JP2002170596A - Nonaqueous electrolyte solution battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte solution battery with a superior safety. SOLUTION: An electrolyte group 12 has two groups, in which a polyethylene separator 7, a negative electrode plate 6, the separator 7, a positive electrode plate 5, and the separator 7 are laminated in the described order. Between the two groups, a plate-shaped partition 30 with the thickness of 1 mm, made of PTFE(polytetrafloroethylene), is provided. Thus, a calorific value per unit time is lowered and the emission of a gas is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte battery, and more particularly, to a non-aqueous electrolyte solution in which an electrode group with a separator between a positive electrode plate and a negative electrode plate is infiltrated by the non-aqueous electrolyte and accommodated in a battery case. A non-aqueous electrolyte battery.

[0002]

2. Description of the Related Art At present, lithium primary batteries, lithium secondary batteries and the like have been put into practical use as nonaqueous electrolyte batteries. Among these batteries, a small lithium secondary battery having an electric capacity of about 1.5 Ah is, for example, a PTC (Positive Temper
ature Coefficient) Insert a device in series with the power generation device to add a current cut-off mechanism to cut off the current when the temperature rises, or to form a metal thin film on the boundary between the inside and outside of the battery and remove the metal thin film when the internal pressure of the battery rises. The safety of the non-aqueous electrolyte battery is ensured, for example, by adding an internal pressure reduction mechanism that breaks the battery and releases generated gas inside the battery and prevents damage to the battery container. As described above, safety is emphasized even in a small battery, and it is needless to say that it is more important to secure the safety of a large battery having an electric capacity exceeding 5 Ah.
Even in a large battery, for example, Japanese Patent Application Laid-Open No. 9-92249.
Japanese Patent Application Laid-Open Publication No. H11-163873 discloses a technique of a secondary battery provided with an opening valve for releasing generated gas inside the battery.

[0003] Large batteries are often used for charging and discharging a large capacity with a large current. The current interrupting mechanism using the PTC element of a small secondary battery is not usually used in a large battery because the PTC element is a resistor, and the rapid charging / discharging characteristics are significantly impaired. Further, since the PTC element is used as a current interrupting element in a current flow path, it cannot cope with a situation in which a large-sized battery body having a large capacity is crushed by external stress, and the safety of the battery itself is not improved. It cannot be said that it improves. Therefore, it is more important to improve the safety of a large battery in a large battery than to a small battery.

[0004]

However, in the mechanism for releasing the gas generated inside the battery by breaking the metal foil film according to the prior art described above, the safety function must be taken into account unless the mechanism for cleaving the metal foil film is sufficiently considered. It is difficult to fulfill. For example,
The gas generated internally when the battery is abnormal releases vigorously as soon as the metal foil film is broken. At this time, there is a problem that the battery contents such as the electrode group move together with the outflow gas in the direction of the metal foil film breaking portion where the pressure is reduced, so that the gas discharge port is closed and the pressure inside the battery container becomes extremely high.

[0005] In addition, since a large battery has a large electric capacity stored in the battery, when a momentary internal short-circuit such as crushing occurs, the stored energy is instantaneously released as heat, and the battery becomes extremely hot. There is a problem.

The present invention has been made in view of the above circumstances, and has as its object to provide a non-aqueous electrolyte battery excellent in safety.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is directed to an electrode group having a separator interposed between a positive electrode plate and a negative electrode plate which is impregnated with a non-aqueous electrolyte and accommodated in a battery case. In the above nonaqueous electrolyte battery, a partition member for partitioning the electrode group is provided inside the electrode group and / or between the electrode groups.

[0008] In the nonaqueous electrolyte battery of the present invention, an electrode group having a separator interposed between a positive electrode plate and a negative electrode plate is impregnated with the nonaqueous electrolyte and accommodated in a battery case. Therefore, for example, when a short circuit occurs inside the electrode group due to crushing due to external stress, the active material applied to the positive electrode plate and the negative electrode plate thermally runs away, and the electrode group generates heat, and the non-aqueous electrolyte in the battery case. Causes evaporation and thermal decomposition, and rapidly gasifies inside the battery case. In the present invention, since the partition member for partitioning the electrode group is provided inside the electrode group and / or between the electrode groups, the partition in the indenter contact direction can be performed even if crushing or the like due to such external stress occurs. One of the electrode groups is short-circuited and generates significant heat due to thermal runaway of the active material.However, heat is not transmitted to the other electrode group by the partition material, so that thermal runaway does not occur and generation in the battery case occurs. The amount of gas can be reduced (the internal pressure of the battery is reduced). Even if a certain period of time has passed and heat has been transferred to the other electrode group and thermal runaway has started, one of the electrode groups in the indenter contact direction has already passed the point at which the most exothermic reaction occurs immediately after the short circuit, and is heading toward calm down. The thermal runaway inside the battery occurs only intermittently. Therefore, due to the presence of the partition plate, even if all of the partitioned electrode groups undergo thermal runaway and have the same total calorific value, the calorific value per unit time can be suppressed low, and the amount of generated gas is reduced. Therefore, a non-aqueous electrolyte battery excellent in safety can be realized.

In this case, if the partition member is made thicker than the separator, heat conduction within the electrode group and / or between the electrode groups can be delayed, so that thermal runaway of the entire electrode group is prevented or intermittently caused. It becomes possible. Further, if the partition member is made of a material having a higher melting point than the separator, the same effect as when the partition member is made thicker than the separator can be obtained. Therefore, if the partition member is made thicker than the separator and made of a high melting point material, the effect of preventing or interrupting thermal runaway of the entire electrode group can be enhanced. Furthermore, if the partition member is made of an insulator, even if the partition member contacts one or both of the positive electrode plate and the negative electrode plate, it is possible to prevent the partition member from being corroded (electrically rot) during normal charge and discharge. .

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a prismatic lithium ion secondary battery will be described below with reference to the drawings.

As shown in FIG. 1, the prismatic lithium ion secondary battery 20 of the present embodiment includes a rectangular stainless steel battery can 8 serving as a container. In the center of the battery can 8,
An electrode group 12 in which a plurality of positive electrode plates 5 and negative electrode plates 6 each having a rectangular shape and whose ears protrude upward is stacked. The positive electrode plate 5 has a 20 μm thick aluminum foil as a positive electrode current collector, and a positive electrode active material mixture is applied to both surfaces of the positive electrode current collector. On the other hand, the negative electrode plate 6 uses a copper foil having a thickness of 10 μm as a negative electrode current collector, and a negative electrode active material mixture is applied to both surfaces of the negative electrode current collector. The prismatic lithium ion secondary battery 20 includes a battery lid 9 made of stainless steel. After the electrode group 12 is inserted into the battery can 8, the periphery of the opening of the battery can 8 and the battery lid 9 are removed.
Is sealed by welding with the peripheral edge.

As shown in FIGS. 1 and 2, the battery cover 9 has a positive electrode terminal 1 made of aluminum and having a screw screwed on the upper side and a negative electrode terminal 2 made of copper and having a screw screwed on the upper side. Fixed. The positive electrode terminal 1 and the negative electrode terminal 2 are a thin annular lower packing 21 interposed between the battery lid 9 and a thin annular upper packing 2 abutting on the battery lid 9, respectively.
2. Fastened with a nut 25 via a flat washer 23 in contact with the upper packing 22 and a toothed washer 24 in contact with the flat washer 23. The sealed state is ensured. Current collector ears 3 and negative electrode plate 6 of positive electrode plate 5
Current collector ears 4 are joined to the lower portions of the positive electrode terminal 1 and the negative electrode terminal 2 by ultrasonic welding, respectively.
Is connected to the positive terminal 1 and the negative plate 6 is connected to the negative terminal 2.

As shown in FIGS. 2A and 2B, the electrode group 1
Reference numeral 2 has two groups of a separator 7 made of polyethylene, a negative electrode plate 6, a separator 7, a positive electrode plate 5, and a separator 7 stacked in this order. Between the two groups, a plate-like partition member 3 which is thicker than the separator 7 and electrically and physically separates the two groups from each other.
0 is provided. The material of the partition member 30 is, for example, polypropylene of the same material as the separator 7 or polyfluoroethylene (PTF) having a melting point higher than that of the separator 7.
E) Various materials such as tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin (PFA) and tetrafluoroethylene-6-fluoropropylene copolymer resin (FEP) can be used.

The battery lid 9 is provided with a safety valve 10 made of stainless steel foil and a liquid inlet. Safety valve 10
Has a function of breaking the stainless steel foil and releasing the gas inside when the battery internal pressure rises. A non-aqueous electrolyte (not shown) in which lithium hexafluorophosphate (LiPF ₆ ) is dissolved in a mixed solvent of ethylene carbonate and dimethyl carbonate is injected from the injection port. , The inlet is closed.

Next, the operation of the prismatic lithium ion secondary battery 20 of this embodiment will be described.

In the prismatic lithium ion secondary battery 20 of the present embodiment, a partition member 30 is disposed between two groups inside the electrode group 12. For this reason, even when crushing due to external stress or the like occurs, one of the electrode groups 12 partitioned in the indenter contact direction.
The group is short-circuited and generates heat due to thermal runaway of the active material. However, heat is not transmitted to the other group of the electrode group 12 by the partition member 30 and thermal runaway does not occur. Even if a certain period of time elapses and heat is transferred to the other group of the electrode groups 12 and thermal runaway starts, one of the groups of the electrode groups 12 in the indenter contact direction already has the most exothermic reaction immediately after the short circuit. It has passed and it is going to calm down. Therefore, due to the presence of the partition member 30, even when the two groups of the electrode groups 12 cause thermal runaway, and the total calorific value is the same, the calorific value per unit time can be suppressed low, and the safety is improved. It has a significant effect.

The electrode group 12 is immersed in a non-aqueous electrolyte. Electrode group 12 causing internal short circuit due to crushing etc.
Generates heat due to thermal runaway of the active material, evaporates the non-aqueous electrolyte,
It thermally decomposes and rapidly gasifies inside the battery. The mechanism for releasing the generated gas to the outside of the battery is extremely important for the safety of the prismatic lithium ion secondary battery 20, and in the worst case, the battery is ruptured. In the prismatic lithium ion secondary battery 20, since the electrode group 12 is divided into two groups by the partition member 30, the heat generated by the short circuit is not transmitted, and there is the electrode group 12 which does not cause thermal runaway (in the indenter contact direction). One group on the side opposite to the group of the electrode groups 12) can reduce the amount of generated gas. Further, even when heat is transmitted from one of the short-circuited electrode groups 12 and all of the electrode groups 12 are short-circuited, the electrode group 12 intermittently undergoes thermal runaway, and the non-aqueous electrolyte also intermittently generates gas. Become For this reason, an increase in battery internal pressure can be suppressed as compared with a case where the battery is short-circuited at once, and safety can be improved.

The separator used for the electrode group 12 of the prismatic lithium ion secondary battery 20 is generally made of polyethylene or polypropylene, has a thickness of about 20 to 50 μm, and has a melting point of 100 μm. ~ 15
It is about 0 ° C. In the case of a large battery, the temperature inside the battery when the electrode group 12 is short-circuited internally due to external stress such as crushing and causes thermal runaway is assumed to be 300 ° C. or higher and exceeds this melting point. Therefore, the thin, low-melting separator is short-circuited in a very short time, causing thermal runaway. However,
In the present embodiment, since the partition member 30 is made of polyethylene or a material having a high melting point, which is thicker than the separator, the transfer of heat is delayed, so that thermal runaway of the electrode group 12 may be prevented or intermittently caused. It becomes possible.

Furthermore, the partition member 30 can be made of a conductor, but in this case, the insulation between the positive electrode and the negative electrode of the electrode group 12 can be improved by inserting the partition member 30 as compared with the case where an insulator is used. Extra care must be taken to ensure that it is not compromised.
If the partition member 30 is an insulator like the prismatic lithium ion secondary battery 20, even if it electrically contacts either the positive or negative electrode,
Since corrosion of the partition member 30 does not occur during charging and discharging of a normal battery, it is preferable from the viewpoint of reliability.

In this embodiment, an example in which the present invention is applied to a prismatic battery has been described. However, the present invention is applicable not only to a prismatic battery but also to a cylindrical battery. In addition, partition material 3
For 0, a metal, a heat-resistant resin, a flame-retardant resin, or the like may be used. In the present embodiment, the partition member 30 is
Although the example in which one is provided has been described, for example, FIG.
As shown in (B), the number of partition members 30 may be three (plural). And it goes without saying that the present invention is not limited to the present embodiment and can adopt various other configurations without departing from the gist of the present invention.

[0021]

EXAMPLE Next, an example of the prismatic lithium ion secondary battery 20 manufactured according to the present embodiment will be described. Note that a battery of a comparative example manufactured for comparison is also described.

(Embodiment 1) As shown in FIG.
0, battery using 1 mm thick polypropylene.

(Embodiment 2) As shown in FIG.
0, a battery using 1 mm thick PTFE.

(Embodiment 3) As shown in FIG.
0, a battery using three 1 mm thick PTFE.

(Comparative Example 1) A battery produced by using the battery of Example 1 without using the partition member 30.

<Test / Evaluation> [Test] Next, for each of the batteries of the examples and the comparative examples manufactured as described above, the batteries were mounted horizontally on a mounting table (FIG. 1).
Is placed in contact with the mounting table on the back side shown in FIG. 3), and a diameter of 15 mm is provided between the positive terminal 1 and the negative terminal 2 at the center of the front side of the battery.
A crush test was performed in which a round rod made of iron having a thickness of 1 mm was applied and the battery can 8 was crushed so as to be displaced in the positive / negative electrode laminating direction (thickness direction) to half the thickness of the battery can 8. As an evaluation method, after crushing, the presence or absence of battery rupture or ignition was checked.
The gas ejection time from 0 was also measured.

[Test Results] The test results of the crush test are shown in Table 1 below. In Table 1, "○" indicates that 80% or more of the burst
No ignition, "△" indicates a result of 50% or more and less than 80% rupture / ignition, and "x" indicates a result of less than 50% rupture / no ignition.

[0028]

[Table 1]

[Evaluation] As shown in Table 1, as a result of the crush test, a majority of the batteries of Comparative Example 1 burst or ignited. 50% or more of the battery of Example 1 did not burst or ignite, and the safety of the battery was improved. In the batteries of Examples 2 and 3, 80% or more did not burst or ignite, and the safety was further improved. Also,
In the batteries of Examples 2 and 3, the gas ejection time also doubled or more, and the gas ejection amount per unit time was reduced. Therefore, since the gas is gently jetted from the safety valve 10, it is understood that the safety is improved.

From this, it is possible to improve the safety by arranging the partition member 30 inside the electrode group 12 and / or between the electrode group 12, and furthermore, the partition member 30 is thicker than the separator 7 and is made of a high melting point material. It was confirmed that the configuration further improved the safety.

[0031]

As described above, according to the present invention,
Since a partition member for partitioning the electrode group is provided inside the electrode group and / or between the electrode groups, even if all of the partitioned electrode groups undergo thermal runaway and the total calorific value is the same, the unit is Since the amount of heat generated per hour can be reduced and the amount of generated gas can be reduced, an effect that a nonaqueous electrolyte battery excellent in safety can be realized can be obtained.

[Brief description of the drawings]

FIG. 1 is a partially broken front view of a prismatic lithium ion secondary battery according to an embodiment to which the present invention can be applied.

FIGS. 2A and 2B are partially cutaway side sectional views of the prismatic lithium ion secondary battery of the embodiment, wherein FIG. 2A is a side view of a positive electrode side and FIG.

FIGS. 3A and 3B are partially cut-away side sectional views of a prismatic lithium ion secondary battery according to another embodiment to which the present invention can be applied, wherein FIG. 3A is a side view of a positive electrode side and FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode terminal 2 Negative electrode terminal 5 Positive electrode plate 6 Negative electrode plate 7 Separator 8 Battery can (part of battery case) 9 Battery cover (part of battery case) 10 Safety valve 12 Electrode group 20 Square lithium ion secondary battery 30 Partition material

Claims (4)

[Claims] 1. A non-aqueous electrolyte battery in which an electrode group interposed between a positive electrode plate and a negative electrode plate with a separator interposed therein is immersed in a non-aqueous electrolyte and accommodated in a battery case. Alternatively, a non-aqueous electrolyte battery, wherein a partition member for partitioning the electrode group is provided between the electrode groups. 2. The non-aqueous electrolyte battery according to claim 1, wherein the partition member is thicker than the separator. 3. The non-aqueous electrolyte battery according to claim 1, wherein the partition member is made of a material having a higher melting point than the separator. 4. The non-aqueous electrolyte battery according to claim 1, wherein the partition member is made of an insulator.