KR20230019794A - Binder for secondary battery, electrode composition for secondary battery and secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a binder for a secondary battery, an electrode composition for a secondary battery including same, and a secondary battery. The binder for a secondary battery according to the present invention has excellent dispersibility, adhesiveness and stability. The binder according to one embodiment of the present invention has balanced amphipathic properties and can uniformly disperse electrode slurry. The binder forms an electrode structure to form a well-organized electron/ion conduction path in a thickness direction.

Description

Binder for secondary battery, electrode composition for secondary battery comprising the same, and secondary battery

The present invention relates to a binder for a secondary battery, an electrode composition for a secondary battery including the same, and a secondary battery, and specifically relates to a binder for a secondary battery having excellent dispersibility, adhesiveness and stability, an electrode composition for a secondary battery including the same, and a secondary battery. .

As interest in environmental issues grows, demand for electric vehicles and hybrid vehicles that can replace internal combustion engine vehicles that use fossil fuels, such as gasoline vehicles and diesel vehicles, which are the main causes of air pollution, is explosively increasing. Lithium secondary batteries are used as a power source for electric vehicles and hybrid vehicles. As the demand for eco-friendly vehicles such as electric vehicles and hybrid vehicles increases, lithium secondary batteries with high capacity and high stability are required, and related research is being actively conducted. The lithium secondary battery proceeds with charging and discharging while repeating the process of inserting and deintercalating lithium ions from the positive electrode to the cathode. As the intercalation and desorption of lithium ions proceed repeatedly, the electrode active material expands and contracts. The higher the capacity of the electrode active material, the greater the degree of expansion and contraction, and in this process, the bond between the electrode active material and the conductive material becomes loose and the contact resistance between the particles increases. As a result, the ohmic resistance in the electrode composition increases, causing a problem in that battery characteristics may deteriorate.

In order to solve these problems, the role of the binder is important. The binder requires sufficient adhesive force to maintain binding force between the electrode active material, the conductive material, and the current collector. In addition, electrolyte swelling of the binder affects the volume expansion of the lithium ion battery, so low electrolyte swelling characteristics are also required. When the battery is charged/discharged, the temperature of the battery rises rapidly, and high-temperature stability is also required because it must stably serve as a binder even at high temperatures. Finally, since it should not be easily decomposed in an electrochemical reaction, electrochemical stability is also required.

Typical commercially available binders include polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), and carboxy methyl cellulose (CMC). Batteries and electrode active materials have been developed and the need for binders with better performance is increasing.

Korean Patent Publication No. 2021-0083061 discloses a binder composition for a lithium secondary battery containing N-vinyl imidazolium ionic liquid and N-vinylacetamide, comprising the binder composition Disclosed are a cathode active material composition and a lithium secondary battery including the binder composition and the cathode active material.

Korean Patent Publication No. 2021-0083061

One object of the present invention is to provide a binder for a secondary battery having excellent dispersibility, adhesiveness and stability, and an electrode composition for a secondary battery and a secondary battery including the same.

One embodiment of the present invention provides a binder for a secondary battery having a bottle brush type structure represented by Formula 1 below.

[Formula 1]

In Formula 1,

A is a substituted or unsubstituted cyclic compound, or a single bond,

R ₁ is a substituted or unsubstituted C ₁ to C ₂₀ alkylene group, wherein one or more -CH ₂ - groups are -O-, -CO-, -CO-O-, -O-CO-, -S- CS-, -CS-S-, -S-CS-S-, a substituted or unsubstituted C ₄ to C ₁₂ carbon ring, or a substituted or unsubstituted C ₃ to C ₁₂ heterocyclic ring,

Wherein R ₂ is a substituted or unsubstituted C ₁ to C ₂₀ alkyl, a substituted or unsubstituted C ₄ to C ₁₂ carbon ring, a substituted or unsubstituted C ₃ to C ₁₂ heterocyclic ring, or a haloalkyl , wherein one or more -CH ₂ -groups are replaced with -O-, -CO-, -CO-O-, -O-CO-, -S-CS-, -CS-S-, or -CS-S- can be,

B and D are each independently C ₂ to C ₁₀ alkyl acrylate, C ₂ to C ₁₀ alkyl methacrylate, or C ₁ to C ₁₀ acrylic acid,

k is an integer from 1 to 1,000, and n is an integer from 1 to 100 (except for Compounds 1 to 3 below).

Another embodiment of the present invention is a binder of a bottle brush type structure according to one embodiment of the present invention; And it provides an electrode composition for a secondary battery comprising an electrode active material.

Another embodiment of the present invention is a cathode comprising a binder according to any one of claims 1 to 5; an anode disposed opposite to the cathode; and a separator disposed between the cathode and the anode.

The bottle brush type copolymer binder according to an embodiment of the present invention may be compatible with a commercial cathode manufacturing process based on an NMP solvent and may have excellent practicality. In particular, a manufacturing process is possible with an electrode active material rich in Ni, which is sensitive to moisture, such as NCM811.

The binder according to one embodiment of the present invention has a balanced amphiphilicity to uniformly disperse the electrode slurry, and the electrode structure to form a well-organized electron / ion conduction path in the thickness direction due to its chemical function and structural uniqueness. formed, can provide strong adhesion with the current collector even in a state of being immersed in the electrolyte, and can form chelation of heavy metal ions dissolved in the electrode active material.

In addition, stable cycling performance can be obtained even with a very low binder content, and high mass loading is possible. This performance is an effect that is difficult to achieve with previously reported cathode binders and commercial PVdF binders.

1 is a schematic diagram schematically illustrating a binder according to an embodiment of the present invention.
2 is a diagram schematically showing the effect of a binder according to an embodiment of the present invention.
3 is a GPC graph of a bottle brush type copolymer synthesized according to an embodiment of the present invention.
4 is a linear sweep voltammetry (LSV) profile of a BBP film and a PVdF film.
5 is a test result of adhesion between a BBP film and a current collector according to the side chain length of a bottle brush type copolymer.
6 is an electrolyte swelling test result of a BBP film.
7 is a comparison result of the characteristics of a BBP film and a PVdF film having a side chain length of 4K.
8 is a UV-vis measurement result of a solution containing a BBP binder and a solution containing a PVdF binder.
9 is a micro-computed tomography (CT) analysis result of BBP slurry and PVdF slurry.
10 and 11 are SEM images of cross-sections and surfaces of a BBP cathode and a PVdF cathode.
12(A) shows surface electrical resistance measurement results of the BBP cathode and PVdF cathode, and FIG. 12(B) shows contact resistance measurement results between the BBP cathode and PVdF cathode and Li metal after the peel test.
13 is a diagram schematically illustrating photographs of a BBP cathode and a PVdF cathode and contact resistance between them and Li metal after a peel test.
14 is a Galvanostatic Intermittent Titration Technique (GITT) analysis result of a BBP cathode and a PVdF cathode.
15 is an initial charge/discharge profile of a BBP cathode and a PVdF cathode.
16(A) and 16(B) show the results of measuring the discharge rate capacity and cycling performance of the BBP cathode and the PVdF cathode.
17 is a result of measuring the amount of metal Ni, Co, and Mn deposited on the Li metal anode.
18 is a SEM image of the surface of a Li metal anode.
19 is a SEM image of NCM811 particles in a BBP cathode and a PVdF cathode.
20 is an X-ray photoelectron spectroscopy (XPS) F1s spectrum of NCM811 particles.
21 is a TEM image having a Fourier transform pattern of NCM811 particles.
22 is an ex-situ XRD pattern of NCM811 particles of BBP cathode and PVdF cathode before and after cycling tests.
23 is a differential scanning calorimeter (DSC) examination result showing the interfacial exothermic reaction of the delithiated NCM811 cathode.
24 is a photograph of a BBP cathode and a PVdF cathode having a binder content of 0.5 wt%.
24 is a photograph of a BBP cathode and a PVdF cathode having a binder content of 0.5 wt%. 25 is a SEM image of the surface and cross section of a BBP cathode.
26 shows the cross-sectional shape of the BBP cathode according to the thickness (ie, areal-mass-loadings).
27 is a photograph of a PVdF cathode having areal-mass-loadings of 23 mg cm ⁻² (85 μm).
28 is a charge/discharge profile of a BBP cathode.
29 and 30 are measurement results of cycling performance of the BBP cathode.

Hereinafter, embodiments and examples of the present invention will be described in detail so that those skilled in the art can easily practice the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments and examples set forth herein.

Since the present invention may have various changes and various forms, specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific form disclosed, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms used in this application are only used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as "comprise" or "have" are intended to designate that there is a feature, step, operation, component, part, or combination thereof described in the specification, but one or more other features or steps However, it should be understood that it does not preclude the possibility of existence or addition of operations, components, parts, or combinations thereof.

In addition, unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in the present application, they should not be interpreted in an ideal or excessively formal meaning. don't

The present invention relates to a secondary battery binder, a secondary battery electrode composition including the same, and a secondary battery.

A binder for a secondary battery according to an embodiment of the present invention may be understood as a bottle brush copolymer having a back bone and a side chain connected to the back bone and disposed in an outward direction. . In the specification of the present invention, the secondary battery binder may also be referred to as a 'binder' or a 'bottle brush type copolymer'. In addition, the binder may be understood as a binder for manufacturing a secondary battery electrode as a binder used for manufacturing an electrode of a secondary battery.

1 is a schematic diagram schematically illustrating a binder for a secondary battery according to an embodiment of the present invention.

Referring to FIG. 1, a binder for a secondary battery according to an embodiment of the present invention is a copolymer having a bottle brush structure as a whole, and a plurality of side chains connected to the back bone and the main chain and disposed toward the outside. has a side chain.

According to one embodiment of the present invention, the bottle brush type copolymer is a polymerized unit, and a portion forming a main chain among the units may be understood as a core portion and a portion forming a side chain may be understood as a shell portion.

According to one embodiment of the present invention, the main chain may have hydrophobicity and the side chain may have a hydrophilic functional group.

According to one embodiment of the present invention, the bottle brush type copolymer may be represented by Formula 1 below.

[Formula 1]

In Formula 1,

A is a substituted or unsubstituted cyclic compound or a single bond,

R ₁ is a substituted or unsubstituted C ₁ to C ₂₀ alkylene group, wherein one or more -CH ₂ - groups are -O-, -CO-, -CO-O-, -O-CO-, -S- CS-, -CS-S-, -S-CS-S-, a substituted or unsubstituted C ₄ to C ₁₂ carbon ring, or a substituted or unsubstituted C ₃ to C ₁₂ heterocyclic ring,

Wherein R ₂ is a substituted or unsubstituted C ₁ to C ₂₀ alkyl, a substituted or unsubstituted C ₄ to C ₁₂ carbon ring, a substituted or unsubstituted C ₃ to C ₁₂ heterocycle, or a haloalkyl; where one or more -CH ₂ -groups are replaced by -O-, -CO-, -CO-O-, -O-CO-, -S-CS-, -CS-S-, or -S-CS-S- can be,

B and D are each independently C ₂ to C ₁₀ alkyl acrylate, C ₂ to C ₁₀ alkyl methacrylate, or C ₁ to C ₁₀ acrylic acid,

k is an integer from 1 to 1,000, and n is an integer from 1 to 100.

However, in Formula 1, the following compounds 1 to 3 are excluded.

According to one embodiment of the present invention, the bottle brush type copolymer may be represented by the following Chemical Formula 1-1. This can be understood as the case where A in Formula 1 is a single bond.

[Formula 1-1]

In Formula 1-1,

R ₃ is hydrogen, deuterium, hydroxy, substituted or unsubstituted C ₁ to C ₂₀ alkyl, amine, substituted or unsubstituted C ₄ to C ₁₂ carbon ring, substituted or unsubstituted C ₃ to C ₁₂ a heterocyclic ring, or a halogen;

R ₁ , R ₂ , B and D, k, n are as defined in Formula 1 above.

Also, according to one embodiment of the present invention, A in Formula 1 may be a substituted or unsubstituted cyclic compound. The cyclic compound is not limited thereto, and may include a pentagonal ring or a hexagonal ring.

Also, according to one embodiment of the present invention, A in Chemical Formula 1 may be formed by ring opening of a cyclic compound.

Specifically, A in Formula 1 may be formed by ROMP (Ring Opening Metathesis Polymerization) of a substituted or unsubstituted cycloalkene. The cyclic alkene is not particularly limited as long as it is a compound capable of ROMP (Ring Opening Metathesis Polymerization), and may be, for example, any one of the following chemical formulas.

In the above formula,

R is halogen, hydroxy, carboxy, amine or alkyl;

q is 0 or an integer from 1 to 6;

는 R₁과 연결되는 것을 의미한다. In addition, the dotted lines in Formulas (2) and (8) mean a substituted or unsubstituted carbon ring or hetero ring. Although not shown above, chemical formulas (3) to (6) may also have carbon rings or heterocycles represented by dotted lines, as in formulas (2) and (8). In addition, the cyclic alkene may include one or more double bonds. also

means being connected with R ₁ .

When the cycloalkene has a substituent R or a ring represented by a dotted line in Formulas (2) and (8), ROMP can be performed more effectively due to steric hinderance.

Although not limited thereto, Formula (2) or Formula (8) may include the following Formula.

Part A of Chemical Formula 1 by ROMP (Ring Opening Metathesis Polymerization) of the cyclic alkene may be represented by the following reaction scheme. In the following reaction scheme, the substituent R of part A and the ring indicated by the dotted line in the above formulas (2) and (8) are omitted.

According to one embodiment of the present invention, R ₁ is a substituted or unsubstituted C ₁ to C ₂₀ alkylene, wherein one or more -CH ₂ - groups are -O-, -CO-, -CO-O-, -O-CO-, -S-CS-, -CS-S-, -S-CS-S-, substituted or unsubstituted C ₄ to C ₁₂ carbon ring, substituted or unsubstituted C ₃ to C ₁₂ It can be replaced by a heterocycle of

Specifically, R ₁ is -CH ₂ -, -CO-O-, -O-CO-, phenyl, 2,2,6,6-tetramethylpiperidine-N-oxyl(2,2,6,6 -tetramethylpiperidine) -N-oxyl, TEMPO) and the like.

In addition, the substituted or unsubstituted C ₁ to C ₂₀ alkylene may have a substituent of -CH ₃ or -CN.

In addition, R ₂ is a substituted or unsubstituted C ₁ to C ₂₀ alkyl, a substituted or unsubstituted C ₄ to C ₁₂ carbon ring, a substituted or unsubstituted C ₃ to C ₁₂ heterocycle, or a haloalkyl , wherein one or more -CH ₂ - groups may be replaced by -O-, -CO-, -CO-O-, or -O-CO-. Specifically, R ₂ may be phenyl, F, Br or the like.

The R ₁ and R ₂ may be variously selected from the viewpoint of easy synthesis of the bottle brush type copolymer as a linking group or an end group.

According to one embodiment of the present invention, the main chain and the linking group including R ₁ and/or R ₂ and the terminal group may be bonded through radical polymerization, and accordingly, R ₁ and R ₂ may be appropriately selected.

B and D may each independently be C ₂ to C ₁₀ alkyl acrylate, C ₂ to C ₁₀ alkyl methacrylate, or C ₁ to C ₁₀ acrylic acid.

wherein k is an integer from 1 to 1,000, and n is an integer from 1 to 100. Outside of the above range, it may be difficult to form a bottle brush type structure.

According to one embodiment of the present invention, the B and / or D may be acrylic acid (-CO-OH). The polyacrylic acid block can improve the dispersibility of the electrode slurry and form a chelate with metal ions.

According to one embodiment of the present invention, B and D form side chains of the bottle brush type copolymer, and may be bonded to the main chain and arranged toward the outside in a brush shape. Gaps may be formed between the side chains and may have fluidity. The fluidity can be controlled through a change in the chemical structure of the shell part, and thus various physical properties can be realized.

The bottle brush type copolymer according to an embodiment of the present invention may be a compound represented by any one of Chemical Formulas 2-1 to 2-8.

[Formula 2-1]

[Formula 2-2]

[Formula 2-3]

[Formula 2-4]

[Formula 2-5]

[Formula 2-6]

[Formula 2-7]

[Formula 2-8]

The molecular weight of the bottle brush copolymer according to an embodiment of the present invention may be 10 to 10,000K Da, specifically 10 to 7,000K Da, 100 to 7,000K Da, 100 to 4,000K Da, 100 to 1,000K Da, 100 to 400 K Da. If the molecular weight of the bottle brush type copolymer is less than 10K Da, there is a concern that sufficient adhesive strength may not be realized, and if it exceeds 10,000K Da, the property of aggregation with each other increases and dispersibility may be reduced.

The manufacturing method of the binder according to an embodiment of the present invention is not particularly limited, and may be synthesized by a method commonly used in the art. It is not limited thereto, but, for example, Grafting-From , Grafting-Through, or Grafting-To may be synthesized. Grafting-From is a method of synthesizing the main chain first and then polymerizing the side chain, and Grafting-Through is a method of synthesizing a large monomer first, then ROMP (ring opening metathesis polymerization). As a method of combining chains, Grafting-To is a method of obtaining high grafting density while overcoming steric interactions.

According to one embodiment of the present invention, a side chain is first synthesized through ATRP (Atom Transfer Radical Polymerization), and a macromonomer can be synthesized by combining the side chain and a cyclic alkene compound through a radical coupling reaction. . Then, a bottle-type copolymer can be synthesized by opening the ring of the cyclic alkene through ROMP to synthesize the main chain.

According to one embodiment of the present invention, the degree of polymerization of the main chain may be 80 to 200.

Another embodiment of the present invention relates to an electrode composition for a secondary battery including the binder represented by Chemical Formula 1 and an electrode active material. The electrode composition may further include a conductive material.

The binder is a bottle brush type copolymer according to an embodiment of the present invention, and specific characteristics are as described above.

According to one embodiment of the present invention, the side chain length of the bottle brush type copolymer (binder) may be 0.1 to 50 K Da. It is not limited thereto, but may be specifically 0.1 to 30K, 1 to 20K, 1 to 10K, 1 to 7K, or 1 to 5K Da.

Since the binder according to one embodiment of the present invention forms a hydrogen bond with the current collector and the hydrophilic group of the side chain, it is possible to improve the adhesion between the electrode active layer and the current collector.

If the length of the side chain is less than 0.1 k Da, adhesive strength may not be sufficient. In addition, when the side chain length exceeds 50 kDa, there is a possibility of expansion by the electrolyte.

Electrolyte expansion of the binder should be minimized because it weakens the adhesion during battery operation and dries the electrolyte that should exist in the electrode, resulting in structural destruction of the electrode and loss of electrochemical performance.

According to one embodiment of the present invention, both the adhesion to the current collector and the effect of reducing swelling due to the electrolyte can be obtained by adjusting the length of the side chain of the binder.

In addition, the binder according to one embodiment of the present invention enables uniform dispersion of the electrode slurry. The dispersion state of the electrode slurry plays an important role in constructing a uniform electron/ion network in the final electrode.

2 is a diagram schematically showing the effect of a binder according to an embodiment of the present invention. Referring to FIG. 2, the binder (BBP) according to an embodiment of the present invention provides a better dispersion state of the electrode slurry, strong adhesion to the current collector, reduced swelling of the electrolyte, and chelation of transition metal ions. They can form well-organized electron/ion networks. Accordingly, electrochemical performance of the cell may be improved.

The binder according to one embodiment of the present invention is a three-dimensional bottle brush type copolymer composed of densely grafted side chains attached to a polymer backbone. These bottle-type copolymers have lower hydrodynamic volume (lower radius of gyration) and viscosity compared to linear polymers of the same molecular weight due to the unique structure of densely grafted side chains that prevent chain entanglement. Accordingly, the binder according to one embodiment of the present invention is advantageous in maintaining its original shape, unlike linear polymers that are entangled with the slurry (matrix). In addition, the hydrophilic side chain of the binder has affinity with electrode active material particles, and the hydrophobic backbone provides a steric hindrance to aggregation of the particle mixture, thereby preventing aggregation of electrode components in the slurry.

Also, the binder according to an embodiment of the present invention may chelate metal ions. In order to use a high-capacity/high-voltage cathode material such as NCM811, it is necessary to prevent interfacial side reactions between transition metal ions dissolved in the electrolyte and deposition of transition metal ions on the anode electrode.

The binder according to one embodiment of the present invention has excellent ability to chelate metal ions and capture performance of metal ions, and thus may be suitable as a binder for a high-capacity/high-voltage cathode material.

According to one embodiment of the present invention, the amount of the binder may be 0.1 to 20 parts by weight. Specifically, 0.1 to 15 parts by weight and 1 to 10 parts by weight may be used. If the content of the binder is less than 0.1, there is a risk of detachment, and if it exceeds 20 parts by weight, there is a risk of loss of electrochemical performance by acting as a resistance layer. The binder according to one embodiment of the present invention can implement excellent electrode characteristics with a small amount of the binder due to strong adhesion and excellent slurry dispersion ability.

According to one embodiment of the present invention, all electrode active materials available in the art may be used as the electrode active material. It is not limited thereto, but examples thereof may include lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium manganese oxide.

The electrode active material may be, for example, Li _a A _1-b B _b D ₂ (0.90 ≤ a ≤ 1.8, and 0 ≤ b ≤ 0.5). In the above formula, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D may be O, F, S, P, or combinations thereof.

The content of the electrode active material may be used as 20 to 99 parts by weight, specifically 30 to 98 parts by weight, 50 to 98 parts by weight, or 70 to 98 parts by weight. If the content is less than 20 parts by weight, energy of the secondary battery may be lost, and if it exceeds 99 parts by weight, electrode manufacturing may be difficult or electrochemical performance may be lost.

According to one embodiment of the present invention, the solvent is not particularly limited, and for example, N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), acetone, water, mixtures thereof, and the like may be used. The amount of the solvent may be 20 to 99 parts by weight based on 100 parts by weight of the electrode active material. Formation of the electrode slurry may be facilitated within the range of the solvent content.

According to one embodiment of the present invention, the conductive material is not limited thereto, but for example, a carbon-based conductive material such as carbon black, carbon fiber, carbon nanotube, or graphite may be used. The carbon black may be, for example, one selected from the group consisting of acetylene black, ketjen black, super P, channel black, furnace black, lamp black, and thermal black. The graphite may be natural graphite or artificial graphite.

The content of the conductive material may be used in an amount of 0.1 to 20 parts by weight. Specifically, 0.1 to 15 parts by weight, 0.1 to 10 parts by weight, or 1 to 10 parts by weight may be used. If the content of the conductive material is less than 0.1 parts by weight, electrochemical performance may be lost due to lack of electronic conductivity, and if it exceeds 20 parts by weight, energy of the secondary battery may be lost.

Thermal stability of an electrode made of the electrode composition according to an embodiment of the present invention may be secured. Practical use is possible only when the thermal stability of the electrode active material is secured along with the electrochemical performance. It is known that when a secondary battery is exposed to high-temperature conditions, oxygen gas is released from the delithiated electrode active material, and interfacial side reactions (including exothermic reactions) between the surface of the electrode active material and the electrolyte may be accelerated. The binder according to one embodiment of the present invention can effectively suppress oxygen release and interfacial exothermic reaction of an electrode active material having thermal instability.

In addition, the electrode composition according to an embodiment of the present invention can manufacture a high-mass-loading cathode by using a binder. Electrodes with high areal-mass-loadings can be fabricated. Although not limited thereto, for example, an electrode having areal-mass-loadings of 15 to 30 mg cm ⁻² may be manufactured.

In addition, an electrode made of the electrode composition according to an embodiment of the present invention may have high initial efficiency and excellent lifespan characteristics.

Another embodiment of the present invention is a cathode including a binder represented by Formula 1; an anode disposed opposite to the cathode; and a separator disposed between the cathode and the anode.

The binder is a bottle brush type copolymer according to an embodiment of the present invention, and specific characteristics are as described above. In addition, the cathode may be made of the electrode composition described above.

The cathode, anode, and separator may be accommodated in a battery case by being wound or folded. An electrolyte may be injected into the battery case and sealed with a cap assembly to complete a lithium secondary battery. The battery case may be cylindrical, prismatic, or thin film.

The separator may use an insulating thin film having high ion permeability and mechanical strength.

The pore diameter of the separator is not limited thereto, but may be, for example, 0.01 to 10 μm and 5 to 20 μm thick. Such a separator is not limited thereto, but includes, for example, olefin-based polymers such as polypropylene; A sheet or non-woven fabric made of glass fiber or polyethylene may be used. When a solid polymer electrolyte is used as the electrolyte, the solid polymer electrolyte may also serve as a separator.

The electrolyte solution may include an electrolyte salt and a non-aqueous electrolyte.

Examples of the electrolyte salt include, but are not limited to, LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ , LiSCN, LiBr, LiI, Li ₂ SO ₄ , Li ₂ B ₁₀ Cl ₁₀ , NaClO ₄ , NaI, NaSCN, An inorganic ion salt containing one of lithium (Li), sodium (Na), or potassium (K) such as NaBr, KClO ₄ , or KSCN may be used.

Further, as an electrolyte salt, for example, LiCF ₃ SO ₃ , LiN(CF ₃ SO ₂ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC(CF ₃ SO ₂ ) ₃ , LiC(C ₂ F ₅ SO ₂ ) ₃ , (CH ₃ ) ₄ NBF ₄ , (CH ₃ ) ₄ NBr, (C ₂ H ₅ ) ₄ NClO ₄ , (C ₂ H ₅ ) ₄ NI, (C ₃ H ₇ ) ₄ NBr, (nC ₄ H ₉ ) ₄ NClO ₄ , (nC ₄ H ₉ ) ₄ NI, (C ₂ H ₅ ) ₄ N-maleate, (C ₂ H ₅ ) ₄ N-benzoate, (C ₂ H ₅ ) ₄ N-phthalate, lithium stearyl sulfate, lithium octyl sulfate, lithium dodecylbenzenesulfonate Organic ionic salts such as (lithium dodecylbenzene sulphonate) can also be used. It is also possible to use the said electrolyte salt individually or in mixture of 2 or more types. The concentration of the electrolyte salt may be any concentration applicable to a general lithium secondary battery, and is not particularly limited. For example, the concentration of the electrolyte salt may be 0.5 mol/L to 2.0 mol/L.

The non-aqueous electrolyte is not limited thereto, but, for example, propylene carbonate (propylene carbonate), ethylene carbonate (ethylene carbonate), butylene carbonate (butylene carbonate), chloroethylene carbonate (chloroethylene carbonate) or vinylene carbonate (vinylene carbonate) ), cyclic esters such as γ-butyrolactone or γ-valerolactone, dimethyl carbonate, diethyl carbonate or ethyl Chain carbonates such as methyl carbonate, chain esters such as methyl formate, methyl acetate or methyl butyrate, tetrahydrofuran or derivatives thereof , 1,3-dioxane, 1,4-dioxane, 1,2-dimethoxyethane, 1,4-dibutoxy Ethers such as 1,4-dibutoxyethane or methyldiglyme, nitriles such as acetonitrile or benzonitrile, dioxolane or derivatives thereof , Ethylene sulfide, sulfolane, sultone or their derivatives may be used alone or in combination of two or more thereof.

Hereinafter, the present invention will be described in more detail through examples according to an embodiment of the present invention, but these examples do not limit the scope of the present invention.

[Example]

Synthesis Example 1: PNB-g-PAA

A bottle-type copolymer (BBP, PNB-g-PAA) was synthesized in the following steps.

[Scheme 1]

1) Synthesis of norbornene carboxylic acid imide

cis-5-norbornene-exo-2,3-dicarboxylic anhydride (1.0 eq., 10 g, 60.9 mmol) with 6-aminohexanoic acid (6-aminohexanoic acid) (1.0 eq., 8 g, 60.9 mmol), triethylamine (0.1 eq., 0.062 g, 0.609 mmol) and toluene (100 mL) were added to a round bottom with stir bar and reflux condenser. Mixed in a flask (250 mL). The mixture was heated at 110° C. and refluxed overnight, cooled to room temperature, and toluene was removed with a rotary evaporator under reduced pressure. The remaining product was redissolved in dichloromethane, washed with water (x3), washed with brine (x3), and the organic layer was dried over magnesium sulfate. The solvent was removed in vacuo to give a white or off-white solid norbornene carboxylic acid imide (95% yield).

¹ H NMR (500 MHz, CDCl3) δ (ppm) 6.22 (t, J = 1.8 Hz, 2H), 3.43 - 3.38 (m, 2H), 3.21 (p, J = 1.7 Hz, 2H), 2.61 (d, J = 1.4 Hz, 2H), 2.28 (t, J = 7.4 Hz, 2H), 1.59 (p, J = 7.5 Hz, 2H), 1.51 (ddt, J = 8.9, 7.5, 3.7 Hz, 2H), 1.45 ( dp, J = 9.9, 1.6 Hz, 1H), 1.32 - 1.25 (m, 2H), 1.15 (dd, J = 9.7, 1.6 Hz, 1H).

2) Synthesis of exo -norbornenyl-functionalized nitroxide radical

In a round bottom flask, exo-norbornene carboxylic acid imide (1.0 eq., 5 g, 18 mmol), 4-hydroxy Tempo (1.1 eq., 3.45 g, 20.0 mmol), N- (3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) (1.2 eq., 4.14 g, 21.5 mmol) and 4-dimethylaminopyridine (DMAP) (0.2 eq., 0.43 g, 3.52 mmol) were added, then 50 ml dry DCM was added. The mixture was deoxygenated by purging with argon for 30 min and overnight at room temperature. The reaction mixture was washed with water (x3), brine (x3) and the organic layer was dried over magnesium sulfate. The organic layer was concentrated using a rotary evaporator under reduced pressure, and the remaining residue was purified by silica gel chromatography (ethyl acetate/hexane, 2:1 v/v) to obtain a reddish-orange solid product (yield: 80%).

¹ H NMR (500 MHz, CDCl3) δ 6.18 (s, 2H), 4.99 - 4.91 (m, 1H), 3.39 - 3.33 (m, 2H), 3.17 (s, 2H), 2.57 (s, 2H), 2.16 (t, J = 7.5 Hz, 2H), 1.88 - 1.77 (m, 2H), 1.59 - 1.39 (m, 7H), 1.25 - 1.19 (m, 2H), 1.16 (s, 6H), 1.13 (s, 6H) ), 1.10 (s, 1H).

1H NMR (500 MHz, CDCl3) δ (ppm) 6.49 (s, 2H), 4.32 (q, J = 6.8 Hz, 1H), 3.68 (s, 2H), 3.48 (s, 2H), 2.88 (s, 2H) ), 2.61 - 1.37 (m, 16H).

[Scheme 2]

3) side chain polymerization and ATRP synthesis

PtBA-Br.

Polymerization of PtBA was performed under normal Cu(0) mediated ATRP conditions. Initiator methyl 2-bromopropionate, CuBr ₂ , and Me ₆ Tren were mixed in a 100 mL Schlenk tube in a ratio of [I] : [CuBr ₂ ] : [Me ₆ Tren] = 1 : 0.05 : 0.1. and tert-butyl acrylate (tBA) monomer was added along with acetone solvent. The solution was degassed by 3 freeze-pump-thaw cycles. During the last cycle, the Schlenk tube was filled with argon and a stir bar with a pre-activated copper wire (5 cm) was quickly added to the freezing reaction.

The Schlenk tube was filled with argon, sealed and emptied three times. Polymerization was initiated by placing the flask in a pre-set oil bath at 50° C. to reach >90% conversion. The polymerization was quenched by immersing the flask in liquid nitrogen and exposing the reaction mixture to air. The mixture was diluted with DCM and filtered through a neutral alumina column to remove the copper catalyst. The diluted mixture was concentrated via a rotary evaporator under reduced pressure. Finally, the product was precipitated into cold methanol/water (5:5 v/v) and dried in vacuo.

NB-PtBA-NRC.

PtBA-Br, exo -norbornenyl-functionalized nitroxide radical, CuBr, Me ₆ in a ratio of [PtBA]:[NB-TEMPO]:[CuBr2]:[Me6Tren] = 1:1.0:1.1:1.1 in a 50 mL round-bottom flask. Tren and toluene/DMSO (5:5 v/v) were charged. The solution was deoxygenated by purging with argon for 30 minutes and carried out in an argon-filled glove box for 2 hours at room temperature. The mixture was diluted with DCM and filtered through a neutral alumina column to remove the copper catalyst. The diluted mixture was concentrated via a rotary evaporator under reduced pressure. The remaining residue was diluted with acetone, transferred to a dialysis tube, and stirred with acetone to remove unreacted NB-TEMPO. After dialysis, the solvent was removed and dried in vacuo.

NB-PtBA (1K)

¹ H NMR (500 MHz, CDCl3) δ (ppm) 6.27 - 6.25 (m, 2H), 4.94 (dq, J = 10.9, 5.6, 4.2 Hz, 1H), 3.63 (d, J = 3.0 Hz, 3H), 3.43 (t, J = 7.4 Hz, 2H), 3.25 (t, J = 2.0 Hz, 2H), 2.65 (s, 2H), 2.27 - 2.16 (m, 9H), 1.61 - 1.07 (m, 147H).

NB-PtBA (4K)

¹ H NMR (500 MHz, CDCl3) δ (ppm) 6.31 (d, J = 2.1 Hz, 2H), 3.67 (d, J = 2.3 Hz, 3H), 3.47 (t, J = 7.5 Hz, 2H), 3.29 (s, 2H), 2.69 (s, 2H), 2.25 (qd, J = 16.9, 7.3 Hz, 26H), 1.46 (s, 240H).

NB-PtBA (7K)

^1H NMR (500 MHz, CHLOROFORM- D ) δ 6.27 (d, J = 2.0 Hz, 2H), 3.64 (d, J = 2.2 Hz, 3H), 3.46 - 3.42 (m, 2H), 3.26 (s, 2H) ), 2.94 (s, 1H), 2.87 (s, 1H), 2.32 - 2.14 (m, 76H), 1.42 (s, 710H).

[Scheme 3]

4) Synthesis of PNB- g -P t BA through ROMP

NB-PtBA was added to glass vial A and anhydrous DCM was added to a glove box at room temperature ([NB-PtBA] = 0.05 M). G3 was added to separate vial B and dissolved in DCM ([G3] = 0.005 M). ROMP of NB-PtBA was initiated by injecting the G3 solution into vial A using a gas-tight syringe ([NB-PtBA]/[G3] = target DP). After 1 hour, vial A was removed from the glove box and the polymerization was quenched with an excess of ethyl vinyl ether. The PNB-g-PtBA bottle-type polymer was precipitated with cold methanol and dried in vacuo.

[Scheme 4]

5) Hydrolysis of PNB- g -P t BA

PNB-g-PAA was dissolved in DCM in a glass vial equipped with a stir bar. An excess of trifluoroacetic acid (TFA) was added to the solution and the mixture was stirred at ambient temperature. The hydrolysis reaction of the tert-butyl group on PtBA proceeded for 24 hours. The reaction mixture was filtered through filter paper, washed with excess DCM and dried in vacuo. The resulting polymer PNB-g-PAA was obtained as a white or slightly yellow solid. An electrode was prepared using this as a binder (BBP binder).

Synthesis Example 2: PVDF- g -PAA

A bottle-type copolymer (BBP, PVDF-g-PAA) was synthesized in the following steps.

[reaction formula]

1) Synthesis of PVDF- g -P t BA through ATRP

The ATRP polymerization method was used to graft the P t BA side chain from the fluorine group of the PVDF main chain. PVDF, tBA , CuBr, and CuBr ₂ were dissolved in a DMF solvent at a molar ratio of 1:70:0.5:0.05 and subjected to argon purging. was added and stirred for 12 hours. After the polymerization was completed, the catalyst and ligand were removed through an alumina column. After the purification process, it was dried under reduced pressure in an oven at 50 °C for 24 hours.

2) Synthesis of PVDF- g -PAA through hydrolysis of PVDF- g -P t BA

PVDF- g -P t BA was dissolved in NMP in a glass vial equipped with a stir bar. An excess of trifluoroacetic acid (TFA) was added to the solution and the mixture was stirred at ambient temperature. The hydrolysis reaction of the tert-butyl group on P t BA proceeded for 24 hours. The reaction mixture was filtered through filter paper, washed with excess DCM and dried in vacuo. The resulting polymer PVDF- g -PAA was obtained as a solid.

Synthesis Example 3: PHEMA-BiBB- g -PAA

A bottle-type copolymer (BBP, PHEMA-BiBB- g -PAA) was synthesized in the following steps.

[Scheme 1]

1) Poly(2-hydroxyethyl methacrylate) through free radical polymerization

(PHEMA) synthesis

Free radical polymerization was used to synthesize the PHEMA backbone. HEMA and AIBN were dissolved in toluene solvent at a 50:1 molar ratio and argon purged. After confirming that they were sufficiently degassed, they were placed in a 90°C oil bath and stirred for 1 hour. After the polymerization was completed, it was purified and dried under reduced pressure in an oven at 50 °C for 24 hours.

2) Synthesis of PHEMA-BiBB main chain including ATRP initiator

To prepare PHEMA-BiBB main chain with ATRP initiator, PHEMA hydroxyl group and triethyl amine were dissolved in DCM solvent at a molar ratio of 1:1.5, and then 2-Bromo-2-methylpropionyl bromide was added at a molar ratio of 1.2 at 0 °C. After the reaction was stirred at room temperature for one day, it was washed three times with distilled water. After removing the DCM solvent with a rotary evaporator, the mixture was precipitated twice in n -hexane solvent, purified, and dried under reduced pressure in an oven at 50 °C for 24 hours.

[Scheme 2]

1) Synthesis of PHEMA-BiBB- g -P t BA through ATRP

PHEMA-BiBB- g -P t BA was synthesized through ATRP using the BiBB initiator included in the PHEMA main chain. PHEMA-BiBB and tBA, CuBr, CuBr ₂ were dissolved in a toluene solvent at a molar ratio of 1:70:0.5:0.05 and argon purged. After confirming that they were sufficiently degassed, the ligand PMDETA was added at a molar ratio of 0.1 and 70°C oil It was put in a bath and stirred for 6 hours. After the polymerization was completed, the catalyst and ligand were removed through an alumina column. After the purification process, it was dried under reduced pressure in an oven at 50 °C for 24 hours.

2) Synthesis of PHEMA-BiBB- g -PAA through hydrolysis of PHEMA-BiBB- g -P t BA

PHEMA-BiBB- g -P t BA was dissolved in DCM in a glass vial equipped with a stir bar. An excess of trifluoroacetic acid (TFA) was added to the solution and the mixture was stirred at ambient temperature. The hydrolysis reaction of the tert-butyl group on P t BA proceeded for 24 hours. The reaction mixture was filtered through filter paper, washed with excess DCM and dried in vacuo. The resulting polymer PHEMA-BiBB- g -PAA was obtained as a solid.

Synthesis Example 4: PHEMA-CTA1- g -PAA

A bottle-type copolymer (BBP, PHEMA-CTA1- g -PAA) was synthesized in the following steps.

[Scheme 1]

1) Poly(2-hydroxyethyl methacrylate) through free radical polymerization

(PHEMA) synthesis

PHEMA main chain was synthesized through the same method as in Synthesis Example 3 above.

2) Synthesis of PHEMA-CTA1 main chain including trithiocarbonate-based RAFT chain transfer agent

To prepare a PHEMA main chain with a trithiocarbonate-based RAFT chain transfer agent (CTA), the hydroxyl group of PHEMA and trithio carbonate RAFT CTA1 (4-Cyano-4-[(dodecyl sulfanylthiocarbonyl) sulfanyl] pentanoic acid), EDC, and DMAP were mixed at a ratio of 1 : 1.5 : 1.5. : It was dissolved in DCM solvent at a molar ratio of 0.3 and stirred at room temperature for one day. After the reaction was completed, it was washed three times with distilled water. The DCM solvent was removed using a rotary evaporator, and after purification, the mixture was dried under reduced pressure in an oven at 50 °C for 24 hours.

[Scheme 2]

1) Synthesis of PHEMA-CTA1- g - PtBA through RAFT

PHEMA-CTA1- g -P tBA was synthesized through RAFT using RAFT CTA included in the PHEMA main chain. PHEMA-CTA1, tBA, and AIBN were dissolved in toluene solvent at a molar ratio of 1:70:0.1 and subjected to argon purging. After confirming that they were sufficiently degassed, they were put in a 70°C oil bath and stirred for 6 hours. After the polymerization was completed, it was purified and dried under reduced pressure in an oven at 50 °C for 24 hours.

2) Synthesis of PHEMA-CTA1- g -PAA through hydrolysis of PHEMA-CTA1- g -P t BA

Hydrolysis of PHEMA-CTA1- g - P t BA to synthesize PHEMA-CTA1- g -PAA was synthesized through the same method as in Synthesis Example 3.

Synthesis Example 5: PHEMA-CTA2- g -PAA

A bottle-type copolymer (BBP, PHEMA-CTA2- g -PAA) was synthesized in the following steps.

[Scheme 1]

1) Poly(2-hydroxyethyl methacrylate) through free radical polymerization

(PHEMA) synthesis

PHEMA main chain was synthesized through the same method as in Synthesis Example 3 above.

2) Synthesis of PHEMA-CTA2 main chain including dithiocarbonate-based RAFT chain transfer agent

To prepare PHEMA-CTA2 main chain with dithiocarbonate-based RAFT chain transfer agent (CTA), PHEMA's hydroxyl group and dithio carbonate RAFT CTA2 (4-Cyano-4-(phenylcarbonothioylthio)pentanoic acid), EDC, and DMAP were mixed at a ratio of 1:1.5:1.5:0.3 It was dissolved in DCM solvent at a molar ratio and stirred at room temperature for one day. After the reaction was completed, it was washed three times with distilled water. The DCM solvent was removed using a rotary evaporator, and after purification, the mixture was dried under reduced pressure in an oven at 50 °C for 24 hours.

[Scheme 2]

1) Synthesis of PHEMA-CTA2- g - PtBA through RAFT

PHEMA-CTA2- g -P tBA was synthesized through RAFT using RAFT CTA included in the PHEMA main chain. PHEMA-CTA2, tBA, and AIBN were dissolved in toluene solvent at a molar ratio of 1:70:0.1 and subjected to argon purging. After confirming that they were sufficiently degassed, they were put in a 70°C oil bath and stirred for 6 hours. After the polymerization was completed, it was purified and dried under reduced pressure in an oven at 50 °C for 24 hours.

2) Synthesis of PHEMA-CTA2- g -PAA through hydrolysis of PHEMA-CTA2- g -P t BA

Hydrolysis of PHEMA-CTA2- g - P t BA to synthesize PHEMA-CTA2- g -PAA was synthesized through the same method as in Synthesis Example 2.

Synthesis Example 6: PVA-BiBB- g -PAA

A bottle-type copolymer (BBP, PVA-BiBB- g -PAA) was synthesized in the following steps.

[Scheme 1]

Synthesis of PVA-BiBB backbone with ATRP initiator

To prepare the PVA-BiBB main chain with ATRP initiator, PVA hydroxyl group and triethyl amine were dissolved in DCM solvent at a molar ratio of 1:1.5, and 2-Bromo-2-methylpropionyl bromide was added at a molar ratio of 1.2 at 0 °C. After the reaction was stirred at room temperature for one day, it was washed three times with distilled water. After removing the DCM solvent with a rotary evaporator, the mixture was precipitated twice in n -hexane solvent, purified, and dried under reduced pressure in an oven at 50 °C for 24 hours.

[Scheme 2]

1) Synthesis of PVA- g -P t BA through ATRP

PVA-BiBB- g -P t BA was synthesized through ATRP using the BiBB initiator included in the PVA main chain. PVA-BiBB, tBA , CuBr, and CuBr ₂ were dissolved in a toluene solvent at a molar ratio of 1:70:0.5:0.05 and argon purged. After confirming that they were sufficiently degassed, the ligand PMDETA was added at a molar ratio of 0.1 and heated to 70°C. It was put in an oil bath and stirred for 6 hours. After the polymerization was completed, the catalyst and ligand were removed through an alumina column. After the purification process, it was dried under reduced pressure in an oven at 50 °C for 24 hours.

2) Synthesis of PVA-BiBB- g -PAA through hydrolysis of PVA-BiBB- g -P t BA

Hydrolysis of PVA-BiBB- g -P t BA to synthesize PVA-BiBB- g -PAA was synthesized through the same method as in Synthesis Example 3.

Synthesis Example 7: PVA-CTA1- g -PAA

A bottle-type copolymer (BBP, PVA-CTA1- g -PAA) was synthesized in the following steps.

[Scheme 1]

1) Synthesis of PVA-CTA1 main chain including trithiocarbonate-based RAFT chain transfer agent

To prepare a PVA main chain with trithiocarbonate-based RAFT chain transfer agent (CTA1), the hydroxyl group of PVA and trithio carbonate RAFT CTA1 (4-Cyano-4-[(dodecyl sulfanylthiocarbonyl) sulfanyl] pentanoic acid), EDC, and DMAP were mixed at a ratio of 1: 1.5: 1.5. : It was dissolved in DCM solvent at a molar ratio of 0.3 and stirred at room temperature for one day. After the reaction was completed, it was washed three times with distilled water. The DCM solvent was removed using a rotary evaporator, and after purification, the mixture was dried under reduced pressure in an oven at 50 °C for 24 hours.

[Scheme 2]

1) Synthesis of PVA-CTA1- g - PtBA through RAFT

PVA-CTA1- g -P tBA was synthesized through RAFT using RAFT CTA1 included in the PVA main chain. PVA-CTA1, tBA, and AIBN were dissolved in a toluene solvent at a molar ratio of 1:70:0.1 and subjected to argon purging. After confirming that they were sufficiently degassed, they were put in a 70°C oil bath and stirred for 6 hours. After the polymerization was completed, it was purified and dried under reduced pressure in an oven at 50 °C for 24 hours.

2) Synthesis of PVA-CTA1- g -PAA through hydrolysis of PVA-CTA1- g -P t BA

Hydrolysis of PVA-CTA1- g -P t BA to synthesize PVA-CTA1- g -PAA was synthesized through the same method as in Synthesis Example 3.

Synthesis Example 8: PVA-CTA2- g -PAA

A bottle-type copolymer (BBP, PVA-CTA2- g -PAA) was synthesized in the following steps.

[Scheme 1]

1) Synthesis of PVA-CTA2 main chain including dithiocarbonate-based RAFT chain transfer agent

To prepare the PVA-CTA2 main chain with dithiocarbonate-based RAFT chain transfer agent (CTA), the hydroxyl group of PVA and dithio carbonate RAFT CTA2 (4-Cyano-4-(phenylcarbonothioylthio)pentanoic acid), EDC, and DMAP were mixed at a ratio of 1:1.5:1.5:0.3 It was dissolved in DCM solvent at a molar ratio and stirred at room temperature for one day. After the reaction was completed, it was washed three times with distilled water. The DCM solvent was removed using a rotary evaporator, and after purification, the mixture was dried under reduced pressure in an oven at 50 °C for 24 hours.

[Scheme 2]

1) Synthesis of PVA-CTA2- g - PtBA through RAFT

PVA-CTA2- g -P tBA was synthesized through RAFT using RAFT CTA2 included in the PVA backbone. PVA-CTA2, tBA, and AIBN were dissolved in a toluene solvent at a molar ratio of 1:70:0.1 and subjected to argon purging. After confirming that the mixture was sufficiently degassed, it was placed in a 70°C oil bath and stirred for 6 hours. After the polymerization was completed, it was purified and dried under reduced pressure in an oven at 50 °C for 24 hours.

2) Synthesis of PVA-CTA2- g -PAA through hydrolysis of PVA-CTA2- g -P t BA

Hydrolysis of PVA-CTA2- g -P t BA to synthesize PVA-CTA2- g -PAA was synthesized through the same method as in Synthesis Example 3.

Example 1: electrode preparation

97wt% of LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM811, LG chem.), 2 wt% carbon black (Super C65), n-methyl pyrrolidone (which is composed of 1 wt% of BBP binder (PNB-g-PAA)) NCM811 cathodes (i.e., BBP cathodes) with BBP binder were fabricated by casting a solvent-based slurry (NMP).

Comparative Example 1: Electrode Preparation

A PVdF cathode was prepared using the same composition and method as in Example 1 except that PVdF was used as a binder.

cell assembly

The electrochemical performance of the BBP cathode was measured using a 2032-type coin cell (BBP cathode/polyethylene separator (thickness = 20 μm, Toray-Tonen)/Li metal anode (200 μm)). A liquid electrolyte of 1 M LiPF ₆ at EC/EMC = 3/7 (w/w) with 10 wt% FEC and 2 wt% VC additive was used. Cells were assembled in an argon-filled glove box.

[evaluation]

The electrochemical/physical properties of the BBP binder were investigated as follows, and the potential of the BBP binder was investigated in comparison with the PVDF binder (control sample).

[Assessment Methods]

Structural/physicochemical properties of BBP binders

1) The electrochemical stability window of the BBP binder was investigated using LSV (Linear Sweep Voltammetry) on the working electrode (stainless steel) and counter/reference electrode (Li metal), and the LSV measurement was performed at a scan rate of 1.0mV s ^-1 did

2) The adhesive strength between the cathode active layer and the Al current collector was measured with a universal tester (DA-01, Petrol LAB) at a peeling rate of 300 mm min ^-1 .

3) For the electrolyte swelling test, the binder film was immersed in the liquid electrolyte at 60° C., and the volume change before and after electrolyte immersion was measured.

4) To quantitatively estimate the transition metal ion chelating ability of the BBP binder, a manganese perchlorate solution (10 mM Mn(ClO ₄ ) ₂ containing 1 M LiPF ₆ at EC/DEC = 1/1 (v/v)) was used as a model solution. prepared with After being immersed in the solution at room temperature for 2 hours, washed with DMC solvent, the amount of Mn ²⁺ captured was measured by ICP-MS (ELAN DRC-2, Perkin Elmer) analysis.

5) In order to characterize the dispersion state of the cathode component in the NMP suspension, the mixture suspension (Combi-514R, Hanil Science Medical) was centrifuged at 2000 rpm for 30 minutes to obtain a supernatant, and then ultraviolet-visible spectroscopy (UV-vis, Agilent, Cary 5000) was performed.

6) The dispersion state of the cathode slurry was also analyzed by fluorescent confocal images using a multiphoton confocal microscope (LSM 780 NLO, Carl Zeiss).

Structural/Physicochemical Characteristics of NCM811 Cathode with BBP Binder

The surface and cross-sectional morphology of the NCM811 cathode were investigated using Field Emission Secondary Electron Microscopy (FE-SEM, S-4800, Hitachi) and energy-dispersive X-ray spectroscopy (EDS, JSM 6400, JEOL). The electrical resistance and contact resistance of the NCM811 cathode were measured using an electrode measurement system (RM2610, Hioki). Inductively Coupled Plasma-Mass Spectrometry (ICP-MS ELAN DRC-2, Perkin Elmer) analysis was performed to quantitatively estimate the metals (Ni, Co, and Mn) deposited on the Li metal anode after the cycling test. The interfacial exothermic reaction between the charged NCM811 and the liquid electrolyte was investigated using Differential Scanning Calorimetry (DSC, Q200, TA). It was disassembled to obtain a charged electrode.

cell performance

The cell performance was investigated using the cycler test (PNE solution) under various charge/discharge conditions. The GITT profile and AC impedance of the cell were obtained using a potentiostat/galvanostat (VSP classic, Bio-Logic). Diffusion coefficients of Li ⁺ ions in the electrode were obtained from GITT results. The diffusion coefficient was calculated using Equation 1 below.

[Equation 1]

In the above formula, m _B is the mass of NCM811, _MB is the molar mass of NCM811 (97.28 g mol ^-1 ), _VM is the molar volume of NCM811 (20.53 cm ³ mol ^-1 ), S is the area of the electrode (1.13 cm ² ), where τ is the current pulse time period, ΔE _s is the voltage change during a single GITT step, and ΔE _τ is the whole cell voltage change during a constant current step.

[result]

1) Measurement of molecular weight and rate of change

The three bottle type polymers with the three different side chain lengths, 1k, 4k and 7k, were measured using GPC-MALLS. The results are shown in Figure 3. Complete terminal modification of the side chain with the novolin moiety was confirmed using NMR. The degree of polymerization was fixed at 100, and a reaction conversion rate of 100% was confirmed using GPC-MALLS and NMR.

2) Linear Sweep Voltammetry Profile

4 is a linear sweep voltammetry (LSV) profile of a BBP film and a PVdF film. Referring to FIG. 4 , the linear sweep voltammetry profile of the BBP film showed similar electrochemical stability to that of the PVdF film.

2) Adhesion test

5 is a test result of adhesion between a BBP film and a current collector according to the side chain length of a bottle brush type copolymer. Referring to Figure 5, the adhesive strength tended to be higher as the side chain length increased.

3) Expansion rate of electrolyte

6 is an electrolyte swelling test result of a BBP film. Referring to FIG. 6 , the BBP films with side chain lengths of 1k and 4k hardly swelled with liquid electrolyte (1M LiPF ₆ in EC/DEC). However, the 7k BBP film with increased side chain length exhibited electrolyte swelling due to an increase in volume.

4) Comparative evaluation of BBP binder and PVdF

The properties of the BBP film having a side chain length of 4k and the PVdF film were compared.

7(A) is a test result of adhesion between a BBP film and a PVdF film. Referring to FIG. 7(A), the BBP film showed higher adhesion (3.76 N cm ⁻¹ ) to the Al current collector than the PVdF film (0.18 N cm ⁻¹ ).

7(B) is an experimental result of the electrolyte expansion rate of the BBP film and the PVdF film. Referring to this, in addition to the high adhesive strength, it can be seen that the BBP film hardly swells with the liquid electrolyte, while the PVdF film has an increased volume change. These results show that the BBP is rationally designed to solve the electrode binder trade-off problem (i.e., adhesion versus electrolyte swelling).

5) Chelation

To examine the metal ion chelating ability, the BBP film was subjected to a model liquid electrolyte (10 mM manganese perchlorate [Mn(ClO ₄ ) ₂ ] containing carbonate liquid electrolyte (1 M LiPF ₆ (1/1 v/v) in EC/DEC) for 2 h. The trapped Mn ²⁺ was quantitatively calculated using ICP-MS (Inductively Coupled Plasma Mass Spectrometry), and the results are shown in Fig. 7(C). It was confirmed that the amount of Mn ²⁺ (180 ppm) was significantly higher than that of the PVdF film (15 ppm) and that the AA side chain of the BBP binder effectively chelated Mn ²⁺ .

6) Slurry Dispersion

NCM811 particles were mixed with BBP binder in a composition ratio of NCM811/BBP=80/20 (w/w) in n-methyl-2-pyrrolidone (NMP) solvent. Thereafter, the supernatant was obtained through centrifugation, and then the dispersion state was investigated through ultraviolet-visible spectroscopy (UV-vis), and the results are shown in FIG. 8. Referring to FIG. 8, the BBP binder-containing solution showed a stronger absorbance than the PVdF binder-containing solution, indicating a better dispersion state.

This effect of the BBP binder was further confirmed by CT (micro-computed tomography) analysis of the cathode slurry whose composition ratio was NCM811/carbon black/BBP binder = 97/2/1 (w/w/w), and the results were shown in Figure 9. Referring to FIG. 9, although there is no noticeable difference between the two slurries in the inset picture, NCM811 particles and carbon black are uniformly dispersed in the BBP slurry, whereas some agglomerates of the particle mixture are observed in the PVdF slurry. This result confirms that the BBP binder plays an important role in obtaining a well-dispersed cathode slurry.

Structural/electrochemical properties of the BBP cathode

The NCM811 cathode was fabricated by casting a cathode slurry (NCM811/carbon black/binder (BBP or PVdF) = 97/2/1 (w/w/w)) on an Al current collector.

1) Electrode thickness

10 and 11 are SEM images of cross-sections and surfaces of a BBP cathode and a PVdF cathode. Referring to FIG. 10 , the fabricated NCM811 cathode exhibited an areal mass loading of ~16mg cm ⁻² and a thickness of ~62 μm for both BBP and PVdF binders. Referring to Fig. 11, the NCM811 cathode with PVdF binder (hereinafter referred to as PVdF cathode) shows that the particles are not uniformly dispersed with some agglomerates (Fig. 11 (left)). In comparison, the NCM811 cathode using BBP binder (referred to as BBP cathode) shows a uniform dispersion of the components (Fig. 11 (right)).

12(A) shows surface electrical resistance measurement results of a BBP cathode and a PVdF cathode. Referring to FIG. 12(A), the BBP cathode exhibited lower electrical resistance than the PVDF cathode due to the well-organized electronic network by the well-dispersed slurry.

2) 180˚ peel-off test after immersion in liquid electrolyte

A 180° peel-off test was performed on the BBP cathode after being immersed in a liquid electrolyte, and a photograph of the result is shown in FIG. 13(A). Referring to Fig. 13(A), the BBP cathode maintained the electrode structure compared to the PVdF cathode, which showed severe separation of components. 13(B) is a diagram schematically showing the contact resistance between the BBP cathode and the PVdF cathode and Li metal after the peel test, and FIG. 12(B) is the contact resistance measurement between the BBP cathode and the PVdF cathode and Li metal after the peel test This is the result. Referring to FIGS. 12(B) and 13(B), the BBP cathode exhibited higher resistance than the PVDF cathode because the less exposed Al current collector could relieve direct contact between the Al current collector and Li metal.

3) Interfacial contact resistance

As an additional experiment, the interfacial contact resistance between the cathode active layer and the Al current collector was measured through electrochemical impedance spectroscopy (EIS) analysis of a symmetrical cell (consisting of two identical cathodes), and is shown in FIG. 14(D). Referring to FIG. 14(D), the Nyquist plot of the BBP cathode showed a smaller semicircle arc, indicating lower interfacial resistance. This result shows that the BBP binder enables strong interfacial adhesion between the cathode active layer and the Al current collector in the state of being immersed in the electrolyte.

The uniform dispersion state of the BBP cathode favorably contributes to constructing a well-organized electron/ion network. GITT (Galvanostatic Intermittent Titration Technique) analysis of the half cell (BBP cathode/Li metal) was performed and is shown in FIG. 14(E). Referring to Fig. 14(E), it is shown that the BBP electrode effectively mitigated the rise in cell polarization following repeated current stimulation (current density = 1 C, interruption time between pulses = 1 hour). The internal cell resistance obtained here was provided as a function of State Of Charge (SOC) and Depth Of Discharge (DOD) (FIG. 14(F)). From the GITT results, the Li ⁺ diffusion coefficient was calculated using the following equation (1).

[Equation 1]

The BBP cathode exhibited a higher diffusion coefficient (4.67x10 ^-8 cm ² S ^-1 ) than the PVdF electrode (3.50 x10 ^-8 cm ² S ^-1 ) due to accelerated Li ⁺ migration.

Cell performance and postmortem analysis

The electrochemical performance of the BBP cathode was evaluated using a 2032-type coin cell (BBP cathode/polyethylene separator/Li metal anode, 1M LiPF ₆ EC/EMC=3/7(w/w) liquid electrolyte and 10 wt% FEC (fluoro ethylene carbonate) , 2 wt% VC (vinylene carbonate)) was used.

15 shows initial charge/discharge profiles of a BBP cathode and a PVdF cathode at current densities of 0.1C/0.1C. Referring to FIG. 15 , the BBP cathode had slightly higher initial discharge capacity than the PVdF cathode (nearly reaching the theoretical value of NCM811 (190mAh g ^-1 )), demonstrating the practicality of the well-organized electron/ion network.

16(A) and 16(B) show the results of measuring the discharge rate capacity and cycling performance of the BBP cathode and the PVdF cathode. Referring to FIG. 16(A), when comparing the discharge rate capability of the BBP cathode with that of the PVdF cathode, the discharge current densities varied from 0.2 to 3.0 C at a charge current density of 0.2 C. . The BBP cathode showed a faster discharge rate than the PVdF cathode, confirming the facile redox kinetics.

As shown in FIG. 16(B), the cycling performance of the BBP cathode was investigated at a charge/discharge current density of 0.5C/0.5C, and the BBP cathode had a higher cycle retention rate (after 240 cycles) than the PVdF cathode (0% after 240 cycles). 80.6%).

A postmortem of the electrode was performed after the cycling test to better explain the excellent cycling performance of the BBP cathode.

17 is a result of measuring the amount of metal Ni, Co, and Mn deposited on the Li metal anode. Referring to this, ICP-MS analysis showed that the amount of metals Ni, Co and Mn deposited on the Li metal anode (combined with the BBP cathode) was lower compared to that in combination with the PVdF cathode. This result is believed to be due to the chelating ability of the AA side chain of the BBP binder.

18 is a SEM image of the surface of a Li metal anode. Referring to FIG. 18, the Li metal anode (combined with the BBP cathode) showed a smooth and even surface with almost no damage, and the Li metal anode (combined with the PVdF cathode) showed an irregular and irregular surface heavily contaminated by transition metal ions. was

19 is a SEM image of NCM811 particles in a BBP cathode and a PVdF cathode. Referring to this, the NCM811 particles of the BBP cathode were relatively clean and less contaminated by by-products compared to the PVdF cathode.

20 is an X-ray photoelectron spectroscopy (XPS) F1s spectrum of NCM811 particles. The peak at 684.7 eV of LiF/MF ₂ (transition metals such as M:Ni, Mn, and Co) is caused by M ²⁺ ions (dissolved in the cathode active material) and hydrofluoric acid (HF, PF ₆ ^- and residues of the electrolyte). ), which is known to be an unwanted by-product occurring between the BBP cathodes (the Li _x PO _y F _z peak at 686.7 eV corresponds to a typical CEI layer).

21 is a TEM image having a Fourier transform pattern of NCM811 particles. Referring to this, in the denitrification state of NCM811, divalent Ni ions (Ni ²⁺ ) tend to move from the transition metal slab to the lithium slab, resulting in structural transformation from layer to spinel phase and rock-salt phase. caused Transmission electron microscopy (TEM) images show that the cyclic NCM811 particles in the PVdF cathode have a stone salt phase and an amorphous region, resulting in structural changes. In comparison, the circulating NCM811 particles in the BBP cathode remained layered with the formation of a thin NiO stone salt phase (~11 nm). This result can be seen that the BBP binder inhibits the phase transition of NCM811 by contributing to the inhibition of Ni ²⁺ dissolution.

22 is an ex-situ XRD pattern of NCM811 particles of BBP cathode and PVdF cathode before and after cycling tests. Referring to this, the ex-situ XRD pattern shows that the (006)/(102) and (108)/(110) peaks corresponding to the layers hardly change before and after. Compared to the cycling test on the BBP cathode, the peak almost disappeared on the PVdF cathode. These results of cycled NCM811 indicate that the BBP binder played a role in preventing interfacial side reactions and dissolution of transition metal ions.

The thermal stability of the cathode active material was evaluated. The interfacial exothermic reaction of the delithiated NCM811 cathode (charged to 4.2 V at a charging current density of 0.1 C) was investigated by differential scanning calorimetry (DSC), and the results are shown in FIG. 23 . Referring to FIG. 23 , the delithiated PVdF cathode exhibited a higher exotherm and a lower exothermic peak temperature (ΔH = 493.5 J g ^-1 and T _peak = 209.39 °C). In contrast, the BBP cathode exhibited substantially improved thermal stability (ΔH = 307.5 J g ^-1 and T _peak = 211.91 °C). This result shows that the BBP binder effectively inhibits the oxygen release and interfacial exothermic reaction of the thermally unstable NCM811 cathode.

High-mass-loading NCM811 cathode with BBP binder

A BBP cathode and a PVdF cathode were fabricated using a binder content of 0.5 wt % (NCM811/carbon black/BBP binder = 97.5/2/0.5 (w/w/w)).

24 is a photograph of a BBP cathode and a PVdF cathode having a binder content of 0.5 wt%. 25 is a SEM image of the surface and cross section of a BBP cathode. Referring to this, the BBP cathode maintained a uniform dispersion state and structural stability even at a binder content of 0.5 wt% (NCM811/carbon black/BBP binder = 97.5/2/0.5 (w/w/w)), which is due to the PVdF binder. is far beyond what is achievable when using .

BBP binders also contribute advantageously to fabricating high-mass-loading cathodes. ^BBP cathodes (NCM811/carbon ^black / ^BBP binder = 97/2/1 (w/w/w)) was successfully fabricated. 26 shows the cross-sectional shape of the BBP cathode according to the thickness (ie, areal-mass-loadings).

27 is a photograph of a PVdF cathode having areal-mass-loadings of 23 mg cm ⁻² (85 μm), and the electrode was not fabricated.

28(A) is a charge/discharge profile of the BBP cathode according to the thickness. Referring to this, the BBP cathode has a tendency for areal discharge capacities to increase as areal-mass-loadings (eg, 27 mg cm ^-2 to 5.2 mAh cm ^-2 ) increase. On the other hand, the specific capacity of the NCM811 particles (190 mAh g ^-1 at 0.1C/0.1C) was hardly affected (FIG. 28(B)). 28(B) is the charge/discharge profile of the high mass load BBP electrode at charge/discharge current density of 0.1C/0.1C.

29 is a measurement result of the cycling performance of the BBP cathode according to the thickness at a charge/discharge current of 0.2C/0.2C under a voltage range of 3.0-4.2V. 30 shows measurement results of cycling performance at charge/discharge current densities of 0.5C/0.5C, respectively. Referring to this, the BBP cathode exhibited stable cycling performance. The high mass load loading of 27 mg cm ⁻² achieved with a lower BBP binder content (1 wt. %) far exceeds other previously reported cathode binders.

As described above, the bottle brush type copolymer binder according to an embodiment of the present invention may be compatible with a commercial cathode manufacturing process based on an NMP solvent and may have excellent practicality. In particular, it was possible to manufacture a Ni-rich electrode active material that is sensitive to moisture, such as NCM811.

The binder according to one embodiment of the present invention has a balanced amphiphilicity to uniformly disperse the electrode slurry, and the electrode structure to form a well-organized electron / ion conduction path in the thickness direction due to its chemical function and structural uniqueness. formed, can provide strong adhesion with the current collector even in a state of being immersed in the electrolyte, and can form chelation of heavy metal ions dissolved in the electrode active material.

In addition, stable cycling performance can be obtained even with a very low binder content, and high mass loading (27 mg cm ⁻² (= 5.2 mAh cm ⁻² )) is possible. This performance is an effect that is difficult to achieve with previously reported cathode binders and commercial PVdF binders.

Although the above has been described with reference to the embodiments of the present invention, those skilled in the art will variously modify the present invention within the scope not departing from the spirit and scope of the present invention described in the claims below. And it will be readily understood that it can be changed.

Claims (13)

A binder for a secondary battery having a bottle brush type structure represented by Formula 1 below;
[Formula 1]

In Formula 1,
A is a substituted or unsubstituted cyclic compound, or a single bond,
R ₁ is a substituted or unsubstituted C ₁ to C ₂₀ alkylene group, wherein one or more -CH ₂ - groups are -O-, -CO-, -CO-O-, -O-CO-, -S- CS-, -CS-S-, -S-CS-S-, a substituted or unsubstituted C ₄ to C ₁₂ carbon ring, or a substituted or unsubstituted C ₃ to C ₁₂ heterocyclic ring,
Wherein R ₂ is a substituted or unsubstituted C ₁ to C ₂₀ alkyl, a substituted or unsubstituted C ₄ to C ₁₂ carbon ring, a substituted or unsubstituted C ₃ to C ₁₂ heterocyclic ring, or a haloalkyl , wherein one or more -CH ₂ -groups are replaced with -O-, -CO-, -CO-O-, -O-CO-, -S-CS-, -CS-S-, or -CS-S- can be,
B and D are each independently C ₂ to C ₁₀ alkyl acrylate, C ₂ to C ₁₀ alkyl methacrylate, or C ₁ to C ₁₀ acrylic acid,
k is an integer from 1 to 1,000, and n is an integer from 1 to 100 (except for Compounds 1 to 3 below).

According to claim 1,
The bottle brush type secondary battery binder having a bottle brush type structure is represented by the following Chemical Formula 1-1.
[Formula 1-1]

In Formula 1-1,
R ₃ is hydrogen, deuterium, hydroxy, substituted or unsubstituted C ₁ to C ₂₀ alkyl, amine, substituted or unsubstituted C ₄ to C ₁₂ carbon ring, substituted or unsubstituted C ₃ to C ₁₂ a heterocyclic ring, or a halogen;
R ₁ , R ₂ , B and D, k, n are as defined in Formula 1.
According to claim 1,
Wherein A is a binder for a secondary battery having a bottle brush structure including a pentagonal ring or a hexagonal ring.
According to claim 1,
Wherein A is formed by ring opening of a cyclic alkene represented by any one of the following chemical formulas:

In the above formula,
R is halogen, hydroxy, carboxy, amine or alkyl;
q is 0 or an integer from 1 to 6;
In addition, the dotted line in Formulas (2) and (8) means a substituted or unsubstituted carbon ring or hetero ring,

means being connected with R ₁ .
According to claim 1,
The bottle brush type secondary battery binder having a bottle brush type structure is represented by any one of the following Chemical Formulas 2-1 to 2-8.
[Formula 2-1]

[Formula 2-2]

[Formula 2- 3]

[Formula 2-4]

[Formula 2-5]

[Formula 2-6]

[Formula 2-7]

[Formula 2-8]

In the above formula, k is an integer from 1 to 1,000, and m is an integer from 1 to 100.
According to claim 1,
The secondary battery binder of the bottle brush type structure has a molecular weight of 10 to 10,000K Da.
A secondary battery binder having a bottle brush type structure including a unit having a core part and a shell part, wherein a main chain formed by polymerization of the core part and the shell part are connected to the main chain to form side chains disposed in an outward direction.
According to claim 7,
The main chain has a hydrophobic property, and the side chain has a bottle-type structure of a secondary battery binder including a hydrophilic functional group.
A binder having a bottle brush type structure according to any one of claims 1 to 8; And an electrode composition for a secondary battery comprising an electrode active material.
According to claim 9,
The binder of the bottle brush type structure has a side chain length of 0.1 to 50 k Da, a secondary battery electrode composition.
According to claim 9,
The content of the binder of the bottle brush type structure is 0.1 to 20 parts by weight, the content of the electrode active material is 20 to 99 parts by weight of the secondary battery electrode composition.
According to claim 9,
The electrode active material is Li _a A _1-b B _b D ₂ (0.90 ≤ a ≤ 1.8, and 0 ≤ b ≤0.5), wherein A is Ni, Co, Mn, or a combination thereof, and B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element or a combination thereof, D is O, F, S, P, or a combination thereof.
A cathode comprising the binder having a bottle brush type structure according to any one of claims 1 to 8;
an anode disposed opposite to the cathode; and
a separator disposed between the cathode and anode;
A lithium secondary battery comprising a.

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