JP2001283920A - Lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium secondary battery, in which the lowering of the output power of the battery due to generation of power quality SEI is restrained by suppressing the effects of radical molecules and HF generated in the nonaqueous electrolyte, and the cycle characteristics is improved. SOLUTION: The lithium secondary battery is equipped with an electrode body 1, comprising a positive electrode plate 2 and a negative electrode plate 3 wound or laminated via a separator 4 and uses a non-aqueous electrolyte containing lithium compound as an electrolyte. A cyclic compound containing N-O radical in the molecular structure is made to be contained in at least one of the positive electrode plate 2, the negative electrode plate 3, the separator 4 or the nonaqueous electrolyte, or a cyclic compound which becomes a Mn2+ supplier is made to be contained in the electrolyte.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a lithium secondary battery having excellent long-term stability, cycle characteristics, and reliability.

[0002]

2. Description of the Related Art In recent years, lithium secondary batteries have been widely used as small, chargeable / dischargeable secondary batteries having a large energy density and serving as power supplies for electronic devices such as portable communication devices and notebook personal computers. It is becoming. In addition, with the growing interest in resource saving and energy saving against the background of international protection of the global environment, lithium secondary batteries are used as motor driving batteries for electric vehicles and hybrid electric vehicles in the automotive industry, In the electric power industry, they are expected as means for effectively utilizing electric power by storing electric power at night, and there is an urgent need to commercialize large-capacity lithium secondary batteries suitable for these uses.

In a lithium secondary battery, a lithium transition metal composite oxide or the like is generally used as a positive electrode active material, and a carbonaceous material such as hard carbon or graphite is used as a negative electrode active material. In addition, the reaction potential of a lithium secondary battery using such a material is as high as about 4.1 V, so that an aqueous nonaqueous electrolyte such as a conventional secondary battery cannot be used as a nonaqueous electrolyte. . Therefore, as a non-aqueous electrolyte for a lithium secondary battery, a non-aqueous electrolyte obtained by dissolving a lithium compound as a lithium ion (Li ⁺ ) electrolyte in an organic solvent is used.

[0004]

Here, ethylene carbonate, diethyl carbonate, or a mixture thereof is often used as an organic solvent as a raw material of the non-aqueous electrolyte. Such an organic solvent can be used as an electron conductor Li
⁺ It is widely used as an electrolyte for lithium secondary batteries because of its good mobility, low internal resistance of the battery, and satisfactory solubility of the electrolyte.

However, it is used as a battery and is repeatedly charged and discharged.
Organic solvent radicalizes by electrochemical reaction
And the presence of radical molecules in the electrolyte
There is. Then, the radical molecule
The decomposition reaction starts, and the decomposition of the electrolyte proceeds in a chain
Organic solvents such as ethylene carbonate are CO 2 _Two, CO_Three ^2-etc
Will be decomposed into small molecules. And yes
Solvent loses its function as electrolyte, and Li⁺Movement is blocked
It will be harmed and the battery resistance will increase.

Therefore, Japanese Patent Application Laid-Open No. 10-106579 discloses that a nitrogen atom is a radical in a non-aqueous electrolyte.
It is disclosed that by adding a compound having a molecular structure containing three benzene rings, a radical reaction in the battery is suppressed and an increase in the internal resistance of the battery is reduced. However, this substance only captures oxygen radicals and has poor reactivity with radical molecules other than oxygen generated in the battery due to steric hindrance due to the molecular skeleton. However, it is completely unsuitable for applications such as electric vehicles that require long-term storage characteristics.

[0007]

Means for Solving the Problems The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a non-aqueous electrolyte in a non-aqueous electrolyte while repeating charge and discharge. By eliminating generated radicals, and at the stage when the battery has been manufactured, it also has the effect of inactivating HF generated from water that will eventually be contained in the electrode body and the non-aqueous electrolyte. An object of the present invention is to provide a lithium secondary battery excellent in cycle characteristics and reliability by suppressing generation of a bad SEI layer in a negative electrode, thereby suppressing inhibition of a battery reaction.

That is, according to the present invention, a lithium secondary battery using a non-aqueous electrolyte containing a lithium compound as an electrolyte is provided with an electrode body formed by winding or laminating a positive electrode plate and a negative electrode plate with a separator interposed therebetween. A battery, wherein at least one of the positive electrode plate, the negative electrode plate, the separator, and the non-aqueous electrolyte contains a cyclic compound containing a NO radical in a molecular structure. Lithium secondary battery is provided.

In the lithium secondary battery of the present invention, as the compound, a compound having one ring in a cyclic compound containing an NO radical in its molecular structure is preferably used. As the molecular structure of the compound, a compound having a molecular structure represented by the following general formula (I) is preferable,
As another molecular structure of the compound, a compound having a molecular structure represented by the following general formula (II) is preferable.

Embedded image

Embedded image (R _{1 to} R ₁₈ : hydrogen group, hydrocarbon group, or cyano group)

Specifically, 2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 4-cyano-2,2,6,6-tetramethyl-1-
Piperidinyloxy free radical, 3-cyano-
2,2,5,5-tetramethyl-1-pyrrolidinyloxy free radical is particularly preferably used.

Further, according to the present invention, a lithium secondary battery using a non-aqueous electrolyte containing a lithium compound as an electrolyte is provided with an electrode body formed by winding or laminating a positive electrode plate and a negative electrode plate with a separator interposed therebetween. A battery, wherein at least one of the positive electrode plate, the negative electrode plate, the separator, and the non-aqueous electrolytic solution includes a cyclic compound serving as a Mn ²⁺ supplier in the electrolytic solution. Lithium secondary battery is provided.

In the lithium secondary battery of the present invention,
As the compound, Mn ²⁺Cyclic compound
Manganese (II) phthalocyanine or manganese (I
I) Phthalocyanine derivatives are preferred. To be specific
And a manganese (II) lid represented by the following chemical formula (III)
Russiannin is particularly preferably used.

Embedded image

In the present invention, it is also preferable that the compound has dispersed therein electron conductive particles such as acetylene black serving as a conductive assistant. Such compounds are
The addition of the conductive additive suppresses an increase in the internal resistance without contributing to the battery reaction, and provides a good radical decomposition inhibitor and / or an HF trapping agent.

The lithium secondary battery of the present invention is suitably used for a large battery having a battery capacity of 2 Ah or more. Further, it is preferably used as an on-vehicle battery, and is suitably used as a power source for starting an engine requiring high output, a power source for driving a motor of an electric vehicle or a hybrid electric vehicle in which a large current is frequently discharged.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The lithium secondary battery of the present invention
An organic solvent containing, as an electrolyte, a lithium compound that dissolves to produce lithium ions (Li ⁺ ) as an electrolyte. The electrolyte has a good SEI at a negative electrode by suppressing deterioration of the electrolyte and corrosion in the battery due to HF. By forming only the layer, the cycle characteristics are improved. Hereinafter, an embodiment of the present invention will be described,
It goes without saying that the present invention is not limited to the following embodiments.

In the lithium secondary battery of the present invention, in FIG. 1, at least one of the positive electrode plate 2, the negative electrode plate 3, the separator 4, and the non-aqueous electrolyte includes a cyclic compound containing an NO radical in a molecular structure. To be included. The N-
As the cyclic compound containing an O radical in the molecular structure, a compound having one ring is preferable. Here, "containing the compound" means that the non-aqueous electrolyte solution to which the compound is added,
By impregnating the electrode plates 2 and 3 and the separator 4,
When the compound is to be included in the electrode plates 2.3 and the separator 4 or when the compound applied in advance to the electrode plates 2.3 and the separator 4 is filled with the non-aqueous electrolyte, This includes the case where it moves in and becomes included in the non-aqueous electrolyte.

In the lithium secondary battery of the present invention,
As a method of including this compound, (1) a positive electrode plate, and / or
Or, dispersed on the surface of the electrode active material particles constituting the negative electrode plate,
Or (2) dispersed on the surface of the separator; and (3) finely powdered and suspended and dispersed in a non-aqueous electrolyte. Therefore, it is also possible to use a plurality of these means in combination.

Specifically, as a method of including the compound in the electrode plates 2 and 3, a method of dipping the electrode plates 2 and 3 in the compound agent dissolved in a soluble solvent (dipping) or a method of spraying Electrode plate 2 using a method such as brushing or brushing.
3 can include a method of applying the compound.
In any case, the compound is included, dried after that, and provided for the subsequent production of the electrode body. The same method can be used to disperse or adhere to the surface of the separator 4, and for the electrolytic solution, the compound may be finely powdered to such an extent that the compound does not settle by gravity, and the compound may be uniformly contained. It is possible.

Here, a method of using a non-aqueous electrolyte to which the compound is added in advance is most preferably employed. In this case, there is an advantage that the battery assembling operation step only requires an addition and mixing step of the compound, and the operation is easy.

That is, as an electrolytic solution to be filled in the battery, an electrolytic solution of a general organic solvent obtained by dissolving an electrolyte described below in a predetermined organic solvent, and further as a radical decomposition inhibitor / HF trapping agent, Use the one to which the compound is added. By adding the compound, it is possible to reduce the concentration of HF generated from the water content of the non-aqueous electrolyte before inserting the internal electrode body into the battery. After the internal electrode body is inserted into the battery, HF generated from moisture adsorbed on the electrode plate or the like is easily removed. And, while starting to use the battery and repeating charge and discharge,
The generated radical molecules can be eliminated. It is considered that the cycle characteristics are improved by suppressing the electrolytic solution decomposition reaction by radical molecules and the bad SEI generation reaction by HF in this manner.

Now, the compounds used in the lithium secondary battery of the present invention will be described. As the cyclic compound containing an N—O radical in its molecular structure that can be used in the present invention, a compound having a molecular structure represented by the general formula (I) is preferable as its molecular structure. As the structure, a compound having a molecular structure represented by the general formula (II) is preferred.

Embedded image

Embedded image (R _{1 to} R ₁₈ : hydrogen group, hydrocarbon group, or cyano group)

Specifically, 2,2,6,6-tetramethyl-1-piperidinyloxy free radical and / or 4-cyano-2,2,6,6-tetramethyl-
Examples thereof include 1-piperidinyloxy free radical and 3-cyano-2,2,5,5-tetramethyl-1-pyrrolidinyloxy free radical. These are small in molecular skeleton, react quickly with radical molecules generated from the organic solvent, are stable in the electrolytic solution and do not inhibit the transfer of Li ^{+ in} the electrolytic solution, and are suitable as the compound. Used for

In addition, the lithium secondary battery of the present invention includes the positive electrode plate, the negative electrode plate, the separator, and the non-aqueous electrolyte in at least one of the positive electrode plate 2, the negative electrode plate 3, the separator 4, and the non-aqueous electrolyte. In at least one of the electrolytes,
A cyclic compound serving as a Mn ²⁺ supplier is contained in the electrolytic solution. The method of including the compound in the battery can be performed in the same manner as described above.

Now, the compounds used in the lithium secondary battery of the present invention will be described. Manganese (II) phthalocyanine or a manganese (II) phthalocyanine derivative is suitably used as the cyclic compound serving as the Mn ²⁺ supplier that can be used in the present invention. Specific examples include manganese (II) phthalocyanine represented by the following chemical formula (III). This is stable and exhibits high Li ⁺ conductivity in the electrolytic solution, and is suitably used as the compound.

Embedded image

Hereinafter, in the present invention, the mechanism by which the compound suppresses a radical decomposition reaction will be described. In the present invention, a mixture of ethylene carbonate and diethyl carbonate is used as the electrolytic solution to fill the inside of the electrode body. However, even in such an organic solvent, when the use of the battery is started and the charge and discharge are repeated, the charge and discharge are repeated. A radical molecule may be generated from an organic solvent molecule by an electric reaction at the time of discharge. If the electrolyte is an organic solvent system, once it is decomposed, it is almost impossible to recover it,
When gas or the like is generated by the decomposition of the organic solvent, the internal pressure of the battery rises, and the battery becomes dangerous.

That is, in a lithium secondary battery,
When the charge and discharge are repeated, the organic solvent R _A H
Part of ( _RA : hydrocarbon group) is decomposed into small molecules as in the following formula (IV).

R _A H → R _A + H ⁺ → CO ₂ , CO ₃ ^2- , etc. (IV) (R _A : radical molecule generated by electrochemical reaction) Radical decomposition reaction as described above The following methods (V) and (VI) can be used to control the reaction: 1) adding a radical compound, and 2) utilizing the chemical equilibrium reaction of radical extinction.

Embedded image _{R A H → R A · +} H + + R B · → R A R B ... (V) (R B ·: Radical cyclic compound added according to the invention)

^{Embedded image} _RA H + Mn ³⁺ ⇔ _RA · + H ⁺ + Mn ²⁺ (VI)

1) In the formula (V), an appropriate amount of a radical compound R _B · which reacts quickly with the radical molecule R _A · generated at the time of charge / discharge is added, and the radicals are reacted and bound together. The idea is to prevent further decomposition. Also, 2) (Formula (VI)) utilizes the fact that the generated radical molecule R _A has a chemical equilibrium relationship with a sound organic solvent molecule and manganese ion eluted from the positive electrode active material, The idea is that an appropriate amount of Mn ²⁺ ion is added to shift the chemical equilibrium toward the organic solvent holding side.

Therefore, in the present invention, a cyclic compound containing the N—O radical of the compound in the molecular structure is
By causing a radical / radical reaction of 1), the cyclic compound serving as a Mn ²⁺ supplier is changed to 2) of
By supplying Mn ²⁺ ions during radical chemical equilibrium, radicals generated during charging and discharging can be eliminated from the battery and the decomposition of organic solvents can be suppressed, so that the electrolyte is kept in a healthy state can do.

Next, in the present invention, the compound is H
A mechanism for inactivating F will be described. The electrolytic solution in the present invention uses a non-aqueous electrolytic solution containing no water.However, when assembling the battery, it is not possible to completely remove the moisture attached to the battery members and the like. Has a small amount of water. Then, due to the moisture, the electrolytic solution and the electrolyte are decomposed, and HF and gas (CO
₂ ) etc. occur.

The HF generated at this time dissolves and corrodes the metal material of the battery case and the current collector, dissolves the positive electrode active material and elutes the transition metal, and induces the generation of malicious SEI containing metal atoms. I do. The decomposition of the electrolyte by water is accelerated as the temperature of the battery becomes higher, and the decomposition proceeds. Since the reaction of generating SEI is an exothermic reaction, the heat promotes decomposition of the electrolyte by water, and further generates HF.

Therefore, in the present invention, an atom exhibiting Lewis basicity, that is, an N atom having an unshared electron pair and exhibiting electron donating property is coordinately bonded to HF having an empty electron orbit. HF is immobilized within the molecular structure of the compound. Thereby, the HF in the battery is inactivated, and the influence of the HF can be suppressed. As a result, even when the battery itself is heated to a high temperature while the battery is repeatedly charged and discharged, the compound fixes HF, thereby suppressing the generation of malicious SEI.

In the present invention, electron conductive particles such as acetylene black may be dispersed in the compound. As a result, the conductivity can be increased, and an increase in the internal resistance can be prevented.

The lithium secondary battery of the present invention uses a non-aqueous electrolyte using a lithium compound that dissolves to generate lithium ions (Li ⁺ ) as an electrolyte. Therefore, there are no restrictions on other materials or battery structures. Hereinafter, the main members constituting the battery and the structure thereof will be outlined.

One structure of an electrode body, which can be said to be the heart of a lithium secondary battery, is a single cell sandwiching a separator formed by pressing each of positive and negative electrode active materials into a disk shape, as seen in a small capacity coin battery. Structure.

For a small capacity battery such as a coin battery, one structure of an electrode body used for a battery having a large capacity is a wound type. As shown in the perspective view of FIG. 1, in the wound electrode body 1, the positive electrode plate 2 and the negative electrode plate 3 are directly connected to each other via a separator 4 made of a porous polymer. It is configured by being wound around the outer periphery of the core 13 so as not to contact. Positive electrode plate 2 and negative electrode plate 3 (hereinafter referred to as “electrode plate 2
3 ". ) Attached to the electrode leads 5 and 6
The number of electrodes may be at least one, and a plurality of electrode leads 5 and 6 may be provided to reduce the current collecting resistance.

As another structure of the electrode body, there is a stacked type in which a single-cell type electrode body used for a coin battery is stacked in a plurality of stages. As shown in FIG. 2, the laminated electrode body 7 includes a positive electrode plate 8 and a negative
At least one electrode lead 11, 12 is attached to one electrode plate 8, 9.
The materials used and the preparation method of the electrode plates 8 and 9 are the same as those of the electrode plates 2 and 3 in the wound electrode body 1.

Next, the configuration of the wound electrode body 1 will be described in more detail by way of example. The positive electrode plate 2 is manufactured by applying a positive electrode active material to both surfaces of a current collecting substrate. As the current collecting substrate, a metal foil having good corrosion resistance to a positive electrode electrochemical reaction such as an aluminum foil or a titanium foil is used, but a punching metal or a mesh (net) can be used instead of the foil. As the positive electrode active material, lithium manganate (LiMn ₂ O ₄ ), lithium cobaltate (LiCoO ₂ ), lithium nickelate (Li
A lithium transition metal composite oxide such as NiO ₂ ) is suitably used, and preferably, a fine carbon powder such as acetylene black is added as a conductive additive thereto.

The coating of the positive electrode active material is performed by applying a slurry or paste prepared by adding a solvent, a binder, or the like to the positive electrode active material powder, using a roll coater method or the like on a current collecting substrate.
The drying is performed, and thereafter, a pressing process or the like is performed as needed.

The negative electrode plate 3 can be made in the same manner as the positive electrode plate 2. As the current collecting substrate of the negative electrode plate 3, a metal foil having good corrosion resistance to a negative electrode electrochemical reaction such as a copper foil or a nickel foil is suitably used. As the negative electrode active material, an amorphous carbonaceous material such as soft carbon or hard carbon, or a highly graphitized carbonaceous powder such as artificial graphite or natural graphite is used.

The separator 4 preferably has a three-layer structure in which a Li ⁺ permeable polyethylene film (PE film) having micropores is sandwiched by a porous Li ⁺ permeable polypropylene film (PP film). Used for When the temperature of the electrode body rises, the PE film softens at about 130 ° C. and the micropores are crushed, which also serves as a safety mechanism for suppressing the movement of Li ⁺ , that is, the battery reaction. And, by sandwiching this PE film with a PP film having a higher softening temperature,
Even when the PE film is softened, the PP film retains its shape to prevent contact / short circuit between the positive electrode plate 2 and the negative electrode plate 3, thereby making it possible to reliably suppress battery reaction and ensure safety.

At the time of winding work of the electrode plates 2 and 3 and the separator 4, the electrode leads 5 and 6 are provided on the portions of the electrode plates 2 and 3 where the current collecting substrate not coated with the electrode active material is exposed.
Are respectively attached. As the electrode leads 5 and 6, foil-like ones made of the same material as the current collecting substrate of each of the electrode plates 2 and 3 are preferably used. Electrode leads 5 and 6
Can be attached to the electrode plates 2 and 3 using ultrasonic welding, spot welding, or the like. At this time, as shown in FIG. 1, when the electrode leads 5 and 6 are attached so that the electrode leads of one electrode are arranged on one end surface of the electrode body 1, contact between the electrode leads 5 and 6 is prevented. Can be preferred.

In assembling the battery, first, while ensuring conduction between the terminals for extracting current to the outside and the electrode leads 5 and 6, the manufactured electrode body 1 is inserted into the battery case to be in a stable position. Hold on. Then, after impregnating with a non-aqueous electrolyte, the battery case is sealed to produce a battery.

Next, the non-aqueous electrolyte used in the lithium secondary battery of the present invention will be described. Examples of the solvent include carbonates such as ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC) and propylene carbonate (PC), and single or mixed solvents such as γ-butyrolactin, tetrahydrofuran, and acetonitrile. It is preferably used.

As a lithium compound dissolved in such a solvent, that is, as an electrolyte, a lithium complex fluorine compound such as lithium hexafluorophosphate (LiPF ₆ ) or lithium borofluoride (LiBF ₄ ), or lithium perchlorate ( Lithium chloride such as LiClO ₄ ), and one or more of them are dissolved in the solvent and used. In particular, it is preferable to use LiPF ₆ which does not easily undergo oxidative decomposition and has high conductivity of the non-aqueous electrolyte.

[0045]

EXAMPLES Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. (Examples 1 to 4, Comparative Example 1) Examples 1 to 4 and Comparative Example 1
The battery according to the above is a cathode active material slurry prepared by adding LiMn ₂ O ₄ spinel as a positive electrode active material, acetylene black as a conductive additive to an external ratio of about 4% by weight, and further adding a solvent and a binder. A positive electrode plate 2 prepared by coating both sides of a 20-μm-thick aluminum foil so as to have a thickness of about 100 μm, respectively;
A negative electrode plate 3 was prepared by coating both sides of the copper foil so as to have a thickness of about 80 μm, and a wound electrode body was prepared. It was produced by Here, as the non-aqueous electrolyte, a solution obtained by dissolving LiPF ₆ as an electrolyte at a concentration of 1 mol / l in an equal volume mixed solvent of EC and DEC was prepared as shown in Table 1.
As shown in Table 2, a compound to which the compound was added in an external ratio of about 0.1% by mass was used. The battery capacities of these various batteries after the first charge were all about 10 Ah.

[0046]

[Table 1]

The cycle test was performed by repeating the charge / discharge cycle shown in FIG. 3 as one cycle. That is, in one cycle, a battery in a charged state with a depth of discharge of 50% has a current 10 corresponding to 10 C (discharge rate).
After discharging at 0A for 9 seconds, rest for 18 seconds.
After charging at A for 6 seconds, the battery was charged at 18A for 27 seconds, and the pattern was again set to a 50% charged state. In addition,
The deviation of the depth of discharge in each cycle was minimized by finely adjusting the current value of the second charge (18 A). In order to know the change in the battery capacity during the endurance test, the charge stop voltage 4.1 at a current intensity of 0.2 C is appropriately set.
V, and a discharge stop voltage of 2.5 V, a capacity measurement was performed, and a relative discharge capacity was obtained from a value obtained by dividing the battery capacity at a predetermined cycle number by the initial battery capacity.

(Evaluation) As can be seen from FIG. 4, the batteries of Examples 1 to 4 according to the present invention achieved a capacity retention of 85% in a 20,000 cycle test, and did not use the compound. Very good cycle characteristics were exhibited compared to Comparative Example 1. This is because a cyclic compound containing an N—O radical in its molecular structure and a cyclic compound serving as a Mn ²⁺ supplier suppress a radical decomposition reaction of an organic solvent, and
It is considered that by trapping F, good SEI was produced and the cycle life was improved.

Here, the batteries according to Examples 1 to 4 and Comparative Example 1 were produced by the above-described method using various battery components adjusted to include the compound in a battery case. The other components and the test environment were the same for all the samples, and the drying of the battery members was fully performed until immediately before the assembly of the battery, and the effects of intrusion of moisture from the outside of the battery due to poor sealing of the battery and the like were also eliminated. .

(Example 5, Comparative Example 2) The batteries according to Example 5 and Comparative Example 2 used LiMn ₂ O ₄ spinel as a positive electrode active material, and added acetylene black as a conductive additive and polyvinylidene fluoride as a binder. By weight ratio, 50: 2:
The mixture obtained at a ratio of 3 was used as a positive electrode material, and 0.02 g of the positive electrode material was added at a pressure of 300 kg / cm ^{2 to} a diameter of 20 mm.
A positive electrode plate produced by press molding into a disk of φ, and a coin cell type electrode body using carbon as the negative electrode plate,
It was prepared by filling the battery case with a non-aqueous electrolyte solution. Here, as the non-aqueous electrolyte, EC and DEC are used.
About 500 ppm of water (H ₂ O), which causes deterioration of battery characteristics, is added to the mixed solvent of the same volume, and the compound is added at about 500 ppm as shown in Table 2, and 1 mol of LiPF ₆ is used as an electrolyte. A solution dissolved to a concentration of / l was used. The battery capacities of these various batteries after the first charge were all about 1.3 mAh.

[0051]

[Table 2]

The cycle test of the coin cell type battery was performed by repeating the following charge / discharge cycle as one cycle. That is, one cycle is 1
After charging to a voltage of 4.1 V with a current of 1.3 mA corresponding to C, the battery was subsequently charged at a constant voltage for a total of 3 hours, and then the battery was charged to a constant current of 1.3 mA corresponding to 1 C (discharge rate). After the battery was discharged until the voltage reached 2.5 V, the pattern was set to pause for 600 seconds, and the same charge / discharge was repeated again. The relative discharge capacity (%) shown in FIG. 5 was calculated using the following equation (1).

[0053]

## EQU1 ## Relative discharge capacity (%) = discharge capacity in each cycle / initial discharge capacity

(Evaluation) As can be seen from FIG. 5, the battery of Example 5 according to the present invention achieved a capacity retention of 93% in 100 cycles of the cycle test, and was a comparative example in which the compound was not used. The cycle performance was much better than that of No. 2. The verification in the examples to which water was intentionally added as described above clearly demonstrates that the compound disclosed by the present invention exerts an excellent effect on cycle life which is an important battery characteristic. Becomes

Here, the batteries according to Example 5 and Comparative Example 2 were prepared in the same manner as in the case of the wound electrode body, by using the above-described method to prepare various battery components prepared by including the compound in a battery case. It was produced using. The other components and the test environment were the same for all the samples, and the drying of the battery members was fully performed until immediately before the assembly of the battery, and the effects of intrusion of moisture from the outside of the battery due to poor sealing of the battery and the like were also eliminated. .

In a battery for starting an engine or a battery for driving a motor such as an electric vehicle, a large current is required to be discharged at the time of starting, accelerating, climbing a hill, or the like. At this time, the battery temperature rises. However, when a non-aqueous electrolyte to which the compound of the present invention is added is used, even if the battery temperature rises, the captured HF may be released again and dissolved in the non-aqueous electrolyte. Is difficult to occur, and good cycle characteristics are maintained.

As described above, the present invention has mainly been described by taking a case where a wound electrode body is used as an example. However, it is needless to say that the present invention does not matter about the battery structure, and the long-term high output performance is not limited. It is a required battery and is suitably adopted for a battery with a large capacity. Specifically, the wound or laminated electrode bodies 1 and 7 are preferably used for those having a battery capacity of 2 Ah or more.

Needless to say, the use of the battery is not limited, but as a vehicle-mounted large-capacity battery that requires high output, low internal resistance and excellent cycle characteristics, it can be used for starting an engine or for an electric vehicle. Alternatively, it can be particularly suitably used for driving a motor of a hybrid electric vehicle.

[0059]

As described above, according to the lithium secondary battery of the present invention, each of the radicals formed by the cyclic compound containing the N—O radical in the molecular structure and the cyclic compound serving as the Mn ²⁺ supplier is obtained. By the annihilation reaction, the decomposition of the organic solvent as the electrolytic solution can be suppressed. Also, N-O
HF can be inactivated by coordinating a nitrogen atom of a cyclic compound containing a radical in its molecular structure and a cyclic compound serving as an Mn ²⁺ donor with HF. As a result, the lithium secondary battery according to the present invention has an excellent effect that the cycle characteristics and reliability are improved particularly at high temperatures.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a structure of a wound electrode body.

FIG. 2 is a perspective view showing a structure of a stacked electrode body.

FIG. 3 is a graph showing a charge / discharge pattern in a cycle test.

FIG. 4 is a graph showing the results of the cycle tests of Examples 1 to 4.

FIG. 5 is a graph showing the results of a cycle test of Example 5.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wound electrode body, 2 ... Positive electrode plate, 3 ... Negative electrode plate, 4 ... Separator, 5 ... Electrode lead, 6 ... Electrode lead, 7 ... Laminated electrode body, 8 ... Positive electrode plate, 9 ... Negative electrode plate, 10 … Separator,
11 ... electrode lead, 12 ... electrode lead, 13 ... winding core.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H029 AJ05 AK03 AL06 AM03 AM04 AM05 AM07 BJ12 BJ14 DJ08 EJ11 HJ02 HJ19 5H050 AA05 AA07 BA17 CA09 CB07 DA09 EA22 EA24 FA02 FA05 FA06 HA02 HA19

Claims (12)

[Claims] 1. A positive electrode plate and a negative electrode plate with a separator interposed therebetween.
A lithium secondary battery using a non-aqueous electrolyte containing a wound or laminated electrode body and containing a lithium compound as an electrolyte, the positive electrode plate, the negative electrode plate, the separator, and the non-aqueous electrolyte Wherein at least one of the above comprises a cyclic compound containing an N—O radical in its molecular structure. 2. The cyclic compound containing the NO radical in its molecular structure is a compound having one ring.
4. The lithium secondary battery according to 1. 3. The lithium secondary battery according to claim 1, wherein the cyclic compound containing an NO radical in a molecular structure is a compound having a molecular structure represented by the following general formula (I). . Embedded image (R _{1 to} R ₈ : hydrogen group, hydrocarbon group, or cyano group) 4. The lithium secondary battery according to claim 1, wherein the cyclic compound containing an NO radical in a molecular structure is a compound having a molecular structure represented by the following general formula (II). . Embedded image (R _{9 to} R ₁₈ : hydrogen group, hydrocarbon group, or cyano group) 5. A cyclic compound containing an NO radical in its molecular structure is a 2,2,6,6-tetramethyl-1-piperidinyloxy free radical and / or 4-cyano-2, The lithium secondary battery according to claim 1, 2 or 3, which is 2,6,6-1-tetramethyl-piperidinyloxy free radical. 6. The cyclic compound containing an NO radical in its molecular structure is a 3-cyano-2,2,5,5-tetramethyl-1-pyrrolidinyloxy free radical. Or the lithium secondary battery according to 4. 7. A positive electrode plate and a negative electrode plate via a separator,
A lithium secondary battery using a non-aqueous electrolyte containing a wound or laminated electrode body and containing a lithium compound as an electrolyte, the positive electrode plate, the negative electrode plate, the separator, and the non-aqueous electrolyte A lithium secondary battery, characterized in that at least one of the above contains a cyclic compound serving as a Mn ²⁺ supplier in the electrolytic solution. 8. The cyclic compound serving as the Mn ²⁺ supplier,
The lithium secondary battery according to claim 7, which is manganese (II) phthalocyanine or a manganese (II) phthalocyanine derivative. 9. The lithium secondary battery according to claim 1, wherein the battery capacity is 2 Ah or more. 10. The lithium secondary battery according to claim 1, wherein the lithium secondary battery is a vehicle-mounted battery. 11. The lithium secondary battery according to claim 10, which is used for an electric vehicle or a hybrid electric vehicle. 12. The lithium secondary battery according to claim 10, which is used for starting an engine.