KR20190140819A - Slurry including the elastic binder for secondary battery electrode, electrodes including the slurry for secondary battery, and secondary battery including the electrode - Google Patents

Abstract

The present invention relates to slurry for a secondary battery electrode, including an elastic binder for binding force of an electrode and high dispersibility of the slurry for the production of high performance secondary battery electrodes. The present invention also relates to an electrode for a secondary battery comprising the same and a secondary battery.

Description

Slurry for a secondary battery electrode comprising an elastic binder for a secondary battery electrode, a secondary battery electrode and a secondary battery comprising the same {Slurry including the elastic binder for secondary battery electrode, electrodes including the slurry for secondary battery, and secondary battery including the electrode}

The present invention relates to a slurry for secondary battery electrodes comprising an elastic binder for secondary battery electrodes, a secondary battery electrode and a secondary battery comprising the same, and more particularly, a secondary battery including an elastic binder for a layered lithium transition metal oxide electrode. It relates to a slurry for an electrode, a secondary battery electrode and a secondary battery comprising the same.

Recently, due to environmental pollution issues, interest in electric vehicles that can reduce the carbon dioxide reduction and pollution factors is increasing rapidly. In this respect, lithium secondary batteries, which are the core energy sources of electric vehicles, are expected to play an important role in the development of electric vehicles because they have a higher energy density than other energy storage devices.

Particularly, the layered oxide material containing lithium nickel manganese cobalt (LiNi _0.8 Mn _0.1 Co _0.1 O ₂ ) having a high nickel content has a high energy density, low material cost, environmental friendliness, and excellent stability. It is a material that has received much attention as a battery positive electrode material. However, the layered oxide material having a high nickel content has a problem of deterioration due to its low electrical conductivity and the exchange phenomenon between nickel and lithium.

To solve this problem, researchers have attempted to solve low electrical conductivity problems by displacing heteroatoms or synthesizing nanoscale materials. However, the existing approach can be expensive for material synthesis and has a large limitation in terms of commercialization because it can have a low electrode density.

However, recent researches have revealed that the existing problems may be improved by changing the binder, which is a secondary battery electrode component. Binder material has a low content in secondary battery electrodes but is a key factor affecting overall electrode performance. In particular, in the published studies, an environmentally friendly and low process cost aqueous-based binder was used to improve the performance of a layered oxide electrode having a high nickel content. However, when the aqueous binder process is applied, lithium ion corrosion problems of the anode material and corrosion problems of the aluminum current collector may occur, and thus they are still major limitations in terms of commercialization.

In addition, the current organic solvent-based commercial PVDF binder, there is a problem of aggregation of the active material and low adhesion to the current collector due to the high molecular weight. Therefore, in order to manufacture a layered oxide electrode having a high nickel content with excellent properties, it is necessary to find an organic solvent-based polymer that is not only electrochemically stable but also immediately applicable to a commercial process, and improves dispersibility of slurry. In addition, it is necessary to find a multifunctional polymer that protects the electrode interface and has high adhesion.

Republic of Korea Patent No. 10-1320381

The present invention is to solve the above-described problems, to improve the dispersibility of the slurry in order to improve the performance of the secondary battery electrode, a slurry for secondary battery electrodes comprising a high elasticity and an elastic binder of the electrode interface protection function To provide a secondary battery electrode and a secondary battery comprising the same.

In order to achieve the above object,

The present invention is a slurry for secondary battery electrodes comprising a binder, an active material and a conductive material,

The binder includes a copolymer polymer including a hard segment capable of hydrogen bonding in the electrode and a soft segment having a polyol structure.

The slurry for secondary battery electrodes is characterized in that the shear stress (shearing stress) is generated in the slurry during the mixing process of the shear rate in the range of 0.1 to 1,000 s ^-1 , the binder is applied to the surface of the active material to provide.

In addition, the present invention provides a secondary battery electrode, characterized in that the slurry for secondary battery electrodes is applied to a current collector.

In addition, the present invention, a secondary battery electrode; And

It includes a non-aqueous electrolyte, the non-aqueous electrolyte provides a secondary battery comprising a compound of the formula (3):

[Formula 3]

.

.

The slurry for secondary battery electrodes according to the present invention includes an elastic binder, and the elastic binder has a hard segment capable of hydrogen bonding with a layered lithium transition metal oxide, a conductive carbon, and a current collector material, and thus between the materials and the active material layer and the current collector. It has high adhesion between the whole and excellent mechanical properties. In addition, since the binder material has a soft segment in the form of a polyol, it is well dispersed during the slurry manufacturing process, thereby reducing the amount of organic solvent used and also minimizing the aggregation of the material.

More specifically, the slurry for secondary battery electrodes according to the present invention is a shearing stress (shearing stress) is generated in the slurry during the mixing process of the shear rate in the range of 0.1 to 1,000 s ^-1 and due to the elasticity of the binder, The binder may be applied uniformly.

In particular, a binder is uniformly coated on the surface of the active material during the mixing process of the slurry for the secondary battery electrode to provide a secondary battery having improved speed characteristics due to improved conductivity, and prevents direct contact between the electrode and the electrolyte as the cycle progresses. Therefore, deterioration of the electrolyte may be suppressed, thereby improving lifetime characteristics of the secondary battery.

1 is a view showing a copolymer polymer structure according to an embodiment of the present invention.
FIG. 2 (a) shows the molecular structure of the copolymer polymer of the elastic binder and the bonding structure of the aluminum current collector according to the present invention, and FIG. (B) shows the molecular functional group analysis through Fourier transform infrared spectroscopy (FT-IR). Drawing.
3 is a view showing the results of the secondary battery life evaluation using the secondary battery prepared in Example 1, Comparative Example 1 of the present invention.
4 is a diagram showing a stress-strain curve of the binder according to Example 1 and Comparative Example 1. FIG.
5 is a view showing the peeling test results of the electrode cross-section according to Example 1 and Comparative Example 1.
6 is a view showing a photograph taken by SEM of the electrode surface prepared in Example 1 and Comparative Example 1.
7 is a graph showing XRD graphs of the electrode surfaces prepared in Example 1 and Comparative Example 1. FIG.
8 (a) is a graph showing the change in specific capacity of the lithium secondary battery of Example 1 and Comparative Example 1 when the charge-discharge rate is changed, Figure 8 (b) is a secondary battery electrode of Example 1 and Comparative Example 1 The graph shows the results of cyclic voltammetry analysis.
9 is a view showing the impedance analysis results of the secondary battery manufactured in Example 1 and Comparative Example 1.
10 is a graph showing capacity retention characteristics at room temperature and high temperature during long-term operation of the secondary batteries prepared in Example 1 and Comparative Example 1 ((a) 25 ℃, (b) 50 ℃).
FIG. 11 is a graph showing the results of XPS spectroscopic analysis on the electrodes of Example 1 and Comparative Example 1 before and after the electrochemical experiment to evaluate the components of the electrode interface ((a), (b) Comparative Example 1 and Example 1 Before the electrochemical cycle of the electrode, (c), (d) after the cycle of Comparative Example 1 and Example 1 electrode).
12 is a view showing SEM photographs of electrode surfaces before and after an electrochemical experiment with respect to the electrodes of Example 1 and Comparative Example 1 ((a), (b) of Comparative Example 1 and Example 1 electrodes) Before the electrochemical cycle, (c), (d) after the cycles of Comparative Example 1 and Example 1 electrodes).

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description.

However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

In the present invention, the terms "comprises" or "having" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

The present invention relates to a slurry for secondary battery electrodes comprising an elastic binder for secondary battery electrodes, a secondary battery electrode and a secondary battery comprising the same.

Conventionally, in the case of commercial PVDF binders, there are problems of aggregation of the active material and low adhesion to the current collector due to the high molecular weight. Therefore, in order to fabricate a secondary battery electrode having excellent characteristics, it is necessary to find an organic solvent-based polymer that is not only electrochemically stable but also immediately applicable to a commercial process. In particular, it is possible to improve the dispersibility of the slurry and to provide high adhesion. There is a need for research on multifunctional polymers having a high molecular weight.

Accordingly, the present invention provides a slurry comprising a binder which is a copolymer polymer comprising a hard segment capable of hydrogen bonding and a soft segment having a polyol structure in the electrode, and in particular, the slurry has a shear rate in the range of 0.1 to 1,000 s ⁻¹ . During the mixing process, shearing stress is generated in the slurry, and a binder is applied to the surface of the active material, thereby providing a slurry for secondary battery electrodes.

Furthermore, it provides a secondary battery electrode and a secondary battery comprising the slurry.

Hereinafter, the present invention will be described in more detail.

The present invention is a slurry for secondary battery electrodes comprising a binder, an active material and a conductive material,

The binder includes a copolymer polymer including a hard segment capable of hydrogen bonding in the electrode and a soft segment having a polyol structure.

The slurry for secondary battery electrodes is characterized in that the shear stress (shearing stress) is generated in the slurry during the mixing process of the shear rate in the range of 0.1 to 1,000 s ^-1 , the binder is applied to the surface of the active material to provide.

The slurry for secondary battery electrodes may be prepared by mixing a copolymer polymer of an binder, an active material and a conductive material in an organic solvent, and the slurry for secondary battery electrodes in the mixing process of the slurry may be prepared at a shear rate of 0.1 to 1,000 s ⁻¹ . In addition, an average shear stress in a range of 20 to 1100 Pa may be generated, and a slurry for secondary battery electrodes may be formed at a shear stress in a range of 20 to 1100 Pa. Can be applied. More specifically, at a shear rate of 1 to 500 s ⁻¹ , shear stress in an average range of 63 to 660 Pa may occur, and at a shear rate of 10 to 100 s ⁻¹ , a shear stress in an average of 111 to 224 Pa ranges. May occur. For example, a shear stress of 141.1 Pa is generated at a shear rate of 46.4 s ⁻¹ , so that the binder may be applied to the surface of the active material. On the other hand, if the shear stress is less than the minimum value of the range, the surface coating function of the active material of the binder may be weakened and the dispersion of the slurry may be lowered. If the shear stress is exceeded, the collision of the active material particles with the reactor wall, the active material The problem of damage to the active material structure occurs due to collision between or overheating the slurry.

In a particular embodiment, due to the functional group contained in the copolymer polymer of the elastic binder described above, it can be applied to the surface of the active material in the form of a polymer film by the strong bonding strength with the active material and the elongation (elastic force) of the elastic binder. In addition, the binder allows the binder to be evenly dispersed in the slurry.

Furthermore, the viscosity of the slurry for secondary battery electrodes according to the present invention is characterized in that the range of 500 to 250,000 cP at 25 ℃. The viscosity of the slurry for secondary battery electrodes may be in the range of 500 to 250,000 cP, in the range of 1,000 to 240,000 cP, in the range of 10,000 to 220,000 cP, in the range of 50,000 to 200,000 cP, or in the range of 130,000 to 180,000 cP. On the other hand, when the viscosity of the slurry is less than 500 cP, the coated electrode is weakly bound with the current collector, there is a limit to increasing the electrode thickness, and when the slurry viscosity is more than 250,000 cP, the viscosity is too high, the components in the slurry Their dispersibility may be significantly reduced.

That is, the slurry for secondary battery electrodes according to the present invention may maintain the slurry viscosity within the above-described range, it may have a suitable viscosity in the mixing process of the slurry. In addition, the binding force may be improved in the subsequent rolling process.

On the other hand, when the slurry is applied to the electrode, the polymer film film on the surface of the active material can act as a protective layer, and as the cycle progresses to prevent direct contact between the electrode and the electrolyte, deterioration due to the electrolyte is suppressed and thus lifespan A secondary battery having improved characteristics and the like can be provided.

The binder is an elastic binder and is a copolymer polymer including a hard segment and a polyol soft segment capable of hydrogen bonding in an electrode, and a modulus of elasticity of 100 MPa or less and an elongation of 50% or more of the copolymer polymer. It is characterized by including.

In the present invention, "elastic binder" refers to a polymer binder for secondary battery electrodes having a predetermined elastic modulus, and more specifically, a secondary battery including a copolymer polymer having an elastic modulus of 100 MPa or less and an elongation of 50% or more. It may mean a polymer binder for an electrode.

More specifically, the modulus of elasticity of the copolymer polymer may be in the range of 500 kPa to 100 MPa, 600 kPa to 80 MPa, 800 kPa to 60 MPa, 1 to 40 MPa, 1 to 25 MPa or 2 to 10 MPa Can be. In particular, the elastic binder for the electrode may include a copolymer polymer having the above-described elastic modulus, so that the elongation may be excellent. More specifically, the elongation of the copolymer polymer may be 50% or more, and may range from 50 to 1000% or 50 to 950%.

The modulus of elasticity and elongation can be obtained from a stress-strain curve through a tensile stress test under a condition of 5 mm / min after the binder is prepared from specimens of JIS K-6301 TYPE 1 specifications. Specifically, after filming the copolymer polymer, when the average thickness of the film is 80 to 95 ㎛, 0.3 cm horizontal and 2.7 cm vertical, the elastic modulus of the film is 500 kPa to 100 MPa, the elongation is 50 to 950% range. For example, under the above conditions, the modulus of elasticity may be about 4 MPa and the elongation may be about 920%.

In the present invention, 'modulus of elasticity' refers to the degree of strain occurring when the elastic material is stressed, and means the degree to which the material resists pressure. That is, the elastic material that is more easily deformed may have a lower modulus of elasticity.

1 is a view showing a copolymer polymer structure according to an embodiment of the present invention.

Referring to FIG. 1, the elastic polymer binder according to the present invention is a copolymer polymer including a hard segment and a soft segment having a polyol structure in the electrode.

The electrode including the copolymer polymer may be reacted with the following Formula 3 compound or electrolyte in the electrolyte to form a polycarbonate-based electrode interfacial film.

[Formula 3]

.

.

Alternatively, the electrode containing the copolymer polymer is at least selected from the group consisting of Li _x PF _y and Li _x PO _y F _z by the reaction of the compound of Formula 3 or the lithium salt in the electrolyte during electrochemical reaction An electrode interfacial film of one component is formed.

The number average molecular weight of the copolymer polymer may be 140,000 to 1,000,000 g mol ⁻¹ .

The hard segment includes an aromatic urethane and an aromatic urea bond, and the soft segment may use an aliphatic polyol compound having a weight average molecular weight of 1,000 to 3,000 g mol ⁻¹ , wherein the aliphatic polyol is polyethylene glycol, polytetramethylene ether glycol It may be at least one selected from the group consisting of polypropylene glycol, polycarbonate diol, polycaprolactone diol and ethylene-propylene glycol copolymer.

Figure 2 (a) is a view showing the molecular structure of the copolymer polymer of the elastic binder according to the invention and Figure 2 (b) shows the results of molecular functional group analysis through Fourier transform infrared spectroscopy (FT-IR). Referring to Figure 2, the polymer is a structure that can be phase-separated into soft-hard segments, a structure capable of hydrogen bonding with the electrode active material through the urea and urethane functional groups of the hard segment.

In addition, the active material may include at least one lithium metal oxide selected from the group consisting of Formula 1 and Formula 2:

[Formula 1]

LiNi _x Mn _y Co _z Al _w O ₂

In Formula 1, 0 ≦ x ≦ 1, y is 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, w is 0 ≦ w ≦ 0.15, and x + y + z + w = 1.

[Formula 2]

LiFe _x Mn _y PO ₄

In Formula 2, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and x + y = 1.

More specifically, the active material may be a layered lithium transition metal oxide (LiNi _x Mn _y Co _z Al _w O ₂ ), or olivine-based iron phosphate (LiFe _x Mn _y PO ₄ ), or the layer It may be a combination of a phase-based lithium transition metal oxide and an olivine-based iron phosphate. As one example, the lithium transition metal oxide may be LiNi _0.8 Co _0.1 Mn _0.1 O ₂ or LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , but is not limited thereto.

On the other hand, the binder may comprise 0.2 to 15% by weight based on the total weight of the active material. More specifically, the binder may be 0.2 to 15 wt%, 1.2 to 10 wt%, 1.4 to 5 wt%, 1.5 to 3 wt% or 1.6 to 3.1 wt%, or 3.0 wt%, based on the total weight of the active material Or 2.0 wt%. On the other hand, when the binder is in the weight range, it is possible to implement a secondary battery with high efficiency.

In addition, the present invention provides a secondary battery electrode, characterized in that the slurry for secondary battery electrodes is applied to the current collector. Specifically, the positive electrode of the electrode may be a slurry containing a positive electrode active material on the positive electrode current collector.

In particular, the binder applied to the surface of the electrode can protect the interface of the electrode, thereby suppressing performance deterioration and the like.

In the present invention, the cathode active material may include at least one lithium metal oxide selected from the group consisting of Formula 1 and Formula 2:

[Formula 1]

LiNi _x Mn _y Co _z Al _w O ₂

In Formula 1, 0 ≦ x ≦ 1, y is 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, w is 0 ≦ w ≦ 0.15, and x + y + z + w = 1.

[Formula 2]

LiFe _x Mn _y PO ₄

In Formula 2, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and x + y = 1.

More specifically, the active material may be a layered lithium transition metal oxide (LiNi _x Mn _y Co _z Al _w O ₂ ), or olivine-based iron phosphate (LiFe _x Mn _y PO ₄ ), or the layer It may be a combination of a phase-based lithium transition metal oxide and an olivine-based iron phosphate.

The copolymer binder may be used as the positive electrode binder.

As the cathode current collector, any one that can be used as a current collector in the art may be used. Specifically, it is preferable to use aluminum foil, foamed aluminum, foamed nickel, and the like having excellent conductivity.

The conductive material may be porous. Therefore, the conductive material may be used without limitation as long as it has porosity and conductivity, and for example, a carbon-based material having porosity may be used. As such a carbon-based material, carbon black, graphite, graphene, activated carbon, carbon fiber, carbon nanotube, or the like can be used. Moreover, organic conductive materials, such as metallic fibers, such as a metal mesh, metallic powders, such as copper, silver, nickel, and aluminum, or a polyphenylene derivative, can also be used. The conductive materials may be used alone or in combination.

The positive electrode as described above may be manufactured according to a conventional method, and specifically, the positive electrode active material layer forming slurry prepared by mixing the positive electrode active material, the conductive material, and the binder on an organic solvent is applied and dried on a current collector, Optionally, it may be manufactured by pressing the current collector in order to improve the electrode density. In this case, the organic solvent may uniformly disperse the positive electrode active material, the binder, and the conductive material, and preferably evaporates easily. Specifically, N-methyl-2-pyrrolidone, acetonitrile, methanol, ethanol, tetrahydrofuran, isopropyl alcohol, etc. can be used.

In addition, in the present invention, the negative electrode in the battery includes a negative electrode active material formed on the negative electrode current collector.

The negative electrode current collector may be specifically selected from the group consisting of copper, stainless steel, titanium, silver, palladium, nickel, alloys thereof, and combinations thereof. The stainless steel may be surface treated with carbon, nickel, titanium, or silver, and an aluminum-cadmium alloy may be used as the alloy. In addition, calcined carbon, a non-conductive polymer surface-treated with a conductive material, or a conductive polymer may be used.

As the negative active material, a material capable of reversibly intercalating or deintercalating lithium ions (Li ⁺ ), a material capable of reacting with lithium ions to form a reversibly lithium-containing compound, a lithium metal or a lithium alloy Can be used. The material capable of reversibly occluding or releasing the lithium ions (Li ⁺ ) may be, for example, crystalline carbon, amorphous carbon, lithium titanium oxide, or a mixture thereof. The material capable of reacting with lithium ions (Li ⁺ ) to form a reversibly lithium-containing compound may be, for example, tin oxide, titanium nitrate, silicon, silicon oxide, or silicon-carbon composite. The lithium alloy is, for example, lithium (Li) and sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium ( It may be an alloy of a metal selected from the group consisting of Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al) and tin (Sn).

The negative electrode may further include a binder for coupling the negative electrode active material and the conductive material and the current collector. Specifically, the binder is the same as described above for the binder of the positive electrode.

The separator is a physical separator having a function of physically separating the electrode, and can be used without particular limitation as long as it is used as a conventional separator, and in particular, it is preferable that the separator is low in resistance to electrolyte migration and has excellent electrolyte-moisture capability.

In addition, the separator enables the transport of lithium ions between the positive electrode and the negative electrode while separating or insulating the positive electrode and the negative electrode from each other. The separator may be made of a porous, non-conductive or insulating material, and the separator may be an independent member such as a film or a coating layer added to the anode and / or the cathode.

Specifically, a porous polymer film made of a polyolefin-based polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer and ethylene / methacrylate copolymer may be used. These may be used alone or in combination thereof, or a conventional porous nonwoven fabric, for example, a non-woven fabric made of high melting glass fibers, polyethylene terephthalate fibers, or the like may be used, but is not limited thereto.

In addition, the present invention provides a secondary battery comprising the secondary battery electrode and a non-aqueous electrolyte.

The non-aqueous electrolyte solution includes a compound of Formula 3 below.

[Formula 3]

.

.

The content of Chemical Formula 3 may be 0.1 to 15.0 wt% in the non-aqueous electrolyte.

In addition, the non-aqueous electrolyte contains a lithium salt, and is composed of a lithium salt and a solvent, and a non-aqueous organic solvent, an organic solid electrolyte, an inorganic solid electrolyte, and the like can be used as the solvent.

The lithium salt is a material that can be easily dissolved in a non-aqueous organic solvent, for example, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiB (Ph) ₄ , LiC ₄ BO ₈ , LiPF ₆ , _{LiCF 3 SO 3, LiCF 3 CO} 2, LiAsF 6, LiSbF 6, LiAlCl 4, LiSO 3 CH 3, LiSO 3 CF 3, LiSCN, LiC (CF 3 SO 2) 3, LiN (CF 3 SO 2) 2, LiN It may be at least one selected from the group consisting of (C ₂ F ₅ SO ₂ ) ₂ , LiN (SO ₂ F) ₂ , lithium chloroborane, lower aliphatic lithium carbonate, lithium phenyl borate, imide.

The concentration of the lithium salt is 0.1 to 6.0, depending on several factors such as the exact composition of the electrolyte mixture, the solubility of the salt, the conductivity of the dissolved salt, the charging and discharging conditions of the battery, the operating temperature and other factors known in the lithium-sulfur battery field. M, preferably 0.5M to 2.0M. If the concentration of the lithium salt is less than the above range, the conductivity of the electrolyte may be lowered, thereby degrading battery performance. If the lithium salt is more than the above range, the viscosity of the electrolyte may increase, thereby reducing the mobility of lithium ions (Li ⁺ ). It is preferable to select an appropriate concentration at.

The non-aqueous organic solvent is a substance capable of dissolving lithium salt well, preferably N-methyl-2-pyrrolidone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate , Diethyl carbonate, ethylmethyl carbonate, gamma-butylo lactone, 1,2-dimethoxy ethane, 1,2-diethoxy ethane, 1-ethoxy-2-methoxy ethane, tetraethylene glycol dimethyl ether, Tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, 4-methyl-1,3-dioxene, diethyl ether, formamide, dimethylformamide, dioxolane , Acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxy methane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate Derivatives, tetrahydrofuran derivatives, ethers, pros Acid methyl, may be used an aprotic organic solvent, e.g., ethyl, can be used in one or two or more types mixed solvent of them.

Preferably, the organic solid electrolyte is a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, poly agitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, ionic Polymers containing a dissociation group and the like can be used.

As the inorganic solid electrolyte of the present invention, Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ Nitrides, halides, sulfates, and the like of Li, such as Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS _2, and the like.

The copolymer polymer of the binder may react with the compound of Formula 3 to form a polycarbonate-based electrode interface film, the binder may be 0.2 to 15% by weight of the electrode.

Alternatively, an electrode including a copolymer polymer of a binder may include an electrode interfacial film of at least one component selected from the group consisting of Li _x PF _y and Li _x PO _y F _z by a reaction involving a compound of Formula 3 or a lithium salt. Can be formed.

Hereinafter, the present invention will be described in more detail with reference to Examples and Experimental Examples.

However, the following Examples and Experimental Examples are only illustrative of the present invention, and the content of the present invention is not limited to the following Examples and Experimental Examples.

<Example>

Example 1.

(Production of Slurry for Secondary Battery Electrode)

The copolymer polymer disclosed in FIG. 1 was prepared by inducing urethane and urea bond formation through condensation polymerization between aromatic diisocyanate, glycol, and diamine. Then, using a binder of Example 1, LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM811) as the cathode active material, carbon black (Super P) as the conductive material, and the binder of Example 1, N-methyl- as a solvent was used. A positive electrode slurry was prepared by addition to 2-pyrrolidone (NMP). On the other hand, during the mixing process was mixed at a speed of 0.1 ~ 1,000 s ^-1 , wherein the shear stress 21.1 ~ 1,071 Pa occurred.

(Electrode manufacture)

The positive electrode slurry was applied to one surface of the aluminum thin film of the positive electrode current collector, dried, and pressed to prepare a single-sided positive electrode having an active material layer having a thickness of 95 μm.

(Manufacture of secondary battery)

A secondary battery including the electrode prepared above was manufactured. At this time, the configuration of the secondary battery used is shown in Table 1 below.

Working electrode NCM811 / super P / (PVDF or Elastic binder) Counter electrode Lithium metal Electrolyte 1 M LiPF ₆ in EC / DMC (v / v = 1/1) + 10 wt.% FEC separator PE

Comparative Example 1.

An electrode was manufactured in the same manner as in Example 1, except that PVDF was used as the binder.

Experimental Example

Experimental Example 1. Evaluation of stability according to the type and composition of the binder

The stability evaluation of this electrode was performed using the secondary battery electrode manufactured in Example 1 and the comparative example 1.

At this time, the active material loading was carried out to 14 mg cm ^-2 . In the experiment, the first cycle was performed at 0.1C, and the current cycle was performed at 0.5C from the next cycle. Thus, cycle retention was calculated based on the capacity of the second and last cycle. And the result is shown in FIG.

The voltage range of the experimental results shown in Figure 3 is 2.8 ~ 4.3V, when the cut-off voltage is set to 4.5 ~ 4.7V, it was confirmed that the reduction of the cycle retention is added (not shown).

Experimental Example 2 Comparison of Slurry Properties by Binder

The viscosity and shear stress of the slurry in Example 1 and Comparative Example 1 were measured. Viscosity was measured by installing a small sample adapter and a thermostat in a viscometer (HBDV II +, Brookfield, USA) to maintain a constant 22 ° C temperature, and then measuring the shear rate with a spindle. The results are shown in Table 2 below.

Shear rate (s ^-1 )
[0.1-1,000] Viscosity (cP) Shear stress (Pa) Slurry of Example 1 1,071-211,000 21.1 to 1,071 Slurry of Comparative Example 1 521 to 122,700 12.27 ~ 521.8 * Shear stress = viscosity × shear rate
* Slurry weight ratio between electrode solids, NCM811: Carbon Black (Super P): Binder = 94: 4: 2
* Solvent type when preparing slurry = N-methyl-2-pyrrolidone (NMP)
* Slurry weight ratio of total electrode solids and solvent, total electrode solids: solvent = 1.72: 1

Referring to Table 2, it can be seen that the viscosity and shear stress of the slurry of Example 1 is superior to the slurry of Comparative Example 1. These results show that the binder of Example 1 is well dispersed during the slurry production process, which not only reduces the amount of organic solvent used, but also is advantageous in exerting a binding force between solids.

Experimental Example 3. Measurement of Elastic Modulus and Elongation of Binder

In order to measure the physical properties of the binder, the binders of Example 1 and Comparative Example 1 were prepared with specimens (0.3 cm × 2.7 cm) of JIS K-6301 TYPE 1 standard, and then the tensile velocity (Grip) in UTM (Universal esting machine) Separation Speed) Elastic modulus and elongation were measured under tension of 5 mm / min. 4 is a diagram showing a stress-strain curve of the binder according to Example 1 and Comparative Example 1. FIG.

The elastic modulus was derived from the stress-strain curve.

4, the elastic modulus and elongation of the binder of Example 1 and Comparative Example 1 can be seen. Specifically, it was found that the binder of Example 1 had excellent elastic force and high elongation. On the other hand, the binder of Comparative Example 1 had high rigidity, the elongation was very low, less than 50%, and the binder of Comparative Example 1 broke at a stress of 35 MPa or more. That is, in Comparative Example 1, the stress-strain curve was very unstable.

Experimental Example 4. Measurement of Adhesion of Electrode Section

After preparing the electrode cross-section prepared in Example 1 and Comparative Example 1 with a specimen having a length of 25 mm × 30 mm, and sequentially stacked the electrode cross-section, 3M tape, glass substrate, using a roll of 2 kg 10 Rolled twice.

The specimen was subjected to a peeling test at a speed of 25 mm / min, and the results are shown in FIG. 5.

5 is a view showing the peeling test results of the electrode cross-section according to Example 1 and Comparative Example 1.

Referring to Figure 5, it could be confirmed that the adhesive strength of Example 1 compared to Comparative Example 1. This is because the binder of Example 1 includes a hard segment capable of hydrogen bonding with the electrode active material, the conductive carbon and the current collector material, thus providing high adhesion between the materials and between the active material layer and the current collector. In addition, it is judged that the high binding force of Example 1 originates in the binder being apply | coated evenly on the surface of an active material at the time of stirring a slurry.

Experimental Example 5. Surface Analysis by Binder

The surfaces of the electrodes prepared in Example 1 and Comparative Example 1 were measured by scanning electron microscope (SEM). And this is shown in FIG.

6 is a view showing a photograph taken by SEM of the electrode surface prepared in Example 1 and Comparative Example 1. Referring to Figure 6, it can be seen that the electrode surface of Example 1 is smoother than the electrode surface of Comparative Example 1. This is due to the good interaction between the binder and the active material and the even dispersion of the binder.

Experimental Example 6. XRD Analysis According to Binder

X-ray diffraction analysis was performed on the electrodes prepared in Example 1 and Comparative Example 1 using CuKα. X-ray diffraction analysis was performed using a Rigaku RINT2200HF + diffractometer using Cu Kαradiation (1.540598 Hz).

The slurry of Example 1 and Comparative Example 1 was subjected to X-ray diffraction analysis to determine the ratio (I ₀₀₃ / I ₁₀₄ ) values of peaks representing the (003) and (104) planes before and after battery driving. The results are shown in FIG. 7 and Table 3.

I ₍₀₀₃₎ / I ₍₁₀₄₎ Comparative Example 1 before 1.11 Comparative Example 1 after 0.75 Example 1 before 1.07 Example 1 after 1.02

According to the results of Fig. 7 and Table 3, Example 1, Comparative Example 1 is decreased by the I ₀₀₃ / I ₁₀₄ value is very large after the same while driving down the I ₀₀₃ / I ₁₀₄ value is very small before and after the driving. This means that in Comparative Example 1, the cation mixing in the layered oxide structure was severe, and the layered structure was deformed into a spinel or rock salt structure. This structural change accelerates the dissolution of the transition metal into the electrolyte and side reactions at the electrode surface. In the same context, the electrode surface protection function of the binder of Example 1 suppressed this structural change, thus maintaining a high I ₀₀₃ / I ₁₀₄ value even after battery operation.

Experimental Example 7 Analysis of Electrochemical Properties According to Binder

The electrochemical characteristics of the battery according to the type of binder were evaluated. And the result is shown in FIG. 8 (a) is a graph showing the change in specific capacity of the lithium secondary battery of Example 1 and Comparative Example 1 when the charge-discharge rate is changed, Figure 8 (b) is a secondary battery electrode of Example 1 and Comparative Example 1 The results of cyclic voltammetry analysis at are performed at various scan rates.

Referring to FIG. 8 (a), it can be seen that the secondary battery of Example 1 compared to Comparative Example 1 maintains excellent electrochemical characteristics. In particular, in the case of Example 1, it was confirmed that the specific capacity of the electrode is maintained at a high C-rate condition

9 is a view showing the impedance analysis results of the secondary battery manufactured in Example 1 and Comparative Example 1. Example 1 showed a lower impedance than Comparative Example 1 while the battery was being driven. This means that the high rate characteristic is good, and is due to the decrease in the interface resistance due to the interface protection function of the binder.

10 is a graph showing capacity retention characteristics during long-term driving of the secondary batteries manufactured in Example 1 and Comparative Example 1. FIG. ((a) 25 degreeC, (b) 50 degreeC). Referring to FIG. 10, it can be seen that Example 1 has excellent life characteristics regardless of secondary battery driving temperature conditions compared to Comparative Example 1. That is, the binder means that the degradation of the electrolyte due to the interface protection function at high temperature due to thermal stability can be suppressed. In addition, it is understood that the dispersion of the conductive material is increased as the binder of Example 1 is excellent, so that conductivity inside the electrode is improved, so that the specific amount is kept high throughout the life measurement period.

Experimental Example 8. Surface Analysis of Secondary Battery Electrode According to Binder Type

(Material characteristics)

The electrode surface functional group according to the electrochemical cycle was analyzed using the lithium secondary batteries prepared in Example 1 and Comparative Example 1. And the result is shown in FIG. FIG. 11 is a graph showing the results of XPS spectroscopic analysis on the electrodes of Example 1 and Comparative Example 1 in order to grasp the components at the electrode interface before and after the electrochemical experiment ((a), (b) Comparative Example 1 and Examples) Example 1 Before the electrochemical cycle of the electrode, (c), (d) after the cycle of Comparative Example 1 and Example 1 electrode).

As a result of the electrode surface analysis, when the copolymer binder of the present invention was used, Li _x PF _y or Li _x PO _y F _z related peaks increased. Due to the active material interface protection function of the binder, deterioration caused by the electrolyte during electrochemical reaction is suppressed, and thus the tendency of LiPF _{6, which} is a lithium salt in the electrolyte, to be finally decomposed to F ^- ions decreases, thereby reducing the proportion of LiF electrode interface membrane. Due to As a result, it was confirmed that an electrode interfacial film having a main component of Li _x PF _y or Li _x PO _y F _z , which is an intermediate decomposition product of the lithium salt in the electrolyte or a reactant of the formula 3 and the lithium salt in the electrolyte, was formed.

(Surface analysis by binder)

Using the lithium secondary battery prepared in Example 1 and Comparative Example 1, the surface of the electrode according to the electrochemical cycle was analyzed by SEM (Scanning Electron Microscope). And this is shown in FIG.

12 is a view showing SEM photographs of electrode surfaces before and after an electrochemical experiment with respect to the electrodes of Example 1 and Comparative Example 1 ((a), (b) of Comparative Example 1 and Example 1 electrodes) Before the electrochemical cycle, and (c), (d) after the cycles of Comparative Example 1 and Example 1 electrodes). Referring to FIG. 12, it can be seen that the electrode surface of Example 1 was smoother before and after the cycle than the electrode surface of Comparative Example 1. This is due to the good interaction between the binder and the active material and even solid dispersion.

Claims (14)

As a slurry for secondary battery electrodes containing a binder, an active material, and a conductive material,
The binder includes a copolymer polymer including a hard segment capable of hydrogen bonding in the electrode and a soft segment having a polyol structure.
In the slurry for secondary battery electrodes, a shear stress is generated in the slurry during a mixing process at a shear rate in the range of 0.1 to 1,000 s ⁻¹ , so that a binder is coated on the surface of the active material. .
The method of claim 1,
The slurry for secondary battery electrodes is a slurry for secondary battery electrodes, characterized in that the shearing stress (shearing stress) in the range of 20 to 1,100 Pa is generated at a shear rate in the range of 0.1 to 1,000 s ^-1 .
The method of claim 1,
The slurry for secondary battery electrodes is a slurry for secondary battery electrodes, characterized in that the range of 500 to 250,000 cP.
The method of claim 1,
Modulus of elasticity of the copolymer polymer (modulus of elasticity) is 100 MPa or less, elongation is a secondary battery electrode slurry, characterized in that more than 50%.
The method of claim 1,
After filming the copolymer polymer, when the average thickness of the film is 80 to 95 μm, 0.3 cm wide and 2.7 cm long,
The elastic modulus of the film is 500 kPa to 100 MPa, the elongation is a slurry for secondary battery electrodes, characterized in that 50 to 950% range.
The method of claim 1,
The number average molecular weight of the copolymer polymer is a slurry for secondary battery electrodes, characterized in that the range of 140,000 to 1,000,000 g mol ^-1 .
The method of claim 1,
Hard segments include aromatic urethane and aromatic urea bonds,
Slurry for secondary battery electrodes, characterized in that the soft segment is an aliphatic polyol compound having a weight average molecular weight in the range of 1,000 to 3,000 g mol ^-1 .
The method of claim 1,
The aliphatic polyol is at least one member selected from the group consisting of polyethylene glycol, polytetramethylene ether glycol, polypropylene glycol, polycarbonate diol, polycaprolactone diol, and ethylene-propylene glycol copolymer.
The method of claim 1,
Slurry for a secondary battery electrode, characterized in that the active material comprises at least one lithium metal oxide or lithium metal phosphate selected from the group consisting of Formula 1 and Formula 2:

[Formula 1]
LiNi _x Mn _y Co _z Al _w O ₂
In Formula 1, 0 ≦ x ≦ 1, y is 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, w is 0 ≦ w ≦ 0.15, and x + y + z + w = 1.

[Formula 2]
LiFe _x Mn _y PO ₄
In Formula 2, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and x + y = 1.
The method of claim 1,
The binder is a slurry for secondary battery electrodes, characterized in that it comprises 0.2 to 15% by weight based on the total weight of the active material.
An electrode according to any one of claims 1 to 10, wherein the slurry for secondary battery electrodes is applied to a current collector.
A secondary battery electrode according to claim 11; And
A secondary battery comprising a non-aqueous electrolyte solution, wherein the non-aqueous electrolyte solution includes a compound of Formula 3 below:
[Formula 3]

.
The method of claim 12,
The electrode of the secondary battery is a secondary battery, characterized in that to form a polycarbonate-based electrode interfacial film by reacting with a non-aqueous electrolyte or a compound of formula (3) or a combination thereof.
The method of claim 12,
The electrode of the secondary battery reacts with a compound of Formula 3 or a lithium salt in an electrolyte or a combination thereof to form an electrode interfacial film of at least one component selected from the group consisting of Li _x PF _y and Li _x PO _y F _z . Secondary battery.

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