KR20120094691A - Prismatic secondary battery employed with safety plate - Google Patents

Abstract

PURPOSE: A prismatic secondary battery is provided to prevent unnecessary tearing, effectively discharge gas after operation of a safety plate, and to able to effectively control pressure. CONSTITUTION: A prismatic secondary battery comprises an electrode assembly consisting of a positive electrode(34), a negative electrode(32), and a separator(36) sealed in a prismatic case. The battery case comprises a rectangular case main body(40) consisting of metal material, and a case cap comprising an electrode terminal, combined to the case main body, and a safety plate formed on the case main body. The safety plate consists of two or more discontinuous linear notch grooves(60,62). The notch grooves consists of a first notch groove formed near a vertical central axis on both sides of the case main body, and one or more second notch groove branched from at least one or more positions of the first notch groove.

Description

Square secondary battery with safety plate {Prismatic Secondary Battery Employed with Safety Plate}

The present invention relates to a rectangular secondary battery provided with a safety plate, and more particularly, a rectangular secondary battery in which an electrode assembly composed of a positive electrode, a negative electrode, and a separator is sealed in a rectangular battery case, and a battery case has an open top and a metal It consists of a rectangular case body made of a material, and a case cap coupled to an open upper end of the case body and including an electrode terminal. A safety plate is formed on the case body when a high pressure is generated inside the battery. A notch groove, wherein the notch grooves are formed on a vertical central axis portion on both sides of the case body, and at least one branch branched at at least one position of the first notch groove. It relates to a square secondary battery consisting of two notched grooves.

As technology development and demand for mobile devices have increased, the demand for secondary batteries as energy sources has been rapidly increasing. Many researches have been conducted on lithium secondary batteries with high energy density and discharge voltage among such secondary batteries. .

According to the shape of the battery case, secondary batteries are classified into cylindrical batteries and rectangular batteries in which the electrode assembly is embedded in a cylindrical or rectangular metal can, and pouch-type batteries in which the electrode assembly is embedded in a pouch type case of an aluminum laminate sheet. .

The electrode assembly incorporated in the battery case is a charge / dischargeable power generating element formed of a laminate structure of a positive electrode / separator / negative electrode. The electrode assembly is composed of a jelly-roll type in which a separator is interposed between a positive electrode and a negative electrode coated with an active material, A stacked type in which a plurality of positive and negative electrodes of a size are stacked in a state in which a separator is interposed, and stacked / folded type stacked units in which unit cells such as bi-cells or pull cells are wound in separate films.

Such a secondary battery may be exposed to various environments depending on usage conditions and conditions, and it is required to prevent the risk of explosion especially for the safety of the user. Generally, the high temperature and high pressure inside the battery, which can be caused by an abnormal operating condition of the battery such as an internal short, an allowable current, a charging state exceeding a voltage, exposure to a high temperature, . Therefore, the secondary battery is provided with a high-voltage relieving means capable of relieving the high voltage which is a direct cause of the explosion of the battery despite the difference in the shape of the battery.

For example, in a cylindrical battery, a safety plate having a specific structure is installed in a cap assembly, a prismatic battery has a notch groove formed in a cap or a case of the battery, and the pouch type battery has a notch groove Sealing portion) are separated from each other.

In a general prismatic secondary battery, a closed type or a partially open type notch groove is formed in the aluminum battery case so as to be cutable.

For example, as shown in Fig. 1, the prismatic secondary battery includes a notch groove of a partially open type on the side surface of the battery case.

The notch groove 30 of FIG. 1 is formed in a small outline at the side edge of the rectangular secondary battery case 20, and is partially formed in an open shape. That is, the notch groove is formed in a portion where the stress value is relatively large in the stress distribution of the case, and is designed to break the curved shape when the battery is excessively increased in internal pressure.

This notch groove has the advantage of relatively sensitive to the high pressure generated inside the battery, but there is a problem that it is difficult to accurately set the intended pressure threshold value in the design of the battery.

That is, as mentioned above, since high stress is applied to the side edges of the case, breakage of the notch groove can easily occur even at low pressure, and above all, it is particularly sensitive to high pressure when the battery case is thin. As a result, unintentional breakage occurs.

Therefore, the size and depth of the notch groove formed in the site where the stress value is large is inevitably small. However, when the size and depth of the notch groove are reduced, a problem of not breaking the notch groove is rather smooth. .

As another example of the rectangular secondary battery, a notch groove may be formed in the upper center portion of the battery case.

However, this structure forms a safety plate consisting of a notch groove in the upper center of the battery case with a relatively low stress, thereby increasing the breaking pressure of the safety plate for a thin battery having a large area and thickness. Increasingly thin, it is difficult to form a symmetrical structure, there is a problem that can cause unnecessary fracture, such as propagation of cracks or deformation to the peripheral area during the operation of the safety plate.

Another example of the rectangular secondary battery is a structure in which an arc-shaped notch groove is formed in the upper left part or the upper right part of the battery case. In particular, such a structure has a separate line extending to prevent unnecessary tearing of the safety plate such as crack propagation or deformation to the surrounding area during the safety plate operation.

However, such a structure has a problem that the length of the safety plate to be engraved is difficult to process and the area around the safety plate is convexly deformed during processing.

Therefore, there is a great need for a technology related to a square secondary battery that can prevent unnecessary tearing of the safety plate, efficiently eject gas after the safety plate is operated, and effectively control the pressure.

In addition, the shape of the notch grooves is expected to be a very important factor for the reliable operation under abnormal conditions.

Therefore, in consideration of the thickness of the battery case, the location of the notch groove according to the stress value, the shape, the length, the depth of the notch groove, and the like, when the internal pressure increases, the gas is quickly discharged by uniform fracture of the notch groove. There is a high need for the development of a square battery that can be made.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems of the prior art and the technical problems required from the past.

After in-depth research and various experiments, the inventors have branched the notch grooves of the safety plate in at least one position of the first notch groove and the first notch groove, which are formed at the vertical central axis portions on both sides of the case body. By constructing one or more second notched grooves, it was confirmed that unnecessary tearing of the safety plate can be prevented, gas can be efficiently ejected after the operation of the safety plate and the pressure can be effectively controlled.

In addition, when the first notch groove and the second notch groove of a specific structure are formed in a portion where the stress value is relatively small in the side of the battery case, and at the same time to form the first notch groove and the second notch groove of a specific shape, It was confirmed that breakage of the first notch groove and the second notch groove occurred reliably under appropriate conditions, and as a result, the safety could be improved.

Accordingly, it is an object of the present invention to provide a rectangular secondary battery having a safety plate of an improved structure that can effectively break.

According to the present invention, a rectangular secondary battery according to the present invention is a rectangular secondary battery in which an electrode assembly composed of a positive electrode, a negative electrode, and a separator is sealed in a rectangular battery case, and the battery case is open at the top and is made of a metallic material. It consists of a rectangular case body made of, and a case cap coupled to the open top of the case body and including an electrode terminal,

A safety plate is formed on the case body when broken inside the battery when the high pressure is generated, the safety plate is made of notched grooves of the line,

The notch grooves include a first notch groove formed at a vertical central axis portion on both sides of the case body, and at least one second notch groove branched at at least one position of the first notch groove.

Therefore, the safety plate of the rectangular secondary battery according to the present invention, the first notch groove formed in the vertical central axis portion on both sides of the case body, and at least one second branch branched at at least one position of the first notch groove. Since the notch grooves are formed of the notch grooves, it is possible to prevent unnecessary tearing of the safety plate and to efficiently eject the gas after the operation of the safety plate.

For reference, both sides of the case body in the present specification means the front or rear of the case body.

As one preferred embodiment, the second notch groove may have a structure branched at an end portion of the first notch groove. Therefore, the breaking stress of the first notched groove can be dispersed by the second notched groove at both end portions thereof, thereby preventing the first notched groove from being torn unnecessarily.

In the above structure, the second notch groove may be branched from the deflected position to the end direction in the range of 0.5L or less with respect to _a distance (L _a) to the end portion from the central axis of the first notched groove, preferably 0.01 It may be in the range of L _a to 0.3L _a .

In the present specification, "the second notched groove is branched from the first notched groove" means not only a case where the two notched grooves are formed continuously, but also a range in which breaking energy (break stress) as described above can be dispersed. This includes all cases that are spaced from. Accordingly, the second notch groove may be a structure that is continuous from the first notch groove or spaced apart from the first notch groove.

In the latter structure, the second notch groove has a size of 0.2L _b or less, for example, 0.05L _b , based on a straight line distance L _b of both ends of the first notch groove. It may be a structure spaced apart from the first notch groove to the size of 0.2L _b .

Specifically, when the portion closest to the first notched groove in the second notched groove exceeds 0.2L _b based on the straight line distance L _b of both ends of the first notched groove, desired dispersion of breaking energy can be achieved. It is not desirable because it is not. On the other hand, the lower limit of the separation distance is not particularly limited. If the second notch groove is not substantially spaced apart from the first notch groove, the second notch groove branches in a continuous shape to the first notch groove as defined above. This is because the structure is made.

As another example, the second notch groove may have a structure branched at one or both ends of the first notch groove, and may be selectively used according to a desired breaking pressure condition.

Meanwhile, the average residual thickness of the second notch groove (the thickness after subtracting the depth of the notch groove from the thickness of the case body) may be the same or smaller than the average residual thickness of the first notch groove. Is more preferable in terms of preventing tearing of the case by offsetting the breaking energy.

As another example, the second notch groove may be curved or straight, depending on the desired breaking pressure. This desired breaking pressure may of course vary with product specifications.

In one preferred embodiment, the case body has a thickness of 0.4 mm or less, and the first notched groove is formed on the case body exhibiting a stress distribution of 40% or less based on the maximum stress S _MAX of the case at high pressure. It can be a structure.

In this way, the first notch groove is formed in a relatively small portion where the stress value is 40% or less in the stress distribution of the case main body, thereby preventing the notch groove from being easily broken even at a low pressure. The provision of pressure and the formation of deep notches are possible.

In another example, the first notch groove is formed in a structure in which the remaining thickness of the case body (the thickness after subtracting the depth of the notch groove from the thickness of the case body) becomes thinner from both ends to the center portion in the longitudinal direction. The notch groove exhibits high operating reliability, and gas is quickly discharged to the outside of the battery by the rupture of the uniform notch groove, thereby ensuring the safety of the battery.

On the other hand, according to the large area of the case due to the high capacity and processing into a thin material, the thickness of the case body to which the present invention is applied may preferably be in the range of 0.2 to 0.4 mm. Thus, the first notch groove and the second notch groove of the specific position and shape may achieve a reliable rupture at an appropriate threshold, although the case body is thinner than the general case body.

In another example, the internal pressure of the battery in which the safety plate is broken may be a pressure exceeding three times the internal pressure of the battery under normal conditions, where the normal condition means a state of atmospheric pressure (1 atm) to 2 atm. .

As mentioned above, the first notch groove may be a structure formed on the case body exhibiting a stress distribution of 40% or less based on the maximum stress S _MAX of the case in the high pressure state as described above.

The stress distribution may be variously changed by the shape, structure, and the like of the battery case, and the stress distribution shown in a general rectangular battery is shown in FIG. 8.

The inventors have confirmed that when the first notch groove is formed on the case body exhibiting a stress distribution exceeding 40% based on the S _MAX of the case, the notch groove is easily broken even at low pressure. . As a result, by satisfying the above conditions, higher pressure than in the case where the first notch groove is formed on the case body showing a high stress distribution, that is, a stress distribution exceeding 40% based on S _MAX as in the prior art, It can be broken at.

The first notch groove may be a structure that is formed on the case body preferably showing a stress distribution of 10 to 40%, more preferably 25 to 35% of S _MAX .

Therefore, the stress value in the stress distribution of the case main body is formed at a relatively small portion, whereby the first notch groove can be easily prevented from breaking even at low pressure, providing a high breaking pressure and forming a deep notch. This is possible.

The first notch groove may be preferably formed at a vertical central axis portion on both sides of the case body, and more preferably, at a central position of 1/4 to 1/2 size based on the left and right widths of the case body. It may be formed.

When the position of the first notch groove is out of the above range, it may be difficult to expect breakage of the first notch groove and gas discharge at high pressure, and the first notch groove may be broken even at a small pressure, thereby ensuring high safety and Not preferred in assembly processability.

According to an experiment conducted by the present inventors, the first notch groove has a constant pressure rise as described above, so that the first notch groove may be uniformly ruptured as described above. It was confirmed that the discharge can improve the stability of the battery as a result.

The first notch groove may be formed on the case main body of a space corresponding to the upper end of the case main body and the upper end of the electrode assembly mounted inside the case main body, while satisfying the range of the formation position. Can be. In one specific example, the first notch groove is close to the upper opening of the case body, and corresponds to a distance between the upper opening and a maximum of 5 mm in the direction of the electrode assembly from the upper end of the anode of the electrode assembly mounted inside the case body. It may be formed on the case body of the space. The first notch groove formed at such a position may be located at the upper portion of the surplus space inside the case, specifically, the electrode assembly mounting portion, to facilitate gas discharge and minimize damage of the electrode assembly.

In particular, the first notch groove according to the present invention is formed in an arc shape, thereby preventing the gas discharge from being excessively biased in any part of the notch groove, thereby minimizing the pressure deviation when the notch groove is broken, and the thin case body With respect to the strength of the case itself can be secured.

The arc shape of the first notch groove may preferably have a radius of curvature of 1/3 to 1.5 times the vertical length of the case body.

If the radius is too small, the curvature becomes large and the width of the arc shape becomes relatively small. On the contrary, if the radius is too large, the first notch groove may be hardly broken even if a high pressure occurs, which is not preferable.

Further, if the position and curvature of the first notch groove do not deviate from the above range, the first notch groove may be an upward arc shape in which the center of curvature of the arc is located at the top, or a downward arc shape in which the center of curvature of the arc is located at the bottom thereof. It may be formed as.

On the other hand, according to the inventors confirmed experimentally, when the residual thickness of the first notch groove is constant, even if the case body is formed in an arc shape in a relatively small stress portion of the case body, the effective first notch groove rupture Was not suitable for.

That is, in the case where the first notched groove is to be formed with a constant residual thickness, it is very difficult to form a uniform residual thickness, so that the site where the pressure is concentrated is set at an arbitrary position, whereby the operation reliability is inferior and even under low pressure. Problems such as the appearance of the deformation of the case appeared. Accordingly, it was confirmed that the stress value and the remaining thickness of the case body are closely related to the rupture of the first notch groove and the gas discharge.

In one preferred example, the average value of the remaining thickness may be determined in the range of 40 to 70% based on the thickness of the body case. This is determined as a range capable of providing an optimal state in consideration of various factors as described above.

In addition, the minimum remaining thickness of the center portion of the first notch groove may be 20 to 50% size based on the thickness of the case body. When the depth is 20% or less, the first notch groove may be easily ruptured even under a small pressure. When the depth is 50% or more, as described above, the thickness of the central portion of the first notch groove and both ends of the first notch groove may be desired. It is not preferable because the operation reliability can be lowered because there is no difference in degree.

In addition, the remaining thickness may have a structure that is sequentially thinned from both ends of the first notch groove toward the center portion. Here, 'sequentially' means gradually thinner in stages. Therefore, it is possible to prevent the pressure from concentrating only on a specific portion and to minimize the pressure deviation when the first notch groove is broken.

The remaining thickness of the center portion of the first notch groove is not particularly limited as long as the thickness of the center portion of the first notch groove is thinner than the remaining thickness of both ends, so that the thickness of the first notch groove is easily broken. It can be formed in 70% size.

As described above, it was confirmed by experiment that the rectangular battery having the first notch grooves having a structure in which the remaining thickness becomes thinner from the both ends toward the portion adjacent to the center portion can exhibit effective operation reliability.

The first notch groove and the second notch groove may be formed by various methods, and preferably, may be formed by rolling using a separate punch. In some cases, a method of scraping off the surface of the case using a predetermined tool may be possible.

The vertical cross-section of the first notch groove and the second notch groove is not particularly limited as long as it can easily break the first notch groove and the second notch groove when internal pressure is generated, and may be, for example, a downward wedge or trapezoid. have. In the case of the downward wedge shape, the fracture occurs due to a crack in the upper end of the first notch groove and the second notch groove, and in the case of the trapezoid, the fracture occurs due to the shear stress while the short side is extended. As a result, uniform and immediate breakage of the first notch groove and the second notch groove can be induced to ensure the safety of the battery.

In some cases, the first notch groove may have a vertical cross section of a downward wedge shape, and the second notch groove may have a trapezoidal vertical cross section. On the contrary, the first notch groove may have a vertical cross section of a trapezoid shape. The notch groove may be a structure having a vertical cross section of a downward wedge shape.

The electrode assembly may not only have a jelly-roll (wound) structure, but also a stacked structure or a stack / foldable structure. Among them, the jelly-roll may be easily manufactured and has a high energy density per weight. Of course, it is not limited.

The secondary battery having such a structure is more preferably a lithium secondary battery.

On the other hand, the notch grooves have a structure in which at least a portion of the notch grooves is located within an area of [(length of the case body (L)-an anode width (W) of the jelly-roll with respect to the length direction of the case) X 2]). Can be. In addition, preferably 50% or less of the notched groove may be located within a specific area of the case body.

Therefore, when the high pressure gas is ejected through the notch grooves, the electrode may block the notch grooves by the fluid flow due to the high pressure, so that the notch grooves can be prevented from being blocked when the notch grooves are located at the specific part defined above. have.

As described above, the rectangular secondary battery according to the present invention has a first notch groove formed in the vertical central axis portion on both sides of the case body, and at least one second branch branched at at least one position of the first notch groove. By constructing a notch groove, it is possible to prevent unnecessary tearing of the safety plate, to efficiently eject gas after the operation of the safety plate, and to effectively control the pressure.

In addition, by forming the first notch groove and the second notch groove of a specific structure in a portion where the stress value is relatively small in the side of the battery case, and at the same time by forming the first notch groove and the second notch groove of a specific shape, Under the conditions, breakage of the first notch groove and the second notch groove occurs reliably, and as a result, safety can be improved.

1 is a schematic diagram of a rectangular secondary battery including a conventional notch groove;
2 is a schematic view of a prismatic secondary battery used in the present invention;
3 is a schematic diagram of a rectangular secondary battery including notched grooves according to one embodiment of the present invention;
4 is a partial front view of a case body including the notches of FIG. 3;
5 and 6 are partial front views of a case body including notched grooves according to another embodiment of the present invention;
FIG. 7 is a photograph showing a stress distribution of the rectangular secondary battery of FIG. 3; FIG.
8 is a photograph showing a stress distribution of a rectangular secondary battery including notched grooves according to another embodiment of the present invention;
9 is a photograph showing a vertical cross section of the first notch groove of FIG. 3;
FIG. 10 is a schematic diagram illustrating a process of winding up a jelly-roll type electrode assembly mounted on the battery case of FIG. 2.

Hereinafter, the present invention will be described in detail with reference to the drawings, but the scope of the present invention is not limited thereto.

Figure 2 shows the structure of a conventional rectangular secondary battery according to one embodiment that can be used in the present invention.

Referring to FIG. 2, the rectangular secondary battery 100 is a inside of a rectangular battery case 200 serving as a negative electrode terminal, and has a jelly-roll structure having a structure in which a sheet-shaped positive electrode and a negative electrode are wound with a separator interposed therebetween. The electrode assembly (see FIG. 10) is inserted.

The battery case 200 has an open upper end and a rectangular case body 210 made of a metal material, and a case cap 220 in which an anode terminal 400 is installed at an open upper end of the case body 210. It consists of a structure. The negative electrode terminal may be the case body 210 or the case cap 220 itself electrically insulated from the positive electrode terminal 400.

In order to manufacture such a rectangular secondary battery 100, first, the electrode assembly is inserted into the case body 210, the case cap 220 is seated in the opening of the case body 210, and then its adhesive surface. The site is sealed by laser welding. Then, the electrolyte is injected into the battery case 200, the electrolyte is injected through the injection port 230 formed on one side of the case cap 220. In detail, after the electrolyte is injected into the injection hole 230, a ball member made of aluminum or the like is inserted into the injection hole 230, and a separate metal sheet is seated on the ball member 600 to completely block the injection hole 230. Seal through laser welding in the state. The sealing method of the injection hole 230 is not limited to the above, various other methods may be possible.

The notched groove according to the present invention is formed on the front side 211 or the rear side (not shown) of the case body of the rectangular secondary battery 100, the thickness of the case body 210 is about 0.3 mm.

3 is a schematic view of a rectangular secondary battery including notched grooves according to one embodiment of the present invention, and FIG. 4 is a partial front view of the case body including the notched grooves of FIG. 3. . For reference, in FIGS. 3 to 6, the size of the safety plate is relatively large compared to the case body for convenience of understanding.

Referring to these drawings, the rectangular secondary battery has a safety plate formed on the case body 40 that breaks when a high pressure is generated in the battery, and the safety plate is formed of linear notch grooves 60 and 62.

Specifically, the notch grooves 60 and 62 are arc-shaped first notch grooves 60 and first notch grooves 60 formed at portions of the vertical central axis 3 on both sides of the case body 40. It consists of two straight second notched grooves 62 branched at both end portions of the.

Further, the second notched groove (62) is branched from the distance (L _a) to the end portion direction in the range of 0.4L for _a deflected position to the end portion from the central axis (3) of the first notched groove 60, and And the first notch groove 60 are continuous.

The first notch groove 60 has an arc shape, and the arc shape has a center position of about 1/2 size and an upper and lower length L of the case body 40 based on the left and right widths W of the case body 40. In the top position of about 3/10 size. In addition, the arc-shaped curvature consists of a curvature formed with a radius R of about 3/10 based on the upper and lower lengths L of the case body 40. By this arc shape, the first notch groove 60 can maintain a constant mechanical strength while making gas discharge uniform.

In addition, the first notch groove 60 has a gradient in the remaining thickness, which is the thickness after subtracting the depth of the first notch groove 60 from the thickness of the case body 40 in a vertical cross section, The remaining thickness of the notch groove located in the central portion 3 has a size of 40% based on the thickness of the case body 40.

The remaining thickness 80 is formed in a structure in which the remaining thickness 80 is gradually thinned from both ends 1 and 5 toward the central portion 3 based on the total length l of the first notch groove 60.

On the other hand, the notch grooves 60 and 62 are areas of [(length of case body L-anode width W of jelly-roll relative to case length direction) X 2] from the top of case body 40. (A) They are all located within. In addition, the jelly roll has a structure in which the cathode 32, the separator 36, and the anode 34 are wound.

5 and 6 schematically show partial front views of a case body including notched grooves according to another embodiment of the present invention.

Referring to these drawings, the safety plate of FIG. 5 is formed in the same structure as the safety plate of FIG. 4 except that the second notch grooves 64 and 68 are spaced apart from the first notch groove 66.

In addition, each of the second notched grooves 64 and 68 has a size of 0.07L _b based on a straight line distance L _b of both ends of the first notched groove 66, the portion closest to the first notched groove 66. The thickness of the second notch grooves 64 and 68 after subtracting the depth of the first notch grooves 66 from the first notch grooves 66 and subtracting the depth of the second notch grooves 64 and 68 from the thickness of the case body 40. It is formed equal to the remaining thickness.

Next, the safety plate of FIG. 6 is the same as the structure of FIG. 4 except that the arc-shaped second notch grooves 61 and 63 are spaced apart from both ends of the first notch groove 66. Will be omitted.

FIG. 7 is a photograph showing a stress distribution of the rectangular secondary battery of FIG. 3, and FIG. 8 is a photograph showing a stress distribution of a rectangular secondary battery including notched grooves according to another embodiment of the present invention. It is.

First, referring to FIG. 7 together with FIG. 3, the first notch groove 60 and the second notch grooves 62 of the case body 40 are cuttable members for discharging high pressure gas, and the maximum of the case The center of curvature of the arc which is the 1st notch groove 63 is formed in the upward arc shape which is located in the upper part in the site | part of the case which shows the stress distribution of about 25 to 35% based on the stress S _MAX .

As shown in FIG. 7, the stress distribution has a tensile stress that appears in each region when a constant pressure is applied, and a high brightness portion (light color portion) is a portion having a relatively high stress as a maximum stress (S _MAX ). The site of distribution, the site of low brightness (dark site) is a site of relatively low stress, and means the site of minimum stress (S _MIN ) distribution.

In addition, although the circular arc may be an upward circular arc shape in which the center of curvature of a circular arc is located in the upper part like FIG. 7, on the contrary, as shown in FIG. 8, the circular arc may be a downward circular arc shape in which the center of curvature of a circular arc is located in the lower part. .

FIG. 9 is a photograph showing a vertical section of the first notch groove of FIG. 3.

Referring to FIG. 9, the vertical cross section of the first notch groove 60 is formed in a downward wedge shape, and the average value of the remaining thickness 80 is about 60% based on the thickness T of the case body 40. It is formed in depth.

Therefore, when the internal pressure gradually rises to generate a pressure not less than twice the normal battery internal pressure, a crack occurs in the first notch groove 61 and is easily ruptured, thereby quickly discharging gas to the outside of the battery, and as a result, the stability of the battery. Can improve.

FIG. 10 is a schematic diagram illustrating a process of winding up a jelly-roll type electrode assembly mounted on the battery case of FIG. 2.

Referring to FIG. 10, the jelly-roll 10a may include the negative electrode tab 31 and the positive electrode tab 33 on the uncoated portion 36 to which the electrode active material is not coated at the left ends of the negative electrode 32 and the positive electrode 34. After attaching vertically, the cathode 32 and the anode 34 are manufactured by winding from the left end to the right end direction.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims (26)

An electrode assembly composed of a positive electrode, a negative electrode, and a separator is a rectangular secondary battery sealed in a rectangular battery case, wherein the battery case is open at the top and is formed of a rectangular case body made of a metallic material, and coupled to an open upper end of the case body. It consists of a case cap containing an electrode terminal,
A safety plate is formed on the case body when broken inside the battery when the high pressure is generated, the safety plate is made of notched grooves of the line,
The notch grooves may include a first notch groove formed at a vertical central axis portion on both sides of the case body, and at least one second notch groove branched at at least one position of the first notch groove. Square secondary battery. The rectangular secondary battery according to claim 1, wherein the second notch groove is branched at an end portion of the first notch groove. The method of claim 2, wherein the second notch groove, characterized in that it is branched in the deflected position as the end direction in the range of 0.5L or less with respect to _a distance (L _a) to the end portion from the central axis of the first notched groove Square secondary battery. The rectangular secondary battery of claim 1, wherein the second notch groove is continuous from the first notch groove. The rectangular secondary battery of claim 1, wherein the second notch groove is spaced apart from the first notch groove. The method of claim 5, wherein the second notch groove has a first portion closest to the straight line distance between opposite ends of the first notched groove in the notch groove (L _b) of spaced-apart from the first notch groove into a size of less than 0.2L _b standard A rectangular secondary battery, characterized in that. The rectangular secondary battery of claim 1, wherein the second notch groove is branched at one side or both ends of the first notch groove. The method of claim 1, wherein the average residual thickness of the second notch groove (the average thickness after subtracting the depth of the notch groove from the thickness of the case body) is equal to or smaller than the average residual thickness of the first notch groove. Square secondary battery. The rectangular secondary battery of claim 1, wherein the second notch grooves are curved or straight. According to claim 1, wherein the thickness of the case body is 0.4 mm or less, the first notched groove is formed on the case body showing a stress distribution of 40% or less based on the maximum stress (S _MAX ) of the case in the high pressure state Square secondary battery characterized in that there is. The method of claim 1, wherein the first notch groove has a structure in which the remaining thickness of the case body (the thickness after subtracting the depth of the notch groove from the thickness of the case body) becomes thinner from both ends to the central portion in the longitudinal direction. Square secondary battery characterized by. The rectangular secondary battery of claim 10, wherein a thickness of the case body is in a range of 0.2 to 0.4 mm. The rectangular secondary battery according to claim 1, wherein the high pressure inside the battery in which the safety plate is broken is at least twice the pressure of the battery under normal conditions. The rectangular secondary battery according to claim 10, wherein the first notch groove is formed on a case body exhibiting a stress distribution of 10 to 40% of the maximum stress S _MAX . 2. The square secondary according to claim 1, wherein the first notch groove is formed on a case body in a space corresponding between an upper end opening of the case body and an upper end of an electrode assembly mounted inside the case body. battery. The rectangular secondary battery of claim 1, wherein the first notch groove has an arc shape. The rectangular secondary battery of claim 16, wherein the first notch groove has an upward arc shape having a center of curvature of an arc or a downward arc shape having a center of curvature of a circular arc. The rectangular rechargeable battery of claim 11, wherein the average thickness of the remaining thickness is 40 to 70% based on the thickness of the body case. 12. The rectangular rechargeable battery of claim 11, wherein a minimum remaining thickness of the center portion of the first notch groove is 20 to 50% in size based on the thickness of the case body. 12. The rectangular rechargeable battery of claim 11, wherein the remaining thickness is sequentially thinned from both ends of the first notch groove toward the center portion. The rectangular secondary battery of claim 11, wherein the remaining thickness of the center portion of the first notch groove is 40 to 70% of the vent thickness of both ends. The rectangular secondary battery of claim 1, wherein the vertical cross sections of the first notch groove and the second notch groove have a downward wedge shape. The rectangular secondary battery of claim 1, wherein the vertical cross sections of the first notch groove and the second notch groove have a trapezoidal shape. The prismatic secondary battery of claim 1, wherein the electrode assembly is a jelly roll. The prismatic secondary battery according to claim 1, wherein the secondary battery is a lithium secondary battery. The method of claim 1, wherein the notched grooves are at least partially within an area of [(length of case body (L) minus width of jelly-roll in the length direction of case) X 2] from an upper end of the case body. Square secondary battery, characterized in that located.

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