JP2000340228A - Nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous secondary battery capable of having high capacity and high safety in over-charging, preventing gas generation under general use conditions, and having excellent storage characteristics at a high temperature. SOLUTION: This nonaqueous secondary battery comprises a positive electrode 1, a negative electrode 2, and electrolyte. The positive electrode 1 contains positive electrode active material of at least LixCoO2 (x is a value in assembling a battery, 1.01<=x<=1.10) and LiyNisCo1-sO2(y is a value in assembling a battery, 1.01<=y<=1.10, 0.65<=s<=0.90). An amount of LiyNisCo1-sO2 contained is 10-35 wt.% of a total amount of LixCoO2 and LiyNisCo1-sO2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous secondary battery, and more particularly, to a high-capacity, high-overcharge safety, low gas generation under normal use conditions, and high-temperature storage. The present invention relates to a non-aqueous secondary battery having excellent characteristics.

[0002]

2. Description of the Related Art A demand for a secondary battery having a high energy density is increasing with the miniaturization of electronic equipment. At present, as a high-capacity secondary battery that meets this demand, a lithium ion secondary battery using Li _x CoO ₂ as a positive electrode active material and a carbon-based material as a negative electrode active material has been commercialized. This lithium ion secondary battery has an average driving voltage of 3.
It is as high as 6 V, about three times the average driving voltage of conventional nickel-cadmium batteries and nickel-metal hydride batteries, and uses a carbon-based material as a negative electrode active material, and the mobility involved in charging and discharging is lithium, which is a light metal. Therefore, it is possible to reduce the weight, and it has been attracting much attention.

On the other hand, while the capacity per unit weight is higher than that of the above-mentioned conventional battery, only the capacity per unit volume of about 60% of the nickel-metal hydride battery has been commercialized. Is required.
However, the theoretical discharge capacity of LiCoO ₂ is 274 mAh.
However, when deep charge / discharge is performed, LiCoO ₂ causes a phase change to affect the cycle life, so that a practical discharge capacity in an actual lithium ion secondary battery is in the range of 125 to 140 mAh / g. There was a problem that would be.

[0004]

SUMMARY OF THE INVENTION Therefore, LiCoO
_{When 2} is used for the positive electrode active material, it is conceivable to use a material having a small particle size, improve the filling property of the positive electrode active material, and increase the capacity. However, as described above, LiCoO ₂
When a positive electrode is prepared using the positive electrode as an active material, a conductive additive, a binder, a solvent, and the like are added thereto, mixed and dispersed, and the prepared positive electrode mixture-containing paste is applied onto a conductive substrate, dried, and dried. Since the positive electrode is manufactured by forming a layer, the positive electrode mixture layer with improved packing density loses the elasticity of the positive electrode mixture layer, cracks the surface, or peels off from the conductive substrate And the charge / discharge characteristics are degraded.

[0005] In the highly filled positive electrode as described above,
Although it is a safety test that intentionally assumes abnormal use, it has been found that the safety test in an overcharged state tends to decrease. The safety test in this abnormal use situation assumes some kind of intention or accident, and cannot occur under normal use conditions. A highly safe battery with no danger of ignition is desired.

Further, in a non-aqueous secondary battery, it is desired to use an active material or an electrolyte which easily generates gas in order to ensure safety at the time of overcharging. Occurrence will increase the failure rate during battery manufacture and must be improved. On the other hand, under the normally used environment, there is almost no generation of gas, but abnormal voltage is applied to the battery, gas is generated efficiently during overcharging where current flows continuously, and the current cutoff mechanism is activated, The battery must be able to reliably avoid abnormal situations.

[0007] The present invention solves the problems and future requirements of the conventional non-aqueous secondary battery as described above, and has a high capacity, high safety at the time of overcharging, and under normal use conditions. It is an object of the present invention to provide a non-aqueous secondary battery that generates little gas and has excellent high-temperature storage characteristics.

[0008]

Means for Solving the Problems The present inventors have solved the above problems.
As a result of intensive research to solve the
At least Li_xCoO_Two(X is the value at the time of battery assembly
1.01 ≦ x ≦ 1.10) and Li_yNi_sCo
_1-sO_Two(Y is a value at the time of battery assembly, and 1.01 ≦ y
≦ 1.10, 0.65 ≦ s ≦ 0.90)
Li_yNi_sCo _1-sO_TwoLi content_xCoO_TwoWhen
Li_yNi_sCo_1-sO_TwoIn the total amount of 10
By using 35% by weight, high capacity and overcharging
High safety and low gas generation under normal use conditions
A non-aqueous secondary battery with excellent high-temperature storage characteristics
And solved the above problem.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, Li _x CoO ₂
Has a smaller capacity that can be actually charged and discharged than the theoretical capacity.
Therefore, the present inventors have higher capacity as a positive electrode active material was subjected to examine the _{Li y Ni s Co 1-s} O 2 can be expected. Li _y capacity Ni _s Co _1-s O ₂ is, Ni and C
It is known that it is affected by the composition ratio of o. Accordingly, the present inventors have various Ni, were investigated _{Li y Ni s Co 1-s} O 2 having a composition ratio of Co, N
i-rich composition, in particular _{Li y Ni s Co 1-s} O 2 (0.
(65 ≦ s ≦ 0.90), it has been found that the capacity can be increased, and moreover, a large amount of gas is generated during overcharge, and the safety is excellent.

[0010] However, the above-mentioned _{Li y Ni s Co 1-s} O
It was found that when ₂ was used, the discharge potential was lower than that of Li _x CoO ₂ .

[0011] Therefore, Li_xCoO_TwoPart of the above L
i_yNi_sCo_1-sO_TwoThe positive electrode is replaced with
The active material system was examined, but such a positive electrode active material was used.
If Li_yNi_sCo_1-sO_TwoThe mixing ratio of
As a result, the current interrupt mechanism during overcharge operates at a low temperature,
The electric capacity increases, but the discharge potential decreases accordingly
It turned out to be. This is Li_yNi_sCo_1-sO
_TwoWith the increase of Li _yNi_sCo_1-sO_TwoThe nature of
This is because they will appear stronger.

[0012] Therefore, the increase in the drop and Li _y Ni _s Co _1-s decreases and heat dissipation of O ₂ in based discharge potential of the capacitor based on _{Li x CoO 2, Li y Ni} s Co 1-s O
Results of examining the _second substitution amount was changed variously, Li _y Ni _s
Co _1-s the amount of O ₂ is Li _x CoO ₂ and Li _y Ni _s Co
When 10 to 35 wt% in a total amount of the _1-s O _2, the discharge capacity is large, it was found that also decrease in discharge potential is small.

[0013] Then, the present inventors have made a combination of Li _x CoO ₂ and _{Li y Ni s Co 1-s} O 2 in a ratio within the above range, considering the safety due to gas generation during overcharging , when the Li amount in Li _x CoO ₂ and _{Li y Ni s Co 1-s} O 2 to 1.01 to 1.10, especially efficient gas is generated, the battery sealing aperture before reaching the thermal runaway It has been found that the current cutoff mechanism incorporated in the device can be operated to improve safety, and furthermore, generation of gas during high-temperature storage can be reduced and high-temperature storage characteristics can be improved.

That is, if the amount of Li is less than 1.01, the gas generation rate becomes slow, and the time required for the current interrupting mechanism to operate during overcharge becomes long, so that the battery becomes hot when the current interrupting mechanism operates. However, if the Li content exceeds 1.10, the amount of gas generated increases even during normal use, and gas is generated during high-temperature storage. The shut-off mechanism operates to increase the battery failure rate.

Next, the fabrication of the non-aqueous secondary battery of the present invention will be described.

In the present invention, Li_xCoO_TwoAnd Li_y
Ni_sCo_1-sO_TwoAnd non-aqueous
To produce a positive electrode for a secondary battery, for example, the above-described positive electrode active material
Quality, as required, eg flake graphite, acetylene bra
Conductive aids such as
Binders such as polyethylene and polyvinylidene fluoride
The mixture is then mixed, and the resulting positive electrode mixture is molded by appropriate means.
Just do it. For example, the above-mentioned positive electrode mixture is pressure-molded, or
Alternatively, the above positive electrode mixture is dispersed in a solvent to form a paste (this
In the case of, the binder should be dissolved in a solvent beforehand.
After mixing with the positive electrode active material).
The paste containing the agent is applied to a conductive substrate that serves as a current collector, and dried.
Drying to form a positive electrode mixture layer.
A pole is created. However, the method of manufacturing the positive electrode is as described above.
Without being limited to the method, another method may be used. Ma
In the above positive electrode, Li_xCoO_TwoX of 1.03
Gas is generated as an additive during overcharge in the following cases
It is preferable to add a lithium (Li) compound. Up
By adding the lithium compound, the positive electrode active material
It becomes easy to control the generation of these gases. Such a Lichu
As the compound, for example, Li_TwoCO_ThreeEtc.
be able to. In addition, when using the positive electrode active material of the present invention,
In this case, the packing density of the positive electrode mixture layer is set to 2.8 to increase the capacity.
3.5 g / cm ^ThreeHigh safety is ensured
The present invention is particularly useful in increasing the capacity.
is there.

In the present invention, the negative electrode active material only needs to be capable of doping and undoping lithium ions. Specific examples of such a negative electrode active material include graphite and graphite.
Examples include pyrolytic carbons, cokes, glassy carbons, fired bodies of organic polymer compounds, carbon-based materials such as mesocarbon microbeads, carbon fibers, and activated carbon, as well as lithium or lithium-containing compounds. As the lithium-containing compound, there are a lithium alloy and others, and as the lithium alloy, for example, lithium-
Aluminum, lithium-lead, lithium-indium,
Lithium-gallium, lithium-indium-gallium and the like, and examples of the lithium-containing compound other than the lithium alloy include, for example, tin oxide, silicon oxide, nickel-silicon alloy, magnesium-silicon alloy, tungsten oxide, Indium oxide, lithium iron composite oxide and the like can be mentioned. Some of these exemplified lithium-containing compounds do not contain lithium at the time of production, but when they act as a negative electrode active material, they contain lithium. Each of these negative electrode active materials can be used alone, or two or more of them can be used in combination.

Further, the inventors of the present invention have proposed a negative electrode active material.
That is, when the above-mentioned positive electrode active material is used, the
-The rise of dance can be suppressed and efficient gas generation is possible.
After examining the combination with the negative electrode active material,
(002) Distance between planes (d ₀₀₂) Is 0.338 nm or less
Lower, preferably 0.336 nm or less, crystallite in c-axis direction
Has a size (Lc) of 35 to 57 nm, preferably 40 to 57 nm.
45 nm, aspect ratio (major axis diameter / minor axis diameter) 2-2
0, preferably 5 to 15, having an average particle diameter of 20 μm or less,
Preferably, a flaky carbon-based material of 6 μm or less is used.
Found that the above characteristics can be improved by
did. By using such a carbon-based material,
The reason why the characteristics can be improved at present is always
Although it is not clear, the layer where these carbon-based materials have developed
Lithium ion doped from the positive electrode
The anode is smoothly inserted into the carbon-based material,
Doping and undoping of lithium ions into a substance
Slides with the expansion and contraction of the positive electrode active material
Keeps contact and maintains conductivity,
Due to the fact that a smooth charge / discharge reaction is possible
it is conceivable that.

As such a carbon-based material, for example,
In addition to natural graphite, those obtained by pyrolysis of various organic compounds, carbonization by calcining, and the like, for example, carbon-based materials obtained by gas phase pyrolysis of carbon compounds such as benzene, methane, and carbon monoxide, and the like. The temperature at the time of the thermal decomposition is preferably from 2000 ° C. to 3300 ° C. Other examples include pitch-based carbon-based materials, and examples of such pitches include petroleum pitch, asphalt pitch, coal tar pitch, crude oil cracking pitch, petroleum such as petroleum sludge pitch, Pitch obtained by thermal decomposition of coal, pitch obtained by thermal decomposition of organic low molecular weight aromatic compounds, and the like are included. Still another example is a calcined carbide of a polymer containing acrylonitrile or the like as a main component.

The negative electrode is mixed with the above-mentioned negative electrode active material, if necessary, by adding the same binder and conductive assistant as in the case of the above-mentioned positive electrode active material, and then molding the obtained negative electrode mixture by an appropriate means. It is produced by For example, pressure-forming the negative electrode mixture, or dispersing the negative electrode mixture in a solvent to form a paste (the binder may be dissolved in the solvent in advance and then mixed with the negative electrode active material),
The negative electrode is prepared by applying the negative electrode mixture-containing paste to a conductive substrate serving as a current collector, and drying the paste to form a negative electrode mixture layer. However, the method for producing the negative electrode is not limited to the method exemplified above, and may be another method.

As a method of applying the paste containing the positive electrode mixture and the paste containing the negative electrode mixture to the conductive substrate, for example, various coating methods such as an extrusion coater, a reverse roller, and a doctor blade are employed. be able to. In addition, as the conductive substrate serving as a current collector for electrodes such as a positive electrode and a negative electrode, for example, a metal mesh such as aluminum, stainless steel, titanium, and copper, punched metal, expanded metal, foam metal, and foil are used. However, aluminum foil is particularly suitable for the conductive substrate of the positive electrode, and copper foil is particularly suitable for the conductive substrate of the negative electrode.

The ratio of the amount of the active material in the positive electrode to the amount of the active material in the negative electrode depends on the type of the negative electrode active material used in combination with the positive electrode active material. It is preferable to set it to 1.0 to 3.5 (weight ratio).

In the nonaqueous secondary battery using the positive electrode active material of the present invention, the electrolyte is usually a liquid electrolyte (hereinafter, referred to as a liquid electrolyte).
This is referred to as “electrolyte solution”). As the electrolyte, a non-aqueous solvent-based electrolyte in which a lithium salt as a solute is dissolved in an organic solvent is used. The organic solvent that is a constituent solvent of the non-aqueous solvent-based electrolytic solution is not particularly limited, but it is particularly suitable to use a chain ester as a main solvent. Examples of such a chain ester include organic solvents having a chain COO-bond such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, ethyl acetate, and methyl propionate. The fact that the chain ester is the main solvent of the electrolytic solution means that the chain ester has a volume of more than 50% by volume in the total electrolyte solvent, and in particular, that the chain ester is It is preferred that 65% by volume or more in the liquid solvent, especially the chain ester accounts for 70% by volume or more in the total electrolyte solution solvent, and that the chain ester occupies 75% by volume or more in the total electrolyte solution solvent. preferable.

It is preferred that the chain ester be used as the main solvent as the solvent of the electrolyte because the chain ester exceeds 50% by volume in the total solvent of the electrolyte, so that the battery characteristics, especially the low-temperature characteristics, are obtained. Is improved.

However, as the solvent for the electrolytic solution, an ester having a high dielectric constant (an ester having a dielectric constant of 30 or more) is used as the above-mentioned chain ester in order to improve the battery capacity as compared with the case of using only the above-mentioned chain ester. It is preferable to use a mixture. The amount of such an ester having a high dielectric constant in the total electrolyte solvent is 10% by volume or more, particularly 20% by volume.
The above is preferred. That is, when the amount of the ester having a high dielectric constant is 10% by volume or more in the total electrolyte solvent, the improvement in capacity is clearly exhibited, and when the amount of the ester having a high dielectric constant becomes 20% by volume or more in the total electrolyte solution. The improvement in capacity is more clearly expressed. However, if the proportion of the ester having a high dielectric constant in the total solvent of the electrolyte is too large, the discharge characteristics of the battery tend to be reduced. As described above, the content is preferably 10% by volume or more, more preferably 20% by volume or more, preferably 40% by volume or less, more preferably 30% by volume or less, and still more preferably 25% by volume or less.

The ester having a high dielectric constant includes, for example, ethylene carbonate, propylene carbonate,
Examples thereof include butylene carbonate, γ-butyrolactone, and ethylene glycol sulphite. Particularly, those having a cyclic structure such as ethylene carbonate and propylene carbonate are preferable, and cyclic carbonates are particularly preferable. Specifically, ethylene carbonate is most preferable.

Examples of the solvent which can be used in combination with the ester having a high dielectric constant include, for example, 1,2-dimethoxyethane, 1,3-dioxolan, tetrahydrofuran,
-Methyl-tetrahydrofuran, diethyl ether and the like. In addition, an amine-based or imide-based organic solvent, a sulfur-containing or fluorine-containing organic solvent, and the like can also be used.

As the lithium salt which becomes a solute of the electrolytic solution,
For example, LiClO_Four, LiPF₆, LiBF_Four, Li
AsF₆, LiSbF₆, LiCF_ThreeSO_Three, LiC_Four
F₉SO_Three, LiCF_ThreeCO_Two, Li_TwoC_TwoF_Four(SO
_Three)_Two, LiN (CF_ThreeSO _Two), LiC (CF_ThreeSO
_Two)_Three, LiC_nF_{2n + 1}SO_Three(N ≧ 2) alone
Alternatively, two or more kinds are used in combination. Especially LiPF₆And
LiC_FourF₉SO_ThreeEtc. have good charge / discharge characteristics
preferable. Of lithium salt as solute in electrolyte
The concentration is not particularly limited, but is 0.3 to 1.
7 mol / l, particularly preferably about 0.4 to 1.5 mol / l
Good.

In the present invention, a solid or gel electrolyte can be used as the electrolyte in addition to the above-mentioned electrolyte. Examples of such electrolytes include, besides inorganic solid electrolytes, organic solid electrolytes and organic gel electrolytes mainly composed of polyethylene oxide, polypropylene oxide or derivatives thereof.

The separator is not particularly limited, but preferably has sufficient strength and can hold a large amount of electrolyte.
m, and a microporous film or nonwoven fabric made of polypropylene, polyethylene, or a copolymer of propylene and ethylene having a porosity of 30 to 70% is preferable.

As a method for producing the battery of the present invention, for example, an electrode body produced by laminating or winding the positive electrode and the negative electrode produced as described above through a separator is inserted into a battery case, And then sealed with a sealing body having a cleavage vent. As the cleavage vent, in order to ensure high safety, 20 to 40 at
m, especially those having an irreversible vent structure operating at 25-35 atm. In addition, the non-aqueous secondary battery of the present invention preferably has a current cut-off mechanism in the above-mentioned sealing portion. In particular, when the positive electrode active material of the present invention is used, the amount of gas generated during overcharge is increased to increase the In order to ensure safety in the event of a change, the operating pressure of the current interrupt mechanism should be 5-20.
atm, preferably 8 to 15 atm.

[0032]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples. Hereinafter, “parts” means “parts by weight”.

Examples 1 to 3 and Comparative Examples 1 to 4 Lis having different compositions and weight ratios shown in Table 1 below_x
CoO_Two, Li_yNi _sCo_1-sO_TwoUsing these activities
91 parts in total, 4 parts of natural graphite as conductive aid
Parts, 4 parts of polyvinylidene fluoride as binder
It was mixed so as to have a ratio. However, mixing is polyfluoride
Vinylidene is previously dissolved in N-methylpyrrolidone
Previously, add the active material and natural graphite to the binder solution.
And further dispersed by adding N-methylpyrrolidone
Then, the viscosity was adjusted to prepare a positive electrode mixture-containing paste.
The paste containing the positive electrode mixture of Examples 1 to 3 was Li_Two
CO_ThreeWas added in 4 parts.

[0034]

[Table 1]

The positive electrode mixture-containing pastes of Examples 1 to 3 and Comparative Examples 1 to 4 were uniformly applied on a 20 μm-thick aluminum foil as a conductive substrate so that the thickness after drying was constant. After drying, a positive electrode mixture layer was formed. Similarly, the positive electrode mixture-containing paste is also applied to the back surface of the aluminum foil, vacuum-dried to form a positive electrode mixture layer, and then rolled by changing the pressure with a roll press,
By cutting, a belt-shaped positive electrode was produced. The packing density of the positive electrode mixture layer was 3.0 to 3.2 g / cm ³ .

Further, a binder solution (a binder solution in which polyvinylidene fluoride is dissolved in N-methylpyrrolidone) similar to that of the above-described positive electrode is prepared, and graphite [as a negative electrode active material] Distance (d ₀₀₂ ): 0.336 nm, crystallite size in the c-axis direction (Lc): 42 nm, aspect ratio: 10, average particle diameter: 10 μm] 180 parts were added and mixed to obtain a negative electrode mixture-containing paste. Prepared. This negative electrode mixture-containing paste is uniformly applied to both sides of a copper foil having a thickness of 18 μm as a conductive substrate, dried to form a negative electrode mixture layer, rolled by a roll-press, and then cut. Thus, a strip-shaped negative electrode was produced. The weight ratio between the positive electrode active material and the negative electrode active material was 2.1: 1 [positive electrode active material / negative electrode active material = 2.1 (weight ratio)].

Next, a separator made of a microporous polyethylene film having a thickness of 25 μm was disposed between the strip-shaped positive electrode and the strip-shaped negative electrode of each of the above-mentioned Examples and Comparative Examples, and wound spirally to form a spiral electrode assembly. After that, outer diameter 18mm, height 6
The battery was inserted into a 7 cm bottomed cylindrical battery case, and the positive electrode lead body and the negative electrode lead body were welded.

After that, 1.0 mol / l in the battery case
Electrolyte solution composed of LiPF ₆ / EC + EMC (volume ratio 1: 3) [that is, LiPF ₆ was added to a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1: 3.
Was dissolved in 1.0 mol / l].

Next, the opening of the battery case was sealed according to a conventional method, and the structure shown in FIG.
A 5 mm cylindrical non-aqueous secondary battery was produced.

The battery shown in FIG. 1 will be described briefly. 1 is the positive electrode and 2 is the negative electrode. However, FIG. 1 does not show the substrates used for producing the positive electrode 1 and the negative electrode 2 in order to avoid complication.
The positive electrode 1 and the negative electrode 2 are spirally wound with a separator 3 interposed therebetween, and are accommodated in a stainless steel battery case 4 together with an electrolytic solution having the above composition as a spiral electrode body.

The battery case 4 also serves as a negative electrode terminal, and an insulator 5 is provided at the bottom thereof, and an insulator 6 is also provided on the spiral electrode body. And battery case 4
The opening 8 is provided with a sealing body 8 through an annular insulating packing 7.
Are arranged, and the inside of the battery is sealed by tightening the open end of the battery case 4 inward.

However, the sealing member 8 has a current cut-off mechanism for preventing a current from flowing inside the battery when an abnormal situation such as overcharging or the like causes a decomposition reaction of the electrolytic solution inside the battery and gas is generated. And, when the gas generated inside the battery rises to a certain pressure, an irreversible vent mechanism is built in to prevent the battery from bursting under high pressure by discharging to the outside of the battery, and the current interruption mechanism is The gas pressure inside is 1
The irreversible vent that operates when the pressure becomes 3 atm or more and operates under high pressure is activated when the gas pressure in the battery becomes 30 atm or more.

With respect to the batteries of Examples 1 to 3 and Comparative Examples 1 to 4 manufactured as described above, the discharge capacity and the average discharge voltage were measured, and a storage test and an overcharge test were performed. Table 2 shows the results. The discharge capacity of each battery was 0.2 at 20 ° C.
The measurement was performed by discharging the battery to a final voltage of 3.0 V at 2C, and the result was indicated by an index when the capacity of the battery of Comparative Example 1 was 100. The average discharge voltage was constant current and constant voltage charging at 20 ° C and 1C up to 4.2V, then the voltage at a discharge depth of 50% when discharging at a final voltage of 3V at 0.2C was measured. Voltage.

In the storage test, 1.5 A under an environment of 20 ° C.
After charging to 4.2 V at a constant current of 2.5 V, charging was performed by a constant voltage method, and charging was performed so that the total charging time was 2.5 hours. 2.75
After 5 charge / discharge cycles of discharging to V, 2
After charging to 4.2 V at a constant current of 1.5 A in an environment of 0 ° C., charging was performed by a constant voltage method, and the total charging time was 2.
After charging for 5 hours, the battery was stored in an environment of 60 ° C. Then, by measuring the impedance of the battery after storage at 60 ° C. for 20 days, it was checked whether or not the current interrupting mechanism was activated.

Further, in the overcharge test, the battery was charged at a constant current of 1.5 A to 4.2 V in an environment of 20 ° C., and then charged by a constant voltage method, for a total charging time of 2.5 hours. Then, the battery was stored at 0 ° C. for 4 hours, and the presence or absence of ignition was examined at a charging current of 3 A.

[0046]

[Table 2]

The batteries of Examples 1 to 3 are as shown in Table 1.
A / B (weight ratio) is in the range of 90/10 to 65/35
(That is, Li_yNi_sCo_1-sO_TwoContent of L
i_xCoO_TwoAnd Li_yNi_sCo_1-sO_TwoIn the total amount with
10 to 35% by weight (Example 1 was 20% by weight,
(Example 2: 10% by weight, Example 3: 35% by weight)
), The batteries of Examples 1 to 3 are shown in Table 2.
Thus, the battery of Comparative Example 1 serving as a reference for comparison (this comparative example)
As shown in Table 1, the positive electrode active material of the battery No. 1 was Li_{1. 00}C
oO_TwoDischarge capacity is larger than that of
Also, the average discharge voltage was slightly lower than that of Comparative Example 1.
Of 3.6 V, which was a sufficiently high voltage.

The batteries of Examples 1 to 3 do not ignite at the time of overcharging and can ensure safety. However, even when stored at 60 ° C. for 20 days, the current cutoff mechanism does not operate, and the batteries are not used under normal operating conditions. It has become clear that the current interrupting mechanism does not operate to make the battery unusable, and that the current interrupting mechanism does not operate during battery manufacture to increase the defect rate. That is, the batteries of Examples 1 to 3 had high capacity, high safety during overcharge, low gas generation under normal use conditions, and excellent high-temperature storage characteristics.

On the other hand, the battery of Comparative Example 1 had a smaller capacity than the batteries of Examples 1 to 3, fired at the time of overcharge, and lacked safety at the time of overcharge.

The battery of Comparative Example 2 is shown in Table 1.
In addition, Li as a positive electrode active material_1.02Ni _0.92C_0.08O_Twoof
Batteries that use only
However, although the capacity was high, the average discharge voltage was low.

Further, lithium (L) in Li _x CoO ₂
Comparative Example Ratio of i) is having a high lithium compound as a cathode active material 3 and Li _y Ni _s Co battery of Comparative Example 4 using _1-s O ratio of lithium is high lithium compound ₂ as a positive electrode active material However, there is a problem in that the current cutoff mechanism operates during storage at 60 ° C. for 20 days and lacks high-temperature storage characteristics.

[0052]

As described above, according to the present invention, a non-aqueous secondary battery having a high capacity, high safety at the time of overcharging, low gas generation under normal use conditions, and excellent high-temperature storage characteristics. Battery could be provided.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional perspective view schematically illustrating an example of a non-aqueous secondary battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Battery case 5 Insulator 6 Insulator 7 Insulation packing 8 Sealing body

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Takahisa Kurusen 1-88 Ushitora, Ibaraki-shi, Osaka F-term in Hitachi Maxell, Ltd. (Reference) 5H003 AA02 AA03 AA04 AA10 BB05 BD00 BD04 5H014 AA02 EE10 HH00 HH01 5H029 AJ03 AJ04 AJ05 AJ12 AK03 AL02 AL03 AL06 AL07 AL08 AL11 AL12 AM02 AM03 AM04 AM05 AM07 BJ02 BJ14 HJ01 HJ02

Claims (1)

[Claims] 1. A non-aqueous electrolyte comprising a positive electrode, a negative electrode, and an electrolyte.
In the secondary battery, the positive electrode has a small amount as a positive electrode active material.
And Li_xCoO_Two(X is a value at the time of battery assembly,
1.01 ≦ x ≦ 1.10) and Li_yNi_sCo_1-sO_Two
(Y is a value at the time of battery assembly, and 1.01 ≦ y ≦ 1.1
0, 0.65 ≦ s ≦ 0.90), wherein the Li_yN
i_sCo_1-sO_TwoContent of Li_xCoO_TwoAnd Li_yN
i_sCo _1-sO_Two10 to 35 weight in the total amount of
% Non-aqueous secondary battery.