KR20130042487A - Alloy negative electrode for lithium battery and process for production thereof, and lithium battery - Google Patents

Abstract

In a negative electrode for lithium batteries using a nonaqueous electrolyte, a lithium metal is filled in an aluminum porous body, and a skeleton of the aluminum porous body is formed of aluminum, and the skeleton of the aluminum porous body is formed of any metal of copper, nickel, or iron. By forming with the aluminum coating material which formed the aluminum layer on the surface of the core material which consists of these, an alloy negative electrode for lithium batteries, a manufacturing method, and a lithium battery with a large capacity density and excellent charge / discharge cycle are provided.

Description

ALLOY NEGATIVE ELECTRODE FOR LITHIUM BATTERY AND PROCESS FOR PRODUCTION THEREOF, AND LITHIUM BATTERY}

TECHNICAL FIELD This invention relates to the alloy negative electrode for lithium batteries using the aluminum porous body, its manufacturing method, and a lithium battery.

In recent years, lithium secondary batteries such as lithium ion batteries used in portable information terminals, electric vehicles, and home electric power storage devices have been actively studied.

As a representative example of this lithium secondary battery, Li-Al (negative electrode) / MnO ₂ (positive electrode) lithium secondary battery is shown by the nonpatent literature 1.

However, the lithium secondary battery is difficult to achieve industrial mass production because the Li-Al alloy serving as the negative electrode is fragile.

In addition, when charging and discharging were carried out by increasing the depth of discharge, a large number of charge and discharge cycles caused significant deterioration in discharge capacity. For example, when charging and discharging were performed at a 100% discharge depth, the cycle life was about several tens of cycles. For this reason, charging / discharging was normally performed with the discharge depth in about 10%.

 Takamura Tsutomu Supervised "The Latest Battery Handbook" Asakura Bookstore, issued December 26, 1996, pages 609-610

In view of these problems, it is desirable to develop an alloy negative electrode for lithium batteries that is suitable for industrial mass production and which does not cause deterioration of the discharge capacity even when charging and discharging is performed in a large number of charge and discharge cycles by increasing the discharge depth. there was.

The said subject can be solved by each invention shown below.

(1) The alloy negative electrode for a lithium battery according to the present invention,

As an alloy negative electrode for lithium batteries using a nonaqueous electrolyte,

A lithium metal is filled in an aluminum porous body.

MEANS TO SOLVE THE PROBLEM This inventor earnestly examined about the solution of said subject. As a result, it was found that it is effective to use a Li-Al alloy produced by filling lithium metal in an aluminum porous body as a negative electrode instead of the conventional Li-Al alloy of a plate-like body.

That is, since the Li-Al alloy negative electrode in which the lithium metal is filled in the aluminum porous body has a skeleton serving as a core, it does not have the same vulnerability as a conventional Li-Al alloy negative electrode and is suitable for industrial mass production.

In addition, even a high discharge depth can ensure a sufficient cycle life.

That is, as a result of the present inventor's investigation, the conventional Li-Al alloy negative electrode is accompanied by a charge / discharge cycle, whereby Al expands during charging, Al contracts during discharge, and expansion and contraction of the entire electrode occurs. It has been found that cracks and the like are generated at the interface, and micronization occurs to cause detachment of the active material, which adversely affects charge and discharge cycle characteristics when the discharge depth is increased.

In contrast, in the Li-Al alloy negative electrode in which the lithium metal is filled in the aluminum porous body according to the present invention, as the Al concentration moves away from the skeleton of the porous body, that is, the concentration gradient that becomes thinner as the center portion of the skeleton of the porous body is formed. The stress of expansion and contraction accompanying the charge and discharge cycles is dispersed and alleviated. As a result, even when the depth of discharge is increased, cracking of the electrode and the like can be suppressed, and the occurrence of micronization can be suppressed to ensure a sufficient charge and discharge cycle.

In addition, it has been found that the decrease in the charge / discharge cycle life is also caused by the occurrence of a short circuit when used for a long time due to Li dendrite growth due to the Li metal negative electrode. Advantageously, in the Li-Al alloy negative electrode in which the lithium metal is filled in the aluminum porous body according to the present invention, since the Li dendrite growth stays in the pores, the decrease in cycle life due to a short circuit is suppressed.

(2) In addition, the alloy negative electrode for lithium batteries,

A skeleton of the aluminum porous body is formed of aluminum.

Since the skeleton itself of the aluminum porous body is formed of aluminum, the Li-Al alloy can be formed only by the skeleton. For this reason, the alloy negative electrode for lithium batteries with high porosity and larger capacity density can be provided.

(3) In addition, the alloy negative electrode for lithium batteries,

The skeleton of the aluminum porous body is formed of an aluminum coating material on which an aluminum layer is formed on a surface of a core material made of any metal of copper, nickel, or iron.

The metal negative electrode of the lithium battery alloy of the present invention is a metal of copper, nickel or iron as a core material of a skeleton of an aluminum porous body. These metals are not alloyed with lithium or aluminum and have a high mechanical strength, so that a porous body having excellent strength can be formed. For this reason, the porous body in which the aluminum layer was formed on the surface of the core material which consists of these metals can provide the alloy negative electrode for lithium batteries strong with respect to expansion contraction.

(4) In addition, the alloy negative electrode for lithium batteries,

The proportion of the volume of the lithium metal in the vacancy of the aluminum porous body is 50% or more and less than 100%.

In the present invention, since the volume ratio of the lithium metal is less than 100%, and the pores remain in the aluminum porous body after Li filling, the dendrite is mainly generated in the pores even when the dendrite is produced. For this reason, the dendrite short is effectively suppressed. On the other hand, when the volume ratio of lithium metal is less than 50%, there exists a possibility that it may not fully exhibit the practical effect | action as an alloy negative electrode for lithium batteries.

(5) In addition, the alloy negative electrode for lithium batteries,

The amount of oxygen on the surface of the aluminum layer forming the skeleton of the aluminum porous body or the aluminum layer of the aluminum coating material is 3.1% by mass or less.

The aluminum porous body of the alloy negative electrode for lithium batteries of the present invention is a battery having a higher capacity density than ever since the oxygen content of the aluminum forming the skeleton of the aluminum porous body or the surface of the aluminum layer of the aluminum coating material is 3.1% by mass or less. An alloy negative electrode can be provided.

Since Al is easily oxidized originally, there has been no aluminum porous body having a sufficiently low amount of oxygen on the surface. For example, after the Al powder is coated on the surface of the Al alloy coating film formed on the surface of the foamed resin described in JP-A-8-170126, heat treatment is performed in a non-oxidizing atmosphere. In the case of the produced aluminum porous body, since the oxide film is formed on the surface, the amount of oxygen on the surface is large. When the amount of oxygen on the surface is large, the charged Li is oxidized by oxygen (O ₂ ) and changes to Li ₂ O, which does not function as an active material, so that a large capacity density is not obtained. In addition, since the generated Li ₂ O becomes a resistive layer, the characteristic is lowered.

For this reason, this inventor researched the aluminum porous body with a small amount of oxygen, and succeeded in developing the aluminum porous body with an oxygen amount of 3.1 mass% or less.

This invention is characterized by using such an aluminum porous body, and since the aluminum porous body of 3.1 mass% or less of oxygen on the surface is used, the alloy negative electrode for lithium batteries with a larger capacity density is obtained.

Here, the manufacturing method of the alloy negative electrode for lithium batteries of this invention is demonstrated in detail, referring drawings. In the first step of the production method, an aluminum porous body having continuous holes is produced, and in the second step, Li metal is filled in the aluminum porous body.

1A to 1C are schematic diagrams showing the outline of the first step. FIG. 1A is an enlarged schematic view showing a part of a cross section of the resin 1 having communication holes, and shows a state in which a hole is formed with the resin 1 as a skeleton. FIG. 1: B has shown the state (aluminum layer film resin 3) in which the aluminum layer 2 was formed in the surface of resin 1 which has a communication hole. FIG. 1C shows a state (aluminum porous body 4) after the resin 1 is thermally decomposed and disappeared from the aluminum layer film resin 3.

2 shows a step of thermally decomposing and disappearing the resin 1 from the aluminum layer film resin 3. The aluminum layer coating resin 3 and the positive electrode 5 are immersed in the molten salt 6 to hold the aluminum layer 2 at a potential lower than the standard electrode potential of aluminum. Oxidation of the aluminum layer 2 is suppressed by immersing in the molten salt to maintain the aluminum layer 2 at a potential lower than the standard electrode potential of aluminum. Moreover, although it can select suitably as the insoluble thing in a molten salt, the positive electrode 5 uses the electrode which consists of platinum, titanium, etc., for example.

In this state, when the molten salt 6 is heated above the decomposition temperature of the resin 1, only the resin 1 in the aluminum layer coating resin 3 is decomposed and lost. As a result, the aluminum porous body 4 is obtained. The aluminum porous body 4 manufactured by this method has a hollow fiber shape on the characteristics of the manufacturing method. In this respect, the structure of the aluminum foam as disclosed in JP-A-2002-371327 is different. In the case of decomposing the resin 1, in order to prevent melting of aluminum, the heating temperature is set to be equal to or lower than the melting point of aluminum. It is preferable to heat to 660 degrees C or less which is melting | fusing point of aluminum specifically ,.

Arbitrary resin can be selected for resin in this invention as long as it thermally decomposes at the temperature below the melting point of aluminum. For example, there are polyurethane, polypropylene, polyethylene and the like. Especially, since urethane foam is a material with high porosity and easy to thermally decompose, urethane foam is preferable as resin used for the manufacturing method of this invention. Moreover, it is preferable that the porosity of resin is 80%-98%, and a pore diameter is about 50 micrometers-500 micrometers. It is preferable that resin has a communication hole. As a result, an aluminum porous body having no closed pores is obtained.

The aluminum of the surface of the aluminum porous body demonstrated above was very low in oxygen amount, and was 3.1 mass% or less which is the precipitation limit of EDX analysis. In addition, although it has a communication hole, there is no waste hole and since it does not use a eutectic alloy etc., it is comprised only aluminum.

Next, as the second step, the aluminum porous body 4 is filled with Li metal. The method for filling is not specifically limited, For example, well-known methods, such as a method by impregnation, a vacuum vapor deposition method, an electroplating method, can be used.

(6) Moreover, the said alloy negative electrode for lithium batteries,

The aluminum porous body has a communication hole, does not have a waste hole,

In addition, it is characterized by consisting of only aluminum.

A lot of waste holes exist in a conventional aluminum porous body, for example, the aluminum porous body which foamed by adding a blowing agent in the state which melted Al of Unexamined-Japanese-Patent No. 2002-371327. Moreover, since the aluminum porous body of Unexamined-Japanese-Patent No. 8-170126 mentioned above is a process metal, it contains metals other than Al, such as Bi and Ca. In this way, when there are many waste holes, a sufficient amount of Li cannot be filled, so that a large capacity density is not obtained. Moreover, since it contains metals other than Al, the function as a negative electrode of Li-Al alloy falls.

On the other hand, in the lithium battery alloy negative electrode of the present invention, since a sufficient amount of Li metal can be filled, an alloy negative electrode for lithium battery with a larger capacity density is obtained. In addition, since the aluminum porous body is made of only aluminum, the function as a negative electrode can be sufficiently exhibited.

(7) The lithium battery according to the present invention,

It is characterized by including the alloy negative electrode for lithium batteries as described in said (1)-(6).

Since the lithium battery of this invention uses the alloy for lithium batteries provided with said characteristics as a negative electrode, it can provide the lithium battery which has a large capacity density and excellent charge / discharge cycle characteristics.

(8) The manufacturing method of the alloy negative electrode for lithium batteries which concerns on this invention is

An aluminum layer forming step of forming an aluminum layer on the surface of the resin having communication holes;

While the resin is immersed in the molten salt, while maintaining the aluminum layer at a potential lower than the standard electrode potential of aluminum, the resin is heated to a temperature below the melting point of aluminum, and the resin is thermally decomposed to produce an aluminum porous body. Aluminum porous body manufacturing process,

It is characterized by having a lithium metal filling step of filling a lithium metal into the aluminum porous body.

According to the method for producing an alloy negative electrode for a lithium battery of the present invention, as described above, the amount of oxygen on the surface of the aluminum layer is 3.1% by mass or less, has a communication hole, does not have a waste hole, and uses an aluminum porous body made of only aluminum. An alloy negative electrode for lithium batteries having a high capacity density and high suppression effect of micronization and dendrites can be provided.

(9) The manufacturing method of the alloy negative electrode for lithium batteries which concerns on this invention,

A metal layer forming step of forming a metal layer made of any metal of copper, nickel or iron on the surface of the resin having communication holes;

An aluminum layer forming step of forming an aluminum layer on a surface of the metal layer;

While the resin is immersed in the molten salt, while maintaining the aluminum layer at a potential lower than the standard electrode potential of aluminum, the resin is heated to a temperature below the melting point of aluminum, and the resin is thermally decomposed to produce an aluminum porous body. Aluminum porous body manufacturing process,

It is characterized by having a lithium metal filling step of filling a lithium metal into the aluminum porous body.

According to the method for producing an alloy negative electrode for a lithium battery of the present invention, as described above, the oxygen content of the surface of the aluminum layer is 3.1% by mass or less, and has a large capacity density using an aluminum porous body having a communication hole and no waste hole, Since the alloy negative electrode for lithium batteries excellent in the charging / discharging cycle can be provided, and since the metal made of any metal of copper, nickel, or iron is made into the aluminum porous body, a strong alloy negative electrode for lithium batteries can be provided. .

(10) Moreover, the manufacturing method of the said alloy negative electrode for lithium batteries is

The aluminum layer is formed by a vacuum deposition method, a sputtering method, a laser ablation method or a plasma CVD method.

In the vacuum vapor deposition method, for example, an aluminum metal layer can be formed by irradiating an electron beam to an aluminum metal as a raw material to melt and evaporate the aluminum metal, and to attach the aluminum metal to the resin surface of the resin body having communication holes. In the sputtering method, for example, an aluminum metal layer can be formed by plasma irradiation of a target of aluminum metal to vaporize the aluminum metal, and by attaching an aluminum alloy to the resin surface of the resin body having communication holes. In the laser ablation method, for example, an aluminum metal layer can be formed by melting and evaporating aluminum metal by laser irradiation, and attaching the aluminum metal to the resin surface of the resin body having communication holes. In the plasma CVD method, an aluminum metal layer can be formed by applying a high frequency to an aluminum compound which is a raw material and making it plasma, and attaching it to the surface of the resin having communication holes.

(11) Moreover, the manufacturing method of the said alloy negative electrode for lithium batteries is

The method of forming the aluminum layer is a plating method in which aluminum is plated after the surface of the resin is subjected to conductive treatment.

(12) Moreover, the manufacturing method of the alloy negative electrode for lithium batteries of this invention,

The method of forming the aluminum layer is a plating method of plating aluminum on the surface of the metal layer.

Since plating of aluminum in aqueous solution is practically impossible, molten salt electrolytic plating for plating aluminum in molten salt is performed. In this case, it is preferable to plate aluminum in molten salt after conducting the surface of the resin beforehand.

The molten salt used here may be the same as or different from the molten salt used in the process of thermally decomposing a resin. Specifically, molten salts such as potassium chloride, aluminum chloride and sodium chloride are used. Moreover, you may use it as a process molten salt using two or more salts. When it is set as process molten salt, since melt temperature falls, it is preferable. This molten salt needs to contain at least aluminum ions.

(13) Moreover, the manufacturing method of the said alloy negative electrode for lithium batteries is

The formation method of the said aluminum layer is a coating method which apply | coats an aluminum paste to the surface of the said resin or the surface of the said metal layer, It is characterized by the above-mentioned.

In the case of applying the aluminum paste to the surface of the resin, the aluminum paste is a mixture of aluminum powder, a binder (binder resin) and an organic solvent, for example. Specifically, the aluminum paste is applied to the surface of the resin, and then heated to minimize the organic solvent and binder resin, and to sinter the aluminum paste. The heating at the time of sintering may be performed in one step, or may be divided into multiple times. For example, after apply | coating an aluminum paste, you may heat at low temperature, lose | disappear an organic solvent, and then immersion in a molten salt and heating may carry out sintering of an aluminum paste simultaneously with decomposition | disassembly of resin.

ADVANTAGE OF THE INVENTION According to this invention, the alloy negative electrode for lithium batteries, a manufacturing method, and a lithium battery with a large capacity density and excellent charge / discharge cycle can be provided.

It is a schematic diagram which shows a part of cross section of resin which has a communication hole in the manufacturing process of an aluminum porous body.
It is a schematic diagram which shows the state (aluminum layer film resin) in which the aluminum layer was formed in the surface of resin which has communication hole in the manufacturing process of an aluminum porous body.
FIG. 1C is a schematic view showing the state (aluminum porous body) after thermal decomposition and disappearing of the resin from the aluminum layer coating resin in the aluminum porous body manufacturing step. FIG.
2 is a schematic view for explaining the decomposition step of the resin in the molten salt.
3 is a SEM photograph of the aluminum porous body of the present invention.
It is a figure which shows the EDX analysis result of the aluminum porous body by this invention.
It is a figure explaining the lithium battery of this invention.

(Mode for carrying out the invention)

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described based on drawing. In addition, in the following drawings, the same code | symbol is attached | subjected to the same or corresponding part, and the description is not repeated. In addition, the dimension ratio of drawing does not necessarily correspond with the thing of description.

(Embodiment 1)

A. Alloy negative electrode for lithium battery

In the alloy negative electrode for lithium batteries in this embodiment, lithium metal is filled in the aluminum porous body, and the skeleton of the aluminum porous body is formed of aluminum. And the alloy negative electrode for lithium batteries in this embodiment is manufactured by the following manufacturing method (refer FIG. 1A-FIG. 1C).

B. Manufacturing Method of Alloy Negative Electrode for Lithium Battery

As the porous resin (1), a foamed resin or nonwoven fabric having a communication hole is used. In particular, a resin having a porosity of 80% to 98% and a pore diameter of about 50 µm to 500 µm is preferable, and foamed urethane is preferably used. do.

Hereinafter, the manufacturing method of the alloy negative electrode for lithium batteries is demonstrated in order of an aluminum layer formation process, an aluminum porous body manufacturing process, and a lithium metal impregnation (charging) process.

(1) aluminum layer forming process

The aluminum layer 2 is formed by directly forming an aluminum layer 2 on the surface of the resin 1 by a vapor deposition method such as vacuum deposition, sputtering, laser ablation, or plasma CVD, plating, or aluminum paste coating. ).

In order to perform electrolytic plating, the surface of resin 1 is electrically conductively processed. For the conductive treatment, any method such as electroless plating of conductive metals such as nickel, vapor deposition or sputtering of aluminum or the like, or coating of conductive paint containing conductive particles such as carbon is selected. In a plating bath for aluminum plating, for example, melting of a multicomponent system of AlCl ₃ -XCl (X: alkali metal) -MCl _X (M is Cr, Mn and an additional element selected from transition metal elements) Salts are used. The resin 1 is immersed in the molten salt, and electrolytic plating is performed using the resin subjected to the conductive treatment as a negative electrode.

Formation of an aluminum layer can also be performed by application | coating of an aluminum paste as mentioned above. The aluminum paste is a mixture of aluminum powder, a binder (binder resin), and an organic solvent, and is sintered in a non-oxidizing atmosphere after coating a predetermined amount of aluminum paste on the surface of the resin (1).

(2) Aluminum porous body manufacturing process

Next, the resin 1 is thermally decomposed and removed. 2 is a schematic view for explaining a step of decomposing the porous resin in the molten salt 6. Among the salts containing at least one member selected from the group consisting of LiCl, KCl, NaCl, and AlCl ₃ , the resin having the aluminum layer formed on the surface thereof (that is, the aluminum layer film resin (3)) is preferably at or below the melting point of aluminum. Preferably, heating is performed at a temperature of 500 ° C. to 600 ° C., and a predetermined voltage is applied between the positive electrode 5 made of platinum or titanium to lower the aluminum layer of the aluminum layer coating resin 3 to a lower level than the standard electrode potential of aluminum. The porous resin 1 is thermally decomposed and removed at the potential (potential higher than the reduction potential of Li, K, Na) to prepare the aluminum porous body 4 of Fig. 1C.

(3) Lithium metal impregnation (charging) process

Next, a predetermined amount of lithium metal is incorporated into the produced aluminum porous body to produce an alloy of lithium and aluminum (Li-Al alloy) to produce an alloy negative electrode for a lithium battery. Specifically, for example, the aluminum porous body is bonded to a lithium foil having a predetermined thickness, and then heated to 180 ° C. or higher to melt the lithium foil to infiltrate the pores of the aluminum porous body. Moreover, you may immerse an aluminum porous body in the molten bath of lithium heated at 180 degreeC or more. In addition, the amount of lithium contained is adjusted so that the ratio of the volume of the lithium metal to the vacancy of an aluminum porous body may be 50% or more and less than 100%. For example, when the aluminum porous body with a porosity of 97% and the lithium foil whose thickness is 1/2 of an aluminum porous body are bonded together, the ratio of the volume of the lithium metal to a vacancy becomes 51.5%.

C. Lithium Battery

In the alloy negative electrode for lithium batteries produced in this way, the concentration of aluminum is high in the vicinity of the skeleton in the produced Li—Al alloy, and a low concentration gradient occurs as the distance from the skeleton increases. For this reason, even when the Li-Al alloy expands and contracts when charging and discharging is performed, stress relaxation is likely to occur, and micronization is suppressed.

In addition, since the proportion of the volume of the lithium metal in the pores of the aluminum porous body is 50% or more, a sufficiently high capacity density is ensured, while if it is less than 100%, the pores remain in the aluminum porous body after Li filling, so that lithium dendrite Even when is generated, dendrites short are suppressed.

(Embodiment 2)

In Embodiment 2, the skeleton of an aluminum porous body is an aluminum coating material in which the aluminum layer was formed in the surface of the core material. The core material is made of any metal of copper, nickel, or iron, and is formed by applying carbon powder to the surface of the resin having communication holes and conducting a conductive treatment, followed by plating with a predetermined thickness.

Embodiment 2 manufactures the alloy negative electrode for lithium batteries and a lithium battery by the same method as Embodiment 1 except the skeleton of an aluminum porous body is an aluminum coating material.

(Embodiment 3)

In each of the above embodiments, the lithium metal is not limited to penetration of the aluminum porous body into the pores, and may be formed on the surface of the aluminum porous body.

In addition, lithium metal does not need to be a single substance, and may be an alloy with other metals. In particular, Li-Si (silicon) and Li-Sn (tin) are suitable as an alloy negative electrode.

In the case where such an alloy negative electrode of Li-Si or Li-Sn is formed in the aluminum porous body, an alloy layer of Li and Si or Sn may be formed on the surface of the aluminum porous body, or a core material such as "aluminum skeleton" or "copper". An Si or Sn metal layer may be formed on the “aluminum layer formed on the surface of the layer”, and a Li metal layer may be further laminated.

Example

(Examples 1 and 2)

Example 1 is a lithium secondary battery which has a negative electrode formed by incorporating lithium metal into the aluminum porous body whose skeleton was formed of aluminum.

Example 2 is a lithium secondary battery which has a negative electrode formed by incorporating a lithium metal into the aluminum porous body which is formed in the surface of the core material whose skeleton is Cu, and is an aluminum coating material.

(1) Fabrication of aluminum porous body

In Example 1, polyurethane foam having a porosity of 97% and a pore diameter of about 300 μm was prepared. An aluminum layer having a thickness of about 50 μm was formed on the surface of the polyurethane foam by vacuum deposition, and then immersed in a LiCl-KCl eutectic molten salt at a temperature of 500 ° C., and the aluminum layer at a potential lower than the standard electrode potential of aluminum. It was preserved for 30 minutes. Thereafter, the mixture was cooled to room temperature in the air, washed with water to remove molten salt, and an aluminum porous body having a thickness of 0.5 mm and a porosity of 97% having an aluminum layer as a skeleton was produced.

In Example 2, polyurethane foam having a porosity of 97% and a pore-size of about 300 µm was prepared. After apply | coating carbon powder to the surface of this polyurethane foam and conducting a conductive process, copper plating of 20 micrometers in thickness was performed, and the core material was formed. After forming a surface layer of aluminum having a thickness of about 50 μm by vacuum evaporation thereon, it is immersed in a LiCl-KCl eutectic molten salt having a temperature of 500 ° C., and the aluminum layer is stored at a potential lower than the standard electrode potential of aluminum for 30 minutes. did. Then, it cooled to room temperature in air | atmosphere, water-washed, molten salt was removed, and the aluminum porous body of thickness 0.5mm and porosity 96% which made the aluminum coating material which formed the surface layer of aluminum on the surface of the core material of Cu as a frame | skeleton was produced.

In the reference example, expanded urethane foam having a pore size of 200 μm to 500 μm, a porosity of 97%, and a thickness of 1.0 mm was prepared. This foamed urethane foam was arrange | positioned in the vacuum vapor deposition apparatus. The aluminum film was deposited on the surface of the urethane foam by the vacuum vapor deposition method of melting and evaporating the aluminum metal. Then, foamed urethane foam was removed by heat-processing 550 degreeC in air | atmosphere. This obtained the aluminum porous body which is a reference example.

(2) Confirmation of structure of aluminum porous body and measurement of oxygen amount

The SEM photograph of the aluminum porous body of Example 1 is shown in FIG. 3 shows that the holes constituting the aluminum porous body communicate with each other. Moreover, it turned out that the aluminum porous body of Example 1 does not have a waste hole.

The surface of the aluminum porous body of Example 1 was analyzed by EDX at an acceleration voltage of 15 kV. The result is shown in FIG. The peak of oxygen was not observed. Therefore, it turned out that the oxygen amount of the aluminum porous body is below the detection limit of EDX. Here, since the detection limit by EDX is 3.1 mass% of oxygen amount, it can be said that the oxygen amount of the surface of the aluminum porous body of Example 1 is 3.1 mass% or less.

Also about Example 2, although SEM photographing and EDX analysis were performed, it confirmed that it was the same result as Example 1.

EDX analysis was also performed on the surface of the aluminum porous body of the reference example under the same conditions. As a result, the peak of oxygen was observed and it turned out that the oxygen amount of an aluminum porous body exceeds 3.1 mass% at least. This is because the surface of the aluminum porous body was oxidized at the time of heat treatment.

In addition, the apparatus used by this analysis is "EDAX Phonenix" by the EDAX company, The form is HIT22 136-2.5.

(3) production of negative electrode

After bonding a 350-micrometer-thick lithium foil to the aluminum porous body, it heated at 250 degreeC, melt | dissolved Li, and let Li permeate | transduced into the cavity. In addition, the ratio of the volume of the lithium metal to a vacancy is 75%.

The aluminum porous body which penetrated lithium metal into the cavity was shape | molded to the circular shape of diameter 15mm, and the alloy negative electrode for lithium batteries was produced.

(4) Preparation of a positive electrode for a lithium battery

MnO ₂ (active material), acetylene black (conductive aid) and PVDF (binder) were mixed at a predetermined ratio to produce a lithium battery positive electrode having a diameter of 15 mm and a capacity density of 10 mAh / cm ² .

(5) Fabrication of lithium secondary battery

Next, the lithium secondary battery was produced for the negative electrode and the positive electrode. 5 is a diagram for explaining the configuration of the lithium battery of this embodiment. In FIG. 5, 11 is a lithium secondary battery, 12 is a positive electrode for lithium batteries, 13 is a separator, 14 is an alloy negative electrode for lithium batteries.

Specifically, a polypropylene separator 13 is sandwiched between the positive electrode 12 and the negative electrode 14, and 1 mol% of LiClO ₄ is dissolved (1M) propylene carbonate / ethylene carbonate / dime It granulated using the electrolyte solution which consists of a mixed liquid of oxyethane.

(Comparative Example)

A comparative example is a lithium secondary battery which has a negative electrode of Al-Li alloy foil.

An Al-Li alloy foil having a ratio of aluminum of 50 atomic% and a diameter of 15 mm was produced to form an alloy negative electrode for a lithium battery, and used for the negative electrode and a lithium battery positive electrode prepared in the same manner as in the examples. In the same manner, a lithium secondary battery was produced.

(Characteristic evaluation of the lithium secondary battery of Example 1, 2 and a comparative example)

(1) yield

In the case of Examples 1 and 2, the yield of the comparative example was as low as about 50% while the yield in the assembly of the battery was 100%. In the case of the comparative example, such a low yield is because the alloy negative electrode for lithium batteries is weak and cracks and cracks occur during handling.

(2) charge and discharge cycle characteristics

end. Test Methods

The charge-discharge cycle test was performed with two types of discharge depths of 6 mA / h and 18 mA / h with cut-off voltage set to 2.0-3.3V, and the number of cycles which discharge capacity becomes 50% or less of the initial stage was investigated.

I. Test result

Table 1 shows the test results of Examples 1 and 2 and Comparative Examples.

From Table 1, it turns out that Example 1, 2 is excellent in cycling characteristics. The cycle characteristic of the Example is excellent because it uses the alloy negative electrode for lithium batteries with high suppression effect of micronization and a dendrite short.

In addition, as described above, the embodiment is a lithium secondary battery having an alloy negative electrode for a lithium battery having a high capacity density because Li is incorporated into an aluminum porous body having no pores and having a small amount of oxygen.

As mentioned above, although embodiment of this invention was described, this invention is not limited to said embodiment. It is possible to add various changes with respect to the said embodiment in the same and equivalent range as this invention.

As described above, according to the present invention, since lithium is incorporated into an aluminum porous body having no waste pores and having a small amount of oxygen, an alloy negative electrode for a lithium battery having a large capacity density and excellent charge / discharge cycles, a manufacturing method thereof, and a lithium battery can be provided. .

1: resin
2: aluminum layer
3: aluminum layer coating resin
4: aluminum porous body
5: positive electrode
6: molten salt
11: lithium secondary battery
12: positive electrode for lithium battery
13: Separator
14: alloy negative electrode for lithium batteries

Claims (13)

As an alloy negative electrode for a lithium battery using a nonaqueous electrolyte,
A lithium metal alloy negative electrode, wherein a lithium metal is filled in an aluminum porous body. The method of claim 1,
The skeleton of the said aluminum porous body is formed of aluminum, The alloy negative electrode for lithium batteries characterized by the above-mentioned. The method of claim 1,
The skeleton of the said aluminum porous body is formed of the aluminum coating material in which the aluminum layer was formed in the surface of the core material which consists of a metal of copper, nickel, and iron, The lithium battery alloy negative electrode characterized by the above-mentioned. 4. The method according to any one of claims 1 to 3,
The proportion of the volume of the lithium metal in the vacancy of the aluminum porous body is 50% or more and less than 100%. 5. The method according to any one of claims 1 to 4,
The amount of oxygen on the surface of the aluminum forming the skeleton of the aluminum porous body or the aluminum layer of the aluminum coating material is 3.1% by mass or less. The method according to any one of claims 1 to 5,
The aluminum porous body has a continuous hole, does not have a closed pore,
Moreover, the alloy negative electrode for lithium batteries which consists of aluminum only. The lithium battery alloy negative electrode in any one of Claims 1-6 is provided. The lithium battery characterized by the above-mentioned. An aluminum layer forming step of forming an aluminum layer on the surface of the resin having communication holes;
While the resin is immersed in the molten salt, while maintaining the aluminum layer at a potential lower than the standard electrode potential of aluminum, the resin is heated to a temperature below the melting point of aluminum, and the resin is thermally decomposed to produce an aluminum porous body. Aluminum porous body manufacturing process,
And a lithium metal filling step of filling a lithium metal into the aluminum porous body. A metal layer forming step of forming a metal layer made of any metal of copper, nickel or iron on the surface of the resin having communication holes;
An aluminum layer forming step of forming an aluminum layer on a surface of the metal layer;
While the resin is immersed in the molten salt, while maintaining the aluminum layer at a potential lower than the standard electrode potential of aluminum, the resin is heated to a temperature below the melting point of aluminum, and the resin is thermally decomposed to produce an aluminum porous body. Aluminum porous body manufacturing process,
And a lithium metal filling step of filling a lithium metal into the aluminum porous body. 10. The method according to claim 8 or 9,
The method for forming the aluminum layer is a vacuum deposition method, a sputtering method, a laser ablation method, or a plasma CVD method. 9. The method of claim 8,
The method for forming the aluminum layer is a plating method in which aluminum is plated after the surface of the resin is conductively treated. 10. The method of claim 9,
The method for forming the aluminum layer is a plating method in which aluminum is plated on the surface of the metal layer. 10. The method according to claim 8 or 9,
The said aluminum layer formation method is a coating method which apply | coats an aluminum paste to the surface of the said resin or the surface of the said metal layer, The manufacturing method of the lithium battery alloy negative electrode characterized by the above-mentioned.

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