JPH10208777A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-aqueous electrolyte secondary battery retaining the strength of a battery container and high weight energy density. SOLUTION: In a non-aqueous electrolyte secondary battery constituted of a cathode comprising a lithium-containing compound, an anode comprising a material which can be doped and dedoped with lithium, and a non-aqueous electrolyte, a plate-like member having a first layer of aluminum 2 or an aluminum alloy and a second layer of a metal which is not alloyed with lithium is produced and a battery container 1 is made of the plate-like member while setting the second layer on the inside. The second layer is made of one of material selected from steel, stainless steel 3, nickel, copper, and titanium. The thickness (a) of the first layer of the plate-like member and the thickness (b) of the second layer are controlled as to have the following relation; 0.25<=a/(a-b)<=0.9.

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 an improvement in weight energy density and reliability of a non-aqueous electrolyte secondary battery.

[0002]

2. Description of the Related Art Recent advances in electronic technology have made electronic devices smaller, higher in performance and more portable, and accordingly, there has been an increasing demand for higher energy density of batteries used in these electronic devices. Conventionally, secondary batteries used in these electronic devices include nickel-cadmium batteries and lead batteries, but these batteries have a low discharge potential and sufficiently meet the demand for batteries with a high energy density. There is no fact.

[0003] Recently, lithium secondary batteries have attracted attention as a battery system that meets these requirements, and are being actively studied. However, lithium secondary batteries using metal lithium or a lithium alloy as a negative electrode have been recognized as having problems such as cycle life and rapid charging performance, and have become a major obstacle to practical use. These problems are considered to be caused by dissolution of metallic lithium as a negative electrode, generation of dendrite at the time of deposition, and miniaturization, and only some of them are practically used as coin type.

In order to solve these problems, research and development of a lithium ion secondary battery (non-aqueous electrolyte secondary battery) using a material capable of doping and undoping lithium ions such as a carbonaceous material as a negative electrode. Has been done. In this lithium ion secondary battery, lithium does not exist in a metal state, so there is no problem such as cycle deterioration caused by the metal lithium negative electrode, and the voltage of the battery is increased by using a lithium compound having a high oxidation-reduction potential for the positive electrode. Therefore, it has the feature of having a high energy density.

Further, self-discharge is smaller than that of nickel-cadmium batteries, and these characteristics make it possible to reduce the discharge rate to 8 m / mV.
Commercialization has started as a power source for portable electronic devices such as TRs, CD players, laptop computers, and cellular telephones. Further, from the viewpoint of space efficiency of electronic devices, batteries having a rectangular or oval shape have been required.

However, rectangular or oblong batteries have the following problems. The battery container of the non-aqueous electrolyte secondary battery is generally made of nickel-plated steel or stainless steel in terms of corrosion resistance and strength. However, these materials have a high specific gravity and are heavy, so that the weight energy density of the battery is small. In particular, in a thin rectangular battery, the weight of the battery container accounts for a large proportion of the battery weight, and the weight energy density is further reduced.

Therefore, as proposed in Japanese Patent Application Laid-Open No. H6-163025, it has been studied to reduce the weight of the battery by using a material having a low specific gravity, such as aluminum, for the battery container. However, when the battery is stored at a high temperature and gas is generated by decomposition of the electrolytic solution to increase the internal pressure of the battery, the battery container may swell and deform because aluminum has a lower strength than steel or stainless steel. was there. In order to prevent this, it is necessary to increase the thickness of the battery container and improve the strength, but as a result,
There is a problem that the volume in the battery container is reduced and the weight energy density is reduced.

Further, Japanese Patent Application Laid-Open No. H4-249072 proposes using an aluminum clad material with an aluminum layer inside a battery container. Since aluminum clad material is used, the strength is higher than a battery container made of only aluminum, and it is possible to suppress the deformation of the battery container even if the internal pressure of the battery rises.However, the aluminum layer is placed inside the battery container. Therefore, there is a problem that the polarity is reversed with respect to a conventionally manufactured battery and compatibility is lost.

[0009]

Accordingly, an object of the present invention is to provide a positive electrode using a lithium-containing compound, a negative electrode using a lithium-doped and undoped material, and a non-aqueous electrolyte comprising a non-aqueous electrolyte. It is an object of the present invention to provide a non-aqueous electrolyte secondary battery having compatibility with conventional batteries, high weight energy density, and high reliability and productivity.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been made in consideration of the above-mentioned problems. The present invention provides a positive electrode using a lithium-containing compound, a negative electrode using a lithium-doped and undoped material, and a non-aqueous material. In a non-aqueous electrolyte secondary battery comprising an electrolyte, a plate-like member having aluminum or an aluminum alloy as a first layer and a metal not forming an alloy with lithium as a second layer is formed, and the plate-like member is formed. The battery container is constituted with the second layer of the above as the inside.

The second layer is made of any one of the group consisting of steel, stainless steel, nickel, copper, and titanium.

Further, the plate thickness of the first layer of the plate member is a
When the thickness of the second layer is b, 0.25 ≦
A battery container is formed from a plate-like member having a relationship of a / (a + b) ≦ 0.9, and a non-aqueous electrolyte secondary battery is configured using the battery container to solve the above problem.

Therefore, the battery container according to the present invention has sufficient strength, and a non-aqueous electrolyte secondary battery using the battery container can be configured such that the outside of the battery container is a negative electrode and the inside is a positive electrode. Therefore, compatibility with the conventional one can be maintained.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have proposed a non-aqueous electrolyte comprising a positive electrode using a lithium-containing compound, a negative electrode using a lithium-doped and undoped material, and a non-aqueous electrolyte. In a secondary battery, a plate-like member (hereinafter, referred to as “aluminum clad material”) having aluminum or an aluminum alloy as a first layer and a metal that does not form an alloy with lithium as a second layer is used. It has been found that by forming a battery container with the above layer inside, a secondary battery having a large weight energy density and being compatible with conventional batteries can be obtained.

Next, the non-aqueous electrolyte secondary battery of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view of a battery container using an aluminum clad material according to the present invention, FIG. 2 is a cross-sectional view of a first experimental example of a nonaqueous electrolyte secondary battery, and FIG. Non-aqueous electrolyte secondary batteries using a battery container in the first to fourth embodiments and the second to fourth embodiments
It is sectional drawing of the experiment example of FIG.

The battery case 1 has a thickness a as shown in FIG.
An aluminum clad material in which aluminum 2 and stainless steel 3 having a thickness b are layered.
Is on the outside and the stainless steel 3 is on the inside to constitute the battery case 1.

First, although the aluminum plate thickness of the conventional battery container was 0.7 mm, the relationship between the plate thicknesses of aluminum 2 and stainless steel 3 was determined so as to obtain an aluminum clad material having the same strength. Table 1 shows the results.

[0018]

[Table 1]

According to Table 1, when the ratio of the aluminum 2 to the total plate thickness is less than 23%, the contribution to the weight of the stainless steel 3 increases, and the battery container 1 becomes heavy, so that an improvement in the weight energy density is prevented. On the other hand, when it is 92% or more, the weight of the battery case 1 is reduced, but the total thickness is increased, the internal volume of the battery case 1 is reduced, and the amount of stored electric energy is reduced.

Therefore, the inventors of the present invention have concluded that the configuration of the aluminum cladding material used as the battery container 1 is such that the thickness of the aluminum 2 is a and the thickness of the stainless steel 3 is b.
Then, those satisfying the relationship of 0.25 ≦ a / (a + b) ≦ 0.90 (1) ensure the strength of the battery container 1,
In addition, it was recognized that the effect was large in increasing the weight energy density, and the range was determined.

The material inside the battery case 1 is not limited to the stainless steel 3 described above, but may be any metal that does not form an alloy with lithium, such as steel, nickel, or the like.
Copper, titanium, or the like can be used. At this time, the relationship between the aluminum 2 and the thickness of these metals is naturally determined based on the strength of each material. Also,
By setting the aluminum 2 to the outside, the same polarity as in the related art is maintained inside and outside of the battery case 1, and compatibility is obtained.

Next, an embodiment and an experimental example of a rectangular non-aqueous electrolyte secondary battery using the above-mentioned battery container 1 will be described with reference to FIGS. 2 and 3. FIG.

First, a lithium-containing composite oxide Li _X MO ₂ (M is one or more kinds of transition metals) is used as a positive electrode active material. In particular, LiCoO ₂ , LiNi
Lithium composite oxides such as O ₂ , LiNi _Y Co _{1 -Y} O ₂ and LiMn ₂ O ₄ are preferred. These lithium composite oxides can be synthesized using, for example, lithium, cobalt, nickel, and manganese carbonates, nitrates, oxides, and hydroxides as starting materials. The starting materials are weighed and mixed according to a predetermined composition, and the starting materials are mixed in an oxygen-containing atmosphere at 600 to 10%.
This is obtained by firing at 00 ° C.

On the other hand, as the negative electrode active material, a carbon material capable of doping and undoping lithium with the charge / discharge reaction can be used, and any material capable of doping and undoping lithium can be used. A low-crystalline carbon material obtained by firing at a relatively low temperature of 2000 ° C. or lower, a high-crystalline carbon material such as artificial graphite obtained by treating a material that is easily crystallized at a high temperature of about 3000 ° C., or natural graphite is used.

For example, pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke, etc.), graphites, glassy carbons, and organic polymer compound fired products (furan resin, etc.) ), Carbon fiber, activated carbon and the like can be used.

The carbon material used in the present invention includes:
A low-crystalline carbon material having a (002) plane spacing of at least 0.370 nm, a true specific gravity of less than 1.70, and having no exothermic peak at 700 ° C. or more in differential thermal analysis in an air stream; In order to obtain the mixture filling property, it is preferable to use a highly crystalline graphite material having a true specific gravity of 2.10.

Furthermore, not only a low-crystalline carbon material and a high-crystalline graphite material can be used alone, but also a coexistence of a graphite material and a low-crystalline carbonaceous material can be used. The proportion of the low crystalline carbon material in the coexisting body is limited to 10% to 90%, more preferably 20% to 80%, based on the total weight of the negative electrode carbon coexisting body.

As the electrolytic solution, an electrolytic solution in which a lithium salt is used as a supporting electrolyte and this is dissolved in an organic solvent is used.
Here, a mixed solvent of a cyclic carbonate and a chain carbonate is used as the organic solvent. As the cyclic carbonate, propylene carbonate, ethylene carbonate, butylene carbonate and the like can be used. In addition, as the chain carbonates, dimethyl carbonate, diethyl carbonate, which are symmetric chain carbonates,
Dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, etc. which are asymmetric chain carbonates can be used.

As the supporting electrolyte, LiCl, LiBr, LiCF ₃ S generally used for lithium batteries are used.
O ₃ , LiClO ₄ , LiAsF ₆ , LiPF ₆ , Li
BF ₄ or the like can be used alone or in combination of two or more. The non-aqueous electrolyte is not limited to a liquid, and a conventionally known solid electrolyte can be used.

Experimental Example 1 The negative electrode 4 was manufactured as follows. The negative electrode active material uses petroleum pitch as a starting material, and this is converted to a functional group containing oxygen of 10 to 10.
After introducing 20% (oxygen crosslinking), 1000% in an inert gas
A non-graphitizable carbon material having properties close to those of a glassy carbon material obtained by firing at ℃ was used. 90% by weight of the carbon material thus obtained and 10% by weight of polyvinylidene fluoride as a binder were mixed to prepare a negative electrode mixture.
It was dispersed in methyl-2-pyrrolidone to form a slurry. Further, the slurry is mixed with a negative electrode current collector 5 having a thickness of 10%.
It was applied on both sides of a copper foil having a thickness of μm, dried and then compression-molded with a roller press to obtain a negative electrode 4.

The positive electrode 6 was manufactured as follows. First, the positive electrode active material is Li / Co with lithium carbonate and cobalt oxide.
Is mixed so that the ratio becomes 1/1, 900 ° C. in air,
It was obtained by firing for 5 hours. X-ray diffraction measurement of this material showed a good match with the JCPDS card. Thereafter, by pulverizing, LiCoO ₂ having a desired particle size is obtained. Next, this LiCoO
₂ as a positive electrode active material, 91% by weight of LiCoO ₂ , 6% by weight of graphite as a conductive material, and 3% by weight of polyvinylidene fluoride to prepare a positive electrode mixture, which is dispersed in N-methyl-2-pyrrolidone. To form a slurry. Further, this slurry was applied to both surfaces of a 20 μm-thick aluminum foil serving as a positive electrode current collector 7, dried, and then compression-molded with a roller press to obtain a positive electrode 6.

The negative electrode 4 and the positive electrode 6 produced as described above are cut into predetermined dimensions, respectively, and they are alternately laminated with a separator 8 made of a microporous polyethylene film having a thickness of 30 μm interposed therebetween. It was created.

As shown in FIG. 2, the above-mentioned electrode body 9 is
The value of / (a + b) is 1.0, that is, the thickness is 0.7 m
Insulating plate 10 was placed under electrode body 9 and housed in battery case 1 consisting of a single layer of m (3003 alloy) alone. Next, the positive electrode lead 11 is led out of the positive electrode current collector 7 and welded to the inside of the battery case 1.
2 is drawn out from the negative electrode current collector 5 and welded to the negative electrode terminal 15 provided on the battery lid 13 via the gasket 14.
The electrolyte used was a solution in which the supporting electrolyte LiPF ₆ was dissolved at a ratio of 1 mol / l in an organic solvent in which propylene carbonate and diethyl carbonate were mixed at a ratio of 1: 1. After electrolyte injection, thickness 9mm, width 34mm, height 48
mm non-aqueous electrolyte secondary battery 20 was produced. In order to obtain a safer sealed non-aqueous electrolyte secondary battery,
It is desirable to have a means for interrupting the current in response to a rise in battery internal pressure when an abnormality occurs during overcharging.

EXPERIMENTAL EXAMPLE 2 As shown in FIG. 3, aluminum (3003 alloy) having a value of a / (a + b) of 0.92 and a thickness of 0.6 mm.
The above-described electrode body 9 was housed in a battery case 1 made of an aluminum clad material made of SUS304 and SUS304, and an insulating plate 10 was arranged below the electrode body. Next, the positive electrode lead 11
From the positive electrode current collector 7 and the gasket 1
4 is welded to the positive electrode terminal 16 provided. On the other hand, the negative electrode lead 12 was led out of the negative electrode current collector 5 and was welded to the stainless steel 3 inside the battery container 1. Otherwise in the same manner as in Experimental Example 1, a non-aqueous electrolyte secondary battery 21 was produced.

In the structure of the battery case 1, the battery case 1 serves as a positive terminal in the experimental example 1, and serves as a negative terminal in the experimental example 2. In Examples 1 to 4 and Experimental Examples 3 to 4 described below, the battery container 1 also serves as a negative electrode terminal.

Example 1 The value of a / (a + b) is 0.82 and the thickness is 0.5 m
A nonaqueous electrolyte secondary battery 21 was produced in the same manner as in Experimental Example 2, except that the battery case 1 made of an aluminum clad material made of m (3003 alloy) and SUS304 was used.

Example 2 The value of a / (a + b) is 0.71 and the thickness is 0.4 m
A nonaqueous electrolyte secondary battery 21 was produced in the same manner as in Experimental Example 2, except that the battery case 1 made of an aluminum clad material made of m (3003 alloy) and SUS304 was used.

Example 3 The value of a / (a + b) is 0.58 and the thickness is 0.3 m
A nonaqueous electrolyte secondary battery 21 was produced in the same manner as in Experimental Example 2, except that the battery case 1 made of an aluminum clad material made of m (3003 alloy) and SUS304 was used.

Example 4 The value of a / (a + b) is 0.42 and the thickness is 0.2 m
A nonaqueous electrolyte secondary battery 21 was produced in the same manner as in Experimental Example 2, except that the battery case 1 made of an aluminum clad material made of m (3003 alloy) and SUS304 was used.

Experimental Example 3 The value of a / (a + b) was 0.23 and the thickness was 0.1 m.
A nonaqueous electrolyte secondary battery 21 was produced in the same manner as in Experimental Example 2, except that the battery case 1 made of an aluminum clad material made of m (3003 alloy) and SUS304 was used.

EXPERIMENTAL EXAMPLE 4 Non-aqueous electrolysis was performed in the same manner as in Experimental Example 2 except that the value of a / (a + b) was 0, that is, the battery container 1 was made of only SUS304 material having a thickness of 0.38 mm. Liquid secondary battery 2
1 was produced.

With respect to the nonaqueous electrolyte secondary batteries 20 and 21 of Examples 1 to 4 and Examples 1 to 4, the charging voltage was 4.2.
The battery was charged under the conditions of 0 V, a charging current of 950 mA, and a charging time of 2.5 h, a discharging current of 190 mA, and a final voltage of 2.75 V.
The battery was discharged under the following conditions, and the initial capacity and average voltage of the battery were measured to determine the weight energy density. Table 2 shows the results.
Shown in

[0043]

[Table 2]

According to Table 2, the ratio of the thickness of the aluminum 2 to the thickness of the aluminum clad material, a / (a + b), is set to 25% or more and 90% or less, and the battery container 1 is formed with the aluminum 2 outside. This indicates that the battery is compatible with the conventional battery and the weight energy density is increased.

Although the material of aluminum 2 is 3003, other aluminum alloys may be used. Also,
Although SUS304 was used as the metal of one layer, any metal that does not form an alloy with lithium may be used as described above. In addition, although the description has been given using a rectangular battery as an example, the present invention can be applied to a cylindrical, coin-type, or button-type battery, and it goes without saying that the same effect can be obtained. Furthermore, it is natural that the electrode body may be formed in a spiral shape.

[0046]

As is apparent from the above description, according to the nonaqueous electrolyte secondary battery of the present invention, the battery container can have sufficient strength and the outside of the battery container can be used as the negative electrode. On the other hand, it is possible to provide a nonaqueous electrolyte secondary battery having a large weight energy density that can be configured with a positive electrode on the inner side and that can maintain compatibility with a conventional battery.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a battery container using an aluminum clad material according to the present invention.

FIG. 2 is a sectional view of a first experimental example of a non-aqueous electrolyte secondary battery.

FIG. 3 is a cross-sectional view of first to fourth embodiments and second to fourth experimental examples of a nonaqueous electrolyte secondary battery using the battery container according to the present invention.

[Explanation of symbols]

1 ... battery container, 2 ... aluminum, 3 ... stainless steel, 4
... a negative electrode, 5 ... a negative electrode current collector, 6 ... a positive electrode, 7 ... a positive electrode current collector,
8 separator, 9 electrode body, 10 insulating plate, 11 positive electrode lead, 12 negative electrode lead, 13 battery cover, 14 gasket, 15 negative electrode terminal, 16 positive electrode terminal, 20, 2
1: Non-aqueous electrolyte secondary battery

Claims (3)

[Claims] A non-aqueous electrolyte secondary battery comprising a positive electrode using a lithium-containing compound, a negative electrode using a lithium-doped and undoped material, and a non-aqueous electrolyte, wherein aluminum or aluminum alloy is used. As a first layer, a plate-like member having a second layer of a metal that does not form an alloy with lithium is formed, and a battery container is configured with the second layer of the plate-like member inside. Non-aqueous electrolyte secondary battery. 2. The second layer is of steel, stainless steel,
The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte secondary battery is formed of any one of a group consisting of nickel, copper, and titanium. 3. When the thickness of the first layer is a and the thickness of the second layer is b, the relationship of 0.25 ≦ a / (a + b) ≦ 0.9 is satisfied. The non-aqueous electrolyte secondary battery according to claim 1, wherein: