JP2000285967A - Lithium ion secondary battery and manufacture of lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery with high capacity and low capacity deterioration attendant on charge-discharge cycles. SOLUTION: This lithium ion secondary battery has an electrode group 3 comprising a positive electrode, a negative electrode made of a material capable of storing and releasing lithium ions, and a separator placed between the positive electrode and the negative electrode, a nonaqueous electrolyte prepared by dissolving a lithium salt in a nonaqueous solvent, an inner container 2 for housing the electrode group 3 and the nonaqueous electrolyte, an outer container 4 for housing the inner container 2, and a means for supplying the nonaqueous electrolyte from the outer container 4 to the inner container 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a portable electronic device,
The present invention relates to a lithium ion secondary battery used for electric vehicles, home electric power storage, and the like, and a method for manufacturing a lithium ion secondary battery.

[0002]

2. Description of the Related Art In recent years, demand for high-performance secondary batteries has been increasing as a power source of portable electronic devices supporting the information-oriented society, and as a key element of electric vehicles and power storage systems for addressing air pollution and global warming. It has increased significantly. The technology for increasing the capacity of secondary batteries has been remarkable, and the capacity of nickel-metal hydride batteries, which can replace conventional NiCad batteries, is increasing year by year.

On the other hand, unlike these secondary batteries using an aqueous electrolyte, development of a lithium ion secondary battery using a non-aqueous electrolyte and featuring a high electromotive force is also rapidly progressing.

[0004] In principle, lithium ion secondary batteries are far superior to conventional secondary batteries in capacity per unit weight. However, the non-aqueous electrolyte has low conductivity, and the electromotive force is high, so that the electrolyte is easily decomposed. Therefore, its potential is not fully utilized, and further improvement in capacity is required.

[0005] Further, there has been a problem that the repetition of charge and discharge causes the non-aqueous electrolyte to dry out inside the electrode, resulting in a capacity deterioration occurring when the charge and discharge cycle is repeated.

The two major problems of increasing the capacity of the lithium ion secondary battery and extending the cycle life will be described in more detail.

First, the expansion of the capacity of a lithium ion secondary battery will be considered.

In the case of a lithium ion secondary battery, when a thick electrode is used for the purpose of increasing the energy capacity, the thickness and the current density are proportional to each other in a normal current density region unlike the case of a nickel hydride battery. do not do. Therefore, in order to increase the battery capacity, it is necessary to increase the effective diffusion coefficient in the electrode.

Many of the conventional lithium ion secondary batteries are:
It is composed of a positive electrode using a layered oxide having a large anisotropic coefficient of anisotropy as an active material, and a negative electrode similarly using a carbon-based compound having a large anisotropic anisotropic coefficient as an active material. In practical electrodes, powder particles (active material grains) of these active materials are applied on a supporting conductor together with a conductive aid and a binder polymer. Lithium ions in the electrode diffuse by moving in and between the active material grains. That is, the effective ion diffusion coefficient in the electrode is affected not only by the ion diffusion coefficient in the active material grains, which is a material constant, but also by the ion diffusion between the active material grains, which depends on the electrode formation method. It is necessary to improve the ion diffusion between the material grains and to improve the effective ion diffusion coefficient, but a battery with sufficient improvement in this respect has not been realized.

Next, the prolongation of the cycle life of the lithium ion secondary battery will be considered.

[0011] In a lithium ion secondary battery, as in the case of other secondary batteries, the capacity deteriorates when charging and discharging are repeated. The main cause of this is that when charge and discharge are repeated, the electrode repeatedly expands and contracts, causing a non-aqueous electrolyte to be unevenly distributed inside the electrode. This is known as the liquid withering phenomenon. Since the capacity of a lithium ion secondary battery that has caused liquid withdrawal is rapidly deteriorated, a battery that does not cause the liquid withering phenomenon is required, but it has not been realized yet.

On the other hand, the importance of safety of lithium ion secondary batteries has also been emphasized. Lithium ion secondary batteries are
Uses flammable organic solvent as solvent for non-aqueous electrolyte with high electromotive force, so it is more resistant to strong vibrations and external shocks due to collisions than batteries using aqueous electrolyte, and less likely to cause ignition Need to increase security.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-capacity lithium-ion secondary battery having a high capacity and having little capacity deterioration when repeated charge / discharge cycles are repeated.

Another object of the present invention is to provide a highly safe lithium-ion secondary battery that withstands an external impact and is unlikely to cause ignition or the like.

[0015]

Means for Solving the Problems A first invention comprises a positive electrode,
A negative electrode including a material that stores and releases lithium ions;
An electrode group composed of the positive electrode and the separator located between the positive electrode and the negative electrode; a non-aqueous electrolyte obtained by dissolving a lithium salt in a non-aqueous solvent; and a content containing the electrode group and the non-aqueous electrolyte And a container for storing the inner container; and a means for supplying a nonaqueous electrolyte from the outer container to the inner container.

According to a second aspect of the present invention, there is provided an electrode group comprising a positive electrode, a negative electrode provided with a material for absorbing and releasing lithium ions, a separator located between the positive electrode and the negative electrode, and a non-aqueous electrolytic solution. In the method for manufacturing a lithium ion secondary battery including a sealing step of sealing the inner container, before the sealing step, performing a charging and discharging step of immersing the inner container into which the electrode group is inserted in the nonaqueous electrolyte to perform charging and discharging. A method for producing a lithium ion secondary battery, which is a feature of the present invention.

According to a third aspect of the present invention, there is provided an electrode group comprising a positive electrode, a negative electrode provided with a material for absorbing and releasing lithium ions, and a separator located between the positive electrode and the negative electrode; A non-aqueous electrolyte obtained by dissolving a salt; an inner container for storing the electrode group and the non-aqueous electrolyte; an outer container for storing the inner container; inserted between the inner container and the outer container A lithium ion secondary battery comprising a shock absorbing material.

As described in the prior art, in order to increase the battery capacity, it is necessary to improve the ion diffusion between the active material grains constituting the electrodes. Further, the first key point for improving the ion diffusion between the active material grains is that the active material grains are covered with a non-aqueous electrolyte that has permeated into the electrode.

In general, the diffusion rate of ions at the solid phase interface is reduced due to disorder of the crystal structure generated on the surface of the fine particles, so that the effective ion diffusion coefficient is significantly lower than the diffusion coefficient in the active material grains.

FIG. 1 is a schematic view showing lithium ion diffusion in the electrode. As shown in FIG. 1, when the active material grain surface is covered with the non-aqueous electrolyte and ion diffusion occurs through the liquid phase, the effective ion diffusion coefficient is greatly improved, and the battery capacity is increased. be able to.

Further, in order to extend the cycle life of the battery, it is necessary to prevent the non-aqueous electrolyte from withering.

When the double-vessel structure as in the first invention is used, even if an organic solvent having a high boiling point and a high viscosity is used as a solvent for the non-aqueous electrolyte, the non-aqueous electrolyte can be sufficiently infiltrated into the electrodes. When the surface of the active material grains is covered with the non-aqueous electrolyte and ion diffusion occurs through the liquid phase, the effective ion diffusion coefficient is greatly improved, and the battery capacity can be increased.

Further, since the non-aqueous electrolyte is naturally replenished from the outer container to the electrode group in the inner container, the liquid can be prevented from withering, and the cycle life is increased.

In particular, in the case of a large lithium ion secondary battery expected to be applied to an electric vehicle, the lithium ion secondary battery is used in a much wider current region than a normal personal computer use region. It is considered that the capacity of the non-aqueous electrolyte was significantly degraded due to withering. Therefore, the use of the battery of the first aspect of the present invention is very useful because it prevents the liquid from dying and improves the cycle life characteristics.

Further, according to the first invention, even when an organic solvent having a high boiling point and a high viscosity is used as a solvent for the non-aqueous electrolyte, the non-aqueous electrolyte can be sufficiently infiltrated into the electrode. As the non-aqueous electrolyte is less likely to evaporate with improved battery life and cycle life characteristics, the non-aqueous electrolyte is less likely to evaporate even during overcharge or internal short-circuit, etc. The safety of the vehicle can also be improved.

According to the second aspect of the present invention, not only is the discharge capacity of the lithium ion secondary battery increased, but also the deterioration of the discharge capacity due to the non-aqueous electrolyte dying phenomenon often caused by repeated charging and discharging is prevented. It becomes possible to do.

That is, if charging and discharging are repeated after the electrode group and the non-aqueous electrolyte are sealed in the container, the distribution of the electrolyte inside the electrodes is biased. This is because the electrodes repeatedly expand and contract due to charge and discharge. Therefore, before the electrode group and the non-aqueous electrolyte are sealed in the container, the electrode group is charged and discharged inside the container in which the electrolyte is immersed, so that the electrolyte is sufficiently infiltrated into the electrode group and the battery is sealed afterwards. In addition to improving the capacity, it is possible to prevent liquid withering that occurs at the time of charging and discharging after sealing, and it is possible to improve cycle life characteristics.

According to the second aspect of the present invention, even when an organic solvent having a high boiling point and a high viscosity is used as a solvent for the non-aqueous electrolyte, the non-aqueous electrolyte can be sufficiently infiltrated into the electrode. As the non-aqueous electrolyte is less likely to evaporate with improved battery life and cycle life characteristics, the non-aqueous electrolyte is less likely to evaporate even during overcharge or internal short-circuit, etc. The safety of the vehicle can also be improved.

When a lithium ion secondary battery is used in an electric vehicle or the like, the most important problem is safety. According to the third aspect of the present invention, since the shock absorbing material is inserted between the inner container and the outer container, the electrode group inside the inner container is protected even if the battery container is crushed in the event of strong vibration or collision. And ignition can be prevented.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the lithium ion secondary battery of the first invention will be described.

FIG. 2 is a schematic diagram showing an example of the configuration of the lithium ion secondary battery of the first invention.

As shown in FIG. 2A, an inner container 2 accommodates an electrode group 3 composed of a positive electrode, a negative electrode and a separator. It is desirable that the electrode group 3 is formed by laminating a positive electrode and a negative electrode, and a separator located between the positive electrode and the negative electrode, and further has a coil shape. The inner container 2 has a lid 1 also serving as an electrode terminal. The inner container 2 has no bottom.

As the inner container 2, a can made of resin can be used in addition to a normal metal can. By using a can made of resin, it is possible to reduce the weight of the entire battery and to prevent corrosion and oxidation by a non-aqueous electrolyte.

Further, as shown in FIG. 2B, the outer container 4 has a bottom. As the outer container 4, a can made of resin can be used in addition to a normal metal can. By using a can made of resin, it is possible to reduce the weight of the entire battery and to prevent corrosion and oxidation by a non-aqueous electrolyte.

The lithium ion secondary battery of the first invention is
As shown in FIG. 2C, the inner container 2 in which the electrode group is stored is stored in the outer container 4. Inner container 2 and outer container 4
Is filled with a non-aqueous electrolyte obtained by dissolving a lithium salt in a non-aqueous solvent. Since the inner container 2 has no bottom,
A conducting path 5 is formed so that the nonaqueous electrolyte can be supplied from the outer container 4 to the inner container 2, so that the nonaqueous electrolyte in the outer container can easily enter the inner container 2. The inner container 2 may be provided with a bottom provided with a hole.

Since the nonaqueous electrolyte is filled between the inner container and the outer container, the replenishment of the electrolyte and the
It acts as a shock absorber, and can protect the electrode group inside the inner container even if strong vibrations or crushing of the battery container at the time of collision occur, thereby preventing ignition.

In manufacturing the lithium ion secondary battery of the first invention, the nonaqueous electrolyte is sufficiently infiltrated into the electrode group consisting of the positive electrode, the negative electrode and the separator in the inner container 2 in advance.
It is desirable that the inner container 2 is inserted into the outer container 4, and a non-aqueous electrolyte is further injected to seal the outer container.

In the lithium ion secondary battery according to the first aspect of the invention, a layer more porous than the separator and having a higher liquid retention property is inserted between the electrode group and the inner container in order to thoroughly prevent the liquid withering phenomenon. A method and a method of providing a mechanism for re-injecting the nonaqueous electrolyte into the cell container are desirable.

Next, a method for manufacturing the lithium ion secondary battery of the second invention will be described.

As in the second invention, before the electrode group and the non-aqueous electrolyte are sealed in the container, the electrode group is housed in the container containing the non-aqueous electrolyte for a certain period of time, and after repeating the charge and discharge, the electrode group And the non-aqueous electrolyte are sealed in a container. As a charging condition, it is desirable to repeat charging and discharging between 4.2V and 3V.

Further, if the battery cells are housed in a non-aqueous electrolyte whose viscosity has been reduced by heating the entire container, the time required for infiltration can be shortened, which is more effective.

In the method for manufacturing a lithium ion secondary battery of the second invention, if the double container structure as in the first invention is used, this manufacturing process can be facilitated, which is more effective. .

Next, the lithium ion secondary battery of the third invention will be described.

FIG. 3 is a schematic diagram showing an example of the configuration of the lithium ion secondary battery of the third invention.

As shown in FIG. 3A, the inner container 2 accommodates an electrode group 3 including a positive electrode, a negative electrode, and a separator. It is desirable that the electrode group 3 is formed by laminating a positive electrode and a negative electrode, and a separator located between the positive electrode and the negative electrode, and further has a coil shape. The inner container 2 is a normal metal can,
It is also possible to use cans made of resin. By using a can made of resin, it is possible to reduce the weight of the entire battery and to prevent corrosion and oxidation by a non-aqueous electrolyte.

As shown in FIG. 3 (b), the outer container 4 has a bottom. As the outer container 4, a can made of resin can be used in addition to a normal metal can. By using a can made of resin, it is possible to reduce the weight of the entire battery and to prevent corrosion and oxidation by a non-aqueous electrolyte.

As shown in FIG. 3 (c), the lithium ion secondary battery of the third invention has an inner container 2 containing the above-mentioned electrode group.
Are stored in the outer container 4. The inner container 2 and the outer container 4 are filled with a shock absorbing material. As a shock absorber,
A method using a rubber-like substance such as SBR (styrene butadiene lavane) as a cushion material, a method using a spring between an inner container and an outer container, a method using a gel-like substance, and the like are conceivable. If the nonaqueous electrolyte is filled between the inner container and the outer container, not only can the nonaqueous electrolyte be replenished,
It is also possible to protect the inside.

Further, it is desirable that the shock absorbing material is a substance exhibiting flame retardancy or fire extinguishing action. Examples of the substance include a powder fire extinguishing material for an ABC fire extinguisher that is generally widely used.

FIG. 4 shows another configuration example of the lithium ion secondary battery of the third invention. FIG. 4 is a schematic diagram showing an example of a configuration in which a plurality of lithium ion secondary batteries are put in one pack to form a battery pack.

In FIG. 4, one lithium ion secondary battery has an inner container 32 in which an electrode group 33 including a positive electrode, a negative electrode, and a separator is housed. It is preferable that the electrode group 33 is formed by laminating a positive electrode and a negative electrode, a separator located between the positive electrode and the negative electrode, and further has a coil shape. The inner container 32 has a lid 31 which also serves as an electrode terminal. Further, the inner container 32 in which the electrode group is stored is stored in an outer container 34. An impact absorbing material may be inserted between the inner container and the outer container, or a conductive path may be provided between the inner container and the outer container by filling with an electrolytic solution as in the first invention. Thereby, the battery capacity and the cycle life characteristics can be improved.

Such lithium ion secondary batteries are connected in series, placed in a container 35, filled with a shock absorbing material between the container 35 and the lithium ion secondary battery, and further provided with a cooling material, a fire extinguishing material, etc. Is useful for safety even when used as a battery pack.

FIG. 5 is a schematic view showing another configuration example of the lithium ion secondary battery of the third invention. FIG. 5 is a schematic diagram showing an example of a configuration in which a plurality of lithium ion secondary batteries are put in one pack to form a battery pack. In FIG. 5, one lithium ion secondary battery has an inner container 42 in which an electrode group 43 including a positive electrode, a negative electrode, and a separator is housed. The electrode group 43 is preferably formed by stacking a positive electrode and a negative electrode, and a separator located between the positive electrode and the negative electrode, and further has a coil shape. Such inner containers 42 are connected in parallel, and are stored in the outer container 44. At this time, the space between the inner container 42 and the outer container 44 is filled with the shock absorbing material. The space between the outer container and the inner container may be filled with a non-aqueous electrolytic solution to serve as both a shock absorbing material and a replenishing electrolytic solution. Thereby, the battery capacity and the cycle life characteristics can be improved.

The lithium ion of the first to third inventions
In the secondary battery, as the positive electrode active material of the positive electrode, various
Oxides, such as manganese dioxide, lithium manganese composite
Oxides, lithium-containing nickel oxides, lithium-containing cores
Baltic compound, lithium-containing nickel cobalt oxide,
Lithium-containing iron oxide, lithium-containing vanadium oxide
And chalcogens such as titanium disulfide and molybdenum disulfide
Compounds. Among them, lithium
Containing cobalt oxide (eg, LiCoO₂), Lichiu
Containing nickel cobalt oxide (eg, LiNi
_0.8Co_0.2O ₂), Lithium manganese composite oxide
(For example, LiMn₂O₄, LiMnO₂)
Is preferable because a high voltage can be obtained. Positive electrode is positive electrode active material
It may contain a conductive agent, a binder, and the like in addition to the quality. The positive electrode is
Positive current collection of slurry containing positive electrode active material, conductive agent and binder
It can be obtained by applying to the body and drying.

In the lithium ion secondary batteries of the first to third inventions, examples of the negative electrode material of the negative electrode include carbonaceous materials that occlude and release lithium ions. Examples of the carbonaceous material include graphite materials such as graphite, coke, carbon fiber, and spherical carbon or carbonaceous materials, thermosetting resins, isotropic pitch, mesophase pitch, mesophase pitch-based carbon fiber, mesophase small spheres, and the like (in particular, Graphite material or carbonaceous material obtained by subjecting mesophase pitch-based carbon fiber to heat treatment at 500 to 3000 ° C. can be used. Among them, the temperature of heat treatment is 2
2,000 ° C. or more, and the (002) plane spacing d ₀₀₂ It is preferable to use a graphitic material having a graphite crystal having a particle size of 0.340 nm or less. A non-aqueous electrolyte secondary battery including a negative electrode containing such a graphite material as a carbonaceous material can significantly improve battery capacity and large current characteristics. The plane distance d ₀₀₂ is 0.336 nm
It is more preferred that:

The carbonaceous material is particularly 2,000
Mesophase pitch-based carbon fibers heat-treated at a temperature of not less than ° C are preferred. When this is used, the electrode density is 1.3 g / cm ³
Even at the above-mentioned high density, the interface impedance between the negative electrode and the separator is small, so that it is excellent in large current discharge characteristics and rapid charge / discharge cycle performance.

As the negative electrode material, in addition to the above-mentioned carbonaceous materials that occlude and release lithium ions, those containing metal oxides, metal sulfides, or metal nitrides, and those made of lithium metal or lithium alloy Can be used.

Examples of the metal oxide include tin oxide, silicon oxide, lithium titanium oxide, niobium oxide, and tungsten oxide.

Examples of the metal sulfide include tin sulfide and titanium sulfide.

Examples of the metal nitride include lithium cobalt nitride, lithium iron nitride, lithium manganese nitride and the like.

Examples of the lithium alloy include a lithium aluminum alloy, a lithium tin alloy, a lithium lead alloy, and a lithium silicon alloy.

The negative electrode may contain a conductive agent, a binder and the like in addition to the negative electrode material. The negative electrode can be obtained by applying a slurry containing a negative electrode active material, a conductive agent, and a binder to a negative electrode current collector and drying the slurry.

In the lithium ion secondary batteries of the first to third inventions, it is desirable to use a porous separator as the separator. As a material of the separator, for example, a porous film containing polyethylene, polypropylene, or polyvinylidene fluoride (PVdF), a synthetic resin nonwoven fabric, or the like can be used. Among them, polyethylene or
Alternatively, a porous film made of polypropylene or both is preferable because the safety of the secondary battery can be improved.

In the lithium ion secondary batteries of the first to third inventions, the non-aqueous electrolyte is prepared by dissolving a lithium salt in a non-aqueous solvent.

As the non-aqueous solvent, a known non-aqueous solvent as a solvent for a lithium ion secondary battery can be used, and it is not particularly limited, but propylene carbonate (PC)
It is preferable to use a non-aqueous solvent mainly composed of a mixed solvent of ethylene or ethylene carbonate (EC) and a non-aqueous solvent having a lower viscosity than PC or EC (hereinafter, referred to as a second solvent).

As the second solvent, for example, chain carbon is preferable. Among them, dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), diethyl carbonate (DEC), ethyl propionate, methyl propionate, γ-butyrolactone (BL) , Acetonitrile (AN), ethyl acetate (EA), toluene, xylene or methyl acetate (MA). These second solvents can be used alone or in the form of a mixture of two or more.

The viscosity of the second solvent is 28 m at 25 ° C.
It is preferably at most p. The blending amount of ethylene carbonate or propylene carbonate in the mixed solvent,
The volume ratio is preferably 10 to 80%. A more preferred blending amount of ethylene carbonate or propylene carbonate is 20 to 75% by volume.

Examples of the electrolyte contained in the non-aqueous electrolyte include:
For example, lithium perchlorate (LiClO ₄), Phosphorus hexafluoride
Lithium oxide (LiPF₆), Lithium borofluoride (Li
BF ₄), Lithium arsenic hexafluoride (LiAsF)₆), To
Lithium trifluorometasulfonate (LiCF₃S
O₃), Bistrifluoromethylsulfonyl imidolithic
[LiN (CF₃SO₂)₂] And other lithium salts
(Electrolyte). Among them, LiPF₆, LiBF
₄It is preferable to use

The amount of the electrolyte dissolved in the non-aqueous solvent is 0.1.
It is desirable to set it as 5 to 2.0 mol / 1.

[0069]

EXAMPLES (Example 1) <Preparation of LiCoO ₂ particles> Co2O3 was mixed with LiOH and heated at 850 (C, 8 hours) in an oxygen stream to prepare LiCoO ₂ powder having an average particle size of 3 (m). LiCoO ₂
LiCoO ₂ particles were produced by pulverizing the powder. <Preparation of Positive Electrode> An Al foil having a thickness of 20 μm was used as a current collector, 5% by weight of acetylene black having an average particle diameter of 30 nm was used as a conductive aid in the above-mentioned LiCoO ₂ active material, and 5% by weight of polyvinylidene fluoride was used as a binder polymer. %added. A slurry was prepared using N-methylpyrrolidone as a solvent, applied on one side of a current collector, and dried. The thickness of the positive electrode after pressing with a roller (250 kg / cm) was adjusted to 100 μm except for the current collector. <Production of Nitrogen-Substituted Graphite> Production of graphite in which a part of carbon atoms near the surface is substituted with nitrogen is performed by using commercially available C
This was performed using a VD device. First, graphite powder having a particle size of about 15 μm was put in a nickel metal container and set in a CVD reactor. After heating the vessel to 850 (C) in vacuum, a partial pressure of 5 mTo using argon as carrier gas.
rr acetonitrile was allowed to flow for 5 minutes to replace about 30% of the carbon atoms with nitrogen atoms over a thickness of several nm near the particle surface. <Preparation of Negative Electrode> A 12 μm thick Cu foil was used as a current collector. Similarly to the positive electrode 1, 5% by weight of acetylene black having an average particle diameter of 30 nm was added to the above-mentioned negative electrode active material as a conductive additive, and 3% by weight of polyvinylidene fluoride was added as a binder polymer. A slurry was prepared using N-methylpyrrolidone as a solvent, applied on one side of the current collector, and dried. The thickness of the negative electrode after pressing with a roller (300 Kg / cm) was adjusted to 100 (m) excluding the current collector. <Infiltration of Nonaqueous Electrolyte and Configuration of Secondary Battery> A coil composed of a porous polyethylene separator having a thickness of 25 μm having a pore of 1 micron and the above-described positive electrode and negative electrode was set in an aluminum inner container shown in Fig. 2, and a lead terminal was attached. The electrolytic solution was obtained by dissolving lithium hexafluorophosphate (LiPF ₆ ) in a mixed solvent of ethylene carbonate / dimethyl carbonate at a concentration of 1 mol / L.The above inner container was set in a stainless steel container having electrode terminals attached. After drying, the container was evacuated, the non-aqueous electrolyte was poured into the container, the container was sealed, and the container was heated to 50 C. The water electrolyte was infiltrated into the positive and negative electrodes.

After the container was returned to room temperature, a charge / discharge cycle was further performed using the electrode terminals of the container. The latter operation is for infiltrating the non-aqueous electrolyte into minute cracks generated by charging and discharging, and is effective in preventing the battery from draining. Subsequently, the inner container sufficiently infiltrated with the non-aqueous electrolyte was taken out of the container, and inserted into a stainless steel outer container.
The outer container was further filled with a non-aqueous electrolyte and sealed, thereby completing a secondary battery. <Charge / Discharge Characteristics> The battery obtained by the above method was charged at a constant current at a current density of 5 mA / cm ² per unit area of the electrode until the battery voltage reached 4.2 V, and then 4.2 V was applied.
The battery was charged at a constant voltage until the current value became 1/20 of the initial value. Thereafter, the direction of the current was reversed, and discharging was performed until the battery voltage became 3 V. When the battery was charged and discharged, it had a high capacity of 1400 mAh or more in terms of a commercially available 18650 type battery. Further, in order to examine the repetition characteristics of charging and discharging, the charging and discharging of these
When the capacity after the repetition of 00 times was measured, the capacity reduction was within 3%. Further, it was found that even if charge / discharge was repeated 500 times, the capacity reduction could be suppressed to within 15%. <Chemical stability> The concentration of carbon dioxide contained in the electrolyte of a battery which was repeatedly charged and discharged 100 times for the purpose of confirming the reaction between the electrode active material and the non-aqueous electrolyte was measured. The concentration was 10 ppm or less, and it was found that the electrode active material and the electrolyte hardly reacted. (Comparative Example 1) A battery was formed by an ordinary method using the electrode formed in the same manner as in Example 1 and the same nonaqueous electrolyte as in Example 1. That is, after the coil including the positive electrode, the negative electrode, and the separator was housed in a stainless steel battery container, an electrolyte was injected at room temperature in an argon dry box and sealed. The initial capacity of this battery is 18650 type conversion,
At a current density of 5 mA / cm ² , it was 1350 mAh. However, the capacity decreased with the charge / discharge cycle, and the capacity after repeating the charge / discharge 100 times decreased by 8%. Further, when the charge and discharge were performed 500 times, the capacity reduction became nearly 25%. When the battery was disassembled and examined, it was found that the electrolyte distribution was uneven, and that a liquid withering phenomenon occurred. Thus, it was found that the lithium ion secondary battery using the present invention can not only increase the capacity in the initial state but also reduce the capacity decrease due to repeated charge and discharge. (Example 2) A positive electrode and a negative electrode were prepared in the same manner as in Example 1, the formed coil was set in an inner container, and a lead wire was attached. The inner container was set in a stainless steel container to which electrode terminals were attached, dried, and then introduced into an argon dry box. After evacuating the container, inject the non-aqueous electrolyte,
The container was sealed. Subsequently, the container was heated to 80 (C) to infiltrate the nonaqueous electrolyte into the positive and negative electrodes. After the container was returned to room temperature, a charge / discharge cycle was further performed using the electrode terminals of the container. The inner container impregnated with the non-aqueous electrolyte was taken out and inserted into an outer container made of stainless steel, at which time a mechanism for injecting the non-aqueous electrolyte into the outer container was attached. After that, the battery was sealed to complete the secondary battery, and lithium hexafluorophosphate (LiPF ₆ ) was added to the non-aqueous electrolyte in a mixed solvent of ethylene carbonate / dimethyl carbonate at a mole ratio of 1 mol / l as in Example 1. The initial discharge capacity was determined in the same manner as in Example 1. The initial discharge capacity was 1400 mAh, which was converted to a 18650 type battery. Is 1200 mAh Therefore, the non-aqueous electrolyte was injected from a non-aqueous electrolyte injection mechanism provided in the outer container.After about 10 charge / discharge cycles, the capacity was determined. 1350
It was found that the capacity had recovered to mAh. When charge and discharge were repeated 100 more times, the capacity decreased to about 1280 mAh. It is proved that the capacity decreases when charge and discharge are repeated because the non-aqueous electrolyte solution withers inside the electrode, and the capacity can be recovered by replenishing the non-aqueous electrolyte solution from the outside. I knew I could do it. Example 3 A positive electrode and a negative electrode were prepared in the same manner as in Example 1, and then a coil was formed using a 25 μm-thick porous polyethylene separator having pores having an average diameter of 0.1 μm. At this time, a polyethylene sheet having a hole having an average diameter of 3 μm was wound around the coil between the coil and the inner container for holding the electrolyte. The coil thus prepared was set in an aluminum inner container, and a lead terminal was attached. The inner container was set in a stainless steel container to which electrode terminals were attached, dried, and then introduced into an argon dry box. After evacuation of the inside of the container, a non-aqueous electrolyte was injected, and the container was sealed. Subsequently, the container was heated to 80 (C) to infiltrate the nonaqueous electrolyte into the positive and negative electrodes. After the container was returned to room temperature, a charge / discharge cycle was further performed using the electrode terminals of the container. The inner container impregnated with the non-aqueous electrolyte was taken out of the container, inserted into a stainless steel outer container, filled with the non-aqueous electrolyte, and sealed to complete the secondary battery. As the water electrolyte, a solution prepared by dissolving lithium hexafluorophosphate (LiPF ₆ ) in a mixed solvent of ethylene carbonate / dimethyl carbonate at a concentration of 1 mol / liter as in Example 1 was used. The initial discharge capacity of the battery was examined.
It had a high capacity of 400 mAh. Next, when charge and discharge were repeated 100 times, the capacity was 1350 mAh (3.5 times).
7%). Further, when charging and discharging were performed 500 times, it was found that the capacity was reduced to 1250 mAh (10.7%). As a result, it has been found that the capacity reduction can be further reduced as compared with the case of the first embodiment. (Example 4) After the same positive electrode and negative electrode as in Example 1 were prepared, a coil was prepared using a 25 μm thick porous polyethylene separator having pores with an average diameter of 0.1 μm. At this time, a porous S is placed between the coil and the inner container.
A BR sheet having a thickness of 1 mm was wound. The coil thus prepared was set in an aluminum inner container, and a lead terminal was attached. The inner container was set in a stainless steel container to which electrode terminals were attached, dried, and then introduced into an argon dry box. After evacuation of the inside of the container, a non-aqueous electrolyte was injected, and the container was sealed. Subsequently, the container was heated to 80 (C) to allow the nonaqueous electrolyte to infiltrate the positive and negative electrodes.
Further, a charge / discharge cycle was performed. Subsequently, the inner container sufficiently infiltrated with the nonaqueous electrolyte was taken out of the container, and inserted into a stainless steel outer container. The outer container was further filled with a non-aqueous electrolyte and then sealed to complete a secondary battery. The non-aqueous electrolyte contains lithium hexafluorophosphate (Li) as in Example 1.
PF ₆ ) dissolved in a mixed solvent of ethylene carbonate / dimethyl carbonate at a concentration of 1 mol / liter was used. The resulting battery had a discharge capacity of 1250 mAh. Since a porous SBR sheet was used, the same discharge capacity as in Example 3 was obtained. Further, when a drop test (dropping 10 times from a height of 1.9 m) was performed on this battery, an internal short circuit occurred with a probability of 3/10 in a battery not wound with an SBR sheet, but the SBR sheet was wound. All batteries did not have internal short circuits. This confirmed that the impact resistance was not good.

[0071]

According to the present invention, it is possible to obtain a high capacity lithium ion secondary battery having a high capacity and a small capacity deterioration when the charge and discharge cycle is repeated.

Further, according to the present invention, a highly safe lithium ion secondary battery can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing lithium ion diffusion in an electrode.

FIG. 2 is a schematic view showing an example of a configuration of a lithium ion secondary battery of the first invention.

FIG. 3 is a schematic diagram showing an example of a configuration of a lithium ion secondary battery of a third invention.

FIG. 4 is a schematic view showing another configuration example of the lithium ion secondary battery of the third invention.

FIG. 5 is a schematic view showing another configuration example of the lithium ion secondary battery of the third invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Lid 2 ... Inner container 3 ... Electrode group 4 ... Outer container 31 ... Lid 32 ... Inner container 33 ... Electrode group 34 ... Outer container 35 ... Container 42 ... Inner container 43 ... Electrode group 43 44 ... Outer container 44

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Hiroyuki Hasebe 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba Kawasaki Office (72) Inventor Shuji Yamada 72-Horikawa-cho, Sachi-ku, Kawasaki-shi, Kanagawa Pref. (72) Inventor Hideyuki Kanai 70, Yanagimachi, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside Toshiba Yanagicho Plant (72) Inventor Shun Shun Egusa 1--1 Komukai Toshiba-cho, Yuki-ku, Kawasaki-shi, Kanagawa Prefecture Toshiba Corporation F-term in R & D center (reference) 5H023 AA03 AS03 CC06 CC11 CC27 CC28 DD01 DD06 DD08 5H029 AJ03 AJ05 AJ11 AJ12 AK02 AK03 AK05 AL01 AL02 AL03 AL04 AL06 AL07 AL12 AM02 AM03 AM07 BJ21 CJ13 CJ16 CJ23 DJ02 DJ04 DJ08

Claims (5)

[Claims] An electrode group comprising: a positive electrode; a negative electrode including a material capable of inserting and extracting lithium ions; and a separator group disposed between the positive electrode and the negative electrode; and dissolving a lithium salt in a non-aqueous solvent. A nonaqueous electrolytic solution comprising: an inner container for storing the electrode group and the nonaqueous electrolytic solution; an outer container for storing the inner container; and at least means for supplying the nonaqueous electrolytic solution from the outer container to the inner container. A lithium ion secondary battery, comprising: 2. The lithium ion secondary battery according to claim 1, wherein a material that is more porous and has higher liquid retention properties than the separator is inserted between the inner container and the electrode group. battery. 3. A hermetic seal for sealing a non-aqueous electrolyte and a group of electrodes comprising a positive electrode, a negative electrode comprising a material capable of inserting and extracting lithium ions, and a separator located between the positive electrode and the negative electrode. In the method for manufacturing a lithium ion secondary battery comprising a step, before the sealing step, performing a charge / discharge step of immersing the container in which the electrode group is inserted in the nonaqueous electrolyte to perform charge / discharge. A method for manufacturing a secondary battery. 4. An electrode group comprising a positive electrode, a negative electrode provided with a material for storing and releasing lithium ions, and a separator located between the positive electrode and the negative electrode; and dissolving a lithium salt in a non-aqueous solvent. A non-aqueous electrolytic solution; an inner container for storing the electrode group and the non-aqueous electrolytic solution; an outer container for storing the inner container; and a shock absorber inserted between the inner container and the outer container. A lithium ion secondary battery comprising: 5. The lithium ion secondary battery according to claim 4, wherein said shock absorbing material is a substance exhibiting flame retardancy or fire extinguishing action.