Secondary battery

Abstract

The present invention relates to a secondary battery in which the upper surface and lower surface of an electrode assembly have surface roughness, and thus the surface roughness of a surface in contact with the upper surface and lower surface of the electrode assembly can be increased in a current collector plate to reduce contact resistance. A secondary battery according to one embodiment of the present invention comprises: an electrode assembly including a first electrode plate, a separator, and a second electrode plate; a case accommodating the electrode assembly and having an open lower end part; a terminal passing through and coupled to an upper surface part of the case; a first current collector plate interposed between the upper surface of the electrode assembly and the case and electrically connecting the first electrode plate and the terminal; and a cap plate sealing the lower end part of the case, wherein the surface roughness of the lower surface of the first current collector plate is greater than the surface roughness of the upper surface of the first current collector plate.

Description

secondary battery

[0001] The present disclosure relates to a secondary battery.

[0002] Secondary batteries are power storage systems that offer superior energy density by converting electrical energy into chemical energy and storing it. Compared to non-rechargeable primary batteries, secondary batteries are rechargeable and are widely used in IT devices such as smartphones, cellphones, laptops, and tablet PCs. Recently, interest in electric vehicles has grown to prevent environmental pollution, leading to the adoption of high-capacity secondary batteries in electric vehicles. These secondary batteries require high density, high output, and stability.

[0003] The above-described information disclosed in the background technology of this invention is only intended to improve understanding of the background of the present invention, and therefore may include information that does not constitute prior art.

[0004] Since the upper and lower surfaces of the electrode assembly of the present invention have surface roughness, the surface roughness of the surface in contact with the upper and lower surfaces of the electrode assembly on the current collector plate can be increased to reduce contact resistance.

[0005] In addition, the present invention can improve the increase in resistance caused by the reduction of the electron movement path in the horizontal direction due to the reduction in the thickness of the current collector plate to increase the capacity of the secondary battery by reducing the contact resistance with the electrode assembly through the increase in surface roughness.

[0006] However, the technical problems to be solved by the present invention are not limited to the problems described above, and other problems not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

[0007] According to one embodiment of the present invention for solving the above technical problem, a secondary battery includes an electrode assembly having a first electrode plate, a separator, and a second electrode plate, a case in which the electrode assembly is accommodated and has an open lower portion, a terminal coupled by penetrating an upper surface of the case, a first current collector plate interposed between an upper surface of the electrode assembly and the case and electrically connecting the first electrode plate and the terminal, and a cap plate sealing the lower portion of the case, wherein the first current collector plate may have a surface roughness of a lower surface greater than a surface roughness of an upper surface.

[0008] The first electrode plate further includes a plurality of first electrode tabs that protrude upward from the upper surface of the electrode assembly and are bent and pressed in the winding axis direction of the electrode assembly.

[0009] The second electrode plate further includes a plurality of second electrode tabs that protrude downwardly and upwardly from the lower surface of the electrode assembly and are bent and pressed in the winding axis direction of the electrode assembly, and the electrode assembly may have a plurality of first electrode tabs exposed on the upper surface and a plurality of second electrode tabs exposed on the lower surface.

[0010] The above first collector plate is a flat circular plate and can be welded to the upper surface of the electrode assembly.

[0011] The first collector plate may include a terminal connection portion that contacts and is electrically connected to the lower surface of the terminal, and a plate connection portion that contacts and is electrically connected to the first electrode tab exposed to the upper surface of the electrode assembly and is located on the outside of the terminal connection portion.

[0012] The above first collector plate may further include a fuse portion positioned between the terminal connection portion and the electrode plate connection portion.

[0013] The above fuse portion may include a fuse hole formed along a portion of the outer periphery of the terminal connection portion, and a plate connection portion connecting the terminal connection portion and the plate connection portion.

[0014] The surface roughness of the electrode plate connection portion on the lower surface of the first collector plate may be greater than or equal to that of other areas.

[0015] The electrode assembly may further include a second collector plate in the shape of a circular plate corresponding to the lower surface of the electrode assembly, and in contact with and electrically connected to the second electrode tab exposed to the lower surface of the electrode assembly.

[0016] The surface roughness of the upper surface of the above second collector plate may be greater than the surface roughness of the lower surface.

[0017] The second collector plate may include a circular flat portion in contact with the lower surface of the electrode assembly and an extension portion extending downward from an edge of the flat portion.

[0018] The surface roughness of the flat portion of the second collector plate may be greater than or equal to that of the extended portion.

[0019] The case may include a beading portion sunken into the interior of the case on the upper portion of the cap plate, and a crimping portion bent inwardly at the lower portion of the case to secure the cap plate.

[0020] It further includes a cap gasket interposed between the cap plate and the beading portion and between the cap plate and the crimping portion, and the cap plate may be non-polar.

[0021] The extension portion of the second collector plate may be interposed between the cap gasket and the beading portion.

[0022] The surface roughness of the lower surface of the above electrode assembly may be greater than the surface roughness of the upper surface.

[0023] The surface roughness of the upper surface of the second collector plate may be greater than the surface roughness of the lower surface of the first collector plate.

[0024] The above plurality of first electrode tabs may be arranged in a plurality of places spaced apart from each other along the winding direction, in the first bare portion where no electrode active material is applied on the first electrode plate.

[0025] The above plurality of first electrode tabs may not be provided at the winding tip and winding end of the first electrode plate.

[0026] The above fuse section includes one or more fuse holes, and the fuse holes can be positioned concentrically with respect to the center of the first collector plate.

[0027] The above fuse part further includes protruding holes formed at both ends of the fuse hole, and the protruding holes can protrude in a direction approaching each other.

[0028] According to the present invention, since the upper and lower surfaces of the electrode assembly have surface roughness, a secondary battery can be provided in which the surface roughness of the surface in contact with the upper and lower surfaces of the electrode assembly on the current collector plate is increased to reduce contact resistance.

[0029] In addition, according to the present invention, a secondary battery can be provided in which the thickness of the current collector plate is reduced to increase the capacity of the secondary battery, thereby improving the increase in resistance caused by the reduction of the electron movement path in the horizontal direction by reducing the contact resistance with the electrode assembly through increasing the surface roughness.

[0030] However, the effects that can be obtained through the present invention are not limited to the effects described above, and other technical effects that are not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

[0031] The following drawings attached to this specification illustrate preferred embodiments of the present invention, and together with the detailed description of the invention described below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0032] Figure 1 is a perspective view illustrating a secondary battery according to the present invention.

[0033] Figure 2 is a cross-sectional view of the secondary battery illustrated in Figure 1.

[0034] Figure 3 is a perspective view illustrating an electrode assembly in the secondary battery of Figure 1.

[0035] Figure 4 is a cross-sectional view of the electrode assembly of Figure 3.

[0036] Figure 5 is an exploded perspective view of the secondary battery of Figure 1, with the electrode assembly and the collector plate disassembled.

[0037] Figure 6 is a cross-sectional view of Figure 5.

[0038] Figure 7 is an enlarged view of part A of Figure 2.

[0039] Figure 8 is a plan view showing four areas randomly selected from the upper and lower surfaces of the electrode assembly in Figure 5.

[0040] Figures 9a to 9c are bottom views showing a roughened area on the lower surface of the first collector plate in the secondary battery of Figure 1.

[0041] FIGS. 10 to 13 are plan views illustrating various examples of the first collector plate in the secondary batteries illustrated in FIGS. 1 to 6.

[0042] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, terms or words used in this specification and claims should not be interpreted as limited to their typical or dictionary meanings, and should be interpreted with meanings and concepts that conform to the technical spirit of the present invention based on the principle that the inventor can appropriately define the concept of a term to best explain his or her own invention. Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are only some of the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention. Therefore, it should be understood that various equivalents and modified examples may exist as substitutes for them at the time of filing this application.

[0043] Additionally, when used herein, the terms "comprise", "include" and / or "comprising", "including" specify the presence of stated features, numbers, steps, operations, elements, elements and / or groups thereof, but do not preclude the presence or addition of one or more other features, numbers, operations, elements, elements and / or groups thereof.

[0044] Additionally, to facilitate understanding of the invention, the attached drawings are not drawn to scale and some components may be exaggerated in size. Furthermore, identical components may be assigned the same reference numbers in different embodiments.

[0045] The statement that two compared objects are "identical" means "substantially identical." Therefore, "substantially identical" may include deviations considered low in the art, such as deviations of less than 5%. Furthermore, uniformity of a parameter over a given region may imply uniformity on average.

[0046] Although the terms "first" and "second" are used to describe various components, these components are not limited by these terms. These terms are used solely to distinguish one component from another, and unless otherwise specified, a "first" component may also be a "second" component.

[0047] Throughout the specification, unless otherwise specifically stated, each element may be singular or plural.

[0048] Any configuration being placed "on (or under)" or "above (or below)" a component may mean not only that any configuration is placed in contact with the upper surface (or lower surface) of said component, but also that other configurations may intervene between said component and any configuration placed on (or below) said component.

[0049] Additionally, when it is described that a component is "connected," "coupled," or "connected" to another component, it should be understood that the components may be directly connected or connected to each other, but that other components may also be "interposed" between the components, or that each component may be "connected," "coupled," or "connected" through another component. Furthermore, when it is said that a part is electrically coupled to another part, this includes not only cases where they are directly connected, but also cases where they are connected with another element in between.

[0050] When reference is made throughout the specification to "A and / or B," this means A, B, or A and B, unless otherwise stated. In other words, "and / or" includes all or any combination of the listed items. When reference is made to "C through D," this means C or more and D or less, unless otherwise stated.

[0051] The terminology used herein is for the purpose of describing embodiments of the present disclosure and is not intended to be limiting of the present disclosure.

[0052] FIG. 1 is a perspective view illustrating a secondary battery according to the present invention, and FIG. 2 is a cross-sectional view of the secondary battery illustrated in FIG. 1.

[0053] As illustrated in FIGS. 1 and 2, the secondary battery (100) may include an electrode assembly (110), a case (120) that accommodates the electrode assembly (110) and an electrolyte therein, a terminal (150) coupled to a terminal hole (122a) provided at one end of the case (120), for example, an upper end, and a cap plate (160) that seals the other end of the case (110), for example, a lower end. In some examples, the secondary battery (100) may have a terminal hole provided on the cap plate (160), so that the terminal (150) may be coupled to the cap plate (160).

[0054] The secondary battery (100) may further include a first collector plate (130) that electrically connects the first electrode (111) of the electrode assembly (110) and the terminal (150) and a second collector plate (140) that electrically connects the second electrode (112) of the electrode assembly (110) and the case (120).

[0055] The electrode assembly (110) may include a separator (113), a first electrode plate (111) and a second electrode plate (112) positioned with the separator (113) between them, and may be wound in a jelly-roll shape.

[0056] The first electrode plate (111) includes a first substrate and a first active material layer positioned on the first substrate. A first electrode tab (111b) may extend outward from a first electrode non-conductive portion (111a) of the first substrate where the first active material layer is not positioned, and the first electrode tab (111b) may be electrically connected to a terminal (150) via the first current collector plate (130).

[0057] The second electrode plate (112) includes a second substrate and a second active material layer positioned on the second substrate. A second electrode tab (112b) may extend outward from a second electrode non-conductive portion (112a) of the second substrate where the second active material layer is not positioned, and the second electrode tab (112b) may be electrically connected to the case (120) via the second current collector plate (140).

[0058] The first electrode tab (111b) and the second electrode tab (112b) may be positioned in opposite directions in the electrode assembly (110). The first electrode plate (111) may function as an anode. In this case, the first substrate may be composed of, for example, aluminum foil, and the first active material layer may include, for example, a transition metal oxide. The second electrode plate (112) may function as an anode. In this case, the second substrate may be composed of, for example, copper foil or nickel foil, and the second active material layer may include, for example, graphite.

[0059] The separator (113) functions to prevent short circuiting between the first electrode (111) and the second electrode (112) while allowing the movement of lithium ions. The separator (113) may be composed of, for example, a polyethylene film, a polypropylene film, a polyethylene-polypropylene film, etc.

[0060] The case (120) accommodates the electrode assembly (110) and the electrolyte, and together with the terminal (150) and the cap plate (160), forms the outer shape of the secondary battery (100). The case (120) may include a body portion (121) having a roughly cylindrical shape, and an upper portion (122) connected to one side of the body portion (121). An inwardly deformed beading portion (123) may be positioned in the body portion (121), and an inwardly bent crimping portion (124) may be positioned at an open end of the body portion (121). The upper portion (122) may be provided with a terminal hole (122a) penetrating through the center. The upper portion (122) may be coupled by having a terminal (150) inserted into the terminal hole (122a). A terminal gasket (125) for sealing and electrical insulation may be further interposed between the terminal hole (122a) and the terminal (150).

[0061] The beading portion (123) can prevent the electrode assembly (110) from moving inside the case (120) and facilitate the settling of the cap gasket (127) and the cap plate (160). The crimping portion (124) can firmly fix the cap plate (160) by pressing the edge of the cap plate (160) through the cap gasket (127). The case (123) can be made of, for example, nickel-plated iron.

[0062] The first collector plate (130) may have one surface that contacts and is coupled to the first electrode tab (111b) of the electrode assembly (110), and the other surface that contacts and is coupled to the terminal (150). The first collector plate (130) may be welded to the first electrode tab (111b) of the electrode assembly (110) and electrically connected. The first collector plate (130) may be welded and electrically connected while the other surface is in contact with the terminal (150).

[0063] The second collector plate (140) may have a central portion (141) that contacts and is coupled to the second electrode tab (112b) of the electrode assembly (110), and an edge portion (142) that contacts and is coupled to the body portion (121) of the case (120). The second collector plate (140) may be electrically connected by welding the central portion (141) to the second electrode tab (112b) of the electrode assembly (110). The second collector plate (140) may be electrically connected by welding the edge portion (142) in contact with the beading portion (123) of the case (120).

[0064] The terminal (150) may include a head (151) positioned on the outside of the case (120), and a fastening portion (152) extending inwardly from the center of the head (151) toward the inside of the case (120). The terminal (150) may be fixed and sealed by having the fastening portion (152) coupled to a terminal hole (122a) together with a terminal gasket (125) so as to pressurize the upper portion (122) of the case (120) from the inside through the terminal gasket (125). The terminal (150) may further be provided with a terminal groove (153) extending from the center of the head (151) toward the fastening portion (152). The terminal (150) may be welded to the first collector plate (130) from the outside through the terminal groove (153). The terminal (150) can be electrically connected to the first electrode (111) of the electrode assembly (110) through the first collector plate (130). The terminal (150) and the case (120) can have different polarities.

[0065] The cap plate (160) can be secured to the inside of the crimping portion (124) via the cap gasket (127) to seal the case (120). The cap plate (160) can include a safety vent (165) that is thinner than other areas due to a notch. When gas is generated due to overcharging or abnormal operation of the secondary battery (100), the safety vent (165) provided in the cap plate (160) can be cut along the notch. The cut safety vent (165) can prevent an explosion of the secondary battery (100) by releasing the gas to the outside.

[0066] Fig. 3 is a perspective view illustrating an electrode assembly in the secondary battery of Fig. 1, and Fig. 4 is a cross-sectional view of the electrode assembly of Fig. 3. In Figs. 3 and 4, the electrode assembly (110) is illustrated before the first electrode tab (111b) protruding upward and the second electrode tab (112b) protruding downward are bent.

[0067] Also, Fig. 5 is a perspective view showing the electrode assembly (110) illustrated in Fig. 3 after the first electrode tab (111b) and the second electrode tab (112b) are bent toward the core. Also, Fig. 5 is an exploded perspective view showing the electrode assembly (110) and the first collector plate (130) and the second collector plate (140) of the secondary battery of Fig. 1, where they are exploded, and Fig. 6 is a cross-sectional view of Fig. 5. Also, Fig. 7 is an enlarged view showing part A of Fig. 2 in an enlarged manner.

[0068] Hereinafter, with reference to FIGS. 3 to 7, the structure and relationship of the electrode assembly (110), the first collector plate (130), and the second collector plate (140) will be described.

[0069] The first electrode plate (111) may be provided with a first electrode non-coated portion (111a) on the upper portion thereof, which is not coated with a first electrode active material. This first electrode non-coated portion (111a) may protrude upward from the electrode assembly (110). In addition, the first electrode non-coated portion (111a) may include a plurality of first electrode tabs (111b). The plurality of first electrode tabs (111b) may be positioned on the upper portion of the first electrode non-coated portion (111a) and may be arranged to be spaced apart from each other in one direction before winding. The plurality of first electrode tabs (111b) may not be provided at the winding leading end and / or the winding ending end. The plurality of first electrode tabs (111b) may be formed on the first electrode non-coated portion (111a) by laser notching, ultrasonic cutting, or punching. The above first electrode tab (111b) may protrude further upward than the second electrode plate (112) and separator (113) in the electrode assembly (110).

[0070] The second electrode plate (112) may be provided with a second electrode non-coated portion (112a) on the lower portion where the second electrode active material is not coated. In addition, the second electrode non-coated portion (112a) may include a plurality of second electrode tabs (112b). The plurality of second electrode tabs (112b) may be positioned on the lower portion of the second electrode non-coated portion (112a) and may be arranged to be spaced apart from each other in one direction before winding. The plurality of second electrode tabs (112b) may not be provided at the winding leading end and / or the winding ending end. The plurality of second electrode tabs (112b) may be formed on the second electrode non-coated portion (112a) by laser notching, ultrasonic cutting, or punching. A plurality of second electrode tabs (112b) like this may protrude further downward in the electrode assembly (110) compared to the first electrode plate (111) and the separator (113).

[0071] The electrode assembly (110) may have a first electrode tab (111b) that protrudes upward, and a second electrode tab (112b) that protrudes downward. The first electrode tab (111b) and the second electrode tab (112b) may be bent toward the core. That is, a plurality of first electrode tabs (111b) and a plurality of second electrode tabs (112b) may be bent and pressed from the winding end region toward the core. At this time, the first electrode tab (111b) and the second electrode tab (112b) may not be provided in some regions of the winding end so as not to cover the core hole of the electrode assembly (110). The electrode assembly (110) may have surface roughness due to the difference in height between the upper surface (110a) and the lower surface (110b) caused by the bending and compaction of the first electrode tab (111b) and the second electrode tab (112b).

[0072] A first electrode tab (111b) may be positioned on the upper surface (110a) of the electrode assembly (110), and a second electrode tab (112b) may be positioned on the lower surface (110b). Fig. 8 shows four regions arbitrarily selected from the upper surface (110a) and the lower surface (110b) of the electrode assembly (110). Here, the four arbitrarily selected regions are shown as being symmetrical to each other with the core as the center, but any region may be selected as long as it has the same area. However, it is preferable that the four arbitrarily selected regions be regions that come into contact with the first collector plate (130) and the second collector plate (140). In addition, the four arbitrarily selected regions may be regions that are not welded to the first collector plate (130) and the second collector plate (140).

[0073] In addition, the surface roughness data, which is the result of the maximum height (Sz) and the average height (Sa) measured in the first region (a1), the second region (a2), the third region (a3), and the fourth region (a4) of the upper surface (110a) of the electrode assembly (110), and the maximum height (Sz) and the average height (Sa) measured in the first region (b1), the second region (b2), the third region (b3), and the fourth region (b4) of the lower surface (110b), may be as shown in Table 1 below. Here, the maximum height (Sz) is the height from the lowest point to the highest point (peak) within the area of ​​each region, and the average height (Sa) may be the average roughness in the area of ​​each region.

[0074] Here, the surface roughness data for the upper surface (110a) and the lower surface (110b) of the electrode assembly (110) were measured for a total of three electrode assemblies (110), and Table 1 shows the experimental results for the first electrode assembly, Table 2 shows the experimental results for the second electrode assembly, and Table 3 shows the experimental results for the third electrode assembly. Here, the first electrode assembly, the second electrode assembly, and the third electrode assembly may be electrode assemblies having the same structure manufactured through the same process. Hereinafter, the unit may be μm.

[0075] Top surface (110a) SaSz Bottom surface (110b) SaSz First area (a1) 14.895 177.730 First area (b1) 39.596 191.190 Second area (a2) 14.140 127.890 Second area (b2) 20.413 154.590 Third area (a3) ​​12.433 123.550 Third area (b3) 35.470 164.840 Fourth area (a4) 14.658 281.420 Fourth area (b4) 38.03 1217.630 Average 14.03 177.648 Average 33.373 182.063 Standard deviation 0.96 363.583 Standard deviation 7.62 724.493

[0076] Top surface (110a) SaSz Bottom surface (110b) SaSz First area (a1) 13.076 128.230 First area (b1) 21.683 156.060 Second area (a2) 15.564 133.240 Second area (b2) 36.667 231.280 Third area (a3) ​​16.712 158.220 Third area (b3) 18.696 147.390 Fourth area (a4) 36.595 502.330 Fourth area (b4) 36.895 182.140 Average 19.97 1230.505 Average 24.485 179.218 Standard deviation 8.509 157.349 Standard deviation 8.363 32.666

[0077] Top surface (110a) SaSz Bottom surface (110b) SaSz First area (a1) 15.553165.060 First area (b1) 41.026214.340 Second area (a2) 18.525250.980 Second area (b2) 37.204211.560 Third area (a3) ​​13.827141.380 Third area (b3) 29.711156.110 Fourth area (a4) 24.906520.360 Fourth area (b4) 38.648236.500 Average 18.203269.445 Average 36.647204.628 Standard deviation 4.219150.496 Standard deviation 4.23129.632

[0078] Referring to the surface roughness data for the upper surface (110a) of the electrode assembly (110) in Tables 1 to 3, the average height (Sa) measured for each region may be 12 µm to 36 µm, and the maximum height (Sz) may be 123 µm to 520 µm. In addition, referring to the surface roughness data for the lower surface (110b) of the electrode assembly (110), the average height (Sa) measured for each region may be 18 µm to 41 µm, and the maximum height (Sz) may be 147 µm to 236 µm. Referring to the surface roughness data of the electrode assembly (110) in Tables 1 to 3, the upper surface (110a) and the lower surface (110b) of the electrode assembly (110) may have surface roughness due to uneven steps caused by the bending and compaction of the first electrode tab (111b) and the second electrode tab (112b). In addition, the surface roughness of the lower surface (110b) of the electrode assembly (110) may be greater than that of the upper surface (110a). When a flat first collector plate (130) comes into contact with the upper surface (110a) of the electrode assembly (110) having such surface roughness, resistance may increase due to the low contact area. To prevent this, the surface roughness of the lower surface (130b) of the first collector plate (130) that comes into contact with the upper surface (110a) of the electrode assembly (110) can be reduced to reduce the contact resistance between the first collector plate (130) and the first electrode tab (111b) of the electrode assembly (110).

[0079] In addition, when a flat second collector plate (140) comes into contact with the lower surface (110b) of the electrode assembly (110) having a surface roughness, resistance may increase due to the low contact area. To prevent this, the upper surface (140a) of the second collector plate (140) that comes into contact with the lower surface (110b) of the electrode assembly (110) may have a surface roughness, thereby reducing the contact resistance between the second collector plate (140) and the second collector plate (140) of the electrode assembly (110).

[0080] First, the first collector plate (130) may be a circular metal plate having a shape corresponding to the upper surface (110a) of the electrode assembly (110). The planar size of the first collector plate (130) may be equal to or smaller than the size of the upper surface (110a) of the electrode assembly (110). The first collector plate (130) may be fixed and electrically connected to the first electrode tab (111b) of the electrode assembly (110) by welding while the lower surface (130b) is in contact with the upper surface (110a) of the electrode assembly (110). The first collector plate (130) may be fixed and electrically connected to the terminal (150) by welding while the upper surface (130a) is in contact with the lower surface of the terminal (150). The first collector plate (130) serves as a passage for current flow between the first electrode plate (111) of the electrode assembly (110) and the terminal (150). The first collector plate (130) may be welded to the electrode assembly (110), then housed in a case (120), and then welded to the terminal (150).

[0081] The first collector plate (130) may have a greater surface roughness on the lower surface (130b) than on the upper surface (130a). A greater surface roughness here may mean a greater average height and / or maximum height in a plane and / or along a unidirectional line. The first collector plate (130) may increase the surface roughness of the lower surface (130b) through roughening treatment. The roughening treatment may be performed by blasting, polishing, or etching, for example.

[0082] The first collector plate (130) may have a surface roughness of a lower surface (130b) having a maximum height (Ry) of 7 µm to 9 µm and an average height (Ra) of 0.6 µm to 0.9 µm. If the average height of the roughness of the lower surface (130b) of the first collector plate (130) is less than 0.6 µm, the contact area between the first collector plate (130) and the electrode assembly (110) may be reduced, thereby increasing resistance. If the average height of the roughness of the lower surface (130b) of the first collector plate (130) is greater than 0.9 µm or the maximum height is greater than 9 µm, the electron movement path in the horizontal direction of the first collector plate (130) (the plane direction of the first collector plate) may be reduced, thereby increasing resistance. The surface roughness of the lower surface (130b) of the first collector plate (130) can be set and changed according to the surface roughness of the upper surface (110a) of the electrode assembly (110).

[0083] The first collector plate (130) may have a thickness that does not reduce the electron movement path after roughening. For example, the first collector plate (130) may have a thickness of 0.2 mm to 1.5 mm.

[0084] The first collector plate (130) may include a terminal connection portion (131), a plate connection portion (132), and a fuse portion (135). The terminal connection portion (131) is located at the center of the first collector plate (130) and may be formed in an approximately circular shape. The lower surface of the fastening portion (152) of the terminal (150) may be welded to the upper surface of the terminal connection portion (131). The plate connection portion (132) is located on the outer side of the terminal connection portion (131) and may be in contact with and electrically connected to the first electrode tab (111b) of the electrode assembly (110). For example, the first electrode tab (111b) exposed to the upper surface (110a) of the electrode assembly (110) may be welded to the lower surface of the plate connection portion (132).

[0085] The fuse part (135) may be formed between the terminal connection part (131) and the plate connection part (132). The fuse part (135) may include a fuse hole (136) and a plate connection part (137). When a short circuit or overcurrent occurs in the secondary battery (100), the fuse part (135) may melt and cut the plate connection part (137) due to the generated heat, thereby blocking the current flowing in the secondary battery (100).

[0086] The fuse hole (136) is formed in a roughly 'C' shape along a portion of the outer periphery of the terminal connection portion (131), so that both ends of the fuse hole (136) can face each other. The fuse hole (136) can separate the terminal connection portion (131) and the plate connection portion (132). That is, the terminal connection portion (131) and the plate connection portion (132) can be separated from each other by the fuse hole (136).

[0087] The plate connector (137) can connect the terminal connector (131) and the plate connector (132). When a short circuit or overcurrent occurs in the secondary battery (100), the plate connector (137) can melt and cut due to the generated heat to block the current, thereby improving safety.

[0088] The shape of the first collector plate (130) can be changed into various forms, for example, having a terminal connection portion (131), a polar plate connection portion (132), and a fuse portion (135).

[0089] Referring to FIGS. 9A to 9C, a bottom view of a first collector plate (130) showing a roughened area of ​​a secondary battery (100) is illustrated. Each bottom view indicates a roughened area on the lower surface of the first collector plate (130) with a hatch.

[0090] In some examples, the first collector plate (130) can be roughened over the entire area of ​​the lower surface (130b) as shown in FIG. 9a.

[0091] In some examples, the first collector plate (130) is roughened only in the area where the electrode plate connection portion (132) is located on the lower surface (130b), as shown in FIG. 9b, so that the surface roughness of the lower surface of the electrode plate connection portion (132) may be greater than that of other areas.

[0092] Accordingly, the surface roughness of the first collector plate (130) illustrated in FIG. 9a or FIG. 9b in the area where the terminal connection portion (131) is located and the area where the plate connection portion (137) of the fuse portion (135) is located may be smaller than or equal to the surface roughness of the plate connection portion (132).

[0093] In some examples, the first collector plate (130) may be roughened only in the central region of the plate connection portion (132) at the lower surface (130b) as illustrated in FIG. 9c, so that the edge region (132a) may not be roughened. Here, the edge region (132a) of the plate connection portion (132) may correspond to the region where the first electrode tab (111b) is not present at the winding end of the electrode assembly (110). That is, the plate connection portion (132) may have a surface roughness of the central region that is greater than or equal to the surface roughness of the edge region (132a).

[0094] The second collector plate (140) may include a circular flat portion (141) corresponding to the lower surface (110b) of the electrode assembly (110), and an extension portion (142) extending downward from the edge of the flat portion (141).

[0095] The second collector plate (140) may have a higher surface roughness on the upper surface (140a) than on the lower surface (140b). A higher surface roughness here may mean a higher average height and / or a higher maximum height in a plane and / or along a unidirectional line. The second collector plate (140) may increase the surface roughness of the upper surface (140a) through roughening treatment. The roughening treatment may be performed by blasting, polishing, or etching, for example.

[0096] The second collector plate (140) may have a maximum roughness (Ry) of 4.6 µm to 5.6 µm on the upper surface (140a) and an average roughness (Ra) of 0.39 µm to 0.44 µm. Here, the average roughness (Ra) may be an average roughness based on the center line. If the average roughness height of the upper surface (140a) of the second collector plate (140) is less than 0.39 µm, the contact area between the second collector plate (140) and the lower surface (110b) of the electrode assembly (110) may be reduced, thereby increasing resistance. If the average height of the roughness of the upper surface (140a) of the second collector plate (140) is greater than 0.44 µm or the maximum height (Ry) is greater than 5.6 µm, the electron movement path in the horizontal direction (plane direction of the second collector plate) of the second collector plate (140) may be reduced, thereby increasing resistance. The roughness of the upper surface (140a) of the second collector plate (140) may be set and changed according to the roughness value of the lower surface (110b) of the electrode assembly (110).

[0097] The second collector plate (140) may have a thickness that does not reduce the electron movement path after roughening. For example, the second collector plate (140) may have a thickness of 0.2 mm to 1.5 mm.

[0098] The surface roughness of the upper surface (140a) of the second collector plate (140) may be greater than the surface roughness of the lower surface (130b) of the first collector plate (130). Since the surface roughness of the lower surface (110b) of the electrode assembly (110) is greater than the surface roughness of the upper surface (110a), it is preferable that the surface roughness of the upper surface (110a) of the second collector plate (140) be greater than the surface roughness of the lower surface (110b) of the first collector plate (130) in order to increase the contact area with the lower surface (110b) having a greater surface roughness.

[0099] The upper surface of the flat portion (141) of the second collector plate (140) can be in contact with and electrically connected to the lower surface (110b) of the electrode assembly (110). The upper surface of the flat portion (141) can be fixed and electrically connected to the second electrode tab (112b) exposed to the lower portion of the electrode assembly (110) by welding while in contact with the lower surface (110b) of the electrode assembly (110).

[0100] The extension portion (142) may extend downward from the edge of the flat portion (141). For example, a plurality of extension portions (142) may be provided so as to be spaced apart from each other along the edge of the flat portion (141). In addition, the extension portion (142) may be in contact with the inner surface of the beading portion (123). That is, the extension portion (142) may be rounded or bent along the beading portion (123). Here, the inner surface may be the inner surface of the case (120). The end of the extension portion (142) may be positioned between the beading portion (123) and the cap gasket (127). Such an extension portion (142) may be in contact with and joined to the beading portion (123) of the case (120). For example, the extension portion (142) may be joined by welding while in contact with the inner surface of the beading portion (123) of the case (120). The second collector plate (140) above serves as a current flow path between the second electrode plate (112) of the electrode assembly (110) and the case (120). That is, the case (120) may be a negative terminal. Additionally, the second collector plate (140) may be roughened only in the area where the flat portion (141) is located on the upper surface (140a). At this time, the surface roughness of the upper surface of the flat portion (141) of the second collector plate (140) may be greater than that of the extended portion (142). Accordingly, the surface roughness of the flat portion (141) of the upper surface (140a) of the second collector plate (140) may be greater than or equal to that of the extended portion (142).

[0101] Since the secondary battery (100) has surface roughness on the upper surface (110a) and the lower surface (110b) due to the bending and compaction of the first electrode tab (111b) and the second electrode tab (112b), the surface roughness in the area in contact with the electrode assembly (110) on the first collector plate (130) and the second collector plate (140) can be increased compared to other areas, thereby reducing the contact resistance between the electrode assembly (110) and the first collector plate (130), and between the electrode assembly (110) and the second collector plate (140).

[0102] In order to increase the capacity of the secondary battery (100), the thickness of the first collector plate (130) and the second collector plate (140) is reduced, so that the electron movement path (cross-sectional area) in the horizontal direction is reduced, and the resulting increase in resistance can be improved by reducing the contact resistance with the electrode assembly (110) through increasing the surface roughness.

[0103] Figures 10 to 13 are plan views illustrating various examples of the first collector plate in the secondary batteries illustrated in Figures 1 to 6.

[0104] Referring to Fig. 10, the first current collector (230) may include a terminal connection portion (131), a plate connection portion (132), and a fuse portion (235). The fuse portion (235) may include a fuse hole (136), a plate connection portion (137), and a protrusion hole (236a). The protrusion hole (236a) may be formed at one end and the other end of the fuse hole (136), respectively. The protrusion holes (236a) formed at both ends of the fuse hole (136) may protrude in a direction approaching each other. The width of the protrusion hole (236a) may be smaller than the width of the fuse hole (136). The protrusion hole (236a) may reduce the width (W2) of the plate connection portion (137), i.e., the cross-sectional area through which current flows, thereby improving the function of the fuse portion (235).

[0105] Referring to Fig. 11, the first collector plate (330) may include a terminal connection portion (131), a plate connection portion (132), and a fuse portion (335). The fuse portion (335) may include a fuse hole (136), a plate connection portion (337), a protrusion hole (236a), and an extension hole (336b). The extension holes (336b) may extend from both ends of the fuse hole (136) toward the outside of the first collector plate (330) by the length of the plate connection portion (337). The extension holes (336b) formed at both ends of the fuse hole (136) may be parallel to each other. The extension holes (336b) may increase the length (L) of the plate connection portion (337), i.e., the length through which current flows, thereby improving the function of the fuse portion (335).

[0106] Referring to Fig. 12, the first collector plate (430) may include a terminal connection portion (131), a plate connection portion (132), and a fuse portion (435). The fuse portion (435) may include two fuse holes (436) spaced apart from each other, and two plate connection portions (437) positioned between the fuse holes (436). The two fuse holes (436) are positioned concentrically with respect to the center of the first collector plate (430) and may be symmetrical to each other. The angle (b) formed by the plate connection portion (437) with respect to the center of the first collector plate (430) may be about 30 to 50 degrees.

[0107] Referring to Fig. 13, the first collector plate (530) may include a terminal connection portion (131), a plate connection portion (132), and a fuse portion (535). The fuse portion (535) may include three fuse holes (536) spaced apart from each other, and three plate connection portions (537) positioned between the fuse holes (536). The three fuse holes (536) may be positioned concentrically with respect to the center of the first collector plate (530) and may be formed to have the same size. The angle (c) formed by the plate connection portions (537) with respect to the center of the first collector plate (530) may be about 8 to 15 degrees.

[0108] Here, the surface roughness treatment of the first collector plate (230, 330, 430, 530) illustrated in FIGS. 10 to 13 can apply various surface treatment areas illustrated in FIGS. 9a to 9c.

[0109] The above description is only one embodiment for implementing the secondary battery according to the present invention, and the present invention is not limited to the above-described embodiment, and as claimed in the following claims, it will be understood that the technical spirit of the present invention exists to the extent that various modifications can be implemented by anyone having ordinary skill in the art to which the present invention pertains without departing from the gist of the present invention.

Claims

1. An electrode assembly having a first electrode plate, a separator, and a second electrode plate; A case in which the electrode assembly is accommodated and the lower part is open; A terminal coupled through the upper surface of the case; A first collector plate interposed between the upper surface of the electrode assembly and the case, electrically connecting the first electrode plate and the terminal; and Includes a cap plate that seals the lower part of the case, The above first collector plate is a secondary battery having a surface roughness on the lower surface greater than that on the upper surface.

2. In paragraph 1, The first electrode plate further includes a plurality of first electrode tabs that protrude upward from the upper surface of the electrode assembly and are bent and pressed in the winding axis direction of the electrode assembly. The second electrode plate further includes a plurality of second electrode tabs that protrude downwardly from the lower surface of the electrode assembly and are bent and pressed in the winding axis direction of the electrode assembly. The above electrode assembly is a secondary battery having a plurality of first electrode tabs exposed on the upper surface and a plurality of second electrode tabs exposed on the lower surface.

3. In paragraph 2, The above first collector plate is a flat circular plate, and is a secondary battery welded to the upper surface of the electrode assembly.

4. In paragraph 3, The above first collector plate A terminal connection portion that contacts and is electrically connected to the lower surface of the terminal; and A secondary battery including a first electrode tab exposed on the upper surface of the electrode assembly and electrically connected to the electrode plate connection portion, the electrode plate connection portion being located on the outside of the terminal connection portion.

5. In paragraph 4, A secondary battery wherein the first collector plate further includes a fuse portion positioned between the terminal connection portion and the electrode plate connection portion.

6. In paragraph 5, The above fuse part A fuse hole formed along a portion of the outer periphery of the terminal connection portion; and A secondary battery including a plate connecting portion connecting the terminal connecting portion and the plate connecting portion.

7. In paragraph 3, The above first collector plate is a secondary battery in which the surface roughness of the electrode plate connection portion on the lower surface is greater than or equal to that of other areas.

8. In paragraph 2, A secondary battery further comprising a second collector plate in a circular plate shape corresponding to the lower surface of the electrode assembly and in contact with and electrically connected to the second electrode tab exposed to the lower surface of the electrode assembly.

9. In paragraph 8, The above second collector plate is a secondary battery having a surface roughness of the upper surface greater than that of the lower surface.

10. In paragraph 8, The second collector plate has a circular flat surface that contacts the lower surface of the electrode assembly; A secondary battery comprising an extension portion extending downward from an edge of the above-mentioned flat portion.

11. In paragraph 10, The above second collector plate is a secondary battery in which the surface roughness of the flat portion on the upper surface is greater than or equal to that of other areas.

12. In paragraph 10, The above case is A beading portion sunken into the interior of the case on the upper portion of the cap plate; and A secondary battery including a crimping portion in which the lower portion of the case is bent inwardly to secure the cap plate to the lower portion of the cap plate.

13. In paragraph 12, It further includes a cap gasket interposed between the cap plate and the beading portion, and between the cap plate and the crimping portion, The above cap plate is a non-polar secondary battery.

14. In paragraph 13, A secondary battery in which the extension of the second collector plate is interposed between the cap gasket and the beading portion.

15. In paragraph 9, The above electrode assembly is a secondary battery having a surface roughness on the lower surface greater than that on the upper surface.

16. In paragraph 15, A secondary battery in which the surface roughness of the upper surface of the second collector plate is greater than the surface roughness of the lower surface of the first collector plate.

17. In paragraph 2, A secondary battery in which the plurality of first electrode tabs are arranged in a plurality of first uncoated portions on the first electrode plate to which no electrode active material is applied, and are spaced apart from each other along the winding direction.

18. In paragraph 2, A secondary battery in which the above plurality of first electrode tabs are not provided at the winding tip and winding end of the first electrode plate.

19. In paragraph 6, The above fuse section includes one or more fuse holes, The above fuse hole is a secondary battery located concentrically with the center of the first collector plate.

20. In paragraph 6, The above fuse part further includes a protruding hole formed at both ends of the fuse hole, The above protrusion holes are secondary batteries that protrude in a direction that approaches each other.

Images