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Negative electrode active material , nonaqueous electrolyte battery, battery pack and vehicle

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Negative electrode active material , nonaqueous electrolyte battery, battery pack and vehicle


A negative electrode active material includes lithium-titanium composite oxide porous particles having an average pore size of 50 to 500 Å.
Related Terms: Electrode Electrolyte Lithium Battery Pack Titanium

USPTO Applicaton #: #20130029228 - Class: 4292311 (USPTO) - 01/31/13 - Class 429 
Chemistry: Electrical Current Producing Apparatus, Product, And Process > Current Producing Cell, Elements, Subcombinations And Compositions For Use Therewith And Adjuncts >Electrode >Chemically Specified Inorganic Electrochemically Active Material Containing >Alkalated Transition Metal Chalcogenide Component Is Active Material

Inventors: Hiroki Inagaki, Norio Takami

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The Patent Description & Claims data below is from USPTO Patent Application 20130029228, Negative electrode active material , nonaqueous electrolyte battery, battery pack and vehicle.

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CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2005-199457, filed Jul. 7, 2005, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a negative electrode active material, a nonaqueous electrolyte battery using the negative electrode active material, a battery pack using the nonaqueous electrolyte battery, and a vehicle having the battery pack mounted thereto.

2. Description of the Related Art

Vigorous research is being conducted on a nonaqueous electrolyte battery in which the battery is charged and discharged by the migration of lithium ions between the negative electrode and the positive electrode in an attempt to develop a high energy density battery.

The nonaqueous electrolyte battery is required to satisfy various characteristics depending on the use of the battery. For example, it is desirable for the nonaqueous electrolyte battery used as a power source of a digital camera to achieve the discharge not lower than about 3 C, and for the nonaqueous electrolyte battery mounted to a vehicle such as a hybrid automobile to achieve the discharge not lower than about 10 C. Such being the situation, the nonaqueous electrolyte battery used in the fields exemplified above is required to exhibit an excellent charge-discharge cycle life when the charge-discharge is repeated under a large current.

The nonaqueous electrolyte battery available on the market nowadays comprises a positive electrode in which a lithium-transition metal composite oxide is used as the positive electrode active material and a negative electrode in which a carbonaceous material is used as the negative electrode active material. In general, Co, Mn, Ni, etc. are used as the transition metals contained in the lithium-transition metal composite oxide used as the positive electrode active material.

In recent years, a nonaqueous electrolyte battery in which lithium-titanium oxide having a high Li ion insertion potential, compared with the carbonaceous material, is used as a negative electrode active material has been put to the practical use. The lithium-titanium oxide is small in change of volume accompanying the charge-discharge operation of the secondary battery, and, thus, permits the nonaqueous electrolyte battery using the lithium-titanium oxide as the negative electrode active material to be excellent in the charge-discharge cycle characteristics, compared with the nonaqueous electrolyte battery using the carbonaceous material as the negative electrode active material. Particularly, it is desirable to use lithium titanate having a spinel structure as the negative electrode active material.

For example, Japanese Patent Disclosure (Kokai) No. 09-199179 discloses a nonaqueous electrolyte battery comprising lithium titanate, which is small in change of volume during the charge-discharge operation of the secondary battery, as the negative electrode active material. It is taught that the nonaqueous electrolyte battery is small in change of volume, and that the short circuiting and the decrease of the battery capacity accompanying the swelling of the electrode are unlikely to take place.

On the other hand, Japanese Patent Disclosure No. 09-309727 refers to secondary particles of lithium titanate having a laminate structure constructed such that a plurality of plate-like or flake-like lithium titanate primary particles are superposed one upon the other. It is taught that pores, each sized about 4 nm (40 Å), are formed among the primary particles to increase the specific surface area of the secondary particles of lithium titanate.

BRIEF

SUMMARY

OF THE INVENTION

An object of the present invention is to provide a negative electrode active material excellent in the large current characteristics and in the charge-discharge cycle characteristics, a nonaqueous electrolyte battery using the negative electrode active material, a battery pack using the nonaqueous electrolyte battery, and a vehicle using the battery pack.

According to a first aspect of the present invention, there is provided a nonaqueous electrolyte battery, comprising:

a positive electrode;

a negative electrode containing lithium-titanium composite oxide porous particles having an average pore size of 50 to 500 Å; and

a nonaqueous electrolyte.

According to a second aspect of the present invention, there is provided a battery pack, comprising nonaqueous electrolyte batteries, each comprising:

a positive electrode;

a negative electrode containing lithium-titanium composite oxide porous particles having an average pore size of 50 to 500 Å; and

a nonaqueous electrolyte.

According to a third aspect of the present invention, there is provided a negative electrode active material comprising lithium-titanium composite oxide porous particles having an average pore size of 50 to 500 Å.

Further, according to a fourth aspect of the present invention, there is provided a vehicle comprising a battery pack including nonaqueous electrolyte batteries, each comprising:

a positive electrode;

a negative electrode containing lithium-titanium composite oxide porous particles having an average pore size of 50 to 500 Å; and

a nonaqueous electrolyte.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a cross sectional view schematically showing the construction of a flat type nonaqueous electrolyte battery according to a first embodiment of the present invention;

FIG. 2 is a cross sectional view showing in detail in a magnified fashion the construction of the circular region A of the nonaqueous electrolyte battery shown in FIG. 1;

FIG. 3 is an oblique view, partly broken away, schematically showing the construction of another nonaqueous electrolyte battery according to the first embodiment of the present invention;

FIG. 4 is a cross sectional view showing in a magnified fashion the construction of region B of the nonaqueous electrolyte battery shown in FIG. 3;

FIG. 5 is an oblique view showing in a dismantled fashion the construction of the battery pack according to a second embodiment of the present invention;

FIG. 6 is a block diagram showing the electric circuit of the battery pack shown in FIG. 5;

FIG. 7 is a graph showing the log differential pore volume distribution of the negative electrode active material measured by the gas adsorption method (BHJ analytical result (desorption side));

FIG. 8 is a graph showing the particle diameter distribution, as determined by the laser diffraction, of the negative electrode active material for Example 1;

FIG. 9 is a photo by a scanning electron microscope (SEM) showing the lithium titanate having the spinel structure for Example 2; and

FIG. 10 shows the X-ray diffraction pattern of the lithium titanate having the spinel structure for Example 2.

DETAILED DESCRIPTION

OF THE INVENTION

A lithium-titanium composite oxide is small in change of volume accompanying the charge-discharge operation of the battery, i.e., accompanying the absorption-release of lithium ions. The electrode containing the composite oxide as the active material is unlikely to be swollen. On the other hand, the volume of the negative electrode available on the market, which contains a carbonaceous material such as graphite as the negative electrode active material, is expanded or shrunk by several percent in accordance with the charge-discharge operation of the battery. As a result, where, for example, graphite is used as the negative electrode active material, the nonaqueous electrolyte is diffused in accordance with the expansion and shrinkage of the electrode. As a result, the impregnation of the negative electrode with the nonaqueous electrolyte tends to be made uniform. Alternatively, the concentration of the lithium salt tends to be made uniform. It has been found, however, that the electrode containing a lithium-titanium composite oxide and, thus, small in change of volume, is markedly poor in the impregnation capability with the nonaqueous electrolyte. Particularly, in the case of manufacturing a large battery mounted to, for example, a vehicle, the poor impregnation capability of the electrode with the nonaqueous electrolyte lowers not only the productivity but also the battery performance, in particular, the large current performance and the charge-discharge cycle characteristics.

Under the circumstances, the present inventors have strongly pulverized the lithium-titanium composite oxide powder containing the lithium-titanium oxide having a spinel structure as the main phase, followed by baking again the pulverized material under an appropriate heat treating condition to succeed in the synthesis of lithium-titanium composite oxide porous particles having an average pore size of 50 to 500 Å. It has been found that, by synthesizing the lithium-titanium composite oxide porous particles having an average pore size of 50 to 500 Å, it is possible to markedly improve the impregnation capability of the negative electrode with the nonaqueous electrolyte to improve not only the productivity but also the large current characteristics and the charge-discharge cycle life of the battery. Incidentally, the impregnation capability of the negative electrode with the nonaqueous electrolyte can be further improved, if the specific pore volume of the lithium-titanium composite oxide porous particles is not smaller than 0.01 mL/g.

It should also be noted that, if the specific volume of pores having a size not larger than 10 Å, i.e., so-called micro pores, is not smaller than 0.001 mL/g in the lithium-titanium composite oxide porous particles having the average pore size noted above, it is possible to permit the lithium ions to be migrated to reach the region that was not involved in the reaction in the past. As a result, it is possible to realize the lithium absorption capability close to the theoretical capacity of the lithium-titanium oxide to increase the energy density of the battery.

Some embodiments of the present invention will now be described with reference to the accompanying drawings. Incidentally, the common constituents of the invention are denoted by the same reference numerals in the accompanying drawings to omit the overlapping description. Also, the accompanying drawings are schematic drawings that are simply intended to facilitate the description and understanding of the invention. It is possible for the shape, the size, the ratio, etc. shown in the drawing to differ from those of the actual battery. Of course, the design relating to the size, shape, etc. can be changed appropriately in view of the description given below and the known technology.

First Embodiment

An example of the construction of the unit cell, i.e., nonaqueous electrolyte battery, according to the first embodiment of the present invention will now be described with reference to FIGS. 1 and 2.

Specifically, FIG. 1 is a cross sectional view schematically showing the construction of a flat type nonaqueous electrolyte battery according to a first embodiment of the present invention, and FIG. 2 is a cross sectional view schematically showing in detail in a magnified fashion the construction of the circular region A of the nonaqueous electrolyte battery shown in FIG. 1.

As shown in FIG. 1, a flat type wound electrode group 6 is housed in a case 7. The wound electrode group 6 is formed of a laminate structure comprising a positive electrode 3, a negative electrode 4, and a separator 5 interposed between the positive electrode 3 and the negative electrode 4. The electrode group 6 is obtained by spirally winding the laminate structure noted above. Further, a nonaqueous electrolyte is retained by the wound electrode group 6.

As shown in FIG. 2, the negative electrode 4 is positioned to constitute the outermost circumferential region of the wound electrode group 6. Also, the positive electrode 3 and the negative electrode 4 are alternately laminated one upon the other with the separator 5 interposed therebetween. For example, the separator 5, the positive electrode 3, the separator 5, the negative electrode 4, the separator 5, the positive electrode 3 and the separator 5 are laminated one upon the other in the order mentioned. The negative electrode 4 comprises a negative electrode current collector 4a and a negative electrode active material-containing layer 4b supported by the negative electrode current collector 4a. In that region of the negative electrode 4 which constitutes the outermost circumferential region, the negative electrode active material-containing layer 4b is formed on one surface of the negative electrode current collector 4a. On the other hand, the positive electrode 3 comprises a positive electrode current collector 3a and a positive electrode active material-containing layer 3b supported by the positive electrode current collector 3a.

As shown in FIG. 1, a band-like positive electrode terminal 1 is electrically connected to the positive electrode current collector 3a in the vicinity of the outer circumferential region of the wound electrode group 6. On the other hand, a band-like negative electrode terminal 2 is electrically connected to the negative electrode current collector 4a in the vicinity of the outer circumferential region of the wound electrode group 6. Further, the tip portions of the positive electrode terminal 1 and the negative electrode terminal 2 are withdrawn to the outside of the case 7 via the same side of the case 7.

The negative electrode, the nonaqueous electrolyte, the positive electrode, the separator, the case, the positive electrode terminal and the negative electrode terminal will now be described in detail.

1) Negative Electrode

The negative electrode comprises a negative electrode current collector and a negative electrode layer supported on one surface or both surfaces of the negative electrode current collector and containing a negative electrode active material, a negative electrode conductive agent and a binder.



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stats Patent Info
Application #
US 20130029228 A1
Publish Date
01/31/2013
Document #
13644500
File Date
10/04/2012
USPTO Class
4292311
Other USPTO Classes
423598, 241 23, 241 17
International Class
/
Drawings
9


Electrode
Electrolyte
Lithium
Battery Pack
Titanium


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