Battery module and battery pack including same

Abstract

A battery module according to one embodiment of the present disclosure comprises: a battery cell laminate in which a plurality of battery cells are laminated; a module frame accommodating the battery cell stack and including side surface portions respectively covering both side surfaces of the battery cell stack in a stacking direction of the battery cells; and at least one compression pad provided at one position between adjacent battery cells among the battery cells, or between an outermost battery cell among the battery cells and the side surface portion. The reserved space ratio of each of the battery cells is 3% or more based on the stacking direction of the battery cells.

Description

Technical Field

[0001] The present disclosure relates to a battery module and a battery pack including the same, and more particularly, to a battery module having improved lifespan performance and a battery pack including the same. Background Art

[0002] In modern society, as portable devices such as mobile phones, laptops, video cameras, and digital cameras have been used daily, the development of technologies in the fields related to the above mobile devices has become active. In addition, rechargeable / dischargeable secondary batteries are used as power sources for electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (P-HEVs), etc., in an attempt to solve problems such as air pollution caused by existing gasoline vehicles using fossil fuels. Therefore, the demand for the development of secondary batteries is growing.

[0003] Currently commercialized secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, and lithium secondary batteries. Among these batteries, lithium secondary batteries have attracted much attention due to their advantages: for example, compared with nickel-based secondary batteries, lithium secondary batteries hardly show memory effect, are freely charged and discharged, and have very low self-discharge rate and high energy density.

[0004] Such lithium secondary batteries mainly use lithium-based oxides and carbonaceous materials as positive electrode active materials and negative electrode active materials, respectively. The lithium secondary battery includes: an electrode assembly in which a positive electrode plate and a negative electrode plate each coated with a positive electrode active material and a negative electrode active material are arranged with a separator interposed therebetween; and an external material (i.e., a battery case) that seals and contains the electrode assembly together with an electrolyte.

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

[0006] Recently, secondary batteries are widely used not only in small devices such as portable electronic devices, but also in medium and large devices such as vehicles and energy storage systems. In order to be applied to such medium and large devices, a large number of secondary batteries can be electrically connected to enhance capacity and output.

[0007] In the case of a secondary battery for a small device, two to three battery cells are provided, but in the case of a secondary battery for a medium or large device such as an automobile, a battery module that electrically connects a plurality of battery cells is used. In such a battery module, a plurality of battery cells are connected to each other in series or in parallel to form a cell assembly, thereby increasing capacity and output. In addition, one or more battery modules may be installed together 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 tend to be more widely used due to their advantages of easy lamination and light weight. Generally, a pouch-type secondary battery can be manufactured by injecting electrolyte in a state where an electrode assembly is accommodated in a pouch-type outer material and then sealing the pouch-type outer material.

[0009] On the other hand, in the case of a battery module containing multiple battery cells, a certain level of life performance must be met. As an example, as a life test evaluation, a battery module applied to an electric vehicle needs to meet a capacity retention rate of more than 80%. Specifically, the capacity retention rate after 800 cycles is calculated according to the formula.

[0010] Capacity retention after 800 cycles [%] = (discharge capacity at 800 cycles / discharge capacity at 1 cycle) × 100

[0011] That is, as life performance, the battery module is required to have a discharge capacity ratio of more than 80% relative to the initial discharge capacity after 800 charge and discharge cycles. However, the battery module is constructed by grouping a plurality of battery cells together, and unlike the case where the battery cells are charged and discharged individually, the life performance may deteriorate due to various factors within the battery module. Therefore, it is necessary to analyze the causes of the reduction in life performance that occurs when the battery cells are constructed as battery modules, derive the factors that affect the life performance, and establish an improvement plan. Summary of the invention

[0012] Technical issues

[0013] An object of the present disclosure is to provide a battery module capable of deriving factors that inhibit life performance of a battery module and establishing an improvement plan therefor, thereby improving life performance, and a battery pack including the battery module.

[0014] However, the technical problems to be solved by the embodiments of the present disclosure are not limited to the above-mentioned problems, and various extensions can be made within the scope of the technical concept included in the present disclosure.

[0015] Technical Solution

[0016] According to one embodiment of the present disclosure, there is provided a battery module, comprising: a battery cell stack formed by stacking a plurality of battery cells; a module frame accommodating the battery cell stack and comprising side surface portions, each side surface portion covering two side surfaces of the battery cell stack along a stacking direction of the battery cells; and at least one compression pad arranged at at least one position between adjacent battery cells among the battery cells, or between an outermost battery cell among the battery cells and the side surface portions among the battery cells, wherein, based on the stacking direction of the battery cells, a reserved space ratio of each battery cell is greater than 3%.

[0017] Based on the stacking direction of the battery cells, the reserved space ratio of each battery cell may be greater than 3% and less than 10%.

[0018] The reserved space ratio of each battery cell can be calculated as (WCP) / C*100, where: W is the distance value between the side surface portions of the module frame, C is a value corresponding to the total thickness of the battery cell, and 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 accommodated in the module frame.

[0019] C may be a value obtained by multiplying the thickness of the center portion of the battery cell by the number of battery cells.

[0020] P may be a value obtained by multiplying the thickness of the compressed pad in a compressed state by the number of compressed pads.

[0021] The battery cell may be a sheet-shaped pouch-type battery cell, and the battery cells may be stacked in an upright state such that one surface of the battery cell is parallel to the side surface portion.

[0022] The battery module may further include: at least one adhesive portion located at at least one position between battery cells facing each other among the battery cells, between the battery cell and the compression pad, or on an inner side surface of the side surface portion.

[0023] The adhesive portion may be a double-sided tape or an adhesive layer formed by coating an adhesive.

[0024] The reserved space ratio of each battery cell can be calculated as (WCPD) / C*100, where: W can be the space value between the side surface portions of the module frame, C can be a value corresponding to the total thickness of the battery cell, P can be 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 accommodated in the module frame, and D can be a value corresponding to the total thickness of the adhesive portion.

[0025] C may be a value obtained by multiplying the thickness value of the center portion of the battery cell by the number of battery cells.

[0026] P may be a value obtained by multiplying the thickness of the compressed pad in a compressed state by the number of compressed pads.

[0027] D may be a value obtained by multiplying the thickness value of the bonding portion by the number of bonding portions.

[0028] The battery cell may be a sheet-shaped pouch-type battery cell, and the battery cells may be stacked in an upright state such that one surface of the battery cell is parallel to the side surface portion.

[0029] The adhesive part may be attached to one surface of the battery cell to cover the one surface of the battery cell.

[0030] The adhesive part may be attached to one surface of the battery cell to cover an area of ​​90% or more and 100% or less of an area of ​​the one surface of the battery cell.

[0031] The adhesive part may be attached to one surface of the battery cell to cover an area of ​​90% or more and 101% or less of an area of ​​the one surface of the battery cell.

[0032] According to another embodiment of the present disclosure, there is provided a battery pack including the above-mentioned battery module.

[0033] Technical Effects

[0034] According to an embodiment of the present disclosure, by setting a standard for a reserve ratio of each battery cell in a battery module, deterioration of life performance of a battery module may be prevented.

[0035] In addition, the adhesive part is provided to cover one surface of the battery cell, thereby ensuring uniformity of pressure applied to the surface of the battery cell within the battery module.

[0036] The effects of the present disclosure are not limited to the above-described effects, and other effects not described above will be clearly understood by those skilled in the art from the description of the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a perspective view of a battery module according to an embodiment of the present disclosure.

[0038] Figure 2 yes Figure 1 An exploded perspective view of a battery module.

[0039] Figure 3 It is shown Figure 2 1 is a plan view of one of the battery cells included in the battery module.

[0040] Figure 4 is along Figure 1 A cross-sectional view taken along the cutting line AA′ in FIG.

[0041] Figure 5 is a cross-sectional view of a battery module according to another embodiment of the present disclosure.

[0042] Figure 6 is a perspective view showing a battery cell stack according to a comparative example of the present disclosure.

[0043] Figure 7 is a perspective view showing a battery cell stack according to an embodiment of the present disclosure.

[0044] Figure 8 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 disclosure. DETAILED DESCRIPTION

[0045] Hereinafter, various embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the embodiments. The present disclosure can be modified in various different ways and is not limited to the embodiments set forth herein.

[0046] In order to clearly describe the present disclosure, parts irrelevant to the description will be omitted, and the same reference numerals refer to the same or similar elements throughout the specification.

[0047] In addition, in the drawings, for the convenience of description, the size and thickness of each element are arbitrarily illustrated, and the present disclosure is not necessarily limited to the size and thickness shown in the drawings. In the drawings, for the sake of clarity, the thickness of layers, regions, etc. is exaggerated. In the drawings, for the convenience of description, the thickness of parts and regions is exaggerated.

[0048] Furthermore, it will be understood that when an element such as a layer, film, region, or plate is referred to as being "on" or "over" another element, it can be directly on the other element, or there can be intervening elements. Conversely, when an element is referred to as being "directly on" another element, this means that there are no other intervening elements. Furthermore, a particular portion that is "on" or "over" a reference portion refers to a particular portion that is above or below the reference portion, and does not specifically refer to a particular portion that is "on" or "over" facing in the opposite direction of gravity.

[0049] Furthermore, throughout the specification, when a portion is referred to as “including” or “comprising” a certain component, unless otherwise specified, it means that the portion may further include other components, rather than excluding the other components.

[0050] Furthermore, throughout the specification, when it is referred to as a “plane”, this means observing the target portion from the upper side, and when it is referred to as a “section”, this means observing the target portion from a side of the section cut vertically.

[0051] Figure 1 is a perspective view of a battery module according to an embodiment of the present disclosure. Figure 2 yes Figure 1 An exploded perspective view of a battery module. Figure 3 It is shown Figure 2 1 is a plan view of one of the battery cells included in the battery module.

[0052] Reference Figures 1 to 3 , a battery module 100 according to an embodiment of the present disclosure includes: a battery cell stack 120 formed by stacking a plurality of battery cells 110 ; a module frame 200 accommodating the battery cell stack 120 ; and at least one compression pad 400 .

[0053] First, the battery cell 110 may be a pouch-type battery cell. A pouch-type battery cell may be formed by accommodating an electrode assembly in a pouch-shaped housing made of a laminate including a resin layer and a metal layer, and then combining the outer periphery of the pouch-shaped housing. Such a battery cell 110 may be formed into a rectangular sheet structure. Specifically, the battery cell 110 according to the present embodiment may have a structure in which two electrode leads 111 and 112 face each other and protrude from one end 114a and the other end 114b of the cell body 113, respectively. The battery cell 110 may be produced by combining the two ends 114a and 114b of the cell housing 114 and one side 114c connecting them while the electrode assembly (not shown) is accommodated in the cell housing 114. In other words, the battery cell 110 according to one embodiment of the present disclosure has a total of three sealing portions, and the remaining other side portions may be composed of a folding portion 115. The longitudinal direction of the battery cell 110 may be defined between the two ends 114a and 114b of the cell case 114 , and the lateral direction of the battery cell 110 may be defined between a side portion 114c connecting the two ends 114a and 114b of the cell case 114 and the folded portion 115 .

[0054] On the other hand, only the battery cell 110 having a structure in which the electrode leads 111 and 112 protrude in both directions on one side and the other side is described, but in another embodiment of the present disclosure, it goes without saying that a unidirectional pouch-type battery cell in which the electrode leads protrude together in one direction may be used.

[0055] The battery cell 110 may be formed in plurality, and a plurality of battery cells 110 may be stacked to be electrically connected to each other to form a battery cell stack 120. The battery cell housing 114 is generally formed as a laminated structure of a resin layer / metal film layer / resin layer. For example, when the surface of the battery housing is formed of an O (oriented)-nylon layer, when a plurality of battery cells are stacked to form a medium or large battery module, it tends to slide easily due to external impact. Therefore, in order to prevent this problem and maintain a stable stacking structure of the battery cells, an adhesive portion may be provided on the surface of the battery housing to form a battery cell stack 120. An adhesive portion may be provided on the surface of the battery housing to form a battery cell stack 120. The adhesive portion may be a sticky adhesive such as a double-sided tape or a chemical adhesive bonded by a chemical reaction during the bonding process. The adhesive portion will be described later.

[0056] A plurality of battery cells 110 are stacked in one direction to form a battery cell stack 120, wherein the battery cells 110 having a rectangular sheet structure may be stacked in one direction in a state where one surface of a battery body 113 faces each other. More specifically, the battery cells 110 may be stacked in an upright state such that one surface of the battery cells 110 is parallel to side surface portions 210 and 220 of a module frame 200 to be described later. Figure 2 1 shows a state in which the battery cells 110 are stacked in a direction parallel to the y-axis to form the battery cell stack 120. Therefore, in the battery cell stack 120, the electrode leads 111 and 112 may protrude toward the x-axis direction and the -x-axis direction.

[0057] The module frame 200 may be a frame having one side and the other side opened. The battery cell stack 120 is inserted through the open one side or the other side of the module frame 200 so that the battery cell stack 120 can be accommodated in the inner space of the module frame 200 .

[0058] The module frame 200 includes side surface portions 210 and 220 that respectively cover both side surfaces of the battery cell stack 120 along the stacking direction of the battery cells 110. In the battery cells 110 stacked along the y-axis direction, each of the side surface portions 210 and 220 of the module frame 200 may cover the side surfaces of the battery cell stack 120 in the y-axis direction and the -y-axis direction.

[0059] Furthermore, the module frame 200 may include an upper surface portion 230 and a lower surface portion 240 connecting the side surface portions 210 and 220. The upper surface portion 230 and the lower surface portion 240 of the module frame 200 may respectively cover the upper surface and the lower surface of the battery cell stack 120 accommodated inside the module frame 200.

[0060] on the other hand, Figure 2The module frame 200 shown may have a form in which the side surface parts 210 and 220, the upper surface part 230 and the lower surface part 240 are integrated, but in another embodiment of the present disclosure, the module frame may have a form in which a U-shaped frame and an upper cover are combined together. The U-shaped frame covering the two 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 combined at corresponding corners to form the module frame.

[0061] The battery module 100 according to the present embodiment may include a bus bar frame 500 housed in the module frame 200 together with the battery cell stack 120. The bus bar frame 500 may include a front surface frame 510 and a rear surface frame 520 respectively located on one surface and the other surface from which the electrode leads 111 and 112 of the battery cell stack 120 protrude. In addition, the bus bar frame 500 may further include an upper frame 530 connected to each of the front surface frame 510 and the rear surface frame 520 and located at the upper portion of the battery cell stack 120.

[0062] The bus bar 540 for connecting the electrode leads 111 and 112 of the battery cells 110 included in the battery cell stack 120 may be mounted on the front surface frame 510 and the rear surface frame 520. Specifically, the electrode leads 111 and 112 of the battery cells 110 are bent after passing through slits formed in the front surface frame 510 and the rear surface frame 520, and may be bonded to the bus bar 540 by welding or the like. In this way, the battery cells 110 included in the battery cell stack 120 may be electrically connected in series or in parallel.

[0063] The battery module 100 according to the present embodiment may include an end plate 300 located on two open sides of the module frame 200 facing each other. The end plate 300 may be provided to cover one open side and the other side of the module frame 200. That is, two end plates 300 may be located on two open sides of the module frame 200 and combined at corresponding corners of the module frame 200 by welding or the like. The end plate 300 may physically protect the battery cell stack 120 and other electrical components from external impact.

[0064] Figure 4 is along Figure 1 A cross-sectional view taken along the cutting line AA′.

[0065] Refer to Figures 2 to 4 , the battery module 100 according to the present embodiment includes at least one compression pad 400 disposed at least between adjacent battery cells 110 or between the outermost battery cell 110 among the battery cells 110 and the side surface parts 210 and 220 .

[0066] The compression pad 400 is a foam-like member and can partially absorb the expansion of the battery cell. Specifically, with repeated charge and discharge, the battery cell 110 may generate gas inside due to degradation, etc. Moreover, when gas is generated from the inside in this way, the internal pressure increases, which may cause an expansion phenomenon, and at least a part of the external material expands. In particular, in the case of a pouch-type secondary battery, the structural rigidity of the external material is weaker than that of a can-type secondary battery, so that the expansion phenomenon may occur more seriously.

[0067] When the expansion phenomenon occurs in the secondary battery in this way, the pressure inside the battery increases and the volume increases, which may have an adverse effect on the structural stability of the battery module. Therefore, by providing a compression pad 400 that is compressed when pressure is applied to the inside of the battery module 100, it is attempted to partially absorb the expansion of the battery cell 110. The material of the compression pad 400 is not particularly limited as long as it can be compressed to absorb the expansion of the battery cell 110, and as an example, a polyurethane material may be included.

[0068] On the other hand, the battery module according to the present embodiment has a reserved space ratio of each battery cell of more than 3% based on the stacking direction of the battery cells 110. In addition, the reserved space ratio of each battery cell may be more than 3% and less than 10%. Additionally, considering the space utilization and energy density of the battery module, the reserved space ratio of each battery cell may be more than 3% and less than 6%, and may be more than 4% and less than 6%.

[0069] The reserved space ratio of each battery cell is a value calculated for a space occupied by one battery cell 110 within the battery module 100 and may be calculated using the following formula.

[0070] Reserved space ratio of each battery cell = (WCP) / C*100

[0071] Among them, W is the distance value between the side surface parts 210 and 220 of the module frame 200, C is the value corresponding to the total thickness of the battery cell 110, and P is the 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 accommodated in the module frame 200. The units of the values ​​of W, C, and P may all be mm.

[0072] like Figure 4 As shown, W corresponds to the distance value between the inner side surfaces of the side surface portions 210 and 220 of the module frame 200. As described above, the side surface portions 210 and 220 in the present embodiment are portions covering both side surfaces of the battery cell stack 120 along the stacking direction of the battery cells 110, and are portions associated with the pressing force applied to the battery cell in which swelling occurs.

[0073] C is a value corresponding to the total thickness of the battery cell 110, and can be calculated as the product of the thickness (Ct) value of the central portion 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 central portion 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. As an example, Figure 4 As shown, the C value can be obtained by multiplying the thickness (Ct) value of a single battery cell 110 by 12, which is the number (Cn) of the battery cells 110. Here, the central portion of the battery cell 110 used to measure the thickness (Ct) refers to the central portion of the battery cell 110 based on its longitudinal direction. More specifically, referring to Figure 3 The center portion may refer to a midpoint between the protruding ends 114 a and 114 b of the electrode leads 111 and 112 of the battery cell 110 .

[0074] For the compression mat 400 in a state where the battery cell stack 120 and the compression mat 400 are accommodated in the module frame 200 and compressed, P can be calculated as the product of the thickness Pt of a single compression mat 400 and the number Pn of the compression mat 400. That is, P=Pt*Pn, where Pt is a value corresponding to the thickness of a single compression mat 400 in a compressed state, and Pn is a value corresponding to the number of compression mats 400. As an example, Figure 4 As shown, the value of P may be found by multiplying the thickness Pt of a single compression mat 400 by 4 (ie, which is the number Pn of compression mats 400).

[0075] Next, we will refer to Figure 5 A battery module according to another embodiment of the present disclosure will be described.

[0076] Figure 5 is a cross-sectional view of a battery module according to another embodiment of the present disclosure, and Figure 4 Similarly, it corresponds to a cross section of the battery module taken along the yz plane.

[0077] Reference Figure 5 The battery module 100 according to the present embodiment may further include at least one adhesive portion 600 located between battery cells 110 facing each other among the battery cells 110, between the battery cells 110 and the compression pad 400, or at least one position of the inner surface of the side surface portions 210 and 220. Here, the inner surface of the side surface portions 210 and 220 refers to the surface of the side surface portions 210 and 220 in the direction toward the battery cell stack 120. With respect to the battery cell stack 120, the module frame 200, and the compression pad 400 included in the battery module 100, the same as previously described in the application is applied. Figures 1 to 4 The configuration is the same as the configuration described in the embodiment, and therefore, its description will be omitted.

[0078] As mentioned above, a plurality of battery cells 110 are stacked to form the middle or large battery module 100 , but in order to maintain a stable stacking structure of the battery cells 110 , the adhesive part 600 is provided on one surface of the battery cells 110 .

[0079] The adhesive portion 600 may be provided not only between the battery cells 110, but also between the battery cell 110 and the compression pad 400 when the compression pad 400 is located between the battery cells 110. In addition, the adhesive portion 600 may also be provided on the inner side surfaces of the side surface portions 210 and 220. As shown in the figure, when the compression pad 400 is provided between the battery cell 110 located at the outermost side among the battery cells 110 and the side surface portions 210 and 220, the adhesive portion 600 may be provided between the compression pad 400 and the side surface portions 210 and 220.

[0080] Specifically, in Figure 5 , an adhesive portion 600 located between the battery cells 110 and adhered to one surface of each adjacent battery cell 110, an adhesive portion 600 adhered between the battery cell 110 and the compression pad 400, and an adhesive portion 600 adhered between the compression pad 400 and the side surface portions 210 and 220 are all shown.

[0081] Although not shown in the drawings, in another embodiment of the present disclosure in which the compression pad 400 is not located between the outermost battery cell 110 among the battery cells 110 and the side surface portions 210 and 220, an adhesive portion 600 may be provided between the outermost battery cell 110 among the battery cells 110 and the side surface portions 210 and 220.

[0082] The adhesive part 600 according to the present embodiment can be applied without limitation as long as it is a material or member having adhesiveness. As an example, the adhesive part 600 can be a double-sided tape. As another example, the adhesive part 600 can be an adhesive layer formed by coating an adhesive.

[0083] At this time, the battery module according to the present embodiment has a reserve ratio per battery cell of 3% or more based on the stacking direction of the battery cells 110 .

[0084] In this embodiment, the reserved space ratio of each battery cell can be calculated by the following formula.

[0085] Reserved space ratio of each battery cell = (WCPD) / C*100

[0086] Among them, W is a distance value between the side surface portions 210 and 220 of the module frame 200, C is a value corresponding to the total thickness of the battery cell 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 accommodated in the module frame 200, and D is a value corresponding to the total thickness of the adhesive portion 600. The units of the values ​​of W, C, P, and D may all be mm.

[0087] like Figure 5 As shown, W corresponds to a distance value between the inner surfaces of the side surface parts 210 and 220 of the module frame 200 .

[0088] C is a value corresponding to the total thickness of the battery cell 110, and can be calculated as the product of the thickness Ct value of the center of the 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 portion 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. As an example, Figure 5 As shown, the C value can be obtained 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 central portion of the battery cell 110 for measuring the thickness Ct refers to the central portion of the battery cell 110 based on its longitudinal direction. More specifically, referring to Figure 3 , the central portion of the battery cell 110 may refer to a midpoint between both ends 114 a and 114 b from which the electrode leads 111 and 112 in the battery cell 110 protrude.

[0089] For the compression mat 400 in a state where the battery cell stack 120 and the compression mat 400 are accommodated together in the module frame 200 and compressed, P can be calculated as the product of the thickness Pt of a single compression mat 400 and the number Pn of the compression mat 400. That is, P=Pt*Pn, where Pt is a value corresponding to the thickness of a single compression mat 400 in a compressed state, and Pn is a value corresponding to the number of compression mats 400. As an example, Figure 5 As shown, the value of P may be obtained by multiplying the thickness Pt of a single compression mat 400 by 4, which is the number Pn of compression mats 400 .

[0090] D may be calculated as the product of the thickness Dt of a single adhesive portion 600 and 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. As an example, the adhesive portion 600 may 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 cell 110 is located at the outermost side, the adhesive portion 600 may also be disposed on the compression pad 400 located at the outermost side or on the outer surface of the battery cell 110. The adhesive portion 600 may also be located between the compression pad 400 or the battery cell 110 located at the outermost side and the side surface portions 210 and 220. In other words, as described above, the adhesive portion 600 may be disposed on the inner side surface of the side surface portions 210 and 220. When the battery cell 110 and the compression pad 400 are regarded as one component, the adhesive portion 600 may be placed between these components. The number Dn of the adhesive portions 600 may be calculated as the sum of the number Cn of the battery cells 110 and the number Pn of the compression pads 400 plus 1. Figure 5 In the example of , in which 12 battery cells 110 and 4 compression pads 400 are arranged inside the module frame 200, a total of 17 adhesive parts 600 may be provided. In this case, D is a value obtained by multiplying the thickness Dt of a single adhesive part 600 by 17 which is the number Dn of the adhesive parts 600.

[0091] In summary, in the case of a battery module without an adhesive portion, the reserved space ratio of each battery cell is calculated as (WCP) / C*100, and in the case of a battery module with an adhesive portion, the reserved space ratio of each battery cell can be calculated as (WCPD) / C*100. In the battery module 100 of the present embodiment, the calculated reserved space ratio values ​​are all above 3%.

[0092] The inventors have confirmed that the space occupied by the battery cells 110 in 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. When an appropriate level of pressing force is applied to the battery cells 110, the appropriate capacity can be maintained even if the battery module 100 is cycled. When the pressing force is lower than or higher than a certain level, the problem of a sudden drop in capacity during the cycle may occur. Based on this, the inventors designed a condition in which the reserved space ratio of each battery cell is 3% or more to control the absolute pressure of the battery cells 110 applied to the battery module 100, and confirmed that when this condition is met, when the battery cells 110 are attached to the battery module 100, no degradation in life performance occurs. Specifically, in the case of a battery module that meets the conditions, the capacity retention rate after 800 cycles can be maintained at more than 80%.

[0093] Hereinafter, the battery module of the present disclosure will be described with reference to specific examples and comparative examples.

[0094] [Table 1]

[0095]

[0096] First, referring to Table 1, battery modules having different standards and specifications were prepared in Examples 1 to 4, and the reserved space ratio (%) of each battery cell of the battery modules in Examples 1 to 4 was calculated. The unit of each factor is all listed in square brackets.

[0097] As described above, W is a measurement of the distance between the inner side surfaces of the side surface parts 210 and 220 of the module frame 200. C corresponding to the total thickness of the battery cell 110 is calculated as the product of the thickness Ct of the central part of the battery cell 110 and the number Cn of the battery cells 110.

[0098] It has been confirmed that the compression mat 400 is compressed by 80% when inserted into the module frame 200 together with the battery cell 110, and the thickness Pt of the compression mat 400 in the compressed state is calculated as 20% of the thickness of the original compression mat 400 before compression. P corresponding to the total value of the thickness of the compression mat in the compressed state may be calculated as the product of the thickness Pt of the compression mat 400 in the compressed state and the number Pn of the compression mats 400.

[0099] D corresponding to the total thickness of the adhesive part 600 may be calculated as the product of the thickness Dt of a single adhesive part 600 and the number Dn of the adhesive parts 600. In the case of the battery modules in Examples 1 to 4, the adhesive parts 600 are located between adjacent battery cells 110, between the battery cells 110 and the compression pads 400, and on the outer surfaces of the outermost compression pads 400 and the battery cells 110. In Examples 1 to 4, the number of adhesive parts 600 is calculated as the sum of the number Cn of the battery cells 110 and the number Pn of the compression pads 400 plus 1.

[0100] The reserved space ratio (%) of each battery cell was calculated using the W, C, P, and D values ​​obtained in Examples 1 to 4, and Examples 1 to 4 were calculated to have reserved space ratio values ​​of each battery cell of 3.65%, 4.27%, 4.43%, and 3.59%, respectively. The reserved space ratio of each battery cell in Examples 1 to 4 was all a value of 3% or more.

[0101] For Examples 1 to 4, the reserved capacity ratio (%) after 800 cycles in battery cells and the reserved capacity ratio (%) after 800 cycles in battery modules were measured. The capacity retention rate after 800 cycles in battery cells is a measurement of the discharge capacity of a single battery cell that does not constitute a battery module after 800 charge and discharge cycles relative to the initial discharge capacity. The capacity retention rate after 800 cycles in battery modules is a measurement of the discharge capacity of a battery module containing the corresponding battery cells after 800 charge and discharge cycles compared to the initial discharge capacity.

[0102] Observing the difference between the capacity retention rate after 800 cycles in terms of battery cells and the capacity retention rate after 800 cycles in terms of battery modules (i.e., the difference in capacity degradation [%] between the battery cells and the battery modules), Examples 1 to 4 were measured to be values ​​of 5, 0.3, -1, and 1, respectively.

[0103] In the case of Examples 1 to 4 where the reserved space ratio of each battery cell is all 3% or more, it has been confirmed that even if the battery cells 110 constitute the battery module 100, its life performance will not be significantly reduced. There is not much difference between the capacity retention rate after 800 cycles in the battery cell unit and the capacity retention rate after 800 cycles in the battery module unit. In other words, even if the battery module 100 is cycled, the appropriate capacity can be maintained, and there will be no problem of sudden capacity drop during cycling.

[0104] [Table 2]

[0105]

[0106] Next, referring to Table 2, battery modules having different standards and specifications were prepared in Comparative Examples 1 to 3, and the reserved space ratio (%) of each battery cell of the battery modules in Comparative Examples 1 to 3 was calculated. The unit of each factor is listed in square brackets.

[0107] The W, C, P, and D values ​​of Comparative Examples 1 to 3 were obtained by the same method as that measured in Examples 1 to 4. Since the description thereof substantially overlaps with the previously described contents, the description thereof is omitted.

[0108] The reserved space ratio (%) of each battery cell was calculated using the W, C, P and D values ​​obtained for Comparative Examples 1 to 3, and Examples 1 to 3 were calculated to have reserved space ratio values ​​of 1.93%, 1.88% and 2.46% for each battery cell, respectively. The reserved space ratios of each battery cell in Comparative Examples 1 to 3 were all values ​​less than 3%.

[0109] The capacity retention rate after 800 cycles, the capacity retention rate after 800 cycles in battery modules, and the capacity degradation difference between the battery cells and the battery modules were calculated similarly to the methods measured in Examples 1 to 4. The capacity degradation difference (%) between the battery cells and the battery modules was observed, and the comparison examples 1 to 3 were measured to be 18.8, 18.8, and 15.8, respectively.

[0110] In the case of Comparative Examples 1 to 3 where the reserved space ratio of each battery cell is all less than 3%, it has been confirmed that when the battery cells 110 constitute the battery module 100, the life performance is significantly reduced compared to Examples 1 to 4. In other words, similar to the battery module according to the present embodiment, when the reserved space ratio of each battery cell satisfies the condition of 3% or more, it has been confirmed through the above experimental results that the life performance of the battery module can be prevented from being significantly reduced.

[0111] Next, refer to Figures 6 to 8 , a formation area of ​​the adhesive part 600 according to an embodiment of the present disclosure will be described in detail together with a comparative example.

[0112] Figure 6 is a perspective view showing a battery cell stack according to a comparative example of the present disclosure.

[0113] First, refer to Figure 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 one position between the battery cells 11. The adhesive portion 60 may be a double-sided tape, or an adhesive layer formed by coating an adhesive. Figure 6 As shown, the adhesive portion 60 according to the present comparative example is not attached to the entire surfaces facing each other of the battery cell 11, but is attached only to a portion thereof. In this case, the inventors have confirmed that due to the locally formed adhesive portion 60, uneven pressure is applied to the battery cell 110, and lithium plating occurs at both ends.

[0114] Specifically, due to the locally formed adhesive portion 60, uneven surface pressure occurs on the surface of the battery cell 110, and gas generated by the uneven surface pressure exists on the surface of the battery cell, which causes lithium plating in which lithium is precipitated on the surface of the battery cell 110. In particular, referring to Figure 3 and Figure 6 , when the adhesive portion 60 is formed only in the central portion of the battery cell 110 , the inventors found the following problem: lithium is mainly precipitated in regions adjacent to both ends 114 a and 114 b from which the electrode leads 111 and 112 in the battery cell 110 protrude.

[0115] The inventors analyzed the relationship between the lithium precipitation rate in lithium plating and the capacity retention rate of the battery cell, and confirmed that the lithium precipitation rate and the capacity retention rate of the battery cell have a strong negative correlation. That is, as the lithium precipitation rate increases, the capacity retention rate after 800 cycles decreases. The uneven surface pressure of the battery cell 110 caused by the adhesive portion 60 has an adverse effect on the life performance of the battery module 100. Therefore, the inventors proposed the following adhesive portion 600 as a uniform pressing structure on the surface of the battery cell 110. Next, reference will be made to Figure 3 , Figure 7 and Figure 8 A formation region of the adhesive portion 600 according to the present embodiment is described.

[0116] Figure 7 is a perspective view showing a battery cell stack according to an embodiment of the present disclosure. Figure 8 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 disclosure.

[0117] Reference Figure 3 , Figure 7 and Figure 8 As described above, the battery cell 110 is a sheet-shaped pouch-type battery cell and may be stacked in an upright state such that one surface of the battery cell 110 is parallel to the side surface portions 210 and 220 (see Figure 2 ). The battery cells 110 may be stacked so that one surface of the battery cells faces each other. That is, one surface of the battery cell 110 described below corresponds to a portion of the battery cell 110 parallel to the side surface portions 210 and 220 of the module frame 200, and may face another battery cell 110, the compression pad 400, or the side surface portions 210 and 220 of the module frame 200.

[0118] At this time, the adhesive part 600 according to the present embodiment may be attached to one surface of the battery cell 110 to cover one surface of the battery cell 110. Specifically, the adhesive part 600 may be attached to one surface of the battery cell 110 to cover an area of ​​90% or more and 100% or less of the area of ​​one surface of the battery cell 110. In addition, considering the design tolerance of one surface of the battery cell 110, the adhesive part 600 may be attached to one surface of the battery cell 110 to cover an area of ​​90% or more and 101% or less of the area of ​​one surface of the battery cell 110.

[0119] Unlike the adhesive part 60 according to the above-mentioned comparative example, the adhesive part 600 according to the present embodiment can be attached to cover most of the surface of the battery cell 110. Therefore, it is possible to achieve a uniform pressing structure on one surface of the battery cell 110. Unlike the adhesive part 60 attached only to a narrow area, the adhesive part 600 according to the present embodiment can ensure the uniformity of the pressure applied to the surface of the battery cell 110, which solves the lithium plating problem occurring in the portions adjacent to the two ends 114a and 114b of the battery cell 110, and can improve the life performance of the battery module 100.

[0120] On the other hand, refer to Figure 4 and Figure 5 The battery module 100 according to the present embodiment may further include a thermally conductive resin layer 700 between the battery cell stack 120 and the lower surface portion 240 of the module frame 200 .

[0121] 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 may be formed by injection through a through hole formed in the lower surface portion 240. In particular, in a battery cell 110 in which the electrode leads 111 and 112 protrude in two opposite directions, a portion of the battery cell stack 120 adjacent to the electrode leads 111 and 112 of the battery cell 110 generates excessive heat. The thermally conductive resin layer 700 may be formed to be divided into two regions to correspond to two portions of the battery cell stack 120 that generate excessive heat.

[0122] The thermally conductive resin may include a thermally conductive adhesive material, specifically, it may include at least one of a silicone material, a polyurethane material, and an acrylic material. The thermally conductive resin may be in a liquid state during coating or injection, and may be cured after coating or injection, thereby being used to fix one or more battery cells 110 constituting the battery cell stack 120. In addition, it has excellent thermal conductivity, allowing the heat generated in the battery cell 110 to be quickly transferred to the lower side of the battery module.

[0123] Terms indicating directions (such as the front side, the back side, the left side, the right side, the upper side, and the lower side) have been used in this embodiment, but the terms used are provided only for the convenience of description and may become different depending on the position of the object, the position of the observer, etc.

[0124] One or more battery modules according to the embodiments of the present disclosure described above may be installed 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.

[0125] The battery pack can be applied to various devices. For example, it can be applied to vehicle devices such as electric bicycles, electric vehicles, hybrid electric vehicles, or ESS (Energy Storage System), and can be applied to various devices that can use secondary batteries, without being limited thereto.

[0126] Although the present invention has been described in detail with reference to the preferred embodiments of the present disclosure, the scope of the present disclosure is not limited thereto, and those skilled in the art may make various modifications and improvements using the basic concepts of the present disclosure defined in the appended claims, which also fall within the scope of the present disclosure.

[0127] Reference numerals list

[0128] 100: Battery module

[0129] 110: Battery cells

[0130] 120: Battery cell stack

[0131] 200: Module Framework

[0132] 300: End plate

[0133] 400: Compression pad

[0134] 500: Busbar frame

[0135] 600: Bonding part

Claims

1. A battery module, comprising: A battery cell stack formed by stacking a plurality of battery cells; a module frame accommodating the battery cell stack and comprising side surface portions, each of which covers two side surfaces of the battery cell stack along a stacking direction of the battery cells; as well as at least one compression pad disposed at at least one position between adjacent battery cells among the battery cells or between an outermost battery cell among the battery cells and the side surface portion, Wherein, based on the stacking direction of the battery cells, the reserved space ratio of each battery cell is greater than 3%.

2. The battery module according to claim 1, wherein: Based on the stacking direction of the battery cells, the reserved space ratio of each battery cell is greater than 3% and less than 10%.

3. The battery module according to claim 1, wherein: The reserved space ratio of each battery cell is calculated as (WCP) / C*100, where: W is the distance value between the side surface portions of the module frame, C is a value corresponding to the total thickness of the battery cell, and P is a value corresponding to the total thickness of the compression mat in a compressed state in a state in which the battery cell stack and the compression mat are accommodated in the module frame.

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

5. 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 module according to claim 1, wherein: The battery cell is a sheet-shaped pouch-type battery cell, and The battery cells are stacked in an upright state such that one surface of the battery cells is parallel to the side surface portion.

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

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

9. The battery module according to claim 7, wherein: The reserved space ratio of each battery cell is calculated according to (WCPD) / C*100, where: W is the space value between the side surface parts of the module frame, C is a value corresponding to the total thickness of the battery cell, P is a value corresponding to the total thickness of the compression mat in a compressed state in a state where the battery cell stack and the compression mat are accommodated in the module frame, and D is a value corresponding to the total thickness of the bonding portion.

10. The battery module according to claim 9, wherein: The C is a value obtained by multiplying the thickness value 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 value of the bonding portion by the number of the bonding portions.

13. The battery module according to claim 7, wherein: The battery cell is a sheet-shaped pouch-type battery cell, and The battery cells are stacked in an upright state such that one surface of the battery cells is parallel to the side surface portion.

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

15. The battery module according to claim 13, wherein: The adhesive portion is attached to the one surface of the battery cell to cover an area of ​​90% or more and 100% or less of an area of ​​the one surface of the battery cell.

16. The battery module according to claim 13, wherein: The adhesive portion is attached to the one surface of the battery cell to cover an area of ​​90% or more and 101% or less of an area of ​​the one surface of the battery cell. 17 . A battery pack comprising the battery module according to claim 1 .

Images