare a carbon-silicon compound .

(Note that the weight ratio of the ball milled silicon powder to the pitch was 7: 3, the heating rate was 5 ° C / min, and the cooling rate was natural temperature lowering at room temperature. )

(Example 1: Production of Porous Electrode Material)

0.3 g of the pulverized carbon-silicon compound of Preparation Example 1 was added to 30 ml of distilled water and sonicated for 60 minutes to disperse. The dispersed solution was mixed with 70 ml of a 0.714 M aqueous NaOH solution, ultrasonicated for 115 minutes, Process. To the wet-etched silicon solution, 300 mL of 0.2 M aqueous HCl solution was added, and the mixture was filtered under reduced pressure, and then dried at a temperature of 80 캜 to prepare an electrode material.

(Example 2: Production of porous secondary battery)

The electrode material of Example 1, carbon black (Super-P, Ensaco) and polyacrylic acid (PAA, Sigma-Aldrich) were dispersed in an aqueous solution at a weight ratio of 8: 0.5: 1.5, Vacuum drying was performed at a temperature to obtain an electrode.

The electrode was assembled with a coin cell (2032 size) using a lithium metal and polyolefin separator to prepare a secondary battery.

(The electrolyte used here is 1 M LiPF 6 , Ethylene carbonate: Diethyl carbonate (1: 1, vol%) + Fluoroethyl carbonate 5%.)

(Comparative Example 1: Production of non-porous secondary battery)

The procedure of Example 2 was repeated except that the carbon-silicon compound of Preparation Example 1 was used instead of Example 1.

1 is an image showing a result of observation of a silicon particle after ball milling with a scanning electron microscope (SEM), wherein (a) shows a magnification of 5.0 × 10 3 , (b) shows a magnification of 1.5 × 10 5 Represents the magnification.

FIG. 2 is an image showing a result of observation of the particles of the carbon-silicon compound of Preparation Example 1 by a scanning electron microscope, which shows that the particle size is much larger than that of FIG. 1 and a smooth carbon layer is formed on the surface have.

(A) is a magnification of 5.0 × 10 3 , and (b) is a magnification of 1.5 × 10 5. )

FIG. 3 is an image showing the result of observation of the electrode material of Example 1 by a scanning electron microscope. It can be confirmed that fine pores are formed in the carbon layer although the overall particle size is not smaller than that of Production Example 1. (A) is a magnification of 5.0 × 10 3 , and (b) is a magnification of 1.5 × 10 5. )

4 is an image showing a result of observation of a cross section of the carbon-silicon compound particle of Production Example 1 by a scanning electron microscope, and FIG. 5 is a graph showing a result of elemental analysis of a part of the cross section by a scanning electron microscope. a) analysis point, (b) element ratio]

6 is an image showing the result of observation of a cross section of the electrode material of Example 1 by a scanning electron microscope, and FIG. 7 is a graph showing a result of elemental analysis of a part of the cross section by a scanning electron microscope. Point, (b) element ratio]

As shown in FIGS. 4 and 6, large particles are formed in the silicon particles surrounded by carbon. In the case of Example 1, large pores are formed inside the particles. It can be confirmed that fine pores are formed by chemical etching using a basic solution.

It can be seen from FIG. 5 (b) and FIG. 7 (b) that the silicon ratio of Example 1 is reduced as compared with that of Production Example 1, and these results indicate that the silicon particles were etched by the basic solution have.

Table 1 below shows the results of analysis of the specific surface areas of Production Example 1 and Example 1 by the BET equation (Brunauer-Emmett-Teller equation, BET equation). As shown in the following Table 1, It can be confirmed that the specific surface area is remarkably improved.

division Production Example 1 Example 1 BET surface area (m 2 / g) 76.7962 123.4492

8 is a graph showing the results of thermogravimetry analysis (TGA) of the carbon-silicon compound of Production Example 1 and the porous electrode material of Example 1. 8, weight loss is observed at a temperature of about 600 ° C. This phenomenon is due to decomposition of carbon. In the case of Example 1, the weight loss is about 50%, which is about 20% Respectively. That is, in the case of Example 1, silicon is etched to show that the silicon content with respect to carbon is lowered, which means that silicon is etched well.

FIG. 9 is a graph showing the results of measurement of the porosity of the carbon-silicon compound of Production Example 1 and the porous electrode material of Example 1. FIG. 9 (a) The size and distribution of pores are measured. Referring to FIG. 9 (a), it can be seen that silicon was etched through the chemical etching step to form pores in Example 1, and as shown in (b), no pores were formed in the case of Production Example 1 , It can be confirmed that pores having an average size of 34 nm are formed in the first embodiment.

FIG. 10 is a graph showing the results of measurement of charge / discharge capacities of secondary batteries of Comparative Example 1 and Example 2. FIG. 10 (a) shows the results in the first cycle, and FIG. 10 And the results of measurement of charge / discharge capacity are shown.

As shown in FIG. 10, in the case of Example 2 in which chemical etching using a basic solution was performed, the charge / discharge capacity was improved as compared with Comparative Example 1, and even after 100 cycles, It can be seen that carbon plays a role of the structure and the lifetime characteristics of the battery are improved.

Fig. 11 is a graph showing the results of the charge / discharge of the secondary batteries of Comparative Example 1 and Example 2, and showing the cross section of the electrode material when it was subjected to Pristine, Lithiated and De-lithiated (A) shows Comparative Example 1, and (b) shows Example 2. Fig.

Referring to FIG. 11, the yellow dotted line indicates the portion of silicon expansion. In Comparative Example 1, silicon rapidly expanded as lithiation occurred. On the other hand, in the case of Example 2, it can be confirmed that the degree of expansion of silicon occurred without significant change. That is, it can be confirmed that the expansion of the silicon particles is effectively suppressed in the second embodiment.

Therefore, according to the present invention, there can be provided an electrode material capable of realizing a carbon-silicon compound having a porous structure without using harmful substances such as hydrofluoric acid, thereby effectively suppressing the volume expansion of silicon, Can be provided.

Also, the electrode material manufactured through the above-described method can improve the charge / discharge capacity and the life characteristics at the same time, and can be applied to a secondary battery, a capacitor, an electric vehicle, a flexible electronic device, and the like.

Claims (18)

  1. delete
  2. delete
  3. (A) ball milling silicon particles;
    (B) adding a carbon precursor to the ball-milled silicon particles to produce a carbon-silicon compound; And
    (C) introducing a basic solution into the carbon-silicon compound to etch the carbon-
    Wherein the basic solution is NaOH, KOH, LiOH, Zn (OH) 2, Mg (OH) 2, RbOH, and Ca (OH) at least one selected from 2,
    Wherein the basic solution has a molar concentration (M) of 0.1 to 3.
  4. delete
  5. delete
  6. The method of claim 3,
    Wherein the step (C) is performed for 1 to 3 hours.
  7. The method of claim 3,
    Wherein the carbon precursor is at least one selected from the group consisting of carbon black, pitch, polydopamine, polyacronitrile, polyvinyl chloride, polyvinyl alcohol, and epoxy resin.
  8. The method of claim 3,
    Wherein the silicon and carbon precursor are charged in a weight ratio of 8: 2 to 2: 8.
  9. The method of claim 3,
    Wherein the step (B) comprises heat-treating the carbon-silicon compound at a temperature of 500 to 1200 ° C for 1 to 5 hours.
  10. 10. The method of claim 9,
    Wherein the heat treatment temperature is raised at a rate of 1 to 10 占 폚 / min.
  11. The method of claim 3,
    Wherein the step (A) is performed under an inert gas atmosphere for 20 to 50 hours.
  12. The method of claim 3,
    Wherein the step (A) is performed by introducing iron balls 10 to 30 times the weight of the silicon particles.
  13. The method of claim 3,
    (D) treating the carbon-silicon compound with an acidic solution to neutralize the carbon-silicon compound; And
    And (E) filtering and drying the neutralized carbon-silicon compound.
  14. A secondary battery comprising an electrode material produced according to any one of claims 3, 6 and 13.
  15. A capacitor comprising an electrode material produced according to any one of claims 3, 6 to 13.
  16. An electric vehicle comprising an electrode material produced according to any one of claims 3, 6 to 13.
  17. A flexible electronic device comprising an electrode material produced according to any one of claims 3, 6, and 13.
  18. A wearable electronic device comprising an electrode material produced according to any one of claims 3, 6, and 13.
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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100818263B1 (en) * 2006-12-19 2008-03-31 삼성에스디아이 주식회사 Porous anode active material, method of preparing the same, and anode and lithium battery containing the material

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100818263B1 (en) * 2006-12-19 2008-03-31 삼성에스디아이 주식회사 Porous anode active material, method of preparing the same, and anode and lithium battery containing the material

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