Battery module and battery pack including same

Abstract

A battery module according to one embodiment of the present invention includes: a battery cell stack in which a plurality of battery cells are stacked; a module frame that houses the battery cell stack and includes side portions that cover both sides of the battery cell stack in a stacking direction of the battery cells; and at least one compression pad disposed at at least one location between adjacent battery cells among the battery cells or between an outermost battery cell among the battery cells and the side portion. A reserved space ratio per battery cell in the stacking direction of the battery cells is 3% or more.

Description

[Technical Field]

[0001] The present invention relates to a battery module and a battery pack including the same, and more particularly to a battery module with improved life performance and a battery pack including the same. [Background technology]

[0002] In modern society, the use of portable devices such as mobile phones, laptops, video cameras, and digital cameras has become commonplace, resulting in active technological development in fields related to these mobile devices. Furthermore, rechargeable secondary batteries are being used as the power source for electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (P-HEVs), and other vehicles as a solution to air pollution caused by existing gasoline-powered vehicles that use fossil fuels, and this has led to an increasing need for the development of secondary batteries.

[0003] Currently commercially available secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, and lithium secondary batteries. Among these, lithium secondary batteries are attracting attention due to their advantages over nickel-based secondary batteries, such as almost no memory effect, freedom in charging and discharging, extremely low self-discharge rate, and high energy density.

[0004] Such lithium secondary batteries mainly use lithium-based oxides and carbon materials as positive and negative electrode active materials, respectively, and include an electrode assembly in which positive and negative electrode plates coated with the positive and negative electrode active materials are disposed with a separator between them, and an exterior material, i.e., a battery case, that hermetically houses the electrode assembly together with an electrolyte.

[0005] Generally, lithium secondary batteries can be classified into can-type secondary batteries, in which an electrode assembly is housed in a metal can, and pouch-type secondary batteries, in which an electrode assembly is housed in a pouch made of an aluminum laminate sheet, depending on the shape of the exterior material.

[0006] In recent years, secondary batteries have been widely used not only in small devices such as portable electronic devices but also in medium- to large-sized devices such as automobiles and power storage devices. For application to medium- to large-sized devices, multiple secondary batteries can be electrically connected to increase capacity and output.

[0007] While secondary batteries used in small devices typically have two or three battery cells, secondary batteries used in medium- to large-sized devices such as automobiles typically use battery modules in which multiple battery cells are electrically connected. These battery modules improve capacity and output by connecting multiple battery cells in series or parallel to form a cell stack. One or more battery modules can also be installed with various control and protection systems, such as a Battery Management System (BMS) and a cooling system, to form a battery pack.

[0008] At this time, pouch-type secondary batteries tend to be more widely used due to their advantages such as easy stacking and light weight, etc. Pouch-type secondary batteries can generally be manufactured by injecting an electrolyte solution into a pouch exterior material with an electrode assembly housed in the pouch exterior material, and then sealing the pouch exterior material.

[0009] Meanwhile, battery modules containing multiple battery cells must meet a certain level of lifespan performance. For example, battery modules used in electric vehicles are required to meet a capacity retention of 80% or more as part of a lifespan test evaluation. Specifically, the capacity retention after 800 cycles is calculated using the following formula:

[0010] Residual capacity rate at 800 cycles [%] = discharge capacity at 800 cycles / discharge capacity at 1 cycle × 100 That is, a battery module is required to have a lifespan performance of 80% or more of its discharge capacity after 800 charge / discharge cycles compared to its initial discharge capacity. However, because a battery module is made up of multiple battery cells assembled together, unlike when battery cells are charged and discharged individually, lifespan performance may deteriorate due to various factors within the battery module. Therefore, when battery cells are configured in a battery module, it is necessary to analyze the causes of the deterioration in lifespan performance, identify factors that affect lifespan performance, and develop improvement plans. Summary of the Invention [Problem to be solved by the invention]

[0011] The problem to be solved by the present invention is to derive factors that hinder the lifespan performance of a battery module, formulate solutions to the factors, and provide a battery module and a battery pack including the same that can improve the lifespan performance.

[0012] However, the problems to be solved by the embodiments of the present invention are not limited to the above-mentioned problems, and can be variously expanded within the scope of the technical ideas included in the present invention. [Means for solving the problem]

[0013] A battery module according to one embodiment of the present invention includes: a battery cell stack in which a plurality of battery cells are stacked; a module frame that houses the battery cell stack and includes side portions that cover both sides of the battery cell stack in a stacking direction of the battery cells; and at least one compression pad disposed at at least one location between adjacent battery cells among the battery cells or between an outermost battery cell among the battery cells and the side portion; and a reserved space ratio per battery cell based on the stacking direction of the battery cells is 3% or more.

[0014] A reserved space ratio per battery cell may be 3% or more and 10% or less based on the stacking direction of the battery cells.

[0015] The free space ratio per battery cell may be calculated as (WCP) / C×100, where W may be the distance between the side portions of the module frame, C may be a value corresponding to the total thickness of the battery cells, and P may be a value corresponding to the total thickness of the compression pads in a compressed state when the battery cell stack and the compression pads are housed in the module frame.

[0016] The value C may be a value obtained by multiplying the thickness of the center portion of the battery cell by the number of the battery cells.

[0017] The value P may be a value obtained by multiplying the thickness of the compression pad in a compressed state by the number of the compression pads.

[0018] The battery cells may be sheet-shaped pouch-type battery cells, and the battery cells may be stacked upright such that one surface of the battery cell is parallel to the side surface.

[0019] The battery module may further include at least one adhesive portion located at at least one of between facing battery cells, between the battery cell and the compression pad, or on an inner surface of the side portion.

[0020] The adhesive portion may be a double-sided tape or an adhesive layer formed by applying an adhesive.

[0021] The free space ratio per battery cell can be calculated by (WCPD) / C×100, where W is the value of the space between the side portions of the module frame, C is a value equivalent to the total thickness of the battery cells, P is a value equivalent to the total thickness of the compression pads in a compressed state when the battery cell stack and the compression pads are housed in the module frame, and D is a value equivalent to the total thickness of the adhesive portions.

[0022] The value C may be a value obtained by multiplying the thickness of the center portion of the battery cell by the number of the battery cells.

[0023] The value P may be a value obtained by multiplying the thickness of the compression pad in a compressed state by the number of the compression pads.

[0024] The value D may be a value obtained by multiplying the thickness of the adhesive joint by the number of the adhesive joints.

[0025] The battery cells may be sheet-like pouch-type battery cells, and the battery cells may be stacked upright so that one surface of each battery cell is parallel to the side surface portion.

[0026] The adhesive portion may be attached to the one surface of the battery cell to cover the one surface of the battery cell.

[0027] The adhesive portion may be attached to the one surface of the battery cell so as to cover 90% to 100% of the area of ​​the one surface of the battery cell.

[0028] The adhesive portion may be attached to the one surface of the battery cell so as to cover an area of ​​90% to 101% of the area of ​​the one surface of the battery cell.

[0029] A battery pack according to an embodiment of the present invention may include the battery module. [Effects of the Invention]

[0030] According to an embodiment of the present invention, a standard for the ratio of free space per battery cell in a battery module is set, thereby preventing a decrease in the life performance of the battery module.

[0031] In addition, an adhesive portion is provided to cover one surface of the battery cell, thereby ensuring uniformity of pressure applied to the surface of the battery cell inside the battery module.

[0032] The effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims. [Brief explanation of the drawings]

[0033] [Figure 1] 1 is a perspective view of a battery module according to an embodiment of the present invention; [Figure 2] FIG. 2 is an exploded perspective view of the battery module of FIG. [Figure 3] 3 is a plan view showing one of the battery cells included in the battery module of FIG. 2. FIG. [Figure 4] FIG. 2 is a cross-sectional view taken along the line AA' in FIG. [Figure 5] 10 is a cross-sectional view of a battery module according to another embodiment of the present invention. [Figure 6] FIG. 10 is a perspective view showing a battery cell stack according to a comparative example of the present invention. [Figure 7] 1 is a perspective view showing a battery cell stack according to an embodiment of the present invention; [Figure 8] 1 is a plan view showing a state in which an adhesive portion is formed on one surface of a battery cell according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention will now be described in detail with reference to the accompanying drawings, so that those skilled in the art can easily carry out the various embodiments of the present invention. The present invention can be embodied in several different forms and is not limited to the examples described herein.

[0035] In order to clearly describe the present invention, parts that are not relevant to the description will be omitted and the same reference numerals will be used throughout the specification to refer to the same or similar components.

[0036] In addition, the size and thickness of each component shown in the drawings are arbitrarily shown for the convenience of explanation, and the present invention is not necessarily limited to those shown in the drawings. In the drawings, thicknesses are exaggerated to clearly show multiple layers and regions. In the drawings, thicknesses of some layers and regions are exaggerated for the convenience of explanation.

[0037] Furthermore, when a layer, film, region, plate, or other part is said to be "on" or "above" another part, this includes not only the case where it is "directly above" that other part, but also the case where there is another part in between. Conversely, when a part is said to be "directly above" another part, it means that there is no other part in the middle. Furthermore, being "on" or "above" a reference part means being located above or below the reference part, and does not necessarily mean being "above" or "above" facing the opposite direction of gravity.

[0038] Furthermore, throughout the specification, when a part "comprises" a certain element, it does not mean that it excludes other elements, but that it may further include other elements, unless otherwise specified.

[0039] Also, throughout the specification, "on a plane" means when the target part is viewed from above, and "on a cross section" means when the target part is cut vertically and viewed from the side.

[0040] Fig. 1 is a perspective view of a battery module according to an embodiment of the present invention, Fig. 2 is an exploded perspective view of the battery module of Fig. 1, and Fig. 3 is a plan view showing one of the battery cells included in the battery module of Fig. 2.

[0041] 1 to 3, a battery module 100 according to one embodiment of the present invention includes a battery cell stack 120 in which a plurality of battery cells 110 are stacked; a module frame 200 that houses the battery cell stack 120; and at least one compression pad 400.

[0042] First, the battery cell 110 may be a pouch-type battery cell. A pouch-type battery cell may be formed by placing an electrode assembly in a pouch case made of a laminate sheet including a resin layer and a metal layer, and then joining the outer periphery of the pouch case. Such a battery cell 110 may be in the form of a rectangular sheet. Specifically, the battery cell 110 according to this embodiment has two electrode leads 111 and 112 facing each other and protruding from one end 114a and the other end 114b of a battery body 113, respectively. The battery cell 110 may be manufactured by joining both ends 114a and 114b of the battery case 114 and one side 114c connecting them, with an electrode assembly (not shown) placed in the battery case 114. That is, the battery cell 110 according to this embodiment may have a total of three sealing portions, and the remaining side may be configured as a folding portion 115. The distance between both ends 114a, 114b of the battery case 114 can be defined as the length direction of the battery cell 110, and the distance between one side portion 114c connecting both ends 114a, 114b of the battery case 114 and the folding portion 115 can be defined as the width direction of the battery cell 110.

[0043] While the present invention has been described with reference to a battery cell 110 having electrode leads 111 and 112 protruding from both sides, a unidirectional pouch-type battery cell in which the electrode leads protrude in one direction is also possible as another embodiment of the present invention. A plurality of such battery cells 110 are stacked in one direction to electrically connect with each other, forming a battery cell stack 120. The battery case 114 generally has a laminate structure of a resin layer / metal thin film layer / resin layer. For example, if the surface of a battery case is made of an O-(oriented)-nylon layer, the battery cells tend to slip easily due to external impact when stacking multiple battery cells to form a medium- to large-sized battery module. Therefore, to prevent this and maintain a stable stacked structure of the battery cells, an adhesive may be provided on the surface of the battery case to form the battery cell stack 120. The adhesive may be a pressure-sensitive adhesive such as double-sided tape or a chemical adhesive that bonds through a chemical reaction during adhesion. The adhesive will be described later.

[0044] A plurality of battery cells 110 are stacked in one direction to form the battery cell stack 120. The battery cells 110, each having a rectangular sheet structure, can be stacked in one direction with one side of the battery bodies 113 facing each other. More specifically, the battery cells 110 can be stacked upright so that the one side of the battery cells 110 is parallel to the side portions 210 and 220 of the module frame 200, which will be described later. FIG. 2 shows the battery cells 110 stacked in a direction parallel to the y-axis to form the battery cell stack 120. This allows the electrode leads 111 and 112 in the battery cell stack 120 to protrude in the x-axis and -x-axis directions.

[0045] The module frame 200 may be a frame with one side and the other side open. The battery cell stack 120 may be inserted through one or the other open side of the module frame 200, and the battery cell stack 120 may be accommodated in the internal space of the module frame 200.

[0046] The module frame 200 includes side portions 210, 220 that respectively cover both side surfaces of the battery cell stack 120 along the stacking direction of the battery cells 110. For battery cells 110 stacked along the y-axis direction, the side portions 210, 220 of the module frame 200 can respectively cover the side surface in the y-axis direction and the side surface in the -y-axis direction of the battery cell stack 120.

[0047] The module frame 200 may also include an upper surface portion 230 and a lower surface portion 240 that connect the side surface portions 210 and 220. The upper surface and lower surface of the battery cell stack 120 housed inside the module frame 200 may be covered by the upper surface portion 230 and the lower surface portion 240 of the module frame 200, respectively.

[0048] 2 may have a form in which side portions 210, 220, upper portion 230, and lower portion 240 are integrated, or in another embodiment of the present invention, the module frame may have a form in which a U-shaped frame and an upper cover are joined together. The module frame may be formed by joining corresponding corners of the U-shaped frame, which covers both side surfaces and the lower surface of the battery cell stack, and the upper cover, which covers the upper surface of the battery cell stack.

[0049] The battery module 100 according to this embodiment may include a bus bar frame 500 that is housed in the module frame 200 together with the battery cell stack 120. The bus bar frame 500 may include a front frame 510 and a rear frame 520 that are respectively located on one side and the other side of the battery cell stack 120 from which the electrode leads 111 and 112 protrude. The bus bar frame 500 may further include an upper frame 530 that is connected to the front frame 510 and the rear frame 520 and is located on the top of the battery cell stack 120.

[0050] Bus bars 540 for connecting the electrode leads 111, 112 of the battery cells 110 included in the battery cell stack 120 may be attached to the front frame 510 and the rear frame 520. Specifically, the electrode leads 111, 112 of the battery cells 110 may pass through slits formed in the front frame 510 and the rear frame 520, be bent, and joined to the bus bars 540 by a method such as welding. In this manner, the battery cells 110 included in the battery cell stack 120 may be electrically connected in series or in parallel.

[0051] The battery module 100 according to this embodiment may include end plates 300 located on both opposing open sides of the module frame 200. The end plates 300 may be provided to cover one and the other open sides of the module frame 200. That is, two end plates 300 may be located on both open sides of the module frame 200 and joined to corresponding corners of the module frame 200 by a method such as welding. Such end plates 300 may physically protect the battery cell stack 120 and other electrical components from external impacts.

[0052] FIG. 4 is a cross-sectional view taken along the line AA' in FIG.

[0053] 2 to 4, the battery module 100 according to this embodiment includes at least one compression pad 400 disposed at at least one of between adjacent battery cells 110 or between the outermost battery cell 110 and the side portion 210, 220.

[0054] The compression pad 400 is a foam-like member that can partially absorb swelling of the battery cell. Specifically, the battery cell 110 may generate gas internally due to degradation caused by repeated charging and discharging. When gas is generated internally, the internal pressure increases, which may cause swelling, in which at least a portion of the exterior material expands. In particular, in the case of pouch-type secondary batteries, the structural rigidity of the exterior material is weaker than in can-type secondary batteries, so swelling may occur more severely.

[0055] When swelling occurs in a secondary battery, the pressure inside the battery increases, causing an increase in volume, which may adversely affect the structural stability of the battery module. Therefore, an attempt has been made to absorb some of the swelling of the battery cells 110 by disposing a compression pad 400 that compresses when pressure is applied inside the battery module 100. There are no particular limitations on the material of the compression pad 400 as long as it can absorb the swelling of the battery cells 110 when compressed, and it may include, for example, a polyurethane material.

[0056] Meanwhile, the battery module according to this embodiment has a reserved space ratio per battery cell of 3% or more based on the stacking direction of the battery cells 110. The reserved space ratio per battery cell may be 3% or more and 10% or less. Furthermore, when taking into consideration the space utilization and energy density of the battery module, the reserved space ratio per battery cell may be 3% or more and 6% or less, or may be 4% or more and 6% or less.

[0057] The reserved space ratio per battery cell is a value calculated by calculating the space that one battery cell 110 has in the battery module 100, and can be calculated by the following formula.

[0058] Reserved Space Ratio per battery cell = (WCP) / C x 100 In the above formula, W is the distance between the side portions 210 and 220 of the module frame 200, C is a value corresponding to the total thickness of the battery cells 110, and P is a value corresponding to the total thickness of the compression pad 400 in a compressed state when the battery cell stack 120 and the compression pad 400 are housed in the module frame 200. The values ​​of W, C, and P may all be expressed in mm.

[0059] 4, W corresponds to the distance between the inner surfaces of the side surface portions 210, 220 of the module frame 200. As described above, the side surface portions 210, 220 in this embodiment are portions that respectively cover both side surfaces of the battery cell stack 120 along the stacking direction of the battery cells 110, and are portions related to the pressure force applied to the battery cells 110 that causes expansion.

[0060] The C is a value corresponding to the total thickness of the battery cells 110 and can be calculated by multiplying the thickness (Ct) of the center of the single battery cell 110 by the number (Cn) of the battery cells 110. That is, C = Ct × Cn, where Ct is a value corresponding to the thickness of the center of the single battery cell 110 along the stacking direction (y-axis direction) of the battery cells 110, and Cn is a value corresponding to the number of the battery cells 110. For example, as shown in FIG. 4, the C value can be calculated by multiplying the thickness (Ct) of the single battery cell 110 by 12, which is the number (Cn) of the battery cells 110. Here, the center of the battery cell 110, which is the target of thickness (Ct) measurement, refers to the center portion of the battery cell 110 in the longitudinal direction. More specifically, referring to FIG. 3, it can refer to the midpoint between both ends 114a and 114b of the battery cell 110 from which the electrode leads 111 and 112 protrude.

[0061] The value P can be calculated by multiplying the thickness (Pt) of a single compression pad 400 by the number (Pn) of the compression pads 400 when the battery cell stack 120 and compression pads 400 are housed in the module frame 200 and compressed. That is, P=Pt×Pn, where Pt is a value corresponding to the thickness of a single compression pad 400 in a compressed state, and Pn is a value corresponding to the number of compression pads 400. For example, as shown in FIG. 4, the value P can be calculated by multiplying the thickness (Pt) of a single compression pad 400 by 4, which is the number (Pn) of the compression pads 400.

[0062] Hereinafter, a battery module according to another embodiment of the present invention will be described with reference to FIG.

[0063] FIG. 5 is a cross-sectional view of a battery module according to another embodiment of the present invention, and corresponds to a cross-section of the battery module taken along the yz plane, similar to FIG.

[0064] 5, the battery module 100 according to this embodiment may further include at least one adhesive portion 600 located at at least one of between the battery cells 110 facing each other, between the battery cell 110 and the compression pad 400, or on the inner surfaces of the side portions 210 and 220. Here, the inner surfaces of the side portions 210 and 220 refer to the surfaces of the side portions 210 and 220 facing the battery cell stack 120. The battery cell stack 120, module frame 200, and compression pad 400 included in the battery module 100 have the same configurations as those described in the embodiments of FIGS. 1 to 4, and therefore further description thereof will be omitted.

[0065] As described above, a large number of battery cells 110 are stacked to form a medium- to large-sized battery module 100, and in order to maintain a stable stacked structure of the battery cells 110, an adhesive portion 600 may be provided on one side of the battery cell 110.

[0066] Not only are adhesive portions 600 provided between the battery cells 110, but when a compression pad 400 is positioned between the battery cells 110, the adhesive portion 600 may also be provided between the battery cell 110 and the compression pad 400. In addition, adhesive portions 600 may also be provided on the inner surfaces of the side portions 210 and 220. As shown, when a compression pad 400 is positioned between the outermost battery cell 110 of the battery cells 110 and the side portions 210 and 220, the adhesive portion 600 may be provided between the compression pad 400 and the side portions 210 and 220.

[0067] Specifically, FIG. 5 shows adhesive portions 600 located between adjacent battery cells 110 and bonded to one side of each battery cell 110, adhesive portions 600 bonded between the battery cells 110 and the compression pad 400, and adhesive portions 600 bonded between the compression pad 400 and the side portions 210, 220.

[0068] Although not shown, in another embodiment of the present invention in which the compression pad 400 is not positioned between the outermost battery cell 110 among the battery cells 110 and the side portions 210, 220, an adhesive portion 600 may be provided between the outermost battery cell 110 among the battery cells 110 and the side portions 210, 220.

[0069] The adhesive part 600 according to this embodiment may be any material or member having adhesive properties. For example, the adhesive part 600 may be a double-sided tape. For another example, the adhesive part 600 may be an adhesive layer formed by applying an adhesive.

[0070] At this time, the battery module according to this embodiment has a reserved space ratio per battery cell of 3% or more based on the stacking direction of the battery cells 110.

[0071] In this embodiment, the reserved space ratio per battery cell can be calculated using the following formula.

[0072] Reserved Space Ratio per battery cell = (WCPD) / C x 100 In the above formula, W is the distance between the side portions 210 and 220 of the module frame 200, C is a value corresponding to the total thickness of the battery cells 110, P is a value corresponding to the total thickness of the compression pad 400 in a compressed state when the battery cell stack 120 and the compression pad 400 are housed in the module frame 200, and D is a value corresponding to the total thickness of the adhesive portion 600. The values ​​of W, C, P, and D may all be in mm.

[0073] As shown in FIG. 5, W corresponds to the distance between the inner surfaces of the side portions 210 and 220 of the module frame 200.

[0074] The C is a value corresponding to the total thickness of the battery cells 110 and can be calculated by multiplying the thickness (Ct) of the center of the single battery cell 110 by the number (Cn) of the battery cells 110. That is, C = Ct × Cn, where Ct is a value corresponding to the thickness of the center of the single battery cell 110 along the stacking direction (y-axis direction) of the battery cells 110, and Cn is a value corresponding to the number of the battery cells 110. For example, as shown in FIG. 5, the C value can be calculated by multiplying the thickness (Ct) of the single battery cell 110 by 12, which is the number (Cn) of the battery cells 110. Here, the center of the battery cell 110, which is the target of thickness (Ct) measurement, refers to the center portion of the battery cell 110 in the longitudinal direction. More specifically, referring to FIG. 3, the center of the battery cell 110 may refer to the midpoint between both ends 114a and 114b of the battery cell 110 from which the electrode leads 111 and 112 protrude.

[0075] The value P can be calculated by multiplying the thickness (Pt) of a single compression pad 400 by the number (Pn) of compression pads 400 when the battery cell stack 120 and compression pads 400 are housed together in the module frame 200 and compressed. That is, P=Pt×Pn, where Pt is a value corresponding to the thickness of a single compression pad 400 in a compressed state, and Pn is a value corresponding to the number of compression pads 400. For example, as shown in FIG. 5, the value P can be calculated by multiplying the thickness (Pt) of a single compression pad 400 by the number (Pn), which is four, of the compression pads 400.

[0076] The distance D can be calculated by multiplying the thickness (Dt) of a single adhesive portion 600 by the number (Dn) of the adhesive portions 600. That is, D = Dt × Dn, where Dt is a value corresponding to the thickness of a single adhesive portion 600 and Dn is a value corresponding to the number of adhesive portions 600. For example, adhesive portions 600 may be positioned between the battery cells 110 and between the battery cells 110 and the compression pads 400. In addition, when the compression pads 400 or the battery cells 110 are positioned at the outermost positions, adhesive portions 600 may also be positioned on the outer surfaces of the outermost compression pads 400 or battery cells 110. Adhesives 600 may also be positioned between the outermost compression pads 400 or battery cells 110 and the side portions 210 and 220. That is, as described above, adhesive portions 600 may be provided on the inner surfaces of the side portions 210 and 220. When the battery cells 110 and the compression pads 400 are considered as one component, an adhesive 600 may be interposed between each of these components. The number of adhesives 600 (Dn) may be calculated by adding 1 to the sum of the number of battery cells 110 (Cn) and the number of compression pads 400 (Pn). As an example, referring to FIG. 5, in which 12 battery cells 110 and four compression pads 400 are arranged inside the module frame 200, a total of 17 adhesives 600 may be provided. In this case, D is the thickness (Dt) of a single adhesive 600 multiplied by 17, which is the number of adhesives 600 (Dn).

[0077] In summary, in the case of a battery module that does not have an adhesive, the reserved space ratio per battery cell can be calculated as (WCP) / C×100, and in the case of a battery module that has an adhesive, the reserved space ratio per battery cell can be calculated as (WCPD) / C×100, and the battery module 100 in this embodiment has a calculated reserved space ratio value of 3% or more.

[0078] The inventors of the present invention have confirmed that the space between the battery cells 110 in the battery module 100, i.e., the pressure applied to the battery cells 110, affects the lifespan performance of the battery module 100. If an appropriate level of pressure is not applied to the battery cells 110, the battery module 100 will not maintain an appropriate capacity even as it undergoes cycles. If the pressure is below or above a certain level, a sudden drop in capacity may occur as the cycles proceed. Based on this, the inventors of the present invention designed a condition in which a reserved space ratio per battery cell is 3% or more in order to control the absolute pressure applied to the battery cells 110 inside the battery module 100. They confirmed that if this condition is met, there will be no deterioration in lifespan performance when the battery cells 110 are installed in the battery module 100. Specifically, a battery module that satisfies this condition can maintain a capacity retention of 80% or more after 800 cycles.

[0079] Hereinafter, the battery module of the present invention will be described with reference to specific examples and comparative examples.

[0080] [Table 1]

[0081] First, referring to Table 1, battery modules having different standards and specifications were prepared in Examples 1 to 4, and the spare space ratio (%) per battery cell was calculated for the battery modules in Examples 1 to 4. The units for each factor are shown in parentheses.

[0082] As mentioned above, W is the measured value of the distance between the inner surfaces of the side portions 210, 220 of the module frame 200. The C, which corresponds to the total thickness of the battery cells 110, is calculated by multiplying the thickness (Ct) of the center of the battery cell 110 by the number of battery cells 110 (Cn).

[0083] It was confirmed that the compression pad 400 was compressed by 80% when inserted into the module frame 200 together with the battery cells 110, and the thickness (Pt) of the compression pad 400 in the compressed state was calculated to be 20% of the original thickness of the compression pad 400 before compression. The total thickness value of the compression pad in the compressed state, P, can be calculated by multiplying the thickness (Pt) of the compression pad 400 in the compressed state by the number of compression pads 400 (Pn).

[0084] The value D, which corresponds to the total thickness of the adhesive portions 600, can be calculated by multiplying the thickness of a single adhesive portion 600 (Dt) by the number of adhesive portions 600 (Dn). In the battery modules of Examples 1 to 4, adhesive portions 600 are located between adjacent battery cells 110, between the battery cells 110 and the compression pads 400, and on the outermost compression pads 400 or on the outer surfaces of the battery cells 110. In Examples 1 to 4, the number of adhesive portions 600 is calculated by adding 1 to the sum of the number of battery cells 110 (Cn) and the number of compression pads 400 (Pn).

[0085] The available space ratio [%] per battery cell was calculated using the derived W, C, P, and D values ​​for Examples 1 to 4, and it was calculated that Examples 1 to 4 had available space ratio values ​​per battery cell of 3.65%, 4.27%, 4.43%, and 3.59%, respectively. The available space ratios per battery cell for Examples 1 to 4 were all 3% or more.

[0086] The remaining capacity rate [%] at 800 cycles for each battery cell and the remaining capacity rate [%] at 800 cycles for each battery module were measured for Examples 1 to 4. The remaining capacity rate at 800 cycles for each battery cell was measured as the discharge capacity after 800 charge / discharge cycles relative to the initial discharge capacity for a single battery cell that was not part of a battery module.

[0087] The remaining capacity rate after 800 cycles for a battery module unit is a value obtained by measuring the discharge capacity after 800 cycles of charge and discharge relative to the initial discharge capacity for a battery module including the battery cell.

[0088] The difference between the remaining capacity rate at 800 cycles in the battery cell unit and the remaining capacity rate at 800 cycles in the battery module unit, i.e., the capacity degradation difference [%] between the battery cell and the battery module, was measured as 5, 0.3, -1, and 1 values ​​for Examples 1 to 4, respectively.

[0089] In Examples 1 to 4, where the surplus space ratio per battery cell was all 3% or more, it was confirmed that there was no significant decrease in lifespan performance even when the battery cells 110 were configured in the battery module 100. There was not much difference in the remaining capacity rate at 800 cycles between the battery cell unit and the battery module unit. That is, even as the battery module 100 was cycled, it was possible to maintain an appropriate capacity, and there was no problem of sudden drop in capacity as the cycles progressed.

[0090] [Table 2]

[0091] Referring to Table 2, battery modules having different standards and specifications were prepared in Comparative Examples 1 to 3, and the spare space ratio (%) per battery cell was calculated for the battery modules of Comparative Examples 1 to 3. The units for each factor are shown in parentheses.

[0092] The W, C, P, and D values ​​for Comparative Examples 1 to 3 were calculated using the same measurement methods as in Examples 1 to 4. The explanation for this will be omitted as it overlaps with the content explained above.

[0093] The available space ratio [%] per battery cell was calculated using the derived W, C, P, and D values ​​for Comparative Examples 1 to 3, and it was calculated that Examples 1 to 3 had available space ratio values ​​per battery cell of 1.93%, 1.88%, and 2.46%, respectively. The available space ratios per battery cell for Comparative Examples 1 to 3 were all less than 3%.

[0094] The remaining capacity rate at 800 cycles, the remaining capacity rate at 800 cycles per battery module, and the difference in capacity degradation between the battery cell and the battery module were calculated using the same methods as in Examples 1 to 4. The difference in capacity degradation [%] between the battery cell and the battery module was measured to be 18.8, 18.8, and 15.8 for Comparative Examples 1 to 3, respectively.

[0095] In the case of Comparative Examples 1 to 3, in which the reserved space ratio per battery cell was all less than 3%, it was confirmed that a significant decrease in lifespan performance occurred when the battery cells 110 were configured in the battery module 100, compared to Examples 1 to 4. That is, it was confirmed through the experimental results that when the condition of the reserved space ratio per battery cell being 3% or more is satisfied, as in the battery module according to this embodiment, a significant decrease in lifespan performance of the battery module can be prevented.

[0096] Hereinafter, with reference to FIGS. 6 to 8, the formation region of the adhesive portion 600 according to one embodiment of the present invention will be described in detail together with a comparative example.

[0097] FIG. 6 is a perspective view showing a battery cell stack according to a comparative example of the present invention.

[0098] First, referring to FIG. 6, a plurality of battery cells 11 are stacked to form a battery cell stack 12, and an adhesive portion 60 may be provided at at least one location between the battery cells 11. Such adhesive portion 60 may be a double-sided tape or an adhesive layer formed by applying an adhesive. As shown in FIG. 6, the adhesive portion 60 according to this comparative example is not attached to the entire surface of the battery cells 11 facing each other, but is attached only to a portion of the surface. In this case, the inventors of the present invention have confirmed that the partially formed adhesive portion 60 applies uneven pressure to the battery cells 110, resulting in lithium plating at both ends.

[0099] Specifically, the partially formed adhesive portion 60 causes uneven surface pressure on the surface of the battery cell 110, and gas generated by the uneven surface pressure is present on the surface of the battery cell, causing lithium plating (Li-plating) in which lithium is deposited on the surface of the battery cell 110. In particular, referring to both Figures 3 and 6, when the adhesive portion 60 is formed only in the center portion of the battery cell 110, a problem has been discovered in which lithium is mainly deposited in the portions adjacent to both end portions 114a, 114b of the battery cell 110 where the electrode leads 111, 112 protrude.

[0100] The inventors of the present invention analyzed the relationship between the lithium deposition rate from lithium plating (Li-Plating) and the remaining capacity rate of a battery cell and found that there is a strong negative correlation between the lithium deposition rate and the remaining capacity rate of a battery cell. That is, the higher the lithium deposition rate, the lower the remaining capacity rate after 800 cycles. Therefore, uneven surface pressure on the battery cells 110 caused by the adhesive 60 adversely affects the lifespan performance of the battery module 100. Therefore, the inventors of the present invention proposed the adhesive 600 shown below as a structure for applying uniform pressure to the surface of the battery cells 110. The formation area of ​​the adhesive 600 according to this embodiment will be described below with reference to FIGS. 3, 7, and 8.

[0101] Fig. 7 is a perspective view showing a battery cell stack according to an embodiment of the present invention, and Fig. 8 is a plan view showing an adhesive part formed on one surface of a battery cell according to an embodiment of the present invention.

[0102] 3, 7, and 8, as described above, the battery cells 110 are sheet-like pouch-type battery cells, and the battery cells 110 can be stacked upright so that one side of the battery cells 110 is parallel to the side surfaces 210 and 220 (see FIG. 2). The battery cells 110 can be stacked so that the one side faces each other. That is, the one side of the battery cells 110 described below corresponds to the part of the battery cell 110 that is parallel to the side surfaces 210 and 220 of the module frame 200, and can face another battery cell 110, a compression pad 400, or the side surfaces 210 and 220 of the module frame 200.

[0103] At this time, the adhesive part 600 according to this embodiment may be attached to the one surface of the battery cell 110 so as to cover the one surface of the battery cell 110. Specifically, the adhesive part 600 may be attached to the one surface of the battery cell 110 so as to cover 90% to 100% of the area of ​​the one surface of the battery cell 110. In addition, when considering the design tolerance for the one surface of the battery cell 110, the adhesive part 600 may be attached to the one surface of the battery cell 110 so as to cover 90% to 101% of the area of ​​the one surface of the battery cell 110.

[0104] Unlike the adhesive 60 according to the comparative example described above, the adhesive 600 according to this embodiment can be attached to cover most of the one surface of the battery cell 110. This makes it possible to achieve a uniform pressure structure for the one surface of the battery cell 110. Unlike the adhesive 60 that is attached only in a small area, the adhesive 600 according to this embodiment can ensure uniform pressure applied to the surface of the battery cell 110. This solves the problem of lithium plating occurring in areas adjacent to both ends 114a, 114b of the battery cell 110 and improves the life performance of the battery module 100.

[0105] Meanwhile, referring to FIGS. 4 and 5, the battery module 100 according to this embodiment may further include a thermally conductive resin layer 700 positioned between the battery cell stack 120 and the lower surface portion 240 of the module frame 200.

[0106] The thermally conductive resin layer 700 may be formed by applying a thermally conductive resin to the lower surface portion 240 and curing the applied thermally conductive resin, or by injecting the thermally conductive resin through through-holes formed in the lower surface portion 240. In particular, in a battery cell 110 in which the electrode leads 111, 112 protrude in opposite directions, heat is generated intensely in the portions of the battery cell stack 120 adjacent to the electrode leads 111, 112 of the battery cell 110. The thermally conductive resin layer 700 may be formed in two separate regions corresponding to the two portions of the battery cell stack 120 where heat is generated intensely.

[0107] The thermally conductive resin may include a thermally conductive adhesive material, specifically, at least one of silicone, urethane, and acrylic. The thermally conductive resin is liquid when applied or injected, and hardens after application or injection, and serves to fix one or more battery cells 110 that constitute the battery cell stack 120. In addition, the thermally conductive resin has excellent thermal conductivity, allowing heat generated in the battery cells 110 to be quickly transferred to the underside of the battery module.

[0108] In this embodiment, terms indicating directions such as front, back, left, right, up, and down are used, but these terms are used for convenience of explanation and may differ depending on the position of the object of interest or the position of the observer.

[0109] One or more battery modules according to the present embodiment described above may be mounted together with various control and protection systems such as a BMS (Battery Management System), a BDU (Battery Disconnect Unit), and a cooling system to form a battery pack.

[0110] The battery module or battery pack can be applied to various devices, specifically, but not limited to, transportation means such as electric bicycles, electric vehicles, and hybrid vehicles, and ESS (Energy Storage Systems).

[0111] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention. [Explanation of symbols]

[0112] 100 Battery Module 110 battery cells 120 Battery cell stack 200 Module Frame 300 End Plate 400 compression pads 500 Busbar Frame 600 Adhesive part

Claims

1. a battery cell stack in which a plurality of battery cells are stacked; a module frame that houses the battery cell stack and includes side portions that cover both side surfaces of the battery cell stack along the stacking direction of the battery cells; and at least one compression pad disposed at least in one of between adjacent battery cells among the battery cells or between an outermost battery cell among the battery cells and the side portion; A battery module in which a reserved space ratio per battery cell is 3% or more based on the stacking direction of the battery cells.

2. The battery module according to claim 1 , wherein a reserved space ratio per battery cell is equal to or greater than 3% and equal to or less than 10% with respect to the stacking direction of the battery cells.

3. The surplus space ratio per battery cell is calculated as (W-C-P) / C×100, W is a value of the distance between the side surfaces of the module frame, C is a value corresponding to the total thickness of the battery cells, 2. The battery module according to claim 1, wherein P is a value corresponding to the sum of the thicknesses of the compression pads in a compressed state when the battery cell stack and the compression pads are housed in the module frame.

4. 4. The battery module according to claim 3, wherein the C is a value obtained by multiplying the thickness of the central portion of the battery cell by the number of the battery cells.

5. 4. The battery module according to claim 3, wherein the P is a value obtained by multiplying the thickness of the compression pad in a compressed state by the number of the compression pads.

6. the battery cells are sheet-like pouch-type battery cells, The battery module according to claim 1 , wherein the battery cells are stacked upright so that one surface of each battery cell is parallel to the side surface.

7. 2. The battery module of claim 1, further comprising at least one adhesive portion located at at least one of between the battery cells facing each other, between the battery cell and the compression pad, or on an inner surface of the side portion.

8. The battery module according to claim 7 , wherein the adhesive portion is a double-sided tape or an adhesive layer formed by applying an adhesive.

9. The surplus space ratio per battery cell is calculated as (WC-PD) / C×100, W is the value of the space between the side portions of the module frame, C is a value corresponding to the total thickness of the battery cells, the P is a value corresponding to the total thickness of the compression pad in a compressed state when the battery cell stack and the compression pad are housed in the module frame, The battery module according to claim 7 , wherein the value D corresponds to the total thickness of the adhesive portions.

10. The battery module according to claim 9 , wherein the C is a value obtained by multiplying the thickness of the central portion of the battery cell by the number of the battery cells.

11. The battery module according to claim 9 , wherein the P is a value obtained by multiplying the thickness of the compression pad in a compressed state by the number of the compression pads.

12. The battery module according to claim 9 , wherein the D is a value obtained by multiplying the thickness of the adhesive portion by the number of the adhesive portions.

13. the battery cells are sheet-like pouch-type battery cells, The battery module according to claim 7 , wherein the battery cells are stacked upright so that one surface of each battery cell is parallel to the side surface.

14. The battery module according to claim 13 , wherein the adhesive portion is attached to the one surface of the battery cell so as to cover the one surface of the battery cell.

15. The battery module of claim 13 , wherein the adhesive portion is attached to the one surface of the battery cell so as to cover 90% to 100% of the area of ​​the one surface of the battery cell.

16. The battery module of claim 13 , wherein the adhesive portion is attached to the one surface of the battery cell so as to cover an area of ​​90% to 101% of the area of ​​the one surface of the battery cell.

17. A battery pack comprising the battery module according to claim 1.

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