KR102314898B1 - Aqueous polyamic acid composition - Google Patents

Abstract

The present application relates to a polyamic acid aqueous solution composition, a binder resin composition for an electrode, an electrode active material composition including the same, and an electrode including the same, applicable for an electrode of a lithium secondary battery, capable of water-based polymerization rather than an organic solvent, and excellent Provided are a polyamic acid aqueous solution composition capable of realizing high capacity retention with mechanical strength and binding force, a binder resin composition for an electrode, an electrode active material composition comprising the same, and an electrode including the same.

Description

Polyamic acid aqueous solution composition {AQUEOUS POLYAMIC ACID COMPOSITION}

The present application relates to a polyamic acid aqueous solution composition, a binder resin composition for an electrode, an electrode active material composition including the same, and an electrode including the same.

Lithium secondary batteries are mainly used in information and communication devices such as mobile phones and laptops, but recently, their use is expanding not only in these information and communication devices, but also in other industries such as electric vehicles.

As the performance of the currently commercialized graphite anode-lithium transition metal oxide anode-based lithium ion secondary battery approaches the theoretical limit, in order to develop a next-generation high-capacity secondary battery applicable to energy storage systems and electric vehicles, various alloys (alloys) ) materials are being proposed as new negative electrode active material candidates.

Among lithium-reactive alloys, materials with high capacity are Si (4,100 mAh/g), Ge (1,600 mAh/g), and Sn (990 mAh/g) in order. is being actively pursued. However, when the silicon negative electrode reacts with lithium ions to form alloy and dealloy, the capacity rapidly decreases due to the phenomenon of peeling from the current collector due to pulverization of particles due to volume expansion of more than 400%. There is a problem of reduction. In order to solve this problem, a method of minimizing the absolute value of volume expansion by reducing the size of the particles, a method of coating a conductor layer on the particles to serve as a buffer during volume expansion and at the same time as a method to minimize capacity reduction and volume expansion even when fine pulverization occurs, etc. , various methods for controlling the shape of the anode active material have been tried. However, considering the technical perfection and business competitiveness of the technology, the above methods have too many limitations to be overcome for commercialization in products, which is an obstacle to commercialization.

As a practical method for the practical commercialization of Si anodes, efforts to improve the performance of silicon anode active materials by using polymer binder materials have been reported in domestic and foreign journals and patents.

The polymer binder not only can maintain the bond between the active material and the conductive agent in the anode, but also plays various roles such as adhesion to the current collector and the conduction path of lithium ions inside the electrode, so the performance of the silicon anode is poor. It is greatly influenced by the physical properties of the polymer binder, such as the binding force between the polymer binder and the surface of the active material, the rigidity of the polymer binder chain itself, and the adhesive strength between the electrode and the current collector.

However, binders such as polyvinylidene fluoride (PVdF), carboxymethyl cellulose (CMC), and polyacrylic acid (PAA) currently applied to silicon anodes have poor heat resistance and are vulnerable to overheating due to prolonged use when applied to batteries. This is a necessary situation.

In the case of polyimide (PI), when applied as a silicone-based negative electrode binder thanks to its excellent heat resistance, mechanical strength, and binding power, it shows superior performance than existing PVdF, CMC, PAA, etc., even though it has a basic linear polymer structure. There is a problem in that it is difficult to directly apply to a commercial water-based anode manufacturing process due to its insolubility. In addition, the initial side reaction and initial efficiency of the lithium battery are problematic.

Accordingly, the present application aims to provide a novel binder material having excellent mechanical strength and binding force, which can be directly used in an already commercialized aqueous anode manufacturing process by synthesizing a water-soluble polyamic acid of various structures and applying it as a silicone-based negative electrode binder.

The present application is applicable for electrodes of lithium secondary batteries, water-based polymerization possible, not organic solvents, polyamic acid aqueous solution composition capable of realizing high capacity retention with excellent mechanical strength and binding force, binder resin composition for electrodes, and the same It provides an electrode active material composition and an electrode comprising the same.

The present application relates to a polyamic acid aqueous solution composition. As the aqueous solution composition will be described later, water is used as a solvent without substantially including an organic solvent, and during repeated charging and discharging of a lithium secondary battery, desorption from the current collector due to contraction and expansion of the anode active material layer and Provided is a binder resin composition capable of maximizing the discharge capacity and charging/discharging efficiency of a lithium secondary battery by suppressing interfacial desorption between the anode active material layers and minimizing the shortening of the charge/discharge cycle life.

An exemplary polyamic acid aqueous solution composition includes a polyamic acid including a diamine monomer and a dianhydride monomer as polymerized units. The polyamic acid may have a siloxane group at the terminal. The present application can improve adhesion through the polyamic acid in which the siloxane group is introduced at the terminal, and realize excellent cycle characteristics.

In one example, the siloxane group may include at least a reactive functional group in the molecular structure. In one example, the reactive functional group may be an amino alkyl group, but is not limited thereto. In addition, the reactive functional group may include an alkyl group having 1 to 4 carbon atoms. The number of carbon atoms of the alkyl group may be, for example, 2 or more or 3 or more, and the upper limit may be 3 or less or 2 or less. The reactive functional group may be a functional group having reactivity with the aforementioned dianhydride monomer. In one example, in the polyamic acid of the present application, a dianhydride monomer is positioned at the end, and the dianhydride at the end reacts with the reactive functional group, and thus, a siloxane group may be positioned at the end of the polyamic acid. In addition, the siloxane group may include at least an alkoxy group in the molecular structure. The alkoxy group may have 1 to 4 carbon atoms. The number of carbon atoms of the alkoxy group may be, for example, 2 or more or 3 or more, and the upper limit may be 3 or less or 2 or less. In the present application, the degree of hydrophobicity can be controlled by controlling the number of carbon atoms, and through this, an appropriate level is introduced at the terminal and an appropriate adhesive force of the aqueous polyamic acid is realized. In one example, the siloxane group is 3-aminomethyltriethoxysilane, 3-aminopropyltriethoxysilane (APTES) aminopropyltrimethoxysilane ((3-Aminopropyl)trimethoxy-silane (APTMS), 3-aminoethyl triethoxysilane, 3-aminobutyltriethoxysilane, 3-aminopentyltriethoxysilane, 3-aminohexyltriethoxysilane or 3-aminoheptyltriethoxysilane. In the present application, by introducing the siloxane group having the specific structure at the end of the polyamic acid, water-based polymerization is possible and excellent adhesion can be realized.

In an embodiment of the present application, the polyamic acid aqueous solution composition may further include a silane coupling agent. The composition may further include a silane coupling agent as an additive separately from the siloxane group introduced at the end of the polyamic acid. The silane coupling agent may include, for example, an amino alkyl group or an alkoxy group in the molecular structure. The number of carbon atoms of the amino alkyl group or the alkoxy group may be the same as described above. For example, the alkyl group among the amino alkyl group may have 1 to 4 carbon atoms. The number of carbon atoms of the alkyl group may be, for example, 2 or more or 3 or more, and the upper limit may be 3 or less or 2 or less. In addition, the alkoxy group may have 1 to 4 carbon atoms. The number of carbon atoms of the alkoxy group may be, for example, 2 or more or 3 or more, and the upper limit may be 3 or less or 2 or less. The silane coupling agent may be at least one selected from the group consisting of epoxy-based, amino-based and thiol-based compounds. Specifically, the epoxy-based compound may include glycidoxypropyl trimethoxysilane (GPTMS), and the amino-based compound is 3-aminomethyltriethoxysilane, 3-aminopropyltriethoxy Silane (APTES) Aminopropyltrimethoxysilane ((3-Aminopropyl)trimethoxy-silane: APTMS), 3-Aminoethyltriethoxysilane, 3-Aminobutyltriethoxysilane, 3-Aminopentyltriethoxysilane, 3 -Aminohexyltriethoxysilane or 3-aminoheptyltriethoxysilane may be included, and the thiol-based compound may include mercapto-propyl-trimethoxysilane (MPTMS), but these It is not limited to The silane coupling agent may be included in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the polyamic acid. The lower limit of the content may be, for example, 0.5 parts by weight or more, 0.8 parts by weight or more, 0.9 parts by weight or more, 1 part by weight or more, 3 parts by weight or more, or 5 parts by weight or more, and the upper limit is, for example, 8 parts by weight or more. parts by weight or less, 6 parts by weight or less, 5 parts by weight or less, 4 parts by weight or less, 3 parts by weight or less, 2.5 parts by weight or less, 2.0 parts by weight or less, 1.8 parts by weight or less, 1.5 parts by weight or less, or 1.3 parts by weight or less. The present application provides a polyamic acid aqueous solution composition that implements a high capacity retention rate through excellent mechanical strength and binding force by including the silane coupling agent in addition to the polyamic acid having a siloxane group at the terminal thereof.

In one example, the polyamic acid aqueous solution composition may include an aqueous catalyst in the range of 0.5 to 1.5 times equivalent to 1 equivalent of carboxyl groups in the polyamic acid. In one example, the aqueous catalyst may be 0.55 fold equivalent or more, 0.6 fold equivalent or more, 0.7 fold equivalent or more, 0.8 fold equivalent or more, 0.83 fold equivalent or more, or 0.93 fold equivalent or more with respect to 1 equivalent of carboxyl group in the polyamic acid, Further, the upper limit may be 1.4 fold equivalent or less, 1.3 fold equivalent or less, 1.2 fold equivalent or less, 1.15 fold equivalent or less, or 1.05 fold equivalent or less.

In addition, in an embodiment of the present application, the polyamic acid aqueous solution composition may further include a metal ion in the range of 0.01 to 1.25 equivalents based on 1 equivalent of carboxyl groups in the polyamic acid. For example, the metal ion may be derived from lithium hydroxide. In an embodiment, the metal ion is 0.01-fold equivalent or more, 0.03-fold equivalent or more, 0.05-fold equivalent or more, 0.1-fold equivalent or more, 0.2-fold equivalent or more, 0.3-fold equivalent or more, 0.4-fold equivalent with respect to 1 equivalent of carboxyl group in the polyamic acid or more, or 0.45 fold equivalent or more, and the upper limit is 1.1 fold equivalent or less, 1.0 fold equivalent or less, 0.9 fold equivalent or less, 0.8 fold equivalent or less, 0.7 fold equivalent or less, 0.6 fold equivalent or less, 0.45 fold equivalent or less, 0.3 It may be equal to or less than twice equivalent or less than or equal to 0.2 times equivalent.

In the case of a lithium secondary battery, an irreversible reaction in which the binder resin and lithium ions are combined may occur during the first charging process, and this reaction consumes lithium ions, resulting in a problem in that initial efficiency is reduced, such as capacity degradation. The present application enables the polymerization of polyamic acid directly in water without an organic solvent by controlling the content of metal ions or water-based catalyst, while reducing the initial side reaction when applied as an electrode binder and preventing the problem of reduced initial efficiency. .

In the present specification, the "equivalent to the carboxyl group in the polyamic acid" defining the amount of the aqueous catalyst or metal ion refers to the aqueous catalyst used for one carboxyl group in the polyamic acid (for example, an imidazole-based compound or amine to be described later) compound) or the number of metal ions (number of moles).

In one example, the ratio (L/I) of the equivalent (L) of the metal ion to the equivalent (I) of the aqueous catalyst may be in the range of 0.01 to 0.8. The equivalent (I) of the aqueous catalyst is the equivalent ratio of the aqueous catalyst to 1 equivalent of the carboxyl group described above, and the equivalent (L) of the metal ion is the equivalent ratio of the metal ion to 1 equivalent of the aforementioned carboxyl group. The lower limit of the ratio (L/I) may be 0.02 or more, 0.03 or more, 0.05 or more, 0.1 or more, 0.13 or more, 0.2 or more, and the upper limit is 0.7 or less, 0.6 or less, 0.5 or less, 0.45 or less, 0.4 or less, 0.3 or less, 0.28 or less or 0.23 or less. In addition, in an embodiment of the present application, the polyamic acid aqueous solution composition may include a metal ion and an aqueous catalyst within a range of 1.0 to 2.0 times based on 1 equivalent of a carboxyl group in the polyamic acid. That is, the total amount of the metal ion and the aqueous catalyst may be in the range of 2.0 to 3.5 times based on 1 equivalent of the carboxyl group, and the lower limit thereof is 1.01 or more, 1.02 or more, 1.03 or more. It may be 1.1 or more, 1.2 or more, or 1.23 or more, and the upper limit thereof may be 1.9 or less, 1.8 or less, 1.7 or less, 1.6 or less, 1.5 or less, 1.4 or less, or 1.3 or less. The present application includes the aqueous catalyst and the metal ion together, but by adjusting the content ratio of the two materials and/or the total amount of the two materials to the above ranges, as well as excellent mechanical strength and binding power, as well as reducing the initial side reaction of the lithium battery and It prevents a decrease in initial efficiency, and also enables polymerization in water without an organic solvent during polymerization of the polyamic acid.

In an embodiment of the present application, the diamine monomer may include a diamine monomer having at least one carboxyl group. The monomer having a carboxyl group may be included, for example, in an amount of 5 to 45 mol% based on the total number of moles of the total diamine monomer. The content range may have a lower limit of, for example, 8 mol%, 10 mol%, 12 mol%, 15 mol%, 18 mol%, 22 mol%, 25 mol%, 28 mol% or more, and the upper limit thereof is 43 mol% or more. mol%, 40 mol%, 38 mol%, 35 mol%, or 32 mol%.

In addition, in an embodiment of the present application, the diamine monomer may include a diamine monomer having at least one or more amide bonds. The monomer having the amide bond may be included, for example, in the range of 5 to 45 mol% based on the total number of moles of the total diamine monomer. The content range may have a lower limit of, for example, 8 mol%, 10 mol%, 12 mol%, 15 mol%, 18 mol%, 22 mol%, 25 mol%, 28 mol% or more, and the upper limit thereof is 43 mol% or more. mol%, 40 mol%, 38 mol%, 35 mol%, or 32 mol%.

The present application provides a composition that improves the performance of a binder in aqueous polymerization by controlling the type and content of the diamine monomer and is applied for a secondary battery electrode to realize excellent binding force and mechanical strength. The diamine monomer having a carboxyl group and the diamine monomer having an amide bond may each independently include at least one of the two monomers or include both monomers together.

In one example, the aqueous catalyst included in the polyamic acid aqueous solution composition of the present application may be dissolved in an aqueous solvent. In the present specification, the water-based catalyst may be used as long as it is a catalyst capable of water-based polymerization, and may include, for example, an imidazole-based compound or an amine-based compound, and in embodiments, may include an alcohol amine compound. The imidazole-based compound may include at least one or more or 2 or more and 10 or less alkyl groups, and the alkyl group may be an alkyl group having 1 to 5 carbon atoms, and the nitrogen of the imidazole and the alkyl group may be connected. can Also, the alcohol amine compound may be a tertiary amine compound. Specific types of the aqueous catalyst are not particularly limited, and for example, dimethylaminoethanol, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, and 4-ethyl-2-methylimidazole. or 1-methyl-4-ethylimidazole. In the present application, by using the catalyst, it is possible to effectively prepare a polyamic acid aqueous solution composition through solubility in water. In the present application, the polyamic acid aqueous solution composition may also include metal ions. The metal ion may be, for example, a metal ion of an alkali metal, and in an embodiment, may be a lithium ion or a sodium ion, but is not limited thereto.

In an embodiment of the present application, hydrogen of a carboxyl group in the polyamic acid may be substituted with a metal ion. The metal ion may be derived from a metal salt. The metal salt is, for example, LiOH, Li ₂ CO ₃ , LiAlH ₄ , Li ₂ SO ₄ , LiNO ₃ , LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , _{LiCF 3 CO 2, LiAsF 6,} LiSbF 6, LiAlCl 4, CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2) 2 NLi, lithium chloro borate, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate or An imide may be used, but is not limited thereto. In the present application, a metal salt may be added to the aqueous solution composition, and a metal ion of the metal salt may be substituted with the aforementioned carboxyl group. The present application can implement excellent electrochemical performance through the specific composition. In one example, as the polyamic acid aqueous solution composition substituted with metal ions through a metal salt is applied as an electrode binder, it has an effect of suppressing an initial side reaction, thereby preventing a decrease in initial efficiency.

As described above, the polyamic acid composition of the present application is an aqueous polymerization composition, and may contain substantially no organic solvent or less than 5% by weight of organic solvent. The water-based polymerizable polyamic acid composition may be advantageous from an environmental point of view.

In the present specification, the terms polyamic acid composition, polyamic acid solution, polyamic acid aqueous solution composition, and polyimide precursor composition may be used as the same meaning.

The dianhydride monomer that can be used in the preparation of the polyamic acid solution may be an aromatic tetracarboxylic dianhydride, and the aromatic tetracarboxylic dianhydride is pyromellitic dianhydride (or PMDA), 3,3 ',4,4'-biphenyltetracarboxylic dianhydride (or BPDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride (or a-BPDA), oxydiphthalic dianhydride (or ODPA), diphenylsulfone-3,4,3',4'-tetracarboxylic dianhydride (or DSDA), bis(3,4-dicarboxyphenyl)sulfide dianhydride, 2 ,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 2,3,3',4'-benzophenonetetracarboxyl ric dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride (or BTDA), bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, p-phenylenebis (trimellitic monoester acid anhydride), p-biphenylenebis (trimellitic monoester acid anhydride), m-terphenyl-3,4,3',4'-tetracarboxylic dianhydride, p-terphenyl-3,4,3',4'-tetracarboxylic dianhydride, 1,3- Bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy) ) biphenyl dianhydride, 2,2-bis [(3,4-dicarboxyphenoxy) phenyl] propane dianhydride (BPADA), 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1 ,4,5,8-naphthalenetetracarboxylic dianhydride, 4,4'-(2,2-hexafluoroisopropylidene)diphthalic acid dianhydride, and the like.

The dianhydride monomer may be used alone or in combination of two or more, if necessary, but in the present application, in consideration of the above-described bond dissociation energy, for example, pyromellitic dianhydride (PMDA), 3, 3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) or 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA) can

In addition, the diamine monomer that can be used for preparing the polyamic acid solution is an aromatic diamine, and may be classified as follows.

1) 1,4-diaminobenzene (or paraphenylenediamine, PDA), 1,3-diaminobenzene, 2,4-diaminotoluene, 2,6-diaminotoluene, 3,5-diaminobenzo Diamines having one benzene nucleus in structure, such as acid acid (or DABA), and the like, having a relatively rigid structure;

2) 4,4'-diaminodiphenyl ether (or oxydianiline, ODA), diaminodiphenyl ether such as 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane (methylenediamine), 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl) ) -4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-dicarboxy-4,4'-diaminodiphenylmethane , 3,3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane, bis(4-aminophenyl)sulfide, 4,4'-diaminobenzanilide, 3,3' -dichlorobenzidine, 3,3'-dimethylbenzidine (or o-tolidine), 2,2'-dimethylbenzidine (or m-tolidine), 3,3'-dimethoxybenzidine, 2,2'-dimethoxy Benzidine, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4' -diaminodiphenylsulfide, 4,4'-diaminodiphenylsulfide, 3,3'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone , 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,3'-diamino-4,4'-dichlorobenzophenone, 3,3'-diamino-4,4' -Dimethoxybenzophenone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 2,2-bis(3- aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 2,2-bis(3-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 2,2-bis(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 3,3'-diaminodiphenylsulfoxide, 3,4'-diaminodi diamines having two benzene nuclei in structure, such as phenyl sulfoxide and 4,4'-diaminodiphenyl sulfoxide;

3) 1,3-bis(3-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, 1,4-bis(3-aminophenyl)benzene, 1,4-bis(4-amino) Phenyl)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene (or TPE-Q), 1,4-bis(4-aminophenoxy) Benzene (or TPE-Q), 1,3-bis (3-aminophenoxy) -4-trifluoromethylbenzene, 3,3'-diamino-4- (4-phenyl) phenoxybenzophenone, 3 ,3'-diamino-4,4'-di(4-phenylphenoxy)benzophenone, 1,3-bis(3-aminophenylsulfide)benzene, 1,3-bis(4-aminophenylsulfide) Benzene, 1,4-bis(4-aminophenylsulfide)benzene, 1,3-bis(3-aminophenylsulfone)benzene, 1,3-bis(4-aminophenylsulfone)benzene, 1,4-bis( 4-aminophenylsulfone)benzene, 1,3-bis[2-(4-aminophenyl)isopropyl]benzene, 1,4-bis[2-(3-aminophenyl)isopropyl]benzene, 1,4- diamines having three benzene nuclei in the structure, such as bis[2-(4-aminophenyl)isopropyl]benzene;

4) 3,3'-bis(3-aminophenoxy)biphenyl, 3,3'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-bis(4-aminophenoxy)biphenyl, bis[3-(3-aminophenoxy)phenyl]ether, bis[3-(4-aminophenoxy)phenyl]ether, bis[4- (3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, bis[3-(3-aminophenoxy)phenyl]ketone, bis[3-(4-aminophenoxy) cy)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]ketone, bis[3-(3-aminophenoxy)phenyl]sulfide , bis[3-(4-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[3- (3-aminophenoxy)phenyl]sulfone, bis[3-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy) cy)phenyl]sulfone, bis[3-(3-aminophenoxy)phenyl]methane, bis[3-(4-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl ]methane, bis[4-(4-aminophenoxy)phenyl]methane, 2,2-bis[3-(3-aminophenoxy)phenyl]propane, 2,2-bis[3-(4) -aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane ( BAPP), 2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [3- (4- aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3 structure, such as ,3,3-hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, etc. Diamine with 4 phase benzene nuclei.

The said diamine monomer can be used individually or in combination of 2 or more types as needed.

In one specific example, the polyamic acid composition may include 1 to 20% by weight or 3 to 15% by weight of solids based on the total weight. According to the present application, by controlling the solid content of the polyamic acid composition, it is possible to prevent the increase in manufacturing cost and process time required to remove a large amount of solvent during the curing process while controlling the increase in viscosity.

The polyamic acid composition of the present application may be a composition having a low viscosity characteristic. The polyamic acid composition of the present application may have a viscosity of 20,000 cps or less, 10,000 cps or less, and 6,000 cps or less, measured ^{at a temperature of 25° C. and a shear rate of 30 s −1 .} The lower limit is not particularly limited, but may be 10 cps or more, 15 cps or more, 30 cps or more, 100 cps or more, 300 cps or more, 500 cps or more, or 1000 cps or more. The viscosity may be measured using, for example, a VT-550 manufactured by Haake, and may be measured at a shear rate of 30/s, a temperature of 25° C., and a 1 mm plate gap. The present application may provide a precursor composition having excellent processability by adjusting the viscosity range.

In one example, the polyamic acid composition may have a logarithmic viscosity of 0.1 or more or 0.2 or more, measured at a temperature of 30° C. and a concentration of 0.5 g/100 mL (dissolved in water) based on its solid content concentration. The upper limit is not particularly limited, but may be 5 or less, 3 or less, or 2.5 or less. In the present application, by adjusting the logarithmic viscosity, it is possible to control the molecular weight of an appropriate amount of polyamic acid and secure fairness.

In one embodiment, the polyamic acid composition of the present application has a weight average molecular weight after curing of 10,000 to 200,000 g/mol, 15,000 to 80,000 g/mol, 18,000 to 70,000 g/mol, 20,000 to 60,000 g/mol, 25,000 to 55,000 g /mol or in the range of 30,000 to 50,000 g/mol. In the present application, the term "weight average molecular weight" refers to a value converted to standard polystyrene measured by gel permeation chromatograph (GPC).

The present application also relates to a method for preparing a polyamic acid aqueous solution composition. The preparation method may be the preparation method of the polyamic acid aqueous solution composition described above.

In one example, the method for preparing the aqueous polyamic acid composition may include preparing a polyamic acid having a siloxane group at the terminal by mixing an aqueous catalyst. In addition, the preparation method may include mixing lithium hydroxide and an aqueous catalyst. The preparation method of the present application may include mixing lithium hydroxide and an aqueous catalyst together during polymerization of the diamine monomer and the dianhydride monomer. That is, in the present application, the lithium hydroxide and the aqueous catalyst may be mixed in the polymerization step before the polymerization of the polyamic acid. In addition, in the present application, water may be mixed as a solvent.

The present application also relates to a binder resin composition for an electrode. The binder resin composition for an electrode may be a binder resin composition for a negative electrode active material, and may include the polyamic acid aqueous solution composition described above.

In addition, the present application relates to an electrode active material composition comprising an electrode active material and the above-described binder resin composition for an electrode.

In addition, the present application relates to an electrode including an electrode current collector and an electrode active material layer including the electrode active material composition described above.

According to an embodiment, the negative electrode may include polyimide derived from the polyamic acid.

The negative electrode includes a negative electrode active material, for example, after preparing a negative electrode active material composition mixed with a negative electrode active material, a binder, optionally a conductive agent, and a solvent, it is molded into a certain shape, or copper foil, etc. It can be prepared by a method of applying to the current collector.

The negative active material is not particularly limited to those generally used in the art. Non-limiting examples of the anode active material include lithium metal, a metal alloyable with lithium, a transition metal oxide, a material capable of doping and dedoping lithium, a material capable of reversibly intercalating and deintercalating lithium ions, etc. may be used. , it is also possible to use two or more of them in a mixed or combined form.

Non-limiting examples of the transition metal oxide may include tungsten oxide, molybdenum oxide, titanium oxide, lithium titanium oxide, vanadium oxide, lithium vanadium oxide, and the like.

The material capable of doping and dedoping lithium is, for example, Si, SiOx (0<x≤2), Si-Y alloy (wherein Y is alkali metal, alkaline earth metal, Group 13 element, Group 14 element, Group 15 element) an element, a group 16 element, a transition metal, a rare earth element, or a combination element thereof, but not Si), Sn, SnO ₂ , a Sn-Y alloy (wherein Y is an alkali metal, an alkaline earth metal, a group 13 element, a group 14 element, A transition metal, a rare earth element, or a combination element thereof, and not Sn) may be used, and at least one of these and SiO ₂ may be mixed and used. The element Y includes 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 a combination thereof.

The material capable of reversibly intercalating and deintercalating lithium ions is a carbon-based material, and any carbon-based negative active material generally used in lithium batteries may be used. For example, crystalline carbon, amorphous carbon, or mixtures thereof. Non-limiting examples of the crystalline carbon include amorphous, plate-like, flake-like, spherical or fibrous natural graphite; or artificial graphite. Non-limiting examples of the amorphous carbon include soft carbon (low temperature calcined carbon) or hard carbon, mesophase pitch carbide, calcined coke, and the like.

According to one embodiment, as the negative active material, Si, SiOx (0<x≤2), a silicon-based active material such as a Si-Y alloy, Sn, SnO ₂ , a tin-based active material such as a Sn-Y alloy, silicon-tin alloy-based An active material capable of implementing a high capacity, such as an active material or a silicon-carbon-based active material, may be used.

As such, the active material capable of implementing a high capacity prevents the active material from being separated by the water-soluble binder bonded between the active materials even during expansion and contraction of the active material by charging and discharging, and the electron transfer path in the electrode is maintained to improve the rate characteristics of the lithium battery. can be improved

The negative active material may further include a carbon-based negative active material in addition to the above-described silicon-based active material, tin-based active material, silicon-tin alloy-based active material, silicon-carbon-based composite, tin-carbon-based composite, or a combination thereof. In this case, the carbon-based negative active material may be a mixture or composite formed with the above-described silicon-based active material, tin-based active material, silicon-tin alloy-based active material, silicon-carbon-based composite, tin-carbon-based composite, or a combination thereof.

The negative active material may have a simple particle shape, or a nanostructure having a nano-sized shape. For example, the negative active material may have various forms such as nanoparticles, nanowires, nanorods, nanotubes, and nanobelts.

The binder used in the anode active material composition may include the above-described water-soluble polyamic acid according to an embodiment, thereby suppressing volume expansion of the anode active material that may occur during lithium charging and discharging. The binder including the water-soluble polyamic acid may be added in an amount of 1 to 50 parts by weight, 10 to 40 parts by weight, 20 to 38 parts by weight, or 25 to 35 parts by weight based on 100 parts by weight of the negative electrode active material.

The negative electrode may optionally further include a conductive agent to further improve electrical conductivity. As the conductive agent, any one generally used in lithium batteries may be used, and examples thereof include carbon-based materials such as carbon black, acetylene black, ketjen black, and carbon fibers (eg, vapor-grown carbon fibers); metal-based substances such as metal powders such as copper, nickel, aluminum, and silver, or metal fibers; A conductive material containing a conductive polymer such as a polyphenylene derivative or a mixture thereof can be used. The content of the conductive material may be appropriately adjusted and used.

As the solvent, N-methylpyrrolidone (NMP), acetone, water, etc. may be used. The amount of the solvent is 10 to 300 parts by weight based on 100 parts by weight of the negative active material. When the content of the solvent is within the above range, the operation for forming the active material layer is easy.

The anode active material composition may contain other additives as necessary, such as an adhesion enhancer such as a silane coupling agent for improving adhesion between the current collector and the active material, and a dispersant for improving dispersibility of the slurry.

In addition, the current collector is generally made to a thickness of 3 to 100 ㎛. The current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface. Carbon, nickel, titanium, one surface-treated with silver, an aluminum-cadmium alloy, etc. may be used. In addition, the bonding strength of the negative electrode active material may be strengthened by forming fine irregularities on the surface, and may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam body, and a nonwoven body.

A negative electrode plate can be prepared by directly coating the prepared negative electrode active material composition on a current collector, or a negative electrode plate can be obtained by casting a negative electrode active material film on a separate support and laminating the negative electrode active material film peeled from the support on a copper foil collector. The negative electrode is not limited to the above-mentioned types and may be of a type other than the above-mentioned types.

Separately, a positive electrode active material composition in which a positive electrode active material, a conductive agent, a binder, and a solvent are mixed in order to manufacture a positive electrode is prepared.

As the cathode active material, a compound capable of reversible intercalation and deintercalation of lithium (a lithiated intercalation compound) may be used. As the cathode active material, a lithium-containing metal oxide may be used as long as it is commonly used in the art.

The binder used in the positive active material composition may be any binder as long as it serves to well adhere the positive active material particles to each other and also to adhere the positive active material to the current collector. For example, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer including ethylene oxide, polyvinyl pyrrolidone , polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, polyamideimide, acrylated styrene-butadiene rubber, epoxy resin, nylon have.

As the binder used in the cathode active material composition, the same binder as the anode active material composition may be used.

As the conductive agent and solvent in the positive active material composition, the same conductive agent and solvent as previously described in the negative active material composition may be used. In some cases, it is also possible to form pores in the electrode plate by further adding a plasticizer to the positive active material composition and the negative active material composition. The content of the positive electrode active material, the conductive agent, the binder, and the solvent is a level commonly used in a lithium battery.

The positive electrode current collector has a thickness of 3 to 100 μm, and is not particularly limited as long as it has high conductivity without causing chemical change in the battery, for example, stainless steel, aluminum, nickel, titanium, sintered carbon, Alternatively, a surface treated with carbon, nickel, titanium, silver, etc. may be used on the surface of aluminum or stainless steel. The current collector may increase the adhesion of the positive electrode active material by forming fine irregularities on the surface thereof, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam body, and a nonwoven body are possible.

The positive electrode and the negative electrode may be separated by a separator, and any separator commonly used in a lithium battery may be used as the separator. In particular, it is suitable that the electrolyte has a low resistance to ion movement and an excellent electrolyte moisture content. As the separator, an insulating thin film having high ion permeability and mechanical strength is used.

The pore diameter of the separator is generally 0.01 to 10 μm, and the thickness may be generally 5 to 20 μm. Examples of such a separator include olefinic polymers such as polypropylene; Sheets or non-woven fabrics made of glass fiber or polyethylene are used. When a solid polymer electrolyte is used as the electrolyte, the solid polymer electrolyte may also serve as a separator.

Specific examples of the olefin-based polymer among the separators include polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof, and a polyethylene/polypropylene two-layer separator, polyethylene/polypropylene/polyethylene A mixed multilayer film such as a three-layer separator, a polypropylene/polyethylene/polypropylene three-layer separator and the like can be used.

As the electrolyte, a lithium salt-containing non-aqueous electrolyte may be used. As the non-aqueous electrolyte, a non-aqueous electrolyte, a solid electrolyte, an inorganic solid electrolyte, and the like are used.

Lithium batteries can be classified into lithium ion batteries, lithium ion polymer batteries, and lithium polymer batteries according to the type of separator and electrolyte used, and can be classified into cylindrical, prismatic, coin-type, pouch-type, etc. Depending on the type, it can be divided into a bulk type and a thin film type. In addition, both a lithium primary battery and a lithium secondary battery are possible.

The lithium battery may be a lithium ion battery. The lithium battery may be a lithium ion battery having a charging voltage of 4.3V or higher.

The lithium battery is suitable for applications requiring high-capacity, high-output and high-temperature driving such as electric vehicles in addition to the existing uses for mobile phones and portable computers. It can also be used in hybrid vehicles and the like. In addition, the lithium battery can be used in all other applications requiring high output, high voltage and high temperature driving.

Since the manufacturing method of these batteries is well known in the art, detailed description thereof will be omitted.

The present application is applicable for electrodes of lithium secondary batteries, water-based polymerization possible, not organic solvents, polyamic acid aqueous solution composition capable of realizing high capacity retention with excellent mechanical strength and binding force, binder resin composition for electrodes, and the same It provides an electrode active material composition and an electrode comprising the same.

1 is a photograph showing the results of copper foil adhesion according to an experimental example of the present invention.

Hereinafter, the present application will be described in more detail through Examples according to the present application, but the scope of the present application is not limited to the Examples to be presented below.

Example 1

In a reactor equipped with a temperature controller and filled with nitrogen, 58.6791 g of distilled water was added as a solvent. Here, 1.0165 g (0.0094 mol) of p-phenylenediamine (pPDA), 0.1136 g (0.0005 mol) of 4,4′-diaminobenzanilide and 2.4033 g of 1,2-dimethylimidazole (DMIZ) (relative to the carboxyl group) 1.25 equivalent) was added, and the mixture was dissolved using a mechanical stirrer at 25° C. for 1 hour. Then, 2.9422 g (0.01 mol) of 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA) was added, and the mixture was reacted at 70° C. for 3 hours, followed by 3- A water-soluble polyamic acid was prepared by adding 0.0443 g (0.0002 mol) of aminopropyltriethoxysilane (APTES) and stirring for overnight to carry out a polymerization reaction.

Example 2

A water-soluble polyamic acid was prepared in the same manner as in Example 1, but 3-aminomethyltriethoxysilane was used instead of APTES for the terminal group.

Example 3

A water-soluble polyamic acid was prepared in the same manner as in Example 1, but 3-aminoethyltriethoxysilane was used instead of APTES for the terminal group.

Example 4

A water-soluble polyamic acid was prepared in the same manner as in Example 1, but 3-aminobutyltriethoxysilane was used instead of APTES for the terminal group.

Example 5

A water-soluble polyamic acid was prepared in the same manner as in Example 1, but 3-aminopentyltriethoxysilane was used instead of APTES for the terminal group.

Example 6

A water-soluble polyamic acid was prepared in the same manner as in Example 1, but 3-aminohexyltriethoxysilane was used instead of APTES for the terminal group.

Example 7

A water-soluble polyamic acid was prepared in the same manner as in Example 1, but 3-aminoheptyltriethoxysilane was used instead of APTES for the terminal group.

Example 8

57.3597 g of distilled water was added as a solvent to a reactor equipped with a temperature controller and filled with nitrogen. Here, 1.0273 g (0.0095 mol) of p-phenylenediamine (pPDA), 0.1136 g (0.0005 mol) of 4,4′-diaminobenzanilide and 2.4033 g of 1,2-dimethylimidazole (DMIZ) (relative to the carboxyl group) 1.25 equivalent) was added, and the mixture was dissolved using a mechanical stirrer at 25° C. for 1 hour. Thereafter, 2.9422 g (0.01 mol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) was added, and the mixture was stirred at 70° C. overnight to proceed with polymerization. to prepare a water-soluble polyamic acid. 0.0408 g (1 part by weight based on 100 parts by weight of polyamic acid)_ of γ-glycidoxypropyltrimethoxy silane (XIAMETER OFS-6040 Silane manufactured by DOW) was added to the synthesized water-soluble polyamic acid.

Example 9

In a reactor equipped with a temperature controller and filled with nitrogen, 58.6791 g of distilled water was added as a solvent. Here, 1.0165 g (0.0094 mol) of p-phenylenediamine (pPDA), 0.1136 g (0.0005 mol) of 4,4′-diaminobenzanilide and 2.4033 g of 1,2-dimethylimidazole (DMIZ) (relative to the carboxyl group) 1.25 equivalent) was added, and the mixture was dissolved using a mechanical stirrer at 25° C. for 1 hour. Then, 2.9422 g (0.01 mol) of 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA) was added, and the mixture was reacted at 70° C. for 3 hours, followed by 3- A water-soluble polyamic acid was prepared by adding 0.0443 g (0.0002 mol) of aminopropyltriethoxysilane (APTES) and stirring for overnight to carry out a polymerization reaction. As much as 0.0412 g (1 part by weight relative to 100 parts by weight of polyamic acid) of γ-glycidoxypropyltrimethoxy silane (XIAMETER OFS-6040 Silane manufactured by DOW) was added to the synthesized water-soluble polyamic acid.

Comparative Example 1

57.3597 g of distilled water was added as a solvent to a reactor equipped with a temperature controller and filled with nitrogen. Here, 1.0273 g (0.0095 mol) of p-phenylenediamine (pPDA), 0.1136 g (0.0005 mol) of 4,4`-diaminobenzanilide and 2.4033 g of 1,2-dimethylimidazole (DMIZ) (relative to the carboxyl group) 1.25 equivalent) was added, and the mixture was dissolved using a mechanical stirrer at 25 °C for 1 hour. Then, 2.9422 g (0.01 mol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) was added, and the mixture was stirred at 70° C. overnight to obtain a water-soluble polyamic acid. prepared.

For the polyamic acid composition prepared above, the physical properties of the experimental examples of the following method were evaluated.

1. Copper Foil Adhesion Measurement

The water-soluble polyamic acid prepared in Examples and Comparative Examples was applied on copper foil and formed into a film in a thickness of 1000 μm using a doctor blade. Thereafter, it was dried at 120° C. for 4 hours to prepare a polyamic acid laminated copper foil film, and adhesion was measured by performing an adhesion cross-cut test. The measured values are shown in Table 1 below, and a photograph is shown in FIG. 1 . In FIG. 1, the left photo is a photo for Comparative Example 1, 2B, and the right photo is for Example 5B.

2. Battery Characteristics Evaluation

<Manufacture of negative electrode and lithium battery>

As an anode active material, 60 wt% of silicon nanoparticles (average particle diameter of 30-50 nm, N&A Materials), 20 wt% of a conductive carbon black conductive material, and 20 wt% of the water-soluble polyamic acid (Examples and Comparative Examples) prepared above as a binder A negative electrode slurry was obtained by mixing in a solvent.

The negative electrode having the negative electrode slurry applied to the copper foil current collector was first dried at 80° C. for 5 minutes, then compressed with a press and dried again in a vacuum oven at 150° C. for 6 hours, with a loading of 0.5 mg/cm ² was prepared.

Using the negative electrode, using Li metal as a counter electrode, using a polyethylene separator (ND420) as a separator, and 1.15M LiPF ₆ as an electrolyte A mixed solvent of EC (ethylene carbonate) and EMC (ethyl methyl carbonate) (3:7 volume ratio) and FEC (fluoroethyl carbonate) using a solution dissolved in 5% by weight to prepare a CR-2032 type coin half cell.

<Evaluation of initial efficiency and capacity retention rate>

The initial efficiency and lifespan characteristics of the prepared lithium battery were measured and compared as follows.

First, in CC mode, charging and discharging was performed once at a current density of 200mA/g to proceed with the formulation step, and the voltage range was 0.05~2.0V. At this time, charging and discharging were repeated 200 times with a current density of 1,200 mA/g in CC mode under the same voltage conditions after initial charging and discharging, and capacity retention according to charging and discharging was evaluated.

The evaluation results of the initial efficiency and the capacity retention rate in the 200th cycle are shown in Table 1 below. Here, the initial efficiency and capacity retention rate are defined by the following Equations 1 and 2.

<Equation 1>

Initial efficiency (%) = (discharge capacity of 1st cycle/charge capacity of 1st cycle) Х 100

<Equation 2>

Capacity retention rate (%) = (discharge capacity in each cycle/discharge capacity in the first cycle) Х 100

adhesion Initial efficiency
(%) Capacity retention rate
(%) Example 1 5B 75.3 81.9 Example 2 5B 75.8 82.3 Example 3 5B 75.6 84.6 Example 4 4B 74.8 80.1 Example 5 3B 72.7 76.0 Example 6 3B 74.1 68.9 Example 7 3B 73.8 58.1 Example 8 5B 73.9 78.4 Example 9 5B 75.8 85.2 Comparative Example 1 2B 72.9 80.4

Claims (20)

A polyamic acid comprising a diamine monomer and a dianhydride monomer as polymerized units, an aqueous catalyst, and a metal ion, wherein the polyamic acid has a siloxane group at the terminal;
A polyamic acid aqueous solution composition wherein the ratio (L/I) of the equivalent (L) of the metal ion to the equivalent (I) of the aqueous catalyst is in the range of 0.01 to 0.8. The polyamic acid aqueous solution composition according to claim 1, wherein the siloxane group includes at least a reactive functional group. The polyamic acid aqueous solution composition according to claim 2, wherein the reactive functional group includes an alkyl group having 1 to 4 carbon atoms. The polyamic acid aqueous solution composition according to claim 1, wherein the siloxane group contains at least an alkoxy group. The polyamic acid aqueous solution composition according to claim 4, wherein the alkoxy group has 1 to 4 carbon atoms. The polyamic acid aqueous solution composition according to claim 1, further comprising a silane coupling agent. The polyamic acid aqueous solution composition according to claim 6, wherein the silane coupling agent is included in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the polyamic acid. According to claim 1, Polyamic acid aqueous solution composition comprising an aqueous catalyst in the range of 0.5 to 1.5 times equivalent to 1 equivalent of the carboxyl group in the polyamic acid. The polyamic acid aqueous solution composition according to claim 1, wherein the aqueous catalyst comprises an imidazole-based compound or an amine-based compound. The polyamic acid aqueous solution composition according to claim 1, wherein the polyamic acid aqueous solution composition contains a metal ion in the range of 0.01 to 1.25 equivalents based on 1 equivalent of carboxyl groups in the polyamic acid. delete The polyamic acid aqueous solution composition according to claim 1, comprising a metal ion and an aqueous catalyst in the range of 1.0 to 2.0 times equivalent to 1 equivalent of carboxyl group in the polyamic acid. The polyamic acid aqueous solution composition according to claim 1, wherein the diamine monomer comprises a diamine monomer having at least one carboxyl group. The polyamic acid aqueous solution composition according to claim 13, wherein the diamine monomer having a carboxyl group is included in an amount of 5 to 45 mol% based on the total number of moles of the total diamine monomers. The polyamic acid aqueous solution composition according to claim 1, wherein the diamine monomer comprises a diamine monomer having at least one amide bond. The polyamic acid aqueous solution composition according to claim 15, wherein the diamine monomer having an amide bond is included in an amount of 5 to 45 mol% based on the total number of moles of the total diamine monomer. The method for preparing a polyamic acid aqueous solution composition according to claim 1, comprising the step of preparing a polyamic acid having a siloxane group at the terminal by mixing an aqueous catalyst. A binder resin composition for an electrode comprising the polyamic acid aqueous solution composition according to claim 1 . An electrode active material composition comprising an electrode active material and the binder resin composition for an electrode of claim 18. An electrode comprising an electrode current collector and an electrode active material layer comprising the electrode active material composition of claim 19.

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