JPH1186853A - Lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium secondary battery, which has high capacity and low irreversible capacity and can perform high-speed charging/discharging and has a long charging discharging cycle service life. SOLUTION: This lithium secondary battery is composed of a negative electrode 22, composed mainly of a negative electrode active material to store/ release a lithium ion at charging/discharging time, a positive electrode 21 and a lithium ion conductive nonaqueous electrolyte or a polymer electrolyte, and the negative electrode active material is composed of particles which contain a phase of an inter-metallic compound containing 3B, 4B, 5B group elements of a periodic table and contains one or more phases of a phase, except for the inter-metallic compound composed of elements which are contained in the inter-metallic compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to a non-aqueous electrolyte secondary battery having charge / discharge characteristics of high voltage, high energy density, high charge / discharge capacity, long cycle life, and safety. Related to high lithium secondary batteries.

[0002]

2. Description of the Related Art In the field of electronic equipment, the demand for portable use of equipment has been increasing and the size and weight of the equipment have been reduced. For this reason, development of a battery having a high energy density, particularly a secondary battery, is required. A lithium secondary battery is a candidate for a secondary battery that satisfies this requirement. Lithium secondary batteries have higher voltage, higher energy density, and are lighter in weight than nickel cadmium batteries, lead storage batteries, and nickel hydrogen batteries.

However, in a lithium secondary battery using lithium metal as a negative electrode active material, lithium dendrite precipitates on the surface of the negative electrode during charging, and internal short-circuit with the positive electrode and negative activation with respect to the electrolytic solution occur. It is a problem in terms of life and safety. Further, in order to avoid the danger of using lithium metal, a lithium secondary battery using a lithium alloy such as Li-Pb or Li-Al as a negative electrode active material has been developed. However, this lithium secondary battery also has problems of dendrite precipitation and pulverization, and a sufficient battery life has not been obtained.

At present, lithium secondary batteries using graphite as a negative electrode active material have been developed and have been put to practical use. This is because lithium ions are inserted and desorbed from the C-plane of graphite by the reaction of inserting and removing lithium ions, and are more stable than chemically active metallic lithium. Absent. For this reason, the cycle life was extended and the safety was improved.

[0005]

When graphite is used as the negative electrode active material, the discharge capacity is 370 mAh / g at the maximum.
Since the weight density of graphite is 2.2 g / cm ³ , the volume capacity density is smaller than that of lithium metal, and the volume capacity density is further reduced in a negative electrode sheet in which a graphite negative electrode active material is applied to a negative electrode current collector. In order to solve this problem, a lithium secondary battery using a metal-based inorganic material having a large weight density as a negative electrode active material has been developed. For example, JP-A-5-159780
According to the publication, it is possible to achieve a high voltage, a large charge / discharge capacity, and a long cycle life by using iron silicide, particularly FeSi or FeSi ₂ as a negative electrode active material.

In Japanese Patent Application Laid-Open No. 8-153517, nickel silicide is used, in Japanese Patent Application Laid-Open No. 8-53537, copper nitride and zinc nitride are used, and in Japanese Patent Application Laid-Open No. 8-153538, manganese silicide is used as a negative electrode active material. It is said that a lithium secondary battery having a large charge / discharge capacity, a high energy density, and a long cycle life can be provided by using the lithium secondary battery. The charge / discharge capacity of the negative electrode active material is 560 mAh / cm ³ at the maximum, which is several tens of percent higher than that of the graphite negative electrode.

On the other hand, the irreversible capacity, which is the difference between the initial charge capacity and the discharge capacity, is larger than that of a graphite material, and poses a problem in forming a lithium secondary battery. When the charge / discharge speed is low, a certain capacity and cycle life are exhibited. However, when the charge / discharge speed is high, the capacity and cycle life are remarkably deteriorated. This is not preferable in practical use of the battery and needs to be improved. It is considered that these characteristics are caused by the metal-based negative electrode active material expanding and contracting during charge / discharge, so that it cannot maintain a stable crystal structure and collapses.

Accordingly, the present invention suppresses the collapse of the negative electrode active material due to repetition of charge and discharge, and provides a high capacity, a low irreversible capacity,
By providing a high-speed charge / discharge, long-life negative electrode active material for lithium secondary batteries, and by using this negative electrode active material,
An object of the present invention is to provide a lithium secondary battery having a large charge / discharge capacity, a high energy density, capable of high-speed charge / discharge, and a long cycle life.

[0009]

SUMMARY OF THE INVENTION The inventors of the present invention have found that the cause of deterioration of the charge / discharge characteristics of a metal-based negative electrode material is a structural change occurring during charge / discharge, ie, collapse of the negative electrode material and inhibition of Li diffusion. In order to solve these problems, various negative electrode materials were manufactured and charge / discharge tests were performed. As a result, they have invented a negative electrode material for a lithium secondary battery and a lithium secondary battery having excellent characteristics.

As a result of charge / discharge tests of various intermetallic compounds by the inventors, an intermetallic compound containing a 3B, 4B, or 5B group element as a constituent element can be charged and discharged as a negative electrode material for a lithium secondary battery. Material. As the material, M
g ₂ Si, Mg ₂ Gg, Mg ₂ Pb, AlSb, Mg ₂ S
n, CoSi ₂ , TiSi ₂ , MoSi ₂ , NiSi _{2 and the} like. A charge / discharge test was performed on Mg ₂ Si among these materials. Mg ₂ Si powder is classified into 32
Those having a size of μm or less were selected. Analysis of this powder by X-ray diffraction revealed that it was a single phase Mg ₂ Si powder. A negative electrode using this powder has an initial charge capacity of 6
Although a very large value exceeding 50 mAh / g was shown, the irreversible capacity was also extremely large at 40% or more, which is not preferable for use as a negative electrode material for a lithium secondary battery. Mg ₂ S
Mg ₂ Si—Si mixed phase particles in which both i and Si were present were produced, and a charge / discharge test was performed. As a result, the charge / discharge capacity increased and the irreversible capacity decreased. In addition, the charge / discharge cycle life was prolonged. From this, if the negative electrode active material for a lithium secondary battery contains two or more phases in the material structure, and the above-mentioned phases are all particles that can occlude Li,
A higher capacity, lower irreversible capacity, and longer life lithium secondary battery can be provided.

[0011] This is considered to be because the negative electrode active material is composed of a plurality of phases, thereby alleviating the mutual structural change due to charging and discharging, and suppressing the collapse of particles. In addition, the decrease in irreversible capacity and the increase in capacity are due to the presence of a plurality of phases, the interface of which is Li
It is considered that this plays a role as a diffusion bypass and promotes the diffusion of Li.

A lithium secondary battery using an intermetallic compound containing a 3B, 4B, or 5B element as a negative electrode active material is expected to have a high capacity. According to the above test results, the life of the negative electrode active material for a lithium secondary battery can be extended by being composed of particles containing two or more phases. However, in the case of mixed-phase particles containing elements other than the constituents of the intermetallic compound, the elements may be dissolved in the electrolytic solution during a charge / discharge test due to an electrochemical reaction. It is preferable to be composed of the contained elements. Therefore, the negative electrode active material includes a phase of an intermetallic compound containing a 3B, 4B, or 5B group element of the periodic table, and a phase other than the intermetallic compound constituted by an element included in the intermetallic compound is one phase. The lithium secondary battery having excellent charge / discharge characteristics can be provided by being constituted by the particles including the above.

Among the intermetallic compounds containing group 3B, 4B and 5B elements, in particular, Al, Ga, In, Si, Ge, Sn,
An intermetallic compound containing at least one of Pb, Sb and Bi can be expected to have a high charge / discharge capacity. Therefore, the negative electrode active material is made of Al, Ga, In, Si, Ge, Sn, Pb,
It is composed of particles containing a phase of an intermetallic compound containing at least one of Sb and Bi, and containing one or more phases other than the intermetallic compound composed of elements contained in the intermetallic compound. Lithium secondary batteries exhibit excellent charge / discharge characteristics.

The negative electrode active material for obtaining a lithium secondary battery having a high charge capacity, a low irreversible capacity, and a long life depends on the material structure.
It has already been mentioned that it must be composed of particles consisting of more than one phase, and in particular it is important that a phase interface exists. Therefore, cross sections of various negative electrode active material powders were observed, and the average value of the interface length per unit area was determined. The longer the interface length, the better the charge / discharge characteristics. For this reason, in order to obtain a lithium secondary battery having excellent charge / discharge characteristics, it is preferable that the interface length is long, and in particular, 5 × 10 ⁶ m /
It is more preferably at least m ² . Further, the test results revealed that the longer the interface length per unit area, the more stable the charge / discharge characteristics can be obtained even when the charge / discharge speed is different, which is advantageous for high-speed charge / discharge.

[0015] From this, the negative electrode active material is Al, G
a, In, Si, Ge, Sn, Pb, Sb, Bi, including a phase of an intermetallic compound containing at least one or more of Bi,
And it is composed of particles containing at least one phase other than the intermetallic compound composed of elements contained in the intermetallic compound,
It is necessary that the interface length between a plurality of intermetallic compound phases adjacent to each other on the sectional structure of the particles is 5 × 10 ⁶ m / m ² or more.

Although there are several methods for producing metal powder, a production method including a quenching step is preferred in order to increase the length of the phase interface, that is, to refine the structure. As this method, for example, there is a gas atomizing method. When the powder produced by this method is a binary system, two to four phases of adjacent intermetallic compounds or metals are observed on the phase diagram. The negative electrode active material of the present invention includes Al, Ga, In, Si,
It contains a phase of an intermetallic compound containing at least one of Ge, Sn, Pb, Sb, and Bi and is composed of an element contained in the intermetallic compound, and is adjacent to the intermetallic compound on a phase diagram. 1 phase of intermetallic compound or metal
It is composed of particles containing more than one phase.

The negative electrode active material according to the present invention is composed of Al, Ga, In, Si, Ge, Sn, P
an intermetallic compound containing at least one of b, Sb, Bi and a phase of an intermetallic compound and being composed of an element contained in the intermetallic compound and adjacent to the intermetallic compound on a phase diagram; or Most preferably, it is composed of particles containing at least one metal phase, and the interface length of a plurality of adjacent phases on the sectional structure of the particles is 5 × 10 ⁶ m / m ² or more.

The negative electrode active material of the present invention has a particle diameter of 100.
It is preferably not more than μm. In particular, the thickness is preferably 40 μm or less from the viewpoint of applicability and charge / discharge characteristics when producing a negative electrode sheet for a lithium secondary battery.

When a negative electrode sheet is prepared using the negative electrode active material of the present invention, it is not necessary to use a conductive material because the particles themselves have good conductivity. However, the conductive material is used to compensate for a decrease in conductivity due to charge and discharge. Mixing can also form a negative electrode. The conductive material used at this time does not have any problem as long as the conductive material has good conductivity and low reactivity with the electrolytic solution regardless of whether carbon powder or metal powder is used.

When a negative electrode is produced, a binder is used. The binder is not particularly limited as long as it does not react with an electrolyte such as EPDM, PVEF, polytetrafluoroethylene, or the like. The compounding amount of the binder is preferably 1 to 30 wt.%, Particularly preferably 4 to 15%, based on the total weight of the negative electrode active material and the conductive material. The shape of the negative electrode using the mixture can be applied to a sheet-like or film-like metal foil, or filled in a foamed metal to form a negative electrode corresponding to the battery shape.

The thus obtained negative electrode can be combined with a generally used positive electrode, a separator and an electrolyte to make an optimal lithium secondary battery. As the active material used for the positive electrode, LiCoO ₂ , LiNiO ₂ ,
A composite oxide containing lithium, such as LiMnO _4, can be used, and a mixture of a conductive material and a binder is applied to a current collector such as an Al foil to form a positive electrode. As the separator, a porous film of polypropylene, polyethylene or polyolefin is used. Examples of the electrolyte include propylene carbonate (PC), ethylene carbonate (EC), and 1,2-dimethoxyethane (DM
E), two or more kinds of mixed solvents such as dimethyl carbonate (DMC) and methyl ethyl carbonate (MEC) are used. As the electrolyte, LiPF ₆ , LiB
There are F ₄ , LiClO _{4 and the} like, and those dissolved in the above solvents are used.

By using the powder comprising the multi-phase mixed phase particles of the present invention as a negative electrode active material for a negative electrode material for a lithium secondary battery, high charge / discharge capacity, low irreversible capacity, long life, and high speed charging are possible. It is possible to provide a simple lithium secondary battery.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION

(Example 1) Mixing and dissolving granular Mg and Si
A g-Si alloy was produced. Here, Mg is 16.5.
g, Si and 9.2 g were mixed and dissolved. The dissolution was carried out at 1.5 atm by introducing a high-purity argon gas after setting the degree of vacuum to 1 × 10 ⁻⁷ mbar or more using a floating type high-frequency dissolution apparatus. The dissolution time at this time was 5 minutes. The obtained Mg-Si ingot is pulverized and classified by a sieve,
Particles having a particle size of 32 μm or less were selected. As a result of a structural analysis of this by an X-ray diffraction method, a diffraction peak corresponding to the Mg ₂ Si crystal was obtained, and it became clear that the powder was Mg ₂ Si powder.

The above-mentioned powder is made of graphite, amorphous carbon and PV.
It was kneaded with a solution of DF in N-methylpyrrolidone and applied to a Cu foil. The weight ratio of each component in the mixture was Mg ₂ Si powder:
TJSP: AB: PVDF = 80: 8: 4: 8. The thickness of the Cu foil is 20 μm. After coating, the coating was dried at 80 ° C. for several hours, pressed at a pressure of 0.5 ton / cm ² , and further dried under vacuum at 120 ° C. for 3 hours.

A negative electrode sheet was produced by the above operation. This negative electrode sheet was subjected to unipolar evaluation using the counter electrode and the reference electrode as Li metal. At this time, the electrolyte is LiPF
EC: DMC = 1: 2 containing 1 mol / l of ₆ was used. The charge / discharge current was adjusted to be 0.2 mA / cm ^2, and the charge / discharge test was performed with the potential of the negative electrode with respect to the reference electrode in the range of 0.01 to 1 V. All processes from the pulverization to the charge / discharge test were performed in a glove box controlled in an argon atmosphere.

Also, 14.6 g of Mg and 11.4 g of Si
Were mixed and dissolved and pulverized in the same manner as above to prepare a powder. X-ray diffraction revealed that this powder was composed of Mg ₂ Si and Si. This powder was also subjected to the same steps as above to produce a negative electrode sheet, which was subjected to a charge / discharge test.

FIG. 1 shows the results of the charge / discharge test. Mg ₂ Si
The powder showed a very large charge capacity with an initial charge capacity of more than 650 mAh / g, but an initial discharge capacity of 400 mAh / g.
h / g, and the irreversible capacity was as large as about 40%. On the other hand, the initial charge capacity of the Mg ₂ Si—Si mixed phase powder was almost the same, but the initial discharge capacity was 550.
It exceeded mAh / g and its irreversible capacity was about 15%. Since the Si phase is also considered to contribute to charge and discharge, the above Mg ₂ Si powder and Si powder having an average particle size of 5 μm were mixed so that the weight ratio was Mg ₂ Si: Si = 9: 1. A negative electrode sheet was prepared from the powder thus obtained in the same manner as described above, and a charge / discharge test was performed.

The results are also shown in FIG. Although the initial charge capacity is increased by adding Si, the initial discharge capacity is decreased, and the charge / discharge characteristics are deteriorated as compared with the powder of Mg ₂ Si alone. From this, Mg ₂ Si and S
A powder having a mixed phase with i has the best charge / discharge characteristics.
FIG. 1 also shows charge / discharge characteristics when a negative electrode sheet was prepared using only TJSP as the negative electrode active material. Mg
_{The 2} Si—Si mixed-phase negative electrode had slightly lower cycle characteristics than the TJSP negative electrode, but had a very large discharge capacity.

On the other hand, 18.4 g of Mg and 8.9 g of Si were mixed and dissolved. This ingot was also ground and its structure was analyzed by an X-ray diffraction method. As a result, diffraction peaks corresponding to Mg ₂ Si and Mg were observed. This powder was buried in a resin, polished in a glove box controlled in an argon atmosphere, and then its cross section was observed with a scanning electron microscope (SEM) to analyze the element distribution of Mg and Si. As a result, Mg single-phase particles were observed to some extent, but most of them were Mg ₂ Si
Alternatively, it was a Mg ₂ Si—Mg mixed phase powder. This Mg ₂
A negative electrode sheet was prepared using the Si-Mg mixed phase powder in the same manner as described above, and a charge / discharge test was performed. This result is also shown in FIG. Mg ₂ Si -Mg multiphase anode, Mg ₂
Although the capacity is lower than that of the Si—Si mixed phase negative electrode, the charge / discharge cycle characteristics are good and the cycle deterioration is very small.

(Example 2) Next, 58.7 g of Ni and S
A Ni-Si alloy was produced using a floating-type high-frequency melting apparatus using 29.2 g of i in Example 1. The obtained Ni-
The Si ingot was pulverized and classified by a sieve, and particles having a particle size of 32 μm or less were selected. The structure was analyzed by X-ray diffraction. As a result, diffraction peaks corresponding to NiSi ₂ and Si were obtained. Further, a diffraction peak corresponding to NiSi was also weakly detected. As a result of observing the cross-sectional structure of this powder with a SEM and analyzing the element distribution, the powder contains a small amount of single-phase particles of Si and NiSi ₂ , respectively, and is mainly NiSi ₂ -Si mixed phase particles. Became clear. No NiSi phase was observed by SEM observation. This powder is called a NiSi ₂ —Si mixed phase.

Ni-Si melted with the same composition as above
Powder was produced from the alloy ingot by a gas atomization method in an argon atmosphere. In this powder, particles having a particle size of 32 μm were selected, and the structure was identified by X-ray diffraction and SEM observation. As a result, most of the powder was a NiSi ₂ single phase powder, and contained a slight amount of a Si single phase and a NiSi ₂ —Si mixed phase powder. We call this powder and NiSi _2.

57.5 g of Ni and 42.5 g of Si were dissolved in the same manner as described above to produce a Ni-Si ingot. The pulverized and classified powder is subjected to X-ray diffraction and SE
As a result of M observation, it was revealed that the powder was a mixed phase powder of NiSi ₂ and NiSi. The powder produced from the ingot by the gas atomization method described above was NiSi ₂
And NiSi mixed phase powders, each of which had a smaller crystal grain size than the above powders, and had a microstructure. Here, the former NiSi ₂ —NiSi mixed phase powder was converted to NiSi ₂ —NiSi mixed phase 1 and the latter NiS 2
The i ₂ -NiSi multiphase powder is referred to as NiSi ₂ -NiSi multiphase 2.

The above NiSi ₂ —Si mixed phase, NiS
i ₂ , NiSi ₂ —NiSi mixed phase 1, NiSi ₂ —NiSi
Mixed phase 2 and Ni just mixed with NiSi ₂ and Si powder
Using a Si ₂ -Si mixed powder, the same compounding ratio as in Example 1,
A negative electrode sheet was prepared under the conditions, and a charge / discharge test was performed. The result is shown in FIG. From this, the NiSi ₂ —Si mixed powder has a very large initial capacity, but the cycle deterioration is remarkable,
It is not suitable for use as a negative electrode material. Other 4
The two materials had better cycle characteristics. Among them, NiSi ₂ —NiSi mixed phase 2 has a capacity,
Both cycle characteristics showed good characteristics.

From the above, it is clear that, in the negative electrode material for a lithium secondary battery, powder having mixed phases inside the particles shows good characteristics, and it is more preferable that each phase is finer in terms of charge and discharge characteristics. It is. NiSi ₂ -Ni
Si mixed phase 1 also showed good charge / discharge characteristics. From the photograph of the cross-sectional structure of this material, the number of points at which the arbitrarily drawn straight line intersected the phase interface was measured, and the interface length per unit area was determined. As a result, the average interface length was 6.7 × 10 ⁶ m / m ² . From this, the interface length is at least 5 × 10 ⁶
If it is at least m / m ² , the charge / discharge characteristics will be good.

Example 3 Using the melting apparatus of Example 1, the weight ratio was Mg: Ge = 16: 84, Mg: Sn = 5.
0:50, Mg: Pb = 37: 63, respectively, dissolving the blended materials to obtain Mg-Ge, Mg-Sn, M
A g-Pb alloy ingot was produced. Crush these,
As a result of X-ray diffraction and SEM observation, the powder obtained by classification was determined to be a Mg ₂ Ge—Ge mixed phase, a Mg ₂ Sn—Mg mixed phase, and a Mg ₂
It turned out that it was a Pb-Mg mixed phase. These also contained some single-phase particles, most of which were mixed phase particles as described above. Using these materials, a negative electrode sheet produced in the same manner as in Example 1 was subjected to a charge / discharge test under the same conditions. The result is shown in FIG. 3 in comparison with the case of the TJSP negative electrode. Each of the mixed phase materials had a larger capacity than TJSP, and the cycle characteristics were almost the same.

Example 4 NiSi fabricated in Example 2
_2, NiSi ₂ -NiSi multiphase 1, NiSi ₂ -NiSi
A charge / discharge test was performed on the mixed phase 2 with a charge / discharge current of 1.0 mA / cm ² and the other test conditions were the same as in Example 2. The result is shown in FIG. NiSi ₂ -NiSi mixed phase 2
Showed almost the same charge / discharge characteristics without depending on the charge / discharge rate, but with NiSi ₂ and NiSi ₂ —NiSi mixed phase 1, when the charge / discharge rate was increased, cycle deterioration was observed. The negative electrode material having a fine mixed phase structure exhibited stable charge / discharge characteristics even at different charge / discharge rates.

Example 5 A 20 μm thick Al foil was coated with Li
CoO ₂ active material, artificial graphite and PVDF in a weight ratio of 87:
A 9: 4 mixture was applied to both sides so as to have a thickness of 90 μm on one side, dried and rolled, and a 20 μm thick Cu
A negative electrode prepared by applying a mixture of NiSi ₂ -NiSi mixed phase 2 powder prepared in Example 2 and artificial graphite and PVDF at a weight ratio of 86: 8: 6 on both sides to a thickness of 50 μm on one side, and then drying and rolling the foil. 22, and a polyethylene porous separator 23 having a thickness of 25 μm were wound as shown in FIG. 5 and housed in a battery can having an outer size of 18 × 65 mm, and 1 M was used as an electrolyte.
The characteristics were evaluated using LiPF ₆ -EC / DMC.

The test conditions were a charge / discharge rate of 0.5 C, a charge end voltage of 4.2 V, and a discharge end voltage of 2.5 V. As a result, an energy density of 400 Wh / l was obtained,
The performance was stable up to the cycle.

[0039]

According to the present invention, an intermetallic compound phase containing a group 3B, 4B, or 5B element as one of the constituent elements, and a phase other than the intermetallic compound constituted by the elements contained in the intermetallic compound are used. By using a multi-phase powder containing more than one phase as a negative electrode active material for a lithium secondary battery, mutual structural changes due to charge and discharge are alleviated, particle collapse is suppressed, and the phase interface is a Li diffusion bypass. In order to promote the diffusion of Li, a lithium secondary battery having a large charge / discharge capacity, a small irreversible capacity, a long charge / discharge cycle life, and excellent rate characteristics can be provided.

[Brief description of the drawings]

FIG. 1 shows charge / discharge cycle characteristics of an Mg ₂ Si-based negative electrode material of the present invention and TJSP.

FIG. 2 shows charge / discharge cycle characteristics of a NiSi ₂ -based negative electrode material.

FIG. 3 shows charge-discharge cycle characteristics of an Mg-containing intermetallic compound.

FIG. 4 shows charge / discharge cycle characteristics of a NiSi ₂ -based negative electrode material by high-speed charge / discharge.

FIG. 5 is a configuration diagram of a cylindrical battery of the present invention.

[Explanation of symbols]

1 ... Charge / discharge cycle characteristic curve of Mg ₂ Si powder, 2 ... M
g ₂ Si—Si mixed phase powder charge / discharge cycle characteristic curve, 3
... Mg ₂ Si -Si mixed charge-discharge cycle characteristics curves of the powder, the charge-discharge cycle characteristics curves of the 4 ... TJSP, 5 ... Mg
Charge-discharge cycle characteristic curve of ₂ Si-Mg mixed phase powder, 6 ...
Charge / discharge cycle characteristic curve of NiSi ₂ -Si mixed phase powder,
7 ... charge-discharge cycle characteristics curves of NiSi ₂ powder, 8 ... N
i Si ₂ -NiSi multiphase 1 charge-discharge cycle characteristics curves of the powder, 9 ... charge-discharge cycle characteristics curves of NiSi ₂ -NiSi multiphase 2 powder, charge-discharge cycle characteristics curves of 10 ... NiSi ₂ -Si mixed powder, 11 ... Mg ₂ Ge charge-discharge cycle characteristics curves of -Ge multiphase powder, 12 ... Mg ₂ Sn-Mg mixed phase charge-discharge cycle characteristics curves of the powder, 13 ... Mg ₂ Pb-
Charge / discharge cycle characteristic curve of Mg mixed phase powder, 14 ... NiS
High-speed charge / discharge cycle characteristic curve of i ₂ powder, 15 ... NiS
i ₂ -NiSi multiphase 1 powder fast charge-discharge cycle characteristic curve, 16 ... NiSi ₂ -NiSi multiphase 2 powder high-speed charge-discharge cycle characteristic curve, 21 ... positive electrode, 22 ... negative electrode, 23 ...
Separator, 24: Positive terminal, 25: Negative terminal.

Continued on the front page (72) Inventor Hideki Shinohara 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Li Sun 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd.Hitachi Research Laboratories (72) Inventor Masatoshi Inagaki 1-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd.Hitachi Research Laboratories (72) Inventor Yasuhisa Aono 7, Omikacho, Hitachi City, Ibaraki Prefecture No. 1-1 Inside Hitachi, Ltd. Hitachi Research Laboratory (72) Inventor Hideyo Kodama 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Research Laboratory

Claims (6)

[Claims] 1. A lithium secondary battery comprising a negative electrode mainly composed of a negative electrode active material that occludes and releases lithium ions during charge and discharge, a positive electrode, and a lithium ion conductive non-aqueous electrolyte or polymer electrolyte. The active material may include a phase of an intermetallic compound containing a 3B, 4B, or 5B group element in the periodic table, and may be composed of particles including two or more phases in the material structure, and all of the phases may occlude Li. A rechargeable lithium battery characterized by being able to. 2. A lithium secondary battery comprising a negative electrode mainly composed of a negative electrode active material that occludes and releases lithium ions during charge and discharge, a positive electrode, and a lithium ion conductive non-aqueous electrolyte or polymer electrolyte. Particles in which the active material contains a phase of an intermetallic compound containing a 3B, 4B, or 5B group element in the periodic table, and contains at least one phase other than the intermetallic compound constituted by an element contained in the intermetallic compound. A lithium secondary battery characterized by comprising: 3. A lithium secondary battery comprising a negative electrode mainly composed of a negative electrode active material that occludes and releases lithium ions during charge and discharge, a positive electrode, and a lithium ion conductive non-aqueous electrolyte or polymer electrolyte. Active material is A
1, Ga, In, Si, Ge, Sn, Pb, Sb, Bi
Characterized by comprising particles of at least one phase of an intermetallic compound containing at least one kind thereof, and at least one phase other than the intermetallic compound, which is composed of an element contained in the intermetallic compound. Lithium secondary battery. 4. A lithium secondary battery comprising a negative electrode mainly composed of a negative electrode active material that occludes and releases lithium ions during charge and discharge, a positive electrode, and a lithium ion conductive non-aqueous electrolyte or polymer electrolyte. Active material is A
1, Ga, In, Si, Ge, Sn, Pb, Sb, Bi
A phase of an intermetallic compound containing at least one or more of the above, and a particle containing at least one phase other than the intermetallic compound composed of elements contained in the intermetallic compound, and a cross section of the particle. A lithium secondary battery, wherein the interface length of a plurality of intermetallic compound phases adjacent on the structure is 5 × 10 ⁶ m / m ² or more. 5. A lithium secondary battery comprising a negative electrode mainly composed of a negative electrode active material that occludes and releases lithium ions during charge and discharge, a positive electrode, and a lithium ion conductive non-aqueous electrolyte or polymer electrolyte. Active material is A
1, Ga, In, Si, Ge, Sn, Pb, Sb, Bi
A phase of an intermetallic compound or a metal which is composed of elements contained in the intermetallic compound and which is adjacent to the intermetallic compound on a phase diagram. A lithium secondary battery comprising particles containing more than one phase. 6. A lithium secondary battery comprising a negative electrode mainly composed of a negative electrode active material that occludes and releases lithium ions during charge and discharge, a positive electrode, and a lithium ion conductive non-aqueous electrolyte or polymer electrolyte. Active material is A
1, Ga, In, Si, Ge, Sn, Pb, Sb, Bi
A phase of an intermetallic compound or a metal which is composed of elements contained in the intermetallic compound and which is adjacent to the intermetallic compound on a phase diagram. A lithium secondary battery comprising particles containing at least one phase, wherein an interface length of a plurality of phases adjacent to each other on the sectional structure of the particles is 5 × 10 ⁶ m / m ² or more.