JP2005063950A - Battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the extreme deterioration of the characteristics of a battery caused by an internal short circuit occurring near a lead, wherein the battery has a separator shrinkable with heat and an electrode having a mixture layer formed on a current collector to which a lead is connected to an exposed portion of a metal foil. <P>SOLUTION: A thermal shrinkage prevention layer is disposed in the counter part of a separator lead, so that the expansion of a short circuit caused by the shrinkage of the separator is prevented even when a micro short circuit occurs and a large current flow in the micro short circuit portion. Thus, the characteristics of the battery is prevented from being extremely deteriorated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a battery having an electrode in which a mixture layer is formed on a current collector in which a lead is bonded to an exposed portion, and a separator that shrinks by heat.

  Batteries requiring high output include a current collector made of metal foil, a mixture layer formed on the current collector and containing an active material, and a lead joined to the exposed portion of the current collector metal foil. It has the electrode which consists of. Such electrodes face each other through a separator that shrinks by heat and are wound. In such a battery, an internal short circuit is likely to occur in a concentrated manner at a lead joint where the current collector and the lead are joined by welding or the like.

  One of the causes is burrs that occur on the cut surface during lead cutting and processing, and irregularities that occur during lead welding (hereinafter referred to as lead burrs). Lead burrs break through the separator during battery construction, transportation, or battery operation, creating an electrical path. The state of such an electrical path (hereinafter referred to as a micro short circuit) is unstable, but usually the lead burr is not in contact with the counter electrode, and is it about several μA between the lead burr and the counter electrode? Since only a minute current below that flows, the battery does not have a problem. Therefore, it is difficult to detect before using the battery. However, the open circuit voltage may decrease slightly while the battery is used for a long time, or noise may be generated in the voltage during battery operation.

Conventionally, various methods have been proposed as countermeasures. For example, a method of reducing lead burrs, which are the cause by chamfering the corners of the side edges of the leads, is disclosed (see, for example, Patent Document 1). In addition, a method is disclosed in which a portion where the lead faces the counter electrode is covered with a multilayer sheet insulating member in which two or more insulating sheets are bonded (see, for example, Patent Document 2). Alternatively, a method is disclosed in which the lead is covered with an insulating tape except for the joint between the lead and the current collector and the joint between the lead and the metal portion for connection to the battery terminal (for example, a patent). Reference 3). As another example, a method of forming a reinforcing layer in a portion of a separator that contacts a lead is disclosed (for example, see Patent Document 4).
Japanese Patent Laid-Open No. 11-265703 Japanese Utility Model Publication No. 1-112562 Japanese Patent Laid-Open No. 10-302751 Japanese Patent Laid-Open No. 11-135097

  However, even though the conventional techniques such as these can reduce the occurrence of micro short-circuits, they have not been completely prevented. In spite of such measures, there are batteries that are short-circuited due to lead burrs. In such a battery, a short-circuit current of several A or more flows in the minute short-circuit portion due to expansion and contraction of the electrode plate during transportation or battery operation, particularly during charging and discharging. Therefore, when the temperature in the vicinity of the micro short-circuit portion rises and the separator in the vicinity of the micro short-circuit portion contracts, there is a case where a larger hole is formed than in the case of the micro short-circuit and the range of the short circuit is expanded. When the range of the short circuit is expanded, the battery characteristics are remarkably deteriorated, for example, the battery voltage greatly decreases beyond the operating voltage range of the battery or the battery temperature rises in a short time.

  SUMMARY OF THE INVENTION The present invention solves the above-described problem. In a battery having an electrode in which a mixture layer is formed on a current collector having a lead bonded to an exposed portion and a separator that shrinks by heat, the battery faces the lead of the separator. The portion is provided with a heat shrinkage prevention layer. Thereby, even if a micro short circuit occurs due to a lead burr and a short circuit current of several A or more flows in the micro short circuit part, it is possible to prevent the expansion of the short circuit range due to the thermal contraction of the separator. And the remarkable fall of the battery characteristic by a short circuit can be prevented very effectively.

  With the configuration of the present invention, even if a micro short circuit occurs due to the presence of lead burrs and a large current flows through the micro short circuit part, it prevents the expansion of the short circuit by preventing the thermal contraction of the separator, and the battery characteristics due to the short circuit are reduced. A significant decrease can be prevented very effectively.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected and demonstrated to what comprises the same structure, and detailed description is abbreviate | omitted.

(Embodiment 1)
FIG. 1 is a schematic diagram of a lithium ion secondary battery according to Embodiment 1 of the present invention. A sheet-like positive electrode plate 1 coated with a mixture on a metal foil is opposed to a sheet-like negative electrode plate 3 coated with a mixture on a metal foil via a separator 2. That is, the positive electrode plate 1 is a first electrode, the negative electrode plate 3 is provided opposite to the first electrode, is a second electrode having a polarity different from that of the first electrode, and the separator 2 includes the first electrode and the second electrode. It is provided between. The gaps between the positive electrode plate 1 and the negative electrode plate 3 and the space between them are filled with the electrolytic solution. These are all housed in an aluminum laminate pack (not shown) and sealed. In the positive electrode plate 1 and the negative electrode plate 3, leads 4 are joined to the exposed portions of the respective metal foils.

  FIG. 2 is a cross-sectional view of the vicinity of the lead portion of positive electrode plate 1 according to Embodiment 1 of the present invention. In FIG. 2, the positive electrode plate 1 has a positive electrode mixture layer 6 on a positive electrode current collector 5 made of a metal foil, and a lead 4 is bonded to an exposed portion 9 of the positive electrode current collector 5. There is a lead burr 7 generated at the time of processing the lead 4 on the end face of the lead 4, and the lead burr tip 7A faces the separator 2 side. Between the lead 4 and the separator 2 facing the lead 4, there is a heat shrinkage prevention layer 8 made of a tape, which is stuck to the separator 2 and fixed.

  The negative electrode plate 3 has a negative electrode mixture layer 11 on a negative electrode current collector 10 made of a metal foil. The positive electrode plate 1, the separator 2, and the negative electrode plate 3 are filled with an electrolyte solution so as to function as a battery.

  The separator 2 is a battery separator that shrinks by heat, such as a microporous resin film separator or a resin nonwoven fabric. In this type of separator, when the internal temperature of the battery becomes equal to or higher than the shutdown temperature of the separator in the event of an abnormality such as an external short circuit of the battery, the holes are clogged and the positive electrode and the negative electrode are electrochemically insulated. The heat shrinkage prevention layer 8 has a heat resistance equal to or higher than the shutdown temperature of the separator 2 and prevents heat shrinkage of a portion of the separator 2 facing the heat shrinkage prevention layer 8. Further, the heat shrinkage prevention layer 8 has resistance to electrolytic solution.

  Next, the operation of the above configuration in a state where a minute short circuit is occurring will be described. The lead burr 7 penetrates the heat shrinkage prevention layer 8 and pierces the separator 2, and the lead burr tip 7 A reaches the vicinity of the boundary with the negative electrode plate 3. That is, a minute current of about several μA or less flows in the minute short-circuit portion 20 of the separator 2 because the minute hole is made by the lead burr 7.

  When a short-circuit current of several A or more flows through the micro short-circuit portion 20 for some reason, the separator 2 contracts due to the generated heat. For this reason, a minute hole formed in the minute short-circuit portion 20 becomes as large as several millimeters in diameter, and the separator 2 near the minute short-circuit portion 20 tends to contract.

  However, the heat shrinkage prevention layer 8 made of tape is fixed to the separator 2 in the vicinity of the minute short-circuit portion 20 by sticking. Therefore, the thermal contraction of the separator 2 in the vicinity of the micro short-circuit portion 20 is suppressed, so that the hole of the micro short-circuit portion 20 does not spread around the lead burr 7. Moreover, since a short-circuit current of several A or more is concentrated on the lead burr tip 7A, the lead burr tip 7A is melted immediately after the short circuit due to heat generated at the time of the short circuit. For this reason, even if the separator 2 has a hole, the short circuit state is not maintained. The above action prevents the short circuit from expanding, and the battery characteristics are not significantly deteriorated.

  In the first embodiment, the heat shrinkage prevention layer 8 is applied to the surface of the separator 2 facing the lead 4. However, it is not always necessary to apply the heat shrinkage prevention layer 8 to the surface of the separator 2 facing the lead 4. As shown in FIG. 3, the structure may be affixed to the back side of the separator 2 facing the lead 4. In any case, the heat shrinkage prevention layer 8 may be attached so as to cover not only the separator 2 at the location facing the lead 4 but also the lead 4. With this configuration, the range in which the separator 2 is fixed by the heat shrinkage prevention layer 8 is widened, so that the separator 2 is fixed more reliably, and the effect of preventing the expansion of the hole at the time of a short circuit is improved.

  In addition, although the lead burrs of the positive electrode are described in the first embodiment, the same effect can be obtained even with the same configuration as the lead burrs of the negative electrode.

  In addition, as long as the above configuration is satisfied, the same effects can be obtained without depending on the details of the type of the battery, the material of the heat shrinkage prevention layer 8, and the like, as long as they do not significantly depart from the gist of the present invention. That is, in the case of a battery having an electrode in which a mixture layer is formed on a current collector in which a lead is bonded to an exposed portion of a metal foil, and a separator that shrinks by heat, the same effect can be obtained. For example, a nickel hydride storage battery or a nickel cadmium storage battery may be used. Alternatively, a battery using lithium metal for the negative electrode may be used. In addition, a primary battery may be used. The current collectors 5 and 10 may be made of expanded metal or a metal net in addition to the metal foil.

  The heat shrinkage prevention layer 8 may be a heat-resistant tape having insulating properties, for example, a tape using a heat-resistant adhesive, such as a silicone-based adhesive, for example, a polyimide tape. Here, the heat resistance means a material or characteristic that does not melt at a temperature of about 120 ° C. reached by the whole battery at the time of an internal short circuit and has a small degree of thermal shrinkage. Therefore, it can be appropriately selected depending on the type of battery.

  Further, as another method of having the heat shrinkage preventing layer 8 on the separator 2, a resin, for example, an aramid resin, may be applied to the surface of the joint portion between the separator 2 and the lead 4. Alternatively, a portion of the separator 2 facing the joint between the lead 4 and the current collector 5 is coated and impregnated with a resin, for example, a solvent containing polyvinylidene fluoride, and then dried or photocured with methacrylate or the like. It may be formed by adding a polymerization initiator to the conductive resin, applying and impregnating it, and then polymerizing. These resins only need to have heat resistance and electrolyte solution resistance equal to or higher than the shutdown temperature of the separator 2, and the type of the resin is not limited.

  Examples of the present invention will be specifically described below. In this embodiment, an example of a lithium ion secondary battery will be described. An electrode formed by forming a mixture layer on a current collector in which a lead is bonded to an exposed portion of a metal foil, and a separator that shrinks by heat. In the case of a battery having the same effect, similar effects can be obtained.

(Example 1)
The negative electrode plate 3 was produced as follows. 97% by mass of graphite and 3% by mass of styrene butadiene rubber as a binder were mixed, and the mixture was dispersed in a 1% aqueous solution of carboxymethyl cellulose to prepare a slurry. This slurry was applied on one surface of a negative electrode current collector 10 made of copper foil to provide a negative electrode mixture layer 11 and dried. Furthermore, it pressure-molded with the roll press and created the negative electrode sheet. In addition, the graphite used the powder graphite which has a specific surface area of 2.4 m < ² > / g and the particle size by a wet laser granulometer in the range of 15-22 micrometers by grind | pulverizing by a turbo mill and particle size adjustment.

  The obtained negative electrode sheet was cut into 6.5 cm × 6.5 cm, and further, the negative electrode mixture layer 11 having a width of 5 mm was removed from one side thereof with a spatula to expose the metal part. A nickel foil having a length of 10 cm, a width of 5 mm, and a thickness of 50 μm serving as a lead was spot-welded to the exposed portion to obtain a negative electrode plate 3.

  The positive electrode plate 1 was produced as follows. 63% by mass of lithium cobaltate powder, 7.4% by mass of carbon powder as a conductive agent, 29.6% by mass of 1-methyl-2-pyrrolidone (NMP) solution in which 12.5% by mass of carboxymethylcellulose is dispersed, Were mixed and kneaded to prepare a slurry. This slurry was applied on one side of a positive electrode current collector 5 made of an aluminum foil having a thickness of 15 μm, dried, and then rolled to prepare a positive electrode sheet having a coating mixture layer thickness of 100 μm.

  The obtained positive electrode sheet was cut into 5 cm × 5 cm, and the positive electrode mixture layer 6 having a width of 12 mm was removed from one side using a spatula to form an exposed portion 9. An aluminum lead 4 cut to a length of 10 cm and a width of 5 mm was disposed on the exposed portion 9 so that the projecting dimension from the positive electrode plate 1 was 5.5 cm. Further, ultrasonic welding was performed at the center of the lead 4 in the width direction with a width of 3 mm, and the lead 4 was joined to the exposed portion 9. The positive electrode plate 1 was obtained as described above. In addition, it is good also as the exposed part 9 by providing the part which does not apply | coat a slurry to the positive electrode collector 5 previously. The exposed portion of the negative electrode plate 3 can be similarly provided.

  The separator 2 was a polyethylene microporous resin film cut to 5 cm × 5 cm and having a thickness of 25 μm and a shutdown temperature of 120 ° C.

  The lead 4 was manufactured by cutting an aluminum foil having a thickness of 50 μm into a length of 10 cm and a width of 5 mm using a cutting machine in which the gap between the constituent blade edges was adjusted to 0.05 mm. It was observed with a laser microscope that the obtained lead had burrs with a maximum height of 0.06 mm on the end face of the lead width.

  Next, the obtained positive electrode plate 1 was placed on a horizontal plate, and a heat shrinkage prevention layer 8 having a length of 7 cm and a width of 7 mm was formed on the surface of the separator 2 facing the lead 4. As the heat shrinkage prevention layer 8, a polyimide tape having a thickness of 50 μm and a heat resistant temperature of 410 ° C. was used. At this time, a tape was affixed so that the lead 4 was not in direct contact with the separator 2. The heat-resistant temperature means a temperature at which melting or heat shrinkage does not occur at that temperature, and melting or heat shrinkage occurs when the temperature is exceeded.

  Thereafter, the negative electrode plate 3 is overlaid on the separator 2 to form an electrode group. At that time, the center of the positive electrode plate 1 and the center of the negative electrode plate 3 coincided, the lead connecting portions of both were positioned facing each other, and the mixture application surface was overlapped. The obtained electrode group was inserted into an aluminum laminate film shaped into a bag with a side of 10 cm in height and 8 cm in width, and then the organic electrolyte was injected under reduced pressure, and the opening was thermally welded. As a result, a lithium ion secondary battery (sample 1) as shown in FIG. 1 was produced.

The organic electrolyte used was a solution of 1.5 mol / liter of LiPF _{6 in} a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1: 1.

(Example 2)
In Example 1, a lithium ion secondary was obtained in the same manner as in Example 1 except that a vinyl chloride tape having a length of 7 cm, a width of 7 mm, a thickness of 50 μm, and a heat resistant temperature of 130 ° C. was used as the heat shrinkage prevention layer 8. A battery (Sample 2) was produced.

(Example 3)
In Example 1, lithium ion was used in the same manner as in Example 1 except that a polyetherimide resin tape having a length of 7 cm, a width of 7 mm, a thickness of 50 μm, and a heat resistant temperature of 280 ° C. was used as the heat shrinkage prevention layer 8. A secondary battery (Sample 3) was produced.

Example 4
In Example 1, a lithium ion secondary was obtained in the same manner as in Example 1 except that a polyphenylene sulfide tape having a length of 7 cm, a width of 7 mm, a thickness of 50 μm, and a heat resistant temperature of 285 ° C. was used as the heat shrinkage prevention layer 8. A battery (Sample 4) was produced.

(Example 5)
In Example 1, an NMP solution in which 10% by mass of polyvinylidene fluoride was dissolved in an area of 7 cm in length and 7 mm in width on the surface of the portion facing the lead of the separator as the heat shrinkage prevention layer 8 was heated at 70 ° C. A lithium ion secondary battery (Sample 5) was prepared in the same manner as in Example 1 except that the battery was dried and the solvent was removed. The heat-resistant temperature of the heat shrinkage prevention layer 8 was 180 ° C.

(Example 6)
In Example 5, the heat shrinkage prevention layer 8 was carried out except that the separator was impregnated with an epoxy resin in an area of 7 cm in length and 7 mm in width, then dried with hot air at 70 ° C. and solvent removal. A lithium ion secondary battery (Sample 6) was produced in the same manner as in Example 5. The heat resistant temperature of the heat shrinkage prevention layer 8 was 220 ° C.

(Example 7)
Example 5 is the same as Example 5 except that the heat-shrinkage preventing layer 8 was prepared by impregnating a separator with an ultraviolet curable silicone resin having an area of 7 cm in length and 7 mm in width and then curing by ultraviolet irradiation. Similarly, a lithium ion secondary battery (sample 7) was produced. The heat-resistant temperature of the heat shrinkage prevention layer 8 was 180 ° C.

(Example 8)
In Example 1, a lithium ion secondary layer was formed in the same manner as in Example 1 except that a polyethylene naphthalate tape having a length of 7 cm, a width of 7 mm, a thickness of 50 μm, and a heat resistant temperature of 265 ° C. was used as the heat shrinkage prevention layer 8. A secondary battery (Sample 8) was produced.

Example 9
In Example 1, a lithium ion secondary battery was formed in the same manner as in Example 1 except that a polyethersulfone tape having a length of 7 cm, a width of 7 mm, a thickness of 50 μm, and a heat resistant temperature of 225 ° C. was used as the heat shrinkage prevention layer 8. A secondary battery (Sample 9) was produced.

(Example 10)
In Example 1, a lithium ion secondary layer was formed in the same manner as in Example 1 except that a polyether ketone tape having a length of 7 cm, a width of 7 mm, a thickness of 50 μm, and a heat resistant temperature of 334 ° C. was used as the heat shrinkage prevention layer 8. A secondary battery (Sample 10) was produced.

(Example 11)
In Example 1, lithium ion was used in the same manner as in Example 1 except that a polytetrafluoroethylene tape having a length of 7 cm, a width of 7 mm, a thickness of 50 μm, and a heat resistant temperature of 327 ° C. was used as the heat shrinkage prevention layer 8. A secondary battery (Sample 11) was produced.

(Comparative Example 1)
Example 1 is the same as Example 1 except that polyimide tape having a length of 7 cm, a width of 7 mm, a thickness of 50 μm, and a heat resistant temperature of 410 ° C. is directly attached on the lead 4 instead of the heat shrinkage prevention layer 8. Similarly, a lithium ion secondary battery (Comparative Sample 1) was produced.

(Comparative Example 2)
In Example 1, instead of the heat shrinkage prevention layer 8, only the base material from which the paste component of the polyimide tape having a length of 7 cm, a width of 7 mm, a thickness of 50 μm, and a heat resistant temperature of 410 ° C. was removed was installed in the same place. In the same manner as in Example 1, a lithium ion secondary battery (Comparative Sample 2) was produced.

(Battery evaluation)
100 cells of Samples 1 to 11 and Comparative Samples 1 and 2 obtained as described above were produced and evaluated as follows.

  The battery was placed on a horizontal surface with the negative electrode on the bottom and the positive electrode on the top, and a metal plate having a weight of 50 g was placed thereon so as to cover the electrode and pressed. In this state, a charge / discharge cycle test was conducted, and changes in battery voltage and battery surface temperature at that time were confirmed.

  The charge / discharge cycle test was performed as follows. The battery was charged in a constant temperature bath at 20 ° C. with a current of 10 mA until it reached 4.2 V, and then charged with a charging voltage of 4.2 V until the current reached 1 mA. Thereafter, discharging was performed at a current of 10 mA until the voltage reached 3.0 V with a pause of 30 minutes. After the end of discharging, charging was performed again after a 30-minute pause. Such a series of charging / discharging was repeated 20 times, and the battery voltage and the battery surface temperature during the charging / discharging cycle test were measured. The battery surface temperature was measured with a thermocouple installed on the battery surface. A battery whose battery voltage dropped to 0.5 V or less during the charge / discharge cycle test was considered short-circuited, and the subsequent test was stopped.

  In addition, during the charge / discharge cycle test, when a battery whose battery voltage is reduced by 0.5 V or more from the voltage during normal charge / discharge is confirmed for a short time of several tens of milliseconds (hereinafter referred to as state A), the test is performed. Continued. Table 1 shows the number of batteries that were short-circuited during the charge / discharge cycle test and the batteries that were in state A.

  As a result of the charge / discharge cycle test, the batteries of Samples 1 to 11 did not generate batteries that were short-circuited and the battery voltage decreased to 0.5 V or less. The battery temperature dropped to 5 V or less and the battery temperature suddenly increased.

  The batteries in state A were confirmed in the batteries of samples 1 to 11, but not confirmed in the batteries of comparative samples 1 and 2.

  Furthermore, among the batteries of Samples 1 to 11 and Comparative Samples 1 and 2, a battery that did not cause a short circuit, a battery that caused a short circuit, and a battery that became a state A were disassembled after the charge / discharge cycle test, and the optical microscope was And observed.

  As a result, no significant change was observed in the separator 2 of the batteries that did not cause a short circuit among the batteries of Samples 1 to 11 and Comparative Samples 1 and 2. This is probably because the lead 4 had the lead burr 7 but the short circuit did not occur or the micro short circuit remained.

  Among the batteries of comparative samples 1 and 2, the separator 2 of the battery in which the short circuit occurred has a hole with a radius of 1.5 cm or more in a portion facing the lead 4, and the positive electrode mixture layer 6 through the hole. And the negative electrode mixture layer 11 were in direct contact with each other. In some separators 2 around the hole, the contraction state was observed due to heat at the time of short circuit. Further, the tip 7A of the lead burr 7 of the lead 4 was melted.

  From the above, it is considered that the battery voltage of the short-circuited battery is 0.5 V or less through the following process. That is, the lead burr 7 on the lead 4 breaks through the separator 2 during the charge / discharge cycle test, reaches the negative electrode plate 3, and the battery is internally short-circuited. Since a large current of more than several A flowing at that time is concentrated on the tip 7A of the lead burr 7, the tip 7A generates heat. Since the temperature locally reaches such a high temperature that the lead burr 7 is melted, the separator 2 is also affected by the heat. Since the separator 2 is perforated by the lead burr 7, the hole becomes larger when attempting to shrink due to heat. Since the tip 7A of the lead burr 7 is melted, the short-circuit at that portion does not continue, but the hole of the separator 2 expands, the mixture layer 6 of the positive electrode plate 1 is exposed, and the opposing negative electrode plate 3 and In order to short-circuit, the short-circuit state is continued. Accordingly, the battery voltage is reduced to 0.5V or less.

  On the other hand, the separator 2 of the battery in the state A among the samples 1 to 11 has a hole with a radius of about 1.5 mm in a portion facing the lead 4 or a separator with a radius of about 1.5 mm. No. 2 was melted and transparent, and no separator with a large hole having a radius of 1.5 cm or more was observed as in the short-circuited batteries of Comparative Samples 1 and 2. Even in the case of a hole having a radius of about 1.5 mm, the hole stays around the lead 4 and the positive electrode mixture layer 6 and the negative electrode mixture layer 11 are in direct contact with each other through the hole. Nothing was observed. Further, the tip 7A of the lead burr 7 was melted.

  From the above, it is considered that the battery in the state A has entered the state A through the following process. That is, during the charge / discharge cycle test, the lead burr 7 breaks through the separator 2, reaches the negative electrode plate 3, and the battery is internally short-circuited. Since a large current of more than several A flowing at that time is concentrated on the tip 7A of the lead burr 7, the tip 7A generates heat. Since the temperature reaches such a high temperature that the lead burr 7 is melted, the separator 2 is also affected by heat. The separator 2 is perforated by lead burrs 7 and tends to shrink due to heat. Here, since the separator 2 has the heat shrinkage preventing layer 8, a hole having a radius of up to about 1.5 mm is formed, but it does not further expand. Therefore, the positive electrode plate 1 and the negative electrode plate 3 are in direct contact with each other through the hole, thereby preventing an internal short circuit. Further, since the tip end portion 7A of the lead burr 7 is melted, the short circuit at that portion does not continue. Therefore, although the battery voltage instantaneously drops by 0.5 V or more, the internal short circuit stays in that moment, so that the charge / discharge cycle test can be continued.

  As described above, even when a large current of several A or more flows through the micro short-circuit portion 20 due to the lead burr 7, the heat-shrinkage prevention layer 8 suppresses the thermal contraction of the separator 2 around it and the battery is short-circuited. To prevent it. The heat shrinkage prevention layer 2 can be formed by sticking a heat resistant tape on the surface of the separator 2 facing the lead 4 or impregnating the separator 2 with a heat resistant resin.

  In addition, when sticking a heat resistant tape to a separator like the samples 1-4 and the samples 8-11, it is preferable to use the heat resistant double-sided tape which has an adhesion part on both surfaces. If such a tape is used, positioning of the lead 4 and the heat shrinkage prevention layer 8 becomes easy.

  In the above description, the battery configuration in which the positive electrode plate 1 and the negative electrode plate 3 are formed in a flat plate shape is described as an example, but the present invention is not limited to this. Even if the present invention is applied to a configuration in which the positive electrode plate 1 and the negative electrode plate 3 are wound through the separator 2, the same effect can be obtained.

  In the battery according to the present invention, the presence of lead burrs causes a micro short circuit, and even when a large current flows through the micro short circuit part, thermal contraction of the separator is prevented. Therefore, the expansion of the short circuit is prevented, and the remarkable deterioration of the battery characteristics due to the short circuit is extremely effectively prevented. This configuration is useful for a battery using a separator that shrinks by heat, such as a lithium ion secondary battery or a lithium primary battery.

Schematic diagram of the lithium ion secondary battery in Embodiment 1 of the present invention Schematic diagram of battery configuration and micro short circuit by lead burr in Embodiment 1 of the present invention Another configuration of the battery in Embodiment 1 of the present invention, and a schematic diagram of a micro short-circuit due to lead burrs

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode plate 2 Separator 3 Negative electrode plate 4 Lead 5 Positive electrode collector 6 Positive electrode mixture layer 7 Lead burr 7A Lead burr tip part 8 Heat shrinkage prevention layer 9 Exposed part 10 Negative electrode collector 11 Negative electrode mixture layer 20 Micro short circuit part

Claims (8)

A first electrode having an exposed portion and made of a metal; a mixture layer formed on the current collector excluding the exposed portion; and a lead joined to the exposed portion; ,
A second electrode provided opposite to the first electrode and having a different polarity from the first electrode;
A separator provided between the first electrode and the second electrode and contracted by heat;
A heat shrinkage prevention layer provided on a portion of the separator facing the lead and preventing heat shrinkage of the portion;
An electrolyte solution that fills between the first electrode, the second electrode, and the separator;
With battery. The battery according to claim 1, wherein the heat shrinkage prevention layer is a tape attached to the separator. The battery according to claim 2, wherein the tape has adhesive portions on both sides. The battery according to claim 1, wherein the heat shrinkage prevention layer is a resin layer provided on the separator. The separator electrochemically insulates the first electrode and the second electrode above the shutdown temperature,
The battery according to any one of claims 1 to 4, wherein the heat shrinkage prevention layer has a heat resistant temperature higher than the shutdown temperature. A) forming a first layer by forming a mixture layer and an exposed exposed portion of the current collector on a current collector made of metal;
B) bonding a lead to the exposed portion;
C) Disposing a separator that shrinks by heat between the first electrode and a second electrode having a different polarity from the first electrode;
D) forming a heat shrinkage preventing layer on a portion of the separator facing the lead;
E) filling an electrolyte between the first electrode, the second electrode, and the separator;
The manufacturing method of the battery provided with. In the D step, the heat shrinkage prevention layer is formed by sticking a tape on a portion of the separator facing the lead.
The battery manufacturing method according to claim 6. In the step D, the thermal shrinkage prevention layer is formed by either applying a resin to a portion of the separator facing the lead or impregnating the resin.
The battery manufacturing method according to claim 6.

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