JPH0878011A - Lithium battery and manufacture of its negative electrode carrier - Google Patents

Abstract

PURPOSE: To provide a negative electrode which is easy to enlarge the area and hardly pulverized during charge/discharge in order to realize a lithium secondary battery with high capacity and long life, capable of applying to an electric vehicle and power storage. CONSTITUTION: The surface of a base metal (current collector) 1 is covered with an Al-Mn alloy 3 containing 10-25wt.% manganese by a molten salt electroplating or sputtering after preplating 2 is conducted if necessary to form a thermodynamic non-equilibrium Al-Mn alloy covering layer comprising a manganese super-saturated fcc-Al phase and an Al-Mn amorphous alloy phase. The covering material obtained is used as a negative electrode single body to constitute a lithium secondary battery.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium battery and a method for manufacturing a negative electrode carrier thereof, and more particularly, it is applicable as a direct current power supply for automobiles, a power storage power supply, etc. and has a high energy density and a long life. The present invention relates to a lithium secondary battery that can be upsized and a method for manufacturing a negative electrode carrier thereof.

[0002]

2. Description of the Related Art Lithium is a very base metal having a standard potential of −3.03 V and has a small atomic weight. Therefore, a lithium battery using lithium as a negative electrode active material has a high output voltage,
The energy density is also very high. Therefore, the wristwatch,
Lithium batteries are very often used in small and lightweight products such as cameras, but most of these are non-rechargeable primary batteries.

As a typical lithium primary battery, metallic lithium is used as a negative electrode, fluorinated graphite or manganese dioxide is used as a positive electrode active material, and a lithium salt is used as an electrolytic solution.
Some use organic solvent solutions of (eg, LiBF ₄ , LiClO _4, etc.). Since metallic Li, which is the negative electrode active material, has extremely high reactivity with water, it is difficult to use the electrolyte in the form of an aqueous solution in a general-purpose lithium battery. A conductive solid is used as the electrolyte.

Since lithium can be electrodeposited from its ions by a cathodic reduction reaction, the lithium battery can also be used as a rechargeable secondary battery. Therefore, the development of high-power lithium secondary batteries has been promoted by taking advantage of the characteristics of lithium.

As a result, recently, rechargeable lithium secondary batteries have begun to be used in mobile phones, portable video cameras and the like. The negative electrode of this lithium secondary battery is manufactured by binding a powder of a graphitic carbon material having a layered structure with a binder, and lithium enters between layers of the carbon material during charging and desorbs during discharging. It works.
However, if the size of this negative electrode is increased, the current density is lowered and the cost is increased.

A practical problem of a lithium secondary battery using a metal-based negative electrode (lithium or lithium alloy) that can be easily increased in size is that lithium, which is a negative electrode active material, is deposited on the negative electrode surface during electrodeposition during charging. It grows in the shape of dendrites and contacts with the positive electrode to cause an internal short circuit, resulting in extremely short charge / discharge cycle life. Therefore, as a large-sized lithium battery intended for electric vehicles and power storage, performance such as charge / discharge cycle life and output density is still insufficient. Moreover, a manufacturing technology for a large-area and inexpensive negative electrode has not been established. for these reasons,
A lithium secondary battery using a metal-based negative electrode has not yet been put to practical use.

As a proposal for improving the charge / discharge cycle life of a lithium secondary battery, for example, in Japanese Patent Laid-Open No. 525423, a lithium using a Li-Al alloy having a Li content of 63 to 92% as a negative electrode is used. Batteries are disclosed. In this battery, utilizing the property that aluminum absorbs and releases lithium,
Lithium is absorbed in aluminum during charging and Li-Al
Since it is an alloy, dendritic growth of lithium is suppressed.

However, it has been found that the strength of the Li-Al alloy is not sufficient and the alloy is pulverized by repeated charging / discharging, so that a sufficient charge / discharge cycle life cannot be obtained. Therefore, it has been proposed to add various alloying elements to aluminum to enhance the strength of the negative electrode and enhance the charge / discharge cycle characteristics of the battery.

For example, Japanese Patent Laid-Open No. 64-86451 discloses Al
A lithium secondary battery using a -Mn-In alloy as a negative electrode carrier is described. It is said that Mn, which is difficult to alloy with Li, plays a role of an aggregate to increase the strength of the negative electrode, and at the same time, the delay of Li diffusion, which is damaged by the addition of Mn, can be compensated by the addition of In, which has a large Li storage capacity. It is explained.

JP-A-3-182058 discloses a Li-Al-XY alloy which is an alloy of a group X consisting of Mn and Cr and a group Y consisting of Be, Bi, Cd, Ge, Pb, Sn and Ta. A lithium secondary battery using an alloy for a negative electrode is described. X is added to increase the strength of the Li-Al alloy, but there is a problem that X, which is not completely dissolved, segregates as an intermetallic compound at the grain boundary portion, and a crack is generated from it as a starting point during charge / discharge. Therefore, it is a proposal that by adding Y, a eutectic or peritectic metal structure is formed, and cracks can be suppressed because Y is a metal that is relatively rich in ductility.

Japanese Unexamined Patent Publication (Kokai) No. 4-58468 discloses that the electrode is locally localized by the non-uniform insertion and removal of lithium during charge and discharge due to the segregation of the third metal element added to the Li-Al alloy. It is pointed out that it deteriorates, and it is described that by inserting 0.01 to 10 wt% of this added metal as a solid solution, the insertion and removal of lithium become uniform and the cycle characteristics are improved.

[0012]

In all of these proposals, an aluminum alloy having excellent strength is used as a carrier for the negative electrode, and the negative electrode carrier is made to occlude lithium as an active material to form the negative electrode. . The metal-based negative electrode having such an aluminum alloy as a carrier has a certain effect in improving the charge / discharge cycle characteristics of a lithium battery,
According to the investigation by the present inventors, the performance is still insufficient, and further improvement is required especially for large-sized applications such as electric vehicles and electric power storage that require long life (long-term use). It was decided that there was. That is, in the lithium secondary battery according to the above proposal, since the negative electrode carrier made of an aluminum alloy is manufactured by a metallurgical method (e.g., melting → casting → rolling), segregation of a metal that does not store lithium occurs. This segregation significantly limits the lithium diffusion performance originally possessed by aluminum metal, and as a result, there is a limit to the improvement of charge / discharge characteristics. In addition, it is extremely difficult to form a highly brittle aluminum alloy into a large plate by a metallurgical method, which makes it difficult to increase the area of the negative electrode (that is, increase the capacity of the battery), and its manufacturing cost is high. .

Therefore, an object of the present invention is to provide a lithium battery which can be used as a secondary battery having excellent charge / discharge cycle characteristics. Another object of the present invention is to make it possible to realize a large-capacity secondary battery for electric vehicles, power storage, etc., so that it is easy to increase the area of the negative electrode and to manufacture the negative electrode carrier at low cost. It is to provide a lithium battery. Yet another object of the present invention is to provide a method for producing such a negative electrode carrier for a lithium battery.

[0014]

Means for Solving the Problems With the existing negative electrode in which an aluminum alloy prepared by a metallurgical method is used as a carrier for storing lithium, it is difficult for the present inventors to make a dramatic progress in the performance of a lithium battery. Therefore, as an anode support material capable of achieving the above object, attention was paid to an aluminum alloy that is thermodynamically in a non-equilibrium state. This is because in aluminum alloys obtained by conventional metallurgical methods, the alloy system is in a thermodynamic equilibrium state and the particles in the precipitation phase grow larger due to growth, so the adverse effect of segregation is unavoidable and performance improvement. However, in the non-equilibrium state, the precipitation phase can be in a fine state close to atomic order. And among the non-equilibrium aluminum alloys,
Attention is paid to Al-Mn alloys, which are known as alloy systems that easily generate amorphous phases and quasi-crystalline phases, and by coating a base metal that serves as a current collector with a specific Al-Mn alloy layer, low cost is achieved. It was found that a negative electrode carrier having a large area can be easily manufactured.

Here, a feature of the present invention is that in a lithium battery composed of a positive electrode, a negative electrode using lithium as an active material, and a non-aqueous solution of a lithium salt or an electrolyte composed of a lithium ion conductive solid, the carrier of the negative electrode. As another point, a coating material having an Al-Mn alloy coating layer composed of a structure containing a thermodynamic nonequilibrium phase on the surface of the base metal is used.

Specifically, the carrier of the negative electrode in the lithium battery of the present invention is a thermodynamically non-equilibrium Al-Mn composed of a mixed phase of Mn supersaturated fcc-Al phase and Al-Mn amorphous alloy phase. The coating material has an alloy coating layer on the surface of the base metal. Other phases may coexist in the Al-Mn alloy coating within a range that does not have a substantial adverse effect.

This negative electrode carrier has a Mn content of 10 to 25 by a coating method for forming a thermodynamic nonequilibrium phase on the surface of the base metal.
It can be manufactured by coating with an Al-Mn alloy in a weight percentage.

The lithium battery of the present invention can be used as a primary battery, but particularly when it is used as a secondary battery, its excellent charge / discharge characteristics can be utilized. The coating method for forming the thermodynamic non-equilibrium phase includes any coating method capable of forming a coating containing the thermodynamic non-equilibrium phase. Examples thereof include dry methods such as sputtering, ion plating, vapor deposition, and CVD, and nonaqueous electroplating methods such as molten salt electrolytic plating and electroplating in a nonaqueous solvent electrolytic solution. Above all, the coating formation by the electroplating method is most preferable from the viewpoint of battery performance.

[0019]

[Function] In the Al-Mn binary system, Al, Al ₆ Mn,
Al ₄ Mn, Al ₁₁ Mn ₄ , Mn, etc. exist, and Al-
When an Mn alloy is produced, a thermodynamically equilibrium alloy structure including any one of these single phases or a mixed phase of two or more phases can be obtained depending on the composition.

On the other hand, the non-equilibrium phases which are not shown in the thermal equilibrium phase diagram of the Al-Mn binary system include an amorphous phase and a quasi-crystalline phase. These non-equilibrium phases are liquid quenching methods, mechanical alloying methods, or dry methods such as sputtering, ion plating, vapor deposition, and CVD, as well as non-aqueous electroplating such as molten salt electrolytic plating and electroplating in organic solvents. It is known to form when an Al-Mn alloy is produced by a plating method or the like.

For example, in the case of electroplating by molten salt electrolysis, fcc-Al (face-centered cubic Al crystal) increases with the increase of Mn concentration.
Single phase, Mn supersaturated fcc-Al phase (hereinafter referred to as Mn supersaturated Al phase)
, The mixed phase of the Mn supersaturated Al phase and the Al-Mn amorphous phase, and the Al-Mn amorphous single phase. Of these, the first fcc-Al
The single phase is the equilibrium phase (the same as Al in the equilibrium phase), but the rest are non-equilibrium phases that cannot be obtained by metallurgical methods.

The inventors of the present invention conducted a charge-discharge life test of a lithium battery in which an Al-Mn alloy system containing these various non-equilibrium phases was alloyed with lithium to form a negative electrode. In the case of mixed phase of Al-Mn amorphous phase and Al-Mn amorphous phase, the deterioration phenomenon of the negative electrode due to the loss of brittle compounds found in conventional negative electrode materials based on aluminum alloy does not occur, and the cycle characteristics (charge and discharge It has been found that the (life) is extremely high. This is because the crystalline part (Mn supersaturated Al phase) fc of the above-mentioned crystalline / amorphous mixed phase structure is present.
(c-Al phase) is responsible for the charge / discharge reaction due to the occlusion / release of lithium, and the Al-Li compound generated at that time falls off during repeated charge / discharge. This is probably due to the support of the Mn amorphous phase). Moreover, the crystalline fcc-Al phase that reacts with lithium becomes a relatively high-strength phase by itself due to the solid solution of Mn in supersaturation (that is, forming the Mn supersaturated Al phase). The amorphous phase that supports this is not a crystalline and brittle phase like the segregated compound phase in the Al-Mn alloy by metallurgy. Therefore, it is considered that excellent cycle characteristics that have never been obtained can be exhibited.

It has been found that it exhibits excellent charge and discharge characteristics,
An Al-Mn alloy having a thermodynamic nonequilibrium structure mainly composed of a mixed phase of an Mn supersaturated Al phase and an Al-Mn amorphous phase is obtained when the Mn content is within the range of 10 to 25% by weight. It turned out to be possible. Such Al-Mn alloy material with a large Mn content,
It is difficult to produce it by a metallurgical method utilizing rolling, and it can be produced by the above method capable of forming a non-equilibrium phase.

In the present invention, in order to increase the area of the electrode and reduce the cost, the surface of the base metal that functions as a current collector is used as the carrier for the negative electrode by inserting and extracting lithium, which is the negative electrode active material. A coating material coated with an Al-Mn alloy layer capable of performing is used. Therefore, the Mn content of the base metal is 10 to 25 wt% by the coating method forming the thermodynamic non-equilibrium phase.
By coating with Al-Mn alloy of
It is possible to form an Al-Mn alloy coating layer having a nonequilibrium structure composed of a mixed phase with an -Mn amorphous phase and exhibiting excellent charge-discharge characteristics. In the present invention, the coating material thus obtained is used as a negative electrode carrier of a lithium battery.

As a coating method, a dry method such as a sputtering method, an ion plating method, a vapor deposition method or a CVD method is used.
(Dry process) is also possible. However, the non-aqueous electroplating method can form an Al-Mn alloy coating exhibiting particularly excellent charge and discharge characteristics. Although the reason is not clear, the metastable non-equilibrium state obtained when Al and Mn in the ionic state become metal state by voltage application in electroplating has excellent characteristics compared with other methods. I think it can be demonstrated.

A method for producing the above covering material used as the negative electrode carrier of the lithium battery of the present invention will be described below. Al
A collector is preferably used as the base metal coated with the —Mn alloy layer. When the base metal is a current collector, Al-
Since the negative electrode with the current collector integrated by the Mn alloy coating can be obtained, the electrical contact is better than in the conventional case where the current collector and the negative electrode are made separately and then joined. This is because the process and battery structure can be simplified. However, since it is not always necessary to use the current collector as the base metal, it is of course also possible to use a different base metal and form the negative electrode part by joining the obtained coating material to the current collector as the negative electrode carrier. It is possible.

The metal material suitable for the substrate is a material which is relatively excellent in corrosion resistance in a battery and is inexpensive, and nickel, iron, stainless steel, titanium, aluminum or the like can be used. The shape of the base metal can be selected from various shapes such as a foil, a plate, a corrugated plate, a mesh, and a perforated plate according to the structure of the battery.

As the coating method, either the dry method or the non-aqueous electroplating method can be adopted as described above, but the electroplating method is preferable. Since the dry method requires vacuum equipment, is costly, and has a manufacturing constraint that the film formation rate is not so fast, and as described above, the coating formed by the electroplating method exhibits particularly excellent charge and discharge characteristics. Is.

The formation of the Al-Mn alloy coating layer by the dry method is
It may be carried out according to a conventionally known method. For example,
Sputtering can be performed by using a conventional sputtering device that uses an Al-Mn alloy plate having almost the same composition as the Al-Mn alloy to be coated as a target material and generates argon gas ions by glow discharge.

In Al-based electroplating containing Al metal and Al alloy, the deposition potential of Al in the aqueous solution system is considerably lower than the hydrogen generation potential from water, and aluminum does not precipitate from the aqueous solution. It must be done in a non-aqueous electrolyte. There are two types of non-aqueous electrolytes: non-aqueous solvent system (organic solvent + inorganic salt) and molten salt system, but industrially the molten salt electroplating method that does not use organic solvent is more suitable. .

The non-aqueous solvent-based Al-Mn alloy plating is carried out, for example, with an aluminum compound such as AlCl ₃ or LiAlH ₄ and MnCl ₂
A solution of a manganese compound such as the above in an organic solvent such as ether or tetrahydrofuran can be used as an electrolytic solution.

As an electrolytic solution for Al-based molten salt electroplating,
Room temperature molten salt using special organic substances (eg AlCl ₃ + EM
There are two types of molten salt consisting of IC <ethylmethylimidazolium chloride>) and an inorganic salt only (eg, AlCl ₃ + NaCl + KCl), both of which can be adopted. An electroplating method of an Al-Mn alloy using a salt will be described as an example.

This molten salt electroplating is carried out, for example, in the following steps. Alkali degreasing → Washing → Pickling → Washing → (Pre-plating → Washing) → Drying → Molten salt plating → Washing → Drying As a pretreatment of the base metal to be coated, usually alkali degreasing, pickling, washing etc. are combined. The surface oxide film on the substrate is removed and activated. The type and order of such pretreatment are not particularly limited as long as surface activation is achieved. Further, as a pretreatment, activation may be performed by anodic dissolution in molten salt.

When the base metal is an easily oxidizable metal such as stainless steel, titanium or aluminum, the surface oxide film is strong, and the above-described pretreatment for surface activation is performed. However, the adhesion between the base material and the plating film may not be secured in some cases. In that case, in addition to the preliminary treatment, pre-plating is performed. The type of metal to be pre-plated is not particularly limited, but nickel is preferable from the viewpoint of adhesion with Al-Mn alloy plating and corrosion resistance in the battery.
The pre-plating method may be a general electroplating method, and there is no problem even if at least one element other than nickel is contained as an unavoidable impurity. The amount of pre-plated coating is about 0.05 to 5 g / m ² (for Ni, the film thickness is 0.006
Equivalent to ˜0.6 μm) is preferred. If the amount of pre-plating is less than 0.05 g / m ² , there are too many pre-plated parts on the surface of the material to be plated, and an oxide film is formed on those parts, resulting in adhesion of Al-Mn alloy plating. May cause defects. The amount of pre-plated coating may be more than 5 g / m ² , but it is not preferable in terms of cost.

The base metal thus pretreated is washed with water and then dried sufficiently so that water will not be mixed in the molten salt bath for Al-Mn alloy plating in the next step. In this drying, the atmosphere or temperature is adjusted so that no oxide film is formed on the pre-plated surface (eg, drying in an inert gas atmosphere)
It is preferable.

Aluminum-based molten salt electroplating is already well known, and the Al-Mn alloy plating coating of the present invention may be carried out according to a conventional method. The molten salt electrolytic bath is not limited as long as it contains aluminum and manganese salts. It is also within the scope of the present invention when other metals are co-deposited in the formed Al-Mn alloy coating due to impurity ions unavoidably mixed in the bath, but the amount of co-deposition is within 1% by weight. Is preferred.

A typical example of the electrolytic bath used is an aluminum chloride-based mixed molten salt, which contains aluminum chloride and manganese chloride, as well as other chlorides such as inorganic salts. Examples of inorganic chlorides include sodium chloride,
Examples thereof include alkali metal chlorides such as potassium chloride and lithium chloride. Although the temperature of the molten salt varies depending on its composition and composition, for example, in the case of an alloy plating bath in which MnCl ₂ is added to the molten salt of AlCl ₃ -NaCl-KCl eutectic composition, plating is performed at around 200 ° C. .

After the molten salt electroplating, the plating material taken out from the molten salt bath is washed with water and dried to obtain a coating material used as the negative electrode carrier of the lithium battery of the present invention. An example of the structure of this negative electrode carrier is shown in FIG. In FIG. 1, 1 is a base metal (current collector, eg 0.4 mm thick SUS430 stainless steel foil), 2 is a pre-plated layer (eg 0.2 μm thick nickel plated layer), 3 is a feature of the present invention. It is an Al-Mn alloy plating layer (eg, an Al-17% Mn alloy plating layer having a thickness of 20 μm) formed by a certain molten salt electroplating method. The pre-plated layer 2 is not necessary when the base metal is a metal such as nickel that is not easily oxidized or when the coating is formed by a dry method such as sputtering.

In the present invention, at least the surface portion of the negative electrode carrier has a structure containing a non-equilibrium phase, specifically, a mixed phase of an Mn supersaturated Al phase and an Al-Mn amorphous phase,
The Al-Mn alloy layer having such a structure can be formed not only by non-aqueous electroplating but also by the dry method described above. Also,
Although it is possible to form the entire negative electrode carrier from an Al-Mn alloy having such a nonequilibrium phase structure by a liquid quenching method or a mechanical alloying method, these methods produce a large area and uniform negative electrode carrier. It is difficult to do so, and the mechanical strength is not sufficient. Furthermore, in this case, the obtained negative electrode carrier must be joined to a separately manufactured current collector. As described above, by constructing the negative electrode carrier from the coating material in which the current collector is coated with the Al-Mn alloy by the dry method or the electroplating method, it has a structure integrated with the current collector,
High mechanical strength makes it possible to easily manufacture a large-area negative electrode carrier.

The Mn content in the Al-Mn alloy coating layer is in the range of 10 to 25% by weight. When the Mn content is less than 10% by weight, almost no Al-Mn amorphous phase that supports the Al crystal phase (Mn supersaturated Al phase) that reacts with Li is generated, and the Mn supersaturated Al phase is substantially isolated. Since it is the same as the phase, it is not possible to effectively prevent pulverization due to loss of the Al-Li compound that is a reaction product during repeated charge and discharge, and the cycle characteristics are degraded.

When the Mn content exceeds 25% by weight, the structure becomes Al.
-Mn changes to a single amorphous phase. In some cases, the Al crystalline phase that reacts with Li to form an alloy may remain, but since the proportion is small, the lithium storage amount is small, the battery capacity is significantly reduced, and the Al crystalline phase disappears. Then, it substantially does not function as a negative electrode. The preferable Mn content of the Al-Mn alloy coating layer is in the range of 13 to 20% by weight.

The thickness of the Al-Mn alloy coating layer is appropriately set depending on the purpose of use of the battery, but is usually in the range of 1 to 100 μm, particularly preferably 3 to 30 μm. If the coating thickness is small,
Film formation is possible in a short time, but the battery capacity becomes small.
Conversely, when the coating thickness increases, the battery capacity increases, but it takes time to form the film. The coating with the Al-Mn alloy layer,
It is not necessary to cover the entire surface of the base metal, and only a part of the surface may be coated. Usually, as illustrated in FIG. 1, the above Al—Mn alloy coating layer is formed on the entire surface of the base metal, but a coin type battery may be coated on only one side.

The lithium battery of the present invention is different from the lithium metal of the present invention except that a coating material having an Al-Mn alloy coating layer having a structure containing the above non-equilibrium phase on the surface of a base metal (preferably a current collector) is used as a negative electrode carrier. Thus, it can be configured similarly to a conventional lithium battery. That is, other constituent elements such as the positive electrode, the electrolyte, and the separator may be the same as conventional ones. In addition, as the electrolyte, a lithium salt that has been generally used conventionally
(E.g. LiBF ₄ , LiClO _4, etc.) as an aprotic organic solvent
In addition to a non-aqueous solution dissolved in (eg, propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, etc.), a lithium ion conductive solid (eg, electrolyte composed of polyethylene oxide and lithium salt, etc.) can also be used.

The lithium battery of the present invention is suitable for a large-capacity lithium secondary battery used for electric vehicles and electric power storage because it is easy to increase the area of the negative electrode and has excellent charge / discharge characteristics. It is self-evident that there is no problem in its performance when used in a lithium primary battery or a small lithium secondary battery used in portable electric products.

[0045]

The present invention will be described in more detail with reference to the following examples. In the examples,% means% by weight unless otherwise specified.
Is.

Example 1 A lithium secondary battery having the following constitution was produced. The positive electrode was prepared by mixing a positive electrode active material MnO ₂ , conductive graphite, and a polyvinylidene fluoride binder as a suspension in DMF (dimethylformamide) to a thickness of 20 μm, a width of 40 mm, and a length of 1250 m.
It was prepared by uniformly applying it to a nickel foil of m 3 and drying it.

The negative electrode was prepared by coating the entire surface of both surfaces of a nickel foil having the same size as described above with a molten salt electroplating method or a sputtering method with an Al—Mn alloy having a thickness of 10 μm. The electroplating conditions were as shown in Table 1. The sputtering method is Al-Mn produced by the melting method.
Using alloy plate as the target material, vacuum degree 10 ^-6 -10 ^-7
A film was formed at an output of 150 W in a torr vacuum container. The film thickness was controlled by adjusting the sputtering time. The Mn content was adjusted by changing the Mn content in the target material.

[0048]

[Table 1] A 40 μm thick polypropylene microporous membrane was used as the separator. Both the positive and negative electrodes are wound into a roll through a separator, put into a battery can, and then filled with a non-aqueous solution of 1M propylene carbonate solution of LiClO ₄ as an electrolytic solution and sealed, and the lithium as shown in FIG. The secondary battery was assembled. In FIG. 2, 4 is a positive electrode, 5 is a separator, 6 is a negative electrode, 7 is an insulating plate, 8 is a nickel positive electrode lead, and 9 is a gasket.

The cycle life of this lithium secondary battery was repeatedly measured by a charge / discharge test. The charge / discharge cycle is
(Charge 500 mA x 30 minutes) → (Pause for 5 minutes) → (Discharge at 500 mA
1.0V vs. Li) → (5 minutes rest), and the cycle life (up to the life) is defined as the life when the charging / discharging efficiency [= (Discharged electricity quantity / charged electricity quantity x 100) decreases to 90%. The number of cycles) was obtained and the charge / discharge characteristics were evaluated.

Table 2 shows the cycle life thus obtained.
The Mn content in the Al-Mn alloy coating in the negative electrode is shown together with the structure of the Al-Mn alloy coating examined by X-ray diffraction and structure observation by a transmission electron microscope.

[0051]

[Table 2]

As is clear from the results in Table 2, among the comparative examples, in Test Nos. 1 to 5, the Mn content in the Al-Mn alloy coating was lower than 10%, and the crystal structure was fcc-Al single phase ( Since Mn is supersaturated (including non-equilibrium ones), the negative electrode alloy falls off due to repeated charging and discharging, resulting in a cycle life of 200
It was as short as less than once. On the other hand, in test Nos. 12 to 14, Al-Mn
Since the Mn content of the alloy coating exceeded 25% by weight, the structure was Al
Since it becomes a -Mn amorphous single phase and alloying with Li does not occur, an efficiency of 90% or more cannot be obtained.

On the other hand, Test No. 6 which is an example of the present invention
In ~ 11, an Al-Mn alloy coating consisting of a mixed phase structure of crystalline fcc-Al phase (Mn supersaturation) and Al-Mn amorphous phase is formed,
The cycle life has been dramatically extended to over 1000 times.

For reference, as a conventional example, a pure Al plate and Al-Mn produced by a metallurgical method (melting, casting, rolling).
An alloy plate (thickness: 100 μm) was pressure-bonded to the nickel foil to form a negative electrode carrier, and a secondary battery was assembled and a repeated charge / discharge test was performed in the same manner as above. The cycle life in this case is about 90 times with a pure Al plate, Al-containing Mn
Even in the case of the Mn alloy plate, even if the Mn content was changed, it was about the same as that of the comparative example in Table 2, and the dramatic improvement in cycle life as in the present invention was not seen.

[0055]

According to the present invention, the Mn content is 10 to 25% by weight.
By coating the base metal with Al-Mn alloy by electroplating method for forming thermodynamic non-equilibrium phase, coating method such as sputtering method, non-equilibrium phase, specifically Mn supersaturated Al crystalline phase and Al An Al-Mn alloy coating layer composed of a mixed phase with -Mn amorphous phase is formed, and the charge / discharge cycle characteristics of the lithium secondary battery are dramatically improved. Further, the negative electrode carrier manufactured by the method of the present invention can be manufactured with a large area at low cost. Therefore, it is possible to manufacture a large-sized and high-power lithium secondary battery for electric vehicles and electric power storage at low cost, and the industrial value of the present invention is extremely high.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an example of a negative electrode carrier according to the present invention.

FIG. 2 is a schematic sectional view of an example of a lithium battery according to the present invention.

[Explanation of symbols]

1: Metal substrate (collector), 2: Pre-plated layer, 3: Al-
Mn alloy coating layer, 4: positive electrode, 5: separator, 6: negative electrode, 7: insulating plate, 8: positive electrode lead, 9: gasket

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noboru Wakabayashi 1-831 Midorigaoka, Ikeda, Osaka Prefecture Industrial Technology Institute, Osaka Institute of Industrial Technology (72) Inventor Shunichi Higuchi 1-8, Midorigaoka, Ikeda, Osaka No. 31 Industrial Technology Institute Osaka Institute of Industrial Technology (72) Inventor Ken Abe 4-5-3 Kitahama, Chuo-ku, Osaka City Sumitomo Metal Industries, Ltd. (72) Inventor Junichi Uchida 4-chome Kitahama, Chuo-ku, Osaka 5-33 Sumitomo Metal Industries, Ltd. (72) Inventor Katsuro Hirayama 4-chome Kitahama, Chuo-ku, Osaka 5-33 Sumitomo Metal Industries Ltd. (72) Inventor Kunihiro Fukui 4-chome, Kitahama, Chuo-ku, Osaka No. 5 33 Sumitomo Metal Industry Co., Ltd.

Claims (4)

[Claims] 1. A lithium battery comprising a positive electrode, a negative electrode using lithium as an active material, and an electrolyte composed of a non-aqueous solution of a lithium salt or a lithium ion conductive solid, wherein the negative electrode is Mn supersaturated fcc- Characterized by using a coating material having a thermodynamically non-equilibrium Al-Mn alloy coating layer consisting of a mixed phase of an Al phase and an Al-Mn amorphous alloy phase on the base metal surface as a carrier, Lithium battery. 2. The lithium battery according to claim 1, which is a secondary battery. 3. A method for producing a negative electrode carrier for a lithium battery, which comprises coating the surface of a base metal with an Al—Mn alloy having a Mn content of 10 to 25% by weight by a coating method for forming a thermodynamic non-equilibrium phase. . 4. The method according to claim 3, wherein the coating method is a non-aqueous electroplating method.