JPH08130005A - Negative electrode and lithium secondary battery - Google Patents

Abstract

PURPOSE: To provide a negative electrode capable of utilizing the advantage brought by the wide area of an electrode and provide a lithium secondary battery with high charge/discharge capacity and long cycle life even when used as a large area body such as a tape-shaped body. CONSTITUTION: A molten plating layer 2 made of a lithium alloy is formed on a current collecting tape 1 through a diffusion barrier layer made of a conductor hardly reacting with a liquid lithium alloy and a wetting accelerating material layer made of a conductor with affinity to the liquid lithium alloy. A negative electrode for a lithium secondary battery does not have the molten plating layer at both edges of the current collecting tape, the negative electrode is arranged on one side of a separator containing an electrolyte, and a positive electrode is arranged on the other side. The negative electrode hardly producing cracks in the molten plating layer made of the lithium alloy is obtained, and a lithium secondary battery with high reliability based on the lithium alloy negative electrode in which dispersion of quality caused by the molten plating layer and deformation such as irregularity are decreased and adhesion is increased can be provided.

Description

Detailed Description of the Invention

[0001]

The present invention relates to electromotive force, charge / discharge capacity,
The present invention relates to a Li alloy-based negative electrode that can form a Li secondary battery having excellent charge / discharge cycle life.

[0002]

2. Description of the Related Art Tape-like electrodes have been proposed in Li secondary batteries using non-aqueous electrolytes because large-area electrodes are advantageous in terms of charge / discharge capacity and energy density. Such a tape-shaped electrode is used for forming a battery, for example, as a positive and negative electrode wound product via a separator.

Conventionally, as the tape-shaped negative electrode in the above, Li-A, which is obtained by dispersing a powder of Li alloy such as Li-Al in a binder resin and coating it on a collector tape, Li-A
It has been known that a solid solution type Li alloy plate such as g or Li-Mg is rolled into a tape shape.

However, L can be obtained in any case due to defects due to variations in quality in the length direction, deformation such as unevenness, and dropping of the active material and the like during winding.
There is a problem in that the secondary battery has poor charge / discharge capacity and charge / discharge cycle life, and the advantages of increasing the area of the negative electrode cannot be fully exerted.

[0005]

The present invention can form a Li secondary battery which is excellent in charge / discharge capacity and charge / discharge cycle life even when used as a large-area body such as a tape-like object, and therefore has a large electrode size. Li that can fully take advantage of the area
The task is to develop an alloy-based negative electrode.

[0006]

According to the present invention, a diffusion barrier layer made of a conductor that does not easily react with a liquid Li alloy and a wetting layer made of a conductor having an affinity with the liquid Li alloy are formed on a current collector tape. A negative electrode for a Li secondary battery, characterized in that it has a hot-dip plating layer made of a Li alloy via an accelerator layer, and does not have the hot-dip plating layer at both ends of a current collector tape, and It is intended to provide a Li secondary battery having the above-mentioned negative electrode on one side of a separator containing an electrolyte and having a positive electrode on the other side.

[0007]

Examples of Embodiments The current collector tape is made of copper, aluminum or silver, the diffusion barrier layer is made of nickel, cobalt or iron, and the wetting promoter layer is made of silver, copper, zinc, magnesium, aluminum or calcium. The hot-dip plated layer is made of barium, bismuth, indium, lead, platinum, palladium, or tin, and is subjected to rapid cooling at a cooling rate of 300 ° C./sec or more. The thickness of each of the current collector tape and the hot dip layer is 10 to 30 μm and 10 to 50 μm, and the lithium content of the Li alloy forming the hot dip layer is based on the atomic ratio. A negative electrode for a Li secondary battery, which has a width of 80% or more and has a width of 1 to 4 mm at both end portions of the current collector tape having no hot-dip layer.

[0008]

In order to form a Li secondary battery having a high discharge capacity, the inventors of the present invention have made extensive studies to overcome the above problems, and increase the amount of the positive electrode active material having a high charge / discharge capacity in the battery. On the other hand, when the area of the positive electrode is increased, on the other hand, when the amount of the negative electrode active material is too small, the discharge capacity is lowered. Therefore, a negative electrode that exhibits a large charge / discharge capacity with a small amount is advantageous.
It was clarified that it is advantageous to expand the area of the alloy by expanding it into a thin layer.

However, regarding the thinning of the Li alloy according to the prior art described above, in the case of the coating layer of the binder dispersion paste, it is difficult to form the desired thin layer evenly by the doctor blade method, and the solid solution is formed. In the case of type Li alloy, the mechanical strength was low and it was difficult to roll it into a thin tape.

Therefore, the inventors of the present invention have conducted further diligent research to develop a thin layer of Li alloy on the current collector tape to a thickness of 50 μm or less by the hot dipping method, and easily form a large area negative electrode such as a tape. It has been found that the charge capacity can be improved and the charge and discharge capacity can be improved. Further, it has been found that, by not providing the hot-dip plating layers on both ends of the current collector tape, damage of the hot-dip plating layer due to cracks can be prevented and the charge / discharge cycle life can be extended.

That is, when forming a rechargeable AA type Li secondary battery, the negative electrode is compactly wound together with the positive electrode and the separator and housed in a battery can. In that case, the negative electrode is wound. Tension is applied. Further, the negative electrode undergoes a thickness change every time the battery is charged and discharged due to Li electrodeposition and release, which causes a fatigue phenomenon in the hot-dip plated layer of the Li alloy composed of a hard and brittle intermetallic compound.

Therefore, as the thickness of the negative electrode is increased, a larger tension is applied and the tension is likely to concentrate on both end portions of the negative electrode tape.
If the alloy hot-dip layer is present, cracks are likely to occur there, and the cracks are likely to grow in the central portion of the negative electrode tape. As described above, the Li
By not providing the hot-dip plated layer of alloy, the occurrence of cracks at both end portions is prevented, and cracks are less likely to occur in the entire hot-dip layer. As a result, there is little variation in quality in the length direction and deformation such as unevenness, and the Li alloy as a hot-dip plating layer has excellent adhesion and excellent electromotive force, charge / discharge capacity, and charge / discharge cycle life. Is obtained.

[0013]

EXAMPLE A negative electrode of the present invention comprises a current collector tape, a diffusion barrier layer made of a conductor which does not easily react with a liquid Li alloy, and
A wet-promoting material layer made of a conductor having an affinity for the liquid Li alloy and a hot-dip plated layer made of Li alloy,
In addition, the hot-dip plated layer is not provided on both end portions of the current collector tape, and is used for forming a Li secondary battery.

The negative electrode of the present invention is illustrated in FIGS. 1 and 2. 1
Is a current collector tape, 11 is a diffusion barrier layer, 12 is a wetting promoting material layer, 2 is a Li alloy hot-dip layer, and 3 is a side end portion not having the hot-dip layer. In the present invention, the hot-dip plating layer and the like may be provided on both sides of the current collector tape, or may be provided on one side.

As the current collector tape, one having excellent conductivity such as copper, aluminum or silver is used. The thickness of the current collector tape is appropriately determined according to the purpose of use of the electrode and the like, and is generally 100 μm or less, and in particular, 5 to 50 μm, particularly 10 to 30 μm from the viewpoint of thinning.

The diffusion barrier layer provided on the current collector tape has a liquid L such as lithium when the current collector tape is hot-dipped.
It has the function of preventing corrosion by the i alloy or its components. In the absence of the diffusion barrier layer, the current collector material rapidly reacts with the liquid Li alloy to be in a semi-molten state, and the current collector tape easily breaks in a short time. Further, the Li alloy component such as lithium in the hot-dip layer gradually penetrates to increase the electric resistance of the current collector tape and increase the internal resistance of the battery.

Therefore, for the formation of the diffusion barrier layer, for example, a liquid Li alloy such as nickel, cobalt, or iron, or an appropriate conductor that does not easily react with the component can be used. The formation is, for example, an electroplating method, an electroless plating method,
It can be performed by an appropriate method such as a physical or chemical vapor deposition method. The thickness of the diffusion barrier layer is 0.01 to 5 μm.
m, preferably 0.05 to 1 μm. Its thickness is 0.0
If it is less than 1 μm, defects such as voids and pinholes are likely to occur, and if it exceeds 5 μm, the electrical resistance of the current collector tape tends to be high.

The wetting promoter layer provided on the diffusion barrier layer is intended to promote wetting of the liquid Li alloy during hot dipping and facilitate formation of a flat negative electrode active material layer having a uniform thickness. . Therefore, for the formation of the wetting promoting material layer, a conductor having an appropriate affinity with the liquid Li alloy or its component, preferably a liquid Li alloy or its component that easily reacts with excellent chemical affinity can be used. Examples are silver, copper, zinc, magnesium, aluminum,
Examples thereof include calcium, barium, bismuth, indium, lead, platinum, palladium and tin.

When the wetting promoting material layer is not provided, the coating by hot dip coating becomes impossible, or Li of a uniform thickness is formed.
It is difficult to form the alloy coating layer, the surface properties of the electrode are easily deteriorated due to unevenness, and it is difficult to form a thin layer having a thickness of 50 μm or less. The wetting promoting material layer can be formed by an appropriate method such as an electroplating method or a physical or chemical vapor deposition method, and the thickness thereof is 0.01 to 5 μm.
m, especially 0.1 to 1 μm is preferable. When the thickness of the wetting promoting material layer is less than 0.01 μm, the wetting promoting effect of the liquid Li alloy is poor, and when it exceeds 5 μm, it may act as an impurity of the negative electrode active material layer to reduce charge / discharge capacity, electromotive force, etc. .

The hot-dip plated layer provided on the wetting promoter layer is made of a Li alloy and becomes the negative electrode active material layer. In the present invention, the thickness is preferably 50 μm or less, more preferably 5 to 25 μm, especially 10 to 20 μm from the viewpoint of thinning.

The formation of the hot-dip layer, and thus the production of the negative electrode of the present invention, is carried out by, for example, introducing a current collector tape provided with a diffusion barrier layer and a wetting promoter layer into a hot-dip bath of Li alloy to form the coating layer. It can be performed by a method of doing. Further, a method of quenching the coating layer after forming the coating layer may be adopted. The rapid-cooled hot-dip layer has a large grain boundary space factor of crystal grains and a large number of atomic vacancies, and is excellent in lithium diffusivity. It has the advantage that lithium absorption / desorption is promoted and the charge / discharge cycle life is improved. .

In forming the hot-dip plated layer, FIGS.
As illustrated in FIG. 1, a continuous method in which a long current collector tape 4 having a diffusion barrier layer and a wetting promoting material layer is continuously introduced into a hot dip plating bath 5 and passed through, or a current collector tape 9 having a predetermined length is used. An appropriate manufacturing method such as a batch method in which the material is immersed in the hot dip plating bath 5 and taken out can be adopted. Note that FIG. 3 or FIG.
6 is a direction change roll, 7 is a coating thickness adjusting means, 8 is a cooling gas nozzle for rapid cooling, and 10 is a weight.

When the hot-dip plated layer is rapidly cooled, the treatment is performed on the coating layer having a predetermined thickness. For the rapid cooling treatment, an appropriate method such as a method of spraying a cooling inert gas such as argon gas or helium gas onto the coating layer having a predetermined thickness can be adopted. In that case, it is preferable to perform rapid cooling at a rate of 300 ° C./sec or more from the viewpoint of improving the negative electrode characteristics by making the crystal grains finer. Such rapid cooling can be easily achieved by controlling the temperature and supply amount of the cooling gas or the like. Moreover, since the solidification time of the hot-dip layer at room temperature is usually about a few seconds,
From the standpoint of achieving a quenching treatment of 300 ° C./sec or more, it is preferable to perform a quenching treatment within 1 second after the coating thickness is adjusted to a predetermined value through a thickness adjusting means if necessary.

When the quenching treatment atmosphere such as the cooling gas reaches the coating thickness adjusting means in the above, the current collector tape is fixed to the means and the wire is broken, or when the coating layer is cooled before reaching a predetermined thickness, the thickness increases. It is desirable to prevent the quenching treatment atmosphere from reaching the coating layer before the predetermined thickness, as illustrated in FIGS. Such a purpose can be easily achieved by a method of controlling the supply direction of the cooling gas or the like and sucking and removing the gas that has finished its role.

In forming the above-mentioned hot-dip plated layer, the current-collecting tape is not provided with the hot-dip-plated layer at both end portions thereof. It can be performed by an appropriate method such as a method of removing it at the end portion. The preferred method from the viewpoint of manufacturing efficiency is
Since the hot-dip plated layer is difficult to be formed on the diffusion barrier layer made of Ni or the like, the formation of the wetting promoting material layer made of Ag or the like on the diffusion barrier layer is performed in the middle portion of the current collector tape leaving both end portions. It is a method to do to.

To achieve the above method, for example, appropriate masking made of an adhesive tape, a polymer coat or the like is provided on both end portions of a current collector tape provided with a diffusion barrier layer, and the current collector tape is used as a wetting promoting material layer. It can be performed according to the method used for formation. Thus, by removing the masking at both end portions of the current collector tape and exposing the diffusion barrier layer to be used for forming the hot dip plated layer, the hot dip plated layer is formed only on the wettability promoting material layer. The desired state is formed.

The width of the portions not having the hot-dip plated layer on both end portions of the current collector tape can be appropriately determined according to the form and size of the battery to be formed, but is generally 1
~ 4mm, especially 1-2mm. If the width is less than 1 mm, the effect of relieving the repetitive tension associated with charge and discharge is poor, and cracks are likely to occur in the hot-dip plated layer. If the width exceeds 4 mm, the width of the hot-dip plated layer is narrowed and the discharge capacity is likely to decrease.

As the Li alloy used for forming the hot-dip plated layer in the above, Li and, for example, Al, Pb, Sn,
In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, S
Examples include alloys of binary or ternary or more with metals such as r and Te, to which Si, Cd, Zn, La, and the like are added, if necessary, and any known material can be used. By the way,
Specific examples of the Li alloy include Al, Bi, S
Li consisting of an intermetallic compound of n or In or the like and Li
Alloys, alloys of Li and Pb with added La or the like to improve mechanical properties, or Li-X- containing X component consisting of at least one of Ag, Al, Mg, Zn or Ca.
Examples include Te-based alloys.

The content of components other than lithium in the Li alloy is 40% or less based on the atomic ratio, preferably 5 to 30.
%, Particularly 10 to 20% is preferable. Its content is 40%
If it exceeds 20%, the energy density of the negative electrode active material may significantly decrease, and if it exceeds 20%, the electromotive force may decrease. If it is less than 5%, the effect of improving the properties due to alloying may be poor. Li-Ag-Te is a Li alloy that can be particularly preferably used in terms of charge / discharge cycle life, high electromotive force, high discharge capacity, and high energy density.
The atomic ratio of Li: Ag: Te made of a system alloy is 80 to 15
0: 1 to 20: 0.001 to 30 and the like, L
The content of i is 80 atomic% or more.

Regarding the negative electrode of the present invention, if necessary, for example, LiF, Li ₃ PO ₄ , or
It is also possible to provide a Li ion permeable solid electrolyte membrane made of Li ₂ S, LiCl, Li ₂ CO _3, or the like. The solid electrolyte membrane is intended to improve the battery life by preventing the contact reaction between the negative electrode and the electrolytic solution, and its attachment is, for example, a solution immersion method, an electrolytic solution additive method, a gas phase reaction method, a low temperature vapor deposition method. It can be done by

The Li secondary battery of the present invention has a structure in which the negative electrode and the positive electrode are arranged via a separator containing an electrolyte. Therefore, except for the above points, it is possible to form a Li secondary battery having specifications according to the related art. The form of the battery may be appropriately determined according to the purpose of use, and may be any form such as coin type, button type, or wound type.

By the way, FIG. 5 illustrates a coin type Li secondary battery. 13, 18 are battery cans, 14 is a collector made of Ni plate, 15 is a positive electrode, 16 is an electrolyte-containing separator,
Reference numeral 17 is a negative electrode, and 19 is an insulating sealing material. A wound Li secondary battery, which is formed by winding a sheet-shaped positive electrode and a negative electrode laminated via a separator, and the like can also be formed according to the coin-type battery.

As the electrolyte, it is possible to use an appropriate electrolyte capable of moving Li ions. Examples thereof include polymer electrolytes such as those obtained by mixing a lithium electrolytic salt with a salt-electrolytic polymer, inorganic Li solid electrolytes, or solid electrolytes such as those obtained by dispersing it in a resin.
Examples include non-aqueous electrolyte-based electrolytes prepared by dissolving a lithium salt in an organic solvent such as ester or ether.

Typical examples of the above salt-electrolytic polymers include polyethylene oxide, polyphosphazene, polyaziridine, polyethylene sulfide, their derivatives, mixtures and complexes. Therefore, in the case of the above-mentioned polymer electrolyte or solid electrolyte, it can be used as it is as a separator containing an electrolyte.

On the other hand, typical examples of the organic solvent include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, dimethoxyethane, dimethylsulfoxide, sulfolane, γ-butyrolactone and 1,2-dimethoxy. Ethane, diethyl ether, 1,3-dioxolane, methyl formate, methyl acetate,
Examples thereof include N, N-dimethylformamide, acetonitrile, a mixture thereof and the like.

Typical examples of the lithium salt dissolved in an organic solvent or the like include LiI, LiCF ₃ SO ₃ and Li (CF ₂ S
O ₂ ) ₂ , LiBF ₄ , LiClO ₄ , LiAlCl ₄ , L
iPF _6, such as LiAsF _6, and the like. The concentration of the lithium salt in the electrolytic solution is generally 0.1 to 3 mol / liter, but is not limited to this.

In forming the above-mentioned non-aqueous electrolyte, etc., 2-methylfuran, thiophene, pyrrole, crown ether, if necessary, for the purpose of improving battery characteristics such as life, discharge capacity, electromotive force, etc. It is also possible to add an organic additive such as a Li complex ion forming agent (macrocyclic compound or the like), or a component forming the above-described solid electrolyte membrane for coating the negative electrode.

In the case of the above-mentioned non-aqueous electrolytic solution or the like, the separator may be a porous insulating film for holding the electrolytic solution, for example, a porous polymer film made of polyolefin such as polypropylene or polyethylene, a glass filter, or a porous material such as nonwoven fabric. For example, a sex material is used. The holding of the electrolytic solution through the porous insulating film may be achieved by an appropriate method such as a method of impregnating or filling the porous insulating film with the electrolytic solution, or a method of filling the electrolytic solution into the battery can. . The thickness of the porous insulating film can be appropriately determined according to the battery for which it is formed, and is generally 500 μm or less, especially 1 to 30.
The thickness is 0 μm, particularly 5 to 100 μm.

The porous insulating film forming the separator may have a coating film made of, for example, polyvinylene carbonate or polyvinylpyrrolidone, which is excellent in the ability to retain the electrolytic solution. The separator has a structure in which a Li ion permeable metal film made of, for example, Al or Bi is interposed between the porous insulating films for the purpose of preventing contact between the negative electrode and the electrolytic solution, or the porous insulating film has a Li film. It may have a structure provided with an ion-permeable cation exchange membrane.

As the positive electrode, carbon or metal type,
Appropriate materials such as organic conductive material materials such as conjugated polymers can be used. Examples of the metal-based positive electrode include Li
Containing Ti, Mo, Cu, Nb, V, Mn, C
Examples thereof include complex oxides of metals such as r, Ni, Co, P, sulfides, selenides, V ₂ O _{5, and the} like. More specifically, for example, LiMnO ₂ , LiMn ₂ O ₄ , LiMn _2-x M _x O ₄ ,
LiNiO ₂ , LiNi _1-x M _x O ₂ , LiCoO ₂ , Li
CrO ₂ , LiFeO ₂ , LiVO ₂ , Li _w Co _1-xy M _x
P _y O _{2 + z} (where M is one or more transition metals,
w is 0 <w ≦ 2, x is 0 ≦ x <1, y is 0 <y <1, z
Is −1 ≦ z ≦ 4. ), Or Li or Li
0.1 mol or more of Co per 1 mol of Li containing a phosphate of Co and / or an oxide of Co or Li · Co
And those containing 0.2 mol or more of P as an active material.

The positive electrode is formed by using, for example, an electrode forming material such as the above-mentioned active material, if necessary, a conductive material such as acetylene black or Ketjen black, and polytetrafluoroethylene, polyethylene, polyvinylidene fluoride, ethylene / propylene / diene. Along with binders such as copolymers, casting methods, compression molding methods, roll molding methods, doctor blade methods, rolling methods, hot extrusion methods, and other appropriate methods, as well as various vapor deposition methods and hot dipping It can be performed by a method of forming a film by a method or the like. The thickness of the positive and negative electrodes is 500 μm or less, especially 300 μm.
Hereinafter, a thickness of 5 to 200 μm is generally used, but the thickness may exceed 1 mm, and the thickness can be appropriately determined.

EXAMPLE 1 Nickel was electroplated with a thickness of 2 μm on both sides of a copper tape having a width of 41 mm and a thickness of 10 μm, and then masking with a width of 1 mm was provided on both sides of the front and back sides of the copper tape to make silver thickness 0. .1μ
The current collector tape obtained by partially electroplating (middle part) with m and removing the masking was used in a high-purity argon atmosphere, and the atomic ratio of Li: Ag: Te was 90: 10: 0.1.
Li-Ag-Te system alloy hot dip bath (350 ℃)
Was continuously introduced and passed through, and the coating thickness on each side was adjusted to 25 μm by a drawing jig, and a cut piece having a length of 420 mm was formed therefrom to obtain a negative electrode tape.

On the other hand, lithium carbonate, basic cobalt carbonate, and a phosphoric acid aqueous solution having a phosphoric acid content of 85% were mixed with Li: Co: P.
= 2: 1.5: 0.5, mixed in an atomic ratio, placed in an alumina crucible and heat-treated at 900 ° C for 24 hours to obtain lithium phosphate, lithium-cobalt phosphate and cobalt oxide. A mixture of substances (active material) was formed and pulverized by a ball mill to obtain a powder having a particle size of 20 μm or less. next,
46 parts by weight of the powder, 4 parts by weight of acetylene black, 2 parts by weight of polyvinylidene fluoride and 50 parts by weight of N-methylpyrrolidone are mixed, and the mixture is 39 mm wide and 25 μm thick.
The aluminum tape was coated on both sides with a thickness of 150 μm and rolled to a thickness of 100 μm, and a 400 mm long cut piece was formed from the aluminum tape to obtain a positive electrode tape.

Next, the above-mentioned negative electrode tape and positive electrode tape are
3m in a battery can, wound with a 25μm thick porous polypropylene film (separator) in between
1 A of the electrolytic solution was injected to form an AA type secondary battery. The cross-sectional area of the wound product is about 90% of the cross-sectional area inside the battery can, and 1 liter of propylene carbonate /
A solution obtained by dissolving 1 mol of LiClO ₄ in a mixed solvent of dimethoxyethane was used.

Example 2 A negative electrode tape was obtained in the same manner as in Example 1 except that the masking width at both ends of the Ni-plated copper tape was 4 mm, and a Li secondary battery was obtained by using the negative electrode tape.

Comparative Example In accordance with Example 1, a negative electrode tape having a hot-dip layer of Li-Ag-Te alloy on the entire surface of the tape was obtained, and using this, a Li secondary battery was obtained.

Evaluation test 100 m of the Li secondary batteries obtained in the examples and comparative examples
4.1 V (charge) to 2.A at the charging current and discharging current of A.
After repeating the charge / discharge cycle 10 times at 75 V (discharge: left for 1 hour after charging), the battery was disassembled and the negative electrode tape was collected to check for cracks in the hot-dip layer of the Li-Ag-Te alloy. Examined.

The above results are shown in the following table.

[0049]

EFFECTS OF THE INVENTION According to the present invention, it is possible to obtain a negative electrode in which a hot-dip plated layer made of a Li alloy is less prone to cracks, and the hot-dip plated layer has little variation in quality and unevenness such as unevenness, and adhesion. Based on the excellent Li alloy negative electrode, a highly reliable Li secondary battery having excellent charge / discharge capacity and charge / discharge cycle life can be obtained.

[Brief description of drawings]

FIG. 1 is a plan view of an example of a negative electrode.

FIG. 2 is a sectional view of another embodiment of the negative electrode.

FIG. 3 is an explanatory diagram of a manufacturing example.

FIG. 4 is an explanatory view of another manufacturing example.

FIG. 5 is an explanatory diagram of a battery example.

[Explanation of symbols]

 1: Current collector tape 11: Diffusion barrier layer 12: Wetting promoter layer 2: Li alloy hot-dip layer 3: Side edge without hot-dip layer 15: Positive electrode 16: Separator 17: Negative electrode

Claims (2)

[Claims] 1. A lithium barrier layer is formed on a current collector tape via a diffusion barrier layer made of a conductor that does not easily react with a liquid Li alloy and a wetting promoter layer made of a conductor having an affinity for the liquid Li alloy on the diffusion barrier layer. A negative electrode for a Li secondary battery, which has a hot-dip layer made of an alloy, and does not have the hot-dip layer on both ends of the current collector tape. 2. A Li secondary battery having the negative electrode according to claim 1 on one side of a separator containing an electrolyte and the positive electrode on the other side.