JP2001273927A - Lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium secondary battery that restrains an inhibition of cell reaction and that improves self-discharge property and cycle property by suppressing the corrosion of copper foil which is a negative electrode current collector and the invasion of eluted Cu into SEI on the negative electrode surface, so that copper SEI layer will be restrained to be generated on the surface of negative electrode active material. SOLUTION: This is the lithium secondary battery that is equipped with an electrode body 1 to wind or laminate a positive electrode plate 2 and a negative electrode plate 3 via a separator 4 and that uses nonaqueous electrolytic solution containing a lithium compound as an electrolyte. An organic and/or inorganic Cu corrosion inhibitor or an inhibitor which m organic and/or inorganic Cu trap agent is added to at least one of the positive electrode plate 2, the negative electrode plate 3, the separator 4 and the nonaqueous electrolyte.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a lithium secondary battery having excellent self-discharge characteristics and cycle characteristics.

[0002]

2. Description of the Related Art In general, a lithium secondary battery uses a lithium transition metal composite oxide or the like as a positive electrode active material and a carbonaceous material such as hard carbon or graphite as a negative electrode active material. Further, the reaction potential of a lithium secondary battery using such a material is as high as about 4.1 V, so that an aqueous electrolyte such as a conventional secondary battery cannot be used as a non-aqueous electrolyte. Therefore, as a non-aqueous electrolyte for a lithium secondary battery, lithium ion (L
i ⁺ ) A non-aqueous electrolyte in which a lithium compound as an electrolyte is dissolved is used.

As the positive electrode plate, a plate obtained by applying a mixture of a positive electrode active material and carbon powder for improving conductivity to an aluminum foil is used. As the positive electrode active material, lithium cobalt oxide (LiCoO ₂ )
And lithium manganate (LiMn ₂ O ₄ ). On the other hand, as the negative electrode plate, a material in which an amorphous carbonaceous material such as soft carbon or hard carbon or a carbonaceous powder such as natural graphite is applied to a copper foil as an anode active material is suitably used.

[0004]

The metal foils of the positive electrode plate and the negative electrode plate have a role of taking out the current generated in the internal electrode body of the lithium secondary battery and conducting the current to the electrode terminal. Called the body. The current collector made of the metal foil of the positive electrode and the negative electrode may have a high reaction potential of the lithium secondary battery, and the current collector may be corroded by an electrochemical reaction to prevent a decrease in battery performance. It is preferable to use a high-purity material.

[0005] Furthermore, a non-aqueous organic solvent from which water is removed as much as possible is used as an electrolyte for the battery, and other chemical substances and members are also free of water. Although it is not possible, a small amount of water is present in the lithium secondary battery. The reason for removing water is simply because it is an impurity.However, if water is present in the battery, the electrolyte that has the role of transmitting current will be decomposed, and the deterioration of the electrolyte will proceed, leading to various battery reactions. It causes inhibition.

For example, when lithium hexafluorophosphate (LiPF ₆ ) is used as the electrolyte and moisture is present in the battery, the internal resistance increases due to a decrease in the current transmitting substance, and , Gas and oxidizing substances (hydrofluoric acid)
Is generated, the gas increases the internal pressure of the battery, and hydrofluoric acid (HF) corrodes the inside of the battery.

The HF dissolves and corrodes the metal material of the battery case and the current collector, dissolves the positive electrode active material to elute the transition metal, and elutes the metal such as Cu and Mn in the electrolytic solution. become. Further, as the temperature becomes higher, lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte is decomposed and HF is more easily generated. That is, the concentration of HF in the electrolytic solution further increases.

In other words, the risk of corrosion of the inside of the battery by HF, which is an acidic substance, is further increased. The metal foil as a body was corroded, and the metal eluted in the electrolytic solution was deposited on the surface of the negative electrode active material. The surface of the negative electrode active material has a reddish copper color. Examination of the composition reveals that SEI (Solid Elect) generated on the carbon surface when Li ⁺ is inserted into the negative electrode carbon.
a compound containing copper (Cu) which is a metal foil of a negative electrode current collector (hereinafter, this composition is referred to as “lithium interface”) in addition to a composition referred to as “lithium interface”. "Copper SEI layer"). This is, CuO, think that it would be ₃ and the like CuCO.

In this way, when the copper SEI layer is added to the SEI layer (lithium SEI layer) formed by the normal reaction on the negative electrode surface, the SEI layer becomes thicker, and different chemical substances are added to the SEI composition. Since it is mixed and becomes complicated, the insertion / removal of Li ⁺ , which is an electron conductor, from / to the negative electrode carbon is hindered.

As described above, the corrosion of the copper foil as the negative electrode current collector causes various reactions in the battery,
This is a major cause of performance degradation. And this appears remarkably in the cycle operation in which charge and discharge are repeated, which becomes a fatal defect of the secondary battery.

[0011]

Means for Solving the Problems The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to suppress the corrosion of a copper foil serving as a negative electrode current collector to thereby improve a battery reaction. It is an object of the present invention to provide a lithium secondary battery having excellent self-discharge characteristics and cycle characteristics while suppressing the inhibition of the lithium secondary battery.

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 the positive electrode plate, the negative electrode plate, the separator, and at least one of the nonaqueous electrolytic solution include an organic, and / or an inorganic Cu corrosion inhibitor, or an organic, and / or There is provided a lithium secondary battery characterized by adding an inhibitor which is an inorganic Cu trapping agent.

As the organic inhibitor, the central element of the polar group of the organic compound is at least one of N, P, O, S, As, and Se of Group 5 b and Group 6 b of the periodic table. It is preferable to include one type.

Further, as the inhibitors, 1,
It is preferable to include at least one of 2,3-benzotriazole or a derivative or an analog thereof. Such derivatives or analogs include 1,2,3-benzotriazole,
It is preferably any one of 4 or 5-benzotriazole, benzimidazole, 2-benzimidazole thiol, 2-benzoxazole thiol, 2-methylbenzothiazole, indole, and 2-mercaptothiazoline.

The organic inhibitor preferably contains at least one of 2-mercaptobenzothiazole and 2.5-dimethylcaptothiazol.

Further, the organic inhibitor preferably contains at least one of dithiocarbamic acid and a derivative thereof. The derivative is preferably any one of diethyldithiocarbamate, dimethyldithiocarbamate, N-methyldithiocarbamate, ethylene-bisdithiocarbamate, and dithiocarbamate.

In addition, the organic inhibitor is preferably a sulfur compound. The sulfur compound preferably contains at least one of thiourea, thioacetamide, thiosemicarbazide, thiophenol, P-thiocresol, thiobenzoic acid, and a derivative of W-methylcaptocarboxylic acid.

The organic inhibitors include didodecyl-trithio-carbamate, didodecyldecane-1,10-dithiolate, dodecyl-11-seleno-cyanateundecanethiolate, octadecylthiocyanate, octadecylselenocyanate, and tri (dodecylthione). ) It is preferable to include at least one phosphine.

Further, the organic inhibitor is preferably a 6-substituted-1,3,5-triazine-2,4 dithiol. As the substituent, OH,
_{SH, OR ', NH 2,} NR 2, and NHR' (R,
R ′: a hydrocarbon group).

In addition, as the organic inhibitor, an amine organic compound, an amide organic compound, a tetrazole derivative, a 3-amino organic compound, and 1,2,2
It is preferable to include at least one of 4-triazole organic compounds.

Further, the organic inhibitor is preferably an imidazole organic compound.
Examples of the imidazole organic compound include at least one of imidazole, 4-methylimidazole, 4-methyl-4-methylimidazole, 1-phenyl-4-methylimidazole, and 1- (p-tolyl) -4-methylimidazole. It is preferred to include.

The content of the organic inhibitor in the non-aqueous electrolyte is preferably in the range of 0.01 to 10.0% by mass, and more preferably in the range of 0.10 to 0.50% by mass. Preferably, there is.

The inorganic inhibitor is preferably a phosphate, a chromate, a simple substance of iron or an iron compound, a nitrite, or a silicate.

The phosphate is preferably any of polyphosphate, glassy phosphate, hexametaphosphate, orthophosphate and metaphosphate, and the chromate is cyclohexylammonium chromate, Or, it is preferably an ammonium chromate, and the iron compound is preferably ferric trioxide or iron sulfide.

The content of the inorganic inhibitor in the non-aqueous electrolyte is preferably in the range of 0.01 to 0.10% by mass, and more preferably in the range of 0.10 to 0.50% by mass. Preferably, there is.

The lithium secondary battery of the present invention is suitably adopted 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.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION The lithium secondary battery of the present invention
A non-aqueous electrolytic solution containing a lithium compound that dissolves to generate lithium ions (Li ⁺ ) as an electrolyte, using a non-aqueous electrolyte to suppress corrosion of the negative electrode current collector copper foil or trap eluted copper And the SE on the negative electrode active material surface
By suppressing the intrusion of copper into I, or by suppressing the formation of a copper SEI layer on the surface of the negative electrode active material, the inhibition of the battery reaction is reduced, thereby improving the self-discharge characteristics and cycle characteristics. It is intended. Hereinafter, embodiments of the present invention will be described, but it goes without saying that the present invention is not limited to the following embodiments.

The lithium secondary battery of the present invention is characterized in that at least one of the positive electrode plate 2, the negative electrode plate 3, the separator 4 and the non-aqueous electrolyte contains an organic and / or inorganic Cu corrosion inhibitor or an organic And / or an inorganic Cu trapping agent is added. Here, a Cu corrosion inhibitor,
And a Cu trapping agent, an organic compound and an inorganic compound that can suppress corrosion of a negative electrode current collector by being included in a lithium secondary battery, and can capture and fix Cu eluted in an electrolytic solution. Although the concept includes a system compound, here, it refers to a group of compounds that have a high Cu corrosion prevention effect and a high Cu trapping effect, are chemically stable even in an organic solvent, and do not inhibit a battery reaction. With such a compound, in a lithium secondary battery, it can be easily included in the battery, exhibits the effect of preventing corrosion of the negative electrode current collector using Cu, and traps the eluted Cu, and exhibits the battery performance. Can be improved.

Conversely, compounds that cannot be included in the present invention refer to compounds having no Cu corrosion inhibitory effect or Cu trapping effect, and if any of these effects are included in the present invention. I do.

In the present invention, “containing the compound” means that the compound is impregnated with the nonaqueous electrolyte solution to which the compound is added into the electrode plates 2 and 3 and the separator 4 so that the compound is contained in the electrode plate 2. 3) When the compound is to be contained in the separator 4 or when the compound previously applied to the electrode plates 2.3 and the separator 4 is filled with the non-aqueous electrolyte, the compound moves into the non-aqueous electrolyte and becomes non-aqueous. This includes the case where it is also included in the water 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.

In the present invention, as a method for adding the compound that brings out the battery performance, the negative electrode current collector is coated with the compound using any appropriate method described above, and the compound is previously added to the electrolytic solution. This is a method using the added one. When included in this manner, when the slurry of the electrode active material is applied to the negative electrode current collector, it is possible to prevent corrosion due to HF generated from water contained in the electrode active material. Further, after the negative electrode plate is inserted into the battery, corrosion due to HF generated in the electrolyte can be prevented. In addition, even with respect to Cu eluted from the negative electrode current collector, by including the compound in the electrolytic solution, Cu can be captured and fixed in the liquid. Moreover, some of the organic compounds may have a function of fixing HF, and in this case, the additive may fix HF before the generated HF corrodes Cu. In addition, the corrosion of the negative electrode current collector can be synergistically suppressed.

As another addition method, a method in which the negative electrode current collector is not coated with the compound and the compound is added only to the non-aqueous electrolyte can be suitably adopted. As can be seen from the results of the examples described later, this method can also sufficiently improve the cycle characteristics of the battery. 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.

Now, the Cu corrosion inhibitor used in the lithium secondary battery of the present invention and the inhibitor which is a Cu trapping agent will be described. As the organic inhibitor that can be used in the present invention, specifically, the central element of the polar group of the organic inhibitor is the fifth element in the periodic table.
N, P, O, S, As, and Se of group b and group 6b
Those containing at least one of the following are preferred.

As the organic inhibitor, those containing at least one of 1,2,3-benzotriazole, a derivative thereof, and a similar substance are preferable.

The organic inhibitors include 1,2,3-benzotriazole, 4 or 5-benzotriazole, benzimidazole, 2-benzimidazole thiol, 2-benzoxazole thiol, 2-methylbenzothiazole, indole , And 2
Those containing at least one of the mercaptothiazolines are preferred.

The organic inhibitor preferably includes at least one of 2-mercaptobenzothiazole and 2.5-dimethylcaptothiazol.

As the organic inhibitor, those containing dithiocarbamic acid or a derivative thereof are preferred. Such derivatives include diethyldithiocarbamate, dimethyldithiocarbamate, N-methyldithiocarbamate, ethylene-bisdithiocarbamate,
And those containing at least one of dithiocarbamates.

The organic inhibitor is preferably a sulfur compound. As the sulfur compound, a compound containing at least one of thiourea, thioacetamide, thiosemicarbazide, thiophenol, P-thiocresol, thiobenzoic acid, and a derivative of W-methylcaptocarboxylic acid is preferable.

The organic inhibitors include didodecyl-trithio-carbamate, didodecyldecane-1,10-dithiolate, dodecyl-11-seleno-cyanateundecanethiolate, octadecylthiocyanate, octadecylselenocyanate, and tri (dodecylthione). ) Those containing at least one phosphine are preferred.

As the organic inhibitor, those which are 6-substituted-1,3,5-triazine-2,4 dithiol are preferred. As the substituent, OH,
_{SH, OR ', NH 2,} NR 2, and NHR' (R,
R ′: a hydrocarbon group).

The organic inhibitors include an amine organic compound, an amide organic compound, a tetrazole derivative, a 3-amino organic compound, and 1,2,2
Those containing at least one of the 4-triazole organic compounds are preferred.

As the organic inhibitor, those which are imidazole organic compounds are preferred.
As the imidazole organic compound, at least one of imidazole, 4-methylimidazole, 4-methyl-4-methylimidazole, 1-phenyl-4-methylimidazole, and 1- (p-tolyl) -4-methylimidazole Are preferred.

These organic inhibitors are stable in an electrolytic solution and exhibit high Li ⁺ conductivity, and are suitably used as the compound. The content of these organic inhibitors in the non-aqueous electrolyte is 0.01 to 1
It is preferably in the range of 0.0% by mass.
It is preferably in the range of 0.10 to 0.50% by mass. As is clear from the examples described below, when the content of the organic inhibitor in the nonaqueous electrolyte is 0.01% by mass, the effect as a Cu corrosion inhibitor or a Cu trapping agent is small, and the battery is manufactured. In such a case, the effect is reduced. On the other hand, when the content of the organic inhibitor in the non-aqueous electrolyte is 1
When the content is more than 0.0% by mass, the effect as a Cu corrosion inhibitor or a Cu trapping agent is increased, but the characteristics of the battery reaction as a whole are worsened. It is not clear why the characteristics of the battery deteriorate, but it is presumed that an excessively high inhibitor content results from a decrease in ionic conductivity due to dilution of the electrolytic solution.

Here, in the present invention, a mechanism by which the organic inhibitor suppresses corrosion of Cu or a mechanism by which Cu is trapped will be described. The organic inhibitor Cu
In general, the adsorption mechanism, the oxide film type,
It is classified into a precipitation film type, an anode type, a cathode type, and a bipolar type. Actually, polar groups such as N, S, and OH in the molecular structure of the organic inhibitor correspond to the surface of the polar group. It is considered to be due to the reaction of adsorbing Cu on the surface. In suppressing the corrosion of the negative electrode current collector (Cu foil), when the added organic inhibitor contains N atoms or S atoms,
It is considered that these polar atoms are chemically bonded to each Cu atom on the Cu foil surface, but it is unknown at present whether the bond is an anode point or a cathode point. In practice, it is speculated that adsorption occurs on the entire surface of the Cu foil, and that the anodic reaction and the cathodic reaction are suppressed.

Next, specific examples of the inorganic inhibitors that can be used in the present invention include phosphates, chromates, simple substances of iron or iron compounds, nitrites, and silicates. Preferred.

The phosphate is preferably any one of polyphosphate, glassy phosphate, hexametaphosphate, orthophosphate and metaphosphate, and the chromate is cyclohexyl ammonium chromate ,
Alternatively, those which are ammonium chromates are preferred, and those which are diiron trioxide or iron sulfide are preferred as the iron compound.

These inorganic inhibitors are stable in an electrolytic solution and exhibit high Li ⁺ conductivity, and are suitably used as the compound. The content of these inorganic inhibitors in the non-aqueous electrolyte is 0.0
It is preferably in the range of 1 to 0.10% by mass, and more preferably in the range of 0.10 to 0.50% by mass. When the content of the inorganic inhibitor in the nonaqueous electrolyte is 0.01% by mass, the effect as a Cu corrosion inhibitor or a Cu trapping agent is small, and the effect of the battery is reduced. On the other hand, when the content of the inorganic inhibitor in the non-aqueous electrolyte is more than 10.0% by mass, the effect as a Cu corrosion inhibitor or a Cu trapping agent is increased, but on the other hand, as a whole in the battery reaction, Its characteristics deteriorate. As with organic inhibitors, it is not clear why the battery characteristics deteriorate, but if the content of the inhibitor is too high, the ionic conductivity will decrease because the electrolyte will be diluted. It is presumed to be caused.

Here, in the present invention, the mechanism by which the inorganic inhibitor suppresses corrosion of Cu or the mechanism by which Cu is trapped will be described. Like organic inhibitors,
The mechanism of the inorganic inhibitor on Cu is generally classified into adsorption type, oxide film type, precipitation film type, anode type, cathode type, and bipolar type. Most of the mechanisms are believed to belong to the film type, anode type, or cathode type.

As described above, in the present invention, by coating the compound on the copper foil as the negative electrode current collector, the corrosion of the negative electrode current collector is suppressed, and the compound is also present in the electrolytic solution. As a result, the negative electrode current collector is corroded, and Cu that is eluted can be captured by the compound. Further, when the compound is an organic compound having a hetero atom, the HF in the electrolytic solution may be reduced due to the effect of the hetero atom.
Can also be captured. As a result, not only can the battery corrosion be suppressed and the deterioration of the nonaqueous electrolyte can be suppressed, but the elution of Cu into the electrolyte can be suppressed, so that the inhibition of the electric reaction can be greatly reduced synergistically. It becomes possible.

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 in which a positive electrode and a negative electrode active material are disc-shaped and press-formed in a disc 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, a stacked type in which a single-cell type electrode body used for a coin battery is stacked in a plurality of stages is exemplified. 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 to apply the slurry or paste to the 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 between porous Li ⁺ permeable polypropylene films (PP films). 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 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, 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 a 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.

[0065]

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 3, Comparative Example 1) Examples 1 to 3 and Comparative Example 1
The battery according to (1) uses LiMn ₂ O ₄ spinel as a positive electrode active material, and mixes acetylene black as a conductive additive and polyvinylidene fluoride as a binder in a weight ratio of 50: 2: 3 as a positive electrode material. , The cathode material 0.0
A positive electrode plate produced by press-molding ² g into a disc having a diameter of 20 mmφ at a pressure of 300 kg / cm ² and a coin cell type electrode body using carbon as a negative electrode plate were produced. It was made by filling a liquid. Here, as a non-aqueous electrolyte, the compound is added to a mixed solvent of EC and DEC at an equal volume ratio of each mass% as shown in Table 1, and LiPF ₆ is used as an electrolyte at 1 mol / l.
The solution dissolved so as to have a concentration of was used.

[0066]

[Table 1]

Next, a cycle test in a coin cell type battery will be described. In the present invention, after charging the manufactured coin cell with a constant current-constant voltage charge until a voltage of 4.1 V is reached at a current equivalent to 1 C according to the capacity of the positive electrode active material,
Also discharges at a constant current with a current equivalent to 1 C, and the voltage is 2.5 V
The charge / discharge cycle was set as one cycle, and the test was repeated. The cycle characteristics (%) shown in FIG.
Is calculated using the following equation (1).

[0068]

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

(Evaluation of Cycle Characteristics) As can be seen from FIG. 3, the batteries of Examples 1 to 3 according to the present invention achieved a capacity retention of 95% in 100 cycle tests.
Very good cycle characteristics were exhibited compared to Comparative Example 1 in which the compound was not used. This means that the compound
It is thought that the cycle life was improved as a result of capturing Cu eluted into the electrolyte solution due to the corrosion of the negative electrode current collector, suppressing the formation of the copper SEI layer and reducing the inhibition of the battery reaction.

In Examples 1 to 3 and Comparative Example 1, the coin cell batteries subjected to the cycle test were disassembled in a glove box, the positive electrode plate and the negative electrode plate were taken out, and washed with a mixed solvent of EC and DEC. did. Then, a secondary electron image of these electrode plates was observed at an accelerating voltage of 20 kV using a scanning electron microscope (SEM / JEM-5410 manufactured by JEOL Ltd.), and an elemental analysis was performed by EDS.

(Evaluation of Observation of Electrode Plate after Cycle Test) In Examples 1 to 3 and Comparative Example 1, no difference was observed in the surface morphology of the positive electrode, but as shown in FIG. A big difference was observed in the negative electrode. In Example 1 to which the compound was added, as shown in FIG. 4 (a), a film (lithium SEI layer) due to decomposition of the electrolytic solution was observed on the surface of the negative electrode carbon. No difference was seen. On the other hand, in Comparative Example 1, as shown in FIG. 4B, on the surface of the negative electrode carbon, particles were observed in addition to the lithium SEI layer.
When these negative electrodes were subjected to EDS elemental analysis, the negative electrode of Comparative Example 1 showed C from the carbon surface and its surroundings including particulate matter.
u was detected, but in the negative electrodes of Examples 1 to 3, C
u was not detected.

This is because, by adding the additive in the present invention to the electrolytic solution, the additive captured Cu eluted from the negative electrode current collector and prevented Cu from being deposited on the surface of the negative electrode carbon. Thus, it is considered that the inhibition of the battery reaction at the negative electrode was suppressed, and the cycle characteristics were improved.

(Example 4, Comparative Example 2) The batteries according to Example 4 and Comparative Example 2 were manufactured in the same manner as in Example 1 above, by preparing a coin cell type electrode body, storing the same in a battery case, and then using a non-aqueous electrolyte. And filled. In this case, as a non-aqueous electrolyte, 500 ppm of water (H ₂ O) causing deterioration of battery characteristics is added to a mixed solvent of EC and DEC at an equal volume ratio.
A solution in which LiPF ₆ was dissolved to a concentration of 1 mol / l as an electrolyte was used in which 1,2,3-benzotriazole as the compound was added in an amount of about 0.3% by mass. Other manufacturing methods are the same as those in the first embodiment. The cycle test was performed in the same manner as in Example 1.

(Evaluation) As can be seen from FIG. 5, the battery of Example 4 according to the present invention achieved a capacity retention of 93% in a 100-cycle test, and 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

Example 5 A battery according to Example 5 was prepared by preparing a coin cell type electrode body in the same manner as in Example 1 described above, storing the same in a battery case, and then filling the battery case with a nonaqueous electrolyte. It is. In this case, as the non-aqueous electrolyte, E
To a mixed solvent of equal volume ratio of C and DEC, about 500 ppm of water (H ₂ O) causing deterioration of battery characteristics was added, and 1,2,3-benzotriazole as the compound was added as shown in Table 2. , Are added in an amount of about each% by mass. Other manufacturing methods are the same as those in the first embodiment. The cycle test was performed in the same manner as in Example 1.

[0076]

[Table 2]

(Evaluation) In Example 5, the change in the capacity retention of the battery with respect to the concentration of the compound was examined. The capacity retention after 100 cycles was evaluated. As can be seen from FIG. 6, only 0.0
Even when 1% by mass was included, the capacity retention increased, and when the concentration added was increased, the capacity retention increased, and the best capacity retention was obtained at about 0.3% by mass. Thereafter, when the addition concentration was increased, the capacity retention decreased, and at 5.0% by mass, the capacity retention was 70% or less, which was not practically usable.

(Example 6) A battery according to Example 6 has an L
A positive electrode slurry prepared by adding iMn 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 to a 20 μm thick slurry. A positive electrode plate 2 prepared by coating both sides of an aluminum foil so as to have a thickness of about 100 μm, respectively, and in addition to the same method, using carbon powder as a negative electrode active material on both sides of a 10 μm thick copper foil. A negative electrode plate 3 was prepared by coating each having a thickness of about 80 μm, and a wound electrode body was manufactured. The battery body was housed in a battery case, and then filled with a non-aqueous electrolyte. . Here, as a non-aqueous electrolyte solution, as in Example 5, 1 was dissolved in 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.
A solution to which 2,3-benzotriazole was added by about each mass% was used. The battery capacities of these various batteries after the first charge were all about 10 Ah.

In addition, the cycle test was performed by repeating the charge / discharge cycle shown in FIG. 7 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) In Example 6, the change in the capacity retention of the battery with respect to the added concentration of the compound in the wound electrode body of the present invention was evaluated using the capacity retention after 20,000 cycles. In the range of 10.0% by mass, the relative capacity retention was 80% or more, and further, in the range of 0.10 to 0.50% by mass, the relative capacity retention was 85% or more. Here, from the comparison of the results of Examples 5 and 6, the wound electrode body is
It has a larger volume than the coin cell electrode body,
Since it is a curved body, it is considered that a larger amount of addition is required.

Here, Examples 1 to 6 and Comparative Examples 1 and 2
Were prepared by using the various battery components prepared by including the compound in a battery case by the above method. 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. .

A battery for starting an engine and a battery for driving a motor such as an electric vehicle require a large current 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 been described mainly on the case where a wound electrode body is used, but it goes without saying that the present invention does not matter on the battery structure. Here, in the case of a small-capacity coin battery, since the battery itself is small, water management is easy, for example, production and storage of the component and battery assembly are performed in an inert gas atmosphere. However, in producing a large-capacity battery using the wound or laminated internal electrode bodies 1 and 7 according to the present invention, for example, the application of an electrode active material to a current collecting substrate requires a relatively large-scale apparatus. It is necessary to use it, and even in a room, it is performed in the same atmosphere as the outside air. Especially, even in a constant temperature and humidity room that performs moisture management, it is manufactured in an environment where moisture is completely removed, which is a point of manufacturing cost. Therefore, it is hard to think realistically.

Therefore, the present invention is suitably adopted for a battery having a large battery capacity, in which water management in the manufacturing process is not easy. Specifically, a wound or laminated electrode body 1.7
Is suitably used for batteries having a battery capacity of 2 Ah or more. It goes without saying that the use of the battery is not limited, but as a large-capacity vehicle-mounted 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 or hybrid electric vehicle. It can be particularly suitably used for driving motors of automobiles.

[0085]

As described above, according to the lithium secondary battery of the present invention, the corrosion of the copper foil serving as the negative electrode current collector is suppressed, and the Cu eluted in the electrolytic solution is also provided.
To prevent Cu from entering SEI on the surface of the negative electrode active material, or remove copper S on the surface of the negative electrode active material.
The formation of the EI layer can be suppressed, and the inhibition of the battery reaction can be suppressed. As a result, the lithium secondary battery according to the present invention has an excellent effect that the self-discharge characteristics and the cycle characteristics are improved.

[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 the results of the cycle tests of Examples 1 to 3.

FIG. 4 is a scanning electron micrograph showing a particle structure of a carbon material on the surface of a negative electrode plate after a cycle test.

FIG. 5 is a graph showing the results of a cycle test of Example 4.

FIG. 6 is a graph showing a change in cycle characteristics with respect to a concentration of a Cu inhibitor added in Example 5.

FIG. 7 is a graph showing a charge / discharge pattern in a cycle test of a wound electrode body.

[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 EJ11 HJ02 HJ19 5H050 AA05 AA07 BA17 CA09 CB07 DA09 EA22 EA24 FA02 FA05 HA02 HA19

Claims (27)

[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 A lithium secondary battery characterized by adding an organic and / or inorganic Cu corrosion inhibitor or an organic and / or inorganic Cu trapping agent to at least one of the above. 2. The organic group according to claim 1, wherein the central element of the polar group of the organic inhibitor is N, P, or V of group 5 b or group 6 b of the periodic table.
The lithium secondary battery according to claim 1, comprising at least one of O, S, As, and Se. 3. The method according to claim 1, wherein the organic inhibitor is 1,2,3.
The lithium secondary battery according to claim 1, wherein the lithium secondary battery includes at least one of benzotriazole, a derivative thereof, and a similar substance. 4. The method according to claim 1, wherein the derivative or the analog is 4 or 5-
Methyl-1H-benzotriazole, toltriazole, benzimidazole, 2-benzimidazole, 2
4. The lithium secondary battery according to claim 3, wherein the lithium secondary battery is any one of mercaptobenzimidazole, 2-benzoxazole, 2-methylbenzothiazole, indole, and 2-mercaptothiazoline. 5. 5. The lithium secondary battery according to claim 1, wherein the organic inhibitor contains at least one of 2-mercaptobenzothiazole and 2.5-dimethylcaptothiazol. 6. The lithium secondary battery according to claim 1, wherein the organic inhibitor contains at least one of dithiocarbamic acid and a derivative thereof. 7. The lithium secondary battery according to claim 6, wherein the derivative is any one of diethyldithiocarbamate, dimethyldithiocarbamate, N-methyldithiocarbamate, ethylene-bisdithiocarbamate, and dithiocarbamate. Next battery. 8. The lithium secondary battery according to claim 1, wherein the organic inhibitor is a sulfur compound. 9. The method according to claim 9, wherein the sulfur compound is thiourea, thioacetamide, thiosemicarbazide, thiophenol, P-
The lithium secondary battery according to claim 8, wherein the lithium secondary battery includes at least one of thiocresol, thiobenzoic acid, and a derivative of W-methylcaptocarboxylic acid. 10. The method according to claim 1, wherein the organic inhibitor is didodecyl-trithio-carbamate, didodecyldecane-1,
The lithium secondary battery according to claim 1, comprising at least one of 10-dithiolate, dodecyl-11-seleno-cyanate undecanethiolate, octadecylthiocyanate, octadecylselenocyanate, and tri (dodecylthio) phosphine. 11. The method according to claim 11, wherein the organic inhibitor is a hexasubstituted compound.
The lithium secondary battery according to claim 1, wherein the lithium secondary battery is 1,3,5-triazine-2,4 dithiol. 12. The method according to claim 12, wherein the substituent is OH, SH, OR ′,
NH ₂ , NR ₂ , and NHR ′ (R, R ′: hydrocarbon group)
The lithium secondary battery according to claim 11, wherein: 13. The method according to claim 1, wherein the organic inhibitor contains at least one of an amine organic compound, an amide organic compound, a tetrazole derivative, a 3-amino organic compound, and a 1,2,4-triazole organic compound. The lithium secondary battery according to claim 1, wherein: 14. The lithium secondary battery according to claim 1, wherein the organic inhibitor is an imidazole organic compound. 15. The method according to claim 15, wherein the imidazole organic compound is imidazole, 4-methylimidazole, or 4-methyl-4.
The lithium secondary battery according to claim 14, comprising at least one of -methylimidazole, 1-phenyl-4-methylimidazole, and 1- (p-tolyl) -4-methylimidazole. 16. The lithium secondary battery according to claim 1, wherein the content of the organic inhibitor in the non-aqueous electrolyte is 0.01 to 10.0% by mass. 17. The lithium secondary battery according to claim 1, wherein the content of the organic inhibitor in the non-aqueous electrolyte is 0.10 to 0.50% by mass. 18. The method according to claim 18, wherein the inorganic inhibitor is a phosphate,
The lithium secondary battery according to claim 1, wherein the lithium secondary battery is any one of a chromate, a simple substance or an iron compound, a nitrite, and a silicate. 19. The lithium secondary battery according to claim 18, wherein the phosphate is any one of polyphosphate, glassy phosphate, hexametaphosphate, orthophosphate, and metaphosphate. battery. 20. The lithium secondary battery according to claim 18, wherein the chromate is cyclohexylammonium chromate or ammonium chromate. 21. The lithium secondary battery according to claim 18, wherein the iron compound is diiron trioxide or iron sulfide. 22. The lithium secondary battery according to claim 1, wherein the content of the inorganic inhibitor in the non-aqueous electrolyte is 0.01 to 10.0% by mass. 23. The lithium secondary battery according to claim 1, wherein the content of the inorganic inhibitor in the non-aqueous electrolyte is 0.10 to 0.50% by mass. 24. The lithium secondary battery according to claim 1, wherein the battery capacity is 2 Ah or more. 25. The lithium secondary battery according to claim 1, wherein the lithium secondary battery is a vehicle-mounted battery. 26. The lithium secondary battery according to claim 25, which is used for an electric vehicle or a hybrid electric vehicle. 27. The lithium secondary battery according to claim 25, which is used for starting an engine.