KR102488679B1 - Aqueous binder for a lithium-ion secondary battery, anode comprising the same, lithium-ion secondary battery comprising the anode, and method for polymerizing copolymer comprised in the binder - Google Patents

Abstract

상기 식에서 a, b 및 c는 각 단량체의 몰비를 나타내며, a는 0.1~1.5, b는 1~8, c는 1~4이며,
상기 R은 수소 또는 1가의 양이온이다. The present invention provides a binder including a copolymer represented by Formula 1 below, a negative electrode for a lithium ion secondary battery including the same, and a lithium ion secondary battery including the negative electrode. In addition, the present invention provides a polymerization method of the following copolymer:
[Formula 1]

In the above formula, a, b and c represent the molar ratio of each monomer, a is 0.1 to 1.5, b is 1 to 8, c is 1 to 4,
R is hydrogen or a monovalent cation.

Description

Aqueous binder for lithium ion secondary battery, negative electrode for lithium ion secondary battery including the same, lithium ion secondary battery including the negative electrode, and polymerization method of copolymer included in the binder {AQUEOUS BINDER FOR A LITHIUM-ION SECONDARY BATTERY, ANODE COMPRISING THE SAME, LITHIUM-ION SECONDARY BATTERY COMPRISING THE ANODE, AND METHOD FOR POLYMERIZING COPOLYMER COMPRISED IN THE BINDER}

The present invention relates to an aqueous binder for a lithium ion secondary battery having improved lifespan characteristics, a negative electrode for a lithium ion secondary battery including the same, a lithium ion secondary battery including the negative electrode, and a polymerization method of a copolymer included in the binder.

In recent years, interest in energy storage technology has been increasing. Efforts in the research and development of electrochemical devices are becoming more and more specific as the fields of application are expanded to mobile phones, camcorders, notebook PCs, and even the energy of electric vehicles.

The electrochemical device is the field that has received the most attention in this respect, and among them, the development of a secondary battery capable of charging and discharging has become a focus of interest. Recently, research and development on the design of new electrodes and batteries are being conducted in order to improve capacity density and specific energy in developing such batteries.

Among the secondary batteries currently applied, lithium ion secondary batteries are in the limelight due to their high operating voltage and significantly higher energy density than conventional batteries such as Ni-MH, Ni-Cd, and sulfuric acid-lead batteries that use aqueous electrolytes. .

Such an electrochemical device generally includes a cathode, an anode, and a separator interposed between the cathode and the anode. At this time, the cathode and the anode are generally coated with an electrode active material slurry containing an electrode active material, a polymer binder, and a solvent for dispersing the electrode active material and dissolving the polymer binder on the surface of the current collector to form an electrode active material layer. are manufactured

On the other hand, among the electrode active materials, the volume expansion of the anode active material occurs according to the insertion and release of lithium. In particular, when a silicon oxide-based (SiOx) active material is used as the anode active material, volume expansion may be further intensified.

As a remedy, Si has been considered as a next-generation anode material for a long time, but extreme volume expansion (~300%) due to alloying/dealloying of Li ions during charging/discharging promotes electrode degradation, which is the biggest obstacle to commercialization of Si materials. It is becoming. This volume change causes the Si active material to be crushed internally, exposing a new interface, and the exposed interface forms a new SEI by a side reaction with the electrolyte, causing a problem of continuous Li ion and electrolyte consumption. In addition, the crushed Si pieces are detached from the original conductive structure so that they cannot participate in charge/discharge and act as a cause of life degradation.

On the other hand, the binder is a very important sub-material for maintaining the integrity of the electrode and the conductive structure of the active material, and is recognized as a component that can solve the problem of volume expansion.

However, conventionally developed various binders (SBR, CMC, PAA, PAA/CMC, Na-PAA, crosslinked PAA, Alginate, PVA, etc.) lack adhesion or too brittle electrodes and lack durability, resulting in It is difficult to expect a solution to the expansion problem.

Republic of Korea Patent Publication No. 10-2015-0049601

The present invention has been made to solve the above problems of the prior art,

By including both a hydrophilic unit and a hydrophobic unit, adhesion to electrode constituent materials is excellent, cracking of the electrode due to volume change of active materials such as Si is effectively suppressed, and charge/discharge characteristics and lifespan characteristics of the battery can be improved. It is an object of the present invention to provide a binder having

In addition, an object of the present invention is to provide a negative electrode for a lithium ion secondary battery in which durability is greatly improved by including the binder, and charge/discharge characteristics and lifespan characteristics of the battery can be improved.

In addition, the present invention provides a lithium ion secondary battery having significantly improved durability, charge/discharge characteristics, and lifespan characteristics by including the negative electrode.

In addition, an object of the present invention is to provide an effective polymerization method of the copolymer included in the binder.

In order to achieve the above object, the present invention,

Provided is a binder comprising a copolymer represented by Formula 1 below:

[Formula 1]

In the above formula, a, b and c represent the molar ratio of each monomer, a is 0.1 to 1.5, b is 1 to 8, c is 1 to 4;

R is hydrogen or a monovalent cation.

In addition, the present invention,

Provided is a negative electrode for a lithium ion secondary battery comprising a negative electrode active material, the binder of the present invention, and a conductive material.

In addition, the present invention,

anode; The negative electrode of the present invention; a separator provided between the positive electrode and the negative electrode; And an electrolyte; it provides a lithium ion secondary battery comprising a.

In addition, the present invention,

(a) adding a styrenic monomer, a surfactant, a polymerization initiator, and a solvent to a polymerization reactor and mixing them;

(b) adding a (meth)acrylate-based monomer and a vinyl alcohol-based monomer protected with a leaving group to the mixture of step (a) and sealing the inlet of the reactor;

(c) removing oxygen within the polymerization reactor using nitrogen;

(d) stirring while heating at 50 to 90° C. in a sealed state;

(e) removing the surfactant; and

(f) removing the protecting group; provides a polymerization method of the copolymer for the binder of the present invention, including.

The binder of the present invention includes both a hydrophilic unit and a hydrophobic unit, so it has excellent adhesion to electrode constituent materials, effectively suppresses cracking of the electrode due to volume change of active materials such as Si, and has charge/discharge characteristics and lifespan of the battery. Provides the effect of enhancing the characteristics.

In addition, the negative electrode for a lithium ion secondary battery of the present invention provides excellent durability, charge/discharge characteristics, and lifespan characteristics by including the binder.

In addition, the lithium ion secondary battery of the present invention provides excellent durability, charge/discharge characteristics, and lifespan characteristics by including the negative electrode.

In addition, the preparation method of the copolymer of the present invention provides an effective polymerization method of the binder copolymer.

1 is a graph showing the results of GPC for measuring the molecular weight (Mn) of a copolymer included in the binder of the present invention (Example 1).
Figure 2 is a graph showing the results of FT-IR for confirming the functional group of the copolymer included in the binder of the present invention (Example 1).
3 is a graph showing the NMR results for confirming the structure of the copolymer included in the binder of the present invention (Example 1).
4 is a graph showing the initial performance of a lithium ion secondary battery using a conventional binder and a lithium ion secondary battery using a binder of the present invention in Test Example 1 of the present invention.
5 is a graph showing life characteristics of a lithium ion secondary battery using a conventional binder and a lithium ion secondary battery using a binder of the present invention in Test Example 1.

Hereinafter, the present invention will be described in detail.

The present invention relates to a binder comprising a copolymer represented by Formula 1 below:

[Formula 1]

In the above formula, a, b and c represent the molar ratio of each monomer, a is 0.1 to 1.5, b is 1 to 8, c is 1 to 4;

R is hydrogen or a monovalent cation.

SBR/CMC-based binders, which are widely used in the prior art, are water-based binders mainly used for graphite-based negative electrodes. Therefore, it has physical properties that are not suitable for alloying / dealloying systems with extreme volume changes, such as Si-based cathodes.

Therefore, research is being conducted to prepare binders suitable for alloying / dealloying systems with extreme volume changes, such as Si-based anodes.

Existing studies have mainly confirmed the performance of Si-based anodes by applying polymeric binders having acrylate and alcohol structures.

When the present inventors apply the conventional binder as described above to a mixed negative electrode in which silicon and graphite are mixed, the adhesion between the graphite active material and the hydrophilic binder is low, which undesirably affects the durability and driving performance of the negative electrode. It was found that a new binder that could be applied well to the negative electrode was needed, and related research was conducted, and as a result, the present invention was completed.

The binder of the present invention is a hydrophobic styrenic monomer introduced into PAAPVA, and has an acrylic acid or acrylate group and -OH group, so it has excellent water solubility, and has a covalent bond with the Si active material and the Cu current collector (during dehydration reaction) or Since hydrogen bonding is possible and randomly arranged styrenic functional groups are capable of hydrophobic bonding and pi-pi interaction bonding with the graphite active material, it has excellent adhesive strength.

Therefore, in the copolymer represented by Formula 1, the molar ratio of a, b and c has an important meaning.

That is, as described above, when the molar ratio of a, b, and c is in the range of 0.1 to 1.5: 1 to 8: 1 to 4, the functions described above can be balanced, thereby providing excellent adhesive strength. can exert

The molar ratio of a, b and c in the copolymer is more preferably 0.5 to 1.5: 4 to 8: 1 to 3.

The number average molecular weight of the copolymer may be 200,000 to 15,000,000, more preferably 1,000,000 to 12,000,000, and even more preferably 5,000,000 to 11,000,000. When the number average molecular weight is less than the above-mentioned range, adhesive strength may be weakened, and when it exceeds the above-mentioned range, the viscosity of the binder becomes too high, which is not preferable.

The copolymer may be preferably a random copolymer. This is because better adhesion can be exhibited when each monomer is distributed as uniformly as possible.

In the copolymer represented by Chemical Formula 1, when R is a monovalent cation, adhesion to the current collector may be enhanced. The monovalent cation may be a lithium or sodium ion.

In the binder of the present invention, the copolymer may be included in an amount of 30 to 100% by weight based on the total weight of the binder. That is, the binder may be in the form of including a copolymer together with a solvent or made of a copolymer without a solvent.

Any solvent known in the art may be used as the solvent as long as it can dissolve the copolymer. Examples of the known solvent include acetone, tetra hydrofuran, methylene chloride, chloroform, dimethylform amide, N-methyl-2-pyrrolidone (N- methyl-2-pyrrolidone, NMP), cyclohexane, water, and the like, and these may be used alone or in combination of two or more. In particular, water may be preferably used in consideration of the environment and physical properties of the binder. Distilled water may be used as the water.

The binder of the present invention may be used as a water-based binder.

The binder may be used for manufacturing a lithium ion secondary battery. That is, the binder may be used for manufacturing a negative electrode, a positive electrode, and the like, and in particular, may be preferably used for manufacturing a negative electrode.

Specifically, the binder may be preferably used for manufacturing an anode including a Si-based active material.

In addition, the present invention

(a) adding a styrenic monomer, a surfactant, a polymerization initiator, and a solvent to a polymerization reactor and mixing them;

(b) adding a (meth)acrylate-based monomer and a vinyl alcohol-based monomer protected with a leaving group to the mixture of step (a) and sealing the inlet of the reactor;

(c) removing oxygen within the polymerization reactor using nitrogen;

(d) stirring while heating at 50 to 90° C. in a sealed state;

(e) removing the surfactant; and

(f) removing the protecting group; relates to a polymerization method of a copolymer for a binder of the present invention, including.

As the solvent in step (a), known solvents capable of dissolving the monomers may be used. Examples of the known solvent include acetone, tetra hydrofuran, methylene chloride, chloroform, dimethylform amide, N-methyl-2-pyrrolidone (N- methyl-2-pyrrolidone, NMP), cyclohexane, water, and the like, and these may be used alone or in combination of two or more. In particular, water may be preferably used.

In the steps (a) and (b), the styrene-based monomer, the (meth)acrylate-based monomer, and the vinyl alcohol-based monomer protected with a leaving group have a ratio of 0.1 to 1.5: 1 to 8: 1 to 4 as described above. It may be used in a molar ratio, and more preferably in a molar ratio of 0.5 to 1.5: 4 to 8: 1 to 3.

In the step (c), as the polymerization initiator and the surfactant, those commonly used in this field may be used according to the conventional content. For example, potassium persulfate (KPS) may be used as the polymerization initiator, and sodium dodeyl sulfate (SDS) may be used as the surfactant.

The heating time in step (d) may be performed for 12 to 72 hours.

In step (e), the surfactant may be removed by dissolving it in a solvent (eg, THF) and removing it using a centrifugal separator. At this time, it may be desirable to first remove the water before removing the surfactant.

After the step (e), a step of precipitating the recovered polymer in a hexane solvent to remove remaining impurities may be further performed.

After dissolving the polymer recovered in step (f) in a solvent (eg, THF), a step of deprotecting the functional group by adding KOH and stirring at room temperature for 1 to 3 days may be further performed.

In addition, as a last step, a step of dissolving the polymer recovered above in water and then adding it to an ethanol solvent to induce precipitation to additionally remove impurities may be performed.

In the polymerization method of the copolymer for the binder, methods known in the art may be applied, except for those specifically limited above.

A brief example of the method for preparing the copolymer of the present invention as a reaction scheme is as follows:

[reaction formula]

In addition, the present invention

In addition, the present invention relates to a negative electrode for a lithium ion secondary battery comprising a negative electrode active material, the binder of the present invention, and a conductive material.

As the anode active material, those known in the art may be used, and in particular, a cathode active material including a Si-based active material may be preferably used, and more specifically, a mixture of SiOx/C and graphite may be used. The SiOx/C includes a carbon coating layer formed on a surface of SiOx.

The negative electrode active material, the binder of the present invention, and the conductive material form a negative electrode active material layer, and the negative electrode active material layer is prepared by preparing a slurry containing the components according to a conventional method, applying the slurry to a current collector and drying it contained within the cathode. Here, a non-limiting example of the current collector may include a foil made of copper, gold, nickel, or a copper alloy or a combination thereof.

With respect to the total weight of the negative electrode active material layer, the negative electrode active material may be included in 70 to 98% by weight, the conductive material may be included in 1 to 20% by weight, and the binder may be included in 1 to 10% by weight, but are limited thereto. it is not going to be

A conventional dispersant may be further included in the slurry for preparing the negative electrode active material layer.

Although the conductive material is not particularly limited, conductive materials such as graphite materials such as KS6, carbon materials such as Super-P, Denka Black, and carbon black, or conductive polymers such as polyaniline, polythiophene, polyacetylene, and polypyrrole may be used alone or in combination.

In the lithium ion secondary battery according to the present invention, stack and lamination processes of separators and electrodes, folding, and stack/folding processes are possible in addition to winding, which is a general process.

In addition, the external shape of the lithium ion secondary battery is not particularly limited, but may be a cylindrical shape using a can, a prismatic shape, a pouch shape, or a coin shape.

In addition, the present invention is the negative electrode of the present invention; anode; a separator provided between the positive electrode and the negative electrode; And an electrolyte; relates to a lithium ion secondary battery comprising a.

Regarding the negative electrode, the above description may be applied as it is.

In the lithium ion secondary battery of the present invention, the positive electrode is not particularly limited, and may be prepared in a form in which a positive electrode active material is bound to a current collector according to a conventional method known in the art.

A known cathode active material may be used as the cathode active material, and for example, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, a three-component cathode material LiNi _x Mn _y Co _z O ₂ (NMC), or A lithium composite oxide combining these may be used. Examples of the current collector include aluminum, nickel, or a foil made of a combination thereof.

The separator positioned between the positive electrode and the negative electrode separates or insulates the positive electrode and the negative electrode from each other and enables lithium ion transport between the positive electrode and the negative electrode. As the separator used in the present invention, any porous polymer substrate commonly used in this field may be used, and for example, a polyolefin-based porous polymer membrane or non-woven fabric may be used, but is not particularly limited thereto.

Examples of the polyolefin-based porous polymer membrane include polyethylene such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene, polyolefin-based polymers such as polypropylene, polybutylene, and polypentene, either alone or as a mixture thereof. A formed membrane is exemplified.

In addition to the polyolefin-based nonwoven fabric, the nonwoven fabric includes, for example, polyethyleneterephthalate, polybutyleneterephthalate, polyester, polyacetal, polyamide, and polycarbonate. ), polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfide, polyethylenenaphthalene, etc. alone or A nonwoven fabric formed from a polymer obtained by mixing these is exemplified. The structure of the nonwoven fabric may be a spunbond nonwoven fabric or a melt blown nonwoven fabric composed of long fibers.

The thickness of the porous polymer substrate is not particularly limited, but may be 5 μm to 50 μm, and the pore size and porosity present in the porous polymer substrate are also not particularly limited, but may be 0.01 μm to 50 μm and 10 to 95%, respectively. there is.

In addition, in order to improve mechanical strength of the separator and safety of the lithium ion secondary battery, a porous coating layer including inorganic particles and a polymer binder may be further included on at least one surface of the porous polymer substrate.

The polymer binder included in the porous coating layer is coated on part or all of the surface of the inorganic particles, the inorganic particles are connected and fixed to each other by the polymer binder in a close contact state, and the inorganic particles present between the inorganic particles It is preferable that pores are formed due to an interstitial volume. That is, the inorganic particles of the porous coating layer exist in close contact with each other, and an interstitial volume generated when the inorganic particles are in close contact may become pores of the porous coating layer.

As the electrolyte, one known in the art may be used, and for example, a non-aqueous electrolyte may be used. The non-aqueous electrolyte may include a lithium salt as an electrolyte salt. As the lithium salt, those commonly used in electrolytes for lithium ion secondary batteries may be used without limitation. For example, the anion of the lithium salt is F ^- , Cl ^- , Br ^- , 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 ^- , (CF ₃ SO ₂ ) ₃ C ^- , CF ₃ (CF ₂ ) ₇ SO ₃ ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , At least one selected from the group consisting of SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- may be used.

As the organic solvent included in the non-aqueous electrolyte, organic solvents commonly used in electrolytes for lithium ion secondary batteries may be used without limitation, and for example, ether, ester, amide, linear carbonate, cyclic carbonate, etc. may be used alone or Two or more may be used in combination. Among them, cyclic carbonates, linear carbonates, or carbonate compounds that are mixtures thereof may be used as representative examples.

Specific examples of the cyclic carbonate compound include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, and any one selected from the group consisting of 2,3-pentylene carbonate, vinylene carbonate, vinylethylene carbonate, and halides thereof, or a mixture of two or more thereof. These halides include, for example, fluoroethylene carbonate (FEC) and the like, but are not limited thereto.

In addition, specific examples of the linear carbonate compound include any one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate and ethylpropyl carbonate, or these A mixture of two or more of them may be used representatively, but is not limited thereto.

In particular, among the carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are high-viscosity organic solvents and have a high dielectric constant, so that lithium salts in the electrolyte can be better dissociated. Such cyclic carbonates, such as dimethyl carbonate and diethyl carbonate An electrolyte with higher electrical conductivity can be made by mixing and using low-viscosity, low-dielectric constant linear carbonates in an appropriate ratio.

In addition, as the ether in the organic solvent, any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methylpropyl ether and ethylpropyl ether or a mixture of two or more thereof may be used. , but is not limited thereto.

In addition, esters in the organic solvent include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone And ε-caprolactone, but any one selected from the group consisting of, or a mixture of two or more of them may be used, but is not limited thereto.

Injection of the non-aqueous electrolyte solution may be performed at an appropriate stage during the manufacturing process of the lithium ion secondary battery according to the manufacturing process and required physical properties of the final product. That is, it may be applied before assembling the lithium ion secondary battery or at the final stage of assembling the lithium ion secondary battery.

The lithium ion secondary battery may be configured by applying techniques known in the art, except for the characteristic techniques of the present invention described above.

Hereinafter, preferred embodiments are presented to aid understanding of the present invention, but the following examples are merely illustrative of the present invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present invention, It goes without saying that these changes and modifications fall within the scope of the appended claims.

Example 1: Preparation of Binder Containing PS-PAAPVA Copolymer

In a 25 ml round flask containing 12 g of distilled water, 1 mg of KPS (Potassium persulfate) and 0.16 g (0.00307 mol) of styrene were sequentially added, and an additional 150 mg of SDS (sodium dodeyl sulfate), a surfactant, was added and stirred to mix well.

After adding 4.3 ml (0.0465 mol) of vinyl acetate and 2.78 ml (0.0310 mol) of methyl acrylate to the solution prepared above, the lid was closed and sealed with a paraffin film.

After removing oxygen in the vessel for 30 minutes by connecting an Ar gas tube, it was once again sealed with a paraffin film and stirred while heating at 70°C for 2 days.

After the reaction was completed, water was first removed, and then the surfactant was removed by dissolving in THF and centrifuging.

The polymer recovered above was precipitated in a hexane solvent to remove remaining impurities.

The molecular weight (Mn) of the polymer synthesized above was confirmed through GPC (see FIG. 1).

After dissolving the synthesized polymer in THF, KOH was added and stirred at room temperature for 2 days to deprotect the functional group.

The polymer recovered above was dissolved in water and then added to an ethanol solvent to induce precipitation to remove impurities. Next, the functional group of the synthesized polymer was confirmed through FT-IR (see FIG. 2), and the structure of the polymer was confirmed by NMR (see FIG. 3).

From FIGS. 2 and 3 below, it can be clearly confirmed that the copolymer represented by Formula 1 was synthesized by the above practice.

Example 2: Preparation of negative electrode for lithium ion secondary battery

A slurry was prepared by applying SiO/C as an active material, super-P as a conductive material, and the PS-PAAPVA binder prepared in Example 1 above. At this time, the ratio of the active material:conductive material:binder was 92:3:5.

Specifically, first, 1 g of the PS-PAAPVA binder prepared in Example 1 was dissolved in 9 ml of distilled water to prepare a solution having a binder concentration of 10%, and then super-P was added to the binder solution and stirred sufficiently. Next, SiO/C was added to prepare a uniform slurry.

The slurry was applied on a copper foil using a doctor blade to prepare a negative electrode.

The slurry prepared above was coated on a 20 μm thick Cu foil using a doctor blade to a thickness of 50 to 150 μm, and primary drying was performed at 80 ° C. for 30 minutes using a convection oven. A portion having a constant loading was taken and secondary drying was performed in a vacuum oven at 150° C. for 2 hours to prepare a negative electrode (designed capacity of 710 mAh/g).

Comparative Example 1: Preparation of negative electrode for lithium ion secondary battery

An anode was prepared in the same manner as in Example 2, except that SBR/CMC (weight ratio 7:3) was used as a binder.

Example 3: Manufacturing of lithium ion secondary battery

Lithium metal was used as a reference and counter electrode for the anode prepared in Example 2 (the porosity was adjusted to about 30% by rolling), and EC: DEC = 3: 7, 10 wt% FEC, 1.3M LiPF ₆ composition was used as the electrolyte. and a 20 micron-thick polyethylene (PE) film was used as a separator to manufacture a coin cell.

Comparative Example 2: Manufacturing of a lithium ion secondary battery

A coin cell was manufactured in the same manner as in Example 3, except that the negative electrode prepared in Comparative Example 1 was used.

Test Example 1: Characteristic evaluation of lithium ion secondary battery

The charge/discharge characteristics, initial efficiency, and lifetime characteristics of the battery of Example 3 and the battery of Comparative Example 2 were evaluated in the following manner, and the results are shown in Table 2 and FIGS. 4 and 5.

<Initial Efficiency Evaluation Method>

The initial efficiency of the battery was evaluated by performing charging and discharging under the conditions shown in Table 1 below.

1st cycle Charge 0.1C rate, 0.005V, 0.02C (CC-CV) / Discharge 0.1C rate, 1.5V (CC) 2nd cycle Charge 0.1C rate, 0.005V, 0.02C (CC-CV) / Discharge 0.1C rate, 1.0V (CC) 3rd~50th cycle Charge 0.5C rate, 0.005V, 0.02C (CC-CV) / Discharge 0.5C rate, 1.5V (CC)

<Method for Evaluating Life Performance> Life characteristics were evaluated by performing charging and discharging for 50 cycles under the charging/reversing conditions of Table 1 above.

battery Battery of Comparative Example 2 Cell of Example 3 Binder used SBR/CMC
(Comparative Example 1) PS-PAAPVA
(Example 2) Electrode loading (mAh/cm ² ) 1.65 2.16 Discharge capacity (mAh/g) 665.6 731.2 Initial Efficiency (%) 80.0 80.9 Lifetime performance (%) 72.1 89.2

As confirmed from Table 2 and FIGS. 4 and 5, the battery of Example 3 using the binder of the present invention showed an equivalent degree in initial efficiency compared to the battery of Comparative Example 2 using the conventional binder. However, the discharge capacity characteristics were remarkably excellent, and the life characteristics were also confirmed to be very remarkable.

Claims (14)

A binder comprising 30 to 100% by weight of a copolymer having a number average molecular weight of 1,000,000 to 12,000,000 represented by the following formula (1) based on the total weight of the binder:
[Formula 1]

In the above formula, a, b and c represent the molar ratio of each monomer, a is 0.5 to 1.5, b is 4 to 8, c is 1 to 3;
R is hydrogen or a monovalent cation. delete delete According to claim 1,
The copolymer is a binder, characterized in that the random copolymer. According to claim 1,
A binder, characterized in that the monovalent cation for R is a lithium or sodium ion. delete According to claim 1,
The binder is acetone, tetra hydrofuran, methylene chloride, chloroform, dimethylform amide, N-methyl-2-pyrrolidone A binder characterized in that it further comprises at least one solvent selected from the group consisting of -pyrrolidone, NMP), cyclohexane, and water. According to claim 1,
The binder, characterized in that the binder is a water-based binder. According to claim 1,
The binder is a binder, characterized in that for producing a lithium ion secondary battery. In the ninth,
The binder is a binder, characterized in that for producing a negative electrode containing a Si-based active material. A negative electrode for a lithium ion secondary battery comprising a negative electrode active material, the binder of claim 1, and a conductive material. The negative electrode of claim 11; anode; a separator provided between the positive electrode and the negative electrode; and
A lithium ion secondary battery comprising an electrolyte; (a) adding a styrenic monomer, a surfactant, a polymerization initiator, and a solvent to a polymerization reactor and mixing them;
(b) adding a (meth)acrylate-based monomer and a vinyl alcohol-based monomer protected with a leaving group to the mixture of step (a) and sealing the inlet of the reactor;
(c) removing oxygen within the polymerization reactor using nitrogen;
(d) stirring while heating at 50 to 90° C. in a sealed state;
(e) removing the surfactant; and
(f) removing the protecting group; polymerization method of the copolymer of claim 1 comprising the. According to claim 13,
The polymerization method of the copolymer, characterized in that the solvent in step (a) is water.

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