KR100521473B1 - Negative electrode for lithium battery and lithium battery comprising same - Google Patents

Abstract

The present invention relates to a lithium battery negative electrode and a lithium battery including the same, wherein the lithium battery negative electrode is a lithium metal plate (average surface roughness (Ra) of the portion to be attached to the negative electrode tab of the lithium metal plate is 0.1 to 5㎛) And a negative electrode tab attached to a surface of the lithium metal plate; Or a lithium metal plate and a negative electrode tab having a porosity of 50 to 100% attached to the lithium metal plate; Or a lithium metal plate and a negative electrode tab attached to both end surfaces of the upper and lower portions of the lithium metal plate.

Description

A negative electrode for a lithium battery and a lithium battery including the same {NEGATIVE ELECTRODE FOR LITHIUM BATTERY AND LITHIUM BATTERY COMPRISING SAME}

[Industrial use]

The present invention relates to a lithium battery negative electrode and a lithium battery including the same, and more particularly, to a lithium battery negative electrode and a lithium battery including the same having excellent capacity characteristics and capable of reducing a short circuit phenomenon of the battery.

[Prior Art] 0.1 to 5

Recently, with the trend toward miniaturization and light weight of portable electronic devices, the need for high performance and high capacity of batteries used as power sources for these devices is increasing. In general, the battery can be divided into a primary battery used for single use and a secondary battery that can be used for recharging. The primary battery may be a manganese battery, an alkaline battery, a mercury battery, a silver oxide battery, or the like, and the secondary battery may be a lead acid battery, a Ni-MH (nickel metal hydride) battery, a sealed nickel-cadmium battery, a lithium metal battery, Lithium ion batteries, lithium polymer batteries, lithium-sulfur batteries and the like.

These cells generate power by using materials capable of electrochemical reactions at the positive and negative electrodes. Factors that determine the performance, safety, and reliability of a battery, such as its capacity, lifespan, and power, are the electrochemical properties of the active material that participates in the electrochemical reaction of the positive and negative electrodes.

Among the battery active materials currently used, lithium has a large electric capacity per unit mass, thereby providing a high capacity battery, and having a high electric negative degree may provide a high voltage battery. When lithium metal is used as a negative electrode active material, since lithium metal may be used simultaneously as an active material and a current collector, a lithium metal plate is used as a negative electrode plate without using a separate current collector.

The structure of the non-aqueous lithium battery 1 is as shown in FIG. The battery is manufactured by inserting the separator 6 between the positive electrode 2 and the negative electrode 4, winding the separator 6 to form an electrode group 8, and then placing the separator 6 in a can 10. The top of the battery is sealed with a battery cover 12 and a gasket 14. The battery cover 12 may be provided with a safety vent to prevent the battery from forming overpressure. The outer surface of the battery cover 12 becomes the positive terminal and the outer surface of the can 10 becomes the negative terminal. The positive electrode tab 16 and the negative electrode tab 18 are connected to connect the electrode to the terminal. Insulators 20 and 22 are inserted to prevent internal short circuit of the battery. The lid 12 is crimped into the can 10 to inject the electrolyte 24 before sealing the battery.

When the lithium metal negative electrode is used as the negative electrode plate and the battery case which is the negative electrode terminal is made of metal, a method of conducting electricity by direct contact of the lithium metal negative electrode with the battery case is used. However, there is a problem that the electrical conduction of the lithium metal reacts with the electrolyte and worsens the outer surface of the battery case. In addition, when the battery case is not made of metal, it is necessary to pull the terminal out of the battery. Therefore, a negative electrode tab made of a material which does not elute or dissolve in the electrolyte is used.

With the trend of demanding light and high capacity batteries such as mobile phones, much attention has been paid to the use of lithium with a large capacity per unit weight as the negative electrode of the battery, and the appearance of the battery is also square and lightweight. It is changed to a battery. In addition to these trends, research on the electrical connection method with the battery terminals has been actively made when using lithium metal as a negative electrode in battery manufacturing.

Japanese Patent Application Laid-open No. Hei 5-251073 is a method of placing a nickel tab on a lithium foil and then placing the lithium back on to wrap the nickel tab with lithium metal, thereby preventing the edge of the nickel tab from damaging the separator and reducing the short phenomenon. The method is described. However, this method has a problem in that the effective capacity of the battery is reduced by the space occupied by lithium to surround the nickel tab.

The present invention is to solve the above-described problems, an object of the present invention is to provide a negative electrode for a lithium battery that can improve the capacity characteristics of the battery, and excellent adhesion of the lithium metal negative electrode and the negative electrode tab.

It is possible to improve the capacity characteristics of another battery of the present invention, and to provide a method of manufacturing a negative electrode for a lithium battery having excellent adhesion between the lithium metal negative electrode and the negative electrode tab.

In order to achieve the above object, the present invention is a lithium metal plate (average surface roughness (Ra) of the portion to be attached to the negative electrode tab of the lithium metal plate is 0.1 to 5㎛); And it provides a negative electrode for a lithium battery comprising a negative electrode tab attached to the surface of the lithium metal plate.

The invention also provides a lithium metal plate; And a negative electrode tab having a porosity of 50 to 100% attached to the lithium metal plate. The invention also provides a lithium metal plate; And it provides a negative electrode for a lithium battery comprising a negative electrode tab attached to both end surfaces of the upper and lower portions of the lithium metal plate.

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The present invention also provides a method of manufacturing a lithium metal plate having a mean surface roughness Ra of 0.1 to 5 μm by brushing the surface of a portion of the lithium metal plate to be attached to the negative electrode tab; And it provides a method for producing a negative electrode for a lithium battery comprising the step of attaching by pressing the negative electrode tab to the lithium metal plate.

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

According to a first preferred embodiment of the present invention, a lithium metal plate (average surface roughness Ra of the portion to be attached to the negative electrode tab of the lithium metal plate is 0.1 to 5 μm); And it provides a negative electrode for a lithium secondary battery comprising a negative electrode tab attached to the surface of the lithium metal plate.

As the lithium metal plate, lithium metal coated on a lithium metal foil or a conductive substrate may be preferably used. Examples of the conductive substrate may be a metal foil, a metal film, a conductive polymer film or a polymer film on which a metal is deposited. Examples of the metal foil and the metal film include copper or nickel foil or a film. The polymer film on which the metal is deposited means that a metal such as copper or nickel is deposited on the polymer film. Such polymer films include polyacetylene, polypyrrole, polyaniline, polythiophene, poly (p-phenylene), poly (phenylene vinylene, polyazulene, poly (perinaphthalene), poly (naphthalene-2,6 -Diyl), polyacene or the like polymer film can be used.

It is preferable to use a thin metal plate or a metal foam having a thickness of 10 to 50 μm as the negative electrode tab. In addition, specific examples of the metal plate or metal foam include, but are not limited to, nickel, copper, iron, stainless steel, and the like.

The lithium metal plate rubs the surface to which the negative electrode tab is attached with a brush to form a range of surface roughness on the surface. It is preferable to exist in the range of 0.1-5 micrometers, and, as for average surface roughness, it is more preferable to exist in the range which is 0.3-0.6 micrometer. If the average surface roughness is less than 0.1 μm, the negative electrode tab may not be firmly attached. If the average surface roughness is more than 5 μm, the negative electrode tab may be damaged, or the tab may be broken or broken in the brushing process.

The negative electrode tab in the form of a sheet is placed on the lithium metal plate on which the surface roughness is formed and pressurized to firmly attach the negative electrode tab to the lithium metal plate. The method of attaching the negative electrode tab to the lithium metal plate is not limited to the pressing method.

According to a second preferred embodiment of the present invention, there is provided a lithium metal plate; And a negative electrode tab having a porosity of 50 to 100% attached to the lithium metal plate.

As the lithium metal plate, lithium metal coated on a lithium metal foil or a conductive substrate may be preferably used, and is the same as that described in the first embodiment.

The negative electrode tab has a foam form having a porosity of 50 to 100%, preferably 80 to 95%. When the negative electrode tab having a porosity is formed, when welding the negative electrode tab to lithium metal, lithium is pressed in between the foam or melted by heat to harden, thereby further improving the welding effect. Specific examples of the negative electrode tab include but are not limited to nickel, copper, iron, stainless steel, and the like.

When the negative electrode tab in the form of foam is placed on the surface of the lithium metal plate and pressure is applied, lithium penetrates into the pores between the foams due to the soft nature of lithium, thereby firmly attaching the negative electrode tab to the lithium metal plate.

According to a third preferred embodiment of the present invention, there is provided a lithium metal plate; And it provides a negative electrode for a lithium battery comprising a negative electrode tab attached to both end surfaces of the upper and lower portions of the lithium metal plate.

As the lithium metal plate, lithium metal coated on a lithium metal foil or a conductive substrate may be preferably used, and is the same as that described in the first embodiment.

The negative electrode tab may be a metal foil or a metal foam. Specific examples of the negative electrode tab include nickel, copper, iron, stainless steel, and the like, but are not limited thereto. The upper and lower tabs are placed side by side on both sides of the end of the lithium metal plate, and the upper tab and lithium, and the lower tab and lithium are welded on the tab.

When the negative electrode tab is firmly attached to the lithium metal plate as in the present invention, internal resistance is reduced during charging and discharging of the battery, thereby reducing the capacity reduction, thereby providing a high capacity battery. In addition, since the negative electrode tab can be easily attached to the lithium metal plate, there is no limitation in the form of the battery.

The negative electrode for lithium batteries of this invention is applicable to all lithium batteries. In particular, it can be usefully used in a lithium-sulfur battery using a sulfur-based material as a positive electrode active material. Such a lithium-sulfur battery includes a negative electrode according to any one of the first to third embodiments; Elemental sulfur as a cathode active material, Li ₂ S _n (n≥1), caviar solrayiteu (catholyte) of Li ₂ S _n (n≥1), organic sulfur compounds, and carbon dissolved in the sulfur polymer ((C ₂ S _{x) n} : an anode comprising at least one material selected from the group consisting of x = 2.5 to 50, n ≧ 2); And electrolytes.

The electrolyte may be a solid electrolyte or a liquid electrolyte.

The solid electrolyte functions as a separator that physically separates an electrode and a transfer medium for moving metal ions, and both an electrochemically stable ion conductive material may be used. As the ion conductive material, a glass electrolyte, a polymer electrolyte, or a ceramic electrolyte may be used. As a particularly preferred solid electrolyte, a suitable supporting electrolyte salt is mixed with a polymer electrolyte such as polyether, polyimine, polythioether, or the like. The solid electrolyte separator may include less than about 20% by weight of a non-aqueous organic solvent, and in this case, may further include a suitable gelling agent in order to reduce the fluidity of the organic solvent.

When used as a liquid electrolyte, the lithium-sulfur battery further includes a separator made of porous glass, plastic, ceramic or polymer as a physical separator having a function of physically separating the electrodes. The liquid electrolyte includes a non-aqueous organic solvent and an electrolytic salt. As this organic solvent, a widely known non-aqueous organic electrolyte such as ethylene carbonate, propylene carbonate, dioxolane, sulfolane, xylene, diglyme, tetrahydrofuran and tetraglyme can be widely used.

As the electrolytic salt, a lithium salt containing a lithium cation, a salt containing an organic cation, or a mixture thereof may be used.

Examples of the lithium salt are LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ ), where x and y are natural numbers, LiCl, LiI, and the like.

The salt containing the organic cation has a low vapor pressure, a very high flash point (flash point) and has a non-combustibility can improve the safety of the battery, has a non-corrosive, mechanically stable film form has the advantage . Salts that can be preferably used in the present invention include a large organic cation having a van der Waals volume of 100Å ³ or more. The larger the van der Waals volume of the cation, the lower the lattice energy of the molecule and the better the ion conductivity.

The salts containing the organic cations can be present in the liquid phase over a wide temperature range, in particular in the liquid phase at the operating temperature of the cell. The salt containing the organic cation is preferably present in the liquid phase at a temperature of 100 ° C or less, more preferably in the liquid phase at a temperature of 50 ° C or less, and most preferably in the liquid phase at a temperature of 25 ° C or less. Do. It is of course also possible to use the liquid phase at different temperatures depending on the application method.

As said organic cation, the cation of a heterocyclic compound is preferable. The hetero atom of the heterocyclic compound is selected from N, O, S or a combination thereof, and the number of hetero atoms is preferably 1 to 4, more preferably 1 to 2 atoms. Cations of such heterocyclic compounds include pyridinium, pyrididazinium, pyrimidinium, pyrazinium, imidazolium, pyrazolium, thiazolium, Cation of the compound selected from the group consisting of Thiazolium, Oxazolium, and Triazium, or substituted compounds thereof. Among these compounds are imides such as 1-ethyl-3-methylimidazolium (EMI), 1,2-dimethyl-3-propylimidazolium (DMPI), 1-butyl-3-methylimidazolium (BMI), and the like. The cation of the solium compound can be preferably used.

Anions that combine with the cation is bis (perfluoroethyl sulfonyl) imide _{(N (C 2 F 5 SO} 2) 2 -, Beti), ( methylsulfonyl-trifluoromethyl) bis-imide (N (CF _{3 ^{SO 2) 2 -, Im)}} , tris (trifluoromethyl sulfonyl methide _{(C (CF 3 SO 2)} 2 -, Me), trifluoromethane sulfonimide, trifluoromethyl sulfonimide, tri- methyl sulfonate, AsF ₆ fluoro ^{_{-, ClO 4 -, PF 6}} -, BF 4 - one.

Preferred examples of the salt having an organic cation include 1-ethyl-3-methylimidazolium bis (perfluoroethyl sulfonyl) imide (EMIBeti) and 1,2-dimethyl-3-propylimidazolium bis (trifluoro Chloromethyl sulfonyl) imide (DMPIIm), or 1-butyl-3-methylimidazolium hexafluorophosphate (BMIPF ₆ ).

The following presents a preferred embodiment to aid the understanding of the present invention. However, the following examples are merely provided to more easily understand the present invention, and the present invention is not limited to the following examples.

(Example 1)

A positive electrode active material slurry was prepared by adding sulfur powder as a positive electrode active material, polyethylene oxide (PEO) as a binder, and ketjen black as a conductive material to acetonitrile in amounts of 75, 12, and 13% by weight, respectively. The uniformly dispersed slurry was poured into carbon coated Al foil and a positive electrode was prepared using a doctor blade. A positive electrode plate was prepared by cutting the positive electrode into a size of 2 × 2 cm ² and welding the Al tab. The 200 탆 thick lithium metal foil was cut to a size of 3 × 3 cm ² , and one surface was rubbed three times with a brush to roughen the surface. At this time, the average surface roughness of lithium metal foil was 0.5 micrometer. Average surface roughness was measured using an optical 3D profiling system (model name NT2000, manufactured by WYKO). A 10 μm copper foil was placed on the surface of the lithium metal foil treated to form a surface roughness and pressurized at a pressure of about 0.3 ton to prepare a negative electrode plate. The positive electrode plate, the vacuum-dried polyethylene separator, and the negative electrode plate were placed in this order and then inserted into the pouch. The pouch-type test cell was assembled by injecting an electrolyte solution into the pouch and sealing it. As an electrolyte, 1,3-dioxolane / dimethoxyethane / diglyme (volume ratio of 2/4/4) in which 1M LiN (CF ₃ SO ₂ ) was dissolved was used.

(Example 2)

A negative electrode plate was manufactured by cutting a lithium metal foil having a thickness of 200 μm into a size of 3 × 3 cm ² and then placing a nickel foam having a porosity of 85% (thickness: 100 μm) on a lithium foil and pressing it at a pressure of about 0.3 ton. And a test cell was prepared in the same manner as in Example 1.

(Example 3)

Tested in the same manner as in Example 1, except that the lithium metal foil having a thickness of 200 μm was cut to a size of 3 × 3 cm ² , and then welded with copper foil (thickness: 10 μm) placed on both sides of the lithium foil to prepare a negative electrode plate. The cell was prepared.

(Comparative Example 1)

The test cell was prepared in the same manner as in Example 1, except that a lithium metal foil having a thickness of 200 μm was cut into a size of 3 × 3 cm ² , and then a nickel tab (thickness: 100 μm) was placed on the lithium foil and pressed to prepare a negative electrode plate. Prepared.

Thirty test cells prepared in Examples 1 to 3 and Comparative Example 1 were prepared, respectively, and the internal resistance (IR) and the open circuit voltage (OCV) were measured and shown in Table 1 below. IR and OCV are subject to HIOKI E.E. It was measured using model 3550 of Corporation.

Example 1 Example 2 Example 3 Comparative Example 1 IR (Ω) OCV IR (Ω) OCV IR (Ω) OCV IR (Ω) OCV One 5.4 3.20 9.3 3.23 8.3 3.22 off 3.20 2 5.8 3.21 8.9 3.19 9.0 3.22 24 3.24 3 5.5 3.20 8.5 3.21 9.7 3.20 26 3.20 4 5.3 3.20 8.8 3.22 16.0 3.22 27 3.20 5 4.8 3.20 10.9 3.04 7.8 3.22 15 3.22 6 5 3.20 10.0 3.17 11.4 3.20 off 3.13 7 5.5 3.22 9.2 3.12 16.0 3.21 25 3.23 8 5.5 3.20 11.7 3.18 15.0 3.23 23 3.22 9 5.3 3.20 6.8 3.22 10.0 3.26 27 3.17 10 6.2 3.20 10.5 3.21 9.6 3.25 off 3.18 11 4.3 3.20 12.5 3.17 9.2 3.16 23 3.19 12 4.0 3.20 10.3 3.21 9.5 3.16 22 3.19 13 3.9 3.20 15.0 3.22 11.6 3.18 17 3.19 14 4.5 3.20 11.1 3.20 10.7 3.14 25 3.21 15 2.8 3.20 7.7 3.22 9.9 3.12 off 3.17 16 4.6 3.20 7.0 3.22 12.4 3.18 off 3.17 17 4.7 3.20 11.3 3.20 7.5 3.22 off 3.21 18 4.2 3.20 8.5 3.21 11.2 3.21 29 3.20 19 4.0 3.21 9.2 3.23 13.2 3.17 24 3.24 20 4.2 3.20 15.0 3.26 11.0 3.21 22 3.20 21 5.2 3.20 7.3 3.25 9.6 3.19 26 3.20 22 4.5 3.20 10.9 3.16 12.5 3.23 24 3.22 23 4.3 3.20 15.5 3.23 11.3 3.19 28 3.18 24 4.2 3.20 14.5 3.26 12.0 3.21 29 3.15 25 4.8 3.20 9.5 3.25 8.6 3.22 off 3.22 26 4.5 3.20 9.1 3.16 7.9 3.04 25 3.17 27 4.8 3.20 8.7 3.16 12.2 3.17 26 3.18 28 4.7 3.20 9.0 3.18 9.4 3.17 23 3.18 29 5.2 3.20 11.1 3.18 9.5 3.16 off 3.21 30 4.8 3.20 10.2 3.18 9.0 3.12 off 3.20

Note) The part marked "off" in Table 1 means that the internal resistance is over 30Ω.

In Table 1, it can be seen that the internal resistance of the test cells of Examples 1 to 3 of the present invention is significantly reduced compared to the test cells of Comparative Example 1. Since the increase in internal resistance means that the contact between the tab and the electrode is unstable, the low internal resistance of Examples 1 to 3 according to the present invention means that the contact between the negative electrode tab and the negative electrode is very stable.

In the negative electrode for a lithium battery of the present invention, the negative electrode tab is firmly attached to the lithium metal plate, thereby reducing internal resistance during charge and discharge of the battery. Therefore, a decrease in capacity due to a decrease in internal resistance is also reduced, thereby providing a battery of high capacity. In addition, since the negative electrode tab can be easily attached to the lithium metal plate, there is no limitation in the form of the battery and short circuit of the cell can be reduced.

Simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

1 is a cross-sectional view of a lithium battery.

* Explanation of symbols for main parts of the drawing

1: battery 2: positive

4: cathode 6: separator

8: electrode group 10: can

12: battery cover 8: case

16: positive electrode tab 18: negative electrode tab

20, 22: insulator

Claims (11)

Lithium metal plates; And a negative electrode tab having a porosity of 50 to 100% attached to the lithium metal plate. The negative electrode of claim 1, wherein the lithium metal plate is lithium metal coated on a lithium metal foil or a conductive substrate. The negative electrode of claim 2, wherein the conductive substrate is selected from the group consisting of a metal foil, a metal film, a conductive polymer film, and a polymer film on which a metal is deposited. The negative electrode tab of claim 1, wherein the negative electrode tab is a metal material selected from the group consisting of nickel, copper, iron, and stainless steel. The negative electrode for a lithium battery of claim 1, wherein a porosity of the negative electrode tab is 80 to 95%. delete delete delete delete A lithium battery comprising the negative electrode according to any one of claims 1 to 5. A negative electrode according to any one of claims 1 to 5; Elemental sulfur as a cathode active material, Li ₂ S _n (n≥1), caviar solrayiteu (catholyte) of Li ₂ S _n (n≥1), organic sulfur compounds, and carbon dissolved in the sulfur polymer ((C ₂ S _{x) n} : an anode comprising at least one material selected from the group consisting of x = 2.5 to 50, n ≧ 2); And A lithium-sulfur cell comprising an electrolyte.