KR19980080397A - Lithium Secondary Battery, Method for Manufacturing the Same, and Battery System - Google Patents

Abstract

According to the present invention, a plurality of electrode groups 10 having a long circular spiral shape wound by stacking a sheet-shaped or film-shaped anode 11, a cathode 13, and a separator 12 are stacked side by side in a battery cell 14 to be internally stored. By connecting to the lithium secondary battery, a large-size lithium secondary battery with high productivity and high safety was realized.

Description

Lithium Secondary Battery, Method for Manufacturing the Same, and Battery System

The present invention relates to a large-capacity large lithium secondary battery suitable for use as a power source for portable devices, electric vehicles, electric power storage, and the like, a manufacturing method thereof, and a battery system.

As a secondary battery in which separators are sandwiched between a sheet-like or plate-shaped positive electrode and a negative electrode, and a plurality of these are laminated alternately, respectively, and each positive electrode or each negative electrode is connected, there is one described in Japanese Patent Laid-Open No. 6-176759.

In addition, as a secondary battery in which a sheet-like or film-shaped positive electrode, a negative electrode, and a separator are superimposed on one another and wound in a cylindrical spiral shape or a long cylindrical spiral shape, and are put in a battery cell as a single electrode group, Japanese Patent Application Laid-Open No. 4 -167375, Japanese Patent Laid-Open Publication No. 5-135780, Japanese Patent Laid-Open Publication No. 5-315009, Japanese Patent Laid-Open Publication No. 6-140077, Japanese Patent Laid-Open Publication No. 8-171917, Japanese Laid-Open Patent Publication 9 -92237 and US Pat. No. 5,439,760. Moreover, there exist some which were described in Unexamined-Japanese-Patent No. 9-7610 as a secondary battery which put one sheet-like or film-shaped positive electrode, the negative electrode, and the separator which overlap | folded each other in the battery cell as a single electrode group.

An object of the present invention is to realize a large capacity large lithium secondary battery with high safety.

Another object is to provide a method for manufacturing a lithium secondary battery that can efficiently produce a large capacity, high capacity lithium secondary battery with high safety.

A first feature of the present invention is a lithium secondary battery, comprising: a positive electrode and a negative electrode for reversibly absorbing and releasing lithium ions, a separator separating the positive electrode and the negative electrode, and an organic electrolyte or organic electrolyte containing the lithium ions The membrane is housed in a storage container such as an outer battery container or an outer container, and a plurality of electrode groups formed by forming the positive electrode, the negative electrode, and the separator into a long circular vortex are housed side by side in the storage container such as the outer battery container or the outer container. You are connected.

In this case, the plurality of electrode groups may be connected in parallel, may be connected in series, or may be connected in combination with parallel. In addition, the thickness of each electrode group is preferably 3 mm to 20 mm, respectively, and the capacitance of each electrode group is also preferably 10 Wh to 100 Wh, respectively. In addition, it is preferable to provide an electrically insulating sheet between each electrode group of the plurality of electrode groups so that adjacent electrode groups are spaced apart from the electrically insulating sheet.

In addition, the positive electrode active material is

LiCoO ₂ , LiNiO ₂ , LiCo _a Ni _1-a O ₂ , LiMn _a Ni _1-a O ₂ , LiBaNi _1-a O ₂ , LiAl _a Ni _1-a O ₂ , LiMn ₂ O ₄ , LiMnO ₂ Range of 0.0001≤a≤0.5)

It contains at least one compound selected from the compound represented by, wherein the electrolyte is propylene carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, methyl acetate, ethyl acetate, At least one compound of methyl propionate, ethyl propionate and dimethoxyethane may be used as a solvent, and at least one compound of LiPF ₆ , LiBF ₄ , LiClO ₄ , and LiCF ₃ SO ₃ may be included as an electrolyte.

It is also possible to construct a combined battery using a plurality of lithium secondary batteries configured as described above, and to configure a battery system by connecting the positive and negative electrodes of the assembled battery in parallel or in series, or in combination with parallel and series.

The second aspect of the present invention is an external battery cell or exterior container comprising a positive electrode and a negative electrode for reversibly absorbing, storing and releasing lithium ions, a separator spaced apart from the positive electrode and the negative electrode, and an organic electrolyte or organic electrolyte film containing the lithium ions. Lithium secondary battery stored in a storage container such as

① process of winding the positive electrode, the negative electrode and the separator to form a cylindrical vortex

② Pressing the cylindrical vortex formed by this process on both sides to form a long circular vortex

③ A step of accommodating a plurality of electrode groups consisting of a molded long circular vortex side by side in a storage container such as a battery outer container or an outer container.

④ A step of connecting a plurality of stored electrode groups

⑤ The process of sealing the opening of the storage container such as battery outer container or outer container

⑥ A process of sealing the injection portion after injecting electrolyte into the storage container.

It is to be manufactured through each process.

In this case, the positive electrode or the negative electrode of the plurality of electrode groups is connected in parallel or in series, or a combination of parallel and series, the thickness of each electrode group is in the range of 3 mm to 20 mm and the capacity is in the range of 10 Wh to 100 Wh.

In addition, the plurality of electrode groups placed side by side so as to be spaced apart by the electrically insulating sheet, respectively.

The third aspect of the present invention is to construct a combination battery using a plurality of such lithium secondary batteries, and to connect the positive and negative electrodes of the assembled battery in parallel or in series to provide a high capacity or high voltage with high productivity and high safety. It constitutes a battery system.

Since a lithium secondary battery can obtain a high energy density, it is already used as a driving power source of a portable device, and is also expected to be applied to power systems such as electric vehicles and power storage of midnight electric power. The use of these devices requires a large capacity as compared with the use of portable devices such as mobile phones and laptop personal computers. Therefore, the demand for large lithium batteries having large capacity as single cells is increasing.

However, there is a problem to be overcome in manufacturing or safety to develop a large-size lithium secondary battery by conventional techniques known to date. That is, when a plurality of positive electrode, negative electrode, and separators are laminated alternately, the production process is complicated and the mass productivity is poor. Therefore, it is difficult to realize a large lithium secondary battery by this method. Can be.

On the other hand, when one vortex body which winds up the positive electrode, the negative electrode, and the separator is put into a battery cell, it is excellent in mass productivity. However, when an internal short circuit occurs inside the battery due to an abnormal situation such as crushing of the battery, the charging energy of the entire vortex is dissipated at once, and heat generation, ignition and rupture easily occur, and sufficient safety cannot be obtained. This problem can be avoided by the present invention.

The above and other features will be described in more detail by the following description and drawings.

1 is a perspective view of a part of a lithium secondary battery according to an embodiment of the present invention;

2 is a cross-sectional view taken along the line a-b of the lithium secondary battery shown in FIG. 1;

3 is a diagram showing a step of manufacturing an electrode group of a lithium secondary battery according to the embodiment of the present invention.

EMBODIMENT OF THE INVENTION Below, embodiment of this invention is described with reference to drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The perspective view which cut | disconnected a part of square lithium secondary battery which is one Embodiment of this invention, FIG. 2 is sectional drawing a-b line, and FIG. 3 is a figure which shows the manufacturing process which manufactures one electrode group. In FIG. 2, each electrode group is shown in an annular form for convenience, and in reality, each electrode group is swirled. Table 1 is a table comparing the data of Examples and Comparative Examples of the present invention.

TABLE 1

Electrode group capacity (Wh) Multilayer Electrode Group Electrode group thickness (mm) Presence of Electrical Insulation Sheet Battery shape Battery capacity (Wh) Time to open pressure valve (seconds) Example 1 First mode 10 20 3.0 radish Square 200 76 2nd mode 20 10 4.8 radish Square 62 3rd mode 50 4 10.2 radish Square 58 Example 2 4th mode 80 5 15.6 radish Square 400 45 5th mode 100 4 19.2 radish Square 42 Example 3 6th mode 10 20 3.0 U Square 200 92 7th mode 20 10 4.8 U Square 83 8th mode 50 4 10.2 U Square 70 Comparative Example 1 9th mode 130 3 24.6 radish Square 400 19 Comparative Example 2 10th mode 200 - - radish Cylindrical 200 13

As shown in FIG. 3, the plurality of electrode groups 10 are laminated in the order of the positive electrode 11, the separator 12, the negative electrode 13, and the separator 12, respectively, to a thickness of about 0.5 mm. The sieve is wound into a cylindrical vortex or rhombic vortex of a predetermined diameter and pressed on both sides to form a long circular vortex of 3 mm to 20 mm thick.

As shown in FIG. 2, the plurality of electrode groups 10 are installed side by side in the battery cell 14 serving as a storage container. The thickness of 3 mm-20 mm here shows the magnitude | size of the shorter diameter of the cross section of the elongate circular vortex body which is the electrode group 10. As shown in FIG. The wound end of the electrode group 10 is covered with an electrically insulating tape.

Anode tub 15 is provided at the anode 11 of each electrode group 10, and a cathode tub (not shown) is installed at the cathode 13, and a cathode tub 15 and a cathode tub of each electrode group 10 are provided. Is connected in parallel or in series in the battery cell 14. Tubs connected in parallel or in series are connected to the positive terminal 17 and the negative terminal 18 of the battery cover 16.

In addition, the battery cover 16 is provided with an internal pressure release valve 19 and an electrolyte injection port 20.

Next, the Example of the lithium secondary battery produced concretely according to this invention is described.

(Example 1)

The lithium secondary battery shown in FIG. 1 was produced as follows.

LiCo ₂ as a positive electrode active material, graphite powder as a conductive aid, and polyvinylidene fluoride (PVDF) as a binder are mixed in a ratio of 88%, 7%, and 5% by weight, and N-methyl-2- as a solvent. Pyrrolidone (NMP) was added to prepare a positive electrode mixture. The positive electrode mixture was applied to both surfaces of an Al film having a thickness of 20 µm, dried and evaporated to NMP, followed by roll press molding to prepare a film-shaped positive electrode 11. In addition, a positive electrode 15 was provided as a current collector.

Meanwhile, graphite powder as a negative electrode active material and polyvinylidene fluoride (PVDF) as a binder are blended in a ratio of 90% by weight and 10% by weight, and N-methyl-2-pyrrolidone (NMP) is added thereto as a solvent. The negative electrode mixture was prepared. This negative electrode mixture was applied to both surfaces of a 20 μm-thick Cu foil, dried, and evaporated NMP, followed by roll press molding to prepare a film-shaped negative electrode 13. In addition, a negative electrode tub was provided as a current collector. As the separator 12, a microporous film made of polyethylene was used.

3, the positive electrode 11, the separator 12, the negative electrode 13, and the separator 12 are laminated in the order of 0.5 mm, wound in a cylindrical spiral shape, and pressed by pressing on both sides. The electrode group 10 of an elongate circular vortex was formed.

As shown in Table 1, the electrode group 10 has a first form (electrode group thickness: 3.0 mm, electrode group capacity: 10 Wh), a second form (electrode group thickness: 4.8 mm, electrode group capacity: 20 Wh) and Three types of three types (electrode group thickness: 10.2 mm, electrode group capacity: 50 Wh) were produced, and each electrode group 10 was used in a plurality (laminated side by side) so that the capacity of the unit cell was 200 Wh. Then, the electrode group 10 is placed in a rectangular battery cell 14, and the positive electrode 15 and the negative electrode tube of each electrode group 10 are connected in parallel to connect the positive electrode terminal 17 of the battery cover 16. And the battery cover 16 was installed in the battery cell 14 by welding to the negative electrode terminal 18, respectively.

As the electrolyte solution, a mixed solvent of ethylene carbonate and diethyl carbonate having a volume ratio of 1: 1, and a solution prepared at a concentration of 1 mol / 1 using an electrolyte of LiPF ₆ was used, and the electrolyte solution was injected from the electrolyte injection port 20. Then, the electrolyte injection port 20 was sealed to manufacture a battery.

Using these lithium secondary batteries, the charge and discharge current was set to 10 A, the charge end voltage was set to 4.2 V, and the discharge end voltage was set to 2.8 V, and the battery capacity was confirmed. Thereafter, charging was carried out under the same conditions, and the time until the pressure-release valve 19 was opened by crushing the center of the battery in the charged state was measured.

(Example 2)

2 types of electrodes of the 4th form (electrode group thickness: 15.6 mm, electrode group capacity: 80 Wh) and the 5th form (electrode group thickness: 19.2 mm, electrode group capacity: 100 Wh) similarly to Example 1 The group 10 was produced and laminated | stacked so that the capacity | capacitance of a unit cell might be 400 Wh using several electrode groups 10 each. In addition, the lithium secondary battery of the present invention was produced in the same manner as in Example 1.

Using these lithium secondary batteries, charging and discharging were performed by setting the charge / discharge current to 20A, the charge end voltage to 4.2V, and the discharge end voltage to 2.8V to check the battery capacity. Thereafter, charging was carried out under the same conditions, and the time until the pressure-release valve 19 was opened by crushing the center of the battery in the charged state was measured.

(Example 3)

Example 1 Example 1 (electrode group thickness: 3.0 mm, electrode group capacity: 10 Wh), 2nd form (electrode group thickness: 4.8 mm, electrode group capacity: 20 Wh) and third form (electrode group thickness: 10.2 mm) For each of the three types of electrode group capacity: 50 Wh, the sixth embodiment of the present embodiment (electrode group thickness: 3.0 mm) was interposed between the electrode groups 10 with a polyimide sheet having a thickness of 100 µm, which is an electrically insulating sheet. Electrode group capacity: 10 Wh), seventh type (electrode group thickness: 4.8 mm, electrode group capacity: 20 Wh) and eighth type (electrode group thickness: 10.2 mm, electrode group capacity: 50 Wh) Produced.

Using these lithium secondary batteries, the charge and discharge current was set to 10 A, the charge end voltage was set to 4.2 V, the discharge end voltage was set to 2.8 V, and the battery capacity was confirmed. Thereafter, charging was carried out under the same conditions, and the time until the pressure-release valve 19 was opened by crushing the center of the battery in the charged state was measured.

(Comparative Example 1)

In the same manner as in Example 1, an electrode group 10 of the ninth form (electrode group thickness: 24.6 mm, electrode group capacity: 130 Wh) shown in Table 1 was produced, and stacked (side by side) so that the capacity of the unit cell was 400 Wh. It was. In addition, a lithium secondary battery was produced in the same manner as in Example 1.

Using these lithium secondary batteries, charge and discharge currents were set to 20 A, the charge end voltage was set to 4.2 V, and the discharge end voltage was set to 2.8 V. Then, the battery capacity was confirmed. Thereafter, charging was carried out under the same conditions, and the time until the pressure-release valve 19 was opened by crushing the center of the battery in the charged state was measured.

(Comparative Example 2)

As shown in the tenth embodiment of Table 1, the positive electrode 11 and the negative electrode 13 were fabricated in the same manner as in the first embodiment, and the positive electrode 11, the separator 12, the negative electrode 13, and the separator 12 were in order. The laminate was wound up into a cylindrical vortex rather than a long circle to form one electrode group having a capacity of 200 Wh. This one electrode group was put into a cylindrical battery cell to produce a cylindrical battery.

Using these lithium secondary batteries, the charge and discharge current was set to 10 A, the charge end voltage was set to 4.2 V, the discharge end voltage was set to 2.8 V, and the battery capacity was confirmed. Thereafter, charging was carried out under the same conditions, and the time until the pressure-release valve 19 was opened by crushing the center of the battery in the charged state was measured.

Next, the comparative result which specifically charged and discharged the lithium secondary battery of the Example and comparative example produced in this way is demonstrated with reference to Table 1. FIG.

First, in the case of Examples 1 and 2 of the present invention (the first to the fifth aspects), the time from the start of crushing until the pressure relief valve 19 is opened is in the range of 42 to 76 seconds. In comparison with the above, in the case of the comparative example 1 (ninth aspect) and the comparative example 2 (tenth aspect), the time until the pressure-release valve 19 is opened is short as 13 seconds and 19 seconds, respectively. Therefore, in the lithium secondary battery according to the present invention, since the heat generated by the crushing is less than that of the lithium secondary battery of the comparative example, it can be considered that the increase in the battery internal pressure was gentle.

In addition, in each of the first to third aspects of Example 1, the lithium secondary battery of the sixth to eighth aspects of Example 3 of the present invention, wherein a polyimide sheet is interposed between the electrode groups 10. It can be seen that the time until the pressure-resistant release valve 19 is opened is longer than that of Example 1, which further improves safety.

As described above, in the lithium secondary battery according to the present embodiment, a plurality of electrode groups formed by stacking a sheet-like or film-shaped positive electrode, a negative electrode, and a separator and forming a long circular vortex are stored side by side in an inner battery container or an outer container. By connecting in parallel or in series, it is possible to manufacture a rectangular lithium battery having a high energy density.

In the conventional organic electrolyte of the lithium secondary battery, it is necessary to make the electrode into a sheet shape having a thickness of about 200 μm and increase its area in order to reduce the electrical conductivity and reduce the resistance inside the battery. In the case of manufacturing a large-sized battery according to the present invention, there is a problem in production because the electrode has insufficient strength and poor handling properties.

On the other hand, an electrode group formed of an elongated circular vortex like the lithium secondary battery according to the present embodiment has sufficient strength as compared with a sheet-shaped electrode having a thickness of about 200 µm, and thus has excellent handling properties and easy assembly of a battery. In addition, this rectangular battery is particularly preferable for an electric vehicle or an electric power storage power supply system because it is possible to reduce the space which becomes unnecessary in volume compared to a cylindrical battery when a plurality of batteries are arranged to form a combination battery. .

In the lithium secondary battery according to the present embodiment, since the positive electrode and the negative electrode are not composed of one electrode sheet in one battery cell, the positive electrode and the negative electrode are divided into a plurality of electrode groups. It does not happen very well and increases safety. That is, in the event of heat generation in an accident, the positive electrode and the negative electrode are composed of one electrode sheet. However, the positive electrode and the negative electrode are divided into a plurality of electrode groups as in the present embodiment. When abnormality such as an internal short circuit or the like occurs, only one electrode group is related to heat generation, so energy dissipated at one time is suppressed.

In addition, it is preferable that each electrode group of the lithium battery of the present embodiment has a thickness of 3 mm or more because the strength is increased to increase the handling in manufacturing. When the thickness of each electrode group is smaller than 3 mm, the handling strength is insufficient because the strength is small and easily bent. On the other hand, when the thickness of each electrode group is larger than 20 mm, useless space increases in circular portions at both ends of the electrode group inside the battery cell, so that the thickness of each electrode group is preferably 20 mm or less. Therefore, the thickness of each electrode group is set in the range of 3 mm to 20 mm.

In order to suppress the amount of heat generated in the event of an accident, the upper limit of the capacity of each electrode group is preferably 100 Wh, and the lower limit of the capacity of each electrode group is preferably 10 Wh from the viewpoint of battery manufacturing and use in order to realize a large capacity battery. .

In the method of connecting a plurality of electrode groups, the positive electrode or the negative electrode can be connected in either parallel or in series, so that a lithium secondary battery having a different capacity or voltage can be easily configured. As can be seen from Example 3, the stacking of a plurality of electrode groups (side-by-side) can protect each electrode group when the battery is crushed by interposing electrically insulating sheets between the electrode groups. As an electrically insulating sheet, an organic resin sheet is preferable and a polypropylene, polyethylene, a polyimide, polytetrafluoroethylene, etc. are mentioned.

As the positive electrode active material, chemical formulas are LiCoO ₂ , LiNiO ₂ , LiCo _a Ni _1-a O ₂ , LiMn _a Ni _1-a O ₂ , LiBaNi _1-a O ₂ , LiAl _a Ni _1-a O ₂ , LiMn ₂ O ₄ , which contains at least one compound selected from the compounds represented by LiMnO ₂ (in the range of 0.0001 ≦ a ≦ 0.5), and contains a carbon material such as graphite and coke as the negative electrode active material. It is suitable for lithium secondary battery with excellent and high energy density.

As the electrolyte solution, at least one or more compounds of propylene carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate and dimethoxyethane are used. It is preferable to use as a solvent and to contain at least one or more types of compounds of LiPF ₆ , LiBF ₄ , LiClO ₄ , and LiCF ₃ SO ₃ as an electrolyte because of high electrical conductivity of the electrolyte solution.

In addition, by using the lithium secondary battery of the present invention in a combination battery composed of a plurality of batteries, a highly stable power supply system can be configured. In addition, since such a power supply system can prevent accidents caused by misuse or malfunction of the device, the power supply system is optimized for use in electric vehicles or power storage devices as well as portable devices. This battery system is constituted by, for example, constructing a combined battery using a plurality of batteries of the embodiment, and connecting the positive and negative electrodes of the assembled battery in parallel or in series, or in combination with parallel and series.

According to the present invention, a plurality of electrode groups formed by forming a stack of sheet- or film-shaped anodes, cathodes, and separators into long circular swirls are housed side by side in a storage container and connected therein to form a lithium secondary battery. Since the battery group is independent in the storage container, a large lithium secondary battery and battery system with high productivity and high safety can be realized.

In addition, the sheet- or film-shaped positive electrode, negative electrode, and separator are stacked and pressed from the side to form a long circular vortex, and then a plurality of electrode groups are stored side by side in the same storage container and connected. Large lithium secondary batteries can be produced.

Claims (10)

A positive electrode and a negative electrode reversibly absorbing and releasing lithium ions, a separator spaced apart from the positive electrode and the negative electrode, a storage container accommodating the organic electrolyte solution or the organic electrolytic film containing the lithium ions therein, And a plurality of electrode groups formed by forming the positive electrode, the negative electrode, and the separator into a long circular vortex, are housed in a plurality of side by side in the storage container and are connected in plurality in the storage container. The lithium secondary battery according to claim 1, wherein the plurality of connections are performed in parallel or in series, or a combination of parallel and series. The lithium secondary battery according to claim 1, wherein the electrode group is formed to have a thickness of 3 mm to 20 mm, respectively. The lithium secondary battery according to claim 1, wherein the electrode group has a capacity of 10 Wh to 100 Wh, respectively. The lithium secondary battery according to claim 1, wherein an electrically insulating sheet is provided between the plurality of electrode groups, and adjacent electrode groups are spaced apart from the electrically insulating sheet. The method of claim 1, wherein the positive electrode active material is LiCoO ₂ , LiNiO ₂ , LiCo _a Ni _1-a O ₂ , LiMn _a Ni _1-a O ₂ , LiBaNi _1-a O ₂ , LiAl _a Ni _1-a O ₂ , LiMn ₂ O ₄ , LiMnO ₂ A lithium secondary battery containing at least one compound selected from the group represented by 0.0001 ≦ a ≦ 0.5). The method of claim 1, wherein the electrolyte is propylene carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, dimethoxyethane A lithium secondary battery comprising at least one compound of at least one as a solvent and at least one compound of LiPF ₆ , LiBF ₄ , LiClO ₄ , and LiCF ₃ SO ₃ as an electrolyte. A combination battery is constructed using a plurality of lithium secondary batteries according to any one of claims 1 to 7, and the positive and negative electrodes of the combination battery are connected in parallel, in series, or in combination with parallel and in series. Battery system. In the method of manufacturing a lithium secondary battery in which a positive electrode and a negative electrode that reversibly absorbs and releases lithium ions, a separator spaced apart from the positive electrode and the negative electrode, an organic electrolyte solution containing the lithium ions or an organic electrolyte film is housed in a storage container, Winding the positive electrode, the negative electrode and the separator to form a cylindrical vortex; This cylindrical vortex is shaped into a long circular vortex, A plurality of electrode groups consisting of a molded long circular vortex is stored side by side in the storage container, Each electrode of this electrode group is connected in parallel or in series, or in combination with parallel, in series, Sealing the opening of the storage container and injecting an electrolyte solution through an injection part into the storage container, and then sealing the injection part to manufacture a lithium secondary battery. The method of claim 9, wherein the elongated circular vortex is formed to a thickness of 3mm to 20mm.