KR20200012514A - Polymeric passivation layer for secondary battery electrode and secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a polymer for an electrode protective layer, comprising a polymer (A) in which a monomer containing a poly(alkylene oxide) and a monomer containing a thermosetting functional group are grafted on a fluorine-based polymer. According to the present invention, when an electrode active material layer is coated by using the polymer and heat-cured to produce an electrode, lithium ion flow is not blocked, excellent lithium ion conductivity is exhibited, and chemical resistance to the electrolyte is high. Due to the uniformity and flexibility of the protective layer, side reactions with the electrolyte generated on the surface of the electrode active material can be suppressed to improve the voltage stability of the secondary battery.

Description

Polymer for electrode protective layer and secondary battery using same {POLYMERIC PASSIVATION LAYER FOR SECONDARY BATTERY ELECTRODE AND SECONDARY BATTERY COMPRISING THE SAME}

The present invention relates to a polymer for an electrode protective layer and a secondary battery to which the polymer is applied, and more particularly, to electrochemical stability by inhibiting side reactions on an active material surface by an electrolyte solution without interfering with the transfer of lithium ions from the active material surface of a secondary battery electrode. It relates to a protective layer and a secondary battery applying the same.

Secondary batteries known as electrochemical devices are devices that convert external electrical energy into chemical energy and store it, and then generate electricity when needed. The term "rechargeable battery" is also used to mean that it can be charged several times. Commonly used secondary batteries include lead acid batteries, nickel cadmium (Ni-Cd) batteries, nickel hydrogen (NiMH) batteries, lithium ion (Li-ion) batteries, and lithium ion polymer (Li-ion polymer) batteries. Secondary batteries provide both economic and environmental advantages over primary batteries that are used once and discarded.

In recent years, as the wireless communication technology is gradually developed, as the weight reduction of portable devices or automobile accessories and the like is required, the demand for secondary batteries used as energy sources of these devices is increasing.

Currently, high energy density lithium secondary batteries mainly used in notebooks and smartphones are composed of a positive electrode made of lithium oxide, a carbon-based negative electrode, a separator, and a liquid or solid electrolyte. As the application area of lithium secondary batteries is expanded to electric vehicles (EVs) and energy storage devices (ESSs), the driving voltage is increased to 4.5 V or more, and the use environment of the batteries is being severed by applying metallic lithium as a negative electrode. Situation. Metal Lithium Cathode has the highest theoretical specific capacity of 3860 mAh / g and has the lowest electrochemical potential of -3.04 V (vs. standard hydrogen electrode), but it has received much attention, but it has side reaction with electrolyte and uneven deposition / dissolution of lithium. Commercialization is delayed due to the problem.

Metal lithium continuously forms a solid electrolyte interface (SEI) through a reaction with an organic electrolyte and a lithium salt dissolved therein. During the charge and discharge cycles of the battery, the SEI layer is continuously destroyed and regenerated, and the newly exposed lithium metal surface reacts with the electrolyte to reduce the coulombic efficiency and lithium dendrite. Commercialization of secondary batteries using metal lithium electrodes has been delayed due to short circuit through dendrite growth.

In order to solve this problem, attempts have been made to apply a stable artificial SEI layer to the surface of an electrode active material such as lithium metal and thereby improve cycle characteristics. For example, polyacetylene, tetraethoxysilane, lithium phosphorus oxynitride, alumina particles, ultra-thin alumina films and the like are coated and coated on a lithium film to improve cycle characteristics through formation of lithium dendrites or suppression of side reactions. The research was actively conducted. However, it was observed that the protection effect of the electrode was still decreased after continuous battery operation, which is due to the occurrence of cracking due to the low lithium ion conductivity, low flexibility, and uneven coating of the electrode.

Republic of Korea Patent Publication No. 2016-0058274 (2016.05.25), "Binder containing a polymer formed by branched block copolymer comprising a polypropylene oxide block and polyethylene oxide block"

Accordingly, the present inventors conducted various studies to solve the above problems, and graft a monomer including a poly (alkylene oxide) having an ion conductivity and a monomer including a photocurable functional group on a fluoropolymer having a high dielectric constant. When the polymer for the electrode protective layer is prepared by copolymerization and applied to the secondary battery to protect the surface of the lithium metal or the active material, the lithium ion conductivity does not interfere with the flow of lithium ions in the electrolyte, thus exhibiting excellent lithium ion conductivity and It has been confirmed that the chemical resistance to the high, uniform and flexible protective layer due to the characteristics of the electrode active material to suppress the side reaction with the electrolyte generated to improve the voltage stability of the secondary battery and completed the present invention.

Accordingly, an object of the present invention is to provide a polymer for electrode protective layer comprising a polymer grafted with a monomer comprising a poly (alkylene oxide) and a monomer comprising a photocurable functional group on the fluorine-based polymer.

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

Provided is a polymer for an electrode protective layer comprising a polymer (A) grafted with a monomer containing poly (alkylene oxide) and a monomer containing a photocurable functional group on a fluorine-based polymer.

One embodiment of the present invention is that the fluorine-based polymer includes a structure of the following formula (1).

[Formula 1]

(In Formula 1, p, q, and r are each independently 0 ≦ p ≦ 20,000, 1 ≦ q ≦ 22,000, and 0 ≦ r ≦ 15,000).

One embodiment of the present invention is that the polymer (A) comprises a structure of formula (2).

[Formula 2]

(In Formula 2, p, q and r are each independently 0 ≦ p ≦ 20,000, 1 ≦ q ≦ 22,000 and 0 ≦ r ≦ 15,000,

R ₁ , R ₂ , R ₃ and R ₄ are each independently hydrogen or methyl,

R ₅ is any one selected from hydrogen, an alkyl group having 1 to 12 carbon atoms, and a phenyl group which is unsubstituted or substituted with an alkyl group having 1 to 12 carbon atoms,

), 우레탄기 함유 탄소수 1 내지 12의 알킬렌옥시카보닐, 에틸렌 옥사이드의 부가몰수 1 내지 10인 폴리(에틸렌 옥사이드)카보닐 및 페닐렌 중에서 선택되는 어느 하나이며,X is a simple link or alkylene having 1 to 12 carbon atoms, alkyloxycarbonyl having 1 to 12 carbon atoms (

), Urethane group-containing alkyleneoxycarbonyl having 1 to 12 carbon atoms, poly (ethylene oxide) carbonyl and phenylene having an added mole number of 1 to 10 ethylene oxide,

l, m and n are each independently 2≤l≤230, 1≤m≤200 and 2≤n≤50,

R ₆ is any one selected from hydrogen, chlorine or bromine)

One embodiment of the present invention is that the poly (alkylene oxide) is poly (ethylene oxide) or poly (propylene oxide).

One embodiment of the present invention is that the photocurable functional group is an unsaturated vinyl group.

In one embodiment of the present invention is a monomer containing a poly (alkylene oxide) and a monomer containing a photocurable functional group is included in a molar ratio of 99.9: 0.1 to 70:30.

In addition, the present invention,

It provides a polymer composition for electrode protective layer comprising the above-mentioned polymer for electrode protective layer, a polyfunctional vinyl-based crosslinking agent and a photoinitiator.

One embodiment of the present invention is that the polyfunctional vinyl-based crosslinking agent is included in 0.1 to 50 parts by weight based on 100 parts by weight of the polymer (A).

One embodiment of the present invention is that the photoinitiator is included in 0.01 to 5 parts by weight based on 100 parts by weight of the polymer (A).

In addition, the present invention,

It provides an electrode protective layer formed by photocuring the above-described polymer composition for electrode protective layer.

In one embodiment of the present invention, the electrode comprises an electrode active material,

The electrode active material is any one selected from the group consisting of metal lithium, a positive electrode active material and a negative electrode active material.

In addition, the present invention,

Provided is a secondary battery including an electrode including the electrode protective layer described above.

The electrode protective layer polymer according to the present invention includes a polymer (A) prepared by grafting a monomer containing a poly (alkylene oxide) and a monomer containing a photocurable functional group on a fluorine-based polymer having a high dielectric constant, When using this to coat the electrode active material layer and photocure it to produce an electrode, it does not interfere with the flow of lithium ions, showing excellent lithium ion conductivity, high chemical resistance to the electrolyte, due to the characteristics of the uniform and flexible protective layer The side reaction with the electrolyte generated on the surface of the electrode active material can be suppressed to improve the voltage stability of the secondary battery.

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

The terms or words used in this specification and claims are not to be construed as limiting in their usual or dictionary meanings, and the inventors may appropriately define the concepts of terms in order to best describe their invention. It should be interpreted as meanings and concepts corresponding to the technical idea of the present invention based on the principle that the present invention.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present invention, the term 'comprise' or 'having' is used to designate that there exists a feature, number, step, operation, component, part, or combination thereof described on the specification, and one or more other It is to be understood that the present invention does not exclude in advance the possibility of the presence or the addition of features or numbers, steps, operations, components, parts, or combinations thereof.

Polymer for Electrode Protective Layer

The fluorine-based polymer has a high dielectric dissociation degree of 9 to 40, and has an advantage of having electrochemical stability even at high voltage (5.0 V) when used in a lithium secondary battery. However, due to high crystallinity, ionic conductivity is very high. There is a low disadvantage.

Therefore, in the present invention, in order to overcome the disadvantages of the fluorine-based polymer, a monomer including poly (alkylene oxide) having lithium ion chelating property is introduced on the fluorine-based polymer having a high dielectric constant through a grafting reaction. In addition, a polymer (A) formed by further grafting copolymerization of a monomer including a poly (alkylene oxide) and a monomer including a photocurable functional group to form a stable protective layer that does not melt or cause side reactions by an electrolyte solution. It provides a polymer for an electrode protective layer comprising a.

The fluorine-based polymer according to one embodiment of the present invention may be a polymer including a poly (chlorotrifluoroethylene) polymer unit, and the fluorine-based polymer may be a compound represented by the following Chemical Formula 1.

[Formula 1]

(In Formula 1, p, q, and r are each independently 0 ≦ p ≦ 20,000, 1 ≦ q ≦ 22,000, and 0 ≦ r ≦ 15,000).

The fluorine-based polymer according to the embodiment is a dimer of vinylidene fluoride (VdF) and chlorotrifluoroethylene (CTFE) or a trimer of VDF, CTFE, and trifluoroethylene (TrFE). It may include, the polymer may be to necessarily include a CTFE.

In order to improve ion conductivity and electrochemical stability of the fluorine-based polymer, graft copolymerization of a monomer including a poly (alkylene oxide) and a monomer including a photocurable functional group may be performed. It may be graft copolymerization using atomic transfer radical polymerization (ATRP).

The fluorine-based polymer according to the present invention is a polymer capable of grafting branched chains by an atom transfer radical polymerization reaction, and any polymer may be used as long as it is a polymer polymer containing such a fluorine atom, but preferably polyvinylidene Polyvinylidene fluoride (PVDF), Polyvinyl fluoride (PVF), Polychlorotrifluoroethylene (PCTFE), Polytetrafluoroethylene (PTFE), Polytrifluoroethylene (Polytrifluoroethylene) PTrFE), poly-1,2-difluoroethylene, or a copolymer including one or more thereof, may be preferably used. Preferably, polychlorotrifluoroethylene (PCTFE) is used. ), More preferably poly (vinylidene fluoride-chlorotrifluoroethylene) (Po ly (vinylidene fluoridechlorotrifluoroethylene), hereinafter P (VDF-CTFE)) or poly (vinylidene fluoride-chlorotrifluoroethylene-trifluoroethylene) (poly (vinylidene fluoridechlorotrifluoroethylene-trifluoroethylene), hereinafter P (VDF-CTFE-TrFE )) Can be used.

In one embodiment of the present invention, by introducing a chain containing a poly (alkylene oxide) having an ion conductivity to the chlorine (Cl) group on the CTFE through an atom transfer radical polymerization can lower the crystallinity of the fluorine-based polymer electrolyte Therefore, there is an advantage that can improve the fluidity of the polymer chain. In addition, by applying a fluorine-based polymer having a large dielectric constant, more lithium ions may be dissociated, thereby exhibiting higher ion conductivity and electrochemical stability than conventional poly (alkylene oxide) polymers.

In addition, in order to secure the physical, chemical, electrochemical strength and stability of the electrode protective layer, the present invention provides a polymer in which a monomer including a photocurable functional group is additionally grafted in the polymer. The photocurable functional group can be photocured in itself or in the presence of a suitable polyfunctional vinyl-based functional group and a photoinitiator to improve the above characteristics.

In one embodiment of the present invention, a structure in which the monomer including the poly (alkylene oxide) and the monomer including the photocurable functional group is copolymerized on the fluorine-based polymer may include the structure of Formula 2 below. have.

[Formula 2]

(In Formula 2, p, q and r are each independently 0 ≦ p ≦ 20,000, 1 ≦ q ≦ 22,000 and 0 ≦ r ≦ 15,000,

R ₁ , R ₂ , R ₃ and R ₄ are each independently hydrogen or methyl,

R ₅ is any one selected from hydrogen, an alkyl group having 1 to 12 carbon atoms, and a phenyl group which is unsubstituted or substituted with an alkyl group having 1 to 12 carbon atoms,

), 우레탄기 함유 탄소수 1 내지 12의 알킬렌옥시카보닐, 에틸렌 옥사이드의 부가몰수 1 내지 10인 폴리(에틸렌 옥사이드)카보닐 및 페닐렌 중에서 선택되는 어느 하나이며,X is a simple link or alkylene having 1 to 12 carbon atoms, alkyloxycarbonyl having 1 to 12 carbon atoms (

), Urethane group-containing alkyleneoxycarbonyl having 1 to 12 carbon atoms, poly (ethylene oxide) carbonyl and phenylene having an added mole number of 1 to 10 ethylene oxide,

l, m and n are each independently 2≤l≤230, 1≤m≤200 and 2≤n≤50,

R ₆ is any one selected from hydrogen, chlorine or bromine)

The poly (alkylene oxide) according to an embodiment of the present invention is a material capable of improving the ion conductivity of the fluorine-based polymer, may be poly (ethylene oxide) or poly (propylene oxide), preferably poly (ethylene Oxide). Examples of the monomer containing the poly (alkylene oxide) include poly (alkylene oxide) (meth) acrylate, poly (alkylene oxide) monoalkyl ether (meth) acrylate, poly (alkylene oxide) monophenyl ether (Meth) acrylates, and the like, but is not limited thereto.

The monomer including the photocurable functional group according to the embodiment of the present invention may include an unsaturated vinyl group, and non-limiting examples thereof include vinyl (meth) acrylate, allyl (meth) acrylate, and 2- (vinyl). Vinyl group-containing (meth) acrylates such as oxy) ethyl methacrylate.

The polymerized unit including the photocurable functional group may be secondarily derived from a (meth) acrylate containing no vinyl group through a post-polymerization reaction. For example, a hydroxy group-containing (meth) acrylate is copolymerized with the poly (alkylene oxide) group-containing monomer and then condensed with 2-isocyanatoethyl (meth) acrylate to introduce a (meth) acrylate group into the side chain. Conversely, (meth) acrylate containing isocyanate groups may be condensed with hydroxy group-containing (meth) acrylate after copolymerization with a poly (alkylene oxide) group-containing monomer. The type of the polymer reaction used to introduce the vinyl group into the side chain is not limited, but for example, a urethane formation reaction of a hydroxy-isocyanate group, an ester group formation reaction of an epoxy group-carboxylic acid group, and an S _N 2 reaction of an amine group-halogen group Etc. can be mentioned.

The monomer including the poly (alkylene oxide) and the monomer including the photocurable functional group may be included in a molar ratio of 99.9: 0.1 to 70:30, and specifically, may be a molar ratio of 99: 1 to 90:10. Can be. If the monomer containing the photocurable functional group is less than the above range, the crosslinking reaction between the polymers is not sufficient, so that the physical, chemical and electrochemical strength and stability of the electrode protective layer are not high enough, and if the monomer is above the above range, the content of alkylene oxide is above. There is little and the polymer network density becomes too high, and ionic conductivity may become remarkably bad, and it adjusts suitably in the said range.

In one embodiment of the present invention, the fluorine-based graft polymer (A) may further introduce a unit derived from a third monomer in the graft chain for the purpose of improving the interfacial adhesion characteristics, mechanical properties of the electrode active material. . Examples of the third monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, t- Butyl (meth) acrylate, pentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate with 2-ethylbutyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate , Isononyl (meth) acrylate, or lauryl (meth) acrylate, styrene, α-methylstyrene, p-methylstyrene, p-methoxystyrene, (meth) acrylonitrile and the like may be exemplified, but It is not limited.

The third monomer according to an embodiment of the present invention may be included in the 1 to 20 middle portion compared to 100 parts by weight of the total fluorine-based graft polymer (A). If it is less than 1 part by weight, the desired physical properties may not be improved, and when 20 parts by weight or more are included, the ionic conductivity may be too low.

The fluorine-based polymer according to Chemical Formula 1 according to one embodiment of the present invention may be included in an amount of 5 to 50 parts by weight, preferably 5 to 40 parts by weight, based on 100 parts by weight of the fluorine-based graft polymer (A). If the content of the fluorine-based polymer is above the above range, the mechanical strength and electrochemical stability of the electrode protective layer may be increased, but the crystallinity of the fluorine-based polymer may not be suppressed, and the content of alkylene oxide is excessively reduced, thereby decreasing the ion conductivity. If the content of less than the above range can not implement the high electrochemical stability and high lithium ion dissociation characteristics of the fluorine-based polymer is selected appropriately in the above range.

In another aspect, the present invention provides a polymer composition for electrode protective layer further comprises a polyfunctional vinyl-based crosslinking agent having a functional group capable of reacting with the polymer composition for the electrode protective layer and a photocurable functional group contained in the fluorine-based graft polymer (A). do. The fluorine-based graft polymer (A) may be photocurable in the presence of a photoinitiator by a vinyl group introduced into the side chain, but may be a photocurable polymer composition further comprising a polyfunctional vinylic crosslinking agent.

The multifunctional vinyl-based crosslinking agent may further react with an unsaturated vinyl functional group included in the graft polymer of Formula 2 to form a crosslinked structure between polymers. The electrode protective layer formed of the crosslinked structure exhibits high chemical and electrochemical stability, and protects the surface of the electrode active material from side reactions with the electrolyte, thereby overcoming problems such as deterioration of cycle characteristics and deterioration of coulombic efficiency of the secondary battery. have.

In one embodiment of the present invention, the polyfunctional vinyl-based crosslinking agent is an organic compound having two or more vinyl groups in one molecule, and includes ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and tri (Propylene glycol) di (meth) acrylate, tris (2- (meth) acryloethyl) isocyanate, trimethylolpropane tri (meth) acrylate, trimethylolpropane ethoxylate tri (meth) acrylate, pentaerythritol di (Meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol di (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) ) Acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and the like. May be, but is not limited thereto.

The polyfunctional vinyl-based crosslinking agent may be included in a ratio of 0.1 to 50 parts by weight, preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the bloso-based graft polymer (A). By controlling the content of the cross-linking agent within the above range it can be appropriately represented to the desired level of the physical properties of the electrolyte.

In one embodiment of the present invention, the photoinitiator is acetophenone compound, biimidazole compound, triazine compound, oxime compound, benzoin compound, hydroxy ketone compound, amino ketone compound or phosphine oxide compound As such, a general initiator capable of generating radicals by irradiation of ultraviolet rays or the like to initiate photopolymerization can be used without limitation.

Acetophenone compounds which can be used as the photoinitiator include 2-hydroxy-2-methyl-1-phenylpropan-1-one and 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropane-1 -One, 4- (2-hydroxyethoxy) -phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexylphenylketone, benzoinmethyl ether, benzoinethyl ether, benzoin iso Butyl ether, benzoin butyl ether, 2,2-dimethoxy-2-phenylacetophenone, 2-methyl- (4-methylthio) phenyl-2-morpholino-1-propan-1-one, 2-benzyl 2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 2- (4-bromo-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butane It is selected from the group consisting of -1-one and 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1-one, and the biimidazole type compound is 2,2-bis (2-chlorophenyl) -4,4 ', 5,5'-tetraphenyl biimidazole, 2,2'-bis (o-chlorophenyl) -4,4', 5,5'-tetrakis (3 , 4,5-? Zrimethoxyphenyl) -1 , 2'-biimidazole, 2,2'-bis (2,3-dichlorophenyl) -4,4 ', 5,5'-tetraphenyl biimidazole, and 2,2'-bis (o-chloro Phenyl) -4,4,5,5'-tetraphenyl-1,2'-biimidazole, and the triazine compound is 3- {4- [2,4-bis (trichloromethyl ) -s-triazin-6-yl] phenylthio} propionic acid, 1,1,1,3,3,3-hexafluoroisopropyl-3- {4- [2,4-bis (trichloro Methyl) -s-triazin-6-yl] phenylthio} propionate, ethyl-2- {4- [2,4-bis (trichloromethyl) -s-triazin-6-yl] phenylthio} Acetate, 2-epoxyethyl-2- {4- [2,4-bis (trichloromethyl) -s-triazin-6-yl] phenylthio} acetate, cyclohexyl-2- {4- [2,4 -Bis (trichloromethyl) -s-triazin-6-yl] phenylthio} acetate, benzyl-2- {4- [2,4-bis (trichloromethyl) -s-triazin-6-yl] Phenylthio} acetate, 3- {chloro-4- [2,4-bis (trichloromethyl) -s-triazin-6-yl] phenylthio} Lopionic acid, 3- {4- [2,4-bis (trichloromethyl) -s-triazin-6-yl] phenylthio} propionamide, 2,4-bis (trichloromethyl) -6-p -Methoxystyryl-s-triazine, 2,4-bis (trichloromethyl) -6- (1-p-dimethylaminophenyl) -1,3, -butadienyl-s-triazine, and 2 -Trichloromethyl-4-amino-6-p-methoxystyryl-s-triazine, and an oxime compound is 1,2-octadione-1- (4-phenylthio) phenyl -2- (o-benzoyloxime) (CGI 124, Shiba-Gaigi Co., Ltd.), and ethanone-1- (9-ethyl) -6- (2-methylbenzoyl-3-yl) -1- (o-acetyl Oxime) (CGI 242), oxime OX-03 (Shiba-Geigi), NCI-831 (Adeka), PI-102 (LG Chemical), PBG 304, PBG 305, PBG 3057 (Trony) There is this.

In addition, α-hydroxy ketone compounds (ex. IRGACURE 184, IRGACURE 500, IRGACURE 2959, DAROCUR 1173; Ciba Specialty Chemicals); Phenylglyoxylate compounds (ex. IRGACURE 754, DAROCUR MBF; Ciba Specialty Chemicals); Benzyl dimethyl ketal compounds (ex. IRGACURE 651; Ciba Specialty Chemicals); α-amino ketone compounds (ex. IRGACURE 369, IRGACURE 907, IRGACURE 1300; Ciba Specialty Chemicals); Monoacylphosphine-based compounds (MAPO) (ex. DAROCUR TPO; Ciba Specialty Chemicals); Bisacylphosphene compounds (BAPO) (ex. IRGACURE 819, IRGACURE 819DW; Ciba Specialty Chemicals); Phosphine oxide compounds (ex. IRGACURE 2100; Ciba Specialty Chemicals); Metallocene compounds (ex. IRGACURE 784; Ciba Specialty Chemicals); Iodonium salts (ex.IRGACURE 250; Ciba Specialty Chemicals); And mixtures of one or more of the above, and the like, but are not limited thereto.

The content of the photoinitiator may be 0.01 to 5 parts by weight based on 100 parts by weight of the fluorine-based graft polymer (A), preferably 0.1 to 1 parts by weight, but is not limited thereto. When the content of the radical initiator is 0.01 or less, curing may not be sufficiently performed, and an electrode protective layer of desired physical properties may not be obtained, and thus, appropriately controlled within the above range.

Method for producing graft polymer

The method for preparing a polymer for electrode protective layer according to the present invention may include a mixing step, a polymerization step and optionally a polymer reaction step.

In the mixing step, a monomer comprising a poly (alkylene oxide) and a monomer including a photocurable functional group or a monomer including a functional group capable of introducing a photocurable functional group in the polymer reaction step are grafted. It may be a step of forming a mixture by mixing the raw materials for preparing the polymer, one exemplary mixing step may be a step of mixing the monomer and the solvent to be polymerized with the fluorine-based polymer. Thereafter, the catalyst and ligand may be further mixed with the solvent.

The fluorine-based polymer is a part which becomes a main chain of the grafted polymer (A), and specific examples thereof are as described above, and in one embodiment according to the present invention, poly (vinylidene-co-chlorodrifluoroethylene) ( Hereinafter, P (VDF-co-CTFE)) may be used. In one embodiment of the present invention, the monomer containing the poly (alkylene oxide) and the monomer having a photocurable functional group are poly (ethylene glycol) monomethyl ether methacrylate) (Poly (ethylene glycol) monomethyl ether methacrylate)) ( MPEGMA) and 2-hydroxyethyl methacrylate (hereinafter referred to as HEMA).

The solvent may use a variety of solvents known in the art, for example, N-methyl-2-pyrrolidone (NMP), gamma-butyrolactone (GBL) dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAc), acetonitrile (AcCN) or tetrahydrofuran (THF) and the like can be used, but is not limited thereto.

In addition to the mixed solution, a catalyst and a ligand may be mixed with the solvent.

The catalyst is for example Cu (I) Cl, Cu (II) Cl ₂ , Cu (I) Br, Cu (II) Br ₂ , Fe (II) Cl ₂ , Fe (III) Cl ₃ or mixtures thereof Etc. may be exemplified, but preferably Cu (I) Cl, Cu (II) Cl ₂ , Cu (I) Br, Cu (II) Br _2, or a mixture thereof.

In addition, the content of the catalyst may be 0.0001 to 1 parts by weight, 0.0005 to 0.5 parts by weight or 0.001 to 0.1 parts by weight relative to 100 parts by weight of the monomer mixture. When the content of the catalyst is less than 0.0001 parts by weight, the reaction rate is very slow, and when it is more than 1 part by weight, there is a problem that gelation or catalyst removal is very difficult before the polymerization of the graft polymer is produced.

The ligand is not particularly limited as long as it can be used in a polymerization reaction in combination with the catalyst.

In one example, the ligand contains one or more ligands capable of coordinating with the catalyst through sigma-bonding or two or more carbon atoms coordinating with the catalyst via π-bonding Ligand may be exemplified, but is not limited thereto. Specifically, PMDETA (N, N, N ', N' '′, N ′' ′ '-pentamethyldiethylenetriamine), bpy (2,2'-bipyridine) , dNbpy (4,4'-di-5-nonyl-2,2'-bipyridine), TPMA (tris (2-pyridylmethyl) amine), Me6TREN (tris (2-dimethylaminoethyl) amine) Can be selected but can be used.

The content of the ligand may be 50 to 2000 parts by weight, 100 to 1000 parts by weight or 200 to 500 parts by weight with respect to 100 parts by weight of the catalyst. If the content of the ligand is less than 50 parts by weight of the metal complex formed by the coupling with the catalyst is too small or the reaction is not very slow or progress, if it is more than 2000 parts by weight of the increase in the manufacturing cost, side reactions due to the use of excess ligand This may occur.

The ATRP reaction may use a catalytic reducing agent as necessary. Reducing agents include, but are not limited to, organic reducing agents, inorganic reducing agents, and radical generators.

When the catalyst, ligand, and a catalytic reducing agent of the ATRP reaction are mixed and stirred at 30 ° C. to 100 ° C., an ATRP reaction occurs to obtain a grafted polymer.

The polymer reaction step is a step required when using a monomer containing a functional group capable of introducing a photocurable functional group in the mixing step, and can be used when the photocurable vinyl monomer has a high risk of causing a gelation reaction in the polymerization step. . The polymer reaction step is a condensation reaction of the grafted polymer and the monomolecular compound prepared in the ATRP reaction step may select the appropriate condensation reaction conditions according to the type of functional group. As a specific example, when the monomer used in the mixing step is an alcohol group-containing monomer such as 2-hydroxyethyl methacrylate, the polymer reaction step may introduce a (meth) acrylate group through condensation with an isocyanate-containing (meth) acrylate compound. have. At this time, the reaction temperature can be selected from the range of 40 ℃ to 100 ℃ and optionally may promote the reaction with a catalyst such as dibutyltin dilaurate (dibutyltin dilaurate).

 Polymer according to an embodiment of the present invention is PVDF-co- (PCTFE-g- (mPEGMA-co-HEMA)) prepared by the ATRP method and the graft polymer and 2-isocyanatoethyl acrylate (2 (PVDF-co- (PCTFE-g- (mPEGMA-co-HEMA-AOI)), a compound in which a (meth) acrylate group is introduced into the side chain through a polymer reaction with -isocyanatoethyl acrylate or 2- (acryloyloxy) ethyl isocyanate (AOI) May be)).

After the grafting polymerization reaction, the resulting polymer may be precipitated in an appropriate nonsolvent to remove unreacted monomers. Thereafter, the polymer may be dried under vacuum conditions to obtain a fluorine-based graft polymer (A) according to the present invention.

Electrode protective layer formation method

The electrode protective layer according to the present invention specifically refers to an electrode protective layer coated on at least one surface of an electrode active material or metal lithium to solve the above problems, the fluorine-based graft polymer (A) or the fluorine-based graft polymer ( 0.1 to 50 parts by weight of the polyfunctional vinyl-based crosslinking agent relative to 100 parts by weight of the total fluorine graft polymer (A) in the solution in which A) is dissolved, and a total of 100 of the fluorine-based graft polymer (A) and the polyfunctional vinyl-based crosslinking agent to the photoinitiator. In an amount of 0.01 to 5 parts by weight with respect to parts by weight and may be appropriately diluted in a solvent, the step of stirring for 1 to 6 hours. Thereafter, the solution is mixed with the active material to be coated to prepare a paste or coated on the surface of a foil-type electrode and irradiated with ultraviolet (UV) light for photocuring, followed by further vacuum drying or heating. The solvent can be removed.

According to the exemplary embodiment of the present invention, the electrode on which the protective layer is formed may include an electrode active material, and the electrode active material may be any one selected from the group consisting of metal lithium, a positive electrode active material, and a negative electrode active material.

Lithium secondary battery

In another aspect, the present invention provides a lithium secondary battery comprising an electrode (anode and cathode) to which the polymer composition for electrode protective layer is applied to form a protective layer, a separator and an electrolyte interposed between the negative electrode and the positive electrode.

The positive electrode of the present invention may be prepared by, for example, preparing and applying a mixture of a positive electrode active material, a conductive material, and a binder in a slurry form on a positive electrode current collector, followed by drying, and further adding a filler to the mixture as necessary. You may.

The positive electrode active material is not limited as long as it is commonly used in the art, for example, a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Lithium manganese oxycyclic (LiMnO ₂ ); Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxide; Nickel site type lithium nickel oxide; It may be a compound containing a lithium intercalation material as a main component, such as a lithium manganese composite oxide, a disulfide compound, or a composite oxide formed by a combination thereof.

The positive electrode current collector may be generally 3 μm to 500 μm thick, 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, calcined carbon, or a surface treated with carbon, nickel, titanium, silver, or the like on the surface of aluminum or stainless steel may be used.

The cathode active material slurry may be prepared by adding and mixing an additive such as a binder, a conductive material, a filler, and a dispersant to the cathode active material.

The binder is a component that assists in the bonding between the positive electrode active material and the conductive material and the positive electrode current collector, and may generally be added in an amount of 1 wt% to 30 wt% based on the total amount of the positive electrode active material. Such a binder is not particularly limited and may be conventional ones known in the art, but for example, vinylidene fluoride-hexafluoropropylene copolymer (PVBF-co-HEP), polyvinylidene fluoride, polyacryl Ronitrile (polyacrylonitrile), polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, poly 1 or 2 or more types selected from the group consisting of propylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butyrene rubber (SBR) and fluorine rubber.

The conductive material may be added at 0.05 wt% to 5 wt% based on the total weight of the positive electrode active material. The conductive material is not particularly limited and is not particularly limited as long as it is conductive without causing side reactions with other elements of the battery. Examples thereof include graphite such as natural graphite and artificial graphite; Carbon blacks such as carbon black (super-p), acetylene black, ketjen black, channel black, furnace black, lamp black and summer black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives.

The filler may be used as necessary to determine whether or not to be used as a component for inhibiting the expansion of the positive electrode, and is not particularly limited as long as it is a fibrous material without causing chemical change in the battery, for example, olefin polymers such as polyethylene polypropylene; It may be a fibrous material such as glass fiber, carbon fiber.

The dispersant (dispersant) is not particularly limited, but may be, for example, isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or the like.

The coating may be performed by a method commonly known in the art, but for example, the positive electrode active material slurry may be distributed on one surface of the positive electrode current collector and then uniformly dispersed using a doctor blade or the like. Can be. In addition, the method may be performed by a die casting method, a comma coating method, a screen printing method, or the like.

The drying is not particularly limited, but may be performed within one day in a vacuum oven at 50 ℃ to 200 ℃.

The negative electrode of the present invention may be prepared by, for example, applying a mixture of a positive electrode active material, a conductive material, and a binder on a negative electrode current collector, followed by drying, and optionally, a filler may be further added to the mixture.

The negative electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium as the negative electrode active material. Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fibers, and amorphous carbon; Metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys or Al alloys; Metal oxides capable of doping and undoping lithium, such as SiO _x (0 <x <2), SnO ₂ , vanadium oxide, lithium vanadium oxide; Or a composite including the above metallic compound and carbonaceous material, such as a Si-C composite or a Sn-C composite, and one or a mixture of two or more of them may be used. In addition, a metal lithium thin film may be used as the anode active material. As the carbon material, both low crystalline carbon and high crystalline carbon can be used. Soft crystalline carbon and hard carbon are typical low crystalline carbon, and high crystalline carbon is amorphous, plate, scaly, spherical or fibrous natural graphite or artificial graphite, Kish graphite (Kish) graphite, pyrolytic carbon, liquid phase pitch based carbon fiber, meso-carbon microbeads, liquid phase pitches and petroleum or coal tar pitch High temperature calcined carbon, such as derived cokes) is typical.

Additives such as binders, conductive materials, fillers, and dispersants used in the negative electrode may be the same as or included in the aforementioned positive electrode.

The separator may be an insulating thin film having high ion permeability and mechanical strength, and may generally have a pore diameter of 0.01 μm to 10 μm and a thickness of 5 μm to 300 μm. As such a separator, a porous polymer film made of a polyolefin-based polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer and ethylene / methacrylate copolymer may be used alone. Alternatively, these may be laminated and used, or a nonwoven fabric made of a conventional porous nonwoven fabric such as glass fibers having high melting point, polyethylene terephthalate fiber, or the like may be used, but is not limited thereto.

In addition, the electrolyte may include an organic solvent and a lithium salt commonly used in the electrolyte, and are not particularly limited.

The lithium salt may be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN (C ₂ F ₅ SO ₃ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ . LiCl, LiI, or LiB (C ₂ O ₄ ) ₂ and the like can be used. The concentration of the lithium salt is preferably used within the range of 0.1 to 2.0M. When the concentration of the lithium salt is included in the above range, since the electrolyte has an appropriate conductivity and viscosity, it can exhibit excellent electrolyte performance, and lithium ions can move effectively.

Typical organic solvents include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxy ethane, diethoxyethane and vinylene. It may be one or more selected from the group consisting of carbonate, sulfolane, gamma-butyrolactone, propylene sulfite and tetrahydrofuran.

In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates among the carbonate-based organic solvents, are highly viscous organic solvents, and thus may be preferably used because they dissociate lithium salts in the electrolyte well. When used by mixing a low viscosity, low dielectric constant linear carbonate in an appropriate ratio, it can be more preferably used to make an electrolyte having a high electrical conductivity.

In the lithium secondary battery of the present invention, an electrode assembly is formed by disposing a separator between a positive electrode and a negative electrode, and the electrode assembly may be manufactured by putting an electrolyte into a cylindrical battery case or a square battery case. Alternatively, after stacking the electrode assembly, it may be prepared by impregnating it in an electrolyte and sealing the resultant obtained in a battery case.

The battery case used in the present invention may be adopted that is commonly used in the art, there is no limitation on the appearance according to the use of the battery, for example, cylindrical, square, pouch (coin) or coin using a can ( coin).

The lithium secondary battery according to the present invention may not only be used in a battery cell used as a power source of a small device, but also preferably used as a unit battery in a medium-large battery module including a plurality of battery cells. Preferred examples of the medium-to-large device include, but are not limited to, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, power storage systems, and the like.

Hereinafter, the present invention will be described in detail with reference to Examples. However, embodiments according to the present invention can be modified in many different forms, the scope of the present invention should not be construed as limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Example

Production Example  (One) Grafting Copolymerized PVDF -co- ( PCTFE -g- ( mPEGMA -co- ( HEMA - AOI Manufacture of))) (A1)

15 g of P (VDF-co-CTFE) with a weight average molecular weight (hereinafter referred to as Mw) of 600,000 in a 1000 ml flask, poly (ethylene glycol) monomethyl ether methacrylate (mPEGMA, ethylene oxide addition mole number) = 9 ) 116 g and 3.35 g of 2-hydroxyethyl methacrylate (HEMA) were added to 450 ml of solvent dimethyl sulfoxide (DMSO), and the mixture was stirred under nitrogen conditions for 1 hour.

Subsequently, 0.003 g of CuCl ₂ as an ATRP reaction catalyst, 0.014 g of TPMA as a ligand and 0.04 g of azobisisobutyronitrile (AIBN) as a reducing agent were added to the flask, followed by stirring at 60 ° C. for 30 hours under nitrogen conditions. The reaction proceeded. Monomer conversion was 82%.

After the polymerization was completed, the reaction was cooled to room temperature and bubbled into the reactor for 2 hours. 0.002 g of BHT (2,6-bis (1,1-dimethylethyl) -4-methylphenol) was added as a thermal polymerization inhibitor, the reaction was heated to 50 ° C., 4.36 g of 2-isocyanatoethyl acrylate (AOI), and DBTDL as a condensation catalyst. 0.16 g of (dibutyltin dilaurate) was added thereto. The reaction was terminated after reacting for 24 hours in the presence of oxygen. In the above method, a mixed solution of PVDF-co- (PCTFE-g- (mPEGMA-co- (HEMA-AOI))) polymer having a fluorine chain content of 11% and a monomer was obtained. The unreacted residual monomer is included in the polymer network in the subsequent photopolymerization process.

Production Example  (2) Grafting Copolymerized PVDF -co- ( PCTFE -g-P ( mPEGA -co- HBA - AOI )) Preparation (A2)

20 g of P (VDF-co-CTFE) having a weight average molecular weight (hereinafter referred to as Mw) of 600,000 in a 1000 ml flask, 112 g of mPEGA (polyethylene glycol monomethyl ether acrylate, number of moles of ethylene oxide = 9) and 4-hydride 3.65 g of hydroxybutyl acrylate (4-hydroxybutyl acrylate, HBA) was added to 480 ml of solvent DMSO and stirred for 1 hour under nitrogen conditions.

Thereafter, 0.003 g of CuCl ₂ as an ATRP reaction catalyst, 0.014 g of TPMA as a ligand, and 0.04 g of AIBN as a reducing agent were added to the flask, followed by stirring at 60 ° C. for 30 hours under nitrogen conditions to perform the ATRP reaction. Monomer conversion was 80%.

After the polymerization was completed, the reaction was cooled to room temperature and bubbled into the reactor for 2 hours. 0.002 g of BHT (2,6-bis (1,1-dimethylethyl) -4-methylphenol) was added as a thermal polymerization inhibitor, and the reaction was heated to 50 ° C., 4.35 g of 2-isocyanatoethyl acrylate (AOI), and DBTDL as a condensation catalyst. 0.16 g of (dibutyltion dilaurate) was added thereto. The reaction is terminated after reacting for 24 hours in the presence of oxygen. In the same manner as above, a mixed solution of PVDF-co- (PCTFE-g- (mPEGA-co- (HBA-AOI))) polymer having a fluorine-based chain content of 15% was obtained. The unreacted residual monomer is included in the polymer network in the subsequent photopolymerization process.

Production Example  (3) Grafting Copolymerized PVDF -co- ( PCTFE -g-P ( mPEGMA -co- ( HEMA - AOI ))) Preparation of co-PTrFE (A3)

In a 1000 ml flask, 15 g of P (VDF-co-CTFE-co-TrFE) having a weight average molecular weight (Mw) of 560,000 in a 1000 ml flask, 116 g of mPEGMA (the number of moles of ethylene oxide added = 9) and the monomer HEMA 0.70 g were solvent dimethyl. It was put into 350 ml of formamide (DMF) and stirred for 1 hour under nitrogen conditions.

Thereafter, 0.003 g of CuCl ₂ as an ATRP reaction catalyst, 0.014 g of TPMA as a ligand, and 0.04 g of AIBN as a reducing agent were added to the flask, followed by stirring at 60 ° C. for 30 hours under nitrogen conditions to perform the ATRP reaction. Monomer conversion was 80%.

After the polymerization was completed, the reaction was cooled to room temperature and air was bubbled into the reactor for 2 hours. 0.0004 g of BHT (2,6-bis (1,1-dimethylethyl) -4-methylphenol) was added as a thermal polymerization inhibitor, the reaction was heated to 50 ° C., 0.84 g of 2-isocyanatoethyl acrylate (AOI), and DBTDL as a condensation catalyst. (dibutyltion dilaurate) 0.031 g was added thereto. The reaction is terminated after reacting for 24 hours in the presence of oxygen. In the same manner as above, a mixed solution of PVDF-co- (PCTFE-g- (mPEGMA-co- (HHEMA-AOI)))-co-PTrFE polymer having a fluorine chain content of 11% was obtained. The unreacted residual monomer is included in the polymer network in the subsequent photopolymerization process.

Comparative Production Example (1) Preparation of fluorine-based chain-free P (mPEGMA-co- (HEMA-AOI)) (B1)

In a 1000 ml flask, 116 g of mPEGMA (ethylene oxide added mole number = 9) and 3.35 g of HEMA were added to 350 ml of solvent DMSO and stirred for 1 hour under nitrogen conditions. 0.10 g of AIBN was added as a radical initiator, followed by stirring at 60 ° C. for 20 hours under a nitrogen atmosphere to proceed with the polymerization reaction. Thereafter, the same procedure as in Preparation Example 1 was performed to obtain a mixed solution (B1) of a P (mPEGMA-co- (HEMA-AOI))) polymer and a monomer.

compare Production Example  (2) photocurable Vinyl chain  Free Grafting Copolymerized PVDF Preparation of -co- (PCTFE-g-P (mPEGMA-co-HEMA)) (B2)

Under the same conditions as in Preparation Example 1, 15 g of P (VDF-co-CTFE) having a weight average molecular weight (hereinafter referred to as Mw) of 600,000, 116 g of mPEGMA (the number of moles of ethylene oxide added = 9) and the monomer H35 3.35 g After graft polymerization with 450 ml of solvent DMSO, a mixed solution (B2) of PCTFE-gP (mPEGMA-co-HEMA) and unreacted equivalents was obtained without performing a vinyl group-introduced polymer reaction on the side chain.

Preparation Examples 1 to 3 and Comparative Preparation Examples 1 to 2 are shown in Table 1 below.

Polymer Poly (alkylene oxide): vinyl side chain ¹ Fluorinated Polymer Content ² Mw (PDI ³ ) A1 90:10 11% 1.6 million (5.9) A2 90:10 15% 1.15 million (4.5) A3 98: 2 11% 1.55 million (5.5) B1 90:10 0% 170,000 (2.9) B2 90: 0 ⁴ 11% 1.6 million (5.9)

* 1: poly (alkylene oxide) -containing polymer unit: molar ratio of photocurable vinyl-based side chain-containing polymer unit

* 2: Content of fluorine-based backbone relative to the sum of graft polymer and residual monomer

* 3: dispersion degree, Mw / Mn

* 4: poly (alkylene oxide) -containing polymerized unit: molar ratio of hydroxy-containing polymerized unit = 90:10

Example-Preparation of Cured Electrode Protective Layer

Using the fluorine-based graft polymer prepared in Preparation Examples 1 to 3 were mixed in a weight ratio (pt) as shown in Table 2 and stirred for 6 hours to prepare a photocurable polymer solution. The solution was coated on a 2 cm ² × 0.1 cm circular SUS substrate in a dry room and then exposed to a metal halide lamp for 3 minutes. After vacuum drying at 60 ℃ for 48 hours to prepare a completely dried polymer electrode protective layer. The coating amount of the polymer solution was adjusted so that the thickness of the final electrode protective layer was about 100 μm.

Comparative Example-Preparation of Cured Polymer Membrane

Using the polymer prepared in Comparative Preparation Examples 1 and 2 were mixed in the composition ratio shown in Table 2 and stirred for 6 hours to prepare a uniform solution. Hereinafter, the same polymer cured film as the method for producing a cured film in the above Example was prepared.

Examples 1 to 5 and Comparative Examples 1 to 3 are shown in Table 2 below.

Polymer (pt) LiTFSI Content (pt) Hardener (pt) Photoinitiator Example 1 A1 (100) 40 0 One Example 2 A2 (100) 40 0 One Example 3 A3 (100) 40 0 One Example 4 A1 (100) 40 5 One Example 5 A3 (100) 40 5 One Comparative Example 1 B1 (100) 40 0 One Comparative Example 2 B1 (100) 40 5 One Comparative Example 3 B2 (100) 40 5 One

* LiTFSI: Lithium bistrifluoromethanesulfonimidate * Hardener: PETA (Pentaerythritol triacrylate)

Photo-initiator: Irgacure 819

Experimental Example (1) Measurement of the ion conductivity of the electrode protective layer

Ion conductivity of the electrode protective layer prepared in Examples 1 to 5 and Comparative Examples 1 to 3 was measured using the following equation 1 after measuring the impedance.

The lithium salt-containing electrode protective layer applied on the circular SUS (stainless steel) substrate was contacted with lithium metal electrodes having the same surface area, and then an alternating voltage was applied through the electrodes on both sides of the sample at room temperature. At this time, the applied frequency was set to an amplitude range of 0.01 Hz to 1 MHz and the impedance was measured using BioLogic VMP3. The bulk electrolyte resistance is obtained from the intersection (R _b ) where the semicircle or straight line of the measured impedance trajectory meets the real axis, and the ion conductivity of the polymer electrode protective layer is calculated from the width and thickness of the sample and is shown in Table 3 below.

[Equation 1]

σ: ion conductivity

R _b : Impedance trajectory intersection with real axis

A: Width of the sample

t: thickness of sample

Experimental Example (2) Evaluation of Electrochemical Stability of Electrode Protective Layer

As in the experimental example, a cell in which a lithium salt-containing polymer electrode protective layer was sandwiched between SUS and lithium metal was prepared. At 60 ° C., a voltage of 0.0 to 5.0 V was applied at a rate of 1 mV / sec, and cyclic voltammetry (IVIUM, Inc.) was performed to evaluate oxidation potential stability at off-set voltage. The results are shown in Table 3.

Ion Conductivity (S / cm) OFF-Set Voltage (V) Cured film shape Example 1 5.1 x 10 ^-7 4.3 ○ Example 2 3.3 x 10 ^-7 4.5 ○ Example 3 4.5 x 10 ^-6 4.2 ○ Example 4 1.0 x 10 ^-7 4.5 ○ Example 5 9.7 x 10 ^-7 4.4 ○ Comparative Example 1 4.6 x 10 ^-7 3.7 x Comparative Example 2 1.1 x 10 ^-7 3.7 x Comparative Example 3 1.5 x 10 ^-6 4.1 △

(○: The film remains on the SUS, retaining the film form; △: The film remains on the SUS, retaining the film form, but pinholes are observed throughout; ×: SUS is completely exposed)

As shown in Table 3, the electrode protective layer according to the present invention in contact with the lithium metal to confirm the ion conductivity and electrochemical stability, the ion conductivity is excellent and the electrochemical stability is obtained, the result of the lithium metal electrode It was confirmed that the protective layer can be applied well. In addition, it was confirmed that the resistance to the electrolyte is high and the possibility of damage to the electrode protective layer due to the side reaction with the electrolyte is low. On the other hand, the electrode protective layer without the fluorinated polymer is excellent in ionic conductivity but poor in electrochemical stability and electrolyte resistance, and in the graft polymer in which the photocurable functional group is not introduced into the side chain, the electrolyte resistance is not sufficient even after photocuring. Therefore, it was found that it is impossible to apply the electrode protective layer.

Claims (12)

A polymer for electrode protective layers comprising a polymer (A) on which a monomer containing poly (alkylene oxide) and a monomer containing a photocurable functional group are grafted onto a fluorine-based polymer.
The method of claim 1,
The fluorine-based polymer is a polymer for electrode protective layer, characterized in that it comprises a structure of the formula (1).
[Formula 1]

(In Formula 1, p, q, and r are each independently 0 ≦ p ≦ 20,000, 1 ≦ q ≦ 22,000, and 0 ≦ r ≦ 15,000).
The method of claim 1,
The polymer (A) is a polymer for electrode protective layer, characterized in that it comprises a structure of the formula (2).
[Formula 2]

(In Formula 2, p, q and r are each independently 0 ≦ p ≦ 20,000, 1 ≦ q ≦ 22,000 and 0 ≦ r ≦ 15,000,
R ₁ , R ₂ , R ₃ and R ₄ are each independently hydrogen or methyl,
R ₅ is any one selected from hydrogen, an alkyl group having 1 to 12 carbon atoms, and a phenyl group which is unsubstituted or substituted with an alkyl group having 1 to 12 carbon atoms,
X is a simple link or alkylene having 1 to 12 carbon atoms, alkyloxycarbonyl having 1 to 12 carbon atoms (

), Urethane group-containing alkyleneoxycarbonyl having 1 to 12 carbon atoms, poly (ethylene oxide) carbonyl and phenylene having an added mole number of 1 to 10 ethylene oxide,
l, m and n are each independently 2≤l≤230, 1≤m≤200 and 2≤n≤50,
R ₆ is any one selected from hydrogen, chlorine or bromine)
The method of claim 1,
The poly (alkylene oxide) is a polymer for electrode protective layer, characterized in that the poly (ethylene oxide) or poly (propylene oxide).
The method of claim 1,
The photocurable functional group is an electrode protective layer polymer, characterized in that the unsaturated vinyl group.
The method of claim 1,
Polymer for electrode protective layer, characterized in that the monomer containing the poly (alkylene oxide) and the monomer containing a photocurable functional group is contained in a molar ratio of 99.9: 0.1 to 70:30.
A polymer composition for electrode protective layer comprising the polymer for electrode protective layer according to claim 1, a polyfunctional vinyl-based crosslinking agent and a photoinitiator.
The method of claim 7, wherein
The polyfunctional vinyl-based crosslinking agent is a polymer composition for electrode protective layer, characterized in that it comprises 0.1 to 50 parts by weight relative to 100 parts by weight of the polymer (A) according to claim 1.
The method of claim 7, wherein
The photoinitiator polymer composition for an electrode protective layer, characterized in that it comprises 0.01 to 5 parts by weight relative to the total 100 parts by weight of the polymer (A) and the polyfunctional vinyl-based crosslinking agent according to claim 1.
An electrode protective layer formed by photocuring the polymer composition for electrode protective layers in any one of Claims 7-9.
The method of claim 10,
The electrode includes an electrode active material,
The electrode active material is an electrode protective layer, characterized in that any one selected from the group consisting of metal lithium, a positive electrode active material and a negative electrode active material.
 A secondary battery comprising an electrode including the electrode protective layer according to claim 10.