JP2009199744A - Negative electrode for lithium secondary battery and its manufacturing method - Google Patents

Abstract

Disclosed is an alloy-based negative electrode for a lithium secondary battery, in which charge / discharge characteristics are further improved, and a negative electrode in which a discharge capacity is not easily deteriorated even when a charge / discharge cycle is repeated.
A negative electrode for a lithium secondary battery according to the present invention is prepared by filling a porous body having a skeleton surface mainly made of nickel with a paste containing an active material powder containing a metal capable of forming an alloy with lithium, Next, it is obtained by heating at 250 ° C. or higher.
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Description

  The present invention relates to a novel negative electrode for a lithium secondary battery and a method for producing the same.

  Conventionally, lithium metal has been proposed as a negative electrode for lithium secondary batteries. However, when lithium metal is used, there is a problem that short-circuiting due to dendritic precipitation during charging tends to occur, and stable charge / discharge identification is difficult to obtain.

  Therefore, in order to avoid this problem, lithium secondary batteries using a graphite-based material for the negative electrode have been put into practical use. A negative electrode made of this graphite material can provide stable charge / discharge performance.

  However, its theoretical capacity is 372 mAh / g, which is much smaller than 3560 mAh / g of lithium metal. Another problem is that the manufacturing process of the carbon-based material is complicated. For this reason, the appearance of a negative electrode material having a high theoretical capacity is desired.

  As such a negative electrode material, in recent years, an alloy-based material, which is an element capable of forming an alloy with lithium, has attracted attention. Among these alloy-based materials, an alloy containing silicon, tin, or the like has attracted attention because it is particularly excellent in theoretical capacity, material cost, and handleability. For example, when a silicon-based alloy is used, its theoretical capacity is about 4200 mAh / g, which is 10 times or more that of a graphite-based material.

  These alloys containing silicon, tin, and the like are different from those in which charging proceeds due to intercalation (a phenomenon in which lithium enters between graphite layers) as in the case of using a graphite-based material. Charging proceeds while forming. As a result, the crystal structure of the alloy changes and large volume expansion occurs. For example, a graphite material has a volume expansion coefficient of about 10% even when fully charged, whereas a silicon material has a volume expansion of about 400%. Thus, the alloy-based negative electrode including silicon and the like has a problem that the volume expands and the discharge capacity deteriorates when the charge / discharge cycle is repeated.

  In order to prevent the deterioration of the charge / discharge cycle accompanying the expansion and contraction of the negative electrode, various techniques have been proposed (Patent Document 1, Patent Document 2, etc.).

  For example, Patent Document 1 uses an electrode in which a thin film is formed by depositing a material containing an element capable of forming an alloy with lithium on a current collector having a three-dimensional structure as a negative electrode. It is disclosed.

  In Patent Document 2, a copper foil current collector having a specific surface roughness is coated with a layer of a mixture of active material particles such as silicon and conductive active material powder on the surface of the current collector in a non-oxidizing atmosphere. A negative electrode obtained by sintering is disclosed.

However, even in the negative electrodes disclosed in Patent Documents 1 and 2, the problem of the charge / discharge cycle has not been sufficiently solved, and further improvement is desired.
JP 2004-071305 A Japanese Patent Laid-Open No. 2002-260637

  Accordingly, the main object of the present invention is to provide a negative electrode in which the charge and discharge characteristics are further improved, and the discharge capacity is not easily deteriorated even when the charge and discharge cycle is repeated, in the alloy-based negative electrode for lithium secondary batteries. .

  As a result of intensive studies in view of the above-described conventional problems, the present invention has solved the above problems by using a current collector having a specific structure and composition and through a manufacturing method. That is, this invention relates to the following negative electrode for lithium secondary batteries, and its manufacturing method.

  Item 1. A porous body having a skeleton surface mainly made of nickel is filled with a paste containing an active material powder containing a metal capable of forming an alloy with lithium, and then heated at 250 ° C. or higher. Negative electrode for secondary battery.

  Item 2. Item 2. The negative electrode for a lithium secondary battery according to Item 1, wherein the metal capable of forming an alloy with lithium is at least one metal selected from the group consisting of silicon and tin.

  Item 3. Item 3. The negative electrode for a lithium secondary battery according to Item 1 or 2, wherein the porous body having a skeleton surface mainly made of nickel is foamed nickel or a non-woven fabric plated with nickel.

Item 4. A method for producing a negative electrode for a lithium secondary battery, comprising:
A first step in which a paste containing an active material powder containing a metal capable of forming an alloy with lithium and a binder is filled in a porous body having a skeleton surface mainly made of nickel, and the porous body at 250 ° C. or higher A second step of heating,
A method for producing a negative electrode for a lithium secondary battery, comprising:

  Item 5. Item 5. The method according to Item 4, wherein the heating temperature in the second step is 350 to 550 ° C.

  Item 6. Item 6. The production method according to Item 4 or 5, wherein the metal capable of forming an alloy with lithium is at least one metal selected from the group consisting of silicon and tin.

  Item 7. Item 7. The production method according to any one of Items 4 to 6, wherein the porous body whose skeleton surface is mainly made of nickel is a foamed nickel or a nonwoven fabric on which nickel plating is applied.

  Item 8. Item 8. The method according to any one of Items 4 to 7, wherein the paste further contains a conductive agent.

  Item 9. Item 9. The method according to Item 8, wherein the conductive agent is at least one selected from the group consisting of acetylene black, ketjen black, and graphite.

  Item 10. Item 10. The production method according to any one of Items 4 to 9, wherein the binder is at least one selected from the group consisting of a fluororesin, a rubber-based resin, and a thickener.

  Item 11. Item 10. The production method according to Items 4 to 9, wherein the binder contains a water-soluble thickener.

  Item 12. Item 12. The production method according to Item 11, wherein the water-soluble thickener is at least one selected from the group consisting of carboxymethylcellulose, chitansan gum, pectin and agarose.

(1) Method for Producing Negative Electrode for Lithium Secondary Battery The method for producing a negative electrode for a lithium secondary battery according to the present invention comprises a paste containing an active material powder containing a metal capable of forming an alloy with lithium and a binder. A first step of filling a porous body whose skeleton surface is mainly made of nickel, and a second step of heating the porous body at 250 ° C. or higher.

<Paste>
It is essential that the paste used in the production method of the present invention contains an active material powder containing a metal capable of forming an alloy with lithium and a binder.

  The active material powder is a metal used as an active material of a negative electrode for a lithium secondary battery, and is not particularly limited as long as it contains a metal capable of forming an alloy with lithium. For example, silicon, Any metal powder containing at least one selected from the group consisting of tin, germanium, aluminum, zinc, cadmium, lead, antimony, bismuth, indium and the like may be used. The active material powder may be composed of these simple metals or an alloy thereof.

  In the present invention, among these, metal powder containing silicon or tin is particularly preferable. By including these, the amount of occlusion and release of the negative electrode can be increased, and it is advantageous in terms of cost and handling. When the active material powder of the present invention is an active material powder containing silicon or tin, it may be a metal powder made of silicon alone or tin alone, or may be an alloy powder containing silicon or tin. In the case of an alloy powder containing silicon or tin, the content ratio of at least one of silicon and tin is preferably about 30 to 95% by weight, particularly about 40 to 85% by weight. Specific examples of the alloy powder include a tin-iron alloy, a tin-nickel alloy, a tin-copper alloy, a tin-zinc alloy, a tin-titanium alloy, a silicon-titanium alloy, and a silicon-nickel alloy. .

  The average particle diameter of the active material powder may be, for example, about 1 to 30 μm, preferably about 5 to 20 μm. If necessary, the active material powder may be in the above average particle size range by a ball mill, mechanical alloying or the like.

  As the binder, any binder that is generally used in a negative electrode for a lithium secondary battery may be used. In the present invention, a binder that melts at 250 ° C. or higher is preferably used. Examples of the binder material include fluororesins such as polyvinylidene fluoride and polytetrafluoroethylene; and rubber resins such as styrene butadiene rubber. In addition, polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymer; polyvinyl pyrrolidone; polyvinyl alcohol; polyimide; Furthermore, thickeners, for example, water-soluble thickeners such as carboxymethylcellulose, chitansan gum, and pectin agarose can also be used as the binder. By containing the binder in this manner, the porous body and the active material powder can be more firmly bound, and the negative electrode expansion due to charge / discharge can be suppressed, so that the charge / discharge cycle characteristics of the battery are further improved. be able to.

  The paste of the present invention may contain a conductive agent. The conductive agent is not limited and may be a known or commercially available one. Examples thereof include carbon black such as acetylene black and ketjen black; graphite and the like. Thereby, a further excellent discharge capacity can be exhibited.

  When graphite is used, the shape of the graphite may be any shape such as a spherical shape, a flake shape, a filament shape, and a fiber shape.

  Examples of the solvent used for the paste include water, N-methyl-2-pyrrolidone (NMP), and the like.

  In addition, the paste may contain a known additive such as a surfactant as necessary.

  The content of each component in the paste is not particularly limited, but for example, the binder is usually about 1 to 30 parts by weight (preferably 3 to 10 parts by weight) with respect to 100 parts by weight of the active material powder.

  When it contains a conductive agent, it may be, for example, about 1 to 20 parts by weight, preferably about 2 to 10 parts by weight with respect to 100 parts by weight of the active material powder.

  The content of the solvent in the paste may be about 100 to 500 parts by weight (preferably 150 to 300 parts by weight) with respect to 100 parts by weight of the active material powder.

<Porous body>
The porous body used in the production method of the present invention has a skeleton surface substantially made of nickel. In the present invention, the porous body has a thickness that can be used as a current collector of a negative electrode for a lithium secondary battery and has a void that can be filled with the paste of the present invention.

  Specific examples of the porous body whose skeleton surface used in the present invention is mainly made of nickel include, for example, (1) foamed nickel (after the foamed resin is subjected to nickel plating and then the foamed resin alone is removed by incineration. And a sintered body further annealed) and (2) a non-woven fabric on which nickel plating is applied.

  Nickel plating may be performed according to a conventional method, for example, electrolytic plating may be used. For example, the plating bath may be a known bath such as a watt bath, a chloride bath, or a sulfamic acid bath. You may carry out by adding additives, such as a pH buffer and an interface buffer, to this bath as needed. Prior to electroplating, electroplating may be performed after a conductive layer is applied to foamed resin, nonwoven fabric, or the like by electroless plating, sputtering, or the like.

  The foamed resin and non-woven fabric used for the porous body are not limited, and known or commercially available products may be used.

  For example, when using foamed resin, foamed urethane, foamed styrene, etc. are mentioned, for example.

  When using a nonwoven fabric, the nonwoven fabric which consists of polyolefin fibers, such as polyethylene, a polypropylene, these copolymers, a mixture, and a core-sheath-type fiber whose center part is a polypropylene and a peripheral part is polyethylene, is preferable. The nonwoven fabric may be produced by either a dry method or a wet method, and may be used as it is, but it is preferably used after entanglement treatment is performed to improve strength characteristics.

  The porosity of the porous body is not limited, but may be, for example, about 70 to 98%, preferably about 85 to 95%.

  The pore diameter of the porous body may be, for example, about 5 to 800 μm, preferably about 10 to 500 μm.

The content of nickel in the porous body is, for example, about 50 to 600 g / m ² , preferably about 100 to 500 g / m ² .

  The thickness of the porous body is not limited, but may be, for example, about 10 to 1500 μm, preferably about 100 to 800 μm.

  The shape of the porous body may be a shape generally used as a negative electrode for a lithium secondary battery, and examples thereof include a rectangle and a circle.

<Manufacturing process>
The production method of the present invention includes a first step of filling a porous body mainly composed of nickel with a skeleton surface with a paste containing an active material powder containing a metal capable of forming an alloy with lithium and a binder, and A second step of heating the porous body at 250 ° C. or higher.

First Step In the first step of the production method of the present invention, first, the above-described paste of the present invention is filled into the above-mentioned porous body of the present invention.

  The method of filling may be performed by immersing the porous body in the paste, for example, as long as the paste can enter the voids inside the porous body. Alternatively, the paste may be applied to the porous body.

The amount of the active material powder to be filled is not limited, but may be, for example, ^{2 to} 30 mg / cm ² , preferably about 3 to 10 mg / cm ² .

Second Step Next, in the second step of the production method of the present invention, it is essential to heat-treat the paste-containing porous material obtained in the first step at 250 ° C. or higher. By performing the heat treatment, the binder can be melted to bind the active material powder and the porous body more firmly, and the strength of the active material powder is improved by firing the active material powder.

  The temperature of the heat treatment is essential to be 250 ° C. or higher, preferably 250 to 600 ° C. At 250 ° C., the effect of the heat treatment is insufficient or not exhibited. On the other hand, when the temperature exceeds 600 ° C., the binder may be decomposed depending on the type of the binder. In this invention, it is most preferable to set it as 350-550 degreeC especially. By setting it as this range, nickel of a porous body and active material powder react more reliably, and the adhesiveness of an active material powder and a porous body improves further.

  In the present invention, the atmosphere during the heat treatment is preferably a vacuum; an inert atmosphere such as argon; a reducing atmosphere such as hydrogen or decomposed ammonia. Thereby, oxidation of nickel skeleton and active material powder can be suppressed, and deterioration of battery characteristics can be prevented.

  The pressure may be normal pressure or may be reduced, but in the present invention, it is particularly preferably performed under reduced pressure. The pressure when the pressure is reduced is, for example, 1000 Pa or less, preferably 1 to 500 Pa.

  The heating time is appropriately determined according to the heating atmosphere, pressure and the like, but is usually 1 to 8 hours, preferably 2 to 4 hours.

  In this invention, you may perform a pressurization process to the paste containing porous body before performing the heat processing of a 2nd process as needed. The pressurizing step is preferably performed by a roller press or the like. Thereby, the effect by the said heat processing can be improved further.

  Furthermore, if necessary, a drying step may be performed between the first step and the second step according to a conventional method.

(2) Negative electrode for lithium secondary battery The negative electrode for a lithium secondary battery of the present invention contains an active material powder containing a metal capable of forming an alloy with lithium in a porous body whose skeleton surface is mainly made of nickel. It is obtained by filling the paste and then heating at 250 ° C. or higher.

  As necessary, a conductive agent, a binder, and the like may be included. The porous body, the active material powder, the conductive agent, the binder and the like are those described above.

  The negative electrode of the present invention can be used as a negative electrode for a lithium secondary battery, and has excellent charge / discharge cycle characteristics. This is presumably due to the synergistic effect of the nickel skeleton and heat treatment. That is, the porous nickel as the current collector and the active material powder partially react with each other by heat treatment, so that the active material powder and the current collector are firmly adhered, and the skeleton of the current collector is substantially nickel. Therefore, according to the present invention, the charge / discharge cycle is remarkably improved, and a high discharge capacity can be exhibited over a long period of time. Therefore, it is possible to reduce the size of the power source for various applications including electronic devices, and to maintain high reliability for a long time.

  According to the present invention, the porous body whose skeleton surface is mainly made of nickel is filled with a paste containing an active material powder containing a metal capable of forming an alloy with lithium, and further heated at 250 ° C. or higher. Therefore, a negative electrode for a lithium secondary battery that exhibits an excellent charge / discharge cycle and exhibits a high discharge capacity over a long period of time can be produced.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to the following examples.

Example 1
<Preparation of active material powder>
After mixing 70 parts by weight of Si and 30 parts by weight of Ti powder, it was melted by a high-frequency heating method in an argon atmosphere to obtain an alloy. This alloy was quenched in helium gas by a gas atomizing method to produce an alloy powder (Si—Ti alloy) having an average particle size of 10 μm, which was used as the negative electrode active material powder of Example 1.

<Preparation of paste>
To 100 parts by weight of this active material powder, 5 parts by weight of ketjen black as a conductive agent, a 60% by weight aqueous dispersion (dispersion) of polytetrafluoroethylene as a binder and a 1% by weight aqueous carboxymethylcellulose solution, Examples were prepared by mixing so that the solid content would be 1 part by weight and 2 parts by weight, respectively, adding about 0.1 part by weight of a polyether-based nonionic surfactant and stirring uniformly. 1 paste was prepared. The water content (solvent) in the paste was about 200 parts by weight with respect to 100 parts by weight of the active material powder.

<Preparation of porous body (nonwoven fabric with nickel plating)>
As the material for the nonwoven fabric, a core-sheath fiber in which polypropylene is coated at the center with polyethylene around it was used. The average fiber diameter of the fibers was 15 μm, and the weight ratio of polypropylene to polyethylene was 1: 1. The nonwoven fabric was manufactured using the wet method, and the process which fuses a well-known fiber part was performed. The nonwoven fabric thus obtained had a basis weight of fibers of 50 g / m ² , an average thickness of 0.65 mm, a porosity of about 94%, and a pore diameter of 10 to 300 μm.

Next, the nonwoven fabric was sputtered to give a conductive layer. Subsequently, the porous body (nonwoven fabric on which nickel plating was performed) was manufactured by performing electrolytic nickel plating using a known Watt bath. The nickel amount was 250 g / m ² . The porosity of the porous body after the nickel plating treatment was about 90%, and the pore diameter was 15 to 250 μm.

<Manufacture of negative electrode>
This porous body was immersed in the paste of Example 1 to obtain a paste-containing porous body. The active material powder in the porous body was 5 mg / cm ² . After drying this, it was pressurized to a thickness of 100 μm with a roller press. Then, after heating at 80 degreeC under reduced pressure (100 Pa) for 1 hour, the negative electrode of Example 1 was manufactured by heat-processing at 450 degreeC for 2 hours further.

Comparative Example 1
Comparative Example 1 was carried out in the same manner as in Example 1 except that it was dried under reduced pressure (100 Pa) at 80 ° C. for 1 hour and then dried at 450 ° C. for 2 hours instead of drying at 100 ° C. under reduced pressure (100 Pa) for 10 hours. The negative electrode was manufactured.

Comparative Example 2
Comparative Example 2 was carried out in the same manner as in Example 1 except that heating was performed at 80 ° C. under reduced pressure (100 Pa) for 1 hour and then heating at 450 ° C. for 2 hours instead of heating at 200 ° C. under reduced pressure (100 Pa) for 10 hours. The negative electrode was manufactured.

Comparative Example 3
The negative electrode obtained by applying the paste to the copper foil was used as the negative electrode of Comparative Example 3. In addition, when the negative electrode of the comparative example 3 was heated on the conditions similar to Example 1, copper foil oxidized and blackening was recognized.

Test example <Manufacture of test cell>
Lithium foil was used as the counter electrode for the negative electrode of Example 1. As the separator, a laminate of a polypropylene nonwoven fabric (thickness 100 μm) and a polypropylene microporous separator (porosity 55%, thickness 20 μm) was used, and this was used between the negative electrode and the counter electrode (lithium foil) of Example 1. Arranged. As an electrolytic solution, an electrolyte (LiPF ₆ ) was dissolved at a concentration of 1.1 mol / L in a solvent obtained by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) at a volume ratio of 40:60. Using the solution, the separator was impregnated. A coin-type test cell of Example 1 was manufactured by punching the electrode thus obtained into a shape having a diameter of 11 mmΦ.

  Coin-type test cells of Comparative Examples 1 to 3 were manufactured in the same manner as in Example 1 except that the negative electrodes of Comparative Examples 1 to 3 were used instead of the negative electrode of Example 1.

<Test measurement>
The test cell was charged and discharged at a current density of 100 mA / g. The potential range of charging / discharging was 0.02-1.0 V (vs. Li / Li ⁺ ). The ambient temperature was 30 ° C. The initial capacity density (2 cycles) of each test cell was 590 mAh / g for the cell of Example 1, 585 mAh / g for the cell of Comparative Example 1, 580 mAh / g for the cell of Comparative Example 2, and the cell of Comparative Example 3 Was 500 mAh / g.

  FIG. 1 shows the measurement results of the rate of change in discharge capacity and the number of charge / discharge cycles with the initial discharge capacity being 100%.

Example 2
<Preparation of active material powder>
After mixing 78 parts by weight of Sn and 22 parts by weight of Ti powder, in the same manner as in Example 1, the alloy was melted by a high-frequency heating method in an argon atmosphere, and the alloy was quenched in a helium gas by a gas atomization method. Then, an alloy powder (Sn—Ti alloy) having an average particle diameter of 15 μm was prepared, and this was used as the negative electrode active material powder of Example 2.

<Preparation of paste>
To 100 parts by weight of this active material powder, 5 parts by weight of ketjen black as a conductive agent, and a 60% by weight aqueous dispersion (dispersion) of polytetrafluoroethylene as a binder and a 1% by weight aqueous carboxymethylcellulose solution, Examples were prepared by mixing so that the solid content would be 1 part by weight and 2 parts by weight, respectively, adding about 0.1 part by weight of a polyether-based nonionic surfactant and stirring uniformly. Two pastes were prepared. The water content (solvent) in the paste was about 200 parts by weight with respect to 100 parts by weight of the active material powder.

<Manufacture of negative electrode>
Foamed nickel (commercial product) was adjusted to an average thickness of 0.66 mm. The porosity was 94%, the pore diameter was 150 to 250 μm, and the nickel amount was 350 g / m ² .

This porous body was immersed in the paste of Example 2 to obtain a paste-containing porous body. The active material powder in the porous body was 5 mg / cm ² . After drying this, it was pressurized to 100 μm with a roller press. Then, the negative electrode of Example 2 was obtained by performing a heat treatment under reduced pressure (100 Pa) at 400 ° C. for 3 hours.

Comparative Example 4
Comparative Example 4 was carried out in the same manner as in Example 1 except that it was heated under reduced pressure (100 Pa) at 80 ° C. for 1 hour and further dried at 450 ° C. for 2 hours instead of drying at 100 ° C. under reduced pressure for 5 hours. The negative electrode was manufactured.

Comparative Example 5
Comparative Example 4 was carried out in the same manner as in Example 1 except that heating was carried out at 80 ° C. under reduced pressure (100 Pa) for 1 hour and further heating at 450 ° C. for 2 hours instead of heating at 200 ° C. under reduced pressure (100 Pa) for 5 hours. The negative electrode was manufactured.

Comparative Example 6
The negative electrode obtained by applying the paste of Example 2 to the copper foil was used as the negative electrode of Comparative Example 6.

Test Example The test cells of Example 2 and Comparative Examples 4 to 6 were produced in the same manner as the test example of Example 1 except that the negative electrodes of Example 2 and Comparative Examples 4 to 6 were used. On the other hand, charging / discharging was performed at a current density of 100 mA / g under the same conditions as in Example 1. The initial capacity density (2 cycles) of each test cell was 490 mAh / g for the cell of Example 2, 485 mAh / g for the cell of Comparative Example 4, 480 mAh / g for the cell of Comparative Example 5, and the cell of Comparative Example 6 Was 445 mAh / g.

  FIG. 2 shows the measurement results of the rate of change in discharge capacity and the number of charge / discharge cycles with the initial discharge capacity being 100%.

As is clear from the evaluation diagrams 1 and 2, when the negative electrodes of Examples 1 and 2 of the present application are used, the capacity is almost deteriorated even when charging and discharging are repeated, compared with the case of using the negative electrodes of Comparative Examples 1 to 6. It exhibits very good charge / discharge cycle characteristics. For this reason, it was found that the life of the lithium secondary battery can be remarkably increased.

FIG. 1 is a graph showing the relationship between the number of charge / discharge cycles and the discharge capacity in the test cells of Example 1 and Comparative Examples 1-3. FIG. 2 is a graph showing the relationship between the number of charge / discharge cycles and the discharge capacity in the test cells of Example 2 and Comparative Examples 4-6.

Claims (12)

  A porous body having a skeleton surface mainly made of nickel is filled with a paste containing an active material powder containing a metal capable of forming an alloy with lithium, and then heated at 250 ° C. or higher. Negative electrode for secondary battery.   The negative electrode for a lithium secondary battery according to claim 1, wherein the metal capable of forming an alloy with lithium is at least one metal selected from the group consisting of silicon and tin.   The negative electrode for a lithium secondary battery according to claim 1 or 2, wherein the porous body whose skeleton surface is mainly made of nickel is foamed nickel or a non-woven fabric plated with nickel. A method for producing a negative electrode for a lithium secondary battery, comprising:
A first step in which a paste containing an active material powder containing a metal capable of forming an alloy with lithium and a binder is filled in a porous body having a skeleton surface mainly made of nickel, and the porous body at 250 ° C. or higher A second step of heating,
A method for producing a negative electrode for a lithium secondary battery, comprising:   The manufacturing method of Claim 4 whose heating temperature in a 2nd process is 350-550 degreeC.   The manufacturing method according to claim 4 or 5, wherein the metal capable of forming an alloy with lithium is at least one metal selected from the group consisting of silicon and tin.   The manufacturing method according to any one of claims 4 to 6, wherein the porous body whose skeleton surface is mainly made of nickel is a foamed nickel or a nonwoven fabric to which nickel plating is applied.   The manufacturing method according to claim 4, wherein the paste further contains a conductive agent.   The manufacturing method according to claim 8, wherein the conductive agent is at least one selected from the group consisting of acetylene black, ketjen black, and graphite.   The manufacturing method in any one of Claims 4-9 whose binder is at least 1 sort (s) selected from the group which consists of a fluororesin, rubber-type resin, and a thickener.   The manufacturing method of Claims 4-9 in which a binder contains a water-soluble thickener.   The production method according to claim 11, wherein the water-soluble thickener is at least one selected from the group consisting of carboxymethylcellulose, chitansan gum, pectin, and agarose.

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