JP2003243037A - Lithium ion battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium ion battery having a very high safety despite its high capacity and high output. <P>SOLUTION: The lithium ion battery 20 has a bunch 6' of electrode windings such that a positive electrode plate and a negative electrode plate are wound centering on a core 11 with a polyethylene separator S1 interposed, in which the periphery of the electrode bunch 6' is enwrapped with the separator S1 more than one turn. On the periphery thereof a second electrode couple 25 is provided approximately half one turn, of such a structure that an aluminum foil 21 and a copper foil 22 are arranged with a separator S2 having a lower melting point than the separator S1 interposed, and further one turn or more the separator S1 is wound round. The aluminum foil 21 and copper foil 22 are connected electrically with the positive and negative electrode plates, respectively. When the battery temperature rises, the separator S2 melts to cause the two sorts of foils 21 and 22 to be shortcircuited. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium ion battery, and more particularly, to a positive electrode using a lithium transition metal complex oxide capable of inserting and extracting lithium ions as a positive electrode active material by charging and discharging, and a lithium ion as a result of charging and discharging. The present invention relates to a lithium-ion battery in which a negative electrode capable of discharging and occluding hydrogen and a group of electrodes facing each other through a separator are soaked in an electrolytic solution and housed in a battery container.

[0002]

2. Description of the Related Art Lithium-ion secondary batteries are mainly used as power sources for portable equipment such as VTR cameras, notebook computers, and mobile phones, taking advantage of their high energy density. The internal structure of this lithium ion secondary battery is usually of the wound type as shown below. Both the positive electrode and the negative electrode have a strip shape in which the active material is applied to the metal foil, and the cross section is spirally wound to form a winding group so that the positive electrode and the negative electrode do not come into direct contact with each other with the separator interposed therebetween. . Then, the winding group is housed in a cylindrical can that serves as a battery container, filled with the electrolyte, and then sealed.

The dimensions of a general cylindrical lithium ion secondary battery are 18 mm in diameter and 65 mm in height.
It is called 650 type and is widely used as a small-sized consumer lithium-ion secondary battery. 18650 type lithium ion 2
Lithium cobalt oxide, which is characterized by high capacity and long life, is mainly used for the positive electrode active material of the secondary battery. The battery capacity is about 1.3 Ah to 1.7 Ah, and the output is about 10 W.

On the other hand, in the automobile industry, in order to deal with environmental problems, an electric vehicle without exhaust gas and a battery whose power source is completely a battery, or a hybrid engine using both an internal combustion engine and a battery ( The development of electric vehicles has accelerated, and some of them are in the stage of practical application. Naturally, a battery that serves as a power source for an electric vehicle is required to have characteristics such that high output and high energy can be obtained, and a lithium ion battery is drawing attention as a battery that meets this requirement. In order to satisfy such required characteristics, for example, in Japanese Patent No. 2701347, the thickness of the positive electrode active material layer using the lithium composite oxide and the thickness of the negative electrode active material layer using the carbonaceous material are set within a predetermined range. By doing so, a technique for obtaining a non-aqueous electrolyte secondary battery having a high energy density is disclosed.

[0005]

However, in the case of a lithium-ion battery, the higher the output, the lower the safety tends to be. Particularly, the lithium-ion battery having a high capacity and a high output, such as used for a power source for electric vehicles, is used. In a battery, safety is not always ensured within the range described in Japanese Patent No. 2701347 mentioned above. In the case of an electric vehicle that carries passengers, overcharging when the charging control system fails, a battery crash that may occur in the event of an accidental collision, a foreign object stab, or an external short circuit Ensuring the safety of the battery itself, such as when it is time, is a minimum and very important battery characteristic. Battery safety here means that the behavior of the battery when it is exposed to abnormal conditions does not cause any physical damage to people, but it also minimizes damage to the vehicle. Means that.

Further, a high capacity, high output lithium ion battery is charged with a large current and discharged with a large current, so that the internal pressure of the battery rises at the time of an abnormality, which is generally adopted in a 18650 type lithium ion battery. It is virtually impossible to provide a corresponding current interruption mechanism (a type of disconnect switch) in the battery structure.

In view of the above problems, it is an object of the present invention to provide a lithium ion battery which has a high capacity and a high output, but is extremely safe.

[0008]

In order to solve the above problems, the first aspect of the present invention uses a lithium transition metal composite oxide capable of inserting and extracting lithium ions by charging and discharging as a positive electrode active material. In a lithium ion battery in which a positive electrode and a negative electrode capable of releasing and occluding lithium ions by charging and discharging are soaked in an electrolyte solution and housed in a battery container, a second melting point lower than the separator is used. And a second electrode pair that is electrically connected to the positive electrode and the negative electrode via the separator and does not absorb and desorb lithium ions.

In this embodiment, a positive electrode using a lithium transition metal composite oxide capable of absorbing and desorbing lithium ions by charging and discharging as a positive electrode active material and a negative electrode capable of desorbing and storing lithium ions by charging and discharging form a separator. The high output and high capacity of the lithium ion battery are ensured by immersing the intervening electrode group in the electrolytic solution and housing it in the battery container. During normal charging / discharging, the second electrode pair is insulated by the second separator, and when the battery is abnormal, the temperature of the battery rises due to the chemical reaction between the electrolytic solution and the active material. Since the low second separator melts quickly and the second electrode pair is short-circuited to prevent the flow of current between the positive and negative electrodes, the chemical reaction between the electrolytic solution and the active material is not promoted, so that the safety of the lithium ion battery is improved. It is possible to secure the sex.

In order to solve the above-mentioned problems, the second aspect of the present invention is to charge a positive electrode using a positive electrode using a lithium transition metal complex oxide capable of inserting and extracting lithium ions by charging and discharging. In a lithium-ion battery in which a negative electrode capable of discharging and occluding lithium ions by discharge is soaked in an electrolyte through an electrode group via a separator and housed in a battery container, a second electrode pair that does not occlude and discharge lithium ions is used. The electrode pair is electrically connected to the positive electrode and the negative electrode via a second separator having a thermal contraction rate that is greater than the thermal contraction rate of the separator and short-circuits the electrode pair when the battery is abnormal. Is characterized by.

In the present aspect, the second electrode pair that does not occlude / desorb lithium ions has a heat contraction rate that is greater than the heat contraction rate of the separator of the electrode group and short-circuits the second electrode pair when the battery is abnormal. Since the positive electrode and the negative electrode are electrically connected via the separator, the second electrode pair is normally insulated by the second separator during charging / discharging, and when the battery is abnormal, the electrolytic solution and the active material are separated from each other. As the battery temperature rises due to the chemical reaction, the second separator having a higher heat shrinkage rate than the separator of the electrode group thermally contracts, and the second electrode pair is short-circuited to prevent the current flow between the positive and negative electrodes. . Therefore, the same effect as that of the above-described first aspect can be obtained.

In the above first and second aspects,
The electrode group is a wound electrode group having a conductive shaft core in the center,
If the shaft core is one of the electrodes of the second electrode pair,
Since the axis serves also as one of the electrodes of the second electrode pair, the volume occupied by the second electrode pair is reduced and the energy density can be increased. Further, by using at least one electrode of the second electrode pair as a metal foil, the volume occupied by the second electrode pair can be reduced.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) A first embodiment in which the present invention is applied to a cylindrical lithium ion battery used for an electric vehicle will be described below with reference to the drawings.

(Preparation of Positive Electrode Plate) 10 parts by weight of scaly graphite (average particle size 20 μm) as a conductive agent was combined with 100 parts by weight of lithium manganate (chemical formula LiMn ₂ O ₄ ) powder as a positive electrode active material. As a binder, 10 parts by weight of polyvinylidene fluoride was mixed, to which N-methyl-2-pyrrolidone as a dispersion solvent was added, and the kneaded positive electrode mixture (slurry) was applied on both sides of an aluminum foil having a thickness of 20 μm. At this time, the width of the positive electrode plate is 50 m at one side edge in the longitudinal direction.
The uncoated part of m was left. Then, it was dried, pressed and cut to obtain a positive electrode plate having a width of 300 mm, a predetermined length, and a predetermined thickness of the positive electrode mixture application portion. The bulk density of the positive electrode material mixture layer is 2.65 g / cm.
^{It was set to 3} . A notch was made in the uncoated portion, and the remaining notch was used as a lead piece. Adjacent lead pieces were spaced at 20 mm, and the width of the lead pieces was 10 mm.

(Preparation of Negative Electrode Plate) 8 parts by weight of polyvinylidene fluoride as a binder was added to 92 parts by weight of an amorphous carbon powder (trade name; Carbotron P, manufactured by Kureha Chemical Industry Co., Ltd.) as an anode active material. Then, N-methyl-21-pyrrolidone as a dispersion solvent was added thereto, and the negative electrode mixture (slurry) kneaded and kneaded was applied to both surfaces of a rolled copper foil having a thickness of 10 μm. At this time, an uncoated portion having a width of 50 mm was left on one side edge in the lengthwise direction of the negative electrode plate. Then, it was dried, pressed and cut to obtain a negative electrode plate having a width of 305 mm, a predetermined length, and a predetermined thickness of the negative electrode mixture application portion. The bulk density of the negative electrode mixture layer was 1.0 g / cm ³ . A notch was made in the uncoated portion similarly to the positive electrode plate, and the remaining notch was used as a lead piece. Adjacent lead pieces are 20 mm apart,
The width of the lead piece was 10 mm.

(Production of the Second Electrode Pair) An aluminum foil having a thickness of 20 μm is cut into a width of 300 mm and a length of 100 mm, and a notch is formed on one side edge in the length direction of the aluminum foil to obtain a width of 10 mm. , 20 pieces of 50 mm long lead pieces
It was formed at mm intervals. On the other hand, a copper foil with a thickness of 10 μm is cut into a width of 300 mm and a length of 100 mm, and a notch is formed on one side edge in the length direction of the copper foil to provide a width of 10 mm and a length of 50 mm.
mm lead pieces were formed at 20 mm intervals. Figure 2 (A)
As shown in, the aluminum foil 2 on which the lead pieces are formed
1 and the copper foil 22 were arranged via a polyethylene film separator S2 as a second separator having a thickness of 15 μm, and a second electrode pair 25 was produced. As the separator S2, a separator having a melting temperature lower than that of the separator S1 used for the electrode winding group 6'described later was used. In order to adjust the melting temperatures of the separator S2 and the separator S1, a material having a lower melting point than that of the separator S1 may be selected as the material of the separator S2.
It is also possible to use 1 and S2 as materials having the same melting point (the same material) so that the thickness of the separator S2 is smaller than that of the separator S1 (for example, 1/2 or less).

(Preparation of Winding Group) As shown in FIG. 1, the positive electrode plate P and the negative electrode plate N are arranged so that the positive electrode plate P and the negative electrode plate N do not come into direct contact with each other around the polyethylene shaft core 11. An electrode winding group 6 ′ was prepared by winding two sheets of polyethylene separator S1 having a thickness of 40 μm and a length of 150 mm. The winding start end of the separator S1 was heat-welded to the shaft core 11. At this time, the separator S1 is wound one or more times around the outer circumference of the electrode winding group 6 ′, and the electrode winding is performed from the positive electrode plate P and the negative electrode plate N wound around the electrode winding group 6 ′. Lead pieces 9 are led out to the opposite sides of the group 6 '.

As shown in FIGS. 2 (A) and 2 (B), the second electrode pair 25 is provided on the outer circumference of the electrode winding group 6'in which the separator S1 is wound one or more times over about half a circumference. The wound group 6 was wound, and further, the separator S1 was wound once or more to form a wound group 6. The winding end of the separator S1 was bonded to the separator S1 with a single-sided tape. Therefore, the winding group 6 has a configuration in which the second electrode pair 25 is inserted and wound between the two-layer separator S1 that is the outer periphery of the electrode winding group 6 ′. Second
The electrode pair 25 was attached to the separator S1 with double-sided tape. Aluminum foil 21 and copper foil 2 of the second electrode pair 25
The lead pieces led out from No. 2 were located on the opposite sides of the winding group 6 in the same manner as the lead pieces 9 led out from both electrodes of the electrode winding group 6 ′. The diameter of the winding group 6 was set to 65 ± 0.1 mm by adjusting the lengths of the positive electrode plate P, the negative electrode plate N, and the separator S1.

(Production of Battery) The lead pieces 9 led out from the positive electrode plate P and the lead pieces led out from the aluminum foil 21 are all deformed (hereinafter referred to as all lead pieces).
Are gathered in the vicinity of the peripheral surface of the collar portion 7 that integrally projects from the periphery of the pole column (positive electrode external terminal 1) that is almost on the extension line of the shaft core 11,
After the contact, all the lead pieces and the peripheral surface of the collar portion 7 were ultrasonically welded to connect and fix all the lead pieces to the peripheral surface of the collar portion 7. As a result, the positive electrode plate P and the aluminum foil 21 are electrically connected.

Negative electrode external terminal 1 ', negative electrode plate N and copper foil 2
The connection with the lead piece derived from No. 2 was performed in the same manner as the positive electrode. As a result, the negative electrode plate N and the copper foil 22 are electrically connected.

After that, an insulating coating 8 was applied to the entire circumference of the flange 7 of the positive electrode external terminal 1 and the negative electrode external terminal 1 '. The insulating coating 8 also applied to the entire outer peripheral surface of the winding group 6. As the insulating coating 8, an adhesive tape was used in which the base material was polyimide, and one surface of which was coated with an adhesive made of hexamethacrylate. This adhesive tape was wound in multiple layers from the peripheral surface of the collar portion 7 to the outer peripheral surface of the winding group 6 to form the insulating coating 8. The number of windings is adjusted so that the maximum diameter portion of the winding group 6 becomes the insulating coating 8 existing portion, and the maximum diameter is set to be slightly smaller than the inner diameter of the battery container 5 made of stainless steel so that the winding group 6 is changed to the battery container 5 Inserted inside. The battery container 5 used had an outer diameter of 67 mm and an inner diameter of 66 mm.

Next, the second ceramic washer 3 '
(Alumina, thickness of the part that contacts the back surface of the battery lid 4 is 2 m
m, inner diameter 16 mm, and outer diameter 25 mm) were respectively fitted into the pole columns whose tip constitutes the positive electrode external terminal 1 and whose tip constitutes the negative electrode external terminal 1 '. Also, the first ceramic washer 3 is placed on the battery lid 4, and the positive electrode external terminal 1 and the negative electrode external terminal 1 ′ are respectively placed in the first ceramic washer 3
Passed through. Thereafter, the peripheral end surface of the disk-shaped battery lid 4 was fitted into the opening of the battery container 5, and the entire contact portions of both were laser-welded. At this time, the positive electrode external terminal 1 and the negative electrode external terminal 1 ′ penetrate the hole in the center of the battery lid 4 and project to the outside of the battery lid 4. And a flat first ceramic washer 3 (made of alumina, thickness 2 mm, inner diameter 16 mm, outer diameter 28 mm),
A metal washer 14 that was smoother than the bottom surface of the nut 2 was fitted into the positive electrode external terminal 1 and the negative electrode external terminal 1 ′ in this order. The battery lid 4 is provided with a cleaving valve 10 that cleaves in response to an increase in the internal pressure of the battery. The cleavage pressure of the cleavage valve 10 is
It was set to 1.3 to 1.8 MPa.

Next, a metal nut 2 is screwed to each of the positive electrode external terminal 1 and the negative electrode external terminal 1 ', and the battery is inserted through the second ceramic washer 3', the first ceramic washer 3 and the metal washer 14. The lid 4 was fixed between the collar portion 7 and the nut 2 by tightening. The tightening torque value at this time was 686 N · cm. The metal washer 14 did not rotate until the tightening work was completed. In this state, the power generation element inside the battery container 5 is shielded from the outside air by the compression of the rubber (EPDM) O-ring 16 interposed between the back surface of the battery lid 4 and the collar portion 7.

After that, a predetermined amount of electrolytic solution was injected into the battery container 5 from the liquid injection port 13 formed in the battery lid 4, and the liquid injection port 13 was sealed to complete the cylindrical lithium ion battery 20. The electrolytic solution was prepared by mixing lithium hexafluorophosphate (L) into a mixed solvent of ethylene carbonate, dimethyl carbonate and diethyl carbonate at a volume ratio of 1: 1: 1.
iPF ₆ ) was used at a concentration of 1 mol / liter.
Further, the cylindrical lithium-ion battery 20 does not have a current interruption mechanism that operates in response to an increase in battery internal pressure.

Next, the operation of the cylindrical lithium ion battery 20 of this embodiment will be described. The battery 20 is provided with an electrode winding group 6 ′ in which a positive electrode plate P using lithium manganate as a positive electrode active material and a negative electrode plate N using amorphous carbon as a negative electrode active material are wound, and has a designed capacity. Is about 70 to 90 Ah,
It has battery characteristics with a design output of about 3500 to 4500W. Further, the battery 20 has a separator S2 having a lower melting temperature than the separator S1 between the aluminum foil 21 and the copper foil 22. Therefore, during normal charge / discharge of the battery 20, the aluminum foil 21 and the copper foil 22 that form the second electrode pair 25 that does not store or release lithium ions.
The spaces are insulated by the separator S2. When the battery 20 reaches an abnormal battery state such as overcharge, the temperature inside the battery 20 rises due to the chemical reaction between the electrolytic solution and the active material, and the battery container 5
Gas is generated inside and the internal pressure of the battery rises. As the battery temperature rises, the chemical reaction between the electrolytic solution and the active material is further promoted, causing a rapid temperature rise (thermal runaway), which causes the electrolytic solution to decompose and generate a large amount of gas rapidly. Therefore, the internal pressure of the battery also rises sharply. When the temperature rises,
In the battery 20, since the separator S2 melts faster than the separator S1, the aluminum foil 21 and the copper foil 22 are short-circuited, a current flows between the second electrode pair 25, and a current between the positive electrode plate P and the negative electrode plate N. Is blocked. Therefore, the electric power continuously supplied from the outside does not further promote the chemical reaction between the electrolytic solution and the active material due to the short circuit of the second electrode pair 25. Further, when the battery internal pressure reaches the above-mentioned set pressure,
The cleaving valve 10 cleaves and the internal pressure is released to the outside. Therefore, the cylindrical lithium-ion battery 20 is
Since the thermal runaway state ends and the battery function is gently lost, safety can be ensured.

Further, in the battery 20, the aluminum foil 21, the separator S2, and the copper foil 2 which form the second electrode pair 25.
The thicknesses of 2 are 20 μm, 15 μm, and 10 μm, respectively.
And the thickness of the second electrode pair 25 is 45 μm. Therefore, even if the second electrode pair 25 is inserted into the separator S1, the volume occupied by the second electrode pair 25 in the battery container 5 is small, so that the battery 20 can secure a high energy density. In other words, since the positive electrode plate P and the negative electrode plate N are not reduced in volume, they have high capacity and high output,
It is possible to ensure safety.

(Second Embodiment) Next, a second embodiment in which the present invention is applied to a cylindrical lithium ion battery will be described. In this embodiment, a separator having a larger heat shrinkage ratio than the separator S1 is used as the second separator. In the following embodiments, the same members as those in the first embodiment are designated by the same reference numerals, the description thereof will be omitted, and only different portions will be described.

In the cylindrical lithium ion battery of the present embodiment, as the separator S2, instead of the separator S2 having a low melting temperature of the first embodiment, the thickness of 15 μm is 120 °.
A polyethylene separator having a heat shrinkage rate in C of 50% is used. This separator has a larger heat shrinkage ratio than the separator S1 of the electrode winding group 6'and heat shrinks so as to short-circuit the second electrode pair when the battery is abnormal.

During normal charging and discharging, the second electrode pair 25 is insulated by a separator having a heat shrinkage rate of 50%. When the battery temperature and the battery internal pressure rapidly increase due to a chemical reaction between the electrolytic solution and the active material when the battery is abnormal, the separator having a heat shrinkage ratio of 50% thermally shrinks, and the aluminum foil 21 and the copper foil 22 are
Short circuit and. Therefore, the battery according to the present embodiment can ensure safety as in the battery 20 according to the first embodiment.

(Third Embodiment) Next, a third embodiment in which the present invention is applied to a cylindrical lithium ion battery will be described. In this embodiment, the winding group 6 is manufactured by using the metal shaft core 11.

As shown in FIG. 3, the cylindrical lithium ion battery 20 'of the present embodiment uses a metal shaft core 11 instead of the polyethylene shaft core 11 of the first embodiment. In the present embodiment, a thickness of 10 μm in which both surfaces are previously covered with a separator S2 having a melting temperature lower than that of the separator S1.
Copper foil 22 (hereinafter referred to as an insulated negative electrode) is prepared. The winding start ends of the two separators S1 are adhered to the outer periphery of the shaft core 11 with a single-sided tape, the insulated negative electrode is adhered to the shaft core 11 with a double-sided tape, and then the separator S1 inserts the insulated negative electrode. It is wound one or more times in a state. After that, the positive electrode plate P having a predetermined length is inserted through the two separators S1.
The positive electrode plate P, the negative electrode plate N, and the separator S1 are wound so that the positive electrode plate P, the negative electrode plate N, and the negative electrode plate N are not in contact with each other, and the winding group 6 is formed. A separator S1 is provided on the outermost circumference of the winding group 6.
Is wound one or more times, and the winding end end of the separator S1 is fixed to the outermost surface of the winding group 6 with a tape. An insulating member (not shown) is interposed between the pole of the negative electrode external terminal 1 ′ inserted in the shaft core 11 and the positive and negative electrodes to prevent a short circuit.

The cylindrical lithium-ion battery 2 of this embodiment
In 0 ′, the shaft core 11 also serves as the positive electrode of the second electrode pair 25, and the copper foil 22 is used for the negative electrode of the second electrode pair 25. Therefore, in the battery container 5, the second electrode pair 25
Since the volume occupied by the battery is small, the battery 20 'can secure a high energy density.

Although a large-sized secondary battery used as a power source for an electric vehicle or the like has been illustrated in the above embodiment, the present invention is not limited to the size and capacity of the battery. Further, it is also applicable to a cylindrical battery having a structure in which a battery upper lid is closed by caulking in a bottomed cylindrical container (can). In particular, a battery used as a power source for an electric vehicle is required to have relatively high capacity and high output characteristics, and thus the application of the present invention is preferable. Further, the battery shape is not limited to the cylindrical shape exemplified in the above embodiment, and may be a square shape or a polygonal shape.

In the above embodiment, the second electrode pair 2
Although the example in which the copper foil 22 is used as the negative electrode of No. 5 is shown, the second electrode pair 25 may be made of a conductive material in an insulated state. Other metal foils such as nickel foil may be used.

Further, in the first and second embodiments, an example in which the second electrode pair 25 is inserted around the outer circumference of the electrode winding group 6'after winding the positive electrode plate P and the negative electrode plate N has been shown. However, the present invention is not limited to the insertion (arrangement) position of the second electrode pair 25. For example, as shown in the third embodiment,
It may be located in the immediate vicinity of the axis 11. Axis 11
In the vicinity of, the temperature becomes higher than the outer peripheral portion of the winding group 6 when the battery is abnormal, and the second electrode pair 25 is short-circuited in a short time compared to the case where the second electrode pair 25 is arranged on the outer peripheral portion of the winding group 6. Can be made (heat sensitivity can be improved). Furthermore, in the first and second embodiments, the winding type winding group 6 is illustrated, but the present invention is also applicable to a laminated winding group.

In the first embodiment, the separator S2 is a polyethylene separator having a thickness of 15 μm. However, it does not affect the battery operation and melts at a temperature lower than the melting temperature of the separator S1 when the battery malfunctions. The material may be, for example, polypropylene or the like. Further, in the second embodiment, the separator S
2 illustrates a polyethylene separator having a heat shrinkage rate of 50% at 120 ° C., the present invention is not limited to this, and may be any one described in the above claims.

Further, in the third embodiment, the example in which the shaft core 11 is the positive electrode has been shown, but the shaft core 11 may be the negative electrode and the aluminum foil may be wound via the separator S2. In this case, an insulating member may be interposed between the positive pole external terminal 1 and the pole column inserted in the shaft core 11. However, the positive electrode external terminal 1 inserted in the shaft core 11
You may make it the insulating resin the part of the pole.

Furthermore, in the above embodiment, an example using lithium manganate as the positive electrode active material and amorphous carbon as the negative electrode active material has been shown. However, as the positive electrode active material, lithium ions are used by charging and discharging the battery. Any lithium transition metal complex oxide that can store and release can be used.
You may use cobalt complex oxide, lithium nickel complex oxide, etc. Further, the negative electrode active material may be any material capable of inserting and extracting lithium ions by charging and discharging the battery, for example, natural graphite, various artificial graphite materials, carbonaceous materials such as coke, etc., Also in the particle shape, a scaly shape, a spherical shape, a fibrous shape, a lump shape or the like may be used.

Furthermore, in the above embodiment, the insulating coating 8
In the above, an example using a pressure-sensitive adhesive tape in which the base material is polyimide and one surface of which is coated with a pressure-sensitive adhesive made of hexamethacrylate is shown, but the present invention is not limited to this. For example, an adhesive tape whose base material is a polyolefin such as polypropylene or polyethylene and one or both surfaces of which is coated with an acrylic adhesive such as hexamethacrylate or butyl acrylate, or a tape made of a polyolefin or polyimide without an adhesive is also available. It can be used preferably.

In the above embodiment, 1 part of lithium hexafluorophosphate is added to polyvinylidene fluoride as a binder and a mixed solvent of ethylene carbonate, dimethyl carbonate and diethyl carbonate at a volume ratio of 1: 1: 1 as an electrolytic solution. Although the one dissolved in mol / liter is exemplified, the method for producing the lithium ion battery of the present invention is not particularly limited,
Any of the commonly used ones can be used. As the binder that can be used in other embodiments,
For example, polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene / butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethyl cellulose, various latexes, acrylonitrile, vinyl fluoride, vinylidene fluoride, fluorine Examples thereof include polymers such as propylene oxide and chloroprene fluoride, and mixtures thereof.

Further, as an electrolytic solution which can be used in the embodiments other than the above-mentioned embodiment, an electrolytic solution in which a general lithium salt is used as an electrolyte and this is dissolved in an organic solvent can be used. The lithium salt or the organic solvent used can be used. Is not particularly limited. For example, as the electrolyte, LiClO ₄ , LiAs
F ₆ , LiPF ₆ , LiBF ₄ , LiB (C
_{6 H 5) 4, CH 3} SO 3 Li, CF 3 SO 3 Li and the like and mixtures thereof. Further, as the organic solvent, propylene carbonate, ethylene carbonate,
1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3
-Dioxolane, 4-methyl-1,3-dioxolane,
Examples thereof include diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile and the like, or a mixed solvent of two or more kinds of these, and the mixing ratio is not limited.

[0042]

EXAMPLE Next, the winding group 6 according to the first embodiment described above.
An example of the cylindrical lithium-ion battery 20 manufactured by changing the position of the second electrode pair 25 will be described. The battery of the comparative example prepared for comparison is also shown.

(Example 1) In Example 1, the second electrode pair 25 was inserted between the separators S1 after the separator S1 was wound around the shaft core 11 by 30 mm. In the cylindrical lithium-ion battery 20 of Example 1, the second electrode pair 25 is inserted near the shaft core 11.

(Example 2) In Example 2, the second electrode pair 25 was inserted between the separators S1 on the outer periphery of the electrode winding group 6 '.

Comparative Example 1 In Comparative Example 1, a cylindrical lithium ion battery was manufactured in the same manner as in Example 1 except that the second electrode pair was not attached.

(Measurement / Test) Next, the following measurements and tests were performed on the batteries of Examples and Comparative Examples thus completed.

The battery was charged at room temperature and then discharged to measure the discharge capacity. Charging condition is 4.2V constant voltage, limiting current 80
A, 3.5 hours. The discharge conditions were a constant current of 20 A and a final voltage of 2.5V. Then, a continuous charge test was performed at a constant current of 80 A at room temperature to observe the battery behavior. During continuous charging, the phenomenon of gas release occurs after the cleaving valve 10 of the battery is cleaved. In order to show the extent of this gas release, the battery weight after the occurrence of the phenomenon was measured and expressed as a percentage (unit%) with respect to the battery weight before the start of the test. In addition, after the gas was released, the presence or absence of deformation of the battery container was confirmed, and the time to internal short circuit during overcharge was also measured. The measurement and evaluation results are shown in Table 1 below.

[0048]

[Table 1]

As shown in Table 1, Example 1 and Example 2
In the cylindrical lithium ion battery 20 of
An internal short-circuit phenomenon occurred in the early minutes of 53 minutes. Cleavage valve 1
After the cleavage of 0, the gas was released only gently, the battery was not deformed, and the battery weight was maintained at 80% or more (the battery contents were hardly released). Therefore, the batteries of Example 1 and Example 2 exhibited extremely gentle behavior at abnormal times. Furthermore, although there was no difference in behavior between these batteries during continuous charging, the battery of Example 1 had a slightly shorter time to reach an internal short circuit. It is considered that in the battery of Example 1, the insertion position of the second electrode pair 25 is close to the center of the battery where the temperature rises rapidly during overcharge. On the other hand, in the battery of Comparative Example 1, after the cleaving valve 10 was cleaved, gas was relatively violently emitted from the cleaving valve 10 with the release of a part of the battery contents. The battery weight after the phenomenon was 71%, and the battery container was deformed.

From the above test results, the separator S2, which has a lower melting temperature than the separator S1, melts due to the rise in the battery temperature during overcharge, and the second electrode pair 25 causes an internal short circuit at an early stage. It was found that the behavior when the ion battery 20 is exposed to an abnormal state is extremely gentle, and safety can be ensured.

[0051]

As described above, according to the present invention, a positive electrode using a lithium transition metal complex oxide capable of inserting and extracting lithium ions in the positive electrode active material by charging and discharging, and releasing lithium ions by charging and discharging. -By immersing the electrode group with the storable negative electrode through the separator into the electrolytic solution and storing it in the battery container, it is possible to secure high output and high capacity of the lithium ion battery, and at the time of normal charging and discharging. , The second electrode pair is insulated by the second separator to maintain the battery function, and when the battery is abnormal, the battery temperature rises due to the chemical reaction between the electrolytic solution and the active material, so that the melting temperature is lower than that of the separator of the electrode group. Since the second separator melts quickly and the second electrode pair is short-circuited to block the flow of current between the positive and negative electrodes, the chemical reaction between the electrolytic solution and the active material is not promoted, so that the lithium ion electrode It is possible to secure the safety,
The effect can be obtained.

[Brief description of drawings]

FIG. 1 is a side sectional view of a cylindrical lithium ion battery according to a first embodiment of the present invention.

FIG. 2 schematically shows the position of the separator of the cylindrical lithium-ion battery of the first embodiment, (A) of FIG.
An enlarged view of (A) part, (B) is 2 (B) -2 (B) of FIG.
It is a line sectional view.

FIG. 3 is a cross-sectional view of a cylindrical lithium ion battery according to a third embodiment of the present invention, corresponding to FIG. 2 (B).

[Explanation of symbols]

5 battery container 6 winding group 6'electrode winding group (electrode group) 11 shaft core 20 Cylindrical lithium-ion battery 21 Aluminum foil 22 Copper foil 25 Second electrode pair S1 separator S2 Second separator

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tsuyoshi Nakano             2-8-7 Nihonbashihonmachi, Chuo-ku, Tokyo             Inside Shin-Kobe Electric Machinery Co., Ltd. F-term (reference) 5H021 AA06 CC15 EE04 HH06                 5H029 AJ12 AK03 AL06 AL08 AM03                       AM05 AM07 BJ02 BJ14 BJ27                       CJ13 DJ04 DJ06 EJ01 EJ04                       EJ12 HJ14                 5H050 AA15 BA17 CA09 CB07 CB09                       DA19 EA09 EA24 FA01 FA05                       GA13 HA14

Claims (4)

[Claims] 1. A positive electrode using a lithium transition metal complex oxide capable of absorbing and desorbing lithium ions as a positive electrode active material by charging and discharging, and a negative electrode capable of desorbing and storing lithium ions as a result of charging and discharging via a separator. In a lithium ion battery in which an electrode group is soaked in an electrolytic solution and accommodated in a battery container, a lithium ion is occluded by being electrically connected to the positive electrode and the negative electrode through a second separator having a lower melting temperature than the separator. A lithium ion battery having a second electrode pair that does not emit. 2. A positive electrode using a lithium transition metal composite oxide capable of absorbing and desorbing lithium ions by charging and discharging as a positive electrode active material, and a negative electrode capable of desorbing and storing lithium ions by charging and discharging via a separator. A lithium ion battery in which an electrode group is soaked in an electrolytic solution and housed in a battery container is provided with a second electrode pair that does not absorb or release lithium ions, and the electrode pair has a thermal contraction rate higher than that of the separator and a battery abnormality. A lithium-ion battery characterized in that it is electrically connected to the positive electrode and the negative electrode through a second separator having a thermal contraction rate that sometimes short-circuits the electrode pair. 3. The electrode group is a wound electrode group having a conductive shaft core in the center, and the shaft core is any one electrode of the second electrode pair. Alternatively, the lithium ion battery according to claim 2. 4. The lithium ion battery according to claim 1, wherein at least one electrode of the second electrode pair is a metal foil.