JP2000277147A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent overcharge, to improve safety and to enhance energy density by including a redox shuttle overcharge controlling agent in a nonaqueous electrolyte and by installing a thermo-sensitive switch or thermo- sensitive sensor. SOLUTION: A compound expressed by the formula can be offered as a redox shuttle overcharge controlling agent. In the formula, X is a halogen. The compound is suitable for a redox shuttle of a battery having an oxidation- reduction potential of around four volts, its oxidation seed and reduction seed are chemically stable, and its battery performance is never degraded by a side- reaction. Its effect on a solvent characteristic of an electrolyte is small and its movement in the electrolyte is good as well. The compound is used as an oxidation-reduction reagent for protecting the battery because it consumes an overcharge current in overcharge. A thermo-sensitive switch or thermo- sensitive sensor detects the heat radiated from the battery, generates an alarm of an overcharge state and stops charge by itself or by interlocking with a facility installed together with it.

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 that obtains an electromotive force by entering and exiting lithium ions, and relates to a so-called redox shuttle overcharge prevention technology.

[0002]

2. Description of the Related Art In recent years, many portable electronic devices such as a camera-integrated video tape recorder, a mobile phone, and a laptop computer have appeared, and their size and weight have been reduced. Research and development for improving the energy density of batteries, particularly secondary batteries, as portable power sources for these electronic devices are being actively promoted.

[0003] Batteries using a non-aqueous electrolyte, in particular, lithium secondary batteries and lithium ion secondary batteries have higher energy densities than lead batteries and nickel cadmium batteries, which are conventional aqueous electrolyte secondary batteries. As a result, the market is growing significantly and expectations are growing.

[0004]

The lithium secondary battery or lithium ion secondary battery has a very high energy density per unit volume and uses a flammable organic solvent as an electrolyte. I have. Therefore, in a lithium secondary battery or a lithium ion secondary battery, ensuring safety is one of the most important issues.

[0005] For example, in a nickel-cadmium battery, when the charging voltage rises during overcharging, an overcharge prevention mechanism operates due to consumption of charging energy by a chemical reaction of water contained in the electrolyte. On the other hand, a non-aqueous lithium secondary battery does not consume charging energy due to the chemical reaction of water, and therefore requires another mechanism instead. As a safety mechanism during heating and an overcharge prevention mechanism in a lithium secondary battery, a method using a chemical reaction (current interruption based on gas generation, a cleavage valve), a method using a physical reaction (PTC element), and A method using an electronic circuit has been proposed. In each of these methods, the mechanism is established based on the initial stage of heat generation and gas generation (so-called thermal runaway) exceeding the control range, and in the event of an abnormality, safety is ensured by disabling the cell. It is an object.

However, in these methods, the cell cannot be used again. And, since these methods are based on uncontrollable heat generation and gas generation, the battery needs a double and triple safety mechanism to prevent ignition and liquid leakage.

The present invention has been proposed in view of such conventional circumstances, and has as its object to provide a non-aqueous electrolyte secondary battery which prevents overcharge, is more safe, and has a high energy density. And

[0008]

In order to achieve the above-mentioned object, a non-aqueous electrolyte secondary battery according to the present invention comprises a metal mainly composed of lithium as a negative electrode or a lithium-doped metal.
In a non-aqueous electrolyte secondary battery using a undoped carbon material, using a composite oxide of lithium and a transition metal as a positive electrode, and using a non-aqueous electrolyte in which an electrolyte is dissolved in a non-aqueous solvent as a non-aqueous electrolyte In addition, the non-aqueous electrolyte contains a redox shuttle overcharge control agent, and a thermal switch or a thermal sensor is provided.

The redox shuttle overcharge control agent consumes an overcharge current when the nonaqueous electrolyte secondary battery is charged in an overcharged state, and converts the excess energy due to the overcharge into thermal energy to convert the nonaqueous electrolyte into a nonaqueous electrolyte. Released outside the electrolyte secondary battery. And the thermal switch or thermal sensor is
By sensing the heat released from the non-aqueous electrolyte secondary battery, it functions alone or in conjunction with a facility provided therewith to issue a warning that the battery is overcharged, or to stop charging.

Therefore, the non-aqueous electrolyte secondary battery according to the present invention does not use uncontrollable runaway heat or gas.
In addition, even in the event of an abnormality, safety can be ensured without making the cell unusable.

The nonaqueous electrolyte secondary battery according to the present invention uses a metal mainly composed of lithium or a carbon material capable of doping and undoping lithium as a negative electrode, and a composite oxide of lithium and a transition metal as a positive electrode. In a non-aqueous electrolyte secondary battery using a non-aqueous electrolyte in which an electrolyte is dissolved in a non-aqueous solvent as a non-aqueous electrolyte, the non-aqueous electrolyte contains a compound represented by the following formula 2, A heat switch or a heat sensor is provided.

When the non-aqueous electrolyte secondary battery is charged in an overcharged state, the compound represented by the following formula 2 consumes overcharge current and converts excess energy due to overcharge into heat energy. Released outside the non-aqueous electrolyte secondary battery.
Then, the heat-sensitive switch or the heat-sensitive sensor issues a warning that it is in an overcharged state by sensing the heat released from the non-aqueous electrolyte secondary battery alone or in conjunction with the equipment provided therewith. Alternatively, it functions such as stopping charging.

Therefore, the non-aqueous electrolyte secondary battery according to the present invention does not use uncontrollable runaway heat or gas.
In addition, even in the event of an abnormality, safety can be ensured without making the cell unusable.

[0014]

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[0015]

Embodiments of the present invention will be described below in detail.

A negative electrode is made of a metal mainly composed of lithium or a material capable of doping and undoping lithium, a composite oxide of lithium and a transition metal is used as a positive electrode, and an electrolyte is dissolved in a nonaqueous solvent as a nonaqueous electrolyte. The non-aqueous electrolyte secondary battery using the non-aqueous electrolyte has a high battery voltage of 4 V or more.

In the present invention, a compound serving as a redox shuttle overcharge control agent is contained in the nonaqueous electrolyte of such a nonaqueous electrolyte secondary battery. As the non-aqueous electrolyte, not only a non-aqueous electrolyte but also a gel-like one can be used.

The redox shuttle overcharge control agent includes, for example, compounds represented by the following formula (3).
The organic compound used as the redox shuttle has a structure in which two methoxy groups and a halogen group are introduced into a benzene ring.

[0019]

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As described above, the compound having a benzene ring as a basic skeleton and having a methoxy group and a halogen group has a suitable oxidation-reduction potential as a redox shuttle of a 4V-class battery, and both the oxidized species and the reduced species are chemically protected. It is stable.

That is, in principle, a covalent bond between two atoms of an organic compound forms one single bond by paired two atoms. Therefore, when an organic compound is oxidized or reduced to remove or add one electron from the electron system of the bond, an unpaired electron is generated in the organic compound. The unpaired electron is stabilized by decomposing the compound or forming a new bond with another molecule, but the state of the organic compound having the unpaired electron is unstable in principle.

However, when an unpaired electron exists in a delocalized orbital such as an aromatic π orbital and extends over two or more atoms in a molecule, it has an unpaired electron. However, the organic compound can exist relatively stably. However, in this case, if the spread of unpaired electrons is too large, the oxidation-reduction potential becomes inappropriate. Considering such points, an organic compound having an aromatic ring having a relatively small molecular weight such as a benzene ring as a basic skeleton is suitable as a redox shuttle.

When a halogen group is introduced into the benzene ring having a methoxy group, the following effects are obtained.

That is, the oxidation-reduction potential of a compound is roughly determined by the basic skeleton of the molecule. When a substituent is introduced into the compound, the electron-withdrawing substituent often increases the oxidation-reduction potential. The electron donating substituent acts to lower the oxidation-reduction potential. It is known that the effects of a plurality of substituents often have additive properties.

Here, when a halogen group is introduced as a substituent on the benzene ring, the halogen group increases the oxidation-reduction potential. In an actual battery system, the potential fluctuates by about several hundred mV depending on the type of the electrolytic solution, but in a benzene ring into which a halogen group is introduced, the oxidation-reduction potential is finely adjusted by the action of such a halogen group. Therefore, regardless of the type of the electrolytic solution, it is oxidized and reduced at an appropriate potential, and exhibits a sufficient function as a redox shuttle.

It is necessary that two methoxy groups are introduced into a benzene ring per molecule. If only one compound is used, the effect as a redox group is small, and the required amount of the compound increases.

As described above, an organic compound having a structure in which two methoxy groups and a halogen group are introduced into a benzene ring is suitable as a redox shuttle for a 4V-class battery having a redox potential, and the oxidized species and the reduced species are chemically changed. Stable
There is no deterioration of battery performance due to side reactions. In addition, this compound has a molecular weight of 78 as a basic skeleton of a benzene ring, and is smaller in molecular weight than metal complexes such as metallocenes, polypyridine complexes, and cerium salts.
The molecular volume is also small. This means that the volume occupied in the electrolytic solution is small and the diffusion rate is high, the influence on the solvent characteristics of the electrolytic solution is small, and the dynamics in the electrolytic solution are good.

Specific examples of such organic compounds include 1,4-dimethoxy-2-fluorobenzene,
3-dimethoxy-5-chlorobenzene, 3,5-dimethoxy-1-fluorobenzene, 1,2-dimethoxy-4
-Fluorobenzene, 1,2-dimethoxy-4-bromobenzene, 1,3-dimethoxy-4-bromobenzene,
Or 2,5-dimethoxy-1-bromobenzene.

Among them, those having two methoxy groups at the 1,2-position or the 1,4-position, in particular, have good reversibility of the oxidation-reduction reaction and are suitable as a redox shuttle.

The redox shuttle overcharge control agent is used as an oxidation-reduction reagent that protects the battery by consuming the overcharge current during overcharge, and transports a constant overcharge current to the non-aqueous electrolyte. Used at a concentration sufficient to perform the reaction.

That is, in order to exert its function effectively, the redox shuttle overcharge controlling agent is preferably dissolved in the nonaqueous electrolyte in a concentration range of 0.1% by weight or more and 30% by weight or less. . It is more preferable to dissolve in a concentration range of 1% by weight or more and 10% by weight or less. When the concentration of the redox shuttle overcharge controlling agent is less than 0.1% by weight, the effect as a redox shuttle is not sufficiently exhibited. On the other hand, when the concentration is higher than 30% by weight, various characteristics of the non-aqueous electrolyte secondary battery are adversely affected, and the battery capacity and cycle characteristics are deteriorated.

The redox shuttle overcharge controlling agent exhibits its function effectively by dissolving it in the non-aqueous electrolyte in the above concentration range, and chemically consumes the overcharge current at the time of overcharging. At the same time, the overcharge energy is converted into heat energy and released outside the non-aqueous electrolyte secondary battery.

Therefore, in the non-aqueous electrolyte secondary battery containing the redox shuttle overcharge controlling agent in the non-aqueous electrolyte, the excess energy due to the overcharge current is not accumulated in the non-aqueous electrolyte secondary battery. Is converted into thermal energy and released outside the non-aqueous electrolyte secondary battery.

In a non-aqueous electrolyte secondary battery using a redox shuttle overcharge controlling agent, for example, even when overcharge is performed with an overcharge current exceeding the limit current of the redox shuttle, at least the excess current up to the limit current is obtained. Energy is not stored in the non-aqueous electrolyte secondary battery,
Released as heat energy outside the non-aqueous electrolyte secondary battery.

Furthermore, a non-aqueous electrolyte secondary battery containing a redox shuttle overcharge controlling agent in a non-aqueous electrolyte can be provided with a heat-sensitive switch or a sensor to reduce the heat released from the non-aqueous electrolyte secondary battery. The detection can be performed by a thermal switch or a sensor, and the thermal switch or the sensor can be used alone or in conjunction with a facility provided therewith to issue a warning of an overcharged state or to stop charging.

As the above-mentioned heat-sensitive switch or heat-sensitive sensor, those whose characteristics change due to the application of heat and whose change can be detected can be used. For example, various property changes such as melting, deformation, resistance value change, and color change by application of heat can be used. And, more specifically, for example,
Examples include a chalk marker, a liquid crystal (alignment agent), a thermocouple, a PTC element (Positive Temperature Coefficient), a bimetal, and a shape memory alloy. Using these, various overcharge prevention measures can be taken, such as, for example, cutting off the overcharge current, displaying a warning by a color change, emitting a warning sound via a circuit, and turning off the power.

Further, DSC (Differential Scanning)
Calorimeter) or a computer equipped with a calorimeter function can also be used. That is, in addition to adding the function of the thermal sensor as described above to the existing protection circuit, the power supply that detects the voltage between terminals and shuts off the current when the voltage between terminals exceeds a certain value and generates heat is detected. It is also possible to build a system such as cutting.

It should be noted that the present invention is not limited to the above-described example, and can be arbitrarily changed without departing from the gist of the present invention.

Therefore, the non-aqueous electrolyte secondary battery according to the present invention contains a redox shuttle overcharge controlling agent in the non-aqueous electrolyte and is provided with a heat-sensitive switch or a heat-sensitive sensor to take measures for preventing overcharge. An excellent safety mechanism that does not use uncontrollable runaway heat or gas and does not make the cell unusable even in the event of an abnormality provides high safety.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on specific experimental results.

Example 1 FIG. 1 shows a cross-sectional view of a coin-type nonaqueous electrolyte secondary battery (outer diameter 20 mm, height 2.5 mm) manufactured in Example 1.

This coin-type non-aqueous electrolyte secondary battery was manufactured as follows.

The negative electrode was produced by pressing a rolled lithium metal sheet (thickness: 1.85 mm, diameter: 15 mm) as the negative electrode active material 1 onto the upper can 2.

On the other hand, the positive electrode was manufactured as follows.

First, a positive electrode active material (LiCoO ₂ )
To obtain lithium carbonate and cobalt carbonate in 0.5
The mixture was mixed in a molar ratio of 1: 1 and calcined in air at 900 ° C. for 5 hours. Next, after preliminarily drying the obtained LiCoO ₂ at 200 ° C. for 90 minutes, this LiCoO ₂ 9
0 parts by weight, 7 parts by weight of graphite as a conductive agent, and 3 parts by weight of polyvinylidene fluoride (PVdF) as a binder are wet-mixed using N, N-dimethylformamide (DMF) and dried at 100 ° C. under reduced pressure. Thus, a positive electrode mixture was obtained. Then, this positive electrode mixture was formed into a pellet type having a diameter of 16 mm together with the aluminum mesh of the current collector, and stored in the lower can 4.

An upper can 2 to which the negative electrode active material 1 is pressed,
The lower can 4 containing the positive electrode active material 3 was laminated via a separator 5 made of a porous polypropylene film. Then, propylene carbonate and dimethyl carbonate 1: a solvent mixture 1 comprising a volume ratio, LiPF ₆ (the electrolyte) 1.
0 mol / l and 200 mmol of 1,2-dimethoxy-4-bromobenzene (redox shuttle overcharge control agent)
/ L was dissolved to prepare a non-aqueous electrolyte, which was injected into the battery can. Subsequently, the outer peripheral edges of the upper can 2 and the lower can 4 were caulked via a sealing gasket 6 and sealed to produce a coin-type non-aqueous electrolyte secondary battery. In addition, 1,2 dimethoxy-4-bromobenzene dissolved in the non-aqueous electrolyte solution was confirmed by cyclic voltammetry to have a reversible oxidation-reduction reaction at around 4.2 V and 4.45 V with respect to lithium. I have.

Comparative Example 1 A non-aqueous electrolyte in which 1.0 mol / l of LiPF ₆ was dissolved in a mixed solvent obtained by mixing propylene carbonate and dimethyl carbonate at a volume ratio of 1: 1 was used. Example 1
In the same manner as in the above, a coin-type nonaqueous electrolyte secondary battery was produced.

The coin-type non-aqueous electrolyte secondary batteries produced in Example 1 and Comparative Example 1 were charged and discharged under overcharge conditions, and the voltage change was examined.

The charge and discharge were performed at a current of 150 μA,
A constant current charge was performed for 100 hours under the condition of an upper limit voltage of 4.5 V, a pause was performed for 10 hours, and then a constant current discharge was performed under a condition of a current of 150 μA until the battery voltage reached 2.7 V. FIG. 2 shows the voltage change of the coin-type nonaqueous electrolyte secondary batteries produced in Example 1 and Comparative Example 1 in such a charge / discharge process.

In FIG. 2, the battery voltage of the coin-type non-aqueous electrolyte secondary battery of Comparative Example 1 is greatly increased by charging.
When the voltage becomes 1 V, the battery voltage hardly rises. This is because in the coin-type non-aqueous electrolyte secondary battery of Example 1, the overcharge current was consumed by 1,2-dimethoxy-4-bromobenzene added to the electrolyte, and the voltage rise was suppressed. . Thereby, in the coin-type nonaqueous electrolyte secondary battery of Example 1, the battery voltage was 4.1 V.
It can be seen that no energy is stored in the coin-type non-aqueous electrolyte secondary battery from the point in time when. That is, in the coin-type non-aqueous electrolyte secondary battery of Example 1, the overcharge current is consumed by the effect of the redox shuttle overcharge control agent from the time when the battery voltage becomes 4.1 V, It is considered that excess energy due to overcharging is converted to heat energy and released outside the coin-type non-aqueous electrolyte secondary battery. On the other hand, in the coin-type non-aqueous electrolyte secondary battery of Comparative Example 1, since the redox shuttle overcharge controlling agent was not added, the battery voltage rose to the upper limit voltage of 4.5 V, and the coin-type non-aqueous electrolyte secondary battery increased. It can be seen that excess energy is accumulated in the water electrolyte secondary battery.

Next, in order to confirm the above opinion, for the coin-type non-aqueous electrolyte secondary batteries manufactured in Example 1 and Comparative Example 1, the voltage change and the heat generation state during overcharge were examined. Was.

The charging was performed by a process such as performing constant-current charging at 150 μA until the battery voltage reached 4.95 V. The heat generation of the coin-type non-aqueous electrolyte secondary battery was measured using a calorimeter (manufactured by SETARAM). FIG. 3 shows a change in voltage of the coin-type non-aqueous electrolyte secondary batteries manufactured in Example 1 and Comparative Example 1 and a corresponding change in calorific value in such a charging process.

FIG. 3 shows that the coin-type non-aqueous electrolyte secondary battery of Comparative Example 1 to which 1,2 dimethoxy-4-bromobenzene, which is a redox shuttle overcharge control agent, was not added, Heat generation is hardly observed until the end of charging, when it is assumed that decomposition and structural destruction of the positive electrode have occurred. On the other hand, in the coin-type non-aqueous electrolyte secondary battery of Example 1 to which 1,2 dimethoxy-4-bromobenzene which is a redox shuttle overcharge control agent was added, the coin-type non-aqueous electrolyte of Comparative Example 1 was used. Time zone when the voltage difference between the battery and the electrolyte secondary battery started to occur (around 45 hours)
, Heat generation of the battery is recognized. Further, in the state where the voltage was constant at 4.2 V to 4.3 V, the calorific value of the battery was about 0.6 mW to 0.7 mW. Since the charging current at the time of constant current charging is 150 μA, the power at 4.2 V to 4.3 V where the voltage is constant is 0.6 μm.
It is expected to be 3 mW to 0.645 mW.
Agrees very well with the results. From this, the overcharge current supplied to the coin-type non-aqueous electrolyte secondary battery in a state where the voltage exceeds 4.3 V, that is, excess energy, is stored in the coin-type non-aqueous electrolyte secondary battery. Is not used for any side reaction,
It is theorized that it is converted to thermal energy at a rate of 0% and released outside the coin-type non-aqueous electrolyte secondary battery.

Example 2 FIG. 4 shows a cross-sectional view of a cylindrical nonaqueous electrolyte secondary battery (outer diameter 18 mm, height 65 mm) manufactured in Example 2.

This cylindrical non-aqueous electrolyte secondary battery was manufactured as follows.

First, the negative electrode 7 was manufactured as follows.

Oxygen crosslinking is carried out by using a petroleum pitch as a starting material and introducing a functional group containing oxygen by 10 to 20%, and then firing at 1000 ° C. in an inert gas stream to obtain a property close to glassy carbon. Was obtained. This non-graphitizable carbon material is pulverized to an average particle size of 10 μm.
Carbon material powder. Next, 90 parts by weight of this carbon material powder and polyvinylidene fluoride (PVd) as a binder
F) was mixed with 10 parts by weight to prepare a negative electrode mixture, which was further dispersed in N-methyl-2-pyrrolidone to form a slurry. Then, the slurry is uniformly applied to both surfaces of a 10 μm-thick strip-shaped copper foil as the negative electrode current collector 14,
After drying, compression molding was performed with a roll press machine to produce a negative electrode 7.

On the other hand, the positive electrode 8 was produced as follows.

First, the positive electrode active material (LiCoO ₂ )
To obtain lithium carbonate and cobalt carbonate in 0.5
The mixture was mixed in a molar ratio of 1: 1 and calcined in air at 900 ° C. for 5 hours. Next, 91 parts by weight of the obtained LiCoO ₂ , 6 parts by weight of graphite as a conductive agent, and 3 parts by weight of polyvinylidene fluoride (PVdF) as a binder were mixed to prepare a positive electrode mixture. Was dispersed in N-methylpyrrolidone to form a slurry. Then, this slurry was uniformly applied to both surfaces of a 20 μm-thick aluminum foil as the positive electrode current collector 15, dried, and then compression-molded with a roll press to produce a positive electrode 8.

Next, the obtained negative electrode 7 and positive electrode 8 were successively laminated via a separator 5 made of a microporous polypropylene film having a thickness of 25 μm, and wound in a spiral form many times to produce a wound body. .

Next, the insulating plate 9 was inserted into the bottom of the nickel-plated iron battery can 10, and the wound body was housed. Then, in order to collect the current of the negative electrode 7, one end of a negative electrode lead 16 made of nickel is pressed against the negative electrode 7, and the other end is connected to the battery can 1.
0 was welded. In order to collect the current of the positive electrode 8, one end of an aluminum positive electrode lead 17 is attached to the positive electrode 8, and the other end is connected to the battery lid 12 via a current interrupting thin plate 13 which interrupts the current according to the internal pressure of the battery. Connected electrically.

Then, 1,2-dimethoxy-4-bromobenzene (a redox shuttle overcharge controlling agent) was mixed in a mixed solvent of 50 vol% of propylene carbonate (PC) and 50 vol% of diethyl carbonate in the battery can 10. ) 5% by volume and L
0.5 mol / l of iPF ₆ (electrolyte) and LiN (C ₂ F
₅ SO _{2) 2} (was injected electrolyte) non-aqueous electrolytic solution obtained by dissolving a 0.5 mol / l. Then, the battery lid 10 is fixed by caulking the battery can 10 through the insulating sealing gasket 11 coated with asphalt, and has a diameter of 18 mm and a height of 6 mm.
A 5 mm cylindrical non-aqueous electrolyte secondary battery was produced.

A chalk marker that changes color when heat is detected is attached to the outside of the battery can 10 of the cylindrical non-aqueous electrolyte secondary battery manufactured as described above.

Comparative Example 2 A cylindrical non-aqueous electrolyte secondary battery was prepared in the same manner as in Example 2 except that 1,2-dimethoxy-4-bromobenzene was not dissolved in the non-aqueous electrolyte.

The cylindrical non-aqueous electrolyte secondary batteries produced in Example 2 and Comparative Example 2 were overcharged,
The voltage change was examined.

The charging was performed by constant current charging at a current of 60 mA. FIG. 5 shows voltage changes of the cylindrical non-aqueous electrolyte secondary batteries manufactured in Example 2 and Comparative Example 2.

In FIG. 5, the battery voltage of the cylindrical non-aqueous electrolyte secondary battery of Comparative Example 2 is greatly increased by charging, whereas the battery voltage of the cylindrical non-aqueous electrolyte secondary battery of Example 2 is large. When the voltage becomes about 4.2 V, the battery voltage hardly rises. This is because, in the cylindrical nonaqueous electrolyte secondary battery of Example 2, 1,2-dimethoxy-4-added to the electrolyte was added.
This is because the bromobenzene consumes an overcharge current and suppresses a voltage rise. In the cylindrical nonaqueous electrolyte secondary battery of Example 2, the color of the choke marker attached to the battery can 10 was confirmed from around 1600 mAh where the battery voltage began to be constant. Thereby, in the cylindrical non-aqueous electrolyte secondary battery of Example 2, the time when the battery voltage started to be constant, that is, the battery voltage was 4.2
It can be seen that no energy is stored in the cylindrical non-aqueous electrolyte secondary battery from the point in time when the voltage has reached around V. That is, in the cylindrical non-aqueous electrolyte secondary battery of Example 2, from the time when the battery voltage becomes around 4.2 V, the overcharge current is consumed due to the effect of the redox shuttle overcharge control agent, and In other words, it can be said that excess energy due to overcharging is converted into heat energy and released outside the cylindrical nonaqueous electrolyte secondary battery.

On the other hand, in the cylindrical non-aqueous electrolyte secondary battery of Comparative Example 2, the battery voltage increased to around 5V. In the cylindrical non-aqueous electrolyte secondary battery of Comparative Example 2, no color change was observed in the choke marker attached to the battery can 10. Thereby, in the cylindrical non-aqueous electrolyte secondary battery of Comparative Example 2, since the redox shuttle overcharge controlling agent was not added, the overcharge current was not consumed, and it was converted to thermal energy and converted into cylindrical energy. It can be seen that the energy is not released to the outside of the non-aqueous electrolyte secondary battery and is stored as excess energy in the cylindrical non-aqueous electrolyte secondary battery.

From the above results, by adding the redox shuttle overcharge controlling agent to the non-aqueous electrolyte, even when the battery is charged in an overcharged state, the excess energy is converted into heat energy. Thus, it can be seen that it is discharged outside the non-aqueous electrolyte secondary battery. Therefore,
This released thermal energy is detected using a thermal switch or a thermal sensor, etc., and by taking measures to prevent overcharging, without using uncontrollable runaway heat or gas, and even in abnormal times Since an excellent safety mechanism that does not render the cell unusable is provided, high security can be ensured.

[0070]

As described above in detail, according to the present invention, overcharge protection of a non-aqueous electrolyte secondary battery having a high energy density of 4 V or more can be achieved without disabling the cell. And it can be provided by a simpler method at a lower cost and without a protective device for lowering the energy density.

Therefore, a non-aqueous electrolyte secondary battery having a light weight, a high capacity and a long life can be supplied at a low cost, and since the battery is excellent in safety and reliability, it can be used in portable equipment and automobile batteries. It can be widely used for applications requiring a secondary battery, such as electric vehicles, road leveling, etc., and the effect is very large.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one configuration example of a battery to which the present invention is applied.

FIG. 2 shows a coin-type non-aqueous electrolyte secondary battery in which 1,2-dimethoxy-4-bromobenzene is added to an electrolyte, and a coin-type non-aqueous electrolyte secondary battery in which this compound is not added to an electrolyte. FIG. 4 is a characteristic diagram showing a comparison between voltage changes in a charge / discharge process.

FIG. 3 shows a coin-type non-aqueous electrolyte secondary battery in which 1,2-dimethoxy-4-bromobenzene is added to an electrolyte, and a coin-type non-aqueous electrolyte secondary battery in which this compound is not added to an electrolyte. FIG. 3 is a characteristic diagram showing a comparison between a voltage change in a charging process and a corresponding calorific value from a coin-type non-aqueous electrolyte secondary battery.

FIG. 4 is a cross-sectional view showing one configuration example of a battery applied to the present invention.

FIG. 5 shows a cylindrical non-aqueous electrolyte secondary battery in which 1,2-dimethoxy-4 bromobenzene is added to the electrolyte and a cylindrical non-aqueous electrolyte secondary battery in which this compound is not added to the electrolyte. FIG. 7 is a characteristic diagram showing a comparison between voltage changes in a charging process.

[Explanation of symbols]

1 negative electrode active material, 2 upper can, 3 positive electrode active material, 4 lower can, 5 separator, 6 sealing gasket, 7 negative electrode, 8
Positive electrode, 9 Insulation plate, 10 Battery can, 11 Insulation sealing gasket, 12 Battery cover, 13 Current interrupting thin plate, 14
Negative electrode current collector, 15 positive electrode current collector, 16 negative electrode lead,
17 Positive electrode lead

Claims (2)

[Claims] 1. A metal mainly composed of lithium as a negative electrode,
Or a non-aqueous electrolyte comprising a carbon material capable of doping and undoping lithium, a composite oxide of lithium and a transition metal as a positive electrode, and a non-aqueous electrolyte in which an electrolyte is dissolved in a non-aqueous solvent as a non-aqueous electrolyte. A non-aqueous electrolyte secondary battery, characterized in that the non-aqueous electrolyte contains a redox shuttle overcharge control agent and is provided with a heat-sensitive switch or a heat-sensitive sensor. 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the redox shuttle overcharge control agent is a compound represented by the following formula 1. Embedded image