JP2003297341A - Negative electrode for secondary battery and secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery having a reduced deterioration in its performance without impairing the energy density of the battery. <P>SOLUTION: The battery is composed of a negative electrode current collector 1c, a positive electrode current collector 2c, a carbon negative electrode 3c, a positive electrode active material 5c containing manganese, and a separator 6c, wherein a manganese capturing layer to capture manganese ions as a cause of a deterioration in battery performance is formed on the carbon negative electrode 3c. The manganese capturing layer is composed of a second capturing layer 8c consisting of a simple substance of metal such as silicon or tin and a first capturing layer 7c consisting of oxide of such a simple substance of silicon or tin. Because the first capturing layer 7c and the second capturing layer 8c have the lithium occluding and emitting abilities, equipment of such layers does not cause a deterioration in energy density. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative electrode for a secondary battery and a secondary battery, and more particularly to a negative electrode for a secondary battery using a positive electrode containing manganese and a secondary battery including the negative electrode.

[0002]

2. Description of the Related Art With the spread of mobile terminals such as mobile phones and notebook computers, the role of a battery serving as a power source of the mobile terminals has been emphasized. These batteries are required to be small and lightweight, have high capacity, and be resistant to deterioration even after repeated charging and discharging.

As the positive electrode material, a material containing Co, manganese, or Ni as a main component is used. However, manganese has a rich reserve as compared with Co, and therefore has an advantage that it can be stably and inexpensively supplied. is there. Further, since the positive electrode using manganese is superior in over-discharge characteristics to the positive electrode using Co, there is also an advantage that the battery life is long.

However, in the positive electrode using manganese, the capacity is deteriorated depending on the progress of the charge / discharge cycle, the standing period, and the storage temperature. The reason for this is considered to be that manganese in the positive electrode active material becomes ions and is eluted into the electrolytic solution, and the eluted manganese ions are deposited on the negative electrode surface, which inhibits occlusion / release of lithium ions in the negative electrode active material. ing.

As a method for preventing the precipitation of manganese ions as described above, Japanese Patent Laid-Open No. 2000-77103 discloses a method of holding active carbon, silica gel, zeolite, aluminum or the like on the surface of a separator, a positive electrode or a negative electrode, and Techniques for capturing cations have been disclosed.

Further, Japanese Unexamined Patent Publication No. 2000-48828 discloses a technique for suppressing precipitation of manganese by adding an aluminum compound, lithium boron oxide or calcium salt to a non-aqueous electrolyte.

Further, Japanese Patent Application Laid-Open No. 2000-21381 discloses a technique for capturing manganese ions by adding a cation exchange resin to a separator.

[0008]

However, in the technique described in the above publication, it is necessary to add a substance that does not participate in charge / discharge, such as a manganese trapping substance or a cation exchange resin, so that a sufficient energy density is obtained. There was a problem that it could not be done.

Further, in the technique described in Japanese Patent Laid-Open No. 2000-48828, an aluminum compound is contained in the electrolytic solution,
There has been a problem that it is difficult to control SEI (Solid Electrolyte Interface solid electrolyte interface) formation by adding an additive such as lithium boron oxide. This is considered due to the following reasons. That is, the concentration of the additive changes as manganese elutes in the electrolytic solution. With this change, the resistance of the electrolytic solution also changes, which makes it difficult to control the SEI formation.

In view of the above circumstances, it is an object of the present invention to provide a battery with reduced performance degradation without impairing the energy density of the battery.

[0011]

According to the present invention for solving the above problems, there is provided a negative electrode for a secondary battery comprising a manganese trapping layer capable of inserting and extracting lithium ions. It

The lithium-manganese composite oxide used for the positive electrode of the secondary battery has a spinel structure, is structurally stable as compared with lithium cobalt oxide, and has a strong resistance to overcharge. However, manganese elutes from the positive electrode into the electrolytic solution due to repeated charging / discharging, storage period, and storage temperature. The eluted manganese deposits on the negative electrode active material and raises the impedance of the battery, which causes deterioration of the negative electrode capacity.

Therefore, by adopting the negative electrode of the present invention provided with a manganese trapping layer capable of trapping manganese and contributing to the negative electrode capacity, the capacity can be reduced without lowering the energy density of the battery. It is possible to prevent deterioration. In addition, since it is not necessary to add a substance that does not participate in charge / discharge to the electrolyte, the electrolyte resistance and SE
The I formation process does not change. Therefore, manganese can be effectively captured without deteriorating the battery performance.

Further, according to the present invention, there is provided a negative electrode for a secondary battery, comprising an active material layer made of a carbon material, wherein the negative electrode for the secondary battery is provided on the active material layer made of the carbon material, lithium Provided is a negative electrode for a secondary battery, which is provided with a manganese trapping layer capable of occluding and releasing ions.

It is necessary to avoid contact between manganese and the carbon negative electrode as much as possible, because manganese is deposited on the surface of the carbon negative electrode, which causes capacity deterioration. Therefore, in the present invention, the surface of the carbon negative electrode is covered with a manganese trapping layer capable of inserting and extracting lithium ions. As a result, manganese eluted from the positive electrode into the electrolytic solution is captured by this manganese capturing layer. Therefore, it is possible to suppress the contact between the manganese that has reached the negative electrode and the carbon negative electrode, and thus it is possible to suppress the impedance increase and prevent the capacity deterioration.

Further, according to the present invention, there is provided a negative electrode for a secondary battery, wherein the manganese trapping layer contains oxygen in the negative electrode for a secondary battery.

According to the present invention, in the above-mentioned secondary battery negative electrode, the manganese trapping layer absorbs lithium.
Provided is a negative electrode for a secondary battery, which comprises a releasable metal and has the surface of the manganese trapping layer oxidized.

Since simple materials of metals such as silicon and tin, and oxides and compounds thereof can store and release lithium, they are expected to be used as battery materials. These materials form an alloy with manganese, but unlike lithium, they do not easily release manganese, so that manganese remains in a simple substance such as silicon or tin, an oxide, or a compound even after charging and discharging. This suppresses manganese precipitation on the surface of the negative electrode. That is, a simple substance material such as silicon or tin, an oxide, or a compound functions not only as a negative electrode active material but also as a material for capturing manganese.

Here, both the simple substance material and the oxide thereof can be used as the manganese trapping layer, but the oxide of the simple substance material is superior from the viewpoint of the manganese trapping ability. Since the oxide of the simple substance contains oxygen, manganese taken into the manganese trapping layer is changed into manganese oxide in the layer. Since manganese oxide is stable, it is difficult to be released as manganese ions into the electrolytic solution again. Therefore, the inclusion of an oxide in the manganese trapping layer makes the manganese trapping function particularly excellent.

Since a simple substance material is more advantageous than an oxide from the viewpoint of capacity, the manganese trapping layer may be configured to include both a layer made of an oxide and a layer made of a simple substance. preferable. This makes it possible to improve the capacity of the negative electrode and the cycle characteristics at the same time.

Further, according to the present invention, there is provided a negative electrode for a secondary battery, wherein the manganese trapping layer has an amorphous structure in the negative electrode for a secondary battery.

Electrochemical lithium doping / dedoping of an amorphous structure occurs at a base potential lower than that of a crystalline structure, so that the battery capacity can be increased while maintaining a high operating voltage and high charge / discharge efficiency. .

The term "amorphous" as used herein means 15 to 4 as a 2θ value of an X-ray diffraction method using CuKα rays.
It has a broad scattering band with an apex at 0 degree. Since the amorphous structure is structurally isotropic as compared with a crystalline body, it is excellent in strength against external stress and is chemically stable. Therefore, it does not easily react with the electrolytic solution, has excellent stability when the charge / discharge cycle is repeated, and does not easily cause capacity deterioration.

The manganese trapping layer is preferably in the form of a film rather than a structure in which particles are bound. Since the manganese trapping layer can be made uniform by forming a film, it becomes possible to stably exhibit the manganese trapping ability.

The manganese trapping layer can be formed by a melt cooling method, a liquid quenching method, an atomizing method, a vapor deposition method, a CVD method or a sputtering method. When these film forming methods are used, an amorphous ion conductive film-like layer is uniformly obtained on the negative electrode. With this film, the positive electrode
The electrolytic distribution between the negative electrodes becomes uniform. Therefore, local concentration of the electric field does not occur and stable battery characteristics can be obtained.

Further, according to the present invention, in the above-mentioned negative electrode for secondary battery, the manganese trapping layer comprises Si, Ge, S.
Provided is a negative electrode for a secondary battery, which contains one or more elements selected from the group consisting of n, In, Pb, Ag, Al, B and P.

The material constituting the manganese trapping layer in the present invention is not particularly limited as long as it is a material capable of inserting and extracting lithium ions and forming an alloy with manganese.
It is preferable to contain one or more elements selected from the group consisting of Si, Ge, Sn, In, Pb, Ag, Al, B and P. By selecting such a material and providing an amorphous structure, it is possible to increase the negative electrode capacity while maintaining a high operating voltage and a high charge / discharge efficiency.

According to the present invention, in the above-mentioned negative electrode for secondary battery, the manganese trapping layer is made of Si, Ge, S.
Provided is a negative electrode for a secondary battery, which is a layer in which a group III element or a group V element is introduced as an impurity in a layer made of n, Pb or an oxide thereof.

By doing so, the resistivity of the manganese trapping layer can be lowered, and the charge / discharge efficiency is improved.

Further, according to the present invention, there is provided a negative electrode for a secondary battery, wherein the negative electrode for a secondary battery further comprises a lithium supplementary layer on the manganese trapping layer.

By providing the lithium compensation layer, the irreversible capacity of the negative electrode can be compensated. as a result,
It becomes possible to contribute to the improvement of the energy density of a battery using this negative electrode as a constituent element.

Further, according to the present invention, there is provided a secondary battery including a positive electrode containing manganese as an active material and a negative electrode, wherein the negative electrode comprises a manganese trapping layer capable of inserting and extracting lithium ions. A secondary battery is provided.

The lithium-manganese composite oxide used for the positive electrode of the secondary battery has a spinel structure, is structurally stable as compared with lithium cobalt oxide, and has a particularly strong resistance to overcharge. However, manganese elutes from the positive electrode into the electrolytic solution due to repeated charging / discharging, a storage period, and a storage temperature. The eluted manganese deposits on the negative electrode active material and raises the impedance of the battery, which causes deterioration of the negative electrode capacity.

Therefore, by providing the negative electrode with a manganese trapping layer capable of trapping manganese on the surface of the negative electrode and contributing to the battery capacity, capacity deterioration can be achieved without lowering the energy density of the battery. It becomes possible to prevent it. Moreover, since it is not necessary to add a substance that does not participate in charge / discharge to the electrolyte, the resistance of the electrolytic solution and the SEI formation process do not change. Therefore, manganese can be effectively captured without deteriorating the battery performance.

Further, according to the present invention, there is provided a secondary battery including a positive electrode containing manganese as an active material and a negative electrode having an active material layer made of a carbon material, wherein the negative electrode is made of the carbon material. Storage of lithium ions on the material layer
There is provided a secondary battery comprising a manganese trapping layer capable of discharging.

It is necessary to avoid contact between manganese and the carbon negative electrode as much as possible, because the deposition of manganese on the surface of the carbon negative electrode causes capacity deterioration. Therefore, in the present invention, the surface of the carbon negative electrode is covered with a manganese trapping layer capable of inserting and extracting lithium ions. As a result, manganese eluted from the positive electrode into the electrolytic solution is captured by this manganese capturing layer. Therefore, it is possible to suppress the contact between the manganese that has reached the negative electrode and the carbon negative electrode, and thus it is possible to suppress the impedance increase and prevent the capacity deterioration.

According to the present invention, there is also provided a secondary battery according to the above secondary battery, wherein the manganese trapping layer contains oxygen.

According to the present invention, in the above secondary battery, the manganese trapping layer contains a metal capable of inserting and extracting lithium, and the surface of the manganese trapping layer is oxidized. A secondary battery is provided.

Since a simple substance material of metal such as silicon or tin and its oxides and compounds can occlude and release lithium, it is expected to be used as a battery material. These materials form an alloy with manganese, but unlike lithium, they do not easily release manganese, so that manganese remains in a simple substance such as silicon or tin, an oxide, or a compound even after charging and discharging. This suppresses manganese precipitation on the surface of the negative electrode. That is, a simple substance material such as silicon or tin, an oxide, or a compound functions not only as a negative electrode active material but also as a material for capturing manganese.

Here, both the simple substance material and the oxide thereof can be used as the manganese trapping layer, but from the viewpoint of manganese trapping ability, the single substance oxide is superior. Since the oxide of the simple substance contains oxygen, manganese taken into the manganese trapping layer is changed into manganese oxide in the layer. Since manganese oxide is stable, it is difficult to be released as manganese ions into the electrolytic solution again. Therefore, the inclusion of an oxide in the manganese trapping layer makes the manganese trapping function particularly excellent.

Since a simple substance material is more advantageous than an oxide from the viewpoint of capacity, the manganese trapping layer may be configured to include both a layer made of an oxide and a layer made of a simple substance. preferable. This makes it possible to improve the capacity of the negative electrode and the cycle characteristics at the same time.

Further, according to the present invention, there is provided a secondary battery according to the above secondary battery, wherein the manganese trapping layer has an amorphous structure.

Electrochemical lithium doping / dedoping of the amorphous structure occurs at a base potential lower than that of the crystalline structure, so that the battery capacity can be increased while maintaining a high operating voltage and high charge / discharge efficiency. .

The amorphous structure has a
Since it is structurally isotropic, it has excellent strength against external stress and is chemically stable. Therefore, it does not easily react with the electrolytic solution, has excellent stability when the charge / discharge cycle is repeated, and does not easily cause capacity deterioration.

The manganese-trapping layer is preferably in the form of a film rather than a structure in which particles are bound together. Since the manganese trapping layer can be made uniform by forming a film, it becomes possible to stably exhibit the manganese trapping ability.

The manganese trapping layer can be formed by a melt cooling method, a liquid quenching method, an atomizing method, a vapor deposition method, a CVD method or a sputtering method. When these film forming methods are used, an amorphous ion conductive film-like layer is uniformly obtained on the negative electrode. With this film, the positive electrode
The electrolytic distribution between the negative electrodes becomes uniform. Therefore, local concentration of the electric field does not occur and stable battery characteristics can be obtained.

According to the present invention, in the above secondary battery, the manganese trapping layer is made of Si, Ge, Sn, I.
Provided is a secondary battery containing one or more elements selected from the group consisting of n, Pb, Ag, Al, B and P.

The material constituting the manganese trapping layer in the present invention is not particularly limited as long as it is a material capable of absorbing and releasing lithium ions and forming an alloy with manganese.
It is preferable to contain one or more elements selected from the group consisting of Si, Ge, Sn, In, Pb, Ag, Al, B and P. By selecting such a material and providing an amorphous structure, it is possible to increase the battery capacity while maintaining a high operating voltage and a high charge / discharge efficiency.

According to the present invention, in the above secondary battery, the manganese trapping layer is made of Si, Ge, Sn, Pb.
Alternatively, a secondary battery is provided which is a layer in which a group III element or a group V element is introduced as an impurity in a layer formed of these oxides.

By doing so, the resistivity of the manganese trapping layer can be lowered, so that the charge / discharge efficiency is improved.

Further, according to the present invention, there is provided the secondary battery, wherein the secondary battery further comprises a lithium supplementary layer on the manganese trapping layer.

By providing the lithium supplementary layer, it becomes possible to supplement the irreversible capacity of the battery, and the energy density of the battery is improved.

[0053]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) Next, a first embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a part of a sectional view of a secondary battery showing a first embodiment of the present invention. The negative electrode current collector 1c and the positive electrode current collector 2c are electrodes that take current out of the battery during charging / discharging or take current into the battery from outside. The negative electrode current collector 1c and the positive electrode current collector 2c may be any conductive metal foil, and examples thereof include aluminum, copper, stainless steel, gold, tungsten, and molybdenum.
The thickness of the negative electrode current collector 1c and the positive electrode current collector 2c is 5
Is about 25 μm.

The carbon negative electrode 3c is a negative electrode member that absorbs or releases lithium during charging and discharging. The carbon negative electrode 3c is carbon capable of occluding lithium, and examples thereof include graphite, fullerene, carbon nanotube, DLC (diamond-like carbon), amorphous carbon, hard carbon, or a mixture thereof. The carbon negative electrode 3c has a thickness of 30 to 300 μm.

The first trapping layer 7c and the second trapping layer 8c are layers for trapping the metal eluted from the positive electrode. First acquisition layer 7c
Is obtained by oxidizing the second trapping layer 8c and has a thickness of 2
nm to 1 μm. The second trapping layer 8c is CVD,
1 of silicon, tin or these metals, amorphous metals and alloys, prepared by vapor deposition and sputtering
It is composed of more than one seed and has a thickness of 0.1 μm to 25 μm.
Is. A film thickness of 0.1 to 1.8 μm is preferable.
Alternatively, the second trapping layer 8c may be doped with boron, phosphorus, arsenic, or antimony to reduce the resistivity.

The negative electrode current collector 1c, the carbon negative electrode 3c, the first trapping layer 7c and the second trapping layer 8c constitute a negative electrode.

The positive electrode active material 5c is a material containing manganese and capable of inserting and extracting lithium, such as Li _x MnO ₂ , Li _x MnF ₂ and Li.
_{x MnS 2, Li x Mn 1} -y M y O 2, Li x Mn 1-y M y O 2, Li x Mn
_{1-y M y O 2-} z F z, Li x Mn 1-y MyO 2-z S z, Li x Mn
₂ O ₄ , Li _x Mn ₂ F ₄ , Li _x Mn ₂ S ₄ , Li _x Mn _{2- y My} O ₄ , Li
_{x Mn 2-y M y O} 4-z F z , and _{Li x Mn 2-y MyO 4} -z S z (0 <x
≦ 1.5, 0 <y <1.0, Z ≦ 1.0, and M represents at least one transition metal), and the thickness thereof is 10 to 500 μm. The positive electrode current collector 2c and the positive electrode active material 5c form a positive electrode.

The carbon negative electrode 3c and the positive electrode active material 5c are conductive materials such as carbon black, polyvinylidene fluoride (PV
A binder such as DF) is added to N-methyl-2-pyrrolidone (NM
A material obtained by dispersing and kneading with a solvent such as P) is applied to each of the negative electrode current collector 1c and the positive electrode current collector 2c for use.

A separator 6c having insulation and ion conductivity is provided between the negative electrode and the positive electrode, and is composed of a polyolefin such as polypropylene or polyethylene, or a porous film such as a fluororesin. After stacking the positive electrode / separator / negative electrode, or winding the stacked product, it is housed in a battery can or sealed by a flexible film or the like made of a laminate of synthetic resin and metal foil to form a battery. It can be manufactured.

Further, as the electrolytic solution, a propylene card is used.
Net (PC), ethylene carbonate (EC), buty
Renka Bonnet (BC), Vinylen Bonnet (V)
C) etc. cyclic carbonates, dimethyl carbonate
(DMC), diethyl carbonate (DEC), ethyl
Methyl carbonate (EMC), dipropyl carbonate
Chain carbonates such as DPC, methyl formate, vinegar
Aliphatic carboxylic acid esters such as methyl acidate and ethyl propionate
Γ-lactones such as steals and γ-butyrolactone,
1,2-ethoxyethane (DEE), ethoxymethoxy
Chain ethers such as ethane (EME), tetrahydrofuran
Cyclic ethers such as orchid and 2-methyltetrahydrofuran
, Dimethylsulfoxide, 1,3-dioxolane, f
Lumamide, acetamide, dimethylformamide, di
Oxolane, acetonitrile, propyl nitrile, nit
Methane, ethyl monoglyme, phosphate triester,
Trimethoxymethane, dioxolane derivative, sulfora
, Methylsulfolane, 1,3-dimethyl-2-imidazole
Zolidinone, 3-methyl-2-oxazolidinone, pro
Pyrene carbonate derivative, tetrahydrofuran derivative
Body, ethyl ether, 1,3-propane sultone, ani
Aprotic such as Sol, N-methylpyrrolidone, etc.
These organic solvents are used alone or in admixture of two or more.
A lithium salt that is soluble in an organic solvent is dissolved. lithium
As the salt, for example, LiPF₆, LiAsF₆, LiAlCl _Four, LiClO
_Four, LiBF_Four, LiSbF₆, LiCF_ThreeSO_Three, LiCF_ThreeCO_Two, Li (CF
_ThreeSO_Two)_Two, LiN (CF_ThreeSO_Two)_Two, LiB₁₀Cl₁₀, Lower fat
Aliphatic carboxylate lithium, lithium chloroborane,
Lithium phenyl borate, LiBr, LiI, LiSCN, LiCl, imimi
There are various kinds of products. Also, instead of the electrolytic solution, a polymer
An electrolyte may be used.

Next, the operation of the negative electrode of the secondary battery shown in FIG. 1 will be described in detail.

During charging, the negative electrode receives lithium ions from the positive electrode side through the electrolytic solution, and during discharging, lithium ions move from the negative electrode toward the positive electrode. When such charging / discharging is repeated or the battery itself is stored at a temperature of 40 ° C. or higher, manganese ions are eluted from the positive electrode in the electrolytic solution. The eluted manganese ions pass through the separator and reach the negative electrode. The manganese ions that have reached the negative electrode diffuse or move into the first trapping layer 7c and the second trapping layer 8c to form an alloy or compound in the trapping layer.
In particular, since the first trapping layer 7c contains oxygen, manganese forms an oxide and is fixed. As a result, manganese does not deposit on the negative electrode, so that an increase in impedance in the battery can be suppressed and a capacity deterioration can be prevented.

During charge / discharge, manganese that has become a compound or manganese that has been alloyed does not elute again as manganese ions. Therefore, it remains in the first acquisition layer 7c and the second acquisition layer 8c. On the other hand, the first trapping layer 7c and the second trapping layer 8c can store and release lithium even after trapping manganese. Therefore, it contributes to efficient charge and discharge without lowering the energy density of the battery.

(Second Embodiment) Next, a second embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a part of a sectional view of a secondary battery showing a second embodiment of the present invention.

Regarding the negative electrode current collector 1e, the positive electrode current collector 2e, the carbon negative electrode 3e, the positive electrode active material 5e, the separator 6e, and the electrolytic solution, the negative electrode current collector 1c and the positive electrode current collector in the first embodiment are used. 2c, the carbon negative electrode 3c, the positive electrode active material 5c, the separator 6c, and the electrolytic solution can have the same configuration.

The first trapping layer 7e and the second trapping layer 8e are layers for trapping the metal eluted from the positive electrode. First acquisition layer 7e
Is obtained by oxidizing the second trapping layer 8e and has a thickness of 2
nm to 1 μm. The second trapping layer 8e is CVD,
It is composed of silicon, tin or one or more of these metals, amorphous metals and alloys produced by vapor deposition or sputtering, and its thickness is 0.1 μm to 25 μm, preferably 0.1 to 1.8 μm. Further, the second trapping layer 8e may be doped with boron, phosphorus, arsenic and antimony to reduce the resistivity.

The lithium supplement layer 9e is a layer for supplying lithium to supplement the irreversible capacity of the battery, and is formed of lithium, a lithium compound or a layer in which lithium is mixed. Examples of these are lithium metal, lithium oxide,
Examples thereof include one containing one or more of lithium nitride, LiF, and LiCO ₃ .

The negative electrode current collector 1e, the carbon negative electrode 3e, the first scavenging layer 7e, the second scavenging layer 8e and the lithium supplementary layer 9e constitute a negative electrode.

Further, the positive electrode collector 2e and the positive electrode active material 5e constitute a positive electrode.

Carbon negative electrode 3e and positive electrode active material 5e are conductive materials such as carbon black, polyvinylidene fluoride (PVD).
A binder obtained by dispersing and kneading a binder such as F) with a solvent such as N-methyl-2-pyrrolidone (NMP) is applied to the negative electrode current collector 1e and the positive electrode current collector 2e, respectively.

After stacking the positive electrode / separator / negative electrode, or winding the stacked product, it is housed in a battery can or sealed with a flexible film or the like made of a laminate of synthetic resin and metal foil. A battery can be manufactured by

Next, the operation of the negative electrode of the secondary battery shown in FIG. 2 will be described in detail.

During charging, the negative electrode receives lithium ions from the positive electrode side through the electrolytic solution, and during discharging, lithium ions move from the negative electrode toward the positive electrode. The irreversible capacity generated in the battery is compensated by the lithium compensation layer 9e. Such charging and discharging may be repeated, or the battery itself
When stored at a temperature of ℃ or more, manganese ions are eluted from the positive electrode in the electrolytic solution. The eluted manganese ions pass through the separator and reach the negative electrode. The manganese ions that have reached the negative electrode diffuse or move into the first trapping layer 7e and the second trapping layer 8e, and form an alloy or a compound in the trapping layer. In particular, since the first trapping layer 7e contains oxygen, manganese forms an oxide and is fixed. As a result, manganese does not deposit on the negative electrode, so that the impedance rise in the battery can be suppressed and the capacity deterioration can be prevented.

During charge and discharge, manganese which has become a compound or manganese which has been alloyed does not elute again as manganese ions. Therefore, it remains in the first acquisition layer 7e and the second acquisition layer 8e. On the other hand, the first trapping layer 7e and the second trapping layer 8e can store and release lithium even after trapping manganese. Therefore, it contributes to efficient charge and discharge without lowering the energy density of the battery.

Further, in the present embodiment, the lithium ion filling layer 9e fills the irreversible capacity of the battery, thereby contributing to the improvement of the energy density of the battery.

[0078]

EXAMPLES Example 1 Example 1 will be described below with reference to FIG.
Indicates.

A copper foil having a thickness of 10 μm was used for the negative electrode current collector 1c, and aluminum having a thickness of 20 μm was used for the positive electrode current collector 2c. Hard carbon having a thickness of 50 μm was used for the carbon negative electrode 3c, and a silicon film having a thickness of 1.8 μm was formed on the second capturing layer 8c by a sputtering method. The first trapping layer 7c is formed by oxidizing the second trapping layer 8c and has a film thickness of 20
nm. The first trapping layer 7c is formed by exposing the second trapping layer 8c to an oxidizing atmosphere. Positive electrode active material 5c
LiCoMnO ₄ with a thickness of 100 μm is used for the separator 6c.
The layered polypropylene and polyethylene were used. The electrolyte used was a mixture of EC / DEC = 3: 7 and LiPF ₆ as a supporting salt added thereto. These were put in a container to prepare a battery, which was then stored at 45 ° C. for 2 weeks, after which the charge amount was measured to determine how much the capacity could be maintained with respect to the designed capacity.

(Second Embodiment) A second embodiment will be described below with reference to FIG.

A copper foil having a thickness of 10 μm was used for the negative electrode current collector 1c, and aluminum having a thickness of 20 μm was used for the positive electrode current collector 2c. Hard carbon having a thickness of 50 μm was used for the carbon negative electrode 3c, and a tin film having a thickness of 1.2 μm was formed on the second capturing layer 8c by a sputtering method. The first trapping layer 7c was formed by oxidizing the second trapping layer 8c and had a thickness of 20 nm. The first trapping layer 7c is formed by exposing the second trapping layer 8c to an oxidizing atmosphere. As the positive electrode active material 5c, 100 μm thick LiCoMnO ₄ was used, and as the separator 6c, polypropylene and polyethylene laminated in layers were used. The electrolyte used was a mixture of EC / DEC = 3: 7 and LiPF ₆ as a supporting salt added thereto. These were put in a container to prepare a battery, which was then stored at 45 ° C. for 2 weeks, after which the charge amount was measured to determine how much the capacity could be maintained relative to the designed capacity.

Example 3 Example 3 will be described below with reference to FIG.

A copper foil having a thickness of 10 μm was used for the negative electrode current collector 1c, and aluminum having a thickness of 20 μm was used for the positive electrode current collector 2c. Hard carbon with a thickness of 50 μm was used for the carbon negative electrode 3c, and SiOx (0 <
x ≦ 2) A film having a thickness of 0.3 μm was formed. In addition, the first acquisition layer 7c
Was formed by oxidizing the second trapping layer 8c and its thickness was set to 20 nm. The first trapping layer 7c is formed by exposing the second trapping layer 8c to an oxidizing atmosphere. As the positive electrode active material 5c, 100 μm thick LiCoMnO ₄ was used, and as the separator 6c, polypropylene and polyethylene laminated in layers were used. EC / DEC = 3 for electrolyte:
The mixture of 7 and the addition of LiPF ₆ as a supporting salt was used. These were put in a container to prepare a battery, which was then stored at 45 ° C. for 2 weeks, after which the charge amount was measured to determine how much the capacity could be maintained relative to the designed capacity.

Comparative Example 1 The structure shown in FIG. 3 as Comparative Example 1.
A battery was prepared. FIG. 3 is a cross-sectional view of the electrode structure of Comparative Example 1.
It is a figure showing a part of. 10 μm for the negative electrode current collector 1b
A thick copper foil is used, and the positive electrode current collector 2b has a thickness of 20 μm.
I used Mi. The carbon anode 3b has a 50 μm thick hard cover.
Carbon was used. 85 μm thick LiCo is used as the positive electrode active material 5b.
MnO_FourUse polypropylene and a separator for the separator 6b.
A layer of polyethylene was used. In electrolyte
Is a mixture of EC / DEC = 3: 7 and L as a supporting salt
iPF ₆Was used. Put these in a container and
After making the pond, the same test as in Examples 1 to 3 was performed and
The quantity retention rate was verified.

Table 1 shows the results of the capacity retention ratios of the batteries of Examples 1 to 3 and Comparative Example 1.

[0086]

[Table 1]

The capacity retention rate is the ratio of the initial charge capacity to the design capacity of the battery.

From this result, the capacity retention rate of Comparative Example 1 was 8
Compared with 5%, in Examples 1 to 3, the capacity was almost 100%, and the capacities were almost as designed.

The above results are considered as follows. In the comparative example, manganese is deposited on the surface of the negative electrode active material to raise the impedance of the battery, whereas in Examples 1 to 3, manganese is trapped in the first trapping layer 7c and the second trapping layer 8c. Therefore, precipitation of manganese on the surface of the negative electrode is suppressed. As a result, it is considered that the high capacity retention ratios in Examples 1 to 3 were obtained because the increase in the battery impedance was suppressed.

Further, comparing the energy densities of the batteries obtained from the charge capacities, Examples 1 to 3 are 1.1 to 1.3 times as high as Comparative Example 1, and the energy densities are even if the manganese trapping layer is provided. It turned out not to drop.

Example 4 Example 4 will be described below with reference to FIG.

A copper foil having a thickness of 15 μm was used for the negative electrode current collector 1e, and aluminum having a thickness of 20 μm was used for the positive electrode current collector 2e. Amorphous carbon having a thickness of 50 μm was used for the carbon negative electrode 3e, and a silicon film having a thickness of 1.5 μm was formed on the second capturing layer 8e by a vapor deposition method. The first trapping layer 7e was formed by oxidizing the second trapping layer 8e and had a film thickness of 5 nm. The first trapping layer 7e is obtained by exposing the second trapping layer 8e to an oxidizing atmosphere. 2 μm of metallic lithium was vapor-deposited on the lithium supplementary layer 9e. 10 for the positive electrode active material 5e
LiMn _0.5 Ni _0.5 O ₄ having a thickness of 0 μm was used, and the separator 6e was a layered structure of polypropylene and polyethylene. The electrolyte used was a mixture of EC / DEC = 3: 7 and LiPF ₆ as a supporting salt added thereto. These were put in a container to prepare a battery, which was then stored at 45 ° C. for 2 weeks, after which the charge amount was measured to determine how much the capacity could be maintained with respect to the designed capacity.

(Fifth Embodiment) A fifth embodiment will be described below with reference to FIG.

A copper foil having a thickness of 15 μm was used for the negative electrode current collector 1e, and aluminum having a thickness of 20 μm was used for the positive electrode current collector 2e. Amorphous carbon having a thickness of 50 μm was used for the carbon negative electrode 3e, and a silicon-tin alloy film having a thickness of 0.3 μm was formed on the second capturing layer 8e by a vapor deposition method. The first trapping layer 7e was formed by oxidizing the second trapping layer 8e, and the thickness thereof was set to 5 nm. The first trapping layer 7e is obtained by exposing the second trapping layer 8e to an oxidizing atmosphere. LiCO ₃ was deposited to a thickness of 1.5 μm on the lithium filling layer 9e. Positive electrode active material 5e
LiMn _0.5 Ni _0.5 O ₄ having a thickness of 100 μm was used as the separator, and polypropylene and polyethylene laminated in layers were used as the separator 6e. EC / DEC = for electrolyte
A mixture of 3: 7 and LiPF ₆ as a supporting salt was used. After putting these in a container and making a battery, 45
The sample was stored at ℃ for 2 weeks, and then the charge amount was measured to measure how much the capacity could be retained with respect to the designed capacity.

(Sixth Embodiment) A sixth embodiment will be described below with reference to FIG.

A copper foil with a thickness of 15 μm was used for the negative electrode current collector 1e, and an aluminum with a thickness of 20 μm was used for the positive electrode current collector 2e. Amorphous carbon having a thickness of 50 μm was used for the carbon negative electrode 3e, and a silicon-tin alloy film having a thickness of 1.4 μm was formed on the second capturing layer 8e by a vapor deposition method. The first trapping layer 7e was formed by oxidizing the second trapping layer 8e and had a film thickness of 5 nm. The first trapping layer 7e is obtained by exposing the second trapping layer 8e to an oxidizing atmosphere. Lithium filling layer 9e
Lithium metal was vapor-deposited at 1.5 μm. Positive electrode active material 5
For e, 100 μm thick LiMn _0.5 Ni _0.5 O ₄ is used,
As the separator 6e, polypropylene and polyethylene laminated in layers were used. EC / DEC for electrolyte
= 3: 7 mixed with LiPF ₆ as a supporting salt was used. After putting these in a container and making a battery, 4
The sample was stored at 5 ° C. for 2 weeks, and then the charge amount was measured to measure how much the capacity could be retained with respect to the designed capacity.

Comparative Example 2 As Comparative Example 2, a battery having the structure shown in FIG. 4 was produced. FIG. 4 is a diagram showing a part of a sectional view of an electrode structure of Comparative Example 2. 10 μm for negative electrode current collector 1f
A thick copper foil was used, and a positive electrode current collector 2f was made of aluminum having a thickness of 20 μm. Hard carbon having a thickness of 50 μm was used for the carbon negative electrode 3f. 85 μm thick LiMn is used for the positive electrode active material 5f.
_0.5 Ni _{0 . 5} O ₄ was used, and as the separator 6 f, polypropylene and polyethylene laminated in layers were used. Metal lithium was vapor-deposited in a thickness of 1 μm on the lithium filling layer 9f. The electrolyte used was a mixture of EC / DEC = 3: 7 and LiPF ₆ as a supporting salt added thereto. After putting these in a container and producing a battery, the same test as in Examples 4 to 6 was performed to verify the capacity retention rate.

Table 2 shows the results of the capacity retention ratios of the batteries of Examples 4 to 6 and Comparative Example 2.

[0099]

[Table 2]

From these results, it was revealed that Examples 4 to 6 had a capacity retention ratio as high as 14% as compared with Comparative Example 2.

The above results are considered as follows. In Comparative Example 2, manganese was deposited on the surface of the negative electrode active material to raise the impedance of the battery, whereas in Examples 4 to 6, manganese was trapped in the first trapping layer 7e and the second trapping layer 8e. Therefore, the precipitation of manganese on the surface of the negative electrode is suppressed. As a result, it is considered that the high capacity retention ratios in Examples 4 to 6 were obtained because the increase in battery impedance was suppressed.

Further, comparing the energy densities of the batteries obtained from the charge capacities, Examples 4 to 6 are 1.2 times that of Comparative Example 2, and even if the manganese trapping layer is provided, the energy density does not decrease. found.

[0103]

As described above, according to the present invention, it is possible to provide a battery with reduced performance deterioration without impairing the energy density of the battery.

[Brief description of drawings]

FIG. 1 is a diagram showing a part of a cross-sectional view of a secondary battery showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a part of a cross-sectional view of a secondary battery showing a second embodiment of the present invention.

FIG. 3 is a part of a cross-sectional view of a negative electrode of a secondary battery of Comparative Example 1.

FIG. 4 is a part of a cross-sectional view of a negative electrode of a secondary battery of Comparative Example 2.

[Explanation of symbols]

1b, 1c, 1e, 1f Negative electrode current collector 2b, 2c, 2e, 2f Positive electrode current collector 3b, 3c, 3e, 3f carbon negative electrode 5b, 5c, 5e, 5f Positive electrode active material 6b, 6c, 6e, 6f Separator 7c, 7e First capture layer 8c, 8e Second acquisition layer 9e, 9f Lithium supplementary layer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yu Sakauchi             5-7 Shiba, Minato-ku, Tokyo NEC Corporation             Inside the company (72) Inventor Mitsuhiro Mori             5-7 Shiba, Minato-ku, Tokyo NEC Corporation             Inside the company (72) Inventor Jiro Iriyama             5-7 Shiba, Minato-ku, Tokyo NEC Corporation             Inside the company (72) Inventor Masato Shirokata             5-7 Shiba, Minato-ku, Tokyo NEC Corporation             Inside the company F term (reference) 5H029 AJ02 AJ03 AK03 AL02 AL06                       AL11 AL18 AM02 AM03 AM04                       AM05 AM07 AM16 DJ18                 5H050 AA02 AA08 BA17 BA18 CA09                       CB02 CB07 CB11 FA20 GA22

Claims (16)

[Claims] 1. A negative electrode for a secondary battery, comprising a manganese trapping layer capable of inserting and extracting lithium ions. 2. A negative electrode for a secondary battery, which comprises an active material layer made of a carbon material, wherein the negative electrode for the secondary battery occludes lithium ions on the active material layer made of the carbon material.
A negative electrode for a secondary battery, comprising a manganese trapping layer capable of releasing. 3. The negative electrode for a secondary battery according to claim 1, wherein the manganese trapping layer contains oxygen. 4. The secondary battery negative electrode according to claim 1, wherein the manganese trapping layer contains a metal capable of inserting and extracting lithium, and the surface of the manganese trapping layer is oxidized. A negative electrode for a secondary battery, which is characterized in that 5. The negative electrode for a secondary battery according to claim 1, wherein the manganese trapping layer has an amorphous structure. 6. The negative electrode for a secondary battery according to claim 1, wherein the manganese trapping layer comprises Si and G.
A negative electrode for a secondary battery, containing one or more elements selected from the group consisting of e, Sn, In, Pb, Ag, Al, B and P. 7. The negative electrode for a secondary battery according to claim 1, wherein the manganese trapping layer comprises Si and G.
II in the layer consisting of e, Sn, Pb or their oxides
A negative electrode for a secondary battery, which is a layer in which a group I element or a group V element is introduced as an impurity. 8. The negative electrode for a secondary battery according to claim 1, further comprising a lithium supplement layer on the manganese trapping layer. 9. A secondary battery including a positive electrode containing manganese as an active material and a negative electrode, wherein the negative electrode comprises a manganese trapping layer capable of inserting and extracting lithium ions. Rechargeable battery. 10. A positive electrode containing manganese as an active material,
A secondary battery including a negative electrode having an active material layer made of a carbon material, wherein the negative electrode traps manganese capable of inserting and extracting lithium ions on the active material layer made of the carbon material. A secondary battery comprising a layer. 11. The secondary battery according to claim 9, wherein the manganese trapping layer contains oxygen. 12. The secondary battery according to claim 9, wherein the manganese trapping layer contains a metal capable of inserting and extracting lithium, and the surface of the manganese trapping layer is oxidized. Secondary battery characterized by. 13. The secondary battery according to claim 9, wherein the manganese trapping layer has an amorphous structure. 14. The secondary battery according to claim 9, wherein the manganese trapping layer comprises Si, Ge,
A secondary battery comprising one or more elements selected from the group consisting of Sn, In, Pb, Ag, Al, B and P. 15. The secondary battery according to claim 9, wherein the manganese trapping layer comprises Si, Ge,
A secondary battery, which is a layer in which a group III element or a group V element is introduced as an impurity in a layer made of Sn, Pb, or an oxide thereof. 16. The secondary battery according to claim 9, further comprising a lithium supplementary layer on the manganese trapping layer.