Battery module and battery pack including same

Abstract

A battery module according to one embodiment of the present invention comprises: a battery cell stack in which a plurality of battery cells are stacked: a module frame which accommodates the battery cell stack and includes side surface parts respectively covering both side surfaces of the battery cell stack in the stacking direction of the battery cells; and at least one compression pad disposed between adjacent battery cells among the battery cells or between the outermost battery cell among the battery cells and the side surface part. The reserved space ratio of each of the battery cells is 3% or more on the basis of the stacking direction of the battery cells.

Description

Battery module and battery pack including the same

[0001] The present invention relates to a battery module and a battery pack including the same, and more specifically, to a battery module having improved life performance and a battery pack including the same.

[0002] In modern society, the widespread use of portable devices like cell phones, laptops, camcorders, and digital cameras has fueled active development of technologies related to these devices. Furthermore, rechargeable secondary batteries are increasingly being used as power sources for electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (P-HEVs) to address air pollution caused by conventional gasoline-powered vehicles. This, in turn, heightens the need for further development of these batteries.

[0003] Currently commercialized secondary batteries include nickel cadmium batteries, nickel hydrogen batteries, nickel zinc batteries, and lithium secondary batteries. Among these, lithium secondary batteries are receiving attention for their advantages of being able to charge and discharge freely, having a very low self-discharge rate, and having a high energy density, as they have almost no memory effect compared to nickel-based secondary batteries.

[0004] These lithium secondary batteries primarily use lithium oxide and carbon materials as the positive and negative electrode active materials, respectively. Lithium secondary batteries comprise an electrode assembly comprising positive and negative plates coated with the positive and negative electrode active materials, respectively, with a separator interposed between them, and an outer case, i.e., a battery case, that seals and encloses the electrode assembly together with an electrolyte.

[0005] In general, lithium secondary batteries can be classified into can-type secondary batteries in which the electrode assembly is built into a metal can and pouch-type secondary batteries in which the electrode assembly is built into a pouch of an aluminum laminate sheet, depending on the shape of the outer packaging material.

[0006] Recently, 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 applications in medium- to large-sized devices, a large number of secondary batteries can be electrically connected to increase capacity and output.

[0007] Secondary batteries used in small devices are typically configured with two or three battery cells. However, for medium- to large-sized devices such as automobiles, battery modules are utilized, in which multiple battery cells are electrically connected. These battery modules enhance capacity and output by forming a cell stack by connecting multiple battery cells in series or parallel. Furthermore, one or more battery modules may be equipped with various control and protection systems, such as a BMS (Battery Management System) and a cooling system, to form a battery pack.

[0008] At this time, pouch-type secondary batteries are becoming increasingly popular due to their advantages, such as ease of stacking and light weight. Pouch-type secondary batteries can generally be manufactured by injecting electrolyte into an electrode assembly housed in a pouch outer case, and then sealing the pouch outer case.

[0009] Meanwhile, battery modules containing multiple battery cells must meet a certain level of life performance. For example, battery modules used in electric vehicles are required to meet a capacity retention of at least 80% as assessed by life testing. Specifically, the capacity retention for 800 cycles is calculated according to the following formula:

[0010] Remaining capacity at 800 cycles [%] = (Discharge capacity at 800 cycles / Discharge capacity at 1 cycle) × 100

[0011] That is, the life performance of a battery module is required to be at least 80% of the initial discharge capacity after 800 charge and discharge cycles. However, since a battery module is composed of multiple battery cells, unlike when a battery cell is charged and discharged individually, there are cases where the life performance deteriorates due to various factors within the battery module. Therefore, it is necessary to analyze the cause of the deterioration in life performance that occurs when battery cells are composed of a battery module, derive the factors that affect life performance, and establish improvement measures.

[0012] The problem to be solved by the present invention is to identify factors that impair the life performance of a battery module, establish an improvement plan for the factors, and provide a battery module and a battery pack including the same that can increase the life performance.

[0013] However, the problems to be solved by the embodiments of the present invention are not limited to the problems described above and can be expanded in various ways within the scope of the technical ideas included in the present invention.

[0014] According to one embodiment of the present invention, a battery module includes: a battery cell stack in which a plurality of battery cells are stacked; a module frame that accommodates the battery cell stack and includes side portions that cover each of two sides of the battery cell stack in a stacking direction of the battery cells; and at least one compression pad that is positioned at least between adjacent battery cells among the battery cells or between an outermost battery cell among the battery cells and the side portion. Based on the stacking direction of the battery cells, a reserved space ratio per battery cell is 3% or more.

[0015] Based on the stacking direction of the battery cells, the reserved space ratio per battery cell may be 3% or more and 10% or less.

[0016] The free space ratio per battery cell may be calculated as (WCP) / C*100, where W may be a distance value between the side portions of the module frame, C may be a value corresponding to the sum total of the thicknesses of the battery cells, and P may be a value corresponding to the sum total of the thicknesses of the compression pads in a compressed state when the battery cell stack and the compression pad are accommodated in the module frame.

[0017] The above C may be a value obtained by multiplying the thickness value of the center of the battery cell by the number of the battery cells.

[0018] The above P may be a value obtained by multiplying the thickness value of the compressed pad in a compressed state by the number of the compressed pads.

[0019] The above battery cells may be pouch-shaped battery cells in the shape of sheets, and the battery cells may be stacked in an upright shape so that one side of the battery cells is parallel to the side surface.

[0020] The battery module may further include at least one adhesive portion located between facing battery cells among the battery cells, between the battery cells and the compression pad, or on at least one of the inner surfaces of the side portions.

[0021] The above adhesive portion may be a double-sided tape or an adhesive layer formed by applying an adhesive.

[0022] The free space ratio per battery cell may be calculated as (WCPD) / C*100, where W may be a value of the space between the side portions of the module frame, C may be a value corresponding to the sum total of the thicknesses of the battery cells, P may be a value corresponding to the sum total of the thicknesses of the compression pad in a compressed state when the battery cell stack and the compression pad are accommodated in the module frame, and D may be a value corresponding to the sum total of the thicknesses of the adhesive portion.

[0023] The above C may be a value obtained by multiplying the thickness value of the center of the battery cell by the number of the battery cells.

[0024] The above P may be a value obtained by multiplying the thickness value of the compressed pad in a compressed state by the number of the compressed pads.

[0025] The above D may be a value obtained by multiplying the thickness value of the adhesive portion and the number of the adhesive portions.

[0026] The above battery cells may be pouch-shaped battery cells in the shape of sheets, and the battery cells may be stacked in an upright shape so that one side of the battery cells is parallel to the side surface.

[0027] The above adhesive portion can be attached to the one surface of the battery cell so as to cover the one surface of the battery cell.

[0028] The above adhesive portion may be attached to the one surface of the battery cell so as to cover an area of ​​90% or more and 100% or less of the area of ​​the one surface of the battery cell.

[0029] The above adhesive portion may be attached to the one surface of the battery cell so as to cover an area of ​​90% or more and 101% or less of the area of ​​the one surface of the battery cell.

[0030] A battery pack according to one embodiment of the present invention may include the battery module.

[0031] According to embodiments of the present invention, by setting a standard for the ratio of free space per battery cell in a battery module, it is possible to prevent a decline in the life performance of a battery module.

[0032] In addition, an adhesive portion is provided to cover one side of the battery cell, thereby ensuring uniformity of pressure applied to the surface of the battery cells inside the battery module.

[0033] The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

[0034] Figure 1 is a perspective view of a battery module according to one embodiment of the present invention.

[0035] Figure 2 is an exploded perspective view of the battery module of Figure 1.

[0036] FIG. 3 is a plan view showing one of the battery cells included in the battery module of FIG. 2.

[0037] Figure 4 is a cross-sectional view taken along the cutting line A-A' of Figure 1.

[0038] Figure 5 is a cross-sectional view of a battery module according to another embodiment of the present invention.

[0039] Figure 6 is a perspective view showing a battery cell stack according to a comparative example of the present invention.

[0040] Figure 7 is a perspective view showing a battery cell stack according to one embodiment of the present invention.

[0041] Figure 8 is a plan view showing an adhesive portion formed on one surface of a battery cell according to one embodiment of the present invention.

[0042] Hereinafter, various embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0043] In order to clearly explain the present invention, parts that are not related to the description are omitted, and the same reference numerals are used for identical or similar components throughout the specification.

[0044] Furthermore, the sizes and thicknesses of each component shown in the drawings are arbitrarily indicated for convenience of explanation, and thus the present invention is not necessarily limited to the illustrated components. In the drawings, the thicknesses are enlarged to clearly represent various layers and regions. Furthermore, in the drawings, the thicknesses of some layers and regions are exaggerated for convenience of explanation.

[0045] Furthermore, when we say that a layer, membrane, region, plate, or other part is "on" or "over" another part, this includes not only cases where it is "directly on" the other part, but also cases where there are other parts in between. Conversely, when we say that a part is "directly on" another part, it means that there are no other parts in between. Furthermore, saying that a part is "on" or "over" a reference part means that it is located above or below the reference part, and does not necessarily mean that it is located "above" or "over" the direction opposite to gravity.

[0046] Additionally, throughout the specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0047] Additionally, throughout the specification, when we say "in plan", we mean when the target portion is viewed from above, and when we say "in cross section", we mean when the target portion is viewed from the side in a cross-section cut vertically.

[0048] Fig. 1 is a perspective view of a battery module according to one embodiment of the present invention. Fig. 2 is an exploded perspective view of the battery module of Fig. 1. Fig. 3 is a plan view showing one of the battery cells included in the battery module of Fig. 2.

[0049] Referring to FIGS. 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 accommodates the battery cell stack (120); and at least one compression pad (400).

[0050] First, the battery cell (110) may be a pouch-type battery cell. The pouch-type battery cell may be formed by housing an electrode assembly in a pouch case made of a laminate sheet including a resin layer and a metal layer, and then bonding the outer periphery of the pouch case. The battery cell (110) may have a rectangular sheet shape. Specifically, the battery cell (110) according to the present embodiment has a structure in which two electrode leads (111, 112) face each other and protrude from one end (114a) and the other end (114b) of the battery body (113), respectively. The battery cell (110) may be manufactured by bonding both ends (114a, 114b) of the battery case (114) and one side (114c) connecting them while housing the electrode assembly (not shown) in the battery case (114). In other words, the battery cell (110) according to one embodiment of the present invention may have a total of three sealing portions, and the remaining other side may be formed as a folding portion (115). The area between the two ends (114a, 114b) of the battery case (114) may be defined in the length direction of the battery cell (110), and the area between the one end (114c) connecting the two ends (114a, 114b) of the battery case (114) and the folding portion (115) may be defined in the width direction of the battery cell (110).

[0051] Meanwhile, only the battery cell (110) having a structure in which the electrode leads (111, 112) protrude in both directions on one side and the other side has been described, but as another embodiment of the present invention, a unidirectional pouch-type battery cell in which the electrode leads protrude together in one direction is also possible.

[0052] These battery cells (110) may be configured in multiple pieces, and the multiple battery cells (110) are stacked along one direction so as to be electrically connected to each other to form a battery cell stack (120). The battery case (114) is generally configured with a laminate structure of a resin layer / metal film layer / resin layer. For example, when the surface of the battery case is composed of an O(oriented)-nylon layer, when a plurality of battery cells are stacked to form a medium- or large-sized battery module, there is a tendency for it to easily slip due to external impact. Therefore, in order to prevent this and maintain a stable stacked structure of the battery cells, an adhesive portion may be provided on the surface of the battery case to form the battery cell stack (120). The adhesive portion may be an adhesive adhesive such as a double-sided tape or a chemical adhesive that is bonded by a chemical reaction during bonding. The adhesive portion will be described later.

[0053] A plurality of battery cells (110) are stacked along one direction to form a battery cell stack (120). The battery cells (110) having a rectangular sheet structure can be stacked along one direction with one side of the battery body (113) facing each other. More specifically, the battery cells (110) can be stacked in an upright shape so that the one side of the battery cells (110) is parallel to the side portion (210, 220) of the module frame (200) described later. FIG. 2 shows a state in which the battery cells (110) are stacked along a direction parallel to the y-axis to form a battery cell stack (120). Accordingly, the electrode leads (111, 112) in the battery cell stack (120) can protrude in the x-axis direction and the -x-axis direction.

[0054] 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 the open one or the other side of the module frame (200), so that the battery cell stack (120) may be accommodated in the internal space of the module frame (200).

[0055] The module frame (200) includes side portions (210, 220) that cover both sides of the battery cell stack (120) according to the stacking direction of the battery cells (110). In the battery cells (110) stacked along the y-axis direction, each of the side portions (210, 220) of the module frame (200) can cover the y-axis direction side and the -y-axis direction side of the battery cell stack (120).

[0056] In addition, the module frame (200) may include an upper surface (230) and a lower surface (240) that connect the side surfaces (210, 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 (230) and lower surface (240) of the module frame (200), respectively.

[0057] Meanwhile, the module frame (200) illustrated in FIG. 2 has side portions (210, 220), an upper surface (230), and a lower surface (240) that are integrated, but as 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. The U-shaped frame covering both side surfaces and the lower surface of the battery cell stack and the upper cover covering the upper surface of the battery cell stack may be joined at corresponding corners to form the module frame.

[0058] The battery module (100) according to the present embodiment may include a busbar frame (500) housed in a module frame (200) together with a battery cell stack (120). The busbar frame (500) may include a front frame (510) and a rear frame (520) positioned on one side and the other side, respectively, of the battery cell stack (120) from which electrode leads (111, 112) protrude. In addition, the busbar frame (500) may further include an upper frame (530) connected to each of the front frame (510) and the rear frame (520) and positioned on the upper side of the battery cell stack (120).

[0059] A bus bar (540) for connecting the electrode leads (111, 112) of the battery cells (110) included in the battery cell stack (120) can be mounted on the front frame (510) and the rear frame (520). Specifically, the electrode leads (111, 112) of the battery cells (110) can pass through slits formed in the front frame (510) and the rear frame (520) and then be bent and joined to the bus bar (540) by a method such as welding. In this way, the battery cells (110) included in the battery cell stack (120) can be electrically connected in series or parallel.

[0060] The battery module (100) according to the present embodiment may include end plates (300) positioned on opposite open sides of the module frame (200). The end plates (300) may be provided to cover one open side and the other open side of the module frame (200). That is, two end plates (300) may be positioned on the open sides of the module frame (200) and may be joined to corresponding corners of the module frame (200) by a method such as welding. These end plates (300) may physically protect the battery cell stack (120) and other electrical components from external impact.

[0061] Figure 4 is a cross-sectional view taken along the cutting line A-A' of Figure 1.

[0062] Referring to FIGS. 2 to 4 together, the battery module (100) according to the present embodiment includes at least one compression pad (400) positioned at at least one of between adjacent battery cells (110) among the battery cells (110) or between the outermost battery cell (110) among the battery cells (110) and the side portion (210, 220).

[0063] The compression pad (400) is a foam-type member that can absorb some of the swelling of the battery cells. Specifically, the battery cells (110) may generate gas internally due to deterioration, etc., as charging and discharging are repeated. In addition, when gas is generated internally in this way, the internal pressure increases, which may cause a swelling phenomenon in which at least a portion of the outer material swells. In particular, in the case of pouch-type secondary batteries, the swelling phenomenon may occur more severely compared to can-type secondary batteries because the structural rigidity of the outer material is weaker.

[0064] In this way, when a swelling phenomenon occurs in a secondary battery, the pressure inside the battery increases and the volume increases, which may have a negative effect on the structural stability of the battery module. Therefore, by arranging a compression pad (400) that is compressed when pressure is applied inside the battery module (100), it was attempted to absorb some of the swelling of the battery cell (110). There is no particular limitation on the material of the compression pad (400) as long as it can be compressed and absorb the swelling of the battery cell (110), and for example, it may include a polyurethane material.

[0065] Meanwhile, the battery module according to the present embodiment has a reserved space ratio per battery cell of 3% or more based on the stacking direction of the battery cells (110). In addition, the reserved space ratio per battery cell may be 3% or more and 10% or less. In addition, when considering the space utilization or energy density of the battery module, the reserved space ratio per battery cell may be 3% or more and 6% or less, or 4% or more and 6% or less.

[0066] The reserved space ratio per battery cell is a value calculated by calculating the space occupied by one battery cell (110) within a battery module (100), and can be calculated using the following equation.

[0067] Reserved Space Ratio per Battery Cell = (WCP) / C*100

[0068] In the above formula, W is a distance value between the side portions (210, 220) of the module frame (200), C is a value corresponding to the sum total of the thicknesses of the battery cells (110), and P is a value corresponding to the sum total of the thicknesses of the compression pad (400) in a compressed state when the battery cell stack (120) and the compression pad (400) are accommodated in the module frame (200). The units of the values ​​of W, C, and P may all be mm.

[0069] As illustrated in FIG. 4, the W corresponds to a distance value between the inner surfaces of the side portions (210, 220) of the module frame (200). As described above, the side portions (210, 220) in the present embodiment are portions that cover both sides of the battery cell stack (120) according to the stacking direction of the battery cells (110), and are portions related to the pressing force applied to the battery cells (110) in which swelling occurs.

[0070] The above C is a value corresponding to the sum of the thicknesses of the battery cells (110), and can be calculated as the product of the thickness (Ct) of the center of a single battery cell (110) and 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 a 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 battery cells (110). For example, as illustrated in FIG. 4, the C value can be derived by multiplying the thickness (Ct) of a single battery cell (110) by 12, which is the number (Cn) of the battery cells (110). Here, the center of the battery cell (110) to be measured for the thickness (Ct) refers to the center portion thereof based on the longitudinal direction of the battery cell (110). More specifically, referring to FIG. 3, the electrode leads (111, 112) may point to the midpoint between the two ends (114a, 114b) of the battery cell (110) from which they protrude.

[0071] The above P can be calculated as the product of the thickness (Pt) of a single compression pad (400) and the number (Pn) of compression pads (400) for the compression pad (400) in a compressed state, in which the battery cell stack (120) and the compression pad (400) are accommodated in the module frame (200). 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 illustrated in FIG. 4, the P value can be derived by multiplying the thickness (Pt) value of a single compression pad (400) by 4, which is the number (Pn) of the compression pads (400).

[0072] Hereinafter, a battery module according to another embodiment of the present invention will be described with reference to FIG. 5.

[0073] 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. 4.

[0074] Referring to FIG. 5, the battery module (100) according to the present embodiment may further include at least one adhesive portion (600) located between facing battery cells (110), between the battery cells (110) and the compression pad (400), or on at least one of the inner surfaces of the side portions (210, 220). Here, the inner surface of the side portions (210, 220) refers to a surface of the side portions (210, 220) facing the battery cell stack (120). The same configuration as that described in the embodiments of FIGS. 1 to 4 is applied to the battery cell stack (120), module frame (200), and compression pad (400) included in the battery module (100), and therefore, a description thereof will be omitted.

[0075] As described above, a plurality of battery cells (110) are stacked to form a medium- to large-sized battery module (100). In order to maintain a stable stacking structure of the battery cells (110), an adhesive portion (600) may be provided on one surface of the battery cells (110).

[0076] Not only can an adhesive portion (600) be provided between the battery cells (110), but also, when a compression pad (400) is positioned between the battery cells (110), an adhesive portion (600) can be provided between the battery cells (110) and the compression pad (400). In addition, an adhesive portion (600) can also be provided on the inner surface of the side portions (210, 220). As illustrated, when a compression pad (400) is positioned between the outermost battery cell (110) among the battery cells (110) and the side portions (210, 220), an adhesive portion (600) can be provided between the compression pad (400) and the side portions (210, 220).

[0077] Specifically, FIG. 5 shows an adhesive portion (600) positioned between battery cells (110) and bonded to one surface of each adjacent battery cell (110), an adhesive portion (600) bonded between a battery cell (110) and a compression pad (400), and an adhesive portion (600) bonded between a compression pad (400) and a side portion (210, 220).

[0078] 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 portion (210, 220), an adhesive portion (600) may be provided between the outermost battery cell (110) among the battery cells (110) and the side portion (210, 220).

[0079] The adhesive portion (600) according to the present embodiment can be applied without limitation to any material or member having adhesive properties. For example, the adhesive portion (600) may be a double-sided tape. As another example, the adhesive portion (600) may be an adhesive layer formed by applying an adhesive.

[0080] At this time, the battery module according to the present embodiment has a reserved space ratio per battery cell of 3% or more based on the stacking direction of the battery cells (110).

[0081] In this embodiment, the reserved space ratio per battery cell can be calculated by the following equation.

[0082] Reserved Space Ratio per Battery Cell = (WCPD) / C*100

[0083] In the above formula, W is a distance value between the side portions (210, 220) of the module frame (200), C is a value corresponding to the sum total of the thicknesses of the battery cells (110), P is a value corresponding to the sum total of the thicknesses of the compressed pad (400) in a compressed state when the battery cell stack (120) and the compressed pad (400) are accommodated in the module frame (200), and D is a value corresponding to the sum total of the thicknesses of the adhesive portion (600). The units of the values ​​of W, C, P, and D may all be mm.

[0084] As illustrated in FIG. 5, the above W corresponds to the distance value between the inner surfaces of the side portions (210, 220) of the module frame (200).

[0085] The above C is a value corresponding to the sum of the thicknesses of the battery cells (110), and can be calculated as the product of the thickness (Ct) of the center of a single battery cell (110) and 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 a 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 battery cells (110). For example, as illustrated in FIG. 5, the C value can be derived by multiplying the thickness (Ct) of a single battery cell (110) by 12, which is the number (Cn) of the battery cells (110). Here, the center of the battery cell (110) to be measured for the thickness (Ct) refers to the center portion thereof based on the longitudinal direction of the battery cell (110). More specifically, referring to FIG. 3, the center of the battery cell (110) may refer to the midpoint between the two ends (114a, 114b) of the battery cell (110) from which the electrode leads (111, 112) protrude.

[0086] The above P can be calculated as the product of the thickness (Pt) of a single compression pad (400) and the number (Pn) of compression pads (400) for the compression pad (400) in a compressed state, when the battery cell stack (120) and the compression pad (400) are accommodated together in the module frame (200). 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 illustrated in FIG. 5, the P value can be derived by multiplying the thickness (Pt) value of a single compression pad (400) by 4, which is the number (Pn) of the compression pads (400).

[0087] The above D can be calculated as the product of the thickness (Dt) of a single adhesive portion (600) and the number (Dn) of 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, the adhesive portion (600) can be located between the battery cells (110) and between the battery cells (110) and the compression pad (400). In addition, when the compression pad (400) or the battery cells (110) are located at the outermost side, the adhesive portion (600) can also be located on the outer surface of the compression pad (400) or the battery cells (110) located at the outermost side. The adhesive portion (600) can also be located between the compression pad (400) or the battery cells (110) located at the outermost side and the side portions (210, 220). In other words, as described above, an adhesive portion (600) may be provided on the inner surface of the side portion (210, 220). When the battery cell (110) and the compression pad (400) are regarded as a single component, an adhesive portion (600) may be interposed between these components. The number (Dn) of adhesive portions (600) may be calculated as a value obtained by adding 1 to the sum of the number (Cn) of battery cells (110) and the number (Pn) of compression pads (400). For example, referring to the case of FIG. 5 in which 12 battery cells (110) and 4 compression pads (400) are arranged inside the module frame (200), a total of 17 adhesive portions (600) may be provided. In this case, D is a value obtained by multiplying the thickness (Dt) of a single adhesive portion (600) by 17, which is the number (Dn) of adhesive portions (600).

[0088] In summary, in the case of a battery module in which no adhesive is provided, the Reserved Space Ratio per battery cell is calculated as (WCP) / C*100, and in the case of a battery module in which an adhesive is provided, the Reserved Space Ratio per battery cell can be calculated as (WCPD) / C*100, and in the battery module (100) of the present embodiment, the values ​​of the calculated Reserved Space Ratios are all 3% or more.

[0089] The inventor of the present invention has confirmed that the space of the battery cells (110) within the battery module (100), in other words, the pressing force applied to the battery cells (110), affects the life performance of the battery module (100). An appropriate level of pressing force must be applied to the battery cells (110) so that an appropriate capacity can be maintained even when the cycle of the battery module (100) is in progress. If the pressing force is below or above a certain level, a problem of sudden drop in capacity may occur when the cycle is in progress. Based on this, the inventor of the present invention designed a condition in which the reserved space ratio per battery cell is 3% or more in order to control the absolute pressure applied to the battery cells (110) within the battery module (100), and confirmed that when the condition is satisfied, no degradation in life performance occurs when the battery cells (110) are mounted in the battery module (100). Specifically, for a battery module that satisfies the conditions, the capacity retention at 800 cycles can be maintained at 80% or more.

[0090] Below, the battery module of the present invention will be described through specific examples and comparative examples.

[0091] Example 1 Example 2 Example 3 Example 4 Distance between inner surfaces of side parts of module frame (W) [mm] 213148217.6217.6 Total thickness of battery cells (C) [mm] 202.32139.44205.2206.88 Total thickness of compressed pad in compressed state (P) [mm] 1.81.761.81.8 Total thickness of adhesive part (D) 1.50.851.51.5 Reserved Space Ratio per battery cell [%] 3.654.274.433.59 Remaining capacity ratio at 800 cycles in battery cell unit [%] 9089.38080 Remaining capacity ratio at 800 cycles in battery module unit [%] 85898179 Difference in capacity degradation between battery cell and battery module [%]50.3-11

[0092] First, referring to Table 1 above, battery modules having different standards and specifications were prepared in Examples 1 to 4, and the free space ratio (%) per battery cell for the battery modules of Examples 1 to 4 was calculated. The units of each factor are indicated in square brackets.

[0093] As explained above, W is a distance value measured between the inner surfaces of the side portions (210, 220) of the module frame (200). The C corresponding to the total thickness of the battery cells (110) was calculated as the product of the thickness (Ct) of the center of the battery cells (110) and the number (Cn) of the battery cells (110).

[0094] The compression pad (400) was confirmed to be compressed by 80% when inserted into the module frame (200) together with the battery cells (110), and thus the thickness (Pt) of the compression pad (400) in the compressed state was calculated as 20% of the thickness of the original compression pad (400) before compression. The above P, which corresponds to the total thickness value of the compression pad in the compressed state, can be calculated as the product of the thickness (Pt) of the compression pad (400) in the compressed state and the number (Pn) of the compression pads (400).

[0095] The above D corresponding to the total thickness value of the adhesive portions (600) can be calculated as the product of the thickness (Dt) of a single adhesive portion (600) and the number (Dn) of the adhesive portions (600). In the battery modules of the present embodiments 1 to 4, the 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 the outer surface of the battery cells (110). In the present embodiments 1 to 4, the number of adhesive portions (600) was calculated as the sum of the number (Cn) of the battery cells (110) and the number (Pn) of the compression pads (400) plus 1.

[0096] The free space ratio [%] per battery cell was calculated using the derived W, C, P, and D values ​​of Examples 1 to 4, and Examples 1 to 4 were calculated to have free space ratio values ​​per battery cell of 3.65%, 4.27%, 4.43%, and 3.59%, respectively. The free space ratios per battery cell of Examples 1 to 4 are all values ​​of 3% or more.

[0097] For Examples 1 to 4, the remaining capacity ratio [%] after 800 cycles in a battery cell unit and the remaining capacity ratio [%] after 800 cycles in a battery module unit were measured. The remaining capacity ratio after 800 cycles in a battery cell unit is a value obtained by measuring the discharge capacity after 800 cycles of charge and discharge compared to the initial discharge capacity for a single battery cell that is not configured as a battery module. The remaining capacity ratio after 800 cycles in a battery module unit is a value obtained by measuring the discharge capacity after 800 cycles of charge and discharge compared to the initial discharge capacity for a battery module including the corresponding battery cells.

[0098] When examining the difference between the remaining capacity rate after 800 cycles in a battery cell unit and the remaining capacity rate after 800 cycles in a battery module unit, i.e., the capacity degradation difference [%] between the battery cell and the battery module, Examples 1 to 4 were measured to have values ​​of 5, 0.3, -1, and 1, respectively.

[0099] In the case of Examples 1 to 4, where the free space ratio per battery cell was all 3% or more, it was confirmed that even when the battery cells (110) were configured as battery modules (100), no significant deterioration in life performance occurred. The difference in the remaining capacity ratio at 800 cycles was not significant between the battery cell unit and the battery module unit. In other words, even when the cycle of the battery module (100) progresses, an appropriate capacity can be maintained, and the problem of sudden drop in capacity during the cycle did not occur.

[0100]

[0101] Comparative Example 1 Comparative Example 2 Comparative Example 3 Distance between inner surfaces of side parts of module frame (W) [mm] 216.22 16.22 17.6 Total thickness of battery cells (C) [mm] 208.968 208.968 209.16 Total thickness of compressed pad in compressed state (P) [mm] 1.8 1.8 1.8 Total thickness of adhesive (D) 1.4 1.5 1.5 Reserved Space Ratio per battery cell [%] 1.93 1.88 2.46 Remaining capacity ratio at 800 cycles in battery cell unit [%] 80 80 80 Remaining capacity ratio at 800 cycles in battery module unit [%] 61.26 1.26 4.2 Capacity degradation difference between battery cell and battery module [%] 18.8 18.8 15.8

[0102] Referring to Table 2 above, battery modules having different standards and specifications were prepared as Comparative Examples 1 to 3, and the free space ratio (%) per battery cell for the battery modules of Comparative Examples 1 to 3 was calculated. The units of each factor are indicated in square brackets.

[0103] The W, C, P, and D values ​​for Comparative Examples 1 to 3 were derived in the same manner as the measurement method in Examples 1 to 4. The description thereof is omitted as it overlaps with the previously explained content.

[0104] The free space ratio [%] per battery cell was calculated using the W, C, P, and D values ​​of Comparative Examples 1 to 3, and it was calculated that Examples 1 to 3 had free space ratio values ​​per battery cell of 1.93%, 1.88%, and 2.46%, respectively. The free space ratios per battery cell of Comparative Examples 1 to 3 are all less than 3%.

[0105] In the same manner as the measurement in Examples 1 to 4, the remaining capacity ratio after 800 cycles, the remaining capacity ratio after 800 cycles in a battery module unit, and the difference in capacity degradation between the battery cell and the battery module were calculated. Looking at the difference in capacity degradation [%] between the battery cell and the battery module, Comparative Examples 1 to 3 were measured as 18.8, 18.8, and 15.8, respectively.

[0106] In Comparative Examples 1 to 3, where the reserve space ratio per battery cell was all less than 3%, it was confirmed that a significant decrease in life performance occurred when the battery cells (110) were configured into a battery module (100), compared to Examples 1 to 4. In other words, it was confirmed through the experimental results above that a significant decrease in life performance of the battery module can be prevented when the condition of a reserve space ratio per battery cell of 3% or more is satisfied, as in the battery module according to the present embodiment.

[0107] Hereinafter, with reference to FIGS. 6 to 8, the formation area of ​​the adhesive portion (600) according to one embodiment of the present invention will be described in detail along with comparative examples.

[0108] Figure 6 is a perspective view showing a battery cell stack according to a comparative example of the present invention.

[0109] 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 least in one location between the battery cells (11). This adhesive portion (60) may be a double-sided tape or an adhesive layer formed by applying an adhesive. As illustrated in FIG. 6, the adhesive portion (60) according to the present comparative example is not attached to the entire surface where the battery cells (11) face each other, but only to a portion thereof. In this case, the inventors of the present invention confirmed that uneven pressure is applied to the battery cells (110) due to the partially formed adhesive portion (60), and lithium plating occurs at both ends.

[0110] Specifically, the partially formed adhesive portion (60) causes an uneven surface pressure on the surface of the battery cell (110), and the gas generated by the uneven surface pressure exists on the surface of the battery cell, causing lithium plating, in which lithium is precipitated on the surface of the battery cell (110). In particular, referring to FIGS. 3 and 6 together, it was found that when the adhesive portion (60) is formed only in the central portion of the battery cell (110), lithium is mainly precipitated in the portions adjacent to both ends (114a, 114b) of the battery cell (110) where the electrode leads (111, 112) protrude.

[0111] The inventor of the present invention analyzed the relationship between the lithium deposition rate in lithium plating and the remaining capacity rate of the battery cell, and confirmed that the lithium deposition rate and the remaining capacity rate of the battery cell have a strong negative correlation. That is, as the lithium deposition rate increases, the remaining capacity rate after 800 cycles decreases, and the uneven surface pressure of the battery cell (110) caused by the adhesive portion (60) adversely affects the life performance of the battery module (100). Accordingly, the inventor of the present invention proposed the adhesive portion (600) as described below as a uniform pressure structure for the surface of the battery cell (110). Hereinafter, the formation area of ​​the adhesive portion (600) according to the present embodiment will be described with reference to FIGS. 3, 7, and 8.

[0112] Fig. 7 is a perspective view showing a battery cell stack according to one embodiment of the present invention. Fig. 8 is a plan view showing an adhesive portion formed on one surface of a battery cell according to one embodiment of the present invention.

[0113] Referring to FIGS. 3, 7, and 8, as described above, the battery cells (110) are pouch-shaped battery cells in a sheet shape, and the battery cells (110) can be stacked in an upright shape so that one side of the battery cells (110) is parallel to the side portions (210, 220, see FIG. 2). The battery cells (110) can be stacked so that the one side thereof faces each other. That is, the one side of the battery cell (110) described below corresponds to a portion of the battery cell (110) that is parallel to the side portions (210, 220) of the module frame (200), and can face another battery cell (110), a compression pad (400), or the side portions (210, 220) of the module frame (200).

[0114] At this time, the adhesive portion (600) according to the present embodiment may be attached to the surface of the battery cell (110) so as to cover the surface of the battery cell (110). Specifically, the adhesive portion (600) may be attached to the surface of the battery cell (110) so as to cover an area of ​​90% or more and 100% or less of the area of ​​the surface of the battery cell (110). In addition, when the design tolerance for the surface of the battery cell (110) is taken into consideration, the adhesive portion (600) may be attached to the surface of the battery cell (110) so as to cover an area of ​​90% or more and 101% or less of the area of ​​the surface of the battery cell (110).

[0115] Unlike the adhesive portion (60) according to the comparative example described above, the adhesive portion (600) according to the present embodiment can be attached so as to cover most of the above-mentioned one surface of the battery cell (110). Accordingly, a uniform pressure structure can be implemented for the above-mentioned one surface of the battery cell (110). Unlike the adhesive portion (60) that was attached only to a narrow area, the adhesive portion (600) according to the present embodiment can ensure uniformity of the pressure applied to the surface of the battery cell (110), and thus solve the problem of lithium plating occurring in the adjacent portions (114a, 114b) of the battery cell (110), thereby improving the life performance of the battery module (100).

[0116] Meanwhile, referring to FIGS. 4 and 5, the battery module (100) according to the present embodiment may further include a thermally conductive resin layer (700) located between the battery cell stack (120) and the lower surface (240) of the module frame (200).

[0117] The thermally conductive resin layer (700) may be formed by applying a thermally conductive resin to the lower surface (240) and curing the applied thermally conductive resin, or by injecting the thermally conductive resin through a through hole formed in the lower surface (240). In particular, in the battery cell (110) in which the electrode leads (111, 112) protrude in opposite directions, heat generation is severe in the portion adjacent to the electrode leads (111, 112) of the battery cell (110) among the battery cell stack (120), and the thermally conductive resin layer (700) may be formed by dividing it into two sections so as to correspond to the two sections of the battery cell stack (120) in which heat generation is severe.

[0118] The thermally conductive resin may include a thermally conductive adhesive material, and specifically, may include at least one of a silicone material, a urethane material, and an acrylic material. The thermally conductive resin may be in a liquid state when applied or injected, or may be cured after application or injection to fix one or more battery cells (110) constituting the battery cell stack (120). In addition, since it has excellent thermal conductivity, it can quickly transfer heat generated from the battery cells (110) to the lower side of the battery module.

[0119] In this example, terms indicating directions such as front, back, left, right, up, and down are used, but these terms are only for convenience of explanation and may vary depending on the location of the target object or the location of the observer.

[0120] One or more battery modules according to the above-described embodiment can 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.

[0121] The above battery module or battery pack can be applied to various devices. Specifically, it can be applied to transportation vehicles such as electric bicycles, electric vehicles, and hybrid vehicles, as well as ESS (Energy Storage Systems), but is not limited thereto. It can also be applied to various devices that can use secondary batteries.

[0122] 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.

[0123] Description of the symbol

[0124] 100: Battery module

[0125] 110: Battery cell

[0126] 120: Battery cell stack

[0127] 200: Module Frame

[0128] 300: End Plate

[0129] 400: Compression pad

[0130] 500: Busbar Frame

[0131] 600: Adhesive

Claims

1. A battery cell stack in which multiple battery cells are stacked; A module frame that accommodates the battery cell stack and includes side portions that cover both sides of the battery cell stack according to the stacking direction of the battery cells; and At least one compression pad is disposed between adjacent battery cells among the battery cells or between the outermost battery cell among the battery cells and the side portion; A battery module having a reserved space ratio per battery cell of 3% or more based on the stacking direction of the battery cells.

2. In paragraph 1, A battery module having a reserved space ratio per battery cell of 3% or more and 10% or less based on the stacking direction of the battery cells.

3. In paragraph 1, The free space ratio per battery cell is calculated as (WCP) / C*100, The above W is the distance value between the side parts of the module frame, The above C is a value corresponding to the sum of the thicknesses of the above battery cells, The above P is a battery module whose value corresponds to the total thickness of the compression pad in a compressed state when the battery cell stack and the compression pad are accommodated in the module frame.

4. In paragraph 3, The above C is a battery module which is a product of the thickness value of the center of the battery cell and the number of the battery cells.

5. In paragraph 3, The battery module wherein the above P is a value obtained by multiplying the thickness value of the compressed pad in a compressed state by the number of the compressed pads.

6. In paragraph 1, The above battery cells are pouch-shaped battery cells in the shape of sheets, A battery module in which the battery cells are stacked in an upright shape so that one side of the battery cells is parallel to the side surface.

7. In paragraph 1, A battery module further comprising at least one adhesive portion located between facing battery cells among the battery cells, between the battery cells and the compression pad, or on at least one of the inner surfaces of the side portions.

8. In paragraph 7, A battery module in which the above adhesive portion is a double-sided tape or an adhesive layer formed by applying an adhesive.

9. In paragraph 7, The free space ratio per battery cell is calculated as (WCPD) / C*100, The above W is the value of the space between the side parts of the module frame, The above C is a value corresponding to the sum of the thicknesses of the above battery cells, The above P is a value corresponding to the total thickness of the compressed pad in a compressed state when the battery cell stack and the compressed pad are accommodated in the module frame, The above D is a battery module whose value corresponds to the total thickness of the above adhesive portion.

10. In paragraph 9, The above C is a battery module which is a product of the thickness value of the center of the battery cell and the number of the battery cells.

11. In paragraph 9, The battery module wherein the above P is a value obtained by multiplying the thickness value of the compressed pad in a compressed state by the number of the compressed pads.

12. In paragraph 9, The above D is a battery module which is a value obtained by multiplying the thickness value of the above adhesive portion and the number of the above adhesive portions.

13. In paragraph 7, The above battery cells are pouch-shaped battery cells in the shape of sheets, A battery module in which the battery cells are stacked in an upright shape so that one side of the battery cells is parallel to the side surface.

14. In paragraph 13, A battery module in which 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. In paragraph 13, A battery module in which the adhesive portion is attached to the one side of the battery cell so as to cover an area of ​​90% or more and 100% or less of the area of ​​the one side of the battery cell.

16. In paragraph 13, A battery module in which the adhesive portion is attached to the one side of the battery cell so as to cover an area of ​​90% or more and 101% or less of the area of ​​the one side of the battery cell.

17. A battery pack including a battery module according to paragraph 1.

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