WO2021085894A1 - Anode binder material for lithium secondary battery, and anode binder comprising cured product thereof - Google Patents

Abstract

The objective of the present invention is to provide, as a prerequisite for improving the performance of a lithium secondary battery, a material that can be converted into an anode binder having all of heat resistance, chemical resistance, excellent binding force, durability and the like. Specifically, provided in one implementation embodiment of the present invention is an anode binder material for a lithium secondary battery, comprising: a vulcanization accelerator comprising a metal-organic framework (MOF); a styrene-butadiene copolymer; and a sulfur molecule (S8).

Description

Anode binder raw material for lithium secondary batteries, anode binder including a cured product thereof

Cross-reference with related application(s)

This application claims the benefit of priority based on Korean Patent Application No. 10-2019-0138185 filed October 31, 2019 and Korean Patent Application No. 10-2020-0131978 filed October 13, 2020. All contents disclosed in the literature are included as part of this specification.

The present invention relates to a negative electrode binder material for a lithium secondary battery, and a negative electrode binder including a cured product thereof.

In recent years, as the application field of lithium secondary batteries has expanded from small electronic devices to large devices such as automobiles and power storage devices, various studies to improve the performance of lithium secondary batteries, such as increasing energy capacity and securing fast charging speeds. Is in progress.

The negative electrode of the lithium secondary battery may include a negative electrode active material that stores lithium ions during charging and releases them during discharge; A conductive material for securing an electrically conductive path while filling a space that cannot be filled by the negative active material; It is composed of a binder that physically couples these to the current collector.

Here, the negative electrode binder plays an important role in physically stabilizing the negative electrode by buffering the volume change of the negative electrode active material during repetitive charging and discharging of the battery, in addition to the role of physically bonding the negative electrode active material and the conductive material.

However, generally known negative electrode binders (e.g., styrene-butadiene-based polymers, styrene-acrylate-based polymers, etc.) are denatured at high temperatures (up to 200°C) during battery manufacturing, or cause side reactions with electrolytes in the battery. It causes problems such as deterioration of the negative electrode due to weakening of the bonding force during repeated charging and discharging of the battery and not being able to buffer the volume change of the negative electrode active material.

In the present invention, as a prerequisite for improving the performance of a lithium secondary battery, it is intended to provide a raw material that can be converted into a negative electrode binder having heat resistance, chemical resistance, excellent bonding strength and durability.

Specifically, in one embodiment of the present invention, a vulcanization accelerator including a metal-organic framework (MOF); Styrene-butadiene-based copolymer; And it provides a negative electrode binder material for a lithium secondary battery comprising a sulfur molecule (S _{8 ).}

The negative electrode binder raw material of the above embodiment may be cured while being applied to the negative electrode current collector to exhibit excellent properties such as heat resistance, chemical resistance, and mechanical properties.

Therefore, the negative electrode binder converted from the raw material of the above embodiment is not denatured or destroyed even when high temperature is applied when manufacturing the negative electrode and the electrode assembly including the same, and side reactions with the electrolyte in the battery are suppressed, and the battery is repeatedly charged and discharged. It can contribute to improving the performance of a lithium secondary battery by maintaining excellent bonding strength and effectively buffering the volume change of the negative active material.

Unless otherwise defined herein, "copolymerization" may mean block copolymerization, random copolymerization, graft copolymerization or alternating copolymerization, and "copolymer" refers to block copolymer, random copolymer, graft copolymer or alternating copolymer It can mean consolidation.

In the drawings, the thicknesses are enlarged in order to clearly express various layers and regions. Like reference numerals are attached to similar parts throughout the specification. When a part of a layer, film, region, plate, etc. is said to be "above" or "on" another part, this includes not only the case where the other part is "directly above", but also the case where there is another part in the middle. Conversely, when one part is "directly above" another part, it means that there is no other part in the middle.

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, and the present invention is not limited thereby, and the present invention is only defined by the scope of the claims to be described later.

Anode binder raw material for lithium secondary battery

In one embodiment of the present invention, in addition to a styrene-butadiene-based copolymer and a sulfur molecule, a material for a negative electrode binder for a lithium secondary battery comprising a vulcanization accelerator including a metal-organic framework (MOF) is provided.

In the negative electrode binder material of the embodiment, the styrene-butadiene-based copolymer is a polymer having a chain structure including a styrene repeating unit and a butadiene repeating unit, and a sulfur molecule (S ₈ ) is a vulcanization reaction with the styrene-butadiene-based copolymer. This is a possible vulcanizing agent.

Here, "Vulcanization" refers to a reaction forming a cured product having a network structure by forming a crosslinked bond including an S-S bond within a polymer chain and between different polymer chains.

The styrene-butadiene-based copolymer and the raw material composed of only sulfur molecules can undergo a vulcanization reaction only when a high temperature of about 159° C. or higher is applied.

This is because the sulfur molecule (S ₈ ) is an octagonal ring-shaped molecule, and can be polymerized (ie, vulcanized) in the styrene-butadiene-based copolymer only by ring-opening at a temperature of about 159° C. or higher to form a radical.

However, the melting point of the styrene-butadiene-based copolymer is about 160 to 200 °C, and is denatured or destroyed at a higher temperature, so that the vulcanization reaction proceeds slowly, and the physical properties of the vulcanization reaction product may be deteriorated.

In this regard, during a general vulcanization reaction, sulfur is activated using a vulcanization accelerator such as N,N-dicyclohexyl-2-benzothiazolesulfenamide (N,N-Dicyclohexyl-2-benzothiazolesulfenamide, DCBS) or ZnO. It is known to change the state and promote vulcanization.

However, such a general vulcanization accelerator alone is insufficient to remarkably increase the physical properties of the cured product, although it is possible to partially increase the speed of the vulcanization reaction.

Accordingly, in one embodiment of the present invention, in addition to the styrene-butadiene-based copolymer and sulfur molecules, a negative electrode binder material including a metal-organic framework (MOF) has been provided.

The metal-organic skeleton may include metal ions or clusters; And it is a two-dimensional or three-dimensional structure comprising an organic ligand coordinated thereto.

The metal-organic skeleton has its own pores due to the coordination of metals and organics, and the size and shape of the pores vary according to the type of the metal-organic skeleton. Due to the presence or absence of the pores in the vulcanization reaction, unreacted monomers enter and exit the pores during the vulcanization crosslinking reaction, and the polymer-polymer crosslinking reaction is more effectively performed than the polymer-unreacted monomer reaction.

This can be said that unlike general vulcanization accelerators such as DCBS and ZnO that effectively cause crosslinking in terms of reaction rate, the metal-organic skeleton selectively promotes crosslinking between polymer chains, thereby remarking its characteristics.

Furthermore, unlike general vulcanization accelerators such as DCBS and ZnO, which only accelerate the vulcanization reaction and have no structural effect, the metal-organic skeleton has its own pores, so the mobility of lithium ions during electrode manufacturing is improved. It can contribute to the improvement of battery performance.

Accordingly, the negative electrode binder raw material of the embodiment includes the vulcanization accelerator including the metal-organic framework (MOF), so that 70 to 90 applied for drying while applied to the negative electrode current collector It is rapidly cured by hot air at °C and can exhibit excellent properties such as heat resistance, chemical resistance, and mechanical properties.

Further, the binder converted from the negative electrode binder raw material of the above embodiment is not denatured or destroyed even when high temperature is applied when manufacturing the negative electrode and the electrode assembly including the same, and side reactions with the electrolyte in the battery are suppressed, and the battery is repeatedly charged. It can contribute to improving the performance of the lithium secondary battery by maintaining excellent bonding strength even during discharge and effectively buffering the volume change of the negative electrode active material.

On the other hand, even if ZnDBC is used alone as the vulcanization accelerator, the effect of lowering the resistance of the negative electrode can be obtained, but if the negative electrode is further improved in terms of adhesion and expansion rate, other vulcanization accelerators such as ZnO may be added.

As mentioned above, since ZnDBC performs its special function as well as the vulcanization accelerating role, even if it is used alone, the resistance of the negative electrode can be lowered.

However, when ZnDBC is used alone as a vulcanization accelerator without the help of other vulcanization accelerators such as ZnO, there is a limit to increasing the degree of vulcanization (crosslinking). In this regard, one method is to increase the degree of vulcanization (crosslinking) by adding another vulcanization accelerator, such as ZnO, in addition to ZnDBC, if a cathode is desired that has a higher cathode adhesion and lower expansion rate while lowering the resistance of the cathode. It will be possible. A more detailed description of other vulcanization accelerators such as DSBS and ZnO will be described later.

Hereinafter, the negative electrode binder material of the embodiment will be described in detail.

Metal-organic skeleton

The metal-organic skeleton is Zn (1,4-Benzenedicarboxylate) (BDC), which will be described later, as well as Zn ₄ O (4,4',4″-[benzene-1,3, 5-triyl-tris(ethyne-2,1-diyl)]tribenzoate)(BPDC ² =biphenyl-4,4′-dicarboxylate) (BTE)(BPDC), Zn ₄ O(1,3,5-benzenetribenzoate) ( BTB) and _{at least one from the group containing Zn 4} O(4,4′,4″-[benzene-1,3,5-triyl-tris(benzene-4,1-diyl)]tribenzoate) (BBC) You can choose.

Styrene-butadiene-based copolymer

The styrene-butadiene-based copolymer; is a copolymer having a chain structure including a styrene repeating unit and a butadiene repeating unit, and is not particularly limited as long as it can be converted into a network structure by a vulcanization reaction.

For example, the styrene-butadiene-based copolymer; is generally selectable from styrene-butadiene-based copolymers known as negative electrode binders, and includes an acrylic-styrene-butadiene copolymer, a styrene-butadiene polymer, or a mixture thereof. It may be, and may further include a butadiene polymer.

Meanwhile, the styrene-butadiene-based copolymer may be commercially available or may be directly prepared and used.

When the styrene-butadiene-based copolymer is directly prepared and used, a monomer mixture comprising a styrene monomer and a butadiene monomer together with a polymerization initiator generally known in the art, and optionally an acrylic monomer, etc. By emulsion polymerization in, it can be prepared into a latex-type composition containing styrene-butadiene-based copolymer particles.

Here, as the polymerization initiator, paramenthane hydroperoxide (PMHP), potassium persulfate, sodium persulfate, ammonium persulfate, and sodium bisulfate At least one polymerization initiator selected from the group containing) may be used.

Mixing ratio of styrene-butadiene-based copolymer, sulfur molecule, and metal-organic skeleton

In the preparation of the negative electrode binder material of the embodiment, based on 100 parts by weight of the styrene-butadiene-based copolymer, the sulfur molecule is 0.5 to 3 parts by weight, and the metal-organic skeleton may be blended so that 0.5 to 2 parts by weight. have.

Within this range, a crosslinking bond including a disulfide bond (SS bond) is formed at an appropriate level within the styrene-butadiene-based copolymer chain and between different polymer chains, while promoting and reacting vulcanization by the metal-organic skeleton. Participation can take place effectively. However, within the above range, the blending of the raw materials may be changed according to the desired physical properties.

Specifically, based on 100 parts by weight of the styrene-butadiene-based copolymer, the lower limit of the content of the sulfur molecule is set to 0.05 or more, 0.1 or more, 0.5 or more, or 1 or more, and the upper limit is 5 or less, 3 or less, 1 or less, or It can be made 0.5 or less. In addition, the lower limit of the content of the metal-organic skeleton may be 0.05 or more, 0.1 or more, 0.5 or more, or 1 or more, and the upper limit may be 4 or less, 2 or less, 1 or less, or 0.5 or less.

Within the range illustrated as described above, as the content of the sulfur molecule increases, heat resistance, chemical resistance, and mechanical properties of the final negative electrode binder may be improved. In addition, as the content of the metal-organic skeleton increases, the vulcanization reaction is accelerated, and physical properties of the final negative electrode binder may be further improved.

Vulcanization accelerators other than metal-organic skeletons

On the other hand, when mixing the negative electrode binder raw material of the embodiment, a general vulcanization accelerator such as N,N-dicyclohexyl-2-benzothiazolesulfenamide (N,N-Dicyclohexyl-2-benzothiazolesulfenamide, DCBS), ZnO, etc. It is also possible to add.

The N,N-dicyclohexyl-2-benzothiazolesulfenamide is a kind of organic vulcanization accelerator, and generally reduces the amount of vulcanizing agent (i.e., the sulfur molecule) to the polymer, while increasing the vulcanization rate to increase the vulcanization time. It is known as a material that shortens the vulcanization temperature, reduces the vulcanization temperature, and improves heat resistance, chemical resistance, bonding strength, and durability of a vulcanization reaction product.

In addition, the zinc oxide is a kind of inorganic vulcanization accelerator, which promotes the initial vulcanization reaction of a polymer mainly containing -COOH, and is known as a material that assists the function of the organic vulcanization accelerator.

In this regard, when the negative electrode binder material of the embodiment is mixed, the N,N-dicyclohexyl-2-benzothiazolesulfenamide and the zinc oxide may be mixed and added.

For example, based on 100 parts by weight of the styrene-butadiene-based copolymer, 0.5 to 2 parts by weight of the N,N-dicyclohexyl-2-benzothiazolesulfenamide is added, and 0.5 to 5 parts by weight of the zinc oxide It may be added partly, wherein the weight ratio of N,N-dicyclohexyl-2-benzothiazolesulfenamide and zinc oxide may be 1:3.5 to 1:5.

Within this range, the vulcanization reaction rate of the styrene-butadiene-based copolymer and the sulfur molecule becomes faster, the vulcanization reaction temperature is lowered, the sulfur molecule remaining after the vulcanization reaction is reduced, and the physical properties of the vulcanization reaction product can be improved. have.

However, this is only an example, and the type of the vulcanization accelerator and the amount of the vulcanization accelerator may be determined by comprehensively considering the type of the styrene-butadiene-based copolymer and the desired negative electrode binder characteristics.

Solvent and emulsifier

In addition, the negative electrode binder material of the embodiment may further include water as a solvent.

In this case, in order to improve dispersibility, stability, etc., sodium lauryl sulfate (SLS), sodium laureth sulfate (SLES), and ammonium lauryl sulfate (Ammonium Lauryl Sulfate, ALS) are included. It may further include at least one emulsifier selected from the group.

For example, based on 100 parts by weight of the styrene-butadiene-based copolymer, the emulsifier may be blended in an amount of 0.2 to 2 parts by weight.

In addition to the above-described components, it is possible to further add additives generally known in the art, and further detailed description thereof will be omitted.

Anode binder composition for lithium secondary battery

In another embodiment of the present invention, a styrene-butadiene-based copolymer vulcanized in the presence of a vulcanization accelerator including a metal-organic framework (MOF); containing, a negative electrode binder composition for a lithium secondary battery to provide.

The styrene-butadiene-based copolymer vulcanized in the presence of a vulcanization accelerator including the metal-organic framework (MOF) is vulcanized in the presence of a vulcanization accelerator without the styrene-butadiene-based copolymer. Compared to the styrene-butadiene-based copolymer, it is structurally stable and can exhibit improved properties in heat resistance, chemical resistance, and mechanical properties.

Here, the metal-organic skeleton has its own pores due to a coordination bond between metals and organics, and the size and shape of the pores vary according to the type of the metal-organic skeleton. Due to the presence or absence of the pores in the vulcanization reaction, unreacted monomers enter and exit the pores during the vulcanization (crosslinking) reaction, so that the polymer-polymer crosslinking reaction can be more effectively performed than the polymer-unreacted monomer reaction.

Here, unlike general vulcanization accelerators such as DCBS and ZnO that effectively cause crosslinking in terms of the reaction rate, the metal-organic skeleton selectively promotes crosslinking between polymer chains, thereby remarking its properties.

Furthermore, unlike general vulcanization accelerators such as DCBS and ZnO, which only accelerate the vulcanization reaction and have no structural effect, the metal-organic skeleton has its own pores, so the mobility of lithium ions in the negative electrode including them is As a result, it can contribute to an increase in the CC (Constant Current) section compared to the capacity of the lithium secondary battery while lowering the internal resistance of the negative electrode.

Accordingly, the binder composition of the embodiment is not denatured or destroyed even when high temperature is applied in the manufacturing process of the negative electrode and the electrode assembly including the same, and side reactions with the electrolyte in the battery are suppressed, and excellent bonding strength even during repetitive charging and discharging of the battery. By maintaining and effectively buffering the volume change of the negative active material, it can contribute to improving the performance of the lithium secondary battery.

Hereinafter, descriptions overlapping with those described above will be omitted, and the negative electrode binder composition of the embodiment will be described in detail.

Existence form of metal-organic skeleton in negative electrode binder composition

In the binder composition of the embodiment, the metal-organic framework (MOF) is present in a bonded state with the vulcanized styrene-butadiene-based copolymer, or the vulcanized styrene-butadiene-based It can exist independently of the copolymer.

Specifically, in the process of vulcanizing the styrene-butadiene-based copolymer in the presence of the vulcanization accelerator including the metal-organic skeleton (MOF), the styrene-butadiene-based copolymer is vulcanized and at the same time, the metal-organic skeleton ( MOF) may be partially complexed with a styrene-butadiene-based copolymer.

More specifically, while the stabilized metal ions inside the metal-organic skeleton (MOF) participate in the vulcanization reaction as a kind of catalyst, the structure of the metal-organic skeleton (MOF) is partially changed, allowing it to be complexed with the styrene-butadiene-based copolymer. have. As such, the catalyst efficiency is higher in the state of being complexed with the styrene-butadiene-based copolymer, and the vulcanization reaction can proceed more effectively.

Here, the metal ions that participated in the vulcanization reaction may mostly return to the metal-organic skeleton (MOF) after the vulcanization reaction, but some may remain in an ionic state.

Thus, in the final negative electrode binder composition, most of the metal-organic framework (MOF) is present in a state independently mixed with the vulcanized styrene-butadiene-based copolymer, and a portion thereof is structurally changed and the vulcanized styrene- It can remain in a complexed state with a butadiene-based copolymer.

Gel content in negative electrode binder composition

The negative electrode binder composition of the embodiment may have a gel content of 80% or more calculated by Equation 1 below:

[Equation 1]

Gel content (%) = M _b /M _a * 100

In Equation 1,

M _a is the negative electrode binder composition dried at room temperature for 24 hours and then dried at 80° C. for 24 hours to obtain a film-type binder composition, and the binder film was cut into a very pellet, and 0.5 g of the binder composition was prepared. It is the weight taken and measured,

M _b is the negative electrode binder composition weighed by immersion in 50 g of THF (Tetrahydrofuran) for 24 hours or more, filtering through 200 Mesh, and drying the mesh and the negative electrode binder remaining in the mesh at 80° C. for 48 hours. It is the weight of the copolymer remaining in the mesh.

The gel content refers to the degree of crosslinking of the copolymer, and is calculated as in Equation 1 and expressed as an insoluble fraction in the electrolyte. Specifically, the gel content in the negative electrode binder according to the embodiment may be 80% or more, 81% or more, or 82% or more. If the gel content is less than 80%, swelling of the electrolyte solution increases, and thus the life of the battery may be reduced. In addition, the upper limit of the gel content is not particularly limited, but may be 99% or less, 98% or less, or 97% or less.

Method for producing a negative electrode binder for a lithium secondary battery

In another embodiment of the present invention, in the presence of a vulcanization accelerator including a metal-organic framework (MOF), a styrene-butadiene-based copolymer and a sulfur molecule (S ₈ ) are subjected to a vulcanization reaction; It provides a method for producing a negative electrode binder composition for a lithium secondary battery comprising a.

This corresponds to a method of manufacturing a negative electrode binder by curing the above-described negative electrode binder raw material.

Hereinafter, descriptions overlapping with those described above will be omitted, and each step of the embodiment will be described in detail.

The vulcanization reaction may be carried out in a temperature range of 70 to 90 °C.

For example, the temperature range for the vulcanization reaction is 70°C or more, or 71°C or more, or 72°C or more, or 73°C or more, or 74°C or more, or 75°C or more, while 90°C or less, or 89°C or less, or It can be adjusted within a range of 88°C or less, or 87°C or less, or 86°C or less, or 85°C or less.

In addition, the vulcanization reaction may be carried out for to 60 minutes.

For example, the vulcanization reaction time is 1 minute or more, 3 minutes or more, 5 minutes or more, 7 minutes or more, or 9 minutes or more, and 60 minutes or less, 50 minutes or less, 40 minutes or less, 30 minutes or less, or 20 minutes or less. It can be adjusted within the range.

The vulcanization reaction may be performed in a state in which the negative electrode binder material is applied to the negative electrode current collector, as mentioned above.

Specifically, the negative electrode binder material of the embodiment may include a negative electrode active material; Conductive material; Aqueous or non-aqueous solvents; It is prepared as a negative electrode slurry by mixing with etc., and is rapidly cured by hot air of 70 to 90°C applied for drying while applied on the negative electrode current collector, providing excellent properties such as heat resistance, chemical resistance, and mechanical properties. It can be an expressing negative electrode binder.

More specifically, before the vulcanization reaction, preparing a negative electrode active material slurry including the negative electrode binder raw material, a conductive material, a binder, and a solvent; And applying the negative active material slurry to one or both surfaces of a negative electrode current collector.

Accordingly, the vulcanization reaction may include applying heat to the negative active material slurry applied to one or both surfaces of the negative electrode current collector; And curing the anode binder material in the anode active material slurry by the heat.

In 100% by weight of the negative electrode active material slurry, the content of the negative electrode binder material may be 0.1 to 0.5% by weight, the content of the negative electrode active material may be 80 to 84% by weight, and the content of the binder may be 0.5 to 2.5% by weight And the balance may be an additive and a solvent. Here, the content of each substance can be adjusted according to common knowledge in the art.

The negative active material, the conductive material, the additive, and the like will be described later.

Negative electrode for lithium secondary battery

In another embodiment of the present invention, a negative electrode current collector; And a styrene-butadiene-based copolymer, a negative electrode active material, and a conductive material vulcanized in the presence of a vulcanization accelerator located on the negative electrode current collector and including a metal-organic framework (MOF). It provides a negative electrode for a lithium secondary battery including a layer.

Since the negative electrode of one embodiment includes a binder converted from the negative electrode binder raw material of the above-described embodiment, side reactions with the electrolyte solution in the battery are suppressed, and excellent bonding strength is maintained even during repetitive charging and discharging of the battery, and the volume of the negative electrode active material By effectively buffering the change, it can contribute to improving the performance of the lithium secondary battery.

In the negative electrode of one embodiment, the negative electrode active material layer is independently, the negative electrode active material is a material capable of reversibly intercalating/deintercalating lithium ions, lithium metal, an alloy of lithium metal, doped with lithium, and It includes a material that can be undoped, or a transition metal oxide.

As a material capable of reversibly intercalating/deintercalating lithium ions, any carbon-based negative active material generally used in lithium ion secondary batteries may be used as a carbon material, and a representative example thereof is crystalline carbon. , Amorphous carbon, or a combination thereof may be used. Examples of the crystalline carbon include graphite such as amorphous, plate-shaped, flake, spherical or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon (low-temperature calcined carbon). Alternatively, hard carbon, mesophase pitch carbide, and fired coke may be used.

The lithium metal alloy includes lithium and a metal of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, or Sn. Alloys can be used.

Materials capable of doping and undoping lithium include Si, SiO _x (0 <x <2), Si-C composites, Si-Q alloys (where Q is an alkali metal, alkaline earth metal, group 13 to group 16 element , Transition metal, rare earth element or a combination thereof, and not Si), Sn, SnO ₂ , Sn-C complex, Sn-R (the R is an alkali metal, alkaline earth metal, group 13 to group 16 element, transition metal, It is a rare earth element or a combination of these, and Sn is not), etc. are mentioned. Specific elements of Q and R include Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, or combinations thereof.

Examples of the transition metal oxide include vanadium oxide and lithium vanadium oxide.

For example, the negative active material layer may include at least one carbon-based negative active material selected from artificial graphite, natural graphite, soft carbon, hard carbon, or a mixture thereof.

Meanwhile, the negative active material layer may further include a conductive material. The conductive material is used to impart conductivity to the electrode, and in the battery constituted, any material can be used as long as it does not cause chemical change and is an electronic conductive material, such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen Carbon-based materials such as black and carbon fiber; Metal-based materials such as metal powders such as copper, nickel, aluminum, and silver, or metal fibers; Conductive polymers such as polyphenylene derivatives; Alternatively, a conductive material containing a mixture thereof may be used.

For example, each of the negative electrode active material layers may independently include at least one selected from the group of carbon-based conductive materials including acetylene black, carbon black, ketjen black, carbon fiber, or a mixture thereof.

The conductive material is used to impart conductivity to the electrode, and any electronically conductive material can be used without causing a chemical change in the configured battery. For example, natural graphite, artificial graphite, carbon black, acetylene black, ketjen black , Carbon-based materials such as carbon fiber; Metal-based materials such as metal powders such as copper, nickel, aluminum, and silver, or metal fibers; Conductive polymers such as polyphenylene derivatives; Alternatively, a conductive material containing a mixture thereof may be used.

As the current collector, a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foam, a polymer substrate coated with a conductive metal, or a combination thereof may be used.

Lithium secondary battery

In another embodiment of the present invention, the cathode of the embodiment; Electrolytes; And it provides a lithium secondary battery including a positive electrode.

The lithium secondary battery of the embodiment may further include a separator between the positive electrode and the negative electrode.

The lithium secondary battery may be classified into a cylindrical type, a square type, a coin type, a pouch type, etc. according to the shape to be used, and may be divided into a bulk type and a thin film type according to the size. Since the structure and manufacturing method of these batteries are widely known in this field, a minimum explanation will be added.

The positive electrode includes a current collector and a positive electrode active material layer formed on the current collector.

As the positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (reitiated intercalation compound) may be used. Specifically, at least one of cobalt, manganese, nickel, or a composite oxide of lithium and a metal of a combination thereof may be used, and a specific example thereof may be a compound represented by any one of the following formulas. Li _a A _1-b R _b D ₂ (where 0.90≦a≦1.8 and 0≦b≦0.5); Li _a E _1-b R _b O _2-c D _c (where 0.90≦a≦1.8, 0≦b≦0.5, and 0≦c≦0.05); LiE _2-b R _b O _4-c D _c (where 0≦b≦0.5, 0≦c≦0.05); Li _a Ni _1-bc Co _b R _c D _α (wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 <α ≤ 2); Li _a Ni _1-bc Co _b R _c O _2-α Z _α (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 <α <2); Li _a Ni _1-bc Co _b R _c O _2-α Z ₂ (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 <α <2); Li _a Ni _1-bc Mn _b R _c D _α (wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 <α ≤ 2); Li _a Ni _1-bc Mn _b R _c O _2-α Z _α (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 <α <2); Li _a Ni _1-bc Mn _b R _c O _2-α Z ₂ (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 <α <2); Li _a Ni _b E _c G _d O ₂ (in the above formula, 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, and 0.001≦d≦0.1); Li _a Ni _b Co _c Mn _d GeO ₂ (wherein, 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0≦d≦0.5, and 0.001≦e≦0.1.); Li _a NiG _b O ₂ (wherein, 0.90≦a≦1.8 and 0.001≦b≦0.1); Li _a CoG _b O ₂ (wherein, 0.90≦a≦1.8 and 0.001≦b≦0.1.); Li _a MnG _b O ₂ (wherein, 0.90≦a≦1.8 and 0.001≦b≦0.1.); Li _a Mn ₂ G _b O ₄ (wherein, 0.90≦a≦1.8 and 0.001≦b≦0.1); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiTO ₂ ; LiNiVO ₄ ; Li _(3-f) J ₂ (PO ₄ ) ₃ (0≦f≦2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0≦f≦2); And LiFePO ₄ .

In the above formula, A is Ni, Co, Mn, or a combination thereof; R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements or combinations thereof; D is O, F, S, P or a combination thereof; E is Co, Mn, or a combination thereof; Z is F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; T is Cr, V, Fe, Sc, Y or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

Of course, one having a coating layer on the surface of the compound may be used, or a mixture of the compound and a compound having a coating layer may be used. The coating layer may include, as a coating element compound, oxide, hydroxide of a coating element, oxyhydroxide of a coating element, oxycarbonate of a coating element, or hydroxycarbonate of a coating element. The compound constituting these coating layers may be amorphous or crystalline. As a coating element included in the coating layer, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof may be used. The coating layer formation process is a method that does not adversely affect the physical properties of the positive electrode active material by using these elements in the compound (e.g., spray coating, dipping method, etc.), any coating method may be used. The detailed description will be omitted because it can be well understood by those in the field.

The positive electrode active material layer also includes a binder and a conductive material.

The binder adheres well the positive electrode active material particles to each other, and also plays a role in attaching the positive electrode active material to the current collector well, and representative examples thereof include polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, and polyvinyl Chloride, carboxylated polyvinylchloride, polyvinylfluoride, polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene- Butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc. may be used, but the present invention is not limited thereto.

The conductive material is used to impart conductivity to the electrode, and in the battery constituted, any material can be used as long as it does not cause chemical change and is an electronic conductive material, such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen Metal powders such as black, carbon fiber, copper, nickel, aluminum, and silver, metal fibers, etc. may be used, and conductive materials such as polyphenylene derivatives may be used alone or in combination of one or more.

Al may be used as the current collector, but is not limited thereto.

Each of the negative electrode and the positive electrode is prepared by mixing an active material, a conductive material, and a binder in a solvent to prepare an active material composition, and then applying the composition to a current collector. Since such an electrode manufacturing method is widely known in the art, a detailed description thereof will be omitted. As the solvent, N-methylpyrrolidone or the like may be used, but is not limited thereto.

The electrolyte includes a non-aqueous organic solvent and a lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

As the non-aqueous organic solvent, a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based, or aprotic solvent may be used. As the carbonate-based solvent, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate ( EC), propylene carbonate (PC), butylene carbonate (BC), and the like may be used, and as the ester solvent, methyl acetate, ethyl acetate, n-propyl acetate, 1,1-dimethylethyl acetate, methylpropionate , Ethyl propionate, γ-butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone, and the like may be used. Dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc. may be used as the ether solvent, and cyclohexanone may be used as the ketone solvent. have. In addition, ethyl alcohol, isopropyl alcohol, etc. may be used as the alcohol-based solvent, and R-CN (R is a C2 to C20 linear, branched, or cyclic hydrocarbon group, wherein Amides such as nitriles such as dimethylformamide, dioxolanes such as 1,3-dioxolane, sulfolanes such as 1,3-dioxolane, and the like may be used.

The non-aqueous organic solvent may be used alone or in combination of one or more, and the mixing ratio in the case of using one or more mixtures may be appropriately adjusted according to the desired battery performance, which is widely understood by those in the field. Can be.

In addition, in the case of the carbonate-based solvent, it is preferable to use a mixture of cyclic carbonate and chain carbonate. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1:1 to about 1:9, the electrolyte may exhibit excellent performance.

The non-aqueous organic solvent may further include the aromatic hydrocarbon-based organic solvent in the carbonate-based solvent. At this time, the carbonate-based solvent and the aromatic hydrocarbon-based organic solvent may be mixed in a volume ratio of about 1:1 to about 30:1.

As the aromatic hydrocarbon-based organic solvent, an aromatic hydrocarbon-based compound of Formula 1 may be used.

[Formula 1]

In Formula 1, R ₁ to R ₆ are each independently hydrogen, halogen, a C1 to C10 alkyl group, a C1 to C10 haloalkyl group, or a combination thereof.

The aromatic hydrocarbon-based organic solvent is benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene , 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1,2, 4-trichlorobenzene, iodobenzene, 1,2-diaiodobenzene, 1,3-diaiodobenzene, 1,4-diaiodobenzene, 1,2,3-triiodobenzene, 1,2,4 -Triiodobenzene, toluene, fluorotoluene, 1,2-difluorotoluene, 1,3-difluorotoluene, 1,4-difluorotoluene, 1,2,3-trifluorotoluene, 1,2,4-trifluorotoluene, chlorotoluene, 1,2-dichlorotoluene, 1,3-dichlorotoluene, 1,4-dichlorotoluene, 1,2,3-trichlorotoluene, 1,2,4 -Trichlorotoluene, iodotoluene, 1,2-diaiodotoluene, 1,3-diaiodotoluene, 1,4-diaiodotoluene, 1,2,3-triiodotoluene, 1,2,4- Triiodotoluene, xylene, or combinations thereof may be used.

The non-aqueous electrolyte may further include vinylene carbonate or an ethylene carbonate-based compound of Formula 2 in order to improve battery life.

[Formula 2]

In Formula 2, R ₇ and R ₈ are each independently hydrogen, a halogen group, a cyano group (CN), a nitro group (NO ₂ ), or a C1 to C5 fluoroalkyl group, and at least one of _{R 7} and R ₈ Is a halogen group, a cyano group (CN), a nitro group (NO ₂ ), or a C1 to C5 fluoroalkyl group.

Representative examples of the ethylene carbonate-based compound include difluoro ethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, fluoroethylene carbonate, and the like. I can. When the vinylene carbonate or the ethylene carbonate-based compound is further used, the lifespan may be improved by appropriately adjusting the amount of the vinylene carbonate-based compound.

The lithium salt is dissolved in the non-aqueous organic solvent, acts as a source of lithium ions in the battery, enables the operation of a basic lithium secondary battery, and promotes the movement of lithium ions between the positive electrode and the negative electrode. to be. Representative examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiC ₄ F ₉ SO ₃ , LiClO ₄ , LiAlO ₂ , LiAlCl ₄ , LiN(C _x F _2x+1 SO ₂ )(C _y F _{2y +1} SO ₂ ) (where x and y are natural numbers), LiCl, LiI, LiB(C ₂ O ₄ ) ₂ (lithium bis(oxalato) borate; LiBOB) or a combination thereof The concentration of the lithium salt is preferably within the range of 0.1 to 2.0 M. If the concentration of the lithium salt falls within the above range, the electrolyte has an appropriate conductivity and viscosity. It can exhibit excellent electrolyte performance, and lithium ions can move effectively.

The separator separates the negative electrode from the positive electrode and provides a passage for lithium ions to move, and any separator commonly used in a lithium battery may be used. That is, those having low resistance to ion movement of the electrolyte and excellent in the ability to impregnate the electrolyte may be used. For example, as selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, it may be in the form of a non-woven fabric or a woven fabric. For example, polyolefin-based polymer separators such as polyethylene, polypropylene, etc. are mainly used for lithium-ion batteries, and coated separators containing ceramic components or polymer materials may be used to secure heat resistance or mechanical strength, and optionally single-layer or multi-layer Can be used as a structure.

Hereinafter, preferred embodiments of the present invention will be described. However, the following examples are only preferred examples of the present invention, and the present invention is not limited to the following examples.

Manufacturing Example 1

In water containing 0.5% by weight of the polymerization initiator Paramenthane hydroperoxide (PMHP), 61 g of butadiene, 57 g of styrene, and 2 g of acrylic acid were added as monomers, and 10 g of sodium lauryl sulfate was added as an emulsifier to mix them. Then, polymerization was performed at 70° C. for about 5 hours to obtain a composition containing butadiene-styrene-acrylic polymer particles.

The solid content in the composition is 30% by weight, and the number average particle diameter of the polymer particles contained therein is 50 nm (measured value by dynamic light scattering (DLS) equipment).

Example 1

(1) Anode binder raw material (acrylic-styrene-butadiene polymer+sulfur+Zn(BDC)+DCBS+ZnO)

Take 20 g of the composition of Preparation Example 1, sulfur (S ₈ ) 0.2 g, Zn (BDC) (here, BDC = 1,4-Benzenedicarboxylate) 0.4 g, DCBS (N,N-Dicyclohexyl-2-benzothiazolesulfenamide) ) 0.2 g, and 0.7 g of ZnO were added and stirred for 1 hour to obtain a negative electrode binder raw material of Example 1.

(2) cathode

150 g of an aqueous solution of carboxy methyl cellulose as a thickener (solid content: 1.5% by weight) and 1.5 g of acetylene black as a conductive material were mixed and stirred for 1 hour to prepare a conductive material dispersion.

0.5 g of the negative electrode binder material of Example 1 was taken and added to the conductive material dispersion, 150 g of artificial graphite (D50: 20 μm), which is a negative electrode active material, and 20 g of distilled water were added thereto, followed by stirring for 10 minutes. A negative active material slurry of Example 1 was prepared.

A copper foil having a thickness of 20 μm was used as a negative electrode current collector, and the negative active material slurry of Example 1 was coated on one side of the negative electrode current collector using a comma coater (application amount per side: 10.8 mg /cm ² ), hot air drying for 10 minutes in an oven at 80° C., rolling at 25° C. to a total thickness of 90 μm, and vacuum drying at 120° C. to obtain a negative electrode of Example 1.

(3) Li-ion half battery

The negative electrode was used as a working electrode, a lithium metal sheet having a thickness of 150 µm was used as a reference electrode, and a polyethylene separator (thickness: 20 µm, porosity: 40%) was inserted between the working electrode and the reference electrode. After putting into a container and injecting an electrolyte, for other matters, a lithium secondary battery was manufactured in the form of a 2032 half-cell according to a conventional manufacturing method.

As the electrolyte, a mixed solvent (EC:PC:DEC=3:2:5) of ethylene carbonate (EC), propylene carbonate (PC) and diethyl carbonate (DEC) _{LiPF 6} was dissolved in a weight ratio) to a concentration of 1.3M, and 10% by weight of an additive fluoroethylene carbonate (FEC) was added to the total weight of the electrolyte.

Example 2

(1) Anode binder raw material (acrylic-styrene-butadiene polymer+sulfur+Zn(BDC)+DCBS+ZnO)

20 g of the composition of Preparation Example 1 was taken, and _{0.2 g of sulfur (S 8} ), 0.4 g of Zn (BDC), 0.1 g of DCBS, and 0.7 g of ZnO were added thereto, followed by stirring for 1 hour. A negative electrode binder raw material was obtained.

(2) Preparation of negative electrode and lithium ion half battery

Instead of the binder composition of Example 1, the negative electrode binder material of Example 2 was used, and the remainder of the negative electrode and lithium ion half battery of Example 2 were prepared in the same manner as in Example 1.

Example 3

(1) Anode binder raw material (acrylic-styrene-butadiene polymer+sulfur+Zn(BDC)+DCBS+ZnO)

20 g of the composition of Preparation Example 1 was taken, and _{0.2 g of sulfur (S 8} ), 0.8 g of Zn (BDC), 0.2 g of DCBS, and 0.7 g of ZnO were added thereto, followed by stirring for 1 hour. A negative electrode binder raw material was obtained.

(2) Preparation of negative electrode and lithium ion half battery

In place of the binder composition of Example 1, the negative electrode binder raw material of Example 3 was used, and the remainder of the negative electrode and lithium ion half battery of Example 3 were prepared in the same manner as in Example 1.

Example 4

(1) Anode binder raw material (acrylic-styrene-butadiene polymer + sulfur + Zn (BDC))

20 g of the composition of Preparation Example 1 was taken, _{0.2 g of sulfur (S 8} ), and 0.4 g of Zn (BDC) were added thereto, followed by stirring for 1 hour to obtain a negative electrode binder raw material of Example 4.

(2) Preparation of negative electrode and lithium ion half battery

Instead of the binder composition of Example 1, the negative electrode binder material of Example 4 was used, and the rest were the same as those of Example 1, to prepare a negative electrode and a lithium ion half battery of Example 4.

Comparative Example 1

(1) anode binder raw material ( Acrylic-styrene-butadiene polymer alone)

The composition of Preparation Example 1 itself was used as the binder composition of Comparative Example 1.

(2) Preparation of negative electrode and lithium ion half battery

Instead of the binder composition of Example 1, the negative electrode binder raw material of Comparative Example 1 was used, and the rest were the same as those of Example 1, to prepare a negative electrode and a lithium ion half battery of Comparative Example 1.

Comparative Example 2

(1) Preparation of negative electrode binder raw material ( Acrylic-styrene-butadiene polymer + sulfur + DCBS)

20 g of the composition of Preparation Example 1 was taken, _{0.2 g of sulfur (S 8} ) and 0.2 g of DCBS were added thereto, followed by stirring for 1 hour, to obtain a binder composition of Comparative Example 2.

(2) Preparation of negative electrode and lithium ion half battery

Instead of the binder composition of Example 1, the binder composition of Comparative Example 2 was used, and the rest were the same as those of Example 1 to prepare a negative electrode and a lithium ion half battery of Comparative Example 2.

Comparative Example 3

(1) Preparation of negative electrode binder raw material (acrylic-styrene-butadiene polymer + sulfur + ZnO)

20 g of the composition of Preparation Example 1 was taken, _{0.2 g of sulfur (S 8} ) and 0.7 g of ZnO were added thereto, followed by stirring for 1 hour to obtain a binder composition of Comparative Example 3.

(2) Preparation of negative electrode and lithium ion half battery

Instead of the binder composition of Example 1, the binder composition of Comparative Example 3 was used, and the rest were the same as those of Example 1 to prepare a negative electrode and a lithium ion half battery of Comparative Example 3.

Experimental Example 1: Evaluation of negative electrode binder composition

In Examples 1 to 4 and Comparative Examples 1 to 3, in the process of applying heat after applying a negative electrode active material slurry including a negative electrode binder raw material, a conductive material dispersion, a negative electrode active material, and an additional solvent to a negative electrode current collector, the At the same time as the solvent in the anode active material slurry is removed to form the anode active material layer, a vulcanization reaction of the material for the anode binder occurs to convert it into a binder. In such a manufacturing process, it is impossible to separate the binder (ie, vulcanized styrene-butadiene-based copolymer) from each of the final negative electrodes of Examples 1 to 4 and Comparative Examples 1 to 3.

However, in this experimental example, for evaluation, the negative electrode binder raw materials of Examples 1 to 4 and Comparative Examples 1 to 3 were dried in an oven at 80° C. for 24 hours to prepare a negative electrode binder composition.

The negative electrode binder compositions of Examples 1 to 4 and Comparative Examples 1 to 3 thus prepared were evaluated under the following conditions, respectively, and the results are recorded in Table 1 below.

Gel content in the binder composition: First, the binder composition was dried at room temperature for 24 hours, and then dried at 80° C. for 24 hours to obtain a film-type binder composition, and the binder film was cut into very small pellets, and then 0.5 Take g of the binder composition and measure the correct weight. (Ma)

Then, the weight-measured binder particles were immersed in about 50 g of tetrahydrofuran (THF) at room temperature for 24 hours, filtered through a 200 mesh sieve, dried at 80° C. for 48 hours, and then accurately weighed. I did. (Mb)

The gel content was calculated through Equation 1 below.

[Equation 1]

Gel content (%) = M _b /M _a * 100

division	Gel content
Example 1	82.7%
Example 2	77.6%
Example 3	77.9%
Example 4	76.8%
Comparative Example 1	71.1%
Comparative Example 2	74.4%
Comparative Example 3	74.6%

In Table 1, compared to Comparative Examples 1 to 3, it can be seen that the gel content in the negative electrode binder compositions of Examples 1 to 4 is higher. Here, the gel content refers to the degree of crosslinking of the copolymer. , Compared to Comparative Examples 1 to 3, it can be seen that the degree of vulcanization (crosslinking) of the vulcanized styrene-butadiene-based copolymer in the negative electrode binder compositions of Examples 1 to 4 is higher.

These results are related to the participation in the vulcanization reaction of the metal-organic skeleton (MOF). As mentioned above, while the stabilized metal ions inside the metal-organic framework (MOF) participate in the vulcanization reaction as a kind of catalyst, the structure of the metal-organic framework (MOF) partially changes, resulting in complexation with the styrene-butadiene-based copolymer. Can be. As a result of the higher catalytic efficiency and more effective vulcanization reaction in the complexed state with the styrene-butadiene-based copolymer, it is inferred that the degree of vulcanization (crosslinking) of the vulcanized styrene-butadiene-based copolymer is higher.

Experimental Example 2: Evaluation of negative electrode and lithium secondary battery

The negative electrodes and lithium secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 3 were evaluated under the following conditions, respectively, and the results are recorded in Table 2 below.

Adhesion of negative electrode: When the negative electrode active material layer of each negative electrode is adhered to a glass substrate in a constant temperature chamber at 25° C., and the negative electrode is pulled at a peel rate of 5 mm/min and a peel angle of 180°, from the glass substrate. The force by which the negative active material layer of the negative electrode is peeled was measured.

Volume resistivity of the negative electrode active material layer (coating layer) : Using an AC resistance measuring device (manufacturer: Hioki), adjust SOC100 to 4.25V/0.05C cu-off, and then the volume resistivity of each negative electrode at 1KHz (ρv = V /I x pi r ² /h) was measured. .

Discharge characteristics of the battery : In a constant temperature chamber at 25°C, discharge each of the lithium ion half cells 3 times in CC/CV mode from 1.5V to 5mV at 1 C, and then to 1 C in CC mode. After discharging, the discharge capacity of the CC section compared to the total discharge capacity was converted into a percentage according to Equation 2 below.

[Equation 2]

=100%*{(1.0C CC)})/{(1.0C CC/CV)}

In addition, in a constant temperature chamber at 25°C, after discharging each of the lithium ion half cells 3 times in CC/CV mode from 1.5V to 5mV at 0.5 C, discharged at 0.5 C in CC mode, According to Equation 2 below, the discharge capacity of the CC section compared to the total discharge capacity was converted into a percentage.

[Equation 3]

=100%*{(0.5C CC)})/{(0.5C CC/CV)}

Anode expansion rate : After evaluating the discharge characteristics, each battery was disassembled to recover the anode. Each recovered negative electrode was washed with a DMC (dimethyl carbonate) solvent and dried within a few minutes using an air blower at room temperature, and then the thickness was measured. Accordingly, the measured thickness was substituted into the following equation to calculate the expansion rate of the negative electrode.

[Cathode expansion rate]

= 100%*{(discharge cathode thickness of battery)-(rolled anode thickness)}/{(rolled anode thickness)-(copper foil thickness)}

Here, the definition of each term is as follows:

Discharge negative electrode thickness of battery = negative electrode thickness during one discharge of lithium ion battery

Rolled negative electrode thickness = thickness of negative electrode before assembly of lithium ion battery

Thickness of copper foil = thickness of negative electrode current collector in rolled electrode

division	Cathode adhesion	Volume resistivity of negative active material layer	(0.5C CC)}) /((0.5C CC/CV)	(1.0C CC)}) /((1.0C CC/CV)	Cathode expansion rate
Example 1	23.9 gf/cm	46.3 mΩ·cm	76.4%	44.3%	26.3%
Example 2	20.6 gf/cm	51.2 mΩ·cm	73.1%	41.1%	28.7%
Example 3	21.7 gf/cm	50.1 mΩ·cm	74.1%	41.5%	27.6%
Example 4	18.8 gf/cm	49.8 mΩ·cm	73.1%	42.0%	29.9%
Comparative Example 1	16.8 gf/cm	63.1 mΩ·cm	71.9%	33.1%	30.9%
Comparative Example 2	19.7 gf/cm	52.7 mΩ·cm	72.6%	38.1%	29.7%
Comparative Example 3	20.1 gf/cm	51.5 mΩ·cm	72.6%	40.6%	29.2%

In Table 2, when comparing Comparative Examples 1 to 3, when a raw material containing an acrylic-styrene-butadiene polymer and a sulfur molecule is cured while being applied to a negative electrode current collector (Comparative Examples 2 and 3), the curing It seems that the bonding strength and durability of water were improved than that of the acrylic-styrene-butadiene polymer itself (Comparative Example 1), and the side reaction with the electrolyte was suppressed, and the resistance was lowered.

Compared to Comparative Examples 2 and 3, Examples 1 to 4 showed a result of further lowering the volume resistivity of the negative active material layer, in particular, and the result improved as described above is believed to be due to Zn (DBC).

Specifically, the metal-organic skeleton has its own pores due to a coordination bond between a metal and an organic material, and the size and shape of the pores vary according to the type of the metal-organic skeleton. Due to the presence or absence of the pores in the vulcanization reaction, unreacted monomers enter and exit the pores during the vulcanization (crosslinking) reaction, so that the polymer-polymer crosslinking reaction can be more effectively performed than the polymer-unreacted monomer reaction.

Here, unlike general vulcanization accelerators such as DCBS and ZnO that effectively cause crosslinking in terms of reaction rate, the metal-organic skeleton is evaluated to have outstanding properties by selectively promoting crosslinking between polymer chains.

Furthermore, unlike general vulcanization accelerators such as DCBS and ZnO, which only accelerate the vulcanization reaction and have no structural effect, the metal-organic skeleton has its own pores, so the mobility of lithium ions in the negative electrode including them is As a result, it can contribute to an increase in the CC (Constant Current) section compared to the capacity of the lithium secondary battery while lowering the internal resistance of the negative electrode.

Therefore, each of the negative electrode binder raw materials of Examples 1 to 4 contained Zn (DBC) as a vulcanization accelerator, compared to Comparative Example 2 containing only DSBS as a vulcanization accelerator and Comparative Example 3 containing only ZnO. It is possible to more effectively promote the vulcanization reaction of the coalescence and sulfur molecules (S ₈ ), and significantly improve the performance of the negative electrode and lithium secondary battery to which the vulcanization reaction product is applied.

On the other hand, Examples 1 to 4 commonly exhibit the effect of lowering the resistance of the negative electrode, and in particular, Examples 1 to 3 showed higher adhesion to the negative electrode and a lower expansion rate than that of Example 4, and this result is a result of DSBS as a vulcanization accelerator. And ZnO is considered to be due to the additional inclusion.

As mentioned above, since ZnDBC performs its special function as well as a vulcanization accelerating role, it shows the effect of lowering the resistance of the negative electrode in Examples 1 to 4.

However, the higher cathode adhesion and lower expansion rates in Examples 1 to 3 than in Example 4 are that when ZnDBC is used alone as a vulcanization accelerator without the aid of other vulcanization accelerators such as DSBS and ZnO, the degree of vulcanization (crosslinking) is reduced. There seems to be a limit to the height.

In this regard, even if ZnDBC is used alone as a vulcanization accelerator, the effect of lowering the resistance of the negative electrode can be obtained, but if a further improved negative electrode in terms of adhesion and expansion is desired, other vulcanization accelerators such as DSBS and ZnO can be added There will be.

The present invention is not limited to the above embodiments, but may be manufactured in a variety of different forms, and those of ordinary skill in the art to which the present invention pertains, other specific forms without changing the technical spirit or essential features of the present invention. It will be appreciated that it can be implemented with.

For example, even if the type and amount of each component are changed within the scope of the above-described exemplary embodiment, the same or higher effects as those of the first to fourth exemplary embodiments may be implemented.

Therefore, it should be understood that the embodiments described above are illustrative and non-limiting in all respects.

Claims (19)

1. A vulcanization accelerator including a metal-organic framework (MOF);

   Styrene-butadiene-based copolymer; And

   Containing a sulfur molecule (S _{8 ),}

   A material for negative electrode binders for lithium secondary batteries.
2. The method of claim 1,

   The metal-organic skeleton,

   Zn(1,4-Benzenedicarboxylate)(BDC), Zn ₄ O(4,4′,4″-[benzene-1,3,5-triyl-tris(ethyne-2,1-diyl)]tribenzoate)(BPDC ² =biphenyl-4,4′-dicarboxylate) (BTE)(BPDC), Zn ₄ O(1,3,5-benzenetribenzoate) (BTB), Zn ₄ O(4,4′,4″-[benzene-1 ,3,5-triyl-tris(benzene-4,1-diyl)]tribenzoate) (BBC), or a mixture of two or more thereof,

   A material for negative electrode binders for lithium secondary batteries.
3. The method of claim 1,

   The styrene-butadiene-based copolymer,

   Acrylic-styrene-butadiene copolymer, styrene-butadiene polymer, or a mixture thereof,

   A material for negative electrode binders for lithium secondary batteries.
4. The method of claim 1,

   Based on 100 parts by weight of the styrene-butadiene-based copolymer,

   It contains 0.5 to 3 parts by weight of the sulfur molecule,

   It contains 0.5 to 2 parts by weight of the metal-organic skeleton,

   A material for negative electrode binders for lithium secondary batteries.
5. The method of claim 1,

   The vulcanization accelerator,

   N,N-dicyclohexyl-2-benzothiazolesulfenamide (N,N-Dicyclohexyl-2-benzothiazolesulfenamide, DCBS), zinc oxide (ZnO), or a mixture thereof,

   A material for negative electrode binders for lithium secondary batteries.
6. The method of claim 5,

   Based on 100 parts by weight of the styrene-butadiene-based copolymer,

   0.5 to 2 parts by weight of the N,N-dicyclohexyl-2-benzothiazolesulfenamide,

   It contains 0.5 to 5 parts by weight of the zinc oxide,

   A material for negative electrode binders for lithium secondary batteries.
7. The method of claim 1,

   Paramenthane hydroperoxide (PMHP), potassium persulfate (Potassium persulfate), sodium persulfate (Sodium persulfate), ammonium persulfate (Ammonium persulfate) and sodium bisulfate (Sodium bisulfate) selected from the group containing Which further comprises at least one polymerization initiator,

   A material for negative electrode binders for lithium secondary batteries.
8. The method of claim 1,

   It further comprises water as a solvent,

   A material for negative electrode binders for lithium secondary batteries.
9. The method of claim 1,

   Sodium lauryl sulfate (SLS), sodium laureth sulfate (Sodium Laureth Sulfate, SLES) and ammonium lauryl sulfate (Ammonium Lauryl Sulfate, ALS) further comprising at least one emulsifier selected from the group containing That,

   A material for negative electrode binders for lithium secondary batteries.
10. A styrene-butadiene-based copolymer vulcanized in the presence of a vulcanization accelerator including a metal-organic framework (MOF); containing, a negative electrode binder composition for a lithium secondary battery.
11. The method of claim 10,

    The negative electrode binder composition has a gel content of 80% or more calculated by Equation 1 below,

    Anode binder composition for lithium secondary battery:

    [Equation 1]

    Gel content (%) = M _b /M _a * 100

    In Equation 1,

    M _a is the negative electrode binder composition dried at room temperature for 24 hours and then dried at 80° C. for 24 hours to obtain a film-type binder composition, and the binder film was cut into a very pellet, and 0.5 g of the binder composition was prepared. It is the weight taken and measured,

    M _b is the negative electrode binder composition weighed by immersion in 50 g of THF (Tetrahydrofuran) for 24 hours or more, filtering through 200 Mesh, and drying the mesh and the negative electrode binder remaining in the mesh at 80° C. for 48 hours. It is the weight of the copolymer remaining in the mesh.
12. In the presence of a vulcanization accelerator including a metal-organic framework (MOF), the step of vulcanizing a styrene-butadiene-based copolymer and a sulfur molecule (S ₈ ); containing, a negative electrode binder composition for a lithium secondary battery Manufacturing method.
13. The method of claim 12,

    The vulcanization reaction,

    That is carried out in a temperature range of 70 to 90 ℃,

    Method for producing a negative electrode binder composition for a lithium secondary battery.
14. The method of claim 12,

    The vulcanization reaction,

    Which is carried out for 1 to 60 minutes,

    Method for producing a negative electrode binder composition for a lithium secondary battery.
15. The method of claim 12,

    The vulcanization reaction,

    It is to be carried out in a state where the negative electrode binder raw material is applied to the negative electrode current collector

    Method for producing a negative electrode binder composition for a lithium secondary battery.
16. The method of claim 12,

    Before the vulcanization reaction,

    Preparing a negative electrode active material slurry including the negative electrode binder raw material, a conductive material, a binder, and a solvent; And

    Including; coating the negative electrode active material slurry on one or both surfaces of a negative electrode current collector

    Method for producing a negative electrode binder composition for a lithium secondary battery.
17. The method of claim 12,

    In 100% by weight of the negative active material slurry, the content of the negative electrode binder raw material is 0.1 to 0.5% by weight,

    Method for producing a negative electrode binder composition for a lithium secondary battery.
18. Negative electrode current collector; And

    A negative electrode active material layer including a styrene-butadiene-based copolymer, a negative electrode active material, and a conductive material, which is located on the negative electrode current collector and vulcanized in the presence of a vulcanization accelerator including a metal-organic framework (MOF) It includes,

    Anode for lithium secondary batteries.
19. The cathode of claim 18;

    Electrolytes; And

    Including an anode,

    Lithium secondary battery.