KR20180027953A - Porous current collector for lithium electrode and lithium electrode comprising the same - Google Patents

Abstract

The present invention relates to a porous collector to which a lithium ion conductive material is coated on a pore, and a lithium electrode including the same. According to the present invention, the porous collector for lithium electrodes is capable of preventing formation and growth of lithium dendrites when applied to the lithium electrodes, since the lithium ion conductive material whose elastic modulus is greater than 1 and less than 5 GPa is coated.

Description

TECHNICAL FIELD [0001] The present invention relates to a porous current collector for a lithium electrode, and a lithium electrode including the same. BACKGROUND OF THE INVENTION [0002]

The present invention relates to a porous current collector coated with a lithium ion conductive material in pores and a lithium electrode including the same.

With the rapid development of the electronics, communications and computer industries, applications of energy storage technology to camcorders, mobile phones, notebooks, PCs, and even electric vehicles are expanding. Accordingly, development of high performance secondary batteries which are light and long-lasting and highly reliable is underway.

Among the currently applied secondary batteries, the lithium secondary battery developed in the early 1990s has advantages such as higher operating voltage and higher energy density than conventional batteries such as Ni-MH, Ni-Cd and sulfuric acid-lead batteries using an aqueous electrolyte solution .

Lithium metal, carbon-based material, silicon and the like are used as an anode active material of a lithium secondary battery, and lithium metal has the advantage of obtaining the highest energy density, and thus, research has been continuously carried out.

The lithium electrode is usually produced by using a flat copper or nickel foil as a current collector and attaching a lithium foil thereon. When such a flat current collector is used, electrons moving to the lithium foil through the current collector move in a unidirectional flow, which causes a non-uniformity of electron density on the lithium surface, and a lithium dendrite There is a problem.

In order to solve such a problem, a porous current collector and a lithium electrode made of lithium metal inserted in the pores of the porous current collector have been proposed. The lithium electrode using the porous current collector is advantageous in that the electron distribution on the lithium metal surface can be made uniform because the contact area between the lithium metal as the active material and the current collector is wide. As a result, the lithium utilization rate and cycle life are increased as compared with the conventional planar current collector, and the lithium dendrite formation is suppressed.

However, the lithium electrode having such a structure has a disadvantage that the lithium metal surface can not receive the pressure due to the cell lamination structure, so that the lithium dendrite growth inhibiting effect by the pressure can not be obtained.

Japanese Patent Application Laid-Open No. 2002-42894, Lithium battery

In order to solve the above problems, the present inventors have made a porous current collector coated with a lithium ion conductive material so that a constant pressure can be applied to the lithium metal. When the porous current collector thus prepared is applied to a lithium electrode, The present inventors have completed the present invention.

Accordingly, an object of the present invention is to provide a porous current collector capable of inhibiting the growth of lithium dendrite and a lithium electrode including the same.

According to an aspect of the present invention, there is provided a porous current collector coated with a lithium ion conductive material in pores, wherein the lithium ion conductive material has a modulus of elasticity of more than 1 Gpa and less than 5 Gpa, Thereby providing a lithium electrode.

The porous current collector for a lithium electrode according to the present invention is coated with a lithium ion conductive material having an elastic modulus of more than 1 Gpa and less than 5 Gpa, thereby exhibiting an effect of inhibiting the formation and growth of lithium dendrite when applied to a lithium electrode.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Porous current collector for lithium electrode

The present invention provides a porous current collector coated with a lithium ion conductive material having an elastic modulus of more than 1 Gpa and less than 5 Gpa.

The current collector serves to supply the electrons provided from the external conductor to the electrode active material or conversely to flow electrons generated as a result of the electrode reaction to the external conductor. In the case of the lithium electrode, flat copper or nickel foil is usually used . Such a flat current collector has a problem that the current and the potential distribution are not constant on the surface of the lithium electrode, thereby causing formation of lithium dendrite.

The porous current collector for a lithium electrode of the present invention is advantageous in that the distribution of electrons on the surface of the lithium metal becomes more uniform since the contact area between the active material lithium and the current collector is wide. As a result, lithium dendrite formation is suppressed compared with the conventional planar current collector. In addition, since the lithium ion conductive material coated on the pores can suppress the growth of lithium dendrites, it is suitable for use as a current collector for a lithium electrode.

The material of the porous current collector for a lithium electrode according to the present invention is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and a material commonly used in the art can be used. As a material of the porous current collector of the present invention, carbon or a metal such as Ni, Cu, Ti, V, Cr, Mn, Fe, Co, Zn, Mo, W, Ag, Au, Ru, Pt, , A metal selected from the group consisting of Bi, Si, Sb, and an alloy thereof, and the like.

The porous carbonaceous material may be at least one selected from the group consisting of, for example, activated carbon, graphite, graphene, carbon nanotube (CNT), carbon fiber, carbon black and carbon aerosol. Further, a polymer surface-treated with the carbon-based material may be used. The shape of the porous carbonaceous material may vary and may be in the form of, for example, felt, paper, cloth, foam, and mesh.

Since the carbon-based material is lighter than a general metal, when the porous carbon-based material is used, the weight of the electrode can be reduced by about 70% as compared with the metal current collector. This has the advantage of increasing the energy density per cell weight. Particularly, when the electrode is formed at a thickness of 250 μm or less, the efficiency of the process can be improved when the porous carbon body is used in comparison with the metal current collector.

When a metallic material is used as the porous collector, the metal may be in the form of a mesh, a foam, a fiber, an etched metal, or a back and forth concave shape. In addition, metal-plated synthetic fibers prepared by dipping, spraying, or vacuum-depositing synthetic fibers having various forms as described above may be used. Such a metal current collector is advantageous in that the flexibility of the substrate is high and the breakage occurs less during the process.

The porous current collector may be a polymer fiber nonwoven fabric having a surface coated with a metal. Such a current collector is lighter than a metal current collector and can realize a high energy density and has an advantage of being more durable than a carbon-based current collector.

As the polymer fiber, at least one selected from the group consisting of polyethylene terephthalate, polyethylene oxide, polyethylene, polypropylene, polymethyl methacrylate, and polyacrylic acid may be used. Preferably, polyethylene terephthalate (PET) use. PET has a small specific gravity and is lightweight, and has excellent strength and flexibility.

The polymer fiber may be a porous nonwoven fabric having micropores. The polymer fiber nonwoven fabric has a three-dimensional network structure in which polymer fibers having a diameter of 0.5 to 20 占 퐉 are intertwined with each other. The polymer fiber nonwoven fabric may be commercially available or may be directly manufactured.

The method for producing the polymer fiber nonwoven fabric is not particularly limited, and examples thereof include electro-spinning using a polymer solution, melt spinning, electro-blowing, melt-blowing Spun-bonded, air laid, or wet laid methods, as disclosed in US Pat. Of these, electrospinning is preferably used.

The porous current collector may be manufactured by coating a metal on the polymer fiber nonwoven fabric.

The metal coated on the polymeric fibrous nonwoven fabric may be one or more selected from the group consisting of copper, nickel, aluminum, chromium, zinc, and stainless steel, although metal materials such as those described above may be used as the conductive metal without limitation. And is preferably copper. Copper has the advantage of being electrochemically inactive in the operating range of the lithium electrode, being stable to the reduction reaction and having high electrical conductivity.

The method of coating the polymeric fibrous nonwoven fabric with a metal is not particularly limited in the present invention. For example, plating, sputtering, ion plating, arc evaporation, ion beam assisted deposition, or vacuum evaporation may be used.

 Alternatively, a method may be used in which a metal powder having a pore size smaller than that of the pore size is mixed with a binder and a solvent to form a slurry, followed by coating, spraying or dipping the slurry on the polymer fiber nonwoven fabric and fixing the metal powder through hot air drying or thermocompression .

Among these, a plating method is preferably used so that the pores of the nonwoven fabric can be uniformly coated without blocking the pores.

At this time, the metal is preferably contained in an amount of 7 to 30% by weight based on the total weight of the lithium electrode. If the content of the metal is less than the above range, the surface of the polymeric fiber nonwoven fabric is difficult to be completely coated with the metal, so that it is difficult to secure the performance of the current collector. In addition, if the amount exceeds the above range, the weight of the current collector increases and the volume of the pore through which the lithium metal can be filled is reduced, so that a high capacity electrode can not be realized.

For the same reason, it is preferable that the metal is uniformly coated on the polymer fiber in a thickness of 0.1 to 2 μm.

The porous current collector used in the present invention has a porosity of 50 to 99%, more preferably 60 to 90%, before coating the lithium ion conductive material. In this case, the porosity refers to a volume ratio occupied by the pores with respect to the total volume of the porous collector, and can be calculated by (weight of the porous collector) / (measured volume of the porous collector * theoretical density of the collector). When the porosity satisfies the above range, the contact surface area with lithium metal as the active material can be maximized, and durability and processability are excellent.

The average particle size of the pores of the porous current collector before coating the lithium ion conductive material may be 5 to 500 μm, preferably 10 to 100 μm. If the average particle diameter of the pores is less than 5 탆, lithium metal can not be inserted into the pores in a sufficient amount, resulting in deterioration of the battery capacity. If the average particle diameter exceeds 100 탆, the durability is lowered and the lithium dendrite growth inhibiting effect Therefore, it is properly adjusted within the above range.

The thickness of the porous current collector is preferably 10 to 200 占 퐉, more preferably 50 to 150 占 퐉. The collector thickness of less than 10 μm is difficult to implement in the process and lithium metal can not be inserted in a sufficient amount, so that the capacity of the battery can not be secured. If the collector thickness exceeds 200 μm, the electrode becomes thick There is a problem that battery performance is deteriorated due to a rapid increase in resistance, so that it is appropriately adjusted within the above range.

The porous current collector for a lithium electrode of the present invention includes a coating layer made of a lithium ion conductive material having an elastic modulus of more than 1 Gpa and less than 5 Gpa to suppress the formation of lithium dendrites.

As described above, the porous current collector maximizes the contact surface area with the lithium metal, which is an electrode active material, so that the imbalance of the current density is reduced as compared with the planar current collector, and the lithium dendrite growth is suppressed. However, in the case of the lithium electrode using the porous current collector, the lithium metal is inserted into the pores of the current collector, and thus the pressure due to the cell lamination structure is not received. As a result, the effect of suppressing the lithium dendrite growth due to pressure can not be obtained have. As a result, the volume and surface area of the lithium dendrite produced becomes large, and the effect of using the porous current collector can no longer be obtained.

In order to solve this problem, the present invention has been made such that a porous current collector is coated with a lithium ion conductive material having a suitable tensile strength so that pressure can be applied to the lithium metal filled in the pores.

The lithium ion conductive material preferably has an elastic modulus of more than 1 Gpa and less than 5 Gpa.

The modulus of elasticity is the degree of strain that occurs when an elastic material is stressed, which is the degree to which the material is pressure resistant. That is, a hard material which does not easily deform has a large elastic modulus value. The elastic modulus in this specification means a volume modulus (k), which can be expressed by the following equation (1).

[Equation 1]

k =? P / (? V / V)

(In the above equation (1),? P is the pressure change,? V is the volume change, and V is the initial volume)

The lithium ion conductive material exhibits a high resistance to changes in the volume of the electrode due to charging and discharging, and the lithium dendrite inhibiting effect is also greater in a material having a high modulus of elasticity. However, as the modulus of elasticity increases, the resistance of the battery increases, and the speed and output characteristics of the battery deteriorate.

As a result of experiments conducted by the inventors of the present invention, it has been confirmed that when the elastic modulus of the lithium ion conductive material satisfies the above range, the lithium dendrite inhibiting effect can be obtained within a range in which the battery resistance is not greatly increased.

The lithium ion conductive material may be an organic or inorganic compound satisfying the elastic modulus and having a lithium ion conductivity of 10 ^-7 S / cm or more.

The organic compound may be a polymer having ionic conductivity. The ion conductive polymer has a plurality of electron donor atoms or atomic groups capable of forming coordination bonds with lithium ions in the chain and can move lithium ions between positions capable of coordination by the local movement of the polymer chain segments.

These ion conductive polymers include, for example, polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol (PEG), polyphosphazene, polysiloxane, polydimethylsiloxane, polyacrylonitrile (PMMA), polyvinyl chloride, polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-co-HFP), polyethyleneimine, polyphenylene terephthalamide, polymethoxy Polyethylene glycol methacrylate, and poly 2-methoxyethyl glycidyl ether. Preferably, polyethylene oxide (PEO) is used.

The ion conductive polymer may further include a lithium salt for improving ionic conductivity. The lithium salt of the type that may be used is not particularly limited, and examples thereof include _{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, LiSCN, LiC (CF 3 SO 2) 3, (CF 3 SO 2) 2 NLi, (FSO 2) 2 NLi, chloroborane lithium, lower aliphatic Lithium carbonate, lithium carbonate, 4-phenyl lithium borate, lithium imide, and combinations thereof.

The inorganic compound may be, for example, LiPON, a hydride compound, a thio-LISICON compound, a NASICON compound, a LISICON compound and a perovskite compound. ) Based compound, or a mixture of two or more thereof.

The hydride (hydride) compound is _{LiBH 4 -LI, Li 3 N,} Li 2 NH, Li 2 BNH 6, Li 1.8 N 0.4 C l0.6, LiBH 4, Li 3 P-LiCl, Li 4 SiO 4, Li ₃ PS _4, or Li ₃ SiS ₄ , but are not limited thereto.

The thio receiving cone (thio-LISICON) based compound is Li ₂ S ₁₀ GeP _12, Li _{3. 25 Ge 0 .25 P 0. 75 S} 4 or _{Li 2 S-GeS-Ga 2} S 3 day, but can be, but is not limited thereto only.

The NASICON-based compound is Li _{1 . 3} Al _{0 . 3} Ge _{1 .7} (PO ₄ ) ₃ , Li _{1 . 3} Al _{0 . 3} Ti _{1 .7} (PO ₄ ) ₃ or LiTi _0.5 Zr _1.5 (PO ₄ ) ₃ .

The LISICON-based compound may be Li ₁₄ Zn (GeO ₄ ) ₄ , but is not limited thereto.

The perovskite-based compound may be Li _x La _{1 - x} TiO ₃ (0 <x <1) or Li ₇ La ₃ Zr ₂ O ₁₂ , and specifically Li _{0 . 35} La _{0 . 55} TiO ₃ , Li _{0 . 5} La _{0 . 5} TiO ₃ or Li ₇ La ₃ Zr ₂ O ₁₂ , but is not limited thereto.

In the present invention, the lithium ion conductive material coated on the porous current collector functions to suppress the growth of lithium dendrite by applying an appropriate pressure to the lithium metal inserted in the current collector pores.

The method of coating the lithium ion conductive material on the porous collector is not particularly limited, and a conventional method can be used.

Specifically, when the lithium ion conductive material is an ion conductive polymer, a method used in a conventional wet process such as spin coating, spray coating, doctor blade coating, dip coating and the like can be used. Preferably, the dip coating method is used so that the lithium ion conductive material can be uniformly coated on the surface of the porous current collector.

When the lithium ion conductive material is an inorganic compound, a method selected from an electron beam deposition method, an organic metal chemical vapor deposition method, a reactive sputtering method, a high frequency sputtering method, and a magnetron sputtering method may be used, but not limited thereto, Lt; / RTI &gt;

The lithium ion conductive material is coated on the porous collector in a thickness of 1 to 20 탆. If the thickness of the coating layer is less than the above range, sufficient lithium dendrite growth inhibiting effect can not be obtained. If the thickness exceeds the above range, the resistance of the battery increases and the capacity decreases.

Lithium electrode

The present invention provides a lithium electrode comprising a porous current collector coated with a lithium ion conductive material as described above.

The lithium electrode includes lithium metal as an active material, and lithium metal may be attached to the outside of the porous current collector or included in the current collector.

Specifically, the lithium electrode according to an embodiment of the present invention may have a structure in which a lithium metal foil is attached to one surface of a porous current collector.

According to another embodiment of the present invention, the lithium metal may be inserted into the pores of the porous current collector. In this case, the method of inserting the lithium metal into the pores is not particularly limited and may be various. For example, lithium metal may be filled in the pores by an electroplating method, a melting method, a thin film manufacturing technique, or a method of uniformly filling lithium particles in collector pores by a paste coating method.

The 'thin film manufacturing technique' refers to a technique of physically depositing in a moisture-free atmosphere. Examples of such thin film manufacturing techniques include a thermal evaporation method, an electron beam evaporation method, an ion beam evaporation method, a sputtering method, an arc evaporation method and a laser ablation evaporation method .

The paste coating method is a method in which lithium or lithium alloy particles and a solvent are applied in a paste form, or a binder such as lithium particles and PVDF is mixed with a solvent and applied in a paste form.

In addition, a lithium metal foil is placed on the porous current collector, followed by compression, thereby manufacturing a high-density lithium electrode. The term 'squeeze' refers to densification by applying pressure. Examples of the means used for squeezing include a roll press or a plate-like press. The pressure applied at this time is usually 1 to 10 kg / cm ² .

In the lithium electrode thus produced, lithium metal is present outside the coating layer of the lithium ion conductive material. However, as the charging and discharging of the battery is repeated, lithium ions penetrate between the porous current collector and the coating layer of the lithium ion conductive material, The lithium metal is located between the current collector and the coating layer. That is, the lithium electrode has a structure such that it further includes a protective layer on the surface of the lithium metal, so that the generation and growth of the lithium dendrite can be effectively suppressed.

The lithium electrode of the present invention may further include a lithium ion conductive protective film.

The protective film may be attached to at least one surface of the lithium electrode to inhibit the growth of the lithium dendrite and may serve as a separator. The material of such a protective film is not particularly limited in the present invention, and the above-mentioned lithium ion conductive material may be used.

Thinner the thickness of the protective film is advantageous to the output characteristics of the battery, but it is preferable that the protective film is thicker than a certain thickness to exhibit the lithium dendrite growth inhibiting effect, and therefore, it is preferably 0.5 to 20 탆.

Lithium secondary battery

The present invention provides a lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed therebetween and an electrolyte, and a lithium electrode according to the present invention as a negative electrode.

The lithium electrode according to the present invention includes a porous current collector coated with a lithium ion conductive material to improve the unevenness of current density and inhibit the formation and growth of lithium dendrite. Therefore, when applied to a lithium secondary battery, The characteristics can be improved.

The constitution of the anode, the separator and the electrolyte of the lithium secondary battery is not particularly limited in the present invention, and is well known in the art.

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

The positive electrode current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery. For example, carbon, nickel , Titanium, silver, or the like may be used. At this time, the cathode current collector may use various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric having fine irregularities formed on the surface so as to increase the adhesive force with the cathode active material.

As the cathode active material constituting the electrode layer, all of the cathode active materials available in the art can be used. As specific examples of such a cathode active material, lithium metal; Lithium cobalt-based oxides such as LiCoO ₂ ; Li _{1 + x} Mn _{2 - x} O ₄ (where x is 0 to 0.33), lithium manganese-based oxides such as LiMnO ₃ , LiMn ₂ O ₃ and LiMnO ₂ ; Lithium copper oxide such as Li ₂ CuO ₂ ; Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; LiNi _{1 - x} M _x O ₂ wherein M is Co, Mn, Al, Cu, Fe, Mg, B, or Ga and x is 0.01 to 0.3; LiMn _{2 - x} MxO ₂ (where, M = Co, Ni, Fe , Cr, and Zn, or Ta, x = 0.01 to 0.1 Im) or Li ₂ Mn ₃ MO ₈ (where, M = Fe, Co, Ni , Cu Or Zn); Nickel-manganese-lithium complex represented by Li (Ni _a Co _b Mn _c ) O ₂ (where 0 <a <1, 0 <b <1, 0 <c < Cobalt oxide; Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; Sulfur or disulfide compounds; _{LiFePO 4, LiMnPO 4, LiCoPO 4} , LiNiPO 4 , such as phosphate; Fe ₂ (MoO ₄ ) ₃ , and the like. However, the present invention is not limited to these.

At this time, the electrode layer may further include a binder resin, a conductive material, a filler, and other additives in addition to the cathode active material.

The binder resin is used for bonding between the electrode active material and the conductive material and bonding to the current collector. Non-limiting examples of such binder resins include polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyacrylic acid (PAA), polymethacrylic acid (PMA), polymethylmethacrylate (PMMA) (PAM), polymethacrylamide, polyacrylonitrile (PAN), polymethacrylonitrile, polyimide (PI), alginic acid, alginate, chitosan, carboxymethylcellulose Propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), polyvinylpyrrolidone, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ), Fluorine rubber, various copolymers thereof, and the like.

The conductive material is used to further improve the conductivity of the electrode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Polyphenylene derivatives and the like can be used.

The filler is optionally used as a component for suppressing the expansion of the electrode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. Examples of the filler include olefin polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

The separator may be made of a porous substrate. The porous substrate may be any porous substrate commonly used in an electrochemical device. For example, the porous substrate may be a polyolefin porous film or a nonwoven fabric. no.

The separator may be formed of a material selected from the group consisting of polyethylene, polypropylene, polybutylene, polypentene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, A porous substrate made of any one selected from the group consisting of polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalate, or a mixture of two or more thereof.

The electrolyte of the lithium secondary battery may be a non-aqueous organic solvent including a lithium salt, an organic solid electrolyte, or an inorganic solid electrolyte, but is not limited thereto.

Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, gamma-butyrolactone, -Dimethoxyethane, 1,2-diethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, 4-methyl- The organic solvent may be selected from the group consisting of diethyl ether, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivative, Dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, ethyl propionate and the like can be used.

The lithium salt is a material that is readily soluble in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO _4, LiBF _4, LiB ₁₀ Cl _10, LiPF _6, LiAsF _6, LiSbF _6, LiAlCl _4, LiSCN, LiC ₄ BO ₈ , LiCF ₃ CO ₂ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiC ₄ F ₉ SO ₃ , LiC ₃ SO ₂ ) ₃ , (CF ₃ SO ₂ ) ₂ NLi, chloroborane lithium, lower aliphatic carboxylate lithium, and lithium tetraphenylborate.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, A polymer including a secondary dissociation group, and the like can be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides and sulfates of Li such as Li ₄ SiO ₄ -LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

In addition, the electrolyte may further contain other additives for the purpose of improving charge / discharge characteristics, flame retardancy, and the like. Examples of the additive include pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, hexaphosphoric triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, (N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, trichloroaluminum, fluoroethylene carbonate (FEC), propenesultone (PRS), vinylene carbonate VC), and the like.

The lithium secondary battery according to the present invention can be laminated, stacked, and folded in addition to winding, which is a general process. The battery case may have a cylindrical shape, a square shape, a pouch shape, a coin shape, or the like.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Changes and modifications may fall within the scope of the appended claims.

[Example]

Production Example 1: Preparation of lithium secondary battery

(1) Example 1

A lithium secondary battery including a porous current collector and a lithium metal was prepared by the following method, and a lithium secondary battery having the negative electrode was prepared.

Copper was plated to a thickness of 0.5 탆 on a PET nonwoven fabric having a porosity of 85% and a thickness of 120 탆 made of PET fibers having a diameter of 10 탆 and a porosity of 85%, a porosity average particle diameter of 50 탆 and a thickness of 120 탆.

A coating solution was prepared by dissolving 2 g of PVDF-HFP (Arkema Kynar2751 model, elastic modulus: 2 GPa) in 8 ml of acetone, and a 5 μm thick layer of lithium ion conductive material was applied to the porous collector by dip coating .

Raise the lithium metal foil having a thickness of 20 μm on one surface of the porous house, by filling the lithium metal through the compression method using a roll press ^(second pressure 2kg / cm) to the pores of the total porosity home, copper 15 wt% and lithium A lithium electrode containing 13 wt% of metal was prepared.

A cathode was prepared using LCO (LiCoO2) as a cathode active material. The slurry was prepared by mixing N-methylpyrrolidone (NMP) as a solvent at a weight ratio of LCO: Super-P: PVDF = 95: 2.5: 2.5 to prepare a slurry, A positive electrode was prepared.

Polyethylene having a thickness of 20 占 퐉 was interposed between the positive electrode and the negative electrode with a separator and lithium was added to a solvent of ethylene carbonate (EC): diethyl carbonate (DEC): dimethyl carbonate (DMC) = 1: 2: LiPF ₆ 1.0 M as a salt, and 2% by weight of vinylene carbonate (VC) as an additive were injected to prepare a lithium secondary battery.

(2) Example 2

A lithium electrode and a lithium secondary battery were fabricated in the same manner as in Example 1, except that the thickness of the PVDF-HFP coating layer was 1 μm.

(3) Example 3

A lithium electrode and a lithium secondary battery were prepared in the same manner as in Example 1, except that the thickness of the PVDF-HFP coating layer was 20 μm.

(4) Example 4

A lithium electrode and a lithium secondary battery were prepared in the same manner as in Example 1 except that PVDF-HFP (Kynar 2800 model manufactured by Arkema) having an elastic modulus of 1 GPa was used.

(5) Example 5

A lithium electrode and a lithium secondary battery were prepared in the same manner as in Example 1, except that PVDF-HFP (Arkema's LBG model) having an elastic modulus of 5 GPa was used.

(6) Comparative Example 1

A lithium foil having a thickness of 20 mu m was laminated on a copper foil having a thickness of 10 mu m to prepare a lithium electrode, and a lithium secondary battery was produced using the same anode, separator, and electrolyte composition as in Example 1. [

(7) Comparative Example 2

A lithium electrode and a lithium secondary battery were prepared in the same manner as in Example 1, except that the porous current collector was formed by laminating lithium metal without forming a PVDF-HFP coating layer.

Experimental Example 1: Evaluation of cell performance

The performance of each of the batteries prepared in Preparation Example 1 was evaluated. The charging and discharging conditions are as follows.

Charging: Rate 0.2C, voltage 4.25V, CC / CV (5% current cut at 1C)

Discharge: Rate 0.5C, Voltage 3V, CC

The number of cycles when the discharge capacity reached 80% was measured in comparison with the initial capacity of the battery while repeating the cycle under the above conditions. The results are shown in Table 1 below.

Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Discharge capacity reaches 80%
Number of cycles 195 145 168 134 126 75 140

As a result of the experiment, the electrode using the porous current collector showed better results than the electrode using the flat current collector. In addition, when the lithium ion electrode was produced by coating the porous collector with an ion conductive material exhibiting a modulus of elasticity of 2 Gpa to a thickness of 1 to 20 μm (Examples 1 to 3) , Respectively.

On the other hand, in Examples 4 and 5, the battery life was somewhat lower than that in the case of no coating layer. From this, it can be confirmed that the elastic modulus of the ion conductive material is preferably in the range of more than 1 Gpa and less than 5 Gpa in order to impart adequate strength to the lithium dendrite to suppress the growth of the lithium dendrite.

Claims (11)

A porous current collector having a surface coated with a lithium ion conductive material,
Wherein the lithium ion conductive material has a modulus of elasticity of more than 1 Gpa and less than 5 Gpa. The method according to claim 1,
The material of the porous current collector is carbon; In the group consisting of Ni, Cu, Ti, V, Cr, Mn, Fe, Co, Zn, Mo, W, Ag, Au, Ru, Pt, Ir, Al, Sn, Bi, Si, Sb, The metal selected; Or a polymer fiber nonwoven fabric having a surface coated with the metal. The method according to claim 1,
Wherein the porosity of the porous current collector before coating the lithium ion conductive material is 50 to 99%. The method according to claim 1,
Wherein the porous collector has an average particle diameter of 5 to 500 mu m prior to the coating of the lithium ion conductive material. The method according to claim 1,
Wherein the thickness of the porous current collector is 10 to 200 占 퐉. The method according to claim 1,
Wherein the lithium ion conductive material is an organic or inorganic compound having a lithium ion conductivity of 10 ^-7 S / cm or more. The method according to claim 1,
Wherein the lithium ion conductive material is selected from the group consisting of polyethylene oxide, polypropylene oxide, polyethylene glycol, polyphosphazene, polysiloxane, polydimethylsiloxane, polyacrylonitrile, polymethylmethacrylate, polyvinyl chloride, polyvinylidene fluoride, polyvinyl At least one organic compound selected from the group consisting of polyoxyethylene glycidyl ether, polyoxyethylene glycidyl ether, polyoxyethylene glycidyl ether, polyoxyethylene glycidyl ether, polyoxyethylene glycidyl ether, polyoxyethylene glycidyl ether, Wherein the positive electrode active material is a compound. The method according to claim 1,
Wherein the lithium ion conductive material is at least one inorganic compound selected from the group consisting of LiPON, a hydride compound, a thioricone compound, a nacicon compound, a ricicon compound, and a perovskite compound. The whole house. The method according to claim 1,
Wherein the lithium ion conductive material is coated to a thickness of 1 to 20 占 퐉. In a lithium electrode comprising a porous collector and a lithium metal,
The lithium electrode according to any one of claims 1 to 9, wherein the porous current collector is a porous current collector for a lithium electrode. A lithium secondary battery comprising the lithium electrode according to claim 10.