JP2002270181A - Non-aqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-aqueous electrolyte battery capable of suppressing the deterioration of battery capacity caused by dissolution of a positive electrode active substance in the repetition of storage at a high temperature and charge and discharge and having excellent storage characteristic and charge and discharge cycle characteristic. SOLUTION: In the battery provided with a positive electrode, a negative electrode made of a material capable of storing and discharging lithium metal, lithium alloy or lithium, and non-aqueous electrolyte composed of a solvent and a solute, a phthalimide compound is added to at least either of the positive electrode and the negative electrode.

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 battery having improved high-temperature charge / discharge cycle characteristics and storage characteristics.

[0002]

_2. Description of the Related Art A lithium ion secondary battery in which lithium cobalt oxide (LiCoO ₂ ) is used as a positive electrode active material and a negative electrode is combined with a graphite-based carbon material has been put into practical use. It is used for
Lithium cobalt oxide has problems such as cost and safety, and spinel-type lithium manganese oxide (LiMn ₂ O ₄ ) is currently being studied by many researchers as an active material to replace it. Is being done. However, a secondary battery using spinel manganese has a rapid capacity deterioration in a short period of time during high-temperature storage or high-temperature charge / discharge cycles, which is a major problem in practical use. This capacity deterioration is caused by a combination of a decrease in the electric capacity of the positive electrode due to the collapse of the crystal structure due to the elution of manganese in the lithium manganese oxide and an increase in the electric resistance of the negative electrode due to the precipitation of the eluted manganese on the negative electrode surface. It is believed that. Therefore, as a method for suppressing the elution of manganese from the positive electrode active material, a method for synthesizing lithium manganate (JP-A-7-245106, JP-A-7-73883, etc.), the addition of a different metal to lithium manganate (see JP-A-7-14572), mixing of lithium manganate and lithium nickelate (WO00 / 13250), addition of additives to non-aqueous electrolyte (JP-A-11-25)
Japanese Patent Application Laid-Open Nos. 0914 and 11-339850) have been proposed, but they still leave room for improvement in cycle life characteristics and storage characteristics especially at high temperatures.

[0003]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and has an object to reduce the capacity deterioration upon repeated charge / discharge at high temperature and storage, and to improve reliability. An object of the present invention is to provide an excellent non-aqueous electrolyte battery.

[0004]

To achieve the above object, a non-aqueous electrolyte battery according to the present invention comprises a positive electrode, a lithium metal,
A negative electrode made of a lithium alloy or a material capable of inserting and extracting lithium, and a non-aqueous electrolytic solution made of an organic solvent and a solute are provided. At least one of the positive electrode and the negative electrode has an active material A phthalimide compound represented by the following chemical formula (2) is contained in the agent.

[0005]

Embedded image (Where X is an alkali metal such as hydrogen, lithium, sodium, or potassium.)

Here, the phthalimide compound is preferably contained at a ratio of 0.5 to 15% by weight based on the weight of the active material of the positive electrode and / or the negative electrode.

As described above, in the battery of the present invention, the phthalimide compound contained in the electrode is dissolved in the electrolytic solution and adsorbed on the surface of the electrode material, thereby suppressing the dissolution factor or the dissolution reaction of the electrode material in the positive electrode. In the negative electrode, the eluted positive electrode material is prevented from depositing on the negative electrode material surface. Therefore, the battery of the present invention has excellent charge / discharge cycle characteristics and storage characteristics at high temperatures.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below.

The phthalimide compound has a structure represented by the following chemical formula (2), and specific compounds are preferably phthalimide, lithium phthalimide, sodium phthalimide, potassium phthalimide, and the like, and particularly preferably phthalimide.

The amount of the phthalimide compound added to the active material mixture is preferably 0.5 to 15% by weight based on the weight of the positive electrode or negative electrode active material. 0.5
When the amount is less than 15% by weight, the effect of adding the phthalimide compound to the electrode is small. On the other hand, when the amount exceeds 15% by weight, the effect of adding the phthalimide compound is recognized. Leads to. More preferably, the effect of adding the phthalimide compound is remarkable, and the range of 0.5 to 5% by weight which does not cause a decrease in the discharge capacity and an increase in the cost of the electrode mixture due to the addition of the compound is optimal.

The phthalimide compound and the electrode mixture can be mixed by a usual method such as dry mixing or wet mixing with the electrode material powder since the phthalimide compound is a granular powder having a size of several tens of μm. Further, in order to sufficiently exert the effect of adding the phthalimide compound, it is more preferable that the fine particles are uniformly present around the active material particles or on the particle surface in the electrode. Therefore, it can be achieved by previously pulverizing the phthalimide compound using a ball mill or the like, or attaching fine particles of the phthalimide compound to the surface of the active material particles by using a facility such as a mechanofusion system or Avromaster (manufactured by Hosokawa Micron Corporation).

The material of the positive electrode in this embodiment includes metal oxides containing lithium, metal oxides not containing lithium, metal sulfides such as TiS ₂ , MoS ₂ and FeS ₂ , (CF) _n , (CF Fluorinated graphite such as C ₂ F) _n can be used. In particular, a metal oxide containing at least one transition metal is preferable, and LiCoO ₂ , LiNiO ₂ , L
Examples include lithium-containing transition metal oxides such as iMn ₂ O ₄ and LiMnO ₂ and transition metal oxides such as MnO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , and V ₃ O ₈ . Further, the present invention has a remarkable effect on manganese oxides such as spinel-type lithium manganese oxide (LiMn ₂ O ₄ ) and manganese dioxide (MnO ₂ ). In other words, manganese-containing oxides that are easily dissolved in organic electrolytes, particularly 4V-class LiMn ₂ O _4, are very easy to dissolve manganese at high temperatures, but manganese is eluted by forming an electrode by adding a phthalimide compound. The reaction can be suppressed.

On the other hand, examples of the material for the negative electrode include lithium alloys such as lithium metal, Li-Al and Li-Si compounds, and materials capable of inserting and extracting lithium such as carbon materials and metal oxides. Graphite materials such as natural graphite and artificial graphite as carbon materials, and S as metal oxides
Preferred are nO, SiO, lithium titanium oxide and the like.
In the case of lithium metal or lithium alloy, it is difficult to apply the present invention because the shape is a metal sheet.

Further, the conductive material is not particularly limited, and a commonly used material such as carbon black, graphite and carbon fiber can be used. As the binder, PTFE,
A fluorine-based resin such as PVDF or a rubber-based one such as SBR or EPDM can be used.

As the organic solvent of the organic electrolyte, propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, dimethyl carbonate, diethyl carbonate, sulfolane, dimethoxyethane, diethoxyethane, tetrahydrofuran,
Single or multiple components such as dioxolane and γ-butyrolactone can be used, but are not limited thereto.

As the solute, LiPF ₆ , LiBF ₄ , L
iClO ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiN (C
_{F 3 SO 2) 2, LiN} (C 2 F 5 SO 2) 2, LiN (CF 3
SO ₂ ) (C ₄ F ₉ SO ₂ ) or a mixture of a plurality of components can be used.

The method for producing the positive electrode and the negative electrode using the above-mentioned respective constituent elements is not particularly limited, and a pellet-shaped or strip-shaped electrode applied to a current collector can be produced according to a conventionally known method. The shape of the battery is not particularly limited, and may be various shapes such as a cylinder, a square, a coin, and a button. Further, it can be configured as either a primary battery or a secondary battery.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described. The content of the present invention is not limited to these examples.

Example 1 As Example 1, in order to evaluate the battery characteristics by adding the phthalimide compound according to the present invention to the electrode of the non-aqueous electrolyte secondary battery, the flat non-aqueous electrolyte shown in FIG. An electrolyte battery was manufactured.

As the positive electrode active material, a spinel type lithium manganese oxide (LiMn ₂ O ₄ ) powder is used, and carbon black powder is used as a conductive agent, and P is used as a binder.
TFE (fluororesin), and phthalimide powder as an additive according to the present invention in a ratio of 100: 8: 10: 2, respectively.
After mixing and kneading at a weight ratio of the mixture, the mixture was tableted and dried to produce a positive electrode 1 having a diameter of 16 mm and a thickness of 0.8 mm. Here, the phthalimide powder was pulverized in advance with a ball mill and used. On the other hand, graphite powder was used as the negative electrode active material, PTFE (fluororesin) as a binder was added, and the mixture was mixed and kneaded at a weight ratio of 100: 10, tablet-formed, dried, and dried to a diameter of 16 mm. A negative electrode 2 having a thickness of 0.8 mm was produced.

The positive electrode 1 and the negative electrode 2 are in contact with each other with a separator 3 interposed therebetween, and are caulked and sealed by a negative electrode can 5 having an insulating packing 4 and a positive electrode can 6.

The non-aqueous electrolytic solution is a coin-type one obtained by dissolving LiPF ₆ at a ratio of 1.0 mol / l as a solute in a solvent in which ethylene carbonate and diethyl carbonate are mixed at a weight ratio of 50:50. Battery A of the present invention
Was prepared. The dimensions of the battery were 20 mm in outer diameter and 2.0 mm in height.

Instead of the positive electrode and the negative electrode of the battery A of the present invention, a mixture composition of LiMn ₂ O ₄ : carbon black: PTFE = 100: 10: 10 (weight ratio) without adding phthalimide to the positive electrode was used. Phthalimide was added to the negative electrode, and graphite: PTFE: phthalimide = 100: 8: 2.
A battery B of the present invention was prepared in the same manner as the battery A of the present invention except that the mixture composition was (weight ratio).

The battery A of the present invention was the same as the battery A of the present invention, except that phthalimide was added to the negative electrode in place of the negative electrode of the battery A of the present invention to obtain a composition of graphite: PTFE: phthalimide = 100: 8: 2 (weight ratio). In the same manner as in the above, a battery C of the present invention was produced.
Further, instead of the positive electrode of the battery A of the present invention, lithium cobalt oxide (LiCoO ₂ ) was used as a positive electrode active material, and Li was used.
Battery D of the present invention was prepared in the same manner as Battery A of the present invention, except that the mixture composition was CoO ₂ : carbon black: PTFE: phthalimide = 100: 8: 10: 2 (weight ratio).

Battery E of the present invention was prepared in the same manner as Battery A of the present invention except that potassium phthalimide was used as the phthalimide compound instead of phthalimide as an additive to the positive electrode of Battery A of the present invention. A battery F of the present invention was produced in the same manner as the battery A of the present invention, except that phthalimide lithium was used as a phthalimide compound instead of phthalimide as an additive to the positive electrode of the battery A of the present invention.

As a battery of a comparative example, instead of the positive electrode of the battery A of the present invention, phthalimide was not added to the positive electrode, and the positive electrode was LiMn ₂ O ₄ : carbon black: PTFE = 100:
10:10 (weight ratio), negative electrode graphite: PTFE = 10
Comparative Battery 1 was prepared in the same manner as Battery A of the present invention, except that the conventional mixture composition was 0:10 (weight ratio).

Instead of the positive electrode of the battery D of the present invention, a phthalimide was not added to the positive electrode, and a mixture composition of LiCoO ₂ : carbon black: PTFE = 100: 10: 10 (weight ratio) was used. Comparative Battery 2 was produced in the same manner as Battery A.

Instead of the positive electrode of the battery A of the present invention, a positive electrode is
LiMn without adding tarimide _TwoO_Four: Carbon bra
Mix: PTFE = 100: 10: 10 (weight ratio)
Electrolysis to which 0.5% by weight of phthalimide was added as a composition
Comparative Example except that a liquid was used.
Battery 3 was manufactured.

The battery thus manufactured was evaluated for storage characteristics at high temperatures and charge / discharge cycle characteristics. The conditions of the charge and discharge in the evaluation were as follows: the current was a constant current of 1 mA, the end voltage of the charge was 4.2 V, and the end voltage of the discharge was 2.7 V. Regarding 3, first, charge and discharge were repeated for 2 cycles at room temperature,
The discharge capacity at the second cycle was determined. Next, regarding the storage characteristics, the battery charged in the third cycle was stored in a thermostat at 60 ° C. for 40 days, and then returned to room temperature and discharged to determine a discharge capacity. The ratio to the discharge capacity in the second cycle was determined from the value, and the ratio was defined as the value of the capacity retention rate at 60 ° C. storage. The results are shown in (Table 1).

[0030]

[Table 1]

The charge / discharge cycle characteristics were obtained by repeating the charge / discharge in a 45 ° C. atmosphere after the completion of the two-cycle charge / discharge, and the discharge capacity at the 100th cycle was determined. From the value, the ratio to the discharge capacity at the second cycle is calculated to be 45
The value was the value of the capacity retention rate of the ° C cycle. The results are also shown in (Table 1).

As is clear from the results in Table 1, the batteries A to F of the present invention in which the phthalimide compound was added to the electrode mixture were the comparative batteries 1 to which the phthalimide compound was not added to the electrode mixture. 2 to 60 ° C. regardless of the type of phthalimide compound and addition to either the positive or negative electrode.
It was found that the deterioration of the discharge capacity due to storage and charge / discharge cycles at 45 ° C. was suppressed. In addition, it was found that the battery 3 of the comparative example in which the phthalimide compound was added to the non-aqueous electrolyte had an effect of addition, but was not sufficiently effective as compared with the battery of the present invention.

Example 2 As Example 2, in order to study the effect of the amount of the phthalimide compound according to the present invention added to the electrode mixture, the amount of the phthalimide added was 0.1% with respect to the amount of the active material. Batteries A and GL varied in the range of ２０20% by weight were produced. Furthermore, these batteries A, G ~
For L, the storage characteristics at 60 ° C. were evaluated in the same manner as in Example 1, and the results of the capacity retention ratio and the discharge capacity at the second cycle are shown in (Table 2).

[0034]

[Table 2]

As is evident from Table 2, when the added amount is 0.5% by weight or more, the capacity deterioration during high-temperature storage can be sufficiently suppressed. Since the phthalimide compound does not contribute to the charge / discharge reaction of the battery, the amount of the phthalimide compound added is 15%.
Exceeding the weight percentage is undesirable because the battery capacity is reduced. Therefore, the addition amount is preferably 0.5 to 15% by weight,
More preferably, it is 0.5 to 5% by weight.

Example 3 As Example 3, in order to evaluate battery characteristics by adding the phthalimide compound according to the present invention to a non-aqueous electrolyte primary battery, as in Example 1, the flat battery shown in FIG. A non-aqueous electrolyte battery was fabricated.

As the active material of the positive electrode 1, manganese dioxide heat-treated at 400 ° C. was used, and the manganese dioxide and carbon black as a conductive material, PTFE (fluororesin) as a binder, and phthalimide as an additive were added in 10 parts each.
The mixture was mixed and kneaded at a weight ratio of 0: 8: 10: 2, tableted, and dried at 250 ° C. After the mixture was tablet-molded, it was dried to produce a positive electrode 1 having a diameter of 16 mm and a thickness of 1.0 mm. On the other hand, the negative electrode 2 is made of lithium metal, and a lithium rolled plate is punched to a diameter of 18 mm and a thickness of 0.8 mm, and this is fixed to the inner surface of the negative electrode can 5.

As the non-aqueous electrolyte, a solution obtained by dissolving LiCF ₃ SO ₂ at a ratio of 1.0 mol / liter in a solvent in which propylene carbonate and dimethoxyethane are mixed at a volume ratio of 50:50 is used. Battery M of the present invention was produced.

In place of the positive electrode of the battery M of the present invention, phthalimide was not added to the positive electrode. Manganese dioxide: carbon black: PTFE (fluororesin) = 100: 10: 10
Comparative Battery 4 was produced in the same manner as Battery M of the present invention except that the mixture composition was (weight ratio).

The storage characteristics of the battery M of the present invention and the battery 4 of the comparative example were evaluated at 60 ° C.

These batteries were first discharged at room temperature with a current of 1 mA to a capacity of 50% of the theoretical capacity of manganese dioxide, and the internal resistance of the battery (AC 1 kHz) was measured.
The samples were stored in a thermostat at 20 ° C. for 20 days. After the storage was completed, the internal resistance of the battery (AC 1 kHz) was measured at room temperature, and then the battery was discharged at a current of 1 mA to a discharge end voltage of 2.0 V to obtain a discharge capacity. The remaining capacity ratio was calculated from the value. Here, the capacity remaining rate is defined as the theoretical capacity of manganese dioxide being 100.
The ratio of the discharge capacity after storage was determined. The results are shown in (Table 3).

[0042]

[Table 3]

As is clear from Table 3, the resistance of the inventive battery M to which phthalimide was added did not change even after storage at 60 ° C., and the residual capacity was as high as 40%. Turned out to be rarely seen. In addition, as a result of disassembling these batteries and examining the negative electrode surface, the battery M of the present invention had a lithium surface with metallic luster, but the comparative battery 4 had its surface blackened and manganese was not detected. Was done. This also indicates that the addition of the phthalimide compound according to the present invention to the electrode can suppress the elution of manganese from the positive electrode.

[0044]

According to the present invention, it is possible to suppress the deterioration of the battery capacity due to the dissolution of the positive electrode active material during repeated charging and discharging at a high temperature of a non-aqueous electrolyte battery and storage at a high temperature. large.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the structure of a flat nonaqueous electrolyte battery according to an embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Insulation packing 5 Positive electrode can 6 Negative electrode can

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Nobuharu Koshiba 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F term (reference) 5H029 AJ02 AJ05 AK03 AL02 AL06 AM03 AM04 AM05 AM07 DJ08 EJ11 HJ01 HJ02 5H050 AA05 AA07 CA08 CA09 CB02 CB07 DA02 DA03 DA09 EA22 HA01 HA02

Claims (5)

[Claims] 1. A non-aqueous electrolyte battery comprising a positive electrode, a negative electrode made of a lithium metal, a lithium alloy or a material capable of inserting and extracting lithium, and a non-aqueous electrolyte, wherein the positive electrode and the negative electrode A non-aqueous electrolyte battery, wherein at least one electrode contains a phthalimide compound represented by the following formula (1) in its active material mixture. Embedded image (Where X is an alkali metal such as hydrogen, lithium, sodium, or potassium.) 2. The method according to claim 1, wherein the phthalimide compound is contained in a weight ratio of 0.5 to 15% by weight based on the weight of the active material.
The non-aqueous electrolyte battery according to the above. 3. The non-aqueous electrolyte battery according to claim 2, wherein the positive electrode active material is a metal oxide containing at least one transition metal. 4. The non-aqueous electrolyte battery according to claim 3, wherein the transition metal is manganese. 5. The non-aqueous electrolyte battery according to claim 2, wherein the negative electrode material is a carbon material.