JP2968447B2 - Anode alloy for lithium secondary battery and lithium secondary battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium secondary battery having a high charge-discharge cycle life and a high output, and a negative electrode alloy used for the lithium secondary battery.

[0002]

2. Description of the Related Art Conventionally, a non-aqueous electrolyte type lithium secondary battery using a non-aqueous electrolyte such as an organic solvent as an electrolyte and pure Li for a negative electrode has been known. .
This aims at achieving a high energy density battery output and a high electromotive force by using a non-aqueous electrolyte and pure Li. However, dendrites (dendrites) tend to grow on the surface of the pure Li negative electrode based on electrodeposition due to a discharge reaction between the negative electrode and Li ions during charging, and the growth significantly lowers the battery function or dendrites. However, there is a problem that the charge / discharge cycle life is inferior because the positive electrode and the negative electrode are short-circuited through the separator (electrolyte layer).

In view of the above, Al, Bi, Pb, Sn,
There has been proposed a method of forming a negative electrode with a Li alloy made of an intermetallic compound of In or the like and Li. This method uses Li
By such an alloying, the electrode potential is raised more than pure Li to lower the activity of the negative electrode, the speed of the discharge reaction between the negative electrode and Li ions is reduced, and the growth of dendrite is suppressed. is there. However, the lowering of the activity of the negative electrode due to the alloying also lowers the electromotive force and the charging / discharging capacity, and the brittleness due to the alloying causes the L during charging and discharging.
There has been a problem that cracks are generated in the negative electrode due to expansion and contraction of the volume due to absorption and release of i, and the negative electrode is eventually powdered, resulting in poor battery life.

On the other hand, for the purpose of high electromotive force and high charge / discharge capacity,
A method of forming a negative electrode with a dilute solid solution alloy obtained by adding Mg, Ag, Zn, or the like to Li has also been proposed. However, in the negative electrode made of such a dilute solid solution alloy, the alloy components are only scattered in the metal crystal matrix of Li, and there is no great difference from the electrochemical properties of the surface of the pure Li negative electrode.
At the time of charging, dendrite growth tends to proceed as in the case of the pure Li negative electrode. Therefore, there is a disadvantage that the charge / discharge cycle life of the lithium secondary battery is short, and there is a disadvantage that the practicability is poor.

It is an object of the present invention to provide an alloy used for a negative electrode for a lithium secondary battery having a large charge / discharge capacity, a high energy density, and little deterioration due to repeated charge / discharge. An object of the present invention is to provide a lithium secondary battery having excellent discharge capacity, high energy density battery output, and excellent charge / discharge cycle life.

[0006]

Means for Solving the Problems The present inventors have proposed the above-mentioned L
As a result of further study on the i-alloy-based negative electrode, it was found that the above object was achieved by forming the negative electrode of the secondary battery with a Li alloy having a specific composition range, and completed the present invention. .

That is, according to the present invention, the composition based on the atomic ratio is L
i: Ag: Te = 15 to 150: 1 to 20: 0.001
The present invention relates to a negative electrode alloy for a lithium secondary battery, comprising a Li-Ag-Te-based alloy of No. 1 to No. 2. The composition based on the atomic ratio is Li: Ag: Te = 80 to 150:
1-20: Li-Ag-Te less than 0.001-2
The present invention relates to the above negative electrode alloy for a lithium secondary battery, comprising a base alloy. Further, the composition based on the atomic ratio is L
i: Ag: Te = 15 to 120: 1 to 20: 0.001
The present invention relates to the above negative electrode alloy for a lithium secondary battery, comprising a Li-Ag-Te alloy.

In the present invention, the composition based on the atomic ratio is L
i: Ag: Te: M1: M2 = 15 to 120: 1 to 2
0: 0.001-2: 1-50: 1-30 [However, M1
Represents a 3B to 5B group metal, and M2 represents a transition metal (excluding Ag).
A negative electrode alloy for a lithium secondary battery, comprising a Li-Ag-Te- (M1-M2) -based alloy, wherein M1 is selected from Al, Si, In, and Sn. Or two or more of the above negative electrode alloys for a lithium secondary battery, wherein M2 is Zn, Fe, Co, Ni, Mn, M
The present invention relates to the negative electrode alloy for a lithium secondary battery, which is one or more selected from o and W.

Further, the present invention relates to a lithium secondary battery having a negative electrode comprising the above negative electrode alloy for a lithium secondary battery.

The Li-Ag-Te alloy in the negative electrode alloy for a lithium secondary battery according to the present invention is composed of a Li-Ag alloy which absorbs and releases Li during charge and discharge to share Li absorption and release,
An alloy containing fine particles of an intermetallic compound such as Ag ₂ Te or Li ₂ Te that realizes crystal grain refinement for promoting the diffusion of Li and Ag.

The Li-Ag-Te alloy is Li-A
and containing gamma _1-phase found in g based alloy and contains more of the gamma _1-phase, long-term discharge capacity retention characteristics, the preferred and also improve the charge-discharge cycle life, the present inventors have investigated . That is, since the γ ₁ phase contains a large amount of vacancies derived from the defect structure, the diffusion of Li and Ag is further promoted, and the composition change in the electrode due to the absorption and release of Li is more rapidly mitigated. , Te act synergistically on the diffusion promoting effect of Li and Ag derived from the crystal grain refining effect, and further improve the reversibility of the charge / discharge reaction. As a result, long-term discharge capacity maintenance characteristics and long cycle life of charge and discharge are achieved. Therefore, in the alloys of the present invention, it is particularly preferred to include a lot of gamma ₁ phase.

Te is formed in the process of forming a high melting point intermetallic compound consisting of a reaction product with Li and Ag, that is, Li-A
In the solidification step in the melting process of the g-Te alloy,
A large number of crystal nuclei are formed to refine crystal grains and increase the grain boundary area. Since the diffusion rate of Li at the grain boundary is several tens times or more than that in the grain, the diffusion of Li is promoted by the increase of the grain boundary area, and the Li electrodeposition at the negative electrode causes the Li diffusion. Is reduced, and the efficiency of Li absorption / release is improved.

Here, by using a negative electrode made of a negative electrode alloy having the above composition containing Ag and having a reduced Te concentration, a lithium secondary battery having excellent charge and discharge cycle life can be obtained. In addition, Li-Ag-Te with a high Te concentration was used.
As in the case of the alloy having a low Te concentration composition according to the present invention, a large Li absorption capacity, suppression of dendrite growth during charging in a wide current density region, a low electrode potential comparable to pure Li, and Advantageous characteristics such as high electromotive force can be exhibited. However, the point of preventing a gradual decrease in charge / discharge capacity due to long-term charge / discharge cycles, that is,
The alloy of the present invention having a low Te concentration composition is particularly excellent in terms of the long cycle life of charge / discharge and the continuity of the initial charge / discharge capacity.

One of the reasons for the above phenomenon is considered to be a decrease in the surface properties of the negative electrode due to segregation and agglomeration of the intermetallic compound in an alloy having a high Te concentration composition. That is, with the charge / discharge cycle, the diffusion of Li and Ag progresses in the negative electrode alloy, but when the Te concentration in the negative electrode alloy is high, the segregation / aggregation of the Te intermetallic compound proceeds by a long charge / discharge cycle. Further, macro-accumulation on the negative electrode surface further progresses, and the properties of the negative electrode surface deteriorate. Therefore, when Te is at a high concentration, the diffusion of Li and Ag near the negative electrode surface is hindered by the macroscopic segregation and aggregation of the intermetallic compound on the negative electrode surface, and the current density distribution on the negative electrode surface is poor. It is considered that the charge / discharge characteristics are degraded due to the progress of uniformization and the like. On the other hand, when the concentration of Te is low, it is considered that the segregation / aggregation phenomenon is suppressed, and a crystal structure having excellent Li diffusivity is formed even when the concentration of Te is reduced.

[0015] Even when the segregated product is in the form of a negative electrode such as a sheet, as described later, cracks are easily generated in the negative electrode in the winding step. It is likely to cause damage to the separator. Therefore, suppression of such segregation is advantageous for forming a high-performance lithium secondary battery and its negative electrode.

The negative electrode alloy for a lithium secondary battery of the present invention may further contain a (M1-M2) alloy component in addition to the above-mentioned Li-Ag-Te alloy component. As described above, the Li-Ag-Te alloy component promotes the diffusion of lithium and performs a function of smoothly absorbing and releasing lithium during charge and discharge. On the other hand, (M1-M
2) The system alloy component itself is a stable intermetallic compound, and the binder effect of this intermetallic compound further suppresses the deterioration of the negative electrode due to the expansion and contraction of the volume due to the absorption and release of lithium. It contributes to the prevention of shortening of service life.

M1 is 3B, 4B, 5 of the long period type periodic table.
Group B metal, which can be used alone or in combination of two or more. It is preferably at least one selected from Al, Si, In, and Sn, and more preferably S
One or more selected from i, In, and Sn. M2 is a transition metal (3A to 7A of the long period type periodic table,
8, 1B, and 2B metals; except for Ag), which may be used alone or in combination of two or more. It is preferably one or more selected from Zn, Fe, Co, Ni, Mn, Mo, and W, and more preferably Zn, F
e or one or more selected from Ni.

The negative electrode alloy for a lithium secondary battery of the present invention comprises:
The composition based on the atomic ratio is Li: Ag: Te = 15 to 15.
Li-Ag-Te that is 0: 1 to 20: 0.001-2
It is made of a system alloy. Further, the composition based on the atomic ratio is Li: Ag: Te = 80 to 150: 1 to 20: 0.0
Li-Ag-Te alloys having an atomic ratio of Li: Ag: Te = 15-1
Li-Ag-T of 20: 1-20: 0.001-2
Those composed of an e-based alloy are preferred. Further, the composition based on the atomic ratio is Li: Ag: Te: M1: M2 = 15-12.
More preferably, it is made of a Li-Ag-Te- (M1-M2) alloy having a ratio of 0: 1 to 20: 0.001 to 2: 1 to 50: 1 to 30.

If the atomic ratio of Li is less than 15, the diffusion of Li is slow, resulting in a decrease in electromotive force and a decrease in charge / discharge capacity. Also,
If the atomic ratio of Li exceeds 150, the electrochemical properties of the alloy become closer to a pure Li electrode, which is not preferable. Note that Li
It is advantageous from the point of charge and discharge efficiency that the atomic ratio of is not more than 120. Preferred atomic ratios of Li are 15 to 120, more preferably 15 to 100, especially 15 to 90, especially 15
~ 80.

If the atomic ratio of Ag is less than ₁ , the γ ₁ phase is hardly formed, and the electrochemical properties of the negative electrode surface approach pure Li, which is not preferable. On the other hand, if the atomic ratio of Ag is more than 20, the diffusion rates of Li and Ag decrease, and it becomes difficult to work the sheet of the alloy, and the electromotive force tends to decrease. The preferred atomic ratio of Ag is 2 to
18, especially 5-18, especially 6-13.

If the atomic ratio of Te is less than 0.001, L
The crystal grain refining effect of promoting the diffusion of i and Ag is poor. On the other hand, when the atomic ratio of Te exceeds 2, segregation of the intermetallic compound easily proceeds as described above. Preferred T
The atomic ratio of e is less than 0.001-2, more preferably 0.002-1.999, especially 0.005-1.0, especially 0.005-0.05.

The atomic ratio of M1 is preferably 1 to 50, and the atomic ratio of M2 is preferably 1 to 30.
When the atomic ratio of M1 and M2 is within the above range, a sufficient binder effect is exhibited, and when the battery is used, the battery has excellent charge / discharge cycle life, high charge / discharge capacity, high electromotive force, and high energy density. . The atomic ratio of M1 is more preferably 2 to 30, particularly preferably 5 to 20, and the atomic ratio of M2 is more preferably 1 to 20, particularly preferably 1 to 1.
0.

The negative electrode alloy for lithium secondary batteries of the present invention (L
i-Ag-Te-based alloy or Li-Ag-Te- (M1
-M2) -based alloy) can be formed by a known appropriate alloying method such as a method of melting and reacting a predetermined ratio of each alloy component (melting method) or a method of reacting by a vapor deposition method. it can.

In the melting method, alloying can be performed by heating and melting the alloy components in an inert gas atmosphere.
In this case, a method of heating and melting to a temperature equal to or higher than the melting point of Li is preferable from the viewpoint of promptly proceeding the alloying reaction. The alloying method by evaporation is to evaporate the alloy components,
This is performed by solidification on the surface of a conductor made of another metal. Examples of the vapor deposition method include various sputtering methods such as ion beam sputtering, an electron beam vapor deposition method, various ion plating methods, a flash plasma vapor deposition method, a pulse plasma vapor deposition method, and CVD (chemical vapor deposition).
An appropriate method such as a method can be adopted.

The method for forming the negative electrode for a lithium secondary battery is not particularly limited, and it can be performed by a usual method. For example, it is performed by an appropriate method such as forming a previously formed negative electrode alloy into a known negative electrode form (a sheet form, a tape form, a thin film form, a substrate form, etc .; hereinafter, these are collectively also referred to as a sheet form). Can be.

Specifically, a method of forming the negative electrode alloy into a sheet or the like by hot rolling or hot extrusion, or a method of providing a negative electrode alloy layer on a current collector by a hot-dip plating method, a low pressure plasma spraying method, or the like. And the like. The latter method using a current collector is advantageous when a sheet-shaped negative electrode is formed,
An alloy layer can be provided on one side or both sides of the current collector.

The hot rolling method is a working method in which the temperature of an alloy material is raised to make it easy to work, and the hot extrusion method is a method in which the alloy material is heated to make it easy to work. This is an extruding method. In addition, the hot-dip plating method is a method in which an alloy is melted in an argon gas, and a current collector is immersed in plating. The low-pressure plasma spraying method is a method in which the current is collected in a low-pressure argon atmosphere (100 mTorr or the like). This is a method of spraying an alloy on the surface.

The sheet-like negative electrode can also be formed by, for example, attaching a component for forming a negative electrode alloy to a current collecting sheet by the above-described vapor deposition method. Also, a laminate of the negative electrode alloy sheet and the current collecting sheet can be formed by joining the sheet-shaped negative electrode alloy to the current collecting sheet by an appropriate method such as brazing, soldering, ultrasonic welding, spot welding, or the like. can do.

Further, Li-Ag-Te- (M1-M
2) As a method of forming a negative electrode made of a system alloy, besides the above method, for example, an appropriate amount of (M1-M2) alloy powder is applied or vapor-deposited on a current collecting sheet in advance, heat-treated, and then L
A method of spraying, impregnating or dipping an i-Ag-Te alloy is exemplified. Note that these steps are preferably performed in an inert gas atmosphere in order to prevent deterioration of each constituent material.

The current collecting sheet is, for example, Ni, A
It refers to a sheet-like current collector made of an appropriate conductor such as l, Cu, Ag, and Fe. Specific examples include a sheet-like metal foil, a metal mesh, a metal porous body, and the like.

The lithium secondary battery of the present invention has the following features except that a negative electrode made of the above negative electrode alloy for a lithium secondary battery is used.
The configuration, manufacturing method, and the like can be according to the related art.

FIG. 1 shows a coin-type lithium secondary battery which is an example of the lithium secondary battery of the present invention. 1, 7 is a battery can, 2, 6 are Ni plates for current collection, 3 is a negative electrode, 4 is a separator (electrolyte layer), 5 is a positive electrode, and 8 is an insulating sealing material.

For the positive electrode of the lithium secondary battery, for example, MnO ₂ , LiCoO 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 phosphate, Li-Co phosphate, Co oxide, Li-C
at least one selected from oxides of o
A positive electrode material or the like having an active material containing 0.1 mol or more of Co and 0.2 mol or more of P per mol of Li can be used.

The sheet-like positive electrode is formed by, for example,
A casting method, a compression molding method, a roll molding method, a doctor blade method together with a conductivity-imparting material (acetylene black, ketjen black, etc.) and a binder (polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc.) as required. It can be obtained by molding with an appropriate method such as. In addition, N-methylpyrrolidone, propylene carbonate, or the like can also be used as a solvent for the binder. Also, as in the case of the negative electrode,
The positive electrode material can be used by appropriately bonding it to the current collecting sheet.

As the electrolyte in the lithium secondary battery, a non-aqueous electrolyte, a solid electrolyte, or the like can be used.

Examples of the non-aqueous electrolyte include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, tetrahydrofuran,
-Methyltetrahydrofuran, dimethylsulfoxide,
Li salt is added to a suitable organic solvent such as sulfolane, γ-butyrolactone, 1,2-dimethoxyethane, diethyl ether, 1,3-dioxolan, methyl formate, methyl acetate, N, N-dimethylformamide, acetonitrile, and a mixture thereof. Are dissolved, and if necessary, 2-
Examples thereof include those in which organic additives such as methylfuran, thiophene, pyrrole, and crown ether are dissolved.

As the Li salt, for example, LiClO
_Four, LiBF_Four, LiPF_Four, LiAsF_Three, LiAl
Cl_Four, Li (CF_TwoSO_Two)_Two, LiI, LiCF_Three
SO _ThreeAnd the like can be used. In addition,
The concentration of Li salt in the solution is 0.1 to 3 mol / liter.
Is common, but is not limited to this.

Examples of the solid electrolyte include those obtained by mixing salts such as the above-mentioned Li salt with a salt-electrolyzing polymer such as polyethylene oxide, polyphosphazene, polyaziridine, polyethylene sulfide, derivatives and mixtures thereof, and composites. .

When the non-aqueous electrolyte is an electrolyte,
The formation of the separator interposed between the positive and negative electrodes, for example, a porous polymer film made of polypropylene or the like, a glass filter, impregnating the electrolyte solution with a nonwoven fabric, or the like,
It can be performed by an appropriate method according to the related art, such as a filling method. Further, when the solid electrolyte is an electrolyte, it has an advantage that it can also serve as a separator between a positive electrode and a negative electrode.

As the battery can, for example, Ni-plated iron, C
Examples include r-plated iron and stainless steel, and Ni-plated iron is preferable. Examples of the insulating sealing material include polypropylene, polyethylene, nylon, and the like, and polypropylene is preferable.

The form of the lithium secondary battery can be appropriately determined according to the purpose of use and the like, and examples thereof include a coin type, a button type and a wound type. In the above-mentioned coin-type, button-type, and wound-type secondary batteries, a sheet-like negative electrode, positive electrode, or the like is usually preferably used.

The method for producing the lithium secondary battery is not particularly limited, and it can be produced by a known method. For example, in a wound lithium secondary battery, the above-described negative electrode and positive electrode are wound with a separator interposed therebetween, housed in a battery can, injected with an electrolytic solution, and further provided with an insulating sealing material at the end of the battery can. Can be produced by attaching In addition, coin-type and button-type lithium secondary batteries can be manufactured by the same method as described above, except that the negative electrode and the positive electrode are housed in a battery can without being wound with a separator interposed therebetween. it can.

The obtained lithium secondary battery can be charged by an appropriate method such as a method of continuously supplying a constant current or a method of supplying a pulse current using a pulse power supply. In the charging method using pulse current,
Since the stoppage is repeated, there is an advantage that the density change is suppressed, and the dendrite hardly grows.

[0044]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.

Example 1 An atomic ratio composition of Li: Ag: Te = 9 formed by a melting method.
A 0: 10: 1 Li-Ag-Te alloy was heated and melted at 300 ° C. 13 μm in thickness and 41 in width in the melt
After immersing a current collector sheet having a thickness of 300 mm and a length of 300 mm, the current collector sheet is lifted up, and a 14 μm-thick Li-Ag-
A negative electrode tape having a Te-based alloy layer was obtained. The current collecting sheet was composed of a Ni plating layer having a thickness of 0.5 μm on both sides of a Cu tape having a thickness of 10 μm, and an A plating having a thickness of 1 μm
g It has a plating layer and has excellent heat resistance and wettability with the melt of the alloy.

On the other hand, lithium carbonate, basic cobalt carbonate, and a phosphoric acid aqueous solution having a phosphoric acid content of 85% were added to L
i: Co: P = 2: 1.5: 0.5 was mixed at an atomic ratio, and the mixture was placed in an alumina crucible at 900 ° C. for 2 hours.
Heat treatment for 4 hours, lithium phosphate and lithium
After forming a mixture (active material) of cobalt phosphate and cobalt oxide, the mixture is pulverized with a ball mill to obtain a particle size of 2.
It was a powder of 0 μm or less. Next, 46 parts by weight of the powder,
Acetylene black 4 parts by weight, polyvinylidene fluoride 2
Parts by weight, and 50 parts by weight of N-methylpyrrolidone, and mixed them with a width of 38 mm, a length of 240 mm, and a thickness of 20 μm.
Was coated on the aluminum tape by a doctor blade method and dried under vacuum to form a coating layer (positive electrode layer) having a thickness of 150 μm to obtain a positive electrode tape.

Next, the negative electrode tape and the positive electrode tape are
It is wound in a state where a porous polypropylene film (separator) having a thickness of 30 μm is interposed and stored in a battery can.
The AA type secondary battery was formed by injecting ml of the electrolyte.
Incidentally, the electrolytic solution is obtained by dissolving 1 mole of LiClO ₄ in 1 liter of propylene carbonate.

Example 2 A negative electrode tape and a lithium secondary battery were prepared in the same manner as in Example 1 except that a Li-Ag-Te alloy having an atomic ratio composition of Li: Ag: Te = 90: 10: 0.1 was used. I got

Example 3 The atomic ratio composition was Li: Ag: Te = 90: 10: 0.01.
A negative electrode tape and a lithium secondary battery were obtained in the same manner as in Example 1 except that the Li-Ag-Te alloy was used.

Example 4 Li—Ag having an atomic ratio composition of Li: Ag: Te = 95: 5: 1
A negative electrode tape and a lithium secondary battery were obtained according to Example 1, except that an Ag-Te alloy was used.

Example 5 L having an atomic ratio composition of Li: Ag: Te = 95: 5: 0.1
A negative electrode tape and a lithium secondary battery were obtained according to Example 1, except that the i-Ag-Te-based alloy was used.

Example 6 A negative electrode tape and a lithium secondary battery were prepared in the same manner as in Example 1 except that a Li-Ag-Te alloy having an atomic ratio composition of Li: Ag: Te = 95: 5: 0.01 was used. I got

Example 7 Li having an atomic ratio composition of Li: Ag: Te = 85: 15: 1
According to Example 1, except that an Ag-Te alloy was used,
A negative electrode tape and a lithium secondary battery were obtained.

Example 8 The atomic ratio composition was Li: Ag: Te = 85: 15: 0.01.
A negative electrode tape and a lithium secondary battery were obtained in the same manner as in Example 1 except that the Li-Ag-Te alloy was used.

Example 9 A Li—Ag—Te alloy having an atomic ratio composition of Li: Ag: Te = 90: 10: 0.2 was applied to both surfaces of a current collecting sheet by a reduced pressure plasma spraying method so as to have a thickness of 20 μm. A lithium secondary battery was obtained in the same manner as in Example 1 except that a negative electrode tape was obtained by providing a layer. The reduced pressure plasma spraying is performed at 100 mTorr.
Under a high purity argon atmosphere.

Comparative Example 1 Li having an atomic composition of Li: Ag: Te = 90: 10: 5
According to Example 1, except that an Ag-Te alloy was used,
A negative electrode tape and a lithium secondary battery were obtained.

Comparative Example 2 A negative electrode tape and a lithium secondary battery were obtained in the same manner as in Example 1 except that a Li—Ag alloy having an atomic ratio composition of Li: Ag = 95: 10 was used.

Comparative Example 3 Li—Ag having an atomic ratio composition of Li: Ag: Te = 95: 5: 5
A negative electrode tape and a lithium secondary battery were obtained according to Example 1, except that an Ag-Te alloy was used.

Comparative Example 4 A negative electrode tape and a lithium secondary battery were obtained in the same manner as in Example 1 except that a Li—Ag alloy having an atomic ratio composition of Li: Ag = 95: 5 was used.

Comparative Example 5 Li having an atomic composition of Li: Ag: Te = 85: 15: 5
According to Example 1, except that an Ag-Te alloy was used,
A negative electrode tape and a lithium secondary battery were obtained.

Comparative Example 6 A negative electrode tape and a lithium secondary battery were obtained in the same manner as in Example 1 except that a Li—Ag alloy having an atomic ratio composition of Li: Ag = 85: 15 was used.

Comparative Example 7 L having an atomic ratio composition of Li: Ag: Te = 90: 10: 10
A negative electrode tape and a lithium secondary battery were obtained according to Example 9, except that an i-Ag-Te-based alloy was used.

Experimental Example 1 For the lithium secondary batteries obtained in Examples 1 to 9 and Comparative Examples 1 to 7, 4.2 V (charge) at a charge and discharge current density of 0.6 mA / cm ^2. Charge-discharge cycles of 200 to 2.5 V (discharge: left for 1 hour after charging)
The discharge capacity retention rate after the repetition was examined. Table 1 shows the results.

[0064]

[Table 1]

Example 10 In a high-purity Ar atmosphere (dew point: −60 ° C. or lower), a sample weighed so that the atomic ratio of Li: Ag: Te = 90: 10: 0.5 was heated to 500 ° C. This was melted and alloyed. Further, in atomic ratio, Si: Fe = 10: 20
What was weighed so that it may become (the ratio with respect to Li: Ag: Te) was heated to 1400 ° C. in the same atmosphere to form an alloy. The obtained Si—Fe-based alloy was pulverized to a mesh of 200, and this was pulverized into a long current collector made of copper (width 42 m
m, thickness of 10 μm) with a roll and then 800 ° C.
For 3 hours to obtain a negative electrode substrate. Next, the molten Li-Ag-Te alloy obtained above was kept at 250 ° C,
The negative electrode substrate is immersed in this, and Li-A
The thickness of the g-Te alloy layer is 50 to 200 μm per side.
And a negative electrode plate was prepared by cutting to a length of 330 mm.

46 parts by weight of LiCoO ₂ as a positive electrode active material, 4 parts by weight of acetylene black as a conductivity-imparting material, 1 part by weight of polyvinylidene fluoride as a binder, and 49 parts by weight of N-methylpyrrolidone were thoroughly mixed. The paste obtained was applied to a long aluminum foil (width 42 mm, thickness 10 μm) by a doctor blade method to have a thickness of 100 per side.
It was coated on both sides so as to have a thickness of μm, temporarily dried at 200 ° C. for 1 minute, and then rolled. This is cut into a length of 300 mm and subjected to main drying at 120 ° C. for 3 hours in a vacuum.
A positive electrode plate was prepared.

Propylene carbonate having a water content of 20 ppm or less and 1,2-dimethoxyethane are mixed at a volume ratio of 1: 1. 1 mol / l of lithium perchlorate is dissolved in the mixture, and did. The porosity is 43
%, A polypropylene film having a thickness of 25 μm was impregnated to prepare a separator. Wound with the separator interposed between the negative electrode plate and the positive electrode plate obtained above,
This is stored in a nickel-plated iron battery can,
AA type lithium secondary batteries were produced.

Example 11 Instead of the Si—Fe alloy used in the negative electrode of Example 10,
In atomic ratio, In: Zn: Ni = 5: 10: 10 (Li: A
g: ratio to Te), heated to 1000 ° C. in the same atmosphere, and alloyed, except that a negative electrode plate and a lithium secondary battery were prepared in the same manner as in Example 10. Obtained.

Example 12 Instead of the Si—Fe alloy used in the negative electrode of Example 10,
All the examples were weighed such that the atomic ratio was Si: Ni = 20: 10 (ratio to Li: Ag: Te), heated to 1200 ° C. in the same atmosphere, and alloyed to be used. In the same manner as in No. 10, a negative electrode plate and a lithium secondary battery were obtained.

Comparative Example 8 In a high purity Ar atmosphere, Li: Ag = 9 in atomic ratio.
A negative electrode plate and a lithium secondary battery were obtained in the same manner as in Example 10 except that the mixture was weighed so as to be 0:10, heated and melted at 500 ° C., and used as a negative electrode.

Experimental Example 2 Using the lithium secondary batteries obtained in Examples 10 to 12 and Comparative Example 8, the electromotive force was measured by a two-terminal method.
The upper limit voltage of 4.2 using the above-mentioned lithium secondary battery.
V and the lower limit voltage of 2.7 V, and charging and discharging were repeated. Then, the energy density and the discharge capacity retention rate at the time of 50 cycles were measured. Table 2 shows the results.

[0072]

[Table 2]

[0073]

When the negative electrode alloy for a lithium secondary battery of the present invention is used, the growth of dendrite is suppressed, a charge / discharge capacity is large, a high energy density is obtained, and a negative electrode with little deterioration due to repeated charge / discharge is obtained. be able to. In addition, when the negative electrode is used, a lithium secondary battery having excellent charge / discharge cycle life and high energy density, high electromotive force, and high charge / discharge capacity that can be used for a long time can be obtained.

[0074]

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example (coin type) of a lithium secondary battery.

[Explanation of symbols]

 1,7 Battery can 2,6 Ni plate for current collection 3 Negative electrode 4 Separator (electrolyte layer) 5 Positive electrode 8 Insulating sealing material

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-62-176053 (JP, A) JP-A-61-100686 (JP, A) JP-A-61-140067 (JP, A) JP-A-48-16 89342 (JP, A) JP-A-62-90860 (JP, A) JP-A-62-90859 (JP, A) JP-A-62-90858 (JP, A) JP-A-62-90857 (JP, A) (58) Field surveyed (Int.Cl. ⁶ , DB name) H01M 4/40 C22C 24/00 H01M 4/02 H01M 10/40

Claims (7)

(57) [Claims] The composition based on the atomic ratio is Li: Ag: Te.
= 15 to 150: 1 to 20: Li which is 0.001 to 2
A negative electrode alloy for a lithium secondary battery, comprising an Ag-Te alloy. 2. The composition based on the atomic ratio is Li: Ag: Te.
2. The negative electrode alloy for a lithium secondary battery according to claim 1, wherein the negative electrode alloy is made of a Li—Ag—Te-based alloy having a ratio of 80 to 150: 1 to 20: less than 0.001 to 2. 2. 3. The composition based on the atomic ratio is Li: Ag: Te.
= 15 to 120: 1 to 20: Li which is 0.001 to 2
2. An alloy comprising an Ag-Te alloy.
The negative electrode alloy for a lithium secondary battery according to the above. 4. The composition based on the atomic ratio is Li: Ag: T.
e: M1: M2 = 15 to 120: 1 to 20: 0.001
From 2: 1 to 50: 1 to 30 [where M1 represents a 3B to 5B group metal and M2 represents a transition metal (excluding Ag)]-based Li-Ag-Te- (M1-M2) -based alloy A negative electrode alloy for a lithium secondary battery, comprising: 5. The negative electrode alloy for a lithium secondary battery according to claim 4, wherein M1 is one or more selected from Al, Si, In, and Sn. 6. M2 is Zn, Fe, Co, Ni, Mn,
The negative electrode alloy for a lithium secondary battery according to claim 4, wherein the negative electrode alloy is one or more selected from Mo and W. 7. A lithium secondary battery comprising a negative electrode comprising the negative electrode alloy for a lithium secondary battery according to claim 1.