KR101990614B1 - Lithium metal electrode and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a porous current collector made of a polymer fiber coated with a conductive metal on a surface thereof and a lithium electrode including a lithium metal filled in the pores of the current collector.
The lithium electrode according to the present invention includes a porous current collector, thereby increasing the contact surface area between the lithium metal and the current collector. As a result, the non-uniformity of the current density during the operation of the battery is solved, and the growth of the lithium dendrite is prevented, so that the stability of the lithium secondary battery can be improved.
In addition, since the porous current collector is made of a polymeric fibrous nonwoven fabric coated with a conductive metal, the weight of the porous current collector is light, so that the energy density of the electrode can be increased and flexibility can be improved.

Description

TECHNICAL FIELD [0001] The present invention relates to a lithium secondary battery and a lithium secondary battery including the lithium secondary battery.

The present invention relates to a porous current collector made of a polymer fiber coated with a conductive metal on a surface thereof and a lithium electrode including a lithium metal filled in the pores of the current collector.

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.

In the case of the above-mentioned lithium electrode, electrons moving to the lithium foil through the current collector move in a single direction flow when the battery is driven. This results in non-uniformity of the electron density on the lithium surface, whereby lithium dendrite can be formed.

Such lithium dendrites may ultimately cause damage to the separator, and short-circuiting of the lithium secondary battery may occur, which may lead to a problem of deteriorating the safety of the lithium secondary battery.

In addition, conventional metal collectors are bulky and heavy, and have limitations in increasing the energy density per unit volume or weight of the electrodes.

Therefore, it is necessary to develop a new lithium electrode capable of suppressing the formation of lithium dendrite and increasing the capacity per unit weight or volume of the lithium secondary battery in order to improve the performance of the lithium secondary battery.

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

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a lithium electrode having a lithium dendrite formation inhibited and high energy density and a lithium secondary battery comprising the same.

In order to accomplish the above object, the present invention provides a porous collector, And a lithium metal filled in the pores of the porous current collector,

The porous collector is a polymer fiber nonwoven fabric having a surface coated with a conductive metal,

Wherein the conductive metal is at least one selected from the group consisting of copper, nickel, aluminum, chromium, zinc and stainless steel,

Wherein the polymer fiber is at least one selected from the group consisting of polyethylene terephthalate, polyethylene oxide, polyethylene, polypropylene, polymethyl methacrylate, and polyacrylic acid, and a lithium secondary battery comprising the same .

The lithium electrode according to the present invention includes a porous current collector, thereby increasing the contact surface area between the lithium metal and the current collector. As a result, the non-uniformity of the current density during the operation of the battery is solved, and the growth of the lithium dendrite is prevented, so that the stability of the lithium secondary battery can be improved.

In addition, since the porous current collector is made of a polymeric fibrous nonwoven fabric coated with a conductive metal, the weight of the porous current collector is light, so that the energy density of the electrode can be increased and flexibility can be improved.

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.

Lithium electrode

The present invention relates to a porous collector; And a lithium metal filled in the pores of the porous current collector,

The porous collector is a polymer fiber nonwoven fabric having a surface coated with a conductive metal,

Wherein the conductive metal is at least one selected from the group consisting of copper, nickel, aluminum, chromium, zinc and stainless steel,

Wherein the polymer fibers are at least one selected from the group consisting of polyethylene terephthalate, polyethylene oxide, polyethylene, polypropylene, polymethyl methacrylate, and polyacrylic acid.

Since the lithium electrode of the present invention uses a three-dimensional porous current collector made of a polymer fiber nonwoven fabric and a conductive metal, it is possible to maximize the contact area between the current collector and the lithium metal as an active material, thereby minimizing a current density imbalance. Further, since the loading amount of the active material per unit weight of the electrode can be increased, the energy density of the electrode can be improved.

Accordingly, the lithium secondary battery employing the lithium electrode of the present invention exhibits excellent safety, capacity characteristics, and life characteristics.

The current collector serves to feed electrons provided from an external conductor to an electrode active material or conversely to collect electrons generated as a result of an electrode reaction and to flow them to an external conductor. In the present invention, a polymeric fiber having a surface coated with a conductive metal A porous collector is used.

The conductive metal may be at least one selected from the group consisting of copper, nickel, aluminum, chromium, zinc and stainless steel, 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 polymer fiber may be at least one selected from the group consisting of polyethylene terephthalate, polyethylene oxide, polyethylene, polypropylene, polymethyl methacrylate, and polyacrylic acid, preferably polyethylene terephthalate (PET). 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 the above-described polymeric fiber nonwoven fabric with a conductive metal.

The method of coating the conductive metal is not particularly limited in the present invention. For example, plating, sputtering, ion plating, arc deposition, ion beam assisted deposition, or vacuum deposition 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, it is preferable that the conductive metal is included in 7 to 30% by weight of the total weight of the lithium electrode. If the content of the conductive metal is less than the above range, the surface of the polymeric fiber nonwoven fabric is difficult to be completely coated with the conductive 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 conductive metal is uniformly coated on the polymer fibers in a thickness of 0.3 to 0.7 μm.

The porous current collector preferably has a porosity of 60 to 90%, more preferably 70 to 90%.

At this time, the porosity is also referred to as a porosity, which means the ratio of the volume occupied by the pores to the total volume of the porous material.

The average pore size of the porous collector used in the present invention is preferably 5 to 500 μm, more preferably 10 to 100 μm.

When the porosity of the porous collector and the average pore size of the pores satisfy the above range, excellent durability and processability can be ensured and the surface area of contact with the lithium metal as the active material can be maximized.

On the other hand, the thickness of the porous current collector may be 10 to 200 μm, more preferably 50 to 150 μm. The current collector having a thickness of less than 10 μm is difficult to manufacture in the process and the amount of the active material to be filled is insufficient, so that it is difficult to secure the capacity of the battery. If the thickness of the collector exceeds 200 μm, There is a problem that the battery performance is deteriorated due to a rapid increase in resistance, so that it is appropriately adjusted within the above range.

The lithium electrode according to the present invention comprises lithium metal filled in pores of the aforementioned porous current collector.

The lithium metal may be 1 to 30 wt%, preferably 10 to 20 wt%, based on the total weight of the electrode. When the content of the lithium metal satisfies the above range, a sufficient battery capacity can be secured and an effect of inhibiting the formation of lithium dendrites can be obtained.

The method of filling the lithium metal into the pores of the porous current collector 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 includes a method of applying lithium or lithium alloy particles and a solvent in paste form, or applying a binder by mixing lithium particles and a binder such as PVdF with a solvent to form a paste.

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 .

Among the above-mentioned methods, a thermal evaporation method or a pressing method is preferably used in the present invention.

The lithium electrode according to the present invention may further include a lithium ion conductive protective layer formed on at least one surface thereof in order to enhance the effect of preventing the growth of lithium dendrites.

The lithium ion conductive material constituting the lithium ion conductive protective layer may be an organic or inorganic compound 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.

The thickness of the lithium ion conductive protective layer is advantageous for battery output characteristics as the thickness is thinner, but the growth of the dendrite can be blocked only if it is formed to a certain thickness or more. Preferably, the thickness of the lithium ion conductive protective layer is 0.01 to 50 mu m.

The lithium electrode according to the present invention can increase the capacity per unit weight by using a porous collector which is light in weight, excellent in mechanical strength and flexibility, and has excellent processability. Further, since the porous collector increases the contact area between the current collector and the lithium metal and improves the uneven density of electrons during the operation of the battery, the formation of lithium dendrite is suppressed. Thus, when applied to a lithium secondary battery, battery performance, stability, and life characteristics can be improved.

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 to improve the unevenness of the current density and inhibit the formation and growth of lithium dendrite, so that the stability and cycle characteristics of the battery can be improved when applied to a lithium secondary battery.

In addition, since the porous current collector is made of a polymer fiber coated with a conductive metal, it is light in weight and excellent in flexibility, so that the capacity per weight of the electrode can be increased and various shapes of electrodes can be realized.

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.

(1) anode

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.

(2) The membrane

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.

(3) electrolyte

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.

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 (LiCoO ₂ ) 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

Except that a lithium electrode having a copper content of 7 wt% and a lithium metal content of 14 wt% was produced by plating copper on the PET nonwoven fabric to a thickness of 0.3 탆, thereby preparing a lithium electrode and a lithium electrode Thereby preparing a lithium secondary battery.

(3) Example 3

Except that a lithium electrode having a copper content of 30 wt% and a lithium metal content of 11 wt% was prepared by plating copper on the PET nonwoven fabric to a thickness of 0.7 탆, thereby preparing a lithium electrode and a lithium electrode Thereby preparing a lithium secondary battery.

(4) Example 4

Except that a porous non-woven fabric having a porosity of 60% was used to produce a porous current collector having a copper plating thickness of 0.5 탆 and a porosity of 60%, except that 15 wt% of copper and 13 wt% of lithium metal A lithium electrode and a lithium secondary battery including the same were produced.

(5) Example 5

Except that a porous non-woven fabric having a porosity of 95% was used to produce a porous current collector having a copper plating thickness of 0.5 탆 and a porosity of 95%, except that 15 wt% of copper and 13 wt% of lithium metal A lithium electrode and a lithium secondary battery including the same were produced.

(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. [

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 Discharge capacity reaches 80%
Number of cycles 140 51 138 94 35 75

As a result of the experiment, it was confirmed that the life characteristics of the battery of Example 1 using the lithium electrode of the present invention were remarkably improved compared to Comparative Example 1 using the conventional flat electrode.

The battery of Example 3, which had a higher copper coating thickness and content as compared to Example 1, also exhibited superior cell performance, but increased electrode weight and lower energy density compared to Example 1 (310 Wh / kg) (280Wh / kg). On the contrary, in the case of Example 2 in which the copper coating thickness and the content of the current collector were lowered, the battery capacity rapidly decreased, which is considered to be a result of an increase in electrode resistance because sufficient electrical conductivity was not secured.

From the above results, it can be confirmed that the conductive metal is coated to a thickness of 0.3 to 0.7 μm in order to secure the performance of the porous current collector, and the content in the electrode is preferably 7 to 30% by weight.

On the other hand, Examples 4 and 5 having different porosities of the current collector exhibited lower cell performance than Example 1. In the case of Example 4 in which the porosity of the current collector is 60%, it was observed that some of the lithium metal escaped to the outside of the collector due to repetition of charge and discharge to form a foil shape, Performance. In the case of Example 5 in which the porosity of the current collector was 95%, the lithium dendrite formation was not suppressed and the battery life was shortened because the porosity of the current collector was too high to allow the lithium metal to grow freely .

From the above results, it is understood that the porosity of the current collector is preferably 60 to 90% in order to obtain the effect of the porous current collector.

Claims (9)

Porous collector; And a lithium metal filled in the pores of the porous current collector,
The porous collector is a polymer fiber nonwoven fabric having a surface coated with a conductive metal,
Wherein the conductive metal is at least one selected from the group consisting of copper, nickel, aluminum, chromium, zinc and stainless steel,
Wherein the polymer fiber is at least one selected from the group consisting of polyethylene terephthalate, polyethylene oxide, polyethylene, polypropylene, polymethyl methacrylate, and polyacrylic acid,
Wherein the conductive metal is comprised between 15 and 30 weight percent of the total weight of the lithium electrode,
The thickness of the conductive metal coated on the polymeric fibrous nonwoven fabric is 0.5 to 0.7 탆,
Wherein the porosity of the porous collector is 70 to 90%. The method according to claim 1,
Wherein the conductive metal is copper, and the polymer fiber is polyethylene terephthalate. delete delete The method according to claim 1,
And the average particle diameter of the pores is 5 to 500 m. The method according to claim 1,
Wherein the porous collector has a thickness of 10 to 200 mu m. The method according to claim 1,
Wherein the lithium metal is 1 to 30 wt% of the total weight of the lithium electrode. The method according to claim 1,
And a lithium ion conductive protective layer formed on at least one surface of the lithium electrode. A lithium secondary battery comprising the lithium electrode according to any one of claims 1, 2, and 5 to 8.