Pressing apparatus for manufacturing secondary battery

Abstract

Disclosed is a pressing apparatus for manufacturing a secondary battery. The pressing apparatus can include a pressing plate; and a pressing pad fixed to a pressing surface of the pressing plate and including a three-dimensional lattice structure provided by repeating or regularly arranging a plurality of unit cells each formed by connecting a plurality of pillars.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2025-0042970, filed on April 2, 2025, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This disclosure relates to a pressing device for manufacturing secondary batteries. Background Technology

[0004] Unlike primary batteries, which are not designed for charging, secondary batteries are designed for discharging and recharging. Low-capacity secondary batteries are used in small portable electronic devices such as smartphones, feature phones, laptops, digital cameras, and camcorders, while high-capacity secondary batteries are widely used as power sources for driving motors in vehicles such as hybrid or electric vehicles, as well as for energy storage. A secondary battery includes an electrode assembly containing positive and negative electrodes, a housing that houses the electrode assembly, and terminals that connect to the electrode assembly.

[0005] Rechargeable batteries offer advantages such as high energy density, discharge voltage, and output stability, leading to high demand. The manufacturing process for rechargeable batteries can be broadly categorized into electrode plate processes, winding processes, assembly processes, and formation processes. The formation process includes a heater press-charge (HPC) process, which activates the battery by heating, pressing, and charging the individual cells. During HPC, it is crucial to apply pressure evenly to the individual cells while pressing them. However, a challenge arises because the structure of each electrode assembly results in varying flatness between the electrode components within a single cell, making it difficult to apply uniform pressure.

[0006] The information disclosed in this background section is intended to enhance the understanding of the background of this disclosure, and therefore may contain information that does not constitute related (or prior art). Summary of the Invention

[0007] The embodiments of this disclosure aim to provide a pressing device for manufacturing secondary batteries, wherein a pressing component having a three-dimensional dot matrix structure is formed on the pressing surface of a pressing plate.

[0008] However, the technical problems to be solved by this disclosure are not limited to those described above, and those skilled in the art will clearly understand from the following description of this disclosure other problems not mentioned herein, as well as aspects and features of this disclosure that will solve these problems.

[0009] A pressing device for manufacturing a secondary battery according to embodiments of the present disclosure may include: a pressing plate; and a pressing pad, fixed to the pressing surface of the pressing plate, and including a three-dimensional lattice structure provided by repeatedly or regularly arranging a plurality of unit cells formed by connecting a plurality of pillars.

[0010] In an embodiment, the lattice structure may include at least one layer comprising a plurality of unit cells arranged in column and row directions, and may include a first region and a second region extending from the first region, the first and second regions being defined in directions intersecting the pressing direction.

[0011] In an embodiment, the density of unit cells allocated to the second region may be higher than the density of unit cells allocated to the first region.

[0012] In an embodiment, the size of each unit cell allocated to the second region may be smaller than the size of each unit cell allocated to the first region.

[0013] In an embodiment, at least one layer may include a plurality of sublayers divided along a pressing direction corresponding to the second region. At least one layer in the first region may include a first unit cell. Each of the plurality of sublayers in the second region may include a second unit cell. The size of the second unit cell may be smaller than the size of the first unit cell.

[0014] In the embodiments, the first unit cell and the second unit cell can be constructed as corresponding unit cells having the same structure.

[0015] In an embodiment, the porosity of a unit cell allocated to the second region can be set to be lower than the porosity of a unit cell allocated to the first region.

[0016] In an embodiment, the thickness of each pillar forming a unit cell allocated to the second region can be set to be greater than the thickness of each pillar forming a unit cell allocated to the first region.

[0017] In an embodiment, a unit cell may include a first unit cell allocated to a first region and a second unit cell allocated to a second region. The second unit cell may have a structure different from that of the first unit cell.

[0018] In an embodiment, the second unit cell may be selected as a structure having higher stiffness or lower deformation than the first unit cell.

[0019] In an embodiment, the second unit cell can be selected as one of an octahedral truss, a kagome, a diamond cell, and a face-centered cubic (FCC) structure. The first unit cell can be selected as one of a Kelvin cell, a tetrahedral cell, and a dodecahedral cell.

[0020] In an embodiment, the second unit cell can be selected as one of the unit cells having a stretch-dominant structure. The first unit cell can be selected as one of the unit cells having a bending-dominant structure.

[0021] In an embodiment, the second region may have a greater thickness than the first region.

[0022] In an embodiment, the second region may further include an additional layer stacked on at least one layer along the pressing direction, the additional layer comprising a plurality of unit cells arranged in the column and row directions.

[0023] In an embodiment, the pressing pad may include: a first plate, including a fixing surface fixed to the pressing surface of the pressing plate and a connecting surface fixed to a surface of the dot matrix structure.

[0024] In an embodiment, the pressing pad may further include: a second plate, configured to face the first plate along the pressing direction, with a dot matrix structure between the second plate and the first plate, and the second plate including a connecting surface fixed to another surface of the dot matrix structure.

[0025] In this embodiment, the first plate and the second plate can be integrally formed with the lattice structure.

[0026] In an embodiment, the first plate and the second plate may be formed of the same material as the lattice structure.

[0027] In this embodiment, the pressure pad may be formed of thermoplastic polyurethane (TPU).

[0028] In an embodiment, each of the plurality of unit cells can be selected as one of the unit cells having a stretched dominant lattice structure.

[0029] According to embodiments of this disclosure, a pressing pad including a three-dimensional dot matrix structure can be used to press a battery cell, thereby improving the uniformity of pressing relative to the battery cell.

[0030] In particular, according to embodiments of this disclosure, different pressing pressures can be applied to different areas, enabling a relatively uniform pressing pressure to be applied even to electrode assemblies with location-dependent thickness variations. Therefore, diaphragm detachment due to adhesive separation caused by thickness variations in the electrode assembly can be prevented, thereby ensuring product reliability and stability.

[0031] However, the aspects and features of this disclosure are not limited to those described above, and those skilled in the art will clearly understand from the detailed description below that other aspects and features not mentioned will be apparent. Attached Figure Description

[0032] Figure 1A This is a perspective view showing an example of the structure of a pouch-type secondary battery, and Figure 1B This is a perspective view showing another example of the structure of a pouch-type secondary battery.

[0033] Figure 2 This is a cross-sectional view showing the electrode assembly of a pouch-type secondary battery.

[0034] Figure 3 This is a graph showing the thickness deviation based on the position of the electrode assembly.

[0035] Figure 4 This is a diagram illustrating an example of a typical heater press-charge (HPC) process.

[0036] Figure 5 This is a schematic diagram illustrating a battery cell pressing device according to an embodiment of the present disclosure.

[0037] Figure 6 This is a schematic diagram illustrating a pressure pad according to an embodiment of the present disclosure.

[0038] Figure 7 This is a diagram illustrating an example of a unit cell forming a pressing pad according to an embodiment of the present disclosure.

[0039] Figure 8 This is a schematic cross-sectional view showing a lattice structure according to an embodiment of the present disclosure.

[0040] Figure 9 This is a schematic cross-sectional view showing a pressure pad according to an embodiment of the present disclosure.

[0041] Figure 10 This is a schematic cross-sectional view showing a pressure pad according to an embodiment of the present disclosure.

[0042] Figure 11 This is a schematic cross-sectional view showing a pressure pad according to an embodiment of the present disclosure. Detailed Implementation

[0043] Exemplary embodiments of this disclosure will now be described in detail with reference to the accompanying drawings. Before the description, it should be noted that the terms or words used in this specification and claims should not be construed as limited to their ordinary or dictionary meanings, but rather as having meanings and concepts consistent with the spirit of this disclosure, based on the principle that the inventor can appropriately define the concept of each term to best describe his / her own invention. Therefore, since the embodiments described in this specification and the configurations shown in the drawings are merely examples of this disclosure and do not cover all the technical spirit of this disclosure, it should be understood that various changes and modifications can be made at the time of filing this application.

[0044] It will be further understood that, when used herein, the term “comprising” specifies the presence of the said feature, integer, step, operation, element, component, and / or group thereof, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0045] To aid in understanding this disclosure, the drawings are not drawn to scale, and the dimensions of some components may be enlarged. It should be noted that the same reference numerals are designated for the same components in different embodiments.

[0046] Referring to two compared elements, features, etc., as “identical” may mean that they are “substantially identical.” Therefore, the phrase “substantially identical” can include cases with deviations considered low in the art, such as less than 5%. The consistency of any parameter over a given region means that it is consistent with respect to the mean.

[0047] Although terms such as “first” and / or “second” are used to describe various components, these components are of course not limited by these terms. These terms are only used to distinguish one component from another. Therefore, unless specifically stated to the contrary, a first component may be referred to as a second component without departing from the teachings of the exemplary embodiments.

[0048] Throughout this specification, unless otherwise stated, each element may be singular or plural.

[0049] Placing any component "above (or below)" or "on (below)" a component can mean that the component is positioned to contact the upper (or lower) surface of the component, and other components may be positioned between the component and any components placed on (or below) the component.

[0050] It will be understood that when a component is referred to as “connected,” “joined,” or “joined” to another component, it can not only be directly “connected,” “joined,” or “joined” to the other component, but it can also be indirectly “connected,” “joined,” or “joined” to the other component, with other components in between.

[0051] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. The use of “may” in describing embodiments of this disclosure refers to “one or more embodiments of this disclosure.” Terms such as “at least one” and “one or more” preceding the list of elements modify the entire list of elements, but not individual elements within the list.

[0052] Throughout the specification, when “A and / or B” is stated, it means A, B, or A and B unless otherwise stated. Similarly, when “C~D” is stated, it means above C and below D unless otherwise stated.

[0053] When a list of elements A, B, and C is specified using phrases such as “at least one of A, B, and C”, “at least one of A, B, or C”, “at least one selected from the group of A, B, and C”, or “at least one selected from A, B, and C”, the phrase can refer to any and all suitable combinations.

[0054] The term “use” may be considered synonymous with the term “utilization”. As used herein, the terms “substantially,” “about,” and similar terms are used as approximations rather than terms of degree and are intended to take into account the inherent variations in measurements or calculations that are readily apparent to those skilled in the art.

[0055] It will be understood that although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers, and / or segments, these elements, components, regions, layers, and / or segments should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or segment from another element, component, region, layer, or segment. Therefore, without departing from the teachings of the exemplary embodiments, the first element, component, region, layer, or segment discussed below may be referred to as the second element, component, region, layer, or segment.

[0056] For ease of explanation, when describing the relationship of one element or feature as shown in the accompanying drawings to other elements or features, spatial relative terms such as “below,” “under,” “down,” “above,” and “above” may be used herein. It will be understood that spatial relative position is intended to include, in addition to the orientation depicted in the figures, different orientations of the device in use or operation. For example, if the device in the figures is flipped, any element described as “below” or “under” another element would be oriented as “above” or “above” another element. Therefore, the term “below” can include both upward and downward directions.

[0057] The terminology used herein is for the purpose of describing embodiments of this disclosure and is not intended to limit this disclosure.

[0058] Examples of secondary batteries include coin-shaped, cylindrical, prismatic, and pouch-shaped batteries. This disclosure is essentially applicable to pouch-shaped secondary batteries. Therefore, pouch-shaped secondary batteries will be briefly described first before describing embodiments of this disclosure.

[0059] Figure 1A This represents an example of a pouch-type secondary battery. Figure 1B Another example of a pouch-type secondary battery.

[0060] Reference Figure 1A and Figure 1BThe pouch-type secondary battery may include: an electrode assembly 40, in which a separator 30 is positioned between a first electrode plate 10 and a second electrode plate 20; and a housing 50 in which the electrode assembly 40 is embedded. The first electrode plate 10, the second electrode plate 20, and the separator 30 may be immersed in an electrolyte (not shown). The pouch-type secondary battery may include electrode terminals 70, namely a first electrode terminal 71 and a second electrode terminal 72, which serve as electrical channels for directing current formed in the electrode assembly 40 to the outside.

[0061] The electrode assembly 40 can be formed by winding or stacking a stacked body comprising a first electrode plate 10, a second electrode plate 20, and a diaphragm 30, each formed in the shape of a plate or membrane. In the case of winding the stacked body, the winding axis of the electrode assembly 40 can be parallel to the length direction of the housing 50. Furthermore, the electrode assembly 40 can be stacked rather than wound, but in one embodiment of this disclosure, the shape of the electrode assembly 40 is not limited. The first electrode plate 10 of the electrode assembly 40 can function as a negative electrode, and its second electrode plate 20 can function as a positive electrode, and vice versa.

[0062] The first electrode plate 10 can be formed by coating a first electrode active material, such as graphite or carbon, onto a first electrode current collector formed of a metal foil such as copper, copper alloy, nickel, or nickel alloy, and may include a first electrode terminal piece 71 (or a first uncoated portion), that is, an area where the first electrode active material is not coated.

[0063] The second electrode plate 20 can be formed by coating a second electrode active material, such as a transition metal oxide, onto a second electrode current collector formed of a metal foil such as aluminum or an aluminum alloy, and may include a second electrode terminal 72 (or a second uncoated portion), that is, an area where the second electrode active material is not coated.

[0064] The separator 30 can be used to prevent short circuits between the first electrode plate 10 and the second electrode plate 20, while allowing lithium ions to move. The separator 30 can be made of, for example, a polyethylene membrane, a polypropylene membrane, or a polyethylene-polypropylene membrane.

[0065] The housing 50 may be made of laminated film or plastic, such as a bag. The housing 50 is sealed while housing the electrode assembly 40 by sealing portions that contact each other at their edges. In this case, the seal is performed with the electrode tabs 70 or the first electrode tab 71 and the second electrode tab 72 placed between the sealing portions. The sealing portions of the housing 50 are made of a thermomeltable material and have a structure that achieves a seal by bonding the thermomeltable layers together.

[0066] Figure 2 This is a cross-sectional view showing the electrode assembly of a pouch cell.

[0067] Reference Figure 2 The electrode assembly 40 of the pouch-type secondary battery can be formed by winding it in the form of an electrode core. The electrode assembly 40 may include a first electrode substrate 11, a first electrode mixture portion 12, a second electrode substrate 21, a second electrode mixture portion 22, a separator 30, a first electrode terminal piece 71, and a second electrode terminal piece 72. The first electrode substrate 11 and the first electrode mixture portion 12 can constitute a first electrode plate 10. The second electrode substrate 21 and the second electrode mixture portion 22 can constitute a second electrode plate 20.

[0068] The flatness of the electrode assembly 40 varies depending on its structural design. Specifically, for example... Figure 2 As shown, a thickness difference exists between electrode plates 10 and 20 depending on whether the coated / uncoated portions or overlapping portions are present. As the thickness difference increases, the membrane adhesion at the corresponding locations separates during high-temperature compression in the heater press-charge (HPC) process. When the membrane adhesion separates at localized locations, additional reactants are generated and accumulated during charging and discharging. As the distance between the plates continues to increase, the battery life shortens and the battery thickness increases due to deposition and non-charging.

[0069] Figure 3 This is a graph showing the thickness deviation based on the position of the electrode assembly.

[0070] The electrode plate of the electrode assembly 40 may include coated areas where electrode material (such as a paste) is applied to the substrate and uncoated portions (uncoated areas) formed on the substrate. Due to the nature of the process, the manufactured electrode plate may experience thickness inhomogeneities depending on its location on the electrode plate. In cases where the electrode assembly 40 is formed by stacking and / or winding electrode plates, location-dependent thickness variations may be further increased. The shading differences in the figure may indicate location-dependent thickness variations in the electrode assembly 40.

[0071] More specifically, in the process of manufacturing the electrode plate, electrode material in a slurry state can be coated onto a substrate to form a coated area. During the above process, due to the scalable nature of the slurry, the coating layer may not have a uniform thickness on the substrate, and location-dependent thickness deviations may occur. Thickness deviations may appear significantly at the boundary between the coated area and the uncoated portion, which is shown separately in the accompanying drawings. Due to the location-dependent thickness deviations of the electrode assembly 40, the aforementioned problems, such as diaphragm separation occurring at the corresponding locations, may occur more frequently during the high-temperature pressing process.

[0072] Figure 4This is a diagram illustrating an example of a typical heater press-charge (HPC) process.

[0073] The HPC process can be a process that performs charging and discharging of the battery cell 1 under the conditions required for activation by the charging / discharging component 80. Charging and discharging can be performed multiple times as needed. The HPC process may include a high-temperature pressing process. The pressing process can be a process that presses the battery cell 1 to tightly bond the electrode plates together and allows the electrolyte to be uniformly impregnated between the electrode plates of the electrode assembly. By performing this process, lifting of the electrode plates can be suppressed, and the bonding force between the electrode plates can be enhanced.

[0074] The pressing device 90 may include a first pressing plate 91 and a second pressing plate 93 facing each other. The first pressing plate 91 and the second pressing plate 93 can be used to press the battery cell 1 during the HPC process. For example, the pressing process may be a process in which pressure is applied to the battery cell 1 from opposite sides while the battery cell 1 is between the first pressing plate 91 and the second pressing plate 93. The pressing process may be performed together with a heating process using a heating unit such as a heater.

[0075] A cushioning pad may be attached to or integrally formed on the pressing surface of each of the first pressing plate 91 and the second pressing plate 93. The cushioning pad can be provided to prevent damage to the battery cell 1 due to pressure applied to the battery cell 1 during the pressing process and to maintain flatness. The cushioning pad may be formed of silicone resin, Vulkollan, etc.

[0076] The cushioning pad can receive pressing pressure from the pressing plate and press the battery cell 1. However, since the cushioning pads fixed to each of the first pressing plate 91 and the second pressing plate 93 are reused in multiple HPC processes, permanent indentations may occur at local locations, which may limit the uniformity of the pressure applied to the battery cell 1. In addition, there may be limitations in overcoming the aforementioned problems of thickness deviations according to the position of the electrode assembly by using the cushioning pad.

[0077] Figure 5 This is a schematic diagram illustrating a battery cell pressing device according to an embodiment of the present disclosure. Figure 6 This is a schematic diagram illustrating a pressure pad according to an embodiment of the present disclosure. Figure 7 This is a diagram illustrating an example of a unit cell forming a pressing pad according to an embodiment of the present disclosure.

[0078] Reference Figures 5 to 7The battery cell pressing device 90 according to an embodiment of the present disclosure may include pressing plates 91, 93 and pressing pad 100. The pressing plates 91, 93 may include a first pressing plate 91 and a second pressing plate 93, arranged facing each other, with the battery cell positioned therebetween. The pressing plates 91, 93 may be formed of a metal material with low deformation to effectively transmit pressure to the battery cell. For example, the pressing plates 91, 93 may be formed of an aluminum alloy, but are not limited thereto.

[0079] The pressing pad 100 can be fixed to the pressing surface 90a of each of the first pressing plate 91 and the second pressing plate 93. Although not shown, each of the first pressing plate 91 and the second pressing plate 93 and the pressing pad 100 can be fixed to each other by at least one fixing unit. For example, an adhesive layer can be between each of the first pressing plate 91 and the second pressing plate 93 and the pressing pad 100. The pressing pad 100 and each of the first pressing plate 91 and the second pressing plate 93 can be fixed to each other by the adhesive layer. The pressing pad 100 may include: a fixing surface 100a, fixed to the pressing surface 90a of each of the first pressing plate 91 and the second pressing plate 93; and a contact surface 100b, which contacts one surface of the battery cell and presses the battery cell.

[0080] The pressing pad 100 may include a three-dimensional lattice structure 101 provided by repeatedly or regularly arranging unit cells 110 formed by connecting pillars 111 (or grid members). The lattice structure 101 may be formed by repeatedly arranging the same unit cells 110, or by periodically arranging different unit cells 110 in an alternating manner. One of various unit cells 110 capable of forming a three-dimensional lattice structure may be selected as the unit cell 110. The unit cell 110 may include a plurality of pillars 111 and nodes 113 connecting the pillars 111. The lattice structure can be effective in terms of pressure distribution and shock absorption, and can have excellent elasticity. Therefore, compared with structures using conventional cushioning components, permanent indentations due to repeated exposure to HPC process conditions can be prevented. This can demonstrate the advantages of the pressing device 90 in terms of maintenance, management, and repair.

[0081] The lattice structure 101 may include one or more layers L1, L2 comprising a plurality of unit cells 110 arranged in the row and column directions. The lattice structure 101 may be formed by stacking a plurality of layers L1, L2 along the pressing direction. In at least one of the layers L1, L2, or at a specific location, adjacent unit cells 110 may be connected to each other, sharing at least one pillar 111 and / or node 113 between them. Alternatively, in at least one of the layers L1, L2, or at a specific location, adjacent unit cells 110 may simply be fixed without sharing pillars 111 or nodes 113.

[0082] In embodiments of this disclosure, the reference size of the unit cell 110 can be defined as the size of a virtual unit hexahedron having a preset width, length, and height. The size of each of layers L1, L2 can be defined as the size of a plurality of unit hexahedrons arranged in the row and column directions. The size of the lattice structure 101 can be defined as the size of the stacked layers L1, L2. In the unit hexahedron, the density of the unit cell 110 can be determined by the porosity or the volume ratio occupied by the pillars 111. To control the relative density within the unit cells 110, the shape and size (or volume) of the unit cells 110 in the unit hexahedron and the size (e.g., thickness (or diameter) and length) of each pillar 111 constituting the unit cell 110 can be selectively changed. As needed, the densities of adjacent unit cells 110 can be different from each other. As needed, the densities of the unit cells 110 constituting the respective layers L1, L2 can also be different from each other between adjacent layers L1, L2.

[0083] like Figure 7 As shown, the unit cell 110 can be an octahedral truss or a Kelvin cell, but is not limited thereto, and can be any known structure. For example, the unit cell 110 can be selected as having at least one topological structure among Gibson-Ashby (GA), diamond-shaped, tetrahedral, pyramidal, kagome, octahedral, and dodecahedral structures. Alternatively, the unit cell 110 can be selected as having at least one topological structure generated by a cubic primitive structure (CP), a body-centered cubic structure (BCC), a face-centered cubic structure (FCC), a combination of CP, BCC, and FCC (e.g., FBCC, FCCP, and BCCP), or a topological structure generated by adding pillars to the above structures (e.g., BCCz, FCCz, FBCCz, and FBCCxyz (FBCCP)). The unit cell 110 can be selected as a bending-dominant lattice structure (e.g., Kelvin structure, tetrahedral structure) and a stretching-dominant lattice structure (e.g., octahedral truss structure, kagome lattice). Compared to bending-dominated lattice structures, stretching-dominated lattice structures can undergo relatively uniform deformation throughout the entire structure under load. Therefore, it is expected that the unit cell 110 will be chosen as the stretching-dominated lattice structure.

[0084] The pressing pad 100 may include at least one of a first plate 103 fixed to one surface of the lattice structure 101 and a second plate 105 fixed to another surface of the lattice structure 101. One surface of the lattice structure 101 may be the surface facing the pressing surface of the pressing plates 91, 93, and the other surface may refer to a surface of the lattice structure 101 opposite to one surface in the pressing direction. In an embodiment, the pressing pad 100 may include both the first plate 103 and the second plate 105. The first plate 103 and the second plate 105 may be arranged to face each other in the pressing direction, with the lattice structure 101 interposed therebetween. The first plate 103 and the second plate 105 may be integrally formed with the lattice structure 101. The first plate 103 and the second plate 105 may be formed of the same material as the lattice structure 101.

[0085] The first plate 103 can be fixed to the pressing surface 90a of the pressing plate 91 or 93. The first plate 103 may include a fixing surface 103a fixed to the pressing surface 90a of the pressing plate 91 or 93 and a connecting surface 103b fixed to a surface of the dot matrix structure 101. The fixing surface 103a of the first plate 103 can be in face-to-face contact with the pressing surface 90a of the pressing plate 91 or 93, and can receive pressing force from the pressing plate 91 or 93 and provide pressing force to the dot matrix structure 101. Since the first plate 103 is further included in the pressing pad 100, it can facilitate the fixation between the pressing pad 100 and the pressing plate 91 or 93.

[0086] During the pressing process, the second plate 105 may contact at least one surface of the battery cell. The second plate 105 may include a contact surface 105a that contacts one surface of the battery cell and a connecting surface 105b that is fixed to another surface of the lattice structure 101. The contact surface 105a of the second plate 105 may make face-to-face contact with one surface of the battery cell and may receive and apply pressing pressure from the lattice structure 101 to the battery cell. Since the second plate 105 is further included in the pressing pad 100, a more uniform pressing pressure can be provided to the battery cell.

[0087] The pressure pad 100 can be manufactured by 3D printing. Selective laser sintering (SLS) can be used as a 3D printing method, but it is not limited to this; projection micro-stereolithography (PuSL), digital light processing (DLP), stereolithography (SLA), self-propagating polymer waveguide (SPPW), fused deposition modeling (FDM or fused filament fabrication (FFF)), and binder jetting can also be used. Factors such as the type and size of the target unit cell 110 and the thickness of the pillars 111 can be considered when selecting the 3D printing method. Through 3D printing, the lattice structure 101, the first plate 103, and the second plate 105 can be formed simultaneously and integrally. The lattice structure 101 of the pressure pad 100 can be formed from a synthetic resin. In an embodiment, the lattice structure 101 can be formed from thermoplastic polyurethane (TPU) material.

[0088] The following describes the structure of a pressure pad for providing relatively uniform pressure to the cell housing the electrode assembly in response to thickness variations depending on the position on the electrode assembly.

[0089] Figure 8 This is a schematic cross-sectional view showing a lattice structure according to an embodiment of the present disclosure.

[0090] Reference Figure 8 The dot matrix structure 101-1 according to embodiments of the present disclosure may include a first region A1 and a second region A2 extending from the first region A1. The first region A1 and the second region A2 may be defined in a direction intersecting the pressing direction. Alternatively, the first region A1 and the second region A2 may be defined in a direction corresponding to the longitudinal direction of the electrode assembly. The second region A2 may be defined as a plurality of regions as needed. A first portion of the electrode assembly pressed by a contact surface corresponding to the first region A1 and a second portion of the electrode assembly pressed by a contact surface corresponding to the second region A2 may have different thicknesses. The second portion may include a portion with a thickness less than that of the first portion. In embodiments, the second portion may include the boundary between a coated area and an uncoated portion in which electrode tabs are formed.

[0091] The lattice structure 101-1 may include one or more layers L1, L2, and L3. An example of layers L1, L2, and L3 being constructed as three layers is shown in the figures, but this disclosure is not limited thereto. Layers L1, L2, and L3 may be stacked in the pressing direction and may be connected to each other. Each of layers L1, L2, and L3 may include a plurality of unit cells 110-1 arranged in the row and column directions.

[0092] The density of unit cells 110-1 allocated to the first region A1 can differ from the density of unit cells 110-1 allocated to the second region A2. A higher density can indicate reduced compressive deformation and provide a relatively higher compressive force to the corresponding region. The density of unit cells 110-1 allocated to the first region A1 can be lower than the density of unit cells 110-1 allocated to the second region A2. Each of the unit cells 110-1 allocated to the first region A1 can be formed with a reference size (or volume). Each of the unit cells 110-1 allocated to the second region A2 can be formed with a size smaller than the reference size. In other words, each of the unit cells 110-1 allocated to the first region A1 can be formed with a unit hexahedral size. Each of the unit cells 110-1 allocated to the second region A2 can be formed with a size smaller than a unit hexahedral size. The foregoing can indicate that, within a space of the same size, a greater number of unit cells 110-1 can be arranged in the second region A2 compared to the first region A1.

[0093] More specifically, in the first region A1, layers L1, L2, and L3 may include a plurality of first unit cells 110-1a arranged in the row and column directions. In the second region A2, each of layers L1, L2, and L3 may include sublayers SL1 and SL2 obtained by dividing the respective layer L1, L2, or L3 into multiple layers. Sublayers SL1 and SL2 may be stacked in the pressing direction and may be connected to each other. Each of sublayers SL1 and SL2 may include a plurality of second unit cells 110-1b arranged in the row and column directions. In an embodiment, the first unit cells 110-1a and the second unit cells 110-1b may be unit cells 110-1 of the same type.

[0094] The size of the second unit cell 110-1b can be set to be smaller than the size of the first unit cell 110-1a. The size of the first unit cell 110-1a can correspond to the size of the virtual unit hexahedron, and the size of the second unit cell 110-1b can correspond to the size of the virtual hexahedron, which is smaller than the unit hexahedron. In the accompanying drawings, an example is shown in which each of layers L1, L2, and L3 includes sublayers SL1, SL2 in the second region A2; however, this disclosure is not limited thereto, and only one of layers L1, L2, and L3 may optionally include sublayers SL1, SL2.

[0095] The pressing pad 100 according to embodiments of the present disclosure may include a lattice structure 101-1 defining a first region A1 and a second region A2 with different densities, and may provide different pressing forces corresponding to positions on the electrode assembly. In other words, a first portion of the electrode assembly having a relatively large thickness can be pressed through a contact surface having a relatively low density first region A1, and a second portion of the electrode assembly having a relatively small thickness can be pressed through a contact surface having a relatively high density second region A2. Therefore, electrode assemblies with thickness variations can be pressed uniformly overall.

[0096] Figure 9 This is a schematic cross-sectional view illustrating a pressure pad according to an embodiment of the present disclosure. In the following description of embodiments of the present disclosure, descriptions of components substantially the same as those in the above embodiments will be omitted.

[0097] Reference Figure 9 The density of unit cells 110-2 allocated to the first region A1 can be different from the density of unit cells 110-2 allocated to the second region A2. A higher density can indicate that compressive deformation can be reduced and that a relatively higher compressive force can be applied to the corresponding region.

[0098] More specifically, each of layers L1, L2, and L3 may include a plurality of unit cells 110-2 arranged in the row and column directions. The unit cells 110-2 may include a first unit cell 110-2a assigned to the first region A1 and a second unit cell 110-2b assigned to the second region A2. In an embodiment, the first unit cell 110-2a and the second unit cell 110-2b may be unit cells 110-2 of the same type.

[0099] In a unit hexahedron, the porosity of the second unit cell 110-2b can be set to be lower than that of the first unit cell 110-2a. For example, the thickness D2 (or diameter) of the pillar 111b forming the second unit cell 110-2b can be set to be greater than the thickness D1 of the pillar 111a forming the first unit cell 110-2a. In the second region A2, all layers L1, L2, and L3 may include the second unit cell 110-2b, but this disclosure is not limited thereto; the second unit cell 110-2b may be selectively disposed only at specific locations in the second region A2.

[0100] The pressing pad 100 according to embodiments of the present disclosure may include a lattice structure 101-2 defining a first region A1 and a second region A2 with different densities, and may provide different pressing forces corresponding to positions on the electrode assembly. In other words, a first portion of the electrode assembly having a relatively large thickness can be pressed through a contact surface of the first region A1 having a relatively low density, and a second portion of the electrode assembly having a relatively small thickness can be pressed through a contact surface of the second region A2 having a relatively high density. Therefore, electrode assemblies with thickness variations can be pressed uniformly overall.

[0101] Figure 10 This is a schematic cross-sectional view illustrating a pressure pad according to an embodiment of the present disclosure. In the following description of embodiments of the present disclosure, descriptions of components substantially the same as those in the above embodiments will be omitted.

[0102] Reference Figure 10 The density of unit cells 110-3 allocated to the first region A1 can be different from the density of unit cells 110-3 allocated to the second region A2. A higher density can indicate that compressive deformation can be reduced and that a relatively higher compressive force can be applied to the corresponding region.

[0103] More specifically, each of layers L1, L2, and L3 may include a plurality of unit cells 110-3 arranged in the row and column directions. The unit cells 110-3 may include a first unit cell 110-3a allocated to the first region A1 and a second unit cell 110-3b allocated to the second region A2. In embodiments, the first unit cell 110-3a and the second unit cell 110-3b may be unit cells 110-3 of different types.

[0104] The second unit cell 110-3b can be constructed to have a predetermined stiffness compared to the first unit cell 110-3a. The structures of the first unit cell 110-3a and the second unit cell 110-3b can be selected considering factors such as resistance to deformation under compression and energy absorption capacity.

[0105] For example, the second unit cell 110-3b can be selected as one of the structures classified as having relatively high stiffness (low deformation), such as an octahedral truss, a kabome lattice, a diamond cell, or an FCC. The first unit cell 110-3a can be selected as one of the structures classified as having relatively low stiffness (high deformation), such as a Kelvin cell, a tetrahedral cell, or a dodecahedral cell. For example, the second unit cell 110-3b can be selected as a tension-dominated unit cell with relatively high stiffness (low deformation) (e.g., an octahedral truss or a kabome lattice), and the first unit cell 110-3a can be selected as a bending-dominated unit cell with relatively low stiffness (high deformation) (e.g., a Kelvin or a tetrahedral cell).

[0106] The pressing pad 100 according to embodiments of the present disclosure may include a lattice structure 101-3 in which a first region A1 and a second region A2 defining unit cells 110-3 with different structures are defined, and may provide different pressing forces corresponding to positions on the electrode assembly. In other words, a first portion of the electrode assembly having a relatively large thickness can be pressed by the contact surface of the first region A1 having relatively low stiffness, and a second portion of the electrode assembly having a relatively small thickness can be pressed by the contact surface of the second region A2 having relatively high stiffness. Therefore, electrode assemblies with thickness variations can be pressed uniformly overall.

[0107] Figure 11 This is a schematic cross-sectional view illustrating a pressure pad according to an embodiment of the present disclosure. In the following description of embodiments of the present disclosure, descriptions of components substantially the same as those in the above embodiments will be omitted.

[0108] Reference Figure 11 The lattice structure 101-4 may include one or more layers L1, L2, and L3. The accompanying drawings show an example of layers L1, L2, and L3 configured as three layers, but this disclosure is not limited thereto. Layers L1, L2, and L3 may be stacked along the pressing direction and may be connected to each other. Each of layers L1, L2, and L3 may include a plurality of unit cells 110-4 arranged in the row and column directions.

[0109] The second region A2 may have a greater thickness than the first region A1. The foregoing may indicate that the contact surface corresponding to the second region A2 of the lattice structure 101-4 protrudes further in the pressing direction than the contact surface corresponding to the first region A1.

[0110] More specifically, the lattice structure 101-4 may include one or more additional layers AL selectively stacked in the second region A2. Since the additional layers AL are formed in the second region A2, the second region A2 of the lattice structure 101-4 can have a greater thickness than the first region A1. That is, the contact surface corresponding to the second region A2 of the lattice structure 101-4 can be positioned to protrude further in the pressing direction than the contact surface corresponding to the first region A1. During the pressing process, the contact surface corresponding to the second region A2 of the lattice structure 101-4 can contact the battery cell earlier than the contact surface corresponding to the first region A1.

[0111] Each of layers L1, L2, and L3 may include a plurality of unit cells 110-4 arranged in the row and column directions. The unit cells 110-4 may include a first unit cell 110-4a assigned to a first region A1 and a second unit cell 110-4b assigned to a second region A2. In an embodiment, the first unit cell 110-4a and the second unit cell 110-4b may be of the same type of unit cell 110-4.

[0112] The additional layer AL can be stacked on top of layers L1, L2, and L3 in the second region A2 along the pressing direction. The additional layer AL can be connected to layers L1, L2, and L3. The additional layer AL can include a plurality of third unit cells 110-4c arranged in the row and column directions. In an embodiment, the third unit cells 110-4c can be unit cells 110-4 of the same type as the first unit cells 110-4a and the second unit cells 110-4b, but this disclosure is not limited thereto.

[0113] The pressing pad 100 according to embodiments of the present disclosure may include a lattice structure 101-4 defining a first region A1 and a second region A2 with different thicknesses, and may provide different pressing forces corresponding to positions on the electrode assembly. In other words, a first portion of the electrode assembly with a relatively large thickness can be pressed through the contact surface of the first region A1 with a relatively small thickness, and a second portion of the electrode assembly with a relatively small thickness can be pressed through the contact surface of the second region A2 with a relatively large thickness. Therefore, electrode assemblies with thickness variations can be pressed uniformly overall.

[0114] In the following, materials that can be used in secondary batteries according to embodiments of the present disclosure are described.

[0115] Compounds capable of reversibly inserting and deintercalating lithium (e.g., lithiation intercalation compounds) can be used as positive electrode active materials. Specifically, one or more composite oxides of lithium selected from metals chosen from cobalt, manganese, nickel, and combinations thereof can be used as positive electrode active materials.

[0116] The composite oxide can be a lithium transition metal composite oxide. Specific examples of composite oxides may include lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free nickel manganese oxides, or combinations thereof.

[0117] For example, a compound represented by one of the following chemical formulas can be used: Li a A 1-b X b O 2-c D c (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05);Li aMn 2-b X b O 4-c D c (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05);Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.5,0<α<2);Li a Ni 1-b-c Mn b X c O 2-α D α (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.5,<α<2);Li a Ni b Co c L 1 d G e O2(0.90≤a≤1.8,0≤b≤0.9,0≤c≤0.5,0≤d≤0.5,0≤e≤0.1); Li a NiG b O2(0.90≤a≤1.8,0.001≤b≤0.1);Li a CoG b O2(0.90≤a≤1.8,0.001≤b≤0.1);Li a Mn 1-b G b O2(0.90≤a≤1.8,0.001≤b≤0.1);Li a Mn2G b O4(0.90≤a≤1.8,0.001≤b≤0.1);Li a Mn 1-g G g PO4(0.90≤a≤1.8,0≤g≤0.5);Li (3-f) Fe2(PO4)3 (0≤f≤2); and Li a FePO4 (0.90≤a≤1.8).

[0118] In the chemical formula, A can be Ni, Co, Mn, or a combination thereof. X can be Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, or a combination thereof; D can be O, F, S, P, or a combination thereof. G can be Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof. L 1may be Mn, Al, or a combination thereof.

[0119] A positive electrode for a lithium secondary battery may include a current collector and a positive electrode active material layer formed on the current collector. The positive electrode active material layer may include a positive electrode active material, and may further include a binder and / or a conductive material.

[0120] Relative to 100 wt% of the positive electrode active material layer, the content of the positive electrode active material may be 90 wt% to 99.5 wt%. Relative to 100 wt% of the positive electrode active material layer, the content of each of the binder and the conductive material may be 0.5 wt% to 5 wt%.

[0121] An Al foil may be used as the current collector, but the present disclosure is not limited thereto.

[0122] The negative electrode active material may include a material capable of reversibly intercalating / deintercalating with respect to lithium ions, lithium metal, an alloy of lithium metal, a material capable of being doped and dedoped with respect to lithium, or a transition metal oxide.

[0123] The material capable of reversibly intercalating / deintercalating with respect to lithium ions may include a carbon-based negative electrode active material, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon may include graphite, such as natural graphite or synthetic graphite. Examples of the amorphous carbon may include soft carbon or hard carbon, mesophase pitch carbide, and calcined coke.

[0124] A Si-based negative electrode active material or a Sn-based negative electrode active material may be used as the material capable of being doped and dedoped with respect to lithium. The Si-based negative electrode active material may be silicon, a silicon-carbon composite, SiO x (0<x≤2), a Si-based alloy, or a combination thereof.

[0125] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to an embodiment, the silicon-carbon composite may include silicon particles, and may have a form in which amorphous carbon is coated on the surfaces of the silicon particles.

[0126] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles, and an amorphous carbon coating layer disposed on the surface of the core.

[0127] A negative electrode for a lithium secondary battery may include a current collector and a negative electrode active material layer disposed on the current collector. The negative electrode active material layer may include a negative electrode active material, and may further include a binder and / or a conductive material.

[0128] For example, the negative electrode active material layer may contain 90 wt% to 99 wt% of the negative electrode active material, 0.5 wt% to 5 wt% of the binder, and 0 wt% to 5 wt% of the conductive material.

[0129] Non-aqueous binders, aqueous binders, dry binders, or combinations thereof may be used as binders. If an aqueous binder is used as the binder for the negative electrode, the binder for the negative electrode may also include cellulose compounds capable of imparting viscosity.

[0130] A current collector selected from nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof can be used as the current collector for the negative electrode.

[0131] Electrolytes used in lithium secondary batteries may include non-aqueous organic solvents and lithium salts.

[0132] Non-aqueous organic solvents can act as a medium through which ions participating in the electrochemical reactions of a battery can move.

[0133] Non-aqueous organic solvents can be carbonates, esters, ethers, ketones, alcohols, aprotic solvents, or combinations thereof. Carbonates, esters, ethers, ketones, alcohols, or aprotic solvents can be used alone or in combination as a non-aqueous organic solvent.

[0134] Furthermore, if carbonate solvents are used, cyclic carbonates and chain carbonates can be mixed.

[0135] Depending on the type of lithium-ion secondary battery, a separator may be present between the positive and negative electrodes. Polyethylene, polypropylene, and polyvinylidene fluoride, or multilayers containing two or more of these materials, can be used as separators.

[0136] The membrane may include a porous substrate and a coating layer comprising organic, inorganic or combinations thereof disposed on one or both sides of the porous substrate.

[0137] Organic substances may include polyvinylidene fluoride-based heavy antibodies or (meth)acrylic acid polymers.

[0138] Inorganic substances may include inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite and combinations thereof, but this disclosure is not limited thereto.

[0139] Organic and inorganic substances can be in the form in which organic and inorganic substances are mixed in a coating layer, or in the form in which a coating layer including organic substances and a coating layer including inorganic substances are stacked.

[0140] Although this disclosure has been described above with reference to limited embodiments and accompanying drawings, this disclosure is not limited to the embodiments. Those skilled in the art to which this disclosure pertains can modify and alter this disclosure within the scope of its technical spirit and the equivalents of the claims.

Claims

1. A pressing device for manufacturing secondary batteries, the pressing device comprising: Press plate; as well as The pressing pad is fixed to the pressing surface of the pressing plate and includes a three-dimensional lattice structure provided by repeatedly or regularly arranging multiple unit cells formed by connecting multiple pillars.

2. The pressing device according to claim 1, wherein, The lattice structure includes at least one layer comprising the plurality of unit cells arranged in column and row directions, and includes a first region and a second region extending from the first region, the first region and the second region being defined in a direction intersecting the pressing direction.

3. The pressing device according to claim 2, wherein, The density of the unit cell allocated to the second region is higher than the density of the unit cell allocated to the first region.

4. The pressing device according to claim 2, wherein, The size of each of the unit cells allocated to the second region is smaller than the size of each of the unit cells allocated to the first region.

5. The pressing device according to claim 2, in, The at least one layer includes a plurality of sub-layers divided along the pressing direction corresponding to the second region. Wherein, the at least one layer in the first region comprises a first unit cell, Wherein, each of the plurality of sublayers in the second region comprises a second unit cell, and The size of the second unit cell is smaller than the size of the first unit cell.

6. The pressing device according to claim 5, wherein, The first unit cell and the second unit cell are constructed as corresponding unit cells with the same structure.

7. The pressing device according to claim 2, wherein, The porosity of the unit cell allocated to the second region is set to be lower than that of the unit cell allocated to the first region.

8. The pressing device according to claim 2, wherein, The thickness of each of the pillars forming the unit cell allocated to the second region is set to be greater than the thickness of each of the pillars forming the unit cell allocated to the first region.

9. The pressing device according to claim 2, in, The unit cell includes a first unit cell allocated to the first region and a second unit cell allocated to the second region. The second unit cell has a structure different from that of the first unit cell.

10. The pressing device according to claim 9, wherein, The second unit cell is selected to have a structure with higher stiffness or lower deformation than the first unit cell.

11. The pressing device according to claim 10, in, The second unit cell is selected as one of an octahedral truss, a cage-like lattice, a diamond cell, and a face-centered cubic structure, and The first unit cell is selected as one of Kelvin cell, tetrahedral cell, and dodecahedral cell.

12. The pressing device according to claim 10, in, The second unit cell is selected as one of the unit cells having a stretch-dominant structure, and The first unit cell is selected as one of the unit cells with a bending-dominant structure.

13. The pressing device according to claim 2, wherein, The second region has a greater thickness than the first region.

14. The pressing device according to claim 13, wherein, The second region further includes an additional layer stacked on the at least one layer along the pressing direction, the additional layer comprising a plurality of unit cells arranged in the column direction and the row direction.

15. The pressing device according to claim 1, wherein, The pressing pad includes: The first plate includes a fixed surface fixed to the pressing surface of the pressing plate and a connecting surface fixed to a surface of the dot matrix structure.

16. The pressing device according to claim 15, wherein, The pressing pad further includes: The second plate is configured to face the first plate along the pressing direction, the dot matrix structure is located between the second plate and the first plate, and the second plate includes a connecting surface fixed to another surface of the dot matrix structure.

17. The pressing device according to claim 16, wherein, The first plate and the second plate are integrally formed with the lattice structure.

18. The pressing device according to claim 16, wherein, The first plate and the second plate are formed of the same material as the lattice structure.

19. The pressing device according to claim 18, wherein, The pressing pad is formed of thermoplastic polyurethane.

20. The pressing device according to claim 1, wherein, Each of the plurality of unit cells is selected as one of the unit cells having a stretched dominant lattice structure.

Images