JP6623074B2 - Bobbin-type lithium primary battery - Google Patents

Description

  The present invention relates to a bobbin-type lithium primary battery using lithium metal or a lithium alloy for a negative electrode.

  A bobbin-type lithium primary battery having an inside-out structure uses lithium metal or a lithium alloy as a negative electrode active material, and has a feature of high energy density and high capacity. For this reason, it is widely used for applications that continue to be used without maintenance for a long period of time, such as batteries for memory backup of various measuring instruments and electronic devices. FIG. 1 shows the structure of a general bobbin-type lithium primary battery 1. FIG. 1 shows a longitudinal section when the extending direction of the cylindrical shaft 100 of the cylindrical bobbin-type lithium primary battery 1 is the vertical (vertical) direction.

  The bobbin-type lithium primary battery 1 includes a bottomed cylindrical battery can 2, a positive electrode mixture 3 formed by forming a positive electrode active material such as manganese dioxide into a hollow cylindrical shape together with a conductive aid such as graphite, and a cylindrical metallic lithium. The battery can 2 is made of metal and serves as both a battery case and a positive electrode current collector, and the negative electrode lithium 4 made of a lithium alloy, a cylindrical cup-shaped separator 5, a gasket 6, a sealing body 7, and the like. A convex positive terminal portion 21 is formed on the outer bottom surface by pressing. In the illustrated bobbin-type lithium primary battery, the opening of the battery can 2 is sealed by a known crimp sealing method, and a beading portion 22 is formed around the opening of the battery can 2 by drawing. . A positive electrode mixture 3, a separator 5, and a negative electrode lithium 4 are accommodated in the battery can 2 together with an electrolyte, and a substantially disc-shaped sealing body 7 is disposed on the opening end side of the battery can 2 via a gasket 6. It is inserted. As a sealing structure of the battery can, there is a known laser sealing method.

  The sealing body 7 is composed of a negative electrode terminal plate 71 and a sealing plate 72, and the negative electrode terminal plate 71 is made of metal. A flange is formed on the edge. The sealing plate 72 is a metal disk and is laminated below the negative electrode terminal plate 71. A gasket 6 made of an integrally molded product of resin such as polypropylene is interposed between the periphery of the sealing plate 72 and the negative electrode terminal plate 71 and the inner surface of the battery can 2 on the opening side.

  As an assembling procedure of the bobbin-type lithium primary battery 1 shown in FIG. 1, first, a hollow cylindrical positive electrode mixture 3 is press-fitted into the battery can 2, and an upper portion opens inside the positive electrode mixture 3. The separator 5 formed into a bottomed cylindrical shape is disposed, and the negative electrode lithium 4 is inserted inside the separator 5. The negative electrode lithium 4 is a plate-shaped metal lithium or lithium alloy rolled into a cylindrical shape, and a negative electrode current collector 40 formed of a thin metal plate such as stainless steel is attached to the negative electrode lithium 4 in advance. The negative electrode current collector 40 is connected to the upper end side of a flat plate-like region (hereinafter also referred to as a current collection region) 41 attached to the inner surface 4i of the negative electrode lithium 4 and is connected to a negative electrode lead portion 42 extending upward in a band shape. It has a structure. In the negative electrode current collector 40, the current collection region 41 and the negative electrode lead portion 42 may be formed separately. In this example, one metal plate is cut into a predetermined planar shape to collect the current collection region 41. And the negative electrode lead portion 42 are integrally provided. FIG. 2 shows a plan view of the negative electrode current collector 40. A negative electrode lead portion 42 extending upward in a strip shape is integrally formed on the upper edge 43 of the rectangular flat current collecting region 41.

  When the cylindrical negative electrode lithium 4 with the negative electrode current collector 40 attached is inserted into the battery can 2, the gasket 6 is attached to the beading portion 22 projecting annularly inward of the battery can 2. The battery can 2 is attached to the open end side. That is, the gasket 6 is inserted into the battery can 2 with the peripheral edge of the lower surface of the bottom portion 61 of the gasket 6 in contact with the upper surface of the beading portion 22. The gasket 6 has an opening 62 at the center of the bottom 61, and the negative electrode lead portion 42 described above is inserted into the opening 62, and the tip 44 side of the negative electrode lead portion 42 is welded to the lower surface of the sealing plate 72. In welding, the base end 461 of the welding region 45 in the negative electrode lead portion 42 may be bent in advance. And the sealing body 7 is mounted in the upper surface of the bottom part 61 of the said gasket 6, pressing the sealing body 7 in the cup-shaped gasket 6. FIG. At this time, the strip-shaped negative electrode lead portion 42 is appropriately bent on the way from the welding position on the tip 44 side to the connection portion with the current collecting region 41. Further, since the negative electrode lead portion 42 made of a flat metal acts like a leaf spring at the bent position 46, the negative electrode lithium 4 is applied to the negative electrode lead portion 42 via the current collecting region 41 by the action of the leaf spring. A function of energizing the battery can 2 toward the bottom is also provided. Then, curling drawing is performed by caulking the opening end inward while reducing the diameter of the region above the beading portion 22 of the battery can 2, and the gasket 6 is compressed by the peripheral edge of the sealing body 7 and the inner surface of the battery can 2. Hold in the state. Thereby, the opening of the battery can 2 is sealed.

  The structure of the bobbin-type lithium primary battery is described in Patent Document 1 below. Non-Patent Document 1 below describes specifications of a bobbin-type lithium primary battery that is actually sold as a product.

JP 2001-273911 A

FDK Corporation, “High-capacity cylindrical lithium primary battery”, [online], [searched on January 19, 2016], Internet <URL: http://www.fdk.co.jp/battery/lithium/lithium_cylindrical .html>

  In a primary battery using negative electrode lithium such as a bobbin-type lithium primary battery, dendritic metal lithium (Li) is formed on the negative electrode side due to charging operation due to misuse or reversal overdischarge when batteries having different remaining capacities are connected. Dendrites) are deposited. In the case where the depth of discharge is deep and there is almost no negative electrode lithium remaining, a chemical reaction occurs between the positive electrode and the negative electrode current collector having a reduced potential, and the metal (Fe, etc.) constituting the negative electrode current collector Elute. Finally, the elution of the negative electrode current collector proceeds, and the thin strip-shaped negative electrode lead portion is ruptured (hereinafter also referred to as elution rupture). If elution rupture occurs, current due to charging and reversal overdischarge is also cut off, and generation of Li dendrite is also stopped.

  By the way, dendritic Li dendrite causes a local internal short circuit through the separator. Especially when the discharge depth is deep and the residual amount of negative electrode lithium is small, the negative electrode current collector is substantially on the negative electrode side, and the potential on the positive electrode side is lower than the potential on the negative electrode side. Li dendrite further grows at the site where the elution reaction of the negative electrode current collector concentrates due to misuse. Lithium primary batteries use a non-aqueous electrolyte containing a flammable organic solvent, and if an internal short circuit occurs due to Li dendrite before the negative electrode lead breaks out, the battery is ignited by the resistance heat associated with the internal short circuit. There is also a risk of doing.

  Therefore, the present invention provides a bobbin-type lithium primary battery having high safety capable of reliably preventing a local internal short circuit even when Li dendrite is generated by charging in a deep discharge state or reversal overdischarge. The purpose is to provide.

In order to achieve the above object, the present invention provides a hollow cylindrical positive electrode mixture and a hollow disposed inside the positive electrode mixture via a separator in a bottomed cylindrical battery can that opens upward. A bobbin-type lithium primary battery in which a cylindrical negative electrode lithium is housed together with an electrolyte solution, and the opening of the battery can is sealed by a sealing body that also serves as a negative electrode terminal plate,
The negative electrode lithium is a plate-like lithium metal or lithium alloy formed into a hollow cylindrical shape,
A negative electrode current collector made of a thin metal plate is attached to the negative electrode lithium,
In the negative electrode current collector, a current collecting region in contact with the inner surface of the hollow cylindrical negative electrode lithium and a negative electrode lead portion extending in a band shape upward from the upper edge of the current collecting region are integrated. Formed,
The negative electrode lead portion has a welding region which is a region formed by welding the tip side to the lower surface of the sealing body, and is machined by machining along the way from the current collection region to the welding region. A strength reduction part with low strength is formed ,
The strength reduction portion is formed at a bending position closest to the positive electrode mixture among a plurality of bending positions provided on the way from the tip of the negative electrode lead portion to the current collecting region.
The bobbin-type lithium primary battery is characterized by this.

It is more preferable if the strength reduction portion is a bobbin-type lithium primary battery formed at a plurality of bent positions excluding the base end of the welding region .

  The bobbin-type lithium primary battery according to the present invention can reliably prevent a local internal short circuit even when Li dendrite is generated by charging or reversal overdischarge. As a result, the bobbin-type lithium primary battery according to the present invention has high safety. Other effects will be clarified in the following description.

It is a figure which shows the conventional bobbin type lithium primary battery. It is a figure which shows the negative electrode electrical power collector which comprises the conventional bobbin-type lithium primary battery. It is a figure which shows the negative electrode electrical power collector which comprises the bobbin-type lithium primary battery which concerns on the 1st Example of this invention. It is a figure which shows the state by which the negative electrode electrical power collector in the said 1st Example was attached to negative electrode lithium. It is a figure which shows the modification of the negative electrode electrical power collector in the said 1st Example. It is a figure which shows the bobbin-type lithium primary battery which concerns on the 2nd Example of this invention. It is a figure which shows the modification of the bobbin type lithium primary battery which concerns on the said 2nd Example. It is a figure which shows the negative electrode electrical power collector which comprises the bobbin-type lithium primary battery which concerns on the 3rd Example of this invention. It is a figure which shows the bobbin type lithium primary battery which concerns on the said 3rd Example.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. Note that in the drawings used for the following description, the same or similar parts may be denoted by the same reference numerals and redundant description may be omitted. In some drawings, reference numerals may be assigned to parts that are not required in other drawings if unnecessary.

=== The process of conceiving the present invention ===
As described above, in a bobbin-type lithium primary battery (hereinafter also referred to as a lithium battery), Li dendrite is generated inside the battery can due to charging, reversal overdischarge, etc. There is a risk of battery ignition due to internal short circuit. Of course, lithium batteries sold as products are secured by high safety testing in accordance with standards such as JIS C 8513. However, safety tests are conducted on some individuals sampled on all manufactured individuals, and it is virtually impossible to eliminate misuse on the user side such as charging and reversal overdischarge. Is impossible. Although it is possible to suppress the production of Li dendrite by modifying the negative electrode lithium or the positive electrode mixture, it is extremely difficult to suppress the production of Li dendrite. Therefore, although the possibility is very low, it is difficult to completely prevent the occurrence of an internal short circuit due to misuse in a state where the remaining capacity is low in the conventional lithium battery. Therefore, the present inventor does not suppress the generation of Li dendrite itself that causes an internal short circuit, but is most concerned about ignition and the like if the internal short circuit can be reliably prevented even if the Li dendrite is generated. It was thought that the danger that should be avoided could be completely avoided, and the technical idea of quickly elution breakage of the negative electrode lead portion at the time of charging or over-discharging of the polarity was reached. The present invention has been made as a result of intensive studies based on such technical ideas.

=== First Embodiment ===
The configuration and basic structure of the lithium battery according to the embodiment of the present invention are the same as those of the conventional lithium battery shown in FIG. However, the lithium battery of this example has a characteristic in the structure of the negative electrode current collector, and due to this characteristic, the negative electrode lead portion quickly elution breaks and the internal short circuit occurs in charging or diverting overdischarge at a deep discharge depth. The chemical reaction in the lithium battery related to the generation of Li dendrite causing the above is stopped. FIG. 3 shows a plan view of a negative electrode current collector 40a included in a lithium battery according to a basic embodiment (hereinafter also referred to as a first embodiment) of the present invention. The negative electrode current collector 40a is similar to the conventional negative electrode current collector 40 shown in FIG. 2 in that the upper edge of the rectangular current collection region 41 that contacts the inner surface of the negative electrode lithium wound in a cylindrical shape in the lithium battery. 43 has a structure in which a strip-shaped negative electrode lead portion 42 protruding upward is integrally formed. However, a predetermined machining process is applied to a part of the negative electrode lead portion 42 in the extended direction so that the other portion is formed. On the other hand, it differs from the prior art in that a portion having a low strength (hereinafter also referred to as a strength reduction portion 47) is formed. In this example, notches 47 a are formed at both ends of the negative electrode lead portion 42 on the way of extension. In the strength reduction portion 47 where the notch 47 a is formed, the negative electrode lead portion 42 is reduced in width, and the strength is clearly lower than that in other regions of the negative electrode lead portion 42. FIG. 4 shows a state where the negative electrode current collector 40 a in the first embodiment is attached to the inner surface 4 i of the negative electrode lithium 4. FIG. 4 is a perspective view showing a state in which a part of the negative electrode lithium 4 is broken. In the assembled lithium battery, the negative electrode current collector 40a in the state shown in FIG. 4 has a sealing plate (FIG. 1, reference numeral 72) at the tip 44 side, as in the conventional lithium battery 1 shown in FIG. It is attached to the lower surface and bent at an appropriate place on its extension.

<Internal short circuit prevention function>
As described above, in the lithium battery according to the first embodiment, the belt-shaped negative electrode lead portion 42 is provided with the reduced strength portion 47 reduced in width by machining, and the negative electrode lead portion 42 has the strength reduction. In the part 47, the volume per unit length is smaller than other parts. That is, the strength reduction part 47 has a volume per unit surface area in the planar shape of the negative electrode current collector 40a smaller than any other part of the negative electrode current collector 40a. When the negative electrode current collector 40a is eluted along with the generation of Li dendrite during charging or overpolarization, the strength reduction portion 47 having the smallest volume per unit surface area in the region of the thin strip-shaped negative electrode lead portion 42 is obtained. The chemical reaction related to the generation of Li dendrite, which is the root cause of internal short circuit in the lithium battery, is stopped in advance. In addition, about the volume per unit surface area of the strength reduction part 47, it can design suitably according to the size of a lithium battery and the timing of the target elution fracture. Further, the negative electrode current collector 40a in the lithium battery according to the first embodiment has a current collecting region 41 and a negative electrode lead portion 42 integrally formed on an integral flat metal, whereby the negative electrode lead Problems such as an increase in cost due to an increase in the number of parts due to the separate part 42 or an increase in resistance due to the connection between the current collecting region 41 and the negative electrode lead part 42 are also avoided.

<Modification>
In the first embodiment, the strength reduction portion is formed by narrowing a part of the negative electrode lead portion. However, the strength reduction portion is a volume per unit surface area with respect to other portions of the negative electrode current collector. As long as is small, the kind of machining may be any. As a modification of the first embodiment, FIG. 5 shows a negative electrode current collector provided with strength reducing portions having different structures. In the negative electrode current collector 40b shown in FIG. 5A, a strength reduction portion 47 formed by forming a plurality of holes 47b in a part of the negative electrode lead portion 42 is provided. FIG. 5B is a perspective view of the negative electrode current collector 40c. In the example shown here, a thin-walled portion 47c whose thickness is reduced by cutting or the like is formed on a part of the negative electrode lead portion 42. The formation region of the thin portion 47 b is the strength reduction portion 47.

=== Second Embodiment ===
In the conventional lithium battery, the negative electrode lead portion bends when the sealing body is attached to the opening of the battery can with the tip side attached to the sealing plate. The bending position is determined by chance except for a position bent in advance (for example, the bending position 461 in FIG. 1), and the bending position varies among individuals. However, in the lithium battery according to the embodiment of the present invention, the strength reduction portion is formed in the negative electrode lead portion, and this strength reduction portion is more easily bent than other portions of the negative electrode lead portion. That is, it is possible to easily bend the negative electrode lead portion at the position where the strength reduction portion is formed using the strength reduction portion as a mark when sealing. Or even if it does not intentionally bend, a negative electrode lead will bend naturally in the formation position of a strength fall part. Thereby, the variation in the bending position among individuals can be made relatively small.

  By the way, the most important function required for the strength-decreasing portion is to break more rapidly than any part of the negative electrode current collector at the time of charging or reversal overdischarge. In the negative electrode lead portion, chemical reaction related to elution is concentrated at a portion closest to the positive electrode mixture. Therefore, if the strength-reduced portion is arranged closest to the positive electrode side in the bent negative electrode lead portion, the strength-reduced portion can be more reliably broken prior to other portions. In other words, if the fact that the strength-reduced portion bends almost certainly at the time of sealing is used, when the sealing body is attached to the battery can, it is easy to arrange the formation position of the strength-reduced portion on the most positive electrode side. Moreover, if it bends in a strength fall part, mechanical strength will also fall and it will become easier to fracture | rupture. Therefore, as a second embodiment of the present invention, a lithium battery configured such that in the negative electrode lead portion, the strength decreasing portion is closest to the positive electrode side will be described. FIG. 6 shows a longitudinal sectional view of a lithium battery 101 according to the second embodiment. In the lithium battery 101 shown in FIG. 6, although the negative electrode current collector 40a in the first embodiment shown in FIG. 3 is used, in the negative electrode lead portion 42 in the bent state, the predetermined bent position 463 has a reduced strength. The bent position 463 coincides with the formation position of the portion 47 and is closest to the positive electrode mixture 3 side in the negative electrode lead portion which is thin and has a tendency to elution break. Of course, the bent shape of the negative electrode lead portion 42 for disposing the strength decreasing portion 47 close to the positive electrode mixture 3 side is not limited to the shape shown in FIG. FIG. 7 shows another bent shape of the negative electrode lead portion. Here, the upper end side of the lithium battery 101 is shown in a longitudinal sectional view. As shown in FIG. 7A, if the length of the negative electrode lead portion 42 is long, the bending position 462 next to the proximal end position 461 of the welding region 45 is bent acutely from the distal end 44 side toward the proximal end. By doing so, the position 462 can be brought closest to the positive electrode mixture 3 side. Alternatively, as shown in FIG. 7B, even when the base end side of the negative electrode lead portion 42 is slightly bent toward the positive electrode mixture 3 side, the bent position 463 closest to the bent position 464 is greater than the current collecting region 41. Is further closer to the positive electrode mixture 3 side.

=== Third embodiment ===
In the conventional lithium battery, the negative electrode lead portion has a function of urging the negative electrode lithium toward the bottom of the battery can by the leaf spring effect by bending. However, in the conventional lithium battery, the negative electrode lead portion has the negative electrode lead portion. In some cases, it may be bent more acutely than intended. When the negative electrode lead part is bent at an acute angle, the leaf spring effect by the negative electrode lead part acts in the opposite direction to the original purpose of preventing the negative electrode lithium from floating, that is, in the direction in which the negative electrode lithium floats from the bottom of the battery can. Resulting in. Further, in the conventional lithium battery, even when the leaf spring effect acts to urge the negative electrode lithium downward as originally intended, when the sealing body is inserted into the battery can when the battery can is sealed, It acts in the direction to push out the sealing body. Therefore, the sealing is performed in a state where the sealing body is not properly attached to the battery can, that is, the sealing body is floated upward, and there is a possibility that a sealing failure may occur. As described above, the conventional lithium battery has various problems due to the leaf spring effect of the negative electrode lead portion.

  Therefore, when the leaf spring effect by the negative electrode lead portion was examined, in the conventional lithium battery 1 shown in FIG. 1, the negative electrode lithium 4 was press-fitted through the separator 5 inside the ring-shaped positive electrode mixture 3. It has been found that the leaf spring effect of the negative electrode lead portion 42 is sufficient to prevent the negative electrode lithium 4 from being lifted rather than positively biasing the negative electrode lithium 4 toward the bottom of the battery can 2. Therefore, in the lithium battery according to the third embodiment, the strength reduction portion used in the lithium battery according to the second embodiment is more actively utilized in the battery can as it is bent prior to sealing. It is possible to reliably prevent the negative electrode lithium from being lifted and the sealing body from being lifted at the time of sealing.

  FIG. 8 is a view showing a negative electrode current collector 40d in a lithium battery according to a third embodiment of the present invention, and FIG. 9 is a longitudinal sectional view showing a lithium battery 201 according to the third embodiment. As shown in FIG. 8, in the negative electrode current collector 40 d used in the third example, strength reduction portions 47 are formed at a plurality of locations of the negative electrode lead portion 42. In this example, there are formed two strength-reducing portions 47 which are reduced in width by providing notches 47a at both ends of a strip-like negative electrode lead portion 42 similar to the first embodiment. Of course, the strength reduction portion 47 may not be formed by the notch 47a, but may be formed by, for example, the hole 47b or the thin portion 47c formed in the negative electrode lead portion 42 shown in FIG. And as shown in FIG. 9, all the strength fall parts 47 in the negative electrode lead part 42 correspond to a bending position (462, 463). Note that not all the bent positions 46 need to be the strength-reduced portions 47. For example, in FIG. 9, the bent position 461 on the most distal end 44 side of the negative electrode lead portion 42 is the base end of the welding region 45. In many cases, it is mechanically bent in advance when it is attached. Even if the leaf spring effect is applied to the bending position 461 where the strength reduction portion 47 is not formed, other bending positions (462, 463) that coincide with the formation position of the strength reduction portion 47 can be freely bent. Thus, the leaf spring effect is absorbed, and the sealing body 7 is not pushed up and the negative electrode lithium 4 is not lifted up. Of course, in the negative electrode lead portion 42 in the bent state, if the predetermined strength reduction portion 47 is closest to the positive electrode mixture 3 side, an internal short-circuit at the time of charging or overpolarization can be more reliably prevented. .

=== Safety performance ===
As described above, in the lithium battery according to the embodiment of the present invention, an internal short circuit at the time of charging or at the time of overpolarization is surely prevented by providing the strength reducing portion at a part of the negative electrode lead portion. Therefore, while using a lithium battery actually sold as a product (hereinafter also referred to as a sample according to a conventional example) and a negative electrode current collector in which a strength reduction portion is formed in the negative electrode lead portion, other configurations and structures are the above products. The same lithium battery (hereinafter also referred to as a sample according to the example) was produced. And the state of inversion overdischarge was reproduced for each sample, and the safety performance of the sample according to the example was confirmed.

  Specifically, a 17335 type lithium battery described as “CR2 / 3 8L” in Non-Patent Document 1 is used as a sample according to the conventional example, and the negative electrode current collector shown in FIG. A lithium battery according to the third example including the body 40d was produced. The sample according to the example has the same configuration and structure as the conventional sample except for the shape of the negative electrode current collector. The negative electrode lead of the negative electrode current collector used in the conventional example is also used for the negative electrode current collector. A part in which the strength reduction portion 47 shown in FIG. 8 was formed by cutting out a part of the portion was used. In addition, 10 individuals were prepared for each sample. In addition, before confirming about the safety of each sample, when the state of the sealing body was confirmed in the sealing process at the time of producing each sample, in the sample which concerns on a prior art example, the sealing body floats at the time of sealing in all ten individuals. confirmed. On the other hand, in the sample according to the example, the negative electrode lead portion was bent at the reduced strength portion due to the weight of the sealing body and the dead weight of the negative electrode lead portion, and the sealing body did not float in all ten individuals.

  Next, about 10 individuals in each completed sample, after confirming that no sealing failure has occurred, discharge all individuals to a discharge depth of 50%, for each of the discharged individuals, An assembled battery was prepared by connecting in series with the same three new lithium batteries as the sample according to the conventional example. And the reversal overdischarge test which short-circuits between the positive / negative electrodes of an assembled battery was done. As a result, in the samples according to the conventional example discharged at a discharge depth of 50%, abnormalities such as ignition and rupture occurred in two samples of all individuals. On the other hand, in the sample according to the example, no abnormality such as ignition or rupture occurred in all the individuals. Moreover, about the sample which concerns on an Example, when all the solids were decomposed | disassembled after the reversal overdischarge test, the strength fall part in the negative electrode lead part was fractured | ruptured. In the negative electrode lead portion, the strength reduction portion and the bending position coincided, and the negative electrode lead portion was bent in the shape shown in FIG. 9, but for example, the base end of the negative electrode lead portion was slightly inward of the battery can In some cases, the strength-decreasing portion was not closest to the positive electrode mixture, for example, bent sideways. Nevertheless, since the strength-decreasing portion is dissolved and broken in all the solid bodies, the lithium battery according to the first to third embodiments of the present invention described above is charged in a state where the depth of discharge is deep. It can be said that it is possible to reliably prevent serious accidents such as ignition due to overdischarge or inversion. In any case, the sample according to the example showed extremely high safety compared to the sample according to the conventional example, which has no problem in terms of specifications as a product. If the strength-reducing portion of the negative electrode lead portion in the bent state is disposed at a position closest to the positive electrode mixture side with respect to the separator, the safety is further enhanced.

1, 101, 201 Bobbin-type lithium primary battery, 2 battery can, 3 cathode mixture,
4 negative electrode lithium, 5 separator, 6 gasket, 7 sealing body,
40 negative electrode current collector, 41 current collecting region of the negative electrode current collector, 42 negative electrode lead part,
44, the tip of the negative electrode lead, 45, the welding area,
46, 461-464 bending position of the negative electrode lead portion, 47, strength reduction portion,
47a-47c parts machined to form reduced strength parts,
71 Negative terminal plate, 72 Sealing plate

Claims (2)

A hollow cylindrical positive electrode mixture and a hollow cylindrical negative electrode lithium placed inside the positive electrode mixture via a separator are stored together with the electrolyte in a bottomed cylindrical battery can that opens upward. And a bobbin-type lithium primary battery in which the opening of the battery can is sealed by a sealing body that also serves as a negative electrode terminal plate,
The negative electrode lithium is a plate-like lithium metal or lithium alloy formed into a hollow cylindrical shape,
A negative electrode current collector made of a thin metal plate is attached to the negative electrode lithium,
In the negative electrode current collector, a current collecting region in contact with the inner surface of the hollow cylindrical negative electrode lithium and a negative electrode lead portion extending in a band shape upward from the upper edge of the current collecting region are integrated. Formed,
The negative electrode lead portion has a welding region which is a region formed by welding the tip side to the lower surface of the sealing body, and is machined by machining along the way from the current collection region to the welding region. A strength reduction part with low strength is formed ,
The strength reduction portion is formed at a bending position closest to the positive electrode mixture among a plurality of bending positions provided on the way from the tip of the negative electrode lead portion to the current collecting region.
A bobbin-type lithium primary battery characterized by that. 2. The bobbin-type lithium primary battery according to claim 1, wherein the strength reduction portion is formed at a plurality of the bent positions excluding a base end of the welding region .

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