JP2000149953A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery whose current breaking means is operated surely, even when a nonaqueous electrolyte secon dary battery with the means is over-charged. SOLUTION: A positive active material is mainly composed of the first active material (LixNiyCo1-yO2; 0<x<=1 and 0<=y<0.50) and the second active material (Lix'Niy'Co1-y'O2; 0<x'<=1 and 0.50<=y'<=1.0), and 0.5-70 pts.wt. of the second active material per 100 pts.wt. of total active material is contained. When over- charged to increase a battery voltage, the second active material acts catalytically to promote decomposition of a nonaqueous electrolyte, and gas is generated thereby to increase internal pressure of a battery, so as to operate surely a current breaking means.

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, which is provided with a means for interrupting current in response to an increase in internal pressure, and which operates reliably when overcharged. And a non-aqueous electrolyte secondary battery as described above.

[0002]

2. Description of the Related Art A so-called non-aqueous electrolyte battery using lithium as a substance to be doped and de-doped with respect to a negative electrode and using a non-aqueous electrolyte as an electrolyte is known as a battery having a small self-discharge and excellent storage stability. Especially 5-10
It has been widely used as an electronic wristwatch and a power source for various memory backups that require long-term use for years.

[0003] These conventional nonaqueous electrolyte batteries are usually primary batteries, but there are many demands for rechargeable nonaqueous electrolyte secondary batteries as power sources that can be used economically for a long time. Research is being conducted in various directions. Among them, in particular, non-aqueous electrolyte secondary batteries using metal lithium, lithium alloy or carbonaceous material for the negative electrode and lithium compounds such as lithium-cobalt composite oxide for the positive electrode have a high battery voltage and high voltage. Energy density,
Because of its excellent cycle characteristics, it is expected as a power source for memory backup and small electronic devices.

In general, when the internal structure of a battery is a sealed type, if the internal pressure of the battery rises for some reason, the battery is relatively rapidly damaged, and the battery loses its function or is damaged by peripheral devices. Can also cause damage. In the above-described non-aqueous electrolyte secondary battery, when charging, when a current higher than usual flows to be in an overcharged state, the electrolytic solution is decomposed and gas is generated, so that the battery internal pressure may increase. . In addition, when the above-described overcharge state continues, an abnormal reaction such as rapid decomposition of the electrolyte or the active material proceeds, and the temperature of the battery may increase rapidly.

As a countermeasure against such a problem, one of the inventors of the present application, together with another inventor, has been described in Japanese Patent Application No. 63-2630.
No. 65783 has proposed an explosion-proof sealed battery. This explosion-proof sealed battery includes a current cutoff device that operates in response to an increase in battery internal pressure. Next, this battery will be described with reference to FIGS.

As shown in FIG. 1, the above explosion-proof sealed battery is provided with a current interrupting device 25 above a cylindrical outer can 1 in which battery elements are stored. This current interruption device 25
Is an annular gasket 2 provided on the inner peripheral surface at the upper end of the outer can 1, an explosion-proof valve 3 fitted and supported by the gasket 2 and also serving as an intermediate lid, and in contact with the lower surface of the explosion-proof valve 3. It is mainly composed of an installed substantially circular stripper 4 and a closing lid 5 for closing the outer can 1. The gasket 2, the explosion-proof valve 3, and the closing lid 5 are caulked and attached to the outer can 1.

A positive electrode 31 and a negative electrode 32 are provided in the outer can 1.
And a pair of separators 33a, 3
A wound body 35 formed by being spirally wound on the winding core 21 across the core 3b is housed as a battery element, and a sheet-shaped insulating plate 7 is provided on the upper part of the wound body 35. Is formed.

In the center of the insulating plate 7, an insertion hole 10 for inserting a positive electrode lead plate 8 having one end side attached to the positive electrode 31 is formed. The positive electrode lead plate 8 is connected to the lower surface of the projection 3a of the explosion-proof valve 3 facing downward from the insertion hole 11 of the stripper 4 by a method such as ultrasonic welding. At this time, the positive electrode lead plate 8 bridges the lower surface of the stripper 4 and the projection 3a of the explosion-proof valve 3.

On the other hand, the gasket 2 is fitted into the upper end 12 of the outer can 1 in which the wound body 35 is stored. The gasket 2 seals the inside of the outer can 1 in order to prevent the electrolyte permeating the separators 33a and 33b housed in the outer can 1 from leaking out of the battery. And this gasket 2
Is formed of an insulating material, for example, a synthetic resin material in order to prevent a short circuit between the positive electrode and the negative electrode.

The explosion-proof valve 3 is made of aluminum, nickel or an alloy thereof, has a disk shape slightly shorter than the diameter of the gasket 2, and is fitted into the gasket 2. At the center of the explosion-proof valve 3, there is provided a projection 3a projecting downward, and further on its upper surface, a plurality of linear grooves extending radially from near the base of the projection 3a and inner ends of these linear grooves. And a thin portion 15 formed by a circular groove connecting the two.

The stripper 4 installed below the explosion-proof valve 3 is made of a material such as aluminum, and has an insertion hole 11 at the center thereof through which the projection 3a of the explosion-proof valve 3 is inserted. A film 16 is formed. The positive electrode lead plate 8 is welded to the lower surface of the protrusion 3a so as to bridge the lower surface of the stripper 4 and the lower surface of the protrusion 3a.

A closing lid 5 is provided above the explosion-proof valve 3 so as to face the explosion-proof valve 3. The closing lid 5 constitutes a positive electrode terminal and has a disk shape slightly shorter than the diameter of the explosion-proof valve 3.
The outer peripheral end thereof is housed in a flange portion 17 provided at the peripheral end portion. The closing lid 5 is formed of a hard metal material, and in this example, is formed of a stainless steel plate to increase the strength of the battery. Further, the closing lid 5 is provided with two gas vent holes 19 and 20.

The gasket 2, the explosion-proof valve 3 and the closing lid 5 are swaged from the outer periphery of the outer can 1 toward the axis of the battery by the upper end 12 of the outer can 1, thereby forming the upper end. 12 attached. As described above, the explosion-proof valve 3 and the closing lid 5 which are attached by caulking and the outer can 1 are integrated via the gasket 2 so as to insulate the battery.

Although not shown, an insulating plate having a through hole at the center is disposed between the lower end surface of the winding body 35 and the bottom surface of the outer can 1 at a lower portion of the outer can 1. A negative electrode lead terminal extending from the negative electrode 32 through the insertion hole is welded to the bottom surface of the outer can 1.

The current interrupting device 25 configured as described above
For example, when the overcharge state progresses and a gas is generated and filled due to a chemical change inside the battery, and the internal pressure in the battery starts to increase due to the filling of the gas, the explosion-proof valve 3 is caused by the increase in the internal pressure. Deform. More specifically, as shown in FIG. 2, the protrusion 3a of the explosion-proof valve 3 is pressed in the direction of the internal pressure, that is, in the direction of the closing lid 5, and moves upward. As the protrusion 3a moves upward, the positive electrode lead plate 8 welded to the lower surface of the protrusion 3a breaks or separates at the welded portion, and the charging current is interrupted. The internal pressure of the battery at which the current interrupter 25 operates can be set as appropriate.

When a large amount of gas is generated inside the battery due to extreme progress of charging or the like, the thin portion 15 of the explosion-proof valve 3 is cleaved, and the gas is guided toward the closing lid 5, and the gas is further discharged. The air is exhausted to the atmosphere through the holes 19 and 20. As described above, since the explosion-proof sealed battery is provided with the current interrupting device 25 that can interrupt the charging current when the internal pressure of the battery is increased due to overcharge, for example, the progress of the abnormal reaction inside the battery is stopped. It is possible to prevent a rise in battery internal pressure and a rapid rise in temperature.

A wound body 35 for a non-aqueous electrolyte secondary battery that can be used for the above battery can be obtained, for example, as follows. That is, first, a lithium-cobalt composite oxide (LiCoO ₂ ) as a positive electrode active material is synthesized as follows. Commercially available lithium carbonate powder (Li ₂ Co ₃ ) and cobalt carbonate (CoCo ₃ ) were weighed such that the ratio of lithium atoms and cobalt atoms was 1: 1 and sufficiently mixed using a vibration mill. It is baked at 900 ° C. for 5 hours using an electric furnace in an atmosphere, and then pulverized using an automatic mortar to obtain LiCoO ₂ powder.

FIG. 3 shows an X-ray diffraction pattern of the obtained LiCoO ₂ . From this X-ray diffraction pattern, the one produced by this production method was used as a standard for JCPDS (Joint Committee on P
owder Diffraction Standards) card LiCoO ₂
It was confirmed that it matched.

Next, the positive electrode 31 is formed as follows. The synthesized lithium-cobalt composite oxide (LiC
oO ₂ ) was used as the positive electrode active material.
6 parts by weight of graphite as a conductive material and 3 parts by weight of polyvinylidene fluoride as a binder are added to the parts by weight and mixed to prepare a positive electrode mixture. Then, these positive electrode mixtures are dispersed in a solvent N-methyl-2-pyrrolidone to form a slurry. Next, these positive electrode mixture slurries are uniformly applied to both sides of a band-shaped aluminum foil as a positive electrode current collector and dried, and thereafter, compression-molded with a roller press to obtain a band-shaped positive electrode 31. .

The negative electrode 32 is manufactured as follows. Pulverized pitch coke is used as a negative electrode active material, and 90 parts by weight of the pitch coke and 10 parts by weight of polyvinylidene fluoride as a binder are added and mixed to prepare a negative electrode mixture. Then, this negative electrode mixture was mixed with the solvent N-methyl-2-
Disperse in pyrrolidone to form a slurry. Next, this negative electrode mixture slurry is uniformly applied to both sides of a strip-shaped copper foil as a negative electrode current collector, and dried. After drying, compression molding is performed with a roller press to obtain a strip-shaped negative electrode 32.

Next, the strip-shaped positive electrode 31 and the strip-shaped negative electrode 3
2 and a pair of separators 33 a and 33 b made of a microporous polypropylene film having a thickness of 25 μm,
2. After laminating in the order of the separator 33a, the positive electrode 31, and the separator 33b, the laminated body is spirally wound around the core 21 many times to produce the wound body 35.

The above-mentioned wound body 35 and non-aqueous electrolyte (obtained by mixing propylene carbonate in which lithium hexafluorophosphate is dissolved at 1 mol / l with 1.2-dimethoxyethane) Can be used to manufacture a non-aqueous electrolyte secondary battery provided with the same current interrupting device 25 as the structure shown in FIG. In this case, the non-aqueous electrolyte secondary battery can be, for example, a cylindrical shape having a diameter of 20.5 mm and a height of 42 mm, and can be used at a voltage of about 4.1 V when normally charged.

[0023]

However, 20 non-aqueous electrolyte secondary batteries were manufactured and charged at a current of 2 A for about 2 hours to obtain an overcharged state.
%) Of the batteries exhibited a damaged state such as heat generation with a rapid temperature rise and relatively rapid damage.

The present inventors have conducted intensive studies on the cause, and have found the following. That is, the non-aqueous electrolyte secondary battery as described above is overcharged and the battery voltage becomes about 4.8.
At about V, the cathode active material (LiCoO ₂ ) is decomposed to generate oxygen gas. This oxygen gas reacts abnormally and rapidly with lithium in the negative electrode, causing the battery to fall into the above-described damaged state. Then, as shown as a conventional example in FIG. 9 described later, when the battery voltage is about 4.8 V, the battery internal pressure does not increase so much. Therefore, the abnormal reaction between oxygen gas and lithium in the negative electrode rapidly proceeds before the above-described current interrupting device operates.

As a measure for preventing such overcharging of the secondary battery, in addition to the provision of the current interrupting means in the battery itself as described above, for example, the charging device for the secondary battery is provided with an overcharge preventing function. is there. However, in consideration of, for example, a case where the battery is charged by a charging device without such a prevention function, it is important for safety measures that the current cutoff means can be reliably operated. SUMMARY OF THE INVENTION It is an object of the present invention to provide a non-aqueous electrolyte secondary battery in which the above-mentioned current interrupting means operates reliably even when the non-aqueous electrolyte secondary battery provided with the current interrupting means is overcharged.

[0026]

To achieve the above object, the present invention provides a positive electrode using a lithium compound as a positive electrode active material, a negative electrode capable of doping and undoping lithium, a non-aqueous electrolyte, In a non-aqueous electrolyte secondary battery equipped with a current interrupting means that operates in response to an increase in internal pressure, a band-shaped positive electrode in which a positive electrode mixture is uniformly applied to both surfaces of a current collector, and a negative electrode mixture of a current collector A band-shaped negative electrode uniformly coated on both sides is wound in a spiral shape with a pair of separators interposed therebetween, and a wound body is housed as a battery element, and the positive electrode active material is a first active material. And the second active material, wherein the first active material is Li _x Ni _y Co _1-
y O ₂ (where 0 <x ≦ 1 and 0 ≦ y <0.50), and the second active material is Li _x 'Ni _y ' Co
_{1-y′O 2} (where 0 <x ′ ≦ 1 and 0.50 ≦ y ′ ≦
1.0), and the second active material is contained in an amount of 0.5 to 70 parts by weight based on 100 parts by weight of the entire positive electrode active material.

The second active material is preferably 2 to 50.
Parts by weight are included. Further, the first or second active material is:
There is no need to use one kind each, and two or more kinds may be used together as long as the above conditions are satisfied.

As the negative electrode active material of the negative electrode, a conductive polymer such as metallic lithium, lithium alloy, and polyacetylene, and a carbonaceous material such as coke can be used, all of which are doped with lithium. In addition, it can be undoped. Further, as the non-aqueous electrolyte, for example, a non-aqueous electrolyte obtained by dissolving a lithium salt in an organic solvent (non-aqueous solvent) as an electrolyte can be used.

Here, as the organic solvent, for example, propylene
Lencarbonate, ethylene carbonate, 1.2-di
Methoxyethane, 1.2-diethoxyethane, γ-butyi
Lolactone, tetrahydrofuran, 1.3-dioxola
, 4-methyl-1.3-dioxolane, diethyl ether
Ter, sulfolane, methyl sulfolane, acetonitrile
, Propionitrile, etc. alone or in combination of two or more
Solvents can be used. As for the electrolyte, those conventionally known are also used.
The displacement can be used, and LiClO_Four , LiAsF ₆ ,
LiPF₆ , LiBF_Four , LiB (C₆ H_Five )_Four , Li
Cl, LiBr, CH_Three SO_ThreeLi, CF_Three SO_Three Li
Etc.

The current interrupting means is shown in FIG.
2 can be used, but the present invention is not limited to this, and any device can be used as long as the current can be interrupted in accordance with an increase in battery internal pressure.

The positive electrode active material is mainly composed of the first active material and the second active material.
In a non-aqueous electrolyte secondary battery using a positive electrode active material containing 0.5 part by weight or more of the second active material as a part by weight, when the battery voltage is overcharged and the battery voltage rises, the second The active material acts as a catalyst to promote the decomposition of the non-aqueous electrolyte, so that gas is generated. Therefore, the internal pressure of the battery rises relatively slowly due to the decomposition gas of the non-aqueous electrolyte.

The decomposition voltage generated by the decomposition gas is not so high as to decompose the positive electrode active material to generate oxygen gas and cause a rapid reaction between the oxygen gas and lithium in the negative electrode. In addition, the battery does not generate heat or is damaged relatively quickly, and the current interrupting means operates reliably due to an increase in the internal pressure of the battery. Therefore, an abnormal reaction inside the battery due to overcharging can be prevented. In addition, since the second active material is contained in an amount of not more than 70 parts by weight, the discharge voltage and the energy density are reduced and the self-discharge is less.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment to which the present invention is applied will be described below with reference to FIGS. In this case, a non-aqueous electrolyte secondary battery provided with a current interrupting device was manufactured in exactly the same manner as described in the section of the prior art except that the configuration of the positive electrode active material of the positive electrode 31 was different. And the positive electrode 31 was produced as follows.

That is, as the first active material, Li _x Ni
_The lithium-cobalt composite oxide (LiCo) described in the conventional example in which x is almost 1 and y is 0 in _y Co _1-y O ₂
O ₂ ) was used. Further, as the second active material, Li _x
A lithium-nickel-cobalt composite oxide (LiN) in which Ni is approximately 1 and y is 0.9 in Ni _y Co _1-y O ₂
i _0.9 Co _0.1 O ₂ ) was synthesized and used as follows.

Commercially available lithium carbonate powder (Li ₂ CO 3
₃ ) Nickel carbonate powder (NiCO ₃ ) and cobalt carbonate powder (CoCO ₃ ) were weighed so that the ratio of lithium atom, cobalt atom and nickel atom was 1: 0.1: 0.9, and was measured using a vibration mill. After satisfactorily mixing, bake at 900 ° C. for 5 hours using an electric furnace in an air atmosphere.
Grinding using an automatic mortar, LiNi _0.9 Co _0.1 O ₂
A powder was obtained. In the following, Li _x Ni _y Co _1-y O
The value of x in ₂ is approximately 1 unless otherwise stated.

As described above, 90% by weight of LiCoO ₂ and L
A mixture obtained by mixing 10% by weight of iNi _0.9 Co _0.1 O _{2 was} used as a positive electrode active material. Other than that, a non-aqueous solution provided with a current interrupting device 25 shown in FIG. An electrolyte secondary battery was manufactured. This battery was used in Table 1 below.
As shown in FIG. In order to confirm the effects of the present invention, the above-mentioned Li _x Ni _y Co _1-y O
_{In 2} , the value of y is 0.3, 0.5, 0.7, 1.0
Lithium-nickel-cobalt composite oxide
Each was synthesized in the same manner as in the above case.

FIGS. 4 to 8 show the X-ray diffraction patterns of the above-mentioned composite oxide. The lithium-nickel-cobalt composite oxide Li _x Ni _y Co _1-y O ₂ synthesized as described above is shown in FIGS.
The X-ray diffraction pattern (FIG. 3) shown for the basic composition of LiCoO ₂ where y = 0 does not change even if the y value of are doing. That is, LiCoO ₂ and Li _x Ni _y Co _1-y O
₂ can be said to be substances having the same crystal structure but different interlayer distances.

The lithium-nickel-cobalt composite oxide is not limited to the above-mentioned synthesis example, but may be synthesized by firing using hydroxides or oxides of lithium, nickel and cobalt. Similarly, it can be obtained and its firing temperature can be in the range of 600 to 900C.

Non-aqueous electrolyte secondary batteries A to F shown in Table 1 were produced in the same manner using the above five kinds of lithium-nickel-cobalt composite oxides alone as the positive electrode active material. Further, a mixture obtained by mixing the above-mentioned lithium-nickel-cobalt composite oxide and lithium-cobalt composite oxide (LiCoO ₂ ) at a weight ratio shown in Table 1 was used as a positive electrode active material to prepare a non-aqueous electrolyte. Secondary batteries G, H, J, K
Was prepared in the same manner. Here, the secondary batteries H, I, and J are examples according to the present invention, and the secondary batteries A to G and K are comparative examples.

[0040]

[Table 1]

Next, 20 non-aqueous electrolyte secondary batteries A to K each were manufactured. Then, by charging these batteries at a current of 2 A for 2 hours to make them overcharged,
The incidence of damaged batteries, such as rapid heat generation and relatively rapid damage to batteries, was examined. Table 1 shows the results. The table also shows the case of the conventional example described above.

In order to examine the ease of decomposition of the electrolyte,
In Li _x Ni _y Co _1-y O ₂ , y = 0, 0.1,
Seven types of non-aqueous electrolyte secondary batteries using a total of seven types of composite oxides, 0.3, 0.5, 0.7, 0.9, and 1.0, as the positive electrode active material were used alone. The battery voltage and the battery internal pressure during charging were measured, and the results are shown in FIG. Note that LiCoO ₂ with y = 0 is the case of the conventional example.

Further, each battery whose internal pressure was increased was disassembled, and the generated gas was collected and analyzed. As a result, it was confirmed that the electrolyte was a gas generated by decomposition. Therefore, it can be said that the increase in the battery internal pressure in FIG. 9 is due to the decomposition gas of the electrolytic solution. From the figure, it can be seen that Li _x Ni _y C
It can be said that the larger the value of y in o _{1 -y} O _2, the more easily the above-mentioned decomposition gas is generated. Therefore, the decomposition voltage of the electrolytic solution decreases as the value of the above y increases.

That is, LiCoO with y = 0_Two (Conventional
Example) LiNi with y = 0.1_0.1 Co_0.9 O_Two as well as
LiNi with y = 0.3_0.3 Co_0.7 O_Two Each of
In this case, the decomposition voltage is about 4.8V. Also y
LiNi = 0.5_0.5 Co _0.5 O_Two , Y = 0.7
LiNi_0.7 Co_0.3 O_Two , Y = 0.9, L
iNi_0.9 Co_0.1 O_Two And LiNiO with y = 1_Two 
In each case, the decomposition voltage is about 4.5V.
is there. These lithium-nickel-cobalt composite oxidation
Substances have a catalytic effect to accelerate the decomposition of the electrolyte
Conceivable.

Based on the conclusions in FIG. 9 described above, the occurrence rates of damaged batteries A to K in Table 1 indicate that Li _x Ni _y Co _{1 -y} O ₂ having y of 0.5 or more is obtained. Batteries C, D, E, F, H, I, J containing any amount as a positive electrode active material
Is clearly not damaged at all. That is, even if only a small amount of the above-mentioned lithium-nickel-cobalt composite oxide is added to the lithium-cobalt composite oxide containing no nickel, the effect appears, and the voltage at which the internal pressure of the battery starts to increase, that is, the decomposition voltage of the electrolyte solution Was confirmed to be lower.

Li _x Ni _y in which y is less than 0.5
Batteries A, B, G, and K containing Co _1-y O ₂ as a positive electrode active material to some extent cause substantially the same damage as in the conventional example. That is, Li _x where y is less than 0.5
It can be said that Ni _y Co _1-y O ₂ cannot expect much of the above catalytic effect.

Also, as in the batteries C, D and E, Li _x Ni
_{The use of y} Co _1-y O ₂ alone as the positive electrode active material of a non-aqueous electrolyte secondary battery is disclosed in Japanese Patent Application Laid-Open No. 63-299056. Li _x N as the positive electrode active material
Comparing i _y Co _1-y O ₂ (y ≠ 0) and LiCoO ₂ , the discharge voltage is somewhat lower in the former case, especially when the value of y is larger, and the energy is lower than in the latter case. Density is reduced, and self-discharge becomes easier.

Batteries H, I and J are made of LiC having a high discharge voltage.
oO ₂ can be used as a positive electrode active material,
It was confirmed that the current interrupting device was activated before the charging voltage became high enough to damage the battery, and that the battery did not fall into a damaged state such as rapidly generating heat or being damaged relatively quickly.

When the batteries H and K were compared, it was found that although the molar ratios of nickel and cobalt in the positive electrode active material were almost the same, the above-mentioned battery damaged product occurrence rates were completely different. You can see that it is. According to the above results, in the case where the decomposition of the electrolytic solution occurs at about 4.6 V or more, during overcharging, decomposition of the positive electrode active material starts simultaneously with decomposition of the electrolytic solution to generate oxygen, and this oxygen and lithium in the negative electrode are generated. Are not preferred because they react rapidly.

That is, the lithium-nickel-cobalt composite oxide Li _x Ni _y Co _1-y O _{2 is} contained in the positive electrode active material.
If y of (0.2 ≦ x ≦ 1) in the range of 0.50 to 1.0 is mixed, the electrolytic solution is decomposed at an appropriate voltage, and the electrolyte is simply dissolved in the positive electrode active material. The decomposition voltage of the electrolytic solution is not determined only by the molar ratio of nickel to cobalt.

Then, such lithium nickel nickel
0.5% by weight of cobalt composite oxide in all positive electrode active materials,
If the content is preferably 2% by weight, the effect is exhibited, and even if the content is 70% by weight, preferably 50% by weight, the discharge voltage does not become so low. Further, a small amount of LiMnO ₂ or the like may be contained as another positive electrode active material.

As the first positive electrode active material, in addition to the above-mentioned LiCoO ₂ , Li _x N _satisfying 0 <y <0.5
i _y Co _1-y O ₂ (0 <x ≦ 1, preferably 0.2 ≦ x
≦ 1) can be used. Further, although the present embodiment is applied to a spiral-type cylindrical secondary battery, the shape is not particularly limited as long as it is a non-aqueous electrolyte secondary battery provided with a current interrupting means that operates by increasing the internal pressure of the battery. The non-aqueous electrolyte may be a solid, and in this case, a conventionally known solid electrolyte can be used.

[0053]

Since the present invention is configured as described above, even if the non-aqueous electrolyte secondary battery provided with the current interrupting means is overcharged, the current interrupting means operates reliably and the overcharging is performed. The accompanying abnormal reaction inside the battery can be prevented. In addition, the discharge voltage and the energy density are low and the self-discharge is small.
Accordingly, a non-aqueous electrolyte secondary battery having high energy density, excellent cycle characteristics and high safety can be provided, and its industrial and commercial value is great.

[Brief description of the drawings]

FIG. 1 shows an example of a non-aqueous electrolyte secondary battery to which the present invention can be applied, and schematically shows an upper half portion of a non-aqueous electrolyte secondary battery provided with a current cutoff device that operates according to an increase in battery internal pressure. FIG.

2 shows an example of a non-aqueous electrolyte secondary battery to which the present invention can be applied, and is a longitudinal sectional view similar to FIG. 1 of the non-aqueous electrolyte secondary battery when the current interrupting device is operated.

FIG. 3 shows Li _x Ni _y Co _1-y for explaining the present invention.
FIG. 4 shows a diffraction pattern by X-ray diffraction of O ₂ (x ≒ 1), and is a curve diagram of the X-ray diffraction pattern when y = 0.

FIG. 4 illustrates Li _x Ni _y Co _1-y for explaining the present invention.
FIG. 3 shows a diffraction pattern by X-ray diffraction of O ₂ (x ≒ 1), and is a curve diagram of the X-ray diffraction pattern when y = 0.1.

FIG. 5 shows Li _x Ni _y Co _1-y for explaining the present invention.
FIG. 4 shows a diffraction pattern by X-ray diffraction of O ₂ (x ≒ 1), and is a curve diagram of the X-ray diffraction pattern when y = 0.3.

FIG. 6 illustrates Li _x Ni _y Co _1-y for describing the present invention.
FIG. 4 shows a diffraction pattern by X-ray diffraction of O ₂ (x ≒ 1), and is a curve diagram of the X-ray diffraction pattern when y = 0.5.

FIG. 7 illustrates Li _x Ni _y Co _1-y for explaining the present invention.
FIG. 3 shows a diffraction pattern by X-ray diffraction of O ₂ (x ≒ 1), and is a curve diagram of the X-ray diffraction pattern when y = 0.7.

FIG. 8 illustrates Li _x Ni _y Co _1-y for describing the present invention.
FIG. 4 shows a diffraction pattern by X-ray diffraction of O ₂ (x ≒ 1), and is a curve diagram of the X-ray diffraction pattern when y = 0.9.

FIG. 9 is a curve diagram showing the relationship between the current voltage and the battery internal pressure at the time of overcharging when the y value of Li _x Ni _y Co _1-y O ₂ (x ≒ 1) is changed in seven ways. is there.

[Explanation of symbols]

25: current interrupting device (current interrupting means), 31: positive electrode, 3
2: Negative electrode

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Naoyuki Kato 1-1 Shimosugishita, Takakura, Hiwada-cho, Koriyama-shi, Fukushima Prefecture Inside Sony Energy Tech Koriyama Factory (72) Yoshikazu Yamamoto Koriyama-shi, Fukushima 1-1, Shimosugishita, Takakura, Hiwadacho Sony Energy Tech Koriyama Factory (72) Inventor Masayuki Endo 1-1, Shimosugishita, Takakura, Hiwadacho, Koriyama-shi, Fukushima Prefecture Sony Energy Tech Koriyama Factory Inside

Claims (2)

[Claims] 1. A positive electrode using a lithium compound as a positive electrode active material, a negative electrode capable of doping and undoping lithium, a non-aqueous electrolyte, and a current cutoff device that operates according to an increase in battery internal pressure. In a non-aqueous electrolyte secondary battery, a band-shaped positive electrode in which a positive electrode mixture is uniformly applied to both surfaces of a current collector, and a band-shaped negative electrode in which a negative electrode mixture is uniformly applied to both surfaces of a current collector, form a pair of separators. A spirally wound spiral body is housed as a battery element, and the positive electrode active material is mainly composed of a first active material and a second active material. Is an active material of Li _x Ni _y C
o _1-y O ₂ (however, 0 <x ≦ 1 and 0 ≦ y <0.50)
Wherein the second active material is Li _x 'Ni _y ' Co
_{1-y′O 2} (where 0 <x ′ ≦ 1 and 0.50 ≦ y ′ ≦
1.0), wherein the second active material is contained in an amount of 0.5 to 70 parts by weight based on 100 parts by weight of the entire positive electrode active material. 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the negative electrode active material of the negative electrode is a carbonaceous material.