JP5605749B2 - Alloy negative electrode for lithium battery, method for producing the same, and lithium battery - Google Patents

Description

  The present invention relates to an alloy negative electrode for a lithium battery using a porous aluminum body, a method for producing the same, and a lithium battery.

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

Non-patent document 1 discloses a Li—Al (negative electrode) / MnO ₂ (positive electrode) lithium secondary battery as a representative example of this lithium secondary battery.

  However, the lithium secondary battery described above has difficulty in achieving industrial mass production because the Li—Al alloy that is the negative electrode is fragile.

  Moreover, when charging / discharging was performed by increasing the depth of discharge, a large number of charging / discharging cycles caused significant deterioration of the discharge capacity. For example, when charging / discharging is performed at a discharge depth of 100%, the cycle life is limited to about several tens of cycles. For this reason, charging / discharging is usually performed at a discharge depth of about 10%.

Supervised by Tsutomu Takamura “Latest Battery Handbook” Asakura Shoten Co., Ltd., issued December 26, 1996, pages 609-610

  In view of these problems, it is suitable for industrial mass production, and even when charging / discharging is performed with a large number of charging / discharging cycles by increasing the depth of discharge, there is no risk of causing deterioration of the discharge capacity. Development of was desired.

Said subject can be solved by each technique of (1)-(13) relevant to this invention shown below.

(1) The alloy negative electrode for lithium batteries related to the present invention is:
An alloy negative electrode for a lithium battery using a non-aqueous electrolyte,
The aluminum porous body is filled with lithium metal.

  The present inventor has intensively studied to solve the above problems. As a result, it has been found that it is effective to use a Li—Al alloy produced by filling lithium metal in a porous aluminum body as a negative electrode instead of the conventional Li—Al alloy having a plate-like body.

  In other words, the Li-Al alloy negative electrode filled with lithium metal in the aluminum porous body has a core skeleton, so it is not as brittle as the conventional Li-Al alloy negative electrode, and is suitable for industrial mass production. Is preferred.

  Moreover, a sufficient cycle life can be ensured even at a high discharge depth.

  In other words, as a result of the study by the present inventors, along with the charge / discharge cycle, Al expands during charging, Al contracts during discharge, and the entire electrode expands and contracts, resulting in cracks at the electrode interface, It was found that micronization occurred and the active material was desorbed, which had an adverse effect on the charge / discharge cycle characteristics when the discharge depth was increased.

On the other hand, in the Li-Al alloy negative electrode in which lithium metal is filled in the aluminum porous body related to the present invention, the Al concentration becomes thinner from the skeleton of the porous body, that is, the thinner the central portion of the skeleton of the porous body. Therefore, the expansion and contraction stress accompanying the charge / discharge cycle is dispersed and relaxed. As a result, even when the depth of discharge is increased, cracking of the electrode and the like are suppressed, generation of pulverization is suppressed, and a sufficient charge / discharge cycle can be ensured.

Moreover, it turned out that the fall of charging / discharging cycle life is also caused by a short circuit occurring when used for a long time due to Li dendrite growth related to the Li metal negative electrode. In this regard, in the Li—Al alloy negative electrode in which lithium metal is filled in an aluminum porous body related to the present invention , since this Li dendrite growth stays in the pores, a reduction in cycle life due to a short circuit is suppressed.

(2) In addition, the alloy negative electrode for lithium battery,
A skeleton of the aluminum porous body is formed of aluminum.

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

(3) The lithium battery alloy negative electrode is
The skeleton of the aluminum porous body is formed by an aluminum coating material in which an aluminum layer is formed on the surface of a core material made of any metal of copper, nickel, and iron.

In the alloy negative electrode for lithium batteries related to the present invention , a metal of copper, nickel, or iron is used as the core material of the skeleton of the porous aluminum body. These metals are not alloyed with lithium or aluminum, but have 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 is formed on the surface of the core material made of these metals can provide an alloy negative electrode for a lithium battery that is strong against expansion and contraction.

(4) In addition, the alloy negative electrode for lithium battery,
The ratio of the volume of the lithium metal to the pores of the aluminum porous body is 50% or more and less than 100%.

In the technology related to the present invention , the volume ratio of lithium metal is less than 100%, and pores are left in the aluminum porous body after filling Li. Therefore, even when dendrites are generated, the dendrites are mainly voids. Generate within. For this reason, a dendrite short is suppressed effectively. On the other hand, when the volume ratio of the lithium metal is less than 50%, there is a possibility that the practical action as an alloy negative electrode for a lithium battery cannot be sufficiently exhibited.

(5) In addition, the alloy negative electrode for lithium battery,
The amount of oxygen on the surface of aluminum forming the skeleton of the aluminum porous body or the aluminum layer of the aluminum covering material is 3.1% by mass or less.

Since the aluminum porous body of the alloy negative electrode for lithium batteries related to the present invention has an aluminum content of 3.1% by mass or less on the surface of aluminum forming the skeleton of the aluminum porous body or the aluminum layer of the aluminum coating material. Thus, an alloy negative electrode for a battery having a higher capacity density than ever before can be provided.

Since Al is easily oxidized, there has been no porous aluminum body having a sufficiently small amount of oxygen on the surface. For example, aluminum produced by applying an Al powder on the surface of an eutectic alloy film of Al formed on the surface of a foamed resin described in JP-A-8-170126 and then heat-treating it in a non-oxidizing atmosphere. In the case of a porous body, since an 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 filled Li is oxidized by oxygen (O ₂ ) and changed to Li ₂ O that does not function as an active material, so that a large capacity density cannot be obtained. Moreover, since the produced Li ₂ O becomes a resistance layer, the characteristics deteriorate.

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

The technology related to the present invention is characterized by using such an aluminum porous body, and since an aluminum porous body having a surface oxygen content of 3.1% by mass or less is used, an alloy for lithium batteries having a higher capacity density. A negative electrode is obtained.

Here, the manufacturing method of the alloy negative electrode for lithium batteries relevant to this invention is demonstrated in detail, referring drawings. In the first stage of the manufacturing method, an aluminum porous body having communication holes is manufactured, and in the second stage, the aluminum porous body is filled with Li metal.

  FIG. 1 is a schematic diagram showing an outline of the first stage. 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 holes are formed with the resin 1 as a skeleton. FIG. 1B shows a state in which the aluminum layer 2 is formed on the surface of the resin 1 having communication holes (aluminum layer coating resin 3). FIG. 1 (c) shows a state (resin aluminum porous body 4) after the resin 1 is thermally decomposed and disappeared from the aluminum layer coating resin 3.

  FIG. 2 shows a process of thermally decomposing the resin 1 from the aluminum layer coating resin 3. The aluminum layer coating resin 3 and the positive electrode 5 are immersed in the molten salt 6, and the aluminum layer 2 is kept at a lower potential than the standard electrode potential of aluminum. By immersing in the molten salt to keep the aluminum layer 2 at a lower potential than the standard electrode potential of aluminum, the oxidation of the aluminum layer 2 is suppressed. The positive electrode 5 can be appropriately selected as long as it shows insolubility in the molten salt. For example, an electrode made of platinum, titanium, or the like is used.

  In this state, when the molten salt 6 is heated to a temperature equal to or higher than the decomposition temperature of the resin 1, only the resin 1 in the aluminum layer coating resin 3 is decomposed and disappears. As a result, the aluminum porous body 4 is obtained. The aluminum porous body 4 manufactured by this method has a hollow fiber shape due to the characteristics of the manufacturing method. In this respect, it differs from the structure of the aluminum foam as disclosed in JP-A-2002-371327. When the resin 1 is decomposed, the heating temperature is set to be equal to or lower than the melting point of aluminum in order to prevent melting of aluminum. Specifically, it is preferable to heat at 660 ° C. or lower, which is the melting point of aluminum.

As the resin in the technique related to the present invention, any resin can be selected as long as it thermally decomposes at a temperature not higher than the melting point of aluminum. For example, there are polyurethane, polypropylene, polyethylene and the like. Among these, urethane foam is a material having a high porosity and is easily thermally decomposed, and therefore, urethane foam is preferable as a resin used in the manufacturing method of the technology related to the present invention. The resin preferably has a porosity of 80% to 98% and a pore diameter of about 50 μm to 500 μm. The resin preferably has a communication hole. Thereby, the aluminum porous body without a closed pore is obtained.

  The aluminum on the surface of the porous aluminum body described above had an extremely low oxygen content and was 3.1% by mass or less, which is the precipitation limit of EDX analysis. In addition, since it has communication holes but no closed pores and does not use a eutectic alloy or the like, it is made of only aluminum.

  Next, as a second stage, the aluminum porous body 4 is filled with Li metal. The method for filling is not particularly limited, and for example, a known method such as a method by inclusion, a vacuum deposition method, or an electroplating method can be used.

(6) Moreover, the alloy negative electrode for lithium batteries described above is
The aluminum porous body has communication holes, no closed pores,
Furthermore, it consists only of aluminum.

  A conventional aluminum porous body, for example, an aluminum porous body foamed by adding a foaming agent in a molten state of Al described in JP-A-2002-371327 has many closed pores. Moreover, since the aluminum porous body described in JP-A-8-170126 is a eutectic metal, it contains Bi, Ca and other metals other than Al. Thus, when there are many closed pores, a sufficient amount of Li cannot be filled, so that a large capacity density cannot be obtained. Moreover, since it contains metals other than Al, the function as a negative electrode of a Li-Al alloy falls.

On the other hand, since the lithium battery alloy negative electrode related to the present invention can be filled with a sufficient amount of Li metal, a lithium battery alloy negative electrode having a higher capacity density can be obtained. Further, since the aluminum porous body is made of only aluminum, the function as the negative electrode can be sufficiently exhibited.

(7) The lithium battery related to the present invention is
It comprises the alloy negative electrode for lithium battery as described in said (1)-(6).

Since the lithium battery related to the present invention uses the lithium battery alloy having the above characteristics as the negative electrode, it can provide a lithium battery having a large capacity density and excellent charge / discharge cycle characteristics.

(8) A method for producing an alloy negative electrode for a lithium battery related to the present invention,
An aluminum layer forming step of forming an aluminum layer on the surface of the resin having communication holes;
In a state where the resin is immersed in the molten salt, the resin is heated to a temperature below the melting point of aluminum while maintaining the aluminum layer at a potential lower than the standard electrode potential of aluminum, and the resin is thermally decomposed to form porous aluminum. An aluminum porous body manufacturing process for manufacturing a body;
A lithium metal filling step of filling the aluminum porous body with lithium metal.

According to the method for producing an alloy negative electrode for a lithium battery related to 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 communication holes, and does not have closed pores. Furthermore, it is possible to provide an alloy negative electrode for a lithium battery having a large capacity density using an aluminum porous body made of only aluminum and having a high effect of suppressing pulverization and dendrite short.

(9) A method for producing an alloy negative electrode for a lithium battery related to the present invention is as follows:
A metal layer forming step of forming a metal layer made of one of copper, nickel, and iron on the surface of the resin having communication holes;
An aluminum layer forming step of forming an aluminum layer on the surface of the metal layer;
In a state where the resin is immersed in the molten salt, the resin is heated to a temperature below the melting point of aluminum while maintaining the aluminum layer at a potential lower than the standard electrode potential of aluminum, and the resin is thermally decomposed to form porous aluminum. An aluminum porous body manufacturing process for manufacturing a body;
A lithium metal filling step of filling the aluminum porous body with lithium metal.

According to the method for producing an alloy negative electrode for a lithium battery related to 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 communication holes, and does not have closed pores. A lithium battery alloy negative electrode with a large capacity density using an aluminum porous body and excellent charge / discharge cycle can be provided, and a metal made of copper, nickel, or iron is used as the skeleton of the aluminum porous body. Therefore, it is possible to provide a lithium battery alloy negative electrode having high strength.

(10) Moreover, the manufacturing method of the said alloy negative electrode for lithium batteries is as follows.
The method for forming the aluminum layer is a vacuum deposition method, a sputtering method, a laser ablation method, or a plasma CVD method.

  In the vacuum deposition method, for example, an aluminum metal layer is formed by irradiating an aluminum beam as a raw material with an electron beam to melt and evaporate the aluminum metal and adhere the aluminum metal to the resin surface of the resin body having communication holes. be able to. In the sputtering method, for example, an aluminum metal target can be vaporized by plasma irradiation on an aluminum metal target, and an aluminum alloy is adhered to the resin surface of a resin body having communication holes, whereby an aluminum metal layer can be formed. 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 the communication holes. In the plasma CVD method, an aluminum metal layer can be formed by applying a high frequency to an aluminum compound as a raw material to form a plasma and attaching it to the surface of a resin having communication holes.

(11) Moreover, the manufacturing method of the said alloy negative electrode for lithium batteries is as follows.
The method for forming the aluminum layer is a plating method in which aluminum is plated after the surface of the resin is subjected to a conductive treatment.

(12) Moreover, the manufacturing method of the alloy negative electrode for lithium batteries relevant to this invention is as follows.
The method for forming the aluminum layer is a plating method for plating aluminum on the surface of the metal layer.

  Since it is practically impossible to plate aluminum in an aqueous solution, molten salt electroplating in which aluminum is plated in molten salt is performed. In this case, it is preferable to plate aluminum in a molten salt after conducting a conductive treatment on the surface of the resin in advance.

  The molten salt used here may be the same as or different from the molten salt to be used in the step of thermally decomposing the resin. Specifically, molten salts such as potassium chloride, aluminum chloride, and sodium chloride are used. Further, a salt of two or more components may be used and used as a eutectic molten salt. The eutectic molten salt is preferable because the melting temperature is lowered. 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 as follows.
The method for forming the aluminum layer is a coating method in which an aluminum paste is applied to the surface of the resin or the surface of the metal layer.

  When an aluminum paste is applied to the surface of the resin, the aluminum paste is, for example, a mixture of aluminum powder, a binder (binder resin), and an organic solvent. Specifically, after the aluminum paste is applied to the surface of the resin, it is heated to eliminate the organic solvent and the binder resin, and the aluminum paste is sintered. Heating at the time of sintering may be performed in one step or in multiple steps. For example, the aluminum paste may be sintered at the same time as the resin decomposition by applying aluminum paste and heating at a low temperature to eliminate the organic solvent and then immersing in molten salt and heating.

The present invention has been made based on the above-described techniques (1) to (13).

(1) That is, the alloy negative electrode for a lithium battery according to the present invention is
An alloy negative electrode for a lithium battery using a non-aqueous electrolyte,
The aluminum porous body is filled with lithium metal,
The skeleton of the aluminum porous body is formed by an aluminum coating material in which an aluminum layer is formed on the surface of a core material made of any metal of copper, nickel, and iron.

(2) Moreover, the alloy negative electrode for lithium batteries according to the present invention comprises:
An alloy negative electrode for a lithium battery using a non-aqueous electrolyte,
The aluminum porous body is filled with lithium metal,
The skeleton of the porous aluminum body is formed of aluminum or an aluminum covering material in which an aluminum layer is formed on the surface of a core material made of copper, nickel, or iron,
The amount of oxygen on the surface of aluminum forming the skeleton of the aluminum porous body or the aluminum layer of the aluminum covering material is 3.1% by mass or less.

(3) The lithium battery alloy negative electrode is
The ratio of the volume of the lithium metal to the pores of the aluminum porous body is 50% or more and less than 100%.

(4) In addition, the alloy negative electrode for lithium battery,
The aluminum porous body has communication holes, no closed pores,
Furthermore, it consists only of aluminum.

(5) The lithium battery according to the present invention is
It comprises the alloy negative electrode for lithium battery as described in said (1)-(4).

(6) A method for producing an alloy negative electrode for a lithium battery according to the present invention comprises:
An aluminum layer forming step of forming an aluminum layer on the surface of the resin having communication holes;
In a state where the resin is immersed in the molten salt, the resin is heated to a temperature below the melting point of aluminum while maintaining the aluminum layer at a potential lower than the standard electrode potential of aluminum, and the resin is thermally decomposed to form porous aluminum. An aluminum porous body manufacturing process for manufacturing a body;
A lithium metal filling step of filling the aluminum porous body with lithium metal;
It is characterized by having.

(7) A method for producing an alloy negative electrode for a lithium battery according to the present invention comprises:
A metal layer forming step of forming a metal layer made of one of copper, nickel, and iron on the surface of the resin having communication holes;
An aluminum layer forming step of forming an aluminum layer on the surface of the metal layer;
In a state where the resin is immersed in the molten salt, the resin is heated to a temperature below the melting point of aluminum while maintaining the aluminum layer at a potential lower than the standard electrode potential of aluminum, and the resin is thermally decomposed to form porous aluminum. An aluminum porous body manufacturing process for manufacturing a body;
A lithium metal filling step of filling the aluminum porous body with lithium metal;
It is characterized by having.

(8) Moreover, the manufacturing method of the said alloy negative electrode for lithium batteries is as follows.
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) Moreover, the manufacturing method of the said alloy negative electrode for lithium batteries is as follows.
The method for forming the aluminum layer is a plating method in which aluminum is plated after the surface of the resin is subjected to a conductive treatment.

(10) Moreover, the manufacturing method of the alloy negative electrode for lithium batteries of this invention,
The method for forming the aluminum layer is a plating method for plating aluminum on the surface of the metal layer.

(11) Moreover, the manufacturing method of the said alloy negative electrode for lithium batteries is as follows.
The method for forming the aluminum layer is a coating method in which an aluminum paste is applied to the surface of the resin or the surface of the metal layer.

  ADVANTAGE OF THE INVENTION According to this invention, the capacity density is large and can provide the alloy negative electrode for lithium batteries excellent in the charging / discharging cycle, its manufacturing method, and a lithium battery.

It is the schematic diagram which showed the manufacturing process of the aluminum porous body. (A) is a figure of resin which has a communicating hole. (B) is a figure which shows the state by which the aluminum layer was formed on the surface of resin. (C) is a figure which shows the aluminum porous body after resin lose | disappears. It is a schematic diagram for demonstrating the decomposition | disassembly process of resin in molten salt. It 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.

  Hereinafter, the present invention will be described with reference to the drawings based on the embodiments.

(Embodiment 1)
A. Lithium battery alloy negative electrode In the lithium battery alloy negative electrode in the present embodiment, an aluminum porous body is filled with lithium metal, 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 with the following manufacturing method (refer FIG. 1).

B. Method for Producing Lithium Battery Alloy Negative Electrode As the porous resin 1, a foamed resin or a nonwoven fabric having communication holes is used, and a resin having a porosity of 80% to 98% and a pore diameter of about 50 μm to 500 μm is particularly preferable. Foam urethane is preferably used.

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 preparation process, and a lithium metal containing (filling) process.
(1) Aluminum layer forming step The aluminum layer 2 is directly formed on the surface of the resin 1 by vapor deposition such as vacuum deposition, sputtering, laser ablation or plasma CVD, plating, aluminum paste coating, etc. Thus, the aluminum layer coating resin 3 is produced.

In order to perform electroplating, the surface of the resin 1 is subjected to a conductive treatment in advance. For the conductive treatment, an arbitrary method such as electroless plating of a conductive metal such as nickel, vapor deposition or sputtering of aluminum, or application of a conductive paint containing conductive particles such as carbon is selected. For example, AlCl ₃ -XCl (X: alkali metal) -MCl _x (M is an additive element selected from Cr, Mn, and transition metal elements) is used as a plating bath for aluminum plating. Is done. Resin 1 is immersed in the molten salt, and electroplating is performed using the conductive resin as the negative electrode.

  As described above, the aluminum layer can also be formed by applying an aluminum paste. The aluminum paste is a mixture of aluminum powder, a binder (binder resin), and an organic solvent. After applying a predetermined amount of aluminum paste to the surface of the resin 1, it is sintered in a non-oxidizing atmosphere.

(2) Aluminum porous body preparation process Next, the resin 1 is thermally decomposed and removed. FIG. 2 is a schematic diagram for explaining a decomposition process of the porous resin in the molten salt 6. Resin (i.e., the aluminum layer coating resin 3) forming an aluminum layer on the surface of LiCl, KCl, NaCl, in a salt containing one or more selected from the group consisting of AlCl _3, aluminum below the melting point, preferably Is heated 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 make the aluminum layer of the aluminum layer coating resin 3 a lower potential than the standard electrode potential of aluminum. The porous resin 1 is thermally decomposed and removed while maintaining at (a potential nobler than the reduction potential of Li, K, Na), and the porous aluminum body 4 of FIG.

(3) Lithium metal containing (filling) step Next, a predetermined amount of lithium metal is contained in the produced porous aluminum body to produce an alloy of lithium and aluminum (Li-Al alloy), and an alloy negative electrode for a lithium battery. Is made. Specifically, for example, an aluminum porous body and a lithium foil having a predetermined thickness are bonded together, and then heated to 180 ° C. or higher to melt the lithium foil and permeate the pores of the aluminum porous body. Alternatively, the aluminum porous body may be immersed in a molten lithium bath heated to 180 ° C. or higher. The amount of lithium to be included is adjusted so that the ratio of the volume of lithium metal in the pores of the aluminum porous body is 50% or more and less than 100%. For example, when an aluminum porous body having a porosity of 97% and a lithium foil having a thickness of ½ of an aluminum porous body are bonded together, the ratio of the volume of lithium metal in the pores is 51.5%.

C. Lithium Battery In the lithium battery alloy negative electrode produced as described above, the concentration of aluminum is high in the vicinity of the skeleton in the produced Li-Al alloy, and a lower concentration gradient is generated as the distance from the skeleton is increased. For this reason, even if the Li—Al alloy expands and contracts during charge and discharge, the stress is easily relaxed and pulverization is suppressed.

  In addition, since the ratio of the volume of lithium metal in the pores of the aluminum porous body is 50% or more, a sufficiently high capacity density is ensured, while in the aluminum porous body after filling Li by setting it to less than 100% As a result, the dendrite short circuit is suppressed even when lithium dendrite is generated.

(Embodiment 2)
In Embodiment 2, the skeleton of the aluminum porous body is an aluminum covering material in which an aluminum layer is formed on the surface of the core material. The core material is made 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. Is done.

  In the second embodiment, an alloy negative electrode for a lithium battery and a lithium battery are manufactured in the same manner as in the first embodiment except that the skeleton of the porous aluminum body is an aluminum coating material.

(Embodiment 3)
In each of the above-described embodiments, the lithium metal inclusion is not limited to the penetration of the porous aluminum body into the pores, but may be formed on the surface of the porous aluminum body.

  Moreover, the lithium metal does not need to be a simple substance, and may be an alloy with another metal. In particular, Li—Si (silicon) and Li—Sn (tin) are suitable as the alloy negative electrode.

  When such a Li—Si or Li—Sn alloy negative electrode is formed in an aluminum porous body, an alloy layer of Li and Si or Sn may be formed on the surface of the aluminum porous body, or “aluminum skeleton” Alternatively, a Si or Sn metal layer may be provided on an “aluminum layer formed on the surface of a core material such as copper”, and a Li metal layer may be further stacked.

(Examples 1 and 2)
Example 1 is a lithium secondary battery having a negative electrode formed by including lithium metal in an aluminum porous body having a skeleton formed of aluminum.

  Example 2 is a lithium secondary battery having a negative electrode formed by including lithium metal in an aluminum porous body that is an aluminum coating material in which an aluminum layer is formed on the surface of a core material having a skeleton made of Cu.

(1) Production of porous aluminum body In Example 1, a 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 is formed on the surface of the polyurethane foam by a vacuum deposition method, and then immersed in a LiCl—KCl eutectic molten salt at a temperature of 500 ° C., so that the aluminum layer has a lower potential than the standard electrode potential of aluminum. For 30 minutes. Thereafter, it was cooled to room temperature in the atmosphere, washed with water to remove the molten salt, and a porous aluminum 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, a polyurethane foam having a porosity of 97% and a pore diameter of about 300 μm was prepared. After applying carbon powder to the surface of this polyurethane foam and conducting a conductive treatment, copper plating with a thickness of 20 μm was applied to form a core material. A surface layer of aluminum having a thickness of about 50 μm was formed thereon by vacuum deposition, and then immersed in a LiCl—KCl eutectic molten salt at a temperature of 500 ° C., and the aluminum layer was formed at a potential lower than the standard electrode potential of aluminum. Hold for a minute. Thereafter, it is cooled to room temperature in the atmosphere, washed with water to remove the molten salt, and an aluminum covering material having a surface layer of aluminum formed on the surface of the Cu core material, having a thickness of 0.5 mm and a porosity of 96%. A porous body was produced.

  In the reference example, a foamed urethane foam having a pore diameter of 200 μm to 500 μm, a porosity of 97%, and a thickness of 1.0 mm was prepared. This foamed urethane foam was placed in a vacuum deposition apparatus. An aluminum film was deposited on the surface of the foamed urethane resin by a vacuum deposition method in which aluminum metal was melted and evaporated. Thereafter, the foamed urethane foam was removed by heat treatment at 550 ° C. in the atmosphere. This obtained the aluminum porous body which is a reference example.

(2) Confirmation of structure of porous aluminum body and measurement of oxygen content An SEM photograph of the porous aluminum body of Example 1 is shown in FIG. From FIG. 3, it was found that the pores constituting the aluminum porous body communicated. Moreover, it turned out that the aluminum porous body of Example 1 does not have a closed pore.

  The surface of the aluminum porous body of Example 1 was subjected to EDX analysis at an acceleration voltage of 15 kV. The result is shown in FIG. No oxygen peak was observed. Therefore, it was found that the oxygen content of the aluminum porous body was below the detection limit of EDX. Here, since the detection limit by EDX is 3.1 mass% of oxygen, it can be said that the oxygen content of the surface of the aluminum porous body of Example 1 is 3.1 mass% or less.

  Regarding Example 2, SEM photography and EDX analysis were performed, and it was confirmed that the result was the same as Example 1.

  The surface of the aluminum porous body of the reference example was also subjected to EDX analysis under the same conditions. As a result, an oxygen peak was observed, and it was found that the oxygen content of the aluminum porous body exceeded at least 3.1% by mass. This is because the surface of the aluminum porous body was oxidized during the heat treatment.

  The apparatus used in this analysis is “EDAX Phoenix” manufactured by EDAX, and the model is HIT22 136-2.5.

(3) Production of negative electrode After a 350 μm-thick lithium foil was bonded to an aluminum porous body, it was heated to 250 ° C. to melt Li, and Li was permeated into the pores. In addition, the ratio of the volume of lithium metal in the vacancies is 75%.

  A porous aluminum body in which lithium metal was infiltrated into the pores was molded into a circle having a diameter of 15 mm to produce an alloy negative electrode for a lithium battery.

(4) Production of positive electrode for lithium battery MnO ₂ (active material), acetylene black (conductive aid), PVDF (binder) are mixed at a predetermined ratio, a lithium battery having a diameter of 15 mm and a capacity density of 10 mAh / cm ² . A positive electrode was prepared.

(5) Production of lithium secondary battery Next, a lithium secondary battery was produced using the negative electrode and the positive electrode. FIG. 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 a lithium battery, 13 is a separator, and 14 is an alloy negative electrode for a lithium battery.

Specifically, it is composed of a mixed liquid of propylene carbonate / ethylene carbonate / dimethoxyethane in which 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). Assemble with electrolyte.

(Comparative example)
The comparative example is a lithium secondary battery having an Al—Li alloy foil negative electrode.

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

(Characteristic evaluation of lithium secondary batteries of Examples 1 and 2 and Comparative Example)
(1) Yield In the case of Examples 1 and 2, the yield in battery assembly was 100%, whereas the yield in the comparative example was as low as about 50%. In the case of the comparative example, the reason for the low yield is that the lithium battery alloy negative electrode is brittle and cracks and chips occur during handling.

(2) Charging / discharging cycle characteristics a. Test method The cut-off voltage is set to 2.0-3.3V, charge / discharge cycle tests are performed at two types of discharge depths of 6 mA / h and 18 mA / h, and the number of cycles in which the discharge capacity is 50% or less of the initial value is examined. It was.

B. Test results Table 1 shows the test results of Examples 1 and 2 and the comparative example.

  From Table 1, it can be seen that Examples 1 and 2 have excellent cycle characteristics. The reason why the cycle characteristics of the examples are excellent in this way is that an alloy negative electrode for a lithium battery having a high effect of suppressing pulverization and dendrite short is used.

  Further, as described above, the embodiment is a lithium secondary battery having a lithium battery alloy negative electrode having a high capacity density because Li is contained in an aluminum porous body having no closed pores and a small amount of oxygen.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to said embodiment. Various modifications can be made to the above-described embodiment within the same and equivalent scope as the present invention.

1 Resin 2 Aluminum layer
DESCRIPTION OF SYMBOLS 3 Aluminum layer coating resin 4 Aluminum porous body 5 Positive electrode 6 Molten salt 11 Lithium secondary battery 12 Positive electrode for lithium batteries 13 Separator 14 Alloy negative electrode for lithium batteries

Claims (12)

An alloy negative electrode for a lithium battery using a non-aqueous electrolyte,
The aluminum porous body is filled with lithium metal,
An alloy negative electrode for a lithium battery, wherein the skeleton of the porous aluminum body is formed by an aluminum coating material in which an aluminum layer is formed on the surface of a core material made of any metal of copper, nickel, and iron. An alloy negative electrode for a lithium battery using a non-aqueous electrolyte,
The aluminum porous body is filled with lithium metal,
The skeleton of the porous aluminum body is formed of aluminum or an aluminum covering material in which an aluminum layer is formed on the surface of a core material made of copper, nickel, or iron,
An alloy negative electrode for a lithium battery, wherein the amount of oxygen on the surface of aluminum forming the skeleton of the porous aluminum body or the aluminum layer of the aluminum covering material is 3.1% by mass or less. 2. The alloy negative electrode for a lithium battery according to claim 1, wherein a ratio of a volume of the lithium metal in pores of the aluminum porous body is 50% or more and less than 100%. 3. The alloy negative electrode for a lithium battery according to claim 2, wherein a ratio of a volume of the lithium metal in pores of the aluminum porous body is 50% or more and less than 100%. The aluminum porous body has communication holes, no closed pores,
Furthermore, it consists only of aluminum, The alloy negative electrode for lithium batteries of Claim 2 or Claim 4 characterized by the above-mentioned. A lithium battery comprising the alloy negative electrode for a lithium battery according to any one of claims 1 to 5 . An aluminum layer forming step of forming an aluminum layer on the surface of the resin having communication holes;
In a state where the resin is immersed in the molten salt, the resin is heated to a temperature below the melting point of aluminum while maintaining the aluminum layer at a potential lower than the standard electrode potential of aluminum, and the resin is thermally decomposed to form porous aluminum. An aluminum porous body manufacturing process for manufacturing a body;
A method for producing an alloy negative electrode for a lithium battery, comprising: a lithium metal filling step of filling the aluminum porous body with lithium metal. A metal layer forming step of forming a metal layer made of one of copper, nickel, and iron on the surface of the resin having communication holes;
An aluminum layer forming step of forming an aluminum layer on the surface of the metal layer;
In a state where the resin is immersed in the molten salt, the resin is heated to a temperature below the melting point of aluminum while maintaining the aluminum layer at a potential lower than the standard electrode potential of aluminum, and the resin is thermally decomposed to form porous aluminum. An aluminum porous body manufacturing process for manufacturing a body;
A method for producing an alloy negative electrode for a lithium battery, comprising: a lithium metal filling step of filling the aluminum porous body with lithium metal. The method for producing an alloy negative electrode for a lithium battery according to claim 7 or 8 , wherein the aluminum layer is formed by a vacuum deposition method, a sputtering method, a laser ablation method, or a plasma CVD method. The method for producing an alloy negative electrode for a lithium battery according to claim 7 , wherein the method for forming the aluminum layer is a plating method in which aluminum is plated after the surface of the resin is subjected to a conductive treatment. The method for producing an alloy negative electrode for a lithium battery according to claim 8 , wherein the aluminum layer is formed by a plating method in which aluminum is plated on the surface of the metal layer. Method of forming the aluminum layer, the production of lithium batteries alloy negative electrode according to claim 7 or claim 8 characterized in that it is a coating method for coating an aluminum paste on the surface of the surface or the metal layer of the resin Method.

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