JP2001076756A - Nonaqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte battery not causing the structural degradation or decomposition of an electrolytic solution even if it is overcharged. SOLUTION: A positive electrode having a graphitic carbon layer 11 formed on a positive electrode collector 12 and a negative electrode having a graphitic carbon layer 13 formed on a negative electrode collector 14 are received in a positive electrode can 16 by facing them to each other through a separator 15, and a negative electrode can 17 is liquid-tightly enclosed in the positive electrode can 16. A nonaqueous electrolyte is impregnated in the separator 15, the solvent of the nonaqueous electrolyte contains ethylene carbonate and chain carbonate such as dimethyl carbonate, methylethyl carbonate and diethyl carbonate by mixing them, and the solvent contains anions intercalated in the graphitic carbon of the positive electrode, and cations intercalated in the graphitic carbon of the negative electrode. Thereby, this nonaqueous electrolyte battery having electromotive force of around 5-6 V in a charged state can be provided.

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 provided with a positive electrode, a negative electrode and a non-aqueous electrolyte, and more particularly to an active material and an electrolyte used for a positive electrode or a negative electrode of this type of non-aqueous electrolyte battery. The improvement of the combination.

[0002]

2. Description of the Related Art In recent years, lithium-cobalt oxide (LiCo-oxide) has been used as a battery used in portable electronic / communication equipment such as a small video camera, a portable telephone, and a notebook personal computer.
O ₂ ), lithium-nickel oxide (LiNiO ₂ ), lithium-manganese oxide (LiMn ₂ O ₄ ) and other lithium-containing transition metal oxides are used as the positive electrode active material, and lithium metal, lithium alloy or lithium ion is used as the positive electrode active material. Occlusion
Attention has been paid to a lithium secondary battery represented by a lithium ion battery using a releasable carbon material as a negative electrode active material, and a lithium secondary battery using a carbon material as a negative electrode active material has come into practical use.

[0003]

In this type of lithium secondary battery, when the battery is overcharged, lithium is desorbed from the lithium-containing transition metal oxide serving as the positive electrode active material in the positive electrode, and the positive electrode active The substance reacts with the electrolyte to cause decomposition of the electrolyte. On the other hand, in the negative electrode, lithium is electrolytically deposited. Here, as lithium is desorbed from the lithium-containing transition metal oxide serving as the positive electrode active material, the structure of the positive electrode deteriorates, and as a result, the battery deteriorates. For this reason, a protection circuit for preventing the battery from being overcharged is provided to prevent the battery from being deteriorated by preventing the battery from being overcharged by the protection circuit.

However, when the above-described protection circuit is provided, there arises a problem that the structure of the battery is complicated and the manufacturing process is also complicated. In addition, the protection circuit itself is complicated and it is difficult to reduce the size, and there has been a problem that this kind of lithium secondary battery cannot be easily and easily manufactured. Therefore, a method for preventing the decomposition of the electrolytic solution even when this type of lithium secondary battery is overcharged and the potential of the positive electrode becomes high is disclosed in Japanese Patent Application Laid-Open No. 5-47416 or Japanese Patent Application Laid-Open No. No. 242074 has been proposed. In the methods proposed in these publications, a transition metal complex is added to the electrolytic solution to suppress the oxidation of the electrolytic solution by the positive electrode kept at a high potential by the oxidation reaction of the transition metal ion, so that the electrolytic solution becomes It is intended to prevent decomposition.

However, even in the method proposed in Japanese Patent Application Laid-Open No. 5-47416 or Japanese Patent Application Laid-Open No. 4-24074, if an overcharged state occurs, the electrolytic solution is decomposed, and as a result, the battery deteriorates. The problem arose. Therefore, the present invention has been made to solve the above problems, and an object of the present invention is to provide a nonaqueous electrolyte battery that does not cause an overcharged state and does not cause structural deterioration of a positive electrode or decomposition of an electrolyte. Is what you do.

[0006]

SUMMARY OF THE INVENTION The present invention is based on the finding that if the anions and cations in the electrolyte are completely consumed before the electrode is overcharged, the electrode will not be overcharged. It was made based on. For this reason, in the nonaqueous electrolyte battery of the present invention, the positive electrode includes a graphitic carbon layer on the surface of the positive electrode current collector, the negative electrode includes the graphitic carbon layer on the surface of the negative electrode current collector, and the nonaqueous electrolyte includes a solvent. At least ethylene carbonate and a chain carbonate.

As described above, when the graphitic carbon is provided in the positive electrode and the negative electrode, the anion in the nonaqueous electrolyte is intercalated into the graphitic carbon of the positive electrode by charging the battery, and the nonaqueous electrolyte in the nonaqueous electrolyte is charged. Is intercalated into the graphite carbon of the negative electrode, so that the electromotive force is 5-6.
A non-aqueous electrolyte battery of about V can be obtained. At this time, if ethylene carbonate is contained in the solvent of the non-aqueous electrolyte, the decomposition of the electrolyte can be suppressed because ethylene carbonate is not easily decomposed at the negative electrode.
In addition, when the solvent contains a chain carbonate, the chain carbonate has a function of suppressing the reaction with the graphitic carbon in the high potential region, so that the stability of the electrolyte in the high potential region is improved. Therefore, the non-aqueous electrolyte needs to contain at least ethylene carbonate and chain carbonate as solvents.

The electrolyte salt of the non-aqueous electrolyte includes L
_{iPF 6, LiBF 4, LiAsF 6} , LiSbF 6, Li
ClO ₄ , LiX (SO ₂ R) _n (where X is N, C, O
Or B and R is CF ₃ or C ₂ F ₅ or C ₃ F ₇
Or a C ₄ F _9, n is preferably selected from any of a 1 to 3) of the integer, it is preferable to use these electrolyte salt containing at least one more.
Of these electrolyte salts, LiX (SO ₂ R) _n (where X is
Is N, C, O or B, and R is CF ₃ or C ₂ F ₅
Or C ₃ F ₇ or C ₄ F ₉ , and n is an integer of 1 to 3), since the capacity remaining rate after overcharge is excellent.

As a positive electrode current collector used in such a non-aqueous electrolyte battery, it is necessary to use a metal current collector that does not dissolve into the electrolytic solution due to charge and discharge. Since it is difficult to dissolve into the inside, it is preferable to use a tantalum-containing tantalum foil or a tantalum alloy foil as the positive electrode current collector.

By charging such a non-aqueous electrolyte battery, anions in the electrolyte are intercalated into graphitic carbon of the positive electrode, and cations in the electrolyte are intercalated into graphitic carbon of the negative electrode. Therefore, when the electrochemical equivalent of the nonaqueous electrolyte is smaller than the smaller capacity of the positive electrode or the negative electrode, all of the anions and cations in the electrolytic solution are intercalated into the graphitic carbon of the positive electrode or the negative electrode ( Strictly speaking, at the end of charging, the charging voltage rises, so not all of the anions and cations in the electrolyte are intercalated into the graphitic carbon of the positive electrode or negative electrode, and they are necessary for the next discharge. As much anions and cations as possible remain), so that charging does not proceed any further. Therefore, with such a configuration, the progress of overcharge can be prevented, and a nonaqueous electrolyte battery having no deterioration in battery capacity can be obtained.

The non-aqueous electrolyte solvent used in the non-aqueous electrolyte battery of the present invention contains ethylene carbonate to prevent the solvent from being decomposed at the negative electrode, and contains a chain carbonate to form a non-aqueous electrolyte in a high potential region. It is an essential requirement to ensure the stability of the electrolyte, but if this ethylene carbonate is contained by mixing at least 10 parts by weight of dimethyl carbonate, methyl ethyl carbonate, and a chain carbonate such as diethyl carbonate. And ether solvents such as 1,2-dimethoxyethane and 1,2-diethoxyethane, γ-butyrolactone (γ-BL), propylene carbonate (PC),
Butylene carbonate (BC), vinylene carbonate (VC), and tetrahydrofuran (THF) may be mixed.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The embodiments of the nonaqueous electrolyte battery of the present invention will be described below in detail, but the present invention is not limited to these embodiments at all, and the scope of the present invention is not changed. It is possible to change and implement as appropriate. FIG. 1 is a cross-sectional view schematically showing the nonaqueous electrolyte battery of the present invention.

1. Preparation of Positive Electrode Natural graphite (d = 3.354 °) having an average particle diameter of 10 μm was used, and 95% by weight of the natural graphite was mixed with 5% by weight of polyvinylidene fluoride (PVdF) as a binder. Thereafter, the mixture was added to N-methyl-2-pyrrolidone (NM
P) was added thereto, followed by mixing and kneading to prepare a positive electrode slurry. Next, the positive electrode slurry was applied to a positive electrode current collector 12 made of tantalum foil by a doctor blade method, and then rolled to a predetermined thickness. Then 130
After vacuum drying at a temperature of ° C., the resultant was cut into a predetermined size to produce a positive electrode in which a positive electrode graphite layer 11 was formed on the surface of a positive electrode current collector 12.

2. Preparation of Negative Electrode Natural graphite having an average particle size of 10 μm (d = 3.354 °) was used, and 95% by weight of this natural graphite was mixed with 5% by weight of polyvinylidene fluoride (PVdF) as a binder. Thereafter, the mixture was added to N-methyl-2-pyrrolidone (NM
P) was added thereto, followed by mixing and kneading to prepare a negative electrode slurry. Next, the negative electrode slurry was applied to a negative electrode current collector 14 made of copper foil by a doctor blade method, and then rolled to a predetermined thickness. Then, after vacuum drying at a temperature of 130 ° C., it is cut into a predetermined size, and the negative electrode current collector 1
A negative electrode having the negative electrode graphite layer 13 formed on the surface of No. 4 was produced.

3. Preparation of electrolyte solution (1) Example 1 Ethylene carbonate (EC:
Hereinafter, LiN (C ₂ F ₅ ) is used as a solute in an equal volume mixed solvent of a chain carbonate and dimethyl carbonate (DMC: hereinafter simply referred to as DMC).
SO ₂ ) ₂ (lithium perfluoroalkyl sulfonimide) was dissolved at 1 mol / l to prepare a non-aqueous electrolyte. This non-aqueous electrolyte was used as the electrolyte a in Example 1.

(2) Example 2 LiN (C ₂ F ₅ ) is used as a solute in an equal volume mixed solvent of EC (cyclic carbonate) and diethyl carbonate (DEC: hereinafter simply referred to as DEC) which is a chain carbonate.
SO ₂ ) ₂ (lithium perfluoroalkyl sulfonimide) was dissolved at 1 mol / l to prepare a non-aqueous electrolyte. This non-aqueous electrolyte was used as electrolyte b in Example 2.

(3) Example 3 EC (cyclic carbonate), DMC (chain carbonate), and 1,2-dimethoxyethane (DME: hereinafter simply referred to as DME) which is an ether solvent are used in a volume ratio of 2%. LiN (C ₂ F ₅ SO ₂ ) ₂ (lithium perfluoroalkylsulfonimide) as a solute was dissolved at 1 mol / liter in a mixed solvent mixed at a mixing ratio of 1: 1 to prepare a non-aqueous electrolyte. This non-aqueous electrolyte was used as an electrolyte c in Example 3.

(4) Comparative Example 1 LiN (C ₂ F ₅ ) was used as a solute in an equal volume mixed solvent of EC (cyclic carbonate) and DME (ether-based solvent).
SO ₂ ) ₂ (lithium perfluoroalkyl sulfonimide) was dissolved at 1 mol / l to prepare a non-aqueous electrolyte. This non-aqueous electrolyte was used as the electrolyte x of Comparative Example 1.

(5) Comparative Example 2 Propylene carbonate (P) which is a cyclic carbonate
C: 1 mol / liter of LiN (C ₂ F ₅ SO ₂ ) ₂ (lithium perfluoroalkylsulfonic acid imide) was dissolved as a solute in a solvent consisting of PC (hereinafter simply referred to as PC) to prepare a non-aqueous electrolyte. This non-aqueous electrolyte was used as the electrolyte y of Comparative Example 2.

(6) Comparative Example 3 LiN (C ₂ F ₅ ) was used as a solute in an equal volume mixed solvent of PC (cyclic carbonate) and DMC (chain carbonate).
SO ₂ ) ₂ (lithium perfluoroalkyl sulfonimide) was dissolved at 1 mol / l to prepare a non-aqueous electrolyte. This non-aqueous electrolyte was used as an electrolyte z of Comparative Example 3.

4. Preparation of Battery Next, the positive electrode prepared as described above, the negative electrode prepared as described above, and the electrolyte solutions a, b, c of Examples 1 to 3 prepared as described above, and Comparative Example 1 A non-aqueous electrolyte battery 10 as shown in FIG. 1 was produced using each of the electrolyte solutions x, y, and z. That is, first, the metal positive electrode can 16 is prepared. Then, the positive electrode was arranged in the positive electrode can 16 such that the positive electrode current collector 12 was on the lower side and the positive electrode graphite layer 11 was on the upper side so that the positive electrode current collector 12 was in contact with the bottom of the can. Then, a separator 15 made of a microporous polypropylene membrane impregnated with the electrolyte solution prepared as described above was disposed on the positive graphite layer 11.

On the other hand, a negative electrode can 17 made of metal is prepared. A green packing 18 made of polypropylene is arranged in advance on the inner peripheral edge of the negative electrode can 17. This negative electrode can 1
In FIG. 7, the negative electrode was arranged such that the negative electrode current collector 14 was on the lower side and the negative electrode graphite layer 13 was on the upper side such that the negative electrode current collector 14 was in contact with the bottom of the can. Next, the negative electrode can 17 was inverted, and the negative electrode can 17 was placed on the positive electrode can 16 so that the negative electrode graphite layer 13 was disposed on the separator 15. Then
The upper end of the positive electrode can 16 was sealed inward by sealing it inward to produce a flat nonaqueous electrolyte battery 10.

Here, the non-aqueous electrolyte battery 10 using the electrolyte a of the first embodiment is referred to as the battery A of the first embodiment, and the non-aqueous electrolyte battery 10 using the electrolyte b of the second embodiment is used as the battery A of the second embodiment. Battery B
And the nonaqueous electrolyte battery 10 using the electrolytic solution c of Example 3.
Was designated as Battery C of Example 3. The electrolyte x of Comparative Example 1
Was used as a battery X of a comparative example, a nonaqueous electrolyte battery 10 using an electrolyte y of a comparative example 2 was used as a battery Y of a comparative example 2, and an electrolyte z of the comparative example 3 was used. The nonaqueous electrolyte battery 10 was designated as Battery Z of Comparative Example 3.

5. Test (1) Overcharge test Each battery A of Examples 1 to 3 produced as described above,
B, C, and each of the batteries X, Y, and Z of Comparative Examples 1 to 3 were used.
After the battery voltage at a current density of cm ² was charged until 6.0V, the battery voltage at a current density of 1 mA / cm ² 2.7
The discharge was performed until the voltage reached 5 V, and the initial discharge capacity was determined from the discharge time. Thereafter, the battery was overcharged at a current density of 1 mA / cm ² until the battery voltage reached 12.0 V, and then 1 mA / cm 2
^The battery was discharged at a current density of ² until the battery voltage reached 2.75 V, and the discharge capacity after overcharge was determined from the discharge time. Then, based on the initial discharge capacity obtained as described above and the discharge capacity after overcharge, a discharge capacity remaining rate after overcharge (residual rate after overcharge) is obtained based on the following equation (1). The results are as shown in Table 1 below. Residual rate after overcharge (%) =
(Discharge capacity after overcharge / initial discharge capacity) × 100% (1)

(2) Cycle Characteristics Test The batteries A, B, and C of Examples 1 to 3 and the batteries X, Y, and Z of Comparative Examples 1 to 3 manufactured as described above were used. 1 mA at room temperature (25 ° C.)
/ After the battery voltage at a current density of cm ² was charged until 6.0V, the battery voltage at a current density of 1 mA / cm ² 2.
A charge / discharge cycle test was performed in which one cycle was set to discharge to 75 V. Next, the ratio between the charge capacity and the discharge capacity for each cycle is determined, and this is defined as the charge / discharge efficiency (%). The charge / discharge efficiency (%) for each cycle is represented by a graph, as shown in FIG. It became. The hatched portions in FIG. 2 indicate batteries A, B, C
In addition, it shows that the charging and discharging efficiencies (%) of the batteries Y and Z vary in the range of oblique lines. After performing such a charge / discharge cycle test, the discharge capacity after 500 cycles was obtained, and the discharge capacity remaining rate after 500 cycles (residual rate after 500 cycles) was obtained from the ratio to the initial discharge capacity. Table 1 shows the results.

[0026]

[Table 1]

As is clear from Table 1 and FIG.
The cycle characteristics (charge / discharge efficiency), the residual ratio after overcharge, and the residual ratio after 500 cycles of each of the batteries A, B, and C of Examples 1 to 3 are all high, whereas Comparative Examples 1 to 5. 3
It can be seen that the cycle characteristics (charge / discharge efficiency), the residual rate after overcharge, and the residual rate after 500 cycles are all low values for each of the batteries X, Y, and Z.

This is presumably because ethylene carbonate (EC), which is a cyclic carbonate, is hardly decomposed at the negative electrode, so that the cycle characteristics at the negative electrode are improved, and as a result, the charge / discharge characteristics are improved. In addition, chain carbonates such as dimethyl carbonate (DMC) and diethyl carbonate (DEC) not only improve the utilization of the positive electrode active material and the negative electrode active material, but also suppress the reaction with the graphite positive electrode in a high potential region. It is considered that the stability of the electrolytic solution in the high-potential region was improved due to the presence of, and the residual ratio after overcharge was improved.

On the other hand, it is considered that propylene carbonate (PC), which is a cyclic carbonate, is easily decomposed at the negative electrode, so that the cycle characteristics at the negative electrode are reduced, and as a result, the charge / discharge characteristics are reduced. In addition, ether solvents such as 1,2-dimethoxyethane (DME) react with the graphite positive electrode in a high potential region and are decomposed, resulting in instability of the electrolyte in the high potential region, and a residual ratio after overcharge. Is considered to have decreased. From the above, as the solvent of the electrolytic solution, a mixed solvent of a cyclic carbonate such as ethylene carbonate (EC) and a chain carbonate such as dimethyl carbonate (DMC) and diethyl carbonate (DEC),
It can be said that it is preferable to use an ether-based solvent or the like added thereto.

6. Examination of electrolyte salt (Examples 4 to 15) Next, discharge capacity remaining after overcharging depending on the type of electrolyte salt
The effect of the rate (residual rate after overcharge) was examined. Above
The electrolyte salt used in producing the battery A of Example 1 was
Lithium perfluoroalkyl sulfonimide
LiN (C_TwoF_FiveSO_Two)_TwoInstead of LiN (CF_ThreeSO
_Two)_Two, LiN (C_FourF₉SO_Two)_Two, LiN (CF_ThreeSO_Two) (C_Four
F₉SO_Two), LiC (CF_ThreeSO_Two)_Three, LiPF₆And LiN
(CF_ThreeSO _Two) (C_FourF₉SO_Two), LiBF_FourAnd LiN (CF_Three
SO_Two) (C_FourF₉SO_Two), LiPF₆, LiBF_Four, LiA
sF₆, LiSbF₆, LiClO_Four, LiCF_ThreeSO_ThreeTo
Except for the fact that each non-
The water electrolyte battery 10 was produced.

Here, LiN (CF ₃ S
The nonaqueous electrolyte battery 10 using O ₂ ) ₂ was replaced with the battery D of Example 4.
And a non-aqueous electrolyte battery 1 using LiN (C ₄ F ₉ SO ₂ ) ₂
0 was used as the battery E of Example 5, and LiN (CF ₃ SO ₂ ) (C ₄ F
₉ SO ₂ ) as a battery F of Example 6, a non-aqueous electrolyte battery 10 using LiC (CF ₃ SO ₂ ) ₃ as a battery G of Example 7, and LiPF ₆ and LiN. (CF
A non-aqueous electrolyte battery 10 using an electrolyte salt in which ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) was mixed at 0.5 mol / liter was used as a battery H of Example 8.

Further, LiBF ₄ and LiN (CF ₃ SO ₂ ) (C
Non-aqueous electrolyte battery 10 using an electrolyte salt mixed with 0.5 mol / L of ₄ F ₉ SO ₂ ) was used for battery I of Example 9.
The nonaqueous electrolyte battery 10 using LiPF ₆ was used as the battery J of Example 10, the nonaqueous electrolyte battery 10 using LiBF ₄ was used as the battery K of Example 11, and the nonaqueous electrolyte battery 10 using LiAsF ₆ was used. Is the battery L of Example 12, and LiS
The nonaqueous electrolyte battery 10 using bF _{6 is referred} to as battery M of Example 13, the nonaqueous electrolyte battery 10 using LiClO _{4 is referred} to as battery N of Example 14, and the nonaqueous electrolyte battery 10 using LiCF ₃ SO ₃ is used. Was used as the battery O of Example 15.

Using each of the batteries D to O produced as described above, these batteries were charged at 1 mA at room temperature (25 ° C.).
/ After the battery voltage at a current density of cm ² was charged until 6.0V, the battery voltage at a current density of 1 mA / cm ² 2.
The battery was discharged until the voltage reached 75 V, and the initial discharge capacity was determined from the discharge time. Thereafter, the battery was overcharged at a current density of 1 mA / cm ² until the battery voltage reached 12.0 V, and then 1 mA / c
The battery was discharged at a current density of m ² until the battery voltage reached 2.75 V, and the discharge capacity after overcharge was determined from the discharge time. Next, when the residual rate after overcharge is determined from the initial discharge capacity determined as described above and the discharge capacity after overcharge based on the above equation (1), the results as shown in Table 2 below are obtained. became. Table 2 also shows the results of the battery A of Example 1.

[0034]

[Table 2]

As is clear from Table 2 above, LiCF_Three
SO_ThreeBattery O with electrolyte salt remains slightly overcharged
Rate, LiN (C_TwoF_FiveSO_Two)_Two, LiN (C
F_ThreeSO _Two)_Two, LiN (C_FourF₉SO_Two)_Two, LiN (CF_ThreeSO
_Two) (C_FourF₉SO_Two), LiC (CF_ThreeSO_Two)_Three, LiPF₆When
LiN (CF_ThreeSO_Two) (C_FourF₉SO_Two), LiBF_FourAnd LiN
(CF_ThreeSO_Two) (C_FourF₉SO_Two), LiPF₆, LiBF_Four,
LiAsF₆, LiSbF₆, LiClO_FourElectrolyte salt
It can be seen that the use of
Call

And, among these electrolyte salts, LiN
(C_TwoF_FiveSO_Two)_Two, LiN (CF_ThreeSO_Two) _Two, LiN (C_FourF₉
SO_Two)_Two, LiN (CF_ThreeSO_Two) (C_FourF₉SO_Two)
Mperfluoroalkyl sulfonimide, or L
iC (CF_ThreeSO_Two)_ThreeLithium perfluoroalkyl such as
Sulfonic acid methide maintains extremely high residual rate after overcharge
You can see that you can. From this, the non-aqueous electrolyte of the present invention
As the electrolyte salt used for the battery, LiX (SO_TwoR_Three)_n
Wherein X is N, C, O or B;_ThreeIs CF_ThreeMa
Or C_TwoF_FiveOr C_ThreeF₇Or C_FourF₉And n is 1 to
It is preferable to use an electrolyte salt represented by the following formula:
I can say good.

7. Investigation of Positive Electrode Current Collector Material Next, the influence of the positive electrode current collector material on the residual ratio after overcharge was examined. Here, the non-aqueous electrolyte battery 10 was manufactured in the same manner as in Example 1 except that an aluminum foil was used as the positive electrode current collector 12 instead of the tantalum foil of Example 1.
This was used as a battery P of Example 16. Also, stainless steel (SU) was used in place of the tantalum foil of Example 1.
S304) A non-aqueous electrolyte battery 10 was produced in the same manner as in Example 1 except that a foil was used, and this was designated as Battery W of Comparative Example 4.

Next, using these batteries P and W, each of these batteries was charged at room temperature (25 ° C.) at a current density of 1 mA / cm ² until the battery voltage reached 6.0 V.
The battery was discharged at a current density of 1 mA / cm ² until the battery voltage reached 2.75 V, and the initial discharge capacity was determined from the discharge time. Thereafter, at a current density of 1 mA / cm ² , the battery voltage becomes 1
After overcharging to 2.0 V, the battery was discharged at a current density of 1 mA / cm ² until the battery voltage reached 2.75 V,
The discharge capacity after overcharge was determined from the discharge time. Next, when the residual rate after overcharge is determined from the initial discharge capacity determined as described above and the discharge capacity after overcharge based on the above-described equation (1), the results as shown in Table 3 below are obtained. became. Table 3 also shows the results of the battery A of Example 1.

[0039]

[Table 3]

As is clear from Table 3 above, the battery W of Comparative Example 4 using the positive electrode current collector 12 made of stainless steel (SUS304) foil has a very low residual rate after overcharge, while the tantalum foil It can be seen that the residual rate after overcharge of the battery A of Example 1 using the positive electrode current collector 12 made of aluminum and the battery P of Example 16 using the positive electrode current collector 12 made of aluminum foil was extremely high.

This is because, when a battery using a stainless steel foil as the positive electrode current collector 12 is overcharged, the stainless steel melts in the electrolytic solution and eventually loses its function as a current collector. In addition, since lithium is bonded to the stainless steel dissolved in the electrolytic solution, self-discharge occurs. For this reason, it is considered that the residual ratio after overcharge of the battery W of Comparative Example 4 in which the stainless steel (SUS304) foil was used as the positive electrode current collector 12 was extremely low.

On the other hand, even when the battery having the positive electrode current collector 12 made of tantalum foil is overcharged, tantalum is unlikely to dissolve into the electrolytic solution, and therefore, it is considered that an extremely high residual rate after overcharge was exhibited. Also, when a battery having an aluminum foil as the positive electrode current collector 12 is overcharged, aluminum is more easily dissolved in the electrolytic solution than tantalum, but is less easily dissolved in the electrolytic solution than stainless steel. Probably showed the rate. From the above, it can be said that as the metal material used for the positive electrode current collector 12, it is preferable to use tantalum which does not easily dissolve into the electrolytic solution even when overcharged.

8. Examination of the capacity ratio (Examples 17 to 21) Next, the ratio of each capacity of the capacity of the positive electrode, the capacity of the negative electrode, and the capacity of the electrolytic solution (electrochemical equivalent), that is, after overcharging when the capacity ratio is changed The effect of the survival rate was studied. Here, the capacities of the positive / negative electrode and the electrolytic solution were determined based on the following equations (2) to (4). Positive electrode capacity = Specific capacity of positive electrode x Positive electrode weight ... (2) Capacity of negative electrode = Specific capacity of negative electrode x Negative electrode weight ... (3) Capacity of electrolytic solution (electrochemical equivalent: hereinafter referred to as capacity) = 26 .8 Ah × concentration of electrolyte salt × valency of anion × liquid amount / cc (4)

The capacity ratio of the batteries A to P in Examples 1 to 16 was as follows: positive electrode: negative electrode: electrolytic solution = 1.5:
1.5: 1. Then, a non-aqueous electrolyte battery 10 was manufactured in the same manner as the battery A of Example 1 except that the capacity ratio was changed. Here, the capacity ratio was defined as positive electrode: negative electrode: electrolytic solution = 2:
The 1: 1 non-aqueous electrolyte battery 10 was replaced with the battery Q of Example 17.
The nonaqueous electrolyte battery 10 in which the positive electrode: the negative electrode: the electrolyte solution was 1: 2: 1 was used as the battery R of Example 18, and the nonaqueous electrolyte battery 10 in which the positive electrode: the negative electrode was the electrolyte solution was 1: 1: 1. Example 1
Non-aqueous electrolyte battery 10 with positive electrode: negative electrode: electrolyte = 1: 1: 2 as battery S of No. 9 and non-aqueous electrolyte with positive electrode: negative electrode: electrolyte = 2: 1: 2 in Example 20 Electrolyte battery 1
0 was designated as battery U of Example 21.

Using each of the batteries Q to U produced as described above, these batteries were charged at room temperature (25 ° C.) at 1 mA.
/ After the battery voltage at a current density of cm ² was charged until 6.0V, the battery voltage at a current density of 1 mA / cm ² 2.
The battery was discharged until the voltage reached 75 V, and the initial discharge capacity was determined from the discharge time. Thereafter, the battery was overcharged at a current density of 1 mA / cm ² until the battery voltage reached 12.0 V, and then 1 mA / c
The battery was discharged at a current density of m ² until the battery voltage reached 2.75 V, and the discharge capacity after overcharge was determined from the discharge time. Next, when the residual rate after overcharge is determined from the initial discharge capacity determined as described above and the discharge capacity after overcharge based on the above equation (1), the result as shown in Table 4 below is obtained. became. Table 4 also shows the results of the battery A of Example 1.

[0046]

[Table 4]

As is clear from Table 4 above, batteries A, Q,
Although R and S show extremely high residual rates after overcharge, batteries T and U whose electrolyte capacity is larger than the capacity of the positive electrode or the negative electrode are inferior in residual rate after overcharge. .

This is because if the capacity of the electrolytic solution is less than the capacity of the positive electrode or the negative electrode, all of the anions and cations in the electrolytic solution are intercalated into the graphite of the positive electrode or the negative electrode by overcharging (strictly speaking, At the end of charging, the charging voltage rises, so not all of the anions and cations in the electrolyte are intercalated into the graphite of the positive electrode or negative electrode, and the only anions and cations required for the next discharge are It is considered that overcharging does not proceed any further.

On the other hand, if the capacity of the electrolyte is larger than the capacity of the positive electrode or the negative electrode, even if the capacity of the positive electrode or the negative electrode is exhausted, the anion and the cation in the electrolyte try to enter the positive electrode or the negative electrode, and the charging voltage increases. It is considered that the liquid was decomposed and the battery capacity was deteriorated. Therefore, it is preferable that the capacity of the electrolytic solution is equal to or less than the capacity of the positive electrode or the negative electrode. With such a configuration, overcharge can be prevented and a nonaqueous electrolyte battery without deterioration of the battery capacity can be obtained. .

As described above, in the present invention, the non-aqueous electrolyte contains the anion intercalated in the graphitic carbon of the positive electrode and the cation intercalated in the graphitic carbon of the negative electrode. By charging, the anion in the non-aqueous electrolyte is intercalated into the graphitic carbon of the positive electrode, and the cation in the non-aqueous electrolyte is intercalated into the graphitic carbon of the negative electrode, and the electromotive force is about 5 to 6 V A non-aqueous electrolyte battery can be obtained. In the battery of the present invention, overcharging does not occur, and the battery may be charged when the anion or cation in the non-aqueous electrolyte has disappeared. It is desirable because it becomes possible to exhibit the characteristics of.

In the above-described embodiment, an example has been described in which natural graphite is used as graphite carbon. However, artificial graphite may be used as graphite carbon other than natural graphite.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a non-aqueous electrolyte battery of the present invention.

FIG. 2 is a diagram showing charge / discharge cycle characteristics (charge / discharge efficiency).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Non-aqueous electrolyte battery, 11 ... Positive electrode can, 12 ... Positive electrode collector, 13 ... Positive electrode, 14 ... Separator, 15 ... Negative electrode can, 1
6 negative electrode current collector, 17 negative electrode, 18 green packing

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masahisa Fujimoto 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. F-term (reference) 5H029 AJ05 AK07 AL07 AM02 AM03 AM07 BJ03 DJ07 EJ01

Claims (5)

[Claims] 1. A non-aqueous electrolyte battery including at least a positive electrode, a negative electrode, and a non-aqueous electrolyte in a battery container, wherein the positive electrode includes a graphitic carbon layer on a surface of a positive electrode current collector, and the negative electrode includes a negative electrode. A non-aqueous electrolyte battery comprising a current collector having a graphitic carbon layer on a surface thereof, wherein the non-aqueous electrolyte contains at least ethylene carbonate and a chain carbonate as solvents. 2. At least a positive electrode, a negative electrode, and a
A non-aqueous electrolyte battery including a water electrolyte, wherein the positive electrode includes a graphitic carbon layer on a surface of a positive electrode current collector; the negative electrode includes a graphitic carbon layer on a surface of a negative electrode current collector; The solvent for the water electrolyte should be at least ethylene carbonate
And a chain carbonate, and LiPF is contained in the solvent.₆, LiBF_Four, LiAsF₆, L
iSbF₆, LiClO _Four, LiX (SO_TwoR)_n(Where
X is N, C, O or B, and R is CF_ThreeOr C_TwoF
_FiveOr C_ThreeF₇Or C_FourF₉And n is an integer of 1 to 3
At least one selected from any of the above)
A non-aqueous electrolyte battery characterized by containing. 3. The non-aqueous electrolyte battery according to claim 1, wherein the positive electrode current collector contains tantalum. 4. LiX (SO ₂ R) _n wherein X is N, C, O or B, and R is CF ₃ or C ₂ F ₅ or C ₃ F ₇ or C ₄ F. ₉ wherein n is an integer of 1 to 3).
Or the non-aqueous electrolyte battery according to claim 3. 5. The nonaqueous electrolyte according to claim 1, wherein the electrochemical equivalent of the nonaqueous electrolyte is smaller than the capacity of the smaller of the positive electrode and the negative electrode. battery.