KR20220052629A - Manufacturing method of pitch coated silicon/carbon composites as anode material of secondary battery - Google Patents

Abstract

The present invention relates to a method for manufacturing a silicon/carbon composite material coated with pitch for a composite negative electrode material for a secondary battery. The present invention includes the steps of: manufacturing a mixed solution; forming a silicon/sucrose composite; and manufacturing a silicone/sucrose/pitch composite material. The present invention can solve environmental problems through efficient waste treatment.

Description

Manufacturing method of pitch coated silicon/carbon composites as anode material of secondary battery

The present invention relates to a method of manufacturing a pitch-coated silicon/carbon composite material for a secondary battery composite anode material.

As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. Among such secondary batteries, lithium secondary batteries exhibiting high energy density and operating potential, long cycle life, and low self-discharge rate. Batteries have been commercialized and widely used.

A lithium secondary battery is generally composed of a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator, and an electrolyte, and is a secondary battery that is charged and discharged by intercalation-decalation of lithium ions. Lithium secondary batteries have advantages of high energy density, high electromotive force, and high capacity, and thus are being applied to various fields.

On the other hand, a metal oxide such as LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ or LiCrO ₂ is used as a positive active material constituting the positive electrode of a lithium secondary battery, and as a negative active material constituting the negative electrode, metal lithium, graphite A carbon-based material such as (graphite) or activated carbon, or a material such as silicon oxide (SiOx) is used. Among the anode active materials, metallic lithium was mainly used in the beginning, but as the charging and discharging cycle proceeds, lithium atoms grow on the metallic lithium surface to damage the separator and damage the battery. Recently, carbon-based materials are mainly used. However, the carbon-based material has a disadvantage in that the theoretical capacity is only about 400 mAh/g and thus the capacity is small.

Accordingly, various studies have been conducted to replace the carbon-based material by using silicon (Si) having a high theoretical capacity (4,200 mAh/g) as an anode active material. The reaction equation when lithium is inserted into silicon is:

[Scheme 1]

22Li + 5Si = Li ₂₂ Si ₅

However, most silicon anode materials have a disadvantage that silicon volume expands by up to 300% due to lithium insertion, which destroys the anode and thus does not exhibit high cycle characteristics. In addition, in the case of silicon, volume expansion occurs due to the lithium insertion as the cycle continues, pulverization, contact losses with conducting agents and current collectors, and unstable solids - May exhibit fading mechanisms such as solid-electrolyte-interphase (SEI) formation.

Therefore, in order to solve this problem, the structure-controlled silicon, such as nanowires, nanotubes, nanoparticles, porous structures, and complex formation with carbon-based materials Studies using nanostructures have been reported. For example, although carbon-coated silicon nanostructures have been studied, a lithium secondary battery using the same as an anode active material has a disadvantage in that the capacity of the anode active material cannot be maintained as the charge/discharge cycle is repeated. In addition, although research on the synthesis of the porous carbon-silicon composite has been conducted, the limitations of the composite synthesis technology are exposed due to problems such as a technology for controlling the shape of a complex structure and a high process cost.

Accordingly, there is still a demand for development of a silicon-containing composite and a method for manufacturing the same, which can be produced in a relatively easy and mass-produced manner at a low cost, and can solve the problems caused by the use of the conventional silicon.

Meanwhile, as the amount of waste plastics generated continues to increase and the seriousness of environmental problems emerges, it is required to solve environmental problems through efficient waste disposal and to activate the recycling industry through economic value added creation. The use of electrode materials in pitch manufacturing technology using low-cost petroleum residues and waste plastics is a key technology that can improve battery life characteristics and output as well as solve environmental problems.

Korean Patent Publication No. 10-1670353

Accordingly, the present invention is a result of diligent efforts to produce a composite anode material for secondary batteries with excellent cycle stability, high capacity and excellent physical properties in order to solve the problems of the conventional anode as described above, dispersing when hydrothermal synthesis of silicon and sucrose Composite material with good overgrowth can be manufactured, and when the anode material is manufactured by coating the composite material with a rich material manufactured using petroleum residue (PFO) and plastic waste (PET), it has a high capacity and has 50 cycles. After confirming that the capacity retention rate of about 85% or more compared to 5 cycles can be exhibited, the present invention has been completed.

the present invention

(A) preparing a mixed solution in which nano silicon, hard carbon, and a first solvent are mixed;

(B) hydrothermal synthesis of the mixed solution at 160 to 210° C. for 6 to 10 hours to form a spherical silicone/sucrose composite; and

(C) Pitch-coated silicon/carbon composite material for secondary battery composite anode material comprising the step of mixing the spherical silicon/sucrose composite, pitch, and a second solvent to prepare a silicon/sucrose/pitch composite material An object of the present invention is to provide a method for manufacturing

Another object of the present invention is to provide a negative electrode comprising a current collector, a pitch-coated silicon/carbon composite material for a secondary battery composite negative electrode material according to the present invention disposed on the current collector.

The present invention also relates to an anode; A negative electrode comprising a pitch-coated silicon/carbon composite material for secondary battery composite negative electrode material according to the present invention; and an electrolyte providing an ion movement path between the positive electrode and the negative electrode.

The method for producing a pitch-coated silicon/carbon composite material for a secondary battery composite anode material according to the present invention uses a pitch derived from petroleum residue (PFO) and waste plastic (PET) to efficiently treat waste It has the advantage of being able to solve environmental problems and revitalize the recycling industry.

A secondary battery manufactured using a pitch-coated silicon/carbon composite material for a secondary battery composite anode material according to the present invention has a capacity, and after 50 cycles, it has the advantage of exhibiting a capacity retention rate of about 85% or more compared to 5 cycles.

1 illustrates a method for manufacturing a composite anode material for a secondary battery according to an embodiment of the present invention.
2 is an EDS analysis result of a composite anode material for a secondary battery according to an embodiment of the present invention.
3 shows the results of SEM analysis of the composite negative electrode material for a secondary battery according to an embodiment of the present invention.
4 is an analysis result of the charging and discharging efficacy of the secondary battery composite negative electrode material according to an embodiment of the present invention.

Aha, a method for producing a pitch-coated silicon/carbon composite material for a secondary battery composite negative electrode material according to a specific embodiment of the present invention will be described in detail. However, this is presented as an example of the invention, thereby not limiting the scope of the invention, it is apparent to those skilled in the art that various modifications to the embodiment are possible within the scope of the invention.

Throughout this specification, unless otherwise specified, "including" or "containing" refers to including any component (or component) without particular limitation, and excludes the addition of other components (or components). cannot be construed as

According to a first embodiment, the present invention

(A) preparing a mixed solution in which nano silicon, hard carbon, and a first solvent are mixed;

(B) hydrothermal synthesis of the mixed solution at 160 to 210° C. for 6 to 10 hours to form a spherical silicone/sucrose composite; and

(C) Pitch-coated silicon/carbon composite material for secondary battery composite anode material comprising the step of mixing the spherical silicon/sucrose composite, pitch, and a second solvent to prepare a silicon/sucrose/pitch composite material To provide a manufacturing method of A method of manufacturing a composite anode material for a secondary battery according to the present invention is shown in FIG. 1 .

In the manufacturing method of the secondary battery composite negative electrode material according to the present invention, the manufacturing method is before the step (A):

(a-1) mixing and stirring the silica precursor and an alcohol-based solvent to prepare a silica precursor solution;

(a-2) after adding aqueous ammonia to the silica precursor solution, heating at 50 to 100° C. for 12 to 24 hours to form silica, and

(a-3) may further include the step of heat-treating the silica and the metal reducing agent at 600 to 800 ℃ in an inert atmosphere to form nano silicon. The silica precursor may be tetraethyl orthosilicate (TEOS), tetramethoxysilane (TMOS), or silicon tetrachloride, but is not limited thereto. The alcohol-based solvent may be methanol, ethanol, iso-propanol, or butanol, but is not limited thereto. The stirring may be performed at a temperature of 0 to 100 ℃ at a speed of 200 to 1600 rpm. The size of the nano silicon may be 5 nm to 100 nm. The metal reducing agent may be titanium (Ti), aluminum (Al), magnesium (Mg), calcium (Ca), beryllium (Be), strontium (Sr), or barium (Ba), but is not limited thereto.

In the manufacturing method of the secondary battery composite negative electrode material according to the present invention, the hard carbon is sucrose, phenol resin, furan resin, furfuryl alcohol, polyacrylonitrile (polyacrylonitrile), polyimide, epoxy resin, cellulose, styrene, citric acid, stearic acid, polyvinylidene fluoride, carboxymethyl cellulose (CMC), hydroxypropyl cellulose, At least one selected from polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated ethylene-propylene-diene monomer (EPDM), starch, glucose, gelatin and saccharides It may include a carbonaceous material formed by carbonization, but is not limited thereto.

In the method for manufacturing a composite anode material for a secondary battery according to the present invention, the first solvent may be distilled water.

In the method of manufacturing a secondary battery composite anode material according to the present invention, the pitch may be formed by mixing petroleum residue (PFO) and waste plastic (PET) and then heat-treating at a temperature of 300 ° C. or higher for 1 to 5 hours. there is. In the case of the pitch according to the present invention, the pitch yield is increased by using the waste plastic, and there is an advantage of having a high specific surface area.

In the manufacturing method of the secondary battery composite negative electrode material according to the present invention, the manufacturing method includes the steps of washing the silicon/sucrose composite formed by hydrothermal synthesis (b-1) with water after the step (B) and drying in a vacuum oven may additionally include.

In the manufacturing method of the secondary battery composite negative electrode material according to the present invention, the step (C)

(c-1) preparing a mixed solution by mixing the silicon/sucrose composite, pitch, and a second solvent;

(c-2) dispersing the mixed solution by applying ultrasonic waves; and

(c-3) drying the mixed solution may be included. The second solvent may be hexane, toluene, or tetrahydrofuran (THF), but is not limited thereto. The silicon/sucrose and pitch may be mixed in a ratio of 90:10 to 80:20 parts by weight. As the mixing ratio of silicon increases, the capacity increases, but the volume expansion ratio due to charging and discharging increases. Sucrose and the pitch are preferably mixed in a ratio of 90:10 to 80:20 parts by weight.

In the manufacturing method of the secondary battery composite anode material according to the present invention, the manufacturing method (D) sintering the prepared silicon/sucrose/pitch composite material in an inert atmosphere at 800 to 1000° C. for 1 to 3 hours. may additionally include.

In the method for manufacturing a secondary battery composite anode material according to the present invention, the silicon/sucrose/pitch composite material is characterized in that it has an average particle diameter (D50) of 50 to 1,000 nm or less.

According to a second embodiment, the present invention also

An object of the present invention is to provide an anode comprising a current collector and a pitch-coated silicon/carbon composite material for a composite anode material for a secondary battery according to the present invention disposed on the current collector.

In the negative electrode comprising the silicon / carbon composite material according to the present invention, the negative electrode is a pitch-coated silicone / carbon composite material, a binder and a solvent, if necessary, the steps of preparing a slurry by mixing a conductive material and a dispersant; and applying and rolling the slurry to the current collector. The binder is vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (polyvinylidenefluoride), polyacrylonitrile (polyacrylonitrile), polymethyl methacrylate (polymethylmethacrylate), polyvinyl Alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers, but is not limited thereto. The solvent may include, but is not limited to, N-methyl-2-pyrrolidone, acetone, or water.

According to a third embodiment, the present invention

anode; A negative electrode comprising a pitch-coated silicon/carbon composite material for secondary battery composite negative electrode material according to the present invention; and an electrolyte providing an ion movement path between the positive electrode and the negative electrode.

In the secondary battery according to the present invention, in the positive electrode, the positive active material is a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; lithium manganese oxides such as Formula Li _1+y Mn _2-y O ₄ (where y is 0 - 0.33), LiMnO ₃ , LiMn ₂ O ₃ , and LiMnO ₂ ; lithium copper oxide (Li ₂ CuO ₂ ); vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , and Cu ₂ V ₂ O ₇ ; Ni site-type lithium nickel oxide represented by the formula LiNi _1-y MyO ₂ (wherein M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and y = 0.01 - 0.3); Formula LiMn _2-y M _y O ₂ (wherein M = Co, Ni, Fe, Cr, Zn or Ta and y = 0.01 - 0.1) or Li ₂ Mn ₃ MO ₈ (where M = Fe, Co, lithium manganese composite oxide represented by Ni, Cu or Zn; LiMn ₂ O ₄ in which a part of Li in the formula is substituted with alkaline earth metal ions, but is not limited thereto.

In the secondary battery according to the present invention, the electrolyte is F ^- , Cl ^- , I ^- , NO ₃ ^- , N(CN) ₂ ^- , BF ₄ ^- , ClO ₄ ^- , PF ₆ ^- , (CF ₃ ) ₂ PF ₄ ^- , (CF ₃ ) ₃ PF ₃ ^- , (CF ₃ ) ₄ PF ₂ ^- , (CF ₃ ) ₅ PF ^- , (CF ₃ ) ₆ P ^- , CF ₃ SO ₃ ^- , CF ₃ CF ₂ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- , CF ₃ CF ₂ (CF ₃ ) ₂ CO ^- , (CF ₃ SO ₂ ) ₂ CH ^- , (SF ₅ ) ₃ C ^- , ( from the group consisting of CF ₃ SO ₂ ) ₃ C ^- , CF ₃ (CF ₂ ) ₇ SO ₃ ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- Any one selected or a mixture of two or more thereof may be used.

Hereinafter, examples and experimental examples for a method of manufacturing a composite negative electrode material for a secondary battery according to an embodiment of the present invention will be described.

<Example>

Example 1. Preparation of silicon/sucrose composite material

Silicone and 1.5 M of sucrose were dissolved in distilled water and stirred at 50 °C at 500 rpm for 1 hour using a Hotplate Stirrier. The mixed solution was put into a Hydrothermal Synthesis Reactor and heat-treated at 180 °C for 6 hours. After filtering the heat-treated material, the solid precursor was prepared by vacuum drying in an oven at 120 °C.

Example 2. Preparation of silicon/carbon/pitch composite material

In order to coat the pitch on the carbon composite prepared in Example 1, PET-added petroleum pitch was dissolved in tetrohydrofuran and dispersed using an ultrasonic cleaner for 10 minutes. After adding the carbon composite, it was uniformly dispersed for 30 minutes again using an ultrasonic cleaner, and then stirred at 200 rpm for 24 hours using a hotplate stirrer. The mixed solution was evaporated in an oven at 80° C. to prepare a solid mixture precursor. The precursor was carbonized at 800 °C for 2 hours in an Ar atmosphere to complete a silicon/carbon/pitch composite material.

Example 3. Confirmation of physical properties of silicon/carbon/pitch composite material

EDS mapping analysis of the silicon/carbon/pitch composite material prepared in Example 2 was performed to confirm the degree of dispersion of silicon in the carbon sphere. As a result, it was confirmed that silicon was evenly dispersed in the carbon spheres (FIG. 2).

In addition, SEM analysis was performed to confirm the surface and particle size characteristics of the composite according to the pitch coating of the negative electrode material. As a result, it was confirmed that the particle size distribution of the coated anode material was improved compared to the uncoated material, and the shape of the particles whose hydrothermal synthesis was not complete was supplemented (FIG. 3).

<Experimental example>

Experimental Example 1. Analysis of charging and discharging performance of silicon/carbon/pitch composite material according to the present invention

In order to confirm the electrochemical properties of the silicon/carbon/pitch composite material prepared in Example 2, a coin cell was manufactured using Li metal as a counter electrode. As the active material, a composite anode material prepared such that the molar concentration of sucrose was varied to 1.0 and 1.5 M and the ratio of silicon/sucrose weight:pitch weight was 9:1 to 8:2, respectively, was used. For the electrode, a slurry was prepared while controlling the viscosity with distilled water by using an active material: a conductive material (Super P): a binder (PVdF) in a weight ratio of 60: 20: 20, and dried for 24 hours. The coated electrode was vacuum dried for 2 hours after passing through a 70% rolling process, and coin cells were manufactured using Li metal as a counter electrode in an Ar atmosphere glove box, and to evaluate the battery performance of a composite anode material for secondary batteries. A cycle charge/discharge test was performed.

As a result, Si/C (1.0M) not coated with pitch, Si/C not coated with pitch (1.5M), Si/C (1.0M) + Pitch and Si/C (1.5M) + Initial of Pitch The discharge capacities were found to be 1512 mAh/g, 1423 mAh/g, 1410 mAh/g and 1264 mAh/g, respectively.

first?? Since it has stable charge and discharge capacity from the second cycle due to the formation of the SEI layer after the cycle, the discharge capacity in the second cycle is Si/C uncoated with pitch (1.0M), Si/C not coated with pitch (1.5M), Si/C (1.0 M) + Pitch and Si/C (1.5 M) + Pitch were confirmed to be 1023 mAh/g, 1021 mAh/g, 1058 mAh/g, and 951 mAh/g, respectively. On the other hand, after 50 cycles, it was confirmed that the capacity retention rate of 85% or more for Si/C(1.0M) + Pitch and 87% or more for Si/C(1.0M) + Pitch compared to 5 cycles was exhibited (FIG. 4). Therefore, it has been demonstrated that the silicon/carbon/pitch composite material according to the present invention can significantly increase high capacity retention and stability.

It looked at the examples mainly. Those of ordinary skill in the art to which the present invention pertains will understand that the present invention can be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments are to be considered in an illustrative rather than a restrictive sense. The scope of the present invention is indicated in the claims rather than the foregoing description, and all differences within the scope equivalent thereto should be construed as being included in the present invention.

Claims (7)

(A) preparing a mixed solution in which nano silicon, hard carbon, and a first solvent are mixed;
(B) hydrothermal synthesis of the mixed solution at 160 to 210° C. for 6 to 10 hours to form a spherical silicone/sucrose composite; and
(C) mixing the spherical silicon/sucrose composite, pitch, and a second solvent to prepare a silicon/sucrose/pitch composite material,
The pitch is a secondary battery composite anode material pitch coating, characterized in that formed by mixing petroleum residue (PFO) and waste plastic (PET) and then heat-treating at a temperature of 300 ° C. or higher for 1 to 5 hours A method of manufacturing a silicon/carbon composite material.
According to claim 1,
The preparation method, before the step (A):
(a-1) mixing a silica precursor and an alcohol-based solvent and stirring to prepare a silica precursor solution;
(a-2) after adding aqueous ammonia to the silica precursor solution, heating at 50 to 100° C. for 12 to 24 hours to form silica, and
(a-3) heat-treating the silica and the metal reducing agent at 600 to 800° C. in an inert atmosphere to form nano silicon,
A method of manufacturing a pitch-coated silicon/carbon composite material for a secondary battery composite anode material.
According to claim 1,
The first solvent is characterized in that distilled water,
A method of manufacturing a pitch-coated silicon/carbon composite material for a secondary battery composite anode material.
The method of claim 1,
The step (C) is
(c-1) preparing a mixed solution by mixing the silicon/sucrose composite, pitch, and a second solvent;
(c-2) applying ultrasonic waves to the mixed solution to disperse and then stir; and
(c-3) characterized in that it comprises the step of drying the mixed solution,
A method of manufacturing a pitch-coated silicon/carbon composite material for a secondary battery composite anode material.
The method of claim 1,
The second solvent is characterized in that hexane, toluene, quinoline or tetrahydrofuran (THF),
A method of manufacturing a pitch-coated silicon/carbon composite material for a secondary battery composite anode material.
According to claim 1,
The silicon / sucrose and pitch are characterized in that they are mixed in a ratio of 90:10 to 80:20 parts by weight,
A method of manufacturing a pitch-coated silicon/carbon composite material for a secondary battery composite anode material.
A negative electrode for a secondary battery comprising a silicon/carbon composite material manufactured by the manufacturing method according to any one of claims 1 to 6.

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